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FLICE-like inhibitory protein blocks transforming growth factor beta 1-induced caspase activation and apoptosis in

Kent L Nastiuk1, Kiwon Yoo, Karen Lo

  • 1Department of Pathology and Laboratory Medicine, School of Medicine, University of California Irvine, Medical Sciences I D450, Irvine, CA 92697-4800, USA.

Molecular Cancer Research : MCR
|March 4, 2008
PubMed

Insights

FLICE-like inhibitory protein (FLIP) reduction triggers prostate cancer cell death. Restoring FLIP levels can prevent apoptosis, offering a potential therapeutic strategy for prostate cancer.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Androgen withdrawal causes prostate cancer regression but leads to androgen independence and metastasis.
  • Understanding androgen withdrawal-induced apoptosis is crucial for developing new prostate cancer therapies.
  • FLICE-like inhibitory protein (FLIP) is an apical caspase inhibitor whose expression decreases during castration-induced apoptosis in rats.

Purpose of the Study:

  • To investigate the functional role of FLIP in inhibiting prostate epithelial cell apoptosis.
  • To determine if FLIP levels influence the sensitivity of prostate cancer cells to apoptosis induced by transforming growth factor beta1 (TGFbeta1).

Main Methods:

  • Utilized the rat prostate epithelial cell line NRP-152, which undergoes apoptosis upon TGFbeta1 treatment, mimicking androgen withdrawal.
  • Assessed FLIP levels, caspase activity, and cell death following TGFbeta1 treatment.
  • Employed small interfering RNA (siRNA) to knock down FLIP expression and created stable cell lines with constitutively expressed FLIP.
  • Investigated the effects of insulin and receptor-Fc fusion proteins (Fas-Fc, sTNFRII-Fc, DR5-Fc) on TGFbeta1-induced apoptosis.

Main Results:

  • FLIP levels decreased with TGFbeta1 treatment, correlating with increased apoptosis.
  • Caspase inhibitor crmA blocked TGFbeta1-induced apoptosis, suggesting caspase-8 involvement.
  • FLIP knockdown enhanced TGFbeta1-induced cell death, while stable FLIP expression rendered cells resistant to apoptosis.
  • TGFbeta1-induced caspase-3 activity was inversely proportional to FLIP levels.
  • Insulin increased FLIP and inhibited TGFbeta1-induced death in a FLIP-dependent manner.
  • TGFbeta1 stimulation increased tumor necrosis factor mRNA, indicating a potential role for TNF in this model.

Conclusions:

  • FLIP plays a critical role in preventing prostate epithelial cell apoptosis induced by TGFbeta1.
  • FLIP levels are a key determinant of cell sensitivity to apoptosis, suggesting FLIP as a therapeutic target.
  • While caspase-8 and tumor necrosis factor may be involved, FLIP might also inhibit other unknown caspase-dependent apoptotic mediators.

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