Persistence of a component of DNA methylation in gastric mucosae after Helicobacter pylori eradication

Gut microbiota in cancer initiation, development and therapy

Cancer has long been associated with genetic and environmental factors, but recent studies reveal the important role of gut microbiota in its initiation and progression. Around 13% of cancers are linked to infectious agents, highlighting the need to identify the specific microorganisms involved. Gut microbiota can either promote or inhibit cancer growth by influencing oncogenic signaling pathways and altering immune responses. Dysbiosis can lead to cancer, while certain probiotics and their metabolites may help reestablish micro-ecological balance and improve anti-tumor immune responses. Research into targeted approaches that enhance therapy with probiotics is promising. However, the effects of probiotics in humans are complex and not yet fully understood. Additionally, methods to counteract harmful bacteria are still in development. Early clinical trials also indicate that modifying gut microbiota may help manage side effects of cancer treatments. Ongoing research is crucial to understand better how gut microbiota can be used to improve cancer prevention and treatment outcomes.

Chronic Inflammation to Cancer: The Impact of Oxidative Stress on DNA Methylation

The genomic landscape of cancer cells is complex and heterogeneous, with aberrant DNA methylation being a common observation. Growing evidence indicates that oxidants produced from immune cells may interact with epigenetic processes, and this may represent a mechanism for the initiation of altered epigenetic patterns observed in both precancerous and cancerous cells. Around 20% of cancers are linked to chronic inflammatory conditions, yet the precise mechanisms connecting inflammation with cancer progression remain unclear. During chronic inflammation, immune cells release oxidants in response to stimuli, which, in high concentrations, can cause cytotoxic effects. Oxidants are known to damage DNA and proteins and disrupt normal signalling pathways, potentially initiating a sequence of events that drives carcinogenesis. While research on the impact of immune cell-derived oxidants on DNA methylation remains limited, this mechanism may represent a crucial link between chronic inflammation and cancer development. This review examines current evidence on inflammation-associated DNA methylation changes in cancers related to chronic inflammation.

A Single Center Study of Genes Involved in Synchronous and Metachronous Multiple Early-Stage Gastric Cancers in Japanese Patients with Current or Former Helicobacter pylori Infection

BACKGROUND

This study aimed to perform a comprehensive gene expression analysis in patients with early-stage gastric cancer (EGC) to identify gene expression profiles specific to gastric cancer (GC) lesions.

METHODS

Biopsy specimens were collected from one EGC lesion and three background mucosal areas of patients scheduled for endoscopic submucosal dissection (ESD). Lesion-specific gene profiles in these four biopsies were analyzed using DNA microarrays. Patients with concurrent EGCs at the time of an ESD or a history of GC were classified into the multiple GC group (n = 26), while those without such histories were assigned to the single GC group (n = 74).

RESULTS

After excluding patients with heterogeneous factors, 55 patients were analyzed. Twenty-one differential genes exhibiting distinct mean expression profiles stratified by background gastric mucosa were extracted between the single and multiple GC groups. A scoring system constructed using these genes to calculate the weighted expression values for each patient, with an optimal cutoff value of -2.574, yielded a sensitivity and specificity of 85.7%.

CONCLUSIONS

This study identified the different gene expression profiles between synchronous and metachronous multiple GCs and single GCs in patients with EGC. The developed scoring system has potential to distinguish between single and multiple GCs.

Characteristics of gastric cancers developed more than 10 years after eradication of Helicobacter pylori

Helicobacter pylori (H pylori) eradication is expected to effectively prevent gastric cancer (GC). However, GC cases may occur even longer than 10 years after H pylori eradication (L10AE). Moreover, the associated factors and characteristics are unknown. In this retrospective, single-center study conducted between 2017 and 2022, patients with GC diagnosed after H pylori eradication were enrolled and categorized into groups according to whether they were shorter than 10 years after H pylori eradication (S10AE) or L10AE. Patients were also categorized according to the depth of cancer invasion. Clinical data, pathological data, and risk factors were analyzed using logistic regression. Clinicopathological characteristics of GC diagnosed at L10AE and those invading the submucosal tissue or deeper (SMD) were investigated. In total, 202 cases of GC occurring after H pylori eradication were identified. Comparison of 158 S10AE and 44 L10AE GC cases revealed a significantly longer surveillance interval (SI) in L10AE cases (median: 2.0 vs 1.0 years, P = .01). Comparison of 150 intramucosal and 52 SMD GC cases revealed that L10AE GC cases were significantly more frequent amongst the SMD cases (18.0% vs 32.7%, P = .03). Pathologically, undifferentiated and mixed types were significantly more frequent in GC cases with SMD invasion (P < .001). Multivariate analysis revealed that L10AE was significantly related to GC cases with SMD invasion (odds ratio, 2.45; 95% confidence interval, 1.15-5.11; P = .019). SI was significantly longer in GC that developed at L10AE than at S10AE. In addition, GC with SMD invasion was more frequently detected in L10AE than in S10AE. Our data indicated that SI should not be groundlessly extended in patients at L10AE.

A Proton Pump Inhibitor Independently Elevates Gastrin Levels as a Marker for Metachronous Gastric Cancer After Endoscopic Submucosal Dissection

Background and Objective: Serum markers such as gastrin and pepsinogen are useful for stratifying gastric cancer risk. However, their utility in predicting metachronous gastric cancer after endoscopic submucosal dissection (ESD) in patients with gastric cancer after Helicobacter pylori eradication (GCAE) is unclear. This study aimed to clarify predictive factors for metachronous gastric cancer after ESD with a focus on serum markers. Methods: A retrospective analysis was conducted on 197 patients with 224 GCAE lesions who underwent ESD at Hiroshima University Hospital between April 2010 and December 2019. In total, 63 patients with 74 differentiated-type lesions were classified into metachronous gastric cancer (MG) and non-metachronous gastric cancer (NMG) groups, excluding proton pump inhibitor (PPI) users, female patients, and undifferentiated-type cases. The predictive value of serum markers was assessed using ROC curve analysis, and their association with carcinogenesis was evaluated using multiple logistic regression. Furthermore, the incidence of MG was compared between long-term PPI users and non-users. Results: ROC analysis revealed that serum gastrin had the highest discriminative ability for MG (AUC 0.77, cut-off 99 pg/mL, sensitivity 61.6%, and specificity 80.0%). Severe mucosal atrophy and high gastrin levels were significantly more common in the MG group and were independent predictors (p < 0.01). Although serum gastrin levels were significantly elevated in PPI users, no increased risk of MG was observed. Conclusions: In addition to severe mucosal atrophy, PPI-independent elevated serum gastrin levels may be associated with an increased risk of MG after ESD. Serum gastrin may serve as a valuable marker for post-ESD cancer surveillance in GCAE patients.

The role of cuproptosis in gastric cancer

As a biologically essential transition metal, copper is widely involved in various enzymatic reactions and crucial biological processes in the body. It plays an increasingly important role in maintaining normal cellular metabolism and supporting the growth and development of the human body. As a trace element, copper maintains the dynamic balance of its concentration in body fluids through active homeostatic mechanisms. Both excess and deficiency of copper ions can impair cell function, ultimately leading to cell damage and death. Cuproptosis is a novel form of cell death where copper ions cause cell death by directly binding to the lipoylated components of the citric acid cycle (CAC) in mitochondrial respiration and interfering with the levels of iron-sulfur cluster (Fe-S cluster) proteins, ultimately causing protein toxic stress. Its primary characteristics are Cu2+ concentration dependence and high expression in mitochondrial respiratory cells. Recent research has revealed that, compared to other forms of programmed cell death such as apoptosis, necrosis, and autophagy, cuproptosis has unique morphological and biochemical features. Cuproptosis is associated with the occurrence and development of various diseases, including cancer, neurodegenerative diseases, and cardiovascular diseases. This article focuses on a review of the relevance of cuproptosis in gastric cancer (GC).

Gastric microbiome signature for predicting metachronous recurrence after endoscopic resection of gastric neoplasm

BACKGROUND

Changes in gastric microbiome are associated with gastric carcinogenesis. Studies on the association between gastric mucosa-associated gastric microbiome (MAM) and metachronous gastric cancer are limited. This study aimed to identify gastric MAM as a predictive factor for metachronous recurrence following endoscopic resection of gastric neoplasms.

METHOD

Microbiome analyses were conducted for 81 patients in a prospective cohort to investigate surrogate markers to predict metachronous recurrence. Gastric MAM in non-cancerous corporal biopsy specimens was evaluated using Illumina MiSeq platform targeting 16S ribosomal DNA.

RESULTS

Over a median follow-up duration of 53.8 months, 16 metachronous gastric neoplasms developed. Baseline gastric MAM varied with Helicobacter pylori infection status, but was unaffected by initial pathologic diagnosis, presence of atrophic gastritis, intestinal metaplasia, or synchronous lesions. The group with metachronous recurrence did not exhibit distinct phylogenetic diversity compared with the group devoid of recurrence but showed significant difference in β-diversity. The study population could be classified into two distinct gastrotypes based on baseline gastric MAM: gastrotype 1, Helicobacter-abundant; gastrotype 2: Akkermansia-abundant. Patients in gastrotype 2 showed higher risk of metachronous recurrence than gastrotype (Cox proportional hazard analysis, adjusted hazard ratio [95% confidence interval]: 5.10 [1.09-23.79]).

CONCLUSIONS

Gastric cancer patients can be classified into two distinct gastrotype groups by their MAM profiles, which were associated with different risk of metachronous recurrence.

DNA methylation drives a new path in gastric cancer early detection: Current impact and prospects

Gastric cancer (GC) is one of the most common and deadly cancers worldwide. Early detection offers the best chance for curative treatment and reducing its mortality. However, the optimal population-based early screening for GC remains unmet. Aberrant DNA methylation occurs in the early stage of GC, exhibiting cancer-specific genetic and epigenetic changes, and can be detected in the media such as blood, gastric juice, and feces, constituting a valuable biomarker for cancer early detection. Furthermore, DNA methylation is a stable epigenetic alteration, and many innovative methods have been developed to quantify it rapidly and accurately. Nonetheless, large-scale clinical validation of DNA methylation serving as tumor biomarkers is still lacking, precluding their implementation in clinical practice. In conclusion, after a critical analysis of the recent existing literature, we summarized the evolving roles of DNA methylation during GC occurrence, expounded the newly discovered noninvasive DNA methylation biomarkers for early detection of GC, and discussed its challenges and prospects in clinical applications.

Characteristics of Gastric Mucosa-Associated Microbiota in Patients with Early Gastric Cancer After Successful Helicobacter pylori Eradication

BACKGROUND

Helicobacter pylori (H. pylori) is widely recognized as a definite carcinogen in gastric cancer (GC). Although H. pylori eradication reduces the risk of GC, GC recurrence has been detected even after successful H. pylori eradication. Recently, the analysis of gut microbiota was reported.

AIMS

This study aimed to evaluate the correlation between gastric mucosa-associated microbiota (G-MAM) and early gastric cancer (EGC) after successful H. pylori eradication.

METHODS

In this pilot study, G-MAM were collected during the esophagogastroduodenoscopy of 17 patients, receiving H. pylori eradication therapy at least 5 years ago. The patients were divided into those with EGC (the EGC group, 8 patients) and those without EGC (the NGC group, 9 patients). Microbial samples in the greater curvature of the pyloric site were obtained using an endoscopic cytology brush, and the G-MAM profiles of each sample were analyzed using 16S rRNA V3-V4 gene sequencing.

RESULTS

Between the two groups, there was no significant difference in the median age, sex, median period after successful eradication of H. pylori, the α diversity, and the average abundance at the phylum level. At the genus level, the average abundance of Unclassified Oxalobacteraceae, Capnocytophaga, and Haemophilus was significantly lower in the EGC group than in the NGC group (0.89 vs. 0.14%, P < 0.01, 0.28 vs. 0.00%, P < 0.01 and 5.84 vs. 2.16%, P = 0.034, respectively).

CONCLUSIONS

We demonstrated alternations in the profiles of G-MAM between the two groups. Our results suggest that G-MAM may influence carcinogenesis after successful H. pylori eradication.

Quality evaluation of the literature on clinical randomized controlled trials of traditional Chinese medicine for treatment of gastric precancerous lesions in the past 20 years

OBJECTIVES

To evaluate the methodological quality of randomized controlled trials (RCTs) of traditional Chinese medicines for the treatment of gastric precancerous lesions in the past 20 years.

METHODS

The RCTs on traditional Chinese medicines for gastric precancerous lesions were searched from the CNKI, Wanfang database, VIP, PubMed, and Embase from January 2001 to December 2021. The retrieved articles were screened, extracted and evaluated based on the 2010 edition of CONSORT statement, Cochrane Risk of Bias Assessment Scale and additional evaluation indicators.

RESULTS

A total of 840 papers were included. According to the Cochrane Risk of Bias Assessment Scale, the high risk of bias in the application of randomized methods was 5.95%; the risk of uncertainty for the allocation scheme concealment was 98.93%; the risk of uncertainty for blinding of patients or testers was 98.69%; the risk of uncertainty for blinding of the outcome assessor was 100.00%; the risk of bias for completeness of the outcome data was 2.86%; and the risk of uncertainty for selective reporting was 98.45%. The CONSORT statement evaluating the quality of reporting showed that 100.00% of the RCT articles reported the 8 entries; 36.79% of the literature mentioned the method of randomized sequence generation, but only 27.62% of the literature mentioned who implemented the randomized program, 1.07% of the literature hid the randomized program and 1.31% of the studies were blinded; 36.67% of the literature reported adverse reactions; no literature reported sample size prediction methods. Additional evaluation indicators showed that 17.02% of the studies had ethical approval; 43.81% of the literature specified Chinese medicine evidence; 16.55% of the studies excluded severe heterotrophic hyperplasia; 7.26% of the studies conducted follow-up; and 65.12% of the literature used composite efficacy indicators; 46.67% of the literature applied pathological histological evaluation; 2.62% of the literature applied quality of life evaluation.

CONCLUSIONS

The overall risk of bias in RCTs of traditional Chinese medicines for gastric precancerous lesions is high, and the quality of most of the study reports needs to be improved. In the future, it is necessary to strengthen the study design of RCTs and refer to appropriate traditional Chinese medicines evidence grading standards, select study protocols according to different purposes, provide objective and strong evidence for clinical studies on traditional Chinese medicines, and carry out clinical study design and result reporting suitable for traditional Chinese medicines according to the CONSORT principle.

Histopathological Evaluation of Gastric Mucosal Atrophy for Predicting Gastric Cancer Risk: Problems and Solutions

Patients suffering from chronic gastritis and developing gastric mucosa atrophy are at increased risk of the development of gastric cancer. The diagnosis of chronic atrophic gastritis (CAG) is a complex procedure involving a detailed history taking, a thorough physical examination and the use of laboratory and instrumental diagnostic methods among which the endoscopy of the upper digestive tract is the cornerstone because it allows the assessment of the topography of gastritis and identification of erosions and areas of intestinal metaplasia with the use of NBI endoscopy. However, the diagnosis of CAG requires morphological examination of the gastric mucosa. So, in addition to assessing macroscopic changes in the gastric mucosa, it is necessary to take biopsy specimens in accordance with the protocols for their morphological and immunohistochemical examination. In the absence of specific diagnostic stigmas of CAG, close cooperation between a clinician, endoscopist and pathologist is necessary. The article presents systematized data on the histopathological assessment of the gastric mucosa atrophy to predict the risk of gastric cancer.

A nomogram model based on the number of examined lymph nodes-related signature to predict prognosis and guide clinical therapy in gastric cancer

BACKGROUND

Increasing evidence suggests that the number of examined lymph nodes (ELNs) is strongly linked to the survivorship of gastric cancer (GC). The goal of this study was to assess the prognostic implications of the ELNs number and to construct an ELNs-based risk signature and nomogram model to predict overall survival (OS) characteristics in GC patients.

METHODS

This inception cohort study included 19,317 GC patients from the U.S. Surveillance, Epidemiology, and End Results (SEER) database, who were separated into a training group and an internal validation group. The nomogram was built with the training set, then internally verified with SEER data, and externally validated with two different data sets. Based on the RNA-seq data, ELNs-related DERNAs (DElncRNAs, DEmiRNAs, andDEmRNAs) and immune cells were identified. The LASSO-Cox regression analysis was utilized to construct ELNs-related DERNAs and immune cell prognostic signature in The Cancer Genome Atlas (TCGA) cohort. The OS of subgroups with high- and low-ELN signature was compared using the Kaplan-Meier (K-M) analysis. A nomogram was successfully constructed based on the ELNs signature and other clinical characteristics. The concordance index (C-index), calibration plot, receiver operating characteristic curve, and decision curve analysis (DCA) were all used to evaluate the nomogram model. The meta-analysis, the Gene Expression Profiling Interactive Analysis database, and reverse transcription-quantitative PCR (RT-qPCR) were utilized to validate the RNA expression or abundance of prognostic genes and immune cells between GC tissues and normal gastric tissues, respectively. Finally, we analyzed the correlations between immune checkpoints, chemotherapy drug sensitivity, and risk score.

