Large-Scale Investigation of Base Excision Repair Genetic Polymorphisms and Lung Cancer Risk in a Multicenter Study

Inherited Genetic Mutations and Polymorphisms in Malignant Mesothelioma: A Comprehensive Review

Malignant mesothelioma (MM) is mainly caused by air-born asbestos but genetic susceptibility is also suspected to be a risk factor. Recent studies suggest an increasing number of candidate genes that may predispose to MM besides the well-characterized BRCA1-associated protein-1 gene. The aim of this review is to summarize the most important studies on germline mutations for MM. A total of 860 publications were retrieved from Scopus, PubMed and Web of Science, of which 81 met the inclusion criteria and were consider for this review. More than 50% of the genes that are reported to predispose to MM are involved in DNA repair mechanisms, and the majority of them have a role in the homologous recombination pathway. Genetic alterations in tumor suppressor genes involved in chromatin, transcription and hypoxia regulation have also been described. Furthermore, we identified several single nucleotide polymorphisms (SNPs) that may promote MM tumorigenesis as a result of an asbestos-gene interaction, including SNPs in DNA repair, carcinogen detoxification and other genes previously associated with other malignancies. The identification of inherited mutations for MM and an understanding of the underlying pathways may allow early detection and prevention of malignancies in high-risk individuals and pave the way for targeted therapies.

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

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

Copy Number Amplification of DNA Damage Repair Pathways Potentiates Therapeutic Resistance in Cancer

Rationale: Loss of DNA damage repair (DDR) in the tumor is an established hallmark of sensitivity to DNA damaging agents such as chemotherapy. However, there has been scant investigation into gain-of-function alterations of DDR genes in cancer. This study aims to investigate to what extent copy number amplification of DDR genes occurs in cancer, and what are their impacts on tumor genome instability, patient prognosis and therapy outcome.

Methods: Retrospective analysis was performed on the clinical, genomics, and pharmacogenomics data from 10,489 tumors, matched peripheral blood samples, and 1,005 cancer cell lines. The key discoveries were verified by an independent patient cohort and experimental validations.

Results: This study revealed that 13 of the 80 core DDR genes were significantly amplified and overexpressed across the pan-cancer scale. Tumors harboring DDR gene amplification exhibited decreased global mutation load and mechanism-specific mutation signature scores, suggesting an increased DDR proficiency in the DDR amplified tumors. Clinically, patients with DDR gene amplification showed poor prognosis in multiple cancer types. The most frequent Nibrin (NBN) gene amplification in ovarian cancer tumors was observed in 15 out of 31 independent ovarian cancer patients. NBN overexpression in breast and ovarian cancer cells leads to BRCA1-dependent olaparib resistance by promoting the phosphorylation of ATM-S1981 and homology-dependent recombination efficiency. Finally, integration of the cancer pharmacogenomics database of 37 genome-instability targeting drugs across 505 cancer cell lines revealed significant correlations between DDR gene copy number amplification and DDR drug resistance, suggesting candidate targets for increasing patient treatment response.

Principal Conclusions: DDR gene amplification can lead to chemotherapy resistance and poor overall survival by augmenting DDR. These amplified DDR genes may serve as actionable clinical biomarkers for cancer management.

Polymorphisms and rare variants identified by next-generation sequencing confer risk for lung cancer in han Chinese population

BACKGROUND

Lung cancer is one of the leading causes of cancer death worldwide, and genetic risk factors account for a large part of its carcinogenesis. The low economic requirements and high efficiency of next-generation sequencing (NGS) make it widely used in detecting genetic alterations in pathogenesis.

METHODS

We performed targeted panel sequencing in 780 Han Chinese lung cancer patients using a commercial probe, and the correlations between dozens of susceptible sites were verified in 1113 healthy controls. This study used Fisher's exact test and Benjamini-Hochberg FDR correction to analyze the mutual exclusion between mutated genes, and Pearson's p was used to verify the correlations between mutations and lung cancer susceptibility.

RESULTS

Our results determined the mutation spectrum and showed that each lung cancer patient carried at least one DNA mutation. The most frequently mutated gene was BRCA2 (mutation rate,10.6 %.). The co-occurrence and mutual exclusion analysis of DNA damage related genes showed that gene ATM was mutually exclusive from MSH6. We conducted a further case-control study in different subtypes of lung cancer and the results described 14 mutations associated with adenocarcinoma, 9 with squamous cell carcinoma, and 4 with small cell lung cancer. These variants were novel de-novo germline mutations in lung cancer. Particularly, rs3864017 in FANCD2 showed a protective effect of lung adenocarcinoma for carriers (OR = 0.146, 95 % CI = 0.052∼0.405, P_adjusted = 3.37 × 10^-4).

CONCLUSIONS

18 candidate mutations might alter the risk of lung cancer in the Han Chinese population, including polymorphisms rs3864017(FANCD2), rs55740729(MSH6) and 16 rare variants. The underlying mechanisms of candidate genes in lung cancer remain unclear and we suggest more functional studies on exploring how these genes affect the risk of lung cancer.

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.

Single nucleotide polymorphisms in DNA repair genes and putative cancer risk

Single nucleotide polymorphisms (SNPs) are the most frequent type of genetic alterations between individuals. An SNP located within the coding sequence of a gene may lead to an amino acid substitution and in turn might alter protein function. Such a change in protein sequence could be functionally relevant and therefore might be associated with susceptibility to human diseases, such as cancer. DNA repair mechanisms are known to play an important role in cancer development, as shown in various human cancer syndromes, which arise due to mutations in DNA repair genes. This leads to the question whether subtle genetic changes such as SNPs in DNA repair genes may contribute to cancer susceptibility. In numerous epidemiological studies, efforts have been made to associate specific SNPs in DNA repair genes with altered DNA repair and cancer. The present review describes some of the common and most extensively studied SNPs in DNA repair genes and discusses whether they are functionally relevant and subsequently increase the likelihood that cancer will develop.

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.

XRCC1 and OGG1 Gene Polymorphisms and Breast Cancer: A Systematic Review of Literature

Context:

Known polymorphisms of DNA repair genes can be associated with the risk of many types of cancer. There is no consensus regarding association between XRCC1 and OGG1 with breast cancer (BC).

Objectives:

The aim of this study is to collect relevant published studies systematically.

Data Sources:

Sixty-two publications were identified through searching PubMed, PubMed Central, ISI web of knowledge, and reference list of related articles.

Study Selection:

We performed a systematic review according MOOSE guideline criteria. All longitudinal cohort and case-control studies investigating association of any type and grade of breast cancer with XRCC1 and OGG1 gene and their polymorphisms were eligible for initial inclusion.

Data Extraction:

Two authors screened titles and abstracts and extracted all needed information from eligible studies. Four research methodological components causing bias for the association between gene polymorphisms and breast cancer risk, including source of controls sampling, population ethnicity, sample size of studies and menopausal status of cases and controls was used for assessment of quality of studies

Results:

A total of 14,793 breast cancer cases and 15,409 controls were included in assessment of XRCC1 Arg194Trp. Four studies showed significant association and one study showed protective effect of XRCC1 Arg194Trp and BC. A total of 7,716 cases and 7,370 controls were included for XRCC1 Arg280His. Only one study showed significant association of XRCC1 Arg280His and breast cancer (OR = 1.82 (1.06 - 3.15). A total of 27,167 cases and 31,998 controls were included to estimate association between XRCC1 Arg399Gln polymorphism and breast cancer. Seven studies showed significant association and one showed protective effect of XRCC1 Arg399Gln and BC. A total of 9,417 cases and 11,087 controls were included for OGG1 Ser326Cys. Among studies focused on OGG1 Ser326Cys, none showed significant association with breast cancer.

Conclusions:

Systematic search of major databases identify many studies addressing the relationship between BC and susceptible alleles in the base excision repair genes and the fact that there are many variations in the magnitude of association depending on inheritance model and the population of the study.

Association of DNA repair and xenobiotic pathway gene polymorphisms with genetic susceptibility to gastric cancer patients in West Bengal, India

Gastric cancer is one of the most common malignancies in India. DNA repair gene or xenobiotic pathway gene polymorphisms have recently been shown to affect individual susceptibility to gastric cancer. Here, the possible interaction between common polymorphisms in X-ray repair cross complementing group I (XRCC1) gene and glutathione S-transferase (GST) genes (GSTM1, GSTT1 and GSTP1), smoking and alcohol consumption and overall survival in gastric cancer patients were evaluated. In this population-based case control study, 70 gastric cancer patients and 82 healthy controls were enrolled. The epidemiological data were collected by a standard questionnaire, and blood samples were collected from each individual. XRCC1 Arg194Trp, Arg280His and Arg399Gln polymorphisms were determined by polymerase chain reaction and direct DNA sequencing. GSTM1 and GSTT1 null polymorphisms and GSTP1 Ile105Val polymorphism were identified by multiplex polymerase chain reaction and restriction fragment length polymorphism (RFLP), respectively. The risk of gastric cancer was significantly elevated in individuals with XRCC1 Arg/Gln +Gln/Gln (p = 0.031; odds ratio = 2.32; 95 % confidence interval (CI) 1.07-5.06) and GSTP1 Val/Val genotype (p = 0.009; odds ratio = 8.64; 95 % CI 1.84-40.55). An elevated risk for GC was observed in smokers and alcohol consumers carrying GSTP1 Ile/Val +Val/Val genotype (p = 0.041; odds ratio = 3.71; 95 % CI 0.98-14.12; p = 0.002; odds ratio = 12.31; 95 % CI 1.71-88.59). These findings suggest that XRCC1 rs25487 and GSTP1 rs1695 can be considered as a risk factor associated with gastric cancer and might be used as a molecular marker for evaluating the susceptibility of the disease.

Differentially expressed and activated proteins associated with non small cell lung cancer tissues

Background

Lung cancer is a leading cause of mortality. The most common cancer subtype, non small cell lung cancer (NSCLC), accounts for 85-90 % all cases and is mainly caused by environmental and genetic factors. Mechanisms involved in lung carcinogenesis include deregulation of several kinases and molecular pathways affecting cell proliferation, apoptosis and differentiation. Despite advances in lung cancer detection, diagnosis and staging, survival rate still remains poor and novel biomarkers for both diagnosis and therapy need to be identified. In the present study, we have explored the potential of novel specific biomarkers in the diagnosis of NSCLC, and the over-expression/activation of several kinases involved in disease development and progression.

Method

Lung tumor tissue specimens and adjacent cancer-free tissues from 8 NSCLC patients undergoing surgery were collected. The differential activation status of ERK1/2, AKT and IKBα/NF-κβ was analyzed. Subsequently, protein expression profile of NSCLC vs normal surrounding tissue was compared by a proteomic approach using LC-MS MS. Subsequently, MS/MS outputs were analyzed by the Protein Discoverer platform for label-free quantitation analysis. Finally, results were confirmed by western blotting analysis.

Results

This study confirms the involvement of ERK1/2, AKT, IKBα and NF-κβ proteins in NSCLC demonstrating a significant over-activation of all tested proteins. Furthermore, we found significant differential expression of 20 proteins (R_sc ≥ 1.50 or ≤ −1.50) of which 7 are under-expressed and 13 over-expressed in NSCLC lung tissues. Finally, we validated, by western blotting, the two most under-expressed NSCLC tissue proteins, carbonic anhydrase I and II isoforms.

Conclusion

Our data further support the possibility of developing both diagnostic tests and innovative targeted therapy in NSCLC. In addition to selective inhibitors of ERK1/2, AKT, IKBα and NF-κβ, as therapeutic options, our data, for the first time, indicates carbonic anhydrase I and II as attractive targets for development of diagnostic tools enabling selection of patients for a more specific therapy in NSCLC.

Note of clarification of data in the paper titled X-ray repair cross-complementing group 1 codon 399 polymorphism and lung cancer risk: an updated meta-analysis

We read with great interest the paper titled "X-ray repair cross-complementing group 1 codon 399 polymorphism and lung cancer risk: an updated meta-analysis" published by Wang et al in Tumor Biology, 2014, 35:411-418. Their results suggest that codon 399 polymorphism of XRCC1 gene might contribute to individual's susceptibility to lung cancer in Asian population and especially in nonsmoking Chinese women. The result is encouraging. Nevertheless, several key issues are worth noticing.

Tobacco smoking, family history, and the risk of nasopharyngeal carcinoma: a case-referent study in Hong Kong Chinese

PURPOSE

This study aimed to investigate the associations of tobacco smoking and family history of nasopharyngeal carcinoma (NPC) with the risk of NPC in Hong Kong Chinese.

METHODS

Between June 2010 and December 2012, we conducted a case-referent study with 352 incident cases and 410 referents in Hong Kong. We collected information on tobacco smoking and family history of NPC via face-to-face interviews.

RESULTS

There were 174 (49.4%) and 131 (32.0%) ever-smokers among cases and referents, respectively. The adjusted odds ratio (OR) for NPC related to current smoking was 1.67 [95% confidence interval (CI) 1.06, 2.61]. Exposure-response relationships were observed between years and total pack-years of smoking, and NPC risk (p = 0.001 and p = 0.018, respectively). History of NPC in first-degree relatives was associated with an increased NPC risk (adjusted OR = 4.52, 95% CI 2.39, 8.55). The increased NPC risk associated with sibling history (adjusted OR = 6.80, 95% CI 2.63, 17.56) was higher than that for parental history (adjusted OR = 3.04, 95% CI 1.27, 7.25). The adjusted OR for ever-smokers with family history using never-smokers without family history as the reference was 4.54 (95% CI 1.67, 12.34).

CONCLUSIONS

This study verified the important roles of tobacco smoking and family history on NPC risk among Hong Kong Chinese. The provided evidence supported the knowledge that both environmental exposures and inherited susceptibility contributed to the risk of NPC.

Effect of occupational exposures on lung cancer susceptibility: a study of gene-environment interaction analysis

BACKGROUND

Occupational exposures are known risk factors for lung cancer. Role of genetically determined host factors in occupational exposure-related lung cancer is unclear.

METHODS

We used genome-wide association (GWA) data from a case-control study conducted in 6 European countries from 1998 to 2002 to identify gene-occupation interactions and related pathways for lung cancer risk. GWA analysis was performed for each exposure using logistic regression and interaction term for genotypes, and exposure was included in this model. Both SNP-based and gene-based interaction P values were calculated. Pathway analysis was performed using three complementary methods, and analyses were adjusted for multiple comparisons. We analyzed 312,605 SNPs and occupational exposure to 70 agents from 1,802 lung cancer cases and 1,725 cancer-free controls.

RESULTS

Mean age of study participants was 60.1 ± 9.1 years and 75% were male. Largest number of significant associations (P ≤ 1 × 10(-5)) at SNP level was demonstrated for nickel, brick dust, concrete dust, and cement dust, and for brick dust and cement dust at the gene-level (P ≤ 1 × 10(-4)). Approximately 14 occupational exposures showed significant gene-occupation interactions with pathways related to response to environmental information processing via signal transduction (P < 0.001 and FDR < 0.05). Other pathways that showed significant enrichment were related to immune processes and xenobiotic metabolism.

CONCLUSION

Our findings suggest that pathways related to signal transduction, immune process, and xenobiotic metabolism may be involved in occupational exposure-related lung carcinogenesis.

IMPACT

Our study exemplifies an integrative approach using pathway-based analysis to demonstrate the role of genetic variants in occupational exposure-related lung cancer susceptibility. Cancer Epidemiol Biomarkers Prev; 24(3); 570-9. ©2015 AACR.

Analysis of polymorphisms in the circadian-related genes and breast cancer risk in Norwegian nurses working night shifts

Introduction

Some studies have suggested that night work may be associated with an increased risk of breast cancer in nurses. We aimed to explore the role of circadian gene polymorphisms in the susceptibility to night work-related breast cancer risk.

Methods

We conducted a nested case-control study of Norwegian nurses comprising 563 breast cancer cases and 619 controls within a cohort of 49,402 Norwegian nurses ages 35 to 74 years. We studied 60 single-nucleotide polymorphisms (SNPs) in 17 genes involved in the regulation of the circadian rhythm in cases and controls. The data were analyzed in relation to the two exposure variables "maximum number of consecutive night shifts ever worked" and "maximum number of consecutive night shifts worked for at least 5 years." The odds of breast cancer associated with each SNP was calculated in the main effects analysis and in relation to night shift work. The statistically significant odds ratios were tested for noteworthiness using two Bayesian tests: false positive report probability (FPRP) and Bayesian false discovery probability (BFDP).

Results

In the main effects analysis, CC carriers of rs4238989 and GG carriers of rs3760138 in the AANAT gene had increased risk of breast cancer, whereas TT carriers of BMAL1 rs2278749 and TT carriers of CLOCK rs3749474 had reduced risk. The associations were found to be noteworthy using both the FPRP and BFDP tests. With regard to the effect of polymorphisms and night work, several significant associations were observed. After applying FPRP and BFDP in women with at least four night shifts, an increased risk of breast cancer was associated with variant alleles of SNPs in the genes AANAT (rs3760138, rs4238989), BMAL1 (rs2290035, rs2278749, rs969485) and ROR-b (rs3750420). In women with three consecutive night shifts, a reduced risk of breast cancer was associated with carriage of variant alleles of SNPs in CLOCK (rs3749474), BMAL1 (rs2278749), BMAL2 (rs2306074), CSNK1E (rs5757037), NPAS2 (rs17024926), ROR-b (rs3903529, rs3750420), MTNR1A (rs131113549) and PER3 (rs1012477).

Conclusions

Significant and noteworthy associations between several polymorphisms in circadian genes, night work and breast cancer risk were found among nurses who had worked at least three consecutive night shifts.

Epidemiological data and cancer risk assessment: cessation LAG and lingering effect concepts

Cessation lag and lingering effect are two important aspects of risk assessment, and have potential applications to dose-response analysis in risk assessment. In addition to providing insight into biological mode of action, the concept of cessation lag is useful for economic benefit analy- sis. Concept of effect lingering can be used to analyze epidemiological data by uncovering the hidden biological implications related to disease endpoints, thereby advancing current efforts to characterize and reduce risk assessment uncertainties. Multicentre study design is proposed as a way to increase study size and to mitigate criticism of meta-analysis of independent studies. Individual studies from a multicentre study can be either pooled using original data, or combined by meta-analysis of summarized results. A multicentre study of large cohort or case-control study also offers an exciting opportunity to study the contribution of epigenetic events that may be associated with life-style and environmental risk factors for human health. Methods for optimizing exposure assessment and reducing exposure misclassification represent important but difficult components in epidemiological studies. Biomarkers present a potentially useful approach for improving exposure estimates.

Putative functional variants of XRCC1 identified by RegulomeDB were not associated with lung cancer risk in a Korean population

The Encyclopedia of DNA elements (ENCODE) project revealed that nearby or distantly located non-coding DNA regulates the expression of coding genes. RegulomeDB (http://regulome.stanford.edu) is a new database that can be used to predict whether a variant affects transcription factor binding and gene expression. We investigated the association between lung cancer risk and potentially functional polymorphisms of XRCC1 that were selected using RegulomeDB in a Korean population. A total of 185 polymorphisms of XRCC1 were evaluated using RegulomeDB. Strong evidence suggested that 10 polymorphisms, from among the 185, affected XRCC1 expression with scores of 1a-1f that were based on the RegulomeDB scoring system. The rs2854510 polymorphism was rare in Asians (minor allele frequency < 0.05). Eight polymorphisms were in strong linkage disequilibrium (LD). The rs2854509 polymorphism, which was one of the 8 polymorphisms in LD, and rs7248167, which was not in the LD block, were genotyped in 610 lung cancer patients and 607 age- and sex-matched controls. Additionally, four polymorphisms of XRCC1 (rs25487, rs25489, rs1799782, and rs3213245), which were investigated with regard to their association with lung cancer risk in previous studies, were also genotyped. Two polymorphisms (rs2854509 and rs7248167) that were predicted to affect XRCC1 expression based on their RegulomeDB scores were not associated with lung cancer risk (P = 0.31 and 0.93, respectively). When stratified according to age, gender, smoking status, and tumor histology, the two polymorphisms of XRCC1 were not associated with lung cancer risk. Among the four polymorphisms that were previously studied, only rs25489 of XRCC1 was significantly associated with lung cancer risk (dominant model, adjusted odds ratio = 0.61, 95% confidence interval = 0.46-0.83, P = 0.002). Although RegulomeDB is an attractive tool for predicting the regulatory potential of variants, the two polymorphisms that were selected using RegulomeDB were not associated with lung cancer risk.

XRCC-1 Gene Polymorphism (Arg399Gln) and Susceptibility to Development of Lung Cancer in Cohort of North Indian Population: A Pilot Study

BACKGROUND

Smoking has been considered to be the major cause of lung cancer. However, only a fraction of cigarette smokers develop this disease. This suggests the importance of genetic constitution in predicting the individual's susceptibility towards lung cancer. This genetic susceptibility may result from inherited polymorphisms in genes controlling carcinogen metabolism and repair of damaged deoxyribonucleic acid (DNA). These repair systems are fundamental to the maintenance of genomic integrity. X-ray repair cross complimenting group I (XRCC1), a major DNA repair gene in the base excision repair (BER) pathway. It is involved in repair by interacting with components of DNA at the site of damage. Inconsistent results have been reported regarding the associations between the Arg399Gln polymorphism of XRCC1. This study demonstrates the importance of recognition of this relationship of lung carcinoma and genetic constitution of the person which will help guide clinicians on the optimal screening of this disease.

AIM

To assess the role of XRCC1 gene polymorphism (Arg399Gln) directly on the variation in susceptibility to development of lung cancer in North Indian subjects.

MATERIALS AND METHODS

One hundred males with diagnosed cases of lung cancer were recruited from Delhi State Cancer Institute (DSCI). Hundred healthy volunteers were taken as controls. DNA isolation was done and Polymerase chain reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) procedure undertaken to amplify the region containing Arg/Gln substitution at codon 399 (in exon 10).

RESULTS

XRCC1 gene polymorphism is associated with increased risk of lung cancer when the Arg/Arg genotype was used as the reference group. The Arg/Gln and Gln/Gln was associated with statistically increased risk for cancer.

CONCLUSION

Arg399Gln polymorphism in XRCC1 gene polymorphism is associated with lung cancer in North Indian subjects and screening for this polymorphism will help in targeting predisposed individuals and its prevention.

Association between the XRCC1 Arg194Trp polymorphism and risk of cancer: evidence from 201 case-control studies

The Arg194Trp polymorphism in the X-ray cross-complementing group 1 (XRCC1) had been implicated in cancer susceptibility. The previous published data on the association between XRCC1 Arg194Trp polymorphism and cancer risk remained controversial. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and XRCC1 Arg194Trp (59,227 cases and 81,587 controls from 201 studies) polymorphism in different inheritance models. We used odds ratios with 95 % confidence intervals to assess the strength of the association. Overall, significantly increased cancer risk was found (recessive model: (odds ration [OR] = 1.18, 95% confidence interval [CI] = 1.09-1.27; homozygous model: OR = 1.21, 95% CI = 1.10-1.33; additive model: OR = 1.05, 95% CI = 1.01-1.09) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, significantly increased glioma risk was found among Asians, significantly decreased lung cancer risk was found among Caucasians, and significant increased breast cancer risk was found among hospital-based studies. In summary, this meta-analysis suggests that Arg194Trp polymorphism may be associated with increased breast cancer risk, Arg194Trp polymorphism is associated with increased glioma risk among Asians, and Arg194Trp polymorphism is associated with decreased lung cancer risk among Caucasians. In addition, our work also points out the importance of new studies for Arg194Trp association in some cancer types, such as gastric, pancreatic, prostate, and nasopharyngeal cancers, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC1 Arg194Trp polymorphism in cancer development (I (2) > 75%).

Polymorphism of DNA repair gene xrcc1 and lung cancer risk

The current large-scale meta-analysis was performed to reach a reliable conclusion on the association between X-ray repair cross-complementing 1 (xrcc1) rs1799782 and the development of lung cancer. Studies that investigated the association between rs1799782 and lung cancer risk were identified by searching PubMed. We calculated odds ratio (OR) with corresponding 95 % confidence interval (CI) for Trp/Trp vs Arg/Arg, Trp/Trp + Arg/Trp vs Arg/Arg, and Trp/Trp vs Arg/Trp + Arg/Arg contrast models. Combining all 25 studies, we yielded three summary ORs: 1.07 (95 % CI 0.92-1.23) for Trp/Trp vs Arg/Arg, 0.93 (95 % CI 0.87-1.00) for Trp/Trp + Arg/Trp vs Arg/Arg, and 1.08 (95 % CI 0.94-1.25) for Trp/Trp vs Arg/Trp + Arg/Arg, suggesting rs1799782 was not associated with overall risk of lung cancer. Strikingly, a significantly deceased risk was found among Caucasian populations (Trp/Trp + Arg/Trp vs Arg/Arg, OR = 0.86, 95 % CI 0.76-0.97). This study confirms that xrcc1 rs1799782 may lower the risk of lung cancer among Caucasians.

Exposure to secondhand tobacco smoke and lung cancer by histological type: a pooled analysis of the International Lung Cancer Consortium (ILCCO)

While the association between exposure to secondhand smoke and lung cancer risk is well established, few studies with sufficient power have examined the association by histological type. In this study, we evaluated the secondhand smoke-lung cancer relationship by histological type based on pooled data from 18 case-control studies in the International Lung Cancer Consortium (ILCCO), including 2,504 cases and 7,276 control who were never smokers and 10,184 cases and 7,176 controls who were ever smokers. We used multivariable logistic regression, adjusting for age, sex, race/ethnicity, smoking status, pack-years of smoking, and study. Among never smokers, the odds ratios (OR) comparing those ever exposed to secondhand smoke with those never exposed were 1.31 (95% CI: 1.17-1.45) for all histological types combined, 1.26 (95% CI: 1.10-1.44) for adenocarcinoma, 1.41 (95% CI: 0.99-1.99) for squamous cell carcinoma, 1.48 (95% CI: 0.89-2.45) for large cell lung cancer, and 3.09 (95% CI: 1.62-5.89) for small cell lung cancer. The estimated association with secondhand smoke exposure was greater for small cell lung cancer than for nonsmall cell lung cancers (OR=2.11, 95% CI: 1.11-4.04). This analysis is the largest to date investigating the relation between exposure to secondhand smoke and lung cancer. Our study provides more precise estimates of the impact of secondhand smoke on the major histological types of lung cancer, indicates the association with secondhand smoke is stronger for small cell lung cancer than for the other histological types, and suggests the importance of intervention against exposure to secondhand smoke in lung cancer prevention.

No association between XRCC1 gene Arg194Trp polymorphism and risk of lung cancer: evidence based on an updated cumulative meta-analysis

X-ray repair cross-complementing group 1 (XRCC1) gene Arg194Trp polymorphism has been reported to be associated with risk of lung cancer in many published studies. Nevertheless, the research results were inconclusive and conflicting. To reach conclusive results, several meta-analysis studies were conducted by combining results from literature reports through pooling analysis. However, these previous meta-analysis studies were still not consistent. Hence, we used an updated and cumulative meta-analysis to get a more comprehensive and precise result from 25 case–control studies searching through the PubMed database up to September 1, 2013. The meta-analysis was carried out by the Comprehensive Meta-Analysis software and the odds ratio (OR) with 95 % confidence interval (CI) was used to estimate the pooled effect. The result involving 8,876 lung cancer patients and 11,210 controls revealed that XRCC1 Arg194Trp polymorphism was not associated with lung cancer risk [(OR = 0.97, 95 %CI = 0.92–1.03) for Trp vs. Arg; (OR = 0.92, 95 % CI = 0.85–0.98) for ArgTrp vs. ArgArg; (OR = 1.07, 95 % CI = 0.92–1.23) for TrpTrp vs. ArgArg; (OR = 0.93, 95 % CI = 0.87–1.00) for (TrpTrp + ArgTrp) vs. ArgArg; and (OR = 1.08, 95 % CI = 0.94–1.25) for TrpTrp vs. (ArgTrp + ArgArg)]. The cumulative meta-analysis showed that the results maintained the same, while the ORs with 95 % CI were more stable with the accumulation of case–control studies. The sensitivity and subgroups analyses showed that the results were robust and not affected by any single study with no publication bias. Relevant studies might not be needed for supporting these results.

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.

DNA repair pathway genes and lung cancer susceptibility: a meta-analysis

OBJECTIVE

DNA repair pathway genes have been implicated to play an important role in the development of lung cancer. However, contradictory results are often reported by various studies, making it difficult to interpret them. So in this meta-analysis, we have assessed the association between lung cancer risk and two DNA repair pathway genes. XRCC1 and ERCC2, by analyzing 67 published case-control studies.

RESEARCH DESIGN AND METHODS

We searched PubMed, Embase and Web of Science using terms "XRCC1" or "XPD" or "ERCC2" and "lung cancer" on August 1, 2012. Three criteria were applied to select included studies for resulting studies. Information was carefully extracted by two investigators independently. We used pooled odds ratio (OR) to assess the effect of a polymorphism, and a dominant model was applied where genotypes that contain the non-reference allele were combined together. All the calculations were performed using STATA version 11.0.

MAIN OUTCOME MEASURES AND RESULTS

Three common nonsynonymous polymorphisms in XRCC1, codon 194, codon 280 and codon 399, and two common nonsynonymous polymorphisms in ERCC2, codon 312 and codon 751, were analyzed. The result showed in total population, Lys751Gln in ERCC2 is associated with an increase of lung cancer risk, with a summary OR as 1.15. No association was found for any other polymorphisms. When studies were stratified by ethnicity, the risk effect of Lys751Gln in ERCC2 was found only in Caucasians, not in Asians.

CONCLUSIONS

In conclusion, Lys751Gln in ERCC2 is associated with lung cancer, and the risk effect probably exists in Caucasians. By contrast, polymorphisms in XRCC1 are less likely to be susceptible to lung cancer risks.

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.

Association between XRCC1 and XRCC3 polymorphisms with lung cancer risk: a meta-analysis from case-control studies

Many studies have reported the association of X-ray repair cross-complementing group 1 (XRCC1) Arg399Gln, Arg194Trp, Arg280His, −77T>C, and X-ray repair cross-complementing group 3 (XRCC3) T241M polymorphisms with lung cancer risk, but the results remained controversial. Hence, we performed a meta-analysis to investigate the association between lung cancer risk and XRCC1 Arg399Gln (14,156 cases and 16,667 controls from 41 studies), Arg194Trp (7,426 cases and 9,603 controls from 23 studies), Arg280His (6,211 cases and 6,763 controls from 16 studies), −77T>C (2,487 cases and 2,576 controls from 5 studies), and XRCC3 T241M (8,560 cases and 11,557 controls from 19 studies) in different inheritance models. We found that −77T>C polymorphism was associated with increased lung cancer risk (dominant model: odds ration [OR] = 1.45, 95% confidence interval [CI] = 1.27–1.66, recessive model: OR = 1.73, 95% CI = 1.14–2.62, additive model: OR = 1.91, 95% CI = 1.24–1.94) when all the eligible studies were pooled into the meta-analysis. In the stratified and sensitive analyses, significantly decreased lung cancer risk was observed in overall analysis (dominant model: OR = 0.83, 95% CI = 0.78–0.89; recessive model: OR = 0.90, 95% CI = 0.81–1.00; additive model: OR = 0.82, 95% CI = 0.74–0.92), Caucasians (dominant model: OR = 0.82, 95% CI = 0.76–0.87; recessive model: OR = 0.89, 95% CI = 0.80–0.99; additive model: OR = 0.81, 95% CI = 0.73–0.91), and hospital-based controls (dominant model: OR = 0.81, 95% CI = 0.76–0.88; recessive model: OR = 0.89, 95% CI = 0.79–1.00; additive model: OR = 0.80, 95% CI = 0.71–0.90) for XRCC3 T241M. In conclusion, this meta-analysis indicates that XRCC1 −77T>C shows an increased lung cancer risk and XRCC3 T241M polymorphism is associated with decreased lung cancer risk, especially in Caucasians.

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.

DNA repair and cytotoxic drugs: the potential role of RAD51 in clinical outcome of non-small-cell lung cancer patients

Many of the cytotoxic drugs used in the treatment of non-small-cell lung carcinoma patients can interfere with DNA activity and the definition of an individual DNA repair profile could be a key strategy to achieve better response to chemotherapeutic treatment. Although DNA repair mechanisms are important factors in the prevention of carcinogenesis, these molecular pathways are also involved in therapy response. RAD51 is a crucial element in DNA repair by homologous recombination and has been shown to interfere with the prognosis of patients treated with chemoradiotherapy. There is increasing evidence that genetic polymorphisms in repair enzymes can influence DNA repair capacity and, consequently, affect chemotherapy efficacy. We conducted this review to show the possible influence of the RAD51 genetic variants in damage repair capacity and treatment response in non-small-cell lung carcinoma patients.

Genetic susceptibility to lung cancer--light at the end of the tunnel?

Lung cancer is one of the most common and deadliest cancers in the world. The major socio-environmental risk factor involved in the development of lung cancer is cigarette smoking. Additionally, there are multiple genetic factors, which may also play a role in lung cancer risk. Early work focused on the presence of relatively prevalent but low-penetrance alterations in candidate genes leading to increased risk of lung cancer. Development of new technologies such as genomic profiling and genome-wide association studies has been helpful in the detection of new genetic variants likely involved in lung cancer risk. In this review, we discuss the role of multiple genetic variants and review their putative role in the risk of lung cancer. Identifying genetic biomarkers and patterns of genetic risk may be useful in the earlier detection and treatment of lung cancer patients.

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.

Impact of DNA polymorphisms in key DNA base excision repair proteins on cancer risk

Genetic variation in DNA repair genes can modulate DNA repair capacity and may be related to cancer risk. However, study findings have been inconsistent. Inheritance of variant DNA repair genes is believed to influence individual susceptibility to the development of environmental cancer. Reliable knowledge on which the base excision repair (BER) sequence variants are associated with cancer risk would help elucidate the mechanism of cancer. Given that most of the previous studies had inadequate statistical power, we have conducted a systematic review on sequence variants in three important BER proteins. Here, we review published studies on the association between polymorphism in candidate BER genes and cancer risk. We focused on three key BER genes: 8-oxoguanine DNA glycosylase (OGG1), apurinic/apyrimidinic endonuclease (APE1/APEX1) and x-ray repair cross-complementing group 1 (XRCC1). These specific DNA repair genes were selected because of their critical role in maintaining genome integrity and, based on previous studies, suggesting that single-nucleotide polymorphisms (SNPs) in these genes have protective or deleterious effects on cancer risk. A total of 136 articles in the December 13, 2010 MEDLINE database (National Center for Biotechnology Information, http://www.ncbi.nlm.nih.gov/pubmed/) reporting polymorphism in OGG1, XRCC1 or APE1 genes were analyzed. Many of the reported SNPs had diverse association with specific human cancers. For example, there was a positive association between the OGG1 Ser326Cys variant and gastric and lung cancer, while the XRCC1 Arg399Gln variant was associated with reduced cancer risk. Gene-environment interactions have been noted and may be important for colorectal and lung cancer risk and possibly other human cancers.

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.

XRCC1 gene polymorphisms and lung cancer susceptibility: a meta-analysis of 44 case-control studies

X-ray repair cross-complementing group 1 gene (XRCC1) has been implicated in risk for lung cancer. However, the results from different studies remain controversial. In this meta-analysis, we have assessed 44 published case-control studies regarding associations of lung cancer risk with three common polymorphisms, codon 194, codon 280 and codon 399, and -77 T > C in the promoter region of XRCC1. The results in total population showed that the risk for lung cancer was increased among the variant homozygote Trp/Trp of codon 194 polymorphism, compared with the wild type Arg/Arg (OR: 1.19; 95 % CI 1.01-1.39), and the variant genotype CC of -77 T > C polymorphism showed a significantly increased risk of developing lung cancer, compared to wild-type genotype TT (OR: 1.91; 95 % CI 1.24-2.94). However, no associations were found between lung cancer risk and codon 280, codon 399. In the subgroup analyses by ethnicity, the OR for the variant homozygote Trp/Trp of codon 194 was 1.21(95 % CI 1.02-1.43) for Asian. When stratified by source of control, we found a protective effect of codon 194 Arg/Trp genotype (OR: 0.87; 95 % CI 0.77-0.98) and risk effect of codon 399 combined Arg/Gln + Gln/Gln variant genotype (OR: 1.09; 95 % CI 1.01-1.18) for lung cancer on the basis of hospital control. Subgroup analyses by histological types of lung cancer indicated that the heterozygote Arg/Trp in codon 194 could decrease and the combined variant genotype Arg/Gln + Gln/Gln in codon 399 could increase the risk of non-small cell lung cancer (OR: 0.69; 95 % CI 0.57-0.85 and OR: 1.14; 95 % CI 1.04-1.24). In conclusion, this meta-analysis has demonstrated that codon 194, codon 399 and -77 T > C polymorphisms of XRCC1 gene might have contributed to individual susceptibility to lung cancer. To further evaluate effect of XRCC1 polymorphisms, gene-gene interaction and gene-environment interaction on lung cancer risk, a single large sample size study with thousands of subjects is required to get conclusive results.

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.

Against Lung Cancer Cells: To Be, or Not to Be, That Is the Problem

Tobacco smoke and radioactive radon gas impose a high risk for lung cancer. The radon-derived ionizing radiation and some components of cigarette smoke induce oxidative stress by generating reactive oxygen species (ROS). Respiratory lung cells are subject to the ROS that causes DNA breaks, which subsequently bring about DNA mutagenesis and are intimately linked with carcinogenesis. The damaged cells by oxidative stress are often destroyed through the active apoptotic pathway. However, the ROS also perform critical signaling functions in stress responses, cell survival, and cell proliferation. Some molecules enhance radiation-induced tumor cell killing via the reduction in DNA repair levels. Hence the DNA repair levels may be a novel therapeutic modality in overcoming drug resistance in lung cancer. Either survival or apoptosis, which is determined by the balance between DNA damage and DNA repair levels, may lender the major problems in cancer therapy. The purpose of this paper is to take a closer look at risk factor and at therapy modulation factor in lung cancer relevant to the ROS.

Influence of the OGG1 Ser326Cys polymorphism on oxidatively damaged DNA and repair activity

Oxidatively damaged DNA base lesions are considered to be mainly repaired by 8-oxoguanine DNA glycosylase (OGG1) mediated pathways. We investigated the effect of the OGG1 Ser326Cys polymorphism on the level and repair of oxidatively damaged DNA in mononuclear blood cells (MNBC) by means of the comet assay. We collected blood samples from 1,019 healthy subjects and genotyped for the OGG1 Ser326Cys polymorphism. We found 49 subjects homozygous for the variant genotype (Cys/Cys) and selected same numbers of age-matched subjects with the heterozygous (Ser/Cys) and homozygous wild-type genotype (Ser/Ser). Carriers of the Cys/Cys genotype had higher levels of formamidopyrimidine DNA glycosylase (FPG) sensitive sites in MNBC (0.31 ± 0.03 lesions/10(6)bp) compared to Ser/Ser (0.19 ± 0.02 lesions/10(6)bp, P<0.01). The level of hOGG1 sensitive sites in MNBC from the Ser326Cys carriers (0.19 ± 0.16 lesions/10(6) bp) was also higher compared to the Ser/Ser genotype (0.11 ± 0.09 lesions/10(6) bp, P<0.05). Still, there was no genotype-related difference in DNA repair incision activity of MNBC extracts on nucleoids with oxidatively damaged DNA induced by Ro19-8022/white light (P=0.20). In addition, there were no differences in the expression of OGG1 (P=0.69), ERCC1 (P=0.62), MUTYH (P=0.85), NEIL1 (P=0.17) or NUDT1 (P=0.48) in whole blood. Our results indicate that the OGG1 Ser326Cys polymorphism has limited influence on the DNA repair incisions by extracts of MNBC, whereas the apparent increased risk of cancer in subjects with the Cys/Cys genotype may be because of higher levels of oxidatively damaged DNA.

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.