title: Caveolin-1 (CAV1) is a target of EWS/FLI-1 and a key determinant of the oncogenic phenotype and tumorigenicity of Ewing's sarcoma cells.
abstract: Tumors of the Ewing's sarcoma family (ESFT), such as Ewing's sarcoma (EWS) and primitive neuroectodermal tumors (PNET), are highly aggressive malignancies predominantly affecting children and young adults. ESFT express chimeric transcription factors encoded by hybrid genes fusing the EWS gene with several ETS genes, most commonly FLI-1. EWS/FLI-1 proteins are responsible for the malignant phenotype of ESFT, but only few of their transcriptional targets are known. Using antisense and short hairpin RNA-mediated gene expression knockdown, array analyses, chromatin immunoprecipitation methods, and reexpression studies, we show that caveolin-1 (CAV1) is a new direct target of EWS/FLI-1 that is overexpressed in ESFT cell lines and tumor specimens and is necessary for ESFT tumorigenesis. CAV1 knockdown led to up-regulation of Snail and the concomitant loss of E-cadherin expression. Consistently, loss of CAV1 expression inhibited the anchorage-independent growth of EWS cells and markedly reduced the growth of EWS cell-derived tumors in nude mice xenografts, indicating that CAV1 promotes the malignant phenotype in EWS carcinogenesis. Reexpression of CAV1 or E-cadherin in CAV1 knockdown EWS cells rescued the oncogenic phenotype of the original EWS cells, showing that the CAV1/Snail/E-cadherin pathway plays a central role in the expression of the oncogenic transformation functions of EWS/FLI-1. Overall, these data identify CAV1 as a key determinant of the tumorigenicity of ESFT and imply that targeting CAV1 may allow the development of new molecular therapeutic strategies for ESFT patients.
authors.affiliation: Laboratory of Experimental Carcinogenesis, Department of Radiation Medicine, Georgetown University Medical Center, Washington, DC 20057, USA.
authors.forename: Oscar M
authors.initials: OM
authors.lastname: Tirado
authors.forename: Silvia
authors.initials: S
authors.lastname: Mateo-Lozano
authors.forename: Joaquín
authors.initials: J
authors.lastname: Villar
authors.forename: Luis E
authors.initials: LE
authors.lastname: Dettin
authors.forename: Anna
authors.initials: A
authors.lastname: Llort
authors.forename: Soledad
authors.initials: S
authors.lastname: Gallego
authors.forename: Jozef
authors.initials: J
authors.lastname: Ban
authors.forename: Heinrich
authors.initials: H
authors.lastname: Kovar
authors.forename: Vicente
authors.initials: V
authors.lastname: Notario
mesh_terms: D000818:Animals; D015820:Cadherins / Q000096:biosynthesis / Q000235:genetics; D051242:Caveolin 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002448:Cell Adhesion / Q000235:genetics; D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051789:Proto-Oncogene Protein c-fli-1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016372:RNA, Antisense / Q000235:genetics; D034802:RNA-Binding Protein EWS; D012512:Sarcoma, Ewing / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D015854:Up-Regulation
chemical_list: C495540:CAV1 protein, human; D015820:Cadherins; D051242:Caveolin 1; C106031:EWS-FLI fusion protein; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D016372:RNA, Antisense; D034802:RNA-Binding Protein EWS; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors