Aberrant TGF-beta function has been implicated in the pathogenesis of many diseases, and it has also suggested that diminished responsiveness to TGF-beta may contribute to the process of malignant transformation. This decreased responsiveness to TGF-beta could be caused by defects not only in TGF-beta expression of activation, but also by defects in the regulation of TGF-beta receptors. Ewing sarcoma (ES) specific chromosomal translocations fuse the EWS gene to a subset of the ets transcription factor family, the FLI1, ERG, or ETV1 gene. EWS-FLI1, EWS-EGR, and EWS-ETV1 are thought to act as aberrant transcription factors that bind DNA through their ETS DNA binding domains. Since ets transcription factors regulate expression of the TGF-beta type II receptor (TGF-beta RII), a putative tumor suppressor gene, we hypothesized that TGF-beta RII may be a target of these fusion proteins. We show that ES cell lines with the EWS-FLI1 gene fusion have reduced TGF-beta sensitivity, and that fusion positive ES cells and primary tumors both express low to undetectable levels of TGF-beta RII mRNA and protein. Co-transfection of the FLI1 gene and the TGF-b RII promoter induces promoter activity, while the EWS-FLI1 gene leads to suppression of TGF-beta RII promoter activity and also FLI1-induced promoter activity. Introduction of EWS-FLI1, EWS-ERG, or EWS-ETV1 in cells without the EWS-FLI1 gene fusion suppresses TGF-beta RII expression, whereas antisense EWS-FLI1 in ES cell lines with the EWS- FLI1 gene fusion restores its expression. Furthermore, introduction of normal TGF-beta RII into ES cell line restores TGF-b sensitivity and blocks tumorigenicity. These results indicate that transcriptional repression of TGF-beta RII is a major target of the EWS-FLI1, EWS-ERG, or EWS-ETV1 oncogene. - ets family proto-oncogenes, promoter, Transcription, Transcription Factors, Transforming growth factor-beta, Tumorigenicity,
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