Repair In Chinese Hamster Cells Research Articles

ERCC1 C8092A polymorphism predicts fair survival outcome in Japanese patients with pharyngo-laryngeal squamous cell carcinoma.

To evaluate the prognostic significance of DNA excision repair gene polymorphisms, excision repair cross-complementation group 1 (ERCC1) and X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1) polymorphisms were investigated in Japanese patients with head and neck squamous cell carcinoma (HNSCC). A total of 225 consecutive patients with HNSCC who underwent surgery or chemoradiotherapy/radiotherapy (CRT/RT) with curative intent as primary treatment from 2006 to 2017 were recruited. ERCC1 C8092A and XRCC1 Arg399Gln polymorphisms in DNA extracted from individual blood samples were determined by the polymerase chain reaction-restriction fragment length polymorphism method. Cumulative survival was estimated by Kaplan-Meier analysis with a log-rank test and Cox proportional hazards model stratified by treatment arm, adjusting for clinical prognostic factors. Multivariate analysis showed that carriers with the ERCC1 8092 (C/A+A/A) genotype (hazard ratio, 3.56; 95% confidence interval, 1.22-7.39; p = 0.02) had significantly worse survival than those with ERCC1 8092 C/C who received CRT/RT. Conversely, the XRCC1 Arg399Gln polymorphism did not influence survival in patients who received CRT/RT as well as surgery. The ERCC1 C8092A polymorphism might be an independent predictor of response to CRT and survival outcome in patients with HNSCC. This is the first report to investigate the role of DNA excision repair gene polymorphisms in patients with head and neck cancer in a Japanese population.

DNA repair gene (XRCC3) polymorphisms and its association with ovarian carcinoma in Egyptian PATIENTS

The DNA repair gene polymorphisms are supposed to boost the tumorigenesis and prognosis of cancers. The X-ray repair complementing defective repair in Chinese hamster cells 3 (XRCC3) gene has a pivotal role in the DNA repair process which if mutated may be entangled in the tumorigenesis. Although there are many studies examining the DNA repair gene polymorphisms in cancers, the association of the XRCC3 SNPs with ovarian cancer in Egypt remains not fully defined. We aimed to examine the impact of the XRCC3 genetic polymorphisms with the ovarian carcinoma development and prognosis. Moreover, to analyze the relation of the SNPs alleles and haplotypes with the different tumor stages and subtypes. MethodsGenomic DNA was extracted from 50 histopathologically confirmed ovarian cancer patients and 20 cancer-free control subjects using PCR-RFLP assays. ResultsThe mean ages of the subjects were non- significantly differed between the patients and controls with significant increase with advanced tumor stage (F = 5.344, P = .003). The serous carcinoma was the most common type of ovarian tumor among our patients (40%) (X2 = 9.49, P =.023). A non-significant association was noticed between the studied SNPs (rs 861539 C > T, rs 1799794 G > A) genotypes with the ovarian cancer stages and subtypes. The rs 861539 T carriers had a higher frequency in cancer patients when compared to controls, otherwise, it showed a non-significant correlation with the tumor subtypes. The rs 861539 T/rs 1799794 A haplotype occurred at a higher frequency in ovarian cancer patients more than controls (X2 = 10.32, P = .016), with non- significant association with tumor subtypes. ConclusionDNA repair gene XRCC3 polymorphism rs 861539 T allele and the rs 861539 T/rs 1799794 A haplotype may boost the susceptibility to ovarian carcinoma with no correlation with the tumor histological subtypes and stages. They may be salutary as a DNA-based diagnostic biomarker for identifying the high-risk Egyptian females susceptible to ovarian cancer. More studies are needed to clarify the underlying mechanisms that can contribute to ovarian cancer, assess the cancer prognosis, and help to determine adequate therapy regimen.

Impact of a Missense Variation (p.S150R:AGC>AGG) in the XRCC2 Gene on Susceptibility to Colorectal Cancer.

The X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2) is an important protein in response to DNA double-strand breaks (DSBs) in human cells. XRCC2, as a functional protein in the homologous recombination repair (HRR) process, has been identified to have several polymorphisms which might be associated with the risk of cancer. Therefore, we aimed to investigate a novel missense variation (AGC>AGG, p.Ser150Arg) in the XRCC2 gene for colorectal cancer susceptibility. We studied 291 colorectal cancer (CRC) patients and 140 healthy individuals. ARMS PCR method was used to detect the AGC>AGG (p.Ser150Arg) variation in the XRCC2 gene. The results showed that there was a significant differential among CRC and controls in the genotypic and allelic frequencies (p < 0.001) of XRCC2; AGC>AGG, p.Ser150Arg. Our results demonstrated that the G allele of XRCC2; AGC>AGG, p.Ser150Arg was associated with increased CRC risk (odds ratio = 59.04, 95% confidence interval = 18.6 - 186). This variation also influenced CRC cancer susceptibility in smokers (p < 0.001). The G allele of XRCC2; AGC>AGG, p.Ser150Arg, may be a potential marker for CRC in Iranians and investigations in other populations are warranted for further universal application in CRC detection and prediction.

MiroRNA-127-3p targets XRCC3 to enhance the chemosensitivity of esophageal cancer cells to a novel phenanthroline-dione derivative

MicroRNAs are small non-coding RNAs with 18–22 nucleotides in length and have been proposed to function in various biological processes by targeting genes for post-transcriptional degradation via their 3′ untranslated region. Moreover, they have been suggested to improve the chemosensitivity in a panel of tumors. However, the biological functions of microRNA-127-3p in esophageal carcinogenesis are still enigmatic. Thus, in the study, we firstly analyzed the roles of microRNA-127-3p in regulating the growth of esophageal cancer cells both in vitro and in vivo. Afterwards, using the microRNA-targeted gene prediction software and the dual-luciferase reporter assays, we confirmed that microRNA-127-3p specifically reduced the expression of X-ray repair complementing defective repair in Chinese hamster cells 3, one of RAD51 recombinase paralogs, at both mRNA and protein levels. Furthermore, using the homologous recombination repair and non-homologous end joining repair reporter systems, we found that microRNA-127-3p specifically compromised the homologous recombination repair and significantly increased DNA double strand breaks in cells. Besides, it statistically increased the chemosensitivity of esophageal cancer cells to a novel phenanthroline-dione derivative in vivo by mechanistically impairing the recruitment of RAD51 to the damage sites. In summary, our findings not only suggest that microRNA-127-3p can be used as a predictor for evaluating the development of esophageal carcinoma, but also show that it can be used to increase the chemosensitivity of esophageal cancer patients to the phenanthroline-dione derivative, which might be a potential anticancer candidate in the future.

High Expression of XRCC6 Promotes Human Osteosarcoma Cell Proliferation through the β-Catenin/Wnt Signaling Pathway and Is Associated with Poor Prognosis.

Increasing evidences show that XRCC6 (X-ray repair complementing defective repair in Chinese hamster cells 6) was upregulated and involved in tumor growth in several tumor types. However, the correlation of XRCC6 and human osteosarcoma (OS) is still unknown. This study was conducted with the aim to reveal the expression and biological function of XRCC6 in OS and elucidate the potential mechanism. The mRNA expression level of XRCC6 was measured in osteosarcoma cells and OS samples by quantitative transcription-PCR (qRT-PCR). The expression of XRCC6 protein was measured using Western blot and immunohistochemical staining in osteosarcoma cell lines and patient samples. Cell Counting Kit 8 (CCK8), colony-forming and cell cycle assays were used to test cell survival capacity. We found that XRCC6 was overexpressed in OS cells and OS samples compared with the adjacent non-tumorous samples. High expression of XRCC6 was correlated with clinical stage and tumor size in OS. Reduced expression of XRCC6 inhibits OS cell proliferation through G2/M phase arrest. Most importantly, further experiments demonstrated that XRCC6 might regulate OS growth through the β-catenin/Wnt signaling pathway. In conclusion, these findings indicate that XRCC6 exerts tumor-promoting effects for OS through β-catenin/Wnt signaling pathway. XRCC6 may serve as a novel therapeutic target for OS 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.

