Inhibition of c-Jun-N-terminal-kinase sensitizes tumor cells to CD95-induced apoptosis and induces G2/M cell cycle arrest

Cancer Res. 2005 Aug 1;65(15):6780-8. doi: 10.1158/0008-5472.CAN-04-2618.

Abstract

Loss of susceptibility to apoptosis signals is a crucial step in carcinogenesis. Therefore, sensitization of tumor cells to apoptosis is a promising therapeutic strategy. c-Jun-N-terminal-kinases (JNK) have been implicated in stress-induced apoptosis, but may also contribute to survival signaling. Here we show that CD95-induced apoptosis is augmented by the JNK inhibitor SP600125 and small interfering RNA directed against JNK1/2. SP600125 potently inhibited methyl methane sulfonate-induced phosphorylation of c-Jun, but had minimal effect on apoptosis alone. In contrast, it strongly enhanced CD95-mediated apoptosis in six of eight tumor cell lines and led to a G2/M phase arrest in all cell lines. SP600125 enhanced cleavage of caspase 3 and caspase 8, the most upstream caspase in the CD95 pathway. JNK inhibition up-regulates p53 and its target genes p21Cip1/Waf1 and CD95. However, although HCT116 p53-/- cells and p21+/+ cells were less sensitive to CD95 stimulation than their p53+/+ and p21-/- counterparts, p53 and p21 were not involved in the JNK-mediated effect. JunD, which was described to be protective in tumor necrosis factor-induced apoptosis, was not regulated by JNK inhibition on the protein level. When transcription was blocked by actinomycin D, JNK inhibition still enhanced apoptosis to a comparable extent. We conclude that JNK inhibition has antitumor activity by inducing growth arrest and enhancing CD95-mediated apoptosis by a transcription-independent mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anthracenes / pharmacology*
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Carcinoma, Hepatocellular / drug therapy
  • Carcinoma, Hepatocellular / enzymology
  • Carcinoma, Hepatocellular / pathology
  • Caspase 3
  • Caspase 8
  • Caspases / metabolism
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / physiology
  • Cell Division / drug effects
  • Cell Division / physiology
  • Cell Line, Tumor
  • Cyclin-Dependent Kinase Inhibitor p21
  • Enzyme Activation / drug effects
  • G2 Phase / drug effects
  • G2 Phase / physiology
  • Humans
  • Jurkat Cells
  • Liver Neoplasms / drug therapy
  • Liver Neoplasms / enzymology
  • Liver Neoplasms / pathology
  • Mitogen-Activated Protein Kinase 8 / antagonists & inhibitors*
  • Mitogen-Activated Protein Kinase 8 / genetics
  • Mitogen-Activated Protein Kinase 8 / metabolism
  • Mitogen-Activated Protein Kinase 9 / antagonists & inhibitors*
  • Mitogen-Activated Protein Kinase 9 / genetics
  • Mitogen-Activated Protein Kinase 9 / metabolism
  • Phosphorylation / drug effects
  • Proto-Oncogene Proteins c-jun / physiology
  • RNA, Small Interfering / genetics
  • Transcription, Genetic
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / physiology
  • fas Receptor / genetics
  • fas Receptor / physiology*

Substances

  • Anthracenes
  • CDKN1A protein, human
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor p21
  • Proto-Oncogene Proteins c-jun
  • RNA, Small Interfering
  • Tumor Suppressor Protein p53
  • fas Receptor
  • pyrazolanthrone
  • Mitogen-Activated Protein Kinase 9
  • Mitogen-Activated Protein Kinase 8
  • CASP3 protein, human
  • CASP8 protein, human
  • Caspase 3
  • Caspase 8
  • Caspases