Polymorphisms in RAD51, XRCC2 and XRCC3 genes of the homologous recombination repair in colorectal cancer--a case control study

Comprehensive analysis of subtypes and risk model based on complement system associated genes in ccRCC

BACKGROUND

Immune therapy is widely used in treating clear cell renal cell carcinoma (ccRCC), yet identifying patient subgroups that are expected to response remains challenging. As complement system can mediate immune effects, including the progression of tumors, a correlation between complement system and immune therapy may exist.

METHODS

Based on 11 complement system associated genes (CSAGs) identified from The Cancer Genome Atlas (TCGA), we performed unsupervised clustering and classified the tumors into two different complement system (CS) patterns. The clinical significance, tumor microenvironment (TME), functional enrichment, and immune infiltration were further analyzed. A novel scoring system named CSscore was developed based on the expression levels of the 11 CSAGs.

RESULTS

Two distinct CS patterns were identified, classified as Cluster1 and Cluster2, and Cluster1 showed poor clinical outcome. Further analysis of functional enrichment, immune cell infiltration, and genetic variation revealed that Cluster1 had high infiltration of TME immune cells, but also exhibited high immune escape. The novel prognostic model, CSscore could act as an independent prognostic factor and effectively predict patients' prognosis and distinguish the therapeutic efficacy of different immune treatment strategies. The pan-cancer analysis of the CSscore indicates its potential to be further generalized to other types of cancer.

CONCLUSIONS

Two distinct CS patterns were identified and were further analyzed in terms of infiltration of TME immune cells and immune escape, providing potential explanations for the impact on prognosis of ccRCC. Our CSscore prognostic model may offer a novel perspective in the management of ccRCC patients, and potentially other types of cancer as well.

Association of RAD51, XRCC1, XRCC2, and XRCC3 Polymorphisms with Risk of Breast Cancer

Background: DNA repair genes are among the low-penetrance genes implicated in breast cancer. However variants of DNA repair genes may alter their protein function thus leading to carcinogenesis. Breast cancer is the most common cancer among women in India. The aim of the present study was to identify association, if any, of single nucleotide polymorphisms (SNP's) in four genes involved in DNA repair pathways including, RAD51 rs1801320, XRCC1 rs25487, XRCC2 rs3218536, and XRCC3 rs861539 with the risk of breast cancer. Materials and Methods: In this case-control study 611 female subjects (311 breast cancer patients and 300 healthy controls) were screened for four SNPs using polymerase chain reaction-restriction fragment length polymorphism analyses. Multifactor dimensionality reduction (MDR) analysis was performed to estimate the gene-gene interaction. Protein-protein interaction network analysis were studied using the STRING database. Results: The GC genotype (p = 0.018) and the combined GC+CC (p = 0.03) genotypes of RAD51 rs1801320 were significantly associated with reduced risk of breast cancer. The CT genotype (p = 0.0001), the combined CT+TT genotypes (p = 0.0002), and the T allele (p = 0.0019) of XRCC3 rs861539 polymorphism were associated with reduced risk of the breast cancer. No association of XRCC1 rs25487 and XRCC2 rs3218536 polymorphisms with breast cancer was observed. MDR analysis indicated a positive interaction between XRCC3 and XRCC2. String network analysis showed that the RAD51, XRCC1, XRCC2, and XRCC3 proteins are in strong interaction with each other and other breast cancer-related proteins such as BRCA2. Conclusion: RAD51 rs1801320 and XRCC3 rs861539 polymorphisms were associated with reduced risk of breast cancer. There is evidence of positive interactions among XRCC1, XRCC2, XRCC3, and RAD51.

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

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

XRCC2 Arg188His polymorphism and colorectal cancer risk: a meta-analysis

OBJECTIVE

To investigate the potential correlation between the Arg188His (rs3218536) polymorphism of X-ray repair cross-complementing 2 (XRCC2) and colorectal cancer (CRC) risk, as the association remains unclear.

METHODS

The CNKI, PubMed, EMBASE and Cochrane library databases were systematically searched for relevant studies published up to July 2021. Data were extracted from included studies, and analysed for pooled or subgroup odds ratios (ORs) with 95% confidence intervals (CIs) using STATA 12.0 software.

RESULTS

Seven published studies were included. Pooled analysis revealed that the XRCC2 Arg188His polymorphism was associated with increased CRC risk (His versus Arg: OR 1.14, 95% CI 1.01, 1.29). Trial Sequential Analysis to test the power of the results showed that they were unreliable and the meta-analysis required additional studies.

CONCLUSION

The current meta-analysis suggests that the XRCC2 Arg188His polymorphism may be a risk factor for CRC.

Single Nucleotide Variants Associated with Colorectal Cancer Among Iranian Patients: A Narrative Review

Colorectal cancer has been considered as one of the complicated multi-stage processes after adenoma-carcinoma sequence. Therefore, studies of the molecular dysregulation basis could present information on the recognition of the potent biomarkers and treatment targets for this disease. Even though outcomes of the patients with colorectal cancer have been improved largely with current annual screening plans, it is necessary to have reliable prognostic biomarkers because of the disease heterogeneity. There is a significant relationship between SNP in IL1RN* 2 (IL1ra), −509 C/T (TGFB1), rs11556218 T>G and rs4778889 T/C (IL16), miRNA-binding site polymorphisms in IL16, rs4464148 (SMAD7), rs6983267 (EGF), GSTT1, TACG haplotype (CTLA4), 1793G> A (MTHFR), Leu/Leu genotype of (EXO1), −137 G/C (IL18), C/T genotype (XRCC3), I3434T (XRCC7), MGMT, C3435T (MDR1), ff genotype of FokI, 677CT+TT (MTHFR), G2677T/A (MDR1) and CRC. Increased risk has been observed in VDR ApaI genotype “aa”. Finally, the protective effect has been explored in the TACA haplotype (CTLA4). According to the findings, the genetic polymorphisms in the immunity-associated genes are related to the CRC amongst the Iranian patients. Therefore, more large-scale functional investigations are necessary for confirming the results.

Genetic Variations of RAD51 and XRCC2 Genes Increase the Risk of Colorectal Cancer in Bangladeshi Population

Objectives:

In case of Bangladeshi population, no report is observed till now showing the genetic variations of RAD51 (rs1801320) and XRCC2 (rs3218536) genes polymorphism having association with colorectal cancer risk. For this reason the aim of this study is to ascertain their interrelation with colorectal cancer occurrence in Bangladeshi population.

Materials and Methods:

A case control study was conducted where 200 colorectal cancer patients and 200 healthy volunteers were figured for this research using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP).

Results:

Here, in case of RAD51 (rs1801320), G/C heterozygous genotype was found significant (p=0.037; OR=1.64; 95% CI=1.03 to 2.6). On the other hand, G/G genotype was not found statistically significant (p=0.423; OR=1.61; 95% CI=0.49 to 5.22) and significance was observed for GC+GG (p=0.030; OR=1.63; 95% CI=1.05 to 2.55). In case of XRCC2 (rs3218536), C/T heterozygous genotype was remarked statistically significant (p=0.033; OR=1.60; 95% CI=1.04 to 2.46). The T/T genotype was not recorded statistically significant (p=0.237; OR=1.65; 95% CI=0.72 to 3.76) but significance found for CT+TT (p=0.027; OR=1.61; 95% CI=1.05 to 2.45). Moreover, it is found that the risk factor of developing CRC is observed in G/C, C/T heterozygote and GC+GG, CT+TT (heterozygote+ mutant) in RAD51 (rs1801320) and XRCC2(rs3218536) respectively although no significance is observed in case of G/G and T/T mutant.

Conclusions:

So, the association of RAD51 (rs1801320) and XRCC2 (rs3218536) genes polymorphism with colorectal cancer risk is observed in Bangladeshi population.

Role of Rad51 and DNA repair in cancer: A molecular perspective

The maintenance of genome integrity is essential for any organism survival and for the inheritance of traits to offspring. To the purpose, cells have developed a complex DNA repair system to defend the genetic information against both endogenous and exogenous sources of damage. Accordingly, multiple repair pathways can be aroused from the diverse forms of DNA lesions, which can be effective per se or via crosstalk with others to complete the whole DNA repair process. Deficiencies in DNA healing resulting in faulty repair and/or prolonged DNA damage can lead to genes mutations, chromosome rearrangements, genomic instability, and finally carcinogenesis and/or cancer progression. Although it might seem paradoxical, at the same time such defects in DNA repair pathways may have therapeutic implications for potential clinical practice. Here we provide an overview of the main DNA repair pathways, with special focus on the role played by homologous repair and the RAD51 recombinase protein in the cellular DNA damage response. We next discuss the recombinase structure and function per se and in combination with all its principal mediators and regulators. Finally, we conclude with an analysis of the manifold roles that RAD51 plays in carcinogenesis, cancer progression and anticancer drug resistance, and conclude this work with a survey of the most promising therapeutic strategies aimed at targeting RAD51 in experimental oncology.

Genetic polymorphisms in DNA repair genes and their association with cervical cancer

Background and objective: Carcinoma of cervix is the second most common cancer among women worldwide. The DNA repair network plays an important role in the maintenance of genetic stability, protection against DNA damage and carcinogenesis. Alterations in repair genes XRCC1, XRCC2 and XRCC3 and been reported in certain cancers. We hypothesised an association between XRCC1+399A/G, XRCC2+31467G/A and XRCC3+18067C/T polymorphisms and the risk of cervical cancer. Subjects and methods: This study included 525 subjects (265 controls and 260 cervical cancer cases). Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results: Women with GA and AA genotypes of XRCC1+399A/G showed 2.4-3.8 fold higher risk of cervical cancer (P = 0.001). The +399A* allele was significantly linked with cervical cancer (P = 0.002). However, XRCC2+31479G/A and XRCC3+18067C/T polymorphisms did not show any statistically significant associations. Conclusion: The XRCC1+399A/G SNP is linked with cervical cancer. We suggest that this variant can be utilized as a prognostic marker for determination of cervical cancer susceptibility.

XRCC4 c.1394G>T Single Nucleotide Polymorphisms and Breast Cancer Risk among Filipinos

Background:

The identification of cancer-associated single nucleotide polymorphisms (SNP) and mutation genes is a promising approach in recognizing individuals who are at risk of developing cancer. Hence, this study was conducted to determine the association between XRCC4 c.1394G>T SNP and breast cancer development among Filipinos.

Methods:

Genotyping for XRCC4 c.1394G>T SNP was performed on breast cancer patients (n=103) and their age- and sex- matched clinically healthy controls (n=103) by polymerase chain reaction – restriction fragment length polymorphism.

Results:

Significant difference in genotype (p=0.007) and allele (p=0.003) frequencies in XRCC4 c.1394G>T was observed between the breast cancer cases and controls. Carriers of the XRCC4 c.1394 G>T genotype were observed to have significantly higher risk of developing breast cancer compared to individuals with T/T genotype (OR=2.67, 95% CI: 1.36 – 5.25). XRCC4 c.1394G>T combined with passive smoking may also significantly increase risk of breast cancer (OR=14.73; 95% CI= 9.88-18.86).

Conclusion:

XRCC4 c. 1394G>T may be associated with breast cancer development among Filipinos.

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.

Positive effect of single nucleotide RAD51 135G>C polymorphism and low Ku70 protein expression on female rectal cancer patients survival after preoperative radiotherapy

BACKGROUND/AIMS

This is a retrospective analysis of 103 patients having locally advanced rectal cancer who received short-course radiotherapy (SCRT). The objective of the study was to check whether a polymorphism in the RAD51 gene (135 G>C), Ku70 protein expression, and tumor microenvironment: proliferation rate measured by BrdUrdLI and Ki-67LI, hypoxia (glucose transporter-1 expression), P53 protein expression, and DNA ploidy can influence DNA repair capacity, the factors contributing to patient overall survival (OS) and the incidence of recurrences and metastases.

MATERIALS AND METHODS

RAD51 (135 G>C) polymorphism was evaluated using restriction fragment length polymorphism polymerase chain reaction, and proteins were identified using immunohistochemistry.

RESULTS

There were 3 (2.9%) tumors with RAD51 CC, 75 (72.8%) with GG, and 25 (24.3%) with GC genotypes. The median follow-up time was 63.1 months (range 2-120). Patients with CC genotype survived significantly longer than those with GG and GC genotypes and did not develop any recurrences or distant metastases. Female patients with Ku70 expression (<75.1) or RAD51CC genotype (impaired DNA damage repair and radiosensitive) had significantly longer OS (p=0.013) than those with Ku70>75.1 % or RAD51GG,GC (radioresistant phenotype) and male patients in the log-rank test. In multivariate analysis, positive prognostic factors for OS in the male patients were grade=1 and <17 days break in the treatment, whereas in the female subgroup, only radiosensitive phenotype (Ku70 <75.1% or RAD51CC genotype).

CONCLUSION

To the best of our knowledge, this is the first study to provide evidence for the positive effect of CC genotype of RAD51 or low Ku70 expression on OS in females with rectal cancer after SCRT.

DNA damage response and repair in colorectal cancer: Defects, regulation and therapeutic implications

DNA damage response, a key factor involved in maintaining genome integrity and stability, consists of several kinase-dependent signaling pathways, which sense and transduce DNA damage signal. The severity of damage appears to determine DNA damage responses, which can include cell cycle arrest, damage repair and apoptosis. A number of recent studies have demonstrated that defection in signaling through this network is thought to be an underlying mechanism behind the development and progression of various types of human malignancies, including colorectal cancer. In this review, colorectal cancer and its molecular pathology as well as DNA damage response is briefly introduced. Finally, the involvement of key components of this network in the initiation/progression, prognosis, response to treatment and development of drug resistance is comprehensively discussed.

