title: Inhibition of Hsp27 radiosensitizes head-and-neck cancer by modulating deoxyribonucleic acid repair.
abstract: OBJECTIVE
  To present a novel method of tumor radiosensitization through Hsp27 knockdown using locked nucleic acid (LNA) and to investigate the role of Hsp27 in DNA double strand break (DSB) repair.
  
  
  METHODS
  Clonogenic survival assays, immunoblotting, the proximity ligation assay, and γH2AX foci analysis were conducted in SQ20B and FaDu human head-and-neck cancer cell lines treated with Hsp27 LNA and Hsp27 short hairpin RNA (shRNA). Additionally, nude mice with FaDu flank tumors were treated with fractionated radiation therapy after pretreatment with Hsp27 LNA and monitored for tumor growth.
  
  
  RESULTS
  Hsp27 LNA and Hsp27 shRNA radiosensitized head-and-neck cancer cell lines in an Hsp27-dependent manner. Ataxia-Telangectasia Mutated-mediated DNA repair signaling was impaired in irradiated cells with Hsp27 knockdown. ATM kinase inhibition abrogated the radiosensitizing effect of Hsp27. Furthermore, Hsp27 LNA and shRNA both attenuated DNA repair kinetics after radiation, and Hsp27 was found to colocalize with ATM in both untreated and irradiated cells. Last, combined radiation and Hsp27 LNA treatment in tumor xenografts in nude mice suppressed tumor growth compared with either treatment alone.
  
  
  CONCLUSIONS
  These results support a radiosensitizing property of Hsp27 LNA in vitro and in vivo, implicate Hsp27 in double strand break repair, and suggest that Hsp27 LNA might eventually serve as an effective clinical agent in the radiotherapy of head-and-neck cancer.
authors.affiliation: Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Guttmann
authors.forename: Lori
authors.initials: L
authors.lastname: Hart
authors.forename: Kevin
authors.initials: K
authors.lastname: Du
authors.forename: Andrew
authors.initials: A
authors.lastname: Seletsky
authors.forename: Constantinos
authors.initials: C
authors.lastname: Koumenis
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D004260:DNA Repair / Q000235:genetics* / Q000528:radiation effects; D004273:DNA, Neoplasm / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D055785:Gene Knockdown Techniques; D055551:HSP27 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000502:physiology; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000378:metabolism / Q000532:radiotherapy*; D006657:Histones / Q000032:analysis; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009841:Oligonucleotides / Q000235:genetics* / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D011836:Radiation Tolerance / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*
chemical_list: D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D055551:HSP27 Heat-Shock Proteins; D006657:Histones; D009841:Oligonucleotides; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; C477371:locked nucleic acid; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases