Reflux of gastric contents can lead to development of reflux esophagitis and Barrett's esophagus. Barrett's esophagus is a risk factor for esophageal adenocarcinoma. Damage to DNA may lead to carcinogenesis but is repaired through activation of pathways involving polymorphic enzymes, including human 8-oxoguanine glycosylase 1 (hOGG1), X-ray repair cross-complementing 1 (XRCC1), and xeroderma pigmentosum group D (XPD). Of the single nucleotide polymorphisms identified in these genes, hOGG1 Ser326Cys, XRCC1 Arg399Gln, and XPD Lys751Gln are particularly common in Caucasians and have been associated with lower DNA repair capacity. Small studies have reported associations with XPD Lys751Gln and esophageal adenocarcinoma. XRCC1 Arg399Gln has been linked to Barrett's esophagus and reflux esophagitis. In a population-based case-control study, we examined associations of the hOGG1 Ser326Cys, XRCC1 Arg399Gln, and XPD Lys751Gln polymorphisms with risk of esophageal adenocarcinoma, Barrett's esophagus, and reflux esophagitis. Genomic DNA was extracted from blood samples collected from cases of esophageal adenocarcinoma (n = 210), Barrett's esophagus (n = 212), reflux esophagitis (n = 230), and normal population controls frequency matched for age and sex (n = 248). Polymorphisms were genotyped using TaqMan allelic discrimination assays. Odds ratios and 95% confidence intervals were obtained from logistic regression models adjusted for potential confounding factors. There were no statistically significant associations between these polymorphisms and risk of esophageal adenocarcinoma, Barrett's esophagus, or reflux esophagitis. (Cancer Epidemiol Biomarkers Prev 2008;17(3):736–9)

Reflux of gastric contents can lead to development of reflux esophagitis and Barrett's esophagus. Barrett's esophagus is an important risk factor for esophageal adenocarcinoma, the incidence of which has increased in recent years (1, 2). Damage to DNA may lead to carcinogenesis (3) but is repaired through activation of pathways involving polymorphic enzymes (4). Human 8-oxoguanine glycosylase 1 (hOGG1) and X-ray repair cross-complementing 1 (XRCC1) act on the base excision repair pathway. Xeroderma pigmentosum group D (XPD) enzyme is involved in the nucleotide excision repair pathway (5). Various single nucleotide polymorphisms have been identified in these genes, but hOGG1 Ser326Cys, XRCC1 Arg399Gln, and XPD Lys751Gln are particularly common in Caucasians and have been associated with lower DNA repair capacity (6-8). Small studies have reported associations with XPD Lys751Gln and esophageal adenocarcinoma (9-11). XRCC1 Arg399Gln has been linked to Barrett's esophagus and reflux esophagitis (11). We investigated associations between hOGG1 Ser326Cys, XRCC1 Arg399Gln, and XPD Lys751Gln and risk of esophageal adenocarcinoma, Barrett's esophagus, and reflux esophagitis in a large case-control study.

Design

The study methods have been described previously in detail (12). In summary, the Factors Influencing the Barrett's Adenocarcinoma Relationship study was carried out in Ireland between March 2002 and July 2005. Data and samples were collected from Caucasians with (a) esophageal adenocarcinoma, (b) Barrett's esophagus, (c) reflux esophagitis, and (d) normal controls.

Genotyping

The Puregene DNA purification kit (Gentra Systems) was used to extract DNA from blood samples. The hOGG1 Ser326Cys (rs1052133), XRCC1 Arg399Gln (rs25487), and XPD Lys751Gln (rs13181) polymorphisms were genotyped using TaqMan allelic discrimination assays (Applied Biosystems). As a quality-control measure, genotyping was repeated for 10% of the samples, and the replicates were 100% concordant.

Statistical Analysis

Departures from Hardy-Weinberg equilibrium were tested for using the goodness-of-fit χ2 test. Genotype frequencies among cases of esophageal adenocarcinoma, Barrett's esophagus, and reflux esophagitis were compared with controls using the χ2 test for association while adjusting for potential confounding factors by logistic regression. Statistical significance was set at P < 0.05. Analyses were done using SPSS for Windows version 13.0 (SPSS).

The Factors Influencing the Barrett's Adenocarcinoma Relationship study recruited a total of 227 esophageal adenocarcinoma patients, 224 Barrett's esophagus patients, 230 reflux esophagitis patients, and 260 population controls. The demographic characteristics of each group are presented in Table 1. The participation rates of Barrett's esophagus and reflux esophagitis patients and control subjects were 82.4%, 68.7%, and 41.8%, respectively. The participation rate of eligible, alive esophageal adenocarcinoma patients was 74.2% and the overall esophageal adenocarcinoma response rate was 63.9%. DNA samples were available for analysis from 210 (92.5%) esophageal adenocarcinoma patients, 212 (94.6%) Barrett's esophagus patients, 230 (100%) reflux esophagitis patients, and 248 (95.4%) controls.

