Engineering a modular FAP-targeting ferritin-based drug nanocarrier for enhanced glioblastoma theranostics.

Rationale: Glioblastoma multiforme (GBM) is an aggressive brain tumor marked by diffuse infiltration, a complex microenvironment, and poor drug delivery due to the blood-brain barrier. Fibroblast activation protein (FAP), widely expressed by cancer-associated fibroblasts (CAFs), emerges as a promising yet underexploited target for drug delivery. Methods: Here, a modular ferritin-based drug carrier (FDC) functionalized with an optimized FAP-targeting ligand using site-specific sortase A-mediated ligation was developed. This approach ensures precise surface modification while preserving ferritin's structure and drug-loading capacity. Monomethyl auristatin E (MMAE), a potent cytotoxin, is stably encapsulated to create a dual-targeting nanocarrier aimed at FAP and transferrin receptor 1. Results: In orthotopic glioma mouse models, the resulting FDC enables pH-responsive MMAE release, enhances tumor targeting and cellular uptake, reduces tumor burden, prolongs survival, and minimizes systemic toxicity compared to free MMAE. Furthermore, spatial transcriptomic analyses and immunohistochemistry data reveal that this therapeutic approach reshapes the tumor microenvironment by enhancing the spatial proximity between CAFs and cytotoxic immune cells and activating multiple immune pathways. Conclusions: This study presents a precision-engineered nanoplatform for FAP-targeted GBM therapy, provides novel insights into the stromal-immune dynamics of GBM under therapeutic pressure and supports the rationale for combining CAF modulation with immunotherapy to achieve durable tumor control.