Endodermal Hedgehog signals modulate Notch pathway activity in the developing digestive tract mesenchyme

Loss-of-Function of CLMP Is Associated With Congenital Short Bowel Syndrome and Impaired Intestinal Development

Coxsackie and adenovirus receptor-like membrane protein (CLMP) mutation is identified as a genetic risk factor of congenital short bowel syndrome (CSBS). However, the specific pathogenic mechanism remains unclear. This study aimed to explore the clinical manifestations, genetic characteristics, and molecular mechanisms underlying CSBS caused by CLMP mutations. Whole-exome sequencing was performed to determine the pathogenic gene mutations in children with CSBS and their family members. In addition, a zebrafish model was established by microinjecting morpholinos into zebrafish embryos to investigate the role of clmp in intestinal embryonic development. This was investigated by measuring the length of zebrafish, evaluating gastrointestinal motility, and performing qRT-PCR assays. Two children with CSBS had CLMP mutations, one with a c.244C>T (p.R82*) mutation and exons 3-5 deletion, and the other with a c.23T>A (p.L8*) mutation and exons 3-5 deletion. After knocking down clmp expression in zebrafish embryos, the intestinal length and the gastrointestinal motility decreased. Furthermore, the expression of smooth muscle-associated genes decreased significantly. Additionally, clmp mRNA partially rescued zebrafish defects caused by clmp morpholino knockdown. Clmp knockdown decreased intestinal transport dynamics and expression of smooth muscle-related genes in zebrafish. CLMP is expected to be a potential gene therapeutic target for CSBS.

Physical organogenesis of the gut

The gut has been a central subject of organogenesis since Caspar Friedrich Wolff’s seminal 1769 work ‘De Formatione Intestinorum’. Today, we are moving from a purely genetic understanding of cell specification to a model in which genetics codes for layers of physical–mechanical and electrical properties that drive organogenesis such that organ function and morphogenesis are deeply intertwined. This Review provides an up-to-date survey of the extrinsic and intrinsic mechanical forces acting on the embryonic vertebrate gut during development and of their role in all aspects of intestinal morphogenesis: enteric nervous system formation, epithelium structuring, muscle orientation and differentiation, anisotropic growth and the development of myogenic and neurogenic motility. I outline numerous implications of this biomechanical perspective in the etiology and treatment of pathologies, such as short bowel syndrome, dysmotility, interstitial cells of Cajal-related disorders and Hirschsprung disease.

Neuron-Glia Interaction in the Developing and Adult Enteric Nervous System

The enteric nervous system (ENS) constitutes the largest part of the peripheral nervous system. In recent years, ENS development and its neurogenetic capacity in homeostasis and allostasishave gained increasing attention. Developmentally, the neural precursors of the ENS are mainly derived from vagal and sacral neural crest cell portions. Furthermore, Schwann cell precursors, as well as endodermal pancreatic progenitors, participate in ENS formation. Neural precursorsenherite three subpopulations: a bipotent neuron-glia, a neuronal-fated and a glial-fated subpopulation. Typically, enteric neural precursors migrate along the entire bowel to the anal end, chemoattracted by glial cell-derived neurotrophic factor (GDNF) and endothelin 3 (EDN3) molecules. During migration, a fraction undergoes differentiation into neurons and glial cells. Differentiation is regulated by bone morphogenetic proteins (BMP), Hedgehog and Notch signalling. The fully formed adult ENS may react to injury and damage with neurogenesis and gliogenesis. Nevertheless, the origin of differentiating cells is currently under debate. Putative candidates are an embryonic-like enteric neural progenitor population, Schwann cell precursors and transdifferentiating glial cells. These cells can be isolated and propagated in culture as adult ENS progenitors and may be used for cell transplantation therapies for treating enteric aganglionosis in Chagas and Hirschsprung's diseases.

Identification and characterization of cellular heterogeneity within the developing renal interstitium

Kidney formation requires the coordinated growth of multiple cell types including the collecting ducts, nephrons, vasculature and interstitium. There is a long-held belief that interactions between progenitors of the collecting ducts and nephrons are primarily responsible for kidney development. However, over the last several years, it has become increasingly clear that multiple aspects of kidney development require signaling from the interstitium. How the interstitium orchestrates these various roles is poorly understood. Here, we show that during development the interstitium is a highly heterogeneous patterned population of cells that occupies distinct positions correlated to the adjacent parenchyma. Our analysis indicates that the heterogeneity is not a mere reflection of different stages in a linear developmental trajectory but instead represents several novel differentiated cell states. Further, we find that β-catenin has a cell autonomous role in the development of a medullary subset of the interstitium and that this non-autonomously affects the development of the adjacent epithelia. These findings suggest the intriguing possibility that the different interstitial subtypes may create microenvironments that play unique roles in development of the adjacent epithelia and endothelia.

Notch signaling: Its essential roles in bone and craniofacial development

Notch is a cell–cell signaling pathway that is involved in a host of activities including development, oncogenesis, skeletal homeostasis, and much more. More specifically, recent research has demonstrated the importance of Notch signaling in osteogenic differentiation, bone healing, and in the development of the skeleton. The craniofacial skeleton is complex and understanding its development has remained an important focus in biology. In this review we briefly summarize what recent research has revealed about Notch signaling and the current understanding of how the skeleton, skull, and face develop. We then discuss the crucial role that Notch plays in both craniofacial development and the skeletal system, and what importance it may play in the future.

Single cell and genetic analyses reveal conserved populations and signaling mechanisms of gastrointestinal stromal niches

Stomach and intestinal stem cells are located in discrete niches called the isthmus and crypt, respectively. Recent studies have demonstrated a surprisingly conserved role for Wnt signaling in gastrointestinal development. Although intestinal stromal cells secrete Wnt ligands to promote stem cell renewal, the source of stomach Wnt ligands is still unclear. Here, by performing single cell analysis, we identify gastrointestinal stromal cell populations with transcriptome signatures that are conserved between the stomach and intestine. In close proximity to epithelial cells, these perictye-like cells highly express telocyte and pericyte markers as well as Wnt ligands, and they are enriched for Hh signaling. By analyzing mice activated for Hh signaling, we show a conserved mechanism of GLI2 activation of Wnt ligands. Moreover, genetic inhibition of Wnt secretion in perictye-like stromal cells or stromal cells more broadly demonstrates their essential roles in gastrointestinal regeneration and development, respectively, highlighting a redundancy in gastrointestinal stem cell niches.

Wnt, Notch, and TGF-β Pathways Impinge on Hedgehog Signaling Complexity: An Open Window on Cancer

Constitutive activation of the Hedgehog (Hh) signaling pathway is associated with increased risk of developing several malignancies. The biological and pathogenic importance of Hh signaling emphasizes the need to control its action tightly, both physiologically and therapeutically. Evidence of crosstalk between Hh and other signaling pathways is reported in many tumor types. Here, we provide an overview of the current knowledge about the communication between Hh and major signaling pathways, such as Notch, Wnt, and transforming growth factor β (TGF-β), which play critical roles in both embryonic and adult life. When these pathways are unbalanced, impaired crosstalk contributes to disease development. It is reported that more than one of these pathways are active in different type of tumors, at the same time. Therefore, starting from a plethora of stimuli that activate multiple signaling pathways, we describe the signals that preferentially converge on the Hh signaling cascade that influence its activity. Moreover, we highlight several connection points between Hh and Notch, Wnt, or TGF-β pathways, showing a reciprocal synergism that contributes to tumorigenesis, supporting a more malignant behavior by tumor cells, such as in leukemia and brain tumors. Understanding the importance of these molecular interlinking networks will provide a rational basis for combined anticancer drug development.

Considerations for the use of Cre recombinase for conditional gene deletion in the mouse lens

Background

Despite a number of different transgenes that can mediate DNA deletion in the developing lens, each has unique features that can make a given transgenic line more or less appropriate for particular studies. The purpose of this work encompasses both a review of transgenes that lead to the expression of Cre recombinase in the lens and a comparative analysis of currently available transgenic lines with a particular emphasis on the Le-Cre and P0-3.9GFPCre lines that can mediate DNA deletion in the lens placode. Although both of these transgenes are driven by elements of the Pax6 P0 promoter, the Le-Cre transgene consistently leads to ocular abnormalities in homozygous state and can lead to ocular defects on some genetic backgrounds when hemizygous.

Result

Although both P0-3.9GFPCre and Le-Cre hemizygous transgenic mice undergo normal eye development on an FVB/N genetic background, Le-Cre homozygotes uniquely exhibit microphthalmia. Examination of the expression patterns of these two transgenes revealed similar expression in the developing eye and pancreas. However, lineage tracing revealed widespread non-ocular CRE reporter gene expression in the P0-3.9GFPCre transgenic mice that results from stochastic CRE expression in the P0-3.9GFPCre embryos prior to lens placode formation. Postnatal hemizygous Le-Cre transgenic lenses express higher levels of CRE transcript and protein than the hemizygous lenses of P0-3.9GFPCre mice. Transcriptome analysis revealed that Le-Cre hemizygous lenses deregulated the expression of 15 murine genes, several of which are associated with apoptosis. In contrast, P0-3.9GFPCre hemizygous lenses only deregulated two murine genes. No known PAX6-responsive genes or genes directly associated with lens differentiation were deregulated in the hemizygous Le-Cre lenses.

Conclusions

Although P0-3.9GFPCre transgenic mice appear free from ocular abnormalities, extensive non-ocular CRE expression represents a potential problem for conditional gene deletion studies using this transgene. The higher level of CRE expression in Le-Cre lenses versus P0-3.9GFPCre lenses may explain abnormal lens development in homozygous Le-Cre mice. Given the lack of deregulation of PAX6-responsive transcripts, we suggest that abnormal eye development in Le-Cre transgenic mice stems from CRE toxicity. Our studies reinforce the requirement for appropriate CRE-only expressing controls when using CRE as a driver of conditional gene targeting strategies.

Electronic supplementary material

The online version of this article (10.1186/s40246-019-0192-8) contains supplementary material, which is available to authorized users.

Signals and forces shaping organogenesis of the small intestine

The adult gastrointestinal tract (GI) is a series of connected organs (esophagus, stomach, small intestine, colon) that develop via progressive regional specification of a continuous tubular embryonic organ anlage. This chapter focuses on organogenesis of the small intestine. The intestine arises by folding of a flat sheet of endodermal cells into a tube of highly proliferative pseudostratified cells. Dramatic elongation of this tube is driven by rapid epithelial proliferation. Then, epithelial-mesenchymal crosstalk and physical forces drive a stepwise cascade that results in convolution of the tubular surface into finger-like projections called villi. Concomitant with villus formation, a sharp epithelial transcriptional boundary is defined between stomach and intestine. Finally, flask-like depressions called crypts are established to house the intestinal stem cells needed throughout life for epithelial renewal. New insights into these events are being provided by in vitro organoid systems, which hold promise for future regenerative engineering of the small intestine.

Transcriptional regulation of cell shape during organ morphogenesis

The emerging field of transcriptional regulation of cell shape changes aims to address the critical question of how gene expression programs produce a change in cell shape. Together with cell growth, division, and death, changes in cell shape are essential for organ morphogenesis. Whereas most studies of cell shape focus on posttranslational events involved in protein organization and distribution, cell shape changes can be genetically programmed. This review highlights the essential role of transcriptional regulation of cell shape during morphogenesis of the heart, lungs, gastrointestinal tract, and kidneys. We emphasize the evolutionary conservation of these processes across different model organisms and discuss perspectives on open questions and research avenues that may provide mechanistic insights toward understanding birth defects.

