Reversible inhibition of mammary gland growth by transforming growth factor-beta.

Transforming growth factor-beta (TGF-beta) can stimulate or inhibit growth of cells in vitro, as well as induce the transformed phenotype. Although widely distributed in animal tissue, the effects of TGF-beta in vivo are largely unknown, and a physiological role for the peptide hormone has not been demonstrated. The effect of TGF-beta on developing epithelial tissue in situ was studied by using slow-release plastic pellets containing TGF-beta to treat developing mouse mammary gland. Powerful inhibition of mammary growth and morphogenesis was observed. This growth-inhibited mammary tissue was histologically normal, and the inhibitory effect was fully reversible. Under the conditions of these experiments, TGF-beta displayed many of the characteristics expected of a physiologically active growth-regulatory molecule.