Polymorphism of glutathione S-transferase mu 1 and theta 1 genes and hepatocellular carcinoma in southern Guangxi, China

Aflatoxin B1 in poultry liver: Toxic mechanism

Aflatoxin B1 (AFB1) is the most common carcinogenic toxin in livestock and poultry feed, seriously endangering poultry production and public health. Liver is the most important organ for the metabolism of exogenous and endogenous substances in the body. AFB1 produces toxicity under the biotransformation of cytochrome P450 microparticle oxidase (CYP450). Hepatocytes are the most important cells for synthesizing CYP450 enzymes, so that AFB1 has the most significant effect on the liver. AFB1 can induce liver cell damage in poultry through a variety of molecular mechanisms, and the main of damage mechanisms have been discovered so far include oxidative damage, promoting apoptosis, influencing hepatocyte gene expression, interfering with hepatocyte autophagy, pyroptosis and necroptosis. This article reviewed the molecular mechanism of AFB1 inducing liver injury in poultry, hopefully, to provid a new direction and theoretical basis for the development of a new AFB1 detoxification method.

GSTM1 polymorphism is related to risks of nasopharyngeal cancer and laryngeal cancer: a meta-analysis

Background

Accumulating data have reported that GSTM1 polymorphism may be related to nasopharyngeal cancer (NPC) and laryngeal cancer (LC). This meta-analysis was performed to investigate the relationship between GSTM1 polymorphism and risks of NPC and LC.

Methods

Pubmed, Embase, and China National Knowledge Infrastructure (CNKI) databases were searched for potential articles. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the relationship of GSTM1 polymorphism with the risks of NPC and LC. I²>50% or P<0.05 indicates significant heterogeneity. When heterogeneity existed, the random-effects model was used to pool data, otherwise, the fixed-effects model was adopted. Publication bias was detected by Begg’s funnel plot and Egger’s regression. Quality of each study was evaluated by Newcastle-Ottawa Scale.

Results

Thirty-two eligible articles were included. Pooled outcome suggested the significant relationship of GSTM1 null genotype with increased risk of LC (OR =1.28, 95% CI =1.05–1.54). Compared with hospital-based (HB) population, GSTM1 null genotype was also related to increased risk of LC (OR =1.38, 95% CI =1.06–1.80). Positive relationship of GSTM1 null genotype with enhanced risk of NPC was observed (OR =1.43, 95% CI =1.26–1.63). A similar trend was also observed in the subgroup analysis by source of control (population-based [PB]: OR =1.39, 95% CI =1.18–1.63; HB: OR =1.52, 95% CI =1.22–1.89).

Conclusion

GSTM1 null genotype is related to increased risk of NPC and LC.

Deficient glutathione in the pathophysiology of mycotoxin-related illness

Evidence for the role of oxidative stress in the pathophysiology of mycotoxin-related illness is increasing. The glutathione antioxidant and detoxification systems play a major role in the antioxidant function of cells. Exposure to mycotoxins in humans requires the production of glutathione on an “as needed” basis. Research suggests that mycotoxins can decrease the formation of glutathione due to decreased gene expression of the enzymes needed to form glutathione. Mycotoxin-related compromise of glutathione production can result in an excess of oxidative stress that leads to tissue damage and systemic illness. The review discusses the mechanisms by which mycotoxin-related deficiency of glutathione may lead to both acute and chronic illnesses.

Quantitative assessment of the effect of glutathione S-transferase genes GSTM1 and GSTT1 on hepatocellular carcinoma risk

Hepatocellular carcinoma (HCC) is one of the most serious health problems worldwide. As in many other diseases, environment and genetic factors are believed to be involved in the pathogenesis of HCC. Numerous epidemiologic investigations including case-control and cohort studies have suggested the association of glutathione S-transferase (GST) genetic polymorphisms and HCC risk. However, some studies have produced conflicting results. Therefore, we performed an updated meta-analysis to clarify this inconsistency and to establish a comprehensive picture of the association of the polymorphisms of GSTM1 and GSTT1 with HCC susceptibility. We searched PubMed, Embase, ISI Web of Science, and CNKI databases to identify eligible studies meeting the inclusion criteria up to August 30, 2013. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of association. Finally, there were a total of 33 studies with 4,232 cases and 6,601 controls included in this meta-analysis. In the pooled analysis, significantly increased HCC risks were found for null genotype of GSTM1 (OR = 1.31, 95% CI = 1.07-1.61, P = 0.010, P heterogeneity < 10(-5)) and GSTT1 (OR = 1.47, 95% CI = 1.25-1.74, P < 10(-5), P heterogeneity < 10(-5)). Potential sources of heterogeneity were explored by subgroup analysis based on ethnicity, sample size, and source of control. Significant results were found among East Asians and Indians when stratified by ethnicity, while no evidence of significant associations was observed among Caucasian and African populations. In the gene-gene interaction analysis, a statistically significant increased risk for HCC was detected for individuals with combined deletion mutations in both genes compared to those with wild genotypes (OR = 1.88, 95% CI = 1.41-2.50, P < 10(-4), P heterogeneity = 0.004). The present meta-analysis demonstrated that the GSTM1 and GSTT1 null genotype may be associated with an increased risk of HCC and that individuals having the combination of both defective GST genotypes may be more susceptible to developing HCC.

Relationship between GSTT1 gene polymorphism and hepatocellular carcinoma in patients from China

OBJECTIVE

The results from studies on associations of the glutathione S-transferase T1 (GSTT1) gene polymorphism and hepatocellular carcinoma (HCC) risk in Chinese populations are still conflicting. This meta- analysis was performed to evaluate the relationship in detail.

METHODS

Eligible reports were recruited into this meta-analysis from the databases of PubMed, Embase, Cochrane Library and CBM-disc (China Biological Medicine Database). Results were expressed with odds ratios (OR) for dichotomous data, and 95% confidence intervals (CI) were also calculated.

RESULTS

Eighteen investigations were identified for the analysis of association between polymorphic deletion of GSTT1 and HCC, consisting of 2,693 patients with HCC and 4,696 controls. Null genotype of GSTT1 was associated with HCC susceptibility in Chinese (OR=1.53, 95%CI: 1.28-1.82; P<0.00001).

CONCLUSION

The GSTT1 null genotype is associated with HCC susceptibility in Chinese.

Association of GST genetic polymorphisms with the susceptibility to hepatocellular carcinoma (HCC) in Chinese population evaluated by an updated systematic meta-analysis

Background

Due to the possible involvement of Glutathione S-transferase Mu-1 (GSTM1) and Glutathione S-transferase theta-1 (GSTT1) in the detoxification of environmental carcinogens, environmental toxins, and oxidative stress products, genetic polymorphisms of these two genes may play important roles in the susceptibility of human being to hepatocellular carcinoma. However, the existing research results are not conclusive.

Methods

A systematic literature search using databases (PubMed, Scopus, Embase, Chinese Biomedical Database, Chinese National Knowledge Infrastructure, Wanfang Data, etc.) for the eligible studies meeting the inclusion criteria including case-control studies or cohort studies is evaluated using an updated systematic meta-analysis.

Results

Significant increase in the risk of HCC in the Chinese population is found in GSTM1 null genotype (OR = 1.47, 95% CI: 1.21 to 1.79, P<0.001) and GSTT1 null genotype (OR = 1.38, 95% CI: 1.14 to 1.65, P<0.001). Analysis using the random-effects model found an increased risk of HCC in GSTM1-GSTT1 dual null population (OR = 1.79, 95% CI: 1.26 to 2.53, P<0.001). In addition, subgroup analyses showed a significant increase in the association of GST genetic polymorphisms (GSTM1, GSTT1, and GSTM1-GSTT1) with HCC in southeast and central China mainland. However, available data collected by this study fail to show an association between GST genetic polymorphisms and HCC in people from the Taiwan region (for GSTM1: OR = 0.78, 95% CI: 0.60 to 1.01, P = 0.06; for GSTT1: OR = 0.94, 95% CI: 0.78 to 1.14, P = 0.546; for GSTM1-GSTT1: OR = 1.04, 95% CI: 0.81 to 1.32, P = 0.77). Sensitivity analysis and publication bias diagnostics confirmed the reliability and stability of this meta-analysis.

Conclusions

Our results indicate that both GSTM1 and GSTT1 null genotypes are associated with an increased HCC risk in Chinese population. Peoples with dual null genotypes of GSTM1-GSTT1 are more susceptible to developing HCC. In conclusion, GST genetic polymorphisms play vital roles in the development of HCC in the Chinese population.

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

BACKGROUND

A number of case-control studies were conducted to investigate the association of glutathione S-transferase (GST) genetic polymorphisms and hepatocellular carcinoma (HCC) risk. However, these studies have yielded contradictory results. We therefore performed a meta-analysis to derive a more precise estimation of the association between polymorphisms on GSTM1, GSTT1 and HCC.

METHODOLOGY/PRINICPAL FINDINGS

PubMed, EMBASE, ISI web of science and the CNKI databases were systematically searched to identify relevant studies. Data were abstracted independently by two reviewers. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to assess the strength of association. Potential sources of heterogeneity were also assessed by subgroup analysis and meta-regression. Funnel plots and Egger's linear regression were used to test publication bias among the articles. A total of 34 studies including 4,463 cases and 6,857 controls were included in this meta-analysis. In a combined analysis, significantly increased HCC risks were found for null genotype of GSTM1 (OR = 1.29, 95% CI: 1.06-1.58; P = 0.01) and GSTT1 (OR = 1.43, 95% CI: 1.22-1.68; P<10(-5)). Potential sources of heterogeneity were explored by subgroup analysis and meta-regression. Significant results were found in East Asians and Indians when stratified by ethnicity; whereas no significant associations were found among Caucasians and African populations. By pooling data from 12 studies that considered combinations of GSTT1 and GSTM1 null genotypes, a statistically significant increased risk for HCC (OR = 1.88, 95% CI: 1.41-2.50; P<10(-4)) was detected for individuals with combined deletion mutations in both genes compared with positive genotypes.

CONCLUSIONS/SIGNIFICANCE

This meta-analysis suggests that the GSTM1 and GSTT1 null genotype may slightly increase the risk of HCC and that interaction between unfavourable GSTs genotypes may exist.

A meta-analysis of the relationship between glutathione S-transferases gene polymorphism and hepatocellular carcinoma in Asian population

The results from the published studies on the association between glutathione S-transferases (GST) gene polymorphism and hepatocellular carcinoma (HCC) in Asian population are still conflicting. GSTM1, GSTT1 and GSTP1 are the mainly mutant sites reported at present. This meta-analysis was performed to evaluate the relationship between GST gene polymorphism and HCC risk in Asians. Association studies were identified from the databases of PubMed, Embase, Cochrane Library and CBM-disc (China Biological Medicine Database) on February 1, 2012, and eligible investigations were synthesized using meta-analysis method. Results were expressed with odds ratios (OR) for dichotomous data, and 95 % confidence intervals (CI) were also calculated. Twenty-five investigations were identified for the analysis of association between polymorphic deletion of GSTM1 and HCC, consisting of 3,547 patients with HCC and 6,132 controls. There was a marked association between GSTM1 null genotype and HCC susceptibility (OR 1.48, 95 % CI 1.19-1.85, P = 0.0004). GSTM1 null genotype was associated with HCC risk in Chinese. Furthermore, null genotype of GSTT1 was associated with HCC susceptibility in Asians. For the GSTM1-GSTT1 interaction analysis, the dual null genotype of GSTM1/GSTT1 was significantly associated with HCC susceptibility in Asian population. However, GSTP1 ile105 val gene polymorphism was not associated with HCC risk in Asian population. In conclusion, GSTM1/GSTT1 null genotype is associated with the HCC susceptibility. However, GSTP1 gene polymorphism is not associated with HCC risk.

Dietary modulation of the biotransformation and genotoxicity of aflatoxin B(1)

