Abstract 3077: Tumor cells with acquired resistance to EGFR inhibitors and overexpression or activation of AXL, MET and FGFR1 are insensitive to single-agent treatment targeting AXL, MET or FGFR
Authors: Bertran-Alamillo Jordi , Molina-VIla Miguel Angel , Teixidó Cristina , Codony-Servat Jordi , Giménez-Capitán Ana , Codony-Servat Carles , García-Román Silvia , Aldeguer Erika , Rodríguez Sonia , Rosell Rafael 
Published: July 2017

Abstract
Background: Aberrant activity of the MET, FGFR1 and AXL receptors has been associated with the development of resistance to first, second and third generation EGFR tyrosine kinase inhibitors (TKI) in EGFR-mutated non-small cell lung cancer (NSCLC) patients.
Methods: We obtained 6 resistant lines by treating EGFR-mutated (exon 19), TKI sensitive PC9 cells with increasing concentrations of gefitinib or erlotinib. The p.T790M resistance mutation emerged in two cell lines (GR1, GR4), which remained sensitive to osimertinib, a third generation EGFR TKI. Six new cell lines to resistant to “second line” osimertinib were generated from GR1 and GR4 by exposure to increasing concentrations of the inhibitor. Finally, six more cell lines resistant to “first line” osimertinib were derived from the PC9 parental cells. All resistant cell lines were genotyped for selected genes (including EGFR) and characterized for AXL, MET and FGFR1 expression and activation by Q-RT-PCR, immunohistochemistry and Western blotting. The effects of AXL (BGB324), MET (crizotinib, capmatinib) and FGFR1 (nindetanib) inhibitors on the parental and the 18 resistant cell lines were analyzed by MTT and, in some cases, by colony formation. AXL was stably silenced in some of the resistant cell lines.
Results: All cell lines resistant to “first line” gefitinib, erlotinib and osimertinib maintained the exon 19 EGFR sensitizing mutation. In contrast, three of the resistant cell lines to “second line” osimertinib lost the exon 19 and the p.T790M mutations. In two more, the p.T790M dropped to low allelic fractions (1% and 0.03%). Regardless of the EGFR status, AXL overexpression was the most common event related to EGFR TKI resistance in our panel of 18 cell lines, with FGFR1 and MET overexpression or activation as less frequent events. In proliferation assays, the IC50 of the EGFR TKI resistant cell lines for BGB324 (AXL inhibitor) was indistinguishable from the IC50 of the parental, EGFR TKI sensitive cell line. Similar results were obtained in the case of capmatinib, crizotinib (MET inhibitors) and nintedanib (FGFR inhibitor). Stable silencing of AXL on some of the AXL-overexpressing resistant cell lines had no effects in terms of doubling times, morphology of cells or sensitivity to EGFR TKIs. In combination experiments, the effect of BGB and MET inhibitors was found to be additive.
Conclusions: In tumor cell line models of acquired resistance to EGFR TKIs, overexpression or activation of AXL, MET and FGFR1 was not associated to sensitivity to single-agent treatment with AXL, MET or FGFR inhibitors. Multitargeted approaches might be more effective in this setting.
Citation Format: Jordi Bertran-Alamillo, Miguel Angel Molina-VIla, Cristina Teixidó, Jordi Codony-Servat, Ana Giménez-Capitán, Carles Codony-Servat, Silvia García-Román, Erika Aldeguer, Sonia Rodríguez, Rafael Rosell. Tumor cells with acquired resistance to EGFR inhibitors and overexpression or activation of AXL, MET and FGFR1 are insensitive to single-agent treatment targeting AXL, MET or FGFR [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3077. doi:10.1158/1538-7445.AM2017-3077