title: Insulin-like growth factor-binding protein 3 induces caspase-dependent apoptosis through a death receptor-mediated pathway in MCF-7 human breast cancer cells.
abstract: Insulin-like growth factor-binding protein (IGFBP)-3 has been shown to potently inhibit cell proliferation in various cell systems. However, the specific mechanisms involved in the antiproliferative action of IGFBP-3 have yet to be elucidated. In the present study, we demonstrate that IGFBP-3 induces apoptosis in an insulin-like growth factor (IGF)-independent manner through the activation of caspases involved in a death receptor-mediated pathway in MCF-7 human breast cancer cells. Induction of IGFBP-3 using an ecdysone-inducible expression system inhibited DNA synthesis in an IGF-IGF receptor axis-independent fashion and resulted in the subsequent induction of apoptosis and an increase in caspase activity. Similar results were obtained when cells were transfected with GGG-IGFBP-3, an IGFBP-3 mutant unable to bind IGFs, corroborating the IGF-independent action of IGFBP-3. Additional caspase activity studies and immunoblot analyses using specific caspase substrates and/or caspase inhibitors revealed that the growth-inhibitory effect of IGFBP-3 results mainly from its induction of apoptosis (in particular, activation of caspase-8 and -7). Analyses of caspase-9 activity and release of cytochrome c into the cytosol confirmed that the mitochondria-mediated pathway is not involved. Taken together, these results show that IGFBP-3 expression leads to the induction of apoptosis through the activation of caspases involved in a death receptor-mediated pathway and that IGFBP-3 functions as a negative regulator of breast cancer cell growth, independent of the IGF-IGF receptor axis.
authors.affiliation: Department of Pediatrics, Oregon Health and Science University, Portland, Oregon, USA.
authors.forename: Ho-Seong
authors.initials: HS
authors.lastname: Kim
authors.forename: Angela R
authors.initials: AR
authors.lastname: Ingermann
authors.forename: Junko
authors.initials: J
authors.lastname: Tsubaki
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Twigg
authors.forename: Gillian E
authors.initials: GE
authors.lastname: Walker
authors.forename: Youngman
authors.initials: Y
authors.lastname: Oh
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism; D004440:Ecdysone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D018972:Insulin-Like Growth Factor Binding Protein 3; D017527:Receptor, IGF Type 2; D014409:Tumor Necrosis Factor-alpha; D004440:Ecdysone; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D045304:Cytochromes c; D017526:Receptor, IGF Type 1; D020169:Caspases