EWS-FLI1 fusion protein up-regulates critical genes in neural crest development and is responsible for the observed phenotype of Ewing's family of tumors.
Tumor-specific translocations are common in tumors of mesenchymal origin. Whether the translocation determines the phenotype, or vice versa, is debatable. Ewing's family tumors (EFT) are consistently associated with an EWS-FLI1 translocation and a primitive neural phenotype. Histogenesis and classification are therefore uncertain. To test whether EWS-FLI1 fusion gene expression is responsible for the primitive neuroectodermal phenotype of EFT, we established a tetracycline-inducible EWS-FLI1 expression system in a rhabdomyosarcoma cell line RD. Cell morphology changed after EWS-FLI1 expression, resembling cultured EFT cells. Xenografts showed typical EFT features, distinct from tumors formed by parental RD. Neuron-specific microtubule gene MAPT, parasympathetic marker cholecystokinin, and epithelial marker keratin 18 were up-regulated. Conversely, myogenesis was diminished. Comparison of the up-regulated genes in RD-EF with the Ewing's signature genes identified important EWS-FLI1 downstream genes, many involved in neural crest differentiation. These results were validated by real-time reverse transcription-PCR analysis and RNA interference technology using small interfering RNA against EWS-FLI1 breakpoint. The present study shows that the neural phenotype of Ewing's tumors is attributable to the EWS-FLI1 expression and the resultant phenotype resembles developing neural crest. Such tumors have a limited neural phenotype regardless of tissue of origin. These findings challenge traditional views of histogenesis and tumor origin.
Hu-Lieskovan
Siwen
S
Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California 90027, USA.
Zhang
Jingsong
J
Wu
Lingtao
L
Shimada
Hiroyuki
H
Schofield
Deborah E
DE
Triche
Timothy J
TJ
D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D045744:Cell Line, Tumor; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D009432:Neural Crest / Q000196:embryology / Q000378:metabolism / Q000502:physiology*; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; D018233:Rhabdomyosarcoma, Embryonal / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D012512:Sarcoma, Ewing / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection; D014183:Transplantation, Heterologous; D015854:Up-Regulation
C106031:EWS-FLI fusion protein; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; D014157:Transcription Factors