US20100092457A1

US20100092457A1 - Diagnosis and Treatment of Cancer Using Anti-Desmoglein-3 Antibodies

Info

Publication number: US20100092457A1
Application number: US12/308,695
Authority: US
Inventors: Hiroyuki Aburatani; Shunpei Ishikawa; Hirotaka Ito; Kiyotaka Nakano; Shigeto Kawai
Original assignee: University of Tokyo NUC; Forerunner Pharma Research Co Ltd
Current assignee: Chugai Pharmaceutical Co Ltd; University of Tokyo NUC
Priority date: 2006-08-14
Filing date: 2007-08-14
Publication date: 2010-04-15
Also published as: JP5651726B2; US20170152314A1; WO2008020586A1; JP2015003912A; JPWO2008020586A1; JP5317697B2; BRPI0713086A2; JP6162864B2; EP2050466A4; EP2050466A1; EP3111955A1; EP2050466B1; US10696743B2; CA2658050A1; JP2016185981A; JP2013189433A; AU2007285217B2; AU2007285217A1; EP3111955B1; EP2548576A1

Abstract

Methods that involve detection of a DSG3 protein for diagnosing cancer are disclosed. In lung cancer, the expression of DSG3 was found to be enhanced at very high frequency at the gene level and protein level. Methods of the present invention can be carried out using an antibody that recognizes a DSG3 protein. Pharmaceutical compositions, cell growth inhibitors, and anticancer agents containing a DSG3-binding antibody as an active ingredient are also disclosed. Methods of inducing cell damage in DSG3-expressing cells and methods of suppressing proliferation of DSG3-expressing cells by contacting the DSG3-expressing cells with DSG3-binding antibodies are also disclosed.

Description

TECHNICAL FIELD

The present invention relates to methods for diagnosing and treating cancer, cell proliferation inhibitors, and anticancer agents.

BACKGROUND ART

Desmoglein 3 (hereinafter referred to as DSG3) was first identified as a glycoprotein having a molecular weight of 130 kDa by immunoprecipitation of keratinocyte extracts with an autoantibody obtained from the serum of patients affected by pemphigus vulgaris (hereinafter referred to as PV), which is an autoimmune blister-forming disease of the skin and mucosa, and was named the PV antigen (hereinafter referred to as PVA) (Non-patent Document 1 and J. Clin. Invest. 74, 313-320, 1984). Then, antibody molecules that react with the above-mentioned 130-kDa protein were isolated from the serum of PV patients by affinity purification. Next, an expression library was constructed using poly(A) RNA isolated from human keratinocytes and was screened using the isolated antibodies, and a cDNA encoding PVA was isolated. Based on analysis of the nucleotide sequence of the isolated cDNA, the PVA molecule was found to be highly homologous to the sequences of a group of molecules belonging to the cadherin gene superfamily which encodes intercellular adhesion factors (Non-patent Document 2).
Cadherin molecules are expressed in a wide variety of tissues and they are involved in cell adhesion in vivo. Within the cadherin group, a group of molecules are expressed in desmosomes, which are adhesion sites between cells on the cell membrane, and are called desmosomal cadherins or desmogleins. Keratinocytes, which were used for isolation and cloning of the DSG3 molecule (a member of the desmoglein family), are cells that occupy a large portion of the epidermis. They are tightly adhered to adjacent cells via desmosomes and the DSG3 molecule is considered to be involved in this adhesion. Anti-DSG3 autoantibodies present in PV patients' sera are thought to cause PV lesions by binding to the DSG3 molecule and inhibiting intercellular adhesion mediated by the DSG3 molecule.
As described above, PV lesions are induced by polyclonal anti-DSG3 autoantibodies present in PV patients' sera. Monoclonal anti-DSG3 antibodies that have the ability to induce PV-like lesions upon transplantation of hybridomas into mice have also been isolated (Non-patent Document 3), and they have been shown to have a cell-dissociating activity that inhibits cell adhesion of keratinocytes in the test tube as well (Non-patent Document 4). As described above, the cell-dissociating activity of anti-DSG3 antibodies observed in the test tube has been suggested to be the activity that induces PV lesions in vivo.
As described above, it is known that the DSG3 protein has an important function in keratinocyte adhesion, and that anti-DSG3 antibodies are involved in the development of PV lesions. However, involvement of the DSG3 protein in other diseases, or functions of anti-DSG3 antibodies other than the cell-dissociating activity have not been elucidated. In particular, connection of the DSG3 molecule with the development of cancer, especially lung cancer, and proliferation, invasion, metastasis, or transformation of lung cancer cells in mammals, in particular, humans, has not been elucidated.
Of the various types of cancers, lung cancer has the highest mortality rate in both men and women. The mortality rate of lung cancer in Japan has increased after 1950; as a result, the number of lung cancer deaths in 1998 was 50,871 individuals, which was approximately 18% of all malignant tumor deaths, and after 1993, the number of deaths has exceeded that of stomach cancer and is ranked number one among malignant tumors for men (Health and Welfare Statistics Association, Kokumin eisei no doko/kousei no shihyou (Trends of national health/indicators of welfare), 47, 52-53, 2000). Furthermore, on a global scale, approximately 3,000,000 people a year are dying of lung cancer. Basic histological types of lung cancer include adenocarcinoma, squamous cell carcinoma, adenosquamous carcinoma, large cell carcinoma, and small cell carcinoma. Since the former four do not show large differences in prognosis or therapeutic strategy, they are collectively referred to as non-small cell lung cancer.
The number of non-small cell lung cancer cases accounts for 80% to 85% of the total number of lung cancer cases. Examples of the characteristics of non-small cell lung cancer are slow progression compared to small-cell cancers, and insufficient response to chemotherapy and radiation therapy. Therefore, when the tumor is localized, surgical resection is the number one choice, but the treatment outcome is very poor compared to other carcinomas such as stomach cancer at the same disease stage by TNM classification. While recent attempts have been actively pursued to improve the outcome by multimodal treatment, effective therapeutic methods that lead to complete remission have not been established. In non-small cell lung cancer, surgical therapy is considered for up to stage IIIa, while in subsequent clinical disease stages, surgery is rarely applied, and chemotherapy and radiation therapy are the main therapies. SCC (squamous cell carcinoma related antigen), Cyfra (cytokeratin 19 fragment), CEA (carcinoembryonic antigen), and SLX (sialyl Lewis x-i antigen) are selected as markers for serodiagnosis, and they are used separately or in combination, but the positive rate for early stage cancers is still low, and development of diagnostic markers that will assure early-stage diagnosis of non-small cell lung cancer by serodiagnosis is anticipated (Shuyo maka no yomikata no jissai; haigan (Practical method for reading tumor markers; lung cancer) Rinsho to Kenkyu (Clinic and Research) 78, 35-40, 2001).
Small cell lung cancer tumors constitute approximately 15% to 20% of all lung cancers in Japan, and their speed of proliferation is fast compared to other lung cancers, but they are highly sensitive to anticancer agents and radiation therapy, and have significantly different clinical characteristics from those of adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and such. For small cell cancer, surgical therapy is considered only in stage Ia (tumor diameter is 20 mm or less, and no invasion or metastasis to lymph nodes and nearby organs is shown), and chemotherapy and radiation therapy are basically the main therapeutic methods employed. As diagnostic markers, NSE (neuron-specific enolase) and proGRP (pro gastrin-releasing peptide) are used as tumor markers with relatively high specificity to small cell cancer, and their positive rates are reported to be approximately 60% and 70%, respectively.
Although there are still no examples of application in clinical practice for lung cancers, the therapeutic response rate in breast cancer, lymphoma, and such is increasing, because targeted therapy using monoclonal antibodies against cancer-specific tumor antigens exhibits a mode of action different from conventional therapy which uses chemotherapeutic agents. In targeted therapy that uses the above-mentioned antibody pharmaceuticals, when the antibodies are functional and effective, their activities include: antibody-dependent cell-mediated cytotoxicity (ADCC) activity via effector cells; complement-dependent cytotoxicity (CDC) activity via complements; and cytotoxic activity as a result of construction of conjugate molecules with chemotherapeutic agents, toxic peptides, or radioactive chemical substances. Additional activities besides those mentioned above include, for example, agonistic activity in which the antibody itself catalyzes an agonistic effect on the antigenic molecule; and neutralizing activity that blocks signals for cell activation, proliferation, or the like. In order to apply molecular-targeting therapy that uses antibodies exhibiting activities such as those mentioned above in the treatment of lung cancer, which has low positive rate of diagnosis, low disease cure rate, and still has room for complete remission, identification of tumor-specific molecules expressed in lung cancer cells and production of antibodies that exhibit desirable activity by targeting such molecules are strongly anticipated.
Prior art literature information relating to the present invention is the following:

[Patent Document 1] WO 99/57149.

[Patent Document 2] WO 02/86443.

[Patent Document 3] WO 03/20769.

[Non-patent Document 1] J. Clin. Invest. 70, 281-288, 1982.

[Non-patent Document 2] Cell 67, 869-877, 1991.

[Non-patent Document 3] J. Immunology 170, 2170-2178, 2003.

[Non-patent Document 4] J. Invest. Dermatol., 124, 939-946, 2005.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

An objective of the present invention is to provide anti-DSG3 antibodies and uses thereof. More specifically, an objective of the present invention is to provide novel methods for diagnosing and treating cancer using anti-DSG3 antibodies, novel cell proliferation inhibitors and anticancer agents comprising anti-DSG3 antibodies, and novel anti-DSG3 antibodies.

Means for Solving the Problems

The present inventors discovered that DSG3 is highly expressed in cancer cells such as lung cancer cells. Furthermore, when complement-dependent cytotoxicity (CDC) activity and antibody-dependent cellular cytotoxicity (ADCC) activity of anti-DSG3 antibodies were measured, the anti-DSG3 antibodies were found to have CDC activity and ADCC activity towards DSG3-expressing cells. Furthermore, from the above-mentioned findings, the present inventors discovered that the anti-DSG3 antibodies were effective for diagnosing, preventing, and treating cancers in which the DSG3 expression is elevated, including lung cancer, and thereby completed the present invention.
The present invention provides pharmaceutical compositions comprising a DSG3 protein-binding antibody as an active ingredient. The present invention also provides cell proliferation inhibitors comprising a DSG3 protein-binding antibody as an active ingredient. The present invention further provides anticancer agents comprising a DSG3 protein-binding antibody as an active ingredient. Preferably, the DSG3 protein-binding antibody has cytotoxic activity. Preferably, the cancer is lung cancer. More preferably, the cancer is non-small cell lung cancer.
In another embodiment, the present invention provides methods for inducing cell injury towards cells that express the DSG3 protein by contacting DSG3-expressing cells with a DSG3 protein-binding antibody. The present invention also provides methods for suppressing proliferation of cells that express a DSG3 protein by contacting cells that express the DSG3 protein with a DSG3 protein-binding antibody. The DSG3 protein-binding antibody preferably has cytotoxic activity. Cells that express a DSG3 protein are preferably cancer cells.
Furthermore, in another embodiment, the present invention provides antibodies that bind to a DSG3 protein and have cytotoxic activity towards cells that express the DSG3 protein. Preferably, the cytotoxic activity is ADCC activity. Preferably, the cytotoxic activity is CDC activity. The present invention also provides antibodies to which a low-molecular-weight chemotherapeutic agent or a toxic peptide is bound, or antibodies having cytotoxic activity to which a low-molecular-weight chemotherapeutic agent or a toxic peptide is bound.
The present invention further provides antibodies that bind to a DSG3 protein, and have cytotoxic activity but not cell-dissociating activity towards cells expressing the DSG3 protein.
In another embodiment, the present invention provides uses of the DSG3 protein as a cancer diagnostic marker.
Furthermore, in another embodiment, the present invention provides methods for diagnosing cancer, which comprise detecting a DSG3 protein using an antibody that binds to the DSG3 protein. In the methods of the present invention, preferably the extracellular region of the DSG3 protein is detected. Preferably, the methods of the present invention are carried out using an antibody that recognizes the DSG3 protein. Preferably, the methods of the present invention detect the DSG3 protein in the blood, serum, or plasma, or DSG3 protein isolated from cells.
In another embodiment, the present invention provides methods for diagnosing cancer which comprise the steps of:
(a) collecting a sample from a subject; and
(b) using a DSG3 protein-binding antibody to detect the DSG3 protein contained in the collected sample.
In the present invention, any substance can be used as the above-mentioned sample so long as it can be collected from the subject. Serum collected from a subject is used in one embodiment, and a biopsy sample collected from a subject is used in another embodiment. In the methods of diagnosis, the cancer may be any cancer so long as the subject cancer cells express a DSG3 protein, but it is preferably lung cancer, and more preferably non-small cell lung cancer. In the present invention, the step of collecting a sample from a subject can also be expressed as the step of providing a sample collected from a subject.
Furthermore, in another embodiment, the present invention provides methods for diagnosing cancer, in which the DSG3 protein-binding antibody is labeled with a nuclide selected from any one of 11C, 13N, 15O, 18F, 45Ti, 55Co, 64Cu, 66Ga, 68Ga, 76Br, 89Zr, and 124I.
Furthermore, in another embodiment, the present invention provides methods for diagnosing cancer, in which the expression of a gene encoding the DSG3 protein is detected.
Furthermore, in another embodiment, the present invention provides diagnostic agents and kits to be used in the methods of diagnosis of the present invention
Thus, the present application provides the following:
[1] a pharmaceutical composition comprising as an active ingredient an antibody that binds to a DSG3 protein;
[2] a cell growth inhibitor comprising as an active ingredient an antibody that binds to a DSG3 protein;
[3] an anticancer agent comprising as an active ingredient an antibody that binds to a DSG3 protein;
[4] the anticancer agent of [3], wherein the antibody that binds to a DSG3 protein is an antibody that has cytotoxic activity;
[5] the anticancer agent of [3] or [4], wherein the antibody that binds to a DSG3 protein is an antibody described in any of (1) to (47) below:
(1) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 2 as CDR1, the amino acid sequence of SEQ ID NO: 4 as CDR2, and the amino acid sequence of SEQ ID NO: 6 as CDR3;
(2) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 8 as CH;
(3) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(4) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 12 as CDR1, the amino acid sequence of SEQ ID NO: 14 as CDR2, and the amino acid sequence of SEQ ID NO: 16 as CDR3;
(5) an antibody comprising the L chain of (4), wherein the L chain has the amino acid sequence of SEQ ID NO: 18 as CL;
(6) an antibody comprising the L chain of (4), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(7) an antibody comprising the H chain of (1) and the L chain of (4);
(8) an antibody comprising the H chain of (2) and the L chain of (5);
(9) an antibody comprising the H chain of (3) and the L chain of (6);
(10) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 22 as CDR1, the amino acid sequence of SEQ ID NO: 24 as CDR2, and the amino acid sequence of SEQ ID NO: 26 as CDR3;
(11) an antibody comprising the H chain of (10), wherein the H chain has the amino acid sequence of SEQ ID NO: 28 as CH;
(12) an antibody comprising the H chain of (10), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(13) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 30 as CDR1, the amino acid sequence of SEQ ID NO: 32 as CDR2, and the amino acid sequence of SEQ ID NO: 34 as CDR3;
(14) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;
(15) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(16) an antibody comprising the H chain of (10) and the L chain of (13);
(17) an antibody comprising the H chain of (11) and the L chain of (14);
(18) an antibody comprising the H chain of (12) and the L chain of (15);
(19) an antibody comprising the H chain of (1) and the L chain of (13);
(20) an antibody comprising the H chain of (2) and the L chain of (14);
(21) an antibody comprising the H chain of (3) and the L chain of (15);
(22) an antibody comprising the H chain of (10) and the L chain of (4);
(23) an antibody comprising the H chain of (11) and the L chain of (5);
(24) an antibody comprising the H chain of (12) and the L chain of (6);
(25) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 81 as CDR1, the amino acid sequence of SEQ ID NO: 83 as CDR2, and the amino acid sequence of SEQ ID NO: 85 as CDR3;
(26) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 28 as CH;
(27) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(28) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 87 as CDR1, the amino acid sequence of SEQ ID NO: 89 as CDR2, and the amino acid sequence of SEQ ID NO: 91 as CDR3;
(29) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;
(30) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(31) an antibody comprising the H chain of (25) and the L chain of (28);
(32) an antibody comprising the H chain of (26) and the L chain of (29);
(33) an antibody comprising the H chain of (27) and the L chain of (30);
(34) an antibody comprising the H chain of (1) and the L chain of (28);
(35) an antibody comprising the H chain of (2) and the L chain of (29);
(36) an antibody comprising the H chain of (3) and the L chain of (30);
(37) an antibody comprising the H chain of (10) and the L chain of (28);
(38) an antibody comprising the H chain of (11) and the L chain of (29);
(39) an antibody comprising the H chain of (12) and the L chain of (30);
(40) an antibody comprising the H chain of (25) and the L chain of (4);
(41) an antibody comprising the H chain of (26) and the L chain of (5);
(42) an antibody comprising the H chain of (27) and the L chain of (6);
(43) an antibody comprising the H chain of (25) and the L chain of (13);
(44) an antibody comprising the H chain of (26) and the L chain of (14);
(45) an antibody comprising the H chain of (27) and the L chain of (15);
(46) an antibody comprising one or more amino acid substitutions, deletions, additions, and/or insertions in the antibody of any of (1) to (45), which has equivalent activity as the antibody of any of (1) to (45); and
(47) an antibody that binds to the same DSG3 protein epitope as the antibody of any of (1) to (45);
[6] the anticancer agent of any one of [3] to [5], wherein the cancer is lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, or uterine cancer;
[7] the anticancer agent of [6], wherein the lung cancer is non-small-cell lung cancer;
[8] a method of inducing cell damage in DSG3-expressing cells by contacting cells that express a DSG3 protein with an antibody that binds to the DSG3 protein;
[9] a method of suppressing growth of DSG3-expressing cells by contacting cells that express a DSG3 protein with an antibody that binds to the DSG3 protein;
[10] the method of [8] or [9], wherein the DSG3 protein-binding antibody has cytotoxic activity;
[11] the method of any one of [8] to [10], wherein the DSG3 protein-binding antibody is an antibody of any of (1) to (47) below:
(1) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 2 as CDR1, the amino acid sequence of SEQ ID NO: 4 as CDR2, and the amino acid sequence of SEQ ID NO: 6 as CDR3;
(2) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 8 as CH;
(3) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(4) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 12 as CDR1, the amino acid sequence of SEQ ID NO: 14 as CDR2, and the amino acid sequence of SEQ ID NO: 16 as CDR3;
(5) an antibody comprising the L chain of (4), wherein the L chain has the amino acid sequence of SEQ ID NO: 18 as CL;
(6) an antibody comprising the L chain of (4), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(7) an antibody comprising the H chain of (1) and the L chain of (4);
(8) an antibody comprising the H chain of (2) and the L chain of (5);
(9) an antibody comprising the H chain of (3) and the L chain of (6);
(10) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 22 as CDR1, the amino acid sequence of SEQ ID NO: 24 as CDR2, and the amino acid sequence of SEQ ID NO: 26 as CDR3;
(11) an antibody comprising the H chain of (10) having the amino acid sequence of SEQ ID NO: 28 as CH;
(12) an antibody comprising the H chain of (10) having the amino acid sequence of SEQ ID NO: 10 as CH;
(13) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 30 as CDR1, the amino acid sequence of SEQ ID NO: 32 as CDR2, and the amino acid sequence of SEQ ID NO: 34 as CDR3;
(14) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;
(15) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(16) an antibody comprising the H chain of (10) and the L chain of (13);
(17) an antibody comprising the H chain of (11) and the L chain of (14);
(18) an antibody comprising the H chain of (12) and the L chain of (15);
(19) an antibody comprising the H chain of (1) and the L chain of (13);
(20) an antibody comprising the H chain of (2) and the L chain of (14);
(21) an antibody comprising the H chain of (3) and the L chain of (15);
(22) an antibody comprising the H chain of (10) and the L chain of (4);
(23) an antibody comprising the H chain of (11) and the L chain of (5);
(24) an antibody comprising the H chain of (12) and the L chain of (6);
(25) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 81 as CDR1, the amino acid sequence of SEQ ID NO: 83 as CDR2, and the amino acid sequence of SEQ ID NO: 85 as CDR3;
(26) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 28 as CH;
(27) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(28) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 87 as CDR1, the amino acid sequence of SEQ ID NO: 89 as CDR2, and the amino acid sequence of SEQ ID NO: 91 as CDR3;
(29) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;
(30) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(31) an antibody comprising the H chain of (25) and the L chain of (28);
(32) an antibody comprising the H chain of (26) and the L chain of (29);
(33) an antibody comprising the H chain of (27) and the L chain of (30);
(34) an antibody comprising the H chain of (1) and the L chain of (28);
(35) an antibody comprising the H chain of (2) and the L chain of (29);
(36) an antibody comprising the H chain of (3) and the L chain of (30);
(37) an antibody comprising the H chain of (10) and the L chain of (28);
(38) an antibody comprising the H chain of (11) and the L chain of (29);
(39) an antibody comprising the H chain of (12) and the L chain of (30);
(40) an antibody comprising the H chain of (25) and the L chain of (4);
(41) an antibody comprising the H chain of (26) and the L chain of (5);
(42) an antibody comprising the H chain of (27) and the L chain of (6);
(43) an antibody comprising the H chain of (25) and the L chain of (13);
(44) an antibody comprising the H chain of (26) and the L chain of (14);
(45) an antibody comprising the H chain of (27) and the L chain of (15);
(46) an antibody comprising one or more amino acid substitutions, deletions, additions, and/or insertions in the antibody of any of (1) to (45), which has equivalent activity as the antibody of any of (1) to (45); and
(47) an antibody that binds to the same DSG3 protein epitope as the antibody of any of (1) to (45);
[12] the method of any one of [8] to [11], wherein the cells that express a DSG3 protein are cancer cells;
[13] an antibody that binds to a DSG3 protein and has cytotoxic activity against cells that express a DSG3 protein;
[14] the antibody of [13], wherein the cytotoxic activity is ADCC activity;
[15] the antibody of [13], wherein the cytotoxic activity is CDC activity;
[16] the antibody of any one of [13] to [15], wherein a low-molecular-weight chemotherapeutic agent or a toxic peptide is bound to the antibody;
[17] an antibody binding to a DSG3 protein, wherein a low-molecular-weight chemotherapeutic agent or a toxic peptide is bound to the antibody;
[18] the antibody of any one of [13] to [17], wherein the antibody is an antibody of any of (1) to (47) below:
(1) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 2 as CDR1, the amino acid sequence of SEQ ID NO: 4 as CDR2, and the amino acid sequence of SEQ ID NO: 6 as CDR3;
(2) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 8 as CH;
(3) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(4) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 12 as CDR1, the amino acid sequence of SEQ ID NO: 14 as CDR2, and the amino acid sequence of SEQ ID NO: 16 as CDR3;
(5) an antibody comprising the L chain of (4) having the amino acid sequence of SEQ ID NO: 18 as CL;
(6) an antibody comprising the L chain of (4) having the amino acid sequence of SEQ ID NO: 20 as CL;
(7) an antibody comprising the H chain of (1) and the L chain of (4);
(8) an antibody comprising the H chain of (2) and the L chain of (5);
(9) an antibody comprising the H chain of (3) and the L chain of (6);
(10) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 22 as CDR1, the amino acid sequence of SEQ ID NO: 24 as CDR2, and the amino acid sequence of SEQ ID NO: 26 as CDR3;
(11) an antibody comprising the H chain of (10), wherein the H chain has the amino acid sequence of SEQ ID NO: 28 as CH;
(12) an antibody comprising the H chain of (10), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(13) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 30 as CDR1, the amino acid sequence of SEQ ID NO: 32 as CDR2, and the amino acid sequence of SEQ ID NO: 34 as CDR3;
(14) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;
(15) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(16) an antibody comprising the H chain of (10) and the L chain of (13);
(17) an antibody comprising the H chain of (11) and the L chain of (14);
(18) an antibody comprising the H chain of (12) and the L chain of (15);
(19) an antibody comprising the H chain of (1) and the L chain of (13);
(20) an antibody comprising the H chain of (2) and the L chain of (14);
(21) an antibody comprising the H chain of (3) and the L chain of (15);
(22) an antibody comprising the H chain of (10) and the L chain of (4);
(23) an antibody comprising the H chain of (11) and the L chain of (5);
(24) an antibody comprising the H chain of (12) and the L chain of (6);
(25) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 81 as CDR1, the amino acid sequence of SEQ ID NO: 83 as CDR2, and the amino acid sequence of SEQ ID NO: 85 as CDR3;
(26) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 28 as CH;
(27) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;
(28) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 87 as CDR1, the amino acid sequence of SEQ ID NO: 89 as CDR2, and the amino acid sequence of SEQ ID NO: 91 as CDR3;
(29) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;
(30) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;
(31) an antibody comprising the H chain of (25) and the L chain of (28);
(32) an antibody comprising the H chain of (26) and the L chain of (29);
(33) an antibody comprising the H chain of (27) and the L chain of (30);
(34) an antibody comprising the H chain of (1) and the L chain of (28);
(35) an antibody comprising the H chain of (2) and the L chain of (29);
(36) an antibody comprising the H chain of (3) and the L chain of (30);
(37) an antibody comprising the H chain of (10) and the L chain of (28);
(38) an antibody comprising the H chain of (11) and the L chain of (29);
(39) an antibody comprising the H chain of (12) and the L chain of (30);
(40) an antibody comprising the H chain of (25) and the L chain of (4);
(41) an antibody comprising the H chain of (26) and the L chain of (5);
(42) an antibody comprising the H chain of (27) and the L chain of (6);
(43) an antibody comprising the H chain of (25) and the L chain of (13);
(44) an antibody comprising the H chain of (26) and the L chain of (14);
(45) an antibody comprising the H chain of (27) and the L chain of (15);
(46) an antibody comprising one or more amino acid substitutions, deletions, additions, and/or insertions in the antibody of any of (1) to (45), which has equivalent activity as the antibody of any of (1) to (45); and
(47) an antibody that binds to the same DSG3 protein epitope as the antibody of any of (1) to (45);
[19] use of a DSG3 protein as a cancer diagnostic marker;
[20] a method of diagnosing cancer, comprising detecting a DSG3 protein using an antibody that binds to the DSG3 protein;
[21] a method of diagnosing cancer, comprising the steps of:
(a) collecting a sample from a subject; and
(b) detecting a DSG3 protein contained in the collected sample using an antibody that binds to the DSG3 protein;
[22] the method of diagnosis of [20] or [21], wherein the DSG3 protein-binding antibody is an antibody labeled with a positron-emitting nuclide;
[23] the method of diagnosis of [22], wherein the positron-emitting nuclide is a nuclide selected from any of 11C, 13N, 15O, 18F, 45Ti, 55Co, 64Cu, 66Ga, 68Ga, 76Br, 89Zr, and 124I;
[24] a method of diagnosing cancer, comprising detecting expression of a gene encoding a DSG3 protein;
[25] the method of diagnosis of any one of [20] to [24], wherein the cancer is lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, or uterine cancer;
[26] the method of diagnosis of [25], wherein the lung cancer is non-small-cell lung cancer;
[27] a diagnostic agent to be used for the diagnostic method of any one of [20] to [26];
[28] a kit to be used for the diagnostic method of any one of [20] to [26];
[29] use of an antibody that binds to a DSG3 protein in the production of a cell growth inhibitor;
[30] use of an antibody that binds to a DSG3 protein in the production of an anticancer agent;
[31] a method of suppressing cell growth, comprising the step of administering to a subject an antibody that binds to a DSG3 protein; and
[32] a method of preventing or treating cancer, comprising the step of administering to a subject an antibody that binds to a DSG3 protein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the result of DSG3 gene expression analysis in normal tissues and cancer tissues using GeneChip U133.

