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

Organoid models of gastrointestinal cancers in basic and translational research

Cancer is a major public health problem worldwide. Gastrointestinal cancers account for approximately one-third of the total global cancer incidence and mortality. Historically, the mechanisms of tumour initiation and progression in the gastrointestinal tract have been studied using cancer cell lines in vitro and animal models. Traditional cell culture methods are associated with a strong selection of aberrant genomic variants that no longer reflect the original tumours in terms of their (metastatic) behaviour or response to therapy. Organoid technology has emerged as a powerful alternative method for culturing gastrointestinal tumours and the corresponding normal tissues in a manner that preserves their genetic, phenotypic and behavioural traits. Importantly, accumulating evidence suggests that organoid cultures have great value in predicting the outcome of therapy in individual patients. Herein, we review the current literature on organoid models of the most common gastrointestinal cancers, including colorectal cancer, gastric cancer, oesophageal cancer, liver cancer and pancreatic cancer, and their value in modelling tumour initiation, metastatic progression and therapy response. We also explore the limitations of current organoid models and discuss how they could be improved to maximally benefit basic and translational research in the future, especially in the fields of drug discovery and personalized medicine.

Gastrointestinal tract modeling using organoids engineered with cellular and microbiota niches

The recent emergence of organoid technology has attracted great attention in gastroenterology because the gastrointestinal (GI) tract can be recapitulated in vitro using organoids, enabling disease modeling and mechanistic studies. However, to more precisely emulate the GI microenvironment in vivo, several neighboring cell types and types of microbiota need to be integrated into GI organoids. This article reviews the recent progress made in elucidating the crosstalk between GI organoids and components of their microenvironment. We outline the effects of stromal cells (such as fibroblasts, neural cells, immune cells, and vascular cells) on the gastric and intestinal epithelia of organoids. Because of the important roles that microbiota play in the physiology and function of the GI tract, we also highlight interactions between organoids and commensal, symbiotic, and pathogenic microorganisms and viruses. GI organoid models that contain niche components will provide new insight into gastroenterological pathophysiology and disease mechanisms.

Nonalcoholic Fatty Liver Disease Is Associated with Helicobacter pylori Infection in North Urban Chinese: A Retrospective Study

Background

The association between nonalcoholic fatty liver disease (NAFLD) and Helicobacter pylori (H. pylori) is controversial. We conducted a retrospective study to clarify the seroprevalence of H. pylori infection and the relationship between NAFLD and H. pylori infection in north urban Chinese.

Methods

The retrospective study was performed at Aerospace Center Hospital in Beijing. All subjects in this study were a healthy population who underwent health examinations at the hospital between 2012 and 2015. A logistic regression model was used to calculate the association between NAFLD and H. pylori infection. Age, gender, underlying diseases, and metabolic syndrome (MS) were adjusted. Effects of NAFLD on H. pylori infection in a different age, gender, and number of MS characteristic subgroups were analyzed.

Results

There were 7803 (43.4%) subjects with H. pylori infection, 3726 (20.7%) with mild NAFLD, 730 (4.1%) with moderate NAFLD, and 369 (2.1%) with severe NAFLD among 17971 subjects. H. pylori infection was related to the seroprevalence of any level of NAFLD, including mild, moderate, and severe NAFLD (OR = 1.607, 95% CI: 1.487-1.736; OR = 1.770, 95% CI: 1.519-2.063; and OR = 2.120, 95% CI: 1.714-2.526, respectively). The results of subgroup analysis showed that the risk of incident NAFLD from H. pylori infection had significant interactions by subjects with or without MS characteristics. Moreover, as the number of MS characteristics in patients with a fatty liver increased, the risk of H. pylori infection also increased.

Conclusions

NAFLD may be associated with H. pylori infection in a Chinese population. Younger, male NAFLD patients and those meeting more characteristics of MS were more likely to have H. pylori infection.

Heterogeneity and dynamics of active Kras-induced dysplastic lineages from mouse corpus stomach

Dysplasia is considered a key transition state between pre-cancer and cancer in gastric carcinogenesis. However, the cellular or phenotypic heterogeneity and mechanisms of dysplasia progression have not been elucidated. We have established metaplastic and dysplastic organoid lines, derived from Mist1-Kras(G12D) mouse stomach corpus and studied distinct cellular behaviors and characteristics of metaplastic and dysplastic organoids. We also examined functional roles for Kras activation in dysplasia progression using Selumetinib, a MEK inhibitor, which is a downstream mediator of Kras signaling. Here, we report that dysplastic organoids die or show altered cellular behaviors and diminished aggressive behavior in response to MEK inhibition. However, the organoids surviving after MEK inhibition maintain cellular heterogeneity. Two dysplastic stem cell (DSC) populations are also identified in dysplastic cells, which exhibited different clonogenic potentials. Therefore, Kras activation controls cellular dynamics and progression to dysplasia, and DSCs might contribute to cellular heterogeneity in dysplastic cell lineages.

Wnt/β-Catenin Signaling as a Molecular Target by Pathogenic Bacteria

The Wnt/β-catenin signaling pathway is crucial to regulate cell proliferation and polarity, cell determination, and tissue homeostasis. The activation of Wnt/β-catenin signaling is based on the interaction between Wnt glycoproteins and seven transmembrane receptors-Frizzled (Fzd). This binding promotes recruitment of the scaffolding protein Disheveled (Dvl), which results in the phosphorylation of the co-receptor LRP5/6. The resultant molecular complex Wnt-Fzd-LRP5/6-Dvl forms a structural region for Axin interaction that disrupts Axin-mediated phosphorylation/degradation of the transcriptional co-activator β-catenin, thereby allowing it to stabilize and accumulate in the nucleus where it activates the expression of Wnt-dependent genes. Due to the prominent physiological function, the Wnt/β-catenin signaling must be strictly controlled because its dysregulation, which is caused by different stimuli, may lead to alterations in cell proliferation, apoptosis, and inflammation-associated cancer. The virulence factors from pathogenic bacteria such as Salmonella enterica sv Typhimurium, Helicobacter pylori, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Citrobacter rodentium, Clostridium difficile, Bacteroides fragilis, Escherichia coli, Haemophilus parasuis, Lawsonia intracellularis, Shigella dysenteriae, and Staphylococcus epidermidis employ a variety of molecular strategies to alter the appropriate functioning of diverse signaling pathways. Among these, Wnt/β-catenin has recently emerged as an important target of several virulence factors produced by bacteria. The mechanisms used by these factors to interfere with the activity of Wnt/β-catenin is diverse and include the repression of Wnt inhibitors' expression by the epigenetic modification of histones, blocking Wnt-Fzd ligand binding, activation or inhibition of β-catenin nuclear translocation, down- or up-regulation of Wnt family members, and inhibition of Axin-1 expression that promotes β-catenin activity. Such a variety of mechanisms illustrate an evolutionary co-adaptation of eukaryotic molecular signaling to a battery of soluble or structural components synthesized by pathogenic bacteria. This review gathers the recent efforts to elucidate the mechanistic details through which bacterial virulence factors modulate Wnt/β-catenin signaling and its physiological consequences concerning the inflammatory response and cancer.

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.

