Genetic dissection of oncogenic Kras signaling

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ABSTRACT Lung cancer is a prevalent cancer type that leads to more deaths than the next four major cancer types combined. KRAS is one of the most frequent oncogenes in human lung cancer. Despite more than 30 years of biochemical and cell culture studies, as well as correlative studies on human tumors and clinical trials, therapeutic options for patients with oncogenic KRAS-driven tumors are just beginning to emerge. KRAS is often mutated at codons 12 and 13, but these mutations are diverse and these different mutant forms of KRAS have dramatically different biochemical features. By integrating conventional genetically-engineered mouse models and CRISPR/Cas9-based somatic genome engineering with quantitative genomics and mathematical modeling, we recently established CRISPR/Cas9-based approaches that enable the generation and quantitative analysis of multiple tumor genotypes in parallel in vivo. By employing homology directed repair in somatic cells, we induce a panel of oncogenic Kras variants, and uncovered an unexpectedly dramatic difference in oncogenic potential of different Kras variants in vivo. In addition to the diversity of different oncogenic KRAS variants, the compendium of important pathways downstream of oncogenic KRAS remains relatively poorly understood. The goals of this proposal are 1) to use genomic and pharmacological methods to generate a quantitative understanding of different signaling requirements in cancers driven by different Kras variants and 2) to uncover novel functional regulators of Kras-driven carcinogenesis. To understand the basis for the differential oncogenic potential of different oncogenic Kras variants, we will use our multiplexed genetic approaches to quantify the impact of increasing either overall Kras signaling or discrete downstream pathways on the in vivo tumorigenic potential of diverse oncogenic Kras variants. We will also use therapeutic treatments to uncover the requirement for sustained PI3K and Raf/Mek/Erk signaling in established lung tumors driven by diverse Kras variants. Finally, to expand our understanding of Kras-driven tumorigenesis beyond the canonical effect pathways, we will directly analyze the function of novel Kras-interacting proteins on lung tumor growth in vivo. By performing multiplexed genomic and pharmacologic analyses of oncogenic Kras signaling in cancer, we will uncover the molecular mechanisms that contribute to tumor growth driven by different variants of KRAS. We will define specific therapeutic sensitivities of lung tumors driven by diverse oncogenic mutations. Our proposed research is significant because it will uncover interesting new areas of biology, motivate genotype-directed clinical trials, and facilitate precision cancer therapy for lung cancer patients with KRAS- mutant tumors.