Lack of involvement of nucleotide excision repair gene polymorphisms in colorectal cancer

Association of base excision repair pathway genes OGG1, XRCC1 and MUTYH polymorphisms and the level of 8-oxo-guanine with increased risk of colorectal cancer occurrence

OBJECTIVES

Reduced efficiency of DNA repair systems has long been a suspected factor in increasing the risk of cancer. In this work authors investigate influence of selected polymorphisms of DNA repair genes (XRCC1, OGG1 and MUTYH) and level of oxidative damage (measured as level of 8-oxo-guanine, 8-oG) on modulation of the risk of colorectal cancer.

MATERIAL AND METHODS

In group of 324 patients with colorectal cancer the occurrence of polymorphic variants in Ser326Cys of OGG1, Arg399Gln of XRCC1 and Gln324His of MUTYH were studied with TaqMan technique. In addition level of 8-oG in isolated DNA was determined.

RESULTS

Studied polymorphisms of OGG1, XRCC1 and MUTYH genes influence the risk of CRC: OGG1 Ser326Cys (OR = 1.259, 95% CI: 1.058-1.499, p = 0.007), XRCC1 Arg399Gln (OR = 2.481, 95% CI: 1.745-3.529, p < 0.0001) and MUTYH Gln324His (OR = 1.421, 95% CI: 1.017-1.984, p = 0.039) increase the risk. At the same time, studies examined level of 8-oG for each of the genotypes in both the patient and control group, and have shown that OGG1 Ser326Cys and XRCC1 Arg399Gln are associated with elevated 8-oG level, while MUTYH Gln324His is not, suggesting, that in case of OGG1 Ser326Cys and XRCC1 Arg399Gln CRC risk modulation is connected to mechanisms associated with 8-oG levels.

CONCLUSIONS

This work shows that patients with CRC not only have an increased level of 8-oG and that the studied polymorphisms modulate risk of cancer, but also indicate a relationship between these 2 phenomena, which may contribute to a better understanding of the mechanism of neoplastic process in case of reduced effectiveness of DNA repair mechanisms. Int J Occup Med Environ Health. 2022;35(5):625-33.

A Nobel-Winning Scientist: Aziz Sancar and the Impact of his Work on the Molecular Pathology of Neoplastic Diseases

Aziz Sancar, Nobel Prize winning Turkish scientist, made several discoveries which had a major impact on molecular sciences, particularly disciplines that focus on carcinogenesis and cancer treatment, including molecular pathology. Cloning the photolyase gene, which was the initial step of his work on DNA repair mechanisms, discovery of the "Maxicell" method, explanation of the mechanism of nucleotide excision repair and transcription-coupled repair, discovery of "molecular matchmakers", and mapping human excision repair genes at single nucleotide resolution constitute his major research topics. Moreover, Sancar discovered the cryptochromes, the clock genes in humans, in 1998, and this discovery led to substantial progress in the understanding of the circadian clock and the introduction of the concept of "chrono-chemoterapy" for more effective therapy in cancer patients. This review focuses on Aziz Sancar's scientific studies and their reflections on molecular pathology of neoplastic diseases. While providing a new perspective for researchers working in the field of pathology and molecular pathology, this review is also an evidence of how basic sciences and clinical sciences complete each other.

Association of XPD Lys751Gln gene polymorphism with susceptibility and clinical outcome of colorectal cancer in Pakistani population: a case-control pharmacogenetic study

BACKGROUND

XPD Lys751Gln polymorphism may modulate inter-individual variation in repair capacity of DNA, which may enhance a person's susceptibility to develop colorectal cancer (CRC). The analysis of XPD Lys751Gln polymorphism may provide important information for identifying high-risk individuals and for selecting the most appropriate treatment for poor prognostic CRC patients.

OBJECTIVE

The overall objective was to find out the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer and the ultimate clinical outcomes. In this study a total of 300 subjects (CRC and Controls), were genotyped for XPD Lys751Gln.

METHODS

Using PCR-RFLP methods, the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer was studied. In addition to overall risk assessment, genotyping results were also investigated with respect to the lifestyle risk factors, patients treated with oxaliplatin-based chemotherapy and clinicopathological characteristics.

RESULTS

The overall correlation between the XPD Lys751Gln genetic variation and the CRC risk was observed to be significant with both the homozygous variant genotype Gln/Gln as well as heterozygous genotype Lys/Gln being associated with the increased risk of CRC. Additional stratified analyses revealed that XPD Lys751Gln variants remarkably increased risk of CRC in males and younger individuals (≤ 50 years), Naswar users (8.09-fold) and high intake of red meat.

CONCLUSIONS

Our findings suggest that the relationship between the XPD Lys751Gln variants and lifestyle factors modulates the risk for CRC in Pakistani population.

Cytogenetic effects of radiation and genetic polymorphisms of the XRCC1 and XRCC3 repair genes in industrial radiographers

Different types of DNA damages caused by ionizing radiation may enhance the cancer risk in exposed individuals. Inherited variations in DNA repair genes cause the inter-individual variability in response to ionizing radiation. The purpose of this study was to determine the association between single nucleotide polymorphism (SNP) of two important DNA repair genes (XRCC1 R399Q and XRCC3 T241M) and the level of DNA damage investigated by micronucleus (MN) frequency in peripheral blood lymphocytes of 120 industrial radiographers (IR) and 120 non-exposed control individuals. The frequencies of MN and nucleoplasmic bridges were significantly higher in the IR group than in the control group (33.83 ± 11.96 vs. 7.47 ± 2.96, p < 0.0001 and 1.69 ± 1.86 vs. 0.12 ± 0.33, p < 0.0001). MN frequencies in the IR group were associated with the cumulative radiation doses (p < 0.0001, r = 0.58 for last 1 year of exposure and p < 0.0001, r = 0.67 for last 5 years of exposure). Polymorphism of XRCC3 T241M was associated with higher MN frequencies in the IR group. However, the same result was not observed between XRCC3 SNP and MN frequency in the control group. Consequently, XRCC3 241Met alleles may cause the increased DNA damage in the industrial radiographers.

Genetic Polymorphisms of DNA Repair Pathways in Sporadic Colorectal Carcinogenesis

DNA repair systems play a critical role in maintaining the integrity and stability of the genome, which mainly include base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR) and double-strand break repair (DSBR). The polymorphisms in different DNA repair genes that are mainly represented by single-nucleotide polymorphisms (SNPs) can potentially modulate the individual DNA repair capacity and therefore exert an impact on individual genetic susceptibility to cancer. Sporadic colorectal cancer arises from the colorectum without known contribution from germline causes or significant family history of cancer or inflammatory bowel disease. In recent years, emerging studies have investigated the association between polymorphisms of DNA repair system genes and sporadic CRC. Here, we review recent insights into the polymorphisms of DNA repair pathway genes, not only individual gene polymorphism but also gene-gene and gene-environment interactions, in sporadic colorectal carcinogenesis.

XPG rs17655 G>C polymorphism associated with cancer risk: evidence from 60 studies

Xeroderma pigmentosum group G (XPG), a key component in nucleotide excision repair pathway, functions to cut DNA lesions during DNA repair. Genetic variations that alter DNA repair gene expression or function may decrease DNA repair ability and impair genome integrity, thereby predisposing to cancer. The association between XPG rs17655 G>C polymorphism and cancer risk has been investigated extensively, but the results remain contradictory. To get a more accurate conclusion, we performed a comprehensive meta-analysis of 60 case-control studies, involving 27,098 cancer cases and 30,535 healthy controls. Crude odds ratios (ORs) and 95% confidence interval (CIs) were calculated to determine the association of interest. Pooled analysis indicated that the XPG rs17655 G>C polymorphism increased the risk of overall cancer (CC vs. GG: OR=1.10, 95% CI=1.00-1.20; CG vs. GG: OR=1.06, 95% CI=1.02-1.11; CG+CC vs. GG: OR=1.07, 95% CI=1.02-1.12; C vs. G: OR=1.05, 95% CI=1.01-1.09). Stratification analysis by cancer type further showed that this polymorphism was associated with increased risk of gastric cancer and colorectal cancer. This meta-analysis indicated that the XPG gene rs17655 G>C polymorphism was associated with increased overall cancer risk, especially the risk of gastric cancer and colorectal cancer. Further validation experiments are needed to strength our conclusion.

XPG Asp1104His, XRCC2 Rs3218536 A/G and RAD51 135G/C Gene Polymorphisms and Colorectal Cancer Risk: A Meta-Analysis

Background:

DNA repair mechanisms are crucial for sustaining DNA integrity and preventing carcinogenesis. The xeroderma pigmentosum group G (XPG), X-ray repair cross complementing group 2 (XRCC2) and RAD51 are candidate genes for DNA repair pathways.

Methods:

We performed a meta-analysis of 26 studies that assessed the impact of XPG Asp1104His, XRCC2 rs3218536 A/G and RAD51 135G/C polymorphisms on colorectal cancer (CRC) risk. This study included 10288 CRC patients and 11885 controls, and odds ratio (OR) with its 95% confidence interval (CI) were used to calculate the strength of association.

Results:

The results of overall meta-analysis suggested an association between the XPG Asp1104His polymorphism and CRC susceptibility in allele (OR=1.06; 95% CI=1.01-1.12) and heterozygote model (OR=1.16; 95%CI=1.02-1.31). In the subgroup analysis based on ethnicity and source of control, we found significantly increased CRC cancer risk in Asians (OR=1.12, 95%CI=1.04-1.21) and in hospital-based (OR=1.22, 95%CI=1.08-1.38) populations. Moreover, the RAD51 135 G/C polymorphism increased the risk of CRC in total using allele (OR=1.21) and recessive models (OR=1.62). However, XRCC2 rs3218536 A/G was not associated with the risk of CRC in total or in subgroups.

Conclusions:

According to the results of our meta-analysis, the XPG Asp1104His and RAD51 135 G/C polymorphisms might influence colorectal cancer risk.

Zeolite-Containing Mixture Supplementation Ameliorated Dextran Sodium Sulfate-Induced Colitis in Mice by Suppressing the Inflammatory Bowel Disease Pathway and Improving Apoptosis in Colon Mucosa

Inflammatory bowel disease (IBD) is induced by multiple environmental factors, and there is still no known treatment capable of curing the disease completely. We propose a zeolite-containing mixture (Hydryeast^®, HY)-a multi-component nutraceutical of which the main ingredients are Azumaceramics (mixture of zeolite and oyster shell burned under high temperature), citric acid, red rice yeast (monascus) and calcium stearate-as a nutraceutical intervention in IBD to ameliorate dextran sodium sulfate (DSS)-induced colitis. We show the mechanism through integrated omics using transcriptomics and proteomics. C57BL6 mice were given an AIN-93G basal diet or a 0.8% HY containing diet and sterilized tap water for 11 days. Colitis was then induced by 1.5% (w/v) DSS-containing water for 9 days. HY fed mice showed significantly improved disease activity index and colon length compared to DSS mice. Colonic mucosa microarray analysis plus RT-PCR results indicate HY supplementation may ameliorate inflammation by inhibiting the intestinal inflammatory pathway and suppress apoptosis by curbing the expression of genes like tumor protein 53 and epidermal growth factor receptor and by upregulating epithelial protection-related proteins such as epithelial cell adhesion molecule and tenascin C, thus maintaining mucosal immune homeostasis and epithelial integrity, mirroring the proteome analysis results. HY appears to have a suppressive effect on colitis.

The Role of the XPF Gene Polymorphism (Xrcc4) Ser835ser in the Risk of Malignant Transformation of Cells in the Colorectal Cancer

Participation of DNA repair systems in the pathogenesis of cancer has been a suspected phenomenon for a long time. Decreased efficiency in DNA repair translates to their ability to fix and consequently leads to mutations and the process of carcinogenesis. Linking individual polymorphisms of DNA repair systems with an increased risk of colorectal cancer will allow the classification of patients to high-risk groups and their placement under preventive program. The aim of the study was to determine the effect of XPF gene polymorphism Ser835Ser on increasing the risk of colorectal cancer in the Polish population.

MATERIAL AND METHODS

as the material blood collected from 146 patients diagnosed with colon cancer was used. The control group consisted of 149 healthy subjects. Genotyping was performed by Taq- Man method.

RESULTS

The results indicate that genotype TCC/TCT is associated with an decreased risk of colorectal cancer (OR 0.574; CI 95% 0.335-0.984; p=0.043).

CONCLUSIONS

Based on these results, we conclude that the XPF gene polymorphism Ser835Ser may be associated with a decreased risk of colorectal cancer.

