| Abstract: | We have generated three hybridoma-producing monoclonal antibodies (MAs) that show a different spectrum of reactivity to human mammary tissues. Two of these antibodies, 1F10B4 and 1F10G2, recognize a cytoplasmic determinant highly expressed in most of the primary and metastatic breast carcinomas studied, and weakly (or not at all) in normal breast and nonbreast tissues. 3C6F9 detected a surface determinant common to both normal and neoplastic mammary epithelium. Five hundred hybridomas were obtained from the fusion of NS-1 myeloma cells with spleen cells of mice hyperimmunized with the well-characterized human breast carcinoma cell line BT-20. After the initial screenings and clonings, three monoclonal antibodies (1F10B4, 1F10G2, and 3C6F9) showing a restricted range of reactivity were selected for further investigation. These three antibodies recognized a panel of neoplastic mammary cell lines; however, the degree of reactivity could not be correlated to any of the various characteristics of these epithelial cell lines. Moreover, immunofluorescence analysis of acetone-fixed cryostat section showed that 1F10B4 and 1F10G2 recognize the vast majority of the 37 primary and metastatic breast cancers tested, binding strongly to 47% and 67% of them respectively. Only one of the primary carcinomas was not recognized by 1F10B4. On the other hand, these two MAs reacted weakly or not at all with normal breast and nonbreast tissues showing only few focal reactivities with the luminal pole of some ducts of the breast; very weak staining in renal tubular epithelial cells, in few keratinocytes and epithelial cells lining some sebaceous glands in the skin; and a moderate staining in biliary ducts of the liver. All mesenchymal structures including smooth and striated muscle tissues, lymph nodes, and connective tissue were negative. On the other hand, 3C6F9 recognized a more limited number of human mammary tumors and reacted with normal ductal epithelium in the breast and with nonbreast tissues. Because of their wide spectrum of reactivity with breast cancer cells and restricted recognition of normal mammary tissues, their cytoplasmic localization, and their heterogeneous distribution within a single neoplasm, 1F10B4 and 1F10G2 are now being used to characterize antigenic phenotypes of tumor-associated antigens in retrospective studies performed on conventional formalin-fixed, paraffin-embedded human mammary carcinomas. |
