title: Potentiation of growth factor signaling by insulin-like growth factor-binding protein-3 in breast epithelial cells requires sphingosine kinase activity.
abstract: We have investigated the mechanism underlying potentiation of epidermal growth factor receptor (EGFR) and type 1 insulin-like growth factor receptor (IGFR1) signaling by IGF-binding protein-3 (IGFBP-3) in MCF-10A breast epithelial cells, focusing on a possible involvement of the sphingosine kinase (SphK) system. IGFBP-3 potentiated EGF-stimulated EGF receptor activation and DNA synthesis, and this was blocked by inhibitors of SphK activity or small interference RNA-mediated silencing of SphK1, but not SphK2, expression. Similarly, IGFR1 phosphorylation and DNA synthesis stimulated by LR3-IGF-I (an IGF-I analog not bound by IGFBP-3), were enhanced by IGFBP-3, and this was blocked by SphK1 silencing. SphK1 expression and activity were stimulated by IGFBP-3 approximately 2-fold over 24 h. Silencing of sphingosine 1-phosphate receptor 1 (S1P1) or S1P3, but not S1P2, abolished the effect of IGFBP-3 on EGF-stimulated EGFR activation. The effects of IGFBP-3 could be reproduced with exogenous S1P or medium conditioned by cells treated with IGFBP-3, and this was also blocked by inhibition of S1P1 and S1P3. These data indicate that potentiation of growth factor signaling by IGFBP-3 in MCF-10A cells requires SphK1 activity and S1P1/S1P3, suggesting that S1P, the product of SphK activity and ligand for S1P1 and S1P3, is the "missing link" mediating IGF and EGFR transactivation and cell growth stimulation by IGFBP-3.
authors.affiliation: Hormones and Cancer Group, Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia. janetlm@med.usyd.edu.au
authors.forename: Janet L
authors.initials: JL
authors.lastname: Martin
authors.forename: Mike Z
authors.initials: MZ
authors.lastname: Lin
authors.forename: Eileen M
authors.initials: EM
authors.lastname: McGowan
authors.forename: Robert C
authors.initials: RC
authors.lastname: Baxter
mesh_terms: D001940:Breast / Q000166:cytology / Q000378:metabolism*; D045744:Cell Line, Tumor; D004247:DNA / Q000096:biosynthesis; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D020868:Gene Silencing; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008246:Lysophospholipids / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D034741:RNA, Small Interfering; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D049349:Receptors, Lysosphingolipid / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology; D000099157:Sphingosine Kinase
chemical_list: D004247:DNA; D066246:ErbB Receptors; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D008246:Lysophospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D034741:RNA, Small Interfering; D017526:Receptor, IGF Type 1; D049349:Receptors, Lysosphingolipid; D013110:Sphingosine; D000099157:Sphingosine Kinase; C515497:IGFBP3 protein, human; C060506:sphingosine 1-phosphate; C512478:EGFR protein, human