Gene Summary

Gene:ALDH2; aldehyde dehydrogenase 2 family member
Summary:This protein belongs to the aldehyde dehydrogenase family of proteins. Aldehyde dehydrogenase is the second enzyme of the major oxidative pathway of alcohol metabolism. Two major liver isoforms of aldehyde dehydrogenase, cytosolic and mitochondrial, can be distinguished by their electrophoretic mobilities, kinetic properties, and subcellular localizations. Most Caucasians have two major isozymes, while approximately 50% of East Asians have the cytosolic isozyme but not the mitochondrial isozyme. A remarkably higher frequency of acute alcohol intoxication among East Asians than among Caucasians could be related to the absence of a catalytically active form of the mitochondrial isozyme. The increased exposure to acetaldehyde in individuals with the catalytically inactive form may also confer greater susceptibility to many types of cancer. This gene encodes a mitochondrial isoform, which has a low Km for acetaldehydes, and is localized in mitochondrial matrix. Alternative splicing results in multiple transcript variants encoding distinct isoforms.[provided by RefSeq, Nov 2016]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:aldehyde dehydrogenase, mitochondrial
Source:NCBIAccessed: 31 August, 2019


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 31 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: ALDH2 (cancer-related)

Zuo W, Zhan Z, Ma L, et al.
Effect of ALDH2 polymorphism on cancer risk in Asians: A meta-analysis.
Medicine (Baltimore). 2019; 98(13):e14855 [PubMed] Free Access to Full Article Related Publications
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.

Zografos E, Anagnostopoulos AK, Papadopoulou A, et al.
Serum Proteomic Signatures of Male Breast Cancer.
Cancer Genomics Proteomics. 2019 Mar-Apr; 16(2):129-137 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: To date, the elucidation of serum protein alterations in male breast cancer (MBC) has not been extensively studied, due to the rarity of the disease.
MATERIALS AND METHODS: In the present work, two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) were employed to detect differences in serum protein expression between patients with MBC and healthy controls.
RESULTS: A panel of differentially expressed serum proteins was identified, including proteins involved in the regulation of the cell cycle [e.g. cell division cycle 7-related protein kinase (CDC7)], in mitochondrial function [e.g. mitochondrial aldehyde dehydrogenase (ALDH2) and dimethyladenosine transferase 1 (TFB1M)], in lipid metabolism and transport [e.g. apolipoprotein A-I (APOA1) and E (APOE)], in apoptosis and immune response [e.g. CD5 antigen-like (CD5L), clusterin (CLUS) and C-C motif chemokine 14 (CCL14)], in transcription (e.g. protein SSX3 and signal transducer and activator of transcription 3 (STAT3)], in invasion and metastasis (e.g. alpha-2-HS-glycoprotein (FETUA)], in estrogen synthesis [aromatase (CYP19A1)] and other diverse biological roles [e.g. actin-related protein 2/3 complex subunit 4 (ARPC4), dual specificity mitogen-activated protein kinase kinase 4 (MP2K4), ectoderm-neural cortex protein 1 (ENC1), and matrix metalloproteinase-27 (MMP27)].
CONCLUSION: These findings provide valuable insight into the distinct clinicopathological features of MBC and indicate that select serum proteomic markers may help improve MBC management.

Chen X, Legrand AJ, Cunniffe S, et al.
Interplay between base excision repair protein XRCC1 and ALDH2 predicts overall survival in lung and liver cancer patients.
Cell Oncol (Dordr). 2018; 41(5):527-539 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: To deliver efficacious personalised cancer treatment, it is essential to characterise the cellular metabolism as well as the genetic stability of individual tumours. In this study, we describe a new axis between DNA repair and detoxification of aldehyde derivatives with important implications for patient prognosis and treatment.
METHODS: Western blot and qPCR analyses were performed in relevant non-transformed and cancer cell lines from lung and liver tissue origin in combination with bioinformatics data mining of The Cancer Genome Atlas database from lung and hepatocellular cancer patients.
RESULTS: Using both biochemical and bioinformatics approaches, we revealed an association between the levels of expression of the aldehyde detoxifying enzyme aldehyde dehydrogenase 2 (ALDH2) and the key DNA base excision repair protein XRCC1. Across cancer types, we found that if one of the corresponding genes exhibits a low expression level, the level of the other gene is increased. Surprisingly, we found that low ALDH2 expression levels associated with high XRCC1 expression levels are indicative for a poor overall survival, particularly in lung and liver cancer patients. In addition, we found that Mithramycin A, a XRCC1 expression inhibitor, efficiently kills cancer cells expressing low levels of ALDH2.
CONCLUSIONS: Our data suggest that lung and liver cancers require efficient single-strand break repair for their growth in order to benefit from a low aldehyde detoxification metabolism. We also propose that the ratio of XRCC1 and ALDH2 levels may serve as a useful prognostic tool in these cancer types.

Hsiao JR, Chang CC, Lee WT, et al.
The interplay between oral microbiome, lifestyle factors and genetic polymorphisms in the risk of oral squamous cell carcinoma.
Carcinogenesis. 2018; 39(6):778-787 [PubMed] Related Publications
Poor oral hygiene may lead to overgrowth of pathogenic oral bacteria, which may induce chronic inflammation to promote the oncogenesis of oral squamous cell carcinoma (OSCC). This study investigated the association between oral bacterial profile and OSCC risk in a case-control study of 138 OSCC cases and 151 controls (88 cases and 90 controls for the discovery group and 50 cases and 61 controls for the validation group). Oral bacterial profiles were characterized by targeted sequencing of the 16S rRNA gene. Three species of periodontopathogenic bacteria, Prevotella tannerae, Fusobacterium nucleatum, and Prevotella intermedia, were associated with an increased OSCC risk. This association was modified by the genetic polymorphisms of TLR2 and TLR4. Use of alcohol, betel quids and cigarettes and poor oral hygiene were associated with a higher percentage of oral periodontopathogenic bacteria. The association between alcohol and periodontopathogenic bacteria was modified by the genetic polymorphism of ALDH2, with a stronger positive association observed among the ALDH2-deficient individuals. The percentage of periodontopathogenic bacteria was positively correlated with the level of salivary IL1β, an inflammatory cytokine. Overall, our results showed a positive association between periodontopathogenic bacteria and OSCC risk and this relationship may be influenced by lifestyle and genetic factors. Our results provided further biological support for the established association between poor oral hygiene and OSCC risk. This suggested that improving oral hygiene may reduce OSCC risk and should be part of a public health campaign to prevent the occurrence of OSCC.

Shih S, Huang YT, Yang HI
A multiple mediator analysis approach to quantify the effects of the ADH1B and ALDH2 genes on hepatocellular carcinoma risk.
Genet Epidemiol. 2018; 42(4):394-404 [PubMed] Free Access to Full Article Related Publications
Previous work suggested a genetic component affecting the risk of hepatocellular carcinoma (HCC) and mediation analyses have elucidated potential indirect pathways of these genetic effects. Specifically, the effects of alcohol dehydrogenase (ADH1B) and aldehyde dehydrogenase (ALDH2) genes on HCC risk vary based on alcohol consumption habits. However, alcohol consumption may not be the only mediator in the identified pathway: factors related to alcohol consumption may contribute to the same indirect pathway. Thus, we developed a multimediator model to quantify the genetic effects on HCC risk through sequential dichotomous mediators under the counterfactual framework. Our method provided a closed form formula for the mediation effects through different indirect paths, which requires no assumption for the rarity of outcome. In simulation studies of a finite sample, we presented the utility of the method with the variance of the effects estimated using the delta method and bootstrapping. We applied our method to data from participants in Taiwan (580 cases and 3,207 controls) and quantified the mediation effects of single nucleotide polymorphisms (SNPs) in the ADH1B and ALDH2 genes on HCC through alcohol consumption (yes/no) and high alanine transaminase (ALT) levels (greater than or equal to 45 U/L or below 45 U/L). Assuming a dominant risk model, we identified that the SNPs' effects through alcohol consumption is more significant than through ALT levels on HCC risk. This new method provides insight to the magnitude of various casual mechanisms as a closed form solution and can be readily applied in other genomic studies.

Mansoori AA, Jain SK
ADH1B, ALDH2, GSTM1 and GSTT1 Gene Polymorphic Frequencies among Alcoholics and Controls in the Arcadian Population of Central India
Asian Pac J Cancer Prev. 2018; 19(3):725-731 [PubMed] Free Access to Full Article Related Publications
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.

Li P, You S, Nguyen C, et al.
Genes involved in prostate cancer progression determine MRI visibility.
Theranostics. 2018; 8(7):1752-1765 [PubMed] Free Access to Full Article Related Publications
MRI is used to image prostate cancer and target tumors for biopsy or therapeutic ablation. The objective was to understand the biology of tumors not visible on MRI that may go undiagnosed and untreated.

Zahra A, Rubab I, Malik S, et al.
Meta-Analysis of miRNAs and Their Involvement as Biomarkers in Oral Cancers.
Biomed Res Int. 2018; 2018:8439820 [PubMed] Free Access to Full Article Related Publications
Oral Squamous Cell Carcinoma (OSCC) is one of the most common cancers worldwide. Recent studies have highlighted the role of miRNA in disease pathology, indicating its potential use as an early diagnostic marker. Dysregulated expression of miRNAs is known to affect cell growth, and these may function as tumor suppressors or oncogenes in various cancers. The main objective of this study was to characterize the extracellular miRNAs involved in

Torrebadell M, Díaz-Beyá M, Kalko SG, et al.
A 4-gene expression prognostic signature might guide post-remission therapy in patients with intermediate-risk cytogenetic acute myeloid leukemia.
Leuk Lymphoma. 2018; 59(10):2394-2404 [PubMed] Related Publications
In intermediate-risk cytogenetic acute myeloid leukemia (IRC-AML) patients, novel biomarkers to guide post-remission therapy are needed. We analyzed with high-density arrays 40 IRC-AML patients who received a non-allogeneic hematopoietic stem-cell transplantation-based post-remission therapy, and identified a signature that correlated with early relapse. Subsequently, we analyzed selected 187 genes in 49 additional IRC-AML patients by RT-PCR. BAALC, MN1, SPARC and HOPX overexpression correlated to refractoriness. BAALC or ALDH2 overexpression correlated to shorter overall survival (OS) (5-year OS: 33 ± 8.6% vs. 73.7 ± 10.1%, p = .006; 32 ± 9.3% vs. 66.4 ± 9.7%, p = .016), whereas GPR44 or TP53INP1 overexpression correlated to longer survival (5-year OS: 66.7 ± 10.3% vs. 35.4 ± 9.1%, p = .04; 58.3 ± 8.2% vs. 23.1 ± 11.7%, p = .029). A risk-score combining these four genes expression distinguished low-risk and high-risk patients (5-year OS: 79 ± 9% vs. 30 ± 8%, respectively; p = .001) in our cohort and in an independent set of patients from a public repository. Our 4-gene signature may add prognostic information and guide post-remission treatment in IRC-AML patients.

Avinçsal MO, Shinomiya H, Teshima M, et al.
Impact of alcohol dehydrogenase-aldehyde dehydrogenase polymorphism on clinical outcome in patients with hypopharyngeal cancer.
Head Neck. 2018; 40(4):770-777 [PubMed] Related Publications
BACKGROUND: The purpose of this research was to investigate the association between alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2) polymorphisms and hypopharyngeal squamous cell carcinoma (SCC) survival.
METHODS: We genotyped ADH1B (rs1229984) and ALDH2 (rs671) single nucleotide polymorphisms (SNPs) in 85 Japanese male patients with hypopharyngeal SCC. The independent prognostic values of ADH1B-ALDH2 genotypes were analyzed by univariate and multivariate proportional hazard Cox regression, taking well-known clinical risk factors into account.
RESULTS: Heavy drinkers with ALDH2*2 allele resulted in significantly worse overall survival (OS; P = .028) and disease-free survival (DFS; P = .029) compared with other patients. Heavy drinkers with ALDH2*2 allele remained statistically significant in multivariate analysis for OS and DFS, indicating independent poor prognostic factor (hazard ratio [HR] 2.251; 95% confidence interval [CI] 1.018-4.975 and HR 2.261; 95% CI 1.021-5.006, respectively).
CONCLUSION: We conclude that heavy drinkers with the ALDH2*2 allele are associated with poor outcome in hypopharyngeal SCC.

Cui Q, Peng L, Wei L, et al.
Genetic variant repressing ADH1A expression confers susceptibility to esophageal squamous-cell carcinoma.
Cancer Lett. 2018; 421:43-50 [PubMed] Related Publications
Genome-wide association studies (GWAS) have discovered numerous genetic susceptibility loci including a cluster of alcohol dehydrogenase (ADH) gene family for esophageal squamous-cell carcinoma (ESCC). However, the underlying mechanism has not fully been elucidated. In this study, we integrated the GWAS data, gene-drinking interaction, expression quantitative trait locus (eQTL) analysis and biochemical experiments to clarify the specific mechanism of the polymorphisms in ADH loci. By imputation and eQTL analysis, we identified rs1154402C>G in intron 1 of ADH5 substantially associated with the expression levels of ADH1A. Association analysis showed that the rs1154402[G] allele was significantly associated with ESCC risk in drinkers (OR = 1.44, 95% CI = 1.20-1.73; P = 7.74 × 10

Salaspuro M
Key role of local acetaldehyde in upper GI tract carcinogenesis.
Best Pract Res Clin Gastroenterol. 2017; 31(5):491-499 [PubMed] Related Publications
Ethanol is neither genotoxic nor mutagenic. Its first metabolite acetaldehyde, however, is a powerful local carcinogen. Point mutation in ALDH2 gene proves the causal relationship between acetaldehyde and upper digestive tract cancer in humans. Salivary acetaldehyde concentration and exposure time are the two major and quantifiable factors regulating the degree of local acetaldehyde exposure in the ideal target organ, oropharynx. Instant microbial acetaldehyde formation from alcohol represents >70% of total ethanol associated acetaldehyde exposure in the mouth. In the oropharynx and achlorhydric stomach acetaldehyde is not metabolized to safe products, instead in the presence of alcohol it accumulates in saliva and gastric juice in mutagenic concentrations. A common denominator in alcohol, tobacco and food associated upper digestive tract carcinogenesis is acetaldehyde. Epidemiological studies on upper GI tract cancer are biased, since they miss information on acetaldehyde exposure derived from alcohol and acetaldehyde present in 'non-alcoholic' beverages and food.

Ghosh S, Bankura B, Ghosh S, et al.
Polymorphisms in ADH1B and ALDH2 genes associated with the increased risk of gastric cancer in West Bengal, India.
BMC Cancer. 2017; 17(1):782 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Gastric cancer (GC) is one of the most frequently diagnosed digestive tract cancers and carries a high risk of mortality. Acetaldehyde (AA), a carcinogenic intermediate of ethanol metabolism contributes to the risk of GC. The accumulation of AA largely depends on the activity of the major metabolic enzymes, alcohol dehydrogenase and aldehyde dehydrogenase encoded by the ADH (ADH1 gene cluster: ADH1A, ADH1B and ADH1C) and ALDH2 genes, respectively. This study aimed to evaluate the association between genetic variants in these genes and GC risk in West Bengal, India.
METHODS: We enrolled 105 GC patients (cases), and their corresponding sex, age and ethnicity was matched to 108 normal individuals (controls). Genotyping for ADH1A (rs1230025), ADH1B (rs3811802, rs1229982, rs1229984, rs6413413, rs4147536, rs2066702 and rs17033), ADH1C (rs698) and ALDH2 (rs886205, rs968529, rs16941667 and rs671) was performed using DNA sequencing and RFLP.
RESULTS: Genotype and allele frequency analysis of these SNPs revealed that G allele of rs17033 is a risk allele (A vs G: OR = 3.67, 95% CI = 1.54-8.75, p = 0.002) for GC. Significant association was also observed between rs671 and incidence of GC (p = 0.003). Moreover, smokers having the Lys allele of rs671 had a 7-fold increased risk of acquiring the disease (OR = 7.58, 95% CI = 1.34-42.78, p = 0.009).
CONCLUSION: In conclusion, rs17033 of ADH1B and rs671 of ALDH2 SNPs were associated with GC risk and smoking habit may further modify the effect of rs671. Conversely, rs4147536 of ADH1B might have a protective role in our study population. Additional studies with a larger patient population are needed to confirm our results.

Xinhua J, Yanfei Z
Association between ALDH
Afr Health Sci. 2017; 17(1):108-115 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The findings from studies on the relationship between aldehyde dehydrogenases(ALDH) gene Glu504Lys polymorphism and colorectal cancer(CRC) were inconsistent.
OBJECTIVES: The aim of this meta-analysis was to assess ALDH gene Glu504Lys polymorphism and CRC risk.
METHODS: All of the relevant studies were identified from PubMed and Embase database. Statistical analyses were conducted with STATA 12.0 software. Odds ratio (OR) with 95% confidence interval (CI) values were applied to evaluate the strength of the association. Nine studies with 2779 cases and 4533 controls were included.
RESULTS: No significant variation in CRC risk was detected in any of the genetic models overall. To explore the sources of heterogeneity,we performed further sub-group analyses by ethnicity and quality assessment of these studies. In the sub-group analysis by race, significant associations between ALDH gene Glu504Lys polymorphism and CRC risk were found in China(Glu/Lys vs Glu/Glu: OR = 0.70, 95%CI = 0.57-0.85; the dominant model: OR =0.69, 95%CI =0.48-0.98) and Japan(Lys/Lys vs Glu/Glu:OR =0.72, 95%CI =0.55-0.95).
CONCLUSION: This meta-analysis suggests that the ALDH2 Glu504Lys polymorphism may be associated with susceptibility to CRC. Furthermore, large and well-designed studies are needed to confirm these conclusions.

Huang CC, Hsiao JR, Lee WT, et al.
Investigating the Association between Alcohol and Risk of Head and Neck Cancer in Taiwan.
Sci Rep. 2017; 7(1):9701 [PubMed] Free Access to Full Article Related Publications
Although alcohol is an established risk factor of head and neck cancer (HNC), insufficiencies exist in the literature in several aspects. We analyzed detailed alcohol consumption data (amount and type of alcoholic beverage) of 811 HNC patients and 940 controls to evaluate the association between alcohol and HNC by HNC sites and by genotypes of ADH1B and ALDH2. Alcohol was associated with an increased HNC risk in a dose-response relationship, with the highest risk observed for hypopharyngeal cancer, followed by oropharyngeal and laryngeal cancers. Liquor showed a stronger positive association with HNC than beer and wine. The highest HNC risk occurred in individuals with the slow ADH1B and slow/non-functional ALDH2 genotype combination. In our study population, 21.8% of HNCs, 55.7% of oropharyngeal cancers, and 89.1% of hypopharyngeal cancers could be attributed to alcohol. Alcohol accounted for 47.3% of HNCs among individuals with the slow ADH1B and slow/non-functional ALDH2 genotype combination. The HNC risk associated with alcohol became comparable to that of never/occasional drinkers after ten or more years of cessation from regular alcohol drinking. In conclusion, alcohol use is associated with an increased HNC risk, particularly for individuals with slow ethanol metabolism. HNC incidence may be reduced by alcohol cessation.

Lee DJ, Lee HM, Kim JH, et al.
Heavy alcohol drinking downregulates ALDH2 gene expression but heavy smoking up-regulates SOD2 gene expression in head and neck squamous cell carcinoma.
World J Surg Oncol. 2017; 15(1):163 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: This study aims to determine the relationship between expression levels of ALDH2 and SOD2 genes and clinical parameters such as alcohol drinking, tobacco smoking, primary site of HNSCC, and human papilloma virus (HPV) state.
METHODS: Gene expression data were obtained from gene expression omnibus (GEO accession number: GSE65858). Clinical data (N = 270) including survival result, gender, age, TNM stage, primary site of HNSCC, HPV status, alcohol drinking, and tobacco smoking habit were analyzed according to gene expression pattern.
RESULTS: ALDH2 gene was expressed in low levels in patients with heavy alcohol consumption. It was expressed in high (p = 0.01) levels in patients with no or light alcohol consumption. ALDH2 gene was also expressed in low levels in patients with oral cavity cancers or hypopharynx cancers. However, ALDH2 gene was expressed in high (p = 0.03) levels in patients with oropharyngeal cancers or laryngeal cancers. HPV-positive patients were found to have high (p = 0.02) expression levels of ALDH2. SOD2 gene was expressed in high (p = 0.005) levels in patients who had greater mean pack-year of tobacco smoking. Based on log rank test, the group of patients with high expression of ALDH2 showed better (p = 0.002) clinical results than those with low expression of ALDH2. Difference of survival results between ALDH2 high-expressed group and ALDH2 low-expressed group was validated in another cohort (GSE39368, N = 138).
CONCLUSIONS: Heavy alcohol drinking downregulates ALDH2 gene expression level. Heavy smoking up-regulates SOD2 gene expression level in patients with head and neck squamous cell carcinoma. The group of patients with low expression levels of ALDH2 showed significantly poorer survival results compared to those with high expression levels of ALDH2.

