XRCC1 R399Q Research Articles

XRCC1 R194W and R399Q Polymorphisms and Colorectal Cancer Risk in a Northeastern Mexican Population.

Colorectal cancer (CRC) is one of the most common cancers worldwide. Its etiopathogenesis is complex, mainly influenced by genetic instability caused by the accumulation of mutations. The XRCC1 gene, which is involved in DNA repair, has been associated with CRC through the R194W (C194T) and R399Q (G399A) polymorphisms, but the results are inconsistent. Here, we analyzed the association of these polymorphisms with sporadic CRC in a northeastern Mexican population, including 155 male CRC patients and 155 male controls. Genotyping was performed using the RFLP method. An association with CRC was found for the 399A allele (G vs A; OR = 1.48 (1.03-2.13), P=0.034) and for the 399AA genotype in a codominant model (AA vs GG; OR = 3.11 (1.06-9.10), P=0.031). In contrast, there were no significant differences between CRC patients and controls for the C194T polymorphism (C vs T; OR = 0.82 (0.52-1.31), P=0.41). These results are consistent with many similar studies, but further research is needed to verify whether the XRCC1 R194W and R399Q polymorphisms play a role in CRC etiology. The functional significance of these polymorphisms is unclear, but some studies suggest that they influence DNA repair capacity and, thus, cancer risk.

Cytogenetic effects of radiation and genetic polymorphisms of the XRCC1 and XRCC3 repair genes in industrial radiographers.

Different types of DNA damages caused by ionizing radiation may enhance the cancer risk in exposed individuals. Inherited variations in DNA repair genes cause the inter-individual variability in response to ionizing radiation. The purpose of this study was to determine the association between single nucleotide polymorphism (SNP) of two important DNA repair genes (XRCC1 R399Q and XRCC3 T241M) and the level of DNA damage investigated by micronucleus (MN) frequency in peripheral blood lymphocytes of 120 industrial radiographers (IR) and 120 non-exposed control individuals. The frequencies of MN and nucleoplasmic bridges were significantly higher in the IR group than in the control group (33.83 ± 11.96 vs. 7.47 ± 2.96, p < 0.0001 and 1.69 ± 1.86 vs. 0.12 ± 0.33, p < 0.0001). MN frequencies in the IR group were associated with the cumulative radiation doses (p < 0.0001, r = 0.58 for last 1year of exposure and p < 0.0001, r = 0.67 for last 5years of exposure). Polymorphism of XRCC3 T241M was associated with higher MN frequencies in the IR group. However, the same result was not observed between XRCC3 SNP and MN frequency in the control group. Consequently, XRCC3 241Met alleles may cause the increased DNA damage in the industrial radiographers.

Association between OGG1 S326C CC genotype and elevated relapse risk in acute myeloid leukemia.

Recent studies have shown that tumors of relapsed acute myeloid leukemia (AML) present additional genetic mutations compared to the primary tumors. The base excision repair (BER) pathway corrects oxidatively damaged mutagenic bases and plays an important role in maintaining genetic stability. The purpose of the present study was to investigate the relationship between BER functional polymorphisms and AML relapse. We focused on five major polymorphisms: OGG1 S326C, MUTYH Q324H, APE1 D148E, XRCC1 R194W, and XRCC1 R399Q. Ninety-four adults with AML who achieved first complete remission were recruited. Genotyping was performed with the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The OGG1 S326C CC genotype (associated with lower OGG1 activity) was observed more frequently in patients with AML relapse [28.9 vs. 8.9%, odds ratio (OR) = 4.10, 95% confidence interval (CI) = 1.35-12.70, P = 0.01]. Patients with the CC genotype exhibited shorter relapse-free survival (RFS). Moreover, the TCGA database suggested that low OGG1 expression in AML cells is associated with a higher frequency of mutations. The present findings suggest that the OGG1 S326C polymorphism increased the probability of AML relapse and may be useful as a prognostic factor for AML relapse risk.

Single Nucleotide Polymorphism TGFβ1 R25P Correlates with Acute Toxicity during Neoadjuvant Chemoradiotherapy in Rectal Cancer Patients

Tovalidate the finding of an association between single nucleotide polymorphisms (SNPs) and toxicity during chemoradiotherapy (CRT) in rectal cancer patients, in an independent population. The cohort consisted of 165 patients who received CRT for rectal cancer from 2006 to 2012. Prospectively recorded toxicity information, graded according to the Common Terminology Criteria for Adverse Events version 3.0, was retrieved from the medical record. Additionally, a subset of 52 patients recorded their gastrointestinal symptoms weekly during CRT, using the 7-item Bowel Problems Scale. Deoxyribonucleic acid was extracted from normal tissue in the proctectomy specimens and screened for 3 SNPs: XRCC1 R399Q, XPD K751Q, and TGFβ1 R25P. Univariable and multivariable logistic regression models were constructed. The median radiation dose was 50.4Gy, and all patients received concurrent chemotherapy. Toxicities measured by the Common Terminology Criteria for Adverse Events were closely associated with patient-reported outcomes for the patients who completed the 7-item Bowel Problems Scale. Grade ≥3 toxicity occurred during CRT in 14 patients (8%). All 14 patients had either XRCC1 R399Q or TGFβ1 R25P polymorphisms. The TGFβ1 R25P polymorphism was significantly associated with grade ≥3 toxicity (odds ratio [OR] 3.47, P=.04) and, in patients who completed the Bowel Problems Scale, with grade ≥4 toxicity (OR 5.61, P=.02). The latter finding persisted in a multivariable logistic regression model controlling for ethnicity, age, and sex (adjusted OR 1.83, P=.02). We have validated the correlation between the TGFβ1 R25P SNP and acute toxicity during CRT in an independent cohort using both clinician- and patient-reported toxicity. The information from our study could be used as a basis to formulate a prospective trial testing the utility of this SNP as a biomarker of acute toxicity during neoadjuvant treatment in locally advanced rectal cancer.

Polymorphisms in cancer susceptibility genes XRCC1, RAD51 and TP53 and the risk of breast cancer in Serbian women.

Thanks to immense improvements in technology over the past few decades, we have witnessed a major shift towards the idea that breast cancer results from a combined effect of multiple common alleles conferring low risk. This study investigates the role of 3 nonsynonymous SNPs in the DNA repair genes XRCC1 (R399Q), RAD51 (G135C) and TP53 (Arg72Pro) in breast cancer in Serbian women. Cases of BRCA1/2-negative hereditary breast cancer (n = 52), sporadic breast cancer (n = 106) and age-matched cancer-free female controls (n = 104) were obtained from the Institute for Oncology and Radiology of Serbia's blood bank. Restriction fragment length polymorphism analysis was used for genotyping. Descriptive analyses included genotype and allelic frequencies; the odds ratio and 95% confidence interval were calculated as an estimate of the relative risk. A significant difference in QQ+RQ versus RR genotype distribution of XRCC1 was observed between hereditary breast cancer patients and cancer-free controls. The association was confirmed among young breast cancer patients from these high-risk families. The existence of 3 recessive alleles in the RAD51 and XRCC1 genotype combination showed an association with hereditary breast cancer. Odds ratio analysis indicated a strong protective role of the RAD51 GG + TP53 ArgArg + XRCC1 RR combined genotype against hereditary breast cancer negative for BRCA1/2 mutations. The XRCC1 R399Q polymorphism showed an association with increased breast cancer risk in Serbia, especially in the hereditary form of the disease and in young breast cancer patients. Dominant alleles of RAD51, TP53 and XRCC1 combined genotypes indicated a strong protective role against hereditary breast cancer.

DNA repair genes XPC, XPD, XRCC1, and XRCC3 are associated with risk and survival of squamous cell carcinoma of the head and neck.

Head and neck squamous cell carcinomas (HNSCC) are a heterogenous group of tumors with a high rate of early recurrences, second primary tumors, and mortality. Despite advances in diagnosis and treatment over the past decades, the overall 5-year survival rate remains around 50%. Since the head-and neck-region is continuously exposed to potentially DNA-damaging exogenous and endogenous factors, it is reasonable to expect that the DNA repair genes play a part in the development, progression, and outcome of HNSCC. The aim of this study was to investigate the SNPs XPC A499V, XPD K751Q, XRCC1 R399Q, and XRCC3 T241M as potential risk factors and indicators of survival among Caucasian patients. One-hundred-sixty-nine patients as well as 344 healthy controls were included and genotyped with PCR-RFLP. We showed that XPC A499V was associated with increased risk of HNSCC, especially laryngeal carcinoma. Among women, XPD K751Q was associated with increased risk of oral SCC. Furthermore, XPD homozygous mutant individuals had the shortest survival time, a survival time that increased however after full dose radiotherapy. Wild-type individuals of XRCC3 T241M demonstrated an earlier age of onset. HPV-positive never smokers had lower frequencies of p53 mutation. Among HNSCC patients, HPV-positivity was significantly associated with XRCC1 R399Q homozygous mutant genotype. Moreover, combinations of putative risk alleles seemed to act synergistically, increasing the risk of HNSCC. In conclusion, our results suggest that SNPs of the DNA repair genes XPC, XPD, XRCC1, and XRCC3 may affect risk and survival of HNSCC.

XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients

Radiotherapy is an important weapon in the treatment of breast cancer, but normal tissue injury after radiotherapy can be a threat for patients. Genetic markers conferring the ability to identify hyper-sensitive patients at risk of normal tissue injury in advance would considerably improve therapy. Association studies on genetic variation and occurrence of normal tissue injury can help us identify such markers, but previous studies on the association between XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients report conflicting findings. We performed a meta-analysis to comprehensively evaluate the association between XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients. The pooled odds ratios (ORs) with their 95% confidence interval (95% CIs) were calculated to assess the strength of the association. Fourteen case-control studies with a total of 2,448 breast cancer cases were finally included into the meta-analysis. Overall, XRCC1 R399Q polymorphism was significantly associated with increased risk of normal tissue injury after radiotherapy under all three models (for QQ versus RR: fixed-effects OR = 1.06, 95% CI 1.00-1.13, P = 0.050; for RQ versus RR: fixed-effects OR = 1.05, 95% CI 1.00-1.10, P = 0.047; for QQ/RQ versus RR: fixed-effects OR = 1.26, 95% CI 1.01-1.58, P = 0.041). The meta-analysis suggests that XRCC1 R399Q polymorphism was significantly associated with increased risk of normal tissue injury after radiotherapy in breast cancer patients, and XRCC1 R399Q polymorphism is a genetic marker of normal tissue injury after radiotherapy in breast cancer patients.

XRCC1 and ERCC1 variants modify malignant mesothelioma risk: A case–control study

Malignant pleural mesothelioma (MPM) is a rare aggressive tumor associated with asbestos exposure. The possible role of genetic factors has also been suggested and MPM has been associated with single nucleotide polymorphisms (SNPs) of xenobiotic and oxidative metabolism enzymes. We have identified an association of the DNA repair gene XRCC1 with MPM in the population of Casale Monferrato, a town exposed to high asbestos pollution. To extend this observation we examined 35 SNPs in 15 genes that could be involved in MPM carcinogenicity in 220 MPM patients and 296 controls from two case–control studies conducted in Casale (151 patients, 252 controls) and Turin (69 patients, 44 controls), respectively. Unconditional multivariate logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). Two DNA repair genes were associated with MPM, i.e. XRCC1 and ERCC1. Considering asbestos-exposed only, the risk increased with the increasing number of XRCC1-399Q alleles (Casale: OR = 1.44, 95%CI 1.02–2.03; Casale + Turin: OR = 1.34, 95%CI 0.98–1.84) or XRCC1 −77T alleles (Casale + Turin: OR = 1.33, 95%CI 0.97–1.81). The XRCC1-TGGGGGAACAGA haplotype was significantly associated with MPM (Casale: OR = 1.76, 95%CI 1.04–2.96). Patients heterozygotes for ERCC1 N118N showed an increased OR in all subjects (OR = 1.66, 95%CI 1.06–2.60) and in asbestos-exposed only (OR = 1.59, 95%CI 1.01–2.50). When the dominant model was considered (i.e. ERCC1 heterozygotes CT plus homozygotes CC versus homozygotes TT) the risk was statistically significant both in all subjects (OR = 1.61, 95%CI 1.06–2.47) and in asbestos-exposed only (OR = 1.56, 95%CI 1.02–2.40). The combination of ERCC1 N118N and XRCC1 R399Q was statistically significant (Casale: OR = 2.02, 95%CI 1.01–4.05; Casale + Turin: OR = 2.39, 95%CI 1.29–4.43). The association of MPM with DNA repair genes support the hypothesis that an increased susceptibility to DNA damage may favour asbestos carcinogenicity.

Genetic polymorphisms in XRCC1 associated with radiation therapy in prostate cancer

Radiation therapy is a potentially curative, important treatment option in localized prostate cancer. However, at 8 years after radiation therapy, even in the best risk subset of patients, approximately 10% of patients will experience clinical disease recurrence. The identification of molecular markers of treatment success or failure may allow for the development of strategies to further improve treatment outcomes. Herein, we investigated five molecular markers of DNA repair. 513 patients with castrate-resistant prostate cancer (CRPC), including 284 patients who received radiotherapy, 229 patients without radiotherapy, and 152 healthy individuals were genotyped for 5 polymorphisms in DNA excision repair genes: ERCC1 N118N (500C>T), XPD K751Q (2282A>C), XRCC1 R194W (685C>T), XRCC1 R399Q (1301G>A) and PARP1 V762A (2446T>C). The distribution of genetic polymorphisms in the patients with CRPC and in healthy controls was compared, and the association between the polymorphisms and overall survival was investigated. The polymorphisms evaluated did not show differences between the patient group and the healthy controls, nor did they show a trend toward an association with survival. However, in the radiation treated subgroup, the median survival time was associated with the XRCC1 haplotype. The median survival time was 11.75 years for patients with the R399Q AA/R194W CC haplotype, 12.17 years for patients with the R399Q AG/R194W CC haplotype, 6.665 years for patients with the R399Q AG/R194W CT haplotype, and 6.21 years for patients with the R399Q GG/R194W CT haplotype (p=0.034). This association was not found when all patients were investigated. We conclude that the genetic polymorphisms in XRCC1 may affect the outcome in patients who received radiotherapy for localized prostate cancer.

APE1 D148E, PARP1 V762A and XRCC1 R399Q polymorphisms and genetic susceptibility to colorectal cancer

APE1 D148E, PARP1 V762A and XRCC1 R399Q polymorphisms and genetic susceptibility to colorectal cancer

XRCC1 polymorphisms and breast cancer risk from the New York Site of the Breast Cancer Family Registry: A family-based case-control study

Background:XRCC1 is a scaffold protein involved in the early and late stages of Base Excision Repair (BER). Three DNA polymorphisms occur in XRCC1, resulting in non-synonymous amino acid changes, which could alter the binding or regulatory activities of XRCC1.Materials and Methods:We used a family-based case-control study design to evaluate the association between XRCC1 polymorphisms and breast cancer risk. Participants were breast cancer cases and their unaffected sisters enrolled in the New York Site of the Breast Cancer Family Registry. Conditional logistic regression was used to assess associations between genotype and breast cancer. XRCC1 mRNA levels and DNA nicking activity were measured in lymphoblastoid cell lines from unaffected sisters to determine whether the XRCC1 R399Q polymorphism has a functional effect on expression or protein activity.Results:XRCC1 194W was associated with a non-significant increase in breast cancer, while XRCC1 280H and XRCC1 399Q were associated with a non-significant decrease in breast cancer. We found a significant increase in XRCC1 expression in 399Q/Q lymphoblastoid cell lines from unaffected sisters (n=28, P=0.03). An increase in median nicking activity was not statistically significant.Conclusions:Our results suggest that XRCC1 399Q may alter mRNA expression and DNA repair phenotype, although the main effects of the genotype were not significantly associated with familial cancer risk. Additional research on the regulation of XRCC1 expression will contribute to an understanding of how this polymorphism may impact disease risk.

