Bik/NBK accumulation correlates with apoptosis-induction by bortezomib (PS-341, Velcade) and other proteasome inhibitors

Hongbo Zhu, Lidong Zhang, Fengqin Dong, Wei Guo, Shuhong Wu, Fuminori Teraishi, John J. Davis, Paul J. Chiao, Bingliang Fang

Research output: Contribution to journalArticlepeer-review

112 Citations (Scopus)


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 IκBα levels or in NFκB 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.

Original languageEnglish
Pages (from-to)4993-4999
Number of pages7
Issue number31
Publication statusPublished - Jul 21 2005
Externally publishedYes


  • Apoptosis
  • Bik
  • Bortezomib
  • PS-341
  • Proteasome inhibitor

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research


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