Polymorphisms of the gene for microsomal epoxide hydrolase and susceptibility to alcoholic liver disease and hepatocellular carcinoma in a Caucasian population

Oxidative stress-related genes (EPHX1 and MnSOD) polymorphism and risk of pre-eclampsia: a meta-analysis

BACKGROUND

Previous studies have detected the association of polymorphisms in oxidative stress-related genes EPHX1 and MnSOD with pre-eclampsia (PE) risk, but the results are inconsistent among studies. Thus, a meta-analysis was performed to obtain more conclusive results.

METHODS

Eligible studies were retrieved in PubMed, Web of Science, EMBASE, Scopus, and CNKI. Odds ratios (ORs) with 95% confidence intervals (CIs) were utilized to evaluate the relationship between EPHX1 rs1051740, EPHX1 rs2234922, MnSOD rs4880 polymorphisms, and PE susceptibility in the genetic models. The subgroup analysis was also performed.

RESULTS

Fourteen studies with a total of 4250 participants were included, including 1784 PE patients and 2466 healthy women. There was a statistically significant association between EPHX1 rs1051740 polymorphism and PE in Caucasians within the allele, dominant, heterozygous, and homozygous models (OR = 0.79, 95% CI = 0.64-0.98; OR = 0.64, 95% CI = 0.47-0.87; OR = 0.61, 95% CI = 0.44-0.85; OR = 0.63, 95% CI = 0.42-0.97, respectively). There was a statistically significant association between EPHX1 rs2234922 polymorphism and PE in Middle Easterners within the recessive and homozygous models (OR = 3.59, 95% CI = 1.25-10.32; OR = 3.99, 95% CI = 1.38-11.49, respectively). There was no statistically significant association between MnSOD rs4880 polymorphism and PE within five genetic models. Subgroup analysis didn't reveal any association between MnSOD rs4880 polymorphism and PE in Asians, Caucasians, or Middle Easterners.

CONCLUSIONS

This meta-analysis shows a significant association between the EPHX1 rs1051740 and PE risk in Caucasians. Meantime, there was a statistically significant association between EPHX1 rs2234922 polymorphism and PE in Middle Easterners.

Microsomal epoxide hydrolase 1 (EPHX1): Gene, structure, function, and role in human disease

Microsomal epoxide hydrolase (EPHX1) is an evolutionarily highly conserved biotransformation enzyme for converting epoxides to diols. Notably, the enzyme is able to either detoxify or bioactivate a wide range of substrates. Mutations and polymorphic variants in the EPHX1 gene have been associated with susceptibility to several human diseases including cancer. This review summarizes the key knowledge concerning EPHX1 gene and protein structure, expression pattern and regulation, and substrate specificity. The relevance of EPHX1 for human pathology is especially discussed.

Meta-analysis of microsomal epoxide hydrolase gene polymorphism and risk of hepatocellular carcinoma

BACKGROUND

Hepatocarcinogenesis is a complex process that may be influenced by many factors, including polymorphism in microsomal epoxide hydrolase (mEH). Previous work suggests an association between the Tyr113His and His139Arg mEH polymorphisms and susceptibility to hepatocellular carcinoma (HCC), but the results have been inconsistent.

METHODS

PubMed, EMBASE, Google Scholar and the Chinese National Knowledge Infrastructure databases were systematically searched to identify relevant studies. A meta-analysis was performed to examine the association between Tyr113His and His139Arg mEH polymorphism and susceptibility to HCC. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

Eleven studies were included in the meta-analysis, involving 1,696 HCC cases and 3,600 controls. The 113His- mEH allele was significantly associated with increased risk of HCC based on allelic contrast (OR = 1.35, 95% CI = 1.04-1.75, p = 0.02), homozygote comparison (OR = 1.65, 95% CI = 1.07-2.54, p = 0.02) and a recessive genetic model (OR = 1.54, 95% CI = 1.21-1.96, p<0.001), while individuals carrying the Arg139Arg mEH genotype had no association with increased or decreased risk of HCC.

