Genetic polymorphisms of glutathione S-transferase genes GSTM1, GSTT1 and risk of hepatocellular carcinoma

Exploring the Molecular Mechanism and Role of Glutathione S-Transferase P in Prostate Cancer

Aims: To investigate the effect of Glutathione metabolism in prostate cancer pathogenesis. Background: There is growing evidence that Glutathione metabolism plays an important role in prostate cancer, with genes encoding key enzymes in this pathway potentially serving as diagnostic or prognostic biomarkers. Objective: To explore whether there is a causal relationship between key enzymes in the Glutathione metabolism and prostate cancer, and to further investigate the molecular mechanisms and roles of the genes encoding their proteins in relation to prostate cancer. Method: Transcriptomic datasets from the Gene Expression Omnibus (GEO) database were analyzed to identify differentially expressed genes (DEGs) and enriched pathways in prostate cancer versus normal tissues. Two-sample bidirectional Mendelian randomization (MR) was employed to assess causal relationships between Glutathione metabolic enzymes (exposure) and prostate cancer risk (outcome). Immune infiltration analysis and LASSO regression were performed to construct a diagnostic model. Single-cell RNA sequencing (scRNA-seq) data were utilized to elucidate cell-type-specific expression patterns and functional associations of target genes. Result: The results of two-sample bidirectional MR showed that Glutathione S-transferase P (GSTP) in Glutathione metabolism could reduce the risk of prostate cancer. The Glutathione S-transferase Pi-1 (GSTP1) gene was lowly expressed in prostate cancer and was able to diagnose prostate cancer more accurately. Single-cell analysis showed that the high expression of GSTP1 in prostate cancer epithelial cells was closely associated with the upregulation of the P53 pathway and apoptosis. Conclusions: Our study reveals that GSTP in Glutathione metabolism reduces the risk of prostate cancer and further analyzes the genetic association and mechanism of action between GSTP1 and prostate cancer.

Unleash Multifunctional Role of miRNA Biogenesis Gene Variants (XPO5*rs34324334 and RAN*rs14035) with Susceptibility to Hepatocellular Carcinoma

Numerous reports have explored the roles of different genetic variants in miRNA biogenesis mechanisms and the progression of various types of carcinomas. The goal of this study is to explore the association between XPO5*rs34324334 and RAN*rs14035 gene variants and susceptibility to hepatocellular carcinoma (HCC). In a cohort of 234 participants (107 HCC patients and 127 unrelated cancer-free controls) from the same geographic region, we characterized allelic discrimination using PCR-RFLP and performed subgroup analysis and multivariate regression. We found that the frequency of the XPO5*rs34324334 (A) variant was correlated with elevated risk of HCC under allelic (OR = 10.09, p-value < 0.001), recessive (OR = 24.1, p-value < 0.001), and dominant (OR = 10.1, p-value < 0.001) models. A/A genotype was associated with hepatitis C cirrhosis (p-value = 0.012), ascites (p-value = 0.003), and higher levels of alpha-fetoproteins (p-value = 0.011). Carriers of the RAN*rs14035 (T) variant were more likely to develop HCC under allelic (OR = 1.76, p-value = 0.003) and recessive (OR = 3.27, p-value < 0.001) models. Our results suggest that XPO5*rs34324334 and RAN*rs14035 variants are independent risk factors for developing HCC.

Influence of GSTM1, T1 genes polymorphisms on oxidative stress and liver enzymes in rural and urban pesticides-exposed workers

Several studies discussed the relationship between the toxicity of organophosphates (OPs) and carbamates pesticides and oxidative stress which affects human health. This study aimed to evaluate the effects of pesticides on the induction of oxidative stress and hepatotoxicity. It was also focused on glutathione-S-transferase gene polymorphism in the modulation of these effects. In addition, the role of the educational level of exposed workers was studied. Acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), liver enzymes, malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), and glutathione S transferase (GST) were estimated at 100 pesticide-exposed workers (50 urban researchers (UE) and 50 rural sprayers (RE)), and 100 matched controls (50 urban controls (UC)and 50 rural controls (RC)). AChE and BuChE were decreased in RE and UE compared to RC. Aspartate aminotransferase (AST) and alkaline phosphatase (ALP) activity were elevated in UE and UC compared to the RE and RC. Alanine aminotransferase (ALT) was elevated in UE compared to RE. MDA in RE and UE showed elevation compared to RC. There was a significant reduction in the levels of GSH, GST, and GPx in UE compared to RE and RC. The most sensitive pesticide-induced hepatotoxicity group were exposed workers with the GSTT1 genotype. Within these workers, ALT and ALP were significantly correlated with MDA and inversely correlated with AChE and BuChE, while AST was inversely correlated with AChE and BuChE only in UE. Conclusion: GST gene polymorphisms appeared to have a significant role in workers' susceptibility to hepatotoxic effects due to occupational exposure to pesticides; GSTT1 was the most sensitive genotype.

Polymorphisms in xenobiotic metabolism-related genes in patients with hepatocellular carcinoma: a case-control study

This study was performed to investigate the relationship between polymorphisms in microsomal epoxide hydrolase (mEH; Tyr113His and His139Arg substitution) and glutathione S-transferase (GST; GSTM1 deletion, GSTT1 deletion, and GSTP1.Ala114Val substitution) and their correlation with clinico-histopathological features in hepatocellular carcinoma (HCC).We evaluated environmental risk factors and genetic alterations in 556 individuals (86 cases and 470 controls). PCR multiplex for GSTM1 and GSTT1, polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) for GSTP1, and real-time PCR for mEH were performed. Statistical analyses were performed using multiple logistic regression tests.Age over 48 years (p < 0.001) and alcohol consumption (p = 0.021) were the predictors of increased risk of developing HCC. GSTP1.Ala114Val for all regression models (p < 0.05), except the recessive model, and the GSTT1 null genotype (odds ratio [OR] = 0.43, 95% confidence interval [CI] = 0.21-0.87, p = 0.019) were predictors of an increased risk of developing HCC. Polymorphic GSTT1, GSTM1, GSTP1.Ala114Val, and mEH.His139Arg and wild-type mEH.Tyr113His (OR = 5.04; 95% CI = 1.59-16.04; p = 0.006) were associated with HCC.Age over 48 years, alcohol consumption, and the presence of polymorphic variants of GSTP1 and GSTT1 were associated with the risk of developing HCC.

The role of glutathione S-transferase omega gene polymorphisms in childhood acute lymphoblastic leukemia: a case-control study

Background

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Glutathione-S-methyl transferase (GSTs) enzymes’ family is known to catalyze carcinogens detoxification. Overexpression of (GSTO) omega class was reported in cancer occurrence. The purpose of the study was to investigate the association of GSTO1*A140D (rs4925) and GSTO2*N142D (rs156697) polymorphisms with the susceptibility to childhood ALL and to evaluate their prognostic impact. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism technique in 96 Egyptian pediatric ALL patients and 99 controls.

Results

No statistically significant different GSTO1*A140D genotype and allele distribution was observed among ALL cases and controls; however, a statistically significant different GSTO1*A140D genotype distribution was found between de novo ALL cases and controls [CC (37% vs. 56.6%), CA (47.8% vs. 40.4%), and AA (15.2% vs. 3.0%), respectively] (0.008). GSTO1*A140D variant genotypes’ frequency was significantly higher in de novo cases than in controls (63% vs. 43.4%) (0.028). The minor allele frequency (MAF) of GSTO1*A140D-A was significantly higher in de novo cases compared to controls (0.39 vs. 0.23) (0.005). Genotyping of GSTO2*N142D revealed a statistically significant difference of genotype distribution between ALL patients and controls [AA (26% vs. 36.3%), AG (62.5% vs. 61.6%), and GG (11.4% vs. 2.0%), respectively] (0.017) and between de novo ALL cases and controls [AA (37% vs. 36.3%), AG (45.7% vs. 61.6%), and GG (17.3% vs. 2.0%), respectively] (0.002). The MAF of GSTO2*N142D-G was significantly higher in ALL patients than in controls (0.42 vs. 0.32) (0.046). The high-risk ALL group had a higher frequency of GSTO1*A140D and GSTO2*N142D variant genotypes compared to corresponding wild genotypes and a higher frequency of combined polymorphisms compared to single polymorphisms and wild genotypes but with no statistically significant difference.

Conclusion

A statistically significant difference of GSTO1*A140D and GSTO2*N142D genotype distribution was detected between de novo ALL cases and controls. Compared to the control group, the MAF of GSTO1*A140D-A was overexpressed in de novo ALL cases and that of GSTO2*N142D-G was significantly higher in ALL patients. These findings suggest that the studied polymorphisms might play a significant role in the susceptibility to de novo childhood ALL in Egypt; however, GSTO1*A140D and/or GSTO2*N142D polymorphisms have no impact on ALL prognosis.

Association of GSTM1 and GSTT1 Null Deletions and GSTP1 rs1695 Polymorphism with the Risk of Hepatocellular Carcinoma: A Systematic Review and Meta-analysis

Context: Hepatocellular carcinoma (HCC), as the most common type of primary liver cancer (accounting for 70% - 90% of all liver cancers), is the seventh most common malignancy worldwide. Glutathione S-transferases (GSTs) are a specific group of enzymes that are responsible for the detoxification of carcinogens. According to the available literature, genetic variations in this group of enzymes may be associated with the risk of HCC. In this study, we aimed to assess the association of GSTM1 and GSTT1 null deletions and GSTP1 rs1695 polymorphism with the risk of HCC. Methods: We systematically searched electronic databases, including PubMed, Scopus, and Web of Science, using appropriate keywords to gather relevant data until March 2019. Studies that met the inclusion criteria were included in the meta-analysis, using either fixed- or random-effects models based on the presence of heterogeneity. Results: This meta-analysis pooled 19 studies for GSTM1 null deletions, 14 studies for GSTT1 null deletions, and five studies for GSTP1 rs1695 polymorphism. In terms of heterogeneity, the pooled odds ratio (OR) was calculated in a random-effects model for both Asian and non-Asian populations. HCC was found to be associated with GSTM1 null deletions (OR = 1.26, 95% CI: 1.00 - 1.58, P = 0.05) and GSTT1 null deletions (OR = 1.39, 95% CI: 1.10 - 1.74, P = 0.005); however, no significant association was found between HCC and GSTP1 rs1695 polymorphism (OR = 1.14, 95% CI: 0.86 - 1.50, P = 0.36). Conclusions: We found that GSTM1 and GSTT1 null deletions increased the risk of HCC; however, the GSTP1 rs1695 polymorphism did not have a similar effect.

Lack of association between glutathione S-transferase M1 and T1 gene polymorphisms and susceptibility to preeclampsia: An updated systematic review and meta-analysis

Insufficient response to oxidative stress in placenta is proposed as a contributing factor for preeclampsia (PE) development. Glutathione S-transferases (GST) have significant role in detoxification processes. Conflicting results were published by several research groups regarding GST T1 and GST M1 deletion polymorphism as risk factors for PE. The aim of the present meta-analysis was to get a better understanding of the impact of these polymorphisms in preeclampsia development. To identify relevant case-control studies, the author team searched Clarivate Analytics Web of Science, Scopus, PubMed, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure, major subject journals, and gray literature. Pooled odds ratios and 95% confidence intervals for GST M1 and GST T1 deletion polymorphism and preeclampsia were derived from random effects models. This meta-analysis included 10 eligible studies. The pooled analyses showed no association between GST M1/GST T1 deletion polymorphisms and susceptibility to PE. Even though high heterogeneity was founded among results for GST M1 and double null genotypes, Egger's and Begg's tests (0.17 and 0.18, respectively) revealed no statistical evidence of publication bias among included studies. The present updated systematic review and meta-analysis found no association between GST M1 and GST T1 deletion polymorphism and PE risk.

