The peculiarities of polymorphism of XPD and XRCC1 repair genes in cells of Down and Ehlers-Danlo syndrome patients characterized by increased radiosensitivity

Codon 312 and 751 polymorphisms ofXPD gene and codon 399 polymorphism of XRCC1 gene of peripheral blood lymphocytes in patients with Down syndrome (DS) (46 individuals), Ehlers-Danlo syndrome (EDS) (47 individuals) and in a group of healthy donors (control) (40 individuals) have been studied. Frequency of XPD genotype (G312G) coding for the most effectively functioning form of XPD protein was lower in patients with DS (26%) than in a group of healthy donors (42.5%) (p = 0.035), whereas no significant differences with the control were revealed for this codon in patients with EDS. No patients with XPD genotype (C751C) (p = 0.036) were revealed in a group of EDS patients, while this genotype was found in 16% of a group of healthy donors and in 17% of patients with DS. The trend of XRCC1 genotype frequency reduction (A399A) (p = 0.085) in EDS patients (3.9%) compared with the group of healthy donors (13.5%) and DS patients (13.3%) has been obtained. These data show that polymorphisms of the excision repair genes under study are accompanied by an elevated individual radio sensitivity in patients with DS. Genes investigated (their polymorphic variants) did not participate in the mechanisms for radio sensitive phenotype formation in EDS patients.     

Impact of DNA repair genes polymorphism (XPD and XRCC1) on the risk of breast cancer in Egyptian female patients

The genes involved in DNA repair system play a crucial role in the protection against mutations. It has been hypothesized that functional deficiencies in highly conserved DNA repair processes resulting from polymorphic variation may increase genetic susceptibility to breast cancer (BC). The aim of the present study was to evaluate the association of genetic polymorphisms in 2 DNA repair genes, XPD (Asp312Asn) and XRCC1 (A399G), with BC susceptibility. We further investigated the potential combined effect of these DNA repair variants on BC risk. Both XPD (xeroderma pigmentosum group D) and XRCC1 (X-ray repair cross-complementing group 1) polymorphisms were characterized in 100 BC Egyptian females and 100 healthy women who had no history of any malignancy by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) method and PCR with confronting two-pair primers (PCR-CTPP), using DNA from peripheral blood in a case control study. Our results revealed that the frequencies of AA genotype of XPD codon 312 polymorphism were significantly higher in the BC patients than in the normal individuals (P ≤ 0.003), and did not observe any association between the XRCC1 Arg399Gln polymorphism and risk of developing BC. Also, no association between both XPD Asp312Asn and XRCC1 A399G polymorphisms and the clinical characteristics of disease. Finally, the combination of AA(XPD) + AG(XRCC1) were significantly associated with BC risk. Our results suggested that, XPD gene is an important candidate gene for susceptibility to BC. Also, gene–gene interaction between XPD(AA) + XRCC1(AG) polymorphism may be associated with increased risk of BC in Egyptian women.     

The polymorphism of DNA repair genes XPD,XRCC1, OGG1, and ERCC6, life expectancy,and the inclination to smoke

The polymorphism of excision repair genes XPD Asp312Asn, XRCC1 Arg399Gln, OGG1 Ser326Cys, and ERCC6 Met1097Val was analyzed by PCR-RFLP in 370 representatives of the Belarusian population of average, old, and elderly ages. Correlation analysis showed that the frequencies of wild-type homozygous combinations significantly increase with age in the group of subjects over 70 years old in the case of the interaction of two genes, XPD 312 and XRCC1 399, or three genes, XPD 312, XRCC1 399, and ERCC6 1097. In a subgroup of the long-lived, this relationship is manifested in case of a pairwise interaction of gene XPD 312 with XRCC1 399 or ERCC6 1097, as well as an interaction of three genes, XPD 312, XRCC1 399, and ERCC6 1097. The data suggest that the optimum activity of repair processes may favor longevity. It is shown that the frequency of the Asp/Asp genotype is reduced, and the frequency of the Asn allele of the XPD 312 gene is increased in the subgroup of smokers as compared with nonsmokers, which apparently indicates an association of this gene polymorphism with an inclination to smoke. The problem requires further study.     

