Genetically engineered human pituitary corticotroph tumor organoids exhibit divergent responses to glucocorticoid receptor modulators

Cushing's disease (CD) is a serious endocrine disorder attributed to an adrenocorticotropic hormone (ACTH)-secreting pituitary neuroendocrine tumor (PitNET) that that subsequently leads to chronic hypercortisolemia. PitNET regression has been reported following treatment with the investigational selective glucocorticoid receptor (GR) modulator relacorilant, but the mechanisms behind that effect remain unknown. Human PitNET organoid models were generated from induced human pluripotent stem cells (iPSCs) or fresh tissue obtained from CD patient PitNETs (hPITOs). Genetically engineered iPSC derived organoids were used to model the development of corticotroph PitNETs expressing USP48 (iPSCUSP48) or USP8 (iPSCUSP8) somatic mutations. Organoids were treated with the GR antagonist mifepristone or the GR modulator relacorilant with or without somatostatin receptor (SSTR) agonists pasireotide or octreotide. In iPSCUSP48 and iPSCUSP8 cultures, mifepristone induced a predominant expression of SSTR2 with a concomitant increase in ACTH secretion and tumor cell proliferation. Relacorilant predominantly induced SSTR5 expression and tumor cell apoptosis with minimal ACTH induction. Hedgehog signaling mediated the induction of SSTR2 and SSTR5 in response to mifepristone and relacorilant. Relacorilant sensitized PitNET organoid responsiveness to pasireotide. Therefore, our study identified the potential therapeutic use of relacorilant in combination with somatostatin analogs and demonstrated the advantages of relacorilant over mifepristone, supporting its further development for use in the treatment of Cushing's disease patients.

An adaptive approach to neoadjuvant therapy to maximize resection rates for pancreatic adenocarcinoma: A phase II trial

TPS771

Background: Curative treatment for potentially resectable (resectable or borderline resectable) pancreatic adenocarcinoma, despite recent advances, leads to only suboptimal outcomes. Recent US national cooperative group trials have demonstrated the safety and feasibility of neoadjuvant chemotherapy (PMID 33475684, PMID 35834226), and also show that the two frontline regimens, FOLFIRINOX (5-fluorouracil, irinotecan, oxaliplatin) and gemcitabine/nab-paclitaxel (GnP), are comparable in this setting. Finally, ability to undergo resection remains the key driver of cure. Therefore, an approach that selects chemotherapy based on early response assessment, to maximize the probability of resection, is likely to improve curative outcomes. Methods: This is a phase II study intended to maximize the probability of surgical resection for pancreatic cancer. Key eligibility requirements include adult patients with a confirmed histopathologic diagnosis of pancreatic carcinoma or adenocarcinoma, an ECOG PS ≤ 1, resectable or borderline resectable disease by central radiology review, no prior therapy for index pancreatic cancer, and adequate bone marrow, liver and kidney function. Treatment includes 4 doses (~ 2 months total treatment time) of FOLFIRINOX (“Chemo1”). After a re-evaluation, using radiologic response, CA19.9 response, and chemotherapy toxicity, patients will either continue with “Chemo1” for another 4 cycles (8 doses) or switch to GnP (“Chemo2”) which will be administered for 4 cycles (12 doses, for ~4 month total treatment time), followed by surgical resection. Primary outcome will measure the proportion of patients undergoing surgical resection using historical dated compared to 32 patients in a current study with a time frame of 16 months. Using historical data, the expected proportion of patients undergoing resection is ~60%. The goal of this study is to increase this to 80% or higher. With a one-sided of 0.05 and power of 80%, 32 patients will be needed to demonstrate this difference. Key translational correlatives will include serial circulating tumor DNA assessment and extensive tumor molecular profiling. Clinical trial information: NCT04594772 .

RF01 | PMON168 Hedgehog-Induced Somatostatin Receptor Expression is Inhibited by the Activation of the Glucocorticoid Receptor Signaling Pathway in Human Pituitary Adenoma Organoids

Background

Cushing's disease (CD) is an endocrine disorder caused by an ACTH-secreting pituitary adenoma that is associated with increased morbidity and mortality. Because somatostatin inhibits pituitary ACTH secretion, the somatostatin receptor subtypes (SSTR) 2 and 5 have been targets of medical therapies for CD. The SSTR5 is most consistently and strongly expressed in corticotroph pituitary tumors but the SSTR dynamics in CD during treatment and responses to cortisol level changes are far from being understood. Studies in adult stomach demonstrated that the Hedgehog (Hh) signaling pathway is critical for the regulation of somatostatin and SSTR signaling. While Hh signaling is known to be essential during the embryonic development of the pituitary and in the adult gland, the mechanism by which Hh signaling regulates SSTR expression in CD is unknown.

Hypothesis

Activation of glucocorticoid receptor (NR3C1, GR) results in the inhibition of Hh transcription factor GLI1 leading to reduced SSTR expression.

Methods

We developed a human pituitary adenoma organoid model (hPITOiPSC) from induced pluripotent stem cells treated with the glucocorticoid receptor (GR) antagonist mifepristone, and co-treated them with or without SSTR agonists pasireotide or octreotide. In a separate series of experiments, the role of Hh transcription factor GLI1 was identified using hPITOiPSC treated with mifepristone with or without GANT61 (GLI inhibitor) or ketoconazole (Smoothened, SMO inhibitor). CRISPR-Cas9 gene editing of hPITOiPSC pituitary organoids were used to model the development of pituitary corticotroph adenomas in the presence of BRAF, USP48 and USP8 mutations. Human pituitary adenoma tissue harvested fresh during pituitary surgery was used to generate pituitary corticotroph subtype adenoma organoids (hPITOs). Dose responses using standard of care drugs were performed using the hPITOs.

Results

1) At baseline SSTR2 was abundantly expressed within hPITOiPSC. Mifepristone induced significant increases in ACTH secretion and POMC expression that correlated with induced SSTR2 and 5. Mifepristone-induced SSTR2 and 5 expression was significantly inhibited in the presence of GANT61, whereas SMO inhibitor ketoconazole had a minimal effect on mifepristone-induced SSTR2/5, POMC expression and ACTH secretion. Dexamethasone alone significantly inhibited both GLI1 and SSTR2 and 5. 2) While pituitary organoids that were differentiated from control iPSCs (iPSCCtrl) expressed all major hormone-producing cell lineages, there was a significant increase in ACTH expression with loss of PIT1, GH, FSH, LH and PRL in iPCSs expressing mutated BRAF, USP48 and USP8. Organoids expressing a mutation in BRAF had significantly higher SSTR2 expression levels compared to controls. 3) HPITOs generated from pituitary adenomas of CD patients showed differential organoid responses to pasireotide, mifepristone, and ketoconazole.

Conclusion

Within pituitary adenomas, the SSTR is a transcriptional target of Gli1, and this response is blocked by the activation of the GR. These data form the basis of combination therapy for CD with mifepristone and pasireotide.

Presentation: Saturday, June 11, 2022 1:37 p.m. - 1:42 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Development of Human Pituitary Neuroendocrine Tumor Organoids to Facilitate Effective Targeted Treatments of Cushing's Disease

(1) Background: Cushing's disease (CD) is a serious endocrine disorder caused by an adrenocorticotropic hormone (ACTH)-secreting pituitary neuroendocrine tumor (PitNET) that stimulates the adrenal glands to overproduce cortisol. Chronic exposure to excess cortisol has detrimental effects on health, including increased stroke rates, diabetes, obesity, cognitive impairment, anxiety, depression, and death. The first-line treatment for CD is pituitary surgery. Current surgical remission rates reported in only 56% of patients depending on several criteria. The lack of specificity, poor tolerability, and low efficacy of the subsequent second-line medical therapies make CD a medical therapeutic challenge. One major limitation that hinders the development of specific medical therapies is the lack of relevant human model systems that recapitulate the cellular composition of PitNET microenvironment. (2) Methods: human pituitary tumor tissue was harvested during transsphenoidal surgery from CD patients to generate organoids (hPITOs). (3) Results: hPITOs generated from corticotroph, lactotroph, gonadotroph, and somatotroph tumors exhibited morphological diversity among the organoid lines between individual patients and amongst subtypes. The similarity in cell lineages between the organoid line and the patient's tumor was validated by comparing the neuropathology report to the expression pattern of PitNET specific markers, using spectral flow cytometry and exome sequencing. A high-throughput drug screen demonstrated patient-specific drug responses of hPITOs amongst each tumor subtype. Generation of induced pluripotent stem cells (iPSCs) from a CD patient carrying germline mutation CDH23 exhibited dysregulated cell lineage commitment. (4) Conclusions: The human pituitary neuroendocrine tumor organoids represent a novel approach in how we model complex pathologies in CD patients, which will enable effective personalized medicine for these patients.

Live-cell imaging in human colonic monolayers reveals ERK waves limit the stem cell compartment to maintain epithelial homeostasis

The establishment and maintenance of different cellular compartments in tissues is a universal requirement across all metazoans. Maintaining the correct ratio of cell types in time and space allows tissues to form patterned compartments and perform complex functions. Patterning is especially evident in the human colon, where tissue homeostasis is maintained by stem cells in crypt structures that balance proliferation and differentiation. Here, we developed a human 2D patient derived organoid (PDO) screening platform to study tissue patterning and kinase pathway dynamics in single cells. Using this system, we discovered that waves of ERK signaling induced by apoptotic cells play a critical role in maintaining tissue patterning and homeostasis. If ERK is activated acutely across all cells instead of in wavelike patterns, then tissue patterning and stem cells are lost. Conversely, if ERK activity is inhibited, then stem cells become unrestricted and expand dramatically. This work demonstrates that the colonic epithelium requires coordinated ERK signaling dynamics to maintain patterning and tissue homeostasis. Our work reveals how ERK can antagonize stem cells while supporting cell replacement and the function of the gut.

STAT3-mediated upregulation of the AIM2 DNA sensor links innate immunity with cell migration to promote epithelial tumourigenesis

OBJECTIVE

The absent in melanoma 2 (AIM2) cytosolic pattern recognition receptor and DNA sensor promotes the pathogenesis of autoimmune and chronic inflammatory diseases via caspase-1-containing inflammasome complexes. However, the role of AIM2 in cancer is ill-defined.

DESIGN

The expression of AIM2 and its clinical significance was assessed in human gastric cancer (GC) patient cohorts. Genetic or therapeutic manipulation of AIM2 expression and activity was performed in the genetically engineered gp130 ^F/F spontaneous GC mouse model, as well as human GC cell line xenografts. The biological role and mechanism of action of AIM2 in gastric tumourigenesis, including its involvement in inflammasome activity and functional interaction with microtubule-associated end-binding protein 1 (EB1), was determined in vitro and in vivo.

RESULTS

AIM2 expression is upregulated by interleukin-11 cytokine-mediated activation of the oncogenic latent transcription factor STAT3 in the tumour epithelium of GC mouse models and patients with GC. Genetic and therapeutic targeting of AIM2 in gp130 ^F/F mice suppressed tumourigenesis. Conversely, AIM2 overexpression augmented the tumour load of human GC cell line xenografts. The protumourigenic function of AIM2 was independent of inflammasome activity and inflammation. Rather, in vivo and in vitro AIM2 physically interacted with EB1 to promote epithelial cell migration and tumourigenesis. Furthermore, upregulated expression of AIM2 and EB1 in the tumour epithelium of patients with GC was independently associated with poor patient survival.

CONCLUSION

AIM2 can play a driver role in epithelial carcinogenesis by linking cytokine-STAT3 signalling, innate immunity and epithelial cell migration, independent of inflammasome activation.

Toll-like Receptor 9 Pathway Mediates Schlafen+-MDSC Polarization During Helicobacter-induced Gastric Metaplasias

BACKGROUND & AIMS

A subset of myeloid-derived suppressor cells (MDSCs) that express murine Schlafen4 (SLFN4) or its human ortholog SLFN12L polarize in the Helicobacter-inflamed stomach coincident with intestinal or spasmolytic polypeptide-expressing metaplasia. We propose that individuals with a more robust response to damage-activated molecular patterns and increased Toll-like receptor 9 (TLR9) expression are predisposed to the neoplastic complications of Helicobacter infection.

METHODS

A mouse or human Transwell co-culture system composed of dendritic cells (DCs), 2-dimensional gastric epithelial monolayers, and Helicobacter were used to dissect the cellular source of interferon-α (IFNα) in the stomach by flow cytometry. Conditioned media from the co-cultures polarized primary myeloid cells. MDSC activity was determined by T-cell suppression assays. In human subjects with intestinal metaplasia or gastric cancer, the rs5743836 TLR9T>C variant was genotyped and linked to TLR9, IFNα, and SLFN12L expression by immunohistochemistry. Nuclear factor-κB binding to the TLR9 C allele was determined by electrophoretic mobility shift assays.

RESULTS

Helicobacter infection induced gastric epithelial and plasmacytoid DC expression of TLR9 and IFNα. Co-culturing primary mouse or human cells with DCs and Helicobacter induced TLR9, IFNα secretion, and SLFN⁺-MDSC polarization. Neutralizing IFNα in vivo mitigated Helicobacter-induced spasmolytic polypeptide-expressing metaplasia. The TLR9 minor C allele creates a nuclear factor-κB binding site associated with higher levels of TLR9, IFNα, and SLFN12L in Helicobacter-infected stomachs that correlated with a greater incidence of metaplasias and cancer.

CONCLUSIONS

TLR9 plays an essential role in the production of IFNα and polarization of SLFN⁺ MDSCs on Helicobacter infection. Subjects carrying the rs5743836 TLR9 minor C allele are predisposed to neoplastic complications if chronically infected.

Genome analysis identifies differences in the transcriptional targets of duodenal versus pancreatic neuroendocrine tumours

Objective

Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) encompass a diverse group of neoplasms that vary in their secretory products and in their location within the gastrointestinal tract. Their prevalence in the USA is increasing among all adult age groups.

Aim

To identify the possible derivation of GEP-NETs using genome-wide analyses to distinguish small intestinal neuroendocrine tumours, specifically duodenal gastrinomas (DGASTs), from pancreatic neuroendocrine tumours.

Design

Whole exome sequencing and RNA-sequencing were performed on surgically resected GEP-NETs (discovery cohort). RNA transcript profiles available in the Gene Expression Omnibus were analysed using R integrated software (validation cohort). Digital spatial profiling (DSP) was used to analyse paraffin-embedded GEP-NETs. Human duodenal organoids were treated with 5 or 10 ng/mL of tumor necrosis factor alpha (TNFα) prior to qPCR and western blot analysis of neuroendocrine cell specification genes.

Results

Both the discovery and validation cohorts of small intestinal neuroendocrine tumours induced expression of mesenchymal and calcium signalling pathways coincident with a decrease in intestine-specific genes. In particular, calcium-related, smooth muscle and cytoskeletal genes increased in DGASTs, but did not correlate with MEN1 mutation status. Interleukin 17 (IL-17) and tumor necrosis factor alpha (TNFα) signalling pathways were elevated in the DGAST RNA-sequencing. However, DSP analysis confirmed a paucity of immune cells in DGASTs compared with the adjacent tumour-associated Brunner’s glands. Immunofluorescent analysis showed production of these proinflammatory cytokines and phosphorylated signal transducer and activator of transcription 3 (pSTAT3) by the tumours and stroma. Human duodenal organoids treated with TNFα induced neuroendocrine tumour genes, SYP, CHGA and NKX6.3.

Conclusions

Stromal–epithelial interactions induce proinflammatory cytokines that promote Brunner’s gland reprogramming.

A Preclinical Human-Derived Autologous Gastric Cancer Organoid/Immune Cell Co-Culture Model to Predict the Efficacy of Targeted Therapies

Tumors expressing programmed cell death-ligand 1 (PD-L1) interact with programmed cell death protein 1 (PD-1) on CD8+ cytotoxic T lymphocytes (CTLs) to evade immune surveillance leading to the inhibition of CTL proliferation, survival, and effector function, and subsequently cancer persistence. Approximately 40% of gastric cancers express PD-L1, yet the response rate to immunotherapy is only 30%. We present the use of human-derived autologous gastric cancer organoid/immune cell co-culture as a preclinical model that may predict the efficacy of targeted therapies to improve the outcome of cancer patients. Although cancer organoid co-cultures with immune cells have been reported, this co-culture approach uses tumor antigen to pulse the antigen-presenting dendritic cells. Dendritic cells (DCs) are then cultured with the patient's CD8+ T cells to expand the cytolytic activity and proliferation of these T lymphocytes before co-culture. In addition, the differentiation and immunosuppressive function of myeloid-derived suppressor cells (MDSCs) in culture are investigated within this co-culture system. This organoid approach may be of broad interest and appropriate to predict the efficacy of therapy and patient outcome in other cancers, including pancreatic cancer.

Hedgehog transcriptional effector GLI mediates mTOR-Induced PD-L1 expression in gastric cancer organoids

Tumors evade immune surveillance by expressing Programmed Death-Ligand 1 (PD-L1), subsequently inhibiting CD8⁺ cytotoxic T lymphocyte function. Response of gastric cancer to immunotherapy is relatively low. Our laboratory has reported that Helicobacter pylori-induced PD-L1 expression within the gastric epithelium is mediated by the Hedgehog (Hh) signaling pathway. The PI3K/AKT/mTOR pathway is activated in gastric cancer and may have immunomodulatory potential. We hypothesize that Hh signaling mediates mTOR-induced PD-L1 expression. Patient-derived organoids (PDOs) were generated from gastric biopsies and resected tumor tissues. Autologous organoid/immune cell co-cultures were used to study the immunosuppressive function of MDSCs. NanoString Digital Spatial Profiling (DSP) of immune-related protein markers using FFPE slide-mounted tissues from gastric cancer patients was performed. DSP analysis showed infiltration of immunosuppressive MDSCs expressing Arg1, CD66b, VISTA and IDO1 within cancer tissues. Orthotopic transplantation of patient derived organoids (PDOs) resulted in the engraftment of organoids and the development of histology similar to that observed in the patient's tumor tissue. PDO/immune cell co-cultures revealed that PD-L1-expressing organoids were unresponsive to nivolumab in vitro in the presence of PMN-MDSCs. Depletion of PMN-MDSCs within these co-cultures sensitized the organoids to anti-PD-1/PD-L1-induced cancer cell death. Rapamycin decreased phosphorylated S6K, Gli2 and PD-L1 expression in PDO/immune cell co-cultures. Transcriptional regulation of PD-L1 by GLI1 and GLI2 was blocked by rapamycin. In conclusion, the PDO/immune cell co-cultures may be used to study immunosuppressive MDSC function within the gastric tumor microenvironment. The mTOR signaling pathway mediates GLI-induced PD-L1 expression in gastric cancer.

Modeling pancreatic pathophysiology using genome editing of adult stem cell-derived and induced pluripotent stem cell (iPSC)-derived organoids

In recent years, organoids have become a novel in vitro method to study gastrointestinal organ development, physiology, and disease. An organoid, in short, may be defined as a miniaturized organ that can be grown from adult stem cells in vitro and studied at the microscopic level. Organoids have been used in multitudes of different ways to study the physiology of different human diseases including gastrointestinal cancers such as pancreatic cancer. The development of genome editing based on the bacterial defense mechanism clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 has emerged as a laboratory tool that provides the opportunity to study the effects of specific genetic changes on organ development, physiology, and disease. The CRISPR/Cas9 approach can be combined with organoid technology including the use of induced pluripotent stem cell (iPSC)-derived and tissue-derived organoids. The goal of this review is to provide highlights on the development of organoid technology, and the use of this culture system to study the pathophysiology of specific mutations in the development of pancreatic and gastric cancers.NEW & NOTEWORTHY The goal of this review is not only to provide highlights on the development of organoid technology but also to subsequently use this information to study the pathophysiology of those specific mutations in the formation of malignant pancreatic and gastric cancer.

Breast tumor stiffness instructs bone metastasis via maintenance of mechanical conditioning

While the immediate and transitory response of breast cancer cells to pathological stiffness in their native microenvironment has been well explored, it remains unclear how stiffness-induced phenotypes are maintained over time after cancer cell dissemination in vivo. Here, we show that fibrotic-like matrix stiffness promotes distinct metastatic phenotypes in cancer cells, which are preserved after transition to softer microenvironments, such as bone marrow. Using differential gene expression analysis of stiffness-responsive breast cancer cells, we establish a multigenic score of mechanical conditioning (MeCo) and find that it is associated with bone metastasis in patients with breast cancer. The maintenance of mechanical conditioning is regulated by RUNX2, an osteogenic transcription factor, established driver of bone metastasis, and mitotic bookmarker that preserves chromatin accessibility at target gene loci. Using genetic and functional approaches, we demonstrate that mechanical conditioning maintenance can be simulated, repressed, or extended, with corresponding changes in bone metastatic potential.

Watson et al. demonstrate that mechanical conditioning by stiff microenvironments in breast tumors is maintained in cancer cells after dissemination to softer microenvironments, including bone marrow. They show that mechanical conditioning promotes invasion and osteolysis and establish a mechanical conditioning (MeCo) score, associated with bone metastasis in patients.

Murine- and Human-Derived Autologous Organoid/Immune Cell Co-Cultures as Pre-Clinical Models of Pancreatic Ductal Adenocarcinoma

Purpose: Pancreatic ductal adenocarcinoma (PDAC) has the lowest five-year survival rate of all cancers in the United States. Programmed death 1 receptor (PD-1)-programmed death ligand 1 (PD-L1) immune checkpoint inhibition has been unsuccessful in clinical trials. Myeloid-derived suppressor cells (MDSCs) are known to block anti-tumor CD8+ T cell immune responses in various cancers including pancreas. This has led us to our objective that was to develop a clinically relevant in vitro organoid model to specifically target mechanisms that deplete MDSCs as a therapeutic strategy for PDAC. Method: Murine and human pancreatic ductal adenocarcinoma (PDAC) autologous organoid/immune cell co-cultures were used to test whether PDAC can be effectively treated with combinatorial therapy involving PD-1 inhibition and MDSC depletion. Results: Murine in vivo orthotopic and in vitro organoid/immune cell co-culture models demonstrated that polymorphonuclear (PMN)-MDSCs promoted tumor growth and suppressed cytotoxic T lymphocyte (CTL) proliferation, leading to diminished efficacy of checkpoint inhibition. Mouse- and human-derived organoid/immune cell co-cultures revealed that PD-L1-expressing organoids were unresponsive to nivolumab in vitro in the presence of PMN-MDSCs. Depletion of arginase 1-expressing PMN-MDSCs within these co-cultures rendered the organoids susceptible to anti-PD-1/PD-L1-induced cancer cell death. Conclusions: Here we use mouse- and human-derived autologous pancreatic cancer organoid/immune cell co-cultures to demonstrate that elevated infiltration of polymorphonuclear (PMN)-MDSCs within the PDAC tumor microenvironment inhibit T cell effector function, regardless of PD-1/PD-L1 inhibition. We present a pre-clinical model that may predict the efficacy of targeted therapies to improve the outcome of patients with this aggressive and otherwise unpredictable malignancy.

MiR130b from Schlafen4+ MDSCs stimulates epithelial proliferation and correlates with preneoplastic changes prior to gastric cancer

The myeloid differentiation factor Schlafen4 (Slfn4) marks a subset of myeloid-derived suppressor cells (MDSCs) in the stomach during Helicobacter-induced spasmolytic polypeptide-expressing metaplasia (SPEM).

OBJECTIVE

To identify the gene products expressed by Slfn4⁺-MDSCs and to determine how they promote SPEM.

DESIGN

We performed transcriptome analyses for both coding genes (mRNA by RNA-Seq) and non-coding genes (microRNAs using NanoString nCounter) using flow-sorted SLFN4⁺ and SLFN4^- cells from Helicobacter-infected mice exhibiting metaplasia at 6 months postinfection. Thioglycollate-elicited myeloid cells from the peritoneum were cultured and treated with IFNα to induce the T cell suppressor phenotype, expression of MIR130b and SLFN4. MIR130b expression in human gastric tissue including gastric cancer and patient sera was determined by qPCR and in situ hybridisation. Knockdown of MiR130b in vivo in Helicobacter-infected mice was performed using Invivofectamine. Organoids from primary gastric cancers were used to generate xenografts. ChIP assay and Western blots were performed to demonstrate NFκb p65 activation by MIR130b.

RESULTS

MicroRNA analysis identified an increase in MiR130b in gastric SLFN4⁺ cells. Moreover, MIR130b colocalised with SLFN12L, a human homologue of SLFN4, in gastric cancers. MiR130b was required for the T-cell suppressor phenotype exhibited by the SLFN4⁺ cells and promoted Helicobacter-induced metaplasia. Treating gastric organoids with the MIR130b mimic induced epithelial cell proliferation and promoted xenograft tumour growth.

CONCLUSION

Taken together, MiR130b plays an essential role in MDSC function and supports metaplastic transformation.

