Resibufogenin Induces G1-Phase Arrest through the Proteasomal Degradation of Cyclin D1 in Human Malignant Tumor Cells

PLoS One. 2015 Jun 29;10(6):e0129851. doi: 10.1371/journal.pone.0129851. eCollection 2015.


Huachansu, a traditional Chinese medicine prepared from the dried toad skin, has been used in clinical studies for various cancers in China. Resibufogenin is a component of huachansu and classified as bufadienolides. Resibufogenin has been shown to exhibit the anti-proliferative effect against cancer cells. However, the molecular mechanism of resibufogenin remains unknown. Here we report that resibufogenin induces G1-phase arrest with hypophosphorylation of retinoblastoma (RB) protein and down-regulation of cyclin D1 expression in human colon cancer HT-29 cells. Since the down-regulation of cyclin D1 was completely blocked by a proteasome inhibitor MG132, the suppression of cyclin D1 expression by resibufogenin was considered to be in a proteasome-dependent manner. It is known that glycogen synthase kinase-3β (GSK-3β) induces the proteasomal degradation of cyclin D1. The addition of GSK-3β inhibitor SB216763 inhibited the reduction of cyclin D1 caused by resibufogenin. These effects on cyclin D1 by resibufogenin were also observed in human lung cancer A549 cells. These findings suggest that the anti-proliferative effect of resibufogenin may be attributed to the degradation of cyclin D1 caused by the activation of GSK-3β.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Annexin A5 / chemistry
  • Apoptosis
  • Bufanolides / pharmacology*
  • Cardiotonic Agents / pharmacology
  • Cell Cycle
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Survival
  • Cellular Senescence
  • Cyclin D1 / biosynthesis*
  • G1 Phase / drug effects*
  • Gene Expression Regulation, Neoplastic
  • Glycogen Synthase Kinase 3 / biosynthesis
  • Glycogen Synthase Kinase 3 beta
  • Humans
  • Indoles / chemistry
  • Maleimides / chemistry
  • Medicine, Chinese Traditional
  • Neoplasms / metabolism
  • Phosphorylation
  • Proteasome Endopeptidase Complex / metabolism*
  • Proteasome Inhibitors / chemistry
  • Retinoblastoma Protein / biosynthesis


  • Annexin A5
  • Bufanolides
  • CCND1 protein, human
  • Cardiotonic Agents
  • Indoles
  • Maleimides
  • Proteasome Inhibitors
  • Retinoblastoma Protein
  • SB 216763
  • Cyclin D1
  • bufogenin
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Glycogen Synthase Kinase 3
  • Proteasome Endopeptidase Complex

Grants and funding

This work was supported by research funding of Kyoto Prefectural University of Medicine. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.