Sonodynamic Cytokine Nanocomplexes with Specific Stimulation towards Effector T Cell for Combination Cancer Immunotherapy

Cytokine therapy mediates the interaction between immune cells and non-immune cells in the tumor microenvironment (TME), forming a promising approach in cancer therapy. However, the dose-dependent adverse effects and non-selective stimulation of cytokines limit their clinical use. We herein report a sonodynamic cytokine nano-immunocomplex (SPN_AI) that specifically activates effector T cells (Teffs) for antitumor immunotherapy. By conjugating anti-interleukin-2 (anti-IL-2) antibodies S4B6 on the semiconducting polymer nanoparticles to afford SPN_A, this nanoantibody SPN_A can bind with IL-2 to form SPN_AI which can block the interaction between IL-2 and regulatory T cells (Tregs), selectively activating Teffs in TME. Moreover, SPN_AI generates ¹O₂ to trigger immunogenic cell death of cancer cells upon sono-irradiation, which promotes the maturation of dendritic cells and the proliferation of Teffs. This SPN_AI-mediated combination sonodynamic immunotherapy thus elevates the ratio of Teffs/Tregs in TME, resulting in inhibition of tumor growth, suppression of lung metastasis and prevention of tumor relapse.     

A Semiconducting Iron-Chelating Nano-immunomodulator for Specific and Sensitized Sono-metallo-immunotherapy of Cancer

Sono-immunotherapy holds great potential for deep tumor inhibition; however, smart sono-therapeutic agents to simultaneously eliminate ‘domestic’ tumor cells and regulate the ‘community’ tumor immune microenvironment have rarely been developed. Herein, we report a spatiotemporally controllable semiconducting iron-chelated nano-metallomodulator (SINM) for hypersensitive sono-metallo-immunotherapy of cancer. SINM consists of a semiconducting polymer (SP) backbone chelating iron ions (Fe³⁺) with thiophene-based Schiff base structure, and a hydrophilic side chain. Upon accumulation in tumors after systemic administration, SINM specifically arouses ferroptosis and M1 macrophage polarization due to its response toward the tumor redox environment; meanwhile, the chelation of Fe³⁺ enhances the sono-sensitizing effect of SPs, leading to enhanced generation of reactive oxygen species for immunogenic cell death. Such combined sonodynamic metallo-immunotherapy of SINM efficiently ablates deep tumor and spatiotemporally regulates immunophenotypes.     

Targeted Protein Upregulation of STING for Boosting the Efficacy of Immunotherapy

Modulating target proteins via the ubiquitin-proteasome system has recently expanded the scope of pharmacological inventions. Stimulator of interferon genes (STING) is an auspicious target for immunotherapy. Seminal studies envisioned the importance of STING as well as the utility of its agonists in immunotherapy outcomes. Herein, we suggest UPPRIS (upregulation of target proteins by protein-protein interaction strategy) to pharmacologically increase cellular STING levels for improved immunotherapy. We discovered the small molecule SB24011 that inhibits STING-TRIM29 E3 ligase interaction, thus blocking TRIM29-induced degradation of STING. SB24011 enhanced STING immunity by upregulating STING protein levels, which robustly potentiated the immunotherapy efficacy of STING agonist and anti-PD-1 antibody via systemic anticancer immunity. Overall, we demonstrated that targeted protein upregulation of STING can be a promising approach for immuno-oncology.     

Smart Nanosensitizers for Activatable Sono-Photodynamic Immunotherapy of Tumors by Redox-Controlled Disassembly

Tumor-targeted and stimuli-activatable nanosensitizers are highly desirable for cancer theranostics. However, designing smart nanosensitizers with multiple imaging signals and synergistic therapeutic activities switched on is challenging. Herein, we report tumor-targeted and redox-activatable nanosensitizers ( 1-NPs ) for sono-photodynamic immunotherapy of tumors by molecular co-assembly and redox-controlled disassembly. 1-NPs show a high longitudinal relaxivity (r₁=18.7±0.3 mM⁻¹ s⁻¹), but “off” dual fluorescence (FL) emission (at 547 and 672 nm), “off” sono-photodynamic therapy and indoleamine 2,3-dioxygenase 1 (IDO1) inhibition activities. Upon reduction by glutathione (GSH), 1-NPs rapidly disassemble and remotely release small molecules 2-Gd , Zn-PPA-SH and NLG919, concurrently switching on (1) dual FL emission, (2) sono-photodynamic therapy and (3) IDO1 inhibition activities. After systemic injection, 1-NPs are effective for bimodal FL and magnetic resonance (MR) imaging-guided sono-photodynamic immunotherapy of orthotropic breast and brain tumors in mice under combined ultrasound (US) and 671-nm laser irradiation.     

A Polymeric Extracellular Matrix Nanoremodeler for Activatable Cancer Photo-Immunotherapy

Cancer immunotherapy has shown tremendous potential to train the intrinsic immune system against malignancy in the clinic. However, the extracellular matrix (ECM) in tumor microenvironment is a formidable barrier that not only restricts the penetration of therapeutic drugs but also prevents the infiltration of antitumor immune cells. We herein report a semiconducting polymer-based ECM nanoremodeler (SPNcb) to combine photodynamic antitumor activity with cancer-specific inhibition of collagen-crosslinking enzymes (lysyl oxidase (LOX) family) for activatable cancer photo-immunotherapy. SPNcb is self-assembled from an amphiphilic semiconducting polymer conjugated with a LOX inhibitor (β-aminopropionitrile, BAPN) via a cancer biomarker (cathepsin B, CatB)-cleavable segment. BAPN can be exclusively activated to inhibit LOX activity in the presence of the tumor-overexpressed CatB, thus blocking collagen crosslinking and decreasing ECM stiffness. Such an ECM nanoremodeler synergizes immunogenic phototherapy and checkpoint blockade immunotherapy to improve the tumor infiltration of cytotoxic T cells, inhibiting tumor growth and metastasis.     

Glutathione-Induced In Situ Michael Addition between Nanoparticles for Pyroptosis and Immunotherapy

Most tumor treatments will fail when ignoring competition and cooperation between each cancer cell and its microenvironment. Inspired by game theory, therapeutic agents can be introduced to compete for intracellular molecules to disrupt the cooperation between molecules and cells. Biomineralized oxidized (−)-epigallocatechin-3-o-gallate (EGCG)–molybdenum ion coordination nanoparticles were prepared for disrupting redox equilibria and simultaneously reacting with intracellular GSH in a Michael addition to form large aggregates that can mechanically disrupt endosomal and plasma membranes, stimulating pyroptosis and anti-tumor immunological responses for versatile inhibition of different types of tumors. This design disrupts the cooperation between molecules and between cancer and immune cells, achieving an optimal payoff in competition and cooperation in cancer therapy.     

Targeted Degradation of PD-L1 and Activation of the STING Pathway by Carbon-Dot-Based PROTACs for Cancer Immunotherapy

Proteolysis targeting chimeras (PROTACs) technology is an emerging approach to degrade disease-associated proteins. Here, we report carbon-dot (CD)-based PROTACs (CDTACs) that degrade membrane proteins via the ubiquitin-proteasome system. CDTACs can bind to programmed cell death ligand 1 (PD-L1), recruit cereblon (CRBN) to induce PD-L1 ubiquitination, and degrade them with proteasomes. Fasting-mimicking diet (FMD) is also used to enhance the cellular uptake and proteasome activity. More than 99 % or 90 % of PD-L1 in CT26 or B16-F10 tumor cells can be degraded by CDTACs, respectively. Furthermore, CDTACs can activate the stimulator of interferon genes (STING) pathway to trigger immune responses. Thus, CDTACs with FMD treatment effectively inhibit the growth of CT26 and B16-F10 tumors. Compared with small-molecule-based PROTACs, CDTACs offer several advantages, such as efficient membrane protein degradation, targeted tumor accumulation, immune system activation, and in vivo detection.     

Reticular Chemistry-Enabled Sonodynamic Activity of Covalent Organic Frameworks for Nanodynamic Cancer Therapy

The development of covalent organic framework (COF) sonosensitizers with intrinsic sonodynamic effects is highly desirable. However, such COFs are generally constructed using small-molecule photosensitizers. Herein, we report that the reticular chemistry-based synthesis of COFs from two inert monomers yields a COF-based sonosensitizer (TPE-NN) with inherent sonodynamic activity. Subsequently, a nanoscale COF TPE-NN is fabricated and embedded with copper (Cu)-coordinated sites to obtain TPE-NN-Cu. Results show that Cu coordination can enhance the sonodynamic effect of TPE-NN, whereas ultrasound (US) irradiation for sonodynamic therapy can augment the chemodynamic efficacy of TPE-NN-Cu. Consequently, TPE-NN-Cu upon US irradiation shows high-performance anticancer effects based on mutually reinforced sono-/chemo-nanodynamic therapy. This study reveals the backbone-originated sonodynamic activity of COFs and proposes a paradigm of intrinsic COF sonosensitizers for nanodynamic therapy.     

Activatable Semiconducting Polymer Pro-nanomodulators for Deep-Tissue Sono-immunotherapy of Orthotopic Pancreatic Cancer

Immunotherapy has provided a promising modality for cancer treatment, while it often has the issues of limited response rates and potential off-target side effects in clinical practice. We herein report the construction of semiconducting polymer pro-nanomodulators (SPpMs) with ultrasound (US)-mediated activatable pharmacological actions for deep-tissue sono-immunotherapy of orthotopic pancreatic cancer. Such SPpMs consist of a sonodynamic semiconducting polymer backbone grafted with poly(ethylene glycol) chains linked with two immunomodulators (a programmed death-ligand 1 blocker and an indoleamine 2,3-dioxygenase inhibitor) via a singlet oxygen (¹O₂)-cleavable segment. In view of the excellent sonodynamic property of the semiconducting polymer core, SPpMs enable effective generation of ¹O₂ under US treatment, even in a deep-tissue depth up to 12 cm. The generated ¹O₂ not only ablates tumors via a sonodynamic effect and induces immunogenic cell death, but also destroys the ¹O₂-cleavable segments to allow in situ release of immunomodulators in tumors. This synergetic action results in boosted antitumor immune response via reversing two tumor immunosuppressive pathways. As such, SPpMs mediate deep-tissue sono-immunotherapy to completely eradicate orthotopic pancreatic cancer and effectively prevent tumor metastasis. Moreover, such an immune activation reduces the possibility of immune-related adverse events. This study thus provides a smart activatable nanoplatform for precise immunotherapy of deep-seated tumors.     

Activation of Stimulation of Interferon Genes (STING) Signal and Cancer Immunotherapy

Stimulator of interferon gene (STING), an intracellular receptor in the endoplasmic reticulum, could induce the production of cytokines such as type I interferon (IFN) by activating the cGAS-STING signal pathway. In recent years, activation of STING has shown great potential to enhance anti-tumor immunity and reshape the tumor microenvironment, which is expected to be used in tumor immunotherapy. A number of STING agonists have demonstrated promising biological activity and showed excellent synergistic anti-tumor effects in combination with other cancer therapies in preclinical studies and some clinical trials. The combination of STING agonists and ICI also showed a potent effect in improving anti-tumor immunity. In this review, we introduce the cGAS-STING signaling pathway and its effect in tumor immunity and discuss the recent strategies of activation of the STING signaling pathway and its research progress in tumor immunotherapy.     

Construction of Multiform Hollow-Structured Covalent Organic Frameworks via a Facile and Universal Strategy for Enhanced Sonodynamic Cancer Therapy

The special structural morphology of hollow covalent organic frameworks (HCOFs) has an important influence on their applications. However, the rapid and precise control of morphology for HCOFs still remains largely challenging. Herein, we present a facile and universal two-step strategy based on solvent evaporation and oxidation of imine bond for the controllable synthesis of HCOFs. The strategy enables to prepare HCOFs in a greatly shortened reaction time and seven kinds of HCOFs are fabricated by the oxidation of imine bond via hydroxyl radicals (⋅OH) generated from Fenton reaction. Importantly, a fascinating library of HCOFs with diverse nanostructures, including bowl-like, yolk-shell, capsule-like and flower-like morphologies, has been ingeniously constructed. Owing to the large cavities, the obtained HCOFs are ideal candidates for drug delivery, which are employed to load five small molecule drugs, achieving the enhanced sonodynamic cancer therapy in vivo.     

Bioorthogonal Reaction-Mediated Tumor-Selective Delivery of CRISPR/Cas9 System for Dual-Targeted Cancer Immunotherapy

CRISPR system-assisted immunotherapy is an attractive option in cancer therapy. However, its efficacy is still less than expected due to the limitations in delivering the CRISPR system to target cancer cells. Here, we report a new CRISPR/Cas9 tumor-targeting delivery strategy based on bioorthogonal reactions for dual-targeted cancer immunotherapy. First, selective in vivo metabolic labeling of cancer and activation of the cGAS-STING pathway was achieved simultaneously through tumor microenvironment (TME)-biodegradable hollow manganese dioxide (H-MnO₂) nano-platform. Subsequently, CRISPR/Cas9 system-loaded liposome was accumulated within the modified tumor tissue through in vivo click chemistry, resulting in the loss of protein tyrosine phosphatase N2 (PTPN2) and further sensitizing tumors to immunotherapy. Overall, our strategy provides a modular platform for precise gene editing in vivo and exhibits potent antitumor response by boosting innate and adaptive antitumor immunity.     

Enhancing the immune response and tumor suppression effect of antitumor vaccines adjuvanted with non-nucleotide small molecule STING agonist

Vaccine adjuvants have been widely used to enhance the immunogenicity of the antigens and elicit long-lasting immune response. However, only few vaccine adjuvants have been approved by the FDA for human use so far. Therefore, there is still an urgent need to develop novel adjuvants for the potential applications in clinical trials. Herein, non-nucleotide small molecule STING agonist di ABZI was employed to construct glycopeptide antigen based vaccines for the first time. Immunological evaluation indicated di ABZI not only enhanced the production of antibodies and T cell immune responses, but also inhibited tumor growth in tumor-bearing mice in glycopeptide-based subunit vaccines. These results indicated that di-ABZI demonstrates a high potential as adjuvant for the development of cancer vaccines.     

Aptamer-Assisted Blockade of the Immune Suppressor Sialic Acid-Binding Immunoglobulin-Like Lectin-15 for Cancer Immunotherapy

The percentage of low response and adaptive resistance to current antibody-based immune checkpoint blockade (ICB) therapy requires the development of novel immunotherapy strategies. Here, we developed an aptamer-assisted immune checkpoint blockade (Ap-ICB) against sialic acid-binding immunoglobulin-like lectin-15 (Siglec-15), a novel immune suppressor broadly upregulated on cancer cells and tumor infiltrating myeloid cells, which is mutually exclusive of programmed cell death ligand 1 (PD-L1). Using protein aptamer selection, we identified WXY3 aptamer with high affinity against Siglec-15 protein/Siglec-15 positive cells. We demonstrated that WXY3 aptamer rescued antigen-specific T cell responses in vitro and in vivo. Importantly, the WXY3 Ap-ICB against Siglec-15 amplified anti-tumor immunity in the tumor microenvironment and inhibited tumor growth/metastasis in syngeneic mouse model, which may result from enhanced macrophage and T cell functionality. In addition, by using aptamer-based spherical nucleic acids, we developed a synergetic ICB strategy of multivalent binding and steric hindrance, which further improves the in vivo anti-tumor effect. Taken together, our results support Ap-ICB targeted Siglec-15 as a potential strategy for normalization cancer immunotherapy.     

Dual-Targeting Biomimetic Semiconducting Polymer Nanocomposites for Amplified Theranostics of Bone Metastasis

Bone metastasis is a type of metastatic tumors that involves the spreads of malignant tumor cells into skeleton, and its diagnosis and treatment remain a big challenge due to the unique tumor microenvironment. We herein develop osteoclast and tumor cell dual-targeting biomimetic semiconducting polymer nanocomposites (SPFeN_OC) for amplified theranostics of bone metastasis. SPFeN_OC contain semiconducting polymer and iron oxide (Fe₃O₄) nanoparticles inside core and surface camouflaged hybrid membrane of cancer cells and osteoclasts. The hybrid membrane camouflage enables their targeting to both metastatic tumor cells and osteoclasts in bone metastasis through homologous targeting mechanism, thus achieving an enhanced nanoparticle accumulation in tumors. The semiconducting polymer mediates near-infrared (NIR) fluorescence imaging and sonodynamic therapy (SDT), and Fe₃O₄ nanoparticles are used for magnetic resonance (MR) imaging and chemodynamic therapy (CDT). Because both cancer cells and osteoclasts are killed synchronously via the combinational action of SDT and CDT, the vicious cycle in bone metastasis is broken to realize high antitumor efficacy. Therefore, 4T1 breast cancer-based bone metastasis can be effectively detected and cured by using SPFeN_OC as dual-targeting theranostic nanoagents. This study provides an unusual biomimetic nanoplatform that simultaneously targets osteoclasts and cancer cells for amplified theranostics of bone metastasis.     

STING-activating drug delivery systems:Design strategies and biomedical applications

The stimulator of interferon genes(STING) shows promising clinical activity in infectious diseases and tumors.However,the lack of targeting capability and intracellular stability of STING agonists severely limits the therapeutic efficacy.Recently,drug delivery systems(DDSs) overcome these delivery barriers of STING agonists via passive or active cell targeting,prolonged blood circulation and drug release,and lysosome escape,etc.In this review,we will describe in detail how existing DDSs are designed to overcome delivery barriers and activate the STING pathway,and the current biomedical applications of STING-activating DDSs in the treatments of infectious diseases and tumors.Finally,the prospects and challenges of DDSs in STING activation are discussed.     

Organic-Platinum Hybrids for Covalent Binding of G-Quadruplexes: Structural Basis and Application to Cancer Immunotherapy

G-quadruplexes (G4s) have been revived as promising therapeutic targets with the development of immunotherapy, but the G4-mediated immune response remains unclear. We designed a novel class of G4-binding organic-platinum hybrids, L¹-cispt and L¹-transpt , with spatial matching for G4 binding and G4 DNA reactivity for binding site locking. The solution structure of L¹-transpt -MYT1L G4 demonstrated the effectiveness of the covalent binding and revealed the covalent binding-guided dynamic balance, accompanied by the destruction of the A5-T17 base pairs to achieve the covalent binding of the platinum unit to N7 of the G6 residue. Furthermore, L¹-cispt- and L¹-transpt- mediated genomic dysfunction could activate the retinoic acid-induced gene I (RIG-I) pathway and induce immunogenic cell death (ICD). The use of L¹-cispt/L¹-transpt- treated dying cells as therapeutic vaccines stimulated a robust immune response and effectively inhibited tumor growth in vivo. Our findings highlight the importance of the rational combination of specific spatial recognition and covalent locking in G4-trageting drug design and their potential in immunotherapy.     

Liquid Metal as Bioinspired and Unusual Modulator in Bioorthogonal Catalysis for Tumor Inhibition Therapy

Bioorthogonal catalysis mediated by Pd-based transition metal catalysts has sparked increasing interest in combating diseases. However, the catalytic and therapeutic efficiency of current Pd⁰ catalysts is unsatisfactory. Herein, inspired by the concept that ligands around metal sites could enable enzymes to catalyze astonishing reactions by changing their electronic environment, a LM-Pd catalyst with liquid metal (LM) as an unusual modulator has been designed to realize efficient bioorthogonal catalysis for tumor inhibition. The LM matrix can serve as a “ligand” to afford an electron-rich environment to stabilize the active Pd⁰ and promote nucleophilic turnover of the π-allylpalladium species to accelerate the uncaging process. Besides, the photothermal properties of LM can lead to the enhanced removal of tumor cells by photo-enhanced catalysis and photothermal effect. We believe that our work will broaden the application of LM and motivate the design of bioinspired bioorthogonal catalysts.     

Molecularly Imprinted Nanobeacons Redirect Innate Immune Killing towards Triple Negative Breast Cancer

Harnessing innate immunity is an appealing strategy for cancer treatment. Herein, we report a new strategy called molecularly imprinted nanobeacons (MINBs) for redirecting innate immune killing towards triple-negative breast cancer (TNBC). The MINBs were molecularly imprinted nanoparticles with the N-epitope of glycoprotein nonmetastatic B (GPNMB) as the template and grafted with plentiful fluorescein moieties as the hapten. The MINBs could tag the TNBC cells via binding with GPNMB and thereby provide navigation for recruiting hapten-specific antibodies. The gathered antibodies could further trigger effective Fc-domain-mediated immune killing towards the tagged cancer cells. In vivo experiments showed that the TNBC growth was significantly inhibited after MINBs treatment by intravenous injection as compared with control groups. This study not only opens a new access for redirecting innate immunity towards TNBC but also paves the way for innate immunity-based therapy of other diseases.     

Click-Chemistry-Mediated Cell Membrane Glycopolymer Engineering to Potentiate Dendritic Cell Vaccines

Dendritic cell vaccine (DCV) holds great potential in tumor immunotherapy owing to its potent ability in eliciting tumor-specific immune responses. Aiming at engineering enhanced DCV, we report the first effort to construct a glycopolymer-engineered DC vaccine (G-DCV) via metabolicglycoengineering and copper-free click-chemistry. Model G-DCV was prepared by firstly delivering tumor antigens, ovalbumin (OVA) into dendritic cells (DC) with fluoroalkane-grafted polyethyleneimines, followed by conjugating glycopolymers with a terminal group of dibenzocyclooctyne (DBCO) onto dendritic cells. Compared to unmodified DCV, our G-DCV could induce stronger T cell activation due to the enhanced adhesion between DCs and T cells. Notably, such G-DCV could more effectively inhibit the growth of the mouse B16-OVA (expressing OVA antigen) tumor model after adoptive transfer. Moreover, by combination with an immune checkpoint inhibitor, G-DCV showed further increased anti-tumor effects in treating different tumor models. Thus, our work provides a novel strategy to enhance the therapeutic effectiveness of DC vaccines.