Role of TGF beta in the anti-estrogen response/resistance of human breast cancer.

Transforming growth factor beta (TGF beta) has potent inhibitory effects upon epithelial proliferation and malignant progression may be associated with breakdown of the autocrine and paracrine inhibitory loops in which TGF beta participates. The therapeutic effecs of anti-estrogens may be partially attributable to boosting of local endogenous levels of TGF beta. This article reviews the evidence in support of TGF beta being a proximate effector in mediation of the anti-neoplastic effects of anti-estrogens. Both the conventional estrogen receptor (ER) dependent and ER independent mechanisms of action are likely to be involved. Evidence for preferential stromal induction of TGF beta by anti-estrogens is emphasized, together with the therapeutic potential of this strategy for improving outcome in early breast cancer irrespective of ER status.