Hedgehog: functions and mechanisms

Concomitant targeting of Hedgehog signaling and MCL-1 synergistically induces cell death in Hedgehog-driven cancer cells

In the present study, we show that concomitant inhibition of Hedgehog (HH) signaling by the glioma-associated oncogene homolog1 (GLI1)-targeting agent GANT61 and the antiapoptotic BCL-2 protein family member MCL-1 by A-1210477 synergistically induces cell death in HH-driven cancers, i.e. rhabdomyosarcoma (RMS) and medulloblastoma (MB) cells. Combined genetic and pharmacological inhibition emphasized that co-treatment of GANT61 and A-1210477 indeed relies on inhibition of GLI1 (by GANT61) and MCL-1 (by A-1210477). Mechanistic studies revealed that A-1210477 triggers the release of BIM from MCL-1 and its shuttling to BCL-x_L and BCL-2. Indeed, BIM proved to be required for GANT61/A-1210477-induced cell death, as genetic silencing of BIM using siRNA significantly rescues cell death upon GANT61/A-1210477 co-treatment. Similarly, genetic silencing of NOXA results in a significant reduction of GANT61/A-1210477-mediated cell death. Also, overexpression of MCL-1 or BCL-2 significantly protects RMS cells from GANT61/A-1210477-triggered cell death. Addition of the pan-caspase inhibitor zVAD.fmk significantly decreases GANT61/A-1210477-stimulated cell demise, indicating apoptotic cell death. In conclusion, GANT61 and A-1210477 synergize to engage mitochondrial apoptosis. These findings provide the rationale for further evaluation of dual inhibition of HH signaling and MCL-1 in HH-driven cancers.

Inhibition of the hedgehog pathway for the treatment of cancer using Itraconazole

Itraconazole (ITZ) is an anti-fungal drug that has been used in clinical practice for nearly 35 years. Recently, numerous experiments have shown that ITZ possesses anti-cancer properties. The Hedgehog (Hh) pathway plays a pivotal role in fundamental processes, including embryogenesis, structure, morphology and proliferation in various species. This pathway is typically silent in adult cells, and inappropriate activity is linked to various tumor types. The most important mechanism of ITZ in the treatment of cancer is inhibition of the Hh pathway through the inhibition of smoothened receptors (SMO), glioma-associated oncogene homologs (GLI), and their downstream targets. In this review, we discuss the mechanisms of ITZ in the treatment of cancer through inhibition of the Hh pathway, which includes anti-inflammation, prevention of tumor growth, induction of cell cycle arrest, induction of apoptosis and autophagy, prevention of angiogenesis, and drug resistance. We also discuss the clinical use of ITZ in many types of cancers. We hope this review will provide more information to support future studies on ITZ in the treatment of various cancers.

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.

Hedgehog pathway inhibition as a therapeutic target in acute myeloid leukemia

Introduction: The Hedgehog (HH) pathway constitutes a collection of signaling molecules which critically influence embryogenesis. In adults, however, the HH pathway remains integral to the proliferation, maintenance, and apoptosis of adult stem cells including hematopoietic stem cells. Areas covered: We discuss the current understanding of the HH pathway as it relates to normal hematopoiesis, the pathology of acute myeloid leukemia (AML), the rationale for and data from combination therapies including HH pathway inhibitors, and ultimately the prospects that might offer promise in targeting this pathway in AML. Expert opinion: Efforts to target the HH pathway have been focused on impeding this disposition and restoring chemosensitivity to conventional myeloid neoplasm therapies. The year 2018 saw the first approval of a HH pathway inhibitor (glasdegib) for AML, though for an older population and in combination with an uncommonly-used therapy. Several other clinical trials with agents targeting modulators of HH signaling in AML and MDS are underway. Further study and understanding of the interplay between the numerous aspects of HH signaling and how it relates to the augmented survival of AML will provide a more reliable substrate for therapeutic strategies in patients with this poor-risk disease.

Regulation of Hedgehog signaling Offers A Novel Perspective for Bone Homeostasis Disorder Treatment

The hedgehog (HH) signaling pathway is central to the regulation of bone development and homeostasis. HH signaling is not only involved in osteoblast differentiation from bone marrow mesenchymal stem cells (BM-MSCs), but also acts upstream within osteoblasts via the OPG/RANK/RANKL axis to control the expression of RANKL. HH signaling has been found to up-regulate parathyroid hormone related protein (PTHrP) expression in osteoblasts, which in turn activates its downstream targets nuclear factor of activated T cells (NFAT) and cAMP responsive element binding protein (CREB), and as a result CREB and NFAT cooperatively increase RANKL expression and osteoclastogenesis. Osteoblasts must remain in balance with osteoclasts in order to avoid excessive bone formation or resorption, thereby maintaining bone homeostasis. This review systemically summarizes the mechanisms whereby HH signaling induces osteoblast development and controls RANKL expression through PTHrP in osteoblasts. Proper targeting of HH signaling may offer a therapeutic option for treating bone homeostasis disorders.

Steroidal alkaloid variation in Veratrum californicum as determined by modern methods of analytical analysis

Veratrum californicum is a rich source of steroidal alkaloids, many of which have proven to be antagonists of the Hedgehog (Hh) signaling pathway that becomes aberrant in over twenty types of cancer. These alkaloids first became known in the 1950's due to their teratogenic properties, which resulted in newborn and fetal lambs developing cyclopia as a result of pregnant ewes consuming Veratrum californicum. It was discovered that the alkaloids in V. californicum were concentrated in the root and rhizome of the plant with much lower amounts of the most active alkaloid, cyclopamine, present in the aerial plant, especially in the late growth season. Inspired by the limitations in analytical instrumentation and methods available to researchers at the time of the original investigation, we have used state-of-the-art instrumentation and modern analytical methods to quantitate four steroidal alkaloids based on study parameters including plant part, harvest location, and growth stage. The results of the current inquiry detail differences in alkaloid composition based on the study parameters, provide a detailed assessment for alkaloids that have been characterized previously (cyclopamine, veratramine, muldamine and isorubijervine), and identify at least six alkaloids that have not been previously characterized. This study provides insight into optimal harvest time, plant growth stage, harvest location, and plant part required to isolate, yet to be characterized, alkaloids of interest for exploration as Hh pathway antagonists with desirable medicinal properties.

Evolution and Developmental Diversity of Skin Spines in Pufferfishes

Teleost fishes develop remarkable varieties of skin ornaments. The developmental basis of these structures is poorly understood. The order Tetraodontiformes includes diverse fishes such as the ocean sunfishes, triggerfishes, and pufferfishes, which exhibit a vast assortment of scale derivatives. Pufferfishes possess some of the most extreme scale derivatives, dermal spines, erected during their characteristic puffing behavior. We demonstrate that pufferfish scale-less spines develop through conserved gene interactions that underlie general vertebrate skin appendage formation, including feathers and hair. Spine development retains conservation of the EDA (ectodysplasin) signaling pathway, important for the development of diverse vertebrate skin appendages, including these modified scale-less spines of pufferfish. Further modification of genetic signaling from both CRISPR-Cas9 and small molecule inhibition leads to loss or reduction of spine coverage, providing a mechanism for skin appendage diversification observed throughout the pufferfishes. Pufferfish spines have evolved broad variations in body coverage, enabling adaptation to diverse ecological niches.

