Type I and type II reactions in TRAIL-induced apoptosis -- results from dose-response studies

Oncogene. 2005 Jan 6;24(1):130-40. doi: 10.1038/sj.onc.1208191.


Death receptor-induced apoptosis is paradigmatically mediated via the recruitment of FADD adapter molecule to the ligand/receptor complex and subsequent activation of caspase-8. However, several observations provided evidence that components of the mitochondrial apoptosis pathway are involved in death receptor-mediated apoptosis. In this regard, caspase-8-mediated activation of Bid induces the release of cytochrome c from the mitochondria, which, in turn, triggers the formation of the apoptosome protein complex, resulting in the activation of caspase-9. Whereas Bax or Bak were shown to be required for the proapoptotic effect of Bid, Bcl-2 was described to interfere with its action. Up to now, contradictory results regarding the role of Bcl-2 in TRAIL-induced apoptosis have been published. In order to study the influence of Bcl-2 on TRAIL-induced cell death more detailed, we utilized a tetracycline-regulated Bcl-2 expression system in Jurkat T cells. After having analysed the dose response for TRAIL-induced activation of caspase-8, -9, -3, breakdown of the mitochondrial membrane potential, and changes in the apoptotic morphology in cells expressing different Bcl-2 levels, we conclude that overexpression of Bcl-2 mediates a partial resistance towards lower doses of TRAIL that can be overcome when higher doses of TRAIL are applied. Thus, the requirement of the mitochondrial pathway for death receptor-induced apoptosis in type II cells should be reconsidered, since the protective effect of Bcl-2 is limited to lower TRAIL doses or early observation time points.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects*
  • Apoptosis Regulatory Proteins
  • Caspases / metabolism
  • Dose-Response Relationship, Drug
  • Humans
  • Jurkat Cells
  • Kinetics
  • Membrane Glycoproteins / pharmacology*
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • TNF-Related Apoptosis-Inducing Ligand
  • Time Factors
  • Tumor Necrosis Factor-alpha / pharmacology*


  • Antineoplastic Agents
  • Apoptosis Regulatory Proteins
  • Membrane Glycoproteins
  • Proto-Oncogene Proteins c-bcl-2
  • TNF-Related Apoptosis-Inducing Ligand
  • TNFSF10 protein, human
  • Tumor Necrosis Factor-alpha
  • Caspases