A high-throughput assay for small molecule destabilizers of the KRAS oncoprotein

PLoS One. 2014 Aug 5;9(8):e103836. doi: 10.1371/journal.pone.0103836. eCollection 2014.

Abstract

Mutations in the Ras family of small GTPases, particularly KRAS, occur at high frequencies in cancer and represent a major unmet therapeutic need due to the lack of effective targeted therapies. Past efforts directed at inhibiting the activity of the Ras oncoprotein have proved difficult. We propose an alternative approach to target Ras by eliminating Ras protein from cells with pharmacological means. In this study, we developed a cell-based, high-content screening platform to identify small molecules that could promote the degradation of the KRAS oncoprotein. We generated an EGFP-KRASG12V fluorescence reporter system and implemented it for automated screening in 1536-well plates using high-throughput cellular imaging. We screened a library of clinically relevant compounds at wide dose range and identified Ponatinib and AMG-47a as two candidate compounds that selectively reduced the levels of EGFP-KRASG12V protein but did not affect EGFP protein in cells. This proof-of-principle study demonstrates that it is feasible to use a high-throughput screen to identify compounds that promote the degradation of the Ras oncoprotein as a new approach to target Ras.

Publication types

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

MeSH terms

  • Antineoplastic Agents / isolation & purification*
  • Antineoplastic Agents / pharmacology*
  • Cells, Cultured
  • Drug Screening Assays, Antitumor
  • Genes, Reporter
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HEK293 Cells
  • HeLa Cells
  • High-Throughput Screening Assays / methods*
  • Humans
  • Protein Stability / drug effects
  • Proto-Oncogene Proteins / antagonists & inhibitors*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins p21(ras)
  • Small Molecule Libraries / analysis*
  • Transfection
  • ras Proteins / antagonists & inhibitors*
  • ras Proteins / genetics
  • ras Proteins / metabolism*

Substances

  • Antineoplastic Agents
  • KRAS protein, human
  • Proto-Oncogene Proteins
  • Small Molecule Libraries
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins