Aberrant epithelial expression of trefoil family factor 2 and mucin 6 in Helicobacter pylori infected gastric antrum, incisura, and body and its association with antralisation

Interleukin 13 Promotes Maturation and Proliferation in Metaplastic Gastroids

BACKGROUND & AIMS

Type 2 innate lymphoid cells (ILC2s) and interleukin-13 (IL-13) promote the onset of spasmolytic polypeptide-expressing metaplasia (SPEM) cells. However, little is known about molecular effects of IL-13 in SPEM cells. We now sought to establish a reliable organoid model, Meta1 gastroids, to model SPEM cells in vitro. We evaluated cellular and molecular effects of ILC2s and IL-13 on maturation and proliferation of SPEM cells.

METHODS

We performed single-cell RNA sequencing to characterize Meta1 gastroids, which were derived from stomachs of Mist1-Kras transgenic mice that displayed pyloric metaplasia. Cell sorting was used to isolate activated ILC2s from stomachs of IL-13-tdTomato reporter mice treated with L635. Three-dimensional co-culture was used to determine the effects of ILC2s on Meta1 gastroids. Mouse normal or metaplastic (Meta1) and human metaplastic gastroids were cultured with IL-13 to evaluate cell responses. Air-Liquid Interface culture was performed to test long-term culture effects of IL-13. In silico analysis determined possible STAT6-binding sites in gene promoter regions. STAT6 inhibition was performed to corroborate STAT6 role in SPEM cells maturation.

RESULTS

Meta1 gastroids showed the characteristics of SPEM cell lineages in vitro even after several passages. We demonstrated that co-culture with ILC2s or IL-13 treatment can induce phosphorylation of STAT6 in Meta1 and normal gastroids and promote the maturation and proliferation of SPEM cell lineages. IL-13 up-regulated expression of mucin-related proteins in human metaplastic gastroids. Inhibition of STAT6 blocked SPEM-related gene expression in Meta1 gastroids and maturation of SPEM in both normal and Meta1 gastroids.

CONCLUSIONS

IL-13 promotes the maturation and proliferation of SPEM cells consistent with gastric mucosal regeneration.

The Importance of Th2 Immune Responses in Mediating the Progression of Gastritis-Associated Metaplasia to Gastric Cancer

Gastric cancer is one of the leading causes of cancer deaths worldwide, with chronic gastritis representing the main predisposing factor initiating the cascade of events leading to metaplasia and eventually progressing to cancer. A widely accepted classification distinguishes between autoimmune and environmental atrophic gastritis, mediated, respectively, by T cells promoting the destruction of the oxyntic mucosa, and chronic H. pylori infection, which has also been identified as the major risk factor for gastric cancer. The original dogma posits Th1 immunity as a main causal factor for developing gastritis and metaplasia. Recently, however, it has become evident that Th2 immune responses play a major role in the events causing chronic inflammation leading to tumorigenesis, and in this context, many different cell types and cytokines are involved. In particular, the activity of cytokines, such as IL-33 and IL-13, and cell types, such as mast cells, M2 macrophages and eosinophils, are intertwined in the process, promoting chronic gastritis-dependent and more diffuse metaplasia. Herein, we provide an overview of the critical events driving the pathology of this disease, focusing on the most recent findings regarding the importance of Th2 immunity in gastritis and gastric metaplasia.

Follow the Metaplasia: Characteristics and Oncogenic Implications of Metaplasia's Pattern of Spread Throughout the Stomach

The human stomach functions as both a digestive and innate immune organ. Its main product, acid, rapidly breaks down ingested products and equally serves as a highly effective microbial filter. The gastric epithelium has evolved mechanisms to appropriately handle the myriad of injurious substances, both exogenous and endogenous, to maintain the epithelial barrier and restore homeostasis. The most significant chronic insult that the stomach must face is Helicobacter pylori (Hp), a stomach-adapted bacterium that can colonize the stomach and induce chronic inflammatory and pre-neoplastic changes. The progression from chronic inflammation to dysplasia relies on the decades-long interplay between this oncobacterium and its gastric host. This review summarizes the functional and molecular regionalization of the stomach at homeostasis and details how chronic inflammation can lead to characteristic alterations in these developmental demarcations, both at the topographic and glandular levels. More importantly, this review illustrates our current understanding of the epithelial mechanisms that underlie the pre-malignant gastric landscape, how Hp adapts to and exploits these changes, and the clinical implications of identifying these changes in order to stratify patients at risk of developing gastric cancer, a leading cause of cancer-related deaths worldwide.

Machine Learning-Based Approach Highlights the Use of a Genomic Variant Profile for Precision Medicine in Ovarian Failure

Ovarian failure (OF) is a common cause of infertility usually diagnosed as idiopathic, with genetic causes accounting for 10-25% of cases. Whole-exome sequencing (WES) may enable identifying contributing genes and variant profiles to stratify the population into subtypes of OF. This study sought to identify a blood-based gene variant profile using accumulation of rare variants to promote precision medicine in fertility preservation programs. A case-control (n = 118, n = 32, respectively) WES study was performed in which only non-synonymous rare variants <5% minor allele frequency (MAF; in the IGSR) and coverage ≥ 100× were considered. A profile of 66 variants of uncertain significance was used for training an unsupervised machine learning model to separate cases from controls (97.2% sensitivity, 99.2% specificity) and stratify the population into two subtypes of OF (A and B) (93.31% sensitivity, 96.67% specificity). Model testing within the IGSR female population predicted 0.5% of women as subtype A and 2.4% as subtype B. This is the first study linking OF to the accumulation of rare variants and generates a new potential taxonomy supporting application of this approach for precision medicine in fertility preservation.

Humulene Inhibits Acute Gastric Mucosal Injury by Enhancing Mucosal Integrity

This study was designed to determine whether α-humulene, a major constituent in many plants used in fragrances, has a protective role against gastric injury in vivo and in vitro. A rat model of hydrochloric acid (HCl)/ethanol-induced gastritis and human mast cells (HMC-1) were used to investigate the mucosal protective effect of α-humulene. α-Humulene significantly inhibited gastric lesions in HCl/ethanol-induced acute gastritis and decreased gastric acid secretion pyloric ligation-induced gastric ulcers in vivo. In addition, α-humulene reduced the amount of reactive oxygen species and malondialdehyde through upregulation of prostaglandin E2 (PGE2) and superoxide dismutase (SOD). In HMC-1 cells, α-humulene decreased intracellular calcium and increased intracellular cyclic adenosine monophosphate (cAMP) levels, resulting in low histamine levels. α-Humulene also reduced the expression levels of cytokine genes such as interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF) by downregulating nuclear factor-κB (NF-κB) nuclear translocation. Finally, α-humulene upregulated the expression levels of mucin 5AC (Muc5ac), Muc6, trefoil factor 1 (Tff1), trefoil factor 2 (Tff2), and polymeric immunoglobulin receptor (pigr). α-Humulene may attenuate HCl/ethanol-induced gastritis by inhibiting histamine release and NF-κB activation and stimulating antioxidants and mucosal protective factors, particularly Muc5ac and Muc6. Therefore, these data suggest that α-humulene is a potential drug candidate for the treatment of stress-induced or alcoholic gastritis.

Development of Pancreatic Acinar Cell Metaplasia During Gastric Repair in a Rat Duodenal Contents Reflux Model

BACKGROUND

We previously reported the development of pancreatic acinar cell metaplasia (PACM) in the glandular stomach of a duodenal contents reflux model (reflux model).

AIMS

We aimed to investigate the characteristics and histogenesis of PACM using a reflux model.

METHODS

A reflux model was created using 8-week-old male Wistar rats, which were killed up to 30 weeks postoperatively. Histological examination was performed to analyze the glandular stomach-jejunal anastomosis. Furthermore, electron microscopic images of PACM samples were compared with pancreatic and gastric glands removed from rats that had not undergone surgery. Immunostaining for α-amylase, HIK1083, TFF2, and Ki-67 was performed, and double fluorescent staining was carried out using antibodies against α-amylase and HIK1083, or α-amylase and TFF2.

RESULTS

In all reflux model rats, PACM was observed proximal to the glandular stomach-jejunal anastomosis, surrounded by pseudopyloric metaplasia. The number of chief cells was decreased in the deep part of the gland, where PACM occurred. Electron microscopy showed that PACM cells had greater numbers of rough endoplasmic reticulum tubules than chief cells, and exhibited pancreatic acinar cell morphology. Upon immunochemical staining, the regenerative foveolar epithelium and part of the pseudopyloric glands stained strongly positive for TFF2, whereas PACM cells were only weakly positive. Double fluorescent staining identified early lesions of PACM in the neck, which were double positive for α-amylase and TFF2, but negative for HIK1083.

CONCLUSIONS

PACM could be induced by duodenal contents reflux. PACM originates from stem cells located in the neck of oxyntic glands during gastric mucosal regeneration.

