Chinese alcoholic patients with esophageal cancer are genetically different from alcoholics with acute pancreatitis and liver cirrhosis

Alcohol, ALDH2, and Esophageal Cancer: A Meta-analysis Which Illustrates the Potentials and Limitations of a Mendelian Randomization Approach

Mendelian randomization, the use of common polymorphisms as surrogates for measuring exposure levels in epidemiologic studies, provides one method of assessing the causal nature of some environmental exposures. This can be illustrated by looking at the association between the ALDH2 polymorphism and esophageal cancer. Alcohol drinking is considered a risk factor for esophageal cancer, and exposure to high levels of acetaldehyde, the principal metabolite of alcohol, may be responsible for the increased cancer risk. The ability to metabolize acetaldehyde is encoded by the ALDH2 gene, which is polymorphic in some populations. The ALDH2*2 allele produces an inactive protein subunit, which is unable to metabolize acetaldehyde. An individual's genotype at this locus may influence their esophageal cancer risk through two mechanisms, first through influencing alcohol intake and second through influencing acetaldehyde levels. We have carried out a meta-analysis of studies looking at the ALDH2 genotype and esophageal cancer and found that risk was reduced among *2*2 homozygotes [odds ratio (OR), 0.36; 95% confidence interval (95% CI), 0.16-0.80] and increased among heterozygotes (OR, 3.19; 95% CI, 1.86-5.47) relative to *1*1 homozygotes. This provides strong evidence that alcohol intake increases the risk of esophageal cancer and individuals whose genotype results in markedly lower intake, because they have an adverse reaction to alcohol are thus protected. This meta-analysis also provides evidence that acetaldehyde plays a carcinogenic role in esophageal cancer. The two different processes operating as a result of the ALDH2 genotype have implications for the interpretation of studies using the Mendelian randomization paradigm.

Phase I/II enzyme gene polymorphisms and esophageal cancer risk: A meta-analysis of the literature

AIM: Phase I/II enzymes metabolize environmental carcin-ogens and several functional polymorphisms have been reported in their encoding genes. Although their significance with regard to esophageal carcinogenicity has been examined epidemiologically, it remains controversial. The present systematic review of the literature was performed to clarify associations.

METHODS: Eligible studies were case-control or cohort studies published until September 2004 that were written in any language. From PubMed and a manual review of refe-rence lists in relevant review articles, we obtained 16 studies related to the CYP1A1 Ile-Val substitution in exon 7, CYP1A1 MspI polymorphisms, CYP2E1 RsaI polymorphisms, GSTM1 null type, GSTT1 null type and GSTP1 Ile104Val. All were of case-control design. Summary statistics were odds ratios (ORs) comparing heterozygous-, homozygous-non-wild type or these two in combination with the homozygous wild type, or the null type with the non-null type for GSTM1 and GSTT1. A random effect model was used to estimate the summary ORs. A meta-regression analysis was applied to explore sources of heterogeneity.

RESULTS: Individuals with the Ile-Val substitution in CYP1A1 exon 7 had increased esophageal cancer risk, with ORs (95%CI) compared with Ile/Ile of 1.37 (1.09-1.71), 2.52 (1.62-3.91) and 1.44 (1.17-1.78) for Ile-Val, Val/Val genotype and the combined group. No significant association was found between esophageal cancer risk and the other genetic parameters.

CONCLUSION: A significant association exists between the CYP1A1 Ile-Val polymorphism and risk of esophageal cancer. Polymorphisms that increase the internal exposure to activated carcinogens may increase the risk of esophageal cancer.

Expression levels of hepatic cytochrome P450 enzymes in Aldh2-deficient mice following ethanol exposure: a pilot study

We determined expression levels of hepatic cytochrome P450 (CYP) 2E1, 2B1/2 and 4B1 enzymes in aldehyde dehydrogenase 2 (Aldh2) +/+ and Aldh2 -/- mice by immunoblotting assay following subchronic ethanol exposure for eight days. Using ethanol exposure, the protein expression levels of CYP2E1, 2B1/2 and 4B1 in Aldh2 +/+ mice were increased by factors of 2.61, 1.88 and 2.01 compared with Aldh2 +/+ mice that were not exposed to ethanol, respectively. On the other hand, in the Aldh2 -/- mice, CYP2E1, 2B1/2 and 4B1 protein expression levels after ethanol treatment were shown to be 1.99, 1.05 and 1.33 greater than those of Aldh2 -/- control mice, respectively. We also found an interesting fact in the present study; the Aldh2 -/- mice were shown to have higher CYP2E1 (by a factor of 4.19), 2B1/2 (by a factor of 2.89) and 4B1 (by a factor of 1.53) protein expression levels than Aldh2 +/+ mice despite the lack of ethanol treatment. These results suggest that CYP2E1, 2B1/2 and 4B1 play some role in ethanol metabolism and that Aldh2-deficient individuals may have higher levels of CYP2E1, 2B1/2 and 4B1 enzymes compared to Aldh2 wild-type individuals.

