Reinforcing the Induction of Immunogenic Cell Death Via Artificial Engineered Cascade Bioreactor-Enhanced Chemo-Immunotherapy for Optimizing Cancer Immunotherapy

Dual Enzyme-Encapsulated Materials for Biological Cascade Chemistry and Synergistic Tumor Starvation

Framework and polymeric nanoreactors (NRs) have distinct advantages in improving chemical reaction efficiency in the tumor microenvironment (TME). Nanoreactor-loaded oxidoreductase enzyme is activated by tumor acidity to produce H2O2 by increasing tumor oxidative stress. High levels of H2O2 induce self-destruction of the vesicles by releasing quinone methide to deplete glutathione and suppress the antioxidant potential of cancer cells. Therefore, the synergistic effect of the enzyme-loaded nanoreactors results in efficient tumor ablation via suppressing cancer-cell metabolism. The main driving force would be to take advantage of the distinct metabolic properties of cancer cells along with the high peroxidase-like activity of metalloenzyme/metalloprotein. A cascade strategy of dual enzymes such as glucose oxidase (GOx) and nitroreductase (NTR) wherein the former acts as an O2-consuming agent such as overexpression of NTR and further amplified NTR-catalyzed release for antitumor therapy. The design of cascade bioreductive hypoxia-responsive drug delivery via GOx regulates NTR upregulation and NTR-responsive nanoparticles. Herein, we discuss tumor hypoxia, reactive oxygen species (ROS) formation, and the effectiveness of these therapies. Nanoclusters in cascaded enzymes along with chemo-radiotherapy with synergistic therapy are illustrated. Finally, we outline the role of the nanoreactor strategy of cascading enzymes along with self-synergistic tumor therapy.

Ultrasound-visible engineered bacteria for tumor chemo-immunotherapy

Our previous work developed acoustic response bacteria, which enable the precise tuning of transgene expression through ultrasound. However, it is still difficult to visualize these bacteria in order to guide the sound wave to precisely irradiate them. Here, we develop ultrasound-visible engineered bacteria and chemically modify them with doxorubicin (DOX) on their surfaces. These engineered bacteria (Ec@DIG-GVs) can produce gas vesicles (GVs), providing a real-time imaging guide for remote hyperthermia high-intensity focused ultrasound (hHIFU) to induce the expression of the interferon (IFN)-γ gene. The production of IFN-γ can kill tumor cells, induce macrophage polarization from the M2 to the M1 phenotype, and promote the maturation of dendritic cells. DOX can be released in the acidic tumor microenvironment, resulting in immunogenic cell death of tumor cells. The concurrent effects of IFN-γ and DOX activate a tumor-specific T cell response, producing the synergistic anti-tumor efficacy. Our study provides a promising strategy for bacteria-mediated tumor chemo-immunotherapy.

Nanoparticle-Mediated Synergistic Chemoimmunotherapy for Cancer Treatment

Until now, there has been a lack of effective strategies for cancer treatment. Immunotherapy has high potential in treating several cancers but its efficacy is limited as a monotherapy. Chemoimmunotherapy (CIT) holds promise to be widely used in cancer treatment. Therefore, identifying their involvement and potential synergy in CIT approaches is decisive. Nano-based drug delivery systems (NDDSs) are ideal delivery systems because they can simultaneously target immune cells and cancer cells, promoting drug accumulation, and reducing the toxicity of the drug. In this review, we first introduce five current immunotherapies, including immune checkpoint blocking (ICB), adoptive cell transfer therapy (ACT), cancer vaccines, oncolytic virus therapy (OVT) and cytokine therapy. Subsequently, the immunomodulatory effects of chemotherapy by inducing immunogenic cell death (ICD), promoting tumor killer cell infiltration, down-regulating immunosuppressive cells, and inhibiting immune checkpoints have been described. Finally, the NDDSs-mediated collaborative drug delivery systems have been introduced in detail, and the development of NDDSs-mediated CIT nanoparticles has been prospected.

Genetically Edited Cascade Nanozymes for Cancer Immunotherapy

Immune checkpoint blockade (ICB) has brought tremendous clinical progress, but its therapeutic outcome can be limited due to insufficient activation of dendritic cells (DCs) and insufficient infiltration of cytotoxic T lymphocytes (CTLs). Evoking immunogenic cell death (ICD) is one promising strategy to promote DC maturation and elicit T-cell immunity, whereas low levels of ICD induction of solid tumors restrict durable antitumor efficacy. Herein, we report a genetically edited cell membrane-coated cascade nanozyme (gCM@MnAu) for enhanced cancer immunotherapy by inducing ICD and activating the stimulator of the interferon genes (STING) pathway. In the tumor microenvironment (TME), the gCM@MnAu initiates a cascade reaction and generates abundant cytotoxic hydroxyl (•OH), resulting in improved chemodynamic therapy (CDT) and boosted ICD activation. In addition, released Mn2+ during the cascade reaction activates the STING pathway and further promotes the DC maturation. More importantly, activated immunogenicity in the TME significantly improves gCM-mediated PD-1/PD-L1 checkpoint blockade therapy by eliciting systemic antitumor responses. In breast cancer subcutaneous and lung metastasis models, the gCM@MnAu showed synergistically enhanced therapeutic effects and significantly prolonged the survival of mice. This work develops a genetically edited nanozyme-based therapeutic strategy to improve DC-mediated cross-priming of T cells against poorly immunogenic solid tumors.

Tumor Microenvironment-Induced Drug Depository for Persistent Antitumor Chemotherapy and Immune Activation

Herein, a drug-loading nanosystem that can in situ form drug depository for persistent antitumor chemotherapy and immune regulation is designed and built. The system (DOX@MIL-LOX@AL) is fabricated by packaging alginate on the surface of Doxorubicin (DOX) and lactate oxidase (LOX) loaded MIL-101(Fe)-NH2 nanoparticle, which can easily aggregate in the tumor microenvironment through the cross-linking with intratumoral Ca2+. Benefiting from the tumor retention ability, the fast-formed drug depository will continuously release DOX and Fe ions through the ATP-triggered slow degradation, thus realizing persistent antitumor chemotherapy and immune regulation. Meanwhile, LOX in the non-aggregated nanoparticles is able to convert the lactic acid to H2O2, which will be subsequently decomposed into ·OH by Fe ions to further enhance the DOX-induced immunogenic death effect of tumor cells. Together, with the effective consumption of immunosuppressive lactic acid, long-term chemotherapy, and oxidation therapy, DOX@MIL-LOX@AL can execute high-performance antitumor chemotherapy and immune activation with only one subcutaneous administration.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

A Mitochondria-Targeted NIR-II AIEgen Induced Pyroptosis for Enhanced Tumor Immunotherapy

Cancer immunotherapy is a favorable strategy for facilitating anti-tumor immunity, but it shows limited benefits in clinical practice owing to the immunosuppressive tumor microenvironment. Pyroptosis shows great immunostimulatory effect on tumor, whereas the lack of pyroptotic inducer with imaging property has restricted its progress in tumor theranostics. Herein, a mitochondria-targeted aggregation-induced emission (AIE) luminogen (TPA-2TIN) with NIR-II emission is designed for highly efficient induction of tumor cell pyroptosis. The fabricated TPA-2TIN nanoparticles can be efficiently taken up by tumor cells and selectively accumulated in tumor for a long term observed by NIR-II fluorescence imaging. More importantly, the TPA-2TIN nanoparticles can effectively stimulate immune responses both in vitro and in vivo mediated by the mitochondrial dysfunctions and the subsequent activation of the pyroptotic pathway. Ultimately, the reversal of the immunosuppressive tumor microenvironment significantly enhances the immune checkpoint therapy. This study paves a new avenue for adjuvant immunotherapy of cancer.

Cascade strategy for glucose oxidase-based synergistic cancer therapy using nanomaterials

Nanomaterial-based cancer therapy faces significant limitations due to the complex nature of the tumor microenvironment (TME). Starvation therapy is an emerging therapeutic approach that targets tumor cell metabolism using glucose oxidase (GOx). Importantly, it can provide a material or environmental foundation for other diverse therapeutic methods by manipulating the properties of the TME, such as acidity, hydrogen peroxide (H2O2) levels, and hypoxia degree. In recent years, this cascade strategy has been extensively applied in nanoplatforms for ongoing synergetic therapy and still holds undeniable potential. However, only a few review articles comprehensively elucidate the rational designs of nanoplatforms for synergetic therapeutic regimens revolving around the conception of the cascade strategy. Therefore, this review focuses on innovative cascade strategies for GOx-based synergetic therapy from representative paradigms to state-of-the-art reports to provide an instructive, comprehensive, and insightful reference for readers. Thereafter, we discuss the remaining challenges and offer a critical perspective on the further advancement of GOx-facilitated cancer treatment toward clinical translation.

Tumor Metabolism-Rewriting Nanomedicines for Cancer Immunotherapy

Cancer immunotherapy has become an established therapeutic paradigm in oncologic therapy, but its therapeutic efficacy remains unsatisfactory in the majority of cancer patients. Accumulating evidence demonstrates that the metabolically hostile tumor microenvironment (TME), characterized by acidity, deprivation of oxygen and nutrients, and accumulation of immunosuppressive metabolites, promotes the dysfunction of tumor-infiltrating immune cells (TIICs) and thereby compromises the effectiveness of immunotherapy. This indicates the potential role of tumor metabolic intervention in the reinvigoration of antitumor immunity. With the merits of multiple drug codelivery, cell and organelle-specific targeting, controlled drug release, and multimodal therapy, tumor metabolism-rewriting nanomedicines have recently emerged as an attractive strategy to strengthen antitumor immune responses. This review summarizes the current progress in the development of multifunctional tumor metabolism-rewriting nanomedicines for evoking antitumor immunity. A special focus is placed on how these nanomedicines reinvigorate innate or adaptive antitumor immunity by regulating glucose metabolism, amino acid metabolism, lipid metabolism, and nucleotide metabolism at the tumor site. Finally, the prospects and challenges in this emerging field are discussed.

Ultrasmall Self-Cascade AuNP@FeS Nanozyme for H2S-Amplified Ferroptosis Therapy

Recently, nanozymes with peroxidase (POD)-like activity have shown great promise for ferroptosis-based tumor therapy, which are capable of transforming hydrogen peroxide (H2O2) to highly toxic hydroxyl radicals (•OH). However, the unsatisfactory therapeutic performance of nanozymes due to insufficient endogenous H2O2 and acidity at tumor sites has always been a conundrum. Herein, an ultrasmall gold (Au) @ ferrous sulfide (FeS) cascade nanozyme (AuNP@FeS) with H2S-releasing ability constructed with an Au nanoparticle (AuNP) and an FeS nanoparticle (FeSNP) is designed to increase the H2O2 level and acidity in tumor cells via the collaboration between cascade reactions of AuNP@FeS and the biological effects of released H2S, achieving enhanced •OH generation as well as effective ferroptosis for tumor therapy. The cascade reaction in tumor cells is activated by the glucose oxidase (GOD)-like activity of AuNP in AuNP@FeS to catalyze intratumoral glucose into H2O2 and gluconic acid; meanwhile, the released H2S from AuNP@FeS reduces H2O2 consumption by inhibiting intracellular catalase (CAT) activity and promotes lactic acid accumulation. The two pathways synergistically boost H2O2 and acidity in tumor cells, thus inducing a cascade to generate abundant •OH by catalyzing H2O2 through the POD-like activity of FeS in AuNP@FeS and ultimately causing amplified ferroptosis. In vitro and in vivo experiments demonstrated that AuNP@FeS presents a superior tumor therapeutic effect compared to that of AuNP or FeS alone. This strategy represents a simple but powerful method to amplify ferroptosis with H2S-releasing cascade nanozymes and will pave a new way for the development of tumor therapy.

Lactate Efflux Inhibition by Syrosingopine/LOD Co-Loaded Nanozyme for Synergetic Self-Replenishing Catalytic Cancer Therapy and Immune Microenvironment Remodeling

An effective systemic mechanism regulates tumor development and progression; thus, a rational design in a one-stone-two-birds strategy is meant for cancer treatment. Herein, a hollow Fe3 O4 catalytic nanozyme carrier co-loading lactate oxidase (LOD) and a clinically-used hypotensor syrosingopine (Syr) are developed and delivered for synergetic cancer treatment by augmented self-replenishing nanocatalytic reaction, integrated starvation therapy, and reactivating anti-tumor immune microenvironment. The synergetic bio-effects of this nanoplatform stemmed from the effective inhibition of lactate efflux through blocking the monocarboxylate transporters MCT1/MCT4 functions by the loaded Syr as a trigger. Sustainable production of hydrogen peroxide by catalyzation of the increasingly residual intracellular lactic acid by the co-delivered LOD and intracellular acidification enabled the augmented self-replenishing nanocatalytic reaction. Large amounts of produced reactive oxygen species (ROS) damaged mitochondria to inhibit oxidative phosphorylation as the substituted energy supply upon the hampered glycolysis pathway of tumor cells. Meanwhile, remodeling anti-tumor immune microenvironment is implemented by pH gradient reversal, promoting the release of proinflammatory cytokines, restored effector T and NK cells, increased M1-polarize tumor-associated macrophages, and restriction of regulatory T cells. Thus, the biocompatible nanozyme platform achieved the synergy of chemodynamic/immuno/starvation therapies. This proof-of-concept study represents a promising candidate nanoplatform for synergetic cancer treatment.

Nanotechnology-Assisted Immunogenic Cell Death for Effective Cancer Immunotherapy

Tumor vaccines have been used to treat cancer. How to efficiently induce tumor-associated antigens (TAAs) secretion with host immune system activation is a key issue in achieving high antitumor immunity. Immunogenic cell death (ICD) is a process in which tumor cells upon an external stimulus change from non-immunogenic to immunogenic, leading to enhanced antitumor immune responses. The immune properties of ICD are damage-associated molecular patterns and TAA secretion, which can further promote dendritic cell maturation and antigen presentation to T cells for adaptive immune response provocation. In this review, we mainly summarize the latest studies focusing on nanotechnology-mediated ICD for effective cancer immunotherapy as well as point out the challenges.

Nanodelivery of scutellarin induces immunogenic cell death for treating hepatocellular carcinoma

Hepatocellular carcinoma (HCC) causes the immunosuppressive tumor microenvironment (TME) resistant to current immunotherapy. The immunogenic apoptosis (currently termed immunogenic cell death, ICD) of cancer cells may induce the adaptive immunity against tumors, thereby providing great potential for treating HCC. In this study, we have confirmed the potential of scutellarin (SCU, a flavonoid found in Erigeron breviscapus) for triggering ICD in HCC cells. To facilitate in vivo application of SCU for HCC immunotherapy, an aminoethyl anisamide-targeted polyethylene glycol-modified poly(lactide-co-glycolide) (PLGA-PEG-AEAA) was produced to facilitate SCU delivery in this study. The resultant nanoformulation (PLGA-PEG-AEAA.SCU) remarkably promoted blood circulation and tumor delivery in the orthotopic HCC mouse model. Consequently, PLGA-PEG-AEAA.SCU reversed the immune suppressive TME and achieved the immunotherapeutic efficacy, resulting in significantly longer survival of mice, without inducing toxicity. These findings uncover the ICD potential of SCU and provide a promising strategy for HCC immunotherapy.

Mesoporous silica/organosilica nanoparticles for cancer immunotherapy

Cancer is one of the fatal diseases in the history of humankind. In this regard, cancer immunotherapeutic strategies have revolutionized the traditional mode of cancer treatment. Silica based nano-platforms have been extensively applied in nanomedicine including cancer immunotherapy. Mesoporous silica nanoparticles (MSN) and mesoporous organosilica nanoparticles (MON) are attractive candidates due to the ease in controlling the structural parameters as needed for the targeted immunotherapeutic applications. Especially, the MON provide an additional advantage of controlling the composition and modulating the biological functions to actively synergize with other immunotherapeutic strategies. In this review, the applications of MSN, MON, and metal-doped MSN/MON in the field of cancer immunotherapy and tumor microenvironment regulation are comprehensively summarized by highlighting the structural and compositional attributes of the silica-based nanoplatforms.

Self-cascade catalytic single-atom nanozyme for enhanced breast cancer low-dose radiotherapy

Radiotherapy (RT) efficacy can be promoted with the help of nanoenzyme that can "re-programing" the tumour's micro-environment by changing the expression level of special bio-molecules. However, problems such as low reaction efficiency, limited endogenous H₂O₂, and/or unsatisfactory results of a single catalysis mode in treatment limit the application in the RT field. Herein, a novel Au nanoparticles (AuNPs) decorated iron SAE (FeSAE@Au) was formulated for self-cascade catalytic RT. In this dual-nanozyme system, embedded AuNPs can sever as GOx and endow FeSAE@Au with self-H₂O₂ supplying ability, which can elevate the H₂O₂ level in tumors by catalyzing cellular glucose in situ, further improving the catalytic performance of FeSAE with peroxidase-like activity. The self-cascade catalytic reaction can significantly increase cellular hydroxyl radicals (•OH) level, further promoting RT's effect. Furthermore, in vivo findings demonstrated that FeSAE can effectively limit tumor growth while causing low damage in important organs. According to our understanding, FeSAE@Au is the first description of a hybrid SAE-based nanomaterial employed in cascade catalytic RT. The research yields new and interesting insights for developing various SAE systems for anticancer therapy.

Manganese-Based Tumor Immunotherapy

As an essential micronutrient, manganese (Mn) participates in various physiological processes and plays important roles in host immune system, hematopoiesis, endocrine function, and oxidative stress regulation. Mn-based nanoparticles are considered to be biocompatible and show versatile applications in nanomedicine, in particular utilized in tumor immunotherapy in the following ways: 1) acting as a biocompatible nanocarrier to deliver immunotherapeutic agents for tumor immunotherapy; 2) serving as an adjuvant to regulate tumor immune microenvironment and enhance immunotherapy; 3) activating host's immune system through the cGAS-STING pathway to trigger tumor immunotherapy; 4) real-time monitoring tumor immunotherapy effect by magnetic resonance imaging (MRI) since Mn²⁺ ions are ideal MRI contrast agent which can significantly enhance the T₁ -weighted MRI signal after binding to proteins. This comprehensive review focuses on the most recent progress of Mn-based nanoplatforms in tumor immunotherapy. The characteristics of Mn are first discussed to guide the design of Mn-based multifunctional nanoplatforms. Then the biomedical applications of Mn-based nanoplatforms, including immunotherapy alone, immunotherapy-involved multimodal synergistic therapy, and imaging-guided immunotherapy are discussed in detail. Finally, the challenges and future developments of Mn-based tumor immunotherapy are highlighted.

Activating Nanomedicines with Electromagnetic Energy for Deep-Tissue Induction of Immunogenic Cell Death in Cancer Immunotherapy

Immunotherapy is an attractive approach for cancer therapy, while its antitumor efficacy is still limited, especially for non-immunogenic tumors. Nanomedicines can be utilized to convert the non-immunogenic "cold" tumors to immunogenic "hot" tumors via inducing immunogenic cell death (ICD), thereby promoting the antitumor immune response. Some nanomedicines that can produce local heat and reactive oxygen species upon the stimulation of electromagnetic energy are the main candidates for inducing the ICD effect. However, their applications are often restricted due to the poor tissue penetration depths of electromagnetic energy, such as light. By contrast, ultrasound, X-ray, alternating magnetic field, and microwave show excellent tissue penetration depths and thereby can be used for sonodynamic therapy, radiotherapy, magnetic hyperthermia therapy, and microwave ablation therapy, all of which can effectively induce ICD. Herein, the combination of deep-tissue electromagnetic energy with nanomedicines for inducing ICD and cancer immunotherapy are summarized. In particular, the designs of nanomedicines to amplify ICD effect in the presence of deep-tissue electromagnetic energy and sensitize tumors to various immunotherapies will be discussed. At the end of this review, a brief conclusion and discussion of current challenges and further perspectives in this subfield are provided.

Nano Delivery of Chemotherapeutic ICD Inducers for Tumor Immunotherapy

Immunogenic cell death (ICD, also known as immunogenic apoptosis) of malignant cells is confirmed to activate the host immune system to prevent, control, and eliminate tumors. Recently, a range of chemotherapeutic drugs have been repurposed as ICD inducers and applied for tumor immunotherapy. However, several hurdles to the widespread application of chemotherapeutic ICD inducers remain, namely poor water solubility, short blood circulation, non-specific tissue distribution, and severe toxicity. Recent advances in nanotechnology and pharmaceutical formulation foster the development of nano drug delivery systems to tackle the aforementioned hurdles and expedite safe, effective, and specific delivery. This review will describe delivery barriers to chemical ICD inducers and highlight recent nanoformulations for these drugs in tumor immunotherapy.

Prospects for the Use of Metal-Based Nanoparticles as Adjuvants for Local Cancer Immunotherapy

Immunotherapy is among the most effective approaches for treating cancer. One of the key aspects for successful immunotherapy is to achieve a strong and stable antitumor immune response. Modern immune checkpoint therapy demonstrates that cancer can be defeated. However, it also points out the weaknesses of immunotherapy, as not all tumors respond to therapy and the co-administration of different immunomodulators may be severely limited due to their systemic toxicity. Nevertheless, there is an established way through which to increase the immunogenicity of immunotherapy-by the use of adjuvants. These enhance the immune response without inducing such severe adverse effects. One of the most well-known and studied adjuvant strategies to improve immunotherapy efficacy is the use of metal-based compounds, in more modern implementation-metal-based nanoparticles (MNPs), which are exogenous agents that act as danger signals. Adding innate immune activation to the main action of an immunomodulator makes it capable of eliciting a robust anti-cancer immune response. The use of an adjuvant has the peculiarity of a local administration of the drug, which positively affects its safety. In this review, we will consider the use of MNPs as low-toxicity adjuvants for cancer immunotherapy, which could provide an abscopal effect when administered locally.

Phosphorous Dendron Micelles as a Nanomedicine Platform for Cooperative Tumor Chemoimmunotherapy via Synergistic Modulation of Immune Cells

Design of effective nanomedicines to modulate multiple immune cells to overcome the immune-suppressive tumor microenvironment is desirable to improve the overall poor clinical outcomes of immunotherapy. Herein, a nanomedicine platform is reported based on chemotherapeutic drug doxorubicin (DOX)-loaded phosphorus dendron micelles (M-G1-TBPNa@DOX, TBP, tyramine bearing two dimethylphosphonate) with inherent immunomodulatory activity for synergistic tumor chemoimmunotherapy. The M-G1-TBPNa@DOX micelles with good stability and a mean particle size of 86.4 nm can deliver DOX to solid tumors to induce significant tumor cell apoptosis and immunogenic cell death (ICD). With the demonstrated intrinsic activity of M-G1-TBPNa that can promote the proliferation of natural killer (NK) cells, the ICD-resulted maturation of dendritic cells of the DOX-loaded micelles, and the combination of anti-PD-L1 antibody, the synergistic modulation of multiple immune cells through NK cell proliferation, recruitment of tumor-infiltrating NK cells and cytotoxic T cells, and decrease of regulatory T cells for effective tumor chemoimmunotherapy with strong antitumor immunity and immune memory effect for effective prevention of lung metastasis are demonstrated. The developed phosphorous dendron micelles may hold great promise to be used as an advanced nanomedicine formulation for synergistic modulation of multiple immune cells through NK cell proliferation for effective chemoimmunotherapy of different tumor types.

Bioinspired nanocatalytic tumor therapy by simultaneous reactive oxygen species generation enhancement and glutamine pathway-mediated glutathione depletion

An insufficient intracellular H₂O₂ level and overexpressed glutathione (GSH) are still the major challenges for effective chemodynamic therapy (CDT). Inspired by the unique glutamine metabolism pathway in cancer cells, herein, intelligent nanocatalytic theranostics is used to enhance intracellular reactive oxygen species (ROS) accumulation via the production of H₂O₂ by a biomimetic nanozyme, and simultaneously reduce ROS consumption via the depression of GSH synthesis by the glutamine metabolic inhibitor. In this reactor, nano-sized Au and Fe₃O₄ coloaded dendritic mesoporous silica nanoparticles (DMSN-Au-Fe₃O₄) serve as the bifunctional nanozyme, where intracellular glucose is catalyzed into H₂O₂ by the glucose oxidase-mimicking Au nanoparticles and then immediately transformed into ˙OH by the peroxidase-like Fe₃O₄ nanoparticles. Then, CB839, the glutaminase (GLS) inhibitor, is grafted on the nanozyme, blocking the glutamine pathway and GSH biosynthesis. As a result, the as-designed nanoplatform with a three-pronged integration of Au-mediated H₂O₂ self-supply, Fe₃O₄-triggered Fenton-like reaction, and glutamine pathway-mediated GSH depletion significantly boosts the CDT efficacy, achieving remarkable and specific antitumor properties both in vitro and in vivo. This work not only paves a new way for rationally designing multi-functional nanozymes for achieving high therapeutic efficacy, but also provides new insights into the construction of bioinspired synergetic therapy by combining CDT and a key anticancer pathway.

Synergistic Reinforcing of Immunogenic Cell Death and Transforming Tumor-Associated Macrophages Via a Multifunctional Cascade Bioreactor for Optimizing Cancer Immunotherapy

Immunogenic cell death (ICD) has aroused widespread attention because it can reconstruct a tumor microenvironment and activate antitumor immunity. This study proposes a two-way enhancement of ICD based on a CaO₂ @CuS-MnO₂ @HA (CCMH) nanocomposite to overcome the insufficient damage-associated molecular patterns (DAMPs) of conventional ICD-inducers. The near-infrared (NIR) irradiation (1064 nm) of CuS nanoparticles generates ¹ O₂ through photodynamic therapy (PDT) to trigger ICD, and it also damages the Ca²⁺ buffer function of mitochondria. Additionally, CaO₂ nanoparticles react with H₂ O to produce a large amount of O₂ and Ca²⁺ , which respectively lead to enhanced PDT and Ca²⁺ overload during mitochondrial damage, thereby triggering a robust ICD activation. Moreover, oxidative-damaged mitochondrial DNA, induced by PDT and released from tumor cells, reprograms the immunosuppressive tumor microenvironment by transforming tumor-associated macrophages to the M1 subphenotype. This study shows that CCMH with NIR-II irradiation can elicit adequate DAMPs and an active tumor-immune microenvironment for both 4T1 and CT26 tumor models. Combining this method with an immune checkpoint blockade can realize an improved immunotherapy efficacy and long-term protection effect for body.

Cancer Cell Membrane Biomimetic Mesoporous Nanozyme System with Efficient ROS Generation for Antitumor Chemoresistance

Single-atom nanozymes (SAZs) with reaction specificity and optimized catalytic properties have great application prospects in tumor therapy. But the complex tumor microenvironment (low content of H2O2) limits its therapeutic effect. In this study, we developed a bionic mesoporous Fe SAZs/DDP nanosystem (CSD) for enhanced nanocatalytic therapy (NCT)/chemotherapy by simultaneously encapsulating the chemotherapeutic drugs cisplatin (DDP) and Fe SAZs with high peroxidase (POD) activity into the cancer cell membrane. CSD could evade immune recognition and actively targets tumor sites, and DDP upregulates endogenous H2O2 levels by activating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, thereby enhancing SAZs-mediated hydroxyl radical (·OH) production, which subsequently leads to mitochondrial damage and intolerance to chemotherapy drug. We used the HGC27/DDP cell line for in vitro and in vivo experiments. The results showed that CSD achieved good therapeutic benefits, without any side effects such as inflammatory reaction. This system can induce multiple antitumor effect with H2O2 self-supply, mitochondrial damage, and ATP downregulation and eventually lead to chemosensitization.

Interface-Engineered Mesoporous with Programmed Drug Release for Synergistic Cancer Theranostics

The pursuit of mesoporous Fe-based nanoagents addresses the field of developing alternative Fe-bearing nanoagents for synergistic cancer therapy with the expectation that the use of an essential element may avoid the issues raised by the exogenous administration of other metal element-based nanoagents. Herein, we highlight the interface-engineered mesoporous FeB (mFeB) where the core mFeB is interfacially oxidized into an FeOOH nanosheet loaded with the chemotherapeutic drug doxorubicin (DOX) and further encapsuled within the double-sulfide-bonded SiO₂ outer layer, denoted as mFeB@DOX-ss-SiO₂, which can realize programmed drug release for synergistic cancer theranostics. When only in a tumor microenvironment, the nanoagent can be activated to release DOX from the mFeB and FeOOH nanosheets as well as expose the easily oxidized mFeB to spontaneously transform to FeOOH nanosheets with Fenton activity to facilitate chemodynamic therapy (CDT). In addition, the high photothermal conversion efficiency of mFeB@DOX-ss-SiO₂ would promote CDT. Also, owing to the inherent nature of ferromagnetism and red fluorescence of DOX, mFeB@DOX-ss-SiO₂ can realize T2-weighted magnetic resonance imaging and fluorescence imaging. In vivo mouse model experiments demonstrate that mFeB@DOX-ss-SiO₂ with good biocompatibility realizing CDT/photothermal therapy/chemotherapy achieved complete tumor suppression. This study opens up a new way to explore theranostic nanoagents.

Crizotinib prodrug micelles co-delivered doxorubicin for synergistic immunogenic cell death induction on breast cancer chemo-immunotherapy

Chemotherapeutic agents can trigger the immune response via inducing immunogenic cell death (ICD), but the weak ICD effect induced by chemotherapy alone limits its lasting antitumor immunotherapy effect. A Cro polymerized prodrug carriers (POEG-b-PCro) with immunostimulatory by ICD induction was developed and co-delivered DOX to generate synergistic ICD induction for chemo-immunotherapy on breast cancer. DOX/POEG-b-PCro micelles displayed prolonged circulation in blood, efficient accumulation in tumors, internalization and then co-released DOX&Cro in tumor cells. Moreover, the DOX/POEG-b-PCro micelles synergistically triggered ICD induction by releasing the nuclear high mobility group box 1 (HMGB1) and down-regulation of c-Met level for generating chemo-immune anti-tumor actions. Importantly, the DOX/POEG-b-PCro micelles synergistically enhanced the tumor cytotoxic T lymphocytes infiltration, concomitant decreasing the immunosuppressive regulatory T (Treg) cells, accompanied with the increased cytokines secretion of IFN-γ and TNF-α, consequently displaying an improved anti-tumor activity in 4T1 breast cancer mice. Overall, POEG-b-PCro prodrug micelles co-delivered DOX could be served as a promising nano drug delivery system for synergistic ICD induction on breast cancer chemo-immunotherapy.

Glucose Metabolism Intervention-Facilitated Nanomedicine Therapy

Ordinarily, cancer cells possess features of abnormally increased nutrient intake and metabolic pathways. The disorder of glucose metabolism is the most important among them. Therefore, starvation therapy targeting glucose metabolism specifically, which results in metabolic disorders, restricted synthesis, and inhibition of tumor growth, has been developed for cancer therapy. However, issues such as inadequate targeting effectiveness and drug tolerance impede their clinical transformation. In recent years, nanomaterial-assisted starvation treatment has made significant progress in addressing these challenges, whether as a monotherapy or in combination with other medications. Herein, representative researches on the construction of nanosystems conducting starvation therapy are introduced. Elaborate designs and interactions between different treatment mechanisms are meticulously mentioned. Not only are traditional treatments based on glucose oxidase involved, but also newly sprung small molecule agents targeting glucose metabolism. The obstacles and potential for advancing these anticancer therapies were also highlighted in this review.

Salicylic acid-based hypoxia-responsive chemodynamic nanomedicines boost antitumor immunotherapy by modulating immunosuppressive tumor microenvironment

The delivery of salicylic acid or its derivatives to tumor tissue in the form of nanomedicine is critical for the studies on their potential synergistic mechanism in tumor therapy and chemoprevention considering the dangerous bleeding in the high-dose oral administration. To deepen the understanding of their role in adjusting immunosuppressive tumor microenvironment (ITM), herein, we firstly developed a hypoxia-sensitive Fe-5,5'-azosalicylic acid nanoscale coordination polymer nanomedicines (FeNCPs) via a "old drugs new tricks" strategy for synergistic chemodynamic therapy (CDT) and remodulation of ITM to elevate antitumor immunotherapy effect. PEGylated FeNCPs could be reductively cleaved to release 5-aminosalicylic acid (5-ASA) and ferric ions by azo-reductase under hypoxic conditions, which could induce tumor cell death by Fenton reaction-catalysis enhanced CDT and 5-ASA-converted carboxylquinone to promote the production of •OH. Meanwhile, cyclooxygenase-2 (COX-2) and its enzymatic product prostaglandin E₂ (PGE₂), as immune negative regulatory molecules, can promote tumor progression and immune tolerance. The released 5-ASA as a COX inhibitor could suppress the expression of PGE₂, and Fe³⁺ was employed to reeducate M2-like tumor-associated macrophages (TAMs) to M1-like phenotype, which could initiate antitumor immune response to reach better antitumor immunotherapy. This work broadens the application of salicylic acid derivatives in antitumor immunotherapy, and provides a new strategy for their "old drugs new tricks". STATEMENT OF SIGNIFICANCE: Cyclooxygenase-2 (COX-2) and its enzymatic product prostaglandin E2 (PGE₂), as immune negative regulatory molecules, facilitate the differentiation of immune cells into immunosuppressive cells to build the immunosuppressive tumor microenvironment, which can promote tumor progression and immune tolerance. Thus, down-regulation of COX-2/PGE₂ expression may be a key approach to tumor treatments. Meanwhile, as a class of inhibitors of COX-2/PGE₂, the potential mechanism of aspirin or 5-aminosalicylic acid has been a mystery in tumor therapy and chemoprevention. To expand the application of aspirin family nanomedicine in biomedicine, herein, we firstly developed a hypoxia-sensitive Fe-5,5'-azosalicylic acid nanoscale coordination polymer nanomedicines via a "old drugs new tricks" strategy for synergistic chemodynamic therapy and remodulation of immunosuppressive tumor microenvironment to elevate antitumor immunotherapy effect.

Mn2+ /Fe3+ /Co2+ and Tetrasulfide Bond Co-Incorporated Dendritic Mesoporous Organosilica as Multifunctional Nanocarriers: One-Step Synthesis and Applications for Cancer Therapy

Enriching the application of multifunctional dendritic mesoporous organosilica (DMOS) is still challenging in anti-cancer research. Herein, manganese ions, iron ions, or cobalt ions and tetrasulfide bonds are co-incorporated into the framework of DMOS to yield multifunctional nanoparticles denoted as Mn-DMOS, Fe-DMOS, or Co-DMOS by directly doping metal ions during the synthetic process. Due to co-incorporation of metal ions and tetrasulfide bonds, these designed nanocarriers have more functions rather than only for cargo delivery. As proof of concept, the nanocomposite is established based on Mn-DMOS as an efficient nanocarrier for indocyanine green (ICG) delivery and modification with polyethylene glycol. In the tumor microenvironment, the generated hydrogen sulfide (H₂ S) arising from the reaction between tetrasulfide bond and over-expressed glutathione (GSH) causes mitochondrial injury to reduce cellular respiration. The released Mn²⁺ from the rapidly decomposed nanocomposite catalyzes the endogenous hydrogen peroxide to produce oxygen (O₂ ). The photothermal effect from the released ICG initiated by the near-infrared light induces cancer cells apoptosis and simultaneously enhances the content of blood O₂ at tumor sites. Therefore, due to the GSH depletion and trimodal O₂ compensation, the photodynamic therapy efficiency of ICG has significantly improved. In brief, these designed nanocarriers will play advanced roles in cancer therapy.

A carrier-free photodynamic nanodrug to enable regulation of dendritic cells for boosting cancer immunotherapy

Immune response is initiated by dendritic cells (DCs), where the cross-presentation of antigens by DCs determines the activating of cytotoxic T cells. However, the efficacy of DCs-initiated immune response is governed by multiple (cascade) steps of immunogenic cell death (ICD), recruitment of DCs, and cross-presentation of DCs. It is urgent but challenging to achieve a platform for simultaneously regulating these multiple steps, amplifying the immune response against tumors. Herein, we reported a photodynamic nanodrug enabling simultaneous regulation of these multiple steps for realizing powerful immune response. The nanodrug was designed by the co-assembling of chlorin e6 (Ce6), celecoxib and 6-thio-2'-deoxyguanosine (6-thio-dG). In our nanodrug, Ce6 enables induction of ICD, while celecoxib down-regulates the prostaglandin E2 (PGE2) for promoting recruitment of DCs enabled by chemokine CCL5 produced from natural killer (NK) cells. Moreover, 6-thio-dG triggers DNA damages in the tumor cells, which in turn activates STING/interferon I pathway for enhancing the cross-presentation ability of DCs. Therefore, an amplified immune therapeutic effect against tumors is achieved, thanks to the simultaneous regulation of these multiple steps. The nanodrug effectively inhibits tumor growth and postoperative recurrence, demonstrating a new approach for boosting immune response initiated by DCs in cancer therapy. STATEMENT OF SIGNIFICANCE: The dendritic cells (DCs)-initiated immune response against tumors is dominated by multiple (cascade) steps including the process of (I) immunogenic cell death (ICD), (II) recruitment of DCs, and (III) cross-presentation of antigens by DCs. Based on this, it is urgent to design a nanoplatform enabling simultaneous regulation of these multiple steps for achieving a potent therapeutic efficacy. A carrier-free photodynamic nanodrug, engineered by a co-assembling approach, was designed to regulate DCs for realizing a powerful DCs-initiated immune response against tumors, thanks to the simultaneous regulation of the above multiple steps. Our nanodrug demonstrated a boosted immune response against tumors, powerfully suppressing primary/abscopal tumor growth and postoperative recurrence, which offers a conceptually innovative strategy for amplifying immunity against tumors.

