Polymorphisms of alcohol dehydrogenase-2 and aldehyde dehydrogenase-2 and esophageal cancer risk in Southeast Chinese males

The effects of ALDH2 Glu487Lys polymorphism on vasovagal syncope patients undergoing head-up tilt test supplemented with sublingual nitroglycerin

Background and objective

Head-up tilt test (HUTT) is clinically advantageous for diagnosing patients with vasovagal syncope (VVS). Nitroglycerin is mainly used as a stimulant during HUTT, and mitochondrial aldehyde dehydrogenase 2 (ALDH2) is involved in the metabolism of nitroglycerin (NTG). ALDH2 Glu487Lys polymorphism (ALDH2 rs671) is the most common variant in the East Asian population. This study aimed to assess the effects of ALDH2 rs671 on VVS patients undergoing HUTT supplemented with sublingual NTG (HUTT-NTG). 

Methods

Patients with recurrent VVS (at least 2 times) who were admitted to the syncope center of our hospital were enrolled. All VVS patients have undergone HUTT. The polymorphism of Glu487Lys gene of ALDH2 was measured by the DNA Microarray Chip Method. The results of HUTT-NTG of VVS patients with different ALDH2 genotypes were compared and their hemodynamic characteristics were assessed.

Results

A total of 199 VVS patients were enrolled, including 101 patients in the ALDH2*1/*1 group and 98 patients in the ALDH2*2 group. Among patients undergoing HUTT-NTG, 70.3% of patients in the ALDH2*1/*1 group and 68.4% of patients in the ALDH2*2 group were positive, and the difference between the two groups was not statistically significant (P = 0.77). The proportions of VASIS I, VASIS II, and VASIS III were 40.6%, 8.9%, and 20.8% in the ALDH2*1/*1 group, respectively, and the corresponding proportions in the ALDH2*2 group were 36.7%, 11.2%, and 20.4%, respectively. There was no statistically significant difference between the two groups (P = 0.91). The hemodynamic characteristics of different genotypes in VVS patients undergoing HUTT-NTG were compared, and no statistically significant difference was found. The median time of syncopal episode occurred after NTG administration in the ALDH2*1/*1 group was 6 min (interquartile range [IQR]: 5.0–9.0), and it was 6.0 min in the ALDH2*2 group (IQR: 4.25–8.0, P = 0.64).

Conclusion

ALDH2 Glu487Lys polymorphism did not affect the outcome of VVS patients undergoing HUTT-NTG, and no significant change in the hemodynamic characteristics of different genotypes was found.

Can gene therapy be used to prevent cancer? Gene therapy for aldehyde dehydrogenase 2 deficiency

Approximately 8% of the world population and 35-45% of East Asians are carriers of the hereditary disorder aldehyde dehydrogenase 2 (ALDH2) deficiency. ALDH2 plays a central role in the liver to metabolize ethanol. With the common E487K variant, there is a deficiency of ALDH2 function; when ethanol is consumed, there is a systemic accumulation of acetaldehyde, an intermediate product in ethanol metabolism. In ALDH2-deficient individuals, ethanol consumption acutely causes the "Alcohol Flushing Syndrome" with facial flushing, tachycardia, nausea, and headaches. With chronic alcohol consumption, ALDH2 deficiency is associated with a variety of disorders, including a remarkably high risk for aerodigestive tract cancers. Acetaldehyde is a known carcinogen. The epidemiologic data relating to the association of ALDH2 deficiency and cancer risk are striking: ALDH2 homozygotes who are moderate-to-heavy consumers of ethanol have a 7-12-fold increased risk for esophageal cancer, making ALDH2 deficiency the most common hereditary disorder associated with an increased cancer risk. In this review, we summarize the genetics and biochemistry of ALDH2, the epidemiology of cancer risk associated with ALDH2 deficiency, the metabolic consequences of ethanol consumption associated with ALDH2 deficiency, and gene therapy strategies to correct ALDH2 deficiency and its associated cancer risk. With the goal of reducing the risk of aerodigestive tract cancers, in the context that ALDH2 is a hereditary disorder and ALDH2 functions primarily in the liver, ALDH2 deficiency is an ideal target for the application of adeno-associated virus-mediated liver-directed gene therapy to prevent cancer.

The Potential Role of Mitochondrial Acetaldehyde Dehydrogenase 2 in Urological Cancers From the Perspective of Ferroptosis and Cellular Senescence

Overproduction of reactive oxygen species (ROS) and superlative lipid peroxidation promote tumorigenesis, and mitochondrial aldehyde dehydrogenase 2 (ALDH2) is associated with the detoxification of ROS-mediated lipid peroxidation-generated reactive aldehydes such as 4-hydroxy-2-nonenal (4-HNE), malondialdehyde, and acrolein due to tobacco smoking. ALDH2 has been demonstrated to be highly associated with the prognosis and chemoradiotherapy sensitivity of many types of cancer, including leukemia, lung cancer, head and neck cancer, esophageal cancer, hepatocellular cancer, pancreatic cancer, and ovarian cancer. In this study, we explored the possible relationship between ALDH2 and urological cancers from the aspects of ferroptosis, epigenetic alterations, proteostasis, mitochondrial dysfunction, and cellular senescence.