Gut organoids: mini-tissues in culture to study intestinal physiology and disease

In vitro, cell cultures are essential tools in the study of intestinal function and disease. For the past few decades, monolayer cellular cultures, such as cancer cell lines or immortalized cell lines, have been widely applied in gastrointestinal research. Recently, the development of three-dimensional cultures known as organoids has permitted the growth of normal crypt-villus units that recapitulate many aspects of intestinal physiology. Organoid culturing has also been applied to study gastrointestinal diseases, intestinal-microbe interactions, and colorectal cancer. These models are amenable to CRISPR gene editing and drug treatments, including high-throughput small-molecule testing. Three-dimensional intestinal cultures have been transplanted into mice to develop versatile in vivo models of intestinal disease, particularly cancer. Limitations of currently available organoid models include cost and challenges in modeling nonepithelial intestinal cells, such as immune cells and the microbiota. Here, we describe the development of organoid models of intestinal biology and the applications of organoids for study of the pathophysiology of intestinal diseases and cancer.

Helicobacter pylori Uses the TlpB Receptor To Sense Sites of Gastric Injury

Helicobacter pylori is a pathogen that chronically colonizes the stomachs of approximately half of the world's population and contributes to the development of gastric inflammation. We demonstrated previously in vivo that H. pylori uses motility to preferentially colonize injury sites in the mouse stomach. However, the chemoreceptor responsible for sensing gastric injury has not yet been identified. In this study, we utilized murine gastric organoids (gastroids) and mutant H. pylori strains to investigate the components necessary for H. pylori chemotaxis. High-intensity 730-nm light (two-photon photodamage) was used to cause single-cell damage in gastroids, and repair of the damage was monitored over time; complete repair occurred within ∼10 min in uninfected gastroids. Wild-type H. pylori accumulated at the damage site after gastric damage induction. In contrast, mutants lacking motility (ΔmotB) or chemotaxis (ΔcheY) did not accumulate at the injury site. Using mutants lacking individual chemoreceptors, we found that only TlpB was required for H. pylori accumulation, while TlpA, TlpC, and TlpD were dispensable. All strains that were able to accumulate at the damage site limited repair. When urea (an identified chemoattractant sensed by TlpB) was microinjected into the gastroid lumen, it prevented the accumulation of H. pylori at damage sites. Overall, our findings demonstrate that H. pylori colonizes and limits repair at damage sites via chemotactic motility that requires the TlpB chemoreceptor to sense signals generated by gastric epithelial cells.

The Hippo and Wnt signalling pathways: crosstalk during neoplastic progression in gastrointestinal tissue

The Hippo and Wnt signalling pathways play crucial roles in maintaining tissue homeostasis and organ size by orchestrating cell proliferation, differentiation and apoptosis. These pathways have been frequently found to be dysregulated in human cancers. While the canonical signal transduction of Hippo and Wnt has been well studied, emerging evidence shows that these two signalling pathways contribute to and exhibit overlapping functions in gastrointestinal (GI) tumorigenesis. In fact, the core effectors YAP/TAZ in Hippo signalling pathway cooperate with β-catenin in Wnt signalling pathway to promote GI neoplasia. Here, we provide a brief review to summarize the molecular mechanisms underlying the crosstalk between these two pathways and elucidate their involvement in GI tumorigenesis, particularly focusing on the intestine, stomach and liver.

Changes of tight junction and interleukin-8 expression using a human gastroid monolayer model of Helicobacter pylori infection

BACKGROUND

Lack of a model that mirrors Helicobacter pylori-induced gastric mucosal inflammation has hampered investigation of early host-bacterial interactions. We used an ex vivo model of human stomach, gastric epithelial organoid monolayers (gastroid monolayers) to investigate interactions of H pylori infection and the apical junctional complex and interleukin-8 (IL-8) expression.

METHOD

Morphology of human antral mucosal gastroid monolayers was evaluated using histology, immunohistochemical (IHC) staining, and transmission electron microscopy (TEM). Functional and gross changes in the apical junctional complexes were assessed using transepithelial electrical resistance (TEER), cytotoxicity assays, and confocal laser scanning microscopy. IL-8 expression was evaluated by real-time quantitative PCR and ELISA.

RESULTS

When evaluated by IHC and TEM, the morphology of gastroid monolayers closely resembled in vivo human stomach. Following inoculation of H pylori, TEER transiently declined (up to 51%) in an H pylori density-dependent manner. TEER recovered by 48 hours post-infection and remained normal despite continued presence and replication of H pylori. Confocal scanning microscopy showed minimal disruption of zonula occludens-1 or E-cadherin structure. IL-8 production was unchanged by infection with either CagA-positive or CagA-negative H pylori and JNK and MEK inhibitors did not suppress IL-8 production, whereas p38 and IKK inhibitor significantly did.

CONCLUSION

Human gastroid monolayers provide a model for experimental H pylori infection more consistent with in vivo human infections than seen with typical gastric epithelial cell lines. This ex vivo system should lead to better understanding of H pylori host-pathogen interactions.

Generation of human antral and fundic gastric organoids from pluripotent stem cells

The human stomach contains two primary domains: the corpus, which contains the fundic epithelium, and the antrum. Each of these domains has distinct cell types and functions, and therefore each presents with unique disease pathologies. Here, we detail two protocols to differentiate human pluripotent stem cells (hPSCs) into human gastric organoids (hGOs) that recapitulate both domains. Both protocols begin with the differentiation of hPSCs into definitive endoderm (DE) using activin A, followed by the generation of free-floating 3D posterior foregut spheroids using FGF4, Wnt pathway agonist CHIR99021 (CHIR), BMP pathway antagonist Noggin, and retinoic acid. Embedding spheroids in Matrigel and continuing 3D growth in epidermal growth factor (EGF)-containing medium for 4 weeks results in antral hGOs (hAGOs). To obtain fundic hGOs (hFGOs), spheroids are additionally treated with CHIR and FGF10. Induced differentiation of acid-secreting parietal cells in hFGOs requires temporal treatment of BMP4 and the MEK inhibitor PD0325901 for 48 h on protocol day 30. In total, it takes ~34 d to generate hGOs from hPSCs. To date, this is the only approach that generates functional human differentiated gastric cells de novo from hPSCs.

Mutated Rnf43 Aggravates Helicobacter Pylori-Induced Gastric Pathology

The E3 ubiquitin ligase ring finger protein 43 (RNF43) is frequently mutated in gastric tumors and loss of RNF43 expression was suggested to be one of the key events during the transition from adenoma to gastric carcinoma. Functional studies on RNF43 have shown that it acts as a tumor suppressor by negatively regulating Wnt signaling. Interestingly, we observed that RNF43^H292R/H295R mice bearing two point mutations in the ring domain displayed thickening of the mucosa at early age but did not develop neoplasia. In this study, we infected these mice for 6 months with Helicobacter pylori, which has been described as one of the major risk factors for gastric cancer. Mice bearing mutant RNF43^H292R/H295R showed higher gastritis scores upon H. pylori infection compared to wild-type mice, accompanied by increased lymphocyte infiltration and Ifng levels. Furthermore, infected Rnf43 mutant mice developed atrophy, hyperplasia and MUC2 expressing metaplasia and displayed higher levels of the gastric stem cell marker CD44 and canonical NF-κB signaling. In summary, our results show that transactivating mutations in the tumor suppressor Rnf43 can worsen H. pylori induced pathology.

