Detection and purification of a novel 72 kDa glycoprotein male breast tumor associated antigen

A male breast tumor associated antigen (MBTAA) was purified and partially characterized from human male breast tumor. Three protein peaks were obtained by DEAE-cellulose column chromatography of a crude extract of human male breast tumor tissues. Circulating antibodies against one of these peaks, MFI, which contained MBTAA, were observed in male breast cancer patients but not in normal male or male patients with carcinoma of other organs (stomach, colon, lung). The MBTAA was partially purified from MFI by subjecting the fraction to SDS-PAGE and eluting the protein from band 3 (MB-3) and by subjecting MFI to size exclusion-high performance liquid chromatography (SE-HPLC). The MBTAA was characterized as a glycoprotein with MW of approximately 72 kDa. It showed no immunological relatedness with TAG-72, a tumor associated antigen expressed in breast epithelial cells. A 72 kDa protein, immunologically related to MBTAA, was detected and partially purified from female breast tumor. The female breast cancer patients did not have circulating antibodies against this 72 kDa protein or MBTAA. Presence of 72 kDa glycoprotein MBTAA in MFI and specificity of the anti-MBTAA antibodies in the sera of male breast cancer patients were further confirmed by Western blot analysis. Absence of anti-MBTAA antibodies in healthy men and in patients with other cancers suggested that expression of MBTAA may be malignancy-associated and is highly overexpressed in male breast cancer.