title: Promotion of cancer cell migration: an insulin-like growth factor (IGF)-independent action of IGF-binding protein-6.
abstract: A family of six high affinity IGF-binding proteins (IGFBPs 1-6) plays an important role in modulating IGF activities. Recent studies suggest that some IGFBPs may have IGF-independent effects, including induction of apoptosis and modulation of cell migration. However, very little is known about possible IGF-independent actions of IGFBP-6. We have generated a non-IGF-binding IGFBP-6 mutant by substituting Ala for four amino acid residues (Pro(93)/Leu(94)/Leu(97)/Leu(98)) in its N-domain IGF-binding site. A >10,000-fold loss of binding affinity for IGF-I and IGF-II was observed using charcoal solution binding assay, BIAcore biosensor, and ligand blotting. Wild-type and mutant IGFBP-6, as well as IGF-II, induced cell migration in RD rhabdomyosarcoma and LIM 1215 colon cancer cells. Cell migration was mediated by the C-domain of IGFBP-6. Transient p38 phosphorylation was observed in RD cells after treatment with IGFBP-6, whereas no change was seen in phospho-ERK1/2 levels. Phospho-JNK was not detected. IGFBP-6-induced cell migration was inhibited by SB203580, an inhibitor of p38 MAPK, and PD98059, an inhibitor of ERK1/2 MAPK activation. In contrast, SP600125, a JNK MAPK inhibitor, had no effect on migration. Knockdown of p38 MAPK using short interfering RNA blocked IGFBP-6-induced migration of RD cells. These results indicate that p38 MAPK is involved in IGFBP-6-induced IGF-independent RD cell migration.
authors.affiliation: Department of Medicine, Central and Eastern Clinical School, Monash University, Prahran Victoria 3181, Australia. ping.fu@med.monash.edu.au
authors.forename: Ping
authors.initials: P
authors.lastname: Fu
authors.forename: Julian A
authors.initials: JA
authors.lastname: Thompson
authors.forename: Leon A
authors.initials: LA
authors.lastname: Bach
mesh_terms: D000873:Anthracenes / Q000494:pharmacology; D002465:Cell Movement; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008024:Ligands; D020935:MAP Kinase Signaling System; D009154:Mutation; D009369:Neoplasms / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011725:Pyridines / Q000494:pharmacology; D012208:Rhabdomyosarcoma / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000873:Anthracenes; D007093:Imidazoles; D018976:Insulin-Like Growth Factor Binding Protein 6; D008024:Ligands; D011725:Pyridines; C432165:pyrazolanthrone; D007334:Insulin-Like Growth Factor I; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580