Phenotypes of human epithelial cell lines immortalized from benign mastopathies

We have cultured cells from normal and benign mastopathy tissues under conditions favoring epithelial cell proliferation. However, such primary cells rapidly lose their ability to grow in vitro. Immortal lines were established after transfection with SV 40 T gene and several cell clones isolated from Normal Breast Adjacent to a tumor (NBAT 32 T2 to T7) and two benign mastopathies (NPM 21 T1 to T14 and NPM 14 T4). This immortalization of epithelial cells reduced the doubling time of cultured cells and increased the densities of the cultured cell populations. Among there cell lines we have characterized five clones and found differences in a number of aspects. Southern blot analysis showed that the SV 40 T gene was stably integrated in the genome of all the established cell lines. Two of the clones (NPM 21 T2 and NPM 21 T4) were nearly diploid showing a high degree of stability. Two other clones (NPM 14 T4 and NPM 21 T1) had near-tetraploid karyotypes, although quite heterogeneous. Comparison of the ultrastructural phenotypes shows that the two near-diploid cell lines were more differentiated than the two others. Estradiol receptors measured by Scatchard analysis and by transactivation of vitellogenin promotor were absent from all the cell lines. Progesterone receptors measured by Scatchard analysis of hormone binding were present in the NPM 14 T4 and NBAT 32 T4 cell lines. The NPM 21 T1 cell line did not contain such steroid receptors. These cell lines are persistent in long-term culture, thus providing a useful in vitro model system for studying factors involved in the proliferation and the transformation of human mammary epithelial cells.