title: The cytoskeletal inhibitors latrunculin A and blebbistatin exert antitumorigenic properties in human hepatocellular carcinoma cells by interfering with intracellular HuR trafficking.
abstract: The impact of the RNA-binding protein HuR for the post-transcriptional deregulation of tumor-relevant genes is well established. Despite of elevations in HuR expression levels, an increase in cytoplasmic HuR abundance in many cases correlates with a high grade of malignancy. Here, we demonstrated that administration of the actin-depolymerizing macrolide latrunculin A, or blebbistatin, an inhibitor of myosin II ATPase activity, caused a dose- and time-dependent reduction in the high cytoplasmic HuR content of HepG2 and Huh7 hepatocellular carcinoma (HCC) cells. Subcellular fractionation revealed that in addition, both inhibitors strongly attenuated cytoskeletal and membrane-bound HuR abundance and conversely increased the HuR amount in nuclear cell fractions. Concomitant with changes in intracellular HuR localization, both cytoskeletal inhibitors markedly decreased the half-lives of cyclooxygenase-2 (COX-2), cyclin A and cyclin D1 encoding mRNAs resulting in a significant reduction in their expression levels in HepG2 cells. Importantly, a similar reduction in the expression of these HuR targets was achieved by a RNA interference (RNAi)-mediated knockdown of either HuR or nonmuscle myoin IIA. Using polysomal fractionation, we further demonstrate that the decrease in cytoplasmic HuR by latrunculin A or blebbistatin is accompanied by a marked change in the allocation of HuR and its mRNA cargo from polysomes to ribonucleoprotein (RNP) particles. Functionally, the basal migration and prostaglandin E2 synthesis are similarly impaired in inhibitor-treated and stable HuR-knockdown HepG2 cells. Our data demonstrate that interfering with the actomyosin-dependent HuR trafficking may comprise a valid therapeutic option for antagonizing pathologic posttranscriptional gene expression by HuR and furthermore emphasize the potential benefit of HuR inhibitory strategies for treatment of HCC.
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Doller
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Amel
authors.initials: A
authors.lastname: Badawi
authors.affiliation: Institut für Biochemie I (Pathobiochemie), Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Schmid
authors.affiliation: Institut für Biochemie I (Pathobiochemie), Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Thilo
authors.initials: T
authors.lastname: Brauss
authors.affiliation: Medizinische Klinik 1, Schwerpunkt Gastroenterologie und Hepatologie, Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pleli
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Dagmar Meyer
authors.initials: DM
authors.lastname: zu Heringdorf
authors.affiliation: Medizinische Klinik 1, Schwerpunkt Gastroenterologie und Hepatologie, Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Piiper
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Pfeilschifter
authors.affiliation: Pharmazentrum Frankfurt/ZAFES, Klinikum der Goethe-Universität Frankfurt, Frankfurt/Main, Germany. Electronic address: w.eberhardt@em.uni-frankfurt.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eberhardt
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D056741:Cyclin D / Q000235:genetics / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects; D015232:Dinoprostone / Q000378:metabolism; D051959:ELAV Proteins / Q000378:metabolism*; D056945:Hep G2 Cells; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism*; D024507:Nonmuscle Myosin Type IIA / Q000235:genetics / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism; D053778:Thiazolidines / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D019086:Bridged Bicyclo Compounds, Heterocyclic; D019925:Cyclin A; D056741:Cyclin D; D051959:ELAV Proteins; D006576:Heterocyclic Compounds, 4 or More Rings; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D053778:Thiazolidines; C472645:blebbistatin; D051546:Cyclooxygenase 2; D024507:Nonmuscle Myosin Type IIA; D015232:Dinoprostone; C037067:latrunculin A
keywords: Cytoskeletal inhibitors; Hepatocellular carcinoma; HuR trafficking; Tumorigenic functions; mRNA-stability