X-ray repair cross-complementing group 1 polymorphisms and cancer risks in Asian populations: A mini review

The Effect of Polymorphisms in DNA Repair Genes and Carcinogen Metabolizers on Leukocyte Telomere Length: A Cohort of Healthy Spanish Smokers

INTRODUCTION

Smoking implies exposure to carcinogenic agents that causes DNA damage, which could be suspected to enhance telomere attrition. To protect and deal with DNA damage, cells possess mechanisms that repair and neutralize harmful substances. Polymorphisms altering DNA repair capacity or carcinogen metabolism may lead to synergistic effects with tobacco carcinogen-induced shorter telomere length independently of cancer interaction. The aim of this study was to explore the association between leukocyte telomere length (LTL) and several genetic polymorphisms in DNA repair genes and carcinogen metabolizers in a cohort of healthy smokers.

METHODS

We evaluated the effect of six genetic polymorphisms in cytochrome P1A1 (Ile462Val), XRCC1 (Arg399Gln), APEX1 (Asp148Glu), XRCC3 (Thr241Met), and XPD (Asp312Asn; Lys751Gln) on LTL in a cohort of 145 healthy smokers in addition to smoking habits.

RESULTS

Logistic regression analysis showed an association between XRCC1 399Gln allele and shorter telomere length (OR = 5.03, 95% CI = 1.08% to 23.36%). There were not association between the rest of polymorphisms analyzed and LTL.

CONCLUSIONS

Continuous exposure to tobacco could overwhelm the DNA repair machinery, making the effect of the polymorphisms that reduce repair capacity more pronounced. Analyzing the function of smoking-induced DNA-repair genes and LTL is an important goal in order to identify therapeutic targets to treat smoking-induced diseases.

Association of DNA base-excision repair XRCC1, OGG1 and APE1 gene polymorphisms with nasopharyngeal carcinoma susceptibility in a Chinese population

BACKGROUND

Numerous carcinogens and reactive oxygen species (ROS) may cause DNA damage including oxidative base lesions that lead to risk of nasopharyngeal carcinoma. Genetic susceptibility has been reported to play a key role in the development of this disease. The base excision repair (BER) pathway can effectively remove oxidative lesions, maintaining genomic stability and normal expression, with X-ray repair crosscomplementing1 (XRCC1), 8-oxoguanine glycosylase-1 (OGG1) and apurinic/apyimidinic endonuclease 1 (APE1) playing important roles.

AIMS

To analyze polymorphisms of DNA BER genes (OOG1, XRCC1 and APE1) and explore their associations, and the combined effects of these variants, with risk of nasopharyngeal carcinoma.

MATERIALS AND METHODS

We detected SNPs of XRCC1 (Arg399Gln), OGG1 (Ser326Cys), APE1 (Asp148Glu and -141T/G) using the polymerase chain reaction (PCR) with peripheral blood samples from 231 patients with NPC and 300 healthy people, furtherly analyzing their relations with the risk of NPC in multivariate logistic regression models.

RESULTS

After adjustment for sex and age, individuals with the XRCC1 399Gln/Gln (OR=1.96; 95%CI:1.02- 3.78; p=0.04) and Arg/Gln (OR=1.87; 95%CI:1.29-2.71; p=0.001) genotype variants demonstrated a significantly increased risk of nasopharyngeal carcinoma compared with those having the wild-type Arg/Arg genotype. APE1- 141G/G was associated with a significantly reduced risk of NPC (OR=0.40;95%CI:0.18-0.89) in the smoking group. The OR calculated for the combination of XRCC1 399Gln and APE1 148Gln, two homozygous variants ,was significantly additive for all cases (OR=2.09; 95% CI: 1.27-3.47; p=0.004).

CONCLUSION

This is the first study to focus on the association between DNA base-excision repair genes (XRCC1, OGG1 and APE1) polymorphism and NPC risk. The XRCC1 Arg399Gln variant genotype is associated with an increased risk of NPC. APE1- 141G/G may decrease risk of NPC in current smokers. The combined effects of polymorphisms within BER genes of XRCC1 399Gln and APE1 148Gln may contribute to a high risk of nasopharyngeal carcinoma.

Deoxyribonucleic acid repair gene X-ray repair cross-complementing group 1 polymorphisms and non-carcinogenic disease risk in different populations: A meta-analysis

PURPOSE

This study aims to assess a meta-analysis of the association of X-ray repair cross-complementing group 1 (XRCC1) polymorphisms with the risk of various non-carcinogenic diseases in different population.

MATERIALS AND METHODS

This meta-analysis was performed by critically reviewing reveals 38 studies involving 10043 cases and 11037 controls. Among all the eligible studies, 14 focused on Arg194Trp polymorphism, 33 described the Arg399Gln and three articles investigated on Arg280His. Populations were divided into three different ethnic subgroups include Caucasians, Asians and other (Turkish and Iranian).

RESULTS

Pooled results showed no correlation between Arg194Trp and non-carcinogenic disease. There was only weak relation in the recessive (odds ratio [OR] =1.11, 95% confidence interval [CI]: 0.86-1.44) model in Asian population and dominant (OR = 1.04, 95% CI: 0.66-1.63) model of other populations. In Arg399Gln polymorphism, there was no relation with diseases of interest generally. In the pooled analysis, there were weak relation in the dominant (OR = 1.08, 95% CI: 0.86-1.35) model of Asian population and quite well-correlation with recessive (OR = 1.49, 95% CI: 1.19-1.88), dominant (OR = 1.23, 95% CI: 0.94-1.62), and additive (OR = 1.23, 95% CI: 0.94-1.62) models of other subgroup. For Arg280His, there was a weak relation only in the dominant model (OR = 1.06, 95% CI: 0.74-1.51).

CONCLUSION

The present meta-analysis correspondingly shows that Arg399Gln variant to be associated with increased non-carcinogenic diseases risk through dominant and recessive modes among Iranian and Turkish population. It also suggests a trend of dominant and recessive effect of Arg280His variant in all population and its possible protective effect on non-carcinogenic diseases.

Meta-analysis of genetic polymorphisms and ophthalmologic disease risk in Asian populations: a case of DNA repair XRCC1 gene

This study aimed to assess a meta-analysis of the association of XRCC1 polymorphisms with the risk of various ophthalmologic diseases in Asian population. This meta-analysis was performed by critically reviewing reveals 38 studies involving 1373 cases and 1745 controls. Among all the eligible studies, one focused on Arg194Trp polymorphism, nine described the Arg399Gln and no article investigated on Arg280His. There was a large between-study heterogeneity in ORs of individual studies of the dominant model (chi2 = 74.18, I2 = 58.9%, p = 0.013) and the additive (chi2 = 56.18, I2 = 41.4%, p = 0.091) models, but a moderate heterogeneity in the recessive model (chi2 = 72.27, I2 = 78.8%, p = 0.000) was observed. So, we pooled the results using the random-effect analysis and found that Arg399Gln has a weak relation with ophthalmologic disease in the recessive (OR = 0.96, 95% CI: 0.64-1.44), the dominant (OR = 1.05, 95% CI: 0.82-1.33) and the additive (OR = 1.15, 95% CI: 0.77-1.70) and models. The present meta-analysis correspondingly shows that comprising diverse population is very important since susceptibility loci might vary indifferent ethnic groups. To ratify our findings, widespread studies with enlarged sample size and various populations are essential to explain the role of all polymorphism of XRCC1 genes in the pathogenesis of ophthalmologic diseases. Finally, our meta-analysis showed Arg399Gln variant was not associated with increased ophthalmologic diseases risk via dominant and recessive modes among Asian population.

XRCC1 399 Arg-related genotype and allele, but not XRCC1 His107Arg, XRCC1 Trp194Arg, KCNQ2, AT1R, and hOGG1 polymorphisms, are associated with higher susceptibility of endometriosis

