CTLA4 and cancer: The discovery of the immune-checkpoint inhibitors [(ipilimumab, an anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) antibody, programmed death 1 (PD-1) and programmed death-ligand 1 (PD-L1)], has placed immunotherapy to the front-line of cancer treatment, especially for advanced NSCLC (197, 198).