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

Radon, Tobacco Exposure and Non-Small Cell Lung Cancer Risk Related to BER and NER Genetic Polymorphisms

INTRODUCTION

Tobacco consumption and radon exposure are considered the first and second most common causes of lung cancer, respectively. The aim of this study was to analyze both whether selected genetic polymorphisms in loci that are in DNA repair pathways, are related to non-small-cell lung cancer (NSCLC) and whether they may modulate the association between residential radon exposure and lung cancer in both smokers and never smokers.

METHODS

A multicentre, hospital-based, case-control study with 826 cases and 1201 controls was designed in a radon-prone area. Genotyping was determined in whole blood and residential radon exposure was measured in participants' dwellings.

RESULTS

Attending to tobacco exposure, the variant in the gene NBN (rs1805794) was associated with lung cancer in never smokers (OR 2.72; 95%1.44-5.2) and heavy smokers (OR 3.04; 95%CI 1.21-7.69). The polymorphism with the highest lung cancer association was OGG1 (rs125701), showing an OR of 8.04 (95%CI 1.64-58.29) for its homozygous variant genotype in heavy smokers. Attending to indoor radon exposure (>200Bq/m3), rs1452584, for its homozygous variant genotype, showed the highest association (OR 3.04 (95%CI 1.15-8.48).

CONCLUSION

The genes analyzed seem to have no association with the fully adjusted model, but they might modulate lung cancer association when different categories of tobacco consumption are considered (i.e. heavy smokers). This association may similarly be elevated for those individuals having high indoor radon exposures, though at a minor extent.

Chromatin and other obstacles to base excision repair: potential roles in carcinogenesis

DNA is comprised of chemically reactive nucleobases that exist under a constant barrage from damaging agents. Failure to repair chemical modifications to these nucleobases can result in mutations that can cause various diseases, including cancer. Fortunately, the base excision repair (BER) pathway can repair modified nucleobases and prevent these deleterious mutations. However, this pathway can be hindered through several mechanisms. For instance, mutations to the enzymes in the BER pathway have been identified in cancers. Biochemical characterisation of these mutants has elucidated various mechanisms that inhibit their activity. Furthermore, the packaging of DNA into chromatin poses another obstacle to the ability of BER enzymes to function properly. Investigations of BER in the base unit of chromatin, the nucleosome core particle (NCP), have revealed that the NCP acts as a complex substrate for BER enzymes. The constituent proteins of the NCP, the histones, also have variants that can further impact the structure of the NCP and may modulate access of enzymes to the packaged DNA. These histone variants have also displayed significant clinical effects both in carcinogenesis and patient prognosis. This review focuses on the underlying molecular mechanisms that present obstacles to BER and the relationship of these obstacles to cancer. In addition, several chemotherapeutics induce DNA damage that can be repaired by the BER pathway and understanding obstacles to BER can inform how resistance and/or sensitivity to these therapies may occur. With the understanding of these molecular mechanisms, current chemotherapeutic treatment regiments may be improved, and future therapies developed.

The Therapeutic Potential of DNA Damage Repair Pathways and Genomic Stability in Lung Cancer

Despite advances in our understanding of the molecular biology of the disease and improved therapeutics, lung cancer remains the most common cause of cancer-related deaths worldwide. Therefore, an unmet need remains for improved treatments, especially in advanced stage disease. Genomic instability is a universal hallmark of all cancers. Many of the most commonly prescribed chemotherapeutics, including platinum-based compounds such as cisplatin, target the characteristic genomic instability of tumors by directly damaging the DNA. Chemotherapies are designed to selectively target rapidly dividing cells, where they cause critical DNA damage and subsequent cell death (1, 2). Despite the initial efficacy of these drugs, the development of chemotherapy resistant tumors remains the primary concern for treatment of all lung cancer patients. The correct functioning of the DNA damage repair machinery is essential to ensure the maintenance of normal cycling cells. Dysregulation of these pathways promotes the accumulation of mutations which increase the potential of malignancy. Following the development of the initial malignancy, the continued disruption of the DNA repair machinery may result in the further progression of metastatic disease. Lung cancer is recognized as one of the most genomically unstable cancers (3). In this review, we present an overview of the DNA damage repair pathways and their contributions to lung cancer disease occurrence and progression. We conclude with an overview of current targeted lung cancer treatments and their evolution toward combination therapies, including chemotherapy with immunotherapies and antibody-drug conjugates and the mechanisms by which they target DNA damage repair pathways.

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.

