Mechanisms and Applications of Manganese-Based Materials in Tumor Immunotherapy.

Manganese-based nanomaterials have been novel multifunctional platforms in tumor immunotherapy because of their tunable multivalent states, biocompatibility, and multi-stimulus responsiveness. Current cancer treatments are insufficient and cause severe side effects; therefore, manganese-based nanomaterials are proposed in combination with immunotherapy to mitigate adverse effects. This review outlines the antitumor effects mediated by four key mechanisms: (1) activation of the cGAS-STING immune signaling pathway, (2) direct activation of immune cells, (3) induction of immunogenic cell death (ICD), and (4) modulation of the tumor microenvironment. These approaches are broadly categorized into two types: monotherapy and multimodal combination therapy. Monotherapy encompasses three specific modalities: (1) direct use as a Stimulator of Interferon Genes (STING) agonist, (2) vector-mediated targeted drug delivery, and (3) mediation of chemodynamic therapy to generate reactive oxygen species, thereby inducing ICD. Multimodal combination therapy involves synergistic integration with traditional or emerging treatment modalities, including chemotherapy, radiotherapy, photodynamic therapy, sonodynamic therapy, and low-level light therapy, as well as multimodal combination treatment methods. It significantly enhances the antitumor efficacy of traditional therapies through immunostimulation, thus achieving synergistic breakthroughs in treatment efficiency and survival rate. Collectively, the multifunctional integration of manganese-based materials is a novel strategy for developing "self-adjuvant" immunotherapeutic platforms and investigating the clinical translation potential.