hOGG1 exon7 polymorphism and gastric cancer in case-control studies of Japanese Brazilians and non-Japanese Brazilians

The Interaction of Smoking with Gene Polymorphisms on Four Digestive Cancers: A Systematic Review and Meta-Analysis

The main purpose of this study was to perform a meta-analysis to assess the interaction between smoking and nine genes (GSTM1, GSTT1, GSTP1, CYP1A1, NAT2, SULT1A1, hOGG1, XRCC1 and p53) on colorectal cancer, gastric cancer, liver cancer and oesophageal cancer. Published articles from the PubMed, ISI and EMBASE databases were retrieved. A total of 67 case-control studies or nested case-control studies were identified for the analysis. The pooled jodds ratio (OR) with 95% confidence interval (CI) was calculated using the random effect model. The overall study showed that the GSTM1 polymorphism was associated with the risk of the four digestive cancers among Asian population (OR 1.284, 95% CI: 1.122-1.470, p: 0). Subgroup analyses by cancer site showed that GSTM1 null genotype increased the gastric cancer risk in total population (OR 1.335, 95% CI: 1.145-1.556, p: 0). However, the association of GSTM1 null genotype with the oesophageal cancer risk was found in smokers (OR 1.382, 95% CI: 1.009-1.894, p:0.044), but not in non-smokers (OR 1.250, 95% CI: 0.826-1.891, p:0.290). Moreover, smokers with the CYP1A1 IIe462Val polymorphism were at an increased cancer risk in Asian population (OR=1.585, 95% CI 1.029-2.442, p: 0.037). None of the other gene-smoking interactions was observed in the above cancers. This meta-analysis reveals two potential gene-smoking interactions, one is between smoking and GSTM1 on oesophageal cancer, and the other is between smoking and CYP1A1 IIe462Val on the four cancers in Asian population. Future studies need to be conducted to verify the conclusions.

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.

Association between hOGG1 polymorphism rs1052133 and gastric cancer

Purpose

To conduct a comprehensive evaluation of the association of the human8-oxoguanine glycosylase 1 (hOGG1) gene polymorphism rs1052133 with gastric cancer (GC) through a systematic review and meta-analysis of genetic association study.

Results

A total of 15 articles from published papers were included in our analysis. The meta-analyses for hOGG1 rs1052133, composed of 4024GC patients and 6022controls, showed low heterogeneity for the included populations in all the genetic models, except for the Caucasian population under allelic genetic model, the Asian population under addictive model and Caucasian population under dominant model. The analyses of all the genetic models in overall pooled populations did not identify any significant association between GC and hOGG1 rs1052133 (Allelic model: C vs. G, p = 0.746; Addictive model: CC vs. GG, p = 0.888; Recessive model: CC +GC vs. GG, p = 0.628; Dominant model: CC vs. GG+GC, p = 0.147), even though stratified analyses were conducted in different ethnicities under each genetic model.

Materials and Methods

All case-control association studies on hOGG1 and GC reported up to December 15, 2016 in PubMed, Embase, Web of Science, and the Chinese Biomedical Database were retrieved. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for single-nucleotide polymorphism (SNP) using fixed- and random- effects models according to between-study heterogeneity. Publication bias analyses were conducted using Begg test.

Conclusions

This meta-analysis showed there was no association between hOGG1 rs1052133 and GC. Given the limited sample size, further investigations including more ethnic groups are required to validate the association.

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.

The hOGG1 Ser326Cys polymorphism contributes to digestive system cancer susceptibility: evidence from 48 case-control studies

The Ser326Cys polymorphism in the human 8-oxogunaine DNA glycosylase (hOGG1) gene had been implicated in cancer susceptibility. Studies investigating the associations between the Ser326Cys polymorphism and digestion cancer susceptibility showed conflicting results. Therefore, a meta-analysis was performed to derive a more precise estimation of the relationship. We conducted a meta-analysis of 48 studies that included 12,073 cancer cases and 19,557 case-free controls. We assessed the strength of the association using odds ratios (ORs) with 95% confidence intervals (CIs). In our analysis, the hOGG1 Ser326Cys polymorphism was significantly associated with the risk of digestive system cancers (Cys/Cys vs. Ser/Ser: OR = 1.17, 95% CI = 1.00-1.35, P < 0.001; Cys/Cys vs. Cys/Ser + Ser/Ser: OR = 1.14, 95% CI = 1.00-1.29, P < 0.001). In subgroup analyses by cancer types, we found that the hOGG1 Ser326Cys polymorphism may increase hepatocellular cancer and colorectal cancer risks, but decrease the risk of oral cancer. These findings supported that hOGG1 Ser326Cys polymorphism may contribute to the susceptibility of digestive cancers.

Role of gene polymorphisms in gastric cancer and its precursor lesions: Current knowledge and perspectives in Latin American countries

Latin America shows one of the highest incidence rates of gastric cancer in the world, with variations in mortality rates among nations or even within countries belonging to this region. Gastric cancer is the result of a multifactorial complex process, for which a multistep model of carcinogenesis is currently accepted. Additionally to the infection with Helicobacter pylori, that plays a major role, environmental factors as well as genetic susceptibility factors are significant players at different stages in the gastric cancer process. The differences in population origin, demographic structure, socio-economic development, and the impact of globalization lifestyles experienced in Latin America in the last decades, all together offer opportunities for studying in this context the influence of genetic polymorphisms in the susceptibility to gastric cancer. The aim of this article is to discuss current trends on gastric cancer in Latin American countries and to review the available published information about studies of association of gene polymorphisms involved in gastric cancer susceptibility from this region of the world. A total of 40 genes or genomic regions and 69 genetic variants, 58% representing markers involved in inflammatory response, have been used in a number of studies in which predominates a low number of individuals (cases and controls) included. Polymorphisms of IL-1B (-511 C/T, 14 studies; -31 T/C, 10 studies) and IL-1RN (variable number of tandem repeats, 17 studies) are the most represented ones in the reviewed studies. Other genetic variants recently evaluated in large meta-analyses and associated with gastric cancer risk were also analyzed in a few studies [e.g., prostate stem cell antigen (PSCA), CDH1, Survivin]. Further and better analysis centered in gene polymorphisms linked to other covariates, epidemiological studies and the information provided by meta-analyses and genome-wide association studies should help to improve our understanding of gastric cancer etiology in order to develop appropriate health programs in Latin America.

Risk factors for gastric cancer in Latin America: a meta-analysis

BACKGROUND

Latin America has among the highest gastric cancer incidence rates in the world, for reasons that are still unknown. In order to identify region-specific risk factors for gastric cancer, we conducted a meta-analysis summarizing published literature.

METHODS

Searches of PubMed and regional databases for relevant studies published up to December 2011 yielded a total of 29 independent case-control studies. We calculated summary odds ratios (OR) for risk factors reported in at least five studies, including socioeconomic status (education), lifestyle habits (smoking and alcohol use), dietary factors (consumption of fruits, total vegetables, green vegetables, chili pepper, total meat, processed meat, red meat, fish, and salt), and host genetic variants (IL1B-511T, IL1B-31C, IL1RN*2, TNFA-308A, TP53 codon 72 Arg, and GSTM1 null). Study-specific ORs were extracted and summarized using random-effects models.

RESULTS

Chili pepper was the only region-specific factor reported in at least five studies. Consistent with multifactorial pathogenesis, smoking, alcohol use, high consumption of red meat or processed meat, excessive salt intake, and carriage of IL1RN*2 were each associated with a moderate increase in gastric cancer risk. Conversely, higher levels of education, fruit consumption, and total vegetable consumption were each associated with a moderately decreased risk. The other exposures were not significantly associated. No prospective study data were identified.

CONCLUSION

Risk factor associations for gastric cancer in Latin America are based on case-control comparisons that have uncertain reliability, particularly with regard to diet; the specific factors identified and their magnitudes of association are largely similar to those globally recognized. Future studies should emphasize prospective data collection and focus on region-specific exposures that may explain high gastric cancer risk.

Lack of association between the hOGG1 Ser326Cys polymorphism and gastric cancer risk: a meta-analysis

AIM

To clarify any association between the hOGG1 Ser326Cys polymorphism and susceptibility to gastric cancer.

METHODS

A meta-analysis based on 11 eligible case-control studies involving 5,107 subjects was carried out to summarize the data on the association between hOGG1 Ser326Cys polymorphism and gastric cancer risk.

RESULTS

No association was found between hOGG1 Ser326Cys polymorphism and gastric cancer risk (dominant model: OR = 0.95, 95% CI: 0.83-1.09, p = 0.486, ph (p values for heterogeneity) = 0.419; additive model: OR = 1.02, 95% CI: 0.81-1.30, p = 0.850, ph = 0.181; recessive model: OR = 1.09, 95% CI: 0.80-1.48, p = 0.586, ph = 0.053). Subgroup analysis based on ethnicity (Asian and Caucasian) and smoking status (ever smoker and never smoker) did did notpresent any significant association. Sensitivity analysis did not perturb the results.

CONCLUSIONS

This study strongly suggested there might be no association between the hOGG1 Ser326Cys polymorphism and gastric cancer risk. However, larger scale studies are needed for confirmation.

Could 8-oxoguanine DNA glycosylase 1 Ser326Cys polymorphism be a biomarker of susceptibility in cancer?

Biomarkers are key molecular or cellular events that give an indication whether there is a threat for disease, whether a disease already exists, or how such disease may develop in an individual case. The discovery of polymorphisms in genes that function in the metabolism of chemicals and in DNA repair has demonstrated the importance of understanding the phenomenon of genetic susceptibility in a population. Polymorphisms in DNA repair genes as an important component of the individual susceptibility to the development of cancer and various hereditary diseases have been commonly studied, since these genes have critical roles in maintaining genome integrity. Furthermore, the evaluation of cancer risk depends on the level of exposure to carcinogenic factors as well as on the genetic codes of the individual. This approach is supported by studies that present positive association between these polymorphic genes and cancers. Although 8-oxoguanine DNA glycosylase 1 (OGG1) is one of the promising biomarker candidates of cancer susceptibility, there are also some controversial results. Epidemiological studies show that the OGG1 might be a biomarker of susceptibility for various cancers; however, the small sample size and difference in the eligibility criteria for inclusion of subjects and sources might limit the studies to demonstrate the association between the OGG1 Ser326Cys polymorphism and the risk of cancer. Thus, meta-analyses may provide more valuable and reliable data to demonstrate the potential of OGG1 Ser326Cys DNA repair enzyme polymorphisms that could be the biomarkers of susceptibility of cancer. Our aim in this review is to compile published studies, including some controversial results on the association between the OGG1 Ser326Cys polymorphism and the risk of cancer.

Association of hOGG1 Ser326Cys polymorphism with gastric cancer risk: a meta-analysis

Studies investigating the association between human 8-oxoguanine glycosylase 1(hOGG1) Ser326Cys polymorphism and gastric cancer (GC) risk have reported conflicting results. We performed a meta-analysis of published case-control studies to better compare results between studies. 11 eligible studies with 2,180 GC cases and 3,985 controls were selected. There were 5 studies involving Caucasians and 5 studies involving Asians. The combined result based on all studies did not show significant difference in any genetics models. Ser/Cys + Cys/Cys versus Ser/Ser (OR = 0.91, 95% CI 0.81-1.03), Cys/Cys versus Ser/Cys + Ser/Ser (OR = 1.07, 95% CI 0.80-1.44), Ser/Cys versus Ser/Ser (OR = 0.91, 95% CI 0.80-1.03), Sys/Cys versus Ser/Cys (OR = 1.10, 95% CI 0.83-1.47), Cys/Cys versus Ser/Ser (OR = 0.99, 95% CI 0.74-1.34), Cys versus Ser (OR = 1.01, 95% CI 0.88-1.17).When stratifying for ethnicity, there was still no significant association found between hOGG1 Ser326Cys polymorphism and GC risk. Funnel plot and Egger’s test showed some evidence of publication bias on the basis of all studies. Two studies were the main reason because their samples were too small. However, the result of sensitivity analysis suggested that the influence of these two studies and one mixed population study on the pooled OR was weak. Our result could explain the association between hOGG1 Ser326Cys polymorphism and GC risk. In conclusion, we did not found the evidence that the Cys allele at codon 326 of hOGG1 could increase GC risk in our analysis.

