XRCC1 genetic polymorphism Arg399Gln and gastric cancer risk: A meta-analysis

The effect of DNA repair gene variants on COVID-19 disease: susceptibility, severity, and clinical course

Oxidative stress (OS), which leads to DNA damage, plays a role in the pathogenesis of Coronavirus disease 2019 (COVID-19). We aimed to evaluate the role of DNA repair gene variants [X-ray repair cross complementing 4 (XRCC4) rs28360071, rs6869366, and X-ray cross-complementary gene 1 (XRCC1) rs25487] in susceptibility to COVID-19 in a Turkish population. We also evaluated its effect on the clinical course of the disease. A total of 300 subjects, including 200 COVID-19 patients and 100 healthy controls, were included in this study. These variants were genotyped using polymerase chain reaction (PCR) and/or PCR-restriction fragment length polymorphism (RFLP) methods. The patients were divided into three groups: those with a mild or severe infection; those who died or lived at the 28-day follow-up; those who required inpatient treatment or intensive care. There were 87 women (43.5%) and 113 men (56.5%) in the patient group. Hypertension was the most common comorbidity (26%). In the patient group, XRCC4 rs6869366 G/G genotype and G allele frequency were increased compared to controls, while XRCC4 rs6869366 G/T and T/T genotype frequencies were found to be higher in controls compared to patients. For XRCC1 rs25487, the A/A and A/G genotypes were significantly associated with COVID-19 disease. All of the patients hospitalized in the intensive care unit had the XRCC4 rs6869366 G/G genotype. In this study, we evaluated for the first time the impact of DNA repair gene variants on COVID-19 susceptibility. Results suggested that XRCC4 rs6869366 and XRCC1 rs25487 were associated with COVID-19 suspectibility and clinical course.

Age- and Gender-Independent Association of XRCC1 Arg399Gln Polymorphism with Chronic Myeloid Leukemia

Purpose

DNA damage to hematopoietic progenitor cells is an essential factor for leukemia development as a failure of the host DNA repair system to fix errors in DNA. This study aimed to assess the association of XRCC1 gene polymorphisms including Arg194Trp, Arg399Gln, and Arg280His with the risk of development of CML in Sudanese population.

Patients and Methods

The present study was conducted on 186 newly diagnosed patients with CML, aged 19–70 years (118 males and 68 females; mean age of 46.15±13.91 years) and 186 normal healthy controls (123 males and 63 females; mean age of 44.94±8.97 years). Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) assay was utilized to analyze the XRCC1 (Arg194Trp, Arg399Gln, and Arg280His) gene polymorphisms.

Results

The genotypic frequencies of Arg399Gln polymorphism in cases were 131 (70.4%) homozygous Arg/Arg, 46 (24.7%) homozygous Gln/Gln, and 9 (4.8%) heterozygous Arg/Gln as compared to the controls ie, 153 (82.3%), 73 (14.5%), and 6 (3.2%), respectively. The Arg399Gln variant genotypic frequencies significantly differed between the cases and controls (χ² = 7.249, P = 0.027). By comparison, no statistically significant difference was observed in the variant genotype frequencies between the cases and controls in terms of Arg194Trp and Arg280His polymorphisms.

Conclusion

XRCC1 Arg399Gln gene polymorphism might have an important role in increasing the risk of chronic myeloid leukemia among Sudanese patients. Furthermore, all tested three polymorphisms showed no association of risk of the development of CML with age and gender.

XRCC1 Arg399Gln Gene Polymorphism and Hepatocellular Carcinoma Risk in the Italian Population

Background

The human X-ray repair cross-complementing protein 1 ( XRCC1) gene encodes for one of the major repair factors involved in base excision repair (BER), which is reported to be associated with the risk of several cancers. A few studies have explored the association between risk of hepatocellular carcinoma (HCC) and single-nucleotide polymorphisms (SNPs) in different DNA repair genes, with contradictory results. The purpose of this study was to evaluate the association between XRCC1 Arg399Gln polymorphism and susceptibility to HCC.

Methods

A total of 89 HCC patients and 99 randomly selected healthy controls were enrolled. Genotyping of XRCC1 rs25487 was performed by high-resolution melting analysis and Sanger sequencing.

Results

On univariate analysis, a statistically significant association was found between risk of HCC and XRCC1 399Arg/Gln genotype (odd ratio [OR] = 1.88; 95% CI, 1.04-3.43), which was confirmed after adjusting by sex (OR = 1.94; 95% CI, 1.04-3.63). Although not significant, Kaplan-Meier analysis showed a decreased median survival in Arg/Gln genotype carriers in comparison with Arg/Arg carriers.

