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RESEARCH PRODUCT

Abstract 1690: Differential autophagy activation in KRAS and EGFR mutant lung adenocarcinomas.

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Abstract Lung cancer is the leading cause of cancer deaths in western countries, and adenocarcinomas (LADs) are the most frequent histological subtype. The aberrant activation of the kinases promotes plethora of tumorigenic processes, mainly through PI3K and MAPK oncogenic pathways leading to oncogene addiction. The activation of PI3K pathway deregulates mTOR, a master kinase for cell growth and autophagy. Autophagy can be pro- or anti- tumorigenic, however its roles in protecting tumors exposed to metabolic stress under chemotherapy are considered as a survival mechanism for the tumors leading to acquired resistance. Consequently, the inhibition of autophagy is an attractive therapy to prevent the emergence of acquired resistance. Activating mutations in EGFR and KRAS are mutually exclusive and are the most frequent oncogene activation in LAD. There are considerable differences in the control of signalling pathways including PI3K-mTOR axis. Therefore, it is hypothesized that the susceptibility to autophagy differs depending on EGFR or KRAS mutational status. To test the hypothesis, we applied nutrient-starvation conditions, the most well-known inducer of autophagy, to a panel of LAD cell lines bearing known EGFR or KRAS mutations. As a positive control, cells were treated with rapamycin, which also induced autophagy inhibiting MTOR activity. Autophagy activation was analyzed by: i) Western blot of LC3-II and p62/SQSTM1 protein levels, that measures autophagy flux and autophagic protein degradation, respectively; and ii) autophagolysosome detection and lysosomal activity by fluorescent microscopy. Our data suggest that KRAS-mutant LAD cell lines are able to activate autophagy, whereas EGFR-mutant are not, under starvation stress. Furthermore, we found a potential interaction between mutant EGFR and Beclin 1 (BECN1, a protein required for the initiation of the autophagosome) at the cell membrane proximity, using co-immunolocalization by confocal microscopy and immunoprecipitation followed by Western blot. Together, these data provide a compelling rationale to investigate anti-autophagy therapy in mutant KRAS LADs and warrant further investigation in the regulation of autophagy via a novel link between Beclin1 and mutant EGFR. Citation Format: Maria L. Rodriguez, Ines Pulido, Margaret Soucheray, Daniel Crespo, Fatima Al-shahrour, Takeshi Shimamura, Angel Ortega, Julian Carretero. Differential autophagy activation in KRAS and EGFR mutant lung adenocarcinomas. [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 1690. doi:10.1158/1538-7445.AM2013-1690