The quinone methide aurin is a heat shock response inducer that causes proteotoxic stress and Noxa-dependent apoptosis in malignant melanoma cells

J Biol Chem. 2015 Jan 16;290(3):1623-38. doi: 10.1074/jbc.M114.592626. Epub 2014 Dec 4.


Pharmacological induction of proteotoxic stress is rapidly emerging as a promising strategy for cancer cell-directed chemotherapeutic intervention. Here, we describe the identification of a novel drug-like heat shock response inducer for the therapeutic induction of proteotoxic stress targeting malignant human melanoma cells. Screening a focused library of compounds containing redox-directed electrophilic pharmacophores employing the Stress & Toxicity PathwayFinder(TM) PCR Array technology as a discovery tool, a drug-like triphenylmethane-derivative (aurin; 4-[bis(p-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one) was identified as an experimental cell stress modulator that causes (i) heat shock factor transcriptional activation, (ii) up-regulation of heat shock response gene expression (HSPA6, HSPA1A, DNAJB4, HMOX1), (iii) early unfolded protein response signaling (phospho-PERK, phospho-eIF2α, CHOP (CCAAT/enhancer-binding protein homologous protein)), (iv) proteasome impairment with increased protein-ubiquitination, and (v) oxidative stress with glutathione depletion. Fluorescence polarization-based experiments revealed that aurin displays activity as a geldanamycin-competitive Hsp90α-antagonist, a finding further substantiated by molecular docking and ATPase inhibition analysis. Aurin exposure caused caspase-dependent cell death in a panel of human malignant melanoma cells (A375, G361, LOX-IMVI) but not in non-malignant human skin cells (Hs27 fibroblasts, HaCaT keratinocytes, primary melanocytes) undergoing the aurin-induced heat shock response without impairment of viability. Aurin-induced melanoma cell apoptosis depends on Noxa up-regulation as confirmed by siRNA rescue experiments demonstrating that siPMAIP1-based target down-regulation suppresses aurin-induced cell death. Taken together, our data suggest feasibility of apoptotic elimination of malignant melanoma cells using the quinone methide-derived heat shock response inducer aurin.

Keywords: Apoptosis; Aurin; Drug Discovery; Heat Shock Protein 90 (Hsp90); Heat Shock Response; Melanoma; Noxa; Oxidative Stress; Proteotoxic Stress.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Vesicular Transport / metabolism*
  • Apoptosis*
  • Aurintricarboxylic Acid / analogs & derivatives*
  • Aurintricarboxylic Acid / chemistry
  • Cell Line, Tumor
  • Cell Survival
  • Drug Screening Assays, Antitumor
  • Flow Cytometry
  • Glutathione / metabolism
  • Heat-Shock Proteins / metabolism*
  • Heat-Shock Response / genetics
  • Humans
  • Indolequinones / chemistry
  • Inhibitory Concentration 50
  • Keratinocytes / drug effects
  • Melanocytes / drug effects
  • Melanoma / drug therapy*
  • Membrane Potential, Mitochondrial
  • Models, Molecular
  • Oxidative Stress
  • Polymerase Chain Reaction
  • RNA, Small Interfering / metabolism
  • Skin Neoplasms / drug therapy*
  • Up-Regulation


  • Adaptor Proteins, Vesicular Transport
  • Heat-Shock Proteins
  • Indolequinones
  • NOXA1 protein, human
  • RNA, Small Interfering
  • quinone methide
  • Aurintricarboxylic Acid
  • aurin
  • Glutathione

Associated data

  • PDB/1YET