Genetic variability in DNA repair and clinical outcome in stage III non-small cell lung cancer (NSCLC) treated with concurrent platinum-based chemoradiation

e14621 Background: Concurrent platinum-based chemoradiation (CRT) is the standard of care for stage III NSCLC. CRT is associated with multiple toxicities and substantial interpatient variability in clinical outcomes, with a 20% cure rate. We evaluated the relationship of genetic polymorphisms in platinum metabolic and DNA repair pathways with clinical outcomes in patients treated for stage III NSCLC. Methods: This pilot study was IRB approved and all patients provided written informed consent. Patients with stage III NSCLC who completed CRT were eligible for enrollment. Genomic DNA was extracted from peripheral blood. Genotyping using Pyrosequencing™ was performed for 5 single nucleotide polymorphisms (SNPs): the detoxification enzyme GSTP1 I105V, and the DNA repair genes ERCC1 N118N, ERCC2 K751Q, ERCC2 R156R and XRCC1 R399Q. Pre-treatment variables, progression-free survival (PFS) and toxicity data were obtained from retrospective review of medical records. Results: 23 pts have been enrolled to date. Median age was 58 yrs (49–81). 5 pts received cisplatin and 18 carboplatin. Median radiation dose was 6480 cGy (5000–7020) and median V20 was 27%. 10 pts had grade 3/4 acute CRT toxicities and 7 pts required treatment breaks. Median duration of follow-up was 21 months (4–100). 14 pts recurred and median PFS was 12 months (4–100). 15 pts remain alive. Controlling for age, V20 and radiation dose and using multivariate cox proportional hazards regression, the ERCC2 K751Q and R156R genotypes were independent predictors of PFS (HRs= 0.404 &amp; 2.184, p-values= 0.0172 &amp; 0.0152, respectively, subjects with at least 1 variant allele being reference group). Using multiple logistic regression, the ERCC2 R156R variant showed a trend towards improved response (OR=2.98, p-value= 0.09). Overall survival data is limited by the majority of pts still being alive. Conclusions: Clinical and treatment variables were typical of a stage III NSCLC population. This pilot pharmacogenomic study indicates that outcomes were independently affected by genetic polymorphisms. Our findings, if validated prospectively, could have significant impact on optimizing treatment selection for stage III NSCLC pts, without need for additional tumor tissue. No significant financial relationships to disclose.

Genetic polymorphisms affecting clinical outcomes in epithelial ovarian cancer patients treated with taxanes and platinum compounds: A Korean population-based study

Objective We sought to evaluate the affect of genetic polymorphisms on clinical outcomes in patients with epithelial ovarian cancer (EOC). Methods Clinical data of 118 patients between March 2001 and November 2006 were reviewed. They underwent staging laparotomy followed by adjuvant chemotherapy using taxanes and platinum compounds. We investigated ERCC1 N118N, ERCC1 8092C> A, ERCC2 K751Q, XRCC1 R399Q, XRCC1 R194W, ABCB1 3435C> T, ABCB1 2677G> T/A, GSTP1 I105V, GSTM1 and GSTT1 polymorphisms with single base primer assay. Results The multivariate logistic regression analysis revealed that non-null genotype in GSTT1 polymorphism was a poor prognostic factors for overall response (adjusted OR, 0.29; 95% CI, 0.17–0.67), and A/A genotype in GSTP1 I105V polymorphism and T/T or T/A or A/A genotype in ABCB1 2677G> T/A polymorphism were significant risk factors for grade 3 or 4 hematological (adjusted OR, 3.08; 95% CI, 1.12–8.43) and gastrointestinal toxicities (adjusted OR, 9.74; 95% CI, 1.59–15.85), respectively. Moreover, The multivariate Cox's proportional hazard regression analysis showed that C/A or A/A genotype in ERCC1 8092C> A polymorphism and non-null genotype in GSTT1 polymorphism were prognostic factors for poor progression-free survival (adjusted HR, 1.94; 95% CI, 1.07–3.51) and poor overall survival (adjusted HR, 1.65; 95% CI, 1.79–3.42), respectively. Conclusion Genetic polymorphisms such as ERCC1 8092C> A, ABCB1 2677G> T/A, GSTP1 I105V and GSTT1 polymorphisms may affect drug response, toxicity and survival in patient with EOC who received taxane- and platinum-based chemotherapy after surgery. However, large-scale, prospective clinical studies are required for evaluating the role of genetic polymorphisms.

