Hedgehog signalling in gut development, physiology and cancer

The Assessment of CDX1, IHH, SHH, GATA4, FOXA2, FOXF1 in Congenital Intra-Abdominal Adhesions

Congenital abdominal adhesions are a rare condition that can result in a small bowel obstruction at any age, more frequently in pediatric populations. The cause remains unknown, and the importance of aberrant congenital bands is related to the difficulty of diagnosis, and cases of death with late detection have been documented. This research examines the expression of Caudal Type Homeobox 1 (CDX1), Indian Hedgehog (IHH), Sonic Hedgehog (SHH), GATA Binding Protein 4 (GATA4), Forkhead Box A2 (FOXA2) and Forkhead Box F1 (FOXF1) gene expression in human abdominal congenital adhesion fibroblast and endothelium cells by chromogenic in situ hybridization, with the aim of elucidating their potential association with the etiology of congenital intra-abdominal adhesion band development. The potential genes' signals were examined using a semi-quantitative approach. Significant correlations were observed between the expression of CDX1 (p <.001) and SHH (p=0.032) genes in fibroblasts from congenital intra-abdominal adhesions compared to fibroblasts from control peritoneal tissue. Statistically significant very strong correlations were found between the CDX1 and IHH comparing endothelium and fibroblast cells in congenital abdominal adhesion bands. There was no statistically significant difference found in the distribution of IHH, FOXA2, GATA4, and FOXF1 between the fibroblasts and endothelium of the patients compared to the control group. The presence of notable distinctions and diverse associations suggests the potential involvement of numerous morpho-pathogenetic processes in the development of intraabdominal adhesions.

Tumor cell stemness in gastrointestinal cancer: regulation and targeted therapy

The cancer stem cells are a rare group of self-renewable cancer cells capable of the initiation, progression, metastasis and recurrence of tumors, and also a key contributor to the therapeutic resistance. Thus, understanding the molecular mechanism of tumor stemness regulation, especially in the gastrointestinal (GI) cancers, is of great importance for targeting CSC and designing novel therapeutic strategies. This review aims to elucidate current advancements in the understanding of CSC regulation, including CSC biomarkers, signaling pathways, and non-coding RNAs. We will also provide a comprehensive view on how the tumor microenvironment (TME) display an overall tumor-promoting effect, including the recruitment and impact of cancer-associated fibroblasts (CAFs), the establishment of an immunosuppressive milieu, and the induction of angiogenesis and hypoxia. Lastly, this review consolidates mainstream novel therapeutic interventions targeting CSC stemness regulation.

Hedgehog/GLI and gastric cancer: Research progress and current status

Hedgehog/GLI (Hh/GLI) is an important signaling pathway. It has been confirmed in various cancer studies that mutated or dysregulated Hh signals may be the behavioral phenotype of tumors, leading to the occurrence of various cancers. The abnormally activated Hh pathway endows tumor cells with a tendency to occur, proliferate, and migrate. In recent years, studies have found that the Hh signaling pathway induces gastric cancer (GC) invasion and epithelial mesenchymal transition. This article reviews the research progress and current status of Hh/GLI related to GC. Unveiling the new veil of GC occurrence will open a new approach for targeted therapy of this malignancy.

ATF4 Transcriptionally Activates SHH to Promote Proliferation, Invasion, and Migration of Gastric Cancer Cells

Activating transcription factor 4 (ATF4) is a DNA-binding protein widely generated in mammals, which has two biological characteristics that bind the cAMP response element (CRE). The mechanism of ATF4 as a transcription factor in gastric cancer affecting the Hedgehog pathway remains unclear. Here, we observed that ATF4 was markedly upregulated in gastric cancer (GC) using immunohistochemistry and Western blotting assays in 80 paraffin-embedded GC samples and 4 fresh samples and para-cancerous tissues. ATF4 knockdown using lentiviral vectors strongly inhibited the proliferation and invasion of GC cells. ATF4 upregulation using lentiviral vectors promoted the proliferation and invasion of GC cells. We predicted that the transcription factor ATF4 is bound to the SHH promoter via the JASPA database. Transcription factor ATF4 is bound to the promoter region of SHH to activate the Sonic Hedgehog pathway. Mechanistically, rescue assays showed that ATF4 regulated gastric cancer cells' proliferation and invasive ability through SHH. Similarly, ATF4 enhanced the tumor formation of GC cells in a xenograft model.

An Update of G-Protein-Coupled Receptor Signaling and Its Deregulation in Gastric Carcinogenesis

G-protein-coupled receptors (GPCRs) belong to a cell surface receptor superfamily responding to a wide range of external signals. The binding of extracellular ligands to GPCRs activates a heterotrimeric G protein and triggers the production of numerous secondary messengers, which transduce the extracellular signals into cellular responses. GPCR signaling is crucial and imperative for maintaining normal tissue homeostasis. High-throughput sequencing analyses revealed the occurrence of the genetic aberrations of GPCRs and G proteins in multiple malignancies. The altered GPCRs/G proteins serve as valuable biomarkers for early diagnosis, prognostic prediction, and pharmacological targets. Furthermore, the dysregulation of GPCR signaling contributes to tumor initiation and development. In this review, we have summarized the research progress of GPCRs and highlighted their mechanisms in gastric cancer (GC). The aberrant activation of GPCRs promotes GC cell proliferation and metastasis, remodels the tumor microenvironment, and boosts immune escape. Through deep investigation, novel therapeutic strategies for targeting GPCR activation have been developed, and the final aim is to eliminate GPCR-driven gastric carcinogenesis.

Targeting hedgehog signaling in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a leading cause of cancer related death. The urgent need for effective therapies is highlighted by the lack of adequate targeting. In PDAC, hedgehog (Hh) signaling is known to be aberrantly activated, which prompted the pathway as a possible target for effective treatment for PDAC patients. Unfortunately, specific targeting of upstream molecules within the Hh signaling pathway failed to bring clinical benefit. This led to the ongoing debate on Hh targeting as a therapeutic treatment for PDAC patients. Additionally, concurrent non-canonical activation routes also result in translocation of Gli transcription factors into the nucleus. Therefore, different downstream targets of the Hh signaling pathway were identified and evaluated in preclinical and clinical research. In this review we summarize the variety of Hh signaling antagonists in different preclinical models of PDAC. Furthermore, we discuss published and ongoing clinical trials that evaluated Hh antagonists and point out the current hurdles and future perspectives in the light of redesigning Hh-targeting therapies for the treatment of PDAC patients.

Morphogen Signals Shaping the Gastric Glands in Health and Disease

The adult gastric mucosa is characterised by deep invaginations of the epithelium called glands. These tissue architectural elements are maintained with the contribution of morphogen signals. Morphogens are expressed in specific areas of the tissue, and their diffusion generates gradients in the microenvironment. Cells at different positions in the gland sense a specific combination of signals that instruct them to differentiate, proliferate, regenerate, or migrate. Differentiated cells perform specific functions involved in digestion, such as the production of protective mucus and the secretion of digestive enzymes or gastric acid. Biopsies from gastric precancerous conditions usually display tissue aberrations and change the shape of the glands. Alteration of the morphogen signalling microenvironment is likely to underlie those conditions. Furthermore, genes involved in morphogen signalling pathways are found to be frequently mutated in gastric cancer. We summarise the most recent findings regarding alterations of morphogen signalling during gastric carcinogenesis, and we highlight the new stem cell technologies that are improving our understanding of the regulation of human tissue shape.

TALPID3/KIAA0586 Regulates Multiple Aspects of Neuromuscular Patterning During Gastrointestinal Development in Animal Models and Human

TALPID3/KIAA0586 is an evolutionary conserved protein, which plays an essential role in protein trafficking. Its role during gastrointestinal (GI) and enteric nervous system (ENS) development has not been studied previously. Here, we analyzed chicken, mouse and human embryonic GI tissues with TALPID3 mutations. The GI tract of TALPID3 chicken embryos was shortened and malformed. Histologically, the gut smooth muscle was mispatterned and enteric neural crest cells were scattered throughout the gut wall. Analysis of the Hedgehog pathway and gut extracellular matrix provided causative reasons for these defects. Interestingly, chicken intra-species grafting experiments and a conditional knockout mouse model showed that ENS formation did not require TALPID3, but was dependent on correct environmental cues. Surprisingly, the lack of TALPID3 in enteric neural crest cells (ENCC) affected smooth muscle and epithelial development in a non-cell-autonomous manner. Analysis of human gut fetal tissues with a KIAA0586 mutation showed strikingly similar findings compared to the animal models demonstrating conservation of TALPID3 and its necessary role in human GI tract development and patterning.

Defining the Role of GLI/Hedgehog Signaling in Chemoresistance: Implications in Therapeutic Approaches

Insight into cancer signaling pathways is vital in the development of new cancer treatments to improve treatment efficacy. A relatively new but essential developmental signaling pathway, namely Hedgehog (Hh), has recently emerged as a major mediator of cancer progression and chemoresistance. The evolutionary conserved Hh signaling pathway requires an in-depth understanding of the paradigm of Hh signaling transduction, which is fundamental to provide the necessary means for the design of novel tools for treating cancer related to aberrant Hh signaling. This review will focus substantially on the canonical Hh signaling and the treatment strategies employed in different studies, with special emphasis on the molecular mechanisms and combination treatment in regard to Hh inhibitors and chemotherapeutics. We discuss our views based on Hh signaling's role in regulating DNA repair machinery, autophagy, tumor microenvironment, drug inactivation, transporters, epithelial-to-mesenchymal transition, and cancer stem cells to promote chemoresistance. The understanding of this Achilles' Heel in cancer may improve the therapeutic outcome for cancer therapy.

Construction and Validation of a Novel Prognostic Signature for Intestinal Type of Gastric Cancer

Background

Intestinal type of gastric cancer (IGC) is the largest subtype of gastric cancer (GC) by Lauren classification. The purpose of this present study was to construct a prognostic signature for IGC patients, based on the high-grade dysplasia (HGD) and IGC tissues, to improve and enhance the prognostic accuracy.

Methods

The microarray datasets and associated clinical characteristics of HGD and IGC were obtained from the Gene Expression Omnibus (GEO) database. Based on the differential expression analysis between HGD and IGC, the prognostic-related differential expression genes (DEGs) were identified in a training set by univariate COX regression analysis. The least absolute shrinkage and selection operator (LASSO) regression was used to construct an optimal prognostic signature. The enrichment analysis was performed by using Gene Set Enrichment Analysis (GSEA). The performance of the nomogram was assessed by the calibration curve and concordance index (C-index). The results were validated by using a testing set.

Results

We identified 35 prognostic-related DGEs in the training set. The nine-gene signature was established by LASSO analysis. The nine-gene signature was an independent risk factor in both the training and testing sets. The areas under the curve (AUC) values of receiver operating characteristic (ROC) analysis were 0.733 and 0.700 for the training and testing sets, respectively. In GSEA analysis, the gene expression in high-risk group was enriched in hedgehog signaling, epithelial mesenchymal transition, and angiogenesis. The nomogram for IGC showed good performance with C-index of 0.81 (95% CI: 0.76-0.86) and 0.70 (95% CI: 0.63-0.77) in the training and testing sets, respectively.

Conclusion

We identified and verified a nine-gene signature for the prognostic prediction of IGC patients, which might identify subgroups of IGC patients and select more suitable therapeutic options.

Plasmacytoid dendritic cells-derived IFN-α is involved in Helicobacter pylori infection-induced differentiation of Schlafen 4-expressing myeloid-derived suppressor cells

During chronic infection with Helicobacter pylori, Schlafen 4-expressing myeloid-derived suppressor cells (SLFN4⁺ MDSCs) create a microenvironment favoring intestinal metaplasia and neoplastic transformation. SLFN4 can be induced by IFN-α, which is mainly secreted from plasmacytoid dendritic cells (pDCs). This study tested the hypothesis that Helicobacter pylori infection promotes SLFN4⁺ MDSC differentiation by inducing pDCs to secrete IFN-α. C57BL/6 mice were gavaged with H. pylori and infection lasted 2, 4, or 6 months. The mouse pDCs were isolated from the bone marrow from wild type C57BL/6J mice. The results showed that H. pylori infection increased the number of SLFN4⁺ MDSCs by inducing IFN-α expression in mice. Further mechanistic experiments unraveled that IFN-α induced SLFN4 transcription by binding to the SLFN4 promoter. Furthermore, H. pylori infection stimulated pDCs to secrete IFN-α by activating the TLR9-MyD88-IRF7 pathway. Collectively, Helicobacter pylori infection promotes SLFN4⁺ MDSC differentiation by inducing secretion of IFN-α from pDCs.

