Hh Activity Research Articles

The PROTAC selectively degrading Bcl-xL represents a novel Hedgehog pathway inhibitor with capacity of combating resistance to Smoothened inhibitors while sparing bone growth.

Rationale: Primary and acquired resistance to Smoothened (Smo) inhibitors largely hampered their clinical efficacy. Given the important functions of hedgehog (Hh) pathway in bone formation and development, the permanent defects in bone growth caused by Smo inhibitors further restrict the use of Smo inhibitors for pediatric tumor patients. Anti-apoptotic Bcl-2 proteins regulate Hh activity by engaging a Bcl-2 homology (BH) domain sequence found in suppressor of fused (Sufu). In this study, we tested the effect of SIAIS361034, a Proteolysis Targeting Chimera (PROTAC) specifically targeting B-cell lymphoma extra large (Bcl-xL) to the celeblon (CRBN) E3 ligase for degradation, on combating the resistance and reducing the toxicity of bone growth caused by Hh inhibition. Methods: Fluorescence polarization, homogeneous time-resolved fluorescence (HTRF) assay, immunoblot, and immunoprecipitation (IP) were used to evaluate whether SIAIS361034 is an appropriate Bcl-xL PROTAC. Dual luciferase reporter assay, real-time quantitative PCR (RT-qPCR), depilatory model, and SmoA1 model were established to assess the effect of SIAIS361034 on the activity of Hh signaling pathway and its ability to overcome drug resistance in vitro and in vivo. Molecular mechanisms of SIAIS361034 for inhibiting Hh activity were demonstrated by dual luciferase reporter assay, immunoblot, and immunofluorescence staining. PET-CT and histopathology of bone tissues were used to assess the effects of SIAIS361034 on bone growth. Results: We observed that SIAIS361034 efficiently and selectively inhibits the activity of the Hh pathway in vitro and in vivo, by interrupting Bcl-xL/Sufu interaction, therefore, promoting the interaction of Sufu with Gli1. Moreover, SIAIS361034 possesses the ability of combating resistance to current Smo inhibitors caused by Smo mutations and Gli2 amplification and remarkably inhibits the growth of SmoA1 tumors in vivo. In contrast to von Hippel-Lindau (VHL) E3 ligase, our result further reveals little detectable expression of CRBN in two types of cells critical for bone development, human articular chondrocytes and human fetal osteoblastic cells. Moreover, treatment with SIAIS361034 results in no impairment on the bone growth of young mice, accompanying no alteration of the expression of Bcl-xL and Gli1 proteins. Conclusion: Our findings demonstrate that selectively targeting Bcl-xL by PROTAC is a promising strategy for combating resistance to Smo inhibitors without causing on-target drug toxicities of bone growth.

Withania somnifera Modulates Radiation-Induced Generation of Lung Cancer Stem Cells via Restraining the Hedgehog Signaling Factors.

Cancer stem cells (CSCs) are implicated in the genesis, development, and recurrence of lung cancer (LC) with great resistance to radiation and chemotherapy. The aim of this study is to assess the inhibitory potential of ethanol extract of Withania somnifera (WS); 500 mg/kg body-weight/day and 8 Gy of ionizing radiation (IR) could inhibit the stemness gene and confer the radiosensitizing effect of W. somnifera extract in the female rat LC model. Compared to IR or WS, the in vitro assay showed that WS + IR potentiates proliferation-inhibition and cell death of the A-549 cell line and suppresses sphere formation. The Hedgehog (Hh) signaling associated with the expression levels of lung CSC markers, octamer-binding transcription factor-4 (OCT4), SRY-box 2 (SOX2), CD133, ATP Binding Cassette Subfamily G Member 2 (ABCG2), and NANOG was upregulated with stimulated epithelial-to-mesenchymal transition (EMT) indicators α-smooth muscle actin (α-SMA), Drosophila embryonic protein (SNAIL-1), Vimentin, and E-cadherin in the LC rat model. The W. somnifera extract plus IR inhibits Hh activation factors, which has resulted in the suppression of CSC gene markers and EMT factors. W. somnifera extract may be a significant adjuvant in the course of radiotherapy, contributing to the termination of tumor progression, and thus providing cure insights into the molecular mechanisms of lung CSCs intervention.

Hedgehog signaling is controlled by Rac1 activity.

Rationale: The nuclear translocation of transcriptional factor Gli is indispensable for Hedgehog (Hh) signaling activation, whose deregulation causes cancer progressions; however, the mechanisms governing Gli nuclear translocation are poorly understood. Here, we report that the Gli translocation in response to Hh requires Rac1 activation.Methods: C3H10T1/2 cell line and mouse embryonic fibroblasts were used to explore the molecular mechanisms underlying Rac1 activity in regulation of Hh signaling transduction. Transgenic mouse strains and human medulloblastoma (MB) tissue samples were utilized to examine the role of Rac1 in Hh-directed limb bud development and MB progression.Results: We show that upon the binding of Hh to receptor Patched1 (Ptch1), receptor Smoothened (Smo) dissociates from Ptch1 and binds to Vav2, resulting in the increased phosphorylation levels of Vav2 at Y172, which further activates Rac1. The role of Rac1 is dependent on the regulation of phosphorylation levels of KIF3A at S689 and T694, which in turn affects IFT88 stability and subsequently dampens SuFu-Gli complex formation, leading to the release of Gli from the complex and the consequent translocation of Gli into the nucleus. Moreover, Vav2 phospho-Y172 levels are up-regulated in GFAP-Cre;SmoM2+/- mouse cerebellum and human Shh type MB tissues, whereas deficiency of Rac1 in mouse embryonic limb bud ectoderm (Prx1-Cre;Rac1f/f) impedes Hh activation by disruption of Gli nuclear translocation.Conclusion: Together, our results uncover the Rac1 activation and the subsequent Gli translocation as a hitherto uncharacterized mechanism controlling Hh signaling and may provide targets for therapeutic intervention of this signaling pathway.

Pan-cancer analyses reveal that increased Hedgehog activity correlates with tumor immunosuppression and resistance to immune checkpoint inhibitors.

BackgroundImmune checkpoint inhibitors (ICIs) have shown numerous clinical benefits in multiple cancer types, but good predictive biomarkers are severely lacking. Although increasing evidence has linked Hedgehog (Hh) signaling pathway with tumor development, a systematic investigation for its potential as a biomarker remains elusive.MethodsWe collected and analyzed the transcriptional data and clinical outcomes of diverse cancers from the Cancer Genome Atlas and four published ICI datasets. Hh activity was estimated by conducting a single‐sample gene‐set enrichment analysis (ssGSEA) for the Hh‐related genes and calculating the ssGSEA score in each tumor sample.ResultsOur findings suggest that tumors with high Hh activity displayed multiple immunosuppressive characteristics, including lack of anti‐tumor response pathways, downregulation of immune effectors, enrichment of immunosuppressive cells and chemokines, and activation of immunosuppressive signaling. Notably, patients in the non‐response group had enriched Hh activity and showed worse overall survival (OS; pooled HR = 1.50, 95% CI = 1.02–2.21, p = 0.039). In the subgroup of high programmed cell death ligand 1 (PD‐L1) expression, patients who harbored high Hh activity displayed a dramatically lower response rate to ICIs and a strikingly worse OS (pooled HR = 2.89, 95% CI = 1.53–5.49, p < 0.001).ConclusionIncreased Hh activity correlates with tumor immunosuppression across diverse cancers. Hh activity is not only a predictive biomarker for resistance to ICIs but can also better predict clinical outcomes in combination with PD‐L1 expression.

Pharmacokinetics and Pharmacodynamics of Huanglian-Houpo Decoction Based on Berberine Hydrochloride and Magnolol Against H1N1 Influenza Virus.

Background and ObjectivesHuanglian-Houpo decoction (HH), which is recorded in the famous traditional Chinese medicine monograph “Puji Fang,” contains two individual herbs, Huanglian (Rhizoma coptidis) and Houpo (Magnoliae officinalis cortex). It was regularly used to treat seasonal epidemic colds and influenzas in ancient China. Our laboratory discovered that HH has a significant anti-H1N1 influenza virus effect. However, no pharmacokinetic and pharmacodynamic data concerning the anti-H1N1 influenza virus activity of HH are available to date. In the current study, the concentration-time profiles of two major components of HH, berberine and magnolol, in rat plasma were investigated.MethodsAn integrate pharmacokinetic approach was developed for evaluating the holistic pharmacokinetic characteristics of berberine and magnolol from HH. Additionally, the inhibition rate and levels of IFN-β in MDCK cells infected by influenza virus were analyzed. Data were calculated using 3p97 with pharmacokinetic analysis.ResultsThe estimated pharmacokinetic parameters were maximum plasma concentration (Cmax) 0.9086 μg/ml, area under the concentration-time curve (AUC) 347.74 μg·min/ml, and time to reach Cmax (Tmax) 64.69 min for berberine and Cmax = 0.9843 μg/ml, AUC= 450.64 μg·min/ml, Tmax = 56.86 min for magnolol, respectively. Furthermore, integrated pharmacokinetic and pharmacodynamic analysis showed that the highest plasma concentration, inhibition rate and interferon-β (IFN-β) secretion of HH first increased and then weakened over time, reaching their peaks at 60 min. The plasma concentration of HH is directly related to the anti-influenza virus effect.ConclusionThe results indicated that berberine and magnolol are the main active ingredients of HH related to its anti-influenza virus effect, which is related to the improvement of IFN-β secretion.

