Contrasting impact of DNA repair gene XRCC1 polymorphisms Arg399Gln and Arg194Trp on the risk of lung cancer in the north-Indian population

Cytokinesis-block micronucleus cytome (CBMN-CYT) assay and its relationship with genetic polymorphisms in welders

Fumes generated in the welding process are composed of micrometric and nanometric particles that form when metal fumes condense. The International Agency for Research on Cancer established that many compounds derived from the welding process are carcinogenic to humans. Still, there are few studies related to the role of genetic polymorphisms. This work aimed to analyze the influence of OGG1 Ser326Cys, XRCC1 Arg280His, XRCC1 Arg194Thr, XRCC1 Arg399Gln, XRCC3 Thr241Met, GSTM1, and GSTT1 gene polymorphisms on DNA damage of 98 subjects occupationally exposed to welding fumes and 100 non exposed individuals. The results showed that individuals exposed to welding fumes with XRCC3 Thr241Thr, XRCC3 Thr241Met, and GSTM1 null genotypes demonstrated a significantly higher micronucleus frequency in lymphocytes. In contrast, individuals with XRCC1 Arg399Gln and XRCC1 Gln399Gln genotypes had significant levels of NPBs. OGG1 326 Ser/Cys, OGG1 326 Cys/Cys, XRCC1 194Arg/Thr, XRCC1 194Thr/Thr, and GSTT1 null genotypes exhibited significantly higher apoptotic values. Also, XRCC1 194Arg/Trp, XRCC1 194Thr/Thr, and GSTM1 null genotype carriers had higher necrotic levels compared to XRCC1 194Arg/Arg and GSTM1 nonnull carriers. Compositional analysis revealed the presence of iron, manganese, silicon as well as particles smaller than 2 μm that adhere to each other and form agglomerates. These results may be associated with a mixture of components, such as nitrogen dioxide, carbon monoxide, and metallic fumes, leading to significant DNA damage and cell death processes. These findings demonstrated the importance of the association between individual susceptibility and DNA damage levels due to occupational exposure to welding fumes; and constitute one of the first studies carried out in exposed workers from Colombia.

Impact of single nucleotide polymorphisms in the OGG1 and XRCC1 genes on modulation of DNA damage in pesticide-exposed agricultural workers in Punjab, North-West India

Pesticide-induced DNA damage is primarily repaired by base excision repair (BER) pathway. However, polymorphism in DNA repair genes may modulate individual's DNA repair capacity (DRC) leading to increased genotoxicity and adverse health effects. Our first study in North-West Indian population aimed to evaluate the impact of OGG1 rs1052133 (Ser326Cys; C1245G), XRCC1 rs1799782 (Arg194Trp; C26304T) and XRCC1 rs25487 (Arg399Gln; G28152A) polymorphisms on the modulation of pesticide-induced DNA damage in a total of 450 subjects (225 pesticide-exposed agricultural workers and 225 age- and sex-matched controls). DNA damage was estimated by alkaline comet assay using silver-staining method. Genotyping was carried out by PCR-RFLP using site-specific restriction enzymes. Mann-Whitney U-test revealed elevation in DNA damage parameters (p < 0.01) in pesticide-exposed agricultural workers than controls. Chi-square test showed significant (p < 0.05) differences in the XRCC1 Arg194Trp (C26304T) and Arg399Gln (G28152A) genotypes among two groups. Multivariate logistic-regression analysis revealed that heterozygous genotypes of OGG1 rs1052133 (326Ser/Cys; 1245CA), XRCC1 rs1799782 (194Arg/Trp; 26304CT) and XRCC1 rs25487 (399Arg/Gln; 2815GA) were positively associated (p < 0.05) with elevated DNA damage parameters in pesticide-exposed agricultural workers. Our results strongly indicate significant positive association of variant OGG1 and XRCC1 genotypes with reduced DRC and higher pesticide-induced DNA damage in North-West Indian agricultural workers.

Genetic Variant XRCC1 rs1799782 (C194T) and Risk of Cancer Susceptibility in Indian Population: A Meta-analysis of Case-Control Studies

X-ray repair cross-complementing group 1 (XRCC1) plays a key role in the base excision repair pathway, as a scaffold protein that brings together proteins of the DNA repair complex. Several studies have reported contradictory results for XRCC1 exon 6 C>T (rs1799782) gene polymorphism and cancer risk in Indian population has provided inconsistent results. Therefore, we have performed this meta-analysis to evaluate the relationship between XRCC1 exon 6 C>T gene polymorphism and risk of cancer by published studies. We searched PubMed and Google scholar web databases to cover all studies published on association between XRCC1 exon 6 C>T gene polymorphism and cancer risk. The meta-analysis was carried out and pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to appraise the strength of association. In order to derive a more precise estimation of the association, A total of 3197 confirmed cancer cases and 3819 controls were included from eligible seventeen case-controls studies. Results from overall pooled analysis demonstrated suggested that that variant allele (T vs. C: OR 1.301, 95% CI 1.003-1.688, p = 0.047) was associated with the risk of overall cancer. Other genetic models; heterozygous (TC vs. CC: OR 1.108, 95% CI 0.827-1.485, p = 0.491), homozygous (TT vs. CC: OR 1.479, 95% CI 0.877-2.493, p = 0.142), dominant (TT+TC vs. CC: OR 1.228, 95% CI 0.899-1.677, p = 0.196) and recessive (TT vs. TC+CC: OR 1.436, 95% CI 0.970-2.125, p = 0.071) did not reveal statistical association. Publication bias observation was also considered and none was detected during the analysis. The present meta-analysis suggested that the variant allele T of XRCC1 exon 6 gene polymorphism was associated with the risk of cancer. It is therefore pertinent to confirm this finding in a large sample size to divulge the mechanism of this polymorphism and cancer risk in Indian population.

Association of 12 polymorphic variants conferring genetic risk to lung cancer in Indian population: An extensive meta-analysis

Candidate gene as well as genome-wide association studies identified several polymorphic variants to be associated with lung cancer worldwide including in India. However, contradictory results have failed to estimate the overall effect of the polymorphic variants on the disease. Textmining was conducted on PubMed following specific search strings to gather all the publications related to genetic association with lung cancer in India. Out of 211 PubMed hits only 30 studies were selected for meta-analysis following specific inclusion criteria. Heterogeneity between studies was calculated by Cochran's Q-test (P < 0.05) and heterogeneity index (I² ). Publication bias was visualized by funnel plots and Egger's regression test. For each variant, following a fixed-effect model, summary odds ratio (OR) along with 95% confidence interval (CI) was estimated. The meta-analysis revealed three polymorphic variants viz. 'deletion polymorphism (del1) (OR = 1.39, 95% CI = 1.03-1.87, P = 0.027) in GSTT1', 'deletion polymorphism (del2) (OR = 1.30, 95% CI = 1.01-1.67, P = 0.038) in GSTM1' and 'rs1048943 (OR = 1.98, 95% CI = 1.27-3.10, P = 0.002) in CYP1A1' to be associated with lung cancer. However, after multiple testing correction, only rs1048943 was found to be significantly associated (P value = 0.0321) with lung cancer. None of the polymorphic variants showed any evidence of heterogeneity between studies or of publication bias. Our meta-analysis revealed strong association of rs1048943 in CYP1A1, but a suggestive association of deletion polymorphisms in GSTT1 and GSTM1 with lung cancer, which provides a comprehensive insight on the overall effect of the polymorphic variants, reported in various case-control studies on Indian population, on the risk of lung cancer development. Environ. Mol. Mutagen. 58:688-700, 2017. © 2017 Wiley Periodicals, Inc.

