Inhibition of AP-1 transcription activator induces myc-dependent apoptosis in HL60 cells

J Cell Biochem. 2004 Apr 1;91(5):973-86. doi: 10.1002/jcb.10768.


Transcriptional activation of AP-1 is intricately involved in cell proliferation and transformation. The natural product, nordihydroguaiaretic acid (NDGA) shows an inhibitory effect on the binding of jun/AP-1 protein to the AP-1 site in 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated HL60 cells. The NDGA inhibits the auto-regulated de novo synthesis of c-jun mRNA in TPA-stimulated HL60 cells. Our data also determine that this compound induces proliferation inhibition and apoptosis in human leukemia HL60 cells. To obtain information on the functional role of the AP-1 inhibition by NDGA in apoptosis signaling, the effects of pharmacological inhibition of AP-1 binding on c-myc, p53, and bax protein level were determined. Our results indicate that treatment of cells with NDGA enhances c-myc, p53, and bax protein levels. To rule out the possibility that NDGA will induce apoptosis because of the effects on proteins other than AP-1, we investigated the effect of another AP-1 inhibitor, SP600125, which is specific to Jun-N-terminal kinase. SP600125 decreased not only the phosphorylation level of jun protein but also AP-1/DNA binding activity. Also, apoptosis was observed to be induced by SP600125, concomitant with the increase in c-myc, p53, and bax protein level. In addition, apoptosis induced by both AP-1 inhibitors was accompanied by the activation of a downstream apoptotic cascade such as caspase 9, caspase 3, and poly[ADP-ribose]polymerase (PARP). When the cells were treated with NDGA or SP600125 in the presence of antisense c-myc oligonucleotides, apoptosis was not observed and an increase of c-myc, p53, and bax proteins was not manifested. All these results show that the inhibition of the transcription factor AP-1 action is related with either the drug-induced apoptosis or the drug toxicity of the HL60 cells. The apoptosis induced by AP-1 inhibition may be dependent on c-myc protein levels suggesting that the c-myc protein induces apoptosis at a low level of AP-1 binding activity. Altogether, our findings suggest that the presence of the AP-1 signal acts as a survival factor that determines the outcome of myc-induced proliferation or apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anthracenes / pharmacology
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • Blotting, Northern
  • Blotting, Western
  • Caspases / metabolism
  • Cell Division / drug effects
  • Cell Extracts / chemistry
  • Cell Nucleus / chemistry
  • Cycloheximide / pharmacology
  • DNA / drug effects
  • DNA / genetics
  • DNA / metabolism
  • DNA Fragmentation
  • Electrophoretic Mobility Shift Assay
  • Flow Cytometry
  • Gene Expression / drug effects
  • HL-60 Cells
  • Humans
  • Masoprocol / pharmacology
  • Models, Biological
  • Oligonucleotides, Antisense / pharmacology
  • Phosphorylation / drug effects
  • Poly(ADP-ribose) Polymerases / metabolism
  • Protein Binding / drug effects
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Proto-Oncogene Proteins c-fos / metabolism
  • Proto-Oncogene Proteins c-jun / genetics
  • Proto-Oncogene Proteins c-jun / metabolism
  • Proto-Oncogene Proteins c-myc / genetics
  • Proto-Oncogene Proteins c-myc / metabolism
  • Proto-Oncogene Proteins c-myc / physiology*
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factor AP-1 / metabolism
  • Transcription Factor AP-1 / physiology*
  • Tumor Suppressor Protein p53 / metabolism
  • bcl-2-Associated X Protein


  • Anthracenes
  • BAX protein, human
  • Cell Extracts
  • MYC protein, human
  • Oligonucleotides, Antisense
  • Proto-Oncogene Proteins c-bcl-2
  • Proto-Oncogene Proteins c-fos
  • Proto-Oncogene Proteins c-jun
  • Proto-Oncogene Proteins c-myc
  • Transcription Factor AP-1
  • Tumor Suppressor Protein p53
  • bcl-2-Associated X Protein
  • pyrazolanthrone
  • Masoprocol
  • DNA
  • Cycloheximide
  • Poly(ADP-ribose) Polymerases
  • Caspases
  • Tetradecanoylphorbol Acetate