Abstract 1629: A protein-protein interaction network for RalB-TBK1 signaling pathway in KRAS mutant non small cell lung cancer

Abstract KRAS mutation accounts for development of approximately 30% of Non Small Cell Lung Cancer (NSCLC) however therapeutic targets for KRAS mutant NSCLC have poorly been identified. A better understanding of the KRAS signaling network could uncover novel therapeutic targets or therapeutic strategies. RalB and TBK1 are important proteins used by KRAS to maintain tumor cell survival. To better understand oncogenic properties of RalB-TBK1 signaling for KRAS mutant lung cancer development, we are currently developing a protein-protein interaction network for RalB and TBK1 using Tandem Affinity Purification (TAP) coupled with Liquid Chromatography-Mass Spectrometry (LC-MS/MS). By interrelating protein-protein interactions and data from a RNA interference screen, a map of signaling will be constructed to highlight important components vulnerable to attack. Data from this mapping will be used to interrogate novel targets in a larger collection of lung cancer cell lines. We have expressed Strep-HA tagged versions of both RalB and TBK1 in KRAS mutant lung cancer cells using retroviruses. A two step purification coupled to LC-MS/MS is used to purify and identify protein complexes. Preliminary studies have identified the bait (TBK1) in the MS results along with HSP90 isoforms. Based on these results, we determined if HSP90 inhibition can modulate TBK1 levels. We found that 17-DMAG and AUY922, two HSP90 inhibitors, lead to reduced levels of TBK1 proteins. AUY922 also had potent effects on cell viability in vitro. Suppression of TBK1 expression using shRNA significantly induced cell death in KRAS mutant NSCLC cells, confirming that TBK1 signaling is essential for survival of those cancer cells, and loss of TBK1 by HSP90 inhibitors could in part lead to their cytotoxic effect. Collectively, we expect this network approach to KRAS-RalB-TBK1 signaling pathways will provide better insight into molecular mechanism by which TBK1 mediates KRAS mutant lung cancer cell survival and novel therapeutic targets for this cancer subtype. Updated work will be presented. Supported by the SPORE in Lung Cancer (P50-CA119997). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1629. doi:10.1158/1538-7445.AM2011-1629