Comprehensive screening for antigens overexpressed on carcinomas via isolation of human mAbs that may be therapeutic

doi:10.1073/pnas.0712202105

Comprehensive screening for antigens overexpressed on carcinomas via isolation of human mAbs that may be therapeutic

^aDivision of Antibody Project and
^dDepartment of Biomedical Polymer Science, Institute for Comprehensive Medical Science,
^b21st Century Center of Excellence Research Center,
Departments of ^cUrology,
^gRadiology,
^hPathology,
^kInternal Medicine, and
^l Surgery, School of Medicine, Fujita Health University, Toyoake, Aichi 470-1192, Japan;
^eInstitute for Antibodies, Ltd., Toyoake, Aichi 470-1192, Japan;
^fDepartment of Biotechnology, United Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan;
ⁱDivision of Clinical Laboratory, Yachiyo Hospital, Anjo, Aichi 446-8510, Japan; and
^jDepartment of Toxicology, Graduate School of Medical Sciences, Nagoya City University, Kawazumi, Mizuho, Nagoya 467-8601, Japan

Edited by Frederick W. Alt, Harvard Medical School, Boston, MA, and approved March 14, 2008 (received for review December 29, 2007)

Abstract

Although several murine mAbs that have been humanized became useful therapeutic agents against a few malignancies, therapeutic Abs are not yet available for the majority of the human cancers because of our lack of knowledge of which antigens (Ags) can become useful targets. In the present study we established a procedure for comprehensive identification of such Ags through the extensive isolation of human mAbs that may become therapeutic. Using the phage-display Ab library we isolated a large number of human mAbs that bind to the surface of tumor cells. They were individually screened by immunostaining, and clones that preferentially and strongly stained the malignant cells were chosen. The Ags recognized by those clones were isolated by immunoprecipitation and identified by MS. We isolated 2,114 mAbs with unique sequences and identified 21 distinct Ags highly expressed on several carcinomas. Of those 2,114 mAbs 356 bound specifically to one of the 21 Ags. After preparing complete IgG₁ Abs the in vitro assay for Ab-dependent cell-mediated cytotoxicity (ADCC) and the in vivo assay in cancer-bearing athymic mice were performed to examine antitumor activity. The mAbs converted to IgG₁ revealed effective ADCC as well as antitumor activity in vivo. Because half of the 21 Ags showed distinct tumor-specific expression pattern and the mAbs isolated showed various characteristics with strong affinity to the Ag, it is likely that some of the Ags detected will become useful targets for the corresponding carcinoma therapy and that several mAbs will become therapeutic agents.

Footnotes

^mTo whom correspondence should be addressed at:
Institute for Comprehensive Medical Science, Fujita Health University, 1-98, Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
E-mail: kurosawa{at}fujita-hu.ac.jp
Author contributions: Y.K. designed research; G.K., Y.A., M.M., M. Sumitomo, N.S., C.M., K.E., K.M., M.T., Y.I., S.H.-T., Y.U., M. Shiraishi, K.S., and M.K. performed research; A.T., S.F., and N.T. contributed new reagents/analytic tools; G.K., Y.A., M.M., A.T., S.F., N.T., R.K., Y.M., M. Shamoto, H.T., M. Sugiura, Y.H., S.M., R.S., K.H., N.H., and A.S. analyzed data; and Y.K. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Freely available online through the PNAS open access option.