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Insulin-like growth factor binding protein-2: contributions of the C-terminal domain to insulin-like growth factor-1

Megan M Kibbey1, Mark J Jameson, Erin M Eaton

  • 1Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29425, USA.

Molecular Pharmacology
|November 25, 2005
PubMed

Insights

Insulin-like growth factor binding protein-2 (IGFBP-2) inhibits cancer cell proliferation by binding to IGF-1. Specific regions of IGFBP-2 are crucial for this IGF-1 binding, supporting its therapeutic potential in cancer treatment.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cancer Research

Background:

  • Insulin-like growth factor (IGF)-1 receptor (IGF-1R) signaling promotes various cancers.
  • IGF binding proteins (IGFBPs) antagonize IGF-1/2, making them potential cancer therapeutics.
  • IGFBP-2 has demonstrated inhibitory effects on cancer cell proliferation.

Purpose of the Study:

  • To investigate the specific regions of IGFBP-2 responsible for IGF-1 binding.
  • To further evaluate IGFBP-2 as a potential therapeutic agent for cancer.

Main Methods:

  • Recombinant human IGFBP-2 was used to attenuate IGF-1-stimulated MCF-7 cell proliferation.
  • Specific domains of IGFBP-2, including Trp-248 and deletion mutants (IGFBP-2(1-248), IGFBP-2(249-289), IGFBP-2(1-190)), were generated and purified.
  • Competition binding assays and kinetic assays were performed to assess IGF-1 binding affinity and kinetics.

Main Results:

  • Full-length IGFBP-2 significantly inhibited MCF-7 cell proliferation.
  • Deletion of residues 249-289 in IGFBP-2 resulted in a 20-fold decrease in IGF-1 binding affinity.
  • Truncated forms (IGFBP-2(1-248) and IGFBP-2(1-190)) showed faster association and dissociation rates compared to full-length IGFBP-2.
  • Regions both upstream and downstream of the CWCV motif are critical for IGF-1 binding.

Conclusions:

  • The study confirms that specific regions of IGFBP-2, flanking the CWCV motif, are essential for high-affinity IGF-1 binding.
  • These findings reinforce the potential of full-length IGFBP-2 as a viable therapeutic strategy for cancer prevention and treatment.

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