A new breast carcinoma antigen defined by a monoclonal antibody

A new monoclonal antibody (MoAb), 3E1-2, to human breast carcinoma cells was made. With the use of the immunoperoxidase technique, 3E1-2 was tested on Formalin-fixed and fresh sections of 27 normal and 81 neoplastic tissues, including 37 carcinomas of the breast, 15 lung tumors, 5 colon tumors, and other tumors. Strong uniform staining of the cytoplasm and membrane occurred with the breast carcinoma, whereas with normal breast tissue less intense staining of the luminal membrane was seen; not all cells were reactive with the MoAb. Most other human tumors (with the exception of some lung, kidney, and uterine carcinomas) were nonreactive, and few normal tissues were reactive. The unique features of this new MoAb are: a) reaction with Formalin-fixed as well as fresh tissue; b) lack of a reaction with the cell surface of 43 established cell lines, including 10 lines derived from breast carcinoma cultures; c) variable staining patterns in different breast carcinomas, varying from all cells staining to dense cytoplasmic staining to minimal membrane staining of a few cells; d) a great differential in staining patterns between normal and neoplastic tissue (nonetheless, some normal tissues were 3E-1.2+). The antibody does not detect a tumor-specific antigen, but has a high carcinoma-to-normal breast ratio of staining. In addition, preliminary studies on the sera of 20 patients with carcinoma of the breast have shown that the antigen detected by 3E1-2 is elevated in their serum; 3E1-2 thus has the potential to be used for diagnosis of this disease.