Discovery of Mdm2-MdmX E3 ligase inhibitors using a cell-based ubiquitination assay

Cancer Discov. 2011 Sep;1(4):312-25. doi: 10.1158/2159-8290.CD-11-0104. Epub 2011 Jul 28.


E3 ubiquitin ligases are of interest as drug targets for their ability to regulate protein stability and function. The oncogene Mdm2 is an attractive E3 ligase to target, as it is the key negative regulator of the tumor suppressor p53, which controls the transcription of genes involved in cell fate. Overexpression of Mdm2 facilitates tumorigenesis by inactivating p53, and through p53-independent oncogenic effects. We developed a high-throughput cellular Mdm2 auto-ubiquitination assay, which we used to discover a class of small-molecule Mdm2 ligase activity inhibitors. These compounds inhibit Mdm2 and p53 ubiquitination in cells, reduce viability of cells with wild-type p53, and synergize with DNA-damaging agents to cause cell death. We determined that these compounds effectively inhibit the E3 ligase activity of the Mdm2-MdmX hetero-complex. This mechanism may be exploitable to create a new class of anti-tumor agents.

Publication types

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

MeSH terms

  • Apoptosis / drug effects
  • Cell Cycle Proteins
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • DNA Damage / drug effects
  • Enzyme Inhibitors / pharmacology*
  • HCT116 Cells
  • High-Throughput Screening Assays / methods*
  • Humans
  • Nuclear Proteins / antagonists & inhibitors*
  • Nuclear Proteins / metabolism
  • Oncogenes / drug effects
  • Proto-Oncogene Proteins / antagonists & inhibitors*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-mdm2 / antagonists & inhibitors*
  • Proto-Oncogene Proteins c-mdm2 / metabolism
  • Transcription, Genetic / drug effects
  • Tumor Suppressor Protein p53 / antagonists & inhibitors
  • Tumor Suppressor Protein p53 / metabolism
  • Ubiquitin-Protein Ligases / antagonists & inhibitors*
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination / drug effects*


  • Cell Cycle Proteins
  • Enzyme Inhibitors
  • MDM4 protein, human
  • Nuclear Proteins
  • Proto-Oncogene Proteins
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • MDM2 protein, human
  • Proto-Oncogene Proteins c-mdm2
  • Ubiquitin-Protein Ligases