A single nucleotide polymorphism in the alcohol dehydrogenase 7 gene (alanine to glycine substitution at amino acid 92) is associated with the risk of squamous cell carcinoma of the head and neck

ALDH2 mutations and defense against genotoxic aldehydes in cancer and inherited bone marrow failure syndromes

Reactive aldehydes, for instance, formaldehyde and acetaldehyde, are important endogenous or environmental mutagens by virtue of their abilities to produce a DNA lesion called interstrand crosslink (ICL). Aldehyde-metabolizing enzymes such as aldehyde dehydrogenases (ALDHs) and the Fanconi anemia (FA) pathway constitute the main defense lines against aldehyde-induced genotoxicity. Biallelic mutations of genes in any one of the FA complementation groups can impair the ICL repair mechanism and cause FA, a heterogeneous disorder manifested by bone marrow failure (BMF), congenital abnormality and a strong predisposition to cancer. The defective ALDH2 polymorphism rs671 (ALDH2*2) is a known risk and prognostic factor for alcohol drinking-associated cancers. Recent studies suggest that it also promotes BMF and cancer development in FA, and its combination with alcohol dehydrogenase 5 (ADH5) mutations causes aldehyde degradation deficiency syndrome (ADDS), also known by its symptoms as aplastic anemia, mental retardation, and dwarfism syndrome. ALDH2*2 and another pathogenic variant in the alcohol-metabolizing pathway, ADH1B1*1, is prevalent among East Asians. Also, other ALDH2 genotypes with disease-modifying potentials have lately been identified in different populations. Therefore, it would be appropriate to summarize current knowledge of genotoxic aldehydes and defense mechanisms against them to shed new light on the pathogenic effects of ALDH2 variants together with other genetic and environmental modifiers on cancer and inherited BMF syndromes. Lastly, we also presented potential treatment strategies for FA, ADDS and cancer based on the manipulation of aldehyde-induced genotoxicity.

Association between alcohol dehydrogenase polymorphisms (rs1229984, rs1573496, rs1154460, and rs284787) and susceptibility to head and neck cancers: A systematic review and meta-analysis

OBJECTIVE

Head and neck cancer (HNC) is a prevalent and complex group of malignancies with increasing incidence globally. Alcohol dehydrogenases (ADHs) play a crucial role in alcohol metabolism, and their polymorphisms have been linked to HNC risk. This systematic review and meta-analysis aims to evaluate the association between ADH polymorphisms and susceptibility to HNCs, incorporating additional analyses and adding more studies to increase power and accuracy of the results.

DESIGN

Subgroup analysis, meta-regression analysis, and sensitivity analyses were conducted to explore potential differences within the data and assess the stability of pooled odds ratios (ORs). To mitigate the risk of false conclusions from meta-analyses, a trial sequential analysis was performed.

RESULTS

For ADH1B rs1229984, the pooled OR (95 % confidence interval (CI)) was 0.73 (0.65, 0.82), 0.42 (0.35, 0.50), 0.57 (0.44, 0.73), 0.56 (0.50, 0.62), and 0.80 (0.73, 0.88), as well as for ADH7 rs1573496, the pooled OR was 0.72 (0.62, 0.85), 0.36 (0.17, 0.74), 0.76 (0.64, 0.91), 0.80 (0.71, 0.91), and 0.38 (0.18, 0.78) with a p < 0.05 in all allelic, homozygous, heterozygous, recessive, and dominant models, respectively. However, no significant association was found between the ADH7 rs1154460 and rs284787 polymorphisms and the risk of HNC with pooled ORs of 1.11 (p = 0.19) and 1.09 (p = 0.24) for the recessive model, respectively. The ethnicities, tumor subsites, control sources, sample sizes, quality scores, and Hardy-Weinberg equilibrium statuses were confounding factors.

CONCLUSION

The ADH1B rs1229984 and ADH7 rs1573496 polymorphisms are significantly associated with a reduced risk of HNC.

An alcohol dehydrogenase 7 gene polymorphism associates with both acute and chronic pain in sickle cell disease

Introduction: As the most distressing complication of sickle cell disease (SCD), pain is marked by considerable heterogenicity. In this study we explored the potential association of alcohol dehydrogenase 7 gene (ADH7) polymorphism rs971074 with sickle cell pain. Methods: We analyzed clinical phenotypes and the rs971074 single-nucleotide polymorphism in ADH7 by MassARRAY-iPlex analysis in a cohort of SCD patients. Results: The synonymous rs971074 was significantly associated with both acute and chronic pain in SCD. Patients with the minor T allele(s) recorded significantly more crisis episodes and severe chronic pain symptoms. Conclusion: Our study has identified the rs971074 minor T allele as a genetic biomarker potentially influencing acute and chronic pain. These findings may ultimately help inform strategies to develop precision pain therapies in SCD.

