title: Histone deacetylase inhibitors induce VHL and ubiquitin-independent proteasomal degradation of hypoxia-inducible factor 1alpha.
abstract: Adaptation to hypoxic microenvironment is critical for tumor survival and metastatic spread. Hypoxia-inducible factor 1alpha (HIF-1alpha) plays a key role in this adaptation by stimulating the production of proangiogenic factors and inducing enzymes necessary for anaerobic metabolism. Histone deacetylase inhibitors (HDACIs) produce a marked inhibition of HIF-1alpha expression and are currently in clinical trials partly based on their potent antiangiogenic effects. Although it has been postulated that HDACIs affect HIF-1alpha expression by enhancing its interactions with VHL (von Hippel Lindau), thus promoting its ubiquitination and degradation, the actual mechanisms by which HDACIs decrease HIF-1alpha levels are not clear. Here, we present data indicating that HDACIs induce the proteasomal degradation of HIF-1alpha by a mechanism that is independent of VHL and p53 and does not require the ubiquitin system. This degradation pathway involves the enhanced interaction of HIF-1alpha with HSP70 and is secondary to a disruption of the HSP70/HSP90 axis function that appears mediated by the activity of HDAC-6.
authors.affiliation: Cardeza Foundation Hematologic Research and Department of Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Xianguo
authors.initials: X
authors.lastname: Kong
authors.forename: Zhao
authors.initials: Z
authors.lastname: Lin
authors.forename: Dongming
authors.initials: D
authors.lastname: Liang
authors.forename: Donna
authors.initials: D
authors.lastname: Fath
authors.forename: Nianli
authors.initials: N
authors.lastname: Sang
authors.forename: Jaime
authors.initials: J
authors.lastname: Caro
mesh_terms: D015687:Cell Hypoxia; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018840:HSP70 Heat-Shock Proteins / Q000187:drug effects / Q000378:metabolism; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D018840:HSP70 Heat-Shock Proteins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; C012589:trichostatin A; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D046988:Proteasome Endopeptidase Complex; C433811:HDAC6 protein, human; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases; C497446:VHL protein, human