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

Unravelling the molecular tapestry of pterygium: insights into genes for diagnostic and therapeutic innovations

Pterygium, an ocular surface disorder, manifests as a wing-shaped extension from the corneoscleral limbus onto the cornea, impacting vision and causing inflammation. With a global prevalence of 12%, varying by region, the condition is linked to UV exposure, age, gender, and socioeconomic factors. This review focuses on key genes associated with pterygium, shedding light on potential therapeutic targets. Matrix metalloproteinases (MMPs), especially MMP2 and MMP9, contribute to ECM remodelling and angiogenesis in pterygium. Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis and is elevated in pterygium tissues. B-cell lymphoma-2, S100 proteins, DNA repair genes (hOGG1, XRCC1), CYP monooxygenases, p53, and p16 are implicated in pterygium development. A protein-protein interaction network analysis highlighted 28 edges between the aforementioned proteins, except for VEGF, indicating a high level of interaction. Gene ontology, microRNA and pathway analyses revealed the involvement of processes such as base excision repair, IL-17 and p53 signalling, ECM disassembly, oxidative stress, hypoxia, metallopeptidase activity and others that are essential for pterygium development. In addition, miR-29, miR-125, miR-126, miR-143, miR-200, miR-429, and miR-451a microRNAs were predicted, which were shown to have a role in pterygium development and disease severity. Identification of these molecular mechanisms provides insights for potential diagnostic and therapeutic strategies for pterygium.

CRISPR/Cas12a trans-cleavage triggered by cleavage ligation of dumbbell DNA for specific detection of human 8-oxoguanine DNA glycosylase activity

Human 8-oxoguanine DNA glycosylase (hOGG1) is an essential enzyme that recognizes and removes 8-oxoguanine (8-oxoG), a common DNA oxidative damage caused by reactive oxygen species, to maintain genomic integrity of living organisms. Abnormal expression of hOGG1 has been proved to be associated with different diseases such as cancer and neurogenerative disorders, making it a potential biomarker and therapeutic target. In this study, we report the development of  a novel strategy for detecting hOGG1 activity based on CRISPR/Cas12a trans-cleavage triggered by cleavage ligation of a dumbbell DNA probe (DBP) designed with a 3' overhang and an 8-oxoG modification. When hOGG1 is present, it cleaves the DBP at the 8-oxoG site, forming a 5' phosphate termini and exposing a single-strand region allowing complementary to the 3' overhang. After hybridization, the 3' and 5' termini in the juxtaposition are ligated by T4 DNA ligase, leading to a closed DBP for CRISPR/Cas12a-crRNA to recognize and initiate the trans-cleavage of the surrounding ssDNAs with fluorophore and quencher. The method achieves a limit of detection (LOD) with 370 μU/mL and high selectivity. Furthermore, it demonstrates a good compatibility for detecting hOGG1 activity in cell lysates, suggesting a good performance for further application in disease diagnosis and scientific research.

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.

Evaluation of the upregulation and surface expression of hypoxanthine guanine phosphoribosyltransferase in acute lymphoblastic leukemia and Burkitt's B cell lymphoma

BACKGROUND

The aim of this study is to determine whether Hypoxanthine Guanine Phosphoribosyltransferase (HPRT) could be used as a biomarker for the diagnosis and treatment of B cell malignancies. With 4.3% of all new cancers diagnosed as Non-Hodgkin lymphoma, finding new biomarkers for the treatment of B cell cancers is an ongoing pursuit. HPRT is a nucleotide salvage pathway enzyme responsible for the synthesis of guanine and inosine throughout the cell cycle.

METHODS

Raji cells were used for this analysis due to their high HPRT internal expression. Internal expression was evaluated utilizing western blotting and RNA sequencing. Surface localization was analyzed using flow cytometry, confocal microscopy, and membrane biotinylation. To determine the source of HPRT surface expression, a CRISPR knockdown of HPRT was generated and confirmed using western blotting. To determine clinical significance, patient blood samples were collected and analyzed for HPRT surface localization.

RESULTS

We found surface localization of HPRT on both Raji cancer cells and in 77% of the malignant ALL samples analyzed and observed no significant expression in healthy cells. Surface expression was confirmed in Raji cells with confocal microscopy, where a direct overlap between HPRT specific antibodies and a membrane-specific dye was observed. HPRT was also detected in biotinylated membranes of Raji cells. Upon HPRT knockdown in Raji cells, we found a significant reduction in surface expression, which shows that the HPRT found on the surface originates from the cells themselves. Finally, we found that cells that had elevated levels of HPRT had a direct correlation to XRCC2, BRCA1, PIK3CA, MSH2, MSH6, WDYHV1, AK7, and BLMH expression and an inverse correlation to PRKD2, PTGS2, TCF7L2, CDH1, IL6R, MC1R, AMPD1, TLR6, and BAK1 expression. Of the 17 genes with significant correlation, 9 are involved in cellular proliferation and DNA synthesis, regulation, and repair.

