Glioma risk associates with polymorphisms of DNA repair genes, XRCC1 and PARP1

A Novel DNA Damage Repair-Related Gene Signature for Predicting Glioma Prognosis

Background

Glioma is one of the most prevalent tumors in the central nervous system of adults and shows a poor prognosis. This study aimed to develop a DNA damage repair (DDR)-related gene signature to evaluate the prognosis of glioma patients.

Methods

Differentially expressed genes (DEGs) were extracted based on 276 DDR genes. Then, a gene signature was developed for the survival prediction in glioma patients by means of univariate, multivariate Cox, and least absolute shrinkage and selector operation (Lasso) analyses. After analyzing the clinical parameters, a nomogram was constructed and assessed. A total of 693 gliomas from the Chinese Glioma Genome Atlas (CGGA) were used for external validation. In addition, we used glioma tumor tissues for qPCR experiment to verify.

Results

A 12-DDR-related gene signature was identified from the 75 DEGs to stratify the survival risk of glioma patients. The overall survival of high-risk group was significantly shorter than that of low-risk group (P < 0.001). Besides, according to the risk score assessment, patients in high- or low-risk group also had significant correlations with clinicopathological parameters, including age (P < 0.01), grade (P < 0.001), IDH status (P < 0.001) and 1p19q codeletion status (P < 0.001). The nomogram provided favorable C-index and calibration plots. The C-index of training set and verification set was 0.761 and 0.746, respectively, and the calibration curve also showed that both training set and verification set were close to the standard curve. The qPCR results showed that there were significant differences in the expression of some typical DDR-related genes in tumor tissues and paracancer tissues (P_(WEE1)=0.0002, P_(RECQL)=0.0117, P_(RPA1)=0.021, P_(RRM1)=0.0035, P_(PARP4)=0.0006, P_(ELOA)=0.0023).

Conclusion

Our study developed a novel 12 DDR-related gene signature as a practical prognostic predictor for glioma patients. A nomogram combining the signature and clinical parameters was established as an individual clinical prediction tool.

The Prognostication Potential of BRCA Genes Expression in Gliomas: A Genetic Survival Analysis Study

BACKGROUND

Gliomas are the most common type of central nervous system tumor in adults, and they have an extremely poor prognosis. Gliomas are classified into 4 grades, with low-grade gliomas (LGGs) constituting grades I and II and glioblastoma multiforme (GBM) constituting grade IV. Breast cancer susceptibility genes BRCA1 and BRCA2 play a role in DNA repair and are required for genome stability.

METHODS

We analyzed the LGG and GBM cohorts from The Cancer Genome Atlas. We used Kaplan-Meier and log-rank analysis to determine the relationship between BRCA1 and BRCA2 expression and survival.

RESULTS

Correlation of BRCA1 and BRCA2 expression with survival in patients with LGG was significant (P = 0.00 and P = 0.00). The higher the levels of expression were, the lower survival rates were in both LGG and GBM cohorts, but the correlation was not significant in patients with GBM (P < 0.01).

CONCLUSIONS

Our findings suggest that BRCA1 and BRCA2 can be regarded as poor prognostic factors in patients with glioma, with greater significance in patients with LGG. In the future, more in-depth experiments will enable us to elucidate the mechanism of gliomagenesis and identify potential gene therapy targets.

Genetic and expression variations of cell cycle pathway genes in brain tumor patients

The present study was designed to determine the association between the genetic polymorphisms/expression variations of RB1 and CCND1 genes and brain tumor risk. For this purpose, 250 blood samples of brain tumor patients along with 250 controls (cohort I) and 96 brain tumor tissues (cohort II) with adjacent control section were collected. Mutation analysis of RB1 (rs137853294, rs121913300) and CCND1 (rs614367, rs498136) genes was performed using ARMS-PCR followed by sequencing, and expression analysis was performed using real-time PCR and immunohistochemistry. The results showed homozygous mutant genotype of RB1 gene polymorphism, rs121913300 (P=0.003) and CCND1 gene polymorphism rs614367 (P=0.01) were associated significantly with brain tumor risk. Moreover, significant down-regulation of RB1 (P=0.005) and up-regulation of CCND1 (P=0.0001) gene was observed in brain tumor sections vs controls. Spearman correlation showed significant negative correlation between RB1 vs proliferation marker, Ki-67 (r = -0.291*, P<0.05) in brain tumors. Expression levels of selected genes were also assessed at protein level using immunohistochemical analysis (IHC) and signification down-regulation of RB1 (P=0.0001) and up-regulation of CCND1 (P=0.0001) was observed in brain tumor compared with control sections. In conclusion, it is suggested that polymorphisms/expression variations of RB1 and CCND1 genes may be associated with increased risk of brain tumor.

Modulation of brain tumor risk by genetic SNPs in PARP1gene: Hospital based case control study

PARP-1 gene plays an essential part in base excision repair pathway and its functional variations result in several types of cancer. In this study we have explored the effect of genetic variations in PARP-1 gene in brain tumorigenesis. This case control study comprised of 500 brain tumor cases along with 500 healthy controls. Three polymorphisms of PARP-1 gene, rs1136410 (Val762Ala), rs1805404 (Asp81Asp) and rs1805414 (Ala284Ala) were analyzed using AS-PCR method followed by DNA sequencing. Joint effect model, haplotype analysis and linkage disequilibrium of these polymorphisms was assessed using Haploview 4.2. In rs1136410 (Val762Ala) heterozygous mutant genotype (CT) was observed notably lower (OR: 0.44., 95% CI: 0.33-0.57., p<0.0001) in brain tumor patients compared to controls and ~2 fold increased frequency of homozygous mutant genotype (CC) was observed in brain tumor patients versus controls (OR: 1.51., 95%CI: 1.16-1.96, p = 0.001). In rs1805414 (Ala284Ala), frequency of heterozygous mutant genotype (CT) was observed lower (OR: 0.77., 95% CI: 0.60-0.99., p = 0.05) in patients versus controls. In rs1805404 (Asp81Asp), heterozygous mutant genotyping (CT) was observed lower in brain tumor patients compared with the healthy controls (OR: 0.63., 95% CI: 0.48-0.83., p = 0.001). However, homozygous mutant genotype (TT) was observed increased in patients compared to controls (OR: 1.41., 95% CI:1.07-1.85., p = 0.01). We assessed the fact that in combination the PARP-1 gene SNPs, rs1136410 (Val762Ala), rs1805414 (Ala284Ala) and rs1805404 (Asp81Asp) may increase the brain pathogenesis at least in Pakistani population.

Impact of four lncRNA polymorphisms (rs2151280, rs7763881, rs1136410, and rs3787016) on glioma risk and prognosis: A case-control study

Long noncoding RNA (lncRNA) polymorphisms are reportedly in connection with tumor susceptibility and prognosis. Glioma is one of the most aggressive and common cancers of the central nervous system. This study aimed to investigate the relationship between four lncRNA variants and glioma susceptibility and prognosis in a Chinese Han population. Sequenom Mass-ARRAY was used to genotype 605 patients with glioma and 1300 cancer-free individuals. Odds ratios or hazard ratios and related 95% confidence intervals were calculated to estimate the correlations. Logistic and Cox regression models, log-rank tests, and Kaplan-Meier curves were used for the statistical analysis. Six inheritance models showed that ANRIL rs2151280 variant genotype (A>G) was related to the susceptibility of glioma, while the other three lncRNAs showed no association. Patients treated with temozolomide or nimustine had better progression-free survival (PFS) and overall survival (OS) than those treated with platinum. Besides, patients aged older than 40 years showed a poorer OS. The Cox multivariate analysis revealed that the rs1136410 GG genotype (A>G) was beneficial for OS and PFS. The Kaplan-Meier analyses indicated that rs1136410 A>G and the rs7763881 A>C were associated with longer OS. ANRIL rs2151280 variant genotype might increase susceptibility of glioma. In addition, PARP1 rs1136410 variant genotype could be beneficial for the overall survival of patients with glioma. More research data are needed to further validate our results.

The Relationship Between Single-Nucleotide Polymorphisms, the Expression of DNA Damage Response Genes, and Hepatocellular Carcinoma in a Polish Population

The molecular mechanism of hepatocellular carcinoma (HCC) is related to DNA damage caused by oxidative stress products induced by hepatitis B virus (HBV) or C (HCV) infection and exposure to environmental pollutants. Single-nucleotide polymorphisms (SNPs) of DNA damage response (DDR) genes may influence individual susceptibility to environmental risk factors and affect DNA repair efficacy, which, in turn, can influence the risk of HCC. The study evaluates a panel of 15 SNPs in 11 DDR genes (XRCC1, XRCC3, XPD, MUTYH, LIG1, LIG3, hOGG1, PARP1, NFIL1, FEN1, and APEX1) in 65 HCC patients, 50 HBV- and 50 HCV-infected non-cancerous patients, and 50 healthy controls. It also estimates the mRNA expression of nine DDR genes in cancerous and adjacent healthy liver tissues. Two of the investigated polymorphisms (rs1052133 and rs13181) were associated with HCC risk. For all investigated genes, the level of mRNA was significantly lower in HCC cancer tissue than in non-cancerous liver tissue. Seven of the investigated polymorphisms were statistically related to gene expression in cancer tissues. The disruption of DDR genes may be responsible for hepatocellular transformation in HCV-infected patients.

Polymorphisms in DNA Repair Gene and Susceptibility to Glioma: A Systematic Review and Meta-Analysis Based on 33 Studies with 15 SNPs in 9 Genes

At present, many publications have evaluated the correlation between the DNA repair gene polymorphisms and glioma susceptibility. However, the results remain inconclusive. The aim of this research is to exhaustively assess the association of genetic polymorphisms in DNA repair genes with glioma risk in human. Meta-analysis method was conducted, and 33 studies with 15 SNPs in 9 genes were included (12553 glioma cases and 17178 controls). Correlation strength was evaluated by odds ratio with a 95 % confidence interval. Rs1799782 T allele and rs25487A allele might bring about higher risk of glioma in Asian population. Rs1805377 G allele was an increased risk genetic factor of glioma. Asian carried with rs3212986 A allele was more likely to have glioma. Rs1800067 G allele was a risk factor of developing glioma. Carriers with rs12917 CC genotype in MGMT gene had higher risk of glioma in Caucasian than other non-CC genotype carriers. Carriers with rs1136410 T allele in PARP1 gene could more likely to develop glioma in Caucasian. This meta-analysis suggests that glioma susceptibility is associated with rs1799782 and rs25487 of X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1), rs1805377 of XRCC4, rs1800067 of excision repair cross-complementing rodent repair deficiency complementation group 4 (ERCC4) and rs3212986 of ERCC1 in Asian population, and rs12917 of O-6-methylguanine-DNA methyltransferase (MGMT) and rs1136410 of poly(ADP-ribose) polymerase 1 (PARP1) in Caucasian population.

Variants of Base Excision Repair Genes MUTYH , PARP1 and XRCC1 in Alzheimer's Disease Risk

BACKGROUND

Many clinical studies have shown that oxidative stress pathways and the efficiency of the oxidative DNA damage base excision repair (BER) system are associated with the pathogenesis of Alzheimer's disease (AD). Reduced BER efficiency may result from polymorphisms of BER-related genes. In the present study, we examine whether single nucleotide polymorphisms (SNPs) of BER genes are associated with increased risk of AD.

METHODS

SNP genotyping was carried out on DNA isolated from peripheral blood mononuclear cells obtained from 120 patients with AD and 110 healthy volunteers. Samples were genotyped for the presence of BER-related SNPs, i.e. XRCC1-rs1799782, rs25487; MUTYH-rs3219489, and PARP1-rs1136410.

RESULTS

We found a positive association between AD risk and the presence of G/A genotype variant of the XRCC1 rs25487 polymorphism [odds ratio (OR) = 3.762, 95% CI: 1.793-7.891]. The presence of the A/A genotype of this polymorphism reduced the risk of AD (OR = 0.485, 95% CI: 0.271-0.870). In cases of the PARP1 gene rs1136410 polymorphism, we observed that the T/C variant increases (OR = 4.159, 95% CI: 1.978-8.745) while the T/T variant reduces risk (OR = 0.240, 95% CI: 0.114-0.556) of AD.

CONCLUSIONS

We conclude that BER gene polymorphisms may play an important role in the etiology of AD. Diagnosing the presence or absence of particular genetic variants may be an important marker of AD. Further research on a larger population is needed. There is also a need to examine polymorphisms of other BER in the context of AD risk.

A Comprehensive Meta-analysis of Genetic Associations Between Key Polymorphic Loci in DNA Repair Genes and Glioma Risk

Genetic variants found in DNA repair genes (ERCC1, rs3212986; ERCC2, rs13181; ERCC4, rs1800067; ERCC5, rs17655; XRCC1, rs1799782, rs25487, rs25489; XRCC3, rs861539) have been reported to have an ambivalent association with the development of glioma. In the present study, a meta-analysis was conducted to confirm the relationship, taking heterogeneity of population into consideration. We analyzed 21 articles of 6 genes along with 8 single nucleotide polymorphisms (SNPs) (24,078 cases and 30,926 healthy individuals), which assessed the relationship between nucleotide excision, base excision, double-strand break repair gene, and the development of glioma under five models. All statistical analysis was implemented by the software of R 3.2.1, and the relationships between key polymorphic loci in DNA repair genes and glioma were quantified by the pooled odds ratio (OR) and 95 % confidential intervals. Overall, the synthesized evidence demonstrated that the SNP of rs13181 and rs1799782 significantly increased the risk of glioma whereas SNP of rs1800067 were significantly associated with a decrease in the risk of glioma. Additionally, subgroup analyses of 8 SNPs by ethnicity indicated that the mutation of rs13181, rs1800067 were apparently protective factors of glioma among Asians, while the mutation of rs13181 was a risk factors of glioma in Caucasians. Furthermore, the mutation of rs1799782 significantly raises the risk of glioma for Asian. Our study suggested that rs13181*C and rs1799782*A are risk alleles for glioma; rs1800067*A are beneficial alleles for decreased susceptibility to glioma. Future studies with large sample size and other races are strongly recommended to confirm the results from this study.

Glioma risks associate with genetic polymorphisms of XRCC1 gene in Chinese population

Glioma is the most common type of primary brain tumors in adults. Previous evidence indicates that the X-ray repair cross-complementing group 1 gene (XRCC1) is an important candidate gene which influencing the pathogenesis of glioma. This study aims to assess the potential associations between glioma risks and genetic polymorphisms of XRCC1 gene. A total of 1,286 Chinese Han ethnic subjects consisting of 638 glioma patients and 648 controls were recruited in this case-control study. The genotyping of XRCC1 genetic polymorphisms (c.482C>T, c.1161G>A, and c.1804C>A) were conducted using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), created restriction site-PCR (CRS-PCR) and DNA sequencing methods. Our data indicated that the allelic and genotypic frequencies of these genetic polymorphisms in glioma patients were significantly different from those of controls. We detected that the alleles/genotypes were statistically associated with the increased risks of glioma (for c.482C>T, TT versus (vs.) CC: OR = 2.24, 95% CI = 1.48-3.39, P < 0.001; T vs. C: OR = 1.30, 95% CI = 1.09-1.53, P = 0.003; for c.1161G>A, AA vs. GG: OR = 1.62, 95% CI = 1.11-2.35, P = 0.012; A vs. G: OR = 1.19, 95% CI = 1.01-1.41, P = 0.040; for c.1804C>A, AA vs. CC: OR = 2.12, 95% CI = 1.45-3.11, P < 0.001; A vs. C: OR = 1.32, 95% CI = 1.12-1.56, P = 0.001). Our findings suggest that these genetic polymorphisms of XRCC1 gene may influence glioma risks in Chinese Han ethnic subjects, and might be potential molecular markers for evaluating glioma risks.

XRCC1 gene polymorphisms and glioma risk in Chinese population: a meta-analysis

Background

Three extensively investigated polymorphisms (Arg399Gln, Arg194Trp, and Arg280His) in the X-ray repair cross-complementing group 1 (XRCC1) gene have been implicated in risk for glioma. However, the results from different studies remain inconsistent. To clarify these conflicts, we performed a quantitative synthesis of the evidence to elucidate these associations in the Chinese population.

Methods

Data were extracted from PubMed and EMBASE, with the last search up to August 21, 2014. Meta-analysis was performed by critically reviewing 8 studies for Arg399Gln (3062 cases and 3362 controls), 8 studies for Arg194Trp (3419 cases and 3680 controls), and 5 studies for Arg280His (2234 cases and 2380 controls). All of the statistical analyses were performed using the software program, STATA (version 11.0).

Results

Our analysis suggested that both Arg399Gln and Arg194Trp polymorphisms were significantly associated with increased risk of glioma (for Arg399Gln polymorphism: Gln/Gln vs. Arg/Arg, OR = 1.82, 95% CI = 1.46–2.27, P = 0.000; Arg/Gln vs. Arg/Arg, OR = 1.25, 95% CI = 1.10–1.42, P = 0.001 and for Arg194Trp polymorphism: recessive model, OR = 1.78, 95% CI = 1.44–2.19, P = 0.000), whereas the Arg280His polymorphism had no influence on the susceptibility to glioma in a Chinese population.

Conclusions

This meta-analysis suggests that there may be no association between the Arg280His polymorphism and glioma risk, whereas the Arg399Gln/Arg194Trp polymorphisms may contribute to genetic susceptibility to glioma in the Chinese population. Nevertheless, large-scale, well-designed and population-based studies are needed to further evaluate gene-gene and gene–environment interactions, as well as to measure the combined effects of these XRCC1 variants on glioma risk.

Association between XRCC1 polymorphisms and glioma risk among Chinese population

The pathogenesis of glioma remains largely unknown now. It has been suggested that the X-ray cross-complementing group 1 (XRCC1) gene may influence the capacity to repair DNA damage leading to an increased gliomas susceptibility. This study aimed to evaluate the relationship between XRCC1 polymorphisms and glioma risk. Genotypes were assessed in 368 Chinese glioma patients and 346 healthy controls. XRCC1 Arg194Trp (rs1799782), Arg280His (rs25489) and Arg399Gln (rs25487) and three additional polymorphisms were directly sequenced. The frequency of Arg280His A allele was significant lower in glioma group than in healthy controls [9.6 vs 16%, OR=0.60 (0.46-0.80), P<0.001]; the frequencies of GA or AA genotypes were different in two groups (16.6 vs 22.8%, 1.3 vs 4.7%). The frequency of Arg399Gln A allele was significant higher in glioma group than in healthy controls [38.7 vs 30.1%, OR=1.29 (1.11-1.49), P=0.001]; the frequencies of GA or AA genotypes were different in two groups (45.4 vs 38.2%, 16 vs 10.9%). This study demonstrates that the rs25489 (Arg280His) and Arg399Gln (rs25487) polymorphisms in XRCC1 gene might influence the risk of developing glioma in Chinese population.

PARP-1 Val762Ala polymorphism and risk of cancer: a meta-analysis based on 39 case-control studies

Background

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear chromatin-associated enzyme involved in several important cellular processes, particularly in the DNA repair system. PARP-1 rs1136410: C>T is among the most studied polymorphisms and likely involved in human carcinogenesis. However, results from previous studies are inconclusive. Thus, a meta-analysis was conducted to derive a more precise estimation of the effects of this enzyme.

Methodology and Principal Findings

A comprehensive search was conducted in the PubMed and EMBASE databases until December 9, 2013. A total of 39 studies with 16,783 cancer cases and 23,063 control subjects were included in the meta-analysis on the basis of the inclusion and exclusion criteria. No significant association between the PARP-1 Val762Ala polymorphism and cancer risk was found when all of the studies were pooled into the analysis (VA + AA vs. VV: OR = 1.03, 95% CI = 0.95–1.11). The subgroup analysis of cancer types revealed that the –762Ala allele was associated with increased risk of gastric, cervical, and lung cancers and a decreased risk of glioma. In addition, a significantly increased risk of cancer associated with the polymorphism was observed in Asian descendents (VA + AA vs. VV: OR = 1.17, 95% CI = 1.09–1.25; AA vs. VV: OR = 1.28, 95% CI = 1.08–1.51; VA vs. VV: OR = 1.12, 95% CI = 1.04–1.20; AA vs. VA + VV: OR = 1.09, 95% CI = 1.03–1.39). These results also indicated that a joint effect between PARP-1 Val762Ala and XRCC1 Arg399Gln could be involved in the risk of cancer development (OR = 3.53, 95% CI = 1.30–9.59).