XRCC2 Polymorphisms and Environmental Factors Predict High Risk of Colorectal Cancer

Background

This case-control study aimed to analyze the association of XRCC2 polymorphisms (rs3218408 and rs3218384) with colorectal cancer (CRC) risk. The interaction of XRCC2 polymorphisms with environmental factors was investigated as well.

Material/Methods

We enrolled 147 CRC patients and 114 healthy individuals into the study. Polymerase chain reaction (PCR)-sequencing method was performed to detect rs3218408 and rs3218384 polymorphisms. Hardy-Weinberg equilibrium (HWE) was checked in the control group. Odds ratio (OR) with 95% confidence interval (CI) represented the risk of CRC. Cross-table method was used in analyzing the interaction effects.

Results

Compared to the control group, the frequency of smokers was much higher in the case group (P<0.001). A similar result was observed in drinkers (55.8% vs. 40.4%, P=0.013). Dietary habits of all subjects were investigated as well, showing that CRC patients ate fewer vegetables than did healthy controls (P<0.001). In the analysis of polymorphisms, rs3218408 appeared to be an independent risk factor of CRC (GG: OR=2.048, 95%CI=1.032–4.061; G allele: OR=1.445, 95%CI=1.019–2.049). There were 68 (76.4%) C allele carriers (rs3218384) among smokers, which was higher than the number of G allele carriers (P<0.001). A similar outcome was observed for alcohol drinkers (P=0.048), which suggests a relationship of rs3218384 with smoking and drinking. Further analysis indicated that interaction of rs3218384 with smoking increased the risk of CRC (GG and smoking: OR=3.250, 95%CI=1.235–8.556; GC+CC and smoking: OR=2.167, 95%CI=1.175–3.996).

Conclusions

We found that rs3218408 was related with increased risk of CRC, and the interaction of rs3218384 with smoking increased the risk of CRC.

DNA Repair Mechanism Gene, XRCC1A ( Arg194Trp) but not XRCC3 ( Thr241Met) Polymorphism Increased the Risk of Breast Cancer in Premenopausal Females: A Case-Control Study in Northeastern Region of India

X-ray repair cross complementary group gene is one of the most studied candidate gene involved in different types of cancers. Studies have shown that X-ray repair cross complementary genes are significantly associated with increased risk of breast cancer in females. Moreover, studies have revealed that X-ray repair cross complementary gene polymorphism significantly varies between and within different ethnic groups globally. The present case–control study was aimed to investigate the association of X-ray repair cross complementary 1A (Arg194Trp) and X-ray repair cross complementary 3 (Thr241Met) polymorphism with the risk of breast cancer in females from northeastern region of India. The present case–control study includes histopathologically confirmed and newly diagnosed 464 cases with breast cancer and 534 apparently healthy neighborhood community controls. Information on sociodemographic factors and putative risk factors were collected from each study participant by conducting face-to-face interviews. Genotyping of X-ray repair cross complementary 1A (Arg194Trp) and X-ray repair cross complementary 3 (Thr241Met) was carried out by polymerase chain reaction-restriction fragment length polymorphism. For statistical analysis, both univariate and multivariate logistic regression analyses were performed. We also performed stratified analysis to find out the association of X-ray repair cross complementary genes with the risk of breast cancer stratified based on menstrual status. This study revealed that tryptophan allele (R/W-W/W genotype) in X-ray repair cross complementary 1A (Arg194Trp) gene significantly increased the risk of breast cancer (adjusted odds ratio = 1.44, 95% confidence interval = 1.06-1.97, P < .05 for R/W-W/W genotype). Moreover, it was found that tryptophan allele (W/W genotype) at codon 194 of X-ray repair cross complementary 1A (Arg194Trp) gene significantly increased the risk of breast cancer in premenopausal females (crude odds ratio = 1.66, 95% confidence interval = 1.11-2.46, P < .05 for R/W-W/W genotype). The present study did not reveal any significant association of X-ray repair cross complementary 3 (Thr241Met) polymorphism with the risk of breast cancer. The present study has explored that X-ray repair cross complementary 1A (Arg194Trp) gene polymorphism is significantly associated with the increased risk of breast cancer in premenopausal females from northeastern region of India which may be beneficial for prognostic purposes.

Haplotype analysis of XRCC2 gene polymorphisms and association with increased risk of head and neck cancer

We aimed to investigate the effect of hotspot variations of XRCC2 gene on the risk of head and neck cancer (HNC) in 400 patients and 400 controls. Five polymorphisms of XRCC2 gene G4234C (rs3218384), G4088T (rs3218373), G3063A (rs2040639), R188H (rs3218536) and rs7802034 were analyzed using Allele- specific polymerase chain reaction (ARMS-PCR) followed by sequence analysis. For rs3218373, the GG genotype indicated a statistically significant 3-fold increased risk of HNC (P < 0.001) after multivariate adjustment. For rs7802034, the GG genotype suggested statistically significant 2-fold increased risk of HNC (P < 0.001). For SNP of rs3218536, the AA genotype indicated a significant 3-fold increased risk of HNC (P < 0.001). Additionally, haplotype analysis revealed that TACAG, TGGAG, TACGG and TAGGA haplotypes of XRCC2 polymorphisms are associated with HNC risk. Two SNPs in XRCC2 (rs2040639 and rs3218384) were found increased in strong linkage disequilibrium. Furthermore, joint effect model showed 20 fold (OR = 19.89; 95% CI = 2.65–149.36, P = 0.003) increased HNC risk in patients carrying four homozygous risk alleles of selected polymorphisms. These results show that allele distributions and genotypes of XRCC2 SNPs are significantly associated with increased HNC risk and could be a genetic adjuster for the said disease.

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.

The Association of Low-Penetrance Variants in DNA Repair Genes with Colorectal Cancer: A Systematic Review and Meta-Analysis

Objectives:

Approximately 35% of colorectal cancer (CRC) risk is attributable to heritable factors known hereditary syndromes, accounting for 6%. The remainder may be due to lower penetrance polymorphisms particularly of DNA repair genes. DNA repair pathways, including base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), direct reversal repair (DRR), and double-strand break repair are complex, evolutionarily conserved, and critical in carcinogenesis. Germline mutations in these genes are associated with high-penetrance CRC syndromes such as Lynch syndrome. However, the association of low-penetrance polymorphisms of DNA repair genes with CRC risk remains unclear.

Methods:

A systematic literature review of PubMed, Embase, and HuGENet databases was conducted. Pre-specified criteria determined study inclusion/exclusion. Per-allele, pooled odds ratios disclosed the risk attributed to each variant. Heterogeneity was investigated by subgroup analyses for ethnicity and tumor location; funnel plots and Egger’s test assessed publication bias.

Results:

Sixty-one polymorphisms in 26 different DNA repair genes were identified. Meta-analyses for 22 polymorphisms in 17 genes revealed that six polymorphisms were significantly associated with CRC risk within BER (APE1, PARP1), NER (ERCC5, XPC), double-strand break (RAD18), and DRR (MGMT), but none within MMR. Subgroup analyses revealed significant association of OGG1 rs1052133 with rectal cancer risk. Egger’s test revealed no publication bias.