CONCLUSIONS

As a surface biomarker that is found on malignant cells and not on healthy cells, HPRT could be used as a surface antigen for targeted immunotherapy. In addition, the gene correlations show that HPRT may have an additional role in regulation of cancer proliferation that has not been previously discovered.

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

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

Structural and Functional Analysis of human lung cancer risk associated hOGG1 variant Ser326Cys in DNA repair gene by molecular dynamics simulation

Oxidative damaged DNA base lesions are repaired through human 8-oxoguanine DNA glycosylase gene (hOGG1) mediated pathways. A recent report based on the meta-analysis has suggested that the DNA Repair Gene hOGG1 variant Ser326Cys [3p26.2; allele S/C in nucleotide position αHelix2 Ser⇒Cys326] was associated with Lung Cancer risk in Caucasian population will alter the level Zhong et al., 2012. To the best of our knowledge, there has not been any such comprehensive in-silico investigation that validates the functional and structural impact of non-synonymous Lung Cancer Risk Associated Protein Domain (LCRAPD) mutation Ser326Cys (rs1052133) by molecular dynamics (MD) simulation approach following prediction of hOGG1 protein before and after the mutation. Further to the native and mutant protein structures, the amino acid residue and its secondary structure were observed through a solvent accessibility model for protein stability confirmation at the point of mutation. Taken together, this study suggests that the protein functional and structural studies could be a reasonable approach for investigating the impact of nsSNPs in future studies. In addition, 4295 patients samples incorporate with the analysis that genomic data types from cBioPortal. In the result, 4295 cases (91.5%) had alterations in all genes but the frequency of alterations in our targeted hOGG1 gene was shown with and without case alteration in the ratio (Logrank Test P-Value: 0.670) Kaplan-Meier by the number of patients at risk of the survival function.

OGG1 methylation mediated the effects of cell cycle and oxidative DNA damage related to PAHs exposure in Chinese coke oven workers

Previous publications have indicated that polycyclic aromatic hydrocarbons (PAHs) exposures are associated with increased DNA damage and abnormal cell cycle arrest; however, the details of mechanisms remain largely unknown. This study aimed to quantify the associations of 8-oxoguanine DNA glycosylase (OGG1) methylation with urinary PAHs metabolites, DNA damage and cell cycle arrest, and further to assess the role of OGG1 methylation in mediating the association of urinary PAHs metabolites with DNA damage and cell cycle arrest. Urinary biomarkers of PAHs exposure and a marker of oxidative DNA damage (8-hydroxy-2'-deoxyguanosin, 8-OHdG) were measured by high performance liquid chromatography. Cell cycle of lymphocyte was analysed with flow cytometry and OGG1 methylation in venous blood was measured by pyrosequencing. After adjusting for covariates, urinary 1-OHP levels were positively associated with lymphocyte S phase arrest and oxidative DNA damage, while were negatively associated with G0/G1 phase arrest. OGG1 methylation was not only positively correlated with urinary 1-OHP in a dose-responsive manner (P trend = 0.008) but was also associated with G0/G1 phase arrest (OR: 0.63, 95% CI: 0.41-0.97), S phase arrest (OR: 1.55, 95% CI: 1.01-2.40) and oxidative DNA damage (OR: 1.71, 95% CI: 1.02-2.86). Mediation analysis estimated that OGG1 methylation mediated about 20% of associations between urinary 1-OHP levels and cell cycle arrest and oxidative DNA damage, respectively (all P < 0.05). Our findings suggested that urinary 1-OHP concentrations were associated with cell cycle arrest and oxidative DNA damage by a mechanism partly involving OGG1 methylation.

Immunological-based approaches for cancer therapy

The immunologic landscape of tumors has been continuously unveiled, providing a new look at the interactions between cancer cells and the immune system. Emerging tumor cells are constantly eliminated by the immune system, but some cells establish a long-term equilibrium phase leading to tumor immunoediting and, eventually, evasion. During this process, tumor cells tend to acquire more mutations. Bearing a high mutation burden leads to a greater number of neoantigens with the potential to initiate an immune response. Although many tumors evoke an immune response, tumor clearance by the immune system does not occur due to a suppressive tumor microenvironment. The mechanisms by which tumors achieve the ability to evade immunologic control vary. Understanding these differences is crucial for the improvement and application of new immune-based therapies. Much effort has been placed in developing in silico algorithms to predict tumor immunogenicity and to characterize the microenvironment via high-throughput sequencing and gene expression techniques. Each sequencing source, transcriptomics, and genomics yields a distinct level of data, helping to elucidate the tumor-based immune responses and guiding the fine-tuning of current and upcoming immune-based therapies. In this review, we explore some of the immunological concepts behind the new immunotherapies and the bioinformatic tools to study the immunological aspects of tumors, focusing on neoantigen determination and microenvironment deconvolution. We further discuss the immune-based therapies already in clinical use, those underway for future clinical application, the next steps in immunotherapy, and how the characterization of the tumor immune contexture can impact therapies aiming to promote or unleash immune-based tumor elimination.

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.

Methylated +322-327 CpG site decreases hOGG1 mRNA expression in non-small cell lung cancer

hOGG1 plays a role in several disease pathways, including various cancers. Despite such functional importance, how hOGG1 is regulated at the transcriptional level in human non-small cell lung cancer (NSCLC) remains unknown, particularly via DNA methylation changes. We obtained NSCLC tissues and adjacent non-cancerous tissues and examined hOGG1 mRNA expression levels. NSCLC cells were treated with 5-Aza to test whether DNA methylation can influence the expression of hOGG1. The MassARRAY EpiTYPER and luciferase reporter gene assays were used to define the functional region of the hOGG1 gene (including CpG sites). Finally, ChIP assay was utilized to verify transcription factor binding to the hOGG1 5'-UTR region. Our previous studies supported the idea that the methylation of the hOGG1 gene promoter region occurs frequently in NSCLC. Treatment with 5-Aza, a demethylating agent, led to a significant restoration of hOGG1 expression in NSCLC cell lines. Quantitative PCR and MassARRAY EpiTYPER assays demonstrated that methylation of the +322-327 CpG site in the 5'-UTR region of hOGG1 was higher in NSCLC tissues compared with adjacent non-cancerous tissues. Notably, the methylation level of +322-327 site (T/N) was inversely correlated with that of hOGG1 mRNA level (T/N) in 25 NSCLC tissues. ChIP assay and in silico prediction showed an association between the +322-327 CpG site and Sp1, which has been reported to be an activator of transcription. Importantly, luciferase reporter gene and ChIP assays showed that +322-327 CpG site methylation particularly reduced the recruitment of Sp1 to the 5'-UTR sequence in hOGG1 and reduced transcriptional activity ~50%. In summary, we have demonstrated that hOGG1 mRNA is downregulated in NSCLC tissues. Moreover, we identified that the methylated +322-327 CpG site in the hOGG1 5'-UTR is associated with reduced expression of hOGG1 by decreasing the recruitment of Sp1 to the 5'-UTR of hOGG1.

Mechanisms for the deamination reaction of 8-oxoguanine catalyzed by 8-oxoguanine deaminase: A combined QM/MM molecular dynamics study

The deamination reaction of 8-oxoguanine (8-oxoG) catalyzed by 8-oxoguanine deaminase (8-oxoGD) plays a critically important role in the DNA repair activity for oxidative damage. In order to elucidate the complete enzymatic catalysis mechanism at the stages of 8-oxoguanine binding, departure of 2-hydroxy-1H-purine-6,8(7H,9H)-dione from the active site, and formation of 8-oxoxanthine, extensive combined QM(PM3)/MM molecular dynamics simulations have been performed. Computations show that the rate-limiting step corresponds to the nucleophilic attack from zinc-coordinate hydroxide group to free 8-oxoguanine. Through conformational analyses, we demonstrate that Trp115, Trp123 and Leu119 connect to O8@8-oxoguanine with hydrogen bonds, and we suggest that mutations of tryptophan (115 and 123) to histidine or phenylalanine and mutation of leucine (119) to alanine could potentially lead to a mutant with enhanced activity. On this ground, a proton transfer mechanism for the formation of 8-oxoxanthine was further discussed. Both Glu218 and water molecule could be used as proton shuttles, and water molecule plays a major role in proton transfer in substrate. On the other hand, comparative simulations on the deamination of guanine and isocytosine reveal that, for the helping of hydrogen bonds between O8@8-oxoguanine and enzyme, O8@8-oxoguanine is the fastest to be deaminated among the three substrates which are also supported by the experimental kinetic constants.

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.

Gut Microbiota Imbalance and Base Excision Repair Dynamics in Colon Cancer

Gut microbiota are required for host nutrition, energy balance, and regulating immune homeostasis, however, in some cases, this mutually beneficial relationship becomes twisted (dysbiosis), and the gut flora can incite pathological disorders including colon cancer. Microbial dysbiosis promotes the release of bacterial genotoxins, metabolites, and causes chronic inflammation, which promote oxidative DNA damage. Oxidized DNA base lesions are removed by base excision repair (BER), however, the role of this altered function of BER, as well as microbiota-mediated genomic instability and colon cancer development, is still poorly understood. In this review article, we will discuss how dysbiotic microbiota induce DNA damage, its impact on base excision repair capacity, the potential link of host BER gene polymorphism, and the risk of dysbiotic microbiota mediated genomic instability and colon cancer.

The role of hOGG1 C1245G polymorphism in the susceptibility to lupus nephritis and modulation of the plasma 8-OHdG in patients with systemic lupus erythematosus

We investigated whether the C1245G polymorphism of human 8-oxoguanine glycosylase 1 (hOGG1) gene confers the susceptibility to systemic lupus erythematosus (SLE) occurrence of lupus nephritis and affects the plasma level of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in patients with SLE. A total of 45 healthy controls and 85 SLE patients were recruited. The C1245G polymorphism of the hOGG1 gene was determined by direct sequencing. The frequency of occurrence of the hOGG1 1245 GG genotype in SLE patients was 31.8% (27/85), which is lower than that of healthy controls of 53.3% (24/45). Thirty-three (33/85, 38.8%) SLE patients developed lupus nephritis. Significantly, SLE patients harboring the hOGG1 1245 GG genotype had a higher incidence to develop lupus nephritis than did those harboring the hOGG1 1245 CC or CG genotype (15/27, 55.6% vs.18/58, 31.0%, p = 0.031). Divided into subgroups, SLE patients harboring the hOGG1 1245 GG genotype had the highest plasma levels of 8-OHdG among patients with all genotypes, with regard to the coexistence of lupus nephritis (p = 0.020, ANOVA), including those with nephritis harboring the hOGG1 1245 CC or CG genotypes (p = 0.037), those without nephritis harboring the hOGG1 1245 GG genotype (p = 0.050), and those without nephritis harboring the hOGG1 1245 CC or CG genotype (p = 0.054). We conclude that the C1245G polymorphism of hOGG1 may be one of the factors that confer the susceptibility to lupus nephritis and modulate the plasma level of 8-OHdG in patients with SLE.

A Meta-analysis of association between hOGG1 Ser326cys polymorphism and esophageal carcinoma

AIM: To explore the association between the human 8-oxoguanine glycosylase (hOGG1) Ser326Cys polymorphism and esophageal carcinoma.

METHODS: Databases, including CBM, CNKI, WanFang, VIP, Medline, Pubmed, and ASP were searched to identify studies assessing the association between the hOGG1 Ser326Cys polymorphism and esophageal carcinoma. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association. Stata/SE 11.0 software was used for statistical analysis.

RESULTS: Fourteen studies involving 2693 cases and 4027 controls were included. The hOGG1 Ser326Cys polymorphism was associated with esophageal carcinoma (recessive model C/C vs C/S+S/S: OR = 1.26, 95%CI: 1.08-1.48; co-dominant model C/C vs S/S: OR = 1.25, 95%CI: 1.05-1.49). In subgroup analyses, it was found that hOGG1 Ser326Cys polymorphism might increase the susceptibility to esophageal carcinoma in Asian populations, squamous cell carcinoma, and population- and tissue-based studies.

CONCLUSION: This study suggested that the hOGG1 Ser326Cys polymorphism has relevance to esophageal carcinoma. Cys326 may increase the susceptibility to esophageal carcinoma. However, the above conclusion still needs validation by large sample studies.

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

BACKGROUND

The base excision repair (BER) pathway removes DNA damage caused by ionizing radiation, reactive oxidative species and methylating agents. OGG1 and APE1 are two important genes in the BER pathway. Many epidemiological studies have evaluated the association between polymorphisms in the two BER genes (OGG1 Ser326Cys and APE1 Asp148Glu) and breast cancer risk. However, the results are inconsistent.

METHODS

We searched the electronic databases including PubMed, Embase and Cochrane library for all eligible studies for the period up to February 2014. Data were extracted by two independent authors and pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the strength of the association.

RESULTS

A total of 17 studies including 9,040 cases and 10,042 controls were available for OGG1 Ser326Cys polymorphism and 7 studies containing 2,979 cases and 3,111 controls were included for APE1 Asp148Glu polymorphism. With respect to OGG1 Ser326Cys polymorphism, we did not find a significant association with breast cancer risk when all eligible studies were pooled into the meta-analysis. However, in subgroup analyses by ethnicity and menopausal status, statistical significant increased breast cancer risk was found in Asian populations (Cys/Cys vs. Ser/Ser: OR=1.157, 95% CI 1.013-1.321, P=0.011; Cys/Cys vs. Ser/Cys+Ser/Ser: OR=1.113, 95% CI 1.009-1.227, P=0.014) and postmenopausal patients (Cys/Cys vs. Ser/Cys+Ser/Ser: OR=1.162, 95% CI 1.003-1.346, P=0.024). In subgroup analysis according to quality score, source of control, and HWE in controls, no any significant association was detected. With respect to APE1 Asp148Glu polymorphism, no significant association with breast cancer risk was demonstrated in the overall and stratified analyses.

CONCLUSIONS

The present meta-analysis suggests that the OGG1 Ser326Cys polymorphism may be a risk factor for breast cancer in Asians and postmenopausal patients. Further large and well-designed studies are needed to confirm this association.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1156934297124915.

DNA repair pathways and their therapeutic potential in lung cancer

SUMMARY: 

Lung cancer is the leading cause of cancer-related mortality. According to WHO, 1.37 million deaths occur globally each year as a result of this disease. More than 70% of these cases are associated with prior tobacco consumption and/or cigarette smoking, suggesting a direct causal relationship. The development and progression of lung cancer and other malignancies involves the loss of genetic stability, resulting in acquisition of cumulative genetic changes; this affords the cell increased malignant potential. As such, an understanding of the mechanisms through which these events may occur will potentially allow for development of new anticancer therapies. This review will address the association between lung cancer and genetic instability, with a central focus on genetic mutations in the DNA damage repair pathways. In addition, we will discuss the potential clinical exploitation of these pathways, both in terms of biomarker staging, as well as through direct therapeutic targeting.

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

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

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

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

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

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

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

Objectives

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

Materials and methods

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

Results

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

Conclusion

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

Virtual slides

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

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

Background

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

Methods

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

Results

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

Conclusions

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

Susceptibility of XPD and hOGG1 genetic variants to prostate cancer

DNA repair genes are important in maintaining genomic stability and integrity. DNA repair gene polymorphisms, such as those of the human homolog of 8-oxoguanine DNA glycosylase 1 (hOGG1) and excision repair cross-complementing rodent repair deficiency, complementation group 2/Xeroderma pigmentosum complementation group D (ERCC2/XPD), contribute to carcinogenesis. The aim of this study was to investigate the association of prostate cancer (PCa) risk with hOGG1 and ERCC2/XPD genetic variants. A case-control study of 200 cases including 100 PCa patients and 100 healthy subjects was conducted. Two single-nucleotide polymorphisms (SNPs) (ERCC2/XPD Arg156Arg and hOGG1 Ser326Cys) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results demonstrated a significant association of the XPD156 homozygous (AA, OR=3.80; 95% CI: 1.19-12.18; P=0.017), heterozygous (AC, OR=2.48; 95% CI: 1.02-6.35; P=0.033) and combined (AA+AC, OR=2.76; 95% CI: 1.18-6.84; P=0.011) mutant genotypes with a predisposition to high-risk PCa. In the stratified analysis, predisposition to high-risk PCa was also associated with the mutant genotypes of hOGG1 326 homozygous mutant (GG, OR=2.93; 95% CI: 1-8.74; P=0.033). The results also showed that the A allele of XPD Arg156Arg and the G allele of hOGG1 Ser326Cys were associated with an increased risk of PCa (OR=1.86 and 1.62; 95% CI: 1.13-3.06 and 1-2.67, respectively). In conclusion, the findings of this study demonstrated that the ERCC2/XPD Arg156Arg and hOGG1 Ser326Cys polymorphisms increased the susceptibility to high-risk PCa.

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.

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

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

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

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

The APE1 Asp/Asp genotype and the combination of APE1 Asp/Asp and hOGG1-Cys variants are associated with increased p53 mutation in non-small cell lung cancer

Background

The hOGG1 Ser326Cys polymorphism is associated with lung cancer risk, but there are limited data regarding an association between the APE1 Asp148Glu polymorphism and lung cancer. Biological evidence shows that the hOGG1-Cys allele results in less DNA repair activity; however, this is not associated with p53 mutation in lung cancer. Therefore, we investigated whether an interaction between hOGG1 and APE1 is associated with the frequency of p53 mutation in lung cancer.

Methods

We studied 217 Taiwanese adults with primary lung cancer. DNA polymorphisms of hOGG1 and APE1 were determined by polymerase chain reaction (PCR)-based restriction fragment length polymorphism. Mutations in p53 exons 5–8 were detected by direct sequencing. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% CIs for the risk of p53 mutation associated with polymorphisms of hOGG1 and APE1 in lung cancer.

Results

As expected, no association between hOGG1 polymorphism and p53 mutation was observed in this population. However, a higher risk of p53 mutation was found in participants with the APE1 Asp/Asp genotype than in those with the APE1-Glu allele (OR, 2.15; 95% CI, 1.19–3.87; P = 0.011). The risk of p53 mutation was also higher in participants with APE1 Asp/Asp plus hOGG1-Cys than in those with APE1-Glu plus hOGG1 Ser/Ser (OR, 3.72; 95% CI, 1.33–10.40; P = 0.012).

Conclusions

These results suggest that the APE1 Asp/Asp genotype and the combination of the APE1 Asp/Asp and hOGG1-Cys variants are associated with increased risk of p53 mutation in non–small cell lung cancer.

Polymorphisms of DNA repair genes in Korean hepatocellular carcinoma patients with chronic hepatitis B: possible implications on survival

BACKGROUND & AIMS

We aimed at determining whether single nucleotide polymorphisms (SNPs) of DNA repair genes influence the development and clinical outcomes of hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC).

METHODS

We evaluated 14 SNPs of eight DNA repair genes in 708 patients with HCC and 388 HBsAg positive controls without HCC. The Kaplan-Meier methods with log-rank test and Cox regression models were used to compare survival of HCC patients according to the genotype.

RESULTS

The SNP of XRCC4 rs1805377 was significantly associated with decreased risk of HCC development (OR, 0.592; p=0.028) and improved overall survival of patients with HCC (median survival time (MST) of 48, 72, and 89 months for the AA, AG, and GG genotypes, respectively; p=0.044). In addition, SNP of OGG1 rs1053133 was significantly associated with postoperative recurrence (OR, 0.604; p=0.049), tumor differentiation (OR, 0.571; p=0.041), and improved survival of resected HCC (MST of 55 and 108 months for the GG and GC/CC genotypes, p=0.001). The multivariate analysis showed that OGG1 rs1052133, XRCC1 rs25487, ERCC5 rs2018836, ERCC5 rs3818356, and XRCC4 rs1805377 had a significant effect on survival. Moreover, a strong dose-dependent association was observed between the number of putative high-risk genotypes of OGG1, XRCC1, ERCC5, and XRCC4 with the overall survival. The MST of HCC with ≥2 putative high-risk genotypes was significantly prolonged compared to those with ≥3 high-risk genotypes (76 vs. 46 months, respectively, p=0.002).

