Abstract 1639: The novel c-MET inhibitor, ARQ 197, shows additive growrh-inhibitory effect with erlotinib through enhanced degradation of c-MET protein via ubiquitin/proteasome pathway

Abstract

Abstract Background c-MET, a receptor of hepatocyte growth factor (HGF), is known to be overexpressed in a variety of human cancers. Recently several c-MET inhibitors are being developed as cancer chemotherapy against this compelling molecular target. ARQ 197 is a new small molecule c-MET inhibitor. Since ARQ 197 shows efficient anti-cancer activity without many severe adverse events in Phase I clinical trials, it is expected to be a useful anticancer agent for clinical treatment. This drug is known to bind to c-MET at neighbor area of its ATP binding site and it does not work as an ATP mimic. In this study, we investigated the molecular mechanism of inhibitory effect on c-MET by ARQ 197 in a non-small cell lung cancer cell (NSCLC) line. Materials and Method We established a c-MET-overexpressed NSCLC line, PC-9/MET, by long term exposure of PC-9 cells to EGFR-tyrosine kinase inhibitor. The cytotoxicity of ARQ 197 was measured by MTT assay. The expression of c-MET protein and mRNA were detected by Western blotting analysis and real time RT-PCR method, respectively. In a c-MET degradation analysis, bortezomib was used for inhibition of proteasome. Results ARQ 197 is equally cytotoxic to parental PC-9 and EGFRTKI-resistant PC-9/MET cell line with GI50 values around 200 nM (?). ARQ 197 showed an additive growth- inhibitory effect with erlotinib in PC-9/MET cells as assessed by an Isobologram analysis. In ARQ 197-treated PC-9/MET cells, a clear decrease of phospho c-MET protein as well as phospho AKT and ERK proteins was observed, however, ARQ 197 also induced a down-regulation of c-MET protein in the cells without any effect on c-MET mRNA level. This ARQ 197 induced degradation was reversed by a concomitant treatment with a proteasome inhibitor, bortezomib in the cells. However, bortezomib did not affect cytotoxicity of ARQ 197 in the same cells. Conclusion These data suggest that ARQ 197 may inhibit c-MET through downregulation of this protein in addition to inhibition of its kinase activity. Furthermore, it may enhance c-MET degradation by the ubiquitin/proteasome pathway. These c-MET inhibitory activities by ARQ 197 should be important for the additive combined effect with erlotinib in PC-9/MET cells. 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 1639.