Association between single-nucleotide polymorphisms in DNA double-strand break repair genes and prostate cancer aggressiveness in the Spanish population

Novel predictors of prognosis and treatment response for prostate cancer (PCa) are required to better individualize treatment. Single-nucleotide polymorphisms (SNPs) in four genes directly (XRCC5 (X-ray repair complementing defective repair in Chinese hamster cells 5) and XRCC6 (X-ray repair complementing defective repair in Chinese hamster cells 6)) or indirectly (PARP1 and major vault protein (MVP)) involved in non-homologous end joining were examined in 494 Spanish PCa patients. A total of 22 SNPs were genotyped in a Biotrove OpenArray NT Cycler. Clinical tumor stage, diagnostic PSA serum levels and Gleason score at diagnosis were obtained for all participants. Genotypic and allelic frequencies were determined using the web-based environment SNPator. (XRCC6) rs2267437 appeared as a risk factor for developing more aggressive PCa tumors. Those patients carrying the GG genotype were at higher risk of developing bigger tumors (odds ratio (OR)=2.04, 95% confidence interval (CI) 1.26-3.29, P=0.004), present higher diagnostic PSA levels (OR=2.12, 95% CI 1.19-3.78, P=0.011), higher Gleason score (OR=1.65, 95% CI 1.01-2.68, P=0.044) and D'Amico higher risk tumors (OR=2.38, 95% CI 1.24-4.58, P=0.009) than those patients carrying the CC/CG genotypes. Those patients carrying the (MVP) rs3815824 TT genotype were at higher risk of presenting higher diagnostic PSA levels (OR=4.74, 95% CI 1.40-16.07, P=0.013) than those patients carrying the CC genotype. When both SNPs were analyzed in combination, those patients carrying the risk genotypes were at higher risk of developing D'Amico higher risk tumors (OR=3.33, 95% CI 1.56-7.17, P=0.002). We believe that for the first time, genetic variants at XRCC6 and MVP genes are associated with risk of more aggressive disease, and would be taken into account when assessing the malignancy of PCa.

Association of Promoter Polymorphisms in Xrcc2 Gene Involved in DNA Double Strand Break Repair and Increased Susceptibility to Thyroid Cancer Risk in Pakistani Population

Introduction: The incidence of thyroid cancer (TC) has rapidly increased globally in recent decades. It is the most frequent endocrine malignancy which is fifth most common cancer in females. Double strand break repair (DSBR) pathway gene, X-Ray Repair Complementing Defective Repair in Chinese Hamster Cells 2 (XRCC2) has high rate of polymorphisms and may cause individual’s susceptibility towards carcinogenesis including thyroid cancer. Objective: Main objective of present study is to find the association of hotspot promotor polymorphisms in XRCC2 gene with thyroid cancer risk. Methods: In this study, we performed genetic association studies in 856 individuals (456 cases and 400 controls) for three promoter region SNPs of XRCC2 gene i.e., G4234C (rs3218384), G4088T (rs3218373) and G3063A (rs2040639). Genotyping was performed by amplification refractory mutation system (ARMS-PCR) followed by direct sequencing. Results: We found association of G4234C with thyroid cancer risk in stage I and II (p>0.0004) cancer patients while no association was observed with other parameters. Significant increased risk of developing thyroid cancer risk was observed in patients for G4088T with variant heterozygote T/G (OR=1.65, 95% CI=1.20-2.24; p<0.001) and polymorphic homozygote G/G (OR=1.66, 95% CI=1.16-2.36; p=0.005) compared with healthy controls. For G3063A polymorphism, a significant difference in genotypes distributions was observed for heterozygous variant G/A (OR=2.11; 95% CI=1.52-2.94; p<0.0001) and A/A variant genotype (OR=2.02; 95% CI=1.37-2.97; p<0.0003). When stratified for different parameters, significant increased risk was observed in female patients, patients with age ≥ 42 years, smoking and stage I and II patients for G4088T and G3063A in comparison to controls. Conclusion: Present study concluded that G4234C, G4088T and G3063A SNPs in XRCC2 gene may modify the risk of thyroid cancer development.

XRCC1 rs25487 genetic variant and TP53 mutation at codon 249 predict clinical outcomes of hepatitis B virus-related hepatocellular carcinoma after hepatectomy: A cohort study for 10years' follow up.

To investigate the effects of rs25487 (the DNA repair gene: x-ray repair complementing defective repair in Chinese hamster cells 1 [XRCC1]) and codon 249 mutation (TP53 gene) on clinical outcomes of post-hepatectomy hepatitis B virus (HBV)-related HCC. The XRCC1 rs25487 polymorphism and TP53 mutation at codon 249 of 485 hepatitis B surface antigen positive patients subjected to hepatectomy were genotyped via direct sequencing. SPSS software version 16.0 (SPSS, Chicago, IL, USA) was used to calculate survival of HCC patients according to primary end-points. The presence of at least one A allele (AA/AG) of rs25487 was associated with unfavorable prognosis (P = 0.005). Moreover, A allele (AA/AG) carriers were significantly associated with high risk of vascular invasion (P = 0.025) and regional invasion (P = 0.005). Differences were not significant between mutant and wild-type TP53 cases with overall survival (adjusted P = 0.400). Among the 485 participants, patients (n = 73) carrying both the A allele (AA/AG) of rs25487 and 249Ser TP53 mutation displayed decreased overall survival, compared with patients (n = 184) with the GG genotype of rs25487 and wild-type codon 249 (adjusted P = 0.007). Polymorphisms of rs25487 may play a potential role in survival of HBV-related hepatocellular carcinoma patients following hepatectomy. While mutation at codon 249 of TP53 is not associated with HBV-related HCC survival in this study.

Polymorphism of the XRCC3 gene and risk of gastric cancer in a Kashmiri population

DNA repair plays a critical role in protecting the genome of the cell from the insults of cancer-causing agents. Genetic polymorphisms in DNA repair genes may influence individual variation in DNA repair capacity, which may be associated with the risk of developing cancer. Inherited polymorphisms of DNA repair genes may contribute to variations in DNA repair capacity and genetic susceptibility to different cancers. The X-ray repair complementing defective repair in Chinese hamster cells 3 (XRCC3) gene is a member of the RAD51 gene family. It encodes an important protein that functions in the homologous recombination repair of a DNA double-strand break. For gastric cancer, the importance of mutations in mismatch repair genes has been well documented, but less is known about other DNA repair pathways in gastric carcinogenesis. In this study, we have focused on the XRCC3 gene, involved in homologous recombinational repair. The Kashmir valley has an increased incidence of gastric cancer and its etiology has not been understood fully as yet. As the Kashmiri population is ethnically and demographically different from that in other parts of the world, the aim of this study was to determine whether a single nucleotide polymorphism of the XRCC3 gene (Thr241Met) of exon 7 can influence the risk of gastric cancer in the population. As many as 80 histopathologically confirmed gastric cancer cases and 70 healthy controls, age, sex, and ethnicity matched for known genotypes of XRCC3 exon 7 were studied. We genotyped for this variant using PCR-restriction fragment length polymorphisms. The XRCC3 genotype and allele frequencies were not significantly different between cases and controls (P=0.92 for the genotype; P=0.72 for the allele). The XRCC3 241Met allele frequency (6.6%) was significantly lower in healthy Kashmiri controls than reported previously in healthy US White controls (38.9%). Compared with the XRCC3 241Thr/Thr genotype, the variant XRCC3 241Thr/Met and Met/Met genotypes were not associated with an increased risk of gastric cancer (adjusted odds ratio=1.19; 95% confidence interval=0.44-3.18). These findings suggest that polymorphisms of XRCC3 Thr241Met may not play a role in the etiology of gastric cancer. Further studies with a larger number of participants and simultaneous measurement of different polymorphisms in DNA repair genes in the same pathway are needed.

Association between the XRCC6 polymorphisms and cancer risks: a systematic review and meta-analysis.

A number of studies have been carried out to investigate the association of X-ray repair complementing defective repair in Chinese hamster cells 6 (XRCC6) polymorphisms and cancer risks, and the results remained inconsistent and inconclusive.To assess the effect of XRCC6 polymorphisms on cancer susceptibility, we conducted a meta-analysis, up to May 23rd 2014, 6267 cases with different types of tumor and 7536 controls from 20 published case–control studies. Summary odds ratios and corresponding 95% confidence intervals for XRCC6 polymorphism and cancer risk were estimated using fixed- or random-effects models when appropriate. Heterogeneity was assessed by chi-squared-based Q-statistic test, and the sources of heterogeneity were explored by subgroup analyses, logistic meta-regression analyses and Galbraith plot. Publication bias was evaluated by Begg funnel plot and Egger test. Sensitivity analyses were also performed.The rs2267437 polymorphism was associated with a significant increase in risks of overall cancers, breast cancer, renal cell carcinoma and hepatocellular carcinoma, and it could increase the cancer risk in Asian population; the rs5751129 polymorphism could increase the cancer risk in overall cancers; the rs132770 polymorphism was associated with the increased renal cell carcinoma risk; furthermore, the rs132793 polymorphism could decrease breast cancer risk and increase risks in “other cancers”.Overall, the results provided evidences that the single nucleotide polymorphisms in XRCC6 promoter region might play different roles in various cancers, indicating different cancers have different tumorigenesis mechanisms. Our studies may perhaps supplement for the disease monitoring of cancers in the future, and additional studies to determine the exact molecular mechanism might provide us with interventions to protect the susceptible subgroups.

DNA repair gene XRCC3 T241M polymorphism and susceptibility to hepatocellular carcinoma in a Chinese population: a meta-analysis.

Numerous studies have evaluated the association between the X-ray repair complementing defective repair in Chinese hamster cells 3 (XRCC3) T241M polymorphism and hepatocellular carcinoma (HCC) risk. However, the results of such investigations have proved inconsistent. Therefore, we performed a meta-analysis of the association between this polymorphism and HCC risk in the Chinese population. Published literature from PubMed and China National Knowledge Infrastructure databases was retrieved, and a total of 5 case-control studies consisting of 2967 patients and 3874 controls were included in this meta-analysis, which revealed a significant association between the XRCC3 T241M polymorphism and HCC risk (TT vs MM: OR = 6.54, 95%CI = 2.14-19.99; TT vs MT: OR = 4.72, 95%CI = 2.26-9.86; dominant model: OR = 0.38, 95%CI = 0.26-0.57; recessive model: OR = 1.27, 95%CI = 0.99-1.62). In a subgroup analysis by sample size (number of subjects > 1000), similar results were obtained. Thus, XRCC3 T241M polymorphism may constitute a risk factor for HCC in the Chinese population.

XRCC2 promotes colorectal cancer cell growth, regulates cell cycle progression, and apoptosis.

X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2) and poly(ADP-ribose) polymerase 1 (PARP1) both play important roles in homologous recombination DNA repair. According to the theory of synthetic lethality, XRCC2-deficient cells are more sensitive to PARP1 inhibitors compared to XRCC2-expressing cells. We investigated XRCC2 expression and function in colorectal cancer (CRC), and the characteristics of sensitivity to PARP1 inhibitor in CRC cells with different XRCC2 levels. We enrolled 153 patients with CRC who had undergone surgery in this study. XRCC2 expression was assessed using immunohistochemistry. Stable CRC SW480 cell lines with low or high XRCC2 expression were constructed. Following treatment with the PARP1 inhibitor olaparib, the viability of cells with different XRCC2 levels was determined; cell cycle distribution and apoptosis were analyzed using flow cytometry. B-cell lymphoma-2 (Bcl-2) protein expression was measured by Western blotting. The positive rates of XRCC2 in primary CRC tissue were significantly higher than that in the matched adjacent noncancerous tissue, and XRCC2 expression status in primary CRC was related to tumor site, Dukes' stage, and tumor-nodes-metastasis (TNM) stage. XRCC2 overexpression inhibited CRC cell apoptosis and promoted proliferation by enriching cells in the G0/G1 phase. Moreover, olaparib suppressed proliferation, and olaparib sensitivity in CRC cells with high XRCC2 expression was greater. High XRCC2 expression promotes CRC cell proliferation and enriches cells in the G0/G1 phase but inhibits apoptosis. High XRCC2 expression cells are more sensitive to olaparib, which inhibits their viability.

Enhanced susceptibility of ovaries from obese mice to 7,12-dimethylbenz[a]anthracene-induced DNA damage

7,12-Dimethylbenz[a]anthracene (DMBA) depletes ovarian follicles and induces DNA damage in extra-ovarian tissues, thus, we investigated ovarian DMBA-induced DNA damage. Additionally, since obesity is associated with increased offspring birth defect incidence, we hypothesized that a DMBA-induced DNA damage response (DDR) is compromised in ovaries from obese females. Wild type (lean) non agouti (a/a) and KK.Cg-Ay/J heterozygote (obese) mice were dosed with sesame oil or DMBA (1mg/kg; intraperitoneal injection) at 18weeks of age, for 14days. Total ovarian RNA and protein were isolated and abundance of Ataxia telangiectasia mutated (Atm), X-ray repair complementing defective repair in Chinese hamster cells 6 (Xrcc6), breast cancer type 1 (Brca1), Rad 51 homolog (Rad51), poly [ADP-ribose] polymerase 1 (Parp1) and protein kinase, DNA-activated, catalytic polypeptide (Prkdc) were quantified by RT-PCR or Western blot. Phosphorylated histone H2AX (γH2AX) level was determined by Western blotting. Obesity decreased (P<0.05) basal protein abundance of PRKDC and BRCA1 proteins but increased (P<0.05) γH2AX and PARP1 proteins. Ovarian ATM, XRCC6, PRKDC, RAD51 and PARP1 proteins were increased (P<0.05) by DMBA exposure in lean mice. A blunted DMBA-induced increase (P<0.05) in XRCC6, PRKDC, RAD51 and BRCA1 was observed in ovaries from obese mice, relative to lean counterparts. Taken together, DMBA exposure induced γH2AX as well as the ovarian DDR, supporting that DMBA causes ovarian DNA damage. Additionally, ovarian DDR was partially attenuated in obese females raising concern that obesity may be an additive factor during chemical-induced ovotoxicity.

