Enhanced expression of activation-induced cytidine deaminase in human gastric mucosa infected by Helicobacter pylori and its decrease following eradication

Metaproteomic assessment of gut microbial and host functional perturbations in Helicobacter pylori-infected patients subjected to an antimicrobial protocol

The impact of therapeutic interventions on the human gut microbiota (GM) is a clinical issue of paramount interest given the strong interconnection between microbial dynamics and human health. Orally administered antibiotics are known to reduce GM biomass and modify GM taxonomic profile. However, the impact of antimicrobial therapies on GM functions and biochemical pathways has scarcely been studied. Here, we characterized the fecal metaproteome of 10 Helicobacter pylori-infected patients before (T0) and after 10 days (T1) of a successful quadruple therapy (bismuth, tetracycline, metronidazole, and rabeprazole) and 30 days after therapy cessation (T2), to investigate how GM and host functions change during the eradication and healing processes. At T1, the abundance ratio between microbial and host proteins was reversed compared with that at T0 and T2. Several pathobionts (including Klebsiella, Proteus, Enterococcus, Muribaculum, and Enterocloster) were increased at T1. Therapy reshaped the relative contributions of the functions required to produce acetate, propionate, and butyrate. Proteins related to the uptake and processing of complex glycans were increased. Microbial cross-feeding with sialic acid, fucose, and rhamnose was enhanced, whereas hydrogen sulfide production was reduced. Finally, microbial proteins involved in antibiotic resistance and inflammation were more abundant after therapy. Moreover, a reduction in host proteins with known roles in inflammation and H. pylori-mediated carcinogenesis was observed. In conclusion, our results support the use of metaproteomics to monitor drug-induced remodeling of GM and host functions, opening the way for investigating new antimicrobial therapies aimed at preserving gut environmental homeostasis.

Identification and Verification of Potential Biomarkers in Gastric Cancer By Integrated Bioinformatic Analysis

Background: Gastric cancer (GC) is a common cancer with high mortality. This study aimed to identify its differentially expressed genes (DEGs) using bioinformatics methods.

Methods: DEGs were screened from four GEO (Gene Expression Omnibus) gene expression profiles. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed. A protein–protein interaction (PPI) network was constructed. Expression and prognosis were assessed. Meta-analysis was conducted to further validate prognosis. The receiver operating characteristic curve (ROC) was analyzed to identify diagnostic markers, and a nomogram was developed. Exploration of drugs and immune cell infiltration analysis were conducted.

Results: Nine up-regulated and three down-regulated hub genes were identified, with close relations to gastric functions, extracellular activities, and structures. Overexpressed Collagen Type VIII Alpha 1 Chain (COL8A1), Collagen Type X Alpha 1 Chain (COL10A1), Collagen Triple Helix Repeat Containing 1 (CTHRC1), and Fibroblast Activation Protein (FAP) correlated with poor prognosis. The area under the curve (AUC) of ADAM Metallopeptidase With Thrombospondin Type 1 Motif 2 (ADAMTS2), COL10A1, Collagen Type XI Alpha 1 Chain (COL11A1), and CTHRC1 was >0.9. A nomogram model based on CTHRC1 was developed. Infiltration of macrophages, neutrophils, and dendritic cells positively correlated with COL8A1, COL10A1, CTHRC1, and FAP. Meta-analysis confirmed poor prognosis of overexpressed CTHRC1.

Conclusion: ADAMTS2, COL10A1, COL11A1, and CTHRC1 have diagnostic values in GC. COL8A1, COL10A1, CTHRC1, and FAP correlated with worse prognosis, showing prognostic and therapeutic values. The immune cell infiltration needs further investigations.

Expansion of gastric intestinal metaplasia with copy number aberrations contributes to field cancerization

Intestinal metaplasia (IM) is a risk factor for gastric cancer following infection with Helicobacter pylori. To explore the susceptibility of pure gastric IM to cancer development, we investigated genetic alterations in single IM gastric glands. We isolated 50 single IM or non-IM glands from the inflamed gastric mucosa of 11 patients with intramucosal gastric carcinoma (IGC) and 4 patients without IGC; nineteen single glands in the non-inflamed gastric mucosa of 11 individuals from our cohort and previous dataset were also included as controls. Whole exome sequencing of single glands revealed significantly higher accumulation of somatic mutations in various genes within IM glands compared with non-IM glands. Clonal ordering analysis showed that IM glands expanded to form clusters with shared mutations. Additionally, targeted-capture deep sequencing and copy number (CN) analyses were performed in 96 clustered IM or non-IM gastric glands from 26 patients with IGC. CN analyses were also performed on 41 IGC samples and the Cancer Genome Atlas-Stomach Adenocarcinoma datasets. These analyses revealed that polyclonally expanded IM commonly acquired copy number aberrations (CNA), including amplification of chromosomes 8, 20, and 2. A large portion of clustered IM glands typically consisted of common CNAs rather than other cancer-related mutations. Moreover, the CNA patterns of clustered IM glands were similar to those of IGC, indicative of precancerous conditions. Taken together, these findings suggest that, in the gastric mucosa inflamed with H. pylori infection, IM glands expand via acquisition of CNAs comparable to those of IGC, contributing to field cancerization.

Genetic Pathogenesis of Inflammation-Associated Cancers in Digestive Organs

Epidemiological, clinical, and biological studies convincingly demonstrate that chronic inflammation predisposes to the development of human cancers. In digestive organs, inflammation-associated cancers include colitis-associated colorectal cancers, Helicobacter pylori-associated gastric cancer, as well as Barrett's esophagus and esophageal adenocarcinoma associated with chronic duodenogastric-esophageal reflux. Cancer is a genomic disease, and stepwise accumulation of genetic and epigenetic alterations of tumor-related genes leads to the development of tumor cells. Recent genome analyses show that genetic alterations, which are evoked by inflammation, are latently accumulated in inflamed epithelial cells of digestive organs. Production of reactive oxygen and aberrant expression of activation-induced cytidine deaminase, a nucleotide-editing enzyme, could be induced in inflamed gastrointestinal epithelial cells and play a role as a genomic modulator of inflammation-associated carcinogenesis. Understanding the molecular linkage between inflammation and genetic alterations will open up a new field of tumor biology and provide a novel strategy for the prevention of inflammation-associated tumorigenesis.

Crosstalk Between DNA Damage and Inflammation in the Multiple Steps of Gastric Carcinogenesis

Over the last years, intensive investigations in molecular biology and cell physiology extended tremendously the knowledge about the association of inflammation and cancer. In frame of this paradigm, the human pathogen Helicobacter pylori triggers gastritis and gastric ulcer disease, and contributes to the development of gastric cancer. Mechanisms, by which the bacteria-induced inflammation in gastric mucosa leads to intestinal metaplasia and carcinoma, are represented in this review. An altered cell-signaling response and increased production of free radicals by epithelial and immune cells account for the accumulation of DNA damage in gastric mucosa, if infection stays untreated. Host genetics and environmental factors, especially diet, can accelerate the process, which offers the opportunity of intervention based on a balanced nutrition. It is supposed that inflammation might influence stem- or progenitor cells in gastric tissue predisposing for metaplasia or tumor relapse. Herein, DNA is strongly mutated and labile, which restricts therapy options. Thus, the understanding of the mechanisms that underlie gastric carcinogenesis will be of preeminent importance for the development of strategies for screening and early detection. As most gastric cancer patients face late-stage disease with a poor overall survival, the development of multi-targeted therapeutic intervention strategies is a major challenge for the future.

Comparison of the Clinicopathological Characteristics and Genetic Alterations Between Patients with Gastric Cancer with or Without Helicobacter pylori Infection

BACKGROUND

Helicobacter pylori (HP) can induce epithelial cells and intestinal metaplasia with genetic damage that makes them highly susceptible to the development of gastric cancer (GC).

MATERIALS AND METHODS

Between 2005 and 2010, 356 patients with gastric cancer who received curative surgery were enrolled. Analysis of HP, Epstein-Barr virus (EBV) infection, PIK3CA amplification, and mutation analysis of 68 mutations in eight genes using a mass spectrometric single-nucleotide polymorphism genotyping technology was conducted. The clinicopathological characteristics of patients with or without HP infection were compared.

RESULTS

Among the 356 patients, 185 (52.0%) had HP infection. For intestinal-type GC, patients with HP infection were more likely to be younger and had fewer PI3K/AKT pathway genetic mutations than those without HP infection. For diffuse-type GC, patients with HP infection were characterized by less male predominance, less lymphoid stroma, fewer microsatellite instability-high tumors, and fewer PI3K/AKT pathway genetic mutations than those without HP infection. Patients with HP infection had less tumor recurrence and a better 5-year overall survival (87.7% vs. 73.9%, p = .012) and disease-free survival (64.1% vs. 51.3%, p = .013) than those without HP infection, especially for intestinal-type GC. For EBV-negative GC, patients with HP infection had fewer PI3K/AKT pathway mutations and a better 5-year overall survival and disease-free survival than those without HP infection. Multivariate analysis demonstrated that HP infection was an independent prognostic factor regarding overall survival and disease-free survival.

CONCLUSION

Patients with GC with HP infection were associated with fewer PI3K/AKT pathway genetic mutations and better survival than those without HP infection, especially for EBV-negative and intestinal-type GC.

IMPLICATIONS FOR PRACTICE

Patients with gastric cancer with Helicobacter pylori (HP) infection had fewer PI3K/AKT pathway genetic mutations, less tumor recurrence, and better survival than those without HP infection, especially for Epstein-Barr virus (EBV)-negative and intestinal-type gastric cancer. HP infection is an independent prognostic factor regarding overall survival and disease-free survival. Future in vivo and in vitro studies of the correlation among HP infection, PI3K/AKT pathway, and EBV infection in gastric cancer are required.

Therapy with omeprazole modulates regulatory T cell/T helper 17 immune response in children with duodenal ulcers

The purpose of this study was to determine the effect of omeprazole on the regulatory T cell (Treg) and T helper 17 (Th17)-mediated response in patients with duodenal ulcers (DUs). DU patients were randomly divided into omeprazole and colloid bismuth subcitrate treatment groups. The ratios of Th17 and Treg in peripheral blood mononuclear cells (PBMCs) were measured. Cytokine production and Foxp3⁺- and RORγt-positive cells were detected. The expressions of STAT3, p-STAT3, STAT5 and p-STAT5 were detected by Western blot. The results showed that DU patients had an imbalanced Treg/Th17 response, as reflected by the higher IL-17 level and Th17 ratio and lower IL-10 level and Treg proportion in serum compared with those in the healthy volunteers. The administration of omeprazole to the patients significantly increased Treg and IL-10 levels and reduced Th17 and IL-17 levels. Omeprazole markedly increased the number of Foxp3-positive cells, decreased the number of RORγt-positive cells and restored the balanced ratio of IL-10/IL-17 in the ulcer tissue. Interestingly, we observed a negative correlation between the ratios of Treg/Th17 and the pathological scores in damaged tissues. Of note, H. pylori-infected PBMCs showed decreased Treg and an increased Th17 proportion, which could be reversed by omeprazole. Finally, omeprazole increased the expression of p-STAT5 and reduced the level of p-STAT3 without any effects on the total expression of STAT5 and STAT3. Our data suggest that omeprazole treatment restores the equilibrium of the Treg/Th17-mediated response in DU patients. Moreover, the modulation of p-STAT3 and p-STAT5 expression by omeprazole induced balanced polarisation of Treg/Th17.

Helicobacter pylori-Mediated Genetic Instability and Gastric Carcinogenesis

Helicobacter pylori infection is the most important cause of human gastric cancer worldwide. Gastric cancer develops over a long time after H. pylori infection via stepwise accumulation of genetic alterations and positive selection of cells with growth advantages. H. pylori itself and the resultant chronic inflammation lead to the emergence of genetic alterations in gastric epithelial cells via increased susceptibility of these cells to DNA damage. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) in inflammatory and gastric epithelial cells, as well as the expression of cytidine deaminase in gastric epithelial cells, may link H. pylori-related inflammation and DNA damage. Recent comprehensive analyses of gastric cancer genomes provide clues for the possible molecular mechanisms of gastric carcinogenesis. In this chapter, we describe how genetic alterations emerge during gastric carcinogenesis related to H. pylori infection.

Helicobacter pylori as an oncogenic pathogen, revisited

Gastric cancer is an inflammation-associated malignancy aetiologically related to infection with the bacterium, Helicobacter pylori, which is considered a necessary but insufficient cause. Unless treated, H. pylori causes life-long acute and chronic gastric inflammation resulting in progressive gastric mucosal damage that may result in gastric cancer. The rate of progression from superficial gastritis, to an atrophic metaplastic mucosa, and ultimately to cancer relates to the virulence of the infecting H. pylori as well as host and environmental factors. H. pylori virulence is a reflection of its propensity to cause severe gastric inflammation. Both mucosal inflammation and H. pylori can cause host genomic instability, including dysregulation of DNA mismatch repair, stimulation of expression of activation-induced cytidine deaminase, abnormal DNA methylation and dysregulation of  micro RNAs, which may result in an accumulation of mutations and loss of normal regulation of cell growth. The difference in cancer risk between the most and least virulent H. pylori strain is only approximately 2-fold. Overall, none of the putative virulence factors identified to date have proved to be disease-specific. The presence, severity, extent and duration of inflammation appear to be the most important factors and current evidence suggests that any host, environmental or bacterial factor that reliably enhances the inflammatory response to the H. pylori infection increases the risk of gastric cancer.

