Project description:Neuroblastoma is a pediatric tumor of the peripheral sympathetic nervous system with diverse clinical behaviors. Even with multimodal therapies, high-risk neuroblastoma has an unfavorable outcome irrespective of MYCN amplification, a well-established oncogenic driver in neuroblastoma pathogenesis, and its genetic heterogeneity has largely impeded efforts to correlate molecular targets with biological consequences for more effective treatment strategies. Here, using a gene expression-based approach, we identified the FDA-approved anthelmintic niclosamide as a potential anti-neuroblastoma drug. By combining the gene expression signature associated with high-risk neuroblastoma and the recurrent drug−transcript relationships inferred from up to one million perturbational gene expression profiles, our algorithm predicted effective therapeutic candidates by evaluating the extent to which a given compound or their combinations could ‘reverse’ the high-risk signature. Furthermore, we performed quantitative polymerase chain reaction (qPCR) to validate top five candidate reverse genes which are involved in DNA replication, including cyclin A2 (CCNA2), minichromosome maintenance 10 replication initiation factor (MCM10), ERCC excision repair 6 like, spindle assembly checkpoint helicase (ERCC6L), kinesin family member 20A (KIF20A), and RuvB like AAA ATPase 1 (RUVBL1). Indeed, those five genes were downregulated in niclosamide-treated cells, indicating niclosamide suppressed DNA replication and then inhibited cell proliferation. Using cell proliferation and clonogenic assays as well as flow cytometry, we determined the cytotoxic effects of niclosamide in MYCN-amplified SK-N-DZ and non-amplified SK-N-AS cells. The results showed that niclosamide could effectively reduce not only cell proliferation and colony formation but also trigger cell cycle arrest and apoptosis. Moreover, we conducted human tumor xenografts in a nude mice model to evaluate the in vivo efficacy of niclosamide and found that it significantly suppressed tumor growth and prolonged survival rate, but doesn’t cause organ damage and change body weight. To explore the molecular mechanism of niclosamide, stable-isotope dimethyl labeling strategy for quantitative proteomics was performed on both cell-based or xenograft-based MYCN-amplified SK-N-DZ and MYCN-nonamplified SK-N-AS models. We confirmed niclosamide not only mediated the function of mitochondrial electron transport chain but also the other functions in high risk neuroblastoma cell lines and xenografts. The results suggest that our developed expression-based strategy is useful for drug discovery and provides the possibility of repurposing the anthelminthic drug niclosamide for treating high-risk neuroblastoma therapy.

Project description:In neuroblastoma, amplification of the oncogenic basic helix-loop-helix (bHLH) transcription factor (TF) MYCN is the defining prognosticator of high-risk disease, occurs in one-third of neuroblastoma, and drastically reduces overall survival rates. As a proto-oncogene, targeted MYCN overexpression in peripheral neural crest is sufficient to initiate disease in mouse models. In MYCN amplified neuroblastoma, elevated expression of the factor is crucial to maintain tumor stemness and is associated with increased proliferation and aberrant cell cycle progression, as these tumors lack the ability to arrest in G1 in response to irradiation. MYCN down-regulation broadly reverses these oncogenic phenotypes in a variety of neuroblastoma models and recent thereapeutic strategies to indirectly target MYCN production or protein stability have reduced tumor growth in vivo. These observations motivate an investigation of MYCN binding in MYCN amplified tumors as it remains fundamentally unclear how elevated levels of the factor occupy the genome and alter transcriptional programs in neuroblastoma. Here we present the first dynamic chromatin and transcriptional landscape of direct MYCN perturbation in neuroblastoma. We find that at oncogenic levels, MYCN associates with E-box (CANNTG) binding motifs in an affinity dependent manner across most active cis-regulatory promoters and enhancers. MYCN shutdown globally reduces histone acetylation and transcription, consistent with prior descriptions of MYC proteins as non-linear amplifiers of gene expression. We establish that MYCN load at the promoter and proximal enhancers predicts transcriptional responsiveness to MYCN shutdown and that MYCN enhancer binding occurs prominently at the most strongly occupied and down-regulated genes, suggesting a role for these tissue specific elements in predicating MYCN responsive âtargetâ genes. At these invaded enhancers, we identify the lineage specific bHLH TWIST1 as a key collaborator and dependency of oncogenic MYCN. These data suggest that MYCN enhancer invasion helps shape transcriptional amplification of the neuroblastoma gene expression program to promote tumorigenesis. ChIP-Seq in SHEP21, BE2C, KELLY, and NGP neuroblastoma cell lines for H3K27ac, H3K4me3, RNA PolII, MYCN, BRD4, or TWIST1

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Homo sapiens

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