Manganese molybdate nanodots with dual amplification of STING activation for "cycle" treatment of metalloimmunotherapy

Certain types of cationic metal ions, such as Mn2+ are able to activate immune functions via the stimulator of interferon genes (STING) pathway, showing potential applications in eliciting antitumor immunity. How anionic ions interact with immune cells remains largely unknown. Herein, selecting from a range of cationic and anionic ions, we were excited to discover that MoO42- could act as a cGAS-STING agonist and further confirmed the capability of Mn2+ to activate the cGAS-STING pathway. Inspired by such findings, we synthesized manganese molybdate nanoparticles with polyethylene glycol modification (MMP NDs) for cancer metalloimmunotherapy. Meanwhile, MMP NDs could consume glutathione (GSH) over-expressed in tumors and induce ferroptosis owing to high-valence Mo and Mn to elicit tumor-specific immune responses, which was further amplified by MMP-triggered the cGAS-STING activation. In turn, activated CD8+ T cells to secrete high levels of interferon γ (IFN-γ) and reduced GPX4 expression in tumor cells to trigger ferroptosis-specific lipid peroxidation, which constituted a "cycle" of therapy. As a result, the metalloimmunotherapy with systemic administration of MMP NDs offered a remarkable tumor inhibition effect for a variety of tumor models. Our work for the first time discovered the ability of anionic metal ions to activate the immune system and rationally designed bimetallic oxide nanostructures as a multifunctional therapeutic nanoplatform for tumor immunotherapy.

Oxygen-Deficient Molybdenum Oxide Nanosensitizers for Ultrasound-Enhanced Cancer Metalloimmunotherapy

Oxygen-deficient molybdenum oxide (MoO_X ) nanomaterials are prepared as novel nanosensitizers and TME-stimulants for ultrasound (US)-enhanced cancer metalloimmunotherapy. After PEGylation, MoO_X -PEG exhibits efficient capability for US-triggered reactive oxygen species (ROS) generation and glutathione (GSH) depletion. Under US irradiation, MoO_X -PEG generates a massive amount of ROS to induce cancer cell damage and immunogenic cell death (ICD), which can effectively suppress tumor growth. More importantly, MoO_X -PEG itself further stimulates the maturation of dendritic cells (DCs) and triggeres the activation of the cGAS-STING pathway to enhance the immunological effect. Due to the robust ICD induced by SDT and efficient DC maturation stimulated by MoO_X -PEG, the combination treatment of MoO_X -triggered SDT and aCTLA-4 further amplifies antitumor therapy, inhibits cancer metastases, and elicits robust immune responses to effectively defeat abscopal tumors.

Multi-signaling pathway activation by pH responsive manganese particles for enhanced vaccination

As metal ions play important roles in the process of immunomodulation, immunotherapy based on metal ions has attracted tremendous interests in recent years. Here, we screened common metal ions and found that Mn²⁺ could enhance the immune function in vitro. A new type of nanovaccine is thus fabricated by a biomimetic approach using nanoscale coordination polymer formed by Mn²⁺ and 2-methylimidazole (2-MI) to encapsulate ovalbumin (OVA) protein, a model antigen, obtaining OVA@MM nanoparticles. Compared to free OVA, OVA@MM nanoparticles could more effectively induce the maturation of bone marrow-derived dendritic cells (BMDCs) and their subsequent antigen cross-presentation. The particles made of Mn²⁺ and 2-MI could activate immune-regulated signal pathways to enhance the immune functions of BMDCs. Such OVA@MM nanovaccine could not only provide prophylactic effect to inhibit the growth of B16-OVA tumor on immunized mice, but also significantly inhibit tumor growth in the mice with B16-OVA tumor combined with anti-programmed cell death protein 1 (anti-PD-1) antibody. Therefore, this nanovaccine platform based on Mn²⁺, 2-MI and antigen may provide a simple, effective and broadly applicable strategy to enhance adaptive immunity against cancer and other diseases.

Engineered NanoAlum from aluminum turns cold tumor hot for potentiating cancer metalloimmunotherapy

The poor cancer immunotherapy outcome has been closely related to immunosuppressive tumor microenvironment (TME), which usually inactivates the antitumor immune cells and leads to immune tolerance. Metalloimmunotherapy by supplementing nutritional metal ions into TME has emerged as a potential strategy to activate the tumor-resident immune cells. Herein, we engineered a magnesium-contained nano-aluminum adjuvant (NanoAlum) through hydrolyzing a mixture of Mg(OH)₂ and Al(OH)₃, which has highly similar components to commercial Imject Alum. Peritumoral injection of NanoAlum effectively neutralized the acidic TME while releasing Mg²⁺ to activate the tumor-resident T cells. Meanwhile, NanoAlum also blocked the autophagy pathway in tumor cells and subsequently induced cell apoptosis. The in vivo studies showed that merely peritumoral injection of NanoAlum successfully inhibited the growth of solid tumors in mice. On this basis, NanoAlum combined with chemical drug methotrexate or immunomodulatory adjuvant CpG further induced potent antigen-specific antitumor immunity. Overall, our study first provides a rational design for engineering tumor-targeted nanomodulator from clinical adjuvants to achieve effective cancer metalloimmunotherapy against solid tumors.