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Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
10:54

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations

Published on: September 17, 2012

Specific chemopreventive agents trigger proteasomal degradation of G1 cyclins: implications for combination therapy

Konstantin H Dragnev1, Ian Pitha-Rowe, Yan Ma

  • 1Norris Cotton Cancer Center, and Department of Medicine, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.

Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
|April 10, 2004
PubMed
Abstract

Insights

Certain cancer chemopreventive agents trigger the degradation of cyclins D1 and E, crucial for cell cycle control. This mechanism offers a strategy for combination cancer prevention, as resistance to one agent does not confer broad resistance.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Cycle Regulation

Background:

  • Identifying cancer chemoprevention mechanisms is critical.
  • All-trans-retinoic acid (RA) previously prevented carcinogenic transformation by inducing G(1) arrest via cyclin D1 proteolysis.
  • This degradation is a ubiquitin-dependent process.

Purpose of the Study:

  • To investigate which chemopreventive agents activate cyclin proteolysis.
  • To determine if cyclin E is also degraded by these agents.
  • To examine cyclin degradation in cells with acquired resistance to RA.

Main Methods:

  • Treatment of BEAS-2B cells and RA-resistant BEAS-2B-R1 cells with various chemopreventive agents.
  • Analysis of cyclin D1 and cyclin E protein levels using proteasomal inhibitors (ALLN).
  • Transfection experiments to assess the role of specific threonine residues in cyclin degradation.

Main Results:

  • All-trans-retinoic acid (RA) induced degradation of both cyclin D1 and cyclin E proteins.
  • Proteasomal inhibitor ALLN blocked RA-induced cyclin degradation.
  • Specific chemopreventive agents, including nonclassical retinoids and a synthetic triterpenoid, activated cyclin degradation, while others did not.

Conclusions:

  • Specific chemopreventive agents activate cyclin proteolysis, a key mechanism in cancer chemoprevention.
  • Acquired resistance to one agent did not lead to broad cross-resistance.
  • Combination chemoprevention strategies targeting non-cross-resistant pathways are therapeutically rational.

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