Sonic hedgehog regulates gastric gland morphogenesis in man and mouse

Sonic Hedgehog promotes tumor cell survival by inhibiting CDON pro-apoptotic activity

The Hedgehog signaling is a determinant pathway for tumor progression. However, while inhibition of the Hedgehog canonical pathway-Patched-Smoothened-Gli-has proved efficient in human tumors with activating mutations in this pathway, recent clinical data have failed to show any benefit in other cancers, even though Sonic Hedgehog (SHH) expression is detected in these cancers. Cell-adhesion molecule-related/down-regulated by Oncogenes (CDON), a positive regulator of skeletal muscle development, was recently identified as a receptor for SHH. We show here that CDON behaves as a SHH dependence receptor: it actively triggers apoptosis in the absence of SHH. The pro-apoptotic activity of unbound CDON requires a proteolytic cleavage in its intracellular domain, allowing the recruitment and activation of caspase-9. We show that by inducing apoptosis in settings of SHH limitation, CDON expression constrains tumor progression, and as such, decreased CDON expression observed in a large fraction of human colorectal cancer is associated in mice with intestinal tumor progression. Reciprocally, we propose that the SHH expression, detected in human cancers and previously considered as a mechanism for activation of the canonical pathway in an autocrine or paracrine manner, actually provides a selective tumor growth advantage by blocking CDON-induced apoptosis. In support of this notion, we present the preclinical demonstration that interference with the SHH-CDON interaction triggers a CDON-dependent apoptosis in vitro and tumor growth inhibition in vivo. The latter observation qualifies CDON as a relevant alternative target for anticancer therapy in SHH-expressing tumors.

Cancer stem cells: the 'heartbeat' of gastric cancer

Gastric cancer (GC) remains one of the most common cancers worldwide. Its prevalence is still on the rise in the developing countries due to the ageing population. The cancer stem cell (CSC) theory provides a new insight into the interpretation of tumor initiation, aggressive growth, recurrence, and metastasis of cancer, as well as the development of new strategies for cancer treatment. This review will focus on the progress of biomarkers and signaling pathways of CSCs, the complex crosstalk networks between the microenvironment and CSCs, and the development of therapeutic approaches against CSCs, predominantly focusing on GC.

MAPKs and signal transduction in the control of gastrointestinal epithelial cell proliferation and differentiation

Mitogen-activated protein kinase (MAPK) pathways are activated by several stimuli and transduce the signal inside cells, generating diverse responses including cell proliferation, differentiation, migration and apoptosis. Each MAPK cascade comprises a series of molecules, and regulation takes place at different levels. They communicate with each other and with additional pathways, creating a signaling network that is important for cell fate determination. In this review, we focus on ERK, JNK, p38 and ERK5, the major MAPKs, and their interactions with PI3K-Akt, TGFβ/Smad and Wnt/β-catenin pathways. More importantly, we describe how MAPKs regulate cell proliferation and differentiation in the rapidly renewing epithelia that lines the gastrointestinal tract and, finally, we highlight the recent findings on nutritional aspects that affect MAPK transduction cascades.

Biomarkers for predicting the response of esophageal squamous cell carcinoma to neoadjuvant chemoradiation therapy

This review summarizes and evaluates the literature regarding the biomarkers for predicting the response and/or prognosis of esophageal squamous cell carcinoma (ESCC) patients treated with neoadjuvant chemoradiation therapy (CRT). There are seven categories of molecules known to correlate with the response and/or prognosis: tumor suppressors (p53, p21), cell cycle regulators (Cyclin D1, CDC25B, 14-3-3sigma), DNA repair molecules (p53R2, ERCC1), drug resistance proteins [metallothionein (MT)], angiogenic factors (VEGF), molecules involved in cell proliferation/invasion/metastasis (Ki-67, COX-2) and hedgehog signaling molecules (Gli-1). Of the above molecules, the tumor suppressor p53 is expected to be a representative biomarker for predicting the response and prognosis. The cell cycle markers CDC25B and 14-3-3sigma have potential as response biomarkers independent of the p53 status. The DNA repair markers, p53R2 or ERCC1, angiogenic molecule (VEGF), and hedgehog signaling pathway factor Gli-1 also have potential to predict the response and prognosis of ESCC. However, there are still many unanswered questions with regard to predicting the clinical effects of neoadjuvant CRT.

Gastric cancer stem cells: a novel therapeutic target

Gastric cancer remains one of the leading causes of global cancer mortality. Multipotent gastric stem cells have been identified in both mouse and human stomachs, and they play an essential role in the self-renewal and homeostasis of gastric mucosa. There are several environmental and genetic factors known to promote gastric cancer. In recent years, numerous in vitro and in vivo studies suggest that gastric cancer may originate from normal stem cells or bone marrow-derived mesenchymal cells, and that gastric tumors contain cancer stem cells. Cancer stem cells are believed to share a common microenvironment with normal niche, which play an important role in gastric cancer and tumor growth. This mini-review presents a brief overview of the recent developments in gastric cancer stem cell research. The knowledge gained by studying cancer stem cells in gastric mucosa will support the development of novel therapeutic strategies for gastric cancer.

Gastric stem cells and gastric cancer stem cells

The gastric epithelium is continuously regenerated by gastric stem cells, which give rise to various kinds of daughter cells, including parietal cells, chief cells, surface mucous cells, mucous neck cells, and enteroendocrine cells. The self-renewal and differentiation of gastric stem cells need delicate regulation to maintain the normal physiology of the stomach. Recently, it was hypothesized that cancer stem cells drive the cancer growth and metastasis. In contrast to conventional clonal evolution hypothesis, only cancer stem cells can initiate tumor formation, self-renew, and differentiate into various kinds of daughter cells. Because gastric cancer can originate from gastric stem cells and their self-renewal mechanism can be used by gastric cancer stem cells, we review here how critical signaling pathways, including hedgehog, Wnt, Notch, epidermal growth factor, and bone morphogenetic protein signaling, may regulate the self-renewal and differentiation of gastric stem cells and gastric cancer stem cells. In addition, the precancerous change of the gastric epithelium and the status of isolating gastric cancer stem cells from patients are reviewed.

Gli1 deletion prevents Helicobacter-induced gastric metaplasia and expansion of myeloid cell subsets

Chronic inflammation in the stomach induces metaplasia, the pre-cancerous lesion that precedes inflammation-driven neoplastic transformation. While Hedgehog signaling contributes to the initiation of some cancers, its role in gastric transformation remains poorly defined. We found that Helicobacter-infected C57BL/6 mice develop extensive mucous cell metaplasia at 6 month but not at 2 months post-infection. Gastric metaplasia coincided with the appearance of CD45⁺MHCII⁺CD11b⁺CD11c⁺ myeloid cells that were normally not present in the chronic gastritis at 2 months. The myeloid regulatory gene Schlafen-4 was identified in a microarray analysis comparing infected WT versus Gli1 null mice and was expressed in the CD11b⁺CD11c⁺ myeloid population. Moreover this same population expressed IL-1β and TNFα pro-inflammatory cytokines. By 6 months, the mucous neck cell metaplasia (SPEM) expressed IL-6, phosphorylated STAT3 and the proliferative marker Ki67. Expression was not observed in Gli1 mutant mice consistent with the requirement of Gli1 to induce this pre-neoplastic phenotype. Ectopic Shh ligand expression alone was not sufficient to induce SPEM, but with Helicobacter infection synergistically increased the histologic severity observed with the inflammation. Therefore Hedgehog signaling is required, but is not sufficient to generate pre-neoplastic changes during chronic gastritis. Gli1-dependent myeloid cell differentiation plays a pivotal role in the appearance of myeloid cell subtypes ostensibly required for SPEM development. Moreover, it suggests that therapies capable of targeting this phenotypic switch might prevent progression to metaplasia, the pre-neoplastic change that develops prior to dysplasia and gastric cancer, which also occurs in other epithelial-derived neoplasias initiated by chronic inflammation.

Hedgehog signaling displays a biphasic expression pattern during intestinal injury and repair

BACKGROUND/PURPOSE

Gastrointestinal injury is common clinically. The exact mechanism by which gastrointestinal repair occurs has yet to be well defined. Hedgehog (Hh) signaling is known to be involved in gastrointestinal development and repair of tissues such as skin and heart. The present study aimed to investigate the role of Hh in the repair of the small intestine.

METHODS

i) To study acute intestinal injury, we optimized a mouse model of 5-flurouracil (5-FU) induced injury of the small intestine. Ileal tissues were evaluated for injury and repair markers at day 0, 2, 5, and 9. ii) Immunohistochemistry (Sonic hedgehog, Shh), in situ hybridization (Shh), and Ptch/LacZ transgenic mice were carried out to localize hedgehog expression. A33CrPr × ShhTg knock-in mice were bred to study the effect of Shh over-expression. qPCR of Shh, Ihh, Ptch, Bmp4 was carried out to quantify hedgehog signaling. iii) 5FU treated mice were then treated with a hedgehog inhibitor or saline (control) and the effects of Shh inhibition including apoptosis, proliferation, and mitosis were then compared.

RESULTS

i) Immunohistochemistry and in situ hybridization of Shh, qPCR of hedgehog signaling pathway genes, and Ptch/LacZ staining results consistently showed down-regulation during the injury phase (P<0.05) followed by up-regulation during the repair phase (P<0.005). ii) Hh signaling inhibition following 5-FU induced injury augmented apoptotic activity (P<0.05), suppressed mitotic activity (P<0.005) in intestinal crypts, and reduced Paneth cell hyperplasia (P<0.005). iii) Shh over-expression in conditionally knock-mice led to increased mitotic, Paneth, and goblet cells.

CONCLUSION

Hedgehog signaling pathway displays a biphasic expression pattern during the injury/repair of small intestine. It may play an important regulatory role in intestinal repair.

Usefulness of endoscopic brushing and magnified endoscopy with narrow band imaging (ME-NBI) to detect intestinal phenotype in columnar-lined esophagus

BACKGROUND

Barrett's esophagus with specialized intestinal metaplasia (SIM), which is at high risk of progressing to esophageal adenocarcinoma, has been identified by obtaining biopsy specimens randomly. Magnified endoscopy with narrow band imaging (ME-NBI) is reported to be useful for detecting SIM or the intestinal phenotype. We aimed to evaluate the usefulness of endoscopic brushing followed by ME-NBI for the detection of the intestinal phenotype.

METHODS

Biopsy and brushing samples were taken following endoscopic observation by ME-NBI. Total RNA was extracted from the whole sample and microdissected samples, and quantitative reverse transcription-polymerase chain reaction (PCR) analysis of SHH, CDX2, and mucin mRNA expression was performed.

RESULTS

Fifty patients (32 men, 18 women, average age 67.3 years) with metaplastic columnar epithelium of the lower esophagus were studied. MUC2 (85 vs. 65 %) and CDX2 (95 vs. 75 %) were detected more frequently in the brushing samples than in the biopsy samples. MUC2 expression levels were significantly higher in the brushing samples than those in the biopsy samples. CDX2 and MUC2 expression levels in the brushing samples were significantly higher in the mucosa with tubular/villous pattern observed by ME-NBI than the levels in mucosae with other patterns.

CONCLUSIONS

Endoscopic brushing in mucosa of columnar epithelium with a tubular/villous pattern visualized by ME-NBI is useful to detect the intestinal phenotype.

ZIC1 modulates cell-cycle distributions and cell migration through regulation of sonic hedgehog, PI(3)K and MAPK signaling pathways in gastric cancer

Background

ZIC1, a vital transcription factor with zinc finger domains, has been implicated in the process of neural development. We previously showed that ZIC1 may function as a tumour suppressor in gastrointestinal cancers. However, the molecular mechanism underlying ZIC1 participation in tumour progression remains unknown.

Methods

The role of ZIC1 on cell proliferation and migration was examined. The regulation of sonic hedgehog (Shh), phosphoinositide 3-kinase (PI₃K) and mitogen-activated protein kinase (MAPK) signaling pathways after ectopic expression of ZIC1 in gastric cancer cells were evaluated.

Results

Overexpression of ZIC1 contributes to the inhibition of cell proliferation migration and cell-cycle distribution in gastric cancer. The modulation of G1/S checkpoint by ZIC1 is mainly mediated through the regulation of cyclin-dependent kinases (p21 ^Waf1/Cip1, p27 ^Kip1 and cyclin D1). In addition, ZIC1 can inactivate the level of phospholated Akt and Erk1/2, and transcriptionally regulate sonic hedgehog (Shh) signaling, thus leading to regulate the expression of p21 ^Waf1/Cip1 and cyclin D1. Finally, we have systemically identified ZIC1 downstream targets by cDNA microarray analysis and revealed that 132 genes are down-regulated and 66 genes are up-regulated after transfection with ZIC1 in gastric cancer cells. These candidate genes play critical roles in cell proliferation, cell cycle and cell motility.

Conclusions

Overexpression of ZIC1 results in inactivation of Shh, PI₃K and MAPK signaling pathways, as well as regulation of multiple downstream targets which are essential for the development and progression of gastric cancer. ZIC1 serves as a potential therapeutic target for gastric cancer.

Eradication of H. pylori did not improve abnormal sonic hedgehog expression in the high risk group for gastric cancer

BACKGROUND

Sonic hedgehog (SHH) acts as a proliferation factor in both the normal mucosa and in malignant lesions. Helicobacter pylori-associated atrophic gastritis is characterized by loss of SHH.

AIM

The purpose of this study was to investigate the effects of H. pylori eradication on SHH mRNA and methylation levels in the patients at high risk for gastric cancer comparing to those in the controls.

METHODS

Gastric corpus biopsies taken from 20 patients with endoscopic resection for early gastric cancer and 14 sex- and age-matched controls before and 1 year after eradication were examined for SHH and downstream regulators mRNA expression using whole biopsy specimens and microdissected gastric glands. Methylation of SHH promoter was evaluated using quantitative methylation-specific PCR.

RESULTS

SHH mRNA levels eradication were significantly lower (2.75 × 10(-2) vs. 7.37 × 10(-2), P = 0.004) in the cancer group than in the controls. PTCH and BMP4 mRNA levels as well as MUC5AC were significantly increased only in the control group and were significantly higher in the controls than those in the cancer group after eradication. After eradication, SHH methylation levels in the non-metaplastic glands were significantly higher (86.4% vs. 22.2%, P < 0.001) in the cancer group than in the controls.

CONCLUSIONS

H. pylori eradication can enhance SHH and its downstream regulators expression diminishing SHH methylation and reverse gastric phenotype, but not in the patients with high risk for gastric cancer.

E. coli-produced BMP-2 as a chemopreventive strategy for colon cancer: a proof-of-concept study

Colon cancer is a serious health problem, and novel preventive and therapeutical avenues are urgently called for. Delivery of proteins with anticancer activity through genetically modified bacteria provides an interesting, potentially specific, economic and effective approach here. Interestingly, bone morphogenetic protein 2 (BMP-2) is an important and powerful tumour suppressor in the colon and is thus an attractive candidate protein for delivery through genetically modified bacteria. It has not been shown, however, that BMP production in the bacterial context is effective on colon cancer cells. Here we demonstrate that transforming E. coli with a cDNA encoding an ileal-derived mature human BMP-2 induces effective apoptosis in an in vitro model system for colorectal cancer, whereas the maternal organism was not effective in this respect. Furthermore, these effects were sensitive to cotreatment with the BMP inhibitor Noggin. We propose that prevention and treatment of colorectal cancer using transgenic bacteria is feasible.

