SUMOylation plays a role in gemcitabine- and bortezomib-induced cytotoxicity in human oropharyngeal carcinoma KB gemcitabine-resistant clone

Vincent Chung, Bingsen Zhou, Xiyong Liu, Lijun Zhu, Lee M. Boo, Ha Van Nguyen, David K. Ann, Jing Song, Yuan Chen, Yun Yen

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5 Citations (Scopus)


Bortezomib, a novel dipeptide boronic acid proteasome inhibitor, has been shown in previous studies to be synergistic with gemcitabine; however, the molecular mechanisms are not fully understood. Because post-translational modification of proteins, such as ubiquitination and SUMOylation, plays a critical role in governing cellular homeostasis, we explored this further by treating human oropharyngeal carcinoma KB wild-type (KBwt) and gemcitabine-resistant (KBGem) cells with gemcitabine and bortezomib in a time-dependent and sequence-dependent manner. Treatment with bortezomib at 4 to 8 hours post-gemcitabine significantly induced cell death in KBwt cell lines. However, in KBGem cells, bortezomib alone was just as cytotoxic. Using reporter assays, nuclear factor-κB (NF-κB) activity was found to be 5-fold higher in KBGem cells than that in KBwt cells, and the combination treatment decreased NF-κB activity by 44% in KBwt cells and 28% in KBGem cells, respectively. By Western blot analyses, treatment with gemcitabine and bortezomib resulted in a cleavage of NF-κB in KBwt but not in KBGem cells. SUMOylation capacity was modulated by transducing KBwt and KBGem cells with lenti-SUMO-1 or the unconjugatable lenti-SUMO-1aa followed by drug treatment. The expression of cyclins A, D1, and E was differentially regulated by SUMOylation capacity in KBGem but not in KBwt cells. We report herein that the activation of NF-κB signaling plays a critical role in eliciting KBwt cell survival against gemcitabine, whereas the role of SUMOylation in modulating the steady-state levels of key cell cycle regulator proteins seems more significant in KBGem cells.

Original languageEnglish
Pages (from-to)533-540
Number of pages8
JournalMolecular Cancer Therapeutics
Issue number3
Publication statusPublished - Mar 1 2006
Externally publishedYes


ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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