CTLA4 and cancer: By interacting with programmed cell death 1/ligand 1(PD-1/PD-L1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), ICIs prevent cancers from escaping from antitumor immune response, leading to significant improvement in clinical outcome (Dafni et al., 2019; Davern and Lysaght, 2020; Galluzzi et al., 2020).