The cGAS-STING pathway and cancer

Nanomedicines harnessing cGAS-STING pathway: sparking immune revitalization to transform 'cold' tumors into 'hot' tumors

cGAS-STING pathway stands at the forefront of innate immunity and plays a critical role in regulating adaptive immune responses, making it as a key orchestrator of anti-tumor immunity. Despite the great potential, clinical outcomes with cGAS-STING activators have been disappointing due to their unfavorable in vivo fate, signaling an urgent need for innovative solutions to bridge the gap in clinical translation. Recent advancements in nanotechnology have propelled cGAS-STING-targeting nanomedicines to the cutting-edge of cancer therapy, leveraging precise drug delivery systems and multifunctional platforms to achieve remarkable region-specific biodistribution and potent therapeutic efficacy. In this review, we provide an in-depth exploration of the molecular mechanisms that govern cGAS-STING signaling and its potential to dynamically modulate the anti-tumor immune cycle. We subsequently introduced several investigational cGAS-STING-dependent anti-tumor agents and summarized their clinical trial progress. Additionally, we provided a comprehensive review of the unique advantages of cGAS-STING-targeted nanomedicines, highlighting the transformative potential of nanotechnology in this field. Furthermore, we comprehensively reviewed and comparatively analyzed the latest breakthroughs cGAS-STING-targeting nanomedicine, focusing on strategies that induce cytosolic DNA generation via exogenous DNA delivery, chemotherapy, radiotherapy, or dynamic therapies, as well as the nanodelivery of STING agonists. Lastly, we discuss the future prospects and challenges in cGAS-STING-targeting nanomedicine development, offering new insights to bridge the gap between mechanistic research and drug development, thereby opening new pathways in cancer treatment.

Recent advances in the structure, function and regulation of the volume-regulated anion channels and their role in immunity

Volume-regulated anion channels (VRACs) are heteromeric complexes formed by proteins of the leucine-rich repeat-containing 8 (LRRC8) family. LRRC8A (also known as SWELL1) is the core subunit required for VRAC function, and it must combine with one or more of the other paralogues (i.e. LRRC8B-E) to form functional heteromeric channels. VRACs were discovered in T lymphocytes over 35 years ago and are found in virtually all vertebrate cells. Initially, these anion channels were characterized for their role in Cl- efflux during the regulatory volume decrease process triggered when cells are subjected to hypotonic challenges. However, substantial evidence suggests that VRACs also transport small molecules under isotonic conditions. These findings have expanded the research on VRACs to explore their functions beyond volume regulation. In innate immune cells, VRACs promote inflammation by modulating the transport of immunomodulatory cyclic dinucleotides, itaconate and ATP. In adaptive immune cells, VRACs suppress their function by taking up cyclic dinucleotides to activate the STING signalling pathway. In this review, we summarize the current understanding of LRRC8 proteins in immunity and discuss recent progress in their structure, function, regulation and mechanisms for channel activation and gating. Finally, we also examine potential immunotherapeutic applications of VRAC modulation.

Classification and functional characterization of regulators of intracellular STING trafficking identified by genome-wide optical pooled screening

Stimulator of interferon genes (STING) traffics across intracellular compartments to trigger innate responses. Mutations in factors regulating this process lead to inflammatory disorders. To systematically identify factors involved in STING trafficking, we performed a genome-wide optical pooled screen (OPS). Based on the subcellular localization of STING in 45 million cells, we defined 464 clusters of gene perturbations based on their cellular phenotypes. A secondary, higher-dimensional OPS identified 73 finer clusters. We show that the loss of the gene of unknown function C19orf25, which clustered with USE1, a protein involved in Golgi-to-endoplasmic reticulum (ER) transport, enhances STING signaling. Additionally, HOPS deficiency delayed STING degradation and consequently increased signaling. Similarly, GARP/RIC1-RGP1 loss increased STING signaling by delaying STING Golgi exit. Our findings demonstrate that genome-wide genotype-phenotype maps based on high-content cell imaging outperform other screening approaches and provide a community resource for mining factors that impact STING trafficking and other cellular processes.

Discovery of orally bioavailable phosphonate prodrugs of potent ENPP1 inhibitors for cancer treatment

Ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1) is the dominant hydrolase of 2',3'-cyclic GMP-AMP (cGAMP). Inhibition of ENPP1 contributes to increased cGAMP concentration and stimulator of interferon gene (STING) activation, with the potential to boost immune response against cancer. ENPP1 is a promising therapeutic target in tumor immunotherapy. To date, orally bioavailable ENPP1 inhibitors with highly potent activity under physiological conditions have been rarely reported. Herein, we report our effort in the design and synthesis of two different series of ENPP1 inhibitors, and in the identification of a highly potent ENPP1 inhibitor 27 (IC50 = 1.2 nM at pH 7.5), which significantly enhanced the cGAMP-mediated STING activity in THP-1 cells. Phosphonate compound 27 has good preclinical pharmacokinetic profiles with low plasma clearance rate in mouse, rat, and dog. It has been developed as bis-POM prodrug 36 which successfully improves the oral bioavailability of 27. In the Pan02 syngeneic mouse model of pancreatic cancer, orally administered 36 showed synergistic effect in combination with radiotherapy.

Immunotherapy for glioblastoma: current state, challenges, and future perspectives

Glioblastoma (GBM) is an aggressive and lethal type of brain tumor in human adults. The standard of care offers minimal clinical benefit, and most GBM patients experience tumor recurrence after treatment. In recent years, significant advancements have been made in the development of novel immunotherapies or other therapeutic strategies that can overcome immunotherapy resistance in many advanced cancers. However, the benefit of immune-based treatments in GBM is limited because of the unique brain immune profiles, GBM cell heterogeneity, and immunosuppressive tumor microenvironment. In this review, we present a detailed overview of current immunotherapeutic strategies and discuss the challenges and potential molecular mechanisms underlying immunotherapy resistance in GBM. Furthermore, we provide an in-depth discussion regarding the strategies that can overcome immunotherapy resistance in GBM, which will likely require combination therapies.

Arsenic trioxide induces innate immune response and inflammatory response in chicken liver via cGAS-STING/NF-κB pathway

Arsenic is a toxic metal-like element widely used in the pesticide, preservative and semiconductor industries. However, accumulation of arsenic through the food chain can cause serious damage to animal and human health. However, the toxic mechanism of arsenic-induced hepatotoxicity in chickens is not clear, and the present study aimed to investigate the potential role of cGAS-STING and NF-κB pathways on inflammatory injury in chicken liver. In this study, 75 white-feathered broilers were divided into a control group, a low-dose arsenic group (4 mg/kg) and a high-dose arsenic group (8 mg/kg) to investigate the toxic effects of arsenic on chicken liver. In this study, we found that pathological changes such as inflammatory cell infiltration and vesicular degeneration occurred in the liver when exposed to ATO. Crucially, exposure to ATO triggered the cGAS-STING pathway and markedly raised the levels of mRNA and protein expression of cGAS, STING, TBK1, and IRF7. The type I interferon response was also triggered. Simultaneously, STING induced the activation of the conventional NF-κB signaling pathway and stimulated the expression of genes associated with inflammation, such as IL-6, TNF-α and IL-1β. In summary, the induction of inflammatory responses via cGAS-STING and NF-κB signaling pathways under high ATO exposure provides new ideas for further studies on the toxicological mechanisms of arsenic.