The wonders of BMP9: From mesenchymal stem cell differentiation, angiogenesis, neurogenesis, tumorigenesis, and metabolism to regenerative medicine

Although bone morphogenetic proteins (BMPs) initially showed effective induction of ectopic bone growth in muscle, it has since been determined that these proteins, as members of the TGF-β superfamily, play a diverse and critical array of biological roles. These roles include regulating skeletal and bone formation, angiogenesis, and development and homeostasis of multiple organ systems. Disruptions of the members of the TGF-β/BMP superfamily result in severe skeletal and extra-skeletal irregularities, suggesting high therapeutic potential from understanding this family of BMP proteins. Although it was once one of the least characterized BMPs, BMP9 has revealed itself to have the highest osteogenic potential across numerous experiments both in vitro and in vivo, with recent studies suggesting that the exceptional potency of BMP9 may result from unique signaling pathways that differentiate it from other BMPs. The effectiveness of BMP9 in inducing bone formation was recently revealed in promising experiments that demonstrated efficacy in the repair of critical sized cranial defects as well as compatibility with bone-inducing bio-implants, revealing the great translational promise of BMP9. Furthermore, emerging evidence indicates that, besides its osteogenic activity, BMP9 exerts a broad range of biological functions, including stem cell differentiation, angiogenesis, neurogenesis, tumorigenesis, and metabolism. This review aims to summarize our current understanding of BMP9 across biology and the body.

The Role of Hedgehog Signaling in Adult Lung Regeneration and Maintenance

As a secreted morphogen, Sonic Hedgehog (SHH) determines differential cell fates, behaviors, and functions by forming a gradient of Hedgehog (Hh) activation along an axis of Hh-receptive cells during development. Despite clearly delineated roles for Hh during organ morphogenesis, whether Hh continues to regulate cell fate and behavior in the same fashion in adult organs is less understood. Adult organs, particularly barrier organs interfacing with the ambient environment, are exposed to insults that require renewal of cellular populations to maintain structural integrity. Understanding key aspects of Hh’s ability to generate an organ could translate into conceptual understanding of Hh’s ability to maintain organ homeostasis and stimulate regeneration. In this review, we will summarize the current knowledge about Hh signaling in regulating adult lung regeneration and maintenance, and discuss how alteration of Hh signaling contributes to adult lung diseases.

Nuclear localization and Overexpression of Smoothened in Pancreatic and Colorectal Cancers

Smoothened (SMO) is a significant signalling protein which functions as a key transducer for the hedgehog signalling pathway, an important signalling mechanism with key roles in development and oncogenesis. The correlation of expression dynamics of SMO with pancreatic and colorectal cancer genesis has been known but with ambiguity. Therefore, in this study, we investigated messenger RNA (mRNA) and protein expression of SMO in pancreatic and colorectal cancers in our population and assessed relationship with various clinicopathological parameters. Surgically resected tumour and adjacent histologically normal tissues from 33 and 61 pancreatic and colorectal cancer patients were investigated in the present study. Expression of SMO was analysed by quantitative real-time polymerase chain reaction and immunohistochemistry. At mRNA level, SMO was overexpressed in 72.72% (24 of 33) and 50.81% (31 of 61) of the pancreatic and colorectal cancer cases as compared with their adjacent normal tissues. SMO immunohistochemical analysis revealed nuclear localization and overexpression was observed in 51.51% (17 of 33) and 40.98% (25 of 61) of pancreatic and colorectal cancer tissues. SMO overexpression was significantly associated with smoking, late-stage disease and lymph node metastasis in patients with Colorectal cancer. Our results showed that SMO is dysregulated in pancreatic and colorectal cancers and may be considered as a target in cancer therapeutics.

Identification of Gli1-interacting proteins during simvastatin-stimulated osteogenic differentiation of bone marrow mesenchymal stem cells

Simvastatin has been shown to promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Our study aimed to illuminate the underlying mechanism, with a specific focus on the role of Hedgehog signaling in this process. BMSCs cultured with or without 10^-7  mol/L simvastatin were subjected to evaluation of osteogenic differentiation capacity. Osteogenic markers such as type 1 collagen (COL1) and osteocalcin (OCN), as well as key molecules of Hedgehog signaling molecules, were examined by Western blot and real-time polymerase chain reaction (PCR). Co-immunoprecipitation and mass spectrometry assays were applied to screen for Gli1-interacting proteins. Cyclopamine (Cpn) was used as a Hedgehog signaling inhibitor. Our results indicated that simvastatin increased alkaline phosphatase (ALP) activity; mineralization of extracellular matrix; mRNA expression of ALP, COL1, and OCN; and expression and nuclear translocation of Gli1. Contrasting effects were observed in Cpn-exposed groups, but were partially rescued by the simvastatin treatment. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses indicated that Gli1-interacting proteins were primarily associated with mitogen-activated protein kinase (MAPK) (P = 7.04E^-04 ), hippo, insulin, and glucagon signaling. Further, hub genes identified by protein-protein interaction network analysis included Gli1-interacting proteins such as Ppp2r1a, Rac1, Etf1, and XPO1/CRM1. In summary, the current study showed that the mechanism by which simvastatin stimulates osteogenic differentiation of BMSCs involves activation of Hedgehog signaling, as indicated by interactions with Gli1 and, most notably, the MAPK signaling pathway.

TGF-β2 Induces Gli1 in a Smad3-Dependent Manner Against Cerebral Ischemia/Reperfusion Injury After Isoflurane Post-conditioning in Rats

Isoflurane (ISO) post-conditioning attenuates cerebral ischemia/reperfusion (I/R) injury, but the underlying mechanism is incompletely elucidated. Transforming growth factor beta (TGF-β) and hedgehog (Hh) signaling pathways govern a wide range of mechanisms in the central nervous system. We aimed to investigate the effect of the TGF-β2/Smad3 and sonic hedgehog (Shh)/Glioblastoma (Gli) signaling pathway and their crosstalk in the hippocampus of rats with ISO post-conditioning after cerebral I/R injury. Adult male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO), 1.5 h occlusion and 24 h reperfusion (MCAO/R). To assess the effect of ISO after I/R injury, various approaches were used, including neurobehavioral tests, TTC staining, HE staining, Nissl staining, TUNEL staining, immunofluorescence (IF), qRT-PCR (quantitative real-time polymerase chain reaction) and Western blot. The ISO post-conditioning group (ISO group) received 1 h ISO post-conditioning when reperfusion was initiated, leading to lower infarct volumes and neurologic deficit scores, more surviving neurons, and less damaged and apoptotic neurons. IF staining, qRT-PCR and Western blot showed high expression levels of TGF-β2, Shh and Gli1 in the hippocampal CA1 of the ISO group. Phosphorylated Smad3 (p-Smad3), Patched (Ptch), and Smoothed (Smo) were also increased at protein level in the ISO group, whereas total Smad3 expression did not change in all groups. When TGF-β2 inhibitor, pirfenidone, or Smad3 inhibitor, SIS3 HCl, were administered, the expression levels of p-Smad3 and Gli1 were reduced, and surviving pyramidal neurons decreased. By contrast, the expression levels of TGF-β2 and p-Smad3 did not change significantly after pre-injection of Smo inhibitor cyclopamine, but reduced the expression levels of Shh, Ptch, and Gli1. Moreover, Gli showed the lowest expression levels with pirfenidone combined with cyclopamine. These findings indicate that the TGF-β and hedgehog signaling pathways mediate the neuroprotection of ISO post-conditioning after cerebral I/R injury, and crosstalk between two pathways at the Gli1 level.

The Drosophila Hedgehog receptor component Interference hedgehog (Ihog) mediates cell-cell interactions through trans-homophilic binding

Hedgehog (Hh) signaling is crucial for establishing complex cellular patterns in embryonic tissues and maintaining homeostasis in adult organs. In Drosophila, Interference hedgehog (Ihog) or its close paralogue Brother of Ihog (Boi) forms a receptor complex with Patched to mediate intracellular Hh signaling. Ihog proteins (Ihog and Boi) also contribute to cell segregation in wing imaginal discs through an unknown mechanism independent of their role in transducing the Hh signal. Here, we report a molecular mechanism by which the Ihog proteins mediate cell-cell interactions. We found that Ihog proteins are enriched at the site of cell-cell contacts and engage in trans-homophilic interactions in a calcium-independent manner. The region that we identified as mediating the trans-Ihog-Ihog interaction overlaps with the Ihog-Hh interface on the first fibronectin repeat of the extracellular domain of Ihog. We further demonstrate that Hh interferes with Ihog-mediated homophilic interactions by competing for Ihog binding. These results, thus, not only reveal a mechanism for Ihog-mediated cell-cell interactions but also suggest a direct Hh-mediated regulation of both intracellular signaling and cell adhesion through Ihog.

Non-canonical Hedgehog Signaling Pathway in Cancer: Activation of GLI Transcription Factors Beyond Smoothened

The Hedgehog-GLI (HH-GLI) pathway is a highly conserved signaling that plays a critical role in controlling cell specification, cell–cell interaction and tissue patterning during embryonic development. Canonical activation of HH-GLI signaling occurs through binding of HH ligands to the twelve-pass transmembrane receptor Patched 1 (PTCH1), which derepresses the seven-pass transmembrane G protein-coupled receptor Smoothened (SMO). Thus, active SMO initiates a complex intracellular cascade that leads to the activation of the three GLI transcription factors, the final effectors of the HH-GLI pathway. Aberrant activation of this signaling has been implicated in a wide variety of tumors, such as those of the brain, skin, breast, gastrointestinal, lung, pancreas, prostate and ovary. In several of these cases, activation of HH-GLI signaling is mediated by overproduction of HH ligands (e.g., prostate cancer), loss-of-function mutations in PTCH1 or gain-of-function mutations in SMO, which occur in the majority of basal cell carcinoma (BCC), SHH-subtype medulloblastoma and rhabdomyosarcoma. Besides the classical canonical ligand-PTCH1-SMO route, mounting evidence points toward additional, non-canonical ways of GLI activation in cancer. By non-canonical we refer to all those mechanisms of activation of the GLI transcription factors occurring independently of SMO. Often, in a given cancer type canonical and non-canonical activation of HH-GLI signaling co-exist, and in some cancer types, more than one mechanism of non-canonical activation may occur. Tumors harboring non-canonical HH-GLI signaling are less sensitive to SMO inhibition, posing a threat for therapeutic efficacy of these antagonists. Here we will review the most recent findings on the involvement of alternative signaling pathways in inducing GLI activity in cancer and stem cells. We will also discuss the rationale of targeting these oncogenic pathways in combination with HH-GLI inhibitors as a promising anti-cancer therapies.

Comparative study of hydroxyapatite, fluor-hydroxyapatite and Si-substituted hydroxyapatite nanoparticles on osteogenic, osteoclastic and antibacterial ability

This study compared the effects of hydroxyapatite (HA), fluor-hydroxyapatite (FHA) and Si-substituted hydroxyapatite (SiHA) on osteogenic differentiation, osteoclastic activity and antibacterial properties. HA, FHA and SiHA were prepared via a sol-gel reaction and characterized by scanning electron microscopic analysis (SEM), transmission electron microscopic analysis (TEM), and X-ray photoelectron spectrometry. Cell proliferation was evaluated using an MTT assay and cytoskeletal morphology was observed by fluorescence microscopy. Osteogenic differentiation was evaluated using alkaline phosphatase activity and Alizarin red staining. Quantitative real-time PCR was used to evaluate the mRNA expression of runt-related transcription factor 2 (Runx2) and osteopontin (OPN). New bone formation was tested using μCT, haematoxylin and eosin staining and TRAP staining. The antibacterial actions against Porphyromonas gingivalis (P. g) were evaluated through plate counting and live-dead bacterial staining. The results demonstrated that HA, FHA and SiHA can promote proliferation of bone mesenchymal stem cells (BMSCs). ALP activity in FHA extract with a concentration of 625 μg mL-1 was the highest after 14 days osteogenic induction; similar results were observed for Runx2 and OPN mRNA expression. HA, FHA and SiHA decreased trabecular space in bone defects, but FHA reduced osteoclastic activity and inhibited P. g growth. In conclusion, FHA can promote osteogenic activity, reduce osteoclastic activity and enhance antibacterial effects.

Colon cancer stem cells: Potential target for the treatment of colorectal cancer

Despite incessant research, colon cancer still is one of the most common causes of fatalities in both men and women worldwide. Also, nearly 50% of patients with colorectal cancer show tumor recurrence. Recent investigations have highlighted the involvement of colon cancer stem cells (CCSCs) in cancer relapse and chemoresistance. CCSCs deliver a significant protumorigenic niche through persistent overexpression of self-renewal capabilities. Moreover, CSCs cross network with stromal cells, immune infiltrates, and cyotokine-chemokine, which potentiate their aggressive proliferative potential. Targeting CCSCs through small molecule inhibitors, miRNAs, and monoclonal antibodies (mAbs) in in vivo studies has generated compelling evidence for the effectiveness of these various treatments. This review effectively compiles the role of CCSC surface markers and dysregulated and/or upregulated pathways in the pathogenesis of colorectal cancer that can be used to target CCSCs for effective colorectal cancer treatment.

Leptin Promotes White Adipocyte Browning by Inhibiting the Hh Signaling Pathway

Leptin is an important secretory protein that regulates the body’s intake and energy consumption, and the functions of the Hh signaling pathway related to white adipocyte browning are controversial. It has been reported that leptin plays a critical role in adipogenesis by regulating the Hh signaling pathway, but whether there is a functional relationship between leptin, the Hh signaling pathway, and adipocyte browning is not clear. In this research, mouse white pre-adipocytes were isolated to explore the influence of the Hh signal pathway and leptin during the process described above. This showed that leptin decreased high fat diet-induced obese mice body weight and inhibited the Hh signaling pathway, which suggested that leptin and the Hh signaling pathway have an important role in obesity. After activation of the Hh signaling pathway, significantly decreased browning fat-relative gene expression levels were recorded, whereas inhibition of the Hh signaling pathway significantly up-regulated the expression of these genes. Similarly, leptin also up-regulated the expression of these genes, and increased mitochondrial DNA content, but decreased the expression of Gli, the key transcription factors of the Hh signaling pathway. In short, the results show that leptin promotes white adipocyte browning through inhibiting the Hh signaling pathway. Overall, these results demonstrate that leptin serves as a potential intervention to decrease obesity by inhibiting the Hh signaling pathway.

Inhibition of GLI2 with antisense-oligonucleotides: A potential therapy for the treatment of bladder cancer

The sonic hedgehog (SHH) signaling pathway plays an integral role in the maintenance and progression of bladder cancer (BCa) and SHH inhibition may be an efficacious strategy for BCa treatment. We assessed an in-house human BCa tissue microarray and found that the SHH transcription factors, GLI1 and GLI2, were increased in disease progression. A panel of BCa cell lines show that two invasive lines, UM-UC-3 and 253J-BV, both express these transcription factors but UM-UC-3 produces more SHH ligand and is less responsive in viability to pathway stimulation by recombinant human SHH or smoothened agonist, and less responsive to inhibitors including the smoothened inhibitors cyclopamine and SANT-1. In contrast, 253J-BV was highly responsive to these manipulations. We utilized a GLI1 and GLI2 antisense oligonucleotide (ASO) to bypass pathway mechanics and target the transcription factors directly. UM-UC-3 decreased in viability due to both ASOs but 253J-BV was only affected by GLI2 ASO. We utilized the murine intravesical orthotopic human BCa (mio-hBC) model for the establishment of noninvasive BCa and treated tumors with GLI2 ASO. Tumor size, growth rate, and GLI2 messenger RNA and protein expression were decreased. These results suggest that GLI2 ASO may be a promising new targeted therapy for BCa.

Next-Generation Hedgehog/GLI Pathway Inhibitors for Cancer Therapy

The Hedgehog/Glioma-associated oncogene homolog (HH/GLI) signaling pathway regulates self-renewal of rare and highly malignant cancer stem cells (CSC), which have been shown to account for the initiation and maintenance of tumor growth as well as for drug resistance, metastatic spread and relapse. Efficacious therapeutic approaches targeting CSC pathways, such as HH/GLI signaling in combination with chemo, radiation or immunotherapy are, therefore, of high medical need. Pharmacological inhibition of HH/GLI pathway activity represents a promising approach to eliminate malignant CSC. Clinically approved HH/GLI pathway inhibitors target the essential pathway effector Smoothened (SMO) with striking therapeutic efficacy in skin and brain cancer patients. However, multiple genetic and molecular mechanisms resulting in de novo and acquired resistance to SMO inhibitors pose major limitations to anti-HH/GLI therapies and, thus, the eradication of CSC. In this review, we summarize reasons for clinical failure of SMO inhibitors, including mechanisms caused by genetic alterations in HH pathway effectors or triggered by additional oncogenic signals activating GLI transcription factors in a noncanonical manner. We then discuss emerging novel and rationale-based approaches to overcome SMO-inhibitor resistance, focusing on pharmacological perturbations of enzymatic modifiers of GLI activity and on compounds either directly targeting oncogenic GLI factors or interfering with synergistic crosstalk signals known to boost the oncogenicity of HH/GLI signaling.

Isoflurane Post-conditioning Ameliorates Cerebral Ischemia/Reperfusion Injury by Enhancing Angiogenesis Through Activating the Shh/Gli Signaling Pathway in Rats

Background: Stroke is the second leading cause of death worldwide. Angiogenesis facilitates the formation of microvascular networks and promotes recovery after stroke. The Shh/Gli signaling pathway is implicated in angiogenesis and cerebral ischemia-reperfusion (I/R) injury. This study aimed at investigating the influence of isoflurane (ISO) post-conditioning on brain lesions and angiogenesis after I/R injury.

Methods: Adult male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO), 1.5 h occlusion and 24 h reperfusion (MCAO/R). The ISO post-conditioning group (ISO group) received 1 h ISO post-conditioning when reperfusion was initiated. Neurobehavioral tests, TTC staining, HE staining, Nissl staining, TUNEL staining, immunofluorescence (IF), immunohistochemistry (IH) and Western blot were performed to assess the effect of ISO after I/R injury.

Results: ISO post-conditioning resulted in lower infarct volumes and neurologic deficit scores, higher rate of neurons survival, and less damaged and apoptotic cells after cerebral I/R injury in rats. Meanwhile, ISO post-conditioning significantly increased the expression levels of vascular endothelial growth factor (VEGF) and CD34 in the ischemic penumbra, relative to that in the Sham and I/R groups. However, cyclopamine, the specific inhibitor of the Sonic hedgehog (Shh) signaling pathway, decreased the expression levels of VEGF and CD34, and counteracted the protective effects of ISO post-conditioning against I/R injury in rats.

Conclusions: ISO post-conditioning enhances angiogenesis in vivo partly via the Shh/Gli signaling pathway. Thus, Shh/Gli may represent new therapeutic targets for aiding recovery from stroke.

Targeting Hedgehog (Hh) Pathway for the Acute Myeloid Leukemia Treatment

The Hedgehog (Hh) pathway, containing the Patched (PTCH) and Smoothened (SMO) multitransmembrane proteins, is the main regulator of vertebrate embryonic development. A non-canonical Hh pathway was recently observed in numerous types of solid cancers and hematological malignancies. Although acute myeloid leukemia (AML) is a common and lethal myeloid malignancy, the chemotherapy for AML has not changed in the last three decades. The Hh pathway and other intracellular signaling pathways are important for the tumor cells’ cycle or therapeutic resistance of AML cells. In this article, we will review the current trends in Hh pathway inhibitors for treating AML.

A novel PTCH1 mutation in basal cell nevus syndrome with rare craniofacial features

Basal cell nevus syndrome (BCNS) is a rare, multisystem, autosomal dominant disorder that is characterized by various phenotypes, including multiple basal cell carcinomas of the skin, odontogenic keratocysts of the jaws, and occasionally cleft lip and/or palate. In this report, we describe a 6-year-old Japanese girl with a novel heterozygous nonsense mutation in PTCH1 who exhibited rare craniofacial phenotypes, such as oligodontia and a short-tooth root.

Sonic hedgehog expression in the postnatal brain

Beyond its role in patterning the neural tube during embryogenesis, additional functions of Sonic hedgehog (Shh) in post-embryonic and mature brains have been coming into focus. However, the question of the abundance of endogenous Shh - the ligand of the signaling pathway - and its changes over time in post-embryonic and mature brains are less well understood. Here we find that while the amounts of Shh transcript and protein in rat brains are nearly undetectable at birth, they increase continuously during postnatal development and remain at readily detectable levels in young adults. This developmental age-associated increase in Shh levels is also seen in hippocampal neurons grown in culture, in which very young neurons produce minimal amounts of Shh protein but, as neurons grow and form synapses, the amounts of Shh increase significantly. Using immunolabeling with antibodies to different residues of Shh, we observed that the N-terminal fragment and the C-terminal fragment of Shh are present in hippocampal neurons, and that these two Shh forms co-exist in most compartments of the neuron. Our findings provide a better understanding of Shh expression in the brain, laying the groundwork for further comprehending the biogenesis of Shh protein in the young and mature brain and neurons.

Cyclopamine Suppresses Human Esophageal Carcinoma Cell Growth by Inhibiting Glioma-Associated Oncogene Protein-1, a Marker of Human Esophageal Carcinoma Progression

BACKGROUND Esophageal carcinoma is a common gastrointestinal tumor in humans. Cyclopamine, a Hedgehog (Hh)-pathway-specific inhibitor, is an effective chemotherapeutic drug for suppressing tumor cell differentiation, with unclear mechanisms. We investigated glioma-associated oncogene protein-1 (Gli-1) expression in human esophageal carcinoma tissue and the inhibition of cyclopamine on EC9706 esophageal carcinoma cell growth. MATERIAL AND METHODS Gli-1 in tumor tissue was measured by immunohistochemistry (IHC). EC9706 cells were treated with different concentrations of cyclopamine and incubated for different times. MTT method, flow cytometry, and Acridine orange/ethidium bromide (AO/EB) double-fluorescence staining were applied to detect cell proliferation and apoptosis. Western blot (WB) analysis was performed to assess Gli-1 expression. RESULTS Gli-1 was associated with patient age, gender, lymphatic metastasis, tumor recurrence, and stage, with significantly (P<0.05) positive correlations with age, lymphatic metastasis, tumor recurrence, and stage. At 12 h (F=214.57), 24 h (F=76.832), 48 h (F=236.90), and 72 h (F=164.55), the higher the concentration of cyclopamine, the higher the inhibition rate of suppressing EC9706 proliferation, and this effect was significant (P<0.05). The number of early-apoptosis cells increased as the concentration of cyclopamine increased. Morphology of EC9706 cells appeared as round with rough edges, karyopyknosis, and karyorrhexis. After 48 h, apoptosis rates of EC9706 cells treated with different concentrations of cyclopamine were (7.73±1.25)% at 2.5 μM, (13.37±1.42)% at 5.0 μM, (22.3±2.92)% at 10.0 μM, and (33.57±1.75)% at 20.0 μM, and the effect was dose-dependent. Gli-1 was obviously reduced after cyclopamine treatment and the effect was dose-dependent. CONCLUSIONS Gli-1 is highly expressed in human esophageal carcinoma, and could be a marker for use in assessing tumor stage and the deciding on treatment target.

Down-regulated WDR35 contributes to fetal anomaly via regulation of osteogenic differentiation

BACKGROUND

Autosomal recessive disorder is closely correlated with congenital fetal malformation. The mutation of WDR35 may lead to short rib-polydactyly syndrome (SRP), asphyxiating thoracic dystrophy (ATD, Jeune syndrome) and Ellis van Creveld syndrome. The purpose of this study is to investigate the role of WDR35 in fetal anomaly.

RESULTS

The fetuses presented malformation with abnormal head shape, cardiac dilatation, pericardial effusion, and non-displayed left pulmonary artery and left lung. After the detection of genomic DNA (gDNA) in amniotic fluid cells (AFC), chromosomal rearrangement was found in arr[hg19] 2p25.3p23.3. It was revealed through multiple PCR-DHPLC that MYCN, WDR35, LPIN1, ODC1, KLF11 and NBAS contained duplicated copy numbers in 2p25.3p23.3. AF-MSCs were mostly positive for CD44, CD105, negative for CD34 and CD14. Western Blot test showed that WDR35-encoded protein was decreased in the patients' AFC compared to that in normal pregnant women. In the patients' amniotic fluid-derived mesenchymal stem cells (AF-MSCs), WDR35 overexpression could repair cilia formation, and the overexpression of WDR35 or Gli2 could significantly enhance ALP activity and expressions of osteogenic differentiation marker genes, including RUNXE2, OCN, BSP and ALP. However, WDR35 silencing in C3H10T1/2 cells could remarkably inhibit cilia formation and osteogenic differentiation. This inhibitory effect could be attenuated by Gli2 overexpression.

CONCLUSIONS

The results demonstrated that copy number variation (CNV) of WDR35 may lead to skeletal dysplasia and fetal anomaly, and that down-regulated WDR35 may damage the cilia formation and sequentially indirectly regulate Gli signal, which would eventually result in negative regulation of osteogenic differentiation.

Genetic deletion of genes in the cerebellar rhombic lip lineage can stimulate compensation through adaptive reprogramming of ventricular zone-derived progenitors

BACKGROUND

The cerebellum is a foliated posterior brain structure involved in coordination of motor movements and cognition. The cerebellum undergoes rapid growth postnataly due to Sonic Hedgehog (SHH) signaling-dependent proliferation of ATOH1+ granule cell precursors (GCPs) in the external granule cell layer (EGL), a key step for generating cerebellar foliation and the correct number of granule cells. Due to its late development, the cerebellum is particularly vulnerable to injury from preterm birth and stress around birth. We recently uncovered an intrinsic capacity of the developing cerebellum to replenish ablated GCPs via adaptive reprogramming of Nestin-expressing progenitors (NEPs). However, whether this compensation mechanism occurs in mouse mutants affecting the developing cerebellum and could lead to mis-interpretation of phenotypes was not known.

METHODS

We used two different approaches to remove the main SHH signaling activator GLI2 in GCPs: 1) Our mosaic mutant analysis with spatial and temporal control of recombination (MASTR) technique to delete Gli2 in a small subset of GCPs; 2) An Atoh1-Cre transgene to delete Gli2 in most of the EGL. Genetic Inducible Fate Mapping (GIFM) and live imaging were used to analyze the behavior of NEPs after Gli2 deletion.

RESULTS

Mosaic analysis demonstrated that SHH-GLI2 signaling is critical for generating the correct pool of granule cells by maintaining GCPs in an undifferentiated proliferative state and promoting their survival. Despite this, inactivation of GLI2 in a large proportion of GCPs in the embryo did not lead to the expected dramatic reduction in the size of the adult cerebellum. GIFM uncovered that NEPs do indeed replenish GCPs in Gli2 conditional mutants, and then expand and partially restore the production of granule cells. Furthermore, the SHH signaling-dependent NEP compensation requires Gli2, demonstrating that the activator side of the pathway is involved.

CONCLUSION

We demonstrate that a mouse conditional mutation that results in loss of SHH signaling in GCPs is not sufficient to induce long term severe cerebellum hypoplasia. The ability of the neonatal cerebellum to regenerate after loss of cells via a response by NEPs must therefore be considered when interpreting the phenotypes of Atoh1-Cre conditional mutants affecting GCPs.

Inhibition of pancreatic cancer stem cell characteristics by α-Mangostin: Molecular mechanisms involving Sonic hedgehog and Nanog

The current investigation was intended to elucidate the molecular mechanism of α‐Mangostin in the regulation of pancreatic cancer stem cell (CSC) characteristics. Here, we demonstrate that α‐Mangostin inhibited cell proliferation in pancreatic CSCs and cancer cell lines while it showed no effect on human pancreatic normal ductal epithelial cells. Also, α‐Mangostin inhibited colony formation and induced apoptosis in these cells. Further, α‐Mangostin inhibited the self‐renewal capacity of CSCs isolated from human primary tumours and Kras^G12D mice. Furthermore, α‐Mangostin inhibited the invasive and metastatic ability of pancreatic CSCs by suppressing the epithelial‐to‐mesenchymal transition (EMT) via up‐regulation of E‐cadherin and down‐regulation of mesenchymal phenotype by inhibiting N‐cadherin, Snail and Slug expression. Interestingly, the pluripotency maintaining factors and CSC markers were inhibited by α‐Mangostin thus suggesting that α‐Mangostin can target CSCs to inhibit pancreatic cancer effectively. Gli signalling plays a crucial role in the self‐renewal and pluripotency of CSCs. α‐Mangostin inhibited the Gli transcription and the expression of Gli target genes (Nanog, Oct4, c‐Myc, Sox‐2 and KLF4) in CSCs. Using ChIP assay, we demonstrated that Nanog could directly bind to promoters of Cdk2, Cdk6, FGF4, c‐Myc and α‐Mangostin inhibited Nanog binding to these promoters. Conversely, the inhibitory effects of the α‐Mangostin on CSC proliferation and Gli or Nanog transcription and their targets were abrogated by either enforced activation of sonic hedgehog (Shh) or by the overexpression of Nanog. Taken together, our studies suggest that α‐Mangostin may act as Gli inhibitor and establishes the pre‐clinical significance of α‐Mangostin for the prevention and treatment of pancreatic cancer.

Hedgehog Signaling Modulates Interleukin-33-Dependent Extrahepatic Bile Duct Cell Proliferation in Mice

Hedgehog (HH) signaling participates in hepatobiliary repair after injury and is activated in patients with cholangiopathies. Cholangiopathies are associated with bile duct (BD) hyperplasia, including expansion of peribiliary glands, the niche for biliary progenitor cells. The inflammation-associated cytokine interleukin (IL)-33 is also up-regulated in cholangiopathies, including cholangiocarcinoma. We hypothesized that HH signaling synergizes with IL-33 in acute inflammation-induced BD hyperplasia. We measured extrahepatic BD (EHBD) thickness and cell proliferation with and without an IL-33 challenge in wild-type mice, mice overexpressing Sonic HH (pCMV-Shh), and mice with loss of the HH pathway effector glioma-associated oncogene 1 (Gli1lacZ/lacZ ). LacZ reporter mice were used to map the expression of HH effector genes in mouse EHBDs. An EHBD organoid (BDO) system was developed to study biliary progenitor cells in vitro. EHBDs from the HH overexpressing pCMV-Shh mice showed increased epithelial cell proliferation and hyperplasia when challenged with IL-33. In Gli1lacZ/lacZ mice, we observed a decreased proliferative response to IL-33 and decreased expression of Il6. The HH ligands Shh and Indian HH (Ihh) were expressed in epithelial cells, whereas the transcriptional effectors Gli1, Gli2, and Gli3 and the HH receptor Patched1 (Ptch1) were expressed in stromal cells, as assessed by in situ hybridization and lacZ reporter mice. Although BDO cells lacked canonical HH signaling, they expressed the IL-33 receptor suppression of tumorigenicity 2. Accordingly, IL-33 treatment directly induced BDO cell proliferation in a nuclear factor κB-dependent manner. Conclusion: HH ligand overexpression enhances EHBD epithelial cell proliferation induced by IL-33. This proproliferative synergism of HH and IL-33 involves crosstalk between HH ligand-producing epithelial cells and HH-responding stromal cells.

The single-cell transcriptional landscape of mammalian organogenesis

Mammalian organogenesis is a remarkable process. Within a short timeframe, the cells of the three germ layers transform into an embryo that includes most of the major internal and external organs. Here we investigate the transcriptional dynamics of mouse organogenesis at single-cell resolution. Using single-cell combinatorial indexing, we profiled the transcriptomes of around 2 million cells derived from 61 embryos staged between 9.5 and 13.5 days of gestation, in a single experiment. The resulting 'mouse organogenesis cell atlas' (MOCA) provides a global view of developmental processes during this critical window. We use Monocle 3 to identify hundreds of cell types and 56 trajectories, many of which are detected only because of the depth of cellular coverage, and collectively define thousands of corresponding marker genes. We explore the dynamics of gene expression within cell types and trajectories over time, including focused analyses of the apical ectodermal ridge, limb mesenchyme and skeletal muscle.

Sulforaphane inhibits gastric cancer stem cells via suppressing sonic hedgehog pathway

Sulforaphane (SFN) is the major component extracted from broccoli/broccoli sprouts. It has been shown to possess anti-cancer activity. Gastric cancer is common cancer worldwide. The objective of this work was to evaluate the inhibitory effect of SFN on gastric cancer by Sonic hedgehog (Hh) Pathway. The results found that tumorsphere formation and the expression levels of gastric cancer stem cells (CSCs) markers were significantly decreased after SFN treatment. SFN also exerted inhibitory effects by suppressing proliferation and inducing apoptosis in gastric CSCs. Intriguingly, SFN inhibited the activation of Sonic Hh, a key pathway in maintaining the stemness of gastric CSCs. Upregulation of Sonic Hh pathway diminished the inhibitory effects of SFN on gastric CSCs. Collectively, these data revealed that SFN could be a potent natural compound targeting gastric CSCs via suppression of Sonic Hh pathway, which might be an promising agent for gastric cancer intervention.

The Role of Thyroid Hormones in Hepatocyte Proliferation and Liver Cancer

Thyroid hormones T3 and T4 (thyroxine) control a wide variety of effects related to development, differentiation, growth and metabolism, through their interaction with nuclear receptors. But thyroid hormones also produce non-genomic effects that typically start at the plasma membrane and are mediated mainly by integrin αvβ3, although other receptors such as TRα and TRβ are also able to elicit non-genomic responses. In the liver, the effects of thyroid hormones appear to be particularly important. The liver is able to regenerate, but it is subject to pathologies that may lead to cancer, such as fibrosis, cirrhosis, and non-alcoholic fatty liver disease. In addition, cancer cells undergo a reprogramming of their metabolism, resulting in drastic changes such as aerobic glycolysis instead of oxidative phosphorylation. As a consequence, the pyruvate kinase isoform M2, the rate-limiting enzyme of glycolysis, is dysregulated, and this is considered an important factor in tumorigenesis. Redox equilibrium is also important, in fact cancer cells give rise to the production of more reactive oxygen species (ROS) than normal cells. This increase may favor the survival and propagation of cancer cells. We evaluate the possible mechanisms involving the plasma membrane receptor integrin αvβ3 that may lead to cancer progression. Studying diseases that affect the liver and their experimental models may help to unravel the cellular pathways mediated by integrin αvβ3 that can lead to liver cancer. Inhibitors of integrin αvβ3 might represent a future therapeutic tool against liver cancer. We also include information on the possible role of exosomes in liver cancer, as well as on recent strategies such as organoids and spheroids, which may provide a new tool for research, drug discovery, and personalized medicine.

Maternal di-(2-ethylhexyl) phthalate exposure inhibits cerebellar granule precursor cell proliferation via down-regulating the Shh signaling pathway in male offspring

Di-(2-ethylhexyl) phthalate (DEHP) is an endocrine disrupting chemical (EDC) widely used as a plasticizer in many materials. Epidemiological investigations have shown that DEHP exposure during early development is related to cerebellar-related adverse neurodevelopmental outcomes. However, animal studies involving the effect of DEHP exposure on cerebellar development have rarely been reported and the potential mechanisms are unclear. The aim of this study was to investigate the effect of maternal DEHP exposure on the proliferation of cerebellar granule cell precursor cells (GCPs) and the mechanisms involved. Wistar rats were randomly assigned to four exposure groups and given 0, 30, 300, or 750 mg/kg/d DEHP by intragastric administration from gestational day (GD) 0 to postnatal day (PN) 21. Exposure to 300 and 750 mg/kg/d DEHP restrained GCPs proliferation and impaired neurodevelopment for males. Furthermore, exposure to 300 and 750 mg/kg/d DEHP decreased male pups protein expressions and mRNA levels of molecules related to proliferation, including Shh, Gli1, N-Myc, CyclinD1. In addition, the estrogen level and aromatase expression also reduced in male pups after maternal exposure to DEHP. However, effects on females were not obvious. These results suggested that 300 and 750 mg/kg/d DEHP exposure inhibit the proliferation of GCPs in male offspring and ultimately contribute to the impairment of neuromotor development. This, may be caused by the down-regulation of Shh signaling. And the susceptibility of male offspring to DEHP exposure may be attributed to the decreased estrogen level and aromatase expression in male pup's cerebellum.

New perspectives on the mechanisms establishing the dorsal-ventral axis of the spinal cord

Distinct classes of neurons arise at different positions along the dorsal-ventral axis of the spinal cord leading to spinal neurons being segregated along this axis according to their physiological properties and functions. Thus, the neurons associated with motor control are generally located in, or adjacent to, the ventral horn whereas the interneurons (INs) that mediate sensory activities are present within the dorsal horn. Here, we review classic and recent studies examining the developmental mechanisms that establish the dorsal-ventral axis in the embryonic spinal cord. Intriguingly, while the cellular organization of the dorsal and ventral halves of the spinal cord looks superficially similar during early development, the underlying molecular mechanisms that establish dorsal vs ventral patterning are markedly distinct. For example, the ventral spinal cord is patterned by the actions of a single growth factor, sonic hedgehog (Shh) acting as a morphogen, i.e., concentration-dependent signal. Recent studies have shed light on the mechanisms by which the spatial and temporal gradient of Shh is transduced by cells to elicit the generation of different classes of ventral INs, and motor neurons (MNs). In contrast, the dorsal spinal cord is patterned by the action of multiple factors, most notably by members of the bone morphogenetic protein (BMP) and Wnt families. While less is known about dorsal patterning, recent studies have suggested that the BMPs do not act as morphogens to specify dorsal IN identities as previously proposed, rather each BMP has signal-specific activities. Finally, we consider the promise that elucidation of these mechanisms holds for neural repair.

Gli2 modulates cell cycle re-entry through autophagy-mediated regulation of the length of primary cilia

The primary cilium is a tiny cell protrusion known to transduce key extracellular signals, including those of the sonic hedgehog pathway, which activates Gli transcription factors for various cellular functions. To understand the significance of the Gli2 transcription factor in fibroblasts, we establish a Gli2-knockout NIH3T3 cell line by CRISPR/Cas9 technology. Surprisingly, NIH3T3 fibroblasts lacking Gli2 expression through gene knockout or RNA interference possess longer primary cilia after stimulation of ciliogenesis by serum starvation. This lengthening of primary cilia is associated with enhanced autophagy-mediated Ofd1 degradation, and can be reversed by pharmacological and genetic inhibition of autophagy. Meanwhile, flow cytometry reveals that Gli2^-/- NIH3T3 fibroblasts exhibit a delay in cell cycle re-entry after serum re-stimulation. Ablation of their primary cilia through Kif3a knockdown rescues the delay in cell cycle re-entry. These results suggest that Gli2 plays an unexpected role in cell cycle re-entry through an autophagy-mediated regulation on ciliary length in fibroblasts.

Hedgehog Pathway Inhibitors and Their Utility in Basal Cell Carcinoma: A Comprehensive Review of Current Evidence

Basal cell carcinoma (BCC) is the most commonly diagnosed malignancy in humans, and as such it poses a significant healthcare burden. The majority of BCC cases are amenable to cure by surgical extirpation. However, until recently there have been no good treatment options for a significant minority of advanced BCC cases, including locally advanced BCC and metastatic BCC. The introduction of a novel class of drugs, the Hedgehog pathway inhibitors, into clinical practice has ushered in a new treatment algorithm for the treatment of difficult BCC cases. In this review we present the latest available evidence and discuss areas for further research in this rapidly evolving field.

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.

Overcoming the emerging drug resistance of smoothened: an overview of small-molecule SMO antagonists with antiresistance activity

Hedgehog (HH) signaling pathway plays vital roles in controlling embryonic cell fate and homeostatic, and becomes dormant in mature individuals, aberrant activation of HH signaling pathway is involved in a number of human cancers. Smoothened (SMO), a vital transducer of HH signaling pathway, attracts significant attentions in HH signaling pathway-related cancer therapy. The approval of SMO antagonists vismodegib proves that SMO is a promising therapeutic target, and a number of SMO antagonists are reported since then. However, high incidence of tumor recurrence with the clinical application of vismodegib urges exploring of novel drugs with antiresistance profiles. This review provides an overview of SMO mutations reported in the literature, crystal structures of SMO, as well as reported antagonists with antiresistance profiles.

Sonic hedgehog protects endometrial hyperplasial cells against oxidative stress via suppressing mitochondrial fission protein dynamin-like GTPase (Drp1)

Hh/Gli1 cascade as well as Gsk3β-Gli1 crosstalk play crucial role in estrogen-dependent progression of endometrial hyperplasia (EH). However, the underlying mechanisms involved in progression of disease still remain unclear. In the present study, we explored the role of Hh signaling in protection of endometrial hyperplasial cells against oxidative stress and the underlying mechanism involved therein. EH cells were found to be more resistant towards H₂O₂-induced oxidative stress (IC₅₀: ~ 3×) as compared with normal endometrial cells. Estrogen (E2) pre-treatment followed by cytotoxic dose of H₂O_2, almost rescued the EH cells from apoptosis and caused the increased expression of downstream Shh signaling molecules i.e., Smo, Ptch and Gli1. Whereas pretreatment with cyclopamine was not able to curtail H₂O₂-induced effects indicating that estrogen protects these cells via activation of Shh pathway. Further, H₂O₂-induced ROS and lipid peroxidation alongwith decreased activities of antioxidant enzymes glutathione peroxidase and superoxide dismutase were found to be reversed in EH cells pre-exposed to E2 or rShh. The rShh suppressed H₂O₂-induced cell death and caused attenuation of mitochondrial apoptotic mediators and prevented disruption in mitochondrial morphology and mitochondrial membrane potential in EH cells. The functional blockage of signaling by Shh siRNA or Gli1siRNA led to significantly increased expression of mitochondrial fission protein dynamin-like GTPase (Drp1). The H₂O₂-treated EH cells showed diminished Gli1 and increased Drp1 expression, concurrent with reduced p-Drp1-(serine637). Whereas rShh pre-treated EH cells presented normal mitochondrial dynamics with dense, long networks of mitochondria alongwith nuclear accumulation of Gli1 and the decreased expression of Drp1. Overall, our results implicated that Shh signaling modulates antioxidant defense system and stabilizes mitochondrial dynamics by suppressing Drp1 protein which maintains survival of EH cells against oxidative stress.

Targeting Smoothened as a New Frontier in the Functional Recovery of Central Nervous System Demyelinating Pathologies

Myelin sheaths on vertebrate axons provide protection, vital support and increase the speed of neuronal signals. Myelin degeneration can be caused by viral, autoimmune or genetic diseases. Remyelination is a natural process that restores the myelin sheath and, consequently, neuronal function after a demyelination event, preventing neurodegeneration and thereby neuron functional loss. Pharmacological approaches to remyelination represent a promising new frontier in the therapy of human demyelination pathologies and might provide novel tools to improve adaptive myelination in aged individuals. Recent phenotypical screens have identified agonists of the atypical G protein-coupled receptor Smoothened and inhibitors of the glioma-associated oncogene 1 as being amongst the most potent stimulators of oligodendrocyte precursor cell (OPC) differentiation in vitro and remyelination in the central nervous system (CNS) of mice. Here, we discuss the current state-of-the-art of studies on the role of Sonic Hedgehog reactivation during remyelination, referring readers to other reviews for the role of Hedgehog signaling in cancer and stem cell maintenance.

Sulforaphene Inhibition of Adipogenesis via Hedgehog Signaling in 3T3-L1 Adipocytes

Obesity is a risk factor for numerous metabolic disorders. In this study, we investigated the effects of the isothiocyanates sulforaphane (SA) and sulforaphene (SE) on adipogenesis in 3T3-L1 adipocytes. SE, a compound that is abundant in radish, inhibited adipogenesis by suppressing the adipogenic transcription factors peroxisome proliferator-activated receptor γ (PPARγ, 69.2 ± 2.4%, P < 0.05) and CCAAT/enhancer-binding protein α (C/EBPα, 36.1 ± 3.1%, P < 0.05), thereby reducing fat accumulation in 3T3-L1 adipocytes (45.6 ± 2.7%, P < 0.05); SA was less effective. SE exerted these activities through the activation of the Hedgehog (Hh) signaling pathway by restoring Smo ((2.1 ± 0.2)-fold, P < 0.05) and Gli1 ((2.8 ± 0.1)-fold, P < 0.05) expression, which was suppressed by adipogenic signals. These effects of SE were abrogated by treatment with the Hh inhibitor vismodegib. Thus, SE inhibits adipocyte differentiation via Hh signaling and may be an effective natural agent for preventing adipocyte hyperplasia and obesity.

Hedgehog Signaling in Cancer: A Prospective Therapeutic Target for Eradicating Cancer Stem Cells

The Hedgehog (Hh) pathway is a signaling cascade that plays a crucial role in many fundamental processes, including embryonic development and tissue homeostasis. Moreover, emerging evidence has suggested that aberrant activation of Hh is associated with neoplastic transformations, malignant tumors, and drug resistance of a multitude of cancers. At the molecular level, it has been shown that Hh signaling drives the progression of cancers by regulating cancer cell proliferation, malignancy, metastasis, and the expansion of cancer stem cells (CSCs). Thus, a comprehensive understanding of Hh signaling during tumorigenesis and development of chemoresistance is necessary in order to identify potential therapeutic strategies to target various human cancers and their relapse. In this review, we discuss the molecular basis of the Hh signaling pathway and its abnormal activation in several types of human cancers. We also highlight the clinical development of Hh signaling inhibitors for cancer therapy as well as CSC-targeted therapy.

Soft Tissue Sarcoma Cancer Stem Cells: An Overview

Soft tissue sarcomas (STSs) are an uncommon group of solid tumors that can arise throughout the human lifespan. Despite their commonality as non-bony cancers that develop from mesenchymal cell precursors, they are heterogeneous in their genetic profiles, histology, and clinical features. This has made it difficult to identify a single target or therapy specific to STSs. And while there is no one cell of origin ascribed to all STSs, the cancer stem cell (CSC) principle—that a subpopulation of tumor cells possesses stem cell-like properties underlying tumor initiation, therapeutic resistance, disease recurrence, and metastasis—predicts that ultimately it should be possible to identify a feature common to all STSs that could function as a therapeutic Achilles' heel. Here we review the published evidence for CSCs in each of the most common STSs, then focus on the methods used to study CSCs, the developmental signaling pathways usurped by CSCs, and the epigenetic alterations critical for CSC identity that may be useful for further study of STS biology. We conclude with discussion of some challenges to the field and future directions.

Large-scale genome-wide enrichment analyses identify new trait-associated genes and pathways across 31 human phenotypes

Genome-wide association studies (GWAS) aim to identify genetic factors associated with phenotypes. Standard analyses test variants for associations individually. However, variant-level associations are hard to identify and can be difficult to interpret biologically. Enrichment analyses help address both problems by targeting sets of biologically related variants. Here we introduce a new model-based enrichment method that requires only GWAS summary statistics. Applying this method to interrogate 4,026 gene sets in 31 human phenotypes identifies many previously-unreported enrichments, including enrichments of endochondral ossification pathway for height, NFAT-dependent transcription pathway for rheumatoid arthritis, brain-related genes for coronary artery disease, and liver-related genes for Alzheimer’s disease. A key feature of our method is that inferred enrichments automatically help identify new trait-associated genes. For example, accounting for enrichment in lipid transport genes highlights association between MTTP and low-density lipoprotein levels, whereas conventional analyses of the same data found no significant variants near this gene.

In genome-wide association studies, variant-level associations are hard to identify and can be difficult to interpret biologically. Here, the authors develop a new model-based enrichment analysis method, and apply it to identify new associated genes, pathways and tissues across 31 human phenotypes.

BMP-IHH-mediated interplay between mesenchymal stem cells and osteoclasts supports calvarial bone homeostasis and repair

Calvarial bones are connected by fibrous sutures. These sutures provide a niche environment that includes mesenchymal stem cells (MSCs), osteoblasts, and osteoclasts, which help maintain calvarial bone homeostasis and repair. Abnormal function of osteogenic cells or diminished MSCs within the cranial suture can lead to skull defects, such as craniosynostosis. Despite the important function of each of these cell types within the cranial suture, we have limited knowledge about the role that crosstalk between them may play in regulating calvarial bone homeostasis and injury repair. Here we show that suture MSCs give rise to osteoprogenitors that show active bone morphogenetic protein (BMP) signalling and depend on BMP-mediated Indian hedgehog (IHH) signalling to balance osteogenesis and osteoclastogenesis activity. IHH signalling and receptor activator of nuclear factor kappa-Β ligand (RANKL) may function synergistically to promote the differentiation and resorption activity of osteoclasts. Loss of Bmpr1a in MSCs leads to downregulation of hedgehog (Hh) signalling and diminished cranial sutures. Significantly, activation of Hh signalling partially restores suture morphology in Bmpr1a mutant mice, suggesting the functional importance of BMP-mediated Hh signalling in regulating suture tissue homeostasis. Furthermore, there is an increased number of CD200+ cells in Bmpr1a mutant mice, which may also contribute to the inhibited osteoclast activity in the sutures of mutant mice. Finally, suture MSCs require BMP-mediated Hh signalling during the repair of calvarial bone defects after injury. Collectively, our studies reveal the molecular and cellular mechanisms governing cell–cell interactions within the cranial suture that regulate calvarial bone homeostasis and repair.

Understanding the signaling mechanisms regulating cells in cranial sutures could help develop strategies for repairing skull defects or fractures. Little is known about how osteoblasts, osteoclasts and mesenchymal stem cells (MSCs) in cranial sutures regulate the homeostasis and repair of skull bones. Yang Chai at the University of Southern California, United States, and colleagues show that preventing the expression of bone morphogenetic protein receptor type IA (Bmpr1a) in MSCs leads to defective cranial sutures in which osteogenic activity is increased and osteoclast activity is reduced. Stimulating the Hedgehog signaling pathway not only partially rescued the defective sutures but also promoted skull bone healing after injury in Bmpr1a mutant mice, highlighting the importance of BMP-mediated Hedgehog signaling for balancing skull bone formation and resorption.