title: The oncogenic properties of EWS/WT1 of desmoplastic small round cell tumors are unmasked by loss of p53 in murine embryonic fibroblasts.
abstract: BACKGROUND
  Desmoplastic small round cell tumor (DSRCT) is characterized by the presence of a fusion protein EWS/WT1, arising from the t (11;22) (p13;q12) translocation. Here we examine the oncogenic properties of two splice variants of EWS/WT1, EWS/WT1-KTS and EWS/WT1 + KTS.
  
  
  METHODS
  We over-expressed both EWS/WT1 variants in murine embryonic fibroblasts (MEFs) of wild-type, p53+/- and p53-/- backgrounds and measured effects on cell-proliferation, anchorage-independent growth, clonogenicity after serum withdrawal, and sensitivity to cytotoxic drugs and gamma irradiation in comparison to control cells. We examined gene expression profiles in cells expressing EWS/WT1. Finally we validated our key findings in a small series of DSRCT.
  
  
  RESULTS
  Neither isoform of EWS/WT1 was sufficient to transform wild-type MEFs however the oncogenic potential of both was unmasked by p53 loss. Expression of EWS/WT1 in MEFs lacking at least one allele of p53 enhanced cell-proliferation, clonogenic survival and anchorage-independent growth. EWS/WT1 expression in wild-type MEFs conferred resistance to cell-cycle arrest after irradiation and daunorubicin induced apoptosis. We show DSRCT commonly have nuclear localization of p53, and copy-number amplification of MDM2/MDMX. Expression of either isoform of EWS/WT1 induced characteristic mRNA expression profiles. Gene-set enrichment analysis demonstrated enrichment of WNT pathway signatures in MEFs expressing EWS/WT1 + KTS. Wnt-activation was validated in cell lines with over-expression of EWS/WT1 and in DSRCT.
  
  
  CONCLUSIONS
  In conclusion, we show both isoforms of EWS/WT1 have oncogenic potential in MEFs with loss of p53. In addition we provide the first link between EWS/WT1 and Wnt-pathway signaling. These data provide novel insights into the function of the EWS/WT1 fusion protein which characterize DSRCT.
authors: Pratiti
authors: P
authors: Bandopadhayay
authors: Anissa M
authors: AM
authors: Jabbour
authors: Christopher
authors: C
authors: Riffkin
authors: Marika
authors: M
authors: Salmanidis
authors: Lavinia
authors: L
authors: Gordon
authors: Dean
authors: D
authors: Popovski
authors: Lin
authors: L
authors: Rigby
authors: David M
authors: DM
authors: Ashley
authors: David N
authors: DN
authors: Watkins
authors: David M
authors: DM
authors: Thomas
authors: Elizabeth
authors: E
authors: Algar
authors: University of Melbourne, Royal Parade, Parkville, Melbourne, Victoria 3052, Australia. Ekert@wehi.edu.au.
authors: Paul G
authors: PG
authors: Ekert
mesh_terms: D000818:Animals; D017209:Apoptosis; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D056915:DNA Copy Number Variations; D003630:Daunorubicin / Q000494:pharmacology; D058405:Desmoplastic Small Round Cell Tumor / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance; D059467:Transcriptome; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics*; D060449:Wnt Signaling Pathway
chemical_list: D018797:Cell Cycle Proteins; C106032:EWS1-WT1 fusion protein, human; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D003630:Daunorubicin