H. pylori infection confers resistance to apoptosis via Brd4-dependent BIRC3 eRNA synthesis

H. pylori infection is one of the leading causes of gastric cancer and the pathogenicity of H. pylori infection is associated with its ability to induce chronic inflammation and apoptosis resistance. While H. pylori infection-induced expression of pro-inflammatory cytokines for chronic inflammation is well studied, the molecular mechanism underlying the apoptosis resistance in infected cells is not well understood. In this study, we demonstrated that H. pylori infection-induced apoptosis resistance in gastric epithelial cells triggered by Raptinal, a drug that directly activates caspase-3. This resistance resulted from the induction of cIAP2 (encoded by BIRC3) since depletion of BIRC3 by siRNA or inhibition of cIAP2 via BV6 reversed H. pylori-suppressed caspase-3 activation. The induction of cIAP2 was regulated by H. pylori-induced BIRC3 eRNA synthesis. Depletion of BIRC3 eRNA decreased H. pylori-induced cIAP2 and reversed H. pylori-suppressed caspase-3 activation. Mechanistically, H. pylori stimulated the recruitment of bromodomain-containing factor Brd4 to the enhancer of BIRC3 and promoted BIRC3 eRNA and mRNA synthesis. Inhibition of Brd4 diminished the expression of BIRC3 eRNA and the anti-apoptotic response to H. pylori infection. Importantly, H. pylori isogenic cagA-deficient mutant failed to activate the synthesis of BIRC3 eRNA and the associated apoptosis resistance. Finally, in primary human gastric epithelial cells, H. pylori also induced resistance to Raptinal-triggered caspase-3 activation by activating the Brd4-dependent BIRC3 eRNA synthesis in a CagA-dependent manner. These results identify a novel function of Brd4 in H. pylori-mediated apoptosis resistance via activating BIRC3 eRNA synthesis, suggesting that Brd4 could be a potential therapeutic target for H. pylori-induced gastric cancer.

Role of metaplasia during gastric regeneration

Spasmolytic polypeptide/trefoil factor 2 (TFF2)-expressing metaplasia (SPEM) is a mucous-secreting reparative lineage that emerges at the ulcer margin in response to gastric injury. Under conditions of chronic inflammation with parietal cell loss, SPEM has been found to emerge and evolve into neoplasia. Cluster-of-differentiation gene 44 (CD44) is known to coordinate normal and metaplastic epithelial cell proliferation. In particular, CD44 variant isoform 9 (CD44v9) associates with the cystine-glutamate transporter xCT, stabilizes the protein, and provides defense against reactive oxygen species (ROS). xCT stabilization by CD44v9 leads to defense against ROS by cystine uptake, glutathione (GSH) synthesis, and maintenance of the redox balance within the intracellular environment. Furthermore, p38 signaling is a known downstream ROS target, leading to diminished cell proliferation and migration, two vital processes of gastric epithelial repair. CD44v9 emerges during repair of the gastric epithelium after injury, where it is coexpressed with other markers of SPEM. The regulatory mechanisms for the emergence of CD44v9 and the role of CD44v9 during the process of gastric epithelial regeneration are largely unknown. Inflammation and M2 macrophage infiltration have recently been demonstrated to play key roles in the induction of SPEM after injury. The following review proposes new insights into the functional role of metaplasia in the process of gastric regeneration in response to ulceration. Our insights are extrapolated from documented studies reporting oxyntic atrophy and SPEM development and our current unpublished findings using the acetic acid-induced gastric injury model.

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.

VacA generates a protective intracellular reservoir for Helicobacter pylori that is eliminated by activation of the lysosomal calcium channel TRPML1

Helicobacter pylori infection is a proven carcinogen for gastric cancer. Its virulence factor vacuolating cytotoxin A (VacA) promotes more severe disease and gastric colonization. VacA, by an unknown mechanism, usurps lysosomal and autophagy pathways to generate a protected reservoir for H. pylori that confers bacterial survival in vitro. Here, we show the existence of a VacA-generated intracellular niche in vivo that protects the bacteria from antibiotic treatment and leads to infection recrudescence after therapy. Furthermore, we report that VacA targets the lysosomal calcium channel TRPML1 to disrupt endolysosomal trafficking and mediate these effects. Remarkably, H. pylori that lack toxigenic VacA colonize enlarged dysfunctional lysosomes in the gastric epithelium of trpml1-null mice, where they are protected from eradication therapy. Furthermore, a small molecule agonist directed against TRPML1 reversed the toxic effects of VacA on endolysosomal trafficking, culminating in the clearance of intracellular bacteria. These results suggest that TRPML1 may represent a therapeutic target for chronic H. pylori infection.

Carcinogenic Helicobacter pylori Strains Selectively Dysregulate the In Vivo Gastric Proteome, Which May Be Associated with Stomach Cancer Progression

Helicobacter pylori is the strongest risk factor for gastric cancer. Initial interactions between H. pylori and its host originate at the microbial-gastric epithelial cell interface, and contact between H. pylori and gastric epithelium activates signaling pathways that drive oncogenesis. One microbial constituent that increases gastric cancer risk is the cag pathogenicity island, which encodes a type IV secretion system that translocates the effector protein, CagA, into host cells. We previously demonstrated that infection of Mongolian gerbils with a carcinogenic cag+H. pylori strain, 7.13, recapitulates many features of H. pylori-induced gastric cancer in humans. Therefore, we sought to define gastric proteomic changes induced by H. pylori that are critical for initiation of the gastric carcinogenic cascade. Gastric cell scrapings were harvested from H. pylori-infected and uninfected gerbils for quantitative proteomic analyses using isobaric tags for relative and absolute quantitation (iTRAQ). Quantitative proteomic analysis of samples from two biological replicate experiments quantified a total of 2764 proteins, 166 of which were significantly altered in abundance by H. pylori infection. Pathway mapping identified significantly altered inflammatory and cancer-signaling pathways that included Rab/Ras signaling proteins. Consistent with the iTRAQ results, RABEP2 and G3BP2 were significantly up-regulated in vitro, ex vivo in primary human gastric monolayers, and in vivo in gerbil gastric epithelium following infection with H. pylori strain 7.13 in a cag-dependent manner. Within human stomachs, RABEP2 and G3BP2 expression in gastric epithelium increased in parallel with the severity of premalignant and malignant lesions and was significantly elevated in intestinal metaplasia and dysplasia, as well as gastric adenocarcinoma, compared with gastritis alone. These results indicate that carcinogenic strains of H. pylori induce dramatic and specific changes within the gastric proteome in vivo and that a subset of altered proteins within pathways with oncogenic potential may facilitate the progression of gastric carcinogenesis in humans.

