The EWS/FLI1 oncogenic protein inhibits expression of the Wnt inhibitor DICKKOPF-1 gene and antagonizes beta-catenin/TCF-mediated transcription.
Tumours of the Ewing family, which comprise Ewing's sarcoma and peripheral primitive neuroectodermal tumours, are highly aggressive and mostly affect children and adolescents. They are characterized by chromosomal translocations leading to the generation of fusion proteins between EWS (or very rarely FUS) and members of the E-twenty-six (ETS) family of transcription factors that are capable of transforming cells. EWS/FLI1, the most frequent fusion, is thought to cause transformation through activation or repression of specific target genes. We present evidence demonstrating that the Wnt inhibitor and beta-catenin/T-cell factor (TCF)-responsive gene DICKKOPF-1 (DKK-1) is a transcriptional target of EWS/FLI1, which can inhibit both basal and beta-catenin-induced transactivation of the DKK-1 promoter. Moreover, our data indicate that EWS/FLI1 has a more general effect on beta-catenin/TCF-mediated transcription since it can block transactivation of a consensus beta-catenin/TCF reporter construct. Consistently, Ewing tumour cells expressing different EWS/ETS translocations cannot engage beta-catenin/TCF-dependent transcription, whereas silencing of EWS/FLI1 restores beta-catenin responsiveness in A673 and RD-ES Ewing tumour cells. Accordingly, gene set enrichment analysis shows that beta-catenin/TCF target genes are significantly enriched among genes downregulated by EWS/FLI1 in the Ewing cell line A673. Mechanistically, the inhibitory effect of EWS/FLI1 can be overcome by a constitutively active TCF4 protein (TCF4-VP16). Moreover, EWS/FLI1 binds lymphoid enhancer factor 1, a TCF family member, and interferes with its binding to beta-catenin, which could explain its negative effect on beta-catenin/TCF-mediated transcription. Our results show that EWS/FLI1 inhibits both DKK-1 expression as well as beta-catenin/TCF-dependent transcription, which could contribute to progression of tumours of the Ewing family.
Navarro
Diego
D
Departamento de Biología del Cáncer, Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Arturo Duperier 4, E-28029, Madrid, Spain.
Agra
Noelia
N
Pestaña
Angel
A
Alonso
Javier
J
González-Sancho
José M
JM
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000037:antagonists & inhibitors*; D005810:Multigene Family; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000502:physiology*; D011401:Promoter Regions, Genetic; D025941:Protein Interaction Mapping; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012512:Sarcoma, Ewing / Q000473:pathology; D051822:T Cell Transcription Factor 1 / Q000037:antagonists & inhibitors*; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D019076:Transgenes; D051153:Wnt Proteins / Q000502:physiology; D051176:beta Catenin / Q000037:antagonists & inhibitors*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C495270:CTNNB1 protein, human; C501126:DKK1 protein, human; C106031:EWS-FLI fusion protein; D036341:Intercellular Signaling Peptides and Proteins; C497573:LEF1 protein, human; D051821:Lymphoid Enhancer-Binding Factor 1; D009363:Neoplasm Proteins; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; D051822:T Cell Transcription Factor 1; C532096:TCF4 protein, human; C497576:TCF7 protein, human; D000073940:Transcription Factor 4; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin