title: Induction of the hypoxia-inducible factor system by low levels of heat shock protein 90 inhibitors.
abstract: The heterodimeric hypoxia-inducible factor-1 (HIF-1) is involved in key steps of tumor progression and therapy resistance and thus represents an attractive antitumor target. Because heat shock protein 90 (HSP90) plays an important role in HIF-1alpha protein stabilization and because HSP90 inhibitors are currently being tested in clinical phase I trials for anticancer treatment, we investigated their role as anti-HIF-1alpha agents. Surprisingly, low-dose (5-30 nmol/L) treatment of HeLa cells with three different HSP90 inhibitors (17-AAG, 17-DMAG, and geldanamycin) increased HIF-1-dependent reporter gene activity, whereas higher doses (1-3 micromol/L) resulted in a reduction of hypoxia-induced HIF-1 activity. In line with these data, low-dose treatment with HSP90 inhibitors increased and high-dose treatment reduced hypoxic HIF-1alpha protein levels, respectively. HIF-1alpha protein stabilized by HSP90 inhibitors localized to the nucleus. As a result of HSP90-modulated HIF-1 activity, the levels of the tumor-relevant HIF-1 downstream targets carbonic anhydrase IX, prolyl-4-hydroxylase domain protein 3, and vascular endothelial growth factor were increased or decreased after low-dose or high-dose treatment, respectively. Bimodal effects of 17-AAG on vessel formation were also seen in the chick chorioallantoic membrane angiogenesis assay. In summary, these results suggest that dosage will be a critical factor in the treatment of tumor patients with HSP90 inhibitors.
authors.affiliation: Cell Physiology Group, Medical Faculty, Martin Luther University Halle, Halle, Germany.
authors.forename: Nadia O
authors.initials: NO
authors.lastname: Ibrahim
authors.forename: Torsten
authors.initials: T
authors.lastname: Hahn
authors.forename: Corinna
authors.initials: C
authors.lastname: Franke
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Stiehl
authors.forename: Renato
authors.initials: R
authors.lastname: Wirthner
authors.forename: Roland H
authors.initials: RH
authors.lastname: Wenger
authors.forename: Dörthe M
authors.initials: DM
authors.lastname: Katschinski
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D016227:Benzoquinones; D002467:Cell Nucleus / Q000378:metabolism; D002642:Chick Embryo; D049033:Chorioallantoic Membrane / Q000098:blood supply; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006367:HeLa Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D047029:Lactams, Macrocyclic; D018919:Neovascularization, Physiologic / Q000187:drug effects; D011809:Quinones / Q000494:pharmacology*; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; C497442:HIF1A protein, human; D018841:HSP90 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047029:Lactams, Macrocyclic; D011809:Quinones; C448659:17-(dimethylaminoethylamino)-17-demethoxygeldanamycin; D017828:Rifabutin; C112765:tanespimycin; C001277:geldanamycin