FIG. 2 depicts the result of DSG3 expression analysis in cancer cell lines using GeneChip U133.

FIG. 3 shows photographs of immunohistological staining in which expression of the DSG3 protein in lung squamous cell carcinoma is visualized by immunostaining. Elevation of the DSG3 protein expression is shown in all five clinical samples.

FIG. 4 depicts the result of flow cytometric analysis which shows binding of all the anti-DSG3 monoclonal antibodies DF120, DF122, DF148, DF151, DF153, DF168, DF331, DF364, and DF366 to a CHO cell line that constitutively expresses full-length DSG3.

FIG. 5 depicts the CDC activity of anti-DSG3 monoclonal antibodies DF120, DF122, DF148, DF151, DF153, DF168, and DF331 towards a CHO cell line that constitutively expresses full-length DSG3.

FIG. 6 depicts the CDC activity of the DF151 anti-DSG3 monoclonal antibody towards the human epidermoid carcinoma cell line A431, and the DSG3-A549 cell line, which is a human lung carcinoma cell line that constitutively expresses DSG3.

FIG. 7 depicts the ADCC activity of anti-DSG3 monoclonal antibodies DF151, DF364, and DF366 towards the DSG3-A549 cell line which is a human lung carcinoma cell line that constitutively expresses DSG3. FIG. 7A depicts the result of analysis using bone marrow-derived effector cells, and FIG. 7B shows the result of analysis using mouse spleen-derived effector cells.

FIG. 8 depicts the CDC activity of anti-DSG3 mouse-human chimeric antibodies DF151c, DF364c, and DF366c towards the DSG3-Ba/F3 cell line, which is a Ba/F3 cell line that constitutively expresses DSG3.

FIG. 9 depicts the ADCC activity of anti-DSG3 mouse-human chimeric antibodies DF364c and DF366c, and low-fucose anti-DSG3 mouse-human chimeric antibodies YB-DF364c and YB-DF366c, towards the DSG3-Ba/F3 cell line, which is a Ba/F3 cell line that constitutively expresses DSG3.

FIG. 10 depicts the ADCC activity of anti-DSG3 antibodies DF366m (mouse IgG2a chimeric antibody), low-fucose DF366m (low-fucose mouse IgG2a chimeric antibody), DF366c (mouse-human chimeric antibody) and YB-DF366c (low-fucose mouse-human chimeric antibody) towards the DSG3-Ba/F3 cell line, which is a Ba/F3 cell line that constitutively expresses DSG3. Mouse spleen cells that have added interleukin-2 were used as effector cells.

FIG. 11 depicts the ADCC activity of anti-DSG3 antibodies DF366m (mouse IgG2a chimeric antibody), low-fucose DF366m (low-fucose mouse IgG2a chimeric antibody), DF366c (mouse-human chimeric antibody) and YB-DF366c (low-fucose mouse-human chimeric antibody) towards the DSG3-Ba/F3 cell line, which is a Ba/F3 cell line that constitutively expresses DSG3. Mouse spleen cells cultured for four days in the presence of interleukin-2 were used as effector cells.

FIG. 12 depicts the antitumor activity of anti-DSG3 antibodies DF366m (mouse IgG2a chimeric antibody) and low-fucose DF366m (low-fucose mouse IgG2a chimeric antibody).

BEST MODE FOR CARRYING OUT THE INVENTION

DSG3 (Desmoglein 3) is an axon guidance receptor protein, and its amino acid sequence and its encoding gene sequence are disclosed in GenBank Accession Number NP_—001935 (SEQ ID NO: 40) and NM_—001944 (SEQ ID NO: 39), respectively. In the present invention, the DSG3 protein refers to both the full-length protein and fragments thereof. “Fragments” refers to polypeptides comprising any region of the DSG3 protein, and may not have the function of the naturally-occurring DSG3 protein. Without being limited thereto, an example of the fragments is a fragment comprising the extracellular region of the DSG3 protein. Positions 1 to 616 in the amino acid sequence of SEQ ID NO: 40 correspond to the extracellular region of the DSG3 protein. Positions 617 to 641 in the amino acid sequence of SEQ ID NO: 40 correspond to the transmembrane region.
In the present invention, DSG3 expression was found to be elevated at very high frequency in lung cancer tissues at the gene and protein levels. Furthermore, analyses of clinical samples and cancer cell lines of other cancer types showed that the expression was elevated not only in lung cancer, but also in colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, and uterine cancer. Furthermore, it was shown that immunohistological diagnosis is possible by using DSG3 protein-specific monoclonal antibodies. In other words, the DSG3 protein is useful as a diagnostic marker for cancer.

Detection of DSG3 Gene Expression

Methods of the present invention comprise detecting the DSG3 gene expression. In an embodiment of the methods of the present invention, the DSG3 protein expression is detected.
In the present invention, detection includes quantitative and qualitative detections. Examples of qualitative detection include simple measurement for the presence or absence of the DSG3 protein, measurement to see whether or not the DSG3 protein is present above a certain amount, and measurement that compares the amount of the DSG3 protein with that of other samples (for example, a control sample). On the other hand, examples of quantitative detection include measurement of the DSG3 protein concentration, and measurement of the amount of the DSG3 protein.
Test samples are not particularly limited so long as they are samples that may contain DSG3 protein, and are preferably samples collected from the body of organisms such as mammals, and more preferably samples collected from humans. Specific examples of the test samples include blood, interstitial fluid, plasma, extravascular fluid, cerebrospinal fluid, synovial fluid, pleural fluid, serum, lymphatic fluid, saliva, and urine, but the test samples are preferably blood, serum, or plasma. Test samples of the present invention also include samples obtained from test samples, such as cell culture solutions and specimens of immobilized tissues or cells collected from the body of an organism.
The cancers that are diagnosed are not particularly limited and may be any cancer, but specific examples include lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, and uterine cancer. Lung cancer is preferable and non-small cell lung cancer is particularly preferable.
In the present invention, when a DSG3 protein is detected in a test sample and if the test sample is judged to have a greater amount of the DSG3 protein than a negative control or a healthy individual, it can be determined that the subject has cancer or has a high risk of being affected with cancer in the future.
Subjects in the present invention may be animal species that genetically carry a DSG3 protein, and many non-human mammals such as monkeys, cattle, sheep, mice, dogs, cats, and hamsters are known as such animal species. Subjects that are suitably used are, in particular, humans, but are not limited thereto.
Preferred embodiments of the diagnostic methods of the present invention include diagnostic methods that comprise detecting a DSG3 protein on a section of immobilized tissue or cells obtained from a patient affected with an aforementioned cancer. Furthermore, other embodiments of the present invention include diagnostic methods comprising detecting cell-released DSG3 protein in the blood. In particular, the present invention is preferably a diagnostic method that detects a fragment comprising the extracellular domain of the DSG3 protein present in the blood.
Methods for detecting a DSG3 protein contained in a test sample are not particularly limited, but an immunological method that uses an anti-DSG3 antibody for detection is preferred. The immunological method includes, for example, radioimmunoassay (RIA), enzyme immunoassay (EIA), fluorescence immunoassay (FIA), luminescence immunoassay (LIA), immunoprecipitation (IP), turbidimetric immunoassay (TIA), Western blotting (WB), immunohistochemical staining (IHC), and single radial immunodiffusion (SRID), and is preferably enzyme immunoassay, in particular, enzyme-linked immunosorbent assay (ELISA), for example, sandwich ELISA as an embodiment thereof. The above-mentioned immunological methods such as ELISA can be performed by methods known to those skilled in the art.
The following method is, for example, a common detection method that uses an anti-DSG3 antibody. After immobilizing an anti-DSG3 antibody to a support, the support is blocked with bovine serum albumin (BSA), gelatin, albumin, or such to avoid non-specific binding of proteins to the support. Next, a test sample is added to the support for incubation, and the DSG3 proteins are left to bind to the anti-DSG3 antibody bound to the support. Subsequently, by washing the complex formed between the DSG3 proteins and the anti-DSG3 antibody bound to the support with a washing solution, DSG3 proteins other than those bound to the anti-DSG3 antibody on the support that bound non-specifically to the support are removed. Examples of detection methods that use an anti-DSG3 antibody include methods for detecting a DSG3 protein in a test sample by qualitatively or quantitatively detecting the DSG3 protein bound to the anti-DSG3 antibody on the support, and several specific examples described below.
In the present invention, a support used to immobilize an anti-DSG3 antibody is, for example, insoluble polysaccharides such as agarose and cellulose, synthetic resins such as silicon resin, polystyrene resin, polyacrylamide resin, nylon resin, and polycarbonate resin, and insoluble support such as glass. Such a support is used in the form of beads or plates. In the case of beads, a column or the like filled with beads can be used. In the case of a plate, a multi-well plate (96-well multi-well plate, or such), or a biosensor chip can be used. For binding between an anti-DSG3 antibody and a support, an anti-DSG3 antibody can be bound to a support by generally used methods such as chemical bonding or physical adsorption. Commercially available supports can be used suitably.
Binding between an anti-DSG3 antibody and a DSG3 protein is generally performed in a buffer. For example, phosphate buffer, Tris buffer, citric acid buffer, borate buffer, carbonate buffer, or such is used as the buffer. Furthermore, incubation can be suitably carried out using conditions that are already commonly used, such as incubation at a temperature between 4° C. and room temperature for one hour to 24 hours. So long as the binding between the DSG3 protein and anti-DSG3 antibody is not interrupted, anything can be used for washing after incubation, and for example, a buffer containing a surfactant such as Tween 20 or such can be used suitably.
In the DSG3 protein detection method of the present invention, a control sample can be prepared suitably in addition to the test sample in which the DSG3 protein content will be detected. The control sample includes, for example, a negative control sample containing no DSG3 protein and a positive control sample containing the DSG3 protein. In this case, by comparing the results obtained from a negative control sample containing no DSG3 protein with the results obtained from a positive control sample containing the DSG3 protein, the presence or absence of the DSG3 protein in the test sample can be confirmed. Furthermore, after preparing a series of control samples with stepwise changes in concentration, and obtaining detection results for each control sample as a numerical value, the DSG3 protein contained in a test sample can be quantitatively detected according to a standard curve produced based on the values of the DSG3 protein concentration and their corresponding measured values.
In a preferred embodiment, an example of detection of the DSG3 protein bound to a support via an anti-DSG3 antibody is a method that uses an anti-DSG3 antibody labeled with a labeling substance. For example, the DSG3 protein can be detected by contacting a test sample with the anti-DSG3 antibody immobilized onto a support, washing it, and then using a labeled antibody that specifically recognizes the DSG3 protein bound to the anti-DSG3 antibody.
Anti-DSG3 antibodies can be labeled by generally known methods. A labeling substance known to those skilled in the art such as fluorescent dyes, enzymes, coenzymes, chemiluminescent substances, and radioactive substances can be used as the labeling substance, and specific examples include radioisotopes (32P, 14C, 125I, 3H, 131I, and such), fluorescein, rhodamine, dansyl chloride, umbelliferone, luciferase, peroxidase, alkaline phosphatase, β-galactosidase, β-glucosidase, horseradish peroxidase, glucoamylase, lysozyme, saccharide oxidase, micro peroxidase, and biotin. When using biotin as a labeling substance, addition of biotin-labeled antibodies is preferably followed by addition of avidin bound to an enzyme such as alkaline phosphatase. For the binding of labeling substance with an anti-DSG3 antibody, known methods such as the glutaraldehyde method, maleimide method, pyridyl disulfide method, or periodic acid method can be used.
Specifically, an anti-DSG3 antibody is immobilized onto a support by addition of a solution containing the anti-DSG3 antibody to the support such as a plate. After the plate is washed, it is blocked with, for example, bovine serum albumin (BSA), gelatin, albumin, or such to avoid non-specific protein binding. After the plate is washed again, incubation is carried out by adding a test sample to the plate. After incubation, the plate is washed, and the labeled anti-DSG3 antibody is added. After appropriate incubation, the plate is washed, and then the labeled anti-DSG3 antibody that remains on the plate can be detected. Detection can be performed by methods known to those skilled in the art, and for example, when detecting an anti-DSG3 antibody labeled with a radioactive substance, the labeled anti-DSG3 antibody can be detected by liquid scintillation or an RIA method. When detecting an enzyme-labeled anti-DSG3 antibody, addition of substrate to the labeled anti-DSG3 antibody can be followed by detecting the substrate's enzymatic change, such as color development, using a spectrophotometer. Specific examples of a substrate include 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 1,2-phenylenediamine (ortho-phenylenediamine), and 3,3′,5,5′-tetramethylbenzidine (TMB). When the substrate is a fluorescence emitting substance, enzymatic change of the substrate can be detected using a spectrofluorometer.
In the present invention, a particularly preferred embodiment of the method for detecting the DSG3 protein is, for example, a method that uses a biotin-labeled anti-DSG3 antibody and avidin. Specifically, addition of a solution containing an anti-DSG3 antibody to a support such as a plate enables immobilization of the anti-DSG3 antibody to the plate. After the plate is washed, it is blocked with, for example, BSA to avoid non-specific protein binding. The plate is washed again, and then a test sample is added to the plate. After incubation, the plate is washed, and a biotin-labeled anti-DSG3 antibody is added to the plate. After suitable incubation, the plate is washed, and avidin bound to an enzyme such as alkaline phosphatase or peroxidase is added to the plate. After incubation, the plate is washed, and the DSG3 protein can be detected after addition of a substrate for the avidin-conjugated enzyme, using the substrate's enzymatic change or such as an indicator.
In the present invention, another embodiment of the method for detecting the DSG3 protein includes a method that uses one or more types of primary antibodies that specifically recognize the DSG3 protein, and one or more types of secondary antibodies that specifically recognize the primary antibodies.
For example, after immobilizing an anti-DSG3 antibody to a support such as a plate, the plate is blocked with bovine serum albumin (BSA), gelatin, albumin, or such to prevent non-specific binding of proteins to the support. Then, after adding a test sample to the plate, it is incubated to allow the DSG3 protein to bind to the anti-DSG3 antibody bound to the plate. Thereafter, the plate is washed with a washing solution so that the DSG3 proteins bound to the support by non-specific binding, and not by specific binding to the anti-DSG3 antibody, are removed from the plate. A different type of anti-DSG3 antibody from the antibody bound to the support binds to the DSG3 protein, and then a secondary antibody that can only bind to the anti-DSG3 antibody that binds to the DSG3 protein but not to the support, is made to react with the DSG3-protein/anti-DSG3-antibody complexes. An example is a method that detects the DSG3 protein in a test sample by qualitatively or quantitatively detecting the secondary antibody that binds as a result of the above-mentioned operation. In this case, the secondary antibody can be more suitably labeled with a labeling substance.
In the present invention, another embodiment of the methods for detecting the DSG3 protein is, for example, a detection method that uses aggregation reaction. In this method, the DSG3 protein can be detected using a carrier onto which an anti-DSG3 antibody is adsorbed. Any carrier may be used for adsorbing the antibody, so long as it is insoluble and stable, and does not cause non-specific reactions. For example, latex particles, bentonite, collodion, kaolin, or immobilized sheep erythrocytes can be used, but the use of latex particles is preferred. Latex particles that can be used are, for example, polystyrene latex particles, styrene-butadiene copolymer latex particles, or polyvinyl toluene latex particles, but the use of polystyrene latex particles is preferred. Sensitized particles are mixed with a sample, and this is stirred for a given period of time. Since the degree of particle aggregation becomes larger as the concentration of DSG3 protein in the sample increases, the DSG3 protein can be detected by assessing the degree of aggregation with the naked eye. Furthermore, the DSG3 protein can also be detected by measuring the increase in turbidity caused by aggregation using a spectrophotometer or such.
In the present invention, another embodiment of the methods for detecting the DSG3 protein includes, for example, a method that uses a biosensor utilizing the surface plasmon resonance phenomenon. The use of a biosensor utilizing the surface plasmon resonance phenomenon enables real-time observation of protein-protein interactions as surface plasmon resonance signals without the need of protein labeling. For example, by using a biosensor such as BIAcore (Biacore), binding between the DSG3 protein and an anti-DSG3 antibody can be detected. Specifically, a test sample is contacted with a sensor chip onto which an anti-DSG3 antibody is immobilized, and the DSG3 protein that binds to the anti-DSG3 antibody can be detected as a change in resonance signals.
Anti-DSG3 antibodies can be labeled by general methods using, in addition to the labels mentioned above, positron-emitting nuclides such as 18F, 55Co, 64Cu, 66Ga, 68Ga, 76Br, 89Zr, and 124I (Acta. Oncol. 32, 825-830, 1993). By using PET (positron emission tomography scanner), which is an instrument for non-invasively obtaining data on the in vivo behavior of drugs, after administering an anti-DSG3 antibody labeled with an above-mentioned positron-emitting nuclide to humans or animals, radiation emitted by the radioactive nuclide is measured from outside the body and then converted into a quantitative image by computed tomography methods. By using PET as described above, antigenic molecules that are highly expressed in a particular cancer can be detected without collecting samples from patients. In addition to the above-mentioned nuclides, anti-DSG3 antibodies can be radiolabeled with short-lived RI using positron-emitting nuclides such as 11C, 13N, 15O, 18F, and 45Ti.
At present, the use of a medical cyclotron for production of short-lived nuclides using the above-mentioned nuclides, techniques for producing short-lived RI-labeled compounds, and such, are currently under research and development, and anti-DSG3 antibodies can be labeled using such techniques. By administering an anti-DSG3 antibody to patients after labeling it with the above-mentioned positron-emitting nuclides, the labeled anti-DSG3 antibody that recognizes the DSG3 protein present in the living body gathers at primary foci and metastatic foci according to the specificity of the anti-DSG3 antibody at each site of the pathological tissue. Therefore, the presence of primary foci and metastatic foci can be diagnosed by detecting their radioactivity. For use in such diagnostic purpose, emission activity values of 25-4000 keV gamma particles or positrons can be used appropriately. Furthermore, therapeutic effects can be expected by selecting a suitable nuclide and administering it in large quantities. In this case, emission of 70-700 keV gamma particles or positrons can be suitably used.
In another embodiment of the methods of the present invention, the expression of DSG3 mRNA is detected. In the present invention, detection includes quantitative and qualitative detections. Examples of qualitative detection include simple measurement for the presence or absence of DSG3 mRNA, measurement to see whether or not the DSG3 mRNA is present above a certain amount, and measurement that compares the amount of DSG3 mRNA to that of other samples (for example, a control sample). On the other hand, quantitative detection includes, for example, measurement of the DSG3 mRNA concentration and measurement of the amount of DSG3 mRNA.
Test samples are not particularly limited so long as they are samples that may contain DSG3 mRNA, and are preferably samples collected from the body of organisms such as mammals, and more preferably samples collected from humans. Specific examples of the test samples include blood, interstitial fluid, plasma, extravascular fluid, cerebrospinal fluid, synovial fluid, pleural fluid, serum, lymphatic fluid, saliva, and urine, but the test samples are preferably blood, serum, or plasma. Test samples of the present invention also include samples obtained from test samples, such as cell culture solutions and specimens of immobilized tissues or cells collected from the body of an organism.
The cancers that are diagnosed are not particularly limited and may be any cancer, and specific examples include lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, and uterine cancer. Lung cancer is preferable and non-small cell lung cancer is particularly preferable.
Subjects in the present invention may be animal species that genetically carry a DSG3 protein, and many non-human mammals such as monkeys, cattle, sheep, mice, dogs, cats, and hamsters are known as such animal species. Subjects that are suitably used are, in particular, humans, but are not limited thereto.
Specific embodiments of the detection method are described below, but the methods of the present invention are not limited to those methods. First, a sample is prepared from a subject. Next, DSG3 mRNAs included in the sample are detected. In the present invention, it is also acceptable to detect cDNAs synthesized from mRNAs. In the present invention, when the DSG3 mRNA or DSG3-encoding cDNA is detected in a test sample, if a greater amount of DSG3 mRNA or DSG3-encoding cDNA is detected in the test sample than in a negative control or a healthy individual, it can be determined that the subject has cancer or has a high risk of being affected by cancer in the future.
Examples of such methods include methods known to those skilled in the art such as the Northern blotting method, RT-PCR method, and DNA array method.
The detection methods of the present invention described above can be automated using various automatic testing devices, and large quantities of sample can be examined at a time.
A further objective of the present invention is to provide diagnostic agents or kits for detecting the DSG3 protein in a test sample for cancer diagnosis. The diagnostic agents or kits contain at least an anti-DSG3 antibody. When the diagnostic agents or kits are based on an EIA method such as the ELISA method, a carrier for immobilizing the antibody may be included, or a carrier may be bound to the antibody in advance. If the diagnostic agents or kits are based on an aggregation method that uses a carrier such as latex, they may include an antibody-adsorbed carrier.
A further objective of the present invention is to provide diagnostic agents or kits for detecting DSG3 mRNA or DSG3-encoding cDNA in a test sample for cancer diagnosis. The diagnostic agents or kits contain at least a DSG3-encoding DNA (a DNA consisting of the nucleotide sequence of SEQ ID NO: 39) or an oligonucleotide comprising at least 15 nucleotides that are complementary to its complementary strand.
Herein, the term “complementary strand” refers to the other strand with respect to one of the strands of a double-stranded nucleic acid consisting of A:T (U in the case of RNA) and G:C base pairs. In addition, “complementary” refers not only to cases of completely complementary sequences within a region of at least 15 consecutive nucleotides, but also to cases of at least 70%, preferably at least 80%, more preferably 90%, and even more preferably 95% homology or higher in a nucleotide sequence. Homology may be determined using an algorithm described herein.
The oligonucleotides of the present invention can be used as probes or primers for detecting or amplifying DSG3-endcoding DNA, and probes or primers for detecting the expression of these DNAs. Furthermore, the oligonucleotides of the present invention can be used in the form of a DNA array substrate.
When such oligonucleotides are used as primers, their lengths are normally 15 by to 100 bp, and preferably 17 by to 30 bp. The primers are not particularly limited as long as at least a portion of the DSG3-encoding DNA, or a complementary strand thereof, can be amplified. Furthermore, when they are used as primers, their 3′-end regions can be made to be complementary, and restriction enzyme recognition sequences or tags can be added to their 5′ ends.
When using these oligonucleotides as probes, the probes are not particularly limited, as long as they specifically hybridize to at least a portion of the DSG3-encoding DNA, or to a complementary strand thereof. The probes may be synthetic oligonucleotides, and are normally at least 15 by or longer.
When the oligonucleotides of the present invention are used as probes, it is preferable to use the labeled ones. Examples of labeling methods include labeling methods that use T4 polynucleotide kinase to phosphorylate the 5′ ends of oligonucleotides with ³²P, and methods that incorporate a substrate nucleotide labeled with an isotope such as ³²P, a fluorescent dye, biotin or the like, by using a DNA polymerase such as Klenow enzyme, and a random hexamer oligonucleotide or such as a primer (random priming methods and so on).
The oligonucleotides of the present invention can be produced using, for example, a commercially available oligonucleotide synthesizer. The probes may be produced as double-stranded DNA fragments obtained by restriction enzyme treatment or the like.
In the diagnostic agents or kits mentioned above, sterilized water, physiological saline, vegetable oil, surfactants, lipids, solubilizers, buffers, protein stabilizers (BSA, gelatin, or such), preservatives, blocking solutions, reaction solution, reaction-stopping solution, reagents for treating samples, and such may be combined as necessary, in addition to the oligonucleotides and antibodies, which are the active ingredients.
The diagnostic methods of the present invention can be performed both in vitro and in vivo, but preferably preformed in vitro.
In a preferred embodiment of the present invention, an example of the methods for diagnosing cancer is a method comprising the following steps of:
(a) providing a sample collected from a subject; and
(b) detecting for DSG3 proteins contained in the sample of (a).
Moreover, in a preferred embodiment of the present invention, an example of the methods for diagnosing cancer is a method comprising the following steps:
(a) providing a sample collected from a subject; and
(b) detecting for DSG3 genes contained in the sample of (a).

Production of Anti-DSG3 Antibodies

The anti-DSG3 antibodies used in the present invention may be derived from any origin, and may be of any type (monoclonal or polyclonal), and in any form, as long as they specifically bind to a DSG3 protein. Specifically, known antibodies such as animal antibodies (for example, mouse antibodies, rat antibodies, and camel antibodies), human antibodies, chimeric antibodies, and humanized antibodies can be used. The antibodies may be polyclonal antibodies, and are preferably monoclonal antibodies.
Anti-DSG3 antibodies to be used in the present invention can be obtained as polyclonal or monoclonal antibodies using known techniques. In particular, monoclonal antibodies derived from a mammal are preferable as the anti-DSG3 antibody to be used in the present invention. Examples of monoclonal antibodies derived from a mammal include antibodies produced by hybridoma, and antibodies produced by a host transformed by genetic engineering techniques with an expression vector containing an antibody gene.
A monoclonal antibody-producing hybridoma can be prepared essentially using known techniques as follows. Specifically, immunization is performed using the DSG3 protein as a sensitizing antigen according to a general immunization method to obtain immunocytes, which are then fused to known parent cells by a general cell fusion method. Then, hybridoma that produce an anti-DSG3 antibody can be selected by screening for monoclonal antibody-producing cells using a general screening method.
Specifically, monoclonal antibodies are prepared as follows. First, the DSG3 gene having the nucleotide sequence disclosed in GenBank Accession No. NM_—001944 (SEQ ID NO: 39) is expressed, and the DSG3 protein is obtained and used as the sensitizing antigen for obtaining the antibody. Specifically, the gene sequence encoding DSG3 is inserted into a known expression vector, and it is used to transform an appropriate host cell. Then, the human DSG3 protein of interest can be purified by a known method from the host cell or its culture supernatant. Alternatively, a purified naturally occurring DSG3 protein can be used in the same manner.
The purified DSG3 protein can be used as a sensitizing antigen for immunization of mammals. A partial peptide of DSG3 can also be used as the sensitizing antigen. In that case, the partial peptide can be obtained from the amino acid sequence of human DSG3 by chemical synthesis, they can also be obtained by incorporating a part of the DSG3 gene into an expression vector and expressing it. Alternatively, the partial peptide can be obtained by degrading the DSG3 protein with a protease, and there are no limitations on the region or size of the partial DSG3 peptides used.
The mammal to be immunized with the sensitizing antigen is not particularly limited, but is preferably selected in consideration of the compatibility with parent cells to be used for cell fusion. For example, rodents such as mice, rats, and hamsters, rabbits, or monkeys are generally used.
The above-described animals can be immunized with a sensitizing antigen according to a known method. For example, as a general method, immunization can be performed by injecting a mammal intraperitoneally or subcutaneously with a sensitizing antigen. Specifically, the sensitizing antigen is diluted at an appropriate dilution with PBS (Phosphate-Buffered Saline), physiological saline, or the like; mixed with a standard adjuvant such as a Freund's complete adjuvant as desired; emulsified; and then administered to mammals several times every four to 21 days. Furthermore, an appropriate carrier can be used when the sensitizing antigen is used for immunization. Particularly when a partial peptide with a small molecular weight is used as a sensitizing antigen, the sensitizing antigen peptide is desirably bound to a carrier protein such as albumin or keyhole limpet hemocyanin, and then used for immunization.
Mammals are immunized as described, and when an increase in the amount of desired antibody in the serum is confirmed, immunocytes are collected from the mammals and subjected to cell fusion. A particularly preferred immunocyte is a splenocyte.
A mammalian myeloma cell is used as a cell to be fused with the above-mentioned immunocyte. A variety of known cell lines can be suitably used as the myeloma cell, and examples include: P3 (P3x63Ag8.653) (J. Immunol. (1979) 123, 1548-1550); P3x63Ag8U.1 (Current Topics in Microbiology and Immunology (1978) 81, 1-7); NS-1 (Kohler. G. and Milstein, C. Eur. J. Immunol. (1976) 6, 511-519); MPC-11 (Margulies. D. H. et al., Cell (1976) 8, 405-415); SP2/0 (Shulman, M. et al., Nature (1978) 276, 269-270); FO (de St. Groth, S. F. et al., J. Immunol. Methods (1980) 35, 1-21); 5194 (Trowbridge, I. S. J. Exp. Med. (1978) 148, 313-323); and 8210 (Galfre, G et al., Nature (1979) 277, 131-133).
Cell fusion of the above-mentioned immunocytes with myeloma cells is essentially performed according to a known method, for example, the method of Kohler and Milstein et al. (Kohler. G and Milstein, C., Methods Enzymol. (1981) 73, 3-46).
More specifically, the above-mentioned cell fusion can be performed in a standard nutritional culture medium in the presence of, for example, a cell-fusion accelerator. A cell-fusion accelerator is, for example, polyethylene glycol (PEG), Sendai virus (HVJ), or the like. If desired, an auxiliary agent such as dimethylsulfoxide can be added to further enhance fusion efficiency.
The ratio of immunocytes to myeloma cells used can be established at one's discretion. For example, the number of immunocytes is preferably set to one to ten times of that of myeloma cells. As a medium to be used for the above-mentioned cell fusion, for example, RPMI1640 medium and MEM medium, which are appropriate for the growth of the above-mentioned myeloma cell line, or other standard media that are used for this type of cell culture can be used. Moreover, a serum supplement solution such as fetal calf serum (FCS) can be suitably added and used in combination.
Cell fusion is performed by thoroughly mixing predetermined amounts of the above-mentioned immunocytes and myeloma cells in the above-mentioned medium, adding and mixing with a PEG solution of generally 30 to 60% (w/v) concentration that has been pre-heated to approximately 37° C. and has, for example, an average molecular weight of approximately 1000 to 6000, so as to form the desired fused cells (hybridomas). Subsequently, the agent for cell fusion or the like which is unfavorable for the growth of hybridomas can be removed by successively adding an appropriate medium such as those listed above, removing the supernatant by centrifugation, and repeating these steps.
Hybridomas obtained in this manner can be selected by culturing the hybridomas in a standard selection medium such as HAT medium (a medium containing hypoxanthine aminopterin, and thymidine). The above-mentioned HAT medium can be used to continue the culturing for a sufficient period of time to kill the cells other than the hybridoma of interest (non-fused cells) (typically, a sufficient period of time is several days to several weeks). Subsequently, hybridomas that produce the antibody of interest can be screened and monocloned by carrying out a standard limiting dilution method.
Alternatively, a DSG3-recognizing antibody can be prepared using the method described in International Patent Publication No. WO 03/104453.
Screening and monocloning an antibody of interest can be suitably performed by a screening method based on known antigen-antibody reaction. For example, the antigen is bound to a carrier such as polystyrene beads or the like, or a commercially available 96-well microtiter plate, followed by reaction with the culture supernatant of the hybridomas. After the carrier is washed, it is reacted with an enzyme-labeled secondary antibody or the like to determine whether or not the antibody of interest that reacts with the sensitizing antigen is contained in the culture supernatant. Hybridomas producing the desired antibodies that have a binding ability to the antigen can be cloned by the limiting dilution method or the like. Antigens used for immunization as well as an operably similar DSG3 protein can be used suitably in this case.
In addition to the above-mentioned method where hybridoma are obtained by immunizing non-human animals with the antigen, desired human antibodies having the activity to bind to a DSG3 protein can also be obtained by sensitizing human lymphocytes with the DSG3 protein in vitro, and fusing the sensitized lymphocytes with human-derived myeloma cells that have infinite division potential (see Japanese Patent Publication Kokoku Publication No. (JP-B) H01-59878 (examined, approved Japanese patent application published for opposition)). Alternatively, desired human antibodies can also be obtained by administering a DSG3 protein that serves as an antigen to a transgenic animal having a complete human antibody gene repertoire to obtain anti-DSG3 antibody-producing cells, immortalizing these cells, and isolating human antibodies against the DSG3 protein from the immortalized cells (see International Patent Publication Nos. WO 94/25585, WO 93/12227, WO 92/03918, and WO 94/02602).
The monoclonal antibody-producing hybridoma produced in this manner can be passaged and cultured in a standard medium, or can be stored for a long period in liquid nitrogen.
To obtain monoclonal antibodies from hybridoma, a method for obtaining monoclonal antibodies as a culture supernatant after culturing the hybridoma according to a standard method, a method for obtaining monoclonal antibodies as an ascites after administering and growing the hybridoma in a compatible mammal, or the like can be suitably carried out. The former method is suitable for obtaining highly purified antibodies, while the latter method is suitable for mass production of antibodies.
In the present invention, a recombinant antibody is produced from recombinant cells generated by genetic engineering techniques that involve cloning the antibody gene from hybridoma, incorporating the gene into an appropriate vector, and introducing the vector into a host, and can be used as a monoclonal antibody (see for example, Vandamme, A. M. et al., Eur. J. Biochem. (1990) 192, 767-775). Specifically, the gene can be obtained from hybridoma cells producing an anti-DSG3 antibody by isolating mRNA that encodes the variable region (V region) of the anti-DSG3 antibody. That is, total RNA can be prepared from the hybridoma cells by a known method such as the guanidine ultracentrifugation method (Chirgwin, J. M. et al., Biochemistry (1979) 18, 5294-5299) or AGPC method (Chomczynski, P. et al., Anal. Biochem. (1987) 162, 156-159), and then, the mRNA of interest can be prepared using an mRNA purification kit (GE Healthcare Bio-Sciences) or the like. In addition, mRNA can also be directly prepared from hybridoma using QuickPrep mRNA Purification Kit (GE Healthcare Bio-Sciences).
cDNA of the antibody V region can be synthesized from the obtained mRNA using reverse transcriptase. cDNA can be synthesized using AMV Reverse Transcriptase First-strand cDNA Synthesis Kit (SEIKAGAKU CORPORATION) or the like. To synthesize and amplify cDNA, for example, 5′-Ampli FINDER RACE Kit (Clontech) and the 5′-RACE method using PCR (Frohman, M. A. et al., Proc. Natl. Acad. Sci. USA (1988) 85, 8998-9002; Belyaysky, A. et al., Nucleic Acids Res. (1989) 17, 2919-2932) can also be used favorably, and in the process of such cDNA synthesis, appropriate restriction enzyme sites, which will be described later, can be introduced into both ends of the cDNA.
The cDNA fragment of interest is purified from the obtained PCR product, and then ligated to a vector DNA. The recombinant vector is prepared in this manner and introduced into Escherichia coli or the like, and after colonies are selected, the desired recombinant vector can be prepared from the E. coli that formed the colonies. Whether or not the recombinant vector has the cDNA nucleotide sequence of interest can be confirmed by a known method, such as the dideoxynucleotide chain termination method. Once cDNA encoding the V region of the anti-DSG3 antibody of interest is obtained, this cDNA is digested by enzymes that recognize the restriction enzyme sites inserted to both ends of this cDNA. The cDNA encoding the anti-DSG3 antibody V region, which has been digested as described above, is incorporated by ligation into an expression vector that contains a desired antibody constant region (C region), so that the DNA encoding this C region can be fused in frame with the cDNA when digested with the same combination of enzymes.
A preferred method for producing the anti-DSG3 antibody used in the present invention is a method that incorporates the antibody gene into an expression vector so that the gene is expressed under the regulation of an expression control region, for example, an enhancer or a promoter. Next, by suitably transforming a host cell with this expression vector, recombinant cells that express the anti-DSG3 antibody-encoding DNA can be obtained.
An antibody gene can be expressed by incorporating a DNA encoding the antibody heavy chain (H-chain) and a DNA encoding the antibody light chain (L-chain) separately into expression vectors, and then simultaneously transforming a host cell with the vectors; or by incorporating a DNA encoding the H-chain and the L-chain into a single expression vector, and then transforming a host cell with the vector (see International Patent Publication No. WO 94/11523).
Appropriate combinations of suitable hosts and expression vectors can be used for isolating an antibody gene and introducing the gene into an appropriate host to produce the antibody. When using eukaryotic cells as a host, animal cells, plant cells, and fungal cells can be used. Known animal cells include (1) mammalian cells such as CHO, COS, myeloma, baby hamster kidney (BHK), HeLa, and Vero cells; (2) amphibian cells such as Xenopus oocytes; and (3) insect cells such as sf9, sf21, and Tn5. Known plant cells include cells derived from the Nicotiana genus such as Nicotiana tabacum, from which callus can be cultured. Known fungal cells include yeasts such as the Saccharomyces genus, for example, Saccharomyces cerevisiae, and filamentous fungi such as the Aspergillus genus, for example, Aspergillus niger. Production systems that utilize bacterial cells can be suitably used when using prokaryotic cells. Known bacterial cells include E. coli and Bacillus subtilis. By introducing expression vectors comprising the antibody genes of interest into these cells by transformation, and then culturing the transformed cells in vitro, the desired antibodies can be obtained from the transformed cell culture.
In addition to the above host cells, transgenic animals can also be used suitably to produce a recombinant antibody. For example, the antibody gene can be inserted in frame into a gene that encodes a protein inherently produced in milk, for example, goat β-casein to construct a fused gene. A DNA fragment containing the fused gene, which has been inserted with the antibody gene, is injected into a goat embryo, and then this injected embryo is introduced into a female goat. Desired antibodies can be obtained from milk produced by the transgenic goat born from the goat that received the embryo or progeny thereof. To increase the volume of milk containing the desired antibody produced by the transgenic goat, hormones can be used on the transgenic goat as necessary (Ebert, K. M. et al., Bio/Technology (1994) 12, 699-702).
Animal-derived antibody C regions can be used for the C regions of a recombinant antibody of the present invention. For example, Cγ1, Cγ2a, Cγ2b, Cγ3, Cμ, Cδ, Cα1, Cα2, and Cε can be used for the mouse antibody H-chain C-region, and Cκ and Cλ can be used for the L-chain C-region. In addition to mouse antibodies, antibodies of animals such as rats, rabbits, goat, sheep, camels, and monkeys can be used as animal antibodies. Their sequences are known. Furthermore, the C region can be modified to improve the stability of the antibodies or their production.
In the present invention, genetically recombinant antibodies that are artificially modified for the purpose of reducing xenoantigenicity against humans, or the like can be used. Examples of such include chimeric antibodies and humanized antibodies. These modified antibodies can be produced using known methods. A chimeric antibody is an antibody comprising the antibody heavy chain and light chain variable regions of a nonhuman mammal such as a mouse, and the antibody heavy chain and light chain constant regions of a human. The DNA encoding a mouse antibody variable region is ligated to the DNA encoding a human antibody constant region, and this is incorporated into an expression vector to produce a recombinant vector expressing the DNA. The recombinant cells that have been transformed with the vector are cultured, and the incorporated DNA is expressed to obtain the chimeric antibody produced in the culture.
A human antibody C region can be used for the C regions of the chimeric antibody and humanized antibody, and for example, Cγ1, Cγ2, Cγ3, Cγ4, Cμ, Cδ, Cα1, Cα2, and Cε can be used for the H chain, and Cκ and Cλ can be used for the L-chain. Their sequences are known. Furthermore, the human antibody C region can be modified to improve the stability of the antibody or its production.
A chimeric antibody consists of the V region of an antibody derived from a non-human animal, and a C region derived from a human antibody. On the other hand, a humanized antibody consists of the complementarity determining region (CDR) of an antibody derived from a non-human animal, and the framework region (FR) and C region derived from a human antibody. Since the antigenicity of a humanized antibody in human body is reduced, a humanized antibody is useful as an active ingredient for therapeutic agents of the present invention.
A humanized antibody, which is also called a reshaped human antibody, is obtained by transplanting, in place of a human antibody CDR, the CDR of a non-human animal antibody such as a mouse antibody, and common genetic recombination techniques for such preparation are also known. Specifically, a DNA sequence is designed for ligating a mouse antibody CDR in frame with a human antibody FR, and is synthesized by PCR using several oligonucleotides designed to contain overlapping portions at their ends as primers. An integration vector can be produced by inserting the DNA obtained as described above and a DNA that encodes a human antibody C region into an expression vector so that they will ligate in frame. After incorporating this integration vector into a host to establish recombinant cells, the recombinant cells are cultured, and the DNA encoding the humanized antibody is expressed to produce the humanized antibody in the cell culture (see, European Patent Application No. EP 239,400, and International Patent Application No. WO 96/02576).
By qualitatively or quantitatively measuring and evaluating the activity of the humanized antibody produced as described above to bind to antigens, human antibody FRs that would make the CDRs form a favorable antigen-binding site when ligated through the CDRs can be suitably selected. As necessary, amino acids in an FR may be substituted such that the CDRs of a reshaped human antibody forms an appropriate antigen-binding site. The above-mentioned amino acid substitution can be introduced by appropriately using the PCR method used when fusing mouse CDR with human FR, and mutant FR sequences having the desired characteristics can be selected by measuring and evaluating the activity of the amino acid-substituted mutant antibody to bind to the antigen by the above-mentioned method (Sato, K. et al., Cancer Res. 1993, 53, 851-856).
Methods for obtaining human antibodies are also known. For example, desired human antibodies with antigen-binding activity can be obtained by sensitizing human lymphocytes with a desired antigen or cells expressing a desired antigen in vitro; and fusing the sensitized lymphocytes with human myeloma cells such as U266 (see JP-B H01-59878). Alternatively, a desired human antibody can be obtained by using a desired antigen to immunize a transgenic animal that comprises the entire repertoire of human antibody genes (see International Patent Application Nos. WO 93/12227, WO 92/03918, WO 94/02602, WO 94/25585, WO 96/34096, and WO 96/33735). Furthermore, techniques to obtain human antibodies by panning a human antibody library are also known. For example, the V region of a human antibody is expressed as a single chain antibody (scFv) on the phage surface using a phage display method, and phages that bind to the antigen can be selected. By analyzing the genes of selected phages, the DNA sequences encoding the V regions of human antibodies that bind to the antigen can be determined. After determining the DNA sequences of scFvs that bind to the antigen, the V region sequence is fused in frame with the desired human antibody C region sequence, and this is inserted into a suitable expression vector to produce an expression vector. This expression vector can be introduced into suitable expression cells such as those described above, and the human antibody-encoding gene can be expressed to obtain the human antibodies. Such methods are well known and one can refer to International Patent Application Nos. WO 92/01047, WO 92/20791, WO 93/06213, WO 93/11236, WO 93/19172, WO 95/01438, and WO 95/15388.
The antibody used in the present invention is not limited to bivalent antibodies represented by IgG, but includes monovalent antibodies and multivalent antibodies represented by IgM, so long as it binds to the DSG3 protein. The multivalent antibody of the present invention includes a multivalent antibody that has the same antigen binding sites, and a multivalent antibody that has partially or completely different antigen binding sites.
The antibody used in the present invention is not limited to the whole antibody molecule, but includes minibodies and modified products thereof, so long as they bind to the DSG3 protein.
A minibody comprises antibody fragments lacking a portion of a whole antibody (for example, whole IgG), and is not particularly limited so long as it has antigen-binding ability. There are no particular limitations on the antibody fragments of the present invention, so long as they are portions of a whole antibody, but they preferably contain a heavy chain variable region (VH) and/or a light chain variable region (VL). The amino acid sequence of VH or VL may have substitutions, deletions, additions, and/or insertions. Furthermore, so long as it has antigen-binding ability, part of VH and/or VL can be deleted. The variable region may be chimerized or humanized. Specific examples of the antibody fragments include Fab, Fab′, F(ab′)₂, and Fv. Specific examples of minibodies include Fab, Fab′, F(ab′)2, Fv, scFv (single chain Fv), diabody, and sc(Fv)2 (single chain (Fv)2). Multimers of these antibodies (for example, dimers, trimers, tetramers, and polymers) are also included in the minibodies of the present invention.
Antibody fragments can be produced by treating an antibody with an enzyme, such as papain or pepsin. Alternatively, genes encoding these antibody fragments can be constructed, introduced into expression vectors, and expressed in appropriate host cells (see, for example, Co, M. S. et al., J. Immunol. (1994) 152, 2968-2976; Better, M. and Horwitz, A. H., Methods in Enzymology (1989) 178, 476-496; Plueckthun, A. and Skerra, A., Methods in Enzymology (1989) 178, 476-496; Lamoyi, E., Methods in Enzymology (1989) 121, 652-663; Rousseaux, J. et al., Methods in Enzymology (1989) 121, 663-669; and Bird, R. E. et al., TIBTECH (1991) 9, 132-137).
A diabody refers to a bivalent antibody fragment constructed by gene fusion (Hollinger P. et al., Proc. Natl. Acad. Sci. USA 90: 6444-6448 (1993); EP 404,097; WO 93/11161; and such). A diabody is a dimer composed of two polypeptide chains, and generally, the polypeptide chains are individually linked by a linker of, for example, five residues or so, which is short enough to prevent binding between VL and VH in the same chain. VL and VH that are encoded by the same polypeptide chain have a short linker between them, and form a dimer because they cannot form a single chain variable region fragment. Therefore, diabodies have two antigen binding sites.
scFv can be obtained by ligating the H-chain V region and L-chain V region of an antibody. In this scFv, the H-chain V region and L-chain V region are ligated via a linker, preferably a peptide linker (Huston, J. S. et al., Proc. Natl. Acad. Sci. U.S.A., 1988, 85, 5879-5883). The H-chain V region and L-chain V region of the scFv and may be derived from any of the antibodies described herein. The peptide linker for ligating the V regions is not particularly limited, but for example, any single-chain peptide consisting of 3 to 25 residues or so, or a peptide linker described below can be used. PCR methods such as those described above can be used for ligating the V regions. An scFv-encoding DNA can be amplified by a PCR method using as a template, either a whole DNA or a partial DNA encoding a desired amino acid sequence selected from a DNA sequence encoding the H chain or the H-chain V region of the above-mentioned antibody, and a DNA sequence encoding the L chain or the L-chain V region of the above-mentioned antibody; and using a primer pair having sequences corresponding to the sequences of the two ends. Next, a DNA comprising the desired sequence can be obtained by performing a PCR reaction using the combination of a DNA encoding the peptide linker portion, and a primer pair having sequences designed so that both ends of the DNA will be ligated to the H chain and L chain. Once the scFv-encoding DNA is constructed, expression vectors containing the DNA, and recombinant cells transformed by these expression vectors can be obtained according to conventional methods. Furthermore, the scFvs can be obtained by culturing the resulting recombinant cells and expressing the scFv-encoding DNA.
sc(Fv)2 is a minibody prepared by ligating two VHs and two VLs with linkers or such to form a single chain (Hudson et al., J. Immunol. Methods 1999; 231: 177-189). sc(Fv)2 can be produced, for example, by joining scFvs with a linker.
Moreover, antibodies in which two VHs and two VLs are arranged in the order of VH, VL, VH, and VL ([VH]-linker-[VL]-linker-[VH]-linker-[VL]), starting from the N-terminal side of a single chain polypeptide, are preferred.
The order of the two VHs and the two VLs is not particularly limited to the above-mentioned arrangement, and they may be placed in any order. Examples include the following arrangements:
[VL]-linker-[VH]-linker-[VH]-linker-[VL]
[VH]-linker-[VL]-linker-[VL]-linker-[VH]
[VH]-linker-[VH]-linker-[VL]-linker-[VL]
[VL]-linker-[VL]-linker-[VH]-linker-[VH]
[VL]-linker-[VH]-linker-[VL]-linker-[VH]
Any arbitrary peptide linker can be introduced by genetic engineering, and synthetic linkers (see, for example, those disclosed in Protein Engineering, 9(3), 299-305, 1996) or such can be used as linkers for linking the antibody variable regions, but in the present invention, peptide linkers are preferable. The length of the peptide linkers is not particularly limited, and can be suitably selected by those skilled in the art according to the purpose; however, the length is generally 1 to 100 amino acids, preferably 3 to 50 amino acids, more preferably 5 to 30 amino acids, and particularly preferably 12 to 18 amino acids (for example, 15 amino acids).
Examples of the peptide linkers include:

Ser

Gly-Ser

Gly-Gly-Ser

Ser-Gly-Gly

Gly-Gly-Gly-Ser	(SEQ ID NO: 72)

Ser-Gly-Gly-Gly	(SEQ ID NO: 73)

Gly-Gly-Gly-Gly-Ser	(SEQ ID NO: 74)

Ser-Gly-Gly-Gly-Gly	(SEQ ID NO: 75)

Gly-Gly-Gly-Gly-Gly-Ser	(SEQ ID NO: 76)

Ser-Gly-Gly-Gly-Gly-Gly	(SEQ ID NO: 77)

Gly-Gly-Gly-Gly-Gly-Gly-Ser	(SEQ ID NO: 78)

Ser-Gly-Gly-Gly-Gly-Gly-Gly	(SEQ ID NO: 79)

(Gly-Gly-Gly-Gly-Ser	(SEQ ID NO: 74))n

(Ser-Gly-Gly-Gly-Gly	(SEQ ID NO: 75))n

in which n is an integer of 1 or larger. The length and sequence of the peptide linkers can be selected appropriately by those skilled in the art according to the purpose.

Therefore, a particularly preferred embodiment of sc(Fv)2 in the present invention is, for example, the following sc(Fv)2:
[VH]-peptide linker (15 amino acids)-[VL]-peptide linker (15 amino acids)-[VH]-peptide linker (15 amino acids)-[VL]
Synthetic chemical linkers (chemical crosslinking agents) which include crosslinking agents routinely used to crosslink peptides and are, for example, N-hydroxy succinimide (NHS), disuccinimidyl suberate (DSS), bis(sulfosuccinimidyl) suberate (BS³), dithiobis(succinimidyl propionate) (DSP), dithiobis(sulfosuccinimidyl propionate) (DTSSP), ethylene glycol bis(succinimidyl succinate) (EGS), ethylene glycol bis(sulfosuccinimidyl succinate) (sulfo-EGS), disuccinimidyl tartrate (DST), disulfosuccinimidyl tartrate (sulfo-DST), bis[2-(succinimidoxycarbonyloxy)ethyl]sulfone (BSOCOES), and bis[2-(sulfosuccinimidoxycarbonyloxy)ethyl]sulfone (sulfo-BSOCOES). These crosslinking agents are commercially available.
Usually, three linkers are required to link four antibody variable regions. The linkers to be used may all be of the same type or different types. In the present invention, a preferred minibody is a diabody or an sc(Fv)2. Such minibody can be obtained by treating an antibody with an enzyme, such as papain or pepsin, to generate antibody fragments, or by constructing DNAs that encode these antibody fragments, introducing them into expression vectors, and then expressing them in appropriate host cells (see, for example, Co, M. S. et al., J. Immunol. (1994) 152, 2968-2976; Better, M. and Horwitz, A. H., Methods Enzymol. (1989) 178, 476-496; Pluckthun, A. and Skerra, A., Methods Enzymol. (1989) 178, 497-515; Lamoyi, E., Methods Enzymol. (1986) 121, 652-663; Rousseaux, J. et al., Methods Enzymol. (1986) 121, 663-669; and Bird, R. E. and Walker, B. W., Trends Biotechnol. (1991) 9, 132-137).
The antibodies of the present invention can be exemplified by the antibodies of (1) to (62) below, but are not limited thereto. The antibodies of (1) to (62) include, for example, full-length antibodies, minibodies, animal antibodies, chimeric antibodies, humanized antibodies, and human antibodies:
(1) an antibody that comprises an H chain having the amino acid sequence of SEQ ID NO: 2 (sequence of the DF151 antibody H-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 4 (sequence of the DF151 antibody H chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 6 (sequence of the DF151 antibody H-chain CDR3) as CDR3;
(2) an antibody that comprises the H chain of (1) having the amino acid sequence of SEQ ID NO: 8 (sequence of the DF151 antibody CH) as CH(H-chain constant region);
(3) an antibody that comprises the H chain of (1) having the amino acid sequence of SEQ ID NO: 10 (sequence of the CH of the mouse-human chimeric DF151 antibody) as CH;
(4) an antibody that comprises an L chain having the amino acid sequence of SEQ ID NO: 12 (sequence of the DF151 antibody L-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 14 (sequence of the DF151 antibody L-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 16 (sequence of the DF151 antibody L-chain CDR3) as CDR3;
(5) an antibody that comprises the L chain of (4) having the amino acid sequence of SEQ ID NO: 18 (sequence of the DF151 antibody CL) as CL (L-chain constant region);
(6) an antibody that comprises the L chain of (4) having the amino acid sequence of SEQ ID NO: 20 (sequence of the mouse-human chimeric DF151 antibody CL) as CL;
(7) an antibody that comprises the H chain of (1) and the L chain of (4);
(8) an antibody that comprises the H chain of (2) and the L chain of (5);
(9) an antibody that comprises the H chain of (3) and the L chain of (6);
(10) an antibody that comprises an H chain having the amino acid sequence of SEQ ID NO: 22 (sequence of the DF364 antibody H-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 24 (sequence of the DF364 antibody H-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 26 (sequence of the DF364 antibody H-chain CDR3) as CDR3;
(11) an antibody that comprises the H chain of (10) having the amino acid sequence of SEQ ID NO: 28 (sequence of the DF364 antibody CH) as CH;
(12) an antibody that comprises the H chain of (10) having the amino acid sequence of SEQ ID NO: 10 (sequence of the mouse-human chimeric DF364 antibody CH) as CH;
(13) an antibody that comprises an L chain having the amino acid sequence of SEQ ID NO: 30 (sequence of the DF364 antibody L-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 32 (sequence of the DF364 antibody L-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 34 (sequence of the DF364 antibody L-chain CDR3) as CDR3;
(14) an antibody that comprises the L chain of (13) having the amino acid sequence of SEQ ID NO: 36 (sequence of the DF364 antibody CL) as CL;
(15) an antibody that comprises the L chain of (13) having the amino acid sequence of SEQ ID NO: 20 (sequence of the mouse-human chimeric DF364 antibody CL) as CL;
(16) an antibody that comprises the H chain of (10) and the L chain of (13);
(17) an antibody that comprises the H chain of (11) and the L chain of (14);
(18) an antibody that comprises the H chain of (12) and the L chain of (15);
(19) an antibody that comprises the H chain of (1) and the L chain of (13);
(20) an antibody that comprises the H chain of (2) and the L chain of (14);
(21) an antibody that comprises the H chain of (3) and the L chain of (15);
(22) an antibody that comprises the H chain of (10) and the L chain of (4);
(23) an antibody that comprises the H chain of (11) and the L chain of (5);
(24) an antibody that comprises the H chain of (12) and the L chain of (6);
(25) an antibody that comprises an H chain having the amino acid sequence of SEQ ID NO: 81 (sequence of the DF366 antibody H-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 83 (sequence of the DF366 antibody H-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 85 (sequence of the DF366 antibody H-chain CDR3) as CDR3;
(26) an antibody that comprises the H chain of (25) having the amino acid sequence of SEQ ID NO: 28 (sequence of the DF366 antibody CH) as CH;
(27) an antibody that comprises the H chain of (25) having the amino acid sequence of SEQ ID NO: 10 (sequence of the mouse-human chimeric DF366 antibody CH) as CH;
(28) an antibody that comprises an L chain having the amino acid sequence of SEQ ID NO: 87 (sequence of the DF366 antibody L-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 89 (sequence of the DF366 antibody L-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 91 (sequence of the DF366 antibody L-chain CDR3) as CDR3;
(29) an antibody that comprises the L chain of (28) having the amino acid sequence of SEQ ID NO: 36 (sequence of the CL of the DF366 antibody) as CL;
(30) an antibody that comprises the L chain of (28) having the amino acid sequence of SEQ ID NO: 20 (sequence of the CL of the mouse-human chimeric DF366 antibody) as CL;
(31) an antibody that comprises the H chain of (25) and the L chain of (28);
(32) an antibody that comprises the H chain of (26) and the L chain of (29);
(33) an antibody that comprises the H chain of (27) and the L chain of (30);
(34) an antibody that comprises the H chain of (1) and the L chain of (28);
(35) an antibody that comprises the H chain of (2) and the L chain of (29);
(36) an antibody that comprises the H chain of (3) and the L chain of (30);
(37) an antibody that comprises the H chain of (10) and the L chain of (28);
(38) an antibody that comprises the H chain of (11) and the L chain of (29);
(39) an antibody that comprises the H chain of (12) and the L chain of (30);
(40) an antibody that comprises the H chain of (25) and the L chain of (4);
(41) an antibody that comprises the H chain of (26) and the L chain of (5);
(42) an antibody that comprises the H chain of (27) and the L chain of (6);
(43) an antibody that comprises the H chain of (25) and the L chain of (13);
(44) an antibody that comprises the H chain of (26) and the L chain of (14);
(45) an antibody that comprises the H chain of (27) and the L chain of (15);
(46) an antibody that comprises the H chain of (1) having the amino acid sequence of SEQ ID NO: 108 (sequence of the CH of a mouse IgG2a antibody) as CH;
(47) an antibody that comprises the L chain of (4) having the amino acid sequence of SEQ ID NO: 112 (sequence of the CL of a mouse IgG2a antibody) as CL;
(48) an antibody that comprises the H chain of (10) having the amino acid sequence of SEQ ID NO: 108 (sequence of the CH of a mouse IgG2a antibody) as CH;
(49) an antibody that comprises the L chain of (13) having the amino acid sequence of SEQ ID NO: 112 (sequence of the CL of a mouse IgG2a antibody) as CL;
(50) an antibody that comprises the H chain of (25) having the amino acid sequence of SEQ ID NO: 108 (sequence of the CH of a mouse IgG2a antibody) as CH;
(51) an antibody that comprises the L chain of (28) having the amino acid sequence of SEQ ID NO: 112 (sequence of the CL of a mouse IgG2a antibody) as CL;
(52) an antibody that comprises the H chain of (46) and the L chain of (47);
(53) an antibody that comprises the H chain of (48) and the L chain of (49);
(54) an antibody that comprises the H chain of (50) and the L chain of (51);
(55) an antibody that comprises the H chain of (46) and the L chain of (49);
(56) an antibody that comprises the H chain of (48) and the L chain of (51);
(57) an antibody that comprises the H chain of (50) and the L chain of (47);
(58) an antibody that comprises the H chain of (46) and the L chain of (51);
(59) an antibody that comprises the H chain of (48) and the L chain of (47);
(60) an antibody that comprises the H chain of (50) and the L chain of (49);
(61) an antibody having one or more amino acid substitutions, deletions, additions, and/or insertions in the antibody of any one of (1) to (60) and having an activity equivalent to that of the antibody of any one of (1) to (60); and
(62) an antibody that binds to the same epitope as the DSG3 protein epitope to which the antibody of any one of (1) to (60) binds.
An example of VH in the above-mentioned “H chain having the amino acid sequence of SEQ ID NO: 2 (sequence of the DF151 antibody H-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 4 (sequence of the DF151 antibody H-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 6 (sequence of the DF151 antibody H-chain CDR3) as CDR3” of (1) includes a VH having the amino acid sequence of SEQ ID NO: 46 (sequence of the DF151 antibody VH).
An example of VL in the above-mentioned “L chain having the amino acid sequence of SEQ ID NO: 12 (sequence of the DF151 antibody L-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 14 (sequence of the DF151 antibody L-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 16 (sequence of the DF151 antibody L-chain CDR3) as CDR3” of (4) includes a VL having the amino acid sequence of SEQ ID NO: 48 (sequence of the DF151 antibody VL).
An example of VH in the above-mentioned “H chain having the amino acid sequence of SEQ ID NO: 22 (sequence of the DF364 antibody H-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 24 (sequence of the DF364 antibody H-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 26 (sequence of the DF364 antibody H-chain CDR3) as CDR3” of (10) includes a VH having the amino acid sequence of SEQ ID NO: 50 (sequence of the DF364 antibody VH).
An example of VL in the above-mentioned “L chain having the amino acid sequence of SEQ ID NO: 30 (sequence of the DF364 antibody L-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 32 (sequence of the DF364 antibody L-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 34 (sequence of the DF364 antibody L-chain CDR3) as CDR3” of (13) includes a VL having the amino acid sequence of SEQ ID NO: 52 (sequence of the DF364 antibody VL).
An example of VH in the above-mentioned “H chain having the amino acid sequence of SEQ ID NO: 81 (sequence of the DF366 antibody H-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 83 (sequence of the DF366 antibody H-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 85 (sequence of the DF366 antibody H-chain CDR3) as CDR3” of (25) includes a VH having the amino acid sequence of SEQ ID NO: 93 (sequence of the DF366 antibody VH).
An example of VL in the above-mentioned “L chain having the amino acid sequence of SEQ ID NO: 87 (sequence of the DF366 antibody L-chain CDR1) as CDR1, the amino acid sequence of SEQ ID NO: 89 (sequence of the DF366 antibody L-chain CDR2) as CDR2, and the amino acid sequence of SEQ ID NO: 91 (sequence of the DF366 antibody L-chain CDR3) as CDR3” of (28) includes a VL having the amino acid sequence of SEQ ID NO: 95 (sequence of the DF366 antibody VL).
A preferred embodiment of the above-mentioned antibody of (61) is an antibody in which CDR has not been modified. As an example, a preferred embodiment of “an antibody having one or more amino acid substitutions, deletions, additions, and/or insertions in the antibody of (1) and having an activity equivalent to that of the antibody of (1)” among the above-mentioned antibody of (61) is “an antibody having an activity equivalent to that of the antibody of (1) and having one or more amino acid substitutions, deletions, additions, and/or insertions in the antibody of (1), and also comprising an H chain having the amino acid sequence of SEQ ID NO: 2 as CDR1, the amino acid sequence of SEQ ID NO: 4 as CDR2, and the amino acid sequence of SEQ ID NO: 6 as CDR3”. Preferred embodiments of other antibodies included in the above-mentioned antibody of (61) can be expressed in a similar manner.
Methods of introducing mutations into polypeptides are well known to those skilled in the art as methods for preparing polypeptides that are functionally equivalent to a certain polypeptide. For example, those skilled in the art can prepare an antibody functionally equivalent to an antibody of the present invention by introducing appropriate mutations into the antibody using site-directed mutagenesis (Hashimoto-Gotoh, T. et al. (1995) Gene 152, 271-275; Zoller, M J, and Smith, M. (1983) Methods Enzymol. 100, 468-500; Kramer, W. et al. (1984) Nucleic Acids Res. 12, 9441-9456; Kramer W, and Fritz H J (1987) Methods. Enzymol. 154, 350-367; Kunkel, T A (1985) Proc. Natl. Acad. Sci. USA. 82, 488-492; Kunkel (1988) Methods Enzymol. 85, 2763-2766) and such. Amino acid mutations may also occur naturally. In this way, the antibodies of the present invention also comprise antibodies comprising amino acid sequences with one or more amino acid mutations in the amino acid sequences of the antibodies of the present invention, and which are functionally equivalent to the antibodies of the present invention. The number of amino acids that are mutated in such mutants is generally considered to be 50 amino acids or less, preferably 30 amino acids or less, and more preferably 10 amino acids or less (for example, 5 amino acids or less).
It is desirable that the amino acid residues are mutated into amino acids in which the properties of the amino acid side chains are conserved. Examples of amino acid side chain properties include: hydrophobic amino acids (A, I, L, M, F, P, W, Y, and V), hydrophilic amino acids (R, D, N, C, E, Q, G H, K, S, and T), amino acids comprising the following side chains: aliphatic side chains (G, A, V, L, I, and P); hydroxyl-containing side chains (S, T, and Y); sulfur-containing side chains (C and M); carboxylic acid- and amide-containing side chains (D, N, E, and Q); basic side chains (R, K, and H); or aromatic ring-containing side chains (H, F, Y, and W) (amino acids are represented by one-letter codes in parentheses).
Polypeptides comprising a modified amino acid sequence, in which one or more amino acid residues in a certain amino acid sequence is deleted, added, and/or substituted with other amino acids, are known to retain their original biological activities (Mark, D. F. et al., Proc. Natl. Acad. Sci. USA (1984) 81, 5662-5666; Zoller, M. J. & Smith, M. Nucleic Acids Research (1982) 10, 6487-6500; Wang, A. et al., Science 224, 1431-1433; Dalbadie-McFarland, G et al., Proc. Natl. Acad. Sci. USA (1982) 79, 6409-6413).
Antibodies that bind to the same epitope as the anti-DSG3 antibodies disclosed in the present invention are also provided. Such antibodies can be obtained, for example, by the following method.
To determine if a test antibody can compete for binding to the same epitope bound by the anti-DSG3 antibodies disclosed in the invention of this application, a cross-blocking assay, for example, a competitive ELISA assay can be performed. For example, in a competitive ELISA assay, DSG3 protein-coated wells of a microtiter plate are pre-incubated with or without a candidate competing antibody, and then a biotin-labeled anti-DSG3 antibody of the present invention is added. The amount of labeled anti-DSG3 antibody bound to the DSG3 protein in the wells can be measured using avidin-peroxidase conjugate and an appropriate substrate. The antibody can be labeled, for example, with a radioactive label or fluorescent label, or some other detectable and measurable label. The amount of labeled anti-DSG3 antibody bound to the DSG3 protein is indirectly correlated to the binding ability of the candidate competing antibody (test antibody) that competes for binding to the same epitope. That is, the greater the affinity of the test antibody for the same epitope, the lower the binding activity of the labeled anti-DSG3 antibody to the DSG3 protein-coated wells. A candidate competing antibody is considered to be an antibody that binds substantially to the same epitope or that competes for binding to the same epitope as an anti-DSG3 antibody of the present invention if the candidate competing antibody can block binding of the DSG3 antibody by at least 20%, preferably by at least 20% to 50%, and even more preferably, by at least 50%, as compared to the binding activity obtained in a control experiment performed in the absence of the candidate competing antibody.
Antibodies that bind to the same epitope as the anti-DSG3 antibodies include, for example, the above-mentioned antibody of (62), but are not limited thereto.
As described above, the above-mentioned antibodies of (1) to (62) include not only monovalent antibodies but also multivalent antibodies with two or more valencies. Multivalent antibodies of the present invention include multivalent antibodies whose antigen binding sites are all the same and multivalent antibodies whose antigen binding sites are partially or completely different.
The following antibodies are examples of multivalent antibodies that have different antigen binding sites, but the antibodies of the present invention are not limited thereto:
an antibody comprising at least two H chain and L chain pairs (hereinafter referred to as HL pairs) selected from the HL pairs of (7), (16), (19), (22), (31), (34), (37), (40), and (43);
an antibody comprising at least two HL pairs selected from the HL pairs of (8), (17), (20), (23), (32), (35), (38), (41), and (44);
an antibody comprising at least two HL pairs selected from the HL pairs of (9), (18), (21), (24), (33), (36), (39), (42), and (45); and
an antibody comprising at least two HL pairs selected from the HL pairs of (52) to (60).
Antibodies bound to various types of molecules such as polyethylene glycol (PEG) can also be used as modified antibodies. Moreover, chemotherapeutic agents, toxic peptides, or radioactive chemical substances can be bound to the antibodies. Such modified antibodies (hereinafter referred to as antibody conjugates) can be obtained by subjecting the obtained antibodies to chemical modification. Methods for modifying antibodies are already established in this field. Furthermore, as described below, such antibodies can also be obtained in the molecular form of a bispecific antibody designed using genetic engineering techniques to recognize not only DSG3 proteins, but also chemotherapeutic agents, toxic peptides, radioactive chemical compounds, or such. These antibodies are included in the “antibodies” of the present invention.
Low-molecular-weight chemotherapeutic agents such as azaribine, anastrozole, azacytidine, bleomycin, bortezomib, bryostatin-1, busulfan, camptothecin, 10-hydroxycamptothecin, carmustine, celebrex, chlorambucil, cisplatin, irinotecan, carboplatin, cladribine, cyclophosphamide, cytarabine, dacarbazine, docetaxel, dactinomycin, daunomycin glucuronide, daunorubicin, dexamethasone, diethylstilbestrol, doxorubicin, doxorubicin glucuronide, epirubicin, ethinyl estradiol, estramustine, etoposide, etoposide glucuronide, floxuridine, fludarabine, flutamide, fluorouracil, fluoxymesterone, gemcitabine, hydroxyprogesterone caproate, hydroxyurea, idarubicin, ifosfamide, leucovorin, lomustine, mechlorethamine, medroxyprogesterone acetate, megestrol acetate, melphalan, mercaptopurine, methotrexate, mitoxantrone, mithramycin, mitomycin, mitotane, phenylbutyrate, prednisone, procarbazine, paclitaxel, pentostatin, semustine streptozocin, tamoxifen, taxanes, taxol, testosterone propionate, thalidomide, thioguanine, thiotepa, teniposide, topotecan, uracil mustard, vinblastine, vinorelbine, and vincristine can be suitably used as chemotherapeutic agents (including prodrugs that are converted to such chemotherapeutic agents nonenzymatically or enzymatically in vivo) that are bound to anti-DSG3 antibodies to bring about cytotoxic activity. Moreover, toxic peptides such as ricin, abrin, ribonuclease, onconase, DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtheria toxin, Pseudomonas exotoxin, Pseudomonas endotoxin, L-asparaginase, and PEG L-Asparaginase can also be suitably used. In another embodiment, one or two or more of the low-molecular-weight chemotherapeutic agents can be suitably used in combination and one or two or more of the toxic peptides. For the bond between an anti-DSG3 antibody and the above-mentioned low-molecular-weight chemotherapeutic agent, a covalent bond or non-covalent bond can be suitably selected, and methods for preparing chemotherapeutic agent-bound antibodies are known.
Furthermore, for binding with proteinaceous pharmaceutical agents or toxins, gene recombination techniques can be used to construct a recombinant vector in which a DNA encoding the above-mentioned toxic peptide and a DNA encoding an anti-DSG3 antibody are fused in frame and inserted into an expression vector. This vector is introduced into suitable host cells, and transformed cells are obtained and cultured. Recombinant proteins can be prepared by expressing the incorporated DNA.
Furthermore, the antibody used in the present invention may be a bispecific antibody. The bispecific antibody may have antigen-binding sites that recognize different epitopes on a DSG3 molecule. Alternatively, one antigen-binding site may recognize DSG3 and the other antigen-binding site may recognize a cytotoxic substance such as a chemotherapeutic agent, toxic peptide, or radioactive chemical substance. This enables the cytotoxic substance to directly act on cells expressing DSG3, thereby specifically damaging tumor cells and suppressing tumor cell proliferation. Alternatively, one may prepare a bispecific antibody in which the other antigen-binding site recognizes an antigen that is similar to but different from DSG3, and specifically expressed on the surface of the target cancer cells. Bispecific antibodies can be produced by linking the HL pairs from two types of antibodies, or by fusing hybridomas producing different monoclonal antibodies to prepare bispecific antibody-producing fused cells. Bispecific antibodies can also be prepared by genetic engineering techniques.
Antibody genes constructed described above can be obtained through expression by known methods. In the case of mammalian cells, the antibody genes can be expressed by operably linking an effective, commonly used promoter, the antibody gene to be expressed, and a polyA signal on its 3′ downstream side. An example of the promoter/enhancer is human cytomegalovirus immediate early promoter/enhancer.
Examples of other promoters/enhancers that can be used for expression of an antibody to be used in the present invention include viral promoters/enhancers from retrovirus, polyoma virus, adenovirus, or simian virus 40 (SV40), and mammalian cell-derived promoters/enhancers such as human elongation factor 1α (HEF1α).
When an SV40 promoter/enhancer is used, gene expression can be readily carried out by the method of Mulligan et al. (Nature (1979) 277, 108), and when an HEF1α promoter/enhancer is used, gene expression can be readily carried out by the method of Mizushima et al. (Nucleic Acids Res. (1990) 18, 5322).
