GPx-1 polymorphism (rs1050450) contributes to tumor susceptibility: evidence from meta-analysis

The Role of Selenium and Manganese in the Formation, Diagnosis and Treatment of Cervical, Endometrial and Ovarian Cancer

Selenium (Se) and manganese (Mn) are essential micronutrients that are important elements of cell metabolism. They are involved in the composition of enzyme systems and regulate enzyme activity. Disturbances in the homeostasis of these micronutrients affect the development of many diseases and carcinogenesis, which can be linked to increased levels of oxidative stress and impaired antioxidant properties of many enzymes. Selenium has a very important function in maintaining immune-endocrine, metabolic and cellular homeostasis. Manganese, on the other hand, is important in development, digestion, reproduction, antioxidant defense, energy production, immune response and regulation of neuronal activity. We review the role of selenium and manganese and their effects on tumor growth, metastasis potential and remodeling of the microenvironment. We also describe their role as potential biomarkers in the diagnosis and the potential for the use of Se- and Mn-containing compounds in composition for the treatment of cancer of the reproductive organs.

Polymorphisms of Antioxidant Enzymes SOD2 (rs4880) and GPX1 (rs1050450) Are Associated with Bladder Cancer Risk or Its Aggressiveness

Background and Objectives: Oxidative stress induced by increased reactive oxygen species (ROS) production plays an important role in carcinogenesis. The entire urinary tract is continuously exposed to numerous potentially mutagenic environmental agents which generate ROS during their biotransformation. In first line defense against free radicals, antioxidant enzymes superoxide dismutase (SOD2) and glutathione peroxidase (GPX1) both have essential roles. Altered enzyme activity and decreased ability of neutralizing free oxygen radicals as a consequence of genetic polymorphisms in genes encoding these two enzymes are well described so far. This study aimed to investigate the association of GPX1 (rs1050450) and SOD2 (rs4880) genetic variants with the urothelial bladder cancer (UBC) risk independently and in combination with smoking. Furthermore, we aimed to determine whether the UBC stage and pathological grade were influenced by GPX1 and SOD2 polymorphisms. Material and Methods: The study population included 330 patients with UBC (mean age 65 ± 10.3 years) and 227 respective controls (mean age 63.4 ± 7.9 years). Single nucleotide polymorphism (SNP) of GPX1 (rs1050450) was analyzed using the PCR-RFLP, while SOD2 (rs4880) SNP was analyzed using the q-PCR method. Results: Our results showed that UBC risk was significantly increased among carriers of at least one variant SOD2 Val allele compared to the SOD2 Ala16Ala homozygotes (OR = 1.55, p = 0.03). Moreover, this risk was even more pronounced in smokers with at least one variant SOD2 Val allele, since they have even 7.5 fold higher UBC risk (OR = 7.5, p < 0.001). Considering GPX1 polymorphism, we have not found an association with UBC risk. However, GPX1 genotypes distribution differed significantly according to the tumor stage (p ˂ 0.049) and pathohistological grade (p ˂ 0.018). Conclusion: We found that SOD2 genetic polymorphism is associated with the risk of UBC development independently and in combination with cigarette smoking. Furthermore, we showed that GPX1 genetic polymorphism is associated with the aggressiveness of the disease.

Glutathione Peroxidase GPX1 and Its Dichotomous Roles in Cancer

As the first identified selenoprotein, glutathione peroxidase 1 (GPX1) is a widely and abundantly expressed antioxidant enzyme. GPX1 utilizes glutathione as a substrate to catalyze hydrogen peroxide, lipid peroxide, and peroxynitrite, thereby reducing intracellular oxidative stress. The GPX1 gene is regulated at transcriptional, post-transcriptional, and translational levels. Numerous case-control studies and meta-analyses have assessed the association between a functional genetic polymorphism of the GPX1 gene, named Pro198Leu (rs1050450 C>T), and cancer susceptibility in different populations. GPX1 polymorphism has type-specific effects as a candidate marker for cancer risk, but the association between GPX1 variants and cancer susceptibility remains controversial in different studies. GPX1 is abnormally elevated in most types of cancer but has complex dichotomous roles as tumor suppressor and promoter in different cancers. GPX1 can participate in various signaling pathways to regulate tumor biological behaviors, including cell proliferation, apoptosis, invasion, immune response, and chemoresistance. In this review, we comprehensively summarize the controversial associations between GPX1 polymorphism and cancer risks and further discuss the relationships between the aberrant expressions of GPX1 and tumorigenesis. Further studies are needed to elucidate the clinical significance of GPX1 as a potential prognostic biomarker and novel therapeutic target in various malignancies.

Human glutathione peroxidase codon 198 variant increases nasopharyngeal carcinoma risk and progression

PURPOSE

Glutathione peroxidase 1 (GPx-1) is a selenium-dependent detoxifying enzyme involved in the protection of cells against oxidative damage. Some genetic association studies reported significant associations between GPx-1 Pro198Leu variant and carcinogenesis across different populations; however, the impact of this variant on nasopharyngeal carcinoma (NPC) has not been explored. Therefore, the present study was planned to evaluate the potential involvement of the GPx-1 Pro198Leu variant and plasma GPx activity in the risk of developing NPC in a Tunisian population.

METHODS

The GPx-1 Pro198Leu genotype was determined in 327 NPC patients and 150 healthy controls by the RFLP-PCR analysis. The correlation between the GPx-1 variant and the clinicopathological parameters was examined. GPx activity was assessed in the plasma of 119 NPC patients and 58 healthy control subjects and according to GPx-1 genotypes and clinicopathological characteristics of NPC patients.

RESULTS

A significant association was found between GPx-1 Pro198Leu variant and NPC risk in a Tunisian population. The allelic frequencies of Pro and Leu alleles were 32% versus 68% and 41% versus 59% in NPC cases and controls, respectively. Thus, the minor 198 Leu allele increased significantly in NPC patients and appeared as a potential risk factor for NPC occurrence (OR = 1.48, CI 95% = 1.14-1.91, p = 0.002). The plasma GPx activity was significantly higher in NPC patients than in controls (p = 0.03). According to the clinicopathological characteristics of NPC patients, GPx activity decreased significantly in patients with lymph node metastasis (p = 0.004).

CONCLUSION

This is the first study showing a strong association between GPx-1 Pro198Leu genetic variant and NPC risk. GPx-1 Pro198Leu variant increased the development of regional lymph node metastasis. Plasma GPx activity was higher in NPC patients. Thus, GPx-1 gene could be considered as a determinant factor influencing NPC risk and progression.

The Association of Polymorphisms in Nrf2 and Genes Involved in Redox Homeostasis in the Development and Progression of Clear Cell Renal Cell Carcinoma

Deleterious effects of SNPs found in genes encoding transcriptional factors, as well as antioxidant and detoxification enzymes, are disputable; however, their functional significance seems to modify the risk for clear cell renal cell carcinoma (ccRCC) development and progression. We investigated the effect of specific Nrf2, SOD2, GPX1 gene variants and GSTP1ABCD haplotype on ccRCC risk and prognosis and evaluated the association between GSTP1 and regulatory (JNK1/2) and executor (caspase-3) apoptotic molecule expression in ccRCC tissue samples and the presence of GSTP1 : JNK1/2 protein : protein interactions. Genotyping was performed in 223 ccRCC patients and 336 matched controls by PCR-CTTP and qPCR. Protein expression was analyzed using immunoblot, while the existence of GSTP1 : JNK1 protein : protein interactions was investigated by immunoprecipitation experiments. An increased risk of ccRCC development was found among carriers of variant genotypes of both SOD2 rs4880 and GSTP1 rs1695 polymorphisms. Nrf2 rs6721961 genetic polymorphism in combination with both rs4880 and rs1695 showed higher ccRCC risk as well. Haplotype analysis revealed significant risk of ccRCC development in carriers of the GSTP1C haplotype. Furthermore, GSTP1 variant forms seem to affect the overall survival in ccRCC patients, and the proposed molecular mechanism underlying the GSTP1 prognostic role might be the presence of GSTP1 : JNK1/2 protein : protein interactions.

Association between glutathione peroxidase 1 codon 198 variant and the occurrence of breast cancer in Rwanda

BACKGROUND

Glutathione peroxidase 1 gene (GPX1) is one of the antioxidant enzyme that remove the reactive oxygen species in a continuous process. Since the identification of a well-characterized functional polymorphism named p.Pro198Leu (rs1050450 C>T) in GPX1 gene, abundant studies have evaluated the association between p.Pro198Leu polymorphism and tumor risk in diverse population. But, the available results related to breast cancer are conflicting and absent in Africa. The present case-control study was planned to assess the presence of GPX1 Pro198Leu polymorphism in Rwanda population to determine whether it is associated with the risk of developing breast cancer.

METHODS

Genomic DNA from peripheral blood leukocytes of 41 patients with breast cancer and 42 healthy controls were enrolled and genotyped GPX1 Pro198Leu polymorphism by PCR amplification and DNA sequencing.

RESULTS

No significant difference in the frequencies of Pro/Pro (49%) and Pro/Leu (51%) genotypes in cancer cases and in controls (50% each) were found. The allelic frequencies of Pro and Leu were 74% versus 26% and 75% versus 25% in breast cancer cases and controls respectively. No association was observed in allele frequencies of Pro and Leu, and familial history. Only an overall association of GPX1 Pro198Leu with grade of cancer (Pro/Leu vs. Pro/Pro: p = .0200) was detected.

CONCLUSION

The result of this study suggested that GPX1 Pro198Leu polymorphism could not be a risk factor for breast cancer in Rwanda. However, large-scale studies on the effect of this polymorphism on the factors disturbing the redox homeostasis are needed for conclusive understanding.

Allele-specific interaction between glutathione peroxidase 1 and manganese superoxide dismutase affects the levels of Bcl-2, Sirt3 and E-cadherin

Manganese superoxide dismutase (MnSOD) is a mitochondrial-resident enzyme that reduces superoxide to hydrogen peroxide (H₂O₂), which can be further reduced to water by glutathione peroxidase (GPX1). Data from human studies have indicated that common polymorphisms in both of these proteins are associated with the risk of several cancers, including breast cancer. Moreover, polymorphisms in MnSOD and GPX1 were shown to interact to increase the risk of breast cancer. To gain an understanding of the molecular mechanisms behind these observations, we engineered human MCF-7 breast cancer cells to exclusively express GPX1 and/or MnSOD alleles and investigated the consequences on the expression of several proteins associated with cancer aetiology. Little or no effect was observed on the ectopic expression of these genes on the phosphorylation of Akt, although allele-specific effects and interactions were observed for the impact on the levels of Bcl-2, E-cadherin and Sirt3. The patterns observed were not consistent with the steady-state levels of H₂O₂ determined in the transfected cells. These results indicate plausible contributing factors to the effects of allelic variations on cancer risk observed in human epidemiological studies.

Functional polymorphisms in antioxidant genes in Hurthle cell thyroid neoplasm - an association of GPX1 polymorphism and recurrent Hurthle cell thyroid carcinoma

Background

Hurthle cells of the thyroid gland are very rich in mitochondria and oxidative enzymes. As a high level oxidative metabolism may lead to higher level of oxidative stress and can be associated with an increased risk for cancer, we investigated whether common functional polymorphisms in antioxidant genes (SOD2, CAT, GPX, GSTP1, GSTM1 and GSTT1) are associated with the development or clinical course of Hurthle cell thyroid carcinoma (HCTC).

