title: Reverse-phase protein array profiling of oropharyngeal cancer and significance of PIK3CA mutations in HPV-associated head and neck cancer.
abstract: OBJECTIVE
  Human papilloma virus (HPV)-associated (HPV+) oropharyngeal squamous cell carcinomas (OPSCC) have different molecular and biologic characteristics and clinical behavior compared with HPV-negative (HPV-) OPSCC. PIK3CA mutations are more common in HPV(+) OPSCC. To define molecular differences and tumor subsets, protein expression and phosphorylation were compared between HPV(+) and HPV(-) OPSCC and between tumors with and without PIK3CA mutations.
  
  
  METHODS
  Expression of 137 total and phosphorylated proteins was evaluated by reverse-phase protein array in 29 HPV(+) and 13 HPV(-) prospectively collected OPSCCs. Forty-seven OPSCCs were tested for hotspot-activating mutations in PIK3CA and AKT. Activation of PIK3CA downstream targets and sensitivity to pathway inhibitors were determined in HPV(+) head and neck cancer cells overexpressing wild-type or mutant PIK3CA.
  
  
  RESULTS
  Analyses revealed 41 differentially expressed proteins between HPV(+) and HPV(-) OPSCC categorized into functional groups: DNA repair, cell cycle, apoptosis, phosphoinositide 3-kinase (PI3K)/AKT/mTOR, and receptor kinase pathways. All queried DNA repair proteins were significantly upregulated in HPV(+) samples. A total of 8 of 33 HPV(+) and 0 of 14 HPV(-) tumors contained activating PIK3CA mutations. Despite all activating PIK3CA mutations occurring in HPV(+) samples, HPV(+) tumors had lower mean levels of activated AKT and downstream AKT target phosphorylation. Ectopic expression of mutant PIK3CA in HPV(+) cells increased mTOR, but not AKT activity. HPV E6/E7 overexpression inhibited AKT phosphorylation in HPV-negative cells. Mutant PIK3CA overexpressing cells were more sensitive to a dual PI3K/mTOR inhibitor compared with an AKT inhibitor.
  
  
  CONCLUSIONS
  Protein expression analyses suggest that HPV(+) and HPV(-) OPSCC differentially activate DNA repair, cell cycle, apoptosis, PI3K/AKT/mTOR, and receptor kinase pathways. PIK3CA mutations are more common in HPV(+) OPSCC and are associated with activation of mTOR, but not AKT. These data suggest that inhibitors for mTOR may have activity against HPV(+) PIK3CA mutant oropharyngeal cancers.
authors.affiliation: Authors' Affiliations: Departments of Surgery Division of Otolaryngology and Pathology; Yale Cancer Center, Yale University, New Haven, Connecticut; Departments of Otolaryngology and Cancer Biology, Vanderbilt University, Nashville, Tennessee; and Systems Biology Department, University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Andrew
authors.initials: A
authors.lastname: Sewell
authors.forename: Brandee
authors.initials: B
authors.lastname: Brown
authors.forename: Asel
authors.initials: A
authors.lastname: Biktasova
authors.forename: Gordon B
authors.initials: GB
authors.lastname: Mills
authors.forename: Yiling
authors.initials: Y
authors.lastname: Lu
authors.forename: Darren R
authors.initials: DR
authors.lastname: Tyson
authors.forename: Natalia
authors.initials: N
authors.lastname: Issaeva
authors.forename: Wendell G
authors.initials: WG
authors.lastname: Yarbrough
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D045744:Cell Line, Tumor; D058534:Class I Phosphatidylinositol 3-Kinases; D016000:Cluster Analysis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006258:Head and Neck Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000401:mortality / Q000628:therapy / Q000821:virology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009367:Neoplasm Staging; D009959:Oropharyngeal Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000401:mortality / Q000628:therapy / Q000821:virology*; D027383:Papillomaviridae; D030361:Papillomavirus Infections / Q000150:complications*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D011379:Prognosis; D040081:Protein Array Analysis; D012307:Risk Factors
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human