The antitumor immune response induced by chemotherapy has attracted considerable attention. However, the immunosuppressive tumor microenvironment hinders the immune activation effect of cancer chemotherapy. TGF-β plays a key role in driving tumor immunosuppression and can prevent effective antitumor immune response through multiple roles. In this study, a dual-responsive prodrug micelle (PAOL) is designed to co-deliver LY2109761 (a TGF-β receptor I/II inhibitor) and oxaliplatin (OXA, a conventional chemotherapy) to remodel tumor microenvironment and trigger immunogenic cell death (ICD) to induce antitumor immunity response. Under hypoxia tumor environment, the polyethylene glycol shell of the micelle cleavages, along with the release of LY2109761 and OXA prodrug. Cytotoxic effect of OXA is then activated by glutathione-mediated reduction in tumor cells and the activated OXA significantly enhances tumor immunogenicity and promotes intratumoral accumulation of cytotoxic T lymphocytes. Meanwhile, TGF-β blockade through LY2109761 reprograms tumor microenvironment by correcting the immunosuppressive state and regulating tumor extracellular matrix, which further maintaining OXA induced immune response. Therefore, due to the capability of boosting tumor-specific antitumor immunity, the bifunctional micelle presents markedly synergistic antitumor efficacies and provides a potent therapeutic strategy for chemoimmunotherapy of solid tumors.
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 .
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