Abstract 4903: AXL inhibition overcomes erlotinib resistance in AXL-activated non-small cell lung cancer cells

Abstract

Abstract Mutations in the tyrosine kinase domain of epidermal growth factor receptor (EGFR) are present in 10-35% patients with NSCLC. In patients with EGFR-mutated NSCLC, EGFR tyrosine kinase inhibitors, including erlotinib, have demonstrated excellent initial responses. However, despite improved outcomes observed in patients treated with EGFR TKIs, most patients eventually develop drug resistance. We and others recently demonstrated that the activation of oncogene AXL is necessary to confers erlotinib resistance in both cell and mouse models as well as in human tumor tissues. While genetic aberrations affecting AXL appear rare, we recently identified two patients with EGFR-mutated lung cancer who simultaneously harbor AXL A273V or AXL V289M mutation. Both patients were resistant to erlotinib treatment (one case of primary and one case of acquired resistance). In this study, we first evaluated whether these AXL mutations conferred resistance to erlotinib treatment. Using HCC827 and PC-9 NSCLC cell lines stably expressing the AXL A273V or V289M mutation, we confirmed that AXL A273V significantly increased resistance to erlotinib treatment. Subsequently we also conducted a preclinical study to test if a new AXL inhibitor MGCD265 could overcome such erlotinib resistance in NSCLC cells. Using an in vitro MTS assay, we first validated that administration of MGCD265 in combination with erlotinib significantly inhibited the viability of erlotinib-resistant HCC827-ER cells, compared to erlotinib- or MGCD265-alone treatment. Through conducting an array of cell functional studies, we found that combination of MGCD265 and erlotinib significantly decreased cell cycle progression in S phase, enhanced apoptosis, and repressed cell migration relative to single-agent erlotinib or MGCD265 treatment in HCC827-ER cells. We further performed RNA-sequencing to evaluate the gene expression profile and the cellular pathways altered in cells treated with erlotinib alone, MGCD265 alone or a combination of erlotinib and MGCD265. RNA-sequencing analysis identified that several groups of genes involved in cell survival inhibition or apoptosis promotion were upregulated, whereas genes involved in cell cycle process, DNA replication or cancer metabolism were downregulated in cells treated with the combination of erlotinib and MGCD265. Taken together, our results indicated that AXL mutations may confer resistance to EGFR TKI treatment, and effective blockade of the AXL pathway may represent a novel strategy to overcome erlotinib resistance for the treatment of NSCLC patients. Citation Format: Feng Wang. AXL inhibition overcomes erlotinib resistance in AXL-activated non-small cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4903.