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

XRCC1 R194W and R399Q Polymorphisms and Colorectal Cancer Risk in a Northeastern Mexican Population

Colorectal cancer (CRC) is one of the most common cancers worldwide. Its etiopathogenesis is complex, mainly influenced by genetic instability caused by the accumulation of mutations. The XRCC1 gene, which is involved in DNA repair, has been associated with CRC through the R194W (C194T) and R399Q (G399A) polymorphisms, but the results are inconsistent. Here, we analyzed the association of these polymorphisms with sporadic CRC in a northeastern Mexican population, including 155 male CRC patients and 155 male controls. Genotyping was performed using the RFLP method. An association with CRC was found for the 399A allele (G vs A; OR = 1.48 (1.03-2.13), P=0.034) and for the 399AA genotype in a codominant model (AA vs GG; OR = 3.11 (1.06-9.10), P=0.031). In contrast, there were no significant differences between CRC patients and controls for the C194T polymorphism (C vs T; OR = 0.82 (0.52-1.31), P=0.41). These results are consistent with many similar studies, but further research is needed to verify whether the XRCC1 R194W and R399Q polymorphisms play a role in CRC etiology. The functional significance of these polymorphisms is unclear, but some studies suggest that they influence DNA repair capacity and, thus, cancer risk.

Association between XRCC3 p.Thr241Met polymorphism and risk of glioma: A systematic review and meta-analysis

BACKGROUND

The XRCC3 p.Thr241Met (rs861539) polymorphism has been extensively studied for its association with glioma risk, but results remain conflicting. Therefore, we performed a systematic review and meta-analysis to resolve this inconsistency.

METHODS

Studies published up to June 10, 2022, were searched in PubMed, Web of Science, Scopus, VIP, Wanfang, and China National Knowledge Infrastructure databases and screened for eligibility. Then, the combined odds ratio (OR) of the included studies was estimated based on five genetic models, i.e., homozygous (Met/Met vs. Thr/Thr), heterozygous (Thr/Met vs. Thr/Thr), dominant (Thr/Met + Met/Met vs. Thr/Thr), recessive (Met/Met vs. Thr/Thr + Thr/Met) and allele (Met vs. Thr). The study protocol was preregistered at PROSPERO (registration number: CRD42021235704).

RESULTS

Overall, our meta-analysis of 14 eligible studies involving 12,905 subjects showed that the p.Thr241Met polymorphism was significantly associated with increased glioma risk in both homozygous and recessive models (homozygous, OR = 1.381, 95% CI = 1.081-1.764, P = 0.010; recessive, OR = 1.305, 95% CI = 1.140-1.493, P<0.001). Subgroup analyses by ethnicity also revealed a statistically significant association under the two aforementioned genetic models, but only in the Asian population and not in Caucasians (P>0.05).

CONCLUSION

We demonstrated that the XRCC3 p.Thr241Met polymorphism is associated with an increased risk of glioma only in the homozygous and recessive models.

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.

Association of XRCC1, XRCC2 and XRCC3 Gene Polymorphism with Esophageal Cancer Risk

Aim

The X-ray repair cross-complementing (XRCC) gene polymorphisms influence esophageal carcinogenesis by altering the DNA repair capacity. The present study was designed to screen five single nucleotide polymorphisms (SNPs) of XRCC genes for their susceptibility to esophageal cancer (EC) risk. There is no previous report on these polymorphisms for EC from India, where EC frequency is high.

Methods

The present study included 497 subjects (213 EC patients and 284 healthy controls). The polymorphisms were screened using the PCR-RFLP method and allele and genotype distribution were compared using chi-square test. Association analysis was done by haplotype analysis and linkage disequilibrium (LD) analysis. Gene–gene interactions were identified using multifactor dimensionality reduction (MDR). The risk was calculated using binary logistic regression.

Results

For XRCC1 p.Arg399Gln, a decreased risk for EC was associated with the AA genotype [OR (95% CI): 0.53 (0.3–0.95), p=0.03] even after adjusting for various covariates [OR (95% CI): 0.49 (0.26–0.9), p=0.024] and with the recessive model [OR (95% CI): 0.49 (0.27–0.8), p=0.016]. The GA genotype of p.Arg280His was associated with an increased risk for EC [OR (95% CI): 1.7 (1.0–2.82), p= 0.045] after adjustments. The two XRCC1 polymorphisms, p.Arg399Gln and p.Arg194Trp were in slight LD among EC patients (D̍́=0.845, r²=0.042). XRCC2 and XRCC3 polymorphisms were not associated with EC risk.

