Abstract 1045: Proteomic analysis of effects of MEK inhibition with BAY86-9766 on LKB1/AMPK and mTOR pathway in lung cancer cell lines.
Authors: Gold Kathryn A. , Byers Lauren A. , Fan You Hong , Diao Lixia , Groth Philip , Paul Julianne , Wang Jing , Giri Uma , Gudikote Jayanthi , Tran Hai T. , Coombes Kevin R. , Minna John D. , Liu Ningshu , Heymach John V. 
Published: August 2014

Abstract
Background: MEK inhibitors such as BAY86-9766 are a new class of agents that show promise in the treatment of non-small cell lung cancer (NSCLC). The downstream effects of MEK inhibition in NSCLC have not been fully elucidated. We performed a broad proteomic analysis to determine which signaling pathways were modulated by BAY86-9766 treatment and how these pathways correlate with sensitivity.
Methods: We treated 109 lung cancer cell lines with MEK inhibitor BAY86-9766 at a concentration of 2200 nM. Drug sensitivity was determined by CellTiter-Glo assay and cell lines were classified as sensitive or resistant based on whether their IC50 values were in the highest or lowest 1/3rd of those tested. Using paired t-tests, we compared pre- versus post-treatment protein levels in the overall group and between the sensitive vs. resistant cell lines.
Results: MEK inhibitor BAY86-9766 was effective in reducing phosphorylation of direct downstream signaling molecules pMAPK (p&lt;0.0001) and p-P90RSK (p&lt;0.02). There was no significant difference in the level of pMAPK suppression between sensitive and resistant cell lines (p=0.55). In contrast, LKB1/AMPK activation was observed following MEK inhibitor treatment, as illustrated by higher post-treatment levels of LKB1 total protein, pAMPK, and pTSC2 (all p values &lt;0.02). As a consequence of these changes, the activity of downstream mTOR was suppressed, as evidenced by decreased pS6 (S235/236), pS6 (S240/244) and phospho-p70S6K and increased pPDK1 (all p≤0.002). All of these changes were significantly more pronounced in sensitive cell lines vs resistant cell lines (all p&lt;0.01). We also saw evidence of activation of feedback loops, as Src significantly increased in sensitive cell lines compared to resistant cell lines (p=0.0009).
Conclusions: We have performed broad proteomic analysis on cell lines treated with MEK inhibitor BAY86-9766 to determine which pathways are modulated by treatment and how they might relate to sensitivity. We conclude that MEK inhibition with BAY86-9766 may exert some of its effects by suppressing mTOR activity via the LKB1/AMPK pathway, and that the degree of modulation of the AMPK pathway correlates with sensitivity. This mechanism may involve decreased activation of p90RSK by MAPK, which leads to decreased degradation and increased activity of LKB1, and thereby increased AMPK activity and decreased mTOR signaling. This works suggests a rational basis for combinations of targeted agents to overcome resistance, such as combinations of MEK inhibitors with mTOR inhibitors or PI3 kinase inhibitors.
Citation Format: Kathryn A. Gold, Lauren A. Byers, You Hong Fan, Lixia Diao, Philip Groth, Julianne Paul, Jing Wang, Uma Giri, Jayanthi Gudikote, Hai T. Tran, Kevin R. Coombes, John D. Minna, Ningshu Liu, John V. Heymach. Proteomic analysis of effects of MEK inhibition with BAY86-9766 on LKB1/AMPK and mTOR pathway in lung cancer cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1045. doi:10.1158/1538-7445.AM2013-1045