Akt mediates an angiogenic switch in transformed keratinocytes

Carcinogenesis. 2004 Jul;25(7):1137-47. doi: 10.1093/carcin/bgh132. Epub 2004 Mar 4.

Abstract

Akt signaling is involved in tumorigenesis via a number of different mechanisms that result in increased proliferation and decreased apoptosis. Previous data have demonstrated that Akt-mediated signaling is functionally involved in keratinocyte transformation. This work investigates the involvement of angiogenesis as a mediator of tumorigenesis in Akt-transformed keratinocytes. Tumors produced by subcutaneous injection of the latter showed increased angiogenic profiles associated with increased vascular endothelial growth factor (VEGF) protein levels. However, in contrast to v-ras(Ha)-transformed keratinocytes, VEGF mRNA levels were not increased. The induction of VEGF protein by Akt is associated with increased phosphorylation and thus activation of p70S6K and eIF4E-binding protein 1, leading to increased VEGF translation. In addition, we observed increased metaloproteinases 2 and 9 expression, but not thrombospondin 1, in tumors derived from Akt-transformed keratinocytes. Collectively, these results demonstrate that Akt is an important mediator of angiogenesis in malignant keratinocytes through a post-transcriptional mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Differentiation / physiology
  • Keratinocytes / metabolism*
  • Matrix Metalloproteinase 2 / genetics
  • Matrix Metalloproteinase 2 / metabolism
  • Matrix Metalloproteinase 9 / genetics
  • Matrix Metalloproteinase 9 / metabolism
  • Mice
  • Neovascularization, Pathologic / metabolism*
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Skin Neoplasms / metabolism*
  • Time Factors
  • Up-Regulation
  • Vascular Endothelial Growth Factor A / genetics
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • Proto-Oncogene Proteins
  • Vascular Endothelial Growth Factor A
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Matrix Metalloproteinase 2
  • Matrix Metalloproteinase 9