Steroid-growth factor interaction in human prostate cancer. 2. Effects of transforming growth factors on androgen metabolism of prostate cancer cells.

The ability of human prostate cancer cells to metabolize androgens was assessed through administration of physiological concentration (0.5-10 nM) of tritiated testosterone (T) as precursor and one-step analysis of both T degradation and products' formation by reverse-phase HPLC and on-line radioactive detection after either 24 h or 72 h incubation. Overall, different prostate cancer cells degraded T quite differently, favoring alternatively reductive or oxidative metabolic pathways. In particular, both LNCaP and DU145 cells retained high levels of unconverted T, with a limited production of androstenedione and its 17-keto derivatives and relatively high amounts of dihydrotestosterone (DHT) and 3 alpha-androstanediol (3 alpha-diol). In contrast, PC3 cells quickly degraded T and exhibited high formation rates of androstenedione and 17-keto metabolites, while neither dihydrotestosterone nor 3 alpha-diol were detected after short or longer incubation times. The effects of both TGF alpha (50 ng/mL) and TGF beta 1 (5 ng/mL) on rates and direction of T metabolism were also explored. In LNCaP cells TGF alpha induced a significant (P < 0.04) decrease of the reductive metabolism of T with a corresponding enhancement of the oxidative pathway (P < 0.002), while TGF beta 1 did not significantly affect T metabolism. On the other hand, both reductive and oxidative pathways were only partially influenced by either growth factor in DU145 and PC3 cells, although TGF alpha significantly raised 5 alpha-androstanedione formation and reduced androsterone production in DU145 cells. All the above evidence was confirmed at both 24 h and 72 h or using increasing doses of TGF alpha and TGF beta 1, a peak activity of 50 ng/mL and 5 ng/mL, respectively, being generally encountered. Overall, our data suggest that TGFs may have a role in the growth regulation of hormone-responsive prostate tumor cells through changes of the intracellular contents of biologically active androgen metabolites.