title: Myxoid liposarcoma-associated EWSR1-DDIT3 selectively represses osteoblastic and chondrocytic transcription in multipotent mesenchymal cells.
abstract: BACKGROUND
  Liposarcomas are the most common class of soft tissue sarcomas, and myxoid liposarcoma is the second most common liposarcoma. EWSR1-DDIT3 is a chimeric fusion protein generated by the myxoid liposarcoma-specific chromosomal translocation t(12;22)(q13;q12). Current studies indicate that multipotent mesenchymal cells are the origin of sarcomas. The mechanism whereby EWSR1-DDIT3 contributes to the phenotypic selection of target cells during oncogenic transformation remains to be elucidated.
  
  
  RESULTS
  Reporter assays showed that the EWSR1-DDIT3 myxoid liposarcoma fusion protein, but not its wild-type counterparts EWSR1 and DDIT3, selectively repressed the transcriptional activity of cell lineage-specific marker genes in multipotent mesenchymal C3H10T1/2 cells. Specifically, the osteoblastic marker Opn promoter and chondrocytic marker Col11a2 promoter were repressed, while the adipocytic marker Ppar-γ2 promoter was not affected. Mutation analyses, transient ChIP assays, and treatment of cells with trichostatin A (a potent inhibitor of histone deacetylases) or 5-Aza-2'-deoxycytidine (a methylation-resistant cytosine homolog) revealed the possible molecular mechanisms underlying the above-mentioned selective transcriptional repression. The first is a genetic action of the EWSR1-DDIT3 fusion protein, which results in binding to the functional C/EBP site within Opn and Col11a2 promoters through interaction of its DNA-binding domain and subsequent interference with endogenous C/EBPβ function. Another possible mechanism is an epigenetic action of EWSR1-DDIT3, which enhances histone deacetylation, DNA methylation, and histone H3K9 trimethylation at the transcriptional repression site. We hypothesize that EWSR1-DDIT3-mediated transcriptional regulation may modulate the target cell lineage through target gene-specific genetic and epigenetic conversions.
  
  
  CONCLUSIONS
  This study elucidates the molecular mechanisms underlying EWSR1-DDIT3 fusion protein-mediated phenotypic selection of putative target multipotent mesenchymal cells during myxoid liposarcoma development. A better understanding of this process is fundamental to the elucidation of possible direct lineage reprogramming in oncogenic sarcoma transformation mediated by fusion proteins.
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, University of Toyama, Toyama, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Suzuki
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Matsui
authors.forename: Mami
authors.initials: M
authors.lastname: Higashimoto
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: Shoji
authors.initials: S
authors.lastname: Seki
authors.forename: Hiraku
authors.initials: H
authors.lastname: Motomura
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hori
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Yahara
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kanamori
authors.forename: Tomoatsu
authors.initials: T
authors.lastname: Kimura
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002460:Cell Line; D019902:Chondrocytes / Q000378:metabolism; D024161:Collagen Type XI / Q000235:genetics; D019175:DNA Methylation; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D016350:Leucine Zippers; D018208:Liposarcoma, Myxoid / Q000235:genetics* / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D039902:Multipotent Stem Cells / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism; D053495:Osteopontin / Q000235:genetics; D047495:PPAR gamma / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D034802:RNA-Binding Protein EWS; D016601:RNA-Binding Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D051742:Transcription Factor CHOP / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014178:Translocation, Genetic
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D002148:Calmodulin-Binding Proteins; C497046:Col11a2 protein, mouse; D024161:Collagen Type XI; C500986:EWSR1 protein, human; C577608:EWSR1-DDIT3 protein, human; D015514:Oncogene Proteins, Fusion; D047495:PPAR gamma; D012333:RNA, Messenger; D034802:RNA-Binding Protein EWS; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D053495:Osteopontin; D051742:Transcription Factor CHOP; D006655:Histone Deacetylases