Establishment and characterization of SV40-transformed human breast epithelial cell lines

Human breast epithelial cells cultured from milk have been transformed with SV40. Indirect immunofluorescence tests using monoclonal antibodies show that cells from clones grown in soft agar have SV40 large T-antigen in their nuclei and epithelia-specific tonofilament antigens on their intermediate filaments. In primary cultures of milk epithelial cells, the tonofilaments form a characteristic delicate basketwork throughout the cytoplasm, but in the SV40-transformed epithelial cell strains, the filament network is grossly distorted. Insulin, hydrocortisone, and serum stimulate the growth of the cell strains. At passages 8 to 11, the cell strains become quiescent and usually die. One cell strain survived this crisis period and gave rise to the fR series of cell lines. Most cell lines have a cuboidal morphology and react with a monoclonal antibody that recognizes a differentiation antigen on the membranes of breast epithelia. Line fR2 expressed the highest level of this antigen whereas fR5, the only fR line isolated with fusiform morphology, had relatively little. The in vitro-transformed lines may be related to the two dominant epithelial cell types seen in primary milk cultures and could be useful for studying the relationship between transformation and differentiation in human mammary epithelial cells.