Project Summary/Abstract Neuroblastoma is the most common tumor of infancy and causes a disproportionate number of children's deaths due to cancer. Pediatric cancers have relatively few oncogenic mutations relative to adult cancers, and most of the known genetic drivers of disease involve transcription factors, which cannot be readily drugged. Indeed, amplification of the transcription factor MYCN occurs in 20-25% of neuroblastomas and is associated with high- risk disease. The development of new therapies for this disease has been a challenge due to this lack of “druggable” genetic alterations. However, epigenetic dysregulation is now appreciated to be a major driver of pediatric cancers and targeting the epigenetic agents that maintain the tumorigenic cell state offers a new approach to treating these intractable cancers. Genome-scale CRISPR-Cas9 functional genomic screens have identified that MYCN-amplified neuroblastoma cells are dependent on several members of the histone-modifying Spt-Ada-Gcn5-acetyltransferase (SAGA) complex. Importantly, this complex has never been studied in the context of MYCN-amplified neuroblastoma. This proposal will address the hypothesis that this complex is a critical regulator of the epigenetic state of MYCN-amplified neuroblastoma and is required for cell survival and tumor maintenance. Aim 1 will discover how genetic and pharmacologic loss of this complex and its histone acetyltransferase activity impacts MYCN-amplified neuroblastoma survival in vitro and in vivo. Aim 2 will elucidate the contribution of SAGA complex activity to the epigenetic landscape of neuroblastoma, and the transcriptional consequences of this activity. This work will expand the understanding of epigenetic factors controlling MYCN-amplified neuroblastoma, as well as establish this complex as a novel therapeutic target in this disease of high-clinical need.