Abstract 4661: Loss of LKB1 in NSCLC confers sensitivity to MEK inhibition by regulating activation of AKT-FOXO3 pathway

Abstract

Abstract The use of MEK inhibitors for non-small cell lung cancer (NSCLC) has shown little efficacy in clinical trials, even in the case of tumors with mutant KRAS where one might predict good outcomes. From these data, it is clear that the success of MEK inhibitors is going to rely on finding a biomarker that predicts sensitivity to this type of therapy. Our area of interest is finding a way to treat LKB1 mutant tumors and, surprisingly, an in silico screen of drug sensitivity data for NSCLC cell lines determined that four MEK inhibitors were among the top drugs that were significantly associated with LKB1 loss. We confirmed the effects MEK inhibition by evaluating 23 lung cancer cell lines with known LKB1 status. The results of the study showed that MEK inhibition with trametinib led to a significant reduction in cell viability in LKB1 mutant cell lines when compared to cell lines with wild type LKB1. In addition, we investigated MEK sensitivity by restoring wild-type (Wt) LKB1 in lung cancer cell lines with LKB1 loss, or by silencing LKB1 in lung cancer cell LKB1-Wt lines. Transduction of LKB1 resulted in significant MEK resistance in three of the five LKB1 add-back lines, while silencing LKB1 induced MEK sensitivity in all five LKB1-Wt lines tested. The mechanism behind these observed results appears to be through phosphorylation of AKT and its downstream target FOXO3, which are important determinants of the apoptotic response to MEK inhibition. With LKB1 transduction into mutant cell lines we see an increase in the activating phosphorylation of AKT, a protein involved in survival mechanisms, and an increase in the deactivating phosphorylation of FOXO3, a transcription factor implicated in increased levels of apoptosis. Our data suggest that the identification of LKB1 activity may be promising biomarker for the sensitivity to MEK inhibition by regulating activation of AKT-FOXO3 pathway in NSCLC. Citation Format: Tadaaki Yamada, Jacob M. Kaufman, Joseph M. Amann, Seiji Yano, David P. Carbone. Loss of LKB1 in NSCLC confers sensitivity to MEK inhibition by regulating activation of AKT-FOXO3 pathway. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4661.