title: Effect of hypoxia on the expression of αB-crystallin in head and neck squamous cell carcinoma.
abstract: BACKGROUND
  The presence of hypoxia in head and neck squamous cell carcinoma (HNSCC) is associated with therapeutic resistance and increased risk of metastasis formation. αB-crystallin (HspB5) is a small heat shock protein, which is also associated with metastasis formation in HNSCC. In this study, we investigated whether αB-crystallin protein expression is increased in hypoxic areas of HNSCC biopsies and analyzed whether hypoxia induces αB-crystallin expression in vitro and in this way may confer hypoxic cell survival.
  
  
  METHODS
  In 38 HNSCC biopsies, the overlap between immunohistochemically stained αB-crystallin and pimonidazole-adducts (hypoxiamarker) was determined. Moreover, expression levels of αB-crystallin were analyzed in HNSCC cell lines under hypoxia and reoxygenation conditions and after exposure to reactive oxygen species (ROS) and the ROS scavenger N-acetylcysteine (NAC). siRNA-mediated knockdown was used to determine the influence of αB-crystallin on cell survival under hypoxic conditions.
  
  
  RESULTS
  In all biopsies αB-crystallin was more abundantly present in hypoxic areas than in normoxic areas. Remarkably, hypoxia decreased αB-crystallin mRNA expression in the HNSCC cell lines. Only after reoxygenation, a condition that stimulates ROS formation, αB-crystallin expression was increased. αB-crystallin mRNA levels were also increased by extracellular ROS, and NAC abolished the reoxygenation-induced αB-crystallin upregulation. Moreover, it was found that decreased αB-crystallin levels reduced cell survival under hypoxic conditions.
  
  
  CONCLUSIONS
  We provide the first evidence that hypoxia stimulates upregulation of αB-crystallin in HNSCC. This upregulation was not caused by the low oxygen pressure, but more likely by ROS formation. The higher expression of αB-crystallin may lead to prolonged survival of these cells under hypoxic conditions.
authors.forename: Chantal
authors.initials: C
authors.lastname: van de Schootbrugge
authors.forename: Elisabeth M J
authors.initials: EM
authors.lastname: Schults
authors.forename: Johan
authors.initials: J
authors.lastname: Bussink
authors.forename: Paul N
authors.initials: PN
authors.lastname: Span
authors.forename: Reidar
authors.initials: R
authors.lastname: Grénman
authors.forename: Ger J M
authors.initials: GJ
authors.lastname: Pruijn
authors.forename: Johannes H A M
authors.initials: JH
authors.lastname: Kaanders
authors.affiliation: Department of Biomolecular Chemistry, Institute for Molecules and Materials and Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, 271, RIMLS, PO Box 9101, 6500 HB Nijmegen, The Netherlands. w.boelens@ncmls.ru.nl.
authors.forename: Wilbert C
authors.initials: WC
authors.lastname: Boelens
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D015687:Cell Hypoxia / Q000235:genetics*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006258:Head and Neck Neoplasms / Q000235:genetics* / Q000473:pathology; D006801:Humans; D012333:RNA, Messenger / Q000096:biosynthesis; D017382:Reactive Oxygen Species / Q000378:metabolism; D038203:alpha-Crystallin B Chain / Q000096:biosynthesis* / Q000235:genetics
chemical_list: C059215:CRYAB protein, human; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D038203:alpha-Crystallin B Chain
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