Inhibition of autophagosome formation by the benzoporphyrin derivative verteporfin

J Biol Chem. 2011 Mar 4;286(9):7290-300. doi: 10.1074/jbc.M110.139915. Epub 2010 Dec 30.

Abstract

Autophagy enables cells to degrade and recycle cytoplasmic materials both as a housekeeping mechanism and in response to extracellular stress such as nutrient deprivation. Recent studies indicate that autophagy also functions as a protective mechanism in response to several cancer therapy agents, making it a prospective therapeutic target. Few pharmacological inhibitors suitable for testing the therapeutic potential of autophagy inhibition in vivo are known. An automated microscopy assay was used to screen >3,500 drugs and pharmacological agents and identified one drug, verteporfin, as an inhibitor of autophagosome accumulation. Verteporfin is a benzoporphyrin derivative used in photodynamic therapy, but it inhibits autophagy without light activation. Verteporfin did not inhibit LC3/Atg8 processing or membrane recruitment in response to autophagic stimuli, but it inhibited drug- and starvation-induced autophagic degradation and the sequestration of cytoplasmic materials into autophagosomes. Transient exposure to verteporfin in starvation conditions reduced cell viability whereas cells in nutrient-rich medium were unaffected by drug treatment. Analysis of structural analogs indicated that the activity of verteporfin requires the presence of a substituted cyclohexadiene at ring A of the porphyrin core but that it can tolerate a number of large substituents at rings C and D. The existence of an autophagy inhibitor among FDA-approved drugs should facilitate the investigation of the therapeutic potential of autophagy inhibition in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology*
  • Autophagy / drug effects*
  • Autophagy / physiology
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Dextrans / pharmacokinetics
  • Drug Design
  • Female
  • Fluorescein-5-isothiocyanate / analogs & derivatives
  • Fluorescein-5-isothiocyanate / pharmacokinetics
  • Green Fluorescent Proteins / pharmacokinetics
  • Humans
  • Microscopy, Electron
  • Phagosomes / drug effects*
  • Phagosomes / physiology
  • Phagosomes / ultrastructure
  • Porphyrins / chemistry
  • Porphyrins / pharmacology*
  • Verteporfin

Substances

  • Antineoplastic Agents
  • Dextrans
  • Porphyrins
  • enhanced green fluorescent protein
  • fluorescein isothiocyanate dextran
  • Verteporfin
  • Green Fluorescent Proteins
  • Fluorescein-5-isothiocyanate