Epithelial mouse mammary cell line exhibiting normal morphogenesis in vivo and functional differentiation in vitro.

An epithelial cell line, designated COMMA-1D, was derived from mammary tissue of BALB/c mice in the middle of pregnancy. This line, in continuous cell culture for 12 months, exhibits several characteristics distinctive of normal mammary epithelial cells, including induction of casein synthesis in vitro and normal duct morphogenesis in the cleared mammary fat pads of syngeneic mice. The cells also form domes in high density culture and are positive for keratin intermediate filaments by indirect immunofluorescence. COMMA-1D cells have a near diploid number of chromosomes and do not grow in suspension culture or produce tumors in syngeneic hosts. This cell line should prove useful for studies examining the regulation of normal cellular differentiation of mammary cells as well as transformation of epithelial cells to the preneoplastic and neoplastic phenotypes.