In the case of E. coli, an effective, commonly used promoter, a signal sequence for antibody secretion, and the antibody gene to be expressed are functionally linked to express the gene. Examples of a promoter include the lacZ promoter and the araB promoter. When the lacZ promoter is used, the gene can be expressed by the method of Ward et al. (Nature (1098) 341, 544-546; FASEB J. (1992) 6, 2422-2427), and when the araB promoter is used, the gene can be expressed by the method of Better et al. (Science (1988) 240, 1041-1043).
With regard to the signal sequence for antibody secretion, the pelB signal sequence (Lei, S. P. et al., J. Bacteriol. (1987) 169, 4379) may be used for production in the periplasm of E. coli. After the antibody produced in the periplasm is isolated, the antibody structure is refolded by using a protein denaturant like guanidine hydrochloride or urea so that the antibody will have the desired binding activity.
The replication origin inserted into the expression vector includes, for example, those derived from SV40, polyoma virus, adenovirus, or bovine papilloma virus (BPV). In order to amplify the gene copy number in the host cell system, the expression vector can have, for example, the aminoglycoside transferase (APH) gene, thymidine kinase (TK) gene, E. coli xanthine guanine phosphoribosyltransferase (Ecogpt) gene, or dihydrofolate reductase (dhfr) gene inserted as a selection marker.
Any expression system, for example, a eukaryotic cell system or a prokaryotic cell system, can be used to produce antibodies used in the present invention. Examples of eukaryotic cells include animal cells such as established mammalian cell system, insect cell system, and filamentous fungus cells and yeast cells. Examples of prokaryotic cells include bacterial cells such as E. coli cells. Antibodies used in the present invention are preferably expressed in mammalian cells such as CHO, COS, myeloma, BHK, Vero, or HeLa cells.
Next, the transformed host cell is then cultured in vitro or in vivo to induce production of the antibody of interest. The host cells are cultured according to known methods. For example, DMEM, MEM, RPMI 1640, or IMDM can be used as the culture medium. A serum supplement solution such as fetal calf serum (FCS) can also be used in combination.
Antibodies expressed and produced as described above can be purified by using a single known method or a suitable combination of known methods generally used for purifying proteins. Antibodies can be separated and purified by, for example, appropriately selecting and combining affinity columns such as protein A column, chromatography column, filtration, ultrafiltration, salt precipitation, dialysis, and such (Antibodies A Laboratory Manual. Ed Harlow, David Lane, Cold Spring Harbor Laboratory, 1988).
Known means can be used to measure the antigen-binding activity of the antibodies (Antibodies A Laboratory Manual. Ed Harlow, David Lane, Cold Spring Harbor Laboratory, 1988). For example, an enzyme linked immunosorbent assay (ELISA), an enzyme immunoassay (EIA), a radioimmunoassay (RIA), or a fluoroimmunoassay can be used.
The antibodies used in the present invention may be antibodies with a modified sugar chain. It is known that the cytotoxic activity of an antibody can be increased by modifying its sugar chain. Antibodies having modified sugar chains are, for example, antibodies with modified glycosylation (for example, WO 99/54342), antibodies deficient in fucose which is added to sugar chains (for example, WO 00/61739 and WO 02/31140), antibodies having a sugar chain with bisecting GlcNAc (for example, WO 02/79255).
The antibodies used in the present invention are preferably antibodies having cytotoxic activity.
In the present invention, the cytotoxic activity includes, for example, antibody-dependent cell-mediated cytotoxicity (ADCC) activity and complement-dependent cytotoxicity (CDC) activity. In the present invention, CDC activity means cytotoxic activity caused by the complement system. ADCC activity refers to the activity of damaging a target cell when a specific antibody attaches to its cell surface antigen, and an Fcγ receptor-carrying cell (immune cell, or such) binds to the Fc portion of the antigen via the Fcγ receptor damages the target cell.
An anti-DSG3 antibody can be tested to see whether it has ADCC activity or CDC activity using known methods (for example, Current Protocols in Immunology, Chapter 7. Immunologic studies in humans, Editor, John E. Coligan et al., John Wiley & Sons, Inc., (1993) and the like).
First, specifically, effector cells, complement solution, and target cells are prepared.
(1) Preparation of Effector Cells
Spleen is removed from a CBA/N mouse or the like, and spleen cells are isolated in RPMI1640 medium (manufactured by Invitrogen). After washing in the same medium containing 10% fetal bovine serum (FBS, manufactured by HyClone), the cell concentration is adjusted to 5×10⁶/mL to prepare the effector cells.
(2) Preparation of Complement Solution
Baby Rabbit Complement (manufactured by CEDARLANE) is diluted 10-fold in a culture medium (manufactured by Invitrogen) containing 10% FBS to prepare a complement solution.
(3) Preparation of Target Cells
The target cells can be radioactively labeled by incubating cells expressing the DSG3 protein (cells transformed with a gene encoding the DSG3 protein, lung cancer cells, colon cancer cells, esophageal cancer cells, gastric cancer cells, pancreatic cancer cells, skin cancer cells, uterine cancer cells, or the like) with 0.2 mCi of sodium chromate-⁵¹Cr (manufactured by GE Healthcare Bio-Sciences) in a DMEM medium containing 10% FBS for one hour at 37° C. After radioactive labeling, cells are washed three times in RPMI1640 medium containing 10% FBS, and the target cells can be prepared by adjusting the cell concentration to 2×10⁵/mL.
ADCC activity or CDC activity can be measured by the method described below. In the case of ADCC activity measurement, the target cell and anti-DSG3 antibody (50 μL each) are added to a 96-well U-bottom plate (manufactured by Becton Dickinson), and reacted for 15 minutes on ice. Thereafter, 100 μL of effector cells are added and incubated in a carbon dioxide incubator for four hours. The final concentration of the antibody is adjusted to 0 or 10 μg/mL. After culturing, 100 μL of the supernatant is collected, and the radioactivity is measured with a gamma counter (COBRAII AUTO-GAMMA, MODEL D5005, manufactured by Packard Instrument Company). The cytotoxic activity (%) can be calculated using the obtained values according to the equation: (A−C)/(B−C)×100, wherein A represents the radioactivity (cpm) in each sample, B represents the radioactivity (cpm) in a sample where 1% NP-40 (manufactured by Nacalai Tesque) has been added, and C represents the radioactivity (cpm) of a sample containing the target cells only.
Meanwhile, in the case of CDC activity measurement, 50 μL of target cell and 50 μL of an anti-DSG3 antibody are added to a 96-well flat-bottomed plate (manufactured by Becton Dickinson), and reacted for 15 minutes on ice. Thereafter, 100 μL of complement solution is added, and incubated in a carbon dioxide incubator for four hours. The final concentration of the antibody is adjusted to 0 or 3 μg/mL. After incubation, 100 μL of supernatant is collected, and the radioactivity is measured with a gamma counter. The cytotoxic activity can be calculated in the same way as in the ADCC activity determination.
On the other hand, in the case of measuring the cytotoxic activity of an antibody conjugate, 50 μL of target cell and 50 μL of an anti-DSG3 antibody conjugate are added to a 96-well flat-bottomed plate (manufactured by Becton Dickinson), and reacted for 15 minutes on ice. Thereafter, this is incubated in a carbon dioxide incubator for one to four hours. The final concentration of the antibody is adjusted to 0 or 3 μg/mL. After culturing, 100 μL of supernatant is collected, and the radioactivity is measured with a gamma counter. The cytotoxic activity can be calculated in the same way as in the ADCC activity determination.
An antibody of the present invention having cytotoxic activity is more preferably an antibody that does not have cell-dissociating activity. An antibody that does not have cell-dissociating activity can be suitably selected and obtained by measuring the cell-dissociating activity that inhibits cell adhesion of keratinocytes even in a test tube. The method of measuring cell-dissociating activity can be carried out in a test tube, for example, by the method described in J. Invest. Dermatol., 124, 939-946, 2005. Furthermore, as a method for observing this cellular activity in vivo, the activity can be evaluated as the activity to induce PV lesions, which are phenotypes of in vivo cell-dissociating activity. The PV-lesion-inducing activity can be evaluated by the method described in J. Immunology 170, 2170-2178, 2003.
The cells whose proliferation is suppressed by the anti-DSG3 antibody are not particularly limited as long as they express a DSG3 protein, but are preferably cancer cells, and more preferably, lung cancer cells, colon cancer cells, esophageal cancer cells, gastric cancer cells, pancreatic cancer cells, skin cancer cells, or uterine cancer cells. More preferably, they are from non-small-cell lung cancer. Therefore, the anti-DSG3 antibody can be used for the purpose of treating or preventing diseases attributed to cell proliferation, for instance, lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, or uterine cancer, more preferably non-small-cell lung cancer, and even more preferably lung squamous cell carcinoma, adenocarcinoma, adenosquamous carcinoma, or large cell carcinoma.
The present invention also provides polynucleotides encoding the antibodies of the present invention, and polynucleotides that hybridize under stringent conditions to these polynucleotides and encode antibodies having an activity equivalent to that of the antibodies of the present invention. The present invention also provides vectors containing these polynucleotides and transformants (including transformed cells) containing such vectors. The polynucleotides of the present invention are polymers comprising multiple nucleotides or base pairs of deoxyribonucleic acids (DNA) or ribonucleic acids (RNA), and are not particularly limited, as long as they encode the antibodies of the present invention. They may also contain non-natural nucleotides. The polynucleotides of the present invention can be used to express antibodies using genetic engineering techniques. Furthermore, they can be used as probes in the screening of antibodies that are functionally equivalent to the antibodies of the present invention. Specifically, a DNA that hybridizes under stringent conditions to the polynucleotide encoding an antibody of the present invention, and encodes an antibody having an activity equivalent to that of the antibody of the present invention, can be obtained by techniques such as hybridization and gene amplification technique (for example, PCR), using the polynucleotide encoding an antibody of the present invention, or a portion thereof, as a probe. Such DNAs are included in the polynucleotides of the present invention. Hybridization techniques are well known to those skilled in the art (Sambrook, J. et al., Molecular Cloning 2nd ed., 9.47-9.58, Cold Spring Harbor Lab. press, 1989). Conditions for hybridization include, for example, those with low stringency. Examples of conditions of low stringency include post-hybridization washing under conditions of 0.1×SSC and 0.1% SDS at 42° C., and preferably under conditions of 0.1×SSC and 0.1% SDS at 50° C. More preferable hybridization conditions include those of high stringency. Highly stringent conditions include, for example, conditions of 5×SSC and 0.1% SDS at 65° C. Under these conditions, the higher the temperature, polynucleotides having high homology would be obtained efficiently. However, several factors such as temperature and salt concentration can influence hybridization stringency, and those skilled in the art can suitably select these factors to realize similar stringencies.
An antibody that is encoded by a polynucleotide obtained by these hybridization and gene amplification techniques, and which is functionally equivalent to antibodies of the present invention, usually has a high homology to the amino acid sequences of these antibodies. The antibodies of the present invention also include antibodies that are functionally equivalent to and have high amino acid sequence homology to the antibodies of the present invention. The term “high homology” generally refers to amino acid identity of at least 50% or higher, preferably 75% or higher, more preferably 85% or higher, still more preferably 95% or higher. Polypeptide homology can be determined by the algorithm described in literature (Wilbur, W. J. and Lipman, D. J. Proc. Natl. Acad. Sci. USA (1983) 80, 726-730).

Pharmaceutical Compositions

In another aspect, the present invention features pharmaceutical compositions comprising an antibody that binds to a DSG3 protein as an active ingredient. In addition, the present invention features a cell proliferation inhibitor, in particular an anticancer agent, comprising an antibody that binds to a DSG3 protein as an active ingredient. Cell proliferation inhibitors and anticancer agents of the present invention are preferably administered to a subject affected by cancer, or to a subject who is likely to be affected by cancer. Subjects in the present invention are animal species that genetically carry a DSG3 protein and are affected by cancer or likely to be affected by cancer, and include, for example, mammals such as humans, monkeys, cattle, sheep, mice, dogs, cats, and hamsters, but are not limited thereto.
In the present invention, a cell proliferation inhibitor comprising as an active ingredient an antibody that binds to a DSG3 protein can also be described as a method for suppressing cell proliferation which comprises the step of administering an antibody that binds to a DSG3 protein to a subject, or as use of an antibody that binds to a DSG3 protein in the production of a cell proliferation inhibitor.
Furthermore, in the present invention, an anticancer agent comprising as an active ingredient an antibody that binds to a DSG3 protein can also be described as a method for preventing or treating cancer which comprises the step of administering an antibody that binds to a DSG3 protein to a subject, or as use of an antibody that binds to a DSG3 protein in the production of an anticancer agent.
In the present invention, the phrase “comprising an antibody that binds to DSG3 as an active ingredient” means comprising an anti-DSG3 antibody as the main active substance, and does not limit the content percentage of the anti-DSG3 antibody.
The antibody included in the pharmaceutical composition of the present invention (for example, cell proliferation inhibitor and anticancer agent; same hereinafter) is not particularly limited so long as it binds to a DSG3 protein, and examples include antibodies described herein.
The pharmaceutical compositions of the present invention can be administered orally or parenterally. Particularly preferably, the method of administration is parenteral administration, and specifically, the method of administration is, for example, administration by injection, transnasal administration, transpulmonary administration, or transdermal administration. Examples of administration by injection include systemic and local administrations of a pharmaceutical composition of the present invention by intravenous injection, intramuscular injection, intraperitoneal injection, subcutaneous injection, or such. A suitable administration method may be selected according to the age of the patient and symptoms. The dosage may be selected, for example, within the range of 0.0001 mg to 1000 mg per kg body weight in each administration. Alternatively, for example, the dosage for each patient may be selected within the range of 0.001 to 100,000 mg/body. However, the pharmaceutical composition of the present invention is not limited to these doses.
The pharmaceutical compositions of the present invention can be formulated according to conventional methods (for example, Remington's Pharmaceutical Science, latest edition, Mark Publishing Company, Easton, U.S.A), and may also contain pharmaceutically acceptable carriers and additives. Examples include, but are not limited to, surfactants, excipients, coloring agents, perfumes, preservatives, stabilizers, buffers, suspending agents, isotonization agents, binders, disintegrants, lubricants, fluidity promoting agents, and flavoring agents; and other commonly used carriers can be suitably used. Specific examples include light anhydrous silicic acid, lactose, crystalline cellulose, mannitol, starch, carmellose calcium, carmellose sodium, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, polyvinylacetal diethylaminoacetate, polyvinylpyrrolidone, gelatin, medium chain fatty acid triglyceride, polyoxyethylene hardened castor oil 60, saccharose, carboxymethyl cellulose, corn starch, inorganic salt, and such.
In addition, the present invention provides methods for inducing damages in a DSG3-expressing cell and methods for inhibiting cell growth by contacting a DSG3-expressing cell with a DSG3 protein-binding antibody. The DSG3 protein-binding antibody is the same as the above-described antibody that binds to a DSG3 protein, which is to be contained in the cell growth inhibitor of the present invention. The cell that is bound by the anti-DSG3 antibody is not particularly limited as long as the cell is expressing DSG3, and is preferably a cancer cell, more preferably a lung cancer cell, a colon cancer cell, an esophageal cancer cell, a stomach cancer cell, a pancreatic cancer cell, a skin cancer cell, or a uterine cancer cell, and more preferably a non-small-cell lung cancer.
In the present invention “contacting” is accomplished, for example, by adding an antibody to a culture solution of DSG3-expressing cells cultured in a test tube. In this case, the antibody can be added in the form of, for example, a solution or a solid obtained by freeze-drying or the like. When adding the antibody as an aqueous solution, the aqueous solution used may purely contain only the antibody, or the solution may include, for example, the above-mentioned surfactants, excipients, coloring agents, perfumes, preservatives, stabilizers, buffers, suspending agents, isotonization agents, binders, disintegrants, lubricants, fluidity promoting agents, or flavoring agents. The concentration for addition is not particularly limited, but the final concentration in the culture that may be suitably used is preferably in the range of 1 pg/mL to 1 g/mL, more preferably 1 ng/mL to 1 mg/mL, and even more preferably 1 μg/mL to 1 mg/mL.
Furthermore, in another embodiment, “contacting” in the present invention is carried out by administration to a non-human animal to which a DSG3-expressing cell has been transplanted into the body, or to an animal carrying cancer cells endogenously expressing DSG3. The method of administration may be oral or parenteral administration. Particularly preferably, the method of administration is parenteral administration, and specifically, the method of administration is, for example, administration by injection, transnasal administration, transpulmonary administration, or transdermal administration. Examples of administration by injection include systemic and local administrations of pharmaceutical compositions, cell proliferation inhibitors and anticancer agents of the present invention by intravenous injection, intramuscular injection, intraperitoneal injection, subcutaneous injection, or such. A suitable administration method may be selected according to the age of the test animal and symptoms. When administering as an aqueous solution, the aqueous solution used may purely contain only the antibody, or the solution may include, for example, the above-mentioned surfactants, excipients, coloring agents, perfumes, preservatives, stabilizers, buffers, suspending agents, isotonization agents, binders, disintegrants, lubricants, fluidity promoting agents, or flavoring agents. The dosage may be selected, for example, within the range of 0.0001 mg to 1000 mg per kg body weight in each administration. Alternatively, for example, the dosage for each patient may be selected within the range of 0.001 to 100,000 mg/body. However, the antibody dose of the present invention is not limited to these doses.
The following method is suitably used as a method for evaluating or measuring cell damage induced by contacting DSG3-expressing cells with an anti-DSG3 antibody. Examples of a method for evaluating or measuring the cytotoxic activity in a test tube include methods for measuring the above-mentioned antibody-dependent cell-mediated cytotoxicity (ADCC) activity, complement-dependent cytotoxicity (CDC) activity, and such. Whether or not an anti-DSG3 antibody has ADCC activity or CDC activity can be measured by known methods (for example, Current protocols in Immunology, Chapter 7. Immunologic studies in humans, Editor, John E. Coligan et al., John Wiley & Sons, Inc., (1993) and the like). For activity measurements, a binding antibody having the same isotype as anti-DSG3 antibody but not having any cell-damaging activity can be used as a control antibody in the same manner as the anti-DSG3 antibody, and it can be determined that the activity is present when the anti-DSG3 antibody shows a stronger cytotoxic activity than the control antibody.
The isotype of an antibody is defined by the sequence of its H chain constant region in the antibody amino acid sequence, and is determined as a result of class switching that arises from genetic recombinations in chromosomes which occur during maturation of antibody-producing B-cells. Difference in isotype is reflected in the difference of physiological and pathological functions of antibodies, and for example, the strength of cytotoxic activity is known to be influenced by antibody isotype in addition to the expression level of the antigen. Therefore, when measuring the above-described cell damaging activity, an antibody of the same isotype as the test antibody is preferably used as the control.
A method for evaluating or measuring cell damaging activity in vivo is, for example, intradermally or subcutaneously transplanting DSG3-expressing cancer cells to a non-human test animal, and then intravenously or intraperitoneally administering a test antibody daily or at the interval of few days, starting from the day of transplantation or the following day. Cytotoxicity can be defined by daily measurement of tumor size. In a similar manner to the evaluation in a test tube, cytotoxicity can be determined by administering a control antibody having the same isotype, and observing that the tumor size in the anti-DSG3 antibody-administered group is significantly smaller than the tumor size in the control antibody-administered group. When using a mouse as the non-human test animal, it is suitable to use a nude (nu/nu) mouse whose thymus has been made genetically defective so that its T lymphocyte function is lost. The use of such a mouse can eliminate the participation of T lymphocytes in the test animals when evaluating or measuring the cytotoxicity of the administered antibody.
The following method can be used suitably as a method for evaluating or measuring the inhibitory effect of an anti-DSG3 antibody on proliferation of DSG3-expressing cells through contact. A method for measuring the incorporation of [³H]-labeled thymidine added to the medium by living cells as an indicator for DNA replication ability is used as a method for evaluating or measuring the cell proliferation inhibitory activity in a test tube. As a more convenient method, a dye exclusion method that measures under a microscope the ability of a cell to exclude a dye such as trypan blue to outside, or the MTT method is used. The latter makes use of the ability of living cells to convert MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), which is a tetrazolium salt to a blue formazan product. More specifically, a test antibody is added to the culture solution of a test cell, and after a certain period of time passes, the MTT solution is added to the culture solution, and this is left to stand for a certain time for MTT to be incorporated into the cell. As a result, MTT which is a yellow compound is converted to a blue compound by the action of succinate dehydrogenase in the mitochondria of the cell. After dissolving this blue product for coloration, absorbance is measured and used as an indicator for the number of viable cells. Besides MTT, reagents such as MTS, XTT, WST-1, and WST-8 are commercially available (Nacalai Tesque, and such) and can be suitably used. For activity measurements, a binding antibody having the same isotype as the anti-DSG3 antibody but not having any cell proliferation inhibitory activity can be used as a control antibody in the same manner as the anti-DSG3 antibody, and it can be determined that the activity is present when the anti-DSG3 antibody has a stronger cell proliferation inhibitory activity than the control antibody.
For a method that evaluates or measures cell proliferation inhibiting activity in vivo, the same method as the one described above for evaluating or measuring cytotoxicity in vivo can be suitably used.
All prior art references cited herein are incorporated by reference into this description.

