Induction of reactive oxygen species-mediated autophagy by a novel microtubule-modulating agent

J Biol Chem. 2010 Jun 11;285(24):18737-48. doi: 10.1074/jbc.M109.091694. Epub 2010 Apr 19.


Autophagy is being increasingly implicated in both cell survival and death. However, the intricate relationships between drug-induced autophagy and apoptosis remain elusive. Here we demonstrate that a tubulin-binding noscapine analog, (R)-9-bromo-5-((S)-4,5-dimethoxy-1,3-dihydroisobenzofuran-1-yl)-4-methoxy-6-methyl-5,6,7,8-tetrahydro-[1,3]-di-oxolo[4,5-g]isoquinoline (Red-Br-nos), exerts a novel autophagic response followed by apoptotic cell death in human prostate cancer PC-3 cells. Red-Br-nos-induced autophagy was an early event detectable within 12 h that displayed a wide array of characteristic features including double membranous vacuoles with entrapped organelles, acidic vesicular organelles, and increased expression of LC3-II and beclin-1. Red-Br-nos-triggered release of reactive oxygen species (ROS) and attenuation of ROS by tiron, a ROS scavenger, reduced the sub-G(1) population suggesting ROS-dependent apoptosis. Abrogation of ROS also reduced autophagy indicating that ROS triggers autophagy. Pharmacological and genetic approaches to inhibit autophagy uncovered the protective role of Red-Br-nos-induced autophagy in PC-3 cells. Direct effects of the drug on mitochondria viz. disruption of normal cristae architecture and dissipation of mitochondrial transmembrane potential revealed a functional link between ROS generation, autophagy, and apoptosis induction. This is the first report to demonstrate the protective role of ROS-mediated autophagy and induction of caspase-independent ROS-dependent apoptosis in PC-3 cells by Red-Br-nos, a member of the noscapinoid family of microtubule-modulating anticancer agents.

Publication types

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

MeSH terms

  • Active Transport, Cell Nucleus
  • Antineoplastic Agents / pharmacology
  • Apoptosis
  • Autophagy*
  • Cell Line, Tumor
  • Green Fluorescent Proteins / chemistry
  • Humans
  • Membrane Potentials
  • Microscopy, Fluorescence / methods
  • Microtubules / metabolism*
  • Mitochondria / metabolism
  • Models, Biological
  • Noscapine / analogs & derivatives*
  • Noscapine / chemistry
  • Noscapine / pharmacology
  • Reactive Oxygen Species*
  • Tubulin Modulators / metabolism*


  • 9-bromo-5-(4,5-dimethoxy-1,3-dihydroisobenzofuran-1-yl)-4-methoxy-6-methyl-5,6,7,8-tetrahydro-(1,3)-dioxolo(4,5-g)isoquinoline
  • Antineoplastic Agents
  • Reactive Oxygen Species
  • Tubulin Modulators
  • Green Fluorescent Proteins
  • Noscapine