The DNA repair gene XPD/ERCC2 polymorphisms Arg156Arg (exon 6) and Lys751Gln (exon 23) are closely associated

Use a survival model to correlate single-nucleotide polymorphisms of DNA repair genes with radiation dose-response in patients with non-small cell lung cancer

PURPOSE

This study utilizes a survival model and clinical data with various radiation doses from prospective trials to determine radiation dose-response parameters, such as radiosensitivity, and identify single-nucleotide-polymorphism (SNP) biomarkers that can potentially predict the dose response and guide personalized radiotherapy.

METHODS

The study included 92 consecutive stage-III NSCLC patients with doses varying from 60 to 91Gy. Logistic regression analysis of survival varying with SNP genotype and radiation dose was used to screen candidates for dose-response analysis. The dose-response parameter, represented by D50, was derived by fitting survival data into a model that takes into account both tumor control and treatment mortality. A candidate would be considered as a predictor if the 90% confident intervals (90% CIs) of D50 for the 2 groups stratified by the SNP genotype were separated.

RESULTS

One SNP-signature (combining ERCC2:rs238406 and ERCC1:rs11615) was found to predict dose-response. D50 values are 63.7 (90% CI: 53.5-66.3) Gy and 76.1 (90% CI: 71.3, 84.6) Gy for the 2 groups stratified by the genotypes. Using this biomarker-based model, a personalized dose prescription may be generated to improve 2-year survival from ∼50% to 85% and ∼3% to 73% for hypothetical sensitive and resistant patients, respectively.

CONCLUSIONS

We have developed a survival model that may be used to identify genomic markers, such as ERCC1/2 SNPs, to predict radiation dose-response and potentially guide personalized radiotherapy.

Excision repair cross-complementing group 2/Xeroderma pigmentousm complementation group D (ERCC2/XPD) genetic variations and susceptibility to diffuse large B cell lymphoma in Egypt

Diffuse large B-cell lymphoma (DLBCL) is a genetically heterogeneous neoplasm. Although several genetic and environmental factors have been postulated, no obvious risk factors have been emerged for DLBCL in the general population. DNA repair systems are responsible for maintaining the integrity of the genome and protecting it against genetic alterations that can lead to malignant transformation. The current study aimed at investigating the possible role of ERCC2/XPD Arg156Arg, Asp312Asn and Lys751Gln genetic polymorphisms as risk factors for DLBCL in Egypt. The study included 81 DLBCL patients and 100 healthy controls. Genotyping of the studied genetic polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism technique. Our results revealed that there was no statistical difference encountered in the distribution of -Asp312Asn and -Lys751Gln polymorphic genotypes between DLBCL cases and controls, thus it could not considered as molecular risk factors for DLBCL in Egyptians. However, Arg156Arg polymorphism at exon-6 conferred twofold increased risk of DLBCL (OR 2.034, 95 %CI 1.015-4.35, p = 0.43), and the risk increased when co-inherited with Lys751Gln at exon-23 (OR 3.304, 95 %CI 1.113-9.812, p = 0.038). In conclusion, ERCC2/XPD Arg156Arg polymorphism might be considered as a genetic risk factor for DLBCL in Egyptians, whether alone or conjoined with Lys751Gln.

ERCC1 and ERCC2 haplotype modulates induced BPDE-DNA adducts in primary cultured lymphocytes

Background

Benzo[a]pyrene(B[a]P), and its ultimate metabolite Benzo[a]pyrene 7,8-diol 9,10-epoxide (BPDE), are classic DNA damaging carcinogens. DNA damage caused by BPDE is normally repaired by Nucleotide Excision Repair (NER), of which ERCC1 and ERCC2/XPD exert an indispensable role. Genetic variations in ERCC1 and ERCC2 have been related to DNA repair efficiency. In this study we used lymphocytes from healthy individuals to show that polymorphisms in ERCC1 and ERCC2 are directly associated with decreased DNA repair efficiency.

Methods

ERCC1 (rs3212986 and rs11615) and ERCC2 (rs13181, rs1799793 and rs238406) were genotyped in 818 healthy Han individuals from the northeast of China. BPDE induced DNA adducts in lymphocytes were assessed by high performance liquid chromatography (HPLC) in 282 randomly selected participants. The effect of ERCC1 rs3212986 and ERCC2 rs238406 on DNA damage caused by B[a]P was assessed with a modified comet assay.

Results

We found that the variant genotypes of ERCC1 rs3212986 and ERCC2 rs238406 were associated with the high levels of BPDE-DNA adducts. Especially ERCC1 rs3212986 A-allele variant was significantly associated with the high BPDE-DNA adducts. Haplotype analysis showed that the ERCC1 haplotype AC (OR = 2.36, 95% CI = 1.84–2.97), ERCC2 haplotype AGA (OR = 1.51, 95% CI = 1.06–2.15) and haplotype block AGAAC (OR = 5.28, 95% CI = 2.95–9.43), AGCAC (OR = 1.35 95% CI = 1.13–1.60) were linked with high BPDE-DNA adducts. In addition, we found that the combined minor alleles of ERCC1 rs3212986 and ERCC2 rs238406 were associated with a reduced DNA repair capacity.

Conclusions

Our results suggest that the variant genotypes of ERCC1 rs3212986 and ERCC2 rs238406 are associated with decreased repair efficiency of BPDE induced DNA damage, and may be predictive for an individual’s DNA repair capacity in response to environmental carcinogens.

DNA Repair Gene Polymorphisms in the Nucleotide Excision Repair Pathway and Lung Cancer Risk: A Meta-analysis

OBJECTIVE

A number of studies have reported the association of "XPA", "XPC", "XPD/ERCC2" gene polymorphisms with lung cancer risk. However, the results were conflict. To clarify the impact of polymorphisms of "XPA", "XPC", "XPD/ERCC2", on lung cancer risk, a meta-analysis was performed in this study.

METHODS

The electronic databases PubMed and Embase were retrieved for studies included in this meta-analysis by "XPA", "XPC", "XPD/ERCC2", "lung", "cancer/neoplasm/tumor/carcinoma", "polymorphism" (An upper date limit of October, 31, 2009). A meta-analysis was performed to evaluate the relationship among XPA, XPC and XPD polymorphism and lung cancer risks.

RESULTS

A total of 31 publications retrieved from Pubmed and Embase included in this study. XPC A939C CC genotype increased lung cancer risk in total population (recessive genetic model: OR=1.23, 95% CI:1.05-1.44; homozygote comparison: OR=1.21,95%CI:1.02-1.43and CC vs. CA contrast: OR=1.25,95%CI:1.06-1.48), except in Asians. XPD A751C, 751C allele and CC genotype also increased lung cancer risk in total population and in Caucasians (recessive genetic model: Total population: OR=1.20, 95%CI:1.07-1.35). No significant correlation was found between XPD A751C and lung cancer risk in Asians and African Americans. XPD G312A AA genotype increased lung cancer risk in total population, in Asians and Caucasians(recessive genetic model: Total population: OR=1.20, 95%CI: 1.06-1.36). No significant association was found between XPA G23A, XPC C499T, XPD C156A and lung cancer risk.

CONCLUSION

Our results suggest that the polymorphisms in XPC and XPD involve in lung cancer risks. XPA polymorphisms is less related to lung cancer risk.

Effects of selected genetic polymorphisms in xeroderma pigmentosum complementary group D on gastric cancer

DNA repair capacity (DRC) can be altered based on sequence variations in DNA repair genes, which may result in cancer susceptibility. The current study was to evaluate the association between genetic polymorphisms, including associated haplotypes of xeroderma pigmentosum complementary group D (XPD), and individual susceptibility to gastric cancer. Two-hundred-eight patients with gastric cancer and 339 healthy controls were enrolled in this study. Their genomic DNA was extracted from peripheral blood leukocytes. The genotypes at exon 6, 10 and 23 were identified by polymerase chain reaction (PCR). Unconditional logistic regression model was used to analyze the effects of the polymorphisms, including the corresponding haplotypes, on the susceptibility to develop gastric cancer. The proportion of genotypes GA or AA at exon 10 in cases was showed to be significantly higher than that in controls (P < 0.01, P < 0.01, respectively). The risk of genotype GA or AA carriers to develop gastric cancer was simultaneously much higher (OR = 3.38, 95% CI 2.30-4.95; OR = 6.13, 95% CI 2.45-15.31, respectively). The allele A at exon 10 was also observed to manifest a substantially higher frequency in cases compared to controls (P < 0.01), which might indicate an increased tendency to gastric cancer (OR = 2.40, 95% CI 1.81-3.17). No significant differences were found in the distribution of genotypes at exon 6 or 23 between the two groups (P = 0.23, P = 0.52; P = 0.44, P = 0.56, respectively). By haplotype analysis, haplotype AAA could individually increase incidence of gastric cancer (P < 0.01, OR = 3.39, 95% CI 2.21-5.21). In contrast, haplotypes CGA and AGA were showed a decline in gastric cancer susceptibility (OR = 0.67, 95% CI 0.46-0.97; OR = 0.58, 95% CI 0.41-0.83, respectively). The rest of haplotypes made no statistically significant difference between cases and controls. Taken together, this study demonstrates that the genetic variation at exon 10 and haplotype AAA may be contributing factors in developing gastric cancer.

Oxidative damage to biological macromolecules in Prague bus drivers and garagemen: impact of air pollution and genetic polymorphisms

DNA integrity was investigated in the lymphocytes of 50 bus drivers, 20 garagemen and 50 controls using the comet assay with excision repair enzymes. In parallel, 8-oxo-7,8-dihydro-2'-deoxyguanosine and 15-F(2t)-isoprostane levels in the urine and protein carbonyl levels in the plasma were assessed as markers of oxidative damage to DNA, lipids and proteins. Exposure to carcinogenic polycyclic aromatic hydrocarbons (cPAHs) and volatile compounds was measured by personal samplers for 48 and 24h, respectively, before the collection of biological specimens. Both exposed groups exhibited a higher levels of DNA instability and oxidative damage to biological macromolecules than the controls. The incidence of oxidized lesions in lymphocyte DNA, but not the urinary levels of 8-oxodG, correlated with exposure to benzene and triglycerides increased this damage. Oxidative damage to lipids and proteins was associated with exposure to cPAHs and the lipid peroxidation levels positively correlated with age and LDL cholesterol, and negatively with vitamin C. The carriers of at least one variant hOGG1 (Cys) allele tended to higher oxidative damage to lymphocyte DNA than those with the wild genotype, while XPD23 (Gln/Gln) homozygotes were more susceptible to the induction of DNA strand breaks. In contrast, GSTM1 null variant seemed to protect DNA integrity.

The polymorphism of DNA repair gene ERCC2/XPD Arg156Arg and susceptibility to breast cancer in a Chinese population

Polymorphisms in DNA repair genes are good candidates for modifying cancer risk. ERCC2/XPD, a gene involved in nucleotide excision repair and basal transcription, may influence individual DNA repair capacity, particularly of bulky adducts. This is implicated in cancer susceptibility. To detect the association between ERCC2/XPD Arg156Arg and susceptibility to breast cancer in a Chinese population, we conducted a hospital-based case-control study consisting of 129 patients with breast cancer and 205 controls matched by age, gender, and ethnicity. PCR-RFLP was used for genotyping. No associations were found between ERCC2/XPD Arg156Arg and risk of breast cancer (AA/AC versus CC: OR = 0.79, 95% CI = 0.49-1.28, P = 0.33; AA versus CC: OR = 0.89, 95% CI = 0.49-1.63, P = 0.72; AC versus CC: OR = 0.74, 95% CI = 0.44-1.24, P = 0.25). Breast cancer cases with the variant AA genotype were marginally younger (mean age 45 years) than cases with the wild CC genotype (mean age 50 years) (P = 0.05). There were no differences in risk estimates in relation to menopause and occurrence of breast cancer. Our findings do not suggest that ERCC2/XPD Arg156Arg contributes to breast cancer susceptibility in a Chinese population.