Association and Interactions between DNA Repair Gene Polymorphisms and Adult Glioma

It is generally accepted that glioma develops through accumulation of genetic alterations. We hypothesized that polymorphisms of candidate genes involved in the DNA repair pathways may contribute to susceptibility to glioma. To address this possibility, we conducted a study on 373 Caucasian glioma cases and 365 cancer-free Caucasian controls to assess associations between glioma risk and 18 functional single-nucleotide polymorphisms in DNA repair genes. We evaluated potential gene-gene and gene-environment interactions using a multianalytic strategy combining logistic regression, multifactor dimensionality reduction and classification and regression tree approaches. In the single-locus analysis, six single-nucleotide polymorphisms [ERCC1 3' untranslated region (UTR), XRCC1 R399Q, APEX1 E148D, PARP1 A762V, MGMT F84L, and LIG1 5'UTR] showed a significant association with glioma risk. In the analysis of cumulative genetic risk of multiple single-nucleotide polymorphisms, a significant gene-dosage effect was found for increased glioma risk with increasing numbers of adverse genotypes involving the aforementioned six single-nucleotide polymorphisms (P(trend) = 0.0004). Furthermore, the multifactor dimensionality reduction and classification and regression tree analyses identified MGMT F84L as the predominant risk factor for glioma and revealed strong interactions among ionizing radiation exposure, PARP1 A762V, MGMT F84L, and APEX1 E148D. Interestingly, the risk for glioma was dramatically increased in ionizing radiation exposure individuals who had the wild-type genotypes of MGMT F84L and PARP1 A762V (adjusted odds ratios, 5.95; 95% confidence intervals, 2.21-16.65). Taken together, these results suggest that polymorphisms in DNA repair genes may act individually or together to contribute to glioma risk.

DNA repair polymorphisms and the risk of stomach adenocarcinoma and severe chronic gastritis in the EPIC-EURGAST study

The contribution of genetic variation in DNA repair genes to gastric cancer (GC) risk remains essentially unknown. The aim of this study was to explore the relative contribution of DNA repair gene polymorphisms to GC risk and severe chronic atrophic gastritis (SCAG). Method A nested case control study within the EPIC cohort was performed including 246 gastric adenocarcinomas and 1175 matched controls. Controls with SCAG (n = 91), as defined by low pepsinogen A (PGA) levels, and controls with no SCAG (n = 1061) were also compared. Twelve polymorphisms at DNA repair genes (MSH2, MLH1, XRCC1, OGG1 and ERCC2) and TP53 gene were analysed. Antibodies against Helicobacter pylori were measured. No association was observed for any of these polymorphisms with stomach cancer risk. However, ERCC2 K751Q polymorphism was associated with an increased risk for non-cardial neoplasm [odds ratio (OR) = 1.78; 95% confidence interval (CI) 1.02-3.12], being ERCC2 K751Q and D312N polymorphisms associated with the diffuse type. ERCC2 D312N (OR = 2.0; 95% CI 1.09-3.65) and K751Q alleles (OR = 1.82; 95% CI 1.01-3.30) and XRCC1 R399Q (OR = 1.69; 95% CI 1.02-2.79) allele were associated with an increased risk for SCAG. Our study supports a role of ERCC2 in non-cardial GC but not in cardial cancer. A concordant result was observed for subjects with low PGA levels. XRCC1 allele was associated also with SCAG. This is the first prospective study suggesting that individual variation in DNA repair may be relevant for gastric carcinogenesis, a finding that will require further confirmation validation in larger independent studies.

Ethnic disparities in Americans of European descent versus Americans of African descent related to polymorphic ERCC1, ERCC2, XRCC1, and PARP1

