Base excision repair modulation as a risk factor for human cancers

Modulation of gene expression and inflammation but not DNA damage after sevoflurane anesthesia

This study assessed, for the first time, the expression of the genes hOGG1, TP53, and IL-6 in leukocytes by real-time quantitative polymerase chain reaction in surgical patients before (baseline), during (2 h of anesthesia) and 1 day after sevoflurane anesthesia. Additionally, DNA damage was detected by the comet assay, serum interleukin (IL)-6 was detected by flow cytometry, and differential leukocyte counting was also performed. TP53 and hOGG1 expression was downregulated on the day after anesthesia compared to before anesthesia. However, IL-6 expression did not change, and no DNA damage induction was observed during or after anesthesia. At the systemic level, mild neutrophilia and an increase in IL-6 levels occurred after anesthesia. Our findings suggest that sevoflurane anesthesia downregulates gene expression (hOGG1 and TP53) and contributes to an inflammatory status (increased systemic IL-6 and mild neutrophilia) but is not associated with DNA damage in patients without comorbidities who undergo minor elective surgery.

Identification and Quantification of Apurinic/Apyrimidinic Endonuclease 1 in Human Peripheral Blood Leukocytes by Liquid Chromatography/Isotope-Dilution High Resolution Mass Spectrometry

Background Increasing evidence in recent years highlights the predictive and prognostic importance of the expression of DNA repair proteins in cancer treatment. Generally, western-blotting or immunohistochemical staining methods are often used to determine the expression of DNA repair proteins. These methods might cause misleading results such as binding to nonspecific molecules by cross-reaction or false negativity as a result of the inability of antibodies to bind; absolute quantitations of proteins can not be performed. Purpose In this study, an analytical measurement technique was developed for human apurinic/apyrimidinic endonuclease 1 (hAPE1) protein for identification and absolute quantification in human leukocyte sample using high resolution mass spectrometry (HR-MS) with the targeted proteomics based approach. Methods Sample preparation was performed by using density gradient centrifugation and total protein extraction cartridges. hAPE1 was analyzed by liquid chromatography isotope-dilution-HR-MS (LC-HR-MS). A fully 15N-labeled analogue of hAPE1 was used for the quantitative measurements. Results Six peptides were identified, which matched to a subset of the theoretically predicted tryptic peptides of hAPE1. Mass accuracy was calculated as

Potential Role of APEX1 During Ferroptosis

Ferroptosis is a recently discovered category of programmed cell death. It is much different from other types of cell death such as apoptosis, necrosis and autophagy. The main pathological feature of ferroptosis is the accumulation of iron-dependent lipid peroxidation. The typical changes in the morphological features of ferroptosis include cell volume shrinkage and increased mitochondrial membrane area. The mechanisms of ferroptosis may be mainly related to lipid peroxidation accumulation, imbalance in amino acid antioxidant system, and disturbance of iron metabolism. Besides, hypoxia-inducible factor (HIF), nuclear factor-E2-related factor 2 (Nrf2), and p53 pathway have been demonstrated to be involved in ferroptosis. At present, the molecular mechanisms of ferroptosis pathway are still unmapped. In this review, an outlook has been put forward about the crucial role of apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1) in the regulation of ferroptosis. APEX1 plays an important role in the regulation of intracellular redox balance and can be used as a potential inhibitor of ferroptotic cell death. Bioinformatics analysis indicated that the mRNA level of APEX1 is decreased in cases of ferroptosis triggered by erastin. Besides, it was found that there was a significant correlation between APEX1 and genes in the ferroptosis pathway. We have discussed the possibility to employ APEX1 inducers or inhibitors in the regulation of ferroptosis as a new strategy for the treatment of various human diseases.

Impact of XRCC1 genetic variants on its tissue expression and breast cancer risk: A case-control study

X-ray repair cross-complementing group 1 (XRCC1), a coordinator protein of the DNA repair complex, is thought to be involved in cancer progression. This case-control study aimed to investigate the association of two biallelic single-nucleotide polymorphisms (SNPs; Arg399Gln, Arg194Trp) of the XRCC1 gene with its tissue expression level and breast cancer (BC) risk in Egyptian women. This study included 100 BC female patients (case group 1) and 100 healthy females (control group 2). The XRCC1 tissue expression was assessed by immunohistochemistry (IHC). Genotyping of the two XRCC1 SNPs (Arg399Gln, Arg194Trp) using real-time polymerase chain reaction (PCR) was also conducted. The XRCC1 expression level was significantly lower in cancerous tissues than adjacent non-cancerous tissues (p < .001). The XRCC1 399Gln/Gln genotype, 399Gln allele, the dominant, and recessive models were significantly associated with lower XRCC1 expression in breast cancerous tissues and increased risk for BC (3.390-, 1.965-, 2.241-, and 2.429-folds, respectively). The XRCC1 399Gln/Gln genotype was associated with lower incidence of advanced tumor grade (OR: 0.06; 95%CI: 0.01-0.74; p = .028). Conversely, the XRCC1 Arg194Trp polymorphism did not show any significant association with either XRCC1 expression in breast cancer tissues or BC risk in all genetic models. The XRCC1 haplotypes, 399Gln/194Arg and 399Gln/194Trp, were associated with 1.800- and 1.675-folds risk for BC, respectively. The XRCC1 gene polymorphism (Arg399Gln) is associated with reduced XRCC1 tissue expression and enhanced BC risk with a well-differentiated nature in Egyptian women. Moreover, XRCC1 haplotypes, 399Gln/194Arg and 399Gln/194Trp, were associated with increased BC risk.

Genetic variations in base excision repair pathway genes and risk of hepatoblastoma: a seven-center case-control study

Hepatoblastoma is a rare childhood liver cancer without known explicit etiology. Base excision repair (BER) pathway genes have been implicated in the pathophysiology of cancer, yet the role of BER pathway gene single nucleotide polymorphisms (SNPs) on hepatoblastoma risk still awaits to be explored. This study aims to determine whether hepatoblastoma risk be modulated by polymorphisms in the BER pathway genes based on genotyped data from 313 cases and 1446 controls. We applied TaqMan assay to genotype these included samples. We comprehensively genotyped 20 SNPs across six genes of BER, and estimated odds ratio (ORs), 95% confidence intervals (CIs), and P-values of the selected SNPs' contribution to the risk of hepatoblastoma using logistic regression models. Only SNP rs293795 in the hOGG1 gene could significantly enhance hepatoblastoma risk under recessive model (adjusted OR=3.78, 95% CI=1.01-14.17, P=0.047). Stratified analysis revealed that rs159153 TC/CC genotype decreased hepatoblastoma risk in male subgroup. Moreover, rs293795 GG and 1-3 risk genotypes could increase hepatoblastoma risk in clinical stages I+II and male subgroups, respectively. False-positive report probability validated the reliability of the significant results. Our findings provide some clues of a potential risk effect of BER pathway gene hOGG1 SNPs on hepatoblastoma. Further investigation is warranted to confirm these findings and to better elucidate the biological pathways involved.

Modulation of the Apurinic/Apyrimidinic Endonuclease Activity of Human APE1 and of Its Natural Polymorphic Variants by Base Excision Repair Proteins

Human apurinic/apyrimidinic endonuclease 1 (APE1) is known to be a critical player of the base excision repair (BER) pathway. In general, BER involves consecutive actions of DNA glycosylases, AP endonucleases, DNA polymerases, and DNA ligases. It is known that these proteins interact with APE1 either at upstream or downstream steps of BER. Therefore, we may propose that even a minor disturbance of protein–protein interactions on the DNA template reduces coordination and repair efficiency. Here, the ability of various human DNA repair enzymes (such as DNA glycosylases OGG1, UNG2, and AAG; DNA polymerase Polβ; or accessory proteins XRCC1 and PCNA) to influence the activity of wild-type (WT) APE1 and its seven natural polymorphic variants (R221C, N222H, R237A, G241R, M270T, R274Q, and P311S) was tested. Förster resonance energy transfer–based kinetic analysis of abasic site cleavage in a model DNA substrate was conducted to detect the effects of interacting proteins on the activity of WT APE1 and its single-nucleotide polymorphism (SNP) variants. The results revealed that WT APE1 activity was stimulated by almost all tested DNA repair proteins. For the SNP variants, the matters were more complicated. Analysis of two SNP variants, R237A and G241R, suggested that a positive charge in this area of the APE1 surface impairs the protein–protein interactions. In contrast, variant R221C (where the affected residue is located near the DNA-binding site) showed permanently lower activation relative to WT APE1, whereas neighboring SNP N222H did not cause a noticeable difference as compared to WT APE1. Buried substitution P311S had an inconsistent effect, whereas each substitution at the DNA-binding site, M270T and R274Q, resulted in the lowest stimulation by BER proteins. Protein–protein molecular docking was performed between repair proteins to identify amino acid residues involved in their interactions. The data uncovered differences in the effects of BER proteins on APE1, indicating an important role of protein–protein interactions in the coordination of the repair pathway.

Genetic polymorphisms in DNA repair genes XRCC1 and 3 are associated with increased risk of breast cancer in Bangladeshi population

BACKGROUND

Genetic polymorphisms in DNA repair genes, XRCC1 (Arg399Gln) and XRCC3 (Thr241Met), may affect their DNA repair capacity leading to individual variation in breast cancer susceptibility among Bangladeshi females.

METHODS

The case-control study comprised 121 breast cancer patients and 133 healthy controls. Genomic DNA isolated from peripheral blood was genotyped for target SNPs using PCR-RFLP method.

RESULTS

For XRCC1, heterozygous Arg/Gln and homozygous Gln/Gln genotypes showed 1.78-fold (95% CI 1.0084 to 3.1442, p = 0.0467) and 2.41-fold (95% CI 1.0354 to 5.5914, p = 0.0413) increased risk of breast cancer, respectively, when compared with Arg/Arg genotype. The presence of any XRCC1 Gln showed association with 1.93-fold increased risk. The variant Gln allele was associated with increased risk of breast cancer (95% CI 1.1885 to 2.6805, p = 0.0052). For XRCC3, Thr/Met heterozygous and combined Thr/Met + Met/Met genotypes were associated with 1.85-fold (95% CI 1.0815 to 3.1834, p = 0.0248) and 1.89-fold (95% CI 1.1199 to 3.1908, p = 0.0171) higher risk, respectively, compared to Thr/Thr genotypes. The variant Met allele showed significant association with increased breast cancer susceptibility. Among cases genotype frequencies were significantly different in patients with age 55 or above, and with menopause and diabetes.

CONCLUSION

XRCC1 (Arg399Gln) and XRCC3 (Thr241Met) polymorphisms may be associated with increased breast cancer risk in Bangladeshi females.

Lamin A/C promotes DNA base excision repair

The A-type lamins (lamin A/C), encoded by the LMNA gene, are important structural components of the nuclear lamina. LMNA mutations lead to degenerative disorders known as laminopathies, including the premature aging disease Hutchinson-Gilford progeria syndrome. In addition, altered lamin A/C expression is found in various cancers. Reports indicate that lamin A/C plays a role in DNA double strand break repair, but a role in DNA base excision repair (BER) has not been described. We provide evidence for reduced BER efficiency in lamin A/C-depleted cells (Lmna null MEFs and lamin A/C-knockdown U2OS). The mechanism involves impairment of the APE1 and POLβ BER activities, partly effectuated by associated reduction in poly-ADP-ribose chain formation. Also, Lmna null MEFs displayed reduced expression of several core BER enzymes (PARP1, LIG3 and POLβ). Absence of Lmna led to accumulation of 8-oxoguanine (8-oxoG) lesions, and to an increased frequency of substitution mutations induced by chronic oxidative stress including GC>TA transversions (a fingerprint of 8-oxoG:A mismatches). Collectively, our results provide novel insights into the functional interplay between the nuclear lamina and cellular defenses against oxidative DNA damage, with implications for cancer and aging.

XRCC1 Is a Promising Predictive Biomarker and Facilitates Chemo-Resistance in Gallbladder Cancer

Gallbladder cancer is a relatively uncommon human malignant tumor with an extremely poor prognosis. Currently, no biomarkers can accurately diagnose gallbladder cancer and predict patients' prognosis. XRCC1 is involved in tumorigenesis, progression, and chemo-resistance of several human cancers, but the role of XRCC1 in gallbladder cancer is never reported. In this study, we investigated the expression of XRCC1 and its clinicopathological and prognostic significance in gallbladder cancer, and explored the biological role of XRCC1 in gallbladder cancer cells. We found that XRCC1 was significantly up-regulated in gallbladder cancer in protein and mRNA levels. Positive XRCC1 expression was correlated with aggressive clinicopathological features and was an independent poor prognostic factor in gallbladder cancer. The ROC curves suggested that XRCC1 expression had potential clinicopathological diagnostic value in gallbladder cancer. In vitro, XRCC1 was overexpression in CD133⁺GBC-SD cells compared to GBC-SD cells. In functional experiment, XRCC1 knockdown had a non-significant impact on proliferation, migration, invasion, and apoptosis of CD133⁺GBC-SD cells. But, XRCC1 knockdown could significantly improve the sensitivity of CD133⁺GBC-SD cells to 5-Fluorouracil via promoting cell necrosis and apoptosis. Thus, this study indicates that XRCC1 may be a promising predictive biomarker of gallbladder cancer and a potential therapeutic target for gallbladder cancer.

XRCC1 Gene Polymorphism Increases the Risk of Hepatocellular Carcinoma in Egyptian Population

Section Title

Several major risk factors for hepatocellular carcinoma (HCC) have been identified, including chronic infection of hepatitis B virus (HBV) and hepatitis C virus (HCV). Nevertheless, only a fraction of infected patients develops HCC during their lifetime suggesting that genetic factors might modulate HCC development. X-ray repair cross complementing group1 (XRCC1) participates in the repair pathways of DNA.

Aim:

to investigate the association between XRCC1 gene polymorphism and HCC in Egyptian chronic hepatitis C patients.

Methods:

This study was assessed on 40 patients with HCC secondary to chronic HCV infection who were compared to 20 cirrhotic HCV patients and 40- age and gender- matched healthy control group. After collection of relevant clinical data and basic laboratory tests, c.1517G>C SNP of XRCC1 gene polymorphism was performed by (PCR-RFLP) technique.

Results:

A statistically higher frequency of XRCC1 (CC, GC) genotypes and increased (C) allele frequency in patients with HCC was found in comparison to cirrhotic HCV patients as well as control group. In addition, patients with the XRCC1 (CC, GC) genotypes had significantly higher number and larger size of tumor foci and significantly higher Child Pugh grades. Multivariate analysis showed that the presence of c.1517G>C SNP of XRCC1 gene is an independent risk for the development of HCC in chronic HCV patients with 3.7 fold increased risk of HCC development.

In conclusion:

XRCC1 gene polymorphism could be associated with increased risk of HCC development in chronic HCV Egyptian patients.

Genetic Variant XRCC1 rs1799782 (C194T) and Risk of Cancer Susceptibility in Indian Population: A Meta-analysis of Case-Control Studies

X-ray repair cross-complementing group 1 (XRCC1) plays a key role in the base excision repair pathway, as a scaffold protein that brings together proteins of the DNA repair complex. Several studies have reported contradictory results for XRCC1 exon 6 C>T (rs1799782) gene polymorphism and cancer risk in Indian population has provided inconsistent results. Therefore, we have performed this meta-analysis to evaluate the relationship between XRCC1 exon 6 C>T gene polymorphism and risk of cancer by published studies. We searched PubMed and Google scholar web databases to cover all studies published on association between XRCC1 exon 6 C>T gene polymorphism and cancer risk. The meta-analysis was carried out and pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to appraise the strength of association. In order to derive a more precise estimation of the association, A total of 3197 confirmed cancer cases and 3819 controls were included from eligible seventeen case-controls studies. Results from overall pooled analysis demonstrated suggested that that variant allele (T vs. C: OR 1.301, 95% CI 1.003-1.688, p = 0.047) was associated with the risk of overall cancer. Other genetic models; heterozygous (TC vs. CC: OR 1.108, 95% CI 0.827-1.485, p = 0.491), homozygous (TT vs. CC: OR 1.479, 95% CI 0.877-2.493, p = 0.142), dominant (TT+TC vs. CC: OR 1.228, 95% CI 0.899-1.677, p = 0.196) and recessive (TT vs. TC+CC: OR 1.436, 95% CI 0.970-2.125, p = 0.071) did not reveal statistical association. Publication bias observation was also considered and none was detected during the analysis. The present meta-analysis suggested that the variant allele T of XRCC1 exon 6 gene polymorphism was associated with the risk of cancer. It is therefore pertinent to confirm this finding in a large sample size to divulge the mechanism of this polymorphism and cancer risk in Indian population.

Potent and specific MTH1 inhibitors targeting gastric cancer

Human mutT homolog 1(MTH1), the oxidized dNTP pool sanitizer enzyme, has been reported to be highly expressed in various malignant tumors. However, the oncogenic role of MTH1 in gastric cancer remains to be determined. In the current study, we found that MTH1 was overexpressed in human gastric cancer tissues and cells. Using an in vitro MTH1 inhibitor screening system, the compounds available in our laboratory were screened and the small molecules containing 5-cyano-6-phenylpyrimidine structure were firstly found to show potently and specifically inhibitory effect on MTH1, especially compound MI-743 with IC50 = 91.44 ± 1.45 nM. Both molecular docking and target engagement experiments proved that MI-743 can directly bind to MTH1. Moreover, MI-743 could not only inhibit cell proliferation in up to 16 cancer cell lines, especially gastric cancer cells HGC-27 and MGC-803, but also significantly induce MTH1-related 8-oxo-dG accumulation and DNA damage. Furthermore, the growth of xenograft tumours derived by injection of MGC-803 cells in nude mice was also significantly inhibited by MI-743 treatment. Importantly, MTH1 knockdown by siRNA in those two gastric cancer cells exhibited the similar findings. Our findings indicate that MTH1 is highly expressed in human gastric cancer tissues and cell lines. Small molecule MI-743 with 5-cyano-6-phenylpyrimidine structure may serve as a novel lead compound targeting the overexpressed MTH1 for gastric cancer treatment.

Genetic variants of XRCC1 and risk of hepatocellular carcinoma in chronic hepatitis C patients

BACKGROUND

Hepatitis C virus (HCV) related liver cirrhosis occurs in about 20% of chronically infected patients over a duration of 10-20 years, and within 5 years approximately 10-20% of these cirrhotic patients will develop hepatocellular carcinoma (HCC). Previous studies report that the X-ray repair cross-complementing group1 gene (XRCC1) is important in the risk of HCC development; however, results obtained from these studies are conflicting rather than conclusive. We hypothesised an association between single nucleotide polymorphisms (SNPs) in XRCC1 with the HCC risk on a background of chronic hepatitis C.

MATERIALS AND METHODS

We recruited 210 subjects, 70 with HCC, 70 with cirrhosis and 70 healthy controls. Two SNPs [c.1254C>T(rs2293035) and c.1517G>C(rs139599857)] in XRCC1 were genotyped using created restriction site-polymerase chain reaction (CRS-PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP) methods.

RESULTS

The TT genotype, CT genotype and T-allele in c.1254C>T (rs2293035) were linked to risk of HCC compared to the CC genotype: OR 3.58 [confidence interval (CI) 95%: 1.19-10.7] p = 0.019; OR 2.16 (CI 95%: 1.04-4.47) p = 0.037 and OR 2.10 (CI 95%: 1.2-3.3) p = 0.006, respectively. Regarding c.1517G>C (rs139599857), the CC genotype, GC genotype and C-allele were linked with higher risk of developing HCC compared to GG genotype: OR 4.77 (CI 95%: 1.3-16.9), p = 0.016; OR 3.02 (CI 95%: 1.46-6.2), p = 0.002 and OR 2.4 (CI 95%: 1.4-4.0), p = 0.001, respectively.

CONCLUSION

We conclude that the T-allele of c.1254C>T (rs2293035) and the C allele of c.1517G>C (rs139599857) genetic variants may be associated with increased HCC risk among chronic hepatitis C patients.

Association Between ERCC1 rs3212986 and ERCC2/XPD rs1799793 and OS in Patients With Advanced Esophageal Cancer

Esophageal cancer (EC) is a very aggressive tumor, and no reliable prognostic markers exist especially for resectable advanced neoplasia. The principal aim of this study was to investigate the association of germline polymorphisms in nucleotide excision repair (NER) pathway genes with the overall survival (OS) of patients with advanced EC. As a second aim, we also studied the association of NER gene variants with response to cisplatin-based chemotherapy. Among the EC patients referred to our Institution between 2004 and 2012, we selected a cohort of 180 patients diagnosed with a clinical tumor stage ranging from IIB and IVA. Patients were genotyped for four NER variants, two in the ERCC1 (rs11615 and rs3212986) and two in the ERCC2/XPD (rs1799793 and rs13181) genes. Kaplan–Meier analyses and Cox proportional hazards model were used to evaluate the associations of the selected variants with OS; association with response to neoadjuvant therapy was investigated using logistic regression. Results showed that the ERCC1 rs3212986 and the ERCC2/XPD rs1799793 were significantly associated with shorter OS. On the contrary, response association analysis displayed that, while rs11615 and rs3212986 in ERCC1 were associated with response, both ERCC2/XPD variants were not. By creating survival prediction models, we showed that the rs3212986 and the rs1799793 have a better predictability of the tumor stage alone. Furthermore, they were able to improve the power of the clinical model (AUC = 0.660 vs. AUC = 0.548, p = 0.004). In conclusion, our results indicate that the ERCC1 rs3212986 and the ERCC2/XPD rs1799793 could be used as surrogate markers for a better stratification of EC patients with advanced resectable tumor.

The Association of XRCC1 Gene Polymorphisms and Chronic Hepatitis C Induced Insulin Resistance in Egyptian Patients

Chronic hepatitis C is implicated in insulin resistance (IR) susceptibility. An X-ray repair cross-complementing group 1 gene (XRCC1) is proposed to be a candidate gene for a study of IR susceptibility. So, this study aims to investigate the possible association of the XRCC1 gene polymorphisms with the risk of IR related to chronic hepatitis C virus (HCV) infection in Egyptian patients. In a case-control study, a total of 210 subjects, including 140 chronic HCV patients (87 patients with IR and 53 without IR) and 70 healthy controls, were included. Two genetic polymorphisms (c.1254C > T and c.1517G > C) of the XRCC1 gene were genotyped via the PCR-restriction fragment length polymorphism (PCR-RFLP) technique. The result of the current study revealed that these two single nucleotide polymorphisms (SNPs) have statistically significant influences on susceptibility to IR in chronic HCV infected Egyptian patients. It could be concluded that c.1254C > T, the TT genotype, CT/CC carriers as well as c.1517G > C, the CC genotype and GC/GG carriers might be associated with increased IR susceptibility. Moreover, T-allele of c.1254C > T and the C-allele of c.1517G > C genetic variants might influence the susceptibility.

