Changes in aberrant DNA methylation after Helicobacter pylori eradication: a long-term follow-up study

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.

Influence of Cytokine Genetic Polymorphisms in Helicobacter pylori-Associated Gastric Inflammation According to Sex in South Korea

Background/Aims

: The relationship between genetic polymorphisms and gastric inflammation remains unclear. This study aimed to evaluate the impact of genetic polymorphisms on Helicobacter pylori (HP)-associated gastritis according to sex.

Methods

: Two hundred thirty-two male and 404 female subjects with current HP infection were prospectively enrolled. The genotyping of IL-1B-511 C/T, IL-1RN variable number of tandem repeats, IL-6-572 G/C, IL-8-251 A/T, IL-8-781 C/T, IL-10-1082 G/A, IL-10-592 C/A, TNF-A-308 G/A, and transforming growth factor (TGF)-B-509 C/T, was determined by polymerase chain reaction-restriction fragment length polymorphism. The degree of monocyte or neutrophil infiltration, atrophic gastritis, and intestinal metaplasia was evaluated using the updated Sydney system.

Results

: Among the male subjects, moderate/severe atrophic gastritis of the corpus was higher in IL-1B-511 CC carriers than in CT and TT carriers independent of age, alcohol consumption, and HP virulence factors (26.9% vs 10.4%; adjusted hazard ratio [HR], 4.377; 95% confidence interval, 1.387 to 13.814). In females, IL-8-251 AA carriers were independently and significantly associated with moderate/severe atrophic gastritis of the corpus compared with that in AT and TT carriers (21.4% vs 6.0%, adjusted HR=3.799). In males, the IL-8-251 TT genotype was associated with moderate/severe intestinal metaplasia of the corpus compared with the AT and AA genotypes (13.4% vs 5.6%, adjusted HR=3.128), while the IL-10-592 CA and CC genotypes were associated with moderate/severe monocyte infiltration of the antrum compared with AA genotype (83.6% vs 71.8%, adjusted HR=2.227).

Conclusions

: Genetic polymorphisms in cytokines play different roles in HP-associated gastritis according to sex.

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.

Sample Collection Methods in Upper Gastrointestinal Research

In recent years, significant translational research advances have been made in the upper gastrointestinal (GI) research field. Endoscopic evaluation is a reasonable option for acquiring upper GI tissue for research purposes because it has minimal risk and can be applied to unresectable gastric cancer. The optimal number of biopsy samples and sample storage is crucial and might influence results. Furthermore, the methods for sample acquisition can be applied differently according to the research purpose; however, there have been few reports on methods for sample collection from endoscopic biopsies. In this review, we suggested a protocol for collecting study samples for upper GI research, including microbiome, DNA, RNA, protein, single-cell RNA sequencing, and organoid culture, through a comprehensive literature review. For microbiome analysis, one or two pieces of biopsied material obtained using standard endoscopic forceps may be sufficient. Additionally, 5 mL of gastric fluid and 3-4 mL of saliva is recommended for microbiome analyses. At least one gastric biopsy tissue is necessary for most DNA or RNA analyses, while proteomics analysis may require at least 2-3 biopsy tissues. Single cell-RNA sequencing requires at least 3-5 tissues and additional 1-2 tissues, if possible. For successful organoid culture, multiple sampling is necessary to improve the quality of specimens.

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.

Aberrant DNA methylation and expression of EYA4 in gastric cardia intestinal metaplasia

BACKGROUND

Intestinal metaplasia (IM) of the gastric cardia is an important premalignant lesion. However, there is limited information concerning its epidemiological and molecular features. Herein, we aimed to provide an overview of the epidemiological data for gastric cardiac IM and evaluate the role of EYA transcriptional coactivator and phosphatase 4 (EYA4) as an epigenetic biomarker for gastric cardiac IM.

METHODS

The study was conducted in the context of the gastric cardiac precancerous lesion program in southern China, which included 718 non-cancer participants, who undertook endoscopic biopsy and pathological examination in three endoscopy centers, between November 2018 and November 2021. Pyrosequencing and immunohistochemistry were performed to examine the DNA methylation status and protein expression level of EYA4.

RESULTS

Gastric cardiac IM presented in 14.1% (101/718) of participants and was more common among older (>50 years; 22.0% [95% CI: 17.8-26.8]) than younger participants (≤50 years; 6.7% [95% CI: 4.5-9.9]; P < 0.001). IM was more common in male participants (16.9% [95% CI: 13.2-21.3] vs. 11.3% [95% CI: 8.3-15.1]; P = 0.04). Pyrosequencing revealed that IM tissues exhibited significantly higher DNA methylation levels in EYA4 gene than normal tissues (P = 0.016). Further, the protein expression level of EYA4 was reduced in IM and absent in intraepithelial neoplasia tissues compared to normal tissues (P < 0.001).

CONCLUSIONS

Detection rates of gastric cardiac IM increase with age and are higher in men. Our findings highlight the important role of promoter hypermethylation and downregulation of EYA4 in gastric cardiac IM development.

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.

Integrated analysis of Helicobacter pylori-related prognostic gene modification patterns in the tumour microenvironment of gastric cancer

Background

Helicobacter pylori (HP) infection is one of the leading causes of gastric cancer (GC). However, the interaction between HP and the TME, and its carcinogenic mechanism remains unknown.

Methods

The HP-related prognostic genes were identified based on HP infection-related gene markers and HP infection sample datasets by risk method and NMF algorithm. Principal component analysis (PCA) algorithm was used to constructed the HPscore system. The “limma” R package was employed to determine differentially expressed genes. In addition, the R packages, such as “xCell” and “GSVA”, was used to analyze the relationship between the HPscore and tumor microenvironment. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to verify the expression levels of 28 HP-related prognostic genes in tissues.

Results

We successfully identified 28 HP-related prognostic genes that accurately classified the GC population. There are significant differences in survival between different subgroups (high-, low-risk and cluster_1,2). Thereafter, the HPscore system was constructed to evaluate the signatures of the 28 HP-related prognostic genes. The overall survival rate in the high-HPscore group was poor and immunological surveillance was reduced, whereas the low-HPscore group had a survival advantage and was related to the inflammatory response. HPscore was also strongly correlated with the tumour stage, TME cell infiltration and stemness. The qRT-PCR results showed that DOCK4 expression level of 28 HP-related prognostic genes was higher in gastric cancer tissues than in adjacent tissues.

Conclusions

HP signatures play a crucial role in the TME and tumourigenesis. HPscore evaluation of a single tumour sample can help identify the TME characteristics and the carcinogenic mechanism of GC patients infected with HP, based on which personalized treatment can be administered.

Association between EPHA5 methylation status in peripheral blood leukocytes and the risk and prognosis of gastric cancer

Purpose

Altered DNA methylation, genetic alterations, and environmental factors are involved in tumorigenesis. As a tumor suppressor gene, abnormal EPHA5 methylation was found in gastric cancer (GC) tissues and was linked to the initiation, progression and prognosis of GC. In this study, the EPHA5 methylation level in peripheral blood leukocytes (PBLs) was detected to explore its relationship with GC risk and prognosis.

Methods

A total of 366 GC cases and 374 controls were selected as the subjects of this study to collect their environmental factors, and the EPHA5 methylation status was detected through the methylation-sensitive high-resolution melting method. Logistic regression analysis was utilized to evaluate the associations among EPHA5 methylation, environmental factors and GC risk. Meanwhile, the propensity score (PS) was used to adjust the imbalance of some independent variables.

Results

After PS adjustment, EPHA5 Pm (positive methylation) was more likely to increase the GC risk than EPHA5 Nm (negative methylation) (OR^b = 1.827, 95% CI [1.202-2.777], P = 0.005). EPHA5 Pm had a more significant association with GC risk in the elderly (OR^a = 2.785, 95% CI [1.563-4.961], P = 0.001) and H. pylori-negative groups (OR^a = 2.758, 95% CI [1.369-5.555], P = 0.005). Moreover, the combined effects of EPHA5 Pm and H. pylori infection (OR_c ^a = 3.543, 95% CI [2.233-5.621], P < 0.001), consumption of alcohol (OR_c ^a = 2.893, 95% CI [1.844-4.539], P < 0.001), and salty food intake (OR_c ^a = 4.018, 95% CI [2.538-6.362], P < 0.001) on increasing the GC risk were observed. In addition, no convincing association was found between EPHA5 Pm and the GC prognosis.

Conclusions

EPHA5 methylation in PBLs and its combined effects with environmental risk factors are related to the GC risk.

rs2671655 single nucleotide polymorphism modulates the risk for gastric cancer in Helicobacter pylori-infected individuals: a genome-wide association study in the Korean population

OBJECTIVE

To identify genetic variations which is associated with gastric cancer (GC) risk according to Helicobacter pylori infection.

METHODS

This study incorporated 527 GC patients and 441 controls from a cohort at Seoul National University Bundang Hospital. The associations between GC risk and single nucleotide polymorphisms were calculated, stratified by H. pylori status, adjusting for age, sex, and smoking. mRNA expression from non-cancerous gastric mucosae was evaluated using reverse transcription quantitative polymerase chain reaction.

