title: DNA strand breaks and hypoxia response inhibition mediate the radiosensitisation effect of nitric oxide donors on prostate cancer under varying oxygen conditions.
abstract: Prostate cancer cells can exist in a hypoxic microenvironment, causing radioresistance. Nitric oxide (NO) is a radiosensitiser of mammalian cells. NO-NSAIDs are a potential means of delivering NO to prostate cancer cells. This study aimed to determine the effect and mechanism of action of NO-sulindac and radiation, on prostate cancer cells and stroma, under normoxia (21% oxygen) and chronic hypoxia (0.2% oxygen). Using clonogenic assays, at a surviving fraction of 10% the sensitisation enhancement ratios of radiation plus NO-sulindac over radiation alone on PC-3 cells were 1.22 and 1.42 under normoxia and hypoxia, respectively. 3D culture of PC-3 cells revealed significantly reduced sphere diameter in irradiated spheres treated with NO-sulindac. Neither NO-sulindac nor sulindac radiosensitised prostate stromal cells under normoxia or hypoxia. HIF-1α protein levels were reduced by NO-sulindac exposure and radiation at 21 and 0.2% oxygen. Alkaline Comet assay analysis suggested an increased rate of single strand DNA breaks and slower repair of these lesions in PC-3 cells treated with NO-sulindac prior to irradiation. There was a higher level of γ-H2AX production and hence double strand DNA breaks following irradiation of NO-sulindac treated PC-3 cells. At all radiation doses and oxygen levels tested, treatment of 2D and 3D cultures of PC-3 cells with NO-sulindac prior to irradiation radiosensitised PC-3, with minimal effect on stromal cells. Hypoxia response inhibition and increased DNA double strand breaks are potential mechanisms of action. Neoadjuvent and concurrent use of NO-NSAIDs have the potential to improve radiotherapy treatment of prostate cancer under normoxia and hypoxia.
authors.affiliation: Prostate Research Group, Department of Urology, University of Edinburgh, Western General Hospital, Crewe Road South, Edinburgh, EH4 2XU, UK. grant.stewart@ed.ac.uk
authors.forename: Grant D
authors.initials: GD
authors.lastname: Stewart
authors.forename: Jyoti
authors.initials: J
authors.lastname: Nanda
authors.forename: Elad
authors.initials: E
authors.lastname: Katz
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Bowman
authors.forename: Jill G
authors.initials: JG
authors.lastname: Christie
authors.forename: D J Gordon
authors.initials: DJ
authors.lastname: Brown
authors.forename: Duncan B
authors.initials: DB
authors.lastname: McLaren
authors.forename: Antony C P
authors.initials: AC
authors.lastname: Riddick
authors.forename: James A
authors.initials: JA
authors.lastname: Ross
authors.forename: George D D
authors.initials: GD
authors.lastname: Jones
authors.forename: Fouad K
authors.initials: FK
authors.lastname: Habib
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D002460:Cell Line; D053960:DNA Breaks / Q000187:drug effects*; D004260:DNA Repair / Q000187:drug effects; D004307:Dose-Response Relationship, Radiation; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism*; D011467:Prostate / Q000166:cytology; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D017154:Stromal Cells / Q000187:drug effects / Q000528:radiation effects
chemical_list: D000970:Antineoplastic Agents; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020030:Nitric Oxide Donors; D011838:Radiation-Sensitizing Agents; D009569:Nitric Oxide; D010100:Oxygen