Identification and characterization of small molecule inhibitors of the ubiquitin ligases Siah1/2 in melanoma and prostate cancer cells

Cancer Lett. 2019 May 1:449:145-162. doi: 10.1016/j.canlet.2019.02.012. Epub 2019 Feb 14.


Inhibition of ubiquitin ligases with small molecule remains a very challenging task, given the lack of catalytic activity of the target and the requirement of disruption of its interactions with other proteins. Siah1/2, which are E3 ubiquitin ligases, are implicated in melanoma and prostate cancer and represent high-value drug targets. We utilized three independent screening approaches in our efforts to identify small-molecule Siah1/2 inhibitors: Affinity Selection-Mass Spectrometry, a protein thermal shift-based assay and an in silico based screen. Inhibitors were assessed for their effect on viability of melanoma and prostate cancer cultures, colony formation, prolyl-hydroxylase-HIF1α signaling, expression of selected Siah2-related transcripts, and Siah2 ubiquitin ligase activity. Several analogs were further characterized, demonstrating improved efficacy. Combination of the top hits identified in the different assays demonstrated an additive effect, pointing to complementing mechanisms that underlie each of these Siah1/2 inhibitors.

Keywords: Melanoma; Prostate cancer; Siah1; Siah2; Ubiquitin ligase.

Publication types

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

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Computer Simulation
  • Down-Regulation
  • Drug Screening Assays, Antitumor
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Male
  • Mass Spectrometry
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Mice
  • Nuclear Proteins / antagonists & inhibitors*
  • Nuclear Proteins / genetics
  • Prostatic Neoplasms / drug therapy*
  • Prostatic Neoplasms / genetics
  • Small Molecule Libraries / administration & dosage*
  • Small Molecule Libraries / isolation & purification
  • Small Molecule Libraries / pharmacology
  • Ubiquitin-Protein Ligases / antagonists & inhibitors*
  • Ubiquitin-Protein Ligases / genetics
  • Xenograft Model Antitumor Assays


  • Nuclear Proteins
  • Small Molecule Libraries
  • Ubiquitin-Protein Ligases
  • seven in absentia proteins