RESULTS

In the entire cohort, genome-wide association study showed no significant variants reached the genome-wide significance level. In the H. pylori-positive group, rs2671655 (chr17:47,468,020;hg19, GH17J049387 enhancer region) was identified at a genome-wide significance level, which was more pronounced in diffuse type GC. There was no significant variant in the H. pylori-negative group, indicating the effect modification of rs2671655 by H. pylori. Among the target genes of GH17J049387 enhancer (PHB1, ZNF652 and SPOP), PHB1 mRNA was expressed more in cases than in controls, who were not affected by H. pylori. By contrast, an increase in ZNF652 and SPOP in GC was observed only in the H. pylori-negative group (P < 0.05). Mediation analysis showed that PHB1 (P = 0.0238) and SPOP (P = 0.0328) mediated the effect of rs2671655 on GC risk. The polygenic risk score was associated with the number of rs2671655 risk alleles only in the H. pylori-positive group (P = 0.0112).

CONCLUSION

After H. pylori infection, rs2671655 may increase GC risk, especially in diffuse-type GC, by regulating the expression of several genes that consequently modify susceptibility to GC.

Effect of Helicobacter pylori Eradication on Epigenetic Changes in Gastric Cancer-related Genes

It is known that gastric carcinogenesis results from the progressive changes from chronic gastritis to gastric atrophy, intestinal metaplasia, dysplasia, and invasive carcinoma. Several genetic and epigenetic alterations are involved in this process, and Helicobacter pylori (H. pylori) infection is believed to induce the initiation and progression of these steps. From an epigenetic point of view, H. pylori induces hypermethylation of genes involved in the development of gastric cancer and regulates the expression of various microRNAs (miRNAs). These H. pylori-related epigenetic changes are accumulated not only at the site of neoplasm but also in the adjacent non-cancerous gastric mucosa. Thereby, a state vulnerable to gastric cancer known as an epigenetic field defect is formed. H. pylori eradication can have an effective chemopreventive effect in gastric carcinogenesis. However, the molecular biological changes that occur in the stomach environment during H. pylori eradication have not yet been established. Several studies have reported that H. pylori eradication can restore infection-related changes, especially epigenetic alterations in gastric cancer-related genes, but some studies have shown otherwise. Simply put, it appears that the recovery of methylated gastric cancer-related genes and miRNAs during H. pylori eradication may vary among genes and may also differ depending on the histological subtype of the gastric mucosa. In this review, we will discuss the potential mechanism of gastric cancer prevention by H. pylori eradication, mainly from an epigenetic perspective.

The Incidence and Risk Factors for Metachronous Gastric Cancer in the Remnant Stomach after Gastric Cancer Surgery

Background/Aims

Less invasive surgical treatment is performed in East Asia to preserve postoperative digestive function and reduce complications such as postgastrectomy syndromes, but there is an issue of metachronous gastric cancer (GC) in the remaining stomach. This study aimed to analyze the incidence of metachronous GC and its risk factors in patients who had undergone partial gastrectomy.

Methods

A total of 3,045 GC patients who had undergone curative gastric partial resection at Seoul National University Bundang Hospital were enrolled and analyzed retrospectively for risk factors, including age, sex, smoking, alcohol, Helicobacterpylori status, family history of GC, histological type, and surgical method.

Results

Metachronous GC in the remaining stomach occurred in 35 of the 3,045 patients (1.1%) 23 in the distal gastrectomy group (18 with Billroth-I anastomosis, five with Billroth-II anastomosis), seven in the proximal gastrectomy (PG) group, and five in the pylorus-preserving gastrectomy (PPG) group. Univariate and multivariate Cox regression analyses showed that age ≥60 years (p=0.005) and surgical method used (PG or PPG, p<0.001) were related risk factors for metachronous GC, while male sex and intestinal type histology were potential risk factors.

Conclusions

Metachronous GC was shown to be related to older age and the surgical method used (PG or PPG). Regular and careful follow-up with endoscopy should be performed in the case of gastric partial resection, especially in patients with male sex and intestinal type histology as well as those aged ≥60 years undergoing the PG or PPG surgical method.

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.

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.

Changes in Gastric Corpus Microbiota With Age and After Helicobacter pylori Eradication: A Long-Term Follow-Up Study

Helicobacter pylori infection changes gastric microbiota profiles. However, it is not clear whether H. pylori eradication can restore the healthy gastric microbiota. Moreover, there has been no study regarding the changes in gastric microbiota with aging. The objective of this study was to investigate the changes in gastric corpus microbiota with age and following H. pylori eradication. Changes in corpus mucosa-associated microbiota were evaluated in 43 individuals with endoscopic follow-up > 1 year, including 8 H. pylori-uninfected and 15 H. pylori-infected subjects with no atrophy/metaplasia by histology and pepsinogen I/II ratio > 4.0; 17 H. pylori-infected subjects with atrophy/metaplasia and pepsinogen I/II ratio < 2.5; and 3 subjects with atrophy/metaplasia, no evidence of active H. pylori infection, negative for anti-H. pylori immunoglobulin G (IgG) antibody testing, and no previous history of H. pylori eradication. Successful H. pylori eradication was achieved in 21 patients. The gastric microbiota was characterized using an Illumina MiSeq platform targeting 16S ribosomal DNA (rDNA). The mean follow-up duration was 57.4 months (range, 12-145 months), and median follow-up visit was 1 (range, 1-3). Relative abundance of Lactobacillales and Streptococcus was increased with atrophy/metaplasia. In H. pylori-uninfected subjects (n = 8), an increase in Proteobacteria (Enhydrobacter, Comamonadaceae, Sphingobium); a decrease in Firmicutes (Streptococcus, Veillonella), Fusobacteria (Fusobacterium), Nocardioidaceae, Rothia, and Prevotella; and a decrease in microbial diversity were observed during the follow-up (p trend < 0.05). In 10 of 21 subjects (47.6%), H. pylori eradication induced restoration of microbial diversity; however, a predominance of Acinetobacter with a decrease in microbial diversity occurred in 11 subjects (52.3%). The presence of atrophy/metaplasia at baseline and higher neutrophil infiltration in the corpus were associated with the restoration of gastric microbiota after successful eradication, whereas a higher relative abundance of Acinetobacter at baseline was associated with the predominance of Acinetobacter after H. pylori eradication (p < 0.05). To conclude, in H. pylori-uninfected stomach, relative abundance of Proteobacteria increases, relative abundance of Firmicutes and Fusobacteria decreases, and microbial diversity decreases with aging. H. pylori eradication does not always restore gastric microbiota; in some individuals, gastric colonization by Acinetobacter species occurs after anti-Helicobacter treatment.

Significance of Helicobacter pylori Eradication on Atrophic Gastritis and Intestinal Metaplasia

There has been an accumulation of data regarding the chemopreventive effects of <i>Helicobacter pylori</i> (<i>H. pylori</i>) eradication. However, it remains unclear how <i>H. pylori</i> infection causes gastric cancer (GC) and how <i>H. pylori</i> eradication can prevent GC. Atrophic gastritis (AG) and intestinal metaplasia (IM) are known as precancerous lesions which mainly lead to intestinal-type GC but to some extent, can also lead to diffuse-type GC. The most important mechanism of AG/IM is <i>H. pylori</i>-induced chronic gastritis. Thus, the reversibility of AG and IM by <i>H. pylori</i> eradication therapy is very important in the prevention of GC. There have been many studies providing data supporting the improvement of AG by the eradication of <i>H. pylori</i> to some extent. In contrast, IM has been regarded as “the point of no return.” However, more recent studies have implied the improvement of IM after eradication, suggesting the importance of early eradication therapy in reversible histological status. In this review, we focused on the reversibility of AG and IM by <i>H. pylori</i> eradication and tried to investigate the predicting factors for the improvement of AG and IM including age, sex, smoking, and diet, as well as <i>H. pylori</i> infection.

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.

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.

Chemoprevention of gastric cancer by Helicobacter pylori eradication and its underlying mechanism

The cascade of gastric cancer, a leading cause of cancer incidence and mortality, is multifactorial. Helicobacter pylori (HP) infection plays a major role in gastric cancer (GC), and there has been an accumulation of data regarding the chemopreventive effect of HP eradication. However, it remains unclear how HP infection causes GC and how HP eradication prevents GC. To clarify this issue, the following approaches were performed in this review article. First, how HP-induced atrophic gastritis (AG) and intestinal metaplasia (IM) provoke the development of GC is shown, followed by how long HP eradication takes to induce a reversible change in AG and IM. Second, epigenetic studies of PTPN6, MOS, DCC, CRK, and VAV1 were performed in noncancerous gastric specimens in terms of HP status. Among these genes, MOS was found to be a possible surrogate marker for GC development. HP eradication decreased aberrant DNA methylation in a gene-specific manner, and MOS played a role in metachronous gastric neoplasms. Third, transforming growth factor-β1 (TGF-β1) and TGF-β1-induced epithelial-mesenchymal transition (EMT) markers were investigated in gastric mucosa. HP infection triggered the TGF-β1-induced EMT pathway and caused the emergence of GC stem cells, such as CD44v8-10. When HP was eradicated, these two pathways were inhibited. Finally, a 2222 cohort study showed that HP eradication significantly decreased the risk of noncardiac GC. Taken together, HP eradication is effective as a primary GC prevention method, and its underlying mechanism includes reversibility of AG and IM, methylation, EMT, and stem cells.