Modulation of oxidative DNA damage by repair enzymes XRCC1 and hOGG1

The influence of DNA repair gene polymorphisms (XRCC1: Arg194Trp, Arg280His, Arg399Gln; APE1: Asp148Glu; hOGG1: Ser326Cys) on oxidative DNA damage is controversial and was investigated in 214 German workers with occupational exposure to vapors and aerosols of bitumen,compared to 87 German construction workers without exposure, who were part of the Human Bitumen Study. Genotypes were determined by real-time polymerase chain reaction (PCR), and actual smoking habits by a questionnaire and cotinine analysis. Oxidative DNA damage in white blood cells (WBC) collected pre- and postshift was measured as 8-oxodGuo adducts/10(6) dGuo by a hjigh-performance liquid chromatography electron capture detection (HPLC-ECD) method, followed by calculation of the difference between post- and preshift values (Δ8-oxodGuo/10(6) dGuo). The 214 bitumen exposed workers showed higher median Δ8-oxodGuo values than the 87 references. In the whole study group (n=301) there was a trend for increasing adduct values for XRCC1 Arg(GG)399Gln(AA) during a shift, especially in nonsmokers (n=108. Referents (n=87) displayed a similar trend for hOGG1 Ser(CC)326Cys(GG). In contrast, XRCC1 Arg(GG)280His(AA) showed a decrease of median Δ8-oxodGuo/10(6) dGuo values in workers with exposure to vapors and aerosols of bitumen (n=214), especially in smokers (n=145). XRCC1 Arg194Trp and APE1 Asp148Glu displayed no marked association with Δ8-oxodGuo levels. Data indicate that the combination of different variants in DNA damage repair enzymes may modulate the production of 8-oxoguanine adducts in WBC produced by xenobiotics during a shift.

The hOGG1 Ser326Cys polymorphism contributes to cancer susceptibility: evidence from 83 case-control studies

The Ser326Cys polymorphism in the human 8-oxogunaine DNA glycosylase (hOGG1) gene had been implicated in cancer susceptibility. Studies investigating the associations between the Ser326Cys polymorphism and cancer susceptibility showed conflicting results. To derive a more precise estimation of the relationship, a meta-analysis was performed. This meta-analysis was performed from 83 case-control studies, including 27,918 cases and 33,399 controls. The fixed and random effect models were used to estimate the odds ratios (ORs) and their 95% confidence interval (CI) for various contrasts of this polymorphism. The combined results based on all studies showed that the hOGG1 Ser326Cys polymorphism was associated with an increased cancer susceptibility in different genetic models. In the stratified analyses, the association was significantly in head and neck cancer (homozygote comparison: OR = 2.19, 95% CI: 1.20-4.01, P(heterogeneity) = 0.002; heterozygote comparison: OR = 1.48, 95% CI: 1.11-1.99, P(heterogeneity) = 0.004; dominant model comparison: OR = 1.58, 95% CI: 1.14-2.19, P(heterogeneity) < 0.001; recessive model comparison: OR = 1.73, 95% CI: 1.02-2.94, P(heterogeneity) = 0.002; and additive model comparison: OR = 1.43, 95% CI: 1.09-1.88, P(heterogeneity) < 0.001) which remained for studies of the Asian populations and hospital-based of control sources. But it was not observed in other cancer types of the European population and population based of control sources. This meta-analysis suggested that the hOGG1 Ser326Cys polymorphism might contribute to an increased risk on cancer susceptibility. More studies based on larger sample size should be performed to confirm the findings.

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.

DNA repair enzyme polymorphisms and oxidative stress in a Turkish population with gastric carcinoma

Although the developmental stages of gastric carcinoma are still not clear, the constantly generated reactive oxygen and nitrogen species (ROS/RNS) may contribute to the process of carcinogenesis by interacting with DNA. 8-oxoguanine DNA glycosylase-1 (OGG1) is an enzyme involved in base excision repair of 8-oxoguanine that is one of the premutagenic lesions generated by ROS in DNA. The bulky adducts, are recognized and repaired by nucleotid excision repair (NER) enzymes, including xeroderma pigmentosum C and D (XPC, XPD). Eligible 106 gastric cancer patients and 116 cancer-free individuals constituted the study and control groups, respectively. Association between OGG1 Ser326Cys, XPC Lys939Gln, XPD Lys751Gln polymorphisms and the susceptibility tho cancer and the oxidative stress status were evaluated. DNA was extracted from peripheral blood cells and genotypes were determined by using PCR-RFLP. Serum nitric oxide, albumin concentrations, total antioxidant status and Helicobacter pylori IgG were determined. Serum albumin and nitric oxide of cancer patients were lower than that of the controls (P < 0.05). None of the evaluated polymorphisms or Helicobacter pylori IgG seropositivity associated with increased risk of gastric cancer, despite of the increased oxidative stress in cancer patients.

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.

Analysis of hOGG1 genotype as a prognostic marker for muscle invasive bladder cancer: a novel approach using peptide nucleic acid-mediated, real-time PCR clamping

OBJECTIVE

DNA damage repair mechanisms are a source of genetic mutation and are believed to play an important role in human cancer. Human 8-oxoguanine DNA glycosylase 1 (hOGG1) is involved in the recognition and repair of DNA damage. The value of the hOGG1 genotype as a prognostic indicator for bladder cancer (BC) was assessed using a novel technological approach.

MATERIALS AND METHODS

The association between genetic polymorphisms of hOGG1 codon 326 and clinicopathologic characteristics of 337 patients with BC was analyzed using peptide nucleic acid (PNA)-mediated real-time PCR clamping.

RESULTS

Tumor grade and size were significantly associated with the hOGG1 codon 326 genotype in non-muscle-invasive bladder cancer (NMIBC). The Cys326Cys polymorphism was significantly associated with progression and cancer specific survival in patients with muscle-invasive bladder cancer (MIBC). Multivariate Cox regression analysis indicated that the hOGG1 Cys326Cys polymorphism is associated with a protective effect on progression and a more dominant survival benefit than the Ser326Ser polymorphism in MIBC (hazard ratio 0.284 and 0.305, respectively).

CONCLUSIONS

Analysis of genotypes and clinical data for 337 BC patients indicates that the hOGG1 genotype may be a useful prognostic genetic marker for MIBC.

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.

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.

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.

