title: p16(ink4a) and retinoic acid modulate rhoA and GFAP expression during induction of a stellate phenotype in U343 MG-A astrocytoma cells.
abstract: We previously showed that the expression of p16(ink4a) (p16), in conjunction with retinoic acid (RA) treatment in the p16-deficient astrocytoma cell line, U343 MG-A, induced a potent cell cycle arrest in G(1) associated with changes in morphology. In this study, we investigated the effects of p16 expression and RA treatment on the expression and distribution of actin, glial fibrillary acidic protein (GFAP), and vimentin within the U343 MG-A astrocytoma cytoskeleton. Changes in expression and location of the small GTPase, rhoA, were also examined after p16 expression and RA treatment. We showed that p16 expression and RA treatment led to an increase in the expression of GFAP, as well as its reorganization but that it did not significantly affect actin or vimentin expression. p16 induction in combination with RA treatment resulted in a decreased expression and activation of rhoA as determined by immunocytochemistry and Western blot analysis of soluble and insoluble fractions of cell lysates. Endogenous levels of rhoA expression varied among samples in a panel of astrocytoma cell lines as determined by Western blot analysis. Introduction of a dominant active rhoA mutant into p16-induced, RA-treated U343 MG-A astrocytoma cells was associated with the loss of long astrocytic processes and stellate morphology. These data are among the first to report the pattern of rhoA expression in human astrocytoma cell lines. They furthermore suggest that the stellate cell phenotype observed in U343 MG-A astrocytoma cells after cyclin-dependent kinase inhibitor (CKI) induction and RA treatment is accompanied by an inhibition and inactivation of rhoA in this cell system.
authors.affiliation: Arthur and Sonia Labatt Brain Tumour Research Centre, and Division of Neurosurgery, Hospital for Sick Children, University of Toronto, Toronto, Canada.
authors.forename: Agnes
authors.initials: A
authors.lastname: Langlois
authors.forename: Sangpyung
authors.initials: S
authors.lastname: Lee
authors.forename: Dong Seok
authors.initials: DS
authors.lastname: Kim
authors.forename: Peter B
authors.initials: PB
authors.lastname: Dirks
authors.forename: James T
authors.initials: JT
authors.lastname: Rutka
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D001254:Astrocytoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D005904:Glial Fibrillary Acidic Protein / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D010641:Phenotype; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D020742:rhoA GTP-Binding Protein / Q000187:drug effects* / Q000378:metabolism
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D005904:Glial Fibrillary Acidic Protein; D014212:Tretinoin; D020742:rhoA GTP-Binding Protein