Proteasomal regulation of caspase-8 in cancer cell apoptosis

Michael V. Fiandalo, Steven R. Schwarze, Natasha Kyprianou

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Previous studies demonstrated that proteasome inhibition sensitizes TRAIL resistant prostate cancer cells to TRAIL-mediated apoptosis via stabilization of the active p18 subunit of caspase-8. The present study investigated the impact of proteasome inhibition on caspase-8 stability, ubiquitination, trafficking, and activation in cancer cells. Using caspase-8 deficient neuroblastoma (NB7) cells for reconstituting non-cleavable mutant forms of caspase-8, we demonstrated that the non-cleavable forms of caspase-8 are capable of inducing apoptosis comparably to wild-type caspase-8, in response to proteasome inhibitor and GST-TRAIL. Moreover in the LNCaP human prostate cancer cells, caspase-8 polyubiquitination occurs after TRAIL stimulation and caspase-8 processing. Subcellular fractionation analysis revealed caspase-8 activity in both cytosol and plasma membrane fractions in both NB7 reconstituted caspase-8 cell lines, as well the LNCaP prostate cancer cells. The present results suggest that caspase-8 stabilization through proteasome inhibition leads to reactivation of the extrinsic pathway of apoptosis and identify E3 ligase mediating caspase-8 polyubiquitination, as a novel molecular target. Inhibition of this E3 ligase in combination with TRAIL towards restoring apoptosis signaling activation may have potential therapeutic significance in resistant tumors.

Original languageEnglish
Pages (from-to)766-776
Number of pages11
Issue number6
StatePublished - Jun 2013

Bibliographical note

Funding Information:
Acknowledgments The authors acknowledge Drs. Douglas Green and Andrew Oberst for generously providing the NB7 cell line and caspase-8 constructs. We also thank Drs. Greg Baumen and Jennifer Strange at the University of Kentucky Flow Cytometry Facility, Sarah with caspase-8 antibody (red), and Na?/K? ATPase (green); composite localization (yellow). Representative images shown at 963 magnification. Representative images from three independent experiments, performed in duplicate Martin for help with the statistical analysis and Lorie Howard for her assistance with the submission process. This work was supported by the Department of Defense USAMRMC PC073314 Grant, National Institutes of Health: NIDDK, R01 DK083761, the Markey Cancer Center, and James F. Hardymon Endowment for Urology Research at the University of Kentucky.


  • Apoptosis
  • Caspase-8
  • Proteasome inhibitors

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Cancer Research


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