Methods

A retrospective study was performed in 139 patients treated by thyroid surgery for a Hurthle cell neoplasm. HCTC, Hurthle cell thyroid adenoma (HCTA) or Hurthle cell thyroid nodule (HCTN) were diagnosed by pathomorphology. DNA was extracted from cores of histologically confirmed normal tissue obtained from formalin-fixed paraffin-embedded specimens and genotyped for investigated polymorphisms. Logistic regression was used to compare genotype distributions between patient groups.

Results

HCTC, HCTA and HCTN were diagnosed in 53, 47 and 21 patients, respectively. Metastatic disease and recurrence of HCTC were diagnosed in 20 and 16 HCTC patients, respectively. Genotypes and allele frequencies of investigated polymorphisms did not deviate from Hardy-Weinberg equilibrium in patients with HCTC, HCTA and HCTN. Under the dominant genetic model we observed no differences in the genotype frequency distribution of the investigated polymorphisms when the HCTA and HCTN group was compared to the HCTC group for diagnosis of HCTC or for the presence of metastatic disease. However, GPX1 polymorphism was associated with the occurrence of recurrent disease (p = 0.040).

Conclusions

GPX1 polymorphism may influence the risk for recurrent disease in HCTC.

Case control feasibility study assessing the association between severity of coronary artery disease with Glutathione Peroxidase-1 (GPX-1) and GPX-1 polymorphism (Pro198Leu)

Background

Glutathione peroxidase-1 (GPX-1) activity was reported to be useful marker for monitoring cardiovascular disease. However, accurate assessment of coronary artery disease (CAD) using GPX-1 polymorphism is limited for South Asian population. Present study aim to assess GPX-1activity and GPX-1 polymorphismin patients with coronary artery disease (CAD) who were confirmed with coronary angiography findings and in apparently healthy subjects.

Methods

Case control study was carried out with 85 patients (58 males and 27 females) 40–60 years of age confirmed as having CAD on coronary angiography findings and 85 age and sex matched healthy volunteers as controls. Blood samples were analyzed for erythrocyte GPX-1 activity and GPX-1 polymorphism in both groups and the severity of CAD was assessed using coronary angiography scoring system based on vessel, stenosis and extent score.

Results

Coronary angiography scores indicated that erythrocyteGPX-1 cutoff value of 23.9 U/gHb showed a high sensitivity and negative predictive value in ruling out major vessel disease. The GPX-1 Pro198Leu (CT) polymorphism was higher in patients with CAD (25.3 %) when compared to controls (10.7 %). Pro198Leu (CT) genotype showed a 2.84 fold risk for CAD [odds ratio 2.84 (95 % CI 1.15–6.98), p = 0.019].

Conclusion

Coronary angiography findings indicated that individuals possessing Pro198Leu (CT) polymorphism were found to be associated with low erythrocyte GPX-1 activity and increased susceptibility for CAD.

Selenium and chronic diseases: a nutritional genomics perspective

Mechanistic data have revealed a key role for selenium (Se) and selenoproteins in biological pathways known to be altered in multifactorial diseases, such as cellular maintenance, response to oxidative stress and correct protein folding. Although epidemiological studies indicate that low Se intake is linked to increased risk for various chronic diseases, supplementation trials have given confusing outcomes, suggesting that additional genetic factors could affect the relationship between Se and health. Genetic data support this hypothesis, as risk for several chronic diseases, in particular cancer, was linked to a number of single nucleotide polymorphisms (SNP) altering Se metabolism, selenoprotein synthesis or activity. Interactions between SNPs in selenoprotein genes, SNPs in related molecular pathways and biomarkers of Se status were found to further modulate the genetic risk carried by the SNPs. Taken together, nutritional genomics approaches uncovered the potential implication of some selenoproteins as well as the influence of complex interactions between genetic variants and Se status in the aetiology of several chronic diseases. This review discusses the results from these genetic associations in the context of selenoprotein functions and epidemiological investigations and emphasises the need to assess in future studies the combined contribution of Se status, environmental stress, and multiple or individual SNPs to disease risk.

rs2070424 of the SOD1 gene is associated with risk of Alzheimer's disease

OBJECTIVE

Oxidative stress plays an important role in Alzheimer's disease (AD) etiopathogenesis. There were several studies that showed impaired antioxidant defense system (ADS) enzymes expression or activity in AD patients. There are only few studies evaluating the importance of ADS gene single nucleotide polymorphisms (SNPs) as risk factors of AD. We evaluated association between chosen SNPs of the enzymes of the ADS and risk of AD.

METHODS

We included 400 AD patients and 402 healthy controls. We studied rs1041740, rs4998557 and rs2070424 of the SOD1 gene, rs2855116, rs5746136 and rs4880 of the SOD2 gene and rs3448, rs1050450 and rs1800668 of the GPx-1 gene (real time PCR). To determine the APOE gene common polymorphism, two single-nucleotide polymorphisms (SNPs; NCBI SNPs rs429358 and rs7412) were genotyped (TaqMan assays, Applied Biosystems [ABI], Foster City, CA, USA). The genotype and gender frequencies were compared between the studied groups by the χ(2) test and mean age by the t-Student test.

RESULTS

Among all studied SNPs only rs2070424 of the SOD1 gene was a protective factor for AD in an additive (OR=0.47; 95% CI=0.30-0.74, p=0.001) and recessive (OR=0.47; 95% CI=0.30-0.75, p=0.002) models including age, gender and APOE gene status.

CONCLUSIONS

rs2070424 polymorphism of the SOD1 gene is a risk factor for AD in Polish population. Allel G and genotype AG and GG are protective factors for AD.

Association of glutathione peroxidase-1 (GPx-1) rs1050450 Pro198Leu and Pro197Leu polymorphisms with cardiovascular risk: a meta-analysis of observational studies

Objective

To clarify the association between rs1050450 polymorphism in Glutathione peroxidase-1 (GPx-1) and the risk of cardiovascular diseases (CVD) by performing a meta-analysis of published studies. There is growing evidence from different study types for an association of the GPx-1 polymorphism and cardiovascular outcomes, but observational studies have so far shown inconsistent results.

Methods

Relevant publications were searched through PubMed, Embase database databases and the Cochrane Library. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of association under the best genetic model. Both Q statistic and the I² were used to check heterogeneity. Meta-regression analysis was performed to explore heterogeneity source. Sensitivity analysis, cumulative meta-analysis analysis and publication bias were used to test the reliability of the results.

Results

Data were available from two cohort studies and 8 case-control studies involving 1,430 cases and 3,767 controls. The pooled ORs for overall CVD risk was 1.36 with 95% CI: 1.08–1.70 under a co-dominant model, and that for East Asian subgroup was 1.84 (95% CI: 1.39–2.43). Substantial heterogeneity for ORs were detected among all the included studies, mainly caused by ethnic differences between East Asian and non-East Asian populations. Although Egger's regression test suggested no statistical significant publication bias, Begg's funnel plot exhibited obvious asymmetry. The statistical significance disappeared after adjusting for potential publication bias in the overall studies. However, no substantial publication bias was found in the East Asian subgroup.

Conclusions

GPx-1 gene Pro198Leu and Pro197Leu polymorphisms considerably increased the risk of CVD in the East Asian population. Large-scale investigations are needed to confirm the results in different ethnicities.