Genetic variants of SULT1A1 and XRCC1 genes and risk of lung cancer in Bangladeshi population

Lung cancer is one of the most frequently occurring cancers throughout the world as well as in Bangladesh. This study aimed to correlate the prognostic and/or predictive value of functional polymorphisms in SULT1A1 (rs9282861) and XRCC1 (rs25487) genes and lung cancer risk in Bangladeshi population. A case-control study was conducted which comprises 202 lung cancer patients and 242 healthy volunteers taking into account the age, sex, and smoking status. After isolation of genomic DNA, genotyping was done by polymerase chain reaction-restriction fragment length polymorphism method and the lung cancer risk was evaluated as odds ratio that was adjusted for age, sex, and smoking status. A significant association was found between SULT1A1 rs9282861 and XRCC1 rs25487 polymorphisms and lung cancer risk. In case of rs9282861 polymorphism, Arg/His (adjusted odds ratio = 5.06, 95% confidence interval = 3.05-8.41, p < 0.05) and His/His (adjusted odds ratio = 3.88, 95% confidence interval = 2.20-6.82, p < 0.05) genotypes were strongly associated with increased risk of lung cancer in comparison to the Arg/Arg genotype. In case of rs25487 polymorphism, Arg/Gln heterozygote (adjusted odds ratio = 4.57, 95% confidence interval = 2.79-7.46, p < 0.05) and Gln/Gln mutant homozygote (adjusted odds ratio = 4.99, 95% confidence interval = 2.66-9.36, p < 0.05) were also found to be significantly associated with increased risk of lung cancer. This study demonstrates that the presence of His allele and Gln allele in case of SULT1A1 rs9282861 and XRCC1 rs25487, respectively, involve in lung cancer prognosis in Bangladeshi population.

Genetic Variant Arg399Gln G>A of XRCC1 DNA Repair Gene Enhanced Cancer Risk Among Indian Population: Evidence from Meta-analysis and Trial Sequence Analyses

The X-ray repair cross-complementation group 1 (XRCC1) gene plays an important role in base excision repair pathway. Several studies have reported contradictory results for XRCC1 exon 10 (Arg399Gln, G23990A, rs25487) gene polymorphism and cancer risk in Indian population, making it difficult to interpret them. Therefore, we have conducted a meta-analysis to evaluate the more precise association between XRCC1 exon 10 G>A gene polymorphism and risk of cancer by published studies. We searched PubMed (Medline) and Google scholar web databases to cover all studies published on association between XRCC1 exon 10 G>A gene polymorphism and cancer risk until August 2016. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to appraise the strength of association. Heterogeneity, publication bias and sensitivity analysis were also assessed. Twenty-five published studies had fulfilled the inclusion criteria comprising 4131 confirmed cancer cases and 5013 controls. When all studies were polled together, overall significant association was found between XRCC1 exon 10 G>A polymorphism and cancer risk in variant allele carrier (A vs. G: OR 1.217, 95% CI 1.056-1.402, p = 0.007), homozygous (AA vs. GG: OR 1.359, 95% CI 1.036-1.783, p = 0.027), dominant (AA+AG vs. GG OR 1.208, 95% CI 1.006-1.450, p = 0.043) and recessive (AA vs. AG+GG: OR 1.315, 95% CI 1.029-1.680, p = 0.029) genetic models. Further sensitivity analysis supported the stability of our result by showing similar ORs before and after removal of a single study. The present meta-analysis suggested that the XRCC1 exon 10 G>A polymorphism contribute cancer risk in Indian population, and supports that individuals with risk allele A and AA genotype are at higher risk of developing cancer.

Variant Alleles in XRCC1 Arg194Trp and Arg399Gln Polymorphisms Increase Risk of Gastrointestinal Cancer in Sabah, North Borneo

BACKGROUND

The XRCC1 protein facilitates various DNA repair pathways; single-nucleotide polymorphisms (SNPs) in this gene are associated with a risk of gastrointestinal cancer (GIC) with inconsistent results, but no data have been previously reported for the Sabah, North Borneo, population. We accordingly investigated the XRCC1 Arg194Trp and Arg399Gln SNPs in terms of GIC risk in Sabah.

MATERIALS AND METHODS

We performed genotyping for both SNPs for 250 GIC patients and 572 healthy volunteers using a polymerase chain reaction- restriction fragment length polymorphism approach. We validated heterozygosity and homozygosity for both SNPs using direct sequencing.

RESULTS

The presence of a variant 194Trp allele in the Arg194Trp SNP was significantly associated with a higher risk of GIC, especially with gastric and colorectal cancers. We additionally found that the variant 399Gln allele in Arg399Gln SNP was associated with a greater risk of developing gastric cancer. Our combined analysis revealed that inheritance of variant alleles in both SNPs increased the GIC risk in Sabah population. Based on our etiological analysis, we found that subjects ≥50 years and males who carrying the variant 194Trp allele, and Bajau subjects carrying the 399Gln allele had a significantly increased risk of GIC.

CONCLUSIONS

Our findings suggest that inheritance of variant alleles in XRCC1 Arg194Trp and Arg399Gln SNPs may act as biomarkers for the early detection of GIC, especially for gastric and colorectal cancers in the Sabah population.

Association and multiple interaction analysis among five XRCC1 polymorphic variants in modulating lung cancer risk in North Indian population

XRCC1 is a scaffold protein that provides for interaction of DNA polymerase, DNA ligase and damaged DNA. Genotyping was done for the five non-synonymous and synonymous variants of XRCC1 i.e. XRCC1, Arg¹⁹⁴Trp, Pro²⁰⁶Pro, Arg²⁸⁰His, Arg³⁹⁹Gln, Gln⁶³²Gln. Logistic regression analysis was used to analyze the association of XRCC1 with lung cancer, followed by data mining analysis which included both Multi-dimensionality reduction (MDR) and Classification and Regression tree (CART) analysis so as to find possible interaction between SNPs on XRCC1 gene. Statistical analysis revealed XRCC1 Gln⁶³²Gln (OR=2.67, p=<0.001) depicted an overall high risk towards lung cancer. Histological subdivision revealed carriers of mutant genotype in case of XRCC1 Arg³⁹⁹Gln imposed a protective effect towards SQCC subtype. Likewise, mutant genotype in XRCC1 Pro²⁰⁶Pro implied a protective effect for SCLC subtype (OR=0.29, p=0.0017) on the contrary XRCC1 Gln⁶³²Gln showed a high risk in SQCC diseased group (OR=4.16, p=<0.0001). Combination of XRCC1 Gln⁶³²Gln with other SNPs revealed XRCC1 Gln⁶³²Gln with Arg¹⁹⁴Trp (OR=2.10, p=0.03) and Pro²⁰⁶Pro (OR=5.6, p<0.0004) increased an overall risk towards lung cancer. Haplotype analysis illustrated haplotype block 11 (CGAGG) carrying minor allele for XRCC1 206 was associated with the highest risk towards lung cancer on the contrary block 4 (CAGAG) carrying mutant allele for XRCC1 399 significantly decreased the risk. Multi-dimensionality reduction (MDR) results showed the three factor model comprising XRCC1 206, 632, 280 as the best model (CVC=10, prediction error=0.34). Further Classification and Regression tree (CART) analysis revealed terminal node 1 carrying mutant of XRCC1 632 and wild type of XRCC1 280 represented the highest risk group. Our results demonstrated high order interaction between SNPs of XRCC1 gene. This study depicted a positive association of XRCC1 Gln⁶³²Gln towards lung cancer, however XRCC1 Arg³⁹⁹Gln, Arg¹⁹⁴Trp showed an overall no effect or protective effect.

The Use of Poly-L-Lysine as a Capture Agent to Enhance the Detection of Antinuclear Antibodies by ELISA

Antibodies to nuclear antigens (antinuclear antibodies or ANAs) are the serological hallmark of systemic lupus erythematosus (SLE). These antibodies bind diverse nuclear antigens that include DNA, histones and non-histone proteins as well as complexes of proteins with DNA and RNA. Because of the frequency of ANA expression in SLE, testing is an important component of clinical evaluation as well as determination of eligibility for clinical trials or utilization of certain therapies. Immunofluorescence assays have been commonly used for this purpose although this approach can be limited by issues of throughput, variability and difficulty in determining positivity. ELISA and multiplex assays are also useful approaches although these assays may give an incomplete picture of antibodies present. To develop a sensitive and quantitative ANA assay, we have explored an ELISA platform in which plates are pre-coated with a positively charged nucleic acid binding polymer (NABP) to increase adherence of antigens containing DNA or RNA. As a source of antigens, we have used supernatants of Jurkat cells undergoing apoptosis in vitro. As results presented show, a poly-L-lysine (PLL) pre-coat significantly enhances detection of antibodies to DNA as well as antigens such as histones, SSA, SSB and RNP. Comparison of the ELISA assay with the PLL pre-coat with a multiplex assay using the BioPlex^® 2200 system indicated good agreement in results for a panel of lupus sera. Together, these studies indicate that a pre-coat with a positively charged polymer can increase the sensitivity of an ANA ELISA using as antigens molecules released from dead and dying cells. This assay platform may facilitate ANA testing by providing an ensemble of antigens more similar in composition and structure with antigens present in vivo, with a NABP promoting adherence via charge-charge interactions.

Arg194–Arg399 haplotype of XRCC1 gene is susceptible to lung cancer in the Han population

Objective:

Lung cancer is still one of the most frequently diagnosed cancers all over the world, especially in developing countries. The aim of this study was to investigate the relationship between two well-characterized non-synonymous polymorphisms (Arg194Trp and Arg399Gln) in X-ray repair cross-complementing group 1 ( XRCC1) gene and the risk of lung carcinoma in the Han population.

Methods:

This study was hospital-based in design and included 159 participants (63 patients with lung carcinoma and 96 cancer-free controls) of Chinese Han descent. Genomic DNA from blood samples was extracted for PCR studies, followed by direct sequencing to determine the variants of the XRCC1 gene.

Results:

Carriers with Arg194–Arg399 haplotype of XRCC1 gene conferred a 189.3% increased risk compared to the non-carriers (95% confidence interval [CI], 1.195–2.998; P = 0.006). And single-locus analysis (both allele and genotype distributions of polymorphism Arg194Trp and Arg399Gln) identified neither association with cancer risk nor with clinico-pathological parameters of lung carcinoma in the Han population.

Conclusions:

Arg194–Arg399 haplotype of XRCC1 gene might increase lung cancer susceptibility and serve as a risk factor for lung cancer in the Han population.

Single nucleotide polymorphisms (SNPs) of hOGG1 and XRCC1 DNA repair genes and the risk of ovarian cancer in Polish women

The aim of this study was to determine single nucleotide polymorphisms in hOGG1 (Ser326Cys (rs13181)) and XRCC1 (Arg194Trp (rs1799782)) genes, respectively, and to identify the correlation between them and the overall risk, grading and staging of ovarian cancer in Polish women. Our study comprised 720 patients diagnosed with ovarian cancer and 720 healthy controls. The genotype analysis of hOGG1 and XRCC1 polymorphisms was performed using polymerase chain reaction (PCR)-based restriction fragment length polymorphism (PCR-RFLP). Odds ratios (OR) and 95 % confidence intervals (CI) for each genotype and allele were calculated. Results revealed an association between hOGG1 Ser326Cys polymorphism and the incidence of ovarian cancer. Variant Cys allele of hOGG1 increased the overall cancer risk (OR 2.89; 95 % CI 2.47-3.38; p < .0001). Moreover, ovarian cancer grading remained in a relationship with both analysed polymorphisms; G1 tumours presented increased frequencies of hOGG1 Cys/Cys homozygotes (OR 18.33; 95 % CI 9.38-35.81; p < .0001) and XRCC1 Trp/Trp homozygotes (OR 20.50; 95 % CI 10.17-41.32; p < .0001). Furthermore, G1 ovarian cancers displayed an overrepresentation of Cys and Trp allele. In conclusion, hOGG1 Ser326Cys and XRCC1 Arg194Trp polymorphisms may be regarded as risk factors of ovarian cancer.

Note of clarification of data in the paper titled X-ray repair cross-complementing group 1 codon 399 polymorphism and lung cancer risk: an updated meta-analysis

We read with great interest the paper titled "X-ray repair cross-complementing group 1 codon 399 polymorphism and lung cancer risk: an updated meta-analysis" published by Wang et al in Tumor Biology, 2014, 35:411-418. Their results suggest that codon 399 polymorphism of XRCC1 gene might contribute to individual's susceptibility to lung cancer in Asian population and especially in nonsmoking Chinese women. The result is encouraging. Nevertheless, several key issues are worth noticing.

Association between the XRCC1 Arg194Trp polymorphism and risk of cancer: evidence from 201 case-control studies

The Arg194Trp polymorphism in the X-ray cross-complementing group 1 (XRCC1) had been implicated in cancer susceptibility. The previous published data on the association between XRCC1 Arg194Trp polymorphism and cancer risk remained controversial. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and XRCC1 Arg194Trp (59,227 cases and 81,587 controls from 201 studies) polymorphism in different inheritance models. We used odds ratios with 95 % confidence intervals to assess the strength of the association. Overall, significantly increased cancer risk was found (recessive model: (odds ration [OR] = 1.18, 95% confidence interval [CI] = 1.09-1.27; homozygous model: OR = 1.21, 95% CI = 1.10-1.33; additive model: OR = 1.05, 95% CI = 1.01-1.09) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, significantly increased glioma risk was found among Asians, significantly decreased lung cancer risk was found among Caucasians, and significant increased breast cancer risk was found among hospital-based studies. In summary, this meta-analysis suggests that Arg194Trp polymorphism may be associated with increased breast cancer risk, Arg194Trp polymorphism is associated with increased glioma risk among Asians, and Arg194Trp polymorphism is associated with decreased lung cancer risk among Caucasians. In addition, our work also points out the importance of new studies for Arg194Trp association in some cancer types, such as gastric, pancreatic, prostate, and nasopharyngeal cancers, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC1 Arg194Trp polymorphism in cancer development (I (2) > 75%).

Polymorphism of DNA repair gene xrcc1 and lung cancer risk

The current large-scale meta-analysis was performed to reach a reliable conclusion on the association between X-ray repair cross-complementing 1 (xrcc1) rs1799782 and the development of lung cancer. Studies that investigated the association between rs1799782 and lung cancer risk were identified by searching PubMed. We calculated odds ratio (OR) with corresponding 95 % confidence interval (CI) for Trp/Trp vs Arg/Arg, Trp/Trp + Arg/Trp vs Arg/Arg, and Trp/Trp vs Arg/Trp + Arg/Arg contrast models. Combining all 25 studies, we yielded three summary ORs: 1.07 (95 % CI 0.92-1.23) for Trp/Trp vs Arg/Arg, 0.93 (95 % CI 0.87-1.00) for Trp/Trp + Arg/Trp vs Arg/Arg, and 1.08 (95 % CI 0.94-1.25) for Trp/Trp vs Arg/Trp + Arg/Arg, suggesting rs1799782 was not associated with overall risk of lung cancer. Strikingly, a significantly deceased risk was found among Caucasian populations (Trp/Trp + Arg/Trp vs Arg/Arg, OR = 0.86, 95 % CI 0.76-0.97). This study confirms that xrcc1 rs1799782 may lower the risk of lung cancer among Caucasians.

The codon 399 Arg/Gln XRCC1 polymorphism is associated with lung cancer in Indians

BACKGROUND

The XRCC1 (X-ray repair cross complimenting group-I) gene in BER (base excision repair) pathway is essential for DNA repair process. Polymorphisms in this gene are associated with variations in the repair efficiency which might predispose individuals to development of various cancers. Two variants of XRCC1gene (at codon 399), Gln/Gln and Arg/Gln, have been shown to be related to lowered DNA repair capacity and increased genomic instability in multiple studies. Hence our investigation focused on genotyping these variants to correlate with other multiple risk factors in lung cancer (NSCLC) patients since we hypothesized that these variants of the XRCC1 gene might influence disease susceptibility.

MATERIALS AND METHODS

We examined the frequency of the polymorphism in one hundred cases and an almost equal number of controls after recording their demographics with a structured questionnaire. Genomic DNA from blood samples was extracted for PCR studies, followed by RFLP to determine the variants. The significance of the data was statistically analyzed.

RESULTS

The three genotypes in cases and controls were Arg/Arg (40% and 54.45%); Gln/Gln (19% and 9.90%), and Arg/Gln (41.0% and 35.64%) respectively. Among these 3 genotypes, we found Gln/Gln and Arg/Gln to show association with lung cancer. Correlating these genotypes with several parameters, we also found that these two variants were associated with risk in males (p<0.05) and with smoking habits (p<0.05). In females Arg/Gln genotype showed association with stage of the disease (p=0.04). This is the first report in South Indian scenario where Arg399Gln genotypes were found to be associated with stage of the disease in females.

CONCLUSIONS

It is concluded that XRCC1 genotypes Gln/Gln and Arg/Gln may influence cancer susceptibility in patients with smoking habits and these functional SNPs in XRCC1 gene may act as attractive candidate biomarkers in lung cancer for diagnosis and prognosis.

DNA repair pathways and their therapeutic potential in lung cancer

SUMMARY: 

Lung cancer is the leading cause of cancer-related mortality. According to WHO, 1.37 million deaths occur globally each year as a result of this disease. More than 70% of these cases are associated with prior tobacco consumption and/or cigarette smoking, suggesting a direct causal relationship. The development and progression of lung cancer and other malignancies involves the loss of genetic stability, resulting in acquisition of cumulative genetic changes; this affords the cell increased malignant potential. As such, an understanding of the mechanisms through which these events may occur will potentially allow for development of new anticancer therapies. This review will address the association between lung cancer and genetic instability, with a central focus on genetic mutations in the DNA damage repair pathways. In addition, we will discuss the potential clinical exploitation of these pathways, both in terms of biomarker staging, as well as through direct therapeutic targeting.

No association between XRCC1 gene Arg194Trp polymorphism and risk of lung cancer: evidence based on an updated cumulative meta-analysis

X-ray repair cross-complementing group 1 (XRCC1) gene Arg194Trp polymorphism has been reported to be associated with risk of lung cancer in many published studies. Nevertheless, the research results were inconclusive and conflicting. To reach conclusive results, several meta-analysis studies were conducted by combining results from literature reports through pooling analysis. However, these previous meta-analysis studies were still not consistent. Hence, we used an updated and cumulative meta-analysis to get a more comprehensive and precise result from 25 case–control studies searching through the PubMed database up to September 1, 2013. The meta-analysis was carried out by the Comprehensive Meta-Analysis software and the odds ratio (OR) with 95 % confidence interval (CI) was used to estimate the pooled effect. The result involving 8,876 lung cancer patients and 11,210 controls revealed that XRCC1 Arg194Trp polymorphism was not associated with lung cancer risk [(OR = 0.97, 95 %CI = 0.92–1.03) for Trp vs. Arg; (OR = 0.92, 95 % CI = 0.85–0.98) for ArgTrp vs. ArgArg; (OR = 1.07, 95 % CI = 0.92–1.23) for TrpTrp vs. ArgArg; (OR = 0.93, 95 % CI = 0.87–1.00) for (TrpTrp + ArgTrp) vs. ArgArg; and (OR = 1.08, 95 % CI = 0.94–1.25) for TrpTrp vs. (ArgTrp + ArgArg)]. The cumulative meta-analysis showed that the results maintained the same, while the ORs with 95 % CI were more stable with the accumulation of case–control studies. The sensitivity and subgroups analyses showed that the results were robust and not affected by any single study with no publication bias. Relevant studies might not be needed for supporting these results.

Single nucleotide polymorphisms (SNPs) of ERCC2, hOGG1, and XRCC1 DNA repair genes and the risk of triple-negative breast cancer in Polish women

Triple-negative breast cancer (TNBC) refers to about 15–20 % of all breast cancer cases. It is characterized by worse clinical outcome, poor prognosis, and absence of prognostic indicators. Several polymorphisms in the nucleotide excision repair (NER) and base excision repair (BER) gene have been extensively studied in association with various human cancers. The aim of this study was to evaluate the role of the hOGG1-Ser326Cys (rs13181), XRCC1-Arg194Trp (rs1799782), and ERCC2-Lys751Gln (rs13181) gene polymorphisms with clinical parameters and the risk for development of triple-negative breast cancer. Our research included 70 patients with TNBC and 70 healthy controls. Gene polymorphisms were genotyped by the PCR-RFLP (restriction fragment length polymorphism) method. The genotype distributions were contrasted by the chi-square test, and the significance of the polymorphism was assessed by multiple logistic regression producing odds ratios (ORs) and 95 % confidence intervals (CIs). In the present work, a relationship was identified between ERCC2-Lys751Gln polymorphism and the incidence of triple-negative breast cancer. An association was observed between triple-negative breast carcinoma occurrence and the presence of Gln/Gln genotype (OR = 5.71 (2.12–5.43), p = 0.0007). A tendency for an increased risk of TNBC was detected with the occurrence of 751Gln allele of ERCC2 polymorphism. No significant associations between Ser326Cys and Arg194Trp genotype and TNBC were observed. We suggest that the Lys751Gln polymorphism of the ERCC2 gene may be risk factors for triple-negative breast cancer development in Polish women.

