Targeting nucleolin facilitates the development of blood-tumor barrier-penetrating and glioblastoma-specific PROTACs

Targeted therapy for glioblastoma (GBM) is challenged by the blood-tumor barrier (BTB). Extracellular vesicles (EVs) from GBM cells play a role in transforming BBB into BTB, although the mechanisms are not fully understood. This study identifies nucleolin (NCL), a nucleomembrane shuttling protein, as being transferred from GBM cells to the surface of brain capillary endothelial cells, facilitating BTB formation. The aptamer AS1411, which targets NCL, is shown to cross the BTB via receptor-mediated transcytosis (RMT) and selectively recognize GBM cells in an NCL-dependent manner. Beyond its targeting capabilities, AS1411 has been repurposed to recruit the E3 ligase MDM2 in PROTACs, leveraging the intracellular interaction of NCL with MDM2. Utilizing AS1411’s multifunctionality in BTB penetration, GBM cell targeting, and MDM2 recruitment, we conjugated AS1411 to VEGFR2 or EGFR ligands to create PROTAC degraders. These constructs induce NCL- and MDM2-dependent ubiquitination and degradation of VEGFR2 or EGFR, demonstrating significant anti-GBM efficacy both in vitro and in vivo, with no toxicity to normal cells. Overall, NCL from GBM-derived EVs emerges as a crucial mediator of BTB formation and serves as a receptor for AS1411-mediated RMT, paving the way for developing PROTACs that effectively traverse BTB and target GBM.