title: Differential regulation of VEGF, HIF1alpha and angiopoietin-1, -2 and -4 by hypoxia and ionizing radiation in human glioblastoma.
abstract: We examined how ionizing radiation (IR) delivered under either severe hypoxia (< 0.1% O2) or normoxia affects the expression of hypoxia inducible factor 1alpha (HIF-1alpha) and the angiogenic factors vascular endothelial growth factor (VEGF) and angiopoietins 1, 2 and 4 in U87 human glioblastoma cells. IR was delivered as single doses of 0, 2, 5, 10 and 20 Gy after 6-hr hypoxic incubation and in normoxic controls. Irradiation at any dose did not affect the cellular protein levels of any of the angiopoietins, whereas hypoxia led to increasing levels of both angiopoietin-4 and angiopoietin-2. Levels of angiopoietin-1 protein were unaltered throughout the observation period. A dose-dependent increase in levels of secreted VEGF in the medium occurred after IR at doses from 5-20 Gy. In hypoxic cells, 20 Gy IR induced an additional significant increase in VEGF relative to nonirradiated hypoxic control cells with elevated baseline VEGF levels induced by hypoxia. HIF-1alpha and glucose transporter-1 (Glut-1) were not correspondingly upregulated by IR. Blocking HIF-1alpha by antisense treatment induced a reduced baseline VEGF at normoxia, while the relative upregulation of VEGF by IR was unaffected. These data provide evidence that VEGF is upregulated by IR by mechanisms independent of HIF-1 transactivation.
authors.affiliation: Laboratory of Experimental Oncology, Department of Molecular Pathology, University of Copenhagen, Frederik V's Vej 11, DK-2100 Copenhagen, Denmark.
authors.forename: Eva L
authors.initials: EL
authors.lastname: Lund
authors.forename: Anja
authors.initials: A
authors.lastname: Høg
authors.forename: Minna W B
authors.initials: MW
authors.lastname: Olsen
authors.forename: Lasse T
authors.initials: LT
authors.lastname: Hansen
authors.forename: Svend A
authors.initials: SA
authors.lastname: Engelholm
authors.forename: Paul E G
authors.initials: PE
authors.lastname: Kristjansen
mesh_terms: D042683:Angiopoietin-1 / Q000096:biosynthesis*; D042702:Angiopoietin-2 / Q000096:biosynthesis*; D042682:Angiopoietins / Q000096:biosynthesis*; D015152:Blotting, Northern; D015153:Blotting, Western; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000188:drug therapy / Q000378:metabolism* / Q000532:radiotherapy; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009841:Oligonucleotides / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011839:Radiation, Ionizing; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism
chemical_list: D042683:Angiopoietin-1; D042702:Angiopoietin-2; D042682:Angiopoietins; D018076:DNA, Complementary; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009004:Monosaccharide Transport Proteins; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; C118117:angiopoietin 4