Checkpoint blockade using antibodies against Programmed Death 1 (PD-1) or its ligand, Programmed Death Ligand 1 (PD-L1), and Cytotoxic T-Lymphocyte-Associated Antigen 4 (CTLA-4) has greatly enhanced the anti-tumor immune response, improving clinical outcomes and leading to durable responses in numerous cancers [4]. This evidence concerns the gene CTLA4 and cancer.