Association of ADH1B Arg47His polymorphism with the risk of cancer: a meta-analysis

Alcohol consumption has been established to be a major factor in the development and progress of cancer. Genetic polymorphisms of alcohol-metabolism genes result in differences between individuals in exposure to acetaldehyde, leading to possible carcinogenic effects. Arg47His (rs1229984 G > A) in ADH1B have been frequently studied for its potential effect on carcinogenesis. However, the findings are as yet inconclusive. To gain a more precise estimate of this potential association, we conducted a meta-analysis including 66 studies from 64 articles with 31999 cases and 50964 controls. The pooled results indicated that ADH1B Arg47His polymorphism is significantly associated with the decreased risk of overall cancer (homozygous model, odds ratio (OR) = 0.62, 95% confidence interval (CI) = 0.49–0.77; heterozygous model, OR = 0.71, 95% CI = 0.60–0.84; recessive model, OR = 0.83, 95% CI = 0.76–0.91; dominant model, OR = 0.62, 95% CI = 0.53–0.72; and allele comparison, OR = 0.82, 95% CI = 0.75–0.89). Stratified analysis by cancer type and ethnicity showed that a decreased risk was associated with esophageal cancer and head and neck cancer amongst Asians. In conclusion, our meta-analysis suggested that ADH1B Arg47His polymorphism was significantly associated with decreased overall cancer risk. These findings need further validation in large multicenter investigations.

Effect of ALDH2 polymorphism on cancer risk in Asians: A meta-analysis

Numerous studies have investigated the association between ALDH2 gene rs671G>A polymorphism and various cancer type in Asians. However, the results remain inconclusive.We conducted a comprehensive meta-analysis including 63 articles with 66 studies containing 25,682 cases and 47,455 controls retrieved by searching PubMed and Embase electronic databases up to March 5, 2018.Pooled results indicated that ALDH2 gene rs671 polymorphism was significantly associated with the overall cancer risk in Asians (homozygous model: odds ratio [OR] = 0.85, 95% confidence interval [CI] = 0.72-0.99, P = .042; heterozygous model: OR = 1.32, 95% CI = 1.14-1.52, P  < .001; recessive model: OR = 0.73, 95% CI = 0.60-0.88, P = .001; dominant model: OR = 1.32, 95% CI = 1.16-1.51, P < .001; and allele comparison model: OR = 1.11, 95% CI = 1.03-1.19, P = .004), especially in esophageal cancer and among the Chinese and the Japanese.Our results suggest that ALDH2 rs671 polymorphism is associated with the overall cancer risk in Asians. Well-designed prospective studies with more information about gene-environment interaction, such as drinking, should be conducted to validate our findings.

ADH1B, ALDH2, GSTM1 and GSTT1 Gene Polymorphic Frequencies among Alcoholics and Controls in the Arcadian Population of Central India

Background: Epidemiological research has highlighted the global burden of primary liver cancer cases due to alcohol consumption, even in a low consumption country like India. Alcohol detoxification is governed by ADH1B, ALDH2, GSTM1 and GSTT1 genes that encode functional enzymes which are coordinated with each other to remove highly toxic metabolites i.e. acetaldehyde as well as reactive oxygen species generated through detoxification processes. Some communities in the population appears to be at greater risk for development of the liver cancer due to genetic predispositions. Methods: The aim of this study was to screen the arcadian population of central India in order to investigate and compare the genotype distribution and allele frequencies of alcohol metabolizing genes (ADH1B, ALDH2, GSTM1 and GSTT1) in both alcoholic (N=121) and control (N=145) healthy subjects. The gene polymorphism analysis was conducted using PCR and RFLP methods. Results: The allele frequency of ALDH2 *1 was 0.79 and of ALDH2*2 was 0.21 (OR:1.12; CI (95%): 0.74-1.71). The null allele frequency for GSTM1 was 0.28 (OR:0.85; CI (95%): 0.50-1.46) and for GSTT1 was 0.20 (OR:1.93; CI (95%): 1.05-3.55). No gene polymorphism for ADH1B was not observed. The total prevalence of polymorphisms was 3.38% for ALDH2, GSTM1 and GSTT1. Conclusion: The results of this study suggested that individuals of the Central India population under study are at risk for liver disorders due to ALDH2, GSTM1 and GSTT1 gene polymorphisms. This results may have significance for prevention of alcohol dependence, alcoholic liver disorders and the likelihood of liver cancer.

Could ALDH2*2 be the reason for low incidence and mortality of ovarian cancer for East Asia women?

It is curious that East Asian women have a low incidence and mortality of ovarian cancer in various epidemiological studies. Although different explanations were given, they appear unsubstantial. We notice that East Asian population usually are inactive aldehyde dehydrogenase 2 mutation (ALDH2 ^* 2) carriers, and ALDH plays an important role in the resistance of ovarian cancer to chemotherapeutics, especially in ovarian cancer stem cells. Therefore, we hypothesize whether ALDH2 mutation is the major reason for low incidence and mortality of ovarian cancer in East Asian women, and use the evidence from literature, transcriptomic data with average 5-year overall survival to confirm our hypothesis.

