title: Radiosensitivity and effect of hypoxia in HPV positive head and neck cancer cells.
abstract: OBJECTIVE
  HPV associated Head and Neck Squamous Cell Carcinoma (HNSCC) represents a distinct subgroup of HNSCC characterized by a favorable prognosis and a distinct molecular biology. Previous data from the randomized DAHANCA 5 trial indicated that HPV positive tumors did not benefit from hypoxic modifications by Nimorazole during radiotherapy, whereas a significant benefit was observed in the HPV negative tumors. However, more studies have demonstrated equal frequencies of hypoxic tumors among HPV-positive and HPV-negative tumors. The aim of the present study was to determine radiosensitivity, the impact of hypoxia and the effect of Nimorazole in HPV positive and HPV negative cell lines.
  
  
  METHODS
  The used cell lines were: UDSCC2, UMSCC47 and UPCISCC90 (HPV positive) and FaDuDD, UTSCC33 and UTSCC5 (HPV negative). Cells were cultured under normoxic or hypoxic conditions, and gene expression levels of previously established hypoxia induced genes were assessed by qPCR. Cells were irradiated with various doses under normoxia, hypoxia or hypoxia +1mM Nimorazole, and the clonogenic survival was determined.
  
  
  RESULTS
  The HPV positive and HPV negative cell lines exhibited similar patterns of upregulation of hypoxia induced genes in response to hypoxia. The HPV positive cell lines were up to 2.4 times more radiation sensitive than HPV negative cell lines. However, all HPV positive cells displayed the same response to hypoxia in radiosensitivity, with an OER in the range 2.3-2.9, and a sensitizer effect of Nimorazole of 1.13-1.29, similar to HPV negative cells.
  
  
  CONCLUSIONS
  Although HPV positive cells had a markedly higher radiosensitivity compared to HPV negative cells, they displayed the same relative radioresistance under hypoxia and the same relative sensitizer effect of Nimorazole. The clinical observation that HPV positive patients do not seem to benefit from Nimorazole treatment is not due to inherent differences in hypoxia sensitivity or response to Nimorazole, but can be accounted for by the overall higher radiosensitivity of HPV positive cells.
authors: Department of Experimental Clinical Oncology, Aarhus University Hospital, Denmark. Electronic address: bsin@mail.dk.
authors: Brita Singers
authors: BS
authors: Sørensen
authors: Morten
authors: M
authors: Busk
authors: Nadine
authors: N
authors: Olthof
authors: Ernst-Jan
authors: EJ
authors: Speel
authors: Michael R
authors: MR
authors: Horsman
authors: Jan
authors: J
authors: Alsner
authors: Jens
authors: J
authors: Overgaard
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000532:radiotherapy* / Q000821:virology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D006258:Head and Neck Neoplasms / Q000378:metabolism / Q000532:radiotherapy* / Q000821:virology; D006801:Humans; D009363:Neoplasm Proteins / Q000032:analysis; D009554:Nimorazole / Q000494:pharmacology; D027383:Papillomaviridae / Q000302:isolation & purification*; D011836:Radiation Tolerance; D000077195:Squamous Cell Carcinoma of Head and Neck
chemical_list: C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009363:Neoplasm Proteins; D009554:Nimorazole
keywords: Gene expression; HPV; Head and neck cancer; Hypoxia; Radiosensitivity