title: Interference with distinct steps of sphingolipid synthesis and signaling attenuates proliferation of U87MG glioma cells.
abstract: Glioblastoma is the most common malignant brain tumor, which, despite combined radio- and chemotherapy, recurs and is invariably fatal for affected patients. Members of the sphingolipid (SL) family are potent effectors of glioma cell proliferation. In particular sphingosine-1-phosphate (S1P) and the corresponding G protein-coupled S1P receptors transmit proliferative signals to glioma cells. To investigate the contribution to glioma cell proliferation we inhibited the first step of de novo SL synthesis in p53(wt) and p53(mut) glioma cells, and interfered with S1P signaling specifically in p53(wt) U87MG cells. Subunit silencing (RNAi) or pharmacological antagonism (using myriocin) of serine palmitoyltransferase (SPT; catalyzing the first committed step of SL biosynthesis) reduced proliferation of p53(wt) but not p53(mut) GBM cells. In U87MG cells these observations were accompanied by decreased ceramide, sphingomyelin, and S1P content. Inhibition of SPT upregulated p53 and p21 expression and induced an increase in early and late apoptotic U87MG cells. Exogenously added S1P (complexed to physiological carriers) increased U87MG proliferation. In line, silencing of individual members of the S1P receptor family decreased U87MG proliferation. Silencing and pharmacological inhibition of the ATP-dependent cassette transporter A1 (ABCA1) that facilitates S1P efflux in astrocytes attenuated U87MG growth. Glyburide-mediated inhibition of ABCA1 resulted in intracellular accumulation of S1P raising the possibility that ABCA1 promotes S1P efflux in U87MG glioma cells thereby contributing to inside-out signaling. Our findings indicate that de novo SL synthesis, S1P receptor-mediated signaling, and ABCA1-mediated S1P efflux could provide pharmacological targets to interfere with glioma cell proliferation.
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Bernhart
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria.
authors.forename: Sabine
authors.initials: S
authors.lastname: Damm
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria.
authors.forename: Andrea
authors.initials: A
authors.lastname: Wintersperger
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria; BioTechMed Graz, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Nusshold
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria.
authors.forename: Anna Martina
authors.initials: AM
authors.lastname: Brunner
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Plastira
authors.affiliation: Institute of Molecular Biosciences, University of Graz, Austria.
authors.forename: Gerald
authors.initials: G
authors.lastname: Rechberger
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria.
authors.forename: Helga
authors.initials: H
authors.lastname: Reicher
authors.affiliation: Department of Obstetrics and Gynecology, Medical University of Graz, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Wadsack
authors.affiliation: BioTechMed Graz, Austria; Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Zimmer
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria.
authors.forename: Ernst
authors.initials: E
authors.lastname: Malle
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Austria; BioTechMed Graz, Austria. Electronic address: wolfgang.sattler@medunigraz.at.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sattler
mesh_terms: D064286:ATP Binding Cassette Transporter 1 / Q000378:metabolism; D017209:Apoptosis; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D020868:Gene Silencing; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D049349:Receptors, Lysosphingolipid / Q000235:genetics / Q000378:metabolism; D051102:Serine C-Palmitoyltransferase / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D013107:Sphingolipids / Q000096:biosynthesis*
chemical_list: D064286:ATP Binding Cassette Transporter 1; D049349:Receptors, Lysosphingolipid; D013107:Sphingolipids; D051102:Serine C-Palmitoyltransferase
keywords: ABC transporter; Myriocin; Proliferation; RNA interference; Sphingolipids; p53