Conclusion

The present meta-analysis provides evidence that the PARP-1 Val762Ala may be involved in cancer development at least in some ethnic groups (Asian) or some specific cancer types (gastric, cervical, and lung cancers, and glioma).

Association between DNA repair gene polymorphisms and risk of glioma: a systematic review and meta-analysis

BACKGROUND

Association studies of germline DNA repair single nucleotide polymorphisms (SNPs) and glioma risk have yielded inconclusive results. We therefore performed a systematic review and meta-analysis of studies investigating this association.

METHODS

We identified 27 eligible studies investigating 105 SNPs in 42 DNA repair genes. Of these, 10 SNPs in 7 genes were analyzed in at least 4 studies and were therefore included in our meta-analysis. The meta-analysis was performed for homozygote comparison, heterozygote comparison, and dominant and recessive models by applying a fixed- or random-effects model. The funnel and forest plots were created using RevMan software.

RESULTS

We found that SNPs rs3212986 (odds ratio [OR] = 1.35 (1.08-1.68), P = .008), rs13181 (OR = 1.18 (1.06-1.31), P = .002), and rs25487 (OR = 1.12 (1.03-1.22), P = .007) in DNA repair genes ERCC1, ERCC2 (XPD), and XRCC1 may increase the risk of glioma, while polymorphisms rs1136410 (OR = 0.78 (0.68-0.89), P = .0004) and rs12917 (OR = 0.84 (0.73-0.96), P = .01) in PARP1(ADPRT) and MGMT are associated with decreased susceptibility to glioma. No evidence of significant associations between ERCC2 rs1799793, OGG1 rs1052133, XRCC1 rs25489, XRCC1 rs1799782, or XRCC3 rs861539 and risk of glioma was observed.

CONCLUSION

This study provides evidence that DNA repair genes ERCC1, ERCC2, and XRCC1 might be low-penetrance glioma-risk genes, while MGMT and PARP1 polymorphisms may confer protection against glioma.

Association between the PARP1 Val762Ala polymorphism and cancer risk: evidence from 43 studies

BACKGROUND

Poly (ADP-ribose) polymerase-1 (PARP-1) plays critical roles in the detection and repair of damaged DNA, as well as cell proliferation and death. Numerous studies have examined the associations between PARP1 Val762Ala (rs1136410 T>C) polymorphism and cancer susceptibility; nevertheless, the findings from different research groups remain controversial.

METHODS

We searched literatures from MEDLINE, EMBASE and CBM pertaining to such associations, and then calculated pooled odds ratio (OR) and 95% confidence interval (CI) by using random-effects model. The false-positive report probability (FPRP) analysis was used to confirm the validity of significant findings. Moreover, potential effects of rs1136410 variants on PARP1 mRNA expression were analyzed for three ethnicities by combining data from HapMap (genotype) and SNPexp (mRNA expression).

RESULTS

The final meta-analysis incorporated 43 studies, consisting of 17,351 cases and 22,401 controls. Overall, our results did not suggest significant associations between Ala variant (Ala/Ala or Ala/Val genotype) and cancer risk. However, further stratification analysis showed significantly increased risk for gastric cancer (Ala/Ala vs. Val/Val: OR = 1.56, 95% CI = 1.01-2.42, Ala/Val vs. Val/Val: OR = 1.34, 95% CI = 1.14-1.58, dominant model: OR = 1.41, 95% CI = 1.21-1.65 and Ala vs. Val: OR = 1.29, 95% CI = 1.07-1.55). On the contrary, decreased risk for brain tumor (Ala/Val vs. Val/Val: OR = 0.77, 95% CI = 0.68-0.87, dominant model: OR = 0.77, 95% CI = 0.68-0.87 and Ala vs. Val: OR = 0.82, 95% CI = 0.74-0.91). Additionally, we found that the Ala carriers had a significantly increased risk in all models for Asians. Our mRNA expression data provided further biological evidence to consolidate this finding.

CONCLUSIONS

Despite some limitations, this meta-analysis found evidence for an association between the PAPR1 Val762Ala and cancer susceptibility within gastric cancer, brain tumor and Asian subgroups.

Therapeutic applications of PARP inhibitors: anticancer therapy and beyond

The aim of this article is to describe the current and potential clinical translation of pharmacological inhibitors of poly(ADP-ribose) polymerase (PARP) for the therapy of various diseases. The first section of the present review summarizes the available preclinical and clinical data with PARP inhibitors in various forms of cancer. In this context, the role of PARP in single-strand DNA break repair is relevant, leading to replication-associated lesions that cannot be repaired if homologous recombination repair (HRR) is defective, and the synthetic lethality of PARP inhibitors in HRR-defective cancer. HRR defects are classically associated with BRCA1 and 2 mutations associated with familial breast and ovarian cancer, but there may be many other causes of HRR defects. Thus, PARP inhibitors may be the drugs of choice for BRCA mutant breast and ovarian cancers, and extend beyond these tumors if appropriate biomarkers can be developed to identify HRR defects. Multiple lines of preclinical data demonstrate that PARP inhibition increases cytotoxicity and tumor growth delay in combination with temozolomide, topoisomerase inhibitors and ionizing radiation. Both single agent and combination clinical trials are underway. The final part of the first section of the present review summarizes the current status of the various PARP inhibitors that are in various stages of clinical development. The second section of the present review summarizes the role of PARP in selected non-oncologic indications. In a number of severe, acute diseases (such as stroke, neurotrauma, circulatory shock and acute myocardial infarction) the clinical translatability of PARP inhibition is supported by multiple lines of preclinical data, as well as observational data demonstrating PARP activation in human tissue samples. In these disease indications, PARP overactivation due to oxidative and nitrative stress drives cell necrosis and pro-inflammatory gene expression, which contributes to disease pathology. Accordingly, multiple lines of preclinical data indicate the efficacy of PARP inhibitors to preserve viable tissue and to down-regulate inflammatory responses. As the clinical trials with PARP inhibitors in various forms of cancer progress, it is hoped that a second line of clinical investigations, aimed at testing of PARP inhibitors for various non-oncologic indications, will be initiated, as well.

Assessment of the association between XRCC1 Arg399Gln polymorphism and glioma susceptibility

The Arg399Gln polymorphism, located in the region of the BRCT-I interaction domain of XRCC1, has been extensively explored in its function and association with glioma risk. However, these studies generated contradictory instead of conclusive results. A meta-analysis was performed to derive a more precise evaluation of the relationship between XRCC1 Arg399Gln polymorphism and glioma risk. We searched the PubMed, EMBASE, and Web of Science and extracted 12 eligible studies with 4,062 glioma cases and 5,302 glioma-free controls for this meta-analysis. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association. In the overall analysis, we found that the XRCC1 Arg399Gln polymorphism was statistically associated with the risk of glioma (OR(GG vs. AG + AA) = 0.90, 95% CI = 0.84-0.97, P(heterogeneity) = 0.020; OR(allele G vs. allele A )= 0.96, 95% CI = 0.91-1.00, P(heterogeneity) = 0.110). We also observed significant association between this polymorphism and glioma risk in Asian populations. The results of the meta-analysis suggest a potential decreased susceptibility to glioma in association with the XRCC1 Arg399Gln polymorphism, especially in Asians. Yet, it is necessary to conduct future prospective explorations to gain a better insight into the impact of XRCC1 Arg399Gln polymorphism on glioma risk.

