Postsynthetic regulation of insulin-like growth factor-binding protein-3 by MCF-7 human breast cancer cells in culture

Randall W. Grimes, Andrea Manni, James M. Hammond

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Breast cancer cells are exposed to insulin-like growth factors (IGFs) which stimulate their proliferation, and to IGF-binding proteins (IGFBPs) which sequester and modulate IGF action. The primary circulatory IGFBP is IGFBP-3. In the present study, cultured MCF-7 breast cancer cells regulated clearance of IGFBP-3 via both cell association and proteolysis. Exogenously added IGFBP-3 was significantly cleared from the medium over time yielding the formation of smaller sized immunodetected fragments. Clearance was inhibited by IGF-I and -II. In contrast, clearance was not affected by growth factors and an IGF-analog having mitogenic activity but not binding to IGFBPs. In fact, activity of the IGFs and analogs paralleled their degree of binding to the IGFBP, suggesting that the IGF-binding altered IGFBP-3 making it less susceptible to clearance. Qualitatively similar results were obtained when these experiments were conducted using cell-free conditioned medium, thus suggesting the presence of secreted protease(s). However, level of proteolytic activity was much less than that found in the presence of cells. Clearance of rhIGFBP-3 also involved binding to the cell. Disappearance of rhIGFBP-3 was shown to be attenuated by heparin, which blocks cell surface binding sites. In contrast, compounds which block internalization did not inhibit IGFBP-3 clearance.

Original languageEnglish (US)
Pages (from-to)187-196
Number of pages10
JournalBreast Cancer Research and Treatment
Volume39
Issue number2
DOIs
StatePublished - Jan 1 1996

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Insulin-Like Growth Factor Binding Protein 3
Cell Culture Techniques
Somatomedins
Insulin-Like Growth Factor Binding Proteins
Breast Neoplasms
Insulin-Like Growth Factor II
Conditioned Culture Medium
Insulin-Like Growth Factor I
Proteolysis
Heparin
Intercellular Signaling Peptides and Proteins
Peptide Hydrolases
Binding Sites

All Science Journal Classification (ASJC) codes

  • Oncology
  • Cancer Research

Cite this

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title = "Postsynthetic regulation of insulin-like growth factor-binding protein-3 by MCF-7 human breast cancer cells in culture",
abstract = "Breast cancer cells are exposed to insulin-like growth factors (IGFs) which stimulate their proliferation, and to IGF-binding proteins (IGFBPs) which sequester and modulate IGF action. The primary circulatory IGFBP is IGFBP-3. In the present study, cultured MCF-7 breast cancer cells regulated clearance of IGFBP-3 via both cell association and proteolysis. Exogenously added IGFBP-3 was significantly cleared from the medium over time yielding the formation of smaller sized immunodetected fragments. Clearance was inhibited by IGF-I and -II. In contrast, clearance was not affected by growth factors and an IGF-analog having mitogenic activity but not binding to IGFBPs. In fact, activity of the IGFs and analogs paralleled their degree of binding to the IGFBP, suggesting that the IGF-binding altered IGFBP-3 making it less susceptible to clearance. Qualitatively similar results were obtained when these experiments were conducted using cell-free conditioned medium, thus suggesting the presence of secreted protease(s). However, level of proteolytic activity was much less than that found in the presence of cells. Clearance of rhIGFBP-3 also involved binding to the cell. Disappearance of rhIGFBP-3 was shown to be attenuated by heparin, which blocks cell surface binding sites. In contrast, compounds which block internalization did not inhibit IGFBP-3 clearance.",
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Postsynthetic regulation of insulin-like growth factor-binding protein-3 by MCF-7 human breast cancer cells in culture. / Grimes, Randall W.; Manni, Andrea; Hammond, James M.

In: Breast Cancer Research and Treatment, Vol. 39, No. 2, 01.01.1996, p. 187-196.

Research output: Contribution to journalArticle

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AB - Breast cancer cells are exposed to insulin-like growth factors (IGFs) which stimulate their proliferation, and to IGF-binding proteins (IGFBPs) which sequester and modulate IGF action. The primary circulatory IGFBP is IGFBP-3. In the present study, cultured MCF-7 breast cancer cells regulated clearance of IGFBP-3 via both cell association and proteolysis. Exogenously added IGFBP-3 was significantly cleared from the medium over time yielding the formation of smaller sized immunodetected fragments. Clearance was inhibited by IGF-I and -II. In contrast, clearance was not affected by growth factors and an IGF-analog having mitogenic activity but not binding to IGFBPs. In fact, activity of the IGFs and analogs paralleled their degree of binding to the IGFBP, suggesting that the IGF-binding altered IGFBP-3 making it less susceptible to clearance. Qualitatively similar results were obtained when these experiments were conducted using cell-free conditioned medium, thus suggesting the presence of secreted protease(s). However, level of proteolytic activity was much less than that found in the presence of cells. Clearance of rhIGFBP-3 also involved binding to the cell. Disappearance of rhIGFBP-3 was shown to be attenuated by heparin, which blocks cell surface binding sites. In contrast, compounds which block internalization did not inhibit IGFBP-3 clearance.

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