RESULTS

The multivariate analysis revealed that the high ELNs improved OS compared with low ELNs (hazard ratio [HR] = 0.659, 95% confidence interval [CI]: 0.626-0.694, p < 0.0001). Using the training set, a nomogram incorporating ELNs was built and proven to have good calibration and discrimination (C-index [95% CI], 0.714 [0.710-0.718]), which was validated in the internal validation set (C-index [95% CI], 0.720 [0.714-0.726]), the TCGA set (C-index [95% CI], 0.693 [0.662-0.724]), and the Chinese set (C-index [95% CI], 0.750 [0.720-0.782]). An ELNs-related signature model based on ELNs group, regulatory T cells (Tregs), neutrophils, CDKN2B-AS1, H19, HOTTIP, LINC00643, MIR663AHG, TMEM236, ZNF705A, and hsa-miR-135a-5p was constructed by the LASSO-Cox regression analysis. The result showed that OS was remarkably lower in patients with high-ELNs signature compared with those with low-ELN signature (HR = 2.418, 95% CI: 1.804-3.241, p < 0.001). This signature performed well in predicting 1-, 3-, and 5-year survival (AUC [95% CI] = 0.688 [0.612-0.763], 0.744 [0.659-0.830], and 0.778 [0.647-0.909], respectively). The multivariate Cox analysis illustrated that the risk score was an independent predictor of survival for patients with GC. Moreover, the expression of prognostic genes (LINC00643, TMEM236, and hsa-miR-135a-5p) displayed differences between GC tissues and adjacent non-tumor tissues. The C-index of the nomogram that can be used to predict the OS of GC patients was 0.710 (95% CI: 0.663-0.753). Both the calibration plots and DCA showed that the nomogram has good predictive performance. Moreover, the signature was significantly correlated with the N stage and T stage. According to our analysis, GC patients in the low-ELN signature group may have a better immunotherapy response and OS outcome.

CONCLUSIONS

We explored the prognostic role of ELNs in GC and successfully constructed an ELNs signature linked to the GC prognosis in TCGA. The findings manifested that the signature is a powerful predictive indicator for patients with GC. The signature might contain potential biomarkers for treatment response prediction for GC patients. Additionally, we identified a novel and robust nomogram combining the characteristics of ELNs and clinical factors for predicting 1-, 3-, and 5-year OS in GC patients, which will facilitate personalized survival prediction and aid clinical decision-making in GC patients.

Degree of Gastric Mucosal Atrophy Correlated Well with Gastric Cancer Occurrence in Patients with Helicobacter pylori-eradicated Status

Objective This study was performed to clarify the association of the degree of gastric mucosal atrophy (GMA) with the occurrence of gastric cancer in patients with Helicobacter pylori-eradicated status. Subjects and Methods The subjects were 3,058 patients (2,035 men, 1,023 women; mean age 57.9 ± 9.5 years old) with H. pylori eradication who underwent esophago-gastroduodenal endoscopy examinations as part of medical checkups conducted between April 2013 and March 2022. The gender, age at eradication, time since eradication, usage of anti-secretory drugs, degree of endoscopic GMA, and FGP prevalence were compared between subjects with and without gastric cancer occurrence. Results Gastric cancer was newly detected in 26 subjects (0.85%) during the study period, with an older age at H. pylori eradication and severe grade of endoscopic GMA being significant risk factors for its occurrence. The gender, smoking history, and usage of anti-secretory drugs were not significantly different between subjects with and without gastric cancer occurrence. A Cox regression analysis showed that an older age at eradication and the degree of GMA were risk factors significantly related to occurrence. Furthermore, the degree of GMA was inversely correlated with FGP development, and gastric cancer was not detected in 467 subjects with FGP prevalence. Conclusion An older age at the time of H. pylori eradication and the degree of GMA are significant risk factors for gastric cancer occurrence in H. pylori-eradicated patients. The FGP prevalence in subjects with H. pylori eradication was inversely associated with GMA, suggesting it was negatively related with gastric cancer occurrence.

Long-term changes in aberrant DNA methylation and gastritis after Helicobacter pylori eradication focused on metachronous gastric cancer

BACKGROUND

A persistently high methylation level in gastric mucosa after Helicobacter pylori (H. pylori) eradication is presumed to be a risk for metachronous gastric cancer (MGC); however, long-term changes in aberrant DNA methylation and histological gastritis have been unclear. Our aim was to examine changes in DNA methylation and histological gastritis according to the occurrence of MGC.

METHODS

Subjects were classified into three groups: 25 patients in whom MGCs occurred after the initial endoscopic resection (ER) for early gastric cancer and H. pylori eradication (MGC group), 17 patients in whom MGC did not occur for more than 5 years after the initial ER and H. pylori eradication (non-MGC group) and 29 patients without a history of gastric cancer who succeeded in eradication more than 5 years ago (HP group). Aberrance of DNA methylation in three genes (miR-124a-3, EMX1, NKX6-1) and histological score of atrophy and intestinal metaplasia (IM) were evaluated using biopsy samples before and more than a mean of 5 years after H. pylori eradication. Also, the mean Z-score was calculated using Z-score values of the three genes.

RESULTS

The methylation level of miR-124a-3 in the HP group and non-MGC group and that of EMX1 in the HP group significantly decreased in the long term after eradication. In the MGC group, H. pylori eradication did not improve aberrant methylation, and the mean Z-score significantly increased. There were significant positive correlations between methylation levels in miR-124a-3 and EMX1 and histological findings after eradication.

CONCLUSIONS

A persistently high methylation level after H. pylori eradication reflected precancerous mucosal conditions and led to long-term MGC.

Genome-wide DNA methylation profiling of stomach cancer in the ethnic population of Mizoram, North East India

Stomach cancer is the fifth most common cancer in terms of prevalence and incidence and the fourth leading cause of mortality in men and women worldwide. It is well-established that aberrant DNA methylation in cells can lead to carcinogenesis. The primary objective of our study was to investigate the aberrant DNA methylation status of genes associated with stomach cancer with a particular reference to the ethnic population of Mizoram, North East India. The site-level analysis identified 2883 CpG sites differentially methylated, representing ~922 genes. Out of which 476 Differentially Methylated Positions (DMPs) were promoter-associated, 452 DMPs were hypermethylated, and 24 were hypomethylated. The region-level analysis identified 462 Differentially Methylated Regions (DMRs) corresponding to ~320 genes, of which ~281 genes were hypermethylated and ~ 40 genes were hypomethylated. TCGA analysis showed that some of the genes had been previously implicated in other cancers including stomach cancer. Five hypermethylated genes were selected as candidate genes for further investigations and they have shown to be novel and could serve as candidate hypermethylation biomarkers for stomach cancer in this particular ethnic group.

Helicobacter pylori infection and DNMT3a polymorphism are associated with the presence of premature coronary artery disease and subclinical atherosclerosis. Data from the GEA Mexican Study

BACKGROUND

The association between H. pylori infection and coronary artery disease (CAD) is well-known. Alterations in DNA methylation in CAD have been reported, which can be induced by H. pylori through the DNA demethylases (DNMTs). The objective was to analyze the association and interaction of H. pylori infection and DMNT3a gene polymorphisms with premature CAD (pCAD) and subclinical atherosclerosis (SA).

METHODS

The study included 561 patients with pCAD, 318 subjects with SA, and 599 healthy controls. Antibodies against H. pylori and DNMT3a rs13420827, rs752208, and rs1550117 polymorphisms were determined.

RESULTS

The pCAD group presented the highest seroprevalence of H. pylori infection (87.7%) compared to the SA (74.5%, p = 1 × 10^-6) and the control group (63.1%, p = 7 × 10^-23). A significant association was observed between H. pylori infection and pCAD (OR = 2.729, p = 1.0 × 10^-6). The rs13420827 polymorphism was associated with a high risk of H. pylori infection in the whole population (p_additive = 0.009, p_dominant = 0.018, and p_codominant2 = 0.013) and in individuals with SA (p_additive = 0.003, p_dominant = 0.020, p_recessive = 0.013, and p_codominant2 = 0.005). The coexistence of H. pylori infection and the rs13420827GG genotype increases the risk of pCAD (p_interaction = 1.1 × 10^-5).

CONCLUSIONS

According to the model adjusted for more confounding variables, H. pylori infection was associated with almost three times the risk of developing pCAD. The rs13420827G allele was associated with an increased risk of H. pylori infection in the whole population and in individuals with SA. Individuals in whom H. pylori infection and the rs13420827GG genotype coexist are at increased risk of pCAD.

Increased 5-hydroxymethylcytosine is a favorable prognostic factor of Helicobacter pylori-negative gastric cancer patients

BACKGROUND

Most gastric cancer (GC) patients are diagnosed at middle or late stage because the symptoms in early stage are obscure, which causes higher mortality rates of GC. Helicobacter pylori (H. pylori) was identified as a class I carcinogen and leads to aberrant DNA methylation/hydroxymethylation. 5-hydroxymethylcytosine (5-hmC) plays complex roles in gene regulation of tumorigenesis and can be considered as an activating epigenetic mark of hydroxymethylation.

AIM

To explore the association between 5-hmC levels and the progression and prognosis of GC patients with or without H. pylori infection.

METHODS

A retrospective cohort study was conducted to estimate the predicted value of 5-hmC level in the progression and prognosis of GC patients with different H. pylori infection status. A total of 144 GC patients were recruited.

RESULTS

The levels of 5-hmC were significantly decreased in tumor tissues (0.076 ± 0.048) compared with the matched control tissues (0.110 ± 0.057, P = 0.001). A high level of 5-hmC was an independent significant favorable predictor of overall survival in GC patients (hazard ratio = 0.61, 95% confidence interval: 0.38-0.98, P = 0.040), the H. pylori-negative GC subgroup (hazard ratio = 0.30, 95% confidence interval: 0.13-0.68, P = 0.004) and the GC patients with TNM stage Ⅰ or Ⅱ (hazard ratio = 0.32, 95% confidence interval: 0.13-0.77, P = 0.011).

CONCLUSION

Increased 5-hmC is a favorable prognostic factor in GC, especially for H. pylori-negative subgroups.

DNA Methylation: An Important Biomarker and Therapeutic Target for Gastric Cancer

Gastric cancer (GC) is a very common malignancy with a poor prognosis, and its occurrence and development are closely related to epigenetic modifications. Methylation of DNA before or during gastric cancer is an interesting research topic. This article reviews the studies on DNA methylation related to the cause, diagnosis, treatment, and prognosis of gastric cancer and aims to find cancer biomarkers to solve major human health problems.

Gastric cancer: An epigenetic view

Gastric cancer (GC) poses a serious threat worldwide with unfavorable prognosis mainly due to late diagnosis and limited therapies. Therefore, precise molecular classification and search for potential targets are required for diagnosis and treatment, as GC is complicated and heterogeneous in nature. Accumulating evidence indicates that epigenetics plays a vital role in gastric carcinogenesis and progression, including histone modifications, DNA methylation and non-coding RNAs. Epigenetic biomarkers and drugs are currently under intensive evaluations to ensure efficient clinical utility in GC. In this review, key epigenetic alterations and related functions and mechanisms are summarized in GC. We focus on integration of existing epigenetic findings in GC for the bench-to-bedside translation of some pivotal epigenetic alterations into clinical practice and also describe the vacant field waiting for investigation.

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.

Preventing Metachronous Gastric Cancer after the Endoscopic Resection of Gastric Epithelial Neoplasia: Roles of Helicobacter pylori Eradication and Aspirin

Whether Helicobacter pylori eradication actually reduces the risk of metachronous gastric cancer (MGC) development remains a controversial question. In this review, we addressed this topic by reviewing the results of clinical investigations and molecular pathological analyses of the roles of H. pylori eradication and aspirin administration in the prevention of MGC. In regard to the clinical studies, the results of meta-analyses and randomized control trials differ from those of retrospective studies: the former trials show that H. pylori eradication has a preventive effect on MGC, while the latter studies do not. This discrepancy may be at least partly attributable to differences in the follow-up periods: H. pylori eradication is more likely to prevent MGC over a long-term follow-up period (≥5 years) than over a short-term follow-up period. In addition, many studies have shown that aspirin may have an additive effect on MGC-risk reduction after H. pylori eradication has been achieved. Both H. pylori eradication and aspirin use induce molecular alterations in the atrophic gastritis mucosa but not in the intestinal metaplasia. Unfortunately, the molecular pathological analyses of these interventions have been limited by short follow-up periods. Therefore, a long-term prospective cohort is needed to clarify the changes in molecular events caused by these interventions.

Elevated Expression of DNA Methyltransferases and Enhancer of Zeste Homolog 2 in Helicobacter pylori - Gastritis and Gastric Carcinoma

AIM

The aim of this study was to study the role of key epigenetic regulators pertaining to DNA methylation and histone-modification systems in Helicobacter pylori (HP)-associated gastritis and gastric carcinogenesis.

METHODS

The expression of DNA methyltransferase (DNMT-1, 3A, and 3B) and the catalytic subunit of polycomb repressive complex-2 (enhancer of zeste homolog 2 [EZH2]) in gastric carcinomas (n = 104), mucosa adjacent to carcinoma (n = 104), HP-associated gastritis (n = 95), and histologically normal mucosa (n = 31) was assessed by immunohistochemistry and qRT-PCR.

RESULTS

The expression of all 3 DNMTs and EZH2 was significantly higher in HP-associated gastritis and carcinoma cases than in those with adjacent and normal mucosa. The expression of DNMT-1 and 3B was maximum in HP-associated gastritis. DNMT-3A showed higher expression in carcinoma-adjacent mucosa than in normal mucosa. Interestingly, the expression of EZH2 was higher in cases of HP-associated gastritis with metaplasia than in those without metaplasia and also in cases of intestinal type of adenocarcinoma. Significant positive correlation of EZH2 was identified with DNMT-1, DNMT-3A, and DNMT-3B. However, none of these markers was associated with survival outcome.

CONCLUSION

This study establishes an important role of the key epigenetic regulators in the pathogenesis of both HP-associated gastritis and gastric carcinoma. Higher expression of all the epigenetic markers in the gastritis and their persistence in the carcinoma point toward their implications in HP-driven gastric carcinogenesis. Further, an inter-relation between the 2 arms of epigenetics, namely, DNA methylation and histone-modification in the pathogenesis of gastric carcinoma, is also documented. Given the reversibility of epigenetic phenomenon, these molecules may be of important therapeutic use.

Risk Factors for Gastric Cancer after the Eradication of Helicobacter pylori Evaluated Based on the Background Gastric Mucosa: A Propensity Score-matched Case-control Study

Objective The eradication of Helicobacter pylori (H. pylori) reduces the risk for gastric cancer (GC) development, but it cannot prevent GC completely. We investigated the risk factors of early GC development after the eradication of H. pylori, based on the histological characteristics of gastric mucosa. Methods Sixty-one patients who underwent endoscopic submucosal dissection for early GC after successful H. pylori eradication (Group A) and 122 patients without developing a gastric neoplasm over 3 years after successful H. pylori eradication (Group B) were analyzed. We compared the histological findings of the patients enrolled in Group A and Group B before and after the propensity score-matching. Results Comparing the characteristics of two the groups, Group A consisted predominantly of males, had significantly more elderly patients, and the years after successful eradication tended to be longer. We performed score matching for these three factors to reduce the influence of any confounding factors. After matching, the scores of inflammation for Group A (n=54) was significantly higher than those of Group B (n=54) at the greater curvature of the antrum, the lesser curvature of the corpus, and the greater curvature of the corpus. According to a multivariate analysis, inflammation of the greater curvature of the antrum and lesser curvature of the corpus were found to be independent risk factors. The risk ratio and 95% CI were 5.92 (2.11-16.6) (p<0.01), and 3.56 (1.05-13.2) (p=0.04), respectively. Conclusion A continuous high level of inflammation of the background gastric mucosa may be a risk factor for gastric cancer onset after H. pylori eradication.

Promising aberrant DNA methylation marker to predict gastric cancer development in individuals with family history and long-term effects of H. pylori eradication on DNA methylation

OBJECTIVE

It remains unknown whether individuals with a family history (FH) of gastric cancer (GC) are associated with aberrant DNA methylation. The aim of this study was to investigate the association between aberrant DNA methylation and FH of GC.

DESIGN

Using quantitative MethyLight assay, MOS, miR124a-3, NKX6-1, EMX1, CDH1, and TWIST1 methylation levels in the noncancerous gastric mucosa was compared between subjects with and without FH based on GC and Helicobacter pylori (Hp) infection. Changes in the methylation levels were evaluated over time after Hp eradication.

RESULTS

In Hp-positive GC patients, MOS (P < 0.001), CDH1 (P < 0.001), and TWIST1 (P = 0.004) methylation were decreased in subjects with FH (n = 64) than in those without FH (n = 58). In Hp-positive controls, MOS methylation was lower in subjects with FH (n = 73) than in those without FH (n = 50) (P = 0.042), while miR124a-3 (P = 0.006), NKX6-1 (P < 0.001), and CDH1 (P < 0.001) methylation were higher in subjects with FH. CDH1 methylation constantly decreased from 2 years in GC patients and 3-4 years in controls after Hp eradication (all P < 0.001). A persistent decrease in methylation over time was not observed in other genes after eradication.

CONCLUSION

The methylation of MOS and CDH1 provided an association between aberrant DNA methylation and gastric carcinogenesis in FH of GC, a useful marker for GC risk in individuals with FH. Furthermore, CDH1 methylation decreased after Hp eradication.

Clinical Outcomes of Metachronous Gastric Cancer after Endoscopic Resection for Early Gastric Cancer

Background/Aims

Patients treated with endoscopic submucosal dissection (ESD) for early gastric cancer (EGC) are at risk of developing metachronous gastric cancer (MGC). The aim of this study was to evaluate the clinical outcomes of MGC after ESD for EGC between the re-ESD and surgery groups.

Methods

In total, data from 1,510 patients who underwent ESD for EGC from January 2005 to May 2014 were retrospectively reviewed, and data from 112 patients with MGC were analyzed according to the type of treatment, namely, re-ESD and surgery. The clinicopathological factors affecting the subsequent treatment and outcomes of MGC were evaluated.

Results

The median duration to the development of MGC was 47 months. In multivariate analysis, lower body mass index (BMI) (p=0.037) and multiplicity (p=0.014) of index cases were significantly associated with subsequent surgery for MGC. In cases of MGC, a diffuse or mixed-type Lauren classification (p=0.009), the depth of tumor mucosal invasion (p=0.001), and an upper stomach location (p=0.049) were associated with surgery. Overall survival was significantly shorter in the surgery group than in the re-ESD group after treatment for MGC (log-rank test, p=0.01).

Conclusions

Lower BMI and multiplicity of index cancers were significantly associated with the surgical resection of MGC. Close follow-up is needed to minimize additional treatment for cases at high risk of advanced MGC after ESD for EGC.

Distinct DNA methylation targets by aging and chronic inflammation: a pilot study using gastric mucosa infected with Helicobacter pylori

Background

Aberrant DNA methylation is induced by aging and chronic inflammation in normal tissues. The induction by inflammation is widely recognized as acceleration of age-related methylation. However, few studies addressed target genomic regions and the responsible factors in a genome-wide manner. Here, we analyzed methylation targets by aging and inflammation, taking advantage of the potent methylation induction in human gastric mucosa by Helicobacter pylori infection-triggered inflammation.

Results

DNA methylation microarray analysis of 482,421 CpG probes, grouped into 270,249 genomic blocks, revealed that high levels of methylation were induced in 44,461 (16.5%) genomic blocks by inflammation, even after correction of the influence of leukocyte infiltration. A total of 61.8% of the hypermethylation was acceleration of age-related methylation while 21.6% was specific to inflammation. Regions with H3K27me3 were frequently hypermethylated both by aging and inflammation. Basal methylation levels were essential for age-related hypermethylation while even regions with little basal methylation were hypermethylated by inflammation. When limited to promoter CpG islands, being a microRNA gene and high basal methylation levels strongly enhanced hypermethylation while H3K27me3 strongly enhanced inflammation-induced hypermethylation. Inflammation was capable of overriding active transcription. In young gastric mucosae, genes with high expression and frequent mutations in gastric cancers were more frequently methylated than in old ones.

Conclusions

Methylation by inflammation was not simple acceleration of age-related methylation. Targets of aberrant DNA methylation were different between young and old gastric mucosae, and driver genes were preferentially methylated in young gastric mucosa.

Helicobacter pylori Infection following Endoscopic Resection of Early Gastric Cancer

The role of Helicobacter pylori (H. pylori) infection in patients following endoscopic resection of early gastric cancer (EGC) remains unclear. This article presents a review of literature published in the past 15 years. H. pylori-mediated persistent methylation levels are associated with the development of metachronous gastric cancer. The methylation of certain specific genes can be used to identify patients with a high risk of metachronous gastric cancer even after H. pylori eradication. H. pylori eradication after endoscopic resection should be performed as early as possible for eradication success and prevention of metachronous precancerous lesions. Although whether the eradication of H. pylori could prevent the development of metachronous cancer after endoscopic resection is controversial, several meta-analyses concluded that H. pylori eradication could reduce the incidence of metachronous gastric cancer significantly. In addition, H. pylori eradication in gastric cancer survivors after endoscopic resection could reduce healthcare cost and save lives in a cost-effective way. Taken together, H. pylori eradication after endoscopic resection of EGC is recommended as prevention for metachronous precancerous lesions and metachronous gastric cancer.

Gastric Mucosal Microarchitectures Associated with Irreversibility with Helicobacter pylori Eradication and Downregulation of Micro RNA (miR)-124a

To investigate the molecular mechanisms of gastric carcinogenesis after Helicobacter pylori (H. pylori) eradication, expression of miR-124a, miR-34b, and miR-34c was examined in nonneoplastic gastric specimens after successful H. pylori eradication. The magnifying narrow-band imaging (NBI) endoscopic features of gastric mucosa were also examined. The atrophic type, an informative endoscopic feature for histological intestinal metaplasia, showed lower expression of miR-124a. Lower expression of miR-124a correlated with hypermethylation of the miR-124a3 locus. The atrophic type represents gastric microarchitectures associated with irreversibility with H. pylori eradication and downregulation of miR-124a.

DNA methylation silencing of microRNA gene methylator in the precancerous background mucosa with and without gastric cancer: Analysis of the effects of H. pylori eradication and long-term aspirin use

The risk of gastric cancer (GC) declines after Helicobacter pylori (H. pylori) eradication and long-term aspirin use. We evaluated the effects of H. pylori eradication (Cohort 1) and aspirin use (Cohort 2) on the methylation of microRNAs (miRNAs), such as miR-34c, miR-124a-3, miR-129-2, and miR-137, in the gastric mucosa with and without GC, i.e., in atrophic mucosal glands without intestinal metaplasia (non-IM) and intestinal metaplastic glands (IM). DNA was isolated from non-IM and IM separately using laser caption microdissection. In Cohort 1, H. pylori eradication was associated with a significant reduction of miR-124a-3 methylation only in non-IM, but not in IM. miR-129-2 methylation in non-IM may be a surrogate marker of GC in H. pylori-infected patients. In Cohort 2, aspirin did not reverse miRNA methylation in either non-IM or IM, irrespective of H. pylori infection. miR-129-2 methylation in non-IM was an independent predictive marker of GC in H. pylori-infected but not -eradicated patients. These results indicate that H. pylori eradication and aspirin use were less effective for improving methylation in IM than in non-IM; thus, these interventions are recommended at an early stage prior to the development of IM to prevent GC development. In addition, the effects of the interventions were not uniform for each miRNA gene.

Epigenetic and inflammatory events in experimental periodontitis following systemic microbial challenge

AIM

The purpose of this study was to determine inflammatory and epigenetic features following induction of oral and gut dysbiosis in experimental periodontitis in order to examine the interplay between oral and systemic infection.

MATERIALS AND METHODS

Periodontitis was induced in 6- to 8-week-old C57BL/6 mice by (a) Ligature placement (Lig group) (oral challenge); (b) P. gingivalis gavage (Pg group) (systemic challenge); and (c) the combination of the two models oral and systemic challenge (Pg + Lig). The duration of the experiment was 60 days, and the animals were then sacrificed for analyses. Alveolar bone loss was assessed, and a multiplex immunoassay was performed. Maxillae and gut tissues were immunostained for DNMT3b (de novo methylation marker), B and T lymphocyte attenuator (BTLA) and IL-18R1 (inflammation markers).

