Abstract
Hypoxia-induced up-regulation of vascular endothelial growth factor (VEGF) expression is a critical event leading to tumor neovascularization. Hypoxia stimulates hypoxia-inducible factor-1alpha (HIF-1alpha), a transcriptional activator of VEGF. Cyclooxygenase (COX)-2, an inducible enzyme that catalyzes the formation of prostaglandins (PGs) from arachidonic acid, is also induced by hypoxia. We reported previously that COX-2 inhibition prevents hypoxic up-regulation of VEGF in human prostate cancer cells and that prostaglandin E(2) (PGE(2)) restores hypoxic effects on VEGF. We hypothesized that PGE(2) mediates hypoxic effects on VEGF by modulating HIF-1alpha expression. Addition of PGE(2) to PC-3ML human prostate cancer cells had no effect on HIF-1alpha mRNA levels. However, PGE(2) significantly increased HIF-1alpha protein levels, particularly in the nucleus. This effect of PGE(2) largely results from the promotion of HIF-1alpha translocation from the cytosol to the nucleus. PGE(2) addition to PC-3 ML cells transfected with a GFP-HIF-1alpha vector induced a time-dependent nuclear accumulation of the HIF-1alpha protein. Two selective COX-2 inhibitors, meloxicam and NS398, decreased HIF-1alpha levels and nuclear localization, under both normoxic and hypoxic conditions. Of several prostaglandins tested, only PGE(2) reversed the effects of a COX-2 inhibitor in hypoxic cells. Finally, PGE(2) effects on HIF-1alpha were specifically inhibited by PD98059 (a MAPK inhibitor). These data demonstrate that PGE(2) production via COX-2-catalyzed pathway plays a critical role in HIF-1alpha regulation by hypoxia and imply that COX-2 inhibitors can prevent hypoxic induction of HIF-mediated gene transcription in cancer cells.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Active Transport, Cell Nucleus
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Arachidonic Acid / metabolism
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Catalysis
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Cell Nucleus / metabolism
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Culture Media, Serum-Free / pharmacology
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Cyclooxygenase 2
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Cyclooxygenase 2 Inhibitors
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Cyclooxygenase Inhibitors / pharmacology
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Cytosol / metabolism
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Dinoprostone / metabolism*
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Endothelial Growth Factors / metabolism
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Enzyme Inhibitors / pharmacology
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Flavonoids / pharmacology
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Green Fluorescent Proteins
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Humans
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Hypoxia*
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Hypoxia-Inducible Factor 1, alpha Subunit
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Immunoblotting
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Intercellular Signaling Peptides and Proteins / metabolism
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Isoenzymes / metabolism*
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Luminescent Proteins / metabolism
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Lymphokines / metabolism
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MAP Kinase Signaling System
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Male
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Meloxicam
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Membrane Proteins
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Nitrobenzenes / pharmacology
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Phosphatidylinositol 3-Kinases / metabolism
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Prostaglandin-Endoperoxide Synthases / metabolism*
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Prostaglandins / metabolism
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Prostatic Neoplasms / pathology*
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RNA, Messenger / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Sulfonamides / pharmacology
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Thiazines / pharmacology
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Thiazoles / pharmacology
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Time Factors
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Transcription Factors / metabolism*
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Transcription, Genetic
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Transfection
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Tumor Cells, Cultured
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Up-Regulation*
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Vascular Endothelial Growth Factor A
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Vascular Endothelial Growth Factors
Substances
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Culture Media, Serum-Free
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Cyclooxygenase 2 Inhibitors
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Cyclooxygenase Inhibitors
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Endothelial Growth Factors
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Enzyme Inhibitors
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Flavonoids
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HIF1A protein, human
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Hypoxia-Inducible Factor 1, alpha Subunit
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Intercellular Signaling Peptides and Proteins
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Isoenzymes
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Luminescent Proteins
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Lymphokines
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Membrane Proteins
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Nitrobenzenes
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Prostaglandins
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RNA, Messenger
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Sulfonamides
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Thiazines
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Thiazoles
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Transcription Factors
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Vascular Endothelial Growth Factor A
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Vascular Endothelial Growth Factors
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N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide
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Green Fluorescent Proteins
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Arachidonic Acid
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Cyclooxygenase 2
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PTGS2 protein, human
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Prostaglandin-Endoperoxide Synthases
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Phosphatidylinositol 3-Kinases
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Dinoprostone
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
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Meloxicam