Roles of transforming growth factor beta in inhibition of androgen-induced growth of Shionogi carcinoma cells in serum-free medium

Shionogi carcinoma 115 (SC115) has been accepted for 20 years as an androgen-responsive mouse mammary tumor. In a serum-free culture system we have established Ham's F-12:Eagle's minimum essential medium (1:1, v/v) containing 0.1% bovine serum albumin], 10(-8) M testosterone markedly stimulates the growth of SC-3 cells (a cloned cell line from a SC115 tumor) via androgen receptor. The testosterone-induced growth of SC-3 cells, which has been shown to be mediated through autocrine fibroblast growth factor (FGF)-like peptide, was almost completely abolished by 1 ng/ml of transforming growth factor beta (TGF-beta). In the present study, mechanisms of the inhibitory effect of TGF-beta on the testosterone-induced growth of SC-3 cells were examined in the serum-free medium. Although the testosterone-induced growth was almost completely inhibited by TGF-beta, basic FGF- or FGF-like peptide (secreted from SC-3 cells by testosterone)-induced growth was only partially inhibited (45%) by TGF-beta. This difference can be explained by the fact that TGF-beta decreased the amount of testosterone-induced FGF-like peptide secreted from SC-3 cells to 18% of control. The TGF-beta-induced inhibition was found to be reversible. Furthermore, no significant effects of the TGF-beta treatment on number or affinity of both androgen and FGF receptors were demonstrated. The present findings show that TGF-beta markedly inhibits testosterone-induced secretion of FGF-like peptide from SC-3 cells and also inhibits growth-stimulatory effects of the secreted factor on SC-3 cells, probably via postreceptor mechanisms.