DNA repair pathway genes and lung cancer susceptibility: a meta-analysis

OBJECTIVE

DNA repair pathway genes have been implicated to play an important role in the development of lung cancer. However, contradictory results are often reported by various studies, making it difficult to interpret them. So in this meta-analysis, we have assessed the association between lung cancer risk and two DNA repair pathway genes. XRCC1 and ERCC2, by analyzing 67 published case-control studies.

RESEARCH DESIGN AND METHODS

We searched PubMed, Embase and Web of Science using terms "XRCC1" or "XPD" or "ERCC2" and "lung cancer" on August 1, 2012. Three criteria were applied to select included studies for resulting studies. Information was carefully extracted by two investigators independently. We used pooled odds ratio (OR) to assess the effect of a polymorphism, and a dominant model was applied where genotypes that contain the non-reference allele were combined together. All the calculations were performed using STATA version 11.0.

MAIN OUTCOME MEASURES AND RESULTS

Three common nonsynonymous polymorphisms in XRCC1, codon 194, codon 280 and codon 399, and two common nonsynonymous polymorphisms in ERCC2, codon 312 and codon 751, were analyzed. The result showed in total population, Lys751Gln in ERCC2 is associated with an increase of lung cancer risk, with a summary OR as 1.15. No association was found for any other polymorphisms. When studies were stratified by ethnicity, the risk effect of Lys751Gln in ERCC2 was found only in Caucasians, not in Asians.

CONCLUSIONS

In conclusion, Lys751Gln in ERCC2 is associated with lung cancer, and the risk effect probably exists in Caucasians. By contrast, polymorphisms in XRCC1 are less likely to be susceptible to lung cancer risks.

Association between XRCC1 and XRCC3 polymorphisms with lung cancer risk: a meta-analysis from case-control studies

Many studies have reported the association of X-ray repair cross-complementing group 1 (XRCC1) Arg399Gln, Arg194Trp, Arg280His, −77T>C, and X-ray repair cross-complementing group 3 (XRCC3) T241M polymorphisms with lung cancer risk, but the results remained controversial. Hence, we performed a meta-analysis to investigate the association between lung cancer risk and XRCC1 Arg399Gln (14,156 cases and 16,667 controls from 41 studies), Arg194Trp (7,426 cases and 9,603 controls from 23 studies), Arg280His (6,211 cases and 6,763 controls from 16 studies), −77T>C (2,487 cases and 2,576 controls from 5 studies), and XRCC3 T241M (8,560 cases and 11,557 controls from 19 studies) in different inheritance models. We found that −77T>C polymorphism was associated with increased lung cancer risk (dominant model: odds ration [OR] = 1.45, 95% confidence interval [CI] = 1.27–1.66, recessive model: OR = 1.73, 95% CI = 1.14–2.62, additive model: OR = 1.91, 95% CI = 1.24–1.94) when all the eligible studies were pooled into the meta-analysis. In the stratified and sensitive analyses, significantly decreased lung cancer risk was observed in overall analysis (dominant model: OR = 0.83, 95% CI = 0.78–0.89; recessive model: OR = 0.90, 95% CI = 0.81–1.00; additive model: OR = 0.82, 95% CI = 0.74–0.92), Caucasians (dominant model: OR = 0.82, 95% CI = 0.76–0.87; recessive model: OR = 0.89, 95% CI = 0.80–0.99; additive model: OR = 0.81, 95% CI = 0.73–0.91), and hospital-based controls (dominant model: OR = 0.81, 95% CI = 0.76–0.88; recessive model: OR = 0.89, 95% CI = 0.79–1.00; additive model: OR = 0.80, 95% CI = 0.71–0.90) for XRCC3 T241M. In conclusion, this meta-analysis indicates that XRCC1 −77T>C shows an increased lung cancer risk and XRCC3 T241M polymorphism is associated with decreased lung cancer risk, especially in Caucasians.

The relationship between XRCC1 and XRCC3 gene polymorphisms and lung cancer risk in northeastern Chinese

Background

The prevalence of lung cancer in China will be the world's highest if allowed to proceed uncurbed. To unravel its genetic underpinnings, we sought to investigate the association of three well-characterized nonsynonymous polymorphisms in XRCC1 (Arg194Trp and Arg399Gln) and XRCC3 (Thr241Met) genes with lung cancer risk in northeastern Chinese.

Methodology/Principal Findings

This study was hospital-based in design, encompassing 684 patients with lung cancer and 604 cancer-free controls. Genotyping was performed using the PCR-LDR (ligase detection reactions) method. Data were analyzed by R language and multifactor dimensionality reduction (MDR) software. Single-locus analysis identified significance in genotype distributions of polymorphism Arg194Trp (P = 0.002) and Arg399Gln (P = 0.017), and in allele distributions of Thr241Met (P = 0.005). Carriers of 399Gln/Gln genotype conferred a 147% increased risk relative to the non-carriers (odds ratio (OR): 2.47; 95% confidence interval (95% CI): 1.48–4.13; P<0.001). For Thr241Met, significance persisted under allelic (OR = 1.63; 95% CI: 1.14–2.33; P = 0.005), additive (OR = 1.64; 95% CI: 1.16–2.32; P = 0.005) and dominant (OR = 1.67; 95% CI: 1.17–2.38; P = 0.004) models. However, common allele combinations were comparable in frequency between patients and controls. In interaction analysis, the overall best MDR model included Arg399Gln and Thr241Met polymorphisms, with a maximal testing accuracy of 63.18% and a maximal cross-validation consistency of 10 out of 10 (P = 0.0175).

Conclusions

Our study significantly demonstrated an independent and synergistic contribution of XRCC1 Arg399Gln and XRCC3 Thr241Met polymorphisms to lung cancer susceptibility in northeastern Chinese.

Association between the XRCC1 polymorphisms and glioma risk: a meta-analysis of case-control studies

Background

X-ray repair cross-complementing group 1 (XRCC1) is one of the DNA repair genes encoding a scaffolding protein that participate in base excision repair (BER) pathway. However, studies on the association between polymorphisms in this gene and glioma have yielded conflicting results. This meta-analysis was performed to derive a more precise estimation between XRCC1 polymorphisms (Arg399Gln, Arg194Trp, and Arg280His) and glioma risk.

Methods

Data were collected from several electronic databases, with the last search up to November 28, 2012. Meta-analysis was performed by critically reviewing 9 studies for Arg399Gln polymorphism (3146 cases and 4296 controls), 4 studies for Arg194Trp polymorphism (2557 cases and 4347 controls), and 4 studies for Arg280His polymorphism (1936 cases and 2895 controls). All of the statistical analyses were performed using the software programs STATA (version 11.0).