Microsatellite polymorphisms in DNA repair genes XRCC1, XRCC3 and XRCC5 in patients with gynecological tumors: association with late clinical radiosensitivity and cancer incidence

This study investigates the association of microsatellite polymorphisms in XRCC1, XRCC3 and XRCC5 with the development of late radiation-induced radiotherapy reactions and examines the correlation between these microsatellites and cancer incidence. Sixty-two women with cervical or endometrial cancer treated with radiotherapy were included in the study. According to the CTCAEv3.0 scale, 22 patients showed late adverse radiotherapy reactions (grade 2 or more). PCR on lymphocyte DNA followed by automated fragment analysis was performed to examine the number of tandem repeat units at each locus. No significant association was found between the repeat length at any of the microsatellites in XRCC1, XRCC3 or XRCC5 and the incidence of late radiotherapy complications. Since higher odds ratios (ORs) were found for the rare XRCC1 [AC]11 and [AC]21 repeats (OR = 2.65, P = 0.325 and OR = 8.67, P = 0.093, respectively), the possible involvement of these small and large repeats in clinical radiosensitivity cannot be completely ruled out. When specific numbers of repeats were examined, no significant correlation was found between the microsatellite repeat length in XRCC1 and XRCC5 and cancer incidence. A weak correlation between XRCC3 [AC]16 homozygotes and cancer incidence was found (OR = 2.56, P = 0.055). A large-scale multicenter study of cancer patients with a high number of radiosensitive individuals is needed to clarify the value of rare polymorphic microsatellite repeats in XRCC1 and XRCC3 as a biomarker of clinical radiosensitivity or increased cancer risk.     

The polymorphism of DNA repair genes XRCC1, XRCC3 and the level of chromosomal aberrations in the Uranium workers

Association between the polymorphism of DNA repair genes XRCC1 Arg399ln and XRCC3 Thr241Met and the frequency of chromosomal aberrations in the uranium workers was studied. The Gln/Gln genotype of gene XRCC1 was associated with a significant increase in the number of chromosomal aberrations as compared to the corresponding homozygous wild type Arg/Arg (p < 0.05). The frequency of chromosomal aberrations in heterozygous carriers of the XRCC3gene Thr/Met was lower than in the homozygous carriers of the wild type Thr/Thr (p < 0.001).     

Influence of polymorphisms in DNA repair genes XPD, XRCC1 and MGMT on DNA damage induced by gamma radiation and its repair in lymphocytes in vitro

DNA single-strand breaks (SSBs) were quantified by single-cell gel electrophoresis and micronucleated and apoptotic cells were quantified by microscopic assays in peripheral blood lymphocytes after irradiation on ice with 2 Gy of 60Co gamma radiation, and their association with polymorphisms of genes that encode proteins of different DNA repair pathways and influence cancer risk (XPD codon 312Asp --> Asn and 751Lys --> Gln, XRCC1 399Arg --> Gln, and MGMT 84Leu --> Phe) was studied. In unirradiated lymphocytes, SSBs were significantly more frequent in individuals older than the median age (52 years) (P = 0.015; n = 81), and the frequency of apoptotic or micronucleated cells was higher in individuals with alleles coding for Asn at XPD 312 or Gln at 751 (P = 0.030 or 0.023 ANOVA, respectively; n = 54). The only polymorphism associated with the background SSB level was MGMT 84Phe (P = 0.04, ANOVA; n = 66). After irradiation, SSB levels and repair parameters did not differ significantly with age or smoking habit. The SSB level varied more than twofold and the repair rate and level of unrepaired SSBs more than 10-fold between individuals. The presence of variant alleles coding for Asn at XPD 312 was associated with more radiation-induced SSBs (P = 0.014) and fewer unrepaired SSBs (P = 0.008), and the phenotype (> median induced SSBs/< median unrepaired SSBs) was seen in the majority of XPD 312Asn/Asn homozygotes; the odds ratio for variant homozygotes to show this phenotype was 5.2 (95% confidence interval 1.4-19.9). The hypothesis is discussed that XPD could participate in repair of ionizing radiation-induced DNA damage. While it cannot be excluded that the effects observed are due to cosegregating polymorphisms or that the responses of lymphocytes are not typical of other cell types, the results suggest that polymorphism of DNA repair genes, particularly XPD, is one factor implicated in the variability of responses to ionizing radiation between different individuals.     

Polymorphism of DNA repair genes (XRCC1, XRCC3, XPC, XPD, XPA) in ethnic groups from Republic of Bashkortostan

Genotype and allele-frequency distributions of the excision and homologous recombination of DNA repair genes XRCC1 (rs25487 and rs25489), XRCC3 (rs861539), XPC (rs2228001), XPD (rs13181), XPA (rs1800975) were examined in three ethnic groups from the Republic of Bashkortostan (Russia), Russians, Tatars, and Bashkirs. The data obtained were compared to those for other ethnic groups from Russia and worldwide. Statistically significant differences in the allele-frequency distribution of the XPA gene polymorphic locus rs1800975 (p = 0.03) between the samples of Russians and Tatars were demonstrated. Russians and Bashkirs differed in the allele-frequency distribution of the rs861539 polymorphic locus of the XRCC3 gene (p < 0.0001), and Tatars and Bashkirs, at the rs861539 locus of the XRCC3 gene (p < 0.0001). In Russians and Tatars from the Republic of Bashkortostan, allele frequencies at the DNA repair gene polymorphic loci examined were consistent with those in the population of Northern and Western Europe, while polymorphic allele-frequency distributions in Bashkirs was similar to that observed in the ethnic group of Gujarati Indians.     

