Abstract
The hormone-dependent human breast cancer cell line MCF-7 secretes transforming growth factor-β (TGF-β), which can be detected in the culture medium in a biologically active form. These polypeptides compete with human platelet-derived TGF-β for binding to its receptor, are biologically active in TGF-β-specific growth assays, and are recognized and inactivated by TGF-β-specific antibodies. Secretion of active TGF-β is induced 8 to 27-fold under treatment of MCF-7 cells with growth inhibitory concentrations of antiestrogens. Antiestrogen-induced TGF-β from MCF-7 cells inhibits the growth of an estrogen receptor-negative human breast cancer cell line in coculture experiments; growth inhibition is reversed with anti-TGF-β antibodies. We conclude that in MCF-7 cells, TGF-β is a hormonally regulated growth inhibitor with possible autocrine and paracrine functions in breast cancer cells.