RESULTS

Pg and Pg + Lig groups exhibited higher bone loss when compared to Sham. BAFF, VEGF, RANKL, RANTES and IP-10 were significantly higher with Pg gavage. Likewise, DNMT3b was overexpressed in both gut and maxilla after the Pg administration. The same pattern was observed for BTLA and IL-18R1 in gut tissues.

CONCLUSIONS

The systemic microbial challenge either alone or in combination with local challenge leads to distinct patterns of inflammatory and epigenetic features when compared to simply locally induced experimental periodontitis.

Eradication of Helicobacter pylori Induces Immediate Regressive Changes in Early Gastric Adenocarcinomas

OBJECTIVE

Helicobacter pylori eradication is expected to prevent gastric cancer. However, morphological alterations after eradication often hinder accurate diagnosis. Therefore, we evaluated endoscopic and histological changes in gastric tumors after eradication of H. pylori in a time-dependent manner.

METHODS

We classified 144 cases of endoscopic submucosal dissection (ESD) of early gastric cancer into the following categories: (i) patients positive for H. pylori with no eradication history, (ii) patients positive for H. pylori who underwent ESD 2 months after eradication, (iii) patients negative for H. pylori with an eradication history of at least 6 months before ESD, and (iv) patients negative for H. pylori with an unknown history. We compared endoscopic and histological factors between the groups.

RESULTS

The characteristics of cancers positive for H. pylori were exploding shape, superficial high-grade atypical epithelium, and a surface proliferating zone. H. pylori eradication induced a series of endoscopic and histological changes, including shape -depression, appearance of surface regenerative and lower-grade atypical epithelium, and a downward shift of the proliferative zone within a period as short as 2 months.

CONCLUSION

H. pylori eradication rapidly causes cancer regression and leads to tumor shrinkage, diminished atypism, and shortened proliferative zone, resulting in drastic morphological changes.

Helicobacter pylori-induced DNA Methylation as an Epigenetic Modulator of Gastric Cancer: Recent Outcomes and Future Direction

Gastric cancer is ranked fifth in cancer list and has the third highest mortality rate. Helicobacter pylori is a class I carcinogen and a predominant etiological factor of gastric cancer. H. pylori infection may induce carcinogenesis via epigenetic alterations in the promoter region of various genes. H. pylori is known to induce hypermethylation-silencing of several tumor suppressor genes in H. pylori-infected cancerous and H. pylori-infected non-cancerous gastric mucosae. This article presents a review of the published literature mainly from the last year 15 years. The topic focuses on H. pylori-induced DNA methylation linked to gastric cancer development. The authors have used MeSH terms "Helicobacter pylori" with "epigenetic," "DNA methylation," in combination with "gastric inflammation", gastritis" and "gastric cancer" to search SCOPUS, PubMed, Ovid, and Web of Science databases. The success of epigenetic drugs such as de-methylating agents in the treatment of certain cancers has led towards new prospects that similar approaches could also be applied against gastric cancer. However, it is very important to understand the role of all the genes that have already been linked to H. pylori-induced DNA methylation in order to in order to evaluate the potential benefits of epigenetic drugs.

Genomic landscape of epithelium with low-grade atypia on gastric cancer after Helicobacter pylori eradiation therapy

BACKGROUND

Gastric cancer may develop after successful eradication of Helicobacter pylori, although the incidence is lower than in non-eradicated individuals. We previously reported the appearance of characteristic epithelium with low-grade atypia (ELA) on the surface of gastric cancer after H. pylori eradication. However, whether ELA originates from cancer after re-differentiation or from the non-cancerous surrounding mucosa is unknown.

METHODS

We isolated ELA regions from 10 early gastric cancer patients and analyzed the nucleotide sequences for 90 oncogenes and 35 fusion oncogenes, comparing them with counterpart cancer tissue, normal gastric mucosa, and blood cell-derived DNA. Somatic mutations in each tissue were identified by comparing them with the sequences from whole blood-derived DNA.

RESULT

Gene alterations were observed in nine of the ten patients, and up to 42 and 70 somatic mutations were seen in cancer and ELA samples, respectively. Common mutations shared between cancer and ELA tissues were found in eight of these nine patients. In contrast, common mutations between non-cancer mucosa and ELA were only detected in one patient, who also had common mutation between cancer and ELA. ELA-specific nucleotide substitutions were seen in seven patients. In contrast, cancer-specific substitutions were only found in two patients. 18 out of 19 amino acid substitutions present in cancer tissue were also identified in ELA. These results suggest that ELA originated from cancer tissue and accumulated further nucleotide substitutions.

CONCLUSIONS

Differential diagnosis of ELA and normal mucosa should be carefully performed to prevent misdiagnosis of ELA as normal mucosa with atypia.

Evaluation of serum markers for gastric cancer and its precursor diseases among high incidence and mortality rate of gastric cancer area

BACKGROUND

Mongolia has the highest mortality rate of gastric cancer. The early detection of cancer and down-staging screening for high risk patients are essential. Therefore, we aimed to validate serum markers for stratifying patients for further management.

METHODS

Endoscopy and histological examination were performed to determine high risk and gastric cancer patients. Rapid urease test, culture and histological tests were performed to diagnose Helicobacter pylori infection. Serum pepsinogen (PG) I and II and anti-H. pylori IgG were measured by ELISA. Receiver Operating Characteristic analysis was used to extract the best cut-off point.

RESULTS

Totally 752 non-cancer and 50 consecutive gastric cancer patients were involved. The corpus chronic gastritis (72%: 36/50 vs. 56.4%: 427/752), corpus atrophy (42.0%: 21/50 vs. 18.2%: 137/752) and intestinal metaplasia (IM) (64.0%: 32/50 vs. 21.5%: 162/752) were significantly higher in gastric cancer than non-cancer patients, respectively. Therefore, corpus chronic gastritis, corpus atrophy and IM were considered as high risk disease. The best serum marker to predict the high risk status was PGI/II < 3.1 (sensitivity 67.2%, specificity 61%) and PGI/II further reduced to < 2.2 (sensitivity 66%, specificity 65.1%) together with PGI < 28 ng/mL (sensitivity 70%, specificity 70%) were the best prediction for gastric cancer. The best cut-off point to diagnose H. pylori infection was anti-H. pylori IgG > 8 U/mL. Multivariate analysis showed that anti-H. pylori IgG > 8 U/mL and PGI/II < 3.1 increased risk for high risk status and PGI/II < 3.1 remained to increase risk for gastric cancer.

CONCLUSION

The serum diagnosis using PGI/II < 3.1 cut-off value is valuable marker to predict high risk patients for population based massive screening.

New Methylation Biomarker Panel for Early Diagnosis of Dysplasia or Cancer in High-Risk Inflammatory Bowel Disease Patients

BACKGROUND

The risk of developing colorectal cancer (CRC) is increased in patients with inflammatory bowel disease (IBD) of the colon. The aim of the study was to evaluate the effectiveness of selected methylation gene panel for the early detection of CRC in high-risk IBD patients.

METHODS

In a discovery phase, 73 biopsies of 48 IBD patients (associated or not to CRC) were analyzed from genome-wide DNA methylation analysis using the Illumina Human Methylation 450K BeadChip. The panel of 5 genes selected (EYA4, SLIT2, FLI1, USP44, and SND1) was validated prospectively using methylation-specific melting curve analysis in biopsies of diseased and adjacent healthy tissue of 203 patients: 38 with IBD and associated neoplasia, 81 patients with IBD (25 of them with high risk), 48 with sporadic CRC, and 36 healthy controls.

RESULTS

The prevalence of methylation was higher in patients with IBD and associated neoplasia (both in diseased and adjacent healthy tissue, 71% and 52%, respectively) than in healthy controls (2/36, 6%; P = 6.72E-05). Methylation in IBD patients at high risk of dysplasia or cancer was more frequently detected than in patients at low risk (92% vs 57%; odds ratio, 8.63; P = 0.001). EYA4 and SLIT2 were the markers most frequently methylated. Differences in methylation levels were more evident in healthy mucosa (82% vs 15% high vs low risk, respectively; P = 1.25E-05).

CONCLUSIONS

Analysis of this panel of methylation markers may help in the early identification of colorectal dysplasia or cancer in high-risk IBD patients.

DNA methylation accumulation in gastric mucosa adjacent to cancer after Helicobacter pylori eradication

Molecular irreversibleness with Helicobacter pylori (H. pylori) infection might have a role in gastric tumorigenesis after H. pylori eradication. We performed comprehensive DNA methylation profiling of gastric mucosa after H. pylori eradication with or without gastric cancer. Using four different groups of biopsies obtained from gastric body without history of H. pylori infection (Hp-), gastric body without cancer after H. pylori eradication (cancer-free body), gastric body with early gastric cancer diagnosed after H. pylori eradication (EGC body) and their paired samples from adjacent mucosa of cancer (EGC ADJ), methylation status of five candidate genes (MYOD1, SLC16A12, IGF2, RORA and PRDM5) was examined by the bisulfite pyrosequencing. An Infinium Methylation EPIC BeadChip array was also used to characterize the methylation status of greater than 850,000 CpG sites. The EGC ADJ group showed highest methylation levels of five candidate genes among the four groups of biopsies. In the gastric body (cancer-free body + EGC body), methylation levels were significantly decreased in patients with longer period after eradication, while such association was not observed in EGC ADJ group. Hyper methylated samples were associated with shorter telomere, an indicator for rapid cell turnover, and higher DNMT1 protein expression, an enzyme related to methyl transfer reaction. The genome-wide methylation analysis demonstrated strikingly higher methylation levels especially at CpG islands in the EGC ADJ group. Exclusively hypermethylated promoter CpG islands in the same group frequently coded zinc finger proteins. Our data show that DNA methylation accumulation is associated with molecular irreversibleness and gastric carcinogenesis after H. pylori eradication.

Long-term effects of H. pylori eradication on epigenetic alterations related to gastric carcinogenesis

The risk of gastric cancer (GC) remains in precancerous conditions, including atrophic mucosa and intestinal mucosa (IM), even after H. pylori treatment. To define the molecular changes following H. pylori eradication, molecular alterations in the gastric mucosa with and without GC were evaluated in a long-term follow-up study. A total of 232 biopsy specimens from 78 consecutive patients, including atrophic gastritis patients with follow-up ≥3 y after successful H. pylori eradication (AG group), patients who developed early GC after successful eradication (≥3 y) (GC group), and patients with H. pylori-positive atrophic gastritis (Hp group), were analyzed. H. pylori eradication was associated with significant reductions of methylation of several genes/loci in atrophic mucosa (non-IM), but not in IM. In contrast, the incidence of CpG island methylator phenotype (CIMP) in IM was significantly higher in the GC group than in the AG group. miR-124a-3 methylation and miR-34c methylation were more frequently identified in IM, with very few in non-IM mucosa among the three groups. H. pylori eradication can reverse methylation only in non-IM mucosa. CIMP in IM may have potential as a surrogate maker of GC development, and methylation of miR-124a-3 and miR-34c is a molecular event in IM that may not be associated with GC development.

Methylation and Expression of Nonclustered Protocadherins Encoding Genes and Risk of Precancerous Gastric Lesions in a High-Risk Population

Nonclustered protocadherins (PCDH) family is a group of cell-cell adhesion molecules. We have found differentially methylated genes in the nonclustered PCDHs family associated with Helicobacter pylori (H. pylori) infection in prior genome-wide methylation analysis. To further investigate the methylation and expression of nonclustered PCDHs encoding genes in H. pylori--related gastric carcinogenesis process, four candidate genes including PCDH7, PCDH10, PCDH17, and PCDH20 were selected, which were reported to be tumor suppressors for digestive cancers. A total of 747 participants with a spectrum of gastric lesions were enrolled from a high-risk population of gastric cancer. Promoter methylation levels of four genes were significantly higher in H. pylori-positive subjects than the negative group (all P < 0.001). Elevated methylation levels of PCDH10 and PCDH17 were observed with the increasing severity of gastric lesions (both P _trend < 0.001). In the protein expression analysis, PCDH17 expression was inversely associated with gastric lesions; the OR [95% confidence interval (CI)] was 0.49 (0.26-0.95) for chronic atrophic gastritis (CAG), 0.31 (0.15-0.63) for intestinal metaplasia, and 0.38 (0.19-0.75) for indefinite dysplasia and dysplasia, compared with superficial gastritis. In addition, PCDH10 expression was significantly lower in CAG (OR, 0.40; 95% CI, 0.24-0.68). The inverse association between methylation and protein expression of PCDH10 and PCDH17 was further supported when we explored the methylation and mRNA expression in The Cancer Genome Atlas database (all P < 0.001). Our study found elevated promoter methylation and decreased expression of PCDH10 and PCDH17 in advanced gastric lesions, suggesting that elevated PCDH10 and PCDH17 methylation may be an early event in gastric carcinogenesis. Cancer Prev Res; 11(11); 717-26. ©2018 AACR.

Novel epigenetic markers for gastric cancer risk stratification in individuals after Helicobacter pylori eradication

BACKGROUND

The risk stratification of healthy individuals after Helicobacter pylori eradication is an urgent issue. The assessment of aberrant DNA methylation accumulated in gastric tissues with normal appearance, which can reflect overall epigenomic damage, is a promising strategy. We aimed to establish novel epigenetic cancer risk markers for H. pylori-eradicated individuals.

METHODS

Gastric mucosa was collected from eight healthy volunteers without H. pylori infection (G1), 75 healthy individuals with gastric atrophy (G2), and 94 gastric cancer patients (G3) after H. pylori eradication. Genome-wide analysis was conducted using Infinium 450 K and differentially methylated probes were screened using large difference and iEVORA-based methods. Bisulfite pyrosequencing was used for validation.

RESULTS

Screening, using 8 G1, 12 G2, and 12 G3 samples, isolated 57 candidates unmethylated in G1 and differentially methylated in G3 compared with G2. Validation for nine candidate markers (FLT3, LINC00643, RPRM, JAM2, ELMO1, BHLHE22, RIMS1, GUSBP5, and ZNF3) in 63 G2 and 82 G3 samples showed that all of them had significantly higher methylation levels in G3 than in G2 (P < 0.0001). Their methylation levels were highly correlated, which indicated that they reflect overall epigenomic damage. The candidates had sufficient performance (AUC: 0.70-0. 80) and high odds ratios (5.43-23.41), some of which were superior to a previous marker, miR-124a-3. The methylation levels of our novel markers were not associated with gastric atrophy, gender, or age.

CONCLUSIONS

Novel epigenetic markers for gastric cancer risk optimized for H. pylori-eradicated individuals were established.

Testin and filamin-C downregulation by acetylated Siah2 increases invasiveness of Helicobacter pylori-infected gastric cancer cells

Helicobacter pylori is the strongest known risk-factor for gastric cancer. However, its role in gastric cancer metastasis remains unclear. Previously we have reported that H. pylori promotes gastric cancer invasiveness by stabilizing the E3 ubiquitin ligase Siah2 which is mediated by Siah2 acetylation at Lys 139 (K¹³⁹) residue. Here we identify that cell adhesion-related proteins testin (TES) and filamin-C (FLN-C) interact with Siah2 and get proteasomally degraded. The efficiency of TES and FLN-C degradation is significantly potentiated by K¹³⁹-acetylated Siah2 (ac-K¹³⁹ Siah2) in infected gastric cancer cells (GCCs). ac-Siah2-mediated downregulation of TES and FLN-C disrupts filopodia structures but promotes lamellipodia formation and enhances invasiveness and migration of infected GCCs. Since H. felis-infected mice as well as human gastric cancer biopsy samples also show high level of ac-K¹³⁹ Siah2 and downregulated TES and FLN-C, we believe that acetylation of Siah2 is an important checkpoint that can be useful for therapeutic intervention.

Helicobacter pylori-induced modulation of the promoter methylation of Wnt antagonist genes in gastric carcinogenesis

BACKGROUND

This study aimed to investigate the changes in the promoter methylation and gene expression of multiple Wnt antagonists between the chronic infection and eradication of Helicobacter pylori (H. pylori) in gastric carcinogenesis.

METHODS

The levels of methylation and corresponding mRNA expression of seven Wnt antagonist genes (SFRP1, -2, -5, DKK1, -2, -3, WIF1) were compared among the patients with H. pylori-positive gastric cancers (GCs), and H. pylori-positive and H. pylori-negative controls, by quantitative MethyLight assay and real-time reverse transcription (RT)-polymerase chain reaction (PCR), respectively. The changes of the methylation and expression levels of the genes were also compared between the H. pylori eradication and H. pylori-persistent groups 1 year after endoscopic resection of GCs.

