Resveratrol-induced G₂ arrest through the inhibition of CDK7 and p34^CDC2 kinases in colon carcinoma HT29 cells

Resveratrol (3,5,4′-trihydroxystilbene), a phytoalexin found in grapes and other food products, has been shown to have cancer chemopreventive activity. However, the mechanism of the anti-carcinogenic activity is not well understood. Here, we offer a possible explanation of its anti-tumor effect. Based on flow cytometric analysis, resveratrol inhibited the proliferation of HT29 colon cancer cells and resulted in their accumulation in the G2 phase of the cell cycle. Western blot analysis and kinase assays demonstrated that the perturbation of G2 phase progression by resveratrol was accompanied by the inactivation of p34CDC2 protein kinase, and an increase in the tyrosine phosphorylated (inactive) form of p34CDC2. Kinase assays revealed that the reduction of p34CDC2 activity by resveratrol was mediated through the inhibition of CDK7 kinase activity, while CDC25A phosphatase activity was not affected. In addition, resveratrol-treated cells were shown to have a low level of CDK7 kinase-Thr161-phosphorylated p34CDC2. These results demonstrated that resveratrol induced cell cycle arrest at the G2 phase through the inhibition of CDK7 kinase activity, suggesting that its anti-tumor activity might occur through the disruption of cell division at the G2/M phase.