Cancer screening of upper aerodigestive tract in Japanese alcoholics with reference to drinking and smoking habits and aldehyde dehydrogenase-2 genotype

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.

Impact of endoscopic surveillance on mortality of metachronous esophageal and head and neck cancer after esophageal endoscopic resection

BACKGROUND AND AIM

As more superficial esophageal cancer (EC) patients are being treated with endoscopic resection (ER), it is important to understand the outcomes, including survival data, of patients who develop metachronous EC and head and neck cancer (HNC). We aimed to evaluate the long-term surveillance and survival outcomes of metachronous EC and HNC after esophageal ER.

METHODS

This study included 627 patients who underwent ER of superficial esophageal squamous cell carcinoma from 2008 to 2016 and were generally followed by annual or biannual esophagogastroduodenoscopy up to 2019 at Osaka International Cancer Institute. Data on metachronous cancer development and causes of death were collected from an integrated database of hospital-based cancer registry and Vital Statistics of Japan.

RESULTS

During a median (range) follow-up period of 67.4 (3.8-142.7) months, 230 patients (36.7%) developed 500 metachronous ECs and 126 patients (20.1%) developed 239 metachronous HNCs, post-ER of index EC. The 3-year, 5-year, and 7-year cumulative incidences were 25.8%, 36.0%, and 43.6% for metachronous EC and 10.9%, 16.0%, and 26.9% for metachronous HNC, respectively. No patients died of metachronous EC, and only seven patients (1.1%) died of metachronous HNC. The 3-year, 5-year, and 7-year disease-specific survival rates were 99.8%, 99.6%, and 98.6%, respectively.

CONCLUSIONS

The incidences of metachronous EC and HNC increase with time over 5 years after esophageal ER; therefore, surveillance endoscopy should be continued over 5 years. Endoscopic surveillance is useful for survivors after esophageal ER given the high incidence and extremely low mortality of metachronous EC and HNC.

Validity of endoscopic resection for clinically diagnosed T1a-MM/T1b-SM1 N0 M0 esophageal squamous cell carcinoma

BACKGROUND

Previous guidelines have not described clear recommendations for performing endoscopic resection (ER) of T1a-muscularis mucosa (MM)/T1b-submucosal (SM1) cancers that have invaded ≤ 200 μm because these are considered to have a non-negligible risk of metastasis based on previous analyses of pathologically diagnosed (p)MM/SM1 cancers. Considering that the indication for ER is determined based on a clinical diagnosis, the applicability of ER should be investigated in clinical (c)MM/SM1 but not pMM/SM1 cancers. This study aimed to evaluate validity of ER for cMM/SM1 cancers.

METHODS

In total, 175 cMM/SM1 esophageal squamous cell carcinoma cases that were endoscopically or surgically resected between January 2008 and December 2018 were identified from a prospectively maintained database. We histologically evaluated resected specimens and divided them into low- (n = 92) and high-risk (n = 83) cancers for metastasis.

RESULTS

Univariate analysis showed that longer tumor length and larger circumferential extent were significantly correlated with high-risk cancer (P < 0.001). Multivariate analysis showed that tumor circumference was an independent predictor of high-risk cancer (P = 0.036). The proportion of low-risk cancers among cases with ≤ 3/4, > 3/4 and < 1, and whole circumferential extent were 59, 17, and 14%, respectively, and the post-ER stricture rates of these groups were 12, 33, and 100%, respectively.

CONCLUSION

ER is the first-line treatment for cMM/SM1 cancers with ≤ 3/4 circumferential extent considering that 59% of cMM/SM1 cancers were low-risk cancers for which ER is mostly curative. ER is not recommended for whole circumferential cMM/SM1 cancers given the low proportion of low-risk cancers and the high risk of stricture after ER.

Excessive risk of second-cancer incidence and cancer mortality in patients with esophageal cancer

BACKGROUND

Second primary cancers have impact on survival in patients who achieved cure for the first esophageal cancer. We, therefore, assessed the risk of incidence and mortality for second primary cancer by calculating standardized incidence ratio (SIR) and standardized mortality ratio (SMR) in patients with superficial or localized esophageal cancer without lymph node metastases as the first cancer (index cancer).

METHODS

Data on cancer development and subsequent causes of deaths were collected from integrated database of the Osaka Cancer Registry and the Vital Statistics of Japan. Records with information on patients with index esophageal cancer diagnosed between 2004 and 2013 were extracted from the database. Then, SIR and SMR for second primary cancers that developed in other organ were calculated with the reference to the general population during the same period. All probability values are two-tailed.

RESULTS

Of 473,784 case records, 3022 cases of patients with index esophageal cancer were identified. Significantly higher SMRs/SIRs for cancers in mouth/pharynx, larynx, pancreas, and leukemia were confirmed with the values of 10.78/16.16, 8.56/6.44, 2.33/2.31, and 3.96/4.42, respectively. Significantly, higher SIRs for stomach, lung, and skin cancers were confirmed with the values of 2.84, 2.36, and 3.38, respectively, while SMRs were not significantly higher in these cancers.

CONCLUSIONS

Significantly higher risks for mouth/pharynx, larynx, pancreas, and leukemia as second cancers were clarified. Careful surveillance for these cancers is required for esophageal cancer patients.

Association Between the Aldehyde Dehydrogenase-2 rs671 G>A Polymorphism and Head and Neck Cancer Susceptibility: A Meta-Analysis in East Asians

BACKGROUND

Aldehyde dehydrogenase-2 (ALDH2) plays an important role in the alcohol detoxification and acetaldehyde metabolism. Published studies have demonstrated some inconsistent associations between ALDH2 rs671 G>A polymorphism and head and neck cancer (HNC) risk.

METHODS

A meta-analysis was performed to provide pooled data on the association between the ALDH2 rs671 G>A polymorphism and HNC risk. Electronic databases were searched to identify relevant studies. Odds ratios and 95% confidence intervals (CIs) were used to examine the pooled effect size of each genetic model. In addition, heterogeneity test, accumulative analysis, sensitivity analysis, and publication bias were conducted to test the statistical power.

RESULTS

Thirteen publications (14 independent case-control studies) involving 10,939 subjects were selected. The stratified analysis indicated that both light/moderated drinking (e.g., GA vs. GG: OR = 1.47, 95% CI = 1.16 to 1.86, p < 0.01, I²  = 81.1%) and heavy drinking would increase HNC risk with rs671 G>A mutation (e.g., GA vs. GG: OR = 2.30, 95% CI = 1.11 to 4.77, p = 0.03, I²  = 81.9%).

CONCLUSIONS

In summary, this meta-analysis suggested that the ALDH2 rs671 G>A polymorphism may play an important synergistic effect in the pathogenesis of HNC development in East Asians.

Protective effects of Alda-1, an ALDH2 activator, on alcohol-derived DNA damage in the esophagus of human ALDH2*2 (Glu504Lys) knock-in mice

Alcohol consumption is the key risk factor for the development of esophageal squamous cell carcinoma (ESCC), and acetaldehyde, a metabolite of alcohol, is an alcohol-derived major carcinogen that causes DNA damage. Aldehyde dehydrogenase2 (ALDH2) is an enzyme that detoxifies acetaldehyde, and its activity is reduced by ALDH2 gene polymorphism. Reduction in ALDH2 activity increases blood, salivary and breath acetaldehyde levels after alcohol intake, and it is deeply associated with the development of ESCC. Heavy alcohol consumption in individuals with ALDH2 gene polymorphism significantly elevates the risk of ESCC; however, effective prevention has not been established yet. In this study, we investigated the protective effects of Alda-1, a small molecule ALDH2 activator, on alcohol-mediated esophageal DNA damage. Here, we generated novel genetically engineered knock-in mice that express the human ALDH2*1 (wild-type allele) or ALDH2*2 gene (mutant allele). Those mice were crossed, and human ALDH2*1/*1, ALDH2*1/*2 and ALDH2*2/*2 knock-in mice were established. They were given 10% ethanol for 7 days in the presence or absence of Alda-1, and we measured the levels of esophageal DNA damage, represented by DNA adduct (N²-ethylidene-2′-deoxyguanosine). Alda-1 significantly increased hepatic ALDH2 activity both in human ALDH2*1/*2 and/or ALDH2*2/*2 knock-in mice and reduced esophageal DNA damage levels after alcohol drinking. Conversely, cyanamide, an ALDH2-inhibitor, significantly exacerbated esophageal DNA adduct level in C57BL/6N mice induced by alcohol drinking. These results indicate the protective effects of ALDH2 activation by Alda-1 on esophageal DNA damage levels in individuals with ALDH2 gene polymorphism, providing a new insight into acetaldehyde-mediated esophageal carcinogenesis and prevention.

High incidence of head and neck cancers after endoscopic resection for esophageal cancer in younger patients

BACKGROUND

Second cancers in patients with esophageal cancer (EC) are common and have a poor prognosis. We evaluated the incidence of second cancers at different sites by patients' ages when their index ECs were diagnosed.

METHODS

This study included patients who underwent endoscopic resection for superficial EC at our hospital between September 1994 and September 2011. Patients' data, including sex, age at diagnosis, sequence of cancer incidence, cancer histology, and cancer site, were extracted from the cancer registry.

RESULTS

Of 544 patients, 255 developed second cancers. Simultaneous head and neck cancers (HNCs) and other organ cancers (OCs) were, respectively, present in 15% (80/544) and 9.6% (52/544) of patients; and 30% (162/544) developed metachronous second cancers over a median follow-up period of 79.5 months (range 2-120), including 44 metachronous HNCs and 70 OCs. The cumulative incidence of metachronous HNCs was significantly higher in younger patients (< 60 years) than in older patients (≥ 60 years; P = 0.001), whereas the cumulative incidence of OCs was significantly higher in older patients than in younger patients (P = 0.03).

CONCLUSIONS

The incidence of second HNC after index EC was higher in younger-onset patients than in older-onset patients. We suggest that younger patients with EC should be carefully monitored for early detection of second HNC.

Impact of age at diagnosis of head and neck cancer on incidence of metachronous cancer

Background

Metachronous cancer in patients with head and neck cancer (HNC) is common and is associated with a poor prognosis. We aimed to evaluate the incidence of metachronous cancer at different sites according to age at diagnosis of index HNC.

Methods

We collected data on 2011 patients with oral cancer, oropharynx cancer, hypopharyngeal cancer, and laryngeal cancer as index cancers using the Osaka International Cancer Institute Cancer Registry database between 2005 and 2016. Among these, we analyzed 1953 patients after excluding 5 patients who were not followed-up and 53 patients with simultaneous multiple index cancers. We evaluated the cumulative incidence of metachronous cancer in the esophagus, lung, and other sites according to age at diagnosis of the index HNC using the Kaplan–Meier method. Multivariate logistic regression analysis was performed to identify factors that influenced the incidence of metachronous cancers following HNC.

Results

The cumulative incidence of metachronous esophageal cancer in young patients (< 65 years) was significantly higher than that in old patients (≥ 65 years) (12.1% vs 8.5% at 5 years, and 16.5% vs 11.2% at 10 years; p = 0.015). On the other hand, the cumulative incidence of the other cancers in young patients was significantly lower than that in old patients (7.8% vs 12.2% at 5 years, and 13.9% vs 15.3% at 10 years; p = 0.017). The cumulative incidence of lung cancer was not significance according to age at diagnosis of the index HNC. In the multivariate analysis, histological type (squamous cell carcinoma) and lesion location (hypopharynx and larynx) were independently associated with metachronous cancers. Moreover, age at diagnosis of the index HNC (< 65 years), histological type (squamous cell carcinoma) and lesion location (hypopharynx) were significant predictors of metachronous esophageal cancer incidence and lesion location (hypopharynx) was a significant predictor of metachronous lung cancer incidence.

Conclusion

Risk stratification of metachronous cancers with age and other predictors may help to properly manage patients with HNC.

Trial registration

The present study is a non-intervention trial.

Endoscopic Screening in Asian Countries Is Associated With Reduced Gastric Cancer Mortality: A Meta-analysis and Systematic Review

BACKGROUND & AIMS

It is not clear how endoscopic screening for gastric cancer affects incidence or mortality. We performed a systematic review and meta-analysis to evaluate the relationship between endoscopic screening for gastric cancer and mortality and incidence.

METHODS

We conducted a systematic search of PubMed and EMBASE for published cohort and case-control studies of adults without gastric cancer who underwent endoscopic screening at least once that included a comparator and reported outcomes of mortality or incidence through March 8, 2018. Two investigators independently reviewed the included studies and extracted relevant data. The effect estimate of interest was the relative risk (RR). We used a random effects model to combine RRs and 95% confidence intervals (Cis).

RESULTS

Our final analysis included 6 cohort studies and 4 nested case-control studies comprising 342,013 individuals, all from Asia. The combined result (RR, 0.60; 95% CI, 0.49-0.73) indicated that endoscopic screening was associated with a 40% RR reduction in gastric cancer mortality. We did not observe an association between endoscopic screening and incidence (RR, 1.14; 95% CI, 0.93-1.40). Subgroup analysis showed significant reductions in gastric cancer mortality after endoscopic screening compared with no screening (RR, 0.58; 95% CI, 0.48-0.70) or radiographic screening (RR, 0.33; 95% CI, 0.12-0.91). However, endoscopic screening did not significantly reduce mortality compared with expected deaths (RR, 0.67; 95% CI, 0.38-1.16).

CONCLUSIONS

In a systematic review and meta-analysis, we found that endoscopic screening may reduce the risk of death from gastric cancer and not affect incidence in Asian countries. Population-based prospective cohort studies are warranted to confirm our findings.

Local Acetaldehyde-An Essential Role in Alcohol-Related Upper Gastrointestinal Tract Carcinogenesis

The resident microbiome plays a key role in exposure of the upper gastrointestinal (GI) tract mucosa to acetaldehyde (ACH), a carcinogenic metabolite of ethanol. Poor oral health is a significant risk factor for oral and esophageal carcinogenesis and is characterized by a dysbiotic microbiome. Dysbiosis leads to increased growth of opportunistic pathogens (such as Candida yeasts) and may cause an up to 100% increase in the local ACH production, which is further modified by organ-specific expression and gene polymorphisms of ethanol-metabolizing and ACH-metabolizing enzymes. A point mutation in the aldehyde dehydrogenase 2 gene has randomized millions of alcohol consumers to markedly increased local ACH exposure via saliva and gastric juice, which is associated with a manifold risk for upper GI tract cancers. This human cancer model proves conclusively the causal relationship between ACH and upper GI tract carcinogenesis and provides novel possibilities for the quantitative assessment of ACH carcinogenicity in the human oropharynx. ACH formed from ethanol present in "non-alcoholic" beverages, fermented food, or added during food preparation forms a significant epidemiologic bias in cancer epidemiology. The same also concerns "free" ACH present in mutagenic concentrations in multiple beverages and foodstuffs. Local exposure to ACH is cumulative and can be reduced markedly both at the population and individual level. At best, a person would never consume tobacco, alcohol, or both. However, even smoking cessation and moderation of alcohol consumption are associated with a marked decrease in local ACH exposure and cancer risk, especially among established risk groups.

Protective role of ALDH2 against acetaldehyde-derived DNA damage in oesophageal squamous epithelium

Acetaldehyde is an ethanol-derived definite carcinogen that causes oesophageal squamous cell carcinoma (ESCC). Aldehyde dehydrogenase 2 (ALDH2) is a key enzyme that eliminates acetaldehyde, and impairment of ALDH2 increases the risk of ESCC. ALDH2 is produced in various tissues including the liver, heart, and kidney, but the generation and functional roles of ALDH2 in the oesophagus remain elusive. Here, we report that ethanol drinking increased ALDH2 production in the oesophagus of wild-type mice. Notably, levels of acetaldehyde-derived DNA damage represented by N²-ethylidene-2′-deoxyguanosine were higher in the oesophagus of Aldh2-knockout mice than in wild-type mice upon ethanol consumption. In vitro experiments revealed that acetaldehyde induced ALDH2 production in both mouse and human oesophageal keratinocytes. Furthermore, the N²-ethylidene-2′-deoxyguanosine levels increased in both Aldh2-knockout mouse keratinocytes and ALDH2-knockdown human keratinocytes treated with acetaldehyde. Conversely, forced production of ALDH2 sharply diminished the N²-ethylidene-2′-deoxyguanosine levels. Our findings provide new insight into the preventive role of oesophageal ALDH2 against acetaldehyde-derived DNA damage.

Continuous taurocholic acid exposure promotes esophageal squamous cell carcinoma progression due to reduced cell loss resulting from enhanced vascular development

BACKGROUND

Refluxogenic effects of smoking and alcohol abuse may be related to the risk of esophageal squamous cell carcinoma (ESCC). The present study attempts to clarify the effects of continuous taurocholic acid (TCA) exposure, which is neither mutagenic nor genotoxic, on ESCC progression.

METHODS

A squamous carcinoma cell line (ESCC-DR) was established from a tumor induced in a rat model of gastroduodenal reflux. ESCC-DR cells were incubated with 2 mM TCA for ≥2 months. The effects of continuous TCA exposure were evaluated in vitro on cell morphology, growth, and invasion and in vivo on xenograft tumor growth in nude mice. Moreover, the mean level of secreted transforming growth factor (TGF)-β1 and vascular endothelial growth factor (VEGF) proteins in cell culture supernatants and mRNA synthesis of TGF-β1 and VEGF-A of ESCC cells were measured. The angiogenic potential was further examined by a migration assay using human umbilical vein endothelial cells (HUVECs).

RESULTS

Continuous TCA exposure induced marked formation of filopodia in vitro. Expression levels of angiogenic factors were significantly higher in the cells treated with TCA than in control cells. Tumor xenografts derived from cells pre-exposed to TCA were larger and more vascularized than those derived from control cells. In addition, TCA exposure increased HUVEC migration.

CONCLUSION

Continuous TCA exposure enhanced ESCC progression due to reduced cell loss in vivo. Cell loss was inhibited by TCA-induced vascular endothelial cell migration, which was mediated by TGF-β1 and VEGF-A released from ESCC cells.

Screening for oesophageal cancer

Oesophageal cancer is a global health problem with high mortality due to the advanced nature of the disease at presentation; therefore, detection at an early stage significantly improves outcome. Oesophageal squamous-cell cancer is preceded by dysplasia and oesophageal adenocarcinoma is preceded by Barrett's oesophagus, which progresses to cancer via intermediate dysplastic stages. Screening to detect these preneoplastic lesions has the potential to substantially reduce mortality and morbidity. However, the risks and benefits of such programmes to individuals and to society need to be carefully weighed. Endoscopic screening is invasive, costly and error prone owing to sampling bias and the subjective diagnosis of dysplasia. Non-endoscopic cell-sampling methods are less invasive and more cost effective than endoscopy, but the sensitivity and specificity of cytological assessment of atypia has been disappointing. The use of biomarkers to analyse samples collected using pan-oesophageal cell-collection devices may improve diagnostic accuracy; however, further work is required to confirm this. The psychological and economic implications of screening as well as the feasibility of implementing such programmes must also be considered.

An Integrative Approach for Studying the Etiology of Alcoholism and Other Addictions

Studies of alcoholism etiology often focus on genetic or psy-chosocial approaches, but not both. Greater understanding of the etiology of alcohol, tobacco and other addictions will come from integration of these research traditions. A research approach is outlined to test three models for the etiology of addictions — behavioral undercontrol, pharmacologic vulnerability, negative affect regulation — addressing key questions including (i) mediators of genetic effects, (ii) genotype-environment correlation effects, (iii) genotype x environment interaction effects, (iv) the developmental unfolding of genetic and environmental effects, (v) subtyping including identification of distinct trajectories of substance involvement, (vi) identification of individual genes that contribute to risk, and (vii) the consequences of excessive use. By using coordinated research designs, including prospective assessment of adolescent twins and their siblings and parents; of adult substance dependent and control twins and their MZ and DZ cotwins, the spouses of these pairs, and their adolescent offspring; and of regular families; by selecting for gene-mapping approaches sibships screened for extreme concordance or discordance on quantitative indices of substance use; and by using experimental (drug challenge) as well as survey approaches, a number of key questions concerning addiction etiology can be addressed. We discuss complementary strengths and weaknesses of different sampling strategies, as well as methods to implement such an integrated approach illustrated for the study of alcoholism etiology. A coordinated program of twin and family studies will allow a comprehensive dissection of the interplay of genetic and environmental risk-factors in the etiology of alcoholism and other addictions.

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.

Unrecorded consumption, quality of alcohol and health consequences

ISSUES

This contribution aims to examine systematically the evidence on the impact of the quality of unrecorded alcohol products on health consequences.

APPROACH

Systematic computer assisted review of the literature.

KEY FINDINGS

There are a number of pathways related to alcohol quality that may lead to acute or chronic health problems. The following constituents and contaminants of alcoholic beverages were identified as likely contributors to these problems: (i) toxic metals (e.g. lead) from contaminated water sources or unsuitable distillation equipment; (ii) volatile constituents, such as acetaldehyde or higher alcohols, which may be produced in significant amounts due to faults in production technology or microbiological spoilage; (iii) ethyl carbamate (urethane), a carcinogenic contaminant with major occurrence in certain fruit and sugarcane spirits; (iv) biologically active flavour compounds (e.g. coumarin in cosmetics used as non-beverage alcohol); (v) toxic compounds used to denature alcohol (e.g. methanol or diethyl phthalate). In addition, the often higher ethanol content may have detrimental health effects. These pathways should not be assumed as present for all subcategories of unrecorded alcohol, but are more relevant to certain types and geographic regions.

IMPLICATIONS

A health impact of unrecorded alcohol over and above the effect of ethanol cannot be excluded. More research is urgently needed, especially with respect to liver disease and alcohol poisoning as endpoints.

CONCLUSION

A feasible approach for new research on the effects of unrecorded alcohol could be based on a representative sample from low socioeconomic regions with high prevalence of unrecorded consumption.

Alcohol drinking, cigarette smoking, and the development of squamous cell carcinoma of the esophagus: epidemiology, clinical findings, and prevention

Both cigarette smoking and alcohol drinking are well-established risk factors for esophageal squamous cell carcinoma (ESCC), and the relationship of dose to cancer risk has already been described. Furthermore, the synergistic effect of these two factors has been reported. Our case-control study revealed the odds ratio of ESCC to be 50.1 for those who were both heavy smokers and heavy drinkers in comparison to people who neither drank nor smoked. In patients with ESCC, head and neck cancers as well as dysplastic lesions are frequently observed. Heavy smoking and heavy drinking are closely related to such multicentric carcinogenesis events in the upper aerodigestive tract (UADT), including the esophagus and head andneck region. Polymorphisms in acetaldehyde dehydrogenase 2 (ALDH2) are reported to be a key event in deciding individual susceptibility to UADT cancer. Patients with inactive ALDH2, in whom facial flushing is usually observed after the drinking of alcohol, are at high risk for ESCC as well as multiple UADT cancers. For the early detection of the disease, effective follow up using endoscopy with Lugol staining or narrow band imaging endoscopy is strongly recommended for high-risk populations, such as smokers, heavy drinkers, people with experience of flushing after the drinking of alcohol, and patients with UADT cancer.

Initiation of malignancy by duodenal contents reflux and the role of ezrin in developing esophageal squamous cell carcinoma

Gastroesophageal reflux has recently been implicated as a causative factor in upper aerodigestive tract carcinogenesis. Esophageal squamous cell carcinomas (ESCCs) have developed in duodenal-content reflux animals without any known carcinogen present. We established a cell line, designated ESCC-DR, from a thoracic metastatic tumor in a reflux animal. To gain insight into the genomic alterations associated with duodenal content reflux-induced carcinogenesis, we first performed comparative genomic hybridization using an Agilent rat 244K array in ESCC-DR and identified many chromosomal gains and losses. Of the many genes identified, we detected an interesting ezrin amplicon that has been recently reported in human ESCC. Ezrin, which cross-links the cytoskeleton and plasma membrane, is involved in the growth and metastatic potential of cancer cells. Overexpression of ezrin protein in ESCC-DR was confirmed by Western blotting. We also compared ezrin protein expression levels and patterns in hyperplastic, dysplastic, ESCC, and metastatic sites developed in two distinct reflux models using immunohistochemistry. Immunohistochemical staining of ezrin revealed overexpression in the nucleus, and the cytoplasm as well as plasma membrane of ESCC cells. Phosphorylated ERM (ezrin, radixin, moesin) was expressed at the leading edge, or invasive front, of larger metastatic sites. Taken together, duodenal reflux has a great potential for initiating malignancy, and thus likely plays a role in development of ESCC. Ezrin probably influences the growth and invasiveness of ESCC cells, and phosphorylation is only required in metastatic behavior of tumor cells at the leading edge and invasive front.

Carcinogenicity of acetaldehyde in alcoholic beverages: risk assessment outside ethanol metabolism

AIMS

In addition to being produced in ethanol metabolism, acetaldehyde occurs naturally in alcoholic beverages. Limited epidemiological evidence points to acetaldehyde as an independent risk factor for cancer during alcohol consumption, in addition to the effects of ethanol. This study aims to estimate human exposure to acetaldehyde from alcoholic beverages and provide a quantitative risk assessment.

METHODS

The human dietary intake of acetaldehyde via alcoholic beverages was estimated based on World Health Organization (WHO) consumption data and literature on the acetaldehyde contents of different beverage groups (beer, wine, spirits and unrecorded alcohol). The risk assessment was conducted using the European Food Safety Authority's margin of exposure (MOE) approach with benchmark doses obtained from dose-response modelling of animal experiments. Life-time cancer risk was calculated using the T25 dose descriptor.

RESULTS

The average exposure to acetaldehyde from alcoholic beverages was estimated at 0.112 mg/kg body weight/day. The MOE was calculated to be 498, and the life-time cancer risk at 7.6 in 10,000. Higher risk may exist for people exposed to high acetaldehyde contaminations, as we have found in certain unrecorded alcohol beverages in Guatemala and Russia, for which we have demonstrated possible exposure scenarios, with risks in the range of 1 in 1000.

CONCLUSIONS

The life-time cancer risks for acetaldehyde from alcoholic beverages greatly exceed the usual limits for cancer risks from the environment set between 1 : 10,000 and 1 : 1,000,000. Alcohol consumption has thus been identified as a direct source of acetaldehyde exposure, which in conjunction with other sources (food flavourings, tobacco) results in a magnitude of risk requiring intervention. An initial public health measure could be to reduce the acetaldehyde content in alcoholic beverages as low as technologically possible, and to restrict its use as a food flavour additive.

Effect of alcohol consumption, cigarette smoking and flushing response on esophageal cancer risk: a population-based cohort study (JPHC study)

We examined the effect of alcohol consumption, cigarette smoking and flushing response on esophageal squamous cell carcinoma (ESCC) in a large-scale population-based cohort study. 44,970 middle-aged and older Japanese men were followed. A total of 215 cases of ESCC were newly diagnosed. Alcohol consumption and cigarette smoking are strongly associated with the incidence of ESCC. Heavy alcohol consumption increased the risk of ESCC especially among heavy smokers with the flushing response (HR = 3.41, 95% CI = 2.10-5.51). Strong effect modification was detected in heavy smokers. Our results suggest that heavy alcohol consumption together with heavy smoking may increase the risk of ESCC particularly in individuals with the flushing response.

Aldehyde dehydrogenase 2 and head and neck cancer: a meta-analysis implementing a Mendelian randomization approach

Alcohol drinking at high doses is a risk factor for head and neck cancer, and exposure to acetaldehyde, the principle metabolite of alcohol, is supposed to account for the increased risk. Individuals homozygous for the 2 variant allele of aldehyde dehydrogenase 2 (ALDH2) are unable to metabolize acetaldehyde, which prevents them from alcohol drinking, whereas 1 2 have 6-fold higher blood acetaldehyde concentration postalcohol consumption with respect to 1 1. According to the concept of Mendelian randomization, because this polymorphism is distributed randomly during gamete formation, its association with head and neck cancer should be not confounded by smoking. We carried out a meta-analysis of ALDH2 and head and neck cancer searching for relevant studies on Medline and Embase up to January 31, 2008, and investigated the consistency between the expected odds ratio (OR) among drinkers from the largest pooled analysis among never smokers and the observed OR from this meta-analysis by an interaction test. Six studies were selected (945 cases, 2,917 controls). The OR of head and neck cancer among 2 2 was 0.53 [95% confidence interval (95% CI), 0.28-1.00] relative to 1 1 and 1.83 (95% CI, 1.21-2.77) among 1 2. The expected OR for head and neck cancer due to alcohol intake among 1 1 was 1.38 (95% CI, 0.88-2.17) and the observed OR among 1 1 compared with 2*2 from this meta-analysis was 1.88 (95% CI, 1.00-3.57; P for interaction = 0.43). Besides showing the effectiveness of the Mendelian randomization approach, these findings support the theory that alcohol increases head and neck cancer risk through the carcinogenic action of acetaldehyde.

Increased formation of gastric N(2)-ethylidene-2'-deoxyguanosine DNA adducts in aldehyde dehydrogenase-2 knockout mice treated with ethanol

We analyzed an acetaldehyde-derived DNA adduct, N(2)-ethylidene-2'-deoxyguanosine (N(2)-Eti-dG) in stomach DNA of aldehyde dehydrogenase (Aldh)-2-knockout mice that were fed with alcohol to determine effects of alcohol consumption and Aldh2 genotype on the level of DNA damage in stomach. Aldh2-active(+/+), heterozygote(+/-) and knockout(-/-) mice were fed 20% ethanol for 5 weeks, then the level of N(2)-Eti-dG in stomach was determined by liquid chromatography tandem mass spectrometry. The average N(2)-Eti-dG level in DNA from untreated mice was not significantly different among Aldh2 genotypes (2.0-3.1 adducts/10(7) bases), however, the average N(2)-Eti-dG level in DNA from ethanol-treated mice was 4.8+/-2.6 adducts/10(7) bases in Aldh2+/+ mice, 7.9+/-1.1 adducts/10(7) bases in Aldh2+/- mice, and 48.6+/-12.0 adducts/10(7) bases in Aldh2-/- mice, respectively. Our data clearly showed that alcohol drinking caused DNA damage in stomach, which was Aldh2 genotype-dependent in this experimental animal model. This result suggests that heavy-alcohol drinking and Aldh2 deficiency might be risk factors of stomach cancer.

Origin and dispersal of atypical aldehyde dehydrogenase ALDH2487Lys

The East Asian respond with a marked facial flushing and mild to moderate symptoms of intoxication after drinking the amounts of alcohol that has no detectable effect on European. The alcohol sensitivity in Orientals is due to a delayed oxidation of acetaldehyde by an atypical aldehyde dehydrogenase ALDH2487Lys, which is resulted from a structural mutation in gene ALDH2. The atypical ALDH2487Lys allele has been associated with various phenotypic statuses, such as protective against alcohol dependence and the risk of alcohol-related digestive tract cancers. Here, we have examined this SNP, adjacent four non-coding SNPs, and one downstream STRP on ALDH2 gene, in total of 1072 unrelated healthy individuals from 14 Chinese populations and 130 Indian individuals. Five major haplotypes based on five SNPs across the ALDH2 gene 40 kb were found in all East Asian populations. The frequencies of the ancestral haplotype GCCTG and the East Asian special haplotype GCCTA containing the atypical ALDH2487Lys allele were 44.8% and 14.9%, respectively. The frequency of the atypical ALDH2487Lys allele or the East Asian specific haplotype GCCTA is high in Yunnan, South coastal, east coastal of China, and decreased gradually toward inland China, West, Northwest and North China. Combined with demographic history in East Asian, our results showed that the presence of ALDH2487Lys allele in peripheral regions of China might be the results of historical migration events from China to these regions. The origin of ALDH2487Lys could be possibly traced back to ancient Pai-Yuei tribe in South China.

