Biological Behavior of Human Breast Carcinoma-associated Antigens Expressed during Cellular Proliferation 1

The cell surface-binding propert ies of two murine monoclonal antibodies reactive with human mammary tumor cells are described. Fluorescence-act ivated cell sorter analyses demonstrate that both monoclonal antibodies, B6.2 and B38.1, are reactive with the surface of the majori ty of human breast tumor cell lines tested but are unreact ive with a variety of normal human cell lines, melanomas, sarcomas, and lymphoid tumors. Ant ibody B6.2 was also reactive with selective carcinomas, while ant ibody B38.1 showed even broader reactivity. The two monoclonal ant ibodies were unreact ive with the surface of a variety of normal human tissues obtained at biopsy, including lymph nodes, bone marrow, and spleen, but were reactive with mammary tumor cells obtained from four of six pleural effusions. Surface binding to mammary tumor cells by both monoclonal antibodies was shown to decrease during densi ty-dependent arrest; fur ther cell cycle analysis demonstrated differential ant ibody surface binding during S phase. Prolonged exposure of mammary tumor cells to ant ibody showed no evidence of antigen capping or internalization. Both monoclonal antibodies were shown to lyse mammary tumor cells in ant ibody-dependent cel l-mediated cytotoxici ty.