CORE B – ORGANOID BIOBANK PROJECT SUMMARY Organoids are microscopic self-organizing, three-dimensional cellular structures that are grown from stem and progenitor cells in vitro. These culture models recapitulate many structural and functional aspects of their in vivo counterpart organs. This versatile technology has led to the development of many novel human cancer models, which have been widely validated as having superior capabilities to conventional 2D cancer cell lines in recapitulating human carcinoma biology. Over the last several years, several investigators at CSHL, including members of the Program, have come together to establish a unique Organoid Biobank. Through a productive collaboration with clinical oncologists, surgeons, and pathologists at several health centers, we have obtained hundreds of fresh tumor specimens, which have been adapted as primary cultures as organoids. Rigorous standard operating procedures annotated the genome and transcriptome of these cultures, resulting in the classification of each tumor organoid into molecular subtypes. Importantly, this biobank includes numerous basal-subtype models of pancreatic and breast carcinoma, which are a major focus of this Program. During the next funding cycle, Core B will support all three Projects in the use of organoid models of cancer, which will include a) establishing novel organoid models of basal-subtype breast and pancreatic cancer b) performing genomic and transcriptomic characterization of these models c) assisting investigators in propagating organoid cultures for various perturbation experiments d) assisting investigators in performing customized assays for characterizing organoid morphology, migration, and lineage identity. Collectively, these valuable resources and services will enable a deep investigation of transcriptional and splicing dependencies in cancer and allow for the identification of biomarkers to predict therapeutic efficacy.