The insulin-like growth factor-I receptor is required for EWS/FLI-1 transformation of fibroblasts.
Ewing's family of tumors is characterized by a well described reciprocal translocation, t(11;22)(q24;q12), which produces a fusion protein (EWS/FLI-1) that transforms mouse fibroblasts. The EWS/FLI-1 fusion protein has been shown to act as a potent chimeric transcription factor. Overexpression of insulin-like growth factor-I receptor (IGF-IR) has been implicated in many tumor models as playing a role in cell growth and tumorigenesis. In addition, blockade of the IGF-IR inhibits the growth of Ewing's family of tumors cells. Therefore, we first studied whether the presence of the IGF-IR is required for transformation by the EWS/FLI-1 fusion protein. To perform this study, we used two previously described fibroblast cell lines, R- and W, derived from an IGF-IR knockout mouse and a wild-type littermate, respectively. Neither W nor R- cells without the fusion protein formed soft agar colonies. However, W clones expressing the fusion message (WF cells) formed soft agar colonies, whereas R- clones expressing the fusion message (R-F cells) did not form soft agar colonies. Because the IGF-IR is required for EWS/FLI-1 transformation, we chose to investigate whether altered signaling occurs from the IGF-IR when the EWS/FLI-1 fusion is present. WF cells demonstrated a greater degree of ligand-stimulated insulin receptor substrate-1 phosphorylation when compared with W cells, suggesting that expression of the EWS/FLI-1 fusion protein alters the IGF-IR signaling pathway.
Toretsky
J A
JA
Pediatric Oncology Branch, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA. jt@helix.nih.gov
Kalebic
T
T
Blakesley
V
V
LeRoith
D
D
Helman
L J
LJ
D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D003001:Cloning, Molecular; D005347:Fibroblasts / Q000166:cytology*; D051379:Mice; D018345:Mice, Knockout; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
C106031:EWS-FLI fusion protein; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; D014157:Transcription Factors; D017526:Receptor, IGF Type 1