Programmed death-1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) are immune checkpoints expressed predominantly on T cells and their inhibition with function-blocking antibodies can enhance antitumor T cell responses.3 4 Antibodies targeting CTLA-4 (ipilimumab) and PD-1 (nivolumab, pembrolizumab) have shown great promise for the treatment of different cancers, including melanoma.5 This evidence concerns the gene CTLA4 and cancer.