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Abstract
Purpose: Our aim was to test whether imaging with 18F-fluorothymidine (18F-FLT) PET/CT was able to detect the combined effects of EGFR and MET inhibitors in oncogene-driven non-small cell lung cancer (NSCLC) and to elucidate the mechanisms underlying the enhanced efficacy of drug combination.Experimental Design: NSCLC cells bearing MET amplification (H1993 and H820) were treated with EGFR and MET inhibitors either alone or in combination and then tested for cell viability and inhibition of signaling. Nude mice bearing H1993 tumors underwent 18F-FLT PET/CT scan before and after treatment with erlotinib and crizotinib alone or in combination (1:1 ratio) and posttreatment changes of 18F-FLT uptake in tumors were determined. The role of inositol trisphosphate receptor type 3 (IP3R3) in mediating the combined action of EGFR and MET inhibitors was tested by transfecting NSCLC cells with IP3R3-targeted siRNA.Results: Imaging studies showed a significant reduction of 18F-FLT uptake in response to combined treatment with EGFR and MET inhibitors that was higher than that obtained with single agents (ANOVA, F-ratio = 6.215, P = 0.001). Imaging findings were confirmed by analysis of surgically excised tumors. Levels of IP3R3 were significantly reduced in both cells and tumors after treatment with crizotinib, whereas EGFR inhibitors caused a reduction of IP3R3 interaction with K-Ras mainly through dephosphorylation of serine residues of K-Ras.Conclusions: Our findings indicate that 18F-FLT PET/CT is able to detect the enhanced efficacy of EGFR and MET inhibitors in oncogene-driven NSCLC and that such enhancement is mediated by IP3R3 through its interaction with K-Ras.

Author information

Iommelli F1,2, De Rosa V1,2, Terlizzi C3, Monti M3, Panico M1, Fonti R1, Del Vecchio S4,3.
1
Institute of Biostructures and Bioimaging, National Research Council, Naples, Italy.
2
CEINGE-Advanced Biotechnologies, Naples Italy.
3
Department of Advanced Biomedical Sciences, University "Federico II", Naples, Italy.
4
Institute of Biostructures and Bioimaging, National Research Council, Naples, Italy. delvecc@unina.it.