As shown in Figures 2D,E, the highest apoptotic level was detected and the apoptotic proteins of cleaved caspase 3, cleaved caspase 7, and cleaved caspase 9 but not cleaved caspase 8 were significantly increased in CDK8 knockdown CRC cells after IR treatment, suggesting that downregulation of CDK8 results in radiosensitivity primarily through the intrinsic apoptotic pathway. This evidence concerns the gene CASP7 and colorectal carcinoma.