Pyloric, pseudopyloric, and spasmolytic polypeptide-expressing metaplasias in autoimmune gastritis: a case series of 22 Japanese patients

There are two types of pyloric gland-like metaplasia in the corpus of stomach: pyloric and pseudopyloric metaplasias. They show the same morphology as the original pyloric glands in H&E staining. Pseudopyloric metaplasia is positive for pepsinogen (PG) I immunohistochemically, whereas pyloric metaplasia is negative. Recently, spasmolytic polypeptide-expressing metaplasia (SPEM) is proposed for pyloric gland-like metaplasia mainly in animal experiments. SPEM expresses trefoil factor family 2 (TFF2) and is often considered synonymous with pseudopyloric metaplasia. We reviewed consecutive 22 Japanese patients with autoimmune gastritis (AIG) to investigate TFF2 expression in pyloric and pseudopyloric metaplasias by counting all pyloric gland-like glands in biopsy specimens taken from greater curvature of the middle corpus according to the Updated Sydney System. Pyloric metaplasia was seen in all the 22 cases, and pseudopyloric metaplasia was found in 15 cases. Of 1567 pyloric gland-like glands in all the cases, 1381 (88.1%) glands were pyloric metaplasia glands, and the remaining 186 (11.9%) glands were pseudopyloric metaplasia glands. TFF2 expression was observed in pyloric or pseudopyloric metaplasia glands in 20 cases. TFF2 expression was recognized in 409 of 1381 (26.9%) pyloric metaplasia glands and 27 of 186 (14.5%) pseudopyloric metaplasia glands (P<0.01, chi-square test). In conclusion, SPEM was not always the same as pseudopyloric metaplasia in human AIG, and the majority of metaplasia in AIG was not pseudopyloric but pyloric metaplasia.

Histological assessment of gastric pseudopyloric metaplasia: Intra- and inter-observer consistency

BACKGROUND

The histological spectrum of oxyntic mucosal atrophy (a major determinant of gastric cancer risk) includes pseudopyloric metaplasia (PPM), which histological assessment has been regarded as unreliable. PPM consistently expresses Trefoil-Factor 2 (TFF2), which is histochemically detecteble (TFF2-IHC).

AIMS

Intra- and inter-observer consistency in assessing PPM was examined using both hematoxylin & eosin (H&E) and TFF2-IHC.

MATERIALS AND METHODS

Seventy-four oxyntic biopsy samples obtained from autoimmune gastritis were considered. Two serial histological sections obtained from the paraffin-embedded tissue-samples were stained with H&E and TFF2-IHC. Three pathologists (Alpha, Beta, Gamma) independently scored PPM by both staining and the Intra- and inter-observer consistency (H&E versus TFF2-IHC) was calculated using k-statistics and/or Spearman's coefficient.

RESULTS

Based on H&E-stain versus TFF2-IHC, intra-observer consistency in PPM assessement was ranked as consistently "good" (k-values: Alpha=0.79; Beta=0.78; Gamma=0.75). Based on H&E, the overall PPM inter-observer consistency among the 3 observers was ranked as "good" (k=0.77) (the inter-observer consistency for pairs of observers was as follows: Alpha versus Beta k=0.88; Alpha versus Gamma k=0.87; Beta versus Gamma k=0.80). Based on TFF2-IHC, the overall PPM inter-observer agreement was ranked as "excellent" (k=0.91) (the inter-observer consistency for pairs of observers was as follows: Alpha versus Beta k=1; Alpha versus Gamma k=0.91; Beta versus Gamma k=0.91).

CONCLUSION

Relying on either H&E staining or TFF2-IHC, pathologists assess PPM consistently.

Histological changes associated with pyloric and pseudopyloric metaplasia after Helicobacter pylori eradication

Pyloric metaplasia (PM) and pseudopyloric metaplasia (PPM) are metaplastic changes resulting in pyloric-type glands in the gastric oxyntic mucosa that mainly occur in chronic gastritis caused by Helicobacter pylori (H. pylori) infection. Focusing on PM and PPM, we classified the histological changes in gastric mucosa according to the Updated Sydney System, using 314 biopsy specimens of gastric greater curvature of the middle body before H. pylori eradication (HPE). Next, the numbers of PM and PPM glands were counted in 47 specimens, and subjects were followed up over 10 years after HPE. PPM was recognized jointly with inflammation, activity, atrophy, and intestinal metaplasia, but PM was recognized more frequently than PPM as atrophy and intestinal metaplasia progressed. Both PM and PPM regressed significantly within 6 years after HPE. Additionally, we demonstrated that PM and PPM are not always coincident with spasmolytic polypeptide-expressing metaplasia (SPEM). In conclusion, PM and PPM are considered different modulations of the same line of differentiation, which are both reversible, with PM potentially emerging from PPM upon progression.

Mucins, trefoil factors and pancreatic duodenal homeobox 1 expression in spasmolytic polypeptide expressing metaplasia and intestinal metaplasia adjacent to gastric carcinomas

INTRODUCTION

Gastric cancers are the second cause of cancer related deaths all around the world but gastric carcinogenesis remains a mystery. Intestinal metaplasia (IM) and spasmolytic polypeptide expressing metaplasia (SPEM) are the two types of preneoplastic metaplasias. In this study, we aimed to investigate expression of Pancreatic duodenal homeobox 1 (PDX1), mucins (MUCs), trefoil factors (TFFs) in SPEM and IM surrounding gastric carcinomas.

MATERIAL AND METHODS

Tissue samples of tumor adjacent gastric mucosa including IM (n = 61) and SPEM (n = 36) from 70 gastrectomy specimens were used for immunohistochemical analysis of PDX1, mucins (MUC5AC, MUC6) and trefoil factors (TFF2, TFF3).

RESULTS

Nuclear expression of PDX1 was present in both SPEM (32/36) and IM (60/61) and there was no significant difference in expression of PDX1 between the two types of metaplasias. While TFF3 and MUC5AC were abundant in IM, SPEM showed 100% expression of TFF2 and MUC6 and also lower positivity with TFF3 and MUC5AC. PDX1 positivity was related to expression of MUC5AC (60/61, p < 0.001) and TFF3 (60/61, p < 0.001) in IM and also associated with expression of MUC5AC (14/32, p < 0.05), MUC6 (32/32, p < 0.001), TFF2 (32/32, p < 0.001) and TFF3 (9/32, p < 0.05) in SPEM. Coexpression of TFF3 and TFF2 was present in 10 of 36 (27.7%) samples of SPEM and also 29 of 61 (47.5%) samples of IM exhibited dual expression of trefoil peptides.

CONCLUSIONS

PDX1 may affect the development of SPEM and IM. Expression patterns of TFFs and MUCs may indicate that IM evolves from SPEM.

Muc5ac null mice are predisposed to spontaneous gastric antro-pyloric hyperplasia and adenomas coupled with attenuated H. pylori-induced corpus mucous metaplasia

Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide and is strongly associated with chronic Helicobacter pylori (Hp) infection. The ability of Hp to closely adhere to the gastric surface protective mucous layer containing mucins (MUC in humans and Muc in animals), primarily Muc5ac, is integral in the stepwise pathogenesis from gastritis to cancer. To probe the role of Muc5ac in Hp-induced gastric pathology, Muc5ac^-/- and Muc5ac^+/+ (WT) mice were experimentally infected with Hp Sydney strain (SS1). At 16 weeks and 32 weeks post infection (wpi), groups of mice were euthanized and evaluated for the following: gastric histopathological parameters, immunohistochemical expression of mucins (Muc5ac, Muc1, Muc2), Trefoil factor family proteins (Tff1 and Tff2), Griffonia (Bandeiraea) simplicifolia lectin II (GSL II) (mucous metaplasia marker) and Clusterin (Spasmolytic Polypeptide Expressing Metaplasia (SPEM) marker), Hp colonization density by qPCR and gastric cytokine mRNA levels. Our results demonstrate that Muc5ac^-/- mice developed spontaneous antro-pyloric proliferation, adenomas and in one case with neuroendocrine differentiation; these findings were independent of Hp infection along with strong expression levels of Tff1, Tff2 and Muc1. Hp-infected Muc5ac^-/- mice had significantly lowered gastric corpus mucous metaplasia at 16 wpi and 32 wpi (P = 0.0057 and P = 0.0016, respectively), with a slight reduction in overall gastric corpus pathology. GSII-positive mucous neck cells were decreased in Hp-infected Muc5ac^-/- mice compared to WT mice and clusterin positivity was noted within metaplastic glands in both genotypes following Hp infection. Additionally, Hp colonization densities were significantly higher in Muc5ac^-/- mice compared to WT at 16 wpi in both sexes (P = 0.05) along with a significant reduction in gastric Tnfα (16 wpi-males and females, P = 0.017 and P = 0.036, respectively and 32 wpi-males only, P = 0.025) and Il-17a (16 wpi-males) (P = 0.025). Taken together, our findings suggest a protective role for MUC5AC/Muc5ac in maintaining gastric antral equilibrium and inhibiting Hp colonization and associated inflammatory pathology.

The Double Face of Mucin-Type O-Glycans in Lectin-Mediated Infection and Immunity

Epithelial human blood group antigens (HBGAs) on O-glycans play roles in pathogen binding and the initiation of infection, while similar structures on secretory mucins exert protective functions. These double-faced features of O-glycans in infection and innate immunity are reviewed based on two instructive examples of bacterial and viral pathogens. Helicobacter pylori represents a class 1 carcinogen in the human stomach. By expressing blood group antigen-binding adhesin (BabA) and LabA adhesins that bind to Lewis-b and LacdiNAc, respectively, H. pylori colocalizes with the mucin MUC5AC in gastric surface epithelia, but not with MUC6, which is cosecreted with trefoil factor family 2 (TFF2) by deep gastric glands. Both components of the glandular secretome are concertedly up-regulated upon infection. While MUC6 expresses GlcNAc-capped glycans as natural antibiotics for H. pylori growth control, TFF2 may function as a probiotic lectin. In viral infection human noroviruses of the GII genogroup interact with HBGAs via their major capsid protein, VP1. HBGAs on human milk oligosaccharides (HMOs) may exert protective functions by binding to the P2 domain pocket on the capsid. We discuss structural details of the P2 carbohydrate-binding pocket in interaction with blood group H/Lewis-b HMOs and fucoidan-derived oligofucoses as effective interactors for the most prevalent norovirus strains, GII.4 and GII.17.

Pyloric metaplasia, pseudopyloric metaplasia, ulcer-associated cell lineage and spasmolytic polypeptide-expressing metaplasia: reparative lineages in the gastrointestinal mucosa

The gastrointestinal mucosae provide a critical barrier between the external and internal milieu. Thus, damage to the mucosa requires an immediate response to provide appropriate wound closure and healing. Metaplastic lineages with phenotypes similar to the mucous glands of the distal stomach or Brunner's glands have been associated with various injurious scenarios in the stomach, small bowel, and colon. These lineages have been assigned various names including pyloric metaplasia, pseudopyloric metaplasia, ulcer-associated cell lineage (UACL), and spasmolytic polypeptide-expressing metaplasia (SPEM). A re-examination of the literature on these various forms of mucous cell metaplasia suggests that pyloric-type mucosal gland lineages may provide a ubiquitous response to mucosal injury throughout the gastrointestinal tract as well as in the pancreas, esophagus, and other mucosal surfaces. While the cellular origin of these putative reparative lineages likely varies in different regions of the gut, their final phenotypes may converge on a pyloric-type gland dedicated to mucous secretion. In addition to their healing properties in the setting of acute injury, these pyloric-type lineages may also represent precursors to neoplastic transitions in the face of chronic inflammatory influences. Further investigations are needed to determine how discrete molecular profiles relate to the origin and function of pyloric-type metaplasias previously described by histological characteristics in multiple epithelial mucosal systems in the setting of acute and chronic damage. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Helicobacter pylori and gastric mucin expression: A systematic review and meta-analysis

AIM: To investigate the relationship between Helicobacter pylori (H. pylori) and mucin expression in gastric mucosa.

METHODS: English Medical literature searches were conducted for gastric mucin expression in H. pylori infected people vs uninfected people. Searches were performed up to December 31^th 2014, using MEDLINE, PubMed, EMBASE, Scopus, and CENTRAL. Studies comparing mucin expression in the gastric mucosa in patients positive and negative for H. pylori infection, were included. Meta-analysis was performed by using Comprehensive meta-analysis software (Version 3, Biostat Inc., Englewood, NJ, United States). Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated compared mucin expression in individual studies by using the random effects model. Heterogeneity between studies was evaluated using the Cochran Q-test, and it was considered to be present if the Q-test P value was less than 0.10. I² statistic was used to measure the proportion of inconsistency in individual studies, with I² > 50% representing substantial heterogeneity. We also calculated a potential publication bias.

RESULTS: Eleven studies, which represent 53 sub-studies of 15 different kinds of mucin expression, were selected according to the inclusion criteria. Every kind of mucin has been considered as one study. When a specific mucin has been studied in more than one paper, we combined the results in a nested meta-analysis of this particular mucin: MUC2, MUC6, STn, Paradoxical con A, Tn, T, Type 1 chain mucin, LeA, SLeA, LeB, AB-PAS, MUC1, and MUC5AC. The odds ratio of mucin expression in random analysis was 2.33, 95%CI: 1.230-4.411, P = 0.009, higher expression in H. pylori infected patients. Odds ratio for mucin expression in H. pylori positive patients was higher for MUC6 (9.244, 95%CI: 1.567-54.515, P = 0.014), and significantly lower for MUC5AC (0.447, 95%CI: 0.211-0.949, P = 0.036). Thus, H. pylori infection may increase MUC6 expression and decrease MUC5AC expression by 924% and 52%, respectively.

CONCLUSION: H. pylori inhibits MUC5AC expression in the gastric epithelium, and facilitates colonization. In contrast, increased MUC6 expression may help inhibiting colonization, using MUC6 antibiotics properties.

Mucosal expression of aquaporin-4 in the stomach of histamine type 2 receptor knockout mice and Helicobacter pylori-infected mice

BACKGROUND AND AIM

Basolateral water channel, aquaporin-4 (AQP4), is known to be expressed in gastric parietal cells, especially in the basal side of gastric mucosa. However, the role of AQP4 in the stomach is still unknown. Histamine type 2 receptor (H2R) knockout mice, which are characterized by suppressed gastric acid secretion, are known as formation of mucosal hyperplasia with cystic dilatation and spasmolytic polypeptide-expressing metaplasia (SPEM) in the stomach. The aim of the present study is to investigate whether the expression of AQP4 is changed by the condition of acid suppression and Helicobacter pylori infection.

METHODS

Male H2 R knockout mice and their controls (C57BL/6) were used. H. pylori was orally infected at the age of 5 weeks. The distributions of AQP4 and H+/K+-ATPase in the gastric mucosa were investigated by fluorescent immunohistochemistry. The mRNA expressions of AQP4, H+/K+-ATPase, sonic hedgehog (Shh), and trefoil factor-2 (TFF2) were investigated by quantitative reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

In the H2 R knockout mice, the distribution of AQP4-positive parietal cells was extended toward the surface of the fundic glands. Although the mRNA expression levels of AQP4 and H+/K+ATPase were elevated in H2 R knockout mice at the age of 20 weeks, the elevations were not maintained by aging or H. pylori infection. In H2 R knockout mice with H. pylori infection, the expression level of TFF2 mRNA was elevated while the ratio between AQP4 and H+/K+ ATPase mRNA expression was decreased compared with the H2 R knockout mice without H. pylori infection.

CONCLUSIONS

In the H2 R knockout mice, massive SPEM was induced by H. pylori colonization and the ratio between AQP4 and H+/K+ATPase mRNA expression was decreased.

Human trefoil factor 2 is a lectin that binds α-GlcNAc-capped mucin glycans with antibiotic activity against Helicobacter pylori

Helicobacter pylori infection is the major cause of gastric cancer and remains an important health care challenge. The trefoil factor peptides are a family of small highly conserved proteins that are claimed to play essential roles in cytoprotection and epithelial repair within the gastrointestinal tract. H. pylori colocalizes with MUC5AC at the gastric surface epithelium, but not with MUC6 secreted in concert with TFF2 by deep gastric glands. Both components of the gastric gland secretome associate non-covalently and show increased expression upon H. pylori infection. Although blood group active O-glycans of the Lewis-type form the basis of H. pylori adhesion to the surface mucin layer and to epithelial cells, α1,4-GlcNAc-capped O-glycans on gastric mucins were proposed to inhibit H. pylori growth as a natural antibiotic. We show here that the gastric glycoform of TFF2 is a calcium-independent lectin, which binds with high specificity to O-linked α1,4-GlcNAc-capped hexasaccharides on human and porcine stomach mucin. The structural assignments of two hexasaccharide isomers and the binding active glycotope were based on mass spectrometry, linkage analysis, (1)H nuclear magnetic resonance spectroscopy, glycan inhibition, and lectin competition of TFF2-mucin binding. Neoglycolipids derived from the C3/C6-linked branches of the two isomers revealed highly specific TFF2 binding to the 6-linked trisaccharide in GlcNAcα1-4Galβ1-4GlcNAcβ1-6(Fucα1-2Galβ1-3)GalNAc-ol(Structure 1). Supposedly, lectin TFF2 is involved in protection of gastric epithelia via a functional relationship to defense against H. pylori launched by antibiotic α1,4-GlcNAc-capped mucin glycans. Lectin-carbohydrate interaction may have also an impact on more general functional aspects of TFF members by mediating their binding to cell signaling receptors.

Role of mucin Lewis status in resistance to Helicobacter pylori infection in pediatric patients

BACKGROUND

Helicobacter pylori causes gastritis, peptic ulcer and is a risk factor for adenocarcinoma and lymphoma of the stomach. Gastric mucins, carrying highly diverse carbohydrate structures, present functional binding sites for H. pylori and may play a role in pathogenesis. However, little information is available regarding gastric mucin in children with and without stomach diseases.

MATERIALS AND METHODS

Expression of mucins and glycosylation was studied by immunohistochemistry on gastric biopsies from 51 children with and without H. pylori infection and/or peptic ulcer disease.

RESULTS

In all children, MUC5AC was present in the surface epithelium and MUC6 in the glands. No MUC6 in the surface epithelium or MUC2 was detected in any section. The Le(b) and Le(a) blood group antigens were present in the surface epithelium of 80% and 29% of children, respectively. H. pylori load was higher in Le(b) negative children than in Le(b) positive individuals (mean +/- SEM 17.8 +/- 3.5 vs 10.8 +/- 1.5; p < 0.05), but there was no correlation between Le(a) or Le(b) status and gastritis, nodularity, and gastric or duodenal ulcer (DU). Expression of sialyl-Le(x) was associated with H. pylori infection, and DU.

CONCLUSIONS

Mucin expression and glycosylation is similar in children and adults. However, in contrast to adults, pediatric H. pylori infection is not accompanied by aberrant expression of MUC6 or MUC2. Furthermore, the lower H. pylori density in Le(b) positive children indicates that H. pylori is suppressed in the presence of gastric mucins decorated with Le(b), the binding site of the H. pylori BabA adhesin.