Hedgehog signaling in gastrointestinal carcinogenesis and the gastrointestinal tumor microenvironment

The Hedgehog (HH) signaling pathway plays important roles in gastrointestinal carcinogenesis and the gastrointestinal tumor microenvironment (TME). Aberrant HH signaling activation may accelerate the growth of gastrointestinal tumors and lead to tumor immune tolerance and drug resistance. The interaction between HH signaling and the TME is intimately involved in these processes, for example, tumor growth, tumor immune tolerance, inflammation, and drug resistance. Evidence indicates that inflammatory factors in the TME, such as interleukin 6 (IL-6) and interferon-γ (IFN-γ), macrophages, and T cell-dependent immune responses, play a vital role in tumor growth by affecting the HH signaling pathway. Moreover, inhibition of proliferating cancer-associated fibroblasts (CAFs) and inflammatory factors can normalize the TME by suppressing HH signaling. Furthermore, aberrant HH signaling activation is favorable to both the proliferation of cancer stem cells (CSCs) and the drug resistance of gastrointestinal tumors. This review discusses the current understanding of the role and mechanism of aberrant HH signaling activation in gastrointestinal carcinogenesis, the gastrointestinal TME, tumor immune tolerance and drug resistance and highlights the underlying therapeutic opportunities.

Dihydroartemisinin Sensitizes Esophageal Squamous Cell Carcinoma to Cisplatin by Inhibiting Sonic Hedgehog Signaling

Platinum-based regimens have been routinely used in the clinical treatment of patients with esophageal squamous cell carcinoma (ESCC). However, administration of these drugs is frequently accompanied by drug resistance. Revealing the underlying mechanisms of the drug resistance and developing agents that enhance the sensitivity to platinum may provide new therapeutic strategies for the patients. In the present study, we found that the poor outcome of ESCC patients receiving platinum-based regimens was associated with co-expression of Shh and Sox2. The sensitivity of ESCC cell lines to cisplatin was related to their activity of Shh signaling. Manipulating of Shh expression markedly changed the sensitivity of ESCC cells to platinum. Continuous treatment with cisplatin resulted in the activation of Shh signaling and enhanced cancer stem cell-like phenotypes in ESCC cells. Dihydroartemisinin (DHA), a classic antimalarial drug, was identified as a novel inhibitor of Shh pathway. Treatment with DHA attenuated the cisplatin-induced activation of the Shh pathway in ESCC cells and synergized the inhibitory effect of cisplatin on proliferation, sphere and colony formation of ALDH-positive ESCC cells in vitro and growth of ESCC cell-derived xenograft tumors in vivo. Taken together, these results demonstrate that the Shh pathway is an important player in cisplatin-resistant ESCC and DHA acts as a promising therapeutic agent to sensitize ESCC to cisplatin treatment.

Tumour suppressor 15-hydroxyprostaglandin dehydrogenase induces differentiation in colon cancer via GLI1 inhibition

Inflammation is an established risk factor for colorectal cancer. We and others have shown that colorectal cancer patients with elevated cysteinyl leukotriene receptor 2 (CysLT₂R) and 15-hydroxyprostaglandin dehydrogenase (15-PGDH) levels exhibit good prognoses. However, both CysLT₂R and 15-PGDH, which act as tumour suppressors, are often suppressed in colorectal cancer. We previously reported that leukotriene C₄ (LTC₄)-induced differentiation in colon cancer via CysLT₂R signalling. Here, we investigated the involvement of Hedgehog (Hh)-GLI1 signalling, which is often hyperactivated in colorectal cancer. We found that the majority of colorectal cancer patients had high-GLI1 expression, which was negatively correlated with CysLT₂R, 15-PGDH, and Mucin-2 and overall survival compared with the low-GLI1 group. LTC₄-induced 15-PGDH downregulated both the mRNA and protein expression of GLI1 in a protein kinase A (PKA)-dependent manner. Interestingly, the LTC₄-induced increase in differentiation markers and reduction in Wnt targets remained unaltered in GLI1-knockdown cells. The restoration of GLI1 in 15-PGDH-knockdown cells did not ameliorate the LTC₄-induced effects, indicating the importance of both 15-PGDH and GLI1. LTC₄-mediated reduction in the DCLK1 and LGR5 stemness markers in colonospheres was abolished in cells lacking 15-PGDH or GLI1. Both DCLK1 and LGR5 were highly increased in tumour tissue compared with the matched controls. Reduced Mucin-2 levels were observed both in zebrafish xenografts with GLI1-knockdown cells and in the cysltr2^-/- colitis-associated colon cancer (CAC) mouse model. Furthermore, GLI1 expression was positively correlated with stemness and negatively correlated with differentiation in CRC patients when comparing tumour and mucosal tissues. In conclusion, restoring 15-PGDH expression via CysLT₂R activation might benefit colorectal cancer patients.

Sonic Hedgehog Signaling in Organogenesis, Tumors, and Tumor Microenvironments

During mammalian embryonic development, primary cilia transduce and regulate several signaling pathways. Among the various pathways, Sonic hedgehog (SHH) is one of the most significant. SHH signaling remains quiescent in adult mammalian tissues. However, in multiple adult tissues, it becomes active during differentiation, proliferation, and maintenance. Moreover, aberrant activation of SHH signaling occurs in cancers of the skin, brain, liver, gallbladder, pancreas, stomach, colon, breast, lung, prostate, and hematological malignancies. Recent studies have shown that the tumor microenvironment or stroma could affect tumor development and metastasis. One hypothesis has been proposed, claiming that the pancreatic epithelia secretes SHH that is essential in establishing and regulating the pancreatic tumor microenvironment in promoting cancer progression. The SHH signaling pathway is also activated in the cancer stem cells (CSC) of several neoplasms. The self-renewal of CSC is regulated by the SHH/Smoothened receptor (SMO)/Glioma-associated oncogene homolog I (GLI) signaling pathway. Combined use of SHH signaling inhibitors and chemotherapy/radiation therapy/immunotherapy is therefore key in targeting CSCs.

Gastrointestinal diseases among relatives of patients with esophageal atresia with or without tracheoesophageal fistula

BACKGROUND

Several studies have identified genetic factors that are associated with the formation of isolated and non-isolated esophageal atresia with or without tracheoesophageal fistula (EA/TEF) in human and mice. Some of these genetic factors like FOXF1/Foxf1 are associated with Barrett syndrome, esophageal carcinoma or tumors of the gastrointestinal tract. Here, we investigated the prevalence of common gastrointestinal diseases among EA/TEF patients and their first- and second-degree relatives (parents and grandparents).

METHODS

We send out a questionnaire to 280 EA/TEF families asking for the presence of Barrett syndrome, Achalasia and carcinoma of the esophagus, the stomach, the small and large intestine among first- and second-degree relatives.

RESULTS

In 32 of 124 families we found at least one affected family member with a possible association of colon carcinoma and the occurrence of EA/TEF within the same family.

CONCLUSIONS

Further studies are needed to evaluate a possible association.

The role of hedgehog signaling in gastric cancer: molecular mechanisms, clinical potential, and perspective

Patients with advanced gastric cancer usually have a poor prognosis and limited therapeutic options. Overcoming this challenge requires novel targets and effective drugs. The Hedgehog (Hh) signaling pathway plays a crucial role in the development of the gastrointestinal tract and maintenance of the physiologic function of the stomach. Aberrantly activated Hh signaling is implicated in carcinogenesis as well as maintenance of cancer stem cells. Somatic mutations in the components of Hh signaling (PTCH1 and SMO) have been shown to be a major cause of basal cell carcinoma, and dozens of Hh inhibitors have been developed. To date, two inhibitors (GDC-0449 and LDE225) have been approved by the U.S. Food and Drug Administration to treat basal cell carcinoma and medulloblastoma. Here, we review the role of the Hh signaling in the carcinogenesis and progression of gastric cancer and summarize recent findings on Hh inhibitors in gastric cancer. Hedgehog signaling is often aberrantly activated and plays an important role during inflammation and carcinogenesis of gastric epithelial cells. Further study of the precise mechanisms of Hh signaling in this disease is needed for the validation of therapeutic targets and evaluation of the clinical utility of Hh inhibitors for gastric cancer.

Sonic Hedgehog Protein is Frequently Up-Regulated in Pancreatic Cancer Compared to Colorectal Cancer

Sonic hedgehog (SHH) is a secreted protein which functions in autocrine or paracrine fashion on target cells to activate hedgehog (HH) signalling cascade responsible for growth and proliferation. This study is an attempt to understand the expression dynamics of SHH protein in colon, rectal and pancreatic cancers. Protein expression of SHH was studied by Western Blotting in the histologically confirmed colon, rectum and pancreatic cancer tissue samples along with their adjacent normal tissues. Only 31.4% (11 of 35) and 26.9% (7 of 26) of colon and rectal cancer cases respectively showed an increase in SHH expression in tumours compared to 72.7% (24 of 33) of the pancreatic cancer cases when compared with their adjacent normal tissues. Our results suggest that SHH may have a strong role in the predisposition of Pancreatic cancer and could possibly be used as a diagnostic or prognostic biomarker.

Roles for selenium and selenoprotein P in the development, progression, and prevention of intestinal disease

Selenium (Se) is a micronutrient essential to human health, the function of which is mediated in part by incorporation into a class of proteins known as selenoproteins (SePs). As many SePs serve antioxidant functions, Se has long been postulated to protect against inflammation and cancer development in the gut by attenuating oxidative stress. Indeed, numerous studies over the years have correlated Se levels with incidence and severity of intestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer (CRC). Similar results have been obtained with the Se transport protein, selenoprotein P (SELENOP), which is decreased in the plasma of both IBD and CRC patients. While animal models further suggest that decreases in Se or SELENOP augment colitis and intestinal tumorigenesis, large-scale clinical trials have yet to show a protective effect in patient populations. In this review, we discuss the function of Se and SELENOP in intestinal diseases and how research into these mechanisms may impact patient treatment.

Are Gastric and Esophageal Metaplasia Relatives? The Case for Barrett's Stemming from SPEM

Chronic injury and inflammation in the esophagus can cause a change in cellular differentiation known as metaplasia. Most commonly, the differentiation changes manifest as Barrett's esophagus (BE), characterized by the normal stratified squamous epithelium converting into a cuboidal-columnar, glandular morphology. BE cells can phenotypically resemble specific normal cell types of the stomach or intestine, or they can have overlapping phenotypes in disorganized admixtures. The stomach can also undergo metaplasia characterized by aberrant gastric or intestinal differentiation patterns. In both organs, it has been argued that metaplasia may represent a recapitulation of the embryonic or juvenile gastrointestinal tract, as cells access a developmental progenitor genetic program that can help repair damaged tissue. Here, we review the normal development of esophagus and stomach, and describe how BE represents an intermixing of cells resembling gastric pseudopyloric (SPEM) and intestinal metaplasia. We discuss a cellular process recently termed "paligenosis" that governs how mature, differentiated cells can revert to a proliferating progenitor state in metaplasia. We discuss the "Cyclical Hit" theory in which paligenosis might be involved in the increased risk of metaplasia for progression to cancer. However, somatic mutations might occur in proliferative phases and then be warehoused upon redifferentiation. Through years of chronic injury and many rounds of paligenosis and dedifferentiation, eventually a cell with a mutation that prevents dedifferentiation may arise and clonally expand fueling stable metaplasia and potentially thereafter acquiring additional mutations and progressing to dysplasia and cancer.

Gastric cancer and Hedgehog signaling pathway: emerging new paradigms

Ever since its initial discovery in Drosophila, hedgehog signaling has been linked to foregut development, The mammalian genome expresses three Hedgehog paralogues, sonic hedgehog (Shh), Indian Hedgehog, and desert hedgehog. In the mucosa of the embryonic and adult foregut, Shh expression is the highest. It has now become clear that hedgehog signaling is of pivotal importance in gastric homeostasis. Aberrant activation of hedgehog signaling is associated with a range of pathological consequences including various cancers. Also in gastric cancer, clinical and preclinical data support a role of Hedgehog signaling in neoplastic transformation, and gastrointestinal cancer development, also through cancer stroma interaction. Technological advance are facilitating monitoring Hedgehog signaling broadening options for the more efficient screening of individuals predisposed to eventually developing gastric cancer and targeting Hedgehog signaling may provide opportunities for prophylactic therapy once atrophic gastritis develops. Nevertheless, convincing evidence that Hedgehog antagonists are of clinically useful in the context of gastric cancer is still conspicuously lacking. Here we analyze review the role of Hedgehog in gastric physiology and the potential usefulness of targeting Hedgehog signaling in gastric cancer.

Sonic hedgehog antagonists reduce size and alter patterning of the frog inner ear

Sonic hedgehog (Shh) signaling plays a major role in vertebrate development, from regulation of proliferation to the patterning of various organs. In amniotes, Shh affects dorsoventral patterning in the inner ear but affects anteroposterior patterning in teleost ears. It remains unknown how altered function of Shh relates to morphogenetic changes that coincide with the evolution of limbs and novel auditory organs in the ear. In this study, we used the tetrapod, Xenopus laevis, to test how increasing concentrations of the Shh signal pathway antagonist, Vismodegib, affects ear development. Vismodegib treatment dose dependently alters the development of the ear, hypaxial muscle, and indirectly the Mauthner cell through its interaction with the inner ear afferents. Together, these phenotypes have an effect on escape response. The altered Mauthner cell likely contributes to the increased time to respond to a stimulus. In addition, the increased hypaxial muscle in the trunk likely contributes to the subtle change in animal C-start flexion angle. In the ear, Vismodegib treatment results in decreasing segregation between the gravistatic sensory epithelia as the concentration of Vismodegib increases. Furthermore, at higher doses, there is a loss of the horizontal canal but no enantiomorphic transformation, as in bony fish lacking Shh. Like in amniotes, Shh signaling in frogs affects dorsoventral patterning in the ear, suggesting that auditory sensory evolution in sarcopterygians/tetrapods evolved with a shift of Shh function in axis specification. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1385-1400, 2017.

Antagonism between Hedgehog and Wnt signaling pathways regulates tumorigenicity

The crosstalk of multiple cellular signaling pathways is crucial in animal development and tissue homeostasis, and its dysregulation may result in tumor formation and metastasis. The Hedgehog (Hh) and Wnt signaling pathways are both considered to be essential regulators of cell proliferation, differentiation and oncogenesis. Recent studies have indicated that the Hh and Wnt signaling pathways are closely associated and involved in regulating embryogenesis and cellular differentiation. Hh signaling acts upstream of the Wnt signaling pathway, and negative regulates Wnt activity via secreted frizzled-related protein 1 (SFRP1), and the Wnt/β-catenin pathway downregulates Hh activity through glioma-associated oncogene homolog 3 transcriptional regulation. This evidence suggests that the imbalance of Hh and Wnt regulation serves a crucial role in cancer-associated processes. The activation of SFRP1, which inhibits Wnt, has been demonstrated to be an important cross-point between the two signaling pathways. The present study reviews the complex interaction between the Hh and Wnt signaling pathways in embryogenesis and tumorigenicity, and the role of SFRP1 as an important mediator associated with the dysregulation of the Hh and Wnt signaling pathways.

From inflammation to gastric cancer - the importance of Hedgehog/GLI signaling in Helicobacter pylori-induced chronic inflammatory and neoplastic diseases

Infections with the human pathogen Helicobacter pylori (H. pylori) are closely associated with the development of inflammatory disorders and neoplastic transformation of the gastric epithelium. Drastic changes in the micromilieu involve a complex network of H. pylori-regulated signal transduction pathways leading to the release of proinflammatory cytokines, gut hormones and a wide range of signaling molecules. Besides controlling embryonic development, the Hedgehog/GLI signaling pathway also plays important roles in epithelial proliferation, differentiation, and regeneration of the gastric physiology, but also in the induction and progression of inflammation and neoplastic transformation in H. pylori infections. Here, we summarize recent findings of H. pylori-associated Hedgehog/GLI signaling in gastric homeostasis, malignant development and the modulation of the gastric tumor microenvironment.

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.

Sonic hedgehog inhibitors prevent colitis-associated cancer via orchestrated mechanisms of IL-6/gp130 inhibition, 15-PGDH induction, Bcl-2 abrogation, and tumorsphere inhibition

Sonic hedgehog (SHH) signaling is essential in normal development of the gastrointestinal (GI) tract, whereas aberrantly activated SHH is implicated in GI cancers because it facilitates carcinogenesis by redirecting stem cells. Since colitis-associated cancer (CAC) is associated with inflammatory bowel diseases, in which SHH and IL-6 signaling, inflammation propagation, and cancer stem cell (CSC) activation have been implicated, we hypothesized that SHH inhibitors may prevent CAC by blocking the above SHH-related carcinogenic pathways. In the intestinal epithelial cells IEC-6 and colon cancer cells HCT-116, IL-6 expression and its signaling were assessed with SHH inhibitors and levels of other inflammatory mediators, proliferation, apoptosis, tumorsphere formation, and tumorigenesis were also measured. CAC was induced in C57BL/6 mice by administration of azoxymethane followed by dextran sodium sulfate administration. SHH inhibitors were administered by oral gavage and the mice were sacrificed at 16 weeks. TNF-α–stimulated IEC-6 cells exhibited increased levels of proinflammatory cytokines and enzymes, whereas SHH inhibitors suppressed TNF-α–induced inflammatory signaling, especially IL-6/IL-6R/gp130 signaling. SHH inhibitors significantly induced apoptosis, inhibited cell proliferation, suppressed tumorsphere formation, and reduced stemness factors. In the mouse model, SHH inhibitors significantly reduced tumor incidence and multiplicity, decreased the expression of IL-6, TNF-α, COX-2, STAT3, and NF-κB, and significantly induced apoptosis. In colosphere xenografts, SHH inhibitor significantly suppressed tumorigenesis by inhibiting tumorsphere formation. Taken together, our data suggest that administration of SHH inhibitors could be an effective strategy to prevent colitis-induced colorectal carcinogenesis, mainly by targeting IL-6 signaling, ablating CSCs, and suppressing oncogenic inflammation, achieving chemoquiescence ultimately.

Hedgehog signaling in the stomach

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

Small hepatocyte-like progenitor cells may be a Hedgehog signaling pathway-controlled subgroup of liver stem cells

The present study aimed to investigate the expression levels of components of the Hedgehog signaling pathway (HH) during the proliferation of a liver stem cell subgroup, namely small hepatocyte-like progenitor cells (SHPCs). Retrorsine-treated Fisher 344 rats underwent a partial hepatectomy (PH) to induce the proliferation of SHPCs, after which reverse transcription-polymerase chain reaction (PCR), quantitative PCR, immunohistochemistry and western blot analysis were performed to analyze the expression of various components of the HH in primary SHPCs at different times points post-PH. A number of components of the HH, including Indian hedgehog (IHH), patched (PTCH), smoothened and glioma-associated oncogene (GLI)1, 2 and 3, were continuously expressed and showed dynamic changes in proliferating SHPCs. In addition, the expression levels of IHH, PTCH and GLI1 were significantly different as compared with those of the control group at the same time point, and there were significant differences among the various time points in the experimental group (P<0.01). Furthermore, there was an association between the postoperative day and expression levels of HH components in the retrorsine-treated group. An immunohistochemical analysis demonstrated that PTCH was also expressed at the protein level. In conclusion, the results of the present study suggested that the HH was continuously activated during the proliferation of SHPCs, thus indicating that SHPCs may be a subgroup of stem cells that are regulated by the HH.

Current evidence for cancer stem cells in gastrointestinal tumors and future research perspectives

Cancer stem cells (CSCs) are a very heterogeneous subpopulation of "stem-like" cancer cells that have been identified in many cancers, including leukemias and solid tumors. It is believed that CSCs drive tumor growth, malignant behavior and are responsible for the initiation of metastatic spread. In addition, CSCs have been implicated in chemotherapy and radiotherapy resistance. Current evidence supports the theory that CSCs share at least two main features of normal stem cells: self-renewal and differentiation, properties that contribute to tumor survival even in the presence of aggressive chemotherapy; however, the mechanism(s) governing the unique biology of CSCs remain unclear. In the field of gastrointestinal cancer, where we face very low survival rates across different tumor types, unraveling the role of CSCs in gastrointestinal tumors should improve our knowledge of cancer biology and chemoresistance, ultimately benefiting patient survival. Towards this end, much effort is being invested in the characterization of CSCs as a means of overcoming drug resistance and controlling metastatic spread. In this review we will cover the concept of CSCs, the current evidence for CSCs in gastrointestinal tumors and future research directions.

Schlafen 4-expressing myeloid-derived suppressor cells are induced during murine gastric metaplasia

Chronic Helicobacter pylori infection triggers neoplastic transformation of the gastric mucosa in a small subset of patients, but the risk factors that induce progression to gastric metaplasia have not been identified. Prior to cancer development, the oxyntic gastric glands atrophy and are replaced by metaplastic cells in response to chronic gastritis. Previously, we identified schlafen 4 (Slfn4) as a GLI1 target gene and myeloid differentiation factor that correlates with spasmolytic polypeptide-expressing metaplasia (SPEM) in mice. Here, we tested the hypothesis that migration of SLFN4-expressing cells from the bone marrow to peripheral organs predicts preneoplastic changes in the gastric microenvironment. Lineage tracing in Helicobacter-infected Slfn4 reporter mice revealed that SLFN4+ cells migrated to the stomach, where they exhibited myeloid-derived suppressor cell (MDSC) markers and acquired the ability to inhibit T cell proliferation. SLFN4+ MDSCs were not observed in infected GLI1-deficient mice. Overexpression of sonic hedgehog ligand (SHH) in infected WT mice accelerated the appearance of SLFN4+ MDSCs in the gastric corpus. Similarly, in the stomachs of H. pylori-infected patients, the human SLFN4 ortholog SLFN12L colocalized to cells that expressed MDSC surface markers CD15+CD33+HLA-DRlo. Together, these results indicate that SLFN4 marks a GLI1-dependent population of MDSCs that predict a shift in the gastric mucosa to a metaplastic phenotype.

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.

Concerted actions of ameliorated colitis, aberrant crypt foci inhibition and 15-hydroxyprostaglandin dehydrogenase induction by sonic hedgehog inhibitor led to prevention of colitis-associated cancer

The sonic hedgehog (Shh) signaling has been known to contribute to carcinogenesis in organ, where hedgehog exerted organogenesis and in cancers, which are developed based on mutagenic inflammation. Therefore, colitis-associated cancer (CAC) can be a good model to prove whether Shh inhibitors can be applied to prevent, as the efforts to discover potent anti-inflammatory agent are active to prevent CAC. Here, under the hypothesis that Shh inhibitors can prevent CAC, mouse model was generated to develop CAC by azoxymethane (AOM)-initiated, dextran sodium sulfate-promoted carcinogenesis. Shh inhibitors, cerulenin and itraconazole were treated by oral gavage and the mice were sacrificed at early phase of 3 weeks and late phase of 16 weeks. Compared to control group, the number of aberrant crypt foci at 3 weeks and tumor incidence at 16 weeks were all significantly decreased with Shh inhibitor. Significant attenuations of macrophage infiltration accompanied with significant decreases of IL-6, COX-2, STAT3 and NF-κB as well as significant ameliorations of β-catenin nuclear translocation, cyclin D1 and CDK4 were imposed with Shh inhibitors. Especially, CAC was accompanied with significant cancellation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), but their levels were significantly preserved with Shh inhibitors. Among inflammatory mediators, significantly decreased levels of IL-6 and TNF-α, regulated with repressed NF-κb and STAT3, were prominent with Shh inhibitor, whereas significant inductions of apoptosis were noted with Shh inhibitors. In conclusion, Shh inhibitors significantly prevented CAC covering either ameliorating oncogenic inflammation or suppressing tumor proliferation, especially supported with significant inhibition of IL-6 and STAT3 signaling, 15-PGDH preservation and apoptosis induction.

The role of cullin proteins in gastric cancer

The cullin proteins are a family of scaffolding proteins that associate with RING proteins and ubiquitin E3 ligases and mediate substrate-receptor bindings. Thus, cullin proteins regulate the specificity of ubiquitin targeting in the regulation of proteins involved in various cellular processes, including proliferation, differentiation, and apoptosis. There are seven cullin proteins that have been identified in eukaryotes: CUL1, CUL2, CUL3, CUL4A, CUL4B, CUL5, and CUL7/p53-associated parkin-like cytoplasmic protein. All of these proteins contain a conserved cullin homology domain that binds to RING box proteins. Cullin-RING ubiquitin ligase complexes are activated upon post-translational modification by neural precursor cell-expressed, developmentally downregulated protein 8. The aberrant expression of several cullin proteins has been implicated in many cancers though the significance in gastric cancer has been less well investigated. This review provides the first systematic discussion of the associations between all members of the cullin protein family and gastric cancer. Functional and regulatory mechanisms of cullin proteins in gastric carcinoma progression are also summarized along with a discussion concerning future research areas. Accumulating evidence suggests a critical role of cullin proteins in tumorigenesis, and a better understanding of the function of these individual cullin proteins and their targets will help identify potential biomarkers and therapeutic targets.

Inhibition of SALL4 suppresses carcinogenesis of colorectal cancer via regulating Gli1 expression

BACKGROUND

SALL4 is a novel oncogene mediating tumorigenesis in multiple carcinomas. However, its actual role and mechanisms participating in the development of colorectal cancer remains unclear.