Conclusion

XRCC1 p.Arg399Gln plays a protective role in the development of the EC. The study is the first report from India, providing baseline data about genetic polymorphisms in DNA repair genes XRCC1, XRCC2 and XRCC3 modulating overall EC risk.

Association of DNA repair gene polymorphisms with colorectal cancer risk and treatment outcomes

Colorectal cancer (CRC) is the third most common carcinoma worldwide. Despite the progress in screening and treatment, CRC remains a leading cause of cancer-related mortality. Alterations to normal nucleic acid processing may drive neoplastic transformation of colorectal epithelium. DNA repair machinery performs an essential function in the protection of genome by reducing the number of genetic polymorphisms/variations that may drive carcinogenicity. Four essential DNA repair systems are known which include nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), and double-strand break repair (DSBR). Polymorphisms of DNA repair genes have been shown to influence the risk of cancer development as well as outcomes of treatment. Several studies demonstrated the association between genetic polymorphism of DNA repair genes and increased risk of CRC in different populations. In this review, we have summarized the impact of DNA repair gene polymorphisms on risk of CRC development and treatment outcomes. Advancements of the current understanding for the impact of DNA repair gene polymorphisms on the risk and treatment of CRC may support diagnostic and predictive roles in patients with CRC.

Polymorphisms of XRCC3 and XRCC7 and Colorectal Cancer Risk in Khorasan Razavi Province, Iran

Background: Colorectal cancer (CRC) is highly prevalent cancer, which should be genetically studied among different peoples of the world. Objective: The aim of this study was to evaluate the effect of XRCC3T241M, XRCC3 A17893G and, for the first time, XRCC7 I3434T polymorphisms on CRC risk in Khorasan Razavi Province, Iran. Materials and Methods: In this case-control study, 180 patients with CRC and 160 sex- and age-matched healthy controls were studied. Genotypes were determined by RFLP-PCR and ARMS-PCR. Results: The incidence of CRC was observed to be significantly more in a heterozygous XRCC3 C/T genotype than in the CC genotype (OR 2.210, 95% CI 1.073-4.548, p=0.030). In the case of the XRCC7 I3434T polymorphism, CRC risk was significantly (4.3 fold) higher in I/T+T/T variant subjects compared to the I/I genotype (OR 4.394, 95% CI 2.721-7.096, p=0.000). Moreover, the XRCC3 A17893G polymorphism did not correlate with CRC. In addition, there was no significant difference between the distribution of genotypes of the three studied polymorphisms with demographic and clinicopathological features in the CRC patients. Conclusion: Polymorphisms of XRRC3 and XRCC7 genes are involved in CRC and should be considered as a risk factor.

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.

Lack of correlation between X-ray repair cross-complementing group 1 gene polymorphisms and the susceptibility to colorectal cancer in a Malaysian cohort

X-ray repair cross-complementing group 1 (XRCC1) is one of the key components in the base excision repair pathway that repairs erroneous DNA lesions and removes nonbulky base adducts for the maintenance of genome integrity. Studies have revealed that differences in individual DNA repair capacity can impact the interindividual variation in cancer susceptibility, tumour aggressiveness and treatment response. The relationship between XRCC1 and sporadic colorectal cancer (CRC) susceptibility, which is hitherto inconclusive, has been explored in many association studies of different populations. In view of the conflicting findings generated, we aimed to investigate the association between XRCC1 and genetic predisposition to CRC among Malaysians. The present case-control association study was conducted on 130 CRC patients and 212 age-matched healthy controls. The genotyping of XRCC1 Arg194Trp, Arg280His and Arg399Gln single nucleotide polymorphisms was performed with allele-specific real-time PCR approach. This was followed by basic statistical analysis on the single nucleotide polymorphisms and haplotype data obtained. No significant difference in the allele and genotype frequencies was observed between CRC patients and healthy controls (P>0.05). There was also no association observed between XRCC1 haplotypes and CRC (P>0.05). In conclusion, a positive association between XRCC1 gene polymorphisms and CRC risk was not established in our Malaysian population.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Association of XRCC1 Arg399Gln Polymorphism with Colorectal Cancer Risk: A HuGE Meta Analysis of 35 Studies

BACKGROUND

Non-synonymous polymorphisms in XRCC1 hase been shown to reduce effectiveness of DNA repair and be associated with risk of certain cancers. In this study we aimed to clarify any association between XRCC1 Arg399Gln and colorectal cancer (CRC) risk by performing a meta-analysis of published case-control studies.

MATERIALS AND METHODS

PubMed and Google Scholar were searched to explore the association between XRCC1 and CRC. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate the association strength. Publication bias was assessed by Egger's and Begg's tests.

