Epigallocatechin-3-gallate(EGCG) suppresses melanoma cell growth and metastasis by targeting TRAF6 activity

Oncotarget. 2016 Nov 29;7(48):79557-79571. doi: 10.18632/oncotarget.12836.

Abstract

TRAF6 (TNF Receptor-Associated Factor 6) is an E3 ubiquitin ligase that contains a Ring domain, induces K63-linked polyubiquitination, and plays a critical role in signaling transduction. Our previous results demonstrated that TRAF6 is overexpressed in melanoma and that TRAF6 knockdown dramatically attenuates tumor cell growth and metastasis. In this study, we found that EGCG can directly bind to TRAF6, and a computational model of the interaction between EGCG and TRAF6 revealed that EGCG probably interacts with TRAF6 at the residues of Gln54, Gly55, Asp57 ILe72, Cys73 and Lys96. Among these amino acids, mutation of Gln54, Asp57, ILe72 in TRAF6 could destroy EGCG bound to TRAF6, furthermore, our results demonstrated that EGCG significantly attenuates interaction between TRAF6 and UBC13(E2) and suppresses TRAF6 E3 ubiquitin ligase activity in vivo and in vitro. Additionally, the phosphorylation of IκBα, p-TAK1 expression are decreased and the nuclear translocation of p65 and p50 is blocked by treatment with EGCG, leading to inactivation of the NF-κB pathway. Moreover, EGCG significantly inhibits cell growth as well as the migration and invasion of melanoma cells. Taken together, these findings show that EGCG is a novel E3 ubiquitin ligase inhibitor that could be used to target TRAF6 for chemotherapy or the prevention of melanoma.

Keywords: EGCG; TRAF6; melanoma; ubiquitination.

MeSH terms

  • Animals
  • Antineoplastic Agents, Phytogenic / chemistry
  • Antineoplastic Agents, Phytogenic / metabolism
  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Catechin / analogs & derivatives*
  • Catechin / chemistry
  • Catechin / metabolism
  • Catechin / pharmacology
  • Cell Line, Tumor
  • Cell Movement / drug effects*
  • Cell Proliferation / drug effects*
  • Enzyme Inhibitors / pharmacology*
  • Gene Expression Regulation, Neoplastic
  • HEK293 Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / prevention & control*
  • Lung Neoplasms / secondary
  • MAP Kinase Kinase Kinases / metabolism
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Melanoma / metabolism
  • Melanoma / secondary
  • Mice, Inbred BALB C
  • Molecular Docking Simulation
  • NF-KappaB Inhibitor alpha / metabolism
  • NF-kappa B / metabolism
  • Neoplasm Invasiveness
  • Phosphorylation
  • Protein Binding
  • Protein Conformation
  • Signal Transduction
  • Skin Neoplasms / drug therapy*
  • Skin Neoplasms / genetics
  • Skin Neoplasms / metabolism
  • Skin Neoplasms / pathology
  • Structure-Activity Relationship
  • TNF Receptor-Associated Factor 6 / antagonists & inhibitors*
  • TNF Receptor-Associated Factor 6 / chemistry
  • TNF Receptor-Associated Factor 6 / genetics
  • TNF Receptor-Associated Factor 6 / metabolism
  • Transfection
  • Tumor Burden / drug effects
  • Ubiquitin-Conjugating Enzymes / metabolism
  • Ubiquitin-Protein Ligases / antagonists & inhibitors*
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination

Substances

  • Antineoplastic Agents, Phytogenic
  • Enzyme Inhibitors
  • Intracellular Signaling Peptides and Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • TNF Receptor-Associated Factor 6
  • Tifab protein, human
  • NF-KappaB Inhibitor alpha
  • Catechin
  • epigallocatechin gallate
  • UBE2N protein, human
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitin-Protein Ligases
  • MAP Kinase Kinase Kinases
  • MAP kinase kinase kinase 7