title: Enhancement of tumor necrosis factor-alpha-induced growth inhibition by insulin-like growth factor-binding protein-5 (IGFBP-5), but not IGFBP-3 in human breast cancer cells.
abstract: Expression of IGF-binding protein-3 (IGFBP-3) and IGFBP-5 in human breast cancer cells induces apoptosis and is associated with modulations in Bcl-2 proteins, suggesting that these IGFBPs induce an intrinsic apoptotic pathway. In this study we demonstrate that although both IGFBPs induced the activation of caspase-8 and caspase-9, the expression of IGFBP-5, but not IGFBP-3, sensitized MDA-MB-231 breast cancer cells to the inhibitory effects of TNFalpha. This sensitivity to TNFalpha was associated with a block in nuclear factor-kappaB-mediated cell survival signals. IGFBP-5 expression was also associated with a caspase-8-independent activation of Bid, increased levels of cytosolic second mitochondria-derived activator of caspase (Smac)/direct inhibitor of apoptosis proteins (IAP) binding protein with low pI (DIABLO), and an enhanced phosphorylation of c-Jun N-terminal kinase, both basally and in response to TNFalpha. These results suggest that IGFBP-5 expression may influence extrinsic apoptotic pathways via a differential modulation of downstream cell survival and cell death pathways. Furthermore, although IGFBP-3 and IGFBP-5 share much structural and functional homology, they can modulate distinct apoptotic pathways in human breast cancer cells.
authors.affiliation: Kolling Institute of Medical Research, University of Sydney, Royan North Shore Hospital, New South Wales 2065, Australia. abutt@garvan.org.au
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Butt
authors.forename: Kristie A
authors.initials: KA
authors.lastname: Dickson
authors.forename: Stan
authors.initials: S
authors.lastname: Jambazov
authors.forename: Robert C
authors.initials: RC
authors.lastname: Baxter
mesh_terms: D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000494:pharmacology*; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D018975:Insulin-Like Growth Factor Binding Protein 5; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D048031:JNK Mitogen-Activated Protein Kinases; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases