blister and Carcinoma--Hepatocellular

Hepatocellular carcinoma (HCC) was usually coupled with increased stiffness of the extracellular matrix (ECM) and elevated level of transforming growth factor-β1 (TGF-β1). However, the mechanism by which substrate rigidity modulated TGF-β1 signaling transduction remained unknown. This paper investigated the molecular mechanism of how matrix stiffness regulating TGF-β1 signaling in HCC cells. By means of stiffness tunable collagen I-coated polyacrylamide (PA) gels, we found that the expressions of β1 integrin, p-FAK

Topics: Amides; Carcinoma, Hepatocellular; Cell Line, Tumor; Cytoskeleton; Extracellular Matrix; Focal Adhesion Protein-Tyrosine Kinases; Gene Expression Regulation, Neoplastic; Hep G2 Cells; Heterocyclic Compounds, 4 or More Rings; Humans; Integrin beta1; Liver Neoplasms; Oligopeptides; Protein Binding; Pyridines; rho GTP-Binding Proteins; Signal Transduction; Smad2 Protein; Transforming Growth Factor beta1; Up-Regulation

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.

Topics: Antineoplastic Agents; Bridged Bicyclo Compounds, Heterocyclic; Carcinoma, Hepatocellular; Cyclin A; Cyclin D; Cyclooxygenase 2; Cytoskeleton; Dinoprostone; ELAV Proteins; Hep G2 Cells; Heterocyclic Compounds, 4 or More Rings; Humans; Liver Neoplasms; Nonmuscle Myosin Type IIA; Polyribosomes; Protein Transport; Ribonucleoproteins; RNA, Messenger; Thiazolidines