Genetic polymorphisms in three Iranian populations with different risks of esophageal cancer, an ecologic comparison

The age-standardized incidence of esophageal cancer (EC) varies from 3 to >100/100,000 per year in different provinces of Iran. This striking variation of incidence is associated with differences in ethnic backgrounds, raising the possibility that genetic factors are involved in the pathogenesis of EC. We compared the frequencies of polymorphisms in ten genes that have been hypothesized to have a role in risk of EC (CYP1A1, CYP2A6, CYP2E1, GSTM1, GSTP1, GSTT1, ADH2, ADH3, ALDH2, and O6-MGMT) among three Iranian ethnic groups with highly varying rates of EC. These three groups included high-risk Turkomans, medium-risk Turks, and low-risk Zoroastrian Persians. Compared to Zoroastrians, Turkomans had higher frequency of four alleles that are speculated to favor carcinogenesis (CYP1A1 m1, CYP1A1 m2, CYP2A6*9, and ADH2*1); these results are consistent with an influence of these allele variants on the population risk of EC. However, none of these four alleles had a high enough prevalence in Turkomans to explain the high rates of EC in this group. Three of these four alleles (CYP1A1 m1, CYP1A1 m2, CYP2A6*9) were less frequent among Turkomans than in some Asian populations with lower risks of EC. We conclude that it is unlikely that variations in these polymorphic genes are major contributors to the high incidence of EC among Turkomans in Iran.

Mean corpuscular volume and the aldehyde dehydrogenase-2 genotype in male Japanese workers

BACKGROUND

Increased mean corpuscular volume (MCV) is common in alcohol abusers and alcoholics. MCV is higher in Japanese heavy drinkers with inactive aldehyde dehydrogenase-2 (ALDH2) encoded by ALDH2*1/2*2 than among those with active ALDH2 encoded by ALDH2*1/2*1. Inactive ALDH2 dramatically increases blood acetaldehyde levels after alcohol intake. Because moderate and heavy drinkers with ALDH2*1/2*2 have very high risks for esophageal cancer, MCV might serve as an indicator of these high-risk drinkers.

METHODS

In this investigation of the association of red cell values with the ALDH2 genotype and possible confounding factors, the drinking, smoking, and dietary habits reported on a structured questionnaire by 163 Japanese working men were subjected to multivariate analyses.

RESULTS

Aging, lower body mass index (BMI), more alcohol consumption, and more smoking were positively associated with increased MCV. Among moderate to heavy drinkers (>or=9 units/week; 1 unit = 22 g of ethanol), both MCV and mean corpuscular hemoglobin were higher and the red cell count was lower in those with ADLH2*1/2*2 than in those with ALDH2*1/2*1. Multiple linear regression analysis after adjustment for age, BMI, and smoking revealed that a positive relationship between the amount of drinking and MCV but inverse relationships for drinking and red cell count, as well as hemoglobin and hematocrit values, were significantly stronger for men with ALDH2*1/2*2 than for those with ALDH2*1/2*1, demonstrating a gene-environment interaction. Drinking accounted for 19.9% of interindividual MCV variance among men with ALDH2*1/*2*2 but for only 1.3% of variance among those with ALDH2*1/2*1. Age, BMI, drinking, and smoking accounted for 52.1 and 34.7% of the variation among those with ALDH2*1/2*2 and ALDH2*1/2*1, respectively. Macrocytosis (MCV >or=100.0 fl) was observed in 18 subjects (11.0%), and use of macrocytosis as a biomarker of moderate to heavy drinkers with ALDH2*1/2*2 had a sensitivity of 54.5% (6 of 11) and a specificity of 92.1% (140 of 152).

