Effects of protein kinase inhibitors on radiation-induced WAF1 accumulation in human cultured melanoma cells.

To examine whether protein kinase C (PKC) and A (PKA) contribute to WAF1 induction by ionizing radiation (IR) in cultured human melanomas, the effect of PK inhibitors 1-(5'-isoquinolinesulphonyl)-2-methylpiperazine dihydrochloride (H7), bisindolylmaleimide (GF) and N-[2(p-dromocinnamylamino)ethyl]-5-isoquinolinesulphonamide (H89) on IR-induced WAF1 accumulation was analysed by Western blot analysis. Gamma-ray-induced accumulation of WAF1 showed a peak at 6 Gy in all the cell lines. After gamma-ray irradiation of 6 Gy, a peak of WAF1 accumulation was observed at 6 h in SK-Mel-26, G361 and HM6KO cells, and at 3 h in MeWo cells. In MeWo and SK-Mel-26 cells, the X-ray-induced WAF1 accumulation was decreased by PK inhibitors, GF (PKC inhibitor) or H89 (PKA inhibitor); this did not occur in G361 and HM6KO. In all the cell lines, accumulation of WAF1 induced by X-ray irradiation was suppressed by H7 (PKC and PKA inhibitor). In addition, polymerase chain reaction-single strand conformational polymorphism analysis detected no aberrations in the p53 gene of the four cell lines used. These results suggest that IR-induced WAF1 expression involves PKC and/or PKA activity depending on cell type.