CYP1A1, GSTs and mEH polymorphisms and susceptibility to esophageal carcinoma: Study of population from a high- incidence area in north China

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Esophageal cancer genetics in South Africa

Esophageal cancer (EC) is an extremely aggressive cancer with one of the highest mortality rates. The cancer is generally only diagnosed at the later stages and has a poor 5-year survival rate due to the limited treatment options. China and South Africa are two countries with a very high prevalence rate of EC. EC rates in South Africa have been on the increase, and esophageal squamous cell carcinoma is the predominant subtype and a primary cause of cancer-related deaths in the black and male mixed ancestry populations in South Africa. The incidence of EC is highest in the Eastern Cape Province, especially in the rural areas such as the Transkei, where the consumption of foods contaminated with Fusarium verticillioides is thought to play a major contributing role to the incidence of EC. China is responsible for almost half of all new cases of EC globally. In China, the prevalence of EC varies greatly. However, the two main areas of high prevalence are the southern Taihang Mountain area (Linxian, Henan Province) and the north Jiangsu area. In both countries, environmental toxins play a major role in increasing the chance that an individual will develop EC. These associative factors include tobacco use, alcohol consumption, nutritional deficiencies and exposure to environmental toxins. However, genetic polymorphisms also play a role in predisposing individuals to EC. These include single-nucleotide polymorphisms that can be found in both protein-coding genes and in non-coding sequences such as miRNAs. The aim of this review is to summarize the contribution of genetic polymorphisms to EC in South Africa and to compare and contrast this to the genetic polymorphisms observed in EC in the most comprehensively studied population group, the Chinese.

Association of Activity Altering Genotypes - Tyr113His and His139Arg in Microsomal Epoxide Hydrolase Enzyme with Esophageal Squamous Cell Carcinoma

The study aimed to explore the relationship of microsomal epoxide hydrolase (mEH) exon 3 (Tyr113His) and exon 4 (His139Arg) polymorphisms and predicted mEH activity with esophageal squamous cell carcinoma (ESCC) risk. 482 histologically confirmed cases and equal number of matched controls were analyzed by polymerase chain reaction-restriction length polymorphism (PCR-RFLP). Conditional logistic regression models were used to examine the association of polymorphisms with ESCC. We noted exon 3 slow genotype (OR = 6.57; CI 3.43-12.57) as well as predicted low mEH activity (OR = 3.99; CI 2.32-6.85) was associated with the ESCC risk. Elevated ESCC risk estimates were seen in smokers independent of genotypes but the association was stronger among smokers with exon 3 variant (OR = 6.67; 3.29-13.53) and low activity (OR = 7.52; CI 3.46-16.37) genotypes. Positive family history of cancer synergistically increased ESCC risk in the individuals who harbored exon 3 (OR = 13.59; CI 5.63-32.81) or altered mEH activity genotypes (OR = 13.35; CI 5.10-34.94). Significant interaction was seen between mEH exon 3 and exon 4 genotypes (P = 0.006) and between predicted mEH activity and positive family history of cancer (P = 0.018). These findings suggest association of ESCC risk with mEH polymorphisms which get modified by tobacco smoking and positive family history of cancer.

Association between the Glutathione-S-transferase T1 null genotype and esophageal cancer susceptibility: a meta-analysis involving 11,163 subjects

Background

Glutathione-S-Transferase T1 (GSTT1) null genotype has been shown to be associated with the risk of esophageal cancer. However, the results remain inconsistent. Thus a comprehensive meta-analysis was conducted to assess the strength of association between GSTT1 null genotype and the risk of esophageal cancer.

Materials and Methods

A literature search of PubMed, Embase, China National Knowledge Infrastructure (CNKI) and Wanfang databases up to March 31, 2017 was conducted and 30 eligible articles with 4482 cases and 6681 controls were finally recruited. The strength of correlation between GSTT1 polymorphism and the susceptibility of esophageal cancer was assessed by the crude odds ratios (ORs) with 95% confidence intervals (CIs). Subgroup analyses and sensitivity analyses were performed to further identify the association.

Results

GSTT1 null genotype significantly increased the risk of esophageal cancer (OR = 1.20; 95% CI 1.04-1.40; P < 0.05). In a subgroup analysis by ethnicity, GSTT1 null genotype was correlated with a significantly increased risk of esophageal cancer among Asians (OR = 1.33; 95% CI 1.12-1.58; P < 0.05), instead of Caucasians or Africans (OR = 0.91; 95% CI 0.65-1.26; P > 0.05 for Caucasians and OR = 1.32; 95% CI 0.98-1.77; P > 0.05 for Africans). In the analysis by histological type, GSTT1 null genotype was correlated with a significantly increased risk of esophageal squamous cell carcinoma (OR = 1.34; 95% CI 1.12-1.61; P < 0.05), particularly among Asians (OR = 1.54; 95% CI 1.30-1.82; P < 0.05), but not among Caucasians or Africans (OR = 0.87; 95% CI 0.48-1.57; P > 0.05 for Caucasians and OR = 1.32; 95% CI 0.98-1.77; P > 0.05 for Africans). In addition, there is no significant correlation between GSTT1 null genotype and the risk of esophageal adenocarcinoma (OR = 0.98; 95% CI 0.71-1.35; P > 0.05).

Conclusions

Our findings demonstrate that GSTT1 null genotype significantly increases esophageal cancer risk, particularly in Asians.

Association between glutathione S-transferase M1 polymorphism and esophageal cancer: a pooled analysis based on Chinese individuals

Many studies have analyzed the association between between glutathione S-transferase M1 (GSTM1) polymorphism and esophageal cancer, however, the results are inconsistent. This meta-analysis updated and reevaluated the possible associations between GSTM1 polymorphism and susceptibility to esophageal cancer based on Chinese individuals. The PubMed, Springer Link, Ovid, Chinese Wanfang Data Knowledge Service Platform, Chinese National Knowledge Infrastructure and Chinese Biology Medicine were searched up to February 2017. A total of 20 case-control studies including 2113 esophageal cancer cases and 2848 relevant controls were screened out. Overall, the meta-analysis demonstrated significant associations between the GSTM1 null genotype and increased risk for esophageal cancer in the Chinese population. In subgroup analyses, it indicated the similar results in population-based and hospital-based studies, as well as in North China and South China. As for subgroup analysis by histological type, a non-significant association was found in esophageal squamous cell carcinoma. Our study suggested that GSTM1 null genotype might contribute to increased risk of esophageal cancer in Chinese population.

Cytochrome P450 1A1 gene polymorphisms and digestive tract cancer susceptibility: a meta-analysis

Cytochrome P450 1A1 (CYP1A1) is a phase I enzyme that regulates the metabolism of environmental carcinogens and alter the susceptibility to various cancers. Many studies have investigated the association between the CYP1A1 MspI and Ile462Val polymorphisms and digestive tract cancer (DTC) risk in different groups of populations, but their results were inconsistent. The PubMed and Embase Database were searched for case–control studies published up to 30th September, 2015. Data were extracted and pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the relationship. Totally, 39 case–control studies (9094 cases and 12,487 controls) were included. The G allele in Ile/Val polymorphism was significantly associated with elevated DTC risk with per‐allele OR of 1.24 (95% CI = 1.09–1.41, P = 0.001). Similar results were also detected under the other genetic models. Evidence was only found to support an association between MspI polymorphism and DTC in the subgroups of caucasian and mixed individuals, but not in the whole population (the dominant model: OR = 1.19, 95% CI = 0.94–1.91, P = 0.146). In conclusion, our results suggest that the CYP1A1 polymorphisms are potential risk factors for DTC. And large sample size and well‐designed studies with detailed clinical information are needed to more precisely evaluate our founding.

Glutathione S-transferase M1 polymorphism and esophageal cancer risk: An updated meta-analysis based on 37 studies

AIM: To evaluate the relationship between glutathione S-transferase M1 (GSTM1) polymorphism and susceptibility to esophageal cancer (EC).

