Polymorphisms of DNA repair genes are associated with renal cell carcinoma

Correlations of SDF-1ɑ and XRCC1 gene polymorphisms with the risk of renal cancer development and bioinformatics studies of SDF-1α and XRCC1 and the prognosis of renal cancer

To study the relationships between stromal cell-derived factor-1 (SDF-1ɑ) and renal cell carcinoma (RCC) susceptibility and the presence of single nucleotide polymorphisms in the human X-ray cross-complementary repair gene (XRCC1). Compare SDF-1 based on RCC related data in the TCGA database α, The expression difference of XRCC1 between RCC tissue and normal tissue; Collect 166 newly diagnosed RCC cases and 166 healthy individuals who underwent physical examinations during the same period, and detect genotype using iMLDR method. The results The rs1801157 locus (C:T) of the SDF-1α gene was not significantly associated with the pathohistological type, the rs1799782 locus (G:A) of the XRCC1 gene was associated with the pathohistological type of RCC, and there were interactions between rs1799782 and smoking, alcohol consumption, pesticide exposure, hair dye, and urine holding. The rs1799782 locus of the XRCC1 gene may be a key factor in the pathogenesis and pathological development of RCC. High SDF-1ɑ expression is a protective factor for the overall survival of patients with RCC, and SDF-1ɑ and XRCC1 may be important for the treatment of RCC.

Radio-adaptive response and correlation of non-homologous end joining repair gene polymorphisms [XRRC5 (3R/2R/1R/0R), XRCC6(C/G) and XRCC7 (G/T)] in human peripheral blood mononuclear cells exposed to gamma radiation

BACKGROUND

Radio-adaptive response (RAR) is transient phenomena, where cells conditioned with a small dose (priming) of ionizing radiation shows significantly reduced DNA damage with a subsequent high challenging dose. The role of DNA double strand break repair gene polymorphism in RAR is not known. In the present study attempt was made to find out the influence of NHEJ repair gene polymorphisms [a VNTR; XRCC5 (3R/2R/1R/0R); two single nucleotide polymorphisms (SNPs); XRCC6 (C/G) and XRCC7 (G/T)] with DNA damage, repair and mRNA expression in human PBMCs in dose and adaptive response studies. Genomic DNA extracted from venous blood samples of 20 random healthy donors (16 adaptive and 4 non-adaptive) and genotyping of NHEJ repair genes was carried out using PCR amplified length polymorphism.

RESULTS

The dose response study revealed significant positive correlation of genotypes at XRRC5 (3R/2R/1R/0R), XRCC6(C/G) and XRCC7 (G/T) with DNA damage. Donors having genotypes with 2R allele at XRCC5 showed significant positive correlation with mRNA expression level (0R/2R: r = 0.846, P = 0.034; 1R/2R: r = 0.698, P = 0.0001 and 2R/2R: r = 0.831, P = 0.0001) for dose response. Genotypes C/C and C/G of XRCC6 showed a significant positive correlation (P = 0.0001), whereas, genotype T/T of XRCC7 showed significant negative correlation (r = - 0.376, P = 0.041) with mRNA expression.

CONCLUSION

Interestingly, adaptive donors having C/G genotype of XRCC6 showed significantly higher (P < 0.05) mRNA expression level in primed cells suggesting their role in RAR. In addition, NHEJ repair gene polymorphisms play crucial role with radio-sensitivity and RAR in human PBMCs.

Association between genetic polymorphism of XRCC7 (G6721T) and risk of acute lymphoblastic leukemia

Background

The DNA non-homologous end joining repair gene XRCC7 is one of the most important genes in the DNA double-strand break (DSBs) repair. It is supposed that DNA repair gene malfunction is the main risk factor in various malignancies. The XRCC7 G6721T (rs7003908) polymorphism impact was investigated on the splicing regulation that cause mRNA instability. The goal of the present hospital-based study was to investigate the association between the common genetic polymorphism of XRCC7 G6721T (rs7003908) and risk of acute lymphoblastic leukemia (ALL). This hospital-based case–control study was performed on 99 ALL patients versus 200 healthy children, as the control group, which were frequent matched by age with cases. The polymorphism of XRCC7 was determined using an RFLP-PCR technique.

Results

The GT (OR = 1.485, 95% CI 0.765–2.334, P = 0.243) and TT (OR = 1.655, 95% CI 00.875–3.128, P = 0.121) genotypes had no significant effect on the risk of ALL, in comparison with the GG genotype. However, TT genotype (OR = 1.996, 95% CI 1.033–3.858, P = 0.04) after adjusting for the parents’ smoking pattern showed a significant impact.

Conclusions

These findings suggest that the TT genotype may increase the ALL susceptibility in children when facing with a tobacco smoke.

Genetic Variants Associated with Chronic Kidney Disease in a Spanish Population

Chronic kidney disease (CKD) patients have many affected physiological pathways. Variations in the genes regulating these pathways might affect the incidence and predisposition to this disease. A total of 722 Spanish adults, including 548 patients and 174 controls, were genotyped to better understand the effects of genetic risk loci on the susceptibility to CKD. We analyzed 38 single nucleotide polymorphisms (SNPs) in candidate genes associated with the inflammatory response (interleukins IL-1A, IL-4, IL-6, IL-10, TNF-α, ICAM-1), fibrogenesis (TGFB1), homocysteine synthesis (MTHFR), DNA repair (OGG1, MUTYH, XRCC1, ERCC2, ERCC4), renin-angiotensin-aldosterone system (CYP11B2, AGT), phase-II metabolism (GSTP1, GSTO1, GSTO2), antioxidant capacity (SOD1, SOD2, CAT, GPX1, GPX3, GPX4), and some other genes previously reported to be associated with CKD (GLO1, SLC7A9, SHROOM3, UMOD, VEGFA, MGP, KL). The results showed associations of GPX1, GSTO1, GSTO2, UMOD, and MGP with CKD. Additionally, associations with CKD related pathologies, such as hypertension (GPX4, CYP11B2, ERCC4), cardiovascular disease, diabetes and cancer predisposition (ERCC2) were also observed. Different genes showed association with biochemical parameters characteristic for CKD, such as creatinine (GPX1, GSTO1, GSTO2, KL, MGP), glomerular filtration rate (GPX1, GSTO1, KL, ICAM-1, MGP), hemoglobin (ERCC2, SHROOM3), resistance index erythropoietin (SOD2, VEGFA, MTHFR, KL), albumin (SOD1, GSTO2, ERCC2, SOD2), phosphorus (IL-4, ERCC4 SOD1, GPX4, GPX1), parathyroid hormone (IL-1A, IL-6, SHROOM3, UMOD, ICAM-1), C-reactive protein (SOD2, TGFB1,GSTP1, XRCC1), and ferritin (SOD2, GSTP1, SLC7A9, GPX4). To our knowledge, this is the second comprehensive study carried out in Spanish patients linking genetic polymorphisms and CKD.

Architecture of The Human Ape1 Interactome Defines Novel Cancers Signatures

APE1 is essential in cancer cells due to its central role in the Base Excision Repair pathway of DNA lesions and in the transcriptional regulation of genes involved in tumor progression/chemoresistance. Indeed, APE1 overexpression correlates with chemoresistance in more aggressive cancers, and APE1 protein-protein interactions (PPIs) specifically modulate different protein functions in cancer cells. Although important, a detailed investigation on the nature and function of protein interactors regulating APE1 role in tumor progression and chemoresistance is still lacking. The present work was aimed at analyzing the APE1-PPI network with the goal of defining bad prognosis signatures through systematic bioinformatics analysis. By using a well-characterized HeLa cell model stably expressing a flagged APE1 form, which was subjected to extensive proteomics analyses for immunocaptured complexes from different subcellular compartments, we here demonstrate that APE1 is a central hub connecting different subnetworks largely composed of proteins belonging to cancer-associated communities and/or involved in RNA- and DNA-metabolism. When we performed survival analysis in real cancer datasets, we observed that more than 80% of these APE1-PPI network elements is associated with bad prognosis. Our findings, which are hypothesis generating, strongly support the possibility to infer APE1-interactomic signatures associated with bad prognosis of different cancers; they will be of general interest for the future definition of novel predictive disease biomarkers. Future studies will be needed to assess the function of APE1 in the protein complexes we discovered. Data are available via ProteomeXchange with identifier PXD013368.

Polymorphic Variation in Double Strand Break Repair Gene in Indian Population: A Comparative Approach with Worldwide Ethnic Group Variations

DNA repair capacity is essential in maintaining cellular functions and homeostasis. Identification of genetic polymorphisms responsible for reduced DNA repair capacity may allow better cancer prevention. Double strand break repair pathway plays critical roles in maintaining genome stability. Present study was conducted to determine distribution of XRCC3 Exon 7 (C18067T, rs861539) and XRCC7 Intron 8 (G6721T, rs7003908) gene polymorphisms in North Indian population and compare with different populations globally. The genotype assays were performed in 224 normal healthy individuals of similar ethnicity using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Allelic frequencies of wild type were 79% (C) in XRCC3 Exon 7 C > T and 57% (G) in XRCC7 Intron 8 (G > T) 57% (G) observed. On the other hand, the variant allele frequency were 21% (T) in XRCC3 Exon 7 C > T and 43% (T) in XRCC7 Intron 8 G > T respectively. Major differences from other ethnic populations were observed. 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.

Role of polymorphic XRCC6 (Ku70)/XRCC7 (DNA-PKcs) genes towards susceptibility and prognosis of lung cancer patients undergoing platinum based doublet chemotherapy

The DNA repair genes XRCC6 and XRCC7 formed an integral part of double strand break repair (DSBR) pathway. The two genes are thought to play an important role in the repair of lethal double strand damage on DNA. Polymorphic DSBR genes are studied to effect genomic stability. We intend to explore the association of DSBR genes i.e. XRCC6 and XRCC7 with susceptibility and survival in North Indian lung cancer patients. DNA isolation and genotyping was done for 320 controls and 330 lung cancer cases enrolled in the study. Each and every lung cancer study subjects were made a telephonic call and were followed for their health after administration of chemotherapy. Statistical analysis for susceptibility was done using logistic regression analysis. Survival analysis was done using Kaplan-Meier followed by Cox-regression. Small cell lung cancer (SCLC) subtype posed an amplified risk towards lung cancer in case of XRCC7 6721G>T (OR = 4.11, p = 0.0040). Gene-environment interaction analysis revealed that non-smokers with heterozygous genotype (CG) in case of XRCC6 61C>G showed a strong protective effect (OR = 0.38, p = 0.01) towards lung cancer. Survival analysis revealed poor prognosis in case of XRCC6 61C>G SCLC subtype. XRCC6 and XRCC7 were not involved in overall susceptibility and survival. However, in case of XRCC7 6721G>T subjects with SCLC subtype showed an increased susceptibility while poor prognosis in case of XRCC6 61C>G.

Association Between Twelve Polymorphisms in Five X-ray Repair Cross-complementing Genes and the Risk of Urological Neoplasms: A Systematic Review and Meta-Analysis

Polymorphisms in X-ray repair cross-complementing (XRCC) genes have been implicated in altering the risk of various urological cancers. However, the results of reported studies are controversial. To ascertain whether polymorphisms in XRCC genes are associated with the risk of urological neoplasms, we conducted present updated meta-analysis and systematic review. Summary odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to estimate the association. Finally, 54 publications comprising 129 case-control studies for twelve polymorphisms in five XRCC genes were enrolled. We identified that XRCC1-rs25489 polymorphism was associated with an increased risk of urological neoplasms in heterozygote and dominant models. Moreover, in the subgroup analysis by cancer type, we found that XRCC1-rs25489 polymorphism was associated with an increased risk of bladder cancer (BC) in heterozygote model. Although overall analyses suggested a null result for XRCC1-rs25487 polymorphism, in the stratified analysis by ethnicity, an increased risk of urological neoplasms for Asians in allelic and homozygote models was identified. While for other polymorphisms in XRCC genes, no significant association was uncovered. To sum up, our results indicated that XRCC1-rs25489 polymorphism is a risk factor for urological neoplasms, particularly for BC. Further studies with large sample size are needed to validate these findings.

XRCC5 VNTR, XRCC6 -61C>G, and XRCC7 6721G>T Gene Polymorphisms Associated with Male Infertility Risk: Evidences from Case-Control and In Silico Studies

We evaluate the association between genetic polymorphisms of XRCC5 VNTR, XRCC6 -61C>G, and XRCC7 6721G>T with male infertility susceptibility. A total of 392 men including 178 infertile males (102 idiopathic azoospermia and 76 severe oligozoospermia) and 214 healthy controls were recruited. XRCC6 -61C>G and XRCC7 6721G>T genotyping was performed by PCR-RFLP whereas XRCC5 VNTR was performed by PCR. The 2R allele and 2R allele carriers of XRCC5 VNTR polymorphism significantly decreased risk of male infertility. The mutant GG genotypes and carriers of the CG and GG genotypes of XRCC6 -61C>G showed increased risk for the male infertility. Furthermore, the G allele of the XRCC6 -61C>G was correlated with increased susceptibility to male infertility. Likewise, the T allele of the XRCC7 6721G>T polymorphism was associated with increased susceptibility to male infertility in azoospermia. In silico analysis predicted that the presence of tandem repeats in XRCC5 gene prompter can be sequence to bind to more nuclear factors. Also, rs2267437 (C>G) variant was located in a well-conserved region in XRCC6 promoter and this variation might lead to differential allelic expression. The XRCC7 6721G>T gene polymorphism occurred in an acceptor-splicing site, but this polymorphism has no severe modification on XRCC7 mRNA splicing. Our results indicate the association of XRCC5 VNTR, XRCC6 -61C>G, and XRCC7 6721G>T gene polymorphisms with male infertility in Iranian men.