Table 1.

Characteristics of controls, reflux esophagitis, Barrett's esophagus, and esophageal adenocarcinoma patients

VariablesControls, n (%)Reflux esophagitis, n (%)P (reflux esophagitis vs controls)Barrett's esophagus, n (%)P (Barrett's esophagus vs controls)Esophageal adenocarcinoma, n (%)P (esophageal adenocarcinoma vs controls)
Sex        
    Male 220 (84.6) 189 (82.2) 0.468 185 (82.6) 0.548 192 (84.6) 0.992 
    Female 40 (15.4) 41 (17.8)  39 (17.4)  35 (15.4)  
Age, mean (y) 63.0 61.7 0.219 62.4 0.567 64.2 0.276 
Education (full-time), mean (y) 12.0 10.8 <0.001 11.3 0.013 10.7 <0.001 
Gastroesophageal reflux symptoms*        
    Never 211 (81.2) 140 (60.9) <0.001 60 (26.8) <0.001 117 (51.5) <0.001 
    Ever 49 (18.8) 90 (39.1)  164 (73.2)  110 (48.5)  
Smoking status        
    Never 102 (40.2) 109 (48.4) 0.026 87 (39.2) 0.400 45 (20.4) <0.001 
    Ex-smoker 107 (42.1) 68 (30.2)  85 (38.3)  99 (44.8)  
    Current 45 (17.7) 48 (21.3)  50 (22.5)  77 (34.8)  
Alcohol, mean (g/d) 26.1 22.0 0.151 22.3 0.214 19.2 0.012 
Body mass index, mean (kg/m227.0 27.8 0.047 27.0 0.895 28.7 <0.001 
VariablesControls, n (%)Reflux esophagitis, n (%)P (reflux esophagitis vs controls)Barrett's esophagus, n (%)P (Barrett's esophagus vs controls)Esophageal adenocarcinoma, n (%)P (esophageal adenocarcinoma vs controls)
Sex        
    Male 220 (84.6) 189 (82.2) 0.468 185 (82.6) 0.548 192 (84.6) 0.992 
    Female 40 (15.4) 41 (17.8)  39 (17.4)  35 (15.4)  
Age, mean (y) 63.0 61.7 0.219 62.4 0.567 64.2 0.276 
Education (full-time), mean (y) 12.0 10.8 <0.001 11.3 0.013 10.7 <0.001 
Gastroesophageal reflux symptoms*        
    Never 211 (81.2) 140 (60.9) <0.001 60 (26.8) <0.001 117 (51.5) <0.001 
    Ever 49 (18.8) 90 (39.1)  164 (73.2)  110 (48.5)  
Smoking status        
    Never 102 (40.2) 109 (48.4) 0.026 87 (39.2) 0.400 45 (20.4) <0.001 
    Ex-smoker 107 (42.1) 68 (30.2)  85 (38.3)  99 (44.8)  
    Current 45 (17.7) 48 (21.3)  50 (22.5)  77 (34.8)  
Alcohol, mean (g/d) 26.1 22.0 0.151 22.3 0.214 19.2 0.012 
Body mass index, mean (kg/m227.0 27.8 0.047 27.0 0.895 28.7 <0.001 
*

Symptoms of heartburn or acid reflux experienced at least once a week or >50 times per year, >5 y before the interview date.

“Never smoker” is defined as those subjects who had never smoked, who had smoked <100 cigarettes in their lifetime, or who had smoked <1 cigarette per day for ≥6 mo. “Ex-smoker” is defined as smokers who had stopped >5 y before the interview date. “Current smoker” is defined as smokers who had smoked at least 1 cigarette per day for ≥6 mo, 5 y before the interview date.

The distribution and frequency of genotypes for cases and controls are shown in Table 2. There were no significant departures from Hardy-Weinberg equilibrium for any of the polymorphisms in any of the subject groups. For controls, the frequency of polymorphic variants was 0.24 (hOGG1 Ser326Cys), 0.36 (XRCC1 Arg399Gln), and 0.38 (XPD Lys751Gln). These were similar to frequencies reported in Caucasians in the SNP500 Database (http://snp500cancer.nci.nih.gov).

Table 2.