Association between genetic polymorphisms of DNA base excision repair genes and evolution of precancerous gastric lesions in a Chinese population

Base excision repair pathway may play an important role in repairing DNA damage related to Helicobacter pylori-induced inflammatory process. To evaluate the association between genetic polymorphisms of X-ray repair cross-complementing group 1 (XRCC1, Arg194Trp and Arg399Gln), adenosine diphosphate ribosyl transferase (ADPRT, Val762Ala), 8-oxoguanine DNA glycosylase (OGG1, Ser326Cys) and apurinic/apyrimidinic endonuclease 1 (APE1, Asp148Glu) and evolution of H.pylori-associated precancerous gastric lesions, a population-based cohort study was conducted in Linqu County, a high-risk area of gastric cancer in China. Genotypes were determined by polymerase chain reaction (PCR)-based denaturing high-performance liquid chromatography and PCR-restriction fragment length polymorphism analysis in 1281 H.pylori-infected subjects. We found that subjects carrying the combined XRCC1-194Arg/Trp+Trp/Trp genotype had an elevated chance of regression of gastric lesions [adjusted odds ratio (OR) = 1.44; 95% confidence interval (CI) = 1.06-1.96], whereas subjects carrying the XRCC1-399Arg/Gln+Gln/Gln genotype had a decreased chance of regression (OR = 0.68; 95% CI = 0.49-0.92). Stratified analysis indicated that an increased risk of progression was observed in subjects carrying the XRCC1-399Arg/Gln+Gln/Gln genotype (OR = 1.60; 95% CI = 1.09-2.36) or OGG1-326Ser/Cys+Cys/Cys genotype (OR = 1.95; 95% CI = 1.03-3.71) with intestinal metaplasia or dysplasia at baseline or carrying the XRCC1-399Arg/Gln+Gln/Gln genotype and smoking (OR = 1.58; 95% CI = 1.02-2.45). Furthermore, a significantly increased risk of progression was observed in subjects carrying one or two hazard genotypes of XRCC1-399 or OGG1-326, the OR was 2.83 (95% CI = 1.32-6.08), 2.22 (95% CI = 1.24-3.98) or 2.27 (95% CI = 1.26-4.10), respectively. These findings suggest that genetic polymorphisms in XRCC1-Arg194Trp, XRCC1-Arg399Gln and OGG1-Ser326Cys may play important roles in the evolution of H.pylori-associated gastric lesions in this high-risk population.

Genetic polymorphisms in hMTH1, hOGG1 and hMYH and risk of chronic benzene poisoning in a Chinese occupational population

Oxidative damage to DNA induced by benzene is an important mechanism of its genotoxicity, which leads to chronic benzene poisoning (CBP). Therefore, genetic variation in DNA repair genes may contribute to susceptibility to CBP in the exposed population. We hypothesized that single nucleotide polymorphisms (SNPs) in hMTH1, hOGG1 and hMYH genes are associated with risk of CBP. We genotyped SNPs at codon 83 of hMTH1, codon 326 of hOGG1, and codon 324 of hMYH in 152 CBP patients and 152 healthy workers occupationally exposed to benzene without poisoning manifestations. The genotypes were determined by polymerase chain reaction-restrained fragment length polymorphism (PCR-RFLP) technique. There were 2.51-fold [adjusted odds ratio (OR(adj)), 2.51; 95% CI, 1.14-5.49; P=0.02] and 2.49-fold (OR(adj), 2.49; 95% CI: 1.52-4.07; P<0.01) increased risk of CBP for individuals carrying genotypes of hMTH1 83Val/Met+Met/Met and hOGG1 326Cys/Cys, respectively. Compared with individuals carrying genotypes of hOGG1 326Cys/Cys and hMYH 324His/His at the same time, there was a 0.33-fold (OR(adj), 0.33; 95% CI: 0.15-0.72; P<0.05) decreased risk of CBP for those with genotypes of hOGG1 326Ser/Cys+Ser/Ser and hMYH 324His/Gln+Gln/Gln. In the smoking group, there was a 0.15-fold (OR(adj), 0.15; 95% CI, 0.03-0.68; P=0.01) decreased risk of CBP for subjects carrying genotypes of hMYH 324His/Gln+Gln/Gln compared with those of genotype of hMYH 324His/His. Therefore, our results suggested that polymorphisms at codons 83 of hMTH1 and codon 326 of hOGG1 might contribute to CBP in a Chinese occupational population.

DNA repair polymorphisms and the risk of stomach adenocarcinoma and severe chronic gastritis in the EPIC-EURGAST study

BACKGROUND

The contribution of genetic variation in DNA repair genes to gastric cancer (GC) risk remains essentially unknown. The aim of this study was to explore the relative contribution of DNA repair gene polymorphisms to GC risk and severe chronic atrophic gastritis (SCAG). Method A nested case control study within the EPIC cohort was performed including 246 gastric adenocarcinomas and 1175 matched controls. Controls with SCAG (n = 91), as defined by low pepsinogen A (PGA) levels, and controls with no SCAG (n = 1061) were also compared. Twelve polymorphisms at DNA repair genes (MSH2, MLH1, XRCC1, OGG1 and ERCC2) and TP53 gene were analysed. Antibodies against Helicobacter pylori were measured.

RESULTS

No association was observed for any of these polymorphisms with stomach cancer risk. However, ERCC2 K751Q polymorphism was associated with an increased risk for non-cardial neoplasm [odds ratio (OR) = 1.78; 95% confidence interval (CI) 1.02-3.12], being ERCC2 K751Q and D312N polymorphisms associated with the diffuse type. ERCC2 D312N (OR = 2.0; 95% CI 1.09-3.65) and K751Q alleles (OR = 1.82; 95% CI 1.01-3.30) and XRCC1 R399Q (OR = 1.69; 95% CI 1.02-2.79) allele were associated with an increased risk for SCAG.

CONCLUSION

Our study supports a role of ERCC2 in non-cardial GC but not in cardial cancer. A concordant result was observed for subjects with low PGA levels. XRCC1 allele was associated also with SCAG. This is the first prospective study suggesting that individual variation in DNA repair may be relevant for gastric carcinogenesis, a finding that will require further confirmation validation in larger independent studies.

Repair system of 7, 8-dihydro-8-oxoguanine as a defense line against carcinogenesis

Reactive oxygen species (ROS) are essentially harmful for living organisms, including human beings. It is well known that ROS-induced damage of cellular components may lead to human diseases, such as inflammatory diseases, degenerative diseases, or cancer. In particular, oxidative DNA damage is premutagenic, and thus, the generation of DNA damage and the failure of its removal are critical events for tumorigenesis or carcinogenesis. To prevent this disadvantage, living organisms have defense mechanisms against ROS-induced gene instability. Studies of 8-oxo-Gua and its main repair enzyme, 8-oxoguanine DNA glycosylase 1 (OGG1), are informative and useful, because 8-oxo-Gua is commonly observed in DNA, and OGG1 enzymes exist in a wide variety of living organisms. The importance of OGG1 was confirmed by polymorphism analyses and studies using knockout mice. Moreover, analyses of the influences of environmental factors on DNA damage and repair systems have confirmed the effects of heavy metals on 8-oxo-Gua formation and OGG1 expression. These studies revealed that the 8-oxo-Gua repair system is crucial for the prevention of mutation-related diseases, such as cancer. In this review, the advances in this field during the last two decades are described.

