Cyclic AMP signaling as a mediator of vasculogenic mimicry in aggressive human melanoma cells in vitro

Cancer Res. 2009 Feb 1;69(3):802-9. doi: 10.1158/0008-5472.CAN-08-2391. Epub 2009 Jan 27.

Abstract

Aggressive melanoma cells can engage in a process termed vasculogenic mimicry (VM) that reflects the ability of tumor cells to express a multipotent, stem cell-like phenotype. Melanoma cell plasticity contributes to the lack of efficient therapeutic strategies targeting metastatic tumors. This study reveals cyclic AMP as a mediator of VM in vitro. In uveal and cutaneous metastatic aggressive human melanoma cells, an increase in cyclic AMP by forskolin, dibutyryl cyclic AMP, or G protein-coupled receptor (GPCR) ligands such as adrenaline and vasoactive intestinal peptide inhibited VM to different extents. Although chemical modulators of protein kinase A (PKA) had no effect, a specific pharmacologic activator of Exchange protein directly activated by cyclic AMP (Epac) impaired VM. Ras-associated protein-1 (Rap1) activation assays revealed that cyclic AMP-elevating agents induce a PKA-independent activation of Epac/Rap1. Pharmacologic inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) activity abolished VM. Phosphorylation of ERK1/2 was PKA-independently inhibited by forskolin but not inhibited by Epac/Rap1 signaling, PKA modulation, or GPCR ligands. Furthermore, the forskolin also inhibited phosphatidyl inositol-3-kinase (PI3K)-mediated activation of protein kinase Akt, as monitored by Ser473 phosphorylation. The pharmacologic activation of Epac and GPCR ligands slightly stimulated Akt, a likely concomitant process of VM modulation. Collectively, these data show that forskolin strongly inhibits VM through PKA-independent activation of Epac/Rap1, PKA-, and Epac-independent inactivation of ERK1/2 and inhibition of PI3K/Akt. The data also show that VM inhibition by GPCR ligands involves mainly the Epac/Rap1-activated signal. Thus cyclic AMP inhibits VM through multiple signaling pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • Cell Line, Tumor
  • Colforsin / pharmacology
  • Cyclic AMP / metabolism*
  • Guanine Nucleotide Exchange Factors / metabolism
  • Humans
  • Ligands
  • MAP Kinase Signaling System / drug effects
  • Melanoma / blood supply
  • Melanoma / metabolism*
  • Melanoma / pathology*
  • Microvessels / drug effects
  • Microvessels / metabolism
  • Microvessels / pathology
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Neovascularization, Pathologic / metabolism
  • Neovascularization, Pathologic / pathology
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Receptors, G-Protein-Coupled / metabolism
  • Shelterin Complex
  • Signal Transduction / drug effects
  • Telomere-Binding Proteins / metabolism
  • Vasoactive Intestinal Peptide / pharmacology
  • alpha-MSH / pharmacology

Substances

  • Guanine Nucleotide Exchange Factors
  • Ligands
  • RAPGEF3 protein, human
  • Receptors, G-Protein-Coupled
  • Shelterin Complex
  • TERF2IP protein, human
  • Telomere-Binding Proteins
  • Colforsin
  • Vasoactive Intestinal Peptide
  • alpha-MSH
  • Cyclic AMP
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • 1-Methyl-3-isobutylxanthine