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SB-431542 and Gleevec inhibit transforming growth factor-beta-induced proliferation of human osteosarcoma cells

Shigeo Matsuyama1, Manabu Iwadate, Miki Kondo

  • 1Department of Molecular Pathology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Cancer Research
|November 25, 2003
PubMed

Insights

Transforming growth factor-beta (TGF-beta) stimulates MG63 osteosarcoma cell proliferation via ALK-5 receptor signaling and platelet-derived growth factor AA induction. This pathway overrides TGF-beta

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Oncology

Background:

  • Transforming growth factor-beta (TGF-beta) exhibits dual roles, stimulating mesenchymal and tumor cell growth, but its precise signaling pathways remain unclear.
  • Understanding TGF-beta's proliferative effects is crucial for developing targeted cancer therapies, particularly in osteosarcoma.

Purpose of the Study:

  • To elucidate the specific signaling mechanisms by which TGF-beta promotes proliferation in MG63 human osteosarcoma cells.
  • To identify key receptors and downstream effectors involved in TGF-beta-induced growth stimulation in this cell line.

Main Methods:

  • Utilized constitutively active receptor expression (ALK-1, ALK-5) to determine receptor involvement in TGF-beta signaling.
  • Employed a specific ALK4/5/7 kinase inhibitor (SB-431542) to block TGF-beta-induced growth.
  • Applied DNA microarray and quantitative real-time PCR to analyze gene expression changes post-TGF-beta treatment.
  • Investigated the role of induced growth factors (e.g., platelet-derived growth factor AA) and c-Myc expression.

Main Results:

  • Both ALK-1 and ALK-5 receptors are expressed in MG63 cells, but ALK-5 activation drives proliferation.
  • Inhibition of ALK4/5/7 kinases with SB-431542 suppressed TGF-beta-induced proliferation.
  • TGF-beta treatment upregulated platelet-derived growth factor AA (PDGF-AA) and c-Myc expression in MG63 cells.
  • Inhibitors of PDGF signaling (Gleevec, AG1296) blocked TGF-beta-induced proliferation, indicating PDGF-AA's critical role.
  • Unlike in other cells, TGF-beta upregulated c-Myc in MG63 cells, potentially counteracting growth-suppressive signals.

Conclusions:

  • TGF-beta stimulates MG63 osteosarcoma cell proliferation primarily through the ALK-5 receptor and subsequent induction of PDGF-AA.
  • The upregulation of c-Myc in MG63 cells represents a mechanism that may override TGF-beta's typical growth-inhibitory functions.
  • These findings provide insights into TGF-beta signaling in osteosarcoma and suggest potential therapeutic targets.

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