Tissue distribution of breast cancer-associated antigens defined by monoclonal antibodies

Balb/c mice were immunized with membrane preparations of primary and metastatic breast carcinomas or with live breast cancer cell lines. Sixty-two fusions were performed between immune splenocytes and SP2/0 mouse myeloma cells, and 107 hybridomas were cloned that produced antibody reactive with breast cancer membrane extract, cell lines, and frozen sections, but not with normal tissue membrane extracts or a human fibroblast line. Ninety-four monoclonal antibodies were purified and tested for binding to 16 normal tissue frozen sections and five blood cell types. Thirty-five of the 94 antibodies were also tested on breast cancer sections from 21 patients, 14 breast cancer cell lines, and 11 non-breast tumor sections. Two of 94 antibodies showed no reactivity to any of the 21 normal tissues or 11 nonbreast neoplasms studied. These two antibodies, 451B7 and 452F2, bound 60% of the breast cancer cell lines and 25% of the breast cancer tissue sections. Eight additional antibodies bound three or fewer of 21 normal tissues. These antibodies bound 25-85% of breast cancer sections, 0-75% of breast cancer cell lines, and many of the nonbreast cancers. A comparison of normal tissues and nonbreast tumors bound by the breast cancer-reactive antibodies indicated that most of the cross-reacting normal tissue structures were epithelial in origin, and that the most cross-reactive nonbreast cancers were those of secondary sex organs (uterus, prostate, ovary).