Project description:Neuroblastoma is a pediatric cancer of the sympathetic nervous system. MYCN amplification is a key indicator of poor prognosis for the disease, however, mechanisms by which MYCN promotes neuroblastoma tumorigenesis are not fully understood. In this study, we analyzed global miRNA and mRNA expression profiles of tissues at different stages of tumorigenesis from TH-MYCN transgenic mice, a model of MYCN-driven neuroblastoma. Based on a Bayesian learning network model in which we compared pre-tumor ganglia from TH-MYCN+/+ mice to age-matched wild-type controls, we devised a predicted miRNA-mRNA interaction network. Among the miRNA-mRNA interactions operating during human neuroblastoma tumorigenesis, we identified that miR-204 is a tumor suppressor miRNA that inhibits a subnetwork of oncogenes strongly associated with MYCN-amplified neuroblastoma and poor patient outcome. Accordingly, we found that MYCN was bound to the miR-204 promoter and repressed miR-204 transcription, while in contrast, miR-204 directly bound MYCN mRNA and repressed MYCN expression. In support of a tumor suppressor role, miR-204 overexpression significantly inhibited neuroblastoma cell proliferation in vitro and tumorigenesis in vivo. Together these findings identify novel tumorigenic miRNA gene networks and miR-204 as a tumor suppressor that regulates MYCN expression in neuroblastoma tumorigenesis.
Project description:MYCN is a master regulator controlling many processes necessary for tumor cell survival. Here, we unravel a microRNA network that causes tumor suppressive effects in MYCN-amplified neuroblastoma cells. In profiling studies, histone deacetylase (HDAC) inhibitor treatment most strongly induced miR-183. Enforced miR-183 expression triggered apoptosis, and inhibited anchorage-independent colony formation in vitro and xenograft growth in mice. Furthermore, the mechanism of miR-183 induction was found to contribute to the cell death phenotype induced by HDAC inhibitors. Experiments to identify the HDAC(s) involved in miR-183 transcriptional regulation showed that HDAC2 depletion induced miR-183. HDAC2 overexpression reduced miR-183 levels and counteracted the induction caused by HDAC2 depletion or HDAC inhibitor treatment. MYCN was found to recruit HDAC2 in the same complexes to the miR-183 promoter, and HDAC2 depletion enhanced promoter-associated histone H4 pan-acetylation, suggesting epigenetic changes preceded transcriptional activation. These data reveal miR-183 tumor suppressive properties in neuroblastoma that are jointly repressed by MYCN and HDAC2, and suggest a novel way to bypass MYCN function. BE(2)-C neuroblastoma cells were treated with the pan-HDACi HC-toxin (20 nM) or solvent control (methanol) for 24 h in three replicates, respectively.Total RNA was isolated using miRNeasy Mini Kit (Qiagen) according to the manufacturer's instructions. RNA was eluted in water. The quality of total RNA was checked by gel analysis using the total RNA Nanochip assay on an Agilent 2100 Bioanalyzer.
Project description:MYCN and HDAC2 jointly repress the transcription of tumor suppressive micro RNA miR-183 in neuroblastoma. Enforced miR-183 expression induces neuroblastoma cell death and inhibits anchorage-independent colony formation and subcutaneous xenograft growth in mice. We here aimed to unravel the miR-183 signaling network and elucidated the role of MYCN mediated transcriptional activation of members of the minichromosome maintenance (MCM) family protein family involving miR-183 . The hexamer protein complex formed by MCM proteins is involved in the initiation and elongation of eukaryotic genome replication, thereby contributing to genomic integrity. Analysis of miR-183 versus negative control transfected neuroblastoma cells identified 85 differentially expressed proteins in a label-free mass spectrometric approach. Six members of the MCM family were found to be lower expressed upon enforced miR-183 expression, and subsequent annotation category enrichment analysis revealed a 14-fold enrichment in the protein module category “MCM”. Down-regulation was confirmed by western blot analysis. MicroRNA target prediction software studies revealed that miR-183 was predicted to directly target several MCMs.
Project description:MYCN is a master regulator controlling many processes necessary for tumor cell survival. Here, we unravel a microRNA network that causes tumor suppressive effects in MYCN-amplified neuroblastoma cells. In profiling studies, histone deacetylase (HDAC) inhibitor treatment most strongly induced miR-183. Enforced miR-183 expression triggered apoptosis, and inhibited anchorage-independent colony formation in vitro and xenograft growth in mice. Furthermore, the mechanism of miR-183 induction was found to contribute to the cell death phenotype induced by HDAC inhibitors. Experiments to identify the HDAC(s) involved in miR-183 transcriptional regulation showed that HDAC2 depletion induced miR-183. HDAC2 overexpression reduced miR-183 levels and counteracted the induction caused by HDAC2 depletion or HDAC inhibitor treatment. MYCN was found to recruit HDAC2 in the same complexes to the miR-183 promoter, and HDAC2 depletion enhanced promoter-associated histone H4 pan-acetylation, suggesting epigenetic changes preceded transcriptional activation. These data reveal miR-183 tumor suppressive properties in neuroblastoma that are jointly repressed by MYCN and HDAC2, and suggest a novel way to bypass MYCN function.
Project description:Neuroblastoma is a pediatric tumor of the developing sympathetic nervous system. We investigate developmental origins of neuroblastoma, the role of oncogenic MYCN in blocking normal differentiation and evaluate therapeutic interventions to overcome differentiation blocks. Here, we provide single cell expression profiles of IMR5/75-shMYCN cells upon knockdown of MYCN and control.
Project description:Changes in epigenetic regulation are believed to be a major contributing factor to neuroblastoma development. Using a large-scale in vivo mutagenesis screen in Th-MYCN transgenic mice, we identified a single point mutation in the transcriptional corepressor Runx1t1, that can block N-myc-driven neuroblastoma tumorigenesis. The loss of function mutation disrupts a highly conserved zinc finger domain (NHR4) within Runx1t1. Crossing an independent Runx1t1 knockout model with Th-MYCN mice, demonstrated that Runx1t1 haploinsufficiency is enough to prevent neuroblastoma development and reverse ganglia hyperplasia. Silencing RUNX1T1 in human neuroblastoma cells resulted in decreased colony formation in vitro, and significant inhibition of tumor growth in vivo. Our results show that RUNX1T1 forms part of a transcriptional LSD1-CoREST3-HDAC repressive complex that regulates the epigenomic landscape and chromatin accessibility, to control neuron-specific pathway genes and maintain an undifferentiated state. Runx1t1 thus represents an entirely novel and highly promising target not previously described in neuroblastoma.
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
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 rates1,2. As a proto-oncogene, targeted MYCN overexpression in peripheral neural crest is sufficient to initiate disease in mouse models3. In MYCN amplified neuroblastoma, elevated expression of the factor is crucial to maintain tumor stemness4,5 and is associated with increased proliferation and aberrant cell cycle progression, as these tumors lack the ability to arrest in G1 in response to irradiation6-9. MYCN down-regulation broadly reverses these oncogenic phenotypes in a variety of neuroblastoma models10-12 and recent thereapeutic strategies to indirectly target MYCN production or protein stability have reduced tumor growth in vivo13-15. 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 â??targetâ?? 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. ATAC-Seq in SHEP21, BE2C, KELLY, NGP, and MM1S cell lines
Project description:Neuroblastoma is a pediatric tumor of the developing sympathetic nervous system. We investigate developmental origins of neuroblastoma, the role of oncogenic MYCN in blocking normal differentiation and evaluate therapeutic interventions to overcome differentiation blocks. Here, we provide expression profiles of SK-N-BE(2)C cells upon treatment with ATRA or solvent control.
Project description:Neuroblastoma is a pediatric tumor of the developing sympathetic nervous system. We investigate the developmental origin of neuroblastoma, the role of oncogenic MYCN in blocking normal differentiation and evaluate therapeutic interventions to overcome differentiation blocks. Here, we provide single cell expression profiles (scRNA-seq MARS-seq) of SK-N-AS cells (n=603).