Effects of soluble CPE on glioma cell migration are associated with mTOR activation and enhanced glucose flux

// Elena I. Ilina 1, 2, 3 , Angela Armento 4 , Leticia Garea Sanchez 1 , Marina Reichlmeir 1 , Yannick Braun 1 , Cornelia Penski 1, 5 , David Capper 5, 6 , Felix Sahm 5, 6 , Lukas Jennewein 1 , Patrick N. Harter 1, 5 , Sven Zukunft 7 , Ingrid Fleming 7 , Dorothea Schulte 1 , Francois Le Guerroue 8 , Christian Behrends 8, 9 , Michael W. Ronellenfitsch 5, 10 , Ulrike Naumann 4 and Michel Mittelbronn 1, 2, 3, 5, 11, 12 1 Institute of Neurology (Edinger Institute), Goethe University, 60528 Frankfurt, Germany 2 Luxembourg Centre of Neuropathology (LCNP), 3555 Dudelange, Luxembourg 3 NORLUX Neuro-Oncology Laboratory, Department of Oncology, Luxembourg Institute of Health (L.I.H.), 1526 Luxembourg, Luxembourg 4 Molecular Neurooncology, Department of Vascular Neurology, Hertie Institute for Clinical Brain Research and Center Neurology, University of Tubingen, 72076 Tubingen, Germany 5 German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany 6 Department of Neuropathology, Institute of Pathology, Ruprecht-Karls-University, 69120 Heidelberg, Germany 7 Institute for Vascular Signaling, Centre for Molecular Medicine, Goethe University, 60590 Frankfurt, Germany 8 Institute of Biochemistry II, Medical School Goethe University, 60528 Frankfurt, Germany 9 Munich Cluster for Systems Neurology (SyNergy), Medical Faculty, Ludwig-Maximilians-University (LMU) Munich, 81377 Munich, Germany 10 Senckenberg Institute of Neurooncology, Goethe University, 60528 Frankfurt, Germany 11 Laboratoire National de Sante, Department of Pathology, 3555 Dudelange, Luxembourg 12 Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, 4361 Esch-sur-Alzette, Luxembourg Correspondence to: Michel Mittelbronn, email: michel.mittelbronn@lns.etat.lu Keywords: CPE, glioblastoma, migration, metabolism, mTOR Received: October 15, 2016      Accepted: February 12, 2017      Published: June 27, 2017 ABSTRACT Carboxypeptidase E (CPE) has recently been described as a multifunctional protein that regulates proliferation, migration and survival in several tumor entities. In glioblastoma (GBM), the most malignant primary brain tumor, secreted CPE (sCPE) was shown to modulate tumor cell migration. In our current study, we aimed at clarifying the underlying molecular mechanisms regulating anti-migratory as well as novel metabolic effects of sCPE in GBM. Here we show that sCPE activates mTORC1 signaling in glioma cells detectable by phosphorylation of its downstream target RPS6. Additionally, sCPE diminishes glioma cell migration associated with a negative regulation of Rac1 signaling via RPS6, since both inhibition of mTOR and stimulation of Rac1 results in a reversed effect of sCPE on migration. Knockdown of CPE leads to a decrease of active RPS6 associated with increased GBM cell motility. Apart from this, we show that sCPE enhances glucose flux into the tricarboxylic acid cycle at the expense of lactate production, thereby decreasing aerobic glycolysis, which might as well contribute to a less invasive behavior of tumor cells. Our data contributes to a better understanding of the complexity of GBM cell migration and sheds new light on how tumor cell invasion and metabolic plasticity are interconnected.