title: Inhibition of AP-1 transcription activator induces myc-dependent apoptosis in HL60 cells.
abstract: 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.
authors.affiliation: School of Chemistry and Molecular Engineering, Seoul National University, Seoul 151-742, Korea.
authors.forename: Seyeon
authors.initials: S
authors.lastname: Park
authors.forename: Eun-Ryeong
authors.initials: ER
authors.lastname: Hahm
authors.forename: Dug-Keun
authors.initials: DK
authors.lastname: Lee
authors.forename: Chul-Hak
authors.initials: CH
authors.lastname: Yang
mesh_terms: D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015152:Blotting, Northern; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002457:Cell Extracts / Q000737:chemistry; D002467:Cell Nucleus / Q000737:chemistry; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D053938:DNA Fragmentation; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D009637:Masoprocol / Q000494:pharmacology; D008954:Models, Biological; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein
chemical_list: D000873:Anthracenes; C494826:BAX protein, human; D002457:Cell Extracts; C489427:MYC protein, human; D016376:Oligonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D016271:Proto-Oncogene Proteins c-myc; D018808:Transcription Factor AP-1; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C432165:pyrazolanthrone; D009637:Masoprocol; D004247:DNA; D003513:Cycloheximide; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases; D013755:Tetradecanoylphorbol Acetate