RESULTS

Up to January 2015, 35 case control studies involving 9,114 CRC cases and 13,948 controls were included in the present meta-analysis. The results showed that the Arg399Gln polymorphism only under an allele genetic model was associated with CRC risk (A vs. G: OR 0.128, 95% CI 0.119-0.138, p<0.001). Also, this meta-analysis suggested that the XRCC1 Arg399Gln polymorphism might associated with susceptibility to CRC in Asians (A vs G: OR 0.124, 95% CI 0.112-0.138, p<0.001) and Caucasian (A vs G: OR 0.132, 95% CI 0.119-0.146, p<0.001) only under an allele genetic model.

CONCLUSIONS

This meta-analysis confirms the association between XRCC1 Arg399Gln polymorphism and CRC risk and suggests that the heterogeneity is not strongly modified by ethnicity and deviation from the Hardy-Weinberg equilibrium.

Correlation between selected XRCC2, XRCC3 and RAD51 gene polymorphisms and primary breast cancer in women in Pakistan

Genetic polymorphisms in homologous recombination repair genes cause an abnormal development of cancerous cells. In the present study we evaluated the possibility of breast cancer association with single nucleotide polymorphisms of RAD51, XRCC2 and XRCC3 genes. Polymorphisms selected in this study were RAD51 135G/C, XRCC2 Arg188His; and XRCC3 Thr241Met. Each polymorphism was genotyped using Polymerase chain reaction-restriction fragment length polymorphism in study cohort of 306 females (156 breast cancer patients and 150 controls). We observed that heterozygous variant genotype (GC) of RAD51 135 G/C polymorphism was associated with a significantly (OR=2.70; 95%CI (0.63-1.79); p<0.03) increased risk of breast cancer. In case of the XRCC3 gene we observed that frequency of heterozygous (OR=2.88; 95%CI (1.02-8.14); p<0.02) and homozygous (OR=1.46; 95%CI (0.89-2.40); p<0.04) genotype of Thr241Met polymorphism were significantly higher in breast cancer patients. For the Arg188His polymorphism of XRCC2, ~2fold increase in breast cancer risk (OR=1.6, 95%CI = 0.73-3.50) was associated with GA genotype with a p value for trend of 0.03. Our results suggest that the 135G/C polymorphism of the RAD51, Thr241Met polymorphism of XRCC3 and Arg188His polymorphism of XRCC2 can be independent markers of breast cancer risk in Pakistan.

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.

Genes and SNPs associated with non-hereditary and hereditary colorectal cancer

BACKGROUND

Colorectal cancer is the third most common cancer in both men and women in the world and the second leading cause of cancer-related deaths. The incidence of colorectal cancer has increased in Iran in the past three decades and is now considered as a serious problem for our society. This cancer has two types hereditary and non-hereditary, 80% of cases being the latter. Considering that the relationship between SNPs with diseases is a concern, many researchers believed that they offer valuable markers for identifying genes responsible for susceptibility to common diseases. In some cases, they are direct causes of human disease. One SNP can increase risk of cancer, but when considering the rate of overlap and frequency of DNA repair pathways, it might be expected that SNP alone cannot affect the final result of cancer, although several SNPs together can exert a significant influence. Therefore identification of these SNPs is very important. The most important loci which include mutations are: MLH1, MSH2, PMS2, APC, MUTYH, SMAD7, STK11, XRCC3, DNMT1, MTHFR, Exo1, XRCC1 and VDR. Presence of SNPs in these genes decreases or increases risk of colorectal cancer.

MATERIALS AND METHODS

In this article we reviewed the Genes and SNPs associated with non-hereditary and hereditary of colorectal cancer that recently were reported from candidate gene y, meta-analysis and GWAS studies.

RESULTS

As with other cancers, colorectal cancer is associated with SNPs in gene loci. Generally, by exploring SNPs, it is feasible to predict the risk of developing colorectal cancer and thus establishing proper preventive measures.

CONCLUSIONS

SNPs of genes associated with colorectal cancer can be used as a marker SNP panel as a potential tool for improving cancer diagnosis and treatment planning.

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

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

XRCC1 genetic polymorphism acts a potential biomarker for lung cancer

Lung cancer is one of the most common but serious cancers in the world. Both the X-ray repair cross-complementing group 1 (XRCC1) gene and the human multidrug resistance 1 (MDR1) gene are important candidate genes influencing the susceptibility to various diseases, including lung cancer. This study aimed to assess the correlation of genetic polymorphisms in XRCC1 and MDR1 with the susceptibility to lung cancer. In this study, a total of 320 lung cancer patients and 346 cancer-free controls in Chinese population were enrolled in this study. Data about the clinical characteristics and related risk factors of lung cancer were collected by questionnaires. The single-nucleotide polymorphisms (SNPs) of XRCC1 and MDR1 genes were genotyped by created restriction site-polymerase chain reaction method. Our data showed that the risk for lung cancer increased significantly among the variant Arg194Trp (C > T, rs1799782) and Arg399Gln (G > A, rs25487) of XRCC1, but there are no significant differences in the allelic and genotypic frequencies of c.1564A > T and c.3073A > C of MDR1 between lung cancer patients and cancer-free controls. In conclusion, these preliminary results suggest that the C > T, rs1799782 and C > T, rs25487 of XRCC1 genetic variants might be used as molecular markers for detecting lung cancer susceptibility.

The XRCC3 Thr241Met polymorphism influences glioma risk - a meta-analysis

BACKGROUND

Findings from previous published studies regarding the association of the XRCC3 Thr241Met polymorphism with glioma susceptibility have often been conflicting. Therefore, a meta-analysis including all available publications was carried out to make a more precise estimation of the potential relationship.

METHODS

By searching the electronic databases of Pubmed and Embase (up to April 1st, 2013), a total of nine case-control studies with 3,752 cases and 4,849 controls could be identified for inclusion in the current meta-analysis. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the strength of the association.

RESULTS

This meta-analysis showed the XRCC3 Thr241Met polymorphism to be significantly associated with decreased glioma risk in the allelic model (Met allele vs. Thr allele: OR= 0.708, 95%CI= 0.631-0.795). Moreover, we also observed a statistically significant association between the XRCC3 Thr241Met polymorphism and reduced glioma risk in analyses stratified by ethnicity (Asian) and source of controls (hospital based) in the allelic model.

CONCLUSIONS

Current evidence suggests that the XRCC3 Thr241Met polymorphism may be a risk factor for glioma development, especially in Asians.

XRCC1 gene polymorphism, diet and risk of colorectal cancer in Thailand

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers worldwide. This study aimed to investigate the interaction between the presence of a polymorphism of the XRCC1 gene and known risk factors for colorectal cancer in Thailand.

MATERIALS AND METHODS

A hospital-based case-control study was conducted in Thailand. The participants were 230 histologically confirmed new cases and 230 controls matched by sex and age and recruited from the same hospital. Information about demographic characteristics, life style, and dietary habits was collected using structured interviews, and blood samples were taken which were used for the detection of a homozygous and heterozygous polymorphisms of XRCC1. Associations were assessed using multiple conditional logistic regression.

RESULTS

In the univariate analysis, factors found to be significantly associated with an increased risk for CRC were the presence of the XRCC1 AA homozygote (OR= 4.95; 95% CI: 1.99-12.3), a first degree family history of cancer (OR= 1.74; 95% CI: 1.18-2.58), and a high frequency of pork consumption (OR= 1.49; 95% CI: 1.00-2.21). Intakes of fish fruit and vegetables appeared to be protective factors, but the associations were not statistically significant. In the multivariate analysis only the XRCC1 AA homozygote polymorphism and a family history of cancer emerged as risk factors (OR= 4.96; 95% CI: 1.90- 12.95 and OR=1.80; 95% CI: 1.18-2.72, respectively).

CONCLUSIONS

While the XRCC1 AA homozygote and a family history of cancer were found to be associated with an increased risk of CRC, none of the dietary intake variables were clearly identified as risk or protective factors. There is a need for further research to determine the reasons for this.

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.

APE1 polymorphisms are associated with colorectal cancer susceptibility in Chinese Hans

AIM: To study the association between four base excision repair gene polymorphisms and colorectal cancer risk in a Chinese population.

METHODS: Two hundred forty-seven colorectal cancer (CRC) patients and three hundred cancer-free controls were enrolled in this study. Four polymorphisms (OGG1 Ser326Cys, APE1 Asp148Glu, -141T/G in the promoter region, and XRCC1 Arg399Gln) in components of the base excision repair pathway were determined in patient blood samples using polymerase chain reaction with confronting two-pair primers. The baseline information included age, gender, family history of cancer, and three behavioral factors [smoking status, alcohol consumption, and body mass index (BMI)]. χ² tests were used to assess the Hardy-Weinberg equilibrium, the distributions of baseline characteristics, and the four gene polymorphisms between the cases and controls. Multivariate logistic regression analyses were conducted to analyze the correlations between the four polymorphisms and CRC risk, adjusted by the baseline characteristics. Likelihood ratio tests were performed to analyze the gene-behavior interactions of smoking status, alcohol consumption, and BMI on polymorphisms and CRC susceptibility.

RESULTS: The APE1 148 Glu/Glu genotype was significantly associated with an increased risk of colorectal cancer (OR = 2.411, 95%CI: 1.497-3.886, P < 0.001 relative to Asp/Asp genotype). There were no associations between OGG1, XRCC1, or APE1 promoter polymorphisms and CRC risk. A multivariate analysis including three behavioral factors showed that the APE1 148 Glu/Glu genotype was associated with an increased risk for CRC among both smokers and non-smokers, non-drinkers and individuals with a BMI ≥ 25 kg/m² (ORs = 2.356, 3.299, 2.654, and 2.581, respectively). The XRCC1 399 Arg/Gln genotype was associated with a decreased risk of CRC among smokers and drinkers (OR = 0.289, 95%CI: 0.152-0.548, P < 0.001, and OR = 0.327, 95%CI: 0.158-0.673, P < 0.05, respectively). The APE1 promoter polymorphism -141 T/G genotype was associated with a reduced risk of colorectal cancer among subjects with a BMI < 25 kg/m² (OR = 0.214, 95%CI: 0.069-0.660, P < 0.05 relative to T/T genotype). There were significant gene-behavior interactions between smoking status and XRCC1 Arg399Gln, as well as BMI and APE1 -141T/G polymorphism (all P < 0.05).

CONCLUSION: APE1 Asp148Glu is associated with increased CRC risk and smoking alters the association between XRCC1 Arg399Gln and CRC risk in the Chinese Han population.

DNA repair gene XRCC3 Thr241Met polymorphism and susceptibility to glioma: A case-control study

The DNA repair gene, X-ray repair cross-complementing group 3 (XRCC3) Thr241Met polymorphism may be associated with a susceptibility to glioma. The present study aimed to investigate the association between the XRCC3 Thr241Met polymorphism and the potential susceptibility to gliomas. A hospital-based case-control study was conducted, which included a total of 886 patients with glioma and 886 healthy control subjects. Peripheral blood samples were extracted and the polymerase chain reaction-restriction fragment length polymorphism method was performed to analyze the genotypes. The glioma patients had a significantly higher frequency of the XRCC3 241 MetMet genotype [odds ratio (OR) = 1.62; 95% confidence interval (CI): 1.09–2.41; P=0.02] compared with the control subjects. When stratified by the grade of the glioma, the patients with stage IV glioma (according to the World Health Organization classification) had a significantly higher frequency of the XRCC3 241 MetMet genotype (OR=1.61; 95% CI: 1.06–2.44; P=0.03). When stratified by the histology of the glioma, there was no significant difference in the distribution of each genotype. The findings of the present study indicate that the XRCC3 Thr241Met polymorphism is associated with a susceptibility to glioma.

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.

Meta-analysis of genetic polymorphisms and ophthalmologic disease risk in Asian populations: a case of DNA repair XRCC1 gene

This study aimed to assess a meta-analysis of the association of XRCC1 polymorphisms with the risk of various ophthalmologic diseases in Asian population. This meta-analysis was performed by critically reviewing reveals 38 studies involving 1373 cases and 1745 controls. Among all the eligible studies, one focused on Arg194Trp polymorphism, nine described the Arg399Gln and no article investigated on Arg280His. There was a large between-study heterogeneity in ORs of individual studies of the dominant model (chi2 = 74.18, I2 = 58.9%, p = 0.013) and the additive (chi2 = 56.18, I2 = 41.4%, p = 0.091) models, but a moderate heterogeneity in the recessive model (chi2 = 72.27, I2 = 78.8%, p = 0.000) was observed. So, we pooled the results using the random-effect analysis and found that Arg399Gln has a weak relation with ophthalmologic disease in the recessive (OR = 0.96, 95% CI: 0.64-1.44), the dominant (OR = 1.05, 95% CI: 0.82-1.33) and the additive (OR = 1.15, 95% CI: 0.77-1.70) and models. The present meta-analysis correspondingly shows that comprising diverse population is very important since susceptibility loci might vary indifferent ethnic groups. To ratify our findings, widespread studies with enlarged sample size and various populations are essential to explain the role of all polymorphism of XRCC1 genes in the pathogenesis of ophthalmologic diseases. Finally, our meta-analysis showed Arg399Gln variant was not associated with increased ophthalmologic diseases risk via dominant and recessive modes among Asian population.

XRCC3 Thr241Met polymorphism and risk of acute myeloid leukemia in a Romanian population

BACKGROUND

DNA repair systems have a critical role in maintaining the genome integrity and stability. DNA repair gene polymorphisms may influence the capacity to repair DNA damage, and thus lead to an increased cancer susceptibility. X-ray repair cross-complementing groups 3 (XRCC3), a DNA repair gene, may be involved in acute myeloid leukemia susceptibility. The objective of the current study was to investigate the association of Thr241Met polymorphism of XRCC3 gene with the risk of acute myeloid leukemia (AML).