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.

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.

Promoter hypermethylation of RAR-β tumor suppressor gene in gastric carcinoma: Association with histological type and clinical outcomes

BACKGROUND

While gastric cancer is a common cancer in the world and Iran, its molecular mechanisms are not fully understood as yet. Epigenetic modifications can lead to alteration of gene expression and development of tumorigenesis mechanisms.

METHODS

To clarify the difference in DNA methylation pattern of histological types in gastric carcinoma, CpG islands in the promoters of retinoic acid receptor β gene (RAR-β) was studied using methylation-specific PCR.

RESULTS

In gastric cancer tissues, hypermethylation frequency of RAR-β gene was respectively 61 and 33% for diffuse and intestinal type. In diffuse type, hypermethylation of RAR-β has been significantly associated with invasion (P= 0.007), differentiation (P= 0.033) and location (P= 0.012) of the tumor. However, hypermethylation of RAR-β correlated only with tumor size (P= 0.029) in intestinal type. For adjacent non-tumor samples, hypermethylation of RAR-β was not detected and there was no significant association between age of diagnosis and hypermethylation of RAR-β in both types of gastric cancer.

CONCLUSIONS

These results support previous findings denoting a distinct profile of promoter hypermethylation status in the development of the intestinal and diffuse type of gastric carcinoma and the process of the tumorigenesis in these subtypes of gastric cancer is different from each other.

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.

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.

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.

Autophagy impairment by Helicobacter pylori-induced methylation silencing of MAP1LC3Av1 promotes gastric carcinogenesis

Helicobacter pylori (H. pylori) infection induces methylation silencing of tumor suppressor genes causing gastric carcinogenesis. Impairment of autophagy induces DNA damage leading to genetic instability and carcinogenesis. We aimed to identify whether H. pylori infection induced methylation silencing of host autophagy-related (Atg) genes, impairing autophagy and enhancing gastric carcinogenesis. Gastric mucosae were obtained from 41 gastric cancer patients and 11 healthy volunteers (8 H. pylori-uninfected and 3 H. pylori-infected). Methylation status of Atg genes was analyzed by a methylation microarray and quantitative methylation-specific PCR (qMSP); mRNA expression was assessed by quantitative reverse transcription PCR (qRT-PCR). Cell proliferation, migration and invasion were assessed in normal rat gastric epithelial cells. Gene knock-down was performed by siRNA. Autophagy was assessed by western blotting. Of 34 Atg genes, MAP1LC3A variant 1 (MAP1LC3Av1) and ULK2 were identified by methylation microarray analysis as exhibiting specific methylation in H. pylori-infected mucosae and gastric cancer tissues. Methylation silencing of MAP1LC3Av1 was confirmed by qMSP, qRT-PCR and de-methylation treatment in two gastric cancer cell lines. Knock-down of map1lc3a, the rat homolog of the human MAP1LC3Av1, inhibited autophagy response and increased cell proliferation, migration and invasion in normal rat gastric epithelial cells, despite the presence of map1lc3b, the rat homolog of the human MAP1LC3B gene important for autophagy. Furthermore, MAP1LC3Av1 was methylation-silenced in 23.3% of gastric cancerous mucosae and 40% of non-cancerous mucosae with H. pylori infection. MAP1LC3Av1 is essential for autophagy and H. pylori-induced methylation silencing of MAP1LC3Av1 may impair autophagy, facilitating gastric carcinogenesis.

Risk Factors for Metachronous Gastric Neoplasms in Patients Who Underwent Endoscopic Resection of a Gastric Neoplasm

Background/Aims

To identify the risk factors for metachronous gastric neoplasms in patients who underwent an endoscopic resection of a gastric neoplasm.

Methods

We prospectively collected clinicopathologic data and measured the methylation levels of HAND1, THBD, APC, and MOS in the gastric mucosa by methylation-specific real-time polymerase chain reaction in patients who underwent endoscopic resection of gastric neoplasms.

Results

A total of 257 patients with gastric neoplasms (113 low-grade dysplasias, 25 high-grade dysplasias, and 119 early gastric cancers) were enrolled. Metachronous gastric neoplasm developed in 7.4% of patients during a mean follow-up of 52 months. The 5-year cumulative incidence of metachronous gastric neoplasm was 4.8%. Multivariate analysis showed that moderate/severe corpus intestinal metaplasia and family history of gastric cancer were independent risk factors for metachronous gastric neoplasm development; the hazard ratios were 4.12 (95% confidence interval [CI], 1.23 to 13.87; p=0.022) and 3.52 (95% CI, 1.09 to 11.40; p=0.036), respectively. The methylation level of MOS was significantly elevated in patients with metachronous gastric neoplasms compared age- and sex-matched patients without metachronous gastric neoplasms (p=0.020).

Conclusions

In patients who underwent endoscopic resection of gastric neoplasms, moderate/severe corpus intestinal metaplasia and a family history of gastric cancer were independent risk factors for metachronous gastric neoplasm, and MOS was significantly hypermethylated in patients with metachronous gastric neoplasms.

BARHL2 Methylation Using Gastric Wash DNA or Gastric Juice Exosomal DNA is a Useful Marker For Early Detection of Gastric Cancer in an H. pylori-Independent Manner

OBJECTIVES

The main purpose of this study was to develop a methylation analysis pipeline by using gastric wash-derived DNA and/or gastric juice-derived exosomal DNA (exoDNA), and to evaluate its suitability for the early detection of gastric cancer (GC) in clinical settings.

METHODS

We analyzed alterations of BarH-like 2 homeobox protein (BARHL2) in GC cell lines and tissues, as well as in DNA obtained from 128 gastric washes and 30 gastric juice-derived exosomes. GC cell lines were transfected with plasmids encoding BARHL2 and subjected to proliferation, colony formation, and gene expression analyses.

RESULTS

High levels of BARHL2 methylation were detected in three of seven GC cell lines; consistent with this, these cell lines expressed low levels of BARHL2. Treatment of these cell lines with 5-aza-2'-deoxycytidine restored BARHL2 expression. Levels of BARHL2 methylation in 18 normal and 14 atrophic gastritis samples were low irrespective of Helicobacter pylori infection. High levels of BARHL2 methylation were observed in gastric wash-derived DNA obtained from early GC patients before endoscopic resection (ER), but methylation was significantly lower after curative ER. Analysis using gastric juice-derived exoDNA samples revealed that BARHL2 methylation yielded an area under the curve of 0.923 with 90% sensitivity and 100% specificity with respect to discriminating GC patients from non-GC controls. BARHL2 nuclear immunoreactivity was found in all normal gastric epithelial cells and in cells from patients with gastritis and adenoma. In contrast, loss of BARHL2 expression was observed in the vast majority of the GC tissues. Finally, transfection of BARHL2 into MKN7 and MKN45 cell lines significantly inhibited their proliferation and ability to form colonies.

CONCLUSIONS

Methylation analysis of BARHL2 using gastric wash-derived DNA and/or gastric juice-derived exoDNA could be useful for early detection of GC in clinical settings.

Interaction between Helicobacter pylori and host genetic variants in gastric carcinogenesis

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

Gastric cancer development after the successful eradication of Helicobacter pylori

Gastric cancer (GC) develops as a result of inflammation-associated carcinogenesis due to Helicobacter pylori (H. pylori) infection and subsequent defects in genetic/epigenetic events. Although the indication for eradication therapy has become widespread, clinical studies have revealed its limited effects in decreasing the incidence of GC. Moreover, research on biopsy specimens obtained by conventional endoscopy has demonstrated the feasibility of the restoration of some genetic/epigenetic alterations in the gastric mucosa. Practically, the number of sporadic cases of primary/metachronous GC that emerge after successful eradication has increased, while on-going guidelines recommend eradication therapy for patients with chronic gastritis and those with background mucosa after endoscopic resection for GC. Accordingly, regular surveillance of numerous individuals who have received eradication therapy is recommended despite the lack of biomarkers. Recently, the focus has been on functional reversibility after successful eradication as another cue to elucidate the mechanisms of restoration as well as those of carcinogenesis in the gastric mucosa after H. pylori eradication. We demonstrated that Congo-red chromoendoscopy enabled the identification of the multi-focal distribution of functionally irreversible mucosa compared with that of restored mucosa after successful eradication in individuals at extremely high risk for GC. Further research that uses functional imaging may provide new insights into the mechanisms of regeneration and carcinogenesis in the gastric mucosa post-eradication and may allow for the development of useful biomarkers.

Effects of Helicobacter pylori eradication on the development of metachronous gastric cancer after endoscopic treatment: analysis of molecular alterations by a randomised controlled trial

BACKGROUND

Whether Helicobacter pylori eradication actually suppresses the development of metachronous gastric cancer (MGC) after endoscopic resection (ER) remains controversial. The aims of this study were to clarify (1) the molecular markers related to carcinogenesis in intestinal metaplasia (IM) by a cross-sectional study, and (2) the changes of those markers by an open-label, randomised controlled trial (RCT) of H. pylori treatment.

METHODS

First, we evaluated microsatellite instability (MSI), the methylation status at hMLH1, CDKN2A and APC genes, and immunoreactivity using the monoclonal antibody (mAb) Das-1 in IM in the background mucosa of 131 patients who underwent ER for gastric neoplasia and 22 chronic gastritis cases (control). Next, we performed an RCT to evaluate the changes of MSI between the H. pylori-eradicated (n=19) and non-eradicated patients (n=17) at 1 year among the H. pylori-positive patients.

RESULTS

Microsatellite instability and mAb Das-1 reactivity showed significantly higher incidences in both the H. pylori-positive and -negative patients compared with the control group, thus suggesting that MSI and mAb Das-1 reactivity are associated with gastric neoplasia (OR=5.06 for MSI; OR=2.51 for mAb Das-1 reactivity). The RCT showed that H. pylori eradication did not provide significant reversals of any molecular alterations including MSI (the primary end point) and other methylation statuses and mAb Das-1 reactivity (secondary end points).

CONCLUSIONS

H. pylori eradication did not produce significant changes in the molecular alterations related to carcinogenesis, suggesting that H. pylori treatment may not prevent the development of MGC in background mucosa with IM.

The influence of Helicobacter pylori eradication on the expression and methylation status of the FHIT gene in non-cancerous gastric mucosa of dyspeptic patients

OBJECTIVE

To investigate the effect of Helicobacter pylori (H. pylori) eradication on the expression level of the FHIT gene and its methylation status in the gastric mucosa of dyspeptic patients with or without a family history of gastric cancer (FHGC).

METHODS

In all, 31 patients with H. pylori infection including 13 with FHGC were enrolled in the study. The effectiveness of H. pylori eradication were confirmed by UBT, RUT and multiplex PCR (the presence of selected H. pylori strains) for biopsy samples from the antrum and corpus. Histopathological assessment was also performed. The expression of FHIT mRNA was determined by quantitative reverse transcription-polymerase chain reaction and the methylation status of the FHIT promoter was assessed by methylation-specific polymerase chain reaction.

RESULTS

After H. pylori eradication, the improvement of inflammation from superficial gastritis to normal mucosa (G → N) was observed in 39% of the patients without FHGC and in 54% of those with FHGC. FHIT mRNA expression was increased in patients without FHGC after H. pylori eradication (P < 0.05), while there was no statistically significant change in gene methylation status after H. pylori eradication (P > 0.05). For the samples from those with FHGC, the FHIT mRNA expression was not significantly changed and the methylation status fluctuated evenly.

CONCLUSIONS

H. pylori eradication results in the improvement of gastric mucosal inflammation and histopathological non-atrophic changes. The FHIT gene expression is increased in patients without FHGC, which may contribute to the prevention of GC development.

Cancer-promoting effects of microbial dysbiosis

Humans depend on our commensal bacteria for nutritive, immune-modulating, and metabolic contributions to maintenance of health. However, this commensal community exists in careful balance that, if disrupted, enters dysbiosis; this has been shown to contribute to the pathogenesis of colon, gastric, esophageal, pancreatic, laryngeal, breast, and gallbladder carcinomas. This development is closely tied to host inflammation, which causes and is aggravated by microbial dysbiosis and increases vulnerability to pathogens. Advances in sequencing technology have increased our ability to catalog microbial species associated with various cancer types across the body. However, defining microbial biomarkers as cancer predictors presents multiple challenges, and existing studies identifying cancer-associated bacteria have reported inconsistent outcomes. Combining metabolites and microbiome analyses can help elucidate interactions between gut microbiota, metabolism, and the host. Ultimately, understanding how gut dysbiosis impacts host response and inflammation will be critical to creating an accurate picture of the role of the microbiome in cancer.

Somatic DNA Hypomethylation in H. pylori-Associated High-Risk Gastritis and Gastric Cancer: Enhanced Somatic Hypomethylation Associates with Advanced Stage Cancer

Objectives:

Helicobacter pylori-related high-risk gastritis (HRG) is a severe risk factor for gastric cancer (GC). The link between HRG and long-term risk for GC may involve genetic and epigenetic alterations underlying a field defect, i.e. a region of the mucosa prone to cancer development. Global DNA hypomethylation is a pervasive alteration in GC that associates with chromosomal instability and poor prognosis. The aim of this study was to determine the chronology of this alteration along the progression of HRG to GC, to test the hypothesis that it occurs early in the chronology of this pathway and plays a mechanistic role in the long-term cancer risk.

