APE1 genotype and risk of bladder cancer: evidence for effect modification by smoking

Polymorphisms of base-excision repair genes and the hepatocarcinogenesis

AIM

To determine the possible association between polymorphisms of DNA repair genes, including XRCC1 Arg194Tryp, Arg280His, and Arg399Glu, APE1 Asp148Glu, and NEIL2 Arg257Leu, and the risk of developing hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC).

METHODS

A total of 264 subjects were recruited in this retrospective case-control study and were categorized into four groups: 88 control subjects (CR), 53 chronic hepatitis C patients (CHC), 36 liver cirrhotic patients (LC), and 87 HCC patients. The XRCC1 Arg194Tryp, Arg280His, and Arg399Glu polymorphisms were detected using PCR-RFLP, while real-time PCR was used to genotype APE1 Asp148Glu and NEIL2 Arg257Leu.

RESULTS

Our data revealed that, compared with the healthy controls, for those subjects with the XRCC1 Arg194Trp genotype, the risk of developing CHC, LC, and HCC was increased by 6.66- (odds ratio (OR) = 6.667; 95% confidence interval (CI) = 3.244-13.701; P > 0.01), 3.85- (OR = 3.852; 95% CI = 1.797-8.256; P > 0.01), and 2.14-fold (OR = 2.14; 95% CI = 1.13-4.06; P > 0.05), respectively. There was no association between the risk of HCC development and the XRCC1 Arg280His or XRCC1 Arg399Gln genotypes. Moreover, the analysis showed a lack of association between APE1 Asp148Glu and the risk of HCC development. The analysis of clinicopathological parameters showed that the HCC patients with the XRCC1 Arg280His polymorphism were 2.9 fold more likely to have hepatic lesions in both hepatic lobes (OR: 2.9; 95% CI: 1.15-7.29). Notably, in the HCC patients, the prevalence of the APE1 polymorphism in the males was four times higher than that in the females (OR = 4; 95% CI = 1.129-14.175; P > 0.05).

CONCLUSION

Our results indicate that the XRCC1 Arg194Trp polymorphism could be a risk factor for HCV-related HCC development in Egypt.

Modulation of trinucleotide repeat instability by DNA polymerase β polymorphic variant R137Q

Trinucleotide repeat (TNR) instability is associated with human neurodegenerative diseases and cancer. Recent studies have pointed out that DNA base excision repair (BER) mediated by DNA polymerase β (pol β) plays a crucial role in governing somatic TNR instability in a damage-location dependent manner. It has been shown that the activities and function of BER enzymes and cofactors can be modulated by their polymorphic variations. This could alter the function of BER in regulating TNR instability. However, the roles of BER polymorphism in modulating TNR instability remain to be elucidated. A previous study has shown that a pol β polymorphic variant, polβR137Q is associated with cancer due to its impaired polymerase activity and its deficiency in interacting with a BER cofactor, proliferating cell nuclear antigen (PCNA). In this study, we have studied the effect of the pol βR137Q variant on TNR instability. We showed that pol βR137Q exhibited weak DNA synthesis activity to cause TNR deletion during BER. We demonstrated that similar to wild-type pol β, the weak DNA synthesis activity of pol βR137Q allowed it to skip over a small loop formed on the template strand, thereby facilitating TNR deletion during BER. Our results further suggest that carriers with pol βR137Q polymorphic variant may not exhibit an elevated risk of developing human diseases that are associated with TNR instability.

Quantified relations between exposure to tobacco smoking and bladder cancer risk: a meta-analysis of 89 observational studies

BACKGROUND

Smoking is a major risk factor for bladder cancer (BC). This meta-analysis updates previous reviews on smoking characteristics and BC risk, and provides a more quantitative estimation of the dose-response relationship between smoking characteristics and BC risk.

METHODS

In total, 89 studies comprising data from 57 145 BC cases were included and summary odds ratios (SORs) were calculated. Dose-response meta-analyses modelled relationships between smoking intensity, duration, pack-years and cessation and BC risk. Sources of heterogeneity were explored and sensitivity analyses were conducted to test the robustness of findings.

RESULTS

Current smokers (SOR = 3.14, 95% CI = 2.53-3.75) and former smokers(SOR = 1.83, 95% CI = 1.52-2.14) had an increased risk of BC compared with never smokers. Age at first exposure was negatively associated with BC risk. BC risk increased gradually by smoking duration and a risk plateau at smoking 15 cigarettes a day and 50 pack-years was observed. Smoking cessation is most beneficial from 20 years before diagnosis. The population-attributable risk of BC for smokers has decreased from 50% to 43% in men and from 35% to 26% in women from Europe since estimated in 2000. Results were homogeneous between sources of heterogeneity, except for lower risk estimates found in studies of Asian populations.

CONCLUSIONS

Active smokers are at an increased risk of BC. Dose-response meta-analyses showed a BC risk plateau for smoking intensity and indicate that even after long-term smoking cessation, an elevated risk of bladder cancer remains.

Association between APE1 Asp148Glu polymorphism and the risk of urinary cancers: a meta-analysis of 18 case-control studies

Background

Several observational studies suggested that APE1 Asp148Glu was significantly associated with urinary cancers; however, the results of published studies are inconsistent.

Materials and methods

The PubMed and EMBASE were searched for case–control studies regarding the association between Asp148Glu and the risk of urinary cancers with a time limit of September 12, 2015. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association between Asp148Glu and the risk of developing prostate cancer, kidney cancer, bladder cancer, as well as all urinary cancers combined.

Results

A total of 18 case–control studies were included in the analysis. Our meta-analysis revealed that the inheritance of at least one APE1 148Glu among Asian men was associated with a 1.26-fold increase in the risk of developing urinary cancers. Meanwhile, APE1 Asp148Glu was significantly associated with the risk of prostate cancer. However, there were no significant relationships between the APE1 SNP (single nucleotide polymorphism) and all urinary cancers combined and bladder cancer and kidney cancer among the men of Caucasian/Asian/African descent or all racial/ethnic groups combined. When stratified by the quality score, no significant association was found in high-quality studies (score ≥7), but a significant increased risk of urinary cancers was observed in lower quality studies (score <7) (dominant model: OR=1.27, 95% CI=1.11–1.45).

Conclusion

Our meta-analysis suggests that APE1 Asp148Glu was not associated with the risk of urinary cancers but might increase the risk of urinary cancers among Asians. Stratification by cancer type identified a significant association of Asp148Glu with prostate cancer.

The relationship between altered mitochondrial DNA copy number and cancer risk: a meta-analysis

Currently, a comprehensive assessment between mitochondrial DNA (mtDNA) content and cancer risk is lacking. We designed this meta-analysis to test the hypothesis that altered mtDNA copy number might influence genetic susceptibility to some specific types of cancer. The processes of literature search, eligibility appraisal and data retrieval were independently completed in duplicate. The mtDNA copy number which was dichotomized or classified into tertiles was compared between cancer cases and controls. Twenty-six articles with 38 study groups were analyzed among 6682 cases and 9923 controls. When dichotomizing mtDNA copy number at the median value, there was an 11% increased cancer risk for carriers of high mtDNA content (P = 0.320). By cancer type, high mtDNA content was associated with an increased risk for lymphoma (OR = 1.76; P = 0.023) but a reduced risk for skeleton cancer (OR = 0.39; P = 0.001). Carriers of the 2^nd and 3^rd tertiles of mtDNA copy number had an 1.74-fold (P = 0.010) and 2.07-fold (P = 0.021) increased risk of lymphoma, respectively. By contrast, there was correspondingly a 56% (P < 0.001) and 80% (P < 0.001) reduced risk of skeleton cancer. Our findings suggested that elevated mtDNA content was associated with a higher risk for lymphoma, but a lower risk for skeleton cancer.

Human AP endonuclease 1: a potential marker for the prediction of environmental carcinogenesis risk

Human apurinic/apyrimidinic endonuclease 1 (APE1) functions mainly in DNA repair as an enzyme removing AP sites and in redox signaling as a coactivator of various transcription factors. Based on these multifunctions of APE1 within cells, numerous studies have reported that the alteration of APE1 could be a crucial factor in development of human diseases such as cancer and neurodegeneration. In fact, the study on the combination of an individual's genetic make-up with environmental factors (gene-environment interaction) is of great importance to understand the development of diseases, especially lethal diseases including cancer. Recent reports have suggested that the human carcinogenic risk following exposure to environmental toxicants is affected by APE1 alterations in terms of gene-environment interactions. In this review, we initially outline the critical APE1 functions in the various intracellular mechanisms including DNA repair and redox regulation and its roles in human diseases. Several findings demonstrate that the change in expression and activity as well as genetic variability of APE1 caused by environmental chemical (e.g., heavy metals and cigarette smoke) and physical carcinogens (ultraviolet and ionizing radiation) is likely associated with various cancers. These enable us to ultimately suggest APE1 as a vital marker for the prediction of environmental carcinogenesis risk.

Redox regulation of apurinic/apyrimidinic endonuclease 1 activity in Long-Evans Cinnamon rats during spontaneous hepatitis

The Long-Evans Cinnamon (LEC) rat is an animal model for Wilson's disease. This animal is genetically predisposed to copper accumulation in the liver, increased oxidative stress, accumulation of DNA damage, and the spontaneous development of hepatocellular carcinoma. Thus, this animal model is useful for studying the relationship of endogenous DNA damage to spontaneous carcinogenesis. In this study, we have investigated the apurinic/apyrimidinic endonuclease 1 (APE1)-mediated excision repair of endogenous DNA damage, apurinic/apyrimidinic (AP)-sites, which is highly mutagenic and implicated in human cancer. We found that the activity was reduced in the liver extracts from the acute hepatitis period of LEC rats as compared with extracts from the age-matched Long-Evans Agouti rats. The acute hepatitis period had also a heightened oxidative stress condition as assessed by an increase in oxidized glutathione level and loss of enzyme activity of glyceraldehyde 3-phosphate dehydrogenase, a key redox-sensitive protein in cells. Interestingly, the activity reduction was not due to changes in protein expression but apparently by reversible protein oxidation as the addition of reducing agents to extracts of the liver from acute hepatitis period reactivated APE1 activity and thus, confirmed the oxidation-mediated loss of APE1 activity under increased oxidative stress. These findings show for the first time in an animal model that the repair mechanism of AP-sites is impaired by increased oxidative stress in acute hepatitis via redox regulation which contributed to the increased accumulation of mutagenic AP-sites in liver DNA.

Association between the STK15 F31I polymorphism and cancer susceptibility: a meta-analysis involving 43,626 subjects

The association between the Serine/threonine kinase 15 (STK15) F31I polymorphism (rs2273535) and cancer susceptibility remains controversial. To further investigate this potential relationship, we conducted a comprehensive meta-analysis of 27 published studies involving a total of 19,267 multiple cancer cases and 24,359 controls. Our results indicate statistical evidence of an association between the STK15 F31I polymorphism and the increased risk of overall cancer in four genetic models: AA vs. TA+TT, AA vs. TT, AA vs. TA, and A vs. T. In a stratified analysis by cancer type, there was an increased risk of breast cancer in four genetic models: AA vs. TA+TT, AA vs. TT, AA vs. TA, and A vs. T, as well as esophageal cancer in two genetic models: AA vs. TA+TT and AA vs. TA. In a stratified analysis by ethnicity, there was a significant increase in cancer risk among Asians, but not Caucasians, in four genetic models: AA vs. TA+TT, AA vs. TT, AA vs. TA and A vs. T. In addition, a stratified analysis by ethnicity in the breast cancer subgroup revealed a significant increase in cancer risk among Asians in two genetic models: AA vs. TA+TT and AA vs. TT, as well as among Caucasians in one genetic model: AA vs. TA. In summary, this meta-analysis demonstrates that the STK15 F31I polymorphism may be a risk factor for cancer.

APEX nuclease (multifunctional DNA repair enzyme) 1 gene Asp148Glu polymorphism and cancer risk: a meta-analysis involving 58 articles and 48903 participants

BACKGROUND

Polymorphisms in the APEX nuclease (multifunctional DNA repair enzyme) 1 gene (APEX1) may be involved in the carcinogenesis by affecting DNA repair. We aimed to summarize available data on the association of the APEX1 Asp148Glu (rs1130409) polymorphism with risk of multiple types of cancer via a meta-analysis.

METHODS AND RESULTS

In total, 58 qualified articles including 22,398 cancer patients and 26,505 controls were analyzed, and the data were extracted independently by two investigators. Analyses of the full data set indicated a marginally significant association of the APEX1 Asp148Glu polymorphism with cancer risk under allelic (odds ratio (OR)=1.05; 95% confidence interval (95% CI): 0.99-1.11; P=0.071), dominant (OR=1.09; 95% CI: 1.01-1.17; P=0.028), and heterozygous genotypic (OR=1.08; 95% CI: 1.01-1.16; P=0.026) models, with significant heterogeneity and publication bias. In subgroup analyses by cancer type, with a Bonferroni corrected alpha of 0.05/6, significant association was observed for gastric cancer under both dominant (OR=1.74; 95% CI: 1.2-2.51; P=0.003) and heterozygous genotypic (OR=1.66; 95% CI: 1.2-2.31; P=0.002) models. In subgroup analysis by ethnicity, risk estimates were augmented in Caucasians, especially under dominant (OR=1.11; 95% CI: 1.0-1.24; P=0.049) and heterozygous genotypic (OR=1.11; 95% CI: 0.99-1.24; P=0.063) models. By study design, there were no significant differences between population-based and hospital-based studies. In subgroup analysis by sample size, risk estimates were remarkably overestimated in small studies, and no significance was reached in large studies except under the heterozygous genotypic model (OR=1.23; 95% CI: 1.06-1.43; P=0.006, significant at a Bonferroni corrected alpha of 0.05/2). By quality score, the risk estimates, albeit nonsignificant, were higher in low-quality studies than in high-quality studies. Further meta-regression analyses failed to identify any contributory confounders for the associated risk estimates.

CONCLUSIONS

Our findings suggest that APEX1 Asp148Glu polymorphism might be a genetic risk factor for the development of gastric cancer. Further investigations on large populations are warranted.

A functional insertion/deletion polymorphism (-94 ins/del ATTG) in the promoter region of the NFKB1 gene is related to the risk of renal cell carcinoma

OBJECTIVE

Activated nuclear factor-ĸB is associated with the pathogenesis of numerous malignancies, including renal cell carcinoma (RCC). This study aimed to clarify the influence of a common insertion/deletion polymorphism (-94 ins/del ATTG, rs28362491) in the NFKB1 promoter on RCC susceptibility.

METHODS

We genotyped the NFKB1 -94 ins/del ATTG promoter polymorphism by the TaqMan method and assessed the association with RCC risk, clinicopathological parameters in a case-control study of 1,027 cases and 1,094 controls.

RESULTS

The genotype frequencies were significantly different between RCC cases and controls (p = 0.046). Compared with individuals carrying the ins/del + del/del genotypes, those with the ins/ins genotype had an increased RCC risk [p = 0.036, adjusted odds ratio (OR) = 1.23, 95% confidence interval (CI) = 1.02-1.48], particularly in the subgroup of younger age (p = 0.005, adjusted OR = 1.42, 95% CI = 1.11-1.83) and never smokers (p = 0.013, adjusted OR = 1.34, 95% CI = 1.07-1.69). Furthermore, the polymorphism was significantly associated with the risk of developing localized stage RCC (p = 0.020, OR = 1.26, 95% CI = 1.04-1.53).

CONCLUSIONS

The functional NFKB1 promoter polymorphism is associated with an increased risk of RCC.

Association of p53 codon 248 (exon7) with urinary bladder cancer risk in the North Indian population

p53 is the most frequently mutated gene in all forms of human cancer. It responds to diverse stresses including UVR-induced DNA damage and regulates many downstream genes to initiate cell-cycle arrest, DNA repair or apoptosis. p53 gene variants at codon 11, Pro47Ser and codon 248 (exon 7) were evaluated for bladder cancer (BC) risk in North Indians. In the present study, the above encoding regions in p53 genes were analyzed in a hospital based study in 200 BC and 200 healthy controls age and gender matched and of similar ethnicity. The genotyping was assessed by the polymerase chain reaction restriction fragment length polymorphism technique and statistically evaluated using SPSS software ver. 15.0. A significant association was found with p53 codon 248 polymorphism and BC risk whereas p53 codon 11 and p53 Pro47Ser polymorphism showed no association with BC risk. The individuals carrying the heterozygous genotype (Arg/Trp-Arg/Gln) in the p53 codon 248 polymorphism showed high BC risk (p < 0.001). Combinations with heterozygous and variant genotypes also showed a high risk for BC (p < 0.001). The minor allele (Trp/Gln) carriers of the p53 codon 248 demonstrated a 1.7-fold risk for BC. Furthermore, haplotype analysis revealed that the Glu-Pro-Trp/Gln haplotype is associated with a 1.9-fold risk for BC. A protective role was observed with tumor stage/grade of BC patients with p53 codon 248 (p = 0.003; OR = 0.32). Thus, it is evident from our study that of all the 3 single nucleotide polymorphisms evaluated, only p53 codon 248 (exon7) gene polymorphism has an implication for risk in BC in the North Indian population.