Correlation between X-ray cross-complementing group 1 polymorphisms and the onset risk of glioma: A meta-analysis

OBJECTIVE:

To evaluate the association of X-ray cross-complementing group 1 (XRCC1) Arg399Gln, Arg194Trp and Arg280His polymorphisms with the risk of glioma.

DATA SOURCES:

A systematic literature search of papers published from January 2000 to August 2012 in PubMed, Embase, China National Knowledge Infrastructure database, and Wanfang database was performed. The key words used were “glioma”, “polymorphism”, and “XRCC1 or X-ray repair cross-complementing group 1”. References cited in the retrieved articles were screened manually to identify additional eligible studies.

STUDY SELECTION:

Studies were identified according to the following inclusion criteria: case-control design was based on unrelated individuals; and genotype frequency was available to estimate an odds ratio (OR) and 95% confidence interval (CI). Meta-analysis was performed for the selected studies after strict screening. Dominant and recessive genetic models were used and the relationship between homozygous mutant genotype frequencies and mutant gene frequency and glioma incidence was investigated. We chose the fixed or random effect model according to the heterogeneity to calculate OR and 95%CI, and sensitivity analyses were conducted. Publication bias was examined using the inverted funnel plot and the Egger's test using Stata 12.0 software.

MAIN OUTCOME MEASURES:

Association of XRCC1 Arg399Gln, Arg194Trp, and Arg280His polymorphisms with the risk of glioma, and subgroup analyses were performed according to different ethnicities of the subjects.

RESULTS:

Twelve articles were included in the meta-analysis. Eleven of the articles were concerned with the Arg399Gln polymorphism and glioma onset risk. Significantly increased glioma risks were found only in the dominant model (Gln/Gln + Gln/Arg versus Arg/Arg: OR = 1.26, 95%CI = 1.03–1.54, P = 0.02). In the subgroup analysis by ethnicity, significantly increased risk was found in Asian subjects in the recessive (OR = 1.46, 95%CI = 1.04–2.45, P = 0.03) and dominant models (OR = 1.40, 95%CI = 1.10–1.78, P = 0.007), and homozygote contrast (OR = 1.69, 95%CI = 1.17–2.45, P = 0.005), but not in Caucasian subjects. For association of the Arg194Trp (eight studies) and Arg280His (four studies) polymorphisms with glioma risk, the meta-analysis did not reveal a significant effect in the allele contrast, the recessive genetic model, the dominant genetic model, or homozygote contrast.

CONCLUSION:

The XRCC1 Arg399Gln polymorphism may be a biomarker of glioma susceptibility, especially in Asian populations. The Arg194Trp and Arg280His polymorphisms were not associated with overall glioma risk.

Genetic polymorphisms in XRCC1 gene and susceptibility to glioma in Chinese Han population

Glioma is the most common type of primary brain malignancy in adults. The X-ray repair cross-complementing group 1 (XRCC1) is an important candidate gene for influencing the pathogenesis of glioma. This study aimed to evaluate the potential association between XRCC1 genetic polymorphisms and glioma susceptibility. This case-control study was conducted in Chinese Han populations consisting of 620 glioma cases and 630 cancer-free controls. XRCC1 genetic polymorphisms were detected by the polymerase chain reaction-restriction fragment length polymorphism and verified using DNA sequencing methods. The c.910A>G and c.1779C>G genetic polymorphisms were identified in this study. Our data suggested that the genotypes/alleles of these two genetic polymorphisms were statistically associated with the increased risk of glioma. As for c.910A>G, the risk of glioma for genotype GG was significantly higher than wild genotype AA (odds ratio (OR) = 1.98, 95% confidence interval (CI) 1.33-2.94, P = 0.001). As for c.1779C>G, the genotype GG was statistically associated with the increased risk of glioma compared to wild genotype CC (OR = 1.80, 95% CI 1.17-2.78, P = 0.007). Both of alleles G in c.910A>G and c.1779C>G may contribute to glioma susceptibility (G versus (vs.) A, OR = 1.30, 95% CI 1.09-1.54, P = 0.003; G vs. C, OR = 1.19, 95% CI 1.00-1.42, P = 0.045). Our findings indicate that the c.910A>G and c.1779C>G genetic polymorphisms are associated with the susceptibility to glioma in Chinese Han populations and might be used as molecular markers for evaluating glioma risk.

Association between XRCC1 gene polymorphisms and risk of glioma development: a meta-analysis

OBJECTIVE

Previous studies of the association between X-ray cross-complementing group 1 (XRCC1) gene polymorphisms and the gliomas risk have yielded conflicting results, and thus a meta-analysis was performed to provide a more accurate estimation.

METHODS

A computerized literature search of 5 electronic databases was conducted to identify the relevant studies. Fixed or random effect models were selected based on the heterogeneity test. Publication bias was estimated using Begg's funnel plots and Egger's regression test.

RESULTS

A total of 11 studies (3,810 cases and 6,079 controls), 7 studies (2,928 cases and 5,048 controls), and 4 studies (1,461 cases and 2,593 controls) were finally included in the analyses of the association between XRCC1 Arg399Gln, Arg194Trp, and Arg280His polymorphisms and glioma risk, respectively. The pooled results showed that GlnGln carriage was associated with moderately increased risk of gliomas in Asians (GlnGln vs. ArgArg, OR=1.490, 95%CI 1.031-2.153; GlnGln/ArgGln vs. ArgArg, OR=1.321, 95%CI 1.037- 1.684), whereas a marginal association was revealed in Caucasians. For the Arg194Trp polymorphism, although a significant association was shown in the homozygous genotype comparisons (TrpTrp vs. ArgArg, OR = 2.209, 95%CI 1.398- 2.945), no significant link was found on subgroup analysis stratified by ethnicity. With regard to the Arg280His polymorphism, no significant association was found in each comparison. No particular study was found to significantly influence the pooled results, and no potential publication bias was detected.

CONCLUSIONS

This meta-analysis suggested that the XRCC1 Arg399Gln polymorphism is moderately associated with increased risk of gliomas in Asians, while Arg194Trp and Arg280His polymorphisms demonstrated no significant influence. Due to the limited studies and the potential confounders, further studies are needed to confirm these results.

DNA repair gene ERCC1 and XPD polymorphisms predict glioma susceptibility and prognosis

AIMS

We conducted a case-control study in a Chinese population to clarify the association between polymorphisms in ERCC1 and XPD and susceptibility and survival of glioma.

METHODS

A total of 393 cases and 410 controls were selected from March 2007 to December 2011. Genotyping of ERCC1 and XPD was conducted by TaqMan assays using the ABI Prism 7911HT Sequence Detection System. All analyses were performed using the STATA statistical package.

RESULTS

Polymorphisms in ERCC1 118C/T, ERCC1 8092C/A and XPD Asp312Asn showed no statistically significant difference between glioma cases and controls. However, individuals with the XPD 751Gln/Gln genotype had an increased risk of developing glioma compared with those with the Lys/Lys genotype (adjusted OR=1.64, 95% CI: 1.06-2.89). The ERCC1 118T/T genotype was associated with significantly higher median survival than the ERCC1 C/C genotype (HR=0.67, 95%CI=0.35-0.96). In addition, individuals with XPD 751Gln/Gln had a lower median survival time than XPD Lys/Lys carriers (HR=0.54, 95%CI=0.37- 0.93).

CONCLUSION

In conclusion, we observed that the XPD 751Gln/Gln genotype is associated with glioma susceptibility, and ERCC1 118 T/T and XPD 751Gln/Gln genotypes confer a significantly better prognosis.

Polymorphisms in DNA repair genes and susceptibility to glioma in a chinese population

The excision repair cross-complementing rodent repair deficiency complementation group 1 (ERCC1), and X-ray repair cross-complementing group 1 (XRCC1) genes appear to protect mammalian cells from the harmful effects of ionizing radiation. We conducted a large case-control study to investigate the association of polymorphisms in ERCC1 C118T, ERCC1 C8092A, XRCC1 A194T, XRCC1 A194T, and XRCC3 C241T, with glioma risk in a Chinese population. Five single nucleotide polymorphisms (SNPs) were genotyped, using the MassARRAY IPLEX platform, in 443 glioma cases and 443 controls. Association analyses based on an χ² test and binary logistic regression were performed to determine the odds ratio (OR) and a 95% confidence interval (95% CI) for each SNP. For XRCC1 Arg194Trp, the variant genotype T/T was strongly associated with a lower risk of glioma cancer when compared with the wild type C/C (OR = 2.45, 95% CI = 1.43–4.45). Individuals carrying the XRCC1 399A allele had an increased risk of glioma (OR = 1.33, 95% CI = 1.02–1.64). The XRCC3 241T/T genotype was associated with a strong increased glioma risk (OR = 3.78, 95% CI = 1.86–9.06). Further analysis of the interactions of two susceptibility-associated SNPs, XRCC1 Arg194Trp and XRCC3 Thr241Met, showed that the combination of the XRCC1 194T and XRCC3 241T alleles brought a large increase in glioma risk (OR = 2.75, 95% CI = 1.54–4.04). XRCC1 Arg194Trp, XRCC1 Arg399Gln, and XRCC3 C241T, appear to be associated with susceptibility to glioma in a Chinese population.

Association between the XRCC1 polymorphisms and glioma risk: a meta-analysis of case-control studies

Background

X-ray repair cross-complementing group 1 (XRCC1) is one of the DNA repair genes encoding a scaffolding protein that participate in base excision repair (BER) pathway. However, studies on the association between polymorphisms in this gene and glioma have yielded conflicting results. This meta-analysis was performed to derive a more precise estimation between XRCC1 polymorphisms (Arg399Gln, Arg194Trp, and Arg280His) and glioma risk.

Methods

Data were collected from several electronic databases, with the last search up to November 28, 2012. Meta-analysis was performed by critically reviewing 9 studies for Arg399Gln polymorphism (3146 cases and 4296 controls), 4 studies for Arg194Trp polymorphism (2557 cases and 4347 controls), and 4 studies for Arg280His polymorphism (1936 cases and 2895 controls). All of the statistical analyses were performed using the software programs STATA (version 11.0).

Results

The combined results showed that Arg399Gln polymorphism was significantly associated with glioma risk (Gln/Gln versus Arg/Arg: OR = 1.52, 95% CI = 1.03–2.23; recessive model: OR = 1.32, 95% CI = 1.01–1.73; additive model: OR = 1.21, 95% CI = 1.00–1.47), whereas Arg194Trp/Arg280His polymorphisms were all not significantly associated with glioma risk. As for ethnicity, Arg399Gln polymorphism was associated with increased risk of glioma among Asians (Gln/Gln versus Arg/Arg: OR = 1.78, 95% CI = 1.29–2.47; Arg/Gln versus Arg/Arg: OR = 1.28, 95% CI = 1.05–1.56; recessive model: OR = 1.59, 95% CI = 1.16–2.17; dominant model: OR = 1.36, 95% CI = 1.13–1.65; additive model: OR = 1.32, 95% CI = 1.15–1.52), but not among Caucasians. Stratified analyses by histological subtype indicated that the Gln allele of Arg399Gln polymorphism showed borderline association with the risk of glioblastoma among Caucasians. However, no evidence was observed in subgroup analyses for Arg194Trp/Arg280His polymorphisms.

Conclusions

Our meta-analysis suggested that Arg399Gln polymorphism was associated with increased risk of glioma among Asians and borderline increased risk for glioblastoma among Caucasians, whereas Arg194Trp/Arg280His polymorphisms might have no influence on the susceptibility of glioma in different ethnicities.

X-ray repair cross complementing protein 1 in base excision repair

X-ray Repair Cross Complementing protein 1 (XRCC1) acts as a scaffolding protein in the converging base excision repair (BER) and single strand break repair (SSBR) pathways. XRCC1 also interacts with itself and rapidly accumulates at sites of DNA damage. XRCC1 can thus mediate the assembly of large multiprotein DNA repair complexes as well as facilitate the recruitment of DNA repair proteins to sites of DNA damage. Moreover, XRCC1 is present in constitutive DNA repair complexes, some of which associate with the replication machinery. Because of the critical role of XRCC1 in DNA repair, its common variants Arg194Trp, Arg280His and Arg399Gln have been extensively studied. However, the prevalence of these variants varies strongly in different populations, and their functional influence on DNA repair and disease remains elusive. Here we present the current knowledge about the role of XRCC1 and its variants in BER and human disease/cancer.

