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

Oxidative genomic damage in humans exposed to high indoor radon levels in Northeast Brazil

Radon gas inhalation is the main source of exposure to ionizing radiation by humans. There is still lack in knowledge concerning the chronic and indirect effects of exposure to this carcinogenic factor. Therefore, the aim of this work is to analyze the levels of oxidative genomic damage in inhabitants of a medium-high background radiation area (HBRA) (N = 82) in Northeastern Brazil and compare them with people living in a low background radiation area (LBRA) (N = 46). 8-hydroxy-2-deoxyguanosine (8-OHdG) was quantified in urine, Ser326Cys polymorphism was determined in the hOGG1 gene and indoor radon was measured. HBRA houses had 6.5 times higher indoor radon levels than those from LBRA (p-value < 0.001). The 8-OHdG mean (95% confidence interval) were significantly different, 8.42 (5.98-11.9) ng/mg creatinine and 29.91 (23.37-38.30) ng/mg creatinine for LBRA and HBRA, respectively. The variables representing lifestyle and environmental and occupational exposures did not have a significant association with oxidized guanosine concentrations. On the other hand, lower 8-OHdG values were observed in subjects that had one mutant allele (326Cys) in the hOGG1 gene than those who had both wild alleles (Ser/Ser (p-value < 0.05). It can be concluded that high radon levels have significantly influenced the genome oxidative metabolism and hOGG1 gene polymorphism would mediate the observed biological response.

The Role of 8-oxoG Repair Systems in Tumorigenesis and Cancer Therapy

Tumorigenesis is highly correlated with the accumulation of mutations. The abundant and extensive DNA oxidation product, 8-Oxoguanine (8-oxoG), can cause mutations if it is not repaired by 8-oxoG repair systems. Therefore, the accumulation of 8-oxoG plays an essential role in tumorigenesis. To avoid the accumulation of 8-oxoG in the genome, base excision repair (BER), initiated by 8-oxoguanine DNA glycosylase1 (OGG1), is responsible for the removal of genomic 8-oxoG. It has been proven that 8-oxoG levels are significantly elevated in cancer cells compared with cells of normal tissues, and the induction of DNA damage by some antitumor drugs involves direct or indirect interference with BER, especially through inducing the production and accumulation of reactive oxygen species (ROS), which can lead to tumor cell death. In addition, the absence of the core components of BER can result in embryonic or early post-natal lethality in mice. Therefore, targeting 8-oxoG repair systems with inhibitors is a promising avenue for tumor therapy. In this study, we summarize the impact of 8-oxoG accumulation on tumorigenesis and the current status of cancer therapy approaches exploiting 8-oxoG repair enzyme targeting, as well as possible synergistic lethality strategies involving exogenous ROS-inducing agents.

hOGG1 rs1052133 Polymorphism and Prostate Cancer Risk: A Chinese Case-Control Study and Meta-Analysis

BACKGROUND We performed a case-control study and an updated meta-analysis to assess the relationship between the hOGG1 rs1052133 polymorphism and prostate cancer (PCa) risk. MATERIAL AND METHODS We recruited 160 PCa cases and 243 healthy controls. For the meta-analysis, relevant studies were recruited from diverse databases up to April 2022. Genetic risk was evaluated by using an odds ratio (OR) with a corresponding 95% confidence interval (95% CI). The genotypes of this polymorphism were genotyped via the SNaPshot genotyping method. RESULTS In the case-control study, we failed to identify any association between the hOGG1 rs1052133 polymorphism and PCa risk. Negative results were also obtained when stratified analyses were performed based on the patient's prostatic-specific antigen (PSA) level and Gleason score, as well as tumor, node, and metastasis (TNM) stage. To enlarge the sample size, we performed a restricted updated meta-analysis by recruiting 10 case-control studies (including the current one), and the results suggested that genotypes of rs1052133 polymorphism were significantly associated with an elevated risk of PCa in 2 genetic models - the heterozygote and dominant models. In the stratification analysis by population ethnicity, a significant association of this polymorphism with susceptibility to PCa was found both in the Asian populations and White populations. CONCLUSIONS Our case-control and updated meta-analysis study suggest that the hOGG1 rs1052133 polymorphism is a susceptibility factor for PCa, but still needs to be further verified in the Chinese population.

Association of hOGG1-Cys variants with occurrence of p53 and EGFR deletion mutations in non-small cell lung cancer

Background

The human 8‐oxoguanine DNA glycosylase 1 (hOGG1) gene encodes a DNA glycosylase that removes 8‐hydroxy‐2‐deoxyguanine (8‐OH‐dG) DNA damage to protect against gene mutations. The association of hOGG1 Ser326Cys polymorphism with lung cancer risk has predicted that hOGG1‐Cys variants are less effective at removing 8‐OH‐dG damage from DNA; therefore, these variants might show an increased occurrence of tumor suppressor gene and oncogene mutations. However, no evidence has yet supported this hypothesis.

Methods

Direct sequencing was performed to examine the mutations of p53 and EGFR genes in lung tumors from patients with non‐small cell lung cancer (NSCLC). Polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) was used to examine hOGG1 Ser326Cys polymorphism in this study population.

Results

A total of 99 p53‐mutated and 99 EGFR‐mutated patients with NSCLC were selected to explore the possible associations of these mutations with hOGG1 Ser326Cys polymorphism. The p53‐mutated and EGFR‐mutated patients were divided into nondeletion and deletion subgroups. P53 deletion mutations were more commonly observed in male than in female patients (P = 0.030). However, EGFR exon 19 deletion mutations were more prevalent in female and adenocarcinoma patients than in male and squamous cell carcinoma patients (P = 0.028 for genders, P = 0.017 for tumor histology). Interestingly, p53 and EGFR exon 19 deletion mutations were more frequent in patients with hOGG1 Ser/Cys + Cys/Cys hOGG1‐Cys variants than with the hOGG1 Ser/Ser genotype (P = 0.010 for p53, P = 0.032 for EGFR).

Conclusions

We suggest that the association of hOGG1 Ser326Cys polymorphism with lung cancer risk could be partially explained by increases in p53 and EGFR deletion mutations.

Key points

Significant findings of the study

NSCLC patients with hOGG1‐Cys variants may have a higher risk of p53 and EGFR deletion mutations than with hOGG1 Ser/Ser genotype.

What this study adds

NSCLC patients with hOGG1‐Cys variants might be helpful to predict patients having higher risk of EGFR exon 19 deletion mutations and these patients who were treated with gefitinib or erlotinib could be a higher risk to occur EGFR T790M mutation.

NSCLC patients with hOGG1‐Cys variants may have higher risk of p53 and EGFR deletion mutations than with hOGG1 Ser/Ser genotype. NSCLC patients with hOGG1‐Cys variants might be helpful to predict patients with higher risk of EGFR exon 19 deletion mutations and these patients who were treated with gefitinib and erlotinib were more common to occur EGFR T790M mutation.

Impairment of Base Excision Repair in Dermal Fibroblasts Isolated From Nevoid Basal Cell Carcinoma Patients

The nevoid basal cell carcinoma syndrome (NBCCS), also called Gorlin syndrome is an autosomal dominant disorder whose incidence is estimated at about 1 per 55,600–256,000 individuals. It is characterized by several developmental abnormalities and an increased predisposition to the development of basal cell carcinomas (BCCs). Cutaneous fibroblasts from Gorlin patients have been shown to exhibit an increased sensitivity to ionizing radiations. Mutations in the tumor suppressor gene PTCH1, which is part of the Sonic Hedgehog (SHH) signaling pathway, are responsible for these clinical manifestations. As several genetic mutations in the DNA repair genes are responsible of photo or radiosensitivity and high predisposition to cancers, we hypothesized that these effects in Gorlin syndrome might be due to a defect in the DNA damage response (DDR) and/or the DNA repair capacities. Therefore, the objective of this work was to investigate the sensitivity of skin fibroblasts from NBCCS patients to different DNA damaging agents and to determine the ability of these agents to modulate the DNA repair capacities. Gorlin fibroblasts showed high radiosensitivity and also less resistance to oxidative stress-inducing agents when compared to control fibroblasts obtained from healthy individuals. Gorlin fibroblasts harboring PTCH1 mutations were more sensitive to the exposure to ionizing radiation and to UVA. However, no difference in cell viability was shown after exposure to UVB or bleomycin. As BER is responsible for the repair of oxidative DNA damage, we decided to assess the BER pathway efficacy in Gorlin fibroblasts. Interestingly, a concomitant decrease of both BER gene expression and BER protein activity was observed in Gorlin fibroblasts when compared to control. Our results suggest that low levels of DNA repair within Gorlin cells may lead to an accumulation of oxidative DNA damage that could participate and partly explain the radiosensitivity and the BCC-prone phenotype in Gorlin syndrome.

Comprehensive analysis of the correlation between base-excision repair gene SNPs and esophageal squamous cell carcinoma risk in a Chinese Han population

This study sought to assess the relationship between single nucleotide polymorphisms (SNPs) affecting DNA base-excision repair (BER) genes and esophageal squamous cell carcinoma (ESCC) risk in a Han Chinese population. Genes screened for such SNPs included 8-oxoguanine DNA glycosylase (OGG1), apurinic/apyrimidinic endonuclease 1 (APE1) and X-ray repair cross-complementing group 1 protein (XRCC1). Blood samples that had been collected in a prospective manner were used for DNA extraction, with all DNA samples then being subjected to PCR-restriction fragment length polymorphism genotyping for BER gene SNPs, including APE1 Asp148Glu and -141T/G, OGG1 Ser326Cys, and XRCC1 Arg399Gln. The relationship between these SNPs and ESCC risk was then assessed, with the comparability of the case and control groups being enhanced via propensity score matching (PSM). This study initially included 642 healthy controls and 321 ESCC patients, with PSM optimization leading to a final analyzed total of 311 matched subjects per group (311 total). Factors associated with elevated ESCC risk in this analysis included advanced age, being male and smoking. We further identified that the XRCC1 399 Gln/Gln genotype was associated with a significant reduction in ESCC risk prior to propensity matching (odds ratio=0.48; 95% CI: 0.23-1.00; P<0.05), although this did not remain true following matching. For the remaining analyzed SNPs, no significant associations between genotype and ESCC risk were detected prior to or following propensity matching. A multivariate analysis incorporating patient age, sex, smoking status and drinking status failed to detect any relationship between the four tested genotypes and ESCC risk. In conclusion, being male, a smoker or of advanced age was associated with an elevated ESCC risk. However, we did not detect any significant relationship between ESCC risk and BER polymorphisms in XRCC1, OGG1, APE1 or the APE1 promoter region in a Han Chinese population.

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.

Cumulative meta-analysis and trial sequential analysis of correlation between hOGG1 Ser326Cys polymorphism and the risk of head and neck squamous cell carcinoma

Background

The human 8-oxoguanine glycosylase 1 (hOGG1) Ser326Cys polymorphism has been involved in the risk of head and neck squamous cell carcinoma (HNSCC), but the results of published studies on this topic still inconsistent.

Results

Finally 11 qualified publications with 13 independent case-control studies were yielded. Overall, we observed significant differences in CysCys vs. SerSer [odds ratio (OR) = 1.55, 95% confidence interval (95% CI) = 1.01–2.38] and CysCys vs. SerCys+SerSer (OR = 1.42, 95% CI = 1.005–1.99) genetic models. Sensitivity analyses showed the results were not robust, cumulative meta-analyses and trial sequential analysis indicated the results didn't not need more studies to identification. Subgroup analyses showed there was a significant association in Caucasian, laryngeal squamous cell carcinoma, studies agreement with Hardy-Weinberg equilibrium, and alcohol drinkers subgroups under the corresponding contrasts. In addition, the results of Egger’s test were contradictory.

Materials and Methods

All eligible studies were searched from the online databases including PubMed, Web of Science, China Knowledge Resource Integrated Database, and Wanfang databases up to February 10, 2017. After study selection and data extraction, the meta-analysis was performed using STATA 12.0 software and TSA software version 0.9 Beta.

Conclusions

Our meta-analysis results indicated that hOGG1 Ser326Cys polymorphism may be associated with increased risk of HNSCC, especially in Caucasians, alcohol drinkers and the patients with laryngeal squamous cell carcinoma.

Effects of the Ser326Cys Polymorphism in the DNA Repair OGG1 Gene on Cancer, Cardiovascular, and All-Cause Mortality in the PREDIMED Study: Modulation by Diet

BACKGROUND

Oxidatively induced DNA damage, an important factor in cancer etiology, is repaired by oxyguanine glycosylase 1 (OGG1). The lower repair capacity genotype (homozygote Cys326Cys) in the OGG1-rs1052133 (Ser326Cys) polymorphism has been associated with cancer risk. However, no information is available in relation to cancer mortality, other causes of death, and modulation by diet.

OBJECTIVE

Our aim was to evaluate the association of the OGG1-rs1052133 with total, cancer, and cardiovascular disease (CVD) mortality and to analyze its modulation by the Mediterranean diet, focusing especially on total vegetable intake as one of the main characteristics of this diet.

DESIGN

Secondary analysis in the PREDIMED (Prevención con Dieta Mediterránea) trial is a randomized, controlled trial conducted in Spain from 2003 to 2010.

PARTICIPANTS/SETTING

Study participants (n=7,170) were at high risk for CVD and were aged 55 to 80 years.

INTERVENTION

Participants were randomly allocated to two groups with a Mediterranean diet intervention or a control diet. Vegetable intake was measured at baseline.

MAIN OUTCOME MEASURES

Main outcomes were all-cause, cancer, and CVD mortality after a median follow-up of 4.8 years.

STATISTICAL ANALYSES

Multivariable-adjusted Cox regression models were fitted.

