Many of these promising therapeutic strategies, which can lead to strong antitumour responses and even long-term tumour remission, are based on the blockade of the activation of immune inhibitory receptors such as programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1) and cytotoxic T lymphocyte–associated protein 4 (CTLA-4) [1, 2]. The gene discussed is PDCD1; the disease is neoplasm.