Mentor Name: Thomas Look

Neuroblastoma is the most common extracranial solid tumor of childhood and arises from progenitor cells of the peripheral sympathetic nervous system that are arrested at early stages of differentiation. Despite intensive multimodal therapy—including high-dose chemotherapy, stem cell rescue, immunotherapy, and post-consolidation treatment with retinoic acid—children with high-risk neuroblastoma continue to have poor outcomes. Tumor recurrence is frequently associated with resistance to conventional therapies, resulting in a devastating prognosis. Thus, there is an urgent need to develop new therapeutic strategies that improve long-term outcomes for patients with high-risk neuroblastoma. Retinoic acid, which is used as post-consolidation therapy to induce neuronal differentiation and growth arrest in neuroblastoma cells, promotes cell cycle arrest and differentiation through rewiring of the enhancer landscape and alteration the transcriptional programs; however, these antiproliferative and gene-regulatory effects are often transient and reversible upon drug withdrawal, limiting its long-term efficacy. To identify pathways that enhance the durability of retinoic acid–induced differentiation, we performed a genome-wide CRISPR/Cas9 dropout screen using approximately 18,000 guide RNAs in retinoic acid–treated neuroblastoma cells. This screen identified members of the SWI/SNF chromatin remodeling complex as key regulators of retinoic acid sensitivity. Preliminary follow-up studies confirmed that pharmacologic inhibition of the SWI/SNF complex enhances the antiproliferative effects of retinoic acid in neuroblastoma. Building on these findings, this project will dissect the molecular mechanisms by which disruption of SWI/SNF chromatin remodeling augments retinoic acid–mediated growth suppression and differentiation. Using genetic silencing of SWI/SNF components that scored highly in our CRISPR screen and pharmacologic inhibition of the complex’s catalytic activity, we will investigate how changes in chromatin accessibility alter retinoid sensitivity, neuronal differentiation and cell fate decisions. We will employ in vitro functional assays and chromatin profiling approaches to define how targeting chromatin remodeling mechanisms may improve differentiation-based therapies for children with high-risk neuroblastoma.