Oxidative DNA damage in gastric cancer: CagA status and OGG1 gene polymorphism

Oxidative DNA damage is thought to play an important part in the pathogenesis of H. pylori-induced mucosal damage. 8-OHdG is a sensitive marker of DNA oxidation and is repaired by a polymorphic glycosylase (OGG1) more effectively than by OGG1-Cys(326). The aims of this study were to ascertain the respective roles of H. pylori, cagA status and OGG1 polymorphism in determining 8-OHdG levels in benign and premalignant stomach diseases and in gastric cancer (GC). The study involved 50 GC patients (for whom both neoplastic tissue and surrounding mucosa were available), 35 with intestinal metaplasia and atrophy (IMA) and 43 controls. H. pylori and cagA status were determined by histology and polymerase chain reaction for urease and cagA. 8-OHdG was assayed using HPLC with an electrochemical detector (HPLC-ED). The OGG1 1245C-->G transversion was identified using RFLP analyses. 8-OHdG levels were significantly higher in GC, with no differences in relation to H. pylori or cagA status. OGG1 polymorphism was documented in 34% of GC (15 Ser/Cys, 2 Cys/Cys). OGG1 1245C-->G polymorphism was detected in 54% of IMA patients, but only 16% of controls (p = 0.0004) and coincided with significantly higher 8-OHdG levels. In the multivariate analysis, 8-OHdG levels were predicted by histotype and OGG1 status. OGG1 1245C-->G polymorphism was common in both GC and IMA, but very rare in controls, and correlated more closely with 8-OHdG levels than do H. pylori infection or cagA status.

Rapid detection of the hOGG1 Ser326Cys polymorphism using LightCycler technology

Human 8-oxoguanine DNA glycosylase 1 (hOGG1) plays an important role in the repair of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodGuo), one of the major constituents in DNA damage. A recent in vitro study showed that the hOGG1 326Cys polymorphism (rs1052133) exhibits reduced 8-oxodGuo repair activity. This study aimed to develop a LightCycler (LC) assay to analyze the C>G polymorphism (Ser326Cys) in exon 7 of the hOGG1 gene followed by validation of the method using DNA samples from 260 polycyclic aromatic hydrocarbons(PAH)-exposed workers with known 8-oxodGuo DNA-adduct values measured by HPLC. Twenty DNA samples were analyzed by a PCR-RFLP analysis with Fnu4H I to generate control DNA. LC melting curve analyses of the hOGG1 exon 7 PCR product were characteristic of the probes hybridized to the non-mutated Ser-type (CC) at 65 degrees C, or to the Cys mutant (GG) at 59 degrees C. The distribution in the population of PAH-exposed workers (N=260) was 58% (CC), 38%(CG), and 4% (GG). The minor G allele displayed a frequency of 23 %. The distribution of 8-oxodGuo adducts for the Ser326Cys variants of hOGG1 revealed geometric means (GM) of 5.83 (CC), 5.27 (CG), and 6.53 (GG) 8-oxodGuo adducts/10(6)dGuo. Corresponding GM values of current smokers were 5.7 (CC), 5.6 (CG) and 7.0 (GG) 8-oxodGuo adducts/10(6) dGuo. The analysis of the Ser326Cys polymorphism in 260 DNA samples with this new LC assay revealed that this method is reliable for high throughput analysis of this key polymorphism in the hOGG1 gene.

A novel single nucleotide polymorphism in XRCC4 gene is associated with gastric cancer susceptibility in Taiwan

BACKGROUND

The DNA repair gene XRCC4, an important caretaker of the overall genome stability, is thought to play a major role in the human carcinogenesis. We investigate some novel and important polymorphic variants of XRCC4, at codon 247 (rs3734091), G-1394T (rs6869366), intron 3 (rs28360071), and intron 7 (rs28360317), of their associated with gastric cancer susceptibility.

MATERIALS AND METHODS

In this hospital-based case-control study, the association of XRCC4 polymorphisms with gastric cancer risk in a Taiwanese population was investigated. In total, 121 patients with gastric cancer and 121 age-matched healthy controls recruited were genotyped investigating these polymorphisms' association with gastric cancer susceptibility.

RESULTS

We found a significant difference in the frequency of the XRCC4 G-1394T genotype, but not others, between the gastric cancer and control groups. Those who had G/T or G/G at XRCC4 G-1394T showed a 3.79-fold (95% confidence interval = 1.47-9.82) increased risk of gastric cancer compared to those with T/T. As for XRCC4 codon 247, intron 3, or intron 7, there was no difference in distribution between the gastric cancer and control groups.

CONCLUSIONS

Our findings suggest that the G allele of the XRCC4 G-1394T may contribute to gastric carcinogenesis and may be useful for gastric cancer early detection and prevention.

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.

Human 8-oxoguanine DNA glycosylase increases resistance to hyperoxic cytotoxicity in lung epithelial cells and involvement with altered MAPK activity

It is unknown whether base excision DNA repair (BER) proteins interact with mitogen-activated protein kinases (MAPK) under oxidation. Here, we explored roles of BER proteins in signaling transduction involving MAPK during hyperoxia. We demonstrated that ERK1/2 phosphorylation in A549 cells was increased in 95% O₂. p38 activity in A549 cells was also increased by exposure to 95% O₂. To evaluate regulatory roles of MAPK, we have transduced A549 cells and primary alveolar epithelial type II cells (AECII) to overexpress 8-oxoguanine DNA glycosylase (hOgg1). Overexpression of hOgg1 reduced hyperoxic toxicity in A549 and AECII cells. Furthermore, protection by BER against hyperoxia appeared to involve an upregulation of ERK1/2 and downregulation of p38. These observations demonstrate, for the first time, that reduction of hyperoxic toxicity by BER proteins may be involved with MAPK activity, thereby impacting cell survival. Furthermore, our studies suggest that modulation of MAPK may be used in combination with BER proteins to counteract hyperoxic toxicity.

Absence of MutY homologue mutation in patients with multiple sporadic adenomatous polyps in Korea

AIM: Recently, germ-line mutation in the base excision repair gene MYH has been identified to cause a novel autosomal recessive form of familial adenomatous polyposis (FAP). Interestingly, a striking evidence for MYH mutations within different ethnic groups has been demonstrated. In this study, we screened 30 patients with multiple adenomatous polyps for MYH mutations to assess its prevalence and ethnic specificity in Korea.

METHODS: Thirty patients (21 men and 9 women; mean age 62.3 years) with multiple adenomatous polyps were examined for MYH mutations. The mean number of adenomas per patient was 10.0. Sixteen exonic regions and their intronic sequences were amplified by PCR and subjected to SSCP and DNA sequencing analyses.

RESULTS: None of the patients was identified to carry any truncating or sequence alterations in MYH. Our screening for the mutational regions, which were recognized from Caucasian patients or affected Indian families, also failed to detect sequence substitutions.

CONCLUSION: Mutation in MYH may be rarely involved in the pathogenesis of multiple sporadic colorectal adenomas in Korean population, although a large-scale analysis will be required to clarify the presence of specific MYH variants in a subset of patients and their role in the predisposition of multiple colorectal adenomas in Korean population.

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.

Genotypes of TNF-alpha, VEGF, hOGG1, GSTM1, and GSTT1: useful determinants for clinical outcome of bladder cancer

OBJECTIVES

To determine whether polymorphisms of tumor necrosis factor-alpha (TNF-alpha), vascular endothelial growth factor (VEGF), human 8-oxoguanine DNA glycosylase 1 (hOGG1), glutathione S-transferase-mu (GSTM1), and glutathione S-transferase-phi (GSTT1) are risk factors for bladder cancer among Koreans.

METHODS

We performed polymerase chain reaction-restriction fragment length polymorphism and multiplex polymerase chain reaction in blood genomic DNA of 153 patients with primary bladder cancer and 153 control subjects.

RESULTS

GSTM1-negative, GSTT1-positive, and hOGG1 Ser326Ser and Ser326Cys genotypes are risk factors for bladder cancer (P = 0.020, P = 0.044, and P = 0.012, respectively). The cancer stage was significantly associated with the TNF-alpha genotype (GG versus GA and AA; P = 0.036). A notable correlation was observed between the VEGF genotype and grade (P = 0.015). In patients with superficial bladder cancer, the hOGG1 genotype was related to recurrence. The hOGG1 Ser326Ser and Ser326Cys genotypes were risk factors for superficial bladder cancer recurrence compared with the Cys326Cys genotype (P = 0.033, adjusted odds ratio 5.580, 95% confidence interval 1.145 to 27.183). Patients with the GSTM1-positive genotype were at a 3.3-fold increased risk of cancer progression compared with those with the GSTM1-negative genotype (P = 0.009, adjusted odds ratio 0.303, 95% confidence interval 0.123 to 0.745).

CONCLUSIONS

Our data collectively suggest that these genetic polymorphisms may be useful as prognostic markers for bladder cancer in the clinical setting.

Dynamic relocalization of hOGG1 during the cell cycle is disrupted in cells harbouring the hOGG1-Cys326 polymorphic variant

Numerous lines of evidence support the role of oxidative stress in different types of cancer. A major DNA lesion, 8-oxo-7,8-dihydroguanine (8-oxoG), is formed by reactive oxygen species in the genome under physiological conditions. 8-OxoG is strongly mutagenic, generating G·C→T·A transversions, a frequent somatic mutation in cancers. hOGG1 was cloned as a gene encoding a DNA glycosylase that specifically recognizes and removes 8-oxoG from 8-oxoG:C base pairs and suppresses G·C→T·A transversions. In this study, we investigated the subcellular localization and expression of hOGG1 during the cell cycle. Northern blots showed cell-cycle-dependent mRNA expression of the two major hOGG1 isoforms. By using a cell line constitutively expressing hOGG1 fused to enhanced green fluorescence protein (EGFP), we observed a dynamic relocalization of EGFP-hOGG1 to the nucleoli during the S-phase of the cell cycle, and this localization was shown to be linked to transcription. A C/G change that results in an amino acid substitution from serine to cysteine in codon 326 has been reported as a genetic polymorphism and a risk allele for a variety of cancers. We investigated the cellular localization of the corresponding protein, hOGG1-Cys³²⁶, fused to EGFP and observed a dramatic effect on its localization that is explained by a change in the phosphorylation status of hOGG1.

Polymorphic variation in hOGG1 and risk of cancer: a review of the functional and epidemiologic literature

The gene encoding human 8-oxoguanine glycosylase 1 (hOGG1) is involved in DNA base excision repair. The encoded DNA glycosylase excises 7,8-dihydro-8-oxoguanine (8-OHdG), a highly mutagenic base produced in DNA as a result of exposure to reactive oxygen species (ROS). Polymorphisms in this gene may alter glycosylase function and an individual's ability to repair damaged DNA, possibly resulting in genetic instability that can foster carcinogenesis. In order to elucidate the possible impact of polymorphisms in hOGG1, we performed a literature review of both functional and epidemiologic studies that assessed the effects of these polymorphisms on repair function, levels of oxidative DNA damage, or associations with cancer risk. Fourteen functional studies and 19 epidemiologic studies of breast, colon, esophageal, head and neck, lung, nasopharyngeal, orolaryngeal, prostate, squamous cell carcinoma of the head and neck (SCCHN), and stomach cancers were identified. Although the larger functional studies suggest reduced repair function with variant alleles in hOGG1, the evidence is generally inconclusive. There is some epidemiologic evidence that risk for esophageal, lung, nasopharyngeal, orolaryngeal, and prostate is related to hOGG1 genotype, whereas risk of breast cancer does not appear related. In studies that explored potential interactions with environmental factors, cancer risk for hOGG1 genotypes differed depending on exposure, especially for colon cancer. In summary, there is limited evidence that polymorphisms in hOGG1 affect repair function and carcinogenesis. Larger, well-designed functional and epidemiologic studies are needed to clarify these relationships, especially with respect to interactions with other DNA repair enzymes and interactions with environmental factors that increase carcinogenic load.

Commentary: DNA base excision repair defects in human pathologies

DNA base excision repair (BER) is the main pathway for repair of endogenous damage in human cells. It was expected that a number of degenerative diseases could derive from BER defects. On the contrary, the link between BER defects and human pathology is elusive and the literature is full of conflicting results. The fact that most studies have investigated DNA variations but not their functional consequences has probably contributed to this confusing picture. From a functional point of view, it is likely that gross BER defects are simply not compatible with life and only limited reductions can be observed. Notwithstanding those limits, the pathological consequences of partial BER defects might be widespread and significant at the population level. This starts to emerge in particular for colorectal and lung cancer.

hOGG1 Ser326Cys polymorphism, interaction with environmental exposures, and gastric cancer risk in Japanese populations

Oxidative DNA damage caused by reactive oxygen species (ROS) generated by Helicobacter pylori (H. pylori ) infection or smoking may be a cause of gastric cancer development. 8-Hydroxydeoxyguanine (8-OHdG) formation is one of the most common types of oxidative DNA damage, while human oxoguanine glycosylase 1 (hOGG1) is responsible for repairing 8-OHdG lesions. Among several hOGG1 gene polymorphisms, the Ser-->Cys polymorphism at position 326 is related to biological function. To investigate the association between Ser326Cys hOGG1 polymorphism and gastric cancer in relation to the potential risk factors of gastric cancer and antioxidant dietary or nutrient intakes, we conducted a case-control study with 142 histologically-confirmed gastric cancer cases and 271 age, sex-matched healthy controls in Japanese populations. Overall, neither the hOGG1 Ser/Cys nor the Cys/Cys genotype was associated with risk of gastric cancer, compared with the Ser/Ser genotype. A significant interaction was observed between hOGG1 Ser/Cys or Cys/Cys genotype and atrophic gastritis (P for interaction=0.03). No significant interaction was found between hOGG1 genotype and antioxidant dietary or nutrient intakes. The results of the present study suggest that patients with atrophic gastritis in conjunction with the hOGG1 Cys allele might have a higher susceptibility to gastric cancer.

The human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) DNA repair enzyme and its association with lung cancer risk

OBJECTIVE

The human 8-oxoguanine DNA N-glycosylase 1 gene encodes a DNA glycosylase that is involved in the base excision repair of 8-hydroxy-2-deoxyguanine from oxidatively-damaged DNA and expressed in lung tissue. The codon 326 polymorphism in the hOGG1 gene has been suggested to reduce DNA repair enzyme activity based on in vitro functional analysis. The goal of the present study is to determine whether the codon 326 polymorphism was significantly associated with alterations in individual risk for lung cancer.

METHODS

To determine whether hOGG1 plays a role in risk for lung cancer, we measured the prevalence of the Ser326Cys polymorphism in incident lung cancer patients and matched non-cancer controls. hOGG1 genotyping was performed by PCR-restriction fragment length polymorphism analysis of genomic DNA isolated from 179 Caucasian lung cancer cases and 358 controls individually matched in a 1:2 ratio by race-, sex- and age (+/- 5 years).

RESULTS

Significantly increased risk for lung cancer was observed for both the hOGG1 326 (odds ratio [OR] = 1.9, 95% confidence interval [CI] = 1.2-2.9) and hOGG1 326 genotypes (OR = 3.8, 95% CI = 1.4-10.6). The increased risk for lung cancer was observed for subjects with both the hOGG1 326 (OR = 1.7, 95% CI = 1.1-2.8) and hOGG1 326 genotypes (OR = 4.9, 95% CI = 1.5-16.1) in ever-smokers. A significant association was found between hOGG1 genotypes and lung cancer risk with a dose-dependent effect with smoking. Significantly increased risk for variant hOGG1 genotypes was observed for all non-small cell lung cancer patients.

CONCLUSION

These results suggest that the hOGG1 Ser326Cys polymorphism plays an important role in the risk for lung cancer and is linked to exposure to tobacco smoke.

An evolutionary perspective on single-nucleotide polymorphism screening in molecular cancer epidemiology

Given that there are millions of single-nucleotide polymorphisms (SNPs) in the entire human genome, a major difficulty faced by scientists in planning costly population-based genotyping is to choose target SNPs that are most likely to affect phenotypic functions and ultimately contribute to disease development. Although it is widely accepted that sequences with important functionality tend to be less variable across species because of selective pressure, to what extent evolutionary conservation is mirrored by epidemiological outcome has never been demonstrated. In this study, we surveyed odds ratios detected for 46 SNPs in 39 different cancer-related genes from 166 molecular epidemiological studies. The conservation levels of amino acid that these SNPs affected were calculated as a tolerance index by comparing sequences from different species. Our results provide evidence of a significant relationship between the detected odds ratios associated with cancer risk and the conservation levels of the SNP-affected amino acids (P = 0.002; R(2) = 0.06). Tolerance indices were further calculated for 355 nonsynonymous SNPs identified in 90 human DNA repair genes, of which 103 caused amino acid changes in very conserved positions. Our findings support the concept that SNPs altering the conserved amino acids are more likely to be associated with cancer susceptibility. Using such a molecular evolutionary approach may hold great promise for prioritizing SNPs to be genotyped in future molecular epidemiological studies.

Oxidative DNA damage in peripheral leukocytes and its association with expression and polymorphisms of hOGG1: A study of adolescents in a high risk region for hepatocellular carcinoma in China

AIM: To study the oxidative DNA damage to adolescents of hepatocellular carcinoma (HCC) families in Guangxi Zhuang Autonomous Region, China.

METHODS: Peripheral leukocytes’ DNA 7,8-dihydro-8-oxoguanine (8-oxoG) and repair enzyme hOGG₁ were quantified by flow-cytometry. hOGG₁-Cys326Ser single nucleotide polymorphism (SNP) was distinguished by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) assay.

RESULTS: There was a positive correlation between 8-oxoG and repair enzyme hOGG₁ expression (P < 0.001). HCC children (n = 21) in Fusui county had a higher level of hOGG₁ (P < 0.01) and a lower level of 8-oxoG (P < 0.05) than the controls (n = 63) in Nanning city. Children in Nanning exposed to passive-smoking had a higher hOGG₁ expression (P < 0.05) than the non-exposers. 8-oxoG and hOGG₁ were negatively correlated with body mass index, while hOGG₁ was positively correlated with age. There was a peak of 8-oxoG level nearby the 12 year point. Individuals with the hOGG₁ 326Ser allele had a significantly marginal higher concentration of leukocyte 8-oxoG level than hOGG₁ 326Cys allele.

CONCLUSION: This is the first report using flow-cytometry to simultaneously quantify both the DNA oxidative damage and its repairing enzyme hOGG1. The results provide new insights towards a better understanding of the mechanisms of oxidative stress in a population highly susceptible to hepatocarcinogenesis.