Helicobacter-based mouse models of digestive system carcinogenesis

Animal models are necessary to reproduce the complex host, microbial and environmental influences associated with infectious carcinogenesis of the digestive system. Today, mouse models are preferred by most researchers because of cost efficiencies, rapid reproduction, choice of laboratory reagents, and availability of genetically engineered mutants to study specific gene functions in vivo. Mouse models have validated the once-provocative hypothesis that Helicobacter pylori infection is a major risk factor for gastric carcinoma, dispelling early skepticism over the pathogenic nature of this organism in the human stomach. Enterohepatic Helicobacter spp. induce inflammatory bowel disease and colorectal carcinoma in susceptible mouse strains, permitting study of host immunity and microbial factors at the cellular and molecular level. H. hepaticus is the only proven infectious hepatocarcinogen of mice and has been used to explore mechanisms of inflammation-associated liver cancer as seen in human chronic viral hepatitis. For example, this model was used to identify for the first time a potential mechanism for male-predominant liver cancer risk independent of circulating sex hormones. Helicobacter-based mouse models of digestive system carcino-genesis are used to investigate the basic biology of inflammation-associated human cancers and to evaluate therapeutic interventions at the discovery level. Because of exciting advances in genetic engineering of mice, in vivo imaging, and system-wide genomics and proteomics, these models will provide even more information in the future. This chapter introduces the mouse as a model species; summarizes important models of inflammation-associated cancer incited by murine Helicobacter infection; and describes methods for the collection, sampling, and histologic grading of mouse digestive system tissues.

Alterations of gastric homeoprotein expression in Helicobacter pylori infection, incisural antralisation, and intestinal metaplasia

PURPOSE

This study was to determine whether gastric expression of homeoproteins is altered in Helicobacter pylori infection, incisural antralisation, and intestinal metaplasia (IM).

METHODS

Gastric biopsy specimens were taken from 98 patients with non-ulcer dyspepsia for the detection of H. pylori infection; histological examinations; immunohistochemical staining of CDX2, PDX1, PAX6, and NKX6.1.

RESULTS

Of the patients, 38 were positive for H. pylori infection, 44 had antral-type mucosa at the incisura, and 22 had IM in the stomach. At the incisura, the expression of PDX1, NKX6.1, and PAX6 in cytoplasm compartment was down-regulated in antral-type mucosa compared with that in the transitional- or body-type mucosa (all P<0.01). The expression of PDX1, PAX6, and NKX6.1 in cytoplasm at the incisura was down-regulated in H. pylori-infected patients compared with that in those without H. pylori infection (all P<0.01). CDX2 expression in whole stomach was up-regulated, but PDX1 expression at the incisura was down-regulated in patients with IM compared with that in those without IM (all P<0.01).

CONCLUSIONS

Gastric expression of PDX1, PAX 6, and NKX6.1 is down-regulated in H. pylori infection and incisural antralisation. CDX2 is up-regulated but PDX1 is down-regulated in the presence of IM.

Decreased expression of gastrokine 1 and the trefoil factor interacting protein TFIZ1/GKN2 in gastric cancer: influence of tumor histology and relationship to prognosis

PURPOSE

Transcriptional profiling showed decreased expression of gastrokine 1 (GKN1) and the related trefoil factor interacting protein (TFIZ1/GKN2) in Helicobacter pylori infection. Decreased GKN1 and GKN2 mRNA expression has been reported in gastric adenocarcinoma. We have examined GKN1 and GKN2 protein expression in a large gastric cancer series, correlated expression with tumor subtype, and evaluated their utility as prognostic biomarkers.

EXPERIMENTAL DESIGN

GKN1, GKN2, and the trefoil factors TFF1 and TFF3 were examined in tissue microarrays from 155 distal gastric adenocarcinomas. Immunohistochemical expression was correlated with clinical outcome. GKN1 and GKN2 expression was measured by real-time PCR and Western analysis in samples of gastric cancer and adjacent nonneoplastic mucosa.

RESULTS

GKN1 was lost in 78% of diffuse and 42% of intestinal cancers (P < 0.0001, diffuse versus intestinal). GKN2 expression was lost in 85% of diffuse and 54% of intestinal type cancers (P < 0.002). GKN1 and GKN2 down-regulation were confirmed by Western and real-time PCR analysis. Loss of either protein was associated with significantly worse outcome in intestinal-type tumors by univariate analysis; and GKN2 loss remained a predictor of poor outcome in multivariate analysis (P < 0.033). TFF1 was lost in >70%, and TFF3 was expressed in approximately 50% of gastric cancers.

CONCLUSIONS

Loss of GKN1 and GKN2 expression occurs frequently in gastric adenocarcinomas, especially in the diffuse subtype. GKN1 and GKN2 loss are associated with shorter overall survival in the intestinal subtype.

Reduced Shh expression in TFF2-overexpressing lesions of the gastric fundus under hypochlorhydric conditions

Expression of sonic hedgehog (Shh), a morphogen for the gastric fundic glands, is reduced in the atrophic mucosa that develops in association with Helicobacter pylori infection, resulting in impaired differentiation of the fundic gland cells, increased expression of trefoil factor family 2 (TFF2) and the formation of spasmolytic polypeptide (SP)-expressing metaplasia (SPEM), a preneoplastic lesion. However, it is still unresolved whether H. pylori-induced inflammation and the resultant reduction in parietal cell number or reduced parietal cell function per se reduces Shh expression. The present study was designed to clarify the expression of Shh and TFF2 in the context of parietal cell dysfunction in the absence of inflammation, using histamine H(2) receptor-knockout (H(2)R-null) mice and an acid exposure model. Age-matched H(2)R-null mice and wild-type (WT) mice were used. The expression of Shh and TFF2 mRNA was quantified by quantitative RT-PCR. Immunohistochemistry was also performed to detect the expression of Shh, TFF2 and cell markers. To study the effects of acid exposure, HCl solution was administered to the animals. The H(2)R-null mice exhibited higher gastric pH, increased TFF2 expression and reduced Shh expression. Impaired mucous neck-to-zymogenic cell differentiation was observed in the H(2)R-null mice. Furthermore, Shh expression increased in the presence of gastric acid and showed a significant correlation with gastric surface pH. In conclusion, our results suggest that persistent parietal cell dysfunction alone (suppressed gastric acid secretion), in the absence of inflammation or parietal cell loss caused by H. pylori infection, may be sufficient to down-regulate Shh expression in TFF2-overexpressing preneoplastic lesions of the gastric fundus. Since exposure to acid restored fundic Shh expression, appropriate gastric acid secretion may play an important role in the morphogen dynamics involved in the maintenance of gastric fundic gland homeostasis.

Helicobacter pylori eradication for gastric cancer prevention

Gastric cancer is the second most common fatal malignancy in the world. Its incidence is high in East Asia. Helicobacter pylori infection is an important factor in the pathogenesis of gastric cancer. Epidemiological studies have established a strong causal relationship between H. pylori infection and gastric cancer. H. pylori eradication is therefore likely to be one of the most promising approaches to gastric cancer prevention. Animal studies have shown that eradication of H. pylori infection, especially at the early stage, is effective in preventing H. pylori-related gastric carcinogenesis. However, the available data from human studies show that H. pylori eradication does not completely prevent gastric cancer and that it might be useful only in patients without atrophic gastritis or intestinal metaplasia at baseline. Longer follow-up and additional studies are needed to clarify this issue.

Topographic expression of MUC5AC and MUC6 in the gastric mucosa infected by Helicobacter pylori and in associated diseases

We investigated the topographic expression of MUC5AC and MUC6 in relationship with gastric diseases. The immunoexpression of MUC5AC and MUC6 was evaluated in 75 adults presenting Helicobacter pylori gastritis (n = 22; 11 cagA positive), duodenal ulcer (DU, n = 11), gastric ulcer (GU, n = 9), gastric carcinoma (GC, n = 20), and normal mucosa (H. pylori negative, n = 13). Five gastric areas (antral and corporeal lesser and greater curvatures and incisura) were studied. H. pylori was detected by carbolfuchsin, urease, and culture; cagA was determined by PCR. All patients with DU (eight with GU and 13 with GC) were H. pylori-positive. In H. pylori gastritis, MUC5AC expression was higher in the antrum than in the corpus; no difference was observed with respect to cagA status. MUC5AC expression was higher in the antrum of gastritis than in DU, and it was lower in the incisura among GU patients compared to DU. MUC6 expression was higher in the antrum of H. pylori gastritis compared to DU and to uninfected patients. No difference was observed in the topographic pattern of expression of MUC5AC and MUC6 among GC cases. The topographic over- and under-expression of mucins in H. pylori-associated gastritis and peptic disease suggest a role for these mucins in the pathogenesis of H. pylori infection and associated diseases.

Upregulation of MUC6 mucin gene expression by NFkappaB and Sp factors

To clarify the mechanism underlying regulation of MUC6 expression, we isolated the 5' flanking region of the MUC6 gene (5'-MUC6). We determined the transcription start site of the MUC6 gene, and found a TATA box at -35 to -29bp, a putative NFkappaB consensus sequence at -173 to -164bp, and putative Sp family binding sites at -530 to -521 and -847 to -838bp. The luciferase activity of 5'-MUC6 gradually decreased with deletion of these sites. NFkappaB inhibitory factor IkappaB decreased the luciferase activity, and forced expression of NFkappaB induced MUC6 transcription. An inhibitor of Sp family binding, mithramycin A, suppressed MUC6 transcripts, and Sp1 and Sp3 overexpression up-regulated them. Binding of Sp family members to their putative sites was confirmed by electrophoretic mobility shift assays. Our results suggest that MUC6 transcription is regulated by NFkappaB and Sp family members.