Interplay of reactive oxygen species, intracellular Ca2+ and mitochondrial homeostasis in the apoptosis of prostate cancer cells by deoxypodophyllotoxin

J Cell Biochem. 2013 May;114(5):1124-34. doi: 10.1002/jcb.24455.


The limited treatment option for recurrent prostate cancer and the eventual resistance to conventional chemotherapy drugs has fueled continued interest in finding new anti-neoplastic agents of natural product origin. We previously reported anti-proliferative activity of deoxypodophyllotoxin (DPT) on human prostate cancer cells. Using the PC-3 cell model of human prostate cancer, the present study reveals that DPT induced apoptosis via a caspase-3-dependent pathway that is activated due to dysregulated mitochondrial function. DPT-treated cells showed accumulation of the reactive oxygen species (ROS), intracellular Ca (i)(2+) surge, increased mitochondrial membrane potential (MMP, ΔΨ(m)), Bax protein translocation to mitochondria and cytochrome c release to the cytoplasm. This resulted in caspase-3 activation, which in turn induced apoptosis. The antioxidant N-acetylcysteine (NAC) reduced ROS accumulation, MMP and Ca (i)(2+) surge, on the other hand the Ca(2+) chelator BAPTA inhibited the Ca( i)(2+) overload and MMP without affecting the increase of ROS, indicating that the generation of ROS occurred prior to Ca(2+) flux. This suggested that both ROS and Ca( i)(2+) signaling play roles in the increased MMP via Ca (i)(2+)-dependent and/or -independent mechanisms, since ΔΨ(m) elevation was reversed by NAC and BAPTA. This study provides the first evidence for the involvement of both ROS- and Ca( i)(2+)-activated signals in the disruption of mitochondrial homeostasis and the precedence of ROS production over the failure of Ca(2+) flux homeostasis.

Publication types

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

MeSH terms

  • Apoptosis / drug effects*
  • Calcium / metabolism*
  • Caspase 3 / metabolism
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Cytochromes c / metabolism
  • Drug Screening Assays, Antitumor
  • Drugs, Chinese Herbal
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Enzyme Activation / drug effects
  • G2 Phase Cell Cycle Checkpoints / drug effects
  • Homeostasis / drug effects*
  • Humans
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • M Phase Cell Cycle Checkpoints / drug effects
  • Male
  • Membrane Potential, Mitochondrial / drug effects
  • Mitochondria / drug effects
  • Mitochondria / metabolism*
  • Models, Biological
  • Podophyllotoxin / analogs & derivatives*
  • Podophyllotoxin / chemistry
  • Podophyllotoxin / pharmacology
  • Prostatic Neoplasms / metabolism
  • Prostatic Neoplasms / pathology*
  • Protein Transport / drug effects
  • Reactive Oxygen Species / metabolism*
  • bcl-2-Associated X Protein / metabolism


  • Drugs, Chinese Herbal
  • Reactive Oxygen Species
  • bcl-2-Associated X Protein
  • Egtazic Acid
  • deoxypodophyllotoxin
  • Cytochromes c
  • Caspase 3
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Podophyllotoxin
  • Calcium