DNA repair system and renal cell carcinoma prognosis: under the influence of NBS1

Nibrin (NBS1) is a protein involved in the maintenance of genomic stability and in DNA repair mechanisms. The NBS1 E185Q polymorphism (rs1805794) has been investigated in several studies, including its influence in the pathogenesis of renal cell carcinoma (RCC), although its prognostic value is still not determined for these patients. The purpose of the present work was to determine the role of NBS1 E185Q polymorphism as a prognostic factor/genetic marker of survival in patients with RCC. We conducted a hospital-based study analyzing 172 caucasian patients with histopathological diagnosis of RCC, for which polymorphism genotyping was performed by TaqMan(®) Allelic Discrimination methodology. In this study, we have found that male patients, non-metastatic at diagnosis and NBS1 C allele carriers (GC/CC) showed a lower 5-years survival when compared with GG genotype patients (P = 0.045). Furthermore, for carriers of low-activity NBS1 C allele, multivariate Cox regression analysis revealed almost a fourfold increase in risk of death at 5 years, after adjustment for age, histological type, Fuhrman's grade, tumor size and vascular permeation (HR 3.92; 95 % CI 1.33-11.57; P = 0.013). There were no statistically significant differences between the NBS1 E185Q genotypes and the assessed patients' clinical-pathological characteristics. Our results demonstrate for the first time the impact of NBS1 E185Q polymorphism in RCC prognosis suggesting that, for RCC male patients non-metastatic at diagnosis, this polymorphism might be a putative genetic marker in the clinical outcome.

DNA double-strand break repair gene XRCC7 genotypes were associated with hepatocellular carcinoma risk in Taiwanese males and alcohol drinkers

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, the prevalence and mortality rates of which are very high in Taiwan. The study aimed at evaluating the contribution of XRCC7 G6721T, together with cigarette smoking and alcohol drinking lifestyles, to the risk of HCC. In this hospital-based case-control study, the association of XRCC7 single nucleotide polymorphism G6721T with HCC risk was examined by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) among 298 HCC patients and 889 age- and gender-matched healthy controls. The results showed that the percentages of TT, GT, and GG XRCC7 G6721T were 53.0, 41.3, and 5.7 % in the HCC patient group and 48.9, 43.1, and 8.0 % in the non-cancer control group, respectively. We have further stratified the populations by genders, cigarette smoking, and alcohol drinking status to investigate their combinative contributions with XRCC7 G6721T genotype to HCC risk. The results showed that the GG genotype of XRCC7 G6721T conducted a protective effect on HCC susceptibility which was obvious among males and drinkers, but not females, smokers, non-smokers, or non-drinkers (p = 0.0058, 0.0069, 0.1564, 0.2469, 0.9354, and 0.3416, respectively). Our results suggested that the GG and GT genotypes of X-ray repair cross-complementing group 7 (XRCC7) G6721T had no effect on HCC risk to the whole population, but had a protective effect on HCC risk among males and alcohol drinkers.

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%).

The rs7003908 (T>G) polymorphism in the XRCC7 gene and the risk of cancers

The association between the rs7003908 (T>G) polymorphism in the XRCC7 gene and the risk of cancers had been widely studied; however, the results were inconsistent. The objective of the current study was to investigate the association between the rs7003908 polymorphism in the XRCC7 gene and the risk of cancers by meta-analysis. We searched PubMed, EMbase, CNKI and Wanfang databases; the last search was performed on January 10th, 2014. Statistical analysis was performed using the Revman4.2 and STATA10.0 softwares. A total of 3,684 cancer cases and 5,232 controls from 11 case-control studies were included for data analysis. In the dominant model analysis, the results suggested a lack of association between the polymorphism and the risk of cancers: OR 1.01, 95% CI 0.83-1.16, P = 0.70. In the subgroup analysis by ethnicity, no significant association was found either for Asians or Caucasians. In the subgroup analysis by cancer types, significant association was found for prostate cancer, but not for bladder cancer, breast cancer and glioma. In summary, the current meta-analysis confirmed that the rs7003908 polymorphism in the XRCC7 gene might be a risk factor for prostate cancer. In the future, more studies are needed to validate these results.

NBN Gene Polymorphisms and Cancer Susceptibility: A Systemic Review

The relationship between DNA repair failure and cancer is well established as in the case of rare, high penetrant genes in high cancer risk families. Beside this, in the last two decades, several studies have investigated a possible association between low penetrant polymorphic variants in genes devoted to DNA repair pathways and risk for developing cancer. This relationship would be also supported by the observation that DNA repair processes may be modulated by sequence variants in DNA repair genes, leading to susceptibility to environmental carcinogens. In this framework, the aim of this review is to provide the reader with the state of the art on the association between common genetic variants and cancer risk, limiting the attention to single nucleotide polymorphisms (SNPs) of the NBN gene and providing the various odd ratios (ORs). In this respect, the NBN protein, together with MRE11 and RAD50, is part of the MRN complex which is a central player in the very early steps of sensing and processing of DNA double-strand breaks (DSBs), in telomere maintenance, in cell cycle control, and in genomic integrity in general. So far, many papers were devoted to ascertain possible association between common synonymous and non-synonymous NBN gene polymorphisms and increased cancer risk. However, the results still remain inconsistent and inconclusive also in meta-analysis studies for the most investigated E185Q NBN miscoding variant.

Associations of Lys939Gln and Ala499Val polymorphisms of the XPC gene with cancer susceptibility: a meta-analysis

XPC polymorphisms may alter DNA repair capacity, thus leading to genetic instability and carcinogenesis. Numerous studies have investigated the associations of XPC Lys939Gln (rs2228001) and Ala499Val (rs2228000) polymorphisms with cancer susceptibility; however, the findings are inconclusive. We searched literature from MEDLINE and EMBASE for eligible publications that assessed the associations between these two polymorphisms and cancer risk. We also assessed genotype-mRNA expression correlation data from HapMap for rs2228001 and rs2228000 in normal cell lines derived from 270 subjects with different ethnicities. The final analysis included 62 published studies of 25,708 cases and 30,432 controls for the Lys939Gln and 34 studies with 14,877 cases and 17,888 controls for the Ala499Val. Overall, Lys939Gln was significantly associated with an increased overall cancer risk (Gln/Gln vs. Lys/Lys: OR = 1.16, 95% CI = 1.07 - 1.25, p < 0.001; recessive model: OR = 1.14, 95% CI = 1.06 - 1.22, p < 0.001; dominant model: OR = 1.06, 95% CI = 1.01 - 1.11, p = 0.015 and Gln vs. Lys: OR = 1.07, 95% CI = 1.03 - 1.10, p < 0.001) and further stratifications showed an increased risk for bladder, lung and colorectal cancer, Asian populations and population-based studies. Likewise, Ala499Val was also significantly associated with an increased overall cancer risk (Val/Val vs. Ala/Ala: OR = 1.21, 95% CI = 1.07 - 1.36, p = 0.003 and recessive model: OR = 1.20, 95% CI = 1.08 - 1.34, p = 0.001) and further stratification showed an increased risk for breast and bladder cancer, particularly in Asian populations. Interestingly, significantly correlation between XPC genotypes and mRNA expression was found only for Asian populations as well. Despite some limitations, this meta-analysis established some solid statistical evidence for an association between XPC polymorphisms and cancer risk, which warrants further validation in single large studies.

Association between the XRCC3 T241M polymorphism and risk of cancer: evidence from 157 case-control studies

The T241M polymorphism in the X-ray cross-complementing group 3 (XRCC3) had been implicated in cancer susceptibility. The previous published data on the association between XRCC3 T241M polymorphism and cancer risk remained controversial. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and XRCC3 T241M (61,861 cases and 84,584 controls from 157 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 observed in any genetic model (dominant model: odds ration [OR]=1.07, 95% confidence interval [CI]=1.00-1.13; recessive model: OR=1.15, 95% CI=1.08-1.23; additive model: OR=1.17, 95% CI=1.08-1.28) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, the elevated risk remained for subgroups of bladder cancer and breast cancer, especially in Caucasians. In addition, significantly decreased lung cancer risk was also observed. In summary, this meta-analysis suggests the participation of XRCC3 T241M in the susceptibility for bladder cancer and breast cancer, especially in Caucasians, and XRCC3 T241M polymorphism is associated with decreased lung cancer risk. Moreover, our work also points out the importance of new studies for T241M association in some cancer types, such as gastric cancer, colorectal cancer, and melanoma skin cancer, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC3 polymorphism in cancer development.

X-ray repair cross-complementing group 1 Arg399Gln gene polymorphism and susceptibility to colorectal cancer:a meta-analysis

X-ray repair cross-complementing group 1 (XRCC1), a DNA repair enzyme, plays a crucial role in the base excision repair by generating a single nucleotide repair patch. It has been demonstrated that the XRCC1 Arg399Gln gene polymorphism was associated with variations in XRCC1 enzyme activity. The aim of this study was to quantitatively summarize the association between the XRCC1 Arg399Gln polymorphism and susceptibility to colorectal cancer (CRC). A comprehensive search of the PubMed, Embase, and China National Knowledge Infrastructure databases was conducted for studies on the association between the XRCC1 Arg399Gln polymorphism and CRC risk. Summary odds ratio (OR) with its corresponding 95 % confidence interval (95 %CI) was estimated, in a fixed-effects model or a random-effects model when appropriate, to assess the association. Totally, 26 case-control studies with 6,979 cases and 11,470 controls were included into this meta-analysis. The pooled results of total studies showed that the XRCC1 Arg399Gln polymorphism was significantly associated with increased risk of CRC in all genetic contrast models (OR(A vs. G) = 1.13, 95 %CI 1.03-1.23, P (OR) = 0.008; OR(Gln/Gln vs. Arg/Arg) = 1.24, 95 %CI 1.04-1.46, P (OR) = 0.015; OR(Gln/Gln vs. Arg/Gln + Arg/Arg) = 1.19, 95 %CI 1.03-1.38, P (OR) = 0.021; OR(Gln/Gln + Arg/Gln vs. Arg/Arg) = 1.14, 95 %CI 1.02-1.28, P (OR) = 0.022), except for the additive contrast model (OR(Arg/Gln vs. Arg/Arg) = 1.11, 95 %CI 0.99-1.25, P (OR) = 0.064). The statistically significant association between the XRCC1 Arg399Gln polymorphism and CRC risk was observed among studies with high quality and in Asians, but not in Caucasians. Sensitivity analyses by sequential omission of any individual studies further identified the significant association. Publication bias was inexistent in this meta-analysis. The meta-analysis suggests that the XRCC1 Arg399Gln polymorphism is associated with increased risk of CRC.

Association between exudative age-related macular degeneration and the G6721T polymorphism of XRCC7 in outdoor subjects

PURPOSE

To investigate whether the G6721T polymorphism (rs.7003908) of the non-homologous end-joining DNA repair XRCC7 gene contributes to the development of exudative age-related macular degeneration (ARMD).

METHODS

The present case-control study consisted of 111 patients with exudative ARMD and 112 sex frequency-matched healthy controls that were randomly selected from unrelated volunteers in the same clinic. Genotypes were determined by the Restriction Fragment Length Polymorphism (PCR-RFLP) based method. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for ARMD risk associated with polymorphism of XRCC7. In all analysis the GG genotype was considered to be the reference genotype.

RESULTS

There was no significant association between genotypes of XRCC7 and susceptibility to ARMD. Considering the significant difference in age distribution between cases and controls, age was used as a covariate in further analysis. After ORs were adjusted for age, the same result was observed. In the next step we stratified our subjects into outdoor and indoor groups according to their job titles. The outdoor and indoor patients were occupationally exposed to sunlight and not exposed to sunlight, respectively. Our present study showed that among indoor subjects there was no association between XRCC7 polymorphism and susceptibility to ARMD. However, among outdoor subjects, the GT + TT genotypes compared to the GG genotype increased the risk of ARMD (OR, 3.13; 95% CI, 1.04-9.39; p = 0.042).

CONCLUSIONS

Our study revealed that the T allele of the G6721T polymorphism of XRCC7 increased the risk of ARMD among outdoor subjects.

Current evidence on the relationship between three polymorphisms in the XRCC7 gene and cancer risk

Inconsistency of the association of polymorphisms of XRCC7 with cancer is noted. Three commonly studied XRCC7 polymorphisms including rs7003908 (T>G), rs7830743 (A>G), and rs10109984 (T>C) were selected to explore their association with risk of development of cancer by meta-analysis of published case-control studies. The results showed that no significant associations with cancer risk were found in any model in terms of rs7003908, rs7830743 and rs10109984 when all studies were pooled into the meta-analysis. But when stratified by cancer type, statistically significantly elevated cancer risk was only found in prostate cancer for rs7003908 (GG vs. TT: OR = 1.845, 95 % CI = 1.178-2.888; dominant model: OR = 1.423, 95 % CI = 1.050-1.929; recessive model: OR = 1.677, 95 % CI = 1.133-2.482). In the subgroup analysis by ethnicity or study design, no significantly increased risks were found for all three polymorphisms. This meta-analysis suggests that XRCC7 rs7003908 polymorphism may contribute to cancer susceptibility for prostate cancer, which is recommended to be included in future large-sample studies and functional assays.

Association between polymorphisms in DNA repair genes (XRCC1 and XRCC7) and risk of preeclampsia

PURPOSE

Although the exact genes involved in preeclampsia (PE) are still not fully discovered, an important role for oxidative stress in its pathogenesis is accepted. XRCC1 (MIM: 194360) and XRCC7 (MIM: 600899) play a crucial role in the DNA repair pathways. Functional polymorphisms in XRCC1 (Arg194Trp and Arg399Gln) and XRCC7 (G6721T) may be risk factors for PE. In the present study, the association between the genetic polymorphisms of XRCC1 and XRCC7 and risk of PE is investigated.

METHODS

The present case-control study was performed on 151 preeclapmtic patients, and a total of 344 normal pregnant women, as a control group. Control women had no history of pregnancies with PE.

RESULTS

Neither polymorphism of Arg194Trp XRCC1 nor polymorphism of G6721T XRCC7 associated with the risk of PE. The Gln/Gln genotype of Arg399Gln XRCC1 polymorphism increased the risk of PE (OR=2.39, 95 % CI: 1.38-4.14, P=0.002). Statistical analysis revealed that the haplotype "194Arg-399Gln" showed higher frequency among PE patients compared to the controls (OR=1.65, 95% CI: 1.23-2.19, P=0.001).

CONCLUSIONS

The present results suggest that the 399Gln allele of the XRCC1 is significant risk factor for PE development.

Genetic variation in DNA repair gene XRCC7 (G6721T) and susceptibility to breast cancer

The human XRCC7 is a DNA double-strand break (DSBs) repair gene, involved in non-homologous end joining (NHEJ). It is speculated that DNA DSBs repair have an important role during development of breast cancer. The human XRCC7 is a NHEJ DSBs repair gene. Genetic variation G6721T of XRCC7 (rs7003908) is located in the intron 8 of the gene. This polymorphism may regulate splicing and cause mRNA instability. In the present study, we specifically investigated whether common G6721T genetic variant of XRCC7 was associated with an altered risk of breast cancer. The present study included 362 females with breast cancer. Age frequency-matched controls (362 persons) were randomly selected from the healthy female blood donors, according to the age distribution of the cases. Using RFLP-PCR based method, the polymorphism of XRCC7 was determined. The TG (OR=1.20, 95% CI: 0.83-1.74, P=0.320) and TT (OR=1.01, 95% CI: 0.67-1.53, P=0.933) genotypes had no significant effect on risk of breast cancer, in comparison with the GG genotype. Our present findings indicate that the TT and TG genotypes were not associated with an altered breast cancer risk.

A functional polymorphism C-1310G in the promoter region of Ku70/XRCC6 is associated with risk of renal cell carcinoma

The DNA repair gene Ku70 plays a key role in the DNA double strand break (DSB) repair system. Defects in DSB repair capacity can lead to genomic instability. We hypothesized that the Ku70 C-1310G polymorphism (rs2267437) was associated with risk of renal cell carcinoma (RCC). We genotyped the Ku70 C-1310G polymorphism in a case-control study of 620 patients and 623 controls in a Chinese population and assessed the effects of C-1310G polymorphism on RCC susceptibility and survival. We then examined the functionality of this polymorphism. Compared with the Ku70-1310CC genotype, the CG and CG/GG genotypes had a significantly increased risk of RCC [adjusted odds ratio (OR) = 1.47, 95% confidence interval (CI) = 1.16-1.87 for CG and OR = 1.47, 95% CI = 1.16-1.86 for CG/GG]. However, the C-1310G polymorphism did not influence the survival of RCC. The in vivo experiments with normal renal tissues revealed statistically significantly lower Ku70 mRNA expression in samples with CG/GG genotypes relative to those with the CC genotype (P < 0.05). In vitro luciferase assays in various cell lines showed lower luciferase activity for the -1310G allele than for the -1310C allele. These results suggest that the Ku70 C-1310G polymorphism is involved in the etiology of RCC and thus may be a marker for genetic susceptibility to RCC in Chinese populations. Larger studies are warranted to validate our findings.

Association of Ku70 A-31G polymorphism and risk of renal cell carcinoma in a Chinese population

The DNA repair gene Ku70 plays a key role in the DNA double-strand breaks (DSBs) repair system. Defects in DSBs repair capacity can lead to genomic instability. We hypothesized that the Ku70 A-31G polymorphism (rs132770) was associated with the risk of renal cell carcinoma (RCC). In a hospital-based case-control study of 620 RCC patients and 623 cancer-free controls frequency matched by age and sex, we genotyped the functional polymorphism Ku70 A-31G (rs132770). Thirty-eight normal renal tissue samples with different genotypes were tested to estimate the Ku70 mRNA expression by real-time quantitative reverse transcription. Compared with the GG genotype, the GA and GA/AA genotypes had a significantly decreased risk of RCC [adjusted odds ratio (OR) = 0.62, 95% confidence interval (CI) = 0.44-0.87 for GA, and OR = 0.62, 95% CI = 0.45-0.86 for GA/AA]. The in vivo experiments with normal renal tissues revealed that a statistically significantly higher Ku70 mRNA expression was identified in samples with GA/AA genotypes compared with those with GG genotypes (p = 0.001). These results suggested that the Ku70 A-31G polymorphism is involved in the etiology of RCC and, thus, may be a marker for genetic susceptibility to RCC in the Chinese populations.

Nucleotide excision repair gene ERCC1 polymorphisms contribute to cancer susceptibility: a meta-analysis

Individual studies of the associations between excision repair cross-complimentary group 1 (ERCC1) polymorphisms and cancer susceptibility have shown inconclusive results. To derive a more precise estimation of the relationship between three well-characterised polymorphisms on ERCC1 and the risk of cancer, we performed a meta-analysis based on 48 publications. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the associations. We found that ERCC1 17677A (rs3212961) variant genotypes were associated with significantly increased overall risk of cancer without substantial heterogeneity (AA versus CC, OR = 1.36, 95% CIs: 1.10-1.68; AC versus CC: OR = 1.11, 95% CIs: 0.99-1.26; dominant comparison: AA/AC versus CC: OR = 1.15, 95% CIs: 1.02-1.29; recessive comparison: AA versus AC/CC: OR = 1.25, 95% CIs: 1.05-1.49). The ERCC1 19007 C (rs11615) allele had null effects on overall risk of cancer; but in the stratified analyses, we observed an elevated association in Asian populations with homozygote variants and hospital-based controls. In addition, during further stratified analyses of cancer groups, homozygote variants were found that are associated with lung cancer and smoking-related cancers. Also, the observed ERCC1 19007 C heterozygote variant contributes to the development of skin cancer. However, the ERCC1 8092C > A (rs3212986) polymorphism did not appear to have an effect on cancer risk. Additionally, no evidence of publication bias was observed in these polymorphisms. Our meta-analysis supports the conclusion that the ERCC1 17677A > C and ERCC1 19007T > C polymorphisms, but not the ERCC1 8092C > A polymorphism, are low-penetrance risk factors for cancer development.

Genetic biomonitoring of inhabitants exposed to uranium in the north region of Brazil

Aiming to assess the susceptibility of populations in the Brazilian Amazon region to ionizing radiation emitted from uranium, mutations frequencies in the DNA repair genes XRCC1 and XRCC3 and in the metabolic gene GSTM1 were evaluated. The XRCC1 allele frequencies for the 194Trp polymorphism in the municipalities of Monte Alegre, Prainha and Alenquer were, respectively, 0.12, 0.13 and 0.07, and for 399Gln polymorphism they were, respectively, 0.28, 0.30 and 0.32. Frequencies for GSTM1 gene deletion homozygotes were, respectively, 0.36, 0.31 and 0.40 for all municipalities. These frequencies are comparable to those described for Brazilian individuals from other regions of the country. Also, allele frequencies of XRCC3 241Met polymorphism of the Monte Alegre and Alenquer populations were 0.28 and 0.33, respectively. In conclusion, frequencies of important polymorphic features of cellular DNA repair and metabolic apparatus in the populations studied do not differ from those of populations in other regions of Brazil.

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.

Role of the XRCC5/XRCC6 dimer in carcinogenesis and pharmacogenomics

Over the past few decades, the incidence of cancer has rapidly increased all over the world and cancer remains a major threat to public health. It is believed that cancer results from a series of genetic alterations that lead to the progressive disorder of the normal mechanisms controlling cell proliferation, differentiation, death and/or genomic stability. The response of the cell to genetic injury and its ability to maintain genomic stability by means of a variety of DNA repair mechanisms are therefore essential in preventing tumor initiation and progression. From the same viewpoint, the relative role of DNA repair as a biomarker for prognosis, predictor of drug and therapy responses or indeed as a target for novel gene therapy, is very promising. In this article, we have summarized the studies investigating the association between the XRCC5/XRCC6 dimer and the susceptibility to multiple cancers and discuss its role in carcinogenesis and its potential application to anticancer drug discovery.

Do DNA repair genes OGG1, XRCC3 and XRCC7 have an impact on susceptibility to bladder cancer in the North Indian population?

OBJECTIVE

Polymorphisms in DNA repair genes may be associated with altered DNA repair capacity, thereby influencing an individual's susceptibility to smoking-related cancers such as bladder cancer. Therefore, we sought to examine the correlation between single nucleotide polymorphisms in DNA repair genes and bladder cancer.

METHODOLOGY

We undertook a case-control study of 212 urothelial bladder cancer (UBC) cases and 250 controls to investigate the association between OGG1 (C1245G rs1052133), XRCC3 (C18067T, rs861539) and XRCC7 (G6721T, rs7003908) polymorphisms and bladder cancer susceptibility by PCR-RFLP and the ARMS method. We also investigated gene-environment interactions.

RESULTS

The OGG1 GG genotype was associated with an elevated risk of urothelial bladder cancer (UBC) (OR, 2.10; p, 0.028). XRCC7 + 6721 GG was also associated with increased susceptibility to UBC (OR, 4.45; p, 0.001). In a recessive model, the OGG1 GG genotype showed an increased risk of TaG(2,3) + T1G(1-3) tumors. Additionally, the OGG1 GG genotype in non-smokers represented a 2.46-fold greater risk (OR, 2.46; p, 0.035) in bladder cancer patients. Subsequent analysis demonstrated more pronounced association of XRCC7 with smokers (OR, 4.39; p, 0.001). XRCC7 also showed increased association with TaG(2,3) + T1G(1-3) tumors and muscle invasive tumors (OR, 3.16; p, 0.001 and OR, 4.24; p, 0.001, respectively). Multiple Cox regression analysis in non-muscle invasive bladder tumor (NMIBT) patients demonstrated an association of the OGG1 GG polymorphism with a high risk of recurrence in patients on cystoscopic surveillance (HR, 4.04; p, 0.013). Subsequently, shorter recurrence-free survival (log rank p, 0.024; CC/GG, 42/24) was observed.

CONCLUSION

Our data suggest association of a variant (GG) genotype of OGG1 with increased UBC susceptibility and a high risk of tumor recurrence in NMIBT patients on cystoscopic surveillance. XRCC7 G allele carriers (TG+GG) are also at an elevated risk for susceptibility to UBC as evidenced by a high odds ratio throughout the analysis.

Renal tumor natural history: the rationale and role for active surveillance

Renal cell carcinoma (RCC) is the most common malignancy of the kidney. Despite widespread treatment at diagnosis, overall mortality rates associated with RCC have not decreased. Partly because of the more frequent use of abdominal imaging, diagnosis as an incidental finding has increased. The largest increase in incidence is in tumors smaller than 4 cm, termed small renal masses (SRMs). SRMs that are RCC may frequently be growth slowly and have a low risk of early progression. Initial active surveillance with delayed treatment for progression for selected patients should be considered. This should result in an overall decrease in treatment burden and cost saving.

Contemporary epidemiology of renal cell cancer

We analyzed renal cell cancer incidence patterns in the United States and reviewed recent epidemiologic evidence with regard to environmental and host genetic determinants of renal cell cancer risk. Renal cell cancer incidence rates continued to rise among all racial/ethnic groups in the United States, across all age groups, and for all tumor sizes, with the most rapid increases for localized stage disease and small tumors. Recent cohort studies confirmed the association of smoking, excess body weight, and hypertension with an elevated risk of renal cell cancer, and suggested that these factors can be modified to reduce the risk. There is increasing evidence for an inverse association between renal cell cancer risk and physical activity and moderate intake of alcohol. Occupational exposure to trichloroethylene has been positively associated with renal cell cancer risk in several recent studies, but its link with somatic mutations of the von Hippel-Lindau gene has not been confirmed. Studies of genetic polymorphisms in relation to renal cell cancer risk have produced mixed results, but genome-wide association studies with larger sample size and a more comprehensive approach are underway. Few epidemiologic studies have evaluated risk factors by subtypes of renal cell cancer defined by somatic mutations and other tumor markers.

Genetic susceptibility to renal cell carcinoma: the role of DNA double-strand break repair pathway

Alterations in DNA repair genes have been shown to cause a reduction in host DNA repair capacity and may influence host susceptibility to carcinogenesis. The double-strand break repair is a major DNA-repair pathway. This study tested the hypothesis that common sequence variants of the double-strand break pathway genes predispose susceptible individuals to an increased risk for renal cell carcinoma. Toward this end, we evaluated the associations of 13 single-nucleotide polymorphisms in 10 candidate genes involved in the double-strand break pathway with renal cell carcinoma risk in a population-based case-control study that included 326 Caucasian renal cell carcinoma patients and 335 controls. Using the homozygous wild type as the reference group, we observed a significantly increased renal cell carcinoma risk associated with the homozygous variant genotype of NBS1 (rs1805794; odds ratio, 2.13; 95% confidence interval (95% CI), 1.17-3.86). Carrying of at least one copy of the variant XRCC4 allele was also associated with a significantly increased risk (rs1805377; odds ratio, 1.56; 95% CI, 1.08-2.26). Importantly, in pathway analysis, compared with the reference group (1 or less adverse alleles), individuals with two (odds ratio, 1.26; 95% CI, 0.83-1.91), three (odds ratio, 1.00; 95% CI, 0.64-1.56), and more than three adverse alleles (odds ratio, 1.75; 95% CI, 1.03-2.98) were at increased risk for renal cell carcinoma with significant association in subjects carrying more than 3 adverse alleles. Results from this study provide evidence that individuals with a higher number of genetic variations in the DBS repair pathway are at an increased risk for renal cell carcinoma. These findings require further validation in independent populations.