Conclusions:

Low-penetrance polymorphisms in DNA repair genes alter susceptibility to CRC. Future studies should therefore analyze whole-genome polymorphisms and any synergistic effects on CRC risk.

Translational impact:

This knowledge may enhance CRC risk assessment and facilitate a more personalized approach to cancer prevention.

Association between a functional variant in RAD51 gene's 3' untranslated region and its mRNA expression in lymphoblastoid cell lines

Object

Variants of microRNA (miRNA)-binding sites in RAD51 gene’s 3′ untranslated region (3′UTR) are significantly associated with cancer risk, but the roles of these genetic variants in post-transcriptional regulation have not been elucidated.

Methods

The SNPs of RAD51 were identified both in the regulatory region and in the coding region by means of the online database. The bioinformatic tool SNP Function Prediction was used to predict the potential functional relevance of the miRNA-binding sites. We used additional data on RAD51 genotypes and mRNA levels available online for the genotype-phenotype association analysis.

Results

We found that rs12593359, rs7180135, rs11855560, and rs45507396 in the RAD51 3′UTR affect possible miRNA-binding sites according to bioinformatic analysis. Only rs12593359 was significantly associated with RAD51 mRNA expression in lymphoblastoid cell lines (P = 0.022).

Conclusion

This study demonstrated that rs12593359 may be a putative variant mediating the post-transcriptional regulation of the RAD51 gene. Deeper understanding of how 3′UTR variants influence RAD51 activity will pave the way to targeting of the RAD51 pathway as a cancer treatment.

XRCC2 as a predictive biomarker for radioresistance in locally advanced rectal cancer patients undergoing preoperative radiotherapy

XRCC2 has been shown to increase the radioresistance of some cancers. Here, XRCC2 expression was investigated as a predictor of preoperative radiotherapy (PRT) treatment response in locally advanced rectal cancer (LARC). XRCC2 was found to be overexpressed in rectal cancer tissues resected from patients who underwent surgery without PRT. In addition, overall survival for LARC patients was improved in XRCC2-negative patients compared with XRCC2-positive patients after treatment with PRT (P < 0.001). XRCC2 expression was also associated with an increase in LARC radioresistance. Conversely, XRCC2-deficient cancer cells were more sensitive to irradiation in vitro, and a higher proportion of these cells underwent cell death induced by G2/M phase arrest and apoptosis. When XRCC2 was knocked down, the repair of DNA double-strand breaks caused by irradiation was impaired. Therefore, XRCC2 may increases LARC radioresistance by repairing DNA double-strand breaks and preventing cancer cell apoptosis. Moreover, the present data suggest that XRCC2 is a useful predictive biomarker of PRT treatment response in LARC patients. Thus, inhibition of XRCC2 expression or activity represents a potential therapeutic strategy for improving PRT response in LARC patients.

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.

Association between single nucleotide polymorphisms (SNPs) of XRCC2 and XRCC3 homologous recombination repair genes and ovarian cancer in Polish women

The variability, perceived in DNA repair genes, may be of clinical importance for evaluation of the risk of occurrence of a given type of cancer, its prophylactics and therapy. The aim of the present work was to evaluate associations between the risk of ovarian cancer and polymorphisms in the genes, encoding for two key proteins of homologous recombination: XRCC2 Arg188His (c. 563 G>A; rs3218536) and XRCC3 Thr241Met (c. 722 C>T; rs861539). The study consisted of 700 patients with ovarian cancer and 700 healthy subjects. Analysis of the gene polymorphisms was performed using PCR-RFLP (restriction length fragment polymorphism). We found a statistically significant increase of the 188His allele frequency (OR=4.01; 95% CI=3.40-4.72; p<.0001) of XRCC2 in ovarian cancer compared to healthy controls. There were no differences in the genotype and allele distributions and odds ratios of the XRCC3 Thr241Met polymorphism between patient and control groups. Association of these genetic polymorphisms with histological grading showed increased XRCC2 188Arg/His (OR=33.0; 95% CI=14.51-75.05; p<.0001) and 188His/His genotypes (OR=9.37; 95% CI=4.79-18.32; p<.0001) and XRCC3 241Thr/Met (OR=24.28; 95% CI=12.38-47.61; p<.0001) and 241Met/Met genotype frequencies (OR=17.00; 95% CI=8.42-34.28; p<.0001) in grading 1 (G1) as well as 188His (OR=2.78; 95% CI=2.11-3.69; p<.0001) and 241Met allele overrepresentation (OR=2.59; 95% CI=2.08-3.22; p<.0001) in G1 ovarian patients. Finally, with clinical FIGO staging under evaluation, an increase in XRCC2 188His/His homozygote and 188Arg/His heterozygote frequencies in staging I (SI) and XRCC3 Thr/Met heterozygote frequencies in SI was observed. The obtained results indicate that XRCC2 Arg188His and XRCC3 Thr241Met polymorphisms may be positively associated with the incidence of ovarian carcinoma in the population of Polish women.

Association between the XRCC3 Thr241Met Polymorphism and Gastrointestinal Cancer Risk: A Meta-Analysis

Background: The x-ray repair cross-complementing group 3 (XRCC3) encodes a protein involved in the homologous recombination repair (HRR) pathway for double-strand DNA repair. Associations of the XRCC3 Thr241Met polymorphism with various cancers have been widely reported. However, published data on links between XRCC3 Thr241Met and gastrointestinal (GI) cancer risk are inconsistent. Objective and Methods: A meta-analysis was conducted to characterize the relationship between XRCC3 Thr241Met polymorphisms and GI cancer risk. Pooled odds ratios (ORs) and 95.0% confidence intervals were assessed using random- or fixed- effect models for 28.0 relevant articles with 30.0 studies containing 7,649.0 cases and 11,123.0 controls. Results: The results of the overall meta-analysis suggested a borderline association between the XRCC3 Thr241Met polymorphism and GI cancer susceptibility (T vs. C: OR=1.18, 9 % CI=1.0–1.4, POR=0.04; TT vs. CT+CC: OR=1.3, 95 % CI=1.0–1.6, POR=0.04). After removing studies not conforming to Hardy–Weinberg equilibrium (HWE), however, this association disappeared (T vs. C: OR=1.00, 95 % CI=0.9–1.1, POR=0.96; TT vs. CT+CC: OR=0.9, 95 % CI=0.8–1.1, POR=0.72). When stratified by ethnicity, source of controls or cancer type, although some associations between XRCC3 Thr241Met polymorphism and GI cancer susceptibility were detected, these associations no longer existed after removing studies not conforming to HWE. Conclusion: Our meta-analysis suggests that the XRCC3 Thr241Met polymorphism is not associated with risk of GI cancer based on current evidence.

Association of the XPD and XRCC3 gene polymorphisms with oral squamous cell carcinoma in a Northeastern Brazilian population: A pilot study

OBJECTIVE

to evaluate the association between XPD and XRCC3 polymorphisms and oral squamous cell carcinoma (OSCC).

DESIGN

the sample consisted of 54 cases of OSCC and 40 cases of inflammatory fibrous hyperplasia (IFH). Genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

XPD-Lys/Gln was more common in IFH (n=28; 70%) than in OSCC (n=24; 44.4%) (OR: 0.3; p<0.05). XPD-Gln was more frequent in high-grade lesions (0.48) than in low-grade lesions (0.21) (OR: 3.4; p<0.05). The Gln/Gln genotype was associated with III and IV clinical stages (OR: 0.07; p<0.05). XRCC3-Met was more frequent in OSCC (0.49) than in IFH (0.35) (OR: 2.6; p<0.05). The Met/Met genotype was associated with the presence of metastases (OR: 8.1; p<0.05) and with III and IV clinical stages (OR: 0.07; p<0.05).

CONCLUSIONS

in this sample, the frequency of XPD-Gln in IFH suggests that this variant may protect against OSCC. The presence of the XRCC3-Met allele seems to contribute to the development of OSCC, metastases and more advanced stages in these lesions.

Polymorphisms in DNA repair and multidrug resistance genes among Sindhis of Central India

Polymorphisms in DNA repair and multidrug resistance genes might contribute to interindividual and interethnic differences in DNA repair capacity and drug disposition respectively. In the present study, we determined the allele and genotype frequencies of four single nucleotide polymorphisms (SNPs) located in the DNA repair genes, XRCC1, XRCC3, XPD, OGG1, namely XRCC1 Arg399Gln, XRCC3 Thr241Met, XPD Lys751Gln, and OGG1 Ser326Cys, respectively and two SNPs located in the multidrug resistance gene, ABCB1, namely ABCB1 C3435T and ABCB1 C1236T, in 33-35 healthy and unrelated Sindhi individuals, residing in the Vidarbha region of Central India and compared them with the Maharashtrian population from the same geographical region and some other HapMap populations from the HapMap database. The study findings reveal that the Indian Sindhis are closely related to the Maharashtrians as well as Utah residents with Northern and Western European ancestry and Gujarati Indians in Houston, Texas in the HapMap database.

Polymorphisms of homologous recombination RAD51, RAD51B, XRCC2, and XRCC3 genes and the risk of prostate cancer

Genetic polymorphisms in DNA repair genes may induce individual variations in DNA repair capacity, which may in turn contribute to the risk of cancer developing. Homologous recombination repair (HRR) plays a critical role in maintaining chromosomal integrity and protecting against carcinogenic factors. The aim of the present study was to evaluate the relationship between prostate cancer risk and the presence of single nucleotide polymorphisms (SNPs) in the genes involved in HRR, that is, RAD51 (rs1801320 and rs1801321), RAD51B (rs10483813 and rs3784099), XRCC2 (rs3218536), and XRCC3 (rs861539). Polymorphisms were analyzed by PCR-RFLP and Real-Time PCR in 101 patients with prostate adenocarcinoma and 216 age- and sex-matched controls. A significant relationship was detected between the RAD51 gene rs1801320 polymorphism and increased prostate cancer risk. Our results indicate that the RAD51 gene rs1801320 polymorphism may contribute to prostate cancer susceptibility in Poland.

Association of reduced XRCC2 expression with lymph node metastasis in breast cancer tissues

The main purpose of this study was to evaluate the association between reduction in XRCC2 gene and involvement of lymph node metastasis in breast cancer. In first part of the study, meta-analysis of 14 published XRCC2 studies was performed to define the role of XRCC2 gene as diagnostic marker and in second part of the study XRCC2 gene expression was observed using real time PCR in study cohort of 100 females (50 breast cancer patients and 50 controls). A statistically significant down regulation of XRCC2 (p < 0.04) and up-regulation of ki-67 (p < 0.05) was observed in breast cancer tissues compared to non-cancerous healthy tissues. In order to explore gene-gene and gene-clinicopathological parameters relationship Spearmen correlation was performed. We observed a significantly negative correlation between XRCC2 and Ki-67 expression (r = -0.376**, p < 0.01). In case of gene-clinicopathological parameters relationship, we observed a significant correlation between XRCC2 expression and lymph node status (r = -0.521***, p < 0.002) and metastatic status (r = -0.303*, p < 0.04) of breast cancer patients. Our data suggests that deregulation of XRCC2 in breast cancer has the potential to predict lymph node metastasis and may serve as a therapeutic target for breast cancer patients at risk of metastasis.

Association between the XRCC3 Thr241Met polymorphism and risk of colorectal cancer: a meta analysis of 5,193 cases and 6,645 controls

BACKGROUND

Many studies have reported associations of the X-ray repair cross-complementing group 3 (XRCC3) Thr241Met polymorphism with colorectal cancer (CRC) risk, but the results remained controversial. Hence, we performed the present meta-analysis with different inheritance models.

MATERIALS AND METHODS

We searched the PubMed and Google scholar databases for studies relating to associations between XRCC3 Thr241Met polymorphism and risk of CRC. 16 studies with 5,193 cases and 6,645 controls were finally included into the meta-analysis.

RESULTS

We found that the XRCC3 Thr241Met polymorphism was associated with increased CRC risk only under a dominant genetic model (CC+CT vs. TT: OR 0.575, 95%CI 0.498-1.665, p<0.001, Pheterogeneity=0.00, I2=83%). There was a significant association between XRCC3 Thr241Met polymorphism and CRC risk in Caucasian in the overall 8 studies under only in the heterozygote genetic model (CT vs. TT: OR=0.929, 95%CI=0.806-1.070, P=0.308, Pheterogeneity=0.002, I2=57%). Four studies evaluated the XRCC3 Thr241Met polymorphism and CRC risk in Asians. Two genetic models of the XRCC3 polymorphism were significantly correlated with increasing risk in Asians (dominant model: CC+CT vs. TT: OR= 0.609, 95%CI=411-0.902, P=0.013, Pheterogeneity=0.54, I2=0.00%; Allele model: C vs. T: OR=0.708, 95 %=CI 0.605-0.829, p=0.000, Pheterogeneity=0.000, I2=92%). The sensitivity analysis suggested stability of this meta-analysis and no publication bias was detected.

CONCLUSIONS

In conclusion, this meta-analysis indicates that XRCC3 Thr241Met shows an increased CRC risk, particularly in Asians rather than Caucasians.

The effect of polymorphism in DNA repair genes RAD51 and XRCC2 in colorectal cancer in Turkish population

The genes RAD51 and XRCC2 encode proteins that are important for the repair of double-strand DNA breaks by recombination. Therefore, genetic variability in these genes may contribute to the occurrence and progression of carcinoma. We investigated the association of polymorphisms in the DNA repair genes XRCC2-A/G and RAD51-135G/C with the colorectal cancer risk. Genotypes were determined by PCR-RFLP assays in 71 patients with colorectal cancer and 86 age-matched healthy controls. After amplification, we used a restriction enzyme (RAD51; MvaI and XRCC2; HphI) and digested the PCR product. Then, this DNA fragments were passed through gel electrophoresis. By examining these images, we identified changes in the nucleotides in these specific regions. To clarify fragments polymorphisms, the PCR products were sequenced with an Applied Biosystems Automated Sequencer. We observed the Arg188His polymorphism of XRCC2 genes in 42.2%, as shown in 30 of the 71 cancer patients. Only 21 out of 86 controls showed this polymorphism (24.2%). We also observed that 21 of the 71 patients (29.5%) carried the RAD51135G/C polymorphism of this gene. The same polymorphism was observed in 11 of the 86 controls (12.7 %; p < 0.05). The obtained results indicate that the polymorphism of RAD51 and XRCC2 genes may be associated with the incidence of colon cancer in the Turkish population. Further studies, including those on a larger group of patients, are required to further clarify this point.

Increased risk of differentiated thyroid carcinoma with combined effects of homologous recombination repair gene polymorphisms in an Iranian population

Homologous recombination (HR) repair has a crucial role to play in the prevention of chromosomal instability, and it is clear that defects in some HR repair genes are associated with many cancers. To evaluate the potential effect of some HR repair gene polymorphisms with differentiated thyroid carcinoma (DTC), we assessed Rad51 (135G>C), Rad52 (2259C>T), XRCC2 (R188H) and XRCC3 (T241M) polymorphisms in Iranian DTC patients and cancer-free controls. In addition, haplotype analysis and gene combination assessment were carried out. Genotyping of Rad51 (135G>C), Rad52 (2259C>T) and XRCC3 (T241M) polymorphisms was determined by PCR-RFLP and PCR-HRM analysis was carried out to evaluate XRCC2 (R188H) . Separately, Rad51, Rad52 and XRCC2 polymorphisms were not shown to be more significant in patients when compared to controls in crude, sex-adjusted and age-adjusted form. However, results indicated a significant difference in XRCC3 genotypes for patients when compared to controls (p value: 0.035). The GCTG haplotype demonstrated a significant difference (p value: 0.047). When compared to the wild type, the combined variant form of Rad52/XRCC2/XRCC3 revealed an elevated risk of DTC (p value: 0.007). It is recommended that Rad52 2259C>T, XRCC2 R188H and XRCC3 T241M polymorphisms should be simultaneously considered as contributing to a polygenic risk of differentiated thyroid carcinoma.

XRCC2 promotes colorectal cancer cell growth, regulates cell cycle progression, and apoptosis

X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2) and poly(ADP-ribose) polymerase 1 (PARP1) both play important roles in homologous recombination DNA repair. According to the theory of synthetic lethality, XRCC2-deficient cells are more sensitive to PARP1 inhibitors compared to XRCC2-expressing cells. We investigated XRCC2 expression and function in colorectal cancer (CRC), and the characteristics of sensitivity to PARP1 inhibitor in CRC cells with different XRCC2 levels. We enrolled 153 patients with CRC who had undergone surgery in this study. XRCC2 expression was assessed using immunohistochemistry. Stable CRC SW480 cell lines with low or high XRCC2 expression were constructed. Following treatment with the PARP1 inhibitor olaparib, the viability of cells with different XRCC2 levels was determined; cell cycle distribution and apoptosis were analyzed using flow cytometry. B-cell lymphoma-2 (Bcl-2) protein expression was measured by Western blotting. The positive rates of XRCC2 in primary CRC tissue were significantly higher than that in the matched adjacent noncancerous tissue, and XRCC2 expression status in primary CRC was related to tumor site, Dukes' stage, and tumor-nodes-metastasis (TNM) stage. XRCC2 overexpression inhibited CRC cell apoptosis and promoted proliferation by enriching cells in the G0/G1 phase. Moreover, olaparib suppressed proliferation, and olaparib sensitivity in CRC cells with high XRCC2 expression was greater. High XRCC2 expression promotes CRC cell proliferation and enriches cells in the G0/G1 phase but inhibits apoptosis. High XRCC2 expression cells are more sensitive to olaparib, which inhibits their viability.

An association between the -41657 C/T polymorphism of X-ray repair cross-complementing 2 (XRCC2) gene and ovarian cancer

X-ray repair cross-complementing group 2 (XRCC2) gene is important for the repair of double-strand DNA breaks (DSB) by homologous recombination (HR). XRCC2 polymorphisms may be associated with the development of certain types of cancers, but little is known about their association with ovarian carcinoma. XRCC2 -41657C/T (rs718282) polymorphisms were genotyped by the PCR-RFLP (restriction fragment length polymorphism) method in 608 patients with ovarian cancer and in 400 cancer-free women, who served as controls. In the present work, a relationship was identified between XRCC2 -41657C/T polymorphism and the incidence of ovarian cancer. An association was observed between ovarian carcinoma occurrence and the presence of T/T genotype [OR = 3.50 (2.46-4.97), p < 0.0001]. A tendency for an increased risk of ovarian cancer was detected with the occurrence of T allele of XRCC2 polymorphism. There were no significant differences between the distribution of XRCC2 -41657C/T genotypes in the subgroups assigned to histological grades. We suggest that the -41657C/T polymorphism of the XRCC2 gene may be risk factors for ovarian cancer development.

XRCC2 gene polymorphisms and its protein are associated with colorectal cancer susceptibility in Chinese Han population

XRCC2 is an essential part of the homologous recombination repair pathway. However, relatively little is known about the effect of XRCC2 gene C41657T and G4234C polymorphisms on the individual susceptibility to colorectal cancer (CRC). The purpose of this study was to investigate the association between XRCC2 gene C41657T and G4234C polymorphisms and CRC and to explore the relationship among the polymorphisms and clinicopathologic parameters and protein expression levels of XRCC2. A hospital-based case-control study was conducted with 246 CRC cases and 262 healthy controls. The genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism. XRCC2 protein was analyzed by immunohistochemistry for the paraffin sections of 120 CRC cases. The study data showed that the C41657T genotypes were associated with the risk of CRC. The CT/TT genotypes and T allele were overrepresented among the CRC cases. Compared with CC, CT/TT enhanced the risk of CRC (odds ratio = 1.646, 95 % confidence interval = 1.127-2.404, P = 0.010). XRCC2 protein expression of CRC patients with CT/TT genotypes was significantly higher than that of the patients with CC genotype (χ (2) = 4.887, P = 0.027). XRCC2 gene G4234C polymorphisms have no relevance to the risk of CRC. Our findings suggest that XRCC2 C41657T polymorphism may adjust the XRCC2 expression and might influence susceptibility of CRC.

DNA repair gene polymorphisms at XRCC1, XRCC3, XPD, and OGG1 Loci in the hyderabad population of India

BACKGROUND

DNA repair is one of the crucial defense mechanism against mutagenic exposure. Inherited SNPs of DNA repair genes may contribute to variation in DNA repair capacity and susceptibility to cancer. Due to the presence of these variants, inter-individual and ethnic differences in DNA repair capacity have been established in various populations. India harbors enormous genetic and cultural diversity.