Correlations of ALDH2 rs671 and C12orf30 rs4767364 polymorphisms with increased risk and prognosis of esophageal squamous cell carcinoma in the Kazak and Han populations in Xinjiang province

OBJECTIVE

Genetic polymorphisms in ALDH2 and C12orf30 genes have been reported to increase the risk of developing esophageal squamous cell carcinoma (ESCC). This study aims to investigate the relationship between ALDH2 rs671 and c12orf30 rs4767364 polymorphisms in the chromosome 12q24 gene, and risk and prognosis of individuals developing esophageal cancer (ESCC) in Xinjiang Kazak and Han populations.

METHODS

The case group consisted of 127 ESCC patients. The control group comprised of 125 healthy individuals. Subjects that were recruited all come from Xinjiang province. TaqMan and the Hardy-Weinberg equilibrium were the main methods employed to detect and examine the distribution of genotypes of rs671 and rs4767364.

RESULTS

The genotype frequencies of ALDH2 rs671 between the Kazak case and control groups were statistically significant, while no significant difference was observed between the Han case and control groups (P>.05). Moreover, ALDH2 rs671 (G>A) was associated with poor prognosis of ESCC in both Kazak and Han populations, and c12orf30 rs4767364 (A>G) was also connected with poor prognosis of ESCC in Kazak but not in Han population.

CONCLUSION

In the chromosome 12q24 locus, ALDH2 rs671 (G>A) is related to the susceptibility to ESCC in Kazak populations, and it is also associated with poor prognosis of EC in Kazak and Han populations. Furthermore, c12orf30 rs4767364 (A>G) may be correlated with poor ESCC prognosis in Kazak population.

Association between ALDH2 Glu487Lys polymorphism and the risk of esophageal cancer

OBJECTIVE

A meta-analysis was carried out to further evaluate the relationship between ALDH2 Glu487Lys polymorphism and esophageal cancer risk.

METHODS

A total number of 15 studies that included 3812 cases and 7376 controls were identified for our meta-analysis.

RESULTS

Our findings indicated that individuals with the combination of Glu/Lys and Lys/Lys genotype had an increased risk of getting esophageal cancer (GA + AA vs. GG: odds ratio [OR] 1.36, 95% confidence interval [CI] 0.93-2.00, P = 0.113) with a shift pattern. Although Lys/Lys genotype carriers showed areduced esophageal cancer risk (AA vs. GA + GG: OR 0.41, 95% CI 0.23-0.72, P = 0.002). Similarly, a negative association was observed under homozygote comparison (AA vs. GG: OR 0.49, 95% CI 0.29-0.85, P = 0.011). In the China subgroup analysis, the similar results were found.

CONCLUSIONS

This meta-analysis concluded that there was a strong association between ALDH2 Glu487Lys polymorphism and the risk of esophageal cancer. It further confirmed that ALDH2 Glu487Lys polymorphism was a high-risk factor for esophageal cancer.

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.

Mitochondrial Dysfunction in Cancer and Neurodegenerative Diseases: Spotlight on Fatty Acid Oxidation and Lipoperoxidation Products

In several human diseases, such as cancer and neurodegenerative diseases, the levels of reactive oxygen species (ROS), produced mainly by mitochondrial oxidative phosphorylation, is increased. In cancer cells, the increase of ROS production has been associated with mtDNA mutations that, in turn, seem to be functional in the alterations of the bioenergetics and the biosynthetic state of cancer cells. Moreover, ROS overproduction can enhance the peroxidation of fatty acids in mitochondrial membranes. In particular, the peroxidation of mitochondrial phospholipid cardiolipin leads to the formation of reactive aldehydes, such as 4-hydroxynonenal (HNE) and malondialdehyde (MDA), which are able to react with proteins and DNA. Covalent modifications of mitochondrial proteins by the products of lipid peroxidation (LPO) in the course of oxidative cell stress are involved in the mitochondrial dysfunctions observed in cancer and neurodegenerative diseases. Such modifications appear to affect negatively mitochondrial integrity and function, in particular energy metabolism, adenosine triphosphate (ATP) production, antioxidant defenses and stress responses. In neurodegenerative diseases, indirect confirmation for the pathogenetic relevance of LPO-dependent modifications of mitochondrial proteins comes from the disease phenotypes associated with their genetic alterations.

Clinical significance of ALDH2 rs671 polymorphism in esophageal cancer: evidence from 31 case-control studies

Background

Aldehyde dehydrogenase 2 (ALDH2), a critical enzyme for the detoxification of alcohol, is associated with many types of cancers. To verify the relationship of ALDH2 rs671 G>A polymorphism and esophageal cancer (EC), we performed a meta-analysis of a total of 31 published data including 8,510 patients and 16,197 controls.

Methods

The pooled odds ratio (OR) and the 95% confidence interval (CI) were calculated using a fixed or random-effects model. Heterogeneity (P_H), publication bias, and sensitivity analysis were also determined.

Results

Although a protective effort was found in the rs671 homozygote comparison (AA/GG: OR=0.69; 95% CI=0.48–0.98), the heterozygote comparison was apparently associated with the risk of EC, particularly in the Chinese population (AG/GG: OR=1.39; 95% CI=1.03–1.87). Alcohol consumption remarkably increased this risk, especially in the AG genotype. Drinking men with the AG genotype appeared to show a higher risk (AG/GG: OR=4.39; 95% CI=1.24–6.55) than drinking women.

Conclusion

The present meta-analysis provided advanced information regarding the association of the ALDH2 A>G polymorphism and EC. Taken together, insights from this study suggested an enhanced effect on the development of EC through a genetic–environmental interaction.

Association between Glu504Lys polymorphism of ALDH2 gene and cancer risk: a meta-analysis

Background

The association of the aldehyde dehydrogenases-2 (ALDH2) Glu504Lys polymorphism (also named Glu487Lys, or rs671) and cancers has been investigated. This meta-analysis aims to comprehensively assess the influence of this polymorphism on the overall cancer risk.

Methods

Eligible publications were retrieved according to inclusion/exclusion criteria and the data were analyzed using the Review Manager software (V5.2).

Results

A meta-analysis based on 51 case-control studies consisting of 16774 cases and 32060 controls was performed to evaluate the association between the ALDH2 Glu504Lys polymorphism and cancer risk. The comparison of genotypes Lys+ (Lys/Lys and Lys/Glu) with Glu/Glu yielded a significant 20% increased cancer risk (OR = 1.20, 95%CI: 1.03–1.39, P = 0.02, I² = 92%). Subgroup analysis by cancer type indicated a significantly increased UADT cancer risk (OR = 1.39, 95%CI: 1.11–1.73, P = 0.004, I² = 94%) in individuals with the Lys+ genotypes. Subgroup analysis by country indicated that individuals from Japan with the Lys+ genotypes had a significant 38% increased cancer risk (OR = 1.38, 95%CI: 1.12–1.71, P = 0.003, I² = 93%).

Conclusions

Our results indicated that the ALDH2 Glu504Lys polymorphism is a susceptible loci associated with overall cancers, especially esophageal cancer and among Japanese population.

Dietary habits and esophageal cancer

Cancer of the esophagus is an underestimated, poorly understood, and changing disease. Its overall 5-year survival is less than 20%, even in the United States, which is largely a function of a delay in diagnosis until its more advanced stages. Additionally, the epidemiologic complexities of esophageal cancer are vast, rendering screening and prevention limited at best. First, the prevalence of esophageal cancer is unevenly distributed throughout the world. Second, the two histological forms (squamous cell and adenocarcinoma) vary in terms of their geographic prevalence and associated risk factors. Third, some populations appear at particular risk for esophageal cancer. And fourth, the incidence of esophageal cancer is in continuous flux among groups. Despite the varied prevalence and risks among populations, some factors have emerged as consistent associations while others are only now becoming more fully recognized. The most prominent, scientifically supported, and long-regarded risk factors for esophageal cancer are tobacco, alcohol, and reflux esophagitis. Inasmuch as the above are regarded as important risk factors for esophageal cancer, they are not the sole contributors. Dietary habits, nutrition, local customs, and the environment may be contributory. Along these lines, vitamins, minerals, fruits, vegetables, meats, fats, salted foods, nitrogen compounds, carcinogens, mycotoxins, and even the temperature of what we consume are increasingly regarded as potential etiologies for this deadly although potentially preventable disease. The goal of this review is to shed light on the less known role of nutrition and dietary habits in esophageal cancer.

Role of lipid peroxidation derived 4-hydroxynonenal (4-HNE) in cancer: focusing on mitochondria

Oxidative stress-induced lipid peroxidation has been associated with human physiology and diseases including cancer. Overwhelming data suggest that reactive lipid mediators generated from this process, such as 4-hydroxynonenal (4-HNE), are biomarkers for oxidative stress and important players for mediating a number of signaling pathways. The biological effects of 4-HNE are primarily due to covalent modification of important biomolecules including proteins, DNA, and phospholipids containing amino group. In this review, we summarize recent progress on the role of 4-HNE in pathogenesis of cancer and focus on the involvement of mitochondria: generation of 4-HNE from oxidation of mitochondria-specific phospholipid cardiolipin; covalent modification of mitochondrial proteins, lipids, and DNA; potential therapeutic strategies for targeting mitochondrial ROS generation, lipid peroxidation, and 4-HNE.

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.

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.

Genetic variants in nicotine addiction and alcohol metabolism genes, oral cancer risk and the propensity to smoke and drink alcohol: a replication study in India

BACKGROUND

Genetic variants in nicotinic acetylcholine receptor and alcohol metabolism genes have been associated with propensity to smoke tobacco and drink alcohol, respectively, and also implicated in genetic susceptibility to head and neck cancer. In addition to smoking and alcohol, tobacco chewing is an important oral cancer risk factor in India. It is not known if these genetic variants influence propensity or oral cancer susceptibility in the context of this distinct etiology.

METHODS

We examined 639 oral and pharyngeal cancer cases and 791 controls from two case-control studies conducted in India. We investigated six variants known to influence nicotine addiction or alcohol metabolism, including rs16969968 (CHRNA5), rs578776 (CHRNA3), rs1229984 (ADH1B), rs698 (ADH1C), rs1573496 (ADH7), and rs4767364 (ALDH2).

RESULTS

The CHRN variants were associated with the number of chewing events per day, including in those who chewed tobacco but never smoked (P =  0.003, P =  0.01 for rs16969968 and rs578776 respectively). Presence of the variant allele contributed to approximately 13% difference in chewing frequency compared to non-carriers. While no association was observed between rs16969968 and oral cancer risk (OR =  1.01, 95% CI =  0.83- 1.22), rs578776 was modestly associated with a 16% decreased risk of oral cancer (OR =  0.84, 95% CI =  0.72- 0.98). There was little evidence for association between polymorphisms in genes encoding alcohol metabolism and oral cancer in this population.

CONCLUSION

The association between rs16969968 and number of chewing events implies that the effect on smoking propensity conferred by this gene variant extends to the use of smokeless tobacco.

Single nucleotide polymorphisms of ADH1B, ADH1C and ALDH2 genes and esophageal cancer: a population-based case-control study in China

Alcohol drinking is a major risk factor for esophageal cancer (EC) and the metabolism of ethanol has been suggested to play an important role in esophageal carcinogenesis. Epidemiologic studies, including genomewide association studies (GWAS), have identified single nucleotide polymorphisms (SNPs) in alcohol dehydrogenases (ADHs) and aldehyde dehydrogenases (ALDHs) to be associated with EC. Using a population-based case-control study with 858 EC cases and 1,081 controls conducted in Jiangsu Province, China, we aimed to provide further information on the association of ADH1B (rs1229984), ADH1C (rs698) and ALDH2 (rs671) polymorphisms with EC in a Chinese population. Results showed that ADH1B (rs1229984) was associated with EC with odds ratios (ORs) of 1.34 [95% confidence interval (CI): 1.08-1.66] for G-allele carriers compared to A/A homozygotes. No heterogeneity was detected on this association across different strata of alcohol drinking and tobacco smoking. Statistical interaction between ALDH2 (rs671) and alcohol drinking on EC susceptibility in both additive and multiplicative scales was observed. Compared to G/G homozygotes, A-allele carriers were positively associated with EC among moderate/heavy drinkers (OR = 1.64, 95% CI: 1.12-2.40) and inversely associated with EC among never/light drinks (OR = 0.75, 95% CI: 0.54-1.03). In addition, statistical interaction between ALDH2 and ADH1B polymorphisms on EC susceptibility among never/light drinkers was indicated. We did not observe association of ADH1C polymorphism with EC. In conclusion, our findings indicated that ADH1B (rs1229984) was associated with EC independent of alcohol drinking and tobacco smoking status and alcohol drinking interacted with ALDH2 (rs671) on EC susceptibility in this high-risk Chinese population.

Population-specific genetic associations with oesophageal squamous cell carcinoma in South Africa

Genetic variants in multiple cellular pathways have been associated with an altered risk of oesophageal cancer. In this study, eight genes previously associated with an altered risk of oesophageal squamous cell carcinoma (OSCC) in European or Asian populations were investigated in two South African populations. We genotyped 12 single-nucleotide polymorphisms and one insertion/deletion variant in 1463 individuals from the Black and Mixed Ancestry populations. No polymorphisms were associated with OSCC in the Black population. In the Mixed Ancestry population, ALDH2 +82 G > A (rs886205) was significantly associated with a reduced risk of OSCC (odds ratio = 0.70, 95% confidence interval = 0.55-0.89; P = 0.0038). Several other polymorphisms showed a suggestive association (P < 0.05), including ADH1B Arg48His (rs1229984), COX-2 -1195G > A (rs689466), CASP8 Asp302His (rs1045485) and MGMT Leu84Phe (rs12917). Haplotype analysis indicated that the FAS polymorphisms -670 A > G (rs1800682) and -1377 G > A (rs2234767) were both associated with OSCC in the Mixed Ancestry population (P = 0.006 and P = 0.004, respectively), as well as the CASP8 (-652 6Ndel:302His) haplotype (P = 0.0013). This study indicates several instances of population-specific differences in the genetic etiology of OSCC between these two South African populations and between them and other high-risk populations, which may reflect differences in their ancestry and environmental exposures.

Alcohol dehydrogenase-1B Arg47His polymorphism and upper aerodigestive tract cancer risk: a meta-analysis including 24,252 subjects

BACKGROUND

Cancers of the upper aerodigestive tract (UADT) include malignant tumors of the oral cavity, pharynx, larynx, and esophagus, account for approximately 4% of all new cancers in world. Alcohol drinking is an established risk factor for UADT cancers, and the rate of alcohol metabolism could significantly been influenced by genetic polymorphisms of alcohol dehydrogenase-1B (ADH1B) His47Arg (rs1229984). To evaluate whether combined evidence shows ADH1B His47Arg as a common genetic variant that influenced the risk of UADT cancers, we considered all available studies in a meta-analysis.

METHODS

Eighteen studies were combined representing data of 8,539 cases and 15,713 controls for meta-analysis. Stratified analyses were carried out to determine the gene-environment interaction between ADH1B His47Arg and alcohol drinking and gene-gene interaction between ADH1B His47Arg and aldehyde dehydrogenase-2 (ALDH2) Glu/Lys related to UADT cancer risk. Potential sources of heterogeneity between studies were explored; sensitivity analysis and publication bias was also evaluated.

