Evidence of the involvement of phosphatidylinositol 3-kinase in the migration, actin stress fiber formation, and alpha v beta 3-integrin-mediated adherence of human melanoma cells.
Tumor invasion and formation of metastases are major obstacles for a successful therapy of melanomas. Metastasis is thought to require multiple steps such as alpha v beta 3-integrin-mediated adhesion, proteolytic digestion of extracellular matrix by metalloproteinase-2, and reorganization of the actin cytoskeleton. To analyze the functional role of phosphatidylinositol 3-kinase in these processes, melanoma cells were treated with the fungal metabolite wortmannin. Wortmannin inhibited phosphatidylinositol 3-kinase activity in melanoma cells and migration in an equally concentration-dependent fashion. Flow cytometric analysis of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phallacidin-stained actin network indicated reduction of actin filaments by wortmannin. Fluorescence laser confocal microscopy experiments revealed breakdown of actin stress fibers. In addition, wortmannin inhibited alpha v beta 3-integrin-mediated adhesion of melanoma cells to vitronectin. Since flow cytometric measurements did not show altered expression of the alpha v beta 3-integrin at the cell surface, avidity changes of the alpha v beta 3-integrin by wortmannin are suggested. In contrast to the actin analysis and adhesion assays, wortmannin had no influence on mRNA expression or on protein secretion of metalloproteinase-2. These data provide evidence that phosphatidylinositol 3-kinase is an essential signal transduction protein required for migration of melanoma cells, regulating formation of the actin stress fiber as well as alpha v beta 3-integrin-mediated adhesion.
Metzner
B
B
Department of Dermatology, University of Freiburg, Germany.
Barbisch
M
M
Bachmann
F
F
Czech
W
W
Norgauer
J
J
D000199:Actins / Q000378:metabolism*; D000730:Androstadienes / Q000494:pharmacology; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D008545:Melanoma / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000502:physiology*; D019030:Receptors, Vitronectin / Q000502:physiology*; D014407:Tumor Cells, Cultured; D019096:Vitronectin; D000077191:Wortmannin
D000199:Actins; D000730:Androstadienes; D004791:Enzyme Inhibitors; D019030:Receptors, Vitronectin; D019096:Vitronectin; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D000077191:Wortmannin