Diet and its various components are consistently identified as among the most important 'risk factors' for cancer worldwide, yet great uncertainty remains regarding the relative contribution of nutritive (e.g., vitamins, calories) vs. non-nutritive (e.g., phytochemicals, fiber, contaminants) factors in both cancer induction and cancer prevention. Among the most potent known human dietary carcinogens is the mycotoxin, aflatoxin B(1) (AFB). AFB and related aflatoxins are produced as secondary metabolites by the molds Aspergillus flavus and Aspergillus parasiticus that commonly infect poorly stored foods including peanuts, pistachios, corn, and rice. AFB is a potent hepatocarcinogenic agent in numerous animal species, and has been implicated in the etiology of human hepatocellular carcinoma. Recent research has shown that many diet-derived factors have great potential to influence AFB biotransformation, and some efficiently protect from AFB-induced genotoxicity. One key mode of action for reducing AFB-induced carcinogenesis in experimental animals was shown to be the induction of detoxification enzymes such as certain glutathione-S-transferases that are regulated through the Keap1-Nrf2-ARE signaling pathway. Although initial studies utilized the dithiolthione drug, oltipraz, as a prototypical inducer of antioxidant response, dietary components such as suforaphane (SFN) are also effective inducers of this pathway in rodent models. However, human GSTs in general do not appear to be extensively induced by SFN, and GSTM1 - the only human GST with measurable catalytic activity toward aflatoxin B(1)-8,9-epoxide (AFBO; the genotoxic metabolite of AFB), does not appear to be induced by SFN, at least in human hepatocytes, even though its expression in human liver cells does appear to offer considerable protection against AFB-DNA damage. Although induction of detoxification pathways has served as the primary mechanistic focus of chemoprevention studies, protective effects of chemoprotective dietary components may also arise through a decrease in the rate of activation of AFB to AFBO. Dietary consumption of apiaceous vegetables inhibits CYP1A2 activity in humans, and it has been demonstrated that some compounds in those vegetables act as potent inhibitors of human CYP1A2 and cause reduced hCYP1A2-mediated mutagenicity of AFB. Other dietary compounds of different origin (e.g., constituents of brassica vegetables and hops) have been shown to modify expression of human hepatic enzymes involved in the oxidation of AFB. SFN has been shown to protect animals from AFB-induced tumors, to reduce AFB biomarkers in humans in vivo and to reduce efficiently AFB adduct formation in human hepatocytes, although it appears that this protective effect is the result of repression of human hepatic CYP3A4 expression, rather than induction of protective GSTs, at least in human hepatocytes. If this mechanism were to occur in vivo in humans, it would raise safety concerns for the use of SFN as a chemoprotective agent as it may have important implications for drug-drug interactions in humans. A dietary chemoprevention pathway that is independent of AFB biotransformation is represented by the potential for dietary components, such as chlorophyllin, to tightly bind to and reduce the bioavailability of aflatoxins. Chlorophyllin has been shown to significantly reduce genotoxic AFB biomarkers in humans, and it therefore holds promise as a practical means of reducing the incidence of AFB-induced liver cancer. Recent reports have demonstrated that DNA repair mechanisms are inducible in mammalian systems and some diet-derived compounds elevated significantly the gene expression of enzymes potentially involved in nucleotide excision repair of AFB-DNA adducts. However, these are initial observations and more research is needed to determine if dietary modulation of DNA repair is a safe and effective approach to chemoprevention of AFB-induced liver cancer.

Association of glutathione S-transferase T1 and M1 genotypes with chronic liver diseases among Filipinos

The glutathione S-transferase (GST) supergene family is made up of four gene families responsible for the biotransformation of drugs and other xenobiotics. Genetic variations in this supergene family influence individual detoxification levels and may contribute to the development of cancer. A hospital-based case-control study was conducted to evaluate the association between GST polymorphism among Filipino patients positive for hepatitis B virus (HBV DNA) and clinically diagnosed as either with chronic active hepatitis, liver cirrhosis, and hepatocellular carcinoma as well as normal individuals negative for HBV infection. Multiplex PCR was used to detect the presence or absence of the GSTT1 and GSTM1 polymorphisms in peripheral blood. DNA sequencing of the S gene region of the virus was used to determine the predominant genotype found among HBV-infected patients. Our results showed that the odds of having a chronic liver disease is only 0.95 (95% CI 0.58-1.57) among those with GSTT1 null genotype compared to those with GSTT1+ genotype. On the other hand, the odds of chronic liver disease is 17.85 times (95% CI 7.34-43.45) for those with GSTM1 null genotype compared to those with GSTM1+ genotype. Using the GSTT1+/GSTM1+ genotype as the reference, both GSTT1+/GSTM1- (OR 16.61; 95% CI 6.69-41.22) and GSTT1-/GSTM1- (OR 11.91; 95% CI 4.48-31.66) genotypes seem to be risk factors for chronic liver disease. From our observations, we conclude that polymorphism in GSTM1 null genotype (OR 17.85; 95% CI 7.34-43.45) seem to be associated with an increased risk of chronic liver disease among Filipinos.

GST polymorphisms are associated with hepatocellular carcinoma risk in Chinese population

AIM: To investigate the association between GSTM1 and GSTT1 polymorphisms and the risk of hepatocellular carcinoma (HCC) in Chinese population.

METHODS: Literature databases including PubMed, ISI web of science and other databases were searched. Pooled odds ratio (OR) and 95% CI were calculated using random- or fixed- effects model. Subgroup analysis and sensitivity analysis were also performed.

RESULTS: Nineteen studies of GSTM1 (2660 cases and 4017 controls) and 16 studies of GSTT1 (2410 cases and 3669 controls) were included. The GSTM1/GSTT1 null genotypes were associated with increased risk of HCC in Chinese population (for GSTM1, OR = 1.487, 95% CI: 1.159 to 1.908, P = 0.002; for GSTT1, OR = 1.510, 95% CI: 1.236 to 1.845, P = 0.000). No publication bias was detected. In subgroup analysis, glutathione S-transferases polymorphisms were significantly associated with HCC risk among the subjects living in high-incidence areas, but not among the subjects living in low-incidence areas.

CONCLUSION: The present meta-analysis suggests that GSTM1/GSTT1 null genotypes are associated with increased risk of HCC in Chinese population.

Null genotypes of GSTM1 and GSTT1 contribute to hepatocellular carcinoma risk: evidence from an updated meta-analysis

BACKGROUND & AIMS

Studies investigating the associations between glutathione S-transferase (GST) genetic polymorphisms and hepatocellular carcinoma (HCC) risk have reported controversial results. Thus, a meta-analysis was performed to clarify the effects of GSTM1 and GSTT1 polymorphisms on HCC risk.

METHODS

We identified 132 relevant records through a literature search up to November 22, 2009, and 24 individual case-control studies from 23 publications were finally included, involving a total of 3349 HCC cases and 5609 controls. Subgroup analyses were performed by ethnicity, or by area according to the incidence rate and hepatitis virus status.

RESULTS

Analyses of total relevant studies showed an increased HCC risk was significantly associated with null genotypes of GSTM1 (OR=1.26, 95% CI 1.03-1.54, p(OR)=0.027) and GSTT1 (OR=1.28, 95% CI 1.09-1.51, p(OR)=0.002). In addition, the GSTM1-GSTT1 interaction analysis showed that the dual null genotype of GSTM1/GSTT1 was significantly associated with increased HCC risk (OR=1.89, 95% CI 1.38-2.60, p(OR)<0.001). Subgroup analyses showed that the associations above were still statistically significant in Asians (p(GSTM1)=0.017, p(GSTT1)=0.001, p(Dual null genotype)<0.001), high-rate areas (p(GSTM1)=0.012, p(GSTT1)=0.006, p(Dual null genotype)<0.001), and HBV-dominant areas (p(GSTM1)=0.003, p(GSTT 1)=0.003, p(Dual null genotype)<0.001).

CONCLUSIONS

This meta-analysis suggests null genotypes of GSTM1 and GSTT1 are both associated with increased HCC risk in Asians, and individuals with the dual null genotype of GSTM1/GSTT1 are particularly susceptible to developing HCC.

Genetic variations in human glutathione transferase enzymes: significance for pharmacology and toxicology

Glutathione transferase enzymes (GSTs) catalyze reactions in which electrophiles are conjugated to the tripeptide thiol glutathione. While many GST-catalyzed transformations result in the detoxication of xenobiotics, a few substrates, such as dihaloalkanes, undergo bioactivation to reactive intermediates. Many molecular epidemiological studies have tested associations between polymorphisms (especially, deletions) of human GST genes and disease susceptibility or response to therapy. This review presents a discussion of the biochemistry of GSTs, the sources-both genetic and environmental-of interindividual variation in GST activities, and their implications for pharmaco- and toxicogenetics; particular attention is paid to the Theta class GSTs.

Sulforaphane- and phenethyl isothiocyanate-induced inhibition of aflatoxin B1-mediated genotoxicity in human hepatocytes: role of GSTM1 genotype and CYP3A4 gene expression

Primary cultures of human hepatocytes were used to investigate whether the dietary isothiocyanates, sulforaphane (SFN), and phenethyl isothiocyanate (PEITC) can reduce DNA adduct formation of the hepatocarcinogen aflatoxin B(1) (AFB). Following 48 h of pretreatment, 10 and 50 microM SFN greatly decreased AFB-DNA adduct levels, whereas 25muM PEITC decreased AFB-DNA adducts in some but not all hepatocyte preparations. Microarray and quantitative reverse transcriptase (RT)-PCR analyses of gene expression in SFN and PEITC-treated hepatocytes demonstrated that SFN greatly decreased cytochrome P450 (CYP) 3A4 mRNA but did not induce the expression of either glutathione S-transferase (GST) M1 or GSTT1. The protective effects of SFN required pretreatment; cotreatment of hepatocytes with SFN and AFB in the absence of pretreatment had no effect on AFB-DNA adduct formation. When AFB-DNA adduct formation was evaluated by GST genotype, the presence of one or two functional alleles of GSTM1 was associated with a 75% reduction in AFB-DNA adducts, compared with GSTM1 null. In conclusion, these results demonstrate that the inhibition of AFB-DNA adduct formation by SFN is dependent on changes in gene expression rather than direct inhibition of catalytic activity. Transcriptional repression of genes involved in AFB bioactivation (CYP3A4 and CYP1A2), but not transcriptional activation of GSTs, may be responsible for the protective effects of SFN. Although GSTM1 expression was not induced by SFN, the presence of a functional GSTM1 allele can afford substantial protection against AFB-DNA damage in human liver. The downregulation of CYP3A4 by SFN may have important implications for drug interactions.

Modulation of aflatoxin B1-mediated genotoxicity in primary cultures of human hepatocytes by diindolylmethane, curcumin, and xanthohumols

This study employed cultured human primary hepatocytes to investigate the ability of the putative chemopreventive phytochemicals curcumin (CUR), 3,3'-diindolylmethane (DIM), isoxanthohumol (IXN), or 8-prenylnaringenin (8PN) to reduce DNA adduct formation of the hepatocarcinogen aflatoxin B1 (AFB). Following 48 h of pretreatment, DIM and 8PN significantly increased AFB-DNA adduct levels, whereas CUR and IXN had no effect. DIM greatly enhanced the transcriptional expression of cytochrome P450 (CYP) 1A1 and CYP1A2 mRNA. Glutathione S-transferase mRNAs were not increased by any of the treatments. In vitro enzyme activity assays demonstrated that 8PN and DIM, but not CUR or IXN, inhibited human CYP1A1, CYP1A2, and CYP3A4 activities. To distinguish between treatment effects on transcription versus direct effects on enzyme activity for DIM, we evaluated the effects of pretreatment alone (transcriptional activation) versus cotreatment alone (enzyme inhibition). The results demonstrated that effects on gene expression, but not catalytic activity, are responsible for the observed effects of DIM on AFB-DNA adduct formation. The increase in AFB-DNA damage following DIM treatment may be explained through its substantial induction of CYP1A2 and/or its downregulation of GSTM1, both of which were significant. The increase in DNA damage by DIM raises potential safety risks for dietary supplements of DIM and its precursor indole-3-carbinol.

Glutathione-S-transferase and microsomal epoxide hydrolase polymorphism and viral-related hepatocellular carcinoma risk in India

Hepatocellular carcinoma (HCC) is the fourth most common cancer worldwide, the main etiological factors being chronic infections with hepatitis B and C viruses. Genetic polymorphic forms of glutathione-S-transferase (GST) and microsomal epoxide hydrolase (mEPHX) have been associated with risk for various malignancies. The present study was undertaken to evaluate the association of GSTT1 and GSTM1 null genotypes and mEPHX polymorphisms with hepatitis virus-related HCC risk in an Indian population. Three groups of subjects were considered, control (n = 169), chronic viral hepatitis (n = 174), and HCC (n = 63). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for this polymorphic study. Genotype distributions between categories were compared using the chi2 test; odds ratios (ORs) and 95% confidence interval were calculated to express the relative risk. GSTT1 null genotype was associated with 2.23-fold (p < 0.05) increased risk for HCC development as compared to the control group. However, GSTM1 null genotype was found to have a protective effect when hepatitis patients were considered. In case of mEPHX, R139R imposed a risk factor for HCC with both control (OR = 1.81) and chronic hepatitis-infected (OR = 2.06) subjects. Combination of heterozygous mutant genotypes at mEPHX exons 3 and 4 revealed a twofold risk (nonsignificant) for HCC. Further, combination of GSTM1 and T1 genotypes with either of exon 3 or 4 polymorphism of mEPHX displayed synergistic associations (risk or protective) for HCC development. GST and mEPHX variants share a positive association with viral-related HCC risk in Indian population, although a larger sample size is still required to confirm the results.

Genetic Polymorphism in Glutathione Transferases (GST): Population distribution of GSTM1, T1, and P1 conjugating activity

Glutathione transferases (GST) catalyze the conjugation of glutathione (GSH) with electrophiles, many of which may otherwise interact with protein or DNA. In select cases such as halogenated solvents, GST-mediated conjugation may lead to a more toxic or mutagenic metabolite. Polymorphisms that exert substantial effects on GST function were noted in human populations for several isozymes. This analysis focuses on three well-characterized isozymes, GSTM1, T1, and P1, in which polymorphisms were extensively studied with respect to DNA adducts and cancer in molecular epidemiologic studies. The current review and analysis focused upon how polymorphisms in these GST contributed to population variability in GST function. The first step in developing this review was to characterize the influence of genotype on phenotype (enzyme function) and the frequency of the polymorphisms across major population groups for all three GST. This information was then incorporated into Monte Carlo simulations to develop population distributions of enzyme function. These simulations were run separately for GSTM1, T1, and P1, and also for the combination of these isozymes, to assess the possibility of overlapping substrate specificity. Monte Carlo simulations indicated large interindividual variability for GSTM1 and T1 due to the presence of the null (zero activity) genotype, which is common in all populations studied. Even for GSTM1 or T1 non-null individuals, there was considerable interindividual variability with a bimodal distribution of enzyme activity evident. GSTP1 polymorphisms are associated with somewhat less variability due to the absence of null genotypes. However, in all cases simulated, the estimated variability is sufficiently large to warrant consideration of GST function distributions in assessments involving GST-mediated activation or detoxification of xenobiotics. Ideally, such assessments would involve physiologically based toxicokinetic (PBTK) modeling to assess population variability in internal dose.

Genetic polymorphism of glutathione S-transferases M1 and T1 in Egyptian patients with bilharzial bladder cancer

OBJECTIVE

To assess the influence of glutathione S-transferases M1 and T1 (GSTM1 and T1) genotype on the risk of bladder cancer in patients with urinary bilharziasis.

MATERIALS AND METHODS

This study was designed as a case-control study that involved 60 individuals who were enrolled into 3 equal groups. The first one included patients with bilharzial bladder cancer, the second one had those with nonmalignant urinary bilharziasis, and the last one was the control group. All of the participants were adult males, nonsmokers, and with matched ages. All of them underwent an assessment of the serum level of the total GST concentration and the polymerase chain reaction (PCR) was used for determination of the GSTM1 and T1 genotypes.

RESULTS

The lower most GST enzyme concentration was reported in patients with bilharzial bladder cancer (26 +/- 4.4 ng/ml) with significant difference between it and that of the second group (36.8 +/- 4.1 ng/ml, P < 0.05) and that of the controls (40.4 +/- 4 ng/ml, P < 0.005). The PCR results have demonstrated that the frequency of combined GSTM1 and T1 genes deletion (M1-ve T1-ve) was significantly higher in cases of bladder cancer (40%) than those of the controls (5%, P < 0.005) and those of the second group (10%, P < 0.05). The unconditional logistic regression test revealed that patients with urinary bilharziasis and combined GSTM1 and T1 genes deletion are at a significant risk for malignant transformation (OR = 6.3, P < 0.05).

CONCLUSIONS

Patients with urinary bilharziasis and GSTM1-ve and T1-ve genes might be at increased risk of bladder cancer. However, larger studies are needed for confirmation of these results.

Identification of the critical regions in hepatitis B virus preS required for its stability

As a hepatitis B virus (HBV) envelope domain, preS plays significant roles in receptor recognition and viral infection. However, the regions critical for maintaining a stable and functional conformation of preS are still unclear and require further investigation. In order to unravel these regions, serially truncated fragments of preS were constructed and expressed in Escherichia coli. Their solubility, stability, secondary structure, and affinity to polyclonal antibodies and hepatocytes were examined. The results showed that amino acids 31-36 were vital for its stable conformation, and the absence of 10-36 amino acids significantly reduced its binding to polyclonal antibodies as well as hepatocytes. The most stable fragment 1-120 (preS1 + N-terminal 12 amino acids of preS2), perhaps the core of preS, was discovered, which bound to HepG2 cells most tightly. Moreover, the availability of large amounts of well-folded and stable preS1-120 enables us to carry out further structural determination and mechanistic study on HBV infection.

Glutathione S-transferases pi 1, alpha 1 and M3 genetic polymorphisms and the risk of hepatocellular carcinoma in humans

INTRODUCTION

Glutathione S-transferases pi1, alpha1 and micro3 are members of an enzymatic superfamily involved in the conjugation and detoxification of carcinogens. Polymorphisms affecting the genes encoding these enzymes may modify their ability to neutralize carcinogens. Our aim was to investigate whether these polymorphisms affect the risk of developing hepatocellular carcinoma in humans.

METHODS

A total of 184 white Spanish patients diagnosed with hepatocellular carcinoma and 248 healthy control subjects from the same ethnic origin were included. GSTA1*B promoter allele, GSTM3*B 3-bp-deleted allele and GSTP1 Ile105Val SNP were identified.

RESULTS

No differences were found between the distribution of the studied polymorphisms, or in the allele frequencies for variant alleles in patients and controls: 0.411 and 0.371 for GSTA1, 0.116 and 0.131 for GSTM3, and 0.285 and 0.309 for GSTP1, respectively. Among patients the GSTP1 mutated allele was more frequent in those drinking more than 50 g ethanol/day (odds ratio: 2.00; 95% confidence intervals: 1.06-3.78). Age at diagnosis, gender, tobacco use and hepatitis B and C viral status did not influence these results.

CONCLUSION

We conclude that the studied polymorphisms affecting GSTP1, GSTA1 and GSTM3 genes are probably not related to the risk of developing hepatocellular carcinoma in the studied population.

Association of CYP1A2 genetic polymorphisms with hepatocellular carcinoma susceptibility: a case-control study in a high-risk region of China

OBJECTIVES

Aflatoxin B1 exposure is one of the major risk factors for hepatocellular carcinoma (HCC). CYP1A2 is a cytochrome P450 isoenzyme that plays an important role in the bioactivation of AFB1 to its carcinogenic metabolite. The study was designed to assess whether genetic polymorphisms in CYP1A2 are associated with HCC susceptibility in a high-risk region.

METHODS

A case-control study of 431 HCC cases and 550 cancer-free controls recruited from an HCC endemic region in China was carried out. Three single nucleotide polymorphisms, namely -3860G > A (CYP1A2*1C), -3113G > A, and 5347T > C (CYP1A2*1B) were genotyped by polymerase chain reaction-restriction fragment length polymorphism methods.

RESULTS

Homozygous carriers of the major haplotype -3860G/-3113G/5347C were associated with increased HCC susceptibility in the overall population (odds ratio [OR] = 1.65, 95% confidence interval [CI]: 1.11-2.46, P = 0.014), in HBsAg seronegative individuals (OR = 2.69, 95% CI: 1.43-5.06, P = 0.002), and in heavy smokers (OR = 2.14, 95% CI: 1.21-3.80, P=0.009). In addition, individuals carrying at least one CYP1A2*1C allele showed significantly decreased HCC risk (OR = 0.49, 95% CI: Q0.27-0.86, P = 0.013) in the HBsAg seronegative subpopulation. Furthermore, as compared with HBsAg seropositive patients, wild-type homozygotes of the CYP1A2*1C polymorphism were significantly over-represented in HBsAg seronegative patients (P = 0.024). No significant association between CYP1A2 genetic polymorphisms and HCC risk was observed in either HBsAg seropositive individuals or non-smokers.

CONCLUSIONS

CYP1A2 genetic polymorphisms are associated with HCC susceptibility in smokers and HBsAg seronegative individuals in the Fusui endemic region.