Increased Programmed Death-Ligand 1 is an Early Epithelial Cell Response to Helicobacter pylori Infection

Helicobacter pylori (H. pylori) is the major risk factor for the development of gastric cancer. Our laboratory has reported that the Sonic Hedgehog (Shh) signaling pathway is an early response to infection that is fundamental to the initiation of H. pylori-induced gastritis. H. pylori also induces programmed death ligand 1 (PD-L1) expression on gastric epithelial cells, yet the mechanism is unknown. We hypothesize that H. pylori-induced PD-L1 expression within the gastric epithelium is mediated by the Shh signaling pathway during infection. To identify the role of Shh signaling as a mediator of H. pylori-induced PD-L1 expression, human gastric organoids generated from either induced pluripotent stem cells (HGOs) or tissue (huFGOs) were microinjected with bacteria and treated with Hedgehog/Gli inhibitor GANT61. Gastric epithelial monolayers generated from the huFGOs were also infected with H. pylori and treated with GANT61 to study the role of Hedgehog signaling as a mediator of induced PD-1 expression. A patient-derived organoid/autologous immune cell co-culture system infected with H. pylori and treated with PD-1 inhibitor (PD-1Inh) was developed to study the protective mechanism of PD-L1 in response to bacterial infection. H. pylori significantly increased PD-L1 expression in organoid cultures 48 hours post-infection when compared to uninfected controls. The mechanism was cytotoxic associated gene A (CagA) dependent. This response was blocked by pretreatment with GANT61. Anti-PD-L1 treatment of H. pylori infected huFGOs, co-cultured with autologous patient cytotoxic T lymphocytes and dendritic cells, induced organoid death. H. pylori-induced PD-L1 expression is mediated by the Shh signaling pathway within the gastric epithelium. Cells infected with H. pylori that express PD-L1 may be protected from the immune response, creating premalignant lesions progressing to gastric cancer.

Oncogenic Transformation of Human-Derived Gastric Organoids

The culture of organoids has represented a significant advancement in the gastrointestinal research field. Previous research studies have described the oncogenic transformation of human intestinal and mouse gastric organoids. Here we detail the protocol for the oncogenic transformation and orthotopic transplantation of human-derived gastric organoids.

Hedgehog signaling induces PD-L1 expression and tumor cell proliferation in gastric cancer

Tumor cells expressing programmed cell death ligand 1 (PD-L1) interact with PD-1 on CD8+ cytotoxic T lymphocytes (CTLs) to inhibit CTL effector function. In gastric cancer, the mechanism regulating PD-L1 is unclear. The Hedgehog (Hh) signaling pathway is reactivated in various cancers including gastric. Here we tested the hypothesis that Hh-induced PD-L1 inactivates effector T cell function and allows gastric cancer cell proliferation. Mouse organoids were generated from tumors of a triple-transgenic mouse model engineered to express an activated GLI2 allele, GLI2A, in Lgr5-expressing stem cells, (mTGOs) or normal mouse stomachs (mGOs). Bone marrow-derived dendritic cells (DCs) were pulsed with conditioned media collected from normal (mGOCM) or cancer (mTGOCM) organoids. Pulsed DCs and CTLs were then co-cultured with either mGOs or mTGOs in the presence of PD-L1 neutralizing antibody (PD-L1Ab). Human-derived gastric cancer organoids (huTGOs) were used in drug and xenograft assays. Hh/Gli inhibitor, GANT-61 significantly reduced the expression of PD-L1 and tumor cell proliferation both in vivo and in vitro. PD-L1Ab treatment induced tumor cell apoptosis in mTGO/immune cell co-cultures. GANT-61 treatment sensitized huTGOs to standard-of-care chemotherapeutic drugs both in vivo and in vitro. Thus, Hh signaling mediates PD-L1 expression in gastric cancer cells and subsequently promotes tumor proliferation.

An Organoid-Based Preclinical Model of Human Gastric Cancer

BACKGROUND & AIMS

Our goal was to develop an initial study for the proof of concept whereby gastric cancer organoids are used as an approach to predict the tumor response in individual patients.

METHODS

Organoids were derived from resected gastric cancer tumors (huTGOs) or normal stomach tissue collected from sleeve gastrectomies (huFGOs). Organoid cultures were treated with standard-of-care chemotherapeutic drugs corresponding to patient treatment: epirubicin, oxaliplatin, and 5-fluorouracil. Organoid response to chemotherapeutic treatment was correlated with the tumor response in each patient from whom the huTGOs were derived. HuTGOs were orthotopically transplanted into the gastric mucosa of NOD scid gamma mice.

RESULTS

Whereas huFGOs exhibited a half maximal inhibitory concentration that was similar among organoid lines, divergent responses and varying half maximal inhibitory concentration values among the huTGO lines were observed in response to chemotherapeutic drugs. HuTGOs that were sensitive to treatment were derived from a patient with a near complete tumor response to chemotherapy. However, organoids resistant to treatment were derived from patients who exhibited no response to chemotherapy. Orthotropic transplantation of organoids resulted in the engraftment and development of human adenocarcinoma. RNA sequencing revealed that huTGOs closely resembled the patient's native tumor tissue and not commonly used gastric cancer cell lines and cell lines derived from the organoid cultures.

CONCLUSIONS

The treatment of patient-derived organoids alongside patients from whom cultures were derived will ultimately test their usefulness to predict individual therapy response and patient outcome.

Mouse- and Human-derived Primary Gastric Epithelial Monolayer Culture for the Study of Regeneration

In vitro studies of gastric wound repair typically involves the use of gastric cancer cell lines in a scratch-wound assay of cellular proliferation and migration. One critical limitation of such assays, however, is their homogenous assortment of cellular types. Repair is a complex process which demands the interaction of several cell types. Therefore, to study a culture devoid of cellular subtypes, is a concern that must be overcome if we are to understand the repair process. The gastric organoid model may alleviate this issue whereby the heterogeneous collection of cell types closely reflects that of the gastric epithelium or other native tissues in vivo. Demonstrated here is a novel, in vitro scratch-wound assay derived from human or mouse 3-dimensional organoids which can then be transferred to a gastric epithelial monolayer as either intact organoids or as a single cell suspension of dissociated organoids. The goal of the protocol is to establish organoid-derived gastric epithelial monolayers that can be used in a novel scratch-wound assay system to study gastric regeneration.

Mouse-Derived Gastric Organoid and Immune Cell Co-culture for the Study of the Tumor Microenvironment

The interaction between the receptor, programmed cell death protein 1 (PD-1) and ligand, programmed cell death 1 (PD-L1) is known to inhibit CD8+ cytotoxic T lymphocyte proliferation, survival, and effector function. The result of this interaction leads to evasion of immune surveillance by tumors and subsequently cancer cell proliferation. Immunotherapy via PD-L1 blockade is used for a variety of malignancies, yet the prognostic value of immune checkpoint inhibition for the treatment of gastric cancer remains controversial. Thus, preclinical models that would predict the efficacy of such therapy in a subgroup of gastric cancer patients would be an advancement in the personalized treatment of this disease. Three-dimensional organoid cultures have not only been used to investigate the mechanisms regulating development and disease, but have also been used for high-throughput drug screening for targeted personalized therapy. Here we present the methodology for the co-culture of mouse-derived gastric cancer organoids with autologous immune cells specifically for the study of PD-L1/PD-1 interactions within the tumor microenvironment in vitro.

