title: Hsp90 inhibitor NVP-AUY922 enhances radiation sensitivity of tumor cell lines under hypoxia.
abstract: NVP-AUY922, a novel inhibitor of Hsp90, was shown to enhance the effect of ionizing radiation (IR) on tumor cells under normoxic conditions. Since low oxygen tension is a common feature of solid tumors, we explore in the present study the impact of hypoxia on the combined treatment of lung carcinoma A549 and glioblastoma SNB19 cell lines with NVP-AUY922 and IR. Cellular analysis included the colony-forming ability, expression of CAIX, Hsp90, Hsp70, Raf-1, Akt, cell cycle progression and associated proteins, as well as DNA damage measured by histone γH2AX.       The clonogenic assay revealed that in both cell lines NVP-AUY922 enhanced the radiotoxicity under hypoxic exposure to a level similar to that observed under oxic conditions. Irrespective of oxygen supply during drug treatment, NVP-AUY922 also reduced the expression of anti-apoptotic proteins Raf-1 and Akt. As judged by the levels of histone γH2AX, drug-treated hypoxic cells exhibited a lower repair rate of DNA double-strand breaks than normoxic cells. The drug-IR mediated changes in the cell cycle, i.e., S-phase depletion and G 2/M arrest, developed not directly during hypoxic exposure but first upon 24 h reoxygenation. Under both oxygen tensions, Hsp90 inhibition downregulated the cell cycle-associated proteins, Cdk1, Cdk4 and pRb.   The finding that NVP-AUY922 can enhance the in vitro radiosensitivity of hypoxic tumor cells may have implications for the combined modality treatment of solid tumors.
authors.affiliation: Department of Radiation Oncology, University of Würzburg, Würzburg, Germany.
authors.forename: Cholpon S
authors.initials: CS
authors.lastname: Djuzenova
authors.forename: Christina
authors.initials: C
authors.lastname: Blassl
authors.forename: Konstanze
authors.initials: K
authors.lastname: Roloff
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kuger
authors.forename: Astrid
authors.initials: A
authors.lastname: Katzer
authors.forename: Natalia
authors.initials: N
authors.lastname: Niewidok
authors.forename: Nadine
authors.initials: N
authors.lastname: Günther
authors.forename: Bülent
authors.initials: B
authors.lastname: Polat
authors.forename: Vladimir L
authors.initials: VL
authors.lastname: Sukhorukov
authors.forename: Michael
authors.initials: M
authors.lastname: Flentje
mesh_terms: D016203:CDC2 Protein Kinase / Q000378:metabolism; D002277:Carcinoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D002453:Cell Cycle / Q000187:drug effects; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D005909:Glioblastoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007555:Isoxazoles / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D012118:Resorcinols / Q000494:pharmacology*
chemical_list: C528044:5-(2,4-dihydroxy-5-isopropylphenyl)-4-(4-morpholin-4-ylmethylphenyl)isoxazole-3-carboxylic acid ethylamide; C468783:H2AX protein, human; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006657:Histones; D007555:Isoxazoles; D011838:Radiation-Sensitizing Agents; D012118:Resorcinols; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D016203:CDC2 Protein Kinase; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4