Hedgehog signaling promotes medulloblastoma survival via Bc/II

Increasing Ciliary ARL13B Expression Drives Active and Inhibitor-Resistant Smoothened and GLI into Glioma Primary Cilia

ADP-ribosylation factor-like protein 13B (ARL13B), a regulatory GTPase and guanine exchange factor (GEF), enriches in primary cilia and promotes tumorigenesis in part by regulating Smoothened (SMO), GLI, and Sonic Hedgehog (SHH) signaling. Gliomas with increased ARL13B, SMO, and GLI2 expression are more aggressive, but the relationship to cilia is unclear. Previous studies have showed that increasing ARL13B in glioblastoma cells promoted ciliary SMO accumulation, independent of exogenous SHH addition. Here, we show that SMO accumulation is due to increased ciliary, but not extraciliary, ARL13B. Increasing ARL13B expression promotes the accumulation of both activated SMO and GLI2 in glioma cilia. ARL13B-driven increases in ciliary SMO and GLI2 are resistant to SMO inhibitors, GDC-0449, and cyclopamine. Surprisingly, ARL13B-induced changes in ciliary SMO/GLI2 did not correlate with canonical changes in downstream SHH pathway genes. However, glioma cell lines whose cilia overexpress WT but not guanine exchange factor-deficient ARL13B, display reduced INPP5e, a ciliary membrane component whose depletion may favor SMO/GLI2 enrichment. Glioma cells overexpressing ARL13B also display reduced ciliary intraflagellar transport 88 (IFT88), suggesting that altered retrograde transport could further promote SMO/GLI accumulation. Collectively, our data suggest that factors increasing ARL13B expression in glioma cells may promote both changes in ciliary membrane characteristics and IFT proteins, leading to the accumulation of drug-resistant SMO and GLI. The downstream targets and consequences of these ciliary changes require further investigation.

hGFAP-mediated GLI2 overexpression leads to early death and severe cerebellar malformations with rare tumor formation

The zinc-finger transcription factor GLI2 is frequently amplified in childhood medulloblastoma of the Sonic-hedgehog type (SHH-MB), with or without amplification of NMYC or deletion of TP53. Despite the aggressive tumor behavior, tumorigenesis is not well understood, and adequate mouse models are lacking. Therefore, we generated mice with a GLI2 overexpression under control of the hGFAP-promoter. These mice died within 150 days. The majority only survived until postnatal day 40. They displayed severe cerebellar hypoplasia, cortical malformations, but no brain tumors, except for one out of 23 animals with an undifferentiated hindbrain lesion. Additional loss of p53 did not result in cerebellar tumors, but partially rescued the cerebellar phenotype induced by GLI2 overexpression. Similarly, the combination of GLI2 and NMYC was neither sufficient for the development of SHH-MB. We therefore assume that the development of childhood SHH-MB in mice is either occurring in cellular origins outside the hGFAP-positive lineage or needs additional genetic drivers.

The Potential Therapeutic Application of Simvastatin for Brain Complications and Mechanisms of Action

Statins are common drugs that are clinically used to reduce elevated plasma cholesterol levels. Based on their solubility, statins are considered to be either hydrophilic or lipophilic. Amongst them, simvastatin has the highest lipophilicity to facilitate its ability to cross the blood-brain barrier. Recent studies have suggested that simvastatin could be a promising therapeutic option for different brain complications and diseases ranging from brain tumors (i.e., medulloblastoma and glioblastoma) to neurological disorders (i.e., Alzheimer's disease, Parkinson's disease, and Huntington's disease). Specific mechanisms of disease amelioration, however, are still unclear. Independent studies suggest that simvastatin may reduce the risk of developing certain neurodegenerative disorders. Meanwhile, other studies point towards inducing cell death in brain tumor cell lines. In this review, we outline the potential therapeutic effects of simvastatin on brain complications and review the clinically relevant molecular mechanisms in different cases.

Profiling and targeting cancer stem cell signaling pathways for cancer therapeutics

Tumorigenic cancer stem cells (CSCs) represent a subpopulation of cells within the tumor that express genetic and phenotypic profiles and signaling pathways distinct from the other tumor cells. CSCs have eluded many conventional anti-oncogenic treatments, resulting in metastases and relapses of cancers. Effectively targeting CSCs' unique self-renewal and differentiation properties would be a breakthrough in cancer therapy. A better characterization of the CSCs' unique signaling mechanisms will improve our understanding of the pathology and treatment of cancer. In this paper, we will discuss CSC origin, followed by an in-depth review of CSC-associated signaling pathways. Particular emphasis is given on CSC signaling pathways' ligand-receptor engagement, upstream and downstream mechanisms, and associated genes, and molecules. Signaling pathways associated with regulation of CSC development stand as potential targets of CSC therapy, which include Wnt, TGFβ (transforming growth factor-β)/SMAD, Notch, JAK-STAT (Janus kinase-signal transducers and activators of transcription), Hedgehog (Hh), and vascular endothelial growth factor (VEGF). Lastly, we will also discuss milestone discoveries in CSC-based therapies, including pre-clinical and clinical studies featuring novel CSC signaling pathway cancer therapeutics. This review aims at generating innovative views on CSCs toward a better understanding of cancer pathology and treatment.

Regulation of Cell Plasticity by Bromodomain and Extraterminal Domain (BET) Proteins: A New Perspective in Glioblastoma Therapy

BET proteins are a family of multifunctional epigenetic readers, mainly involved in transcriptional regulation through chromatin modelling. Transcriptome handling ability of BET proteins suggests a key role in the modulation of cell plasticity, both in fate decision and in lineage commitment during embryonic development and in pathogenic conditions, including cancerogenesis. Glioblastoma is the most aggressive form of glioma, characterized by a very poor prognosis despite the application of a multimodal therapy. Recently, new insights are emerging about the glioblastoma cellular origin, leading to the hypothesis that several putative mechanisms occur during gliomagenesis. Interestingly, epigenome dysregulation associated with loss of cellular identity and functions are emerging as crucial features of glioblastoma pathogenesis. Therefore, the emerging roles of BET protein in glioblastoma onco-biology and the compelling demand for more effective therapeutic strategies suggest that BET family members could be promising targets for translational breakthroughs in glioblastoma treatment. Primarily, “Reprogramming Therapy”, which is aimed at reverting the malignant phenotype, is now considered a promising strategy for GBM therapy.

Towards Precision Oncology: The Role of Smoothened and Its Variants in Cancer

The G protein-coupled receptor Smoothened (Smo) is a central signal transducer of the Hedgehog (Hh) pathway which has been linked to diverse forms of tumours. Stimulated by advancements in structural and functional characterisation, the Smo receptor has been recognised as an important therapeutic target in Hh-driven cancers, and several Smo inhibitors have now been approved for cancer therapy. This receptor is also known to be an oncoprotein itself and its gain-of-function variants have been associated with skin, brain, and liver cancers. According to the COSMIC database, oncogenic mutations of Smo have been identified in various other tumours, although their oncogenic effect remains unknown in these tissues. Drug resistance is a common challenge in cancer therapies targeting Smo, and data analysis shows that healthy individuals also harbour resistance mutations. Based on the importance of Smo in cancer progression and the high incidence of resistance towards Smo inhibitors, this review suggests that detection of Smo variants through tumour profiling could lead to increased precision and improved outcomes of anti-cancer treatments.

Targeting the apoptosis pathway to treat tumours of the paediatric nervous system

New, more effective therapeutics are required for the treatment of paediatric cancers. Current treatment protocols of cytotoxic treatments including chemotherapy trigger cancer-cell death by engaging the apoptosis pathway, and chemotherapy efficacy is frequently impeded by apoptosis dysregulation. Apoptosis dysregulation, through genetic or epigenetic mechanisms, is a feature of many cancer types, and contributes to reduced treatment response, disease progression and ultimately treatment resistance. Novel approaches are required to overcome dysregulated apoptosis signalling, increase the efficacy of cancer treatment and improve patient outcomes. Here, we provide an insight into current knowledge of how the apoptosis pathway is dysregulated in paediatric nervous system tumours, with a focus on TRAIL receptors, the BCL-2 proteins and the IAP family, and highlight preclinical evidence demonstrating that pharmacological manipulation of the apoptosis pathway can restore apoptosis signalling and sensitise cancer cells to treatment. Finally, we discuss the potential clinical implications of these findings.

Saikosaponin B1 and Saikosaponin D inhibit tumor growth in medulloblastoma allograft mice via inhibiting the Hedgehog signaling pathway

Medulloblastoma (MB), accounting for nearly 10% of all childhood brain tumors, are implicated with aberrant activation of the Hedgehog (Hh) signaling pathway. Saikosaponin B1 (SSB1) and Saikosaponin D (SSD), two bioactive constituents of Radix Bupleuri, are reported to have many biological activities including anticancer activities. In our work, we evaluated the inhibition of SSB1 and SSD on MB tumor growth in allograft mice and explored the underlying mechanisms. The associated biological activity was investigated in Shh Light II cells, an Hh-responsive fibroblast cell line, using the Dual-Glo^® Luciferase Assay System. First, SSB1 (IC₅₀, 241.8 nM) and SSD (IC₅₀, 168.7 nM) inhibited GLI-luciferase activity in Shh Light II cells stimulated with ShhN CM, as well as Gli1 and Ptch1 mRNA expression. In addition, both compounds suppressed the Hh signaling activity provoked by smoothened agonist (SAG) or excessive Smoothened (SMO) expression. Meanwhile, SSB1 and SSD did not inhibit glioma-associated oncogene homolog (GLI) luciferase activity activated by abnormal expression of downstream molecules, suppressor of fuse (SUFU) knockdown or GLI2 overexpression. Consequently, SSB1 (30 mg/kg, ip) and SSD (10 mg/kg, ip) displayed excellent in vivo inhibitory activity in MB allografts, and the tumor growth inhibition ratios were approximately 50% and 70%, respectively. Our findings, thus, identify SSB1 and SSD significantly inhibit tumor growth in MB models by inhibiting the Hedgehog pathway through targeting SMO.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Immunosuppression in Medulloblastoma: Insights into Cancer Immunity and Immunotherapy

OPINION STATEMENT

Medulloblastoma (MB) is the most common pediatric brain malignancy, with a 5-year overall survival (OS) rate of around 65%. The conventional MB treatment, comprising surgical resection followed by irradiation and adjuvant chemotherapy, often leads to impairment in normal body functions and poor quality of life, especially with the increased risk of recurrence and subsequent development of secondary malignancies. The development and progression of MB are facilitated by a variety of immune-evading mechanisms such as the secretion of immunosuppressive molecules, activation of immunosuppressive cells, inhibition of immune checkpoint molecules, impairment of adhesive molecules, downregulation of the major histocompatibility complex (MHC) molecules, protection against apoptosis, and activation of immunosuppressive pathways. Understanding the tumor-immune relationship in MB is crucial for effective development of immune-based therapeutic strategies. In this comprehensive review, we discuss the immunological aspect of the brain, focusing on the current knowledge tackling the mechanisms of MB immune suppression and evasion. We also highlight several key immunotherapeutic approaches developed to date for the treatment of MB.

GLI3 Is Associated With Neuronal Differentiation in SHH-Activated and WNT-Activated Medulloblastoma

Glioma-associated oncogene homolog 3 (GLI3), whose main function is to inhibit GLI1, has been associated with neuronal differentiation in medulloblastoma. However, it is not clear what molecular subtype(s) show increased GLI3 expression. GLI3 levels were assessed by immunohistochemistry in 2 independent cohorts, including a total of 88 cases, and found to be high in both WNT- and SHH-activated medulloblastoma. Analysis of bulk mRNA expression data and single cell RNA sequencing studies confirmed that GLI1 and GLI3 are highly expressed in SHH-activated medulloblastoma, whereas GLI3 but not GLI1 is highly expressed in WNT-activated medulloblastoma. Immunohistochemical analysis has shown that GLI3 is expressed inside the neuronal differentiated nodules of SHH-activated medulloblastoma, whereas GLI1/2 are expressed in desmoplastic areas. In contrast, GLI3 is diffusely expressed in WNT-activated medulloblastoma, whereas GLI1 is suppressed. Our data suggest that GLI3 may be a master regulator of neuronal differentiation and morphology in these subgroups.

Drug repurposing towards targeting cancer stem cells in pediatric brain tumors

In the pediatric population, brain tumors represent the most commonly diagnosed solid neoplasms and the leading cause of cancer-related deaths globally. They include low-grade gliomas (LGGs), medulloblastomas (MBs), and other embryonal, ependymal, and neuroectodermal tumors. The mainstay of treatment for most brain tumors includes surgical intervention, radiation therapy, and chemotherapy. However, resistance to conventional therapy is widespread, which contributes to the high mortality rates reported and lack of improvement in patient survival despite advancement in therapeutic research. This has been attributed to the presence of a subpopulation of cells, known as cancer stem cells (CSCs), which reside within the tumor bulk and maintain self-renewal and recurrence potential of the tumor. An emerging promising approach that enables identifying novel therapeutic strategies to target CSCs and overcome therapy resistance is drug repurposing or repositioning. This is based on using previously approved drugs with known pharmacokinetic and pharmacodynamic characteristics for indications other than their traditional ones, like cancer. In this review, we provide a synopsis of the drug repurposing methodologies that have been used in pediatric brain tumors, and we argue how this selective compilation of approaches, with a focus on CSC targeting, could elevate drug repurposing to the next level.

The use of hedgehog antagonists in cancer therapy: a comparison of clinical outcomes and gene expression analyses

Hedgehog (HH) signaling, a critical developmental pathway, has been implicated in cancer initiation and progression. With vismodegib and sonidegib having been approved for clinical use, increasing numbers of HH inhibitors alone and in combination with chemotherapies are in clinical trials. Here we highlight the clinical research on HH antagonists and the genetics of response to these compounds in human cancers. Selectivity of HH inhibitors, determined by decreased pathway transcriptional activity, has been demonstrated in many clinical trials. Patients with advanced/metastatic basal cell carcinoma have benefited the most, whereas HH antagonists did little to improve survival rates in other cancers. Correlation between clinical response and HH gene expression vary among different cancer types. Predicting response and resistance to HH inhibitors presents a challenge and continues to remain an important area of research. New approaches combine standard of care chemotherapies and molecularly targeted therapies to increase the clinical utility of HH inhibitors.

Stem cells in cancer initiation and progression

Bajaj et al. review how cancers originate, how their heterogeneity is linked to cancer stem cells, and the signals fundamental to driving these processes.

While standard therapies can lead to an initial remission of aggressive cancers, they are often only a transient solution. The resistance and relapse that follows is driven by tumor heterogeneity and therapy-resistant populations that can reinitiate growth and promote disease progression. There is thus a significant need to understand the cell types and signaling pathways that not only contribute to cancer initiation, but also those that confer resistance and drive recurrence. Here, we discuss work showing that stem cells and progenitors may preferentially serve as a cell of origin for cancers, and that cancer stem cells can be key in driving the continued growth and  functional heterogeneity of established cancers. We also describe emerging evidence for the role of developmental signals in cancer initiation, propagation, and therapy resistance and discuss how targeting these pathways may be of therapeutic value.

Construction and Validation of a 13-Gene Signature for Prognosis Prediction in Medulloblastoma

Background: Recent studies have identified several molecular subgroups of medulloblastoma associated with distinct clinical outcomes; however, no robust gene signature has been established for prognosis prediction. Our objective was to construct a robust gene signature-based model to predict the prognosis of patients with medulloblastoma.

Methods: Expression data of medulloblastomas were acquired from the Gene Expression Omnibus (GSE85217, n = 763; GSE37418, n = 76). To identify genes associated with overall survival (OS), we performed univariate survival analysis and least absolute shrinkage and selection operator (LASSO) Cox regression. A risk score model was constructed based on selected genes and was validated using multiple datasets. Differentially expressed genes (DEGs) between the risk groups were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and protein–protein interaction (PPI) analyses were performed. Network modules and hub genes were identified using Cytoscape. Furthermore, tumor microenvironment (TME) was evaluated using ESTIMATE algorithm. Tumor-infiltrating immune cells (TIICs) were inferred using CIBERSORTx.

Results: A 13-gene model was constructed and validated. Patients classified as high-risk group had significantly worse OS than those as low-risk group (Training set: p < 0.0001; Validation set 1: p < 0.0001; Validation set 2: p = 0.00052). The area under the curve (AUC) of the receiver operating characteristic (ROC) analysis indicated a good performance in predicting 1-, 3-, and 5-year OS in all datasets. Multivariate analysis integrating clinical factors demonstrated that the risk score was an independent predictor for the OS (validation set 1: p = 0.001, validation set 2: p = 0.004). We then identified 265 DEGs between risk groups and PPI analysis predicted modules that were highly related to central nervous system and embryonic development. The risk score was significantly correlated with programmed death-ligand 1 (PD-L1) expression (p < 0.001), as well as immune score (p = 0.035), stromal score (p = 0.010), and tumor purity (p = 0.010) in Group 4 medulloblastomas. Correlations between the 13-gene signature and the TIICs in Sonic hedgehog and Group 4 medulloblastomas were revealed.

Conclusion: Our study constructed and validated a robust 13-gene signature model estimating the prognosis of medulloblastoma patients. We also revealed genes and pathways that may be related to the development and prognosis of medulloblastoma, which might provide candidate targets for future investigation.

Skp2 modulates proliferation, senescence and tumorigenesis of glioma

Background

Gliomas represent the largest class of primary central nervous system neoplasms, many subtypes of which exhibit poor prognoses. Surgery followed by radiotherapy and chemotherapy has been used as a standard strategy but yielded unsatisfactory improvements in patient survival outcomes. The S-phase kinase protein 2 (Skp2), a critical component of the E3-ligase SCF complex, has been documented in tumorigenesis in various cancer types but its role in glioma has yet to be fully clarified. In this study, we investigated the function of Skp2 in the proliferation, stem cell maintenance, and drug sensitivity to temozolomide (TMZ) of glioma.

Methods

To investigate the role of Skp2 in the prognosis of patients with glioma, we first analyzed data in databases TCGA and GTEx. To further clarify the effect of Skp2 on glioma cell proliferation, we suppressed its level in glioblastoma (GBM) cell lines through knockdown and small molecule inhibitors (lovastatin and SZL-P1-41). We then detected cell growth, colony formation, sphere formation, drug sensitivity, and in vivo tumor formation in xenograft mice model.

Results

Skp2 mRNA level was higher in both low-grade glioma and GBM than normal brain tissues. The knockdown of Skp2 increased cell sensitivity to TMZ, decreased cell proliferation and tumorigenesis. In addition, Skp2 level was found increased upon stem cells enriching, while the knockdown of Skp2 led to reduced sphere numbers. Downregulation of Skp2 also induced senescence. Repurposing of lovastatin and novel compound SZL-P1-41 suppressed Skp2 effectively, and enhanced glioma cell sensitivity to TMZ in vitro and in vivo.

Conclusion

Our data demonstrated that Skp2 modulated glioma cell proliferation in vitro and in vivo, stem cell maintenance, and cell sensitivity to TMZ, which indicated that Skp2 could be a potential target for long-term treatment.

Destined to Die: Apoptosis and Pediatric Cancers

Apoptosis (programmed cell death) is a systematic and coordinated cellular process that occurs in physiological and pathophysiological conditions. Sidestepping or resisting apoptosis is a distinct characteristic of human cancers including childhood malignancies. This review dissects the apoptosis pathways implicated in pediatric tumors. Understanding these pathways not only unraveled key molecules that may serve as potential targets for drug discovery, but also molecular nodes that integrate with other signaling networks involved in processes such as development. This review presents current knowledge of the complex regulatory system that governs apoptosis with respect to other processes in pediatric cancers, so that fresh insights may be derived regarding treatment resistance or for more effective treatment options.

State of the art of Smo antagonists for cancer therapy: advances in the target receptor and new ligand structures

Since the Hedgehog signaling pathway has been associated with cancer, it has emerged as a therapeutic target for cancer therapy. The main target among the key Hedgehog proteins is the GPCR-like Smo receptor. Therefore, some Smo antagonists that have entered clinical trials, including the US FDA-approved drugs vismodegib and sonidegib, to treat basal cell carcinoma and medulloblastoma. However, early resistance of these drugs has spawned the need to understand the molecular bases of this phenomena. We therefore reviewed details about Smo receptor structures and the best Smo antagonist chemical structures. In addition, we discussed strategies that should be considered to develop new, safer generations of Smo antagonists that avoid current clinical limitations.

Reproducibility of academic preclinical translational research: lessons from the development of Hedgehog pathway inhibitors to treat cancer

Academic translational research is growing at a great pace at a time in which questions have been raised about the reproducibility of preclinical findings. The development of Hedgehog (HH) pathway inhibitors for the treatment of cancer over the past two decades offers a case study for understanding the root causes of failure to predict clinical outcomes arising from academic preclinical translational research. Although such inhibitors were once hoped to be efficacious in up to 25% of human cancer, clinical studies showed responses only in basal cell carcinoma and the HH subtype of medulloblastoma. Close examination of the published studies reveals limitations in the models used, lack of quantitative standards, utilization of high drug concentrations associated with non-specific toxicities and improper use of cell line and mouse models. In part, these issues arise from scientific complexity, for example, the failure of tumour cell lines to maintain HH pathway activity in vitro, but a greater contributing factor appears to be the influence of unconscious bias. There was a strong expectation that HH pathway inhibitors would make a profound impact on human cancer and experiments were designed with this assumption in mind.

Inhibition of sonic hedgehog and PI3K/Akt/mTOR pathways cooperate in suppressing survival, self-renewal and tumorigenic potential of glioblastoma-initiating cells

Since PI3K/Akt/mTOR and sonic hedgehog (SHH) signaling pathways are highly activated in glioblastoma-initiating cells (GICs), we examined the effects of inhibiting these pathways on GIC characteristics and tumor growth in mice. NVP-LDE-225 (inhibitor of Smoothened) inhibited the expression of Gli1, Gli2, Smoothened, Patched1, and Patched2, and induced the expression of SuFu, whereas NVP-BEZ-235 (dual inhibitor of PI3K and mTOR) inhibited the expression of p-PI3K, p-Akt, p-mTOR, and p-p70S6K. NVP-LDE-225 co-operated with NVP-BEZ-235 in inhibiting the self-renewal capacity of GICs, expression of pluripotency maintaining factors (Nanog, c-Myc, Oct4, and Sox2), Musashi1, cyclin D1, and Bcl-2, and transcription and expression of Gli, and in inducing the expression of cleaved caspase-3, cleaved PARP and Bim. Additionally, NVP-LDE-225 co-operated with NVP-BEZ-235 in inhibiting epithelial-mesenchymal transition. Finally, the combination of NVP-LDE-225 and NVP-BEZ-235 was superior in inhibiting tumor growth, regulating the expression of pluripotency promoting factors, stem cell markers, cell cycle, and cell proliferation, and modulating EMT compared to single agent alone. In conclusion, the combined inhibition of PI3K/Akt/mTOR and SHH pathways was superior to single pathway inhibition in suppressing glioblastoma growth by targeting GICs.

Widespread Expression of Hedgehog Pathway Components in a Large Panel of Human Tumor Cells and Inhibition of Tumor Growth by GANT61: Implications for Cancer Therapy

The sonic Hedgehog/GLI signaling pathway (HH) is critical for maintaining tissue polarity in development and contributes to tumor stemness. Transcription factors GLI1–3 are the downstream effectors of HH and activate oncogenic targets. To explore the completeness of the expression of HH components in tumor cells, we performed a screen for all HH proteins in a wide spectrum of 56 tumor cell lines of various origin using Western blot analysis. Generally, all HH proteins were expressed. Important factors GLI1 and GLI2 were always expressed, only exceptionally one of them was lowered, suggesting the functionality of HH in all tumors tested. We determined the effect of a GLI inhibitor GANT61 on proliferation in 16 chosen cell lines. More than half of tumor cells were sensitive to GANT61 to various extents. GANT61 killed the sensitive cells through apoptosis. The inhibition of reporter activity containing 12xGLI consensus sites by GANT61 and cyclopamine roughly correlated with cell proliferation influenced by GANT61. Our results recognize the sensitivity of tumor cell types to GANT61 in cell culture and support a critical role for GLI factors in tumor progression through restraining apoptosis. The use of GANT61 in combined targeted therapy of sensitive tumors, such as melanomas, seems to be immensely helpful.

A highlight on Sonic hedgehog pathway

Hedgehog (Hh) signaling pathway plays an essential role during vertebrate embryonic development and tumorigenesis. It is already known that Sonic hedgehog (Shh) pathway is important for the evolution of radio and chemo-resistance of several types of tumors. Most of the brain tumors are resistant to chemotherapeutic drugs, consequently, they have a poor prognosis. So, a better knowledge of the Shh pathway opens an opportunity for targeted therapies against brain tumors considering a multi-factorial molecular overview. Therefore, emerging studies are being conducted in order to find new inhibitors for Shh signaling pathway, which could be safely used in clinical trials. Shh can signal through a canonical and non-canonical way, and it also has important points of interaction with other pathways during brain tumorigenesis. So, a better knowledge of Shh signaling pathway opens an avenue of possibilities for the treatment of not only for brain tumors but also for other types of cancers. In this review, we will also highlight some clinical trials that use the Shh pathway as a target for treating brain cancer.

Statins Synergize with Hedgehog Pathway Inhibitors for Treatment of Medulloblastoma

Purpose: The role of cholesterol biosynthesis in hedgehog pathway activity and progression of hedgehog pathway medulloblastoma (Hh-MB) were examined in vivo Statins, commonly used cholesterol-lowering agents, were utilized to validate cholesterol biosynthesis as a therapeutic target for Hh-MB.Experimental Design: Bioinformatic analysis was performed to evaluate the association between cholesterol biosynthesis with hedgehog group medulloblastoma in human biospecimens. Alterations in hedgehog signaling were evaluated in medulloblastoma cells after inhibition of cholesterol biosynthesis. The progression of endogenous medulloblastoma in mice was examined after genetic blockage of cholesterol biosynthesis in tumor cells. Statins alone, or in combination with vismodegib (an FDA-approved Smoothened antagonist), were utilized to inhibit medulloblastoma growth in vivoResults: Cholesterol biosynthesis was markedly enhanced in Hh-MB from both humans and mice. Inhibition of cholesterol biosynthesis dramatically decreased Hh pathway activity and reduced proliferation of medulloblastoma cells. Statins effectively inhibited medulloblastoma growth in vivo and functioned synergistically in combination with vismodegib.Conclusions: Cholesterol biosynthesis is required for Smoothened activity in the hedgehog pathway, and it is indispensable for the growth of Hh-MB. Targeting cholesterol biosynthesis represents a promising strategy for treatment of Hh-MB. Clin Cancer Res; 24(6); 1375-88. ©2018 AACR.

