MONOCLONAL-ANTIBODIES AGAINST HUMAN BREAST TUMOR-ASSOCIATED ANTIGENS - CHARACTERIZATION OF B21-ANTIGEN

Background: Monoclonal antibodies (MAbs) show promise in the early det ection and monitoring of cancer and may have therapeutic applications as well. Purpose: The purpose of this study was to characterize MAb B2 1, a novel murine-derived antibody that has strong reactivity with MCF -7 and T47D cell lines from human breast cancer. Methods: A number of MAbs that react with breast cancer cell lines were obtained from cultu red mouse spleen cells, and one. MAb B21, was selected for detailed an alysis. MAb B21 was characterized by immunocytochemical, immunofluores cence, immunoprecipitation, and Western blotting procedures. Results: We found a strong reactivity of MAb B21 with cultured breast cancer ce lls and cells from human breast tumors, although some reactivity was s een sporadically in non-breast or normal tissue. Negligible reactivity was detected in a series of non-breast cell lines and with normal bre ast epithelial cell line MCF-10A. However, when MCF-10A cells were per meabilized, allowing the antibody to penetrate within the cells, react ion became apparent. MCF-10A cells, when transfected with the oncogene c-Ha-ras (MCF-10T), gave a positive immunostaining similar to that ob served with MCF-7 and T47D cells. Sodium dodecyl sulfate-polyacrylamid e gel electrophoresis (SDS-PAGE) analysis of L-[S-35]methionine-labele d MCF-7 and T47D cell extracts showed distinct immunoprecipitated comp onents, with molecular weight values ranging from 150000 to 20000 with the addition of MAb B21. Western blot assays using MAb B21 of SDS-PAG E fractionated/electroblotted proteins from breast cancer cell lines a nd MCF-10A cells showed specific reaction with a 95000 component. Conc lusions: Our results indicate that B21 antigen is expressed in neoplas tic cells of epithelial origin, mainly breast cancer, and to a minor e xtent in other cell lines. In addition, MAb B21 recognizes an antigen that is differentially localized during cell transformation. Implicati ons: Our future studies will address the full characterization of MAb B21 and explore its capacity as a tool for therapeutic manipulation.