METHODS: A comprehensive search of the United States National Library of Medicine PubMed database and the Elsevier, Springer, and China National Knowledge Infrastructure databases for all relevant studies was conducted using combinations of the following terms: “glutathione S-transferase M1”, “GSTM1”, “polymorphism”, and “EC” (until November 1, 2014). The statistical analysis was performed using the SAS software (v.9.1.3; SAS Institute, Cary, NC, United States) and the Review Manager software (v.5.0; Oxford, England); crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association between the GSTM1 null genotype and the risk of EC.

RESULTS: A total of 37 studies involving 2236 EC cases and 3243 controls were included in this meta-analysis. We observed that the GSTM1 null genotype was a significant risk factor for EC in most populations (OR = 1.33, 95%CI: 1.12-1.57, P_{heterogeneity} < 0.000001, and I² = 77.0%), particularly in the Asian population (OR = 1.53, 95%CI: 1.26-1.86, P_{heterogeneity} < 0.000001, and I² = 77.0%), but not in the Caucasian population (OR = 1.02, 95%CI: 0.87-1.19, P_{heterogeneity} = 0.97, and I² = 0%).

CONCLUSION: The GSTM1 null polymorphism may be associated with an increased risk for EC in Asian but not Caucasian populations.

Meta-analysis of association studies of CYP1A1 genetic polymorphisms with digestive tract cancer susceptibility in Chinese

BACKGROUND

A great number of studies have shown that cytochrome P450 1A1 (CYP1A1) genetic polymorphisms, CYP1A1 Msp I and CYP1A1 Ile/Val, might be risk factors for digestive tract cancers, including esophageal cancer (EC), gastric cancer (GC), hepatic carcinoma (HC), as well as colorectal cancer (CC), but the results are controversial. In this study, a meta-analysis of this literature aimed to clarify associations of CYP1A1 genetic polymorphisms with digestive tract cancer susceptibility in Chinese populations.

MATERIALS AND METHODS

Eligible case-control studies published until December 2013 were retrieved by systematic literature searches from PubMed, Embase, CBM, CNKI and other Chinese databases by two investigators independently. The associated literature was acquired through deliberate search and selection based on established inclusion criteria. Fixed- effects or random-effects models were used to estimate odds ratios (ORs and 95%CIs). The meta-analysis was conducted using Review Manager 5.2 and Stata 12.0 softwares with stability evaluated by both stratified and sensitivity analyses. Moreover, sensitivity analysis and publication bias diagnostics confirmed the reliability and stability.

RESULTS

Eighteen case control studies with 1, 747 cases and 2, 923 controls were selected for CYP1A1 MspI polymorphisms, and twenty case-control studies with 3, 790 cases and 4, 907 controls for the CYP1A1 Ile/ Val polymorphisms. Correlation associations between CYP1A1 Ile/Val polymorphisms and digestive tract cancers susceptibility were observed in four genetic models in the meta-analysis (GG vs AA:OR= 2.03, 95%CI =1.52- 2.72; AG vs AA: OR=1.26, 95%CI =1.07-1.48; [ GG+AG vs AA] :OR =1.42, 95%CI=1.20-1.68, [GG vs AA+AG ]:OR=1.80, 95%CI =1.40-2.31). There was no association between CYP1A1 Msp I polymorphisms and digestive tract cancer risk. Subgroup analysis for tumor type showed a significant association of CYP1A1 Ile/Val genetic polymorphisms with EC in China. However, available data collected by the study failed to reveal remarkable associations of GC or HC with CYP1A1 Ile/Val genetic polymorphisms and EC, GC or CC with CYP1A1 MspI genetic polymorphisms.

CONCLUSIONS

Our results indicated that CYP1A1 Ile/Val genetic polymorphisms, but not CYP1A1 Msp I polymorphisms, are associated with an increased digestive tract cancer risk in Chinese population. Additional well-designed studies, with larger sample size, focusing on different ethnicities and cancer types are now warranted to validate this finding.

Cytochrome P450 in Cancer Susceptibility and Treatment

Cytochrome 450 (CYP450) designates a group of enzymes abundant in smooth endoplasmic reticulum of hepatocytes and epithelial cells of small intestines. The main function of CYP450 is oxidative catalysis of various endogenous and exogenous substances. CYP450 are implicated in phase I metabolism of 80% of drugs currently in use, including anticancer drugs. They are also involved in synthesis of various hormones and influence hormone-related cancers. CYP450 genes are highly polymorphic and their variants play an important role in cancer risk and treatment. Association studies and meta-analyses have been performed to decipher the role of CYP450 polymorphisms in cancer susceptibility. Cancer treatment involves multimodal therapies and evaluation of CYP450 polymorphisms is necessary for pharmacogenetic assessment of anticancer therapy outcomes. In addition, CYP450 inhibitors are being evaluated for improved pharmacokinetics and oral formulation of several anticancer drugs.

Association of GSTP1 Ile105Val polymorphism with risk of esophageal cancer: a meta-analysis of 21 case-control studies

BACKGROUND

The association of glutathione s-transferase P1 (GSTP1) Ile105Val polymorphism with risk of esophageal cancer (EC) has been evaluated in many studies; however, the results from these studies are controversial. Thus, further analysis on association between GSTP1 Ile105Val polymorphism and risk of EC is needed among a larger study population.

METHOD

We searched the relevant electronic databases and performed a meta-analysis based on 21 published case-control studies. The Chi-square based I(2)-statistic test was performed to evaluate possible heterogeneity across the studies. Additionally, random-effects models were used to calculate crude pooled odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

Overall, this meta-analysis did support a significant association between GSTP1 Ile105Val polymorphism and risk of EC (pooled OR 1.25, 95% CI, 1.05-1.49). Furthermore, the stratified analysis showed that, in comparison to GSTP1 Ile105Val Ile/Ile genotype, the Val/Val genotype was significantly associated with risk of esophageal squamous cell carcinoma (ESCC) (pooled OR 1.45, 95% CI, 1.07-1.96), particularly in the Caucasian population (pooled OR 1.41, 95% CI, 1.01-1.95). Such a significant association was not observed for esophageal adenocarcinoma (EAC) patients or subjects of an Asian ethnicity. Moreover, substantial evidence of heterogeneity among the studies was not observed.

CONCLUSION

The results from this meta-analysis support a significant association between the GSTP1 Ile105Val polymorphism and risk of EC, particularly in a subgroup with ESCC and in the Caucasian population. Further studies with larger sample sizes are needed to validate our findings.

Association between glutathione S-transferases P1 Ile105Val polymorphism and susceptibility to esophageal cancer: evidence from 20 case-control studies

Available epidemiological studies had estimated the correlation between glutathione S-transferases P1 (GSTP1) Ile105Val polymorphism and esophageal cancer (EC) risk. However, the conclusions were controversial and inconclusive. An updated meta-analysis was conducted to explore whether GSTP1 polymorphism could be contributed to the EC risk. Ultimately, a total of 2,992 cases and 4,758 controls from 20 previous studies were included. Crude odds ratios (ORs) with 95 % confidence intervals (95 % CIs) were used to assess the strength of the associations. Pooled results suggested that GSTP1 Ile105Val polymorphism significantly increased the risk of developing EC in Caucasians under three genetic models (G vs. A, OR 1.146, 95 % CI 1.031-1.275, P = 0.012, I(2) = 30.40 %; GA vs. AA, OR 1.208, 95 % CI 1.036-1.408, P = 0.016, I(2) = 50.30 %; GG+GA vs. AA, OR 1.219, 95 % CI 1.053-1.410, P = 0.008, I(2) = 44.50 %). However, no significant correlation was found in Asians, African and mixed ethnicities analyses. Moreover, similar results were detected for any genetic model in esophageal squamous cell carcinoma and esophageal adenocarcinoma when stratifying for pathologic types. This meta-analysis provides new evidences that GSTP1 Ile105Val gene polymorphism contributes to EC susceptibility in Caucasians.