Genetic variants in telomere-maintenance genes and bladder cancer risk

Telomeres are critical in maintaining genomic stability. Genetic variants in telomere pathway genes may affect telomere and telomerase function, and subsequently cancer risk. We evaluated 126 SNPs from 10 genes related to telomere regulation in relation to bladder cancer risk. Five SNPs, 4 from TEP1 gene and 1 from PINX1 gene, were found to be highly significant (P<0.01). Out of these, the most significant association was found in rs2228041 of TEP1 (OR 1.66, 95% CI 1.19–2.31) while rs1469557 of PINX1 had a protective effect (OR 0.75, 95% CI 0.61–0.93). Haplotype analysis showed that a TEP1 haplotype consisting of the variant alleles of 7 SNPs exhibited a 2.28 fold increased risk (95% CI 1.13–4.60). We then performed cumulative analysis of multiple risk variants, as well as Classification and Regression Tree (CART) to look for gene-gene interactions. In cumulative effect analysis, the group with 4–5 risk variants had an OR of 2.57 (95% CI = 1.62–4.09) versus the reference group with 0 risk variants. The CART analysis categorized individuals into five subgroups with different bladder cancer risk profiles based on their distinct genotype background. To our knowledge, this is one of the largest, most comprehensive studies on bladder cancer risk concerning telomere-regulating pathway gene SNPs and our results support that genetic variations of telomere maintenance modulate bladder cancer risk individually and jointly.

The association of APE1 -656T > G and 1349 T > G polymorphisms and cancer risk: a meta-analysis based on 37 case-control studies

Background

APE1 (apurinic/apyrimidinic endonuclease 1) is an important DNA repair protein in the base excision repair pathway. Polymorphisms in APE1 have been implicated in susceptibility to cancer; however, results from the published studies remained inconclusive. The objective of this study was to conduct a meta-analysis investigating the association between polymorphisms in APE1 and the risk for cancer.

Methods

The PubMed and Embase databases were searched for case-control studies published up to June, 2011 that investigated APE1 polymorphisms and cancer risk. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the associations.

Results

Two polymorphisms (−656 T > G, rs1760944 and 1349 T > G, rs1130409) in 37 case-control studies including 15, 544 cancer cases and 21, 109 controls were analyzed. Overall, variant genotypes (GG and TG/GG) of −656 T > G polymorphism were associated with significantly decreased cancer risk in homozygote comparison (OR = 0.81, 95%CI: 0.67-0.97), dominant model comparison (OR = 0.89, 95%CI: 0.81-0.97) and recessive model comparison (OR = 0.90, 95%CI: 0.82-0.98), whereas the 1349 T > G polymorphism had no effects on overall cancer risk. In the stratified analyses for −656 T > G polymorphism, there was a significantly decreased risk of lung cancer and among Asian populations.

Conclusions

Although some modest bias could not be eliminated, the meta-analysis suggests that APE1 −656 T > G polymorphism has a possible protective effect on cancer risk particularly among Asian populations whereas 1349 T > G polymorphism does not contribute to the development of cancer.

Genetic polymorphisms in APE1 are associated with renal cell carcinoma risk in a Chinese population

Apurinic/apyrimidinic endonuclease 1 (APE1) is a DNA repair protein, which plays important roles in the base excision repair (BER) pathway. Genetic variations of APE1 have been shown to influence an individual's susceptibility to carcinogenesis. We hypothesized the genetic polymorphisms of APE1 are associated with the risk of renal cell carcinoma (RCC). In a case-control study of 612 RCC patients and 632 age and sex matched healthy controls, we genotyped two APE1 functional polymorphisms (-656 T>G, rs1760944 and 1349 T>G, rs1130409) and assessed their associations with risk of RCC. We found that, compared with 1349 TT/TG genotypes, the variant genotype 1349 GG had a significantly increased RCC risk [adjusted odds ratio (OR) = 1.47, 95% confidence interval (CI) = 1.10-1.95], particularly among subgroups of BMI > 23 kg/m(2) (OR = 1.54, 95% CI = 1.06-2.22), male (OR = 1.70, 95% CI = 1.17-2.46), never smokers (OR = 1.56, 95% CI = 1.11-2.21), light smokers (OR = 2.01, 95%CI = 1.02-3.95), and drinkers (OR = 2.00, 95% CI = 1.13-3.54). Furthermore, the polymorphism was significantly associated with risk of developing localized stage RCC. No altered RCC risk was associated with the -656 T>G polymorphism, but we found individuals who were homozygous for both risk alleles of the two SNPs had a 2.17-fold increased risk for RCC, compared to individuals with 0 risk alleles. Our results suggest that polymorphisms of APE1 may confer susceptibility to RCC.