CD44 variant isoform 9 emerges in response to injury and contributes to the regeneration of the gastric epithelium

The CD44 gene encodes several protein isoforms due to alternative splicing and post translational modifications. Given that CD44 variant isoform 9 (CD44v9) is expressed within Spasmolytic Polypeptide/TFF2-Expressing Metaplasia (SPEM) glands during repair, CD44v9 may be play a funcitonal role during the process of regeneration of the gastric epithelium. Here we hypothesize that CD44v9 marks a regenerative cell lineage responsive to infiltrating macrophages during regeneration of the gastric epithelium. Ulcers were induced in CD44-deficient (CD44KO) and C57BL/6 (BL6) mice by a localized application of acetic acid to the serosal surface of the stomach. Gastric organoids expressing CD44v9 were derived from mouse stomachs and transplanted at the ulcer site of CD44KO mice. Ulcers, CD44v9 expression, proliferation and histology were measured 1, 3, 5 and 7-days post-injury. Human-derived gastric organoids were generated from stomach tissue collected from elderly (>55 years) or young (14-20 years) patients. Organoids were transplanted into the stomachs of NOD scid gamma (NSG) mice at the site of injury. Gastric injury was induced in NRG-SGM3 (NRGS) mice harboring human-derived immune cells (hnNRGS) and the immune profile anlayzed by CyTOF. CD44v9 expression emerged within regenerating glands the ulcer margin in response to injury. While ulcers in BL6 mice healed within 7-days post-injury, CD44KO mice exhibited loss of repair and epithelial regeneration. Ulcer healing was promoted in CD44KO mice by transplanted CD55v9-expressing gastric organoids. NSG mice exhibited loss of CD44v9 expression and gastric repair. Transplantation of human-derived gastric organoids from young, but not aged stomachs promoted repair in NSG mouse stomachs in response to injury. Finally, compared to NRGS mice, huNRGS animals exhibited reduced ulcer sizes, an infiltration of human CD162+ macrophages and an emergence of CD44v9 expression in SPEM. Thus, during repair of the gastic epithelium CD44v9 emerges within a regenerative cell lineage that coincides with macrophage inflitration within the injured mucosa. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Hedgehog signalling in myeloid cells impacts on body weight, adipose tissue inflammation and glucose metabolism

AIMS/HYPOTHESIS

Recently, hedgehog (Hh) was identified as a crucial player in adipose tissue development and energy expenditure. Therefore, we tested whether Hh ligands are regulated in obesity. Further, we aimed at identifying potential target cells of Hh signalling and studied the functional impact of Hh signalling on adipose tissue inflammation and glucose metabolism.

METHODS

Hh ligands and receptors were analysed in adipose tissue or serum from lean and obese mice as well as in humans. To study the impact on adipose tissue inflammation and glucose metabolism, Hh signalling was specifically blocked in myeloid cells using a conditional knockout approach (Lys-Smo ^-/-).

RESULTS

Desert Hh (DHH) and Indian Hh (IHH) are local Hh ligands, whereas Sonic Hh is not expressed in adipose tissue from mice or humans. In mice, obesity leads to a preferential upregulation of Hh ligands (Dhh) and signalling components (Ptch1, Smo and Gli1) in subcutaneous adipose tissue. Further, adipose tissue macrophages are Hh target cells owing to the expression of Hh receptors, such as Patched1 and 2. Conditional knockout of Smo (which encodes Smoothened, a mandatory Hh signalling component) in myeloid cells increases body weight and adipose tissue inflammation and attenuates glucose tolerance, suggesting an anti-inflammatory effect of Hh signalling. In humans, adipose tissue expression of DHH and serum IHH decrease with obesity and type 2 diabetes, which might be explained by the intake of metformin. Interestingly, metformin reduced Dhh and Ihh expression in mouse adipose tissue explants.

CONCLUSIONS/INTERPRETATION

Hh signalling in myeloid cells affects adipose tissue inflammation and glucose metabolism and may be a potential target to treat type 2 diabetes.

Initiation and Maintenance of Gastric Cancer: A Focus on CD44 Variant Isoforms and Cancer Stem Cells

Gastric cancer is the third most common cause of cancer-related death. Although the incidence of gastric cancer in the United States is relatively low, it remains significantly higher in some countries, including Japan and Korea. Interactions between cancer stem cells and the tumor microenvironment can have a substantial impact on tumor characteristics and contribute to heterogeneity. The mechanisms responsible for maintaining malignant cancer stem cells within the tumor microenvironment in human gastric cancer are largely unknown. Tumor cell and genetic heterogeneity contribute to either de novo intrinsic or the therapy-induced emergence of drug-resistant clones and eventual tumor recurrence. Although chemotherapy often is capable of inducing cell death in tumors, many cancer patients experience recurrence because of failure to effectively target the cancer stem cells, which are believed to be key tumor-initiating cells. Among the population of stem cells within the stomach that may be targeted during chronic Helicobacter pylori infection and altered into tumor-initiating cells are those cells marked by the cluster-of-differentiation (CD)44 cell surface receptor. CD44 variable isoforms (CD44v) have been implicated as key players in malignant transformation whereby their expression is highly restricted and specific, unlike the canonical CD44 standard isoform. Overall, CD44v, in particular CD44v9, are believed to mark the gastric cancer cells that contribute to increased resistance for chemotherapy- or radiation-induced cell death. This review focuses on the following: the alteration of the gastric stem cell during bacterial infection, and the role of CD44v in the initiation, maintenance, and growth of tumors associated with gastric cancer.

Hedgehog signaling in the stomach

The Hedgehog (Hh) signaling pathway not only plays a key part in controlling embryonic development, but in the adult stomach governs important cellular events such as epithelial cell differentiation, proliferation, gastric disease, and regeneration. In particular, Sonic Hedgehog (Shh) signaling has been well studied for its role in gastric physiology and pathophysiology. Shh is secreted from the gastric parietal cells and contributes to the regeneration of the epithelium in response to injury, or the development of gastritis during Helicobacter pylori infection. Dysregulation of the Shh signaling pathway leads to the disruption of gastric differentiation, loss of gastric acid secretion and the development of cancer. In this chapter, we will review the most recent findings that reveal the role of Shh as a regulator of gastric physiology, regeneration, and disease.