XRCC5 as a risk gene for alcohol dependence: evidence from a genome-wide gene-set-based analysis and follow-up studies in Drosophila and humans.

Genetic factors have as large role as environmental factors in the etiology of alcohol dependence (AD). Although genome-wide association studies (GWAS) enable systematic searches for loci not hitherto implicated in the etiology of AD, many true findings may be missed owing to correction for multiple testing. The aim of the present study was to circumvent this limitation by searching for biological system-level differences, and then following up these findings in humans and animals. Gene-set-based analysis of GWAS data from 1333 cases and 2168 controls identified 19 significantly associated gene-sets, of which 5 could be replicated in an independent sample. Clustered in these gene-sets were novel and previously identified susceptibility genes. The most frequently present gene, ie in 6 out of 19 gene-sets, was X-ray repair complementing defective repair in Chinese hamster cells 5 (XRCC5). Previous human and animal studies have implicated XRCC5 in alcohol sensitivity. This phenotype is inversely correlated with the development of AD, presumably as more alcohol is required to achieve the desired effects. In the present study, the functional role of XRCC5 in AD was further validated in animals and humans. Drosophila mutants with reduced function of Ku80-the homolog of mammalian XRCC5-due to RNAi silencing showed reduced sensitivity to ethanol. In humans with free access to intravenous ethanol self-administration in the laboratory, the maximum achieved blood alcohol concentration was influenced in an allele-dose-dependent manner by genetic variation in XRCC5. In conclusion, our convergent approach identified new candidates and generated independent evidence for the involvement of XRCC5 in alcohol dependence.

XRCC2 rs3218536 polymorphism decreases the sensitivity of colorectal cancer cells to poly(ADP-ribose) polymerase 1 inhibitor

Single nucleotide polymorphisms (SNPs) are associated with the development of certain types of cancer. The present study aimed to investigate the association between X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2) SNPs and colorectal cancer (CRC) cell sensitivity to the poly(ADP-ribose) polymerase (PARP) 1 inhibitor olaparib (AZD2281). SNaPshot® analysis of XRCC2 SNPs was performed in five CRC cell lines. The AZD2281-sensitivities of the CRC cells were also analyzed using MTT assays. The effect of AZD2281 on XRCC2 and PARP1 expression was investigated in the five cell lines using quantitative polymerase chain reaction and western blot analyses. Parallel investigations were performed using a cisplatin (DDP) model of DNA damage. The XRCC2 rs3218536 SNP was found to be associated with the LoVo microsatellite instability CRC cell line. The relative rate of growth inhibition was found to be lower in the LoVo cells following treatment with AZD2281 compared with the other four cell lines (P=0.002). Furthermore, the XRCC2 mRNA level in the LoVo cells was observed to be significantly higher than that in the other four cell lines (P<0.05). Similar results were found using the DDP model of DNA damage (P<0.05). The present study indicated that the XRCC2 rs3218536 polymorphism decreases the sensitivity of CRC cells to AZD2281.

Neonatal Genome-Wide Methylation Patterns in Relation to Birth Weight in the Norwegian Mother and Child Cohort

Although epigenetic regulation plays a critical role in embryonic development, few studies have examined the relationship of epigenome-wide methylation with fetal growth. Using the Infinium HumanMethylation450 BeadChip (Illumina, Inc., San Diego, California) in a substudy of 1,046 infants from the Norwegian Mother and Child Cohort Study (MoBa) enrolled between 1999 and 2008, we examined epigenome-wide cord blood DNA methylation in relation to birth weight. In multivariable-adjusted robust linear regression models, we identified differential methylation at 19 cytosine-guanine dinucleotides (CpGs) associated with either decreased (AT-rich interactive domain 5B (MRF1-like) (ARID5B), 2 CpGs) or increased (x-ray repair complementing defective repair in Chinese hamster cells 3 (XRCC3), 4 CpGs) birth weight. ARID5B knockout mice have less adipose tissue and significantly lower weight in the postnatal period. XRCC3 plays a key role in the maintenance of chromosome stability and the repair of DNA damage. Although there are fewer data on the other implicated genes, many of these genes have been shown to have roles in developmental processes. This constitutes the largest and most robust study of birth weight using an epigenome-wide methylation platform and offers potential insights into epigenetic mechanisms of fetal growth.

MiR-7 inhibits colorectal cancer cell proliferation and induces apoptosis by targeting XRCC2

BackgroundAnalysis using publicly available algorithms predicts that X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2), a key component in the homologous recombination repair pathway, is a potential target of micro-ribonucleic acid-7 (miR-7). Some studies have shown that both miR-7 and XRCC2 are associated with cancer development. For this purpose, we searched for the possible relationship between miR-7 and XRCC2 in the development of colorectal cancer (CRC).MethodsmiR-7 expression was assessed in CRC specimens and cell lines using real-time polymerase chain reaction (PCR). Luciferase reporter assay was used to confirm the target associations. The effect of miR-7 on cell proliferation and apoptosis was confirmed in vitro by the methylthiazol tetrazolium (MTT) assay, colony formation assay, and flow cytometry. Gene and protein expression were examined using real time PCR and western blotting, respectively.ResultsmiR-7 was downregulated in CRC specimens and cell lines, and targeted the 3′ untranslated region of XRCC2. miR-7 overexpression reduced cyclin D1 expression and increased p21, caspase-3, and BAX expression, which subsequently inhibited CRC cell proliferation and induced CRC cell apoptosis. However, XRCC2 can repress the inhibitory effects of miR-7 on proliferation.ConclusionOur findings suggest that miR-7 plays a protective role by inhibiting proliferation and increasing apoptosis of CRC cells. It may identify new targets for anti-cancer treatment.

Expression of base excision repair key factors and miR17 in familial and sporadic breast cancer

Understanding of BRCA1/2 interaction with the base excision repair (BER) pathway could improve therapy based on ‘synthetic lethality', whose effectiveness is based on homologous recombination deficiency in cells lacking functional BRCA genes. However, poly (ADP-ribose) polymerase (PARP) inhibitors failed in some patients and for this reason we explored BER key enzyme expression. In this study, the expression of BER enzymes (redox factor 1/apurinic-apyrimidinic endonuclease 1 (REF1/APEX1), NTH endonuclease III-like 1 (NTHL1), 8-oxoguanine DNA glycosylase (OGG1), PARP1) and of the scaffold protein XRCC1 (X-ray repair complementing defective repair in Chinese hamster cells 1) were investigated in familial (BRCA-related and not) and sporadic breast cancer cases. Furthermore, miR17 expression was measured because of its role in the epigenetic regulation of BRCA1. Gene expression was evaluated in BRCA1-mutated cell lines, SUM149PT and SUM1315MO2, and in a BRCA1-proficient triple-negative MDA-MB-231 cell line. A cohort of 27 familial and 16 sporadic breast cancer patients was then examined to confirm results obtained from the cell line model. APEX1/REF1 was found to be upregulated in familial BRCA-wild-type and sporadic cases, indicating this enzyme as a potential therapeutic target. Furthermore, XRCC1 was overexpressed in BRCAX patients; consequently, we suggest to test the effectiveness of inhibitors targeting two different BER components in preclinical studies. XRCC1, which is also involved in the non-homologous end-joining pathway, was found to be downregulated in BRCA2-related patients concurrently with no change in PARP1 expression. Interestingly, no difference in PARP1 and miR17 expression was found in BRCA-related and sporadic breast cancer cases. PARP1 and miR17 could therefore be further investigated as molecular biomarkers of ‘BRCAness' phenotype, indicating patients which could really benefit from PARP inhibitor therapies.

XRCC5 (X-ray repair complementing defective repair in Chinese hamster cells 5 (double-strand-break rejoining))

Review on XRCC5 (X-ray repair complementing defective repair in Chinese hamster cells 5 (double-strand-break rejoining)), with data on DNA, on the protein encoded, and where the gene is implicated.