Immune evasion is one of the hallmarks of cancer [2], especially driven by immune suppression through cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) or programmed cell death protein 1 (PD-1), both immunomodulatory receptors expressed on immune T cells [3], with an emerging amount of preclinical and clinical data centered around the immune checkpoint PD-1 and its ligand PD-L1 [4]. This evidence concerns the gene PDCD1 and cancer.