Multiple roles of epithelial heparan sulfate in stomach morphogenesis

Heparan sulfate proteoglycans (HSPGs) have been shown to regulate various developmental processes. However, the function of heparan sulfate (HS) during the development of mammalian stomach has not been characterized yet. Here, we investigate the role of epithelial HS in embryonic stomach by examining mice deficient in the glycosyltransferase gene Ext1 We show that HS exhibits a specific and dynamic expression pattern in mouse embryonic stomach. Depletion of the epithelial HS leads to stomach hypoplasia, with phenotypic differences in the gastric mucosa between the forestomach and hindstomach. In the posterior stomach, HS depletion disrupts glandular stomach patterning and cytodifferentiation via attenuation of Fgf signaling activity. Inhibition of Fgf signaling in vitro recapitulates the patterning defect. Ligand and carbohydrate engagement assay (LACE) reveals a diminished assembly of Fgf10 and Fgfr2b in the mutant. In the anterior stomach, loss of epithelial HS leads to stratification and differentiation defects of the multilayered squamous epithelium, along with reduced Hh and Bmp signaling activity. Our data demonstrate that epithelial HS plays multiple roles in regulating mammalian stomach morphogenesis in a regional-specific manner.

Adult gastric stem cells and their niches

Adult gastric stem cells replenish the gastric epithelium throughout life. Recent studies have identified diverse populations of stem cells, progenitor cells, and even differentiated cells that can regain stem cell capacity, so highlighting an unexpected plasticity within the gastric epithelium, both in the corpus and antrum. Two niches seem to co-exist in the gastric unit: one in the isthmus region and the other at the base of the gland, although the precise features of the cell populations and the two niches are currently under debate. A variety of gastric organoid models have been established, providing new insights into niche factors required by the gastric stem cell populations. Here we review our current knowledge of gastric stem cell populations, their markers and interactions, important niche factors, and different gastric organoid systems. WIREs Dev Biol 2017, 6:e261. doi: 10.1002/wdev.261 For further resources related to this article, please visit the WIREs website.

Stomach development, stem cells and disease

The stomach, an organ derived from foregut endoderm, secretes acid and enzymes and plays a key role in digestion. During development, mesenchymal-epithelial interactions drive stomach specification, patterning, differentiation and growth through selected signaling pathways and transcription factors. After birth, the gastric epithelium is maintained by the activity of stem cells. Developmental signals are aberrantly activated and stem cell functions are disrupted in gastric cancer and other disorders. Therefore, a better understanding of stomach development and stem cells can inform approaches to treating these conditions. This Review highlights the molecular mechanisms of stomach development and discusses recent findings regarding stomach stem cells and organoid cultures, and their roles in investigating disease mechanisms.

Generation of intestinal surface: an absorbing tale

The vertebrate small intestine requires an enormous surface area to effectively absorb nutrients from food. Morphological adaptations required to establish this extensive surface include generation of an extremely long tube and convolution of the absorptive surface of the tube into villi and microvilli. In this Review, we discuss recent findings regarding the morphogenetic and molecular processes required for intestinal tube elongation and surface convolution, examine shared and unique aspects of these processes in different species, relate these processes to known human maladies that compromise absorptive function and highlight important questions for future research.

Fibroblasts and myofibroblasts of the intestinal lamina propria in physiology and disease

In this Review we summarize our current understanding of the biology of mesenchymal cells of the intestinal lamina propria focusing mainly on fibroblasts and myofibroblasts. The topics covered include 1) the embryonic origin of mesenchymal cells of the intestinal lamina propria and their heterogeneity in adults, 2) the role of the mesenchyme in intestinal development, 3) the physiological function of fibroblasts and myofibroblasts in adults as part of the intestinal stem cell niche and the mucosal immune system and 4) the involvement of fibroblasts and myofibroblasts in epithelial homeostasis upon injury and in the pathogenesis of diseases such as Inflammatory Bowel Diseases, fibrosis and cancer. We emphasize studies addressing the function of intestinal mesenchymal cells in vivo, and also discuss major open questions and current challenges in this field.

The thyroid hormone nuclear receptor TRα1 controls the Notch signaling pathway and cell fate in murine intestine

Thyroid hormones control various aspects of gut development and homeostasis. The best-known example is in gastrointestinal tract remodeling during amphibian metamorphosis. It is well documented that these hormones act via the TR nuclear receptors, which are hormone-modulated transcription factors. Several studies have shown that thyroid hormones regulate the expression of several genes in the Notch signaling pathway, indicating a possible means by which they participate in the control of gut physiology. However, the mechanisms and biological significance of this control have remained unexplored. Using multiple in vivo and in vitro approaches, we show that thyroid hormones positively regulate Notch activity through the TRα1 receptor. From a molecular point of view, TRα1 indirectly controls Notch1, Dll1, Dll4 and Hes1 expression but acts as a direct transcriptional regulator of the Jag1 gene by binding to a responsive element in the Jag1 promoter. Our findings show that the TRα1 nuclear receptor plays a key role in intestinal crypt progenitor/stem cell biology by controlling the Notch pathway and hence the balance between cell proliferation and cell differentiation.

From Definitive Endoderm to Gut-a Process of Growth and Maturation

The intestine and colon carries out vital functions, and their lifelong maintenance is of the upmost importance. Research over the past decades has carefully addressed bowel function, how it is maintained and begun to unravel how disorders such as cancer and inflammatory bowel disease form. In contrast, very little is known about the molecular mechanisms that trigger tissue maturation during development. With this review, our aim is to carefully provide a critical appraisal of the literature to give a state-of-the-art view of intestinal development. Starting from definitive endoderm at gastrulation to the emergence of a structure with mature properties, the tissue undergoes complex morphogenetic processes that rely on both biophysical changes and secreted signaling molecules. We will also discuss how new and exciting developments using in vitro models are likely to provide new insights into this process and potential therapeutic strategies for gastrointestinal disorders.

Enteric neural crest cells regulate vertebrate stomach patterning and differentiation

In vertebrates, the digestive tract develops from a uniform structure where reciprocal epithelial-mesenchymal interactions pattern this complex organ into regions with specific morphologies and functions. Concomitant with these early patterning events, the primitive GI tract is colonized by the vagal enteric neural crest cells (vENCCs), a population of cells that will give rise to the enteric nervous system (ENS), the intrinsic innervation of the GI tract. The influence of vENCCs on early patterning and differentiation of the GI tract has never been evaluated. In this study, we report that a crucial number of vENCCs is required for proper chick stomach development, patterning and differentiation. We show that reducing the number of vENCCs by performing vENCC ablations induces sustained activation of the BMP and Notch pathways in the stomach mesenchyme and impairs smooth muscle development. A reduction in vENCCs also leads to the transdifferentiation of the stomach into a stomach-intestinal mixed phenotype. In addition, sustained Notch signaling activity in the stomach mesenchyme phenocopies the defects observed in vENCC-ablated stomachs, indicating that inhibition of the Notch signaling pathway is essential for stomach patterning and differentiation. Finally, we report that a crucial number of vENCCs is also required for maintenance of stomach identity and differentiation through inhibition of the Notch signaling pathway. Altogether, our data reveal that, through the regulation of mesenchyme identity, vENCCs act as a new mediator in the mesenchymal-epithelial interactions that control stomach development.

Effect of Helicobacter pylori lipopolysaccharide on expression of Ptch-1 and Gli proteins in gastric cancer AGS cells

AIM: To explore the expression of Ptch-1 and Gli, two members in the sonic hedgehog (Shh) signaling pathway, in gastric cancer AGS cells after stimulation with Helicobacter pylori (H. pylori) lipopolysaccharide (LPS) and cyclopamine.

METHODS: Different concentrations of H. pylori LPS were used to stimulate AGS cells for 24 h, and the expression of Ptch-1 and Gli was assayed by Western blot to find the optimal stimulation concentration. AGS cells were then treated with H. pylori LPS at the optimal concentration for 24, 48 and 72 h, and the expression of Ptch-1 and Gli was detected by Western blot. MTT assay was applied to explore the effect of cyclopamine on AGS cell proliferation, and the half maximal inhibitory concentration (IC₅₀) was calculated. AGS cells were then treated with cyclopamine at IC₅₀ for 24, 48 and 72 h, and the expression of Ptch-1 and Gli was detected by Western blot. AGS cells were divided into three groups and stimulated with H. pylori LPS, cyclopamine and H. pylori LPS plus cyclopamine for 24 h, respectively, and the expression of Ptch-1 and Gli was then detected by Western blot.

RESULTS: After different concentrations of H. pylori LPS were used to stimulate AGS cells for 24 h, the expression of Ptch-1 and Gli was increased (P < 0.05) and eventually reached a plateau. After treatment of AGS cells with H. pylori LPS at the optimal concentration for 24, 48 and 72 h, the expression of Ptch-1 and Gli was increased in a time dependent manner (P < 0.05). After treatment of AGS cells with different concentrations of cyclopamine for 24 h, the proliferation of AGS cells was inhibited in a concentration dependent manner (P < 0.05). Treatment with cyclopamine at IC₅₀ decreased the expression of Gli in a time dependent manner (P < 0.05), but showed no significant effect on expression of Ptch-1 (P > 0.05). The expression of Ptch-1 in the H. pylori LPS plus cyclopamine group was significantly higher than that in the control group and cyclopamine group (P < 0.05), but was not significantly different from that in the H. pylori LPS group (P > 0.05). The expression of Gli in the H. pylori LPS plus cyclopamine group was significantly lower than that in the control group and H. pylori LPS group (P < 0.05), but was not significantly different from that in the cyclopamine group (P > 0.05).

CONCLUSION: H. pylori may alter the expression of components of the Shh signaling pathway through its virulence factor LPS in AGS cells. Cyclopamine can inhibit the growth of AGS cells by inhibition of the Shh signaling pathway. H. pylori LPS may play a role by influencing the upstream molecules of the Shh signaling pathway.

Molecular cross talk between Notch1, Shh and Akt pathways during erythroid differentiation of K562 and HEL cell lines

Erythropoiesis is a tightly regulated process dependent on extrinsic signals conveyed by the bone marrow niche. The signalling pathways thus activated or repressed do not act in isolation; rather an intricate cross talk among these pathways ensues homoeostasis within the erythroid compartment. In this study, we describe the effects of two such signalling pathways namely the Notch1 and the Shh pathway on erythropoiesis in immortalised K562 and HEL cell lines as well as the cross talk that ensues between them. We show that while activation of the Notch1 pathway inhibits differentiation of erythroid lineage cell lines as well as in in-vitro primary erythroid cultures from the human CD34(+) cells; Shh pathway favours erythroid differentiation. Further, the Notch1 pathway activates the Akt pathway and constitutively active Akt partially mimics the effect of Notch1 activation on erythropoiesis. Moreover, the Notch1, Akt and Shh pathways were found to cross talk with each other. In this process, activation of Notch1 was found to down regulate the Shh pathway independent of Akt activation. Significantly, Notch1 not only down regulated the Shh pathway, but also inhibited recombinant Shh mediated erythropoiesis. Our study thus reveals an intricate crosstalk among the Notch1, Shh and Akt pathways wherein Notch1 emerges as a key regulator of erythropoiesis.

Thyroid hormone-induced cell-cell interactions are required for the development of adult intestinal stem cells

The mammalian intestine has long been used as a model to study organ-specific adult stem cells, which are essential for organ repair and tissue regeneration throughout adult life. The establishment of the intestinal epithelial cell self-renewing system takes place during perinatal development when the villus-crypt axis is established with the adult stem cells localized in the crypt. This developmental period is characterized by high levels of plasma thyroid hormone (T3) and T3 deficiency is known to impair intestinal development. Determining how T3 regulates adult stem cell development in the mammalian intestine can be difficult due to maternal influences. Intestinal remodeling during amphibian metamorphosis resembles perinatal intestinal maturation in mammals and its dependence on T3 is well established. A major advantage of the amphibian model is that it can easily be controlled by altering the availability of T3. The ability to manipulate and examine this relatively rapid and localized formation of adult stem cells has greatly assisted in the elucidation of molecular mechanisms regulating their formation and further revealed evidence that supports conservation in the underlying mechanisms of adult stem cell development in vertebrates. Furthermore, genetic studies in Xenopus laevis indicate that T3 actions in both the epithelium and the rest of the intestine, most likely the underlying connective tissue, are required for the formation of adult stem cells. Molecular analyses suggest that cell-cell interactions involving hedgehog and BMP pathways are critical for the establishment of the stem cell niche that is essential for the formation of the adult intestinal stem cells.

