Abstract 1028: Genetic disruption of Kras sensitizes lung cancer cells to Fas-mediated apoptosis

Abstract

Abstract Genetic lesions that activate KRAS account for ~30% of the 1.6 million annual cases of lung cancer. Despite clinical need, KRAS is still undruggable using traditional small molecule drugs/inhibitors. When oncogenic Kras is suppressed by RNA interference, tumors initially regress but eventually recur and proliferate despite suppression of Kras. Here we show that tumor cells can survive CRISPR-mediated knockout of oncogenic Kras, indicating the existence of Kras-independent survival pathways. Thus even if clinical KRAS inhibitors were available, resistance would remain an obstacle to treatment. Kras-independent cancer cells exhibit decreased colony formation in vitro but retain the ability to form tumors in mice. Comparing the transcriptomes of oncogenic Kras cells and Kras knockout cells, we identified 603 genes that were specifically upregulated in Kras knockout cells, including the Fas gene, which encodes a cell surface death receptor involved in physiological regulation of apoptosis. Antibodies recognizing Fas-receptor efficiently induced apoptosis of Kras knockout cells but not oncogenic Kras expressing cells. Increased Fas expression in Kras knockout cells was attributed to decreased association of repressive epigenetic marks at the Fas promoter. Concordant with this observation, treating oncogenic Kras cells with histone-deacetylase inhibitor and Fas-activating antibody efficiently induced apoptosis, thus bypassing the need to inhibit Kras. Our results suggest that activation of Fas could be exploited as an Achilles’ heel in tumors initiated by oncogenic Kras. Citation Format: Haiwei Mou, Jill Moore, Sunil Malonia, Yingxiang Li, Deniz Ozata, Soren Hough, Chunqing Song, Jordan Smith, Has Yin, Andrew Fisher, Daniel Anderson, Shipping Weng, Michael Green, Wen Xue. Genetic disruption of Kras sensitizes lung cancer cells to Fas-mediated apoptosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1028. doi:10.1158/1538-7445.AM2017-1028