The Programmed Cell Death Protein 1 (PD-1)/Programmed Death-Ligand 1 (PD-L1) pathway is one of the most extensively investigated immune checkpoints, where PD-L1 expressed on tumor cells or within the tumor microenvironment binds to PD-1 on immune cells, leading to immune suppression and facilitating immune escape 17-19. This evidence concerns the gene PDCD1 and neoplasm.