Alcohol and aldehyde dehydrogenase gene polymorphisms and oropharyngolaryngeal, esophageal and stomach cancers in Japanese alcoholics

Crystal structures of an atypical aldehyde dehydrogenase having bidirectional oxidizing and reducing activities

Aldehyde dehydrogenases (ALDHs) are NAD(P)⁺-dependent oxidoreductases that catalyze the oxidation of a variety of aldehydes to their acid forms. In this study, we determined the crystal structures of ALDH from Bacillus cereus (BcALDH), alone, and in complex with NAD⁺ and NADP⁺. This enzyme can oxidize all-trans-retinal to all-trans-retinoic acid using either NAD⁺ or NADP⁺ with equal efficiency, and atypically, as a minor activity, can reduce all-trans-retinal to all-trans-retinol using NADPH. BcALDH accommodated the additional 2'-phosphate of NADP⁺ by expanding the cofactor-binding pocket and upshifting the AMP moiety in NADP⁺. The nicotinamide moiety in NAD⁺ and NADP⁺ had direct interactions with the conserved catalytic residues (Cys300 and Glu266) and caused concerted conformational changes. We superimposed the structure of retinoic acid bound to human ALDH1A3 onto the BcALDH structure and speculated a model of the substrate all-trans-retinal bound to BcALDH. We also proposed a plausible mechanism for the minor reducing activity of BcALDH. These BcALDH structures will be useful in understanding cofactor specificity and the catalytic mechanism of an atypical bacterial BcALDH and should help the development of a new biocatalyst to produce retinoic acid and related high-end products.

HLA traits linked to development of head and neck squamous cell carcinoma affect the progression-free survival of patients

BACKGROUND

Personalized medicine and treatment stratification of patients with head and neck squamous cell carcinoma (HNSCC) today mostly ignore genetic heterogeneity in HNSCC but especially the patient's genetic background. We hypothesized that particular human leukocyte antigen (HLA) class I (HLA-A, B, Cw) and II proteins (DR, DQ) confer susceptibility for and influence development of HNSCC and may be prognostic factors for progression-free survival (PFS).

METHODS

90 consecutive HNSCC patients of the prospective observational cohort study LIFE treated between 08/2010 and 05/2011 at the University Leipzig underwent low resolution typing of HLA-A, B, Cw, DR, and DQ. Antigen and haplotype frequencies were compared to those in German blood donors. Effects on PFS were analyzed using Kaplan-Meier curves and Cox models.

RESULTS

HNSCC patients had overall altered HLA-B frequencies (P<0.05); frequencies of B∗44 were lower, those of B∗13, B∗52, and B∗57 increased (P<0.05). Almost all other antigen frequencies showed no deviation. Homozygous HLA-Cw and DRB4 were frequent and associated with reduced PFS (P<0.05). Altered haplotype frequencies were common and particular haplotypes accompanied by differing PFS. B∗13/Cw∗06 carriers had poorest outcome (P=0.011). However, multivariate Cox proportional hazard models revealed 3 clinical covariates (localization oropharynx, loco-regional metastasis, and T4 category), HPV16-DNA positivity, and 10 HLA traits as independent predictors for PFS.

CONCLUSIONS

The relevance of the genetic background of HNSCC patients calls for future research to clarify the role of HLA traits in HNSCC and if PFS depends on HLA.

Recovery from anemia and leukocytopenia after abstinence in Japanese alcoholic men and their genetic polymorphisms of alcohol dehydrogenase-1B and aldehyde dehydrogenase-2

BACKGROUND

The combination of the fast-metabolizing alcohol dehydrogenase-1B (ADH1B*2 allele) and inactive heterozygous aldehyde dehydrogenase-2 (ALDH2*1/*2) increases susceptibility to macrocytic anemia and leukocytopenia in alcoholics due to severe acetaldehydemia. More than half of Japanese drinkers with esophageal cancer have this genotype combination.

METHODS

To assess the recovery of hematologic abnormalities after drinking cessation, changes in blood erythrocyte indices and leukocyte count during 8-week hospital stay were evaluated in 925 Japanese alcoholic men. We used four categories in ascending order for high blood acetaldehyde exposure from drinking: A, ADH1B*1/*1 plus ALDH2*1/*1; B, ADH1B*2 plus ALDH2*1/*1; C, ADH1B*1/*1 plus ALDH2*1/*2; and D, ADH1B*2 plus ALDH2*1/*2.

RESULTS

Mean values of hemoglobin and hematocrit were the lowest, and those of mean corpuscular volume (MCV) were markedly the highest in the D group on admission, and returning toward normal after abstinence, but the inter-group differences remained significant throughout the 8 weeks. The mean leukocyte count was the lowest in the D group on admission, but increased during 4-week abstinence when the inter-group differences were no longer significant. Frequencies of MCV ≥110 fl (50.5%), hemoglobin levels <11.5 g/dL (32.7%), hemoglobin levels <10.0 g/dL (9.9%) and leukocytopenia <4000/μL (22.8%) were the highest in the D group on the admission day and decreased at the 4-week abstinence (28.7%, 18.8%, 4.0% and 7.9%, respectively). The inter-group differences in frequencies of the severe anemia and leukocytopenia disappeared after 4-week abstinence.

CONCLUSIONS

Drinking cessation before surgery and/or chemoradiation treatment for esophageal cancer may be effective for recovery from anemia and leukocytopenia in drinkers belonging to the D group.

ALDH2-deficiency as genetic epidemiologic and biochemical model for the carcinogenicity of acetaldehyde

Humans are cumulatively exposed to acetaldehyde from various sources including alcoholic beverages, tobacco smoke, foods and beverages. The genetic-epidemiologic and biochemical evidence in ALDH2-deficient humans provides strong evidence for the causal relationship between acetaldehyde-exposure due to alcohol consumption and cancer of the upper digestive tract. The risk assessment has so far relied on thresholds based on animal toxicology with lower one-sided confidence limit of the benchmark dose values (BMDL) typically ranging between 11 and 63 mg/kg bodyweight (bw)/day dependent on species and endpoint. The animal data is problematic for regulatory toxicology for various reasons (lack in study quality, problems in animal models and appropriateness of endpoints - especially cancer - for transfer to humans). In this study, data from genetic epidemiologic and biochemical studies are reviewed. The increase in the daily exposure dose to acetaldehyde in alcohol-consuming ALDH2-deficients vs. ALDH2-actives was about twofold. The acetaldehyde increase due to ALDH2 inactivity was calculated to be 6.7 μg/kg bw/day for heavy drinkers, which is associated with odds ratios of up to 7 for head and neck as well as oesophageal cancer. Previous animal toxicology based risk assessments may have underestimated the risk of acetaldehyde. Risk assessments of acetaldehyde need to be revised using this updated evidence.

Crystal structure of human aldehyde dehydrogenase 1A3 complexed with NAD+ and retinoic acid

The aldehyde dehydrogenase family 1 member A3 (ALDH1A3) catalyzes the oxidation of retinal to the pleiotropic factor retinoic acid using NAD⁺. The level of ALDHs enzymatic activity has been used as a cancer stem cell marker and seems to correlate with tumour aggressiveness. Elevated ALDH1A3 expression in mesenchymal glioma stem cells highlights the potential of this isozyme as a prognosis marker and drug target. Here we report the first crystal structure of human ALDH1A3 complexed with NAD⁺ and the product all-trans retinoic acid (REA). The tetrameric ALDH1A3 folds into a three domain-based architecture highly conserved along the ALDHs family. The structural analysis revealed two different and coupled conformations for NAD⁺ and REA that we propose to represent two snapshots along the catalytic cycle. Indeed, the isoprenic moiety of REA points either toward the active site cysteine, or moves away adopting the product release conformation. Although ALDH1A3 shares high sequence identity with other members of the ALDH1A family, our structural analysis revealed few peculiar residues in the 1A3 isozyme active site. Our data provide information into the ALDH1As catalytic process and can be used for the structure-based design of selective inhibitors of potential medical interest.

Aldehyde dehydrogenase 2 is associated with cognitive functions in patients with Parkinson's disease

Neurotransmitter degradation has been proposed to cause the accumulation of neurotoxic metabolites. The metabolism of these metabolites involves aldehyde dehydrogenase 2 (ALDH2). The Asian-specific single nucleotide polymorphism rs671 causes reduced enzyme activity. This study aims to explore whether Parkinson's disease (PD) patients with reduced ALDH2 activity owing to the rs671 polymorphism are at risk for neuropsychological impairments. A total of 139 PD patients were recruited. Each participant was assessed for medical characteristics and their ALDH2 genotype. The Mini-Mental State Examination (MMSE), the Clinical Dementia Rating Scale and the Frontal Behavioral Inventory were used to measure neuropsychological functions. We found that the MMSE scores were significantly lower in patients with inactive ALDH2 (U = 1873.5, p = 0.02). The presence of cognitive impairments was significantly more frequent in the inactive ALDH2 group (46.0%) than in the active ALDH2 group (26.3%) (χ(2) = 5.886, p = 0.01). The inactive group showed significant deterioration in hobbies and exhibited more severe "disorganization" and "hyper-sexuality" behaviours. The additive effects of the allele on the development of cognitive impairments in PD patients may be an important finding that provides further insight into the pathogenic mechanism of cognitive dysfunction in PD.