Base Excision Repair Gene Polymorphisms and Wilms Tumor Susceptibility

Base excision repair (BER) is the main mechanism to repair endogenous DNA lesions caused by reactive oxygen species. BER deficiency is linked with cancer susceptibility and premature aging. Single nucleotide polymorphisms (SNPs) within BER genes have been implicated in various human malignancies. Nevertheless, a comprehensive investigation of their association with Wilms tumor susceptibility is lacking. In this study, 145 cases and 531 sex and age-matched healthy controls were recruited. We systematically genotyped 18 potentially functional SNPs in six core BER pathway genes, using a candidate SNP approach. Logistic regression was employed to evaluate odds ratio (OR) and 95% confidence interval (CI) adjusted for age and gender. Several SNPs showed protective effects against Wilms tumor. Significant associations with Wilms tumor susceptibility were shown for hOGG1 rs1052133 (dominant: adjusted OR = 0.66, 95% CI = 0.45-0.96, P = .030), FEN1 rs174538 (dominant: adjusted OR = 0.66, 95% CI = 0.45-0.95, P = .027; recessive: adjusted OR = 0.54, 95% CI = 0.32-0.93 P = .027), and FEN1 rs4246215 (dominant: adjusted OR = 0.55, 95% CI = 0.38-0.80, P = .002) polymorphisms. Stratified analysis was performed by age, gender, and clinical stage. Moreover, there was evidence of functional implication of these significant SNPs suggested by online expression quantitative trait locus (eQTL) analysis. Our findings indicate that common SNPs in BER genes modify susceptibility to Wilms tumor.

Meta-analysis of XRCC1 polymorphism and risk of female reproductive system cancer

Numerous epidemiological studies have evaluated the association between polymorphism in the gene encoding x-ray repair cross complementing 1 (XRCC1) protein and the risk of female reproductive system cancer, but results are inconclusive. To gain a comprehensive picture of available evidence, we searched for relevant studies in the PubMed, EMBASE, Scopus, and Chinese National Knowledge Infrastructure databases up to December 17, 2016. A total of 26 case-control studies were picked out. The pooled odds ratio (OR) with its 95% confidence interval (CI) was calculated to estimate the association. Based on data of all study participants, we did not find a positive association of rs25487 or rs1799782 polymorphism with risk of female reproductive cancer risk. Subgroup analysis, however, identified two alleles as being associated with an increased risk of female reproductive system cancer in Asians: the A allele of rs25487 (heterozygous genetic model, OR 1.16, 95%CI 1.00-1.36), and the T allele of rs1799782 (homozygous model, OR 2.30, 95%CI 1.39-3.82; dominant model, OR 1.28, 95%CI 1.10-1.50; recessive model, OR 2.11, 95%CI 1.33-3.34). Moreover, the AA genotype at rs25489 was determined to be a risk factor for cervical cancer etiology (homozygous model, OR 2.91, 95%CI, 1.17-7.26; recessive model, OR 3.16, 95%CI 1.91-5.24). This meta-analysis suggests that no association between rs25487 or rs1799782 gene polymorphism and risk of female reproductive cancer risk was found. These results should be validated in larger studies.

Association between Polymorphisms of X-Ray Repair Cross Complementing Group 1 Gene and Pancreatic Cancer Risk: a Systematic Review with Meta-Analysis

Emerging evidences have shown that common genetic polymorphisms in X-ray repair cross complementing group 1 (XRCC1) gene may be associated with the development of pancreatic cancer, but individually published studies and previous meta-analyses revealed inconclusive results. The aim of our study was to investigate the association between polymorphisms in XRCC1 gene and pancreatic cancer risk. We conducted a search of PubMed, Embase, the Cochrane Library and Web of Science databases. Odds ratios (ORs) with 95% confidence intervals (CIs) were determined as measures of the strength of association between polymorphisms of XRCC1 and pancreatic cancer risk. Sensitivity analysis and publication bias were evaluated. All analyses were undertaken using the STATA 13.0. A total of 10 studies were included in this systematic review. Five common functional single-nucleotide polymorphisms (SNPs) in XRCC1 gene were found, including Arg399Gln G > A (rs25487), Arg194Trp C > T (rs1799782), Arg280His G > A (rs25489), c.1517G > C, c.1471G > A. Results from our stratified analysis based on Hardy-Weinberg equilibrium (HWE) showed that there was a robust significant association between Arg280His polymorphism and pancreatic cancer risk (allelic model, OR 0.743, 95% CI 0.576-0.958, P = 0.022; heterozygous model, OR 0.701, 95% CI 0.525-0.936, P = 0.016; dominant model, OR 0.710, 95% CI 0.537-0.939, P = 0.016). We also found a statistically significant association between c.1517G > C polymorphism and pancreatic cancer risk (Allelic model, OR 1.252, 95% CI 1.064-1.473, P = 0.007). No significant results were obtained for Arg399Gln, Arg194Trp and c.1471G > A polymorphisms. The present meta-analysis suggested that Arg280His and c.1517G > C polymorphisms in XRCC1 gene were associated with pancreatic cancer risk.

Polymorphisms in XRCC1, ERCC2, and ERCC3 DNA repair genes, CYP1A1 xenobiotic metabolism gene, and tobacco are associated with bladder cancer susceptibility in Tunisian population

Other than the established environmental risk factors associated with bladder cancer (BC), little is known about the genetic variations determining the individual susceptibility of this complex disease. This study aimed to investigate the relationship of BC with environmental agents and polymorphisms in XRCC1, ERCC2, and ERCC3 DNA repair genes and CYP1A1, CYP2D6, NAT1, and NAT2 xenobiotic metabolism genes through a hospital-based case-control study in Tunisia. The selection of the single nucleotide polymorphisms (SNPs) (rs25487, rs 13181, rs415407, rs446421, rs1058172, rs4921880, and rs1208) was performed using the dbSNP database. DNA genotyping was determined by PCR-RFLP after DNA extraction from whole blood. The risks of BC associated with every polymorphism as well as the studied environmental factors were estimated by multivariate-adjusted logistic regression using R software. In addition, gene-gene interactions were analyzed using generalized multifactor dimensionality reduction (GMDR) methods. Results showed that tobacco smoking and chewing parameters were significantly associated with BC risk. Single-gene variant analysis showed significant associations of the TT genotype of CYP1A1 and the rare GG genotype of ERCC2 with bladder cancer susceptibility (OR = 1.34, 95% CI 1.22-1.40, P < 0.0001). According to GMDR analysis, our findings indicated a significant association between BC and gene-gene interaction among the CYP1A1, ERCC3, and XRCC1. The present results suggest a potential role of XRCC1, ERCC2, ERCC3, and CYP1A1 besides tobacco intake in susceptibility to BC.

Electronic cigarette aerosols suppress cellular antioxidant defenses and induce significant oxidative DNA damage

Background

Electronic cigarette (EC) aerosols contain unique compounds in addition to toxicants and carcinogens traditionally found in tobacco smoke. Studies are warranted to understand the public health risks of ECs.

Objective

The aim of this study was to determine the genotoxicity and the mechanisms induced by EC aerosol extracts on human oral and lung epithelial cells.

Methods

Cells were exposed to EC aerosol or mainstream smoke extracts and DNA damage was measured using the primer anchored DNA damage detection assay (q-PADDA) and 8-oxo-dG ELISA assay. Cell viability, reactive oxygen species (ROS) and total antioxidant capacity (TAC) were measured using standard methods. mRNA and protein expression were evaluated by RT-PCR and western blot, respectively.

Results

EC aerosol extracts induced DNA damage in a dose-dependent manner, but independently of nicotine concentration. Overall, EC aerosol extracts induced significantly less DNA damage than mainstream smoke extracts, as measured by q-PADDA. However, the levels of oxidative DNA damage, as indicated by the presence of 8-oxo-dG, a highly mutagenic DNA lesion, were similar or slightly higher after exposure to EC aerosol compared to mainstream smoke extracts. Mechanistically, while exposure to EC extracts significantly increased ROS, it decreased TAC as well as the expression of 8-oxoguanine DNA glycosylase (OGG1), an enzyme essential for the removal of oxidative DNA damage.

Conclusions

Exposure to EC aerosol extracts suppressed the cellular antioxidant defenses and led to significant DNA damage. These findings emphasize the urgent need to investigate the potential long-term cancer risk of exposure to EC aerosol for vapers and the general public.

