Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed death 1 (PD-1), and its ligand (PD-L1), as well as the B7 family of immune checkpoints, could be considered to be the main immunotherapy targets to inhibit tumor growth in a variety of cancers [14,15,16]. Here, CTLA4 is linked to cancer.