title: New aspects of an anti-tumour drug: sorafenib efficiently inhibits HCV replication.
abstract: OBJECTIVE
  Hepatitis C virus (HCV) infection is a major cause of chronic liver disease and is associated with significant morbidity and mortality. Since there is evidence for an interaction of NS5A with c-Raf we studied whether the c-Raf inhibitor sorafenib affects HCV replication.
  
  
  METHODS
  HCV replicating HuH7.5 cells were treated with sorafenib and examined for HCV RNA titres by northern blotting or real time polymerase chain reaction (PCR), for core, NS3 and NS5A expression by immunostaining, and for replication by luciferase reporter assays.
  
  
  RESULTS
  Here we demonstrate that in cells replicating infectious HCV particles, NS5A recruits c-Raf to the replicon complex resulting in the activation of c-Raf. Therefore, we studied the effect of inhibition of c-Raf on HCV replication using the anti-tumour drug sorafenib that is known to inhibit c-Raf with high specificity. Sorafenib efficiently blocks HCV replication and viral gene expression. In addition, in HCV-replicating cells sorafenib decreased the hyperphosphorylated form of NS5A and resulted in the formation of additional hypophosphorylated forms. Further, sorafenib caused a rapid dissociation of lipid droplets. We provide evidence that the antiviral effect of sorafenib indeed is caused by inhibition of c-Raf. By contrast, inhibition of targets downstream of c-Raf or inhibition of tyrosine kinases by sunitinib did not affect HCV replication.
  
  
  CONCLUSIONS
  Our data demonstrate that the well-characterised anti-tumour drug sorafenib efficiently blocks HCV replication in vitro. This novel effect of sorafenib should be further explored as an antiviral strategy for patients with chronic HCV infection.
authors.affiliation: University of Kiel-UKSH, Institute of Infection Medicine, Molecular Medical Virology, Brunswiker Strasse. 4, D-24105 Kiel, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Himmelsbach
authors.forename: D
authors.initials: D
authors.lastname: Sauter
authors.forename: T F
authors.initials: TF
authors.lastname: Baumert
authors.forename: L
authors.initials: L
authors.lastname: Ludwig
authors.forename: H E
authors.initials: HE
authors.lastname: Blum
authors.forename: E
authors.initials: E
authors.lastname: Hildt
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D001557:Benzenesulfonates / Q000494:pharmacology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016174:Hepacivirus / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D022781:Hepatocytes / Q000821:virology; D006801:Humans; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology*; D012093:Replicon / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D000077157:Sorafenib; D017361:Viral Nonstructural Proteins / Q000378:metabolism; D014779:Virus Replication / Q000187:drug effects; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; D012324:RNA-Dependent RNA Polymerase
chemical_list: D000998:Antiviral Agents; D001557:Benzenesulfonates; D004791:Enzyme Inhibitors; D009536:Niacinamide; D010671:Phenylurea Compounds; D019908:Proto-Oncogene Proteins c-raf; D011725:Pyridines; D000077157:Sorafenib; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase