Regulation of Ion Homeostasis for Enhanced Tumor Radio-Immunotherapy

Intra/extracellular ion content affects the growth and metastasis of tumor cells, as well as the efficacy of various antitumor therapies. Herein, a carbonic anhydrase inhibitor (CAI) is loaded onto pH-responsive calcium carbonate (CaCO₃ ) nanoparticles and then modify theses nanoparticles with liposomes to obtain biocompatible CaCO₃ /CAI@Lipsome (CCL) for enhance tumor radio-immunotherapy. CCL can specially decompose in tumor microenvironment, releasing calcium ion (Ca²⁺ ) and CAI, as well as increasing the pH value of extracellular fluid. CAI restrains the flow of hydrogen ion (H⁺ ) inside and outside the tumor cells, resulting in the reversal of tumor acidic microenvironment and the increase of intracellular H⁺ , both of which can improve the sensitivity of tumor to radiotherapy. Afterward, the increased intracellular H⁺ together with radiotherapy-causes reactive oxygen species promotes calcium influx, leading to cellular calcium overload. Moreover, the CCL-tailored content of H⁺ and Ca²⁺ strengthens radiotherapy-induced immunogenic cell death and dendritic cell maturation, amplifying systemic anti-tumor adaptive immunity. Meanwhile, macrophages in the CCL-treated tumors are polarized from pro-tumor M2 to anti-tumor M1 under X-ray exposure, owing to the neutralization of tumor acidic microenvironment and enhances Ca²⁺ content. Therefore, multi-directional regulation of the intra/extra tumor cell pH/calcium by simple nano-preparation would provide a powerful way to improve the efficacy of radio-immunotherapy.