The role of epoxide hydrolases in health and disease

Epoxide hydrolases (EH) are ubiquitously expressed in all living organisms and in almost all organs and tissues. They are mainly subdivided into microsomal and soluble EH and catalyze the hydration of epoxides, three-membered-cyclic ethers, to their corresponding dihydrodiols. Owning to the high chemical reactivity of xenobiotic epoxides, microsomal EH is considered protective enzyme against mutagenic and carcinogenic initiation. Nevertheless, several endogenously produced epoxides of fatty acids function as important regulatory mediators. By mediating the formation of cytotoxic dihydrodiol fatty acids on the expense of cytoprotective epoxides of fatty acids, soluble EH is considered to have cytotoxic activity. Indeed, the attenuation of microsomal EH, achieved by chemical inhibitors or preexists due to specific genetic polymorphisms, is linked to the aggravation of the toxicity of xenobiotics, as well as the risk of cancer and inflammatory diseases, whereas soluble EH inhibition has been emerged as a promising intervention against several diseases, most importantly cardiovascular, lung and metabolic diseases. However, there is reportedly a significant overlap in substrate selectivity between microsomal and soluble EH. In addition, microsomal and soluble EH were found to have the same catalytic triad and identical molecular mechanism. Consequently, the physiological functions of microsomal and soluble EH are also overlapped. Thus, studying the biological effects of microsomal or soluble EH alterations needs to include the effects on both the metabolism of reactive metabolites, as well as epoxides of fatty acids. This review focuses on the multifaceted role of EH in the metabolism of xenobiotic and endogenous epoxides and the impact of EH modulations.

Cytochrome P450 1A1 (CYP1A1) polymorphism and susceptibility to esophageal cancer: an updated meta-analysis of 27 studies

Cytochrome P450 1A1 (CYP1A1) polymorphisms are known to play a crucial role in the development and metastasis of malignant diseases including esophageal cancer. However, the results of previous studies investigating the association between CYP1A1 polymorphisms and esophageal cancer risk have been inconsistent. This meta-analysis of 27 eligible studies, encompassing 4,215 esophageal cancer cases and 6,339 control subjects, pooled the odds ratios (ORs) with corresponding 95 % confidence intervals (95 % CI) to assess this association. The effects of ethnicity (Caucasian and Asian) and histopathology type (esophageal squamous cell carcinoma and esophageal adenocarcinoma) were considered in subgroup analyses. A significant association was observed between the CYP1A1 Ile/Val gene polymorphism and esophageal cancer in all of the genetic models (Ile/Val vs. Ile/Ile, OR = 1.41, 95 % CI = 1.25-1.58; Val/Val vs. Ile/Ile, OR = 1.94, 95 % CI = 1.34-2.82; Ile/Val + Val/Val vs. Ile/Ile, OR = 1.49, 95 % CI = 1.33-1.66). The subgroup analysis based on ethnicity showed that the association between the CYP1A1 Ile/Val polymorphism and esophageal cancer existed in Asian and Caucasian populations. However, no association was observed between the CYP1A1 MspI polymorphism and esophageal cancer in either subgroup or in the overall population. These results suggested that the CYP1A1 Ile/Val polymorphism was associated with an increased risk of esophageal cancer, whereas the CYP1A1 MspI polymorphism may not have increased susceptibility to esophageal cancer. Further studies are required to confirm these findings.

Lack of association between EPHX1 polymorphism and esophageal cancer risk: evidence from meta-analysis

The microsomal epoxide hydrolase 1 (EPHX1) Tyr113His and His139Arg polymorphisms have been reported to be associated with esophageal cancer (EC) risk, yet the results of these previous results have been inconsistent or controversial. The objective of this study was to explore whether the EPHX1 Tyr113His and His139Arg polymorphisms confer risk to EC. The relevant studies were identified through a search of PubMed, Excerpta Medica Database (Embase), Elsevier Science Direct, and Chinese Biomedical Literature Database until May 2013. The association between the EPHX1 Tyr113His and His139Arg polymorphisms and EC risk was pooled by odds ratios (ORs) together with their 95% confidence intervals (95%CIs). A total of eight case-control studies with 1163 EC patients and 1868 controls (seven studies for both Tyr113His and His139Arg polymorphisms, one study only for Tyr113His polymorphism) were eventually identified. We found no association between EPHX1 Tyr113His and His139Arg polymorphisms and EC risk in overall population (For Tyr113His: His vs. Tyr: OR = 1.05, 95%CI = 0.95-1.15, P = 0.379; His/His vs. Tyr/Tyr: OR = 1.04, 95%CI = 0.88-1.22, P = 0.208; His/Tyr vs. Tyr/Tyr: OR = 0.96, 95%CI = 0.80-1.15, P = 0.577; His/His vs. His/Tyr + Tyr/Tyr: OR = 1.10, 95%CI = 0.96-1.26, P = 0.164; His/His + His/Tyr vs. Tyr/Tyr: OR = 1.01, 95%CI = 0.90-1.12, P = 0.543. For His139Arg: Arg vs. His: OR = 1.04, 95%CI = 0.94-1.14, P = 0.465; Arg/Arg vs. His/His: OR = 1.06, 95%CI = 0.91-1.24, P = 0.470; Arg/His vs. His/His: OR = 1.03, 95%CI = 0.91-1.16, P = 0.673; Arg/Arg vs. Arg/His + His/His: OR = 1.04, 95%CI = 0.85-1.27, P = 0.708; Arg/Arg + Arg/His vs. His/His: OR = 1.02, 95%CI = 0.93-1.13, P = 0.617). In subgroup analysis based on ethnicity, significant association has been found in neither EPHX1 Tyr113His nor His139Arg polymorphism. The current meta-analysis suggests no evidence of association between the EPHX1 polymorphism and EC risk.

Investigation of the Association between Genetic Polymorphism of Microsomal Epoxide Hydrolase and Primary Brain Tumor Incidence

mEH is a critical biotransformation enzyme that catalyzes the conversion of xenobiotic epoxide substrates into more polar diol metabolites: it is also capable of inactivating a large number of structurally different molecules. Two polymorphisms affecting enzyme activity have been described in the exon 3 and 4 of the mEH gene. The hypothesis of this study is that inherent genetic susceptibility to a primary brain tumor is associated with mEH gene polymorphisms. The polymorphisms of the mEH gene were determined with PCR-RFLP techniques and 255 Turkish individuals. Our results indicate that the frequency of the mEH exon 4 polymorphism (in controls) is significantly higher than that of primary brain tumor patients (OR = 1.8, 95% CI = 1.0–3.4). This report, however, failed to demonstrate a significant association between mEH exon 3 polymorphism and primary brain tumor susceptibility in this population. Analysis of patients by both histological types of primary brain tumor and gene variants showed no association, although analysis of family history of cancer between cases and controls showed a statistically significant association (χ² = 7.0, P = 0.01). Our results marginally support the hypothesis that genetic susceptibility to brain tumors may be associated with mEPHX gene polymorphisms.

CYP1A1 genetic polymorphisms and risk for esophageal cancer: a case-control study in central China

The purpose of this study was to evaluate the associations of CYP1A1 genetic polymorphisms with the risk of developing esophageal cancer (EC). A case-control study was carried out in a Chinese population in which 157 hospital based EC cases and 157 population based healthy controls with 1:1 match by age and sex were included. PCR based restriction fragment length polymorphisms (PCR-RFLP) were used to detect genotypes in case and control groups. For the CYP1A1 Ile/Val polymorphism, comparing with wild genotype Ile/Ile, both the heterozygote genotype Ile/Val and the combined variant genotype Ile/Val+Val/Val increased the risk of esophageal cancer (OR: 2.05, 95%CI: 1.19-3.54, OR: 1.86, 95%CI: 1.11-3.12). No significant association was found between the CYP1A1 MspI polymorphism and EC. According to analysis of combined genotypes, the TC/AG combined genotype which contained both variant alleles of these two polymorphisms increased the risk of developing EC (OR: 2.12, 95%CI: 1.16-3.85). Our results suggested that genetic polymorphisms of CYP1A1 may increase the susceptibility to EC.

Association of microsomal epoxide hydrolase exon 3 Tyr113His and exon 4 His139Arg polymorphisms with gastric cancer in India

BACKGROUND

Microsomal epoxide hydrolase, an important phase II xenobiotic enzyme, exhibits polymorphisms at exon 3 (Tyr113His [T/C]) and exon 4 (His139Arg [A/G]), which modulate enzyme activity; this may affect susceptibility to cancers. We studied association between these polymorphisms and gastric cancer (GC).

METHODS

In a prospective study, 77 patients with GC, 50 with peptic ulcer, and 160 healthy controls (HC) were genotyped for exon 3 (PCR-RFLP followed by sequencing) and exon 4 (PCR-RFLP). Helicobacter pylori was considered to be present if two of three tests (histology, rapid urease test, and IgG antibody) were positive.

RESULTS

Tyr113His and His139Arg genotypes and haplotypes were comparable among groups. 113His carriers were commoner among H. pylori-negative patients with GC than HC (p-value = 0.019, odds ratio (OR) = 2.5, 95 % confidence interval (CI) = 1.2-5.4). Haplotype combination of exons 3 and 4 113Tyr-139Arg (TA) were associated with higher and reduced risk in patients with GC than HC in presence and absence of H. pylori (25 % vs. 11 %; p-value = 0.033, OR = 2.61, 95 % CI = 1.08-6.3 and 11.6 % vs. 28.7 %; p-value = 0.004, OR = 0.33, 95 % CI = 0.15-0.7, respectively).

CONCLUSIONS

Though 113Tyr-139Arg was associated with GC in presence of H. pylori, in its absence, it appeared to be protective. Exon 3, 113His, however, was associated with GC even in absence of H. pylori infection.

Combining proteomics, serum biomarkers and bioinformatics to discriminate between esophageal squamous cell carcinoma and pre-cancerous lesion

OBJECTIVE

Biomarker assay is a noninvasive method for the early detection of esophageal squamous cell carcinoma (ESCC). Searching for new biomarkers with high specificity and sensitivity is very important for the early detection of ESCC. Serum surface-enhanced laser desorption/ionization-time of flight mass spectrometry (SELDI-TOF-MS) is a high throughput technology for identifying cancer biomarkers using drops of sera.

METHODS

In this study, 185 serum samples were taken from ESCC patients in a high incidence area and screened by SELDI. A support vector machine (SVM) algorithm was adopted to analyze the samples.

RESULTS

The SVM patterns successfully distinguished ESCC from pre-cancerous lesions (PCLs). Also, types of PCL, including dysplasia (DYS) and basal cell hyperplasia (BCH), and healthy controls (HC) were distinguished with an accuracy of 95.2% (DYS), 96.6% (BCH), and 93.8% (HC), respectively. A marker of 25.1 kDa was identified in the ESCC patterns whose peak intensity was observed to increase significantly during the development of esophageal carcinogenesis, and to decrease obviously after surgery.

CONCLUSIONS

We selected five ESCC biomarkers to form a diagnostic pattern which can discriminate among the different stages of esophageal carcinogenesis. This pattern can significantly improve the detection of ESCC.

Glutathione-S-transferase T1 polymorphism is associated with esophageal cancer risk in Chinese Han population

BACKGROUND

Glutathione-S-Transferase T1 (GSTT1) gene has been shown to be involved in the development of esophageal cancer. However, the results have been inconsistent. In this study, the authors performed a meta- analysis to clarify the association between GSTT1 polymorphism and esophageal cancer risk among Chinese Han population.

METHODS

Published literature from PubMed, the China National Knowledge Infrastructure and Wanfang Data were searched. Pooled odds ratio (OR) and 95% confidence interval (95%CI) was calculated using a fixed- or random-effects model.

RESULTS

Eleven studies with a total of 2779 individuals were included in the meta-analysis. The results showed that GSTT1 null genotype was significantly associated with esophageal cancer risk in Chinese (OR = 1.31, 95%CI 1.12 to 1.53, p = 0.001). Further sensitivity analyses confirmed the significant association. The cumulative meta-analysis showed a trend of an obvious association between GSTT1 null genotype and esophageal cancer risk as information accumulated by year.

CONCLUSIONS

This meta-analysis suggests a significant association of GSTT1 null genotype with esophageal cancer risk in the Chinese Han population.

GSTM1 and GSTT1 polymorphism and susceptibility to esophageal cancer in high- and low-risk regions of India

Glutathione transferases, a super family of dimeric phase II metabolic enzymes play a vital role in biotransformation of many substances. This study evaluates the influence of genetic polymorphism of GSTM1 and GSTT1 gene loci on esophageal cancer risk in Assam and Delhi from India. DNA from blood samples of esophageal cancer cases (203,112) and controls (286,150) from Assam and Delhi, respectively, were extracted. GSTM1 and GSTT1 polymorphisms were analyzed by multiplex PCR procedure. Differences in proportions were tested using Pearson's chi-square test with odds ratio (OR) and 95 % confidence interval (CI). Risk of esophageal cancer was approximately twice in individuals having homozygous GSTM1 (OR-2.1, 95 % CI, 1.44-3.13) and GSTT1 null genotypes (OR-1.7,95 % CI, 0.99-2.77) in Assam, and around three times in GSTT1 null genotype (OR-2.9, 95 % CI, 1.56-5.27) in Delhi population. GSTM1 null genotype seems to play a protective role (OR-0.7, 95 % CI, 0.39-1.27) in Delhi. A significant association of GSTM1 null genotype with esophageal cancer was observed in a younger age group in Assam (OR-2.7, 95 % CI, 1.48-5.01), and in Delhi population association was observed in smokers with GSTT1 null genotype (OR-2.5, 95 % CI, 1.04-6.07), and alcoholics having GSTM1 null genotype (OR-2.6, 95 % CI, 0.99-6.77). Significant association of GSTM1 null genotype in Assam was observed between cancer cases and controls in fermented betel nut chewers only (OR-2.8, 95 % CI, 1.19-6.72), whereas, smoking and alcohol failed to show any correlation with GSTM1/GSTT1 genotypes. Cancer development is not only due to exogenous or endogenous carcinogens but depends on their interaction with genes that are involved in the detoxification of these carcinogens.

Null genotype of GSTT1 contributes to esophageal cancer risk in Asian populations: evidence from a meta-analysis

BACKGROUND/AIMS

Glutathione S-transferase T1 (GSTT1), a phase-II enzyme, plays an important role in detoxification of carcinogen electrophiles. Many studies have investigated the association between GSTT1 polymorphism and esophageal cancer risk in Asian populations, but its actual impact is not clear owing to apparent inconsistencies among those studies. Thus, a meta-analysis was performed to explore the effect of GSTT1 polymorphism on the risk of developing esophageal cancer.

METHODS

A literature search of PubMed, Embase, and Wanfang databases up to August 2012 was conducted and 15 eligible papers were finally selected, involving a total of 1,626 esophageal cancer cases and 2,216 controls. We used the pooled odds ratio (OR) with its corresponding 95% confidence interval (95%CI) to estimate the association of GSTT1 polymorphism with esophageal cancer risk. Subgroup analyses and sensitivity analyses were performed to further identify the association.

RESULTS

Meta-analysis of total studies showed the null genotype of GSTT1 was significantly associated with an increased risk of esophageal cancer in Asians (OR=1.26, 95%CI=1.05-1.52, POR=0.015, I2=42.7%). Subgroup analyses by sample size and countries also identified a significant association. Sensitivity analysis further demonstrated a relationship of GSTT1 polymorphism to esophageal cancer risk in Asians.

CONCLUSIONS

The present meta-analysis of available data showed a significant association between the null genotype of GSTT1 and an increased risk of esophageal cancer in Asians, particularly in China.

Glutathione S-transferase M1 null genotype contributes to increased risk of esophageal carcinoma in Chinese population

Glutathione S-transferases (GSTs) play important roles in the detoxification of electrophilic carcinogens, and GSTM1 null genotype is associated with the dysfunction of GSTs. Previous studies investigating the association between GSTM1 null genotype and risk of esophageal carcinoma in Chinese provided inconsistent findings. To provide a more precise estimation on the association between GSTM1 null genotype and risk of esophageal carcinoma in Chinese population, a meta-analysis was performed. Eligible studies were searched in PubMed, Embase, and China National Knowledge Infrastructure databases. Odds ratio (OR) with the corresponding 95 % confidence interval (95 %CI) was used to assess the association. A total of 18 case-control studies involving 1,947 cases and 3,506 controls were finally included in the meta-analysis. Meta-analysis of those 18 studies showed that GSTM1 null genotype was associated with an increased risk of esophageal carcinoma in Chinese (random effect model OR = 1.49, 95 %CI = 1.11-2.00, P = 0.008). The findings from cumulative meta-analysis showed that the association was more obvious as the data increased by publication year. There was no risk of publication bias in the meta-analysis. Therefore, the findings from our meta-analysis provide a strong evidence for the association between GSTM1 null genotype and risk of esophageal carcinoma in Chinese population, and GSTM1 null genotype contributes to increased risk of esophageal carcinoma in Chinese.

Significant association of glutathione S-transferase T1 null genotype with esophageal cancer risk: a meta-analysis

Recent studies on the association between glutathione S-transferase T1 (GSTT1) polymorphism and risk of esophageal cancer showed inconclusive results. To clarify this possible association, we conducted a meta-analysis of published studies. Data were collected from the following electronic databases: Pubmed, Embase, and Chinese Biomedical Database (CBM). The odds ratio (OR) and its 95 % confidence interval (95 % CI) was used to assess the strength of this association. We summarized the data on the association between GSTT1 null genotype and risk of esophageal cancer in the overall population, and performed subgroup analyses by ethnicity. Finally, a total of 24 independent studies including a total of 7,801 subjects (2,965 cases and 4,836 controls) were eligible for meta-analysis. In the overall analysis, there was no significant association between GSTT1 null genotype and esophageal cancer risk (OR = 1.15, 95 % CI 0.99-1.33, P = 0.067). However, meta-analysis of adjusted ORs showed a significant association between GSTT1 null genotype and increased risk of esophageal cancer (OR = 1.30, 95 % CI 1.08-1.56, P = 0.005). Subgroup analyses by ethnicity showed there was an obvious association between GSTT1 null genotype and increased risk of esophageal cancer in East Asians (OR = 1.24, 95 % CI 1.10-1.39, P < 0.001), but not in Caucasians (OR = 0.89, 95 % CI 0.71-1.11, P = 0.300). There was no obvious risk of publication bias in this meta-analysis (Egger's test, P = 0.784). This meta-analysis demonstrates that GSTT1 null genotype is independently associated with increased risk of esophageal cancer, and a race-specific effect may exist in this association.

Polymorphisms of cytochrome p450 genes in three ethnic groups from Russia

OBJECTIVE

To determine the prevalence of the most common allelic variants of CYP1A1, CYP1A2, CYP1B1, CYP2C9, CYP2E1, CYP2F1, CYP2J2 and CYP2S1 in a representative sample of the three ethnic groups (Russians, Tatars and Bashkirs) from Republic of Bashkortostan (Russia), and compare the results with existing data published for other populations.

MATERIAL AND METHODS

CYPs genotypes were determined in 742 DNA samples of healthy unrelated individuals representative of three ethnic groups. The CYPs gene polymorphisms were examined using the PCR-RLFP method.

RESULTS

Analysis of the CYP1A1 (rs1048943, rs4646903), CYP1A2 (rs762551), CYP2E1 (rs2031920) allele, genotype and haplotype frequencies revealed significant differences among healthy residents of the Republic of Bashkortostan of different ethnicities. Distribution of allele and genotype frequencies of CYP1A2 (rs35694136), CYP1B1 (rs1056836), CYP2C9 (rs1799853, rs1057910), CYP2F1 (rs11399890), CYP2J2 (rs890293), CYP2S1 (rs34971233, rs338583) genes were similar in Russians, Tatars, and Bashkirs. Analysis of the CYPs genes allele frequency distribution patterns among the ethnic groups from the Republic of Bashkortostan in comparison with the different populations worldwide was conducted.

CONCLUSION

The peculiarities of the allele frequency distribution of CYPs genes in the ethnic groups of the Republic of Bashkortostan should be taken into consideration in association and pharmacogenetic studies. The results of the present investigation will be of great help in elucidating the genetic background of drug response, susceptibility to cancer and complex diseases, as well as in determining the toxic potentials of environmental pollutants in our region.

Genetic polymorphism of CYP2D6∗2 C→T 2850, GSTM1, NQO1 genes and their correlation with biomarkers in manganese miners of Central India

Manganese (Mn) intoxication is most often regarded as an occupational manifestation and occurs in places such as manganese mines, dry cell battery plants and ceramic industries. In the present study, the influence of genetic polymorphism in cytochrome P450 2D6 (CYP2D6∗2), glutathione S-transferase M1 (GSTM1) and NAD(P)H quinone oxidoreductase 1 (NQO1) genes on blood manganese and plasma prolactin concentrations in manganese miners was investigated. Genotyping of CYP2D6∗2 C→T 2850 and NQO1 C→T 609 was carried out using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) whereas the genotyping of GSTM1 was carried out by multiplex PCR using beta globin as an internal control. Manganese miners with CYP2D6∗2 C→T 2850 variant genotype had relatively low Mn concentration [GM: 21.4±8.9 μg L(-1)] than the subjects with wild (GM: 36.3±8.5 μg L(-1)) and heterozygous (GM: 34.4±6.9 μg L(-1)) genotypes. Miners with CYP2D6∗2 variant genotypes showed low prolactin levels (GM: 13.13±1.6 ng mL(-1)) compared to the wild (GM: 16.4.4±1.5 μg L(-1)) and heterozygous (GM: 18.7±1.6 ng mL(-1)) genotypes. Gene-gene interaction studies also revealed that the subjects with CYP2D6∗2 C→T 2850 variant genotypes had low levels of Mn and prolactin. Our new findings suggest that CYP2D6∗2 C→T 2850 variant genotypes can regulate plasma prolactin levels in manganese miners of Central India and could be involved in the fast metabolism of blood manganese, compared to wild and heterozygous genotypes.

Role of epoxide hydrolase 1 gene polymorphisms in esophageal cancer in a high-risk area in India

BACKGROUND AND AIM

Microsomal epoxide hydrolase 1 (EPHX1) is involved in the metabolism of environmental and tobacco carcinogens. Tobacco smoking, betel quid chewing, and alcohol consumption are the major known risk factors for esophageal cancer. The present case-control study evaluated the influence of EPHX1 genetic variations on esophageal cancer susceptibility in 142 patients and 185 healthy controls from a high-incidence region of India where tobacco use and alcohol consumption are widespread and the users of these two substances are also betel quid chewers.

METHODS

EPHX1 polymorphic alleles (exon 3, Tyr113His and exon 4, His139Arg) were genotyped by polymerase chain reaction-restriction fragment length polymorphism method and direct sequencing. The results were analyzed using logistic regression to calculate odds ratios (OR) and confidence intervals (CI).

RESULTS

Patients with exon 4 genotypes (139His/Arg, 139Arg/Arg) and the 139Arg allele were significantly associated with a risk of esophageal cancer (OR(His139Arg) 1.887, 95% CI = 1.112-3.201, P = 0.019; OR(Arg139Arg) 7.140, 95% CI = 1.276-393.953, P = 0.025 and OR(Arg) 1.83, 95% CI = 1.19-2.82, P = 0.003). The 139His/Arg genotype was a significant risk factor for esophageal cancer in tobacco chewers and betel quid chewers. Patients with the 139Arg/Arg genotype were at significantly higher risk for developing a well-differentiated and moderately-differentiated grade of tumor. In contrast, the 113His/His genotype of exon 3 was a significant protective factor for esophageal cancer in tobacco smokers (OR 0.291, 95% CI = 0.138-0.616, P = 0.001), betel quid chewers (OR 0.434, 95% CI = 0.236-0.797, P = 0.007), and alcohol users.

CONCLUSION

EPHX1 exon 4 139His/Arg, and 139Arg/Arg genotypes were associated with a higher risk of esophageal cancer in a high-risk area of India.

Interactions between Glutathione-S-Transferase M1, T1 and P1 polymorphisms and smoking, and increased susceptibility to esophageal squamous cell carcinoma

BACKGROUND

A complex of genetic and environmental factors is involved in carcinogenesis of the esophageal squamous cell carcinoma (ESCC). Glutathione-S-Transferases (GSTs) are phase-II enzymes playing role in detoxification of carcinogen electrophiles. Genetic polymorphisms of GSTM1, GSTT1 and GSTP1 in association with some environmental factors and their impact on esophageal cancer susceptibility were assessed in the Iranian population.

METHODS

Genomic DNA of peripheral blood leukocytes from 148 confirmed esophageal cancer cases and 137 healthy individuals as control group was assayed for restriction fragment length polymorphisms in the GSTP1 loci by PCR amplification followed by digestion with Alw26I. Deletion of the GSTM1 and GSTT1 genes was detected by multiplex PCR. A data-mining method based on decision trees was applied to produce a predictive model of interactions between genotypes.

RESULTS

Smoking was independently associated with ESCC (p<0.05, OR: 2.286, 95% CI=1.311-3.983). Smoking along with GSTP1 Val/Val genotype was associated to ESCC (p<0.001, OR: 3.886, 95% CI=1.830-8.251), while non-smokers with GSTP1 Val/Val were significantly more frequent in non-cancerous group. (p=0.007, OR: 0.507, 95% CI=0.309-0.830).

CONCLUSIONS

Data-mining methods are useful tools to map out a scheme for predicting complex relations and combinations of different genotypes. Genotyping analysis of GSTP1 together with assessment of smoking seems to be important in determining the risk of ESCC in the Iranian population.

Role of the CYP2D6, EPHX1, MPO, and NQO1 genes in the susceptibility to acute lymphoblastic leukemia in Brazilian children

Polymorphic variations of several genes associated with dietary effects and exposure to environmental carcinogens may influence susceptibility to leukemia development. The objective of the present study was to evaluate the effect of the polymorphisms of debrisoquine hydroxylase (CYP2D6), epoxide hydrolase (EPHX1), myeloperoxidase (MPO), and quinone-oxoreductase (NQO1), which have been implicated in xenobiotic metabolism, on the risk of childhood acute lymphoblastic leukemia (ALL). We evaluated the frequency of polymorphisms in the CYP2D6 (*3 and *4), EPHX1 (*2 and *3), MPO (*2), and NQO1 (*2) genes in 206 patients with childhood ALL and in 364 healthy individuals matched for age and gender from a Brazilian population separated by ethnicity (European ancestry and African ancestry), using the PCR-RFLP method. The CYP2D6 polymorphism variants were associated with an increased risk of ALL. The EPHX1, NQO1, and MPO variant genotypes were significantly associated with a reduced risk of childhood ALL. A significantly stronger protective effect is observed when the EPHX1, NQO1, and MPO variant genotypes are combined suggesting that, CYP2D6 polymorphisms may play a role in the susceptibility to pediatric ALL, whereas the EPHX1, NQO1, and MPO polymorphisms might have a protective function against leukemogenesis.

Functional alterations in the glutathione S-transferase family associated with enhanced occurrence of esophageal carcinoma in China

Glutathione S-transferases (GST) belong to a superfamily of phase II enzymes believed to be associated with enhanced frequency of esophageal carcinoma. This study was performed to evaluate whether the GST family was associated with susceptibility to esophageal carcinoma in China. Ninety-seven patients with newly diagnosed, untreated esophageal squamous-cell carcinoma (ESCC) and 97 healthy controls matched in age, gender, and residence were recruited in this community-based case-control study. Null genotypes of GSTM1 and GSTT1 were determined by multiplex polymerase chain reaction (PCR) technique. Ile105Val polymorphism in the fifth exon, mRNA level, CpG island hypermethylation of promoter, and protein levels of GSTP1 gene were measured with peripheral blood mononuclear cell (PBMC) by PCR-restriction fragment length polymorphism (PCR-RFLP) techniques, quantitative real-time reverse transcription PCR, methylation-specific PCR (MSP), and Western blotting, respectively. The results showed that GSTM1 null genotype and GSTT1 null genotype were significantly associated with increased risk for esophageal cancer in Chinese population. Compared with the control, the relative expression levels of mRNA were significantly reduced in ESCC patients. The conditional logistic regression analysis demonstrated that increased risk for esophageal cancer was associated with CpG island hypermethylation of promoter of GSTP1 gene. GSTP1 protein levels also showed significant decrease in ESCC when adjusted for age, gender, smoking status, and alcohol use. An individual with GSTM1 or GSTT1 null genotype may thus be more susceptible to esophageal cancer development. Reduced expression in mRNA and protein levels were the main manifestations noted in aberrant function of GSTP1 gene. Data thus suggest that the CpG island hypermethylation of promoter gene may serve as a useful biomarker for early diagnosis of esophageal carcinoma development.

Polymorphisms in genes encoding drugs and xenobiotic metabolizing enzymes in a Brazilian population

Polymorphic variations of several genes associated with drugs and xenobiotic metabolism have been linked to the factors that predispose to the carcinogenesis process. As considerable interindividual and interethnic variation in metabolizing enzyme activity has been associated with polymorphic alleles, we evaluated the frequency of the polymorphisms of CYP2D6, EPHX1 and NQO1 genes in 361 Brazilian individuals separated by ethnicity (European and African ancestry), using the polymerase chain reaction-restriction fragment length (PCR-RFLP) method. The allele frequencies of the variants *3 and *4 for the gene CYP2D6 were 0.04 and 0.14 for white subjects and 0.03 and 0.10 for black individuals, respectively. For the both variants of the gene EPHX1, we found higher allele frequencies among white individuals compared with mulatto subjects (0.62 vs 0.54 and 0.18 vs 0.14, respectively); however, these differences were not statistically significant (p = 0.39 and 0.56, respectively). For the NQO1 gene we observed a higher frequency of the homozygous genotype among black individuals (7.9%) compared with white subjects (6.3%) (p = 0.003). The genotype frequencies were within the Hardy-Weinberg equilibrium. We concluded that the allele frequencies of CYP2D6, EPHX1 and NQO1 gene polymorphisms in this Brazilian population showed ethnic variability when compared with those observed in other populations.

Association studies of CYP1A1 and GSTM1 polymorphisms with esophageal cancer risk: evidence-based meta-analyses

BACKGROUND AND AIMS

Previous studies have implicated cytochrome P450 1A1 (CYP1A1) and glutathione S-transferase M1 (GSTM1) polymorphisms as risk factors for various cancers. A number of studies have been devoted to the association of CYP1A1 or GSTM1 polymorphism with susceptibility to esophageal carcinoma and have yielded conflicting results. We undertook this study to assess possible associations of esophageal cancer risk with CYP1A1 genetic variation and GSTM1 null genotype, respectively.

METHODS

We conducted a search in MEDLINE, EMBASE and Chinese National Knowledge Infrastructure (CNKI) without a language limitation, covering all papers published until May 2008. The associated literature was acquired through deliberate searching and selected based on the established inclusion criteria for publications.

RESULTS

Ultimately, 26 studies met the included criteria and thus were selected. Relevant data were extracted and further analyzed using systematic meta-analyses. Results showed that the overall OR for CYP1A1 Msp1 polymorphism was 1.24 (95% CI = 0.84-1.83). Restricting analyses to ethnic groups and histological groups, data failed to show a correlation between CYP1A1 Msp1 polymorphism and esophageal cancer risk. Overall OR for CYP1A1 exon7 polymorphism was 1.37 (95% CI = 1.06-1.77), and subgroup analyses showed that CYP1A1 exon7 polymorphism increases esophageal cancer risk in Asians but not in Caucasians. As for GSTM1 deficiency, the overall OR was 1.20 (95% CI = 0.96-1.49), and further subgroup analyses failed to show a marked association of GSTM1 deletion with esophageal cancer.

CONCLUSIONS

Results of the present study suggest that CYP1A1 exon7 polymorphisms may be a risk factor for esophageal cancer in Asians but not in Caucasians, whereas neither CYP1A1 Msp1 nor GSTM1 polymorphism was associated with increased susceptibility to esophageal cancer.

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed ton-hexane: A preliminary study

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR=?.58, 95% CI=1.32-23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.

Microsomal epoxide hydrolase (EPHX1), slow (exon 3, 113His) and fast (exon 4, 139Arg) alleles confer susceptibility to squamous cell esophageal cancer

Genetic polymorphisms in xenobiotic metabolizing enzymes may alter risk of various cancers. Present case-control study evaluated the influence of EPHX1 genetic variations on squamous cell esophageal cancer (ESCC) susceptibility in 107 patients and 320 controls. EPHX1 polymorphic alleles were genotyped by direct sequencing (exon 3, Tyr113His) or PCR-RFLP (exon 4, His139Arg). Patients with exon 3 genotypes (Tyr113His, His113His) and 113His allele were at risk of ESCC (OR(Tyr113His) 2.0, 95% CI=1.2-3.4, p=0.007; OR(His113His) 2.3 95% CI=1.0-5.2, p=0.03 and OR(His) 1.5, 95% CI=1.0-2.1, p=0.01). In contrast, individuals with exon 4, 139Arg allele were at low risk of cancer (OR 0.34, 95% CI=0.20-0.56, p=0.001). However, none of haplotype combinations of exon 3 (Tyr113His) and exon 4 (His139Arg) polymorphisms showed modulation of risk for ESCC. Sub-grouping of patients based on anatomical location of tumor predicted that patients with exon 3, His113His and Tyr113His genotypes were at higher risk for developing ESCC tumor at upper and middle third locations (OR 4.4, 95% CI=1.0-18.5, p=0.04; OR 2.5, 95% CI=1.3-5.0, p=0.005 respectively). The frequency of exon 4, His139Arg genotype was significantly lower in ESCC patients with lower third tumor location as compared to controls (14.8% vs. 36.3%, p=0.02). In case-only study, gene-environment interaction of EPHX1 genotypes with tobacco, alcohol and occupational exposures did not appear to modulate the cancer susceptibility. In conclusion, exon 3, Tyr113His genotype was associated with higher risk of ESCC particularly at upper and middle-third anatomical locations of tumor. However, His139Arg genotype of exon 4, exhibited low risk for ESCC as well as its clinical characteristics.

Distribution of detoxifying genes polymorphism in Maharastrian population of central India

The present study is aimed at evaluating the genotype frequency of detoxifying genes such as GSTM1, GSTT1 and NQO1 in Maharastrian population of central India. The study revealed about 64.6% of GSTM1-positive and 35.4% GSTM1-null population. GSTT1-positive genotype was found to be 87.5% and GSTT1-null showed 12.5%. The NQO1 genotype of Maharastrian population showed 52.3% of C/C, 42.48% C/T and 5.18% T/T. The NQO1 of this population does not deviate from the expected Hardy-Weinberg equilibrium. The genotype frequencies GSTM1 and GSTT1 of the population when compared with other ethnic groups of Asia and Caucasians show distinct nature of Maharastrian population from other Asian and Caucasian population.

Genetic polymorphisms and esophageal cancer risk

The aim of this paper is to review and evaluate, in a comprehensive manner, the published data regarding the contribution of genetic polymorphisms to risk of esophageal cancer, including squamous cell carcinoma (SCC) and adenocarcinoma, in humans. All relevant studies available in MEDLINE and published before February 2007 were identified. Studies carried out in humans and that compared esophageal cancer patients with at least 1 standard control group were considered for analysis. One-hundred studies and 3 meta-analyses were identified. Eighty (80%) studies were conducted in Asian countries, particularly China including Taiwan (60 (60%) studies). The most intensively examined genes were those encoding carcinogen metabolic enzymes. The most widely studied gene was GSTM1 (15 studies), followed by ALDH2 (11 studies). ALDH2, MTHFR C677T, CYP1A1 Ile/Val, CYP1A1MspI, CYP2E1, GSTP1, GSTM1 and GSTT1 were examined by meta-analyses and significant relations were found between ALDH2*1*2 and the CYP1A1 Val allele and increased risk of esophageal cancer. In addition, increased risk of esophageal SCC was consistently associated with the ADH2*1*2 and the p53 codon 72 Pro/Pro genotypes. Cohort studies that simultaneously consider multiple genetic and environmental factors possibly involved in esophageal carcinogenesis are needed to ascertain not only the relative contribution of these factors to tumor development but also the contributions of their putative interactions.

Etiological study of esophageal squamous cell carcinoma in an endemic region: a population-based case control study in Huaian, China

BACKGROUND

Continuous exposure to various environmental carcinogens and genetic polymorphisms of xenobiotic-metabolizing enzymes (XME) are associated with many types of human cancers, including esophageal squamous cell carcinoma (ESCC). Huaian, China, is one of the endemic regions of ESCC, but fewer studies have been done in characterizing the risk factors of ESCC in this area. The aims of this study is to evaluate the etiological roles of demographic parameters, environmental and food-borne carcinogens exposure, and XME polymorphisms in formation of ESCC, and to investigate possible gene-gene and gene-environment interactions associated with ESCC in Huaian, China.

METHODS

A population based case-control study was conducted in 107 ESCC newly diagnosed cases and 107 residency- age-, and sex-matched controls in 5 townships of Huaian. In addition to regular epidemiological and food frequency questionnaire analyses, genetic polymorphisms of phase I enzymes CYP1A1, CYP1B1, CYP2A6, and CYP2E1, and phase II enzymes GSTM1, GSTT1, GSTP1, and microsomal epoxide hydrolase (EPHX) were assessed from genomic DNA using PCR based techniques.

RESULTS

Consuming acrid food, fatty meat, moldy food, salted and pickled vegetables, eating fast, introverted personality, passive smoking, a family history of cancer, esophageal lesion, and infection with Helicobacter pylori were significant risk factors for ESCC (P < 0.05). Regular clean up of food storage utensils, green tea consumption, and alcohol abstinence were protective factors for ESCC (P < 0.01). The frequency of the GSTT1 null genotype was higher in cases (59.4%) compared to controls (47.2%) with an odds ratio (OR) of 1.68 and 95% confidence interval (CI) from 0.96 to 2.97 (P = 0.07), especially in males (OR = 2.78; 95% CI = 1.22-6.25; P = 0.01). No associations were found between polymorphisms of CYP1A1, CYP1B1, CYP2A6, CYP2E1, GSTM1, GSTP1, and EPHX and ESCC (P > 0.05).

CONCLUSION

Our results demonstrated that dietary and environmental exposures, some demographic parameters and genetic polymorphism of GSTT1 may play important roles in the development of ESCC in Huaian area, China.

Polymorphisms in metabolic genes related to tobacco smoke and the risk of gastric cancer in the European prospective investigation into cancer and nutrition

Metabolizing enzymes, which often display genetic polymorphisms, are involved in the activation of compounds present in tobacco smoke that may be relevant to gastric carcinogenesis. We report the results of a study looking at the association between risk of gastric adenocarcinoma and polymorphisms in genes CYP1A1, CYP1A2, EPHX1, and GSTT1. A nested case-control study was carried out within the European Prospective Investigation into Cancer and Nutrition, developed in 10 European countries. The study includes 243 newly diagnosed cases of histologically confirmed gastric adenocarcinoma and 946 controls matched by center, age, sex, and date of blood collection. Genotypes were determined in nuclear DNA from WBCs. We found an increased risk of gastric cancer for homozygotes for C (histidine) variant in Y113H of EPHX1 (odds ratio, 1.91; 95% confidence interval, 1.19-3.07) compared with subjects with TC/TT. There was also a significant increased risk for smokers carrying at least one variant allele A in Ex7+129C>A (m4) of CYP1A1 and never smokers with null GSTT1 and allele A in the locus -3859G>A of CYP1A2. Most of these genes are involved in the activation and detoxification of polycyclic aromatic hydrocarbons, suggesting a potential role of these compounds in gastric carcinogenesis.

Genetic polymorphisms in glutathione S-transferases T1, M1 and P1 and susceptibility to reflux esophagitis

Recent studies indicate that the prevalence of reflux esophagitis (RE) in China is increasing. RE is one of the most common esophageal complications associated with gastroesophageal reflux disease (GERD) and RE-Barrett's esophagus-esophageal adenocarcinoma (EAC) sequence has been considered as an histogenesis model for EAC in Western countries. RE is only present in a subset of patients with GERD, suggesting an altered susceptibility to RE may exist in these GERD individuals. However, the genetic changes related with high susceptibility to RE is largely unknown. The polymorphisms in glutathione S-transferases (GSTs) T1, M1 and P1 have been reported with high susceptibity to esophageal cancer in Chinese people. The present case-control study was thus undertaken to characterize the genetic polymorphisms of GSTs and their correlation with susceptibility to RE. One hundred and nine patients with RE, 97 patients with nonerosive reflux disease (NERD) and 97 normal controls were recruited in this study. All the subjects were from Beijing, China, and received endoscopic examination and questionnaires for RE. Genomic DNA was extracted from the lymphocytes of peripheral blood for each subject. Genotypes of the GSTM1 and GSTT1 genes were analyzed by a multiplex PCR method. A-->G polymorphism of codon 104 of the GSTP1 gene was detected using PCR-based restriction fragment length polymorphisms (RFLP). The variant GSTP1 genotypes (*A/*Bomicron*B/*B) was found with a high frequency in the case with RE (40%), and followed by NERD (25%) and normal control (22%). The differences were statistically significant (P < 0.05). The risk for RE increased 2.42-fold [odds ratio (OR); 95% confidence interval (95% CI), 2.42 (1.22-4.80)] in the subjects with variant GSTP1 genotype. The subjects with positive variant GSTP1 genotypes and negative H. pylori infection showed increasing tendency for risk of RE [OR (95% CI), 2.67 (1.06-6.70)]. However, the subjects with GSTT1 and GSTM1 polymorphisms did not show any correlation with high risk for RE or NERD. No significant interactions were identified between the variant GSTs and cigarette smoking, or alcohol drinking and subtype of RE. The present result suggests that GSTP1 genetic polymorphism may be one of the high susceptibility factors involved in the mechanisms of RE. H. pylori infection may play a protective role against RE.

Variation in genes relevant to aromatic hydrocarbon metabolism and the risk of adult brain tumors

Genes involved in phase I and phase II regulation of aromatic hydrocarbon-induced effects exhibit sequence variability that may mediate the risk of adult brain tumors. We evaluated associations between gene variants in CYP1A1, CYP1B1, GSTM3, EPHX1, and NQO1 and adult brain tumor incidence. Cases were patients with glioma (n = 489), meningioma (n = 197), or acoustic neuroma (n = 96) diagnosed from 1994 to 1998 at three U.S. hospitals. Controls were 799 patients admitted to the same hospitals for nonmalignant conditions. DNA was extracted from blood samples collected from 1277 subjects, and genotyping was conducted for CYP1A1 I462V, CYP1B1 V432L, EPHX1 Y113H, GSTM3 *A/*B (intron 6 deletion), and NQO1 P187S. The CYP1B1 V432L homozygous variant was associated with decreased risk of meningioma (odds ratio [OR] = 0.6; 95% CI, 0.3-1.0) but not the other tumor types. The GSTM3 *B/*B genotype was associated with increased risk of glioma (OR = 2.3; 95% CI, 1.0-5.2) and meningioma (OR = 3.6; 95% CI, 1.3-9.8). Increased risks associated with GSTM3 *B/*B were observed in younger subjects (age < 50) and older subjects (age > or = 50), in men and women, and within each study site. The magnitude of association for GSTM3 with glioma and meningioma was greater among ever-smokers than among those who had never smoked. None of the other genotypes showed consistent associations with any tumor type. The association with the GSTM3 *B allele, while intriguing, requires replication, and additional research is needed to clarify the function of the GSTM3 alleles studied here.

The association between microsomal epoxide hydrolase genotypes and esophageal squamous-cell-carcinoma in Taiwan: interaction between areca chewing and smoking

One hundred and forty-five ESCC patients and 352 controls were recruited from three hospitals in Taiwan to determine the association between esophageal squamous-cell-carcinoma (ESCC) and microsomal epoxide hydrolase (mEH) genotypes at Thy113His and His139Arg. Stratified by their exposures, the His113His genotype was a significant protective factor for ESCC in areca chewers and tobacco smokers. Stratified by His113 polymorphisms, the risk of contracting ESCC for participants with His113His who chewed areca and smoked was >50% less than for those with Thy113Thy. We suggest that the mEH His113His genotype can differentiate the association between smoking, areca chewing, and ESCC.

Epoxide hydrolases: mechanisms, inhibitor designs, and biological roles

Organisms are exposed to epoxide-containing compounds from both exogenous and endogenous sources. In mammals, the hydration of these compounds by various epoxide hydrolases (EHs) can not only regulate their genotoxicity but also, for lipid-derived epoxides, their endogenous roles as chemical mediators. Recent findings suggest that the EHs as a family represent novel drug discovery targets for regulation of blood pressure, inflammation, cancer progression, and the onset of several other diseases. Knowledge of the EH mechanism provides a solid foundation for the rational design of inhibitors, and this review summarizes the current understanding of the catalytic mechanism of the EHs. Although the overall EH mechanism is now known, the molecular basis of substrate selectivity, possible allosteric regulation, and many fine details of the catalytic mechanism remain to be solved. Finally, recent development in the design of EH inhibitors and the EH biological role are discussed.

Epoxide hydrolases: their roles and interactions with lipid metabolism

The epoxide hydrolases (EHs) are enzymes present in all living organisms, which transform epoxide containing lipids by the addition of water. In plants and animals, many of these lipid substrates have potent biologically activities, such as host defenses, control of development, regulation of inflammation and blood pressure. Thus the EHs have important and diverse biological roles with profound effects on the physiological state of the host organisms. Currently, seven distinct epoxide hydrolase sub-types are recognized in higher organisms. These include the plant soluble EHs, the mammalian soluble epoxide hydrolase, the hepoxilin hydrolase, leukotriene A4 hydrolase, the microsomal epoxide hydrolase, and the insect juvenile hormone epoxide hydrolase. While our understanding of these enzymes has progressed at different rates, here we discuss the current state of knowledge for each of these enzymes, along with a distillation of our current understanding of their endogenous roles. By reviewing the entire enzyme class together, both commonalities and discrepancies in our understanding are highlighted and important directions for future research pertaining to these enzymes are indicated.

Microsomal Epoxide Hydrolase Polymorphisms and Risk for Advanced Colorectal Adenoma

Cigarette smoking is a risk factor for colorectal adenoma, a precursor of colorectal cancer. Microsomal epoxide hydrolase (EPHX1) metabolizes polycyclic aromatic hydrocarbons, carcinogens found in cigarette smoke. Nonsynonymous variants of EPHX1 at Tyr113His (exon 3) and His139Arg (exon 4) are associated, respectively, with low (113His) and high (139Arg) predicted activity. Among participants randomized to the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we evaluated risks for advanced adenoma in relation to cigarette use and these two EPHX1 variants. We compared 772 cases with advanced adenoma (adenoma ≥1 cm or containing high-grade dysplasia or villous, including tubulovillous, elements) of the distal colon (left-sided, descending colon and sigmoid or rectum) to 777 gender- and age-matched controls who were screen-negative for left-sided adenoma. Compared to those with homozygous genotypes predicting low EPHX1 activity, advanced adenoma risks tended to be elevated for carriers of 113TyrTyr [odds ratios (OR), 1.5; 95% confidence intervals (CI), 1.0-2.2] and 139ArgArg (OR, 1.4; 95% CI, 0.8-2.5) and for subjects who carried a greater number of the alleles (113Tyr or 139Arg) associated with high predicted enzymatic activity (Ptrend = 0.03). The increased risk associated with the increasing number of putative high-activity alleles was most apparent among current and recent (quit &lt;10 years) cigarette smokers (Ptrend = 0.02). In conclusion, EPHX1 variants at codon 113 and 139 associated with high predicted enzymatic activity appear to increase risk for colorectal adenoma, particularly among recent and current smokers.