Activation Of Hedgehog Signaling Research Articles

Activation of Hedgehog Signaling in Aggressive Hepatic Hemangioma in Newborns and Infants.

Hepatic hemangiomas (HH) can show an aggressive course with significant complications. Prognostic markers that identify an aggressive course are entirely absent. Since we have showed that Hedgehog signaling is overexpressed in aggressive hemangiomas of the skin. Here, we hypothesize that it is also altered in aggressive HH. Immunohistological staining for GLUT1 and quantitative PCR was performed in seven specimens with aggressive HH. For comparison, we included specimens of kaposiform hemangioendothelioma (KHE), skin hemangioma and normal liver tissue. Overexpression of the Hedgehog signaling components SHH and GLI2 and its target gene FOXA2 in HH were similar to those found in aggressive skin hemangioma and KHE, their expression being significantly higher than in mild skin hemangioma. High expression levels of SHH and FOXA2 positively correlated with HH, but not with normal liver tissue. Hedgehog signaling is up-regulated in aggressive HH. This finding may lead to a biomarker allowing early intervention.

Suppressor of fused controls perinatal expansion and quiescence of future dentate adult neural stem cells.

Adult hippocampal neurogenesis requires the quiescent neural stem cell (NSC) pool to persist lifelong. However, establishment and maintenance of quiescent NSC pools during development is not understood. Here, we show that Suppressor of Fused (Sufu) controls establishment of the quiescent NSC pool during mouse dentate gyrus (DG) development by regulating Sonic Hedgehog (Shh) signaling activity. Deletion of Sufu in NSCs early in DG development decreases Shh signaling activity leading to reduced proliferation of NSCs, resulting in a small quiescent NSC pool in adult mice. We found that putative adult NSCs proliferate and increase their numbers in the first postnatal week and subsequently enter a quiescent state towards the end of the first postnatal week. In the absence of Sufu, postnatal expansion of NSCs is compromised, and NSCs prematurely become quiescent. Thus, Sufu is required for Shh signaling activity ensuring expansion and proper transition of NSC pools to quiescent states during DG development.

Regulation of the hedgehog pathway by the ketogenic diet with radiation exposure

Hedgehog signaling is a pathway that directs morphogenesis during embryonic development. In adult healthy liver, Hedgehog signaling is inactive. It, however, becomes drastically reactivated upon liver injury. This pathway is responsible for regulating cell differentiation by promoting proliferative activities in multiple liver cells including hepatocytes and progenitor cells. Activation of Hedgehog signaling is implicated in clinical pathology of many liver diseases including liver fibrosis, alcoholic and non-alcoholic liver diseases, and liver cancers. Radiation can induce oxidative stress which causes serious cell damage; the hedgehog pathway typically is activated when the liver is exposed to radiation. Related, the ketogenic diet lowers the prevalence of inflammation response by mitigating the effects of oxidative stress. Therefore, the main goal of this study is to understand how the ketogenic diet influences inflammation response when the subject is exposed to radiation. The hypothesis of this study is that inflammatory response can be modified through the Hedgehog pathway and influence inflammatory status of liver. Since the ketogenic diet may alleviate any damage caused by the radiation treatment, we will be reviewing how much damage has occurred, if any, by examining the prevalence of the Hedgehog pathway. In this study, 5weekold mice were either treated with control diet (10% fat, no radiation), control diet and radiation treatment, or ketogenic diet (60% fat) and radiation. Radiation treatment started at 13 weeks of age, and mice are sacrificed and analyzed at 18 weeks. Critical genes involved in hedgehog signaling, Cdh2, Gli2, Tgfb1, Ihh, Col1a1, Ctnnb1 and cMyc, were analyzed in the mouse liver. Compared to animals fed with control diet before radiation, animals fed with ketogenic diet after radiation have significantly increased mRNA expression of Cdh2 and Tgfb1 (P<0.05), while animals fed with control diet after radiation remain unchanged. On the other hand, compared to animals fed with control diet before radiation, animals fed with ketogenic diet after radiation have significantly decreased mRNA expression of Gli2, Ihh and Col1a1(P<0.05), while animals fed with control diet after radiation remain unchanged. In addition, mRNA expression of cMyc was found to be significantly increased (P<0.05) in animals fed with control diet after radiation, while animals fed with ketogenic diet after radiation remain unchanged comparing to animals fed with control diet before radiation. These preliminary data suggest that ketogenic diet may affect the responses triggered by radiation exposure by hedgehog pathway in liver, however, further investigation is required to fully understand the mechanism of how the hedgehog pathway is regulated by the ketogenic diet. Support or Funding Information This project was supported by UIUC Research Board grant #12192, the USDA Cooperative State Research, Education and Extension Service, Hatch project numbers # ILLU-698-923 and ILLU-698-369, ILLU-698-391, and the Data Purchase Program from the University of Illinois Library. Animals fed with the ketogenic diet after radiation have significantly increased mRNA expression of the Cdh2 gene. Animals fed with the control diet after radiation have no significant change in mRNA expression. Animals fed with the ketogenic diet after radiation have significantly increased mRNA expression of the Tgfb1 gene. Animals fed with the control diet after radiation have no significant change in mRNA expression. There is decreased mRNA expression of the Gli2 gene among animals fed with the ketogenic diet after radiation. The mRNA expression in animals fed with the control diet after radiation remains unchanged. There is decreased mRNA expression of the Ihh gene among animals fed with the ketogenic diet after radiation. The mRNA expression in animals fed with the control diet after radiation remains unchanged. There is decreased mRNA expression of the Col1a1 gene among animals fed with the ketogenic diet after radiation. The mRNA expression in animals fed with the control diet after radiation remains unchanged. The mRNA expxression of the cMyc gene was significantly increased in animals fed with the control diet after radiation. Animals fed with the ketogenic diet after radiation did not show a change in mRNA expression when compared with the animals fed with the control diet before radiation. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Role of Protein Kinases in Hedgehog Pathway Control and Implications for Cancer Therapy.

Hedgehog (HH) signaling is an evolutionarily conserved pathway that is crucial for growth and tissue patterning during embryonic development. It is mostly quiescent in the adult, where it regulates tissue homeostasis and stem cell behavior. Aberrant reactivation of HH signaling has been associated to several types of cancer, including those in the skin, brain, prostate, breast and hematological malignancies. Activation of the canonical HH signaling is triggered by binding of HH ligand to the twelve-transmembrane protein PATCHED. The binding releases the inhibition of the seven-transmembrane protein SMOOTHENED (SMO), leading to its phosphorylation and activation. Hence, SMO activates the transcriptional effectors of the HH signaling, that belong to the GLI family of transcription factors, acting through a not completely elucidated intracellular signaling cascade. Work from the last few years has shown that protein kinases phosphorylate several core components of the HH signaling, including SMO and the three GLI proteins, acting as powerful regulatory mechanisms to fine tune HH signaling activities. In this review, we will focus on the mechanistic influence of protein kinases on HH signaling transduction. We will also discuss the functional consequences of this regulation and the possible implications for cancer therapy.

Krüppel-like factor 2 inhibits hepatocarcinogenesis through negative regulation of the Hedgehog pathway.

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. The most important reason for the occurrence of HCC is hepatitis C or B infection. Moreover, genetic factors play an important role in the tumorigenesis of HCC. Here, we demonstrated that Krüppel‐like factor 2 (KLF2) expression was downregulated in HCC samples compared with adjacent tissues. Additionally, KLF2 was shown to inhibit the growth, migration and colony‐formation ability of liver cancer cells. Further mechanistic studies revealed that KLF2 can compete with Gli1 for interaction with HDAC1 and restrains Hedgehog signal activation. Together, our results suggest that KLF2 has potential as a diagnostic biomarker and therapeutic target for the treatment of HCC.

In Vitro Analysis of Hedgehog Acyltransferase and Porcupine Fatty Acyltransferase Activities.

