A human breast tissue-associated antigen detected by a monoclonal antibody

Two monoclonal antibodies were produced in mice immunized with the human breast carcinoma cell line MCF-7. One antibody (24-17.1) reacted with MCF-7 and other breast tumor cell lines and detected an antigen of Mr 95,000. This antigen was not breast-specific because other tumor cell lines were also reactive. The second antibody (24-17.2) detected an antigen of Mr 100,000 (initially appearing to be specific for breast tissue and possibly for breast carcinomas) which was present on 10 of 10 malignant breast lines and absent from 41 of 43 other cell lines of differing origins. The antigen could not be detected by absorption or a direct test on normal tissues (liver, kidney, heart, spleen) or on lymphocytes. In addition, the 24-17.2 antibody reacted absorptively with 12 of 13 fresh breast carcinoma samples but not with fresh colon carcinoma samples. The 100,000-Mr antigen detected by the 24-17.2 antibody appeared to be distinct from the other components of normal breast, such as casein, lactalbumin, or milk fat globulin protein. This evidence indicated that the 24-17.2 antibody detected a human breast carcinoma-associated antigen (HBCAA). However, further histologic studies were used to determine the cellular distribution of the HBCAA, which was found on malignant breast epithelium, the epithelium of gynecomastia, and in lesser amounts and differently distributed on normal breast epithelium. The antigen was also found in several other tissues; nonetheless, the anti-HBCAA could be detected in increased amounts in the sera of patients with breast cancer.