Amplifying STING Activation and Alleviating Immunosuppression through a Mn 2+ -Based Metal-Organic Framework Nanosystem for Synergistic Cancer Therapy

The field of immunotherapy, particularly immune checkpoint blockade (ICB), holds immense potential in mitigating the progression of cancer. However, the challenges of insufficient tumor antigen production and the immunosuppressive state in the tumor microenvironment substantially impede patients from deriving benefits. In this research, we present a tumor-microenvironment-modulation manganese-based nanosystem, PEG-MnMOF@PTX, aiming to improve the responsiveness of ICB. Under acidic conditions, the released Mn 2+ accomplishes multiple objectives. It generates toxic hydroxyl radicals (•OH), together with the released paclitaxel (PTX), inducing immunogenic cell death of tumor cells and normalizing tumor blood vessels. Concurrently, it facilitates the in situ generation of oxygen (O 2 ) from hydrogen peroxide (H 2 O 2 ), ameliorating the microenvironmental immunosuppression and increasing the efficacy of immunotherapy. In addition, this study demonstrates that PEG-MnMOF@PTX can promote the maturation of dendritic cells and augment the infiltration of cytotoxic T lymphocytes through activation of the cyclic guanosine 5′-monophosphate–adenosine 5′-monophosphate synthase (cGAS) and interferon gene stimulator (STING) pathways, namely cGAS–STING pathways, thereby heightening the sensitivity to ICB immunotherapy. The findings of this study present a novel paradigm for the progress in cancer immunotherapy.