Amplification of Wild-type <i>KRAS</i> Imparts Resistance to Crizotinib in <i>MET</i> Exon 14 Mutant Non-Small Cell Lung Cancer.

Abstract

MET inhibitors can be effective therapies in patients with <i>MET</i> exon 14 (<i>MET</i>ex14) mutant non-small cell lung cancer (NSCLC). However, long-term efficacy is limited by the development of drug resistance. In this study, we characterize acquired amplification of wild-type (WT) <i>KRAS</i> as a molecular mechanism behind crizotinib resistance in three cases of <i>MET</i>ex14-mutant NSCLC and propose a combination therapy to target it. The patient-derived cell line and xenograft (PDX) DFCI358 were established from a crizotinib-resistant <i>MET</i>ex14-mutant patient tumor with massive focal amplification of WT <i>KRAS</i>. To characterize the mechanism of KRAS-mediated resistance, molecular signaling was analyzed in the parental cell line and its KRAS siRNA-transfected derivative. Sensitivity of the cell line to ligand stimulation was assessed and KRAS-dependent expression of EGFR ligands was quantified. Drug combinations were screened for efficacy <i>in vivo</i> and <i>in vitro</i> using viability and apoptotic assays. <i>KRAS</i> amplification is a recurrent genetic event in crizotinib-resistant <i>MET</i>ex14-mutant NSCLC. The key characteristics of this genetic signature include uncoupling MET from downstream effectors, relative insensitivity to dual MET/MEK inhibition due to compensatory induction of PI3K signaling, KRAS-induced expression of EGFR ligands and hypersensitivity to ligand-dependent and independent activation, and reliance on PI3K signaling upon MET inhibition. Using patient-derived cell line and xenografts, we characterize the mechanism of crizotinib resistance mediated by <i>KRAS</i> amplification in <i>MET</i>ex14-mutant NSCLC and demonstrate the superior efficacy of the dual MET/PI3K inhibition as a therapeutic strategy addressing this resistance mechanism.