METHODS

This study included 78 AML patients and 121 healthy individuals without cancer. We used polymerase chain reaction-restriction fragment length polymorphism assay to determine XRCC3 genotypes.

RESULTS

The XRCC3 variant genotype (Thr/Met+Met/Met) was more frequent in AML patients than in healthy controls (OR=2.76, 95% CI: 1.52-4.98, P=0.001). Our study revealed a statistically significant association between variant genotype (Thr/Met+Met/Met) and AML de novo compared to secondary AML (P=0.007). No significant associations were found between any genotype and age at diagnosis, number of white blood cells and subtype of AML. Overall survival of patients with Thr/Thr genotype was better than those of variant Thr/Met and Met/Met genotypes.

CONCLUSIONS

Our findings indicate that the XRCC3 Thr241Met polymorphism may be a genetic risk factor for AML, particularly in male patients with de novo AML from the central part of Romania.

Association between polymorphisms of XRCC1 Arg399Gln and XPD Lys751Gln genes and prognosis of colorectal cancer in a Chinese population

We conducted this study to detect associations between XRCC1 Arg399Gln and XPD Lys751Gln genotypes and survival of colorectal cancer patients treated with 5-FU/oxalipatin chemotherapy. We included 289 Chinese patients with advanced colorectal cancer, who had received 5-FU/oxalipatin chemotherapy as first-line treatment from January 2005 to January 2007. All patients were followed up till Nov. 2011. Genotyping for XRCC1 Arg399Gln and XPD Lys751Gln polymorphisms was based upon duplex polymerase-chain-reaction with the PCR-RFLP method. In our study, we found the XRCC1 399 Gln/Gln genotype to confer significantly higher rates of response to chemotherapy when compared to the Arg/Arg genotype [OR (95% CI)=2.56(1.57-2.55)]. patients with the XPD 751 Gln/Gln genotype had significantly higher rates of response to chemotherapy [OR (95% CI)=1.54(0.87-2.65)] and those with the XRCC1 399 Gln/Gln genotype had a longer average survival time and significantly lower risk of death than did those with the Arg/Arg genotype [HR (95% CI)=0.66(0.36-0.95)]. Similarly, those carrying the XPD 751Gln/Gln genotype had 0.51-fold the risk of death of those with XPD 751Lys/Lys [HR (95% CI)=0.51(0.33-0.94)]. In conclusion, it is suggested that the XRCC1 Arg399Gln and XPD Lys751Gln polymorphisms should be routinely assessed to determine colorectal patients who are more likely to benefit from 5-FU/oxalipatin chemotherapy.

GSTP1, ERCC1 and ERCC2 polymorphisms, expression and clinical outcome of oxaliplatin-based adjuvant chemotherapy in colorectal cancer in Chinese population

AIM

Platinum agents have shown to be effective in the treatment of colorectal cancer. We assessed whether single nucleotide polymorphisms (SNPs) in GSTP1, ERCC1 Asn118Asn and ERCC2 Lys751Gln might predict the overall survival in patients receiving oxaliplatin-based chemotherapy in a Chinese population.

METHODS

SNPs of GSTP1, ERCC1 Asn118Asn and ERCC2 Lys751Gln in 335 colorectal cancer patients were assessed using TaqMan nuclease assays.

RESULTS

At the time of final analysis on Nov. 2011, the median follow-up period was 37.7 months (range from 1 to 60 months). A total of 229 patients died during follow-up. Our study showed GSTP1 Val/Val (HR=0.44, 95% CI=0.18-0.98), ERCC1 C/C (HR=0.20, 95% CI=0.10-0.79) and ERCC2 G/G (HR=0.48, 95% CI=0.19-0.97) to be significantly associated with better survival of colorectal cancer. GSTP1 Val/Val, ERCC1 C/C and ERCC2 G/G were also related to longer survival among patients with colon cancer, with HRs (95% CIs) of 0.41 (0.16-0.91), 0.16 (0.09-0.74) and 0.34 (0.16-0.91), respectively.

CONCLUSION

GSTP1, GSTP1, ERCC1 Asn118Asn and ERCC2 Lys751Gln genotyping might facilitate tailored oxaliplatin-based chemotherapy for colorectal cancer patients.

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.