A meta-analysis of an association between the XRCC1 polymorphisms and gliomas risk

The associations of the X-ray repair cross complementing group 1 (XRCC1) gene single nucleotide polymorphisms (SNPs) Arg194Trp, Arg280His, Arg399Gln with the risk of gliomas have been studied recently, but contradictions exist whether the XRCC1 SNPs were a risk factor. We examined these associations by performing a meta-analyse. Nine studies tested the associations between XRCC1 SNPs and gliomas were retrieved. Overall odds ratios (ORs) and corresponding 95 % confidence intervals were estimated using genetic models. Heterogeneity and publication bias were evaluated. The pooled OR for Arg194Trp TT versus CC were significant, which was 2.208 (95 % CI: 1.099, 4.435; P = 0.026), but it was non-significant after removal of the studies which deviated from the Hardy-Weinberg equilibrium (HWE). The pooled OR for Arg399Gln AA+GA versus GG of genotype methods subgroup and the low study appraisal score subgroup were significant in the stratification analysis, but the meta-regression results were non-significance. No significant associations were found between the Arg280His SNPs and gliomas' risk. There was no evidence of publication bias. We conclude that SNPs in XRCC1 are not associated with the risk of gliomas. We should do more work on the relevant variants like those in TERT, RTEL1, EGFR, CDKN2A, CCDC26, and PHLDB1 and their products rather than the XRCC1. More GWAS will also need to involve sufficiently larger study populations along with analysis of tumor or gender subtypes in order to assess these risks.

Association between XRCC1 polymorphism 399 G->A and glioma among Caucasians: a systematic review and meta-analysis

Background

The x-ray cross complementing group 1 gene (XRCC1) is crucial to proper repair of DNA damage such as single-strand DNA breaks. A non-synonymous polymorphism in XRCC1, 399 G → A, has been shown to reduce effectiveness of such DNA repair and has been associated with the risk of certain cancers. The known risk for glioma from high dose ionizing radiation makes associations between this polymorphism and glioma of particular interest.

Methods

A systematic literature review and meta-analysis was conducted to explore the association between XRCC1 399 G → A and glioma. Subgroup analyses by grade, gender, genotyping method, country in which study was conducted, and study size were conducted when data were available and validity of the results were assessed by influence analyses and exploration of potential publication bias.

Results

Six studies were eligible for meta-analysis including data on 2,362 Caucasian glioma cases and 3,085 Caucasian controls. Pooled analysis yielded a significant association between the variant of interest and risk of glioma (OR = 1.17, 95% CI: 1.05-1.30) which was found to be disproportionately driven by a single study. Exclusion of this study, in an influence analysis, produced no statistically significant evidence of association with glioma (OR = 1.10, 95% CI: 0.98-1.23), and no evidence of publication bias.

Conclusions

This meta-analysis does not suggest a major role of the XRCC1 399 G → A polymorphism in influencing risk of glioma among Caucasians. Future studies should report data separately for glioma subtypes to permit stratified analyses for Grade III and Grade IV glioma and examine other polymorphisms in this gene.

A functional polymorphism in XRCC1 is associated with glioma risk: evidence from a meta-analysis

Previous studies show that X-ray cross-complementing group 1 (XRCC 1) Arg399Gln may result in variations in repair efficiency of DNA damage, and this repair deficit may eventually cause individual susceptibility to glioma. However, published data regarding the association between XRCC 1 Arg399Gln polymorphism and glioma risk was contradictory. The aim of this study was to derive a more precise estimation of the association of XRCC 1 Arg399Gln polymorphism with glioma risk by performing a meta-analysis of eligible studies. Odds ratios (ORs) and 95 % confidence intervals (95 %CIs) were used to assess the strength of the association. We performed a meta-analysis of eleven published studies that included 2,808 glioma cases and 3,114 controls. Overall, there was a significant association between XRCC1 Arg399Gln polymorphism and glioma risk in two genetic models (for ArgGln vs ArgArg: OR = 1.30, 95 % CI 1.01-1.68; for GlnGln/ArgGln vs ArgArg: OR = 1.28, 95 % CI 1.01-1.62). In the stratified analysis by ethnicity, the XRCC1 Arg399Gln polymorphism had a higher risk of glioma development among Asians (for Gln vs Arg: OR = 1.34, 95 % CI 1.12-1.61; for GlnGln vs ArgArg: OR = 1.72, 95 % CI 1.18-2.51; for ArgGln vs ArgArg: OR = 1.31, 95 % CI 1.01-1.71; for GlnGln/ArgGln vs ArgArg: OR = 1.41, 95 % CI 1.10-1.80; for GlnGln vs ArgArg/ArgGln: OR = 1.48, 95 % CI 1.05-2.09)., but not among Caucasians. In conclusion, the results suggest that the XRCC 1 Arg399Gln polymorphism may contribute to the susceptibility of glioma in Asians.

Racial and tissue-specific cancer risk associated with PARP1 (ADPRT) Val762Ala polymorphism: a meta-analysis

The Val762Ala polymorphism poly [ADP-ribose] polymerase 1 (PARP1) gene [ADPRT (adenosine diphosphate ribosyltransferase) gene] affects enzymatic activity, which modulates cancer susceptibility among human populations. Individual data on 13,745 cases and 16,947 controls from 28 published case-control studies were re-evaluated. Odds ratios (OR) were estimated for ethnic group, cancer type, smoking joint effects and studies confined to the Hardy-Weinberg equilibrium. We applied subgroup, sensitivity and outlier analyses as well as the Bonferroni correction for multiple testing. The results show strong evidence that the variant (C) allele confers significant increased risk in the Chinese (OR 1.20-1.44, P < 0.0001-0.002), exacerbated by smoking (OR 1.66-2.53, P < 0.0001) and joint interaction with XRCC1 Arg399Gln (OR 1.39, P < 0.0001) as well as adjustment for tumor type (gastric carcinoma ORs 1.39-2.01, P < 0.0001). These significant effects were unaltered following conservative correction for multiple tests. By contrast, this procedure erased the protective significance in Caucasians, but not in two American subgroups, (i) those in the brain tumor category (0.77-0.79, P < 0.0001) and (ii) smokers in the dominant model (OR 0.86, P < 0.0001). These differential findings between the two ethnicities maybe correlated with significantly (P < 0.0001) greater allele frequency of the variant allele (C) among the Chinese compared to Caucasians. Our racial and tissue-specific summary estimates imply consideration of the Val762Ala polymorphism as candidate gene marker for screening cancer patients' best suited for PARP inhibitor therapy.

X-ray repair cross-complementing gene 1 Arg399Gln polymorphism and glioma risk among Asians: A meta-analysis based on 2 326 cases and 3 610 controls

OBJECTIVE:

Previous reports have demonstrated that X-ray repair cross-complementing gene 1 (XRCC1) Arg399Gln polymorphism is a possible risk factor for several cancers. Published data on the association of XRCC1 Arg399Gln polymorphism with glioma susceptibility have generated conflicting results. This study is designed to precisely estimate the relationship.

DATA RETRIEVAL:

A computer-based online retrieval of Medline, EMBASE, OVID, Sciencedirect, and Chinese National Knowledge Infrastructure was performed to search papers regarding association of XRCC1 Arg399Gln polymorphisms with glioma published up to April 2012.

SELECTION CRITERIA:

Two investigators selected data independently. Meta analysis was then performed for the selected studies using STATA 11.0 software after strict selection. Heterogeneity test, sensitivity analysis and publication bias assessments were then conducted.

MAIN OUTCOME MEASURES:

Association of XRCC1 Arg399Gln polymorphism with glioma risk.

