Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of human neuroblastoma cells with and without MYCN oncogene induction and doxorubicin treatment

ABSTRACT: Purpose: Clinical courses of neuroblastomas (NBs) range from rapid progression with fatal outcome despite intensive multimodality therapies to spontaneous regression. Amplified MYCN oncogene defines a subgroup with poor outcome. However, a substantial number of MYCN single-copy NBs exhibits an aggressive phenotype similar to that of MYCN-amplified NBs even in the absence of high MYCN mRNA and/or protein levels. Experimental Design: To identify shared molecular mechanisms that mediate the aggressive phenotype in MYCN amplified and single-copy high-risk NBs, we defined genetic programs evoked by ectopically expressed MYCN in vitro and analyzed them in high-risk versus low-risk NB tumors (n=49) using cDNA microarrays. Candidate gene and protein expression was validated in a separate cohort of 117 patients using quantitative PCR (QPCR) and in a panel of NB tumors using immunohistochemistry. Results: We identified a genetic signature characterized by Skp2, encoding the F-box protein of the SCFSkp2 E3-ligase, and a subset of MYCN and of E2F targets to be highly expressed in high-risk NBs. We validated the findings for Skp2 and analyzed its expression in relation to MYCN and E2F-1 expression in a separate cohort (n=117) using QPCR. Most importantly, high Skp2 expression proved to be a highly significant marker of dire prognosis independent of both MYCN status and disease stage, on the basis of multivariate analysis of event-free survival (hazard ratio, 3.54

ORGANISM(S): Homo sapiens

SUBMITTER: Frank Westermann

PROVIDER: E-CVDE-3 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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:MYCN is an oncogene amplified in approximately 20% of all neuroblastomas and 50% of high risk neuroblastoma. It is a transcription factor regulating the expression of genes involved in proliferation and apoptosis.We would like to identify genes potentially regulated by MYCN in a conditional MYCN expression system. The SHEP Tet21N system is a conditional, tetracycline-regulated MYCN expression system established in the MYCN non-amplified SHEP neuroblastoma cell line (Lutz et al., 1996). Expression of MYCN is switched off by the addition of tetracycline to the growth medium. Levels of MYCN protein and RNA in the absence of tetracycline are comparable with those present in MYCN amplified cell lines (Bell et al., 2006). By performing microarray analyses on the Tet21n cell lines in the presence and absence of MYCN we hope to identify genes whose expression had been altered by MYCN either upregulated or downregulated and may be potential MYCN targets. The altered expression of some of these genes will then be validated using quantitative RTPCR and a selection will be further investigated to determine if they are MYCN transcriptional targets and may be potential candidates for anti-MYCN therapies for neuroblastoma Specific objectives 1) To investigate genes which are altered by 2 fold or more in the presence of or absence of MYCN in Tet21N cells. Refs: Bell, E., Premkumar, R., Carr, J., Lu, X., Lovat, P.E., Kees, U.R., Lunec, J. & Tweddle, D.A. (2006). The role of MYCN in the failure of MYCN amplified neuroblastoma cell lines to G1 arrest after DNA damage. Cell Cycle, 5, 2639-47. Lutz, W., Stohr, M., Schurmann, J., Wenzel, A., Lohr, A. & Schwab, M. (1996). Conditional expression of N-myc in human neuroblastoma cells increases expression of alpha-prothymosin and ornithine decarboxylase and accelerates progression into S-phase early after mitogenic stimulation of quiescent cells. Oncogene, 13, 803-12.

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Transcription profiling of human neuroblastoma cells with and without MYCN oncogene induction and doxorubicin treatment

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