Transcription of sonic hedgehog, a potential factor for gastric morphogenesis and gastric mucosa maintenance, is up-regulated in acidic conditions

Hedgehog Signaling Links Chronic Inflammation to Gastric Cancer Precursor Lesions

Since its initial discovery in Drosophila, Hedgehog (HH) signaling has long been associated with foregut development. The mammalian genome expresses 3 HH ligands, with sonic hedgehog (SHH) levels highest in the mucosa of the embryonic foregut. More recently, interest in the pathway has shifted to improving our understanding of its role in gastrointestinal cancers. The use of reporter mice proved instrumental in our ability to probe the expression pattern of SHH ligand and the cell types responding to canonical HH signaling during homeostasis, inflammation, and neoplastic transformation. SHH is highly expressed in parietal cells and is required for these cells to produce gastric acid. Furthermore, myofibroblasts are the predominant cell type responding to HH ligand in the uninfected stomach. Chronic infection caused by Helicobacter pylori and associated inflammation induces parietal cell atrophy and the expansion of metaplastic cell types, a precursor to gastric cancer in human subjects. During Helicobacter infection in mice, canonical HH signaling is required for inflammatory cells to be recruited from the bone marrow to the stomach and for metaplastic development. Specifically, polarization of the invading myeloid cells to myeloid-derived suppressor cells requires the HH-regulated transcription factor GLI1, thereby creating a microenvironment favoring wound healing and neoplastic transformation. In mice, GLI1 mediates the phenotypic shift to gastric myeloid-derived suppressor cells by directly inducing Schlafen 4 (slfn4). However, the human homologs of SLFN4, designated SLFN5 and SLFN12L, also correlate with intestinal metaplasia and could be used as biomarkers to predict the subset of individuals who might progress to gastric cancer and benefit from treatment with HH antagonists.

The Prognostic Significance of the Hedgehog Signaling Pathway in Colorectal Cancer

Despite significant advances in the management of colorectal cancer (CRC) the identification of new prognostic biomarkers continues to be a challenge. Since its initial discovery, the role of the Hedgehog (Hh) signaling pathway in carcinogenesis has been extensively studied. We herein review and comment on the prognostic significance of the Hh signaling pathway in CRC. The differential expression of Hh pathway components between malignant and nonmalignant conditions as well as correlation of Hh activation markers with various clinicopathological parameters and the effect on disease-free survival, overall survival, and disease recurrence in patients with CRC is summarized and discussed. According to the studies reviewed herein the activation of the Hh pathway seems to be correlated with adverse clinicopathological features and worse survival. However, to date study results show significant variability with regard to the effect on outcomes. Such results need to be interpreted carefully and emphasize the need for further well designed studies to characterize the actual influence of the Hh pathway in CRC prognosis.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

Histopathological and Immunohistochemical Characterization of Methyl Eugenol-induced Nonneoplastic and Neoplastic Neuroendocrine Cell Lesions in Glandular Stomach of Rats

Methyl eugenol induces neuroendocrine (NE) cell hyperplasia and tumors in F344/N rat stomach. Detailed histopathological and immunohistochemical (IHC) characterization of these tumors has not been previously reported. The objective of this study was to fill that data gap. Archived slides and paraffin blocks were retrieved from the National Toxicology Program Archives. NE hyperplasias and tumors were stained with chromogranin A, synaptophysin, amylase, gastrin, H(+)/K(+) adenosine triphosphatase (ATPase), pepsinogen, somatostatin, and cytokeratin 18 (CK18) antibodies. Many of the rats had gastric mucosal atrophy, due to loss of chief and parietal cells. The hyperplasias and tumors were confined to fundic stomach, and females were more affected than the males. Hyperplasia of NE cells was not observed in the pyloric region. Approximately one-third of the females with malignant NE tumors had areas of pancreatic acinar differentiation. The rate of metastasis was 21%, with liver being the most common site of metastasis. Immunohistochemically, the hyperplasias and tumors stained consistently with chromogranin A and synaptophysin. Neoplastic cells were also positive for amylase and CK18 and negative for gastrin, somatostatin, H(+)/K(+) ATPase, and pepsinogen. Metastatic neoplasms histologically similar to the primary neoplasm stained positively for chromogranin A and synaptophysin. Based on the histopathological and IHC features, the neoplasms appear to arise from enterochromaffin-like cells.

Expression level of sonic hedgehog correlated with the speed of gastric mucosa regeneration in artificial gastric ulcers

BACKGROUND AND AIM

Gastric ulcer healing is a complex process involving cell proliferation and tissue remodeling. Sonic hedgehog (Shh) activates the Shh signaling pathway, which plays a key role in processes such as tissue repair. Shh and interleukin 1β (IL1β) have been reported to influence the proliferation of gastric mucosa. We evaluated the relationships between the speed of gastric ulcer healing and the levels of expression of Shh and IL1β.

METHODS

The study included 45 patients (mean age 71.9 ± 9.0 years; M/F, 30/15) who underwent endoscopic submucosal dissection (ESD) for gastric cancer, followed by standard dose of oral proton-pump inhibitor for 4 weeks. Subsequently, the size of ESD-induced artificial ulcers were measured to determine the speed of gastric ulcer healing, and regenerating mucosa around the ulcers and appropriately matched controls were collected from patients by endoscopic biopsy. Polymerase chain reaction (PCR) array analysis of genes in the Shh signaling pathway was performed, and quantitative reverse transcription (RT)-PCR was used to measure IL1β mRNA.

RESULTS

The levels of Shh and IL1β mRNA were 3.0 ± 2.7-fold and 2.5 ± 2.5-fold higher, respectively, in regenerating mucosa of artificial ulcers than in appropriately matched controls, with the two being positively correlated (r = 0.9, P < 0.001). Shh (r = 0.8, P < 0.001) and IL1β (r = 0.7, P < 0.005) expression was each positively correlated with the speed of gastric ulcer healing, but multivariate analysis showed that Shh expression was the only significant parameter (P = 0.045).

CONCLUSIONS

Expression of Shh was correlated with the speed of gastric ulcer healing, promoting the regeneration of gastric mucosa.

Characterization of esophageal defects in the Crouzon mouse model

BACKGROUND

Mutations in Fibroblastic Growth Factor Receptors (FGFR) have been associated with human craniosynostotic birth defects like Crouzon syndrome. Several anecdotes and case reports have indicated higher incidence of gastrointestinal tract disorders in FGFR-associated craniosynostotic birth defects. Our objective was to characterize esophageal defects in a mouse model of human Crouzon syndrome, with a mutation in codon 290 of FGFR2.

METHODS

Dissected esophagi of Fgfr2(W290R) postnatal heterozygous (HET) and wild-type mice were analyzed by histological staining, immunohistochemically with cell proliferation marker, and functionally by strain gauge measures of electrically evoked contractile force.

RESULTS

The esophagi of HETs were noticeably smaller but with wider lumen than those of wild-type littermates. The HET esophagi showed a decrease in proliferation and an increase in expression of Sonic Hedgehog as compared to wild-type esophagi. Histological investigations revealed reduced amounts and disorganization of collagen in muscle layers. Functional analysis revealed altered contractile properties in HET with reduced peak amplitude and prolonged duration of evoked contractile force response and lower stimulation threshold.

CONCLUSION

The defects observed in the esophagus of the mutant may explain some of the clinical symptoms observed in humans, for example, recurrent vomiting, gastroesophageal reflux, and esophageal strictures. Taken together, our results provide evidence for the importance of Fibroblastic Growth Factor signaling in the growth and patterning of the esophagus, providing a possible scientific basis for the gastrointestinal tract clinical findings in craniosynostotic patients. Furthermore, the findings also provide a sound scientific rationale for any changes in the clinical management of gastrointestinal tract problems in patients with craniosynostotic defects.

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.

Activation of sonic hedgehog signaling pathway is an independent potential prognosis predictor in human hepatocellular carcinoma patients

OBJECTIVE

The activation of hedgehog (HH) pathway is implicated in the development of human malignancies including hepatocellular carcinoma (HCC). However, the clinical impact of HH activation in HCC patients is still unclear. This study was conducted to confirm whether the expression of HH pathway components was associated with HCC progression and clinical outcome.

METHODS

This study was a sample-expanded and prolonged follow up of one of our previous studies. It included 46 HCC patients who underwent surgical treatment from 2002 to 2005. The expression of sonic HH (SHH), patched-1 (PTCH1), smoothened (SMOH) and glioma-associated oncogene-1 (GLI1) genes in tumor and adjacent normal tissues extracted from the patients were examined by reverse transcription-polymerase chain reaction (RT-PCR) to explore the relationship between these genes and the clinical prognosis of HCC.

RESULTS

The expression levels of SHH, PTCH1, SMOH and GLI1 in HCC tissues were 60.87%, 50.00%, 32.61% and 54.35%, respectively. The expression levels of SHH-related molecules were relatively intense in cancer tissue, but insignificantly correlated with any clinicopathological factors of tumor. Transcriptional factor GLI1 was the only molecule associated with poor prognosis among the HCC patients. The expression of GLI1 gene in tumor tissues was significantly related with disease-free survival (DFS) (P=0.042) and overall survival (OS) (P=0.030). The simultaneous expression of GLI1 in tumor and adjacent normal liver tissues correlated with DFS (P<0.029) and OS (P<0.025).

CONCLUSIONS

HH signaling activation is an important event in the development of human HCC. The expression of GLI1 in SHH pathway is possibly involved in HCC progression, which may be a useful prognostic indicator of HCC.

Activation of sonic hedgehog signaling pathway is an independent potential prognosis predictor in human hepatocellular carcinoma patients

OBJECTIVE

The activation of hedgehog (HH) pathway is implicated in the development of human malignancies including hepatocellular carcinoma (HCC). However, the clinical impact of HH activation in HCC patients is still unclear. This study was conducted to confirm whether the expression of HH pathway components was associated with HCC progression and clinical outcome.

METHODS

This study was a sample-expanded and prolonged follow up of one of our previous studies. It included 46 HCC patients who underwent surgical treatment from 2002 to 2005. The expression of sonic HH (SHH), patched-1 (PTCH1), smoothened (SMOH) and glioma-associated oncogene-1 (GLI1) genes in tumor and adjacent normal tissues extracted from the patients were examined by reverse transcription-polymerase chain reaction (RT-PCR) to explore the relationship between these genes and the clinical prognosis of HCC.

RESULTS

The expression levels of SHH, PTCH1, SMOH and GLI1 in HCC tissues were 60.87%, 50.00%, 32.61% and 54.35%, respectively. The expression levels of SHH-related molecules were relatively intense in cancer tissue, but insignificantly correlated with any clinicopathological factors of tumor. Transcriptional factor GLI1 was the only molecule associated with poor prognosis among the HCC patients. The expression of GLI1 gene in tumor tissues was significantly related with disease-free survival (DFS) (P=0.042) and overall survival (OS) (P=0.030). The simultaneous expression of GLI1 in tumor and adjacent normal liver tissues correlated with DFS (P<0.029) and OS (P<0.025).

CONCLUSIONS

HH signaling activation is an important event in the development of human HCC. The expression of GLI1 in SHH pathway is possibly involved in HCC progression, which may be a useful prognostic indicator of HCC.

Methylation-dependent activation of CDX1 through NF-κB: a link from inflammation to intestinal metaplasia in the human stomach

The caudal homeobox factor 1 (CDX1) is an essential transcription factor for intestinal differentiation. Its aberrant expression in intestinal metaplasia of the upper gastrointestinal tract is a hallmark within the gastritis-metaplasia-carcinoma sequence. CDX1 expression is influenced by certain pathways, such as Wnt, Ras, or NF-κB signaling; however, these pathways alone cannot explain the transient expression of CDX1 in intestinal metaplasia or the molecular inactivation mechanism of its loss in cases of advanced gastric cancer. In this study, we investigated the epigenetic inactivation of CDX1 by promoter methylation, as well as the functional link of CDX1 promoter methylation to the inflammatory NF-κB signaling pathway. We identified methylation-dependent NF-κB binding to the CDX1 promoter and quantified it using competitive electrophoretic mobility shift assays and chromatin immunoprecipitation. A methylated CDX1 promoter was associated with closed chromatin structure, reduced NF-κB binding, and transcriptional silencing. Along the gastritis-metaplasia-carcinoma sequence, we observed a biphasic pattern of tumor necrosis factor-α (TNF-α) protein expression and an inverse biphasic pattern of CDX1 promoter methylation; both are highly consistent with CDX1 protein expression. The stages of hyper-, hypo-, and hyper-methylation patterns of the CDX1 promoter were inversely correlated with the NF-κB signaling activity along this sequence. In conclusion, these functionally interacting events drive CDX1 expression and contribute to intestinal metaplasia, epithelial dedifferentiation, and carcinogenesis in the human stomach.

Activation of Hedgehog pathway in gastrointestinal cancers

The hedgehog (Hh) pathway is a major regulator for cell differentiation, tissue polarity, and cell proliferation in embryonic development and homeostasis in adult tissue. Studies from many laboratories reveal activation of this pathway in a variety of human cancer, including basal cell carcinomas (BCCs), medulloblastomas, leukemia, gastrointestinal, lung, ovarian, breast, and prostate cancers. It is thus believed that targeted inhibition of Hh signaling may be effective in treatment and prevention of human cancer. Even more exciting is the discovery and synthesis of specific signaling antagonists for the Hh pathway, which have significant clinical implications in novel cancer therapeutics. In this review, we summarize major advances in the past 2 years in our understanding of Hh signaling activation in human gastrointestinal cancer and their potential in clinical treatment with Hh pathway inhibitors.

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.

Barrett's esophagus

Barrett's esophagus is an acquired metaplastic abnormality in which the normal stratified squamous epithelium lining of the esophagus is replaced by an intestinal-like columnar epithelium. While in itself a benign and asymptomatic disorder, the clinical importance of this relatively common condition relates to its role as a precursor lesion to esophageal adenocarcinoma, the incidence of which has dramatically increased in Western populations in recent years. Although known to arise as a consequence of chronic gastroesophageal reflux, the cellular and molecular mechanisms underlying development Barrett's esophagus and its progression to cancer remain unclear.

The role of sonic hedgehog reemergence during gastric cancer

Sonic Hedgehog (Shh) signaling has been extensively studied for its role in developmental biology and cancer biology. The association between Shh and cancer development in general is well established but the functional role of Shh in the development and progression of gastric cancer specifically is largely unknown. Bone marrow-derived stem cells, specifically mesenchymal stem cells (MSCs) infiltrate and engraft into the gastric mucosa in response to the chronic inflammatory environment of Helicobacter infection. In this review, MSC infiltration and changes in the cytokine and cellular profiles of later-stage chronic environments will be tied into their interactions with the Shh pathway. We will discuss how these changes shape tumorigenesis and tumor progression in the gastric mucosa. The current review focuses on the Shh signaling pathway and its role in the development of gastric cancer, specifically in response to Helicobacter pylori infection. We follow with an in-depth discussion of the regulation of the Hedgehog pathway during acute and chronic gastric inflammation with a focus on signaling within the MSC compartment.

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.

