title: Temporal profiling of lapatinib-suppressed phosphorylation signals in EGFR/HER2 pathways.
abstract: Lapatinib is a clinically potent kinase inhibitor for breast cancer patients because of its outstanding selectivity for epidermal growth factor receptor (EGFR) and EGFR2 (also known as HER2). However, there is only limited information about the in vivo effects of lapatinib on EGFR/HER2 and downstream signaling targets. Here, we profiled the lapatinib-induced time- and dose-dependent phosphorylation dynamics in SKBR3 breast cancer cells by means of quantitative phosphoproteomics. Among 4953 identified phosphopeptides from 1548 proteins, a small proportion (5-7%) was regulated at least twofold by 1-10 μm lapatinib. We obtained a comprehensive phosphorylation map of 21 sites on EGFR/HER2, including nine novel sites on HER2. Among them, serine/threonine phosphosites located in a small region of HER2 (amino acid residues 1049-1083) were up-regulated by the drug, whereas all other sites were down-regulated. We show that cAMP-dependent protein kinase is involved in phosphorylation of this particular region of HER2 and regulates HER2 tyrosine kinase activity. Computational analyses of quantitative phosphoproteome data indicated for the first time that protein-protein networks related to cytoskeletal organization and transcriptional/translational regulation, such as RNP complexes (i.e. hnRNP, snRNP, telomerase, ribosome), are linked to EGFR/HER2 signaling networks. To our knowledge, this is the first report to profile the temporal response of phosphorylation dynamics to a kinase inhibitor. The results provide new insights into EGFR/HER2 regulation through region-specific phosphorylation, as well as a global view of the cellular signaling networks associated with the anti-breast cancer action of lapatinib.
authors.affiliation: Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan.
authors.forename: Koshi
authors.initials: K
authors.lastname: Imami
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Sugiyama
authors.forename: Haruna
authors.initials: H
authors.lastname: Imamura
authors.forename: Masaki
authors.initials: M
authors.lastname: Wakabayashi
authors.forename: Masaru
authors.initials: M
authors.lastname: Tomita
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ueno
authors.forename: Masakazu
authors.initials: M
authors.lastname: Toi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ishihama
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D000077341:Lapatinib; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D066246:ErbB Receptors; D000077341:Lapatinib; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; C512478:EGFR protein, human; C508053:ERBB2 protein, human