Essential role of caspases in epigallocatechin-3-gallate-mediated inhibition of nuclear factor kappa B and induction of apoptosis

Oncogene. 2004 Apr 1;23(14):2507-22. doi: 10.1038/sj.onc.1207353.

Abstract

Green tea constituent (-) epigallocatechin-3-gallate (EGCG) has shown remarkable cancer-preventive and some cancer-therapeutic effects. This is partially because of its ability to induce apoptosis in cancer cells without affecting normal cells. Previous studies from our laboratory have shown the involvement of NF-kappa B pathway in EGCG-mediated cell-cycle deregulation and apoptosis of human epidermoid carcinoma A431 cells. Here we show the essential role of caspases in EGCG-mediated inhibition of NF-kappa B and its subsequent apoptosis. Treatment of A431 cells with EGCG (10-40 microg/ml) resulted in dose-dependent inhibition of NF-kappa B/p65, induction of DNA breaks, cleavage of poly(ADP-ribose) polymerase (PARP) and morphological changes consistent with apoptosis. EGCG treatment of cells also resulted in significant activation of caspases, as shown by the dose- and time-dependent increase in DEVDase activity, and protein expression of caspase-3, -8 and -9. EGCG-mediated caspase activation induces proteolytic cleavage of NF-kappa B/p65 subunit, leading to the loss of transactivation domains, and driving the cells towards apoptosis. EGCG-mediated induction of apoptosis was significantly blocked by the caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (Z-VAD-FMK), and moderately blocked by the specific caspase-3 inhibitor Z-DEVD-FMK. Further, pretreatment of cells with Z-VAD-FMK was found to suppress the cleavage of NF-kappa B/p65 subunit, thereby increasing nuclear translocation, DNA binding and transcriptional activity, thus protecting the cells from EGCG-induced apoptosis. Taken together, these studies for the first time demonstrate that EGCG-mediated activation of caspases is critical, at least in part, for inhibition of NF-kappa B and subsequent apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Chloromethyl Ketones / pharmacology
  • Apoptosis / drug effects*
  • Carcinoma, Squamous Cell
  • Caspase Inhibitors
  • Caspases / metabolism*
  • Catechin / analogs & derivatives*
  • Catechin / pharmacology*
  • Cell Line, Tumor
  • Cell Nucleus / metabolism
  • Cell Survival
  • DNA / metabolism
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • Humans
  • Male
  • Models, Biological
  • NF-kappa B / antagonists & inhibitors*
  • NF-kappa B / chemistry
  • NF-kappa B / metabolism
  • Oligopeptides / pharmacology
  • Poly(ADP-ribose) Polymerases / drug effects
  • Prostatic Neoplasms
  • Protein Structure, Tertiary / drug effects
  • Time Factors
  • Transcription, Genetic

Substances

  • Amino Acid Chloromethyl Ketones
  • Caspase Inhibitors
  • NF-kappa B
  • Oligopeptides
  • benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone
  • benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
  • Catechin
  • DNA
  • epigallocatechin gallate
  • Poly(ADP-ribose) Polymerases
  • Caspases