Micronuclei in EM9 cells expressing polymorphic forms of human XRCC1

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.

Assessment of genotoxic and molecular mechanisms of cancer risk in smoking and smokeless tobacco users

Inexpensive forms of tobacco are widely used in developing countries such as India. We have evaluated genotoxicity endpoints (chromosome aberrations, micronucleus frequency, comet assay) and polymorphisms of the XRCC1 and p53 genes among smokers and smokeless tobacco (SLT) users in rural Tamilnadu, South India. Cytogenetic, DNA damage and SNP analyses were performed on peripheral blood samples; micronucleus frequency was measured in peripheral blood and buccal mucosa exfoliated cells. Both categories of tobacco users had elevated levels of genotoxic damage. SNP analysis of tobacco users revealed that 17% carry the XRCC1 gln399gln genotype and 19% carry the p53 pro72pro genotype. Both genotypes are associated with increased risk of cancer.

Therapy-related myeloid neoplasms after autologous hematopoietic stem cell transplantation in lymphoma patients

Lymphoma patients treated with autologous transplantation (ASCT) live an increasingly long life with the recent advancement in therapeutic modalities. This has resulted in an increase in the incidence of therapy-related myeloid neoplasms (t-MN), which is one of the leading causes of non-relapse mortality. Several observational studies have linked the development of t-MN after ASCT with the intensity and frequency of chemotherapy, particularly alkylating agents, use of total body irradiation (TBI), and peripheral blood progenitor cells. In addition, role of genetic factors is increasingly being identified. It is postulated that the use of chemotherapy prior to ASCT results in DNA damage of progenitor cells, mitochondrial dysfunction, and altered gene expression related to DNA repair, metabolism as well as hematopoietic regulation. Cytogenetic studies have shown the presence of abnormalities in the peripheral blood progenitor cells prior to ASCT. It is, therefore, likely that the reinfusion of peripheral blood progenitor cells, proliferative stress on infused progenitor cells during hematopoietic regeneration and associated telomere shortening ultimately result in clonal hematopoiesis and blastic transformation. Cytopenias, myelodysplasia, or cytogenetic abnormalities are common and can be transient after ASCT; therefore, only when present together, they do confirm the diagnosis of t-MN. Attempts to reduce the occurrence of t-MN should be directed toward minimizing the exposure to the identified risk factors. Although the median survival is few months to less than a year, studies have shown the promising role of allogeneic transplantation in select young t-MN patients without high-risk cytogenetics. In this review we will explain the recent findings in the field of t-MN in lymphoma patients that have implications for identifying the molecular and genetic mechanisms of leukemogenesis and discuss potential strategies to reduce the risk of t-MN in this patient population.

Lack of an association between the XRCC1 Arg399Gln polymorphism and gastric cancer based on a meta-analysis

Association between the XRCC1 Arg399Gln polymorphism and susceptibility to gastric cancer has been investigated; overall, the results have been inconclusive. We made a meta-analysis of 13 case-control studies, including 3278 cases and 6243 controls. Crude odds ratios (OR) with 95% confidence intervals (95%CI) were used to assess this possible association. We found no evidence of a significant association between the XRCC1 Arg399Gln polymorphism and gastric cancer risk (in the additive inheritance model, OR = 0.986, 95%CI = 0.831-1.156, in the dominant inheritance model, OR = 1.044, 95%CI = 0.890-1.224 and in the recessive inheritance model, OR = 0.975, 95%CI = 0.894-1.063). We conclude that the XRCC1 Arg399Gln polymorphism is not a risk factor for developing gastric cancer.

Reprint of: gene susceptibility to oxidative damage: from single nucleotide polymorphisms to function

Oxidative damage to DNA can cause mutations, and mutations can lead to cancer. DNA repair of oxidative damage should therefore play a pivotal role in defending humans against cancer. This is exemplified by the increased risk of colorectal cancer of patients with germ-line mutations of the oxidative damage DNA glycosylase MUTYH. In contrast to germ-line mutations in DNA repair genes, which cause a strong deficiency in DNA repair activity in all cell types, the role of single nucleotide polymorphisms (SNPs) in sporadic cancer is unclear also because deficiencies in DNA repair, if any, are expected to be much milder. Further slowing down progress are the paucity of accurate and reproducible functional assays and poor epidemiological design of many studies. This review will focus on the most common and widely studied SNPs of oxidative DNA damage repair proteins trying to bridge the information available on biochemical and structural features of the repair proteins with the functional effects of these variants and their potential impact on the pathogenesis of disease.

XRCC1 Arg399Gln was associated with repair capacity for DNA damage induced by occupational chromium exposure

Background

Occupational chromium exposure may induce DNA damage and lead to lung cancer and other work-related diseases. DNA repair gene polymorphisms, which may alter the efficiency of DNA repair, thus may contribute to genetic susceptibility of DNA damage. The aim of this study was to test the hypothesis that the genetic variations of 9 major DNA repair genes could modulate the hexavalent chromium (Cr (VI))-induced DNA damage.

