title: Selective disruption of insulin-like growth factor-1 (IGF-1) signaling via phosphoinositide-dependent kinase-1 prevents the protective effect of IGF-1 on human cancer cell death.
abstract: Insulin-like growth factor-1 (IGF-1) signaling system exerts a broad antiapoptotic function and plays a crucial role in resistance to anticancer therapies. Exposure of MCF-7 breast cancer cells to IGF-1 rapidly and transiently induced tyrosine phosphorylation and activation of phosphoinositide-dependent kinase-1 (PDK1). This was paralleled by Akt/protein kinase B and protein kinase C-zeta phosphorylation, at Thr(308) and Thr(410), respectively. IGF-1 treatment also enhanced PDK1 interaction with IGF-1 receptor (IGF-1R) in intact MCF-7 cells. Pulldown assays revealed that PDK1 bound IGF-1R in vitro and that the region encompassing amino acids 51-359 of PDK1 was necessary for the interaction. Synthetic peptides corresponding to IGF-1R C terminus amino acids 1295-1337 (C43) and to PDK1 amino acids 114-141 reduced in vitro IGF-1R/PDK1 interaction in a concentration-dependent manner. Loading of fluoresceinated-C43 (fluorescein isothiocyanate (FITC)-C43) into MCF-7 cells significantly reduced IGF-1R/PDK1 interaction and phosphorylation of PDK1 substrates. Moreover, FITC-C43 intracellular loading reverted the protective effect of IGF-1 on growth factor deprivation-induced cell death. Finally, the inhibition of IGF-1R/PDK1 interaction and signaling by FITC-C43 was accompanied by 2-fold enhanced killing capacity of cetuximab in human GEO colon adenocarcinoma cells and was sufficient to restore cell death in cetuximab-resistant cell clones. Thus, disruption of PDK1 interaction with IGF-1R reduces IGF-1 survival effects in cancer cells and may enhance cell death by anticancer agents.
authors.affiliation: Dipartimento di Biologia e Patologia Cellulare e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Università di Napoli Federico II, 80131 Naples, Italy.
authors.forename: A Teresa
authors.initials: AT
authors.lastname: Alberobello
authors.forename: Vittoria
authors.initials: V
authors.lastname: D'Esposito
authors.forename: Daniela
authors.initials: D
authors.lastname: Marasco
authors.forename: Nunzianna
authors.initials: N
authors.lastname: Doti
authors.forename: Menotti
authors.initials: M
authors.lastname: Ruvo
authors.forename: Roberto
authors.initials: R
authors.lastname: Bianco
authors.forename: Giampaolo
authors.initials: G
authors.lastname: Tortora
authors.forename: Iolanda
authors.initials: I
authors.lastname: Esposito
authors.forename: Francesca
authors.initials: F
authors.lastname: Fiory
authors.forename: Claudia
authors.initials: C
authors.lastname: Miele
authors.forename: Francesco
authors.initials: F
authors.lastname: Beguinot
authors.forename: Pietro
authors.initials: P
authors.lastname: Formisano
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D016923:Cell Death; D045744:Cell Line, Tumor; D002470:Cell Survival; D000068818:Cetuximab; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000494:pharmacology; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D010446:Peptide Fragments; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D064413:3-Phosphoinositide-Dependent Protein Kinases; C578562:PDPK1 protein, human; C578564:Pdpk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D000068818:Cetuximab