X-ray repair cross-complementing group 1 (XRCC1) and human 8-oxoguanine glycosylase 1 (hOGG1) play important roles in base excision repair. KCNQ genes comprising voltage-gated ion-channels related with cell stability. Angiotensin II type 1 receptor (AT1R) is related with angiogenesis, which influence endometriosis growth, invasion and regression. We aimed to investigate whether these polymorphisms were associated with endometriosis susceptibility. Women were divided [ 1 ]: endometriosis (n = 136 [ 2 ]); non-endometriosis groups (n = 112). XRCC1 (codon 107, 194, 399), hOGG1, KCNQ2, AT1R polymorphisms were amplified by PCR and detected by electrophoresis after restriction enzyme (RsaI, HpaII, MspI, Fnu4HI, Ava II, Dde I) digestions. Genotypes and allelic frequencies in both groups were compared. Proportions of XRCC1 Arg399Gln*GG/GA/AA and G/A allele between both groups were [ 1 ]: 41.9/53.7/4.4% and 68.8/31.2% [ 2 ]; 30.4/54.5/15.1% and 57.6/42.4% (p < 0.05). Other 5 polymorphisms (XRCC1 codon 107 and 194, hOGG1, KCNQ2, and AT1R) between both groups were non-significantly different. Proportions of XRCC1 107*AA/AG/GG and XRCC1 194*TT/TC/CC between both groups were [ 1 ]: 3.7/27.2/69.1% and 5.8/34.6/59.6% [ 2 ]; 2.6/21.4/75.8% and 11.6/37.5/50.9%. HOGG1*CC/CG/GG, KCNQ2*AA/AC/CCC and AT1R*AA/AC/CC were [ 1 ]: 14.8/42.6/42.6, 14/41.9/44.1 and 92.6/7.4/0% [ 2 ]; 11.6/50/38.4, 17/50/33 and 100/0/0%. We concluded that XRCC1 399 Arg-related genotype and allele are correlated with higher susceptibility to endometriosis, which suggested its association with endometriosis pathogenesis. XRCC1 107 and 194, hOGG1, KCNQ2, and AT1R are not associated with endometriosis susceptibility.

Multiple pathway-based genetic variations associated with tobacco related multiple primary neoplasms

BACKGROUND

In order to elucidate a combination of genetic alterations that drive tobacco carcinogenesis we have explored a unique model system and analytical method for an unbiased qualitative and quantitative assessment of gene-gene and gene-environment interactions. The objective of this case control study was to assess genetic predisposition in a biologically enriched clinical model system of tobacco related cancers (TRC), occurring as Multiple Primary Neoplasms (MPN).

METHODS

Genotyping of 21 candidate Single Nucleotide Polymorphisms (SNP) from major metabolic pathways was performed in a cohort of 151 MPN cases and 210 cancer-free controls. Statistical analysis using logistic regression and Multifactor Dimensionality Reduction (MDR) analysis was performed for studying higher order interactions among various SNPs and tobacco habit.

RESULTS

Increased risk association was observed for patients with at least one TRC in the upper aero digestive tract (UADT) for variations in SULT1A1 Arg²¹³His, mEH Tyr¹¹³His, hOGG1 Ser³²⁶Cys, XRCC1 Arg²⁸⁰His and BRCA2 Asn³⁷²His. Gene-environment interactions were assessed using MDR analysis. The overall best model by MDR was tobacco habit/p53(Arg/Arg)/XRCC1(Arg³⁹⁹His)/mEH(Tyr¹¹³His) that had highest Cross Validation Consistency (8.3) and test accuracy (0.69). This model also showed significant association using logistic regression analysis.

CONCLUSION

This is the first Indian study on a multipathway based approach to study genetic susceptibility to cancer in tobacco associated MPN. This approach could assist in planning additional studies for comprehensive understanding of tobacco carcinogenesis.

Genetic polymorphism of DNA base-excision repair genes (APE1, OGG1 and XRCC1) and their correlation with risk of lung cancer in a Chinese population

BACKGROUND AND AIMS

Reactive oxygen species (ROS) and numerous carcinogens may cause DNA damage including oxidative base lesions that contribute to the risk of lung cancer. The base excision repair (BER) pathway could effectively remove oxidative lesions in which 8-oxoguanine glycosylase-1 (OGG1), x-ray repair cross-complementing 1 (XRCC1), and apurinic/apyimidinic endonuclease 1 (APE1) play key roles. The aim of this study was to analyze the polymorphisms of DNA BER genes (OOG1, XRCC1 and APE1) and explore their associations, and the combined effects of these variants, with risk of lung cancer.

METHODS

In a hospital-based, case-control study of 455 lung cancer cases and 443 cancer-free hospital controls, the SNPs of OGG1 (Ser326Cys), XRCC1 (Arg399Gln), APE1 (Asp148Glu and -141T/G) were genotyped and analyzed for their correlation with the risk of lung cancer in multivariate logistic regression models.