Findings

The median (P₂₅-P₇₅) of Olive tail moment was 0.93 (0.58–1.79) for individuals carrying GG genotype of XRCC1 Arg399Gln (G/A), 0.73 (0.46–1.35) for GA heterozygote and 0.50 (0.43–0.93) for AA genotype. Significant difference was found among the subjects with three different genotypes (P = 0.048) after adjusting the confounding factors. The median of Olive tail moment of the subjects carrying A allele (the genotypes of AA and GA) was 0.66 (0.44–1.31), which was significantly lower than that of subjects with GG genotype (P = 0.043). The A allele conferred a significantly reduced risk of DNA damage with the OR of 0.39 (95% CI: 0.15–0.99, P = 0.048). No significant association was found between the XRCC1Arg194Trp, ERCC1 C8092A, ERCC5 His1104Asp, ERCC6 Gly399Asp, GSTP1 Ile105Val, OGG1 Ser326Cys, XPC Lys939Gln, XPD Lys751Gln and DNA damage.

Conclusion

The polymorphism of Arg399Gln in XRCC1 was associated with the Cr (VI)- induced DNA damage. XRCC1 Arg399Gln may serve as a genetic biomarker of susceptibility for Cr (VI)- induced DNA damage.

Association between polymorphisms of XRCC1, p53 and MDR1 genes, the expression of their protein products and prognostic significance in human breast cancer

BACKGROUND

This study aimed to examine the relationship between XRCC1, p53 and MDR1 protein, along with polymorphisms of their genes and their prognostic values in breast cancer. The following clinical and pathological parameters were evaluated: histopathological type of tumor, grade, stage, Her2/neu expression, ER, PR positivity and involvement of regional lymph nodes.

MATERIAL/METHODS

Expression of proteins was determined in 39 samples of breast cancer by immunohistochemistry. Nucleotide polymorphisms were analyzed by PCR-RFLP. For statistical analysis, chi-square test (Yates), Fisher's exact test, and correlation test were used to analyze the data.

RESULTS

The highest protein expression was immunohistochemically found in MDR1 protein, with 54% of samples testing positive. In addition, the evaluation of MDR1 expression revealed higher positive immunoreactivity in lobular (LIC) and other types of tumor in comparison to ductal (DIC) type. The expression of p53 and XRCC1 protein was equal, but lower compared to MDR1, both testing positive in 36% of all tissue samples. Comparison of XRCC1 protein and histopathological type of tumor revealed that DIC and LIC types were mostly XRCC1-negative, while other types, papillary and mucinous were more likely to be XRCC1-positive. Interestingly, when evaluating LIC samples separately, a negative correlation between the Her2/neu and expression of XRCC1 was detected. Apparently, all Her2/neu-positive samples were XRCC1-negative (6/86%). The correlation test indicated a negative correlation between Her2/neu-positive samples and XRCC1-negative specimens (r = 1, p < 0.05). Statistical analysis did not reveal a correlation of p53 expression with clinical and pathological parameters. Similarly, no statistically significant difference was found between the tested polymorphisms and protein expression.

CONCLUSIONS

We did not find statistically significant correlation between tested polymorphisms and their protein expression.

Gene susceptibility to oxidative damage: from single nucleotide polymorphisms to function

Oxidative damage to DNA can cause mutations, and mutations can lead to cancer. DNA repair of oxidative damage should therefore play a pivotal role in defending humans against cancer. This is exemplified by the increased risk of colorectal cancer of patients with germ-line mutations of the oxidative damage DNA glycosylase MUTYH. In contrast to germ-line mutations in DNA repair genes, which cause a strong deficiency in DNA repair activity in all cell types, the role of single nucleotide polymorphisms (SNPs) in sporadic cancer is unclear also because deficiencies in DNA repair, if any, are expected to be much milder. Further slowing down progress are the paucity of accurate and reproducible functional assays and poor epidemiological design of many studies. This review will focus on the most common and widely studied SNPs of oxidative DNA damage repair proteins trying to bridge the information available on biochemical and structural features of the repair proteins with the functional effects of these variants and their potential impact on the pathogenesis of disease.

Undetectable role of oxidative DNA damage in cell cycle, cytotoxic and clastogenic effects of Cr(VI) in human lung cells with restored ascorbate levels