CONCLUSION

The 113His- allele polymorphism in mEH may be a risk factor for hepatocarcinogenesis, while the mEH 139Arg- allele may not be a risk or protective factor. There is substantial evidence that mEH polymorphisms interact synergistically with other genes and the environment to modulate risk of HCC. Further large and well-designed studies are needed to confirm these conclusions.

Microsomal Epoxide Hydrolase Polymorphisms and Haplotypes as Determinants of Hepatitis B Virusand Hepatitis C Virus-related Liver Disease in Indian Population

BACKGROUND

Hepatocellular carcinoma (HCC) is the fifth most common cancer and third leading cause of death worldwide. Main causes of HCC are hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. mEPHX, a xenobiotic metabolizing enzyme, exhibits a dual role of procarcinogen detoxification and activation, hence considered as a cancer risk factor as well as a protective factor. Two known polymorphic forms of mEPHX, exon in exon 3 and 4, are associated with the development of HCC.

OBJECTIVE

To determine the association of genotypes and haplotypes of mEPHX with risk of HCC developments separately in HBV- and HCV-infected carriers and patients with hepatitis.

METHODS

Polymerase chain reactions (PCR) were carried out using primers to amplify exon 3 (113 Tyr→His variant) and exon 4 (139 His→Arg) polymorphic sites. To distinguish the wild and variant forms, PCR amplification products were digested with restriction endonucleases EcoRV and Rsa1 for exons 3 and 4, respectively.

RESULT

Exon 3 genotypes, Y113H and H113H, shared a protective association with HBV-chronic hepatitis infection (P < 0.001 and P< 0.01, respectively) as well as HBV-HCC development (P < 0.001) among HBV-carrier group, while Y113H acts as a risk factor for HCV-chronic hepatitis development (P < 0.001) as well as for HCC development (P < 0.01) with HCV-carrier group as reference. Both H139R and R139R, exon 4 genotypes, acted as a risk factor for HBV/HCV-chronic hepatitis infection and for HBV/HCV-HCC development (P ranges from < 0.05 to < 0.001) with HBV/HCV carriers as reference. 113His-139His and 113His-139Arg haplotypes shared a significant negative and positive association, respectively, with HBV hepatitis and HBV-HCC risk. 113Tyr-139Arg haplotype acted as a risk for HCV-HCC development.

CONCLUSION

Polymorphic and haplotypic variant forms of mEPHX exon 3 and 4 variably determine the susceptibility to develop HCC in HBV- and HCV-carrier subjects.

dbHCCvar: a comprehensive database of human genetic variations in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common cancer with a high mortality rate. The complete pathogenesis of HCC is not completely understood, and highly efficient therapy is still unavailable. In the past several decades, various genetic variations such as mutations and polymorphisms have been reported to be associated with HCC risk, progression, survival, and recurrence. However, to our knowledge, these genetic variations have not been comprehensively and systematically compiled. In this study we constructed dbHCCvar, a free online database of human genetic variations in HCC. Eligible publications were collected from PubMed, and detailed information and major research data from each eligible study were then extracted and recorded in our database. As a result, dbHCCvar contains almost all human genetic variations reported to be associated or not associated with HCC risk, clinical pathology, drug reaction, survival, or recurrence to date. It is expected that dbHCCvar will function as a useful tool for researchers to facilitate the search and identification of new genetic markers for HCC. dbHCCvar is free for all visitors at http://GenetMed.fudan.edu.cn/dbHCCvar.

UPLC-MS-based urine metabolomics reveals indole-3-lactic acid and phenyllactic acid as conserved biomarkers for alcohol-induced liver disease in the Ppara-null mouse model

Since the development and prognosis of alcohol-induced liver disease (ALD) vary significantly with genetic background, identification of a genetic background-independent noninvasive ALD biomarker would significantly improve screening and diagnosis. This study explored the effect of genetic background on the ALD-associated urinary metabolome using the Ppara-null mouse model on two different backgrounds, C57BL/6 (B6) and 129/SvJ (129S), along with their wild-type counterparts. Reversed-phase gradient UPLC-ESI-QTOF-MS analysis revealed that urinary excretion of a number of metabolites, such as ethylsulfate, 4-hydroxyphenylacetic acid, 4-hydroxyphenylacetic acid sulfate, adipic acid, pimelic acid, xanthurenic acid, and taurine, were background-dependent. Elevation of ethyl-β-d-glucuronide and N-acetylglycine was found to be a common signature of the metabolomic response to alcohol exposure in wild-type as well as in Ppara-null mice of both strains. However, increased excretion of indole-3-lactic acid and phenyllactic acid was found to be a conserved feature exclusively associated with the alcohol-treated Ppara-null mouse on both backgrounds that develop liver pathologies similar to the early stages of human ALD. These markers reflected the biochemical events associated with early stages of ALD pathogenesis. The results suggest that indole-3-lactic acid and phenyllactic acid are potential candidates for conserved and pathology-specific high-throughput noninvasive biomarkers for early stages of ALD.