The XRCC2 and XRCC3 repair genes are required for chromosome stability in mammalian cells.

The irs1 and irs1SF hamster cell lines are mutated for the XRCC2 and XRCC3 genes, respectively. Both show heightened sensitivity to ionizing radiation and particularly to the DNA cross-linking chemical mitomycin C (MMC). Frequencies of spontaneous chromosomal aberration have previously been reported to be higher in these two cell lines than in parental, wild-type cell lines. Microcell-mediated chromosome transfer was used to introduce complementing or non-complementing human chromosomes into each cell line. irs1 cells received human chromosome 7 (which contains the human XRCC2 gene) or, as a control, human chromosome 4. irs1SF cells received human chromosome 14 (which contains the XRCC3 gene) or human chromosome 7. For each set of hybrid cell lines, clones carrying the complementing human chromosome recovered MMC resistance to near-wild-type levels, while control clones carrying noncomplementing chromosomes remained sensitive to MMC. Fluorescence in situ hybridization with a human-specific probe revealed that the human chromosome in complemented clones remained intact in almost all cells even after extended passage. However, the human chromosome in noncomplemented clones frequently underwent chromosome rearrangements including breaks, deletions, and translocations. Chromosome aberrations accumulated slowly in the noncomplemented clones over subsequent passages, with some particular deletions and unbalanced translocations persistently transmitted throughout individual subclones. Our results indicate that the XRCC2 and XRCC3 genes, which are now considered members of the RAD51 gene family, play essential roles in maintaining chromosome stability during cell division. This may reflect roles in DNA repair, possibly via homologous recombination.     

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

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

DNA repair genes XRCC1 and XRCC3 polymorphisms and their relationship with the level of micronuclei in breast cancer patients

Breast cancer (BC) is the most prevalent type worldwide, besides being one of the most common causes of death among women. It has been suggested that sporadic BC is most likely caused by low-penetrance genes, including those involved in DNA repair mechanisms. Furthermore, the accumulation of DNA damage may contribute to breast carcinogenesis. In the present study, the relationship between two DNA repair genes, viz., XRCC1 (Arg399Gln) and XRCC3 (Thr241Met) polymorphisms, and the levels of chromosome damage detected in 65 untreated BC women and 85 healthy controls, was investigated. Chromosome damage was evaluated through micronucleus assaying, and genotypes determined by PCR-RFLP methodology. The results showed no alteration in the risk of BC and DNA damage brought about by either XRCC1 (Arg399Gln) or XRCC3 (Thr241Met) action in either of the two groups. Nevertheless, on evaluating BC risk in women presenting levels of chromosome damage above the mean, the XRCC3Thr241Met polymorphism was found to be more frequent in the BC group than in the control, thereby leading to the conclusion that there is a slight association between XRCC3 (241 C/T) genotypes and BC risk in the subgroups with higher levels of chromosome damage.     

DNA repair XPCC1 and XPD genes polymorphism as associated with the development of bladder cancer and renal cell carcinoma

We examined the associations between the polymorphic alleles of the DNA repair genes XRCC1 (c.839G>A, rs25489; and c.1196A>G, rs25487), XPA (c.-4A>G, rs1800975), and XPD (c.2251A>C, rs13181) and the progression and severity of neoplasias in the urinary bladder and kidney in patients of three distinct ethnic groups, Bashkir, Russians, and Tatar, residing in the Republic of Bashkorostan. The study enrolled 468 cancer patients and 351 healthy individuals. Genotyping for polymorphic alleles was carried out using the PCR-RFLP method. We identified an association between allele A of the c.839G>A locus of the XRCC1 gene and the incidence of the bladder cancer (BC) and renal cell carcinoma (RCC) in the Tatar study group, using the additive genetic effects model (Odds Ratio (OR) = 5.23 and OR = 3.90). In turn, the heterozygous G/A genotype frequency was significantly higher in the RCC patients of Bashkir ethnic origin, compared with the control group (p = 0.0061, OR = 4.72). Additional analysis with consideration of participants smoking status showed that the G/A genotype is significantly more frequent in smokers with BC (OR = 1.96, p = 0.05) than in healthy smokers. We also determined, using the recessive genetic model, that the genotype A/A of the c.1196A>G locus of the XRCC1 gene was associated with a higher risk of BC in the Russian cohort (OR = 2.29, p = 0.0082) and an increased incidence of RCC in the Bashkir group (OR = 4.06, p = 0.05). A similar association was obtained for smokers. In contrast, the allele c.2251A>C in the XPD gene associated with a lower risk for BC and RCC in the Tatars (p = 0.0003, OR = 0.48 and p < 0.0001, OR = 0.37) in the additive model and in the Bashkirs (p = 0.0083, OR = 0.12) and Russians (p = 0.0001, OR = 0.14) in the recessive model. Further, we uncovered that polymorphism c.839G>A in the XRCC1 gene contributes to the progression of noninvasive and invasive BC and promotes RCC at early and advanced stages of the disease. Thus, we identified similar associations between DNA repair gene polymorphisms and the incidence and progression of BC and RCC. We propose that this result points to the involvement of common pathogenetic mechanisms in the initiation and progression of the urinary neoplasias.     

