Tumor-Repopulating Cell-Derived Microparticle-Based Therapeutics Amplify the Antitumor Effect through Synergistic Inhibition of Chemoresistance and Immune Evasion.

Traditional chemotherapy often encounters failure attributed to drug resistance mediated by tumor-repopulating cells (TRCs) and chemotherapy-triggered immune suppression. The effective inhibition of TRCs and the mitigation of drug-induced immune suppression are pivotal for the successful chemotherapy. Here, TRC-derived microparticles (3D-MPs), characterized by excellent tumor-targeting and high TRC uptake properties, are utilized to deliver metformin and the chemotherapeutic drug doxorubicin ((DOX+Met)@3D-MPs). (DOX+Met)@3D-MPs efficiently enhance tumor accumulation and are highly internalized in tumor cells and TRCs. Additionally, (DOX+Met)@3D-MPs significantly decrease the chemotherapy-triggered upregulation in P-glycoprotein expression to enhance intracellular doxorubicin retention, resulting in increased chemotherapy sensitivity and immunogenic cell death in tumor cells and TRCs for improved antitumor immunity. Importantly, (DOX+Met)@3D-MPs also remarkably reduce chemotherapy-induced PD-L1 expression, efficiently alleviating immune suppression facilitated by the PD-L1/PD-1 axis to further enhance immunological response against malignancy. These results underscore the (DOX+Met)@3D-MPs' potential as a viable platform for augmenting the efficacy of antitumor therapies.