Cell types and morphogenesis in the mammary gland.

Cell types present in the mammary gland and their evolution were studied by labeling female rats with radioactive thymidine at various phases of the estrus cycle. The results suggest that the stem cells for mammary development are present in the terminal end buds and that they generate a lineage for lumenal cells and possibly a distinct one for myoepithelial cells. Growth and differentiation are controlled by both hormones and local factors.

Generation of fibroblast-like cells from cloned epithelial mammary cells in vitro: a possible new cell type.

We have isolated clonal cell lines from a nitrosomethylurea-induced mammary tumor in Wistar--Furth rats. The epithelial-like cells of these lines give rise to fibroblast-like cells. A study of several markers showed that the epithelial-like cells are similar to epithelial mammary cells. The fibroblastic cells, however, were similar to stromal cells, except for the production of collagen IV. The events occurring in these cultures are identical to those observed in previously isolated mammary cultures [Bennett, D. C., Peachey, L. A., Durbin, H. & Rudland, P. S. (1976) Cell 15, 283--298], suggesting their generality. The fibroblast-like cells generated in culture may be a hitherto unrecognized type of mammary cell.