title: Bik/NBK accumulation correlates with apoptosis-induction by bortezomib (PS-341, Velcade) and other proteasome inhibitors.
abstract: Proteasome inhibitors have emerged as promising anticancer therapeutic agents. Bortezomib (PS-341), a specific proteasome inhibitor, exhibits antitumor activity against a wide range of malignancies and has been approved by the US Food and Drug Administration for the treatment of relapsed or refractory multiple myeloma. However, the molecular mechanisms of bortezomib-mediated apoptosis remain unclear. To characterize the mechanisms of apoptosis induction by proteasome inhibitors, we examined levels of Bcl-2 protein family members (Bik/NBK, Bax, Bak, Bcl-2, and Bcl-XL), release of cytochrome c, and activation of caspase-9 and -3 in human colon cancer cell lines DLD1, LOVO, SW620, and HCT116; human lung cancer cell line H1299; and human ovarian cancer cell line SKOV3 after they were treated with bortezomib. The result showed that bortezomib induced rapid accumulation of Bik/NBK but not other Bcl-2 family members in all six cell lines. Bortezomib-mediated Bik/NBK accumulation and apoptosis were also observed in human embryonic kidney cells 293 and normal human bronchial epithelial cells. Moreover, dramatic Bik/NBK accumulation and apoptosis induction were observed when cells were treated with proteasome inhibitor MG132 and calpain inhibitor I (ALLN). Furthermore, no detectable changes in IkappaBalpha levels or in NFkappaB functionality were found after treatment with bortezomib. Finally, Bik/NBK accumulation was caused by stabilization of the protein from degradation and was associated with bortezomib cytotoxicity and apoptosis induction. Pretreatment of DLD1 cells with Bik/NBK siRNA reduced bortezomib-mediated Bik/NBK accumulation and cell death. Our results suggested that Bik/NBK is one of the mediators of proteasome inhibitor-induced apoptosis.
authors.affiliation: Department of Surgical Oncology, Sir Run Run Shaw Hospital, Zhejiang University, People's Republic of China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Zhu
authors.forename: Lidong
authors.initials: L
authors.lastname: Zhang
authors.forename: Fengqin
authors.initials: F
authors.lastname: Dong
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.forename: Shuhong
authors.initials: S
authors.lastname: Wu
authors.forename: Fuminori
authors.initials: F
authors.lastname: Teraishi
authors.forename: John J
authors.initials: JJ
authors.lastname: Davis
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Chiao
authors.forename: Bingliang
authors.initials: B
authors.lastname: Fang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D002460:Cell Line; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D005260:Female; D006801:Humans; D007668:Kidney; D008565:Membrane Proteins / Q000502:physiology*; D024101:Mitochondrial Proteins; D016328:NF-kappa B / Q000378:metabolism; D010051:Ovarian Neoplasms; D011480:Protease Inhibitors / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C096820:BIK protein, human; D001897:Boronic Acids; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D016328:NF-kappa B; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D000069286:Bortezomib