CONCLUSIONS

Polymorphisms of DNA repair genes play a potential role in the development, progression, and survival of Korean HCC patients with chronic HBV infection.

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

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

The association between OGG1 Ser326Cys polymorphism and lung cancer susceptibility: a meta-analysis of 27 studies

Background

Numerous studies have investigated association of OGG1 Ser326Cys polymorphism with lung cancer susceptibility; however, the findings are inconsistent. Therefore, we performed a meta-analysis based on 27 publications encompass 9663 cases and 11348 controls to comprehensively evaluate such associations.

Methods

We searched publications from MEDLINE and EMBASE which were assessing the associations between OGG1 Ser326Cys polymorphism and lung cancer risk. We calculated pooled odds ratio (OR) and 95% confidence interval (CI) by using either fixed-effects or random-effects model. We used genotype based mRNA expression data from HapMap for SNP rs1052133 in normal cell lines among 270 subjects with four different ethnicities.

Results

The results showed that individuals carrying the Cys/Cys genotype did not have significantly increased risk for lung cancer (OR = 1.15, 95% CI = 0.98–1.36) when compared with the Ser/Ser genotype; similarly, no significant association was found in recessive, dominant or heterozygous co-dominant model (Ser/Cys vs. Cys/Cys). However, markedly increased risks were found in relatively large sample size (Ser/Ser vs. Cys/Cys: OR = 1.29, 95% CI = 1.13–1.48, and recessive model: OR = 1.19, 95% CI = 1.07–1.32). As to histological types, we found the Cys/Cys was associated with adenocarcinoma risk (Ser/Ser vs. Cys/Cys: OR = 1.32, 95% CI = 1.12–1.56; Ser/Cys vs. Cys/Cys: OR = 1.19, 95% CI = 1.04–1.37, and recessive model OR = 1.23, 95% CI = 1.08–1.40). No significant difference of OGG1 mRNA expression was found among genotypes between different ethnicities.

Conclusions

Despite some limitations, this meta-analysis established solid statistical evidence for an association between the OGG1 Cys/Cys genotype and lung cancer risk, particularly for studies with large sample size and adenocarcinoma, but this association warrants additional validation in larger and well designed studies.

Repair of oxidative DNA damage is delayed in the Ser326Cys polymorphic variant of the base excision repair protein OGG1

Gene-environment interactions influence an individual's risk of disease development. A common human 8-oxoguanine DNA glycosylase 1 (OGG1) variant, Cys326-hOGG1, has been associated with increased cancer risk. Evidence suggests that this is due to reduced repair ability, particularly under oxidising conditions but the underlying mechanism is poorly understood. Oxidising conditions may arise due to internal cellular processes, such as inflammation or external chemical or radiation exposure. To investigate wild-type and variant OGG1 regulation and activity under oxidising conditions, we generated mOgg1 (-/-) null mouse embryonic fibroblasts cells stably expressing Ser326- and Cys326-hOGG1 and measured activity, gene expression, protein expression and localisation following treatment with the glutathione-depleting compound L-buthionine-S-sulfoximine (BSO). Assessment of OGG1 activity using a 7,8-dihydro-8-oxodeoxyguanine (8-oxo dG) containing molecular beacon demonstrated that the activity of both Ser326- and Cys326-hOGG1 was increased following oxidative treatment but with different kinetics. Peak activity of Ser326-hOGG1 occurred 12 h prior to that of Cys326-hOGG1. In both variants, the increased activity was not associated with any gene expression or protein increase or change in protein localisation. These findings suggest that up-regulation of OGG1 activity in response to BSO-induced oxidative stress is via post-transcriptional regulation and provide further evidence for impaired Cys326-hOGG1 repair ability under conditions of oxidative stress. This may have important implications for increased mutation frequency resulting from increased oxidative stress in individuals homozygous for the Cys326 hOGG1 allele.

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.

Parameters of oxidative stress, DNA damage and DNA repair in type 1 and type 2 diabetes mellitus

OBJECTIVES

(i) to determine the extent of oxidative stress and DNA damage and repair using a panel of selected markers in patients with type 1 and type 2 diabetes mellitus (T1DM, T2DM), (ii) to find their possible relationships with diabetes compensation and duration, and finally (iii) to test for the effect of functional polymorphisms in the 8-oxoguanin DNA glycosylase (rs1052133), catalase (rs1001179) and superoxide dismutase (rs4880) genes on respective intermediate phenotypes.

METHODS

A total of 207 subjects (23 children and 44 adults with T1DM, 52 adult patients with T2DM and 88 healthy adult control subjects) were enrolled in the study. The following markers of redox state were determined in participants: erythrocyte superoxide dismutase (Ery-SOD), whole blood glutathione peroxidase (WB-GPx), erythrocyte glutathione (Ery-GSH), plasma total antioxidant capacity (P-tAOC) and plasma malondialdehyde (P-MDA). Furthermore, the extent of DNA damage and repair was ascertained using the following parameters: DNA single strand breaks (DNAssb), DNA repair capacity (DNArc) and DNA repair index (DNRI).

RESULTS

Comparison of T1DM vs. T2DM patients revealed significantly higher Ery-GSH content (P < 0.0001) and significantly lower Ery-SOD activity (P = 0.0006) and P-tAOC level (P < 0.0001) in T1DM subjects. T2DM diabetics exhibited a significant increase in DNAssb (P < 0.0001) and significant decrease in both DNArc (P < 0.0001) and DNRI (P <  .0001) compared with T1DM patients. Patient's age (irrespective of DM type) significantly correlated with DNAssb (r = 0.48, P < 0.0001), DNArc (r = -0.67, P < 0.0001) and DNRI (r = -0.7, P < 0.0001). Allele frequencies of all studied polymorphisms did not exhibit any significant association with the investigated parameters.

CONCLUSION

We demonstrated significant age- and DM type-related changes of oxidative DNA modification and capacity for its repair in subjects with T1DM and T2DM.

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

背景与目的

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

方法

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

结果

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

结论

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

[Mutational analysis of hOGG1 gene promoter in patients with non-small cell lung cancer]

背景与目的

8-羟基鸟嘌呤DNA糖苷酶（8-hydroxygumine DNA glycosylase 1, OGG1）是一种DNA修复酶，可以从DNA切除修复8-羟基鸟嘌呤（8-dihydro-8-oxoguanine, 8-OH-G）。人类OGG1基因（hOGG1）的多态性可能会改变酶的活性而影响个体修复损伤DNA的能力，促进癌变。然而，hOGG1基因启动子区域的突变与非小细胞肺癌（non-small cell lung cancer, NSCLC）的关系尚不明晰。我们拟探讨hOGG1基因启动子区域的突变与NSCLC发生发展的潜在关系。

方法

选取苏州大学附属第一医院2003年1月-2005年12月新鲜手术切除的40例NSCLC组织标本，采用PCR-SSCP和直接测序的方法检测NSCLC及其对应的癌旁组织中hOGG1基因启动子区域的突变。

结果

在40例NSCLC患者中未发现hOGG1基因启动子区域的异常突变，但发现单核苷酸多态位点rs159153与TNM分期明显相关（P=0.008）；同时发现吸烟者中淋巴结转移率明显较低（P=0.034）。

结论

单核苷酸多态位点rs159153和吸烟史可能对NSCLC的侵袭和转移潜在性提供预测。

Gallbladder cancer predisposition: a multigenic approach to DNA-repair, apoptotic and inflammatory pathway genes

Gallbladder cancer (GBC) is a multifactorial disease with complex interplay between multiple genetic variants. We performed Classification and Regression Tree Analysis (CART) and Grade of Membership (GoM) analysis to identify combinations of alleles among the DNA repair, inflammatory and apoptotic pathway genetic variants in modifying the risk for GBC. We analyzed 16 polymorphisms in 8 genes involved in DNA repair, apoptotic and inflammatory pathways to find out combinations of genetic variants contributing to GBC risk. The genes included in the study were XRCC1, OGG1, ERCC2, MSH2, CASP8, TLR2, TLR4 and PTGS2. Single locus analysis by logistic regression showed association of MSH2 IVS1+9G>C (rs2303426), ERCC2 Asp312Asn (rs1799793), OGG1 Ser326Cys (rs1052133), OGG1 IVS4-15C>G (rs2072668), CASP8 -652 6N ins/del (rs3834129), PTGS2 -1195G>A (rs689466), PTGS2 -765G>C (rs20417), TLR4 Ex4+936C>T (rs4986791) and TLR2 –196 to –174del polymorphisms with GBC risk. The CART analysis revealed OGG1 Ser326Cys, and OGG1 IVS4-15C>G polymorphisms as the best polymorphic signature for discriminating between cases and controls. In the GoM analysis, the data was categorized into six sets representing risk for GBC with respect to the investigated polymorphisms. Sets I, II and III described low intrinsic risk (controls) characterized by multiple protective alleles while sets IV, V and VI represented high intrinsic risk groups (GBC cases) characterized by the presence of multiple risk alleles. The CART and GoM analyses also showed the importance of PTGS2 -1195G>A polymorphism in susceptibility to GBC risk. In conclusion, the present multigenic approach can be used to define individual risk profiles for gallbladder cancer in North Indian population.