DNA base excision repair genetic risk scores, oxidative balance, and incident, sporadic colorectal adenoma

Associations of individual base excision repair (BER) genotypes with colorectal adenoma risk are unclear, but likely modest. However, genetic risk scores (GRS) that aggregate information from multiple genetic variants might be useful for assessing genetic predisposition to colorectal adenoma. We analyzed data pooled from three colonoscopy-based case-control studies of incident, sporadic colorectal adenoma (n = 488 cases, 604 controls) that collected blood for genotyping and extensive dietary and other data. We randomly split our population sample into training samples (half of the participants) and validation samples (the remaining participants) 10 times. Associations of 65 individual single nucleotide polymorphisms (SNPs) in 15 BER genes were assessed in the training samples and used to combine information from multiple risk variants into a BER GRS among the validation samples using unweighted and weighted methods. We also combined 15 extrinsic exposures with known pro- or antioxidant properties into an oxidative balance score (OBS). Associations of the BER GRS with colorectal adenoma, overall and jointly with the OBS, were assessed using multivariable logistic regression. The odds ratio for those in the highest relative to the lowest tertile of the weighted BER GRS was 2.07 (95% confidence interval, 1.26-3.40; p_trend  = 0.01). Relative to those with both a low GRS and a high (more antioxidant) OBS, the estimated direct association for those with both a high BER GRS and a low OBS was stronger than for those in other GRS/OBS categories. Our findings suggest that BER genotypes collectively may be associated with incident sporadic colorectal adenomas.

Copper oxide nanoparticles and copper sulphate act as antigenotoxic agents in drosophila melanogaster

The biological reactivity of metal and metal oxide nanomaterials is attributed to their redox properties, which would explain their pro- or anti-cancer properties depending on exposure circumstances. In this sense, copper oxide nanoparticles (CuONP) have been proposed as a potential anti-tumoral agent. The aim of this study was to assess if CuONP can exert antigenotoxic effects using Drosophila melanogaster as an in vivo model. Genotoxicity was induced by two well-known genotoxic compounds, namely potassium dichromate (PD) and ethyl methanesulfonate (EMS). The wing-spot assay and the comet assay were used as biomarkers of genotoxic effects. In addition, changes in the expression of Ogg1 and Sod genes were determined. The effects of CuONP cotreatment were compared with those induced by copper sulfate (CS), an agent releasing copper ions. Using the wing-spot assay, CuONP and CS were not able to reduce the genotoxic effects of EMS exposure, but had the ability to decrease the effects induced by PD, reducing the frequency of mutant twin-spots that arise from mitotic recombination. In addition, CuONP and CS were able to reduce the DNA damage induced by PD as determined by the comet assay. In general, similar qualitative antigenotoxic effects were obtained with both copper compounds. The antigenotoxic effects of environmentally relevant and non-toxic doses of CuONP and CS may be explained by their ability to partially restore the expression levels of the repair gene Ogg1 and the antioxidant gene Cu,ZnSod, both of which are inhibited by PD treatment. Environ. Mol. Mutagen. 58:46-55, 2017. © 2016 Wiley Periodicals, Inc.

Association of Leukotrichia in Vitiligo and Asp148Glu Polymorphism of Apurinic/Apyrimidinic Endonuclease 1

Background:

Oxidative stress and increased DNA damage have been implicated in the etiopathogenesis of vitiligo. Oxidative DNA damage is mainly repaired by the base excision repair (BER) pathway.

Aim:

We sought to determine whether polymorphisms in DNA repair genes may have a role in the pathogenesis of vitiligo.

Materials and Methods:

We conducted a study including 100 patients with vitiligo and age- and sex-matched 193 control subjects to examine the role of single-nucleotide polymorphisms of BER genes, human 8-oxoG DNA N-glycosylase 1 (codon 326), apurinic/apyrimidinic endonuclease 1 (APE1) (codon 148), and X-ray repair cross-complementing group 1 (codon 399) as risk factors for vitiligo. These polymorphisms were determined by quantitative real-time polymerase chain reaction and melting curve analysis.

Results:

No significant association was observed between the variant alleles of studied genes and vitiligo.

Conclusion:

However, we showed that the presence of APE1 148Glu variant allele is associated with leukotrichia. This preliminary study suggests that APE1 (codon 148) polymorphism may play a role in vitiligo pathogenesis.

A genome-wide analysis of gene-caffeine consumption interaction on basal cell carcinoma

Animal models have suggested that oral or topical administration of caffeine could inhibit ultraviolet-induced carcinogenesis via the ataxia telangiectasia and rad3 (ATR)-related apoptosis. Previous epidemiological studies have demonstrated that increased caffeine consumption is associated with reduced risk of basal cell carcinoma (BCC). To identify common genetic markers that may modify this association, we tested gene-caffeine intake interaction on BCC risk in a genome-wide analysis. We included 3383 BCC cases and 8528 controls of European ancestry from the Nurses' Health Study and Health Professionals Follow-up Study. Single nucleotide polymorphism (SNP) rs142310826 near the NEIL3 gene showed a genome-wide significant interaction with caffeine consumption (P = 1.78 × 10-8 for interaction) on BCC risk. There was no gender difference for this interaction (P = 0.64 for heterogeneity). NEIL3, a gene belonging to the base excision DNA repair pathway, encodes a DNA glycosylase that recognizes and removes lesions produced by oxidative stress. In addition, we identified several loci with P value for interaction <5 × 10-7 in gender-specific analyses (P for heterogeneity between genders < 0.001) including those mapping to the genes LRRTM4, ATF3 and DCLRE1C in women and POTEA in men. Finally, we tested the associations between caffeine consumption-related SNPs reported by previous genome-wide association studies and risk of BCC, both individually and jointly, but found no significant association. In sum, we identified a DNA repair gene that could be involved in caffeine-mediated skin tumor inhibition. Further studies are warranted to confirm these findings.

Gene-environment interactions between ERCC2, ERCC3, XRCC1 and cadmium exposure in nasal polyposis disease

Gene-environment interactions have long been known to play an important role in complex disease aetiology, such as nasal polyposis (NP). The present study supports the concept that DNA repair gene polymorphisms play critical roles in modifying individual susceptibility to environmental diseases. In fact, we investigated the role of polymorphisms in DNA repair genes and cadmium as risk factors for Tunisian patients with NP. To the best of our knowledge, this is the first report on the impact of combined effects of cadmium and ERCC3 7122 A>G (rs4150407), ERCC2 Lys751Gln (rs13181) and XRCC1 Arg399Gln (rs25487) genes in the susceptibility to NP disease. Significant associations between the risk of developing NP disease and ERCC2 [odds ratio (OR) = 2.0, 95 % confidence interval (CI) = 1.1-3.7, p = 0.023] and ERCC3 (OR = 2.2, 95 % CI = 1.2-4.1, p = 0.013) genotypes polymorphisms were observed. Blood concentrations of Cd in NP patients (2.2 μg/L) were significantly higher than those of controls (0.5 μg/L). A significant interaction between ERCC3 (7122 A>G) polymorphism and blood-Cd levels (for the median of blood-Cd levels: OR = 3.8, 95 % CI = 1.3-10.8, p = 0.014 and for the 75th percentiles of blood-Cd levels: OR = 2.7, 95 % CI = 1.1-7.2, p = 0.041) was found in association with the risk of NP disease. In addition, when we stratified ERCC2, ERCC3 and XRCC1 polymorphism genotypes by the median and 75th percentiles of blood-Cd levels, we found also significant interactions between ERCC2 (Lys751Gln) and ERCC3 (7122 A>G) genotypes polymorphism and this metal in association with NP disease. However, no interaction was found between XRCC1 (Arg399Gln) polymorphism genotypes and Cd in association with NP disease.