Flow Cytometry-based Drug Screening System for the Identification of Small Molecules That Promote Cellular Differentiation of Glioblastoma Stem Cells

Glioblastoma (GBM) is the most common and most lethal primary brain tumor in adults, causing roughly 14,000 deaths each year in the U.S. alone. Median survival following diagnosis is less than 15 months with maximal surgical resection, radiation, and temozolomide chemotherapy. The challenges inherent in developing more effective GBM treatments have become increasingly clear, and include its unyielding invasiveness, its resistance to standard treatments, its genetic complexity and molecular adaptability, and subpopulations of GBM cells with phenotypic similarities to normal stem cells, herein referred to as glioblastoma stem cells (GSCs). Because GSCs are required for tumor growth and progression, differentiation-based therapy represents a viable treatment modality for these incurable neoplasms. The following protocol describes a collection of procedures to establish a high throughput screening platform aimed at the identification of small molecules that promote GSC astroglial differentiation. At the core of the system is a glial fibrillary acidic protein (GFAP) differentiation reporter-construct. The protocol contains the following general procedures: (1) establishing GSC differentiation reporter lines; (2) testing/validating the relevance of the reporter to GSC self-renewal/clonogenic capacity; and (3) high-capacity flow-cytometry based drug screening. The screening platform provides a straightforward and inexpensive approach to identify small molecules that promote GSCs differentiation. Furthermore, utilization of libraries of FDA-approved drugs holds the potential for the identification of agents that can be repurposed more rapidly. Also, therapies that promote cancer stem cell differentiation are expected to work synergistically with current "standard of care" therapies that have been shown to target and eliminate primarily more differentiated cancer cells.

Glypican-6 promotes the growth of developing long bones by stimulating Hedgehog signaling

Autosomal-recessive omodysplasia (OMOD1) is caused by mutations in glypican-6. Capurro et al. show that glypican-6 stimulates Hedgehog (Hh) signaling, and reduced Hh signaling may contribute to the pathogenesis of OMOD1.

Autosomal-recessive omodysplasia (OMOD1) is a genetic condition characterized by short stature, shortened limbs, and facial dysmorphism. OMOD1 is caused by loss-of-function mutations of glypican 6 (GPC6). In this study, we show that GPC6-null embryos display most of the abnormalities found in OMOD1 patients and that Hedgehog (Hh) signaling is significantly reduced in the long bones of these embryos. The Hh-stimulatory activity of GPC6 was also observed in cultured cells, where this GPC increased the binding of Hh to Patched 1 (Ptc1). Consistent with this, GPC6 interacts with Hh through its core protein and with Ptc1 through its glycosaminoglycan chains. Hh signaling is triggered at the primary cilium. In the absence of Hh, we observed that GPC6 is localized outside of the cilium but moves into the cilium upon the addition of Hh. We conclude that GPC6 stimulates Hh signaling by binding to Hh and Ptc1 at the cilium and increasing the interaction of the receptor and ligand.

Identification of Diverse Adenosine-to-Inosine RNA Editing Subtypes in Colorectal Cancer

PURPOSE

RNA editing generates protein diversity by altering RNA sequences in coding regions without changing the overall DNA sequence. Adenosine-to-inosine (A-to-I) RNA editing events have recently been reported in some types of cancer, but they are rare in human colorectal cancer (CRC). Therefore, this study was conducted to identify diverse RNA editing in CRC.

MATERIALS AND METHODS

We compared transcriptome data of 39 CRC samples and paired adjacent tissues from The Cancer Genome Atlas database to identify RNA editing patterns in CRC, focusing on canonical A-to-I RNA edits in coding sequence regions. We investigated nonsynonymous RNA editing patterns by comparing tumor and normal tissue transcriptome data.

RESULTS

The number of RNA edits varied from 12 to 42 per sample. We also observed that hypoand hyper-RNA editing patterns were distinguishable within the samples. We found 10 recurrent nonsynonymous RNA editing candidates in nine genes (PDLIM, NEIL1, SRP9, GLI1, APMAP, IGFBP7, ZNF358, COPA, and ZNF587B) and validated some by Sanger sequencing and the inosine chemical erasing assay. We further showed that editing at these positions was performed by the adenosine deaminase acting on RNA 1 enzyme. Most of these genes are hypoedited in CRC, but editing of GLI1 was increased in cancer tissues compared with normal tissues.

CONCLUSION

Our results show that nonsynonymous RNA editing patterns can be used to identify CRC patients and could serve as novel biomarkers for CRC.

Targeting sonic hedgehog signaling in neurological disorders

Sonic hedgehog (Shh) signaling influences neurogenesis and neural patterning during the development of central nervous system. Dysregulation of Shh signaling in brain leads to neurological disorders like autism spectrum disorder, depression, dementia, stroke, Parkinson's diseases, Huntington's disease, locomotor deficit, epilepsy, demyelinating disease, neuropathies as well as brain tumors. The synthesis, processing and transport of Shh ligand as well as the localization of its receptors and signal transduction in the central nervous system has been carefully reviewed. Further, we summarize the regulation of small molecule modulators of Shh pathway with potential in neurological disorders. In conclusion, further studies are warranted to demonstrate the potential of positive and negative regulators of the Shh pathway in neurological disorders.

Inhibition of Hedgehog-dependent tumors and cancer stem cells by a newly identified naturally occurring chemotype

Hedgehog (Hh) inhibitors have emerged as valid tools in the treatment of a wide range of cancers. Indeed, aberrant activation of the Hh pathway occurring either by ligand-dependent or -independent mechanisms is a key driver in tumorigenesis. The smoothened (Smo) receptor is one of the main upstream transducers of the Hh signaling and is a validated target for the development of anticancer compounds, as underlined by the FDA-approved Smo antagonist Vismodegib (GDC-0449/Erivedge) for the treatment of basal cell carcinoma. However, Smo mutations that confer constitutive activity and drug resistance have emerged during treatment with Vismodegib. For this reason, the development of new effective Hh inhibitors represents a major challenge for cancer therapy. Natural products have always represented a unique source of lead structures in drug discovery, and in recent years have been used to modulate the Hh pathway at multiple levels. Here, starting from an in house library of natural compounds and their derivatives, we discovered novel chemotypes of Hh inhibitors by mean of virtual screening against the crystallographic structure of Smo. Hh functional based assay identified the chalcone derivative 12 as the most effective Hh inhibitor within the test set. The chalcone 12 binds the Smo receptor and promotes the displacement of Bodipy-Cyclopamine in both Smo WT and drug-resistant Smo mutant. Our molecule stands as a promising Smo antagonist able to specifically impair the growth of Hh-dependent tumor cells in vitro and in vivo and medulloblastoma stem-like cells and potentially overcome the associated drug resistance.