RESULTS

Three hundred eighteen deaths were detected (cancer, n=127; CVD, n=81; and other, n=110). Cys326Cys individuals (prevalence 4.2%) presented higher total mortality rates than Ser326-carriers (P=0.009). The multivariable-adjusted hazard ratio for Cys326Cys vs Ser326-carriers was 1.69 (95% CI 1.09 to 2.62; P=0.018). This association was greater for CVD mortality (P=0.001). No relationship was detected for cancer mortality in the whole population (hazard ratio 1.07; 95% CI 0.47 to 2.45; P=0.867), but a significant age interaction (P=0.048) was observed, as Cys326Cys was associated with cancer mortality in participants <66.5 years (P=0.029). Recessive effects limited our ability to investigate Cys326Cys×diet interactions for cancer mortality. No statistically significant interactions for total or CVD mortality were found for the Mediterranean diet intervention. However, significant protective interactions for CVD mortality were found for vegetable intake (hazard ratio interaction per standard deviation 0.42; 95% CI 0.18 to 0.98; P=0.046).

CONCLUSIONS

In this population, the Cys326Cys-OGG1 genotype was associated with all-cause mortality, mainly CVD instead of cancer mortality. Additional studies are needed to provide further evidence on its dietary modulation.

DNA repair genes polymorphisms and genetic susceptibility to Philadelphia-negative myeloproliferative neoplasms in a Portuguese population: The role of base excision repair genes polymorphisms

The role of base excision repair (BER) genes in Philadelphia-negative (PN)-myeloproliferative neoplasms (MPNs) susceptibility was evaluated by genotyping eight polymorphisms [apurinic/apyrimidinic endodeoxyribonuclease 1, mutY DNA glycosylase, earlier mutY homolog (E. coli) (MUTYH), 8-oxoguanine DNA glycosylase 1, poly (ADP-ribose) polymerase (PARP) 1, PARP4 and X-ray repair cross-complementing 1 (XRCC1)] in a case-control study involving 133 Caucasian Portuguese patients. The results did not reveal a correlation between individual BER polymorphisms and PN-MPNs when considered as a whole. However, stratification for essential thrombocythaemia revealed i) borderline effect/tendency to increased risk when carrying at least one variant allele for XRCC1_399 single-nucleotide polymorphism (SNP); ii) decreased risk for Janus kinase 2-positive patients carrying at least one variant allele for XRCC1_399 SNP; and iii) decreased risk in females carrying at least one variant allele for MUTYH SNP. Combination of alleles demonstrated an increased risk to PN-MPNs for one specific haplogroup. These findings may provide evidence for gene variants in susceptibility to MPNs. Indeed, common variants in DNA repair genes may hamper the capacity to repair DNA, thus increasing cancer susceptibility.

The hOGG1 Ser326Cys Gene Polymorphism and Breast Cancer Risk in Saudi Population

The purpose of this study was to test the association between human 8-oxoguanine glycosylase 1 (hOGG1) gene polymorphisms and susceptibility to breast cancer in Saudi population. We have also aimed to screen the hOGG1 Ser326Cys polymorphism effect on structural and functional properties of the hOGG1 protein using in silico tools. We have analyzed four SNPs of hOGG1 gene among Saudi breast cancer patients along with healthy controls. Genotypes were screened using TaqMan SNP genotype analysis method. Experimental data was analyzed using Chi-square, t test and logistic regression analysis using SPSS software (v.16). In silco analysis was conducted using discovery studio and HOPE program. Genotypic analysis showed that hOGG1 rs1052133 (Ser326Cys) is significantly associated with breast cancer samples in Saudi population, however rs293795 (T >C), rs2072668 (C>G) and rs2075747 (G >A) did not show any association with breast cancer. The hOGG1 SNP rs1052133 (Ser326Cys) minor allele T showed a significant association with breast cancer samples (OR = 1.78, χ2 = 7.86, p = 0.02024). In silico structural analysis was carried out to compare the wild type (Ser326) and mutant (Cys326) protein structures. The structural prediction studies revealed that Ser326Cys variant may destabilize the protein structure and it may disturb the hOGG1 function. Taken together this is the first In silico study report to confirm Ser326Cys variant effect on structural and functional properties of hOGG1 gene and Ser326Cys role in breast cancer susceptibility in Saudi population.

