TGF-β blockade-improved chemo-immunotherapy with pH/ROS cascade-responsive micelle via tumor microenvironment remodeling.

Immunosuppressive tumor microenvironment and low delivery efficiency severely impede the tumor chemotherapy effect. To address this issue, we develop a pH/ROS cascade-responsive prodrug micelle to deliver siTGF-β with size-shrinkage and charge-reversal property, leading to synergistical tumor microenvironment remodeling. The nanosystem highly improved endocytosis efficiency and tumor penetration depth through charge reversal and size reduction upon exposure to weakly acidic tumor microenvironment. Moreover, the nanocarrier would rapidly escape from endo/lysosome, disassemble and release siTGF-β and hydroxycamptothecin in response to high intracellular ROS. Furthermore, the nanosystem significantly boosted antitumor immune response and reduced immune tolerance with remodeling tumor microenvironment, which significantly prolonged the survival time of tumor-bearing mice (75% survival rate upon 35 days). It is realized by the combined effects of chemotherapy-enhanced immunogenicity and recruitment of effector T cells, TGF-β-blockade immunotherapy-activated inhibition immunosuppressive tumor microenvironment and epithelial-to-mesenchymal transition (EMT), and regulation physical tumor microenvironment via reducing the dense tumor extracellular matrix and the high tumor interstitial pressure obstacles. To this end, the nanosystem not only overcame biobarriers and reinforced antitumor immune response, but also effectively inhibited tumor growth, metastasis and recurrence in vivo.