Immunotherapeutic methods, such as the immune checkpoint inhibitors targeting cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4) or programmed cell death 1 (PD‐1) / programmed cell death 1 ligand (PD‐L1), have made a breakthrough in improving the survival rate of cancer patients, which makes people pay more and more attention on the anti‐tumour properties of the immune system.3, 4, 5. This evidence concerns the gene PDCD1 and cancer.