Novel targets in esophageal and gastric cancer: beyond antiangiogenesis

Cancers of the stomach, gastroesophageal junction and esophagus are a major cause of cancer-related deaths worldwide. In Western countries, adenocarcinomas of the distal esophagus, gastroesophageal junction and proximal stomach have been increasing in frequency more rapidly than other malignancies. The majority of newly diagnosed patients present with advanced disease and the overall survival remains dismal at approximately 10% at 5 years. Better understanding of tumor biology has led to the development of promising novel therapeutic strategies. There is therefore increasing optimism that some of these approaches will improve the outcomes in these increasingly common cancers. Given the success of antiangiogenesis as a therapeutic strategy in various types of cancer, there are ongoing efforts to investigate the utility of other targeted therapies in the treatment of gastric and esophageal cancers. This review will focus on novel therapeutic targets other than angiogenesis and provide a rationale for the further clinical evaluation of these agents in patients with upper gastrointestinal tract cancers.

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.

Negative regulation of Hedgehog signaling by liver X receptors

Hedgehog (Hh) signaling is indispensable in embryonic development, and its dysregulated activity results in severe developmental disorders as shown by genetic models of naturally occurring mutations in animal and human pathologies. Hh signaling also functions in postembryonic development and adult tissue homeostasis, and its aberrant activity causes various human cancers. Better understanding of molecular regulators of Hh signaling is of fundamental importance in finding new strategies for pathway modulation. Here, we identify liver X receptors (LXRs), members of the nuclear hormone receptor family, as previously unrecognized negative regulators of Hh signaling. Activation of LXR by specific pharmacological ligands, TO901317 and GW3965, inhibited the responses of pluripotent bone marrow stromal cells and calvaria organ cultures to sonic Hh, resulting in the inhibition of expression of Hh-target genes, Gli1 and Patched1, and Gli-dependent transcriptional activity. Moreover, LXR ligands inhibited sonic Hh-induced differentiation of bone marrow stromal cells into osteoblasts. Elimination of LXRs by small interfering RNA inhibited ligand-induced inhibition of Hh target gene expression. Furthermore, LXR ligand did not inhibit Hh responsiveness in mouse embryonic fibroblasts that do not express LXRs, whereas introduction of LXR into these cells reestablished the inhibitory effects. Daily oral administration of TO901317 to mice after 3 d significantly inhibited baseline Hh target-gene expression in liver, lung, and spleen. Given the importance of modulating Hh signaling in various physiological and pathological settings, our findings suggest that pharmacological targeting of LXRs may be a novel strategy for Hh pathway modulation.

Achlorhydria is associated with gastric microbial overgrowth and development of cancer: Lessons learned from the gastrin knockout mouse

Gastrin and gastrin receptor-deficient mice have been used for genetic dissection of the role of gastrins in maintaining gastric homeostasis and control of acid secretion. The gastrin knockout mice are achlorhydric due to inactivation of the ECL and parietal cells. Moreover, this achlorhydria is associated with intestinal metaplasia and bacterial overgrowth, which ultimately leads to the development of gastric tumours. The association between progastrin, progastrin-derived processing intermediates and colorectal carcinogenesis has also been examined through genetic or chemical cancer induction in several mouse models, although the clinical relevance of these studies remains unproven. While others have focused on models of increased gastrin production, the present review describes the lessons learned from gastrin-deficient mice. Study of these mice helps our understanding of how dysregulation of gastrin secretion may be implicated in human disease.

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 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.

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.

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.

Sonic hedgehog is associated with H+-K+-ATPase-containing membranes in gastric parietal cells and secreted with histamine stimulation

Sonic hedgehog (Shh) is found within gastric parietal cells and processed from a 45-kDa to a 19-kDa bioactive protein by an acid- and protease-dependent mechanism. To investigate whether Shh is associated with the parietal cell membrane compartment that becomes exposed to both acid and proteolytic enzymes during acid secretion, the cellular location of Shh within resting and stimulated gastric parietal cells was examined. Immunofluorescence microscopy of rabbit stomach sections showed that Shh colocalized predominantly with parietal and pit, not chief/zymogen or neck, cell markers. In resting and histamine-stimulated rabbit gastric glands Shh was expressed only in parietal cells close to H+-K+-ATPase-containing tubulovesicular and secretory membranes with some colocalizing with gamma-actin at the basolateral membrane. Gastric gland microsomal membranes were prepared by differential and sucrose gradient centrifugation and immunoisolation with an anti-H+-K+-ATPase-alpha subunit antibody. The 45- and 19-kDa Shh proteins were detected by immunoblot in immunopurified H+-K+-ATPase-containing membranes from resting and stimulated gastric glands, respectively. Incubating glands with a high KCl concentration removed Shh from the membranes. Histamine stimulated 19-kDa Shh secretion from gastric glands into the medium. In human gastric cancer 23132/87 cells cultured on permeable membranes, histamine increased 19-kDa Shh secretion into both apical and basolateral media. These findings show that Shh is a peripheral protein associated with resting and stimulated H+-K+-ATPase-expressing membranes. In addition, Shh appears to be expressed at or close to the basolateral membrane of parietal cells.

Biology of intestinal metaplasia in 2008: more than a simple phenotypic alteration

This review concentrates on one main aspect of cancerization in the oesophagus and stomach: principally, intestinal metaplasia. There are at least two other important pathways that lead to cancer and do not need such a morphological transformation. One is the gastric type of carcinoma on the Lauren classification, which arises directly from the stem cell zone and is the signet ring form of cancer, while the other is spasmolytic polypeptide-expressing metaplasia (SPEM)--spasmolytic polypeptide (TFF2) expressing metaplasia, where the gastric glands become filled with TFF2-expressing cells and may also lead to gastric dysplasia and cancer. The development of intestinal metaplasia is complex. Here, we examine intestinal metaplasia in molecular terms, noting the over-expression of Cdx1, Cdx2, Pdx1, Oct1, TFF3 and the downregulation of Hedgehog signalling; Runx3 is deactivated by epigenetic silencing, and pathways such as Wnt and MARK/ERK are involved. These changes start to explain the principles of the development of intestinal metaplasia and suggest that the regulation of these genes is of importance in the development of gastric cancer.

The adventures of sonic hedgehog in development and repair. IV. Sonic hedgehog processing, secretion, and function in the stomach

Sonic hedgehog (Shh) is recognized as one of the main morphogens that regulates cell differentiation during early development of the stomach. In the adult stomach, Shh is expressed and secreted from the acid-producing parietal cells, where it is believed to play an essential role in gastric tissue homeostasis and normal differentiation of the epithelium. The present Themes article focuses on reviewing the literature and controversies surrounding the processing and secretion and the role of Shh in the adult stomach.

The pathogenesis of Helicobacter pylori-induced gastro-duodenal diseases

Helicobacter pylori is the main cause of peptic ulceration, distal gastric adenocarcinoma, and gastric lymphoma. Only 15% of those colonized develop disease, and pathogenesis depends upon strain virulence, host genetic susceptibility, and environmental cofactors. Virulence factors include the cag pathogenicity island, which induces proinflammatory, pro-proliferative epithelial cell signaling; the cytotoxin VacA, which causes epithelial damage; and an adhesin, BabA. Host genetic polymorphisms that lead to high-level pro-inflammatory cytokine release in response to infection increase cancer risk. Pathogenesis is dependent upon inflammation, a Th-1 acquired immune response and hormonal changes including hypergastrinaemia. Antral-predominant inflammation leads to increased acid production from the uninflamed corpus and predisposes to duodenal ulceration; corpus-predominant gastritis leads to hypochlorhydria and predisposes to gastric ulceration and adenocarcinoma. Falling prevalence of H. pylori in developed countries has led to a falling incidence of associated diseases. However, whether there are disadvantages of an H. pylori-free stomach, for example increased risk of esosphageal adenocarcinoma, remains unclear.

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

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

Hedgehog signaling in development and homeostasis of the gastrointestinal tract

The Hedgehog family of secreted morphogenetic proteins acts through a complex evolutionary conserved signaling pathway to regulate patterning events during development and in the adult organism. In this review I discuss the role of Hedgehog signaling in the development, postnatal maintenance, and carcinogenesis of the gastrointestinal tract. Three mammalian hedgehog genes, sonic hedgehog (Shh), indian hedgehog (Ihh), and desert hedgehog (Dhh) have been identified. Shh and Ihh are important endodermal signals in the endodermal-mesodermal cross-talk that patterns the developing gut tube along different axes. Mutations in Shh, Ihh, and downstream signaling molecules lead to a variety of gross malformations of the murine gastrointestinal tract including esophageal atresia, tracheoesophageal fistula, annular pancreas, midgut malrotation, and duodenal and anal atresia. These congenital malformations are also found in varying constellations in humans, suggesting a possible role for defective Hedgehog signaling in these patients. In the adult, Hedgehog signaling regulates homeostasis in several endoderm-derived epithelia, for example, the stomach, intestine, and pancreas. Finally, growth of carcinomas of the proximal gastrointestinal tract such as esophageal, gastric, biliary duct, and pancreatic cancers may depend on Hedgehog signaling offering a potential avenue for novel therapy for these aggressive cancers.

Re-expression of sonic hedgehog and reduction of CDX2 after Helicobacter pylori eradication prior to incomplete intestinal metaplasia

Loss of Sonic Hedgehog (Shh) and aberrant CDX2 expression are early changes correlating with the presence of intestinal metaplasia that occur in the gastric mucosa prior to neoplastic transformation. The aim of this study was to compare the improvement in corpus gastritis with Shh and CDX2 expression after H. pylori eradication between subjects at high risk for gastric cancer and controls. The usefulness of serum pepsinogen levels as a predictor of resolved corpus gastritis was also examined. Seventy patients with endoscopic resection for early gastric cancer and 30 controls were studied. Expression of Shh and CDX2 were evaluated by immunostaining. Serum levels of pepsinogen I before eradication in the patients scored as having improvement of corpus atrophy were significantly higher than in the patients without improvement (<0.01). Residual inflammation at the corpus lesser curve was more frequently detected in the cancer group than in the controls (OR 4.6 95% C.I. 1.6-13.5) and in the mucosa with incomplete intestinal metaplasia rather than in those without incomplete intestinal metaplasia (OR 7.6 95% C.I. 2.4-24.3). Atrophy, expression of Shh and CDX2 at the corpus lesser curve significantly improved in mucosa without incomplete intestinal metaplasia (p < 0.01), but not in mucosa with incomplete intestinal metaplasia. In conclusion, H. pylori eradication prior to development of incomplete intestinal metaplasia improves corpus gastritis and may prevent gastric cancer. Pepsinogen I may be a useful marker in patients with a residual higher risk of gastric cancer after H. pylori eradication.

Reduced pepsin A processing of sonic hedgehog in parietal cells precedes gastric atrophy and transformation

Sonic hedgehog (Shh) is not only essential to the development of the gastrointestinal tract, but is also necessary to maintain the characteristic acid-secreting phenotype of the adult stomach. Gastrin is the only hormone capable of stimulating gastric acid and is thus required to maintain functional parietal cells. We have shown previously that gastrin-null mice display gastric atrophy and metaplasia prior to progression to distal, intestinal-type gastric cancer. Because reduced levels of Shh peptide correlate with gastric atrophy, we examined whether gastrin regulates Shh expression in parietal cells. We show here that gastrin stimulates Shh gene expression and acid-dependent processing of the 45-kDa Shh precursor to the 19-kDa secreted peptide in primary parietal cell cultures. This cleavage was blocked by the proton pump inhibitor omeprazole and mediated by the acid-activated protease pepsin A. Pepsin A was also the protease responsible for processing Shh in tissue extracts from human stomach. By contrast, extracts prepared from neoplastic gastric mucosa had reduced levels of pepsin A and did not process Shh. Therefore processing of Shh in the normal stomach is hormonally regulated, acid-dependent, and mediated by the aspartic protease pepsin A. Moreover parietal cell atrophy, a known pre-neoplastic lesion, correlates with loss of Shh processing.

Precancerous lesions upon sporadic activation of beta-catenin in mice

BACKGROUND & AIMS

Inappropriate activation of beta-catenin in adult tissues is associated with a wide variety of cancers, especially in the digestive tract. Classic transgenic and knockout murine models in which beta-catenin is activated in large fields of cells have provided experimental support in favor of a role for this molecule in tumorigenesis. However, these models do not reproduce the sporadic nature of the majority of human cancers, beginning with the activation of an oncogene at random in a single cell.

METHODS

We used the "hit and run" strategy to generate a mouse model in which the expression of an activated form of beta-catenin occurs sporadically in vivo.

RESULTS

Sporadic, multifocal lesions were observed in the stomach of 3% of mice aged 8 months and older. These lesions were associated with loss of Sonic hedgehog (Shh), and a causal relationship between beta-catenin activation and Shh inhibition was established in gastric cells in vitro. No lesion was detected in the intestine or in the liver. In addition, one third of female mutant mice developed benign perimammary papillomas. Mutant mice were also hypersensitive to chemically induced premalignant skin lesions.

CONCLUSIONS

These results challenge the view that activation of beta-catenin induces malignant cancerogenesis, because they show in mice that sporadically activated beta-catenin is sufficient for tumor initiation, yet without further malignant progression, and that it sensitizes cells to environmental hits. This model represents a powerful tool to investigate the interplay between genetic and environmental factors in tumor progression.

Expression of Sonic hedgehog gene, interleukin-1β, tumor necrosis factor-α in gastric epithelium of mongolian gerbils after H pylori inoculation

AIM: To investigate the expression of morphogene Sonic hedgehog (Shh), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) in gastric epithelium of mongolian gerbils after H pylori inoculation and their correlations with the pathologic changes of Helicobacter pylori related gastritis.

METHODS: A total of 50 male mongolian gerbils were inoculated with H pylori and another 50 gerbils served as controls. The levels of Shh, IL-1β and TNF-α mRNA expression were detected by reverse transcription-polymerase chain reaction (RT-PCR), and the level of Shh protein expression was examined by immunohistochemistry 4, 12, 24, 36 and 48 weeks after inoculation.

RESULTS: As compared with those in the controls, both the expression levels of Shh mRNA and protein were decreased significantly at the 36^th (t = 3.24, P < 0.05; Z = 4.84, P < 0.001) and 48^th week (t = 3.01, P < 0.05; Z = 4.65, P < 0.001) after H pylori inoculation. Furthermore, the level of Shh mRNA expression was negatively correlated with the expression of IL-1β mRNA, TNF-α mRNA and the grade of gastritis, respectively (r = -0.372, P < 0.01; r = -0.301, P < 0.05; r = -0.397, P < 0.001). Similarly, the level of Shh protein expression was negatively correlated with the expression of IL-1β mRNA, TNF-α mRNA and the grade of gastritis (r = -0.321, P < 0.05; r = -0.313, P < 0.05; r = -0.371, P < 0.001) respectively.

CONCLUSION: After H pylori infection, the expression of IL-1β and TNF-α is increased and positively correlated with the grade of gastritis, and while the expression of Shh is decreased and negatively correlated with the expression of IL-1β, TNF-α and gastritis grades.

Helicobacter pylori-induced atrophic gastritis progressing to gastric cancer exhibits sonic hedgehog loss and aberrant CDX2 expression

BACKGROUND

The loss of sonic hedgehog is an early change that occurs in the mucosa prior to neoplastic transformation and correlates with the type of intestinal metaplasia. Aberrant expression of CDX has also been shown to correlate with the development of intestinal metaplasia.

AIM

To examine CDX2 expression in the non-cancerous mucosa of patients with gastric cancer and compared it to CDX2 expression in controls with intestinal metaplasia.

METHODS

Sixty patients who had undergone endoscopic mucosal resection for early gastric cancer and 60 gender- and age-matched controls were studied. Two specimens each were obtained from the greater and lesser curves of the corpus and from the greater curve of the antrum. Expression of CDX2 and sonic hedgehog were evaluated by immunostaining.