Analysis of DNA Repair Genes Polymorphisms in Breast Cancer

Genetic polymorphisms in the DNA repair genes may be associated with increased cancer risk. The purpose of this study was to evaluate the association of the DNA repair genes polymorphisms with the risk of breast cancer development. The study included 200 breast cancer patients and 200 healthy controls. The following polymorphisms were studied: C/G (Ser326Cys, rs1052133) of the hOGG1, A/C (IVS5 + 33, rs3212961) of the ERCC1, A/C (Lys939Gln, rs2228001) of the XPC, C/T (Thr241Met, rs861539) of the XRCC3, G/T (Leu787Leu, rs1800392) of the WRN and G/T (Ser307Ser, rs1056503) of the XRCC4 gene. Presented study showed statistically significant increase in the breast cancer development risk of the G/G hOGG1 genotype (OR 8.13; 95 % CI, 4.37-15.14; p < 0.001) and for the G hOGG1 allele (OR 5.11; 95 % CI, 3.69-7.06; p < 0.001), as well as for the C/C ERCC1 genotype (OR 10.61; 95 % CI, 5.72-19.69; p < 0.001) and the C ERCC1 allele (OR 4.66; 95 % CI, 3.43-6.34; p < 0.001) in patients with breast cancer in comparison with healthy control group. We also observed positive association of the C/C XPC genotype (OR 3.80; 95 % CI, 2.27-6.38; p < 0.001) as well as the C XPC allele occurrence with an increased breast cancer development risk (OR 2.65; 95 % CI, 1.98-3.55; p < 0.001). Furthermore, we found an association of the G/T WRN gene polymorphism with increased risk of carcinoma. The hOGG1, ERCC1, XPC and WRN genes polymorphisms may be related to development of breast cancer.

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.

Molecular insights into the OGG1 gene, a cancer risk modifier in BRCA1 and BRCA2 mutations carriers

We have recently shown that rs2304277 variant in the OGG1 glycosidase gene of the Base Excision Repair pathway can increase ovarian cancer risk in BRCA1 mutation carriers. In the present study, we aimed to explore the role of this genetic variant on different genome instability hallmarks to explain its association with cancer risk.We have evaluated the effect of this polymorphism on OGG1 transcriptional regulation and its contribution to telomere shortening and DNA damage accumulation. For that, we have used a series of 89 BRCA1 and BRCA2 mutation carriers, 74 BRCAX cases, 60 non-carrier controls and 23 lymphoblastoid cell lines (LCL) derived from BRCA1 mutation carriers and non-carriers.We have identified that this SNP is associated to a significant OGG1 transcriptional down regulation independently of the BRCA mutational status and that the variant may exert a synergistic effect together with BRCA1 or BRCA2 mutations on DNA damage and telomere shortening.These results suggest that this variant, could be associated to a higher cancer risk in BRCA1 mutation carriers, due to an OGG1 transcriptional down regulation and its effect on genome instability.

Genetic association between hOGG1 C8069G polymorphism and colorectal cancer risk

BACKGROUND

hOGG1 C8069G polymorphism has been extensively investigated in single studies as well as meta-analyses in terms of the association with colorectal cancer (CRC). But the results remain contradictory. This study was undertaken to comprehensively evaluate the association of the commonly studied hOGG1 C8069G polymorphism and the susceptibility to CRC.

METHODS

By searching the electronic databases of PubMed, Embase, and Web of science, 16 available publications consisting of 4,866 cases and 7,363 controls were finally included in our meta-analysis. Stratified analyses by ethnicity and source of control were also carried out to further assess the association between hOGG1 C8069G polymorphism and CRC risk.

RESULTS

hOGG1 C8069G polymorphism was not observed to have statistical significance with the susceptibility to CRC (ORCC vs. GG = 0.97, 95% CI = 0.91-1.05; P = 0.995; ORCC + CG vs. GG = 0.98, 95% CI = 0.93-1.04; P = 0.993; ORCC vs. CG + GG = 0.96, 95% CI = 0.90-1.02; P = 0.339; ORallele C vs. allele G = 0.98, 95% CI = 0.94-1.02; P = 0.912; ORCG vs. GG = 0.95, 95% CI = 0.88-1.03; P = 0.526). Similarly, no association was found in the subgroup analysis by ethnicity or the source of control.

CONCLUSIONS

The results of our meta-analysis did not demonstrate any evidence for significant association between hOGG1 C8069G polymorphism and CRC risk. Future large-scale studies are expected to be conducted to further confirm our findings.

The Ser326Cys polymorphism of hOGG1 is associated with intrahepatic cholangiocarcinoma susceptibility in a Chinese population

OBJECTIVE

Intrahepatic cholangiocarcinoma is a rare disease whose etiology is far from clear, the Ser326Cys polymorphism in human 8-hydroxyguanine glycosylase (hOGG1) has been shown associated with various cancers, however, the association of Ser326Cys (rsl052133) polymorphism and intrahepatic cholangiocarcinoma susceptibility has not been clarified. The purpose of this study is to investigate whether this polymorphism is related to the genetic susceptibility of intrahepatic cholangiocarcinoma.

METHODS

A total 150 patients and 150 normal people were included in this study, the Ser326Cys polymorphisms in each group were genotyped using PCR-RFLP method.