EXAMPLES

Herein below, the present invention will be specifically described with reference to the Examples, but it is not to be construed as being limited thereto.

Example 1

DSG3 mRNA Expression Analysis in Various Types of Cancers

Gene chip was used to perform DSG3 gene expression analysis. To search for a gene whose expression is enhanced in cancer cells, various RNAs and total RNAs prepared from various extracted tissues by conventional methods using ISOGEN (manufactured by Nippon Gene) shown in Tables 1 and 2 were used. More specifically, gene expression analysis was carried out using 10 μg each of total RNAs, and subjecting them to GeneChip U-133A (manufactured by Affymetrix) according to the Expression Analysis Technical Manual (manufactured by Affymetrix). When analyzing lung adenocarcinoma and hepatocellular carcinoma, a total of 10 μg was obtained by combining total RNAs of twelve lung adenocarcinoma cases and three hepatocellular carcinoma cases to perform the analysis (Table 1).

	TABLE 1

	Tissue	Source

	Whole brain	Clontech 64020-1
	Lung	Clinical sample, 1 case
	Trachea	Clontech 64091-1
	Heart	Ambion 7966
	Kidney	Ambion 7976
	Liver	Clinical sample (Surgery)
	Pancreas	Ambion 7954
	Stomach	Clinical sample (Surgery)
	Small intestine	Ambion 7984
	Large intestine	Ambion 7986
	Bone marrow	Clontech 64106-1
	Peripheral blood mononuclear cell	Clinical sample, 1 case
	Testis	Clontech 64027-1
	Prostate	Ambion 7988
	Ovary	Ambion 7974
	Skin	Stratagene 735031
	Lung cancer (adenocarcinoma)	Clinical sample, 12 cases
	Lung cancer (squamous cell carcinoma)	Clinical sample, 1 case
	Lung cancer (squamous cell carcinoma)	Clinical sample, 1 case
	Lung cancer (squamous cell carcinoma)	Clinical sample, 1 case
	Lung cancer (squamous cell carcinoma)	Clinical sample, 1 case
	Lung cancer (squamous cell carcinoma)	Clinical sample, 1 case
	Liver cancer (moderately differentiated)	Clinical sample, 3 cases
	Liver cancer (well differentiated)	Clinical sample, 3 cases
	Colon cancer	Clinical sample, 1 case
	Colon cancer	Clinical sample, 1 case
	Colon cancer	Clinical sample, 1 case

Tissues Used for DSG3 Gene Expression Analysis

TABLE 2

Type of cancer	Cell line	Medium	Serum (%)

Brain tumor	U251	DMEM		10
Breast cancer	MCF7	RPMI1640		10
Esophageal	TE2	RPMI1640		10
cancer
Stomach cancer	AGS	RPMI1640		10
	GT3	DMEM		10
	KatoIII	RPMI1640:DMEM = 1:1	10
	MKN45	RPMI1640		10
	MKN74	RPMI1640		10
	2M	DMEM	10
	2MD3	DMEM		10
Colon cancer	CACO2	DMEM		20
	DLD1	RPMI1640		10
	hCT116	McCoy5A		10
	LOVO	HamF12:DMEM = 1:1	10
	SW480	RPMI1640		10
Liver cancer	Alexander	DMEM		10
	HepG2	DMEM		10
	HLE	DMEM		10
	HuH6	DMEM		10
	HuH7	DMEM		10
Pancreatic	Capan1	DMEM		20
cancer
	KLM1	RPMI1640
	10
	Panc1	RPMI1640		10
	Paca2	RPMI1640		10
	PK-1	RPMI1640	10
Kidney cancer	Caki2	RPMI1640		10
Lung cancer	A549	DMEM		10
	Lu130	RPMI1640		10
	H1359	RPMI1640		10
	H157	RPMI1640		10
	H1648	HamF12:DMEM = 1:1	10
	H2009	HamF12:DMEM = 1:1	10
	H23	RPMI1640		10
	H2347	RPMI1640		10
	H522	RPMI1640		10
Cervical	Hela	DMEM		10
cancer

Cancer Cell Lines and Culturing Conditions Used for the DSG3 Gene Expression Analysis

Search for genes whose expression is enhanced in cancer tissues or cancer cells was performed by setting the mean value of the expression scores for all genes to 100, and comparing the relative expression levels of each gene. As a result, while expression of the DSG3 mRNA (probe ID: 205595_at HG-U133A) in normal tissues was limited to the skin, it was enhanced in lung cancer (lung squamous cell carcinoma) and colon cancer tissues, and in TE2 (esophageal cancer), 2M (stomach cancer), and PK-1 (pancreatic cancer) cancer cell lines (FIGS. 1 and 2).
From the above, it became apparent that while expression of the DSG3 gene (probe ID: 205595_at HG-U133A) is very low in normal tissues other than the skin, expression of the DSG3 gene is enhanced in a wide variety of cancers including lung cancer, colon cancer, esophageal cancer, stomach cancer, and pancreatic cancer. These results suggested that there is a high possibility that development of the above-mentioned cancers can be diagnosed using the DSG3 expression as an indicator.

Example 2

Immunohistological Staining of DSG3 in Lung Squamous Cell Carcinoma

Since transcription of the DSG3 gene is enhanced in cancer cells, in particular, lung squamous cell carcinoma cells, immunohistological staining analysis was performed to confirm expression of the DSG3 protein.
Each sample was prepared as a fixed paraffin embedded preparation, and a section sliced to a thickness of 4 μm was mounted on a slide glass and then left at 37° C. for about 16 hours to dry sufficiently. The section was deparaffinized by soaking three times in 100% xylene for five minutes each, and then hydrophilized by soaking three times in 100% ethanol for five minutes each and further soaking in 70% ethanol for five minutes. Then, after washing three times in a 50 mM TBS buffer solution for five minutes, the antigen in the section was activated by treating the section with a citrate buffer (10 mM, pH 7.0) at 120° C. for ten minutes. The section in which the antigen had been activated was washed three times in a TBS buffer for five minutes each, and then treated for one hour at room temperature in a TBS buffer containing an anti-DSG3 antibody (5G11) (Zymed) diluted to a final concentration of 50 μg/mL. To inactivate the endogenous peroxidase, the anti-DSG3 antibody-bound section was treated with 0.3% hydrogen peroxide for 15 minutes at room temperature. After washing three times with a TBS buffer solution, the above-mentioned section was treated with the secondary antibody, ENVISION+kit/HRP (DAKO), for one hour at room temperature. After washing three times with the TBS buffer solution for five minutes each, DAB (3,3′-diaminobenzamide tetrahydrochloride) was added as a coloring substrate to stain the section. Hematoxylin was used as a staining agent for counter staining of the nucleus.
As a result, of the five cases of tissue sections from cancer patients affected by lung squamous cell carcinoma, all five cases showed a positive reaction in which the section is stained by the anti-DSG3 antibody (5G11) (FIG. 3). Since a lung cancer-specific staining image was obtained, it became apparent that in lung cancer, the DSG3 expression is enhanced at the protein level as well. This indicated that development of lung cancer can be detected using an anti-DSG3 antibody.

Example 3

Preparation of Anti-DSG3 Antibody

3-1) Cloning of a Full-Length cDNA Encoding Human DSG3
A full-length cDNA encoding human DSG3 was obtained by PCR amplification using Human Small Intestine Marathon-Ready cDNA (CLONTECH) as a template. Specifically, 50 μL of a reaction solution containing 2 μL of cDNA, 1 μL of sense primer (SEQ ID NO: 37), 1 μL of antisense primer (SEQ ID NO: 38), 5 μL of 10×KOD-Plus buffer, 5 μL of 2 mM dNTPs, 2 μL of 25 mM MgSO₄, and 1 μL of KOD-Plus was subjected to a PCR reaction performed by five cycles of a reaction cycle consisting of reactions at 94° C. for 15 seconds and 70° C. for two minutes, five cycles of a reaction cycle consisting of reactions at 94° C. for 15 seconds and 68° C. for two minutes, and 28 cycles of a reaction cycle consisting of reactions at 94° C. for 15 seconds and 66° C. for two minutes. The amplified product obtained by the above-mentioned PCR reaction was inserted into pGEM-T easy using a pGEM-T Easy Vector System I (Promega). This was sequenced using an ABI3730 DNA sequencer to confirm that the human DSG3-encoding cDNA sequence was successfully cloned. The sequence represented by SEQ ID NO: 39 shows the nucleotide sequence of the human DSG3 gene, and the sequence represented by SEQ ID NO: 40 shows the amino acid sequence of the human DSG3 protein.

3-2) Establishment of Cells Showing Constant Expression of Full-Length Human DSG3

The full-length human DSG3 cDNA was cloned into a vector (pMCN) for expression in mammalian cells (pMCN/hDSG3). pMCN enables induced expression under the control of a mouse CMV promoter (ACCESSION No. U68299), and is a vector into which a neomycin resistance gene has been incorporated. A CHO cell line that shows constant expression of full-length human DSG3 was established by introducing pMCN/hDSG3 into the CHO DG44 cell strain (Invitrogen) by electroporation, and subjecting them to selection with 500 μg/mL of Geneticin. Similarly, an A549 cell line that shows constant expression of full-length human DSG3 was established by introducing pMCN/hDSG3 into A549 cells (human lung epithelial cancer cell line) that do not show DSG3 expression, and selection with 1000 μg/mL of Geneticin.

3-3) Preparation of Soluble Human DSG3/Mouse IgG2a Fc-Fusion Protein

Soluble human DSG3/mouse IgG2a Fc-fusion protein (hereinafter, shDSG3_mIgG2aFc) was prepared as an immunizing antigen for anti-DSG3 antibody production. shDSG3_mIgG2aFc was prepared by linking the extracellular domain of human DSG3 (Met1-Leu616) with the mouse IgG2a constant region through the CpoI recognition sequence in the hinge region, and cloned into the pMCDN vector prepared by incorporating the DHFR gene to the pMCN expression vector (pMCDN/shDSG3_mIgG2aFc). The sequence represented by SEQ ID NO: 41 shows the nucleotide sequence of the shDSG3_mIgG2aFc gene, and the sequence represented by SEQ ID NO: 42 shows the amino acid sequence of shDSG3_mIgG2aFc. A CHO cell line that shows constant expression of shDSG3_mIgG2aFc was established by introducing pMCDN/shDSG3_mIgG2aFc into DG44 cells by electroporation, and selection with 500 μg/mL of Geneticin. Next, shDSG3_mIgG2aFc was purified from culture supernatant of the established shDSG3 mIgG2aFc-expressing CHO cell line. The culture supernatant was applied to a Hi Trap Protein G HP (GE Healthcare Bio-Sciences) column, and after washing with a binding buffer (20 mM sodium phosphate (pH 7.0)), elution was carried out using an elution buffer (0.1 M glycine-HCl (pH 2.7)). The eluate was immediately neutralized by elution into a tube containing a neutralization buffer (1 M Tris-HCl (pH 9.0)). This eluate was subjected to gel filtration using Superdex 200 HR 10/30 (GE Healthcare Bio-Sciences) so that the solvent of the solution containing the desired antibody is replaced by a PBS buffer. The purified protein was quantified using a DC protein assay kit (BIO-RAD) and converted into a concentration using bovine IgG included in the kit as standard preparation.

3-4) Preparation of Anti-DSG3 Antibody

Balb/c mice or MRL/MpJUmmCrj-lpr/lpr mice (hereinafter MRL/lpr mice, purchased from Charles River Japan) were used as the animals for immunization. Immunization was initiated at the 7^thweek or 8th week. For the first immunization, an antigen was prepared using a PBS buffer so as to include 100 μg of shDSG3_mIgG2aFc for each mouse, emulsified using Freund's complete adjuvant (Beckton Dickinson), and administered subcutaneously. Two weeks later, an antigen was prepared using a PBS buffer so as to include 50 μg for each mouse, emulsified using Freund's incomplete adjuvant (Beckton Dickinson), and administered subcutaneously. Subsequently, boosting immunization was performed at 1-week intervals for two to four times, and for the final immunization, the antigen was diluted in PBS at 50 μg/mouse, and then administered into the tail vein. Four days after the final immunization, spleen cells were extirpated and mixed with mouse myeloma cells P3-X63Ag8U1 (P3U1, purchased from ATCC) at 2:1 ratio, and cell fusion was carried out by gradual addition of PEG 1500 (Roche Diagnostics). Next, RPMI1640 medium (Invitrogen) was added carefully to dilute PEG 1500, and then PEG 1500 was removed by centrifuging and removing the supernatant. The group of fused cells suspended in RPMI1640 containing 10% FBS was seeded into a 96-well culture plate at 100 μL/well. The following day, RPMI1640 containing 10% FBS, 1×HAT media supplement (SIGMA), and 0.5×BM-Condimed H1 Hybridoma cloning supplement (Roche Diagnostics) (hereinafter referred to as HAT medium) was added at 100 μL/well. On the second or third day, half of the culture solution was replaced with HAT medium, and the culture supernatant from the seventh day was used in the screening in which binding activity to the DSG3 molecule was used as an indicator. The screening was performed by flow cytometric analysis which detects binding to CHO cells that show constant expression of full-length human DSG3. Positive clones obtained by this analysis were monocloned by the limiting dilution method. Specifically, DF120, DF122, DF148, DF151, DF153, DF168, DF331, DF364, and DF366 were established as antibodies that specifically bind to DSG3.
In a similar manner to the case with shDSG3 mIgG2aFc, the monoclonal antibodies were purified using a Hi Trap Protein G HP column, from the culture supernatant of hybridomas cultured in HAT medium that uses FBS (Ultra low IgG) (Invitrogen) as the serum. The eluted fractions were subjected to solvent replacement with PBS using a PD-10 column (GE Healthcare Bio-Sciences), and then stored at 4° C. The purified antibodies were quantified using a DC protein assay kit (BIO-RAD) and converted into concentration using bovine IgG included in the kit as the standard preparation.

3-5) Evaluation of Binding Activity by Flow Cytometry

Flow cytometry was used to evaluate the binding of the obtained antibodies to CHO cells that show constant expression of full-length human DSG3. The cells were suspended in FACS Buffer (1% FBS/PBS) at 5×10⁵cells/mL and dispensed into Multiscreen-HV Filter Plates (Millipore), and the supernatant was removed from this cell suspension solution by centrifugation. After adding to the supernatant-free cells an FACS buffer containing anti-DSG3 monoclonal antibodies which have been diluted to a suitable concentration (3 μg/mL) in the FACS buffer, this was left to stand for 30 minutes on ice to let the cells react with the monoclonal antibodies. After removing the supernatant from this reaction solution by centrifugation, the cells were washed once with FACS buffer. Next, by suspending the cells in a FACS buffer containing FITC-labeled anti-mouse IgG antibody as the secondary antibody, the cells were reacted with the secondary antibody for 30 minutes on ice. After the reaction was completed, the supernatant was removed from the cells by centrifugation. The cells were suspended in 100 μL of FACS buffer, and then subjected to flow cytometric analysis. FACS Calibur (Becton Dickinson) was used as the flow cytometer. The living cell population was gated to a histogram of forward scatter and side scatter. As shown in FIG. 4, 3 μg/mL of anti-DSG3 monoclonal antibodies (DF120, DF122, DF148, DF151, DF153, DF168, DF331, DF364, and DF366) bound strongly to the DSG3-expressing CHO cells and did not bind to the parent CHO cells, indicating that the anti-DSG3 monoclonal antibodies specifically bind to DSG3 present on the cell membrane.

Example 4

Measurement of Cytotoxic Activities of the Anti-DSG3 Antibodies

4-1) Measurement of Complement-Dependent Cytotoxicity (CDC) Activities of the Anti-DSG3 Antibodies

The CHO cell line showing constant expression of full-length human DSG3 (DSG3-CHO, described in Example 3-2)) was used as the target cell. CHO-S-SFM II medium (Invitrogen) containing 500 μg/mL Geneticin (Invitrogen), HT supplement (Invitrogen), and penicillin/streptomycin (Invitrogen) (hereinafter referred to as “medium”) was used to culture the DSG3-CHO cell line. The cell pellet obtained by centrifuging 5×10⁵DSG3-CHO cell line cells (1000 rpm) for five minutes at 4° C. was suspended in approximately 200 μL of medium containing 3.7 MBq of Chromium-51 (GE Healthcare Bio-Sciences), and then cultured in a 5% carbon dioxide incubator for one hour at 37° C. These cells were washed three times with the medium, then adjusted to cell density of 1×10⁵cells/mL in the medium, and then dispensed into a 96-well flat-bottomed plate at 100 μL/well. Next, the anti-DSG3 antibodies and a control mouse IgG2a antibody (BD Biosciences Pharmingen) diluted with the medium were individually added at 50 μL/well. The final concentration of the antibodies was adjusted to 10 μg/mL. Next, baby rabbit complement (Cederlane) diluted 5-fold in the medium was added at 50 μL/well, and then the plate was left to stand in a 5% carbon dioxide incubator for 1.5 hours at 37° C. Thereafter, this was centrifuged (1000 rpm) for five minutes at 4° C., 1004 of the supernatant was collected from each well of the plate, and the radioactivity was measured using a gamma counter (1480 WIZARD 3″, Wallac). The specific chromium release rate was determined based on the following equation:
Specific chromium release rate (%)=(A−C)×100/(B−C)
where A represents the radioactivity (cpm) in each well, B represents the mean value of radioactivity (cpm) in wells where 100 μL of the cells and 100 μL of 2% Nonidet P-40 solution (Nacalai Tesque) have been added, and C represents the mean value of radioactivity (cpm) in wells where 100 μL of the cells and 100 μL of the medium have been added. The measurements were conducted in duplicate, and the mean value and standard deviation were calculated for the specific chromium release rate.
All of the anti-DSG3 antibodies used in the experiment were confirmed to have CDC activity (FIG. 5). On the other hand, the control mouse IgG2a antibody did not show CDC activity at the same concentration.
Next, human epidermoid carcinoma cell line A431 (purchased from ATCC), human lung epithelial cancer cell line A549 (purchased from ATCC), and an A549 cell line showing constant expression of full-length human DSG3 (DSG3-A549, described in Example 3-2)) were used as target cells to examine whether the antibodies have CDC activity. A431 and DSG3-A549 express DSG3 on the cell membrane. Dulbecco's Modified Eagle Medium (Invitrogen) (hereinafter referred to as DMEM medium) containing 10% fetal bovine serum (Invitrogen) and penicillin/streptomycin was used to culture A431 and A549. DMEM medium containing 1 mg/mL Geneticin was used to culture the DSG3-A549 cell line. A431, A549, and DSG3-A549 cells were individually added to a 96-well flat-bottomed plate at 2×10³cells/well (A549 and DSG3-A549) or 4×10³cells/well (A431), and cultured in a 5% carbon dioxide incubator for three days at 37° C. After culturing, Chromium-51 was added at a final concentration of 1.85 MBq/mL, and culturing was continued for another hour. Each well was washed with 300 μL of DMEM medium, and then 1004 of DMEM medium was added. Next, specific chromium release rates were determined by adding an anti-DSG3 antibody and baby rabbit complement under conditions similar to those used for the examination using DSG3-CHO cell line.
Anti-DSG3 antibody DF151 induced concentration-dependent CDC activity against DSG3-expressing A431 and DSG3-A549 cell lines, but did not show CDC activity against A549 cell line which does not express DSG3 (FIG. 6). These results showed that the anti-DSG3 antibody exhibits antigen-specific CDC activity.

