Genome-wide functional screening identifies CDC37 as a crucial HSP90-cofactor for KIT oncogenic expression in gastrointestinal stromal tumors

Oncogene. 2014 Apr 3;33(14):1872-6. doi: 10.1038/onc.2013.127. Epub 2013 Apr 15.

Abstract

Most gastrointestinal stromal tumors (GISTs) contain KIT or PDGFRA kinase gain-of-function mutations, and therefore respond clinically to imatinib and other tyrosine kinase inhibitor (TKI) therapies. However, clinical progression subsequently results from selection of TKI-resistant clones, typically containing secondary mutations in the KIT kinase domain, which can be heterogeneous between and within GIST metastases in a given patient. TKI-resistant KIT oncoproteins require HSP90 chaperoning and are potently inactivated by HSP90 inhibitors, but clinical applications in GIST patients are constrained by the toxicity resulting from concomitant inactivation of various other HSP90 client proteins, beyond KIT and PDGFRA. To identify novel targets responsible for KIT oncoprotein function, we performed parallel genome-scale short hairpin RNA (shRNA)-mediated gene knockdowns in KIT-mutant GIST-T1 and GIST882. GIST cells were infected with a lentiviral shRNA pooled library targeting 11 194 human genes, and allowed to proliferate for 5-7 weeks, at which point assessment of relative hairpin abundance identified the HSP90 cofactor, CDC37, as one of the top six GIST-specific essential genes. Validations in treatment-naive (GIST-T1, GIST882) vs imatinib-resistant GISTs (GIST48, GIST430) demonstrated that: (1) CDC37 interacts with oncogenic KIT; (2) CDC37 regulates expression and activation of KIT and downstream signaling intermediates in GIST; and (3) unlike direct HSP90 inhibition, CDC37 knockdown accomplishes prolonged KIT inhibition (>20 days) in GIST. These studies highlight CDC37 as a key biologic vulnerability in both imatinib-sensitive and imatinib-resistant GIST. CDC37 targeting is expected to be selective for KIT/PDGFRA and a subset of other HSP90 clients, and thereby represents a promising strategy for inactivating the myriad KIT/PDGFRA oncoproteins in TKI-resistant GIST patients.

Publication types

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

MeSH terms

  • Cell Cycle Proteins / metabolism*
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Survival
  • Chaperonins / metabolism*
  • Drug Resistance, Neoplasm
  • Gastrointestinal Stromal Tumors / metabolism*
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic*
  • Gene Library
  • HSP90 Heat-Shock Proteins / metabolism*
  • Humans
  • Lentivirus / metabolism
  • Oncogenes
  • Protein Kinase Inhibitors / chemistry
  • Proto-Oncogene Proteins c-kit / metabolism*
  • RNA, Small Interfering / metabolism
  • Triterpenes / chemistry

Substances

  • CDC37 protein, human
  • Cell Cycle Proteins
  • HSP90 Heat-Shock Proteins
  • Protein Kinase Inhibitors
  • RNA, Small Interfering
  • Triterpenes
  • Proto-Oncogene Proteins c-kit
  • Chaperonins
  • tripterine