The role of Sonic Hedgehog as a regulator of gastric function and differentiation

The Hedgehog (Hh) genes play a key role in the regulation of embryonic development and govern processes such as cell differentiation, cell proliferation, and tissue patterning. In vertebrate embryos, Hh gene expression regulates correct formation of limbs, skeleton, muscles, and organs including stomach. In the adult, the Hh pathway functions in tissue repair and regeneration, along with maintenance of stem cells. Sonic Hedgehog (Shh) signaling has been extensively studied for its role in developmental and cancer biology. Recent advances in the field of gastroenterology show that in the stomach, Shh is responsible for proper differentiation of the gastric glands. The aberrant activity of the Shh signaling pathway leads to an altered gastric differentiation program and loss of gastric acid secretion that is the predominant function of the stomach. In this chapter, we review the most recent findings that reveal the role of Shh as a regulator of gastric function and differentiation and how this signaling is dysregulated during the development of gastric cancer in response bacterial infection.

Myofibroblast-derived PDGF-BB promotes Hedgehog survival signaling in cholangiocarcinoma cells

Cholangiocarcinoma (CCA) cells paradoxically express the death ligand, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and, therefore, are dependent upon potent survival signals to circumvent TRAIL cytotoxicity. CCAs are also highly desmoplastic cancers with a tumor microenvironment rich in myofibroblasts (MFBs). Herein, we examine a role for MFB-derived CCA survival signals. We employed human KMCH-1, KMBC, HuCCT-1, TFK-1, and Mz-ChA-1 CCA cells, as well as human primary hepatic stellate and myofibroblastic LX-2 cells, for these studies. In vivo experiments were conducted using a syngeneic rat orthotopic CCA model. Coculturing CCA cells with myofibroblastic human primary hepatic stellate cells or LX-2 cells significantly decreased TRAIL-induced apoptosis in CCA cells, a cytoprotective effect abrogated by neutralizing platelet-derived growth factor (PDGF)-BB antiserum. Cytoprotection by PDGF-BB was dependent upon Hedgehog (Hh) signaling, because it was abolished by the smoothened (SMO; the transducer of Hh signaling) inhibitor, cyclopamine. PDGF-BB induced cyclic adenosine monophosphate-dependent protein kinase-dependent trafficking of SMO to the plasma membrane, resulting in glioma-associated oncogene (GLI)2 nuclear translocation and activation of a consensus GLI reporter gene-based luciferase assay. A genome-wide messenger RNA expression analysis identified 67 target genes to be commonly up- (50 genes) or down-regulated (17 genes) by both Sonic hedgehog and PDGF-BB in a cyclopamine-dependent manner in CCA cells. Finally, in a rodent CCA in vivo model, cyclopamine administration increased apoptosis in CCA cells, resulting in tumor suppression.

CONCLUSIONS

MFB-derived PDGF-BB protects CCA cells from TRAIL cytotoxicity by a Hh-signaling-dependent process. These results have therapeutical implications for the treatment of human CCA.

Bone morphogenetic protein-2 and -4 play tumor suppressive roles in human diffuse-type gastric carcinoma

A relationship exists between defects in bone morphogenetic protein (BMP) signaling and formation of hamartoma and adenoma in the gastric epithelium; however, the role of BMP signaling in the progression of diffuse-type gastric carcinoma remains unknown. We investigated whether BMP functions as a tumor suppressor in human diffuse-type gastric carcinoma using three different human diffuse-type gastric carcinoma cell lines (OCUM-12, HSC-39, and OCUM-2MLN). Overexpression of the dominant-negative form of BMP-2/4-specific type I receptor (ALK-3) in OCUM-12 and HSC-39 cells accelerated their growth in vivo. BMP-4 induced cell cycle arrest in these cells via p21 induction through the SMAD pathway. Moreover, overexpression of the constitutively active form of ALK-3 in HSC-39 and OCUM-2MLN cells suppressed the proliferation of these cells in vitro and in vivo. Our findings suggest that BMP-2 and BMP-4 function as potent tumor suppressors in diffuse-type gastric carcinoma.

Gastric epithelial cell modality and proton pump inhibitor

Proton pump inhibitors (PPIs) are now commonly used for the treatment of acid related diseases such as peptic ulcer and reflux esophagitis. Because of their ability to produce direct inhibition of the proton pump, PPIs provide more sustained increase of the gastric pH than H(2)-receptor (H(2)R) antagonists. Diverse reports have been published on gastric epithelial cell modality associated with PPI treatment both in animal models and clinical settings. The present review summarizes the recent accumulated evidence on gastric epithelial cell modality associated with PPI treatment, including the formation of gastric carcinoid tumors and fundic gland polyps, and the development of gastric mucosal atrophy. Long-term PPI treatment has been reported to cause enlargement of the parietal cells and enterochromaffin-like cells, and to decrease the number of chief cells without affecting A-like cell. Although the development of gastric carcinoid tumors after chronic PPI treatment has been reported in animal studies, no such occurrences have been demonstrated in humans. The effect of PPIs on the formation of fundic gland polyps and the development of atrophic gastritis should be investigated in future studies.

Manifestation of spontaneous and early autoimmune gastritis in CCR7-deficient mice

Autoimmune gastritis is a common autoimmune disorder characterized by chronic inflammatory cell infiltrates, atrophy of the corpus and fundus, and the occurrence of autoantibodies to parietal cell antigen. In CCR7-deficient mice, autoimmune gastritis developed spontaneously and was accompanied by metaplasia of the gastric mucosa and by the formation of tertiary lymphoid organs at gastric mucosal sites. T cells of CCR7-deficient mice showed an activated phenotype in the gastric mucosa, mesenteric lymph nodes, and peripheral blood. In addition, elevated serum IgG levels specific to gastric parietal cell antigen were detected. Because the role of organized lymphocytic aggregates at this inflammatory site is not completely understood, we first analyzed the cellular requirements for the formation of these structures. Autoreactive CD4(+) T cells were pivotal for tertiary lymphoid follicle formation, most likely in cooperation with dendritic cells, macrophages, and B cells. Second, we analyzed the necessity of secondary lymph nodes and tertiary lymphoid organs for the development of autoimmune gastritis using CCR7 single- and CCR7/lymphotoxin α double-deficient mice. Strikingly, manifestation of autoimmune gastritis was observed in the absence of secondary lymph nodes and preceded the development of tertiary lymphoid organs. Taken together, these findings identify an inflammatory process where gastric autoreactive T cells independent of organized tertiary lymphoid organs and classic lymph nodes can induce and maintain autoimmune gastritis.

Expression of bone morphogenic protein-4 is inversely related to prevalence of lymph node metastasis in gastric adenocarcinoma

PURPOSE

Bone morphogenic proteins (BMPs) are the largest subfamily of the transforming growth factor-β superfamily. Initially characterized as factors that induce bone and cartilage formation, BMPs have been found to be critical during mesoderm formation, organogenesis, and cellular differentiation. Bone morphogenic proteins are also known to modulate the morphologic alteration, adhesion, motility, and invasion of carcinoma cells derived from several organs. However, BMP-4 expression in gastric adenocarcinoma has not yet been clarified. We conducted the present study to define the clinical significance of BMP-4 expression in gastric carcinoma.

METHODS

Using immunohistochemistry, we investigated the expression of BMP-4 in normal mucosae and gastric adenocarcinoma samples from 64 patients with gastric carcinoma.

RESULTS

The expression of BMP-4 was significantly higher in the adenocarcinoma than in the normal mucosae. Moreover, increased BMP-4 expression was associated with the presence of Helicobacter pylori infection. By contrast, the BMP-4 expression rate in gastric carcinoma was inversely related to the prevalence of lymph node metastasis and tumor invasiveness.

CONCLUSIONS

The findings of this study suggest that BMP-4 expression may be a useful prognostic factor for predicting the outcome of patients with gastric carcinoma. Continued investigation to define the pathophysiologic mechanism underlying the role of BMP-4 in gastric carcinoma is warranted.

The adult Drosophila gastric and stomach organs are maintained by a multipotent stem cell pool at the foregut/midgut junction in the cardia (proventriculus)

Stomach cancer is the second most frequent cause of cancer-related death worldwide. Thus, it is important to elucidate the properties of gastric stem cells, including their regulation and transformation. To date, such stem cells have not been identified in Drosophila. Here, using clonal analysis and molecular marker labeling, we identify a multipotent stem-cell pool at the foregut/midgut junction in the cardia (proventriculus). We found that daughter cells migrate upward either to anterior midgut or downward to esophagus and crop. The cardia functions as a gastric valve and the anterior midgut and crop together function as a stomach in Drosophila; therefore, we named the foregut/midgut stem cells as gastric stem cells (GaSC). We further found that JAK-STAT signaling regulates GaSCs' proliferation, Wingless signaling regulates GaSCs' self-renewal, and hedgehog signaling regulates GaSCs' differentiation. The differentiation pattern and genetic control of the Drosophila GaSCs suggest the possible similarity to mouse gastric stem cells. The identification of the multipotent stem cell pool in the gastric gland in Drosophila will facilitate studies of gastric stem cell regulation and transformation in mammal.

Bone morphogenetic protein signaling regulates gastric epithelial cell development and proliferation in mice

BACKGROUND & AIMS

We investigated the role of bone morphogenetic protein (BMP) signaling in the regulation of gastric epithelial cell growth and differentiation by generating transgenic mice that express the BMP inhibitor noggin in the stomach.

METHODS

The promoter of the mouse H+/K+-ATPase β-subunit gene, which is specifically expressed in parietal cells, was used to regulate expression of noggin in the gastric epithelium of mice. The transgenic mice were analyzed for noggin expression, tissue morphology, cellular composition of the gastric mucosa, gastric acid content, and plasma levels of gastrin. Tissues were analyzed by immunohistochemical, quantitative real-time polymerase chain reaction, immunoblot, microtitration, and radioimmunoassay analyses.

RESULTS

In the stomachs of the transgenic mice, phosphorylation of Smad 1, 5, and 8 decreased, indicating inhibition of BMP signaling. Mucosa were of increased height, with dilated glands, cystic structures, reduced numbers of parietal cells, and increased numbers of cells that coexpressed intrinsic factor, trefoil factor 2, and Griffonia (Bandeiraea) simplicifolia lectin II, compared with wild-type mice. In the transgenic mice, levels of the H+/K+-ATPase α-subunit protein and messenger RNA were reduced, whereas those of intrinsic factor increased. The transgenic mice were hypochloridric and had an increased number of Ki67- and proliferating cell nuclear antigen-positive cells; increased levels of plasma gastrin; increased expression of transforming growth factor-α, amphiregulin, and gastrin; and activation of extracellular signal-regulated kinase 2.

CONCLUSIONS

Inhibiting BMP signaling in the stomachs of mice by expression of noggin causes loss of parietal cells, development of transitional cells that express markers of mucus neck and zymogenic lineages, and activation of proliferation. BMPs are therefore important regulators of gastric epithelial cell homeostasis.

Intracellular calcium release and protein kinase C activation stimulate sonic hedgehog gene expression during gastric acid secretion

BACKGROUND & AIMS

Hypochlorhydria during Helicobacter pylori infection inhibits gastric Sonic Hedgehog (Shh) expression. We investigated whether acid-secretory mechanisms regulate Shh gene expression through intracellular calcium (Ca2(+)(i))-dependent protein kinase C (PKC) or cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) activation.

METHODS

We blocked Hedgehog signaling by transgenically overexpressing a secreted form of the Hedgehog interacting protein-1, a natural inhibitor of hedgehog ligands, which induced hypochlorhydria. Gadolinium, ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) + 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), PKC-overexpressing adenoviruses, and PKC inhibitors were used to modulate Ca(2+)(i)-release, PKC activity, and Shh gene expression in primary gastric cell, organ, and AGS cell line cultures. PKA hyperactivity was induced in the H(+)/K(+)-β-cholera-toxin-overexpressing mice.

RESULTS

Mice that expressed secreted hedgehog-interacting protein-1 had lower levels of gastric acid (hypochlorhydria), reduced production of somatostatin, and increased gastrin gene expression. Hypochlorhydria in these mice repressed Shh gene expression, similar to the levels obtained with omeprazole treatment of wild-type mice. However, Shh expression also was repressed in the hyperchlorhydric H(+)/K(+)-β-cholera-toxin model with increased cAMP, suggesting that the regulation of Shh was not solely acid-dependent, but pertained to specific acid-stimulatory signaling pathways. Based on previous reports that Ca(2+)(i) release also stimulates acid secretion in parietal cells, we showed that gadolinium-, thapsigargin-, and carbachol-mediated release of Ca(2+)(i) induced Shh expression. Ca(2+)-chelation with BAPTA + EGTA reduced Shh expression. Overexpression of PKC-α, -β, and -δ (but not PKC-ϵ) induced an Shh gene expression. In addition, phorbol esters induced a Shh-regulated reporter gene.

CONCLUSIONS

Secretagogues that stimulate gastric acid secretion induce Shh gene expression through increased Ca(2+)(i)-release and PKC activation. Shh might be the ligand transducing changes in gastric acidity to the regulation of G-cell secretion of gastrin.

Acid suppression by proton pump inhibitors enhances aquaporin-4 and KCNQ1 expression in gastric fundic parietal cells in mouse

BACKGROUND

The widespread use of proton pump inhibitors (PPIs) is known to cause sporadic gastric fundic gland polyps (FGPs). Altered expression and localization of the water or ion transport proteins might contribute to the excess fluid secretion into the cystic lumen for the development of FGPs.

AIMS

We investigated the alteration of the murine gastric fundic mucosa after PPI treatment, and examined the expression of water channel aquaporin-4 (AQP4) and potassium channel KCNQ1, which are expressed only in the parietal cells in the gastric mucosa.

METHODS

Male 5-week-old C57BL/6J mice were administered lansoprazole (LPZ) by subcutaneous injection for 8 weeks. The expression of AQP4 and KCNQ1 were investigated by Western blotting, quantitative RT-PCR, and immunohistochemistry. The expression of mucin-6 (Muc6), pepsinogen, and sonic hedgehog (Shh) were also investigated as mucosal cell lineage markers.

RESULTS

Gastric mucosal hyperplasia with multiple cystic dilatations, exhibiting similar histological findings to the FGPs, was observed in the LPZ-treated mice. An increase in the number of AQP4-positive parietal cells and KCNQ1-positive parietal cells was observed. The extension of the distribution of AQP4-positive cells toward the surface of the fundic glands was also observed. The expression levels of AQP4 mRNA and protein were significantly enhanced. The expression of KCNQ1 mRNA was correlated with that of AQP4 mRNA in the LPZ-treated mice. Mucous neck-to-zymogenic cell lineage differentiation was delayed in association with decreased expression of Shh in the LPZ-treated mice.

CONCLUSIONS

PPI administration increased the number of parietal cells with enhanced expression of AQP4 and KCNQ1.

Identification of signature genes for detecting hedgehog signaling activation in gastric cancer

The aim of this study was to investigate the expression of hedgehog signaling molecules in gastric cancer. In situ hybridization, immunohistochemistry and RT-PCR for hedgehog signaling molecules, smoothened (SMO), suppressor of fused [Su(Fu)], and the target genes hedgehog-interacting protein (HIP) and platelet-derived growth factor receptor α (PDGFRα) were performed in 30 gastric cancer and two gastritis specimens. Using in situ hybridization, SMO expression was detected in 18/30 cancerous specimens (60%) as well as in 1/2 gastritis specimens (50%). Su(Fu) was expressed in 15/30 (50%), HIP in 14/30 (≈47%), and PDGFRα in 6/30 (20%) gastric cancer specimens. Despite the heterogeneous expression pattern, SMO, Su(Fu) and PDGFRα transcripts were highly correlated with the HIP transcript in the 30 gastric cancer specimens (p=0.0006, 0.0003 and 0.0441, respectively). Results from the in situ hybridization were further confirmed by RT-PCR for the expression of all of the genes and by immunohistochemistry for SMO expression. The findings revealed a set of genes for detecting Hh signaling activation in gastric cancer.

Aberrant epithelial-mesenchymal Hedgehog signaling characterizes Barrett's metaplasia

BACKGROUND & AIMS

The molecular mechanism underlying epithelial metaplasia in Barrett's esophagus remains unknown. Recognizing that Hedgehog signaling is required for early esophageal development, we sought to determine if the Hedgehog pathway is reactivated in Barrett's esophagus, and if genes downstream of the pathway could promote columnar differentiation of esophageal epithelium.

METHODS

Immunohistochemistry, immunofluorescence, and quantitative real-time polymerase chain reaction were used to analyze clinical specimens, human esophageal cell lines, and mouse esophagi. Human esophageal squamous epithelial (HET-1A) and adenocarcinoma (OE33) cells were subjected to acid treatment and used in transfection experiments. Swiss Webster mice were used in a surgical model of bile reflux injury. An in vivo transplant culture system was created using esophageal epithelium from Sonic hedgehog transgenic mice.

RESULTS

Marked up-regulation of Hedgehog ligand expression, which can be induced by acid or bile exposure, occurs frequently in Barrett's epithelium and is associated with stromal expression of the Hedgehog target genes PTCH1 and BMP4. BMP4 signaling induces expression of SOX9, an intestinal crypt transcription factor, which is highly expressed in Barrett's epithelium. We further show that expression of Deleted in Malignant Brain Tumors 1, the human homologue of the columnar cell factor Hensin, occurs in Barrett's epithelium and is induced by SOX9. Finally, transgenic expression of Sonic hedgehog in mouse esophageal epithelium induces expression of stromal Bmp4, epithelial Sox9, and columnar cytokeratins.

CONCLUSIONS

Epithelial Hedgehog ligand expression may contribute to the initiation of Barrett's esophagus through induction of stromal BMP4, which triggers reprogramming of esophageal epithelium in favor of a columnar phenotype.

Direct repression of Sonic Hedgehog expression in the stomach by Cdx2 leads to intestinal transformation

Shh (Sonic Hedgehog) is a morphogen involved in gastric fundic gland differentiation in the adult. Shh expression is reduced in Helicobacter pylori-associated intestinal metaplastic change of the gastric epithelium and mice that lack Shh show intestinal transformation of the gastric mucosa. Similarly, in the stomach of Cdx2 (caudal-type homeobox 2)-transgenic mice, the gastric mucosa is replaced by intestinal metaplastic mucosa. The aim of the present study was to use Cdx2-transgenic mice to investigate: (i) Shh expression in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach; and (ii) the relationship between Shh and Cdx2. We determined that Shh mRNA levels were dramatically reduced in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach compared with the normal (wild-type) mouse stomach. This was not due to hypermethylation of the Shh promoter, but instead we showed that Cdx2 directly bound to the TATA box region of the Shh promoter. Cdx2 also down-regulated transcription of the Shh gene in the human gastric carcinoma cell lines AGS, MKN45 and MKN74. In conclusion, Cdx2 reduced Shh expression by binding to the unmethylated Shh promoter in the intestinal metaplastic mucosa of Cdx2-transgenic mouse stomach.

Hedgehog signaling and gastrointestinal cancer

Hedgehog (Hh) signaling is critical for embryonic development and in differentiation, proliferation, and maintenance of multiple adult tissues. De-regulation of the Hh pathway is associated with birth defects and cancer. In the gastrointestinal tract, Hh ligands Sonic (Shh) and Indian (Ihh), as well as the receptor Patched (Ptch1), and transcription factors of Glioblastoma family (Gli) are all expressed during development. In the adult, Shh expression is restricted to the stomach and colon, while Ihh expression occurs throughout the luminal gastrointestinal tract, its expression being highest in the proximal duodenum. Several studies have demonstrated a requirement for Hh signaling during gastrointestinal tract development. However to date, the specific role of the Hh pathway in the adult stomach and intestine is not completely understood. The current review will place into context the implications of recent published data related to the biochemistry and cell biology of Hh signaling on the luminal gastrointestinal tract during development, normal physiology and subsequently carcinogenesis.

Gastric carcinogenesis and the cancer stem cell hypothesis

Normal stem cells (NSCs) are reported to exist in most tissues, including the brain, bone marrow, and probably the gastrointestinal tract. In the latter case, they are thought to possess both the self-renewal capacity and asymmetrical division capacity to generate progenitor cells which differentiate into epithelial cells. NSCs in the normal gastric mucosa are thought to be present in the proliferative zone of the neck/isthmus region, and to undergo a complex bipolar migration from the neck/isthmus region either upward or downward, becoming differentiated normal epithelial cells. NSCs in human gastric mucosa are difficult to identify due to the current lack of a useful marker. A precise definition of cancer stem cells (CSCs) is still under discussion. CSCs are generally defined as malignant cells with NSC capacity. However, many studies of CSCs have demonstrated their rapid growth and high metastatic potential, while NSCs are thought to be slow-growing and self-renewing, and to lack functional capacities such as cell migration and attachment. Recent evidence suggests the existence of CSCs in a wide variety of solid tumors. In this review, we will discuss the existence and cell biology of gastric NSCs and CSCs. We will also discuss whether gastric CSCs originate as organ-specific stem cells or as bone marrow-derived cells (BMDCs). Under certain conditions, the local microenvironment may promote the development of gastric cancer. Thus, Helicobacter pylori infection and the accompanying chronic inflammatory processes will supply critical initiators inducing cell growth and the tissue repair response, leading to carcinogenesis. This mechanism will be discussed in light of stem cell research. Progress in stem cell research in the gastric field is still limited to experimental animal models. However, recent studies should enhance our understanding of human cancer biology, and provide novel tools for the treatment of incurable gastric cancer.

Interleukin-1beta promotes gastric atrophy through suppression of Sonic Hedgehog

BACKGROUND & AIMS

In both human subjects and rodent models, Helicobacter infection leads to a decrease in Shh expression in the stomach. Sonic Hedgehog (Shh) is highly expressed in the gastric corpus and its loss correlates with gastric atrophy. Therefore, we tested the hypothesis that proinflammatory cytokines induce gastric atrophy by inhibiting Shh expression.

METHODS

Shh-LacZ reporter mice were infected with Helicobacter felis for 3 and 8 weeks. Changes in Shh expression were monitored using beta-galactosidase staining and immunohistochemistry. Gastric acidity was measured after infection, and interleukin (IL)-1beta was quantified by quantitative reverse-transcription polymerase chain reaction. Mice were injected with either IL-1beta or omeprazole before measuring Shh mRNA expression and acid secretion. Organ cultures of gastric glands from wild-type or IL-1R1 null mice were treated with IL-1beta then Shh expression was measured. Primary canine parietal or mucous cells were treated with IL-1beta. Shh protein was determined by immunoblot analysis. Changes in intracellular calcium were measured by Fura-2.

RESULTS

All major cell lineages of the corpus including surface pit, mucous neck, zymogenic, and parietal cells expressed Shh. Helicobacter infection reduced gastric acidity and inhibited Shh expression in parietal cells by 3 weeks. IL-1beta produced during Helicobacter infection inhibited gastric acid, intracellular calcium, and Shh expression through the IL-1 receptor. Suppression of parietal cell Shh expression by IL-1beta and omeprazole was additive. IL-1beta did not suppress Shh expression in primary gastric mucous cells.

CONCLUSIONS

IL-1beta suppresses Shh gene expression in parietal cells by inhibiting acid secretion and subsequently the release of intracellular calcium.

Oestrogen receptor-alpha contributes to the regulation of the hedgehog signalling pathway in ERalpha-positive gastric cancer

BACKGROUND

Oestrogen receptor-alpha (ERalpha) is highly expressed in diffuse-type gastric cancer and oestrogen increases the proliferation of ERalpha-positive gastric cancer. However, a detailed mechanism by which oestrogen increases the proliferation of these cells is still unclear.

METHODS

We used 17-beta-oestradiol (E2) as a stimulator against the ERalpha pathway. Pure anti-oestrogen drug ICI 182 780 (ICI) and small interfering RNA against ERalpha (ERalpha siRNA) were used as inhibitors. Cyclopamine (Cyc) was used as the hedgehog (Hh) pathway inhibitor. Two human ERalpha-positive gastric cancer cells were used as target cells. Effects of the stimulator and inhibitor on E2-induced cell proliferation were also examined.

RESULTS

In ERalpha-positive cells, E2 increased not only cell proliferation but also one of the ligands of the Hh pathway, Shh expression. 17-beta-Oestradiol-induced cell proliferation was suppressed by ICI, ERalpha siRNA or Cyc. The increased expression of Shh induced by E2 was suppressed by ICI and ERalpha siRNA but not by Cyc. Furthermore, recombinant Shh activated the Hh pathway and increased cell proliferation, whereas anti-Shh antibody suppressed E2-induced cell proliferation. When a relationship between ERalpha and Shh expressions was analysed using surgically resected gastric cancer specimens, a positive correlation was found, suggesting a linkage between the ERalpha and Hh pathways.

CONCLUSION

Our data indicate that activation of the ERalpha pathway promotes cell proliferation by activating the Hh pathway in a ligand-dependent manner through Shh induction of ERalpha-positive gastric cancer.

Hedgehog signaling in gastric physiology and cancer

The Hedgehog family of ligands was originally identified in mutagenesis screens of Drosophila embryos. Hedgehog signaling in multiple tissues is important during embryonic development. A common theme regarding Hedgehog expression in adult tissues is that tissue injury reactivates the developmental pattern of expression. In most instances, this appears to be important to initiate tissue repair. In the gastrointestinal (GI) tract, where epithelial cells are constantly replenished from progenitor populations, Hedgehog signaling also appears to be essential for regeneration. By contrast, reactivated Hedgehog signaling in adult tissues does not automatically predispose the tissue to transformation, but instead requires sustained tissue injury in the form of chronic inflammation. In this chapter, we review what is known about Hedgehog ligands and signaling during development of relevant organs, and discuss how the patterns of Hedgehog regulation are recapitulated in the GI tract during embryogenesis, adult homeostasis, and neoplastic transformation.

The gastric mucosa development and differentiation

The development and differentiation of the gastric mucosa are controlled by a complex interplay of signaling proteins and transcriptional regulators. This process is complicated by the fact that the stomach is derived from two germ layers, the endoderm and the mesoderm, with the first giving rise to the mature epithelium and the latter contributing the smooth muscle required for peristalsis. Reciprocal epithelial-mesenchymal interactions dictate the formation of the stomach during fetal development, and also contribute to its continuous regeneration and differentiation throughout adult life. In this chapter, we discuss the discoveries that have been made in different model systems, from zebrafish to human, which show that the Hedgehog, Wnt, Notch, bone morphogenetic protein, and fibroblast growth factor (FGF) signaling systems play essential roles during various stages of stomach development.

Identification of a bone marrow-derived mesenchymal progenitor cell subset that can contribute to the gastric epithelium

Recent studies with Helicobacter-infected mice have shown that bone marrow-derived cells can repopulate the gastric epithelium and progress to cancer. However, it has not been established which cellular subset can potentially contribute to the epithelium. The aim of this study was to investigate the ability of bone marrow-derived mesenchymal stem cells (MSCs) that express cytokeratin 19 (K19) to contribute to the gastric epithelium. MSCs cultures were established from whole bone marrow and expression of K19 was detected in a minority (1 of 13) of clones by real-time PCR and immunostaining. Transfection of a K19-green fluorescent protein (GFP) vector and isolation of GFP-expressing colonies generated high K19-expressing MSC clones (K19GFPMSC). Incubation of MSCs with gastric tissue extract markedly induced mRNA expression of gastric phenotypic markers and was observed to a greater extent in K19GFPMSCs compared with parental MSCs and mock transfectants. Both K19GFPMSCs and GFP-labeled control MSCs gave rise to gastric epithelial cells after injection into the murine stomach. In addition, after blastocyst injections, K19GFPMSCs gave rise to GFP-positive gastric epithelial cells in all 13 pups, whereas only 3 of 10 offspring showed GFP-positive gastric epithelial cells after injection of GFP-labeled control MSCs. Although K19 expression could not be detected in murine whole bone marrow, H. felis infection increased K19-expressing MSCs in the circulation. Taken together, our results show that bone marrow-derived MSCs can contribute to the gastric epithelium. The K19-positive MSC fraction that is induced by chronic H. felis infection appears to be the important subset in this process.

BMP2 accelerates the motility and invasiveness of gastric cancer cells via activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway

Up-regulation of bone morphogenetic proteins (BMPs) and their receptors by tumor is an important hallmark in cancer progression, as it contributes through autocrine and paracrine mechanisms to tumor development, invasion, and metastasis. Generally, increased motility and invasion are positively correlated with the epithelial-mesenchymal transition (EMT). The purpose of the present study was to determine whether BMP-2 signaling to induce gastric cancer cells to undergo EMT-mediated invasion might pass through the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Herein we showed that gastric cancer cell lines express all the components of BMP-2 signaling, albeit to different extents. Moreover, an increased concentration of BMP-2 strongly enhanced motility and invasiveness in gastric cancer cells, whereas no increase was observed in cells treated with either Noggin (a BMP-2 inhibitor) or BMP-2 blocking antibodies. The stimulation of BMP-2 in gastric cancer cells induces a full EMT characterized by Snail induction, E-cadherin delocalization and down-regulation, and up-regulation of mesenchymal and invasiveness markers. Furthermore, blockade of BMP-2 signaling by Noggin or BMP-2 blocking antibodies also restored these changes in EMT markers. In addition, phosphorylation of Akt was also enhanced by treatment with BMP-2, but not Noggin or BMP-2 blocking antibodies. Pretreatment of gastric cancer cells with PI-3 kinase/Akt kinase inhibitor (kinase-dead Akt [DN-Akt], Akt siRNA, or LY294002) significantly inhibited BMP-2-induced EMT and invasiveness. Overall, our studies suggest that BMP-2 promotes motility and invasion of gastric cancer cells by activating PI-3 kinase/Akt and that targeting of this signaling pathway may provide therapeutic opportunities in preventing metastasis mediated by BMP-2.

Hedgehog and epithelial-mesenchymal transition signaling in normal and malignant epithelial cells of the esophagus

It has been established that the Hedgehog (Hh) and epithelial-mesenchymal transition (EMT) signals act on morphogenesis of embryonic and adult tissues. Recently, both signals have been involved in tumor malignancy. However, little is known as to whether Hh and EMT signals act on normal and malignant epithelial cells in the esophagus. By laser microdissection (LMD)-based microarray and reverse transcription polymerase chain reaction in the undifferentiated and differentiated epithelial cells of the esophagus, we compared the expression profiles of Hh and EMT signaling molecules of these cells with those of cancers. Whether and how both signalings act in undifferentiated cells and in cancer cells are investigated by treatment of a Hh-signal inhibitor and/or siRNAs of Hh and EMT transcriptional key regulator genes on a mouse primary culture and on human esophageal squamous cell carcinoma (ESCC) cell lines. Undifferentiated esophageal epithelial cells and most ESCCs coexpressed Hh and EMT signaling genes. Some mesenchymal-related genes were regulated by an EMT regulator SIP1/ZEB2/ZFHX1B, which was a downstream gene of a primary transcriptional transducer GLI1 in Hh signaling. Hh signal block inhibited esophageal keratinocyte differentiation and cancer cell invasion and growth. These findings suggest that the mesenchymal gene expression of undifferentiated cells is maintained or strengthened in cancer cells through Hh signaling. This is a first report showing the presence of crosstalk between Hh and EMT pathways.

Paracrine Hedgehog signaling in stomach and intestine: new roles for hedgehog in gastrointestinal patterning

BACKGROUND & AIMS

Hedgehog signaling is critical in gastrointestinal patterning. Mice deficient in Hedgehog signaling exhibit abnormalities that mirror deformities seen in the human VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, limb) association. However, the direction of Hedgehog signal flow is controversial and the cellular targets of Hedgehog signaling change with time during development. We profiled cellular Hedgehog response patterns from embryonic day 10.5 (E10.5) to adult in murine antrum, pyloric region, small intestine, and colon.

METHODS

Hedgehog signaling was profiled using Hedgehog pathway reporter mice and in situ hybridization. Cellular targets were identified by immunostaining. Ihh-overexpressing transgenic animals were generated and analyzed.

RESULTS

Hedgehog signaling is strictly paracrine from antrum to colon throughout embryonic and adult life. Novel findings include the following: mesothelial cells of the serosa transduce Hedgehog signals in fetal life; the hindgut epithelium expresses Ptch but not Gli1 at E10.5; the 2 layers of the muscularis externa respond differently to Hedgehog signals; organogenesis of the pyloric sphincter is associated with robust Hedgehog signaling; dramatically different Hedgehog responses characterize stomach and intestine at E16; and after birth, the muscularis mucosa and villus smooth muscle consist primarily of Hedgehog-responsive cells and Hh levels actively modulate villus core smooth muscle.

CONCLUSIONS

These studies reveal a previously unrecognized association of paracrine Hedgehog signaling with several gastrointestinal patterning events involving the serosa, pylorus, and villus smooth muscle. The results may have implications for several human anomalies and could potentially expand the spectrum of the human VACTERL association.

Late reactivation of sonic hedgehog by Helicobacter pylori results in population of gastric epithelial cells that are resistant to apoptosis: implication for gastric carcinogenesis

As much as that a disturbance of tissue homeostasis through dysregulated apoptosis is generally associated with carcinogenesis, gastric carcinogenesis after Helicobacter pylori infection could be the accumulated consequence of imbalances between apoptosis and proliferation. Since sonic hedgehog (Shh) has been reported to play versatile roles in various tumorigenesis, we hypothesized that late reactivation of sonic hedgehog by H. pylori infection results in population of gastric epithelial cells that are resistant to apoptosis. The Resistant Clones against H. pylori-induced Apoptosis (RCHA) were established and maintained up to 19th cell passages, during which the serial changes of Shh expression were measured. Apoptosis was measured in N-Shh over-expressed stable cell lines and compared with parent cell line after either infected with H. pylori or treated with cyclopamine. For clinical relevance, the expressions of Shh were compared in tissues from gastric adenoma or adenocarcinoma according to H. pylori infection. Longer passages of RCHA after H. pylori infection, the higher expressions of Shh, suggesting RCHA was associated with the reactivation of Shh. Significant decrement in subG1 phase of cell cycle and attenuated executions of apoptosis after H. pylori infection in cells of Shh overexpression, whereas either Shh siRNA or cyclopamine increased the H. pylori-induced cytotoxicity and significantly abrogated anti-apoptotic actions imposed by Shh. Significantly higher expressions of Shh were seen in H. pylori-associated gastric cancers than H. pylori-not associated gastric cancer. Late reactivation of sonic hedgehog by H. pylori infection results in population of gastric epithelial cells that are resistant to apoptosis and imposes proliferative changes under the background of atrophic gastritis, providing the carcinogenic basis.

Depletion of the colonic epithelial precursor cell compartment upon conditional activation of the hedgehog pathway

BACKGROUND & AIMS

The intestinal epithelium is a homeostatic system in which differentiated cells are in dynamic equilibrium with rapidly cycling precursor cells. Wnt signaling regulates intestinal epithelial precursor cell fate and proliferation. Homeostatic systems exist by virtue of negative feedback loops, and we have previously identified the Hedgehog (Hh) pathway as a potential negative feedback signal in the colonic epithelium. Indian hedgehog (Ihh) is produced by the differentiated enterocytes and negatively regulates Wnt signaling in intestinal precursor cells. We studied the role of members of the Hh signaling family in the intestine using a conditional genetic approach.

METHODS

We inactivated the Hh receptor Patched1 (Ptch1) in adult mice, resulting in constitutive activation of the Hh signaling pathway. Effects on colonic mucosal homeostasis were examined. Colon tissues were examined by immunohistochemistry, in situ hybridization, transmission electron microscopy, and real-time polymerase chain reaction.

RESULTS

Ihh but not Sonic hedgehog (Shh) was expressed in colonic epithelium. Expression of Ptch1 and Gli1 was restricted to the mesenchyme. Constitutive activation of Hh signaling resulted in accumulation of myofibroblasts and colonic crypt hypoplasia. A reduction in the number of epithelial precursor cells was observed with premature development into the enterocyte lineage and inhibition of Wnt signaling. Activation of Hh signaling resulted in induction of the expression of bone morphogenetic proteins (Bmp) and increased Bmp signaling in the epithelium.

CONCLUSIONS

Hh signaling acts in a negative feedback loop from differentiated cells via the mesenchyme to the colonic epithelial precursor cell compartment in the adult mouse.

Hedgehog signaling is essential for normal wound healing

The hedgehog family of morphogens (sonic [Shh], Indian, and desert hedgehog) are central regulators of embryologic growth and tissue patterning. Although recent work implicates Shh in postnatal tissue repair and development, conclusive evidence is lacking. Here, we demonstrated the importance of Shh in wound repair, by examining the effects of cyclopamine, a specific inhibitor of the Shh signaling cascade, on tissue repair. Using a murine-splinted excisional wound model, which attenuates wound contraction in this loose-skinned rodent, we established that, by all measures (wound closure, epithelialization, granulation formation, vascularity, and proliferation), wound healing was profoundly impaired when Shh signaling was disrupted. Because embryonic disruption of Shh is associated with distinct phenotypic defects, our findings invite investigation of the potential role of Shh signaling under postnatal conditions associated with disregulated wound healing.

Hedgehog signaling is involved in differentiation of normal colonic tissue rather than in tumor proliferation

The Hedgehog (Hh) pathway is a main regulation cascade in embryonic differentiation. It is also present in adult tissues and unusual expression has been associated with formation of benign and malignant lesions. We examined the presence of the Hedgehog pathway in normal and pathological human colon tissue. Components investigated include Sonic (Shh), Indian (Ihh), and Desert Hedgehog (Dhh), Gli1, Gli2, Gli3, and Patched (Ptch). Pathological tissue samples comprised 23 benign and 20 malignant lesions of human colon. The influence of the Hedgehog pathway on differentiation and proliferation has been investigated by analyzing the effect of the pathway inhibitor Cyclopamine on human colon cancer cell lines HT29 and CaCo2. In normal colon, we detected expression of Shh and Dhh within the lining epithelium and Patched, Gli1, and Gli2 along the whole crypts. Within all benign lesions, positive staining of Shh, Dhh, Gli1, Gli2, and Ptch was detected. Expression of Shh and Dhh was restricted to single cell aggregates. Malignant lesions also displayed focal staining pattern for Shh and Dhh but to a much lesser extent. We conclude that Hedgehog signaling is involved rather in constant differentiation and renewing of the colonic lining epithelium than in cancer formation, growth, or proliferation.

The role of hedgehog signaling during gastric regeneration

BACKGROUND

Hedgehog signaling plays critical roles during embryonic development. It is also involved in tissue regeneration and carcinogenesis in various adult tissues. Moreover, it regulates the maintenance of cancer stem cells and adult stem cells. Although hedgehog signaling is important in gastric carcinogenesis, its role in gastric regeneration has not been previously examined. In the present study, we evaluated the expression and roles of hedgehog signaling during gastric regeneration.

METHODS

Gastric ulcers were induced by serosal application of an acetic acid solution in mice. Sham-operated mice served as controls. The proliferation of gastric progenitor cells was studied using bromodeoxyuridine (BrdU). The expression of hedgehog signaling molecules and the differentiation of gastric progenitor cells were examined by immunohistochemical staining and Western blotting.

RESULTS

One day after the induction of gastric ulcer, the proliferation of gastric progenitor cells increased; however, the expression of hedgehog signaling molecules, including sonic hedgehog (Shh), Indian hedgehog (Ihh), desert hedgehog (Dhh), and patched (Ptch1) decreased at the ulcer margin. From 5 days after the induction of gastric ulcer, newly generated gastric glands and their differentiation were observed at the ulcer margin. The expression of hedgehog signaling molecules gradually increased in the newly generated gastric glands of the ulcer margin. Cyclopamine, a specific inhibitor of hedgehog signaling, significantly inhibited the differentiation of mucous cells and parietal cells during the gastric regeneration process.

CONCLUSION

The above results suggest that hedgehog signaling is involved in the differentiation of gastric progenitor cells during the gastric ulcer repair process.

Intestinal metaplasia: a premalignant lesion involved in gastric carcinogenesis

Despite a plateau in incidence, gastric cancer remains a significant problem globally. The majority of gastric cancer is associated with histologically recognizable premalignant stages as first described by Pelayo Correa in the mid-1970s. The mortality from gastric cancer remains high especially in Western countries where, arguably, the index of suspicion of gastric cancer in patients presenting with upper abdominal symptoms is lower than in high prevalence countries. What is the evidence that intestinal metaplasia (IM) is a premalignant condition? What should the clinician know about IM and the relative risks of progression to gastric cancer? Finally, what are the current and future strategies that may help stratify patients into high risk and low risk for the development of gastric cancer? This review focuses on gastric IM and outlines some of the literature that discusses it as a premalignant condition. It also reviews the issue of surveillance of patients with IM in order to attempt to reduce the significant mortality of gastric cancer by detection of earlier stages of disease which are eminently treatable.

Sonic hedgehog in gastric physiology and neoplastic transformation: friend or foe?

PURPOSE OF REVIEW

To understand the role of sonic hedgehog (Shh) in normal gastric physiology and neoplastic transformation.

RECENT FINDINGS

Emerging evidence shows that gastric epithelial cells produce Shh ligand, which subsequently targets the mesenchyme. This paracrine signaling event is recapitulated by Shh-producing tumors that signal to the supporting stroma to encourage growth. Primary cilia contain components of the hedgehog signaling apparatus, and thus are typically found on responding stromal cells.

SUMMARY

In the stomach, Shh is produced in epithelial cells and received by responding cells in the mesenchyme. In vitro, Shh enhances gastric acid secretion and induces mucin expression. It remains to be determined whether the canonical signaling pathway mediates the observed epithelial effects. Shh expression and signaling is reduced in chronic gastritis, and Shh(-/-) embryos exhibit hyperplasia and metaplastic changes in the gastric mucosa. After its loss in the corpus, Shh is re-expressed in some gastric carcinomas typically arising in the distal stomach or antrum, suggesting that it promotes tumor growth.

The gastric epithelial progenitor cell niche and differentiation of the zymogenic (chief) cell lineage

In the mammalian gastrointestinal tract, the cell fate decisions that specify the development of multiple, diverse lineages are governed in large part by interactions of stem and early lineage progenitor cells with their microenvironment, or niche. Here, we show that the gastric parietal cell (PC) is a key cellular component of the previously undescribed niche for the gastric epithelial neck cell, the progenitor of the digestive enzyme secreting zymogenic (chief) cell (ZC). Genetic ablation of PCs led to failed patterning of the entire zymogenic lineage: progenitors showed premature expression of differentiated cell markers, and fully differentiated ZCs failed to develop. We developed a separate mouse model in which PCs localized not only to the progenitor niche, but also ectopically to the gastric unit base, which is normally occupied by terminally differentiated ZCs. Surprisingly, these mislocalized PCs did not maintain adjacent zymogenic lineage cells in the progenitor state, demonstrating that PCs, though necessary, are not sufficient to define the progenitor niche. We induced this PC mislocalization by knocking out the cytoskeleton-regulating gene Cd2ap in Mist1(-/-) mice, which led to aberrant E-cadherin localization in ZCs, irregular ZC-ZC junctions, and disruption of the ZC monolayer by PCs. Thus, the characteristic histology of the gastric unit, with PCs in the middle and ZCs in the base, may depend on establishment of an ordered adherens junction network in ZCs as they migrate into the base.

Cross talk between hedgehog and epithelial-mesenchymal transition pathways in gastric pit cells and in diffuse-type gastric cancers

We previously reported hedgehog (Hh) signal activation in the mucus-secreting pit cell of the stomach and in diffuse-type gastric cancer (GC). Epithelial–mesenchymal transition (EMT) is known to be involved in tumour malignancy. However, little is known about whether and how both signallings cooperatively act in diffuse-type GC. By microarray and reverse transcription–PCR, we investigated the expression of those Hh and EMT signalling molecules in pit cells and in diffuse-type GCs. How both signallings act cooperatively in those cells was also investigated by the treatment of an Hh-signal inhibitor and siRNAs of Hh and EMT transcriptional key regulator genes on a mouse primary culture and on human GC cell lines. Pit cells and diffuse-type GCs co-expressed many Hh and EMT signalling genes. Mesenchymal-related genes (WNT5A, CDH2, PDGFRB, EDNRA, ROBO1, ROR2, and MEF2C) were found to be activated by an EMT regulator, SIP1/ZFHX1B/ZEB2, which was a target of a primary transcriptional regulator GLI1 in Hh signal. Furthermore, we identified two cancer-specific Hh targets, ELK1 and MSX2, which have an essential role in GC cell growth. These findings suggest that the gastric pit cell exhibits mesenchymal-like gene expression, and that diffuse-type GC maintains expression through the Hh–EMT pathway. Our proposed extensive Hh–EMT signal pathway has the potential to an understanding of diffuse-type GC and to the development of new drugs.

Sonic hedgehog and CDX2 expression in the stomach

Sonic hedgehog (Shh) is an essential regulator of patterning processes throughout development, and CDX proteins act as the master regulators for intestinal development and differentiation. Shh and CDX2 seem to be interdependently linked with cellular differentiation through different signal cascades. We have recently shown that the loss of Shh and aberrant expression of CDX2 in Helicobacter pylori (H. pylori)-associated atrophic gastritis can be modified by H. pylori eradication prior to incomplete intestinal metaplasia. On the other hand, abnormal signaling of the hedgehog pathway has been reported in gastric cancer, especially diffuse-type cancer and advanced gastric cancer, and Shh acts as a proliferation factor in both the normal mucosa and malignant lesions. CDX2 expressed in the early stage of gastric carcinogenesis is associated with the intestinal phenotypic region and thus with a better outcome. However, it remains unclear how Shh and CDX2 are involved with intestinal transformation and further carcinogenesis.