Nod1 Imprints Inflammatory and Carcinogenic Responses toward the Gastric Pathogen Helicobacter pylori

Helicobacter pylori (H. pylori) is the strongest known risk for gastric cancer. The H. pylori cag type IV secretion system is an oncogenic locus that translocates peptidoglycan into host cells, where it is recognized by NOD1, an innate immune receptor. Beyond this, the role of NOD1 in H. pylori-induced cancer remains undefined. To address this knowledge gap, we infected two genetic models of Nod1 deficiency with the H. pylori cag ⁺ strain PMSS1: C57BL/6 mice, which rarely develop cancer, and INS-GAS FVB/N mice, which commonly develop cancer. Infected C57BL/6 ^Nod1-/- and INS-GAS ^Nod1-/- mice acutely developed more severe gastritis, and INS-GAS ^Nod1-/- mice developed gastric dysplasia more frequently compared with Nod1^+/+ mice. Because Nod1 genotype status did not alter microbial phenotypes of in vivo-adapted H. pylori, we investigated host immunologic responses. H. pylori infection of Nod1^-/- mice led to significantly increased gastric mucosal levels of Th1, Th17, and Th2 cytokines compared with Nod1 wild-type (WT) mice. To define the role of specific innate immune cells, we quantified cytokine secretion from H. pylori-infected primary gastric organoids generated from WT or Nod1^-/- mice that were cocultured with or without WT or Nod1^-/- macrophages. Infection increased cytokine production from gastric epithelial cells and macrophages and elevations were significantly increased with Nod1 deficiency. Furthermore, H. pylori infection altered the polarization status of Nod1^-/- macrophages compared with Nod1^+/+ macrophages. Collectively, these studies demonstrate that loss of Nod1 augments inflammatory and injury responses to H. pylori. Nod1 may exert its restrictive role by altering macrophage polarization, leading to immune evasion and microbial persistence. SIGNIFICANCE: These findings suggest that manipulation of NOD1 may represent a novel strategy to prevent or treat pathologic outcomes induced by H. pylori infection.

Downregulation of CLDN7 due to promoter hypermethylation is associated with human clear cell renal cell carcinoma progression and poor prognosis

BACKGROUND

Metastasis is the primary cause of death in renal cell carcinoma (RCC). Loss of cell-to-cell adhesion, including tight junctions (TJs) is the initial step in the process of metastasis. Claudin-7 (CLDN7) is a major component of TJs. However, the clinical significance and its regulation of kidney tumorigenesis remain poorly understood.

METHODS

A total of 120 fresh clear cell RCC (ccRCC) specimens and 144 primary RCC and adjacent nonmalignant renal paraffin specimens were obtained from Department of Urology, Peking University First Hospital. Expression of CLDN7 in ccRCC tissues and cell lines were determined using bioinformatic data mining, quantitative real-time PCR (qRT-PCR), Western blotting and immunostaining. The clinical significance of CLDN7 expression and promoter DNA methylation status was analyzed in ccRCC patients from Peking University First Hospital and The Cancer Genome Atlas. Additionally, the methylation specific-PCR, bisulfite genomic sequencing and demethylation analysis of CLDN7 were performed. Biological functions of CLDN7 were investigated by examining cell proliferation using MTS assays and EdU incorporation assays, cell migration by in vitro wound healing assays and transwell migration assays, cell invasion by transwell invasion assays, and cell apoptosis by flow cytometry. Mouse model experiments were performed to confirm the effects of CLDN7 on tumor growth and metastasis in vivo. The molecular mechanism of CLDN7 function was investigated using gene-set enrichment analysis (GSEA) and high-throughput cDNA sequencing (RNA-Seq) and confirmed by qRT-PCR, Western blot and immunostaining in vitro and in vivo.

RESULTS

Our findings revealed that CLDN7 is frequently downregulated via hypermethylation of its promoter in ccRCC. CLDN7 can help predict aggressive tumor status and poor prognosis in ccRCC patients. Interestingly, hypermethylation of the CLDN7 promoter was related to advanced ccRCC status and poor prognosis. Moreover, overexpression of CLDN7 induced cell apoptosis, suppressed proliferation, migration and invasion abilities of ccRCC cells both in vitro and in vivo. Additionally, GSEA and RNA-Seq results showed that CLDN7 had negative effects in cancer-associated signaling pathways and (epithelial-mesenchymal transition) EMT-related pathways. These results were validated by qRT-PCR, Western blot and immunostaining.

CONCLUSIONS

We have demonstrated a previously undescribed role of CLDN7 as a ccRCC suppressor and suggest that loss of CLDN7 potentiates EMT and tumor progression. CLDN7 may serve as a functional tumor suppressor in tumor progression and a potential biomarker and target in patients with ccRCC.

Afadin Downregulation by Helicobacter pylori Induces Epithelial to Mesenchymal Transition in Gastric Cells

Afadin is a cytoplasmic protein of the adherens junctions, which regulates the formation and stabilization of both the adherens and the tight junctions. Aberrant expression of Afadin has been shown in cancer and its loss has been associated with epithelial-to-mesenchymal transition (EMT). EMT is characterized by the change from an epithelial to a mesenchymal phenotype, with modifications on the expression of adhesion molecules and acquisition of a migratory and invasive cell behavior. While it is known that Helicobacter pylori disrupts the tight and the adherens junctions and induces EMT, the effect of the bacteria on Afadin is still unknown. The aim of this study was to disclose the effect of H. pylori on Afadin and its impact in the induction of an EMT phenotype in gastric cells. Using two different cell lines, we observed that H. pylori infection decreased Afadin protein levels, independently of CagA, T4SS, and VacA virulence factors. H. pylori infection of cell lines recapitulated several EMT features, displacing and downregulating multiple proteins from cell–cell junctions, and increasing the expression of ZEB1, Vimentin, Slug, N-cadherin, and Snail. Silencing of Afadin by RNAi promoted delocalization of junctional proteins from the cell–cell contacts, increased paracellular permeability, and decreased transepithelial electrical resistance, all compatible with impaired junctional integrity. Afadin silencing also led to increased expression of the EMT marker Snail, and to the formation of actin stress fibers, together with increased cell motility and invasion. Finally, and in line with our in vitro data, the gastric mucosa of individuals infected with H. pylori showed decrease/loss of Afadin membrane staining at cell–cell contacts significantly more frequently than uninfected individuals. In conclusion, Afadin is downregulated by H. pylori infection in vitro and in vivo, and its downregulation leads to the emergence of EMT and to the acquisition of an aggressive phenotype in gastric cells, which can contribute to gastric carcinogenesis.

