A limited association of OGG1 Ser326Cys polymorphism for adenocarcinoma of the lung

Impact of single nucleotide polymorphisms in the OGG1 and XRCC1 genes on modulation of DNA damage in pesticide-exposed agricultural workers in Punjab, North-West India

Pesticide-induced DNA damage is primarily repaired by base excision repair (BER) pathway. However, polymorphism in DNA repair genes may modulate individual's DNA repair capacity (DRC) leading to increased genotoxicity and adverse health effects. Our first study in North-West Indian population aimed to evaluate the impact of OGG1 rs1052133 (Ser326Cys; C1245G), XRCC1 rs1799782 (Arg194Trp; C26304T) and XRCC1 rs25487 (Arg399Gln; G28152A) polymorphisms on the modulation of pesticide-induced DNA damage in a total of 450 subjects (225 pesticide-exposed agricultural workers and 225 age- and sex-matched controls). DNA damage was estimated by alkaline comet assay using silver-staining method. Genotyping was carried out by PCR-RFLP using site-specific restriction enzymes. Mann-Whitney U-test revealed elevation in DNA damage parameters (p < 0.01) in pesticide-exposed agricultural workers than controls. Chi-square test showed significant (p < 0.05) differences in the XRCC1 Arg194Trp (C26304T) and Arg399Gln (G28152A) genotypes among two groups. Multivariate logistic-regression analysis revealed that heterozygous genotypes of OGG1 rs1052133 (326Ser/Cys; 1245CA), XRCC1 rs1799782 (194Arg/Trp; 26304CT) and XRCC1 rs25487 (399Arg/Gln; 2815GA) were positively associated (p < 0.05) with elevated DNA damage parameters in pesticide-exposed agricultural workers. Our results strongly indicate significant positive association of variant OGG1 and XRCC1 genotypes with reduced DRC and higher pesticide-induced DNA damage in North-West Indian agricultural workers.

The correlation of combined OGG1, CYP1A1 and GSTP1 gene variants and risk of lung cancer of male Iraqi waterpipe tobacco smokers

Genetic polymorphisms of genes whose products are responsible for activities, such as xenobiotic metabolism, mutagen detoxification and DNA-repair, have been predicted to be associated with the risk of developing lung cancer (LC). The association of LC with tobacco smoking has been extensively investigated, but no studies have focused on the Arab ethnicity. Previously, we examined the association between genetic polymorphisms among Phase I and Phase II metabolism genes and the risk of LC. Here, we extend the data by examining the correlation of OGG1 Ser326Cys combined with CYP1A1 (Ile462Val and MspI) and GSTP1 (Ile105Val and Ala103Val) polymorphisms with the risk of LC. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and gene sequencing were carried out for genotyping the OGG1 polymorphisms of 123 LC patients and 129 controls. No significant differences in the frequencies of the OGG1 mutant allele between patients and controls were found. The distributions of heterozygous Ser/Cys or Cys/Cys genotypes of OGG1 were not associated with the risk of LC either according to the histological types of LC or based on waterpipe tobacco (WP) smoking status. In contrast, the combined effect of OGG1 variants with CYP1A1 and GSTP1 variants revealed a significant correlation with the OGG1 Ser326Cys-CYP1A1 MspI variants pairing. This association was significant (p = 0.001) in individuals who carried homozygous or heterozygous variant type genotypes of both genes in a reference with carriers of both wild-type genotypes (wt/wt - wt/wt). The odds ratios were 2.99 (95% CI 1.67-5.36), 2.68 (95% CI 1.08-6.62), and 2.80 (95% CI 1.18-6.69) for those who carried (wt/wt - wt/vt + vt/vt), (wt/vt + vt/vt - wt/wt), and (wt/vt + vt/vt - wt/vt + vt/vt), respectively. The study suggests a limited correlation is present between carrying OGG1 Ser326Cys polymorphism and the risk of developing LC in Arab populations.

Association of TERT, OGG1, and CHRNA5 Polymorphisms and the Predisposition to Lung Cancer in Eastern Algeria

Lung cancer remains the most common cancer in the world. The genetic polymorphisms (rs2853669 in TERT, rs1052133 in OGG1, and rs16969968 in CHRNA5 genes) were shown to be strongly associated with the risk of lung cancer. Our study's aim is to elucidate whether these polymorphisms predispose Eastern Algerian population to non-small-cell lung cancer (NSCLC). To date, no study has considered this association in the Algerian population. This study included 211 healthy individuals and 144 NSCLC cases. Genotyping was performed using TaqMan probes and Sanger sequencing, and the data were analyzed using multivariate logistic regression adjusted for covariates. The minor allele frequencies (MAFs) of TERT rs2853669, CHRNA5 rs16969968, and OGG1 rs1052133 polymorphisms in controls were C: 20%, A: 31%, and G: 29%, respectively. Of the three polymorphisms, none shows a significant association, but stratified analysis rs16969968 showed that persons carrying the AA genotype are significantly associated with adenocarcinoma risk (pAdj = 0.03, ORAdj = 2.55). Smokers with an AA allele have a larger risk of lung cancer than smokers with GG or GA genotype (pAdj = 0.03, ORAdj = 3.91), which is not the case of nonsmokers. Our study suggests that CHRNA5 rs16969968 polymorphism is associated with a significant increase of lung adenocarcinoma risk and with a nicotinic addiction.

Human 8-oxoguanine DNA glycosylase gene polymorphism (Ser326Cys) and cancer risk: updated meta-analysis

Genetic polymorphism of human 8-oxoguanine glycosylase 1 (hOGG1) has been reported to have a relationship with the risk of the development of various cancers. Many studies have described the influence of Ser326Cys polymorphism of the hOGG1 gene on cancer susceptibility. However, the results have remained inconclusive and controversial. Therefore, we performed a meta-analysis to more precisely determine the relationship between the hOGG1 polymorphism and the development of cancer.Electronic databases including PubMed, Embase, Google Scholar, and the Korean Studies Information Service System (KISS) were searched. The odds ratio (OR), 95% confidence interval (CI), and p value were calculated to assess the strength of the association with the risk of cancer using Comprehensive Meta-analysis software (Corporation, NJ, USA). The 127 studies including 38,757 cancer patients and 50,177 control subjects were analyzed for the meta-analysis.Our meta-analysis revealed that G allele of Ser326Cys polymorphism of the hOGG1 gene statistically increased the susceptibility of cancer (all population, OR = 1.092, 95% CI = 1.051-1.134, p < 0.001; in Asian, OR = 1.095, 95% CI = 1.048-1.145, p < 0.001; in Caucasian, OR = 1.097, 95% CI = 1.033-1.179, p = 0.002). Also, other genotype models showed significant association with cancer (p < 0.05, respectively).The present meta-analysis concluded that the G allele was associated with an increased risk of cancer. It suggested that the hOGG1 polymorphism may be a candidate marker of cancer.

Genetic Investigation of Polymorphic OGG1 and MUTYH Genes Towards Increased Susceptibility in Lung Adenocarcinoma and its Impact on Overall Survival of Lung Cancer Patients Treated with Platinum Based Chemotherapy

Genes OGG1 and MUTYH are the two primary genes in Base excision repair pathway. OGG1 hydrolyzes the sugar phosphate backbone and remove the damaged base creating abasic site. MUTYH complements OGG1 as it particularly remove adenine mispaired with 8-oxo-G. Both OGG1 and MUTYH act as a check for the mis-incorporation of bases may be due to damages incurred on DNA. DNA isolation for 326 lung cancer cases and 330 controls was followed by genotyping making use of PCR-RFLP. Logistic regression was done to analyze the risk towards lung cancer. Patients were followed through telephonic conversation. Kaplan meier and Cox-regression were used for survival analysis. OGG1 presented a high risk towards lung cancer (CG: OR = 2.44, p = 0.0003; CG + GG: OR = 1.88, p = 0.0093). On the same lines adenocarcinoma for OGG1 were potent risk factors towards lung cancer (CG: OR = 4.72, p = 0.0002; CG + GG: OR = 3.63, p = 0.0018). Single allelic carriers for MUTYH gene imposed a high risk towards overall lung susceptibility and for all the three histology. Stratified analysis for chemotherapeutic drugs revealed administration of Cisplatin/Carboplatin + Pemtrexed for OGG1Ser ³²⁶ Cys showed a better survival (MST CG vs. CC: 9.1 vs. 0.56, p = <0.0001; HR =0.051, p = 0.0025). Whereas, MUTYH Gln³²⁴His showed a smaller survival for mutant genotype (CC) (MST CC vs. GG: 4.0 vs. 9.4, p = 0.05; HR = 1.75, p = 0.26). Single allelic carriers for both OGG1 and MUTYH were risk factors towards lung cancer. The risk was amplified on combining both OGG1 and MUTYH.

Association between the OGG1 Ser326Cys Polymorphism and Cancer Risk: Evidence from 152 Case-Control Studies

Although it has been suggested that the 8-oxoguanine DNA glycosylase (OGG1) gene Ser326Cys polymorphism may be a risk factor for cancer, the conclusions from previous studies are inconsistent. Thus, we conducted an updated meta-analysis to estimate the effect of OGG1 variant genotypes on cancer susceptibility. We searched the PubMed for all eligible studies published in English for the period ending September 2014. We found the association between OGG1 Ser326Cys polymorphism and cancer susceptibility based on 152 case-control studies in different genetic model comparisons (dominant model: OR = 1.053, P = 0.018; recessive model: OR = 1.108, P < 0.001; homozygote: OR = 1.135, P < 0.001; additive model: OR = 1.059, P < 0.001). However, the results from the subgroup analyses based on types of cancer, health population as controls or studies with relatively large sample size did not support the conclusion. Although the overall results of this meta-analysis showed a positive association between OGG1 variant genotypes and cancer susceptibility, the subgroup analyses by cancer type, sample size, and source of controls presented inconsistent results. Therefore, the current evidence from the meta-analysis did not support the hypothesis of OGG1 Ser326Cys polymorphism as a risk factor of cancer.

Oxidatively induced DNA damage and its repair in cancer

Oxidatively induced DNA damage is caused in living organisms by endogenous and exogenous reactive species. DNA lesions resulting from this type of damage are mutagenic and cytotoxic and, if not repaired, can cause genetic instability that may lead to disease processes including carcinogenesis. Living organisms possess DNA repair mechanisms that include a variety of pathways to repair multiple DNA lesions. Mutations and polymorphisms also occur in DNA repair genes adversely affecting DNA repair systems. Cancer tissues overexpress DNA repair proteins and thus develop greater DNA repair capacity than normal tissues. Increased DNA repair in tumors that removes DNA lesions before they become toxic is a major mechanism for development of resistance to therapy, affecting patient survival. Accumulated evidence suggests that DNA repair capacity may be a predictive biomarker for patient response to therapy. Thus, knowledge of DNA protein expressions in normal and cancerous tissues may help predict and guide development of treatments and yield the best therapeutic response. DNA repair proteins constitute targets for inhibitors to overcome the resistance of tumors to therapy. Inhibitors of DNA repair for combination therapy or as single agents for monotherapy may help selectively kill tumors, potentially leading to personalized therapy. Numerous inhibitors have been developed and are being tested in clinical trials. The efficacy of some inhibitors in therapy has been demonstrated in patients. Further development of inhibitors of DNA repair proteins is globally underway to help eradicate cancer.

hOGG1 Ser326Cys polymorphism and lung cancer susceptibility: a meta-analysis

The Ser326Cys polymorphism in the human 8-oxogunaine glycosylase (hOGG1) gene with lung cancer susceptibility had been investigated by the approaches of PCR-RFLP, PCR-SSCP and ASA. Due to limited specimen and different approaches the conclusion was drawn toughly. To evaluate this correlation comprehensively, a meta-analysis was performed based on 30 case-control studies, including 10,327 cases and 12,148 controls. The random-effects model was used to estimate the odds ratios and 95 % confidence interval for various contrasts of this polymorphism. The combined results suggested that the hOGG1 Ser326Cys polymorphism was not associated with lung cancer susceptibility in different genetic models. Similarly, in the stratified analyses by ethnicity and source of control, no risk was observed between all the genetic models and lung cancer risk. Our meta-analysis revealed that there was little correlation between the hOGG1 Ser326Cys polymorphism and the risk of lung cancer.

Smoking and hOGG1 Ser326Cys polymorphism contribute to lung cancer risk: evidence from a meta-analysis

The human 8-oxoguanine DNA glycosylase (hOGG1) gene plays an important role in the repair of oxidatively damaged DNA base lesions and its functional single nucleotide polymorphisms (SNPs) may alter DNA repair capacity and thus contributes to cancer susceptibility. Numerous studies have investigated the association between hOGG1 Ser326Cys polymorphism and lung cancer susceptibility; however, the conclusions are still inconclusive. We searched eligible publications from MEDLINE, EMBASE, and CBM and performed a meta-analysis to assess the associations between hOGG1 Ser326Cys polymorphism and lung cancer risk. Pooled odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated to estimate risk associations, and false-positive report probability (FPRP) analysis was also carried out to evaluate significant findings. A total of 31 investigations with 10,220 cases and 12,284 controls were identified. When all studies were pooled, a significantly increased overall lung cancer risk was found (Cys/Cys vs. Ser/Ser: OR = 1.24, 95 % CI = 1.05-1.47, P = 0.013; recessive model: OR = 1.22, 95 % CI = 1.05-1.41, P = 0.008, and Cys vs. Ser: OR = 1.11, 95 % CI = 1.02-1.21, P = 0.022), and further stratification analysis showed that the association was stronger in Asians, never smokers, and more-cigarette takers. These results were confirmed by FPRP analysis. Despite some limitations, this meta-analysis provides solid evidence that hOGG1 Ser326Cys polymorphism may contribute to lung cancer risk, particularly for Asian populations, never smokers, and more-cigarette takers. Nevertheless, these findings warrant further validation in single large investigations.

Polymorphisms of DNA repair genes XPD, XRCC1, and OGG1, and lung adenocarcinoma susceptibility in Chinese population

Lung adenocarcinoma (ADC) is one of the major histological types of lung cancer. Genetic polymorphism in DNA repair genes and lung ADC susceptibility is well documented. In this case-control study, the association between the polymorphic sites of DNA repair genes XPD-751, XRCC1-399, and OGG1-326, and lung ADC susceptibility in ethnic Han Chinese population has been investigated. Genomic DNA was isolated from the peripheral blood of 201 healthy controls and 82 lung ADC patients from the people of Hunan Province, China. Polymorphisms of the investigated genes were analyzed by using polymerase chain reaction-restriction fragment length polymorphism. There was no significant difference between the samples from lung ADC patients and healthy controls about the genotype frequencies of XPD-751, XRCC1-399, and OGG1-326 sites. However, multifactor dimensionality reduction analysis showed that the genetic polymorphisms of the three-loci models of DNA repair genes (XPD-751/XRCC1-399/OGG1-326) are associated with lung ADC. Thus, this study reveals that a three-order interaction among the polymorphic sites of XPD-751, XRCC1-399, and OGG1-326 is associated with lung ADC risk in the studied population, although polymorphism in individual gene was not associated.

Association between the hOGG1 Ser326Cys polymorphism and lung cancer susceptibility: a meta-analysis based on 22,475 subjects

Objectives

The Ser326Cys polymorphism in the human 8-oxogunaine glycosylase (hOGG1) gene with lung cancer susceptibility had been investigated, but results were inconsistent and underpowered. The aim of this study was to conduct a meta-analysis assessing the association of hOGG1 Ser326Cys polymorphism with risk of lung cancer.

Materials and methods

Relevant studies were identified through a search of MEDLINE, PubMed, Web of Science, EMBASE, and Chinese Biomedical Literature database (CBM) using terms “lung cancer”, “hOGG1” or “OGG1”, “polymorphism” or “variation” and the last search updated on May 1, 2013. In this meta-analysis, we assessed 30 published studies involving 22,475 subjects that investigated the association between the hOGG1 Ser326Cys polymorphism and lung cancer susceptibility.

Results

Overall, the hOGG1 Ser326Cys polymorphism was not associated with lung cancer susceptibility in different genetic models (dominant model comparison: OR = 0.133; 95% CI = 0.111–0.161; P_{heterogeneity} = 0.000), and recessive model: OR = 0.543; 95% CI = 0.399–0.739; P_{heterogeneity} = 0.000). Similarly, in the stratified analyses by ethnicity, significantly increased risks were found among Asians for homozygote comparison (OR = 0.850; 95% CI = 0.732 0.986; P_{heterogeneity} = 0.064), and dominant model (OR = 0.160; 95% CI = 0.137–0.187; P_{heterogeneity} = 0.001), and Caucasians for dominant model (OR = 1.35; 95% CI = 1.03–1.77; P_{heterogeneity} = 0.015), and recessive model (OR = 1.35; 95% CI = 1.03–1.77; P_{heterogeneity} = 0.015). In population-based populations, marginally significant increased risks were found in dominant model (OR = 0.143; 95% CI = 0.111 0.184; P_{heterogeneity} = 0.000) and recessive model (OR = 0.429; 95% CI = 0.261–0.705; P_{heterogeneity} = 0.000). We also found a significant difference between hOGG1 Ser326Cys genotype and lung cancer susceptibility in studies with hospital-based controls for homozygote model (OR = 0.798; 95% CI = 0.649–0.982; P_{heterogeneity} = 0.007),dominant model (OR = 0.122; 95% CI = 0.091–0.163; P_{heterogeneity} = 0.000).

Conclusion

Our data showed that the hOGG1 Ser326Cys polymorphism contributed to the risk of lung cancer.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3842531131031605

The joint effect of hOGG1, APE1, and ADPRT polymorphisms and cooking oil fumes on the risk of lung adenocarcinoma in Chinese non-smoking females

Background

The human 8-oxoguanine DNA glycosylase 1 (hOGG1), apurinic/apyrimidinic endonuclease 1 (APE1), and adenosine diphosphate ribosyl transferase (ADPRT) genes play an important role in the DNA base excision repair pathway. Single nucleotide polymorphisms (SNPs) in critical genes are suspected to be associated with the risk of lung cancer. This study aimed to identify the association between the polymorphisms of hOGG1 Ser326Cys, APE1 Asp148Glu, and ADPRT Val762Ala, and the risk of lung adenocarcinoma in the non-smoking female population, and investigated the interaction between genetic polymorphisms and environmental exposure in lung adenocarcinoma.

Methods

We performed a hospital-based case-control study, including 410 lung adenocarcinoma patients and 410 cancer-free hospital control subjects who were matched for age. Each case and control was interviewed to collect information by well-trained interviewers. A total of 10 ml of venous blood was collected for genotype testing. Three polymorphisms were analyzed by the polymerase chain reaction-restriction fragment length polymorphism technique.

Results

We found that individuals who were homozygous for the variant hOGG1 326Cys/Cys showed a significantly increased risk of lung adenocarcinoma (OR = 1.54; 95% CI: 1.01–2.36; P = 0.045). When the combined effect of variant alleles was analyzed, we found an increased OR of 1.89 (95% CI: 1.24–2.88, P = 0.003) for lung adenocarcinoma individuals with more than one homozygous variant allele. In stratified analyses, we found that the OR for the gene-environment interaction between Ser/Cys and Cys/Cys genotypes of hOGG1 codon 326 and cooking oil fumes for the risk of lung adenocarcinoma was 1.37 (95% CI: 0.77–2.44; P = 0.279) and 2.79 (95% CI: 1.50–5.18; P = 0.001), respectively.

Conclusions

The hOGG1 Ser326Cys polymorphism might be associated with the risk of lung adenocarcinoma in Chinese non-smoking females. Furthermore, there is a significant gene-environment association between cooking oil fumes and hOGG1 326 Cys/Cys genotype in lung adenocarcinoma among female non-smokers.

hOGG1, p53 genes, and smoking interactions are associated with the development of lung cancer

This study aimed to investigate the effects of Ser/Cys polymorphism in hOGG1 gene, Arg/Pro polymorphism in p53 gene, smoking and their interactions on the development of lung cancer. Ser/Cys polymorphism in hOGG1 and Arg/Pro polymorphism in p53 among 124 patients with lung cancer and 128 normal people were detected using PCR-RFLP. At the same time, smoking status was investigated between the two groups. Logistic regression was used to estimate the effects of Ser/Cys polymorphism and Arg/Pro polymorphisms, smoking and their interactions on the development of lung cancer. ORs (95% CI) of smoking, hOGG1 Cys/Cys and p53 Pro/ Pro genotypes were 2.34 (1.41-3.88), 2.12 (1.03-4.39), and 2.12 (1.15-3.94), respectively. The interaction model of smoking and Cys/Cys was super-multiplicative or multiplicative, and the OR (95% CI) for their interaction item was 1.67 (0.36 -7.78). The interaction model of smoking and Pro/Pro was super-multiplicative with an OR (95%CI) of their interaction item of 5.03 (1.26-20.1). The interaction model of Pro/Pro and Cys/Cys was multiplicative and the OR (95%CI) of their interaction item was 0.99 (0.19-5.28). Smoking, hOGG1 Cys/Cys, p53 Pro/Pro and their interactions may be the important factors leading to the development of lung cancer.

Association between the OGG1 Ser326Cys and APEX1 Asp148Glu polymorphisms and lung cancer risk: a meta-analysis

The previous published data on the association between the 8-oxo-guanine glycosylase-1 (OGG1) and apurinic/apyrimidinic-endonuclease-1 (APEX1/APE1) polymorphisms and lung cancer risk remained controversial. Several polymorphisms in the OGG1 and APEX1 gene have been described, including the commonly occurring Ser326Cys in OGG1 and Asp148Glu in APEX1. This meta-analysis of literatures was performed to derive a more precise estimation of the relationship. A total of 37 studies were identified to the meta-analysis, including 9,203 cases and 10,994 controls for OGG1 Ser326Cys (from 25 studies) and 3,491 cases and 4,708 controls for APEX1 Asp148Glu (from 12 studies). When all the eligible studies were pooled into the meta-analysis of OGG1 Ser326Cys polymorphism, significantly increased lung cancer risk was observed in recessive model (OR = 1.17, 95 % CI = 1.03-1.33) and in additive model (OR = 1.21, 95 % CI = 1.03-1.42). In the stratified analysis, significantly increased risk of lung cancer was also observed on the population-based studies (recessive model: OR = 1.26, 95 % CI = 1.08-1.46, additive model: OR = 1.42, 95 % CI = 1.06-1.73) and non-smokers (dominant model: OR = 1.20, 95 % CI = 1.02-1.42, recessive model: OR = 1.20, 95 % CI = 1.02-1.40, additive model: OR = 1.35, 95 % CI = 1.08-1.68). Additionally, when one study was deleted in the sensitive analysis, the results of OGG1 Ser326Cys were changed in Asians (recessive model: OR = 1.16, 95 % CI = 1.06-1.27, additive model: OR = 1.23, 95 % CI = 1.09-1.38). When all the eligible studies were pooled into the meta-analysis of APEX1 Asp148Glu polymorphism, there was no evidence of significant association between lung cancer risk and APEX1 Asp148Glu polymorphism in any genetic model. In the stratified analysis, significantly decreased lung adenocarcinoma risk was observed in recessive model (OR = 0.68, 95 % CI = 0.48-0.97, P (h) = 0.475, I(2) = 0.0 %). Additionally, when one study was deleted in the sensitive analysis, the results of APEX1 Asp148Glu were changed in Asians (recessive model: OR = 1.21, 95 % CI = 1.03-1.43) and smokers (dominant model: OR = 1.62, 95 % CI = 1.08-2.44, additive model: OR = 1.37, 95 % CI = 1.02-1.84). In summary, this meta-analysis indicates that OGG1 Ser326Cys show an increased lung cancer risk in Asians and non-smokers, APEX1 Asp148Glu polymorphism may be associated with decreased lung adenocarcinoma risk, and APEX1 Asp148Glu polymorphism show an increased lung cancer risk in Asians and smokers. However, a study with the larger sample size is needed to further evaluated gene-environment interaction on OGG1 Ser326Cys and APEX1 Asp148Glu polymorphisms and lung cancer risk.

An association between hOGG1 Ser326Cys polymorphism and the risk of bladder cancer in non-smokers: a meta-analysis

Background

Bladder cancer results from complex interactions between many genetic and environment factors. The polymorphism Ser326Cys in hOGG1 gene has been reported to be associated with bladder cancer in some studies, though the results remain inconclusive. To explore this relationship of hOGG1 polymorphism and the susceptibility for bladder cancer and the impact of smoking exposures, a cumulative meta-analysis was performed in this study.

Methods

We extracted the data from the Pubmed database up to January 9, 2012 using the search phrases “hOGG1, Ser326Cys polymorphism and bladder cancer”. Seven case–control studies were identified, including 2474 patients and 2408 controls. Four of them provided the analysis of smoking effects, with 1372 smokers and 947 non-smokers. The odds ratios (ORs) and associated 95 % confidence intervals (CIs) were calculated using fixed- or random- effects models.

Results

Regarding the overall association between the hOGG1 326Cys allele and bladder cancer risk, the meta-analysis did not reveal a significant effect in the additive model (OR: 1.06, 95 % CI: 0.96-1.26; p = 0.49), the recessive genetic model (OR: 1.05, 95 % CI: 0.65-1.70; p = 0.85) or the dominant genetic model (OR: 1.07, 95 % CI: 0.87-1.32; p = 0.53). Similarly, no significant relationship was observed in the stratified analysis by ethnicity, study design and Hardy-Weinberg equilibrium (all p > 0.05). In the non-smokers, however, hOGG1 326Cys allele significantly increased the risk for bladder cancer and the ORs in the additive model, homozygote contrast and recessive genetic model were 1.59 (p = 0.02), 2.53(p = 0.003) and 2.41(p = 0.0005), respectively. Nevertheless, in the smoker subgroup, similar findings could not be found in all genetic models (all p > 0.05).

Conclusions

The association between the hOGG1 326Cys allele and bladder cancer was significant in non-smoker population, while was non-detectable in common or smoker populations. This meta-analysis suggests that the hOGG1 Ser326Cys polymorphism may be a risk factor for bladder cancer without exposure to smoking. Further functional studies are needed to elucidate the gene polymorphism-bladder cancer relationship and gene-environment interactions.

The hOGG1Ser326Cys polymorphism and increased lung cancer susceptibility in Caucasians: an updated meta-analysis

hOGG1 encodes a DNA repair enzyme responsible for the excision of reactive oxygen species (ROS) in damaged DNA. Previous studies have obtained inconsistent results. To validate the association between the hOGG1Ser326Cys polymorphism and lung cancer risk, we performed an updated meta-analysis of 20 studies (8739 cases and 10385 controls) using STATA version 11.1. With this approach, we tested the overall and subgroup association between the SNP and lung cancer susceptibility stratified by ethnicity, control sources, cell histotypes, and smoking status. We demonstrated a novel, significant correlation between the hOGG1 Ser326Cys polymorphism and increased lung cancer susceptibility in Caucasians. Our findings indicate a need for larger-scale studies to verify the association of this SNP with lung cancer risk in Caucasians.

Oxidatively induced DNA damage: mechanisms, repair and disease

Endogenous and exogenous sources cause oxidatively induced DNA damage in living organisms by a variety of mechanisms. The resulting DNA lesions are mutagenic and, unless repaired, lead to a variety of mutations and consequently to genetic instability, which is a hallmark of cancer. Oxidatively induced DNA damage is repaired in living cells by different pathways that involve a large number of proteins. Unrepaired and accumulated DNA lesions may lead to disease processes including carcinogenesis. Mutations also occur in DNA repair genes, destabilizing the DNA repair system. A majority of cancer cell lines have somatic mutations in their DNA repair genes. In addition, polymorphisms in these genes constitute a risk factor for cancer. In general, defects in DNA repair are associated with cancer. Numerous DNA repair enzymes exist that possess different, but sometimes overlapping substrate specificities for removal of oxidatively induced DNA lesions. In addition to the role of DNA repair in carcinogenesis, recent evidence suggests that some types of tumors possess increased DNA repair capacity that may lead to therapy resistance. DNA repair pathways are drug targets to develop DNA repair inhibitors to increase the efficacy of cancer therapy. Oxidatively induced DNA lesions and DNA repair proteins may serve as potential biomarkers for early detection, cancer risk assessment, prognosis and for monitoring therapy. Taken together, a large body of accumulated evidence suggests that oxidatively induced DNA damage and its repair are important factors in the development of human cancers. Thus this field deserves more research to contribute to the development of cancer biomarkers, DNA repair inhibitors and treatment approaches to better understand and fight cancer.

The effect of hOGG1 Ser326Cys polymorphism on cancer risk: evidence from a meta-analysis

Background

Human oxoguanine glycosylase 1 (hOGG1) in base excision repair (BER) pathway plays a vital role in DNA repair. Numerous epidemiological studies have evaluated the association between hOGG1 Ser326Cys polymorphism and the risk of cancer. However, the results of these studies on the association remain conflicting. To derive a more precise estimation of the association, we conducted a meta-analysis.

Methodology/Principal Findings

A comprehensive search was conducted to identify the eligible studies of hOGG1 Ser326Cys polymorphism and cancer risk. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. We found that the hOGG1 Ser326Cys polymorphism was significantly associated with overall cancer risk (Cys/Cys vs. Ser/Ser: OR = 1.19, 95%CI = 1.09–1.30, P<0.001; Cys/Cys vs. Cys/Ser+Ser/Ser: OR = 1.16, 95%CI = 1.08–1.26, P<0.001). Moreover, in subgroup analyses by cancer types, the stronger significant association between hOGG1 Ser326Cys polymorphism and lung cancer risk was found (Cys/Cys vs. Ser/Ser: OR = 1.29, 95%CI = 1.16–1.44, P<0.001; Cys/Cys vs. Cys/Ser+Ser/Ser: OR = 1.22, 95%CI = 1.12–1.33, P<0.001). The significant effects of hOGG1 Ser326Cys polymorphism on colorectal, breast, bladder, prostate, esophageal, and gastric cancer were not detected. In addition, in subgroup analyses by ethnicities, we found that the hOGG1 Ser326Cys polymorphism was associated with overall cancer risk in Asians (Cys/Cys vs. Ser/Ser: OR = 1.21, 95%CI = 1.10–1.33, P<0.001).

Conclusions

This meta-analysis showed that hOGG1 326Cys allele might be a low-penetrant risk factor for lung cancer.

Role of OGG1 Ser326Cys polymorphism and 8-oxoguanine DNA damage in risk assessment of squamous cell carcinoma of head and neck in North Indian population

Squamous cell carcinoma of head and neck (SCCHN), one of the leading cancers worldwide, is most prevalent in Indian sub-continent. The major risk factors involved are smoking and consumption of alcohol, since they provide high free radical generating environment. We studied 8-oxoguanine DNA-glycosylase (OGG1) Ser326Cys polymorphism in 278 SCCHN cases and 278 matched controls by PCR-RFLP and observed that the variant genotype Ser/Cys exhibited an enhanced risk of ∼1.7 folds (OR=1.71, 95% CI=1.20-2.93) and Cys/Cys ∼2.5 folds (OR=2.55, 95% CI=1.29-5.00). Furthermore, we found a significant increase in salivary cell 8-OHdG with respect to Ser/Cys and Cys/Cys genotypes of OGG1 in SCCHN cases, when compared to Ser/Ser and Ser/Cys genotypes of the control population. Our results demonstrate that Ser326Cys variant genotype is associated with an increased risk of SCCHN in north India. Ser326Cys variant genotype was found to accumulate more of 8-OHdG, which may serve as a biomarker for early diagnosis of SCCHN.

DNA repair gene 8-oxoguanine DNA glycosylase Ser326Cys polymorphism and colorectal cancer risk in a Kashmiri population

8-Oxoguanine DNA glycosylase (OGG1) is one of the important base excision repair enzymes that repair 8-oxoguanine lesion incorporated within the DNA of an individual by reactive oxygen species. The aim of this study was to detect the role of OGG1 Ser326Cys polymorphism in susceptibility to colorectal cancer (CRC) in a Kashmiri population. We investigated the genotype distribution of the OGG1 gene in 114 CRC cases in comparison with 200 healthy subjects. There was no significant association between OGG1 Ser326Cys polymorphism and CRC, but the homozygous Cys/Cys variant genotype was associated with an increased risk of colon cancer (p<0.05). This study suggests that the OGG1 polymorphism is not associated with the risk of development of CRC in the Kashmiri population in general but modulates the risk of cancer development in colon via interaction with many dietary factors.

[Meta analysis of association between Ser326Cys polymorphism of hOGG1 gene and risk of lung cancer]

背景与目的

就全世界范围内而言，肺癌是一种常见疾病。人8-羟基鸟嘌呤糖苷酶（human 8-hydroxyguanine glycosylase, hOGG1）是一种DNA修复酶，它能特异切除8-羟基鸟嘌呤（8-dihydro-8-oxoguanine, 8-OH-G），对损伤的DNA进行修复。hOGG1 Ser326Cys基因多态性与癌症易感性的关系一直是研究的热点，而该多态性与肺癌易感性的关系尚存在争议。本研究采用meta分析旨在更好地探讨hOGG1 Ser326Cys多态性与肺癌易感性之间的关系。

方法

使用MEDLINE数据库检索2010年11月以前的相关文献，按照纳入标准，全面搜索含有研究hOGG1 Ser326Cys多态性与肺癌易感性相关的信息。由至少两位评论员做独立文献筛选和资料提取，并交叉审核。使用STATA 10.1软件进行统计分析。

结果

根据检索条件，共有22篇文献（包括8, 575例肺癌患者和9, 484名正常对照个体）被纳入当前的meta分析。分析结果表明22项研究的结果存在明显异质性，当排除不符合Hard-Weinberg平衡定律的两篇文献后，其余的文献呈现出较好的同质性。与hOGG1 Ser326相比，Cys326基因型明显增加了肺癌发病风险（OR=1.24, 95%CI:1.10-1.39, P < 0.001）。这种正相关在亚洲人群和医院来源的样本中尤为明显（OR=1.28, 95%CI: 1.11-1.49; OR=1.26, 95%CI: 1.09-1.46）。

结论

hOGG1 Ser326Cys多态性与肺癌易感性之间存在明显相关性，Cys326基因型能明显增加肺癌发病风险。

BER gene polymorphisms (OGG1 Ser326Cys and XRCC1 Arg194Trp) and modulation of DNA damage due to pesticides exposure

The susceptibility of individuals to the genotoxic effect of pesticides can be modulated by genetic variations in the xenobiotic detoxification and DNA repair processes. This study evaluates if the two BER polymorphisms (XRCC1Arg194Trp and OGG1Ser326Cys) or the combined genotypes of these polymorphisms with PON1Gln192Arg could modify individual susceptibility to pesticide exposure in vineyard workers, as measured by micronucleus formation and DNA damage induction in peripheral leukocytes. The study population comprised 108 agricultural workers exposed to pesticides and 65 nonexposed. Our results demonstrate that individuals with the variant allele (OGG1Cys) showed higher DNA damage, detected by the comet assay, in relation to individuals carrying the wild-type OGG1Ser allele. Considering the combined influence of metabolizing PON1 and the DNA repair OGG1 genes, we observed significantly higher DNA damage in the comet assay in the exposed group when a less efficient OGG1Cys allele was acting independently of the PON1 genotype, reinforcing the importance of the OGG1 repair enzyme in the response to DNA damage by pesticide exposure. The association of the PONGln/Gln genotype with higher MN frequency suggests that the PON1 genotype is a major determinant of genotoxic risk in individuals exposed to pesticides. Analysis of the compared effect of XRCC1 and PON1 genotypes in the exposed group suggested that, among the poorly metabolizing PON1Gln/Gln individuals, the XRCC1Arg/Trp genotype has a protective effect with respect to MN formation. These results indicate that enhanced XRCC1 function may provide some protection from the enhanced genotoxic risk associated with inefficient xenobiotic detoxification in the studied population.

Lung Cancer Susceptibility and hOGG1 Ser326Cys Polymorphism: A Meta-Analysis

Recent lung cancer studies have focused on identifying the effects of single nucleotide polymorphisms (SNPs) in candidate genes, among which DNA repair genes are increasingly being studied. Genetic variations in DNA repair genes are thought to modulate DNA repair capacity and are suggested to be related to lung cancer risk. In this study, we tried to assess reported studies of association between polymorphism of human 8-oxoguanine DNA glycosylase 1 (hOGG1) Ser326Cys and lung cancer. We conducted MEDLINE, Current Contents and Web of Science searches using "hOGG1", "lung cancer" and "polymorphism" as keywords to search for papers published (from January 1995 through August 2010). Data were combined using both a fixed effects (the inverse variance-weighted method) and a random effects (DerSimonian and Laird method) models. The Cochran Q test was used for the assessment of heterogeneity. Publication bias was assessed by both Begg’s and Egger’s tests. We identified 20 case-control studies in 21 different ethnic populations. As two studies were not in the Hardy-Weinberg equilibrium, 18 case-control studies in 19 different ethnic populations (7,792 cases and 9,358 controls) were included in our meta-analysis. Summary frequencies of the Cys allele among Caucasians and Asians based on the random effects model were 20.9% (95% confidence interval (CI) = 18.9–22.9) and 46.1% (95% CI = 40.2–52.0), respectively. The distribution of the Cys allele was significantly different between Asians and Caucasians (P < 0.001). The Cys/Cys genotype was significantly associated with lung cancer risk in Asian populations (odds ratio = 1.27, 95% CI = 1.09–1.48) but not in Caucasian populations. This ethnic difference in lung cancer risk may be due to environmental factors such as cigarette smoking and dietary factors. Although the summary risk for developing lung cancer may not be large, lung cancer is such a common malignancy that even a small increase in risk can translate to a large number of excess lung cancer cases. As lung cancer is a multifactorial disease, further investigations of the gene-gene and gene-environment interactions on the hOGG1 polymorphism-associated lung cancer risk may help to better understand of the molecular pathogenesis of human lung cancer.

Lung cancer risk and genetic polymorphisms in DNA repair pathways: a meta-analysis

Genetic variations in DNA repair genes are thought to modulate DNA repair capacity and are suggested to be related to lung cancer risk. We conducted a meta-analysis of epidemiologic studies on the association between genetic polymorphisms in both base excision repair and nucleotide excision repair pathways, and lung cancer. We found xeroderma pigmentosum complementation group A (XPA) G23A (odds ratio (OR) = 0.76, 95% confidence interval (CI) = 0.61–0.94), 8-oxoguanine DNA glycosylase 1 (OGG1) Ser326Cys (OR = 1.22, 95% CI = 1.02–1.45), and excision repair cross-complementing group 2 (ERCC2) Lys751Gln (OR = 1.27, 95% CI = 1.10–1.46) polymorphisms were associated with lung cancer risk. Considering the data available, it can be conjectured that if there is any risk association between a single SNP and lung cancer, the risk fluctuation will probably be minimal. Advances in the identification of new polymorphisms and in high-throughput genotyping techniques will facilitate the analysis of multiple genes in multiple DNA repair pathways. Therefore, it is likely that the defining feature of future epidemiologic studies will be the simultaneous analysis of large samples of cases and controls.

OGG1 Ser326Cys polymorphism and susceptibility to esophageal cancer in low and high at-risk populations of northern India

BACKGROUND

Esophageal cancer has diverse incidence worldwide, and genetic/environmental risk factors are supposed to be responsible for it. OGG1 Ser326Cys gene polymorphism (rs1052133) has been found to be associated with different cancer susceptibilities and interaction with different environmental factors.

AIM OF THE STUDY

The aim of this study is to detect the role of OGG1 Ser326Cys polymorphism in susceptibility to esophageal cancer in two Northern Indian populations having different incidence rates.

METHODS

A total of 737 cases and controls from two high and low at-risk populations were selected for the study. All the subjects were genotyped by PCR with confronting two-pair primers.

RESULTS

No significant association was found between OGG1 Ser326Cys genotypes and esophageal cancer risk in both of the populations. Gene-environment analysis revealed no significant interaction between OGG1 Ser326Cys genotypes and smoking/high-salted tea intake habits.

CONCLUSION

OGG1 Ser326Cys polymorphism does not have a role in determining susceptibility to esophageal cancer either in high or in low at-risk populations of Northern India.

HOGG1 polymorphism in atrophic gastritis and gastric cancer after Helicobacter pylori eradication

AIM: To investigate the association between Ser326Cys human oxoguanine glycosylase 1 (hOGG1) polymorphism and atrophic gastritis and gastric cancer after Helicobacter pylori (H. pylori) eradication.

METHODS: A total of 488 subjects (73 patients with gastric cancer, 160 with atrophic gastritis after H. pylori eradication and 255 controls) were prospectively collected. Polymerase chain reaction-restriction fragment length polymorphism analysis was performed to distinguish hOGG1 Ser326Cys polymorphism. Statistical analysis was conducted by two-sample t test for continuous variables and χ² test for categorical variables. Logistic regression models were used to find the risk factors for gastric cancer and atrophic gastritis.

RESULTS: Neither the hOGG1 Ser/Cys nor the Cys/Cys genotype was associated with gastric cancer. Compared with the Ser/Ser genotype, odds ratio (OR) for Ser/Cys was 0.96, (95% CI: 0.51-1.84) and OR for Cys/Cys was 1.1 (95% CI: 0.48-2.1). No association was detected between hOGG1 polymorphism and Lauren type of gastric cancer (P = 0.61) either. However, Ser/Cys and Cys/Cys were significantly associated with atrophic gastritis with OR: 1.76 for Ser/Cys (95% CI: 1.03-3.0) and 2.38 for Cys/Cys (95% CI: 1.34-4.23). After controlling for age, gender, smoking and alcohol, there were still significant associations with OR: 2.05 for Ser/Cys (95% CI: 1.14-3.68) and 2.76 for Cys/Cys (95% CI: 1.47-5.18).

CONCLUSION: HOGG1 polymorphisms (Cys/Cys and Ser/Cys) are associated with atrophic gastritis. No significant association is detected between hOGG1 polymorphisms (Cys/Cys or Ser/Cys) and gastric cancer.

The Cys326 allele of the 8-oxoguanine DNA N-glycosylase 1 gene as a risk factor in smoking- and drinking-associated larynx cancer

Tobacco smoke-related products and ethanol would induce oxidative modifications to the DNA bases, thereby contributing to larynx cancer. Human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) deals with oxidative DNA damage, and the base changes in the hOGG1 gene may alter the susceptibility of the human cells to tobacco smoke-related compounds and/or ethanol. In the present work, we investigated the association between smoking, drinking or the Ser326Cys polymorphism of the hOGG1 gene and the risk of larynx cancer in a Polish population. It has been reported that the Ser326 allele exhibits higher activity than the Cys326 variant. In this study, 253 age-matched controls and 253 patients with larynx cancer were enrolled. The polymorphism was determined with DNA from blood lymphocytes by polymerase chain reaction. The frequencies (%) of the genotypes were Ser/Ser 65.6, Ser/Cys 30.4, and Cys/Cys 4.0 in the controls and those in patients were 55.7, 36.0 and 8.3, respectively. Stratification of individuals according to their smoking and drinking habits indicated that these habits might be significant risk factors in larynx cancer. The Ser/Cys and Cys/Cys genotypes are significantly associated with the increased risk of larynx cancer. These genotypes increased the risk ratio of larynx cancer among heavy smokers, but did not change the risk in former smokers and moderate smokers. These genotypes also increased the risk of larynx cancer in moderate and heavy drinkers. Therefore, the Cys326 allele of the hOGG1 gene may increase the risk of larynx cancer associated with smoking or alcohol consumption.

The hOGG1 Ser326Cys polymorphism and breast cancer risk: a meta-analysis

It was reported that the functional polymorphism Ser326Cys in the human 8-oxoguanine DNA glycosylase gene was associated with breast cancer risk; however, the published studies have inconsistent conclusions. To elucidate the effect of hOGG1 Ser326Cys on the susceptibility to breast cancer, all available studies were collected in this meta-analysis. We extracted the data from 10 case-control studies that were published in the PubMed database from 2003 to 2008 using the search phrases "human 8-oxoguanine DNA glycosylase, hOGG1, OGG1, OGG, polymorphism, genetic variation, and breast cancer." This meta-analysis included 4,963 breast cancer cases and 4,776 control subjects. The results showed that individuals who carrying the hOGG1 326Cys allele in the additive model did not have significantly increased risk of breast cancer compared with those carrying the 326Ser allele (P = 0.47, OR = 1.02; 95% CI = 0.96-1.09); similarly, no significant association between the hOGG1 326Cys allele and breast cancer risk was found either in the recessive genetic model (P = 0.34, OR = 1.06; 95% CI = 0.94-1.18) for Cys/Cys versus Ser/Cys + Ser/Ser, or dominant genetic model (P = 0.78, OR = 1.01; 95% CI = 0.93-1.11) for Cys/Cys + Ser/Cys versus Ser/Ser. In the stratified analysis, the meta-analysis showed the association between hOGG1 326Cys allele in the additive model and breast cancer was significant in European subjects (P = 0.04, OR = 0.71; 95% CI = 0.51-0.98), and dominant genetic model (P = 0.004, OR = 0.44; 95% CI = 0.25-0.77). However, the association was not significant between this polymorphism and different menopausal status (premenopausal and postmenopausal) and the other ethnicities (Asians and Americans). The meta-analysis suggested that the hOGG1 326Cys allele plays a significant protective effect to breast cancer in European women.

Interactive effect of cigarette smoking with human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) polymorphisms on the risk of lung cancer: a case-control study in Taiwan

Human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) plays an important role in repairing oxidative DNA damage induced by tobacco carcinogens. In this case-control study, the authors examined the interactive effect of hOGG1 gene polymorphisms and cigarette smoking on the risk of lung cancer in Taiwan. A total of 1,096 cases and 1,007 controls were enrolled from 6 medical centers in Taiwan during 2002-2004. hOGG1 Ser326Cys genetic polymorphisms were determined using the MassARRAY system (SEQUENOM, Inc., San Diego, California). Tobacco smoking history was obtained through personal interview according to a structured questionnaire. Logistic regression analysis was used to estimate multivariate-adjusted odds ratios and 95% confidence intervals. The odds of developing lung cancer for persons with the Cys/Cys genotype versus the Ser/Ser genotype were 1.11 (95% confidence interval (CI): 0.74, 1.65) for never smokers, 1.45 (95% CI: 0.74, 2.83) for moderate smokers, and 3.52 (95% CI: 1.54, 8.06) for heavy smokers. The P value for interaction in the logistic model was 0.01. The increased risk associated with the Cys/Cys genotype among heavy smokers remained statistically significant for various histologic types of lung cancer, including adenocarcinoma, squamous cell carcinoma, and small cell carcinoma. The authors conclude that there was a noticeable modifying effect on the association between hOGG1 genotype and lung cancer risk by cigarette smoking status.

Reactive Oxygen Species And Lung Tumorigenesis By Mutant K-ras: A Working Hypothesis

Wild-type K-ras is tumor suppressive in mouse lung, but mutant K-ras is actively oncogenic. Thus, the mutant protein must acquire new, dominant protumorigenic properties. Generation of reactive oxygen species could be one such property. The authors demonstrate increased peroxides in lung epithelial cells (E10)-transfected with mutant hK-ras(va112). An associated increase in DNA damage (comet assay) correlates with increased cyclooxygenase-2 protein. This DNA damage is completely abrogated by a specific cyclooxygenase-2 inhibitor (SC58125) or by a cell-permeable modified catalase. Literature is reviewed regarding generation of reactive oxygen and cyclooxygenase-2 induction by ras, cyclooxygenase-2 release of DNA-damaging reactive oxygen, and involvement of cyclooxygenase-2 and reactive oxygen in lung cancer

Single nucleotide polymorphisms in DNA repair genes and prostate cancer risk

The specific causes of prostate cancer are not known. However, multiple etiologic factors, including genetic profile, metabolism of steroid hormones, nutrition, chronic inflammation, family history of prostate cancer, and environmental exposures are thought to play significant roles. Variations in exposure to these risk factors may explain interindividual differences in prostate cancer risk. However, regardless of the precise mechanism(s), a robust DNA repair capacity may mitigate any risks conferred by mutations from these risk factors. Numerous single nucleotide polymorphisms (SNPs) in DNA repair genes have been found, and studies of these SNPs and prostate cancer risk are critical to understanding the response of prostate cells to DNA damage. A few SNPs in DNA repair genes are associated with significantly increased risk of prostate cancer; however, in most cases, the effects are moderate and often depend upon interactions among the risk alleles of several genes in a pathway or with other environmental risk factors. This report reviews the published epidemiologic literature on the association of SNPs in genes involved in DNA repair pathways and prostate cancer risk.

Formamidopyrimidines in DNA: mechanisms of formation, repair, and biological effects

Oxidatively induced damage to DNA results in a plethora of lesions comprising modified bases and sugars, DNA-protein cross-links, tandem lesions, strand breaks, and clustered lesions. Formamidopyrimidines, 4,6-diamino-5-formamidopyrimidine (FapyAde) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua), are among the major lesions generated in DNA by hydroxyl radical attack, UV radiation, or photosensitization under numerous in vitro and in vivo conditions. They are formed by one-electron reduction of C8-OH-adduct radicals of purines and thus have a common precursor with 8-hydroxypurines generated upon one-electron oxidation. Methodologies using mass spectrometry exist to accurately measure FapyAde and FapyGua in vitro and in vivo. Formamidopyrimidines are repaired by base excision repair. Numerous prokaryotic and eukaryotic DNA glycosylases are highly specific for removal of these lesions from DNA in the first step of this repair pathway, indicating their biological importance. FapyAde and FapyGua are bypassed by DNA polymerases with the insertion of the wrong intact base opposite them, leading to mutagenesis. In mammalian cells, the mutagenicity of FapyGua exceeds that of 8-hydroxyguanine, which is thought to be the most mutagenic of the oxidatively induced lesions in DNA. The background and formation levels of the former in vitro and in vivo equal or exceed those of the latter under various conditions. FapyAde and FapyGua exist in living cells at significant background levels and are abundantly generated upon exposure to oxidative stress. Mice lacking the genes that encode specific DNA glycosylases accumulate these lesions in different organs and, in some cases, exhibit a series of pathological conditions including metabolic syndrome and cancer. Animals exposed to environmental toxins accumulate formamidopyrimidines in their organs. Here, we extensively review the mechanisms of formation, measurement, repair, and biological effects of formamidopyrimidines that have been investigated in the past 50 years. Our goal is to emphasize the importance of these neglected lesions in many biological and disease processes.

The Association of OGG1 Ser326Cys Polymorphism and Urinary 8-OHdG Levels With Lung Cancer Susceptibility: A Hospital-Based Case-Control Study in Turkey

High incidence and poor prognosis of lung cancer make it a major health problem worldwide. Although smoking is a major cause of lung cancer, only some smokers develop lung cancer, which suggests that there is a genetic predisposition in some individuals. 8-OHG is an important oxidative base lesion and may elevate due to cancer and smoking. It is repaired by 8-hydroxyguanine DNA glycosylase 1 (OGG1), which has several polymorphisms. Although the Ser326Cys polymorphism is consistently associated with a range of cancers, findings about this polymorphism and lung cancer risk are contradictory. To date, no study has examined this association in the Turkish population. We conducted a case-control study to investigate the association between OGG1 Ser326Cys polymorphism and the risk of lung cancer using PCR-RFLP. We also evaluated gene-smoking interaction and excretion of urinary 8-OHdG. Our results suggest that the OGG1 Ser326Cys polymorphism is not a genetic risk factor for lung cancer, and that the heterozygous genotype is associated with a significantly reduced risk for lung cancer. The levels of 8-OHdG did not correlate with the polymorphism and smoking. Larger association studies are needed to validate our findings, and mechanistic studies are needed to elucidate the underlying molecular mechanisms of this association.

Molecular epidemiology of cancer

In this review the role of molecular markers for the assessment of individual exposure to carcinogenic agents was analyzed. Examples of the studies describing mutation patterns related to specific carcinogenic exposures are presented. The results of epidemiological studies of gene polymorphism and its role in the interaction between inheritance, environmental factors, and lifestyles are analyzed in detail. Adequate planning and performance of the epidemiological component of a study is a requirement for obtaining reproducible results reflecting molecular mechanisms of interest. Individual information on lifestyle factors (smoking, alcohol consumption, nutrition, physical activity, reproductive anamnesis) and environmental factors (occupational activity and carcinogen load at workplace), which influence not only the risk of developing cancer, but also the molecular features of a tumor, is crucial for adequate analysis and proper assessment of the results.

The hOGG1 Ser326Cys polymorphism and lung cancer risk: a meta-analysis

The potentially functional polymorphism Ser326Cys in the human 8-oxoguanine DNA glycosylase (hOGG1) gene has been implicated in lung cancer risk, but published studies have mixed findings. To summarize published data, we did a comprehensive meta-analysis. Two investigators extracted data independently from 17 case control studies published in the PubMed using the search phrases "hOGG1/OGG1/OGG and polymorphism/genetic variation and lung cancer." The meta-analysis included 6,375 cancer cases and 6,406 control subjects. The results showed that individuals carrying the hOGG1 Cys/Cys genotype did not have significantly increased risk of lung cancer [odds ratios (OR), 1.15; 95% (confidence interval) CI, 0.94-1.41] compared with those with the Ser/Ser genotype; similarly, no significant association with lung cancer risk was found either in the recessive (OR, 1.09; 95% CI, 0.90-1.32 for Cys/Cys versus Ser/Cys+Ser/Ser) or dominant model of the Ser326 allele (OR, 1.06; 95% CI, 0.93-1.21 for Cys/Cys+Ser/Cys versus Ser/Ser). However, significantly increased risks were found among Asian subjects (OR, 1.18; 95% CI, 1.01-1.38 for Cys/Cys+Ser/Cys versus Ser/Ser) in a dominant model. In stratified analyses by control source, compared with the Ser/Ser genotype, lung cancer risk associated with the hOGG1 Cys/Cys genotype was significantly increased in population-based studies (OR, 1.32; 95% CI, 1.04-1.67) but not in hospital-based studies (OR, 1.18; 95% CI, 0.98-1.42); in stratified analyses by the smoking status, however, the increased risk was observed only among nonsmokers in a dominant model (OR, 1.32; 95% CI, 1.04-1.67). The meta-analysis suggested that a careful matching should be considered in future larger genetic association studies including multiple ethnic groups.

OGG1 expression and OGG1 Ser326Cys polymorphism and risk of lung cancer in a prospective study

Oxidative DNA damage is believed to be implicated in lung carcinogenesis. 8-OxodG is a mutagenic and abundant oxidative modification induced in DNA. OGG1, NEIL1 and MUTYH are all involved in the repair and prevention of 8-oxodG-derived mutations and may be up-regulated by oxidative stress. The polymorphism OGG1 Ser326Cys has in some studies been associated with risk of lung cancer. In a population-based cohort of 57,053 Danes, we examined associations between mRNA levels of OGG1, NEIL1, MUTYH and NUDT in buffy coat material and subsequent lung cancer risk. 260 cases with lung cancer were identified and a sub-cohort of 263 individuals was matched on sex, age and smoking duration. We found that OGG1 mRNA levels in healthy individuals were not associated with risk of subsequent getting lung cancer. However, subjects with the OGG1 Cys326/Cys326 genotype had a higher expression level of OGG1 mRNA than wildtype-allele carriers. For homozygous Cys326 carriers, the incidence rate ratio (IRR) was 1.51 (95% CI: 1.09-2.08) for a doubling of the OGG1 mRNA level and there was a statistically significant interaction between the genotype and mRNA level. Among never-smokers, the IRR was 4.29 (1.09-16.9) per doubling of the OGG1 mRNA level, which was not found among smokers. Furthermore, we found a positive correlation between OGG1 mRNA expression and urinary excretion of 8-oxodG (RS=0.18; p<0.005). NUDT1 mRNA levels were omitted due to low and unreliable expression levels. The results suggest that OGG1 mRNA levels should be regarded as a biomarker of exposure to oxidative stress with induction of DNA rather than a marker of inborn DNA repair capacity.

hOGG1 Ser326Cys polymorphism and risk of hepatocellular carcinoma among Japanese

BACKGROUND

The Ser326Cys polymorphism in human oxoguanine glycosylase 1 (hOGG1), which is involved in the repair of 8-hydroxy-2-deoxyguanine in oxidatively damaged DNA, has been associated with susceptibility to certain cancers, but has not been examined in causation of hepatocellular carcinoma (HCC).

METHODS

We conducted a case-control study to investigate whether this polymorphism was related to HCC risk with any interaction with alcohol consumption and cigarette smoking. Genotyping was performed by a polymerase chain reaction with confronting two-pair primers among 209 newly diagnosed HCC cases, 275 hospital controls, and 381 patients with chronic liver disease (CLD) without HCC.

RESULTS

Overall, the hOGG1 genotype was not significantly associated with HCC; adjusted odds ratios (and 95% confidence intervals) for the Ser/Cys and Cys/Cys genotypes compared with the Ser/Ser genotype were 0.79 (0.35-1.79) and 0.48 (0.18-1.27) against hospital controls, and 1.51 (0.96-3.37) and 0.86 (0.50-1.47) against CLD patients. We could not detect any significant gene-alcohol interaction (p = 0.95 or 0.16) or gene-smoking interaction (p = 0.70 or 0.69).

CONCLUTIONS

These results suggest that the hOGG1 Ser326Cys polymorphism may not play a major role as an independent factor in hepatocarcinogenesis.

DNA damage repair and genetic polymorphisms: Assessment of individual sensitivity and repair capacity

PURPOSE

To study the repair capacity after X-ray irradiation in human peripheral blood cells of healthy subjects, in relation to their genotypes.

METHODS AND MATERIALS

The peripheral blood of 50 healthy subjects was irradiated in vitro with 2 Gy of X rays and the induced DNA damage was measured by Comet assay immediately after irradiation. DNA repair was detected by analyzing the cells at defined time intervals after the exposure. Furthermore, all subjects were genotyped for XRCC1, OGG1, and XPC genes.

RESULTS

After X-ray irradiation, persons bearing XRCC1 homozygous variant (codon 399) genotype exhibited significantly lower Tail DNA values than those bearing wild-type and heterozygous genotypes. These results are also confirmed at 30 and 60 min after irradiation. Furthermore, XPC heterozygous subjects (variant codon 939) showed lower residual DNA damage 60 min after irradiation compared with wild-type and homozygous genotypes.

CONCLUSION

The results of the present study show that polymorphisms in DNA repair genes could influence individual DNA repair capacity.

Association of genetic polymorphisms in the base excision repair pathway with lung cancer risk: a meta-analysis

Lung cancer is a major cause of cancer-related death in the developed countries and the overall survival rate has still an extremely poor. Although cigarette smoking is the main cause of lung cancer, not all smokers develop lung cancer, and a fraction of lifelong non-smokers will die from lung cancer. Genetic host factors have recently been implicated to account for some of the observed differences in lung cancer susceptibility. Various DNA alterations can be caused by exposure to environmental and endogenous carcinogens. Most of these alterations, if not repaired, may result in genetic instability, mutagenesis and cell death. DNA repair mechanisms are important for maintaining DNA integrity and preventing carcinogenesis. Recent genetic association studies on lung cancer risk have focused on identifying effects of single nucleotide polymorphisms (SNPs) in candidate genes, among which DNA repair genes are increasingly studied. Genetic variations in DNA repair genes are thought to modulate DNA repair capacity and are suggested to be related to lung cancer risk. We identified a sufficient number of epidemiologic studies on lung cancer to conduct a meta-analysis for genetic polymorphisms in nucleotide base repair (BER) pathway, focusing on 8-oxoguanine DNA glycosylase 1, X-ray cross-complementing group 1 (XRCC1) and apurinic/apyrimidinic endonuclease 1. The 399Gln/Gln genotype of the XRCC1 Arg399Gln polymorphism was associated with an increased risk of lung cancer among Asians (OR=1.34, 95% CI=1.16-1.54) but not among Caucasians. Little evidence of associations has been found between other BER genes and lung cancer risk. Considering the data available, it can be conjectured that if there is any risk association between single SNP and lung cancer, this risk increase/decrease will probably be minimal. Advances in identification of new polymorphisms and in high-throughput genotyping techniques will facilitate analysis of multiple genes in multiple DNA repair pathways. Therefore, it is likely that the defining feature of future epidemiologic studies will be the simultaneous analysis of large samples of cases and controls.

Association of the OGG1-Ser326Cys polymorphism with lung adenocarcinoma risk

Adenocarcinoma (ADC) is the most frequent histological type of lung cancer and comprises the majority of lung cancers in non-smokers. Thus, genetic factors responsible for ADC susceptibility need to be determined to establish efficient ways of preventing the disease. The OGG1 gene, encoding a glycosylase for 8-hydroxyguanine, an oxidatively damaged promutagenic base, has the polymorphism Ser326Cys, and OGG1-326Cys protein was indicated to have a lower ability to prevent mutagenesis than the OGG1-326Ser protein. Case-control studies to date suggest that the OGG1-326Cys allele is associated with a higher risk for several types of cancers, including overall lung cancer. However, the contribution of this polymorphism to lung ADC risk is unclear. In the present study, the OGG1-Ser326Cys polymorphism was assessed for association with lung ADC risk using a case-control study of a Japanese population consisting of 1097 cases and 394 controls. Odds ratios (OR) of the 326Cys allele carriers increased in a dose-dependent manner with allele number (P for the trend test = 0.04). The OR of homozygotes for the 326Cys allele was increased significantly when homozygotes for the 326Ser allele were used as a reference (OR = 1.5, 95% confidence interval [CI] = 1.0-2.1, P = 0.04). Furthermore, the overall OR for lung ADC of the Cys/Cys homozygotes out of a total of 1925 ADC patients and 3449 controls from six case-control studies reported up to the present were 1.43 (95% CI = 1.11-1.84, P = 0.0045). These results indicate that OGG1-326Cys functions as a risk allele for lung ADC development.

DNA damage and repair in gastric cancer--a correlation with the hOGG1 and RAD51 genes polymorphisms

The cell's susceptibility to mutagens and its ability to repair DNA lesions are important for cancer induction, promotion and progression. Both the mutagens' sensitivity and the efficacy of DNA repair may be affected by variation in several genes, including DNA repair genes. The hOGG1 gene encodes glycosylase of base excision repair and RAD51 specifies a key protein in homologues recombination repair. Both can be involved in the repair of oxidative DNA lesions, which can contribute to stomach cancer. In the present work we determined the level of basal and oxidative DNA damage and the kinetics of removal of DNA damage induced by hydrogen peroxide in peripheral blood lymphocytes of 30 gastric cancer patients and 30 healthy individuals. The metrics from DNA damage and repair study were correlated with the genotypes of common polymorphisms of the hOGG1 and RAD51 genes: a G-->C transversion at 1245 position of the hOGG1 gene producing a Ser-->Cys substitution at the codon 326 (the Ser326Cys polymorphism) and a G-->C substitution at position 135 (5'-untranslated region) of the RAD51 gene (the G135C polymorphism). DNA damage and repair were evaluated by alkaline single cell gel electrophoresis (comet assay) assisted by DNA repair enzymes: endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg), preferentially recognizing oxidized DNA bases. The genotypes of the polymorphism were determined by restriction fragment length polymorphism PCR. We observed a strong association between gastric cancer occurrence, impaired DNA repair in human lymphocytes and the G/C genotype of the G135C polymorphism of the RAD51 gene. Moreover, there was a strong correlation between that genotype and stomach cancer occurrence in subjects with high level of oxidatively damaged DNA. We did not observe any correlation between the Ser1245Cys polymorphism of the hOGG1 gene and gastric cancer, including subjects with impaired DNA repair and/or high levels of endogenous oxidative DNA lesions. Therefore, our result suggest that the G135C polymorphism of the RAD51 gene may be linked with gastric cancer by the modulation of the cellular response to oxidative stress and this polymorphism may be a useful additional marker in this disease along with the genetic or/and environmental indicators of oxidative stress.

Association of the OGG1 Ser326Cys polymorphism with tooth loss

Although tooth loss is a serious health problem for elderly people, little is known about the genetic basis for susceptibility to it. In the present study we aimed to find a single nucleotide polymorphism (SNP) associated with tooth loss. DNA samples from 119 outpatients (mean age=78.8 years) were genotyped on seven polymorphisms (tumor necrosis factor-alpha -1031T/C, interleukin-1beta -511C/T, interleukin-6 -634C/G, macrophage migration inhibitory factor -173G/C, interleukin-1 receptor antagonist variable number of tandem repeat in intron 2, matrix metalloproteinase-1 -16071G/2G, and oxoguanine glycosylase 1 (OGG1) Ser326Cys (1245C/G)), and the results were statistically evaluated. Of the seven polymorphisms tested, only OGG1 Ser326Cys was revealed to associate with tooth loss at a statistically significant level (P=0.0086). In addition, a multivariate logistic regression analysis in which age, gender, body mass index (BMI), and ischemic heart disease were included as independent variables indicated that Ser326Cys could be an independent factor affecting tooth loss (OR, 3.191; 95%CI, 1.174-8.672). The data suggest that the OGG1 Ser326Cys polymorphism may be associated with tooth loss.

Interaction ofOGG1 Ser326Cys polymorphism with cigarette smoking in head and neck squamous cell carcinoma

Recent molecular epidemiological studies have demonstrated that the human oxoguanine glycosylase 1 (OGG1) gene polymorphism may be associated with various cancers. To determine whether the OGG1 Ser326Cys polymorphism interacts with clinicopathological parameters including smoking and alcohol intake in head and neck squamous cell carcinoma (HNSCC), DNA samples from 192 patients with primary HNSCC were genotyped and studied by the case-only design. We observed an association between the Cys/Cys genotype and HNSCC with cigarette smoking of more than 40 pack-years by a multivariate logistic regression analysis (OR=8.10, 95% CI=1.06-61.73). No significant association of this genotype with alcohol intake was observed. Our present data suggest a possible interaction between the OGG1 Ser326Cys polymorphism and smoking in HNSCC.

Genetic polymorphisms in the base excision repair pathway and cancer risk: a HuGE review

Genetic variations in DNA repair genes are thought to modulate DNA repair capacity and are suggested to be related to cancer risk. However, epidemiologic findings have been inconsistent. The authors conducted meta-analyses of associations between genes in the base excision repair pathway and cancer risk, focusing on three key genes: 8-oxoguanine DNA glycosylase (OGG1), apurinic/apyrimidinic endonuclease (APE1/APEX1), and x-ray repair cross-complementing group 1 (XRCC1). They found increased lung cancer risk among subjects carrying the OGG1 Cys/Cys genotype (odds ratio (OR) = 1.24, 95% confidence interval (CI): 1.01, 1.53), using 3,253 cases and 3,371 controls from seven studies; this is consistent with experimental evidence that this isoform exhibits decreased activity. They found a protective effect of the XRCC1 194Trp allele for tobacco-related cancers (OR = 0.86, 95% CI: 0.77, 0.95), using 4,895 cases and 5,977 controls from 16 studies; this is compatible with evidence of lower mutagen sensitivity for this allele. The XRCC1 399Gln/399Gln genotype was associated with increased risk of tobacco-related cancers among light smokers (OR = 1.38, 95% CI: 0.99, 1.94) but decreased risk among heavy smokers (OR = 0.71, 95% CI: 0.51, 0.99), suggesting effect modification by tobacco smoking. There was no association between cancer risk and the APE1/APEX1 Asp148Glu and XRCC1 Arg280His polymorphisms. Recommendations for future studies include pooling of individual data to facilitate evaluation of multigenic effects and detailed analysis of effect modification by environmental exposure.

GPX Pro198Leu and OGG1 Ser326Cys polymorphisms and risk of development of colorectal adenomas and colorectal cancer

Little is known about genetic risk factors for colorectal cancer. We assessed the association between polymorphisms in two genes involved in DNA repair of oxidative stress, GPX and OGG1, and risk of colorectal carcinoma or adenomas. We studied 166 cases with adenocarcinoma, 974 with adenomas and 397 controls recruited from the Norwegian cohort NORCCAP. No associations were found between the polymorphism GPX Pro198Leu and risk of colorectal adenomas or carcinomas. Carriers of the variant allele OGG1 Ser326Cys polymorphism had a lowered risk of colorectal cancer, OR=0.56 (95% confidence interval 0.33-0.95), while no association were found with risk of adenomas. This indicates that a low repair capacity of oxidative DNA damage may not be a risk factor for development of colorectal adenomas or carcinoma.

Association of XRCC1 Arg399Gln and OGG1 Ser326Cys polymorphisms with the risk of cervical cancer in Japanese subjects

OBJECTIVE

In this study, genetic polymorphisms, XRCC1 Arg399Gln and OGG1 Ser326Cys were examined with reference to cervical cancer risk in a population-based incident case-control study in Japan.

METHODS

The cases comprised 131 cervical cancer patients: 87 cases with squamous cell carcinoma (SCC) and 44 with adenocarcinoma (ADC) or adenosquamous carcinoma (ADSC). Controls were sampled from 320 healthy women who underwent a health checkup.

RESULTS

The frequency of the XRCC1 399GlnGln genotype was higher in individuals with adenocarcinoma/adenosquamous carcinoma than in the healthy controls (OR = 2.98, 95% CI = 1.11-8.01, P = 0.030). However, no association was demonstrated in SCC. Analysis of OGG1 Ser326Cys polymorphism showed no significant differences between cervical cancer patients and controls. In stratification analysis, significant elevated risk of adenocarcinoma/adenosquamous carcinoma was associated with the XRCC1 399GlnGln genotype among nonsmokers (OR = 3.85, 95% CI = 1.28-11.59, P = 0.017), but not among smokers. No gene-gene interaction was observed in our case subjects.

CONCLUSION

This is the first report that the XRCC1 Arg399Gln polymorphism might be important in relation to the risk of adenocarcinoma/adenosquamous carcinoma of the cervix.

Modulation of oxidative mutagenesis and carcinogenesis by polymorphic forms of human DNA repair enzymes

Chromosome DNA is continuously exposed to various endogenous and exogenous mutagens. Among them, oxidation is one of the most common threats to genetic stability, and multiple DNA repair enzymes protect chromosome DNA from the oxidative damage. In Escherichia coli, three repair enzymes synergistically reduce the mutagenicity of oxidized base 8-hydroxy-guanine (8-OH-G). MutM DNA glycosylase excises 8-OH-G from 8-OH-G:C pairs in DNA and MutY DNA glycosylase removes adenine incorporated opposite template 8-OH-G during DNA replication. MutT hydrolyzes 8-OH-dGTP to 8-OH-dGMP in dNTP pool, thereby reducing the chance of misincorporation of 8-OH-dGTP by DNA polymerases. Simultaneous inactivation of MutM and MutY dramatically increases the frequency of spontaneous G:C to T:A mutations, and the deficiency of MutT leads to the enhancement of T:A to G:C transversions more than 1000-fold over the control level. In humans, the functional homologues of MutM, MutY and MutT, i.e., OGG1, MUTYH (MYH) and MTH1, contribute to the protection of genomic DNA from oxidative stress. Interestingly, several polymorphic forms of these proteins exist in human populations, and some of them are suggested to be associated with cancer susceptibility. Here, we review the polymorphic forms of OGG1, MUTYH and MTH1 involved in repair of 8-OH-G and 8-OH-dGTP, and discuss the significance of the polymorphisms in the maintenance of genomic integrity. We also summarize the polymorphic forms of human DNA polymerase eta, which may be involved in damage tolerance and mutagenesis induced by oxidative stress.