RESULTS

Individuals homozygous for the variants APE1 -141GG showed a protective effect for lung cancer overall (OR=0.62; 95% CI: 0.42-0.91; p=0.02) and for lung adenocarcinoma (OR=0.65; 95% CI, 0.44-0.96; p=0.03). When analyzing the combined effects of variant alleles, 84 patients and controls were identified who were homozygous for two or three of the potential protective alleles (i.e., OGG1 326Cys, XRCC1 399Gln and APE1 -141G). ORs were significantly reduced when all patients were analyzed (OR=0.62; 95% CI: 0.38-0.99; p=0.05).

CONCLUSIONS

The combined effects of polymorphisms within BER genes may contribute to the tumorigenesis of lung cancer.

Smoking and selected DNA repair gene polymorphisms in controls: systematic review and meta-analysis

BACKGROUND

When the case-only study design is used to estimate statistical interaction between genetic (G) and environmental (E) exposures, G and E must be independent in the underlying population, or the case-only estimate of interaction (COR) will be biased. Few studies have examined the occurrence of G-E association in published control group data.

METHODS

To examine the assumption of G-E independence in empirical data, we conducted a systematic review and meta-analysis of G-E associations in controls for frequently investigated DNA repair genes (XRCC1 Arg399Gln, Arg194Trp, or Arg280His, XPD Lys751Gln, and Asp312Asn, and XRCC3 Thr241Met), and smoking (ever/never smoking, current/not current smoker, smoking duration, smoking intensity, and pack-years).

RESULTS

Across the 55 included studies, single nucleotide polymorphisms SNP-smoking associations in controls (OR(z)) were not reliably at the null value of 1.0 for any SNP-smoking combinations. Two G-E combinations were too heterogeneous for summary estimates: XRCC1 399 and ever-never smoking (N = 21), and XPD 751 and pack-years (N = 12). OR(z) ranges for these combinations were: [OR(z) (95% confidence interval (CI)] 0.7 (0.4, 1.2)-1.9 (1.2, 2.8) and 0.8 (0.5, 1.3)-2.3 (0.8, 6.1), respectively). Estimates for studies considered homogeneous (Cochran's Q P-value <0.10) varied 2- to 5-fold. No study characteristics were identified that could explain heterogeneity.

CONCLUSIONS

We recommend the independence assumption be evaluated in the population underlying any potential case-only study, rather than in a proxy control group(s) or pooled controls.

IMPACT

These results suggest that G-E association in controls may be population-specific. Increased access to control data would improve evaluation of the independence assumption.

Genetic polymorphisms of DNA repair gene XRCC1 and risk of uterine leiomyoma

The objective was to study the relationship between the polymorphisms of the DNA repair gene XRCC1 Arg399Gln, Arg194Trp, and Arg280His uterine leiomyoma in a Chinese population. In the case-control study, we compared the XRCC1 gene polymorphism of 136 uterine leiomyoma patients and 140 healthy controls by using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results suggested that the genotype Arg/Arg of codon 280 was significantly different from its heterozygote (odds ratio [OR] = 3.633, 95% confidence interval [CI]: 2.147-6.148). In conclusion, the results suggest that polymorphism of XRCC1 Arg280His was associated with the increased risk of uterine leiomyoma in a Chinese population.

XRCC4 codon 247*A and XRCC4 promoter -1394*T related genotypes but not XRCC4 intron 3 gene polymorphism are associated with higher susceptibility for endometriosis