Association between alcohol dehydrogenase-2 gene polymorphism and esophageal cancer risk: a meta-analysis

BACKGROUND

It has been shown that gene polymorphisms may play an important role in the carcinogenesis of esophageal cancer. This study is to investigate the role of alcohol dehydrogenase 1B (ADH1B) gene Arg47His polymorphism in esophageal cancer susceptibility.

METHODS

Case-control studies published between January 2000 and June 2015 were searched to retrieve relevant articles. The pooled odds ratio (OR) and 95 % confidence interval (CI) were employed to calculate the strength of association.

RESULTS

A total of 23 relevant articles were finally selected for the analysis, including 9338 esophageal cancer patients and 14,896 matched controls. Overall, we found that the 47His allele was significant associated with the decreased risk of esophageal cancer when compared with the 47Arg allele in total populations (A vs. G: OR = 0.67, 95 % CI = 0.59-0.76, P < 0.00001). This protective relationship was observed under other genetic models as well (P < 0.00001). Subgroup analysis by ethnicity showed that ADH1B Arg47His variant was associated with the decreased esophageal cancer risk under all the genetic models (P < 0.00001) among Asians, especially in Chinese and Japanese; while in non-Asians, no significant correlation was detected in any genetic models (P > 0.05). Furthermore, Arg/Arg genotype of ADH1B Arg47His variant combined with drinking, smoking and males appeared to show a high risk in patients with esophageal cancer.

CONCLUSIONS

Our results suggested that ADH1B gene Arg47His variant was associated with the decreased esophageal cancer risk. Genetic-environmental interaction should be further considered in the future researches.

Prognostic Value of Drinking Status and Aldehyde Dehydrogenase 2 Polymorphism in Patients With Head and Neck Squamous Cell Carcinoma

Background

The association between alcohol drinking, aldehyde dehydrogenase 2 (ALDH2) polymorphism, and survival in patients with head and neck squamous cell carcinoma (HNSCC) remains unclear.

Methods

We performed a retrospective cohort study of 267 HNSCC patients at Aichi Cancer Center. Of these, 65 patients (24%) were non-drinkers, 104 (39%) were light drinkers (ethanol <46 g or <5 days/week), 46 (17%) were moderate drinkers (ethanol intake 46–68 g/day and ≥5 days/week), and 52 (20%) were heavy drinkers (ethanol intake ≥69 g and ≥5 days/week). The prognostic value of pre-treatment drinking status and ALDH2 polymorphism was investigated using multivariate proportional hazard models.

Results

Drinking status was associated with disease-free survival (DFS) in HNSCC patients, with marginal statistical significance (5-year DFS: 67.9% [95% confidence interval {CI}, 53.8–78.4%] for non-drinkers, 57.6% [95% CI, 47.4–66.6%] for light drinkers, 46.1% [95% CI, 30.8–60.1%] for moderate drinkers, and 43.5% [95% CI, 29.3–56.9%] for heavy drinkers; P = 0.088). However, this association lost significance when multivariate analyses were adjusted for established prognostic factors. ALDH2 genotype was not significantly associated with DFS in HNSCC patients (5-year DFS: 85.7% [95% CI, 53.9–96.2%] for Lys/Lys, 56.2% [95% CI, 47.4–64.1%] for Glu/Lys, and 50.5% [95% CI, 40.3–59.7%] for Glu/Glu; P = 0.154). After stratification by ALDH2 genotype, we observed a significant positive dose-response relationship between drinking status and DFS in HNSCC patients with ALDH2 Glu/Glu (P_trend = 0.029).

Conclusions

In this study, we identified a significant positive dose-response relationship between pre-treatment drinking status and DFS in HNSCC patients with ALDH2 Glu/Glu. To confirm this association, further study is warranted.

Aldehyde dehydrogenase 2 polymorphism for development to hepatocellular carcinoma in East Asian alcoholic liver cirrhosis

BACKGROUND AND AIM

We aimed to clarify the influences of aldehyde dehydrogenase 2 (ALDH2), alcohol dehydrogenase 1B (ADH1B) polymorphisms, and ethanol consumption profile to hepatocellular carcinoma (HCC) development in alcoholic liver cirrhosis without chronic hepatitis B and C virus infection (non-B non-C).

METHODS

Of 236 freshly diagnosed non-B non-C alcoholic liver cirrhosis patients, 67 were diagnosed as HCC and the remaining 169 as not having HCC. The relationship between the genetic polymorphisms and development to HCC were evaluated in well-matched patients with HCC (HCC group, n = 67) and without HCC (non-HCC group, n = 67) using propensity scores in age, sex, and prevalence of diabetes mellitus.

RESULTS

Daily amount of ethanol consumption was significantly lower (P = 0.005), and consumptive period was significantly longer (P = 0.003) in HCC group than non-HCC group. Of 134 well-matched patients, 113 (84.3%) had ALDH2*1/*1 genotype and 21 (15.7%) had ALDH2*1/*2 genotype. In HCC development, consumptive long period (P = 0.007) and carrying ALDH2*1/*2 genotype (P = 0.026) were identified as significant factors independently participated, while there was no relation to ADH1B polymorphism. In addition, consumptive period was significantly longer in HCC group than non-HCC group in ALDH2*1/*1 genotype patients (P = 0.0005), while there was no difference in profile of ethanol consumption in ALDH2*1/*2 genotype patients. Among HCC group, daily (P = 3.78 × 10(-6) ) and cumulative amount (P = 4.89 × 10(-6) ) of ethanol consumption were significantly higher in ALDH2*1/*1 genotype patients than ALDH2*1/*2 genotype patients.

CONCLUSION

In alcoholic liver cirrhosis, investigations of ALDH2 polymorphism and ethanol consumption profile are useful for prediction of HCC development.

Mitochondrial dysfunction and tissue injury by alcohol, high fat, nonalcoholic substances and pathological conditions through post-translational protein modifications

Mitochondria are critically important in providing cellular energy ATP as well as their involvement in anti-oxidant defense, fat oxidation, intermediary metabolism and cell death processes. It is well-established that mitochondrial functions are suppressed when living cells or organisms are exposed to potentially toxic agents including alcohol, high fat diets, smoking and certain drugs or in many pathophysiological states through increased levels of oxidative/nitrative stress. Under elevated nitroxidative stress, cellular macromolecules proteins, DNA, and lipids can undergo different oxidative modifications, leading to disruption of their normal, sometimes critical, physiological functions. Recent reports also indicated that many mitochondrial proteins are modified via various post-translation modifications (PTMs) and primarily inactivated. Because of the recently-emerging information, in this review, we specifically focus on the mechanisms and roles of five major PTMs (namely oxidation, nitration, phosphorylation, acetylation, and adduct formation with lipid-peroxides, reactive metabolites, or advanced glycation end products) in experimental models of alcoholic and nonalcoholic fatty liver disease as well as acute hepatic injury caused by toxic compounds. We also highlight the role of the ethanol-inducible cytochrome P450-2E1 (CYP2E1) in some of these PTM changes. Finally, we discuss translational research opportunities with natural and/or synthetic anti-oxidants, which can prevent or delay the onset of mitochondrial dysfunction, fat accumulation and tissue injury.

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Hepatotoxic agents including alcohol and high fat elevate nitroxidative stress.

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Increased nitroxidative stress promotes post-translational protein modifications.

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Post-translational protein modifications of many proteins lead to their inactivation.

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Inactivation of mitochondrial proteins contributes to mitochondrial dysfunction.

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Mitochondrial dysfunction contributes to necrotic or apoptotic tissue injury.

Translational Implications of the Alcohol-Metabolizing Enzymes, Including Cytochrome P450-2E1, in Alcoholic and Nonalcoholic Liver Disease

Fat accumulation (hepatic steatosis) in alcoholic and nonalcoholic fatty liver disease is a potentially pathologic condition which can progress to steatohepatitis (inflammation), fibrosis, cirrhosis, and carcinogenesis. Many clinically used drugs or some alternative medicine compounds are also known to cause drug-induced liver injury, which can further lead to fulminant liver failure and acute deaths in extreme cases. During liver disease process, certain cytochromes P450 such as the ethanol-inducible cytochrome P450-2E1 (CYP2E1) and CYP4A isozymes can be induced and/or activated by alcohol and/or high-fat diets and pathophysiological conditions such as fasting, obesity, and diabetes. Activation of these P450 isozymes, involved in the metabolism of ethanol, fatty acids, and various drugs, can produce reactive oxygen/nitrogen species directly and/or indirectly, contributing to oxidative modifications of DNA/RNA, proteins and lipids. In addition, aldehyde dehydrogenases including the mitochondrial low Km aldehyde dehydrogenase-2 (ALDH2), responsible for the metabolism of acetaldehyde and lipid aldehydes, can be inactivated by various hepatotoxic agents. These highly reactive acetaldehyde and lipid peroxides, accumulated due to ALDH2 suppression, can interact with cellular macromolecules DNA/RNA, lipids, and proteins, leading to suppression of their normal function, contributing to DNA mutations, endoplasmic reticulum stress, mitochondrial dysfunction, steatosis, and cell death. In this chapter, we specifically review the roles of the alcohol-metabolizing enzymes including the alcohol dehydrogenase, ALDH2, CYP2E1, and other enzymes in promoting liver disease. We also discuss translational research opportunities with natural and/or synthetic antioxidants, which can prevent or delay the onset of inflammation and liver disease.

Aldehyde dehydrogenase 2 polymorphism as a protective factor for intracranial vascular stenosis in ischemic stroke in Han Chinese

AIM

Aldehyde dehydrogenase 2 (ALDH2) is a key enzyme that metabolizes acetaldehyde to acetic acid. ALDH2 gene polymorphism modifies its activity and the mutation of ALDH2 gene has been reported to be associated with the protection against ischemic stroke. However, the potential association of allelic variation of ALDH2 with intracranial vascular stenosis and the clinical characteristics of ischemic stroke without coronary artery disease remains unclear.

METHODS

In this study, ischemic stroke patients were recruited, National Institutes of Health Stroke Scale scores were analyzed, intracranial arterial stenosis were evaluated by magnetic resonance angiography and gene typing of ALDH2 was determined by polymerase chain reaction and sequencing.

RESULTS

We found that the rate of heavy drinking was significantly lower in the ALDH2 mutation group ((*)1/(*)2 and (*)2/(*)2) than in wild-type group ((*)1/(*)1) (18.6% vs. 38.0%, p = 0.01). Plasma homocysteine (Hcy) levels were significantly different in the two groups (15.45 ± 6.39 vs. 13.14 ± 4.45, p = 0.015). The ALDH2 mutation genotype was negatively correlated with severe intracranial vascular stenosis (OR, 0.34; p = 0.002), even after adjustment for high-density lipoprotein cholesterol, Hcy, and heavy drinking (adjusted OR, 0.44; p = 0.03).

CONCLUSION

ALDH2(*)2 could be a protective factor and negative predictor for severe intracranial vascular stenosis in ischemic stroke in Han Chinese.

Estimates of alcohol-related oesophageal cancer burden in Japan: systematic review and meta-analyses

OBJECTIVE

To refine estimates of the burden of alcohol-related oesophageal cancer in Japan.

METHODS

We searched PubMed for published reviews and original studies on alcohol intake, aldehyde dehydrogenase polymorphisms, and risk for oesophageal cancer in Japan, published before 2014. We conducted random-effects meta-analyses, including subgroup analyses by aldehyde dehydrogenase variants. We estimated deaths and loss of disability-adjusted life years (DALYs) from oesophageal cancer using exposure distributions for alcohol based on age, sex and relative risks per unit of exposure.

FINDINGS

We identified 14 relevant studies. Three cohort studies and four case-control studies had dose-response data. Evidence from cohort studies showed that people who consumed the equivalent of 100 g/day of pure alcohol had an 11.71 fold, (95% confidence interval, CI: 2.67-51.32) risk of oesophageal cancer compared to those who never consumed alcohol. Evidence from case-control studies showed that the increase in risk was 33.11 fold (95% CI: 8.15-134.43) in the population at large. The difference by study design is explained by the 159 fold (95% CI: 27.2-938.2) risk among those with an inactive aldehyde dehydrogenase enzyme variant. Applying these dose-response estimates to the national profile of alcohol intake yielded 5279 oesophageal cancer deaths and 102,988 DALYs lost - almost double the estimates produced by the most recent global burden of disease exercise.

CONCLUSION

Use of global dose-response data results in an underestimate of the burden of disease from oesophageal cancer in Japan. Where possible, national burden of disease studies should use results from the population concerned.

Different levels in alcohol and tobacco consumption in head and neck cancer patients from 1957 to 2013

Objective

To provide a precise quantification of the association between alcohol and tobacco consumption trends in head and neck cancer patients over the past 45 years.

Methods

We combined findings from all studies published until March 2014 and evaluated the association between different levels in alcohol and tobacco consumption and head and neck cancers through a meta-analytic approach.

Results

We included 28 studies involving 13830 patients with head and neck cancer. In patients with alcohol consumption, the pooled odds ratio (OR) and 95% confidence interval (CI) were 1.29(1.06-1.57), 2.67(2.05-3.48) and 6.63(5.02-8.74) for light drinkers, moderate drinkers and heavy drinkers, respectively. In patients with tobacco consumption, the pooled OR and 95% CI were 2.33(1.84-2.95), 4.97(3.67-6.71) and 6.77(4.81-9.53) for light smokers, moderate smokers and heavy smokers, respectively.

Conclusion

The increased alcohol and tobacco consumption trends increased the risk of head and neck cancer over the past 45 years. Tobacco consumption was found to be a stronger risk factor for head and neck cancer than alcohol consumption. Thus, the control should be considered to limit the intake of alcohol and tobacco.

Characterization of two distinct structural classes of selective aldehyde dehydrogenase 1A1 inhibitors

Aldehyde dehydrogenases (ALDH) catalyze the irreversible oxidation of aldehydes to their corresponding carboxylic acid. Alterations in ALDH1A1 activity are associated with such diverse diseases as cancer, Parkinson's disease, obesity, and cataracts. Inhibitors of ALDH1A1 could aid in illuminating the role of this enzyme in disease processes. However, there are no commercially available selective inhibitors for ALDH1A1. Here we characterize two distinct chemical classes of inhibitors that are selective for human ALDH1A1 compared to eight other ALDH isoenzymes. The prototypical members of each structural class, CM026 and CM037, exhibit submicromolar inhibition constants but have different mechanisms of inhibition. The crystal structures of these compounds bound to ALDH1A1 demonstrate that they bind within the aldehyde binding pocket of ALDH1A1 and exploit the presence of a unique glycine residue to achieve their selectivity. These two novel and selective ALDH1A1 inhibitors may serve as chemical tools to better understand the contributions of ALDH1A1 to normal biology and to disease states.

Genetic polymorphisms of ADH1B, ADH1C and ALDH2, alcohol consumption, and the risk of gastric cancer: the Japan Public Health Center-based prospective study

The association between alcohol consumption, genetic polymorphisms of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) and gastric cancer risk is not completely understood. We investigated the association between ADH1B (rs1229984), ADH1C (rs698) and ALDH2 (rs671) polymorphisms, alcohol consumption and the risk of gastric cancer among Japanese subjects in a population-based, nested, case-control study (1990-2004). Among 36 745 subjects who answered the baseline questionnaire and provided blood samples, 457 new gastric cancer cases matched to 457 controls were used in the analysis. The odds ratios (OR) and corresponding 95% confidence intervals (CI) were calculated using logistic regression models. No association was observed between alcohol consumption, ADH1B (rs1229984), ADH1C (rs698) and ALDH2 (rs671) polymorphisms and gastric cancer risk. However, considering gene-environmental interaction, ADH1C G allele carriers who drink ≥150 g/week of ethanol had a 2.5-fold increased risk of gastric cancer (OR = 2.54, 95% CI = 1.05-6.17) relative to AA genotype carriers who drink 0 to <150 g/week (P for interaction = 0.02). ALDH2 A allele carriers who drink ≥150 g/week also had an increased risk (OR = 2.08, 95% CI = 1.05-4.12) relative to GG genotype carriers who drink 0 to < 150 g/week (P for interaction = 0.08). To find the relation between alcohol consumption and gastric cancer risk, it is important to consider both alcohol consumption level and ADH1C and ALDH2 polymorphisms.

Association between ADH1B and ADH1C polymorphisms and the risk of head and neck squamous cell carcinoma

Alcohol consumption is one of the major risk factors for head and neck squamous cell carcinoma (HNSCC), and the alcohol dehydrogenase (ADH) family proteins are key enzymes in ethanol metabolism. We examined the associations between single nucleotide polymorphisms (SNPs) of ADH1B and ADH1C and the risk of HNSCC. We analyzed six SNPS of ADH1B, namely -992C > G, -957C > A, +3170A>G, +3377G>T, +3491G>A, and +13543A>G, and five SNPs of ADH1C, namely -1064C>T, -325G>C, +5702A>G, +7462T>C, and +13044A>G, in 260 Korean HNSCC patients and 330 controls, using single base extension and the TaqMan assay. The odds ratios (ORs) and 95 % confidence intervals (95 % CIs) of the CG and GG genotypes of ADH1B -992C>G, the AA genotype of -957C>A, the GG genotype of +3170A>G, the GA genotype of +3491G>A, and +13543A>G were 0.51 (0.32-0.82), 0.63 (0.42-0.94), 1.84 (1.13-2.99), 1.77 (1.15-2.73), 2.34 (1.44-3.79), and 2.21 (1.23-3.95), respectively. The ORs of ADH1C +13044A>G were 1.94 (1.01-3.71) and 1.97 (1.05-3.71) in the dominant and co-dominant models, respectively. The ORs of the GC genotype of ADH1C -325G>C and the AG genotype of +5702A>G were 2.52 (1.51-4.21) and 2.43 (1.36-4.32), respectively. ADH1B +3170A>G and ADH1C +13044A>G were in strong linkage disequilibrium with the other SNPs of ADH1B and ADH1C, respectively. There were gene-environment interactions between ADH1B +3170A>G and ADH1C +13044A>G and alcohol consumption and smoking. ADH1B +3170A>G and ADH1C +13044A>G SNPs are associated with an increased risk of HNSCC, and they could be used as biomarkers for the high-risk group of HNSCC in Koreans.