Mitochondrial stress signaling promotes cellular adaptations

Mitochondrial dysfunction has been implicated in the aetiology of many complex diseases, as well as the ageing process. Much of the research on mitochondrial dysfunction has focused on how mitochondrial damage may potentiate pathological phenotypes. The purpose of this review is to draw attention to the less well-studied mechanisms by which the cell adapts to mitochondrial perturbations. This involves communication of stress to the cell and successful induction of quality control responses, which include mitophagy, unfolded protein response, upregulation of antioxidant and DNA repair enzymes, morphological changes, and if all else fails apoptosis. The mitochondrion is an inherently stressful environment and we speculate that dysregulation of stress signaling or an inability to switch on these adaptations during times of mitochondrial stress may underpin mitochondrial dysfunction and hence amount to pathological states over time.

GPX1 gene Pro200Leu polymorphism, erythrocyte GPX activity, and cancer risk

A meta-analysis was conducted to assess the effect of glutathione peroxidase1 (GPX1) gene Pro200Leu (rs1050450) polymorphism on cancer risk. A comprehensive search was performed to identify all studies on the association of GPX1 gene Pro200Leu polymorphism with cancer risk. The fixed or random effect pooled measure was selected based on homogeneity test among studies. Heterogeneity among studies was evaluated using the I (2). Potential sources of between-study heterogeneity were explored by meta-regression and the sensitivity analysis. Publication bias was estimated using Egger's linear regression test. 35 published articles with 36 results were identified involving 16,920 cases and 19,946 controls. Results from the articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed no significant association of GPX1 gene Pro200Leu polymorphism with cancer risk in any of dominant (OR = 1.05, 95 %CI = 0.98-1.12), recessive (OR = 1.04 (0.95-1.13), and TT versus CC (OR = 1.05, 95 %CI = 0.97-1.15) models, and the findings were consistent considering the stratified analysis by cancer type. However, multivariate-adjusted ORs from articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed a significant association considering dominant (OR = 1.22, 95 %CI = 1.06-1.41), TT versus CC (OR = 1.16, 95 %CI = 1.02-1.32) models, and a marginally significant association was found considering TC versus CC (OR = 1.11, 95 %CI = 0.99-1.25) model. And compared with the CC genotype, the erythrocyte GPX activity was significantly lower for TT genotype: the standardized mean difference (SMD) = -0.37, 95 %CI = (-0.624, -0.118), and CT genotype: SMD = -0.19, 95 %CI = (-0.37, -0.002). The association of GPX1 gene Pro200Leu polymorphism with cancer risk might be influenced by confounders.

The impact of GPX1 on the association of groundwater selenium and depression: a Project FRONTIER study

BACKGROUND

Prior animal model and human-based studies have linked selenium concentrations to decreased risk for depression; however, this work has not focused on household groundwater levels or specific depressive symptoms. The current study evaluated the link between groundwater selenium levels and depression. We also sought to determine if a functional polymorphism in the glutathione peroxidase 1 (GPX1) gene impacted this link.

METHODS

We used a cross-sectional design to analyze data from 585 participants (183 men and 402 women) from Project FRONTIER, a study of rural health in West Texas. Residential selenium concentrations were estimated using Geospatial Information System (GIS) analyses. Linear regression models were created using Geriatric Depression Scale (GDS-30) total and subfactor scores as outcome variables and selenium concentrations as predictor variables. Analyses were re-run after stratification of the sample on GPX1 Pro198Leu genotype (rs1050454).

RESULTS

Selenium levels were significantly and negatively related to all GDS and subfactor scores accounting for up to 17% of the variance beyond covariates. Selenium was most strongly protective against depression among homozygous carriers of the C allele at the Pro198Leu polymorphism of the GPX1 gene. Analyses also point towards a gene-environmental interaction between selenium exposure and GPX1 polymorphism.

CONCLUSION

Our results support the link between groundwater selenium levels and decreased depression symptoms. These findings also highlight the need to consider the genetics of the glutathione peroxidase system when examining this relationship, as variation in the GPX1 gene is related to depression risk and significantly influences the protective impact of selenium, which is indicative of a gene-environment interaction.