Abstract 4123: Induction of motility, invasion, and proliferation by wild-type EGFR depends on c-Met in NSCLC

Abstract

Abstract The complex signaling networks promoting non-small cell lung cancer (NSCLC) progression are currently being dissected to identify novel therapeutic targets or potential drug combinations. One cascade that is at the forefront of drug discovery in NSCLC is the Epidermal Growth Factor Receptor (EGFR) pathway. EGFR is a receptor tyrosine kinase (RTK) that interacts with ligands Epidermal Growth Factor (EGF), Transforming Growth Factor-alpha, and Amphiregulin, to promote invasive growth, a program requiring growth, motility, and invasion. Recently, there has been strong evidence linking c-Met to EGFR tyrosine kinase inhibitor (TKI) resistance. c-Met is a RTK that interacts with its natural ligand Hepatocyte Growth Factor (HGF), also known as Scatter Factor, to activate invasive growth, similar to EGFR, in many cancers including NSCLC. We previously reported an HGF independent mechanism of c-Met activation through EGFR that required c-Src. Here, we demonstrate that c-Met activation is necessary for known EGF-induced phenotypes in 201T and A549 NSCLC cell lines expressing moderate levels of wild-type (wt) EGFR and c-Met. Stimulation with EGF (50 ng/mL) in serum-free media induced cell invasion at 48 h that was inhibited by ∼74% when pretreated with the c-Met TKI, PF2341066 (1 uM) (Pfizer). Motility, initiated through EGFR, was reduced by 47% and 42% in 201T and A549 cells, respectively by PF2341066. Similarly, c-Met inhibition partially abrogated EGF-induced proliferation by 31% in 201T cells and 43% in A549 cells. To confirm these findings, the invasion assay was repeated with c-Met siRNA in 201T cells. Knockdown of c-Met resulted in an 80% reduction in EGF-stimulated invasion. Together, this suggests that EGFR action relies, in part, on activation of c-Met to modulate invasive growth in wt-EGFR NSCLC cell lines. Based on these data, it was addressed whether combined EGFR (gefitinib) and c-Met (PF2341066) targeting in a 3-week 201T xenograft murine model could lead to enhanced anti-tumor effects. PF2341066 (50 mg/kg) alone had no significant effect on inhibiting tumor xenograft growth, whereas gefitinib (150 mg/kg) alone significantly reduced tumor volume by 51%. Combining TKI therapies produced a 66% decrease in tumor volume, a significantly greater effect compared to PF2341066 and gefitinib groups, individually. These findings indicate that EGFR activation of c-Met plays a critical role in lung tumor progression and that combined EGFR and c-Met targeting hold strong therapeutic potential in lung cancer without EGFR and c-Met mutations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4123.