Both Microtubule-Stabilizing and Microtubule-Destabilizing Drugs Inhibit Hypoxia-Inducible Factor-1α 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-1A. 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-1A protein, but not mRNA, was down-regulated in a drug dose-dependent manner. In addition, HIF-1A 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-1A protein in the human ovarian cancer cell line 1A9 and its B-tubulin mutant epothilone-resistant subclone 1A9/A8. Our data showed that epothilone B treatment down-regulated HIF-1A 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-1A 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-1A 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 B-tubulin drug binding with HIF-1A protein inhibition. Our results further provide a strong rationale for testing taxanes and epothilones in clinical trials targeting HIF-1 in cancer patients. (Cancer Res 2005; 65(19): 9021-8)

Regulation of VEGF-expression by patupilone and ionizing radiation in lung adenocarcinoma cells

“…A variety of microtubule targeting drugs has previously been described to exhibit anti-HIF properties in tumor cells exposed to hypoxia [3,5]. 2-Methoxyestradiol and classic microtubule stabilizing (taxanes) and microtubule destabilizing (vincristine, discodermolide) agents downregulated HIF-1α at the posttranscriptional level resulting in reduced HIF-1α protein synthesis and subsequent reduced nuclear accumulation and transcriptional activity.…”

“…The use of microtubule interfering agents is therefore a promising strategy for anti-cancer therapy alone and as part of combined treatment modalities with cytotoxic agents [1]. The effects of microtubule interfering agents at the biochemical level are well investigated, but additional cytotoxic effects due to signaling interference have been identified, which merit further investigation [2][3][4][5].…”

“…Microtubule stabilizing and destabilizing agents block the nuclear translocation and correct assembly of the hypoxia inducible factor (HIF) by disrupting the structural organization of the microtubule cytoskeleton. In consequence, the downstream signaling of HIF-1 target genes in response to hypoxia is compromised [2][3]5]. A reduction of pro-angiogenic (and cytoprotective) cytokine secretion by patupilone via inhibition of HIF could contribute to this mechanism [14][15].…”

“…Here we investigated the treatment response of low-dose, sub-nanomolar concentrations of patupilone alone and in combination with IR specifically on hypoxia-driven VEGF expression and secretion in the patupilone-sensitive lung adenocarcinoma cell line A549 and the mutant derivative A549.EpoB40, which is strongly resistant to patupilone due to a genetically defined β-tubulin-mutation [3,[19][20][21].…”

Cyclin-dependent kinase inhibitor, P276-00, inhibits HIF-1α and induces G2/M arrest under hypoxia in prostate cancer cells

“…29 A number of anticancer drugs have been shown to inhibit HIF, but none of these drugs have been shown to directly and specifically target HIF-1. [30][31][32][33][34][35][36][37] Moreover, only a few of the reported HIF-1a inhibitors demonstrated antitumor activity in vivo. 38,39 This lack of specificity increases the difficulty in attributing any antitumorigenic effects of these drugs specifically to the inhibition of HIF-1a.…”