Role of Glutathione in Cancer: From Mechanisms to Therapies

Glutathione (GSH) is the most abundant non-protein thiol present at millimolar concentrations in mammalian tissues. As an important intracellular antioxidant, it acts as a regulator of cellular redox state protecting cells from damage caused by lipid peroxides, reactive oxygen and nitrogen species, and xenobiotics. Recent studies have highlighted the importance of GSH in key signal transduction reactions as a controller of cell differentiation, proliferation, apoptosis, ferroptosis and immune function. Molecular changes in the GSH antioxidant system and disturbances in GSH homeostasis have been implicated in tumor initiation, progression, and treatment response. Hence, GSH has both protective and pathogenic roles. Although in healthy cells it is crucial for the removal and detoxification of carcinogens, elevated GSH levels in tumor cells are associated with tumor progression and increased resistance to chemotherapeutic drugs. Recently, several novel therapies have been developed to target the GSH antioxidant system in tumors as a means for increased response and decreased drug resistance. In this comprehensive review we explore mechanisms of GSH functionalities and different therapeutic approaches that either target GSH directly, indirectly or use GSH-based prodrugs. Consideration is also given to the computational methods used to describe GSH related processes for in silico testing of treatment effects.

Clinical significance and biological mechanisms of glutathione S-transferase mu gene family in colon adenocarcinoma

Background

Colon adenocarcinoma (COAD) is the most common form of colon cancer. The glutathione S-transferase Mu (GSTM) gene belongs to the GST gene family, which functions in cell metabolism and detoxification. The relationship between GSTM and COAD and the underlying mechanism remain unknown.

Methods

Data extracted from The Cancer Genome Atlas included mRNA expression and clinical information such as gender, age, and tumor stage. Prognostic values of GSTM genes were identified by survival analysis. Function and mechanism of prognostic GSTM genes were identified by gene set enrichment analysis. A nomogram was used to predict the contribution of risk factors to the outcome of COAD patients.

Results

Low expression of GSTM1 and GSTM2 was related to favorable OS (adjusted P = 0.006, adjusted HR = 0.559, 95% CI = 0.367–0.849 and adjusted P = 0.002, adjusted HR = 0.519, 95% CI = 0.342–0.790, respectively) after adjusting for tumor stage. Enrichment analysis also showed that genes involved were related to cell cycle, metabolism, and detoxification processes, as well as the Wnt signaling and NF-κB pathways.

Conclusions

In conclusion, low expression of GSTM1 and GSTM2 were significantly associated with favorable prognosis in COAD. These two genes may serve as potential biomarkers of COAD prognosis.

Mode of action-based risk assessment of genotoxic carcinogens

The risk assessment of chemical carcinogens is one major task in toxicology. Even though exposure has been mitigated effectively during the last decades, low levels of carcinogenic substances in food and at the workplace are still present and often not completely avoidable. The distinction between genotoxic and non-genotoxic carcinogens has traditionally been regarded as particularly relevant for risk assessment, with the assumption of the existence of no-effect concentrations (threshold levels) in case of the latter group. In contrast, genotoxic carcinogens, their metabolic precursors and DNA reactive metabolites are considered to represent risk factors at all concentrations since even one or a few DNA lesions may in principle result in mutations and, thus, increase tumour risk. Within the current document, an updated risk evaluation for genotoxic carcinogens is proposed, based on mechanistic knowledge regarding the substance (group) under investigation, and taking into account recent improvements in analytical techniques used to quantify DNA lesions and mutations as well as "omics" approaches. Furthermore, wherever possible and appropriate, special attention is given to the integration of background levels of the same or comparable DNA lesions. Within part A, fundamental considerations highlight the terms hazard and risk with respect to DNA reactivity of genotoxic agents, as compared to non-genotoxic agents. Also, current methodologies used in genetic toxicology as well as in dosimetry of exposure are described. Special focus is given on the elucidation of modes of action (MOA) and on the relation between DNA damage and cancer risk. Part B addresses specific examples of genotoxic carcinogens, including those humans are exposed to exogenously and endogenously, such as formaldehyde, acetaldehyde and the corresponding alcohols as well as some alkylating agents, ethylene oxide, and acrylamide, but also examples resulting from exogenous sources like aflatoxin B1, allylalkoxybenzenes, 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), benzo[a]pyrene and pyrrolizidine alkaloids. Additionally, special attention is given to some carcinogenic metal compounds, which are considered indirect genotoxins, by accelerating mutagenicity via interactions with the cellular response to DNA damage even at low exposure conditions. Part C finally encompasses conclusions and perspectives, suggesting a refined strategy for the assessment of the carcinogenic risk associated with an exposure to genotoxic compounds and addressing research needs.

Gene-environment interactions between GSTs polymorphisms and targeted epigenetic alterations in hepatocellular carcinoma following organochlorine pesticides (OCPs) exposure

Exposure to environmental pollutant organochlorine pesticides (OCPs) and the role of tumour suppressor GSTs gene polymorphisms as well as epigenetic alterations have all been well reported in hepatocarcinogenesis. However, the interplay between environmental risk factors and polymorphic tumour suppressor genes or epigenetic factors in hepatocellular carcinoma (HCC) development remains ambiguous. Herein, we investigated the relationship of three GSTs polymorphisms (GSTT1 deletion, GSTM1 deletion, GSTP1 rs1695) as well as GSTP1 promoter region DNA methylation and HCC risk with a particular focus on the interaction with OCPs exposure among 90 HCC cases and 99 controls in a Chinese population. Serum samples were analysed for OCPs exposure employing gas chromatography coupled with mass selective detector (GC-MS). GSTs polymorphisms and epigenetic alterations were determined using high-resolution melting PCR (HRM PCR) and DNA sequencing. After adjusting for confounders (HBV infection, smoking, alcohol consumption, BMI, age, gender), OCPs exposure and GSTP1 methylation is significantly associated with elevated risk of HCC, while no significance is observed for GSTs polymorphisms. Moreover, the effects of OCPs exposure on HCC risk are more pronounced amongst GSTP1 (Ile/Val + Val/Val) and GSTP1 promoter methylation subjects than those who were GSTP1 (Ile/Ile) and unmethylated subjects. The interactions between OCPs exposure and GSTP1 genotype as well as GSTP1 epigenetic status are statistically significant. The current study demonstrates the importance of gene-environment interactions in the multifactorial development of HCC.

Age- and gender-independent association of glutathione S-transferase null polymorphisms with chronic myeloid leukemia

The glutathione S-transferase (GST) genes encode enzymes that mediate the detoxification of xenobiotics by catalyzing the conjugation of glutathione (GSH) to xenobiotic substrates. The aim of the current study is to investigate the association between GSTT1 and GSTM1 polymorphisms and chronic myeloid leukemia (CML) among Sudanese patients. Patients with CML (n = 115) were recruited to the study from the Radiation and Isotope Centre Khartoum (RICK)-Sudan. Healthy individuals (n = 104) were included as controls. Genotyping of GSTT1 and GSTM1 polymorphisms was performed using multiplex PCR. Null deletions in the GSTT1 and GSTM1 genes are common in the Sudanese population (control group), with frequencies of 33.9% and 38.2%, respectively. The frequencies of GSTT1 (OR: 3.25, 95% CI: 1.87-5.65, p < 0.001) and GSTM1 (OR: 2.14, 95% CI: 1.25-3.67, p < 0.005) null genotypes were significantly higher in CML patients vs. controls. The distribution of GSTT1 and GSTM1 null polymorphisms was not different between male and female (p > 0.01) and young and old CML patients (p > 0.05). Hematological parameters were not affected by null polymorphisms in the patient group (p > 0.05). In addition, the frequency of GSTM1 null polymorphism was lower in advanced-phase CML patients compared to chronic-phase patients (p < 0.05). The GSTT1 and GSTM1 null polymorphisms are associated with CML among Sudanese patients, independently of their age and gender.

GSTM1 and GSTT1 null genotype increase the risk of hepatocellular carcinoma: evidence based on 46 studies

BACKGROUND

It is well known that hepatocellular carcinoma (HCC) has been one of the most life-threatening diseases all over the world. Plenty of internal and extrinsic factors have been proven to be related to HCC, such as gene mutation, viral hepatitis, and Nitrosamines. Though previous studies demonstrated that glutathione S-transferase (GST) genotypes are associated with HCC, the conclusions are inconsistent. Therefore, we carried on a renewed meta-analysis to expound the connection between the null GSTM1, GSTT1 polymorphisms and the risk of HCC.

METHODS

We searched PubMed, Web of Science, Embase, and CNKI databases to select qualified researches which satisfied the inclusion criteria up to July 31, 2018. Finally, we selected 41 articles with 6124 cases and 9781 controls in this meta-analysis. We use ORs and 95% confidence interval (CI) to evaluate the correlation intension between the GSTM1 and GSTT1 null genes and the risk of HCC. All the statistical processes were executed by Stata (version 12.0).

RESULTS

The pooled analysis showed that both GSTM1 null genotypes (OR = 1.37, 95% CI = 1.18-1.59) and GSTT1 null genotypes (OR = 1.43, 95% CI = 1.23-1.66) increased the risk of HCC. And GSTM1-GSTT1 dual-null genotypes also increased the risk of HCC (OR = 1.58, 95% CI = 1.22-2.05). In the subgroup analysis, we obtained significant results among Asians when stratified by race, and the results are GSTM1 null OR = 1.44, 95% CI = (1.22-1.71), GSTT1 null OR = 1.48, 95% CI = (1.25-1.77), GSTM1-GSTT1 null OR = 1.58, 95% CI = (1.19-2.09), while we didn't obtain significant results among Caucasians or Africans. Stratified analyses on the type of control indicated a higher risk of HCC associated with GSTM1, GSTT1 single null genotypes and GSTM1-GSTT1 dual-null genotypes in healthy people. No evidence of significant connection was discovered in chronic liver disease (CLD) except in GSTT1 single null.

CONCLUSIONS

Our study indicated that an individual who carries the GSTM1, GSTT1 single null genotypes and GSTT1-GSTM1 dual-null genotypes is more likely to develop HCC.

Glutathione-S-transferase M1 polymorphism and pro-inflammatory cytokines tumour necrosis factor-α and interleukin-1β are associated with preeclampsia in Serbian women

PROBLEM

Preeclampsia has a multifactorial origin with genetic, immunological, and environmental factors described as main contributors to its onset. This study aimed to investigate glutathione-S-transferase M1 (GSTM1) and glutathione-S-transferase T1 (GSTT1) gene polymorphisms, the expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), and the potential relationship between GST polymorphisms and cytokine expression levels in preeclampsia and uncomplicated pregnancy.

METHOD OF STUDY

This prospective case-control study included 50 women with preeclampsia and 50 healthy pregnant women. DNA and RNA were extracted from women leukocytes. Deletion polymorphisms were analyzed by PCR, while cytokine mRNA expression was analyzed by real-time PCR.

RESULTS

GSTM1 null genotype with present GSTT1 increased the risk for preeclampsia development. Deletion of GSTT1 without deletion of GSTM1 increased the risk for early preeclampsia. Relative mRNA expression of TNF-α was significantly higher in preeclampsia compared to healthy pregnant women (P = 0.006). Expression of IL-1β was significantly higher in severe and late preeclampsia compared to the control group (P = 0.005, P = 0.007, respectively). A significant positive correlation between TNF-α and IL-1β was observed (Spearman's ρ = 0.312, P = 0.028) and between IL-1β and IL-6, in preeclampsia group (Spearman's ρ = 0.296, P = 0.037). IL-1β was significantly increased in patients with GSTT1 null genotype (P = 0.015) while IL-6 was increased in patients with GSTM1 null genotype (P = 0.015).

CONCLUSIONS

GSTM1 null genotype represents a risk factor for preeclampsia development, while GSTT1 null genotype favors early preeclampsia. Preeclampsia is also associated with increased expression of pro-inflammatory cytokines, predominantly TNF-α and IL-1β.

Autophagy activation contributes to glutathione transferase Mu 1-mediated chemoresistance in hepatocellular carcinoma

Glutathione transferase Mu 1 (GSTM1) induces cancer drug resistance by hydrolyzing cancer chemotherapeutics or activating the anti-apoptosis pathway. However, the chemoresistance-inducing mechanism of GSTM1 in hepatocellular carcinoma (HCC) remains unknown. In the present study, the expression of GSTM1 was examined in three HCC cell lines. Oxaliplatin and sorafenib were selected as chemotherapeutic agents. Small interfering RNA was used to decrease GSTM1 expression. Cell death was measured using MTT and annexin V/propidium iodide assays. Activation of autophagy was evaluated by green fluorescent protein-light chain 3 redistribution and analysis of autophagy-related 5 expression in MHCC97-H and Huh-7 cells. A stepwise increase in GSTM1 expression with increasing metastatic potential of HCC cell lines was revealed. Cell death induced by oxaliplatin and sorafenib was significantly increased following GSTM1-knockdown in MHCC97-H and Huh-7 cells. Activation of autophagy was significantly inhibited by silencing GSTM1 expression. The results of the present study suggest that GSTM1 may protect HCC cells against the effect of oxaliplatin treatment through activating autophagy. The present study provides a novel perspective on HCC drug-resistance.

GSTT1 and GSTM1 null variants in Mestizo and Amerindian populations from northwestern Mexico and a literature review

The GSTT1 and GSTM1 genes are key molecules in cellular detoxification. Null variants in these genes are associated with increase susceptibility to developing different types of cancers. The aim of this study was to determine the prevalence of GSTT1 and GSTM1 null genotypes in Mestizo and Amerindian individuals from the Northwestern region of Mexico, and to compare them with those reported worldwide. GSTT1 and GSTM1 null variants were genotyped by multiplex PCR in 211 Mestizos and 211 Amerindian individuals. Studies reporting on frequency of GSTT1 and GSTM1 null variants worldwide were identified by a PubMed search and their geographic distribution were analyzed. We found no significant differences in the frequency of the null genotype for GSTT1 and GSM1 genes between Mestizo and Amerindian individuals. Worldwide frequencies of the GSTT1 and GSTM1 null genotypes ranges from 0.10 to 0.51, and from 0.11 to 0.67, respectively. Interestingly, in most countries the frequency of the GSTT1 null genotype is common or frequent (76%), whereas the frequency of the GSMT1 null genotype is very frequent or extremely frequent (86%). Thus, ethnic-dependent differences in the prevalence of GSTT1 and GSTM1 null variants may influence the effect of environmental carcinogens in cancer risk.

Glutathione-s-transferase A 4 (GSTA4) suppresses tumor growth and metastasis of human hepatocellular carcinoma by targeting AKT pathway

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies of cancers and its prognosis remains dismal due to the paucity of effective therapeutic targets. Up-regulation of glutathione-s-transferase A 4 (GSTA4) is associated with poor prognosis of HCC, but its functional mechanism in HCC remains unclear. In this study, we investigated the roles of GSTA4 in tumor growth and metastasis of HCC and found that GSTA4 was frequently up-regulated in HCC tissues. Through gain- and loss-of-function studies, GSTA4 was demonstrated to significantly regulate cell proliferation, migration, and invasion in vitro. Furthermore, GSTA4 overexpressing significantly promoted the tumorigenicity and metastasis of HCC cells in nude mice models bearing human HCC, whereas silencing endogenous GSTA4 caused an opposite outcome. Moreover, we demonstrated that GSTA4 enhanced HCC aggressiveness by activating protein kinase B (AKT) signaling. In multivariate analysis, our results GSTA4 overexpression promotes the progression of hepatocellular carcinoma and might represent a novel therapeutic target for its treatment.

The rs3957357C>T SNP in GSTA1 Is Associated with a Higher Risk of Occurrence of Hepatocellular Carcinoma in European Individuals

Glutathione S-transferases (GSTs) detoxify toxic molecules by conjugation with reduced glutathione and regulate cell signaling. Single nucleotide polymorphisms (SNPs) of GST genes have been suggested to affect GST functions and thus to increase the risk of human hepatocellular carcinoma (HCC). As GSTA1 is expressed in hepatocytes and the rs3957357C>T (TT) SNP is known to downregulate GSTA1 mRNA expression, the aims of this study were: (i) to explore the relationship between the TT SNP in GSTA1 and the occurrence of HCC; (ii) to measure GSTA1 mRNA expression in HCCs. For that purpose, we genotyped non-tumor-tissue-derived DNA from 48 HCC patients and white-blood-cell-derived DNA from 37 healthy individuals by restriction fragment length polymorphism (RFLP). In addition, expression of GSTA1 mRNA was assessed by real-time PCR in 18 matching pairs of HCCs and non-tumor livers. Survival analysis was performed on an annotated microarray dataset containing 247 HCC patients (GSE14520). The GSTA1 TT genotype was more frequent in HCC than in non-HCC patients (27% versus 5%, respectively), suggesting that individuals carrying this genotype could be associated with 2-fold higher risk of developing HCCs (odds ratio = 2.1; p = 0.02). Also, we found that GSTA1 mRNA expression was lower in HCCs than in non-tumor livers. HCCs expressing the highest GSTA1 mRNA levels were the smallest in size (R = -0.67; p = 0.007), expressed the highest levels of liver-enriched genes such as ALB (albumin, R = -0.67; p = 0.007) and COL18A1 (procollagen type XVIII, R = -0.50; p = 0.03) and showed the most favorable disease-free (OR = 0.54; p<0.001) and overall (OR = 0.56; p = 0.006) outcomes. Moreover, GSTA1 was found within a 263-gene network involved in well-differentiated hepatocyte functions. In conclusion, HCCs are characterized by two GSTA1 features: the TT SNP and reduced GSTA1 gene expression in a context of hepatocyte de-differentiation.

GSTM1 and GSTT1 polymorphisms contribute to renal cell carcinoma risk: evidence from an updated meta-analysis

Emerging evidences suggest that GSTM1 and GSTT1 are involved in the detoxification of carcinogens, and polymorphisms in this gene that result in a loss of enzyme activity may increase the risk of renal cell carcinoma (RCC). Thus, to evaluate the association of GSTM1 and GSTT1 polymorphisms and RCC, we performed an updated meta-analysis of 10 case-control studies by RevMan 5.2, and the publication bias was tested using STATA 11.0. The meta-analysis showed that the single locus GSTM1 and GSTT1 polymorphisms were not significantly associated with a risk of RCC in a recessive model. However, that wild-type genotype versus the dual null genotype of GSTM1-GSTT1 showed a positive association with RCC risk (OR = 0.70; 95% CI = 0.51-0.98; P = 0.04). In another analysis of subjects exposed to pesticides, we found that the GSTM1 wild-type genotype was associated with increased RCC risk in Europeans (OR = 2.72; 95% CI = 1.54-4.82; P = 0.0006). We also identified an association between the GSTT1 wild-type and lower RCC TNM staging (I + II versus III + IV: OR = 1.88; 95% CI = 1.09-3.26; P = 0.02). This meta-analysis suggests that there may be a relationship between the GSTM1 and GSTT1 wild-type genotype and RCC.

Significance of Polymorphisms and Expression of Enzyme-Encoding Genes Related to Glutathione in Hematopoietic Cancers and Solid Tumors

Antioxidant compounds such as glutathione and its enzymes have become the focus of attention of medical sciences. Glutathione, a specific tripeptide, is involved in many intercellular processes. The glutathione concentration is determined by the number of GAG repeats in gamma-glutamylcysteine synthetase. GAG polymorphisms are associated with an increased risk of schizophrenia, berylliosis, diabetes, lung cancer, and nasopharyngeal tumors. Cancer cells with high glutathione concentration are resistant to chemotherapy treatment. The oxidized form of glutathione is formed by glutathione peroxidases (GPXs). The changes in activity of GPX1, GPX2, and GPX3 isoforms may be associated with the development of cancers, for example, prostate cancer or even colon cancer. Detoxification of glutathione conjugates is possible due to activity of glutathione S-transferases (GSTs). Polymorphisms in GSTM1, GSTP1, and GSTO1 enzymes increase the risk of developing breast cancer and hepatocellular carcinoma. Gamma-glutamyl transpeptidases (GGTs) are responsible for glutathione degradation. Increased activity of GGT correlates with adverse prognosis in patients with breast cancer. Studies on genes encoding glutathione enzymes are continued in order to determine the correlation between DNA polymorphisms in cancer patients.

Gene-environment interactions in esophageal cancer

Esophageal cancer (EC) is one of the most common malignancies in low- and medium-income countries and represents a disease of public health importance because of its poor prognosis and high mortality rate in these regions. The striking variation in the prevalence of EC among different ethnic groups suggests a significant contribution of population-specific environmental and dietary factors to susceptibility to the disease. Although individuals within a demarcated geographical area are exposed to the same environment and share similar dietary habits, not all of them will develop the disease; thus genetic susceptibility to environmental risk factors may play a key role in the development of EC. A wide range of xenobiotic-metabolizing enzymes are responsible for the metabolism of carcinogens introduced via the diet or inhaled from the environment. Such dietary or environmental carcinogens can bind to DNA, resulting in mutations that may lead to carcinogenesis. Genes involved in the biosynthesis of these enzymes are all subject to genetic polymorphisms that can lead to altered expression or activity of the encoded proteins. Genetic polymorphisms may, therefore, act as molecular biomarkers that can provide important predictive information about carcinogenesis. The aim of this review is to discuss our current knowledge on the genetic risk factors associated with the development of EC in different populations; it addresses mainly the topics of genetic polymorphisms, gene-environment interactions, and carcinogenesis. We have reviewed the published data on genetic polymorphisms of enzymes involved in the metabolism of xenobiotics and discuss some of the potential gene-environment interactions underlying esophageal carcinogenesis. The main enzymes discussed in this review are the glutathione S-transferases (GSTs), N-acetyltransferases (NATs), cytochrome P450s (CYPs), sulfotransferases (SULTs), UDP-glucuronosyltransferases (UGTs), and epoxide hydrolases (EHs), all of which have key roles in the detoxification of environmental and dietary carcinogens. Finally, we discuss recent advances in the study of genetic polymorphisms associated with EC risk, specifically with regard to genome-wide association studies, and examine possible challenges of case-control studies that need to be addressed to better understand the interaction between genetic and environmental factors in esophageal carcinogenesis.

Gene-gene and gene-environment interactions in meta-analysis of genetic association studies

Extensive genetic studies have identified a large number of causal genetic variations in many human phenotypes; however, these could not completely explain heritability in complex diseases. Some researchers have proposed that the “missing heritability” may be attributable to gene–gene and gene–environment interactions. Because there are billions of potential interaction combinations, the statistical power of a single study is often ineffective in detecting these interactions. Meta-analysis is a common method of increasing detection power; however, accessing individual data could be difficult. This study presents a simple method that employs aggregated summary values from a “case” group to detect these specific interactions that based on rare disease and independence assumptions. However, these assumptions, particularly the rare disease assumption, may be violated in real situations; therefore, this study further investigated the robustness of our proposed method when it violates the assumptions. In conclusion, we observed that the rare disease assumption is relatively nonessential, whereas the independence assumption is an essential component. Because single nucleotide polymorphisms (SNPs) are often unrelated to environmental factors and SNPs on other chromosomes, researchers should use this method to investigate gene–gene and gene–environment interactions when they are unable to obtain detailed individual patient data.

The effect of CYP, GST, and SULT polymorphisms and their interaction with smoking on the risk of hepatocellular carcinoma

Aim. The aim of our study was to assess whether selected single nucleotide polymorphisms of CYP1A1 and 2E1, GSTM1, GSTT1, and SULT1A1 influence susceptibility towards HCC, considering their interaction with cigarette smoking. Methods. We recruited HCC cases and controls among patients admitted to the hospital "Agostino Gemelli," from January 2005 until July 2010. Odds ratios (OR) of HCC were derived from unconditional multiple logistic regression. Gene-gene and gene-smoking interaction were quantified by computing the attributable proportion (AP) due to biological interaction. Results. The presence of any CYP2E1 (*) 5B variant allele (OR: 0.23; 95% CI: 0.06-0.71) and CYP2E1 (*) 6 variant allele (OR: 0.08; 95% CI: 0.01-0.33) was inversely related to HCC. There was a borderline increased risk among carriers of combined CYP1A1 (*) 2A and SULT1A1 variant alleles (OR: 1.67; 95% CI: 0.97-3.24). A significant biological interaction was observed between GSTT1 and smoking (AP = 0.48; 95% CI: 0.001-0.815), with an OR of 3.13 (95% CI: 1.69-5.82), and borderline significant interaction was observed for SULT1A1 and smoking (AP = 0.36; 95% CI: -0.021-0.747), with an OR of 3.05 (95% CI: 1.73-5.40). Conclusion. CYP2E1 (*) 5B and CYP2E1 (*) 6 polymorphisms have a favourable effect on the development of HCC, while polymorphisms of GSTT1 and SULT1A1 might play role in increasing the susceptibility among smokers.

Ozone inhalation modifies the rat liver proteome

Ozone (O₃) is a serious public health concern. Recent findings indicate that the damaging health effects of O₃ extend to multiple systemic organ systems. Herein, we hypothesize that O₃ inhalation will cause downstream alterations to the liver. To test this, male Sprague-Dawley rats were exposed to 0.5 ppm O₃ for 8 h/day for 5 days. Plasma liver enzyme measurements showed that 5 day O₃ exposure did not cause liver cell death. Proteomic and mass spectrometry analysis identified 10 proteins in the liver that were significantly altered in abundance following short-term O₃ exposure and these included several stress responsive proteins. Glucose-regulated protein 78 and protein disulfide isomerase increased, whereas glutathione S-transferase M1 was significantly decreased by O₃ inhalation. In contrast, no significant changes were detected for the stress response protein heme oxygenase-1 or cytochrome P450 2E1 and 2B in liver of O₃ exposed rats compared to controls. In summary, these results show that an environmentally-relevant exposure to inhaled O₃ can alter the expression of select proteins in the liver. We propose that O₃ inhalation may represent an important unrecognized factor that can modulate hepatic metabolic functions.

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Rats were exposed to filtered air (FA) or 0.5 ppm ozone (O₃) 8 h/day for 5 days.

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Using this exposure protocol, O₃ caused no detectable lung injury or liver cell death.

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O₃ altered the expression of some drug metabolism and stress proteins in liver.

Genetic polymorphisms in Glutathione S-transferase Omega (GSTO) and cancer risk: a meta-analysis of 20 studies

Glutathione S-transferase Omega (GSTO) plays an important role in the development of cancer. Recently, a number of studies have investigated the association between single nucleotide polymorphisms on GSTO and susceptibility to cancer; however, the results remain inconclusive. We performed a meta-analysis of 20 studies, involving 4770 cases and 5701 controls to identify the strength of association by pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs). Overall, the pooled results revealed a significantly increased risk of susceptibility for GSTO2 polymorphism (GG vs. AA: OR = 1.20, 95%CI: 1.02-1.41, Pheterogeneity = 0.116), but no significant association was found for GSTO1 polymorphism. Subgroup analysis showed that GSTO2 polymorphism significantly increased cancer risk in Caucasian population (GG vs. AA: OR = 1.32, 95%CI 1.06-1.64, Pheterogeneity = 0.616) and GSTO2 polymorphism was significantly associated with elevated risk of breast cancer (GG vs. AA OR = 1.37, 95%CI: 1.06-1.77; Pheterogeneity = 0.281). This meta-analysis demonstrates that GSTO2 polymorphism may significantly increase cancer risk in Caucasian population and is associated with elevated risk of breast cancer; while GSTO1 polymorphism is not associated with cancer risk.

Hepatocellular carcinoma epidemiology

Primary liver cancer (namely hepatocellular carcinoma, HCC) is worldwide the fifth most common cancer in men and the seventh one in women, and it represents the third most frequent cause of cancer death. HCC rates are particularly high in eastern/south-eastern Asia and in Africa, intermediate in Southern Europe, and low in most high-income countries. Persistent infections by HBV or HCV are the main recognized risk factors for HCC. Aflatoxin exposure is also an important risk factor for HCC development in Africa and eastern Asia. In high-income countries heavy alcohol drinking, tobacco smoking, overweight, diabetes, familial/genetic factors, and selected dietary aspects, have a relevant role. Updated geographic patterns and time trends in mortality from HCC in Europe, USA, Japan, and Australia are provided in the present review, together with an overview of relevant etiologic factors for HCC and main measures for the prevention of this neoplasm.

Glutathione S-conjugates as prodrugs to target drug-resistant tumors

Living organisms are continuously exposed to xenobiotics. The major phase of enzymatic detoxification in many species is the conjugation of activated xenobiotics to reduced glutathione (GSH) catalyzed by the glutathione-S-transferase (GST). It has been reported that some compounds, once transformed into glutathione S-conjugates, enter the mercapturic acid pathway whose end products are highly reactive and toxic for the cell responsible for their production. The cytotoxicity of these GSH conjugates depends essentially on GST and gamma-glutamyl transferases (γGT), the enzymes which initiate the mercapturic acid synthesis pathway. Numerous studies support the view that the expression of GST and γGT in cancer cells represents an important factor in the appearance of a more aggressive and resistant phenotype. High levels of tumor GST and γGT expression were employed to selectively target tumor with GST- or γGT-activated drugs. This strategy, explored over the last two decades, has recently been successful using GST-activated nitrogen mustard (TLK286) and γGT-activated arsenic-based (GSAO and Darinaparsin) prodrugs confirming the potential of GSH-conjugates as anticancer drugs.

Risk effects of GST gene polymorphisms in patients with acute myeloid leukemia: a prospective study

Glutathione S-transferase (GST) enzyme levels are associated with risk of many cancers, including hematologic tumours. We here aimed to investigate the relationships between GSTM1, GSTT1 and GSTP1 polymorphisms and the risk of AML. Genotyping of GSTs was based upon duplex polymerase-chain-reactions with the confronting- two-pair primer (PCR-CTPP) method in 163 cases and 204 controls. Individuals carrying null GSTT1 genotype had a 1.64 fold risk of acute leukemia relative to a non-null genotype (P<0.05). A heavy risk was observed in those carrying combination of null genotypes of GSTM1 and GSTT1 and GSTP1 Val allele genotypes when compared with those carrying wild genotypes, with an OR (95% CI) of 3.39 (1.26-9.26) (P<0.05). These findings indicate that genetic variants of GST and especially the GSTT1 gene have a critical function in the development of AML. Our study offers important insights into the molecular etiology of AML.

Bone marrow injury induced via oxidative stress in mice by inhalation exposure to formaldehyde

OBJECTIVE

Formaldehyde, a ubiquitous environmental pollutant has been classified as a human leukemogen. However, toxicity of formaldehyde in bone marrow, the target site of leukemia induction, is still poorly understood.

METHODOLOGY/PRINCIPAL FINDINGS

To investigate bone marrow toxicity (bone marrow pathology, hematotoxicity) and underlying mechanisms (oxidative stress, inflammation, apoptosis) in formaldehyde-exposed mice. Male Balb/c mice were exposed to formaldehyde (0, 0.5, and 3.0 mg/m(3)) by nose-only inhalation for 8 hours/day, over a two week period designed to simulate a factory work schedule, with an exposure-free "weekend" on days 6 and 7, and were sacrificed on the morning of day 13. Counts of white blood cells, red blood cells and lymphocytes were significantly (p<0.05) decreased at 0.5 mg/m(3) (43%, 7%, and 39%, respectively) and 3.0 mg/m(3) (52%, 27%, and 43%, respectively) formaldehyde exposure, while platelet counts were significantly increased by 109% (0.5 mg/m(3)) and 67% (3.0 mg/m(3)). Biomarkers of oxidative stress (reactive oxygen species, glutathione depletion, cytochrome P450 1A1 and glutathione s-transferase theta 1 expression), inflammation (nuclear factor kappa-B, tomour necrosis factor alpha, interleukin-1 beta), and apoptosis (activity of cysteine-aspartic acid protease 3) in bone marrow tissues were induced at one or both formaldehyde doses mentioned above.

CONCLUSIONS/SIGNIFICANCE

Exposure of mice to formaldehyde by inhalation induced bone marrow toxicity, and that oxidative stress, inflammation and the consequential apoptosis jointly constitute potential mechanisms of such induced toxicity.

GSTT1 and GSTM1 polymorphisms and prostate cancer risk in Asians: a systematic review and meta-analysis

Glutathione S-transferases (GSTs) enzymes are involved in conjugation of electrophilic compounds to glutathione, and glutathione S-transferase T 1 (GSTT1) and glutathione S-transferase M 1 (GSTM1) polymorphisms have been implicated as risk factors for prostate cancer. We conducted a systematic review and meta-analysis to define the effect of GSTM1 and GSTT1 null genotypes on prostate cancer risk in Asians. We searched the PubMed and Wanfang Medical databases to identify published case-control studies investigating the associations of GSTM1 and GSTT1 null genotypes with risk of prostate cancer in Asians. Heterogeneity was assessed using Cochran's Q statistic and odds ratios (OR) with corresponding 95 % confidence intervals (95 % CI) from individual studies were pooled using fixed or random effects models according to the heterogeneity. There were 18 studies (2,046 cases, 2,876 controls) on GSTM1 polymorphism, 15 studies (1,677 cases, 2,431 controls) on GSTT1 polymorphism, and 6 studies (675 cases, 853 controls) on GSTM1/GSTT1 interaction analysis. Overall, GSTM1 null genotype was significantly associated with increased risk of prostate cancer in Asians (random effects OR 1.80, 95 % CI 1.48-2.18, P < 0.001), and GSTT1 null genotype was also significantly associated with increased risk of prostate cancer in Asians (random effects OR 1.40, 95 % CI 1.10-1.80, P < 0.001). In addition, the GSTM1/GSTT dual null genotype was associated with higher risk of prostate cancer in Asians (random effects OR 2.14, 95 % CI 1.59-2.89, P = 0.007). In conclusion, GSTM1 and GSTT1 null genotypes are associated with increased risk of prostate cancer in Asians, and GSTM1 and GSTT1 null genotypes are risk factors for the development of prostate cancer.

Interactive effects of smoking and glutathione S-transferase polymorphisms on the development of non-alcoholic fatty liver disease

Glutathione S-transferases (GSTs) protect cells against exogenous and endogenous oxidative stress. GST polymorphisms are associated with the development of cardiovascular disease (CVD) and diabetes mellitus (DM), especially in current-smokers. Non-alcoholic fatty liver disease (NAFLD) is a predictor of future CVD or DM, because oxidative stress contributes to their pathogenesis. This study investigated whether the combination of smoking status and GST genotypes could affect the risk for NAFLD. A cross-sectional analysis was conducted among 713 Japanese participants (458 males and 255 females) during a health screening program. The GSTM1 null, GSTT1 null, GSTP1 A/B or B/B and GSTA1 A/B or B/B genotypes were determined and deemed to be high-risk genotypes. The prevalence of NAFLD was 18.7%. Among never-smokers, carriers of one, and those of two or more high-risk GSTM1, GSTP1 or GSTA1 genotypes were at a higher risk for NAFLD than those who were not carriers [odds ratio (95% confidence interval): 2.6 (1.1-5.9) and 3.3 (1.3-8.1), respectively], and the risk was further increased among current-smokers [4.6 (1.6-13.0) and 5.4 (1.2-23.7), respectively]. This is the first report to show that the combination of current-smoking and harboring high-risk GSTM1, GSTP1 and/or GSTA1 genotypes is interactively associated with the risk of NAFLD.