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Cancer Res. 2019 May 1;79(9):2404-2414. doi: 10.1158/0008-5472.CAN-18-3066. Epub 2019 Feb 12.

MDM2 and MDM4 Are Therapeutic Vulnerabilities in Malignant Rhabdoid Tumors.

Author information

1
Department of Pediatric Oncology, Dana-Farber Cancer Institute and Division of Hematology/Oncology, Boston Children's Hospital, Boston, Massachusetts.
2
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts.
3
Broad Institute of Harvard and MIT, Cambridge, Massachusetts.
4
Harvard Medical School, Boston, Massachusetts.
5
Department of Biomedical Informatics, Harvard Medical School, Boston, Massachusetts.
6
Linde Program in Cancer Chemical Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.
7
Experimental Therapeutics Core and Belfer Center for Applied Cancer Science, Dana-Farber Cancer Institute, Boston, Massachusetts.
8
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts. Charles.roberts@stjude.org william_hahn@dfci.harvard.edu.
9
Department of Pediatric Oncology, Dana-Farber Cancer Institute and Division of Hematology/Oncology, Boston Children's Hospital, Boston, Massachusetts. Charles.roberts@stjude.org william_hahn@dfci.harvard.edu.
10
Department of Oncology, Comprehensive Cancer Center, St. Jude Children's Research Hospital, Memphis, Tennessee.

Abstract

Malignant rhabdoid tumors (MRT) are highly aggressive pediatric cancers that respond poorly to current therapies. In this study, we screened several MRT cell lines with large-scale RNAi, CRISPR-Cas9, and small-molecule libraries to identify potential drug targets specific for these cancers. We discovered MDM2 and MDM4, the canonical negative regulators of p53, as significant vulnerabilities. Using two compounds currently in clinical development, idasanutlin (MDM2-specific) and ATSP-7041 (MDM2/4-dual), we show that MRT cells were more sensitive than other p53 wild-type cancer cell lines to inhibition of MDM2 alone as well as dual inhibition of MDM2/4. These compounds caused significant upregulation of the p53 pathway in MRT cells, and sensitivity was ablated by CRISPR-Cas9-mediated inactivation of TP53. We show that loss of SMARCB1, a subunit of the SWI/SNF (BAF) complex mutated in nearly all MRTs, sensitized cells to MDM2 and MDM2/4 inhibition by enhancing p53-mediated apoptosis. Both MDM2 and MDM2/4 inhibition slowed MRT xenograft growth in vivo, with a 5-day idasanutlin pulse causing marked regression of all xenografts, including durable complete responses in 50% of mice. Together, these studies identify a genetic connection between mutations in the SWI/SNF chromatin-remodeling complex and the tumor suppressor gene TP53 and provide preclinical evidence to support the targeting of MDM2 and MDM4 in this often-fatal pediatric cancer. SIGNIFICANCE: This study identifies two targets, MDM2 and MDM4, as vulnerabilities in a deadly pediatric cancer and provides preclinical evidence that compounds inhibiting these proteins have therapeutic potential.

PMID:
30755442
PMCID:
PMC6497578
[Available on 2020-05-01]
DOI:
10.1158/0008-5472.CAN-18-3066

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