Oxidative stress, Helicobacter pylori, and OGG1 Ser326Cys, XPC Lys939Gln, and XPD Lys751Gln polymorphisms in a Turkish population with colorectal carcinoma

Polymorphisms of nucleotide excision repair genes associated with colorectal cancer risk: Meta-analysis and trial sequential analysis

Background: Reduced DNA repair capacity in nucleotide excision repair (NER) pathways owing to genetic variant may influence cancer susceptibility. According to published studies, variants of NER genes associations with colorectal cancer (CRC) risk were inconclusive. Thus, this meta-analysis aimed to explore the possible association. A trial sequence analysis (TSA) analysis was performed to control the risk of false positive or false negative.

Methods: PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Network (CNKI), Wanfang Database and Scientific and Technical Journal Database (VIP) were searched to identify relative studies until April 2022. The association was assessed by odds ratio (OR) in Allele, homozygous, heterozygous, dominant, recessive, and over-dominant models. In addition, Begg’s and Egger’s tests, sensitivity analysis, subgroup analysis and TSA analysis were performed.

Results: A total of 29 studies were eventually included in the meta-analysis, including 12,153 CRC patients and 14,168 controls. It showed that excision and repair cross complementary group 1 (ERCC1) rs11615 CC genotype decreased the risk of CRC, compared with TT genotype (CC vs. TT: OR = 0.816, 95% CI = 0.673–0.990, p = 0.039). For ERCC1 rs3212986, the significant impact was detected on increased the risk of CRC in the allele (OR = 1.267, 95% CI = 1.027–1.562, p = 0.027), homozygous (OR = 1.805, 95% CI = 1.276–2.553, p = 0.001), dominant (OR = 1.214, 95% CI = 1.012–1.455, p = 0.037) and recessive (OR = 1.714, 95% CI = 1.225–2.399, p = 0.002) models, especially in the Asian population. The results revealed the association of ERCC2 rs1799793 A allele with a higher risk of CRC (A vs. G: OR = 1.163, 95% CI = 1.021–1.325, p = 0.023). It also showed that ERCC5 rs17655 increased CRC risk in the allele (OR = 1.104, 95% CI = 1.039–1.173, p = 0.001), homozygous (OR = 1.164, 95% CI = 1.018–1.329, p = 0.026), heterozygous (OR = 1.271, 95% CI = 1.018–1.329, p < 0.001), dominant (OR = 1.241, 95% CI = 1.135–1.358, p < 0.001) and over-dominant (OR = 0.828, 95% CI = 0.762–0.900, p < 0.001) models, especially among Asians.

Conclusion: This meta-analysis based on current evidence suggests that the significant association was observed between ERCC1 rs11615, ERCC1 rs3212986, ERCC2 rs1799793, and ERCC5 rs17655 and CRC susceptibility. However, given the limited sample size and the influence of genetic background, studies of a larger scale and well-designed are required to confirm the results.

Interaction between microbiota and immunity and its implication in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the world. Besides genetic causes, colonic inflammation is one of the major risk factors for CRC development, which is synergistically regulated by multiple components, including innate and adaptive immune cells, cytokine signaling, and microbiota. The complex interaction between CRC and the gut microbiome has emerged as an important area of current CRC research. Metagenomic profiling has identified a number of prominent CRC-associated bacteria that are enriched in CRC patients, linking the microbiota composition to colitis and cancer development. Some microbiota species have been reported to promote colitis and CRC development in preclinical models, while a few others are identified as immune modulators to induce potent protective immunity against colitis and CRC. Mechanistically, microbiota regulates the activation of different immune cell populations, inflammation, and CRC via crosstalk between innate and adaptive immune signaling pathways, including nuclear factor kappa B (NF-κB), type I interferon, and inflammasome. In this review, we provide an overview of the potential interactions between gut microbiota and host immunity and how their crosstalk could synergistically regulate inflammation and CRC, thus highlighting the potential roles and mechanisms of gut microbiota in the development of microbiota-based therapies to prevent or alleviate colitis and CRC.

Are Inflammatory Bowel Disease and Colorectal Carcinoma Associated with Helicobacter pylori? A Prospective Study and Meta-analysis

Observational studies regarding the correlation between colorectal carcinoma, inflammatory bowel disease and Helicobacter pylori infection are inconsistent. The present study aims to investigate the association between colorectal adenocarcinoma (CRA) and inflammatory bowel disease (IBD) with H. pylori status in 100 patients who have inflammatory bowel disease and colorectal carcinoma was confirmed disease by histological approach. Besides, a meta-analysis was performed of published studies, to evaluate the link between H. pylori infection and an increased risk of CRC and IBD. Among 67 cases with CRA and 33 cases with IBD, 59.7% and 51.5% were H. pylori positive; respectively. In the meta-analysis, thirty-nine articles were included, involving 13 231 cases with CRC and 2477 with IBD. The pooled odds ratio for CRC and IBD was 1.16 (95%CI = 0.73-1.82) and 0.42 (95%CI = 0.32-0.56); respectively. Our meta-analysis indicates that H. pylori is not associated with CRC.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Association Between the hOGG1 1245C>G (rs1052133) Polymorphism and Susceptibility to Colorectal Cancer: a Meta-analysis Based on 7010 Cases and 10,674 Controls

BACKGROUND

The 1245C>G (rs1052133) polymorphism of human 8-oxoguanine DNA glycosylase 1 (hOGG1) gene has been indicated to be correlated with colorectal (CRC) susceptibility, but studies have yielded conflicting results. Thus, the present meta-analysis was performed to derive a more precise estimation between hOGG1 1245C>G polymorphism and CRC risk.

METHODS

Data were collected from several electronic databases such as PubMed, EMBASE, and Google Scholar databases, with the last search up to September 01, 2020. Pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the strength of the association.

RESULTS

A total of 24 case-control studies with 7010 CRC cases and 10,674 controls were selected. Pooled data showed that the hOGG1 1245C>G polymorphism was significantly associated with CRC risk under three genetic models, i.e., homozygote (GG vs. CC: OR = 1.229, 95% CI 1.031-1.465, p = 0.022); heterozygote (GC vs. CC: OR = 1.142, 95% CI 1.008-1.294, p = 0.037); and dominant (GG+GC vs. CC: OR = 1.162, 95% CI 1.034-1.304, p = 0.011). When stratified analysis by ethnicity, a significant association of the hOGG1 1245C>G polymorphism with risk of CRC was found in the Caucasians, but not in Asians. Moreover, there were significant associations between hOGG1 1245C>G polymorphism and CRC by PCR-RFLP and hospital-based subgroups.

CONCLUSIONS

Inconsistent with the previous meta-analysis, these meta-analysis results revealed that the hOGG1 1245C>G polymorphism might be associated with an increased risk of CRC, especially in Caucasians.

Association between Helicobacter pylori infection and the risk of colorectal cancer: A systematic review and meta-analysis

BACKGROUND

The existing evidence on the relationship between Helicobacter pylori infection and the risk of colorectal cancer is inconsistent. We conducted a systematic review with a meta-analysis to explore this relationship and to determine whether the relationship varies according to the study characteristics.

METHODS

We searched the PubMed, OVID, EMBASE database, and the reference lists of pertinent articles published up to October 2019 by 2 researchers independently. Summary odds ratios (OR) with their 95% confidence intervals (CIs) were estimated using a random-effects model.

RESULTS

Forty seven studies including 17,416 cases of colorectal cancer (CRC) and 55,811 cases of control were included. Overall, H. pylori infection was associated with an increased risk of CRC (OR = 1.70 95% CI 1.64-1.76, I = 97%), although there was significant heterogeneity among the studies. Subgroup analysis revealed that the positive correlation might vary by the design of study conducted.

CONCLUSION

This meta-analysis demonstrates a positive association between H. pylori infection and the risk of colorectal cancer.

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.

Helicobacter pylori infection and the risk of colorectal carcinoma: a systematic review and meta-analysis

INTRODUCTION

Helicobacter pylori is a gram-negative bacterium that is colonized in the stomach. H. pylori infection can lead to a series of stomach diseases. However, the relationship between H. pylori infection and colorectal cancer is currently controversial. Therefore, we performed this meta-analysis to further understand the relationship between H. pylori infection and colorectal cancer.

EVIDENCE ACQUISITION

We conducted a comprehensive retrieval from electronic databases, included the PubMed, Medline, China National Knowledge Infrastructure (CNKI), and China Wanfang Data Knowledge Service Platform databases (Wanfang Databases) through May 1st, 2018. We used the search terms H. pylori and colorectal cancer or colorectal carcinoma and collected all relevant studies to explore the association between H. pylori infection and colorectal cancer.

EVIDENCE SYNTHESIS

Twenty-seven studies including 14357 cases were included. H. pylori infection was associated with an increased risk of colorectal cancer. A pooled odds ratio (OR) of 1.27 with a 95% CI of 1.17-1.37 (P<0.001) was calculated by using a fixed-effects model (I2=45.5%, P=0.006). The subgroup analysis revealed that H. pylori infection was associated with an increased risk of colorectal cancer in the subgroups of Western countries (OR=1.34, 95% CI: 1.14-1.57) (P<0.001), serological testing (OR=1.20, 95% CI: 1.08-1.34) (P=0.001), multiple methods of testing (OR=2.63, 95% CI: 1.09-6.31) (P=0.031), cross-sectional studies (OR=1.92, 95% CI: 1.17-3.16) (P=0.010) and case-control studies (OR 1.26, 95% CI: 1.16-1.36) (P<0.001).

CONCLUSIONS

The present meta-analysis provides evidence suggests that a positive association between H. pylori infection and the risk of colorectal cancer.

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.

Human 8-oxoguanine DNA glycosylase gene polymorphism (Ser326Cys) and cancer risk: updated meta-analysis

Genetic polymorphism of human 8-oxoguanine glycosylase 1 (hOGG1) has been reported to have a relationship with the risk of the development of various cancers. Many studies have described the influence of Ser326Cys polymorphism of the hOGG1 gene on cancer susceptibility. However, the results have remained inconclusive and controversial. Therefore, we performed a meta-analysis to more precisely determine the relationship between the hOGG1 polymorphism and the development of cancer.Electronic databases including PubMed, Embase, Google Scholar, and the Korean Studies Information Service System (KISS) were searched. The odds ratio (OR), 95% confidence interval (CI), and p value were calculated to assess the strength of the association with the risk of cancer using Comprehensive Meta-analysis software (Corporation, NJ, USA). The 127 studies including 38,757 cancer patients and 50,177 control subjects were analyzed for the meta-analysis.Our meta-analysis revealed that G allele of Ser326Cys polymorphism of the hOGG1 gene statistically increased the susceptibility of cancer (all population, OR = 1.092, 95% CI = 1.051-1.134, p < 0.001; in Asian, OR = 1.095, 95% CI = 1.048-1.145, p < 0.001; in Caucasian, OR = 1.097, 95% CI = 1.033-1.179, p = 0.002). Also, other genotype models showed significant association with cancer (p < 0.05, respectively).The present meta-analysis concluded that the G allele was associated with an increased risk of cancer. It suggested that the hOGG1 polymorphism may be a candidate marker of cancer.

Association of XPC Gene Polymorphisms with Colorectal Cancer Risk in a Southern Chinese Population: A Case-Control Study and Meta-Analysis

Xeroderma pigmentosum group C (XPC) is a key component of the nucleotide excision repair (NER) pathway. Dysfunctional XPC protein may impair NER-mediated DNA repair capacity and further lead to genomic instability and carcinogenesis. Two common nonsynonymous polymorphisms in the XPC gene, Lys939Gln (rs2228001 A > C) and Ala499Val (rs2228000 C > T), have been investigated in various types of cancer. We genotyped these two polymorphisms in 1141 cases with histologically confirmed colorectal cancer (CRC) and 1173 healthy controls to explore their causative association with CRC susceptibility. Overall, no association was observed between these two variants and the risk of CRC. Our meta-analysis also confirmed a lack of overall association. Stratified analyses were performed by age, gender, smoking status, pack-year, drinking status, tumor sites, and Duke's stages. We found that XPC Lys939Gln polymorphism was significantly associated with an increased CRC risk in subjects at 57 years of age or younger (adjusted odds ratio (OR) = 1.37, 95% confidence interval (CI) = 1.004-1.86, p = 0.047) and non-drinkers (adjusted OR = 1.53, 95% CI = 1.10-2.12, p = 0.011). Our results indicated that XPC Lys939Gln may be a low-penetrance CRC susceptibility polymorphism. Our findings warrant further validation.

Association between the OGG1 Ser326Cys Polymorphism and Cancer Risk: Evidence from 152 Case-Control Studies

Although it has been suggested that the 8-oxoguanine DNA glycosylase (OGG1) gene Ser326Cys polymorphism may be a risk factor for cancer, the conclusions from previous studies are inconsistent. Thus, we conducted an updated meta-analysis to estimate the effect of OGG1 variant genotypes on cancer susceptibility. We searched the PubMed for all eligible studies published in English for the period ending September 2014. We found the association between OGG1 Ser326Cys polymorphism and cancer susceptibility based on 152 case-control studies in different genetic model comparisons (dominant model: OR = 1.053, P = 0.018; recessive model: OR = 1.108, P < 0.001; homozygote: OR = 1.135, P < 0.001; additive model: OR = 1.059, P < 0.001). However, the results from the subgroup analyses based on types of cancer, health population as controls or studies with relatively large sample size did not support the conclusion. Although the overall results of this meta-analysis showed a positive association between OGG1 variant genotypes and cancer susceptibility, the subgroup analyses by cancer type, sample size, and source of controls presented inconsistent results. Therefore, the current evidence from the meta-analysis did not support the hypothesis of OGG1 Ser326Cys polymorphism as a risk factor of cancer.

Correlation between Helicobacter pylori-associated gastric diseases and colorectal neoplasia

AIM: To explore the correlation between Helicobacter pylori (H. pylori)-associated gastric diseases and colorectal neoplasia.

METHODS: Patients included in this study underwent a colonoscopy and esophago-gastro-duodenoscopy (EGD) along with histopathological measurement between March 2012 and March 2015 at Qi-Lu Hospital of Shandong University, who also had results of H. pylori detection. A total of 233 cases were selected. Demographic data, H. pylori infection status (including results of rapid urease tests and gastric mucosa pathological examinations) and histopathological examination results of gastric and colorectal mucosa were gathered and analyzed. The statistical analysis focused on the prevalence of colorectal neoplasms among patients with various histopathological categories of the stomach. ORs and their 95%CI were calculated to describe the strengths of the associations.

RESULTS: The incidence rates of colorectal adenoma without high-grade intraepithelial neoplasia (HGIEN) (OR = 2.400, 95%CI: 0.969-5.941), adenoma with HGIEN (5.333, 1.025-27.758) and adenocarcinoma (1.455, 0.382-5.543) were all higher for patients with H. pylori-associated gastritis than for those in the control group. The incidence rate of colorectal adenoma with HGIEN (3.218, 0.767-13.509) was higher in patients with intestinal metaplasia than in the control group, while the incidence rates of adenoma without HGIEN (0.874, 0.414-1.845) and adenocarcinoma (0.376, 0.096-1.470) were lower in the intestinal metaplasia group than in the control group. The incidence rate of colorectal adenoma without HGIEN (3.111, 1.248-7.753) was significantly higher in the gastric intraepithelial neoplasia group than in the control group, while the rates of adenoma with HGIEN (1.481, 0.138-15.941) and adenocarcinoma (2.020, 0.561-7.272) were higher in the gastric intraepithelial neoplasia group. Incidence rates of colorectal adenoma without HGIEN (1.067, 0.264-4.314), adenoma with HGIEN (2.667, 0.231-30.800) and adenocarcinoma (2.182, 0.450-10.585) were all higher in the gastric adenocarcinoma group than in the control group.

CONCLUSION: H. pylori infection as well as H. pylori-associated gastric diseases are risk factors for colorectal neoplasia.

OGG1 Mutations and Risk of Female Breast Cancer: Meta-Analysis and Experimental Data

In first part of this study association between OGG1 polymorphisms and breast cancer susceptibility was explored by meta-analysis. Second part of the study involved 925 subjects, used for mutational analysis of OGG1 gene using PCR-SSCP and sequencing. Fifteen mutations were observed, which included five intronic mutations, four splice site mutations, two 3'UTR mutations, three missense mutations, and a nonsense mutation. Significantly (p < 0.001) increased (~29 fold) breast cancer risk was associated with a splice site variant g.9800972T>G and 3'UTR variant g.9798848G>A. Among intronic mutations, highest (~15 fold) increase in breast cancer risk was associated with g.9793680G>A (p < 0.009). Similarly ~14-fold increased risk was associated with Val159Gly (p < 0.01), ~17-fold with Gly221Arg (p < 0.005), and ~18-fold with Ser326Cys (p < 0.004) in breast cancer patients compared with controls, whereas analysis of nonsense mutation showed that ~13-fold (p < 0.01) increased breast cancer risk was associated with Trp375STOP in patients compared to controls. In conclusion, a significant association was observed between OGG1 germ line mutations and breast cancer risk. These findings provide evidence that OGG1 may prove to be a good candidate of better diagnosis, treatment, and prevention of breast cancer.

Helicobacter pylori and serum kynurenine-tryptophan ratio in patients with colorectal cancer

AIM: To evaluate how Helicobacter pylori (H. pylori) is able to evade the immune response and whether it enhances systemic immune tolerance against colorectal cancer.

METHODS: This prospective randomized study involved 97 consecutive colorectal cancer patients and 108 cancer-free patients with extra-digestive diseases. Colorectal cancer and cancer-free patients were assigned into subgroups according to H. pylori IgG seropositivity. Exposure to H. pylori was determined by IgG seropositivity which was detected by enzyme linked immunoassay (ELISA). Serum neopterin levels were measured by ELISA. Serum tryptophan, kynurenine, and urinary biopterin concentrations were measured by high performance liquid chromatography. Serum nitrite levels were detected spectrophotometrically. Serum indoleamine 2,3-dioxygenase activity was estimated by the kynurenine to tryptophan ratio and by assessing the correlation between serum neopterin concentrations and the kynurenine to tryptophan ratio. The frequencies of increased serum kynurenine to tryptophan ratio of H. pylori seronegative and seropositive colorectal cancer subgroups were estimated by comparing them with the average kynurenine to tryptophan ratio of H. pylori seronegative tumor-free patients.

RESULTS: Compared with respective controls, in both H. pylori seronegative and seropositive colorectal cancer patients, while serum tryptophan levels were decreased (controls vs patients; seronegative: 20.37 ± 0.89 μmol/L vs 15.71 ± 1.16 μmol/L, P < 0.05; seropositive: 20.71 ± 0.81 μmol/L vs 14.97 ± 0.79 μmol/L, P < 0.01) the kynurenine to tryptophan ratio was significantly increased (controls vs patients; seronegative: 52.85 ± 11.85 μmol/mmol vs 78.91 ± 8.68 μmol/mmol, P < 0.01, seropositive: 47.31 ± 5.93 μmol/mmol vs 109.65 ± 11.50 μmol/mmol, P < 0.01). Neopterin concentrations in cancer patients were significantly elevated compared with controls (P < 0.05). There was a significant correlation between serum neopterin levels and kynurenine/tryptophan in control and colorectal cancer patients groups (r_s = 0.494, P = 0.0001 and r_s = 0.293, P = 0.004, respectively). Serum nitrite levels of H. pylori seropositive cancer cases were significantly decreased compared with seropositive controls (controls vs patients; 26.04 ± 2.39 μmol/L vs 20.41 ± 1.48 μmol/L, P < 0.05) The decrease in the nitrite levels of H. pylori seropositive cancer patients may be attributed to excessive formation of peroxynitrite and other reactive nitrogen species.

CONCLUSION: A significantly high kynurenine/tryptophan suggested that H. pylori may support the immune tolerance leading to cancer development, even without an apparent upper gastrointestinal tract disease.

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

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

The hOGG1 Ser326Cys polymorphism contributes to digestive system cancer susceptibility: evidence from 48 case-control studies

The Ser326Cys polymorphism in the human 8-oxogunaine DNA glycosylase (hOGG1) gene had been implicated in cancer susceptibility. Studies investigating the associations between the Ser326Cys polymorphism and digestion cancer susceptibility showed conflicting results. Therefore, a meta-analysis was performed to derive a more precise estimation of the relationship. We conducted a meta-analysis of 48 studies that included 12,073 cancer cases and 19,557 case-free controls. We assessed the strength of the association using odds ratios (ORs) with 95% confidence intervals (CIs). In our analysis, the hOGG1 Ser326Cys polymorphism was significantly associated with the risk of digestive system cancers (Cys/Cys vs. Ser/Ser: OR = 1.17, 95% CI = 1.00-1.35, P < 0.001; Cys/Cys vs. Cys/Ser + Ser/Ser: OR = 1.14, 95% CI = 1.00-1.29, P < 0.001). In subgroup analyses by cancer types, we found that the hOGG1 Ser326Cys polymorphism may increase hepatocellular cancer and colorectal cancer risks, but decrease the risk of oral cancer. These findings supported that hOGG1 Ser326Cys polymorphism may contribute to the susceptibility of digestive cancers.

Association of hOGG1 Ser326Cys polymorphism with colorectal cancer risk: an updated meta-analysis including 5235 cases and 8438 controls

It has been suggested that hOGG1 Ser326Cys polymorphism may be a risk factor for colorectal cancer. Published data on its association with colorectal cancer generated contradictory results; thus, we performed an updated meta-analysis of eligible published studies to estimate the effect of hOGG1 Ser326Cys polymorphism on colorectal cancer susceptibility. We reviewed many abstracts and finally included 18 eligible case-control studies comprising 5235 cases and 8438 controls. We pooled data with a fixed or random-effect model. Subgroup analysis by ethnicity was also performed. The overall data indicated a significant association of hOGG1 Ser326Cys polymorphism on colorectal cancer risk (allele model OR = 1.14, 95 %CI 1.02-1.27; homozygote model OR = 1.32, 95 %CI 0.92-1.92; recessive model OR = 1.12, 95 %CI 1.00-1.26; dominant model OR = 1.15, 95 %CI 1.00-1.32). Furthermore, in the subgroup analysis by ethnicity, increased cancer risk was observed among Caucasians under the allele, heterogeneity, recessive, and dominant models (allele model OR = 1.23, 95 %CI = 1.05-1.44; homozygote model OR = 1.49, 95%CI 1.05-2.12; recessive model OR = 1.40, 95 %CI 1.16-1.69; dominant model OR = 1.21, 95 %CI = 1.12-1.45). In summary, the present meta-analysis suggested that hOGG1 Ser326Cys polymorphism might modify the susceptibility to colorectal cancer among the total population, especially among Caucasians.

XPC Lys939Gln polymorphism contributes to colorectal cancer susceptibility: evidence from a meta-analysis

Abstract

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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.

Helicobacter pylori infection and normal colorectal mucosa-adenomatous polyp-adenocarcinoma sequence: a meta-analysis of 27 case-control studies

AIM

The study aimed to determine whether Helicobacter pylori infection is associated with colorectal adenocarcinoma and to quantify the extent of the risk.

METHOD

A literature search was performed to identify studies published between 1995 and 2012 for relevant risk estimates. Fixed and random effect meta-analytical techniques were conducted for colorectal adenocarcinoma and adenomatous polyp.

RESULTS

Twenty-seven case-controlled studies involving 3450 adenocarcinoma patients, 1304 adenomatous polyp patients and more than 4000 controls were included. Helicobacter pylori was associated with an increased risk of colorectal adenocarcinoma and adenomatous polyp [odds ratio (OR) 1.24, 95% CI 1.12-1.37, P = 0.66; OR 1.87, 95% CI 1.53-2.28, P = 0.81]. There was a significant association between the CagA-positive strain and adenocarcinoma risk (OR 1.22, 95% CI 1.08-1.37, P = 0.05). In addition, there was an increased risk of tubular adenoma and villous adenoma formation (OR 3.06, 95% CI 1.98-4.73, P = 0.14; OR 2.05, 95% CI 0.84-4.97, P = 0.86).

CONCLUSION

The meta-analysis suggests a promoting effect of Helicobacter pylori on the risk of adenocarcinoma. It also suggests that Helicobacter infection might have its influence at the start of the adenomatous polyp disease sequence.

Association between six genetic polymorphisms and colorectal cancer: a meta-analysis

OBJECTIVE

The aim of this study was to determine whether six genetic polymorphisms confer susceptibility to colorectal cancer (CRC).

METHODS

A systematic search for candidate genes of CRC was performed among several online databases, including PubMed, Embase, Web of Science, the Cochrane Library, CNKI, and Wanfang online libraries. After a comprehensive filtering procedure, we harvested five genes, including MGMT (rs12917 and rs2308321), ADH1B (rs1229984), SOD2 (rs4880), XPC (rs2228001), and PPARG (rs1801282). Using the REVMAN and Stata software, six meta-analyses were conducted for associations between CRC and the just-mentioned genetic variants.

RESULTS

A total of 34 comparative studies among 17,289 cases and 54,927 controls were involved in our meta-analyses. Significant association was found between ADH1B rs1229984 polymorphism and CRC (p=0.03, odds ratio [OR]=1.18, 95% confidence interval [CI]=1.01-1.36). We also found significant association between PPARG rs1801282 polymorphism and CRC (p=0.004, OR=1.498, 95% CI=1.139-1.970), and this significant association is specific in Caucasians (p=0.004, OR=1.603, 95% CI=1.165-2.205).

CONCLUSIONS

The current meta-analysis has established that ADH1B (rs1229984) and PPARG (rs1801282) are two risk variants of CRC.

XPC Lys939Gln and Ala499Val polymorphisms in colorectal cancer susceptibility: a meta-analysis of case-control studies

The XPC Lys939Gln and Ala499Val polymorphisms were likely to be involved with the development of colorectal cancer. However, there had been inconsistent reports of association. This meta-analysis of literatures was performed to draw a more precise estimation of the relationship. We systematically searched PubMed, Embase and Web of Science for relevant articles with a time limit of December 2012. The strength of association between the XPC Lys939Gln and Ala499Val polymorphisms and colorectal cancer susceptibility were assessed by odds ratio (OR) with the corresponding 95 % confidence interval (95 % CI). This meta-analysis including six case-control studies evaluated the associations between the two XPC polymorphisms (Lys939Gln, Ala499Val) and colorectal cancer susceptibility. For XPC Lys939Gln, no obvious associations were found for all genetic models [CC vs AA: OR (95 % CI) = 1.12 (0.94-1.32); CA vs AA: OR (95 % CI) = 1.08 (0.94-1.24); the dominant model: OR (95 % CI) = 1.09 (0.97-1.23); the recessive model: OR (95 % CI) = 1.07 (0.92-1.25)]. For XPC Ala499Val, no obvious associations were also not found for all genetic models [TT vs CC: OR (95 % CI) = 0.84 (0.65-1.10); CT vs CC: OR (95 % CI) = 1.00 (0.86-1.15); the dominant model: OR (95 % CI) = 0.98 (0.85-1.12); the recessive model: OR (95 % CI) = 0.87 (0.67-1.12)]. This meta-analysis suggested that both the XPC Lys939Gln and Ala499Val polymorphisms were not risk factors for increasing colorectal cancer.

