title: 15-lipoxygenase-1 expression upregulates and activates insulin-like growth factor-1 receptor in prostate cancer cells.
abstract: We previously discovered that a fat-metabolizing enzyme, 15-lipoxygenase-1 (15-LO-1), is high in human prostate cancer (PCa) and correlates with disease progression. The biologic link between the aberrant 15-LO-1/linoleic acid (LA) metabolism and fat (which is a rich source of growth factors) in PCa is unknown. Therefore, we tested the hypothesis that the metabolic product of the polyunsaturated fatty acid LA (i.e., 13-S-hydroxyoctadecadienoic acid or 13-(S)-HODE) affects the proliferation status of PCa cells through one or more growth factors. We used parental prostate cancer cell line-3 (PC-3) and engineered PC-3 cell lines [PC3-Zeo (mock-transfected), PC3-15LOS (15-LO-1-overexpressing), and PC3-15LOAS (15-LO-1-blocked)] to test our hypothesis. Of the growth factors examined, only insulin-like growth factor-1 (IGF-1) exhibited a two-fold to three-fold increase in growth response on PC3-15LOS cells compared to PC3-Zeo (control) cell line (P <.01). Insulin-like growth factor-1 receptor (IGF-1R) immunohistochemical analyses of human normal and adenocarcinoma prostate tissues, as well as levels in tumors derived from nude mice injected with PC-3 cells, demonstrated that elevated IGF-1R expression correlated with 15-LO-1 levels. Radioligand binding assays demonstrated two-fold higher IGF-1 binding sites in PC3-15LOS cells (P <.05 vs PC3-Zeo cells). IGF-1R promoter reporter assay and affinity-purified IGF-1R receptor levels demonstrated a four-fold higher activity in PC3-15LOS cells (P <.01 vs PC3-Zeo cells). IGF-1R promoter activation is 13-(S)-HODE-dependent. IGF-1R blockade with a dominant-negative adenovirus caused significant growth inhibition in PC-3 cells (P <.0001; PC3-15LOAS versus PC3-15LOS cells), as well as affected the IGF-1-stimulated mitogen-activated protein (MAP) kinase (Erk1/2) and Akt activation levels. Our study suggests that overexpression of 15-LO-1 in PCa contributes to the cancer progression by regulating IGF-1R expression and activation.
authors.affiliation: Urological Research Laboratories, Department of Urology, University of Pittsburgh, Pittsburgh, PA 15232, USA. kelavkarup@msx.upmc.edu
authors.forename: Uddhav P
authors.initials: UP
authors.lastname: Kelavkar
authors.forename: Cynthia
authors.initials: C
authors.lastname: Cohen
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism*; D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008954:Models, Biological; D011471:Prostatic Neoplasms / Q000378:metabolism*; D017451:Receptors, Somatomedin / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D015854:Up-Regulation
chemical_list: D017451:Receptors, Somatomedin; D001093:Arachidonate 15-Lipoxygenase