Beta-catenin expression in intramucosal neoplastic lesions of the stomach. Comparative analysis of adenoma/dysplasia, adenocarcinoma and signet-ring cell carcinoma

Mucin expression in gastric- and gastro-oesophageal signet-ring cell cancer: results from a comprehensive literature review and a large cohort study of Caucasian and Asian gastric cancer

BACKGROUND

The literature on the prognostic relevance of signet-ring cell (SRC) histology in gastric cancer (GC) is controversial which is most likely related to inconsistent SRC classification based on haematoxylin-eosin staining. We hypothesised that mucin stains can consistently identify SRC-GC and predict GC patient outcome.

METHODS

We performed a comprehensive literature review on mucin stains in SRC-GC and characterised the mucin expression in 851 Caucasian GC and 410 Asian GC using Alcian Blue (AB)-Periodic Acid-Schiff (PAS), MUC2 (intestinal-type mucin), and MUC5AC (gastric-type mucin). The relationship between mucin expression and histological phenotype [poorly cohesive (PC) including proportion of SRCs, non-poorly cohesive (non-PC), or mucinous (MC)], clinicopathological variables, and patient outcome was analysed.

RESULTS

Depending on mucin expression and cut-offs, the positivity rates of SRC-GC reported in the literature varied from 6 to 100%. Patients with MUC2 positive SRC-GC or SRC-GC with (gastro)intestinal phenotype had poorest outcome. In our cohort study, PC with ≥ 10% SRCs expressed more frequently MUC2, MUC5AC, and ABPAS (p < 0.001, p = 0.004 and p < 0.001, respectively). Caucasians with AB positive GC or combined ABPAS-MUC2 positive and MUC5AC negative had poorest outcome (all p = 0.002). This association was not seen in Asian patients.

CONCLUSIONS

This is the first study to suggest that mucin stains do not help to differentiate between SRC-GC and non-SRC-GC. However, mucin stains appear to be able to identify GC patients with different outcome. To our surprise, the relationship between outcome and mucin expression seems to differ between Caucasian and Asian GC patients which warrants further investigations.

The Cancer Microbiota: EMT and Inflammation as Shared Molecular Mechanisms Associated with Plasticity and Progression

With the advent of novel molecular platforms for high-throughput/next-generation sequencing, the communities of commensal and pathogenic microorganisms that inhabit the human body have been defined in depth. In the last decade, the role of microbiota-host interactions in driving human cancer plasticity and malignant progression has been well documented. Germ-free preclinical models provided an invaluable tool to demonstrate that the human microbiota can confer susceptibility to various types of cancer and can also modulate the host response to therapeutic treatments. Of interest, besides the detrimental effects of dysbiosis on cancer etiopathogenesis, specific microorganisms have been shown to exert protective activities against cancer growth. This has strong clinical implications, as restoration of the physiologic microbiota is being rapidly implemented as a novel anticancer therapeutic strategy. Here, we reviewed past and recent literature depicting the role of microbiota-host interactions in modulating key molecular mechanisms that drive human cancer plasticity and lead to malignant progression. We analyzed microbiota-host interactions occurring in the gut as well as in other anatomic sites, such as oral and nasal cavities, lungs, breast, esophagus, stomach, reproductive tract, and skin. We revealed a common ground of biological alterations and pathways modulated by a dysbiotic microbiota and potentially involved in the control of cancer progression. The molecular mechanisms most frequently affected by the pathogenic microorganisms to induce malignant progression involve epithelial-mesenchymal transition- (EMT-) dependent barrier alterations and tumor-promoting inflammation. This evidence may pave the way to better stratify high-risk cancer patients based on unique microenvironmental/microbial signatures and to develop novel, personalized, biological therapies.

Targeted mobilization of Lrig1+ gastric epithelial stem cell populations by a carcinogenic Helicobacter pylori type IV secretion system

Helicobacter pylori-induced gastritis is the strongest risk factor for gastric adenocarcinoma, a malignancy preceded by a series of well-defined histological stages, including metaplasia. One microbial constituent that augments cancer risk is the cag type 4 secretion system (T4SS), which translocates the oncoprotein CagA into host cells. Aberrant stem cell activation is linked to carcinogenesis, and Lrig1 (leucine-rich repeats and Ig-like domains 1) marks a distinct population of progenitor cells. We investigated whether microbial effectors with carcinogenic potential influence Lrig1 progenitor cells ex vivo and via lineage expansion within H. pylori-infected gastric mucosa. Lineage tracing was induced in Lrig1-CreERT2/+;R26R-YFP/+ (Lrig1/YFP) mice that were uninfected or subsequently infected with cag+H. pylori or an isogenic cagE- mutant (nonfunctional T4SS). In contrast to infection with wild-type (WT) H. pylori for 2 wk, infection for 8 wk resulted in significantly increased inflammation and proliferation in the corpus and antrum compared with uninfected or mice infected with the cagE- mutant. WT H. pylori-infected mice harbored significantly higher numbers of Lrig1/YFP epithelial cells that coexpressed UEA1 (surface cell marker). The number of cells coexpressing intrinsic factor (chief cell marker), YFP (lineage marker), and GSII lectin (spasmolytic polypeptide-expressing metaplasia marker) were increased only by WT H. pylori In human samples, Lrig1 expression was significantly increased in lesions with premalignant potential compared with normal mucosa or nonatrophic gastritis. In conclusion, chronic H. pylori infection stimulates Lrig1-expressing progenitor cells in a cag-dependent manner, and these reprogrammed cells give rise to a full spectrum of differentiated cells.

The Possible Role of Helicobacter pylori in Gastric Cancer and Its Management

Helicobacter pylori (HP) is a facultative anaerobic bacterium. HP is a normal flora having immuno-modulating properties. This bacterium is an example of a microorganism inducing gastric cancer. Its carcinogenicity depends on bacteria-host related factors. The proper understanding of the biology of HP inducing gastric cancer offers the potential strategy in the managing of HP rather than eradicating it. In this article, we try to summarize the biology of HP-induced gastric cancer and discuss the current pharmacological approach to treat and prevent its carcinogenicity.

Helicobacter pylori targets cancer-associated apical-junctional constituents in gastroids and gastric epithelial cells

OBJECTIVE

Helicobacter pylori strains that express the oncoprotein CagA augment risk for gastric cancer. However, the precise mechanisms through which cag(+) strains heighten cancer risk have not been fully delineated and model systems that recapitulate the gastric niche are critical for understanding pathogenesis. Gastroids are three-dimensional organ-like structures that provide unique opportunities to study host-H. pylori interactions in a preclinical model. We used gastroids to inform and direct in vitro studies to define mechanisms through which H. pylori modulates expression of the cancer-associated tight junction protein claudin-7.

DESIGN

Gastroids were infected by luminal microinjection, and MKN28 gastric epithelial cells were cocultured with H. pylori wild-type cag(+) strains or isogenic mutants. β-catenin, claudin-7 and snail localisation was determined by immunocytochemistry. Proliferation was assessed using 5-ethynyl-2'-deoxyuridine, and levels of claudin-7 and snail were determined by western blot and flow cytometry.

RESULTS

Gastroids developed into a self-organising differentiation axis and H. pylori induced mislocalisation of claudin-7 and increased proliferation in a CagA- and β-catenin-dependent manner. In MKN28 cells, H pylori-induced suppression of claudin-7 was regulated by β-catenin and snail. Similarly, snail expression was increased and claudin-7 levels were decreased among H. pylori-infected individuals.

CONCLUSIONS

H. pylori increase proliferation in a strain-specific manner in a novel gastroid system. H. pylori also alter expression and localisation of claudin-7 in gastroids and human epithelial cells, which is mediated by β-catenin and snail activation. These data provide new insights into molecular interactions with carcinogenic potential that occur between H. pylori and epithelial cells within the gastric niche.

Gastric microbiome and gastric cancer

Cancer of the stomach is the fourth most common cancer worldwide. The single strongest risk factor for gastric cancer is Helicobacter pylori-associated chronic gastric inflammation. Among persons with H. pylori infection, strain-specific components, host immune responses, and environmental factors influence the risk for gastric disease, including adenocarcinoma of the stomach, although only a small proportion of infected persons develop the malignancy. Recent advances in DNA sequencing technology have uncovered a complex community of noncultivatable inhabitants of the human stomach. The interaction between these inhabitants, collectively referred to as the gastric microbiota, and H. pylori likely affects gastric immunobiology and possibly the sequelae of H. pylori infection. Thus, characterization of the gastric microbiota in subjects with and without H. pylori infection could provide new insight into gastric homeostasis and the pathogenesis of H. pylori-associated disease, including gastric cancer.

"Targeted disruption of the epithelial-barrier by Helicobacter pylori"

Helicobacter pylori colonizes the human gastric epithelium and induces chronic gastritis, which can lead to gastric cancer. Through cell-cell contacts the gastric epithelium forms a barrier to protect underlying tissue from pathogenic bacteria; however, H. pylori have evolved numerous strategies to perturb the integrity of the gastric barrier. In this review, we summarize recent research into the mechanisms through which H. pylori disrupts intercellular junctions and disrupts the gastric epithelial barrier.

Helicobacter pylori activates calpain via toll-like receptor 2 to disrupt adherens junctions in human gastric epithelial cells

Helicobacter pylori is a risk factor for the development of gastritis, gastroduodenal ulcers, and gastric adenocarcinoma. H. pylori-induced disruption of epithelial adherens junctions (AJs) is thought to promote the development of severe disease; however, the mechanisms whereby H. pylori alters AJ structure remain incompletely understood. The present study demonstrates that H. pylori infection in human patients is associated with elevated serum levels of an 80-kDa E-cadherin ectodomain, whose presence is independent of the presence of serum antibodies against CagA. In vitro, a heat-labile H. pylori surface component activates the host protease calpain in human gastric MKN45 cells independently of the virulence factors CagA and VacA. H. pylori-induced calpain activation results in cleavage of E-cadherin to produce a 100-kDa truncated form and induce relocalization of E-cadherin and β-catenin. Stimulation of MKN45 cells with the toll-like receptor 2 (TLR2) ligand P3C activated calpain and disrupted E-cadherin and β-catenin in a pattern similar to that induced by H. pylori. Inhibition of TLR2 prevented H. pylori-induced calpain activation and AJ disassembly. Together, these findings identify a novel pathway whereby H. pylori activates calpain via TLR2 to disrupt gastric epithelial AJ structure.

Nuclear translocation of β-catenin correlates with CD44 upregulation in Helicobacter pylori-infected gastric carcinoma

Infection with Helicobacter pylori CagA-positive strains is associated with gastric adenocarcinoma. CagA H. pylori activates the β-catenin signal by translocation into nucleus which promotes carcinogenesis. Deregulated accumulation of nuclear β-catenin enhances transcription of β-catenin target genes including CD44 and promotes malignant transformation. The aim of this study was to investigate whether nuclear translocation of β-catenin correlates with CD44 expression in CagA H. pylori-infected gastric carcinoma. To address these issues, we examined 140 gastric biopsy specimens by using immunohistochemical and immunofluorescence staining, Western blot, and mutational analysis of the exon 3 β-catenin gene. The nuclear localization of β-catenin was significantly (χ(2) = 21.175; P < 0.001) increased in advanced gastric carcinoma and also correlated (χ(2) = 22.857; P < 0.001) with the CagA H. pylori positive specimens. We also observed that tyrosine-phosphorylated β-catenin was significantly (χ(2) = 14.207; P < 0.001) increased in samples showing nuclear localization of β-catenin and also it correlated (χ(2) = 43.69; P < 0.03) with the CagA H. pylori positive specimens. Exon 3 β-catenin gene mutation was not detected in H. pylori-infected gastric carcinoma. CD44 up regulation was significantly associated with tyrosine-phosphorylated β-catenin (χ(2) = 22.5; P < 0.001), and this change was closely associated with nuclear translocation of β-catenin (χ(2) = 13.393; P < 0.001) in CagA H. pylori-infected gastric carcinoma. In conclusion, our data suggest that CagA H. pylori infection is responsible for the tyrosine phosphorylation of β-catenin and its nuclear translocation, which upregulates β-catenin target gene CD44 in gastric carcinoma.

Molecular cross-talk between Helicobacter pylori and human gastric mucosa

Helicobacter pylori (H. pylori) has co-evolved with humans to be transmitted from person to person and to colonize the stomach persistently. A well-choreographed equilibrium between the bacterial effectors and host responses permits microbial persistence and health of the host, but confers a risk for serious diseases including gastric cancer. During its long coexistence with humans, H. pylori has developed complex strategies to limit the degree and extent of gastric mucosal damage and inflammation, as well as immune effector activity. The present editorial thus aims to introduce and comment on major advances in the rapidly developing area of H. pylori/human gastric mucosa interaction (and its pathological sequelae), which is the result of millennia of co-evolution of, and thus of reciprocal knowledge between, the pathogen and its human host.

Helicobacter pylori and gastric cancer: factors that modulate disease risk

Helicobacter pylori is a gastric pathogen that colonizes approximately 50% of the world's population. Infection with H. pylori causes chronic inflammation and significantly increases the risk of developing duodenal and gastric ulcer disease and gastric cancer. Infection with H. pylori is the strongest known risk factor for gastric cancer, which is the second leading cause of cancer-related deaths worldwide. Once H. pylori colonizes the gastric environment, it persists for the lifetime of the host, suggesting that the host immune response is ineffective in clearing this bacterium. In this review, we discuss the host immune response and examine other host factors that increase the pathogenic potential of this bacterium, including host polymorphisms, alterations to the apical-junctional complex, and the effects of environmental factors. In addition to host effects and responses, H. pylori strains are genetically diverse. We discuss the main virulence determinants in H. pylori strains and the correlation between these and the diverse clinical outcomes following H. pylori infection. Since H. pylori inhibits the gastric epithelium of half of the world, it is crucial that we continue to gain understanding of host and microbial factors that increase the risk of developing more severe clinical outcomes.

The expression of E-cadherin-catenin complex in patients with advanced gastric cancer: role in formation of metastasis

The E-cadherin-catenin complex plays an important role in the process of cell adhesion. Its dysfunction is associated with a decrease in cell differentiation and with increased invasiveness and metastasis. Our aim was to evaluate the expression of E-cadherin and B-catenin in advanced gastric cancer in relation to selected clinico-pathomorphological parameters. Formalin-fixed, paraffin-embedded tissue specimens were immunohistochemically stained with monoclonal antibodies E-cadherin (NCL-E-Cad, Novocastra Laboratiries Ltd; dilution 1:50), beta-catenin (NCL-B-CAT, Novocastra Laboratories Ltd; dilution 1:100), alpha-catenin (alpha-E-caten, Santa Cruz Biotechnology; dilution 1:300) and gamma-catenin (gamma-catenin, Santa Cruz Biotechnology; dilution 1:100). The expressions of E-cadherin and alpha-, beta-, gamma-catenins in the main mass of tumor and lymph node metastasis were investigated in 91 patients with gastric cancer. No statistically significant correlation was observed between the expressions of E-cadherin, alpha-, beta-catenins and histological differentiation and between the expressions of E-cadherin, alpha-, gamma-catenins and location or depth of invasion. Moreover, the expression of alpha-, gamma-catenins in the main mass of tumor was not associated with lymph node metastasis. However, we found a relationship between the expression of beta-catenin in the main mass of tumor and lymph node metastasis and tumor location. The depth of invasion was correlated with positive expression of beta-catenin in the main mass of gastric cancer. A statistically significant association was observed between the expressions of E-cadherin and beta-catenin in the main mass of tumor and lymph node involvement. The expression of alpha-catenin in the main mass of tumor was also associated with histological differentiation and Lauren's classification. Statistical analysis showed an association between the expression of E-cadherin and postoperative survival time. No significant correlation was found between the expression of alpha-, beta-, gamma-catenins and survival time. Our results may suggest that the E-cadherin-catenin complex is the factor indicative of metastasis and disease progression in gastric cancer. Also the expression of E-cadherin may play a role as a prognostic factor.