MATERIALS AND METHODS

In the present study we aimed to determine the genotypes and allele frequencies of XRCC1 Arg399Gln (rs25487), XRCC3 Thr241Met (rs861539), XPD Lys751Gln (rs13181), and OGG1 Ser326Cys (rs1052133) gene polymorphisms in 186 healthy individuals residing in the Hyderabad region of India and to compare them with HapMap and other populations.

RESULTS AND CONCLUSIONS

The genotype and allele frequency distribution at the four DNA repair gene loci among Hyderabad population of India revealed a characteristic pattern. Comparison of these gene polymorphisms with other populations revealed a distinctiveness of Hyderabad population from the Deccan region of India. To the best of our knowledge, this is the first report of such DNA repair gene polymorphisms in the Deccan Indian population.

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.

Polymorphisms in DNA repair genes XRCC2 and XRCC3 risk of gastric cancer in Turkey

We studied the prevalence of polymorphisms in genes XRCC2 and XRCC3 in stomach cancer patients who lived in North Eastern Turkey. A total of 61 cancer patients and 78 controls were included in this study. Single nucleotide changes were studied in XRCC2 and XRCC3 genes at locus Arg188His and Thr241Met. Blood samples were taken from the patients and controls, and DNA was isolated. The regions of interest were amplified using a polymerase chain reaction method. After amplification, we used restriction enzymes (HphI and NcoI) to digest the amplified product. Digested product was then run through gel electrophoresis. We identified changes in the nucleotides in these specific regions. It was found that the Arg188His polymorphism of the XRCC2 gene was about 39% (24 out of the 61) among cancer patients. However, only 15% (12 out of 78) of the control group indicated this polymorphism. We also observed that 18 of the 61 cancer patients (29%) carried the Thr241Met polymorphism of the XRCC3 gene whereas 11 of the 78 (14%) individuals in the control group had the polymorphism. Our results showed a significant difference in polymorphism ratios between the cancer patients and health control group for the regions of interest. This result clearly showed that these polymorphisms increase the risk of stomach cancer and might be a strong marker for early diagnosis of gastric cancer.

Polymorphisms in RETN gene and susceptibility to colon cancer in Saudi patients

BACKGROUND AND OBJECTIVES

Resistin is an adipocytokine, which has been studied for its role in insulin resistance and recently in inflammation. Several single-nucleotide polymorphisms (SNPs) have been identified in the human resistin gene (RETN). This study aims to investigate the association of RETN rs1862513 (C-420G) and rs3745367 (G+299A) SNPs with the colon cancer risk in Saudi patients.

DESIGN AND SETTING

This is a case-control study conducted among Saudi adult colon cancer patients recruited from King Abdulaziz Hospital and Oncology Center in Jeddah, Saudi Arabia.

SUBJECTS AND METHODS

In this study, 120 Saudi volunteers (60 colon cancer patients and 60 disease-free controls) were studied. The SNPs were determined by polymerase chain reaction (PCR) and genotyping using PCR- restriction fragment length polymorphism analysis.

RESULTS

In comparing the result obtained for the patient group with that of the controls, colon cancer group displayed different genotype distribution of the RETN C-420G and G+299A SNPs. The study indicated that the SNP-420 heterozygous (CG) genotype (odds ratio [OR]=2.48, 95% CI 1.07-5.74, P=.03) and the SNP +299 heterozygous (GA) genotype (OR=6.5, 95% CI 1.77-24.18, P=.002) significantly increased the risk of colon cancer. A further analysis of the genotype combination of SNPs RETN C-420G and G+299A showed a larger increase in the colon cancer risk.

CONCLUSION

These preliminary results suggested a potential role for RETN C-420G and G+299A polymorphisms in the genetic predisposition to colon cancer disease.

Combined effect of tobacco and DNA repair genes polymorphisms of XRCC1 and XRCC2 influence high risk of head and neck squamous cell carcinoma in northeast Indian population

Tobacco consumption in various forms is one of the major risk factor for the development of head and neck squamous cell carcinoma. Polymorphisms in XRCC1 and XRCC2 genes may alter an individual's susceptibility to tobacco-related cancers. Here, we have investigated the interaction of XRCC1 (Arg399Gln) and XRCC2 (Arg188His) polymorphism and tobacco exposure in the progression of HNSCC in northeast Indian population. The population-based case-control study includes 110 HNSCC patients and 140 controls. The polymorphisms of XRCC1 and XRCC2 were studied by means of PCR-RFLP, and the results were confirmed by DNA sequencing. Smokers and tobacco-betel quid chewers were significantly higher in cases (P = 0.045 and 0.033). The variant homozygote AA genotype of XRCC1 Arg399Gln and heterozygote GA genotype of XRCC2 Arg188His has an increased risk toward HNSCC (OR 2.43; P = 0.031 and OR 3.29; P < 0.01, respectively). The interaction between tobacco-betel quid chewing and variant genotypes of XRCC1 and XRCC2 resulted in several fold increase the risk of HNSCC, when compared to non-chewers. Heavy smokers carrying XRCC1 AA and XRCC2 GA genotypes had a significantly higher risk of HNSCC compared to never smokers (P = 0.017 and 0.003, respectively). Upon gene-gene interaction analysis, individuals carrying both XRCC1 GA (Arg/Gln) and XRCC2 GA (Arg/His) genotypes had the highest risk of HNSCC (P = 0.001).Our finding suggests that interaction of tobacco and polymorphisms of XRCC1 and XRCC2 increases the risk of HNSCC. Furthermore, cross talk between these two DNA repair genes might modulate susceptibility toward HNSCC.

Association of polymorphisms in the 5' untranslated region of RAD51 gene with risk of endometrial cancer in the Polish population

Purpose

Many of the studies have analyzed cell repair capabilities, following cancer development. The cellular reaction to DNA damaging agents can modulate the susceptibility to various tumors. This reaction is mainly determined by DNA repair efficacy which, in turn, may be influenced by the variability of DNA repair genes, expressed by their polymorphisms.

Methods

This report describes studies of the distribution of genotypes and the frequency of alleles of the G135C (rs1801320) and G172T (rs1801321) RAD51 polymorphism in 630 paraffin-embedded samples of tumor tissue from patients with endometrial cancer. DNA from 630 normal endometrial tissues served as control. RAD51 polymorphisms were determined by PCR–RFLP.

Results

In the present work, a relationship was identified between RAD51 G135C polymorphism and the incidence of endometrial cancer. Endometrial cancer patients had an overrepresentation of 135C allele. The 135C/C homozygous variant increased cancer risk. A tendency towards a decreased risk of endometrial cancer was observed with the occurrence of combined G135C–G172G genotype of RAD51 polymorphism. An association was confirmed between RAD51 G135C and G172T polymorphisms and endometrial cancer progression, assessed by the histological grades.

Conclusions

The results support the hypothesis that RAD51 G135C and G172T polymorphisms may be associated with endometrial cancer occurrence and/or progression.

XRCC2 rs3218536 polymorphism decreases the sensitivity of colorectal cancer cells to poly(ADP-ribose) polymerase 1 inhibitor

Single nucleotide polymorphisms (SNPs) are associated with the development of certain types of cancer. The present study aimed to investigate the association between X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2) SNPs and colorectal cancer (CRC) cell sensitivity to the poly(ADP-ribose) polymerase (PARP) 1 inhibitor olaparib (AZD2281). SNaPshot^® analysis of XRCC2 SNPs was performed in five CRC cell lines. The AZD2281-sensitivities of the CRC cells were also analyzed using MTT assays. The effect of AZD2281 on XRCC2 and PARP1 expression was investigated in the five cell lines using quantitative polymerase chain reaction and western blot analyses. Parallel investigations were performed using a cisplatin (DDP) model of DNA damage. The XRCC2 rs3218536 SNP was found to be associated with the LoVo microsatellite instability CRC cell line. The relative rate of growth inhibition was found to be lower in the LoVo cells following treatment with AZD2281 compared with the other four cell lines (P=0.002). Furthermore, the XRCC2 mRNA level in the LoVo cells was observed to be significantly higher than that in the other four cell lines (P<0.05). Similar results were found using the DDP model of DNA damage (P<0.05). The present study indicated that the XRCC2 rs3218536 polymorphism decreases the sensitivity of CRC cells to AZD2281.

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.

Impact of XRCC2 Arg188His polymorphism on cancer susceptibility: a meta-analysis

Background

Association between the single nucleotide polymorphism rs3218536 (known as Arg188His) located in the X-ray repair cross complementing group 2 (XRCC2) gene and cancer susceptibility has been widely investigated. However, results thus far have remained controversial. A meta-analysis was performed to identify the impact of this polymorphism on cancer susceptibility.

Methods

PubMed and Embase databases were searched systematically until September 7, 2013 to obtain all the records evaluating the association between the XRCC2 Arg188His polymorphism and the risk of all types of cancers. We used the odds ratio (OR) as measure of effect, and pooled the data in a Mantel-Haenszel weighed random-effects meta-analysis to provide a summary estimate of the impact of this polymorphism on breast cancer, ovarian cancer and other cancers. All the analyses were carried out in STATA 12.0.

Results

With 30868 cases and 38656 controls, a total of 45 case-control studies from 26 publications were eventually included in our meta-analysis. No significant association was observed between the XRCC2 Arg188His polymorphism and breast cancer susceptibility (dominant model: OR = 0.94, 95%CI = 0.86–1.04, P = 0.232). However, a significant impact of this polymorphism was detected on decreased ovarian cancer risk (dominant model: OR = 0.83, 95%CI = 0.73–0.95, P = 0.007). In addition, we found this polymorphism was associated with increased upper aerodigestive tract (UADT) cancer susceptibility (dominant model: OR = 1.51, 95%CI = 1.04–2.20, P = 0.032).

Conclusion

The Arg188His polymorphism might play different roles in carcinogenesis of various cancer types. Current evidence did not suggest that this polymorphism was directly associated with breast cancer susceptibility. However, this polymorphism might contribute to decreased gynecological cancer risk and increased UADT cancer risk. More preclinical and epidemiological studies were still imperative for further evaluation.

Equivocal association of RAD51 polymorphisms with risk of esophageal squamous cell carcinoma in a Chinese population

AIM

To study the contribution of genetic variation in RAD51 to risk of esophageal squamous cell carcinoma (ESCC).

METHODS

Three single nucleotide polymorphisms (SNPs) in RAD51 (rs1801320, rs4144242 and rs4417527) were genotyped in 316 ESCC patients and 316 healthy controls in Anyang area of China using PCR- RFLP (polymerase chain reaction-restriction fragment length polymorphism). Demographic variables between cases and controls were statistically compared by T test and Chi-square test. Hardy-Weinberg equilibrium was evaluated by the Chi-square test. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to measure any association with ESCC. Haplotype frequencies were estimated by Phase 2.1.

RESULT

The genotype frequencies of rs1801320, rs4144242 and rs4417527 in patients with ESCC demonstrated no significant differences from those in control group (P>0.05). When the haplotypes of these three SNPs were constructed and their relationships with ESCC risk investigated, however, CGG was observed to increase the risk (P=0.020, OR=2. 289).

CONCLUSIONS

There was no association between the three SNPs of RAD51 and ESCC susceptibility in our Chinese population. However, the CGG haplotype might be a risk factor.

miR-7 inhibits colorectal cancer cell proliferation and induces apoptosis by targeting XRCC2

BACKGROUND

Analysis using publicly available algorithms predicts that X-ray repair complementing defective repair in Chinese hamster cells 2 (XRCC2), a key component in the homologous recombination repair pathway, is a potential target of micro-ribonucleic acid-7 (miR-7). Some studies have shown that both miR-7 and XRCC2 are associated with cancer development. For this purpose, we searched for the possible relationship between miR-7 and XRCC2 in the development of colorectal cancer (CRC).

METHODS

miR-7 expression was assessed in CRC specimens and cell lines using real-time polymerase chain reaction (PCR). Luciferase reporter assay was used to confirm the target associations. The effect of miR-7 on cell proliferation and apoptosis was confirmed in vitro by the methylthiazol tetrazolium (MTT) assay, colony formation assay, and flow cytometry. Gene and protein expression were examined using real time PCR and western blotting, respectively.

RESULTS

miR-7 was downregulated in CRC specimens and cell lines, and targeted the 3' untranslated region of XRCC2. miR-7 overexpression reduced cyclin D1 expression and increased p21, caspase-3, and BAX expression, which subsequently inhibited CRC cell proliferation and induced CRC cell apoptosis. However, XRCC2 can repress the inhibitory effects of miR-7 on proliferation.

CONCLUSION

Our findings suggest that miR-7 plays a protective role by inhibiting proliferation and increasing apoptosis of CRC cells. It may identify new targets for anti-cancer treatment.

shRNA-mediated XRCC2 gene knockdown efficiently sensitizes colon tumor cells to X-ray irradiation in vitro and in vivo

Colon cancer is one of the most common tumors of the digestive tract. Resistance to ionizing radiation (IR) decreased therapeutic efficiency in these patients’ radiotherapy. XRCC2 is the key protein of DNA homologous recombination repair, and its high expression is associated with enhanced resistance to DNA damage induced by IR. Here, we investigated the effect of XRCC2 silencing on colon tumor cells’ growth and sensitivity to X-radiation in vitro and in vivo. Colon tumor cells (T84 cell line) were cultivated in vitro and tumors originated from the cell line were propagated as xenografts in nude mice. The suppression of XRCC2 expression was achieved by using vector-based short hairpin RNA (shRNA) in T84 cells. We found that the knockdown of XRCC2 expression effectively decreased T84 cellular proliferation and colony formation, and led to cell apoptosis and cell cycle arrested in G2/M phase induced by X-radiation in vitro. In addition, tumor xenograft studies suggested that XRCC2 silencing inhibited tumorigenicity after radiation treatment in vivo. Our data suggest that the suppression of XRCC2 expression rendered colon tumor cells more sensitive to radiation therapy in vitro and in vivo, implying XRCC2 as a promising therapeutic target for the treatment of radioresistant human colon cancer.