Association between MPO-463G > A polymorphism and cancer risk: evidence from 60 case-control studies

Elevated levels of iodide promote peroxidase-mediated protein iodination and inhibit protein chlorination

At inflammatory sites, immune cells generate oxidants including H₂O₂. Myeloperoxidase (MPO), released by activated leukocytes employs H₂O₂ and halide/pseudohalides to form hypohalous acids that mediate pathogen killing. Hypochlorous acid (HOCl) is a major species formed. Excessive or misplaced HOCl formation damages host tissues with this linked to multiple inflammatory diseases. Previously (Redox Biology, 2020, 28, 101331) we reported that iodide (I⁻) modulates MPO-mediated protein damage by decreasing HOCl generation with concomitant hypoiodous acid (HOI) formation. HOI may however impact on protein structure, so in this study we examined whether and how HOI, from peroxidase/H₂O₂/I⁻ systems ± Cl⁻, modifies proteins. Experiments employed MPO and lactoperoxidase (LPO) and multiple proteins (serum albumins, anastellin), with both chemical (intact protein and peptide mass mapping, LC-MS) and structural (SDS-PAGE) changes assessed. LC-MS analyses revealed dose-dependent iodination of anastellin and albumins by LPO/H2O2 with increasing I⁻. Incubation of BSA with MPO/H2O2/Cl⁻ revealed modest chlorination (Tyr286, Tyr475, ∼4 %) and Met modification. Lower levels of these species, and extensive iodination at specific Tyr and His residues (>20 % modification with ≥10 μM I⁻) were detected with increasing I⁻. Anastellin dimerization was inhibited by increasing I⁻, but less marked changes were observed with albumins. These data confirm that I⁻ competes with Cl⁻ for MPO and is an efficient HOCl scavenger. These processes decrease protein chlorination and oxidation, but result in extensive iodination. This is consistent with published data on the presence of iodinated Tyr on neutrophil proteins. The biological implications of protein iodination relative to chlorination require further clarification.

Myeloperoxidase creates a permissive microenvironmental niche for the progression of multiple myeloma

Expression of myeloperoxidase (MPO), a key inflammatory enzyme restricted to myeloid cells, is negatively associated with the development of solid tumours. Activated myeloid cell populations are increased in multiple myeloma (MM); however, the functional consequences of myeloid-derived MPO within the myeloma microenvironment are unknown. Here, the role of MPO in MM pathogenesis was investigated, and the capacity for pharmacological inhibition of MPO to impede MM progression was evaluated. In the 5TGM1-KaLwRij mouse model of myeloma, the early stages of tumour development were associated with an increase in CD11b+ myeloid cell populations and an increase in Mpo expression within the bone marrow (BM). Interestingly, MM tumour cell homing was increased towards sites of elevated myeloid cell numbers and MPO activity within the BM. Mechanistically, MPO induced the expression of key MM growth factors, resulting in tumour cell proliferation and suppressed cytotoxic T-cell activity. Notably, tumour growth studies in mice treated with a small-molecule irreversible inhibitor of MPO (4-ABAH) demonstrated a significant reduction in overall MM tumour burden. Taken together, our data demonstrate that MPO contributes to MM tumour growth, and that MPO-specific inhibitors may provide a new therapeutic strategy to limit MM disease progression.

Myeloperoxidase: Growing importance in cancer pathogenesis and potential drug target

Myeloperoxidase is a heme-peroxidase which makes up approximately 5% of the total dry cell weight of neutrophils where it is predominantly found in the primary (azurophilic) granules. Other cell types, such as monocytes and certain macrophage subpopulations also contain myeloperoxidase, but to a much lesser extent. Initially, the function of myeloperoxidase had been mainly associated with its ability as a catalyzer of reactive oxidants that help to clear pathogens. However, over the past years non-canonical functions of myeloperoxidase have been described both in health and disease. Attention has been specially focused on inflammatory diseases, in which an exacerbate infiltration of leukocytes can favor a poorly-controlled production and release of myeloperoxidase and its oxidants. There is compelling evidence that myeloperoxidase derived oxidants contribute to tissue damage and the development and propagation of acute and chronic vascular inflammation. Recently, neutrophils have attracted much attention within the large diversity of innate immune cells that are part of the tumor microenvironment. In particular, neutrophil-derived myeloperoxidase may play an important role in cancer development and progression. This review article aims to provide a comprehensive overview of the roles of myeloperoxidase in the development and progression of cancer. We propose future research approaches and explore prospects of inhibiting myeloperoxidase as a strategy to fight against cancer.

Role of myeloperoxidase and oxidant formation in the extracellular environment in inflammation-induced tissue damage

The heme peroxidase family generates a battery of oxidants both for synthetic purposes, and in the innate immune defence against pathogens. Myeloperoxidase (MPO) is the most promiscuous family member, generating powerful oxidizing species including hypochlorous acid (HOCl). Whilst HOCl formation is important in pathogen removal, this species is also implicated in host tissue damage and multiple inflammatory diseases. Significant oxidant formation and damage occurs extracellularly as a result of MPO release via phagolysosomal leakage, cell lysis, extracellular trap formation, and inappropriate trafficking. MPO binds strongly to extracellular biomolecules including polyanionic glycosaminoglycans, proteoglycans, proteins, and DNA. This localizes MPO and subsequent damage, at least partly, to specific sites and species, including extracellular matrix (ECM) components and plasma proteins/lipoproteins. Biopolymer-bound MPO retains, or has enhanced, catalytic activity, though evidence is also available for non-catalytic effects. These interactions, particularly at cell surfaces and with the ECM/glycocalyx induce cellular dysfunction and altered gene expression. MPO binds with higher affinity to some damaged ECM components, rationalizing its accumulation at sites of inflammation. MPO-damaged biomolecules and fragments act as chemo-attractants and cell activators, and can modulate gene and protein expression in naïve cells, consistent with an increasing cycle of MPO adhesion, activity, damage, and altered cell function at sites of leukocyte infiltration and activation, with subsequent tissue damage and dysfunction. MPO levels are used clinically both diagnostically and prognostically, and there is increasing interest in strategies to prevent MPO-mediated damage; therapeutic aspects are not discussed as these have been reviewed elsewhere.

Myeloperoxidase and CYBA genetic variants in polycystic ovary syndrome

BACKGROUND

Oxidative stress plays a pivotal role in the pathogenesis of polycystic ovary syndrome (PCOS). Genetic variations in myeloperoxidase (MPO; G-463A) and NADPH oxidase p22phox subunit (CYBA; C242T) cause inter-individual variability in enzyme activities. Here, we investigated the associations between MPO activity and the MPO G-463A and CYBA C242T polymorphisms in Chinese women with PCOS.

METHODS

This case-control study included 1003 patients with PCOS and 810 controls. The G-463A and C242T polymorphisms were detected by polymerase chain reaction and restriction analysis, and clinical, hormonal, metabolic and oxidative stress parameters and MPO activity were analysed.

RESULTS

The frequencies of the GA + AA genotype and A allele frequency of the MPO G-463A polymorphism were significantly higher in the PCOS group than in the control group. Logistic regression analysis showed that the MPO-463A allele is a risk factor for PCOS (OR = 1.261, 95% CI: 1.042-1.526, P = .017). Patients with the AA genotype tended to have higher plasma MPO activity than those with the GG genotype. No statistical significance was found in the genotype and allele frequencies of the CYBA C242T polymorphism between the PCOS and control groups. However, we demonstrated that the coexistence of the MPO A allele (GA + AA genotypes) and the CYBA CC genotype was associated with an increased risk of PCOS when compared with the wild-type GG/CC genotypes (OR = 1.302, 95% CI: 1.030-1.646, P = .027).

CONCLUSION

The MPO G-463A variant, but not CYBA C242T variant, is associated with a risk of PCOS in Chinese women.

The Role of Myeloperoxidase in Biomolecule Modification, Chronic Inflammation, and Disease

Significance: The release of myeloperoxidase (MPO) by activated leukocytes is critical in innate immune responses. MPO produces hypochlorous acid (HOCl) and other strong oxidants, which kill bacteria and other invading pathogens. However, MPO also drives the development of numerous chronic inflammatory pathologies, including atherosclerosis, neurodegenerative disease, lung disease, arthritis, cancer, and kidney disease, which are globally responsible for significant patient mortality and morbidity. Recent Advances: The development of imaging approaches to precisely identify the localization of MPO and the molecular targets of HOCl in vivo is an important advance, as typically the involvement of MPO in inflammatory disease has been inferred by its presence, together with the detection of biomarkers of HOCl, in biological fluids or diseased tissues. This will provide valuable information in regard to the cell types responsible for releasing MPO in vivo, together with new insight into potential therapeutic opportunities. Critical Issues: Although there is little doubt as to the value of MPO inhibition as a protective strategy to mitigate tissue damage during chronic inflammation in experimental models, the impact of long-term inhibition of MPO as a therapeutic strategy for human disease remains uncertain, in light of the potential effects on innate immunity. Future Directions: The development of more targeted MPO inhibitors or a treatment regimen designed to reduce MPO-associated host tissue damage without compromising pathogen killing by the innate immune system is therefore an important future direction. Similarly, a partial MPO inhibition strategy may be sufficient to maintain adequate bacterial activity while decreasing the propagation of inflammatory pathologies.

Efficacy analysis of trastuzumab, carboplatin and docetaxel in HER-2-positive breast cancer patients

Efficacy of trastuzumab, carboplatin and docetaxel in human epidermal growth factor receptor-2 (HER-2)-positive breast cancer patients was investigated. A total of 180 HER-2-positive breast cancer patients admitted to The First People's Hospital of Yunnan Province were selected, of which 80 patients were treated with carboplatin and docetaxel and served as the control group (CG), and 100 patients were treated with trastuzumab, carboplatin and docetaxel and served as the research group (RG). Clinical efficacy, pathological efficacy, adverse reactions, inflammatory factors interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), cellular immune indexes of T-lymphocyte subsets (CD4⁺, CD8⁺, CD4⁺/CD8⁺), and the oxidative stress indexes superoxide dismutase (SOD) and myeloperoxidase (MPO) were observed before and after treatment and were compared between both groups. Patients were followed up for 5 years, and the 5-year disease-free survival (DFS), as well as the overall survival (OS) were compared. Clinical efficacy and pathological efficacy in the RG were significantly higher than those in the CG, and the incidence rate of adverse reactions had no significant difference between the two groups. There was no significant difference in inflammatory factors, cellular immune indexes and oxidative stress indexes between the two groups before treatment. After treatment, the levels of IL-6, TNF-α, CD8⁺ and MPO in both groups were significantly reduced and were significantly lower in RG than those in CG. However, the levels of CD4⁺, CD4⁺/CD8⁺ and SOD in both groups were significantly increased after treatment and were significantly higher in RG than those in CG. The 5-year DFS and OS of the RG were significantly higher than those of the CG. In conclusion, trastuzumab, carboplatin and docetaxel present high efficacy, safety, and 5-year DFS and OS in HER-2-positive breast cancer patients, and have good recovery effect on inflammation, immune response and oxidative stress.

Human myeloperoxidase (hMPO) is expressed in neurons in the substantia nigra in Parkinson's disease and in the hMPO-α-synuclein-A53T mouse model, correlating with increased nitration and aggregation of α-synuclein and exacerbation of motor impairment

α-Synuclein (αSyn) is central to the neuropathology of Parkinson's disease (PD) due to its propensity for misfolding and aggregation into neurotoxic oligomers. Nitration/oxidation of αSyn leads to dityrosine crosslinking and aggregation. Myeloperoxidase (MPO) is an oxidant-generating enzyme implicated in neurodegenerative diseases. In the present work we have examined the impact of MPO in PD through analysis of postmortem PD brain and in a novel animal model in which we crossed a transgenic mouse expressing the human MPO (hMPO) gene to a mouse expressing human αSyn-A53T mutant (A53T) (hMPO-A53T). Surprisingly, our results show that in PD substantia nigra, the hMPO gene is expressed in neurons containing aggregates of nitrated αSyn as well as MPO-generated HOCl-modified epitopes. In our hMPO-A53T mouse model, we also saw hMPO expression in neurons but not mouse MPO. In the mouse model, hMPO was expressed in neurons colocalizing with nitrated αSyn, carbamylated lysine, nitrotyrosine, as well as HOCl-modified epitopes/proteins. RNAscope in situ hybridization confirmed hMPO mRNA expression in neurons. Interestingly, the hMPO protein expressed in hMPO-A53T brain is primarily the precursor proMPO, which enters the secretory pathway potentially resulting in interneuronal transmission of MPO and oxidative species. Importantly, the hMPO-A53T mouse model, when compared to the A53T model, exhibited significant exacerbation of motor impairment on rotating rods, balance beams, and wire hang tests. Further, hMPO expression in the A53T model resulted in earlier onset of end stage paralysis. Interestingly, there was a high concentration of αSyn aggregates in the stratum lacunosum moleculare of hippocampal CA2 region, which has been associated in humans with accumulation of αSyn pathology and neural atrophy in dementia with Lewy bodies. This accumulation of αSyn aggregates in CA2 was associated with markers of endoplasmic reticulum (ER) stress and the unfolded protein response with expression of activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), MPO, and cleaved caspase-3. Together these findings suggest that MPO plays an important role in nitrative and oxidative damage that contributes to αSyn pathology in synucleinopathies.

