title: Differential IGF-independent effects of insulin-like growth factor binding proteins (1-6) on apoptosis of breast epithelial cells.
abstract: We have demonstrated previously that insulin-like growth factor binding protein (IGFBP)-3 alone has little growth inhibitory effect on Hs578T human breast cancer cells, but that it can dramatically accentuate the apoptotic response to the physiological trigger, ceramide, in an IGF-independent manner. We have now studied the potential of other IGFBPs (1-6) to interact with apoptotic signalling pathways. Hs578T cells were preincubated with a binding protein (100 ng/ml) for 24 h, followed by co-incubation of the binding protein with an apoptotic dose of ceramide or RGD-containing peptide for a further 24 h. Apoptosis was assessed using flow cytometry, MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide; thiazolyl blue) assay and morphological assessment. Binding protein profiles were determined using ligand and immunoblotting techniques. Each of the IGFBPs (1-6) alone had no significant (P > 0. 05) growth inhibitory effects relative to control cells. In contrast to IGFBP-3, which significantly (P < 0.05) accentuated C2-induced apoptosis, IGFBP-1, -2, and -6 had no effect, whereas IGFBP-4 and -5 each caused marked (P < 0.01) inhibition of ceramide-induced programmed cell death. Apoptosis induced by RGD was also significantly (P < 0.05) reduced by IGFBP-5, whereas IGFBP-3 had no effect. These data provide evidence to suggest that individual IGFBPs have specific IGF-independent effects and act differentially on apoptotic signalling pathways.
authors.affiliation: Division of Surgery, Department of Hospital Medicine, Bristol Royal Infirmary, Bristol BS2 8HW, United Kingdom. claire.m.perks@bris.ac.uk
authors.forename: C M
authors.initials: CM
authors.lastname: Perks
authors.forename: S
authors.initials: S
authors.lastname: Bowen
authors.forename: Z P
authors.initials: ZP
authors.lastname: Gill
authors.forename: P V
authors.initials: PV
authors.lastname: Newcomb
authors.forename: J M
authors.initials: JM
authors.lastname: Holly
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002518:Ceramides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis / Q000494:pharmacology*; D008024:Ligands; D009842:Oligopeptides / Q000494:pharmacology; D013002:Somatomedins; D013778:Tetrazolium Salts; D013844:Thiazoles; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D002518:Ceramides; D018969:Insulin-Like Growth Factor Binding Proteins; D008024:Ligands; D009842:Oligopeptides; D013002:Somatomedins; D013778:Tetrazolium Salts; D013844:Thiazoles; C047981:arginyl-glycyl-aspartic acid; C022616:thiazolyl blue