title: G2-checkpoint targeting and radiosensitization of HPV/p16-positive HNSCC cells through the inhibition of Chk1 and Wee1.
abstract: HPV-positive HNSCC cells are characterized by radiosensitivity, inefficient DNA double-strand break repair and a profound and prolonged arrest in G2. Here we explored the effect of clinically relevant inhibitors of Chk1 and Wee1 to inhibit the radiation-induced G2-arrest in order to achieve further radiosensitization.
  
  
  
  Assessment of Chk1 activity by Western blot; assessment of cell cycle distribution by propidium iodide staining and flow cytometry; assessment of cell survival by colony formation assay. HPV+ HNSCC cell lines: UD-SCC-2, UM-SCC-47 and UPCI-SCC-154; Chk1 inhibitors: LY2603618, MK8776; Wee1 inhibitor: AZD1775.
  
  
  
  Specific Chk1 inhibitors efficiently abrogated the radiation-induced G2-arrest and caused radiosensitization. Wee-inhibition by AZD1775 resulted in the activation of Chk1. This feedback mechanism is likely to counteract some of the effects of Wee1 inhibition but could be antagonized through the combined inhibition of both kinases. Combined inhibition was effective using profoundly reduced concentrations of both inhibitors and resulted in more efficient radiosensitization of the HPV-positive cell lines compared to p53 proficient normal human fibroblasts.
  
  
  
  Specific Chk1 inhibitors as well as the combined inhibition of Chk1 and Wee1 radiosensitize HPV-positive HNSCC cells.
authors.affiliation: Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Chia-Jung
authors.initials: CJ
authors.lastname: Busch
authors.affiliation: Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Germany; Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Marie Sophie
authors.initials: MS
authors.lastname: Kröger
authors.affiliation: Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Germany; Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Jensen
authors.affiliation: Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Malte
authors.initials: M
authors.lastname: Kriegs
authors.affiliation: Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Germany; Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Fruzsina
authors.initials: F
authors.lastname: Gatzemeier
authors.affiliation: Department of Radiotherapy and Radiation Oncology, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Cordula
authors.initials: C
authors.lastname: Petersen
authors.affiliation: Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Adrian
authors.initials: A
authors.lastname: Münscher
authors.affiliation: Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Rothkamm
authors.affiliation: Department of Otolaryngology and Head and Neck Surgery, University Medical Center Hamburg Eppendorf, Germany; Laboratory of Radiobiology & Experimental Radiation Oncology, University Medical Center Hamburg Eppendorf, Germany. Electronic address: t.rieckmann@uke.uni-hamburg.de.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Rieckmann
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy* / Q000821:virology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors*; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1 / Q000037:antagonists & inhibitors*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis*; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000821:virology; D006801:Humans; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D000077195:Squamous Cell Carcinoma of Head and Neck
chemical_list: C000614131:CDKN2A protein, human; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009687:Nuclear Proteins; D011838:Radiation-Sensitizing Agents; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; D000071877:Checkpoint Kinase 1
keywords: Chk1; G2-arrest; HNSCC; HPV; Radiosensitization; Wee1