SAG therapy restores bone growth and reduces enchondroma incidence in a model of skeletal chondrodysplasias caused by Ihh deficiency

Inactivation mutations in the Indian hedgehog (Ihh) gene in humans cause numerous skeletal chondrodysplasias, including acrocapitofemoral dysplasia, brachydactyly type A1, and human short stature. The lack of an appropriate human-relevant model to accurately represent these chondrodysplasias has hampered the identification of clinically effective treatments. Here, we established a mouse model of human skeletal dysplasia induced by Ihh gene mutations via ablation of Ihh in Aggrecan-positive (Acan+) cells using Aggrecan (Acan)-creERT transgenic mice. Smoothen agonist (SAG) promoted Hh activity and rescued chondrocyte proliferation and differentiation by stimulating smoothened trafficking to the cilium in Ihh-silenced cells. SAG treatment corrected mouse stature and significantly decreased mortality without evidence of toxicity. Moreover, Ihh ablation in Acan+ cells produced enchondroma-like tissues near the growth plates that were significantly reduced by SAG treatment. These results demonstrated that SAG effectively treats skeletal dysplasia caused by Ihh gene mutations in a mouse model, suggesting that SAG may represent a potential drug for the treatment of these diseases and/or enchondromas.

Quantitative Longitudinal Imaging Reveals that Inhibiting Hedgehog Activity Alleviates the Hypoxic Tumor Landscape.

Metastases account for the majority of mortalities related to breast cancer. The onset and sustained presence of hypoxia strongly correlates with increased incidence of metastasis and unfavorable prognosis in patients with breast cancer. The Hedgehog (Hh) signaling pathway is dysregulated in breast cancer, and its abnormal activity enables tumor progression and metastasis. In addition to programming tumor cell behavior, Hh activity enables tumor cells to craft a metastasis-conducive microenvironment. Hypoxia is a prominent feature of growing tumors that impacts multiple signaling circuits that converge upon malignant progression. We investigated the role of Hh activity in crafting a hypoxic environment of breast cancer. We used radioactive tracer [18F]-fluoromisonidazole (FMISO) positron emission tomography (PET) to image tumor hypoxia. We show that tumors competent for Hh activity are able to establish a hypoxic milieu; pharmacologic inhibition of Hh signaling in a syngeneic mammary tumor model mitigates tumor hypoxia. Furthermore, in hypoxia, Hh activity is robustly activated in tumor cells and institutes increased HIF signaling in a VHL-dependent manner. The findings establish a novel perspective on Hh activity in crafting a hypoxic tumor landscape and molecularly navigating the tumor cells to adapt to hypoxic conditions. IMPLICATIONS: Importantly, we present a translational strategy of utilizing longitudinal hypoxia imaging to measure the efficacy of vismodegib in a preclinical model of triple-negative breast cancer.

Aberrant activation of the Hedgehog signalling pathway in squamous cell carcinoma of the vulva as a potential target for cancer therapy

In a previous study, we showed that the Hedgehog (Hh) signalling pathway is aberrantly activated in vulval squamous cell carcinoma (VSCC). In this study, we further validated our findings on a prospective cohort of primary VSCC cases, where immunohistochemical staining confirmed that key Hh pathway components were overexpressed in VSCC compared to normal vulval epithelium. We also undertook a series of in vitro studies to determine the extent of Hh pathway activation in VSCC-derived cell lines, and examine the consequences of pathway inhibition on the growth of these cells. We found that of six cell lines tested, four displayed elevated baseline Hh pathway activity that was dependent on SHH ligand, or in one case, a PTCH1 gene mutation. Hh signalling appeared necessary to sustain cell growth, as SHH ligand depletion with Robotikinin or SMO inhibition, either with chemical inhibitors (Itraconazole or LDE-225) or SMO-specific siRNA, attenuated GLI1 activity and cell proliferation in both monolayer and organotypic raft culture. Furthermore, treatment of Hh-dependent cell lines with SMO inhibitors sensitised cells to Cisplatin. Findings from our study offer us the opportunity to explore further the development of targeted chemotherapy for women with VSCC driven by aberrant Hh activation.

Caudatin suppresses adipogenesis in 3T3-L1 adipocytes and reduces body weight gain in high-fat diet-fed mice through activation of hedgehog signaling

BackgroundThe regulative effects of caudatin, a C-21 steroid that is identified from Cynanchum bungee roots, on adipogenesis and obesity have not been studied. Many studies have demonstrated that the activation of hedgehog (Hh) signaling can help prevent obesity. Therefore, we hypothesized that caudatin can inhibit adipogenesis and obesity via activating the Hh signaling pathway. MethodsTo investigate the effects of caudatin on adipogenesis in 3T3-L1 preadipocytes and high-fat diet induced obesity in C57BL/6 mice, in vitro and in vivo experiments were performed. For in vitro evaluation, Oil red O staining were used to represent lipid accumulation in differentiated 3T3-L1 adipocytes. For in vivo assessment, male 5 week-old C57BL/6 mice were fed with standard chow diet, high-fat diet (HFD), HFD with 25 mg/kg caudatin, HFD with 1mg/kg purmorpharmine for 10 weeks, respectively. Hh signaling and key adipogenic marker involved in adipogenesis were evaluated by real-time PCR and western blot. The adipocyte size of white adopose tissue and lipid storage of liver were visualized by hematoxylin and eosin staining. In addition, the expression of Gli1 and peroxisome proliferator-activated receptor γ (PPARγ) in white adipose tissue were investigated by immunohistochemistry staining. ResultsCaudatin suppressed the accumulation of lipid droplets and downregulated the expression of key adipogenic factors, i.e., peroxisome proliferator-activated receptor γ PPARγ and CCAAT-enhancer binding protein α (C/EBPα), through activating Hh signaling in differentiated 3T3-L1 cells. Furthermore, caudatin and the Hh activator purmorpharmine significantly decreased body weight gain and white adipose tissue (WAT) weight in HFD-induced mice and affected adipogenic markers and Hh signaling mediators in WAT, which were in line with the in vitro experimental results. ConclusionTo our best knowledge, it is the first report to demonstrate that caudatin downregulated adipocyte differentiation and suppressed HFD-induced body weight gain through activating the Hh signaling pathway, suggesting that caudatin can potentially counteract obesity.

Hedgehog Signaling Regulates Metabolism and Polarization of Mammary Tumor-Associated Macrophages.

Elevated infiltration of immunosuppressive alternatively polarized (M2) macrophages is associated with poor prognosis in patients with cancer. The tumor microenvironment remarkably orchestrates molecular mechanisms that program these macrophages. Here we identify a novel role for oncogenic Hedgehog (Hh) signaling in programming signature metabolic circuitries that regulate alternative polarization of tumor-associated macrophages. Two immunocompetent orthotopic mouse models of mammary tumors were used to test the effect of inhibiting Hh signaling on tumor-associated macrophages. Treatment with the pharmacologic Hh inhibitor vismodegib induced a significant shift in the profile of tumor-infiltrating macrophages. Mass spectrometry-based metabolomic analysis showed Hh inhibition induced significant alterations in metabolic processes, including metabolic sensing, mitochondrial adaptations, and lipid metabolism. In particular, inhibition of Hh in M2 macrophages reduced flux through the UDP-GlcNAc biosynthesis pathway. Consequently, O-GlcNAc-modification of STAT6 decreased, mitigating the immune-suppressive program of M2 macrophages, and the metabolically demanding M2 macrophages shifted their metabolism and bioenergetics from fatty acid oxidation to glycolysis. M2 macrophages enriched from vismodegib-treated mammary tumors showed characteristically decreased O-GlcNAcylation and altered mitochondrial dynamics. These Hh-inhibited macrophages are reminiscent of inflammatory (M1) macrophages, phenotypically characterized by fragmented mitochondria. This is the first report highlighting the relevance of Hh signaling in controlling a complex metabolic network in immune cells. These data describe a novel immunometabolic function of Hh signaling that can be clinically exploited. SIGNIFICANCE: These findings illustrate that Hh activity regulates a metabolic and bioenergetic regulatory program in tumor-associated macrophages that promotes their immune-suppressive polarization.

Abstract 2416: Upregulation of amplified in breast cancer 1 contributes to pancreatic ductal adenocarcinoma progression and vulnerability to blockage of hedgehog activation