Analysis and estimates of the attributable risk for environmental and genetic risk factors in gastric cancer in a Chinese population

Development of gastric cancer is a multistage, multifactorial process. This study determined the population attributable risk for environmental and genetic risk factors in development of gastric cancer. A 1:1 cancer case-control study was undertaken in Nanjing, Jiangsu Province, China. A conditional-logistic regression model was used to determine environmental and genetic risk factors and calculate attributable risk (AR%) for each environmental and genetic risk factor in gastric cancer. In addition, the summary attributable risk (sAR) for all of the risk factors among 503 cases of gastric cancer patients and controls was determined. The environmental risk factors for gastric cancer in the Nanjing area were family history of tumor, consumption of pickled food, engorgement after hunger, irregular dietary habits, and lack of fruit intake. The genetic risk factors included the following genotypes: CYP2E1 wild, NAT2 M1 mutation, NAT2 slow-acetylators, XRCC1 194 mutation, MTHFR A1298C mutation, and IL-1B mutation. Combining environmental and genetic risk factors, sAR was 76.34%. Data suggest that genetic polymorphisms and environmental risk factors play concurrent roles in the development of gastric cancer. The results of this study indicate preventive strategies to avoid development of gastric cancer based on identified genetic polymorphisms and control of environmental risk factors.

Salivary acetaldehyde concentration according to alcoholic beverage consumed and aldehyde dehydrogenase-2 genotype

BACKGROUND

Acetaldehyde is suspected of playing a critical role in cancer development in the upper aerodigestive tract (UADT). The high salivary acetaldehyde levels after alcohol drinking are partly due to acetaldehyde production by oral bacteria. Some alcoholic beverages, especially Calvados and shochu, contain very high levels of acetaldehyde. Inactive heterozygous aldehyde dehydrogenase-2 (ALDH2) increases the risk of UADT cancer in drinkers.

METHODS

In a randomized cross-over design study, 19 healthy Japanese volunteers ingested 0.6 g ethanol/kg body weight in the form of 13% ethanol Calvados, 13% ethanol shochu, 13% ethanol red wine, and 5% ethanol beer under the fasting conditions at 3-week intervals. We monitored blood and salivary acetaldehyde concentrations immediately after drinking, and 30, 60, 90, 120, and 180 minutes after completion of drinking.

RESULTS

The acetaldehyde concentration of each beverage was: Calvados 0.60 mM (1.86 mM in 40% undiluted solution), shochu 0.60 mM (1.16 mM in 25% undiluted solution), red wine 0.25 mM, and beer 0.14 mM. The salivary acetaldehyde concentration immediately after drinking wine was significantly lower than the other beverages, and it was significantly lower immediately after drinking beer than Calvados. The acetaldehyde concentrations 30 to 180 minutes after drinking were unrelated to the beverage type. Throughout the observation period the salivary acetaldehyde concentrations were much higher than the blood acetaldehyde concentrations in all 12 active ALDH2 homozygotes (24 to 53 microM in saliva vs. 2 to 5 microM in blood) and in all 7 inactive ALDH2 heterozygotes (37 to 76 microM in saliva vs. 12 to 25 microM in blood), and they were 13 to 25 microM higher in the ALDH2 heterozygotes than in the ALDH2 homozygotes after adjusting for age, body weight, sex, smoking and drinking habits, and time since the last toothbrushing. The values after subtracting the blood acetaldehyde concentration from the salivary acetaldehyde concentration were also higher in the ALDH2 heterozygotes than in the ALDH2 homozygotes.

CONCLUSIONS

There are differences in exposure of the UADT to high salivary acetaldehyde concentrations according to the type of alcoholic beverage and ALDH2 genotype, and the differences partly explain the differences in the cancer susceptibility of the UADT according to alcoholic beverage and ALDH2 genotype.

Pueraria lobata (Kudzu root) hangover remedies and acetaldehyde-associated neoplasm risk

Recent introduction of several commercial Kudzu root (Pueraria lobata) containing hangover remedies has occurred in western countries. The available data is reviewed to assess if there are any potential concerns in relationship to the development of neoplasm if these products are used chronically. The herb Pueraria has two components that are used as traditional therapies; Pueraria lobata, the root based herb and Pueraria flos, the flower based herb. Both of these herbal components have different traditional claims and constituents. Pueraria flos, which enhances acetaldehyde removal, is the traditional hangover remedy. Conversely, Pueraria lobata is a known inhibitor of mitochondrial aldehyde dehydrogenase (ALDH2) and increases acetaldehyde. Pueraria lobata is being investigated for use as an aversion therapy for alcoholics due to these characteristics. Pueraria lobata is not a traditional hangover therapy yet has been accepted as the registered active component in many of these hangover products. The risk of development of acetaldehyde pathology, including neoplasms, is associated with genetic polymorphism with enhanced alcohol dehydrogenase (ADH) or reduced ALDH activity leading to increased acetaldehyde levels in the tissues. The chronic usage of Pueraria lobata at times of high ethanol consumption, such as in hangover remedies, may predispose subjects to an increased risk of acetaldehyde-related neoplasm and pathology. The guidelines for Disulfiram, an ALDH2 inhibitor, provide a set of guidelines for use with the herb Pueraria lobata. Pueraria lobata appears to be an inappropriate herb for use in herbal hangover remedies as it is an inhibitor of ALDH2. The recommendations for its use should be similar to those for the ALDH2 inhibitor, Disulfiram.

Overview of the role of alcohol dehydrogenase and aldehyde dehydrogenase and their variants in the genesis of alcohol-related pathology

Alcohol dehydrogenase (ADH) and mitochondrial aldehyde dehydrogenase (ALDH2) are responsible for metabolizing the bulk of ethanol consumed as part of the diet and their activities contribute to the rate of ethanol elimination from the blood. They are expressed at highest levels in liver, but at lower levels in many tissues. This pathway probably evolved as a detoxification mechanism for environmental alcohols. However, with the consumption of large amounts of ethanol, the oxidation of ethanol can become a major energy source and, particularly in the liver, interferes with the metabolism of other nutrients. Polymorphic variants of the genes for these enzymes encode enzymes with altered kinetic properties. The pathophysiological effects of these variants may be mediated by accumulation of acetaldehyde; high-activity ADH variants are predicted to increase the rate of acetaldehyde generation, while the low-activity ALDH2 variant is associated with an inability to metabolize this compound. The effects of acetaldehyde may be expressed either in the cells generating it, or by delivery of acetaldehyde to various tissues by the bloodstream or even saliva. Inheritance of the high-activity ADH β2, encoded by theADH2*2gene, and the inactiveALDH2*2gene product have been conclusively associated with reduced risk of alcoholism. This association is influenced by gene–environment interactions, such as religion and national origin. The variants have also been studied for association with alcoholic liver disease, cancer, fetal alcohol syndrome, CVD, gout, asthma and clearance of xenobiotics. The strongest correlations found to date have been those between theALDH2*2allele and cancers of the oro-pharynx and oesophagus. It will be important to replicate other interesting associations between these variants and other cancers and heart disease, and to determine the biochemical mechanisms underlying the associations.

Smoking, alcohol drinking, green tea consumption and the risk of esophageal cancer in Japanese men

BACKGROUND

Although smoking and alcohol drinking are established risk factors of esophageal cancer, their public health impact is unclear. Furthermore, the effect of green tea is controversial.

METHODS

The present study was based on a pooled analysis of two prospective cohort studies. A self-administered questionnaire about health habits was distributed to 9,008 men in Cohort 1 and 17,715 men in Cohort 2, aged 40 years or older, with no previous history of cancer. We identified 38 and 40 patient cases with esophageal cancer among the subjects in Cohort 1 (9.0 years of follow-up) and Cohort 2 (7.6 years of follow-up), respectively. Cox proportional hazards regression was used to estimate hazard ratios (HRs) of the risk of esophageal cancer incidence.

