title: Androgens up-regulate the insulin-like growth factor-I receptor in prostate cancer cells.
abstract: In this study, we show that androgens up-regulate insulin-like growth factor-I receptor (IGF-IR) expression and sensitize prostate cancer cells to the biological effects of IGF-I. Both dihydrotestosterone and the synthetic androgen R1881 induced an approximately 6-fold increase in IGF-IR expression in androgen receptor (AR)-positive prostate cancer cells LNCaP. In accordance with IGF-IR up-regulation, treatment with the nonmetabolizable androgen R1881 sensitized LNCaP cells to the mitogenic and motogenic effects of IGF-I, whereas an IGF-IR blocking antibody effectively inhibited these effects. By contrast, these androgens did not affect IGF-IR expression in AR-negative prostate cancer cells PC-3. Reintroduction of AR into PC-3 cells by stable transfection restored the androgen effect on IGF-IR up-regulation. R1881-induced IGF-IR up-regulation was partially inhibited by the AR antagonist Casodex (bicalutamide). Two other AR antagonists, cyproterone acetate and OH-flutamide, were much less effective. Androgen-induced IGF-IR up-regulation was not dependent on AR genomic activity, because two AR mutants, AR-C619Y and AR-C574R, devoid of DNA binding activity and transcriptional activity were still able to elicit IGF-IR up-regulation in HEK293 kidney cells in response to androgens. Moreover, androgen-induced IGF-IR up-regulation involves the activation of the Src-extracellular signal-regulated kinase pathway, because it was inhibited by both the Src inhibitor PP2 and the MEK-1 inhibitor PD98059. The present observations strongly suggest that AR activation may stimulate prostate cancer progression through the altered IGF-IR expression and IGF action. Anti-androgen therapy may be only partially effective, or almost ineffective, in blocking important biological effects of androgens, such as activation of the IGF system.
authors.affiliation: Dipartimento di Medicina Interna e di Medicina Specialistica, Cattedra di Endocrinologia, University of Catania, Ospedale Garibaldi, Catania, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pandini
authors.forename: Rossana
authors.initials: R
authors.lastname: Mineo
authors.forename: Francesco
authors.initials: F
authors.lastname: Frasca
authors.forename: Charles T
authors.initials: CT
authors.lastname: Roberts
authors.forename: Marco
authors.initials: M
authors.lastname: Marcelli
authors.forename: Riccardo
authors.initials: R
authors.lastname: Vigneri
authors.forename: Antonino
authors.initials: A
authors.lastname: Belfiore
mesh_terms: D000726:Androgen Antagonists / Q000494:pharmacology; D059002:Androgen Receptor Antagonists; D000728:Androgens / Q000494:pharmacology*; D000813:Anilides / Q000494:pharmacology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D004247:DNA / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007668:Kidney / Q000378:metabolism; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009376:Neoplasms, Hormone-Dependent / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009570:Nitriles; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011944:Receptors, Androgen / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013936:Thymidine / Q000378:metabolism; D014105:Tosyl Compounds; D014158:Transcription, Genetic; D015854:Up-Regulation; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D000726:Androgen Antagonists; D059002:Androgen Receptor Antagonists; D000728:Androgens; D000813:Anilides; D004791:Enzyme Inhibitors; D009570:Nitriles; D011944:Receptors, Androgen; D014105:Tosyl Compounds; D007334:Insulin-Like Growth Factor I; D004247:DNA; C053541:bicalutamide; D017526:Receptor, IGF Type 1; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D013936:Thymidine