RESULTS

The methylation levels of SFRP and DKK family genes were significantly increased in the patients with H. pylori-positive GCs and followed by H. pylori-positive controls compared with H. pylori-negative controls (P < 0.001). SFRP1, -2, and DKK3 gene expression was stepwise downregulated from H. pylori-negative controls, H. pylori-positive controls, and to H. pylori-positive GCs (P < 0.05). Among the Wnt antagonists, only the degrees of methylation and downregulation of DKK3 were significantly reduced after H. pylori eradication (P < 0.05).

CONCLUSION

Epigenetic silencing of SFRP and DKK family genes may facilitate the formation of an epigenetic field during H. pylori-associated gastric carcinogenesis. The epigenetic field may not be reversed even after H. pylori eradication except by DKK3 methylation.

Quantitative proteomics reveals FLNC as a potential progression marker for the development of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) caused by hepatitis B virus (HBV) infection is one of the most life-threatening human cancers in China. However, the pathogenesis of HCC development is still unclear. Here, we systemically analyzed liver tissues from different stages of HCC patients through 8-plex Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) approach. A total of 4,620 proteins were identified and 3,781 proteins were quantified. When T1, T2 and T3 tumor tissues were compared with T1 non-tumor cells, 330, 365 and 387 differentially expressed proteins were identified respectively. IPA (Ingenuity Pathway Analysis) analysis revealed that these differentially expressed proteins were involved in endothelial cancer, cell spreading, cell adhesion and cell movement of tumor cell lines pathway and so on. Further study showed that the filamin C (FLNC) protein was significantly overexpressed with the development of HCC, which might play an important role in HCC invasion and metastasis. These results were also confirmed with western blot (WB). The mRNA levels were significantly increased in 50 pairs of tumor and adjacent non-tumor tissues from TCGA database. The higher expression of FLNC in HCC might be a common phenomenon, thereby shedding new light on molecular mechanism and biomarker for the diagnosis purpose of HCC development.

Effects of long-term aspirin use on molecular alterations in precancerous gastric mucosa in patients with and without gastric cancer

The risk of gastric cancer (GC) remains even after H. pylori eradication; thus, other combination treatments, such as chemopreventive drugs, are needed. We evaluated the effects of aspirin on genetic/epigenetic alterations in precancerous conditions, i.e., atrophic mucosa (AM) and intestinal metaplasia (IM), in patients with chronic gastritis who had taken aspirin for more than 3 years. A total of 221 biopsy specimens from 74 patients, including atrophic gastritis (AG) cases without aspirin use (control), AG cases with aspirin use (AG group), and GC cases with aspirin use (GC group), were analyzed. Aspirin use was associated with a significant reduction of CDH1 methylation in AM (OR: 0.15, 95% CI: 0.06-0.41, p = 0.0002), but was less effective in reversing the methylation that occurred in IM. Frequent hypermethylation including that of CDH1 in AM increased in the GC group compared to the AG group, and CDH1 methylation was an independent predictive marker of GC (OR: 8.50, 95% CI: 2.64-25.33, p = 0.0003). In patients with long-term aspirin use, the changes of molecular events in AM but not IM may be an important factor in the reduction of cancer incidence. In addition, methylation of the CDH1 gene in AM may be a surrogate of GC.

Morphologic characterization of residual DNA methylation in the gastric mucosa after Helicobacter pylori eradication

Residual DNA methylation in the gastric mucosa after Helicobacter pylori (H. pylori) eradication may have a role in gastric carcinogenesis. We examined the association between morphologic features and promoter methylation status of non-neoplastic gastric mucosa especially after H. pylori eradication. A total of 140 gastric specimens from 99 participants who had at least 6 months of post-eradication period were examined. The magnifying narrow-band imaging (NBI) endoscopic feature of gastric mucosa was divided into two types: restored-small, round pits, accompanied with honeycomb-like subepithelial capillary networks; atrophic-well-demarcated oval or tubulovillous pits with clearly visible coiled or wavy vessels. Methylation status of five candidate genes (MYOD1, SLC16A12, IGF2, RORA, and PRDM5) were examined by bisulfite pyrosequencing. The atrophic type, informative endoscopic features of intestinal metaplasia, demonstrated higher methylation levels in all five genes compared to the restored type (all P < 0.0001). In the restored type, methylation levels were significantly lower among the samples with longer post-eradication period (for all genes, P < 0.0001), which was not observed in atrophic type (for all genes, P > 0.1). Multivariate analysis demonstrated that atrophic type or presence of intestinal held an independent factor for hyper methylation (odds ratio: 24.69, 95% confidence interval: 6.95-87.76, P < 0.0001). The atrophic type by the magnifying NBI and presence of intestinal metaplasia are the morphologic characteristics of residual DNA methylation of after H. pylori eradication, regardless of the post-eradication period and it might be considered as the epigenetic irreversible point with H. pylori eradication.

Influences of the Gut Microbiota on DNA Methylation and Histone Modification

The gut microbiota is a vast ensemble of microorganisms inhabiting the mammalian gastrointestinal tract that can impact physiologic and pathologic processes. However, our understanding of the underlying mechanism for the dynamic interaction between host and gut microbiota is still in its infancy. The highly evolved epigenetic modifications allow hosts to reprogram the genome in response to environmental stimuli, which may play a key role in triggering multiple human diseases. In spite of increasing studies in gut microbiota and epigenetic modifications, the correlation between them has not been well elaborated. Here, we review current knowledge of gut microbiota impacts on epigenetic modifications, the major evidence of which centers on DNA methylation and histone modification of the immune system.

Transient receptor potential vanilloid 4 (TRPV4) silencing in Helicobacter pylori-infected human gastric epithelium

BACKGROUND

Helicobacter pylori (HP) infection induces methylation silencing of specific genes in gastric epithelium. Various stimuli activate the nonselective cation channel TRPV4, which is expressed in gastric epithelium where it detects mechanical stimuli and promotes ATP release. As CpG islands in TRPV4 are methylated in HP-infected gastric epithelium, we evaluated HP infection-dependent changes in TRPV4 expression in gastric epithelium.

MATERIALS AND METHODS

Human gastric biopsy samples, a human gastric cancer cell line (AGS), and a normal gastric epithelial cell line (GES-1) were used to detect TRPV4 mRNA and protein expression by RT-PCR and Western blotting, respectively. Ca²⁺ imaging was used to evaluate TRPV4 ion channel activity. TRPV4 methylation status was assessed by methylation-specific PCR (MSP). ATP release was measured by a luciferin-luciferase assay.

RESULTS

TRPV4 mRNA and protein were detected in human gastric biopsy samples and in GES-1 cells. MSP and demethylation assays showed TRPV4 methylation silencing in AGS cells. HP coculture directly induced methylation silencing of TRPV4 in GES-1 cells. In human samples, HP infection was associated with TRPV4 methylation silencing that recovered after HP eradication in a time-dependent manner.

CONCLUSION

HP infection-dependent DNA methylation suppressed TRPV4 expression in human gastric epithelia, suggesting that TRPV4 methylation may be involved in HP-associated dyspepsia.

Mechanisms for the induction of gastric cancer by Helicobacter pylori infection: aberrant DNA methylation pathway

Multiple pathogenic mechanisms by which Helicobacter pylori infection induces gastric cancer have been established in the last two decades. In particular, aberrant DNA methylation is induced in multiple driver genes, which inactivates them. Methylation profiles in gastric cancer are associated with specific subtypes, such as microsatellite instability. Recent comprehensive and integrated analyses showed that many cancer-related pathways are more frequently altered by aberrant DNA methylation than by mutations. Aberrant DNA methylation can even be present in noncancerous gastric mucosae, producing an "epigenetic field for cancerization." Mechanistically, H. pylori-induced chronic inflammation, but not H. pylori itself, plays a direct role in the induction of aberrant DNA methylation. The expression of three inflammation-related genes, Il1b, Nos2, and Tnf, is highly associated with the induction of aberrant DNA methylation. Importantly, the degree of accumulated aberrant DNA methylation is strongly correlated with gastric cancer risk. A recent multicenter prospective cohort study demonstrated the utility of epigenetic cancer risk diagnosis for metachronous gastric cancer. Suppression of aberrant DNA methylation by a demethylating agent was shown to inhibit gastric cancer development in an animal model. Induction of aberrant DNA methylation is the major pathway by which H. pylori infection induces gastric cancer, and this can be utilized for translational opportunities.