Genetic variants of XRCC1, APE1, and ADPRT genes and risk of bladder cancer

DNA damaged by exposure to exogenous and endogenous carcinogens could be removed effectively by the base excision repair pathway, in which the XRCC1, APE1, and ADPRT genes play a key role. Genetic variations in these important genes may alter repair function and contribute to cancer risk. We hypothesized that XRCC1, APE1, and ADPRT polymorphisms are associated with risk of bladder cancer. In a hospital-based case-control study of 234 patients with bladder cancer and 253 cancer-free controls, we genotyped the XRCC1-77T>C, Arg194Trp, Arg280His, Arg399Gln, APE1-656T>G, Asp148Glu, ADPRT-442G>A, and Val762Ala polymorphisms using polymerase chain reaction-restriction fragment length polymorphism method. We found an increased risk of bladder cancer associated with the XRCC1 194Trp/Trp and 280Arg/His genotypes (adjusted odds ratio = 3.90, 95% confidence interval = 1.69-8.98 for 194Trp/Trp and 2.53, 1.67-3.83 for 280Arg/His) compared with the 194Arg/Arg and 280Arg/Arg genotypes, respectively. In contrast, the APE1-656GG genotype was associated with a decreased risk of bladder cancer (0.57, 0.33-0.98) compared with the TT genotype. When we evaluated these eight polymorphisms together, we found that the combined genotypes with 9-13 variant (risk) alleles were associated with an increased risk of bladder cancer (2.25, 1.48-3.40) compared with those with 3-8 variants. These findings suggest that the XRCC1 and APE1 polymorphisms may contribute to susceptibility to bladder cancer. Larger studies are warranted to verify these findings.

The DNA repair gene APE1 T1349G polymorphism and cancer risk: a meta-analysis of 27 case-control studies

Published data regarding the association between the apurinic/apyrimidinic endonuclease 1 (APE1) T1349G (Asp148Glu) polymorphism and cancer risk show inconclusive results. To derive a more precise estimation of the relationship, we performed a meta-analysis of 27 published studies that included 12 432 cancer cases and 17 349 controls. We used odds ratios (ORs) and 95% confidence intervals (CIs) to evaluate the strength of the associations. The overall results suggested that the variant genotypes were associated with a moderately increased risk of all cancer types (OR = 1.09, 95% CI = 1.01-1.18 for TG versus TT; OR = 1.08, 95% CI = 1.00-1.18 for GG/TG versus TT). In the stratified analyses, the risk remained for studies of colorectal cancer, European populations and population-based studies. Although some modest bias could not be eliminated, this meta-analysis supported that the APE1 T1349G polymorphism is a low-penetrance risk factor for cancer development.

Molecular epidemiology of DNA repair genes in bladder cancer

Bladder cancer is a common disease, whose major risk factors include smoking and occupational exposure to chemicals. Superficial bladder cancer has significant healthcare cost implications due to the need for repeated cystoscopic surveillance. Chemical carcinogens can undergo metabolic activation and detoxification in the liver and polymorphisms in the relevant genes have been shown to be associated with bladder cancer risk. In addition, DNA repair enzymes are required to repair the DNA damage associated with carcinogen exposure. The main pathways involved are nucleotide excision repair, base excision repair, and double strand break repair. Investigation of individual polymorphisms in DNA repair genes in bladder cancer has yielded few robust positive findings, which is not surprising given the multifactorial nature of the disease. Pathway approaches using novel genotyping technologies will allow more comprehensive studies of multiple polymorphisms in multiple genes. It will also be possible to investigate gene-environment interaction more rigorously than heretofore, using novel statistical methodology, in larger studies and through collaborative efforts within consortia. The results of the genome-wide association studies in bladder cancer are awaited with interest. In the future, genetic tests might be used in the prevention of bladder cancer to encourage lifestyle changes in those at highest risk of developing the disease, and in the treatment of bladder cancer to optimise cure rates whilst minimising morbidity in a cost-effective manner.