Putative EPHX1 enzyme activity is related with risk of lung and upper aerodigestive tract cancers: a comprehensive meta-analysis

Background

EPHX1 is a key enzyme in metabolizing some exogenous carcinogens such as products of cigarette-smoking. Two functional polymorphisms in the EPHX1 gene, Tyr113His and His139Arg can alter the enzyme activity, suggesting their possible association with carcinogenesis risk, particularly of some tobacco-related cancers.

Methodology/Principal Findings

A comprehensive systematic review and meta-analysis was performed of available studies on these two polymorphisms and cancer risk published up to November 2010, consisting of 84 studies (31144 cases and 42439 controls) for Tyr113His and 77 studies (28496 cases and 38506 controls) for His139Arg primarily focused on lung cancer, upper aerodigestive tract (UADT) cancers (including oral, pharynx, larynx and esophagus cancers), colorectal cancer or adenoma, bladder cancer and breast cancer. Results showed that Y113H low activity allele (H) was significantly associated with decreased risk of lung cancer (OR = 0.88, 95%CI = 0.80–0.96) and UADT cancers (OR = 0.86, 95%CI = 0.77–0.97) and H139R high activity allele (R) with increased risk of lung cancer (OR = 1.18, 95%CI = 1.04–1.33) but not of UADT cancers (OR = 1.05, 95%CI = 0.93–1.17). Pooled analysis of lung and UADT cancers revealed that low EPHX1 enzyme activity, predicted by the combination of Y113H and H139R showed decreased risk of these cancers (OR = 0.83, 95%CI = 0.75–0.93) whereas high EPHX1 activity increased risk of the cancers (OR = 1.20, 95%CI = 0.98–1.46). Furthermore, modest difference for the risk of lung and UADT cancers was found between cigarette smokers and nonsmokers both in single SNP analyses (low activity allele H: OR = 0.77/0.85 for smokers/nonsmokers; high activity allele R: OR = 1.20/1.09 for smokers/nonsmokers) and in combined double SNP analyses (putative low activity: OR = 0.73/0.88 for smokers/nonsmokers; putative high activity: OR = 1.02/0.93 for smokers/ nonsmokers).

Conclusions/Significance

Putative low EPHX1 enzyme activity may have a potential protective effect on tobacco-related carcinogenesis of lung and UADT cancers, whereas putative high EPHX1 activity may have a harmful effect. Moreover, cigarette-smoking status may influence the association of EPHX1 enzyme activity and the related cancer risk.

The role of epoxide hydrolase Y113H gene variant in pancreatic diseases

OBJECTIVES

Chronic pancreatitis (CP) and pancreatic adenocarcinoma (pCA) are associated with risk factors such as alcohol intake and tobacco smoking. Microsomal epoxide hydrolase (EPHX1) is a phase II detoxifying enzyme capable of tobacco-borne toxicant inactivation. We studied the role of the EPHX1 c.337T>C (p.Y113H) variant, whichleads to altered enzyme activity, in pancreatic diseases.

METHODS

We genotyped 2391 patients by melting curve analysis. We enrolled 367 patients with pCA, 341 patients with alcoholic CP (aCP), 431 patients with idiopathic CP or hereditary pancreatitis, 192 patients with acute pancreatitis, and 679 controls of German descent. We replicated data in 77 patients with aCP and 304 controls from The Netherlands.

