Polymorphic DNA repair and metabolic genes: a multigenic study on gastric cancer

Independent and Interactive Effect of CYPs and GSTs Genetic Variants and Tobacco Smoking on the Risk of Non-Small Cell Lung Carcinoma

BACKGROUND

CYP and GST gene families detoxify tobacco carcinogens and have been linked to the risk of non-small cell lung carcinoma (NSCLC).

AIM

Independent and combined effects of CYP and GST genetic variations and smoking on the risk of non-small cell lung carcinoma (NSCLC) and its sub-histological types.

METHODS

We modelled an epistatic interaction via the effects of particular genotypes in two genes as OR (odds ratio), OR1, and OR2, a combination of both genotypes were characterized as OR_combine. In contrast, the two ORs' epistatic interaction for the individual genotypes has been represented as OR_interaction = OR_combine/(OR1 × OR2).

RESULTS

The variant genotypes of CYP2A6 (OR:4.2, p <0.001), GSTT1 (OR:3.9, p <0.001), and GSTM1 (OR: 4.5, p <0.001) were showed a significant risk with NSCLC. GSTM1 (del.)/CYP2A6 (variant) genotype was associated with a higher risk of NSCLC (OR:12.5, p <0.001). GSTM1 (del.)/CYP2A6 (Ser/Pro+Pro/Pro) and GSTM1 (del.)/CYP2A13 (CT+TT) interacted redundantly (OR_intraction = 0.66 and 0.64). A co-suppressive interaction was observed between GSTT1 (del.)/CYP2A6 (Ser/Pro+Pro/Pro) (OR_intraction = 0.41). Simultaneously, both GSTT1/GSTM1 del. genotype was associated with a significantly higher risk to NSCLC. In contrast, GSTT1 del./GSTM1 del. genotype interaction displayed a co-suppressive effect (OR_intraction = 0.15). CYP1A1(TC+CC)/CYP2A13(CT+TT)mutually interacted synergistically (OR_intraction = 1.27).CYP1A1 (TC+CC)/GSTP1 (Val/Val+Ile/Val) genotype demonstrated an additive (OR_intraction = 1) effect. GSTP1(Val/Val+Ile/Val) interacts with GSTT1 (del.) genotype exerted a suppressive effect (OR_intraction = 0.69). CYP2A6 in smokers increased risk by 4.2 (p = 0.001) to 5.6 fold (p <0.001), while GSTM1 and GSTT1 were independent of smoking.

CONCLUSION

Epistatic interactions revealed that CYPs/GSTs might follow a web of the interactions to modify the risk of NSCLC.

Clinicopathological features and differential diagnosis of gastrofibromatosis-like undifferentiated carcinoma

Objective

To study the clinicopathological features and differential diagnosis of gastrofibromatosis-like undifferentiated carcinoma (GFLUC).

Methods

Three patients with GFLUC underwent histological and immunophenotypic analyses and fluorescence in situ hybridization to detect human epidermal growth factor receptor (HER2) gene amplification.

Results

Among the three patients (2 male [36 and 44 years old], 1 female [58 years old]), two had lesions in the gastric body and one had lesions in the gastric antrum. Histological analysis revealed mixtures of aggressive fibromatosis and undifferentiated carcinoma in all three cases. Highly invasive fibromatous tissue, consisting of fibroblasts, proliferating myofibroblasts, and collagenous fibrous tissues, accounted for >90% of the tumor, with undifferentiated cancerous tissue accounting for <10% scattered in the gaps within the invasive fibromatous tissue, with no glandular ducts or nests. Immunophenotypic analysis showed that the undifferentiated cancerous cells were positive for pan-cytokeratin, CDX2, villin, and p53, while the cytoplasm of invasive fibromatous cells was positive for vimentin, β-catenin, and smooth muscle actin. No HER2 gene amplification was detected.

Conclusions

Unlike other gastric carcinomas, GFLUC shows specific histological, biological, and immunophenotypic characteristics.

XPD Polymorphisms and Risk of Hepatocellular Carcinoma and Gastric Cancer: A Meta-Analysis

Background:

Cancer is associated with genetic variants of DNA repair genes that alter DNA repair capacity. The aim of this meta-analysis was to evaluate the relations between the rs13181 and rs1799793 XPD gene polymorphisms and risk for hepatocellular carcinoma (HCC) and gastric cancer.

Methods:

Relevant publications were systematically sought from Web of Science, Pubmed, and China Academic Journals Full-text Database. The selection of eligible studies was performed by 2 independent authors. A total of 32 case-control studies were included. Meta-analyses were undertaken in all study participants and each ethnic group.

Results:

The risk of HCC was significantly increased with the XPD rs13181 G allele (P = 0.028, pooled odds ratio (OR) = 1.36, 95% confidence interval (CI) = 1.03-1.80) in all study participants. A subgroup analysis by ethnicity showed that the association was significant in Chinese (P = 0.009, pooled OR = 1.49, 95% CI = 1.11-2.02), but not in Caucasians (P = 0.619, pooled OR = 1.17, 95% CI = 0.64-2.13). Meta-analysis of the XPD rs1799793 polymorphism and HCC showed an association between its variant T allele and increased HCC risk in all study participants (P = 0.017, pooled OR = 1.23, 95% CI = 1.04-1.46, all Chinese). Our results showed no associations between the XPD rs13181 G allele and rs1799793 T allele and gastric cancer risk (rs13181: P = 0.298, pooled OR = 1.10, 95% CI = 0.92-1.31; rs1799793: P = 0.068, pooled OR = 1.31, 95% CI = 0.98-1.74).

Conclusions:

This meta-analysis demonstrated that the XPD rs13181 G allele and rs1799793 T allele have significant associations with HCC and may be risk factors for HCC in the Chinese population. Current evidence indicated that they are not related to gastric 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.

Association of human XPA rs1800975 polymorphism and cancer susceptibility: an integrative analysis of 71 case-control studies

BACKGROUND

The objective of the present study is to comprehensively evaluate the impact of the rs1800975 A/G polymorphism within the human xeroderma pigmentosum group A (XPA) gene on susceptibility to overall cancer by performing an integrative analysis of the current evidence.

METHODS

We retrieved possible relevant publications from a total of six electronic databases (updated to April 2020) and selected eligible case-control studies for pooled assessment. P-values of association and odds ratio (OR) were calculated for the assessment of association effect. We also performed Begg's test and Egger's test, sensitivity analysis, false-positive report probability (FPRP) analysis, trial sequential analysis (TSA), and expression/splicing quantitative trait loci (eQTL/sQTL) analyses.

RESULTS

In total, 71 case-control studies with 19,257 cases and 30,208 controls from 52 publications were included for pooling analysis. We observed an enhanced overall cancer susceptibility in cancer cases compared with negative controls in the Caucasian subgroup analysis for the genetic models of allelic G vs. A, carrier G vs. A, homozygotic GG vs AA, heterozygotic AG vs. AA, dominant AG + GG vs. AA and recessive GG vs. AA + AG (P < 0.05, OR > 1). A similar positive conclusion was also detected in the "skin cancer" or "skin basal cell carcinoma (BCC)" subgroup analysis of the Caucasian population. Our FPRP analysis and TSA results further confirmed the robustness of the conclusion. However, our eQTL/sQTL data did not support the strong links of rs1800975 with the gene expression or splicing changes of XPA in the skin tissue. In addition, even though we observed a decreased risk of lung cancer under the homozygotic, heterozygotic and dominant models (P < 0.05, OR < 1) and an enhanced risk of colorectal cancer under the allelic, homozygotic, heterozygotic, dominant (P < 0.05, OR > 1), our data from FPRP analysis and another pooling analysis with only the population-based controls in the Caucasian population did not support the strong links between the XPA rs1800975 A/G polymorphism and the risk of lung or colorectal cancer.

CONCLUSIONS

Our findings provide evidence of the close relationship between the XPA rs1800975 A/G polymorphism and susceptibility to skin cancer in the Caucasian population. The potential effect of XPA rs1800975 on the risk of developing lung or colorectal cancer still merits the enrollment of larger well-scaled studies.

The potential role of MGMT rs12917 polymorphism in cancer risk: an updated pooling analysis with 21010 cases and 34018 controls

In the present study, we aimed at determining the potential role of rs12917 polymorphism of the O-6-methylguanine-DNA methyltransferase (MGMT) gene in the occurrence of cancer. Based on the available data from the online database, we performed an updated meta-analysis. We retrieved 537 articles from our database research and finally selected a total of 54 case–control studies (21010 cases and 34018 controls) for a series of pooling analyses. We observed an enhanced risk in cancer cases compared with controls, using the genetic models T/T compared with C/C (P-value of association test <0.001; odds ratio (OR) = 1.29) and T/T compared with C/C+C/T (P<0.001; OR = 1.32). We detected similar positive results in the subgroups ‘Caucasian’, and ‘glioma’ (all P<0.05; OR > 1). However, we detected negative results in our analyses of most of the other subgroups (P>0.05). Begg’s and Egger’s tests indicated that the results were free of potential publication bias, and sensitivity analysis suggested the stability of the pooling results. In summary, the T/T genotype of MGMT rs12917 is likely to be linked to an enhanced susceptibility to cancer overall, especially glioma, in the Caucasian population.

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.

Relevance of DNA repair gene polymorphisms to gastric cancer risk and phenotype

Variations in DNA repair genes have been reported as key factors in gastric cancer (GC) susceptibility but results among studies are inconsistent. We aimed to assess the relevance of DNA repair gene polymorphisms and environmental factors to GC risk and phenotype in a Caucasian population in Spain. Genomic DNA from 603 patients with primary GC and 603 healthy controls was typed for 123 single nucleotide polymorphisms in DNA repair genes using the Illumina platform. Helicobacter pylori infection with CagA strains (odds ratio (OR): 1.99; 95% confidence interval (CI): 1.55–2.54), tobacco smoking (OR: 1.77; 95% CI: 1.22–2.57), and family history of GC (OR: 2.87; 95% CI: 1.85–4.45) were identified as independent risk factors for GC. By contrast, the TP53 rs9894946A (OR: 0.73; 95% CI: 0.56–0.96), TP53 rs1042522C (OR: 0.76; 95% CI: 0.56–0.96), and BRIP1 rs4986764T (OR: 0.55; 95% CI: 0.38–0.78) variants were associated with lower GC risk. Significant associations with specific anatomopathological GC subtypes were also observed, most notably in the ERCC4 gene with the rs1799801C, rs2238463G, and rs3136038T variants being inversely associated with cardia GC risk. Moreover, the XRCC3 rs861528 allele A was significantly increased in the patient subgroup with diffuse GC (OR: 1.75; 95% CI: 1.30–2.37). Our data show that specific TP53, BRIP1, ERCC4, and XRCC3 polymorphisms are relevant in susceptibility to GC risk and specific subtypes in Caucasians.

Association between hOGG1 polymorphism rs1052133 and gastric cancer

Purpose

To conduct a comprehensive evaluation of the association of the human8-oxoguanine glycosylase 1 (hOGG1) gene polymorphism rs1052133 with gastric cancer (GC) through a systematic review and meta-analysis of genetic association study.

Results

A total of 15 articles from published papers were included in our analysis. The meta-analyses for hOGG1 rs1052133, composed of 4024GC patients and 6022controls, showed low heterogeneity for the included populations in all the genetic models, except for the Caucasian population under allelic genetic model, the Asian population under addictive model and Caucasian population under dominant model. The analyses of all the genetic models in overall pooled populations did not identify any significant association between GC and hOGG1 rs1052133 (Allelic model: C vs. G, p = 0.746; Addictive model: CC vs. GG, p = 0.888; Recessive model: CC +GC vs. GG, p = 0.628; Dominant model: CC vs. GG+GC, p = 0.147), even though stratified analyses were conducted in different ethnicities under each genetic model.

Materials and Methods

All case-control association studies on hOGG1 and GC reported up to December 15, 2016 in PubMed, Embase, Web of Science, and the Chinese Biomedical Database were retrieved. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for single-nucleotide polymorphism (SNP) using fixed- and random- effects models according to between-study heterogeneity. Publication bias analyses were conducted using Begg test.

Conclusions

This meta-analysis showed there was no association between hOGG1 rs1052133 and GC. Given the limited sample size, further investigations including more ethnic groups are required to validate the association.

Gene-gene interactions in gastrointestinal cancer susceptibility

Cancer arises from complex, multi-layer interactions between diverse genetic and environmental factors. Genetic studies have identified multiple loci associated with tumor susceptibility. However, little is known about how germline polymorphisms interact with one another and with somatic mutations within a tumor to mediate acquisition of cancer traits. Here, we survey recent studies showing gene-gene interactions, also known as epistases, affecting genetic susceptibility in colorectal, gastric and esophageal cancers. We also catalog epistasis types and cancer hallmarks with respect to the interacting genes. A total of 22 gene variation pairs displayed all levels of statistical epistasis, including synergistic, redundant, suppressive and co-suppressive interactions. Five genes primarily involved in base excision repair formed a linear topology in the interaction network, MUTYH-OGG1-XRCC1-PARP1-MMP2, and three genes in mTOR cell-proliferation pathway formed another linear network, PRKAG2-RPS6KB1-PIK3CA. Discrete pairwise epistasis was also found in nucleotide excision repair, detoxification, proliferation, TP53, TGF-β and other pathways. We propose that three modes of biological interaction underlie the molecular mechanisms for statistical epistasis. The direct binding, linear pathway and convergence modes can exhibit any level of statistical epistasis in susceptibility to gastrointestinal cancers, and this is likely true for other complex diseases as well. This review highlights the link between cancer hallmarks and susceptibility genes.

Impact of SNP-SNP interactions of DNA repair gene ERCC5 and metabolic gene GSTP1 on gastric cancer/atrophic gastritis risk in a Chinese population

AIM

To investigate the interactions of the DNA repair gene excision repair cross complementing group 5 (ERCC5) and the metabolic gene glutathione S-transferase pi 1 (GSTP1) and their effects on atrophic gastritis (AG) and gastric cancer (GC) risk.

METHODS

Seven ERCC5 single nucleotide polymorphisms (SNPs) (rs1047768, rs2094258, rs2228959, rs4150291, rs4150383, rs751402, and rs873601) and GSTP1 SNP rs1695 were detected using the Sequenom MassARRAY platform in 450 GC patients, 634 AG cases, and 621 healthy control subjects in a Chinese population.

RESULTS

Two pairwise combinations (ERCC5 rs2094258 and rs873601 with GSTP1 rs1695) influenced AG risk (P_interaction = 0.008 and 0.043, respectively), and the ERCC5 rs2094258-GSTP1 rs1695 SNP pair demonstrated an antagonistic effect, while ERCC5 rs873601-GSTP1 rs1695 showed a synergistic effect on AG risk OR = 0.51 and 1.79, respectively). No pairwise combinations were observed in relation to GC risk. There were no cumulative effects among the pairwise interactions (ERCC5 rs2094258 and rs873601 with GSTP1 rs1695) on AG susceptibility (P_trend > 0.05). When the modification effect of Helicobacter pylori (H. pylori) infection was evaluated, the cumulative effect of one of the aforementioned pairwise interactions (ERCC5 rs873601-GSTP1 rs1695) was associated with an increased AG risk in the case of negative H. pylori status (P_trend = 0.043).

CONCLUSION

There is a multifarious interaction between the DNA repair gene ERCC5 SNPs (rs2094258 and rs873601) and the metabolic gene GSTP1 rs1695, which may form the basis for various inter-individual susceptibilities to AG.

Genetic variants in the nucleotide excision repair pathway genes and gastric cancer susceptibility in a southern Chinese population

BACKGROUND

Potentially functional polymorphisms can modulate protein activities and host's DNA repair capacity, thereby influencing cancer susceptibility. The association of the polymorphisms in the nucleotide excision repair core pathway genes and gastric cancer susceptibility remains largely unknown.

METHODS

Here, we systematically analyzed the associations between nine polymorphisms in four key genes (XPA, ERCC1, ERCC2, and ERCC4) in the nucleotide excision repair pathway and gastric cancer risk in a Chinese population including 1142 patients and 1173 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the risk associations.

RESULTS

We observed that ERCC1 rs2298881 CA variant genotype was associated with an increased gastric cancer risk (CA vs. CC: adjusted OR [AOR]=1.33, 95% CI=1.09-1.62; dominant model: AOR=1.32, 95% CI=1.10-1.60). However, ERCC1 rs3212986 AA variant genotype was identified as a protective factor for gastric cancer (AA vs. CC: AOR=0.73, 95% CI=0.54-0.98; recessive model: AOR=0.72, 95% CI=0.54-0.96). Genotype-based mRNA expression analysis further indicated that the rs2298881 A allele was associated with decreased ERCC1 mRNA expression.

CONCLUSION

In all, these results indicated that the ERCC1 polymorphisms may affect the risk of gastric cancer in the Chinese Han population.

GSTT1 and GSTM1 null variants in Mestizo and Amerindian populations from northwestern Mexico and a literature review

The GSTT1 and GSTM1 genes are key molecules in cellular detoxification. Null variants in these genes are associated with increase susceptibility to developing different types of cancers. The aim of this study was to determine the prevalence of GSTT1 and GSTM1 null genotypes in Mestizo and Amerindian individuals from the Northwestern region of Mexico, and to compare them with those reported worldwide. GSTT1 and GSTM1 null variants were genotyped by multiplex PCR in 211 Mestizos and 211 Amerindian individuals. Studies reporting on frequency of GSTT1 and GSTM1 null variants worldwide were identified by a PubMed search and their geographic distribution were analyzed. We found no significant differences in the frequency of the null genotype for GSTT1 and GSM1 genes between Mestizo and Amerindian individuals. Worldwide frequencies of the GSTT1 and GSTM1 null genotypes ranges from 0.10 to 0.51, and from 0.11 to 0.67, respectively. Interestingly, in most countries the frequency of the GSTT1 null genotype is common or frequent (76%), whereas the frequency of the GSMT1 null genotype is very frequent or extremely frequent (86%). Thus, ethnic-dependent differences in the prevalence of GSTT1 and GSTM1 null variants may influence the effect of environmental carcinogens in cancer risk.

Characterization of a low expression haplotype in canine glutathione S-transferase (GSTT1) and its prevalence in golden retrievers

Glutathione S-transferase-theta (GSTT1) is a carcinogen detoxification enzyme, and low activity variants are associated with lymphoma in humans. We recently found a variant in the 3' untranslated region (UTR) of canine GSTT1, *101_102insT, which was predicted to change miRNA binding and was found in 5 of 17 golden retriever (GR) dogs with lymphoma but none of 14 healthy GRs. The aim of this study was to determine whether this variant led to decreased GSTT1 expression and was a discernible risk factor for lymphoma within the GR breed. On resequencing, *101_102insT appeared to be in complete linkage disequilibrium with 3 additional 3'UTR variants, leading to the inferred haplotype *3T>C; *101_102insT; *190C>A; *203T>C. In canine livers that were heterozygous for this variant haplotype, GSTT1 protein expression was significantly lower compared to the reference haplotype (densitometry .40 vs .64, P = .022), and GSTT1 transcript levels by qPCR were also significantly lower (fold difference .52, P = .012), without evidence of substantial allelic expression imbalance. The variant haplotype led to >50% decrease in expression in vitro (.31 ± .07 vs .64 ± .19; P = .019). We found no significant difference in minor allele frequencies between 71 GR dogs with lymphoma (MAF .162) and 33 healthy age-matched controls (MAF .136, P = .69). Our results indicate that the variant GSTT1 3'UTR haplotype containing *101_102insT reduces gene expression, which could lead to impaired carcinogen detoxification, but was not a detectable risk factor for lymphoma in GR dogs.

GENOTYPE ASSOCIATION GSTM1 NULL AND GASTRIC CANCER: EVIDENCE-BASED META-ANALYSIS

BACKGROUND

Gastric cancer is the fourth most common cancer in men and the sixth among women, except for non-melanoma skin tumors, in Brazil. Epidemiological evidences reveal the multifactorial etiology of this cancer, highlighting risk factors such as: infection by the bacterium Helicobacter pylori, advanced age, smoking, chronic alcohol abuse, eating habits and genetic polymorphisms. Considering the context of genetic polymorphisms, there is the absence of the GSTM1 gene. The lack of GSTM1 function to detoxify xenobiotics and promote defense against oxidative stress leads to increased DNA damage, promoting gastric carcinogenesis. This process is multifactorial and the development of gastric cancer results from a complex interaction of these variables.

OBJECTIVE

The aim of this study was to investigate the association of GSTM1 null polymorphism in the pathogenesis of gastric cancer.

METHODS

A meta-analysis was conducted from 70 articles collected in SciELO and PubMed databases, between September 2015 and July 2016. In order to evaluate a possible association, we used the odds ratio (OR) and confidence interval of 95% (CI 95%). To assess the heterogeneity of the studies was used the chi-square test. Statistical analysis was performed using the BioEstat® 5.3.

RESULTS

This study included 70 studies of case-control, including 28,549 individuals, which were assessed for the null polymorphism of the GSTM1 gene, and of which 11,208 (39.26%) were cases and 17,341 (60.74%) were controls. The final analysis showed that the presence of the GSTM1 gene acts as a protective factor against the development of gastric cancer (OR=0.788; 95%CI 0.725-0.857; P<0.0001). Positive statistical association was found in Asia (OR=0.736; 95%CI 0.670-0.809; P<0.0001) and Eurasia (OR=0.671; 95%CI 0.456-0.988; P=0.05). However, statistically significant data was not obtained in Europe (OR=1.033; 95%CI 0.873-1.222; P=0.705) and America (OR=0.866; 95%CI 0.549-1.364; P=0.534). Therefore, the results can not be deduced around the world.

CONCLUSION

This meta-analysis concluded that the presence of the GSTM1 gene is a protector for the emergence of gastric cancer, especially in Asian countries, but this result was not found in Europe and America.

Association of nucleotide excision repair pathway gene polymorphisms with gastric cancer and atrophic gastritis risks

Polymorphisms of NER genes could change NER ability, thereby altering individual susceptibility to GC. We systematically analyzed 39 SNPs of 8 key genes of NER pathway in 2686 subjects including 898 gastric cancer (GC), 851 atrophic gastritis (AG) and 937 controls (CON) in northern Chinese. SNP genotyping were performed using Sequenom MassARRAY platform. The results demonstrated that DDB2 rs830083 GG genotype was significantly associated with increased GC risk compared with wildtype CC (OR=2.32, P = 6.62 × 10⁻⁹); XPC rs2607775 CG genotype conferred a 1.73 increased odds of GC risk than non-cancer subjects compared with wild-type CC (OR=1.73, P= 3.04 × 10⁻⁴). The combined detection of these two polymorphisms demonstrated even higher GC risk (OR=3.05). Haplotype analysis suggested that DDB2 rs2029298-rs326222-rs3781619-rs830083 GTAG haplotype was significantly associated with disease risk in each step of CON→AG→GC development (AG vs. CON: OR=2.88, P= 7.51 × 10⁻⁷; GC vs. AG: OR=2.90, P=5.68 × 10⁻¹⁵; GC vs. CON: OR=8.42, P=2.22 × 10⁻¹⁵); DDB2 GTAC haplotype was associated with reduced risk of GC compared with CON (OR=0.63, P= 8.31 × 10⁻¹²). XPC rs1870134-rs2228000- rs2228001-rs2470352-rs2607775 GCAAG haplotype conferred increased risk of GC compared with AG (OR=1.88, P= 6.98 × 10⁻⁴). XPA rs2808668 and drinking, DDB2 rs326222, rs3781619, rs830083 and smoking demonstrated significant interactions in AG; XPC rs2607775 had significant interaction with smoking in GC. In conclusion, NER pathway polymorphisms especially in “damage incision” step were significantly associated with GC risk and had interactions with environment factors. The detection of NER pathway polymorphisms such as DDB2 and XPC might be applied in the prediction of GC risk and personalized prevention in the future.

