title: Growth inhibition by insulin-like growth factor-binding protein-3 in T47D breast cancer cells requires transforming growth factor-beta (TGF-beta ) and the type II TGF-beta receptor.
abstract: This study explores the relationship between anti-proliferative signaling by transforming growth factor-beta (TGF-beta) and insulin-like growth factor-binding protein-3 (IGFBP-3) in human breast cancer cells. In MCF-7 cells, the expression of recombinant IGFBP-3 inhibited proliferation and sensitized the cells to further inhibition by TGF-beta1. To investigate the mechanism, we used T47D cells that lack type II TGF-beta receptor (TGF-betaRII) and are insensitive to TGF-beta1. After introducing the TGF-betaRII by transfection, the basal proliferation rate was significantly decreased. Exogenous TGF-beta1 caused no further growth inhibition, but immunoneutralization of endogenous TGF-beta1 restored the proliferation rate almost to the control level. The addition of IGFBP-3 did not inhibit the proliferation of control cells but caused dose-dependent inhibition in TGF-betaRII-expressing cells when exogenous TGF-beta1 was also present. Similarly, receptor-expressing cells showed dose-dependent sensitivity to exogenous TGF-beta1 only in the presence of exogenous IGFBP-3. This indicates that in these cells, anti-proliferative signaling by exogenous IGFBP-3 requires both the TGF-betaRII and exogenous TGF-beta1. To investigate this synergism, the phosphorylation of TGF-beta signaling intermediates, Smad2 and Smad3, was measured. Phosphorylation of each Smad was stimulated by TGF-beta1 and, independently, by IGFBP-3 with the two agents together showing a cumulative effect. These data suggest that IGFBP-3 inhibitory signaling requires an active TGF-beta signaling pathway and implicate Smad2 and Smad3 in IGFBP-3 signal transduction.
authors.affiliation: Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Fanayan
authors.forename: S M
authors.initials: SM
authors.lastname: Firth
authors.forename: A J
authors.initials: AJ
authors.lastname: Butt
authors.forename: R C
authors.initials: RC
authors.lastname: Baxter
mesh_terms: D015152:Blotting, Northern; D001943:Breast Neoplasms / Q000378:metabolism*; D002455:Cell Division; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D051899:Smad2 Protein; D051900:Smad3 Protein; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II