title: The 5-lipoxygenase inhibitor tepoxalin induces oxidative damage and altered PTEN status prior to apoptosis in canine osteosarcoma cell lines.
abstract: The 5-lipoxygenase (5-LOX) inhibitor tepoxalin has been shown to slow canine osteosarcoma (OSA) tumour xenografts growth, yet the mechanisms are poorly elucidated. Further examination of tepoxalin in canine OSA cell lines shows that tepoxalin treated cells undergo apoptosis through caspase-3 activation and annexin staining. Interestingly, apoptosis is superseded by an increase in reactive oxygen species (ROS), as measured by activation of dihydrorhodamine 123 and mitosox. This increase in ROS appears to be related to the 5-LOX inhibitor regardless of cellular 5-LOX status, and was not observed after treatment with the tepoxalin metabolite RWJ20142. Additionally, 5-LOX inhibition by tepoxalin appears to increase phosphatase and tensin (PTEN) homolog activity by preventing its alkylation or oxidation. PTEN modification or inhibition allows phosphoinositide-3 (PI3) kinase activity thereby heightening activation of protein kinase B (AKT) phosphorylation. Our data suggest that off target oxidation and LOX inhibition play roles in the apoptotic response.
authors.affiliation: Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Loftus
authors.affiliation: Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.
authors.forename: D
authors.initials: D
authors.lastname: Cavatorta
authors.affiliation: Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Bushey
authors.affiliation: Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Levine
authors.affiliation: Department of Molecular Medicine, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Sevier
authors.affiliation: Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Wakshlag
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D012516:Osteosarcoma / Q000188:drug therapy / Q000378:metabolism / Q000662:veterinary*; D018384:Oxidative Stress / Q000187:drug effects*; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology*
chemical_list: D016861:Cyclooxygenase Inhibitors; D007166:Immunosuppressive Agents; D016859:Lipoxygenase Inhibitors; D011720:Pyrazoles; D051059:PTEN Phosphohydrolase; C073135:tepoxalin
keywords: 5-lipoxygenase; cell culture; eicosanoids; osteosarcoma; tumour suppressor