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

Radiation and Environmental Biophysics - Different types of DNA damages caused by ionizing radiation may enhance the cancer risk in exposed individuals. Inherited variations in DNA repair genes...     

Lymphocyte DNA adducts and polymorphism in the DNA repair enzyme XPD

The effect of genetic polymorphism of DNA repair enzyme on the DNA adduct levels was evaluated in this study. We explored the relationship between polymorphism in the nucleotide excision repair enzyme XPD and DNA adduct levels in lymphocytes. Lymphocyte DNA adducts were measured by a ³²     

Lymphocyte DNA adducts and polymorphism in the DNA repair enzyme XPD

The effect of genetic polymorphism of DNA repair enzyme on the DNA adduct levels was evaluated in this study. We explored the relationship between polymorphism in the nucleotide excision repair enzyme XPD and DNA adduct levels in lymphocytes. Lymphocyte DNA adducts were measured by a ³²     

Polymorphisms of DNA repair genes ERCC2 and XRCC1 in populations of Russia

We have conducted a comparative study of allele frequencies of single nucleotide polymorphisms (SNPs) rs1799793 and rs13181 of the ERCC2 gene as well as rs1799782 and rs25487 of the XRCC1 gene in population samples from European regions of Russia as well as in populations of Izhemsk and Priluzsk Komi and Yakuts. Significant differences in the distribution of polymorphic variants of the ERCC2 gene were demonstrated between populations of Yakuts and populations of Russians and Komi. In case of XRCC1 gene Izhemsk Komi population exhibited dissimilar allele frequencies compared to other populations.     

The XRCC genes: expanding roles in DNA double-strand break repair

Functional analysis of the XRCC genes continues to make an important contribution to the understanding of mammalian DNA double-strand break repair processes and mechanisms of genetic instability leading to cancer. New data implicate XRCC genes in long-standing questions, such as how homologous recombination (HR) intermediates are resolved and how DNA replication slows in the presence of damage (intra-S checkpoint). Examining the functions of XRCC genes involved in non-homologous end joining (NHEJ), paradoxical roles in repair fidelity and telomere maintenance have been found. Thus, XRCC5-7 (DNA-PK)-dependent NHEJ commonly occurs with fidelity, perhaps by aligning ends accurately in the absence of sequence microhomologies, but NHEJ-deficient mice show reduced frequencies of mutation. NHEJ activity seems to be involved in both mitigating and mediating telomere fusions; however, defective NHEJ can lead to telomere elongation, while loss of HR activity leads to telomere shortening. The correct functioning of XRCC genes involved in both HR and NHEJ is important for genetic stability, but loss of each pathway leads to different consequences, with defects in HR additionally leading to mitotic disruption and aneuploidy. Confirmation that these responses are likely to contribute to cancer induction and/or progression, is given by studies of humans and mice with XRCC gene disruptions: those affecting NHEJ show increased lymphoid tumours, while those affecting HR lead to breast cancer and perhaps to gynaecological tumours.     

The mammalian XRCC genes: their roles in DNA repair and genetic stability

Analysis of the XRCC genes has played an important part in understanding mammalian DNA repair processes, especially those involved in double-strand break (DSB) repair. Most of these genes were identified through their ability to correct DNA damage hypersensitivity in rodent cell lines, and they represent components of several different repair pathways including base-excision repair, non-homologous end joining, and homologous recombination. We document the phenotypic effects of mutation of the XRCC genes, and the current state of our knowledge of their functions. In addition to their continuing importance in discovering mechanisms of DNA repair, analysis of the XRCC genes is making a substantial contribution to the understanding of specific human disorders, including cancer.