CaCO₃-complexed pH-responsive nanoparticles encapsulating mitoxantrone and celastrol enhance tumor chemoimmunotherapy

Modulating the immunosuppressive tumor microenvironment (TME) while enhancing antitumor immune responses is a promising strategy. In this study, we designed an acid-sensitive nanosystem (MCCaNPs) to demonstrate effective immunotherapy against cancer through the systemic delivery of immune-stimulating chemotherapy combinations. A pH-responsive nanoplatform containing CaCO₃ was prepared by the double emulsion method, and mitoxantrone (MIT) and celastrol (CEL) were simultaneously encapsulated as immunogenic cell death (ICD) inducers. Due to the acid responsiveness of CaCO₃, the nanoparticles rapidly consume H⁺ to relieve the acidic tumor microenvironment and explosively release CEL and MIT, showing inherent immunomodulatory activity in collaborative tumor chemoimmunotherapy. MIT and CEL synergistically trigger stronger ICD by inducing tumor cells to release calreticulin (CRT), high mobility group box 1 protein (HMGB1). Following the intravenous administration of MCCaNPs, the local tumor microenvironment(TME) was reprogrammed in mice-bearing tumors. This reprogramming was characterized by a significant increase in the density of tumor-infiltrating cytotoxic T lymphocytes(CTLs), ultimately prolonging survival. Therefore, this research proposes a promising approach to trigger immunogenic cell death collaboratively, aiming to boost the tumor CTLs infiltration for anticancer immunotherapy.