Zinc and zinc-containing biomolecules in childhood brain tumors

Zinc ions are essential cofactors of a wide range of enzymes, transcription factors, and other regulatory proteins. Moreover, zinc is also involved in cellular signaling and enzymes inhibition. Zinc dysregulation, deficiency, over-supply, and imbalance in zinc ion transporters regulation are connected with various diseases including cancer. A zinc ion pool is maintained by two types of proteins: (i) zinc-binding proteins, which act as a buffer and intracellular donors of zinc and (ii) zinc transporters responsible for zinc fluxes into/from cells and organelles. The decreased serum zinc ion levels have been identified in patients suffering from various cancer diseases, including head and neck tumors and breast, prostate, liver, and lung cancer. On the contrary, increased zinc ion levels have been found in breast cancer and other malignant tissues. Zinc metalloproteomes of a majority of tumors including brain ones are still not yet fully understood. Current knowledge show that zinc ion levels and detection of certain zinc-containing proteins may be utilized for diagnostic and prognostic purposes. In addition, these proteins can also be promising therapeutic targets. The aim of the present work is an overview of the importance of zinc ions, zinc transporters, and zinc-containing proteins in brain tumors, which are, after leukemia, the second most common type of childhood cancer and the second leading cause of death in children after accidents.

Pharmacological evaluation of a series of smoothened antagonists in signaling pathways and after topical application in a depilated mouse model

The Hedgehog (HH) pathway has been linked to the formation of basal cell carcinoma (BCC), medulloblastoma, and other cancers. The recently approved orally active drugs vismodegib (GDC-0449) and sonidegib (LDE-225) were not only efficacious for the treatment of advanced or metastatic BCC by antagonizing the smoothened (SMO) receptor, but also produced important side effects, limiting their use for less invasive BCC. Herein, we compared a large series of SMO antagonists, including GDC-0449 and LDE-225, the clinically tested BMS-833923, CUR-61414, cyclopamine, IPI-926 (saridegib), itraconazole, LEQ-506, LY-2940680 (taladegib), PF-04449913 (glasdegib), and TAK-441 as well as preclinical candidates (PF-5274857, MRT-83) in two SMO-dependent cellular assays and for G-protein activation. We report marked differences in inhibitor potencies between compounds as well as a notable disparity between the G-protein assay and the cellular tests, suggesting that classification of drugs is assay dependent. Furthermore, we explored topical efficacies of SMO antagonists on depilated mice using Gli1 and Ptch1 mRNA quantification in skin as biomarkers of the HH signaling inhibition. This topical model rapidly discriminated drugs in terms of efficacies and potencies for inhibition of both biomarkers. SMO antagonists showed also a large variation in their blood and skin partition, suggesting that some drugs are more favorable for topical application. Overall, our data suggested that in vitro and in vivo efficacious drugs such as LEQ-506 and TAK-441 may be of interest for topical treatment of less invasive BCC with minimal side effects.

Survivin, a novel target of the Hedgehog/GLI signaling pathway in human tumor cells

Survivin, an important antiapoptotic protein, is expressed in tumors, whereas in normal tissues the expression of this protein is extremely low, defining a role for survivin as a cancer gene. Survivin exhibits multifunctional activity in tumor cells. However, why survivin expression is sharply and invariably restricted to tumor tissue remains unclear. Here, we identified 11 putative consensus binding sites for GLI transcription factors in the survivin promoter and characterized the promoter activity. Inhibitors of the Hedgehog/GLI pathway, cyclopamine and GANT61, decreased the promoter activity in reporter assays. ΔNGLI2 (which lacks the repressor domain) was the most potent vector in activating the survivin promoter–reporter. Moreover, GANT61, a GLI1/2 inhibitor, repressed endogenous survivin protein and mRNA expression in most cells across a large panel of tumor cell lines. Chromatin immunoprecipitation showed GLI2 binding to the survivin promoter. The ectopic GLI2-evoked expression of endogenous survivin was observed in normal human fibroblasts. GANT61 decreased survivin level in nude mice tumors, mimicking the activity of GANT61 in cultured cells. The immunohistochemistry and double immunofluorescence of human tumors revealed a correlation between the tissue regions showing high GLI2 and survivin positivity. Thus, these results demonstrated that survivin is a classical transcriptional target of GLI2, a Hedgehog pathway signaling effector. This potentially reflects the high expression of survivin in human tumor cells. As the Hedgehog pathway is upregulated in virtually all types of cancer cells, these findings substantially contribute to the explanation of uniform survivin expression in tumors as a potential target for the development of a more effective treatment of cancers through the inhibition of GLI2 to restrain survivin activity.

Role of nestin in glioma invasion

AIM: To determine the role for the intermediate filament protein nestin in glioma invasion.

METHODS: We examined the expression and function of nestin in gliomas (Grades II-IV as defined by the World Health Organization). We determined nestin expression using Immunohistochemical methods. To elucidate nestin’s biological function(s), we reduced mRNA levels by 61% and 87% in two glioblastoma-derived neurosphere lines using short hairpin RNAs and determined the effect of reduced nestin expression on glioma cell proliferation and invasion using MTS and matrigel migration assays, respectively. We also utilized quantitative real time polymerase chain reaction assays to determine the effect of reduced nestin expression on the expression of other markers associated with glioma stem cells and their differentiated progenies.

RESULTS: We found a significant correlation between nestin immunoreactivity and astrocytoma tumor grade, with 36% of grade II, 75% of grade III, and 100% of grade IV tumors expressing significant levels of the protein when assessed using immunohistochemistry. Reduction in nestin expression had no effect on cell growth in culture, but did retard the capacity of one line to migrate in-vitro on matrigel. Interestingly, in the line whose migration was not affected, mRNA levels of a second intermediate filament, synemin (also knowns as desmuslin), were elevated following introduction of shRNA targeting nestin. As synemin was not induced in the line which required nestin for migration, it is a possibility that synemin may compensate for the loss of nestin in this process.

CONCLUSION: Nestin expression is prominent in high-grade astrocytomas. Nestin is not required for cell growth but it may, however, be required for cell motility.

Cooperative integration between HEDGEHOG-GLI signalling and other oncogenic pathways: implications for cancer therapy

The HEDGEHOG-GLI (HH-GLI) signalling is a key pathway critical in embryonic development, stem cell biology and tissue homeostasis. In recent years, aberrant activation of HH-GLI signalling has been linked to several types of cancer, including those of the skin, brain, lungs, prostate, gastrointestinal tract and blood. HH-GLI signalling is initiated by binding of HH ligands to the transmembrane receptor PATCHED and is mediated by transcriptional effectors that belong to the GLI family, whose activity is finely tuned by a number of molecular interactions and post-translation modifications. Several reports suggest that the activity of the GLI proteins is regulated by several proliferative and oncogenic inputs, in addition or independent of upstream HH signalling. The identification of this complex crosstalk and the understanding of how the major oncogenic signalling pathways interact in cancer is a crucial step towards the establishment of efficient targeted combinatorial treatments. Here we review recent findings on the cooperative integration of HH-GLI signalling with the major oncogenic inputs and we discuss how these cues modulate the activity of the GLI proteins in cancer. We then summarise the latest advances on SMO and GLI inhibitors and alternative approaches to attenuate HH signalling through rational combinatorial therapies.

Sonic hedgehog pathway contributes to gastric cancer cell growth and proliferation

The Sonic Hedgehog (Shh) signaling pathway is commonly activated in gastrointestinal cancer. However, our understanding of the Shh pathway in gastric cancer remains limited. Here we examined the effects of cyclopamine, a specific inhibitor of the Shh signaling pathway, on cell growth and proliferation in gastric primary cancer cells GAM-016 and the MKN-45 cell line. The results showed that the Shh signaling molecules SHH, PTCH, SMO, GLI1, and GLI2 were intact and activated in both types of cells. Furthermore, we observed that cyclopamine inhibited gastric cancer cell proliferation through cell cycle arrest and apoptosis. An in vivo study using NOD/SCID mouse xenografts demonstrated that cyclopamine significantly prevented tumor growth and development. Our study indicated that Shh signaling pathway could promote gastric cancer cell proliferation and tumor development, and blocking this pathway may be a potential strategy in gastric cancer treatment.

Glioblastoma stem cells: Molecular characteristics and therapeutic implications

Glioblastoma Multiforme (GBM) is a grade IV astrocytoma, with a median survival of 14.6 mo. Within GBM, stem-like cells, namely glioblastoma stem cells (GSCs), have the ability to self-renew, differentiate into distinct lineages within the tumor and initiate tumor xenografts in immunocompromised animal models. More importantly, GSCs utilize cell-autonomous and tumor microenvironment-mediated mechanisms to overcome current therapeutic approaches. They are, therefore, very important therapeutic targets. Although the functional criteria defining GSCs are well defined, their molecular characteristics, the mechanisms whereby they establish the cellular hierarchy within tumors, and their contribution to tumor heterogeneity are not well understood. This review is aimed at summarizing current findings about GSCs and their therapeutic importance from a molecular and cellular point of view. A better characterization of GSCs is crucial for designing effective GSC-targeted therapies.

Histone acetyltransferase PCAF is required for Hedgehog-Gli-dependent transcription and cancer cell proliferation

The Hedgehog (Hh) signaling pathway plays an important role in embryonic patterning and development of many tissues and organs as well as in maintaining and repairing mature tissues in adults. Uncontrolled activation of the Hh-Gli pathway has been implicated in developmental abnormalities as well as in several cancers, including brain tumors like medulloblastoma and glioblastoma. Inhibition of aberrant Hh-Gli signaling has, thus, emerged as an attractive approach for anticancer therapy; however, the mechanisms that mediate Hh-Gli signaling in vertebrates remain poorly understood. Here, we show that the histone acetyltransferase PCAF/KAT2B is an important factor of the Hh pathway. Specifically, we show that PCAF depletion impairs Hh activity and reduces expression of Hh target genes. Consequently, PCAF downregulation in medulloblastoma and glioblastoma cells leads to decreased proliferation and increased apoptosis. In addition, we found that PCAF interacts with GLI1, the downstream effector in the Hh-Gli pathway, and that PCAF or GLI1 loss reduces the levels of H3K9 acetylation on Hh target gene promoters. Finally, we observed that PCAF silencing reduces the tumor-forming potential of neural stem cells in vivo. In summary, our study identified the acetyltransferase PCAF as a positive cofactor of the Hh-Gli signaling pathway, leading us to propose PCAF as a candidate therapeutic target for the treatment of patients with medulloblastoma and glioblastoma.

The role of the sonic hedgehog signaling pathway in early brain injury after experimental subarachnoid hemorrhage in rats

Previous studies have demonstrated that the sonic hedgehog (Shh) pathway plays a neuro-protective role. However, whether the Shh pathway is induced by subarachnoid hemorrhage (SAH) has not been investigated. We sought to investigate Shh activation in the cortex in the early stage of SAH, and assessed the effect of cyclopamine (a specific inhibitor of the Shh pathway) on Shh pathway regulation and evaluated the impact of cyclopamine on SAH. We found that the Shh pathway was up-regulated in the cortex after SAH, and that blocking the Shh pathway increased cell apoptosis. Early brain damages, including brain edema, blood-brain barrier impairment, and cortical apoptosis were significantly aggravated following with cyclopamine treatment compared with vehicle treatment. Our results suggest that the Shh pathway should be activated in the brain after SAH, and plays a beneficial role in SAH development, possibly by inhibiting cerebral oxidative stress through induction of antioxidant and detoxifying enzymes.

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

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

Identification of vitamin d3-based hedgehog pathway inhibitors that incorporate an aromatic a-ring isostere

Previous structure-activity relationship studies for vitamin D3 (VD3) inhibition of Hedgehog (Hh) signaling directed the design, synthesis, and evaluation of a series of VD3-based analogues that contain an aromatic A-ring mimic. Characterization of these compounds in a series of cellular assays demonstrated their ability to potently and selectively down-regulate Hh pathway signaling. The most active of these, 17, inhibited pathway signaling in Hh-dependent mouse fibroblasts (IC50 = 0.74 ± 0.1 μM) and cultured cancer cells (IC50 values 3.8 ± 0.1 to 5.2 ± 0.2 μM). In addition, 17 demonstrated reduced activation of the vitamin D receptor (VDR) compared to VD3 in these cellular models. These results suggest that VD3-based analogues with an aromatic A-ring are a valid scaffold for the development of more selective and potent Hh pathway inhibitors and identify 17 as an intriguing lead from this class of compounds for further development. In addition, our analysis of Hh pathway inhibitors in cancer cells suggests that the murine basal cell carcinoma cell line ASZ001 and the human medulloblastoma cell line DAOY are appropriate in vitro cancer models for early stage evaluation of pathway inhibition.

Hedgehog signaling in prostate cancer and its therapeutic implication

Activation of Hedgehog (Hh) signaling is implicated in the development and progression of several tumor types, including prostate cancer, which is still the most common non-skin malignancy and the third leading cause of cancer-related mortality in men in industrialized countries worldwide. Several studies have indicated that the Hh pathway plays a crucial role in the development as well as in the progression of this disease to more aggressive and even therapy-resistant disease states. Moreover, preclinical data have shown that inhibition of Hh signaling has the potential to reduce prostate cancer invasiveness and metastatic potential. Clinical trials investigating the benefit of Hh inhibitors in patients with prostate cancer have recently been initiated. However, acquired drug resistance has already been observed in other tumor types after long-term Hh inhibition. Therefore, combining Hh inhibitors with ionizing radiation, chemotherapy or other molecular targeted agents could represent an alternative therapeutic strategy. In this review, we will highlight the role of Hh signaling in the development and progression of prostate cancer and summarize the different therapeutic applications of Hedgehog inhibition.

