LEVERAGING PHENOTYPIC PLASTICITY TO OVERCOME DRUG RESISTANCE IN PEDIATRIC NEUROBLASTOMA

Neuroblastoma (NB) is the most common extracranial solid tumor in children and is often associated with poor prognosis in high-risk patients due to the development of therapy resistance and tumor relapse. One of the critical contributors to this therapeutic failure is cellular plasticity, allowing tumor cells to dynamically switch phenotypic states and escape treatment pressure. However, the molecular and epigenetic mechanisms driving this plasticity and subsequent drug resistance remain poorly understood. This study investigates the epigenetic mechanisms governing the phenotypic switch in NB, specifically between the adrenergic (ADR) and mesenchymal (MES) cell states. The project is structured around three primary aims:1) investigation of the role of key microRNAs in modulating NB cell plasticity and resistance to chemotherapy, 2) characterization of the histone modifications and epigenetic vulnerabilities involved in regulating phenotypic transitions and drug resistance in NB, and 3) exploring the contribution of Lamin A/C to nuclear organization and its role in stabilizing cell identity in NB. As part of aim 1, our study identified miR-124-3p as a critical regulator of NB phenotypic plasticity. Its expression was significantly higher in ADR-NB cells compared to MES-NB cells, and functional assays demonstrated that modulating miR-124-3p levels could regulate the ADR–MES switch. Notably, restoration of miR-124-3p expression in MES cells re-sensitized them to chemotherapy, implicating this miRNA as an important mediator of drug resistance and its reintroduction in NB cells as a potential therapeutic intervention. As part of aim 2, epigenetic profiling revealed that the repressive histone mark H3K9me3 was enriched in MES-NB cells relative to ADR-NB cells. This differential chromatin landscape correlated with silencing of lineage-specific transcriptional programs and reinforcing the MES phenotype, unveiling epigenetic vulnerabilities potentially targetable to overcome drug resistance. Finally, as part of aim 3, we investigated how Lamin A/C, a key component of the nuclear lamina, changes in more motile/metastatic prone NB cells demonstrating its role in regulating nuclear architecture and maintaining tumor cell identity. Our findings suggest that Lamin A/C contributes to the stabilization of the MES phenotypic state, further influencing NB cell plasticity and therapy response. Collectively, this study provides novel findings into the epigenetic regulation of NB cell plasticity and nuclear deformation in more motile MES cells. It also reveals novel potential actionable targets to counteract therapy resistance. The novelty of data presented offers promising avenues for advanced therapeutics evaluations aiming to improve outcomes in high-risk metastatic patients affected by NB.