RESULTS

Gastric cancer was associated with a higher frequency of incomplete intestinal metaplasia (OR = 8.3; 95%CI, 3.7-18.9, P < 0.001). CDX2 negatively correlated with sonic hedgehog expression, however, multivariate analysis revealed that CDX2 correlated with the intestinal metaplasia scores. Sonic hedgehog indices were lower and CDX2 staining in the corpus lesser curve was higher in the cancer group than in the controls. Sonic hedgehog indices in the corpus decreased and CDX2 indices in both areas increased in patients in the ascending order of those without intestinal metaplasia, those with complete intestinal metaplasia and those with incomplete intestinal metaplasia (P < 0.001).

CONCLUSIONS

Loss of sonic hedgehog expression and aberrant expression of CDX2 correlates with the type of intestinal metaplasia and may play a role in carcinogenesis.

Gastrin - active participant or bystander in gastric carcinogenesis?

Gastrin is a pro-proliferative, anti-apoptotic hormone with a central role in acid secretion in the gastric mucosa and a long-standing association with malignant progression in transgenic mouse models. However, its exact role in human gastric malignancy requires further validation. Gastrin expression is tightly regulated by two closely associated hormones, somatostatin and gastrin-releasing peptide, and aspects of their interaction may be deregulated during progression to gastric adenocarcinoma. Furthermore, agonists and antagonists of the receptors for all three hormones have shown modest clinical efficacy against gastric adenocarcinoma, which might provide useful information on the future combined use of these agents.

Study of Sonic hedgehog signaling pathway related molecules in gastric carcinoma

AIM: To study the expression of Sonic hedgehog pathway-related molecules, Sonic hedgehog (Shh) and Gli1 in gastric carcinoma.

METHODS: Expression of Shh in 56 gastric specimens including non-cancerous gastric tissues, gastric adenocarcinoma, gastric squamous cell carcinoma was detected by RT-PCR, in situ hybridization and immunohistochemistry. Expression of Gli1 was observed by in situ hybridization.

RESULTS: The positive rate of Shh and Gli1 expression was 0.0%, 0.0% in non-cancerous gastric tissues while it was 66.7%, 57.8% respectively in gastric adenocarcinoma, and 100%, 100% respectively in gastric squamous cell carcinoma. There was a significant difference between the non-cancerous gastric tissues and gastric carcinoma (P < 0.05). Elevated expression of Shh and Gli1 in gastric tubular adenocarcinoma was associated with poorly differentiated tumors while the expression was absent in gastric mucinous adenocarcinoma.

CONCLUSION: The elevated expression of Shh and Gli1 in gastric adenocarcinoma and gastric squamous cell carcinoma shows the involvement of activated Shh signaling in the cellular proliferation of gastric carcinogenesis. It suggests Shh signaling gene may be a new and good target gene for gastric tumor diagnosis and therapy.

Gastric inflammation, metaplasia, and tumor development in gastrin-deficient mice

BACKGROUND & AIMS

Gastrin deficiency and proton pump inhibitor treatment cause achlorhydria, which predisposes to disease. To elucidate the underlying molecular biology, we examined the changes in gastric gene expression in both types of achlorhydria. We also explored the associated changes in the gastric microflora and the long-term consequences of gastrin-deficient achlorhydria.

METHODS

Expression profiles were generated from gastric RNA from wild-type mice, gastrin knockout (KO) mice, gastrin KO mice after 1 week of gastrin infusion, and wild-type mice treated for 1 month with a proton pump inhibitor. The results were confirmed using real-time polymerase chain reaction and immunohistochemistry. Selective media were used to characterize the gastric microflora.

RESULTS

The number of gastric bacteria was increased in both gastrin KO and PPI-treated mice. The expression profiles revealed activation of immune defense genes, interferon-regulated response genes, and intestinal metaplasia of the gastric mucosa. In young gastrin-deficient mice, gastrin infusions reversed the changes. Over time, the changes accumulated, became irreversible, and progressed into metaplasia and polyp development. Finally, the study showed that gastrin regulated the expression of genes encoding extracellular matrix proteins.

CONCLUSIONS

Independently of gastrin, achlorhydria is associated with gastric bacterial overgrowth and intestinal gene expression patterns and is associated with predisposition to disease. Gastrin is therefore essential for prevention of gastric disease, mainly through control of acid secretion but to a lesser extent also through control of gastric gene expression. The gastrin-deficient mouse serves as a useful new model for gastric metaplasia and neoplasia.

Sonic hedgehog mRNA expression by real-time quantitative PCR in normal and tumor tissues from colorectal cancer patients

Shh is expressed in the early stages of embryogenesis and in the foregut development. Although Shh has been shown to be overexpressed in brain, pancreas, gastric and lung cancers, its role in the development of colorectal cancer has not been examined. We used real-time quantitative PCR to assess Shh mRNA expression levels in tumor and matched normal tissue from 57 colorectal cancer patients and correlated the results with patient clinicopathological characteristics. Shh expression levels were higher in tumor tissue than in normal tissue from the same patient (P=0.00001). Higher levels of Shh expression were associated with early stage disease (P=0.02). Shh overexpression may influence the development of colorectal cancer.

