title: JNK activation is required for TNFα-induced apoptosis in human hepatocarcinoma cells.
abstract: BACKGROUND
  A frequent distinctive feature of tumors, hepatocellular carcinomas included, is resistance to apoptosis induced by a variety of agents, among which the pleiotropic cytokine tumor necrosis factor-α (TNF). Compared to other cell types, hepatocytes and hepatoma-derived cell lines are poorly susceptible to TNF-induced apoptosis, which is largely ascribed to activation of the prosurvival transcription factor NF-κB and can be overcome by associating TNF to low doses of protein synthesis inhibitors or other drugs.
  
  
  OBJECTIVE
  This study analyses the molecular mechanisms by which TNF, in combination with cycloheximide (CHX), induces apoptosis in human hepatoma-derived Huh7 cells, focusing on the role played by JNK.
  
  
  METHODS
  Huh7 cell cultures were treated with TNF + CHX in the presence or in the absence of the pancaspase inhibitor zVADfmk or of the JNK inhibitor SP600125 as well as after suppression of JNK expression by RNAi. Apoptosis was assessed both by light microscopy and by flow cytometry, JNK and caspase activation by western blotting and/or enzymatic assay.
  
  
  RESULTS
  TNF + CHX-induced death of Huh7 cells involved JNK activation since it was partially prevented by suppressing JNK activity or expression. Moreover, apoptosis was significantly reduced also by zVADfmk, while SP600125 and zVADfmk combined totally abrogated cell death in an additive fashion.
  
  
  CONCLUSIONS
  These results demonstrate a causal role for JNK and caspases in TNF+CHX-induced apoptosis of Huh7 human hepatoma cells. Therefore, strategies aimed at enhancing both pathways should provide a profitable basis to overcome the resistance of hepatocarcinoma cells to TNF-dependent apoptosis.
authors.affiliation: Department of Experimental Medicine and Oncology, University of Turin, Italy.
authors.forename: Valerio Giacomo
authors.initials: VG
authors.lastname: Minero
authors.forename: Amina
authors.initials: A
authors.lastname: Khadjavi
authors.forename: Paola
authors.initials: P
authors.lastname: Costelli
authors.forename: Francesco Maria
authors.initials: FM
authors.lastname: Baccino
authors.forename: Gabriella
authors.initials: G
authors.lastname: Bonelli
mesh_terms: D000873:Anthracenes / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D002083:Butylated Hydroxyanisole / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008113:Liver Neoplasms / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D000873:Anthracenes; D000975:Antioxidants; D002614:Chelating Agents; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D014810:Vitamin E; C432165:pyrazolanthrone; D002083:Butylated Hydroxyanisole; D003513:Cycloheximide; D048031:JNK Mitogen-Activated Protein Kinases; D020169:Caspases; D003676:Deferoxamine
keywords: Apoptosis; Caspases; Hepatocarcinoma; JNK; TNF