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Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c
07:42

Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c

Published on: June 29, 2011

X chromosome-linked inhibitor of apoptosis regulates cell death induction by proapoptotic receptor agonists

Eugene Varfolomeev1, Bruno Alicke, J Michael Elliott

  • 1Department of Protein Engineering, Genentech, Inc., South San Francisco, California 94080, USA.

The Journal of Biological Chemistry
|October 27, 2009
PubMed

Insights

IAP antagonists synergize with death receptor agonists to kill cancer cells. This combination bypasses the need for mitochondrial pathways, offering a novel therapeutic strategy for cancer treatment.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • Inhibitor of apoptosis (IAP) proteins are key regulators that prevent programmed cell death (apoptosis).
  • Targeting IAP proteins offers a potential strategy to enhance cancer cell death.
  • Proapoptotic receptor agonists activate extrinsic and intrinsic apoptotic pathways.

Purpose of the Study:

  • To investigate the synergistic effects of IAP antagonists with death receptor agonists (FasL and DR5 antibody) in cancer cells.
  • To elucidate the mechanisms underlying the synergistic cell death induction.
  • To determine the role of mitochondrial pathways and specific proteins in this process.

Main Methods:

  • Combination treatment of cancer cell lines with IAP antagonists and FasL or DR5 agonist antibody.
  • Assessment of synergistic cell death and tumor growth inhibition.
  • Analysis of apoptotic pathways, including caspase activation, Bid-mediated signaling, and mitochondrial involvement.
  • Gene knockdown experiments (Bid, XIAP) to dissect signaling pathways.

Main Results:

  • IAP antagonists combined with FasL or DR5 agonist antibody showed synergistic cancer cell death and tumor growth inhibition.
  • Single-agent IAP antagonists' activity depended on tumor necrosis factor-alpha signaling, but this was not required for the synergistic effect.
  • The combination therapy activated effector caspases independently of the mitochondrial pathway, even in the presence of Bid knockdown.

Conclusions:

  • IAP antagonists combined with death receptor agonists represent a potent strategy for cancer therapy.
  • This combination overcomes resistance mechanisms by bypassing the mitochondrial apoptotic pathway.
  • Targeting XIAP (X chromosome-linked IAP) is crucial for enabling death receptor agonists to induce apoptosis without mitochondrial amplification.

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