Conclusions

To our knowledge, this is the first study reporting an association between BER SNP and HCC risk in a population of central-southern Italy.

XRCC1 R399Q polymorphism and colorectal cancer risk in the Chinese Han population: a meta-analysis

X-ray repair cross-complementing group 1 (XRCC1) plays a key role in DNA repair, genetic instability, and tumorigenesis. The XRCC1 R399Q polymorphism has been reported in some studies to influence the risk of colorectal cancer (CRC), though this remains controversial. We performed a meta-analysis to determine the association of XRCC1 R399Q polymorphisms with CRC risk in the Chinese Han population. A literature search was conducted using PubMed, EMBASE, and the China National Knowledge Infrastructure to identify eligible studies published before June 2014. The pooled odds ratio (OR) and corresponding 95% confidence interval (CI) were used to estimate the effect of XRCC1 R399Q polymorphisms on CRC risk. Eleven case-control studies with a total of 3194 CRC cases and 4472 controls were identified. No significant association between the XRCC1 R399Q polymorphism and CRC risk was observed in the Chinese Han population (Gln/Gln vs. Arg/Arg, OR = 1.26, 95% CI = 0.85-1.87, P OR = 0.242; Arg/Gln vs. Arg/Arg, OR = 0.95, 95% CI = 0.70-1.18, P OR = 0.651; dominant model, OR = 1.09, 95% CI = 0.86-1.38, P OR = 0.480; and recessive model, OR = 1.24, 95% CI = 0.91-1.70, P OR = 0.177). After excluding two studies that deviated from the Hardy-Weinberg equilibrium, there remained no significant association between XRCC1 R399Q and CRC risk. No publication bias was found using the funnel plot and Egger's test. Our meta-analysis results suggest that the XRCC1 R399Q polymorphism is not associated with increased risk of CRC in the Chinese Han population.

An updated meta-analysis of transforming growth factor-β1 gene: three polymorphisms with gastric cancer

To derive a more precise estimation of the relationship between TGF-β1 polymorphisms and gastric cancer (GC) risk, we conducted a meta-analysis of all available case-control studies relating the C-509 T, T869C, and G 915C polymorphisms of the TGF-β1 gene to the risk of developing GC. The effect summary odds ratio (OR) and 95% confidence intervals (CIs) were obtained. Funnel plots and Egger's test were used to estimate publication bias. Finally, 11 studies were included in the final meta-analysis. With respect to C-509 T polymorphism, it was found that significantly increased GC risk was associated with the TT genotype in the recessive genetic model in overall analysis (TT vs. CC + CT: OR = 1.23, 95% CI 1.09-1.38, P(heterogeneity) = 0.13) and in Asian population (TT vs. CC + CT: OR = 1.24, 95% CI 1.10-1.39, P(heterogeneity) = 0.18). With respect to T869C and G915C polymorphisms, no significant association with GC risk was demonstrated in overall analysis and subgroup analyses according to ethnicity for all genetic models. This meta-analysis suggested that the T allele of TGF-β1 509C/T polymorphism is probably the susceptibility factor for GC.

Association study of single nucleotide polymorphisms in XRCC1 gene with the risk of gastric cancer in Chinese population

Gastric cancer is one of highly cancer-related deaths in the world. Previous evidence suggests that the X-ray repair cross-complementing group 1 gene (XRCC1) is one of the most important candidate genes for influencing gastric cancer risk. The objective of this study was to detect the potential association of genetic variants in XRCC1 gene with gastric cancer risk in Chinese Han population. In total, we enrolled 395 gastric cancer patients and 398 cancer-free controls in this study. The genotyping of c.910A>G and c.1804C>A genetic variants in XRCC1 gene were investigate by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and created restriction site-PCR (CRS-PCR) methods, respectively. We found the genotypes/alleles from these two genetic variants were statistically associated with the increased risk of gastric cancer (for c.910A>G, GG versus (vs.) AA: OR = 2.00, 95% CI 1.21-3.31; AG vs. AA: OR = 1.50, 95% CI 1.12-2.02; GG/AG vs. AA: OR = 1.59, 95% CI 1.20-2.10; GG vs.

AG/AA

OR = 1.68, 95% CI 1.03-2.73; G vs. A: OR = 1.47, 95% CI 1.18-1.83; for c.1804C>A, AA vs. CC: OR = 2.68, 95% CI 1.46-4.94; AA vs.

CA/CC

OR = 2.62, 95% CI 1.44-4.76; A vs. C: OR = 1.33, 95% CI 1.06-1.66). The allele-G of c.910A>G and allele-A of c.1804C>A genetic variants may contribute to gastric cancer susceptibility. These preliminary results indicate that these XRCC1 genetic variants are potentially related to gastric cancer susceptibility in Chinese Han population, and might be used as molecular markers.

Genetic polymorphisms of XRCC1 gene and susceptibility to gastric cancer in Chinese Han population

This study aims to evaluate whether the c.1471G > A and c.1686C > G genetic polymorphisms of XRCC1 gene influencing gastric cancer susceptibility. A total of 813 subjects with Chinese Han ethnicity were enrolled. Our data suggest that the allele and genotype frequencies are significantly different from gastric cancer patients with cancer-free controls. We find that c.1471G > A and c.1686C > G genetic polymorphisms statistically increase the risk of gastric cancer. Our findings indicate these two genetic polymorphisms are related with the susceptibility to gastric cancer, and could be used as molecular markers for detecting gastric cancer in Chinese Han ethnicity.

XRCC1 Arg399Gln gene polymorphism and hepatocellular carcinoma risk in the Chinese Han population: a meta-analysis

PURPOSE

Numerous studies have evaluated the association between XRCC1 Arg399Gln gene polymorphism and hepatocellular carcinoma risk in the Chinese Han population. However, the results have been inconsistent. We therefore here examined whether the XRCC1 Arg399Gln gene polymorphism confers hepatocellular carcinoma risk by conducting a meta-analysis.

METHODS

PubMed, Google scholar and China National Knowledge Infrastructure databases were searched for eligible articles in English and Chinese that were published before April 2012.

RESULTS

6 studies involving 1,246 patients with hepatocellular carcinoma and 1,953 controls were included. The association between XRCC1 Arg399Gln gene polymorphism and hepatocellular carcinoma in the Chinese Han population was significant under GG vs AA (OR = 1.48, 95% CI = 1.13 to 1.94). Limiting the analysis to the studies with controls in the Hardy-Weinberg equilibrium, the results were persistent and robust.

CONCLUSIONS

In the Chinese Han population, the XRCC1 Arg399Gln gene polymorphism is associated with an increased hepatocellular carcinoma risk.

Association of XRCC1 gene polymorphisms with chronic myeloid leukemia in the population of Andhra Pradesh, India

Chronic myeloid leukemia (CML), a clonal myeloproliferative disorder, is characterized primarily by the presence of chimeric BCR-ABL oncogene, and its progression from chronic to blast phase is associated with the accumulation of additional molecular and chromosomal abnormalities. The molecular mechanisms underlying this genetic instability are poorly understood. The activity of BCR-ABL is known to be associated with the increased production of intracellular reactive oxygen species and spontaneous DNA damage, which when effected by impaired/inaccurate DNA repair systems result in increased susceptibility to CML progression. Using case-control study design, we explored possible association of the repair gene, XRCC1, particularly the codons 399, 280, and 194 polymorphisms screened through PCR-RFLP, with the CML in the sample of 350 cases (206 male and 144 female) and 350 controls from Hyderabad, the capital city of state of the Andhra Pradesh, India. The patient group constituted 301 early chronic phase cases followed by 28 accelerated and 21 blast phase cases. The median age of the patients was 42 years (range, 9-70 years). The genotype distribution revealed significant association of codons 399 (χ(2) = 11.904, degree of freedom (d.f.) = 2; P = 0.002) and 194 (χ(2) = 8.091, d.f. = 2, P = 0.017) with CML, not 280 (P = 0.29). Although these polymorphisms are known to affect the function of XRCC1, the nature and extent of their genetic association with CML does not indicate their direct role in its development. The results seem to suggest that XRCC1 gene might have an important role in CML progression but not in its causation.