Impact of Alcohol Dehydrogenase 7 Polymorphism and Alcohol Consumption on Risk of Head and Neck Squamous Cell Carcinoma: A Korean Case-Control Study

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is closely associated with alcohol consumption and individual genetic susceptibility, such as single nucleotide polymorphism (SNP) of alcohol dehydrogenase (ADH). This study aimed to investigate the association of ADH7 SNPs with the risk of HNSCC.

METHODS

We analyzed ADH7 rs1573496C>G, rs3737482T>C, rs1154460G>A, and rs284787T>C SNPs in 250 patients with HNSCC and 322 controls in the Korean populations. Genotyping was conducted using the TaqMan assay. Linkage disequilibrium and haplotypes were analyzed.

RESULTS

The odds ratios (OR) and 95% confidence intervals (CI) of the CT and CC genotypes of ADH7 rs3737482T>C were 0.48 (0.29-0.78) and 0.69 (0.49-0.96), indicating a significantly decreased risk. In SNP of rs1154460G>A, the OR and 95% CI of the AA genotype was 1.63 (1.11-2.40), showing a significant increase in the risk. Furthermore, SNPs of ADH7 rs3737482T>C and ADH7 rs1154460G>A exhibit synergistic interactions with alcohol composition on the risk of HNSCC. None of the haplotypes were associated with the risk of HNSCC.

CONCLUSIONS

ADH7 rs3737482T>C and rs1154460G>A SNPs are associated with the risk of development of HNSCC in Koreans. They could serve as molecular biological markers to screen high-risk groups for HNSCC.

Reviewing the epidemiology of head and neck cancer: definitions, trends and risk factors

Introduction Head and neck cancer appears to be increasing in incidence, with potential changes in aetiology proposed. This paper aims to provide a narrative overview of the epidemiological literature to describe the disease burden and trends in terms of incidence and mortality both in the UK and globally and to review the evidence on current risk factors.

Methods A search was performed on multiple databases (PubMed and Epistemonikos), applying filters to identify systematic reviews and meta-analyses which investigated head and neck cancer incidence, mortality and risk factors. International and UK cancer registries and sources were searched for incidence and mortality data.

Results Multiple definitions of head and neck cancer are employed in epidemiology. Globally, incidence rates have increased in recent decades, largely driven by oropharyngeal cancer. Mortality rates over the last decade have also started to rise, reflecting the disease incidence and static survival rates. Major risk factors include tobacco smoking alone and in combination with alcohol consumption, betel chewing (particularly in Southeast Asian populations) and the human papillomavirus in oropharyngeal cancer.

Conclusions These epidemiological data can inform clinical and preventive service planning for head and neck cancer.

Head and neck cancer incidence is increasing and is projected to continue to rise, largely driven by increases in oropharyngeal cancer.

Mortality rates have started to increase within the last decade, reflecting a rising incidence and static survival rates.

Major risk factors that are associated with the risk of head and neck cancer are tobacco smoking and tobacco used in combination with alcohol consumption. Human papillomavirus is an additional major risk factor for oropharyngeal cancer. Cancers of the head and neck are clearly socioeconomically patterned but this socioeconomic risk is not entirely explained by smoking and alcohol behaviours.

Investigation of miR-21-5p Key Target Genes and Pathways in Head and Neck Squamous Cell Carcinoma Based on TCGA Database and Bioinformatics Analysis

Aim: Head and neck squamous cell carcinoma (HNSCC) is the sixth most commonly diagnosed malignancy worldwide. Overexpressed of microRNA-21-5p (miR-21-5p) has been reported to be involved in the development of HNSCC. However, the role of miR-21-5p in HNSCC is still not fully elucidated. The purpose of this study was to explore the underlying molecular mechanisms of miR-21-5p in HNSCC. Methods: RT-qPCR was used to determine the differential expression levels of miR-21-5p in tissue samples of HNSCC patients. Meta-analysis was performed based on miRNA expression data collected from the Gene Expression Omnibus (GEO) database, The Cancer Genome Atlas (TCGA), and published articles to evaluate the expression of miR-21-5p in HNSCC. We investigated the biological function of miR-21-5P by gene ontology enrichment and target prediction analysis. Furthermore, RT-qPCR and IHC were conducted to verify the expression of target genes. Finally, Kaplan–Meier survival analysis was performed to assessed the prognostic value of the putative miR-21-5p target genes. Results: MiR-21-5p was significantly overexpressed in HNSCC compared to healthy tissues (P < .05) and showed potent predictive power with a summary receiver operating characteristic of 0.90. Meanwhile, the expression of miR-21-5p was significantly correlated with tumor stage, T stage and smoking in HNSCC (P < .05). A total of 71 down-regulated genes, both HNSCC-related and miR-21-p5-related, were obtained from the analytical integration. Two predicted genes (ADH7, RDH12) were down-regulated in HNSCC, and significantly negatively correlated with miR-21-5p. IHC and RT-qPCR demonstrated that the expression of ADH7 and RDH12 in HNSCC samples was significantly lower than control. And high expression of ADH7 was associated with better DFS of HNSCC patients. Conclusions: miR-21-5p may target at ADH7, RDH12 and participate in regulation of retinol metabolism, which might affect the prognosis of HNSCC. High expression of ADH7 may indicate better prognosis in HNSCC patients.

Inverse molecular docking reveals a novel function of thymol: Inhibition of fat deposition induced by high-dose glucose in Caenorhabditis elegans

As a natural product isolated from thyme oil in thyme, thymol (2-isopropyl-5-methylphenol) harbors antiviral, antioxidant, and other properties, and thus could be potentially used for the treatment of various diseases. However, the function of thymol has not been comprehensively studied. Here, we applied an inverse molecular docking approach to identify unappreciated functions of thymol. Potential targets of thymol in humans were identified by the server of DRAR-CPI, and targets of interest were then assessed by GO and KEGG pathway analysis. Subsequently, homologous proteins of these targets in Caenorhabditis elegans were identified by Blast tool, and their three-dimensional structures were achieved using Swiss-Model workspace. Interaction between thymol and the targeted proteins in worms was verified using AutoDock 4.0. Analyses of the targets revealed that thymol could be potentially involved in the glycolysis/gluconeogenesis and fatty acid degradation pathways. To verify the activity of thymol on lipid deposition in vivo, the C. elegans model was established. The lipid content of nematodes induced by high-dose glucose was determined by Oil Red O and Nile Red staining, and gene expression was assessed by qRT-PCR. The results showed that thymol might lead to the acceleration of β-oxidation by upregulating cpt-1, aco, fabp, and tph-1, causing the descent of lipid content in nematodes. Our findings indicated that thymol could be potentially used for the treatment of chronic metabolic diseases associated with increased fatty acid deposition.

A Genome-Wide Association Study Identifies Two Novel Susceptible Regions for Squamous Cell Carcinoma of the Head and Neck

To identify genetic variants for risk of squamous cell carcinoma of the head and neck (SCCHN), we conducted a two-phase genome-wide association study consisting of 7,858,089 SNPs in 2,171 cases and 4,493 controls of non-Hispanic white, of which, 434,839 typed and 7,423,250 imputed SNPs were used as the discovery. SNPs with P < 1 × 10-3 were further validated in the OncoArray study of oral and pharynx cancer (5,205 cases and 3,232 controls of European ancestry) from databases of Genotypes and Phenotypes. Meta-analysis of the discovery and replication studies identified one novel locus 6p22.1 (P = 2.96 × 10-9 for the leading rs259919) and two cancer susceptibility loci 6p21.32 (rs3135001, HLA-DQB1) and 6p21.33 (rs1265081, CCHCR1) associated with SCCHN risk. Further stratification by tumor site revealed four known cancer loci (5p15.33, 6p21.32, 6p21.33, and 2p23.1) associated with oral cavity cancer risk and oropharyngeal cancer risk, respectively. In addition, one novel locus 18q22.2 (P = 2.54 × 10-9 for the leading SNP rs142021700) was identified for hypopharynx and larynx cancer risk. For SNPs in those reported or novel loci, we also performed functional annotations by bioinformatics prediction and expression quantitative trait loci analysis. Collectively, our identification of four reported loci (2p23.1, 5p15.33, 6p21.32, and 6p21.33) and two novel loci (6p22.1 and 18q22.2) for SCCHN risk highlight the importance of human leukocyte antigen loci for oropharyngeal cancer risk, suggesting that immunologic mechanisms are implicated in the etiology of this subset of SCCHN. SIGNIFICANCE: Two novel risk loci for SCCHN in non-Hispanic white individuals highlight the importance of immunologic mechanism in the disease etiology.

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.

Impact of alcohol dehydrogenase-aldehyde dehydrogenase polymorphism on clinical outcome in patients with hypopharyngeal cancer

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.