RESULTS

In German patients with aCP, Y113 was more common than in controls (allele frequencies, 0.73 vs 0.68; risk ratio, 1.21 [95% confidence interval, 1.05-1.39]). However, we could not confirm this association in the Dutch population (allele frequencies, 0.62 vs 0.68, P=not significant). In total, Y113 frequency was 0.71 in aCP and 0.68 in controls (P = not significant). Allele frequencies did not differ in the other disease groups (acute pancreatitis, 0.69; idiopathic CP or hereditary pancreatitis, 0.68; pCA, 0.68; and control, 0.68).

CONCLUSIONS

The EPHX1 Y113H variant is not associated with pancreatic diseases indicating that EPHX1 does not play a significant role in the initiation of pancreatic inflammation or cancer.

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.

Maternal and fetal single nucleotide polymorphisms in the epoxide hydrolase and gluthatione S-transferase P1 genes are not associated with pre-eclampsia in the Coloured population of the Western Cape, South Africa

Oxidative stress is thought to play an important role in the pathophysiology of pre-eclampsia. A defect in certain enzymes responsible for detoxification may cause prolonged exposure to reactive by-products and contribute to maternal endothelial as well as placental damage. Two polymorphisms affecting the function of the biotransformation enzymes epoxide hydrolase and glutathione S-transferase P1 were shown previously to be associated with pre-eclampsia in a Dutch population. The aim of this study was to determine if these two polymorphisms (maternal or fetal) contribute to pre-eclampsia in an anthropologically distinct population (the Western Cape region of South Africa) with a high incidence of the disease. Genomic DNA of mother - infant pairs with severe pre-eclampsia (n = 144), a population control group (n = 156) and control mother - infant pairs with uncomplicated pregnancy outcome (n = 45) were analysed for the EPHX and GSTP1 polymorphisms by polymerase chain reaction amplification and restriction enzyme digestion. Each polymorphism had a similar distribution in case and control subjects (mother and infant). The Val105/Val105 genotype of GSTP1 occurred at a higher frequency than reported for other populations. Neither maternal nor fetal EPHX Tyr113His and GSTP1 Ile105Val polymorphisms appear to contribute significantly to the pathophysiology of pre-eclampsia in the Coloured population of the Western Cape region of South Africa.

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.

Functional analysis of human microsomal epoxide hydrolase genetic variants

Human microsomal epoxide hydrolase (EPHX1) is active in the metabolism of many potentially carcinogenic or otherwise genotoxic epoxides, such as those derived from the oxidation of polyaromatic hydrocarbons. EPHX1 is polymorphic and encodes allelic variation at least two amino acid positions, Y113H and H139R. In a number of recent molecular epidemiological investigations, EPHX1 polymorphism has been suggested as a susceptibility factor for several human diseases. To better evaluate the functional contribution of EPHX1 genetic polymorphism, we characterized the enzymatic properties associated with each of the respective variant proteins. Enzymatic profiles were evaluated with cis-stilbene oxide (cSO) and benzo[a]pyrene-4,5-epoxide (BaPO), two prototypical substrates for the hydrolase. In one series of experiments, activities of recombinant EPHX1 proteins were analyzed subsequent to their expression using the pFastbac baculovirus vector in Spodoptera frugiperda-9 (Sf9) insect cells, and purification by column chromatography. In parallel studies, EPHX1 activities were evaluated with human liver microsomes derived from individuals of known EPHX1 genotype. Using the purified protein preparations, rates of cSO and BaPO hydrolysis for the reference protein, Y113/H139, were approximately 2-fold greater than those measured with the other EPHX1 allelic variants. However, when activities were analyzed using human liver microsomal fractions, no major differences were evident in the reaction rates generated among preparations representing the different EPHX1 alleles. Collectively, these results suggest that the structural differences encoded by the Y113H and H139R variant alleles exert only modest impact on EPHX1-specific enzymatic activities in vivo.

The Tyr113His polymorphism in exon 3 of the microsomal epoxide hydrolase gene is a risk factor for perinatal mortality

BACKGROUND

A genetic predisposition to impaired detoxification of oxidative or chemical stress could play a role in the etiology of perinatal mortality. In this pilot study we investigated the risk of perinatal mortality in relation to genetic polymorphism in microsomal epoxide hydrolase (EPHX) and glutathione S-transferase P1 (GSTP1) in women who experienced perinatal mortality caused by placental pathology, congenital disorders and complications of premature delivery and their male partners.

METHODS

Genomic DNA of couples (72 females and 46 males) with a history of perinatal mortality and control couples (71 females and 66 males) with no complications in their obstetric history were analyzed for the presence of the polymorphisms in exon 3 of EPHX (Tyr113His) and GSTP1 (Ile105Val).

RESULTS

A similar distribution of the GSTP1 polymorphism was found in all subjects investigated. In women who experienced perinatal mortality, we demonstrated a higher prevalence of the EPHX His113/His113 genotype, which could result in a lower enzyme activity, compared with controls (25% vs. 9%; chi2 = 5.7 and p < 0.02), with an odds ratio (95% confidence interval) of 3.5 (1.1-12.7).

CONCLUSION

Our results suggest that the maternal Tyr113His polymorphism in EPHX may be a risk factor for perinatal mortality. However, more research is needed to determine the implication of this finding.

Interaction between smoking and glutathione S-transferase polymorphisms in solvent-induced chronic toxic encephalopathy

Exposure to organic solvents is still common in industrial and other work environments, and increases the risk of chronic toxic encephalopathy (CTE). Genetic variation in metabolic enzymes for solvents and other xenobiotics may modify the risk of developing toxic effects. Therefore, we investigated the presence of null genotypes for glutathione S-transferases M1 and T1 (GSTM1, GSTT1) and two genetic polymorphisms of microsomal epoxide hydrolase (mEPHX) in relation to the risk for chronic toxic encephalopathy (CTE) when exposed to solvents and smoking. We genotyped 115 patients who were classified into three categories: CTE (n = 56), incipient CTE (n = 27) and non-CTE (n = 32) patients. DNA was isolated from leucocytes and the GSTM1 and GSTT1 null genotypes were determined by multiplex-polymerase chain reaction. The two polymorphisms of mEPHX were analysed by PCR-RFLP (restriction fragment length polymorphism) based assays. All analyses were performed blindly with regard to both exposure and disease status. An increased binomial regression risk ratio = 2.5, 95% confidence interval (CI) 1.5-4.2, of the GSTM1 null genotype for CTE was found in smokers and for the GSTT1 null genotype (binomial regression risk ratio 1.5, 95% CI 1.0-2.0). In nonsmokers, the GSTM1 null genotype did not confer any risk for CTE. None of the studied mEPHX polymorphisms were associated with an increased risk for CTE. We suggest that the GSTM1 null genotype in smokers is a possible risk for solvent-induced CTE.

SV40 Tag DNA sequences, present in a small proportion of human hepatocellular carcinomas, are associated with reduced survival

AIMS

To study the association between simian virus 40 (SV40) and human hepatocarcinogenesis.

METHODS

Polymerase chain reaction (PCR) to detect SV40 large T antigen (Tag) DNA was performed on: 50 human hepatocellular carcinoma (HCCs) diagnosed between 1978 and 1989 (cohort A); 20 cases of alcoholic liver cirrhosis from the same period; and 20 HCCs diagnosed after 1997 (cohort B). PCR to detect SV40 regulatory sequence and SV40 Tag immunohistochemistry were performed on selected cases from cohorts A and B. Amplified products were directly sequenced. Immunohistochemistry for p53 and pRb and clinicopathological analyses were performed on selected cases from cohorts A and B. Complete survival data were collected for cohort A.

RESULT

SV40 Tag DNA was found in five cohort A HCCs but not in alcoholic liver cirrhosis cases or cohort B HCCs. Neither SV40 regulatory sequence nor SV40 Tag protein were demonstrated in Tag DNA positive HCCs. No clinicopathological differences existed between Tag DNA positive and negative HCCs, but the presence of Tag DNA was associated with reduced disease specific survival. Relatively fewer Tag DNA positive than negative HCCs expressed p53, but loss of pRb expression was similar in the two groups. Patients with Tag DNA positive HCCs were unlikely to have received SV40 contaminated poliovirus vaccine.

CONCLUSIONS

SV40 Tag DNA is present in a small proportion of historical HCCs and may contribute to their pathogenesis and influence their outcome. The source of the virus is uncertain and more recent HCCs show no evidence of SV40.

