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Reactive oxygen species regulate caspase activation in tumor necrosis factor-related apoptosis-inducing

Kamel Izeradjene1, Leslie Douglas, David M Tillman

  • 1Division of Molecular Therapeutics, Department of Hematology-Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA. kamel.izeradjene@stjude.org

Cancer Research
|August 17, 2005
PubMed

Insights

Carbonyl cyanide m-chlorophenylhydrazone (CCCP) enhances tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cancer cell death by generating reactive oxygen species (ROS). This ROS generation is crucial for caspase activation and apoptosis, even in TRAIL-resistant cells.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Oncology

Background:

  • The role of reactive oxygen species (ROS) in tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in solid tumors remains unclear.
  • TRAIL is a critical mediator of apoptosis, but resistance is a significant challenge in cancer therapy.

Purpose of the Study:

  • To investigate the impact of mitochondrial uncoupling agents on TRAIL-induced apoptosis in colon carcinoma cells.
  • To elucidate the role of ROS and caspase activation in this process.

Main Methods:

  • Utilized carbonyl cyanide m-chlorophenylhydrazone (CCCP) to induce mitochondrial uncoupling and ROS generation.
  • Assessed TRAIL-induced apoptosis, caspase activation, and mitochondrial membrane potential (DeltaPsim) in colon cancer cell lines (RKO, HT29, HCT8).
  • Employed ROS scavengers, caspase inhibitors, and overexpression of apoptosis-regulating proteins (Bcl-2, X-linked inhibitor of apoptosis) to dissect molecular pathways.

Main Results:

  • CCCP treatment reduced DeltaPsim and increased ROS production, enhancing TRAIL-induced apoptosis in TRAIL-resistant colon cancer cells.
  • ROS generation by CCCP was essential for TRAIL-induced activation of Bax and caspases, including caspase-8.
  • Overexpression of Bcl-2 protected cells from death, while X-linked inhibitor of apoptosis (XIAP) overexpression inhibited apoptosis, indicating a role for effector caspases and XIAP inactivation.
  • Apoptosis proceeded via a caspase-9-independent pathway, involving caspase-3 activation and Smac/DIABLO release.

Conclusions:

  • Mitochondrial uncoupling, through ROS generation, sensitizes TRAIL-resistant colon cancer cells to apoptosis.
  • The mechanism involves caspase-9-independent activation of caspase-3, facilitated by ROS and leading to XIAP inactivation.

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