title: Perturbation of proteasome function by bortezomib leading to ER stress-induced apoptotic cell death in cholangiocarcinoma.
abstract: OBJECTIVE
  Cholangiocarcinoma (CCA) or cancer of the biliary tract is heterogeneous; however, chronic inflammatory-related features are unique in CCA. Moreover, the genes involved in proteasome functions are evidently increased in CCA. Hence, CCA might be vulnerable to endoplasmic reticulum (ER) stressors, particularly a proteasome inhibitor. Therefore, bortezomib (BTZ), a specific 26S proteasome inhibitor, was selected, and its antitumor effects against CCA were investigated.
  
  
  METHODS
  Liver fluke-associated CCA cell lines were used. Cell proliferation and apoptosis detection were determined by a tetrazolium-based assay, caspase detection and annexin V binding assay. The accumulations of proteasome substrates, the inductions of ER stress and unfolded protein response (UPR) proteins were demonstrated by western blot and reporter systems. The in vivo anti-proliferative effect was accessed in a subcutaneous transplantation mouse model.
  
  
  RESULTS
  BTZ inhibited CCA proliferation and induced caspase-dependent apoptosis, independently of the NF-κB pathway. Inhibition of protein degradation by BTZ led to the induction of UPR; induction of XBP1 splicing, ATF6 proteolysis and nuclear ATF4 as well as BiP and CHOP expressions were evident. Nevertheless, ER stress-induced UPR was overwhelming, leading to the activation of apoptosis demonstrated by proteolytic cleavages of ER-related caspase 4 and 12 as well as classical caspase 8, 9 and 3. The growth inhibitory effect of BTZ was supported by an in vivo model.
  
  
  CONCLUSIONS
  BTZ treatment could be a promising therapeutic approach for CCA treatment.
authors.affiliation: Division of Hematopoiesis, Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Kumamoto, 860-0811, Japan.
authors.forename: Kulthida
authors.initials: K
authors.lastname: Vaeteewoottacharn
authors.forename: Ryusho
authors.initials: R
authors.lastname: Kariya
authors.forename: Kouki
authors.initials: K
authors.lastname: Matsuda
authors.forename: Manabu
authors.initials: M
authors.lastname: Taura
authors.forename: Chaisiri
authors.initials: C
authors.lastname: Wongkham
authors.forename: Sopit
authors.initials: S
authors.lastname: Wongkham
authors.forename: Seiji
authors.initials: S
authors.lastname: Okada
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001650:Bile Duct Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D001653:Bile Ducts, Intrahepatic / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D015153:Blotting, Western; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D049109:Cell Proliferation / Q000187:drug effects; D018281:Cholangiocarcinoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006801:Humans; D053616:Janus Kinase 3 / Q000502:physiology*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D016688:Mice, Inbred NOD; D018345:Mice, Knockout; D016513:Mice, SCID; D016328:NF-kappa B / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology*; D051742:Transcription Factor CHOP / Q000378:metabolism; D014407:Tumor Cells, Cultured; D056811:Unfolded Protein Response / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D016328:NF-kappa B; D011719:Pyrazines; D051742:Transcription Factor CHOP; D000069286:Bortezomib; D008156:Luciferases; C507935:Jak3 protein, mouse; D053616:Janus Kinase 3; D046988:Proteasome Endopeptidase Complex