Genome-scale CRISPR-Cas9 screen identifies druggable dependencies in TP53 wild-type Ewing sarcoma

J Exp Med. 2018 Aug 6;215(8):2137-2155. doi: 10.1084/jem.20171066. Epub 2018 Jul 25.


Ewing sarcoma is a pediatric cancer driven by EWS-ETS transcription factor fusion oncoproteins in an otherwise stable genomic background. The majority of tumors express wild-type TP53, and thus, therapies targeting the p53 pathway would benefit most patients. To discover targets specific for TP53 wild-type Ewing sarcoma, we used a genome-scale CRISPR-Cas9 screening approach and identified and validated MDM2, MDM4, USP7, and PPM1D as druggable dependencies. The stapled peptide inhibitor of MDM2 and MDM4, ATSP-7041, showed anti-tumor efficacy in vitro and in multiple mouse models. The USP7 inhibitor, P5091, and the Wip1/PPM1D inhibitor, GSK2830371, decreased the viability of Ewing sarcoma cells. The combination of ATSP-7041 with P5091, GSK2830371, and chemotherapeutic agents showed synergistic action on the p53 pathway. The effects of the inhibitors, including the specific USP7 inhibitor XL-188, were rescued by concurrent TP53 knockout, highlighting the essentiality of intact p53 for the observed cytotoxic activities.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminopyridines / pharmacology
  • Animals
  • CRISPR-Associated Protein 9 / metabolism*
  • CRISPR-Cas Systems / genetics*
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival
  • Dipeptides / pharmacology
  • Drug Synergism
  • Female
  • Genome, Human*
  • Humans
  • Mice, Nude
  • Mutation / genetics
  • Neoplasm Proteins / metabolism
  • Peptides, Cyclic / pharmacology
  • Reproducibility of Results
  • Sarcoma, Ewing / genetics*
  • Sarcoma, Ewing / pathology
  • Thiophenes / pharmacology
  • Transcription, Genetic / drug effects
  • Tumor Suppressor Protein p53 / genetics*
  • Xenograft Model Antitumor Assays


  • ATSP-7041
  • Aminopyridines
  • Dipeptides
  • GSK2830371
  • Neoplasm Proteins
  • P5091
  • Peptides, Cyclic
  • TP53 protein, human
  • Thiophenes
  • Tumor Suppressor Protein p53
  • CRISPR-Associated Protein 9