Matejcic M, Gunter MJ, Ferrari P
Alcohol metabolism and oesophageal cancer: a systematic review of the evidence.
Carcinogenesis. 2017; 38(9):859-872 [PubMed] Related Publications
Alcohol is a major risk factor for oesophageal squamous cell carcinoma (OSCC), the most prevalent histological subtype of oesophageal cancer (OC) worldwide. The metabolism of alcohol is regulated by specific enzymes whose activity and expression is influenced by genetic polymorphisms. We conducted a systematic review of current epidemiological evidence of the relationship between alcohol intake and OC risk, including the role of tobacco smoking and functional polymorphisms of alcohol dehydrogenases (ADHs) and aldehyde dehydrogenases (ALDHs). Potential biological mechanisms underlying oesophageal carcinogenesis are also discussed. Frequency and intensity of alcohol intake have been consistently associated with an increased risk of OSCC in regions with low and high incidence of the disease. The highest risk was reported among tobacco smokers, whereas the association between alcohol and OSCC risk was weak in the absence of tobacco use. The ADH1B, ADH1C and ALDH2 gene polymorphisms influence the risk of OSCC through modulation of acetaldehyde metabolism and propensity to alcohol intake. These functional variants may be suitable proxies of alcohol exposure for use in Mendelian randomization studies if complemented by reported alcohol intake data. Recent epidemiological and experimental studies investigating the role of alcohol consumption in OC development have implicated the microbiome as a new promising avenue for research, which entail novel potential mechanisms of alcohol-related oesophageal carcinogenesis. Microbial communities associated with alcohol consumption might be used as biomarkers to raise the potential of intervening among susceptible individuals.

Sanchez AC, Li C, Andrews B, et al.
AAV Gene Therapy for Alcoholism: Inhibition of Mitochondrial Aldehyde Dehydrogenase Enzyme Expression in Hepatoma Cells.
Hum Gene Ther. 2017; 28(9):717-725 [PubMed] Free Access to Full Article Related Publications
Most ethanol is broken down in the liver in two steps by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH2) enzymes, which metabolize down ethanol into acetaldehyde and then acetate. Some individuals from the Asian population who carry a mutation in the aldehyde dehydrogenase gene (ALDH2*2) cannot metabolize acetaldehyde as efficiently, producing strong effects, including facial flushing, dizziness, hypotension, and palpitations. This results in an aversion to alcohol intake and protection against alcoholism. The large prevalence of this mutation in the human population strongly suggests that modulation of ALDH2 expression by genetic technologies could result in a similar phenotype. scAAV2 vectors encoding ALDH2 small hairpin RNA (shRNA) were utilized to validate this hypothesis by silencing ALDH2 gene expression in human cell lines. Human cell lines HEK-293 and HepG2 were transduced with scAAV2/shRNA, showing a reduction in ALDH2 RNA and protein expression with the two viral concentration assayed (1 × 10

Na HK, Lee JY
Molecular Basis of Alcohol-Related Gastric and Colon Cancer.
Int J Mol Sci. 2017; 18(6) [PubMed] Free Access to Full Article Related Publications
Many meta-analysis, large cohort studies, and experimental studies suggest that chronic alcohol consumption increases the risk of gastric and colon cancer. Ethanol is metabolized by alcohol dehydrogenases (ADH), catalase or cytochrome P450 2E1 (CYP2E1) to acetaldehyde, which is then further oxidized to acetate by aldehyde dehydrogenase (ALDH). Acetaldehyde has been classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen to humans. The acetaldehyde level in the stomach and colon is locally influenced by gastric colonization by

Liu P, Zhao HR, Li F, et al.
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.
J Clin Lab Anal. 2018; 32(2) [PubMed] Related Publications
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.

Chang JS, Hsiao JR, Chen CH
ALDH2 polymorphism and alcohol-related cancers in Asians: a public health perspective.
J Biomed Sci. 2017; 24(1):19 [PubMed] Free Access to Full Article Related Publications
The occurrence of more than 200 diseases, including cancer, can be attributed to alcohol drinking. The global cancer deaths attributed to alcohol-consumption rose from 243,000 in 1990 to 337,400 in 2010. In 2010, cancer deaths due to alcohol consumption accounted for 4.2% of all cancer deaths. Strong epidemiological evidence has established the causal role of alcohol in the development of various cancers, including esophageal cancer, head and neck cancer, liver cancer, breast cancer, and colorectal cancer. The evidence for the association between alcohol and other cancers is inconclusive. Because of the high prevalence of ALDH2*2 allele among East Asian populations, East Asians may be more susceptible to the carcinogenic effect of alcohol, with most evidence coming from studies of esophageal cancer and head and neck cancer, while data for other cancers are more limited. The high prevalence of ALDH2*2 allele in East Asian populations may have important public health implications and may be utilized to reduce the occurrence of alcohol-related cancers among East Asians, including: 1) Identification of individuals at high risk of developing alcohol-related cancers by screening for ALDH2 polymorphism; 2) Incorporation of ALDH2 polymorphism screening into behavioral intervention program for promoting alcohol abstinence or reducing alcohol consumption; 3) Using ALDH2 polymorphism as a prognostic indicator for alcohol-related cancers; 4) Targeting ALDH2 for chemoprevention; and 5) Setting guidelines for alcohol consumption among ALDH2 deficient individuals. Future studies should evaluate whether these strategies are effective for preventing the occurrence of alcohol-related cancers.