The Development of Spasmolytic Polypeptide/TFF2-Expressing Metaplasia (SPEM) During Gastric Repair Is Absent in the Aged Stomach

BACKGROUND & AIMS

During aging, physiological changes in the stomach result in more tenuous gastric tissue that is less capable of repairing injury, leading to increased susceptibility to chronic ulceration. Spasmolytic polypeptide/trefoil factor 2-expressing metaplasia (SPEM) is known to emerge after parietal cell loss and during Helicobacter pylori infection, however, its role in gastric ulcer repair is unknown. Therefore, we sought to investigate if SPEM plays a role in epithelial regeneration.

METHODS

Acetic acid ulcers were induced in young (2-3 mo) and aged (18-24 mo) C57BL/6 mice to determine the quality of ulcer repair with advancing age. Yellow chameleon 3.0 mice were used to generate yellow fluorescent protein-expressing organoids for transplantation. Yellow fluorescent protein-positive gastric organoids were transplanted into the submucosa and lumen of the stomach immediately after ulcer induction. Gastric tissue was collected and analyzed to determine the engraftment of organoid-derived cells within the regenerating epithelium.

RESULTS

Wound healing in young mice coincided with the emergence of SPEM within the ulcerated region, a response that was absent in the aged stomach. Although aged mice showed less metaplasia surrounding the ulcerated tissue, organoid-transplanted aged mice showed regenerated gastric glands containing organoid-derived cells. Organoid transplantation in the aged mice led to the emergence of SPEM and gastric regeneration.

CONCLUSIONS

These data show the development of SPEM during gastric repair in response to injury that is absent in the aged stomach. In addition, gastric organoids in an injury/transplantation mouse model promoted gastric regeneration.

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.

Co-culture of Gastric Organoids and Immortalized Stomach Mesenchymal Cells

Three-dimensional primary epithelial-derived gastric organoids have recently been established as an important tool to study gastric development, physiology, and disease. Specifically, mouse-derived fundic gastric organoids (mFGOs) co-cultured with Immortalized Stomach Mesenchymal Cells (ISMCs) reflect expression patterns of mature fundic cell types seen in vivo, thus allowing for long-term in vitro studies of gastric epithelial cell physiology, regeneration, and bacterial-host interactions. Here, we describe the development and culture of mFGOs, co-cultured with ISMCs.

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.

The use of murine-derived fundic organoids in studies of gastric physiology

KEY POINTS

An in vitro approach to study gastric development is primary mouse-derived epithelium cultured as three-dimensional spheroids known as organoids. We have devised two unique gastric fundic-derived organoid cultures: model 1 for the expansion of gastric fundic stem cells, and model 2 for the maintenance of mature cell lineages. Organoids maintained in co-culture with immortalized stomach mesenchymal cells express robust numbers of surface pit, mucous neck, chief, endocrine and parietal cells. Histamine induced a significant decrease in intraluminal pH that was reversed by omeprazole in fundic organoids and indicated functional activity and regulation of parietal cells. Localized photodamage resulted in rapid cell exfoliation coincident with migration of neighbouring cells to the damaged area, sustaining epithelial continuity. We report the use of these models for studies of epithelial cell biology and cell damage and repair.

ABSTRACT

Studies of gastric function and disease have been limited by the lack of extended primary cultures of the epithelium. An in vitro approach to study gastric development is primary mouse-derived antral epithelium cultured as three-dimensional spheroids known as organoids. There have been no reports on the use of organoids for gastric function. We have devised two unique gastric fundic-derived organoid cultures: model 1 for the expansion of gastric fundic stem cells, and model 2 for the maintenance of mature cell lineages. Both models were generated from single glands dissociated from whole fundic tissue and grown in basement membrane matrix (Matrigel) and organoid growth medium. Model 1 enriches for a stem cell-like niche via simple passage of the organoids. Maintained in Matrigel and growth medium, proliferating organoids expressed high levels of stem cell markers CD44 and Lgr5. Model 2 is a system of gastric organoids co-cultured with immortalized stomach mesenchymal cells (ISMCs). Organoids maintained in co-culture with ISMCs express robust numbers of surface pit, mucous neck, chief, endocrine and parietal cells. Histamine induced a significant decrease in intraluminal pH that was reversed by omeprazole in fundic organoids and indicated functional activity and regulation of parietal cells. Localized photodamage resulted in rapid cell exfoliation coincident with migration of neighbouring cells to the damaged area, sustaining epithelial continuity. Thus, we report the use of these models for studies of epithelial cell biology and cell damage and repair.

CD44 plays a functional role in Helicobacter pylori-induced epithelial cell proliferation

The cytotoxin-associated gene (Cag) pathogenicity island is a strain-specific constituent of Helicobacter pylori (H. pylori) that augments cancer risk. CagA translocates into the cytoplasm where it stimulates cell signaling through the interaction with tyrosine kinase c-Met receptor, leading cellular proliferation. Identified as a potential gastric stem cell marker, cluster-of-differentiation (CD) CD44 also acts as a co-receptor for c-Met, but whether it plays a functional role in H. pylori-induced epithelial proliferation is unknown. We tested the hypothesis that CD44 plays a functional role in H. pylori-induced epithelial cell proliferation. To assay changes in gastric epithelial cell proliferation in relation to the direct interaction with H. pylori, human- and mouse-derived gastric organoids were infected with the G27 H. pylori strain or a mutant G27 strain bearing cagA deletion (∆CagA::cat). Epithelial proliferation was quantified by EdU immunostaining. Phosphorylation of c-Met was analyzed by immunoprecipitation followed by Western blot analysis for expression of CD44 and CagA. H. pylori infection of both mouse- and human-derived gastric organoids induced epithelial proliferation that correlated with c-Met phosphorylation. CagA and CD44 co-immunoprecipitated with phosphorylated c-Met. The formation of this complex did not occur in organoids infected with ∆CagA::cat. Epithelial proliferation in response to H. pylori infection was lost in infected organoids derived from CD44-deficient mouse stomachs. Human-derived fundic gastric organoids exhibited an induction in proliferation when infected with H. pylori that was not seen in organoids pre-treated with a peptide inhibitor specific to CD44. In the well-established Mongolian gerbil model of gastric cancer, animals treated with CD44 peptide inhibitor Pep1, resulted in the inhibition of H. pylori-induced proliferation and associated atrophic gastritis. The current study reports a unique approach to study H. pylori interaction with the human gastric epithelium. Here, we show that CD44 plays a functional role in H. pylori-induced epithelial cell proliferation.