Spatial-temporal modulation of lamin defines the malignant features of sarcomas

Ewing sarcoma (EWS) is a fusion-driven malignancy with few recurrent mutations but extensive epigenetic reprogramming. A-type Lamins (lamin A/C), core components of the nuclear lamina, regulate nuclear mechanics and genome organization and are typically low in EWS, a state associated with nuclear deformability and motility. This thesis investigates how spatial-temporal modulation of lamin A/C shapes nuclear architecture, chromatin accessibility, transcriptional programs, and malignant phenotypes in EWS. We established and validated stable and doxycycline-inducible lamin A/C overexpression models in multiple EWS cell lines and a patient-derived line, enabling controlled and reversible perturbations. Across models, enforced lamin A/C consistently reduced cell migration and invasion and was accompanied by neuron-like morphology (βIII-tubulin upregulation), indicating altered cytoskeletal organization and polarity. RNA-seq revealed a robust transcriptional shift in Lamin-high cells, including upregulation of adhesion/ECM and differentiation programs and downregulation of canonical EWS::FLI1 targets (IGF1, NR0B1, CXCR4). The Lamin-dependent signature converged with independent EWS::FLI1 knockdown profiles, suggesting partial antagonism of the fusion’s oncogenic circuitry. ATAC-seq showed genome-wide remodeling with a bias toward increased accessibility at noncoding regulatory regions; differentially accessible regions were enriched for ETS (including EWS::FLI1) and CTCF/BORIS motifs and mapped to enhancer and super-enhancer hubs. Integrative analysis linked accessibility changes to gene expression, and computational footprinting inferred reduced EWS::FLI1 occupancy in lamin-high conditions, a prediction to be validated. So far, these findings position lamin A/C as a context-dependent regulator of EWS chromatin and phenotype, however, further studies are needed to confirm causality and assess translational relevance.