Implications of acetaldehyde-derived DNA adducts for understanding alcohol-related carcinogenesis

Among various potential mechanisms that could explain alcohol carcinogenicity, the metabolism of ethanol to acetaldehyde represents an obvious possible mechanism, at least in some tissues. The fundamental principle of genotoxic carcinogenesis is the formation of mutagenic DNA adducts in proliferating cells. If not repaired, these adducts can result in mutations during DNA replication, which are passed on to cells during mitosis. Consistent with a genotoxic mechanism, acetaldehyde does react with DNA to form a variety of different types of DNA adducts. In this chapter we will focus more specifically on N2-ethylidene-deoxyguanosine (N2-ethylidene-dG), the major DNA adduct formed from the reaction of acetaldehyde with DNA and specifically highlight recent data on the measurement of this DNA adduct in the human body after alcohol exposure. Because results are of particular biological relevance for alcohol-related cancer of the upper aerodigestive tract (UADT), we will also discuss the histology and cytology of the UADT, with the goal of placing the adduct data in the relevant cellular context for mechanistic interpretation. Furthermore, we will discuss the sources and concentrations of acetaldehyde and ethanol in different cell types during alcohol consumption in humans. Finally, in the last part of the chapter, we will critically evaluate the concept of carcinogenic levels of acetaldehyde, which has been raised in the literature, and discuss how data from acetaldehyde genotoxicity are and can be utilized in physiologically based models to evaluate exposure risk.

Human ALDH1B1 polymorphisms may affect the metabolism of acetaldehyde and all-trans retinaldehyde--in vitro studies and computational modeling

PURPOSE

To elucidate additional substrate specificities of ALDH1B1 and determine the effect that human ALDH1B1 polymorphisms will have on substrate specificity.

METHODS

Computational-based molecular modeling was used to predict the binding of the substrates propionaldehyde, 4-hydroxynonenal, nitroglycerin, and all-trans retinaldehyde to ALDH1B1. Based on positive in silico results, the capacity of purified human recombinant ALDH1B1 to metabolize nitroglycerin and all-trans retinaldehyde was explored. Additionally, metabolism of 4-HNE by ALDH1B1 was revisited. Databases queried to find human polymorphisms of ALDH1B1 identified three major variants: ALDH1B1*2 (A86V), ALDH1B1*3 (L107R), and ALDH1B1*5 (M253V). Computational modeling was used to predict the binding of substrates and of cofactor (NAD(+)) to the variants. These human polymorphisms were created and expressed in a bacterial system and specific activity was determined.

RESULTS

ALDH1B1 metabolizes (and appears to be inhibited by) nitroglycerin and has favorable kinetics for the metabolism of all-trans retinaldehyde. ALDH1B1 metabolizes 4-HNE with higher apparent affinity than previously described, but with low throughput. Recombinant ALDH1B1*2 is catalytically inactive, whereas both ALDH1B1*3 and ALDH1B1*5 are catalytically active. Modeling indicated that the lack of activity in ALDH1B1*2 is likely due to poor NAD(+) binding. Modeling also suggests that ALDH1B1*3 may be less able to metabolize all-trans retinaldehyde and that ALDH1B1*5 may bind NAD(+) poorly.

CONCLUSIONS

ALDH1B1 metabolizes nitroglycerin and all-trans-retinaldehyde. One of the three human polymorphisms, ALDH1B1*2, is catalytically inactive, likely due to poor NAD(+) binding. Expression of this variant may affect ALDH1B1-dependent metabolic functions in stem cells and ethanol metabolism.

Alcohol dehydrogenase-1B Arg47His polymorphism is associated with head and neck cancer risk in Asian: a meta-analysis

Head and neck cancers (HNCs) include cancers which arise in oral cavity, pharynx, and larynx. Recent studies have demonstrated that alcohol drinking is an established risk factor for HNC. The alcohol dehydrogenase-1B (ADH1B) plays a major role in the oxidized process of alcohol. To investigate the association of ADH1B Arg47His with HNC in Asian populations, we combined all available studies into a meta-analysis. A total of 2186 cases and 4488 controls were analyzed for this meta-analysis. We used odds ratios (ORs) to assess the strength of the association and 95% confidence intervals (CIs) to give a sense of the precision of the estimate. The ADH1B*47Arg allele was found to be associated with increased risk of HNC in Asians, with the pooled odds ratios (ORs) (Arg/Arg vs. Arg/His + His/His: OR = 2.35, 95% CI = 1.56-3.55, P < 0.0001) in all eight studies. In the subgroup analysis by alcohol consumption, the Arg/Arg vs. Arg/His + His/His genotype was found to be interacted with alcohol consumption, with the OR = 2.44, 95% CI = 1.85-3.20 among ever drinkers. Besides, no significant association was found in non-drinkers. This meta-analysis revealed that ADH1B Arg47His (rs1229984) polymorphism could increase the risk of HNC in Asians significantly.

Tag single nucleotide polymorphisms of alcohol-metabolizing enzymes modify the risk of upper aerodigestive tract cancers: HapMap database analysis

Although alcohol is associated with higher upper aerodigestive tract (UADT) cancer risk, only a small fraction of alcoholics develop cancers. There is a lack of evidence proving the association of tag single nucleotide polymorphisms of alcohol-metabolizing enzymes with cancer risk. The aim of this study was to determine the association of these genetic polymorphisms with UADT cancer risk in a Chinese population. It was a hospital-based case-control candidate gene study. The databases of the International HapMap Project were searched for haplotype tag single nucleotide polymorphisms of the genes alcohol dehydrogenase (ADH)1B, ADH1C, and aldehyde dehydrogenase (ALDH)2. The genotyping was performed by the Sequenom MassARRAY system. Totally, 120 head and neck squamous cell carcinoma, 138 esophageal squamous cell carcinoma patients, and 276 age- and gender-matched subjects were enrolled between June 2008 and June 2010.Minor alleles of ADH1B (rs1229984) and ALDH2(rs671) were not only associated with the risk of UADT cancers (odds ratio [OR] [95% confidence interval, CI]: 3.53 [2.14-5.80] and 2.59 [1.79-3.75], respectively) but also potentiated the carcinogenic effects of alcohol (OR [95% CI]: 53.44 [25.21-113.29] and 70.08 [33.65-145.95], respectively). Similar effects were observed for head/neck and esophageal cancer subgroups. Multivariate logistic regression analysis identified four significant risk factors, including habitual use of cigarettes, alcohol, betel quid, and lower body mass index (P < 0.001). The haplotypes GAGC (OR 1.61, 95% CI 1.08-2.40, P = 0.018) and CCAATG (OR 1.69, 95% CI 1.24-2.30, P < 0.001) on chromosomes 4 and 12, respectively, were associated with higher cancer risk. These findings suggested that risk allele or haplotype carriers who consume alcohol and other carcinogens should be advised to undergo endoscopy screening. The information can be used to determine the degree of susceptibility of each subject and can be combined with other environmental factors, like carcinogen consumption, in the screening analysis.

Alcohol drinking and risk of leukemia-a systematic review and meta-analysis of the dose-risk relation

The association between alcohol and leukemia risk has been addressed in several studies in the past two decades, but results have been inconsistent. Therefore, we conducted a systematic review and meta-analysis to quantify the dose-risk relation. Through the literature search up to August 2013, we identified 18 studies, 10 case-control and 8 cohorts, carried out in a total of 7142 leukemia cases. We derived pooled meta-analytic estimates using random-effects models, taking into account the correlation between estimates, and we performed a dose-risk analysis using a class of nonlinear random-effects meta-regression models. Stratified analyses were carried out on leukemia subtypes and groups, in order to identify possible etiologic differences. Compared with nondrinkers, the relative risks (RRs) for all leukemia were 0.94 [95% confidence interval (CI), 0.85-1.03], 0.90 (95% CI, 0.80-1.01) and 0.91 (95% CI, 0.81-1.02) for any, light (≤ 1 drink/day) and moderate to heavy (>1 drink/day) alcohol drinking, respectively. The summary RRs for any alcohol drinking were 1.47 (95% CI, 0.47-4.62) for acute lymphoblastic leukemia, 0.94 (95% CI 0.77-1.15) for chronic lymphocytic leukemia, 1.02 (95% CI, 0.86-1.21) for acute myeloid leukemia and 0.93 (95% CI 0.75-1.14) for chronic myeloid leukemia. The subgroup analysis on geographical area for all leukemia combined showed RRs of 0.84 (95% CI, 0.76-0.93), 0.92 (95% CI, 0.83-1.01) and 1.32 (95% CI, 1.02-1.70) for studies conducted in America, Europe and Asia, respectively. We did not find an increased risk of leukemia among alcohol drinkers. If any, a modest favorable effect emerged for light alcohol drinking, with a model-based risk reduction of approximately 10% in regular drinkers.

Functional polymorphism in aldehyde dehydrogenase-2 gene associated with risk of tuberculosis

Background

The well-known genetic polymorphisms in ADH1B(His47Arg) and ALDH2(Glu487Lys) have dramatic effects on the rate of metabolizing alcohol and acetaldehyde. We investigated possible involvement of these functional polymorphisms in other common complex-trait diseases.

Methods

The genetic effects of these two polymorphisms on hepatitis, asthma, type-2 diabetes mellitus (T2DM), and tuberculosis (TB) were examined in a Korean population.

Results

We demonstrated that the well-known functional polymorphism of a primary alcohol-metabolizing enzyme (ALDH2 Glu487Lys) has a strong genetic association with the risk of TB. The frequency of the minor allele (ALDH2*487Lys) was found to be much lower in TB patients (freq. = 0.099/n = 477) than among controls (freq. = 0.162/n = 796) (P = 0.00001, OR (95% confidential interval) = 0.57 (0.45-0.74)). Our data may indicate that TB was once an endemic disease, which exerted selection pressure for higher frequencies of ALDH2*487Lys in Asian populations. In addition, the calculated attributable fraction (AF) indicates that 39.5% of TB patients can attribute their disease to the detrimental effects of ALDH2Glu487Glu.

Conclusion

Our results suggest that this polymorphism is one of the genetic components of TB, at least in the Korean population.

Targeting aldehyde dehydrogenase 2: new therapeutic opportunities

A family of detoxifying enzymes called aldehyde dehydrogenases (ALDHs) has been a subject of recent interest, as its role in detoxifying aldehydes that accumulate through metabolism and to which we are exposed from the environment has been elucidated. Although the human genome has 19 ALDH genes, one ALDH emerges as a particularly important enzyme in a variety of human pathologies. This ALDH, ALDH2, is located in the mitochondrial matrix with much known about its role in ethanol metabolism. Less known is a new body of research to be discussed in this review, suggesting that ALDH2 dysfunction may contribute to a variety of human diseases including cardiovascular diseases, diabetes, neurodegenerative diseases, stroke, and cancer. Recent studies suggest that ALDH2 dysfunction is also associated with Fanconi anemia, pain, osteoporosis, and the process of aging. Furthermore, an ALDH2 inactivating mutation (termed ALDH2*2) is the most common single point mutation in humans, and epidemiological studies suggest a correlation between this inactivating mutation and increased propensity for common human pathologies. These data together with studies in animal models and the use of new pharmacological tools that activate ALDH2 depict a new picture related to ALDH2 as a critical health-promoting enzyme.

The resveratrol attenuates ethanol-induced hepatocyte apoptosis via inhibiting ER-related caspase-12 activation and PDE activity in vitro

BACKGROUND

Endoplasmic reticulum (ER) stress plays a key role in cell apoptosis pathways. Caspase-12, a proapoptotic gene induced by ER stress, is also the key molecule in ER-related apoptosis. The purpose of this study is to evaluate the protective activity and possible mechanism of resveratrol (ResV) against ethanol (EtOH)-induced apoptosis in human hepatocyte Chang cell line.

METHODS

The human hepatocyte Chang cell line was used to test the hypothesis that ResV may alleviate the liver cell apoptosis induced by EtOH. ER stress-inducible proteins and silent mating type information regulation 2 homolog 1 (SIRT1) were assayed by Western blot. Cell viability was studied by MTT assay and apoptosis was measured by Annexin-V and propidium iodide assay. Caspase-12 activation was examined by immunofluorescence staining. Alcohol dehydrogenase-2 (ADH-2) and aldehyde dehydrogenase-2 (ALDH-2) were measured by polymerase chain reaction amplified product length polymorphism. Phosphodiesterase (PDE) activity was assayed in cell lysates using a cyclic nucleotide PDE assay.

RESULTS

EtOH exposure significantly increased the expression of ER stress markers and activated signaling pathways associated with ER stress. These include GRP78, p-IRE1α, p-eIF2α, p-PERK, ATF4 as well as cleaved caspase-3/12, CHOP/GADD153, and Bax in human hepatocyte Chang cell line. The expression of these proteins were significantly down-regulated by ResV (10 μM) in a SIRT1-dependent manner. ResV can inhibit EtOH-, tunicamycin-, thapsigargin-induced caspase-12 activation. ADH-2 and ALDH-2 activities are lower in this cell line. PDE activity increased by EtOH was inhibited by ResV (10 μM).

CONCLUSIONS

The results indicate that (i) EtOH-induced activation of caspase-12 could be one of the underlying mechanisms of hepatocyte apoptosis; (ii) EtOH-induced cell apoptosis was alleviated via ResV (10 μM) by inhibiting ER stress and caspase-12 activation in a SIRT1-dependent manner; and (iii) SIRT1 activated indirectly by ResV (10 μM) attenuates EtOH-induced hepatocyte apoptosis partly through inhibiting PDE activity.

Second cancer incidence, risk factor, and specific mortality in head and neck squamous cell carcinoma

OBJECTIVE

Second primary malignancies (SPMs) are common in patients with head and neck squamous cell carcinoma (HNSCC) and have a negative impact on their survival. This study aimed to evaluate risk factors for SPM occurrence and cause-specific mortality in Asian HNSCC patients.

STUDY DESIGN

A retrospective cohort study.

SETTING

University teaching hospital.

SUBJECTS

Nine hundred and thirty-seven patients without previous cancer history who were treated between 2000 and 2009 and followed for at least 2 years.

METHODS

Confirmation of SPMs was performed by histopathology. The cumulative probability of a SPM among survivors of index HNSCC was calculated using a competing risk model. Univariate and multivariate analyses were utilized to determine factors predictive of SPM occurrence and cause-specific mortality.

RESULTS

Of 937 patients, cumulative incidence of SPMs was 7.2% at 0 to 6 months (synchronous), 17.9% at 5 years, and 23.1% at 10 years after index tumor diagnosis. In multivariate analyses, old age (>60 years) (P = .002), hypopharyngeal index tumor site (P = .001), and heavy drinker (P = .001) were independently associated with the development of SPMs, and hypopharyngeal index tumor site were independent variables for SPM-specific survival (P < .001). Cumulative incidence function of SPM-specific mortality according to index tumor sites was significantly higher in the hypopharynx than other sites (P = .011).

CONCLUSION

Elderly patients, hypopharyngeal index cancer patients, or heavy drinkers may require careful surveillance for the development of SPMs. Our results may help identify and properly manage Asian patients at high risk of SPMs.

Telomere shortening in the esophagus of Japanese alcoholics: relationships with chromoendoscopic findings, ALDH2 and ADH1B genotypes and smoking history

Chromoendoscopy with Lugol iodine staining provides important information on the development of squamous cell carcinoma (SCC). In particular, distinct iodine-unstained lesions (DIULs) larger than 10 mm show a high prevalence in high-grade intraepithelial neoplasia. It has also been reported that inactive ALDH2*1/*2 and less-active ADH1B*1/*1, and smoking, are risk factors for esophageal SCC. We previously examined telomere shortening in the esophageal epithelium of alcoholics, and suggested a high prevalence of chromosomal instability in such individuals. In the present study, we attempted to analyze telomere lengths in 52 DIULs with reference to both their size and multiplicity, ALDH2 and ADH1B genotypes, and smoking history. Patients with DIULs <10 mm (n = 42) had significantly longer telomeres than those with DIULs ≥10 mm (n = 10, p = 0.008). No significant differences in telomere length were recognized between the ALDH2 and ADH1B genotypes (ALDH2 active/inactive = 35/17, ADH1B active/inactive = 32/20; p = 0.563, 0.784, respectively) or among four groups of patients divided according to smoking history (never-, ex-, light, and heavy smokers = 3, 6, 21, and 22 patients, respectively; p = 0.956). Patients without multiple DIULs (n = 17) had significantly longer telomeres than patients with multiple DIULs (n = 35, p = 0.040). It is suggested that alcoholism reduces telomere length in the esophagus, irrespective of genotype or smoking habit. Telomere shortening may not generate cancer directly, but may create conditions under which SCC can develop more easily, depending on subsequent exposure to carcinogens.

