Targeting the epigenetic readers in Ewing sarcoma inhibits the oncogenic transcription factor EWS/Fli1

Oncotarget. 2016 Apr 26;7(17):24125-40. doi: 10.18632/oncotarget.8214.


Ewing Sarcoma is a rare bone and soft tissue malignancy affecting children and young adults. Chromosomal translocations in this cancer produce fusion oncogenes as characteristic molecular signatures of the disease. The most common case is the translocation t (11; 22) (q24;q12) which yields the EWS-Fli1 chimeric transcription factor. Finding a way to directly target EWS-Fli1 remains a central therapeutic approach to eradicate this aggressive cancer. Here we demonstrate that treating Ewing Sarcoma cells with JQ1(+), a BET bromodomain inhibitor, represses directly EWS-Fli1 transcription as well as its transcriptional program. Moreover, the Chromatin Immuno Precipitation experiments demonstrate for the first time that these results are a consequence of the depletion of BRD4, one of the BET bromodomains protein from the EWS-Fli1 promoter. In vitro, JQ1(+) treatment reduces the cell viability, impairs the cell clonogenic and the migratory abilities, and induces a G1-phase blockage as well as a time- and a dose-dependent apoptosis. Furthermore, in our in vivo model, we observed a tumor burden delay, an inhibition of the global vascularization and an increase of the mice overall survival. Taken together, our data indicate that inhibiting the BET bromodomains interferes with EWS-FLi1 transcription and could be a promising strategy in the Ewing tumors context.

Keywords: EWS/Fli1; Ewing sarcoma; JQ1; bromodomain; epigenetic.

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Apoptosis / drug effects
  • Azepines / pharmacology*
  • Biomarkers, Tumor / genetics
  • Bone Neoplasms / drug therapy
  • Bone Neoplasms / genetics
  • Bone Neoplasms / pathology*
  • Cell Cycle / drug effects
  • Cell Movement / drug effects
  • Cell Proliferation / drug effects
  • Epigenesis, Genetic*
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects*
  • Humans
  • Male
  • Mice
  • Mice, Nude
  • Oncogene Proteins, Fusion / antagonists & inhibitors*
  • Proteins / antagonists & inhibitors*
  • Proto-Oncogene Protein c-fli-1 / antagonists & inhibitors*
  • RNA-Binding Protein EWS / antagonists & inhibitors*
  • Sarcoma, Ewing / drug therapy
  • Sarcoma, Ewing / genetics
  • Sarcoma, Ewing / pathology*
  • Triazoles / pharmacology*
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays
  • Young Adult


  • (+)-JQ1 compound
  • Azepines
  • Biomarkers, Tumor
  • EWS-FLI fusion protein
  • Oncogene Proteins, Fusion
  • Proteins
  • Proto-Oncogene Protein c-fli-1
  • RNA-Binding Protein EWS
  • Triazoles
  • bromodomain and extra-terminal domain protein, human