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

Genetic variation perspective reveals potential drug targets for subtypes of endometrial cancer

The study aims to identify potential drug targets for endometrial cancer (EC) subtypes through a Mendelian randomization (MR) approach, assessing their clinical relevance. We utilized genetic instruments for 4,907 plasma proteins from the deCODE Genetics study dataset, and data with EC (n = 12,906) from a genome-wide study (GWAS) meta-analysis in European populations for MR analyses. Complementary analyses included protein-protein interactions (PPI) network analysis, therapeutic efficacy evaluation, differential gene expression assessment, and prognosis evaluation. The expression levels of key drug targets were quantitatively measured at both the transcriptional and translational stages utilizing reverse transcription quantitative PCR (RT-qPCR) and immunohistochemistry (IHC). Additionally, we analyzed various clinicopathological features. Five drug targets for EC (CBR3, GSTO1, HHIP, IGF2R, and MMP10), seven for endometrioid subtypes (ACAP2, CBR3, GSTO1, HHIP, IGF2R, MMP10, and TLR2), and seven for non-endometrioid subtypes (CST3, DNAJB14, FSTL5, GMPR2, IFI16, MAPK9, and NEO1) were identified. Among these, IGF2R (OR = 1.165; 95% CI 1.067-1.272; p = 1.046 × 10- 2) and CST3 (OR = 0.523; 95% CI 0.339-0.804; p = 7.010 × 10- 3) were highlighted as key drug targets with causal evidence both at transcriptional and translational levels. This study preliminarily confirms that IGF2R and CST3 may serve as novel targets for the treatment of EC, providing a foundational reference for innovative clinical approaches to this disease.

Glutathione-Dependent Pathways in Cancer Cells

The most abundant tripeptide-glutathione (GSH)-and the major GSH-related enzymes-glutathione peroxidases (GPxs) and glutathione S-transferases (GSTs)-are highly significant in the regulation of tumor cell viability, initiation of tumor development, its progression, and drug resistance. The high level of GSH synthesis in different cancer types depends not only on the increasing expression of the key enzymes of the γ-glutamyl cycle but also on the changes in transport velocity of its precursor amino acids. The ability of GPxs to reduce hydroperoxides is used for cellular viability, and each member of the GPx family has a different mechanism of action and site for maintaining redox balance. GSTs not only catalyze the conjugation of GSH to electrophilic substances and the reduction of organic hydroperoxides but also take part in the regulation of cellular signaling pathways. By catalyzing the S-glutathionylation of key target proteins, GSTs are involved in the regulation of major cellular processes, including metabolism (e.g., glycolysis and the PPP), signal transduction, transcription regulation, and the development of resistance to anticancer drugs. In this review, recent findings in GSH synthesis, the roles and functions of GPxs, and GST isoforms in cancer development are discussed, along with the search for GST and GPx inhibitors for cancer treatment.

The Role of Glutathione Transferase Omega-Class Variant Alleles in Individual Susceptibility to Ovarian Cancer

The tumor microenvironment is affected by reactive oxygen species and has been suggested to have an important role in ovarian cancer (OC) tumorigenesis. The role of glutathione transferases (GSTs) in the maintenance of redox balance is considered as an important contributing factor in cancer, including OC. Furthermore, GSTs are mostly encoded by highly polymorphic genes, which further highlights their potential role in OC, known to originate from accumulated genetic changes. Since the potential relevance of genetic variations in omega-class GSTs (GSTO1 and GSTO2), with somewhat different activities such as thioltransferase and dehydroascorbate reductase activity, has not been clarified as yet in terms of susceptibility to OC, we aimed to investigate whether the presence of different GSTO1 and GSTO2 genetic variants, individually or combined, might represent determinants of risk for OC development. Genotyping was performed in 110 OC patients and 129 matched controls using a PCR-based assay for genotyping single nucleotide polymorphisms. The results of our study show that homozygous carriers of the GSTO2 variant G allele are at an increased risk of OC development in comparison to the carriers of the referent genotype (OR1 = 2.16, 95% CI: 0.88-5.26, p = 0.08; OR2 = 2.49, 95% CI: 0.93-6.61, p = 0.06). Furthermore, individuals with GST omega haplotype H2, meaning the concomitant presence of the GSTO1*A and GSTO2*G alleles, are more susceptible to OC development, while carriers of the H4 (*A*A) haplotype exhibited lower risk of OC when crude and adjusted haplotype analysis was performed (OR1 = 0.29; 95% CI: 0.12-0.70; p = 0.007 and OR2 = 0.27; 95% CI: 0.11-0.67; p = 0.0054). Overall, our results suggest that GSTO locus variants may confer OC risk.