Association between XRCC3 Thr241Met polymorphism and nasopharyngeal carcinoma risk: evidence from a large-scale case-control study and a meta-analysis

The X-ray repair cross-complementing group 3 (XRCC3) Thr241Met polymorphism (rs861539, C > T) has drawn wide attentions as its association with cancer risk and its involvement in DNA repair. Several studies have attempted to link rs861539 to nasopharyngeal cancer (NPC) risk; however, the sample sizes of these studies are small and the results are controversial. To investigate the relationship of rs861539 and NPC susceptibility, we conducted a large-scale case-control study involving 4001 NPC cases and 2967 controls of southern Chinese. Logistic regression analysis revealed significant association for rs861539 and NPC risk under the recessive model (TT vs. CT + CC) with adjustment of age and gender (odds ratio, OR = 2.72; 95 % CI 1.10-6.72; P = 0.03). Further, meta-analysis involving 4457 NPC cases and 4132 controls from four studies showed consistent association of TT carriers and NPC risk (OR = 3.12; 95 % CI 1.58-6.13; P = 0.001). Taken together, our findings based on large-scale sample size suggested rs861539 at XRCC3 to be associated with NPC risk through recessive model.

XPG Gene Polymorphisms Contribute to Colorectal Cancer Susceptibility: A Two-Stage Case-Control Study

Previous studies have reported that xeroderma pigmentosum group G (XPG) gene polymorphisms may modulate colorectal cancer (CRC) susceptibility. In this study, we performed a two-stage case-control study to comprehensively investigate the associations of five polymorphisms in the XPG gene with CRC risk in 1,901 cases and 1,976 controls from Southern China, including rs2094258 C>T, rs751402 C>T, rs2296147 T>C, rs1047768 T>C and rs873601 G>A. After combining data from two stages, we found that three of the studied polymorphisms (rs2094258 C>T, rs751402 C>T, and rs873601 G>A) were significantly associated with CRC susceptibility. After adjustment for age and gender, multivariate logistic regression analysis indicated that carriers of the rs2094258 T alleles had an increased CRC risk [CT vs. CC: adjusted odds ratio (OR)=1.17, 95% confidence interval (CI)=1.01-1.36; TT vs. CC: adjusted OR=1.49, 95% CI=1.18-1.89; TT vs. CT/CC: adjusted OR=1.38, 95% CI=1.10-1.72]. Likely, rs873601 A allele also conferred increased CRC susceptibility. In contrast, a protective association was identified between rs751402 C>T polymorphism and the risk of CRC. In summary, our results indicated that these three polymorphisms were found to associate with CRC susceptibility in a Southern Chinese population.

Single nucleotide polymorphisms in DNA repair genes and putative cancer risk

Single nucleotide polymorphisms (SNPs) are the most frequent type of genetic alterations between individuals. An SNP located within the coding sequence of a gene may lead to an amino acid substitution and in turn might alter protein function. Such a change in protein sequence could be functionally relevant and therefore might be associated with susceptibility to human diseases, such as cancer. DNA repair mechanisms are known to play an important role in cancer development, as shown in various human cancer syndromes, which arise due to mutations in DNA repair genes. This leads to the question whether subtle genetic changes such as SNPs in DNA repair genes may contribute to cancer susceptibility. In numerous epidemiological studies, efforts have been made to associate specific SNPs in DNA repair genes with altered DNA repair and cancer. The present review describes some of the common and most extensively studied SNPs in DNA repair genes and discusses whether they are functionally relevant and subsequently increase the likelihood that cancer will develop.

XPG rs2296147 T>C polymorphism predicted clinical outcome in colorectal cancer

Xeroderma pigmentosum group G (XPG), one of key components of nucleotide excision repair pathway (NER), is involved in excision repair of UV-induced DNA damage. Single nucleotide polymorphisms (SNPs) in the XPG gene have been reported to associate with the clinical outcome of various cancer patients. We aimed to assess the impact of four potentially functional SNPs (rs2094258 C>T, rs2296147 T>C, rs751402 G>A, and rs873601 G>A) in the XPG gene on prognosis in colorectal cancer (CRC) patients. A total of 1901 patients diagnosed with pathologically confirmed CRC were genotyped for four XPG polymorphisms. Cox proportional hazards model analysis controlled for several confounding factors was conducted to compute hazard ratios (HRs) and 95% confidence intervals (CIs). Of the four included SNPs, only rs2296147 was shown to significantly affect progression-free survival (PFS) in CRC. Patients carrying rs2296147 CT/TT genotype had a significantly shorter median 10 years PFS than those carrying CC genotype (88.5 months vs. 118.1 months), and an increased progression risk were observed with rs2296147 (HR = 1.324, 95% CI = 1.046-1.667). Moreover, none of the four SNPs were associated with overall survival. In conclusion, our study showed that XPG rs2296147 CT/TT variants conferred significant survival disadvantage in CRC patients in term of PFS. XPG rs2296147 polymorphism could be predictive of unfavorable prognosis of CRC patients.

Polymorphisms in DNA Repair Gene XRCC3 and Susceptibility to Breast Cancer in Saudi Females

We investigated three common polymorphisms (SNPs) in the XRCC3 gene (rs861539, rs1799794, and rs1799796) in 143 Saudi females suffering from breast cancer (median age = 51.4 years) and 145 age matched normal healthy controls. DNA was extracted from whole blood and genotyping was conducted using PCR-RFLP. rs1799794 showed significant association, where AA and AA+AG occurred at a significantly higher frequency in the cancer patients compared to the control group (OR: 28.1; 95% CI: 3.76-21.12; χ (2): 22.82; p < 0.0001). The G allele was protective and presented with a dominant model. The genotype and allele frequencies of rs861539 C>T and rs1799796 A>G did not show a significant difference when the results in the patients and controls were compared. However, the frequency of rs1799796 differed significantly in patients with different age of diagnosis, tumor grade, and ER and HER2 status. The wild type A allele occurred at a higher frequency in the ER- and HER2- group. Our results among Saudis suggest that some variations in XRCC3 may contribute to breast cancer susceptibility. In conclusion, the results obtained during this study suggest that rs1799794 in XRCC3 shows strong association with breast cancer development in Saudi females.

Efficiency of Base Excision Repair of Oxidative DNA Damage and Its Impact on the Risk of Colorectal Cancer in the Polish Population

DNA oxidative lesions are widely considered as a potential risk factor for colorectal cancer development. The aim of this work was to determine the role of the efficiency of base excision repair, both in lymphocytes and in epithelial tissue, in patients with CRC and healthy subjects. SNPs were identified within genes responsible for steps following glycosylase action in BER, and patients and healthy subjects were genotyped. A radioisotopic BER assay was used for assessing repair efficiency and TaqMan for genotyping. Decreased BER activity was observed in lymphocyte extract from CRC patients and in cancer tissue extract, compared to healthy subjects. In addition, polymorphisms of EXO1, LIG3, and PolB may modulate the risk of colorectal cancer by decreasing (PolB) or increasing (LIG3 and EXO1) the chance of malignant transformation.

XPG Asp1104His polymorphism and gastrointestinal cancers risk: a meta-analysis

Several studies have reported the association between the Asp1104His polymorphism in xeroderma pigmentosum group G (XPG) gene and risk of gastrointestinal cancers. However, the results are inconsistent. This meta-analysis was performed to assess the association between XPG Asp1104His polymorphism and gastrointestinal cancers risk. Relevant studies were identified using PubMed, Web of Science, CNKI, WanFang and VIP databases up to July 22, 2014. The pooled odds ratio (OR) with a 95% confidence interval (CI) was calculated using the fixed- or random effects model. 13 case-control studies from twelve publications with 4275 patients and 5735 controls were included. Overall, a significant association was found between the XPG Asp1104His polymorphism and the risk of gastrointestinal cancers (dominant model: OR = 1.15, 95% CI: 1.05-1.26; His/His vs. Asp/Asp: OR = 1.15, 95% CI: 1.01-1.32). When the analysis was stratified by ethnicity, similar results were observed in Asians under homozygote model; in stratification analysis by cancer type, increased cancer risk was detected in colorectal and hepatocellular carcinoma, but not for other gastrointestinal cancers. Furthermore, in subgroup analysis by source of control, we failed to detect any association among population, hospital and family-based populations. This meta-analysis indicated that the XPG Asp1104His polymorphism may be a risk factor for gastrointestinal cancers, especially of colorectal cancer.

Polymorphisms in nucleotide excision repair genes and susceptibility to colorectal cancer in the Polish population

Xeroderma pigmentosum (XP) is a rare autosomal recessive disease that is associated with a severe deficiency in nucleotide excision repair. Genetic polymorphisms in XP genes may be associated with a change in DNA repair capacity, which could be associated with colorectal cancer development. We assessed the association between 94 single nucleotide polymorphisms (SNPs) within seven XP genes (XPA-XPG) and the colorectal cancer risk in the Polish population. We genotyped 758 unselected patients with colorectal cancer and 1,841 healthy adults. We found that a significantly decreased risk of colorectal cancer was associated with XPC polymorphism rs2228000_CT genotype (OR 0.59; p < 0.0001) and the rs2228000_TT genotype (OR 0.29; p < 0.0001) compared to the reference genotype (CC). And an increased disease risk was associated with the XPD SNP, rs1799793_AG genotype (OR 1.44, p = 0.018) and rs1799793_AA genotype (OR 3.31, p < 0.0001) compared to the reference genotype. Haplotype analysis within XPC, XPD and XPG revealed haplotypes associated with an altered colorectal cancer risk. Stratified analysis by gender showed differences between the association of three SNPs: XPC rs2228000, XPD rs1799793 and XPD rs238406 in females and males. Association analysis between age of disease onset and polymorphisms in XPD (rs1799793) and XPC (rs2228000) revealed differences in the prevalence of these variants in patients under and over 50 years of age. Our results confirmed that polymorphisms in XPC and XPD may be associated with the risk of colorectal cancer.

Association study between XPG Asp1104His polymorphism and colorectal cancer risk in a Chinese population

Previous studies have reported that the Asp1104His polymorphism in Xeroderma Pigmentosum complementation group G (XPG) was associated with the susceptibility to colorectal cancer (CRC), although the results were inconsistent. This study was aim to investigate whether there existed an association between XPG Asp1104His polymorphism and CRC risk in the Chinese population, and a further meta-analysis was performed to consolidate the results. We found that XPG Asp1104His polymorphism was associated with a significantly increased CRC risk (dominant model: His/His + Asp/His vs. Asp/Asp, adjusted OR = 1.39, 95% CI = 1.14–1.69). Stratification analysis by clinical characteristics indicated that the His/His + Asp/His genotypes were associated with increased CRC susceptibility in patients with moderately differentiated grade, but not in poorly and well differentiated grade. Furthermore, a total of 5 eligible studies, including 2,649 CRC cases and 2,848 controls, were recruited for the meta-analysis. We identified that the meta-analysis reported a similar result in dominant model (OR = 1.35; 95% CI = 1.20–1.51). Especially, when stratified by ethnicity, an evidently increased risk was identified in the Asian population. In conclusion, our findings suggest that XPG Asp1104His polymorphism may increase the susceptibility of CRC, especially in Asian populations.

Haplotype analyses of DNA repair gene polymorphisms and their role in ulcerative colitis

Ulcerative colitis (UC) is a major clinical form of inflammatory bowel disease. UC is characterized by mucosal inflammation limited to the colon, always involving the rectum and a variable extent of the more proximal colon in a continuous manner. Genetic variations in DNA repair genes may influence the extent of repair functions, DNA damage, and thus the manifestations of UC. This study thus evaluated the role of polymorphisms of the genes involved in DNA repair mechanisms. A total of 171 patients and 213 controls were included. Genotyping was carried out by ARMS PCR and PCR-RFLP analyses for RAD51, XRCC3 and hMSH2 gene polymorphisms. Allelic and genotypic frequencies were computed in both control & patient groups and data was analyzed using appropriate statistical tests. The frequency of ‘A’ allele of hMSH2 in the UC group caused statistically significant increased risk for UC compared to controls (OR 1.64, 95% CI 1.16–2.31, p = 0.004). Similarly, the CT genotype of XRCC3 gene was predominant in the UC group and increased the risk for UC by 1.75 fold compared to controls (OR 1.75, 95% CI 1.15–2.67, p = 0.03), further confirming the risk of ‘T’ allele in UC. The GC genotype frequency of RAD51 gene was significantly increased (p = 0.02) in the UC group (50.3%) compared to controls (38%). The GC genotype significantly increased the risk for UC compared to GG genotype by 1.73 fold (OR 1.73, 95% CI 1.14–2.62, p = 0.02) confirming the strong association of ‘C’ allele with UC. Among the controls, the SNP loci combination of hMSH2:XRCC3 were in perfect linkage. The GTC and ACC haplotypes were found to be predominant in UC than controls with a 2.28 and 2.93 fold significant increase risk of UC.