Potential role of 8-oxoguanine DNA glycosylase 1 as a STAT1 coactivator in endotoxin-induced inflammatory response

Human 8-oxoguanine DNA glycosylase 1 (OGG1) is the major DNA repair enzyme that plays a key role in excision of oxidative damaged DNA bases such as 8-oxoguainine (8-oxoG). Recent studies suggest another function of OGG1, namely that it may be involved in the endotoxin- or oxidative stress-induced inflammatory response. In this study, we investigated the role of OGG1 in the inflammatory response. OGG1 expression is increased in the organs of endotoxin-induced or myelin oligodendrocyte glycoprotein (MOG)-immunized mice and immune cells, resulting in induction of the expression of pro-inflammatory mediators at the transcriptional levels. Biochemical studies showed that signal transducer and activator of transcription 1 (STAT1) plays a key role in endotoxin-induced OGG1 expression and inflammatory response. STAT1 regulates the transcriptional activity of OGG1 through recruiting and binding to the gamma-interferon activation site (GAS) motif of the OGG1 promoter region, and chromatin remodeling by acetylation and dimethylation of lysine-14 and -4 residues of histone H3. In addition, OGG1 acts as a STAT1 coactivator and has transcriptional activity in the presence of endotoxin. The data presented here identifies a novel mechanism, and may provide new therapeutic strategies for the treatment of endotoxin-mediated inflammatory diseases.

Association between polymorphisms of APE1 and OGG1 and risk of colorectal cancer in Taiwan

AIM: To evaluate the effects of OGG1 (Ser326Cys, 11657A/G, and Arg154His) and APE1 (Asp148Glu, and T-656G) polymorphisms on colorectal cancer (CRC) risk.

METHODS: We enrolled 727 cases newly diagnosed with colorectal adenocarcinoma and 736 age- and sex-matched healthy controls from a medical center in Taiwan. Genomic DNA isolated from the buffy coat was used for genotyping through polymerase chain reaction. Unconditional logistic regressions were used for calculating ORs and 95%CIs to determine the association between the genetic polymorphisms and CRC risk. Haplotype frequencies were estimated using PHASE software. Moreover, stratification analyses on the basis of sex, age at diagnosis, and tumor subsite and stage were performed.

RESULTS: The CRC risk was higher in patients with the OGG1 326Ser/Cys + Cys/Cys genotype (OR = 1.38, 95%CI: 1.03-1.85, P = 0.030), particularly high in patients with stage III + IV cancer (OR = 1.48, 95%CI: 1.03-2.13) compared with patients with the Ser/Ser genotype. In addition, OGG1 11657G allele carriers had a 41% reduced CRC risk among stage 0-II patients (OR = 0.59, 95%CI: 0.35-0.98). The CRC risk was significantly higher among females with the APE1 Glu allele (OR = 1.41, 95%CI: 1.02-1.96). The APE1 148Glu/-656G haplotype was also associated with a significant CRC risk in females (OR = 1.36, 95%CI: 1.03-1.78).

CONCLUSION: OGG1 and APE1 polymorphisms are associated with stage- and sex-specific risk of CRC in the Taiwanese population.

Efficiency of Base Excision Repair of Oxidative DNA Damage and Its Impact on the Risk of Colorectal Cancer in the Polish Population

DNA oxidative lesions are widely considered as a potential risk factor for colorectal cancer development. The aim of this work was to determine the role of the efficiency of base excision repair, both in lymphocytes and in epithelial tissue, in patients with CRC and healthy subjects. SNPs were identified within genes responsible for steps following glycosylase action in BER, and patients and healthy subjects were genotyped. A radioisotopic BER assay was used for assessing repair efficiency and TaqMan for genotyping. Decreased BER activity was observed in lymphocyte extract from CRC patients and in cancer tissue extract, compared to healthy subjects. In addition, polymorphisms of EXO1, LIG3, and PolB may modulate the risk of colorectal cancer by decreasing (PolB) or increasing (LIG3 and EXO1) the chance of malignant transformation.

Theoretical considerations for thresholds in chemical carcinogenesis

There is increasing evidence for non-linear relationships for gene mutations, chromosomal aberrations and even tumor incidences in response to low doses of genotoxic carcinogens. To attain the biological relevance of such non-linear responses, there is a need to identify the underlying defense mechanisms that allow tolerance to low doses of genotoxicants. This communication discusses presumptive cancer prevention mechanisms that may contribute to thresholds, i.e. points of departure, for each endpoint, from initial DNA lesion to tumor formation. We discuss a sequential order of genome protection during carcinogenesis where genotoxicant scavenging, cellular efflux, DNA repair, elimination of damaged cells by apoptosis, autophagy, silencing by DNA damage-triggered replicative senescence, and finally, elimination of transformed (premalignant) cells by the immune system are thought to be responsible for a threshold in tumor formation. We highlight DNA repair, for which experimental evidence has been recently provided to dictate a role in PoDs. In conclusion, from a theoretical perspective it is reasonable to posit that tolerance to low dose levels exists for each requisite step of tumor formation and these tolerance mechanisms are critical in determining thresholds in chemical carcinogenesis.

Oxidative balance scores and risk of incident colorectal cancer in a US prospective cohort study

Although oxidative stress is implicated in colorectal carcinogenesis, human studies on associations of individual prooxidants and antioxidants with colorectal cancer (CRC) have been inconclusive. We incorporated individual environmental factors known to affect oxidative stress into 4 oxidative balance scores (OBS) and investigated their associations with CRC in the Cancer Prevention Study II Nutrition Cohort. During 1999-2009, a total of 1,109 incident CRC cases were identified among 80,063 participants in the Nutrition Cohort who had completed detailed questionnaires. Four OBS with different weighting methods (equal weights, literature review-based, a posteriori data-based, and weights based on Bayesian analysis) were created by combining 16 dietary and nondietary lifestyle factors. Higher values for all 4 OBS, representing more antioxidant exposures than prooxidant exposures, were associated with 41%-53% lower risks of CRC; for example, the relative risk for the highest OBS quartile versus the lowest in the Bayesian analysis was 0.50 (95% confidence interval: 0.41, 0.61). The associations were more modest when OBS was restricted to either dietary or nondietary components. These results, obtained using comprehensive summary measures of oxidative balance-especially considering the similarity of the findings derived using the different weighting methods-support the hypothesis that a predominance of antioxidant lifestyle exposures (both dietary and nondietary) over prooxidant lifestyle exposures reduces risk of CRC.

The influence of XRCC1 genetic variants on lung cancer susceptibility in Chinese Han population

Growing evidence suggests that genetic variants of X-ray repair cross-complementing group 1 proteins (XRCC1) contribute to genetic effects on the development of lung cancer. This case-control study aims to evaluate the genetic effects of XRCC1 c.482C>T and c.1686C>G single nucleotide polymorphisms (SNPs) on lung cancer susceptibility. 391 lung cancer patients and 398 cancer-free controls were enrolled in this study. The genotypes of c.482C>T and c.1686C>G genetic variants were detected by the created restriction site-polymerase chain reaction (CRS-PCR), PCR-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing methods. The genetic effects on lung cancer susceptibility were evaluated using association analyses by the unconditional logistic regression model. Our data indicated that there were significant differences in the distribution of allelic and genotypic frequencies between lung cancer patients and cancer-free controls. The XRCC1 c.482C>T and c.1686C>G genetic variants were significantly associated with the susceptibility to lung cancer (for c.482C>T, TT versus (vs.) CC: OR=2.14, 95% CI 1.31-3.48, P=0.002; T vs. C: OR=1.37, 95% CI 1.10-1.69, P=0.004; for c.1686C>G, GG vs. CC: OR=2.53, 95% CI 1.46-4.38, P=0.001; G vs. C: OR=1.33, 95% CI 1.06-1.65, P=0.012). These preliminary results suggested that the XRCC1 c.482C>T and c.1686C>G genetic variants might play genetic effects on the susceptibility to lung cancer in the studied population.

Association of DNA base-excision repair XRCC1, OGG1 and APE1 gene polymorphisms with nasopharyngeal carcinoma susceptibility in a Chinese population

BACKGROUND

Numerous carcinogens and reactive oxygen species (ROS) may cause DNA damage including oxidative base lesions that lead to risk of nasopharyngeal carcinoma. Genetic susceptibility has been reported to play a key role in the development of this disease. The base excision repair (BER) pathway can effectively remove oxidative lesions, maintaining genomic stability and normal expression, with X-ray repair crosscomplementing1 (XRCC1), 8-oxoguanine glycosylase-1 (OGG1) and apurinic/apyimidinic endonuclease 1 (APE1) playing important roles.