The hedgehog signalling pathway in the gastrointestinal tract: implications for development, homeostasis, and disease

The hedgehog signalling pathway is critical to normal mammalian gastrointestinal development. Through epithelial-mesenchymal interactions, hedgehog signalling ensures appropriate axial patterning of the embryonic gut. Congenital abnormalities, including malrotations, anorectal malformations, and tracheoesophageal fistula are associated with germ-line mutations/deletion of genes encoding hedgehog signalling components in man and present in genetically engineered animal models. In adults, there is evidence that the pathway plays a role in maintaining stem cell populations in the stomach and directing epithelial cell differentiation in the intestine. Recent data implicate hedgehog signalling in the formation and maintenance of a number of malignancies, including those of the upper gastrointestinal (GI) tract and pancreas, in which abrogation of the pathway offers a novel therapeutic approach in animal models. Most recently, evidence in vitro indicates that there is a recapitulation of embryonic hedgehog signalling in acute epithelial injury and chronic inflammation, a finding with key implications for inflammatory disorders of the intestine, such as inflammatory bowel diseases. This pathway may provide an important link between chronic inflammation and cancer. We summarize the available evidence demonstrating that this developmental pathway has continuing roles in adult homeostasis and is dysregulated in malignancy and inflammation of the gastrointestinal tract.

Aberrant expression of TTF-1 and forkhead factor HFH-4 in atrophic gastritis and ciliated metaplasia suggests gastric broncho-pulmonary transdetermination

Ciliated metaplasia (CM) in the stomach is mainly found in gastric mucosa that harbours gastric cancer. The true nature of this lesion and the regulatory factors responsible for the formation of CM are unknown. Broncho-pulmonary differentiation is controlled by the homeodomain transcription factor TTF-1 and ciliogenesis by the forkhead transcription factor HFH-4, respectively. Using immunohistochemistry, the present study shows that gastric CM is associated with the expression of TTF-1 and HFH-4. Furthermore, TTF-1 expression was found in non-ciliated cells in 50% of cases with atrophic gastritis, whereas TTF-1 and HFH-4 were not expressed in normal gastric mucosa or in non-atrophic gastritis. These data suggest that CM in the gastric mucosa can be regarded as gastric broncho-pulmonary transdetermination. Evidence for this particular transdetermination is frequently found in atrophic gastritis even without fully developed ciliated cells.

Accurate discrimination of Barrett's esophagus and esophageal adenocarcinoma using a quantitative three-tiered algorithm and multimarker real-time reverse transcription-PCR

Esophageal adenocarcinoma (EA) is increasing faster than any other cancer in the U.S. In this report, we first show that EA can be distinguished from normal esophagus (NE) and esophageal squamous cell carcinoma by plotting expression values for EpCam, TFF1, and SBEM in three-dimensional Euclidean space. For monitoring progression of Barrett's esophagus (BE) to EA, we developed a highly sensitive assay for limited quantities of tissue whereby 50 ng of RNA are first converted to cDNA using 16 gene-specific primers. Using a set of training tissues, we developed a novel quantitative three-tiered algorithm that allows for accurate (overall accuracy = 61/63, 97%) discrimination of BE versus EA tissues using only three genes. The gene used in the first tier of the algorithm is TSPAN: samples not diagnosed as BE or EA by TSPAN in the first tier are then subjected to a second-tier analysis using ECGF1, followed by a third-tier analysis using SPARC. Addition of TFF1 and SBEM to the first tier (i.e., a five-gene marker panel) increases the overall accuracy of the assay to 98% (62/63) and results in mean molecular diagnostic scores (+/- SD) that are significantly different between EA and BE samples (3.19 +/- 1.07 versus -2.74 +/- 1.73, respectively). Our results suggest that relatively few genes can be used to monitor progression of BE to EA.

Evidence that loss of sonic hedgehog is an indicator of Helicobater pylori-induced atrophic gastritis progressing to gastric cancer

BACKGROUND

The absence of sonic hedgehog (Shh) correlates with the development of intestinal metaplasia (IM) suggesting the possibility of an association between Shh expression and neoplastic transformation.

AIM

To examine Shh expression in the noncancerous mucosa of patients with gastric cancer and compare it to Shh expression in Helicobater pylori-infected and uninfected controls. We also assessed the relationship between the type of IM and Shh expression.

METHODS

Fifty-three patients with endoscopic mucosal resection (EMR) for early gastric cancer and 48 sex- and age-matched controls were studied. Two specimens each were obtained from the greater and lesser curves of the corpus and from the greater curve of the antrum. The histopathological grading used was the updated Sydney System. IM was categorized by staining with Alcian blue/high iron diamine. Expression of Shh was evaluated by immunostaining.

RESULTS

The Shh immunostaining in the corpus lesser curve significantly correlated with the scores of atrophy and IM. Shh staining in the antrum was significantly higher in H. pylori-negative controls than those in H. pylori-positive controls as well as in patients without IM compared to those with IM (p < 0.001). The Shh staining in the corpus lesser curve decreased in H. pylori-negative controls, -positive controls and the cancer group respectively (p= 0.003), and was significantly higher (p= 0.006) in the complete IM group compared to those in the incomplete IM group.

CONCLUSIONS

Loss of Shh is an early change that occurs in the mucosa prior to neoplastic transformation. Its loss correlates with the type of IM and may play a role in carcinogenesis.