PDCD1 and cancer: The new immunotherapies aimed at targeting of immunosuppressive checkpoint receptors, using antibodies against the inhibitory programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) pathway or cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) pathway, have vigorously changed the landscape of anti-cancer immunotherapy in the last decades (1).