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

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.

Source: The Journal of Experimental Medicine - August 6, 2018 Category: Internal Medicine Authors: Stolte, B., Iniguez, A. B., Dharia, N. V., Robichaud, A. L., Conway, A. S., Morgan, A. M., Alexe, G., Schauer, N. J., Liu, X., Bird, G. H., Tsherniak, A., Vazquez, F., Buhrlage, S. J., Walensky, L. D., Stegmaier, K. Tags: Solid Tumors Articles Source Type: research