Effect of alcohol and aldehyde dehydrogenase gene polymorphisms on alcohol-associated hypertension: the Guangzhou Biobank Cohort Study

The effects of alcohol dehydrogenase (ADH) 2 and aldehyde dehydrogenase (ALDH) 2 genotypes on the alcohol–blood pressure association are unclear. We examined the association of ADH2 or ALDH2 genotypes with blood pressure in older Chinese men. Based on the Guangzhou Biobank Cohort Study (GBCS), 4792 men with valid ADH2, ALDH2 genotypes were included, and genotyping of rs1229984 ADH2 and rs671 ALDH2 (AA, AG/GA or GG) was performed using a Sequenom Mass-Array platform. Information on socio-demographics and lifestyle factors, including alcohol use, was obtained from a questionnaire, and blood pressure was measured. Among alcohol drinkers, systolic and diastolic blood pressure (SBP and DBP) and mean arterial pressure (MAP) were highest for men with the GG ADH2 genotype (136.6, 77.9 and 97.5 mm Hg, respectively), followed by those with the (AA/AG ADH2+GG ALDH2) genotype (133.4, 77.6 and 96.2 mm Hg, respectively) and then the (AA/AG ADH2+AA/AG ALDH2) genotype (SBP=132.6, DBP=76.6 and MAP=95.2 mm Hg) (P for trend ranged 0.025–0.035). After adjustment for potential confounders, as well as frequency or amount of alcohol use, men with the GG ADH2 genotype were more likely to have hypertension (odds ratio (OR)=1.62, 95% confidence interval 1.15–2.28) as were men with the (AA/AG ADH2+AA/AG ALDH2) genotype (OR=1.40, 95% confidence interval 1.01–1.96) compared with men with the (AA/AG ADH2+GG ALDH2) genotype). ADH2 or ALDH2 genotypes were unrelated to hypertension among those who never drink alcohol. ADH2 genotype influences blood pressure and risk of hypertension among male alcohol drinkers, suggesting that the hypertensive effect of alcohol is due to ethanol rather than acetaldehyde.

The aldehyde dehydrogenase 2 (ALDH2) Glu504Lys polymorphism interacts with alcohol drinking in the risk of stomach cancer

The impact of alcohol on the risk of stomach cancer is controversial. Although aldehyde dehydrogenase 2 (ALDH2) Glu504Lys (rs671) polymorphism has a strong effect on acetaldehyde metabolism, little is known about its impact on stomach cancer risk when combined with alcohol drinking. This case-control study included a total of 697 incident stomach cancer case subjects and 1372 non-cancer control subjects who visited Aichi Cancer Center between 2001 and 2005. We estimated odds ratios (OR) and 95% confidence intervals (CI) for ALDH2 genotypes and alcohol consumption using logistic regression models after adjustment for potential confounders, including Helicobacter pylori infection. The ALDH2 504Lys allele was associated with the risk of stomach cancer, with adjusted ORs of 1.40 (95% CI, 1.11-1.76) for Glu/Lys and 1.73 (1.12-2.68) for Lys/Lys compared with Glu/Glu. Heavy drinking was associated with risk (OR 1.72, 1.17-2.52) after adjustment for ALDH2 genotype and other confounders. Moreover, ORs for heavy drinking were 1.28 (0.77-2.12) for those with ALDH2 Glu/Glu and 3.93 (1.99-5.79) for those with the ALDH2 Lys allele relative to non-drinkers with the Glu/Glu genotype (P for interaction = 0.0054). In conclusion, ALDH2 and alcohol drinking showed interaction for risk factors of stomach cancer, indicating that acetaldehyde plays a role in stomach carcinogenesis.

Aldehyde dehydrogenases in cellular responses to oxidative/electrophilic stress

Reactive oxygen species (ROS) are continuously generated within living systems and the inability to manage ROS load leads to elevated oxidative stress and cell damage. Oxidative stress is coupled to the oxidative degradation of lipid membranes, also known as lipid peroxidation. This process generates over 200 types of aldehydes, many of which are highly reactive and toxic. Aldehyde dehydrogenases (ALDHs) metabolize endogenous and exogenous aldehydes and thereby mitigate oxidative/electrophilic stress in prokaryotic and eukaryotic organisms. ALDHs are found throughout the evolutionary gamut, from single-celled organisms to complex multicellular species. Not surprisingly, many ALDHs in evolutionarily distant, and seemingly unrelated, species perform similar functions, including protection against a variety of environmental stressors such as dehydration and ultraviolet radiation. The ability to act as an "aldehyde scavenger" during lipid peroxidation is another ostensibly universal ALDH function found across species. Upregulation of ALDHs is a stress response in bacteria (environmental and chemical stress), plants (dehydration, salinity, and oxidative stress), yeast (ethanol exposure and oxidative stress), Caenorhabditis elegans (lipid peroxidation), and mammals (oxidative stress and lipid peroxidation). Recent studies have also identified ALDH activity as an important feature of cancer stem cells. In these cells, ALDH expression helps abrogate oxidative stress and imparts resistance against chemotherapeutic agents such as oxazaphosphorine, taxane, and platinum drugs. The ALDH superfamily represents a fundamentally important class of enzymes that contributes significantly to the management of electrophilic/oxidative stress within living systems. Mutations in various ALDHs are associated with a variety of pathological conditions in humans, highlighting the fundamental importance of these enzymes in physiological and pathological processes.

Alcohol drinking and non-Hodgkin lymphoma risk: a systematic review and a meta-analysis

BACKGROUND

Whether an association between alcohol drinking and non-Hodgkin lymphoma (NHL) risk exists is an open question. In order to provide quantification of the issue, we carried out a meta-analysis of published data.

METHODS

We identified 21 case-control and 8 cohort studies, including a total of 18,759 NHL cases. We derived meta-analytic estimates using random-effects models, taking into account correlation between estimates.

RESULTS

The overall relative risk (RR) of NHL for drinkers versus non-drinkers was 0.85 [95% confidence interval (CI) 0.79-0.91]. Compared with non-drinkers, the pooled RRs were 0.88 for light (≤1 drink per day), 0.87 for moderate (1 to <4 drinks per day), and 0.84 for heavy (≥4 drinks per day) alcohol drinking. There was no association for light drinkers in cohort studies, whereas for moderate and heavy drinkers, the RRs were similar in case-control (0.85 for moderate, 0.92 for heavy) and cohort (0.89 for moderate, 0.79 for heavy) studies. The inverse relation with alcohol consumption (drinkers versus non-drinkers) was similar in men (RR = 0.83) and women (RR = 0.86), but apparently stronger in studies from Asia (RR = 0.69) than other world areas (RR = 0.88).

CONCLUSION

This meta-analysis provides quantitative evidence of a favourable role of alcohol drinking on NHL risk, though the lack of a biological explanation suggests caution in the interpretation of results.

The role of ALDH2 and ADH1B polymorphism in alcohol consumption and stroke in Han Chinese

The genes encoding the enzymes for metabolising alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2) -- exhibit genetic polymorphism and ethnic variations. Although the ALDH2*2 variant allele has been widely accepted as protecting against the development of alcoholism in Asians, the association of the ADH1B*2 variant allele with drinking behaviour remains inconclusive. The goal of this study was to determine whether the polymorphic ADH1B and ALDH2 genes are associated with stroke in male Han Chinese with high alcohol consumption. Sixty-five stroke patients with a history of heavy drinking (HDS) and 83 stroke patients without such a history (NHDS) were recruited for analysis of the ADH1B and ALDH2 genotypes from the stroke registry in the Tri-Service General Hospital, Taipei, Taiwan, between January 2000 and December 2001. The allelotypes of ADH1B and ALDH2 were determined using the polymerase chain reaction-restriction fragment length polymorphism method. The HDS patients (3 per cent) showed a significantly lower ALDH2*2 allele frequency than NHDS patients (27 per cent) (p < 0.001). After controlling for age, patients with HDS were associated with a significantly higher occurrence of cigarette smoking (p < 0.01) and liver dysfunction (p < 0.01). Multiple logistic regression analyses revealed that the ALDH2*2 variant allele was an independent variable exhibiting strong protection (odds ratio 0.072; 95 per cent confidence interval 0.02-0.26) against HDS after adjustment for hypertension, diabetes mellitus, smoking status and liver dysfunction. By contrast, allelic variations in ADH1B exerted no significant effect on HDS. The present study indicated that, unlike ALDH2*2, ADH1B*2 appears not to be a significant negative risk factor for high alcohol consumption in male Han Chinese with stroke.

A meta-analysis on alcohol drinking and gastric cancer risk

BACKGROUND

Whether an association between alcohol drinking and gastric cancer risk exists is an open question. In order to provide a definite quantification of the association between alcohol drinking and gastric cancer risk, we conducted a meta-analysis of available data.

PATIENTS AND METHODS

We carried out a PubMed search of articles published up to June 2010 and identified 44 case-control and 15 cohort studies, including a total of 34 557 gastric cancer cases. We derived meta-analytic estimates using random-effects models, taking into account correlation between estimates. We carried out a dose-risk analysis using nonlinear random-effects meta-regression models.

