title: Bortezomib primes neuroblastoma cells for TRAIL-induced apoptosis by linking the death receptor to the mitochondrial pathway.
abstract: OBJECTIVE
  Searching for novel strategies to modulate apoptosis in neuroblastoma, we investigated the potential of the proteasome inhibitor bortezomib.
  
  
  METHODS
  The effect of bortezomib on TRAIL (TNF-related apoptosis-inducing ligand)-induced apoptosis signaling pathways was analyzed in neuroblastoma cell lines, primary neuroblastoma cultures, and in an in vivo model.
  
  
  RESULTS
  Bortezomib synergistically cooperates with TRAIL to induce apoptosis and to reduce colony formation of neuroblastoma cells (combination index: 0.5). Mechanistic studies reveal that bortezomib profoundly enhances TRAIL-induced cleavage of Bid into tBid, accumulation of tBid in the cytosol, and its insertion into mitochondrial membranes, pointing to a concerted effect on Bid cleavage (TRAIL) and stabilization of tBid (bortezomib), which links the death receptor to the mitochondrial pathway. In addition, bortezomib increases expression of p53 and Noxa. All these changes lead to increased activation of Bax and Bak, loss of the mitochondrial membrane potential, cytochrome c release, caspase activation, and caspase-dependent apoptosis on treatment with bortezomib and TRAIL. Knockdown of Bid, Noxa, or p53 significantly delays the kinetic of bortezomib- and TRAIL-induced apoptosis, whereas it does not confer long-term protection. By comparison, overexpression of Bcl-2, which simultaneously antagonizes tBid and p53, significantly inhibits bortezomib- and TRAIL-induced apoptosis and even rescues clonogenic survival. Importantly, bortezomib and TRAIL act in concert to trigger apoptosis and to suppress tumor growth in patient-derived primary neuroblastoma cells and in an in vivo model of neuroblastoma.
  
  
  CONCLUSIONS
  Bortezomib represents a promising new approach to prime neuroblastoma cells toward TRAIL, which warrants further investigation.
authors: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors: Ivonne
authors: I
authors: Naumann
authors: Roland
authors: R
authors: Kappler
authors: Dietrich
authors: D
authors: von Schweinitz
authors: Klaus-Michael
authors: KM
authors: Debatin
authors: Simone
authors: S
authors: Fulda
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D001897:Boronic Acids / Q000008:administration & dosage*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004357:Drug Synergism; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011719:Pyrazines / Q000008:administration & dosage*; D053218:Receptors, Death Domain / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D001897:Boronic Acids; D011719:Pyrazines; D053218:Receptors, Death Domain; D053221:TNF-Related Apoptosis-Inducing Ligand; D000069286:Bortezomib