RESULTS

Cigarette smoking, alcohol drinking and green tea consumption were significantly associated with an increased risk of esophageal cancer. Compared with men who had never smoked, never drunk alcohol or green tea, the pooled multivariate HRs (95% confidence intervals) were 5.09 (1.80-14.40) (p for trend <0.0001), 2.73 (1.55-4.81) (p for trend=0.0002), or 1.67 (0.89-3.16) (P for trend=0.04) for men who were currently smoking ≥20 cigarettes/day, drinking alcohol daily, or drinking ≥5 cups green tea/day, respectively. The population attributable fractions of esophageal cancer incidence that was attributable to smoking, alcohol drinking and green tea consumption were 72.0%, 48.6%, and 22.1%, respectively.

CONCLUSIONS

Among the variables studied, smoking has the largest public health impact on esophageal cancer incidence in Japanese men, followed by alcohol drinking and green tea drinking.

Dietary selenium intake, aldehyde dehydrogenase-2 and X-ray repair cross-complementing 1 genetic polymorphisms, and the risk of esophageal squamous cell carcinoma

BACKGROUND

To the authors' knowledge, few studies have been conducted to date regarding dietary selenium and the potential gene-nutrient interactions with single-nucleotide polymorphisms (SNPs) in different pathways on the risk of esophageal cancer.

METHODS

The authors investigated the role of dietary selenium intake and its interplay with SNPs of the ALDH2 (glutamic acid [Glu] 487 lysine [Lys]) and the X-ray repair cross-complementing 1 (XRCC1) (arginine [Arg] 399 glutamine [Gln]) genes on the risk of esophageal squamous cell carcinoma (ESCC) in a population-based, case-control study in China. In total, 218 patients with ESCC and 415 healthy population control participants were interviewed. Dietary selenium intake was estimated from a food frequency questionnaire with 97 food items. ALDH2 and XRCC1 polymorphisms were detected with a polymerase chain reaction-restriction fragment length polymorphism assay.

RESULTS

The adjusted odds ratio (OR) for the highest quintile of dietary selenium intake, compared with the lowest quintile of intake, was 0.48 (95% confidence interval [95% CI], 0.25-0.89), with a strong dose-response relation (P for trend, <.01). The ALDH2 Lys and XRCC1 Gln variant alleles were associated with an increased risk of ESCC with adjusted ORs of 1.91 (95% CI, 0.96-3.80) and 1.67 (95% CI, 1.08-2.59), respectively. An elevation of the risk for ESCC was pronounced most among carriers of ALDH2 Lys/Lys and XRCC1 399Gln/Gln or Gln/Arg who consumed a low level of dietary selenium (adjusted OR, 4.16; 95% CI, 1.14-15.12).

CONCLUSIONS

To the authors' knowledge, this is the first in-depth study to suggest that genetic susceptibility may modify the association between selenium intake and the risk of ESCC. The findings indicated that individuals with low dietary selenium intake and ALDH2 Lys/Lys and XRCC1 399Gln/Gln or Gln/Arg genotypes were associated with an increased ESCC risk, especially in the presence of exposure to tobacco and alcohol carcinogens.

Esophageal melanosis, an endoscopic finding associated with squamous cell neoplasms of the upper aerodigestive tract, and inactive aldehyde dehydrogenase-2 in alcoholic Japanese men

BACKGROUND

Esophageal melanosis is often observed in alcoholic Japanese men, in whom the prevalence of squamous cell dysplasia and carcinoma (SCC) in the upper aerodigestive tract are high. This study evaluated the associations of esophageal melanosis with these neoplasms, and the factors contributing to the development of esophageal melanosis in this population.

METHODS

Endoscopic screening was combined with esophageal iodine staining in 1535 alcoholic Japanese men (aged 40-79 years), of whom 1007 underwent aldehyde dehydrogenase-2 (ALDH2) genotyping.

RESULTS

Fifty patients (3.3%) were diagnosed with esophageal melanosis, which had a higher incidence in those with noncancerous distinct iodine-unstained lesions (DIULs; 16/268; 6.0%), esophageal SCC (9/66; 13.6%), and oropharyngolaryngeal SCC (4/19; 21.1%) than in cancer- and DIUL-free controls (24/1182; 2.0%). The presence of esophageal melanosis was associated with higher risks for noncancerous DIULs, esophageal SCC, and oropharyngolaryngeal SCC (odds ratios, 2.81, 6.54, and 14.77, respectively). Men with the inactive ALDH2*1/2*2 genotype had a higher risk for esophageal melanosis (2.66-fold), as well as for DIULs and SCCs.

CONCLUSIONS

The presence of esophageal melanosis in alcoholic Japanese men could indicate a high risk for DIULs and SCCs in the upper aerodigestive tract. The high incidence of esophageal melanosis may be partially linked to high acetaldehyde exposure, a consequence of drinking alcohol in persons with inactive ALDH2.

Alcohol-related diseases of the mouth and throat

Chronic consumption of alcoholic beverages is an accepted social custom worldwide. In the upper aerodigestive tract, local morphologic, metabolic and functional alterations are present due to alcohol consumption. A clinical link between the chronic consumption of alcohol and head and neck cancer has been observed for decades. While alcohol was described initially as a risk enhancer only in smokers, a number of epidemiological studies have now provided sufficient evidence that chronic alcohol consumption increases the risk of head and neck cancer independent of exposure to tobacco smoke. The systemic effects of alcohol interact with local changes in the morphology and function of the salivary glands. In addition, alcohol leads to accumulation of pathologic microbes within the mucosa, leading to chronic infection. Susceptibility to carcinogens and cell proliferation in the mucosa are increased, resulting in genetic changes with the development of dysplasia, leukoplacia and carcinoma. Chronic alcohol consumption is correlated with an increased risk of cancer and an increased mortality in a dose-effect relationship. A number of biologically plausible mechanisms exist by which alcohol may cause cancer. These mechanisms are discussed in this article.

[Alcohol related diseases of the head and neck]

Chronic consumption of alcohol is an accepted social custom worldwide. In the upper aerodigestive tract, local morphologic, metabolic and functional alterations can be present due such consumption. Gastroesophageal reflux or alterations in sleep structure are typical examples of functional disorders. While alcohol was initially described as a risk enhancer only in smokers, a number of epidemiological studies have now shown that chronic alcohol consumption increases the risk of head and neck cancer independently of exposure to tobacco smoke. In addition, alcohol leads to an accumulation of pathologic microbes within the mucosa, leading to chronic infection. Susceptibility to carcinogens and cell proliferation in the mucosa are increased, resulting in genetic changes with the development of dysplasia, leucoplakia and carcinoma. Chronic alcohol consumption is correlated with an increased risk of cancer and increased mortality in a dose-dependent relationship. A number of biologically plausible mechanisms exist by which alcohol may cause cancer.

Human aldehyde dehydrogenases: potential pathological, pharmacological, and toxicological impact

Aldehyde dehydrogenases catalyze the pyridine nucleotide-dependent oxidation of aldehydes to acids. Seventeen enzymes are currently viewed as belonging to the human aldehyde dehydrogenase superfamily. Summarized herein, insofar as the information is available, are the structural composition, physical properties, tissue distribution, subcellular location, substrate specificity, and cofactor preference of each member of this superfamily. Also summarized are the chromosomal locations and organization of the genes that encode these enzymes and the biological consequences when enzyme activity is lost or substantially diminished. Broadly, aldehyde dehydrogenases can be categorized as critical for normal development and/or physiological homeostasis (1). even when the organism is in a friendly environment or (2). only when the organism finds itself in a hostile environment. The primary, if not sole, evolved raison d'être of first category aldehyde dehydrogenases appears to be to catalyze the biotransformation of a single endobiotic for which they are relatively specific and of which the resultant metabolite is essential to the organism. Most of the human aldehyde dehydrogenases for which the relevant information is available fall into this category. Second category aldehyde dehydrogenases are relatively substrate nonspecific and their evolved raison d'être seems to be to protect the organism from potentially harmful xenobiotics, specifically aldehydes or xenobiotics that give rise to aldehydes, by catalyzing their detoxification. Thus, the lack of a fully functional first category aldehyde dehydrogenase results in a gross pathological phenotype in the absence of any insult, whereas the lack of a functional second category aldehyde dehydrogenase is ordinarily of no consequence with respect to gross phenotype, but is of consequence in that regard when the organism is subjected to a relevant insult.

Analysis of risk factors for hepatocellular carcinoma in patients with HBs antigen- and anti-HCV antibody-negative alcoholic cirrhosis: clinical significance of prior hepatitis B virus infection

BACKGROUND

The hepatitis B virus (HBV) or hepatitis C virus (HCV) markers frequently are detected in alcoholic patients with hepatocellular carcinoma (HCC). However, risk factors for the development of HCC in patients with HBs antigen (Ag)- and anti-HCV antibody (anti-HCV)-negative alcoholic cirrhosis have not been clearly documented. The present study was conducted to elucidate the occurrence rates of HCC in HBs Ag- and anti-HCV-negative male alcoholic cirrhosis and to assess the risk factors for hepatocellular carcinogenesis.

METHOD

We prospectively studied 91 consecutive patients with HBs Ag- and anti-HCV-negative alcoholic cirrhosis for 0.5 to 12.5 years (median 5.9 years). Potential risk factors assessed for liver carcinogenesis included the following six variables: age, total alcohol intake, association of continuing alcohol intake after diagnosis, indocyanine green retention rate at 15 min, anti-HB core antibodies (anti-HBc), and association of diabetes mellitus.

RESULTS

Cumulative occurrence rates of HCC were 6.4%, 18.9%, and 28.7% at the end of the 5th, 7th and 10th years, respectively. When classified by anti-HBc, the occurrence rates of HCC in 31 patients with anti-HBc and 60 patients without anti-HBc were 15.6% and 2.9% at the 5th year, 28.4% and 13.5% at the 7th year, and 40.4% and 22.1% at the 10th year, respectively. The occurrence rates of HCC were also significantly related to the cumulative alcohol intake. Cox proportional hazard model identified that cumulative alcohol intake (p = 0.0047) and positive anti-HBc antibodies (p = 0.0598) were independently associated with the occurrence rates of HCC.

CONCLUSION

These epidemiologic results suggest that heavy cumulative alcohol intake and prior exposure to HBV infection are risk factors for the development of HCC in patients with HBs Ag- and anti-HCV-negative alcoholic cirrhosis.

Alcohol-related diseases of the mouth and throat

Chronic consumption of alcoholic beverages is an accepted social custom worldwide. In the upper aerodigestive tract, local morphological, metabolic and functional alterations can be present as a result of alcohol consumption. A clinical link between the chronic consumption of alcohol and head and neck cancer has been observed for decades. While alcohol was described initially as a risk enhancer only in smokers, a number of epidemiological studies have now provided sufficient evidence that chronic alcohol consumption increases the risk of head and neck cancer independent of exposure to tobacco smoke. Systemic effects of alcohol interact with local changes in the morphology and function of the salivary glands. In addition, alcohol leads to the accumulation of pathological microbes within the mucosa, leading to chronic infection. Susceptibility to carcinogens and cell proliferation in the mucosa are increased, resulting in genetic changes with the development of dysplasia, leucoplakia and carcinoma. Chronic alcohol consumption has been correlated with an increased risk of cancer and increased mortality in a dose-effect relationship. A number of biologically plausible mechanisms exist by which alcohol may cause cancer. These mechanisms are discussed in this chapter.

Risk factors for multicentric occurrence of carcinoma in the upper aerodigestive tract-analysis with a serial histologic evaluation of the whole resected-esophagus including carcinoma

BACKGROUND AND OBJECTIVES

We have reported that both lifestyle and family history might be related to multiplicity of carcinoma in the upper aerodigestive tract (UADT). The aim of this study was to elucidate the relationship between the number of carcinomas and risk factors.

METHODS

A serial histologic evaluation of the entire non-irradiated esophagus was performed in 114 males with esophageal cancer who were divided into three groups (group I: 88 cases with solitary cancer, group II: 11 with double cancers, group III: 15 with three or more cancers). As controls, 228 males with benign diseases were selected.

RESULTS

Among group III patients, both the incidence of heavy smoking and that of heavy drinking were 67% and 60%, which were significantly higher than those of group I (28% and 30%) and control subjects (14% and 10%, respectively). Heavy drinkers who were also heavy smokers were observed in 2, 10, 27, and 47% in control subjects, groups I, II, and III, respectively. Regarding family history, 27% of group III had a close relative with UADT or lung cancer, while the incidence was 7% in the control.

CONCLUSIONS

These findings strongly support the hypothesis that heavy smoking and heavy drinking, as well as a family history of both UADT and lung cancer, might be risk factors for multicentric occurrence of UADT cancer.

Genotyping of alcohol dehydrogenase type 2 and 3 using a two-buffer polyacrylamide gel electrophoresis system

Genetic polymorphisms in the alcohol dehydrogenase genes, ADH2 and ADH3, have been shown to affect individual susceptibility to diseases such as alcoholism and oesophageal cancer. Although several PCR-based methods for genotyping these enzymes have been previously developed, the two-buffer polyacrylamide gel electrophoresis system has the ability to rapidly resolve all classes of point mutations within 2-3 hours instead of the conventional overnight separation. The success of this technique is partly attributable to a discontinuous two-phase buffer system and horizontal flatbed gel electrophoresis rather than conventional vertical gels. Using a modification of this system, we were able to detect all of the known polymorphisms within ADH2 exons 3 and 9 and ADH3 exon 8, as well as a rare variant within ADH2 exon 9. This method is rapid, cost-effective, and is ideal for large scale screening programmes.

Smoking-related increase of O(6)-methylguanine-DNA methyltransferase expression in squamous cell carcinoma of the esophagus

DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) has a defensive role against alkylating agents associated with increased incidence of malignant tumors. The aim of the current study was to elucidate the significance of immunohistochemical expression of MGMT in squamous cell carcinoma (SCC) of the esophagus, with a special reference to the correlation of smoking. Immunohistostaining of MGMT was performed in the specimens collected from 100 patients with SCC of the esophagus. The relationship between the personal history of smoking and MGMT expression was examined and the value of Brinkman index was compared between patients with and without MGMT expression. Fifty-five SCCs (55.0%) had a positive response to MGMT inununostaining. The proportion of patients who had tumors with MGMT expression among patients with smoking habits was 62.0% (49 out of 79), which was significantly higher than that among patients without smoking habits (28.6%, 6 out of 21; P=0.005). The mean value of Brinkman index in patients who had tumors with MGMT expression (1189+/-604) was significantly higher than that in patients who had tumors without MGMT expression (871+/-656; P=0.020). Our results suggested that MGMT expression in esophageal SCC might be correlated with smoking habits of the patients.

Risk factors for esophageal cancer and the multiple occurrence of carcinoma in the upper aerodigestive tract

The multiple occurrence of squamous cell carcinoma is frequent in the upper aerodigestive tract (UADT). Risk factors not only for esophageal cancer, but also for multiple cancer in the UADT, were reviewed. Both cigarettes smoking and alcohol drinking are will known risk factors for esophageal cancer. The joint effect of these 2 factors on the occurrence of esophageal cancer is considered to be synergetic, but familial aggregation of esophageal cancer is also reported. Regarding the multiple occurrence of cancer of the UADT, both heavy smoking and heavy drinking play an important role. In addition, our studies revealed that a family history of UADT cancer might also be a risk factor for multiple cancer. Recent improvement of molecular biology techniques have helped to show that tumor-suppressor genes, such as p53 and FHIT, may be candidates for target genes of these risk factors.

Alcohol and upper gastrointestinal tract cancer: the role of local acetaldehyde production

Alcohol is, together with tobacco smoke, the main cause for upper GI tract cancer in industrialized countries. However, the tumour-promoting effects of alcohol intake are poorly understood and alcohol itself is not carcinogenic in the animal model. There is increasing evidence that alcohol metabolism, rather than the alcohol itself, generates carcinogenic and cell-toxic compounds. Acetaldehyde, first metabolite of ethanol, is highly toxic, mutagenic and carcinogenic. Polymorphisms in the genes coding for enzymes responsible for acetaldehyde accumulation and detoxification have been associated with an increased cancer risk. Acetaldehyde can also be produced in the mucosa and by the physiological microflora. This review summarizes the scientific evidence that alcohol intake leads to a local production of acetaldehyde. It describes the role of the oral microflora, the mucosa and the salivary glands in this process and shows that local acetaldehyde production from ethanol may contribute to the carcinogenesis of alcohol intake in the upper GI tract.

Hypochlorhydria induced by a proton pump inhibitor leads to intragastric microbial production of acetaldehyde from ethanol

BACKGROUND

Acetaldehyde, produced locally in the digestive tract, has recently been shown to be carcinogenic in humans.

AIM

To examine the effect of iatrogenic hypochlorhydria on intragastric acetaldehyde production from ethanol after a moderate dose of alcohol, and to relate the findings to the changes in gastric flora.

METHODS

Eight male volunteers ingested ethanol 0.6 g/kg b.w. The pH, acetaldehyde level and microbial counts of the gastric juice were then determined. The experiment was repeated after 7 days of lansoprazole 30 mg b.d.

RESULTS

The mean (+/- S.E.M.) pH of the gastric juice was 1.3 +/- 0.06 and 6.1 +/- 0.5 (P < 0.001) before and after lansoprazole, respectively. This was associated with a marked overgrowth of gastric aerobic and anaerobic bacteria (P < 0. 001), by a 2.5-fold (P=0.003) increase in gastric juice acetaldehyde level after ethanol ingestion, and with a positive correlation (r=0. 90, P < 0.001) between gastric juice acetaldehyde concentration and the count of aerobic bacteria.

CONCLUSIONS

Treatment with proton pump inhibitors leads to hypochlorhydria, which associates with intragastric overgrowth of aerobic bacteria and microbially-mediated acetaldehyde production from ethanol. Since acetaldehyde is a local carcinogen in the concentrations found in this study, long-term use of gastric acid secretory inhibitors is a potential risk-factor for gastric and cardiac cancers.

Increased salivary acetaldehyde levels in heavy drinkers and smokers: a microbiological approach to oral cavity cancer

The pathogenetic mechanisms behind alcohol-associated carcinogenesis in the upper digestive tract remain unclear, as alcohol is not carcinogenic. However, there is increasing evidence that a major part of the tumour-promoting action of alcohol might be mediated via its first, toxic and carcinogenic metabolite acetaldehyde. Acetaldehyde is produced from ethanol in the epithelia by mucosal alcohol dehydrogenases, but much higher levels derive from microbial oxidation of ethanol by the oral microflora. In this study we investigated factors that might alter the composition and quantities of the oral microflora and, consequently, influence microbial acetaldehyde production. Information about dental health, smoking habits, alcohol consumption and other factors was obtained by a questionnaire from 326 volunteers with varying social backgrounds and health status, e.g. oral cavity malignancy. Paraffin-induced saliva was collected and the microbial production of acetaldehyde from ethanol was measured. Smoking and heavy drinking were the strongest factors increasing microbial acetaldehyde production. Whether poor dental status may alter local acetaldehyde production from ethanol remained unanswered. Bacterial analysis revealed that mainly gram-positive aerobic bacteria and yeasts were associated with higher acetaldehyde production. Increased local microbial salivary acetaldehyde production due to ethanol among smokers and heavy drinkers could be a biological explanation for the observed synergistic carcinogenic action of alcohol and smoking on upper gastrointestinal tract cancer. It offers a new microbiological approach to ethanol-associated carcinogenesis at these anatomic sites.

Aldehyde dehydrogenase 2 and glutathione S-transferase M 1 polymorphisms in relation to the risk for oral cancer in Japanese drinkers

We investigated 191 patients with oral cancer (121 males and 70 females) and 121 non oral cancer patients (69 males and 52 females), both groups with a history of alcohol use. Blood was analyzed with aldehyde dehydrogenase 2 (ALDH 2) and glutathione S-transferase M 1 (GSTM 1) genotyping. ALDH 2 genotyping was performed by polymerase chain reaction (PCR)-Restriction fragment length polymorphism (RFLP) method and GSTM 1 genotyping was amplified with PCR using GSTM 1 specific primers. In the oral cancer group, the alcohol-drinking rate (59.7%) was significantly higher than in the non cancer group (alcohol-drinking rate 27.3%, p < 0.01). The incidence of inactive ALDH 2 and GSTM 1 in the cancer group with an alcohol-drinking habit was 34.2 and 67.5% and was higher than in the non cancer group with an alcohol-drinking habit (15.1, 45.5%).

Genotype difference of aldehyde dehydrogenase 2 gene in alcohol drinkers influences the incidence of Japanese colorectal cancer patients

A case-control study was conducted to explore the possible etiologic role of alcohol and aldehyde dehydrogenase 2 (ALDH2) gene among Japanese colorectal cancer patients. Information on their drinking, smoking and dietary habits was collected from 265 colon and 164 rectum cancer patients, and 794 non-cancer patients as a control group. Genotypes of the ALDH2 gene at codon 487, glutamic acid (ALDH2*1) as a wild-type or lysine (ALDH2*2) as a mutated type with reduced enzyme activity, were analyzed by polymerase chain reaction in 160 colon and 110 rectum cancer patients and 121 control persons. Univariate analysis with the chi 2 statistical test showed that heavy alcohol drinking (P < 0.01), frequent meat intake (P < 0.001), and irregular (P < 0.01), hasty (P < 0.01) and excessive (P < 0.001) eating habits were associated with the incidence of both colon and rectum cancers, whereas heavier smoking (P < 0.05) and infrequent fish (P < 0.03) and fruit (P < 0.01) intake were solely associated with incidence of rectum cancer. Infrequent green vegetable intake was not correlated with the incidence of colorectal cancer. Multivariate unconditional logistic regression analysis confirmed the association of alcohol consumption (P < 0.01) and meat intake (P < 0.05). Homozygous and heterozygous carriers of ALDH2*2 allele tended to be found in colon (trend P = 0.04) but not in rectum cancer patients compared to controls. Risk elevation for colon cancer due to alcohol consumption was pronounced among the heterozygotes and it was statistically significant especially for distal colon cancer (trend P = 0.02). We conclude that alcohol consumption is a risk factor for colorectal cancer and the risk can be enhanced in ALDH2 heterozygotes.

Genetic polymorphism of aldehyde dehydrogenase 2 in patients with upper aerodigestive tract cancer

BACKGROUND

Alcohol consumption is one of the major risk factors of the upper aerodigestive tract (UADT) cancers, and combined cancers are frequently discovered in the patients with UADT cancer. The association between esophageal cancer and alcohol-related metabolizing enzymes is well studied, but only a few examinations about the association between head and neck cancer and the enzymes were performed.

METHODS

Fifty-two patients with UADT cancer (head and neck cancer in 25, esophageal cancer in 19, and multiple cancers in 8) were examined in the alcohol habit and in the polymorphisms of aldehyde dehydrogenase 2 (ALDH2) and cytochrome P-4502E1.

RESULTS

Patients with multiple cancers had significantly higher ethanol consumption than the other two groups (p < 0.001). The frequency of ALDH2*1/2*2 heterozygote was significantly lower (p = 0.009) in patients with head and neck cancer (5/25) than patients with esophageal cancer (11/19). The allele frequency of P-4502E1 did not show a significant difference between the groups (p = 0.700).

CONCLUSIONS

These results demonstrated the difference in the frequency of ALDH2 heterozygote between the patients with esophageal cancer and patients with head and neck cancer.