MET inhibition with and without erlotinib as treatment strategy for T790M-EGFR mediated EGFR inhibitor-resistance in H1975 lung cancer cells
Authors: Patrick Ma, Zhe Tang, Runlei Du, Shan Jiang, Chunying Wu, Deborah Barkauskas, John Richey, Joseph Molter, Minh Lam, Chris Flask, Stanton Gerson, Afshin Dowlati, Lili Liu, Balazs Halmos, Zhenghong Lee, Yanming Wang, Jeffrey Kern
Journal: Cancer Research (2008)

AACR Annual Meeting-- Apr 12-16, 2008; San Diego, CA

1337 

EGFR tyrosine kinase inhibitors (TKI) erlotinib/gefitinib have been clinically approved for treatment of advanced lung cancer in recent years. Despite initial response in some patients, most patients still remain as primary non-responders. Moreover, initial responders invariably develop secondary resistance in relapse relatively soon. It is estimated that the “gatekeeper” mutation T790M of EGFR contributes to approximately half of the acquired EGFR TKI resistance. MET kinase plays key role in human tumorigenesis and tumor progression, and has been shown to be an attractive therapeutic target in lung cancer. SU11274 is a selective MET kinase inhibitor that has been characterized recently. In this study, we evaluated the role of MET inhibition in EGFR TKI resistance, using the erlotinib-resistant H1975 cell line (expressing L858R/T790M) as the model. Nine of eleven (82%) non-small cell lung cancer (NSCLC) cell lines examined co-expressed both MET and EGFR, including H1975 which also had co-activated p-MET and p-EGFR. SU11274 inhibited the downstream AKT and MAPK signaling and effectively induced 79.24 ±7.0% (n=3, P<0.0001) of cellular apoptosis. The MET(-) and EGFR(-) H520 cell line, as negative control, did not undergo any significant apoptosis (0.44 ±0.30%; n=3) by SU11274 (5µM), supporting the specificity of the inhibition. To test for in vivo MET inhibition of H1975 cells, we developed a highly sensitive bioluminesence imaging model (Xenogen IVIS 200) by lentiviral transduction of H1975 cells with a luciferase-expressing vector. SU11274 (100µg/xenograft) resulted in statistically significant retardation of the H1975 tumor xenograft growth (104.24 ±2.92%, n=4, P=0.0251), when compared to untreated control (905 ±162.72%, n=4 per group). In vivo multimodal microPET/MRI imaging demonstrated that SU11274 induced early tumor metabolic response in H1975 xenografts within the first 24 hours. We show that both MET and EGFR pathways are functional in H1975 cells, with the EGFR ligand EGF cross-activating the MET receptor phosphorylation. We observed that erlotinib modestly enhanced the inhibitory efficacy of SU11274 on phospho-MET. Erlotinib enhanced SU11274 when in combination to induce complete abrogation of cytoskeletal functions of H1975 cells in serum-growth conditions under digital time-lapse video microscopy. Dual targeted inhibition (SU11274: 50µg/xenograft plus erlotinib: 100mg/kg) in our in vivo xenograft model induced complete regression of the tumor xenograft growth (n=4 per group, P=0.0003) within two weeks, while suboptimal dose of SU11274 alone here was partially effective in slowing the tumor growth. Here, we provide in vitro and in vivo evidence to show that optimized dual MET-EGFR inhibition represents a potential alternative therapeutic approach in treating EGFR TKI resistant lung cancers.