Characterization of clarithromycin heteroresistance among Helicobacter pylori strains isolated from the antrum and corpus of the stomach

Mixed infections and heteroresistance of Helicobacter pylori contribute to decreased efficacy of treatments. This study aimed to investigate frequency of clarithromycin heteroresistance and its link with mixed infections, medication history, and disease severity. A total of 40 pairs of H. pylori strains were isolated from the antrum and corpus of 97 patients. Susceptibility of the strains to clarithromycin was measured by agar dilution method. Site-specific mutations of 23S rRNA at A2143G, A2142G, and A2142C positions were analyzed by PCR and genomic relatedness of pairs of the strains was determined by random amplified polymorphic DNA (RAPD)-PCR. The results showed a prevalence of 35% (14/40) clarithromycin resistance. Diversity of the antrum and corpus isolates in resistance to clarithromycin was detected among 17.5% (7/40) of the patients. Similarly, diversity in MIC value was also detected in two patients infected with the sensitive strains. Significant difference in frequency of resistance was detected among patients with peptic ulcer disease (PUD) (MIC90 32 μg/mL) and severe gastritis (MIC90 16 μg/mL), compared with those who suffered from non-ulcer dyspepsia (NUD) (MIC90 8 μg/mL) and chronic gastritis (MIC90 0.25 μg/mL). MIC values showed 8-32 folds increased levels in the corpus. A2142G, A2143G, and A2142C mutations were detected in three, two, and two patients, respectively, but not observed in 46% of the resistant strains. RAPD-PCR fingerprints showed identical molecular patterns for the isolates of the corpus and antrum in each patient. In conclusion, microevolution of H. pylori strains during chronic infection, rather than mixed infection, and inappropriate medication appear to be main reasons of treatment failure in adults.

Host-microbe interaction in the gastrointestinal tract

The gastrointestinal tract is a highly complex organ in which multiple dynamic physiological processes are tightly coordinated while interacting with a dense and extremely diverse microbial population. From establishment in early life, through to host-microbe symbiosis in adulthood, the gut microbiota plays a vital role in our development and health. The effect of the microbiota on gut development and physiology is highlighted by anatomical and functional changes in germ-free mice, affecting the gut epithelium, immune system and enteric nervous system. Microbial colonisation promotes competent innate and acquired mucosal immune systems, epithelial renewal, barrier integrity, and mucosal vascularisation and innervation. Interacting or shared signalling pathways across different physiological systems of the gut could explain how all these changes are coordinated during postnatal colonisation, or after the introduction of microbiota into germ-free models. The application of cell-based in-vitro experimental systems and mathematical modelling can shed light on the molecular and signalling pathways which regulate the development and maintenance of homeostasis in the gut and beyond.

A High-Throughput Organoid Microinjection Platform to Study Gastrointestinal Microbiota and Luminal Physiology

Background & Aims

The human gut microbiota is becoming increasingly recognized as a key factor in homeostasis and disease. The lack of physiologically relevant in vitro models to investigate host-microbe interactions is considered a substantial bottleneck for microbiota research. Organoids represent an attractive model system because they are derived from primary tissues and embody key properties of the native gut lumen; however, access to the organoid lumen for experimental perturbation is challenging. Here, we report the development and validation of a high-throughput organoid microinjection system for cargo delivery to the organoid lumen and high-content sampling.

Methods

A microinjection platform was engineered using off-the-shelf and 3-dimensional printed components. Microinjection needles were modified for vertical trajectories and reproducible injection volumes. Computer vision (CVis) and microfabricated CellRaft Arrays (Cell Microsystems, Research Triangle Park, NC) were used to increase throughput and enable high-content sampling of mock bacterial communities. Modeling preformed using the COMSOL Multiphysics platform predicted a hypoxic luminal environment that was functionally validated by transplantation of fecal-derived microbial communities and monocultures of a nonsporulating anaerobe.

Results

CVis identified and logged locations of organoids suitable for injection. Reproducible loads of 0.2 nL could be microinjected into the organoid lumen at approximately 90 organoids/h. CVis analyzed and confirmed retention of injected cargos in approximately 500 organoids over 18 hours and showed the requirement to normalize for organoid growth for accurate assessment of barrier function. CVis analyzed growth dynamics of a mock community of green fluorescent protein- or Discosoma sp. red fluorescent protein-expressing bacteria, which grew within the organoid lumen even in the presence of antibiotics to control media contamination. Complex microbiota communities from fecal samples survived and grew in the colonoid lumen without appreciable changes in complexity.

Conclusions

High-throughput microinjection into organoids represents a next-generation in vitro approach to investigate gastrointestinal luminal physiology and the gastrointestinal microbiota.

Downregulation of miR-491-5p promotes gastric cancer metastasis by regulating SNAIL and FGFR4

Gastric cancer (GC) is among the most fatal cancers in China. MicroRNAs (miRNAs) are versatile regulators during GC development and progression. miR‐491‐5p has been demonstrated to act as a tumor suppressor in several types of cancer. However, the role of miR‐491‐5p in GC metastasis remains unknown. Here, we found that miR‐491‐5p was significantly decreased in GC tissues compared with adjacent non‐cancerous tissues, and low miR‐491‐5p level was associated with large tumor size. Overexpression of miR‐491‐5p significantly suppressed GC cell epithelial‐to‐mesenchymal transition (EMT) and tumor metastasis in vitro and in vivo. Mechanistically, SNAIL was identified as a direct target of miR‐491‐5p. The silencing of SNAIL phenocopied the tumor suppressive function of miR‐491‐5p, whereas re‐expression of SNAIL in GC cells rescued the EMT markers and cell migratory ability that were inhibited by miR‐491‐5p. In addition, miR‐491‐5p inhibited FGFR4 indirectly. Inhibition of FGFR4 also decreased the SNAIL level and impaired EMT and cell migration. Taken together, these findings indicate that downregulation of miR‐491‐5p promoted GC metastasis by inducing EMT via regulation of SNAIL and FGFR4.

Modulation of Intestinal Paracellular Transport by Bacterial Pathogens

The passive and regulated movement of ions, solutes, and water via spaces between cells of the epithelial monolayer plays a critical role in the normal intestinal functioning. This paracellular pathway displays a high level of structural and functional specialization, with the membrane-spanning complexes of the tight junctions, adherens junctions, and desmosomes ensuring its integrity. Tight junction proteins, like occludin, tricellulin, and the claudin family isoforms, play prominent roles as barriers to unrestricted paracellular transport. The past decade has witnessed major advances in our understanding of the architecture and function of epithelial tight junctions. While it has been long appreciated that microbes, notably bacterial and viral pathogens, target and disrupt junctional complexes and alter paracellular permeability, the precise mechanisms remain to be defined. Notably, renewed efforts will be required to interpret the available data on pathogen-mediated barrier disruption in the context of the most recent findings on tight junction structure and function. While much of the focus has been on pathogen-induced dysregulation of junctional complexes, commensal microbiota and their products may influence paracellular permeability and contribute to the normal physiology of the gut. Finally, microbes and their products have become important tools in exploring host systems, including the junctional properties of epithelial cells. © 2018 American Physiological Society. Compr Physiol 8:823-842, 2018.

Organoids as a Model to Study Infectious Disease

The advent of the gastric organoid culture system has provided a new model to emulate native epithelial tissue in vitro. Gastric organoids grow from isolated epithelial stem cells and develop into three dimensional structures that can be used to study host physiology. Here we describe current laboratory protocols for growing gastric organoids and the microinjection of pathogens such as Helicobacter pylori into the lumen of gastric organoids in order to study the cellular response following infection.