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and devastating cancers without effective treatments. Amplified in breast cancer 1 (AIB1) is a member of the steroid receptor coactivator family that mediates the transcriptional activities of nuclear receptors. While AIB1 is associated with the initiation and progression of multiple cancers, the mechanism by which AIB1 contributes to PDAC progression remains largely unknown. In this study, we aimed to explore the role of AIB1 in the progression of PDAC and elucidate the underlying mechanisms. Methods: The clinical significance and mRNA level of AIB1 in PDAC were studied by database analysis. To demonstrate whether AIB1 mediates the malignant features of PDAC cells, namely, proliferation, migration, invasion, we performed real-time PCR and Western blot analysis, established xenograft models and used in vivo metastasis assay. With insights into the mechanism of AIB1, we performed RNA sequencing (Seq), ChIP-Seq, luciferase reporter assays and pull-down assays. Furthermore, we analyzed the relationship between AIB1 expression and its target expression in PDAC cells and patients and explored whether PDAC cells with high AIB1 levels are sensitive to inhibitors of its target. Results: We found that AIB1 was significantly upregulated in PDAC and associated with its malignancy. Silencing AIB1 impaired hedgehog (Hh) activation by reducing the expression of smoothened (SMO), leading to cell cycle arrest and the inhibition of PDAC cell proliferation. In addition, AIB1, via upregulation of integrin αv (ITGAV) expression, promoted extracellular matrix (ECM) signaling, which played an important role in PDAC progression. Further studies showed that AIB1 preferably bound to AP-1 related elements and served as a coactivator for enhancing the transcriptional activity of MafB, which promoted the expression of SMO and ITGAV. PDAC cells with high AIB1 levels were sensitive to Hh signaling inhibitors, suggesting that blocking Hh activation is an effective treatment against PDAC with high AIB1 expression. Conclusions: These findings reveal that AIB1 is a crucial oncogenic regulator associated with PDAC progression via Hh and ECM signaling and suggest potential therapeutic targets for PDAC treatment. Citation Format: Licen Li, Jiaolin Bao, Haitao Wang, Haipeng Lei, Peng Cheng, Jianming Zeng, Wenhui Hao, Xu Zhang, Xiaoling Xu, Chundong Yu, Chu-Xia Deng, Qiang Chen. Upregulation of amplified in breast cancer 1 contributes to pancreatic ductal adenocarcinoma progression and vulnerability to blockage of hedgehog activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2416.

PGE2-JNK signaling axis non-canonically promotes Gli activation by protecting Gli2 from ubiquitin-proteasomal degradation

Both bench and bedside investigations have challenged the supportive role of Hedgehog (Hh) activity in the progression of colorectal cancers, thus raising a critical need to further deeply determine the contribution of Hh to the growth of colorectal cancer. Combining multiple complementary means, including in vitro and in vivo inflammatory colorectal cancer models, and pathological analysis of clinical colorectal cancer patients samples. We report that colorectal cancer cells hijack prostaglandin E2 (PGE2) to non-canonically promote Hh transcriptional factor Gli activity and Gli-dependent proliferation of colorectal cancer cells in a Smo-independent manner. Mechanistically, PGE2 activates c-Jun N-terminal kinase (JNK), which in turn enables Gli2 to evade ubiquitin-proteasomal degradation by phosphorylating Gli2 at Thr1546. This study not only presents evidence for understanding the contribution of Hh to colorectal cancers, but also provides a novel molecular portrait underlying how PGE2-activated JNK fine-tunes the evasion of Gli2 from ubiquitin-proteasomal degradation. Therefore, it proposes a rationale for the future evaluation of chemopreventive and selective therapeutic strategies for colorectal cancers by targeting PGE2-JNK-Gli signaling route.

Multifaceted Functions of Rab23 on Primary Cilium-Mediated and Hedgehog Signaling-Mediated Cerebellar Granule Cell Proliferation.

Sonic hedgehog (Shh) signaling from the primary cilium drives cerebellar granule cell precursor (GCP) proliferation. Mutations of hedgehog (Hh) pathway repressors commonly cause medulloblastoma, the most prevalent and malignant childhood brain tumor that arises from aberrant GCP proliferation. We demonstrate that Nestin Cre-driven conditional knock-out (CKO) of a Shh pathway repressor-Rab23 in the mouse brain of both genders caused mis-patterning of cerebellar folia and elevated GCP proliferation during early development, but with no prevalent occurrence of medulloblastoma at adult stage. Strikingly, Rab23-depleted GCPs exhibited upregulated basal level of Shh pathway activities despite showing an abnormal ciliogenesis of primary cilia. In line with the compromised ciliation, Rab23-depleted GCPs were desensitized against Hh pathway activity stimulations by Shh ligand and Smoothened (Smo) agonist-SAG, and exhibited attenuated stimulation of Smo-localization on the primary cilium in response to SAG. These results implicate multidimensional actions of Rab23 on Hh signaling cascade. Rab23 represses the basal level of Shh signaling, while facilitating primary cilium-dependent extrinsic Shh signaling activation. Collectively, our findings unravel instrumental roles of Rab23 in GCP proliferation and ciliogenesis. Furthermore, Rab23's potentiation of Shh signaling pathway through the primary cilium and Smo suggests a potential new therapeutic strategy for Smo/primary cilium-driven medulloblastoma.SIGNIFICANCE STATEMENT Primary cilium and Sonic hedgehog (Shh) signaling are known to regulate granule cell precursor (GCP) proliferation. Aberrant overactivation of Shh signaling pathway ectopically increases GCP proliferation and causes malignant childhood tumor called medulloblastoma. However, the genetic and molecular regulatory cascade of GCP tumorigenesis remains incompletely understood. Our finding uncovers Rab23 as a novel regulator of hedgehog (Hh) signaling pathway activity and cell proliferation in GCP. Intriguingly, we demonstrated that Rab23 confers dual functions in regulating Shh signaling; it potentiates primary cilium and Shh/Smoothened (Smo)-dependent signaling activation, while antagonizes basal level Hh activity. Our data present a previously underappreciated aspect of Rab23 in mediating extrinsic Shh signaling upstream of Smo. This study sheds new light on the mechanistic insights underpinning Shh signaling-mediated GCP proliferation and tumorigenesis.

Aberrant Hedgehog Signaling in Myelodysplastic Syndrome Accelerates Leukemic Transformation Via Smoothened-Dependent and Smoothened-Independent Gli1 Activation

Introduction: Myelodysplastic syndromes (MDS) are malignant hematopoietic stem cell disorders with increased risk of transformation to secondary acute myeloid leukemia (sAML) that carries uniformly dismal prognosis. The exact mechanisms driving this process remain obscure. Aberrant Hedgehog (Hh) signaling has been demonstrated in a number of solid tumors and hematologic malignancies. An emerging body of literature suggests the importance of Hh signaling in leukemic transformation of MDS. Moreover, a recent Phase II clinical trial using Smoothened (SMO) inhibitor with low-dose chemotherapy resulted in significant prolongation of overall survival (Lancet et al. Blood 2016). Thus, we sought to examine the clinical impact of aberrant Hh activation in MDS and further explore the mechanism of Hh-driven leukemic transformation.Methods/Results:To determine the pathway activity, we quantified the level of GLI1 in CD34+ cells from patients with MDS and healthy controls in published databases (N=17 and N=159, respectively; GSE58831) and while absent in controls, GLI1 was significantly upregulated in MDS patients (p<0.05). Analysis of serial samples revealed Hh activation at disease progression in 67% of patients (4/6). In addition, GLI1 levels were significantly higher in poor-risk AML with complex cytogenetics comparing to favorable risk disease (p<0.001, TCGA).To further evaluate the impact of of Hh activation in MDS progression, we crossed Nup98-HoxD13 (NHD13) mice with mice conditionally expressing the constitutively active mutant of Smoothened (SmoM2). Double transgenic NHD13/SmoM2 mice succumbed to aggressive myeloid leukemia (median survival of NHD13/SmoM2 and NHD13 controls, 3 months vs. 13 months, respectively, p<0.0001) characterized by leukocytosis (p<0.05), splenomegaly (p<0.0001) and significant expansion of immature myeloid progenitors in peripheral blood (p<0.0001) and bone marrow (p<0.0001). Analysis of hematopoietic stem/progenitor (HSPC) compartment revealed expansion of phenotypic granulocyte macrophage progenitors (GMP) (6244 vs. 131487 mean GMPs/femur , in NHD13 v. NHD13/SmoM2 respectively, p<0.05). To determine whether Hh activation resulted in aberrant self-renewal in GMP compartment, we carried out an in vivo repopulation assay. While NHD13 GMPs showed only transient engraftment, characteristic of non-self-renewing progenitors, NHD13/SmoM2 GMPs robustly engrafted and significantly expanded over time, and all recipient animals developed aggressive leukemia within 2-3 months. The engraftment was sustained through secondary transplantation. Our results suggest that Hh activation resulted in abnormal self-renewal in normally non-self-renewing progenitors.To delineate the mechanism leading to aberrant activation of self-renewal we compared the transcriptome of GMPs isolated from NHD13/SmoM2 and NHD13 controls. In addition to expected Hh activation, Gene Set Enrichment Analysis (GSEA) showed enrichment in gene signatures associated with other developmental pathways such as Wnt or TGF-β signaling as well as EWS/FLI1-protooncogen signature. Interestingly, these pathways have been found to act via direct activation of GLI1 .Using human AML (TF-1) and MDS (MDS-L) cell lines we confirmed that GLI1 may be activated in the absence of SMO. GLI1 knock-down and/or inhibition with GANT61 resulted in growth arrest (p<0.05, both) and significantly lower clonogenic potential in vitro (p<0.05, both) more so than upstream SMO inhibition.Conclusions: Our data suggest that aberrant Hh/GLI1 signaling is frequent in MDS and marks disease progression and leukemic transformation. In some cases, GLI1 can be activated in a SMO-independent manner and therapeutic strategies focused on targeting downstream Gli transcription factors may be more effective than currently used Smo inhibitors. DisclosuresNo relevant conflicts of interest to declare.

GAB1 overexpression identifies hedgehog-activated anterior skull base meningiomas.

Mutations activating the hedgehog (Hh) signalling pathway have been described in anterior skull base meningiomas, raising hope for the use of targeted therapies. However, identification of Hh-activated tumours is hampered by the lack of a reliable immunohistochemical marker. We report the evaluation of GAB1, an immunohistochemical marker used to detect Hh pathway activation in medulloblastoma, as a potential marker of Hh-activated meningiomas. GAB1staining was compared to SMO mutation detection with Sanger and NGS techniques as well as Hh pathway activation study through mRNA expression level analyses in a discovery set of 110 anterior skull base meningiomas and in a prospective validation set of 21meningiomas. Using an expression score ranging from 0 to 400, we show that a cut-off score of 250lead to excellent detection of Hh pathway mutations (sensitivity 100%, specificity 86%). The prospective validation set confirmed the excellent negative predictive value of GAB1 to exclude Hh-independent meningiomas. We describe a large series of 32 SMO-mutant meningiomas and define multiple ways of Hh activation, either through somatic mutations or associated with mutually co-exclusive sonic hedgehog (SHH) or Indian hedgehog (IHH) overexpression independent of the mutations. The assessment of GAB1 expression by an immunohistochemical score is a fast and cost-efficient tool to screen anterior skull base meningiomas for activation of the Hh pathway. It could facilitate the identification of selected cases amenable to sequencing for Hh pathway genes as predictive markers for targeted therapy.

Hherisomes, Hedgehog specialized recycling endosomes, are required for high level Hedgehog signaling and tissue growth.

In metazoans, tissue growth and patterning is partly controlled by the Hedgehog (Hh) morphogen. Using immuno-electron microscopy on Drosophila wing imaginal discs, we identified a cellular structure, the Hherisomes, which contain the majority of intracellular Hh. Hherisomes are recycling tubular endosomes, and their formation is specifically boosted by overexpression of Hh. Expression of Rab11, a small GTPase involved in recycling endosomes, boosts the size of Hherisomes and their Hh concentration. Conversely, increased expression of the transporter Dispatched, a regulator of Hh secretion, leads to their clearance. We show that increasing Hh density in Hherisomes through Rab11 overexpression enhances both the level of Hh signaling and disc pouch growth, whereas Dispatched overexpression decreases high-level Hh signaling and growth. We propose that, upon secretion, a pool of Hh triggers low-level signaling, whereas a second pool of Hh is endocytosed and recycled through Hherisomes to stimulate high-level signaling and disc pouch growth. Altogether, our data indicate that Hherisomes are required to sustain physiological Hh activity necessary for patterning and tissue growth in the wing disc.

Hh pathway expression in the blood, synovial cells and chondrocytes of different rheumatoid arthritis models

Purpose: To investigate the effect of the hedgehog (Hh) pathway inhibitor, cyclopamine, and activator purmorphamine on articular cartilage cell proliferation.&#x0D; Methods: Rats were subjected to AA and CIA models. Secondary paw swelling was measured at 12, 15, 18, 21, 24, 27, and 30 days. The rats were sacrificed on day 30. Tissues from the cartilage and knee joints were collected. Cell proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay while cell apoptosis was determined by annexin V-fluorescein isothiocyanate/propidium iodide assay. Protein expression levels of Shh, Ptch1 and Gli1 were determined by Western blotting.&#x0D; Results: Compared with the control group, arthritis index and secondary foot swelling of the adjuvant arthritis (AA) and collagen-induced arthritis (CIA) groups deteriorated significantly (p &lt; 0.05). MTT data revealed that cyclopamine promoted articular cartilage cell proliferation of the AA and CIA groups. The cell proliferation rates of AA and CIA groups were significantly higher than that of control group (p &lt; 0.05). Flow cytometry showed that the cell apoptosis rates of AA and CIA groups were significantly lower than that of control group (p &lt; 0.05). Compared with control, cyclopamine decreased the protein expression levels of sonic Hh, patched homologue 1 and glioma-associated oncogene homologue, but the effect of purmorphamine was the reverse.&#x0D; Conclusion: Hh pathway inhibitor (cyclopamine) and activator (purmorphamine) affect the expression of Hh pathway. Disruption of the Hh pathway may be of potential therapeutic significance in protecting articular cartilage from rheumatoid arthritis.

Hedgehog signaling interfaces with the Hexoseamine Biosynthetic Pathway to promote M2 polarization of mammary tumor associated macrophages

Abstract The Hedgehog (Hh) signaling pathway is aberrantly activated in breast cancer, and contributes to tumor cell survival, proliferation, and migration. The success of these events is heavily influenced by the surrounding immune microenvironment. One such cell type, macrophages (MΦ) can make up to 50% of the tumor mass. MΦs can be polarized to M1 (tumor-eradicating) or M2 (tumor-promoting), and a high M2/M1 ratio within the tumor microenvironment (TME) is correlated with worse prognosis. We have uncovered a novel role for Hh signaling in promoting M2 polarization. We propose that the mechanism underlying this phenomenon is due to changes in the Hexoseamine Biosynthetic Pathway and consequently cellular O-GlcNAcylation. M2 MΦs have considerably higher levels of UDP-GlcNAc, the substrate for O-GlcNAcylation, compared to M1s, but the consequences of this are unknown. We hypothesize that O-GlcNAc modifications on key M2-specific proteins contribute to enhanced M2 phenotype and function within the TME, and that this phenomenon can be reversed with Hh blockade. Methodology: mouse model of mammary carcinoma, flow cytometry, RNA-seq, metabolomics, IP. This study is the first to elucidate Hh signaling’s role in recalibrating the metabolism of tumor-supporting MΦs. Inhibition of Hh signaling reduces MΦ O-GlcNAcylation resulting in weakened suppressive properties of M2 MΦs through the reduced activity of STAT6. Moreover, mitigating O-GlcNAcylation through Hh blockade pivots M2 MΦs to resemble M1s. Our work provides evidence for modulating Hh activity, and consequently MΦ metabolism, to sculpt the plasticity of MΦs. This knowledge will help us to better understand how to target and diminish the pro-tumorigenic phenotypes of MΦs in the TME.

Activation of Cilia-Independent Hedgehog/GLI1 Signaling as a Novel Concept for Neuroblastoma Therapy

Simple SummaryElevated GLI1 expression levels are associated with improved survival in NB patients and GLI1 overexpression exerts tumor-suppressive traits in cultured NB cells. However, NB cells are protected from increased GLI1 levels as they have lost the ability to form primary cilia and transduce Hedgehog signals. This study identifies an isoxazole (ISX) molecule with primary cilia-independent GLI1-activating properties, which blocks NB cell growth. Mechanistically, ISX combines the removal of GLI3 repressor and the inhibition of class I HDACs, providing proof-of-principle evidence that small molecule-mediated activation of GLI1 could be harnessed therapeutically in the future.Although being rare in absolute numbers, neuroblastoma (NB) represents the most frequent solid tumor in infants and young children. Therapy options and prognosis are comparably good for NB patients except for the high risk stage 4 class. Particularly in adolescent patients with certain genetic alterations, 5-year survival rates can drop below 30%, necessitating the development of novel therapy approaches. The developmentally important Hedgehog (Hh) pathway is involved in neural crest differentiation, the cell type being causal in the etiology of NB. However, and in contrast to its function in some other cancer types, Hedgehog signaling and its transcription factor GLI1 exert tumor-suppressive functions in NB, rendering GLI1 an interesting new candidate for anti-NB therapy. Unfortunately, the therapeutic concept of pharmacological Hh/GLI1 pathway activation is difficult to implement as NB cells have lost primary cilia, essential organelles for Hh perception and activation. In order to bypass this bottleneck, we have identified a GLI1-activating small molecule which stimulates endogenous GLI1 production without the need for upstream Hh pathway elements such as Smoothened or primary cilia. This isoxazole compound potently abrogates NB cell proliferation and might serve as a starting point for the development of a novel class of NB-suppressive molecules.

Dual activation of Hedgehog and Wnt/β-catenin signaling pathway caused by downregulation of SUFU targeted by miRNA-150 in human gastric cancer.

Mounting evidence has shown that miRNA-150 expression is upregulated in gastric cancer (GC) and is associated with gastric carcinogenesis, but the underlying oncogenic mechanism remains elusive. Here, we discovered that miRNA-150 targets the tumor suppressor SUFU to promote cell proliferation, migration, and the epithelial–mesenchymal transition (EMT) via the dual activation of Hedgehog (Hh) and Wnt signaling. MiRNA-150 was highly expressed in GC tissues and cell lines, and the level of this miRNA was negatively related to that of SUFU. In addition, both the miRNA-150 and SUFU levels were associated with tumor differentiation. Furthermore, miRNA-150 activated GC cell proliferation and migration in vitro. We found that miRNA-150 inhibitors repressed not only Wnt signaling by promoting cytoplasmic β-catenin localization, but also repressed Hh signaling and EMT. MiRNA-150 inhibition also resulted in significant tumor volume reductions in vivo, suggesting the potential application of miRNA-150 inhibitors in GC therapy. The expression of genes downstream of Hh and Wnt signaling was also reduced in tumors treated with miRNA-150 inhibitors. Notably, anti-SUFU siRNAs rescued the inhibitory effects of miRNA-150 inhibitors on Wnt signaling, Hh activation, EMT, cell proliferation, cell migration, and colony formation. Taken together, these findings indicate that miRNA-150 is oncogenic and promotes GC cell proliferation, migration, and EMT by activating Wnt and Hh signaling via the suppression of SUFU expression.