Association between the XRCC3 T241M polymorphism and risk of cancer: evidence from 157 case-control studies

The T241M polymorphism in the X-ray cross-complementing group 3 (XRCC3) had been implicated in cancer susceptibility. The previous published data on the association between XRCC3 T241M polymorphism and cancer risk remained controversial. Hence, we performed a meta-analysis to investigate the association between cancer susceptibility and XRCC3 T241M (61,861 cases and 84,584 controls from 157 studies) polymorphism in different inheritance models. We used odds ratios with 95% confidence intervals to assess the strength of the association. Overall, significantly increased cancer risk was observed in any genetic model (dominant model: odds ration [OR]=1.07, 95% confidence interval [CI]=1.00-1.13; recessive model: OR=1.15, 95% CI=1.08-1.23; additive model: OR=1.17, 95% CI=1.08-1.28) when all eligible studies were pooled into the meta-analysis. In further stratified and sensitivity analyses, the elevated risk remained for subgroups of bladder cancer and breast cancer, especially in Caucasians. In addition, significantly decreased lung cancer risk was also observed. In summary, this meta-analysis suggests the participation of XRCC3 T241M in the susceptibility for bladder cancer and breast cancer, especially in Caucasians, and XRCC3 T241M polymorphism is associated with decreased lung cancer risk. Moreover, our work also points out the importance of new studies for T241M association in some cancer types, such as gastric cancer, colorectal cancer, and melanoma skin cancer, where at least some of the covariates responsible for heterogeneity could be controlled, to obtain a more conclusive understanding about the function of the XRCC3 polymorphism in cancer development.

Association of a newly identified variant of DNA polymerase beta (polβΔ63-123, 208-304) with the risk factor of ovarian carcinoma in India

BACKGROUND

DNA polymerase is a single-copy gene that is considered to be part of the DNA repair machinery in mammalian cells. The encoded enzyme is a key to the base excision repair (BER) pathway. It is evident that pol beta has mutations in various cancer samples, but little is known about ovarian cancer.

AIM

Identification of any variant form of polβ cDNA in ovarian carcinoma and determination of association between the polymorphism and ovarian cancer risk in Indian patients. We used 152 samples to isolate and perform RT-PCR and sequencing.

RESULTS

A variant of polymerase beta (deletion of exon 4-6 and 11-13, comprising of amino acid 63-123, and 208-304) is detected in heterozygous condition. The product size of this variant is 532 bp while wild type pol beta is 1 kb. Our study of association between the variant and the endometrioid type shows that it is a statistically significant factor for ovarian cancer [OR=31.9 (4.12-246.25) with p<0.001]. The association between variant and stage IV patients further indicated risk (χ2 value of 29.7, and OR value 6.77 with 95% CI values 3.3-13.86). The correlation study also confirms the association data (Pearson correlation values for variant/stage IV and variant/endometrioid of 0.44 and 0.39).

CONCLUSION

Individuals from this part of India with this type of variant may be at risk of stage IV, endometrioid type ovarian carcinoma.

Application of Crossover Analysis-logistic Regression in the Assessment of Gene- environmental Interactions for Colorectal Cancer

BACKGROUND

Analysis of gene-gene and gene-environment interactions for complex multifactorial human disease faces challenges regarding statistical methodology. One major difficulty is partly due to the limitations of parametric-statistical methods for detection of gene effects that are dependent solely or partially on interactions with other genes or environmental exposures. Based on our previous case-control study in Chongqing of China, we have found increased risk of colorectal cancer exists in individuals carrying a novel homozygous TT at locus rs1329149 and known homozygous AA at locus rs671.

METHODS

In this study, we proposed statistical method- crossover analysis in combination with logistic regression model, to further analyze our data and focus on assessing gene-environmental interactions for colorectal cancer.

RESULTS

The results of the crossover analysis showed that there are possible multiplicative interactions between loci rs671 and rs1329149 with alcohol consumption. Multi- factorial logistic regression analysis also validated that loci rs671 and rs1329149 both exhibited a multiplicative interaction with alcohol consumption. Moreover, we also found additive interactions between any pair of two factors (among the four risk factors: gene loci rs671, rs1329149, age and alcohol consumption) through the crossover analysis, which was not evident on logistic regression.

CONCLUSIONS

In conclusion, the method based on crossover analysis-logistic regression is successful in assessing additive and multiplicative gene-environment interactions, and in revealing synergistic effects of gene loci rs671 and rs1329149 with alcohol consumption in the pathogenesis and development of colorectal cancer.