METHODS

Immunohistochemical staining and Western blot were conducted to detect the expression of SALL4 and other molecules. siRNA of SALL4 was transfected to silence SALL4 expression in Caco-2 cell line. Flow cytometry was used for cell cycle and apoptosis analysis. Wound healing and transwell assay were used for invasion test. CCK-8 test was employed for cell proliferation and drug sensitivity assessment.

RESULTS

By inhibition of SALL4 expression, the proliferation, invasiveness and drug resistance were dramatically reduced while apoptosis rate was up-regulated. Gli1 was found to decrease its expression in SALL4 silencing cells. Moreover, the inhibition on tumorigenesis of Caco-2 by SALL4 silencing was antagonized by Gli1 up-regulation, suggesting Gli1 as a downstream target of SALL4 in cancer development.

CONCLUSION

SALL4 inhibition limited oncogenesis on colorectal cancer by reducing Gli1 expression.

Current Status on Stem Cells and Cancers of the Gastric Epithelium

Gastric cancer is still a leading cause of cancer-related mortality worldwide in spite of declining incidence. Gastric cancers are, essentially, adenocarcinomas and one of the strongest risk factors is still infection with Helicobacter pylori. Within the last years, it became clear that gastric self-renewal and carcinogenesis are intimately linked, particularly during chronic inflammatory conditions. Generally, gastric cancer is now regarded as a disease resulting from dysregulated differentiation of stem and progenitor cells, mainly due to an inflammatory environment. However, the situation in the stomach is rather complex, consisting of two types of gastric units which show bidirectional self-renewal from an unexpectedly large variety of progenitor/stem cell populations. As in many other tumors, cancer stem cells have also been characterized for gastric cancer. This review focuses on the various gastric epithelial stem cells, how they contribute to self-renewal and which routes are known to gastric adenocarcinomas, including their stem cells.

A comprehensive review of the role of the hedgehog pathway and vismodegib in the management of basal cell carcinoma

BACKGROUND

Basal cell carcinoma (BCC) is the most common cancer. Most cases of BCCs are treated with only optimal surgical resection. However, unresectable, locally advanced or metastatic tumors might have potential to progress. In this patient group, there is no standardized treatment approach. Vismodegib is a new selective inhibitor of the hedgehog (Hh) pathway. This manuscript is aimed to review the efficacy of the Hh pathway inhibitor vismodegib in BCC patients with locally advanced or metastatic disease.

SCOPE

Vismodegib showed positive results in clinical studies. A computerized search of the PubMed and American Society of Clinical Oncology Meeting abstracts was performed, by searching for the following keywords: 'vismodegib', 'pathway', 'inhibitor', and 'targeted therapies for BCC'. The last search was done on 1 September 2014. Most of the vismodegib data depend on phase I and II trials.

FINDINGS

Preclinical and clinical studies have shown that Hh pathway activation occurs in BCC. In BCC patients the role of chemotherapy is not completely known. Although conventional chemotherapies like cisplatins increase the response rate in BCC, improvement in overall survival and progression free survival were not demonstrated. Results of both phase I and phase II studies have shown that vismodegib is a potential new treatment strategy for patients with locally advanced and metastatic BCC. As in previously published phase I trials, in the ERIVANCE BCC study the primary endpoint, objective response rate, significantly increased by 43% and 30% in patients with locally advanced and metastatic BCC, respectively. Because of the promising results in phase I and II trials, vismodegib was approved by the Food and Drug Administration (FDA) in the treatment of patients with BCC who are not suitable for surgery or radiotherapy or with relapsed locally advanced disease following surgery or metastatic disease.

CONCLUSION

Recent trials have shown that vismodegib has produced promising activity in patients with locally advanced and metastatic BCC. The ongoing studies with vismodegib in other solid tumors and BCC will shed light on more certain treatment pathways.

SPOP suppresses tumorigenesis by regulating Hedgehog/Gli2 signaling pathway in gastric cancer

Background

Recent evidence suggests that aberrant activation of Hedgehog (Hh) signaling by Gli transcription factors is characteristic of a variety of aggressive human carcinomas including gastric cancer. Speckle-type POZ protein, SPOP, is an E3 ubiquitin ligase adaptor, and it is found to inhibit oncogenic signaling. However, the molecular mechanisms are largely unknown.

Methods

In this study, we characterized the expression of SPOP in 88 pairs of gastric cancer tissues and adjacent tissues by immunohistochemical staining and Western blotting. The relationship between SPOP expression and clinical pathologic factors was analyzed. Transfected gastric cancer cell lines were used in cell viability, wound healing and colony formation assays. The interaction of SPOP with Gli2 and other related apoptotic proteins was assessed by immunoprecipitation, Western blotting, real-time PCR and dual luciferase reporter assays. Intracellular interaction of SPOP and Gli2 was visualized by immunofluorescent staining in gastric cancer cells.

Results

Immunohistochemical staining of SPOP can be detected in gastric cancer tissues but much less than adjacent gastric tissues (P < 0.01). High SPOP expression is negatively correlated with lymph node metastasis, poor histological differentiation, and tumor malignancy according to TNM staging. In vitro experiments revealed that over-expression of SPOP prevented tumor cells from proliferation, migration and colony formation in gastric cancer cell lines. Likewise, repression of SPOP promoted cell viability, migration, proliferation, and attenuated apoptosis. Mechanistic studies revealed that increasing SPOP accelerated Gli2 degradation but regardless of Gli2 synthesis. Furthermore, cytoplasmic Gli2 decreased markedly along with the abundant expression of SPOP in MKN45 cells.

Conclusions

Our findings indicate that SPOP plays critical roles in suppressing gastric tumorigenesis through inhibiting Hh/Gli2 signaling pathway. It may provide an alternative strategy for developing therapeutic agents of gastric cancer in future.

GLI2 is a novel therapeutic target for metastasis of osteosarcoma

Aberrant activation of the Hedgehog (Hh) pathway has been reported in several malignancies. We previously demonstrated that knockdown of GLI2 inhibited proliferation of osteosarcoma cells through regulation of the cell cycle. In this study, we analyzed the function of GLI2 in the pathogenesis of osteosarcoma metastasis. Immunohistochemical studies showed that GLI2 was overexpressed in patient osteosarcoma specimens. Knockdown of GLI2 inhibited migration and invasion of osteosarcoma cells. In contrast, the forced expression of constitutively active GLI2 in mesenchymal stem cells promoted invasion. In addition, xenograft models showed that knockdown of GLI2 decreased lung metastasis of osteosarcomas. To examine clinical applications, we evaluated the efficacy of arsenic trioxide (ATO), which is a Food and Drug Administration-approved antitumor drug, on osteosarcoma cells. ATO treatment suppressed the invasiveness of osteosarcoma cells by inhibiting the transcriptional activity of GLI2. In addition, the combination of Hh inhibitors including ATO, vismodegib and GANT61 prevented migration and metastasis of osteosarcoma cells. Consequently, our findings suggested that GLI2 regulated metastasis as well as the progression of osteosarcomas. Inhibition of the GLI2 transcription may be an effective therapeutic method for preventing osteosarcoma metastasis.

