Effects of ras and von Hippel-Lindau (VHL) gene mutations on hypoxia-inducible factor (HIF)-1alpha, HIF-2alpha, and vascular endothelial growth factor expression and their regulation by the phosphatidylinositol 3'-kinase/Akt signaling pathway.
Many oncogenes induce expression of vascular endothelial growth factor (VEGF), a key factor in tumor angiogenesis. Phosphatidylinositol 3'-kinase (PI3K)/Akt is a common signaling pathway for oncogenes and tumor suppressor genes and is involved in VEGF regulation. Because hypoxia is a major stimulus for VEGF production, we examined the effects of LY294002, a selective PI3K inhibitor, on hypoxia-inducible factor (HIF)-1alpha and HIF-2alpha expression and on endogenous VEGF responses to hypoxia. A panel of breast cancer cell lines reflecting the different genetic changes occurring in human breast cancer was analyzed. LY294002 inhibited HIF-1alpha induction and phosphorylation under hypoxia. However, HIF-2alpha expression was not affected. Basal and hypoxia-inducible VEGF expression was reduced at both mRNA and protein levels by 50%. V12-ras overexpression resulted in an increase in hypoxia-induced HIF-1alpha and HIF-2alpha expression. This effect was blocked by PI3K inhibitor, demonstrating one mechanism for ras synergy with hypoxia-mediated induction of genes. The decreased HIF-1alpha expression was not dependent on VHL interaction because a renal carcinoma cell line with VHL mutation and constitutive high HIF-1alpha expression also showed down-regulation of HIF-1alpha after treatment with LY294002. These results have implications for the use of PI3K inhibitors to inhibit synergistic effects of hypoxia with a wide range of common oncogenes.
Blancher
C
C
Imperial Cancer Research Fund, Molecular Oncology Unit, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
Moore
J W
JW
Robertson
N
N
Harris
A L
AL
D051792:Basic Helix-Loop-Helix Proteins; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology; D002867:Chromones / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D016228:Endothelial Growth Factors / Q000096:biosynthesis* / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007680:Kidney Neoplasms / Q000235:genetics / Q000378:metabolism; D008025:Ligases; D008222:Lymphokines / Q000096:biosynthesis* / Q000235:genetics; D009025:Morpholines / Q000494:pharmacology; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D015534:Trans-Activators / Q000096:biosynthesis* / Q000235:genetics; D014157:Transcription Factors; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D018631:ras Proteins / Q000096:biosynthesis / Q000235:genetics*; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D002867:Chromones; D004268:DNA-Binding Proteins; D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008025:Ligases; D008222:Lymphokines; D009025:Morpholines; D009687:Nuclear Proteins; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D018631:ras Proteins; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; C494929:PTEN protein, human; C497446:VHL protein, human