Identification of Ethanol and 4-Nitroquinoline-1-Oxide Induced Epigenetic and Oxidative Stress Markers During Oral Cavity Carcinogenesis

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a cancer that is characterized by its high morbidity and mortality rates. While tobacco use and alcohol consumption are 2 major contributing factors for HNSCC carcinogenesis, how the combination of tobacco and alcohol increases HNSCC risk is not understood.

METHODS

We combined the 4-nitroquinoline-1-oxide (4-NQO) oral carcinogenesis and Meadows-Cook alcohol mouse models to elucidate the molecular events and to identify the novel biomarkers associated with oral cancer development.

RESULTS

By genome-wide RNA-seq of tongue samples (3 mice per group), we identified changes in transcripts that mediate alcohol metabolism and oxidative stress (Aldh2, Aldh1a3, Adh1, Adh7, and Cyp2a5) in mice treated with 4-NQO followed by ethanol (4-NQO/EtOH) as compared to the vehicle control/untreated (V.C./Untr.) samples. We measured major, global increases in specific histone acetylation and methylation epigenetic marks (H3K27ac, H3K9/14ac, H3K27me3, and H3K9me3) in the oral cavities of V.C./EtOH, 4-NQO/Untr., and 4-NQO/EtOH treatment groups compared to the V.C./Untr. group. We detected changes in histone epigenetic marks near regulatory regions of genes involved in ethanol metabolism by chromatin immunoprecipitation. For instance, the Aldh2 promoter showed increased H3K27me3 marks, and Aldh2 mRNA levels were reduced by 10-fold in 4NQO/EtOH versus V.C./Untr. tongue samples. 4-NQO/EtOH treatment also caused increases in markers of oxidative stress, including 4-HNE, MCT4/SLC16a3, and TOM20, as measured by immunohistochemistry.

CONCLUSIONS

We delineate a mechanism by which 4-NQO and ethanol can regulate gene expression during the development of HNSCC and suggest that histone epigenetic marks and oxidative stress markers could be the novel biomarkers and targets for the prevention of HNSCC.

An enhancer-blocking element regulates the cell-specific expression of alcohol dehydrogenase 7

The class IV alcohol dehydrogenase gene ADH7 encodes an enzyme that is involved in ethanol and retinol metabolism. ADH7 is expressed mainly in the upper gastrointestinal tract and not in the liver, the major site of expression of the other closely related ADHs. We identified an intergenic sequence (iA1C), located between ADH7 and ADH1C, that has enhancer-blocking activity in liver-derived HepG2 cells that do not express their endogenous ADH7. This enhancer blocking function was cell- and position-dependent, with no activity seen in CP-A esophageal cells that express ADH7 endogenously. iA1C function was not specific to the ADH enhancers; it had a similar cell-specific effect on the SV40 enhancer. The CCCTC-binding factor (CTCF), an insulator binding protein, bound iA1C in HepG2 cells but not in CP-A cells. Our results suggest that in liver-derived cells, iA1C blocks the effects of ADH enhancers and thereby contributes to the cell specificity of ADH7 expression.

Single-nucleotide polymorphisms interact to affect ADH7 transcription

BACKGROUND

The class IV alcohol dehydrogenase (ADH7, μ-ADH, σ-ADH) is important in the metabolism of ethanol and retinol. ADH7 is the only ADH not expressed in liver, instead being expressed mainly in the upper gastrointestinal tract. Genome-wide studies have identified significant associations between single-nucleotide polymorphisms in ADH7 and alcoholism and cancer, but the causative variants have not been identified.

METHODS

In vitro studies of gene expression by transient transfection into cell lines that express endogenous ADH7 (CP-A cells) and that do not (HepG2 cells).

RESULTS

We have identified transcriptional regulatory elements of ADH7 and observed differences in the effects of variants on gene expression in CP-A cells and HepG2 cells. Two haplotypes of the proximal promoter that differ in a single nucleotide at rs2851028, A7P-G and A7P-A, have different transcriptional activities. There is an interaction between variants farther upstream and these proximal variants: Upstream regulatory sequences generally showed a greater increase or smaller reduction in activity when combined with the A7P-A promoter than with the A7P-G promoter. A sequence located 12.5-kb upstream (7P10) can function as an enhancer. In CP-A cells, both haplotypes of 7P10 increased A7P-A activity by 2.5-fold while having only 1.2-fold effect on A7P-G. In HepG2 cells, the 7P10-TTT haplotype had no effect on the A7P-A promoter but decreased A7P-G promoter activity by 50%, whereas the CTT haplotype increased A7P-A activity by 50%, but had no effect on A7P-G.

