title: Non-receptor mediated, post-transcriptional regulation of insulin-like growth factor binding protein (IGFBP)-3 in Hs578T human breast cancer cells.
abstract: Hs578T human breast cancer cells secrete insulin-like growth factor binding protein 3 (IGFBP-3) as the major BP species. In addition, cell surface-associated IGFBP-3 is demonstrable by the use of cell monolayer affinity cross-linking or immunoperoxidase staining of the cell surface with a specific polyclonal anti-human IGFBP-3 antibody (alpha IGFBP-3 gamma 1). In this study, we have demonstrated that regulation of Hs578T IGFBP-3 by IGF peptides is specific, non-receptor mediated, and post-translational by showing: 1) dose-dependent increase of IGFBP-3 in conditioned media (CM) following addition of IGF-I and -II (maximum 13 fold increase at 100 ng/ml), but not by insulin up to 1 mg/ml; 2) no change in CM IGFBP-3 level by [Gln3,Ala4,Tyr15,Leu16] IGF-I, which has decreased affinity for IGFBPs; 3) no change in IGFBP-3 mRNA following addition of IGFs; 4) release of cell surface-associated IGFBP-3 into CM by the addition of IGFs, but not by [Gln3,Ala4,Tyr15,Leu16]IGF-I. These studies demonstrate that IGF peptides regulate CM concentrations of IGFBP-3 through non-receptor mediated dissociation of cell surface-associated IGFBP-3.
mesh_terms: D015152:Blotting, Northern; D001943:Breast Neoplasms / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics*; D003432:Cross-Linking Reagents; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013002:Somatomedins / Q000494:pharmacology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I