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

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

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

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

Novel mechanism of regulation of the DNA repair enzyme OGG1 in tuberin-deficient cells

Tuberin (protein encodes by tuberous sclerosis complex 2, Tsc2) deficiency is associated with the decrease in the DNA repair enzyme 8-oxoG-DNA glycosylase (OGG1) in tumour kidney of tuberous sclerosis complex (TSC) patients. The purpose of this study was to elucidate the mechanisms by which tuberin regulates OGG1. The partial deficiency in tuberin expression that occurs in the renal proximal tubular cells and kidney cortex of the Eker rat is associated with decreased activator protein 4 (AP4) and OGG1 expression. A complete deficiency in tuberin is associated with loss of AP4 and OGG1 expression in kidney tumour from Eker rats and the accumulation of significant levels of 8-oxo-deoxyguanosine. Knockdown of tuberin expression in human renal epithelial cells (HEK293) with small interfering RNA (siRNA) also resulted in a marked decrease in the expression of AP4 and OGG1. In contrast, overexpression of tuberin in HEK293 cells increased the expression of AP4 and OGG1 proteins. Downregulation of AP4 expression using siRNA resulted in a significant decrease in the protein expression of OGG1. Immunoprecipitation studies show that AP4 is associated with tuberin in cells. Gel shift analysis and chromatin immunoprecipitation identified the transcription factor AP4 as a positive regulator of the OGG1 promoter. AP4 DNA-binding activity is significantly reduced in Tsc2(-/-) as compared with Tsc2(+/+) cells. Transcriptional activity of the OGG1 promoter is also decreased in tuberin-null cells compared with wild-type cells. These data indicate a novel role for tuberin in the regulation of OGG1 through the transcription factor AP4. This regulation may be important in the pathogenesis of kidney tumours in patients with TSC disease.

Polymorphisms in ERCC2, MSH2, and OGG1 DNA repair genes and gallbladder cancer risk in a population of Northern India

BACKGROUND

Genetic variants of DNA repair enzymes may lead to genetic instability and contribute to gallbladder (GB) carcinogenesis.

METHODS

A case-control study (230 GB carcinogenesis patients and 230 controls) was undertaken to evaluate whether genetic variations in 3 DNA repair genes ERCC2 (Asp312Asn [rs1799793] and Lys751Gln [rs13181]), MSH2 (-118T > C [rs2303425] and IVS1 + 9G>C [rs2303426]), and OGG1 (Ser326Cys [rs1052133] and 748-15C > G [rs2072668]) are associated with GB carcinogenesis risk in a North Indian population.

RESULTS

The authors found that the ERCC2 Asp312Asn AA, MSH2 IVS1 + 9G > C CC, OGG1 Ser326Cys GG and CG + GG, and OGG1 748-15C > G GG and CG + GG genotypes were significantly associated with an increased risk of GB carcinogenesis (odds ratio [OR], 2.1, 1.8, 2.5, 1.8, 2.0, and 1.6, respectively). In contrast, ERCC2 Lys751Gln, and MSH2 -118T > C markers showed no significant associations with GB carcinogenesis risk, although because of the small sample size their effects cannot be ruled out. Female GB carcinogenesis patients with the OGG1 748-15C > G GG, OGG1 Ser326Cys GG, and ERCC2 Asp312Asn genotypes had a greater risk for developing the disease (OR, 3.6, 7.7, and 2.7, respectively). There was a significant interaction between MSH2 IVS1 + 9G > C and OGG1 748-15C > G polymorphisms (P = .001). Furthermore, individuals with > 6 variant alleles of the studied polymorphisms were at 4-fold increased risk for developing GB carcinogenesis. Classification and Regression Tree analysis revealed potential higher-order gene-gene interactions and categorized a few higher-risk subgroups for GB carcinogenesis.

CONCLUSIONS

These results suggest that genetic variants in the DNA repair pathways may be involved in GB carcinogenesis etiology.

DNA damage and repair in endometrial cancer in correlation with the hOGG1 and RAD51 genes polymorphism

The cellular reaction to the DNA-damaging agents may modulate individual's cancer susceptibility. This reaction is mainly determined by the efficacy of DNA repair, which in turn, may be influenced by the variability of DNA repair genes, expressed by their polymorphism. The hOGG1 gene encodes a glycosylase of base excision repair and RAD51 specifies a key protein in homologues recombination repair. Both proteins can be involved in the repair of DNA lesions, which are known to contribute to endometrial cancer. In the present work we determined the extent of basal DNA damage and the efficacy of removal of DNA damage induced by hydrogen peroxide and N-methyl-N'-nitro N-nitrosoguanidyne (MNNG) in peripheral blood lymphocytes of 30 endometrial cancer patients and 30 individuals without cancer. The results from DNA damage and repair study were correlated with the genotypes of two 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 135 position of the RAD51 gene (the 135G>C polymorphism). DNA damage and repair were evaluated by alkaline single cell gel electrophoresis and genotypes were determined by restriction fragment length polymorphism PCR. We observed a strong association between endometrial cancer and the C/C genotype of the 135G>C polymorphism of the RAD51 gene. Moreover, there was a strong correlation between that genotype and endometrial cancer occurrence in subjects with a high level of basal DNA damage. We did not observe any correlation between the Ser326Cys polymorphism of the hOGG1 gene and endometrial cancer. Our result suggest that the 135G>C polymorphism of the RAD51 gene may be linked to endometrial cancer and can be considered as an additional marker of this disease.