Regulation of Apoptosis Induced by Transforming Growth

Transforming growth factor-fl (TGF-fil), which is induced in the prostate following castration, has been speculated to mediate apoptosis of epithelial cells during prostatic involution. Here, we report the first evi dence of a direct effect of TGF-fi on induction of apoptosis in prostatic epithelial cells in vitro, using NRP-152 nontumorigenic and NRP-154 tumorigemc rat prostatic epithelial cell lines. TGF.@1 induces apoptosis of both cell lines within 24 h, as shown by a decrease in cell viability, in situ DNA nick-end labeling, and internucleosomal DNA fragmentation. More over, the ability of TGF-fi to induce apoptosis of NRP-152 is strictly dependent on culture conditions, because dexamethasone enhances while insulin and insulin-like growth factor-I specifically block apoptosis in duced by TGF-13. We suggest that TGF43s are direct physiological regu lators of apoptosis of prostatic epithelial cells.