Purification and partial characterization of a murine mammary tumor-associated antigen

A mammary tumor-associated antigen (MTAA) of the murine mammary tumor virus (MuMTV)-induced spontaneous mammary tumors of C3H/J mice was purified and partially characterized. The crude extract of the mammary tumor, when subjected to DEAE-cellulose chromatography and eluted with a discontinuous NaCl gradient, provided three major protein peaks, of which only the first (F1) possessed the MTAA activity. The antigen was further purified by subjecting F1 to polyacrylamide gel electrophoresis. The MTAA was a glycoprotein with a molecular weight of approximately 83,000. The antigen was localized in the plasma membrane and was different from the MuMTV structural antigens. Circulating antibodies against the MTAA were observed in the sera of tumor-bearing mice but not in that of tumor-free mice.