Galectin-1 promotes lung cancer tumor metastasis by potentiating integrin α6β4 and Notch1/Jagged2 signaling pathway

Lung cancer is a major cancer, leading in both incidence and mortality in the world, and metastasis underlies the majority of lung cancer-related deaths. Galectin-1, a glycan-binding protein, has been shown to be overexpressed in lung cancer and involved in tumor-mediated immune suppression. However, the functional role of galectin-1 in lung cancer per se remains unknown. We demonstrate that ectopic expression of galectin-1 in a low-metastatic CL1-0 lung cancer cell line promotes its migration, invasion and epithelial-mesenchymal transition. Conversely, we also show that suppression of galectin-1 expression in highly invasive CL1-5 and A549 cells inhibits migration and invasion of lung cancer cell and causes a mesenchymal-epithelial transition. These effects may be transduced by increasing the expression of integrin α6β4 and Notch1/Jagged2, which in turn co-operates in the phosphorylation of AKT. The effects of galectin-1 on cancer progression are reduced when integrin β4 and Notch1 are absent. Further study has indicated that galectin-1 knockdown prevents the spread of highly metastatic Lewis lung carcinoma in vivo. Our study suggests that galectin-1 represents a crucial regulator of lung cancer metastasis. Thus, the detection and targeted treatment of galectin-1-expressing cancer serves as a new therapeutic target for lung cancer.

Notch in the intestine: regulation of homeostasis and pathogenesis

The small and large intestines are tubular organs composed of several tissue types. The columnar epithelium that lines the inner surface of the intestines distinguishes the digestive physiology of each region of the intestine and consists of several distinct cell types that are rapidly and continually renewed by intestinal stem cells that reside near the base of the crypts of Lieberkühn. Notch signaling controls the fate of intestinal stem cells by regulating the expression of Hes genes and by repressing Atoh1. Alternate models of Notch pathway control of cell fate determination are presented. Roles for Notch signaling in development of the intestine, including mesenchymal and neural cells, are discussed. The oncogenic activities of Notch in colorectal cancer, as well as the tumor suppressive activities of Atoh1, are reviewed. Therapeutic targeting of the Notch pathway in colorectal cancers is discussed, along with potential caveats.

Role of Sonic Hedgehog signaling during progression from inflammation to cancer in the stomach

Despite advances in treatment and the declining incidence, gastric cancer remains the second leading cause of cancer-related deaths in the world. Understanding the progression from inflammation to cancer in the stomach is crucial in the development of novel therapies and strategies for treating this disease. Chronic inflammation of the stomach is typically caused by Helicobacter pylori (H. pylori) and resulting lesions may lead to gastric cancer. During the progression from inflammation to cancer, the stomach epithelium changes with evidence of the disruption of normal epithelial cell differentiation and infiltrating inflammatory cells. Coincident with the development of atrophic gastritis and metaplasia, is the loss of the gastric morphogen Sonic Hedgehog (Shh). Given its critical role as a regulator of gastric tissue homeostasis, the disruption of Shh expression during inflammation correlates with the loss of normal epithelial cell differentiation, but this has only recently been rigorously tested in vivo using a unique mouse model of targeted gastric Shh deletion. While pre-neoplastic lesions such as atrophic gastritis and intestinal metaplasia are associated with the loss of Shh within the acid-secreting glands of the stomach, there is a clear link between elevated Shh and signaling to gastric cancers. The current review focuses on the effects of aberrant Shh expression and its role in the development of gastric cancer, specifically in response to H. pylori infection.