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RIP1 is required for IAP inhibitor-mediated sensitization for TRAIL-induced apoptosis via a RIP1/FADD/caspase-8 cell

B A Abhari1, S Cristofanon, R Kappler

  • 1Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.

Oncogene
|August 15, 2012
PubMed

Insights

Small-molecule inhibitors of apoptosis proteins (IAPs) synergize with TRAIL receptor antibodies to kill neuroblastoma cells. Receptor-interacting protein 1 (RIP1) is essential for this combined cell death, offering a new therapeutic strategy.

Area of Science:

  • Oncology
  • Molecular Biology
  • Drug Discovery

Background:

  • Inhibitor of apoptosis (IAP) proteins are highly expressed in many cancers, making them promising therapeutic targets.
  • TRAIL receptor agonists (Mapatumumab, Lexatumumab) show potential for cancer treatment but often face resistance.

Purpose of the Study:

  • To investigate the synergistic effects of IAP inhibitors and TRAIL receptor agonists in neuroblastoma.
  • To identify the molecular mechanisms underlying this synergism, particularly the role of receptor-interacting protein 1 (RIP1).

Main Methods:

  • Combination treatment of neuroblastoma cells with small-molecule IAP inhibitors and TRAIL receptor antibodies (Mapatumumab/Lexatumumab).
  • Assessment of apoptosis induction and synergy using combination index calculations.
  • Analysis of RIP1 involvement through knockdown and kinase inhibition (Necrostatin-1).
  • Investigation of signaling pathways, including RIP1/FADD/caspase-8 complex formation and TNFα/NF-κB independence.

Main Results:

  • IAP inhibitors and TRAIL receptor antibodies exhibited strong synergy (combination index <0.1) in inducing apoptosis in neuroblastoma cells.
  • Receptor-interacting protein 1 (RIP1) was identified as a critical mediator, essential for forming the RIP1/FADD/caspase-8 complex and subsequent caspase activation.
  • RIP1 knockdown or kinase inhibition abrogated the synergistic apoptosis, confirming RIP1's central role.
  • The synergistic cell death mechanism was independent of nuclear factor-κB (NF-κB) and tumor necrosis factor-alpha (TNFα).

Conclusions:

  • Small-molecule IAP inhibitors sensitize neuroblastoma cells to TRAIL receptor agonists, leading to potent synergistic apoptosis.
  • RIP1 is a key mediator of this synergism, facilitating the formation of a death-inducing signaling complex and downstream caspase activation.
  • These findings provide critical insights into the mechanism of IAP inhibitor and TRAIL receptor agonist cooperation and suggest RIP1 as a potential therapeutic target in neuroblastoma.

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