XRCC1 Arg194Trp and Arg399Gln polymorphisms and arsenic methylation capacity are associated with urothelial carcinoma

The association between DNA repair gene polymorphisms and bladder cancer has been widely studied. However, few studies have examined the correlation between urothelial carcinoma (UC) and arsenic or its metabolites. The aim of this study was to examine the association between polymorphisms of the DNA repair genes, XRCC1 Arg194Trp, XRCC1 Arg399Gln, XRCC3 Thr241Met, and XPD Lys751Gln, with urinary arsenic profiles and UC. To this end, we conducted a hospital-based case-control study with 324 UC patients and 647 age- and gender-matched non-cancer controls. Genomic DNA was used to examine the genotype of XRCC1 Arg194Trp, XRCC1 Arg399Gln, XRCC3 Thr241Met, and XPD Lys751Gln by PCR-restriction fragment length polymorphism analysis (PCR-RFLP). Urinary arsenic profiles were measured by high performance liquid chromatography (HPLC) linked with hydride generator and atomic absorption spectrometry. The XRCC1 399 Gln/Gln and 194 Arg/Trp and Trp/Trp genotypes were significantly related to UC, and the odds ratio (OR) and 95% confidence interval (95%CI) were 1.68 (1.03-2.75) and 0.66 (0.48-0.90), respectively. Participants with higher total urinary arsenic levels, a higher percentage of inorganic arsenic (InAs%) and a lower percentage of dimethylarsinic acid (DMA%) had a higher OR of UC. Participants carrying XRCC1 risk diplotypes G-C/G-C, A-C/A-C, and A-T/G-T, and who had higher total arsenic levels, higher InAs%, or lower DMA% compared to those with other XRCC1 diplotypes had a higher OR of UC. Our results suggest that the XRCC1 399 Gln/Gln and 194 Arg/Arg DNA repair genes play an important role in poor arsenic methylation capacity, thereby increasing the risk of UC in non-obvious arsenic exposure areas.

DNA repair gene--XRCC1 in relation to genome instability and role in colorectal carcinogenesis

Colorectal carcinogenesis is a multifactorial and multi-gene process, involving 3 major genetic instability pathways: chromosomal instability, microsatellite instability and CpG island methylator phenotype. Inefficient DNA repair is one of the causes of genetic instability leading to tumorigenesis. Defects in DNA repair genes are associated with cancer development. The XRCC1 gene is an important DNA repair genes and forms the component of several different damage recovery pathways, including base excision repair and single-strand breaks repair - the processes frequently involved in cancer transformation. In this review we have shed light on the structure and functioning of the XRCC1 gene and its protein, and the role played by XRCC1 in colorectal carcinogenesis.

DNA repair gene variants in migraine

AIMS

Migraine is a common and debilitating episodic disorder characterized by recurrent headache attacks associated with autonomic symptoms. It affects an estimated 12% of the population. The etiology of the underlying neurodegenerative process is widely unknown; however, oxidative stress is a unifying factor in the current theories of migraine pathogenesis. After demonstrating the observation that oxidative DNA damage is detectable in migraine disease, searching the role played by DNA repair systems in migraine diseases could bring us much significant information about the pathogenesis of migraine. We prospectively investigated whether DNA repair gene polymorphisms (XRCC1 Arg399Gln, XRCC3 Thr241Met XPD Lys751Gln, XPG Asp1104His, APE1 Asp148Glu, hOGG1 Ser326Cys) account for an increased risk of migraine. The present analyses are based on 135 case subjects with migraine disease and 101 noncase subjects. Genotyping of DNA repair gene polymorphisms (XRCC1 Arg399Gln, XRCC3 Thr241Met XPD Lys751Gln, XPG Asp1104His, APE1 Asp148Glu, hOGG1 Ser326Cys) was detected by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

We demonstrated that apurinic endonuclease (APE), X-ray repair complementing defective repair in Chinese hamster cells 3 (XRCC3), xeroderma pigmentosum D (XPD), and hOGG1 gene variants were associated with an increased risk for development of migraine disease (p<0.05). In contrast, no statistically significant differences were found in genotype distributions of X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1) and XPG between migraine cases and controls (p>0.05).

CONCLUSIONS

Our findings have suggested that APE1, XRCC3, XPD, and hOGG1 gene variants could facilitate the development of migraine disease.

No association between XRCC3 Thr241Met and XPD Lys751Gln polymorphisms and the risk of colorectal cancer in West Algerian population: a case-control study

Colorectal cancer (CRC) is a complex and multifactorial disease, in which genetic and environmental factors both seem to play a part. Many epidemiological studies have explored the association between genetic polymorphisms of X-ray repair cross-complementing group 3 (XRCC3) (Thr241Met) and Xeroderma pigmentosum group D (XPD) lysine to glutamine at codon 751 (Lys751Gln) and risk of CRC in various populations; however, the results are controversial. We conducted this case-control study in a West Algerian population to assess the potential role of this genetic polymorphism on the risk of CRC in this population. Genomic DNA was extracted from blood samples collected from 129 sporadic CRC patients and 148 normal controls. The polymorphisms were determined by pyrosequencing technique. The distribution of XRCC3 Thr241Met and XPD Lys751Gln genotypes among controls did not differ significantly from those predicted by the Hardy-Weinberg distribution (p > 0.05). There were no significant differences in the genotypes distribution and allele frequencies between CRC patients and controls. A significant association was found between the combined heterozygous of XRCC3 and homozygous variant of XPD gene and CRC. This is the first study on DNA repair genetic polymorphisms in West Algerian population, and it suggests that the XRCC3 Thr241Met and XPD Lys751Gln polymorphisms may not be associated with the CRC risk in this population.

Association between XRCC3 Thr241Met SNP and systemic lupus erythematosus in Han Chinese patients in Taiwan, and a meta-analysis of healthy populations

BACKGROUND

X-ray repair cross-complementing group 3 (XRCC3) plays a crucial role in mammalian DNA repair processes. The polymorphism of XRCC3, rs861539 (Thr > Met at codon 241), is common in populations worldwide. This study analyzed the relationship between this functional single nucleotide polymorphism and systemic lupus erythematosus (SLE) in the Han Chinese population in Taiwan (HC-TW).

METHODS

Genotyping was performed using polymerase chain reaction restriction fragment length polymorphism on 163 SLE patients and 191 healthy participants in the control group.

RESULTS

The data showed that the genotype frequency at codon 241 did not differ significantly between the SLE patients and the healthy participants in the control group; however, the allele frequency analysis indicated a significant difference between these groups. In addition, we used the genotype and allele frequencies of 191 healthy HC-TW participants for comparison with HapMap populations. The results indicated a significant difference of XRCC3 Thr241Met allele and genotype frequencies between the HC-TW population and HapMap populations, except for the other Han Chinese populations. A prior study showed that Thr241 > Met substitution in XRCC3 protein was positive as damaging and functional consequences as well.

CONCLUSION

This is the first study to demonstrate the difference of XRCC3 Thr241 > Met variant between the HC-TW population and HapMap population.

An association selected polymorphisms of XRCC1, OGG1 and MUTYH gene and the level of efficiency oxidative DNA damage repair with a risk of colorectal cancer

Oxidative damage has been implicated in the pathogenesis of colorectal cancer (CRC). The base excision repair (BER) pathway is the major DNA repair pathway for oxidative DNA damage and genetic variation associated with impaired BER might thus increase a risk of CRC. In this work, we evaluated associations between the repair efficiency of oxidative DNA lesions and single-nucleotide polymorphisms of BER genes: the 194Trp/Arg and the 399Arg/Gln XRCC1, the 326Ser/Cys OGG1 and the 324Gln/His MUTYH and CRC occurrence in a Polish population. These polymorphisms were genotyped in 182 CRC patients and 245 control subjects, using a PCR-RFLP approach. The level of oxidative damage and DNA repair capacity in lymphocytes and CRC tissue samples was evaluated by comet assay using FPG and Nth glycosidases. The 326Ser/Cys OGG1 and the 324Gln/His as well as the 324His/His MUTYH genotypes were found to be associated with an increased CRC risk, while no association was found for the XRCC1 gene polymorphisms. It was also demonstrated the reduced capacity of oxidative damage repair in CRC patients in comparison to healthy controls. Moreover, the decrease efficiency of DNA repair were correlated with the 399Gln/Gln XRCC1 and the 324His/His MUTYH genotypes occurrence in CRC patients. The results obtained in our study indicated an association of OGG1 and MUTYH genes polymorphisms involved in oxidative DNA lesions repair with the risk occurrence of colorectal cancer in Polish patients. It was also found that studied polymorphisms might affect DNA repair capacity suggesting their role in CRC pathogenesis. Finally, we conclude that BER pathway may be an important target for the diagnosis and treatment of colorectal patients.

Predictive value of XRCC1 and XRCC3 gene polymorphisms for risk of ovarian cancer death after chemotherapy

OBJECTIVE

To investigate any association between XRCC1 and XRCC3 polymorphisms and outcome of platinum-based chemotherapy in ovarian cancer patients.

METHODS

With a prospective study design was cases were consecutively collected from January 2005 to January 2007. All 310 included patients were followed-up until the end of January 2010. Genotyping of XRCC1 and XRCC3 polymorphisms was conducted by TaqMan Gene Expression assays.

RESULTS

A total of 191 patients died during follow-up. Our study showed a lower survival rate in XRCC1 399 Arg/Arg genotype than Gln/ Gln, with a significant increased risk of death (HR=1.69, 95%CI=1.07-2.78). Similarly, those carrying XRCC3 Thr/ Thr genotype had a increased risk as compare to the Met/Met genotype, with a HR (95% CI) of 1.90 (1.12-3.41). There was no significant association between XRCC1 Arg194Trp and XRCC1Arg280His gene polymorphisms and ovarian cancer death.

CONCLUSION

Our study demonstrates that polymorphisms in DNA repair genes have roles in the susceptibility and survival of ovarian cancer patients.

Association between genetic variants of DNA repair genes and coronary artery disease

Polymorphisms in DNA repair genes may be associated with differences in the repair efficiency of DNA damage and may influence an individual's risk of atherosclerosis. Genetic research on coronary artery disease (CAD) has traditionally focused on investigation aimed at identifying disease-susceptibility genes. The aim of this study was to investigate the relationship between AP-endonuclease-1 (Asp148Glu), XRCC1 (Arg399Gln), XRCC3 (Thr241Met), XPD (Lys751Gln), XPG (Asp1104His), and hOGG1 (Ser326Cys), gene polymorphisms and the risk of developing CAD in a Turkish population. The study population consisted of 197 patients with acute coronary syndrome (ACS) with chronic CAD and 135 healthy subjects' age and sex matched. Gene polymorphisms were determined by the polymerase chain reaction-restriction fragment length polymorphism method. We demonstrated for the first time, a positive association of XRCC3 and hOGG1 DNA repair gene variants with CAD risk. XRCC3 Thr/Thr genotype and Thr allele frequencies were significantly increased in ACS and chronic CAD patients compared with the control group (p<0.05). It was also observed that there is a protective role of XRCC3 Met alleles against both ACS and chronic CAD (p<0.05). hOGG1 Cys alleles were found significantly higher in ACS patients than in the control group and carriers of the Cys allele had a 1.7-fold increased risk for ACS. In addition, we confirmed the association of XRCC3 Thr241Met and hOGG1 Ser326Cys gene variants with CAD by haplotype analysis. We found that CAD risk is associated with XRCC3 Thr: hOGG1 Cys haplotype, whereas XRCC3 Met: hOGG1 Ser haplotype was found to be protective against the disease. The preliminary results suggested that XRCC3 and hOGG1 genetic variants may be risk factors by affecting the enzyme's function that may lead to development of CAD.

Arg399Gln polymorphism of XRCC1 gene and risk of colorectal cancer in Kashmir: A case control study

The aim of this study was to investigate the role of the XRCC1 Arg399Gln polymorphism in the susceptibility of a Kashmiri population to colorectal cancer (CRC). We investigated the genotype distribution of the XRCC1 gene in 130 CRC cases in comparison with that of 150 healthy subjects. There was no direct significant association between the XRCC1 genotypes and CRC; however, the Arg/Gln genotype was associated with an elevated risk of CRC (OR>1.47) and the Gln/Gln variant genotype was associated with an increased risk of CRC in various clinicopathological parameters. This study suggests that the XRCC1 polymorphism is associated with an increased risk of CRC.

Relationship between XPD Lys 751 Gln polymorphism and colorectal cancer risk: a case-control study in a population-based study

AIM

In our study, we analyzed the allelic frequency of XPD Lys751Gln polymorphism of the XPD gene and the correlation between its variant alleles with colorectal cancer in patients and control groups.