Methods:

We comparatively measured the genomic methylation level in gastric biopsies from 94 GC patients and 16 of their cancer-free relatives, 38 HRG patients, and 17 GERD patients, using a quantitative enzymatic method.

Results:

GC biopsies were hypomethylated compared to their matching non-tumor mucosa (P=9.4 × 10⁻¹²), irrespective of the tumor location or patients' country of origin. Genome-wide hypomethylation was also found in gastric mucosa of GC (P=1.5 × 10⁻⁵) and HRG (P=0.004) patients compared with healthy donors and GC relatives, regardless of the biopsy location within the stomach or previous H. pylori eradication therapy. An enhanced hypomethylation, distinguished by a bi-slope distribution of the differences in methylation between tumor and normal tissues, associated with a more invasive (P=0.005) and advanced stage (P=0.017) type of GC.

Conclusions:

Universal DNA demethylation in normal gastric mucosa in GC patients appears sporadic rather than familial. Genomic hypomethylation in HRG possibly contributes to a field defect for cancerization that is not reversed by bacterial eradication. Enhanced somatic hypomethylation may stratify GC for prognostic purposes.

The clinicopathological significance of CDH1 in gastric cancer: a meta-analysis and systematic review

Background

CDH1 is a protein encoded by the CDH1 gene in humans. Loss of CDH1 function contributes to cancer progression by increasing proliferation, invasion, and/or metastasis. However, the association and clinicopathological significance between CDH1 hypermethylation and gastric cancer (GC) remains unclear. In this study, we systematically reviewed the studies of CDH1 hypermethylation and GC, and evaluated the association between CDH1 hypermethylation and GC using meta-analysis methods.

Methods

A comprehensive search of the PubMed and Embase databases was performed for publications up to July 2014. Methodological quality of the studies was also evaluated. The data were extracted and assessed by two reviewers independently. Analyses of pooled data were performed. Odds ratios (ORs) were calculated and summarized.

Results

A final analysis of 1,079 GC patients from 14 eligible studies was performed. CDH1 hypermethylation level in the cancer group was significantly higher compared to the normal gastric mucosa (OR =8.55, 95% confidence interval [CI]: 2.39–33.51, Z=5.47, P<0.00001). CDH1 hypermethylation was not significantly higher in GC than in adjacent gastric mucosa (OR =3.68, 95% CI: 0.96–14.18, Z=1.90, P=0.06). However, CDH1 hypermethylation was higher in adjacent gastric mucosa compared to that in normal gastric mucosa (OR =2.55, 95% CI: 1.22–5.32, Z=2.49, P<0.01). In addition, CDH1 hypermethylation was correlated with Helicobacter pylori (HP) status in GC. The pooled OR from six studies including 280 HP-positive GCs and 193 HP-negative GCs is 1.72 (95% CI: 1.13–2.61, Z=2.55, P=0.01).

Conclusion

The results of this meta-analysis reveal that CDH1 hypermethylation levels in cancer and adjacent gastric mucosa are significantly higher compared to normal gastric mucosa. Thus, CDH1 hypermethylation is significantly correlated with GC risk. CDH1 hypermethylation is correlated with HP status, indicating that it plays a more important role in the pathogenesis of HP-positive GC and might be an interesting potential drug target for GC patients.

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.

Pathogens hijack the epigenome: a new twist on host-pathogen interactions

Pathogens have evolved strategies to promote their survival by dramatically modifying the transcriptional profile and protein content of the host cells they infect. Modifications of the host transcriptome and proteome are mediated by pathogen-encoded effector molecules that modulate host cells through a variety of different mechanisms. Recent studies highlight the importance of the host chromatin and other epigenetic regulators as targets of pathogens. Host gene regulatory mechanisms may be targeted through cytoplasmic signaling, directly by pathogen effector proteins, and possibly by pathogen RNA. Although many of these changes are short-lived and persist only during the course of infection, several studies indicate that pathogens are able to induce long-term, heritable changes that are essential to pathogenesis of infectious diseases and persistence of pathogens within their hosts. In this review, we discuss how pathogens modulate the epigenome of host cells, a new and flourishing avenue of host-pathogen interaction studies.

Streptococcus infantarius and carcinogenesis: a new chapter in colorectal pathology

As mirrored by several topics throughout history, the causal link between infectious diseases and cancer was initially viewed with disbelief and subsequently forgotten, only to be rediscovered decades later, when it started flourishing into a vibrant multidisciplinary field . Just a few years ago, it was estimated that over 20% of all cancers are causally linked to infectious diseases, most frequently caused by bacteria, viruses, and parasites .