CTLA4 and cancer: ICIs are promising novel agents for malignancies, which work by blocking inhibitory immune checkpoint pathways to reactivate immune responses against cancer, such as anti-programmed death-1 (anti-PD-1), anti-programmed death-1 ligand (anti-PD-L1), and anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) antibodies (Ferris, 2015).