Role of autophagy in chemoresistance: regulation of the ATM-mediated DNA-damage signaling pathway through activation of DNA-PKcs and PARP-1

Biochem Pharmacol. 2012 Mar 15;83(6):747-57. doi: 10.1016/j.bcp.2011.12.029. Epub 2011 Dec 29.


Capsaicin treatment was previously reported to reduce the sensitivity of breast cancer cells, but not normal MCF10A cells, to apoptosis. The present study shows that autophagy is involved in cellular resistance to genotoxic stress, through DNA repair. Capsaicin treatment of MCF-7 cells induced S-phase arrest and autophagy through the AMPKα-mTOR signaling pathway and the accumulation of p53 in the nucleus and cytosol, including a change in mitochondrial membrane potential. Capsaicin treatment also activated δ-H2AX, ataxia telangiectasia mutated (ATM), DNA-dependent protein kinase catalytic subunit (DNA-PKcs), and poly(ADP-ribose) polymerase (PARP)-1. Genetic or pharmacological disruption of autophagy attenuated capsaicin-induced phospho-ATM and phospho-DNA-PKcs and enhanced apoptotic cell death. ATM inhibitors, including Ku55933 and caffeine, and the genetic or pharmacological inhibition of p53 prevented capsaicin-induced DNA-PKcs phosphorylation and stimulated PARP-1 cleavage, but had no effect on microtubule-associated protein light chain 3 (LC3)-II levels. Ly294002, a DNA-PKcs inhibitor, boosted the capsaicin-induced cleavage of PARP-1. In M059K cells, but not M059J cells, capsaicin induced ATM and DNA-PKcs phosphorylation, p53 accumulation, and the stimulation of LC3II production, all of which were attenuated by knockdown of the autophagy-related gene atg5. Ku55933 attenuated capsaicin-induced phospho-DNA-PKcs, but not LC3II, in M059K cells. In human breast tumors, but not in normal tissues, AMPKα, ATM, DNA-PKcs, and PARP-1 were activated and LC3II was induced. The induction of autophagy by genotoxic stress likely contributes to the sustained survival of breast cancer cells through DNA repair regulated by ATM-mediated activation of DNA-PKcs and PARP-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • Ataxia Telangiectasia Mutated Proteins
  • Autophagy*
  • Breast Neoplasms / enzymology*
  • Breast Neoplasms / pathology
  • Caffeine / pharmacology
  • Capsaicin / pharmacology
  • Cell Cycle Proteins / antagonists & inhibitors
  • Cell Cycle Proteins / metabolism*
  • Cell Line, Tumor
  • Chromones / pharmacology
  • DNA Damage*
  • DNA-Activated Protein Kinase / metabolism*
  • DNA-Binding Proteins / antagonists & inhibitors
  • DNA-Binding Proteins / metabolism*
  • Drug Resistance, Neoplasm*
  • Enzyme Activation
  • Female
  • Humans
  • Morpholines / pharmacology
  • Nuclear Proteins / metabolism*
  • Phosphorylation
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases / metabolism*
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein Serine-Threonine Kinases / metabolism*
  • Pyrones / pharmacology
  • S Phase Cell Cycle Checkpoints / drug effects
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • Tumor Suppressor Protein p53 / antagonists & inhibitors
  • Tumor Suppressor Protein p53 / metabolism
  • Tumor Suppressor Proteins / antagonists & inhibitors
  • Tumor Suppressor Proteins / metabolism*


  • 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one
  • Cell Cycle Proteins
  • Chromones
  • DNA-Binding Proteins
  • Morpholines
  • Nuclear Proteins
  • Pyrones
  • Tumor Suppressor Protein p53
  • Tumor Suppressor Proteins
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Caffeine
  • PARP1 protein, human
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases
  • ATM protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • DNA-Activated Protein Kinase
  • PRKDC protein, human
  • Protein Serine-Threonine Kinases
  • Capsaicin