RESULTS:

A total of nine case-controlled studies comprising 2 326 cases and 3 610 controls were selected for final analysis. The overall data failed to indicate a significant association of XRCC1 Arg399Gln polymorphism with glioma risk (Gln/Gln vs. Arg/Arg: odds ratio (OR) = 1.11; 95% confidence interval (CI) = 0.94–1.31; dominant model: OR = 1.06; 95%CI = 0.95–1.18; recessive model: OR = 1.04; 95%CI = 0.81–1.34). However, subgroup analysis regarding ethnicity showed an increased risk among Asians (Gln/Gln vs. Arg/Arg: OR = 1.70; 95%CI = 1.17–2.46; dominant model: OR = 1.40; 95%CI = 1.10–1.78; recessive model: OR = 1.46; 95%CI = 1.04–2.05) but not Caucasians or mixed ethnicities.

CONCLUSION:

XRCC1 Arg399Gln polymorphism might modify the susceptibility to glioma among Asians but not Caucasians. Further large and well-designed studies are needed to confirm this conclusion.

Genetic polymorphisms in the DNA repair gene XRCC1 and susceptibility to glioma in a Han population in northeastern China: a case-control study

BACKGROUND

Several single nucleotide polymorphisms (SNPs) in the X-ray cross-complementing group 1 (XRCC1) gene have been shown to influence DNA repair and to modify cancer susceptibility. To investigate the role of these loci further, we examined the association of three XRCC1 polymorphisms with the risk of gliomas in a Han population in northeastern China.

METHODS

Using a PCR-RFLP method, XRCC1 Arg194Trp, Arg280His and Arg399Gln were genotyped in 624 glioma patients and 580 healthy controls.

RESULTS

Significant differences in the distribution of the Arg399Gln allele were detected between glioma patients and healthy controls by a logistic regression analysis (OR=1.35, 95%CI 1.17-1.68, P=0.001). Our data also revealed that the Arg399Gln variant (allele A) carriers had an increased glioma risk compared to the wild-type (allele G) homozygous carriers (OR=1.40, 95%CI 1.12-1.76, P=0.003).

CONCLUSIONS

These results suggest that the XRCC1 Arg399Gln might influence the risk of developing glioma in a Han population in northeastern Chinese.

Correlation between base-excision repair gene polymorphisms and levels of in-vitro BPDE-induced DNA adducts in cultured peripheral blood lymphocytes

In vitro benzo[a]pyrene diol epoxide (BPDE)-induced DNA adducts in cultured peripheral lymphocytes have been shown to be a phenotypic biomarker of individual’s DNA repair phenotype that is associated with cancer risk. In this study, we explored associations between genotypes of base-excision repair genes (PARP1 Val762Ala, APEX1 Asp148Glu, and XRCC1 Arg399Gln) and in vitro BPDE-induced DNA adducts in cultured peripheral blood lymphocytes in 706 cancer-free non-Hispanic white subjects. We found that levels of BPDE-induced DNA adducts were significantly higher in ever smokers than in never smokers and that individuals with the Glu variant genotypes (i.e., Asp/Glu and Glu/Glu) exhibited lower levels of BPDE-induced DNA adducts than did individuals with the common Asp/Asp homozygous genotype (median RAL levels: 32.0 for Asp/Asp, 27.0 for Asp/Glu, and 17.0 for Glu/Glu, respectively; P_trend = 0.030). Further stratified analysis showed that compared with individuals with the common APEX1-148 homozygous Asp/Asp genotype, individuals with the APEX1-148Asp/Glu genotype or the Glu/Glu genotype had a lower risk of having higher-level adducts (adjusted OR = 0.60, 95% CI: 0.36–0.98 and adjusted OR = 0.47, 95% CI: 0.26–0.86, respectively; P_trend = 0.012) among smokers. Such an effect was not observed in non-smokers. However, there was no significant interaction between the APEX1 Asp148Glu polymorphism and smoking exposure in this study population (P = 0.512). Additional genotype-phenotype analysis found that the APEX1-148Glu allele had significantly increased expression of APEX1 mRNA in 270 Epstein-Barr virus-transformed lymphoblastoid cell lines, which is likely associated with more active repair activity. Our findings suggest that the functional APEX1-148Glu allele is associated with reduced risk of having high levels of BPDE-induced DNA adducts mediated with high levels of mRNA expression.

Association between PARP-1 V762A polymorphism and cancer susceptibility: a meta-analysis

Poly(ADP-ribose) polymerase-1 (PARP-1 catalyzes poly(ADP-ribosyl)ation to various proteins involved in many cellular processes, including DNA damage detection and repair and cell proliferation and death. PARP-1 has been implicated in human carcinogenesis, but the association between the most-studied PARP-1 V762A polymorphism (rs1136410) and risk of various cancers was reported with inconclusive results. The aim of this study was to assess the association between the PARP-1 V762A polymorphism and cancer risk. A meta-analysis of 21 studies with 12,027 cancer patients and 14,106 cancer-free controls was conducted to evaluate the strength of the association using odds ratio (OR) with 95% confidence interval (CI). Overall, no significant association was found between the PARP-1 V762A polymorphism and cancer risk. In the stratified analyses, however, it was found that the variant A allele of the PARP-1 V762A polymorphism was associated with an increased risk of cancer among Asian populations (VA + AA vs. VV: OR = 1.11, 95% CI: 1.01-1.23; P(heterogeneity) = 0.210), but a decreased risk of cancer (VA + AA vs. VV: OR = 0.89, 95% CI: 0.80-1.00; P(heterogeneity) = 0.004) among Caucasian populations, especially for glioma risk (OR = 0.79, 95% CI: 0.69-0.90; P(heterogeneity) = 0.800). This meta-analysis found evidence for an association of the PARP-1 V 762A polymorphism with increased risk of cancer among Asians, but decreased risk of cancer among Caucasians, particularly of glioma. Further well-designed studies with large sample sizes of different ethnic populations and different cancer types are warranted to confirm these findings.

A functional polymorphism in the epidermal growth factor gene is associated with risk for glioma in a Chinese population

Epidermal growth factor (EGF) plays a key role in survival of neural and glial precursor cells. A single nucleotide polymorphism of the EGF gene +61G/A in the 5'-untranslated region has been reported to be associated with susceptibility to glioma. The purpose of this study was to investigate the potential association between EGF +61G/A and brain glioma in a Chinese population. A case-control study involving 180 patients with glioma and 360 controls was done. Polymerase chain reaction restriction fragment-length polymorphism assay was used to analyze the EGF +61G/A genotypes. Patients with glioma had a significantly higher frequency of AA genotype (odds ratio, 2.25; 95% confidence interval, 1.20, 4.21; p=0.01] than controls. When stratified by histologic features and World Health Organization grade of glioma, distribution of each genotype did not significantly differ. Our data suggested that the EGF +61G AA genotype was associated with a higher glioma risk in a Chinese population. This finding is in contrast with previous studies that reported the G allele as a risk factor for glioma in white patients.