Nucleotide excision repair (NER) and base excision repair (BER) pathways are DNA repair pathways that are important in carcinogenesis and in response to DNA-damaging chemotherapy. ERCC1 and ERCC2 are important molecular markers for NER; XRCC1 and PARP1 are important molecular markers for BER. Functional polymorphisms have been described that are associated with altered expression levels of these genes and with altered DNA repair capability. We assayed genomic DNA from 156 Americans of European descent and 164 Americans of African descent for the allelic frequencies of specific polymorphisms of ERCC1 N118N (500C>T), ERCC1 C8092A, ERCC2 K751Q (2282A>C), XRCC1 R399Q (1301G>A), XRCC1 R194W (685C>T), and PARP1 V762A (2446T>C). Differences were observed between Americans of European descent and Americans of African descent in the allelic frequencies of the ERCC1 N118N polymorphism (P < 0.000001). Differences were also observed between these two ethnic groups for ERCC2 K751Q (P = < 0.006675), XRCC1 R399Q (P < 0.000001), and PARP1 V762A (P = 0.000001). The ERCC1 N118N polymorphic variant that is seen most commonly in Americans of European descent is associated with a measurable reduction in NER function. ERCC1-mediated reduction in NER functionality affects the repair of cisplatin-DNA lesions.

Commonly Studied Single-Nucleotide Polymorphisms and Breast Cancer: Results From the Breast Cancer Association Consortium

The Breast Cancer Association Consortium (BCAC) is an international collaboration that was established to provide large sample sizes for examining genetic associations. We conducted combined analyses on all single-nucleotide polymorphisms (SNPs) whose associations with breast cancer have been investigated by at least three participating groups. Data from up to 12 studies were pooled for each SNP (ADH1C I350V, AURKA F31I, BRCA2 N372H, CASP8 D302H, ERCC2 D312N, IGFBP3 -202 c>a, LIG4 D501D, PGR V660L, SOD2 V16A, TGFB1 L10P, TP53 R72P, XRCC1 R399Q, XRCC2 R188H, XRCC3 T241M, XRCC3 5' UTR, and XRCC3 IVS7-14). Genotype frequencies in case and control subjects were compared, and genotype-specific odds ratios for the risk of breast cancer in heterozygotes and homozygotes for the rare allele compared with homozygotes for the common allele were estimated with logistic regression. Statistical tests were two-sided. The total number of subjects for analysis of each SNP ranged from 12,013 to 31,595. For five SNPs--CASP8 D302H, IGFBP3 -202 c>a, PGR V660L, SOD2 V16A, and TGFB1 L10P--the associations with breast cancer were of borderline statistical significance (P = .016, .060, .047, .056, and .0088 respectively). The remaining 11 SNPs were not associated with breast cancer risk; genotype-specific odds ratios were close to unity. There was some evidence for between-study heterogeneity (P<.05) for four of the 11 SNPs (ADH1C I350V, ERCC2 D312N, XRCC1 R399Q, and XRCC3 IVS5-14). Pooling data within a large consortium has helped to clarify associations of SNPs with breast cancer. In the future, consortia such as the BCAC will be important in the analysis of rare polymorphisms and gene x gene or gene x environment interactions, for which individual studies have low power to identify associations, and in the validation of associations identified from genome-wide association studies.

XRCC1 R399Q polymorphism is associated with response to platinum-based neoadjuvant chemotherapy in bulky cervical cancer

The aim of the study was to assess whether the genetic polymorphisms were associated with the tumor response in patients treated with platinum-based neoadjuvant chemotherapy (NAC) for bulky cervical cancer. We retrospectively reviewed the clinical data and recruited paraffin-embedded, formalin-fixed tissues of 36 patients with bulky cervical carcinoma. All patients underwent two or three cycles of platinum-based NAC followed by radical hysterectomy. We determined the genotypes of each single nucleotide polymorphism (SNP) of ERCC1, ERCC2, GGH, GSTP1, MTHFR, SLC19A1 and XRCC1 using single base primer extension assay. The response to platinum-based NAC was higher in patients with SNP of XRCC1 R399Q (P=0.015), and there was a significant increased chance of treatment response in women with the G/G genotype (OR 38.0; 95% CI 1.66-870.45; P=0.023). The probability of response was also higher in patients with SNP of SLC19A1 6318C/T (P=0.032). There were dose-dependent influence of the number of alleles on the response to platinum-based chemotherapy (chi2 test for linear-by-linear association; P=0.009 for XRCC1 R399Q and P=0.017 for SLC19A1 6318C/T, respectively). Moreover, the multifactor dimensionality reduction (MDR) analysis documented that the combinations of XRCC1 R399Q and GGH-401C/T genetic polymorphisms were significantly associated with response to chemotherapy (P<0.0001). Genetic polymorphism of XRCC1 R399Q is associated with response to platinum-based NAC in bulky cervical cancer, and MDR analysis documented association between gene-gene interaction of XRCC1 R399Q and treatment response.