Hedgehog and Wnt proteins are modified by covalent attachment of the fatty acids palmitate and palmitoleate, respectively. These lipid modifications are essential for Hedgehog and Wnt protein signaling activities and are catalyzed by related, but distinct fatty acyltransferases: Hedgehog acyltransferase (Hedgehog) and Porcupine (Wnt). In this chapter, we provide detailed methods to directly monitor Hedgehog and Wnt protein fatty acylation in vitro. Palmitoylation of Sonic hedgehog (Shh), a representative Hedgehog family member, is assayed using purified Hedgehog acyltransferase (Hhat) or Hhat-enriched membranes, a recombinant 19kDa Shh protein or C-terminally biotinylated Shh 10-mer peptide, and 125I-iodopalmitoyl CoA as the donor fatty acyl CoA substrate. The radiolabeled reaction products are quantified by SDS-PAGE and phosphorimaging or by γ-counting. To assay Wnt acylation, the reaction consists of a biotinylated, double disulfide-bonded Wnt peptide containing the sequence surrounding the Wnt3a acylation site, [125I] iodo-cis-9-pentadecenoyl CoA, and Porcupine-enriched membranes. Radiolabeled, biotinylated Wnt3a peptide is captured on streptavidin coated beads and the reaction product is quantified by γ-counting.

DDX5 Silencing Suppresses the Migration of Basal cell Carcinoma Cells by Downregulating JAK2/STAT3 Pathway.

Basal cell carcinoma is driven by the aberrant activation of hedgehog signaling. DEAD (Asp-Glu-Ala-Asp) box protein 5 is frequently overexpressed in human cancer cells and associated with the tumor growth and invasion. The purpose of this study was to investigate the role of DEAD (Asp-Glu-Ala-Asp) box protein 5 in the growth, migration, and invasion of basal cell carcinoma. The role of DEAD (Asp-Glu-Ala-Asp) box protein 5 was detected by quantitative real-time polymerase chain reaction, Western blot, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay in basal cell carcinoma cells. The associations between JAK2/STAT3 pathway and DEAD (Asp-Glu-Ala-Asp) box protein 5 were analyzed in basal cell carcinoma cells. Results showed that DEAD (Asp-Glu-Ala-Asp) box protein 5 is overexpressed in basal cell carcinoma cells. DEAD (Asp-Glu-Ala-Asp) box protein 5 knockdown inhibited the migration and invasion of basal cell carcinoma cells. DEAD (Asp-Glu-Ala-Asp) box protein 5 knockdown increased the apoptosis of basal cell carcinoma cells induced by tunicamycin. Results found that DEAD (Asp-Glu-Ala-Asp) box protein 5 knockdown increased JAK2 and STAT3 expression in basal cell carcinoma cells. JAK2 inhibitor decreased STAT3 expression and abolished the inhibitory effects of DEAD (Asp-Glu-Ala-Asp) box protein 5 silencing on migration and invasion in basal cell carcinoma cells. In conclusion, these results indicate that DEAD (Asp-Glu-Ala-Asp) box protein 5 is a potential target for inhibiting basal cell carcinoma cells growth, migration, and invasion by downregulating JAK2/STAT3 pathway.

The Loss of SMAD4/DPC4 Expression Associated with a Strongly Activated Hedgehog Signaling Pathway Predicts Poor Prognosis in Resected Pancreatic Cancer.

Background: Pancreatic ductal adenocarcinoma (PDAC) progression is mediated by mutations in driver genes and a complex stroma that is mainly dependent on the Sonic hedgehog (Shh) signaling pathway. However, the association between driver genes and Shh-pathway proteins and their potential prognostic significance remain unclear.Methods: We analyzed protein expressions of the KRAS, TP53, SMAD4, and CDKN2A/P16 driver genes and the Shh-pathway molecules, including Shh, glioma-associated oncogene (Gli) 1, Gli2, and smoothened (SMO) by immunohistochemistry using tissue microarrays in 237 patients with resectable PDAC and statistically determined their prognostic significance.Results: SMAD4lost mutation was associated with shorter survival outcomes [overall survival (OS): Hazard ratio (HR) 1.887, p < 0.001]; recurrence-free survival (RFS): HR 1.886, p < 0.001) and abnormal p53 immunolabeling was associated with poor OS (HR 1.436, p = 0.011) in patients with PDAC. The mutational status of p16 had no effect on patient survival. High levels of SMO and Gli1 expression were associated with poor survival outcomes in both univariate and multivariate analyses. Pearson's χ2 test showed a medium correlation between the SMAD4lost mutation and Shh (R = 0.343) and Gli1 (R = 0.505) expression levels (p < 0.001). Patients with the SMAD4lost mutation and high levels of Shh and Gli1 expression showed the poorest survival outcomes (RFS: HR 2.976; OS: HR 3.598; p < 0.001 for both) compared with other patients in the study.Conclusion: Loss of SMAD4 associated with a strongly activated Shh pathway resulted in poor survival outcomes in patients with resected PDAC.

Activation of hedgehog signaling by systemic agonist improves fracture healing in aged mice.

Fracture healing is a complex process of many coordinated biological pathways. This system can go awry resulting in nonunion, which leads to significant patient morbidity. The Hedgehog (Hh) signaling pathway is upregulated in fracture healing. We hypothesized that the Hh signaling pathway can be pharmacologically modulated to positively affect fracture healing. Diaphyseal femur fractures were created in elderly mice (18 months, C57BL/6 females), which have a blunted and delayed healing response compared to younger mice, and were stabilized with intramedullary pins. To activate the Hh pathway we targeted the receptor Smoothened using an agonist (Hh-Ag1.5 [Hh-Ag]) and compared this to a vehicle control. Expression of Hh target genes were significantly increased in the fracture callus of the agonist group compared to controls, indicating pathway activation. Expression of osteogenic and chondrogenic-related genes was greatly upregulated in fracture callus versus intact femora, although Hh agonist treatment did not consistently enhance this response. Blindly graded, radiographic callus healing scores were significantly higher in the Hh-Ag groups at post operative day (POD) 14, indicating earlier callus bridging. On microCT, Hh-Ag treatment led to greater callus volume (+40%) and bone volume (+25%) at POD21. By day 14, callus vascularity, as assessed by 3D microCT angiography vessel volume, was 85% greater in the Hh-Ag group. Finally, mechanical strength of the calluses in the Hh-Ag groups was significantly greater than in the control groups at POD21. In conclusion, systemic administration of a Hh agonist appears to improve the osseous and vascular healing responses in a mouse fracture healing-impaired model. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

The long non-coding RNA LncHDAC2 drives the self-renewal of liver cancer stem cells via activation of Hedgehog signaling

Liver cancer is the second leading cause of cancer death worldwide. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults. The aim of this study was to define the role of the long non-coding RNA lncHDAC2 in the tumorigenesis of HCC. CD13+CD133+ cells (hereafter called liver cancer stem cells [CSCs]) and CD13-CD133- cells (referred to as non-CSCs) were sorted from 3 primary HCC tumor tissues and followed by transcriptome microarray. The expression and function of lncHDAC2 were further assessed by northern blot, sphere formation and xenograft tumor models. LncHDAC2 is highly expressed in HCC tumors and liver CSCs. LncHDAC2 promotes the self-renewal of liver CSCs and tumor propagation. In liver CSCs, lncHDAC2 recruits the NuRD complex onto the promoter of PTCH1 to inhibit its expression, leading to activation of Hedgehog signaling. Moreover, HDAC2 expression levels are positively related to HCC severity and PTCH1 levels are negatively related to HCC severity. Additionally, the Smo inhibitor cyclopamine was shown to impair the self-renewal of liver CSCs and suppress tumor propagation. Our findings reveal that lncHDAC2 promotes the self-renewal of liver CSCs and tumor propagation by activating the Hedgehog signaling pathway. Downregulating lncHDAC2 is a promising antitumor strategy in HCC. Liver cancer stem cells harbor high tumor-initiating potential and confer resistance to typical therapies, but the mechanism underlying their self-renewal remains elusive. LncHDAC2 augments the self-renewal of these cells, promoting tumor propagation. In liver cancer stem cells, lncHDAC2 activates Hedgehog signaling to initiate liver tumorigenesis. Therefore, lncHDAC2 and the Hedgehog signaling pathway may serve as biomarkers and potential drug targets for hepatocellular carcinoma.

SOX2 knockdown inhibits the migration and invasion of basal cell carcinoma cells by targeting the SRPK1-mediated PI3K/AKT signaling pathway.

Basal cell carcinoma (BCC) is the most common type of human skin cancer, which is driven by the aberrant activation of Hedgehog signaling. Previous evidence indicated that sex determining region Y-box 2 (SOX2) is associated with the tumor metastasis. However, the expression and role of SOX2 in BCC remain unknown. Therefore, the aim of the current study was to analyze the possible mechanism of SOX2 in the progression of BCC. The levels of SOX2 in BCC cells were detected by reverse transcription-quantitative polymerase chain reaction. Transwell assays were also used to determine the migration and invasion of BCC cells. Immunoblotting and immunofluorescence were used for analyzing the role of SOX2 knockdown in the serine-arginine protein kinase 1 (SRPK1)-mediated phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) signaling pathway in BCC cells. The results demonstrated that SOX2 is overexpressed in BCC tissues and cells. In addition, SOX2 knockdown inhibited the migration and invasion of BCC cells, and the epithelial-mesenchymal transition (EMT) progress of BCC cells. It was also observed that SOX2 knockdown decreased SRPK1 expression, which further led to the downregulation of PI3K and AKT expression levels in BCC cells. Furthermore, SRPK1 transfection or PI3K/AKT pathway activation abolished the inhibitory effects of SOX2 knockdown on the migration, invasion and EMT progress of BCC cells. In conclusion, these results indicated that SOX2 may potentially serve as a target for BCC therapy by targeting the SRPK1-mediated PI3K/AKT signaling pathway.

Coordinated Hedgehog Signaling Induces De Novo Hair Follicles in Primed Epithelial Structures

Mammalian organ development is orchestrated by coordinated molecular signals from epithelial and mesenchymal cells. In the skin, such anatomically adjacent signals cooperate to induce hair follicles (HF). However, this process only occurs during embryonic development, and viable strategies to induce new HFs in adult skin are lacking. Here, we reveal that supra-physiological activation of Hedgehog signaling in both epithelial and adjacent stromal cells induces new HFs in adult mouse skin. Importantly, the cells from which the new HFs derived were lineage traced from their originating touch-dome structure, and demonstrated similar molecular characteristics to embryonic HF development. Therefore, reactivation of productive, embryonic HF programs in adult skin has been achieved. In stark contrast, Hh-pathway activation in either epithelial or stromal cells alone resulted in tumor formation and stromal cell condensation, respectively, without induction of new HFs. Altogether, we demonstrate that cell-type specific modulation of a single pathway was sufficient to induce development of complex epithelial structures in the adult body, an important discovery with widespread implications for regenerative medicine.

Mitogen-activated kinase kinase kinase 1 inhibits hedgehog signaling and medulloblastoma growth through GLI1 phosphorylation.

The aberrant activation of hedgehog (HH) signaling is a leading cause of the development of medulloblastoma, a pediatric tumor of the cerebellum. The FDA-approved HH inhibitor, Vismodegib, which targets the transmembrane transducer SMO, has shown limited efficacy in patients with medulloblastoma, due to compensatory mechanisms that maintain an active HH-GLI signaling status. Thus, the identification of novel actionable mechanisms, directly affecting the activity of the HH-regulated GLI transcription factors is an important goal for these malignancies. In this study, using gene expression and reporter assays, combined with biochemical and cellular analyses, we demonstrate that mitogen-activated kinase kinase kinase 1 (MEKK1), the most upstream kinase of the mitogen-activated protein kinase (MAPK) phosphorylation modules, suppresses HH signaling by associating and phosphorylating GLI1, the most potent HH-regulated transcription factor. Phosphorylation occurred at multiple residues in the C-terminal region of GLI1 and was followed by an increased association with the cytoplasmic proteins 14-3-3. Of note, the enforced expression of MEKK1 or the exposure of medulloblastoma cells to the MEKK1 activator, Nocodazole, resulted in a marked inhibitory effect on GLI1 activity and tumor cell proliferation and viability. Taken together, the results of this study shed light on a novel regulatory mechanism of HH signaling, with potentially relevant implications in cancer therapy.

