Melatonin, used for insomnia in usual, was found to reduce cell viability, promote apoptosis, and reverse 5‐FU resistance in SW480/5‐FU and HCT116/5‐FU cells by downregulating thymidylate synthase (TYMS) via upregulating miR‐215‐5p.24 The gene discussed is TYMS; the disease is insomnia.