Cultured human cells are invaluable biological models for mechanistic studies of genotoxic chemicals and drugs. Continuing replacement of animals in toxicity testing will further increase the importance of in vitro cell systems, which should accurately reproduce key in vivo characteristics of toxicants such as their profiles of metabolites and DNA lesions. In this work, we examined how a common severe deficiency of cultured cells in ascorbate (Asc) impacts the formation of oxidative DNA damage by hexavalent chromium (chromate). Cr(VI) is reductively activated inside the cells by both Asc and small thiols but with different rates and spectra of intermediates and DNA adducts. We found that Cr(VI) exposure of H460 human lung epithelial cells in standard culture (<0.01 mM cellular Asc) induced biologically significant amounts of oxidative DNA damage. Inhibition of oxidative damage repair in these cells by stable XRCC1 knockdown strongly enhanced cytotoxic effects of Cr(VI) and led to depletion of cells from G(1) and accumulation in S and G(2) phases. However, restoration of physiological levels of Asc (≈ 1 mM) completely eliminated Cr(VI) hypersensitivity of XRCC1 knockdown. The induction of chromosomal breaks assayed by the micronucleus test in Asc-restored H460, primary human lung fibroblasts, and CHO cells was also unaffected by the XRCC1 status. Centromere-negative (clastogenic) micronuclei accounted for 80-90% of all Cr(VI)-induced micronuclei. Consistent with the micronuclei results, Asc-restored cells also showed no increase in the levels of poly(ADP-ribose), which is a biochemical marker of single-stranded breaks. Asc had no effect on cytotoxicity of O(6)-methylguanine, a lesion produced by direct DNA alkylation. Overall, our results indicate that the presence of physiological levels of Asc strongly suppresses pro-oxidant pathways in Cr(VI) metabolism and that the use of standard cell cultures creates a distorted profile of its genotoxic properties.

XRCC1 gene variants and possible links with chromosome aberrations and micronucleus in active and passive smokers

Tobacco addiction is a major risk for diseases such as cancers, heart attack, etc. Tobacco smoke constitutes environmental toxins that are the major preventable leading cause of death worldwide. We investigated the influence of tobacco smoke on cytogenetic parameters (chromosomal aberrations and micronuclei) and the influence of XRCC1 arg399gln polymorphism on the cytogenetic parameters of the exposed subjects. The cases for this study include active and passive smokers. They were divided into three groups in accordance with duration of exposure to tobacco smoke. We observed changes in the frequency of chromosomal aberrations and micronuclei among the exposed subjects and controls. Of the three groups of exposed subjects, group III of active smokers and group III of passive smokers showed higher number of chromosomal aberrations and micronuclei when compared to controls, group I and group II of active and passive smokers. The XRCC1 arg399gln polymorphic variant gln/gln, influenced the extent of genotoxic damage in chromosomes and frequency of in micronuclei the three variants (arg/arg, arg/gln and gln/gln), gln/gln harbored significantly (P<0.05) higher number of aberrations than the arg/arg and arg/gln. In this context, the results observed in our study indicated that the single nucleotide polymorphism on XRCC1codon 399 influenced the frequencies of chromosomal aberrations and micronuclei.

Evaluating chromosomal damage in workers exposed to hexavalent chromium and the modulating role of polymorphisms of DNA repair genes

PURPOSE

Welders have been chronically exposed to hexavalent chromium with potential consequences on chromosomal integrity. Our study is focused on the extent of any such chromosomal aberrations with respect to chromium levels in the blood of welders as well as on the tentative modulating role of polymorphisms in DNA repair genes XPD Lys751Gln, XPG Asn114His, XPC Lys939Gln, hOGG1 Ser326Cys and XRCC1 Arg399Gln on chromosomal damage.

METHODS

The study was conducted on 144 individuals consisting of 73 welders exposed to chromium for 10.2 ± 1.67 years and 71 control individuals without known exposures. Chromosomal aberrations, their chromatid-type and chromosome-type aberrations were detected by conventional cytogenetic analysis. XPD, XPG, XPC, hOGG1 and XRCC1 gene polymorphisms were assayed for by Taqman SNP genotyping assay ("Assay-by-Demand") using Real-Time allelic discrimination on AB 7500 equipment. Chromium concentration in the blood was determined by atomic absorption spectrophotometry.

RESULTS

The level of chromium in the blood of welders ranged between 0.032 and 0.182 μmol l(-1) and was significantly higher than that in controls (0.07 ± 0.04 μmol l(-1) vs. 0.03 ± 0.007 μmol l(-1)). Parameters of chromosomal damage were similar in both the exposed and the control individuals (1.89% vs. 1.70% for total chromosomal aberrations, 0.97% vs. 0.88% for chromosome-type and 0.92% vs. 0.80% for chromatid-type, respectively). Chromatid-type of aberrations positively correlated with the level of chromium in the blood (r = 0.28; P = 0.02). Significantly higher total chromosomal aberrations were detected in individuals with homozygous variant polymorphism in XRCC1 Arg399Gln gene as compared to those with heterozygous and homozygous wild-type genotypes (2.20, 1.89 and 1.48%, respectively; P = 0.01). A similar tendency was found for chromatid-type aberrations (1.30% for homozygous variant genotype bearers, 0.94% for those with heterozygous genotype and 0.75% for carriers of homozygous wild-type genotype, respectively; P = 0.04).

CONCLUSIONS

Although no apparent increase in chromosomal damage was recorded in chromium-exposed welders in comparison with controls, genetic make-up in DNA repair genes may increase susceptibility toward adverse effect of chromium.

