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

Role of Integrins in Thrombosis,Angiogenesis and Tumor BiologyThe integrin family of cell-surface moleculesmediates multiple, diverse cellularresponses, ranging from cell adhesion,migration and reorganization of extracellularmatrix to gene expression and apoptosis. Ourlaboratory’s overall goal is to understand the roleand the mechanisms of regulation of integrins inthe broad spectrum of physiological andpathophysiological responses, such as hemostasis/thrombosis, angiogenesis and tumor growth. Ourresearch focus is on the regulation of thefunctional activities of the integrin family ofadhesion receptors,specifically the beta-3integrins α vβ 3(expressedprimarily on vascular andtumor cells) and α IIbβ 3(platelet GPIIb-IIIacomplex).Our major project isto define the mechanismsof communication betweentwo receptor-ligandsystems, integrins/extracellular matrix andgrowth factors and theirreceptors. We recentlydescribed a new mechanismof vascular endothelialgrowth factor (VEGF)action in physiological andpathological responses(Byzova et al., MolecularCell, 2000). We demonstratedthat VEGF candirectly activate integrin α vβ 3, leading toenhanced adhesion and migration of endothelialcells (ECs) to a variety of ligands. We found thatVEGFR2 (flk-1) ligation, but not VEGFR1 (flt-1) ligation, is responsible for integrin activation.Using several in vivo models of angiogenesis, wedemonstrated that VEGFR-2-specific (andVEGFR-3-specific) VEGFs can induce completeangiogenic or lymphangiogenic response (Byzovaet al., Blood, 2002). Because VEGF exerts strikingeffects on ECs, we are interested in the signaltransduction pathways leading from occupiedVEGF receptors to downstream responses such asintegrin activation, cell proliferation andapoptosis. We have generated substantial dataindicating the direct involvement ofphosphatidylinositol 3'-kinase (PI3k)/proteinkinase B (Akt) pathway, which is negativelyregulated by the phosphatase and tensin homologuedeleted from chromosome 10 (PTEN)tumor suppressor protein, in integrin activationby VEGFs (Byzova et al., Molecular Cell, 2000).We are also investigating the role ofVEGFs and their receptors in pathology,specifically in prostate tumor growth and in thedevelopment of bone metastasis. We found thatThe Department of Molecular CardiologyTatiana V. Byzova, Ph.D.enhanced recognition of bone matrix proteins bythe activated integrins contributes to prostatecancer osteotrophism. The angiogenic growthfactors may be released from tumor cells andengage receptors, which are also expressed by thetumor cells, leading to an autocrine mechanism oftumor-cell stimulation. To extend these ourstudies into the clinical arena, we are analyzingthe expression levels of VEGF/VEGFR andintegrins on prostate cancer cells and in the tumorvasculature to determine whether the autocrinemechanism of tumor cells stimulation is operativein vivo. These studies areconducted in collaboration withDrs. W. Heston and J. Brainard.Some of our studies focuson the role of thrombospondin(TSP)/platelet interactions in theprocess of thrombus formation.A recent large-scale genetic studyconducted at the Cleveland Clinicrevealed that novel variants inthe TSP gene family areassociated with familial prematuremyocardial infarction.Patients with the mutationN700S in TSP-1 have a nine-foldhigher risk of early coronaryartery disease. This novelobservation prompted us toinitiate a study focused on thefunction of TSP-1 in plateletaggregation and in EC biology.Since we have access to manypatients who are homozygous forthe N700S mutation, we are uniquely positionedto investigate the role of this mutation in TSP-1biology. The overall goal of this study is toinvestigate the molecular mechanism responsiblefor differential activities of N700S and WT TSP-1 that can contribute to the development of earlycardiovascular disease.THE BYZOVALABORATORYPOSTDOCTORAL FELLOWSJuhua Chen, M.D., Ph.D.Sarmistha De, Ph.D.Natalia Narijneva, Ph.D.TECHNICAL ASSOCIATESVicky Byers-Ward, M.S.COLLABORATORSMarc Achen, Ph.D. 1Deepak L. Bhatt, M.D. 2Jennifer Brainard, M.D. 3Graham Casey, Ph.D. 4Nissim Hay, Ph.D. 5Warren (Skip) Heston, Ph.D. 4Ronald Midura, Ph.D. 6Maria Siemionow, M.D., Ph.D. 7Sanford J. Shattil, M.D. 8Steven Stacker, Ph.D. 1Eric J. Topol, M.D. 21Angiogenesis Laboratory, LudwigInst. for Cancer Res.,Melbourne, Australia2Dept. of CardiovascularMedicine, CCF3Dept. of Anatomic Pathology,CCF4Dept. of Cancer Biology, CCF5Dept of Molecular Genetics,Univ. of Illinois at Chicago6Dept. of Biomedical Engineering,CCF7Dept. of Plastic and ReconstructiveSurgery, CCF8Scripps Research Institute, LaJolla, CAByzova, T.V., and E.F. Plow (1998) Activation of α Vβ 3on vascular cells controlsrecognition of prothrombin. J. Cell Biol. 143:2081-2092.Topol, E.J., Byzova, T.V., and E.F. Plow (1999) Of platelets, integrin of α IIbβ 3and GPIIb-IIIa blockers: past, present and future perspectives. Lancet 143:227-231.Byzova, T.V., Kim, W., Midura, R.J., and E.F. Plow (2000) Activation of integrin α Vβ 3regulates cell adhesion and migration to bone sialoprotein. Exp. Cell Res. 254:299-308.Byzova, T.V., Goldman, C.K., Pampori, N., Thomas, K.A., Bett, A., Shattil S.J., and E.F.Plow (2000) A mechanism for modulation of cellular responses to VEGF: activation ofthe integrins. Mol. Cell 6:851-860.Byzova, T.V., Goldman, C.K., Jankau, J., Chen, J., Cabrera, G., Achen, M.G., Stacker,S.A., Carnevale, K.A., Siemionow, M., Deitcher, S.R., and P.E. DiCorleto (2002)Adenovirus encoding vascular endothelial growth factor-D induces tissue-specificvascular patterns in vivo. Blood 99:4434-4442.121