Abstract A31: Activity-based protein profiling reveals adaptive response to pharmacological MEK inhibition in KRAS mutant non-small cell lung cancer

KRAS mutations account for development of approximately 30% of lung adenocarcinomas. While RAF-MEK-ERK signaling cascade is a key regulator of RAS-mediated proliferation and survival, the clinical efficacy of MEK inhibitors is still underwhelming in RAS-driven cancers. We treated KRAS mutant non-small cell lung cancer (NSCLC) cell lines with two MEK inhibitors (AZD6244 and MEK162) currently in clinical development. In all cell lines tested (N=11), we failed to observe significant effects on cell viability or induction of apoptosis. Because increasing evidence indicates that cancer cells undergo adaptive proteomic rewiring in response to kinase inhibitors, we performed activity-based protein profiling (ABPP) after treating 11 KRAS mutant NSCLC cell lines with MEK inhibitors in order to identify global enzymatic changes potentially involved in these adaptive processes. Our ABPP approach employs desthiobiotin-ATP probe, which enables selective labeling of active sites in ATP-binding proteins including kinases, chaperones and metabolic enzymes. Labeled proteins were subsequently purified and analyzed by mass spectrometry-based proteomics technique. Our ABPP results revealed that MEK inhibitors increased levels of multiple receptor tyrosine kinases (RTK) including EGFR and MET. MEK inhibitors induced MET phosphorylation and EGF-mediated AKT phosphorylation was markedly enhanced in the presence of MEK inhibitors, indicating increased RTK activity in adaptive response to MEK inhibition. We also found that MEK inhibition led to increased multiple heat shock proteins including HSP90 and HSP70, suggesting the possibility of chaperone-mediated adaptive resistance. Finally, MEK inhibitors globally increased enzymes involved in glucose utilization pathways implicating metabolic alterations in adaptive response to MEK inhibition. Collectively, our systematic activity-based proteomic profiling approach provides novel insights into adaptive resistance mechanisms to MEK inhibitors, suggesting rational combination treatment strategies for KRAS mutant NSCLC. Updated works will be presented. Citation Format: Jae-Young Kim, Bin Fang, Eric A. Welsh, Fumi Kinose, Jiannong Li, Steven A. Eschrich, John M. Koomen, Eric B. Haura. H. Activity-based protein profiling reveals adaptive response to pharmacological MEK inhibition in KRAS mutant non-small cell lung cancer. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr A31. doi: 10.1158/1557-3125.RASONC14-A31