CHARACTERIZATION OF A NEW BREAST CANCER-ASSOCIATED ANTIGEN AND ITS RELATIONSHIP TO MUC1 AND TAG-72 ANTIGENS

We have characterized a new tumor-associated antigen defined by monocl onal antibody (MAb) generated against HMA-1 breast cancer cell line. M Ab AM-1 was selected based on its preferential reactivity to breast ca ncer cells versus to normal or benign epithelial cells by immunofluore scence and immunohistochemical assays of cultured, or fresh specimens. AM-1 demonstrated strong reactivity to breast cancer cell lines inclu ding HMA-1, YMB-1-E, YMB-1 and MDA-MB-231 in flow cytometry. In immuno precipitation, BM-l recognized high molecular weight components of 160 -210 kDa and >370 kDa. Reactivity with HMA-1 cells was diminished mark edly when treated by heat, protease or periodate, suggesting that the antigenic epitope is composed with carbohydrates and peptides. Enzyme digestion of precipitated antigens demonstrated that the antigen conta ins O-linked and N-linked carbohydrates with neuraminic acid structure s. Furthermore, binding inhibition and sandwich ELISA assays using MAb s reactive with known breast cancer-associated antigens and synthetic MUC1 core peptide (PDTRPAPGSTAPPAHGVTSAPDTR) demonstrated that the ant igen is distinct from CEA, TAG-72 or MUC1, while the antigen conjoins with MUC1 and TAG-72 as a trimmer form in HMA-1 cells. These results s uggest that AM-1 recognizes a novel glycoprotein which is abundant in breast cancer, and may be utilized in the management of breast cancer patients.