Nature Genetics
23, 222 - 227 (1999)
doi:10.1038/13854
Repression of the gene encoding the TGF- type II receptor is a major target of the EWS-FLI1 oncoproteinKi-Baik Hahm1, Keuna Cho1, Cecile Lee1, Young-Hyuck Im1, Jay Chang1, Shin-Geon Choi1, Poul H.B. Sorensen3, Carol J. Thiele2
& Seong-Jin Kim11
Laboratory of Cell Regulation and Carcinogenesis, DBS, National Cancer Institute, Bethesda, Maryland 20892-5055, USA. 2
Pediatric Oncology Branch, DCS, National Cancer Institute, Bethesda, Maryland 20892-5055, USA. 3
Department of Pathology, British Columbia's Children's Hospital, Vancouver, British Columbia V6H 3V4, Canada.
Correspondence should be addressed to Seong-Jin Kim Kims@dce41.nci.nih.govChromosomal translocations resulting in the expression of chimaeric transcription factors are frequently observed in tumour cells1, 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 factors2,
3,
4 (which bind DNA through the conserved ETS domain5,
6). 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 ability5,
6,
7,
8. 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- type II receptor, TGF- 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 embryonic stem (ES) cell lines with the EWSR1-FLI1 fusion have reduced TGF- 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- RII expression, whereas antisense to EWSR1-FLI1 in ES cell lines positive for this gene fusion restores TGF- RII expression. Furthermore, introduction of normal TGF- RII into ES cell lines restores TGF- sensitivity and blocks tumorigenicity. Our results implicate TGF- RII as a direct target of EWS-FLI1.
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