title: Androgen-dependent regulation of Her-2/neu in prostate cancer cells.
abstract: The mechanisms underlying the progression of prostate cancer to a state of resistance to hormone ablation remain poorly understood. Here, we have investigated the relationship between androgen receptor (AR) and Her-2/neu in prostate cancer cells. Overexpression of Her-2/neu (c-ErbB2) activates the AR pathway and confers a survival and growth advantage to prostate cancer cells in an androgen-deficient milieu. In vitro, the absence of androgens or AR blockade induced Her-2/neu protein expression and phosphorylation. In contrast, upon readministration of androgens, Her-2/neu mRNA, protein, and phosphorylation levels decreased linearly with increasing concentrations of dihydrotestosterone as LNCaP cells reentered the cell cycle. In vivo, induction of Her-2/neu by castration in orthotopically injected LNCaP cells resulted in a progressive increase in prostate-specific antigen secretion into the mouse serum, indicating that Her-2/neu-mediated, AR-dependent transcription occurs following castration and results in tumor cell growth. Finally, selection of LNCaP cells stably transfected with short hairpin RNA specific for AR resulted in Her-2/neu overexpression. Similarly, knockdown of Her-2/neu led to induction of AR. However, when Her-2/neu and AR were simultaneously targeted, we observed cell death, whereas surviving cells retained low level expression of Her-2/neu. Thus, induction and activation of Her-2/neu occurs in an androgen-depleted environment or as a result of AR inactivation, promoting ablation-resistant survival of prostate cancer cells. These data provide the biochemical rationale to target Her-2/neu in hormone-refractory prostate cancer.
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA.
authors.forename: Raanan
authors.initials: R
authors.lastname: Berger
authors.forename: Douglas I
authors.initials: DI
authors.lastname: Lin
authors.forename: Maria
authors.initials: M
authors.lastname: Nieto
authors.forename: Ewa
authors.initials: E
authors.lastname: Sicinska
authors.forename: Levi A
authors.initials: LA
authors.lastname: Garraway
authors.forename: Heiner
authors.initials: H
authors.lastname: Adams
authors.forename: Sabina
authors.initials: S
authors.lastname: Signoretti
authors.forename: William C
authors.initials: WC
authors.lastname: Hahn
authors.forename: Massimo
authors.initials: M
authors.lastname: Loda
mesh_terms: D059002:Androgen Receptor Antagonists; D000728:Androgens / Q000494:pharmacology; D000818:Animals; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D013196:Dihydrotestosterone / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D009376:Neoplasms, Hormone-Dependent / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011944:Receptors, Androgen / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D059002:Androgen Receptor Antagonists; D000728:Androgens; D013196:Dihydrotestosterone; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D011944:Receptors, Androgen