Multiscale positive feedbacks contribute to unidirectional gastric disease progression induced by helicobacter pylori infection

Background

Helicobacter Pylori (HP) is the most common risk factor for gastric cancer. Nearly half the world’s population is infected with HP, but only a small percentage of those develop significant pathology. The bacteria itself does not directly cause cancer; rather it promotes an environment that is conducive to tumor formation. Upon infection, HP induces transcriptional changes in the host, leading to enhanced proliferation and host immune response. In addition, HP causes direct damage to gastric epithelial cells.

Results

We present a multiscale mechanistic model of HP induced changes. The model includes four modules representing the host transcriptional changes in response to infection, gastric atrophy, the Hedgehog pathway response, and the restriction point that controls cell cycle. This model was able to recapture a number of literature reported observations and was used as an “in silico” representation of the biological system for further analysis. Dynamical analysis of the model revealed that HP might induce the activation of multiple interplayed positive feedbacks, which in turn might result in a “ratchet ladder” system that promotes a unidirectional progression of gastric disease.

Conclusions

The current multiscale model is able to recapitulate the observed experimental features of HP host interactions and provides dynamic insights on the epidemiologically observed heterogeneity in disease progression. This model provides a solid framework that can be further expanded and validated to include additional experimental evidence, to understand the complex multi-pathway interactions characterizing HP infection, and to design novel treatment protocols for HP induced diseases.

Electronic supplementary material

The online version of this article (10.1186/s12918-017-0497-y) contains supplementary material, which is available to authorized users.

Helicobacter pylori Employs a Unique Basolateral Type IV Secretion Mechanism for CagA Delivery

The Helicobacter pylori (Hp) type IV secretion system (T4SS) forms needle-like pili, whose binding to the integrin-β1 receptor results in injection of the CagA oncoprotein. However, the apical surface of epithelial cells is exposed to Hp, whereas integrins are basolateral receptors. Hence, the mechanism of CagA delivery into polarized gastric epithelial cells remains enigmatic. Here, we demonstrate that T4SS pilus formation during infection of polarized cells occurs predominantly at basolateral membranes, and not at apical sites. Hp accomplishes this by secreting another bacterial protein, the serine protease HtrA, which opens cell-to-cell junctions through cleaving epithelial junctional proteins including occludin, claudin-8, and E-cadherin. Using a genetic system expressing a peptide inhibitor, we demonstrate that HtrA activity is necessary for paracellular transmigration of Hp across polarized cell monolayers to reach basolateral membranes and inject CagA. The contribution of this unique signaling cascade to Hp pathogenesis is discussed.

Creation and Initial Characterization of Isogenic Helicobacter pylori CagA EPIYA Variants Reveals Differential Activation of Host Cell Signaling Pathways

The polymorphic CagA toxin is associated with Helicobacter pylori-induced disease. Previous data generated using non-isogenic strains and transfection models suggest that variation surrounding the C-terminal Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs as well as the number of EPIYA motifs influence disease outcome. To investigate potential CagA-mediated effects on host cell signaling, we constructed and characterized a large panel of isogenic H. pylori strains that differ primarily in the CagA EPIYA region. The number of EPIYA-C motifs or the presence of an EPIYA-D motif impacted early changes in host cell elongation; however, the degree of elongation was comparable across all strains at later time points. In contrast, the strain carrying the EPIYA-D motif induced more IL-8 secretion than any other EPIYA type, and a single EPIYA-C motif induced comparable IL-8 secretion as isolates carrying multiple EPIYA-C alleles. Similar levels of ERK1/2 activation were induced by all strains carrying a functional CagA allele. Together, our data suggest that polymorphism in the CagA C-terminus is responsible for differential alterations in some, but not all, host cell signaling pathways. Notably, our results differ from non-isogenic strain studies, thus highlighting the importance of using isogenic strains to study the role of CagA toxin polymorphism in gastric cancer development.

Gastric Organoids: An Emerging Model System to Study Helicobacter pylori Pathogenesis

Helicobacter research classically uses fixed human tissue, animal models or cancer cell lines. Each of these study objects has its advantages and has brought central insights into the infection process. Nevertheless, in model systems for basic and medical research, there is a gap between two-dimensional and most often transformed cell cultures and three-dimensional, highly organized tissues. In recent years, stem cell research has provided the means to fill this gap. The identification of the niche factors that support growth, expansion and differentiation of stem cells in vitro has allowed the development of three-dimensional culture systems called organoids. Gastric organoids are grown from gastric stem cells and are organized epithelial structures that comprise all the differentiated cell types of the stomach. They can be expanded without apparent limitation and are amenable to a wide range of standard laboratory techniques. Here, we review different stem cell-derived organoid model systems useful for Helicobacter pylori research and outline their advantages for infection studies.

Targeting the Mucosal Barrier: How Pathogens Modulate the Cellular Polarity Network

The mucosal barrier is composed of polarized epithelial cells with distinct apical and basolateral surfaces separated by tight junctions and serves as both a physical and immunological barrier to incoming pathogens. Specialized polarity proteins are critical for establishment and maintenance of polarity. Many human pathogens have evolved virulence mechanisms that target the polarity network to enhance binding, create replication niches, move through the barrier by transcytosis, or bypass the barrier by disrupting cell-cell junctions. This review summarizes recent advances and compares and contrasts how three important human pathogens that colonize mucosal surfaces, Pseudomonas aeruginosa, Helicobacter pylori, and Neisseria meningitidis, subvert the host cell polarization machinery during infection.

Cellular self-assembly and biomaterials-based organoid models of development and diseases

Organogenesis and morphogenesis have informed our understanding of physiology, pathophysiology, and avenues to create new curative and regenerative therapies. Thus far, this understanding has been hindered by the lack of a physiologically relevant yet accessible model that affords biological control. Recently, three-dimensional ex vivo cellular cultures created through cellular self-assembly under natural extracellular matrix cues or through biomaterial-based directed assembly have been shown to physically resemble and recapture some functionality of target organs. These "organoids" have garnered momentum for their applications in modeling human development and disease, drug screening, and future therapy design or even organ replacement. This review first discusses the self-organizing organoids as materials with emergent properties and their advantages and limitations. We subsequently describe biomaterials-based strategies used to afford more control of the organoid's microenvironment and ensuing cellular composition and organization. In this review, we also offer our perspective on how multifunctional biomaterials with precise spatial and temporal control could ultimately bridge the gap between in vitro organoid platforms and their in vivo counterparts.

STATEMENT OF SIGNIFICANCE

Several notable reviews have highlighted PSC-derived organoids and 3D aggregates, including embryoid bodies, from a development and cellular assembly perspective. The focus of this review is to highlight the materials-based approaches that cells, including PSCs and others, adopt for self-assembly and the controlled development of complex tissues, such as that of the brain, gut, and immune system.

Integrated expression analysis identifies transcription networks in mouse and human gastric neoplasia

Gastric cancer (GC) is a leading cause of cancer-related deaths worldwide. The Tff1 knockout (KO) mouse model develops gastric lesions that include low-grade dysplasia (LGD), high-grade dysplasia (HGD), and adenocarcinomas. In this study, we used Affymetrix microarrays gene expression platforms for analysis of molecular signatures in the mouse stomach [Tff1-KO (LGD) and Tff1 wild-type (normal)] and human gastric cancer tissues and their adjacent normal tissue samples. Combined integrated bioinformatics analysis of mouse and human datasets indicated that 172 genes were consistently deregulated in both human gastric cancer samples and Tff1-KO LGD lesions (P < .05). Using Ingenuity pathway analysis, these genes mapped to important transcription networks that include MYC, STAT3, β-catenin, RELA, NFATC2, HIF1A, and ETS1 in both human and mouse. Further analysis demonstrated activation of FOXM1 and inhibition of TP53 transcription networks in human gastric cancers but not in Tff1-KO LGD lesions. Using real-time RT-PCR, we validated the deregulated expression of several genes (VCAM1, BGN, CLDN2, COL1A1, COL1A2, COL3A1, EpCAM, IFITM1, MMP9, MMP12, MMP14, PDGFRB, PLAU, and TIMP1) that map to altered transcription networks in both mouse and human gastric neoplasia. Our study demonstrates significant similarities in deregulated transcription networks in human gastric cancer and gastric tumorigenesis in the Tff1-KO mouse model. The data also suggest that activation of MYC, STAT3, RELA, and β-catenin transcription networks could be an early molecular step in gastric carcinogenesis.

Expression of claudin-11, -23 in different gastric tissues and its relationship with the risk and prognosis of gastric cancer

Claudins play an important role in regulating the permeability of epithelial and endothelial cells and in the maintenance of cell polarity. We aimed to investigate expression of claudin-11, -23 in different gastric tissues and its relationship with clinicopathologic parameters and prognosis of gastric cancer. We compared their expression levels in the paired cancerous tissues versus those in the adjacent noncancerous tissues by real-time PCR, western blotting and immunohistochemistry. The results showed that the expression of claudin-11, -23 was greatly increased in paracancerous gastric tissue compared with cancerous tissue. We also compared their expression levels of tissues from gastric cancer, superficial gastritis, and atrophic gastritis by immunohistochemistry. The results indicated that the expression of claudin-11 and 23 was significantly higher in superficial gastritis than that in atrophic gastritis and gastric cancer. The expression of claudin-23 was significantly lower in atrophic gastritis than that in gastric cancer, but no obviously difference was observed for claudin-11. As for analysis of clinicopathologic parameters of gastric cancer, logistic multiple regression indicated that claudin-11 was significantly associated with sex, smoking, alcohol, H. pylori infection and Borrmann classification while claudin-23 was significantly associated with vessel cancer embolus. Cox multivariate survival analysis indicated that gastric cancer patients with negative claudin-23 expression had significantly longer overall survival. In conclusion, the expression of claudin-11, -23 was remarkably downregulated in gastric cancer. Abnormal expression of these proteins was significantly correlated with some clinicopathologic parameters. In particular, claudin-23 positive expression was associated with poor prognostic outcomes of gastric cancer patients and may therefore serve as an independent prognosticator of patient survival.

Type IV Secretion and Signal Transduction of Helicobacter pylori CagA through Interactions with Host Cell Receptors

Helicobacter pylori is a highly successful human bacterium, which is exceptionally equipped to persistently inhabit the human stomach. Colonization by this pathogen is associated with gastric disorders ranging from chronic gastritis and peptic ulcers to cancer. Highly virulent H. pylori strains express the well-established adhesins BabA/B, SabA, AlpA/B, OipA, and HopQ, and a type IV secretion system (T4SS) encoded by the cag pathogenicity island (PAI). The adhesins ascertain intimate bacterial contact to gastric epithelial cells, while the T4SS represents an extracellular pilus-like structure for the translocation of the effector protein CagA. Numerous T4SS components including CagI, CagL, CagY, and CagA have been shown to target the integrin-β₁ receptor followed by translocation of CagA across the host cell membrane. The interaction of CagA with membrane-anchored phosphatidylserine and CagA-containing outer membrane vesicles may also play a role in the delivery process. Translocated CagA undergoes tyrosine phosphorylation in C-terminal EPIYA-repeat motifs by oncogenic Src and Abl kinases. CagA then interacts with an array of host signaling proteins followed by their activation or inactivation in phosphorylation-dependent and phosphorylation-independent fashions. We now count about 25 host cell binding partners of intracellular CagA, which represent the highest quantity of all currently known virulence-associated effector proteins in the microbial world. Here we review the research progress in characterizing interactions of CagA with multiple host cell receptors in the gastric epithelium, including integrin-β₁, EGFR, c-Met, CD44, E-cadherin, and gp130. The contribution of these interactions to H. pylori colonization, signal transduction, and gastric pathogenesis is discussed.

Gastrointestinal Organoids: Understanding the Molecular Basis of the Host-Microbe Interface

In recent years, increasing attention has been devoted to the concept that microorganisms play an integral role in human physiology and pathophysiology. Despite this, the molecular basis of host-pathogen and host-symbiont interactions in the human intestine remains poorly understood owing to the limited availability of human tissue, and the biological complexity of host-microbe interactions. Over the past decade, technological advances have enabled long-term culture of organotypic intestinal tissue derived from human subjects and from human pluripotent stem cells, and these in vitro culture systems already have shown the potential to inform our understanding significantly of host-microbe interactions. Gastrointestinal organoids represent a substantial advance in structural and functional complexity over traditional in vitro cell culture models of the human gastrointestinal epithelium while retaining much of the genetic and molecular tractability that makes in vitro experimentation so appealing. The opportunity to model epithelial barrier dynamics, cellular differentiation, and proliferation more accurately in specific intestinal segments and in tissue containing a proportional representation of the diverse epithelial subtypes found in the native gut greatly enhances the translational potential of organotypic gastrointestinal culture systems. By using these tools, researchers have uncovered novel aspects of host-pathogen and host-symbiont interactions with the intestinal epithelium. Application of these tools promises to reveal new insights into the pathogenesis of infectious disease, inflammation, cancer, and the role of microorganisms in intestinal development. This review summarizes research on the use of gastrointestinal organoids as a model of the host-microbe interface.

Kidney Organoids: A Translational Journey

Human pluripotent stem cells (hPSCs) are attractive sources for regenerative medicine and disease modeling in vitro. Directed hPSC differentiation approaches have derived from knowledge of cell development in vivo rather than from stochastic cell differentiation. Moreover, there has been great success in the generation of 3D organ-buds termed 'organoids' from hPSCs; these consist of a variety of cell types in vitro that mimic organs in vivo. The organoid bears great potential in the study of human diseases in vitro, especially when combined with CRISPR/Cas9-based genome-editing. We summarize the current literature describing organoid studies with a special focus on kidney organoids, and discuss goals and future opportunities for organoid-based studies.