Associations of Lys939Gln and Ala499Val polymorphisms of the XPC gene with cancer susceptibility: a meta-analysis

XPC polymorphisms may alter DNA repair capacity, thus leading to genetic instability and carcinogenesis. Numerous studies have investigated the associations of XPC Lys939Gln (rs2228001) and Ala499Val (rs2228000) polymorphisms with cancer susceptibility; however, the findings are inconclusive. We searched literature from MEDLINE and EMBASE for eligible publications that assessed the associations between these two polymorphisms and cancer risk. We also assessed genotype-mRNA expression correlation data from HapMap for rs2228001 and rs2228000 in normal cell lines derived from 270 subjects with different ethnicities. The final analysis included 62 published studies of 25,708 cases and 30,432 controls for the Lys939Gln and 34 studies with 14,877 cases and 17,888 controls for the Ala499Val. Overall, Lys939Gln was significantly associated with an increased overall cancer risk (Gln/Gln vs. Lys/Lys: OR = 1.16, 95% CI = 1.07 - 1.25, p < 0.001; recessive model: OR = 1.14, 95% CI = 1.06 - 1.22, p < 0.001; dominant model: OR = 1.06, 95% CI = 1.01 - 1.11, p = 0.015 and Gln vs. Lys: OR = 1.07, 95% CI = 1.03 - 1.10, p < 0.001) and further stratifications showed an increased risk for bladder, lung and colorectal cancer, Asian populations and population-based studies. Likewise, Ala499Val was also significantly associated with an increased overall cancer risk (Val/Val vs. Ala/Ala: OR = 1.21, 95% CI = 1.07 - 1.36, p = 0.003 and recessive model: OR = 1.20, 95% CI = 1.08 - 1.34, p = 0.001) and further stratification showed an increased risk for breast and bladder cancer, particularly in Asian populations. Interestingly, significantly correlation between XPC genotypes and mRNA expression was found only for Asian populations as well. Despite some limitations, this meta-analysis established some solid statistical evidence for an association between XPC polymorphisms and cancer risk, which warrants further validation in single large studies.

The effect of oxoguanine glycosylase 1 rs1052133 polymorphism on colorectal cancer risk in Caucasian population

Human oxoguanine glycosylase 1 (OGG1) is an important part of the base excision repair pathway in the DNA repair. Numerous epidemiological studies have evaluated the association between OGG1 rs1052133 polymorphism and the risk of colorectal cancer, but the results of these studies from the Caucasian population were conflicting. To derive a more precise assessment on the association between OGG1 rs1052133 polymorphism and risk of colorectal cancer in Caucasian population, we performed a meta-analysis. The odds ratios (OR) with 95% confidence intervals (CI) were used to assess the strength of the association. Thirteen case-control studies with a total of 4,103 cases and 5,400 controls were finally included into the meta-analysis. Meta-analysis of all 13 studies showed that OGG1 rs1052133 polymorphism was significantly associated with the risk of colorectal cancer in Caucasian population (Cys versus Ser OR = 1.20, 95% CI = 1.03-1.39, P = 0.02; CysCys versus SerSer OR = 1.44, 95% CI = 1.04-2.00, P = 0.03; CysCys versus SerSer/SerCys OR = 1.39, 95% CI = 1.15-1.67, P = 0.0005). In the sensitivity analysis, omitting each study one at a time had no obvious influence on the pooled OR, which confirmed the stability of meta-analysis. The meta-analysis suggests that OGG1 rs1052133 polymorphism is significantly associated with the risk of colorectal cancer in Caucasian population.

Association between Helicobacter pylori infection and the risk of colorectal neoplasia: a systematic review and meta-analysis

AIM

The existing evidence on the relationship between Helicobacter pylori infection and the risk of colorectal neoplasia is inconsistent. We conducted a systematic review with a meta-analysis to explore this relationship and to determine whether the relationship varies according to the study characteristics.

METHOD

We searched the PubMed database and the reference lists of pertinent articles published up to July 2012. Summary odds ratios (ORs) with their 95% confidence intervals (CIs) were estimated using a random-effects model.

RESULTS

Twenty-seven studies including 3792 cases of colorectal adenoma (CRA) and 3488 cases of colorectal cancer (CRC) were identified. Overall, H. pylori infection was associated with an increased risk of CRA (OR = 1.66, 95% CI 1.39-1.97, I(2)  = 54.3%) and CRC (OR = 1.39, 95% CI 1.18-1.64, I(2)  = 35.8%), although there was significant heterogeneity among the studies. Subgroup analysis revealed that the positive correlation did not differ by sex, geographic variation or subsite of neoplasia, but might vary by the method of detection of H. pylori. The study was underpowered to determine the risk of colorectal neoplasia associated with cytotoxin-associated gene A-positive H. pylori.

CONCLUSION

This meta-analysis demonstrates a positive association between H. pylori infection and the risk of colorectal neoplasia.

XPC Polymorphism Increases Risk of Digestive System Cancers: Current Evidence from A Meta-Analysis

OBJECTIVE

Xeroderma pigmentosum complementation group C (XPC) participates in the initial recognition of DNA damage during nucleotide excision repair process in global genomic repair. Our meta-analysis was performed to evaluate the association between three polymorphisms (Lys939Gln, PAT+/- and Ala499Val) of XPC gene and risk of digestive system cancers.

METHODS

All the relevant case-control studies published to April 2011 were identified through searching PubMed. Digestive system cancer risk with the three polymorphisms was estimated for each study by odds ratio (OR) with its 95% confidence interval (95% CI).

RESULTS

We found an increased overall risk for digestive system cancers in all three models of Lys939Gln A>C (AC/CC vs. AA: OR, 1.20; 95% CI, 1.11-1.30; CC vs. AC/AA: OR, 1.24; 95% CI, 1.11-1.39; CC vs. AA: OR, 1.36; 95% CI, 1.21-1.53). When stratified by ethnicity, results remained significant in Asian population (AC/CC vs. AA: OR, 1.18; 95% CI, 1.02-1.37; CC vs. AC/AA: OR, 1.32; 95% CI, 1.1-1.51; CC vs. AA: OR, 1.35; 95% CI, 1.08-1.70), but not for Caucasians. However for Ala499Val C>T, a significant protective effect of T allele was only observed in the dominant model. Otherwise, no significant results were observed for PAT+/-.

CONCLUSION

XPC Lys939Gln A>C polymorphism may play an important role in digestive system cancer susceptibility.

Could 8-oxoguanine DNA glycosylase 1 Ser326Cys polymorphism be a biomarker of susceptibility in cancer?

Biomarkers are key molecular or cellular events that give an indication whether there is a threat for disease, whether a disease already exists, or how such disease may develop in an individual case. The discovery of polymorphisms in genes that function in the metabolism of chemicals and in DNA repair has demonstrated the importance of understanding the phenomenon of genetic susceptibility in a population. Polymorphisms in DNA repair genes as an important component of the individual susceptibility to the development of cancer and various hereditary diseases have been commonly studied, since these genes have critical roles in maintaining genome integrity. Furthermore, the evaluation of cancer risk depends on the level of exposure to carcinogenic factors as well as on the genetic codes of the individual. This approach is supported by studies that present positive association between these polymorphic genes and cancers. Although 8-oxoguanine DNA glycosylase 1 (OGG1) is one of the promising biomarker candidates of cancer susceptibility, there are also some controversial results. Epidemiological studies show that the OGG1 might be a biomarker of susceptibility for various cancers; however, the small sample size and difference in the eligibility criteria for inclusion of subjects and sources might limit the studies to demonstrate the association between the OGG1 Ser326Cys polymorphism and the risk of cancer. Thus, meta-analyses may provide more valuable and reliable data to demonstrate the potential of OGG1 Ser326Cys DNA repair enzyme polymorphisms that could be the biomarkers of susceptibility of cancer. Our aim in this review is to compile published studies, including some controversial results on the association between the OGG1 Ser326Cys polymorphism and the risk of cancer.

Impact of DNA polymorphisms in key DNA base excision repair proteins on cancer risk

Genetic variation in DNA repair genes can modulate DNA repair capacity and may be related to cancer risk. However, study findings have been inconsistent. Inheritance of variant DNA repair genes is believed to influence individual susceptibility to the development of environmental cancer. Reliable knowledge on which the base excision repair (BER) sequence variants are associated with cancer risk would help elucidate the mechanism of cancer. Given that most of the previous studies had inadequate statistical power, we have conducted a systematic review on sequence variants in three important BER proteins. Here, we review published studies on the association between polymorphism in candidate BER genes and cancer risk. We focused on three key BER genes: 8-oxoguanine DNA glycosylase (OGG1), apurinic/apyrimidinic endonuclease (APE1/APEX1) and x-ray repair cross-complementing group 1 (XRCC1). These specific DNA repair genes were selected because of their critical role in maintaining genome integrity and, based on previous studies, suggesting that single-nucleotide polymorphisms (SNPs) in these genes have protective or deleterious effects on cancer risk. A total of 136 articles in the December 13, 2010 MEDLINE database (National Center for Biotechnology Information, http://www.ncbi.nlm.nih.gov/pubmed/) reporting polymorphism in OGG1, XRCC1 or APE1 genes were analyzed. Many of the reported SNPs had diverse association with specific human cancers. For example, there was a positive association between the OGG1 Ser326Cys variant and gastric and lung cancer, while the XRCC1 Arg399Gln variant was associated with reduced cancer risk. Gene-environment interactions have been noted and may be important for colorectal and lung cancer risk and possibly other human cancers.

Meta-analysis of the association between hOGG1 Ser326Cys polymorphism and risk of colorectal cancer based on case--control studies

PURPOSE

Oxidative DNA damage caused by reactive oxygen species plays an important role in cancer development. The association between colorectal cancer and hOGG1 Ser326Cys polymorphisms has been analyzed in several published studies, but mixed findings have been reported. The main purpose of this study was to integrate previous results and explore whether the polymorphism of hOGG1 is associated with susceptibility to colorectal cancer.

METHODS

PubMed, Embase, Google Scholar, and Cbmdisc were searched for studies on the relationship of hOGG1 SNPs and the incidence of colorectal cancer (CRC). Eligible articles were included for data extraction. The main outcome was the frequency of hOGG1 Ser326Cys polymorphisms between cases and controls. Comparison of the distribution of SNP was mainly performed using Review Manager 5.0.

RESULTS

A total of 4,174 cases and 6,196 controls from 12 studies were included for this meta-analysis. Overall, stratified by ethnicity or population source, no significant associations between the hOGG1 Ser326Cys polymorphism and colorectal cancer risk were found for Cys/Cys allele (OR = 1.146; 95 % CI: 0.978-1.342, P = 0.091), Cys/Cys + Cys/Ser versus Ser/Ser (OR = 1.045; 95 % CI: 0.975-1.121, P = 0.213) Cys/Cys Versus Ser/Ser (OR = 1.243; 95 % CI: 0.979-1.578, P = 0.074) and Cys/Cys versus Cys/Ser + Ser/Ser (OR = 1.198; 95 % CI: 0.959-1.496, P = 0.111) in a recessive model and (OR = 1.494; 95 % CI: 1.023-2.181, P = 0.038) in a homozygote contrast. However, if apart from sensitivity analysis, there was some evidence to indicate that significantly increased risks were found among European plus American subjects, who are mostly Caucasian (OR = 1.444; 95 % CI: 1.017-2.05 Cys/Cys vs. Ser/Cys + Ser/Ser; P = 0.04). In the subgroup analyses, we also did not found any association between hOGG1 Ser326Cys polymorphism and certain populations and smokers.

CONCLUSIONS

This meta-analysis suggests that there is no robust association between hOGG1 Ser326Cys polymorphism and colorectal cancer. Because of the limitation of meta-analysis, this finding demands further investigation.

Helicobacter pylori infection and colorectal cancer risk: evidence from a large population-based case-control study in Germany

Evidence concerning the role of Helicobacter pylori infection in the development of colorectal cancer remains controversial. The authors assessed the association of H. pylori seroprevalence with risk of colorectal cancer in a large population-based case-control study from Germany in 2003-2007. Serum antibodies to H. pylori in general and the cytotoxin-associated gene A protein (CagA) were measured in 1,712 incident colorectal cancer cases and 1,669 controls. The association between H. pylori seroprevalence and colorectal cancer risk was estimated by logistic regression, with adjustment for potential confounders and stratification by age group, sex, anatomic subsites, and cancer stage. Overall, H. pylori seroprevalence was higher in cases (46.1%) than in controls (40.1%), resulting in an age- and sex-adjusted odds ratio of 1.30 (95% confidence interval (CI): 1.14, 1.50). Adjustment for established colorectal cancer risk factors decreased the odds ratio to 1.26 (95% CI: 1.09, 1.47), with a further reduction to 1.18 (95% CI: 1.01, 1.38) after additional adjustment for previous colorectal endoscopy. Stratified analyses showed risk elevation to be essentially confined to left-sided colorectal cancer, with an odds ratio of 1.22 (95% CI: 1.02, 1.45), suggesting that H. pylori infection may be associated with a small yet relevant risk increase in the left colorectum.

