Breaking the stromal barrier in bladder tumor with a urea-powered platelet nanomotor for potentiated BCG immunotherapy.

Abstract

e16604 Background: Intravesical Bacillus Calmette-Guérin (BCG) therapy for bladder cancer is severely limited by poor tumor penetration and an immunosuppressive tumor microenvironment. We identified death-associated protein like 1 (DAPL1) as a critical regulator of BCG resistance: low DAPL1 expression in bladder cancer promotes pathological extracellular matrix (ECM) stiffening and immune exclusion, driving a BCG-refractory phenotype. This prompted the development of a targeted delivery strategy to overcome this stromal barrier. Methods: DAPL1’s role in BCG resistance was validated via bioinformatics, immunohistochemistry, transcriptomic/proteomic profiling, and in vitro/in vivo functional assays. We engineered a platelet-derived nanomotor (BCG@PLTm) that encapsulated BCG and harnessed urine urea decomposition for autonomous propulsion, enabling active tumor penetration. Nanomotor properties were characterized via microscopy and 3D tumor models; therapeutic efficacy and biosafety were evaluated in orthotopic bladder cancer mouse models using live imaging, flow cytometry, and histology. Results: DAPL1 was downregulated in bladder cancer tissues, where its deficiency drove ECM barrier and immune desert. In vivo and in vitro, BCG@PLTm significantly restored DAPL1 expression, reversed pathological ECM remodeling, and reactivated intratumoral cytotoxic T-cell infiltration. These effects translated to potent tumor suppression (tumor growth inhibition rate > 90%) with a favorable safety profile, as no overt toxicity was observed in major organs. Conclusions: Our findings established the DAPL1-ECM-immune exclusion axis as a targetable driver of BCG resistance. The urea-powered BCG@PLTm represented an autonomously propelled delivery platform to reprogram stromal-rich bladder tumors, providing a translatable therapeutic strategy for immunotherapy-refractory bladder cancer.