The PD-1/PD-L1 pathway is one such immune regulatory nexus that has been shown to have a promising anti-tumor role in the non-small cell lung cancer, head and neck squamous cell carcinoma, cervical cancer, renal cancer, gastric cancer, chronic Hodgkin’s lymphoma, hepatocellular carcinoma, urothelial cancer, and melanoma (12). Here, PDCD1 is linked to melanoma.