Immune checkpoint inhibitors (ICIs) have provided breakthroughs in cancer patients and have been widely used in cancer therapy in the past decade, including the programmed death 1 receptor (PD-1), programmed cell death receptor ligand 1 (PD-L1), and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) blockade. Here, CTLA4 is linked to cancer.