DNA damage repair and genetic polymorphisms: Assessment of individual sensitivity and repair capacity

Effects of the XRCC1 gene-environment interactions on DNA damage in healthy Japanese workers

X-ray repair crosscomplementing group 1 (XRCC1) has a central role in base excision repair (BER) and single-strand break repair (SSBR). XRCC1 gene polymorphisms (codons 194, 280, and 399) have been identified, and in some cases have been reported to contribute to variations in DNA repair capacity and susceptibility to cancer. To further characterize the effects of XRCC1 gene polymorphisms and their possible interactions with environmental factors on individual levels of DNA damage, we investigated the XRCC1 genotypes of 222 healthy Japanese workers and analyzed data with respect to smoking, drinking habits, age, and health practice index (HPI). Our results showed that poor HPI would associate with a higher level of tail moment (TM). Individuals with one or two XRCC1(R280H) variant alleles exhibited significantly higher TM values, and these differences were enhanced by alcohol consumption and aging, whereas smoking and poor HPI may cover up the differences. On the other hand, using a stratified analysis, we found that the XRCC1(R194W) variant was associated with a higher TM value in the 40-50 year-old age group, and the XRCC1(R399Q) variant was associated with a lower TM value in the < or =20 pack-years group or in the 40-50 year-old age group. These data suggest that XRCC1 polymorphisms could influence individual DNA repair capacity by interacting with lifestyle factors, and specifically, the data indicated that the XRCC1(R280H) allele may be more important than codon 194 or 399 alleles.

Influence of DNA repair gene polymorphisms on the initial repair of MMS-induced DNA damage in human lymphocytes as measured by the alkaline comet assay

We have applied the alkaline comet assay to study the functional impact of gene polymorphisms in base excision repair (APEX1 Asp148Glu, XRCC1 Arg194Trp, XRCC1 Arg399Gln) and homologous recombination repair (XRCC3 Thr241Met, NBS1 Glu185Gln), two pathways that play crucial roles in the repair of DNA damage induced by methylmethane sulphonate (MMS). We also examined the effect of polymorphisms in mismatch repair (MLH1 -93 A/G) and nucleotide excision repair (XPD Lys751Gln) as putative negative controls based on the limited roles of these pathways in MMS-induced repair. Phytohemagglutinin-stimulated peripheral lymphocytes from 52 healthy individuals were treated with MMS and allowed to repair for 0, 15, 40, or 120 min after a 6-min washing step. DNA damage was measured as a pseudo-percentage score (comparable to % tail DNA) converted from a total visual score calculated from the distribution of cells with different degrees of damage (normal, mild, moderate and severe). The repair was faster at the beginning of the observation period than towards the end, and was not complete after 2 hr. Presence of the APEX1 148Asp, XRCC3 241Met or NBS1 185Gln alleles were significantly associated with a high pseudo-percentage score (above median) at early time points, with the APEX1 effect being most prolonged (up to 40 min after washing, odds ratio 5.6, 95% confidence interval 2.0-15.5). No significant effects were seen with the XRCC1 Arg194Trp, XRCC1 Arg399Gln, MLH1 -93A/G and XPD Lys751Gln polymorphisms. Our results provide evidence for the functional nature of the variant alleles studied in the APEX1, XRCC3, and NBS1 genes.

DNA repair gene polymorphisms may be associated with prognosis of upper urinary tract transitional cell carcinoma

Upper urinary tract transitional cell carcinoma (UUT-TCC) is quite an uncommon disease, and its prognosis differs among individuals irrespective of tumor stage. DNA repair gene polymorphisms are reported to result in the modulation of the repair capacity and might influence the prognosis of UUT-TCC. We examined the associations between functional polymorphisms in five DNA repair genes, and the prognosis of UUT-TCC in 103 UUT-TCC patients. Variant alleles in xeroderma pigmentosum complementation group C, more than three total variant alleles in all DNA repair genes studied and more than two total variant alleles in three nucleotide excision repair genes were independently associated with improved overall and disease-specific survival of UUT-TCC patients in multivariate analysis (P = .0063 and P = .0005 for xeroderma pigmentosum complementation group C, P = .016 and P = .0016 for all genes, and P = .0053 and P = .018 for nucleotide excision repair genes, respectively). These results suggest that some DNA repair gene polymorphisms may preoperatively be valuable as prognostic factors for UUT-TCC beyond tumor stage and grade, helping to provide optimal treatment strategies for individual patients.

