Project description:The identification of subtype-specific translocations has revolutionized diagnostics of sarcoma and provided new insight into oncogenesis. We used RNA-Seq to investigate samples diagnosed as small round cell tumors of bone, possibly Ewing sarcoma, but lacking the canonical EWSR1-ETS translocation. A new fusion was observed between the BCL6 co-repressor (BCOR) and the testis specific cyclin B3 (CCNB3) genes on chromosome X. RNA-Seq results were confirmed by RT-PCR and cloning the tumor-specific genomic translocation breakpoints. 24 BCOR-CCNB3-positive tumors were identified among a series of 594 sarcomas. Gene profiling experiments indicate that BCOR-CCNB3-positive cases are biologically distinct from other sarcomas, particularly EwingM-bM-^@M-^Ys sarcoma. Finally, we show that CCNB3 immunohistochemistry is a powerful diagnostic marker for this group of sarcoma and that over-expression of BCOR-CCNB3 or of a truncated CCNB3 activates S-phase in NIH3T3 cells. Thus the intrachromosomal X fusion described here represents a new subtype of bone sarcoma caused by a novel gene fusion mechanism. Comparison of expression profiles of 10 BCOR-CCNB3 samples (plus 4 EWS-FLI1 Ewing sarcomas samples as control) with publicly available profiles of other tumor types.
Project description:The identification of subtype-specific translocations has revolutionized diagnostics of sarcoma and provided new insight into oncogenesis. We used RNA-Seq to investigate samples diagnosed as small round cell tumors of bone, possibly Ewing sarcoma, but lacking the canonical EWSR1-ETS translocation. A new fusion was observed between the BCL6 co-repressor (BCOR) and the testis specific cyclin B3 (CCNB3) genes on chromosome X. RNA-Seq results were confirmed by RT-PCR and cloning the tumor-specific genomic translocation breakpoints. 24 BCOR-CCNB3-positive tumors were identified among a series of 594 sarcomas. Gene profiling experiments indicate that BCOR-CCNB3-positive cases are biologically distinct from other sarcomas, particularly Ewing’s sarcoma. Finally, we show that CCNB3 immunohistochemistry is a powerful diagnostic marker for this group of sarcoma and that over-expression of BCOR-CCNB3 or of a truncated CCNB3 activates S-phase in NIH3T3 cells. Thus the intrachromosomal X fusion described here represents a new subtype of bone sarcoma caused by a novel gene fusion mechanism.
Project description:Ewing sarcoma (EwS) is an adolescent and young adult sarcoma characterized by chromosome translocations between members of the FET family of RNA binding proteins and members of the ETS family of transcription factors, the most frequent fusion being EWS-FLI1. EWS-FLI1 acts as a pioneer factor, creating de novo enhancers and activating genes located in the vicinity of EWS-FLI1-bound microsatellite sequences. recent results from our lab indicate that EWS-FLI1, which activates transcription through binding to the DNA at specific sites, can generate fully novel, unconventional transcription units in regions of the genome that are fully quiescent in normal cells (manuscript in preparation). The hypothesis of the project is that the open reading frames (ORFs) of these transcripts may encode peptides presented at the cell surface by HLA class I molecules and hence be recognized as non-self by the immune system. The aim of this study is to detect Ewing-specific neo-peptides/proteins using proteomics approach.
Project description:Ewing sarcoma is an aggressive pediatric small round cell tumor that predominantly occurs in bone. Approximately 85% of Ewing sarcomas harbor the EWS/FLI fusion protein, which arises from a chromosomal translocation, t(11:22)(q24:q12). EWS/FLI interacts with numerous lineage-essential transcription factors to maintain mesenchymal progenitors in an undifferentiated state. We previously showed that EWS/FLI binds the osteogenic transcription factor RUNX2 and prevents osteoblast differentiation. In this study, we investigated the role of another Runt-domain protein, RUNX3, in Ewing sarcoma. RUNX3 participates in mesenchymal-derived bone formation and is a context dependent tumor suppressor and oncogene. RUNX3 was detected in all Ewing sarcoma cells examined, whereas RUNX2 was detected in only 73% of specimens. Like RUNX2, RUNX3 binds to EWS/FLI via its Runt domain. EWS/FLI prevented RUNX3 from activating the transcription of a RUNX-responsive reporter, p6OSE2. Stable suppression of RUNX3 expression in the Ewing sarcoma cell line A673 delayed colony growth in anchorage independent soft agar assays and reversed expression of EWS/FLI-responsive genes. These results demonstrate an important role for RUNX3 in Ewing sarcoma. RNA-seq to compare transcriptiome of control A673 ewing sarcoma cells stably expression a non-target or RUNX3 shRNA
Project description:Oncogenic transformation in Ewing sarcoma tumors is driven by the fusion oncogene EWS-FLI1. The inducible expression of EWS-FLI1 (EF) in embryoid bodies, or collections of differentiating stem cells, generates cells with properties of Ewing sarcoma tumors, including characteristics of transformation. These cell lines exhibit anchorage-independent growth, a lack of contact inhibition and a strong Ewing sarcoma gene expression signature. These cells also demonstrate a requirement for the persistent expression of EWS-FLI1 for cell survival and growth. We used microarrays to detail the effects of doxycycline-inducible expression of EWS-FLI1 on the gene expression signature of cells derived from differentiating stem cells, or embryoid bodies. Triplicate biological replicates were collected and analyzed.
Project description:Fusion-transcription factors (fusion-TFs) represent a class of driver oncoproteins that are difficult to therapeutically target. Recently, protein degradation has emerged as a strategy to target these challenging oncoproteins. The mechanisms that regulate fusion-TF stability, however, are generally unknown. Using CRISPR-Cas9 screening, we discovered tripartite motif- containing 8 (TRIM8) as an E3 ubiquitin ligase that ubiquitinates and degrades EWS/FLI, a driver fusion-TF in Ewing sarcoma. Moreover, we identified TRIM8 as a selective dependency in Ewing sarcoma compared to >700 other cancer cell lines. Mechanistically, TRIM8 knockout led to an increase in EWS/FLI protein levels that was not tolerated. EWS/FLI acts as a neomorphic substrate for TRIM8, defining the selective nature of the dependency. Our results demonstrate that fusion-TF protein stability is tightly regulated and highlight fusion-oncoprotein specific regulators as selective therapeutic targets. This study provides a tractable strategy to therapeutically exploit oncogene overdose in Ewing sarcoma and potentially other fusion-TF driven cancers.
Project description:Oncogenic transformation in Ewing sarcoma tumors is driven by the fusion oncogene EWS-FLI1. The inducible expression of EWS-FLI1 (EF) in embryoid bodies, or collections of differentiating stem cells, generates cells with properties of Ewing sarcoma tumors, including characteristics of transformation. These cell lines exhibit anchorage-independent growth, a lack of contact inhibition and a strong Ewing sarcoma gene expression signature. These cells also demonstrate a requirement for the persistent expression of EWS-FLI1 for cell survival and growth.
Project description:Posterior homeobox D genes, in particular HOXD13, are over-expressed by Ewing sarcoma, a tumor driven by the oncogenic fusion protein EWS-FLI1. Here, we have found that EWS-FLI1 maintains HOXD13 expression through a GGAA microsatellite enhancer in the developmental posterior HOXD regulatory domain. Activation of this enhancer is EWS-FLI1 dependent and epigenomic silencing of this region leads to loss of HOXD13 expression in Ewing sarcoma cells, but not in unrelated cells. To determine the function of HOXD13 activation in Ewing sarcoma we performed nascent RNA sequencing or RNA sequencing upon HOXD13 knockdown.
Project description:Ewing sarcoma is a prototypical fusion transcription factor-associated pediatric cancer that expresses EWS/FLI or highly related fusions. EWS/FLI dysregulates transcription to induce and maintain sarcomagenesis, but the mechanisms utilized are not fully understood. We therefore sought to define the global effects of EWS/FLI on chromatin conformation and transcription in Ewing sarcoma. We found that EWS/FLI (and EWS/ERG) genomic localization is largely conserved across multiple patient-derived Ewing sarcoma cell lines. EWS/FLI binding is primarily associated with compartment activation, establishment of topologically-associated domain (TAD) boundaries, enhancer-promoter looping that involve both intra- and inter-TAD interactions, and gene activation. Importantly, local chromatin features provide the basis for transcriptional heterogeneity in regulation of direct EWS/FLI target genes across different Ewing sarcoma cell lines. These data demonstrate a key role of EWS/FLI in mediating genome-wide changes in chromatin configuration and support the notion that fusion transcription factors serve as master regulators through three-dimensional reprogramming of chromatin.
Project description:Ewing sarcoma is a prototypical fusion transcription factor-associated pediatric cancer that expresses EWS/FLI or highly related fusions. EWS/FLI dysregulates transcription to induce and maintain sarcomagenesis, but the mechanisms utilized are not fully understood. We therefore sought to define the global effects of EWS/FLI on chromatin conformation and transcription in Ewing sarcoma. We found that EWS/FLI (and EWS/ERG) genomic localization is largely conserved across multiple patient-derived Ewing sarcoma cell lines. EWS/FLI binding is primarily associated with compartment activation, establishment of topologically-associated domain (TAD) boundaries, enhancer-promoter looping that involve both intra- and inter-TAD interactions, and gene activation. Importantly, local chromatin features provide the basis for transcriptional heterogeneity in regulation of direct EWS/FLI target genes across different Ewing sarcoma cell lines. These data demonstrate a key role of EWS/FLI in mediating genome-wide changes in chromatin configuration and support the notion that fusion transcription factors serve as master regulators through three-dimensional reprogramming of chromatin.