The hierarchical micro-/nanotextured topographies promote the proliferation and angiogenesis-related genes expression in human umbilical vein endothelial cells by initiation of Hedgehog-Gli1 signaling

The hierarchical microtextured/nanotextured topographies have been recognized to have better tissue integration properties, but the underlying mechanisms are only partially understood. Hedgehog signaling plays a pivotal role in developmental and homeostatic angiogenesis. We suppose that the Hedgehog-Gli1 signaling may play a significant role in the response of endothelial cells to microtextured/nanotextured topographies (MNTs). To confirm this hypothesis, we produced the MNTs decorated with TiO2 nanotubes of two different diameters (25 and 70 nm), and the proliferation, apoptosis, angiogenesis-related genes expression and Hedgehog signaling activity of human umbilical vein endothelial cells (HUVECs) grown onto these MNTs were measured. Our results showed that the MNTs induced significantly high expression of Sonic Hedgehog (SHH), Smoothened (SMO) and GLI1 in the HUVECs as well as high activation of Hedgehog-Gli1 signaling, compared to the smooth surface. The HUVECs grown on the MNTs showed significantly high levels of adhesion, proliferation and expression of angiogenesis-related genes, including angiopoietin-1 (ANG-1), vascular endothelial growth factor (VEGFA), vascular endothelial growth factor receptor 2 (VEGFR2) and endothelial nitric oxide synthase (ENOS); these enhancements were attenuated by siRNA-mediated depletion of SMO, which indicated a significant role of Hedgehog-Gli1 signaling in mediating the enhanced effect of the MNTs on the angiogenic potential of HUVECs. This study may contribute to the modification of biomaterial surfaces for better tissue integration and clinical performance.

Phosphatidylethanolamine-binding protein 4 promotes the epithelial-to-mesenchymal transition in non-small cell lung cancer cells by activating the sonic hedgehog signaling pathway.

Phosphatidylethanolamine-binding protein 4 (PEBP4), a member of the PEBP family, has been reported to play a pivotal role in tumor progression. However, its role in epithelial-to-mesenchymal transition (EMT) in non-small cell lung cancer (NSCLC) cells remains unclear. Here, we investigated the effects and underlying mechanism of PEBP4 in NSCLC EMT. Three human NSCLC cell lines (A549, H1299, and H460) were transfected with pcDNA3.1-PEBP4 or PEBP4-targeting small interfering RNA. Then, cell proliferation was analyzed by the MTT assay, and cell migration and invasion were analyzed by the transwell chamber assay. Protein and messenger RNA expression of the related genes and proteins were assessed by Western blot analysis and quantitative real-time polymerase chain reaction, respectively. Results showed that PEBP4 was highly expressed in the human lung cancer tissues and three human NSCLC cell lines. Pretreatment with pcDNA3.1-PEBP4 promoted the proliferation, invasion, and migration of NSCLC cells and increased EMT in vitro and lung tumor metastasis in vivo. Whereas knockdown of PEBP4 suppressed NSCLC cell migration, PEBP4, and invasion with prevented EMT. Furthermore, PEBP4 overexpression significantly promoted the transcriptional activity of sonic hedgehog (Shh) signaling in NSCLC cells. Further analysis showed that using cyclopamine to inhibit Shh signaling significantly ameliorated the effect on cell proliferation, invasion, and migration, as well as EMT triggered by PEBP4 overexpression. Together, these results suggest that PEBP4 may promote tumorigenesis in NSCLC by regulating cell proliferation and EMT via activation of the Shh signaling pathway.

A dual role of cholesterol in osteogenic differentiation of bone marrow stromal cells.

Osteoblasts, the chief bone-forming cells, are differentiated from mesenchymal stromal/stem cells. Disruption of this differentiation process can cause osteoporosis, a bone disease characterized by low bone mass and deteriorated bone structure. Cholesterol has been implicated in pathogenesis of osteoporosis, and was recently identified as an endogenous activator of Hedgehog (Hh) signaling. However, its pathological and physiological roles in osteoblast differentiation are still poorly understood. Moreover, it is unclear whether these potential roles played by cholesterol are related to its capability to modulate Hh pathway. In this study, we investigated the role of exogenous versus endogenous cholesterol in osteogenesis and Hh pathway activation using ST2 cells, a bone marrow stromal cell line. We found that exogenous cholesterol significantly inhibited alkaline phosphatase (ALP) activity and messenger RNA expression of osteoblast markers genes (Alpl, Sp7, and Ibsp) while modestly activating expression of Gli1 (a readout of Hh signaling) under both basal osteogenic culture condition and Wnt3a treatment. Similarly, exogenous cholesterol suppressed osteogenic response of ST2 cells to sonic Hh (Shh) or purmorphamine (Purmo) treatment, which, however, was accompanied by diminished induction of Gli1, indicating the involvement of a Hh-dependent mechanism. Interestingly, depletion of endogenous cholesterol also reduced Shh-induced ALP activity and Gli1 expression. Likewise, cholesterol depletion inhibited osteogenic response to Purmo, although it did not affect Gli1 induction. Taken together, our findings have demonstrated that cholesterol plays a dual role in osteoblast differentiation likely through both Hh-dependent and -independent mechanisms.

Abstract PR12: Hedgehog pathway drives fusion-negative rhabdomyosarcoma initiated from nonmyogenic endothelial progenitors

Abstract Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Despite aggressive chemotherapy, radiotherapy, and surgery, clinical outcomes for RMS have not improved for three decades, emphasizing the need to uncover the molecular underpinnings of the disease. RMS has been presumed to originate from derailed muscle progenitors based on the histologic appearance and gene expression pattern of the tumors. However, an origin restricted to skeletal muscle does not explain RMS occurring in tissues devoid of skeletal muscle, such as the prostate, bladder, salivary gland, biliary tree, and the omentum. Previously, we described that activation of Sonic Hedgehog signaling through expression of a conditional, constitutively active Smoothened allele, SmoM2, under control of an adipocyte-restricted adipose protein 2 (aP2)-Cre recombinase transgene in mice gives rise to aggressive skeletal muscle tumors that display the histologic and molecular characteristics of human embryonal RMS (ERMS). With the short latency and anatomic restricted tumor location in the neck, we sought to leverage this model to explore the cell of origin of ERMS. Lineage tracing experiments identified aP2-Cre labeled cells are distinctly nonmyogenic and were identified as endothelial cells found in the interstitium between muscle fibers. We illustrate that aP2-Cre is not expressed in the quiescent or activated muscle stem cells or satellite cells. Expression of oncogenic SmoM2 with aP2-Cre results in proliferation and expansion of the aP2-Cre labeled muscle interstitial cells and myogenic transdifferentiation resulting in ERMS. Activation of the Hedgehog pathway in aP2-Cre labeled endothelial progenitors results in Tbx1 expression, which is a skeletal muscle specification factor in the head and neck. We illustrate that endothelium and skeletal muscle within the head and neck arise from Kdr (Vegfr2) expressing progenitors. Hedgehog pathway activation in committed KDR+ endothelial progenitors results in Tbx1 expression and subsequent Myod1 expression driving a partially myogenic program characteristic of ERMS. Our work identifies reprogramming cell fate as a mechanism of transformation in pediatric sarcoma. Citation Format: Catherine J. Drummond, Jason A. Hanna, Matthew R. Garcia, Daniel J. Devine, Alana J. Heyrana, David Finkelstein, Jerold E. Rehg, Mark E. Hatley. Hedgehog pathway drives fusion-negative rhabdomyosarcoma initiated from nonmyogenic endothelial progenitors [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr PR12.

Different Response of Ptch Mutant and Ptch Wildtype Rhabdomyosarcoma Toward SMO and PI3K Inhibitors

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma with poor prognosis. RMS frequently show Hedgehog (HH) pathway activity, which is predominantly seen in the embryonal subtype (ERMS). They also show activation of Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) signaling. Here we compared the therapeutic effectiveness and the impact on HH target gene expression of Smoothened (SMO) antagonists with those of the PI3K inhibitor pictilisib in ERMS with and without mutations in the HH receptor Patched1 (PTCH). Our data demonstrate that growth of ERMS showing canonical Hh signaling activity due to Ptch germline mutations is efficiently reduced by SMO antagonists. This goes along with strong downregulation of the Hh target Gli1. Likewise Ptch mutant tumors are highly responsive toward the PI3K inhibitor pictilisib, which involves modulation of AKT and caspase activity. Pictilisib also modulates Hh target gene expression, which, however, is rather not correlated with its antitumoral effects. In contrast, sporadic ERMS, which usually express HH target genes without having PTCH mutation, apparently lack canonical HH signaling activity. Thus, stimulation by Sonic HE (SHH) or SAG (Smoothened agonist) or inhibition by SMO antagonists do not modulate HH target gene expression. In addition, SMO antagonists do not provoke efficient anticancer effects and rather exert off-target effects. In contrast, pictilisib and other PI3K/AKT/mTOR inhibitors potently inhibit cellular growth. They also efficiently inhibit HH target gene expression. However, of whether this is correlated with their antitumoral effects it is not clear. Together, these data suggest that PI3K inhibitors are a good and reliable therapeutic option for all ERMS, whereas SMO inhibitors might only be beneficial for ERMS driven by PTCH mutations.

Construction of a GLI3 compound heterozygous knockout human embryonic stem cell line WAe001-A-20 by CRISPR/Cas9 editing

The human GLI3 protein has a dual function as a transcriptional activator or repressor of hedgehog signaling, depending on the proteolytic processing forms of GLI3. In this study, we established a compound heterozygous GLI3 mutant human embryonic stem cell line (WAe001-A-20) through CRISPR/Cas9 editing. The WAe001-A-20 cells carried two deletions on two different alleles of exon 2 of GLI3, respectively, which resulted in a frame shift and early termination in the translation of GLI3. Moreover, WAe001-A-20 maintains a normal karyotype, parental cell morphology, pluripotent phenotype and the ability to differentiate into three germ layers.Resource tableUnlabelled TableUnique stem cell line identifierWAe001-A-20Alternative name(s) of stem cell lineH1-GLI3-KOInstitutionGuangzhou Institutes of Biomedicine and Health, Chinese Academy of SciencesContact information of distributorYin-xiong Li, li_yinxiong@gibh.ac.cnType of cell lineEmbryonic stem cell lineOriginWAe001-AAdditional origin infoAge: blastocyst stageSex: male, 46, XYCell SourceN/AClonalityClonalMethod of reprogrammingN/AGenetic ModificationYESType of ModificationDeletionAssociated diseaseGreig Cephalopolysyndactyly Syndrome, Pallister-Hall Syndrome, Postaxial PolydactylyGene/locusGLI3/7p14.1Method of modificationCRISPR/Cas9Name of transgene or resistanceN/AInducible/constitutive systemN/ADate archived/stock dateApril 20, 2018Cell line repository/bankN/AEthical approvalCell line was used according to institutional ethical guidelines of GIBH

Enpp1 inhibits ectopic joint calcification and maintains articular chondrocytes by repressing hedgehog signaling.

The differentiated phenotype of articular chondrocytes of synovial joints needs to be maintained throughout life. Disruption of the articular cartilage, frequently associated with chondrocyte hypertrophy and calcification, is a central feature in osteoarthritis (OA). However, the molecular mechanisms whereby phenotypes of articular chondrocytes are maintained and pathological calcification is inhibited remain poorly understood. Recently, the ecto-enzyme Enpp1, a suppressor of pathological calcification, was reported to be decreased in joint cartilage with OA in both human and mouse, and Enpp1 deficiency causes joint calcification. Here, we found that hedgehog (Hh) signaling activation contributes to ectopic joint calcification in the Enpp1-/- mice. In the Enpp1-/- joints, Hh signaling was upregulated. Further activation of Hh signaling by removing the patched 1 gene in the Enpp1-/- mice enhanced ectopic joint calcification, whereas removing Gli2 partially rescued the ectopic calcification phenotype. In addition, reduction of Gαs in the Enpp1-/- mice enhanced joint calcification, suggesting that Enpp1 inhibits Hh signaling and chondrocyte hypertrophy by activating Gαs-PKA signaling. Our findings provide new insights into the mechanisms underlying Enpp1 regulation of joint integrity.