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

Cancer Res. 2001 Oct 1;61(19):7349-55.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Basic Helix-Loop-Helix Transcription Factors
  • Blotting, Western
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism
  • Carcinoma, Renal Cell / genetics
  • Carcinoma, Renal Cell / metabolism
  • Cell Hypoxia / physiology
  • Chromones / pharmacology
  • DNA-Binding Proteins / biosynthesis*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Endothelial Growth Factors / biosynthesis*
  • Endothelial Growth Factors / genetics
  • Enzyme Inhibitors / pharmacology
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Kidney Neoplasms / genetics
  • Kidney Neoplasms / metabolism
  • Ligases*
  • Lymphokines / biosynthesis*
  • Lymphokines / genetics
  • Morpholines / pharmacology
  • Mutation
  • Nuclear Proteins / biosynthesis*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • PTEN Phosphohydrolase
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphoric Monoester Hydrolases / biosynthesis
  • Phosphoric Monoester Hydrolases / genetics
  • Protein Serine-Threonine Kinases*
  • Proteins / genetics*
  • Proto-Oncogene Proteins / biosynthesis
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / physiology*
  • Proto-Oncogene Proteins c-akt
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Signal Transduction / physiology
  • Trans-Activators / biosynthesis*
  • Trans-Activators / genetics
  • Transcription Factors*
  • Tumor Cells, Cultured
  • Tumor Suppressor Proteins*
  • Ubiquitin-Protein Ligases*
  • Ubiquitins / metabolism
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors
  • Von Hippel-Lindau Tumor Suppressor Protein
  • ras Proteins / biosynthesis
  • ras Proteins / genetics*

Substances

  • Basic Helix-Loop-Helix Transcription Factors
  • Chromones
  • DNA-Binding Proteins
  • Endothelial Growth Factors
  • Enzyme Inhibitors
  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Lymphokines
  • Morpholines
  • Nuclear Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • Proteins
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • Trans-Activators
  • Transcription Factors
  • Tumor Suppressor Proteins
  • Ubiquitins
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors
  • endothelial PAS domain-containing protein 1
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Ubiquitin-Protein Ligases
  • Von Hippel-Lindau Tumor Suppressor Protein
  • AKT1 protein, human
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Phosphoric Monoester Hydrolases
  • PTEN Phosphohydrolase
  • PTEN protein, human
  • ras Proteins
  • Ligases
  • VHL protein, human