Repression of the gene encoding the TGF-beta type II receptor is a major target of the EWS-FLI1 oncoprotein

Nat Genet. 1999 Oct;23(2):222-7. doi: 10.1038/13854.

Abstract

Chromosomal translocations resulting in the expression of chimaeric transcription factors are frequently observed in tumour cells, and have been suggested to be a common mechanism in human carcinogenesis. Ewing sarcoma and related peripheral primitive neuroectodermal tumours share recurrent translocations that fuse the gene EWSR1 (formerly EWS) from 22q-12 to FLI1 and genes encoding other ETS transcription factors (which bind DNA through the conserved ETS domain). It has been shown that transduction of the gene EWSR1-FLI1 (encoding EWS-FLI1 protein) can transform NIH3T3 cells, and that mutants containing a deletion in either the EWS domain or the DNA-binding domain in FLI1 lose this ability. This indicates that the EWS-FLI1 fusion protein may act as an aberrant transcription factor, but the exact mechanism of oncogenesis remains unknown. Because ETS transcription factors regulate expression of TGFBR2 (encoding the TGF-beta type II receptor, TGF-beta RII; Refs 9,14), a putative tumour suppressor gene, we hypothesized that TGFBR2 may be a target of the EWS-FLI1 fusion protein. We show here that Ewing sarcoma [corrected] (ES) cell lines with the EWSR1-FLI1 fusion have reduced TGF-beta sensitivity, and that fusion-positive ES cells and primary tumours both express low or undetectable levels of TGFBR2 mRNA and protein product. Co-transfection of FLI1 and the TGFBR2 promoter induces promoter activity, whereas EWSR1-FLI1 leads to suppression of TGFBR2 promoter activity and FLI1-induced promoter activity. Introduction of EWSR1-FLI1 into cells lacking the EWSR1-FLI1 fusion suppresses TGF-beta RII expression, whereas antisense to EWSR1-FLI1 in ES cell lines positive for this gene fusion restores TGF-beta RII expression. Furthermore, introduction of normal TGF-beta RII into ES cell lines restores TGF-beta sensitivity and blocks tumorigenicity. Our results implicate TGF-beta RII as a direct target of EWS-FLI1.

MeSH terms

  • Animals
  • Cell Line
  • DNA-Binding Proteins / genetics
  • Gene Expression Regulation / drug effects
  • Humans
  • Immunohistochemistry
  • Luciferases / genetics
  • Luciferases / metabolism
  • Mice
  • Mice, Nude
  • Neuroblastoma / genetics
  • Neuroblastoma / metabolism
  • Neuroblastoma / pathology
  • Oncogene Proteins, Fusion / genetics
  • Oncogene Proteins, Fusion / physiology*
  • Promoter Regions, Genetic / genetics
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Protein c-fli-1
  • Proto-Oncogene Proteins*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA-Binding Protein EWS
  • Receptor, Transforming Growth Factor-beta Type II
  • Receptors, Transforming Growth Factor beta / genetics*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sarcoma, Ewing / genetics
  • Sarcoma, Ewing / metabolism
  • Sarcoma, Ewing / pathology
  • Sequence Deletion
  • Trans-Activators / genetics
  • Transcription Factors / genetics
  • Transcription Factors / physiology*
  • Transfection
  • Transforming Growth Factor beta / pharmacology
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / metabolism

Substances

  • DNA-Binding Proteins
  • EWS-FLI fusion protein
  • Fli1 protein, mouse
  • Oncogene Proteins, Fusion
  • Proto-Oncogene Protein c-fli-1
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • RNA-Binding Protein EWS
  • Receptors, Transforming Growth Factor beta
  • Recombinant Fusion Proteins
  • Trans-Activators
  • Transcription Factors
  • Transforming Growth Factor beta
  • Luciferases
  • Protein-Serine-Threonine Kinases
  • Receptor, Transforming Growth Factor-beta Type II