Currently, four immune checkpoint inhibitors (ICI) are approved for treatment of cancer, including ipilimumab (anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA4)), nivolumab, pembrolizumab (anti-programmed death-1 (anti-PD-1)), and atezolizumab (anti-programmed death ligand-1 (anti-PD-L1)). This evidence concerns the gene CTLA4 and cancer.