ISOLATION AND CHARACTERIZATION OF A SPONTANEOUSLY TRANSFORMED MALIGNANT MOUSE MAMMARY EPITHELIAL-CELL LINE IN CULTURE

A method is described that permits the selection of spontaneously tran sformed mammary epithelial colonies from an untransformed mouse mammar y epithelial cell line, NMuMG, and utilizes a long-term anchorage-inde pendent growth of the transformants on soft agarose. These transformed cells (NMuMG-ST) are shown to be distinguishable from the untransform ed cells by morphology, growth characteristics, induced carcinomas whe n transplanted into nude mice and ability to metastasize. This transfo rmed phenotype displayed focal, multilayer growth and higher saturatio n density in comparison with the untransformed phenotype. Transplanted tumors as well as metastatic lung tumors in nude mice were adenocarci nomas morphologically similar to typical mammary tumors in humans. Thi s selection procedure of mutant mammary cells from an immortalized cel l line derived from normal mammary glands could be very useful to iden tify the genomic biomarkers in the growth regulation and malignant pro gression of breast cancer.