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Inhibition of TRAIL-induced apoptosis by Bcl-2 overexpression

Simone Fulda1, Eric Meyer, Klaus-Michael Debatin

  • 1University Children's Hospital, Prittwitzstr. 43, D-89075 Ulm, Germany.

Oncogene
|April 12, 2002
PubMed

Insights

Bcl-2 protein can block tumor cell death induced by TRAIL, a cancer therapy. This resistance mechanism varies by cancer type, suggesting tailored therapeutic strategies are needed for effective cancer treatment.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Death Research

Background:

  • Cancer treatment resistance is a significant clinical challenge, often linked to apoptosis pathway defects.
  • Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) shows promise for cancer therapy by inducing programmed cell death (apoptosis).
  • Bcl-2, an anti-apoptotic protein, can confer resistance to various cancer treatments.

Purpose of the Study:

  • To investigate the role of Bcl-2 in regulating TRAIL-induced apoptosis across different cancer cell types.
  • To elucidate the molecular mechanisms by which Bcl-2 influences TRAIL signaling pathways.
  • To identify potential cell type-specific resistance mechanisms to TRAIL therapy.

Main Methods:

  • Overexpression of Bcl-2 in neuroblastoma, glioblastoma, breast carcinoma, and lymphoblastoid cell lines.
  • Assessment of TRAIL-induced apoptosis markers, including caspase cleavage (caspase-8, -9, -7, -3), substrate cleavage (DFF45, PARP), and mitochondrial integrity (cytochrome c, AIF, Smac release).
  • Evaluation of X-linked inhibitor of apoptosis protein (XIAP) involvement in TRAIL resistance.

Main Results:

  • Bcl-2 overexpression conferred resistance to TRAIL in neuroblastoma, glioblastoma, and breast carcinoma cells by inhibiting caspase activation and mitochondrial apoptosis.
  • Bcl-2's protective effect involved blocking caspase-8 activation upstream and downstream of mitochondria, as well as inhibiting caspase-9, -7, and -3 activation.
  • In contrast, TRAIL induced apoptosis in SKW lymphoblastoid cells independently of Bcl-2, although Bcl-2 still inhibited mitochondrial damage.
  • XIAP overexpression also conferred TRAIL resistance, indicating a role for XIAP in apoptosis amplification.

Conclusions:

  • Bcl-2 and XIAP represent cell type-dependent regulators of TRAIL signaling, contributing to treatment resistance in certain cancers.
  • Understanding these resistance mechanisms is crucial for developing effective TRAIL-based cancer therapies.
  • Targeting molecular pathways that mediate resistance to TRAIL may be necessary for optimizing its clinical application in oncology.

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