Bortezomib enhances radiosensitivity in oral cancer through inducing autophagy-mediated TRAF6 oncoprotein degradation

Yuan Hua Wu, Wun Syuan Wu, Li Ching Lin, Chiang Shin Liu, Sheng Yow Ho, Bour Jr Wang, Bu Miin Huang, Ya Ling Yeh, Hui Wen Chiu, Wei Lei Yang, Ying Jan Wang

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Background: Oral squamous cell carcinoma (OSCC) is a malignant tumor that may occur anywhere within the oral cavity. The survival rate of OSCC patients has not improved over the past decades due to its heterogeneous etiology, genetic aberrations, and treatment outcomes. We investigated the role of tumor necrosis factor receptor-associated factor 6 (TRAF6) in OSCC cells treated with bortezomib (a proteasome inhibitor) combined with irradiation (IR) treatment. Methods: The effects of combined treatment in OSCC cells were investigated using assays of cell viability, autophagy, apoptosis, western blotting, and immunofluorescence staining. The ubiquitination of proteins was analyzed by immunoprecipitation. Stable knockdown of TRAF6 in OSCC cells was constructed with lentivirus. The xenograft murine models were used to observe tumor growth. Results: We found synergistic effects of bortezomib and IR on the viability of human oral cancer cells. The combination of bortezomib and IR treatment induced autophagic cell death. Furthermore, bortezomib inhibited IR-induced TRAF6 ubiquitination and inhibited TRAF6-mediated Akt activation. Bortezomib reduced TRAF6 protein expression through autophagy-mediated lysosomal degradation. TRAF6 played an oncogenic role in tumorigenesis of human oral cancer cells and oral tumor growth was suppressed by bortezomib and IR treatment. In addition, OSCC patients with expression of TRAF6 showed a trend towards poorer cancer-specific survival when compared with patients without TRAF6 expression. Conclusions: A combination of a proteasome inhibitor, IR treatment and TRAF6 inhibition could be a novel therapeutic strategy in OSCC.

Original languageEnglish
Article number91
JournalJournal of Experimental and Clinical Cancer Research
Volume37
Issue number1
DOIs
Publication statusPublished - 2018 Apr 27

All Science Journal Classification (ASJC) codes

  • Oncology
  • Cancer Research

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