Up-regulation of p21(WAF1/CIP1) levels leads to growth suppression of prostate cancer cell lines.

In a previous study, we found that TPA-mediated up-regulation of p21(WAF1/CIP1) induces growth arrest and differentiation of the human prostate cancer cell line TSU-Pr1. We investigated the effect of 12-O-tetra-decanoylphorbol-13-acetate (TPA) on growth and p21(WAF1/CIP1) protein levels in four prostate cancer cell lines. TPA treatment suppressed proliferation of the androgen-insensitive prostate cancer cell lines DU145 and PC-3. DU145 and PC-3 cells, however, showed neither morphological changes nor differentiation after TPA treatment. In contrast, TPA induced apoptosis of the androgen-sensitive prostate cancer cell line LNCaP. TPA induced up-regulation of p21(WAF1/CIP1) protein levels in all four cancer cell lines and this up-regulation was regulated by PKC in all four, but MAP kinase was associated with regulation only in TSU-Pr1 cells. Moreover, transient transfection with Adv-p21 resulted in growth arrest of all four cell lines. These data suggest that increased p21(WAF1/CIP1) production directly suppresses proliferation of prostate cancer cells regardless of androgen sensitivity. The pathway of TPA-induced increases in p21(WAF1/CIP1) levels was regulated by PKC. We thus conclude that p21(WAF1/CIP1) is a good candidate for use in treatment of prostate cancers because it suppresses proliferation of several prostate cancer cell lines.