CTLA4 and cancer: Antibodies targeting immunoregulatory molecules such as programmed death-1 (PD-1), its ligand PD-L1, and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) are in widespread use for the treatment of lung, gastric, bladder, kidney, urothelial, head and neck, hepatocellular, and mismatch repair deficient/microsatellite instability-high cancers.