Ectopic expression of the CDK inhibitor p21Cip1 enhances deregulated E2F activity and increases cancer cell-specific cytotoxic gene expression mediated by the ARF tumor suppressor promoter

We show here that ectopic expression of the CDK inhibitor p21Cip1 enhanced deregulated E2F activity and pro-apoptotic E2F target gene expression in cancer cells. Moreover, ectopic expression of p21Cip1 augmented cancer specific cytotoxicity of Ad-ARF-TK, and apoptosis induced by p21Cip1 was dependent on deregulated E2F activity. These results suggest that p21Cip1 specifically enhances deregulated E2F activity and that a combination of the CDK inhibitor with Ad-ARF-TK could be effectively employed for cancer therapy.