RESULTS

Compared with nondrinkers, the pooled relative risk (RR) was 1.07 [95% confidence interval (CI) 1.01-1.13] for alcohol drinkers and 1.20 (95% CI 1.01-1.44) for heavy alcohol drinkers (≥4 drinks per day). The pooled estimates were apparently higher for gastric noncardia (RR for heavy drinkers=1.17, 95% CI 0.78-1.75) than for gastric cardia (RR=0.99, 95% CI 0.67-1.47) adenocarcinoma. The dose-risk model estimated a RR of 0.95 (95% CI 0.91-0.99) for 10 g/day and 1.14 (95% CI 1.08-1.21) for 50 g/day.

CONCLUSIONS

This meta-analysis provides definite evidence of a lack of association between moderate alcohol drinking and gastric cancer risk. There was, however, a positive association with heavy alcohol drinking.

Genetic variation in alcohol dehydrogenase (ADH1A, ADH1B, ADH1C, ADH7) and aldehyde dehydrogenase (ALDH2), alcohol consumption and gastric cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort

Studies that have examined the association between alcohol consumption and gastric cancer (GC) risk have been inconsistent. We conducted an investigation of 29 genetic variants in alcohol metabolism loci (alcohol dehydrogenase, ADH1 gene cluster: ADH1A, ADH1B and ADH1C; ADH7 and aldehyde dehydrogenase, ALDH2), alcohol intake and GC risk. We analyzed data from a nested case-control study (364 cases and 1272 controls) within the European Prospective Investigation into Cancer and Nutrition cohort. Single nucleotide polymorphisms (SNPs) were genotyped using a customized array. We observed a statistically significant association between a common 3'-flanking SNP near ADH1A (rs1230025) and GC risk [allelic odds ratio (OR)(A v T) = 1.30, 95% confidence interval (CI) = 1.07-1.59]. Two intronic variants, one in ADH1C (rs283411) and one in ALDH2 (rs16941667), also were associated with GC risk (OR(T v C) = 0.59; 95% CI = 0.38-0.91 and OR(T v C) = 1.34; 95% CI = 1.00-1.79, respectively). Individuals carrying variant alleles at both ADH1 (rs1230025) and ALDH2 (rs16941667) were twice as likely to develop GC (OR(A+T) = 2.0; 95% CI = 1.25-3.20) as those not carrying variant alleles. The association between rs1230025 and GC was modified by alcohol intake (<5 g/day: OR(A) = 0.89, 95% CI = 0.57-1.39; ≥5 g/day: OR(A) = 1.45, 95% CI = 1.08-1.94, P-value = 0.05). The association was also modified by ethanol intake from beer. A known functional SNP in ADH1B (rs1229984) was associated with alcohol intake (P-value = 0.04) but not GC risk. Variants in ADH7 were not associated with alcohol intake or GC risk. In conclusion, genetic variants at ADH1 and ALDH2 loci may influence GC risk, and alcohol intake may further modify the effect of ADH1 rs1230025. Additional population-based studies are needed to confirm our results.

The role of alcohol dehydrogenase genes in head and neck cancers: a systematic review and meta-analysis of ADH1B and ADH1C

Alcohol drinking is a major risk factor for head and neck cancer (HNC). This risk may be modified by alcohol dehydrogenase (ADH) genes, particularly ADH1B and ADH1C, that oxidise ethanol to its carcinogenic metabolite, acetaldehyde. A meta-analysis was conducted to assess the association between ADH1B and ADH1C and HNC risk. Twenty-nine studies from 28 articles identified from a literature search were included. Summary odds ratios (meta-ORs) were generated using random effect models. A reduced risk for HNC was associated with carrying the ADH1B*2 and ADH1C*1 alleles that confer faster metabolism of ethanol to acetaldehyde [meta-OR ADH1B, 0.50; 95% confidence interval (CI): 0.37-0.68, 13 studies; meta-OR ADH1C, 0.87; 95% CI: 0.76-0.99, 22 studies]. ADH1B*2 and ADH1C*1 alleles appear to be protective for HNC, possibly due to: (i) decreasing the opportunity for oral microflora to produce acetaldehyde locally from a prolonged systemic circulation of ethanol, (ii) preventing ethanol from acting as a solvent for other carcinogens, and (iii) decreasing the amount of ethanol a person consumes since a consequent peak in systemic acetaldehyde could cause discomfort. These results underscore the importance of ADH1B and ADH1C in the association between alcohol consumption and the risk for HNC.

Development of squamous neoplasia in esophageal iodine-unstained lesions and the alcohol and aldehyde dehydrogenase genotypes of Japanese alcoholic men

We investigated the development of esophageal neoplasia in biopsy specimens of the distinct iodine-unstained lesions (DIULs) ≥ 5 mm detected in 280 of 2,115 Japanese alcoholic men who underwent screening by esophageal iodine staining. Low-grade intraepithelial neoplasia (LGIN) was diagnosed in 155 of them, high-grade intraepithelial neoplasia (HGIN) in 57, and invasive SCC in 35. The size of the DIULs increased with the degree of neoplasia. Most LGINs were flat and were missed before iodine staining. Some DIULs became a light pink color (PC) about 2 min after staining, and 2.6, 56.1 and 96.0% of the LGIN, HGIN and invasive SCC lesions, respectively, were PC-sign-positive. Multiple DIULs of any size markedly increased the risk of LGIN [adjusted OR (95%CI) = 10.1 (7.12-14.5)], HGIN [27.9 (14.6-53.4)] and invasive SCC [21.6 (10.1-46.4)], and were strongly associated with the presence vs. absence of DIULs ≥ 5 mm [13.3 (9.21-19.1)], inactive heterozygous aldehyde dehydrogenase-2 (ALDH2*1/*2) vs. ALDH2*1/*1 [2.60 (1.79-3.78)], and less-active alcohol dehydrogenase-1B (ADH1B*1/*1) vs. ADH1B*2 allele [2.61 (1.87-3.64)]. The combination of ALDH2*1/*2 and ADH1B*1/*1 synergistically increased the risk of LGIN [4.53 (2.17-9.47)], HGIN [10.4 (4.34-24.7)] and invasive SCC [21.7 (7.96-59.3)]. Esophageal neoplasia developed at earlier ages in those with ALDH2*1/*2. Biopsy-proven HGIN was diagnosed as invasive SCC in 15 (39.5%) of 38 patients after endoscopic mucosectomy or surgery. In conclusion, large size, non-flat appearance, positive PC sign and multiplicity of DIULs and ALDH2*1/*2 and ADH1B*1/*1 were associated with development of esophageal neoplasia in Japanese alcoholics. Biopsy-proven HGIN should be totally resected for both diagnostic and therapeutic purposes.

Sequence Variants and the Risk of Head and Neck Cancer: Pooled Analysis in the INHANCE Consortium

Previous molecular epidemiological studies on head and neck cancer have examined various single nucleotide polymorphisms (SNPs), but there are very few documented associations. In the International head and neck cancer epidemiology (INHANCE) consortium, we evaluated associations between SNPs in the metabolism, cell cycle, and DNA repair pathways and the risk of head and neck cancer. We analyzed individual-level pooled data from 14 European, North American, Central American, and Asia case-control studies (5,915 head and neck cancer cases and 10,644 controls) participating in the INHANCE consortium. Unconditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for SNP effects, adjusting for age, sex, race, and country. We observed an association between head and neck cancer risk and MGMT Leu84Phe heterozygotes (OR = 0.79, 95% CI = 0.68-0.93), XRCC1 Arg194Trp homozygotes Arg/Arg (OR = 2.3, 95% CI = 1.1-4.7), ADH1B Arg48His homozygotes Arg/Arg (OR = 2.7, 95% CI = 1.9-4.0), ADH1C Ile350Val homozygotes Ile/Ile (OR = 1.2, 95% CI = 1.1-1.4), and the GSTM1 null genotype (OR = 1.1, 95% CI = 1.0-1.2). Among these results, MGMT Leu84Phe, ADH1B Arg48His, ADH1C Ile350Arg, and the GSTM1 null genotype had fairly low false positive report probabilities (<20%). We observed associations between ADH1B Arg48His, ADH1C Ile350Arg, and GSTM1 null genotype and head and neck cancer risk. No functional study currently supports the observed association for MGMT Leu84Phe, and the association with XRCC1 Arg194Trp may be a chance finding.

p53 protein accumulation, iodine-unstained lesions, and alcohol dehydrogenase-1B and aldehyde dehydrogenase-2 genotypes in Japanese alcoholic men with esophageal dysplasia

Inactive heterozygous aldehyde dehydrogenase-2 (ALDH2(*)1/(*)2) and less-active alcohol dehydrogenase-1B (ADH1B(*)1/(*)1) increase the risk of esophageal cancer in East Asian drinkers, and esophageal cancer multiplicity is strongly associated with ALDH2(*)1/(*)2. p53 alterations are key molecular events in multifocal carcinogenesis in the esophagus. We studied 260 esophageal-cancer free Japanese alcoholics with esophageal dysplasia diagnosed by biopsy of distinct iodine-unstained lesions (DIULs) ≥5mm. The degree of p53 protein accumulation was positively associated with the degree of atypia (p<0.0001) and size (p=0.040) of DIULs and with the presence of multiple DIULs (p=0.070), but not with ALDH2(*)1/(*)2 or ADH1B(*)1/(*)1.

Head and neck cancer: effective prevention in youth and predictive diagnostics for personalised treatment strategies according to biological differences

This article focuses on squamous cell carcinomas of the larynx, pharynx and oral cavity which count nearly 90% of the head and neck squamous cell carcinomas (HNSCC). Individual susceptibility depends on an individually given genetic background and/or acquired conditions or factors elevating the risk of HNSCC including smoking, alcohol abuse, and improper oral hygiene. A key issue in HNSCC pathogenesis is their development within large preneoplastic fields of mucosal epithelium made up of genetically altered cells that are clonally related to the carcinoma. Other individual differences in development of HNSCC comprise infection with pathogenic microbes and oncogenic human papillomavirus (HPV) subtypes like HPV 16 (a strong risk factor mainly for oropharyngeal cancer). Interestingly, the presence of HPV 16 also goes in line with better outcome after therapy. Vaccination against HPV infection in children plays an increasing role in prevention strategies and probably also reduces the oncogenic risk for HNSCC.

ADH1B and ALDH2 polymorphisms and their associations with increased risk of squamous cell carcinoma of the head and neck in the Korean population

Alcohol consumption is a major risk factor for squamous cell carcinoma of the head and neck (SCCHN). Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are key enzymes in ethanol metabolism. The objective of this study was to investigate the relationships of ADH and ALDH single nucleotide polymorphisms (SNPs) with the risk of developing SCCHN in a Korean sample. We genotyped ADH1B +3170A>G (rs1229984) and ALDH2 +1951G>A (rs671) SNPs in 225 Korean SCCHN patients and 301 healthy controls by single base extension and TaqMan assay. The frequencies of the ADH1B +3170A>G (*2*2/*2*1/*1*1) genotypes were 48.0%/38.7%/13.3% in SCCHN patients, and 57.8%/37.2%/5.0% in controls, respectively. The odds ratio (OR) and 95% confidence interval of the ADH1B*1*1 genotype was 1.89 (1.23-2.92) relative to the *2*2 genotype. The frequencies of the ALDH2 +1951G>A (*1*1/*1*2/*2*2) genotypes were 67.6%/31.6%/0.9% in SCCHN patients, and 67.8%/29.6%/2.7% in controls, respectively. In subgroup analyses according to smoking and alcohol drinking status, the OR of the ADH1B*1*1 genotype was increased in the heavy drinker group [8.85 (1.095-40.0)] and in the heavy smoker group [4.7 (1.54-14.29)]. We conclude that the ADH1B*1*1 genotype is associated with an increased risk of SCCHN, especially in heavy drinkers and heavy smokers. This genotype could be a useful biomarker for identifying Koreans with a greater risk of SCCHN.

Alcohol and aldehyde dehydrogenase polymorphisms and a new strategy for prevention and screening for cancer in the upper aerodigestive tract in East Asians

The ethanol in alcoholic beverages and the acetaldehyde associated with alcohol consumption are Group 1 human carcinogens (WHO, International Agency for Research on Cancer). The combination of alcohol consumption, tobacco smoking, the inactive heterozygous aldehyde dehydrogenase-2 genotype (ALDH2*1/*2) and the less-active homozygous alcohol dehydrogenase-1B genotype (ADH1B*1/*1) increases the risk of squamous cell carcinoma (SCC) in the upper aerodigestive tract (UADT) in a multiplicative fashion in East Asians. In addition to being exposed to locally high levels of ethanol, the UADT is exposed to a very high concentration of acetaldehyde from a variety of sources, including that as an ingredient of alcoholic beverages per se and that found in tobacco smoke; acetaldehyde is also produced by salivary microorganisms and mucosal enzymes and is present as blood acetaldehyde. The inefficient degradation of acetaldehyde by weakly expressed ALDH2 in the UADT may be cri! tical to the local accumulation of acetaldehyde, especially in ALDH2*1/*2 carriers. ADH1B*1/*1 carriers tend to experience less intense alcohol flushing and are highly susceptible to heavy drinking and alcoholism. Heavy drinking by persons with the less-active ADH1B*1/*1 leads to longer exposure of the UADT to salivary ethanol and acetaldehyde. The ALDH2*1/*2 genotype is a very strong predictor of synchronous and metachronous multiple SCCs in the UADT. High red cell mean corpuscular volume (MCV), esophageal dysplasia, and melanosis in the UADT, all of which are frequently found in ALDH2*1/*2 drinkers, are useful for identifying high-risk individuals. We invented a simple flushing questionnaire that enables prediction of the ALDH2 phenotype. New health appraisal models that include ALDH2 genotype, the simple flushing questionnaire, or MCV are powerful tools for devising a new strategy for prevention and screening for UADT cancer in East Asians.

Acetaldehyde burst protection of ADH1B*2 against alcoholism: an additional hormesis protection against esophageal cancers following alcohol consumption?

This account of recent work presented at the 4th International Symposium on Alcohol Pancreatitis and Cirrhosis reports animal studies aimed at determining the role of the "acetaldehyde burst," generated shortly upon ethanol intake, as the mechanism of protection against alcoholism conferred by the ADH1B*2 polymorphism. Literature studies discussed suggest an additional role of the acetaldehyde burst on the paradoxical (hormesis) protection of the ADH1B*2 polymorphism against esophageal cancers in alcoholics.

Association between alcohol intake and risk for gastric cancer with regard to ALDH2 genotype in the Korean population

BACKGROUND

The relationship between alcohol intake and the risk for gastric cancer is not fully understood. The association between alcohol consumption and the risk for gastric cancer was investigated in the Korean population with the ALDH2 genotype.

METHODS

From 2003 to 2008, 445 patients with gastric cancer and 370 control subjects ≥ 50 years of age were included in the analysis. Logistic regression models including age, gender, education, smoking and drinking status, Helicobacter pylori infection and ALDH2 genotype were evaluated to estimate the adjusted odds ratios (ORs) for the development of gastric cancer.

RESULTS

For all subjects, the risk for gastric cancer was increased in ex-drinkers [OR 1.68, 95% confidence interval (CI) 1.07-2.64], but not in current drinkers. Subjects with inactive ALDH2 *2 allele(s) showed a lower level of alcohol consumption than ALDH2 *1/*1 homozygotes (P < 0.001). Among the ALDH2 *1/*2 carriers (n = 243), current/ex-drinkers had a significantly increased risk for gastric cancer compared with never/rare drinkers (OR 2.80, 95% CI 1.51-5.19). Among heavy drinkers (n = 115), ALDH2 *1/*2 heterozygotes had a 4-fold increased risk for gastric cancer compared with *1/*1 homozygotes (OR 4.26, 95% CI 1.10-16.47); however, no risk increase was seen among never/rare drinkers.

CONCLUSIONS

A dose-response association between alcohol intake and the risk for gastric cancer was not observed. However, ALDH2 polymorphisms were found to modify the susceptibility to the development of gastric cancer associated with alcohol intake, especially in case of ALDH2 *1/*2 genotype. The findings suggest an alcohol-ALDH2 genotype interaction in gastric carcinogenesis.

Deficient aldehyde dehydrogenase 2 is associated with increased risk for esophageal squamous cell carcinoma in the presence of gastric hypochlorhydria

OBJECTIVE

In Orientals, deficient aldehyde dehydrogenase 2 (ALDH2) is associated with an increased risk for esophageal squamous cell carcinoma (ESCC). The local metabolism of carcinogenic acetaldehyde in the upper gastrointestinal tract could be involved in the association, but the underlying mechanism has not been fully elucidated. Since an anacidic stomach can promote bacteria-catalyzed local acetaldehyde production, the gastric acid level could also affect acetaldehyde metabolism. This study investigated whether ALDH2-related susceptibility to ESCC differs depending on the gastric secretion level.

MATERIAL AND METHODS

Sixty-two patients with ESCC and sex- and age-matched normal controls were enrolled in this study. ALDH2 polymorphism was analyzed by polymerase chain-restriction fragment length polymorphism, and those with an inactive allele (ALDH2-1/2-2 or ALDH2-2/2-2) were defined as ALDH2 deficient. Gastrin-stimulated acid output was assessed by endoscopic gastrin test and hypochlorhydria was defined as 0.6 mEq/10 min or lower. Multiple logistic regression analyses were used to adjust for other potential confounders.

RESULTS

ALDH2 deficiency or hypochlorhydria was more prevalent in ESCC compared with controls and both showed increased independent associations with ESCC in multivariate analysis. Stratified analysis by the gastric acid secretion level revealed that the associations between the ALDH2 genotype and ESCC differed according to the individual gastric acid secretion levels and that ALDH2 deficiency was a significant risk factor for ESCC exclusively in individuals with hypochlorhydria with an odds ratio (95% confidence interval): 5.0 (1.2-21.2).

CONCLUSION

Microbial production of carcinogen acetaldehyde in the presence of gastric hypochlorhydria is most probably involved in the mechanism of ALDH2-related susceptibility to ESCC.