DNA repair genes XPC, XPG polymorphisms: relation to the risk of colorectal carcinoma and therapeutic outcome with Oxaliplatin-based adjuvant chemotherapy

Xeroderma pigmentosum complementation group C and G (XPC, XPG) play important roles in DNA damage repairing machinery. Genetic variations in the XPC and XPG may be associated with increased risk for colorectal carcinoma (CRC). In this study, we evaluated the relation between the XPC Lys939Gln, XPG Asp1104His polymorphisms, and CRC susceptibility in a population-based case-control study, which included 1,028 CRC cases and 1,085 controls. Compared with the corresponding wild genotypes, we found that individuals with at least one copy of the XPC Lys939Gln (AC or CC genotype) and XPG Asp1104His (GC or CC genotype) had an increased risk for CRC. In addition, the variant genotypes of the XPC Lys939Gln AC/CC (P = 0.027) or XPG Asp1104His GC/CC (P = 0.003) reduced the elevation of preoperative carcinoembryonic antigen (CEA) level. Moreover a significantly longer progression-free survival (PFS) after Oxaliplatin-based adjuvant chemotherapy was observed in patients with XPG Asp1104His wide-type GG genotype (n = 432, Log-rank test: P = 0.033). Cox proportional hazards analyses demonstrated that variant genotypes of XPG Asp1104His [hazard ratio (HR) = 1.692, 95% confidence interval (95%CI): 1.202-2.383, P = 0.003] as well as pathology grade (HR = 2.545, 95%CI: 2.139-3.030, P < 0.001), and lymph node metastases (HR = 1.851, 95%CI: 1.306-2.625, P < 0.001) were predictive of shorter PFS for the CRC patients with Oxaliplatin-based adjuvant chemotherapy. In conclusion, the current data suggested that XPC Lys939Gln and XPG Asp1104His polymorphisms might contribute to the identification of patients with increased risk for CRC.

The hOGG1 Ser326Cys polymorphism contributes to cancer susceptibility: evidence from 83 case-control studies

The Ser326Cys polymorphism in the human 8-oxogunaine DNA glycosylase (hOGG1) gene had been implicated in cancer susceptibility. Studies investigating the associations between the Ser326Cys polymorphism and cancer susceptibility showed conflicting results. To derive a more precise estimation of the relationship, a meta-analysis was performed. This meta-analysis was performed from 83 case-control studies, including 27,918 cases and 33,399 controls. The fixed and random effect models were used to estimate the odds ratios (ORs) and their 95% confidence interval (CI) for various contrasts of this polymorphism. The combined results based on all studies showed that the hOGG1 Ser326Cys polymorphism was associated with an increased cancer susceptibility in different genetic models. In the stratified analyses, the association was significantly in head and neck cancer (homozygote comparison: OR = 2.19, 95% CI: 1.20-4.01, P(heterogeneity) = 0.002; heterozygote comparison: OR = 1.48, 95% CI: 1.11-1.99, P(heterogeneity) = 0.004; dominant model comparison: OR = 1.58, 95% CI: 1.14-2.19, P(heterogeneity) < 0.001; recessive model comparison: OR = 1.73, 95% CI: 1.02-2.94, P(heterogeneity) = 0.002; and additive model comparison: OR = 1.43, 95% CI: 1.09-1.88, P(heterogeneity) < 0.001) which remained for studies of the Asian populations and hospital-based of control sources. But it was not observed in other cancer types of the European population and population based of control sources. This meta-analysis suggested that the hOGG1 Ser326Cys polymorphism might contribute to an increased risk on cancer susceptibility. More studies based on larger sample size should be performed to confirm the findings.

The effect of hOGG1 Ser326Cys polymorphism on cancer risk: evidence from a meta-analysis

Background

Human oxoguanine glycosylase 1 (hOGG1) in base excision repair (BER) pathway plays a vital role in DNA repair. Numerous epidemiological studies have evaluated the association between hOGG1 Ser326Cys polymorphism and the risk of cancer. However, the results of these studies on the association remain conflicting. To derive a more precise estimation of the association, we conducted a meta-analysis.

Methodology/Principal Findings

A comprehensive search was conducted to identify the eligible studies of hOGG1 Ser326Cys polymorphism and cancer risk. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. We found that the hOGG1 Ser326Cys polymorphism was significantly associated with overall cancer risk (Cys/Cys vs. Ser/Ser: OR = 1.19, 95%CI = 1.09–1.30, P<0.001; Cys/Cys vs. Cys/Ser+Ser/Ser: OR = 1.16, 95%CI = 1.08–1.26, P<0.001). Moreover, in subgroup analyses by cancer types, the stronger significant association between hOGG1 Ser326Cys polymorphism and lung cancer risk was found (Cys/Cys vs. Ser/Ser: OR = 1.29, 95%CI = 1.16–1.44, P<0.001; Cys/Cys vs. Cys/Ser+Ser/Ser: OR = 1.22, 95%CI = 1.12–1.33, P<0.001). The significant effects of hOGG1 Ser326Cys polymorphism on colorectal, breast, bladder, prostate, esophageal, and gastric cancer were not detected. In addition, in subgroup analyses by ethnicities, we found that the hOGG1 Ser326Cys polymorphism was associated with overall cancer risk in Asians (Cys/Cys vs. Ser/Ser: OR = 1.21, 95%CI = 1.10–1.33, P<0.001).

Conclusions

This meta-analysis showed that hOGG1 326Cys allele might be a low-penetrant risk factor for lung cancer.

Lack of association between XPD Lys751Gln and Asp312Asn polymorphisms and colorectal cancer risk: a meta-analysis of case-control studies

PURPOSE

The published data on the association between xeroderma pigmentosum group D (XPD) Lys751Gln and Asp312Asn polymorphisms and colorectal cancer remained controversial. The present meta-analysis of literatures was performed to derive a more precise estimation of the relationship.

MATERIALS AND METHODS

A comprehensive literature search was conducted to identify all case-control studies of Lys751Gln and Asp312Asn polymorphisms on the susceptibility of different tumor site of colorectal cancer (colon, rectum, and colon/rectum cancer). A total of 22 eligible studies were selected for this meta-analysis, including 3,042 cases and 4,627 controls for Lys751Gln and 1,581 cases and 2,846 controls for Asp312Asn.

