Abstract 5259: Ubiquitination and degradation of EGFR mutants by C-terminus hsp70 interacting protein (CHIP) in non-small cell lung cancer (NSCLC).

Abstract

Abstract Several somatic mutations in the kinase domain of the epidermal growth factor receptor (EGFR), including L858R and exon 19 deletions, are predictive markers for EGFR tyrosine kinase inhibitor treating non-small cell lung cancer (NSCLC), especially adenocarcinoma. The mutational activation of EGFR is stabilized by Hsp90. Therefore Hsp90 inhibition may promote ubiquitin-mediated degradation of EGFR mutants. C-terminus hsp70 interacting protein (CHIP) has been shown to negatively regulate Hsp70 and Hsp90 function and to convert Hsp90 complexes from a chaperone function to one that promotes the ubiquitination and degradation of interacting proteins. Here, we report a novel interaction of EGFR mutants with an E3 ubiquitin ligase CHIP, which can ubiquitinate, and destabilize EGFR mutants. In CHO cells expressing either wild-type or mutant EGFR, inhibition of expression of its mutants: L858R, G719S and del L747_E749del, occurred following overexpression with CHIP, whereas diminution of wild-type EGFR was not in CHIP transfected cells. In full-down assay, CHIP especially interacted with G719S and del L747_E749del, but not L858R, and simultaneously induced ubiquitination of its proteins. Similarly, EGFR proteins in NSCLC cell lines harboring EGFR mutations, PC9, were also declined by CHIP mediated ubiquitination and degradation compared with the protein in wild-type cells. In EGFR mutant cell lines, CHIP inhitibited cell proliferation as well as depletion of phosphor-Akt and ERK. These data suggest that CHIP regulates and stabilizes EGFR mutants and that CHIP may be a novel regulator and marker in EGFR-mutants NSCLC. We confirmed these results by tumor xenograft model. Based on above findings, we conclude that CHIP is a new modulator in EGFR mutant pathway in NSCLC. Citation Format: Jeong Eun Lee, Kang Won Jang, Hye Rim Cha, Jo-ock Kim, Sung Soo Jung, Dong Il Park, Myoung Rin Park, Chaeuk Chung. Ubiquitination and degradation of EGFR mutants by C-terminus hsp70 interacting protein (CHIP) in non-small cell lung cancer (NSCLC). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5259. doi:10.1158/1538-7445.AM2013-5259 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.