Yan H, Li Z, Shen Q, et al.
Aberrant expression of cell cycle and material metabolism related genes contributes to hepatocellular carcinoma occurrence.
Pathol Res Pract. 2017; 213(4):316-321 [PubMed] Related Publications
This study aims to deepen our understanding of the molecular mechanism underlying the occurrence of hepatocellular carcinoma (HCC). We first downloaded a gene expression profile dataset GSE29721 (10 HCC and 10 control samples) from Gene Expression Omnibus database ( Differentially expressed genes (DEGs) were identified by the paired t-test using limma package. Pathway and functional enrichment analyses were performed with DAVID tools. Transcription factors were annotated with TRANSFAC database and tumor associated genes (TAGs) were annotated with TAG and TSGene databases. Protein-protein interaction (PPI) network was conducted using STRING online tool and function module was further identified with BioNet package. Totally, 527 up-regulated DEGs and 587 down-regulated DEGs were identified. GO functional and KEGG pathway enrichment analyses showed that the up-regulated DEGs were mainly related to cell division and cell cycle, while the down-regulated DEGs were largely related to material metabolism, especially secondary metabolism. Proteins encoded by DEGs CDK1, BUB1, CDC20, NCAPG, NDC80, CDCA8, MAD2L1, CCNB1, CCNA2 and BIRC5 were hub genes with high degrees in the PPI network; further module analysis detected a subnetwork consisting of 55 proteins, such as CYP2B6, ACAA1, BHMT and ALDH2. Taken together, aberrant expression of cell cycle related genes (e.g., CDK1, CCNA2, CCNB1, BUB1, MAD2L1 and CDC20) and material metabolism related genes (e.g., CYP2B6, ACAA1, BHMT and ALDH2) may contribute to HCC occurrence.

Álvarez-Avellón SM, Fernández-Somoano A, Navarrete-Muñoz EM, et al.
Effect of alcohol and its metabolites in lung cancer: CAPUA study.
Med Clin (Barc). 2017; 148(12):531-538 [PubMed] Related Publications
BACKGROUND AND OBJECTIVE: Alcohol and its metabolites play an important role in carcinogenesis. This effect could be modulated by polymorphisms in genes encoding enzymes involved in the metabolism of alcohol and folate. Therefore, we analyzed the effect of alcohol consumption and ADH1B Arg48His, ADH1B Arg370Cys, ADH1C Ile349Val, ALDH2 Glu540Lys, CYP2E1 RsaI, CYP2E1 DraI, CYP2E1 TaqI and MTHFR C677T polymorphisms on the risk of developing lung cancer.
PATIENTS AND METHODS: We included 876 lung cancer cases and 840 controls of the CAPUA hospital-based case-control study. Genotyping was performed using the Sequenom MassArray (iPLEX GOLD) technology.
RESULTS: An alcohol consumption of 0.1-9.9g/day decreased lung cancer risk (OR
CONCLUSIONS: Alcohol and polymorphisms in genes involved in the metabolism of alcohol and folate are related to the onset of lung cancer.

Yang S, Lee J, Choi IJ, et al.
Effects of alcohol consumption, ALDH2 rs671 polymorphism, and Helicobacter pylori infection on the gastric cancer risk in a Korean population.
Oncotarget. 2017; 8(4):6630-6641 [PubMed] Free Access to Full Article Related Publications
The effect of alcohol consumption on the risk of gastric cancer (GC) has not yet been fully elucidated, and an aldehyde dehydrogenase 2 (ALDH2) polymorphism, rs671, is a genetic variant that influences alcohol consumption in East Asians. Additionally, the discrepancy between the Helicobacter pylori (H. pylori) infection prevalence and GC incidence across Asian countries has not been explained. This study evaluated the effects of alcohol consumption and genetic susceptibility to defective acetaldehyde metabolism on the GC risk and their interactions with H. pylori infection. This study included 450 Korean GC cases and 1,050 controls recruited at the National Cancer Center. Data for 795 patients and 4,893 controls were used for further confirmation of the effect of rs671. Increased GC risks were evident for rs671 A allele carriers (odds ratio (OR), 1.23; 95% confidence interval (CI), 1.08-1.41) and H. pylori-infected individuals (OR, 7.07; 95% CI, 4.60-10.86), but no dose-response association with alcohol consumption was observed. Furthermore, the interactions between these factors were not significant. This study has demonstrated that alcohol consumption and rs671 should be considered simultaneously when assessing the GC risk. Additionally, alcohol-related factors were not found to interact with H. pylori infection, and further studies evaluating other environmental factors are required to explain the Asian enigma.

