title: Studies on the regulation of insulin-like growth factor binding protein 3 secretion in human osteosarcoma cells in vitro.
abstract: Previous studies demonstrated that insulin-like growth factors (IGFs) are important autocrine and paracrine mitogens for human bone cells in vitro and that IGF binding proteins (IGFBPs) are important regulators of the biologic actions of IGFs. Thus, the actions of IGFs may be determined not only by their concentrations but also by the type and amount of IGFBPs produced by human bone cells at a local site in bone. In this study, we sought to determine the effects of dexamethasone, 1,25-(OH)2D3, and parathyroid hormone (PTH) on the secretion of IGFBP-3 in human osteosarcoma cell lines. Serum-free cultures of low- and high-alkaline phosphatase (ALP) SaOS-2, MG-63, and TE89 human osteosarcoma cells were treated for 24 or 48 h with the effectors and the conditioned media used for determination of IGFBP-3 using a radioimmunoassay. We report that (1) the basal rate of IGFBP-3 secretion (ng/mg cellular protein) was dependent upon cell type, with TE89 > low-ALP Saos-2 > MG-63 > high-ALP SaOS-2 cells, and did not correlate with either basal cell proliferation or basal cellular ALP activity; (2) dexamethasone (10(-12)-10(-7) M) inhibited IGFBP-3 secretion in a dose-dependent manner in low-ALP SaOS-2, MG-63, and TE89 cells but not in high-ALP SaOS-2 cells; (3) 1,25-(OH)2D3 (10(-11)-10(-8) M) stimulated IGFBP-3 secretion in a dose-dependent manner in MG-63, low-ALP SaOS-2, and high-ALP SaOS-2 cells, and the coaddition of TGF-beta and 1,25-(OH)2D3 increased synergistically IGFBP-3 secretion and cellular ALP activity in MG-63 cells; and (4) human PTH-(1-34) (0.1-100 ng/ml) had no significant effect on IGFBP-3 secretion in MG-63, low-ALP SaOS-2, or high-ALP SaOS-2 cells. We conclude that such agents as dexamethasone, 1,25-(OH)2D3, and PTH differentially regulate IGFBP-3 secretion in human osteosarcoma cells in vitro.
authors.affiliation: Department of Medicine, Loma Linda University, California.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakao
authors.forename: S
authors.initials: S
authors.lastname: Hilliker
authors.forename: D J
authors.initials: DJ
authors.lastname: Baylink
authors.forename: S
authors.initials: S
authors.lastname: Mohan
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000704:Analysis of Variance; D001842:Bone and Bones / Q000166:cytology*; D002117:Calcitriol / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011863:Radioimmunoassay; D013002:Somatomedins; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D010281:Parathyroid Hormone; D013002:Somatomedins; D016212:Transforming Growth Factor beta; D003907:Dexamethasone; D000469:Alkaline Phosphatase; D002117:Calcitriol