title: Both microtubule-stabilizing and microtubule-destabilizing drugs inhibit hypoxia-inducible factor-1alpha accumulation and activity by disrupting microtubule function.
abstract: We have recently identified a mechanistic link between disruption of the microtubule cytoskeleton and inhibition of tumor angiogenesis via the hypoxia-inducible factor-1 (HIF-1) pathway. Based on this model, we hypothesized that other microtubule-targeting drugs may have a similar effect on HIF-1alpha. To test that hypothesis, we studied the effects of different clinically relevant microtubule-disrupting agents, including taxotere, epothilone B, discodermolide, vincristine, 2-methoxyestradiol, and colchicine. In all cases, HIF-1alpha protein, but not mRNA, was down-regulated in a drug dose-dependent manner. In addition, HIF-1alpha transcriptional activity was also inhibited by all drugs tested. To further examine whether these effects were dependent on microtubule network disruption, we tested the ability of epothilone B to inhibit HIF-1alpha protein in the human ovarian cancer cell line 1A9 and its beta-tubulin mutant epothilone-resistant subclone 1A9/A8. Our data showed that epothilone B treatment down-regulated HIF-1alpha protein in the parental 1A9 cells but had no effect in the resistant 1A9/A8 cells. These observations were confirmed by confocal microscopy, which showed impaired nuclear accumulation of HIF-1alpha in parental 1A9 cells at epothilone B concentrations that induced extensive microtubule stabilization. In contrast, epothilone B treatment had no effect on either microtubules or HIF-1alpha nuclear accumulation in the resistant 1A9/A8 cells. Furthermore, epothilone B inhibited HIF-1 transcriptional activity in 1A9 cells, as evidenced by a hypoxia response element-luciferase reporter assay, but had no effect on HIF-1 activity in the resistant 1A9/A8 cells. These data directly link beta-tubulin drug binding with HIF-1alpha protein inhibition. Our results further provide a strong rationale for testing taxanes and epothilones in clinical trials targeting HIF-1 in cancer patients.
authors.affiliation: Department of Hematology and Oncology, Winship Cancer Institute, Robert Woodruff Health Sciences Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Escuin
authors.forename: Erik R
authors.initials: ER
authors.lastname: Kline
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Giannakakou
mesh_terms: D000077584:2-Methoxyestradiol; D000470:Alkaloids / Q000494:pharmacology*; D000473:Alkanes / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002219:Carbamates / Q000494:pharmacology; D045744:Cell Line, Tumor; D003078:Colchicine / Q000494:pharmacology; D000077143:Docetaxel; D015536:Down-Regulation / Q000187:drug effects; D034261:Epothilones / Q000494:pharmacology; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007783:Lactones / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D011753:Pyrones / Q000494:pharmacology; D043823:Taxoids / Q000494:pharmacology; D014750:Vincristine / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D000473:Alkanes; D000970:Antineoplastic Agents; D002219:Carbamates; D034261:Epothilones; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007783:Lactones; D011753:Pyrones; D043823:Taxoids; D000077143:Docetaxel; D004958:Estradiol; D014750:Vincristine; D000077584:2-Methoxyestradiol; C071229:discodermolide; D003078:Colchicine; C093788:epothilone B