title: Heat shock protein 90 (HSP90) is overexpressed in p16-negative oropharyngeal squamous cell carcinoma, and its inhibition in vitro potentiates the effects of chemoradiation.
abstract: OBJECTIVE
  Cisplatin and radiation therapy remain the current standard for treating locally advanced SCCHN. Novel treatment approaches are needed, especially in patients with human papilloma virus (HPV)-negative disease who have worse outcomes despite multimodality therapy.
  
  
  METHODS
  Using our institutional review board approved database, we obtained twenty oropharyngeal squamous cell carcinoma (SCC) tissue samples: ten p16 positive, ten p16-negative. Because p16 expression is strongly associated with HPV positivity in oropharyngeal SCC, p16 status was used as a marker of HPV. We subsequently analyzed, via immunohistochemistry, heat shock protein 90 (HSP90) protein levels. Using HPV-positive and HPV-negative SCC cell lines, we compared baseline HSP90 expression levels and the effect of the HSP90 inhibitor ganetespib on viability and apoptosis. Clonogenic survival of HPV-negative cells treated with ganetespib, radiation therapy, and/or cisplatin was then investigated. We characterize the effects of ganetespib on proteins that are thought to drive DNA damage resistance in HPV-negative cells.
  
  
  RESULTS
  HSP90 expression was significantly higher in p16-negative compared with p16-positive samples (p = 0.016) and in HPV-negative cell lines compared with positive cells. Ganetespib increased cytotoxicity and induced apoptosis in HPV-negative more than positive cells. Adding ganetespib to cisplatin and/or radiation therapy in HPV-negative cells further decreased clonogenic survival. Finally, ganetespib downregulated expressions of EGFR, ERK, AKT, p53, and HIF-1α.
  
  
  CONCLUSIONS
  Ganetespib inhibited HPV-negative SCCHN viability and potentiated cell kill when combined with cisplatin or radiation therapy in vitro. With HSP90 expression higher in HPV-negative cells and in p16-negative patients, further exploration of the clinical activity of HSP90 inhibitors in SCCHN is warranted.
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, 1365 Clifton Rd NE, Suite C-3082, Atlanta, GA, 30322, USA, kirtesh.patel@emory.edu.
authors.forename: Kirtesh
authors.initials: K
authors.lastname: Patel
authors.forename: Jing
authors.initials: J
authors.lastname: Wen
authors.forename: Kelly
authors.initials: K
authors.lastname: Magliocca
authors.forename: Susan
authors.initials: S
authors.lastname: Muller
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liu
authors.forename: Zhuo Georgia
authors.initials: ZG
authors.lastname: Chen
authors.forename: Nabil
authors.initials: N
authors.lastname: Saba
authors.forename: Roberto
authors.initials: R
authors.lastname: Diaz
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002945:Cisplatin / Q000494:pharmacology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005260:Female; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D009959:Oropharyngeal Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D027383:Papillomaviridae / Q000502:physiology; D014230:Triazoles / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D019941:Cyclin-Dependent Kinase Inhibitor p16; D018841:HSP90 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C533237:STA 9090; D014230:Triazoles; D003676:Deferoxamine; D002945:Cisplatin