Scientific Report 2003-2004 - Cleveland Clinic Lerner Research ...

The Department of Cancer BiologyRole, Signaling Mechanisms of BioactiveLysophospholipids/Receptors in CancerTHE XU LABORATORYVISITING PROFESSORKwan-sik Kim, M.D., Ph.D.My main research interests center onunderstanding, at the molecular level,the mechanism of development ofovarian, breast, and prostate cancers. Theseinclude revealing the molecular signalingmechanisms of cancer development andidentifying effective diagnostic and prognosticbiomarkers and novel therapeutic targets forthese diseases.We have pioneered research in the role ofsignaling lipid molecules in ovarian cancer. Weidentified the first lipid growth factor in ovariancancer cells and demonstrated that lysophosphatidicacid (LPA) is a potential marker for theearly detection of ovarian cancer. We havedeveloped a highly effective method to analyzelysophospholipids in body fluids and have shownthat certain bioactive lysophospholipids areelevated in blood, ascites, and peritonealwashings from patients with ovarian cancer.These findings suggest that these lipid moleculesare likely to be pathologically relevant to ovariancancer.We have investigated the role and signalingmechanisms of sphingosine-1-phosphate (S1P),sphingosylphosphorylcholine (SPC), LPA, andother lysophospholipids in ovarian cancerdevelopment. In addition, we have successfullyemployed the Clontech PCR-select cDNAsubtraction kit, Affymetrix GeneChip and cDNAarrays in identification of genes up- ordownregulated by LPA, S1P, and SPC.Lysophospholipids and other smallbioactive molecules function through G-proteincoupledreceptors (GPCRs). There is increasingevidence that abnormalities in the structure andfunction of GPCRs are responsible for manydiseases, including cancers. Molecular cloningand characterization of novel GPCRs willcontribute to a better understanding of thenormal functioning and signaling mechanisms ofthese receptors, as well as the role that thesereceptors play in cancer. GPCRs hold enormouspromise for therapeutic drug discovery, sinceabout 50% of all existing pharmaceuticals aretargeted towards these receptors. To identifyGPCRs in ovarian cancer cells, we have cloned anovel GPCR gene (ovarian cancer G-proteincoupledreceptor 1, or OGR1) from HEY ovariancancer cells by degenerate oligonucleotide PCRamplification (Nature Cell Biol. 2:261, 2000). Wehave shown that SPC is a high-affinity ligand forOGR1 through calcium mobilization, ligandbinding, receptor internalization, MAP kinase,and cell proliferation assays. LPC is known toplay an important role in human systemicautoimmune disease and atherosclerosis. G2A isan orphan GPCR, expressed predominantly inlymphocytes. Genetic ablation of G2A functionin mice results in the development of autoimmunityassociated with hyperproliferative responsesof T lymphocytes to antigen receptor stimulation.We have shown recently that G2A is a highaffinityreceptor for LPC (Science 293:618, 2001;a commentary describes the importance of ourfinding). More recently, we have identified anOGR1-related GPCR, GPR4, as not only anotherhigh-affinity receptor for SPC, but also a receptorfor LPC (J. Biol. Chem. 276:41325, 2001).Calcium mobilization, ligand binding, receptorinternalization, MAP kinase activation, cellproliferation, and cell migration assays wereconducted to establish the ligand-receptorrelationship.We will continue to: 1) investigate the roleand signaling mechanisms of LPA, LPC, and SPCand their receptors in cancer and other diseases; 2)determine the structure-function relationship ofthe OGR1-subfamily receptors and establishmolecular models of these receptors for drugdevelopment; and 3) determine the physiologicaland pathological roles and functions of OGR1-subfamily receptors using knockout-mousemodels.INVESTIGATORSYing Jiang, Ph.D.Juan Ren, M.D., Ph.D.Saubhik Sengupta, Ph.D.Lisam Shanjukumar Singh, Ph.D.Zeneng Wang, Ph.D.RESEARCH ASSOCIATESYijian Xiao, Ph.D.Xiaoxian Zhao, Ph.D.LEAD TECHNOLOGISTMichael Berk, M.S.RESEARCH TECHNOLOGISTRussel TippsGRADUATE STUDENTSJanice Battistuta, B.S.Alexander Zaslavsky, B.S.Yan Xu, Ph.D.Kabarowski, J.H., Zhu, K., Le, L.Q., Witte, O.N., and Y. Xu (2001) Lysophosphatidyl-choline as a ligand for the immunoregulatory receptor G2A. Science 293:702-705.Zhu, K., Baudhuin, L.M., Hong, G., Williams, F.S., Cristina, K.L., Kabarowski, J.H., Witte, O.N., and Y. Xu (2001) Sphingosylphosphorylcholine and lysophosphatidylcholineare ligands for the G protein-coupled receptor GPR4. J. Biol. Chem. 276:41325-41335.Baudhuin, L.M., Cristina, K.L., Lu, J., and Y. Xu (2002) Akt activation induced by lysophosphatidic acid and sphingosine-1-phosphate requires both mitogen-activatedprotein kinase kinase and p38 mitogen-activated protein kinase and is cell-line specific. Mol. Pharmacol. 62:660-671.Xu, Y., Xiao, Y.J., Zhu, K., Baudhuin, L.M., Lu, J., Hong, G., Kim, K.S., Cristina, K.L., Song, L.S, Williams, F., Elson, P., Markman, M., and J. Belinson (2003)Unfolding the pathophysiological role of bioactive lysophospholipids. Curr. Drug Targets Immune Endocr. Metabol. Disord. 3:23-32.Xu, Y. (2002) Sphingosylphosphorylcholine and lysophosphatidylcholine: G protein coupled receptors and receptor-mediated signal transduction. Biochim. Biophys.Acta 1582:81-88.Lauber, K., Bohn, E., Kröber, S.M., Xiao, Y., Blumenthal, S.G., Lindemann, R.K., Marini, P., Baksh, S., Schulze-Osthoff, K., Xu, Y., et al. (2003) Apoptotic cellsinduce migration of phagocytes via caspase-3 mediated release of a lipid attraction signal. Cell 113:717-730.Sengupta, S., Xiao, Y., and Y. Xu (2003) A novel laminin-induced LPA autocrine loop in the migration of ovarian cancer cells. FASEB J. June 3, 10.1096/fj.02-0963.63