Repression of the gene encoding the TGF-beta type II receptor is a major target of the EWS-FLI1 oncoprotein.
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.
Hahm
K B
KB
Laboratory of Cell Regulation, DBS, National Cancer Institute, Bethesda, Maryland 20892-5055, USA.
Cho
K
K
Lee
C
C
Im
Y H
YH
Chang
J
J
Choi
S G
SG
Sorensen
P H
PH
Thiele
C J
CJ
Kim
S J
SJ
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034802:RNA-Binding Protein EWS; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012512:Sarcoma, Ewing / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017384:Sequence Deletion; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D004268:DNA-Binding Proteins; C106031:EWS-FLI fusion protein; C497426:Fli1 protein, mouse; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D034802:RNA-Binding Protein EWS; D018125:Receptors, Transforming Growth Factor beta; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D008156:Luciferases; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II