Unknown,Transcriptomics,Genomics,Proteomics

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A functional liaison between E2F and the aberrant ETS oncogene EWS/FLI1 in Ewing's sarcoma

ABSTRACT: Translocations of ETS transcription factors are driver mutations in diverse cancers. We investigated the genomic network of the ETS fusion EWS/FLI1 in Ewing's sarcoma (ESFT) as a model of ETS-driven tumorigenesis. ChIP-Seq and transcriptional analysis identified E2F3 as a principle co-factor of EWSFLI1 defining functionally distinct gene sets. While EWS/FLI1 binding independent of E2F3 predominantly associated with repressed differentiation genes, significant co-localization with E2F3 was discovered at proximal promoters of activated growth-related genes. Thus, EWS/FLI1 promotes oncogenesis by simultaneously perturbing differentiation state and augmenting the expression of genes co-regulated by E2F3. Integration of additional E2F3 and ERG localization data from prostate cancer containing TMPRSS2/ERG verified that the ETS-E2F module is also found in prostate cancer and may be of general relevance to ETS driven cancers. Timecourse with 6 timepoints of a doxicyclin inducible EWS-FLI1 knockdown in the A673 Ewing's Sarcoma celline

ORGANISM(S): Homo sapiens

SUBMITTER: Maximilian Kauer

PROVIDER: E-GEOD-27524 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:EWS-FLI1 is a chimeric ETS transcription factor that is, due to a chromosomal rearrangement, specifically expressed in Ewingâs sarcoma family tumors (ESFT) and is thought to be the initiating event in the development of the disease. Previous genomic profiling experiments have identified a number of EWS-FLI1 regulated genes and genes that discriminate ESFT from other sarcomas, but so far a comprehensive analysis of EWS-FLI1 dependent molecular functions characterizing this aggressive cancer is lacking. In this study a molecular function map of ESFT was constructed based on an integrative analysis of gene expression profiling experiments on a uniform microarray platform following EWS-FLI1 knockdown in a panel of five ESFT cell lines, and on gene expression data from the same platform of 59 primary ESFT tumors. Based on the assumption that EWS-FLI1 is the driving transcriptional force in ESFT pathogenesis, we predicted an inverse correlation of gene expression for EWS-FLI1 regulated genes between the putative tissue of origin and the cell lines under EWS-FLI1 knockdown conditions. Consistent with recent reports, mesenchymal progenitor cells (MPC) were found to fit this hypothesis best and were therefore used as the reference tissue for the construction of the molecular function map in ESFT. The interrelations of molecular pathways were visualized by measuring the similarity among annotated gene functions by gene sharing. The molecular function map highlighted distinct clusters of activities for EWS-FLI1 regulated genes in ESFT and revealed a striking difference between EWS-FLI1 up- and down-regulated genes: EWS-FLI1 induced genes mainly belong to cell cycle regulation, proliferation and response to DNA damage, while repressed genes were associated with differentiation and cell communication. This study revealed that EWS-FLI1 combines by distinct molecular mechanisms two important functions of cellular transformation in one protein, growth promotion and differentiation blockage. By taking MPC as a reference tissue a significant EWS-FLI1 signature was discovered in ESFT that only partially overlapped with previously published EWS-FLI1 dependent gene expression patterns, identifying a series of novel targets for the chimeric protein in ESFT. Our results may guide target selection for future ESFT specific therapies. Experiment Overall Design: EWS-FLI1 knock down was performed by expressing specific siRNAs against EWS-FLI1 as small hairpin (sh) RNAs from pSUPER-based retroviral expression constructs in 5 different Ewing's sarcoma cell lines (WE68, SK-N-MC, TC252, STA-ET-1, STA-ET-7.2). As a negative control in each cell line, pSTNeg (Ambion, Applied Biosystems, Brunn am Gebirge, Austria) encoding a scrambled shRNA with no significant similarity to human sequences was used.

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A functional liaison between E2F and the aberrant ETS oncogene EWS/FLI1 in Ewing's sarcoma

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