Up-regulation of hypoxia-inducible factors HIF-1alpha and HIF-2alpha under normoxic conditions in renal carcinoma cells by von Hippel-Lindau tumor suppressor gene loss of function.
Hypoxia induces transcription of a range of physiologically important genes including erythropoietin and vascular endothelial growth factor. The transcriptional activation is mediated by the hypoxia-inducible factor-1 (HIF-1), a heterodimeric member of the basic helix-loop-helix PAS family, composed of alpha and beta subunits. HIF-1alpha shares 48 per cent identity with the recently identified HIF-2alpha protein that is also stimulated by hypoxia. In a previous study of hemangioblastomas, the most frequent manifestation of hereditary von Hippel-Lindau disease (VHL), we found elevated levels of vascular endothelial growth factor and HIF-2alpha mRNA in stromal cells of the tumors. Mutations of the VHL tumor suppressor gene are associated with a variety of tumors such as renal clear cell carcinomas (RCC). In this study, we analysed the expression of the hypoxia-inducible factors HIF-1alpha and HIF-2alpha in a range of VHL wildtype and VHL deficient RCC cell lines. In the presence of functional VHL protein, HIF-1alpha mRNA levels are elevated, whereas HIF-2alpha mRNA expression is increased only in cells lacking a functional VHL gene product. On the protein levels, however, in VHL deficient cell lines, both HIF-alpha subunits are constitutively expressed, whereas re-introduction of a functional VHL gene restores the instability of HIF-1alpha and HIF-2alpha proteins under normoxic conditions. Moreover, immunohistochemical analyses of RCCs and hemangioblastomas demonstrate up-regulation of HIF-1alpha and HIF-2alpha in the tumor cells. The data presented here provide evidence for a role of the VHL protein in regulation of angiogenesis and erythropoiesis mediated by the HIF-1alpha and HIF-2alpha proteins.
Krieg
M
M
Neurocenter, Freiburg University Medical School, Germany.
Haas
R
R
Brauch
H
H
Acker
T
T
Flamme
I
I
Plate
K H
KH
D051792:Basic Helix-Loop-Helix Proteins; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism / Q000502:physiology; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D016228:Endothelial Growth Factors / Q000096:biosynthesis / Q000235:genetics; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D051272:Glucose Transporter Type 1; D018325:Hemangioblastoma / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000235:genetics* / Q000378:metabolism; D008025:Ligases; D008222:Lymphokines / Q000096:biosynthesis / Q000235:genetics; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D010100:Oxygen / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000096:biosynthesis* / Q000235:genetics; D014157:Transcription Factors; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D006623:von Hippel-Lindau Disease / Q000235:genetics; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D016228:Endothelial Growth Factors; D051272:Glucose Transporter Type 1; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008025:Ligases; D008222:Lymphokines; D009004:Monosaccharide Transport Proteins; D009687:Nuclear Proteins; D010100:Oxygen; D011506:Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C495677:SLC2A1 protein, human; C497446:VHL protein, human