CG0009, a novel glycogen synthase kinase 3 inhibitor, induces cell death through cyclin D1 depletion in breast cancer cells

PLoS One. 2013;8(4):e60383. doi: 10.1371/journal.pone.0060383. Epub 2013 Apr 2.

Abstract

Glycogen synthase kinase 3α/β (GSK3α/β) is a constitutively active serine/threonine kinase involved in multiple physiological processes, such as protein synthesis, stem cell maintenance and apoptosis, and acts as a key suppressor of the Wnt-β-catenin pathway. In the present study, we examined the therapeutic potential of a novel GSK3 inhibitor, CG0009, in the breast cancer cell lines, BT549, HS578T, MDA-MB-231, NCI/ADR-RES, T47D, MCF7 and MDA-MB-435, from the NCI-60 cancer cell line panel. Assessment of cytotoxicity, apoptosis and changes in estrogen-signaling proteins was performed using cell viability assays, Western blotting and quantitative real-time PCR. CG0009 enhanced the inactivating phosphorylation of GSK3α at Ser21 and GSK3β at Ser9 and simultaneously decreased activating phosphorylation of GSK3β at Tyr216, and induced caspase-dependent apoptosis independently of estrogen receptor α (ERα) expression status, which was not observed with the other GSK3 inhibitors examined, including SB216763, kenpaullone and LiCl. CG0009 treatment (1 µmol/L) completely ablated cyclin D1 expression in a time-dependent manner in all the cell lines examined, except T47D. CG0009 alone significantly activated p53, leading to relocation of p53 and Bax to the mitochondria. GSK3 inhibition by CG0009 led to slight upregulation of the β-catenin target genes, c-Jun and c-Myc, but not cyclin D1, indicating that CG0009-mediated cyclin D1 depletion overwhelms the pro-survival signal of β-catenin, resulting in cell death. Our findings suggest that the novel GSK3 inhibitor, CG0009, inhibits breast cancer cell growth through cyclin D1 depletion and p53 activation, and may thus offer an innovative therapeutic approach for breast cancers resistant to hormone-based therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects
  • Benzazepines / pharmacology
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / metabolism*
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cyclin D1 / metabolism*
  • Female
  • Glycogen Synthase Kinase 3 / antagonists & inhibitors
  • Glycogen Synthase Kinase 3 / metabolism*
  • Humans
  • Indoles / pharmacology
  • Lithium Chloride / pharmacology
  • Maleimides / pharmacology
  • Real-Time Polymerase Chain Reaction

Substances

  • Antineoplastic Agents
  • Benzazepines
  • Indoles
  • Maleimides
  • SB 216763
  • kenpaullone
  • Cyclin D1
  • Glycogen Synthase Kinase 3
  • Lithium Chloride

Grant support

This work was supported by a grant (A062254) from the Korea Health 21 R&D Project, Ministry of Health, Welfare and Family Affairs, Republic of Korea, the Mid-career Researcher Program through an NRF grant funded by the MEST (No. 2009-0081016), and a grant from the Asan Institute for Life Science (2003-309). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.