CTLA4 and cancer: The indications for use of ICIs targeting the inhibitory immune checkpoints PD-1/PD-L1 and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) have grown exponentially over the past few years, and these drugs, especially antibodies targeting the PD-1/PD-L1 axis, are currently used for the treatment of a wide variety of cancers [38].