DNA repair systems act to maintain genome integrity in the face of replication errors, environmental insults, and the cumulative effects of age. Genetic variants in DNA repair genes such as X-ray repair cross-complementing group 4 (XRCC4) might influence the ability to repair damaged DNA. Herein we aimed to investigate whether some XRCC4-related polymorphisms were associated with endometriosis susceptibility. Women were divided: (1) severe endometriosis (rAFS stage IV, n = 136) and (2) nonendometriosis groups (n = 112). The polymorphisms of XRCC4 codon 247, XRCC4 promoter -1394, and XRCC4 intron 3 insertion/deletion (I/D) polymorphism were amplified by PCR and detected by electrophoresis after restriction enzyme (BBS I, Hinc II) digestions. Genotypes and allelic frequencies in both groups were compared. We observed that XRCC4 codon 247*A and XRCC4 promoter -1394*T related genotypes, but not XRCC4 intron 3 I/D polymorphism, are associated with higher susceptibility for endometriosis. Distributions of XRCC4 codon 247*C homozygote/heterozygote/A homozygote, and C/A allele in both groups were: (1) 89/9.5/1.5% and 93.7/6.3%; (2) 97.3/2.7/0%, and 98.7/1.3% (P < 0.05). Proportions of XRCC4 promoter -1394*T homozygote/heterozygote/G homozygote and T/G allele in both groups were: (1) 94.1/5.2/0.7% and 96.7/3.3%, and (2) 79.4/17.9/2.7% and 88.4/11.6% (P < 0.005). Proportions of XRCC4*I homozygote/heterozygote/D homozygote and A/C allele in both groups were: (1) 67.6/30.9/1.5% and 83.2/16.8%, and (2) 70.5/24.1/5.4% and 82.6/17.4% (nondifference). We conclude that XRCC4 codon 247*A and XRCC4 promoter -1394*T related genotypes and alleles, but not XRCC4 intron 3 I/D polymorphism, might be associated with endometriosis susceptibilities and pathogenesis.

Polymorphism of XRCC1 (at codon 399) and susceptibility to breast cancer, a meta-analysis of the literatures

The X-ray repair cross-complementation group 1 (XRCC1) protein plays an important role in base excision repair. Several polymorphisms in the XRCC1 gene have been described, including Arg399Gln. Previous studies investigating the association between genetic polymorphism of Arg399Gln XRCC1 and risk of breast cancer have provided inconsistent results. A meta-analysis was conducted to investigate the association between common genetic variant in the XRCC1 gene (exon 10, Arg399Gln) with breast cancer risk. We identified 36 eligible studies, in relation to the Arg399Gln polymorphism of XRCC1 and risk of breast cancer. These studies comprised of 43,716 subjects (20,837 patients and 22,879 controls). We first estimated the risk of the genotypes Arg/Gln and Gln/Gln compared with the wild-type Arg/Arg homozygote, and then evaluated the risk of Gln/Gln versus (Arg/Gln+Arg/Arg) and (Gln/Gln+Arg/Gln) versus Arg/Arg, which assumed recessive and dominant effects, respectively, of the variant 399Gln allele. There was significant heterogeneity between studies. The overall ORs showed that the breast cancer risk were not associated with the XRCC1 genotypes. The heterogeneity between studies decreased dramatically when studies stratified into Asian and Western countries. There was significant association between the polymorphism of XRCC1 and breast cancer risk among studies of Asian countries. In Asian countries the Arg/Gln versus Arg/Arg (OR = 0.98, 95% CI: 0.88-1.10) and Gln/Gln+Arg/Gln versus Arg/Arg (OR = 1.05, 95% CI: 0.95-1.18) were not associated with increased risk of breast cancer. On the other hand, both Gln/Gln versus Arg/Arg (OR = 1.46, 95% CI: 1.19-1.79) and Gln/Gln versus Arg/Gln+Arg/Arg (OR = 1.49, 95% CI: 1.22-1.81) increased the risk. Therefore, it could be concluded that 399Gln allele might act as a recessive allele in its association with breast cancer risk.

Genetic polymorphism in the DNA repair gene XRCC1 and susceptibility to schizophrenia

The X-ray repair cross-complementation group 1 (XRCC1) protein plays an important role in base excision repair. A high level of XRCC1 mRNA and/or protein has been found in rat and baboon brains. An exon 10 variant at codon 399 of XRCC1 leads to an Arg to Gln amino acid change. The 399Gln allele is associated with an increased risk of several types of cancers, increased DNA adducts and chromosomal changes; therefore, it appears that the 399Gln allele may alter the role of the XRCC1 protein in DNA repair. The present case-control study was performed on 303 (223 males, 80 females) in-patients with chronic schizophrenia and 303 healthy blood donors matched to the patients by age (+/-5 years) and gender. The XRCC1 genotypes were determined using a PCR-based method. Heterozygosity (OR=1.48, 95% CI: 1.05-2.09) and homozygosity (OR=2.00, 95% CI: 1.17-3.42) for the Gln399 allele increased the risk of schizophrenia. There was a significant linear trend in risk associated with zero, one, and two 399Gln alleles. The present finding indicates that XRCC1 is a candidate gene for susceptibility to schizophrenia.

Association of XRCC1 gene polymorphisms with idiopathic azoospermia in a Chinese population

AIM

To assess the possible role of genetic polymorphisms in DNA repair gene XRCC1 (X-ray repair cross-complementing group 1) during spermatogenesis by investigating the associations of one promoter polymorphism (T-77C) and two exonic polymorphisms (Arg194Trp and Arg399Gln) in XRCC1 gene with risk of idiopathic azoospermia in a Chinese population.

METHODS

The genotype and allele frequencies of three observed polymorphisms were examined by polymerase chain reaction-restriction fragment length polymorphism based on a Chinese population consisting of 171 idiopathic azoospermia subjects and 247 normal-spermatogenesis controls.

RESULTS

In our study, all the observed genotype frequencies were in agreement with Hardy-Weinberg equilibrium. The 399A (GA+AA) allele frequency for idiopathic azoospermia subjects and controls was 0.216 and 0.269, respectively. Compared with GG genotype, the AA genotype of Arg399Gln showed a significant association with a decreased risk of idiopathic azoospermia (odds ratio = 0.315; 95% confidence interval = 0.12-0.86). However, no significant differences were found between the cases and controls for T-77C and Arg194Trp polymorphisms. The major haplotypes of XRCC1 gene were TCG, TTG and TCA, whereas no haplotypes appeared to be significantly associated with idiopathic azoospermia based on the cutoff of P < 0.05.

CONCLUSION

In a selected Chinese population, AA genotype of Arg399Gln appears to contribute to a decreased risk of idiopathic azoospermia, while we have not any evidence of involvement of XRCC1 T-77C and Arg194Trp polymorphisms in idiopathic azoospermia.

XRCC1 down-regulation in human cells leads to DNA-damaging agent hypersensitivity, elevated sister chromatid exchange, and reduced survival of BRCA2 mutant cells

Previous studies using rodent cells indicate that a deficiency in XRCC1 results in reduced single-strand break repair, increased sensitivity to DNA-damaging agents, and elevated levels of sister chromatid exchange (SCE). Epidemiological studies have suggested an association of certain human XRCC1 polymorphisms with genetic instability and cancer susceptibility. However, investigations on the molecular functions of XRCC1 in human cells are limited. To determine the contributions of this nonenzymatic scaffold protein, we suppressed XRCC1 levels in several human cell lines using small interfering RNA (siRNA) technology. We report that XRCC1 down-regulation in HeLa cells leads to a concomitant decrease in the DNA ligase 3 protein level and an impaired nick ligation capacity. In addition, depletion of XRCC1 resulted in a significantly increased sensitivity to the alkylating agent methyl methanesulfonate and the thymidine base analog 5-hydroxymethyl-2'-deoxyuridine, a slightly increased sensitivity to ethyl methanesulfonate and 1,3-bis(2-chloroethyl)-1-nitrosourea, and no change in the response to camptothecin. We also discovered that a 70-80% reduction in XRCC1 protein leads to an elevated level of SCE in both HeLa cells and normal human fibroblasts, but does not affect chromosome aberrations in the diploid fibroblasts. Last, XRCC1 siRNA transfection led to an approximately 40% decrease in the survival of BRCA2-deficient cells, supporting a model whereby the accumulation of unrepaired SSBs leads to the accumulation of cytotoxic DNA double strand breaks following replication fork collapse in cells defective in homologous recombination.

Polymorphisms of DNA repair genes are risk factors for prostate cancer

DNA repair gene alterations have been shown to cause a reduction in DNA repair capacity. We hypothesised that DNA repair gene polymorphisms may be risk factors for prostate cancer (PC). To test this hypothesis, DNA samples from 165 cases of prostate cancer and healthy controls were analyzed by PCR-RFLP to determine the genotypic frequency of three DNA repair genes (XRCC1, XPC and XRCC7). We found that the frequency of 939Gln variant at XPC Lys939Gln was significantly lower in PC cases (OR=0.39, P=0.016). Haplotype analysis of XRCC1 Arg194Trp (C/T) and Arg399Gln (G/A) revealed that the frequency of the T-A haplotype was significantly higher in PC patients. This is the first report on the studies of XPC and XRCC1 Arg194Trp polymorphisms in PC, and our present data suggest that XPC Lys939Gln and the T-A haplotype of XRCC1 Arg194Trp and Arg399Gln may be risk factors for PC in Japanese.

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.