An intronic polymorphism associated with increased XRCC1 expression, reduced apoptosis and familial breast cancer

XRCC1 coordinates the activities of DNA polymerase-beta and DNA ligase for base excision repair of oxidative DNA damage. In addition, there is some evidence that XRCC1 is a negative regulator of apoptosis. Single nucleotide polymorphisms in XRCC1 have been inconsistently associated with breast cancer risk. We evaluated XRCC1 gene expression in breast cancer cell lines and carcinogen-induced apoptosis in benign breast epithelial cells in relation to XRCC1 genotypes. XRCC1 IVS10+141G>A was associated with increased expression of XRCC1 mRNA and protein, and reduced apoptosis in response to benzo-[a]-pyrene or ionizing radiation, but XRCC1 R399Q was not. These genotypes were also assessed in a clinic-based sample that included 190 breast cancer patients with a family history of breast cancer and 95 controls with no family history of breast cancer. Heterozygous XRCC1 IVS10+141G>A was associated with an increased breast cancer risk (O.R. = 1.7, 95% C.I. 1.016-2.827, P = 0.04) as was homozygous XRCC1 IVS10+141G>A (O.R. = 4.7, 95% C.I. 1.028-21.444, P = 0.03). XRCC1 R399Q was not associated with breast cancer (O.R. 1.00, 95% C.I. 0.61-1.64). The XRCC1 IVS10+141G>A locus is centered in a sequence that is nearly identical to the consensus binding site for the PLAG1 transcription factor. XRCC1 IVS10+141G>A is an intronic polymorphism that is associated with XRCC1 expression, apoptosis and familial breast cancer. It may occur within an intronic regulatory sequence.

Polymorphisms in Genes of Nucleotide and Base Excision Repair: Risk and Prognosis of Colorectal Cancer

We have undertaken a comprehensive study of common polymorphisms in genes of DNA repair, exploring both the risk of developing colorectal cancer and the prognosis of patients. Subjects from a case-control study (377 cases and 329 controls) designed to assess gene-environment interactions were genotyped by use of an oligonucleotide microarray and the arrayed primer extension technique. Twenty-eight single nucleotide polymorphisms in 15 DNA repair genes were included. The candidate genes belong to different DNA repair pathways: base excision repair (OGG1, LIG3, APEX, POLB, XRCC1, PCNA, and MUTYH), nucleotide excision repair (ERCC1, ERCC2, ERCC4, and ERCC5), double-strand breaks repair (XRCC2, XRCC3, and XRCC9), and reversion repair (MGMT) genes. Polymorphism OGG1 S326C was associated with an increased risk of colorectal cancer [odds ratio (OR), 2.3; 95% confidence interval (95% CI), 1.1-5.0], the risk being higher in younger individuals. A haplotype of ERCC1 was associated with increased risk (OR, 2.3; 95% CI, 1.0-5.3). POLB P242R was also associated with decreased risk (OR, 0.23; 95% CI, 0.05-0.99), although the number of variant allele carriers was low. In the univariate analysis, adjusted for age, sex, and Dukes' stage, three polymorphisms were significantly associated with better prognosis: XRCC1 R399Q [hazard ratio (HR), 0.38; 95% CI, 0.17-0.85], XRCC3 T141M (HR, 0.66; 95% CI, 0.45-0.97), and MGMT L84F (HR, 0.14; 95% CI, 0.02-0.99). ERCC1 19007T>C was associated with worse prognosis (HR, 1.51; 95% CI, 1.01-2.27). In a multivariate analysis, only XRCC1 R399Q and ERCC1 19007T>C remained significant. These associations were stronger among patients receiving adjuvant chemotherapy. Although the overall effect of DNA repair genes in colorectal cancer etiology seems limited, their influence in the response to chemotherapy and prognosis may be more relevant. This knowledge may help to clarify the utility of specific adjuvant treatments according to the individual genetic background.