This thesis aimed to unveil new insights into breast cancer (BC) vasculature, since this could potentially have a large clinical impact. To do so, single-cell RNA-sequencing was performed on the breast cancer vasculature and tumour microenvironment. The analysis revealed novel interactions between immune cells and endothelial cells (ECs), and identified a capillary EC subtype, called lipid processing ECs (LIPECs), expressing genes regulated by PPAR-γ. Retrospectively, this study uncovered breast cancer-specific clinical benefits of PPAR-γ agonist (metformin) treatment, positively correlated with LIPEC abundance. In conclusion, these findings unravelled heterogeneity in breast ECs, and raise the question of whether targeting specific EC subtypes is a potential avenue for BC treatment.

(Belg J Med Oncol 2023;17(3):88–90)