Cascade targeting codelivery of ingenol-3-angelate and doxorubicin for enhancing cancer chemoimmunotherapy through synergistic effects in prostate cancer

Immunotherapy has led to an expansion of the treatment of malignancies, but its effect in prostate cancer (PCa) patients is modest. Chemoimmunotherapy is a promising approach that has attracted substantial attention. Although the widely used clinical chemotherapeutic drug doxorubicin (DOX) elicits immunogenic cell death (ICD), its weak ICD effect and the abnormal vasculature of tumors severely limit its efficacy in chemoimmunotherapy. Ingenol-3-angelate (I3A), an emerging antitumor drug with dual chemotherapeutic and immune response-eliciting effects, is expected to exert synergistic effects when administered in combination with DOX. I3A induces the ICD of PCa cells by triggering mitophagy and apoptosis and promotes the normalization of tumor vessels, resulting in sufficient infiltration of immune cells into tumors. A synergistic effect of I3A and DOX was observed in vitro at a molar ratio of 1:4. To codeliver this ratio of I3A and DOX to tumor and ensure their uptake, we designed a dual-targeting delivery system, polylactide-poly(ethylene) glycol-2-(3-((S)-5-amino-1-carboxypentyl)-ureido) pentanedioate/triphenylphosphonium (PLA-PEG-ACUPA/TPP), which targets prostate-specific membrane antigen (PSMA) and mitochondria. Delivery of these nanomedicines led to inhibited tumor growth and a strong antitumor immune response. This study sheds light on the mitophagic and antiangiogenic mechanisms underlying I3A treatment of PCa and provides a strategy for combining vascular normalization and chemoimmunotherapy for PCa treatment.

Nanozyme Catalytic Turnover and Self-Limited Reactions

Enzymes have catalytic turnovers. The field of nanozyme endeavors to engineer nanomaterials as enzyme mimics. However, a discrepancy in the definition of "nanozyme concentration" has led to an unrealistic calculation of nanozyme catalytic turnovers. To date, most of the reported works have considered either the atomic concentration or nanoparticle (NP) concentration as nanozyme concentration. These assumptions can lead to a significant under- or overestimation of the catalytic activity of nanozymes. In this article, we review some classic nanozymes including Fe₃O₄, CeO₂, and gold nanoparticles (AuNPs) with a focus on the reported catalytic activities. We argue that only the surface atoms should be considered as nanozyme active sites, and then the turnover numbers and rates were recalculated based on the surface atoms. According to the calculations, the catalytic turnover of peroxidase Fe₃O₄ NPs is validated. AuNPs are self-limited when performing glucose-oxidase like activity, but they are also true catalysts. For CeO₂ NPs, a self-limited behavior is observed for both oxidase- and phosphatase-like activities due to the adsorption of reaction products. Moreover, the catalytic activity of single-atom nanozymes is discussed. Finally, a few suggestions for future research are proposed.

Fenton/Fenton-like metal-based nanomaterials combine with oxidase for synergistic tumor therapy

Chemodynamic therapy (CDT) catalyzed by transition metal and starvation therapy catalyzed by intracellular metabolite oxidases are both classic tumor treatments based on nanocatalysts. CDT monotherapy has limitations including low catalytic efficiency of metal ions and insufficient endogenous hydrogen peroxide (H₂O₂). Also, single starvation therapy shows limited ability on resisting tumors. The “metal-oxidase” cascade catalytic system is to introduce intracellular metabolite oxidases into the metal-based nanoplatform, which perfectly solves the shortcomings of the above-mentioned monotherapiesIn this system, oxidases can not only consume tumor nutrients to produce a “starvation effect”, but also provide CDT with sufficient H₂O₂ and a suitable acidic environment, which further promote synergy between CDT and starvation therapy, leading to enhanced antitumor effects. More importantly, the “metal-oxidase” system can be combined with other antitumor therapies (such as photothermal therapy, hypoxia-activated drug therapy, chemotherapy, and immunotherapy) to maximize their antitumor effects. In addition, both metal-based nanoparticles and oxidases can activate tumor immunity through multiple pathways, so the combination of the “metal-oxidase” system with immunotherapy has a powerful synergistic effect. This article firstly introduced the metals which induce CDT and the oxidases which induce starvation therapy and then described the “metal-oxidase” cascade catalytic system in detail. Moreover, we highlight the application of the “metal-oxidase” system in combination with numerous antitumor therapies, especially in combination with immunotherapy, expecting to provide new ideas for tumor treatment.