In:
Molecular Cancer Therapeutics, American Association for Cancer Research (AACR), Vol. 10, No. 11_Supplement ( 2011-11-12), p. B7-B7
Abstract:
Background: Hypoxia inducible factor-1α (HIF-1α) is a therapeutic target in solid tumors because it activates transcription of the genes associated with tumor growth, angiogenesis and chemo/radio-resistance. Activation of PPARα has been demonstrated to inhibit tumor growth and angiogenesis, yet the mechanisms behind these actions remain obscure. The present study examined the effects of PPARα activation on HIF-1α mediated signaling in human cancer cells. Methods: The human cancer lines MCF-7 (breast) and A2780 (ovarian), and human endothelial line, EA.hy926 were used as model systems for this study. Hypoxia was achieved via a hypoxia chamber. The HRE-luciferase reporter gene and Western blot were applied to analyze HIF-1α expression and activity. RT-PCR and co-immunoprecipitation were performed to understand the molecular mechanisms of PPARα-mediated suppression of HIF-1α signaling. The level of vascular endothelial growth factor (VEGF) in cultured medium was determined using an ELISA, and in vitro angiogenesis was evaluated using the tube formation assay. Results: Incubation of cancer cells with 1 % oxygen for 16 hours significantly induced HIF-1α expression and activity. Treatment of the cells with PPARα agonists, but not a PPARγ agonist, prior to hypoxia diminished hypoxia-induced HIF-1α expression and activity. Consistently, a PPARα antagonist attenuated PPARα agonist-induced suppression of HIF-1α signaling. Over-expression of an HA-tagged HIF-1α and HIF-1α-P402/P564A mutant protein demonstrated that activation of PPARα promotes HIF-1 α degradation in our model system. This was further confirmed by the use of MG-132, a proteasome inhibitor, which reversed PPARα-mediated suppression of the HIF-1α signaling, and by RT-PCR analysis of HIF-1α mRNA, which was unchanged by PPARα activation. Using the co-immunoprecipitation technique, we found that activation of PPARα enhances the binding of hydroxylated HIF-1α to the Von Hippel-Lindau tumor suppressor, a protein known to mediate HIF-1α degradation through the ubiquitin-proteasome pathway. Consequential to the PPARα-mediated suppression of HIF-1α signaling, vascular endothelial growth factor secretion from cancer cells was found to be significantly reduced, and the tube formation by EA.hy926 cells was dramatically impaired. Summary: Activation of PPARα suppresses HIF-1α expression and activity by promoting HIF-1α degradation in cancer cells. PPARα agonists are potential anticancer agents that inhibit tumor angiogenesis via the suppression of HIF-1α signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B7.
Type of Medium:
Online Resource
ISSN:
1535-7163
,
1538-8514
DOI:
10.1158/1535-7163.TARG-11-B7
Language:
English
Publisher:
American Association for Cancer Research (AACR)
Publication Date:
2011
detail.hit.zdb_id:
2062135-8
SSG:
12