4-2) Measurement of Antibody-Dependent Cellular Cytotoxicity (ADCC) Activity of Anti-DSG3 Antibodies

DSG3-A549 cell line and A431 cell line were used for ADCC activity measurements. Similar to the case of CDC activity measurements, the above-mentioned cells were cultured in a 96-well flat-bottomed plate and then reacted with Chromium-51. Thereafter, each well was washed with RPMI1640 medium (Invitrogen) containing 10% fetal bovine serum and penicillin/streptomycin (hereinafter referred to as RPMI medium), and then 100 μL of RPMI medium was added. Next, 50 μL each of an anti-DSG3 antibody and the control mouse IgG2a antibody diluted in RPMI medium was added to each well. The final concentration of the antibody was adjusted to 10 μg/mL (bone marrow-derived effector cells) or 1 μg/mL (spleen-derived effector cells). Next, 50 μL of an effector cell solution (1×10⁷cells/mL), which will be described later, was added to each well, and then the plate was left to stand in a 5% carbon dioxide incubator for four hours at 37° C. Specific chromium release rate was determined from the measured radioactivity of each well in this plate. Cells obtained by culturing the spleen cells of a Balb/c mouse (Charles River Japan) in RPMI medium containing 50 ng/mL recombinant human interleukin-2 (Peprotech) for five days or cells obtained by culturing the bone marrow cells of the same mouse in RPMI medium containing 50 ng/mL of recombinant human interleukin-2 and 10 ng/mL of recombinant mouse GM-CSF (Peprotech) for six days were used as effector cells.
Anti-DSG3 antibodies DF151, DF364, and DF366 induced ADCC against DSG3-A549 and A431 cell lines (FIG. 7). The above-mentioned results showed that anti-DSG3 antibodies induce cell damage in DSG3 protein-expressing cells through ADCC activity.

Example 5

Determination of the Anti-DSG3 Antibody Variable-Region Gene Sequences

Antibody variable region genes were cloned from hybridomas that produce monoclonal antibodies DF151, DF364, and DF366, which are antibodies showing ADCC activity and CDC activity in DSG3-expressing cells, and their sequences were determined. Antibody genes encoding monoclonal antibodies DF151, DF364, and DF366 were amplified by the RT-PCR method using total RNAs extracted from the anti-DSG3 antibody-producing hybridomas. Total RNA was extracted from 1×10⁷hybridoma cells using the RNeasy Plant Mini Kit (QIAGEN). Using 1 μg of total RNA, the 5′-end gene fragment was amplified by the SMART RACE cDNA Amplification Kit (CLONTECH), using synthetic oligonucleotide MHC-IgG2b (SEQ ID NO: 43) complementary to the mouse IgG2b constant region sequence, synthetic oligonucleotide MHC-IgG1 (SEQ ID NO: 100) complementary to the mouse IgG1 constant region sequence, or synthetic oligonucleotide kappa (SEQ ID NO: 44) complementary to the mouse κ chain constant region nucleotide sequence. The reverse transcription reaction was performed for one hour and thirty minutes at 42° C. The PCR reaction was performed in 50 μL of PCR reaction solution containing 5 μL of 10× Advantage 2 PCR Buffer, 5 μL of 10× Universal Primer A Mix, 0.2 mM dNTPs (dATP, dGTP, dCTP, and dTTP), 1 μL of Advantage 2 Polymerase Mix (the above were manufactured by CLONTECH), 2.5 μL of reverse transcription reaction product, and 10 pmol of synthetic oligonucleotide MHC-IgG2b, MHC-IgG1, or kappa. The PCR reaction was performed under the reaction conditions of reaction at an initial temperature of 94° C. for 30 seconds, followed by five cycles of a reaction cycle consisting of reactions at 94° C. for 5 seconds and 72° C. for three minutes, five cycles of a reaction cycle consisting of reactions at 94° C. for 5 seconds, 70° C. for 10 seconds, and 72° C. for three minutes, and 25 cycles of a reaction cycle consisting of reactions at 94° C. for five seconds, 68° C. for ten seconds, and 72° C. for three minutes. Finally, the reaction product was heated at 72° C. for seven minutes. Each PCR product was purified from agarose gel using the QIAquick Gel Extraction Kit (manufactured by QIAGEN), then cloned into pGEM-T Easy vector (manufactured by Promega), and the nucleotide sequence of the clone was determined.
For the H chain of DF151, the nucleotide sequence and amino acid sequence of CDR1 are shown in SEQ ID NO: 1 and SEQ ID NO: 2, respectively, the nucleotide sequence and amino acid sequence of CDR2 are shown in SEQ ID NO: 3 and SEQ ID NO: 4, respectively, and the nucleotide sequence and amino acid sequence of CDR3 are shown in SEQ ID NO: 5 and SEQ ID NO: 6, respectively. For the L chain of DF151, the nucleotide sequence and amino acid sequence of CDR1 are shown in SEQ ID NO: 11 and SEQ ID NO: 12, respectively, the nucleotide sequence and amino acid sequence of CDR2 are shown in SEQ ID NO: 13 and SEQ ID NO: 14, respectively, and the nucleotide sequence and amino acid sequence of CDR3 are shown in SEQ ID NO: 15 and SEQ ID NO: 16, respectively.
For the H chain of DF364, the nucleotide sequence and amino acid sequence of CDR1 are shown in SEQ ID NO: 21 and SEQ ID NO: 22, respectively, the nucleotide sequence and amino acid sequence of CDR2 are shown in SEQ ID NO: 23 and SEQ ID NO: 24, respectively, and the nucleotide sequence and amino acid sequence of CDR3 are shown in SEQ ID NO: 25 and SEQ ID NO: 26, respectively. For the L chain of DF364, the nucleotide sequence and amino acid sequence of CDR1 are shown in SEQ ID NO: 29 and SEQ ID NO: 30, respectively, the nucleotide sequence and amino acid sequence of CDR2 are shown in SEQ ID NO: 31 and SEQ ID NO: 32, respectively, and the nucleotide sequence and amino acid sequence of CDR3 are shown in SEQ ID NO: 33 and SEQ ID NO: 34, respectively.
For the H chain of DF366, the nucleotide sequence and amino acid sequence of CDR1 are shown in SEQ ID NO: 80 and SEQ ID NO: 81, respectively, the nucleotide sequence and amino acid sequence of CDR2 are shown in SEQ ID NO: 82 and SEQ ID NO: 83, respectively, and the nucleotide sequence and amino acid sequence of CDR3 are shown in SEQ ID NO: 84 and SEQ ID NO: 85, respectively. For the L chain of DF366, the nucleotide sequence and amino acid sequence of CDR1 are shown in SEQ ID NO: 86 and SEQ ID NO: 87, respectively, the nucleotide sequence and amino acid sequence of CDR2 are shown in SEQ ID NO: 88 and SEQ ID NO: 89, respectively, and the nucleotide sequence and amino acid sequence of CDR3 are shown in SEQ ID NO: 90 and SEQ ID NO: 91, respectively.
For DF151, the nucleotide sequence and the amino acid sequence of the H-chain variable region are shown in SEQ ID NO: 45 and SEQ ID NO: 46, respectively, and the nucleotide sequence and the amino acid sequence of the L-chain variable region are shown in SEQ ID NO: 47 and SEQ ID NO: 48, respectively. For DF364, the nucleotide sequence and the amino acid sequence of the H-chain variable region are shown in SEQ ID NO: 49 and SEQ ID NO: 50, respectively, and the nucleotide sequence and the amino acid sequence of the L-chain variable region are shown in SEQ ID NO: 51 and SEQ ID NO: 52, respectively. For DF366, the nucleotide sequence and the amino acid sequence of the H-chain variable region are shown in SEQ ID NO: 92 and SEQ ID NO: 93, respectively, and the nucleotide sequence and the amino acid sequence of the L-chain variable region are shown in SEQ ID NO: 94 and SEQ ID NO: 95, respectively.

Example 6

Determination of Full-Length Gene Sequences of Anti-DSG3 Antibodies

When the variable region gene sequences of DF151, DF364, and DF366 were determined, the gene sequences of the constant regions adjacent to the variable regions were also determined. By searching for genes that have the same sequences as these sequences using the Basic Local Alignment Search Tool (BLAST) of the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/BLAST/), the nucleotide sequences of the entire constant regions can be obtained. The full-length nucleotide sequence can be determined by linking the obtained nucleotide sequence of the constant region to the variable region nucleotide sequence. In this manner, the mouse IgG2b nucleotide sequence (DDBJ Accession No. BC025447), mouse kappa light chain nucleotide sequence (DDBJ Accession No. AY704179), and mouse IgG1 nucleotide sequence (DDBJ Accession No. BCO57688) can be obtained from the nucleotide sequence of the H-chain constant region of DF151 (SEQ ID NO: 53), the nucleotide sequence of the L-chain constant region of DF151, DF364, and DF366 (SEQ ID NO: 54), and the nucleotide sequence of the H-chain constant region of DF364 and DF366 (SEQ ID NO: 55), respectively.
The isotypes of DF151 (mouse IgG2bκ), DF364 (mouse IgG1κ), and DF366 (mouse IgG1κ) were determined in advance using the IsoStrip Mouse Monoclonal Antibody Isotyping Kit (ROCHE). The predicted nucleotide sequence and amino acid sequence of the full-length DF151H chain are shown in SEQ ID NO: 56 and SEQ ID NO: 57, respectively, and the predicted nucleotide sequence and amino acid sequence of the full-length DF151 L chain are shown in SEQ ID NO: 58 and SEQ ID NO: 59, respectively. The predicted nucleotide sequence and amino acid sequence of the full-length DF364H chain are shown in SEQ ID NO: 60 and SEQ ID NO: 61, respectively, and the predicted nucleotide sequence and amino acid sequence of the full-length DF364 L chain are shown in SEQ ID NO: 62 and SEQ ID NO: 63, respectively. The predicted nucleotide sequence and amino acid sequence of the full-length DF366H chain are shown in SEQ ID NO: 101 and SEQ ID NO: 102, respectively, and the predicted nucleotide sequence and amino acid sequence of the full-length DF366 L chain are shown in SEQ ID NO: 103 and SEQ ID NO: 104, respectively. For DF151, the nucleotide sequence and the amino acid sequence of the H-chain constant region are shown in SEQ ID NO: 7 and SEQ ID NO: 8, respectively, and the nucleotide sequence and the amino acid sequence of the L-chain constant region are shown in SEQ ID NO: 17 and SEQ ID NO: 18, respectively. For DF364 and DF366, the nucleotide sequence and the amino acid sequence of the H-chain constant region are shown in SEQ ID NO: 27 and SEQ ID NO: 28, respectively, and the nucleotide sequence and the amino acid sequence of the L-chain constant region are shown in SEQ ID NO: 35 and SEQ ID NO: 36, respectively.

Example 7

Production of Anti-DSG3 Mouse-Human Chimeric Antibodies

The H-chain and L-chain variable region sequences of each antibody were ligated in frame with human H-chain and L-chain constant region sequences. PCR was performed using a synthetic oligonucleotide having a sequence complementary to a Kozak sequence and an EcoRI site at the 5′ end of a nucleotide sequence encoding the H-chain variable region, and a synthetic oligonucleotide complementary to the 3′ end nucleotide sequence which has a NheI site inserted. PCR was performed using a synthetic oligonucleotide having a sequence complementary to a Kozak sequence and a BamHI site at the 5′ end of a nucleotide sequence encoding the L-chain variable region, and a synthetic oligonucleotide complementary to the 3′ end nucleotide sequence which has a BsiWI site inserted. The obtained PCR products were cloned into antibody expression plasmid pMCDN_G1k. pMCDN_G1k has the human IgG1 constant region (the nucleotide sequence is shown in SEQ ID NO: 9 and the amino acid sequence is shown in SEQ ID NO: 10) cloned into the pMCDN vector, and has a structure in which the mouse H-chain variable region and the human H-chain (κ chain) constant region are linked by a NheI site. Furthermore, another expression unit comprising a mouse CMV promoter, and a human κ constant region (the nucleotide sequence is shown in SEQ ID NO: 19, and the amino acid sequence is shown in SEQ ID NO: 20) are inserted, and it has a structure in which the mouse L-chain variable region and human L chain (κ chain) constant region are linked by a BsiWI site. This plasmid expresses the neomycin resistance gene, DHFR gene, and anti-DSG3 mouse-human chimeric antibody gene in animal cells.
pMCDN_G1k_DF151, pMCDN_G1k_DF364, and pMCDN_G1k_DF366 prepared as described above were introduced into DG44 cells by electroporation. Geneticin selection (500 μg/mL) established CHO cells that show constant expression of DF151 mouse-human chimeric antibody (hereinafter referred to as DF151c), DF364 mouse-human chimeric antibody (hereinafter referred to as DF364c), and DF366 mouse-human chimeric antibody (hereinafter referred to as DF366c). Next, the anti-DSG3 mouse-human chimeric antibodies were purified from the culture supernatants of the CHO cells using a Hi Trap rProtein A column (GE Healthcare Bio-Sciences). The purified antibodies were subjected to buffer replacement with PBS buffer using PD-10 columns (GE Healthcare Bio-Sciences), quantified by DC Protein Assay, and then stored at 4° C. The purified anti-DSG3 mouse-human chimeric antibodies were subjected to flow cytometric analysis to confirm that they bind specifically to DSG3 in the same way as the mouse antibodies. The nucleotide sequence and amino acid sequence of the full-length DF151c H chain are shown in SEQ ID NO: 64 and SEQ ID NO: 65, respectively, and the nucleotide sequence and amino acid sequence of the full-length DF151c L chain are shown in SEQ ID NO: 66 and SEQ ID NO: 67, respectively. The nucleotide sequence and amino acid sequence of the full-length DF364c H chain are shown in SEQ ID NO: 68 and SEQ ID NO: 69, respectively, and the nucleotide sequence and amino acid sequence of the full-length DF364c L chain are shown in SEQ ID NO: 70 and SEQ ID NO: 71, respectively. The nucleotide sequence and amino acid sequence of the full-length DF366c H chain are shown in SEQ ID NO: 96 and SEQ ID NO: 97, respectively, and the nucleotide sequence and amino acid sequence of the full-length DF366c L chain are shown in SEQ ID NO: 98 and SEQ ID NO: 99, respectively.

Example 8

Production of Low-Fucose Anti-DSG3 Mouse-Human Chimeric Antibodies

The method of modifying the sugar chain of an antibody is a known method for enhancing the ADCC activity of an antibody. For example, improvement of ADCC activity by modified antibody glycosylation is described in WO 99/54342. Furthermore, WO 00/61739 describes the adjustment of ADCC activity by the presence or absence of fucose on an antibody sugar chain. WO 02/31140 describes the use of a YB2/0 cell line to prepare an antibody comprising a sugar chain that does not have α-1,6-core fucose. Whether the ADCC improvement techniques described above enhance the activity of the anti-DSG3 antibodies was examined. First, as host cells, the YB2/0 cell line (purchased from ATCC) was cultured in RPMI1640 medium containing 10% FBS. An anti-DSG3 mouse-human chimeric antibody expression vector prepared in Example 7 was introduced into the YB2/0 cell line by the electroporation method under conditions of 1.4 kV and 25 μF. By Geneticin selection (500 μg/mL), YB2/0 cell lines that show constant expression of low-fucose DF151 mouse-human chimeric antibody (hereinafter referred to as YB-DF151c), low-fucose DF364 mouse-human chimeric antibody (hereinafter referred to as YB-DF364c), and low-fucose DF366 mouse-human chimeric antibody (hereinafter referred to as YB-DF366c) were established. Next, the low-fucose anti-DSG3 mouse-human chimeric antibodies were purified from the culture supernatant using a Hi Trap rProtein A column. Purified antibodies were subjected to buffer exchange with PBS buffer using a PD-10 column, quantified by DC Protein Assay, and then stored at 4° C. The purified low-fucose anti-DSG3 mouse-human chimeric antibodies were subjected to flow cytometric analysis to confirm that they bind specifically to DSG3 in the same way as the anti-DSG3 mouse-human chimeric antibodies.

Example 9

Measurement of CDC Activity and ADCC Activity of Anti-DSG3 Mouse-Human Chimeric Antibodies and Low-Fucose Anti-DSG3 Mouse-Human Chimeric Antibodies

9-1) Establishment of Cell Lines that Show Constant Expression of Full-Length Human DSG3
The full-length human DSG3 cDNA was cloned into a vector (pMCDN) for expression in mammalian cells (pMCDN/hDSG3). The pMCDN vector, into which a neomycin resistance gene and a DHFR gene are incorporated, enables induced expression under the control of a mouse CMV promoter (ACCESSION No. U68299). A Ba/F3 cell line (DSG3-Ba/F3) that shows constant expression of full-length human DSG3 was established by introducing pMCDN/hDSG3 into Ba/F3 cells (purchased from RIKEN BioResource Center) by electroporation, and subjecting them to selection with 500 μg/mL of Geneticin (Invitrogen). DSG3-Ba/F3 cells were cultured using RPMI1640 medium (Invitrogen) containing 500 μg/mL Geneticin, penicillin/streptomycin (Invitrogen), recombinant mouse interleukin-3 (R&D Systems), and 10% fetal bovine serum (Invitrogen).

9-2) Establishment of Cells Showing Constant Expression of Full-Length Human CD16

Full-length human CD16 (RefSeq ID, NM_—000569) was cloned into pMCDN, then introduced into NK-92 cells (purchased from ATCC) by electroporation and then subjected to Geneticin selection (500 μg/mL) to establish a NK-92 cell line (CD16-NK92) that shows constant expression of full-length human CD16. The CD16-NK92 cell line was cultured using Minimum Essential Medium Alpha Medium with L-glutamine, without ribonucleosides, deoxyribonucleosides (Invitrogen) containing 500 μg/mL Geneticin, penicillin/streptomycin, 0.2 mM inositol (Sigma), 0.1 mM 2-mercaptoethanol (Invitrogen), 0.02 mM folic acid (Sigma), 100 U/mL recombinant human interleukin-2 (Peprotech), 12.5% horse serum (Invitrogen), and 12.5% fetal bovine serum.

9-3) Measurement of CDC Activity of Anti-DSG3 Mouse-Human Chimeric Antibodies

A suspension of 5×10⁵DSG3-Ba/F3 cells was centrifuged (1000 rpm for five minutes at 4° C.), the resulting cell pellet was suspended in approximately 200 μL of RPMI1640 medium containing 10% fetal bovine serum, penicillin/streptomycin, and 3.7 MBq of Chromium-51 (GE Healthcare Bio-Sciences) (hereinafter referred to as medium), and the cells were cultured in a 5% carbon dioxide incubator for one hour at 37° C. These cells were washed three times in the medium, then adjusted to 2×10⁵cells/mL, and then added to a 96-well round-bottomed plate at 50 μL/well. Next, DF151c, DF364c, DF366c, and a control human IgG antibody (Zymed) were individually added at 50 pt/well. Final concentration of the antibodies was adjusted to 10 μg/mL. Next, baby rabbit complement (Cederlane) diluted 5-fold in the medium was added at 100 μL each. The plate was left to stand in a 5% carbon dioxide incubator at 37° C. for four hours. After the culturing, the plate was centrifuged (1000 rpm for five minutes at 4° C.), and 100 μL of the supernatant was used for the radioactivity measurement on a gamma counter (1480 WIZARD 3″, Wallac). The specific chromium release rate was determined according to the following equation:
Specific chromium release rate (%)=(A−C)×100/(B−C)
where A represents the radioactivity (cpm) in each well, B represents the mean value of radioactivity (cpm) in wells where 50 μL of the cells and 150 μL of 2% Nonidet P-40 solution (Nacalai Tesque) have been added, and C represents the mean value of radioactivity (cpm) in wells where 50 μL of the cells and 150 μL of the medium have been added. The assay was conducted in duplicate, and the mean value and standard deviation were calculated for the specific chromium release rate. DF151c, DF364c, and DF366c were shown to have CDC activity (FIG. 8).

9-4) Measurement of ADCC Activity of Anti-DSG3 Mouse-Human Chimeric Antibodies and Low-Fucose Anti-DSG3 Mouse-Human Chimeric Antibodies

DSG3-Ba/F3 cells were labeled with Chromium-51, and then added to a 96-well round-bottomed plate at 50 μL/well. Next, DF364c, DF366c, YB-DF364c, YB-DF366c, and a control human IgG antibody were individually added at 50 μL/well. Final concentrations of the antibodies were adjusted by four 10-fold serial dilutions starting from 1 μg/mL. Subsequently, CD16-NK92 cells at 2×10⁵cells/mL were added at 100 μL/well. The plate was left to stand in a 5% carbon dioxide incubator at 37° C. for four hours, and then the specific chromium release rate was determined using the same method as that of 8-3).
All antibodies showed ADCC activity in an antibody concentration-dependent manner (FIG. 9). In particular, low-fucose antibodies YB-DF364c and YB-DF366c showed strong ADCC activity.

Example 10

Immunohistological Staining of DSG3 in Lung Cancer, Skin Cancer, and Uterine Cancer

The DSG3 expression was enhanced at the protein level in lung squamous cell carcinoma (see Example 2). Therefore, immunohistological staining analyses were newly performed to confirm the DSG3 protein expression in skin cancer, uterine cancer, and lung adenocarcinoma which is a lung cancer that affects a large number of people. First, 4% paraformaldehyde (PFA) or periodate-lysine-paraformaldehyde (PLP)-fixed AMeX embedded paraffin block and 10% neutral buffer formaldehyde (NBF)-fixed paraffin-embedded block were prepared from each sample, and 3-μm-thin sections were prepared. After deparaffinization, these sections were stained immunohistochemically as described below using the Ventana HX Discovery System (Ventana Medical Systems, Inc., Arizona, USA). Each preparation was washed with water after deparaffinization, and reacted with 3.0% hydrogen peroxide solution (Inhibitor D) for four minutes at room temperature to eliminate endogenous peroxidase. This was washed, and with addition of protein blocker to eliminate non-specific reactions, this was reacted for 30 minutes at room temperature. After washing, a mouse anti-human Desmoglein 3 antibody (Clone 5G11, ZYMED Laboratories Inc., California, USA) was added as a primary antibody, and then reacted for one hour at room temperature. After washing, a secondary antibody (Ventana Universal Secondary Antibody, Ventana Medical Systems) was added and reacted for 30 minutes at room temperature. After washing, reaction with Blocker D was carried out for two minutes at room temperature to remove non-specific reactions, and then streptavidin horseradish peroxidase (SA-HRP, Ventana Medical Systems) was added and reacted at 37° C. for 16 minutes. After washing, a mixture of diaminobenzidine (DAB map solution, Ventana Medical Systems) and hydrogen peroxide solution (DAB map solution, Ventana Medical Systems) was added and reacted for eight minutes at 37° C. for substrate color development. Next, the color was intensified using a copper sulfate solution (Ventana Medical Systems). After washing, this was subjected to nuclear staining with hematoxylin, dehydration, penetration, and inclusion.
As a result, the DSG3 expression was confirmed in two out of three cases in lung squamous cell carcinoma, one out of nine cases in lung adenocarcinoma, two out of two cases in skin squamous cell carcinoma, one out of one case in skin basal cell carcinoma, and one out of one case in uterine squamous cell carcinoma (Table 3).

