PDCD1 and neoplasm: Given the immunosuppressive role of CXCR2-recruited MDSC in the tumor microenvironment, CXCR2 antagonists like navarixin might complement the action of programmed cell death protein 1 (PD-1) or programmed cell death ligand 1 (PD-L1) inhibitors in tumor types with low response rates to these agents.