The development of acquired drug resistance limits the effectiveness of targeted therapies for lung cancer. In 50% of patients with EGFR mutant non-small cell lung cancer (NSCLC), acquired resistance to EGFR inhibitors can be attributed to the development of a secondary T790M mutation that prevents drug binding. Third generation irreversible EGFR inhibitors that effectively inhibit EGFR with T790M are currently under clinical development. Using patient-derived EGFR mutant NSCLC models of T790M+ acquired resistance, we observed that the presence of a mesenchymal phenotype was associated with a decreased response to subsequent irreversible EGFR inhibitor therapy. Epithelial-to-mesenchymal transformation (EMT) led to suppression of pro-apoptotic signaling and a blunted apoptotic response to EGFR inhibition. Combination BCL-XL and irreversible EGFR inhibitor therapy restored the apoptotic response and resulted in regressions of T790M+ resistant tumors that exhibited poor response to single agent irreversible EGFR inhibitors. This suggests that combining BCL-XL and irreversible EGFR inhibitors may be an effective treatment strategy for T790M+ resistant EGFR mutant lung cancers with suppressed apoptotic signaling due co-acquisition of a mesenchymal phenotype.

Citation Format: Aaron N. Hata, Matthew J. Niederst, Hannah L. Archibald, Hillary Mulvey, Jungoh Ham, Maria Gomez-Caraballo, Anuj Kalsy, Anthony C. Faber, Jeffrey Engelman. Co-acquisition of T790M and EMT in resistant EGFR mutant non-small cell lung cancer can be overcome by combined irreversible EGFR and BCL-XL inhibition. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2845. doi:10.1158/1538-7445.AM2015-2845