title: Differential bortezomib sensitivity in head and neck cancer lines corresponds to proteasome, nuclear factor-kappaB and activator protein-1 related mechanisms.
abstract: Head and neck squamous cell carcinomas (HNSCC) exhibit constitutive activation of transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), which are modulated by the proteasome and promote resistance to cell death. HNSCC show variable sensitivity to the proteasome inhibitor bortezomib in vitro as well as in murine xenografts and patient tumors in vivo, and the mechanisms are not well understood. To address this question, the sensitivities of nine HNSCC cell lines to bortezomib were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, and the potential relationship between the sensitivity and bortezomib effects on biological processes was examined in HNSCC lines of differential bortezomib sensitivity. The most sensitive cell line (UM-SCC-11B) underwent cell death at 10(-9) mol/L in vitro and tumor regression at a maximally tolerated dose of bortezomib in a murine xenograft model. The differential sensitivity between UM-SCC-11A and UM-SCC-11B cells corresponded to differences in the extent of suppression of proteasome activity, ubiquitinated protein degradation, and NF-kappaB and AP-1 activation. Lower concentrations of bortezomib transiently increased NF-kappaB and sustained AP-1 activation in UM-SCC-11A cells. AP-1 reporter activity and cell density of UM-SCC-11A were suppressed when bortezomib was combined with c-Jun NH(2)-terminal kinase and p38 kinase pathways inhibitors. Thus, the differential sensitivities to bortezomib corresponded to dissimilar effects on the proteasome, NF-kappaB and AP-1 activities. Inhibition of c-Jun NH(2)-terminal kinase and p38 pathways blocked AP-1 activity and enhanced the antitumor effects. These findings revealed molecular mechanisms of bortezomib sensitivity and resistance, which are under development as biomarkers for clinical trials in patients with HNSCC.
authors.affiliation: Tumor Biology Section, Head and Neck Surgery Branch, National Institute on Deafness and Other Communication Disorders, NIH, 10/5D55, MSC-1419, Bethesda, MD 20892-1419, USA.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
authors.forename: Justin L
authors.initials: JL
authors.lastname: Ricker
authors.forename: Pramit S
authors.initials: PS
authors.lastname: Malhotra
authors.forename: Liesl
authors.initials: L
authors.lastname: Nottingham
authors.forename: Lorena
authors.initials: L
authors.lastname: Bagain
authors.forename: Tin Lap
authors.initials: TL
authors.lastname: Lee
authors.forename: Ning T
authors.initials: NT
authors.lastname: Yeh
authors.forename: Carter
authors.initials: C
authors.lastname: Van Waes
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D017930:Genes, Reporter; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000873:Anthracenes; D000970:Antineoplastic Agents; D001897:Boronic Acids; D016328:NF-kappa B; D061988:Proteasome Inhibitors; D011719:Pyrazines; D018808:Transcription Factor AP-1; C432165:pyrazolanthrone; D000069286:Bortezomib; D046988:Proteasome Endopeptidase Complex