Non-synonymous single nucleotide alterations in the microsomal epoxide hydrolase gene and their functional effects

1. By sequencing genomic DNA from 72 established cell lines derived from Japanese individuals, we detected 25 single nucleotide alterations in the microsomal epoxide hydrolase (EPHX1) gene. Of them, five were exonic alterations resulting in amino acid alterations (77C>G, T26S; 128G>C, R43T; 337T>C, Y113H; 416A>G, H139R; 823A>G, T275A). The T26S, R43T, Y113H and H139R substitutions were found at relatively high frequencies and seemed to be polymorphic, and T26S and T275A were novel. 2. To examine the effects of these amino acid alterations on EPHX1 function, EPHX1 cDNA constructs of wild-type and five variants were transfected into COS-1 cells, and their hydrolytic activities for cis-stilbene oxide were determined in vitro. Although all of the transfectants expressed EPHX1 mRNA and protein at similar levels, the variant H139R protein was expressed at a significantly higher level (128% of the wild-type). K(m) values were not significantly different between the wild-type and variants. 3. Increase (140%) in the enzymatic activity (V(max)) of the variant H139R was accompanied by the increased EPHX1 protein level without any significant change in the intrinsic EPHX1 activity. On the other hand, the variant R43T showed increased values for V(max) and clearance (V(max)/K(m)) (around 130%) both on a microsomal protein basis and on a EPHX1 protein basis. 4. These results suggest that R43T as well as H139R increase epoxide hydrolase activity.

Polymorphisms of microsomal epoxide hydrolase gene and severity of HCV-related liver disease

Factors influencing the progression of liver disease and the development of hepatocellular carcinoma (HCC) in chronic hepatitis C virus (HCV) infection are poorly understood. Inherited variations of drug-metabolizing enzyme (DME) activities may affect liver damage and cancer risk by modifying individual susceptibility to endogenous or exogenous toxic compounds. We investigated the association of liver disease severity with common alleles of microsomal epoxide hydrolase (mEH), an enzyme involved in the metabolism of highly reactive epoxide intermediates. Three polymorphisms (Tyr113His, His139Arg, and -613C/T) were analyzed by polymerase chain reaction (PCR) restriction fragment length polymorphisms (RFLPs) in 394 patients at different stages of disease, including 92 asymptomatic carriers, 109 patients with chronic hepatitis, 100 patients with cirrhosis, and 93 patients with HCC. Reference allele frequencies were obtained from 99 healthy blood donors. Allele distributions between categories were compared using the chi(2) test; odds ratios (ORs) and 95% CI were calculated to express relative risks. Allele frequencies among 99 healthy controls were as follows: 15.1% for 113His/His, 4.0% for 139Arg/Arg, and 46.5% for -613C/T. mEH 113His/His homozygotes were overrepresented in advanced stages of disease, in particular among HCC patients (27.9%; P =.03; OR, 2.2; 95% CI, 1.0-4.6). Differences were more pronounced among men and between extreme patient categories. When mEH genotypes were combined to express a metabolic phenotype, very slow metabolizers were highly prevalent among cirrhotic and HCC patients (18% vs. 3.3% in carriers; P <.001). In conclusion, mEH gene polymorphisms were significantly associated with HCV-related liver disease severity and HCC risk. Men were at higher risk than women; this might be explained by hormonal regulation of gene expression or by differential exposure to environmental toxins.

Single nucleotide polymorphisms and microsatellite alleles of tumor necrosis factor alpha and interleukin-10 genes and the risk of advanced chronic alcoholic liver disease

BACKGROUND

Only a minority of ethanol abusers develop advanced chronic alcoholic liver disease (CALD). In CALD there is a imbalance between TNF alpha and IL-10, which may be modulated by several polymorphisms at both genetic loci. Our aim has been to elucidate the possible relation between these polymorphisms and the risk of CALD.

PATIENTS AND METHODS

147 patients with advanced CALD and 355 healthy controls (all white Spaniards) were included. TNF alpha biallelic single nucleotide polymorphisms (SNP) at positions -238, -308, and -376 and IL-10 biallelic SNP at positions -597, - 824, and - 1087 were investigated by polymerase chain reaction (PCR) amplification and dot blot hybridization. Moreover, polymorphic microsatellites TNFa, TNFb, IL-10.R and IL-10.G were investigated in a multiplex PCR and alleles were estimated in an automatic sequencer.

RESULTS

No differences were found in the distribution of any of the studied polymorphisms, except by an excess of the haplotype formed by the allele 11 of the microsatellite IL-10.G and the GCC arrangement of the SNPs at the promoter of IL-10 gene in patients (15.7 vs. 8.24%, odds ratio: 2.08, 95% C.I. = 1.31-3.31).

CONCLUSIONS

The studied polymorphisms at TNF alpha and IL-10 genetic loci are not clearly related to the risk of CALD. The excess of G11-GCC haplotype found in CALD patients needs independent confirmation.

Microsomal epoxide hydrolase polymorphism and susceptibility to ovarian cancer

Polymorphic variants of microsomal epoxide hydrolase (mEPHX) with altered enzyme activity have been associated with an increased risk for ovarian cancer. We assessed the frequency of exon 3 and exon 4 variants of mEPHX among 291 ovarian cancers and 257 controls from a UK-based population. The distribution of the exon 3 alleles among both the cancer and control groups was significantly different from that expected under Hardy-Weinberg equilibrium suggesting that the PCR restriction fragment length polymorphism (PCR-RFLP) genotyping assay might be flawed. The codon 113 polymorphism was reassessed using a two-color allele-specific PCR-based assay. We found that a codon 119 G>A polymorphism, present in 20% of the British population and linked to the wild-type exon 3 allele, resulted in some Tyr113/His113 heterozygotes being falsely classified as His113/His113 homozygotes when using the PCR-RFLP assay. Consequently, we reassessed all our codon 113 data using the new allele-specific assay. We found no evidence of an association of ovarian cancer risk with the exon 3 Tyr113>His113 variant. Similarly the frequencies of the exon 4 His139>Arg139 genotypes were not significantly different between cases and controls. Stratifying the genotyping data according to the predicted mEPHX activity revealed a highly significant decrease in high mEPHX activity among the serous ovarian cancers (P=0.01) suggesting that high mEPHX activity may be protective for this histological sub-type. Furthermore previous disease association studies of exon 3 alleles which utilized the PCR-RFLP assay may be compromised by the existence of a codon 119 G>A polymorphism which may be common in Caucasian populations.

Microsomal epoxide hydrolase polymorphisms and lung cancer risk in non-Hispanic whites

Microsomal epoxide hydrolase (mEPHX) is a critical metabolic enzyme involved in the activation and subsequent detoxification of specific tobacco carcinogens. mEPHX harbors polymorphisms in exon 3 and exon 4 that modulate enzymatic activity. The exon 3 polymorphism decreases mEPHX metabolic activity, whereas the exon 4 polymorphism increases activity. We hypothesized that the mEPHX polymorphisms modulate lung cancer risk. Using a case-control study design and restriction fragment length polymorphism polymerase chain reaction assay, we determined the mEPHX polymorphic genotypes of 181 lung cancer cases among non-Hispanic whites and 163 controls (matched for age, sex, ethnicity, and smoking history). Our results showed that the variant allele of mEPHX exon 4 increased the overall lung cancer risk by 56% (odds ratio [OR]=1.56, 95% confidence interval [CI]=0.99-2.46). Additionally, the risk estimates were elevated significantly for younger people (<64 yr) (OR=2.27, 95% CI=1.15-4.50) and current smokers (OR=2.22, 95% CI=1.06-4.65). The variant allele of mEPHX exon 3 had no effect overall (OR=0.88, 95% CI=0.56-1.38), but there was a 53% protective effect (OR=0.47, 95% CI=0.22-0.99) in younger people. When we analyzed the exon 3 and exon 4 polymorphisms together, those people with the high enzymatic activity genotype had an elevated lung cancer risk of 1.72 (95% CI=0.90-3.29). This elevated risk was also evident only in younger people. These findings suggest that these variant alleles of exon 3 and exon 4 of mEPHX modulates lung cancer risk.