TABLE 3

Lung^a	Skin	Uterus

SCC^b

Adenocarcinoma

SCC

BCC

SCC

	2^c	3	3-M	1	2	2	2-M	3	3	3	3-M	3-M	1	3	—	2
Desmoglein-3	1^d	2	3	4	5	6	7	8	9	10	11	12	14	15	16	17

Intensity	3-4^e	2-4	0	0	0	0	0	2-4	0	0	0	0	2-4	1-4	1-4	2-4
Frequency	4^f	4	—	—	—	—	—	2	—	—	—	—	4	3	3	4

Abbreviations:
BCC, basal cell carcinoma;
M, metastatic cancer;
SCC, squamous cell carcinoma
^atissue site of cancer
^bPL tissue type
^cgrade of cancer (1, well-differentiated; 2, moderately-differentiated; 3, poorly-differentiated)
^d case number
^e1, faint; 2, weak; 3, moderate; 4, strong
^f1, rare (less than 10%); 2, occasional (10% and above, less than 50%); 3, frequent (50% and above, less than 90%); 4, constant (90% and above)

Example 11

Evaluation of Antitumor Activity of Anti-DSG3 Antibodies

11-1) Production of Mouse IgG2a Chimeric DF366 Antibody (DF366m)

The nucleotide sequence of the H-chain variable region gene of DF366 antibody was ligated in frame to the nucleotide sequence of H-chain constant region gene of mouse IgG2a. First, PCR was performed using a primer (SEQ ID NO: 105) having the 5′ end nucleotide sequence of the H-chain variable region gene, a Kozak sequence, and an EcoRI restriction enzyme sequence, and an antisense primer (SEQ ID NO: 106) having a c residue attached to a sequence complementary to the 3′-end nucleotide sequence. The obtained amplified product was treated with the EcoRI restriction enzyme, and then incorporated into the EcoRI-NruI site of a mouse IgG2a chimeric H-chain expression plasmid (pMCD/G2a) to construct a mouse IgG2a chimeric DF366 antibody H-chain expression vector (pMCD/G2a-DF366). pMCD/G2a has the H-chain constant region gene of mouse IgG2a (nucleotide sequence: SEQ ID NO: 107; amino acid sequence: SEQ ID NO: 108) cloned into a pMCD plasmid for expression in mammalian cells, and the NruI restriction enzyme sequence of the H-chain constant region is ligated to the H-chain variable region. The pMCD vector, into which a DHFR gene has been incorporated, enables induced expression under the control of a mouse CMV promoter (ACCESSION No. U68299).
The nucleotide sequence of the L-chain variable region gene of DF366 antibody was ligated in frame to the nucleotide sequence of the L-chain (κ chain) constant region gene of mouse IgG2a. First, PCR was performed using a primer (SEQ ID NO: 109) having the 5′-end nucleotide sequence of the L-chain variable region gene, a Kozak sequence, and the EcoRI restriction enzyme sequence, and an antisense primer (SEQ ID NO: 110) having gcccg residues attached to a sequence complementary to the 3′-end nucleotide sequence. The amplified product obtained was treated with EcoRI restriction enzyme, and then incorporated into the EcoRI-NruI site of a mouse IgG2a chimeric L-chain (κ chain) expression plasmid (pMCN/k) to construct a mouse IgG2a chimeric DF366 antibody L-chain expression vector (pMCN/k-DF366). pMCN/k has the L-chain (κ chain) constant region gene of mouse IgG2a (nucleotide sequence: SEQ ID NO: 111; amino acid sequence: SEQ ID NO: 112) cloned into the plasmid pMCN, and the NruI restriction enzyme sequence of the L-chain (κ chain) constant region is ligated to the L-chain variable region.
The plasmid pMCD/G2a-DF366 and the plasmid pMCN/k-DF366 were introduced into DG44 cells by electroporation. CHO cells (DF366m-DG44) showing constant expression of the mouse IgG2a chimeric DF366 antibody (DF366m) were established by Geneticin selection (500 μg/mL) and nucleic acid (HT supplement)-free medium. Subsequently, the DF366m antibody was purified from the culture supernatant of DF366m-DG44 using a Hi Trap Protein G HP column. The solvent was substituted with PBS using a PD-10 column. The concentration of the purified DF366m antibody was quantified using a DC Protein Assay kit. The DF366m antibody was subjected to flow cytometric analysis to confirm that it specifically binds to DSG3 in the same way as the DF366 antibody (described in Example 3-5). The nucleotide sequence of the full-length DF366m antibody H-chain gene and the corresponding amino acid sequence are shown in SEQ ID NO: 113 and SEQ ID NO: 114, respectively, and the nucleotide sequence of the full-length DF366m antibody L-chain gene and the corresponding amino acid sequence are shown in SEQ ID NO: 115 and SEQ ID NO: 116, respectively.

11-2) Production of Low-Fucose Mouse IgG2a Chimeric DF366 Antibody (Low Fucose DF366m)

The plasmid pMCD/G2a-DF366 and the plasmid pMCN/k-DF366 were introduced into fucose transporter knockout CHO cells (FTPKO-DXB11 cells, International Patent Publication Nos. WO 2006/067913 and WO 2006/067847) by electroporation. CHO cells (DF366m-DXB11) showing constant expression of the low-fucose mouse IgG2a chimeric DF366 antibody (low fucose DF366m) were established by Geneticin selection (500 μg/mL) and nucleic acid (HT supplement)-free medium. Subsequently, the low-fucose DF366m antibody was purified from the culture supernatant of DF366m-DXB11 using a Hi Trap Protein G HP column. The solvent was substituted with PBS using a PD-10 column, and the antibody concentration was quantified using a DC Protein Assay kit.

11-3) Measurement of ADCC Activity

RPMI1640 medium (Invitrogen) containing penicillin/streptomycin and 10% fetal bovine serum (hereinafter referred to as RPMI medium) was used for the experiment. 1×10⁶DSG3-Ba/F3 cells were suspended in approximately 2004 of RPMI medium containing 3.7 MBq of Chromium-51 (GE Healthcare Bio-Sciences), and then cultured in a 5% carbon dioxide incubator for one hour at 37° C. After washing, the cell density was adjusted to 2×10⁵cells/mL, and then dispensed into a 96-well U-bottom plate at 50 μL/well. Next, the antibody solution was added at 50 μL/well. After incubating at room temperature for 15 minutes, effector cells (described later) were added at 100 μL each. The plate was left to stand in a 5% carbon dioxide incubator at 37° C. for six hours. Thereafter, 100 μL of the supernatant was collected from each well, and the radioactivity was measured with a gamma counter (1480 WIZARD 3″, Wallac). The specific chromium release rate was calculated according to the following equation:
Specific chromium release rate (%)=(A−C)×100/(B−C)
where A represents the radioactivity (cpm) in each well, B represents the mean value of radioactivity (cpm) in wells where 50 μL of the cells and 150 μL of 2% Nonidet P-40 solution (Nacalai Tesque) have been added, and C represents the mean value of radioactivity (cpm) in wells where 50 μL of the cells and 150 μL of RPMI medium have been added. The measurements were conducted in duplicate, and the mean value and standard deviation were calculated for the specific chromium release rate.
Cells obtained by adding 50 ng/mL recombinant human interleukin-2 (Peprotech) to spleen cells prepared from a C3H mouse (Charles River Japan) (hereinafter referred to as SPL) or cells obtained by culturing spleen cells for four days in the presence of 50 ng/mL of recombinant human interleukin-2 (hereinafter referred to as SPL-LAK) were used as effector cells. The number of effector cells per well was set to 5×10⁵cells (SPL) or 2×10⁵cells (SPL-LAK). Mouse IgG2a (Cat. No. 553453, Becton Dickinson) and human IgG1 (Cat. No. PHP010, Serotec) were used as negative controls.
ADCC activity was detected in DF366m and low-fucose DF366m, but ADCC activity was hardly observed in DF366c and YB-DF366c (FIGS. 10 and 11). Therefore, DF366m and low-fucose DF366m were considered to show stronger medicinal effect than DF366c and YB-DF366c in mice.

11-4) Establishment of Cell Line Showing Constant Expression of Full-Length Human DSG3

After digesting pMCDN/hDSG3 with the PvuI restriction enzyme, this was introduced into SK-HEP-1 cells (purchased from ATCC) by transfection using FuGENE (Roche), and a SK-HEP-1 cell line (hereinafter referred to as DSG3-SK) showing constant expression of full-length human DSG3 was established by Geneticin selection (1 mg/mL). D-MEM medium (Sigma) containing 1 mg/mL Geneticin and 10% fetal bovine serum was used to culture the DSG3-SK cells.

11-5) Evaluation of Antitumor Activity of DF366m and Low-Fucose DF366m

DSG3-SK cells were adjusted to 1×10⁸cells/mL in a solution containing a 1:1 ratio of D-MEM medium and MATRIGEL (Cat. No. 354234, BD Bioscience), and 100 μL of this cell solution was subcutaneously transplanted to the abdomen of a SCID mouse (female, 9-weeks old, CLEA Japan) that had been subjected to intraperitoneal administration of 100 μL of anti-asialo GM1 antibody (Wako Pure Chemicals, after dissolving one vial using 1 mL of distilled water for injection, 4 mL of physiological saline solution was added) on the previous day. From the 19th day after transplantation, DF366m and low-fucose DF366m were administered through the tail vein once a week for four weeks. The antibodies were prepared in PBS at 1 mg/mL (10 mg/kg administration group) or 0.2 mg/mL (2 mg/kg administration group), and administered at 10 mL/kg. PBS (vehicle) was administered similarly as a negative control. The assay was carried out using five animals in each group. Antitumor activity was evaluated based on tumor volume. The tumor volume was determined based on the following equation, and the mean value and standard deviation were calculated:
Tumor volume=major axis×minor axis×minor axis/2
Non-parametric Dunnett's multiple comparison was used for the significant difference test, and P value less than 0.05 was considered significant.
As a result of the examination, DF366m and low-fucose DF366m significantly suppressed tumor growth in the 10 mg/kg administration group as compared to the vehicle administration group (FIG. 12). Furthermore, although not significant, low-fucose DF366m indicated a suppressive tendency also at 2 mg/kg. From the above, anti-DSG3 antibodies were confirmed to show antitumor activity.

INDUSTRIAL APPLICABILITY

The DSG3 protein-specific antibodies of the present invention can be used as a diagnostic agent not only for lung cancer but also for colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, and uterine cancer. Furthermore, by using the anti-DSG3 antibodies after labeling them with a chemical substance or a radioisotope, the presence of lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, or uterine cancer can be detected in vivo.
Furthermore, anti-DSG3 antibodies having cytotoxic activity according to the present invention can be used as cytotoxic agents or cell growth inhibitors for various types of cancer cells that express a DSG3 protein, such as cells of lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, or uterine cancer.
Furthermore, anti-DSG3 antibodies having cytotoxic activity according to the present invention can be used as therapeutic agents against various types of cancers such as lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, or uterine cancer. In addition, anti-DSG3 antibodies of the present invention can be used as therapeutic agents for these cancers without inducing pemphigus conditions.
Additionally, genes encoding antibodies of the present invention and recombinant cells transformed by these genes can be used to produce recombinant antibodies that exhibit the above-mentioned effects and more preferred effects.

Claims

1. A pharmaceutical composition comprising as an active ingredient an antibody that binds to a DSG3 protein.

2. A cell growth inhibitor comprising as an active ingredient an antibody that binds to a DSG3 protein.

3. An anticancer agent comprising as an active ingredient an antibody that binds to a DSG3 protein.

4. The anticancer agent of claim 3, wherein the antibody that binds to a DSG3 protein is an antibody that has cytotoxic activity.

5. The anticancer agent of claim 3, wherein the antibody that binds to a DSG3 protein is an antibody described in any of (1) to (47) below:

(1) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 2 as CDR1, the amino acid sequence of SEQ ID NO: 4 as CDR2, and the amino acid sequence of SEQ ID NO: 6 as CDR3;

(2) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 8 as CH;

(3) an antibody comprising the H chain of (1), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;

(4) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 12 as CDR1, the amino acid sequence of SEQ ID NO: 14 as CDR2, and the amino acid sequence of SEQ ID NO: 16 as CDR3;

(5) an antibody comprising the L chain of (4), wherein the L chain has the amino acid sequence of SEQ ID NO: 18 as CL;

(6) an antibody comprising the L chain of (4), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;

(7) an antibody comprising the H chain of (1) and the L chain of (4);

(8) an antibody comprising the H chain of (2) and the L chain of (5);

(9) an antibody comprising the H chain of (3) and the L chain of (6);

(10) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 22 as CDR1, the amino acid sequence of SEQ ID NO: 24 as CDR2, and the amino acid sequence of SEQ ID NO: 26 as CDR3;

(11) an antibody comprising the H chain of (10), wherein the H chain has the amino acid sequence of SEQ ID NO: 28 as CH;

(12) an antibody comprising the H chain of (10), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;

(13) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 30 as CDR1, the amino acid sequence of SEQ ID NO: 32 as CDR2, and the amino acid sequence of SEQ ID NO: 34 as CDR3;

(14) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;

(15) an antibody comprising the L chain of (13), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;

(16) an antibody comprising the H chain of (10) and the L chain of (13);

(17) an antibody comprising the H chain of (11) and the L chain of (14);

(18) an antibody comprising the H chain of (12) and the L chain of (15);

(19) an antibody comprising the H chain of (1) and the L chain of (13);

(20) an antibody comprising the H chain of (2) and the L chain of (14);

(21) an antibody comprising the H chain of (3) and the L chain of (15);

(22) an antibody comprising the H chain of (10) and the L chain of (4);

(23) an antibody comprising the H chain of (11) and the L chain of (5);

(24) an antibody comprising the H chain of (12) and the L chain of (6);

(25) an antibody comprising an H chain having the amino acid sequence of SEQ ID NO: 81 as CDR1, the amino acid sequence of SEQ ID NO: 83 as CDR2, and the amino acid sequence of SEQ ID NO: 85 as CDR3;

(26) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 28 as CH;

(27) an antibody comprising the H chain of (25), wherein the H chain has the amino acid sequence of SEQ ID NO: 10 as CH;

(28) an antibody comprising an L chain having the amino acid sequence of SEQ ID NO: 87 as CDR1, the amino acid sequence of SEQ ID NO: 89 as CDR2, and the amino acid sequence of SEQ ID NO: 91 as CDR3;

(29) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 36 as CL;

(30) an antibody comprising the L chain of (28), wherein the L chain has the amino acid sequence of SEQ ID NO: 20 as CL;

(31) an antibody comprising the H chain of (25) and the L chain of (28);

(32) an antibody comprising the H chain of (26) and the L chain of (29);

(33) an antibody comprising the H chain of (27) and the L chain of (30);

(34) an antibody comprising the H chain of (1) and the L chain of (28);

(35) an antibody comprising the H chain of (2) and the L chain of (29);

(36) an antibody comprising the H chain of (3) and the L chain of (30);

(37) an antibody comprising the H chain of (10) and the L chain of (28);

(38) an antibody comprising the H chain of (11) and the L chain of (29);

(39) an antibody comprising the H chain of (12) and the L chain of (30);

(40) an antibody comprising the H chain of (25) and the L chain of (4);

(41) an antibody comprising the H chain of (26) and the L chain of (5);

(42) an antibody comprising the H chain of (27) and the L chain of (6);

(43) an antibody comprising the H chain of (25) and the L chain of (13);

(44) an antibody comprising the H chain of (26) and the L chain of (14);

(45) an antibody comprising the H chain of (27) and the L chain of (15);

(46) an antibody comprising one or more amino acid substitutions, deletions, additions, and/or insertions in the antibody of any of (1) to (45), which has equivalent activity as the antibody of any of (1) to (45); and

(47) an antibody that binds to the same DSG3 protein epitope as the antibody of any of (1) to (45).

6. The anticancer agent of claim 3, wherein the cancer is selected from the group consisting of lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, and uterine cancer.

7. The anticancer agent of claim 6, wherein said lung cancer is non-small-cell lung cancer.

8. A method of inducing cell damage in DSG3-expressing cells by contacting cells that express a DSG3 protein with an antibody that binds to the DSG3 protein.

9. A method of suppressing growth of DSG3-expressing cells by contacting cells that express a DSG3 protein with an antibody that binds to the DSG3 protein.

10. The method of claim 8, wherein the antibody that binds to the DSG3 protein has cytotoxic activity.

11. The method of claim 8, wherein the antibody that binds to the DSG3 protein is an antibody of any of (1) to (47) below:

(7) an antibody comprising the H chain of (1) and the L chain of (4);

(8) an antibody comprising the H chain of (2) and the L chain of (5);

(9) an antibody comprising the H chain of (3) and the L chain of (6);

(11) an antibody comprising the H chain of (10) having the amino acid sequence of SEQ ID NO: 28 as CH;

(12) an antibody comprising the H chain of (10) having the amino acid sequence of SEQ ID NO: 10 as CH;

(16) an antibody comprising the H chain of (10) and the L chain of (13);

(17) an antibody comprising the H chain of (11) and the L chain of (14);

(18) an antibody comprising the H chain of (12) and the L chain of (15);

(19) an antibody comprising the H chain of (1) and the L chain of (13);

(20) an antibody comprising the H chain of (2) and the L chain of (14);

(21) an antibody comprising the H chain of (3) and the L chain of (15);

(22) an antibody comprising the H chain of (10) and the L chain of (4);

(23) an antibody comprising the H chain of (11) and the L chain of (5);

(24) an antibody comprising the H chain of (12) and the L chain of (6);

(31) an antibody comprising the H chain of (25) and the L chain of (28);

(32) an antibody comprising the H chain of (26) and the L chain of (29);

(33) an antibody comprising the H chain of (27) and the L chain of (30);

(34) an antibody comprising the H chain of (1) and the L chain of (28);

(35) an antibody comprising the H chain of (2) and the L chain of (29);

(36) an antibody comprising the H chain of (3) and the L chain of (30);

(37) an antibody comprising the H chain of (10) and the L chain of (28);

(38) an antibody comprising the H chain of (11) and the L chain of (29);

(39) an antibody comprising the H chain of (12) and the L chain of (30);

(40) an antibody comprising the H chain of (25) and the L chain of (4);

(41) an antibody comprising the H chain of (26) and the L chain of (5);

(42) an antibody comprising the H chain of (27) and the L chain of (6);

(43) an antibody comprising the H chain of (25) and the L chain of (13);

(44) an antibody comprising the H chain of (26) and the L chain of (14);

(45) an antibody comprising the H chain of (27) and the L chain of (15);

12. The method of claim 8, wherein the cells that express a DSG3 protein are cancer cells.

13. An antibody that binds to a DSG3 protein and has cytotoxic activity against cells that express a DSG3 protein.

14. The antibody of claim 13, wherein the cytotoxic activity is ADCC activity.

15. The antibody of claim 13, wherein the cytotoxic activity is CDC activity.

16. The antibody of claim 13, wherein a low-molecular-weight chemotherapeutic agent or a toxic peptide is bound to the antibody.

17. An antibody binding to a DSG3 protein, wherein a low-molecular-weight chemotherapeutic agent or a toxic peptide is bound to the antibody.

18. The antibody of claim 13, wherein the antibody is an antibody of any of (1) to (47) below:

(5) an antibody comprising the L chain of (4) having the amino acid sequence of SEQ ID NO: 18 as CL;

(6) an antibody comprising the L chain of (4) having the amino acid sequence of SEQ ID NO: 20 as CL;

(7) an antibody comprising the H chain of (1) and the L chain of (4);

(8) an antibody comprising the H chain of (2) and the L chain of (5);

(9) an antibody comprising the H chain of (3) and the L chain of (6);

(16) an antibody comprising the H chain of (10) and the L chain of (13);

(17) an antibody comprising the H chain of (11) and the L chain of (14);

(18) an antibody comprising the H chain of (12) and the L chain of (15);

(19) an antibody comprising the H chain of (1) and the L chain of (13);

(20) an antibody comprising the H chain of (2) and the L chain of (14);

(21) an antibody comprising the H chain of (3) and the L chain of (15);

(22) an antibody comprising the H chain of (10) and the L chain of (4);

(23) an antibody comprising the H chain of (11) and the L chain of (5);

(24) an antibody comprising the H chain of (12) and the L chain of (6);

(31) an antibody comprising the H chain of (25) and the L chain of (28);

(32) an antibody comprising the H chain of (26) and the L chain of (29);

(33) an antibody comprising the H chain of (27) and the L chain of (30);

(34) an antibody comprising the H chain of (1) and the L chain of (28);

(35) an antibody comprising the H chain of (2) and the L chain of (29);

(36) an antibody comprising the H chain of (3) and the L chain of (30);

(37) an antibody comprising the H chain of (10) and the L chain of (28);

(38) an antibody comprising the H chain of (11) and the L chain of (29);

(39) an antibody comprising the H chain of (12) and the L chain of (30);

(40) an antibody comprising the H chain of (25) and the L chain of (4);

(41) an antibody comprising the H chain of (26) and the L chain of (5);

(42) an antibody comprising the H chain of (27) and the L chain of (6);

(43) an antibody comprising the H chain of (25) and the L chain of (13);

(44) an antibody comprising the H chain of (26) and the L chain of (14);

(45) an antibody comprising the H chain of (27) and the L chain of (15);

19. (canceled)

20. A method of diagnosing cancer, comprising detecting a DSG3 protein using an antibody that binds to the DSG3 protein.

21. A method of diagnosing cancer, comprising:

(a) collecting a sample from a subject; and

(b) detecting a DSG3 protein contained in the collected sample using an antibody that binds to the DSG3 protein.

22. The method of diagnosis of claim 20, wherein the antibody that binds to the DSG3 protein is labeled with a positron-emitting nuclide.

23. The method of diagnosis of claim 22, wherein the positron-emitting nuclide is a nuclide selected from the group consisting of ¹¹C, ¹³N, ¹⁵O, ¹⁸F, ⁴⁵Ti, ⁵⁵Co, ⁶⁴Cu, ⁶⁶Ga, ⁶⁸Ga, ⁷⁶Br, ⁸⁹Zr, and ¹²⁴I.

24. A method of diagnosing cancer, comprising detecting expression of a gene encoding a DSG3 protein.

25. The method of diagnosis of claim 20, wherein the cancer is selected from the group consisting of lung cancer, colon cancer, esophageal cancer, stomach cancer, pancreatic cancer, skin cancer, and uterine cancer.

26. The method of diagnosis of claim 25, wherein said lung cancer is non-small-cell lung cancer.

27.-30. (canceled)

31. A method of suppressing cell growth, comprising the step of administering to a subject an antibody that binds to a DSG3 protein.

32. A method of preventing or treating cancer, comprising the step of administering to a subject an antibody that binds to a DSG3 protein.