Hormone-dependent enhancement of neoplastic phenotype expression by MuMTV-infected heterologous cells, and MuMTV-induced cellular antigens.

A new property, i.e. acquisition of insulin (insulin + dexamethasone)-mediated enhancement of anchorage independence by heterologous MuMTV-infected cells, is described. Hormone-mediated anchorage-independent growth enhancement in MuMTV-infected cells is followed by expression of a cell-surface antigen, recognized by allogeneic (C3H----AKR) anti-Thy 1.2 antigen serum. The absorption test and the use of monoclonal antibody to the Thy 1.2 antigen showed that hormone-dependent antigen on the cell surfaces of experimentally and naturally MTV-infected cells was different from the Thy 1.2 antigen itself. Utilization of anti-p53 ("protein of transformation") monoclonal antibody enabled us to identify this cell membrane antigen as p53.