RESULTS

The ADH1B 47Arg allele was found to be associated with increased risk of UADT cancers, the pooled odds ratios (ORs) being 1.66 (95% CI: 1.54 to 1.79) and 3.47 (95% CI: 2.76 to 4.36) for the His/Arg and Arg/Arg genotypes compared with the His/His genotype, respectively. An 18.48-fold increase in OR (95% CI: 12.95 to 26.40) for UADT cancers among alcohol drinkers with Arg/Arg genotype was found, when compared among nondrinkers with the His/His genotype. Significant interaction between carriers with ADH1B 47Arg and ALDH2 487Lys allele related to risk for UADT cancers was more evident, compared with noncarriers (OR = 10.31, 95% CI: 5.45 to 18.85).

CONCLUSIONS

ADH1B 47Arg allele is a common genetic variant that increased the risk of UADT cancers; furthermore, it modulates the susceptibility to UADT cancers coupled with alcohol drinking and interaction with the ALDH2 487Lys allele.

Multi-susceptibility genes associated with the risk of the development stages of esophageal squamous cell cancer in Feicheng County

BACKGROUND

The purpose of this study was to evaluate the association of multi-genotype polymorphisms with the stepwise progression of esophageal squamous cell cancer (ESCC) and the possibility of predicting those at higher risk.

METHODS

A total of 1,004 subjects were recruited from Feicheng County, China, between Jan. 2004 and Dec. 2007 and examined by endoscopy for esophageal lesions. These subjects included 270 patients with basal cell hyperplasia (BCH), 262 patients with esophageal squamous cell dysplasia (ESCD), 226 patients with ESCC, and 246 controls with Lugol-voiding area but diagnosed as having normal esophageal squamous epithelial cells by histopathology. The genotypes for CYP2E1 G1259C, hOGG1 C326G, MTHFR C677T, MPO G463A, and ALDH2 allele genes were identified in blood samples collected from all participants.

RESULTS

The alleles ALDH2 and MTHFR C677T were critical for determining individual susceptibility to esophageal cancer. Compared to the ALDH 1*1 genotype, the ALDH 2*2 genotype was significantly associated with increased risks of BCH, ESCD, and ESCC. However, the TT genotype of MTHFR C677T only increased the risk of ESCC. Further analysis revealed that the combination of the high-risk genotypes 2*2/1*2 of ALDH 2 and TT/TC of MTHFR C677T increased the risk of BCH by 4.0 fold, of ESCD by 3.7 fold, and ESSC by 8.72 fold. The generalized odds ratio (ORG) of the two combined genotypes was 1.83 (95%CI: 1.55-2.16), indicating a strong genetic association with the risk of carcinogenic progression in the esophagus.

CONCLUSIONS

The study demonstrated that the genotypes ALDH2*2 and MTHFR 677TT conferred elevated risk for developing esophageal carcinoma and that the two susceptibility genotypes combined to synergistically increase the risk.

Multi-susceptibility genes associated with the risk of the development stages of esophageal squamous cell cancer in Feicheng County

Background

The purpose of this study was to evaluate the association of multi-genotype polymorphisms with the stepwise progression of esophageal squamous cell cancer (ESCC) and the possibility of predicting those at higher risk.

Methods

A total of 1,004 subjects were recruited from Feicheng County, China, between Jan. 2004 and Dec. 2007 and examined by endoscopy for esophageal lesions. These subjects included 270 patients with basal cell hyperplasia (BCH), 262 patients with esophageal squamous cell dysplasia (ESCD), 226 patients with ESCC, and 246 controls with Lugol-voiding area but diagnosed as having normal esophageal squamous epithelial cells by histopathology. The genotypes for CYP2E1 G1259C, hOGG1 C326G, MTHFR C677T, MPO G463A, and ALDH2 allele genes were identified in blood samples collected from all participants.

Results

The alleles ALDH2 and MTHFR C677T were critical for determining individual susceptibility to esophageal cancer. Compared to the ALDH 1*1 genotype, the ALDH 2*2 genotype was significantly associated with increased risks of BCH, ESCD, and ESCC. However, the TT genotype of MTHFR C677T only increased the risk of ESCC. Further analysis revealed that the combination of the high-risk genotypes 2*2/1*2 of ALDH 2 and TT/TC of MTHFR C677T increased the risk of BCH by 4.0 fold, of ESCD by 3.7 fold, and ESSC by 8.72 fold. The generalized odds ratio (OR_G) of the two combined genotypes was 1.83 (95%CI: 1.55-2.16), indicating a strong genetic association with the risk of carcinogenic progression in the esophagus.

Conclusions

The study demonstrated that the genotypes ALDH2*2 and MTHFR 677TT conferred elevated risk for developing esophageal carcinoma and that the two susceptibility genotypes combined to synergistically increase the risk.

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.

Association between alcohol consumption and cancers in the Chinese population--a systematic review and meta-analysis

BACKGROUND

Alcohol consumption is increasing worldwide and is associated with numerous cancers. This systematic review examined the role of alcohol in the incidence of cancer in the Chinese population.

METHODS

Medline/PubMed, EMBASE, CNKI and VIP were searched to identify relevant studies. Cohort and case-control studies on the effect of alcohol use on cancers in Chinese were included. Study quality was evaluated using the Newcastle-Ottawa Scale. Data were independently abstracted by two reviewers. Odds ratios (OR) or relative risks (RR) were pooled using RevMan 5.0. Heterogeneity was evaluated using the Q test and I-squared statistic. P<.01 was considered statistically significant.

