Abstract 5255: EGFR is a conspiring kinase in gene fusion positive lung cancer
Authors: Vaishnavi Aria , Le Anh T. , Keysar Stephen B. , Lovly Christine M. , Kako Severine , Varella-Garcia Marileila , Jimeno Antonio , Doebele Robert C. 
Published: May 2015

Abstract
The use of kinase inhibitors directed at dominant oncogenes has proven a successful treatment strategy for non-small cell lung cancer (NSCLC) harboring ALK gene fusions, but intrinsic or acquired drug resistance limits clinical benefit. We recently identified a novel class of oncogenes generated by translocations of the NTRK1 gene, which encodes the TRKA receptor tyrosine kinase. ROS1 and RET gene fusions represent additional oncogene targets in lung cancer and gene fusion positive tumors currently comprise ∼10% of lung adenocarcinomas. Previous results from our laboratory have demonstrated that EGFR signaling can mediate both intrinsic and acquired resistance in a ROS1+ NSCLC cell line. We asked whether EGFR might play a common role in other NSCLC cell lines harboring gene fusions with the aim of developing combination therapies that may delay drug resistance to oncogene-targeted kinase inhibitors in these tumors. We have observed high protein expression of the epidermal growth factor receptor (EGFR) in NSCLC cell lines positive for ALK (H3122, H2228, and STE-1), ROS1 (HCC78 and CUTO-2), RET (LC-2/Ad), and NTRK1 gene fusions (CUTO-3), and in a NTRK1 patient-derived xenograft (PDX) model. We observed increased inhibition of downstream signaling and in vitro cellular proliferation with the addition of EGFR tyrosine kinase inhibitors in these gene fusion positive cell lines. Furthermore, stimulation of EGFR with EGF rescues targeted inhibition with oncogene-specific kinase inhibitors in the critical downstream signaling pathways such as PI3K/AKT and MEK/ERK. Inhibition of cellular proliferation of these cell lines using oncogene-specific kinase inhibitors was also rescued by stimulation of EGFR. Interestingly, we observed transactivation of the TRKA and RET kinase domains by EGFR stimulation in the CUTO-3 and LC-2/Ad cell lines, respectively, despite treatment with a TRKA or RET kinase inhibitor. Additionally, co-immunoprecipitation experiments show that EGFR and the chimeric protein RIP-TRKA (encoded by the fusion gene MPRIP-NTRK1) associate in the CUTO-3 cells or when ectopically expressed in 293T cells. Collectively, these data demonstrate a critical role for EGFR in gene fusion positive lung cancer and suggest that signaling via this receptor may provide a survival mechanism for cancer cells treated with an oncogene-specific kinase inhibitor. Further investigation of EGFR inhibition in addition to oncogene-specific kinase inhibitors may be warranted.
Citation Format: Aria Vaishnavi, Anh T. Le, Stephen B. Keysar, Christine M. Lovly, Severine Kako, Marileila Varella-Garcia, Antonio Jimeno, Robert C. Doebele. EGFR is a conspiring kinase in gene fusion positive lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5255. doi:10.1158/1538-7445.AM2014-5255