The Polymorphisms in GSTO Genes (GSTO1 rs4925, GSTO2 rs156697, and GSTO2 rs2297235) Affect the Risk for Testicular Germ Cell Tumor Development: A Pilot Study

Members of the omega class of glutathione transferases (GSTs), GSTO1, and GSTO2, catalyze a range of reduction reactions as a part of the antioxidant defense system. Polymorphisms of genes encoding antioxidant proteins and the resultant altered redox profile have already been associated with the increased risk for testicular germ cell cancer (GCT) development. The aim of this pilot study was to assess the individual, combined, haplotype, and cumulative effect of GSTO1rs4925, GSTO2rs156697, and GSTO2rs2297235 polymorphisms with the risk for testicular GCT development, in 88 patients and 96 matched controls, through logistic regression models. We found that carriers of the GSTO1*C/A*C/C genotype exhibited an increased risk for testicular GCT development. Significant association with increased risk of testicular GCT was observed in carriers of GSTO2rs2297235*A/G*G/G genotype, and in carriers of combined GSTO2rs156697*A/G*G/G and GSTO2rs2297235*A/G*G/G genotypes. Haplotype H7 (GSTO1rs4925*C/GSTO2rs2297235*G/GSTO2rs156697*G) exhibited higher risk of testicular GCT, however, without significant association (p > 0.05). Finally, 51% of testicular GCT patients were the carriers of all three risk-associated genotypes, with 2.5-fold increased cumulative risk. In conclusion, the results of this pilot study suggest that GSTO polymorphisms might affect the protective antioxidant activity of GSTO isoenzymes, therefore predisposing susceptible individuals toward higher risk for testicular GCT development.

GSTT1 null and rs156697 Polymorphism in GSTO2 Influence the Risk and Therapeutic Outcome of B-Acute Lymphoblastic Leukemia Patients

INTRODUCTION

Glutathione S-transferase (GST) gene deletion or polymorphic sequence variations lead to decreased enzyme activity that influences susceptibility and response to chemotherapy in acute lymphoblastic leukemia (ALL). This case-control study investigated the association of GST gene polymorphisms with the etiology and therapeutic outcome of B-ALL among Kashmiri population.

METHODS

A total of 300 individuals including 150 newly diagnosed B-ALL patients and an equal number of age and gender matched controls were genotyped for five GST gene polymorphisms by polymerase chain reaction-restriction fragment length polymorphism technique (PCR-RFLP) and multiplex PCR techniques.

RESULTS

Higher frequency of GSTT1 null, GSTO2-AG, and GSTO2-GG genotypes was observed in ALL cases compared to controls that associated significantly with ALL risk (GSTT1 null: OR = 2.93, p = 0.0001; GSTO2-AG: OR = 2.58, p = 0.01; GSTO2-GG: OR = 3.13, p = 0.01). GSTM1, GSTP1, and GSTO1 SNPs showed no significant association (p > 0.05). Combined genotype analysis revealed significant association of GSTT1 null/GSTM1 null (OR = 4.11, p = 0.011) and GSTT1 null/GSTP1-AG (OR = 4.93, p = 0.0003) with B-ALL susceptibility. Haplotype analysis of rs4925 and rs156697 revealed that carriers of CG haplotype had increased risk of B-ALL (p = 0.04). Kaplan-Meier plots revealed significantly inferior 3-year disease-free survival for GSTO2-GG carriers (p = 0.002). Multivariate analysis confirmed GSTO2-GG as an independent poor prognostic factor for DFS (HR = 4.5, p = 0.034). Among combined genotypes, only GSTT1 null/GSTP1-AG associated significantly with poorer DFS rates (p = 0.032).

CONCLUSION

This study demonstrated that GSTT1 null individually or in combination with GSTM1null and GSTP1-AG genotypes associated with increased B-ALL risk. Also, rs156697 variant genotypes (AG and GG) associated with B-ALL, whereas the GG genotype of rs156697 influenced the treatment outcome.

Polymorphisms in Genes Encoding Glutathione Transferase Pi and Glutathione Transferase Omega Influence Prostate Cancer Risk and Prognosis

Considering the pleiotropic roles of glutathione transferase (GST) omega class members in redox homeostasis, we hypothesized that polymorphisms in GSTO1 and GSTO2 might contribute to prostate cancer (PC) development and progression. Therefore, we performed a comprehensive analysis of GSTO1 and GSTO2 SNPs' role in susceptibility to PC, as well as whether they might serve as prognostic biomarkers independently or in conjunction with other common GST polymorphisms (GSTM1, GSTT1, and GSTP1). Genotyping was performed in 237 PC cases and 236 age-matched controls by multiplex PCR for deletion of GST polymorphisms and quantitative PCR for SNPs. The results of this study, for the first time, demonstrated that homozygous carriers of both GSTO1*A/A and GSTO2*G/G variant genotypes are at increased risk of PC. This was further confirmed by haplotype analysis, which showed that H2 comprising both GSTO1*A and GSTO2*G variant alleles represented a high-risk combination. However, the prognostic relevance of polymorphisms in GST omega genes was not found in our cohort of PC patients. Analysis of the role of other investigated GST polymorphisms (GSTM1, GSTT1, and GSTP1) in terms of PC prognosis has shown shorter survival in carriers of GSTP1*T/T (rs1138272) genotype than in those carrying at least one referent allele. In addition, the presence of GSTP1*T/T genotype independently predicted a four-fold higher risk of overall mortality among PC patients. This study demonstrated a significant prognostic role of GST polymorphism in PC.

Glutathione S‑transferase ω 1 promotes the proliferation, migration and invasion, and inhibits the apoptosis of non‑small cell lung cancer cells, via the JAK/STAT3 signaling pathway

Glutathione S‑transferase ω 1 (GSTO1) expression levels have been discovered to be upregulated in various types of cancer. However, to the best of our knowledge, the role of GSTO1 in non‑small cell lung cancer (NSCLC) has not been investigated. The present study aimed to investigate the role of GSTO1 in NSCLC and to determine the potential molecular mechanism. GSTO1 expression levels in A549 cells were knocked down using short hairpin RNA and GSTO1 overexpression in H2122 cells was achieved using cDNA constructs. Reverse transcription‑quantitative PCR was used to analyze the mRNA expression levels of GSTO1. Cell proliferation was determined using a Cell Counting Kit‑8 assay, whereas cell migration and invasion were analyzed using Transwell assays. Flow cytometric analysis was performed to determine the levels of cell apoptosis. The expression levels of GSTO1, Bax, caspase 3, JAK and STAT3 were analyzed using western blotting. The results revealed that GSTO1 overexpression significantly promoted the proliferation, migration and invasion, and inhibited the apoptosis of H2122 cells, whereas the opposite trend was achieved in A549 cells with GSTO1 knockdown. GSTO1 overexpression also significantly increased the phosphorylation levels of JAK and STAT3, whereas the knockdown of GSTO1 promoted the opposite effects. In conclusion, the findings of the present study indicated that GSTO1 may serve as an oncogene in NSCLC. The results suggested that GSTO1 may have an important role in NSCLC by regulating the JAK/STAT3 signaling pathway. Therefore, inhibiting the expression levels of GSTO1 may represent a potential novel therapeutic strategy for NSCLC.

Human variability in glutathione-S-transferase activities, tissue distribution and major polymorphic variants: Meta-analysis and implication for chemical risk assessment

The input into the QIVIVE and Physiologically-Based kinetic and dynamic models of drug metabolising enzymes performance and their inter-individual differences significantly improve the modelling performance, supporting the development and integration of alternative approaches to animal testing. Bayesian meta-analyses allow generating and integrating statistical distributions with human in vitro metabolism data for quantitative in vitro-in vivo extrapolation. Such data are lacking on glutathione-S-transferases (GSTs). This paper reports for the first time results on the human variability of GST activities in healthy individuals, their tissue localisation and the frequencies of their major polymorphic variants by means of extensive literature search, data collection, data base creation and meta-analysis. A limited number of papers focussed on in vivo GST inter-individual differences in humans. Ex-vivo total GST activity without discriminating amongst isozymes is generally reported, resulting in a high inter-individual variability. The highest levels of cytosolic GSTs in humans are measured in the kidney, liver, adrenal glands and blood. The frequencies of GST polymorphisms for cytosolic isozymes in populations of different geographical ancestry were also presented. Bayesian meta-analyses to derive GST-related uncertainty factors provided uncertain estimates, due to the limited database. Considering the relevance of GST activities and their pivotal role in cellular adaptive response mechanisms to chemical stressors, further studies are needed to identify GST probe substrates for specific isozymes and quantify inter-individual differences.

Identification and Single-Cell Analysis of Viable Circulating Tumor Cells by a Mitochondrion-Specific AIE Bioprobe

Liquid biopsies of cancer via single-cell molecular profiling of circulating tumor cells (CTCs) are hampered by the lack of ideal CTC markers. In this study, it is reported that TPN, a bioprobe with aggregation-induced emission (AIE) activity is capable of distinguishing various tumor cells from blood leukocytes based on the difference in cell mitochondria. TPN is a cell-permeant live-cell stain that has little effect on cell viability and integrity, enabling single-cell DNA/RNA analysis with improved efficiency compared with traditional antibody-based methods. Using TPN labeling, CTCs and CTC cluster are detected in the blood from patients with lung or liver cancer. The capability of TPN to identify rare tumor cells in the malignant pleural effusion samples is also demonstrated. Furthermore, RNA sequencing of single lung CTC identified by TPN is successfully performed. The findings presented here provide an antibody-free, low-cost, and nondisruptive approach for detection and genomic characterization of viable tumor cells based on a mitochondria-targeting AIE luminogen. It might serve as a new tool for monitoring of genomics dynamic of tumor and unraveling the mechanisms of tumor metastasis.

Cadmium tolerance pathway in Anopheles gambiae senso stricto

Cadmium is one of the widely used heavy metals (HM) in commercial and industrial products and contributes to environmental contamination in an urban setting. In our previous studies, we established that An. gambiae sensu stricto, a vector of malaria, had adapted to HM pollutants in nature despite their proclivity for unpolluted aquatic habitats. We further demonstrated that heavy metal tolerance adaptation process impacts a biological cost to the fitness of the mosquito and potentially involves the induction of specific HM-responsive transcripts and proteins. Here we interrogated differential proteomic profiles of the cadmium tolerant vs. naïve strains of An. gambiae to shed light on proteomic processes that underpinned biological cost to fitness. We identified a total of 1067 larval proteins and observed significant down-regulation of proteins involved in larval immune responses, energy metabolism, antioxidant enzymes, protein synthesis, and proton transport. Our results suggest that mosquitoes can adjust their biological program through proteome changes to counter HM pollution. Since our study was done in controlled laboratory settings, we acknowledge this may not wholly represent the conditions HM polluted environments. Nevertheless, mosquitoes deploying this strategy have the potential of creating an urban enclave for breeding and thrive and become agents of sporadic malaria epidemics.

Concomitance of Polymorphisms in Glutathione Transferase Omega Genes Is Associated with Risk of Clear Cell Renal Cell Carcinoma

Glutathione S-transferases (GSTs), a superfamily of multifunctional enzymes, play an important role in the onset and progression of renal cell carcinoma (RCC). However, novel GST omega class (GSTO), consisting of GSTO1-1 and GSTO2-2 isoenzymes, has not been studied in RCC yet. Two coding single nucleotide polymorphisms (SNPs) supposedly affect their functions: GSTO1*C419A (rs4925) causing alanine to aspartate substitution (*A140D) and GSTO2*A424G (rs156697) causing asparagine to aspartate substitution (*N142D), and have been associated with several neurodegenerative diseases and cancers. Functional relevance of yet another GSTO2 polymorphism, identified at the 5' untranslated (5'UTR) gene region (GSTO2*A183G, rs2297235), has not been clearly discerned so far. Therefore, we aimed to assess the effect of specific GSTO1 and GSTO2 gene variants, independently and in interaction with established risk factors (smoking, obesity and hypertension) on the risk for the most aggressive RCC subtype, the clear cell RCC (ccRCC). Genotyping was performed in 239 ccRCC patients and 350 matched controls, while plasma levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, were determined by ELISA. As a result, combined effect of all three variant genotypes exhibited almost 3-fold risk of RCC development. Additionally, this association was confirmed at the haplotype level [variant GSTO1*A/GSTO2*G (rs156697)/GSTO2*G (rs2297235) haplotype], suggesting a potential role of those variants in propensity to RCC. Regarding the gene-environment interactions, variant GSTO2*G (rs156697) homozygous smokers are at higher ccRCC risk. Association in terms of oxidative DNA damage was found for GSTO2 polymorphism in 5'UTR and 8-OHdG. In conclusion, the concomitance of GSTO polymorphisms may influence ccRCC risk.

Glutathione S-transferase omega gene polymorphism as a biomarker for human papilloma virus and cervical cancer in Iranian women

Objective

Human papillomavirus (HPV) infection is an important sexually-transmitted infection worldwide. Persistent infections with different high-risk HPV genotypes may cause cervical intraepithelial neoplasia and cervical cancer. Single nucleotide polymorphisms of glutathione S-transferase omega (GSTO) 1 and 2 play an important role in cancer progression. To evaluate GSTO gene polymorphism influence on women’s susceptibility to low-risk or high-risk HPV infections and also risk of cervical cancer development.

Material and Methods

We examined 50 patients with cervical cancer, 43 patients who were positive for HPV, and 43 healthy individuals as negative controls. We used polymerase chain reaction-restriction fragment length polymorphism to determine GSTO1 A140D and GSTO2 N142D variants in study participants.

Results

We found a significant association between the GSTO1 A140D gene polymorphism and HPV 6, 16, 18, 16/18 infections and cervical cancer in Iranian women. We noted a significant difference for the 140AD/142NN combination genotype between patients in the cervical cancer group and healthy controls. There were no significant differences for the GSTO2 N142D genotype and allele frequencies between the patient (i.e., cervical cancer and HPV-positive) groups and controls.

Conclusion

The 140AD genotype, 140D allele, and 140AD/142NN combination genotype seem to confer a protective property in women’s susceptibility to HPV 6, 16, 18, 16/18 infections and cervical cancer. However, the GSTO2 N142D polymorphism is not associated with HPV infections and cervical cancer. It would appear that GSTO1 A140D SNPs likely play a role in the level of susceptibility to HPV-related cervical cancer.

Glutathione S-transferase π: a potential role in antitumor therapy

Glutathione S-transferase π (GSTπ) is a Phase II metabolic enzyme that is an important facilitator of cellular detoxification. Traditional dogma asserts that GSTπ functions to catalyze glutathione (GSH)-substrate conjunction to preserve the macromolecule upon exposure to oxidative stress, thus defending cells against various toxic compounds. Over the past 20 years, abnormal GSTπ expression has been linked to the occurrence of tumor resistance to chemotherapy drugs, demonstrating that this enzyme possesses functions beyond metabolism. This revelation reveals exciting possibilities in the realm of drug discovery, as GSTπ inhibitors and its prodrugs offer a feasible strategy in designing anticancer drugs with the primary purpose of reversing tumor resistance. In connection with the authors' current research, we provide a review on the biological function of GSTπ and current developments in GSTπ-targeting drugs, as well as the prospects of future strategies.