Results

The combined results showed that Arg399Gln polymorphism was significantly associated with glioma risk (Gln/Gln versus Arg/Arg: OR = 1.52, 95% CI = 1.03–2.23; recessive model: OR = 1.32, 95% CI = 1.01–1.73; additive model: OR = 1.21, 95% CI = 1.00–1.47), whereas Arg194Trp/Arg280His polymorphisms were all not significantly associated with glioma risk. As for ethnicity, Arg399Gln polymorphism was associated with increased risk of glioma among Asians (Gln/Gln versus Arg/Arg: OR = 1.78, 95% CI = 1.29–2.47; Arg/Gln versus Arg/Arg: OR = 1.28, 95% CI = 1.05–1.56; recessive model: OR = 1.59, 95% CI = 1.16–2.17; dominant model: OR = 1.36, 95% CI = 1.13–1.65; additive model: OR = 1.32, 95% CI = 1.15–1.52), but not among Caucasians. Stratified analyses by histological subtype indicated that the Gln allele of Arg399Gln polymorphism showed borderline association with the risk of glioblastoma among Caucasians. However, no evidence was observed in subgroup analyses for Arg194Trp/Arg280His polymorphisms.

Conclusions

Our meta-analysis suggested that Arg399Gln polymorphism was associated with increased risk of glioma among Asians and borderline increased risk for glioblastoma among Caucasians, whereas Arg194Trp/Arg280His polymorphisms might have no influence on the susceptibility of glioma in different ethnicities.

Genetic susceptibility to lung cancer--light at the end of the tunnel?

Lung cancer is one of the most common and deadliest cancers in the world. The major socio-environmental risk factor involved in the development of lung cancer is cigarette smoking. Additionally, there are multiple genetic factors, which may also play a role in lung cancer risk. Early work focused on the presence of relatively prevalent but low-penetrance alterations in candidate genes leading to increased risk of lung cancer. Development of new technologies such as genomic profiling and genome-wide association studies has been helpful in the detection of new genetic variants likely involved in lung cancer risk. In this review, we discuss the role of multiple genetic variants and review their putative role in the risk of lung cancer. Identifying genetic biomarkers and patterns of genetic risk may be useful in the earlier detection and treatment of lung cancer patients.

Impact of DNA polymorphisms in key DNA base excision repair proteins on cancer risk

Genetic variation in DNA repair genes can modulate DNA repair capacity and may be related to cancer risk. However, study findings have been inconsistent. Inheritance of variant DNA repair genes is believed to influence individual susceptibility to the development of environmental cancer. Reliable knowledge on which the base excision repair (BER) sequence variants are associated with cancer risk would help elucidate the mechanism of cancer. Given that most of the previous studies had inadequate statistical power, we have conducted a systematic review on sequence variants in three important BER proteins. Here, we review published studies on the association between polymorphism in candidate BER genes and cancer risk. We focused on three key BER genes: 8-oxoguanine DNA glycosylase (OGG1), apurinic/apyrimidinic endonuclease (APE1/APEX1) and x-ray repair cross-complementing group 1 (XRCC1). These specific DNA repair genes were selected because of their critical role in maintaining genome integrity and, based on previous studies, suggesting that single-nucleotide polymorphisms (SNPs) in these genes have protective or deleterious effects on cancer risk. A total of 136 articles in the December 13, 2010 MEDLINE database (National Center for Biotechnology Information, http://www.ncbi.nlm.nih.gov/pubmed/) reporting polymorphism in OGG1, XRCC1 or APE1 genes were analyzed. Many of the reported SNPs had diverse association with specific human cancers. For example, there was a positive association between the OGG1 Ser326Cys variant and gastric and lung cancer, while the XRCC1 Arg399Gln variant was associated with reduced cancer risk. Gene-environment interactions have been noted and may be important for colorectal and lung cancer risk and possibly other human cancers.

XRCC1 gene polymorphisms and lung cancer susceptibility: a meta-analysis of 44 case-control studies

X-ray repair cross-complementing group 1 gene (XRCC1) has been implicated in risk for lung cancer. However, the results from different studies remain controversial. In this meta-analysis, we have assessed 44 published case-control studies regarding associations of lung cancer risk with three common polymorphisms, codon 194, codon 280 and codon 399, and -77 T > C in the promoter region of XRCC1. The results in total population showed that the risk for lung cancer was increased among the variant homozygote Trp/Trp of codon 194 polymorphism, compared with the wild type Arg/Arg (OR: 1.19; 95 % CI 1.01-1.39), and the variant genotype CC of -77 T > C polymorphism showed a significantly increased risk of developing lung cancer, compared to wild-type genotype TT (OR: 1.91; 95 % CI 1.24-2.94). However, no associations were found between lung cancer risk and codon 280, codon 399. In the subgroup analyses by ethnicity, the OR for the variant homozygote Trp/Trp of codon 194 was 1.21(95 % CI 1.02-1.43) for Asian. When stratified by source of control, we found a protective effect of codon 194 Arg/Trp genotype (OR: 0.87; 95 % CI 0.77-0.98) and risk effect of codon 399 combined Arg/Gln + Gln/Gln variant genotype (OR: 1.09; 95 % CI 1.01-1.18) for lung cancer on the basis of hospital control. Subgroup analyses by histological types of lung cancer indicated that the heterozygote Arg/Trp in codon 194 could decrease and the combined variant genotype Arg/Gln + Gln/Gln in codon 399 could increase the risk of non-small cell lung cancer (OR: 0.69; 95 % CI 0.57-0.85 and OR: 1.14; 95 % CI 1.04-1.24). In conclusion, this meta-analysis has demonstrated that codon 194, codon 399 and -77 T > C polymorphisms of XRCC1 gene might have contributed to individual susceptibility to lung cancer. To further evaluate effect of XRCC1 polymorphisms, gene-gene interaction and gene-environment interaction on lung cancer risk, a single large sample size study with thousands of subjects is required to get conclusive results.

Polymorphisms of DNA repair genes in endometrial cancer

Endometrial cancer belongs to the commonest malignancy in females. Its development may be associated with the high exposure of endometrium to exo- and endogenous estrogens. Estrogens produce DNA bulky adducts and oxidative base damages which are removed in nucleotide excision repair (NER) and base excision repair (BER) pathways. The reaction of endometrial cells to DNA damage may be crucial for their susceptibility to cancer transformation. This reaction is executed mainly by DNA repair, which can be modulated by the variability in the genes encoding DNA repair proteins. In this report we genotyped 4 polymorphisms of 3 DNA repair genes in 94 endometrial cancer patients and 114 age-matched cancer-free women using RFLP-PCR. The following polymorphisms were studied: p.Arg194Trp, p.Arg399Gln of the XRCC1 gene, p.Ser326Cys of the hOGG1 gene and p.Lys751Gln of the ERCC2 gene. We found an association between the ERCC2 751Gln variant and endometrial cancer occurrence (OR 3.95; 95 % CI 1.88–8.31). Gene-gene interaction between the ERCC2 751Gln and XRCC1 194Trp variants also increased the risk of endometrial cancer (OR 4.41; 95 % CI 2.01–9.67). The risk in the carriers of the ERCC2 751Gln variant was increased by a positive cancer history in first degree relatives (OR 4.97; 95 % CI 1.98–12.48). The risk of endometrial cancer was not alter by polymorphism p.Ser326Cys of the hOGG1 gene. The 751 Lys/Gln polymorphism of the ERCC2 gene may be linked with endometrial cancer occurrence and its effect can be potentiated by variants of the XRCC1 gene or first degree relatives positive cancer history.

Associated risk of XRCC1 and XPD cross talk and life style factors in progression of head and neck cancer in north Indian population

Effective DNA repair machinery ensures maintenance of genomic integrity. Environmental insults, ageing and replication errors necessitate the need for proper DNA repair systems. Any alteration in DNA repair efficacy would play a dominant role in progression of squamous cell carcinoma of head and neck (SCCHN). Genotypes of XRCC1 gene-Arg194Trp, Arg280His, Arg399Gln and XPD Lys751Gln, by PCR-RFLP were studied in 278 SCCHN patients and an equal number of matched healthy controls residing in north India. In XRCC1 polymorphisms, Arg194Trp and Arg399Gln variants showed a reduced risk, whereas, XPD Lys751Gln variants exhibited ∼2-fold increase in SCCHN risk. With XRCC1-Arg280His variants, there was no association with SCCHN risk. Arg399Gln of XRCC1 appears to have a protective role in people those consume alcohol, while XPD Lys751Gln variants indicated ∼2-fold increased risk of SCCHN in all the co-variate groups. Comparison of gene-gene interaction among XRCC1 Arg280His and XPD Lys751Gln suggested enhanced risk of SCCHN by ∼2.3-fold in group one and ∼6.1-fold in group two. In dichotomized groups of this combination, the risk was ∼2.4 times. Haplotype analysis revealed the frequency of C-G-G-G and C-A-G-G to be significantly associated with an increased risk of SCCHN. On the contrary, T-G-A-A significantly diminished the risk. CART analysis results showed that the terminal node that contains homozygous mutants of XPD Lys751Gln and XRCC1 Arg194Trp, wild type of XRCC1 Arg399Gln and homozygous mutant of XRCC1 Arg280His, represent the highest risk group. Our results demonstrate high degree of gene-gene interaction involving DNA repair genes of NER and BER pathways, namely XRCC1 and XPD. This study amply demonstrates positive association of XPD Arg751Gln polymorphism with an increased risk of SCCHN. Further, XRCC1 Arg280His variant though dormant individually, may also contribute to the development of cancer in combination with XPD Arg751Gln.

ERCC1 and XRCC1 as biomarkers for lung and head and neck cancer

Advanced stage non-small cell lung cancer and head and neck squamous cell carcinoma are both treated with DNA damaging agents including platinum-based compounds and radiation therapy. However, at least one quarter of all tumors are resistant or refractory to these genotoxic agents. Yet the agents are extremely toxic, leading to undesirable side effects with potentially no benefit. Alternative therapies exist, but currently there are no tools to predict whether the first-line genotoxic agents will work in any given patient. To maximize therapeutic success and limit unnecessary toxicity, emerging clinical trials aim to inform personalized treatments tailored to the biology of individual tumors. Worldwide, significant resources have been invested in identifying biomarkers for guiding the treatment of lung and head and neck cancer. DNA repair proteins of the nucleotide excision repair pathway (ERCC1) and of the base excision repair pathway (XRCC1), which are instrumental in clearing DNA damage caused by platinum drugs and radiation, have been extensively studied as potential biomarkers of clinical outcomes in lung and head and neck cancers. The results are complex and contradictory. Here we summarize the current status of single nucleotide polymorphisms, mRNA, and protein expression of ERCC1 and XRCC1 in relation to cancer risk and patient outcomes.

Polymorphisms and haplotypes in the XRCC1 gene and the risk of advanced non-small cell lung cancer

INTRODUCTION AND HYPOTHESIS

Single-nucleotide polymorphisms (SNPs) and haplotypes in the x-ray repair cross-complementing group 1 (XRCC1) gene, which is one of the base excision repair genes, are thought to be associated with the risk of non-small cell lung cancer (NSCLC).

METHODS

We genotyped three coding (Arg280His, Arg399Gln, and Gln632Gln) SNPs and six haplotype-tagging SNPs (htSNPs) for 140 advanced NSCLC cases and 217 healthy controls (all Koreans) using unconditional logistic regression analysis, and this was adjusted for age, gender, and the smoking status. The haplotypes were reconstructed according to the genotyping data and the linkage disequilibrium status of these nine SNPs.

RESULTS

The minor allele heterozygotes of the rs1001581 htSNP showed an increased risk of NSCLC (adjusted odds ratio = 2.118, p = 0.013), and the minor allele homozygotes of the rs2293036 htSNP showed a decreased risk of NSCLC (adjusted odds ratio = 0.363, p = 0.020). Seven possible haplotypes were demonstrated in this study (haplotype frequency >1%). The GGGGGGGGG haplotype, which is composed of nine major alleles, showed a protective effect for developing NSCLC (odds ratio = 0.433, p = 0.002); however, the GGGGGGAGG haplotype that contained the minor allele of the rs1001581 demonstrated an increased risk of NSCLC (odds ratio = 1.597, p = 0.044). The above associations were similarly noted for the never smokers, and so the smoking status might modify the associations between the x-ray repair cross-complementing group 1 (XRCC1) genetic variants and the risk of developing NSCLC. On 10-million permutation testing, only the GGGGGGGGG haplotype was significantly associated with a decreased risk of NSCLC in the total group (p = 0.001).

CONCLUSIONS

This study presents several novel aspects of the genetic susceptibility to develop NSCLC. Larger studies that will focus on the role of the rs1001581 and rs2293036 htSNPs and haplotypes for developing NSCLC are needed in the future.

DNA repair gene X-ray repair cross complementing group 1 Arg194Trp polymorphism on the risk of lung cancer: a meta-analysis on 22 studies

BACKGROUND

DNA repair gene X-ray repair cross complementing group 1 (XRCC1) Arg194Trp polymorphism has been investigated widely on lung cancer risk. However, the results are inconclusive. To derive a more precise estimation of the relationship between XRCC1 Arg194Trp polymorphism and lung cancer risk, we performed this meta-analysis.

METHODS

An electronic search of the database PubMed, Embase, and Chinese National Knowledge Infrastructure was performed. The odds ratio (OR) was pooled by STATA 10.1. Subgroup analyses by ethnicity, gender, smoking, and histologic types of lung cancer were performed.

RESULTS

Twenty-two studies including 7515 cases and 9560 controls were identified ultimately. The pooled OR for total population showed that homozygous Trp/Trp variant genotype could increase lung cancer risk compared with the homozygous wild Arg/Arg genotype (OR = 1.22, 95% confidence interval [CI] = 1.04-1.44, p = 0.01); however, heterozygote Arg/Trp variant genotype could decrease lung cancer risk (OR = 0.91, 95% CI = 0.85-0.99, p = 0.02). Subgroup analyses by ethnicity confirmed the result that homozygous Trp/Trp variant genotype increased lung cancer risk in Asians (OR = 1.19, 95% CI = 1.01-1.41, p = 0.04) but not in whites. It was interesting to find that both the heterozygote Arg/Trp and the combined Trp/Trp + Arg/Trp variant genotypes could decrease the risk of lung cancer in whites (OR = 0.83, 95% CI = 0.72-0.96, p = 0.01; OR = 0.85, 95% CI = 0.74-0.98, p = 0.03, respectively) but not in Asians. Subgroup analyses by gender, smoking, and histologic types of lung cancer did not indicate any significant difference between cases and controls, excepted for male population, which carried heterozygote Arg/Trp variant genotype that could decrease lung cancer risk (OR = 0.54, 95% CI = 0.31-0.95, p = 0.03).

CONCLUSIONS

Homozygous Trp/Trp variant genotype of XRCC1 Arg194Trp polymorphism could increase lung cancer risk in total population, especially in Asians. However, the heterozygote Arg/Trp variant genotype might decrease the risk of lung cancer, especially in whites.

Lung cancer risk and genetic polymorphisms in DNA repair pathways: a meta-analysis

Genetic variations in DNA repair genes are thought to modulate DNA repair capacity and are suggested to be related to lung cancer risk. We conducted a meta-analysis of epidemiologic studies on the association between genetic polymorphisms in both base excision repair and nucleotide excision repair pathways, and lung cancer. We found xeroderma pigmentosum complementation group A (XPA) G23A (odds ratio (OR) = 0.76, 95% confidence interval (CI) = 0.61–0.94), 8-oxoguanine DNA glycosylase 1 (OGG1) Ser326Cys (OR = 1.22, 95% CI = 1.02–1.45), and excision repair cross-complementing group 2 (ERCC2) Lys751Gln (OR = 1.27, 95% CI = 1.10–1.46) polymorphisms were associated with lung cancer risk. Considering the data available, it can be conjectured that if there is any risk association between a single SNP and lung cancer, the risk fluctuation will probably be minimal. Advances in the identification of new polymorphisms and in high-throughput genotyping techniques will facilitate the analysis of multiple genes in multiple DNA repair pathways. Therefore, it is likely that the defining feature of future epidemiologic studies will be the simultaneous analysis of large samples of cases and controls.

Association between X-ray repair cross complementing group 1 codon 399 and 194 polymorphisms and lung cancer risk: a meta-analysis

Genetic variations in DNA repair genes are thought to modify DNA repair capacity and suggested to be related to cancer risk. However, epidemiological results have been inconsistent. In this meta-analysis, we assessed reported studies of association between polymorphisms of X-ray repair cross complementing group 1 (XRCC1) codon 399 and 194, and lung cancer risk. We found decreased lung cancer risk among subjects carrying XRCC1 codon 194 Arg/Trp genotype [odds ratio (OR)=0.88, 95% confidence interval (95% CI): 0.79-0.97], using 4848 cases and 6592 controls from 16 studies. There was no association between lung cancer risk and XRCC1 codon 399 polymorphism in total population, when stratified by source of control, we found a protective effect of the XRCC1 codon 399 Gln/Gln and Arg/Gln or Gln/Gln polymorphisms for lung cancer on the basis of population control (OR=0.73, 95% CI: 0.58-0.92; OR=0.86, 95% CI: 0.77-0.97, respectively). Data indicated that certain XRCC1 codon 399 and 194 variant may affect the susceptibility of lung cancer. Recommendations for further studies include pooling of individual data to facilitate evaluation of multigenic effects and detailed analysis of effect modification by environmental exposure.

Base excision repair genes and risk of lung cancer among San Francisco Bay Area Latinos and African-Americans

Base excision repair (BER) is the primary DNA damage repair mechanism for repairing small base lesions resulting from oxidation and alkylation damage. This study examines the association between 24 single-nucleotide polymorphisms (SNPs) belonging to five BER genes (XRCC1, APEX1, PARP1, MUTYH and OGG1) and lung cancer among Latinos (113 cases and 299 controls) and African-Americans (255 cases and 280 controls). The goal was to evaluate the differences in genetic contribution to lung cancer risk by ethnic groups. Analyses of individual SNPs and haplotypes were performed using unconditional logistic regressions adjusted for age, sex and genetic ancestry. Four SNPs among Latinos and one SNP among African-Americans were significantly (P < 0.05) associated with either risk of all lung cancer or non-small cell lung cancer (NSCLC). However, only the association between XRCC1 Arg399Gln (rs25487) and NSCLC among Latinos (odds ratio associated with every copy of Gln = 1.52; 95% confidence interval: 1.01-2.28) had a false-positive report probability of <0.5. Arg399Gln is a SNP with some functional evidence and has been shown previously to be an important SNP associated with lung cancer, mostly for Asians. Since the analyses were adjusted for genetic ancestry, the observed association between Arg399Gln and NSCLC among Latinos is unlikely to be confounded by population stratification; however, this result needs to be confirmed by additional studies among the Latino population. This study suggests that there are genetic differences in the association between BER pathway and lung cancer between Latinos and African-Americans.

Genetic susceptibility to cancer: the role of polymorphisms in candidate genes

CONTEXT

Continuing advances in genotyping technologies and the inclusion of DNA collection in observational studies have resulted in an increasing number of genetic association studies.

OBJECTIVE

To evaluate the overall progress and contribution of candidate gene association studies to current understanding of the genetic susceptibility to cancer.

DATA SOURCES

We systematically examined the results of meta-analyses and pooled analyses for genetic polymorphisms and cancer risk published through March 2008.

STUDY SELECTION

We identified 161 meta-analyses and pooled analyses, encompassing 18 cancer sites and 99 genes. Analyses had to meet the following criteria: include at least 500 cases, have cancer risk as outcome, not be focused on HLA antigen genetic markers, and be published in English.

DATA EXTRACTION

Information on cancer site, gene name, variant, point estimate and 95% confidence interval (CI), allelic frequency, number of studies and cases, tests of study heterogeneity, and publication bias were extracted by 1 investigator and reviewed by other investigators.

RESULTS

These 161 analyses evaluated 344 gene-variant cancer associations and included on average 7.3 studies and 3551 cases (range, 508-19 729 cases) per investigated association. The summary odds ratio (OR) for 98 (28%) statistically significant associations (P value <.05) were further evaluated by estimating the false-positive report probability (FPRP) at a given prior probability and statistical power. At a prior probability level of 0.001 and statistical power to detect an OR of 1.5, 13 gene-variant cancer associations remained noteworthy (FPRP <0.2). Assuming a very low prior probability of 0.000001, similar to a probability assumed for a randomly selected single-nucleotide polymorphism in a genome-wide association study, and statistical power to detect an OR of 1.5, 4 associations were considered noteworthy as denoted by an FPRP value <0.2: GSTM1 null and bladder cancer (OR, 1.5; 95% CI, 1.3-1.6; P = 1.9 x 10(-14)), NAT2 slow acetylator and bladder cancer (OR, 1.46; 95% CI, 1.26-1.68; P = 2.5 x 10(-7)), MTHFR C677T and gastric cancer (OR, 1.52; 95% CI, 1.31-1.77; P = 4.9 x 10(-8)), and GSTM1 null and acute leukemia (OR, 1.20; 95% CI, 1.14-1.25; P = 8.6 x 10(-15)). When the OR used to determine statistical power was lowered to 1.2, 2 of the 4 noteworthy associations remained so: GSTM1 null with bladder cancer and acute leukemia.

CONCLUSION

In this review of candidate gene association studies, nearly one-third of gene-variant cancer associations were statistically significant, with variants in genes encoding for metabolizing enzymes among the most consistent and highly significant associations.