Hou G, Chen L, Liu G, et al.
Aldehyde dehydrogenase-2 (ALDH2) opposes hepatocellular carcinoma progression by regulating AMP-activated protein kinase signaling in mice.
Hepatology. 2017; 65(5):1628-1644 [PubMed] Related Publications
Potential biomarkers that can be used to determine prognosis and perform targeted therapies are urgently needed to treat patients with hepatocellular carcinoma (HCC). To meet this need, we performed a screen to identify functional genes associated with hepatocellular carcinogenesis and its progression at the transcriptome and proteome levels. We identified aldehyde dedydrogenase-2 (ALDH2) as a gene of interest for further study. ALDH2 levels were significantly lower at the mRNA and protein level in tumor tissues than in normal tissues, and they were even lower in tissues that exhibited increased migratory capacity. A study of clinical associations showed that ALDH2 is correlated with survival and multiple migration-associated clinicopathological traits, including the presence of metastasis and portal vein tumor thrombus. The result of overexpressing or knocking down ALDH2 showed that this gene inhibited migration and invasion both in vivo and in vitro. We also found that ALDH2 altered the redox status of cells by regulating acetaldehyde levels and that it further activated the AMP-activated protein kinase (AMPK) signaling pathway.
CONCLUSION: Decreased levels of ALDH2 may indicate a poor prognosis in HCC patients, while forcing the expression of ALDH2 in HCC cells inhibited their aggressive behavior in vitro and in mice largely by modulating the activity of the ALDH2-acetaldehyde-redox-AMPK axis. Therefore, identifying ALDH2 expression levels in HCC might be a useful strategy for classifying HCC patients and for developing potential therapeutic strategies that specifically target metastatic HCC. (Hepatology 2017;65:1628-1644).

Matsumoto A, Thompson DC, Chen Y, et al.
Roles of defective ALDH2 polymorphism on liver protection and cancer development.
Environ Health Prev Med. 2016; 21(6):395-402 [PubMed] Free Access to Full Article Related Publications
Because serum transaminases elevate alcohol dose dependently as a consequence of liver injury, they serve as useful biological markers of excessive drinking. However, these markers are inadequate in individuals with a defective allele of the aldehyde dehydrogenase 2 gene, ALDH2*2, because they show a different correlation with the amount of ethanol. For example, the serum alanine aminotransferase (ALT) level could become even lower than the baseline after alcohol intake in ALDH2*2 carriers. In fact, multiple studies suggest that ALDH2*2 is a hepato-protective factor in healthy individuals. Importantly, excessive drinking is particularly dangerous in carriers of ALDH2*2 because the risk of alcohol-related cancer is much higher than that for ALDH2*1/*1 carriers. Without recognizing the genotype interaction on serum transaminase, the opportunity to warn people about potential cancer risks is missed owing to incorrect interpretation. This is particularly important in East Asian countries where approximately half of the population carries the ALDH2*2 allele. To date, the mechanism of liver protection from ethanol load in individuals with ALDH2*2 has not been fully elucidated. However, some reasonable mechanisms have been suggested by experimental studies, including remodelling of detoxifying systems. Further studies to uncover the whole mechanism are anticipated.

Zhong Q, Wu RR, Zeng ZM
Association of ADH1B Arg47His and ALDH2 Glu487Lys polymorphisms with risk of colorectal cancer and their interaction with environmental factors in a Chinese population.
Genet Mol Res. 2016; 15(3) [PubMed] Related Publications
Human colorectal cancer (CRC) is a major worldwide health concern, and its development has been shown to be associated with alcohol intake. We carried out a study to investigate the effect of the ADH1B Arg47His and ALDH2 Glu487Lys genetic polymorphisms and their interaction with alcohol consumption on development of CRC. Between March 2013 and May 2015, a total of 274 CRC patients and 358 healthy controls were recruited. Genotyping of sequence variations was performed using the polymerase chain reaction-restriction fragment length polymorphism method. Under a co-dominant model, individuals with the ADH1B Arg47His AA genotype showed increased CRC risk compared to those carrying the GG genotype, with an adjusted odds ratio (and 95% confidence interval) of 3.37 (2.00-5.70). Moreover, under dominant and recessive models, ADH1B Arg47His variant genotypes were associated with greater susceptibility to CRC when compared with the wild-type sequence. Both polymorphisms examined were positively associated with alcohol consumption in a Spearman correlation analysis of CRC risk. In conclusion, our study suggests that the ADH1B Arg47His polymorphism, but not the ALDH2 Glu487Lys variation, may influence development of CRC in the Chinese population.

Zhao S, Du XM, Ma SS, Wang LM
Association between aldehyde dehydrogenase 2 (ALDH2) Glu504Lys polymorphism and susceptibility to colorectal cancer: a meta-analysis.
Genet Mol Res. 2016; 15(3) [PubMed] Related Publications
Numerous studies have evaluated the association between Glu504Lys polymorphism in the aldehyde dehydrogenase 2 (ALDH2) gene and colorectal cancer (CRC) risk. However, the specific association remains controversial. To assess the relationship between the ALDH2 Glu504Lys polymorphism and CRC, we conducted a comprehensive meta-analysis of five case-control studies comprising 1664 patients with CRC and 2777 controls. The results of this meta-analysis showed that the ALDH2 Glu504Lys polymorphism was associated with a significantly reduced risk of CRC [Lys/Lys vs Glu/Glu: odds ratio (OR) = 0.95, 95% confidence interval (CI) = 0.58-1.54; Glu/Lys vs Glu/Glu: OR = 0.85, 95%CI = 0.75-0.97; dominant model: OR = 0.86, 95%CI = 0.76-0.98; recessive model: OR = 1.00, 95%CI = 0.62-1.61]. No significant heterogeneity or publication bias was observed in our meta-analysis. Based on the statistical data, our meta-analysis indicates that the ALDH2 Glu504Lys polymorphism is associated with reduced risk of developing CRC.

Thomas ML, de Antueno R, Coyle KM, et al.
Citral reduces breast tumor growth by inhibiting the cancer stem cell marker ALDH1A3.
Mol Oncol. 2016; 10(9):1485-1496 [PubMed] Free Access to Full Article Related Publications
Breast cancer stem cells (CSCs) can be identified by increased Aldefluor fluorescence caused by increased expression of aldehyde dehydrogenase 1A3 (ALDH1A3), as well as ALDH1A1 and ALDH2. In addition to being a CSC marker, ALDH1A3 regulates gene expression via retinoic acid (RA) signaling and plays a key role in the progression and chemotherapy resistance of cancer. Therefore, ALDH1A3 represents a druggable anti-cancer target of interest. Since to date, there are no characterized ALDH1A3 isoform inhibitors, drugs that were previously described as inhibiting the activity of other ALDH isoforms were tested for anti-ALDH1A3 activity. Twelve drugs (3-hydroxy-dl-kynurenine, benomyl, citral, chloral hydrate, cyanamide, daidzin, DEAB, disulfiram, gossypol, kynurenic acid, molinate, and pargyline) were compared for their efficacy in inducing apoptosis and reducing ALDH1A3, ALDH1A1 and ALDH2-associated Aldefluor fluorescence in breast cancer cells. Citral was identified as the best inhibitor of ALDH1A3, reducing the Aldefluor fluorescence in breast cancer cell lines and in a patient-derived tumor xenograft. Nanoparticle encapsulated citral specifically reduced the enhanced tumor growth of MDA-MB-231 cells overexpressing ALDH1A3. To determine the potential mechanisms of citral-mediated tumor growth inhibition, we performed cell proliferation, clonogenic, and gene expression assays. Citral reduced ALDH1A3-mediated colony formation and expression of ALDH1A3-inducible genes. In conclusion, citral is an effective ALDH1A3 inhibitor and is able to block ALDH1A3-mediated breast tumor growth, potentially via blocking its colony forming and gene expression regulation activity. The promise of ALDH1A3 inhibitors as adjuvant therapies for patients with tumors that have a large population of high-ALDH1A3 CSCs is discussed.

Kagemoto K, Urabe Y, Miwata T, et al.
ADH1B and ALDH2 are associated with metachronous SCC after endoscopic submucosal dissection of esophageal squamous cell carcinoma.
Cancer Med. 2016; 5(7):1397-404 [PubMed] Free Access to Full Article Related Publications
A previous genome-wide association study identified two novel esophageal squamous cell carcinoma (ESCC) susceptibility genes, ADH1B and ALDH2. We investigated the characteristics of ESCC, and the relationship between metachronous esophageal and/or pharyngeal squamous cell carcinoma (SCC) and the ADH1B & ALDH2 risk alleles. One hundred and seventeen superficial ESCC patients who underwent treatment with endoscopic submucosal dissection (ESD) were followed up using endoscopy for ≥12 months. First, we performed a replication analysis to confirm the relationship between ESCC and the ADH1B & ALDH2 risk alleles using 117 superficial ESCC cases and 1125 healthy controls. Next, we investigated the incidence and genetic/environmental factors associated with metachronous SCC development after ESD. We also analyzed the potential risk factors for metachronous SCC development using Cox's proportional hazards model. rs1229984 GG located on ADH1B and rs671 GA located on ALDH2 were significantly associated with ESCC progression (P = 7.93 × 10(-4) and P = 1.04 × 10(-5) ). Patients with rs1229984 GG, those with rs671 GA, smokers, heavy alcohol drinkers (44 g/day ethanol), and presence of multiple Lugol-voiding lesions (LVLs) developed metachronous SCC more frequently (P = 3.20 × 10(-3) , 7.00 × 10(-4) , 4.00 × 10(-4) , 2.15 × 10(-2) , and 4.41 × 10(-3) , respectively), with hazard ratios were 2.84 (95% confidence interval [CI] = 1.43-5.63), 4.57 (95% CI = 1.80-15.42), 4.84 (95% CI = 1.89-16.41), and 2.34 (95% CI = 1.12-5.31), respectively. Multiple logistic regression analysis revealed that rs1229984 GG, rs671 GA, and smoking status were independently associated with the risk of developing metachronous SCCs after ESD. Moreover, we found cumulative effects of these two genetic factors (rs1229984 GG and rs671 GA) and one environmental factor (tobacco smoking) which appear to increase metachrous SCCs after ESD of ESCC risk approximately nearly 12-fold. Our findings elucidated the crucial role of multiple genetic variations in ADH1B and ALDH2 as biomarkers of metachronous ESCC.

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