CTLA4 and cancer: Immune checkpoint inhibitors (ICIs) have been considered as an emerging standard-of-care for a variety of cancers, greatly improve the prognosis of advanced cancer.[1] ICIs mainly target the programmed death protein-1 (PD-1), programmed death-ligand 1 (PD-L1), or cytotoxic-T lymphocyte-antigen-4 (CTLA-4) to regulate the immune response.[2] Due to their effect of immune system, especially T cell activity, immune-related adverse effects (irAEs) have always been reported.