Project description:Primary pediatric Ewing sarcoma (ES), one uncharacterized sarcoma as well as primary and well established ES cell lines were compared to probes of different normal tissues 8 Ewing sarcoma patient samples (MuET-x), 3 primary ES cell lines (SB-KMS-y), 3 well established ES cell lines (A673, SK-N-MC, RD-ES) and 22 normal tissues (PBMC, spleen, thymus, stomach, ...., uterus, fetal brain, fetal liver) were analyzed.
Project description:Primary pediatric Ewing sarcoma (ES), one uncharacterized sarcoma as well as primary and well established ES cell lines were compared to probes of different normal tissues
Project description:In this study, we characterize the fusion protein produced by the EPC1-PHF1 translocation in Low Grade Endometrial Stromal Sarcoma (LG-ESS) and Ossifying FibroMyxoid Tumors (OFMT). We express the fusion protein and necessary controls in K562 Cells. The fusion protein assembles a mega-complex harboring both NuA4/TIP60 and PRC2 subunits and enzymatic activities and leads to mislocalization of chromatin marks in the genome, linked to aberrant gene expression.
Project description:Ewing sarcoma is a malignant small round blue cell tumor of bones and soft tissues, predominantly affecting children, adolescents and young adults. Ewing sarcoma is caused by chromosomal translocations that generate aberrant chimeric transcription factors, most frequently EWSR1::FLI1. Ewing sarcomas exhibit features of both neural and mesenchymal cells. The cell of origin of Ewing sarcoma and the mechanisms of EWSR1::FLI1-driven cell transformation are the subjects of long-standing debates, largely due to the absence of a representative animal model. By developing a robust Ewing sarcoma model in zebrafish, we provide evidence for a neural crest origin of this cancer. We show that neural crest-derived cells (NCCs) uniquely tolerate expression of the human EWSR1::FLI1 oncofusion protein in vivo and that targeted expression of the oncofusion in NCCs is sufficient to generate Ewing sarcoma tumors. In the trunk, EWSR1::FLI1 reprogrammed NCCs to a mesoderm-like state, including upregulation of the early mesoderm specifier tbxta (Brachyury/T) and mesenchymal genes pdgfra, twist1a, and prrx1a. Mesodermal reprogramming of trunk neural crest was evident by the ability of EWSR1::FLI1-expressing cells to induce ectopic fins throughout the body. Single-nucleus analysis of RNA expression and chromatin accessibility, combined with genome-wide profiling of EWSR1::FLI1 binding, revealed that EWSR1::FLI1 targets single GGAA-containing ETS sites in mesodermal developmental enhancers for neural crest to mesoderm reprogramming during cancer initiation, also binding to GGAA repeats in established tumors. These findings show that EWSR1::FLI1 hijacks normal ETS-dependent developmental pathways in embryonic NCCs to drive initiation of Ewing sarcoma.
Project description:Ewing sarcoma is a malignant small round blue cell tumor of bones and soft tissues, predominantly affecting children, adolescents and young adults. Ewing sarcoma is caused by chromosomal translocations that generate aberrant chimeric transcription factors, most frequently EWSR1::FLI1. Ewing sarcomas exhibit features of both neural and mesenchymal cells. The cell of origin of Ewing sarcoma and the mechanisms of EWSR1::FLI1-driven cell transformation are the subjects of long-standing debates, largely due to the absence of a representative animal model. By developing a robust Ewing sarcoma model in zebrafish, we provide evidence for a neural crest origin of this cancer. We show that neural crest-derived cells (NCCs) uniquely tolerate expression of the human EWSR1::FLI1 oncofusion protein in vivo and that targeted expression of the oncofusion in NCCs is sufficient to generate Ewing sarcoma tumors. In the trunk, EWSR1::FLI1 reprogrammed NCCs to a mesoderm-like state, including upregulation of the early mesoderm specifier tbxta (Brachyury/T) and mesenchymal genes pdgfra, twist1a, and prrx1a. Mesodermal reprogramming of trunk neural crest was evident by the ability of EWSR1::FLI1-expressing cells to induce ectopic fins throughout the body. Single-nucleus analysis of RNA expression and chromatin accessibility, combined with genome-wide profiling of EWSR1::FLI1 binding, revealed that EWSR1::FLI1 targets single GGAA-containing ETS sites in mesodermal developmental enhancers for neural crest to mesoderm reprogramming during cancer initiation, also binding to GGAA repeats in established tumors. These findings show that EWSR1::FLI1 hijacks normal ETS-dependent developmental pathways in embryonic NCCs to drive initiation of Ewing sarcoma.
Project description:Ewing sarcoma is an aggressive bone tumor of adolescence characterized by a hallmark EWSR1::FLI1 fusion oncogene. This chimeric protein drives tumorigenesis by reshaping transcriptional and epigenetic landscapes. However, how it is transcriptionally regulated and whether additional master transcription factors (MTFs) form a core regulatory circuit (CRC) in Ewing sarcoma remain unclear. Here, using an extensive panel of Ewing sarcoma cell lines and primary tumors, we mapped super-enhancers and identified strong enrichment of GGAA microsatellites, confirming their specificity to Ewing sarcoma as compared to other pediatric cancers and normal tissues. Integrating transcriptomic, epigenetic, 3D chromatin conformation, and dependency data, we predicted a set of MTFs potentially comprising a CRC. However, functional validation demonstrated that these MTFs neither establish auto-regulatory loops nor confer proliferative dependencies typical of CRC s in other pediatric tumors. Instead, EWSR1::FLI1 emerged as an “hegemonic” oncogene, regulating the expression of these MTFs without reciprocal regulation. Knockdown (KD) of EWSR1::FLI1 strongly reduced Ewing sarcoma cell proliferation and shifted H3K27ac profiles toward mesenchymal states, whereas silencing of individual or combined MTFs did not alter cell growth or EWSR1::FLI1 expression. These findings highlight the absence of a classical CRC in Ewing sarcoma and emphasize EWSR1::FLI1 as the dominant oncogene but also as a major vulnerability in this disease.