RESULTS

We found that individuals carrying Cys/Cys genotype were exposed to higher riskof intrahepatic cholangiocarcinoma (OR=2.924, 95% CI=1.475-5.780) compared with the individuals with wild type genotype Ser/Ser. Further analysis revealed that male individuals carrying Cys/Cys genotype also had increased risk (OR=2.762, 95% CI=1.233-6.173), whereas no significant difference was observed in female group.

CONCLUSIONS

Therefore, our data indicates that the Ser326Cys (rs1052133) polymorphism is associated with intrahepatic cholangiocarcinoma susceptibility, and it shows preference in male population.

Polymorphisms in base excision repair genes: Breast cancer risk and individual radiosensitivity

Breast cancer (BC) is the most common cancer among women worldwide. The aetiology and carcinogenesis of BC are not clearly defined, although genetic, hormonal, lifestyle and environmental risk factors have been established. The most common treatment for BC includes breast-conserving surgery followed by a standard radiotherapy (RT) regimen. However, radiation hypersensitivity and the occurrence of RT-induced toxicity in normal tissue may affect patients’ treatment. The role of DNA repair in cancer has been extensively investigated, and an impaired DNA damage response may increase the risk of BC and individual radiosensitivity. Single nucleotide polymorphisms (SNPs) in DNA repair genes may alter protein function and modulate DNA repair efficiency, influencing the development of various cancers, including BC. SNPs in DNA repair genes have also been studied as potential predictive factors for the risk of RT-induced side effects. Here, we review the literature on the association between SNPs in base excision repair (BER) genes and BC risk. We focused on X-ray repair cross complementing group 1 (XRCC1), which plays a key role in BER, and on 8-oxoguanine DNA glycosylase 1, apurinic/apyrimidinic endonuclease 1 and poly (ADP-ribose) polymerase-1, which encode three important BER enzymes that interact with XRCC1. Although no association between SNPs and radiation toxicity has been validated thus far, we also report published studies on XRCC1 SNPs and variants in other BER genes and RT-induced side effects in BC patients, emphasising that large well-designed studies are needed to determine the genetic components of individual radiosensitivity.

Oxidative stress in susceptibility to breast cancer: study in Spanish population

Background

Alterations in the redox balance are involved in the origin, promotion and progression of cancer. Inter-individual differences in the oxidative stress regulation can explain a part of the variability in cancer susceptibility.

The aim of this study was to evaluate if polymorphisms in genes codifying for the different systems involved in oxidative stress levels can have a role in susceptibility to breast cancer.

Methods

We have analyzed 76 single base polymorphisms located in 27 genes involved in oxidative stress regulation by SNPlex technology. First, we have tested all the selected SNPs in 493 breast cancer patients and 683 controls and we have replicated the significant results in a second independent set of samples (430 patients and 803 controls). Gene-gene interactions were performed by the multifactor dimensionality reduction approach.

Results

Six polymorphisms rs1052133 (OGG1), rs406113 and rs974334 (GPX6), rs2284659 (SOD3), rs4135225 (TXN) and rs207454 (XDH) were significant in the global analysis. The gene-gene interactions demonstrated a significant four-variant interaction among rs406113 (GPX6), rs974334 (GPX6), rs105213 (OGG1) and rs2284659 (SOD3) (p-value = 0.0008) with high-risk genotype combination showing increased risk for breast cancer (OR = 1.75 [95% CI; 1.26-2.44]).

Conclusions

The results of this study indicate that different genotypes in genes of the oxidant/antioxidant pathway could affect the susceptibility to breast cancer. Furthermore, our study highlighted the importance of the analysis of the epistatic interactions to define with more accuracy the influence of genetic variants in susceptibility to breast cancer.

Association of hOGG1 Ser326Cys polymorphism with colorectal cancer risk: an updated meta-analysis including 5235 cases and 8438 controls

It has been suggested that hOGG1 Ser326Cys polymorphism may be a risk factor for colorectal cancer. Published data on its association with colorectal cancer generated contradictory results; thus, we performed an updated meta-analysis of eligible published studies to estimate the effect of hOGG1 Ser326Cys polymorphism on colorectal cancer susceptibility. We reviewed many abstracts and finally included 18 eligible case-control studies comprising 5235 cases and 8438 controls. We pooled data with a fixed or random-effect model. Subgroup analysis by ethnicity was also performed. The overall data indicated a significant association of hOGG1 Ser326Cys polymorphism on colorectal cancer risk (allele model OR = 1.14, 95 %CI 1.02-1.27; homozygote model OR = 1.32, 95 %CI 0.92-1.92; recessive model OR = 1.12, 95 %CI 1.00-1.26; dominant model OR = 1.15, 95 %CI 1.00-1.32). Furthermore, in the subgroup analysis by ethnicity, increased cancer risk was observed among Caucasians under the allele, heterogeneity, recessive, and dominant models (allele model OR = 1.23, 95 %CI = 1.05-1.44; homozygote model OR = 1.49, 95%CI 1.05-2.12; recessive model OR = 1.40, 95 %CI 1.16-1.69; dominant model OR = 1.21, 95 %CI = 1.12-1.45). In summary, the present meta-analysis suggested that hOGG1 Ser326Cys polymorphism might modify the susceptibility to colorectal cancer among the total population, especially among Caucasians.

Polymorphism of DNA repair genes OGG1, XRCC1, XPD and ERCC6 in bladder cancer in Belarus

CONTEXT

The study of DNA base and nucleotide excision repair gene polymorphisms in bladder cancer seems to have a predictive value because of the evident relationship between the DNA damage response induced by environmental mutagens and cancer predisposition.

OBJECTIVE

The objective was to determine OGG1 Ser326Cys, XRCC1 Arg399Gln, XPD Asp312Asn, and ERCC6 Met1097Val polymorphisms in bladder cancer patients as compared to controls.

METHODS

Both groups were predominantly represented by Belarusians and Eastern Slavs. DNA samples from 336 patients and 370 controls were genotyped using a PCR-RFLP method.

RESULTS

The genotype distributions were in agreement with the Hardy-Weinberg equilibrium. The minor allele frequencies in the control population were in the range of those in Caucasians in contrast to Asians. The OGG1 326 Ser/Cys and XPD 312 Asp/Asn heterozygous genotypes were inversely associated with cancer risk (OR [95% CI] = 0.69 [0.50-0.95] and 1.35 [1.0-1.82], respectively). The contrasting effects of these genotypes were potentiated due to their interactions with smoking habit or age.

CONCLUSIONS

Among four DNA repair gene polymorphisms, the OGG1 326 Ser/Cys and XPD 312 Asp/Asn heterozygous genotypes might be recognized as potential genetic markers modifying susceptibility to bladder cancer in Belarus.

Associations between hOGG1 Ser326Cys polymorphism and increased body mass index and fasting glucose level in the Japanese general population

Background

Evidence suggests that Ser326Cys, a genetic polymorphism of human 8-oxoguanine glycosylase 1 (hOGG1), is associated with insulin resistance and type 2 diabetes; however, the underlying mechanism is unclear. Recently, an animal study showed a significant association between the hOGG1 genotype and obesity, although evidence for such an association in humans is limited. The purpose of this study was to examine the association between the hOGG1 genotype and body mass index (BMI) and fasting blood glucose (FBG) levels.

Methods

Cross-sectional analysis was conducted using the baseline survey data from a Japan Multi-Institutional Collaborative Cohort Study, which included 1793 participants aged 40–69 years. The hOGG1 polymorphism was detected using a multiplex polymerase chain reaction-based invader assay. Multiple linear regression, analysis of covariance, and logistic regression were used to control for confounding variables.

Results

The Cys allele was significantly associated with increased BMI, FBG level, and total cholesterol (TC) level, even after adjustment for gender, age, energy intake, alcohol, smoking, physical activity, and family history of diabetes. An association with BMI was still observed after further adjustment for FBG and TC, but not for the study area (Amami or the mainland). The Cys/Cys genotype was significantly more prevalent in the participants with higher BMI (>27.5 kg/m²). However, the impact of genotype decreased and significance disappeared after adjusting for the study area.

Conclusions

The present results suggest that the study area being inside Japan confounds the association between hOGG1 genotype and obesity.

Comprehensive analyses of DNA repair pathways, smoking and bladder cancer risk in Los Angeles and Shanghai

Tobacco smoking is a bladder cancer risk factor and a source of carcinogens that induce DNA damage to urothelial cells. Using data and samples from 988 cases and 1,004 controls enrolled in the Los Angeles County Bladder Cancer Study and the Shanghai Bladder Cancer Study, we investigated associations between bladder cancer risk and 632 tagSNPs that comprehensively capture genetic variation in 28 DNA repair genes from four DNA repair pathways: base excision repair (BER), nucleotide excision repair (NER), non-homologous end-joining (NHEJ) and homologous recombination repair (HHR). Odds ratios (ORs) and 95% confidence intervals (CIs) for each tagSNP were corrected for multiple testing for all SNPs within each gene using pACT and for genes within each pathway and across pathways with Bonferroni. Gene and pathway summary estimates were obtained using ARTP. We observed an association between bladder cancer and POLB rs7832529 (BER) (pACT = 0.003; ppathway = 0.021) among all, and SNPs in XPC (NER) and OGG1 (BER) among Chinese men and women, respectively. The NER pathway showed an overall association with risk among Chinese males (ARTP NER p = 0.034). The XRCC6 SNP rs2284082 (NHEJ), also in LD with SREBF2, showed an interaction with smoking (smoking status interaction pgene = 0.001, ppathway = 0.008, poverall = 0.034). Our findings support a role in bladder carcinogenesis for regions that map close to or within BER (POLB, OGG1) and NER genes (XPC). A SNP that tags both the XRCC6 and SREBF2 genes strongly modifies the association between bladder cancer risk and smoking.

Genotype-phenotype analysis of S326C OGG1 polymorphism: a risk factor for oxidative pathologies

8-Oxoguanine DNA glycosylase (OGG) activity was measured by an in vitro assay in lymphocytes of healthy volunteers genotyped for various OGG1 polymorphisms. Only homozygous carriers of the polymorphic C326 allele showed a significantly lower OGG activity compared to the homozygous S326 genotype. The purified S326C OGG1 showed a decreased ability to complete the repair synthesis step in a base excision repair reaction reconstituted in vitro. The propensity of this variant to dimerize as well as its catalytic impairment were shown to be enhanced under oxidizing conditions. Mass spectrometry revealed that the extra cysteine of the variant protein is involved in disulfide bonds compatible with significant conformational changes and/or dimerization. We propose that the S326C OGG1 catalytic impairment and its susceptibility to dimerization and disulfide bond formation in an oxidizing environment all concur to decrease repair capacity. Consequently, the C326 homozygous carriers may be at increased risk of oxidative pathologies.

Genetic polymorphism in hOGG1 is associated with triple-negative breast cancer risk in Chinese Han women

8-hydroxy-2'-deoxyguanine (8-OHdG), a typical product of oxidative stress-induced DNA damage, can cause a G-T transversion during DNA replication if it is not removed. Human 8-oxoguanine glycosylase 1 (hOGG1), a key DNA repair gene, recognizes and excises 8-OHdG from damaged DNA accurately; however, a c.977C>G (Ser326Cys) polymorphism in hOGG1 can inhibit the gene's ability to remove 8-OHdG. The aim of present study was to investigate the association between the c.977C>G polymorphism in hOGG1 and the risk of breast cancer in Chinese Han women. We used high-resolution melting and sequencing to analyze the genotypes of 630 patients with sporadic breast cancer patients and 777 healthy controls. We also performed risk-stratified subgroup analyses to determine the association between the c.977C>G polymorphism and other characteristics of breast cancer subgroups. Breast cancer patients and healthy controls did not have significantly different of c.977C/G genotypes (odds ratio [OR] = 1.10, 95% confidence interval [CI] = 0.82-1.49, p = 0.57) and c.977G/G genotypes (OR = 1.34, 95% CI = 0.97-1.84, p = 0.09). However, the c.977G/G genotype was especially prevalent in breast cancer patients who were younger than 55 years (OR = 1.58, 95% CI = 1.05-2.39, p = 0.04), were premenopausal status (OR = 1.87, 95% CI = 1.14-3.06, p = 0.02), had triple-negative disease (OR = 2.14, 95% CI = 1.06-4.29, p = 0.04), or p53-positive disease (OR = 1.56, 95% CI = 1.14-2.12, p = 0.005). These findings suggest that the c.977C>G polymorphism in hOGG1 is associated with an increased risk of breast cancer in Chinese Han women who are younger than 55 years, premenopausal, triple-negative, or p53-positive subgroups.

Polymorphisms in base excision repair genes and thyroid cancer risk

Thyroid cancer (TC) is the most frequent endocrine malignancy, accounting however for only 1-2% of all human cancers, and the best-established risk factor for TC is radiation exposure, particularly during childhood. Since the BER pathway seems to play an important role in the repair of DNA damage induced by IR and other genotoxicants, we carried out a hospital-based case-control study in order to evaluate the potential modifying role of 6 BER polymorphisms on the individual susceptibility to non-familial TC in 109 TC patients receiving iodine-131, and 217 controls matched for age (± 2 years), gender and ethnicity. Our results do not reveal a significant involvement of XRCC1 Arg194Trp and Arg399Gln, OGG1 Ser326Cys, APEX1 Asp148Glu, MUTYH Gln335His and PARP1 Val762Ala polymorphisms on the individual susceptibility towards TC, mostly in agreement with the limited available evidence. By histological stratification analysis, we observed that the association between the presence of heterozygosity in the MUTYH Gln335His polymorphism and TC risk almost reached significance for the papillary subtype of TC. This was the first time that the putative association between this polymorphism and TC susceptibility was evaluated. However, since the sample size was modest, the possibility of a type I error should not be excluded and this result should, therefore, be interpreted with caution. More in depth studies involving larger populations should be pursued in order to further clarify the potential usefulness of the MUTYH Gln335His genotype as a predictive biomarker of susceptibility to TC and the role of the remaining BER polymorphisms on TC susceptibility.