CONCLUSIONS

These complex interactions indicate that the effects of variants in the ADH7 regulatory elements depend on both sequence and cellular context and should be considered in interpretation of the association of variants with alcoholism and cancer.

Risk genes in head and neck cancer: a systematic review and meta-analysis of last 5 years

The aim of this work was to identify risk genes related to the development and progression of squamous cell carcinoma head and neck (SCCHN) and do a meta-analysis of available estimates. Eligible gene/polymorphism studies were identified by electronic searches. Individual participant data of 8540 patients with HNC and 9844 controls from 19 genetic studies were analyzed, yielding adjusted (tobacco, gender, age and alcohol) odds ratios (OR) and 95% confidence intervals (CIs) comparing cases with controls. A meta-analysis was done on the studies that applied fixed and random models. People have an increase of polymorphism expression related to inflammation (NFKB1-294-ATTG, TNFα308-A2A2/A2A1, and TNFβ252- B2B2/B2B1) or carcinogenic metabolism (GSTM1 null, and CYP1A1 m1/m1), representative of malignancy development. Furthermore, the increased expression of genes associated with the stabilization and repair of the cellular (OGG1-Asp267Asn, Ser279Gly Ile253Phe, 1578A>T, 1582C>T Ala399Glu (1542C>A) 1582insG 1543_1544delCT), and genes associated with the regulation of proliferation, apoptosis or tumor survival (miRNA499-CT/CC, CRYABC802G-CG/GG) are considered as risk factors. In this scheme, only the polymorphisms of ADH7A92G-GG and DEC1606-T/C genes are protective against malignancy transformation. The TP53, GSTM1 and CYPA1genes have been evaluated in more than one study and analyzed for homogeneity in each genotype. The meta-analysis showed no significant association between different allelic variants of Arg72Pro rs1042522 and SCCHN risk. In a model of tumorigenesis, an increased risk of SCCHN is associated with DNA repair and DNA stabilization genes. In addition, the polymorphisms involved in inflammation and carcinogenic metabolism processes represent an increased risk of SCCHN.

Retinoid metabolism is altered in human and mouse cicatricial alopecia

C57BL/6 mice develop dermatitis and scarring alopecia resembling human cicatricial alopecias (CA), particularly the central centrifugal cicatricial alopecia (CCCA) type. To evaluate the role of retinoids in CA, expression of retinoid metabolism components were examined in these mice with mild, moderate, or severe CA compared to hair cycle matched mice with no disease. Two feeding studies were performed with dams fed either NIH 31 diet (study 1) or AIN93G diet (study 2). Adult mice were fed AIN93M diet with 4 (recommended), 28, or 56 IU vitamin A/g diet. Feeding the AIN93M diet to adults increased CA frequency over NIH 31 fed mice. Increased follicular dystrophy was seen in study 1 and increased dermal scars in study 2 in mice fed the 28 IU diet. These results indicate that retinoid metabolism is altered in CA in C57BL/6J mice that require precise levels of dietary vitamin A. Human patients with CCCA, pseudopelade (end stage scarring), and controls with no alopecia were also studied. Many retinoid metabolism proteins were increased in mild CCCA, but were undetectable in pseudopelade. Studies to determine if these dietary alterations in retinoid metabolism seen in C57BL/6J mice are also involved in different types of human CA are needed.

Single nucleotide polymorphisms of mucosa-associated lymphoid tissue 1 in oral carcinoma cells and gingival fibroblasts

Oral carcinoma patients with inactivation of mucosa-associated lymphoid tissue 1 (MALT1) expression worsen their prognoses. Although the genetic mutation could be responsible for the inactivation, no information is available at present. In the present study, genomic DNA of oral carcinoma cells (HOC313, TSU, HSC2, HSC3, KOSC2, KOSC3, SCCKN, OSC19, Ca9.22, and Ho1u1 cells) and normal gingival fibroblasts (GF12 cells) derived from a Japanese population were amplified by polymerase chain reaction using primer sets spanning MALT1 exons, and nucleotide substitutions were analyzed by the single strand conformation polymorphism analysis. The substitutions were commonly observed in all cells, which express MALT1 at various levels. The substitutions at exons 1 and 9 were located at the 5' untranslated region and replaced (336)Asp to Asn, respectively, and others were positioned at the introns. Among the intronic substitutions, four were matched with the single nucleotide polymorphisms (SNPs) registered at the database. Since all cells were derived from a Japanese population, all substitutions detected are the SNPs. Absence of the carcinoma cell-specific mutation suggests that the inactivation of MALT1 expression but not the mutation promotes oral carcinoma progression.

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

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

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.

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

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