Involvement of PI3K and MAPK signaling in bcl-2-induced vascular endothelial growth factor expression in melanoma cells

Mol Biol Cell. 2005 Sep;16(9):4153-62. doi: 10.1091/mbc.e04-12-1087. Epub 2005 Jun 29.

Abstract

We have previously demonstrated that bcl-2 overexpression in tumor cells exposed to hypoxia increases the expression of vascular endothelial growth factor (VEGF) gene through the hypoxia-inducible factor-1 (HIF-1). In this article, we demonstrate that exposure of bcl-2 overexpressing melanoma cells to hypoxia induced phosphorylation of AKT and extracellular signal-regulated kinase (ERK)1/2 proteins. On the contrary, no modulation of these pathways by bcl-2 was observed under normoxic conditions. When HIF-1alpha expression was reduced by RNA interference, AKT and ERK1/2 phosphorylation were still induced by bcl-2. Pharmacological inhibition of mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) signaling pathways reduced the induction of VEGF and HIF-1 in response to bcl-2 overexpression in hypoxia. No differences were observed between control and bcl-2-overexpressing cells in normoxia, in terms of VEGF protein secretion and in response to PI3K and MAPK inhibitors. We also demonstrated that RNA interference-mediated down-regulation of bcl-2 expression resulted in a decrease in the ERK1/2 phosphorylation and VEGF secretion only in bcl-2-overexpressing cell exposed to hypoxia but not in control cells. In conclusion, our results indicate, for the first time, that bcl-2 synergizes with hypoxia to promote expression of angiogenesis factors in melanoma cells through both PI3K- and MAPK-dependent pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / physiology
  • Cell Line, Tumor
  • DNA / metabolism
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Gene Expression Regulation, Neoplastic / physiology
  • Humans
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / genetics
  • MAP Kinase Signaling System / physiology*
  • Melanoma / enzymology*
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinases / physiology
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation
  • Promoter Regions, Genetic
  • Proto-Oncogene Proteins c-bcl-2 / physiology*
  • RNA Interference
  • RNA, Messenger / metabolism
  • Vascular Endothelial Growth Factor A / biosynthesis*
  • Vascular Endothelial Growth Factor A / genetics

Substances

  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • Vascular Endothelial Growth Factor A
  • DNA
  • Extracellular Signal-Regulated MAP Kinases
  • Mitogen-Activated Protein Kinases