XPC polymorphisms play a role in tissue-specific carcinogenesis: a meta-analysis

XPC participates in the initial recognition of DNA damage during the DNA nucleotide excision repair process in global genomic repair. Polymorphisms in XPC gene have been analyzed in case-control studies to assess the cancer risk attributed to these variants, but results are conflicting. To clarify the impact of XPC polymorphisms in cancer risk, we performed a meta-analysis that included 33 published case-control studies. Polymorphisms analyzed were Lys939Gln and Ala499Val. The overall summary odds ratio (OR) for the associations of the 939Gln/Gln genotype with risk of cancer was 1.01 (95% confidence interval (95% CI): 0.94-1.09), but there were statistically significant associations for lung cancer, observed for the recessive genetic model (Lys/Lys+Lys/Gln vs Gln/Gln), (OR 1.30; 95% CI: 1.113-1.53), whereas for breast cancer a reduced but nonsignificant risk was observed for the same model (OR 0.87; 95% CI: 0.74-1.01). The results for Ala499Val showed a significant overall increase in cancer risk (OR 1.15; 95% CI: 1.02-1.31), and for bladder cancer in both the simple genetic model (Ala/Ala vs Val/Val) (OR 1.30; 95% CI: 1.04-1.61) and the recessive genetic model (Ala/Ala+Ala/Val vs Val/Val) (OR 1.32; 95% CI: 1.06-1.63). Our meta-analysis supports that polymorphisms in XPC may represent low-penetrance susceptibility gene variants for breast, bladder, head and neck, and lung cancer. XPC is a good candidate for large-scale epidemiological case-control studies that may lead to improvement in the management of highly prevalent cancers.

Polymorphism of XRCC1 and the frequency of mutation in codon 249 of the p 53 gene in hepatocellular carcinoma among guangxi population, China

In hepatocellular carcinoma (HCC), hotspot mutation in codon 249 of the p53 gene has been associated with exposure to aflatoxin B1 (AFB1). While the polymorphism of DNA repair gene X-ray repair cross-complementary group 1 (XRCC1) Arg399Gln may be related with AFB1-DNA adducts and gene mutations. Five hundred one HCCs were included in this study to investigate the role of the XRCC1 codon 399 polymorphism on hotspot mutation in codon 249 of the p53 gene. The genotypes of XRCC1 codon 399 and p53 codon 249 were examined by PCR-RFLP. The HCC patients with XRCC1 genotypes with 399 Gln (namely: XRCC1-AG/GG) exhibited a significantly higher frequency of the p53 hotspot mutations in codon 249 than those with the wild-type homozygote of XRCC1 [namely: XRCC1-AA, adjusted odds ratio (OR) = 6.77, 95% confidence interval (CI) = 4.34-10.57]. Compared with those individuals who did express XRCC1-AA as reference (OR = 1), moreover, individuals featuring XRCC1-AG/GG and AFB1-DNA adducts did experience a significantly greater frequency of the hotspot mutation in codon 249 of the p53 gene (adjusted OR = 28.37, 95% CI = 13.19-61.02, P < 0.01). This study suggests that the XRCC1 Arg399Gln polymorphism and AFB1-DNA adducts are associated with the increased frequency of the p53 mutations in codon 249.

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.

The association of DNA repair gene polymorphisms with the development and progression of renal cell carcinoma

BACKGROUND

DNA repair enzymes repair some of the DNA damage associated with risk factors for renal cell carcinoma (RCC), including smoking. DNA repair gene polymorphisms modulate the repair capacity and might influence individual risk and progression of RCC. We examined associations between functional polymorphisms and risk, clinicopathologic characteristics and survival of RCC.

PATIENTS AND METHODS

The study groups comprised 215 RCC patients and 215 age- and gender-matched healthy controls. Polymorphisms in xeroderma pigmentosum complementation groups C, D and G and X-ray repair cross-complementing groups 1 and 3 genes were genotyped.

RESULTS

No significant differences in DNA repair genotype were observed between RCC cases and controls. In all patients, however, greater numbers (> or =3) of total variant alleles in all DNA repair genes studied were associated with less frequent venous extension (P = 0.0079). In smokers, some genotypes were associated with characteristics of RCC (Ps < or = 0.0067) and smokers with greater numbers of total variant alleles had improved overall survival (P = 0.040).

CONCLUSION

These results suggest that DNA repair gene polymorphisms may not influence RCC susceptibility, but that some of them may influence RCC progression, especially in smokers, possibly due to altered DNA repair capacity by these polymorphisms.

Polymorphisms of DNA repair genes are risk factors for prostate cancer

DNA repair gene alterations have been shown to cause a reduction in DNA repair capacity. We hypothesised that DNA repair gene polymorphisms may be risk factors for prostate cancer (PC). To test this hypothesis, DNA samples from 165 cases of prostate cancer and healthy controls were analyzed by PCR-RFLP to determine the genotypic frequency of three DNA repair genes (XRCC1, XPC and XRCC7). We found that the frequency of 939Gln variant at XPC Lys939Gln was significantly lower in PC cases (OR=0.39, P=0.016). Haplotype analysis of XRCC1 Arg194Trp (C/T) and Arg399Gln (G/A) revealed that the frequency of the T-A haplotype was significantly higher in PC patients. This is the first report on the studies of XPC and XRCC1 Arg194Trp polymorphisms in PC, and our present data suggest that XPC Lys939Gln and the T-A haplotype of XRCC1 Arg194Trp and Arg399Gln may be risk factors for PC in Japanese.