Recently, substantial progress has been achieved in cancer treatments by directing cytotoxic T‐lymphocyte antigen‐4 (CTLA‐4), programmed death receptor‐1 (PD‐1) or its associated ligand (PD‐L1) to enhance immunologic responses and anti‐tumor activity, which has significantly improved cancer patient prognosis.1 Despite the impressive clinical benefits, however, the adverse events concomitant with immune checkpoint blockades (ICBs) cannot be ignored. This evidence concerns the gene CTLA4 and cancer.