Amplification of wild type KRAS imparts resistance to crizotinib in MET exon 14 mutant non-small cell lung cancer

Purpose: MET inhibitors can be effective therapies in patients with MET exon 14 (METex14) 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) KRAS as a molecular mechanism behind crizotinib resistance in three cases of METex14 mutant NSCLC and propose a combination therapy to target it. Experimental Design: The patient-derived cell line and xenograft (PDX) DFCI358 were established from a crizotinib-resistant METex14 mutant patient tumor with massive focal amplification of WT KRAS. 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 in vivo and in vitro using viability and apoptotic assays. Results: KRAS amplification is a recurrent genetic event in crizotinib-resistant METex14 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. Conclusions: Using patient-derived cell line and xenografts, we characterize the mechanism of crizotinib resistance mediated by KRAS amplification in METex14 mutant NSCLC and demonstrate the superior efficacy of the dual MET/PI3K inhibition as a therapeutic strategy addressing this resistance mechanism.

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