Abstract A145: In vivo and in vitro generation and characterization of EGFR TKI resistance in a patient-derived and a cell line-derived xenograft model of NSCLC with activating EGFR mutations.

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Abstract Introduction: Most non-small cell lung cancer (NSCLC) patients that have activating mutations in the EGFR gene will respond to treatment with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) e.g. erlotinib and gefitinib. 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 c-MET kinase, HER2 and epithelial-mesenchymal transition (EMT) conversion; however, additional routes of resistance are poorly defined. Using a novel Caucasian NSCLC patient-derived xenograft (PDX) model and a cell line derived 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: LU6422 is a Caucasian NSCLC adenocarcinoma PDX model with an activating EGFR mutation (L858R) which is maintained subcutaneously in vivo admixed with a human stromal cell component. HCC827 is NSCLC adenocarcinoma cell line with an activating EGFR mutation (del E746-A750). Resistant models of LU6422 and HCC827 were generated in vivo and in vitro (respectively) through repeated dosing or exposure to EGFR TKIs. Resistant tumour material was characterised for further mutations in the EGFR gene by direct sequencing as well as for c-MET, AXL and HER2 over-expression and genomic amplification by quantitative PCR. Results: Naïve LU6422 and HCC827 tissue exhibited exquisite sensitivity to EGFR TKIs (100% & 30% reduction respectively in pre-treatment tumor volume, p<0.0001). Following successive cycles of EGFR-TKI treatment several resistant subtypes were generated, cloned and characterized. Conclusions: EGFR TKI resistant subtypes were generated in vivo and in vitro from a proprietary Caucasian NSCLC PDX model (LU6422) and the HCC827 NSCLC cell line and were characterized for their resistance mechanisms. 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 Information: Mol Cancer Ther 2013;12(11 Suppl):A145. Citation Format: Andrew J. McKenzie, Aaron N. Cranston, Nektaria Papadopoulou, Simon Jiang, Jane Wrigley, Yinfei Yin, Henry Li, Martin Page, Rajendra Kumari. In vivo and in vitro generation and characterization of EGFR TKI resistance in a patient-derived and a cell line-derived xenograft model of NSCLC with activating EGFR mutations. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A145.