An XRCC1 polymorphism is associated with the outcome of patients with lymphoma undergoing autologous stem cell transplant

High-dose chemotherapy supported by autologous stem cell transplant (ASCT) remains the treatment of choice for patients with lymphoma failing first-line chemotherapy. Recent evidence suggests a relationship between the genetic variations in genes involved in DNA repair and the outcome of patients with a number of malignancies. In this work, we retrospectively evaluated the influence of an XRCC1 polymorphism (rs25487) on the treatment results in a series of 73 patients with lymphoma subjected to ASCT. The factors correlated to overall survival were the disease status at transplant and XRCC1 genotype. Carriers of a mutant A allele had a two-fold higher risk of death than those with the wild-type genotype. In addition, patients harboring one or two copies of the A allele (GA/AA) were 4.5-fold more likely to develop therapy-related acute myeloid (t-AML). Thus, the cumulative probability of t-AML at 10 years was 37 ± 13% in patients with the mutant A allele as compared to 8.5 ± 6% in the remaining cases (p = 0.04). Our findings suggest that genetic variation in the DNA repair gene XRCC1 may play a role in the results of transplant in patients with lymphoma.

Variation in base excision repair capacity

The major DNA repair pathway for coping with spontaneous forms of DNA damage, such as natural hydrolytic products or oxidative lesions, is base excision repair (BER). In particular, BER processes mutagenic and cytotoxic DNA lesions such as non-bulky base modifications, abasic sites, and a range of chemically distinct single-strand breaks. Defects in BER have been linked to cancer predisposition, neurodegenerative disorders, and immunodeficiency. Recent data indicate a large degree of sequence variability in DNA repair genes and several studies have associated BER gene polymorphisms with disease risk, including cancer of several sites. The intent of this review is to describe the range of BER capacity among individuals and the functional consequences of BER genetic variants. We also discuss studies that associate BER deficiency with disease risk and the current state of BER capacity measurement assays.

XRCC1 deficiency sensitizes human lung epithelial cells to genotoxicity by crocidolite asbestos and Libby amphibole

BACKGROUND

Asbestos induces DNA and chromosomal damage, but the DNA repair pathways protecting human cells against its genotoxicity are largely unknown. Polymorphisms in XRCC1 have been associated with altered susceptibility to asbestos-related diseases. However, it is unclear whether oxidative DNA damage repaired by XRCC1 contributes to asbestos-induced chromosomal damage.

OBJECTIVES

We sought to examine the importance of XRCC1 in protection against genotoxic effects of crocidolite and Libby amphibole asbestos.

METHODS

We developed a genetic model of XRCC1 deficiency in human lung epithelial H460 cells and evaluated genotoxic responses to carcinogenic fibers (crocidolite asbestos, Libby amphibole) and nongenotoxic materials (wollastonite, titanium dioxide).

RESULTS

XRCC1 knockdown sensitized cells to the clastogenic and cytotoxic effects of oxidants [hydrogen peroxide (H₂O₂), bleomycin] but not to the nonoxidant paclitaxel. XRCC1 knockdown strongly enhanced genotoxicity of amphibole fibers as evidenced by elevated formation of clastogenic micronuclei. Crocidolite induced primarily clastogenic micronuclei, whereas Libby amphibole induced both clastogenic and aneugenic micronuclei. Crocidolite and bleomycin were potent inducers of nuclear buds, which were enhanced by XRCC1 deficiency. Libby amphibole and H₂O₂ did not induce nuclear buds, irrespective of XRCC1 status. Crocidolite and Libby amphibole similarly activated the p53 pathway.

CONCLUSIONS

Oxidative DNA damage repaired by XRCC1 (oxidized bases, single-strand breaks) is a major cause of chromosomal breaks induced by crocidolite and Libby amphibole. Nuclear buds are a novel biomarker of genetic damage induced by exposure to crocidolite asbestos, which we suggest are associated with clustered DNA damage. These results provide mechanistic evidence for the epidemiological association between XRCC1 polymorphisms and susceptibility to asbestos-related disease.

Haplotype analysis of XRCC1 (at codons 194 and 399) and susceptibility to breast cancer, a meta-analysis of the literatures

To clarify the association between XRCC1 haplotypes and susceptibility to breast cancer, a meta-analysis of case-control studies were conducted. Eligible studies were identified by searching several databases for relevant reports published before March 2010. In total, 10 studies were included in the present meta-analysis. XRCC1 haplotypes for Arg194Trp and Arg399Gln polymorphisms were included in the analysis. The association was measured using random-effect model or fixed-effect model odds ratio (OR) combined with 95% confidence intervals (CIs) according to the between studies' heterogeneity. Large between-study heterogeneity was observed (Q = 25.587, df = 9, P < 0.001). The meta-analysis showed a borderline increased risk of breast cancer associated with the Arg194-Gln399 haplotype versus the Arg194-Arg399 haplotype (OR = 1.07, 95% CI: 1.01-1.14). There was no significant association between XRCC1 haplotypes and risk of breast cancer among Caucasoid subjects. In the next step, studies were classified according to geographical locations. Studies reported form Western populations did not show heterogeneity, and the Arg194-Gln399 haplotype was not associated with risk of breast cancer in comparison with the Arg194-Arg399 haplotype (OR = 1.02, 95% CI: 0.95-1.09). Among studies reported form Asian countries, significant heterogeneity was observed. After excluding of one study which did not show linkage disequilibrium, heterogeneity between studies decreased and haplotype Arg194-Gln399 revealed significant association with increased risk of breast cancer compared with haplotype Arg194-Arg399 (OR = 1.26, 95% CI: 1.04-1.50). There was no significant association between Trp194-Arg399 haplotype and risk of breast cancer, neither in Western nor Asian countries. The present meta-analysis has indicated that the Arg194-Gln399 haplotype of XRCC1 might be a risk factor for breast cancer in Asian countries.

Functional capacity of XRCC1 protein variants identified in DNA repair-deficient Chinese hamster ovary cell lines and the human population

XRCC1 operates as a scaffold protein in base excision repair, a pathway that copes with base and sugar damage in DNA. Studies using recombinant XRCC1 proteins revealed that: a C389Y substitution, responsible for the repair defects of the EM-C11 CHO cell line, caused protein instability; a V86R mutation abolished the interaction with POLβ, but did not disrupt the interactions with PARP-1, LIG3α and PCNA; and an E98K substitution, identified in EM-C12, reduced protein integrity, marginally destabilized the POLβ interaction, and slightly enhanced DNA binding. Two rare (P161L and Y576S) and two frequent (R194W and R399Q) amino acid population variants had little or no effect on XRCC1 protein stability or the interactions with POLβ, PARP-1, LIG3α, PCNA or DNA. One common population variant (R280H) had no pronounced effect on the interactions with POLβ, PARP-1, LIG3α and PCNA, but did reduce DNA-binding ability. When expressed in HeLa cells, the XRCC1 variants—excluding E98K, which was largely nucleolar, and C389Y, which exhibited reduced expression—exhibited normal nuclear distribution. Most of the protein variants, including the V86R POLβ-interaction mutant, displayed normal relocalization kinetics to/from sites of laser-induced DNA damage: except for E98K and C389Y, and the polymorphic variant R280H, which exhibited a slightly shorter retention time at DNA breaks.

Genetic polymorphisms of DNA repair genes and chromosomal damage in workers exposed to 1,3-butadiene

The base excision repair (BER) pathway is important in repairing DNA damage incurred from occupational exposure to 1,3-butadiene (BD). This study examines the relationship between inherited polymorphisms of the BER pathway (x-ray repair cross-complementing group 1 (XRCC1) Arg194Trp, Arg280His, Arg399Gln, T-77C, ADPRT Val762Ala, MGMT Leu84Phe and APE1 Asp148Glu) and chromosomal damage in BD-exposed workers, using the cytokinesis-blocked (CB) micronucleus (MN) assay in peripheral lymphocytes of 166 workers occupationally exposed to BD and 41 non-exposed healthy individuals. The MN frequency of exposed workers (3.39 +/- 2.42) per thousand was higher than that of the non-exposed groups (1.48 +/- 1.26) per thousand (P < 0.01). Workers receiving greater than median annual BD exposures had higher MN values than lower exposed workers: frequency ratio (FR) of 1.30, 95% confidence interval (CI) 1.14-1.53; P < 0.05. Workers who carried the following genotypes were associated with greater frequency of MN (P < 0.05 for each comparison, unless specified): XRCC1 -77 C/T genotype (FR = 1.28, 95% CI: 1.04-1.57; reference C/C), ADPRT 762 Ala/Ala (FR = 1.54, 95% CI: 1.17-2.03; P < 0.01), XRCC1 194 Arg/Trp (FR = 1.13, 95% CI: 0.87-1.27; reference, Arg/Arg), XRCC1 280 Arg/His (FR = 1.67, 95% CI: 1.10-2.42; reference, Arg/Arg), XRCC1 399 Arg/Gln and Gln/Gln genotypes (FR = 1.26, 95% CI: 1.03-1.53 and FR = 1.24, 95% CI 1.03-1.49; reference Arg/Arg, respectively). As XRCC1 polymorphisms were linked, workers carrying the XRCC1 (-77)-(194)-(280)-(399) diplotype, TCGA/TCGA, had a higher MN frequency compared with individuals carrying the wild-type CCGG/CCGG (FR = 1.57, 95% CI: 1.02-2.41; P < 0.05). In conclusion, CB-MN is a sensitive index of early damage among BD-exposed workers. In workers exposed to BD, multiple BER polymorphisms and a XRCC1 haplotype were associated with differential levels of chromosome damage.

Genetic polymorphisms of DNA repair gene XRCC1 and risk of uterine leiomyoma

The objective was to study the relationship between the polymorphisms of the DNA repair gene XRCC1 Arg399Gln, Arg194Trp, and Arg280His uterine leiomyoma in a Chinese population. In the case-control study, we compared the XRCC1 gene polymorphism of 136 uterine leiomyoma patients and 140 healthy controls by using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results suggested that the genotype Arg/Arg of codon 280 was significantly different from its heterozygote (odds ratio [OR] = 3.633, 95% confidence interval [CI]: 2.147-6.148). In conclusion, the results suggest that polymorphism of XRCC1 Arg280His was associated with the increased risk of uterine leiomyoma in a Chinese population.

