As we know, cell cycle regulation is crucial to cellular DNA damage response to IR, and both of CDK6 and cyclin E2 are essential regulatory factors that drive cell cycle transitions and their activities are under stringent control to ensure normal cell division (17–19), hinting us that CDK6 and cyclin E2 might be involved in the regulation of CRC radiosensitivity by miR-5197. The gene discussed is CCNE2; the disease is colorectal carcinoma.