Abstract 3718: Adaptive drug escape of EML4-ALK lung cancer against targeted ALK inhibitor involving TGFβ2-mitochondrial priming

Abstract

Abstract Lung cancer is the second most common malignancy with the highest cancer-mortality rate. EML4-ALK chromosomal translocation is now known to represent a highly actionable unique molecular target in approximately 5% of non-small cell lung cancer (NSCLC) patients. The ALK tyrosine kinase inhibitor (TKI) crizotinib induces remarkably high response rates in molecularly-selected NSCLC patients harboring EML4-ALK driven tumors, and is being used in first-line therapy. Nonetheless, responsive tumors ultimately develop acquired drug resistance. We have recently investigated non-mutational mechanisms of tumor resistant escape emerging under early TKI treatment time-window. Our recent studies in EGFR-mutant NSCLC in early adaptive drug escape against EGFR TKI identified an autocrine upregulation of TGFβ2 within these survivor cells. Here, we found that TGFβ2 was elevated significantly in the EML4-ALK-driven H3122 cells undergoing early adaptive drug escape against ALK TKI (TAE684) at treatment day 14. Interestingly, we found that the augmented TGFβ signaling was specific to TGFβ2, but not TGFβ1 or TGFβ3. We also found correlative enhanced mitochondrial BCL-2/BCL-xL prosurvival signaling in the day 14 TKI surviving H3122 cells. The upregulated TGFβ2-BCL-2/BCL-xL prosurvival mitochondrial priming was further validated in H3122 xenografts by IHC. Exogenous TGFβ2 stimulation in vitro for 7 days induced a dose-dependent upregulated BCL-2 and BCL-xL expression. Inhibiting mitochondrial BCL-2/BCL-xL priming using dual BCL-2/BCL-xL inhibitor ABT-263 as BH3-mimetic led to significant reduction in early adaptive drug escape induced by ALK TKIs. Our study showed that EML4-ALK NSCLC could escape ALK TKI early in treatment through cell plasticity that involved TGFβ2-mitochondrial priming in an upregulated prosurvival state. We also found that the early adaptive drug-escaping cancer cells possessed inherently increased EMT-ness (upregulated vimentin, AXL, GAS6) and cancer stemness (upregulated OCT4, NANOG). These findings provide deeper insights into the process of drug resistance emergence and highlighted potential window-of-opportunities to therapeutically target early adaptive escape to eradicate targeted drug resistance and impact long term survival. Citation Format: Lihong Yin, Wei Zhang, Ivy Shi, Yan Feng, Rakesh Bagai, Daniel Lindner, Patrick C. Ma. Adaptive drug escape of EML4-ALK lung cancer against targeted ALK inhibitor involving TGFβ2-mitochondrial priming. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3718. doi:10.1158/1538-7445.AM2014-3718