254 A systems genomics approach to identify novel drug targets of Ewing sarcoma through ancestry-informed human iPSC modeling

OBJECTIVES/GOALS: We leverage the disparate incidence of Ewing sarcoma (ES) between European (EUR) and African (AFR) ancestry to study ES tumorigenesis in iPSC-derived cells from donors with a range of AFR ancestry via functional / molecular profiling. Integrated multi-omics analysis furthers explore local regulatory networks in pursuit of novel drug targets of ES. METHODS/STUDY POPULATION: In our pilot, eight induced pluripotent stem cell lines were obtained, differentiated into neural crest cells, and then transduced with a lentivirus expressing GFP-2A-EWS/FLI1. We compared wild type (WT) to EWS-FLI1-induced cells and then compared cell survival, gene expression, and EWS-FLI1 binding differences at varying levels of EUR / AFR ancestry admixture. We will build on this pilot data by expanding the number of cell lines and measuring chromatin state. Subsequently we will refine our understanding of the relationships between local ancestry, epigenetic and gene expression changes, and phenotype in tumor progression via integration of multi-omics datasets. Our systems genomics approach will utilize directed local regulatory networks in a Bayesian structure learning framework. RESULTS/ANTICIPATED RESULTS: Induction by EWS-FLI1 resulted in gene expression changes enriched in known ES gene sets. Higher %EUR ancestry correlated with prolonged maintenance of EWS-FLI1. We identified thousands of ancestry-linked changes to gene expression and EWS-FLI1 binding. Eighty of these genes are both differentially expressed and differentially bound based on AFR ancestry admixture level and may be some of the early critical targets that initiate the cascade of molecular changes in ES. We will identify novel drug targets, with potential cross functional use of known drugs. Once we have developed directed local regulatory networks, we will use them to test in silico potential perturbations due to small molecules or novel drugs and predict expression changes. DISCUSSION/SIGNIFICANCE: With a limited number of cell lines, we identify 80 ancestry-linked candidate loci for functional validation through genome engineering. As EWS-FLI1 itself has proven elusive to direct targeting, studying its immediate downstream effects has the potential for establishing new druggable biologic pathways for treatment of ES.