THE MULTIFUNCTIONAL ROLE OF TRANSFORMING GROWTH-FACTOR (TGF)-BETA-S ON MAMMARY EPITHELIAL-CELL BIOLOGY

The transforming growth factor-beta s are potent growth inhibitors of normal and transformed breast epithelial cells in culture. In vivo, th ese peptides modulate the development of the mouse mammary gland. Tiss ue-specific overexpression of mature TGF-beta 1 in transgenic mice res ults in mammary gland atrophy and prevention of carcinogen-induced bre ast tumorigenesis. However, the inhibitory effect of endogenous or exo genous TGF-beta s on established tumor cells is less clear. Several pu blished circumstantial and more direct data argue that, in some cases, the tumor cell TGF-beta s may contribute to the maintenance and/or pr ogression of tumor cells in an intact host by modulating their interac tion with host factors. This differential role of the TGF-beta s on ma mmary cells as determined by their normal or transformed phenotype as well as the biological and clinical implications of these data are dis cussed.