Polymorphisms of XRCC1 gene, alcohol consumption and colorectal cancer

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 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.

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.

XRCC1 gene polymorphisms and risk of neuroblastoma in Chinese children

Neuroblastoma is a common pediatric extra-cranial tumor of the sympathetic nervous system. XRCC1 is a scaffold protein that participates in DNA single-strand break repair by complexing with other proteins. XRCC1 gene polymorphisms are being increasingly explored in cancer epidemiology studies. However, the contribution of XRCC1 gene polymorphisms to neuroblastoma risk remains unclarified. Herein, we conducted a case-control study with 393 neuroblastoma patients and 812 controls to explore the association of XRCC1 gene polymorphisms (rs1799782 G>A, rs25487 C>T, rs25489 C>T and rs915927 T>C) with neuroblastoma risk. Results showed that none of the studied polymorphisms was associated with neuroblastoma risk. However, individuals with 2 risk genotypes seemed to be at significantly higher risk for neuroblastoma compared with those without risk genotype (adjusted odds ratio=1.69; 95% confidence interval=1.06-2.69). Stratified analysis revealed that the XRCC1 rs25489 CT/TT was strongly associated with reduced risk of neuroblastoma in the children ≤ 18 months of age and subgroup with clinical stage I+II+4s diseases, compared with CC genotypes. We also identified an increased neuroblastoma risk for carrier of 2-3 risk genotypes among children ≤ 18 months of age and subgroup with clinical stage I+II+4s. More evidence of the association between XRCC1 gene polymorphisms and neuroblastoma risk is needed.

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.

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.

Association of DNA repair and xenobiotic pathway gene polymorphisms with genetic susceptibility to gastric cancer patients in West Bengal, India

Gastric cancer is one of the most common malignancies in India. DNA repair gene or xenobiotic pathway gene polymorphisms have recently been shown to affect individual susceptibility to gastric cancer. Here, the possible interaction between common polymorphisms in X-ray repair cross complementing group I (XRCC1) gene and glutathione S-transferase (GST) genes (GSTM1, GSTT1 and GSTP1), smoking and alcohol consumption and overall survival in gastric cancer patients were evaluated. In this population-based case control study, 70 gastric cancer patients and 82 healthy controls were enrolled. The epidemiological data were collected by a standard questionnaire, and blood samples were collected from each individual. XRCC1 Arg194Trp, Arg280His and Arg399Gln polymorphisms were determined by polymerase chain reaction and direct DNA sequencing. GSTM1 and GSTT1 null polymorphisms and GSTP1 Ile105Val polymorphism were identified by multiplex polymerase chain reaction and restriction fragment length polymorphism (RFLP), respectively. The risk of gastric cancer was significantly elevated in individuals with XRCC1 Arg/Gln +Gln/Gln (p = 0.031; odds ratio = 2.32; 95 % confidence interval (CI) 1.07-5.06) and GSTP1 Val/Val genotype (p = 0.009; odds ratio = 8.64; 95 % CI 1.84-40.55). An elevated risk for GC was observed in smokers and alcohol consumers carrying GSTP1 Ile/Val +Val/Val genotype (p = 0.041; odds ratio = 3.71; 95 % CI 0.98-14.12; p = 0.002; odds ratio = 12.31; 95 % CI 1.71-88.59). These findings suggest that XRCC1 rs25487 and GSTP1 rs1695 can be considered as a risk factor associated with gastric cancer and might be used as a molecular marker for evaluating the susceptibility of the disease.

Genetic polymorphisms in XRCC1 genes and colorectal cancer susceptibility

Background

The objective of this study is to investigate the association among the polymorphisms of XRCC1 gene, smoking, drinking, family history of tumors, and the risk of colorectal cancer (CRC) in the population of Han nationality in Jiangsu Province, China.

Methods

A case–control study of 320 patients with CRC and 350 cancer-free subjects as a control group was conducted. The three polymorphic sites, codons 194, 280, and 399, of XRCC1 genes were analyzed by PCR-RFLP.

Results

We find that heavy smoking (>500 cigarettes per year) significantly increased the susceptibility of CRC (OR = 1.89, 95 % confidence interval (CI) 1.27–2.84) after stratification by total smoking amount. There was also significant difference between cases and controls when family history of tumors (OR = 2.96, 95 % CI 1.76–4.99) was considered. Comparing with individuals carrying XRCC1 399Arg/Arg genotype, the subjects with 399Arg/Gln (OR = 1.46, 95 % CI 1.06–2.01) or 399Gln/Gln genotype (OR = 1.93, 95 % CI 1.05–3.54) had a significantly increased risk for CRC. Taking smoking and drinking habits into consideration, we found that subjects with heavy smoking history and XRCC1 194Arg allele had the significantly increased risk for CRC (OR = 2.91, 95 % CI 1.35–6.24). Individuals, who carry 399Gln allele and have a heavy smoking (OR = 2.72, 95 % CI 1.52–4.89) or drinking habit (OR = 1.98, 95 % CI 1.06–3.67), also have higher risk. In smoking population, 194Arg (P = 0.491) and 399Gln (P = 0.912) had not significantly increased risk for CRC, so did 399Gln (P = 0.812) in smoking population.

Conclusions

Individuals carrying XRCC1 399Gln allele with a smoking or drinking habit were in increased risk, and heavy-smoking subjects with 194Arg allele also have higher risk for CRC in the Han nationality population of Jiangsu Province, which also showed a positive correlation with exposure dose of tobacco. But XRCC1 399Gln allele or 194Arg allele were not independent risk factors for CRC in smoking or drinking population.

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.

The XRCC1 Arg399Gln gene polymorphism and risk of colorectal cancer: a study in Kashmir

BACKGROUND

The DNA repair gene XRCC1 Arg399Gln gene polymorphism has been found to be implicated in the development of various cancers, including colorectal cancer (CRC), in different populations. We aimed to determine any association of this polymorphism with the risk of CRC in Kashmir.

MATERIALS AND METHODS

A total of 120 confirmed cases of CRC and 146 healthy cancer free controls from the Kashmiri population were included in this study. Genotyping was carried out by the polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Genotype frequencies of XRCC1 Arg399Gln observed in controls were 34.2%, 42.5% and 23.3% for GG (Arg/Arg), GA (Arg/Gln), AA( Gln/Gln), respectively, and 28.3%, 66.7% and 5% in cases, with an odds ratio (OR)=5.7 and 95% confidence interval (CI) =2.3-14.1 (p=0.0001). No significant association of Arg399Gln SNP with any clinicopathological parameters of CRC was found.

CONCLUSIONS

We found the protective role of 399Gln allele against risk to the development of CRC. The XRCC1 heterozygote status appears to be a strong risk factor for CRC development in the Kashmiri population.

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

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

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

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

Background

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

Methods

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

Results

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

Conclusions

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

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

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

Association between XRCC1 and XRCC3 polymorphisms and colorectal cancer risk: a meta-analysis of 23 case-control studies

Several potential functional polymorphisms in the DNA repair gene X-ray repair cross-complementing group 1 (XRCC1) Arg399Gln (rs25487), Arg194Trp (rs1799782), Arg280His (rs25489) and X-ray repair cross-complementing group 3 (XRCC3) T241M (rs861539) have been implicated in colorectal cancer (CRC) risk, but the results are conflicting. Here, we performed a meta-analysis of 23 published case control datasets and assessed genetic heterogeneity between those datasets. All the case-control studies published from January 2000 to June 2012 on the association between those polymorphisms and CRC risk were identified by searching the electronic literature Medline. Statistical analysis was performed with the software programs Review Manager (version 4.2). For overall CRC, no significant association was observed, the pooled odds ratios for XRCC1 Arg399Gln, Arg194Trp, Arg280His, and XRCC3 T241M were 1.02 (95 % CI: 0.93, 1.12), 1.03 (95 % CI: 0.94, 1.14), 0.98 (95 % CI: 0.85, 1.13) and 1.03 (95 % CI: 0.85, 1.26), respectively. Furthermore, no significant association was observed in subgroup analyses based on ethnicity. The results suggested that these four SNPs evaluated are not associated with risk of CRC.

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.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Involvement of the XRCC1 Arg399Gln gene polymorphism in the development of cervical carcinoma

BACKGROUND

Although infection with the human papillomavirus (HPV) is crucial to the development of cervical cancer, it is not considered a sufficient isolated factor to cause this malignancy. The association of the XRCC1 Arg399Gln (rs25487) polymorphism with cervical cancer has been demonstrated in some populations.

METHODS

The XRCC1 Arg399Gln genetic variants were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in patients with advanced cervical cancer (n=189) and controls (n=308).

RESULTS

We observed that patients with advanced cervical cancer having the Gln/Gln or Gln/Arg vs Arg/Arg genotype displayed a 1.726-fold increased risk of cervical cancer (95% confidence interval [CI]=1.158-2.572, p=0.007). The odds ratio (OR) for Gln/Gln vs Gln/Arg or Arg/Arg was 1.742 (95% CI=1.073-2.827; p=0.0236). We also found a significantly higher frequency of the XRCC1 399Gln allele in patients with cancer than in controls, with OR=1.489 (95% CI=1.148-1.930, p=0.0026). The p value of the chi-square test for the trend observed for the XRCC1 Arg399Gln polymorphism was also statistically significant (ptrend=0.002). The statistical power of this study amounted to 78% for the Gln/Gln or Gln/Arg genotypes and 61% for the Gln/Gln genotype.

CONCLUSION

Although the statistical power of our study did not reach 80%, we found a statistically significant association between the XRCC1 399Gln variant and the incidence of cervical cancer.

Genetic polymorphisms of XRCC1, alcohol consumption, and the risk of colorectal cancer in Japan

Background

X-ray cross-complementing group 1 (XRCC1) polymorphisms affect DNA repair capacity and may therefore be of importance in colorectal carcinogenesis. Alcohol consumption, an important risk factor for colorectal cancer, may induce carcinogenesis through DNA damage caused by the toxic effects of alcohol or its metabolites. Therefore, we examined the associations of XRCC1 Arg399Gln, Arg280His, and Arg194Trp polymorphisms with colorectal cancer and the impact of the association between alcohol consumption and colorectal cancer risk.

Methods

This case-control study in Fukuoka, Japan including 685 cases and 778 controls. The cases were incident patients with histologically confirmed colorectal adenocarcinoma. The controls were randomly selected community subjects.

Results

The XRCC1 399Gln/Gln genotype was significantly associated with colorectal cancer risk (adjusted odds ratio [OR] 1.57, 95% CI 1.01–2.42; relative to 399Arg/Arg genotype). The association was strongest in individuals with high alcohol consumption. The Arg280His polymorphism modified the association between alcohol consumption and colorectal cancer risk (interaction P = 0.049). The OR of colorectal cancer in individuals with the 280His allele was 0.45 (95% CI 0.26–0.78) as compared with the 280Arg/Arg genotype limited to the 399Gln allele (interaction P = 0.001). The adjusted ORs for 399Gln/Gln-280Arg/Arg-194Arg/Arg and 399Arg/Gln-280Arg/Arg-194Arg/Trp were 1.71 (95% CI 1.02–2.87) and 1.57 (95% CI 1.05–2.33), respectively, with 399Arg/Arg-280Arg/Arg-194Arg/Arg as reference (interaction P = 0.418).

Conclusions

The findings are additional evidence that individuals with the XRCC1 399Gln/Gln genotype have an increased risk of colorectal cancer, and that XRCC1 polymorphisms have an important role in colorectal cancer risk associated with alcohol consumption or gene-gene interaction.

XRCC1 Arg399Gln gene polymorphism and the risk of systemic lupus erythematosus in the Polish population

It has been shown that DNA repair is reduced in patients with systemic lupus erythematosus (SLE) and that the X-ray repair cross-complementing (XRCC1) Arg399Gln (rs25487) polymorphism may contribute to DNA repair. We evaluated the frequency of the XRCC1 Arg399Gln substitution in patients with SLE (n=265) and controls (n=360) in a sample of the Polish population. The odds ratio (OR) for SLE patients with the Gln/Gln versus Gln/Arg or Arg/Arg genotypes was 1.553 (95% confidence interval [CI]=0.9573-2.520; p=0.0729). OR for the Gln/Gln or Gln/Arg versus Arg/Arg genotype was 1.551 (95% CI=1.122-2.144, p=0.0077). The OR for the 399 Gln allele in patients with SLE was 1.406 (95% CI=1.111-1.779, p=0.0045). There was also a statistically significant p-value of the χ(2) test for the trend observed in the XRCC1 Arg399Gln polymorphism (ptrend=0.0048). We also found a significant contribution of the Gln/Gln or Arg/Gln versus Arg/Arg genotype to the presence of either the malar rash or photosensitivity manifestations of SLE OR=2.241 (1.328-3.781, p=0.0023, pcorr=0.0414). Moreover, the meta-analysis of Taiwanese Han Chinese, Brazilian, and Polish populations showed that the Gln/Gln or Gln/Arg genotype and Gln allele were associated with SLE incidence. OR for the Gln/Gln or Gln/Arg versus Arg/Arg genotype was 1.440 (95% CI=1.15-1.80, p=0.0019) and OR for the Gln allele was 1.27 (95% CI=1.08-1.51, p=0.0051). Our studies may confirm that the XRCC1 Arg399Gln polymorphism may increase the risk of incidence of SLE and the occurrence of some SLE manifestations.

Association between single-nucleotide polymorphisms of selected genes involved in the response to DNA damage and risk of colon, head and neck, and breast cancers in a Polish population

Single-nucleotide polymorphisms in genes involved in DNA-damage-induced responses are reported frequently to be a risk factor in various cancer types. Here we analysed polymorphisms in 5 genes involved in DNA repair (XPD Asp312Asn and Lys751Gln, XRCC1 Arg399Gln, APE1 Asp148Glu, NBS1 Glu185Gln, and XPA G-4A) and in a gene involved in regulation of the cell-cycle (CCND1 A870G). We compared their frequencies in groups of colon, head and neck, and breast cancer patients, and 2 healthy control groups: (1) matched healthy Polish individuals and (2) a NCBI database control group. Highly significant differences in the distribution of genotypes of the APE1, XRCC1 and CCND1 genes were found between colon cancer patients and healthy individuals. The 148Asp APE1 allele and the 399Gln XRCC1 allele apparently increased the risk of colon cancer (OR = 1.9-2.3 and OR = 1.5-2.1, respectively). Additionally, frequencies of XPD genotypes differed between healthy controls and patients with colon or head and neck cancer. Importantly, no differences in the distribution of these polymorphisms were found between healthy controls and breast cancer patients. The data clearly indicate that the risk of colon cancer is associated with single-nucleotide polymorphism in genes involved in base-excision repair and DNA-damage-induced responses.

