Then more studies found that hypoxia inducible factor 1 (HIF-1) induced the migration of MDSCs into PMN by up regulating the expression of CCL26 (37), programmed death-ligand 1 (PD-L1) (38) and ectonucleoside triphosphate diphosphohydrolase 2 in tumor cells (39). This evidence concerns the gene HIF1A and neoplasm.