CTLA4 and melanoma: By enhancing the host’s immune response against tumor cells, immune checkpoint inhibitors such as anti programmed death-1 (PD-1)/anti programmed death ligand-1 (PD-L1) and anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) monoclonal antibodies have revolutionized the treatment of multiple cancers including melanoma, non-small cell lung cancer and renal carcinoma [11–13].