ERCC1 and XRCC1 but not XPA single nucleotide polymorphisms correlate with response to chemotherapy in endometrial carcinoma

Our study aimed to investigate the correlation between single nucleotide polymorphisms of ERCC1/XRCC1/XPA genes and postoperative chemotherapy efficacy and prognosis of endometrial carcinoma. Our study included 108 patients with endometrial carcinoma and 100 healthy participants. ERCC1 rs11615/XRCC1 rs25487/XPA rs1800975 gene polymorphisms were detected by polymerase chain reaction-restriction fragment length polymorphism. Then the chemotherapy efficacy and toxic effects of the patients were assessed. The genotype and allele frequency of ERCC1 rs11615/XRCC1 rs25487 in the case group were significantly different from that in the control group (all P<0.05). The patients with AA + GA in ERCC1 rs11615 had an increased risk of endometrial carcinoma than those with GG, and the risk of endometrial carcinoma for patients with AA + GA was also higher in comparison with patients with GG genotype in XRCC1 rs25487 (all P<0.05). GG on both ERCC1 rs11615/XRCC1 rs25487 had a higher effective rate of chemotherapy than GA + AA (all P<0.05). ERCC1 rs11615/XRCC1 rs25487 gene polymorphisms were linked with toxic effects in liver, kidney, and nervous system. ERCC1 rs11615/XRCC1 rs25487, muscular invasion, and tumor stage were independent risk factors for the prognosis of endometrial carcinoma (all P<0.05). However, no significant associations were observed between XPA rs1800975 polymorphism and chemotherapy efficacy and prognosis of endometrial carcinoma (all P>0.05). These results indicated that ERCC1 and XRCC1 but not XPA polymorphisms correlate with response to chemotherapy in endometrial carcinoma.

Analysis of DNA Repair Genes Polymorphisms in Breast Cancer

Genetic polymorphisms in the DNA repair genes may be associated with increased cancer risk. The purpose of this study was to evaluate the association of the DNA repair genes polymorphisms with the risk of breast cancer development. The study included 200 breast cancer patients and 200 healthy controls. The following polymorphisms were studied: C/G (Ser326Cys, rs1052133) of the hOGG1, A/C (IVS5 + 33, rs3212961) of the ERCC1, A/C (Lys939Gln, rs2228001) of the XPC, C/T (Thr241Met, rs861539) of the XRCC3, G/T (Leu787Leu, rs1800392) of the WRN and G/T (Ser307Ser, rs1056503) of the XRCC4 gene. Presented study showed statistically significant increase in the breast cancer development risk of the G/G hOGG1 genotype (OR 8.13; 95 % CI, 4.37-15.14; p < 0.001) and for the G hOGG1 allele (OR 5.11; 95 % CI, 3.69-7.06; p < 0.001), as well as for the C/C ERCC1 genotype (OR 10.61; 95 % CI, 5.72-19.69; p < 0.001) and the C ERCC1 allele (OR 4.66; 95 % CI, 3.43-6.34; p < 0.001) in patients with breast cancer in comparison with healthy control group. We also observed positive association of the C/C XPC genotype (OR 3.80; 95 % CI, 2.27-6.38; p < 0.001) as well as the C XPC allele occurrence with an increased breast cancer development risk (OR 2.65; 95 % CI, 1.98-3.55; p < 0.001). Furthermore, we found an association of the G/T WRN gene polymorphism with increased risk of carcinoma. The hOGG1, ERCC1, XPC and WRN genes polymorphisms may be related to development of breast cancer.

Single nucleotide polymorphisms in DNA repair genes and putative cancer risk

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

Interaction between Helicobacter pylori and host genetic variants in gastric carcinogenesis

Helicobacter pylori (H. pylori) is the definite carcinogen of gastric cancer. H. pylori infection induces chronic inflammation, causes DNA damage and aberrant methylation of genes and these pathways are involved in H. pylori-related gastric carcinogenesis. Polymorphisms of the genes involved in these pathways could alter susceptibility to gastric cancer. In this mini review, we focused on the role of polymorphisms in these genes on the susceptibility to gastric cancer, with a particular emphasis on their possible interactions with H. pylori infection. We found that many studies on this theme did not simultaneously report H. pylori infection and the interactions remained inconclusive.

Association between OGG1 Ser326Cys polymorphism and risk of upper aero-digestive tract and gastrointestinal cancers: a meta-analysis

Cancers of the upper aero-digestive and gastrointestinal tract are one of the major causes of mortality around the world. DNA repair genes play a vital role in preventing carcinogenesis by maintaining genomic integrity. Polymorphisms in the nucleotide sequence of DNA repair genes are often reported to be associated with an increased risk for different cancers. The OGG1 gene encodes the enzyme 8-oxoguanine DNA glycosylase which removes oxidatively damaged bases of DNA. Several studies report that the OGG1 Ser326Cys polymorphism increases the risk for cancers of the upper aero-digestive and gastrointestinal tract. However, other studies provide evidence that such an association does not exist. A meta-analysis to assess the role of OGG1 Ser326Cys polymorphism in the cancers of the upper aero-digestive and gastrointestinal tract was therefore undertaken in order to resolve this ambiguity. Seventeen studies were recruited for this meta-analysis after screening 58 articles with a total of 5533 cases and 6834 controls for which the odds ratio with 95 % confidence interval was calculated. Begg’s funnel test and Egger’s test were performed for calculating publication bias. Our study reveals an association between OGG1 Ser326Cys polymorphism and cancer susceptibility of the upper aero-digestive and gastrointestinal tract (CG + GG vs CC; odds ratio, OR 1.22; 95 % CI 1.05–1.41; GG vs CG + CC; OR 1.36; 95 % CI 1.09–1.70; GG vs CC; OR 1.46; 95 % CI 1.12–1.92). Subgroup analysis based on cancer types and ethnicity also revealed the association of OGG1 Ser326Cys polymorphism to the risk for upper aero-digestive and gastrointestinal tract cancers among both the Asian and the Caucasian populations. No risk was however observed for smoking habits and OGG1 Ser326Cys polymorphism. In conclusion, OGG1 Ser326Cys polymorphism may be associated with the increased risk for aero-digestive tract and gastro-intestinal cancers in both Asian and Caucasian populations.

Potential risk of esophageal squamous cell carcinoma due to nucleotide excision repair XPA and XPC gene variants and their interaction among themselves and with environmental factors

The association of nucleotide excision repair (NER) gene polymorphisms with esophageal squamous cell carcinoma (ESCC) is inconclusive. The aim of the current study was to assess the association of repair gene xeroderma pigmentosum A (XPA) (rs-1800975) and xeroderma pigmentosum C (XPC) (rs-2228000) polymorphisms with ESCC risk as well as modifying effects of environmental factors. The genotyping was done in 450 confirmed ESCC cases and equal number of individually matched controls by the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) and direct sequencing methods. Conditional logistic regression models were used to assess the genotypic associations and interactions. A high ESCC risk was found in subjects who carried the homozygous minor allele of XPA (odds ratio (OR) = 3.57; 95 % confidence interval (CI) = 1.76-7.23), and the risk was higher when analysis was limited to participants who were ever smokers (OR = 4.22; 95 % CI = 2.01-8.88), lived in adobe houses (OR = 8.42; 95 % CI = 3.74-18.95), consumed large volumes of salt tea (OR = 7.42; 95 % CI = 3.30-16.69), or had a positive family history of cancer (FHC) (OR = 9.47; 95 % CI = 4.67-19.20). In case of XPC, a homozygous minor allele also showed strong association with ESCC risk (OR = 4.43; 95 % CI = 2.41-8.16). We again observed a very strong effect of the above environmental factors in elevating the risk of ESCC. Further, the variant genotypes of both genes in combination showed an increased risk towards ESCC (OR = 7.01; 95 % CI = 3.14-15.64) and such association was synergistically significant. Salt tea consumption showed an interaction with genotypes of XPA and XPC. However, an interaction with FHC was significant in the case of XPA genotype only. XPA and XPC genotypes are associated with an increased risk of ESCC, and such association was reasonably modulated by different exposures.