RESULTS

Pooled results from cohort studies indicated that alcohol consumption was not associated with gastric cancer, esophageal cancers (EC) or lung cancer. Meta-analysis of case-control studies showed that alcohol consumption was a significant risk factor for five cancers; the pooled ORs were 1.79 (99% CI, 1.47-2.17) EC, 1.40 (99% CI, 1.19-1.64) gastric cancer, 1.56 (99% CI, 1.16-2.09) hepatocellular carcinoma, 1.21 (99% CI, 1.00-1.46) nasopharyngeal cancer and 1.71 (99% CI, 1.20-2.44) oral cancer. Pooled ORs of the case-control studies showed that alcohol consumption was protective for female breast cancer and gallbladder cancer: OR 0.76 (99% CI, 0.60-0.97) and 0.70 (99% CI, 0.49-1.00) respectively. There was no significant correlation between alcohol consumption and lung cancer, colorectal cancer, pancreatic cancer, cancer of the ampulla of Vater, prostate cancer or extrahepatic cholangiocarcinoma. Combined results of case-control and cohort studies showed that alcohol consumption was associated with 1.78- and 1.40-fold higher risks of EC and gastric cancer but was not significantly associated with lung cancer.

CONCLUSIONS

Health programs focused on limiting alcohol intake may be important for cancer control in China. Further studies are needed to examine the interaction between alcohol consumption and other risk factors for cancers in Chinese and other populations.

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 of mitochondrial haplogroup D and risk of esophageal cancer in Taihang Mountain and Chaoshan areas in China

Both the Taihang Mountain area in north-central China and Chaoshan area in the southeastern littoral of China are areas with high risk of esophageal cancer (EC). Our previous study confirmed that populations from the two areas might share similar matrilineal backgrounds and found that mitochondrial DNA (mtDNA) haplogroup D, especially subhaplogroups D4a and D5a, might be genetic background markers of EC in Chaoshan area. Here, to further determine whether D4a, D5a, and D might be susceptibility markers for EC in the two high-risk areas, we performed a case-control study with larger samples and analyzed the distributions of these three haplogroups in subjects (controls [n = 898] and patients [n = 768]) from the two areas. D4a haplogroup was significantly associated with increased risk of EC in Taihang Mountain subjects, especially women. D5 haplogroup was associated with EC at the general population level in the Taihang Mountain area and in subjects ≤ 60 years, especially women ≤ 60 years, in the Chaoshan area. D haplogroup was associated with EC only in subjects ≤ 60 years, especially men ≤ 60 years, in the Chaoshan area. D4a and D5 showing positive association with EC in the Taihang Mountain area became the predominant subhaplogroups of D in Chaoshan controls. In conclusion, D, D4a, and D5 haplogroups might be susceptibility markers for EC in the two high-risk areas in China, particularly D4a and D5 for the Taihang Mountain area and D and D5 for the Chaoshan area.

Meta-analysis of ADH1B and ALDH2 polymorphisms and esophageal cancer risk in China

AIM: To evaluate whether alcohol dehydrogenase-1B (ADH1B) His47Arg and aldehyde dehydrogenase-2 (ALDH2) Glu487Lys polymorphism is involved in the esophageal squamous cell carcinoma (ESCC) risk in Chinese Han population.

METHODS: Seven studies of ADH1B and ALDH2 genotypes in Chinese Han population in 1450 cases and 2459 controls were included for meta-analysis. Stratified analyses were carried out to determine the gene-alcohol and gene-gene interaction with ESCC risk. Potential sources of heterogeneity between studies were explored, and publication bias was also evaluated.

RESULTS: Individuals with ADH1B arginine (Arg)/Arg genotype showed 3.95-fold increased ESCC risk in the recessive genetic model [Arg/Arg vs Arg/histidine (His) + His/His: odds ratio (OR) = 3.95, 95% confidence interval (CI): 2.76-5.67]. Significant association was found in the dominant model for ALDH2 lysine (Lys) allele [glutamate (Glu)/Lys + Lys/Lys vs Glu/Glu: OR = 2.00, 95% CI: 1.54-2.61]. Compared with the non-alcoholics, Arg/Arg (OR = 25.20, 95% CI: 10.87-53.44) and Glu/Lys + Lys/Lys (OR = 21.47, 95% CI: 6.44-71.59) were found to interact with alcohol drinking to increase the ESCC risk. ADH1B Arg+ and ALDH2 Lys+ had a higher risk for ESCC (OR = 7.09, 95% CI: 2.16-23.33).

CONCLUSION: The genetic variations of ADH1B His47Arg and ALDH2 Glu487Lys are susceptible loci for ESCC in Chinese Han population and interact substantially with alcohol consumption. The individuals carrying both risky genotypes have a higher baseline risk of ESCC.

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.

ADH1B Arg47His polymorphism is associated with esophageal cancer risk in high-incidence Asian population: evidence from a meta-analysis

BACKGROUND AND OBJECTIVES

Incidence of Esophageal squamous cell carcinoma (ESCC) is prevalent in Asian populations, especially in the ones from the "Asian esophageal cancer belt" along the Silk Road and the ones from East Asia (including Japan). Silk Road and Eastern Asia population genetics are relevant to the ancient population migration from central China. The Arg47His (rs1229984) polymorphism of ADH1B is the highest in East Asians, and ancient migrations along the Silk Road were thought to be contributive to a frequent ADH1B*47His allele in Central Asians. This polymorphism was identified as responsible for susceptibility in the first large-scale genome-wide association study of ESCC and that's explained by its modulation of alcohol oxidization capability. To investigate the association of ADH1B Arg47His with ESCC in Asian populations under a common ancestry scenario of the susceptibility loci, we combined all available studies into a meta-analysis.

METHODS

A dataset composed of 4,220 cases and 8,946 controls from twelve studies of Asian populations was analyzed for ADH1B Arg47His association with ESCC and its interactions with alcohol drinking and ALDH2 Glu504Lys. Heterogeneity among studies and their publication bias were also tested.

RESULTS

The ADH1B*47Arg allele was found to be associated to increased risk of ESCC, with the odds ratios (OR) being 1.62 (95% CI: 1.49-1.76) and 3.86 (2.96-5.03) for the His/Arg and the Arg/Arg genotypes, respectively. When compared with the His/His genotype of non-drinkers, the Arg/Arg genotype can interact with alcohol drinking and greatly increase the risk of ESCC (OR = 20.69, 95%CI: 5.09-84.13). Statistical tests also showed gene-gene interaction of ADH1B Arg+ with ALDH2 Lys+ can bring more risk to ESCC (OR  = 13.46, 95% CI: 2.32-78.07).

CONCLUSION

Revealed by this meta-analysis, ADH1B*47Arg as a common ancestral allele can significantly increase the risk of ESCC in Asians, especially when coupled with alcohol drinking or the ALDH2*504Lys allele.

Relationship between genetic polymorphisms of ALDH2 and ADH1B and esophageal cancer risk: A meta-analysis

AIM: To evaluate the contribution of alcohol dehydrogenase-1B (ADH1B) and aldehyde dehydrogenase-2 (ALDH2) polymorphisms to the risk of esophageal cancer.

METHODS: Nineteen articles were included by searching MEDLINE, EMBASE and the Chinese Biomedical Database, 13 on ADH1B and 18 on ALDH2. We performed a meta-analysis of case-control studies including 13 studies on ADH1B (cases/controls: 2390/7100) and 18 studies on ALDH2 (2631/6030).

RESULTS: The crude odds ratio [OR (95% confidence interval)] was 2.91 (2.04-4.14) for ADH1B*1/*1 (vs ADH1B*2/*2) and 1.32 (1.17-1.49) for ADH1B*1/*2. The crude OR for ALDH2*1/*2 (vs ALDH2*1/*1) was 2.52 (1.76-3.61). ADH1B*1/*1 increased the risk of esophageal cancer among never/rare [1.56 (0.93-2.61)], moderate [2.71 (1.37-5.35)], and heavy drinkers [3.22 (2.27-4.57)]. ADH1B*1/*2 was associated with a modest risk among moderate drinkers [1.43 (1.09-1.87)]. ALDH2*1/*2 increased the risk among never/rare [1.28 (0.91-1.80)], moderate [3.12 (1.95-5.01)], and heavy [7.12 (4.67-10.86)] drinkers, and among ex-drinkers [5.64 (1.57-20.25)]. ALDH2*2/*2 increased the risk among drinkers [4.42 (1.72-11.36)]. ADH1B*1/*1 plus ALDH2*1/*2 was associated with the highest risk for heavy drinkers [12.45 (2.9-53.46)]. The results of the meta-regression analysis showed that the effects of ADH1B*1/*1 and ALDH2*1/*2 increased with the level of alcohol consumption. ALDH2*1/*2 was associated with a high risk among Taiwan Chinese and Japanese drinkers, as opposed to a moderate risk among drinkers in high-incidence regions of Mainland China. ADH1B*1/*1 in heavy drinkers and ALDH2*1/*2 in moderate-to-heavy drinkers was associated with similarly high risk among both men and women.

CONCLUSION: ADH1B/ALDH2 genotypes affect the risk of esophageal cancer, and the risk is modified by alcohol consumption, ethnicity, and gender.

Association of genetic polymorphisms of aldehyde dehydrogenase-2 with esophageal squamous cell dysplasia

AIM: To demonstrate the possible associations between genetic polymorphisms of aldehyde dehydrogenase-2 (ALDH2) and esophageal squamous cell dysplasia (ESCD).

METHODS: All participants came from an area of high incidence of esophageal cancer and underwent an endoscopic staining examination; biopsies were taken from a non-staining area of the mucosa and diagnosed by histopathology. Based on the examinations, the subjects were divided into the control group with normal esophageal squamous epithelial cells and the ESCD group. ALDH2 genotypes of 396 cases were determined including 184 ESCD cases and 212 controls. The odds ratio (OR) and 95% confidence intervals (95% CI) were calculated by binary logistic regression models.

RESULTS: The distribution of ALDH2 genotypes showed significant differences between the two groups. The adjustment factors were gender and age in the logistic regression models. Compared with 2*2/2*2 genotype, 2*1/2*1 genotype was found to be a risk factor for ESCD, and the OR (95% CI) was 4.50 (2.21-9.19). There were significant correlations between ALDH2 genotypes and alcohol drinking/smoking/history of esophageal cancer.

CONCLUSION: The ALDH2 polymorphism is significantly associated with ESCD.