RESULTS

Overall, no significantly elevated colorectal cancer risk was found in all genetic models when all studies were pooled into the meta-analysis (for Lys751Gln polymorphism: Lys/Gln vs. Lys/Lys, OR = 1.01, 95% CI = 0.90-1.14; Gln/Gln vs. Lys/Lys, OR = 1.04, 95% CI = 0.85-1.26; dominant model, OR = 1.03, 95% CI = 0.93-1.15; recessive model, OR = 1.04, 95% CI = 0.87-1.25; and for Asp312Asn polymorphism: Asp/Asn vs. Asp/Asp, OR = 1.11, 95% CI = 0.91-1.35; Asn/Asn vs. Asp/Asp, OR = 1.13, 95% CI = 0.87-1.47; dominant model, OR = 1.09, 95% CI = 0.94-1.26; recessive model, OR = 1.11, 95% CI = 0.88-1.41). And for the additive model, individuals carrying the 751Gln or 312Asn allele were not significantly associated with increased risk to colorectal cancer (OR = 1.02, 95% CI = 0.94-1.11, OR = 1.07, 95% CI = 0.95-1.20).

CONCLUSION

This meta-analysis suggests that XPD Lys751Gln and Asp312Asn polymorphisms may not be associated with colorectal cancer development.

Association of APE1 and hOGG1 polymorphisms with colorectal cancer risk in a Turkish population

BACKGROUND

There is growing evidence describing DNA repair genes polymorphisms are related to increased cancer risk including colorectal cancer (CRC). The aim of this study was to investigate the associations between the APE1 Asp148Glu, hOGG1 Ser326Cys, XRCC1 Arg399Gln, XRCC3 Thr241Met, XPD Lys751Gln, XPG Asp1104His polymorphisms and CRC risk in Turkish population.

PATIENTS AND METHODS

Polymorphisms of APE1 Asp148Glu (rs3136820), hOGG1 Ser326Cys (rs1052133), XRCC1 Arg399Gln(rs25487), XRCC3 Thr241Met (rs861539), XPD Lys751Gln (rs13181), and XPG Asp1104His (rs17655) were determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) methods in blood samples of 79 CRC patients at their initial staging and 247 healthy controls. Of the CRC patients, 26 out of 40 were diagnosed with rectal cancer and received neoadjuvant chemoradiotherapy following diagnosis; 39 others were diagnosed as colon cancer.

RESULTS

Our preliminary results showed that frequencies of Glu allele of APE1 Asp148Glu and Cys allele of hOGG1 Ser326Cys were higher in CRC patients than in controls (p = 0.006, OR: 3.43; 95% CI: 1.76-6.70; p = 0.000, OR: 2.77; 95% CI: 1.40-5.48, respectively). Higher frequency of Met allele of XRCC3 Thr241Met was detected in patients treated with neoadjuvant chemoradiotherapy (p = 0.024, OR: 5.25; 95% CI: 1.23-23.39) and with proximal colon tumors (p = 0.04, OR: 2; 95% CI: 1.18-3.34). Increased frequency of Ser/Ser genotype of hOGG1 Ser326Cys was found to be associated both with higher grade (p = 0.001, OR: 6.4; 95% CI: 2.69-62.69) and liver metastasis (p = 0.005, OR: 7.5; 95% CI: 0.7-68.36).

CONCLUSION

APE1 Asp148Glu and hOGG1 Ser326Cys polymorphisms might be associated with increasing risk of CRC in a Turkish population. Future studies with larger-sized samples, as well as detecting the association of DNA repair genes with other confounding factors will help elucidate the exact roles of DNA repair genes polymorphisms in development and progression of CRC.

The C/A polymorphism in intron 11 of the XPC gene plays a crucial role in the modulation of an individual's susceptibility to sporadic colorectal cancer

Epidemiological data show that colorectal cancer (CRC) is the second most frequent malignancy worldwide. The involvement of "minor impact genes" such as XME and DNA-repair genes in the etiology of sporadic cancer has been postulated by other authors. We focused on analyzing polymorphisms in DNA-repair genes in CRC. We considered the following genes involved in DNA-repair pathways: base excision repair (OGG1 Ser326Cys, XRCC1 Trp194Arg and Arg399Gln); nucleotide excision repair [XPA (-4)G/A, XPC C/A (i11) and A33512C (Lys939Gln), XPD Asp312Asn and A18911C (Lys751Gln), XPF Arg415Gln, XPG Asp1104His, ERCC1 C118T]; homologous recombination repair [NBS1 Glu185Gln, Rad51 135G/C, XRCC3 C18067 (Thr241Met)]. The study group consisted of 133 patients diagnosed with sporadic CRC, while the control group was composed of 100 age-matched non-cancer volunteers. Genotyping was performed by PCR and PCR-RFLP. Fisher's exact test with a Bonferroni correction for multiple testing was used. We found that: (i) XPC C/A (i11) heterozygous variant is associated with increased risk of CRC [OR is 2.07 (95% CI 1.1391, 3.7782) P=0.038], (ii) XPD A18911C (Lys751Gln) is associated with decreased risk of CRC [OR=0.4497, (95% CI 0.2215, 0.9131) P=0.031] for an individual with at least one A allele at this locus. (1) The XPC C/A (i11) genotype is associated with an increased risk of sporadic colorectal cancer. (2) The NER pathway has been highlighted in our study, as a most important in modulation of individual susceptibility to sCRC.

The C/A polymorphism in intron 11 of the XPC gene plays a crucial role in the modulation of an individual's susceptibility to sporadic colorectal cancer

Epidemiological data show that colorectal cancer (CRC) is the second most frequent malignancy worldwide. The involvement of "minor impact genes" such as XME and DNA-repair genes in the etiology of sporadic cancer has been postulated by other authors. We focused on analyzing polymorphisms in DNA-repair genes in CRC. We considered the following genes involved in DNA-repair pathways: base excision repair (OGG1 Ser326Cys, XRCC1 Trp194Arg and Arg399Gln); nucleotide excision repair [XPA (-4)G/A, XPC C/A (i11) and A33512C (Lys939Gln), XPD Asp312Asn and A18911C (Lys751Gln), XPF Arg415Gln, XPG Asp1104His, ERCC1 C118T]; homologous recombination repair [NBS1 Glu185Gln, Rad51 135G/C, XRCC3 C18067 (Thr241Met)]. The study group consisted of 133 patients diagnosed with sporadic CRC, while the control group was composed of 100 age-matched non-cancer volunteers. Genotyping was performed by PCR and PCR-RFLP. Fisher's exact test with a Bonferroni correction for multiple testing was used. We found that: (i) XPC C/A (i11) heterozygous variant is associated with increased risk of CRC [OR is 2.07 (95% CI 1.1391, 3.7782) P=0.038], (ii) XPD A18911C (Lys751Gln) is associated with decreased risk of CRC [OR=0.4497, (95% CI 0.2215, 0.9131) P=0.031] for an individual with at least one A allele at this locus. (1) The XPC C/A (i11) genotype is associated with an increased risk of sporadic colorectal cancer. (2) The NER pathway has been highlighted in our study, as a most important in modulation of individual susceptibility to sCRC.