Helicobacter pylori infection and gastric carcinoma: Not all the strains and patients are alike

Gastric carcinoma (GC) develops in only 1%-3% of Helicobacter pylori (H. pylori) infected people. The role in GC formation of the bacterial genotypes, gene polymorphisms and host's factors may therefore be important. The risk of GC is enhanced when individuals are infected by strains expressing the oncoprotein CagA, in particular if CagA has a high number of repeats containing the EPIYA sequence in its C'-terminal variable region or particular amino acid sequences flank the EPIYA motifs. H. pylori infection triggers an inflammatory response characterised by an increased secretion of some chemokines by immunocytes and colonised gastric epithelial cells; these molecules are especially constituted by proteins composing the interleukin-1beta (IL-1β) group and tumour necrosis factor-alpha (TNF-α). Polymorphisms in the promoter regions of genes encoding these molecules, could account for high concentrations of IL-1β and TNF-α in the gastric mucosa, which may cause hypochlorhydria and eventually GC. Inconsistent results have been attained with other haplotypes of inflammatory and anti-inflammatory cytokines. Genomic mechanisms of GC development are mainly based on chromosomal or microsatellite instability (MSI) and deregulation of signalling transduction pathways. H. pylori infection may induce DNA instability and breaks of double-strand DNA in gastric mucocytes. Different H. pylori strains seem to differently increase the risk of cancer development run by the host. Certain H. pylori genotypes (such as the cagA positive) induce high degrees of chronic inflammation and determine an increase of mutagenesis rate, oxidative-stress, mismatch repair mechanisms, down-regulation of base excision and genetic instability, as well as generation of reactive oxygen species that modulate apoptosis; these phenomena may end to trigger or concur to GC development.

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.

Association of APE1 Gene Asp148Glu Variant with Digestive Cancer: A Meta-Analysis

Background

Apurinic/apyrimidinic endonuclease-1 (APE1) is a rate-limiting enzyme in DNA base excision repair and has been implicated in carcinogenesis. In this study, we summarize available data to examine the susceptibility of APE1 gene Asp148Glu variant to digestive cancer via a meta-analysis.

Material/Methods

Study selection and data abstraction were conducted independently by 2 authors. Random-effects model was utilized to pool effect estimates. Heterogeneity and publication bias were addressed.

Results

Sixteen articles involving 4916 digestive cancer patients and 7748 controls were qualified for this meta-analysis. Overall association showed an indicative association between Asp148Glu variant and digestive cancer under allelic (odds ratio or OR=1.11; 95% confidence interval or CI: 0.99–1.25; P=0.074) and dominant (OR=1.18; 95% CI: 1.00–1.40; P=0.056) models, with strong evidence of heterogeneity. Deviation from Hardy-Weinberg equilibrium was an obvious source of heterogeneity. In subgroup analyses by cancer sites, this variant was significantly associated with the increased risk for hepatocellular cancer under allelic (OR=1.50; 95% CI: 1.25–1.80; P<0.001) and homozygous genotypic (OR=1.55; 95% CI: 1.02–2.29; P=0.028) models. There were low probabilities of publication bias for the above comparisons.

Conclusions

The results of this meta-analysis collectively suggest that APE1 gene Asp148Glu variant is not a risk-conferring factor for digestive cancer. Further large and well-designed studies are required.

Effect of ERCC8 tagSNPs and their association with H. pylori infection, smoking, and alcohol consumption on gastric cancer and atrophic gastritis risk

Excision repair cross-complementing group 8 (ERCC8) plays a critical role in DNA repair. Genetic polymorphisms in ERCC8 may contribute to the risk of cancer development. We selected tag single nucleotide polymorphisms (tagSNPs) in Chinese patients from the HapMap database to investigate associations with gastric cancer and its precursors. Genomic DNA was extracted from 394 controls, 394 atrophic gastritis, and 394 gastric cancer cases in northern Chinese patients, and genotypes were identified using the Sequenom MassARRAY system. We found that the ERCC8 rs158572 GG+GA genotype showed a 1.651-fold (95 % confidence interval (CI) = 1.109-2.457, P = 0.013) increased risk of gastric cancer compared with the AA genotype, especially in diffuse type. Stratified analysis comparing the common genotype revealed significantly increased gastric cancer risk in males and individuals older than 50 years with rs158572 GA/GG/GG+GA genotypes, while individuals older than 50 years with rs158916 CT/CC+CT genotypes were less susceptible to atrophic gastritis. Haplotype analysis showed that the G-T haplotype was associated with increased risk of gastric cancer. Statistically significant interactions between the two ERCC8 tagSNPs and Helicobacter pylori infection were observed for gastric cancer and atrophic gastritis risk (P < 0.05). Smokers and drinkers with ERCC8 rs158572 GG+GA genotype were more susceptible to gastric cancer compared with non-smokers and non-drinkers homozygous for AA. Our findings suggested that ERCC8 rs158572 and rs158916, alone or together with environmental factors, might be associated with gastric cancer and atrophic gastritis susceptibility. Further validation of our results in larger populations along with additional studies evaluating the underlying molecular function is required.

Relationship between apurinic endonuclease 1 Asp148Glu polymorphism and gastrointestinal cancer risk: An updated meta-analysis

AIM: To evaluate the relationship between apurinic endonuclease 1 (APE1) Asp148Glu polymorphism and the susceptibility to gastrointestinal (GI) cancers.

METHODS: We searched PubMed, ISI Web of Knowledge, and Chinese National Knowledge Infrastructure (CNKI) databases updated on July 15, 2014 for relevant studies. Only case-control studies comparing APE1 Asp148Glu polymorphism and GI cancer risk were included. We excluded studies reporting only standardized incidence ratios without control groups and those without detailed genotyping data. Meta-analysis was performed on 17 studies involving 4856 cancer patients and 6136 cancer-free controls. Review Manager version 5.1 was used to perform the meta-analysis. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated under the allele contrast, homozygous, heterozygous, dominant and recessive genetic models. We also conducted subgroup analyses stratified by ethnicity and cancer type. Publication bias was evaluated using Begg’s test.

RESULTS: The meta-analysis showed a significant association between APE1 Asp148Glu polymorphism and GI cancer risk in three genetic models in the overall population (G vs T: OR = 1.18; 95%CI: 1.05-1.32; TG vs TT: OR = 1.28; 95%CI: 1.08-1.52; TG + GG vs TT: OR = 1.32; 95%CI: 1.10-1.57). Stratified analysis by ethnicity revealed a statistically increased GI cancer risk in Asians (G vs T: OR = 1.27; 95%CI: 1.07-1.51; GG vs TT: OR = 1.58; 95%CI: 1.05-2.38; TG vs TT: OR = 1.30; 95%CI, 1.01- 1.67; and TG + GG vs TT: OR = 1.38; 95%CI: 1.07-1.78), but not in Caucasians. Further subgroup analysis by cancer type indicated that APE1 Asp148Glu polymorphism may contribute to gastric cancer risk. However, Asp148Glu has no significant association with colorectal or esophageal cancer risk in any genetic model.

CONCLUSION: This meta-analysis suggests that the APE1 Asp148Glu polymorphism G allele is associated with an increased GI cancer risk, especially in gastric cancer.

Complement receptor 1 genetic variants contribute to the susceptibility to gastric cancer in chinese population

As the receptor for C3b/C4b, type 1 complement receptor (CR1/CD35) plays an important role in the regulation of complement activity and is further involved in carcinogenesis. This study aimed to elucidate the association of CR1 genetic variants with the susceptibility to gastric cancer in Chinese population. Based on the NCBI database, totally 13 tag single nucleotide polymorphisms (SNPs) were selected by Haploview program and genotyped using iPlex Gold Genotyping Assay and Sequenom MassArray among 500 gastric cancer cases and 500 healthy controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression to evaluate the association of each SNP with gastric cancer. Of all selected Tag SNPs , CR1 rs9429942 T > C was found to confer to the risk of developing gastric cancer. Compared with the carriers with rs9429942 TT genotype, those with CT genotype had 88% decreased risk of developing gastric cancer with OR (95%CI) of 0.12 (0.03-0.50). Generalized multifactor dimensionality reduction (GMDR) analysis revealed a significant three-way interaction among rs75422544 C > A, rs10494885 C > T and rs7525160 G > C in the development of gastric cancer with a maximum testing balance accuracy of 56.07% and a cross-validation consistency of 7/10 (P = 0.011). In conclusion, our findings demonstrated the genetic role of CR1 gene in the development of gastric cancer in Chinese population.

Technical reproducibility of single-nucleotide and size-based DNA biomarker assessment using DNA extracted from formalin-fixed, paraffin-embedded tissues

DNA extracted from formalin-fixed, paraffin-embedded (FFPE) tissues has been used in the past to analyze genetic polymorphisms. We evaluated the technical reproducibility of different types of assays for gene polymorphisms using DNA extracted from FFPE material. By using the MassARRAY iPLEX system, we investigated polymorphisms in DPYD (rs1801159 and rs3918290), UMPS (rs1801019), ERCC1 (rs11615), ERCC1 (rs3212986), and ERCC2 (rs13181) in 56 FFPE DNA samples. By using PCR, followed by size-based gel electrophoresis, we also examined TYMS 5' untranslated region 2R/3R repeats and GSTT1 deletions in 50 FFPE DNA samples and 34 DNAs extracted from fresh-frozen tissues and cell lines. Each polymorphism was analyzed by two independent runs. We found that iPLEX biomarker assays measuring single-nucleotide polymorphisms provided consistent concordant results. However, by using FFPE DNA, size-based PCR biomarkers (GSTT1 and TYMS 5' untranslated region) were discrepant in 32.7% (16/49, with exact 95% CI, 19.9%-47.5%; exact binomial confidence limit test) and 4.2% (2/48, with exact 95% CI, 0.5%-14.3%) of cases, respectively, whereas no discrepancies were observed using intact genomic DNA. Our findings suggest that DNA from FFPE material can be used to reliably test single-nucleotide polymorphisms. However, results based on size-based PCR biomarkers, and particularly GSTT1 deletions, using FFPE DNA need to be interpreted with caution. Independent repeated assays should be performed on all cases to assess potential discrepancies.

XPA A23G polymorphism and risk of digestive system cancers: a meta-analysis

Background

Several studies have reported an association between the A23G polymorphism (rs 1800975) in the xeroderma pigmentosum group A (XPA) gene and risk of digestive system cancers. However, the results are inconsistent. In this study, we performed a meta-analysis to assess the association between XPA A23G polymorphism and the risk of digestive system cancers.

Methods

Relevant studies were identified using the PubMed, Web of Science, China National Knowledge Infrastructure, WanFang, and VIP databases up to August 30, 2014. The pooled odds ratio (OR) with a 95% confidence interval (CI) was calculated using the fixed or random effects model.

Results

A total of 18 case-control studies from 16 publications with 4,170 patients and 6,929 controls were included. Overall, no significant association was found between XPA A23G polymorphism and the risk of digestive system cancers (dominant model: GA + AA versus GG, OR 0.89, 95% CI 0.74–1.08; recessive model: AA versus GA + GG, OR 0.94, 95% CI 0.74–1.20; GA versus GG, OR 0.89, 95% CI 0.77–1.03; and AA versus GG, OR 0.87, 95% CI 0.64–1.19). When the analysis was stratified by ethnicity, similar results were observed among Asians and Caucasians in all genetic models. In stratified analysis based on tumor type, we also failed to detect any association between XPA A23G polymorphism and the risk of esophageal, gastric, or colorectal cancers.

Conclusion

This meta-analysis indicates that the XPA A23G polymorphism is not associated with a risk of digestive system cancers.

Glutathione S-transferase gene GSTM1, gene-gene interaction, and gastric cancer susceptibility: evidence from an updated meta-analysis

Background

The null genotype of GSTM1 have been implicated in gastric cancer risk, but numerous individual studies showed mixed, or even conflicting results. Thus, a meta-analysis was performed.

Results

We identified 54 individual studies involving 9,322 cases and 15,118 controls through computer-based searches of PubMed, Embase, and Cochrane Library. It was found that the null genotype of GSTM1 was associated with an increased gastric cancer risk (OR = 1.207, 95% CI: 1.106-1.317, P < 0.001), under the random-effects model (I² : 49.9%, P_Q <0.001). From stratification analyses for ethnicity, alcohol drinking, Helicobacter pylori infection, an effect modification of gastric cancer risk was found in the subgroups of ethnicity, smoking status, Helicobacter pylori infection, whereas null result was found in the subgroups of alcohol drinking. We also undertook gene-gene interaction analysis between GSTM1 and GSTT1 genes for gastric cancer risk, and the results indicated that the dual null genotypes of GSTM1 and GSTT1 might elevate the risk of gastric cancer (OR = 1.505, 95% CI: 1.165-1.944, P = 002).

Conclusions

This meta-analysis suggests that the null genotype of GSTM1 may be a important genetic risk factor for gastric cancer development.

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 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%).

Glutathione S-transferase M1 null genotype meta-analysis on gastric cancer risk

Background

Glutathione S-transferases (GSTs) have proved to be involved in the detoxifying several carcinogens and may play an important role in carcinogenesis of cancer. Previous studies on the association between Glutathione S-transferase M1 (GSTM1) polymorphism and gastric cancer (GC) risk reported inconclusive results. To get a precise result, we conducted this present meta-analysis through pooling all eligible studies.

Methods

A comprehensive databases of Pubmed, Embase, Web of Science, and the Chinese Biomedical Database (CBM) were searched for case–control studies investigating the association between GSTM1 null genotype and GC risk. Odds ratios (OR) and 95% confidence intervals (95% CI) were used to assess this possible association. A χ2-based Q-test was used to examine the heterogeneity assumption. Begg’s and Egger’s test were used to examine the potential publication bias. The leave-one-out sensitivity analysis was conducted to determine whether our assumptions or decisions have a major effect on the results of present work. Statistical analyses were performed with the software program STATA 12.0.

Results

A total of 47 eligible case–control studies were identified, including 6,678 cases and 12,912 controls. Our analyses suggested that GSTM1 null genotype was significantly associated with increased risk of GC (OR = 1.186, 95% CI = 1.057-1.329, P_{heterogenetiy} = 0.000, P = 0.004). Significant association was also found in Asians (OR = 1.269, 95% CI = 1.106-1.455, P_{heterogenetiy} = 0.002, P = 0.001). However, GSTM1 null genotype was not contributed to GC risk in Caucasians (OR = 1.115, 95% CI = 0.937-1.326, P_{heterogenetiy} = 0.000, P = 0.222). In the subgroup analysis stratified by sources of controls, significant association was detected in hospital-based studies (OR = 1.355, 95% CI = 1.179-1.557, P_{heterogenetiy} = 0.001, P = 0.000), while there was no significant association detected in population-based studies (OR = 1.017, 95% CI = 0.862-1.200, P_{heterogenetiy} = 0.000, P = 0.840).

Conclusion

This meta-analysis showed the evidence that GSTM1 null genotype contributed to the development of GC.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1644180505119533.

Association between TLR2, MTR, MTRR, XPC, TP73, TP53 genetic polymorphisms and gastric cancer: a meta-analysis

OBJECTIVE

The aim of our meta-analyses is to test the association between six genetic polymorphisms and gastric cancer.

METHODS

A systematic search was performed for all the available candidate genes and gastric cancer among several online databases including PubMed, Embase, Web of Science, the Cochrane Library, CNKI and Wanfang online libraries. After a comprehensive screening, a total of six genes were harvested for the current meta-analyses. These genes include TLR2 (-196 to -174 ins>del), MTR (rs1805087), MTRR (rs1801394), XPC (rs2228001), TP73 (G4C14-A4T14), and TP53 (rs1042522).

RESULTS

Altogether 49 comparative studies among 11 776 cases and 18 633 controls were involved in our meta-analyses. TP53 rs1042522 polymorphism was shown to be associated with gastric cancer risk under the dominant model (P=0.02, OR=1.03, 95% CI=1.00-1.05). A subgroup meta-analysis indicated a significant association under dominant model between TP53 rs1042522 and gastric cancer in the Eastern Asians (P=0.03, OR=1.17, 95%=1.02-1.34).

CONCLUSIONS

These results suggest that TP53 rs1042522 polymorphism might contribute to the susceptibility of gastric cancer under the dominant model, especially in Eastern Asians.

Current evidences on XPC polymorphisms and gastric cancer susceptibility: a meta-analysis

Background

Reduced DNA repair capacities due to inherited polymorphisms may increase the susceptibility to cancers including gastric cancer. Previous studies investigating the association between Xeroderma Pigmentosum group C (XPC) gene polymorphisms and gastric cancer risk reported inconsistent results. We performed a meta-analysis to summarize the possible association.

Methods

All studies published up to January 2014 on the association between XPC polymorphisms and gastric cancer risk were identified by searching electronic databases PubMed, EMBASE, Cochrane library, and Chinese Biomedical Literature database (CBM). The association between XPC polymorphisms and gastric cancer risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs).

Results

Six studies with 1,355 gastric cancer cases and 2,573 controls were finally included in the meta-analysis. With respect to Lys939Gln polymorphism, we did not observe a significant association when all studies were pooled into the meta-analysis. When stratified by ethnicity, source of control, and study quality, statistical significant association was not detected in all subgroups. With respect to Ala499Val and PAT−/+polymorphisms, we also did not observe any significant association with gastric cancer risk in the pooled analysis.

Conclusions

This meta-analysis based on current evidences suggested that the XPC polymorphisms (Lys939Gln, Val499Arg, and PAT−/+) did not contribute to gastric cancer risk. Considering the limited sample size and ethnicity included in the meta-analysis, further larger scaled and well-designed studies are needed to confirm our results.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1485880312555069

The effect of XPD polymorphisms on digestive tract cancers risk: a meta-analysis

Background

The Xeroderma pigmento-sum group D gene (XPD) plays a key role in nucleotide excision repair. Single nucleotide polymorphisms (SNP) located in its functional region may alter DNA repair capacity phenotype and cancer risk. Many studies have demonstrated that XPD polymorphisms are significantly associated with digestive tract cancers risk, but the results are inconsistent. We conducted a comprehensive meta-analysis to assess the association between XPD Lys751Gln polymorphism and digestive tract cancers risk. The digestive tract cancers that our study referred to, includes oral cancer, esophageal cancer, gastric cancer and colorectal cancer.

Methods

We searched PubMed and EmBase up to December 31, 2012 to identify eligible studies. A total of 37 case-control studies including 9027 cases and 16072 controls were involved in this meta-analysis. Statistical analyses were performed with Stata software (version 11.0, USA). Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association.

Results

The results showed that XPD Lys751Gln polymorphism was associated with the increased risk of digestive tract cancers (homozygote comparison (GlnGln vs. LysLys): OR = 1.12, 95% CI = 1.01–1.24, P = 0.029, P_{heterogeneity} = 0.133). We found no statistical evidence for a significantly increased digestive tract cancers risk in the other genetic models. In the subgroup analysis, we also found the homozygote comparison increased the susceptibility of Asian population (OR = 1.28, 95% CI = 1.01–1.63, P = 0.045, P_{heterogeneity} = 0.287). Stratified by cancer type and source of control, no significantly increased cancer risk was found in these subgroups. Additionally, risk estimates from hospital-based studies and esophageal studies were heterogeneous.

Conclusions

Our meta-analysis suggested that the XPD 751Gln/Gln genotype was a low-penetrate risk factor for developing digestive tract cancers, especially in Asian populations.

Role of gene polymorphisms in gastric cancer and its precursor lesions: Current knowledge and perspectives in Latin American countries

Latin America shows one of the highest incidence rates of gastric cancer in the world, with variations in mortality rates among nations or even within countries belonging to this region. Gastric cancer is the result of a multifactorial complex process, for which a multistep model of carcinogenesis is currently accepted. Additionally to the infection with Helicobacter pylori, that plays a major role, environmental factors as well as genetic susceptibility factors are significant players at different stages in the gastric cancer process. The differences in population origin, demographic structure, socio-economic development, and the impact of globalization lifestyles experienced in Latin America in the last decades, all together offer opportunities for studying in this context the influence of genetic polymorphisms in the susceptibility to gastric cancer. The aim of this article is to discuss current trends on gastric cancer in Latin American countries and to review the available published information about studies of association of gene polymorphisms involved in gastric cancer susceptibility from this region of the world. A total of 40 genes or genomic regions and 69 genetic variants, 58% representing markers involved in inflammatory response, have been used in a number of studies in which predominates a low number of individuals (cases and controls) included. Polymorphisms of IL-1B (-511 C/T, 14 studies; -31 T/C, 10 studies) and IL-1RN (variable number of tandem repeats, 17 studies) are the most represented ones in the reviewed studies. Other genetic variants recently evaluated in large meta-analyses and associated with gastric cancer risk were also analyzed in a few studies [e.g., prostate stem cell antigen (PSCA), CDH1, Survivin]. Further and better analysis centered in gene polymorphisms linked to other covariates, epidemiological studies and the information provided by meta-analyses and genome-wide association studies should help to improve our understanding of gastric cancer etiology in order to develop appropriate health programs in Latin America.

Nucleotide excision repair related gene polymorphisms and genetic susceptibility, chemotherapeutic sensitivity and prognosis of gastric cancer

Human genomic DNA is in a dynamic balance of damage and repair. Cells employ multiple and specific repair pathways, such as nucleotide excision repair (NER), as unrepaired DNA damage has deleterious consequences and could give rise to carcinogenesis. Gene polymorphisms play a crucial role in predicting the risk and prognosis of cancer. Polymorphisms of NER-related genes could alter the ability of NER to effectively monitor and repair DNA damage, and thus may be associated with genetic susceptibility, chemotherapeutic sensitivity and prognosis of cancer. In recent years, increasing studies have focused on the association between polymorphisms of NER genes and gastric cancer, the world's fourth most common cancer and the second most common cause for cancer-related death. Here we reviewed the recent studies on the associations between polymorphisms of NER genes and gastric cancer from perspectives of genetic susceptibility, chemotherapeutic sensitivity and prognosis.

XRCC3 Thr241Met polymorphism and gastric cancer susceptibility: a meta-analysis

BACKGROUND AND OBJECTIVE

X-ray repair cross-complementing group 3 (XRCC3) is responsible for maintaining the integrity of the genome, playing a critical role in protecting it against mutations which lead to cancer. Polymorphisms at exons 7 of the XRCC3 gene may alter the XRCC3 repair efficiency. The aim of this study is to derive a precise estimation of the relationship between XRCC3 Thr241Met polymorphism and gastric cancer (GC) risk.

METHODS

Two investigators independently searched the databases of Pubmed, EMBASE and China National Knowledge Infrastructure (CNKI) up to May 15, 2013. Odds ratio (OR) and 95% confidence intervals (CI) for XRCC3 Thr241Met polymorphism and GC were calculated in a fixed- or random- effects model depending on statistical heterogeneity.

RESULTS

This meta-analysis included 9 case-control studies, which included 2209 cases and 3269 controls. Overall, the combined results based on all studies indicated that there was no association between XRCC3 Thr241Met polymorphism and GC susceptibility for all genetic models. When stratifying for race, we found the 241Met/Met genotype carriers might be at high risk of GC among Asians, but not among Caucasians. When stratifying by the location of gastric cancer, the combined results showed that Met/Met genotype carriers might have an increased risk of GC in non-cardiac gastric cancer, but not in cardiac cancer.

CONCLUSION

This meta-analysis confirmed that the XRCC3 Thr241Met gene polymorphism might be a risk factor for GC among Asians, and that differences in genotype distribution may be related to the location of gastric cancer. More well-designed studies based on larger population are needed to confirm our results.

Meta-analysis of the association of glutathione S-transferase T1 null/presence gene polymorphism with the risk of gastric carcinoma

A possible association of glutathione S-transferase T1 (GSTT1) null/presence gene polymorphism and an increased risk of developing gastric carcinoma is still unclear and hotly debated. This investigation was performed to assess the association of the GSTT1 null/presence gene polymorphism with the risk of gastric carcinoma via a meta-analysis to increase sample size and statistical significance. PubMed, Cochrane Library and CBM-disc (China Biological Medicine Database) were searched on March 1, 2013, association reports were identified, and eligible studies were recruited and synthesized. Fifty-two reports were found to be suitable for this meta-analysis for the association of the GSTT1 null genotype with gastric carcinoma risk. The results showed that there was a significantly increased gastric carcinoma risk when the GSTT1 null genotype was present in the overall population (OR 1.21, 95 % CI 1.11-1.32, P < 0.0001), Caucasians (OR 1.25, 95 % CI 1.05-1.48, P = 0.01), East-Asians (OR 1.18, 95 % CI 1.06-1.31, P = 0.003), and Chinese (OR 1.24, 95 % CI 1.07-1.44, P = 0.005). However, no statistically relevant association could be established for the Indian ethnic group (OR 1.33, 95 % CI 0.94-1.90, P = 0.11). In conclusion, the GSTT1 null genotype is associated with an increased gastric carcinoma risk in the overall population, Caucasians, East-Asians, and Chinese.

APEX nuclease (multifunctional DNA repair enzyme) 1 gene Asp148Glu polymorphism and cancer risk: a meta-analysis involving 58 articles and 48903 participants

BACKGROUND

Polymorphisms in the APEX nuclease (multifunctional DNA repair enzyme) 1 gene (APEX1) may be involved in the carcinogenesis by affecting DNA repair. We aimed to summarize available data on the association of the APEX1 Asp148Glu (rs1130409) polymorphism with risk of multiple types of cancer via a meta-analysis.

METHODS AND RESULTS

In total, 58 qualified articles including 22,398 cancer patients and 26,505 controls were analyzed, and the data were extracted independently by two investigators. Analyses of the full data set indicated a marginally significant association of the APEX1 Asp148Glu polymorphism with cancer risk under allelic (odds ratio (OR)=1.05; 95% confidence interval (95% CI): 0.99-1.11; P=0.071), dominant (OR=1.09; 95% CI: 1.01-1.17; P=0.028), and heterozygous genotypic (OR=1.08; 95% CI: 1.01-1.16; P=0.026) models, with significant heterogeneity and publication bias. In subgroup analyses by cancer type, with a Bonferroni corrected alpha of 0.05/6, significant association was observed for gastric cancer under both dominant (OR=1.74; 95% CI: 1.2-2.51; P=0.003) and heterozygous genotypic (OR=1.66; 95% CI: 1.2-2.31; P=0.002) models. In subgroup analysis by ethnicity, risk estimates were augmented in Caucasians, especially under dominant (OR=1.11; 95% CI: 1.0-1.24; P=0.049) and heterozygous genotypic (OR=1.11; 95% CI: 0.99-1.24; P=0.063) models. By study design, there were no significant differences between population-based and hospital-based studies. In subgroup analysis by sample size, risk estimates were remarkably overestimated in small studies, and no significance was reached in large studies except under the heterozygous genotypic model (OR=1.23; 95% CI: 1.06-1.43; P=0.006, significant at a Bonferroni corrected alpha of 0.05/2). By quality score, the risk estimates, albeit nonsignificant, were higher in low-quality studies than in high-quality studies. Further meta-regression analyses failed to identify any contributory confounders for the associated risk estimates.

CONCLUSIONS

Our findings suggest that APEX1 Asp148Glu polymorphism might be a genetic risk factor for the development of gastric cancer. Further investigations on large populations are warranted.

Influence of ERCC1 and ERCC4 polymorphisms on response to prognosis in gastric cancer treated with FOLFOX-based chemotherapy

Polymorphisms in the excision repair cross-complimentary group 1 (ERCC1)-excision repair cross-complimentary group 4 (ERCC4) genes have been implicated in the prognosis of various cancers. We conducted a cohort study to investigate the role of ERCC1-ERCC4 gene polymorphisms on the response to chemotherapy and the role of these two gene polymorphisms on the clinical outcomes of gastric cancer. Four hundred forty-seven patients with newly diagnosed and histopathologically confirmed primary gastric cancer were collected in our study and were followed up until March 2012. ERCC1 (rs11615, rs3212986C>A, and rs2298881) and ERCC4 (rs226466C>G, rs2276465, and rs6498486) were selected and genotyped. The overall chemotherapy response rate for treatment was 68 %. Carriers of the rs11615 TT and T allele and ERCC1 rs2298881 CC and C allele had a marginally significantly higher response rate to the chemotherapy. In the Cox proportional hazard model, the hazard ratios (HRs) for overall survival (OS) in patients carrying ERCC1 rs11615 TT genotype and T allele were 0.53 (0.29-0.95) and 0.63 (0.42-0.94), respectively. Similarly, we found a significant decreased risk of death from gastric cancer among patients carrying ERCC1 rs2298881 CC genotype and C allele when compared with CC genotype, and HRs (95% confidence interval (CI)) of OS were 0.50 (0.24-0.98) and 0.62 (0.40-0.96), respectively. Moreover, individuals carrying ERCC1 rs11615 T allele and rs2298881 C allele could decrease a 0.62-fold risk of death from gastric cancer. This study reported a carriage of ERCC1 rs11615, and rs2298881 polymorphism can be used as a predictor of response to folinic acid/5-fluorouracil (5-FU)/oxaliplatin (FOLFOX)-based chemotherapy in gastric cancer patients.

Two DNA repair gene polymorphisms on the risk of gastrointestinal cancers: a meta-analysis

PARP-1 and MGMT play an important role in the DNA repair system and therefore have been implicated in human carcinogenesis. However, the association between the most studied PARP-1 rs1136410: T > C and MGMT rs12917: C > T polymorphism and risk of gastrointestinal (GI) cancers was reported with inconclusive results. Accordingly, a meta-analysis of 23 published case-control studies was conducted to assess the strength of association using crude odds ratios (ORs) with 95% confidence intervals (CIs). Overall, the C allele of PARP-1 rs1136410: T > C polymorphism was significantly associated with increased susceptibility of GI cancers (homozygote comparison: OR = 1.43, 95% CI 1.14-1.81; heterozygote comparison: OR = 1.18, 95% CI 1.07-1.29; dominant model: OR = 1.23, 95% CI 1.12-1.35; recessive model: OR = 1.30, 95% CI 1.04-1.62; allelic comparison: OR = 1.19, 95% CI 1.07-1.32). In the subgroup analysis, still obvious associations were found in the Asian population, gastric cancer, and high-quality studies. For MGMT rs12917: C > T polymorphism, no obvious associations were found for all genetic models overall. However, in the subgroup analysis, we found that the T allele was significantly associated with reduced colorectal cancer risk for heterozygote (OR = 0.83, 95% CI 0.70-0.97) and dominant model (OR = 0.84, 95% CI 0.72-0.98). In conclusion, this meta-analysis suggests that the PARP-1 rs1136410: T > C polymorphism is a susceptibility factor for GI cancers, but the variant allele of MGMT rs12917: C > T polymorphism appears to be a protective factor for colorectal cancer. Large-scale and well-designed case-control studies are necessary to validate the risk identified in the present meta-analysis.

The GSTM1 null genotype increased risk of gastric cancer: a meta-analysis based on 46 studies

Background

Glutathione S-transferases M1 (GSTM1) is an important phase II metabolizing enzyme. The null genotype of GSTM1 causes total loss of GSTM1 enzyme activity and numerous studies have investigated the association between GSTM1 null genotype and gastric cancer risk.

Methods

This meta-analysis was designed to investigate the relationship between GSTM1 null genotype and susceptibility to gastric cancer and assess the influence of Helicobacter pylori infection, smoking, Lauren’s classification, and other factors. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate the association strength.

Results

A total of 46 eligible studies were indentified and analyzed in this meta-analysis, including 8138 cases of gastric cancer and 13867 controls. Pooled results showed that the GSTM1 null genotype was associated with a significantly increased risk of gastric cancer (OR=1.217, 95% CI: 1.113-1.331, P_{heterogeneity}<0.001). Sub-group analysis suggested that the significant association was only observed in Asians (OR=1.273, 95%: 1.137-1.426, P_{heterogeneity} = 0.002), but not in Caucasians. The increased risk was found among H. pylori positive population (OR=1.928, 95% CI: 1.028-3.615, P_{heterogeneity}=0.065), while no association was found among H. pylori negative population (OR=0.969, 95% CI: 0.618-1.521, P_{heterogeneity}=0.168). For smoking status, the GSTM1 null genotype increased risk of gastric cancer in both ever-smokers and non-smokers. Source of control, sample size, location of tumor and Lauren’s classification did not modify the association.

Conclusions

In this meta-analysis based on 46 epidemiological studies, we show that the GSTM1 null genotype is associated with an increased risk of gastric cancer among Asians but not among Caucasians. H. pylori infection but not smoking status could modify the association.