BACKGROUND

Human cells are routinely exposed to mutagenic and carcinogenic aromatic amines via smoking, pollution areas and other sources. These chemicals can form DNA adducts in vivo and thus lead to DNA damage. Amongst the known genetic polymorphisms of the DNA-repair genes the xeroderma pigmentosum group D (XPD, also known as ERCC2) has been the most extensively studied most commonly.

PATIENTS AND METHODS

This study has examined the relationship between the XPD Lys 751 Gln polymorphism and colorectal cancer in 88 patients and their 88 age and sex-matched controls. Genomic DNA from peripheral whole blood was extracted using Miller method to determine the genotype of subjects with RFLP-PCR analysis.

RESULTS

This study shows cancer patients have more of the heterozygous genotype (XPD Lys 751 Gln) compared to control group. However the results are not statistically significant. Furthermore, colorectal cancer was less common in individuals with recessive homozygous genotype (P< 0.0001).

CONCLUSION

This study suggests that individuals with heterozygous polymorphism (Lys/Gln) may have an increased susceptibility to colorectal cancer compared to other polymorphisms (Lys/Lys and Gln/Gln).

Genetic polymorphisms of DNA repair genes XRCC1 and XRCC3 and risk of colorectal cancer in Chinese population

AIM

The distribution of DNA repair gene XRCC1 and XRCC3 genotypes was used to assess the potential influence of genetic polymorphisms on risk of colorectal cancer, and interactions with other factors.

METHODS

A 1:2 matched case-control study was conducted with 485 cases and 970 controls. XRCC1 and XRCC2 genotype polymorphisms were based upon duplex polymerase-chain-reaction with the confronting-two-pairprimer (PCR-CTPP) method.

RESULTS

The XRCC1 399Cln allele polymorphism was found to be associated with an increased colorectal cancer risk, while an non-significant inversely association was noted for XRCC3 241Thr/Thr genotype. We also found that individuals with the XRCC1 399 Gln and XRCC3 241Met alleles had an elevated risk, while XRCC3241Thr/Thr was proctective.

CONCLUSION

This study is the first to provide evidence of importance of XRCC1 and XRCC3 gene polymorphisms for risk of colorectal cancer in the Chinese population.

An integrated approach to identify causal network modules of complex diseases with application to colorectal cancer

BACKGROUND

Many methods have been developed to identify disease genes and further module biomarkers of complex diseases based on gene expression data. It is generally difficult to distinguish whether the variations in gene expression are causative or merely the effect of a disease. The limitation of relying on gene expression data alone highlights the need to develop new approaches that can explore various data to reflect the casual relationship between network modules and disease traits.

METHODS

In this work, we developed a novel network-based approach to identify putative causal module biomarkers of complex diseases by integrating heterogeneous information, for example, epigenomic data, gene expression data, and protein-protein interaction network. We first formulated the identification of modules as a mathematical programming problem, which can be solved efficiently and effectively in an accurate manner. Then, we applied our approach to colorectal cancer (CRC) and identified several network modules that can serve as potential module biomarkers for characterizing CRC. Further validations using three additional gene expression datasets verified their candidate biomarker properties and the effectiveness of the method. Functional enrichment analysis also revealed that the identified modules are strongly related to hallmarks of cancer, and the enriched functions, such as inflammatory response, receptor and signaling pathways, are specific to CRC.

RESULTS

Through constructing a transcription factor (TF)-module network, we found that aberrant DNA methylation of genes encoding TF considerably contributes to the activity change of some genes, which may function as causal genes of CRC, and that can also be exploited to develop efficient therapies or effective drugs.

CONCLUSION

Our method can potentially be extended to the study of other complex diseases and the multiclassification problem.

Association between the ERCC5 Asp1104His polymorphism and cancer risk: a meta-analysis

BACKGROUND

Excision repair cross complementing group 5 (ERCC5 or XPG) plays an important role in regulating DNA excision repair, removal of bulky lesions caused by environmental chemicals or UV light. Mutations in this gene cause a rare autosomal recessive syndrome, and its functional single nucleotide polymorphisms (SNPs) may alter DNA repair capacity phenotype and cancer risk. However, a series of epidemiological studies on the association between the ERCC5 Asp1104His polymorphism (rs17655, G>C) and cancer susceptibility generated conflicting results.

METHODOLOGY/PRINCIPAL FINDINGS

To derive a more precise estimation of the association between the ERCC5 Asp1104His polymorphism and overall cancer risk, we performed a meta-analysis of 44 published case-control studies, in which a total of 23,490 cases and 27,168 controls were included. To provide additional biological plausibility, we also assessed the genotype-gene expression correlation from the HapMap phase II release 23 data with 270 individuals from 4 ethnic populations. When all studies were pooled, we found no statistical evidence for a significantly increased cancer risk in the recessive genetic models (His/His vs. Asp/Asp: OR = 0.99, 95% CI: 0.92-1.06, P = 0.242 for heterogeneity or His/His vs. Asp/His + Asp/Asp: OR = 0.98, 95% CI: 0.93-1.03, P = 0.260 for heterogeneity), nor in further stratified analyses by cancer type, ethnicity, source of controls and sample size. In the genotype-phenotype correlation analysis from 270 individuals, we consistently found no significant correlation of the Asp1104His polymorphism with ERCC5 mRNA expression.

CONCLUSIONS/SIGNIFICANCE

This meta-analysis suggests that it is unlikely that the ERCC5 Asp1104His polymorphism may contribute to individual susceptibility to cancer risk.

Polymorphisms of XPG/ERCC5 and risk of squamous cell carcinoma of the head and neck

OBJECTIVES

Xeroderma pigmentosum group G (XPG) protein is essential for the nucleotide excision repair system, and genetic variations in XPG/ERCC5 that affect DNA repair capacity may contribute to the risk of tobacco-induced cancers, including squamous cell carcinoma of the head and neck (SCCHN). We investigated the association between XPG/ERCC5 polymorphisms and risk of SCCHN.

METHODS

We genotyped 12 tagging and potentially functional single nucleotide polymorphisms (SNPs) of XPG/ERCC5 in a case-control study of 1059 non-Hispanic white patients with SCCHN and 1066 cancer-free age- and sex-matched controls, and evaluated their associations with the risk of SCCHN.

RESULTS

Multivariate logistic regression showed that only an intronic tagging SNP (rs4150351A/C) of XPG/ERCC5 was associated with a decreased risk of SCCHN (adjusted odds ratio=0.76, 95% confidence interval=0.62-0.92 for AC vs. AA; adjusted odds ratio=0.81, 95% confidence interval=0.67-0.98 for AC/CC vs. AA), but this association was nonsignificant after corrections by the permutation test (empirical P=0.105). In the genotype-phenotype correlation analysis using peripheral lymphocytes from 44 patients with SCCHN, we found that rs4150351 AC/CC was associated with a statistically significant increase in the XPG/ERCC5 mRNA expression.

CONCLUSION

These findings suggest that genetic variation in XPG/ERCC5 may not affect the risk of SCCHN, although rs4150351 C variant genotypes were associated with an increased expression of XPG/ERCC5 mRNA and nonsignificantly decreased risk of SCCHN. Larger population-based and additional functional studies are warranted to validate our findings.

Genetic polymorphisms in key DNA repair genes and risk of head and neck cancer in a Chinese population

Although tobacco and alcohol consumption are the major risk factors of head and neck cancer (HNC), genetic variations of genes involved in several biological pathways, such as DNA repair genes, may affect an individual's susceptibility to HNC. However, few studies have investigated the associations between polymorphisms in DNA repair genes and HNC risk in the Chinese population. Thus, we genotyped five common, non-synonymous single-nucleotide polymorphisms (SNPs) [APEX1 (Asp148Glu), XRCC1 (Arg399Gln), ADPRT (Val762Ala), XPD (Lys751Gln) and XPG (His1104Asp)] in a hospital-based, case-control study of 397 HNC cases and 900 cancer-free controls in China. The results showed that none of the five SNPs in the DNA repair pathway was significantly associated with HNC risk, suggesting that these polymorphisms may not play a major role in HNC susceptibility in this Chinese population.

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 gene variants in endometrial carcinoma

Several polymorphisms in the DNA repair gene are thought to have significant effects on cancer risk. In this study, we investigated the association of the polymorphisms in the DNA repair genes, XRCC1 Arg399Gln, XRCC3 Thr241Met, XPD Lys751Gln, XPG Asp1104His, APE1 Asp148Glu, and HOGG1 Ser326Cys, with endometrium cancer risk. Two hundred and sixty-two women were included in the study. Endometrial biopsy was performed, and on the basis of diagnosis and histological examination, women were divided into two groups: a control group (n=158) and an endometrial cancer group (n=104). Genotypes were determined by PCR-RFLP assays in endometrial carcinoma patients and age-matched controls. In this study, we found that the frequencies of Glu+ and Asp/Glu genotypes in APE, Gln/Gln genotype of XRCC1, Met/Met genotype of XRCC3, Cys+ and Ser/Cys genotypes of HOGG1, His+ and Asp/His genotypes of XPG, and Gln+ and Gln/Gln genotypes of XPD are more prevalent in patients than controls. Frequencies of Thr/Thr genotype in XRCC3 were increased in controls compared with patients and seem to be protected from endometrial cancer. Our findings suggest that XRCC1, XRCC3, XPD, XPG, APE1, and HOGG1 genetic variants may be associated with endometrial cancer in Turkish women.

Association between XPF polymorphisms and cancer risk: a meta-analysis

BACKGROUND

Xeroderma pigmentosum complementation group F (XPF or ERCC4) plays a key role in DNA repair that protects against genetic instability and carcinogenesis. A series of epidemiological studies have examined associations between XPF polymorphisms and cancer risk, but the findings remain inconclusive.

METHODOLOGY/PRINCIPAL FINDINGS

In this meta-analysis of 47,639 cancer cases and 51,915 controls, by searching three electronic databases (i.e., MEDLINE, EMBASE and CNKI), we summarized 43 case-control studies from 29 publications on four commonly studied polymorphisms of XPF (i.e., rs1800067, rs1799801, rs2020955 and rs744154), and we did not find statistical evidence of any significant association with overall cancer risk. However, in stratification analyses, we found a significant association of XPF-rs1799801 with a reduced cancer risk in Caucasian populations (4,845 cases and 5,556 controls; recessive model: OR=0.87, 95% CI=0.76-1.00, P=0.049, P=0.723 for heterogeneity test, I(2) =0). Further genotype-phenotype correlation analysis showed that the homozygous variant CC genotype carriers had higher XPF expression levels than that of the TT genotype carriers (Student's t test for a recessive model: P=0.046). No publication bias was found by using the funnel plot and Egger's test.

CONCLUSION

This meta-analysis suggests a lack of statistical evidence for the association between the four XPF SNPs and overall risk of cancers. However, XPF-rs1799801 may be associated with cancer risk in Caucasian populations, which needs to be further validated in single large, well-designed prospective studies.

Functional polymorphisms in XRCC-1 and APE-1 contribute to increased apoptosis and risk of ulcerative colitis

OBJECTIVE

The present study was designed to investigate the role of X-ray cross-complementing group 1 (XRCC1) and apurinic/apyrimidinic endonuclease 1 (APE1) polymorphisms in apoptosis and the risk of ulcerative colitis (UC).

MATERIALS AND METHODS

Blood samples from 384 unrelated subject (age range 18-65 years; 171 with UC, 213 healthy controls) were collected after colonoscopy. Genomic DNA was isolated and genotyped for XRCC1 Arg399Gln and APE1 Asp148Glu using a confronting two-pair primers polymerase chain reaction. Apoptosis and intracellular reactive oxygen species (ROS) levels in peripheral blood mononuclear cells were measured using annexin-V and H(2)DCFDA assay, respectively.

RESULTS

The frequency of genotype Arg399Gln (heterozygous) of XRCC1 gene was significantly higher in patients with UC than the controls (odds ratio [OR] 1.73; 95% confidence interval [CI] 1.13-2.64; p = 0.01). Similarly the genotypic frequency of APE1 Asp148Glu showed statistically significant incidence among UC subjects (OR 1.54; 95% CI 1.02-2.33; p = 0.04). Polymorphism in XRCC1 Arg399Gln and APE1 Asp148Glu together considerably increased the risk of UC (OR 2.303; 95% CI 1.43-3.69; p = 0.0007). ROS levels were high in UC subjects compared with controls (p = 0.01).

CONCLUSION

Polymorphisms in XRCC1 Arg399Gln and APE1 Asp148Glu significantly increased the rate of apoptosis and risk of ulcerative colitis.