Abstract 5651: In vivo generation of EGFR-TKI resistance in a patient-derived xenograft (PDX) with an activating EGFR mutation (L858R), and molecular characterisation of resistance mechanisms..
Authors: Mckenzie Andrew , Cranston Aaron , Mallinder Phil , Papadopoulou Nektaria , Jiang Simon , Moakes Kerry , Yin Yinfei , Onion David , Grabowska Anna , Page Martin , Kumari Rajendra 
Published: August 2014

Abstract
BACKGROUND: Non-small cell lung cancer (NSCLC) patients that have activating mutations in the EGFR gene are treated with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) e.g. Erlotinib (Tarceva®) and Gefitinib (Iressa®). Most NSCLC patients with activating EGFR mutations will respond to EGFR-TKIs; however, in about 50% of these cases a secondary mutation in EGFR (T790M) subsequently occurs which results in resistance to treatment. Other mechanisms of clinical resistance can also occur such as amplification of MET kinase and EMT conversion; however, additional routes of resistance are poorly defined. Using a novel patient-derived NSCLC xenograft model, driven by the L858R EGFR mutation, we set out to recapitulate the reported clinical routes of resistance to EGFR inhibitors and to evaluate if additional mechanism could also be identified.
METHODS: LION102 is a NSCLC adenocarcinoma patient-derived xenograft (PDX) model with an activating EGFR mutation (L858R) which is maintained subcutaneously in vivo admixed with a human stromal cell component. Resistant models were generated in vivo through repeated cycling of treatment for up to 10 weeks with EGFR-TKI alone or in combination with a MET inhibitor. Resistant tumour material was characterised for further mutations in the EGFR gene by direct sequencing as well as for MET, AXL and HER2 over-expression and genomic amplification by quantitative PCR; Epithelial-to-Mesenchymal transition (EMT) was assessed by immunohistochemistry (IHC).
RESULTS: Naïve LION102 PDX tumours exhibited exquisite sensitivity to EGFR-TKIs (100% reduction in pre-treatment tumour volume, p&lt;0.0001). Following successive cycles of EGFR-TKI treatment in vivo several resistant subtypes were generated and characterized.
CONCLUSIONS: EGFR-TKI resistant subtypes were generated in vivo from a proprietary patient-derived xenograft model (LION102) bearing an activating EGFR mutation (L858R) and characterised for their resistance mechanism. PDX models of resistance will be invaluable in assessing novel agents targeting the EGFR pathway and the development of new combination strategies which seek to prevent or overcome resistance to EGFR-TKIs.
Citation Format: Andrew Mckenzie, Aaron Cranston, Phil Mallinder, Nektaria Papadopoulou, Simon Jiang, Kerry Moakes, Yinfei Yin, David Onion, Anna Grabowska, Martin Page, Rajendra Kumari. In vivo generation of EGFR-TKI resistance in a patient-derived xenograft (PDX) with an activating EGFR mutation (L858R), and molecular characterisation of resistance mechanisms. [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 5651. doi:10.1158/1538-7445.AM2013-5651