AIMS

To analyze polymorphisms of DNA BER genes (OOG1, XRCC1 and APE1) and explore their associations, and the combined effects of these variants, with risk of nasopharyngeal carcinoma.

MATERIALS AND METHODS

We detected SNPs of XRCC1 (Arg399Gln), OGG1 (Ser326Cys), APE1 (Asp148Glu and -141T/G) using the polymerase chain reaction (PCR) with peripheral blood samples from 231 patients with NPC and 300 healthy people, furtherly analyzing their relations with the risk of NPC in multivariate logistic regression models.

RESULTS

After adjustment for sex and age, individuals with the XRCC1 399Gln/Gln (OR=1.96; 95%CI:1.02- 3.78; p=0.04) and Arg/Gln (OR=1.87; 95%CI:1.29-2.71; p=0.001) genotype variants demonstrated a significantly increased risk of nasopharyngeal carcinoma compared with those having the wild-type Arg/Arg genotype. APE1- 141G/G was associated with a significantly reduced risk of NPC (OR=0.40;95%CI:0.18-0.89) in the smoking group. The OR calculated for the combination of XRCC1 399Gln and APE1 148Gln, two homozygous variants ,was significantly additive for all cases (OR=2.09; 95% CI: 1.27-3.47; p=0.004).

CONCLUSION

This is the first study to focus on the association between DNA base-excision repair genes (XRCC1, OGG1 and APE1) polymorphism and NPC risk. The XRCC1 Arg399Gln variant genotype is associated with an increased risk of NPC. APE1- 141G/G may decrease risk of NPC in current smokers. The combined effects of polymorphisms within BER genes of XRCC1 399Gln and APE1 148Gln may contribute to a high risk of nasopharyngeal carcinoma.

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

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

Oxidatively induced DNA damage and its repair in cancer

Oxidatively induced DNA damage is caused in living organisms by endogenous and exogenous reactive species. DNA lesions resulting from this type of damage are mutagenic and cytotoxic and, if not repaired, can cause genetic instability that may lead to disease processes including carcinogenesis. Living organisms possess DNA repair mechanisms that include a variety of pathways to repair multiple DNA lesions. Mutations and polymorphisms also occur in DNA repair genes adversely affecting DNA repair systems. Cancer tissues overexpress DNA repair proteins and thus develop greater DNA repair capacity than normal tissues. Increased DNA repair in tumors that removes DNA lesions before they become toxic is a major mechanism for development of resistance to therapy, affecting patient survival. Accumulated evidence suggests that DNA repair capacity may be a predictive biomarker for patient response to therapy. Thus, knowledge of DNA protein expressions in normal and cancerous tissues may help predict and guide development of treatments and yield the best therapeutic response. DNA repair proteins constitute targets for inhibitors to overcome the resistance of tumors to therapy. Inhibitors of DNA repair for combination therapy or as single agents for monotherapy may help selectively kill tumors, potentially leading to personalized therapy. Numerous inhibitors have been developed and are being tested in clinical trials. The efficacy of some inhibitors in therapy has been demonstrated in patients. Further development of inhibitors of DNA repair proteins is globally underway to help eradicate cancer.

Single nucleotide polymorphisms of DNA base-excision repair genes (APE1, OGG1 and XRCC1) associated with breast cancer risk in a Chinese population

Altered DNA repair capacity can result in increased susceptibility to cancer. The base excision repair (BER) pathway effectively removes DNA damage caused by ionizing radiation and reactive oxidative species (ROS). In the current study, we analyzed the possible relation of polymorphisms in BER genes, including 8-oxoguanine DNA glycosylase (OGG1), apurinic/apyrimidinic endonuclease 1 (APE1), and X-ray repair cross-complementing group 1 protein (XRCC1), with breast cancer risk in Chinese Han women. This case-control study examined 194 patients with breast cancer and 245 cancer-free hospitalized control subjects. Single nucleotide polymorphisms (SNPs) of OGG1 (Ser326Cys), XRCC1 (Arg399Gln), and APE1 (Asp148Glu and -141T/G) were genotyped and analyzed for their association with breast cancer risk using multivariate logistic regression models. We found that XRCC1 Arg399Gln was significantly associated with an increased risk of breast cancer. Similarly, the XRCC1 Gln allele was significantly associated with an elevated risk in postmenopausal women and women with a high BMI (≥ 24 kg/m2). The OGG1 Cys allele provided a significant protective effect against developing cancer in women with a low BMI (< 24 kg/m2). When analyzing the combined effects of these alleles on the risk of breast cancer, we found that individuals with ≥ 2 adverse genotypes (XRCC1 399Gln, APE1 148Asp, and OGG1 326Ser) were at a 2.18-fold increased risk of breast cancer (P = 0.027). In conclusion, our data indicate that Chinese women with the 399Gln allele of XRCC1 have an increased risk of breast cancer, and the combined effects of polymorphisms of BER genes may contribute to tumorigenesis.

The association between XRCC1 genetic polymorphisms and the risk of endometrial carcinoma in Chinese

Accumulated evidences report that X-ray repair cross-complementing group 1 gene (XRCC1) genetic polymorphisms play an important role in the development of endometrial carcinoma (EC). This study aims to evaluate the association of XRCC1 c.1161G>A and c.1804C>A genetic polymorphisms with the risk of EC. A total of 218 EC patients and 243 cancer-free controls were included in this study. The genotypes of XRCC1 genetic polymorphisms were determined by the created restriction site-polymerase chain reaction (CRS-PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP) methods. We found that these two genetic polymorphisms were statistically associated with the risk of EC. As for c.1161G>A, in comparison with GG wild genotype, the AA genotype was significantly associated with the increased risk of EC (OR=2.36, 95% CI 1.28-4.37, χ(2)=7.71, P=0.005). As for c.1804C>A, the CC genotype significantly increased the risk of EC in comparison with CC wild genotype (OR=2.77, 95% CI 1.38-5.58, χ(2)=8.54, P=0.003). Our data indicate that the A allele of c.1161G>A and c.1804C>A genetic polymorphisms could contribute to increase the risk of EC (for c.1161G>A: A versus (vs.) G, OR=1.34, 95% CI 1.02-1.76, χ(2)=4.56, P=0.033; for c.1804C>A: A vs. C, OR=1.34, 95% CI 1.01-1.77, χ(2)=4.03, P=0.045). Our results indicate that the XRCC1 c.1161G>A and c.1804C>A genetic polymorphisms significantly influenced the risk of EC in Chinese populations, and might be used as molecular markers for evaluating EC risk.

APE1 polymorphisms are associated with colorectal cancer susceptibility in Chinese Hans

AIM: To study the association between four base excision repair gene polymorphisms and colorectal cancer risk in a Chinese population.

METHODS: Two hundred forty-seven colorectal cancer (CRC) patients and three hundred cancer-free controls were enrolled in this study. Four polymorphisms (OGG1 Ser326Cys, APE1 Asp148Glu, -141T/G in the promoter region, and XRCC1 Arg399Gln) in components of the base excision repair pathway were determined in patient blood samples using polymerase chain reaction with confronting two-pair primers. The baseline information included age, gender, family history of cancer, and three behavioral factors [smoking status, alcohol consumption, and body mass index (BMI)]. χ² tests were used to assess the Hardy-Weinberg equilibrium, the distributions of baseline characteristics, and the four gene polymorphisms between the cases and controls. Multivariate logistic regression analyses were conducted to analyze the correlations between the four polymorphisms and CRC risk, adjusted by the baseline characteristics. Likelihood ratio tests were performed to analyze the gene-behavior interactions of smoking status, alcohol consumption, and BMI on polymorphisms and CRC susceptibility.

RESULTS: The APE1 148 Glu/Glu genotype was significantly associated with an increased risk of colorectal cancer (OR = 2.411, 95%CI: 1.497-3.886, P < 0.001 relative to Asp/Asp genotype). There were no associations between OGG1, XRCC1, or APE1 promoter polymorphisms and CRC risk. A multivariate analysis including three behavioral factors showed that the APE1 148 Glu/Glu genotype was associated with an increased risk for CRC among both smokers and non-smokers, non-drinkers and individuals with a BMI ≥ 25 kg/m² (ORs = 2.356, 3.299, 2.654, and 2.581, respectively). The XRCC1 399 Arg/Gln genotype was associated with a decreased risk of CRC among smokers and drinkers (OR = 0.289, 95%CI: 0.152-0.548, P < 0.001, and OR = 0.327, 95%CI: 0.158-0.673, P < 0.05, respectively). The APE1 promoter polymorphism -141 T/G genotype was associated with a reduced risk of colorectal cancer among subjects with a BMI < 25 kg/m² (OR = 0.214, 95%CI: 0.069-0.660, P < 0.05 relative to T/T genotype). There were significant gene-behavior interactions between smoking status and XRCC1 Arg399Gln, as well as BMI and APE1 -141T/G polymorphism (all P < 0.05).

CONCLUSION: APE1 Asp148Glu is associated with increased CRC risk and smoking alters the association between XRCC1 Arg399Gln and CRC risk in the Chinese Han population.

Deregulation of base excision repair gene expression and enhanced proliferation in head and neck squamous cell carcinoma

Defects in the DNA damage repair pathway contribute to cancer. The major pathway for oxidative DNA damage repair is base excision repair (BER). Although BER pathway genes (OGG1, APEX1 and XRCC1) have been investigated in a number of cancers, our knowledge on the prognostic significance of these genes and their role in head and neck squamous cell carcinoma is limited. Protein levels of OGG1, APEX1 and XRCC1 and a proliferation marker, Ki-67, were examined by immunohistochemical analysis, in a cohort of 50 HNSCC patients. Significant downregulation of OGG1 (p<0.04) and XRCC1 (p<0.05) was observed in poorly differentiated HNSCC compared to mod-well-differentiated cases. Significant upregulation of APEX1 (p<0.05) and Ki-67 (p<0.05) was observed in poorly differentiated HNSCC compared to mod-well-differentiated cases. Significant correlation was observed between XRCC1 and OGG1 (r=0.33, p<0.02). Inverse correlations were observed between OGG1 and Ki-67 (r=-0.377, p<0.005), between APEX1 and XRCC1 (r=-0.435, p<0.002) and between OGG1 and APEX1 (r=-0.34, p<0.02) in HNSCC. To confirm our observations, we examined BER pathway genes and a proliferation marker, Ki-67, expression at the mRNA level on 50 head and neck squamous cell carcinoma (HNSCC) and 50 normal control samples by quantitative real-time polymerase chain reaction. Significant downregulation was observed in case of OGG1 (p<0.04) and XRCC1 (p<0.02), while significant upregulation was observed in case of APEX1 (p<0.01) and Ki-67 (p<0.03) in HNSCC tissue samples compared to controls. Our data suggested that deregulation of base excision repair pathway genes, such as OGG1, APEX1 and XRCC1, combined with overexpression of Ki-67, a marker for excessive proliferation, may contribute to progression of HNSCC in Pakistani population.

Effects of silver nanoparticles on oxidative DNA damage-repair as a function of p38 MAPK status: a comparative approach using human Jurkat T cells and the nematode Caenorhabditis elegans

The large-scale use of silver nanoparticles (AgNPs) has raised concerns over potential impacts on the environment and human health. We previously reported that AgNP exposure causes an increase in reactive oxygen species, DNA damage, and induction of p38 MAPK and PMK-1 in Jurkat T cells and in Caenorhabditis elegans. To elucidate the underlying mechanisms of AgNP toxicity, here we evaluate the effects of AgNPs on oxidative DNA damage-repair (in human and C. elegans DNA glycosylases hOGG1, hNTH1, NTH-1, and 8-oxo-GTPases-hMTH1, NDX-4) and explore the role of p38 MAPK and PMK-1 in this process. Our comparative approach examined viability, gene expression, and enzyme activities in wild type (WT) and p38 MAPK knock-down (KD) Jurkat T cells (in vitro) and in WT and pmk-1 loss-of-function mutant strains of C. elegans (in vivo). The results suggest that p38 MAPK/PMK-1 plays protective role against AgNP-mediated toxicity, reduced viability and greater accumulation of 8OHdG was observed in AgNP-treated KD cells, and in pmk-1 mutant worms compared with their WT counterparts, respectively. Furthermore, dose-dependent alterations in hOGG1, hMTH1, and NDX-4 expression and enzyme activity, and survival in ndx-4 mutant worms occurred following AgNP exposure. Interestingly, the absence or depletion of p38 MAPK/PMK-1 caused impaired and additive effects in AgNP-induced ndx-4(ok1003); pmk-1(RNAi) mutant survival, and hOGG1 and NDX-4 expression and enzyme activity, which may lead to higher accumulation of 8OHdG. Together, the results indicate that p38 MAPK/PMK-1 plays an important protective role in AgNP-induced oxidative DNA damage-repair which is conserved from C. elegans to humans.

Genetic polymorphisms of XRCC1 gene and susceptibility to hepatocellular carcinoma in Chinese population

Hepatocellular carcinoma (HCC) is a common cancer in the worldwide. Accumulated evidences indicate that genetic polymorphisms of human X-ray repair complementing group 1 gene (XRCC1) are associated with the susceptibility to HCC. This study aims to investigate the potential association between XRCC1 c.482C>T and c.1178G>A genetic polymorphisms and the susceptibility to HCC. A total of 1,069 Chinese Han subjects consisting of 530 HCC patients and 539 cancer-free controls were recruited in this case-control study. The created restriction site-polymerase chain reaction and directly DNA sequencing methods were utilized to analyze the genotyping of XRCC1 genetic polymorphisms. Our data suggested that the XRCC1 c.482C>T and c.1178G>A genetic polymorphisms were statistically associated with the increased risks of HCC [for c.482C>T, TT vs. CC: OR 2.05, 95% CI 1.26-3.32, P = 0.003; T vs. C: OR 1.26, 95% CI 1.04-1.51, P = 0.017; for c.1178G>A, AA vs. GG: OR 2.15, 95% CI 1.26-3.67, P = 0.004; A vs. G: OR 1.33, 95% CI 1.10-1.61, P = 0.004]. The allele-T and genotype-TT of c.482C>T and allele-A and genotype-AA of c.1178G>A genetic polymorphisms may enhance the susceptibility to HCC. Our findings indicate that the studied XRCC1 genetic polymorphisms may influence the risk of HCC in Chinese populations and might be used as molecular markers for assessing the risk of HCC.

XRCC1 Arg399Gln polymorphism confers risk of breast cancer in American population: a meta-analysis of 10846 cases and 11723 controls

Background

In the X-ray repair cross-complementing group 1 (XRCC1) gene, a polymorphism, Arg399Gln (rs25487), has been shown to change neoconservative amino acid and thus result in alternation of DNA repair capacity. Numerous studies have investigated the association between Arg399Gln and breast cancer risk in the American population, but yielding inconsistent results. This study aimed to clarify the role of this polymorphism in susceptibility to breast cancer.

Methods

Literatures were searched in multiple databases including PubMed, Springer Link, Ovid, EBSCO and ScienceDirect databases up to April 2013. A comprehensive meta-analysis was conducted to estimate the overall odds ratio (OR), by integrating data from 18 case control studies of 10846 cases and 11723 controls in the American population.

Results

Overall, significant association was observed between the Arg399Gln polymorphism and breast cancer risk under the random-effects model (OR for dominant model = 1.12, 95% CI: 1.02–1.24, P_{heterogeneity} = 0.003; OR for additive model = 1.07, 95% CI: 1.01–1.14, P_{heterogeneity} = 0.017). Further sensitivity analysis supported the robust stability of this current result by showing similar ORs before and after removal of a single study.

Conclusions

This meta-analysis suggests that the XRCC1 Arg399Gln polymorphism may significantly contribute to susceptibility of breast cancer in the American population.