title: Suppression of FOXO1 is responsible for a growth regulatory repressive transcriptional sub-signature of EWS-FLI1 in Ewing sarcoma.
abstract: The Ewing sarcoma (ES) EWS-FLI1 chimeric oncoprotein is a prototypic aberrant ETS transcription factor with activating and repressive regulatory functions. We report that EWS-FLI1-repressed promoters are enriched in forkhead box (FOX) recognition motifs, and identify FOXO1 as a EWS-FLI1-suppressed regulator orchestrating a major subset of EWS-FLI1-repressed genes. In addition to FOXO1 regulation by direct promoter binding of EWS-FLI1, its subcellular localization and activity is regulated by cyclin-dependent kinase 2- and AKT-mediated phosphorylation downstream of EWS-FLI1. Restoration of nuclear FOXO1 expression in ES cells impaired proliferation and significantly reduced clonogenicity. Gene-expression profiling revealed a significant overlap between EWS-FLI1-repressed and FOXO1-activated genes. As a proof of principle for a potential therapeutic application of our findings, the treatment of ES cell lines with methylseleninic acid (MSA) reactivated endogenous FOXO1 in the presence of EWS-FLI1 in a dose- and time-dependent manner and induced massive cell death dependent on FOXO1. In an orthotopic xenograft mouse model, MSA increased FOXO1 expression in the tumor paralleled by a significant decrease in ES tumor growth. FOXO1 reactivation by small molecules may therefore serve as a promising strategy for a future ES-specific therapy.
authors.affiliation: Children's Cancer Research Institute, St Anna Kinderkrebsforschung, Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Niedan
authors.affiliation: Children's Cancer Research Institute, St Anna Kinderkrebsforschung, Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Kauer
authors.affiliation: 1] Children's Cancer Research Institute, St Anna Kinderkrebsforschung, Vienna, Austria [2] Department of Pediatrics, Medical University, Vienna, Austria.
authors.forename: D N T
authors.initials: DN
authors.lastname: Aryee
authors.affiliation: Division of Molecular Pathophysiology, Biocenter, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Kofler
authors.affiliation: Children's Cancer Research Institute, St Anna Kinderkrebsforschung, Vienna, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Schwentner
authors.affiliation: Division of Pediatric Hematology and Oncology, Department of Pediatrics and Adolescent Medicine, University Medical Center, Freiburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Meier
authors.affiliation: Children's Cancer Research Institute, St Anna Kinderkrebsforschung, Vienna, Austria.
authors.forename: U
authors.initials: U
authors.lastname: Pötschger
authors.affiliation: Division of Pediatric Hematology and Oncology, Department of Pediatrics and Adolescent Medicine, University Medical Center, Freiburg, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Kontny
authors.affiliation: 1] Children's Cancer Research Institute, St Anna Kinderkrebsforschung, Vienna, Austria [2] Department of Pediatrics, Medical University, Vienna, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Kovar
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D001665:Binding Sites; D001859:Bone Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016384:Consensus Sequence; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D051379:Mice; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D016566:Organoselenium Compounds / Q000494:pharmacology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D051789:Proto-Oncogene Protein c-fli-1 / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034802:RNA-Binding Protein EWS / Q000235:genetics / Q000378:metabolism*; D012512:Sarcoma, Ewing / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; C106031:EWS-FLI fusion protein; C085126:FOXO1 protein, human; C499517:FOXO3 protein, human; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D015514:Oncogene Proteins, Fusion; D016566:Organoselenium Compounds; D051789:Proto-Oncogene Protein c-fli-1; D034802:RNA-Binding Protein EWS; C008493:methylselenic acid; D051057:Proto-Oncogene Proteins c-akt; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2