The xeroderma pigmentosum group C gene polymorphisms and genetic susceptibility of nasopharyngeal carcinoma

AIMS

Nasopharyngeal cancer (NPC) is a multi-factorial disease, and the genetic background may be a crucial etiologic factor. The xeroderma pigmentosum complementation group C (XPC) is mainly involved in DNA damage repair, and the sequence variants in XPC gene may modulate DNA repair capacity and consequently lead to an individual's susceptibility to NPC. The aims of this study were to examine the association between XPC Val499Ala, Lys939Gln, PAT polymorphisms and the genetic susceptibility of nasopharyngeal carcinoma (NPC) in Chinese population.

METHODS

We analyzed the three XPC gene polymorphisms in 153 patients with NPC and 168 age- and sex-matched controls in a Chinese population, using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) procedure.

RESULTS

There were significant differences in the genotype and allele distribution of XPC Val499Ala among cases and controls. The 499Val allele carriers were associated with a significantly increased risk of NPC compared with the non-carriers (OR=1.603; 95%CI,1.160 approximately 2.216, p=0.005). Consistent with the results of the genotype analysis, the 499Val/939Lys/PAT haplotype was associated with a significantly increased risk of NPC as compared with the 499Ala/939Lys/PAT haplotype (OR=1.901;95% CI, 1.284 approximately 2.814, p=0.002). The interaction between the Val499Ala polymorphism and gender or smoking status did not been found in NPC risk.

CONCLUSIONS

Our data demonstrated that XPC 499Val allele and its haplotype were strongly associated with NPC, which indicated that Val499Ala polymorphism may be a contributing factor in the NPC development.

Associations between XPC polymorphisms and risk of cancers: A meta-analysis

Several polymorphisms (Lys(939)Gln, PAT+/- and Ala(499)Val) in the DNA nuclear excision repair gene xeroderma pigmentosum complementation group C (XPC) are thought to have significant effects on cancer risk. In this meta-analysis, we assessed reported studies of associations between three XPC polymorphisms and risk of cancers from 16 studies with 6797 cases and 9018 controls for Lys(939)Gln, from 11 studies with 5581 cases and 6351 controls for Ala(499)Val and from 16 studies with 4514 cases and 5538 controls for PAT+/-. We found an increased overall cancer risk for variant homozygotes of Lys(939)Gln (OR=1.16, 95% CI, 1.05-1.28) and Ala(499)Val (OR=1.24, 95% CI, 1.08-1.42) compared with their corresponding wild-type homozygotes. When stratified by cancer type, the variant (939)Gln homozygous genotype was a risk factor for lung cancer (OR=1.28, 95% CI, 1.07-1.53), whereas the (499)Val variant homozygous genotype was a risk factor for bladder cancer (OR=1.33, 95% CI, 1.06-1.68) compared with their corresponding wild-type homozygous genotypes. For the XPC-PAT polymorphism, we found a decreased cancer risk associated with the PAT+/- genotype only in Asians compared with the PAT-/- genotype. Five studies were pooled for stratification analysis to explore the gene-smoking interaction. There was a joint effect of PAT +/+ and smoking in cancer risk. These analyses suggest that XPC Lys(939)Gln, PAT+/- and Ala(499)Val likely contribute to susceptibility to cancers. However, single larger studies with subjects of the same ethnic background and tissue-specific biochemical and biological characterisation are warranted to validate these findings.

Case-control analysis of nucleotide excision repair pathway and the risk of renal cell carcinoma

In this population-based case-control study with 325 Caucasian renal cell carcinoma (RCC) patients and 335 controls matched to cases by age, gender and county of residence, we evaluated the associations between 13 potential functional polymorphisms in nine major nucleotide excision repair (NER) genes and RCC risk. In individual single nucleotide polymorphism analysis, after adjustment for multiple comparisons, a significantly decreased RCC risk was observed for the heterozygous genotype of XPD Asp312Asn [odds ratio (OR) = 0.62; 95% confidence interval (CI): 0.43-0.90] and for the heterozygous and homozygous variant genotypes combined in a dominant model (OR = 0.64; 95% CI: 0.46-0.89). The heterozygous AG genotype of XPA 5'untranslated region was at 1.78-fold increased risk (95% CI: 1.18-2.69) and the risk reached 2.43-fold (95% CI: 1.57-3.75) for the homozygous variant GG genotype; the risk was significant both in the dominant model and in the recessive model. In joint analysis, compared with individuals with fewer than five adverse alleles, individuals with five (OR = 1.17; 95% CI: 0.71-1.93), six (OR = 1.66; 95% CI: 1.03-2.67), seven or more (OR = 1.85; 95% CI: 1.16-2.95) exhibited a progressively increased risk of RCC (P for trend = 0.004). Further, there were significant interactions between NER pathway genes and sex, hypertension and obesity (all P for interaction <0.05). Our results strongly support that common sequence variants of the NER pathway genes predispose susceptible individuals to increased risk of RCC and that the association may be modified by gender, history of hypertension and obesity. These results need to be replicated in larger studies.

Genetic variants of the XRCC7 gene involved in DNA repair and risk of human bladder cancer

OBJECTIVE

To investigate the association between the polymorphisms of the KU70 and X-ray repair cross complementing group 7 (XRCC7) genes and the risk of bladder cancer.

METHODS

This hospital-based case-control study included 213 patients with newly diagnosed bladder transitional cell carcinoma and 235 cancer-free controls frequency-matched by age and sex. Two polymorphisms, KU70 and XRCC7, using a method involving polymerase chain reaction-restriction fragment length polymorphism were genotyped.

RESULTS

The risk of bladder cancer decreased in a dose-response manner as the number of XRCC76721G alleles increased (adjusted odds ratio [OR] = 0.70, 95% confident interval [CI] = 0.47-1.03 for 6721GT and OR = 0.31, 95% CI = 0.10-0.99 for 6721GG; P(trend) = 0.013). However, when we used 6721 (GT + GG) as the reference, we found a statistically significant increased risk of bladder cancer associated with the 6721TT genotype (OR = 1.53, 95% CI = 1.04-2.25). In the stratification analysis, this increased risk was more pronounced among subgroups of patients aged >65 years (OR = 2.27; 95% CI = 1.25-4.10) and ever smokers (OR = 2.06, 95% CI = 1.15-3.68). Furthermore, we observed a 3.24-fold increased risk (95% CI = 1.35-7.78) for smokers aged >65 years carrying 6721TT genotype compared with those carrying the 6721 (GG + GT) genotype. However, the KU70-61C > G polymorphism was not associated with a significantly increased risk of bladder cancer.

CONCLUSIONS

The XRCC7 but not the KU70 polymorphism appears to be involved in the etiology of human bladder cancer. Larger studies with more detailed data on environmental exposure are needed to verify these initial findings.

XPC polymorphisms play a role in tissue-specific carcinogenesis: a meta-analysis

XPC participates in the initial recognition of DNA damage during the DNA nucleotide excision repair process in global genomic repair. Polymorphisms in XPC gene have been analyzed in case-control studies to assess the cancer risk attributed to these variants, but results are conflicting. To clarify the impact of XPC polymorphisms in cancer risk, we performed a meta-analysis that included 33 published case-control studies. Polymorphisms analyzed were Lys939Gln and Ala499Val. The overall summary odds ratio (OR) for the associations of the 939Gln/Gln genotype with risk of cancer was 1.01 (95% confidence interval (95% CI): 0.94-1.09), but there were statistically significant associations for lung cancer, observed for the recessive genetic model (Lys/Lys+Lys/Gln vs Gln/Gln), (OR 1.30; 95% CI: 1.113-1.53), whereas for breast cancer a reduced but nonsignificant risk was observed for the same model (OR 0.87; 95% CI: 0.74-1.01). The results for Ala499Val showed a significant overall increase in cancer risk (OR 1.15; 95% CI: 1.02-1.31), and for bladder cancer in both the simple genetic model (Ala/Ala vs Val/Val) (OR 1.30; 95% CI: 1.04-1.61) and the recessive genetic model (Ala/Ala+Ala/Val vs Val/Val) (OR 1.32; 95% CI: 1.06-1.63). Our meta-analysis supports that polymorphisms in XPC may represent low-penetrance susceptibility gene variants for breast, bladder, head and neck, and lung cancer. XPC is a good candidate for large-scale epidemiological case-control studies that may lead to improvement in the management of highly prevalent cancers.

A meta-analysis of DNA repair gene XPC polymorphisms and cancer risk

Polymorphisms (A33512C, C21151T and PAT -/+) of the xeroderma pigmentosum group C (XPC) were shown to contribute to genetic susceptibility to cancer. However, association studies on these polymorphisms in cancer have shown conflicting results. Thus, we performed a meta-analysis. Overall, there was no significant association between 33512C (9,091 patients and 11,553 controls) and cancer risk. No significant association was found in stratification analysis by tumor sites and ethnicities except an elevated lung cancer risk under the recessive genetic model in all subjects [P = 0.04, odds ratio (OR) = 1.20, 95% confidence interval (CI) 1.00-1.45, P (heterogeneity) = 0.88]. There was no significant association between 21151T (5,227 patients and 5,959 controls) and cancer risk in all subjects but an increased cancer risk in Caucasians under the recessive genetic model (P = 0.006, OR = 1.45, 95% CI 1.11-1.90, P (heterogeneity) = 0.75) and homozygote comparison (P = 0.02, OR = 1.41, 95% CI 1.07-1.81, P (heterogeneity) = 0.41). It might be that 21151T increases bladder cancer risk under the recessive genetic model (P = 0.02, OR = 1.49, 95% CI 1.06-2.09, P (heterogeneity) = 0.47) and homozygote comparison (P = 0.02, OR = 1.49, 95% CI 1.05-2.11, P (heterogeneity) = 0.23). There was no significant association between PAT + (4,600 patients and 4,866 controls) and cancer risk in all subjects. An increased cancer risk in Caucasians was found under the recessive genetic model (P = 0.02, OR = 1.20, 95% CI 1.03-1.40, P (heterogeneity) = 0.37) and homozygote comparison (P = 0.008, OR = 1.26, 95% CI 1.06-1.50, P (heterogeneity) = 0.13). The XPC PAT + allele might increase head and neck cancer risk (P = 0.02, OR = 1.29, 95% CI 1.04-1.59, P (heterogeneity) = 0.15). More studies based on larger, stratified, case-control population, especially studies investigate the combined effect of XPC A33512C, C21151T, and PAT, are required to further evaluate the role of these polymorphisms in different cancers.

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.

Current status of excision repair cross complementing-group 1 (ERCC1) in cancer

Cisplatin, carboplatin and oxaliplatin are some of the most widely used anti-cancer agents in solid tumours. The cytotoxicity of platinating agents is directly related to their ability to cause DNA intra-strand crosslinks that trigger a series of intracellular events that ultimately result in cell death. DNA intra-strand crosslinks are processed and repaired by the nucleotide excision repair pathway. It is now clear that nucleotide excision repair (NER) capacity may have a major impact on the emergence of resistance, normal tissue tolerance and patient outcomes. ERCC1 is a key player in NER. In this review, we provide an overview of mammalian NER and then focus on biochemical, structural and pre-clinical aspects of ERCC1. We then present current clinical evidence implicating ERCC1 as a predictive and prognostic marker in cancer. Early evidence also suggests that ERCC1 or the pathways involved in the regulation of ERCC1 expression may be attractive anti-cancer targets. Such agents are expected to potentiate the cytotoxicity of platinating agents and could have a major impact on cancer therapy.

No association of ERCC1 C8092A and T19007C polymorphisms to cancer risk: a meta-analysis

ERCC1 (excision repair cross complementation group 1) is a subunit of the nucleotide excision repair complex, which can perform DNA strand incision correction of DNA damage. Association studies on the ERCC1 polymorphisms (C8092A and T19007C) in cancer had shown conflicting results. We performed a meta-analysis from all eligible case-control studies to assess the purported associations. Overall, the 19007C allele (3 853 patients and 4 349 controls) showed no significant effect on cancer risk compared to 19007T allele (P=0.39, odds ratio (OR)=0.95; 95% confidence interval (CI) 0.85-1.06, P(heterogeneity)=0.001) in all subjects. Meta-analysis under other genetic contrasts did not reveal any significant association of T19007C to cancer in all subjects, Caucasians and Asians. The 19007C allele (2 279 patients and 2 808 controls) showed no significant effect on lung cancer risk compared to 19007T allele (P=0.72, OR=0.94, 95% CI 0.69-1.29, P(heterogeneity)=0.0001) in all subjects. No significant effect of 8092A allele (3 865 patients and 3 750 controls) on cancer risk in all subjects (P=0.85, OR=1.01, 95% CI 0.94-1.08, P(heterogeneity)=0.92) and in Caucasians and Asians compare to 8092C. No evidences of association of C8092A (501 patients and 620 controls) to squamous cell carcinoma were found. The accumulated evidence indicated ERCC1 T19007C and C8092A might not be risk factors for cancer. Significant between-study heterogeneity existed in T19007C, which arose from a study showing significant protecting effect of 19007C allele compare to 19007T allele in smokers. More studies based on larger, stratified case-control population should be required to further evaluate the role of ERCC1 C8092A and T19007C polymorphisms in different cancer, especially in smokers.