CTLA4 and cancer: The advent of immune-checkpoint inhibitors (ICIs) which block cytotoxic T lymphocyte-associated protein-4 (CTLA-4) and the programmed death-1 (PD-1)/programmed death ligand-1 (PD-L1) axis, both as monotherapy or in combination strategies, have revolutionized cancer treatment (Pardoll, 2012; Postow et al., 2015; Gong et al., 2018; Liu and Guo, 2018).