PDCD1 and cancer: By the better understanding of the interaction between the immune system and tumor cells, treatment of non-small cell lung cancer (NSCLC) has recently been implemented with the introduction of immune checkpoint inhibitors, such as monoclonal antibodies directed against cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) pathway, which boost the host’s own immune response against cancer [1].