Project 2 abstract Project 2 will investigate the changes in neoplastic and stromal compartments during the acquisition of resistance to ALK and KRAS targeting therapies, with specific emphasis on the therapy-sheltering impact of the stromal niche, observed in multiple experimental models. Despite the growing appreciation of the potential contribution of stromal on the sensitivity of tumor cells to targeted therapies, there are no established conceptual frameworks and experimental pipelines to account for this effect on evolving resistance. Confounding the challenge, acquired resistance cannot be understood just with before-after snapshot analyses, as the sensitivity of tumor cells to therapies, stroma-tumor ratio, and stromal composition and effect are dynamically changing over the course of treatment. To understand the Decology of acquired resistance we will perform system-level characterization of temporal and spatial phenotypic changes within the tumor and stromal compartments, including changes in proliferation/death and clonal dynamics. These changes will be captured in the formalism of in silico models through careful integration of experimental and modeling tools. The quality and utility of the models will be assessed by making experimentally testable predictions. Following calibration, the models will be used to find novel strategies for combination therapies that optimize long-term remission. Initial model development and calibration will be performed in a xenograft model of ALK+ NSCLC that has been the focus of our recent interdisciplinary studies. Subsequently, we will use the pipelines to gain an understanding of the eco-evolutionary dynamics of other xenograft and syngeneic models of ALK+ and KRASG12C NSCLC. These studies will help develop the robust knowledge base required for the development of novel and impactful translational strategies.