title: Bortezomib sensitises TRAIL-resistant HPV-positive head and neck cancer cells to TRAIL through a caspase-dependent, E6-independent mechanism.
abstract: Human papillomavirus (HPV) is causative for a new and increasing form of head and neck squamous cell carcinomas (HNSCCs). Although localised HPV-positive cancers have a favourable response to radio-chemotherapy (RT/CT), the impact of HPV in advanced or metastatic HNSCC remains to be defined and targeted therapeutics need to be tested for cancers resistant to RT/CT. To this end, we investigated the sensitivity of HPV-positive and -negative HNSCC cell lines to TRAIL (tumour necrosis factor-related apoptosis-inducing ligand), which induces tumour cell-specific apoptosis in various cancer types. A clear correlation was observed between HPV positivity and resistance to TRAIL compared with HPV-negative head and neck cancer cell lines. All TRAIL-resistant HPV-positive cell lines tested were sensitised to TRAIL-induced cell death by treatment with bortezomib, a clinically approved proteasome inhibitor. Bortezomib-mediated sensitisation to TRAIL was associated with enhanced activation of caspase-8, -9 and -3, elevated membrane expression levels of TRAIL-R2, cytochrome c release and G2/M arrest. Knockdown of caspase-8 significantly blocked cell death induced by the combination therapy, whereas the BH3-only protein Bid was not required for induction of apoptosis. XIAP depletion increased the sensitivity of both HPV-positive and -negative cells to TRAIL alone or in combination with bortezomib. In contrast, restoration of p53 following E6 knockdown in HPV-positive cells had no effect on their sensitivity to either single or combination therapy, suggesting a p53-independent pathway for the observed response. In summary, bortezomib-mediated proteasome inhibition sensitises previously resistant HPV-positive HNSCC cells to TRAIL-induced cell death through a mechanism involving both the extrinsic and intrinsic pathways of apoptosis. The cooperative effect of these two targeted anticancer agents therefore represents a promising treatment strategy for RT/CT-resistant HPV-associated head and neck cancers.
authors.affiliation: Department of Molecular Oncology, King's College London, Guy's Campus, Hodgkin Building, London SE1 1UL, UK.
authors.forename: J
authors.initials: J
authors.lastname: Bullenkamp
authors.affiliation: Department of Molecular Oncology, King's College London, Guy's Campus, Hodgkin Building, London SE1 1UL, UK.
authors.forename: N
authors.initials: N
authors.lastname: Raulf
authors.affiliation: Department of Oral Pathology, King's College London, Guy's Campus, Dental Institute, London SE1 9RT, UK.
authors.forename: B
authors.initials: B
authors.lastname: Ayaz
authors.affiliation: Centre for Cell Death, Cancer and Inflammation (CCCI), UCL Cancer Institute, 72 Huntley Street, London WC1E 6BT, UK.
authors.forename: H
authors.initials: H
authors.lastname: Walczak
authors.affiliation: Experimental Dermatology, Department of Dermatology, TU Dresden, Dresden 01307, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Kulms
authors.affiliation: Department of Oral Pathology, King's College London, Guy's Campus, Dental Institute, London SE1 9RT, UK.
authors.forename: E
authors.identifier: 0000000184350048
authors.initials: E
authors.lastname: Odell
authors.affiliation: Department of Oral Pathology, King's College London, Guy's Campus, Dental Institute, London SE1 9RT, UK.
authors.forename: S
authors.initials: S
authors.lastname: Thavaraj
authors.affiliation: Department of Molecular Oncology, King's College London, Guy's Campus, Hodgkin Building, London SE1 1UL, UK.
authors.forename: M
authors.initials: M
authors.lastname: Tavassoli
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D053181:Caspase 8 / Q000378:metabolism*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D057809:HEK293 Cells; D006258:Head and Neck Neoplasms / Q000473:pathology* / Q000821:virology*; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D027383:Papillomaviridae / Q000502:physiology*; D055550:Protein Stability / Q000187:drug effects; D011719:Pyrazines / Q000494:pharmacology*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D001897:Boronic Acids; D009856:Oncogene Proteins, Viral; D011719:Pyrazines; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D016159:Tumor Suppressor Protein p53; D051636:X-Linked Inhibitor of Apoptosis Protein; D000069286:Bortezomib; D053181:Caspase 8