PROJECT SUMMARY/ABSTRACT Rhabdoid tumors (RT) are rare and aggressive childhood cancers with exceptionally high rates of mortality. Most children suffering with RT will die within 18 months of diagnosis. There is currently no standard of care for these children and—with fewer than 25 cases of RT diagnosed in the U.S. each year—the likelihood of developing new treatment strategies for this cancer are low. Despite its aggressive characteristics, however, RT has an unusually simple genetic profile in that it is driven by loss of a single gene, SMARCB1, which encodes the SNF5 component of the SWI/SNF chromatin remodeling complex. Recent work has shown that SNF5 loss leads to RT, in part, by activating MYC, an oncoprotein transcription factor with extensive pro- tumorigenic functions. By extension, anti-MYC therapies could have immense value in treating RT. But MYC itself is widely considered to be undruggable, meaning that pharmacological strategies to target MYC, if successful, will most likely focus on the co-factors MYC uses to function. A MYC cofactor for which inhibitors are being developed is WDR5, which facilitates the recruitment of MYC to chromatin at "protein synthesis genes" (PSGs) that stimulate biomass accumulation, a critical part of the oncogenic repertoire of MYC. Importantly, genetic disruption of the WDR5-MYC interaction decreases transcription of PSGs and promotes tumor regression in vivo. WDR5 "WIN site" inhibitors quickly and comprehensively displace WDR5 from chromatin and as a result, selectively reduce MYC levels at PSGs. These findings predict that WIN site inhibitors could also be used for treating RT. The goal of this project is to understand the response of RT cells to WIN site inhibitors and to identify important modulators conferring sensitivity or resistance. To characterize the response to WIN site inhibition in RT cells, Specific Aim 1 will combine genomic and cellular approaches to identify changes in WDR5 and MYC chromatin association and in transcription to inform mechanisms by which WIN site inhibitors promote growth inhibition and cell death in RT cells. In Specific Aim 2, whole genome CRIPSR screens and synergy screens will define genes that confer sensitivity or resistance and identify drugs that improve the efficacy of WIN site inhibitors. Completion of this work will uncover how RT cells respond to WIN site blockade and inform new treatment strategies for RT and potentially other MYC- driven tumors. The combination of a rigorous research project, an exceptional mentor, and the stimulating research environment at Vanderbilt will yield an outstanding training experience. The project and training plan detailed in this proposal will equip me with the tools to become an impactful independent cancer researcher.