PROJECT SUMMARY – TOOLKIT CORE The majority of cancer-related deaths are caused by metastatic disease, highlighting the glaring deficiency in our understanding of the processes of tumor dissemination. Research is substantially hampered by lack of physiologically-relevant tumor models and molecular tools necessary for discovering life-saving therapies. The Stanford Brain Metastasis Consortium (SBMC) is focused on identifying the genetic underpinnings regulating brain metastases, a disease with limited treatment options and meager survival rates. In support of this goal, the Toolkit Core provides innovative experimental solutions from leading experts in organoid modeling (Dr. Calvin Kuo), genomic functional screens (Dr. Michael Bassik), and glycoproteomics (Dr. Sharon Pitteri) to execute the projects proposed within the SBMC. The Toolkit Core team has diverse yet complementary areas of expertise and is qualified to specifically address the unmet needs outlined in this RFA: Metastasis Research Network by providing novel experimental organoid models, and cutting-edge CRISPR and proteomic tools for characterizing and manipulating the poorly understood signaling nodes driving brain metastatic disease. Specifically, the Kuo lab will provide patient and murine-derived brain metastatic 3D organoids to study radiation response in Project 1, explore the intricate crosstalk between metastatic epithelium and the immune microenvironment in Projects 1 and 2, and develop novel lymphoid organoids for modeling T-cell priming in Project 3. The Bassik lab will provide innovative CRISPR tools for targeted genetic screens in Project 1 to explore the interaction between tumor-associated microglia and metastatic epithelial cells, along with engineering iPSCs for Project 3 to develop vaccine strategies for brain metastasis. The Pitteri lab will provide proteomic analysis for Projects 1–3, to characterize glycosylation patterns and features in brain metastatic tissue and organoids, thus providing critical biological insights into metastatic disease. Together, these resources will empower the diverse investigations of the SBMC toward improved therapeutic approaches.