PDCD1 and neoplasm: Adding CXCR4 blockade to PD-1 targeted therapy increased tumor cell death concomitantly with lymphocyte expansion [56], thus ongoing trials are evaluating the efficacy of targeting CXCR4–CXCL12 axis in potentiating the immune checkpoint inhibitors-based therapy in pancreatic cancer (NCT03277209, NCT02907099 NCT04177810).