Analysis of cell cycle-related proteins in gastric intramucosal differentiated-type cancers based on mucin phenotypes: a novel hypothesis of early gastric carcinogenesis based on mucin phenotype

Background

Abnormalities of cell cycle regulators are common features in human cancers, and several of these factors are associated with the early development of gastric cancers. However, recent studies have shown that gastric cancer tumorigenesis was characterized by mucin expression. Thus, expression patterns of cell cycle-related proteins were investigated in the early phase of differentiated-type gastric cancers to ascertain any mechanistic relationships with mucin phenotypes.

Methods

Immunostaining for Cyclins D1, A, E, and p21, p27, p53 and β-catenin was used to examine impairments of the cell cycle in 190 gastric intramucosal differentiated-type cancers. Mucin phenotypes were determined by the expressions of MUC5AC, MUC6, MUC2 and CD10. A Ki-67 positive rate (PR) was also examined.

Results

Overexpressions of p53, cyclin D1 and cyclin A were significantly more frequent in a gastric phenotype than an intestinal phenotype. Cyclin A was overexpressed in a mixed phenotype compared with an intestinal phenotype, while p27 overexpression was more frequent in an intestinal phenotype than in a mixed phenotype. Reduction of p21 was a common feature of the gastric intramucosal differentiated-type cancers examined.

Conclusions

Our results suggest that the levels of some cell cycle regulators appear to be associated with mucin phenotypes of early gastric differentiated-type cancers.

Helicobacter pylori: gastric cancer and beyond

Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.

Helicobacter pylori: gastric cancer and beyond

Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.

Helicobacter pylori virulence and the diversity of gastric cancer in Asia

Infection with cagPAI positive strains of Helicobacter pylori is recognized as being associated with an increased risk of gastric cancer. This article reviews the current knowledge on the structures and pathological functions of cagPAI and the CagA protein, focusing especially on the molecular mechanism through which CagA may be involved in gastric carcinogenesis. The possible link between the geographical distribution of cagPAI and cagA variations and gastric cancer diversity in Asia is also discussed.

HNPCC-associated synchronous early-stage signet-ring cell carcinomas of colonic origin. A comparative morphological and immunohistochemical study of an intramucosal and a submucosal example

Signet-ring cell carcinoma (SRCC) developing in the colorectum (CR) is infrequently identified at an early stage (no deeper than submucosa). Most such examples involve the submucosa. Merely 13 cases of intramucosal CR SRCC are at hand. We recently had the opportunity to study a specimen with two synchronous early-stage SRCC, developed in a 65-year-old hereditary nonpolyposis colorectal cancer male patient with a known disease-causing mutation in MLH1. A right hemicolectomy specimen comprised a 15-mm intramucosal cecal lesion, featuring zones of conventional tubular adenoma and intraepithelial SRCC as well as tumor cells multifocally permeating the lamina propria and a 12-mm submucosally expanding SRCC of the ascending colon. The intramucosal and intraepithelial as well as stromal lesional cells displayed a normal membranous expression of beta-catenin and E-cadherin; submucosally infiltrating cells featured alterations in this complex with loss of membranous expression of both proteins and a shift with nuclear accumulation of beta-catenin, suggesting a disruption of the Wingless signaling pathway taking place at the transition from the intramucosal to the submucosal level.

Beta-catenin and E-cadherin expression in salivary gland tumors

This study evaluated the expression of E-cadherin and beta-catenin in salivary gland tumors. Twelve biopsy specimens from cases diagnosed as pleomorphic adenoma, 17 adenoid cystic carcinomas, 10 epithelial-myoepithelial carcinomas, and 4 polymorphous low-grade adenocarcinomas were immunohistochemically labeled for E-cadherin and beta-catenin antibodies. Healthy salivary glands were used as controls. Membrane-associated E-cadherin and beta-catenin expression was present in all the tumor types studied. E-cadherin and beta-catenin showed a similar distribution; however, beta-catenin labeling was weaker than that for E-cadherin. In the epithelial-myoepithelial carcinomas, myoepithelial cells exhibited diffuse nuclear staining, although occasional cells presented only focal labeling. Epithelial-myoepithelial carcinomas present changes in [.beta]-catenin expression but the other salivary tumors studied do not, which may reflect divergence in tumorigenesis of this extensive subset of salivary gland tumors.

Activation of beta-catenin by carcinogenic Helicobacter pylori

Persistent gastritis induced by Helicobacter pylori is the strongest known risk factor for adenocarcinoma of the distal stomach, yet only a fraction of colonized persons ever develop gastric cancer. The H. pylori cytotoxin-associated gene (cag) pathogenicity island encodes a type IV secretion system that delivers the bacterial effector CagA into host cells after bacterial attachment, and cag+ strains augment gastric cancer risk. A host effector that is aberrantly activated in gastric cancer precursor lesions is beta-catenin, and activation of beta-catenin leads to targeted transcriptional up-regulation of genes implicated in carcinogenesis. We report that in vivo adaptation endowed an H. pylori strain with the ability to rapidly and reproducibly induce gastric dysplasia and adenocarcinoma in a rodent model of gastritis. Compared with its parental noncarcinogenic isolate, the oncogenic H. pylori strain selectively activates beta-catenin in model gastric epithelia, which is dependent on translocation of CagA into host epithelial cells. Beta-catenin nuclear accumulation is increased in gastric epithelium harvested from gerbils infected with the H. pylori carcinogenic strain as well as from persons carrying cag+ vs. cag- strains or uninfected persons. These results indicate that H. pylori-induced dysregulation of beta-catenin-dependent pathways may explain in part the augmentation in the risk of gastric cancer conferred by this pathogen.

Changes in the Wnt signalling pathway in gastrointestinal cancers and their prognostic significance

Many steps in the Wnt signalling pathway may be altered during the process of carcinogenesis. This Review focuses on the changes observed in gastrointestinal cancers. A literature search was undertaken and the currently available data summarised. Understanding the alterations to this signalling pathway may help to reveal future targets for therapeutic agents. In addition, since in some tumours, levels of components of the Wnt pathway have been found to correlate with clinical stage, their potential use as prognostic indicators is highlighted.

Nucleotide variants within theIQGAP1 gene in diffuse-type gastric cancers

IQGAP1 is recognized as a negative regulator of cell-cell adhesion at adherens junctions in several cell types, including gastric mucosal cells. The histopathologic appearance of diffuse gastric carcinoma is defined by non- or poorly cohesive tumor cells, indicating abnormal intercellular adhesion. Hence, we screened 38 gastric cancers for activating point mutations in IQGAP1. In 2 of the 33 diffuse gastric cancers, there was a missense nucleotide change predicted to alter the amino acid sequence in the GAP-related domain, which includes part of the binding site for the activated small G proteins Cdc42 and Rac1. Many intronic IQGAP1 gene changes were observed, and several occurred more frequently in diffuse-type gastric cancers than in intestinal-type gastric cancers. A highly variable pentanucleotide repeat was identified in the final intron of IQGAP1. The most expanded six-repeat sequence was present exclusively in diffuse-type gastric cancers. Additionally, 19 diffuse cases and two intestinal cases exhibited silent coding region nucleotide alterations. Taken together, our results suggest that IQGAP1 coding sequence mutations are not a frequent event in gastric cancer, but do occur in a subset of diffuse-type gastric carcinomas. Additional studies analyzing other proteins involved in cell adhesion may lead to a better molecular understanding of the histopathologic appearance of diffuse gastric cancers.