CONCLUSIONS

Alcohol-related red cell value changes associated with inactive ALDH2 in Japanese men suggest the importance of acetaldehyde's role in increasing MCV and the potential for using MCV as a marker for high-risk drinkers for esophageal cancer.

Genetic susceptibility and environmental factors of esophageal cancer in Xi’an

AIM: To analyse the role of genetic susceptibility and environmental factors in the process of esophageal cancer (EC) formation in Xi’an, China.

METHODS: A hospital based case-control study, combined with molecular epidemiological method, was carried out. A total of 127 EC cases and 101 controls were interviewed with questionnaires containing demographic items, habit of tobacco smoking, alcohol drinking, and family history of EC. Polymorphism of CYP1A1 and GSTM1 of 127 EC cases and 101 controls were detected by PCR method. The interactions between genetic susceptibility and environmental factors were also discussed.

RESULTS: Tobacco smoking, alcohol drinking and a family history of EC were risk factors for EC with an OR of 2.04 (95%CI 1.15-3.60), 3.45(95%CI 1.74-6.91), 3.14 (95%CI 1.28-7.94), respectively. Individuals carrying CYP1A1 Val/Val genotype compared to those with CYP1A1 Ile/Ile genotype had an increased risk for EC (OR 3.35, 95%CI 1.49-7.61). GSTM1 deletion genotype was a risk factor for EC (OR1.81, 95%CI 1.03-3.18). Gene-environment interaction analysis showed that CYP1A1 Val/Val genotype, GSTM1 deletion genotype had synergetic interactions with tobacco smoking, alcohol drinking and family history of EC.

CONCLUSION: Tobacco smoking, alcohol drinking and a family history of EC are risk factors for EC. CYP1A1 Val/Val and GSTM1 deletion genotypes are genetic susceptibility biomarkers for EC. There are synergic interactions between genetic susceptibility and environmental factors.

The epidemiology of alcohol-induced pancreatitis

Although the association between alcohol and pancreatitis has been recognized for centuries, the precise magnitude of the impact of alcohol remains poorly quantified. Epidemiologic research on this condition has been seriously handicapped by several factors. Classifications are based on morphology rather than on etiology; the diagnostic differences between acute and chronic pancreatitis are imprecise and confusing; and coding by the International Classification of Diseases (ICD) has been inadequate. The current ICD (ICD-10), used in the United States since 1999, identifies alcohol-induced chronic pancreatitis as a separate code for the first time, an enhancement that will greatly improve the quality of data collected in current and future studies. Unfortunately, no code yet exists for acute alcoholic pancreatitis. Of the approximately 2.4 million deaths in the United States in 1999, pancreatitis was listed as the underlying cause for 3289 deaths, making it the 235th leading cause of death. Acute pancreatitis accounted for 84% of these deaths, and chronic pancreatitis the remaining 16%. Alcohol is a primary cause of both acute and chronic pancreatitis in most developed countries. About one-third of acute pancreatitis in the United States is alcohol-induced. In the United States and other developed countries, 60%-90% of chronic pancreatitis is alcohol induced. Both forms are more common in men. The development of chronic pancreatitis is proportional to the dose and duration of alcohol consumption (minimum, 6-12 years of approximately 80 g of alcohol per day). Autopsy studies reveal subclinical chronic pancreatitis in another 10% of alcohol abusers. Yet, since <10% of chronic alcoholics develop chronic pancreatitis, clearly other predisposing factors besides alcohol are involved. Genetic variability and environmental exposures, such as diet, are prime candidates for further investigation. To date, there have been few large epidemiological studies of alcoholic pancreatitis in the United States or other developed countries. Additional studies are needed to improve the quality of existing baseline epidemiologic data and allow better assessment of risk. Improved diagnostic precision, more complete and specific coding, and greater understanding of covariables and mechanisms would also advance the field.

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.

Investigation of alcohol metabolizing enzyme genes in Chinese alcoholics with avascular necrosis of hip joint, pancreatitis and cirrhosis of the liver

AIMS AND METHODS

Alcoholism may cause a range of diseases including avascular necrosis of the hip joint (AVN), cirrhosis of the liver, pancreatitis and oesophageal carcinoma. Chinese alcoholic patients diagnosed with AVN have a higher incidence of cirrhosis than of acute pancreatitis or oesophageal cancer. Thus, the aim of this study was to investigate genetic differences in polymorphisms of the alcohol-metabolizing enzymes ADH2, ADH3, ALDH2 and P4502E1 for subgroups of Chinese alcoholic patients, defined by diagnoses of AVN (n = 51), acute pancreatitis (n = 92) and liver cirrhosis (n = 159), and for 280 non-alcoholic patients.

