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Insulin-like growth factor-binding protein 3 induces caspase-dependent apoptosis through a death receptor-mediated

Ho-Seong Kim1, Angela R Ingermann, Junko Tsubaki

  • 1Department of Pediatrics, Oregon Health and Science University, Portland, Oregon, USA.

Cancer Research
|March 18, 2004
PubMed

Insights

Insulin-like growth factor-binding protein-3 (IGFBP-3) inhibits breast cancer cell growth by triggering apoptosis, independent of insulin-like growth factor signaling. This occurs via activation of death receptor-mediated caspase pathways, not mitochondrial routes.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Insulin-like growth factor-binding protein-3 (IGFBP-3) is known to inhibit cell proliferation.
  • The precise mechanisms underlying IGFBP-3's antiproliferative effects remain unclear.

Purpose of the Study:

  • To elucidate the mechanisms by which IGFBP-3 inhibits cell proliferation in MCF-7 human breast cancer cells.
  • To determine if IGFBP-3's action is dependent on the insulin-like growth factor (IGF) signaling pathway.

Main Methods:

  • Utilized an ecdysone-inducible expression system to induce IGFBP-3 expression.
  • Performed transfection with a mutant IGFBP-3 (GGG-IGFBP-3) that cannot bind IGFs.
  • Conducted caspase activity assays, immunoblot analyses, and cytochrome c release measurements.

Main Results:

  • IGFBP-3 induction inhibited DNA synthesis independently of the IGF-IGF receptor axis.
  • IGFBP-3 triggered apoptosis, evidenced by increased caspase-8 and -7 activity.
  • Mitochondria-mediated apoptosis pathways were not involved, as indicated by normal caspase-9 activity and lack of cytochrome c release.

Conclusions:

  • IGFBP-3 induces apoptosis in breast cancer cells via the death receptor-mediated pathway, independent of IGF signaling.
  • IGFBP-3 acts as a negative regulator of breast cancer cell growth through caspase activation.

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