title: Osteopontin-dependent CD44v6 expression and cell adhesion in HepG2 cells.
abstract: The interaction of osteopontin (OPN) with CD44 and alphavbeta3-integrin has been implicated in numerous signal transduction pathways that may promote cancer metastasis. CD44v6 is a splice variant of CD44 which has been identified as a marker of cancer progression. In this study, immortalized liver carcinoma cells (HepG2) were used to examine the effect of OPN on two isoforms of CD44: CD44 standard (CD44 s) and CD44v6. Western blots demonstrated that OPN up-regulated plasma membrane CD44v6 protein expression in a concentration- and time-dependent fashion. CD44v6 levels returned to control levels when OPN-alphavbeta3-integrin binding was blocked by an RGD peptide or tyrosine kinase activity was inhibited. OPN significantly increased CD44v6 protein synthesis, while simultaneously decreasing protein degradation. Steady-state mRNA levels of both CD44s and CD44v6 were unaltered in the presence of OPN stimulation. OPN increased HepG2 in vitro adhesion to hyaluronate (HA); excess soluble HA extinguished OPN-mediated HepG2 adhesion, indicating CD44 dependence. In conclusion, OPN binds to the alphavbeta3-integrin to increase plasma membrane CD44v6 expression and augment in vitro adhesion to HA. This may contribute to the mechanism by which OPN enhances metastatic behavior in hepatocellular cancer cells.
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Chengjiang
authors.initials: C
authors.lastname: Gao
authors.forename: Hongtao
authors.initials: H
authors.lastname: Guo
authors.forename: Laura
authors.initials: L
authors.lastname: Downey
authors.forename: Carlos
authors.initials: C
authors.lastname: Marroquin
authors.forename: Junping
authors.initials: J
authors.lastname: Wei
authors.forename: Paul C
authors.initials: PC
authors.lastname: Kuo
mesh_terms: D015152:Blotting, Northern; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D002448:Cell Adhesion; D002455:Cell Division; D002460:Cell Line; D002465:Cell Movement; D003094:Collagen / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000096:biosynthesis*; D006801:Humans; D018960:Hyaluronan Receptors / Q000096:biosynthesis*; D006820:Hyaluronic Acid / Q000737:chemistry; D015151:Immunoblotting; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D007797:Laminin / Q000494:pharmacology; D009842:Oligopeptides / Q000737:chemistry; D053495:Osteopontin; D020033:Protein Isoforms; D011509:Proteoglycans / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012795:Sialoglycoproteins / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D015854:Up-Regulation
chemical_list: C112697:CD44v6 antigen; D004338:Drug Combinations; D006023:Glycoproteins; D018960:Hyaluronan Receptors; D039302:Integrin alphaVbeta3; D007797:Laminin; D009842:Oligopeptides; D020033:Protein Isoforms; D011509:Proteoglycans; D012333:RNA, Messenger; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D053495:Osteopontin; C059485:matrigel; D012313:RNA; C047981:arginyl-glycyl-aspartic acid; D006820:Hyaluronic Acid; D003094:Collagen