Abstract 5128: Physical EGFR network mapping and dynamic regulation in lung cancer cells

Abstract

Abstract Aberrant activation of Epidermal Growth Factor Receptor (EGFR) through somatic mutations plays a critical role in the development and progression in lung cancer. A better understanding of the downstream signaling network driven by EGFR mutations could uncover novel therapeutics targets and/or resistance mechanisms. We characterized a physical EGFR network by integrating (i) protein-protein interaction data derived from tandem affinity purification (TAP) and liquid chromatography mass spectrometry (LC-MS/MS) and (ii) global phospho-tyrosine protein profile identified by immunoaffinity purification of tyrosine phosphorylated peptides coupled to LC-MS/MS. All experiments were performed in lung cancer cell lines harboring activating EGFR mutations and highly sensitive to EGFR inhibitors. We identified 266 proteins in this network including other ERBB family member (ERBB2 and ERBB3), adaptors (GRB2, SHC1, MIG6 and STS1), heat shock proteins and chaperones (HSP90 isoforms, CDC37 and BIP), proteins involved in RTK endocytosis (AP family proteins), and phosphatases (PTPN12 and PTPRA). We found ERBB3 bound EGFR but not ERBB2 while PI3K subunits are exclusively in complex with ERBB3 suggesting ERBB3 is a key linkage between EGFR and downstream PI3K/AKT signaling. CDC37, as a co-chaperone of HSP90, bound multiple kinases suggesting possible functional importance in these cells. ARHGEF5, an activator of RHO pathway signaling, was found to interact with GRB2 and SHC1. MIG6 (also known as ERRFI1 and RALT), a known negative regulator of ERB signaling, interacts with numerous components of this network, including EGFR, GRB2, STS1, SHC1, ERBB2. We found that forced expression of MIG6 in PC9 and HCC827 cells inhibits EGFR-ERK signaling. Interestingly, cells maintain AKT signaling independently of EGFR through unknown mechanism. These cells become resistance to EGFR inhibitors but are sensitized to PI3K/mTOR inhibition. STS1, a tyrosine phosphatase, can also regulate EGFR signal pathway and lead to resistance to EGFR inhibitor. Updated work will be presented. Supported by the SPORE in Lung Cancer (P50-CA119997), National Functional Genomics Center, and Austrian Proteomics Platform GZ 200.145/1-VI/1/2006, part of the GEN-AU initiative of the BM:WF. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5128. doi:10.1158/1538-7445.AM2011-5128