title: Cyclic AMP signaling as a mediator of vasculogenic mimicry in aggressive human melanoma cells in vitro.
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.
authors.affiliation: Institut National de la Sante et de la Recherche Medicale UMR911, Centre de Recherche en Oncologie Biologique et Onco-pharmacologie, Aix-Marseille University, School of Medicine Timone, Marseille, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lissitzky
authors.forename: Danielle
authors.initials: D
authors.lastname: Parriaux
authors.forename: Elodie
authors.initials: E
authors.lastname: Ristorcelli
authors.forename: Alain
authors.initials: A
authors.lastname: Vérine
authors.forename: Dominique
authors.initials: D
authors.lastname: Lombardo
authors.forename: Patrick
authors.initials: P
authors.lastname: Verrando
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D045744:Cell Line, Tumor; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D008024:Ligands; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008545:Melanoma / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology*; D055806:Microvessels / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D000089804:Shelterin Complex; D015398:Signal Transduction / Q000187:drug effects; D034501:Telomere-Binding Proteins / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D000521:alpha-MSH / Q000494:pharmacology
chemical_list: D015056:1-Methyl-3-isobutylxanthine; D005576:Colforsin; D000242:Cyclic AMP; D020662:Guanine Nucleotide Exchange Factors; D008024:Ligands; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D043562:Receptors, G-Protein-Coupled; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D014660:Vasoactive Intestinal Peptide; D000521:alpha-MSH; C116122:RAPGEF3 protein, human; C440809:TERF2IP protein, human