Influence of XPD and APE1 DNA repair gene polymorphism on bladder cancer susceptibility in north India

OBJECTIVES

To explore the association between xerodema pigmentosum group D (XPD) Asp(312)Asn and Lys(751)Gln and apurinic apyrimidic endonuclease 1 (APE1) Asp(148)Glu gene polymorphism and risk of bladder cancer (BC) susceptibility.

METHODS

This hospital-based case-control study included 206 patients with newly diagnosed bladder transitional cell carcinoma and 250 cancer-free controls who had been frequency matched by age, sex, and ethnicity. Polymorphisms in XPD Asp(312)Asn and Lys(751)Gln and APE1 Asp(148)Glu gene using polymerase chain reaction-restriction fragment length polymorphism and amplification refractory mutation system were genotyped.

RESULTS

The XPD Asp(312)Asn AA genotype was associated with an elevated risk of BC (odds ratio [OR] 3.30, P = .001.) The AA genotype was significantly associated with nonmuscle-invasive BC (OR 4.62, corrected P = .003). Both the heterozygous GA and the homozygous AA was associated with a greater risk of low-grade (grade 1) BC (OR 2.51, corrected P = .006 and OR 5.21, corrected P = .003, respectively). The APE1 GG genotype showed a decreased risk of BC (OR 0.27, P = .027.) Haplotype AC (codon 312A-codon 751C) of XPD demonstrated an association with a greater susceptibility to BC (OR 2.16, correct P = .0008).

CONCLUSIONS

Reduced DNA repair capacity due to XPD Asp(312)Asn AA genotype might be a risk factor for BC. The AA genotype predisposed to a greater risk at the initial stage and grade of BC. The APE1 148GG genotype conferred a protective association with BC susceptibility.

Implications of XRCC1, XPD and APE1 gene polymorphism in North Indian population: a comparative approach in different ethnic groups worldwide

Identifying risk factors for human cancers should consider combinations of genetic variations and environmental exposures. Several polymorphisms in DNA repair genes have impact on repair and cancer susceptibility. We focused on X-ray repair cross-complementing group 1 (XRCC1), Xeroderma pigmentosum D (XPD) and apurinic/apyrimidinic endonuclease (APE1) as these are most extensively studied in cancer. Present study was conducted to determine distribution of XRCC1 C26304T, G27466A, G23591A, APE1 T2197G and XPD A35931C gene polymorphisms in North Indian population and compare with different populations globally. PCR-based analysis was conducted in 209 normal healthy individuals of similar ethnicity. Allelic frequencies in wild type of XRCC1 C26304T were 91.1% C(Arg); G27466A 62.9% G(Arg); G23591A 60.3% G(Arg); APE1 T2197G 75.1% T(Asp) and XPD A35931C 71.8% A(Lys). The variant allele frequency were 8.9% T(Trp) in XRCC1 C26304T; 37.1% A(His) in G27466A; 39.7% A(Gln) in G23591A; 24.9% G(Glu) in APE1 and 28.2% C(Gln) in XPD respectively. We further compared frequency distribution for these genes with various published studies in different ethnicity. Our results suggest that frequency in these DNA repair genes exhibit distinctive pattern in India that could be attributed to ethnicity variation. This could assist in high-risk screening of humans exposed to environmental carcinogens and cancer predisposition in different ethnic groups.

Genetic polymorphisms in DNA base-excision repair genes ADPRT, XRCC1, and APE1 and the risk of squamous cell carcinoma of the head and neck

BACKGROUND

Tobacco smoke contains numerous carcinogens that cause DNA damage, including oxidative lesions that are removed effectively by the base-excision repair (BER) pathway, in which adenosine diphosphate ribosyl transferase (ADPRT), x-ray repair cross-complementing 1 (XRCC1), and apurinic/apyimidinic endonuclease (APE1) play key roles. Genetic variations in the genes encoding for these DNA repair enzymes may alter their functions. Although there have been several studies that generated mixed results on the association between XRCC1 variants and the risk of squamous cell carcinoma of the head and neck (SCCHN), no reported studies have investigated the association between ADPRT and APE1 variants and SCCHN risk.

