PDCD1 and neoplasm: The efficiency of the PD-1/PD-L1 pathway to upend the protective shielded blockage against anti-tumor immune responses has been demonstrated in the clinic with anti-PD-L1 ICI blockade in patients with melanoma, non-small cell lung cancer, urothelial carcinoma, Hodgkin lymphoma, head and neck squamous cell carcinoma, renal cell carcinoma (RCC), Merkel cell carcinoma, hepatocellular carcinoma, and gastric carcinomas [35].