title: HSP90 inhibition sensitizes head and neck cancer to platin-based chemoradiotherapy by modulation of the DNA damage response resulting in chromosomal fragmentation.
abstract: Concurrent cisplatin radiotherapy (CCRT) is a current standard-of-care for locally advanced head and neck squamous cell carcinoma (HNSCC). However, CCRT is frequently ineffective in patients with advanced disease. It has previously been shown that HSP90 inhibitors act as radiosensitizers, but these studies have not focused on CCRT in HNSCC. Here, we evaluated the HSP90 inhibitor, AUY922, combined with CCRT.
  
  
  
  The ability of AUY922 to sensitize to CCRT was assessed in p53 mutant head and neck cell lines by clonogenic assay. Modulation of the CCRT induced DNA damage response (DDR) by AUY922 was characterized by confocal image analysis of RAD51, BRCA1, 53BP1, ATM and mutant p53 signaling. The role of FANCA depletion by AUY922 was examined using shRNA. Cell cycle checkpoint abrogation and chromosomal fragmentation was assessed by western blot, FACS and confocal. The role of ATM was also assessed by shRNA. AUY922 in combination with CCRT was assessed in vivo.
  
  
  
  The combination of AUY922 with cisplatin, radiation and CCRT was found to be synergistic in p53 mutant HNSCC. AUY922 leads to significant alterations to the DDR induced by CCRT. This comprises inhibition of homologous recombination through decreased RAD51 and pS1524 BRCA1 with a corresponding increase in 53BP1 foci, activation of ATM and signaling into mutant p53. A shift to more error prone repair combined with a loss of checkpoint function leads to fragmentation of chromosomal material. The degree of disruption to DDR signalling correlated to chromosomal fragmentation and loss of clonogenicity. ATM shRNA indicated a possible rationale for the combination of AUY922 and CCRT in cells lacking ATM function.
  
  
  
  This study supports future clinical studies combining AUY922 and CCRT in p53 mutant HNSCC. Modulation of the DDR and chromosomal fragmentation are likely to be analytical points of interest in such trials.
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK. martin.mclaughlin@icr.ac.uk.
authors.forename: Martin
authors.initials: M
authors.lastname: McLaughlin
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
authors.forename: Holly E
authors.initials: HE
authors.lastname: Barker
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
authors.forename: Aadil A
authors.initials: AA
authors.lastname: Khan
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
authors.forename: Malin
authors.initials: M
authors.lastname: Pedersen
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
authors.forename: Magnus
authors.initials: M
authors.lastname: Dillon
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
authors.forename: David C
authors.initials: DC
authors.lastname: Mansfield
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
authors.forename: Radhika
authors.initials: R
authors.lastname: Patel
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
authors.forename: Joan N
authors.initials: JN
authors.lastname: Kyula
authors.affiliation: The Royal Marsden Hospital, 203 Fulham Road, London, SW3 6JJ, UK.|Division of Radiotherapy and Imaging, The Institute of Cancer Research, 237 Fulham Road, London, UK.
authors.forename: Shreerang A
authors.initials: SA
authors.lastname: Bhide
authors.affiliation: The Royal Marsden Hospital, 203 Fulham Road, London, SW3 6JJ, UK.|Division of Radiotherapy and Imaging, The Institute of Cancer Research, 237 Fulham Road, London, UK.
authors.forename: Kate L
authors.initials: KL
authors.lastname: Newbold
authors.affiliation: The Royal Marsden Hospital, 203 Fulham Road, London, SW3 6JJ, UK.|Division of Radiotherapy and Imaging, The Institute of Cancer Research, 237 Fulham Road, London, UK.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Nutting
authors.affiliation: Targeted Therapy Team, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.|The Royal Marsden Hospital, 203 Fulham Road, London, SW3 6JJ, UK.|Division of Radiotherapy and Imaging, The Institute of Cancer Research, 237 Fulham Road, London, UK.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Harrington
mesh_terms: D000818:Animals; D019313:BRCA1 Protein / Q000235:genetics; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000532:radiotherapy; D045744:Cell Line, Tumor; D059248:Chemoradiotherapy / Q000379:methods; D002875:Chromosomes / Q000187:drug effects* / Q000235:genetics; D004249:DNA Damage / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects; D053938:DNA Fragmentation / Q000187:drug effects*; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D005260:Female; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000532:radiotherapy; D059765:Homologous Recombination / Q000187:drug effects; D006801:Humans; D007555:Isoxazoles / Q000494:pharmacology*; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012118:Resorcinols / Q000494:pharmacology*; D000077195:Squamous Cell Carcinoma of Head and Neck; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
chemical_list: C528044:5-(2,4-dihydroxy-5-isopropylphenyl)-4-(4-morpholin-4-ylmethylphenyl)isoxazole-3-carboxylic acid ethylamide; D019313:BRCA1 Protein; D018841:HSP90 Heat-Shock Proteins; D007555:Isoxazoles; D009944:Organoplatinum Compounds; D047428:Protein Kinase Inhibitors; D012118:Resorcinols; D016159:Tumor Suppressor Protein p53
keywords: ATM; AUY922; DDR; FANCA; HNSCC; RAD51