Polymorphic variants of DNA repair gene XRCC3 and XRCC7 and risk of prostate cancer: a study from North Indian population

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.

DNA repair, NFKβ, and TP53 polymorphisms associated with potentially malignant disorders and oral squamous cell carcinoma in Argentine patients

OBJECTIVE

An important strategy in cancer prevention is to identify individual susceptibilities for cancer development through the genomic profile. Developing countries such as Argentina have no data on genetic composition. The aim of this study was to evaluate the single nucleotide polymorphisms of genes related to DNA repair (XCCR3, XPD), cell cycle arrest/apoptosis (TP53), and inflammation (NFKβ) of patients with precancer and oral cancer and to contribute to recognizing potential risk of developing these pathologies, and incorporate the risk patients into a clinical follow-up program in Córdoba, Argentina.

STUDY DESIGN

A cross-sectional study was performed on 140 patients with oral squamous cell carcinoma (OSCC), oral potentially malignant disorders (OPMDs), and controls. Genotyping of single nucleotide polymorphisms was performed using allele-specific polymerase chain reaction or restriction fragment length polymorphism techniques. The variables were evaluated by bivariate and multivariate statistical methods, with P < .05 statistically significant.

RESULTS

The multiple correspondence analyses showed that patients with OSCC are clustered with the T allele of XRCC3 T241 M and the C allele of TP53 R72 P, and patients with OPMDs are clustered with the T allele of NFKβ-519.

CONCLUSION

Our preliminary results showed that the C allele of the Pro72 variant of TP53 was related to OSSC and OPMD, and the T allele of NFKβ-519 is related to OPMDs in Argentine patients.

Genetic variations in DNA-repair genes (XRCC1, 3, and 7) and the susceptibility to hepatocellular carcinoma in a cohort of Egyptians

Chronic hepatitis C (CHC) is a worldwide etiology of chronic hepatic insult particularly in Egypt. DNA-repair systems are responsible for maintaining genomic integrity by countering threats posed by DNA lesions. Deficiency in the repair capacity due to genetic alterations in DNA-repair genes can lead to genomic instability and increased risk of cancer development. The present work aimed at studying the possible association between XRCC1-G28152A (rs25487), XRCC3-C18067T (rs861539), and XRCC7-G6721T (rs7003908) single nucleotide polymorphisms (SNPs) and the susceptibility to hepatocellular carcinoma (HCC) in Egyptian population. The study was conducted on 100 newly diagnosed HCC patients and 100 age- and sex-matched healthy controls. Laboratory workup revealed that all HCC patients have chronic hepatitis C viral infection. Genotyping of the studied SNPs was performed by real-time PCR. The heteromutant genotype of XRCC1 (GA) conferred an almost two-fold increased risk of HCC (OR ,  2.35; 95% CI, 1.33-4.04). Regarding XRCC7, the heteromutant (TG) genotype conferred a two-fold increased risk of HCC (OR ,  2.17; 95% CI, 1.23-3.82). Coinheritance of the polymorphic genotypes of XRCC1 and 7 was significantly higher in HCC cases than controls and was associated with an 11-fold increased risk of HCC (OR , 11.66; 95% CI,  2.77-49.13). The frequency of XRCC3 polymorphic genotypes in HCC patients was close to that of the controls.

Centenarian Exomes as a Tool for Evaluating the Clinical Relevance of Germline Tumor Suppressor Mutations

Objectives:

The aim of the present study was to evaluate the clinical relevance of mutations in tumor suppressor genes using whole-exome sequencing data from centenarians and young healthy individuals.

Methods:

Two pools, one of centenarians and one of young individuals, were constructed and whole-exome sequencing was performed. We examined the whole-exome sequencing data of Bulgarian individuals for carriership of tumor suppressor gene variants.

Results:

Of all variants annotated in both pools, 5080 (0.06%) are variants in tumor suppressor genes but only 46 show significant difference in allele frequencies between the two studied groups. Four variants (0.004%) are pathogenic/risk factors according to single nucleotide polymorphism database: rs1566734 in PTPRJ, rs861539 in XRCC3, rs203462 in AKAP10, and rs486907 in RNASEL.

Discussion:

Based on their high minor allele frequencies and presence in the centenarian group, we could reclassify them from pathogenic/risk factors to benign. Our study shows that centenarian exomes can be used for re-evaluating the clinically uncertain variants.

DNA-PK in human malignant disorders: Mechanisms and implications for pharmacological interventions

The DNA-PK holoenzyme is a fundamental element of the DNA damage response machinery (DDR), which is responsible for cellular genomic stability. Consequently, and predictably, over the last decades since its identification and characterization, numerous pre-clinical and clinical studies reported observations correlating aberrant DNA-PK status and activity with cancer onset, progression and responses to therapeutic modalities. Notably, various studies have established in recent years the role of DNA-PK outside the DDR network, corroborating its role as a pleiotropic complex involved in transcriptional programs that operate biologic processes as epithelial to mesenchymal transition (EMT), hypoxia, metabolism, nuclear receptors signaling and inflammatory responses. In particular tumor entities as prostate cancer, immense research efforts assisted mapping and describing the overall signaling networks regulated by DNA-PK that control metastasis and tumor progression. Correspondingly, DNA-PK emerges as an obvious therapeutic target in cancer and data pertaining to various pharmacological approaches have been published, largely in context of combination with DNA-damaging agents (DDAs) that act by inflicting DNA double strand breaks (DSBs). Currently, new generation inhibitors are tested in clinical trials. Several excellent reviews have been published in recent years covering the biology of DNA-PK and its role in cancer. In the current article we are aiming to systematically describe the main findings on DNA-PK signaling in major cancer types, focusing on both preclinical and clinical reports and present a detailed current status of the DNA-PK inhibitors repertoire.

Polymorphisms of XRCC3 and XRCC7 and Colorectal Cancer Risk in Khorasan Razavi Province, Iran

Background: Colorectal cancer (CRC) is highly prevalent cancer, which should be genetically studied among different peoples of the world. Objective: The aim of this study was to evaluate the effect of XRCC3T241M, XRCC3 A17893G and, for the first time, XRCC7 I3434T polymorphisms on CRC risk in Khorasan Razavi Province, Iran. Materials and Methods: In this case-control study, 180 patients with CRC and 160 sex- and age-matched healthy controls were studied. Genotypes were determined by RFLP-PCR and ARMS-PCR. Results: The incidence of CRC was observed to be significantly more in a heterozygous XRCC3 C/T genotype than in the CC genotype (OR 2.210, 95% CI 1.073-4.548, p=0.030). In the case of the XRCC7 I3434T polymorphism, CRC risk was significantly (4.3 fold) higher in I/T+T/T variant subjects compared to the I/I genotype (OR 4.394, 95% CI 2.721-7.096, p=0.000). Moreover, the XRCC3 A17893G polymorphism did not correlate with CRC. In addition, there was no significant difference between the distribution of genotypes of the three studied polymorphisms with demographic and clinicopathological features in the CRC patients. Conclusion: Polymorphisms of XRRC3 and XRCC7 genes are involved in CRC and should be considered as a risk factor.

RAD51 and XRCC3 Polymorphisms Are Associated with Increased Risk of Prostate Cancer

Genetic polymorphisms in DNA repair genes may affect DNA repair efficiency and may contribute to the risk of developing cancer. The aim of our study was to investigate single nucleotide polymorphisms (SNPs) in RAD51 (rs2619679, rs2928140, and rs5030789) and XRCC3 (rs1799796) involved in DNA double-strand break repair and their relationship to prostate cancer. The study group included 99 men diagnosed with prostate cancer and 205 cancer-free controls. SNP genotyping was performed using the PCR-RFLP method. A significant association was detected between RAD51 rs5030789 polymorphism and XRCC3 rs1799796 polymorphism and an increased risk of prostate cancer. Our results indicate that RAD51 and XRCC3 polymorphism may contribute to prostate cancer.

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.

IL-10 and PRKDC polymorphisms are associated with glioma patient survival

Interleukin-10 (IL-10) and DNA repair gene PRKDC mutations are implicated in the development of multiple human cancers, including glioma. We investigated associations between IL-10 and PRKDC gene polymorphisms and prognosis in low- and high-grade glioma patients. We analyzed the associations of one IL-10 and one PRKDC single nucleotide polymorphism with patient clinical factors in 481 glioma patients using Cox proportional hazard models and Kaplan-Meier curves. We also assessed associations between patient clinical characteristics and prognosis. Our data showed that the extent of tumor resection (gross-total resection) and application of chemotherapy were associated with improved patient outcomes in all glioma cases. Additionally, univariate (Log-rank p = 0.019) and multivariate Cox regression analyses (p = 0.022) showed that the IL-10 rs1800871 C/T genotype correlates with improved overall survival in cases of low-grade glioma, whereas the PRKDC rs7003908 C/C genotype correlated with reduced overall and progression-free survival in high-grade glioma patients in univariate (Log-rank p = 0.000 and p = 0.000, respectively) and multivariate Cox regression analyses (p = 0.001; p = 0.002, respectively). These results suggest that IL-10 rs1800871 and PRKDC rs7003908 may be useful biomarkers for predicting glioma patient outcome. Further functional studies are needed to evaluate the mechanisms by which these polymorphisms affect glioma progression.

The Role of the Core Non-Homologous End Joining Factors in Carcinogenesis and Cancer

DNA double-strand breaks (DSBs) are deleterious DNA lesions that if left unrepaired or are misrepaired, potentially result in chromosomal aberrations, known drivers of carcinogenesis. Pathways that direct the repair of DSBs are traditionally believed to be guardians of the genome as they protect cells from genomic instability. The prominent DSB repair pathway in human cells is the non-homologous end joining (NHEJ) pathway, which mediates template-independent re-ligation of the broken DNA molecule and is active in all phases of the cell cycle. Its role as a guardian of the genome is supported by the fact that defects in NHEJ lead to increased sensitivity to agents that induce DSBs and an increased frequency of chromosomal aberrations. Conversely, evidence from tumors and tumor cell lines has emerged that NHEJ also promotes chromosomal aberrations and genomic instability, particularly in cells that have a defect in one of the other DSB repair pathways. Collectively, the data present a conundrum: how can a single pathway both suppress and promote carcinogenesis? In this review, we will examine NHEJ's role as both a guardian and a disruptor of the genome and explain how underlying genetic context not only dictates whether NHEJ promotes or suppresses carcinogenesis, but also how it alters the response of tumors to conventional therapeutics.

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.

Polymorphisms in DNA Repair Gene XRCC3 and Susceptibility to Breast Cancer in Saudi Females

We investigated three common polymorphisms (SNPs) in the XRCC3 gene (rs861539, rs1799794, and rs1799796) in 143 Saudi females suffering from breast cancer (median age = 51.4 years) and 145 age matched normal healthy controls. DNA was extracted from whole blood and genotyping was conducted using PCR-RFLP. rs1799794 showed significant association, where AA and AA+AG occurred at a significantly higher frequency in the cancer patients compared to the control group (OR: 28.1; 95% CI: 3.76-21.12; χ (2): 22.82; p < 0.0001). The G allele was protective and presented with a dominant model. The genotype and allele frequencies of rs861539 C>T and rs1799796 A>G did not show a significant difference when the results in the patients and controls were compared. However, the frequency of rs1799796 differed significantly in patients with different age of diagnosis, tumor grade, and ER and HER2 status. The wild type A allele occurred at a higher frequency in the ER- and HER2- group. Our results among Saudis suggest that some variations in XRCC3 may contribute to breast cancer susceptibility. In conclusion, the results obtained during this study suggest that rs1799794 in XRCC3 shows strong association with breast cancer development in Saudi females.

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.

The association of XRCC3 Thr241Met genetic variant with risk of prostate cancer: a meta-analysis

BACKGROUND

Previous studies suggest that the X-ray repair cross-complementing group 3 gene (XRCC3) Thr241Met genetic variant could be potentially associated with the risk of prostate cancer. However, results from these published studies were conflicting rather than conclusive.

OBJECTIVES

his meta-analysis aimed to conduct a better understanding of the effects of XRCC3 Thr241Met genetic variant on prostate cancer risk.

METHODS

We identified three eligible studies, 499 prostate cancer cases and 571 controls.

RESULTS

Overall, significant associations were detected in the heterozygote comparison genetic model (CT versus (vs.) CC: OR = 0.71, 95% CI 0.53-0.94, Z =2.38, p= 0.017), and the dominant genetic model (TT/CT vs. CC: OR = 0.74, 95% CI 0.57-0.98, Z = 2.11, p =0.035). In the subgroup analysis by ethnicities, we found that this genetic variant was significantly associated with the decrease risk of prostate cancer in Caucasians for heterozygote comparison genetic model (CT vs. CC: OR = 0.66, 95% CI 0.44-0.98, Z = 2.04, p = 0.042). No publication bias was found in this study.

CONCLUSIONS

Results from this meta-analysis indicate that the XRCC3 Thr241Met genetic variant is associated with prostate cancer risk.

Genetic variation in a DNA double strand break repair gene in saudi population: a comparative study with worldwide ethnic groups

DNA repair capacity is crucial in maintaining cellular functions and homeostasis. However, it can be altered based on DNA sequence variations in DNA repair genes and this may lead to the development of many diseases including malignancies. Identification of genetic polymorphisms responsible for reduced DNA repair capacity is necessary for better prevention. Homologous recombination (HR), a major double strand break repair pathway, plays a critical role in maintaining the genome stability. The present study was performed to determine the frequency of the HR gene XRCC3 Exon 7 (C18067T, rs861539) polymorphisms in Saudi Arabian population in comparison with epidemiological studies by "MEDLINE" search to equate with global populations. The variant allelic (T) frequency of XRCC3 (C>T) was found to be 39%. Our results suggest that frequency of XRCC3 (C>T) DNA repair gene exhibits distinctive patterns compared with the Saudi Arabian population and this might be attributed to ethnic variation. The present findings may help in high-risk screening of humans exposed to environmental carcinogens and cancer predisposition in different ethnic groups.

Role of the functional variant (-652T>G) in the XRCC4 promoter in prostate cancer

Several genes encoding DNA repair molecules have been proposed as cancer-susceptibility genes. Many studies have suggested that SNPs in XRCC4 could be implicated in altering the risk of prostate cancer (PCa). We examined the role of the functional variant (-652T>G) in the XRCC4 promoter in PCa. The transcriptional activity of XRCC4 gene was measured by luciferase assay. We performed real-time PCR/immunohistochemical assay to verify the association between expression level of XRCC4 mRNA/protein and XRCC4 -652T>G polymorphism. In addition, electrophoretic mobility shift assay (EMSA) was used to confirm whether this polymorphism has an effect on binding ability of the transcription factor. We found that the G variant significantly increased the transcription activity of the XRCC4 gene and the binding ability of transcriptional factor GATA-1 to the XRCC4 promoter. Furthermore, the results suggested that the XRCC4 protein and mRNA were overexpressed in individuals who carried the -652G allele compared to carriers of the -652T allele. In addition, the expression of XRCC4 in PCa tissues was lower than in adjacent normal tissues. Our data suggest that the XRCC4 promoter -652G>T polymorphism is functional and may influence genetic susceptibility to prostate cancer. Case-control studies are required to validate our findings in the future.

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.

XRCC7 rs#7003908 Polymorphism and Helicobacter pylori Infection-Related Gastric Antrum Adenocarcinoma

The X-ray repair cross-complementing group 7 (XRCC7) plays a key role in DNA repair that protects against genetic instability and carcinogenesis. To determine whether XRCC7 rs#7003908 polymorphism (XRCC7P) is associated with Helicobacter pylori (H. pylori) infection-related gastric antrum adenocarcinoma (GAA) risk, we conducted a hospital-based case-control study, including 642 patients with pathologically confirmed GAA and 927 individually matched controls without any evidence of tumours or precancerous lesions, among Guangxi population. Increased risks of GAA were observed for individuals with cagA positive (odds ratio (OR) 6.38; 95% confidence interval (CI) 5.03-8.09). We also found that these individuals with the genotypes of XRCC7 rs#7003908 G alleles (XRCC7-TG or -GG) featured increasing risk of GAA (ORs 2.80 and 5.13, resp.), compared with the homozygote of XRCC7 rs#7003908 T alleles (XRCC7-TT). GAA risk, moreover, did appear to differ more significantly among individuals featuring cagA-positive status, whose adjusted ORs (95% CIs) were 15.74 (10.89-22.77) for XRCC7-TG and 38.49 (22.82-64.93) for XRCC7-GG, respectively. Additionally, this polymorphism multiplicatively interacted with XRCC3 codon 241 polymorphism with respect to HCC risk (ORinteraction = 1.49). These results suggest that XRCC7P may be associated with the risk of Guangxiese GAA related to cagA.

The role of Ile3434Thr XRCC7 gene polymorphism in differentiated thyroid cancer risk in an Iranian population

BACKGROUND

The aim of this study was to understand any association between differentiated thyroid carcinoma (DTC) and Ile3434Thr XRCC7 gene polymorphism (GenBank accession number: rs7830743). DTC is the most prevalent thyroid neoplasm, which includes papillary and follicular cell carcinoma. XRCC7 gene encodes a protein that functions in non-homologous end joining DNA repair pathway. Non-synonymous polymorphisms in this gene may alter DNA repair capacity of the cell and change the risk of developing cancers.

METHODS

DTC patients (n = 173) and cancer free individuals (n = 204) were enrolled in a case-control study. The Ile3434Thr polymorphic alleles were discriminated by using amplification refractory mutation system-PCR method. The frequencies of this single nucleotide polymorphism in case and control groups were compared. Also, risk ratio for developing DTC in dichotomized genotypes was estimated by multivariate logistic regression analysis.

RESULTS

Dichotomized genotypes into those with and without the 3434Thr allele showed that this allele was associated with DTC (OR [odd ratio]: 1.89, 95% confidence interval (CI) = 1.29-2.79, P<0.001). Also, TC genotype was significantly associated with increased risk of DTC (OR: 2.42, 95% CI = 1.55-3.81, P = 0.0001) in individuals carrying this genotype.

CONCLUSION

Allele 3434Thr in XRCC7 gene might be associated with differentiated thyroid cancer risk. Further studies with larger samples are needed to verify these initial findings.

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.

Comprehensive SNP scan of DNA repair and DNA damage response genes reveal multiple susceptibility loci conferring risk to tobacco associated leukoplakia and oral cancer

Polymorphic variants of DNA repair and damage response genes play major role in carcinogenesis. These variants are suspected as predisposition factors to Oral Squamous Cell Carcinoma (OSCC). For identification of susceptible variants affecting OSCC development in Indian population, the "maximally informative" method of SNP selection from HapMap data to non-HapMap populations was applied. Three hundred twenty-five SNPs from 11 key genes involved in double strand break repair, mismatch repair and DNA damage response pathways were genotyped on a total of 373 OSCC, 253 leukoplakia and 535 unrelated control individuals. The significantly associated SNPs were validated in an additional cohort of 144 OSCC patients and 160 controls. The rs12515548 of MSH3 showed significant association with OSCC both in the discovery and validation phases (discovery P-value: 1.43E-05, replication P-value: 4.84E-03). Two SNPs (rs12360870 of MRE11A, P-value: 2.37E-07 and rs7003908 of PRKDC, P-value: 7.99E-05) were found to be significantly associated only with leukoplakia. Stratification of subjects based on amount of tobacco consumption identified SNPs that were associated with either high or low tobacco exposed group. The study reveals a synergism between associated SNPs and lifestyle factors in predisposition to OSCC and leukoplakia.

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.

Role of the functional MKK4 promoter variant (-1304T>G) in a decreased risk of prostate cancer: case-control study and meta-analysis

PURPOSE

MKK4 has been suggested as a tumor suppressor. The functional variant (-1304T>G) in the MKK4 promoter has been implicated as a risk factor for many types of cancer. However, its role in prostate cancer (PCa) is unclear. To determine whether this SNP constitutes a risk factor for PCa susceptibility and to derive a more precise estimation of the associations between this SNP and cancer risk, we performed a case-control study and then a meta-analysis covering previous case-control studies.

METHODS

In this study, 222 male patients with PCa and 244 cancer-free controls were evaluated MKK4-1304T>G genotype. The transcriptional activity of MKK4 gene was measured by luciferase assay, and MKK4 serum expression was measured by ELISA.

RESULTS

As a whole, we found that compared to the most common -1304TT genotype, carriers of -1304G variant genotypes had a decreased risk of PCa (OR = 0.670; 95 % CI = 0.452-0.993, P = 0.046 for TG, and OR = 0.647; 95 % CI = 0.441-0.948, P = 0.025 for TG + GG). We found that carriers of the -1304G variant genotypes had greater transcriptional activity and serum expression of MKK4 than carriers of the -1304T allele. Our meta-analysis also suggested that the -1304G variant contributes to decreased risk of various cancers.

CONCLUSION

Our results suggest that the functional -1304G variant in the MKK4 promoter decreases the risk of PCa by increasing the promoter activity. In the future, prospective researches on patients from many parts of the world may validate our findings.

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.

DNA repair gene XRCC7 polymorphisms (rs#7003908 and rs#10109984) and hepatocellular carcinoma related to AFB1 exposure among Guangxi population, China

AIM

  The X-ray repair cross-complementing group 7 (XRCC7) plays an important role in the repair of DNA double-strand breaks by nonhomologous end-joining repair (NEJR) pathway. However, the role of XRCC7 polymorphisms (rs#7003908 and rs#10109984) possibly influencing NEJR capacity in hepatocellular carcinoma (HCC) induced by aflatoxin B1 (AFB1) has not been well elaborated.

METHODS

  This hospital-based case-control study, including 348 patients with newly diagnosed HCC and 597 controls without any evidence of liver diseases, was conducted to elucidate the association between these two polymorphisms and the risk of HCC related to AFB1 exposure among a Guangxi population from a high AFB1-exposure area by means of TaqMAN-polymerase chain reaction technique.

RESULTS

  We observed that HCC patients featured higher AFB1 exposure than control group (odds ratios [OR] = 6.49 and 6.75 for exposure years and exposure levels, respectively). Furthermore, these individuals with the genotypes of XRCC7 rs#7003908 G alleles (namely XRCC7-TG or -GG), compared the homozygote of XRCC7 rs#7003908 T alleles (XRCC7-TT), faced increasing risk of HCC (OR, 3.45 and 5.04; 95% confidence intervals [CIs], 2.40-4.94 and 3.28-7.76, respectively). We also found some evidence that this polymorphism interacted with AFB1-expousure years or levels in the process of HCC carcinogenesis. Additionally, XRCC7 rs#7003908 polymorphism was correlated with the levels of AFB1-DNA adducts (r = 0.142, P < 0.001). XRCC7 rs#10109984 polymorphism, however, did not modify the risk of HCC related to AFB1 exposure (P > 0.05).

CONCLUSION

  These data suggest that XRCC7 rs#7003908 polymorphism may be one of the genetic modifiers for AFB1-related HCC among Guangxi population.