Project description:We have performed a high-throughput RNA interference screen to identify targets inhibiting EWS-FLI1 driven cell proliferation in Ewing sarcoma cells. EWS-FLI1 expressing A673 Ewing sarcoma cells were screened both in presence and absence of EWS-FLI1 shRNA induction with druggable siRNA library. Leucine rich repeats and WD repeat Domain containing 1 (LRWD1) targeting siRNA pool was the strongest anti-proliferative hit identified only in presence of EWS-FLI1. Validation experiments confirmed the anti-proliferative effect of LRWD1 depletion especially in EWS-FLI1 expressing cells. Functional analysis of differentially expressed genes in LRWD1 depleted Ewing sarcoma cells showed over-representation of connective tissue development, cell projection morphogenesis and neuronal processes.
Project description:Ewing sarcoma (EWS) is a malignant pediatric bone cancer. Most Ewing sarcomas are driven by EWS-FLI1 oncogenic transcription factor that plays roles in transcriptional regulation, DNA damage response, cell cycle checkpoint control, and alternative splicing. USP1, a deubiquitylase which regulates DNA damage and replication stress responses, is overexpressed at both the mRNA and protein levels in EWS cell lines compared to human mesenchymal stem cells, the EWS cell of origin. The functional significance of high USP1 expression in Ewing sarcoma is not known. Here, we identify USP1 as a transcriptional target of EWS-FLI1 and a key regulator of EWS cell survival. We show that EWS-FLI1 knockdown decreases USP1 mRNA and protein levels. ChIP and ChIP-seq analyses show EWS-FLI1 occupancy on the USP1 promoter. Importantly, USP1 knockdown or inhibition arrests EWS cell growth and induces cell death by apoptosis. We observe destabilization of Survivin (also known as BIRC5 or IAP4) and activation of caspases-3 and -7 following USP1 knockdown or inhibition in the absence of external DNA damage stimuli. Notably, EWS cells display hypersensitivity to combinatorial treatment of doxorubicin or etoposide, EWS standard of care drugs, and USP1 inhibitor compared to single agents alone. Together, our study demonstrates that USP1 is regulated by EWS-FLI1, the USP1-Survivin axis promotes EWS cell survival, and USP1 inhibition sensitizes EWS cells to standard of care chemotherapy.
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 a highly aggressive tumor characterized by a translocation between members of the FET family of RNA binding proteins and one of several ETS transcription factors, with the most common translocation being EWS-FLI1. EWS-FLI1 leads to changes in gene expression through mechanisms that are not completely understood. We performed RNA sequencing analysis on primary pediatric human mesenchymal progenitor cells (pMPCs) expressing EWS-FLI1 in order to identify novel target genes. This analysis identified lnc277 as a previously uncharacterized long non-coding RNA upregulated by EWS-FLI1 in pMPCs. Inhibiting the expression of lnc277 diminished the ability of Ewing sarcoma cell lines to proliferate and form colonies in soft agar whereas inhibiting lnc277 had no effect on other cell types tested. By analyzing gene expression after shRNA knockdown, we found that both EWS-FLI1 and lnc277 repressed many more genes that they induced and that a significant fraction of EWS-FLI1 repressed targets were also repressed by lnc277. Analysis of primary human Ewing sarcoma RNA sequencing data further supports a role for lnc277 in mediating gene repression. We identified hnRNPK as an RNA binding protein that interacts directly with lnc277. We found a significant overlap in the genes repressed by hnRNPK and those repressed by both EWS-FLI1 and lnc277, suggesting that hnRNPK participates in lnc277 mediated gene repression. Thus, lnc277 is a previously uncharacterized long non-coding RNA downstream of EWS-FLI1 that facilitates the development of Ewing sarcoma via the repression of target genes. Our studies identify a novel mechanism of oncogenesis downstream of a chromosomal translocation and underscore the importance of lncRNA-mediated gene repression as a mechanism of EWS-FLI1 transcriptional regulation. A673 Ewing cells expressing an shRNA targeting hnRNPK or control were subjected to paired end RNA sequencing and compared to shGFP control.
Project description:We show that EWS-FLI1, an aberrant transcription factor responsible for the pathogenesis of Ewing sarcoma, reprograms gene regulatory circuits by directly inducing or directly repressing enhancers. At GGAA repeats, which lack regulatory potential in other cell types and are not evolutionarily conserved, EWS- FLI1 multimers potently induce chromatin opening, recruit p300 and WDR5, and create de novo enhancers. GGAA repeat enhancers can loop to physically interact with target promoters, as demonstrated by chromosome conformation capture assays. Conversely, EWS-FLI1 inactivates conserved enhancers containing canonical ETS motifs by displacing wild-type ETS transcription factors and abrogating p300 recruitment. ChIP-seq for of 4 histone modifications (H3K27ac, H3K4me1, H3K4me3 and H3K27me3), FLI1, p300, WDR5, ELF1 and GABPA in primary Ewing sarcomas, Ewing sarcoma cell lines (A673 and SKMNC cells), and mesenchymal stem cells (MSC). EWS-FLI1 was knocked down in Ewing sarcoma cell lines with lentiviral shRNAs (shFLI1 and shGFP control). EWS-FLI1 was expressed in MSCs with lentiviral expression vectors (pLIV EWSFLI1 or pLIV empty vector control). * Raw data not provided for the MSC and Primary Ewing sarcoma samples. *
Project description:Purpose: Our experimental results demonstrate an essential role for the lncRNA HOTAIR in Ewing sarcoma. We have repressed HOTAIR expression in three Ewing sarcoma cell lines and overexpressed HOTAIR, alone and with EWS-FLI1, in htert-immortalized human mesenchymal stem cells to evaluate its effects on gene expression in this cancer. Methods: RNA-Seq of Ewing sarcoma cell lines with HOTAIR represssed by GapmeR or treated with nonsilencing control, and hTERT-immortalized hMSCs with expression of control GFP, HOTAIR, or HOTAIR and EWS-FLI1, was used for gene expression analysis. Results: Defined gene expression signatures were defined as driven by HOTAIR in each cell line model, with a consensus set of gene identified in the Ewing sarcoma cell lines. Additionally, a set of genes regulated by HOTAIR independently of EWS-FLI1 was identified in the hTERT-hMSC models. Conclusions: HOTAIR expression regulates a set of genes critical to viability, cell adhesion, cell motility, and other markers of EMT and metastasis in Ewing sarcoma, independently of EWS-FLI1.
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:We show that EWS-FLI1, an aberrant transcription factor responsible for the pathogenesis of Ewing sarcoma, reprograms gene regulatory circuits by directly inducing or directly repressing enhancers. At GGAA repeats, which lack regulatory potential in other cell types and are not evolutionarily conserved, EWS- FLI1 multimers potently induce chromatin opening, recruit p300 and WDR5, and create de novo enhancers. GGAA repeat enhancers can loop to physically interact with target promoters, as demonstrated by chromosome conformation capture assays. Conversely, EWS-FLI1 inactivates conserved enhancers containing canonical ETS motifs by displacing wild-type ETS transcription factors and abrogating p300 recruitment. Mesenchymal stem cells (MSCs) and a Ewing sarcoma cell line (SKNMC) were analyzed by ATAC-seq. EWS-FLI1 was expressed in MSCs using a lentiviral vector (pLIV EWSFLI1 or pLIV empty vector control). * Raw data not provided for the MSC samples. *
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.