CTLA4 and cancer: Large‐scale clinical trials have demonstrated that immune checkpoint inhibitors (ICIs), such as anti‐programmed cell death 1 (anti‐PD‐1), anti‐programmed cell death ligand 1 (anti‐PD‐L1), anti‐cytotoxic T‐lymphocyte antigen 4 (anti‐CTLA‐4), play a revolutionary role in improving the prognosis of various cancers.2, 3, 4, 5, 6, 7, 8, 9, 10