Polymorphisms in DNA repair genes XRCC1, XRCC3 and XPD, and colorectal cancer risk: a case-control study in an Indian population

PURPOSE

Genetic polymorphisms in DNA repair genes may influence variations in individual DNA repair capacity, which could be associated with the development of cancer. We detected the distributions of three single-nucleotide polymorphisms (XRCC1 Arg399Gln, XRCC3 Thr241Met and XPD Lys751Gln) in DNA repair genes, and assessed the associations of these genetic polymorphisms with colon and rectal cancer susceptibility as well as evaluated the interactions of gene-gene and gene-environment in a case-control study of an Indian population.

METHODS

This case-control study was conducted with 302 cases (including 59 colon and 243 rectal cancer patients) and 291 cancer-free healthy controls. Genotypes were determined by PCR-RLFP assays. The effects [odds ratios (ORs) and 95% confidence intervals (95% CIs)] of genetic polymorphisms on colorectal cancer were estimated using unconditional logistic regression.

RESULTS

The XRCC1 399Gln allele was found to be associated with a significantly increased rectal cancer risk among men (OR = 1.65, 95% CI 1.04-2.64). Whereas the XRCC3 241Met allele showed a protective tendency against rectal cancer (OR = 0.68, 95% CI 0.46-1.02) for both men and women. Furthermore, a combination of the XRCC1 399Gln allele with XRCC3 Thr/Thr genotype and the XPD 751Gln allele demonstrated the highest rectal cancer risk (OR = 3.52, 95% CI 1.43-9.44).

CONCLUSIONS

The combined effects of putative risk alleles/genotypes for different DNA repair pathways may strengthen the susceptibility to rectal cancer.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

A meta-analysis on XRCC1 and XRCC3 polymorphisms and colorectal cancer risk

PURPOSE

Studies on polymorphism of X-ray repair cross-complementing group 1 (XRCC1), group 3 (XRCC3), and colorectal cancer risk are inconclusive. The purpose of this study is to evaluate the role of XRCC1 R399Q, R194W, and XRCC3 T241M genotypes in colorectal cancer susceptibility.

METHODS

We performed a meta-analysis on all available studies that provided 3,514/4,686 cases/controls for R399Q, 2,767/3,907 cases/controls for R194W and 3,183/3,926 cases/controls for T241M.

RESULTS

Overall, no apparent effects of 194 W allele compared to 194R on colorectal cancer risk were found in all subjects and subgroups (Asians and Caucasians). Insignificant effects were also found under other genetic contrasts (homologous contrast, dominant model, and recessive model). The same pattern of results was produced in T241M polymorphism. The 399Q allele compared to 399R showed no significant association with colorectal cancer risk in all subjects and subgroups. However, protective effects of 399QQ genotype were observed under recessive model (QQ/QR + RR) [P = 0.02, OR = 0.84, 95% CI (0.72, 0.97)] and homozygote contrast (QQ/RR) [P = 0.01, OR = 0.81; 95% CI (0.69, 0.95)] in all subjects.

CONCLUSION

Results suggested that 399Q allele might act as a recessive allele in its association with colorectal cancer.

Polymorphisms in the DNA repair gene XRCC1 and associations with systemic lupus erythematosus risk in the Taiwanese Han Chinese population

XRCC1 plays a central role in mammalian DNA repair processes. Two polymorphisms of XRCC1, rs1799782 (Arg > Trp at codon 194) and rs25487 (Arg > Gln at codon 399), are common in the Han Chinese population. Our objective was to analyze the relationship between these two functional single-nucleotide polymorphisms (SNPs) and systemic lupus erythematosus (SLE) in the Taiwanese Han Chinese population. Genotyping was performed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) on 172 SLE patients and 160 normal controls. Our data indicate that the frequency of A/G at codon 399 differed between patients and controls (p = 0.01; odds ratio: 1.80; 95% confidence interval: 1.17-2.75), but the allelic frequency analysis did not reveal significant differences. For the SNP at codon 194, there were no differences in either allelic or genotype frequencies between SLE patients and normal subjects. Clinical association studies of SLE symptoms revealed the involvement of the A/G polymorphism at codon 399 in SLE pathogenesis. Our results indicate that a functional SNP at codon 399 of XRCC1 is associated with the development of SLE.

Polymorphisms of DNA repair genes: ADPRT, XRCC1, and XPD and cancer risk in genetic epidemiology

Many studies have suggested that adenosine diphosphate ribosyl transferase (ADPRT), X-ray repair cross-complementing 1 (XRCC1), and xeroderma pigmentosum complementary group D (XPD) are three major DNA base excision repair (BER) genes and that they act interactively in stimulating and executing BER processes. Polymorphisms of these genes may influence the rate of gene transcription, the stability of the messenger RNA, or the quantity and activity of the resulting protein. Thus, the susceptibility or severity of several disorders is influenced by possession of specific alleles of polymorphic genes. So, it is plausible that variations and mutations in these genes affect DNA repair capacity in normal populations, and thus facilitate cancer development in normal or exposed individuals. To promote translation of scientific findings for potential clinical application of DNA repair function, we have searched publications relevant to molecular epidemiology studies of associations between single-nucleotide polymorphisms (SNPs) in the genes, and several frequent human cancer. We have focused on five particular polymorphisms as our starting point: the T-->C polymorphism (Val762Ala) in exon 17 of ADPRT, the novel transition at the promoter region (-77T-->C) of XRCC1, two common nonsynonymous polymorphisms (Arg194Trp and Arg399Gln), and the C-->A silent polymorphism (Arg156Arg) in exon 6 of XPD. We review here the case-control studies examining whether these polymorphisms are correlated with reduced DNA repair efficiency, their influence on the development of different solid tumors, and their possible interactions with other genetic factors and environmental exposures.

Effects of the XRCC1 gene-environment interactions on DNA damage in healthy Japanese workers

X-ray repair crosscomplementing group 1 (XRCC1) has a central role in base excision repair (BER) and single-strand break repair (SSBR). XRCC1 gene polymorphisms (codons 194, 280, and 399) have been identified, and in some cases have been reported to contribute to variations in DNA repair capacity and susceptibility to cancer. To further characterize the effects of XRCC1 gene polymorphisms and their possible interactions with environmental factors on individual levels of DNA damage, we investigated the XRCC1 genotypes of 222 healthy Japanese workers and analyzed data with respect to smoking, drinking habits, age, and health practice index (HPI). Our results showed that poor HPI would associate with a higher level of tail moment (TM). Individuals with one or two XRCC1(R280H) variant alleles exhibited significantly higher TM values, and these differences were enhanced by alcohol consumption and aging, whereas smoking and poor HPI may cover up the differences. On the other hand, using a stratified analysis, we found that the XRCC1(R194W) variant was associated with a higher TM value in the 40-50 year-old age group, and the XRCC1(R399Q) variant was associated with a lower TM value in the < or =20 pack-years group or in the 40-50 year-old age group. These data suggest that XRCC1 polymorphisms could influence individual DNA repair capacity by interacting with lifestyle factors, and specifically, the data indicated that the XRCC1(R280H) allele may be more important than codon 194 or 399 alleles.

Association of single nucleotide polymorphisms in SOD2, XRCC1 and XRCC3 with susceptibility for the development of adverse effects resulting from radiotherapy for prostate cancer

The objective of this study was to determine whether an association exists between certain single nucleotide polymorphisms (SNPs), which have previously been linked with adverse normal tissue effects resulting from radiotherapy, and the development of radiation injury resulting from radiotherapy for prostate cancer. A total of 135 consecutive patients with clinically localized prostate cancer and a minimum of 1 year of follow-up who had been treated with radiation therapy, either brachytherapy alone or in combination with external-beam radiotherapy, with or without hormone therapy, were genotyped for SNPs in SOD2, XRCC1 and XRCC3. Three common late tissue toxicities were investigated: late rectal bleeding, urinary morbidity, and erectile dysfunction. Patients with the XRCC1 rs25489 G/A (Arg280His) genotype were more likely to develop erectile dysfunction after irradiation than patients who had the G/G genotype (67% compared to 24%; P=0.048). In addition, patients who had the SOD2 rs4880 T/C (Val16Ala) genotype exhibited a significant increase in grade 2 late rectal bleeding compared to patients who had either the C/C or T/T genotype for this SNP (8% compared to 0%; P=0.02). Finally, patients with the combination of the SOD2 rs4880 C/T genotype and XRCC3 rs861539 T/C (Thr241Met) genotype experienced a significant increase in grade 2 late rectal bleeding compared to patients without this particular genotypic arrangement (14% compared to 1%; P=0.002). These results suggest that SNPs in the SOD2, XRCC1 and XRCC3 genes are associated with the development of late radiation injury in patients treated with radiation therapy for prostate adenocarcinoma.

DNA repair single-nucleotide polymorphisms in colorectal cancer and their role as modifiers of the effect of cigarette smoking and alcohol in the Singapore Chinese Health Study

Recently, we reported that among Singapore Chinese, cigarette smoking and alcohol drinking were independent risk factors for colorectal cancer. Both tobacco smoking and alcohol use are plausible colorectal cancer risk factors, partly due to their ability to induce mutations in the colorectal lumen. In the present study, we investigated the role in colorectal cancer of single-nucleotide polymorphisms in five DNA repair genes: XRCC1 (Arg(194)Trp and Arg(399)Gln), PARP (Val(762)Ala, Lys(940)Arg), XPD (Asp(312)Asn, Lys(751)Gln), OGG1 (Ser(326)Cys), and MGMT (Leu(84)Phe). We conducted this study within the Singapore Chinese Health Study, a population-based cohort of 63,257 middle-aged and older Singapore Chinese men and women enrolled between 1993 and 1998. Our study included 1,176 controls and 310 cases (180 colon and 130 rectum cancer). We observed a positive association between the PARP codon 940 Lys/Arg and Arg/Arg genotypes and colorectal cancer risk [odds ratio (OR), 1.8; 95% confidence interval (95% CI), 1.1-3.1], and an inverse association between the MGMT codon 84 Leu/Phe or Phe/Phe genotypes and colon cancer risk (OR, 0.6; 95% CI, 0.3-0.9), but not rectal cancer (test of heterogeneity by tumor site, P=0.027). We observed evidence that XRCC1 may modify the effects of smoking (interaction P=0.012). The effect of smoking among carriers of the Arg(194)-Gln(399) haplotype was OR=0.7 (95% CI, 0.4-1.1), whereas, among carriers of the Trp(194)-Arg(399) haplotype, it was OR=1.6 (95% CI, 1.1-2.5). We also observed a nonstatistically significant modification of XRCC1 on the effects of alcohol (P=0.245). Whereas alcohol had no effect among carriers of the codon 194 Arg/Arg (OR, 1.0; 95% CI, 0.6-1.7) or Arg/Trp genotypes (OR, 1.1; 95% CI, 0.6-1.9), there was a positive association among carriers of the Trp/Trp genotype (OR, 2.8; 95% CI, 1.0-8.1). Our results support a role for reactive oxygen species as relevant genotoxins that may account for the effects of both smoking and alcohol on colorectal cancer risk.

Polynucleotide kinase 3' phosphatase variant, dietary variables and risk of adenoma recurrence in the Polyp Prevention Trial

Polymorphisms in a number of genes encoding for DNA repair enzymes have been associated with altering the function of these enzymes and increasing risk of a number of cancers, including colon cancer. We have investigated the association between a common variant in polynucleotide kinase 3' phosphatase (PNKP), a putative DNA repair enzyme, and risk of adenoma recurrence in the Polyp Prevention Trial participants. We also investigated possible interaction or effect modification between carriage of the variant allele, dietary components and risk of adenoma recurrence. Unconditional logistic regression models were used to calculate the odds ratios and 95% confidence intervals for an association between the G/T polymorphism, PNKP T5644G and risk of adenoma recurrence. We observed no association between carriage of the variant allele and risk of adenoma recurrence. Furthermore, we found no effect modification between genotype, dietary components and risk of adenoma recurrence. The PNKP T5644G variant does not seem to be involved in adenoma recurrence in the Polyp Prevention Trial.

ERCC2 2251A>C genetic polymorphism was highly correlated with early relapse in high-risk stage II and stage III colorectal cancer patients: a preliminary study

Background

Early relapse in colorectal cancer (CRC) patients is attributed mainly to the higher malignant entity (such as an unfavorable genotype, deeper tumor invasion, lymph node metastasis and advance cancer stage) and poor response to chemotherapy. Several investigations have demonstrated that genetic polymorphisms in drug-targeted genes, metabolizing enzymes, and DNA-repairing enzymes are all strongly correlated with inter-individual differences in the efficacy and toxicity of many treatment regimens. This preliminary study attempts to identify the correlation between genetic polymorphisms and clinicopathological features of CRC, and evaluates the relationship between genetic polymorphisms and chemotherapeutic susceptibility of Taiwanese CRC patients. To our knowledge, this study discusses, for the first time, early cancer relapse and its indication by multiple genes.

Methods

Six gene polymorphisms functional in drug-metabolism – GSTP1 Ile105Val, ABCB1 Ile1145Ile, MTHFR Ala222Val, TYMS double (2R) or triple (3R) tandem repeat – and DNA-repair genes – ERCC2 Lys751Gln and XRCC1 Arg399Gln – were assessed in 201 CRC patients using a polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) technique and DNA sequencing. Patients were diagnosed as either high-risk stage II (T2 and 3 N0 M0) or III (any T N1 and 2 M0) and were administered adjuvant chemotherapy regimens that included 5-fluorouracil (5FU) and leucovorin (LV). The correlations between genetic polymorphisms and patient clinicopathological features and relapses were investigated.

Results

In this study, the distributions of GSTP1 (P = 0.003), ABCB1 (P = 0.001), TYMS (P < 0.0001), ERCC2 (P < 0.0001) and XRCC1 (P = 0.006) genotypes in the Asian population, with the exception of MTHFR (P = 0.081), differed significantly from their distributions in a Caucasian population. However, the unfavorable genotype ERCC2 2251A>C (P = 0.006), tumor invasion depth (P = 0.025), lymph node metastasis (P = 0.011) and cancer stage (P = 0.008) were significantly correlated with early relapse. Patients carrying the ERCC2 2251AC or2251CC genotypes had a significantly increased risk of early relapse (OR = 3.294, 95% CI, 1.272–8.532).

Conclusion

We suggest that ERCC2 2251A>C alleles may be genetic predictors of early CRC relapse.

Biomarkers for diet and cancer prevention research: potentials and challenges

As cancer incidence is projected to increase for decades there is a need for effective preventive strategies. Fortunately, evidence continues to mount that altering dietary habits is an effective and cost-efficient approach for reducing cancer risk and for modifying the biological behavior of tumors. Predictive, validated and sensitive biomarkers, including those that reliably evaluate "intake" or exposure to a specific food or bioactive component, that assess one or more specific biological "effects" that are linked to cancer, and that effectively predict individual "susceptibility" as a function of nutrient-nutrient interactions and genetics, are fundamental to evaluating who will benefit most from dietary interventions. These biomarkers must be readily accessible, easily and reliably assayed, and predictive of a key process(es) involved in cancer. The response to a food is determined not only by the effective concentration of the bioactive food component(s) reaching the target tissue, but also by the amount of the target requiring modification. Thus, this threshold response to foods and their components will vary from individual to individual. The key to understanding a personalized response is a greater knowledge of nutrigenomics, proteomics and metabolomics.

Ancillary risk information and pharmacogenetic tests: social and policy implications

Some pharmacogenetic tests may provide ancillary disease risk information. To evaluate evidence and assess the social and policy implications of ancillary disease risk information associated with candidate pharmacogenetic variants, We conducted a literature search and abstract review of disease susceptibility studies for each of 42 gene variants potentially associated with drug response. Twenty-two variants (53%) had suggested association with disease risk in at least two studies, and sixteen (38%) were for diseases other than the pharmacogenetic indication. Seven variants (16%) were associated with risk for at least two different diseases. Pharmacogenetic tests have the potential to provide ancillary disease risk information, and this potential should be considered as pharmacogenetic tests are brought into clinical use. Implications will vary with each test but tests should be evaluated individually within a framework that outlines the potential implications of ancillary information.

The nonsynonymous single nucleotide polymorphisms of DNA repair geneXRCC1and susceptibility to the development of cervical carcinoma and high-risk human papillomavirus infection

To evaluate contribution of single nucleotide polymorphisms (SNPs) of X-ray repair cross-complementing group 1 (XRCC1) gene to the risk of cervical carcinoma, we conducted a case-control study of 1012 patients including 539 carcinoma and 473 cervical intraepithelial neoplasia (CIN) and 800 normal women controls and genotyped three XRCC1 SNPs (Arg194Trp, Arg280His, and Arg399Gln). We found that compared with the Arg399Gln (GG), subjects carrying the homozygous Gln399Gln (AA) genotype had a significantly 2.32-fold increased risk of cervical carcinoma (95% CI 1.47-3.65), heterozygous Arg399Gln (GA) genotype were also associated with a significantly increased risk of cervical carcinoma, with the adjusted odds ratio (OR) being 1.58 (95% CI 1.24-2.00). Similarly, compared with Arg194Arg (CC) wild-type genotype, elevated risks were associated with the Trp194Trp (TT) for carcinoma (ORs and 95% CIs being 2.09 [1.45-3.02]) but not for heterozygote Arg194Trp (CT). In addition, three common haplotypes were found to be associated with an increased risk of cervical carcinoma. Using 194Arg-280Arg-399Arg as the reference, the OR and 95% confidence interval for 194Arg-280Arg-399Gln, 194Arg-280His-399Arg, 194Trp-280Arg-399Arg were 2.30 (1.86-2.85), 1.85 (1.41-2.41), 1.98 (1.62-2.40), respectively. The significantly increased risk associated with the haplotypes was also observed in squamous cell carcinoma (SCC) for all three common haplotypes using 194Arg-280Arg-399Arg as the reference. Neither difference was found for adenocarcinoma and CIN. All three SNPs and haplotypes did not confer more risk of high-risk human papillomavirus infection in carcinoma, CIN, and normal subgroup. Our findings suggest that XRCC1 polymorphisms including genotypes and haplotypes contribute to susceptibility to the development of cervical SCC, and the increased susceptibility is probably not through increasing susceptibility to human papillomavirus infection.

Genetic variation in base excision repair genes and the prevalence of advanced colorectal adenoma

Base excision repair (BER) corrects DNA damage caused by oxidative stress and low folate intake, which are putative risk factors for colorectal neoplasia. To examine the relationship between genetic variation in BER genes and colorectal adenoma risk, we conducted a case-control study of 767 cases of advanced colorectal adenoma and 773 controls from the baseline screening exam of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cases included participants diagnosed with advanced left-sided adenoma, and controls were subjects without evidence of a left-sided polyp by sigmoidoscopy, frequency-matched to cases on race and gender. Twenty single nucleotide polymorphisms were genotyped in four BER genes (APEX1, PARP1, POLB, and XRCC1), and conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) for the association with colorectal adenoma. Two variants with possible functional significance were associated with risk. The APEX1 51H variant was associated with a borderline significant decreased risk of colorectal adenoma (OR, 0.66; 95% CI, 0.44-1.00), and the XRCC1 399Q variant was inversely associated with risk among Caucasians (OR, 0.80; 95% CI, 0.64-0.99). Homozygotes at two PARP1 loci (A284A and IVS13+118G>A) were also associated with a decreased risk of colorectal adenoma compared with wild-type carriers (OR, 0.70; 95% CI, 0.49-0.98 for both), which was restricted to advanced adenomas displaying histologically aggressive characteristics (OR, 0.51; 95% CI, 0.33-0.78, P = 0.002 for PARP1 A284A). This study suggests that polymorphisms in APEX1, XRCC1, and PARP1 may be associated with advanced colorectal adenoma.

Sporadic colorectal cancer and individual susceptibility: a review of the association studies investigating the role of DNA repair genetic polymorphisms

Mutations in one of the DNA repair genes are one of the most common reasons for cancer, and it may be assumed that the individual genetic background modulating the DNA repair capacity may affect the susceptibility to cancer. Numerous polymorphisms (mainly SNPs) have been identified for DNA repair genes, although their functional outcome and phenotypic effect is often unknown. The aim of the present review is to evaluate the studies investigating a possible influence of DNA repair polymorphisms in the risk of sporadic colorectal cancer and/or adenoma. Overall, no relevant common findings emerge among the studies, except for some statistically significant associations between polymorphisms in the XRCC1 and XPD genes, mainly for colorectal adenoma risk. Other individual associations remain to be confirmed. This inconclusive data may suggest that the modulation of cancer risk depends not only on a single gene/SNP, but also on a joint effect of multiple polymorphisms (or haplotypes) within different genes or pathways, in close interaction with environmental factors. The relevance of many low-penetrance genes in cancer susceptibility is supposed to be very subtle. Several reviewed association studies revealed weaknesses in their design. However, there has been a progressive improvement over the years in aspects such as simultaneous genotyping and combined analyses of different polymorphisms in larger numbers of patients and controls, as well as stratification of results by ethnicity, gender, and tumor localization. This gained experience shows that only carefully designed studies of a sufficient statistical power may resolve the relationships between polymorphisms and colorectal cancer risk.

Estimating the effect of human base excision repair protein variants on the repair of oxidative DNA base damage

Epidemiologic studies have revealed a complex association between human genetic variance and cancer risk. Quantitative biological modeling based on experimental data can play a critical role in interpreting the effect of genetic variation on biochemical pathways relevant to cancer development and progression. Defects in human DNA base excision repair (BER) proteins can reduce cellular tolerance to oxidative DNA base damage caused by endogenous and exogenous sources, such as exposure to toxins and ionizing radiation. If not repaired, DNA base damage leads to cell dysfunction and mutagenesis, consequently leading to cancer, disease, and aging. Population screens have identified numerous single-nucleotide polymorphism variants in many BER proteins and some have been purified and found to exhibit mild kinetic defects. Epidemiologic studies have led to conflicting conclusions on the association between single-nucleotide polymorphism variants in BER proteins and cancer risk. Using experimental data for cellular concentration and the kinetics of normal and variant BER proteins, we apply a previously developed and tested human BER pathway model to (i) estimate the effect of mild variants on BER of abasic sites and 8-oxoguanine, a prominent oxidative DNA base modification, (ii) identify ranges of variation associated with substantial BER capacity loss, and (iii) reveal nonintuitive consequences of multiple simultaneous variants. Our findings support previous work suggesting that mild BER variants have a minimal effect on pathway capacity whereas more severe defects and simultaneous variation in several BER proteins can lead to inefficient repair and potentially deleterious consequences of cellular damage.

Polymorphisms of the XRCC1, XRCC3 and XPD genes and risk of colorectal adenoma and carcinoma, in a Norwegian cohort: a case control study

Background

Genetic polymorphisms in DNA repair genes may influence individual variation in DNA repair capacity, which may be associated with risk of developing cancer. For colorectal cancer the importance of mutations in mismatch repair genes has been extensively documented. Less is known about other DNA repair pathways in colorectal carcinogenesis. In this study we have focused on the XRCC1, XRCC3 and XPD genes, involved in base excision repair, homologous recombinational repair and nucleotide excision repair, respectively.

Methods

We used a case-control study design (157 carcinomas, 983 adenomas and 399 controls) to test the association between five polymorphisms in these DNA repair genes (XRCC1 Arg¹⁹⁴Trp, Arg²⁸⁰His, Arg³⁹⁹Gln, XRCC3 Thr²⁴¹Met and XPD Lys⁷⁵¹Gln), and risk of colorectal adenomas and carcinomas in a Norwegian cohort. Odds ratio (OR) and 95% confidence interval (95% CI) were estimated by binary logistic regression model adjusting for age, gender, cigarette smoking and alcohol consumption.

Results

The XRCC1 280His allele was associated with an increased risk of adenomas (OR 2.30, 95% CI 1.19–4.46). The XRCC1 399Gln allele was associated with a reduction of risk of high-risk adenomas (OR 0.62, 95% CI 0.41–0.96). Carriers of the variant XPD 751Gln allele had an increased risk of low-risk adenomas (OR 1.40, 95% CI 1.03–1.89), while no association was found with risk of carcinomas.

Conclusion

Our results suggest an increased risk for advanced colorectal neoplasia in individuals with the XRCC1 Arg²⁸⁰His polymorphism and a reduced risk associated with the XRCC1 Arg³⁹⁹Gln polymorphism. Interestingly, individuals with the XPD Lys⁷⁵¹Gln polymorphism had an increased risk of low-risk adenomas. This may suggest a role in regression of adenomas.