Lack of an association between the XRCC1 Arg399Gln polymorphism and gastric cancer based on a meta-analysis

Association between the XRCC1 Arg399Gln polymorphism and susceptibility to gastric cancer has been investigated; overall, the results have been inconclusive. We made a meta-analysis of 13 case-control studies, including 3278 cases and 6243 controls. Crude odds ratios (OR) with 95% confidence intervals (95%CI) were used to assess this possible association. We found no evidence of a significant association between the XRCC1 Arg399Gln polymorphism and gastric cancer risk (in the additive inheritance model, OR = 0.986, 95%CI = 0.831-1.156, in the dominant inheritance model, OR = 1.044, 95%CI = 0.890-1.224 and in the recessive inheritance model, OR = 0.975, 95%CI = 0.894-1.063). We conclude that the XRCC1 Arg399Gln polymorphism is not a risk factor for developing gastric cancer.

Association of a tgf-b1-509c/t polymorphism with gastric cancer risk: a meta-analysis

Published data on the association between the transforming growth factor B1 (TGF-B1) gene 509C/T polymorphism and gastric cancer risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis of the TGFB1-509C/T polymorphism (with 2130 cases and 2374 controls) from seven published case-control studies was performed. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association in the codominant model, the dominant model, and the recessive model. In the overall analysis, the T allele was significantly associated with susceptibility to gastric cancer in the recessive model (TT vs. CC+CT) (TT vs. CC+CT: OR = 1.35, 95% CI: 1.10-1.66, P = 0.10 for heterogeneity) when all the included studies were pooled into the meta-analysis. In the stratified analysis by country, the T allele was also found to be significantly associated with increased gastric cancer risk in the recessive model (TT vs. CC+CT) in Chinese studies and in T versus C in the Indian study. In conclusion, this meta-analysis supports the TGFB1-509T polymorphism as a susceptibility factor for gastric cancer.

Polymorphisms of DNA repair gene XRCC1 and hepatocellular carcinoma risk among East Asians: a meta-analysis

Association studies on the X-ray repair cross-complementing group 1 (XRCC1) polymorphisms (Arg194Trp, Arg280His, and Arg399Gln) in hepatocellular carcinoma (HCC) have shown conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Published literatures from PubMed, Embase, CNKI, and Chinese Biomedicine Database were retrieved. Pooled odds ratio (OR) with 95 % confidence interval (CI) was calculated using fixed- or random-effects model. Thirteen studies including 3,011 HCC cases and 3,619 controls were included in the meta-analysis of the association between XRCC1 Arg399Gln polymorphism and HCC risk. The results indicated that Arg399Gln polymorphism was significantly associated with risk of HCC in a codominant model (Gln/Gln vs. Arg/Arg, OR = 1.32, 95 % CI = 1.08-1.61; Arg/Gln vs. Arg/Arg, OR = 1.41, 95 % CI = 1.12-1.80) and a dominant model (Gln/Gln + Arg/Gln vs. Arg/Arg, OR = 1.39, 95 % CI = 1.15-1.69), but not in a recessive model (Gln/Gln vs. Arg/Gln + Arg/Arg, OR = 1.13, 95 % CI = 0.95-1.35). Limiting the analysis to the studies within Hardy-Weinberg equilibrium, the results were persistent and robust. When stratifying for region and source of controls, persistent results were observed in any subgroup. No evidence of association of Arg194Trp (980 HCC cases and 966 controls) and Arg280His (1,200 HCC cases and 1,236 controls) with HCC risk was found. No publication bias was found in the present study. The results from the present meta-analysis indicated that the Arg399Gln polymorphisms of XRCC1 may be a genetic susceptibility for HCC in the East Asian population. Further, large and well-designed studies are needed to confirm this conclusion.

X-ray repair cross-complementing group 1 (XRCC1) genetic polymorphisms and cervical cancer risk: a huge systematic review and meta-analysis

BACKGROUND

Previous studies investigating the association between X-ray repair cross-complementation group 1(XRCC1) polymorphisms and cervical cancer (CC) risk has provided inconsistent results. The aim of our study was to assess the association between the XRCC1 gene Arg399Gln, Arg194Trp, Arg280His polymorphisms and risk of CC.

METHODS

Two investigators independently searched the Medline, Embase, CNKI, and Chinese Biomedicine Databases for studies published before March 2011.Summary odds ratios (ORs) and 95% confidence intervals (CIs) for XRCC1 polymorphisms and CC were calculated in a fixed-effects model or a random-effects model when appropriate.

RESULTS

Ultimately, 9, 5 and 2 studies were found to be eligible for meta-analyses of Arg399Gln, Arg194Trp and Arg280His, respectively. Our analysis suggested that the variant genotypes of Arg194Trp were associated with a significantly increased CC risk (Trp/Trp vs Arg/Arg, OR = 2.21, 95% CI = 1.60-3.06; Arg/Trp vs Arg/Arg, OR = 1.23, 95% CI = 1.02-1.49; dominant model, OR = 1.36, 95% CI = 1.14-1.63; recessive model, OR = 2.06, 95% CI = 1.51-2.82). For Arg280His polymorphism, no obvious associations were found for all genetic models. For Arg399Gln polymorphism, also no obvious associations were found for all genetic models. In the subgroup analyses by ethnicity/country, a significantly increased risk was observed among Asian, especially among Chinese. To get more precise evidences, adjusted ORs (95%CI) by potential confounders (such as age, ethnicity or smoking, etc) were also calculated for XRCC1 Arg399Gln and Arg194Trp, however, the estimated pooled adjusted OR still did not change at all.

CONCLUSION

This meta-analysis suggests that Arg194Trp polymorphism may be associated with CC risk, Arg399Gln polymorphism might be a low-penetrent risk factor for CC only in Asians, and there may be no association between Arg280His polymorphism and CC risk.

Evaluation of DNA repair gene XRCC1 polymorphism in prediction and prognosis of hepatocellular carcinoma risk

We conducted a case-control study in China to clarify the association between XRCC1-Arg399Gln polymorphism and HCC risk. A total of 150 cases and 158 controls were selected from the the Affiliated Hospital of Qingdao University from May 2008 to May 2010. XRCC1-Arg399Gln polymorphism was based upon duplex polymerase-chain-reaction with the confronting-two-pair primer (PCR-CTPP) method. All analyses were performed using the STATA statistical package. A significantly increased risk was associated with the Arg/Gln genotype (adjusted OR 1.78, 95%CI=1.13-2.79) compared with genotype Arg/Arg. In contrast, the Gln/Gln genotype had non-significant increased risk of HCC with adjusted OR (95%CI) of 1.69 (0.93-2.66). A significant association was found between positive HBsAg and Arg/Gln, with an OR of 3.43 (95% CI=1.45-8.13). Patients carrying Gln/Gln genotypes showed significantly lower median survival than Arg/Arg genotypes (HR=1.38, 95% CI=1.04-1.84). Further Kaplan-Meier analysis showed decreased median survival in Arg/Gln+Gln/Gln genotype carriers in comparison to Arg/Arg carriers (HR=1.33, 95% CI=1.02-1.76). In conclusion, we observed that XRCC1-Arg399Cln polymorphism is associated with susceptibility to HCC, and XRCC1 Gln allele genotype showed significant prognostic associations.

Association between XRCC1 ARG399GLN and P53 ARG72PRO polymorphisms and the risk of gastric and colorectal cancer in Turkish population

Gastric cancer is one of the most common cancers of the gastrointestinal system, and its overall five-year survival rate is still 15 % to 20 %, as it can mostly be diagnosed at an advanced stage. On the other hand, although colorectal cancer has a rather good prognosis, mortality is one half that of the incidence.As carcinogenesis is believed to involve reactive radicals that cause DNA adduct formation, impaired repair activity, and weakened tumour suppression, it would help to understand the role of the polymorphisms of nucleotide excision repair enzyme XRCC1 and of tumour suppressor gene p53 in gastric and colorectal cancers. Our study included 94 gastric cancer patients, 96 colorectal cancer patients, and 108 cancer-free individuals as control with the aim to see if there was an association between XRCC1 Arg399Gln and p53 Arg72Pro polymorphisms and cancer susceptibility. DNA was extracted from peripheral blood cells and genotypes were determined using the polymerase chain reaction-restriction fragment length polymorphism. Polymorphism p53 Arg72Pro was not associated with either gastric or colorectal carcinoma, while XRCC1 Arg399Gln was not associated with the increased risk of colorectal cancer. However, XRCC1 homozygous Gln allele at codon 399 was associated with 2.54 times higher risk of gastric cancer.