The possible association between the presence of an MPO -463 G > A (rs2333227) polymorphism and cervical cancer risk

PURPOSE

The association between myeloperoxidase (MPO) polymorphism and the risk of cervical cancer is inconclusive. We performed a meta-analysis to clarify if a correlation exists between MPO polymorphism and the risk for developing cervical cancer.

METHODS

All case-control research studies that determined a relationship between MPO and cervical cancer reported up until March 1, 2018 in PubMed, Web of Science, VIP, WanFang, and the CNKI Database were accessed and included. The strength of association was evaluated with pooled odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs). We used sensitivity analysis to detect the stability of our results, conducted Q-test to evaluate heterogeneity and applied Begg's funnel plot and Egger's test to investigate any publication bias among selected studies.

RESULTS

In this meta-analysis, we included 5 eligible studies in the final evaluation, which included 1125 patients with cervical cancer and 1150 cancer-free control patients. A potential association between the MPO -463 G > A polymorphism and cervical cancer risk was observed (recessive model: OR = 0.65, 95%, CI: 0.43-0.98, P = 0.038; homozygous model: OR = 0.65, 95%, CI: 0.43-0.99, P = 0.045), which indicates that genotype AA reduces the risk of cervical cancer by 35% compared to GG/GA or GG genotypes in our results. A stratified analysis by ethnicity identified a significant correlation among Caucasian patients (recessive model: OR = 0.57, 95%, CI: 0.34-0.95, P = 0.029; homozygous model: OR = 0.60, 95%, CI: 0.36-0.99, P = 0.048) and a stratified analysis by source of control identified a significant correlation among population-based studies.

CONCLUSIONS

Our results suggest that the presence of polymorphism, -463 G > A in patients might offer them protection against cervical cancer. By implementing randomized case-control or cohort studies with larger sample sizes, the clinical significance of our results can be further strengthened and verified.

Relationship of SNP rs2645429 in Farnesyl-Diphosphate Farnesyltransferase 1 Gene Promoter with Susceptibility to Lung Cancer

Background and Purpose

The mevalonate pathway is one of the major metabolic pathways that use acetyl-CoA to produce sterols and isoprenoids. These compounds can be effective in the growth and development of tumors. One of the enzymes involved in the mevalonate pathway is FDFT1. Different variants of this gene are involved in the risk of suffering various diseases. The present study examined the relationship between FDFT1 rs2645429 polymorphism and the risk of nonsmall cell lung cancer (NSCLC) in a population from southern Iran.

Method

The genotypes of rs2645429 polymorphism of FDFT1 gene were examined in 95 samples: 34 patients with NSCLC and 61 healthy individuals by RFLP method.

Results

The results of this study indicated that C allele of this polymorphism was effectively associated with the risk of NSCLC in the Iranian population (p value = 0.023; OR = 2.71; 95% CI = 1.12–6.59) and CC genotype has significant relation with susceptibility to NSCLC (p value = 0.029; OR = 3.02; 95% CI = 1.09–8.39). This polymorphism is located in the promoter region FDFT1 gene, and CC genotype may increase the activity of this promoter. This study also found a significant relationship between C allele and metastatic status. C allele was more common in NSCLC patients. (p = 0.04).

Conclusion

C allele of FDFT1 rs2645429 polymorphism gene can be a risk factor for NSCLC, whereas T allele probably has a low protective role.