Frequency of hOGG1, XRCC1, and XPD genotypes and risk of reflux esophagitis, Barrett's esophagus, and esophageal adenocarcinoma, relative to asymptomatic controls

GenotypeControls (n = 248)
Reflux esophagitis (n = 230)
Barrett's esophagus (n = 212)
Esophageal adenocarcinoma (n = 209)
nnUnadjusted OR (95% CI)Adjusted OR* (95% CI)nUnadjusted OR (95% CI)Adjusted OR* (95% CI)nUnadjusted OR (95% CI)Adjusted OR* (95% CI)
hOGG1           
Ser326Cys           
    Ser/Ser 141 146 1.00 1.00 124 1.00 1.00 138 1.00 1.00 
    Ser/Cys 96 71 0.71 (0.49-1.05) 0.73 (0.48-1.12) 75 0.89 (0.60-1.31) 0.93 (0.62-1.39) 67 0.71 (0.48-1.05) 0.73 (0.47-1.12) 
    Cys/Cys 11 13 1.14 (0.50-2.63) 1.01 (0.42-2.45) 12 1.24 (0.53-2.91) 1.18 (0.49-2.84) 0.37 (0.12-1.20) 0.33 (0.10-1.14) 
Ser/Cys + Cys/Cys 107 84 0.76 (0.53-1.10) 0.77 (0.51-1.14) 87 0.93 (0.64-1.34) 0.96 (0.65-1.41) 71 0.68 (0.46-1.00) 0.68 (0.45-1.03) 
XRCC1           
Arg399Gln           
    Arg/Arg 100 99 1.00 1.00 73 1.00 1.00 84 1.00 1.00 
    Arg/Gln 115 104 0.91 (0.62-1.34) 0.86 (0.56-1.31) 113 1.35 (0.90-2.00) 1.24 (0.82-1.88) 99 1.03 (0.69-1.52) 1.00 (0.65-1.55) 
    Gln/Gln 33 27 0.83 (0.46-1.48) 0.75 (0.40-1.40) 26 1.08 (0.60-1.96) 1.01 (0.55-1.87) 26 0.94 (0.52-1.69) 0.86 (0.45-1.64) 
    Arg/Gln + Gln/Gln 148 131 0.89 (0.62-1.29) 0.83 (0.56-1.24) 139 1.29 (0.88-1.88) 1.19 (0.80-1.77) 125 1.01 (0.69-1.46) 0.97 (0.64-1.47) 
XPD           
Lys751Gln           
    Lys/Lys 91 89 1.00 1.00 76 1.00 1.00 80 1.00 1.00 
    Lys/Gln 121 108 0.91 (0.62-1.35) 0.84 (0.55-1.28) 100 0.99 (0.66-1.48) 0.95 (0.63-1.45) 94 0.88 (0.59-1.32) 0.84 (0.54-1.31) 
    Gln/Gln 35 33 0.96 (0.55-1.69) 0.89 (0.48-1.64) 36 1.23 (0.71-2.15) 1.14 (0.64-2.04) 34 1.11 (0.63-1.93) 0.97 (0.52-1.81) 
    Lys/Gln + Gln/Gln 156 141 0.92 (0.64-1.34) 0.85 (0.57-1.27) 136 1.04 (0.71-1.53) 1.00 (0.67-1.48) 128 0.93 (0.64-1.37) 0.87 (0.57-1.32) 
GenotypeControls (n = 248)
Reflux esophagitis (n = 230)
Barrett's esophagus (n = 212)
Esophageal adenocarcinoma (n = 209)
nnUnadjusted OR (95% CI)Adjusted OR* (95% CI)nUnadjusted OR (95% CI)Adjusted OR* (95% CI)nUnadjusted OR (95% CI)Adjusted OR* (95% CI)
hOGG1           
Ser326Cys           
    Ser/Ser 141 146 1.00 1.00 124 1.00 1.00 138 1.00 1.00 
    Ser/Cys 96 71 0.71 (0.49-1.05) 0.73 (0.48-1.12) 75 0.89 (0.60-1.31) 0.93 (0.62-1.39) 67 0.71 (0.48-1.05) 0.73 (0.47-1.12) 
    Cys/Cys 11 13 1.14 (0.50-2.63) 1.01 (0.42-2.45) 12 1.24 (0.53-2.91) 1.18 (0.49-2.84) 0.37 (0.12-1.20) 0.33 (0.10-1.14) 
Ser/Cys + Cys/Cys 107 84 0.76 (0.53-1.10) 0.77 (0.51-1.14) 87 0.93 (0.64-1.34) 0.96 (0.65-1.41) 71 0.68 (0.46-1.00) 0.68 (0.45-1.03) 
XRCC1           
Arg399Gln           
    Arg/Arg 100 99 1.00 1.00 73 1.00 1.00 84 1.00 1.00 
    Arg/Gln 115 104 0.91 (0.62-1.34) 0.86 (0.56-1.31) 113 1.35 (0.90-2.00) 1.24 (0.82-1.88) 99 1.03 (0.69-1.52) 1.00 (0.65-1.55) 
    Gln/Gln 33 27 0.83 (0.46-1.48) 0.75 (0.40-1.40) 26 1.08 (0.60-1.96) 1.01 (0.55-1.87) 26 0.94 (0.52-1.69) 0.86 (0.45-1.64) 
    Arg/Gln + Gln/Gln 148 131 0.89 (0.62-1.29) 0.83 (0.56-1.24) 139 1.29 (0.88-1.88) 1.19 (0.80-1.77) 125 1.01 (0.69-1.46) 0.97 (0.64-1.47) 
XPD           
Lys751Gln           
    Lys/Lys 91 89 1.00 1.00 76 1.00 1.00 80 1.00 1.00 
    Lys/Gln 121 108 0.91 (0.62-1.35) 0.84 (0.55-1.28) 100 0.99 (0.66-1.48) 0.95 (0.63-1.45) 94 0.88 (0.59-1.32) 0.84 (0.54-1.31) 
    Gln/Gln 35 33 0.96 (0.55-1.69) 0.89 (0.48-1.64) 36 1.23 (0.71-2.15) 1.14 (0.64-2.04) 34 1.11 (0.63-1.93) 0.97 (0.52-1.81) 
    Lys/Gln + Gln/Gln 156 141 0.92 (0.64-1.34) 0.85 (0.57-1.27) 136 1.04 (0.71-1.53) 1.00 (0.67-1.48) 128 0.93 (0.64-1.37) 0.87 (0.57-1.32) 
*

Adjusted for age, sex, years of full-time education, body mass index, smoking, alcohol, and gastroesophageal reflux symptoms. 95% CI, 95% confidence interval.

One subject was “undetermined” and excluded from analysis.

Two subjects were “undetermined” and excluded from analysis.

There were no statistically significant associations between the hOGG1 Ser326Cys, XRCC1 Arg399Gln, and XPD Lys751Gln polymorphisms and the risk of esophageal adenocarcinoma, Barrett's esophagus, or reflux esophagitis.

To date, this is the largest case-control study to explore the association between DNA repair gene polymorphisms and risk of esophageal adenocarcinoma. In addition, it is the first population-based study to evaluate the role of these polymorphisms in Barrett's esophagus and reflux esophagitis. All three polymorphisms were in Hardy-Weinberg equilibrium and had sufficient statistical power (>80%) to detect an odds ratio (OR) of >2.0. Further strengths of our study include the population-based design and clear characterization of phenotypes to minimize misclassification bias. Detailed interview data allowed us to control for a range of potential confounding factors, and DNA was available for analysis in almost all subjects.

Our findings are in contrast to results from a Swedish case-control study, which suggested that the XPD Lys751Gln polymorphism was associated with a significantly increased risk of esophageal adenocarcinoma (10). This study also had a population-based design, strict definition of phenotypes, and detailed interview data. However, DNA was available for analysis in only 50% of interviewed subjects, questioning the internal validity of the study. In addition, the present study included over two times the number of esophageal adenocarcinoma subjects. Liu et al. also reported an increased risk of esophageal adenocarcinoma in association with the XPD Lys751Gln polymorphism (9). Although this study was a reasonable size, with 183 esophageal adenocarcinoma subjects recruited, major limitations were its hospital-based design and lack of complete case ascertainment. In a Canadian study, Casson et al. reported further conflicting results, suggesting that the XPD Lys751Gln polymorphism was associated with a reduced risk of esophageal adenocarcinoma (11). This study was limited by its hospital-based design and small sample size, including only 56 esophageal adenocarcinoma subjects.

In keeping with our results, all three previous studies have reported no association with the XRCC1 Arg399Gln polymorphism and risk of esophageal adenocarcinoma (9-11). However, in the only previous study to investigate DNA repair polymorphisms in Barrett's esophagus and reflux esophagitis, Casson et al. reported a reduced risk of these conditions in association with XRCC1 Arg399Gln (11). The limitations of this study have been discussed and it is likely that results from our study are more robust given that we recruited over double the number of study subjects.

We reported no association between the hOGG1 Ser326Cys polymorphism and risk of esophageal adenocarcinoma, Barrett's esophagus, or reflux esophagitis. No previous study has investigated this polymorphism in relation to these conditions.

However, association studies in esophageal squamous cell carcinoma have produced conflicting results (13, 14). A limitation of our study was inadequate power to detect a modest excess risk (OR < 2.0) or to examine the role of possible gene-environment interactions.

In summary, we found no significant associations between the hOGG1 Ser326Cys, XRCC1 Arg399Gln, and XPD Lys751Gln polymorphisms and the risk of esophageal adenocarcinoma, Barrett's esophagus, or reflux esophagitis.

Grant support: Ireland-Northern Ireland Co-operation Research Project grant sponsored by the Research and Development Office (Belfast, Northern Ireland) and Health Research Board (Dublin, Ireland) and by the Ulster Cancer Foundation (Belfast, Northern Ireland); Northern Ireland Research and Development Office Clinical Fellowship.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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