Suppression of growth and migration by blocking the Hedgehog signaling pathway in gastric cancer cells

PURPOSE

Previous studies have indicated that Hedgehog signaling is essential for gastric cancer development, but its precise role is still unclear. The aim of this study was to clarify the role of Hedgehog signaling in gastric cancer development.

METHODS

The expression of key Hedgehog signaling components in clinical samples of sequential gastric cancer stages was assessed by immunohistochemistry. The roles and regulatory mechanisms of Hedgehog signaling in human gastric cancer cells and normal gastric epithelial cells were investigated using multiple cell biological approaches and cDNA microarray analyses.

RESULTS

Hedgehog signaling was found to be abnormally activated in a ligand-independent manner during gastric cancer development. Gli1 over-expression and reduced SuFu expression were found to be typical events in gastric cancer tissues. Gli1 over-expression was found to correlate with a poorly differentiated histology, advanced clinical stage, membrane serosa infiltration and lymph node metastasis in patients with gastric cancer. Data obtained from multiple cell biological assays showed that human gastric cancer cells require active Hedgehog signaling for survival, proliferation, migration and colony formation. N-Shh treatment significantly enhanced the migration, invasion and colony formation of gastric cancer cells. Moreover, the results of cDNA microarray analyses indicated that after treatment with cyclopamine or GANT61 (inhibitors of Hedgehog signaling), differentially expressed genes in gastric cancer cells were enriched in the apoptosis and MAPK pathways. Inhibitors of the Hedgehog pathway were found to suppress gastric cancer cell growth via apoptosis induction.

CONCLUSIONS

Our findings indicate a vital role of the activated Hedgehog signaling pathway in promoting gastric initiation and progression. The Hedgehog signaling pathway may serve as a target for gastric cancer therapy.

Inhibition of Hedgehog signaling in the gastrointestinal tract: targeting the cancer microenvironment

This review summarizes emerging information regarding the Hedgehog (Hh) signaling pathway during neoplastic transformation in the gastrointestinal tract. Although there is a role for the well-established canonical pathway in which Hedgehog ligands interact with their receptor Patched, there is sufficient evidence that downstream components of the Hh pathway, e.g., Gli1, are hijacked by non-Hh signaling pathways to promote the conversion of the epithelium to dysplasia and carcinoma. We review the canonical pathway and involvement of primary cilia, and then focus on current evidence for Hh signaling in luminal bowel cancers as well as accessory organs, i.e., liver, pancreas and biliary ducts. We conclude that targeting the Hh pathway with small molecules, nutriceuticals and other mechanisms will likely require a combination of inhibitors that target Gli transcription factors in addition to canonical modulators such as Smoothened.

Aberrant expression of sonic hedgehog pathway in colon cancer and melanosis coli

OBJECTIVE

To determine the hedgehog (Hh) signaling pathway correlated with the development of colon cancer and melanosis coli.

METHODS

Protein and mRNA levels of Hh signaling pathway components (sonic hedgehog [Shh], protein patched homolog 1 [Ptch 1], GLI family zinc finger 1 [Gli 1] and suppressor of fused homolog [Drosophila] [Sufu]) in 127 patients with colon cancer, 36 with melanosis coli and 20 adjacent normal mucosal tissues taken from surgical specimens were evaluated using antibody staining and quantitative real-time polymerase chain reaction.

RESULTS

In adjacent normal tissue Shh and Ptch1, but not Gli1 or Sufu, were weakly expressed and mainly in the lining epithelium of the colonic mucosa. In cancerous tissues Shh and Gli1 were uniformly strong while Ptch1 was patchy and weak, and Sufu uniformly weak, which paralleled their levels of corresponding mRNA. Elevated protein levels of Shh and Ptch were significantly associated with mucinous colonic tissues. Elevated Sufu protein levels were positively correlated with the diameter and invasion of the tumor. In patients with melanosis coli, mRNA levels of Shh, Ptch1, Gli1 and Sufu were very low, which was similar to those of adjacent normal tissues; but protein levels of Shh, Ptch1 and Gli1, but not Sufu, were high, which was similar to those of cancerous tissues.

CONCLUSIONS

The mRNA and protein levels of Hh pathway components are aberrantly elevated in colon cancer, which may be the potential molecular classification markers. Further studies are required to determine the role of melanosis coli in the colon tumorigenesis.

Profile of vismodegib and its potential in the treatment of advanced basal cell carcinoma

Basal cell carcinoma (BCC) is the most common human malignancy. Recent advances in our understanding of the critical biologic pathways implicated in the development and progression of BCC have led to the development of the first molecular targeted therapy for this disease. The hedgehog pathway is mutated in virtually all patients with BCC and recent trials with vismodegib, an inhibitor of this pathway, have shown significant responses. This review will discuss the importance of the hedgehog pathway in the pathogenesis of BCC and describe in detail the pharmacology of vismodegib in relation to its activity in advanced BCC.

Hedgehog signaling pathway and ovarian cancer

Epithelial ovarian carcinoma (EOC) is the most common form of ovarian malignancies and the most lethal gynecologic malignancy in the United States. To date, in spite of treatment to it with the extensive surgical debulking and chemotherapy, the prognosis of EOC remains dismal. Recently, it has become increasingly clear that in many instances, the signaling and molecular players that control development are the same, and when inappropriately regulated, drive tumorigenesis and cancer development. Here, we discuss the possible involvement of Hedgehog (Hh) pathway in the cellular regulation and development of cancer in the ovaries. Using the in vitro and in vivo assays developed has facilitated the dissection of the mechanisms behind Hh-driven ovarian cancers formation and growth. Based on recent studies, we propose that the inhibition of Hh signaling may interfere with spheroid-like structures in ovarian cancers. The components of the Hh signaling may provide novel drug targets, which could be explored as crucial combinatorial strategies for the treatment of ovarian cancers.

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.