Polymorphisms of XRCC1 gene and risk of gastric cardiac adenocarcinoma

X-ray repair cross complementing 1 (XRCC1) protein plays an important role in base excision repair. Single nucleotide polymorphisms (SNPs) in XRCC1 gene may affect DNA repairing ability and genetic susceptibility to cancer. This study was designed to investigate the correlation of XRCC1 Arg194Trp Arg280His and Arg399Gln SNPs with the risk of gastric cardiac adenocarcinoma (GCA). Genotypes were analyzed by polymerase chain reaction-restriction fragment length polymorphism assay in 455 patients with GCA and 650 age and sex-matched controls. We did not find any significant difference in allele and genotype distributions of Arg194Trp Arg399Gln between the groups (P > 0.05). However, a significant increase in GCA risk was seen among smokers if they carried at least one XRCC1 280His (Arg280His + His280His) genotype (odds ratio = 1.59, 95%confidence interval = 1.01-2.51) compared with smokers not carrying these genotype. Our results indicated that XRCC1 Arg194Trp and Arg399Gln SNPs might not be associated with the risk of GCA. However, smokers with His allele at codon 280 had a significantly increased risk of GCA.

Base excision repair, aging and health span

DNA damage and mutagenesis are suggested to contribute to aging through their ability to mediate cellular dysfunction. The base excision repair (BER) pathway ameliorates a large number of DNA lesions that arise spontaneously. Many of these lesions are reported to increase with age. Oxidized guanine, repaired largely via base excision repair, is particularly well studied and shown to increase with age. Spontaneous mutant frequencies also increase with age which suggests that mutagenesis may contribute to aging. It is widely accepted that genetic instability contributes to age-related occurrences of cancer and potentially other age-related pathologies. BER activity decreases with age in multiple tissues. The specific BER protein that appears to limit activity varies among tissues. DNA polymerase-beta is reduced in brain from aged mice and rats while AP endonuclease is reduced in spermatogenic cells obtained from old mice. The differences in proteins that appear to limit BER activity among tissues may represent true tissue-specific differences in activity or may be due to differences in techniques, environmental conditions or other unidentified differences among the experimental approaches. Much remains to be addressed concerning the potential role of BER in aging and age-related health span.

Polymorphism of XRCC1 (at codon 399) and susceptibility to breast cancer, a meta-analysis of the literatures

The X-ray repair cross-complementation group 1 (XRCC1) protein plays an important role in base excision repair. Several polymorphisms in the XRCC1 gene have been described, including Arg399Gln. Previous studies investigating the association between genetic polymorphism of Arg399Gln XRCC1 and risk of breast cancer have provided inconsistent results. A meta-analysis was conducted to investigate the association between common genetic variant in the XRCC1 gene (exon 10, Arg399Gln) with breast cancer risk. We identified 36 eligible studies, in relation to the Arg399Gln polymorphism of XRCC1 and risk of breast cancer. These studies comprised of 43,716 subjects (20,837 patients and 22,879 controls). We first estimated the risk of the genotypes Arg/Gln and Gln/Gln compared with the wild-type Arg/Arg homozygote, and then evaluated the risk of Gln/Gln versus (Arg/Gln+Arg/Arg) and (Gln/Gln+Arg/Gln) versus Arg/Arg, which assumed recessive and dominant effects, respectively, of the variant 399Gln allele. There was significant heterogeneity between studies. The overall ORs showed that the breast cancer risk were not associated with the XRCC1 genotypes. The heterogeneity between studies decreased dramatically when studies stratified into Asian and Western countries. There was significant association between the polymorphism of XRCC1 and breast cancer risk among studies of Asian countries. In Asian countries the Arg/Gln versus Arg/Arg (OR = 0.98, 95% CI: 0.88-1.10) and Gln/Gln+Arg/Gln versus Arg/Arg (OR = 1.05, 95% CI: 0.95-1.18) were not associated with increased risk of breast cancer. On the other hand, both Gln/Gln versus Arg/Arg (OR = 1.46, 95% CI: 1.19-1.79) and Gln/Gln versus Arg/Gln+Arg/Arg (OR = 1.49, 95% CI: 1.22-1.81) increased the risk. Therefore, it could be concluded that 399Gln allele might act as a recessive allele in its association with breast cancer risk.

Molecular biomonitoring of a population of nurses handling antineoplastic drugs

Many antineoplastic drugs have been found to have carcinogenic, mutagenic and teratogenic activity and so hospital personnel handling these substances are potentially exposed to health risk. Understanding this risk derived from protracted occupational exposure has great relevance even if the workers normally adopt individual and environmental protective measures. To address this question we have studied the presence of DNA and chromosome damage in a population of nurses employed in Italian oncology units and in matched controls. We used the comet assay to evidence the presence of DNA strand breaks, due to both acute and chronic exposure, and the micronucleus (MN) test, which is a measure of clastogenic and aneugenic events. Furthermore, since the individual response to the exogenous insults may be genetically determined, we studied the possible influence of single nucleotide polymorphism in XRCC1 and XRCC3 DNA repair genes on induced genetic damage. We also considered the effects of confounding factors like smoking, age and gender. The results indicated that the exposed subjects had significantly high levels of genetic damage. Age and gender were associated with increased values in MN, both in control and in exposed groups; the smoking habit affects MN frequency in controls, but not in workers. Furthermore we found that exposed subjects bearing at least one XRCC1 variant allele (399Gln) show higher values of MN. The present data provide the evidence to show that occupational exposure to antineoplastic drugs, even if in safety controlled conditions, represents a serious health risk. Furthermore we have shown that the presence of XRCC1 genetic polymorphism could contribute to increase the genetic damage in susceptible individuals who are occupationally exposed to dangerous substances.

XRCC1 down-regulation in human cells leads to DNA-damaging agent hypersensitivity, elevated sister chromatid exchange, and reduced survival of BRCA2 mutant cells

Previous studies using rodent cells indicate that a deficiency in XRCC1 results in reduced single-strand break repair, increased sensitivity to DNA-damaging agents, and elevated levels of sister chromatid exchange (SCE). Epidemiological studies have suggested an association of certain human XRCC1 polymorphisms with genetic instability and cancer susceptibility. However, investigations on the molecular functions of XRCC1 in human cells are limited. To determine the contributions of this nonenzymatic scaffold protein, we suppressed XRCC1 levels in several human cell lines using small interfering RNA (siRNA) technology. We report that XRCC1 down-regulation in HeLa cells leads to a concomitant decrease in the DNA ligase 3 protein level and an impaired nick ligation capacity. In addition, depletion of XRCC1 resulted in a significantly increased sensitivity to the alkylating agent methyl methanesulfonate and the thymidine base analog 5-hydroxymethyl-2'-deoxyuridine, a slightly increased sensitivity to ethyl methanesulfonate and 1,3-bis(2-chloroethyl)-1-nitrosourea, and no change in the response to camptothecin. We also discovered that a 70-80% reduction in XRCC1 protein leads to an elevated level of SCE in both HeLa cells and normal human fibroblasts, but does not affect chromosome aberrations in the diploid fibroblasts. Last, XRCC1 siRNA transfection led to an approximately 40% decrease in the survival of BRCA2-deficient cells, supporting a model whereby the accumulation of unrepaired SSBs leads to the accumulation of cytotoxic DNA double strand breaks following replication fork collapse in cells defective in homologous recombination.

DNA repair polymorphisms might contribute differentially on familial and sporadic breast cancer susceptibility: a study on a Portuguese population

The purpose of this study was to evaluate the role of polymorphisms in DNA repair genes as genetic indicators of susceptibility to familial and sporadic breast cancer. We analysed DNA samples from 285 breast cancer patients and 442 control subjects, for XRCC1 Arg399Gln, XPD Lys751Gln, RAD51 G135C and XRCC3 Thr241Met polymorphisms using PCR-RFLP. We observed that women carriers of XRCC1 399Gln genotypes and without family history of breast cancer have a protective effect concerning this disease (OR = 0.54 95% CI 0.35-0.84; p = 0.006). Furthermore, we found that carriers of XRCC3 241Met genotypes without FH have an increased susceptibility of breast cancer (OR = 2.21 95% CI 1.42-3.44; p < 0.001). Additionally, we verified an increased risk of breast cancer in women with FH and carrying RAD51 135C genotypes (OR = 2.17 95% CI 1.19-3.98; p = 0.012). Our results suggest XRCC1 Arg399Gln and XRCC3 Thr241Met DNA repair polymorphisms as important biomarkers to sporadic breast cancer susceptibility, as well as, RAD51 G135C polymorphism as a real risk modifier in familial breast cancer cases.

Adenosine diphosphate ribosyl transferase and x-ray repair cross-complementing 1 polymorphisms in gastric cardia cancer

BACKGROUND & AIMS

Adenosine diphosphate ribosyl transferase (ADPRT) and x-ray repair cross-complementing 1 (XRCC1) are major DNA base excision repair proteins acting interactively in repair processes. This study examined the effects of ADPRT Val762Ala and XRCC1 Arg399Gln polymorphisms on ADPRT-XRCC1 interaction in vitro in cells and their contributions to gastric cardia adenocarcinoma (GCA) risk.

METHODS

The ADPRT-XRCC1 interaction in cells transfected with ADPRT and XRCC1 variant complementary DNA (cDNA) constructs were examined by immunoprecipitation and immunoblotting analysis. Genotypes were analyzed in 500 patients and 1000 controls, and odds ratios (ORs) were estimated by logistic regression.

RESULTS

Interactions between ADPRT-762Val and XRCC1-399Arg or XRCC1-399Gln were robust, but interactions between ADPRT-762Ala and either XRCC1-399Arg or XRCC1-399Gln were very weak. A case-control analysis showed ORs of 2.17 (95% CI, 1.55-3.04) and 1.61 (95% CI, 1.06-2.44) for GCA in the ADPRT Ala/Ala or XRCC1 Gln/Gln genotype carriers, respectively, compared with noncarriers. Gene-gene interaction of ADPRT and XRCC1 polymorphisms increased the OR of GCA in a multiplicative manner (OR for the presence of both ADPRT Ala/Ala and XRCC1 Gln/Gln genotypes, 6.43; 95% CI, 1.80-22.97). A supermultiplicative joint effect between the ADPRT polymorphism and smoking was observed. The ORs (95% CIs) of the Ala/Ala genotype for nonsmokers and smokers who smoked < or = 24 or > 24 pack-years were 1.44 (0.89-2.32), 2.00 (1.09-3.67), or 3.19 (1.59-6.42), respectively (Ptrend test = .008).

CONCLUSIONS

The ADPRT and XRCC1 polymorphisms confer host susceptibility to GCA, which might result from reduced ADPRT-XRCC1 interaction and attenuated base excision repair capacity.

Genotoxicity associated to exposure to Prestige oil during autopsies and cleaning of oil-contaminated birds

After the accident involving the oil tanker Prestige in November 2002 near 63,000 tons of heavy oil reached Galician coast (Northwest of Spain). This unleashed a large movement of volunteers to collaborate in several cleaning tasks. The aim of this study was to determine whether handling of Prestige oil-contaminated birds during autopsies and cleaning may have resulted in genotoxic damage. We have also evaluated the possible influence of DNA repair genetic polymorphisms (XRCC1 codons 194 and 399, XRCC3 codon 241 and APE1 codon 148) on susceptibility to the genotoxic effects evaluated. Exposure levels were analysed by determining volatile organic compounds in air samples. Peripheral blood samples were obtained from 34 exposed and 35 controls, and comet assay and micronucleus (MN) test were carried out. Genotyping was performed following PCR-RFLP procedures. Results obtained have shown significantly higher DNA damage, but not cytogenetic damage, in exposed individuals than in controls, related to time of exposure. Among exposed individuals, carriers of the variant alleles XRCC1 399Gln and APE1 148Glu have shown altered DNA damage with regard to wild-type homozygotes, suggesting exposure-genotype interactions. No effect of the DNA repair genetic polymorphisms analysed was observed in the MN test.

Risk assessment of welders using analysis of eight metals by ICP-MS in blood and urine and DNA damage evaluation by the comet and micronucleus assays; influence of XRCC1 and XRCC3 polymorphisms

The aims of the present study were to assess the occupational risk of welders using analysis of metals in biological fluids, DNA damage evaluation by complementary genotoxic endpoints and the incidence of polymorphisms in DNA repair genes. A biomonitoring study was conducted that included biometrology (blood and urinary concentrations of aluminium, cadmium, chromium, cobalt, lead, manganese, nickel, zinc by ICP-MS), comet and cytokinesis-block micronucleus assays in peripheral lymphocytes and genetic polymorphisms of XRCC1 (p.Arg399Gln) and XRCC3 (p.Thr241Met). This study included 60 male welders divided into two groups: group 1 working without any collective protection device and group 2 equipped with smoke extraction systems. A control group (n = 30) was also included in the study. Higher chromium, lead and nickel blood and urinary concentrations were detected in the two groups of welders compared to controls. Statistically differences between welders of group 1 and group 2 were found for blood concentration of cobalt and urinary concentrations of aluminium, chromium, lead and nickel. The alkaline comet assay revealed that welders had a significant increase of OTMchi2 distribution at the end of a work week compared to the beginning; a significant induction of DNA strand breaks at the end of the week was observed in 20 welders out of 30. The cytokinesis-block micronucleus assay showed that welders of group 1 had a higher frequency of chromosomal damage than controls. The XRCC1 variant allele coding Gln amino acid at position 399 was found to be associated with a higher number of DNA breaks as revealed by the comet assay. Increased metal concentrations in biological fluids, DNA breaks and chromosomal damage in lymphocytes emphasized the need to develop safety programmes for welders.

X-ray repair cross-complementing group 1 polymorphisms and cancer risks in Asian populations: A mini review

X-ray repair cross-complementing group 1 (XRCC1) is an important DNA repair protein. Arg194Trp, Arg280His, and Arg399Gln are three polymorphisms of XRCC1 that commonly exist in human. In this context, we obtained the relevant articles through a PubMed search and examined the association of XRCC1 polymorphisms and the risk of cancer in Asian populations. Generally, a single XRCC1 polymorphism is weakly associated with cancer in Asian populations. However, when combined with other genetic polymorphisms or such lifestyle factors as smoking, XRCC1 polymorphisms show a stronger association with the risk of cancer. The interaction of the 399Gln/Gln genotype and smoking might be associated with a three-fold increase in the risk of cancer. In this paper we provide some important information for practical future cancer prevention programs. To further clarify the association of XRCC1 polymorphisms and cancer risks, additional studies are required from the perspectives of epidemiology and in vitro.