Modulation of p53 during bacterial infections

In recent years, numerous bacterial pathogens have been shown to inactivate the major tumour suppressor p53 during infection. This inactivation impedes the protective response of the host cell to the genotoxicity that often results from bacterial infection. Moreover, a new aspect of the antibacterial activity of p53 that has recently come to light - downregulation of host cell metabolism to interfere with intracellular bacterial replication - has further highlighted the crucial role of p53 in host-pathogen interactions, as host cell metabolism is relevant for all intracellular bacteria, as well as other pathogens that replicate inside host cells and use host metabolites. In this Progress article, we summarize recent work that has advanced our knowledge of the interaction between pathogenic bacteria and p53, and we discuss the known and expected outcomes of this interaction for pathogenesis.

Molecular Pathogenesis of Helicobacter pylori-Related Gastric Cancer

Helicobacter pylori infection plays a crucial role in gastric carcinogenesis. H pylori exerts oncogenic effects on gastric mucosa through complex interaction between bacterial virulence factors and host inflammatory responses. On the other hand, gastric cancer develops via stepwise accumulation of genetic and epigenetic alterations in H pylori-infected gastric mucosa. Recent comprehensive analyses of gastric cancer genomes indicate a multistep process of genetic alterations as well as possible molecular mechanisms of gastric carcinogenesis. Both genetic processes of gastric cancer development and molecular oncogenic pathways related to H pylori infection are important to completely understand the pathogenesis of H pylori-related gastric cancer.

AID, p53 and MLH1 expression in early gastric neoplasms and the correlation with the background mucosa

A number of tumor-associated genes have been associated with gastric cancer development. The present study evaluated differences in tumor-associated protein expression and phenotype among early gastric neoplasms, and correlated these data with those of the background mucosa. The expression of activation-induced cytidine deaminase (AID), p53 and MLH1 in 151 early gastric neoplasms [22 gastric adenomas, 92 intramucosal carcinomas (MCs), and 37 submucosal carcinomas (SMCs)] was examined immunohistochemically and compared with that of the corresponding background mucosal condition. The cellular phenotypes of the neoplasms and the corresponding background intestinal metaplasia were also determined. Aberrant AID, p53 and MLH1 expression was detected in 36.4, 0 and 0% of the adenomas, in 35.9, 32.6 and 16.3% of the MCs, and in 56.8, 62.2 and 21.6% of the SMCs, respectively. The frequency of aberrant AID and p53 expression in the SMCs was significantly increased compared with that in the MCs (AID, P<0.05; p53, P<0.01). Aberrant AID expression was significantly associated with p53 overexpression in the SMCs (P<0.01), but not in the adenomas or MCs. In addition, AID expression was associated with the severity of mononuclear cell activity in the non-cancerous mucosa adjacent to the tumor (P<0.05), particularly in the SMC cases. The percentage of MCs (34.8%) and SMCs (24.3%) that were of the gastric phenotype was higher compared with the percentage of adenomas (18.2%). These results indicated that p53 and MLH1 expression and a gastric phenotype may be important for carcinogenesis, and that chronic inflammation and AID and p53 expression are associated with submucosal progression.

Helicobacter pylori virulence factor CagA promotes tumorigenesis of gastric cancer via multiple signaling pathways

Helicobacter pylori (H. pylori) infection is strongly associated with the development of gastric diseases but also with several extragastric diseases. The clinical outcomes caused by H. pylori infection are considered to be associated with a complex combination of host susceptibility, environmental factors and bacterial isolates. Infections involving H. pylori strains that possess the virulence factor CagA have a worse clinical outcome than those involving CagA-negative strains. It is remarkable that CagA-positive H. pylori increase the risk for gastric cancer over the risk associated with H. pylori infection alone. CagA behaves as a bacterial oncoprotein playing a key role in H. pylori-induced gastric cancer. Activation of oncogenic signaling pathways and inactivation of tumor suppressor pathways are two crucial events in the development of gastric cancer. CagA shows the ability to affect the expression or function of vital protein in oncogenic or tumor suppressor signaling pathways via several molecular mechanisms, such as direct binding or interaction, phosphorylation of vital signaling proteins and methylation of tumor suppressor genes. As a result, CagA continuously dysregulates of these signaling pathways and promotes tumorigenesis. Recent research has enriched our understanding of how CagA effects on these signaling pathways. This review summarizes the results of the most relevant studies, discusses the complex molecular mechanism involved and attempts to delineate the entire signaling pathway.

Gastric Carcinogenesis and Underlying Molecular Mechanisms: Helicobacter pylori and Novel Targeted Therapy

The oxygen-derived free radicals that are released from activated neutrophils are one of the cytotoxic factors of Helicobacter pylori-induced gastric mucosal injury. Increased cytidine deaminase activity in H. pylori-infected gastric tissues promotes the accumulation of various mutations and might promote gastric carcinogenesis. Cytotoxin-associated gene A (CagA) is delivered into gastric epithelial cells via bacterial type IV secretion system, and it causes inflammation and activation of oncogenic pathways. H. pylori infection induces epigenetic transformations, such as aberrant promoter methylation in tumor-suppressor genes. Aberrant expression of microRNAs is also reportedly linked to gastric tumorogenesis. Moreover, recent advances in molecular targeting therapies provided a new interesting weapon to treat advanced gastric cancer through anti-human epidermal growth factor receptor 2 (HER-2) therapies. This updated review article highlights possible mechanisms of gastric carcinogenesis including H. pylori-associated factors.

Accumulation of somatic mutations in TP53 in gastric epithelium with Helicobacter pylori infection

BACKGROUND & AIMS

Helicobacter pylori infection is a risk factor for gastric cancer. To explore the genetic basis of gastric cancer that develops in inflamed gastric mucosa, we investigated genetic aberrations that latently accumulate in nontumorous gastric epithelium with H pylori infection.

METHODS

We performed whole-exome sequencing of gastric tumors, noncancerous tissues with gastritis, and peripheral lymphocytes from 5 patients. We performed additional deep-sequencing analyses of selected tumor-related genes using 34 gastritis mucosal samples from patients with or without gastric cancer. We also performed deep sequencing analyses of gastric mucosal tissues from mice that express transgenic human TP53 and constitutively express activation-induced cytidine deaminase (AICDA or AID) (human TP53 knock-in/AID-transgenic mice).

RESULTS

Whole-exome sequencing revealed that somatic mutations accumulated in various genes in inflamed gastric tissues. Additional deep-sequencing analyses of tissues from regions of gastritis confirmed nonsynonymous low-abundance mutations in TP53 in 15 cases (44.1%) and ARID1A in 5 cases (14.7%). The mutations that accumulated in gastric mucosal tissues with H pylori-induced gastritis, as well as gastric tumors, were predominantly C:G>T:A transitions in GpCpX motifs-a marker of cytidine deamination induced by AID. Constitutive expression of AID in the gastric mucosa of mice led to mutations in the human TP53, at amino acid coding positions identical to those detected in human gastric cancers.

CONCLUSIONS

Studies of gastric tumors and tissues from humans and mice indicate that somatic mutations accumulate in various genes in gastric mucosal tissues with H pylori infection. Increased cytidine deaminase activity in these tissues appears to promote the accumulation of these mutations and might promote gastric carcinogenesis in patients with H pylori infection.

Novel mouse models of hepatocarcinogenesis with stepwise accumulation of genetic alterations

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Various risk factors are involved in hepatocarcinogenesis. Among them, chronic inflammation, including chronic hepatitis and cirrhosis mainly caused by hepatitis B virus and/or hepatitis C virus infection, plays an important role in HCC development. On the other hand, comprehensive genetic analyses of HCC using whole genome and exome sequencing revealed that cancer cells possess a large number of somatic mutations, suggesting that a wide variety of genetic alterations and the resultant dysregulated molecular pathways contribute to the development of HCC. Activation-induced cytidine deaminase (AID) is a nucleotide-editing enzyme, and aberrant expression of AID induced by inflammatory responses contributes to hepatocarcinogenesis via the accumulation of genetic alterations in various tumor-related genes. Constitutive expression of AID in hepatocyte-lineage cells provides novel mouse models that recapitulate the tumorigenesis of human HCC through stepwise accumulation of genetic alterations.