Abstract 4445: Dual ALK and EGFR inhibition targets a mechanism of acquired resistance to the tyrosine kinase inhibitor crizotinib in ALK translocated lung cancer.

Abstract

Abstract ABSTRACT Introduction: The multitargeted tyrosine kinase inhibitor (TKI) crizotinib is active against ALK translocated non-small-cell lung cancer (NSCLC); however acquired resistance invariably develops over time. ALK mutations have previously been implicated in only a third of resistant tumors. We sought to evaluate alternative mechanisms of resistance and preclinical strategies to overcome these in a cell line driven by EML4-ALK. Methods: We selected the NSCLC cell line NCI-H3122 (H3122: EML4-ALK E13;A20) and derived resistant variants that were able to grow in the presence of 1μM crizotinib. These were analyzed for ALK mutations, sensitivity to crizotinib in combination to other TKIs (imatinib, sorafenib, erlotinib and afatinib), and for activation of alternative tyrosine kinases. Results: All H3122 crizotinib resistant (CR) clones lacked mutations in the kinase domain of ALK. To evaluate if possible alternative kinases functioned as “bypass” tracks for downstream signaling activation in these resistance cells, we used a functional approach of dual ALK TKI (with crizotinib) with combinatory TKI inhibition to screen for possible targets. Crizotinib + sorafenib (BRAF, RET, PDGFR, VEGFR TKI) and crizotinib + imatinib (ABL, PDGFR, KIT TKI) were ineffective. In contrast, crizotinib + erlotinib (reversible EGFR TKI) and crizotinib + afatinib (irreversible EGFR/ERBB2 TKI) were able to inhibit the growth of H3122 CR clones, indicating potential EGFR activation as a mechanism of resistance. Analyses of phosho-receptor tyrosine kinase arrays demonstrated that CR clones had 5-25 times higher phospho-EGFR signal than H3122 parental cells did after the exposure to 1μM crizotinib, indicating phospho-EGFR was the most predominant phosphorylated signal in crizotinib-resistant cells. Conclusions: Using a functional approach of combining ALK and EGFR TKIs, we identified activation of EGFR as a mechanism of resistance to crizotinib in preclinical models of ALK translocated NSCLC. If EGFR activation is confirmed as a predominant mechanism of crizotinib resistance in patient-derived tumors, the use of crizotinib + EGFR TKIs should be tested in future clinical trials for this important cohort of NSCL Citation Format: Norihiro Yamaguchi, Sohei Nakayama, Lorena L. de Figueiredo-Pontes, Susumu Kobayashi, Daniel B. Costa. Dual ALK and EGFR inhibition targets a mechanism of acquired resistance to the tyrosine kinase inhibitor crizotinib in ALK translocated lung cancer. [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 4445. doi:10.1158/1538-7445.AM2013-4445