EGFR mutations determine EGFR-MET crosstalk and MET inhibition in lung cancer

Abstract

Introduction: Lung cancer is the commonest cause of cancer deaths worldwide with very poor prognosis. EGFR Tyrosine Kinase Inhibitors (TKI) are approved for patients with activating EGFR mutations (e.g. L858R), but resistance is common: The EGFR T790M mutation accounts for ∼50% of resistance. Amplification of another Tyrosine Kinase Receptor MET is also common and preclinical data suggest synergy between MET and EGFR TKI. Objectives: To understand EGFR-MET crosstalk in EGFR-TKI resistance. To assess if EGFR-MET crosstalk is altered by MET TKI and its consequence. Methods: Using NCI-H1975 cells, which co-express L858R and T790M mutations, we generated a model representing clinical phenotypes relevant to EGFR TKI therapy in lung cancer: 1) H1975: Signified acquired resistance; 2) 9 H1975 L858R 9:Sensitised to EGFR-TKI; 3) 9 H1975 WT 9 (EGFR Wild-type): Not currently treated. Tumour cell behavior was assessed in response to a MET TKI (SGX523) and EGFR-MET crosstalk explored by Fluorescence Lifetime Imaging (FLIM). Results: In vitro and in vivo characterization showed that H1975 tumour cells are more migratory but less proliferative than H1975 L858R and WT. H1975 L858R conversely was the most proliferative but least migratory cell line. Response to MET TKI depended on EGFR mutations. Using FLIM in cells and paraffinised tissue we saw different EGFR-MET crosstalk in the three cell types and a unique response to MET TKI in each. Conclusion: Our data suggest that EGFR mutations determine MET TKI effect. We suggest that this is due to the effect of EGFR±MET TKI on EGFR-MET dimerisation which is altered by EGFR mutations. The consequences for this dimerization on tumour behaviour could determine treatment efficacy.