Helicobacter pylori, Cancer, and the Gastric Microbiota

Gastric adenocarcinoma is one of the leading causes of cancer-related death worldwide and Helicobacter pylori infection is the strongest known risk factor for this disease. Although the stomach was once thought to be a sterile environment, it is now known to house many bacterial species leading to a complex interplay between H. pylori and other residents of the gastric microbiota. In addition to the role of H. pylori virulence factors, host genetic polymorphisms, and diet, it is now becoming clear that components of the gastrointestinal microbiota may also influence H. pylori-induced pathogenesis. In this chapter, we discuss emerging data regarding the gastric microbiota in humans and animal models and alterations that occur to the composition of the gastric microbiota in the presence of H. pylori infection that may augment the risk of developing gastric cancer.

Genome engineering of stem cell organoids for disease modeling

Precision medicine emerges as a new approach that takes into account individual variability. Successful realization of precision medicine requires disease models that are able to incorporate personalized disease information and recapitulate disease development processes at the molecular, cellular and organ levels. With recent development in stem cell field, a variety of tissue organoids can be derived from patient specific pluripotent stem cells and adult stem cells. In combination with the state-of-the-art genome editing tools, organoids can be further engineered to mimic disease-relevant genetic and epigenetic status of a patient. This has therefore enabled a rapid expansion of sophisticated in vitro disease models, offering a unique system for fundamental and biomedical research as well as the development of personalized medicine. Here we summarize some of the latest advances and future perspectives in engineering stem cell organoids for human disease modeling.

Exploiting the Gastric Epithelial Barrier: Helicobacter pylori's Attack on Tight and Adherens Junctions

Highly organized intercellular tight and adherens junctions are crucial structural components for establishing and maintenance of epithelial barrier functions, which control the microbiota and protect against intruding pathogens in humans. Alterations in these complexes represent key events in the development and progression of multiple infectious diseases as well as various cancers. The gastric pathogen Helicobacter pylori exerts an amazing set of strategies to manipulate these epithelial cell-to-cell junctions, which are implicated in changing cell polarity, migration and invasive growth as well as pro-inflammatory and proliferative responses. This chapter focuses on the H. pylori pathogenicity factors VacA, CagA, HtrA and urease, and how they can induce host cell signaling involved in altering cell-to-cell permeability. We propose a stepwise model for how H. pylori targets components of tight and adherens junctions in order to disrupt the gastric epithelial cell layer, giving fresh insights into the pathogenesis of this important bacterium.

Drug Discovery via Human-Derived Stem Cell Organoids

Patient-derived cell lines and animal models have proven invaluable for the understanding of human intestinal diseases and for drug development although both inherently comprise disadvantages and caveats. Many genetically determined intestinal diseases occur in specific tissue microenvironments that are not adequately modeled by monolayer cell culture. Likewise, animal models incompletely recapitulate the complex pathologies of intestinal diseases of humans and fall short in predicting the effects of candidate drugs. Patient-derived stem cell organoids are new and effective models for the development of novel targeted therapies. With the use of intestinal organoids from patients with inherited diseases, the potency and toxicity of drug candidates can be evaluated better. Moreover, owing to the novel clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 genome-editing technologies, researchers can use organoids to precisely modulate human genetic status and identify pathogenesis-related genes of intestinal diseases. Therefore, here we discuss how patient-derived organoids should be grown and how advanced genome-editing tools may be applied to research on modeling of cancer and infectious diseases. We also highlight practical applications of organoids ranging from basic studies to drug screening and precision medicine.

Pathogenesis of Helicobacter pylori infection

Helicobacter pylori is estimated to infect more than half of the worlds human population and represents a major risk factor for chronic gastritis, peptic ulcer disease, MALT lymphoma, and gastric adenocarcinoma. H. pylori infection and clinical consequences are controlled by highly complex interactions between the host, colonizing bacteria, and environmental parameters. Important bacterial determinants linked with gastric disease development include the cag pathogenicity island encoding a type IV secretion system (T4SS), the translocated effector protein CagA, vacuolating cytotoxin VacA, adhesin BabA, urease, serine protease HtrA, secreted outer membrane vesicles, and many others. The high quantity of these factors and allelic changes in the corresponding genes reveals a sophisticated picture and problems in evaluating the impact of each distinct component. Extensive work has been performed to pinpoint molecular processes related to H. pylori-triggered pathogenesis using Mongolian gerbils, mice, primary tissues, as well as novel in vitro model systems such as gastroids. The manipulation of host signaling cascades by the bacterium appears to be crucial for inducing pathogenic downstream activities and gastric disease progression. Here, we review the most recent advances in this important research area.

Wnt/β-catenin, an oncogenic pathway targeted by H. pylori in gastric carcinogenesis

A section of gastric cancers presents nuclear β-catenin accumulation correlated with H. pylori infection. H. pylori stimulate Wnt/β-catenin pathway by activating oncogenic c-Met and epidermal growth factor receptor (EGFR), or by inhibiting tumor suppressor Runx3 and Trefoil factor 1 (TFF1). H. pylori also trigger Wnt/β-catenin pathway by recruiting macrophages. Moreover, Wnt/β-catenin pathway is found involved in H. pylori-induced gastric cancer stem cell generation. Recently, by using gastroids, researchers have further revealed that H. pylori induce gastric epithelial cell proliferation through β-catenin. These findings indicate that Wnt/β-catenin is an oncogenic pathway activated by H. pylori. Therefore, this pathway is a potential therapy target for H. pylori-related gastric cancer.

Phosphorylation and inactivation of PTEN at residues Ser380/Thr382/383 induced by Helicobacter pylori promotes gastric epithelial cell survival through PI3K/Akt pathway

Phosphorylation of PTEN at residues Ser380/Thr382/383 leads to loss of phosphatase activity and tumor suppressor function. Here, we found that phosphorylation of PTEN at residues Ser380/Thr382/383 was increased with gastric carcinogenesis, and more importantly, Helicobacter pylori was a trigger of this modification in chronic non-atrophic gastritis. H. pylori could phosphorylate and inactivate PTEN in vivo and in vitro, resulting in survival of gastric epithelial cells. Furthermore, stable expression of dominant-negative mutant PTEN or inhibition of Akt prevented the enhanced survival induced by H. pylori. These results indicate that PTEN phosphorylation at residues Ser380/Thr382/383 is a novel mechanism of PTEN inactivation in gastric carcinogenesis, and H. pylori triggers this modification, resulting in activation of the PI3K/Akt pathway and promotion of cell survival.

Helicobacter pylori CagA and IL-1β Promote the Epithelial-to-Mesenchymal Transition in a Nontransformed Epithelial Cell Model

Gastric cancer is the third cause of cancer death worldwide and infection by Helicobacter pylori (H. pylori) is considered the most important risk factor, mainly by the activity of its virulence factor CagA. H. pylori/CagA-induced chronic inflammation triggers a series of gastric lesions of increased severity, starting with gastritis and ending with cancer. IL-1β has been associated with tumor development and invasiveness in different types of cancer, including gastric cancer. Currently, it is not clear if there is an association between CagA and IL-1β at a cellular level. In this study, we analyzed the effects of IL-1β and CagA on MCF-10A nontransformed cells. We found evidence that both CagA and IL-1β trigger the initiation of the epithelial-to-mesenchymal transition characterized by β-catenin nuclear translocation, increased expression of Snail1 and ZEB1, downregulation of CDH1, and morphological changes during MCF-10A acini formation. However, only CagA induced MMP9 activity and cell invasion. Our data support that IL-1β and CagA target the β-catenin pathway, with CagA leading to acquisition of a stage related to aggressive tumors.

Organoids as an in vitro model of human development and disease

The in vitro organoid model is a major technological breakthrough that has already been established as an essential tool in many basic biology and clinical applications. This near-physiological 3D model facilitates an accurate study of a range of in vivo biological processes including tissue renewal, stem cell/niche functions and tissue responses to drugs, mutation or damage. In this Review, we discuss the current achievements, challenges and potential applications of this technique.

Modeling human disease using organotypic cultures

Reliable disease models are needed in order to improve quality of healthcare. This includes gaining better understanding of disease mechanisms, developing new therapeutic interventions and personalizing treatment. Up-to-date, the majority of our knowledge about disease states comes from in vivo animal models and in vitro cell culture systems. However, it has been exceedingly difficult to model disease at the tissue level. Since recently, the gap between cell line studies and in vivo modeling has been narrowing thanks to progress in biomaterials and stem cell research. Development of reliable 3D culture systems has enabled a rapid expansion of sophisticated in vitro models. Here we focus on some of the latest advances and future perspectives in 3D organoids for human disease modeling.

Rebamipide attenuates Helicobacter pylori CagA-induced self-renewal capacity via modulation of β-catenin signaling axis in gastric cancer-initiating cells

Rebamipide, a mucosal-protective agent, is used clinically for treatment of gastritis and peptic ulcers induced by Helicobacter pylori (H. pylori) which is associated with increased risk of gastric cancer. Although rebamipide is known to inhibit the growth of gastric cancer cells, the action mechanisms of rebamipide in gastric carcinogenesis remains elusive. Here, we show that rebamipide suppresses H. pylori CagA-induced β-catenin and its target cancer-initiating cells (C-IC) marker gene expression via upregulation of miRNA-320a and -4496. Rebamipide attenuated in vitro self-renewal capacity of H. pylori CagA-infected gastric C-IC via modulation of miRNA-320a/-4496-β-catenin signaling axis. Moreover, rebamipide enhanced sensitivity to chemotherapeutic drugs in CagA-expressed gastric C-IC. Furthermore, rebamipide suppressed tumor-initiating capacity of gastric C-IC, probably via suppression of CagA-induced C-IC properties. These data provide novel insights for the efficacy of rebamipide as a chemoprotective drug against H. pylori CagA-induced carcinogenic potential.

Molecular mechanisms of gastric cancer initiation and progression by Helicobacter pylori

PURPOSE OF REVIEW

Infection with the Gram-negative, microaerophilic pathogen Helicobacter pylori results in gastric cancer in a subset of infected individuals. As such, H. pylori is the only WHO classified bacterial class I carcinogen. Numerous studies have identified mechanisms by which H. pylori alters host cell signaling pathways to cause disease. The purpose of this review is to highlight recent studies that explore mechanisms associated with induction of gastric cancer.

RECENT FINDINGS

Over the last year and a half, new mechanisms contributing to the etiology of H. pylori-associated gastric cancer development have been discovered. In addition to utilizing the oncogenic CagA toxin to alter host cell signaling pathways, H. pylori also induces host DNA damage and alters DNA methylation to perturb downstream signaling. Furthermore, H. pylori activates numerous host cell pathways and proteins that result in epithelial-to-mesenchymal transition and induction of cell survival and proliferation.

SUMMARY

Mounting evidence suggests that H. pylori promotes gastric carcinogenesis using a multifactorial approach. Intriguingly, many of the targeted pathways and mechanisms show commonality with diverse forms of cancer.

Loss of TFF1 promotes Helicobacter pylori-induced β-catenin activation and gastric tumorigenesis

Using in vitro and in vivo models, we investigated the role of TFF1 in suppressing H. pylori-mediated activation of oncogenic β-catenin in gastric tumorigenesis. A reconstitution of TFF1 expression in gastric cancer cells decreased H. pylori-induced β-catenin nuclear translocation, as compared to control (p < 0.001). These cells exhibited significantly lower β-catenin transcriptional activity, measured by pTopFlash reporter, and induction of its target genes (CCND1 and c-MYC), as compared to control. Because of the role of AKT in regulating β-catenin, we performed Western blot analysis and demonstrated that TFF1 reconstitution abrogates H. pylori-induced p-AKT (Ser473), p-β-catenin (Ser552), c-MYC, and CCND1 protein levels. For in vivo validation, we utilized the Tff1-KO gastric neoplasm mouse model. Following infection with PMSS1 H. pylori strain, we detected an increase in the nuclear staining for β-catenin and Ki-67 with a significant induction in the levels of Ccnd1 and c-Myc in the stomach of the Tff1-KO, as compared to Tff1-WT mice (p < 0.05). Only 10% of uninfected Tff1-KO mice, as opposed to one-third of H. pylori-infected Tff1-KO mice, developed invasive adenocarcinoma (p = 0.03). These findings suggest that loss of TFF1 could be a critical step in promoting the H. pylori-mediated oncogenic activation of β-catenin and gastric tumorigenesis.

The expression of IGF-1R in Helicobacter pylori-infected intestinal metaplasia and gastric cancer

Overexpression of IGF-1R has been demonstrated in gastrointestinal cancers, and its expression is reported as the result of the loss of tumor suppressors. IL-16 is involved in the pathophysiological process of chronic inflammatory diseases. The aim of this study is to determine the changes in the expression of IGF-1R in intestinal metaplasia (IM) and gastric cancer (GC) as well as the effect of Helicobacter pylori (H. pylori) and IL-16 on cell proliferation and IGF-1R expression in gastric cells. AGS cells were incubated with combinations of IL-16 and H. pylori. Gastric cell proliferation was studied by BrdU uptake. In H. pylori infected mucosa, IGF-1R was significantly higher in IM than chronic gastritis (CG), and also higher in GC than CG and IM. H. pylori significantly decreased BrdU uptake. IL-16 increased BrdU uptake and IGF-1R on AGS cells which had been decreased by H. pylori. Co-incubation with IL-16 increased the expression of IGF-1R mRNA in H. pylori infected cells. We conclude that the expression of IGF-1R in H. pylori infected gastric mucosa may indicate an early stage of carcinogenesis. The IL-16 secretion by H. pylori can be a trigger for the expression of IGF-1R, and it may also be a factor for gastric carcinogenesis.

Organoid Models of Human Gastrointestinal Development and Disease

We have greatly advanced our ability to grow a diverse range of tissue-derived and pluripotent stem cell-derived gastrointestinal (GI) tissues in vitro. These systems, broadly referred to as organoids, have allowed the field to move away from the often nonphysiological, transformed cell lines that have been used for decades in GI research. Organoids are derived from primary tissues and have the capacity for long-term growth. They contain varying levels of cellular complexity and physiological similarity to native organ systems. We review the latest discoveries from studies of tissue-derived and pluripotent stem cell-derived intestinal, gastric, esophageal, liver, and pancreatic organoids. These studies have provided important insights into GI development, tissue homeostasis, and disease and might be used to develop personalized medicines.