The strategy of blocking inhibitory immune checkpoints such as cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), programmed death ligand 1 (PD-L1), and lymphocyte activation gene 3 (LAG-3) has revolutionized the landscape of cancer treatment. This evidence concerns the gene CTLA4 and cancer.