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Troglitazone inhibits growth of MCF-7 breast carcinoma cells by targeting G1 cell cycle regulators

F Yin1, S Wakino, Z Liu

  • 1Division of Endocrinology, Diabetes and Hypertension, UCLA School of Medicine, Los Angeles, California 90095, USA.

Biochemical and Biophysical Research Communications
|August 31, 2001
PubMed

Insights

Troglitazone (TRO), a PPARgamma ligand, halts breast cancer cell proliferation by blocking G1 to S phase progression. This mechanism involves inhibiting cyclin-dependent kinases and reducing key G1 regulatory proteins.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Oncology

Background:

  • Peroxisome proliferator activated receptor gamma (PPARgamma) is a nuclear receptor.
  • PPARgamma ligand activation can induce growth arrest in human tumor cells, but mechanisms are unclear.

Purpose of the Study:

  • To elucidate the molecular mechanism by which the PPARgamma ligand troglitazone (TRO) inhibits MCF-7 breast cancer cell proliferation.

Main Methods:

  • MCF-7 cells were treated with TRO.
  • Cell cycle progression was analyzed using flow cytometry.
  • Rb protein phosphorylation, CDK activities, and levels of G1 regulatory proteins (cyclin D1, CDK2, CDK4, CDK6) were assessed.

Main Results:

  • TRO (20 microM) increased G1 phase cell population from 51% to 69% after 24 hours.
  • TRO attenuated Rb protein phosphorylation, decreasing CDK4 and CDK2 activities.
  • TRO reduced protein levels of cyclin D1, CDK2, CDK4, and CDK6.
  • Overexpression of cyclin D1 partially reversed TRO-induced G1 arrest.

Conclusions:

  • TRO inhibits MCF-7 cell proliferation by blocking G1 to S phase transition.
  • This effect is mediated by the inhibition of CDK activity and downregulation of G1 regulatory proteins, particularly cyclin D1.
  • Targeting these G1 regulators with TRO may offer a novel therapeutic strategy for breast cancer.

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