Oxidative stress and DNA damage in the mechanism of fetal alcohol spectrum disorders

This review covers molecular mechanisms involving oxidative stress and DNA damage that may contribute to morphological and functional developmental disorders in animal models resulting from exposure to alcohol (ethanol, EtOH) in utero or in embryo culture. Components covered include: (a) a brief overview of EtOH metabolism and embryopathic mechanisms other than oxidative stress; (b) mechanisms within the embryo and fetal brain by which EtOH increases the formation of reactive oxygen species (ROS); (c) critical embryonic/fetal antioxidative enzymes and substrates that detoxify ROS; (d) mechanisms by which ROS can alter development, including ROS-mediated signal transduction and oxidative DNA damage, the latter of which leads to pathogenic genetic (mutations) and epigenetic changes; (e) pathways of DNA repair that mitigate the pathogenic effects of DNA damage; (f) related indirect mechanisms by which EtOH enhances risk, for example by enhancing the degradation of some DNA repair proteins; and, (g) embryonic/fetal pathways like NRF2 that regulate the levels of many of the above components. Particular attention is paid to studies in which chemical and/or genetic manipulation of the above mechanisms has been shown to alter the ability of EtOH to adversely affect development. Alterations in the above components are also discussed in terms of: (a) individual embryonic and fetal determinants of risk and (b) potential risk biomarkers and mitigating strategies. FASD risk is likely increased in progeny which/who are biochemically predisposed via genetic and/or environmental mechanisms, including enhanced pathways for ROS formation and/or deficient pathways for ROS detoxification or DNA repair.

DNA Base-Excision Repair Genes OGG1 and NTH1 in Brazilian Lung Cancer Patients

INTRODUCTION

Lung cancer is the leading global cause of cancer-related mortality and is associated with poor prognosis. To improve survival rates of lung cancer patients, better understanding of tumorigenic mechanisms is necessary, which may lead to development of new therapeutic strategies. The hOGG1 and NTH1 genes act in the DNA BER repair pathway and their involvement in lung cancer pathogenesis has been analyzed in several populations.

METHODS

We analyzed targeted regions of the hOGG1 and NTH1 genes in 96 Brazilian patients with non-small-cell lung cancer (NSCLC) and 89 cancer-free, ethnically matched controls.

RESULTS

The NTH1 c.98G>T polymorphism rs2302172 (p = 0.02 and p = 0.02 for allele and genotype frequency between cases and controls, respectively) and the 140-17C> T variant (rs2233518) (p = 0.02 and p = 0.02 for allele and genotype frequency between cases and controls, respectively) were detected in four lung cancer cases (4 %) while the NTH1 Q131K (C391A) polymorphism was found in seven lung cancer cases (7 %) (p = 0.001 and p = 0.008, for allele and genotype frequency between cases and controls, respectively). None of these sequence variants were detected in controls. The Ser326Cys (C1245G, rs1052133) polymorphism in the OGG1 gene was detected in 42 % of analyzed NSCLC patients and in 34 % of the controls (p = 0.11 and p = 0.25 for allele and genotype frequency between cases and controls, respectively).

CONCLUSIONS

Our study provides preliminary evidence that polymorphisms in OGG1 do not contribute to development of NSCLC in Brazilian patients and that NTH1 polymorphisms may be associated with NSCLC pathogenesis.

Analysis of oxidative DNA damage and its repair in Polish patients with diabetes mellitus type 2: Role in pathogenesis of diabetic neuropathy

PURPOSE

Distal symmetric polyneuropathy (DSPN) is common complication of type 2 diabetes (T2DM). In this work we investigated the role of oxidative damage in connection with particular polymorphisms of DNA repair genes and their repair capacity.

MATERIAL/METHODS

Materials constitute the peripheral blood of patients with T2DM with and without DSPN and control subjects without disturbance of the carbohydrate fraction. The study of gene polymorphisms which products take part in base excision repair (BER) pathway: 726 Val/Ala adenosine diphosphate ribosyl transferase (ADPRT), 324 His/Glu MutYhomolog (MUTYH) and 148 Asp/Glu human apurinic/apyrimidinic endonuclease (APE) was carried out using restriction fragment length polymorphism polymerase chain reaction (PCR-RFLP) method. The study of DNA damage induced by hydrogen peroxide and the efficiency of their repair was carried out using comet assay.

RESULTS

None of the 3 polymorphisms were associated with the risk of DSPN. However, in group of patients together with T2DM and T2DM/DSPN 726 Ala ADPRT allele was significantly susceptible to increased risk of T2DM (OR=1.59; 95% CI: 1.08-2.36). Investigation of DNA damage and repair revealed that T2DM patients have decreased ability to DNA repair. This capacity even drops down in the group of T2DM/DSPN patients compared to subjects with diabetes alone. ADPRT and APE polymorphisms were significantly associated with higher DNA damages (P<0.05) in heterozygous and mutant homozygous in correlation to homozygous wild type, but for MUTYH polymorphism relation was not confirmed.

CONCLUSIONS

Pathogenesis of T2DM and development of DSPN may be related to oxidative stress connected with BER gene polymorphisms.

The interaction of APEX1 variant with polycyclic aromatic hydrocarbons on increasing chromosome damage and lung cancer risk among male Chinese

Polycyclic aromatic hydrocarbons (PAHs) are the most significant contributors to tobacco-induced lung carcinogenesis. Apurinic/apyrimidinic endonuclease 1 (APE1) is a central enzyme in the removal of apurinic/apyrimidinic sites caused by DNA damaging agents. This study aimed to investigate the potential interaction of APEX1 polymorphisms and PAHs on genetic damage and lung cancer risk among male Chinese. We recruited an occupational cohort of 922 male coke oven workers and determined their DNA damage levels by calculating the lymphocytic micronucleus (MN) frequencies. Two well-studied APEX1 polymorphisms (-307A > C and Asp148Glu) and their associations with MN frequencies were examined. The impact of MN-related single nucleotide polymorphism (SNP) on lung cancer risk was further investigated in two case-control studies including 1634 male lung cancer patients and 1678 controls. It was shown that, the APEX1 148Glu allele was associated with significantly higher MN frequencies than 148Asp allele, with strongest associations among the highest PAH-exposure workers (P = 0.008). The APEX1 148Glu allele was also associated with increased lung cancer risk among male smokers, especially among heavy smokers in both case-control studies (odd ratio: 4.40, 95%CI: 3.29-5.72). In addition, APEX1 148Glu variant interacts with smoking in increasing male lung cancer risk, as measured by the attributable proportion due to interaction, which was 0.23 (95%CI: 0.06-0.39). This study showed evidence on interaction between APEX1 148Glu variant and cigarette smoking in increasing lung cancer susceptibility among male Chinese, which may be due to the synergistic effects of APEX1 148Glu and PAHs in increasing chromosome damage levels. The results provide a new insight into gene-interactions in lung carcinogenesis.

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.

DNA glycosylases involved in base excision repair may be associated with cancer risk in BRCA1 and BRCA2 mutation carriers

Single Nucleotide Polymorphisms (SNPs) in genes involved in the DNA Base Excision Repair (BER) pathway could be associated with cancer risk in carriers of mutations in the high-penetrance susceptibility genes BRCA1 and BRCA2, given the relation of synthetic lethality that exists between one of the components of the BER pathway, PARP1 (poly ADP ribose polymerase), and both BRCA1 and BRCA2. In the present study, we have performed a comprehensive analysis of 18 genes involved in BER using a tagging SNP approach in a large series of BRCA1 and BRCA2 mutation carriers. 144 SNPs were analyzed in a two stage study involving 23,463 carriers from the CIMBA consortium (the Consortium of Investigators of Modifiers of BRCA1 and BRCA2). Eleven SNPs showed evidence of association with breast and/or ovarian cancer at p<0.05 in the combined analysis. Four of the five genes for which strongest evidence of association was observed were DNA glycosylases. The strongest evidence was for rs1466785 in the NEIL2 (endonuclease VIII-like 2) gene (HR: 1.09, 95% CI (1.03-1.16), p = 2.7 × 10(-3)) for association with breast cancer risk in BRCA2 mutation carriers, and rs2304277 in the OGG1 (8-guanine DNA glycosylase) gene, with ovarian cancer risk in BRCA1 mutation carriers (HR: 1.12 95%CI: 1.03-1.21, p = 4.8 × 10(-3)). DNA glycosylases involved in the first steps of the BER pathway may be associated with cancer risk in BRCA1/2 mutation carriers and should be more comprehensively studied.

NEIL2 protects against oxidative DNA damage induced by sidestream smoke in human cells

Secondhand smoke (SHS) is a confirmed lung carcinogen that introduces thousands of toxic chemicals into the lungs. SHS contains chemicals that have been implicated in causing oxidative DNA damage in the airway epithelium. Although DNA repair is considered a key defensive mechanism against various environmental attacks, such as cigarette smoking, the associations of individual repair enzymes with susceptibility to lung cancer are largely unknown. This study investigated the role of NEIL2, a DNA glycosylase excising oxidative base lesions, in human lung cells treated with sidestream smoke (SSS), the main component of SHS. To do so, we generated NEIL2 knockdown cells using siRNA-technology and exposed them to SSS-laden medium. Representative SSS chemical compounds in the medium were analyzed by mass spectrometry. An increased production of reactive oxygen species (ROS) in SSS-exposed cells was detected through the fluorescent detection and the induction of HIF-1α. The long amplicon–quantitative PCR (LA-QPCR) assay detected significant dose-dependent increases of oxidative DNA damage in the HPRT gene of cultured human pulmonary fibroblasts (hPF) and BEAS-2B epithelial cells exposed to SSS for 24 h. These data suggest that SSS exposure increased oxidative stress, which could contribute to SSS-mediated toxicity. siRNA knockdown of NEIL2 in hPF and HEK 293 cells exposed to SSS for 24 h resulted in significantly more oxidative DNA damage in HPRT and POLB than in cells with control siRNA. Taken together, our data strongly suggest that decreased repair of oxidative DNA base lesions due to an impaired NEIL2 expression in non-smokers exposed to SSS would lead to accumulation of mutations in genomic DNA of lung cells over time, thus contributing to the onset of SSS-induced lung cancer.

Repair of oxidative DNA damage and cancer: recent progress in DNA base excision repair

SIGNIFICANCE

Reactive oxygen species (ROS) are generated by exogenous and environmental genotoxins, but also arise from mitochondria as byproducts of respiration in the body. ROS generate DNA damage of which pathological consequence, including cancer is well established. Research efforts are intense to understand the mechanism of DNA base excision repair, the primary mechanism to protect cells from genotoxicity caused by ROS.

RECENT ADVANCES

In addition to the notion that oxidative DNA damage causes transformation of cells, recent studies have revealed how the mitochondrial deficiencies and ROS generation alter cell growth during the cancer transformation.

CRITICAL ISSUES

The emphasis of this review is to highlight the importance of the cellular response to oxidative DNA damage during carcinogenesis. Oxidative DNA damage, including 7,8-dihydro-8-oxoguanine, play an important role during the cellular transformation. It is also becoming apparent that the unusual activity and subcellular distribution of apurinic/apyrimidinic endonuclease 1, an essential DNA repair factor/redox sensor, affect cancer malignancy by increasing cellular resistance to oxidative stress and by positively influencing cell proliferation.

FUTURE DIRECTIONS

Technological advancement in cancer cell biology and genetics has enabled us to monitor the detailed DNA repair activities in the microenvironment. Precise understanding of the intracellular activities of DNA repair proteins for oxidative DNA damage should provide help in understanding how mitochondria, ROS, DNA damage, and repair influence cancer transformation.

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 in the vitamin D receptor gene and the lung cancer risk

The relationship between the vitamin D receptor (VDR) polymorphisms and the susceptibility to lung cancer remains unclear. The present meta-analysis was performed to estimate the polymorphisms of VDR and lung cancer risk. The pooled odds ratios (ORs) and corresponding 95 % confidence intervals (CIs) were calculated. Subgroup analysis by smoking status was carried out for further elucidation. The VDR BsmI polymorphism seemed to be negatively associated with the lung cancer risk (A vs. G, OR = 0.71, 95 % CI, 0.52-0.96; GA vs. GG, OR = 0.54, 95 % CI, 0.35-0.83; AA + GA vs. GG, OR = 0.55, 95 % CI, 0.36-0.84), particularly among the smokers (AA + GA vs. GG, OR = 0.39, 95 % CI, 0.21-0.72). The VDR ApaI variant genotypes did not alter the risk of lung cancer under all gene models in overall analysis. However, smokers carrying the variant G allele were more susceptible to lung cancer (G vs. T, OR = 1.60, 95 % CI, 1.14-2.25). The polymorphism of VDR TaqI was related to a decreased risk of lung cancer (C vs. T, OR = 0.62, 95 % CI, 0.26-1.46; CC vs. TT, OR = 0.44, 95 % CI, 0.21-0.91; TC vs. TT, OR = 0.58, 95 % CI, 0.38-0.90; CC + TC vs. TT, OR = 0.55, 95 % CI, 0.36-0.84). Besides, the CC + TC carriers in the smokers were at a significantly reduced risk of lung cancer (CC + TC vs. TT, OR = 0.48, 95 % CI, 0.16-1.44). The study supports that the polymorphisms of VDR BsmI and TaqI play protective roles in the lung carcinogenesis, particularly among the smokers. The association of VDR ApaI polymorphism with the lung cancer risk needs to be further elucidated.

Impact of genetic polymorphisms in base excision repair genes on the risk of breast cancer in a Korean population

The contribution of single nucleotide polymorphisms (SNPs) in base excision repair (BER) genes to the risk of breast cancer (BC) was evaluated by focusing on two key genes: apurinic/apyrimidinic endonuclease 1 (APEX1) and 8-oxoguanine DNA glycosylase (OGG1). Genetic variations in the genes encoding these DNA repair enzymes may alter their functions and increase susceptibility to carcinogenesis. The aim of this study was to analyze polymorphisms in two BER genes, exploring their associations and particularly the combined effects of these variants on BC risk in a Korean population. Three SNPs of two BER genes were genotyped using the Illumina GoldenGate™ method. In total, 346 BC patients and 361 cancer-free controls were genotyped for these BER gene polymorphisms and analyzed for their correlation with BC risk in multiple logistic regression models. Multiple logistic regression models adjusted for age, family history of BC, and body mass index were used. The APEX1 Asp148Glu polymorphism was weakly associated with BC risk. The combined analysis among the BER genes, however, showed significant effects on BC risk. The APEX1 Asp148Glu carrier, in combination with OGG1 rs2072668 and OGG1 Ser326Cys, was strongly associated with an increased risk of BC. Moreover, the combination of the C-C haplotype of OGG1 with the APEX1 Asp148Glu genotype was also associated with an additive risk effect of BC [ORs=2.44, 2.87, and 3.50, respectively]. The combined effect of APEX1 Asp148Glu was found to be associated with an increased risk of BC. These results suggest that the combined effect of different SNPs within BER genes may be useful in predicting BC risk.

Excision of 8-oxoguanine from methylated CpG dinucleotides by human 8-oxoguanine DNA glycosylase

CpG dinucleotides are targets for epigenetic methylation, many of them bearing 5-methylcytosine (mCyt) in the human genome. Guanine in this context can be easily oxidized to 8-oxoguanine (oxoGua), which is repaired by 8-oxoguanine-DNA glycosylase (OGG1). We have studied how methylation affects the efficiency of oxoGua excision from damaged CpG dinucleotides. Methylation of the adjacent cytosine moderately decreased the oxoGua excision rate while methylation opposite oxoGua lowered the rate of product release. Cytosine methylation abolished stimulation of OGG1 by repair endonuclease APEX1. The OGG1 S326C polymorphic variant associated with lung cancer showed poorer base excision and lost sensitivity to the opposite-base methylation. The overall repair in the system reconstituted from purified proteins decreased for CpG with mCyt in the damaged strand.

Contributory role of five common polymorphisms of RAGE and APE1 genes in lung cancer among Han Chinese

BACKGROUND

Lung cancer is the leading cause of cancer mortality in China. Given the ubiquitous nature of gene-to-gene interaction in lung carcinogenesis, we sought to evaluate five common polymorphisms from advanced glycosylation end product-specific receptor (RAGE) and apurinic/apyrimidinic endonuclease 1 (APE1) genes in association with lung cancer among Han Chinese.

METHODS AND RESULTS

819 patients with lung cancer and 803 cancer-free controls were recruited from Qiqihar city. Genotypes of five examined polymorphisms (RAGE gene: rs1800625, rs1800624, rs2070600; APE1 gene: rs1760944, rs1130409) were determined by ligase detection reaction method. Data were analyzed by R software and multifactor dimensionality reduction (MDR). Hardy-Weinberg equilibrium was satisfied for all five polymorphisms. Overall differences in the genotype and allele distributions were significant for rs1800625 (Pgenotype<0.0005; Pallele<0.0005), rs2070600 (Pgenotype = 0.005; Pallele = 0.004) and rs1130409 (Pgenotype = 0.009; Pallele = 0.004) polymorphisms. Haplotype C-A-A (alleles in order of rs1800625, rs1800624 and rs2070600) of RAGE gene was overrepresented in patients, and conferred a 2.1-fold increased risk of lung cancer (95% confidence interval: 1.52-2.91), independent of confounding factors. Further application of MDR method to five examined polymorphisms identified the overall best interaction model including rs2070600 and rs1130409 polymorphisms. This model had a maximal testing accuracy of 64.63% and a maximal cross-validation consistency of 9 out of 10 at the significant level of 0.006.

CONCLUSIONS

Our findings demonstrated a potential interactive contribution of RAGE and APE1 genes to the pathogenesis of lung cancer among Han Chinese. Further studies are warranted to confirm or refute these findings.