DNA repair genes polymorphism (XPG and XRCC1) and association of prostate cancer in a north Indian population

Prostate cancer is the most commonly diagnosed cancer in men worldwide and is the second leading cause of cancer related mortality. Genetic background may account for the difference in susceptibility of individuals to different diseases and the relationship between genetic polymorphism and some diseases has been extensively studied. There are several common polymorphisms in genes encoding DNA repair enzymes, some of these polymorphisms are reported to result in subtle structural alterations of the repair enzyme and modulation of the repair capacity. The aim of the present study was to analyze the effect of XPG Asp 1104His and XRCC1 Arg309Gln polymorphisms on risk of prostate cancer in north Indian population. Statistically significant increased risk of prostate cancer was observed on individuals that posses His/His genotype of XPG (OR 2.53, 95% CI 0.99-6.56, P = 0.031). In this study 150 prostate cancer diagnosed patients, 150 healthy controls and 150 BPH (benign prostate hyper plasia) were recruited from north Indian population. Moreover, individuals that carried the Gln/Gln genotype of XRCC1 also showed statistically increased risk of prostate cancer (OR 2.06, 95% CI 1.07-4.00, P = 0.033). The Asp/Asp of XPG and Gln/Gln of XRCC1 in combination showed statistically increased risk of prostate cancer in cases (OR 3.29, 95% CI 1.09-10.16, P = 0.032).

Polymorphisms of XRCC1 and gastric cancer susceptibility: a meta-analysis

Studies investigating the association between X-ray repair cross-complementing gene 1 (XRCC1) polymorphisms and gastric cancer (GC) risk have reported conflicting results. We performed a meta-analysis of published case-control and cohort studies to better compare results between studies. Published literature from PubMed, EMBASE, and China National Knowledge Infrastructure were retrieved. 18 studies with 3,915 GC cases and 6,759 controls were selected. For XRCC1 Arg194Trp polymorphism, we only found the Trp/Trp genotype carriers might be at high risk of GC (TT vs. CC+CT: OR = 1.31, 95%CI = 1.04-1.65). When stratifying for ethnicity, the results showed there was a significant difference in genotype distribution between GC cases and controls among Asians (especially, in Chinese population), but not among Caucasians. When stratifying for control sources, significant association between Arg194Trp polymorphism and GC risk was only observed in the hospital-based controls' subgroup (TT vs. CC+CT: OR = 1.45, 95%CI = 1.13-1.87). Additionally, no significant association was detected in the gastric cardia cancer's subgroup. The results of the overall meta-analysis did not suggest any association between Arg280His/Arg399Gln polymorphisms and GC susceptibility for all genetic models. There was no evidence for the association between these two gene polymorphisms and GC risk in subgroup analyses based on study design, ethnicity, country, tumor location, Helicobacter pylori infection and the Lauren's classification of GC. In conclusion, XRCC1 Arg194Trp homozygous mutant genotype (Trp/Trp) was found to be associated with increased risk of GC.

Polymorphism in the DNA repair enzyme XRCC1: utility of current database and implications for human health risk assessment

Genetic polymorphisms are increasingly recognized as sources of variability not only in toxicokinetic but also in toxicodynamic response to environmental agents. XRCC1 is involved in base excision repair (BER) of DNA; it has variant genotypes that are associated with modified repair function. This analysis focuses on four polymorphisms: three in the coding region that affect protein structure and one in an upstream regulatory sequence that affects gene expression. The Arg399Gln variant is the most widely studied with evidence supporting a quantitative effect of genotype on phenotype. The homozygous variant (Gln/Gln) can have 3-4-fold diminished capacity to remove DNA adducts and oxidized DNA damage. This variant is relatively common in Caucasians and Asians where approximately 10% are homozygous variant. In contrast, the Arg194Trp variant appears to protect against genotoxic effects although the degree to which DNA repair is enhanced by this polymorphism is uncertain. The homozygous variant is rare in Caucasians and African Americans but it is present at 7% in Asians. A third coding region polymorphism at codon 280 appears to decrease repair function but additional quantitative information is needed and the homozygous variant is rare across populations studied. A polymorphism in an upstream promoter binding sequence (-77T>C) appears to lower XRCC1 levels by decreasing gene expression. Based upon genotype effect on phenotype and allele frequency, the current analysis finds that the codon 399 and upstream (-77) polymorphisms have the greatest potential to affect the toxicodynamic response to DNA damaging agents. However, the implications for risk assessment are limited by the likelihood that polymorphisms in multiple BER genes interact to modulate DNA repair.

X-ray repair cross-complementing group 1 (XRCC1) genetic polymorphisms and gastric cancer risk: A HuGE review and meta-analysis

The authors performed a systematic review and meta-analysis of associations of the x-ray repair cross-complementing 1 gene (XRCC1) single nucleotide polymorphisms (SNPs) Arg194Trp, Arg280His, and Arg399Gln with gastric cancer risk, based on eligible studies retrieved from electronic databases for the period January 2000-December 2009. Ultimately, 12, 6, and 3 studies were found to be eligible for meta-analyses of Arg399Gln, Arg194Trp, and Arg280His, respectively. Regrouping was adopted in accordance with the most probably appropriate genetic models. Potential sources of heterogeneity were sought out. For overall gastric cancer, the pooled odds ratios for Arg399Gln, Arg194Trp, and Arg280His were 1.04 (95% confidence interval (CI): 0.90, 1.20; P = 0.572), 0.83 (95% CI: 0.68, 1.01; P = 0.059), and 1.18 (95% CI: 0.92, 1.50; P = 0.194), respectively. After stratification of the Arg399Gln SNP data by anatomic type (cardia vs. noncardia), the pooled odds ratio was 1.07 (95% CI: 0.84, 1.37; P = 0.568). The authors conclude that the 3 SNPs evaluated are not associated with risk of gastric cancer. The Arg399Gln SNP is not associated with the cardia type of gastric cancer. Evidently, the heterogeneity regarding the Arg399Gln SNP across studies is not explained by ethnicity, genotyping technique, sample size, or date of publication.

XRCC1 downregulated through promoter hypermethylation is involved in human gastric carcinogenesis

OBJECTIVE

To analyze the expression and aberrant methylation of X-ray repair cross-complementing gene 1 (XRCC1) in gastric carcinogenesis, and identify the molecular mechanism of gastric carcinogenesis.

METHODS

The method based on methyl binding domain protein (MBD) immuno-precipitation and promoter microarray was employed to screen the gastric cancer-related methylation-sensitive gene. An immunohistochemistry assay was applied to detect the protein expression of XRCC1 in the multistep progression of gastric carcinogenesis. The mRNA expression of XRCC1 was determined by real-time PCR in tumor tissues and their corresponding non-tumorous tissues. The methylation status and Arg194Trp and Arg399Gln polymorphisms of XRCC1 in gastric cancer and gastritis tissues were analyzed by methylation-specific PCR, bisulfite genomic sequencing and direct DNA sequencing, respectively.

RESULTS

Promoter microarray screening and identification suggested that XRCC1 was a methylation-sensitive gene. Immunochemistry results showed that XRCC1 protein expression gradually decreased with progression of gastric mucosal lesions (P < 0.05). The positive rate of XRCC1 in patients with well/moderately differentiated gastric cancer was significantly higher than patients with poorly differentiated gastric cancer (P < 0.05). The mRNA expression of XRCC1 in gastric cancer tissues was significantly lower than that in the non-tumorous tissues (P < 0.05). Meanwhile, XRCC1 methylation in gastric cancer tissues was more frequent than that in the gastritis tissues (P < 0.05), and the downregulation of XRCC1 expression was relevant to methylation (P < 0.05).

CONCLUSION

The expression of XRCC1 is downregulated in gastric carcinogenesis, and promoter hypermethylation may be one of the mechanisms contributing to its downregulation.

Very low frequencies of Toll-like receptor 2 supposed-2029T and 2258A (RS5743708) mutant alleles in southern Brazilian critically ill patients: would it be a lack of worldwide-accepted clinical applications of Toll-like receptor 2 variants?

Toll-like receptor 2 (TLR2) is a recognition receptor for the widest repertoire of pathogen-associated molecular patterns. Two polymorphisms of TLR2 could be linked to reduced nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) activation and to increased risk of infection (supposed-2029C>T and 2258G>A). We investigated the supposed-2029C>T and 2258G>A TLR2 polymorphisms in 422 critically ill patients of European origin from southern Brazil (295 with sepsis and 127 without sepsis) and reviewed 33 studies on these polymorphisms, conducting a quality assessment with a score system. Among our patients we found only one heterozygote (1/422) for the supposed-2029C>T and none for the 2258G>A (0/422) single nucleotide polymorphism (SNP). We were unable to find a clinical application of supposed-2029T and 2258A allele analyses in our southern Brazilian population. Our review detected that current TLR2 SNP assays had very controversial and contradictory results derived from reports with a variety of investigation quality criteria. We suggest that, if analyzed alone, the supposed-2029C>T and 2258G>A TLR2 SNP are not good candidates for genetic markers in studies that search for direct or indirect clinical applications between genotype and phenotype. Future efforts to improve the knowledge and to provide other simultaneous genetic markers might reveal a more effective TLR2 effect on the susceptibility to infectious diseases.

A functional -77T>C polymorphism in XRCC1 is associated with risk of breast cancer

X-ray repair cross-complementing 1 (XRCC1) plays a critical role in base excision repair and genetic variations of XRCC1 may be associated with cancer susceptibility. We tested this hypothesis by examining the contribution of polymorphism in the regulatory region of XRCC1 -77T>C to risk of breast cancer in 995 patients and 1,004 controls. We found this polymorphism was associated with an increased risk of breast cancer, with an OR of 1.25 (95% CI, 1.00-1.56) for the -77TC genotype and 2.55 (95% CI, 1.11-5.86) for the -77CC genotype compared with the -77TT genotype. Haplotype analysis combining the -77T>C with three well-studied non-synonymous polymorphisms (Arg194Trp, Arg280His, and Arg399Gln) showed that only the -77C-containing haplotype was associated with the risk. Moreover, the C allele had more than 3-fold decreased luciferase expression compared with the T allele in breast cancer cell line MCF-7 (P < 0.001). A meta-analysis of seven publications with a total 2,888 cancer cases and 3,177 controls demonstrated that -77C was significantly associated with cancer risk, with an OR of 1.34 (95% CI, 1.18-1.51) for the TC genotype and 1.53 (95% CI, 1.14-2.07) for the CC genotype compared with the TT genotype. In conclusion, these findings indicated that XRCC1 -77T>C polymorphism may be a genetic determinant for developing breast cancer.

XRCC1 polymorphisms and risk of colorectal cancer: a meta-analysis

PURPOSE

Previous studies investigating the association between X-ray repair cross-complementation group 1 (XRCC1) polymorphisms and colorectal cancer (CRC) risk has provided inconsistent results. The aim of our study was to clarify the effects of XRCC1variants on CRC risk.

MATERIALS AND METHODS

We conducted searches of the published literature in PubMed, Embase, and CBM databases up to July 6, 2009. Meta-analysis was performed by critically reviewing 14 studies with a total of 2,776 CRC cases and 4,402 controls on Arg399Gln polymorphism, four studies with a total of 931 CRC cases and 1,547 controls on Arg280His polymorphism, and nine studies with a total of 1,709 CRC cases and 3,233 controls on Arg194Trp polymorphism, respectively. Statistical analysis was performed with the software programs Review Manager (version 5.0.10) and STATA (version 9.2).

RESULTS

No significant association between Arg399Gln polymorphism and CRC risk was observed in both total population analyses and subgroup analyses based on ethnicity (OR(Co-dominant model) = 1.04, 95% CI 0.74-1.45, P (OR) = 0.82; OR(Dominant model) = 1.02, 95% CI 0.80-1.30, P (OR) = 0.88; OR (Recessive model) = 1.04, 95% CI 0.81-1.34, P (OR) = 0.78). Arg280His polymorphism also had no significant association with CRC risk (OR(Co-dominant model) = 0.85, 95% CI 0.32-2.31, P (OR) = 0.76; OR(Dominant model) = 1.11, 95% CI 0.87-1.40, P (OR) = 0.40; OR(Recessive model) = 0.85, 95% CI 0.32-2.31, P (OR) = 0.75). Besides, there was also no evidence of association between Arg194Trp polymorphism and CRC risk (OR(Co-dominant model) = 1.43, 95% CI 0.83-2.48, P (OR) = 0.20; OR(Dominant model) = 1.14, 95% CI 0.87-1.51, P (OR) = 0.34; OR(Recessive model) = 1.32, 95% CI 0.82-2.13, P (OR) = 0.25).

CONCLUSIONS

No association is found between the polymorphisms in XRCC1 (Arg399Gln, Arg280His, and Arg194Trp) and risk of colorectal cancer.

Genetic polymorphisms of DNA repair gene XRCC1 and risk of uterine leiomyoma

The objective was to study the relationship between the polymorphisms of the DNA repair gene XRCC1 Arg399Gln, Arg194Trp, and Arg280His uterine leiomyoma in a Chinese population. In the case-control study, we compared the XRCC1 gene polymorphism of 136 uterine leiomyoma patients and 140 healthy controls by using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results suggested that the genotype Arg/Arg of codon 280 was significantly different from its heterozygote (odds ratio [OR] = 3.633, 95% confidence interval [CI]: 2.147-6.148). In conclusion, the results suggest that polymorphism of XRCC1 Arg280His was associated with the increased risk of uterine leiomyoma in a Chinese population.