Honokiol inhibits TNF-alpha-stimulated NF-kappaB activation and NF-kappaB-regulated gene expression through suppression of IKK activation

Biochem Pharmacol. 2005 Nov 15;70(10):1443-57. doi: 10.1016/j.bcp.2005.08.011. Epub 2005 Sep 21.


Honokiol, a small molecular weight lignan originally isolated from Magnolia officinalis, shows anti-angiogenic, anti-invasive and anti-proliferative activities in a variety of cancers. In this study, we investigated whether honokiol affects the transcription factor nuclear factor-kappa B (NF-kappaB) which controls a large number of genes involved in angiogenesis, metastasis and cell survival. We observed that the tumor necrosis factor-alpha (TNF-alpha)-induced NF-kappaB activation was blocked by honokiol in four different cancer cell lines as evidenced by EMSA. Honokiol did not directly affect the NF-kappaB-DNA binding. Immunoblot experiments demonstrated that honokiol inhibited the TNF-alpha-stimulated phosphorylation and degradation of the cytosolic NF-kappaB inhibitor IkappaBalpha. Furthermore, honokiol suppressed the intrinsic and TNF-alpha-stimulated upstream IkappaB kinases (IKKs) activities measured by a non-radioactive kinase assay using immunoprecipitated IKKs, suggesting a critical role of honokiol in abrogating the phosphorylation and degradation of IkappaBalpha. In a HeLa cell NF-kappaB-dependent luciferase reporter system, honokiol suppressed luciferase expression stimulated by TNF-alpha and by the transient transfection and expression of NIK (NF-kappaB-inducing kinase), wild type IKKbeta, constitutively active IKKalpha and IKKbeta, or the p65 subunit. Honokiol was also found to inhibit the nuclear translocation and phosphorylation of p65 subunit of NF-kappaB. RT-PCR results showed that honokiol suppressed NF-kappaB-regulated inflammatory and carcinogenic gene products including MMP-9, TNF-alpha, IL-8, ICAM-1 and MCP-1. In line with the observation that NF-kappaB activation may up-regulate anti-apoptotic genes, it was shown that honokiol enhanced TNF-alpha-induced apoptotic cell death. In summary, our results demonstrate that honokiol suppresses NF-kappaB activation and NF-kappaB-regulated gene expression through the inhibition of IKKs, which provides a possible mechanism for its anti-tumor actions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects
  • Biphenyl Compounds / chemistry
  • Biphenyl Compounds / pharmacology*
  • Cell Line, Tumor
  • Electrophoretic Mobility Shift Assay / methods
  • Gene Expression / drug effects
  • Genes, Reporter / physiology
  • Humans
  • I-kappa B Kinase / antagonists & inhibitors
  • I-kappa B Kinase / drug effects
  • I-kappa B Kinase / metabolism*
  • Lignans / chemistry
  • Lignans / pharmacology*
  • Lipopolysaccharides / antagonists & inhibitors
  • Lipopolysaccharides / pharmacology
  • Luciferases / antagonists & inhibitors
  • Luciferases / drug effects
  • Luciferases / genetics
  • Lymphotoxin-alpha / metabolism
  • NF-kappa B / antagonists & inhibitors*
  • NF-kappa B / genetics*
  • NF-kappa B / metabolism
  • NF-kappa B p50 Subunit / drug effects
  • NF-kappa B p50 Subunit / metabolism
  • Phosphorylation
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Tetradecanoylphorbol Acetate / antagonists & inhibitors
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factor AP-1 / antagonists & inhibitors
  • Transcription Factor AP-1 / drug effects
  • Transcription Factor RelA / drug effects
  • Transcription Factor RelA / metabolism
  • Tumor Necrosis Factor-alpha / antagonists & inhibitors*
  • Tumor Necrosis Factor-alpha / drug effects
  • Tumor Necrosis Factor-alpha / metabolism


  • Antineoplastic Agents
  • Biphenyl Compounds
  • Lignans
  • Lipopolysaccharides
  • Lymphotoxin-alpha
  • NF-kappa B
  • NF-kappa B p50 Subunit
  • Transcription Factor AP-1
  • Transcription Factor RelA
  • Tumor Necrosis Factor-alpha
  • honokiol
  • Luciferases
  • I-kappa B Kinase
  • Tetradecanoylphorbol Acetate