title: Pyruvate induces transient tumor hypoxia by enhancing mitochondrial oxygen consumption and potentiates the anti-tumor effect of a hypoxia-activated prodrug TH-302.
abstract: BACKGROUND
  TH-302 is a hypoxia-activated prodrug (HAP) of bromo isophosphoramide mustard that is selectively activated within hypoxic regions in solid tumors. Our recent study showed that intravenously administered bolus pyruvate can transiently induce hypoxia in tumors. We investigated the mechanism underlying the induction of transient hypoxia and the combination use of pyruvate to potentiate the anti-tumor effect of TH-302.
  
  
  RESULTS
  The hypoxia-dependent cytotoxicity of TH-302 was evaluated by a viability assay in murine SCCVII and human HT29 cells. Modulation in cellular oxygen consumption and in vivo tumor oxygenation by the pyruvate treatment was monitored by extracellular flux analysis and electron paramagnetic resonance (EPR) oxygen imaging, respectively. The enhancement of the anti-tumor effect of TH-302 by pyruvate treatment was evaluated by monitoring the growth suppression of the tumor xenografts inoculated subcutaneously in mice. TH-302 preferentially inhibited the growth of both SCCVII and HT29 cells under hypoxic conditions (0.1% O2), with minimal effect under aerobic conditions (21% O2). Basal oxygen consumption rates increased after the pyruvate treatment in SCCVII cells in a concentration-dependent manner, suggesting that pyruvate enhances the mitochondrial respiration to consume excess cellular oxygen. In vivo EPR oxygen imaging showed that the intravenous administration of pyruvate globally induced the transient hypoxia 30 min after the injection in SCCVII and HT29 tumors at the size of 500-1500 mm(3). Pretreatment of SCCVII tumor bearing mice with pyruvate 30 min prior to TH-302 administration, initiated with small tumors (∼ 550 mm(3)), significantly delayed tumor growth.
  
  
  CONCLUSIONS
  Our in vitro and in vivo studies showed that pyruvate induces transient hypoxia by enhancing mitochondrial oxygen consumption in tumor cells. TH-302 therapy can be potentiated by pyruvate pretreatment if started at the appropriate tumor size and oxygen concentration.
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Takakusagi
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Shingo
authors.initials: S
authors.lastname: Matsumoto
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Keita
authors.initials: K
authors.lastname: Saito
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Matsuo
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Shun
authors.initials: S
authors.lastname: Kishimoto
authors.affiliation: H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, United States of America.
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Wojtkowiak
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: William
authors.initials: W
authors.lastname: DeGraff
authors.affiliation: Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Aparna H
authors.initials: AH
authors.lastname: Kesarwala
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Rajani
authors.initials: R
authors.lastname: Choudhuri
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Nallathamby
authors.initials: N
authors.lastname: Devasahayam
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Sankaran
authors.initials: S
authors.lastname: Subramanian
authors.affiliation: National Institute of Neurological Diseases and Stroke, Bethesda, Maryland, United States of America.
authors.forename: Jeeva P
authors.initials: JP
authors.lastname: Munasinghe
authors.affiliation: H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, United States of America.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gillies
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
authors.affiliation: Threshold Pharmaceuticals, South San Francisco, California, United States of America.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Hart
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Murali C
authors.initials: MC
authors.lastname: Krishna
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D005260:Female; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D009593:Nitroimidazoles / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects*; D010752:Phosphoramide Mustards / Q000494:pharmacology*; D011355:Prodrugs / Q000494:pharmacology*; D019289:Pyruvic Acid / Q000494:pharmacology*; D013997:Time Factors; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D009593:Nitroimidazoles; D010752:Phosphoramide Mustards; D011355:Prodrugs; C552526:TH 302; D019289:Pyruvic Acid; D010100:Oxygen