CTLA4 and cancer: In recent years, cancer immunotherapy has achieved revolutionary improvements in the treatment of many cancers, especially antibodies against cytotoxic T lymphocyte‐associated antigen‐4 (CTLA‐4), programmed death‐1 (PD‐1), and programmed death‐ligand 1 (PD‐L1), which have brought significant survival benefits [6, 7, 8, 9].