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The proteasome inhibitor MG132 potentiates TRAIL receptor agonist-induced apoptosis by stabilizing tBid and Bik in human head and neck squamous cell carcinoma cells

Sung, ES; Park, KJ; Choi, HJ; Kim, CH; Kim, YS
Experimental cell research, 318(13):1564-1576, 2012
Journal Title
Experimental cell research
Head and neck squamous cell carcinoma (HNSCC) is often resistant to conventional chemotherapy and thus requires novel treatment regimens. Here, we investigated the effects of the proteasome inhibitor MG132 in combination with tumor necrosis factor-related apoptosis inducing ligand (TRAIL) or agonistic TRAIL receptor 1 (DR4)-specific monoclonal antibody, AY4, on sensitization of TRAIL- and AY4-resistant human HNSCC cell lines. Combination treatment of HNSCC cells synergistically induced apoptotic cell death accompanied by caspase-8, caspase-9, and caspase-3 activation and Bid cleavage into truncated Bid (tBid). Generation and accumulation of tBid through the cooperative action of MG132 with TRAIL or AY4 and Bik accumulation through MG132-mediated proteasome inhibition are critical to the synergistic apoptosis. In HNSCC cells, Bak was constrained by Mcl-1 and Bcl-X(L), but not by Bcl-2. Conversely, Bax did not interact with Mcl-1, Bcl-X(L), or Bcl-2. Importantly, tBid plays a major role in Bax activation, and Bik indirectly activates Bak by displacing it from Mcl-1 and Bcl-X(L), pointing to the synergistic mechanism of the combination treatment. In addition, knockdown of both Mcl-1 and Bcl-X(L) significantly sensitized HNSCC cells to TRAIL and AY4 as a single agent, suggesting that Bak constraint by Mcl-1 and Bcl-X(L) is an important resistance mechanism of TRAIL receptor-mediated apoptotic cell death. Our results provide a novel molecular mechanism for the potent synergy between MG132 proteasome inhibitor and TRAIL receptor agonists in HNSCC cells, suggesting that the combination of these agents may offer a new therapeutic strategy for HNSCC treatment.
MeSH terms
Antibodies, Monoclonal/administration & dosageApoptosis/drug effectsApoptosis Regulatory Proteins/antagonists & inhibitors/genetics/metabolismBH3 Interacting Domain Death Agonist Protein/antagonists & inhibitors/genetics/metabolismBase SequenceCarcinoma, Squamous Cell/*drug therapy/metabolism/pathologyCell Line, TumorDrug SynergismGene Knockdown TechniquesHead and Neck Neoplasms/*drug therapy/metabolism/pathologyHumansLeupeptins/*administration & dosageMembrane Proteins/antagonists & inhibitors/genetics/metabolism*Proteasome InhibitorsProtein Stability/drug effectsProtein Transport/drug effectsProto-Oncogene Proteins c-bcl-2/antagonists & inhibitors/genetics/metabolismRNA InterferenceRNA, Small Interfering/geneticsReceptors, TNF-Related Apoptosis-Inducing Ligand/*agonistsTNF-Related Apoptosis-Inducing Ligand/administration & dosagebcl-2 Homologous Antagonist-Killer Protein/metabolismbcl-2-Associated X Protein/metabolismbcl-X Protein/antagonists & inhibitors/genetics/metabolism
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Journal Papers > School of Medicine / Graduate School of Medicine > Otolaryngology
AJOU Authors
김, 철호
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