title: Role of cyclic AMP response element-binding protein in insulin-like growth factor-i receptor up-regulation by sex steroids in prostate cancer cells.
abstract: Insulin-like growth factor-I receptor (IGF-IR) overexpression may play a role in prostate cancer progression. We found previously that, in prostate cancer cells, IGF-IR is up-regulated by both androgens and estrogens via a nongenotropic pathway. We now show that, in prostate cancer cells, stimulation with either androgens or estrogens up-regulates IGF-IR by inducing cyclic AMP response element-binding protein (CREB) activation. Both sex steroids phosphorylated CREB at Ser(133) in a dose-dependent manner in androgen receptor (AR)-positive LNCaP cells, whereas only estrogens phosphorylated CREB in AR-negative PC3 cells. CREB phosphorylation involved c-Src-dependent extracellular signal-regulated kinase 1/2 activation, but not protein kinase A, protein kinase C, or calmodulin-dependent kinase II, and occurred also in cells transfected with AR or estrogen receptor mutants that do not localize into the nucleus. CREB silencing abrogated IGF-IR up-regulation and promoter activation. We also showed that CREB binds to IGF-IR promoter region and identified the relevant CREB-binding site at the 5'-untranslated region fragment of IGF-IR promoter. In conclusion, we describe a novel mechanism of IGF-IR up-regulation and promoter activity by CREB activation, induced by sex steroids, through a nongenotropic signaling.
authors.affiliation: Endocrinology, Department of Internal Medicine and Medical Specialties, University of Catania, Catania, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Genua
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pandini
authors.forename: Diego
authors.initials: D
authors.lastname: Sisci
authors.forename: Gabriella
authors.initials: G
authors.lastname: Castoria
authors.forename: Marcello
authors.initials: M
authors.lastname: Maggiolini
authors.forename: Riccardo
authors.initials: R
authors.lastname: Vigneri
authors.forename: Antonino
authors.initials: A
authors.lastname: Belfiore
mesh_terms: D050882:CREB-Binding Protein / Q000378:metabolism*; D045744:Cell Line, Tumor; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D015741:Metribolone / Q000494:pharmacology*; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D015741:Metribolone; D004958:Estradiol; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D017526:Receptor, IGF Type 1