Deterioration of multi-level 3D genome organization during breast cancer progression

Breast cancer progression entails intricate, multi-level alterations in genome organization and expression. To gain insights into the modifications in chromatin's three-dimensional (3D) structure during breast cancer progression, we conducted an analysis combining Hi-C data with lamina-associated domains (LADs), epigenomic marks, and gene expression in an in vitro model of breast cancer progression. Our results reveal that while the fundamental properties of topologically associating domains (TADs) remain largely stable, significant changes occur in the organization of compartments and subcompartments. These changes are closely correlated with alterations in the expression of oncogenic genes. We also observed a restructuring of TAD-TAD interactions, coinciding with a loss of spatial compartmentalization and radial positioning of the 3D genome. Notably, we identified a previously unrecognized interchromosomal insertion event, wherein a locus on chromosome 8 housing the MYC oncogene becomes inserted into a highly active region on chromosome 10. This insertion event leads to the formation of de novo enhancer contacts and activation of the oncogene, illustrating how structural variants can interact with the 3D genome to drive oncogenic states. In summary, our findings provide evidence for the degradation of genome organization at multiple scales during breast cancer progression revealing the complex interplay between genomic structure and oncogenic processes.