Ewing sarcoma is consistently associated with chromosomal translocation and functional fusion of the EWSR1 gene to any of several structurally related transcription factor genes of the E26 transformation-specific family.
Fluorescence in situ hybridization (FISH) indicated a rearrangement of the EWS region on chromosome 22, which is highly specific for Ewing's sarcoma and PNET, which are referred to as the Ewing's sarcoma family of tumors (EFT).
It is proposed that EWSR1-hSNF2H may act as an oncogenic chromatin-remodeling factor and that its expression contributes to Ewing sarcoma/primitive neuroectodermal tumorigenesis.
EWSR1-FEV translocation is exceedingly rare in Ewing sarcoma, as FEV expression is restricted to prostate, brain and serotonin neuroendocrine cells (NE) and related tumours.
Ewing sarcoma (ES) family of tumors includes bone and soft tissue tumors that are often characterized by a specific translocation between chromosome 11 and 22, resulting in the EWS-FLI1 fusion gene.
The EWS/FLI1 fusion gene found in Ewing's sarcoma and primitive neuroectodermal tumor, is able to transform certain cell lines by acting as an aberrant transcription factor.
Trib1 and Nrg1 were demonstrated as target genes that are co-regulated by EWS-FLI1 and Foxq1, and are important for cell proliferation and survival of Ewing sarcoma.
We review recent progress in selected areas of Ewing sarcoma research, including the application of genome-wide chromatin immunoprecipitation analyses, to provide a comprehensive view of the EWS-FLI1 target gene repertoire, the identification of EWS-FLI1 target genes that may also point to therapeutically targetable pathways, and data from model systems as they relate to the elusive cell of origin of Ewing sarcoma and its possible similarities to mesenchymal stem cells.
The interaction between c-Jun, p300 and EWS-ER81 or EWS-Fli-1 may also be relevant to the regulation of other yet-to-be-identified genes that are responsible for EWS formation.
Exploring the mechanism of PAX7 expression in Ewing sarcoma using curated RNA- and ChIP-sequencing data, we demonstrate that the EWSR1 fusion protein is required for PAX7 expression in Ewing sarcoma and identify a candidate EWSR1-FLI1-bound PAX7 enhancer that coincides with both a consensus GGAA repeat-containing binding site and a peak of regulatory H3K27 acetylation.
Taken together, the authors demonstrated the role of EWS-FLI1 and ATG4B in autophagy in ES cells, and suggested EWS-FLI1 and ATG4B as potential therapeutic targets for ES.
We characterized the A673 cell line using a combination of spectral karyotyping (SKY), fluorescence in situ hybridization (FISH), and reverse transcriptase polymerase chain reaction (RT-PCR), which revealed the presence of a complex karyotype and a translocation involving chromosomes 11 and 22 and the fusion of EWS and FLI1 genes, both events being specific to ET.
The results indicated that Notch1 and its target genes, Hes family BHLH transcription factor 1 and Hes‑related family BHLH transcription factor with YRPW motif 1, were suppressed by miR‑34b directly In conclusion, EWS‑FLI1 may modulate miR‑34b expression directly or indirectly, and miR‑34b potentially has an oncogenic role in Ewing's sarcoma by downregulating Notch1.
In this issue of Cancer Cell, Riggi and colleagues use a genomic approach to define two distinct molecular mechanisms through which the chimeric EWS/FLI1 oncoprotein regulates target genes in Ewing sarcoma, expanding a framework upon which to model the target gene network and test strategies for antagonizing growth of this tumor.
All 30 clinical specimens had been confirmed to contain sufficient ES/PNET DNA by the demonstration of a rearrangement of the t(11;22)-associated EWS gene using an EWS cDNA probe on the same blots.
Rh1, which was previously categorized as an alveolar rhabdomyosarcoma cell line, also has a gene expression profile suggestive of Ewing sarcoma and expresses EWS-FLI1 fusion transcripts in which exon 7 of EWS is joined with exon 6 of FLI1.
Using CRISPR-mediated epigenome editing, repression of EWS-FLI1 targeted microsatellite enhancers halted aberrant gene expression and impaired the growth of Ewing sarcoma xenografts in vivo.