title: Inducible expression of 15-lipoxygenase-2 and 8-lipoxygenase inhibits cell growth via common signaling pathways.
abstract: Human 15-lipoxygenase (LOX)-2 and mouse 8-LOX represent orthologous members of the LOX family but display different positional specificities and tissue distribution. To study the functional role of 15-LOX-2 and 8-LOX in keratinocytes, an inducible Tet-On gene expression system was established in the premalignant mouse keratinocyte cell line 308. Doxycycline (dox)-induced expression of enzymatically active 15-LOX-2 and 8-LOX led to an inhibition of cell growth that was associated with an inhibition of DNA synthesis, as shown by a 15-46% reduction of 5-bromo-2-deoxy-uridine (BrdU) incorporation. The inhibitory effects were increased in the presence of exogenous arachidonic acid. In contrast, addition of linoleic acid or the LOX inhibitor baicalein reversed the growth-inhibitory effects. Treatment of the cells with 15-hydroxyeicosatetraenoic acid (HETE) or 8-HETE resulted in a similar inhibition of BrdU incorporation, whereas 13-hydroxyoctadecadienoic acid (HODE) and 9-HODE, in contrast, had no effects. Dox-induced keratinocytes showed increased levels of reactive oxygen species (ROS). The antioxidant N-acetyl-L-cysteine and a specific inhibitor of p38 mitogen-activated protein kinase, but not of extracellular signal-regulated kinase 1/2 or c-Jun N-terminal kinase/stress-activated kinases, completely abolished the LOX-induced growth inhibition, indicating a critical role of ROS and p38. Our data suggest that 15-LOX-2 and 8-LOX, although displaying different positional specificity, may use common signaling pathways to induce growth inhibition in premalignant epithelial cells.
authors.affiliation: Division of Eicosanoids and Tumor Development, German Cancer Research Center, D-69120 Heidelberg, Germany.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Schweiger
authors.forename: Gerhard
authors.initials: G
authors.lastname: Fürstenberger
authors.forename: Peter
authors.initials: P
authors.lastname: Krieg
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D001091:Arachidonate Lipoxygenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016718:Arachidonic Acid / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019787:Linoleic Acid / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D051379:Mice; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D006893:Hydroxyeicosatetraenoic Acids; D016859:Lipoxygenase Inhibitors; D017382:Reactive Oxygen Species; D016718:Arachidonic Acid; C095123:15-hydroxyeicosatrienoic acid; D004247:DNA; D019787:Linoleic Acid; D001091:Arachidonate Lipoxygenases; D001093:Arachidonate 15-Lipoxygenase; C054192:arachidonate 8-lipoxygenase; D048051:p38 Mitogen-Activated Protein Kinases; D004318:Doxycycline; D000111:Acetylcysteine