Expression of proteins immunologically related to murine mammary tumour virus (MMTV) core proteins in the cells of breast cancer continuous lines MCF-7, T47D, MDA-231 and cells from human milk.

Expression of antigens immunologically related to the gag gene products of murine mammary tumour virus (MMTV) in continuous cell lines MCF-7, T47D and MDA-231 was followed by indirect enzyme immunoassay (EIA). Some cells of the 2 clonal lines derived from MCF-7 and T47D cells contained MMTV antigens, but these were not detected in MDA-231 cells and in epithelial cells from the milk of healthy women. The expression of antigens related to MMTV gag proteins correlated with the expression of proteins immunologically related to MMTV gp52. Cells positive for antigens related to p27 were also found when healthy women sera containing antibodies against MMTV p27 were examined. Before testing, the donor sera containing antibodies against MMTV protein p27 were absorbed to the negative MCF-7 cell clone and their antibody activity to MMTV p27 was also tested by immunoblotting.