METHODS

In a hospital-based, case-control study of 830 non-Hispanic white patients with SCCHN and 854 cancer-free, matched control participants, the authors genotyped the ADPRT alanine 762 valine (Ala762Val) single-nucleotide polymorphism (SNP), the XRCC1 arginine 399 glutamine (Arg399Gln) SNP, and the APE aspartic acid 148 glutamic acid (Asp148Glu) SNP and assessed their associations with the risk of SCCHN in multivariate logistic regression models.

RESULTS

The findings indicated that a significantly decreased risk of SCCHN was associated with the ADPRT 762Ala/Ala genotype (adjusted odds ratio [OR], 0.51; 95% confidence interval [95% CI], 0.27-0.97) and the combined ADPRT 762Ala/Val and Ala/Ala genotypes (OR, 0.79; 95% CI; 0.63-1.00) compared with the ADPRT 762Val/Val genotype, but no altered risk was associated with the XRCC1 Arg399Gln or APE Asp148Glu polymorphisms, and no evidence of interactions was observed between the 3 selected SNPs and age, sex, smoking status, drinking status, or tumor site.

CONCLUSIONS

The ADPRT Ala762Val polymorphism may play a role in the etiology of SCCHN or in linkage disequilibrium with other untyped protective alleles. Larger studies with more SNPs in the BER genes will be needed to verify these findings.

The association of DNA repair gene polymorphisms with the development and progression of renal cell carcinoma

BACKGROUND

DNA repair enzymes repair some of the DNA damage associated with risk factors for renal cell carcinoma (RCC), including smoking. DNA repair gene polymorphisms modulate the repair capacity and might influence individual risk and progression of RCC. We examined associations between functional polymorphisms and risk, clinicopathologic characteristics and survival of RCC.

PATIENTS AND METHODS

The study groups comprised 215 RCC patients and 215 age- and gender-matched healthy controls. Polymorphisms in xeroderma pigmentosum complementation groups C, D and G and X-ray repair cross-complementing groups 1 and 3 genes were genotyped.

RESULTS

No significant differences in DNA repair genotype were observed between RCC cases and controls. In all patients, however, greater numbers (> or =3) of total variant alleles in all DNA repair genes studied were associated with less frequent venous extension (P = 0.0079). In smokers, some genotypes were associated with characteristics of RCC (Ps < or = 0.0067) and smokers with greater numbers of total variant alleles had improved overall survival (P = 0.040).

CONCLUSION

These results suggest that DNA repair gene polymorphisms may not influence RCC susceptibility, but that some of them may influence RCC progression, especially in smokers, possibly due to altered DNA repair capacity by these polymorphisms.

High-order interactions among genetic variants in DNA base excision repair pathway genes and smoking in bladder cancer susceptibility

Cancer is a common multifactor human disease resulting from complex interactions between many genetic and environmental factors. In this study, we used a multifaceted analytic approach to explore the relationship between eight single nucleotide polymorphisms in base excision repair (BER) pathway genes, smoking, and bladder cancer susceptibility in a hospital-based case-control study. Overall, we did not find an association between any single BER gene single nucleotide polymorphism and bladder cancer risk. However, in stratified analysis, the OGG1 S326C variant genotypes in ever smokers (odds ratio, 0.74; 95% confidence interval, 0.56-0.99) and ADP-ribosyltransferase (ADPRT) V762A variant genotypes in never smokers (odds ratio, 0.58; 95% confidence interval, 0.37-0.91) conferred a significantly reduced risk. Using logistic regression, we observed that there was a two-way interaction between ADPRT V762A and smoking status. We next used classification and regression tree analysis to explore high-order gene-gene and gene-environment interactions. We found that smoking is the most important influential factor for bladder cancer risk. Consistent with the above findings, we found that the ADPRT V762A was only significantly involved in bladder cancer risk in never smokers and the OGG1 S326C was only significantly involved in ever smokers. We also observed gene-gene interactions among OGG1 S326C, XRCC1 R194W, and MUTYH H335Q in ever smokers. Using multifactor dimensionality reduction approach, the four-factor model, including smoking status, OGG1 S326C (rs1052133), APEX1 D148E (rs3136820), and ADPRT762 (rs1136410), had the best ability to predict bladder cancer risk with the highest cross-validation consistency (100%) and the lowest prediction error (37.02%; P < 0.001). These results support the hypothesis that genetic variants in BER genes contribute to bladder cancer risk through gene-gene and gene-environmental interactions.