Mutant IkappaBalpha suppresses hypoxia-induced VEGF expression through downregulation of HIF-1alpha and COX-2 in human glioma cells.
Our previous study demonstrated that mutant IkappaBalpha (IkappaBalphaM) could inhibit glioma angiogenesis and tumorigenesis through the downregulation of vascular endothelial growth factor (VEGF) and IL-8. However, the pathways involved in VEGF expression are not well understood. Growing evidence indicates that hypoxia-inducible factor-1alpha (HIF-1alpha) and cyclooxygenases-2 (COX-2) play important roles in this progression. In this study, we first examined the expressions of hypoxia-induced genes in human glioma cells transfected with IkappaBalphaM (IN500deltaM) or control plasmid (IN500delta) in vitro. We found that hypoxic stress induced the expressions of HIF-1alpha, COX-2, and VEGF, and that IkappaBalphaM completely suppressed these expressions in vitro. Next, we injected these glioma cells into nude mice. After 3 weeks, the mice were moved to a hypoxic chamber (10% oxygen) for 3, 12, 24, 48, 96, or 144 h. The expressions of HIF-1alpha, COX-2, and VEGF in vivo were then analyzed by Northern blot and immunohistochemistry. IkappaBalphaM suppressed the expression of hypoxia-induced HIF-1alpha gene in vivo, but hypoxic stress induced the expression of COX-2 after 72 h. VEGF induction followed after 96 h of hypoxia in IN500deltaM cells. These findings suggest that VEGF expression appears to be regulated through dual interdependent mechanisms involving HIF-1 and COX-2 genes, and IkappaBalphaM could inhibit VEGF expression through these two pathways. Thus, IkappaBalphaM is identified as a pivotal factor in angiogenesis and is a potential target for neoplasm therapy.
Kimba
Yoshihira
Y
Department of Neurosurgery, Oita University School of Medicine, 1-1, Idaigaoka, Hasama-machi, Oita, 879-5593 Japan.
Abe
Tatsuya
T
Wu
Jian Liang
JL
Inoue
Ryo
R
Fukiki
Minoru
M
Kohno
Kimitoshi
K
Kobayashi
Hidenori
H
D000818:Animals; D015152:Blotting, Northern; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D015536:Down-Regulation; D005910:Glioma / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020672:I-kappa B Proteins / Q000235:genetics*; D007150:Immunohistochemistry; D008565:Membrane Proteins; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D000072000:NF-KappaB Inhibitor alpha; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis*; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D014157:Transcription Factors / Q000096:biosynthesis*; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis*
D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020672:I-kappa B Proteins; D008565:Membrane Proteins; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D009687:Nuclear Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D000072000:NF-KappaB Inhibitor alpha; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases