title: Identification of P450 Oxidoreductase as a Major Determinant of Sensitivity to Hypoxia-Activated Prodrugs.
abstract: Hypoxia is a prevalent feature of many tumors contributing to disease progression and treatment resistance, and therefore constitutes an attractive therapeutic target. Several hypoxia-activated prodrugs (HAP) have been developed, including the phase III candidate TH-302 (evofosfamide) and the preclinical agent SN30000, which is an optimized analogue of the well-studied HAP tirapazamine. Experience with this therapeutic class highlights an urgent need to identify biomarkers of HAP sensitivity, including enzymes responsible for prodrug activation during hypoxia. Using genome-scale shRNA screens and a high-representation library enriched for oxidoreductases, we identified the flavoprotein P450 (cytochrome) oxidoreductase (POR) as the predominant determinant of sensitivity to SN30000 in three different genetic backgrounds. No other genes consistently modified SN30000 sensitivity, even within a POR-negative background. Knockdown or genetic knockout of POR reduced SN30000 reductive metabolism and clonogenic cell death and similarly reduced sensitivity to TH-302 under hypoxia. A retrospective evaluation of head and neck squamous cell carcinomas showed heterogeneous POR expression and suggested a possible relationship between human papillomavirus status and HAP sensitivity. Taken together, our study identifies POR as a potential predictive biomarker of HAP sensitivity that should be explored during the clinical development of SN30000, TH-302, and other hypoxia-directed agents.
authors: Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
authors: Francis W
authors: FW
authors: Hunter
authors: Research Division, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia. Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia.
authors: Richard J
authors: RJ
authors: Young
authors: Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.
authors: Zvi
authors: Z
authors: Shalev
authors: Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.
authors: Ravi N
authors: RN
authors: Vellanki
authors: Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
authors: Jingli
authors: J
authors: Wang
authors: Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. AnQual Laboratories, School of Pharmacy, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
authors: Yongchuan
authors: Y
authors: Gu
authors: Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
authors: Naveen
authors: N
authors: Joshi
authors: Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
authors: Sreevalsan
authors: S
authors: Sreebhavan
authors: Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.
authors: Ilan
authors: I
authors: Weinreb
authors: Department of Otolaryngology-Head and Neck Surgery, University of Toronto, Toronto, Ontario, Canada.
authors: David P
authors: DP
authors: Goldstein
authors: Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
authors: Jason
authors: J
authors: Moffat
authors: Donnelly Centre and Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada.
authors: Troy
authors: T
authors: Ketela
authors: Donnelly Centre and Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada.
authors: Kevin R
authors: KR
authors: Brown
authors: Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada. Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada. Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors: Marianne
authors: M
authors: Koritzinsky
authors: Research Division, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia. Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia. Department of Medical Oncology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors: Benjamin
authors: B
authors: Solomon
authors: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia. Department of Medical Oncology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors: Danny
authors: D
authors: Rischin
authors: Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
authors: William R
authors: WR
authors: Wilson
authors: Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada. Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada. Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada. Ontario Institute for Cancer Research, Toronto, Ontario, Canada. bwouters@uhnresearch.ca.
authors: Bradly G
authors: BG
authors: Wouters
mesh_terms: D065767:Activation, Metabolic; D000970:Antineoplastic Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D015415:Biomarkers; D002294:Carcinoma, Squamous Cell / Q000201:enzymology* / Q000628:therapy / Q000821:virology; D015687:Cell Hypoxia / Q000502:physiology*; D045744:Cell Line, Tumor; D059248:Chemoradiotherapy; D003497:Cyclic N-Oxides / Q000493:pharmacokinetics*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D006258:Head and Neck Neoplasms / Q000201:enzymology* / Q000821:virology; D057166:High-Throughput Screening Assays; D006801:Humans; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009593:Nitroimidazoles / Q000493:pharmacokinetics; D027383:Papillomaviridae / Q000302:isolation & purification; D030361:Papillomavirus Infections / Q000821:virology; D010752:Phosphoramide Mustards / Q000493:pharmacokinetics; D011355:Prodrugs / Q000493:pharmacokinetics* / Q000627:therapeutic use; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D012189:Retrospective Studies; D000077704:Tirapazamine; D014227:Triazines / Q000493:pharmacokinetics* / Q000627:therapeutic use; D059016:Tumor Microenvironment; D014410:Tumor Stem Cell Assay
chemical_list: D000970:Antineoplastic Agents; D015415:Biomarkers; C570601:CEN-209; D003497:Cyclic N-Oxides; D009363:Neoplasm Proteins; D009593:Nitroimidazoles; C000602470:POR protein, human; D010752:Phosphoramide Mustards; D011355:Prodrugs; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C552526:TH 302; D014227:Triazines; D000077704:Tirapazamine; D003577:Cytochrome P-450 Enzyme System