RESULTS

Analysis revealed that ADH2*1 allele frequency was significantly lower for the alcoholic AVN than for the cirrhosis subgroup. However, no significant difference was found between the alcoholic AVN and pancreatitis subgroups. Furthermore, ALDH2*2 prevalence was not found to differ significantly between the alcoholic subgroups. When compared with our previously published data for alcoholic patients with oesophageal carcinoma, ADH2*1 carriage was significantly less frequent for the alcoholic AVN patients in the current study. Further, ALDH2*2 carriage was significantly less frequent for the alcoholic AVN subgroup than for the oesophageal carcinoma patients.

CONCLUSIONS

The allele frequencies for ADH2*1 and ALDH2*2 are different when comparing subpopulations of alcoholics defined by presence of specific alcohol-induced diseases, suggesting that genetic variation in alcohol-metabolizing enzyme genes accounts for, at least in part, the specific types of organ damage observed. We also found the combination of AVN and cirrhosis to be more prevalent than that of AVN and acute pancreatitis. In contrast, the ADH2 and ALDH2 allele frequencies for the AVN subgroup were more similar to those of the acute-pancreatitis than to the cirrhosis subgroup. These data indicate the possibility that other genetic variations may also influence the type of organ-specific complications in Chinese alcoholics.

Duplex polymerase chain reaction with confronting two-pair primers (PCR-CTPP) for genotyping alcohol dehydrogenase beta subunit (ADH2) and aldehyde dehydrogenase 2 (ALDH2)

AIMS

Alcohol dehydrogenase beta subunit (ADH2) Arg47His and aldehyde dehydrogenase 2 (ALDH2) Glu487Lys were genotyped by a duplex polymerase chain reaction (PCR) with confronting two-pair primers (PCR-CTPP), which allows DNA amplification with one-tube PCR including eight primers, and subsequent electrophoresis.

METHODS

Several PCR conditions were tested to establish the optimal conditions for distinguishing the allele-specific bands for the two polymorphisms. Under the optimal PCR conditions, 454 Japanese health check-up examinees were genotyped.

RESULTS

The allele-specific bands were successfully amplified under the optimal conditions of the duplex PCR-CTPP. The genotype distributions were within the Hardy-Weinberg equilibrium. The bands produced by the duplex PCR-CTPP genotyping were clearer than those produced by PCR-CTPP, conducted solely for ADH2.

CONCLUSIONS

ADH2 Arg47His and ALDH2 Glu487Lys were successfully genotyped by this newly developed duplex PCR-CTPP, an inexpensive and time-saving genotyping tool, which will be useful in epidemiological studies on alcoholism, as well as risk estimation of alcohol-related diseases.

Detection of alcohol dehydrogenase isoenzymes in liver and serum by electrophoresis in liver disease

AIM

To establish an agarose gel electrophoretic method for detecting alcohol dehydrogenase isoenzymes in human serum or liver tissue.

METHODS

The samples of human liver tissue or serum were electrophoresed with 74 mmol/L diethylbarbital buffer (pH 8.6) of 10 g/L agarose gel. Electrophoresis can separate the Alcohol Dehydrogenase (ADH) isoenzymes to three bands clearly at 20 mA for 20 min in serum.

RESULTS

The total ADH activity in serum of sixty-seven patients with liver diseases was ranged from 0.013 Kat/L to 0.021 Kat/L. ADHⅠ isoenzyme was ranged from 0.01 to 0.30 of the total activities . ADH Ⅲ isoenzyme was from 0.12 to 0.31 . ADH Ⅲ was from 0.39 to 0.80. Total ADH activity in liver tissues of ten healthy subjects was ranged from 0.136 Kat/L to 0.196 Kat/L. ADHⅠ isoenzyme was from 0.07 to 0.25 of the total activities. ADH Ⅲ isoenzyme was ranged from 0.19 to 0.27. ADH Ⅲ was from 0.56 to 0.73.

CONCLUSION

ADH activity is high in normal human liver. Three ADH isoenzymes can be separated with agarose gel electrophoresis . But serum ADH activity is low. High activities were obtained in serum from persons suffering from serious liver diseases.

Acetaldehyde, microbes, and cancer of the digestive tract

Excessive alcohol consumption and heavy smoking are the main risk factors of upper digestive tract cancer in industrialized countries. The association between heavy drinking and cancer appears to he particularly prominent in Asian individuals who have an inherited deficient ability to detoxify the first metabolite of ethanol oxidation, acetaldehyde. Alcohol itself is not carcinogenic. However, according to cell culture and animal experiments acetaldehyde is highly toxic, mutagenic, and carcinogenic. In addition to somatic cells, microbes representing normal human gut flora are also able to produce acetaldehyde from ethanol. After the ingestion of alcoholic beverages, this results in high local acetaldehyde concentrations in the saliva, gastric juice, and the contents of the large intestine. In addition, microbes may produce acetaldehyde endogenously without alcohol administration. This review summarizes the epidemiological, genetic, and biochemical evidence supporting the role of locally produced acetaldehyde in the pathogenesis of digestive tract cancer. Special emphasis is given to those factors that regulate local acetaldehyde concentration in the contents of the gastrointestinal tract. The new evidence presented in this review may open a microbiological approach to the pathogenesis of digestive tract cancer and may have an influence on future preventive strategies.

Lifestyle habits and genetic susceptibility and the risk of esophageal cancer in the Thai population

The association of lifestyle habits and polymorphism of ADH2 and ALDH2 genes with the risk of esophageal cancer in Thai population was investigated in a hospital-based case-control study: 202 cases and 261 controls. The results of multivariate logistic analysis showed that alcohol consumption >60g/day, smoking >10 cigarettes/day and chewing betel >or=10 quids/day significantly increased risk (odds ratio (OR) 5.84, 95% confidence interval (CI) 3.15-10.83; 4.65, 95% CI 1.99-10.84; and 4.68, 95% CI 2.05-10.72, respectively). ADH2*1/*1 also increased the risk significantly (OR 1.56, 95% CI 1.01-2.39) while ALDH2 did not (OR of ALDH2*1/*2 1.57, 95% CI 0.89-2.76). However, the combined at risk genotypes, ADH2*1/*1 and ALDH2*1/*2 increased risk to four-fold. In addition, significant gene-environment interaction was found. Heavy drinkers >60g/d harboring ADH2*1/*1 or ALDH2*1/*2 had about an 11-fold increased risk.

Population distribution of aldehyde dehydrogenase-2 genetic polymorphism: implications for risk assessment

The role of genetic polymorphisms in modulating xenobiotic metabolism and susceptibility to cancer and other health effects has been suggested in numerous studies. However, risk assessments have generally not used this information to characterize population variability or adjust risks for susceptible subgroups. This paper focuses upon the aldehyde dehydrogenase-2 (ALDH2) system because it exemplifies the pivotal role genetic polymorphisms can play in determining enzyme function and susceptibility. Allelic variants in ALDH2 cause decreased ability to clear acetaldehyde and other aldehyde substrates, with homozygous variants (ALDH2*2/2) having no activity and heterozygotes (ALDH2*1/2) having intermediate activity relative to the predominant wild type (ALDH2*1/1). These polymorphisms are associated with increased buildup of acetaldehyde following ethanol ingestion and increased immediate symptoms (flushing syndrome) and long-term cancer risks. We have used Monte Carlo simulation to characterize the population distribution of ALDH2 allelic variants and inter-individual variability in aldehyde internal dose. The nonfunctional allele is rare in most populations, but is common in Asians such that 40% are heterozygotes and 5% are homozygote variants. The ratio of the 95th or 99th percentiles of the Asian population compared to the median of the U.S. population is 14- to 26-fold, a variability factor that is larger than the default pharmacokinetic uncertainty factor (3.2-fold) commonly used in risk assessment. Approaches are described for using ALDH2 population distributions in physiologically based pharmacokinetic-Monte Carlo refinements of risk assessments for xenobiotics which are metabolized to aldehyde intermediates (e.g., ethanol, toluene, ethylene glycol monomethyl ether).

Familial factors in the etiology of gastroesophageal reflux disease, Barrett's esophagus, and esophageal adenocarcinoma

Familial aggregation of gastroesophageal reflux symptoms has been established clearly in patients with gastroesophageal reflux disease and its complications. Preliminary reports of twin studies suggest that this aggregation has a significant genetic component. A genetic predisposition to gastroesophageal reflux may be expressed phenotypically as disordered gastroesophageal motility and hiatus hernia but these disorders may be secondary to chronic gastroesophageal reflux. Linkage studies, the discovery of candidate genes for gastroesophageal reflux, and their phenotypic expression are awaited with interest.

Relationship of tobacco smoking CYP1A1 GSTM1 gene polymorphism and esophageal cancer in Xi'an

AIM

To analyze the association of tobacco smoking polymorphism of CYP1A1 (7th exon) and GSTM1 genotype and esophageal cancer(EC) in Xi'an.

METHODS

A hospital based case-control study, with molecular epidemiological method, was carried out. Polymorphism of CYP1A1 and GSTM1 of samples from 127 EC cases and 101 controls were detected by PCR method.

RESULTS

There were no significant difference of age and gender between cases and controls. Tobacco smoking was the main risk factor OR=1.97;95% CI=1.12-3.48 for EC in Xi'an. The proportions of CYP1A1 Ile/Ile, Ile/Val and Val/Val gene types in cases and controls was 19.7% 45.7% 34.6% and 30.7%,47.5%, 21.8% respectively(P=0.049). Individuals with CYP1A1 Val/Val genotype compared to those with CYP1A1 Ile/Ile genotype had higher risk for EC increased (OR=2.48, 95%CI=1.12-5.54). The proportions of GSTM1 deletion genotype in cases and controls were 58.3% and 43.6%(OR=1.81, 95%CI=1.03-3.18, P=0.028). Analysis of gene-environment interaction showed that tobacco smoking and CYP1A1 Val/Val genotype; tobacco smoking and GSTM1 deletion genotype had synergism interaction respectively. Analysis of gene-gene interaction did not find synergistic interaction between these two genes. But in GSTM1 deletion group there was significant difference of distribution of CYP1A1 genotype between cases and controls (P=0.011).

CONCLUSION

CYP1A1 Val/Val and GSTM1 deletion genotypes are genetic susceptibility biomarkers for EC. The risk increases, when person with CYP1A1 Val/Val and/or GSTM1 deletion genotype. And these two-metabolic enzymes seem to have interactions with tobacco smoking, in which the mechanism still needs further study.

Cytochrome P450 2E1 genetic polymorphism and gastric cancer in Changle, Fujian Province

AIM: Genetic polymorphism in enzymes of carcinogen metabolism has been found to have the influence on the susceptibility to cancer. Cytochrome P450 2E1 (CYP2E1) is considered to play an important role in the metabolic activation of procarcinogens such as N-nitrosoamines and low molecular weight organic compounds. The purpose of this study is to determine whether CYP450 2E1 polymorphisms are associated with risks of gastric cancer.

METHODS: We conducted a population based case-control study in Changle county, Fujian Province, a high-risk region of gastric cancer in China. Ninety-one incident gastric cancer patients and ninety-four healthy controls were included in our study. Datas including demographic characteristcs, diet intake, and alcohol and tobacco consumption of indivduals in our study were completed by a standardized questionnaire. PCR-RFLP revealed three genotypes:heterozygote (C1/C2) and two homozygotes (C1/C1 and C2/C2) in CYP2E1.

RESULTS: The frequency of variant genotypes (C1/C2 and C2/C2) in gastric cancer cases and controls was 36.3% and 24.5%, respectively. The rare homozygous C2/C2 genotype was found in 6 indivduals in gastric cancer group (6.6%), whereas there was only one in the control group (1.1%). However, there was no statistically significan difference between the two groups (two-tailed Fisher’s exact test, P = 0.066). Indivduals in gastric cancer group were more likely to carry genotype C1/C2 (odds ratio, OR = 1.50) and C2/C2 (OR = 7.34) than indivduals in control group (χ² = 4.597, for trend P = 0.032). The frequencies of genotypes with the C2 allele (C1/C2 and C2/C2 genotypes) were compared with those of genotypes without C2 allele (C1/C1 genotype) among indivduals in gastric cancer group and control group according to the pattern of gastric cancer risk factors. The results show that indivduals who exposed to these gastric cancer risk factors and carry the C2 allele seemed to have a higher risk of developing gastric cancer.

CONCLUSION: Polymorphism of CYP2E1 gene may have some effct in the development of gastric cancer in Changle county, Fujian Province.

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.