Targeting of EWS/FLI-1 by RNA interference attenuates the tumor phenotype of Ewing's sarcoma cells in vitro

J Orthop Res. 2004 Jul;22(4):910-7. doi: 10.1016/j.orthres.2003.12.008.


The defining cytogenetic abnormality of Ewing's sarcoma is the presence of a balanced t(11;22) translocation expressing the EWS/FLI-1 chimeric fusion protein. The effect of EWS/FLI-1 appears to be dominant negative since over-expression of EWS does not overcome the sarcoma phenotype. Previous studies have shown that EWS/FLI-1 as well as related sarcoma fusion proteins are necessary and sufficient to induce transformation both in vitro and in vivo. In this study we report that synthetic small interfering RNA (siRNA) specifically suppresses EWS/FLI-1 fusion gene expression in SK-ES Ewing's sarcoma cells. Knockdown of the EWS/FLI-1 fusion protein is correlated with decreased cell proliferation and increased apoptosis. We demonstrate that Ewing's sarcoma tumors as well as Ewing's sarcoma cell lines predominantly express the CXCR4 chemokine receptor. Using an in vitro invasion assay, the SDF-1 ligand of CXCR4 was shown to be a potent stimulus of invasion by SK-ES cells. Knockdown of EWS/FLI-1 by RNA interference abrogates the invasiveness of SK-ES cells. These experiments suggest that targeted silencing of the EWS/FLI-1 fusion gene by siRNA represents a promising strategy to study the loss of EWS/FLI-1 protein in Ewing's sarcoma cells of otherwise identical genetic background.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects
  • Cell Division / drug effects
  • Cell Line, Tumor
  • Gene Silencing / drug effects
  • Genes, Suppressor / physiology
  • Humans
  • Oncogene Proteins, Fusion / genetics*
  • Oncogene Proteins, Fusion / metabolism
  • Phenotype
  • Proto-Oncogene Protein c-fli-1
  • RNA, Small Interfering / pharmacology*
  • RNA-Binding Protein EWS
  • Receptors, CXCR4 / metabolism
  • Sarcoma, Ewing / drug therapy*
  • Sarcoma, Ewing / metabolism
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism


  • Antineoplastic Agents
  • EWS-FLI fusion protein
  • Oncogene Proteins, Fusion
  • Proto-Oncogene Protein c-fli-1
  • RNA, Small Interfering
  • RNA-Binding Protein EWS
  • Receptors, CXCR4
  • Transcription Factors