Gene expression imputation identifies candidate genes and susceptibility loci associated with cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (cSCC) is a common skin cancer with genetic susceptibility loci identified in recent genome-wide association studies (GWAS). Transcriptome-wide association studies (TWAS) using imputed gene expression levels can identify additional gene-level associations. Here we impute gene expression levels in 6891 cSCC cases and 54,566 controls in the Kaiser Permanente Genetic Epidemiology Research in Adult Health and Aging (GERA) cohort and 25,558 self-reported cSCC cases and 673,788 controls from 23andMe. In a discovery-validation study, we identify 19 loci containing 33 genes whose imputed expression levels are associated with cSCC at false discovery rate < 10% in the GERA cohort and validate 15 of these candidate genes at Bonferroni significance in the 23andMe dataset, including eight genes in five novel susceptibility loci and seven genes in four previously associated loci. These results suggest genetic mechanisms contributing to cSCC risk and illustrate advantages and disadvantages of TWAS as a supplement to traditional GWAS analyses.

Genetic loci linked to susceptibility for the common skin cancer cutaneous squamous cell carcinoma (cSCC) have been identified by genome wide association studies (GWAS). Here, the authors impute gene expression levels from GWAS data to perform a transcriptome wide association study (TWAS), identifying five novel genetic loci linked to cSCC susceptibility.

Electromagnetic Field Could Protect SH-SY5Y Cells Against Cisplatin Cytotoxicity, But Not MCF-7 Cells

Cisplatin [cis-dichlorodiammine platinum (II), CDDP], morphine (Mor), and electromagnetic field (EMF) induced oxidative stress. In this study, we tried to increase the cytotoxicity of CDDP in combination with Mor and/or EMF in MCF-7 and SH-SY5Y cells. Furthermore, we evaluate the expression levels of 11 antioxidant genes in both cell lines. We designed four treatments: CDDP alone, "CDDP+Mor," "CDDP+EMF," and "CDDP+Mor+EMF." Serial dilutions of CDDP, Mor (5.0 μM), and EMF (50 Hz, 0.50 mT, "15 min field-on/15 min field-off") were used for estimation of relative IC₅₀ values. The mRNA expression levels of antioxidant genes were determined by real-time PCR. The IC₅₀ value of CDDP in "CDDP+Mor+EMF" treatment was significantly higher than CDDP alone and "CDDP+Mor" treatments in both cell lines. Whereas the expression levels of antioxidant genes in the four treatments showed similar patterns in MCF-7 cells, in SH-SY5Y cells, most of the antioxidant genes showed an upregulation with "CDDP+EMF" and "CDDP+Mor+EMF" treatments. Moreover, significant differences in the number of upregulated genes were observed between different treatments in SH-SY5Y cells. The molecular mechanism of CDDP-reduced cytotoxicity in our designed combinations is probably different in MCF-7 and SH-SY5Y cells. CDDP in combination with EMF could protect SH-SY5Y cells from the cytotoxicity, whereas it has no significant change in MCF-7 cells.

Glutathione transferases: substrates, inihibitors and pro-drugs in cancer and neurodegenerative diseases

Glutathione transferase classical GSH conjugation activity plays a critical role in cellular detoxification against xenobiotics and noxious compounds as well as against oxidative stress. However, this feature is also exploited by cancer cells to acquire drug resistance and improve their survival. As a result, various members of the family were found overexpressed in a number of different cancers. Moreover several GST polymorphisms, ranging from null phenotypes to point mutations, were detected in members of the family and found to correlate with the onset of neuro-degenerative diseases. In the last decades, a great deal of research aimed at clarifying the role played by GSTs in drug resistance, at developing inhibitors to counteract this activity but also at exploiting GSTs for prodrugs specific activation in cancer cells. Here we summarize some of the most important achievements reached in this lively area of research.

Association between arsenic metabolism gene polymorphisms and arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China

Individuals in a given environment contaminated with arsenic have different susceptibilities to disease, which may be related to arsenic metabolism, age, gender, genetics and other factors. This study recruited 850 subjects, including 331 cases and 519 controls, from populations exposed to high levels of arsenic in drinking water in northwest China. Genotypes were determined using a custom-by-design 48-Plex SNPscan^TM kit. The results indicated that subjects who carried at least one C allele for GSTO1 rs11191979 polymorphism, at least one A allele for GSTO1 rs2164624, at least one A allele for GSTO1 rs4925, the AG genotype for GSTO2 rs156697, the AG genotype or at least one G allele for GSTO2 rs2297235 or the GG genotype or at least one G allele for PNP rs3790064 had an increased risk of arsenic-related skin lesions. In addition, the haplotype CT between rs4925 and rs11191979 appeared to confer a high risk of arsenic-included skin lesions (OR = 1.377, 95% CI = 1.03–1.84), as did the haplotype GCG among rs156697, rs157077 and rs2297235 (OR = 2.197, 95% CI = 1.08–4.44). The results showed that the variants of GSTO1, GSTO2 and PNP render the susceptible toward developing arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China.

Dietary myo-inositol deficiency decreased the growth performances and impaired intestinal physical barrier function partly relating to nrf2, jnk, e2f4 and mlck signaling in young grass carp (Ctenopharyngodon idella)

In this study, we investigated the effects of dietary myo-inositol on the growth and intestinal physical barrier functions of young grass carp (Ctenopharyngodon idella). A total of 540 young grass carp (221.83 ± 0.84 g) were fed six diets containing graded levels of myo-inositol (27.0, 137.9, 286.8, 438.6, 587.7 and 737.3 mg/kg) for 10 weeks. After the growth trial, fish were challenged with Aeromonas hydrophila for 14 days. The results indicated that compared with optimal myo-inositol levels, myo-inositol deficiency (27.0 mg/kg diet): (1) decreased glutathione (GSH) contents and antioxidant enzymes activities, and down-regulated the mRNA levels of antioxidant enzymes [not glutathione-S-transferase (gst) p1 and gstp2] and NF-E2-related factor 2 (nrf2), whereas up-regulated the reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC) contents, and the mRNA levels of Kelch-like-ECH-associated protein 1 (keap1) in three intestinal segments of young grass carp (P < 0.05). (2) Up-regulated cysteinyl aspartic acid-protease (caspase)-2, -3, -7, -8, -9, apoptotic protease activating factor-1 (apaf-1), Bcl2-associated X protein (bax), fas ligand (fasl), gen-activated protein kinase (p38mapk) and c-Jun N-terminal protein kinase (jnk) mRNA levels, whereas down-regulated B-cell lymphoma-2 (bcl-2), inhibitor of apoptosis proteins (iap) and myeloid cell leukemia-1 (mcl-1) mRNA levels in three intestinal segments of young grass carp (P < 0.05). (3) Down-regulated mRNA levels of cell cycle proteins cyclin b, cyclin d, cyclin e and E2F transcription factor 4 (e2f4) in three intestinal segments of young grass carp (P < 0.05). (4) Down-regulated the mRNA levels of zonula occludens (zo) 1, zo-2, occludin, claudin-b, -c, -f, -3c, -7a, -7b as well as -11, and up-regulated the mRNA levels of claudin-12, -15a (not -15b) and myosin light chain kinase (mlck) in three intestinal segments of young grass carp (P < 0.05). All above data indicated that dietary myo-inositol deficiency could damage physical barrier function in three intestinal segments of fish. Finally, the myo-inositol requirements based on the percent weight gain (PWG), reactive oxygen species (ROS) contents in the proximal intestine (PI), relative mRNA levels of caspase-2 (PI), cyclin b (MI) as well as claudin-b (PI) were estimated to be 276.7, 304.1, 327.9, 416.7 and 313.2 mg/kg diet, respectively.

Association of GSTO1 A140D and GSTO2 N142D Gene Variations with Breast Cancer Risk

Background:

Polymorphisms in glutathione S-transferase (GST) genes may contribute to breast cancer risk. The aim of this study was to investigate any association of two common GSTO1 A140D and GSTO2 N142D gene polymorphisms with breast cancer risk in an Iranian population followed by a protein structure analysis.

Materials and Methods:

In the case-control study, 303 subjects comprising 153 women with breast cancer and 150 healthy controls were included. Genotypes of GSTO1 A140D and GSTO2 N142D polymorphisms were assessed by PCR-RFLP. Bioinformatics tools were employed to evaluate the damaging effects of A140D and N142D on the structures of GSTO1 and GSTO2 proteins.

Results:

Our genetic association study revealed that the GSTO1 A140D polymorphism was associated with breast cancer in a dominant model (OR= 1.75, 95%CI= 1.07-2.86, p= 0.026). Also, the A allele was significantly associated with breast cancer risk (OR= 1.69, 95%CI= 1.09-2.60, p= 0.018). With regard to the N142D polymorphism, there were significant associations between the GG genotype (OR= 2.20, 95%CI= 1.14-4.27, p= 0.019) and the G allele (OR= 1.47, 95%CI= 1.06-2.05, p= 0.021) and risk of breast cancer. Structural analysis revealed that A140D and N142D polymorphisms cause changes in both primary and secondary structures of GSTO1 and GSTO2, respectively.

Conclusion:

Based on our results, GSTO1 A140D and GSTO2 N142D polymorphisms could be genetic risk factors for breast cancer, but further studies with larger sample sizes focusing on different ethnicities are needed to obtain more comprehensive results.

Structure, function and disease relevance of Omega-class glutathione transferases

The Omega-class cytosolic glutathione transferases (GSTs) have distinct structural and functional attributes that allow them to perform novel roles unrelated to the functions of other GSTs. Mammalian GSTO1-1 has been found to play a previously unappreciated role in the glutathionylation cycle that is emerging as significant mechanism regulating protein function. GSTO1-1-catalyzed glutathionylation or deglutathionylation of a key signaling protein may explain the requirement for catalytically active GSTO1-1 in LPS-stimulated pro-inflammatory signaling through the TLR4 receptor. The observation that ML175 a specific GSTO1-1 inhibitor can block LPS-stimulated inflammatory signaling has opened a new avenue for the development of novel anti-inflammatory drugs that could be useful in the treatment of toxic shock and other inflammatory disorders. The role of GSTO2-2 remains unclear. As a dehydroascorbate reductase, it could contribute to the maintenance of cellular redox balance and it is interesting to note that the GSTO2 N142D polymorphism has been associated with multiple diseases including Alzheimer's disease, Parkinson's disease, familial amyotrophic lateral sclerosis, chronic obstructive pulmonary disease, age-related cataract and breast cancer.

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.

GSTP1 and GSTO1 single nucleotide polymorphisms and the response of bladder cancer patients to intravesical chemotherapy

SNPs may restrict cell detoxification activity and be a potential risk factor for cancer chemosensitivity. We evaluated the predictive value of these polymorphisms on the sensitivity of bladder cancer patients to epirubicin and mitomycin chemotherapy instillation as well as their toxicities. SNPs were analyzed by TaqMan genotyping assays in 130 patients treated with epirubicin and 114 patients treated with mitomycin. Recurrence-free survival (RFS) was estimated by the Kaplan-Meier method, and hazard ratios (HRs) and 95% confidence intervals (CIs) of the HRs were derived from multivariate Cox proportional hazard models. GSTP1 rs1695 and GSTO1 rs4925 were also associated with RFS in the epirubicin group. Patients carrying the GSTP1 AG+GG and GSTO1 AC+AA genotypes had an unfavorable RFS. Patients with the GSTP1 AA and GSTO1 CC genotypes had a reduced risk of recurrence after the instillation of epirubicin. In addition, patients with the GSTP1 rs1695 AA genotype had an increased risk of irritative voiding symptoms; while patients with the GSTO1 rs4925 CC genotype had a decreased risk of hematuria. Our results suggest that GSTP1 and GSTO1 polymorphisms are associated with epirubicin treatment outcomes as well as with epirubicin-related toxicity.