title: Dissecting and targeting the growth factor-dependent and growth factor-independent extracellular signal-regulated kinase pathway in human schwannoma.
abstract: Schwannomas are tumors of the nervous system that occur sporadically and in patients with the cancer predisposition syndrome neurofibromatosis type 2 (NF2). Schwannomas and all NF2-related tumors are caused by loss of the tumor suppressor merlin. Using our human in vitro model for schwannoma, we analyzed extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT signaling pathways, their upstream growth factor receptors, and their role in schwannoma cell proliferation and adhesion to find new systemic therapies for these tumors that, to date, are very difficult to treat. We show here that human primary schwannoma cells show an enhanced basal Raf/mitogen-activated protein/ERK kinase/ERK1/2 pathway activity compared with healthy Schwann cells. Due to a strong and prolonged activation of platelet-derived growth factor receptor beta (PDGFRbeta), which is highly overexpressed, ERK1/2 and AKT activation was further increased in schwannoma, leading to increased proliferation. Using specific inhibitors, we discovered that ERK1/2 activation involves the integrin/focal adhesion kinase/Src/Ras signaling cascades and PDGFRbeta-mediated ERK1/2 activation is triggered through the phosphatidylinositol 3-kinase/protein kinase C/Src/c-Raf pathway. Due to the complexity of signals leading to schwannoma cell proliferation, potential new therapeutic agents should target several signaling pathways. The PDGFR and c-Raf inhibitor sorafenib (BAY 43-9006; Bayer Pharmaceuticals), currently approved for treatment of advanced renal cell cancer, inhibits both basal and PDGFRbeta-mediated ERK1/2 and AKT activity and decreases cell proliferation in human schwannoma cells, suggesting that this drug constitutes a promising tool to treat schwannomas. We conclude that our schwannoma in vitro model can be used to screen for new therapeutic targets in general and that sorafenib is possible candidate for future clinical trials.
authors.affiliation: Clinical Neurobiology, Peninsula College for Medicine and Dentistry, Research Way, Plymouth, United Kingdom.
authors.forename: Sylwia
authors.initials: S
authors.lastname: Ammoun
authors.forename: Christine
authors.initials: C
authors.lastname: Flaiz
authors.forename: Natalia
authors.initials: N
authors.lastname: Ristic
authors.forename: Jennifer
authors.initials: J
authors.lastname: Schuldt
authors.forename: C Oliver
authors.initials: CO
authors.lastname: Hanemann
mesh_terms: D002478:Cells, Cultured; D016503:Drug Delivery Systems; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D008222:Lymphokines / Q000494:pharmacology; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008954:Models, Biological; D009442:Neurilemmoma / Q000201:enzymology / Q000209:etiology / Q000235:genetics / Q000378:metabolism*; D016518:Neurofibromatosis 2 / Q000150:complications; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000235:genetics / Q000378:metabolism
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; C427493:PDGFD protein, human; D010982:Platelet-Derived Growth Factor; C482128:MAP2K2 protein, human; D020797:Receptor, Platelet-Derived Growth Factor beta; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D051058:Oncogene Protein v-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human