Association between polymorphisms in UDP-glucuronosyltransferase 1A6 and 1A7 and colorectal cancer risk

Genetic polymorphisms of uridine diphosphate-glucuronosyltransferases 1A6 (UGT1A6) and 1A7 (UGT1A7) may lead to genetic instability and colorectal cancer carcinogenesis. Our objective was to measure the interaction between polymorphisms of these repair genes and tobacco smoking in colorectal cancer (CRC). A total of 68 individuals with CRC and 112 non-cancer controls were divided into non-smoker and smoker groups according to pack-years of smoking. Genetic polymorphisms of UGT1A6 and UGT1A7 were examined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). We found a weak association of UGT1A6 polymorphisms with CRC risk (crude odds ratio [OR], 1.65; 95% confidence interval [95%CI], 0.9-3.1, P=0.107; adjusted OR 1.95, 95%CI 1.0-3.8, P=0.051). The ORs for the UGT1A7 polymorphisms were statistically significant (crude OR: 26.40, 95%CI: 3.5-198.4, P=0.001; adjusted OR: 21.52, 95%CI: 2.8-164.1, P=0.003). The joint effect of tobacco exposure and UGT1A6 polymorphisms was significantly associated with colorectal cancer risk in non-smokers (crude OR, 2.11; 95%CI, 0.9-5.0, P=0.092; adjusted OR 2.63, 95%CI 1.0-6.7, P=0.042). In conclusion, our findings suggest that UGT1A6 and UGT1A7 gene polymorphisms are associated with CRC risk in the Japanese population. In particular, UGT1A6 polymorphisms may strongly increase CRC risk through the formation of carcinogens not associated with smoking.

X-ray repair cross-complementing group 1 Arg399Gln gene polymorphism and susceptibility to colorectal cancer:a meta-analysis

X-ray repair cross-complementing group 1 (XRCC1), a DNA repair enzyme, plays a crucial role in the base excision repair by generating a single nucleotide repair patch. It has been demonstrated that the XRCC1 Arg399Gln gene polymorphism was associated with variations in XRCC1 enzyme activity. The aim of this study was to quantitatively summarize the association between the XRCC1 Arg399Gln polymorphism and susceptibility to colorectal cancer (CRC). A comprehensive search of the PubMed, Embase, and China National Knowledge Infrastructure databases was conducted for studies on the association between the XRCC1 Arg399Gln polymorphism and CRC risk. Summary odds ratio (OR) with its corresponding 95 % confidence interval (95 %CI) was estimated, in a fixed-effects model or a random-effects model when appropriate, to assess the association. Totally, 26 case-control studies with 6,979 cases and 11,470 controls were included into this meta-analysis. The pooled results of total studies showed that the XRCC1 Arg399Gln polymorphism was significantly associated with increased risk of CRC in all genetic contrast models (OR(A vs. G) = 1.13, 95 %CI 1.03-1.23, P (OR) = 0.008; OR(Gln/Gln vs. Arg/Arg) = 1.24, 95 %CI 1.04-1.46, P (OR) = 0.015; OR(Gln/Gln vs. Arg/Gln + Arg/Arg) = 1.19, 95 %CI 1.03-1.38, P (OR) = 0.021; OR(Gln/Gln + Arg/Gln vs. Arg/Arg) = 1.14, 95 %CI 1.02-1.28, P (OR) = 0.022), except for the additive contrast model (OR(Arg/Gln vs. Arg/Arg) = 1.11, 95 %CI 0.99-1.25, P (OR) = 0.064). The statistically significant association between the XRCC1 Arg399Gln polymorphism and CRC risk was observed among studies with high quality and in Asians, but not in Caucasians. Sensitivity analyses by sequential omission of any individual studies further identified the significant association. Publication bias was inexistent in this meta-analysis. The meta-analysis suggests that the XRCC1 Arg399Gln polymorphism is associated with increased risk of CRC.

Comprehensive study on associations between nine SNPs and glioma risk

AIM

Glioma cancer is the most common type of adult brain tumor. Recent genome-wide association studies (GWAS) have identified various new susceptibility regions and here we conducted an extensive analysis of associations between 12 single nucleotide polymorphisms (SNPs) and glioma risk.

METHODS

A total of 197 glioma cases and 197 health controls were selected, and 9 SNPs in 8 genes were analyzed using the Sequenom MassARRAY platform and Sequenom Assay Design 3.1 software.

RESULTS

We found the MAF among selected controls were consistent with the MAF from the NCBI SNP database. Among 9 SNPs in 8 genes, we identified four significant SNP genotypes associated with the risk of glioma, C/C genotype at rs730437 and T/T genotype at rs1468727 in ERGF were protective against glioma, whereas the T/T genotype at rs1799782 in XRCC1 and C/C genotype at rs861539 in XRCC3 conferred elevated risk.

CONCLUSION

Our comprehensive analysis of nine SNPs in eight genes suggests that the rs730437 and rs1468727 in ERGF, rs1799782 in XRCC1 gene, and rs861539 in XRCC3 gene are associated with glioma risk. These findings indicate that genetic variants of various genes play a complex role in the development of glioma.