Polymorphisms of the DNA methyltransferase 1 associated with reduced risks of Helicobacter pylori infection and increased risks of gastric atrophy

An updated meta-analysis investigating the association between DNMTs gene polymorphism andgastric cancer risk

Gastric cancer (GC) is a prominent global health issue, as it ranks as the fifth most prevalent type of cancer and the fourth most significant cause of cancer-related mortality worldwide. Although H. pylori is known to play a role in the development of GC, genetic factors also play a role in its onset and progression. Recent studies have shown that genetic polymorphisms are strongly associated with the development of GC and that certain single nucleotide polymorphisms (SNPs) can be used as biomarkers for early diagnosis and prevention. Epigenetic disturbances, such as DNA methylation, are involved in the development of GC, and mutations in the DNA methyltransferase (DNMT) gene have been found to increase the risk of GC. However, previous findings on the association between DNMTs SNPs and GC risk have been inconsistent. In this study, an updated meta-analysis of three well-studied and controversial DNMTs polymorphic loci, DNMT1 rs16999593, DNMT3A rs1550117 and DNMT3B rs1569686, was performed to provide more reliable results. It was found that DNMT1 rs16999593 was not associated with GC, DNMT3A rs1550117 may have a positive association with GC risk, and DNMT3B rs1569686 may be a protective factor for GC. These findings may provide valuable information for early diagnosis and prevention of GC, but further studies are needed to confirm these results.

The Role of Host Cell DNA Methylation in the Immune Response to Bacterial Infection

Host cells undergo complex transcriptional reprogramming upon infection. Epigenetic changes play a key role in the immune response to bacteria, among which DNA modifications that include methylation have received much attention in recent years. The extent of DNA methylation is well known to regulate gene expression. Whilst historically DNA methylation was considered to be a stable epigenetic modification, accumulating evidence indicates that DNA methylation patterns can be altered rapidly upon exposure of cells to changing environments and pathogens. Furthermore, the action of proteins regulating DNA methylation, particularly DNA methyltransferases and ten-eleven translocation methylcytosine dioxygenases, may be modulated, at least in part, by bacteria. This review discusses the principles of DNA methylation, and recent insights about the regulation of host DNA methylation during bacterial infection.

Epigenetic Mechanisms in Gastric Cancer: Potential New Therapeutic Opportunities

Gastric cancer (GC) is one of the deadliest malignancies worldwide. Complex disease heterogeneity, late diagnosis, and suboptimal therapies result in the poor prognosis of patients. Besides genetic alterations and environmental factors, it has been demonstrated that alterations of the epigenetic machinery guide cancer onset and progression, representing a hallmark of gastric malignancies. Moreover, epigenetic mechanisms undergo an intricate crosstalk, and distinct epigenomic profiles can be shaped under different microenvironmental contexts. In this scenario, targeting epigenetic mechanisms could be an interesting therapeutic strategy to overcome gastric cancer heterogeneity, and the efforts conducted to date are delivering promising results. In this review, we summarize the key epigenetic events involved in gastric cancer development. We conclude with a discussion of new promising epigenetic strategies for gastric cancer treatment.

The Role of Host Genetic Polymorphisms in Helicobacter pylori Mediated Disease Outcome

The clinical outcome of infection with the chronic gastric pathogen Helicobacter pylori is not the same for all individuals and also differs in different ethnic groups. Infection occurs in early life (<3 years of age), and while all infected persons mount an immune response and develop gastritis, the majority of individuals are asymptomatic. However, up to 10-15% develop duodenal ulceration, up to 1% develop gastric cancer (GC) and up to 0.1% can develop gastric mucosa-associated lymphoid tissue (MALT) lymphoma. The initial immune response fails to clear infection and H. pylori can persist for decades. H. pylori has been classified as a group one carcinogen by the WHO. Interestingly, development of duodenal ulceration protects against GC. Factors that determine the outcome of infection include the genotype of the infecting strains and the environment. Host genetic polymorphisms have also been identified as factors that play a role in mediating the clinical outcome of infection. Several studies present compelling evidence that polymorphisms in genes involved in the immune response such as pro and anti-inflammatory cytokines and pathogen recognition receptors (PRRs) play a role in modulating disease outcome. However, as the number of studies grows emerging confounding factors are small sample size and lack of appropriate controls, lack of consideration of environmental and bacterial factors and ethnicity of the population. This chapter is a review of current evidence that host genetic polymorphisms play a role in mediating persistent H. pylori infection and the consequences of the subsequent inflammatory response.

Therapeutic approach of Cancer stem cells (CSCs) in gastric adenocarcinoma; DNA methyltransferases enzymes in cancer targeted therapy

Cancer stem cells (CSCs) show a remarkable sub class of cancer cells population which have a potential to organize and regulate stemness properties which possess a main particular responsibility for uncontrolled growth in carcinogenesis, production of different cancers in differentiated situation and also resistancy to radiotherapy and chemotherapy. Correspondingly, gastric cancer (GC) as a very serious type in cancer mortality in the world, has received a deep attention in molecular therapy recently. Besides the main characteristics of CSCs like differentiation, epithelial mesenchymal transition, self-renewal and metastasis, they are so effective in expression of stemness genes resistancy in radiotherapy and chemotherapy. In this way, the regulation of epigenetic elements including DNA methylation and the performance of DNA methyltransferase (DNMT) which is a notable epigenetic trait in GC, is of great importance. Inhibitors of DNA methylation are the first epigenetic drugs in cancer therapy. Considerably, recent studies indicate that low doses of DNMT inhibitors have a high potential in sustaining reduced DNA methylation and related with re-expression of silenced genes in tumorigenesis. Importantly, these certain doses have the ability to decrease the carcinogenesis and tumorigenesis in CSC populations within GC. Meaningly, the inhibition of DNMTs are able to reduce the accumulation of tumorigenic ability of GC CSCs. Furthermore, many epigenetic drugs have a great potential in cancer therapy, including histone methyltransferases, lysine demethylases, histone deacetylasesand, bromodomain and extra-terminal domain proteins and DNA methyltransferases inhibitors. In this review article, we try to focus on the therapeutic mechanism of DNMTs alongside with their impact on CSCs in GC.

DNA methyltransferases and gastric cancer: insight into targeted therapy

Gastric cancer is a major health problem worldwide occupying most frequent causes of cancer-related mortality. In addition to genetic modifications, epigenetic alterations catalyzed by DNA methyltransferases (DNMTs) are a well-characterized epigenetic hallmark in gastric cancer. The reversible nature of epigenetic alterations and central role of DNA methylation in diverse biological processes provides an opportunity for using DNMT inhibitors to enhance the efficacy of chemotherapeutics. In this review, we discussed key factors or mechanisms such as SNPs, infections and genetic modifications that trigger DNMTs level modification in gastric cancer, and their potential roles in cancer progression. Finally, we focused on how inhibitors of the DNMTs can most effectively be used for the treatment of gastric cancer with multidrug resistance.

Association of five genetic variations in DNMT1 and DNMT3A with gastric cancer in a Chinese population

AIM

To determine whether genetic variations in DNMT1 and DNMT3A could be associated with gastric cancer risk.

MATERIALS & METHODS

A total of 466 patients and 452 healthy controls were enrolled in this study. Genotypes were examined by using the Sequenom MassARRAY platform.

RESULTS

No significant differences in the distribution frequencies were observed between the groups. However, subgroup analysis revealed that, in the group aged ≤60 years, DNMT3A rs13420827 was associated with reduced gastric cancer risk, and that carrier of GC/GG genotype was associated with reduced risk of gastric cancer with low differentiation or at the T3-T4 stage.

CONCLUSION

This study suggests that five genetic variations of interest in DNMT1 and DNMT3A are not associated with the presence of gastric cancer, but that rs13420827 may contribute to the gastric cancer risk for those younger individuals, the risk of which may be influenced by the characteristics of tumor.

A Meta-Analysis of the Association between DNMT1 Polymorphisms and Cancer Risk

Previous studies have examined the associations of DNA methyltransferase 1 (DNMT1) polymorphisms, including single nucleotide polymorphisms rs16999593 (T/C), rs2228611 (G/A), and rs2228612 (A/G), with cancer risk. However, the results are inconclusive. The aim of this meta-analysis is to elucidate the associations between DNMT1 polymorphisms and cancer susceptibility. The PubMed, Embase, Web of Science, and Chinese National Knowledge Infrastructure databases were searched systematically to identify potentially eligible reports. Odd ratios and 95% confidence intervals were used to evaluate the strength of association between three DNMT1 polymorphisms and cancer risk. A total of 16 studies were finally included in the meta-analysis, namely, nine studies of 3378 cases and 4244 controls for rs16999593, 11 studies of 3643 cases and 3866 controls for rs2228611, and three studies of 1343 cases and 1309 controls for rs2228612. The DNMT1 rs2228612 (A/G) polymorphism was significantly related to cancer risk in the recessive model. The meta-analysis also suggested that DNMT1 rs16999593 (T/C) may be associated with gastric cancer, while rs2228611 (G/A) may be associated with breast cancer. In future research, large-scale and well-designed studies are required to verify these findings.

Genetic polymorphism in DNMTs and gastric cancer: A systematic review and meta-analysis

Highlights

Single nucleotide polymorphisms (SNPs) in DNA methyltransferases (DNMTs) modulate protein expression and affect DNA methylation.Aberrant DNA methylation, have been associated with gastric carcinogenesis.DNMT2 rs11254413 is associated with protection for GC development.DNMT3A rs7560488, DNMT3A rs36012910 and, specially, DNMT1 rs16999593 are associated with increased susceptibility for GC development.

Abstract

Epigenetics alterations, including aberrant DNA methylation, have been associated with gastric carcinogenesis. Single nucleotide polymorphisms (SNPs) in DNA methyltransferases (DNMTs) may influence protein expression and therefore affect DNA regulation and susceptibility for Gastric Cancer (GC).We have performed a systematic review and meta-analysis involving 11 studies and a total of 24 SNPs in DNMTs were analyzed. According to literature, only 4 SNPs, DNMT1 rs16999593, DNMT2 rs11254413 and DNMT3A rs7560488 and DNMT3A rs36012910, were associated with GC. DNMT1 rs16999593 and DNMT3A rs7560488C allele and DNMT3A rs36012910 G allele showed an increased risk for GC. On the other hand, DNMT2 rs11254413 G allele presented a protective effect for GC. Additionally, the meta-analysis evaluated the SNPs analyzed in more than one study (n = 6). Results revealed that only DNMT1 rs16999593 had a statistically significant association with GC development (OR = 1.31; 95% CI = 1.08-1.60; p = 0.006 for TC + CC genotypes).Our study suggests that DNMT2 rs11254413, DNMT3A rs7560488, DNMT3A rs36012910 and, specially, DNMT1 rs16999593 may have an association with GC development. Nevertheless, further studies are need using different populations to clarify this association with GC risk.

DNMT1, DNMT3A and DNMT3B Polymorphisms Associated With Gastric Cancer Risk: A Systematic Review and Meta-analysis

BACKGROUND

Increasing studies showed that abnormal changes in single nucleotide polymorphisms (SNPs) of DNMTs (DNMT1, DNMT3A and DNMT3B) were associated with occurrence or decrease of various tumors. However, the associations between DNMTs variations and gastric cancer (GC) risk were still conflicting. We aimed to assess the effect of DNMTs polymorphisms on the susceptibility to GC.

METHODS

Firstly, we did a meta-analysis for 7 SNPs (rs16999593, rs2228611, rs8101866 in DNMT1, rs1550117, rs13420827 in DNMT3A, rs1569686, rs2424913 in DNMT3B). Four genetic models (homozygote, heterozygote, dominant and recessive model) were used. Moreover, a meta-sensitivity and subgroup analysis was performed to clarify heterogeneity source. Lastly, 17 SNPs that couldn't be meta-analyzed were presented in a systematic review.

FINDINGS

20 studies were included, 13 studies could be meta-analyzed and 7 ones could not. Firstly, a meta-analysis on 13 studies (3959 GC cases and 5992 controls) for 7 SNPs showed that GC risk increased in rs16999593 (heterozygote model: OR 1.36, 95%CI 1.14-1.61; dominant model: OR 1.36, 95%CI 1.15-1.60) and rs1550117 (homozygote model: OR 2.03, 95%CI 1.38-3.00; dominant model: OR 1.20, 95%CI 1.01-1.42; recessive model: OR 1.96, 95%CI 1.33-2.89) but decreased in rs1569686 (dominant model: OR 0.74, 95%CI 0.61-0.90). The remaining SNPs were not found associated with GC risk. Furthermore, the subgroup analysis indicated that for rs1550117 and rs1569686, the significant associations were particularly found in people from Chinese Jiangsu province (rs1550117, OR 1.77, 95%CI 1.25-2.51; rs1569686, OR 0.48, 95%CI 0.36-0.64) and that PCR-RFLP was a sensitive method to discover significant associations (rs1550117, OR 1.77, 95%CI 1.25-2.51; rs1569686, OR 0.49, 95%CI 0.37-0.65). Lastly, a systematic review on 7 studies for 17 SNPs suggested that rs36012910, rs7560488 and rs6087990 might have a potential effect on GC initiation.

CONCLUSION

This meta-analysis demonstrated that rs16999593 and rs1550117 could contribute to GC risk and that rs1569686 might be a protective factor against gastric carcinogenesis. By using these SNPs as biomarkers, it is feasible to estimate the risk of acquiring GC and thus formulate timely preventive strategy.

Helicobacter pylori Infection Rates in Patients Undergoing Endoscopy in the Interior of Borneo

INTRODUCTION

Very limited data are available on the Helicobacter pylori infection among the population of interior Borneo. We aimed to investigate the H. pylori infection rate among an endoscoped interior Borneo population and to report the differences between the infected and noninfected patients.

METHODS

We retrospectively analyzed the data of the rapid urease test (RUT) records in Endoscopy Unit Hospital Keningau from January 2009 to May 2014. Student's t-test, chi-square test or Fisher's exact test were used accordingly. Multiple logistic regression analysis was used to identify independent risk factors for H. pylori infection. Birth cohort was analyzed against H. pylori infection rate with chi-square test.

RESULTS

Overall, there were 215 of 774 (27.8%) positive RUTs. Patients with H. pylori infection were younger (47.66 ± 14.93 vs 50.50 ± 15.02 years, p = .019), more likely to be female (OR = 1.54, 95% CI 1.12-2.13, p = .008) and originated from the Pensiangan district (OR = 1.63, 95% CI 1.01-2.64, p = .047). Chinese patients were less likely infected with H. pylori (OR = 0.36, 95% CI 0.16-0.80, p = .013). Birth cohort was significantly associated with H. pylori infection rate (χ(2) (7) = 14.71, p = .040) with an increasing trend of H. pylori infection rate in patients born later (χ(2) (1) = 5.26, p = .022).

CONCLUSION

The overall H. pylori infection rate in this population was unexpectedly low. Accordingly, it may be a recent arrival in this community. Gender, age, dietary practice, socioeconomic status, and ethnicity were among the factors associated with H. pylori infection.

Polymorphisms of the DNA Methyltransferase 1 Gene Predict Survival of Gastric Cancer Patients Receiving Tumorectomy

DNA methyltransferase 1 (DNMT1) plays a pivotal role in maintaining DNA methylation status. Polymorphisms of DNMT1 may modify the role of DNMT1 in prognosis of gastric cancer (GC). Our aim was to test whether polymorphisms of DNMT1 gene were associated with overall survival of GC. Four hundred and forty-seven GC patients who underwent radical tumorectomy were enrolled in the study. Five tagging SNPs (rs10420321, rs16999593, rs2228612, rs2228611, and rs2288349) of the DNMT1 gene were genotyped by TaqMan assays. Kaplan-Meier survival plots and Cox proportional hazard regression were used to analyze the associations between SNPs of DNMT1 and survival of GC. Patients carrying rs2228611 GA/AA genotype tended to live longer than those bearing the GG genotype (HR 0.68, 95% CI: 0.51–0.91, P = 0.007). Further multivariate Cox regression analysis showed that rs2228611 was an independent prognostic factor (GA/AA versus GG: OR 0.67, 95% CI 0.49–0.91, P = 0.010). Nevertheless, other SNPs did not show any significant associations with survival of GC. Polymorphisms of the DNMT1 gene may affect overall survival of GC. The SNP rs2228611 has the potentiality to serve as an independent prognostic marker for GC patients.

Genetic variants involved in oxidative stress, base excision repair, DNA methylation, and folate metabolism pathways influence myeloid neoplasias susceptibility and prognosis

Myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) share common features: elevated oxidative stress, DNA repair deficiency, and aberrant DNA methylation. We performed a hospital-based case-control study to evaluate the association in variants of genes involved in oxidative stress, folate metabolism, DNA repair, and DNA methylation with susceptibility and prognosis of these malignancies. To that end, 16 SNPs (one per gene: CAT, CYBA, DNMT1, DNMT3A, DNMT3B, GPX1, KEAP1, MPO, MTRR, NEIL1, NFE2F2, OGG1, SLC19A1, SOD1, SOD2, and XRCC1) were genotyped in 191 patients (101 MDS and 90 AML) and 261 controls. We also measured oxidative stress (reactive oxygen species/total antioxidant status ratio), DNA damage (8-hydroxy-2'-deoxyguanosine), and DNA methylation (5-methylcytosine) in 50 subjects (40 MDS and 10 controls). Results showed that five genes (GPX1, NEIL1, NFE2L2, OGG1, and SOD2) were associated with MDS, two (DNMT3B and SLC19A1) with AML, and two (CYBA and DNMT1) with both diseases. We observed a correlation of CYBA TT, GPX1 TT, and SOD2 CC genotypes with increased oxidative stress levels, as well as NEIL1 TT and OGG1 GG genotypes with higher DNA damage. The 5-methylcytosine levels were negatively associated with DNMT1 CC, DNMT3A CC, and MTRR AA genotypes, and positively with DNMT3B CC genotype. Furthermore, DNMT3A, MTRR, NEIL1, and OGG1 variants modulated AML transformation in MDS patients. Additionally, DNMT3A, OGG1, GPX1, and KEAP1 variants influenced survival of MDS and AML patients. Altogether, data suggest that genetic variability influence predisposition and prognosis of MDS and AML patients, as well AML transformation rate in MDS patients. © 2016 Wiley Periodicals, Inc.

CD24 genetic variants contribute to overall survival in patients with gastric cancer

AIM

To investigate the role of single nucleotide polymorphisms (SNPs) in CD24 gene in susceptibility and overall survival of gastric cancer (GC).

METHODS

We genotyped 3 tagging SNPs of CD24-P-534 in the promoter region, P170 in the coding region of exon 2 and P1527 in the 3' untranslated region - using polymerase chain reaction-restriction fragment length polymorphism in specimens from 679 histologically-confirmed GC cases, 111 gastric atrophy (GA) cases and 976 tumor-free controls. Serum immunoglobulin G antibodies to Helicobacter pylori (H. pylori) of all subjects were detected by enzyme-linked immunosorbent assay. CD24 expression was evaluated by immunohistochemistry in 131 GC specimens. Correlations between SNPs and risk of GC or GA were shown by P values and odd ratios (ORs) with 95% confidence intervals (95%CI) compared with the most common genotype of each SNP using the unconditional logistic regression model after adjusting for age, sex and H. pylori infection. Survival within each SNP group was plotted by Kaplan-Meier method and compared by log-rank test (recessive model). Hazard ratios with 95%CIs were computed by Cox regression model after adjusting for age, sex, histological type, tumor differentiation, clinical stage and post-operational chemotherapy.

RESULTS

All of the three loci were in Hardy-Weinberg equilibrium in the control group. Median follow-up time for the 600 GC patients included in the survival analysis was 36.2 mo (range, 2.1-66.7 mo; 95%CI: 34.3-36.5 mo). Patients with the P-534 A/A genotype had significantly shorter survival (HR = 1.38, 95%CI: 1.01-1.88, P = 0.042) than did the C/C or C/A genotype carriers after adjusting for age, sex, histological type, tumor differentiation, clinical stage and post-operational chemotherapy. This trend was more evident in patients who lived longer than 2.5 years (HR = 7.55, 95%CI: 2.16-26.32, P = 0.001). The P170 T/T genotype was associated with a shorter lifespan than the non-T/T genotypes, but not significantly so. None of the three genetic variants was found to be associated with risk of GC (including tumor stage, grade and distant metastasis) or with risk of gastric atrophy. Furthermore, no difference of CD24 expression was found among the genotypes.

CONCLUSION

The P-534 site in CD24 gene affects the overall survival of gastric cancer and may serve as a prognostic marker for gastric cancer.

The possible role of EZH2 and DNMT1 polymorphisms in sporadic triple-negative breast carcinoma in southern Chinese females

Triple-negative breast cancer (TNBC) has a more invasive and metastatic potential than the other types of breast cancer and hence is associated with poor prognosis. Zeste homolog 2 (EZH2) and DNA methyltransferase 1 (DNMT1) could lead to tumorigenesis by separately methylating histone H3K27 and CpG islands in tumor suppressor genes. In order to investigate the association between oncogenesis and the distribution of single nucleotide polymorphisms (SNPs) of EZH2, DNMT1, a case-control study on SNPs in TNBC cases from south China was conducted. A total of 13 SNPs were genotyped from 234 cases of TNBC tissues, and 300 normal blood samples from age-matched control group were analyzed using Snapshot technology. The expressions of EZH2 and DNMT1 were examined in the 234 cases of TNBC tissues by immunohistochemistry (IHC). The T allele of rs2288349 and the C allele of rs16999593 increase the risk of TNBC, with relative risk coefficients of 1.76 and 1.69, respectively (p < 0.001). The TC genotypes of rs2288349 and rs16999593 were higher in TNBC compared with the control group; the cancer risk increased to 5.27 and 4.13, respectively (p < 0.001). There were no significant differences between the frequencies of the other 10 SNPs and the risk of TNBC (p > 0.05). Five common haplotypes (>8 % frequency) were identified with a cumulative frequency of 96 % in the controls, while the haplotypes of AAGTAG, GGGTGA, and GACCAG were significantly increased in the control group compared to that in patients (p < 0.05). The G allele of rs10274701 significantly increased the EZH2 expression level in TNBC (p = 0.01). This is the first study to demonstrate a significant association between TNBC risk and the polymorphisms of EZH2 and DNMT1, and our researches indicate that the SNPs of EZH2 and DNMT1 are risk predictors for TNBC.

DNA methyltransferase3a expression is an independent poor prognostic indicator in gastric cancer

AIM

To explore the alteration of DNA methyltransferase expression in gastric cancer and to assess its prognostic value.

METHODS

From April 2000 to December 2010, 227 men and 73 women with gastric cancer were enrolled in the study. The expression of DNA methyltransferases (DNMTs), including DNMT1, DNMT3a and DNMT3b, in the 300 cases of gastric carcinoma, of which 85 had paired adjacent normal gastric mucus samples, was evaluated by immunohistochemistry using a tissue microarray. Serum anti-Helicobacter pylori (H. pylori) IgG was detected by enzyme-linked immunosorbent assay (ELISA). The relationships between the above results and the clinicopathological characteristics were analyzed. Their prognostic value was evaluated using the Cox proportional hazards model.

RESULTS

In gastric cancer, expression of DNMTs was mainly seen in the nucleus. Weak staining was also observed in the cytoplasm. Expression of DNMT1, DNMT3a and DNMT3b in gastric cancer was significantly higher compared to that in the paired control samples (60.0% vs 37.6%, 61.2% vs 4.7%, and 94.1% vs 71.8%, P < 0.01). The overall survival rate was significantly higher in the DNMT3a negative group than in the DNMT3a positive group in gastric cancer patients (Log-rank test, P = 0.032). No significant correlation was observed between DNMT1 and DNMT3b expression and the overall survival time (Log-rank test, P = 0.289, P = 0.347). Multivariate regression analysis indicated that DNMT3a expression (P = 0.025) and TNM stage (P < 0.001), but not DNMT1 (P = 0.54) or DNMT3b (P = 0.62), were independent prognostic factors in gastric cancer. H. pylori infection did not induce protein expression of DNMTs.

CONCLUSION

The results suggest that expression of DNMT3a is an independent poor prognostic indicator in gastric cancer. DNMT3a might play an important role in gastric carcinogenesis.

Helicobacter pylori and gastric cancer

Infection with Helicobacter pylori is established as the major risk factor for gastric cancer development. Damage of the mucosal barrier due to H. pylori-induced inflammation enhances the carcinogenic effect of other risk factors such as salt intake or tobacco smoking. The genetic disposition of both the bacterial strain and the host can increase the potential towards gastric cancer formation. Genetic variance of the bacterial proteins CagA and VacA is associated with a higher gastric cancer risk, as are polymorphisms and epigenetic changes in host gene coding for interleukins (IL1β, IL8), transcription factors (CDX2, RUNX3) and DNA repair enzymes. Application of high-throughput assays for genome-wide assessment of either genetic structural variance or gene expression patterns may lead to a better understanding of the pathobiological background of these processes, including the underlying signaling pathways. Understanding of the stepwise alterations that take place in the transition from chronic atrophic gastritis, via metaplastic changes, to invasive neoplasia is vital to define the 'point of no return' before which eradication of H. pylori has the potential to prevent gastric cancer. Currently, eradication as preventive strategy is only recommended for high-incidence regions in Asia; large population studies with an adequate follow-up are required to demonstrate the effectiveness of such an approach in Western populations.

Identifying gastric cancer related genes using the shortest path algorithm and protein-protein interaction network

Gastric cancer, as one of the leading causes of cancer related deaths worldwide, causes about 800,000 deaths per year. Up to now, the mechanism underlying this disease is still not totally uncovered. Identification of related genes of this disease is an important step which can help to understand the mechanism underlying this disease, thereby designing effective treatments. In this study, some novel gastric cancer related genes were discovered based on the knowledge of known gastric cancer related ones. These genes were searched by applying the shortest path algorithm in protein-protein interaction network. The analysis results suggest that some of them are indeed involved in the biological process of gastric cancer, which indicates that they are the actual gastric cancer related genes with high probability. It is hopeful that the findings in this study may help promote the study of this disease and the methods can provide new insights to study various diseases.

Helicobacter pylori infection--a boon or a bane: lessons from studies in a low-prevalence population

Helicobacter pylori (H. pylori) infection is etiologically associated with gastric cancer and peptic ulcer diseases which are both important public health burdens which could be largely eliminated by H. pylori eradication. However, some investigators urge caution based on the hypothesis that eradication of H. pylori may result in an increase in the incidence of gastroesophageal reflux disease, esophageal adenocarcinoma, and childhood asthma. The ethnic Malays of northeastern Peninsular Malaysia have long had a low prevalence of H. pylori infection and, as expected, the incidence of gastric cancer and its precursor lesions is exceptionally low. The availability of a population with a low H. pylori prevalence and generally poor sanitation allows separation of H. pylori from the hygiene hypothesis and direct testing of whether absence of H. pylori is associated with untoward consequence. Contrary to predictions, in Malays, erosive esophagitis, Barrett's esophagus, distal esophageal cancers, and childhood asthma are all of low incidence. This suggests that H. pylori is not protective rather the presence of H. pylori infection is likely a surrogate for poor hygiene and not an important source of antigens involved in the hygiene hypothesis. Helicobacter pylori in Malays is related to transmission from H. pylori-infected non-Malay immigrants. The factors responsible for low H. pylori acquisition, transmission, and burden of H. pylori infection in Malays remain unclear and likely involves a combination of environmental, host (gene polymorphisms), and strain virulence factors. Based on evidence from this population, absence of H. pylori infection is more likely to be boon than a bane.