Project Summary/Abstract We have analyzed Kras mutant lung adenocarcinoma and demonstrated that the cell of origin is the alveolar Type II cell. Alveolar Type II cells undergo a Notch-dependent dedifferentiation to bipotent progenitor cells. These cells have markers of both Type I and Type II cells and initiate and propagate tumors both in vitro and in vivo. Thus, finding methods of inhibiting these cells could quickly lead to important therapeutic advances for patients with KRAS mutant tumors. Sphingolipid pathways downstream of Kras are promising therapeutic targets in these cells. In the current application, we will use mechanistic and high throughput methods to test existing drugs against 3-dimensional cultures of Kras mutant bipotent progenitor cells. We will also use Cas/Crispr technology to identify sphingolipid genes and pathways that will be effective in inhibiting these cells. Finally, because macrophages are intimately involved with the tumor cells during initiation and progression and sphingolipids are involved in tumor immune suppression, we will test unique inhibitors of immunosuppressive tumor macrophages and sphingolipid inhibitors to allow immune surveillance of forming tumors. In addition, additive mutations of p53 and Lkb1 which are common in lung adenocarcinoma will be used in all assays so that the broad range of KRAS mutant lung adenocarcinomas will be addressed.