Macrophage-reprogramming calcium alginate microspheres enhance exosome-mediated antigen cross-presentation to boost embolization-immunotherapy in hepatocellular carcinoma.

Transarterial chemoembolization (TACE) is a first-line therapeutic modality for hepatocellular carcinoma (HCC). Nevertheless, its therapeutic efficacy remains constrained by the hostile tumor microenvironment (TME), typified by acidity and an immunosuppressive milieu. Here, multifunctional microspheres (RC6CaAlgMS) were developed to neutralize the acidic TME and relieve immunosuppression. The uniform-sized calcium alginate microspheres were fabricated using microfluidic technology, incorporating pH-responsive CaCO3 nanocarriers to efficiently encapsulate R848 and C6-ceramide (C6). Their physicochemical properties were characterized, and the embolization efficiency was validated using decellularized liver and rabbit kidney models. Furthermore, their antitumor activities and mechanism were evaluated in both in vitro and in vivo. R848 and C6 were efficiently encapsulated into RC6CaAlgMS, where they acted synergistically to reprogram tumor-associated macrophages (TAMs) toward an M1-like phenotype and to enhance both exosome secretion and exosome-mediated antigen cross-presentation. RC6CaAlgMS produced uniform vascular embolization and efficiently occluded the renal arterial branches. In vitro studies demonstrated that RC6CaAlgMS synergized with DOX-based chemotherapy to suppress the growth of murine HCC by neutralizing acidic TME and remodeling the immune landscape. When combined with PD-L1 blockade therapy, DOX-loaded RC6CaAlgMS effectively inhibited both primary and distant tumors, eliciting an abscopal-like effect driven by enhanced antigen dissemination and T-cell priming. In an orthotopic rat TACE model, the combination of DOX-loaded RC6CaAlgMS with PD-L1 blockade achieved complete tumor eradication. Collectively, this study establishes a multifunctional microsphere platform that effectively remodels and overcomes the post-TACE immunosuppressive TME, offering a potent strategy for integrating embolization with immunotherapy in HCC.