Oxidative DNA damage: mechanisms, mutation, and disease

Oxidative DNA damage is an inevitable consequence of cellular metabolism, with a propensity for increased levels following toxic insult. Although more than 20 base lesions have been identified, only a fraction of these have received appreciable study, most notably 8-oxo-2'deoxyguanosine. This lesion has been the focus of intense research interest and been ascribed much importance, largely to the detriment of other lesions. The present work reviews the basis for the biological significance of oxidative DNA damage, drawing attention to the multiplicity of proteins with repair activities along with a number of poorly considered effects of damage. Given the plethora of (often contradictory) reports describing pathological conditions in which levels of oxidative DNA damage have been measured, this review critically addresses the extent to which the in vitro significance of such damage has relevance for the pathogenesis of disease. It is suggested that some shortcomings associated with biomarkers, along with gaps in our knowledge, may be responsible for the failure to produce consistent and definitive results when applied to understanding the role of DNA damage in disease, highlighting the need for further studies.

hOGG1 Ser326Cys polymorphism and breast cancer risk among Asian women

To evaluate the potential association between breast cancer risk and Ser326Cys polymorphism of hOGG1 gene, encoding for an enzyme involved in the base excision repair of 8-hydroxyguanine, hospital based case-control studies were conducted in two Asian populations consisting of 475 breast cancer cases (271 Korean and 204 Japanese) and 500 controls (314 Korean and 186 Japanese). PCR-based methods were employed for the genotyping analyses and the statistical evaluations were performed by unconditional logistic regression model. The frequency of hOGG1 Ser/Ser, Ser/Cys, and Cys/Cys genotypes were 22.5, 48.7, and 28.8% in all cases, and 23.7, 52.1, and 24.1% in the controls. No statistically significant associations between the genotypes and breast cancer risk were observed, neither when the ethnic groups were examined separately nor when the total study population was included. Neither did stratification by menopausal status reveal any association between hOGG1 genotypes and breast cancer. Our novel findings therefore suggest that hOGG1 Ser326Cys polymorphism is unlikely to play a modifying role in individual susceptibility to breast cancer among Asian women.

Multiple colorectal adenomas, classic adenomatous polyposis, and germ-line mutations in MYH

BACKGROUND

Germ-line mutations in the base-excision-repair gene MYH have been associated with recessive inheritance of multiple colorectal adenomas. Tumors from affected persons displayed excess somatic transversions of a guanine-cytosine pair to a thymine-adenine pair (G:C-->T:A) in the APC gene.

METHODS

We screened for germ-line MYH mutations in 152 patients with multiple (3 to 100) colorectal adenomas and 107 APC-mutation-negative probands with classic familial adenomatous polyposis (>100 adenomas). Subgroups were analyzed for changes in the related genes MTH1 and OGG1. Adenomas were tested for somatic APC mutations.

RESULTS

Six patients with multiple adenomas and eight patients with polyposis had biallelic germline MYH variants. Missense and protein-truncating mutations were found, and the spectrums of mutations were very similar in the two groups of patients. In the tumors of carriers of biallelic mutations, all somatic APC mutations were G:C-->T:A transversions. In the group with multiple adenomas, about one third of patients with more than 15 adenomas had biallelic MYH mutations. In the polyposis group, no patient with biallelic MYH mutations had severe disease (>1000 adenomas), but three had extracolonic disease. No clearly pathogenic MTH1 or OGG1 mutations were identified.

CONCLUSIONS

Germ-line MYH mutations predispose persons to a recessive phenotype, multiple adenomas, or polyposis coli. For patients with about 15 or more colorectal adenomas--especially if no germ-line APC mutation has been identified and the family history is compatible with recessive inheritance--genetic testing of MYH is indicated for diagnosis and calculation of the level of risk in relatives. Clinical care of patients with biallelic MYH mutations should be similar to that of patients with classic or attenuated familial adenomatous polyposis.

Genetic susceptibility and gastric cancer risk

The aim of the present paper is to review and evaluate, in a comprehensive manner, the most recent published evidence on the contribution of genetic susceptibility to gastric cancer risk in humans. We have identified all studies available in MEDLINE published up to October 2001. Only studies carried out in humans and comparing gastric cancer cases with at least 1 standard control group were included in the analysis. We were able to find 31 articles based on 25 case-control studies carried out in Caucasian, Asian and African populations. Most of the studies assess the effect of genes involved in detoxifying pathways (n = 12) and inflammatory responses (n = 7). The most widely studied is the GSTM1 null polymorphism. Only a very few studies have evaluated the risk of gastric cancer associated with genes acting on mucosa protection, oxidative damage and DNA repair. The most consistent results are the increased gastric cancer risk associated with IL1B and NAT1 variants, which may account for up to 48% of attributable risk of gastric cancer. Only polymorphisms at HLA-DQ, TNF and CYP2E genes may confer some protective effect against gastric cancer. The most important limitations that preclude definitive conclusions are (i) the lack of appropriate control of potential sources of bias (only 5 population-based studies have been published so far); (ii) the low number of cases analyzed (14 studies included fewer than 99 cases); and (iii) the low number of studies (n = 3) offering concomitant analysis of genetic susceptibility and exposure to relevant cofactors (Helicobacter pylori infection, diet and smoking). We conclude that the scientific data on the role of genetic factors in gastric cancer risk are promising. The lack of association reported so far should be considered with caution due to significant limitations in study design. Cohort studies taking into account simultaneously the different genetic and environmental factors potentially involved in gastric tumorigenesis are needed to ascertain not only the relative contribution of these factors to tumor development but also the contribution of their putative interactions.

hOGG1 Ser(326)Cys polymorphism and modification by environmental factors of stomach cancer risk in Chinese

Oxidative stress is involved in many types of DNA damage, e.g., resulting in 8-hydroxyguanine adducts. Since a human counterpart exists for the yeast gene OGG1 (hOGG1) encoding an enzyme that repairs 8-hydroxyguanine, its polymorphism, Ser(326)Cys, might have potential as a genetic marker for cancer susceptibility. To investigate its association with stomach cancer risk and possible interactions with environmental factors, we conducted a case-control study of 101 stomach cancer cases and 198 controls using PCR-single-strand conformation polymorphism and a questionnaire approach. The proportional distribution of the Cys/Cys alleles did not differ between stomach cancer cases and controls, but subgroup analyses revealed that a frequent drinking habit elevated the odds ratio (OR) for stomach cancer in Cys/Cys compared to Ser/Ser and Ser/Cys carriers. The ORs with frequent consumption of pickled vegetables and meat tended to be higher in Cys/Cys than in Ser/Ser and Ser/Cys carriers, these interactions being on the borderline of statistical significance. Our findings suggest that the hOGG1 Ser(326)Cys polymorphism may alter the impact of some environmental factors on stomach cancer development. For confirmation, an additional study with a larger number of subjects is now required.