CD274 and cancer: Inhibitory immune-checkpoint molecules, including the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1) and its ligand (PD-L1), T-cell immunoglobulin and mucin-domain containing molecule (TIM-3), ligands belonging to the B7 family, and others are promising targets for novel cancer immunotherapeutics.