Global transcriptome analysis in the MYCN-amplified neuroblastoma cell line IMR5-75 upon inducible MYCN-knockdown
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ABSTRACT: Inducible MYCN-knockdown, followed by RNA-seq analysis in the MYCN-amplified neuroblastoma cell line IMR5-75, reveals profound time-dependent transcriptome changes. For modulation of MYCN levels, stable neuroblastoma cell models were used where MYCN can be downregulated via vector-based hairpin RNA induction upon addition of 1µg/ml tetracycline (IMR5-75-shMYCN. From cells treated either with tetracycline or solvent (ethanol), RNA was isolated at time points 6 hours, 12 hours and 24 hours. Experiments were done in duplicates. RNA was sequenced.
Project description:Inducible MYCN-knockdown, followed by RNA-seq analysis in the MYCN-amplified neuroblastoma cell line IMR5-75, reveals profound time-dependent transcriptome changes.
Project description:RNA-seq upon TBX2, MYCN or combination of TBX2 and MYCN knockdown in the neuroblastoma cell line IMR-5/75. Cells were transduced with two different shRNAs (shTBX2_2 and shTBX2_4) targeting TBX2 and a non-targeting control (NTC), and selected with puromycin. Cells were treated with doxycycline for shMYCN induction (with DOX or not). Analysis was performed three days upon TBX2 knockdown and two days upon MYCN knockdown, including six biological replicates per condition.
Project description:Here we sought metabolic alterations specifically associated with amplified MYCN as nodes to indirectly target the MYCN oncogene. Liquid chromatography-mass spectrometry-based proteomics identified 7 proteins consistently correlated with MYCN in proteomes from 49 neuroblastoma biopsies and 13 cell lines. Among these were phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in de novo serine synthesis. MYCN associated with two regions in the PHGDH promoter, supporting transcriptional PHGDH regulation by MYCN. Pulsed stable isotope-resolved metabolomics utilizing 13C-glucose labeling demonstrated higher de novo serine synthesis in MYCN-amplified cells compared to cells with diploid MYCN. An independence of MYCN-amplified cells from exogenous serine and glycine was demonstrated by serine and glycine starvation, which attenuated nucleotide pools and proliferation only in cells with diploid MYCN but did not diminish these endpoints in MYCN-amplified cells. Proliferation was attenuated in MYCN-amplified cells by CRISPR/Cas9-mediated PHGDH knockout or treatment with PHGDH small molecule inhibitors without affecting cell viability. PHGDH inhibitors administered as single-agent therapy to NMRI-Foxn1nu/nu mice harboring patient-derived MYCN-amplified neuroblastoma xenografts slowed tumor growth. However, combining a PHGDH inhibitor with the standard-of-care chemotherapy drug, cisplatin, revealed antagonism of chemotherapy efficacy in vivo. Emergence of chemotherapy resistance was confirmed in the genetic PHGDH knockout model in vitro. Altogether, PHDGH knockout and inhibition by small molecules consistently slows proliferation, but stops short of killing the cells, which then establish resistance to classical chemotherapy. Although PHGDH inhibition with small molecules has produced encouraging results in other preclinical cancer models, this approach must be considered with caution in patients with neuroblastoma.
Project description:MYCN amplification in neuroblastoma leads to aberrant expression of MYCN oncoprotein, which binds active genes promoting transcriptional amplification. Yet how MYCN coordinates transcription elongation to meet productive transcriptional amplification and which elongation machinery represents MYCN-driven vulnerability remain to be identified. We conducted a targeted screen of transcription elongation factors and identified the super elongation complex (SEC) as a unique vulnerability in MYCN-amplified neuroblastomas. MYCN directly binds EAF1 and recruits SEC to enhance processive transcription elongation. Depletion of EAF1 or AFF1/AFF4, another core subunit of SEC, leads to a global reduction in transcription elongation and elicits selective apoptosis of MYCN-amplified neuroblastoma cells. A combination screen reveals SEC inhibition synergistically potentiates the therapeutic efficacies of FDA-approved BCL2 antagonist ABT-199, in part due to suppression of MCL1 expression, both in MYCN-amplified neuroblastoma cells and in patient-derived xenografts. These findings identify disruption of the MYCN-SEC regulatory axis as a promising therapeutic strategy in neuroblastoma.
Project description:The aim of the experiment is to identify genome wide binding sites for the transcription factor MYCN in MYCN non-amplified and MYCN amplified human neuroblastoma cell lines. Datasets are presented for the ChIP-seq analysis in the tetracycline inducible cell line SH-SY5Y-MYCN (SH-SY5Y/6TR(EU)/pTrex-Dest-30/MYCN), derivative of the parental cell line SH-SY5Y; for noninduced cells and for 24 and 48 hours of Tet induction. Analysis for patinet matched MYCN amplified cell lines SMS-KCN and SMS-KCNR is also included.
Project description:The ALK^F1174L mutation is associated with intrinsic and acquired resistance to crizotinib and cosegregates with MYCN in neuroblastoma. In this study, we generated a mouse model overexpressing ALK^F1174L in the neural crest. Comapred to mice expressing ALK^F1174L or MYCN alone, combined expression of the two aberrations led to development of neuroblastoma with a shorter latency and higher penetrance. Here, we evaluated the transcriptional profiles of MYCN-driven neuroblastomas with or without the expression of ALK^F1174L to determine the pathogenic consequences of the ALK^F1174L/MYCN interaction in neuroblastoma. 10 mice were analysed in this study. Five ALK^F1174L/MYCN tumors were compared with five MYCN tumors. Total RNA was extracted, samples were labeled and processed using the Agilent Low Input Quick Amp two color Cy3(sample) and Cy5 (mouse reference) labeling kit and hybridized to Agilent SurePrint G3 Mouse Gene Expression arrays.
Project description:Neuroblastoma is a pediatric tumor of the sympathetic nervous system. MYCN (V-myc myelocytomatosis viral-related oncogene, neuroblastoma derived [avian]) is amplified in 20% of neuroblastomas, and these tumors carry a poor prognosis. However, tumors without MYCN amplification also may have a poor outcome. Here, we identified downstream targets of MYCN by shRNA-mediated silencing MYCN in neuroblastoma cells. From these targets, 157 genes showed an expression profile correlating with MYCN mRNA levels in NB88, a series of 88 neuroblastoma tumors, and therefore represent in vivo relevant MYCN pathway genes. This 157-gene signature identified very poor prognosis tumors in NB88 and independent neuroblastoma cohorts and was more powerful than MYCN amplification or MYCN expression alone. Remarkably, this signature also identified poor outcome of a group of tumors without MYCN amplification. Most of these tumors have low MYCN mRNA levels but high nuclear MYCN protein levels, suggesting stabilization of MYCN at the protein level. One tumor has an MYC amplification and high MYC expression. Chip-on-chip analyses showed that most genes in this signature are directly regulated by MYCN. MYCN induces genes functioning in cell cycle and DNA repair while repressing neuronal differentiation genes. The functional MYCN-157 signature recognizes classical neuroblastoma with MYCN amplification, as well as a newly identified group marked by MYCN protein stabilization.
Project description:Bromodomain inhibition comprises a promising therapeutic strategy in cancer, particularly for hematologic malignancies. To date, however, genomic biomarkers to direct clinical translation have been lacking. We conducted a cell-based screen of genetically-defined cancer cell lines using a prototypical inhibitor of BET bromodomains. Integration of genetic features with chemosensitivity data revealed a robust correlation between MYCN amplification and sensitivity to bromodomain inhibition. We characterized the mechanistic and translational significance of this finding in neuroblastoma, a childhood cancer with frequent amplification of MYCN. Genome-wide expression analysis demonstrated downregulation of the MYCN transcriptional program accompanied by suppression of MYCN transcription. Functionally, bromodomain-mediated inhibition of MYCN impaired growth and induced apoptosis in neuroblastoma. BRD4 knock-down phenocopied these effects, establishing BET bromodomains as transcriptional regulators of MYCN. BET inhibition conferred a significant survival advantage in three in vivo neuroblastoma models, providing a compelling rationale for developing BET bromodomain inhibitors in patients with neuroblastoma. Significance: Biomarkers of response to small-molecule inhibitors of BET bromodomains, a new compound class with promising anti-cancer activity, have been lacking. Here, we reveal MYCN amplification as a strong genetic predictor of sensitivity to BET bromodomain inhibitors, demonstrate a mechanistic rationale for this finding, and provide a translational framework for clinical trial development of BET bromodomain inhibitors for pediatric patients with MYCN-amplified neuroblastoma. JQ1 is a novel thieno-triazolo-1,4-diazepine, which displaces BET bromodomains from chromatin by competitively binding to the acetyl lysine recognition pocket. BE(2)-C and Kelly cells were treated in triplicate with 1 µM JQ1 or DMSO for 24 hours. RNA was extracted and a decrease in MYCN transcript was confirmed by real time RT-PCR as described above. The samples were profiled using the Affymetrix PrimeView Human Gene Expression Array (Affymetrix) at Beth Israel Deaconess Medical Center (Boston, MA, USA).
Project description:Neuroblastoma is an embryonic tumor arising from immature sympathetic nervous system progenitor cells. MYCN and ALK are driver oncogenes both of which are specifically expressed during early neurogenesis. This is in line with the assumption that neuroblastoma arises through disruption of normal developmental processes. MYCN has a broad impact on the tumor phenotype; however, the details of the MYCN driven oncogenic program are far from clear. In order to gain further insight into the role of gene expression during neuroblastoma initiation and progression, we evaluated gene expression profiles of hyperplastic ganglia and tumors isolated from MYCN transgenic mice.
Project description:The MYCN locus is amplified in about half of high-risk neuroblastoma tumors. To identify genomic loci occupied by MYCN protein in the MYCN-amplified neuroblastoma cell lines NGP, Kelly and NB-1643, we performed chromatin immunoprecipitation coupled with Next-Generation Sequencing (ChIP-seq) using an anti-MYCN antibody.