Native Myeloperoxidase (pANCA) (>95%)

DCs are a critical component of immune responses in cancer primarily due to their ability to cross-present tumor-associated antigens. Cross-presentation by DCs in cancer is impaired, which may represent one of the obstacles for the success of cancer immunotherapies. Here, we report that polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) blocked cross presentation by DCs without affecting direct presentation of antigens by these cells. This effect did not require direct cell-cell contact and was associated with transfer of lipids. Neutrophils (PMN) and PMN-MDSC transferred lipid to DCs equally well; however, PMN did not affect DC cross-presentation. PMN-MDSC generate oxidatively truncated lipids previously shown to be involved in impaired cross-presentation by DCs. Accumulation of oxidized lipids in PMNMDSC was dependent on myeloperoxidase (MPO). MPO-deficient PMN-MDSC did not affect cross-presentation by DCs. Cross-presentation of tumor-associated antigens in vivo by DCs was improved in MDSC-depleted or tumor-bearing MPO-KO mice. Pharmacological inhibition of MPO in combination with checkpoint blockade reduced tumor progression in different tumor models. These data suggest MPO-driven lipid peroxidation in PMN-MDSC as a possible non-cell autonomous mechanism of inhibition of antigen cross-presentation by DCs and propose MPO as potential therapeutic target to enhance the efficacy of current immunotherapies for patients with cancer.

Previous studies shown that myeloperoxidase (MPO) level is higher in patients with atrial fibrillation (AF); however, no genetic evidence betweenMPOand AF risk in human population was observed. Therefore, the present study was aimed to investigate the association between rs2243828, a variant in promoter region ofMPOand the risk of AF in Chinese GeneID population. The results demonstrated that the minor G allele of rs2243828 showed a significant association with AF in two independent population (GeneID-north population with 694 AF cases and 710 controls, adjustedP(-adj) = 6.25 x 10(-3)with an odds ratio was 0.77, GeneID-central population with 1106 cases and 1501 controls,P-adj = 9.88 x 10(-5)with an odds ratio was 0.75). The results also showed G allele was significantly associated with lower plasma concentration of myeloperoxidase in general population. We also observed a significant difference of odds ratio between subgroups of hypertension and non-hypertension. Therefore, our findings identified variant inMPOassociated with risk of AF and it may give strong evidence to link the inflammation with the incidence of AF.