The KDM1A histone demethylase is a promising new target for the epigenetic therapy of medulloblastoma

Background

Medulloblastoma is a leading cause of childhood cancer-related deaths. Current aggressive treatments frequently lead to cognitive and neurological disabilities in survivors. Novel targeted therapies are required to improve outcome in high-risk medulloblastoma patients and quality of life of survivors. Targeting enzymes controlling epigenetic alterations is a promising approach recently bolstered by the identification of mutations in histone demethylating enzymes in medulloblastoma sequencing efforts. Hypomethylation of lysine 4 in histone 3 (H3K4) is also associated with a dismal prognosis for medulloblastoma patients. Functional characterization of important epigenetic key regulators is urgently needed.

Results

We examined the role of the H3K4 modifying enzyme, KDM1A, in medulloblastoma, an enzyme also associated with malignant progression in the closely related tumor, neuroblastoma. Re-analysis of gene expression data and immunohistochemistry of tissue microarrays of human medulloblastomas showed strong KDM1A overexpression in the majority of tumors throughout all molecular subgroups. Interestingly, KDM1A knockdown in medulloblastoma cell lines not only induced apoptosis and suppressed proliferation, but also impaired migratory capacity. Further analyses revealed bone morphogenetic protein 2 (BMP2) as a major KDM1A target gene. BMP2 is known to be involved in development and differentiation of granule neuron precursor cells (GNCPs), one potential cell of origin for medulloblastoma. Treating medulloblastoma cells with the specific KDM1A inhibitor, NCL-1, significantly inhibited growth in vitro.

Conclusion

We provide the first evidence that a histone demethylase is functionally involved in the regulation of the malignant phenotype of medulloblastoma cells, and lay a foundation for future evaluation of KDM1A-inihibiting therapies in combating medulloblastoma.

Guggulsterone sensitizes glioblastoma cells to Sonic hedgehog inhibitor SANT-1 induced apoptosis in a Ras/NFκB dependent manner

Since Shh pathway effector, Gli1, is overexpressed in gliomas, we investigated the effect of novel Shh inhibitor SANT-1 on glioma cell viability. Though SANT-1 failed to induce apoptosis, it reduced proliferation of glioma stem-like cells. Apart from canonical Shh cascade, Gli1 is also induced by non-canonical pathways including NFκB. Therefore, a combinatorial strategy with Ras/NFκB inhibitor, Guggulsterone, was employed to enhance effectiveness of SANT-1. Guggulsterone inhibited Ras and NFκB activity and sensitized cells to SANT-1 induced apoptosis via intrinsic apoptotic mechanism. Inhibition of either Ras or NFκB activity was sufficient to sensitize cells to SANT-1. Guggulsterone induced ERK activation also contributed to Caspase-9 activation. Since SANT-1 and Guggulsterone differentially target stem-like and non-stem glioma cells respectively, this combination warrants investigation as an effective anti-glioma therapy.

Hedgehog signaling inhibitor cyclopamine induces apoptosis by decreasing Gli2 and Bcl2 expression in human salivary pleomorphic adenoma cells

Pleomorphic adenoma is the most common benign neoplasm of the salivary gland. Few studies are currently available on pleomorphic adenoma cell apoptosis. The aim of this study was to investigate the effect of cyclopamine induction apoptosis in human salivary pleomorphic adenoma (HSPA) cells and the impact on Gli2 and Bcl2 mRNA levels. Cells were quantified and cell morphology was visualized under microscope. Flow cytometry was used to detect the apoptotic rate. Cyclopamine is considered an efficient blocker of the hedgehog (Hh) signaling pathway. Following treatment with 10 μmol/l cyclopamine for 48 h, the number of cells were reduced, and nuclear pycnosis or fragmentation, as well as chromatospherite disfiguration apoptotic morphology were observed under microscope. One-way ANOVA test results revealed a significantly greater decrease (P<0.01) of Gli2 and Bcl2 mRNA levels in the cyclopamine-treated group as compared to the blank control group and dimethyl sulfoxide (DMSO)-treated group. Following treatment with 10 μmol/l cyclopamine for 24 h, the apoptotic rate of the cyclopamine-treated group was significantly higher than that of the blank control and DMSO-treated group (P<0.01). Findings of this study showed that cyclopamine affected the mechanism of HSPA cell apoptosis, which may be associated with the downregulation of Gli2 and Bcl2 mRNA expression levels and the activation of the mitochondrial apoptotic pathways.

A statin-regulated microRNA represses human c-Myc expression and function

c-Myc dysregulation is one of the most common abnormalities found in human cancer. MicroRNAs (miRNAs) are functionally intertwined with the c-Myc network as multiple miRNAs are regulated by c-Myc, while others directly suppress c-Myc expression. In this work, we identified miR-33b as a primate-specific negative regulator of c-Myc. The human miR-33b gene is located at 17p11.2, a genomic locus frequently lost in medulloblastomas, of which a subset displays c-Myc overproduction. Through a small-scale screening with drugs approved by the US Food and Drug Administration (FDA), we found that lovastatin upregulated miR-33b expression, reduced cell proliferation and impaired c-Myc expression and function in miR-33b-positive medulloblastoma cells. In addition, a low dose of lovastatin treatment at a level comparable to approved human oral use reduced tumour growth in mice orthotopically xenografted with cells carrying miR-33b, but not with cells lacking miR-33b. This work presents a highly promising therapeutic option, using drug repurposing and a miRNA as a biomarker, against cancers that overexpress c-Myc.

Concise review: self-renewal in the central nervous system: neural stem cells from embryo to adult

The recent discovery of neural stem cells (NSCs) in the adult mammalian brain has fostered a plethora of translational and preclinical studies to investigate future therapeutic approaches for the cure of neurodegenerative diseases. These studies are finally at the clinical stage, and some of them are already under way. The definition of a bona fide stem cell has long been the object of much debate focused on the establishment of standard and univocal criteria to distinguish between stem and progenitor cells. It is commonly accepted that NSCs have to fulfill two basic requirements, the capacity for long-term self-renewal and the potential for differentiation, which account for their physiological role, namely central nervous system tissue homeostasis. Strategies such as immortalization or reprogramming of somatic cells to the embryonic-like stage of pluripotency indicate the relevance of extensive self-renewal ability of NSCs either in vitro or in vivo. Moreover, the discovery of stem-like tumor cells in brain tumors, such as gliomas, accompanied by the isolation of these cells through the same paradigm used for related healthy cells, has provided further evidence of the key role that self-renewal plays in the development and progression of neurodegenerative diseases and cancer. In this review we provide an overview of the current understanding of the self-renewal capacity of nontransformed human NSCs, with or without immortalization or reprogramming, and of stem-like tumor cells, referring to both research and therapeutic studies.