Steady state expression of cell-cycle regulatory genes in prostate carcinoma cell lines

The transforming growth factor-β (TGF-β) signal transduction system has been reported to play a role in prostate tumorigenesis and the regulation of cell cycle-related gene expression including the cyclins, cyclin dependent kinases (Cdks), and Cdk inhibitors. The objective of this investigation was to examine the expression of TGF-β receptors I and II and five cell cycle-related genes—Cdk-4, p15, p21(WAF1/CIP1), p27, and cyclin E—in three prostate carcinoma cell lines and normal prostate by quantitative reverse transcriptase (RT)/polymerase chain reaction (PCR). The expression of the TGF-β receptor II was reduced by 5.5- and 2.2-fold in the LNCaP and DU145 cells, respectively, compared with normal prostate tissue. A similar decrease was observed for the TGF-β receptor I transcript in the LNCaP cells. In addition, 20-fold less of the TGF-β inducible p15inkb transcript was produced by the LNCaP and DU145 cell lines compared with the PC-3 cell line. The p21(WAF1/CIP1) transcript, although present, was only 6% of normal in the DU145 and PC-3 cell lines. Furthermore, the steady state levels of p21(WAF1/CIP1) mRNA significantly increased within 15 minutes after the addition of exogenous TGF-β to PC-3 cells. Likewise, addition of TGF-β antibodies to the PC-3 cells significantly reduced p21(WAF1/CIP1) transcript levels to less than 2% of normal. This suggests that p21(WAF1/CIP1) expression in PC-3 cells is related not only to p53 induction but may function through alternative pathways including TGF-β. We conclude that the expression of specific cell cycle-related genes may be entirely or partially regulated by alterations in TGF-β pathway and may play a role in prostate carcinoma development.