Genetic Polymorphisms in XRCC1, CD3EAP, PPP1R13L, XPB, XPC, and XPF and the Risk of Chronic Benzene Poisoning in a Chinese Occupational Population

<div><p>Objectives</p><p>Individual variations in the capacity of DNA repair machinery to relieve benzene-induced DNA damage may be the key to developing chronic benzene poisoning (CBP), an increasingly prevalent occupational disease in China. ERCC1 (Excision repair cross complementation group 1) is located on chromosome 19q13.2–3 and participates in the crucial steps of Nucleotide Excision Repair (NER); moreover, we determined that one of its polymorphisms, ERCC1 rs11615, is a biomarker for CBP susceptibility in our previous report. Our aim is to further explore the deeper association between some genetic variations related to ERCC1 polymorphisms and CBP risk.</p><p>Methods</p><p>Nine single nucleotide polymorphisms (SNPs) of XRCC1 (X-ray repair cross-complementing 1), CD3EAP (CD3e molecule, epsilon associated protein), PPP1R13L (protein phosphatase 1, regulatory subunit 13 like), XPB (Xeroderma pigmentosum group B), XPC (Xeroderma pigmentosum group C) and XPF (Xeroderma pigmentosum group F) were genotyped by the Snapshot and TaqMan-MGB^® probe techniques, in a study involving 102 CBP patients and 204 controls. The potential interactions between these SNPs and lifestyle factors, such as smoking and drinking, were assessed using a stratified analysis.</p><p>Results</p><p>An XRCC1 allele, rs25487, was related to a higher risk of CBP (<i>P</i><0.001) even after stratifying for potential confounders. Carriers of the TT genotype of XRCC1 rs1799782 who were alcohol drinkers (OR = 8.000; 95% CI: 1.316–48.645; <i>P</i> = 0.022), male (OR = 9.333; 95% CI: 1.593–54.672; <i>P</i> = 0.019), and had an exposure of ≤12 years (OR = 2.612; 95% CI: 1.048–6.510; <i>P</i> = 0.035) had an increased risk of CBP. However, the T allele in PPP1R13L rs1005165 (P<0.05) and the GA allele in CD3EAP rs967591 (OR = 0.162; 95% CI: 0039~0.666; <i>P</i> = 0.037) decreased the risk of CBP in men. The haplotype analysis of XRCC1 indicated that XRCC1 rs25487^A, rs25489^G and rs1799782^T (OR = 15.469; 95% CI: 5.536–43.225; <i>P</i><0.001) were associated with a high risk of CBP.</p><p>Conclusions</p><p>The findings showed that the rs25487 and rs1799782 polymorphisms of XRCC1 may contribute to an individual’s susceptibility to CBP and may be used as valid biomarkers. Overall, the genes on chromosome 19q13.2–3 may have a special significance in the development of CBP in occupationally exposed Chinese populations.</p></div

DNA damage caused by B[a]P exposure detected by a modified comet assay.

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060006#pone-0060006-g002" target="_blank">Figure 2</a> shows a typical image to reflect the damage levels caused by BPDE-DNA adducts in a randomly selected sample. BPDE covalently binds to cellular DNA and forms interactive complexes. 50 µmol H₂O₂ was used to induce DNA fragmentation, resulting in long tails after electrophoreses in control lymphocytes (see Fig. 2A. control or non-exposed group). BPDE-DNA adducts will capture the short H₂O₂ induced DNA fragments, and consequently, a shorter tail olive (or tail area) will be found in BPDE-exposed cells compared to non-exposed cells (see Fig. 2B. BPDE-exposed group).</p

Association between <i>ERCC1</i> rs3212986 and <i>ERCC2</i> rs238406 polymorphisms and BPDE-DNA adducts stratified by age.

<p>Association between <i>ERCC1</i> rs3212986 and <i>ERCC2</i> rs238406 polymorphisms and BPDE-DNA adducts stratified by age.</p

Multiple covariates analysis for BPDE-DNA adduct.

<p><i>β_j</i> partial regression coefficient of multiple linear regression.</p><p><i>β_s</i> standardization partial regression coefficient of multiple linear regression.</p>d<p><i>P</i> value for the partial regression coefficient of all covariates to BPDE-DNA adduct levels using multiple linear regression.</p

<i>ERCC1</i>, <i>ERCC2</i> genotypes and BPDE-DNA adducts levels (, n = 282).

a<p><i>P</i> value was obtained using the LSD test or t-test analysis comparing with reference.</p>b<p><i>P</i> value was obtained using one-way ANVOA.</p

BPDE-DNA adducts levels and characteristics of study population (, n = 282).

a<p><i>P</i> value was obtained using the LSD test or t-test analysis comparing with reference.</p>b<p><i>P</i> value was obtained using one-way ANVOA.</p

Association between <i>ERCC1</i> rs3212986 and <i>ERCC2</i> rs238406 polymorphism and BPDE-DNA adducts stratified by smoking index.

<p>Smoking index 1: never smoking;</p><p>Smoking index = average cigarette numbers/day×years.</p

Chromatograms of blank, DNA, BPDE and DNA+BPDE solutions using HPLC-UV detection.

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060006#pone-0060006-g001" target="_blank">Figure 1</a> reflects the representive HPLC readouts. We used the Chromatograms to detect BPDE-DNA adducts level. The retention time of 9.38 minute was identified to be BPDE-DNA adducts.</p

Comparison of DNA damage caused by B[a]P in different combined minor alleles of ERCC1 rs3212986 and ERCC2 rs238406.

<p>We selected the participants carrying different ERCC1 rs3212986 and ERCC2 rs238406 genotypes and analyzed their induced DNA damage levels induced by B[a]P using the modified comet assay. The damage levels were evaluated by the tail olive moment ratio, tail area ratio and the combined holistic marking respectively. The relationship between the combined minor alleles of ERCC1 rs3212986 and ERCC2 rs238406 and the effect on the repair efficacy of the DNA damage level caused by B[a]P were evaluated. Interestingly, we found following the increasing copies of the combined minor alleles, a reduced DNA repair capacity had been found in the tail olive moment ratio, tail area ratio and the combined holistic marking. (<i>P</i><0.01).</p