Spatiotemporal release of non-nucleotide STING agonist and AKT inhibitor from implantable 3D-printed scaffold for amplified cancer immunotherapy

Immunotherapy through the activation of the stimulator of interferon genes (STING) signaling pathway is increasingly recognized for its robust anti-tumor efficacy. However, the effectiveness of STING activation is often compromised by inadequate anti-tumor immunity and a scarcity of primed immune cells in the tumor microenvironment. Herein, we design and fabricate a co-axial 3D-printed scaffold integrating a non-nucleotide STING agonist, SR-717, and an AKT inhibitor, MK-2206, in its respective shell and core layers, to synergistically enhance STING activation, thereby suppressing tumor recurrence and growth. SR-717 initiates the STING activation to enhance the phosphorylation of the factors along the STING pathway, while MK-2206 concurrently inhibits the AKT phosphorylation to facilitate the TBK1 phosphorylation of the STING pathway. The sequential and sustained release of SR-717 and MK-2206 from the scaffold results in a synergistic STING activation, demonstrating substantial anti-tumor efficacy across multiple tumor models. Furthermore, the scaffold promotes the recruitment and enrichment of activated dendritic cells and M1 macrophages, subsequently stimulating anti-tumor T cell activity, thereby amplifying the immunotherapeutic effect. This precise and synergistic activation of STING by the scaffold offers promising potential in tumor immunotherapy.

Integration of STING activation and COX-2 inhibition via steric-hindrance effect tuned nanoreactors for cancer chemoimmunotherapy

Integrating immunotherapy with nanomaterials-based chemotherapy presents a promising avenue for amplifying antitumor outcomes. Nevertheless, the suppressive tumor immune microenvironment (TIME) and the upregulation of cyclooxygenase-2 (COX-2) induced by chemotherapy can hinder the efficacy of the chemoimmunotherapy. This study presents a TIME-reshaping strategy by developing a steric-hindrance effect tuned zinc-based metal-organic framework (MOF), designated as CZFNPs. This nanoreactor is engineered by in situ loading of the COX-2 inhibitor, C-phycocyanin (CPC), into the framework building blocks, while simultaneously weakening the stability of the MOF. Consequently, CZFNPs achieve rapid pH-responsive release of zinc ions (Zn2+) and CPC upon specific transport to tumor cells overexpressing folate receptors. Accordingly, Zn2+ can induce reactive oxygen species (ROS)-mediated cytotoxicity therapy while synchronize with mitochondrial DNA (mtDNA) release, which stimulates mtDNA/cGAS-STING pathway-mediated innate immunity. The CPC suppresses the chemotherapy-induced overexpression of COX-2, thus cooperatively reprogramming the suppressive TIME and boosting the antitumor immune response. In xenograft tumor models, the CZFNPs system effectively modulates STING and COX-2 expression, converting "cold" tumors into "hot" tumors, thereby resulting in ≈ 4-fold tumor regression relative to ZIF-8 treatment alone. This approach offers a potent strategy for enhancing the efficacy of combined nanomaterial-based chemotherapy and immunotherapy.

Cytosolic delivery of innate immune agonists

Solute carrier proteins (SLCs) are pivotal for maintaining cellular homeostasis by transporting small molecules across cellular membranes. Recent discoveries have uncovered their involvement in modulating innate immunity, particularly within the cytosol. We review emerging evidence that links SLC transporters to cytosolic innate immune recognition and highlight their role in regulating inflammation. We explore how SLC transporters influence the activation of endosomal Toll-like receptors, cytosolic NODs, and STING sensors. Understanding the contribution of SLCs to innate immune recognition provides insight into their fundamental biological functions and opens new avenues to develop possible therapeutic interventions for autoimmune and inflammatory diseases. This review aims to discuss current knowledge and identify key gaps in this rapidly evolving field.

cGAS deficiency mitigated PM2.5-induced lung injury by inhibiting ferroptosis

Ferroptosis emerges as one of the pivotal types of cell death during fine particulate matter (PM2.5)-induced lung injury. The recently discovered cytosolic DNA sensor, cyclic GMP-AMP synthase (cGAS), triggers the activation of the downstream adaptor protein STING by synthesizing cyclic GMP-AMP, playing vital roles in innate immunity and cell death. Nonetheless, the specific function of cGAS in lung injury caused by PM2.5 remains to be elucidated. The present study aimed to explore the involvement of cGAS in the pathogenesis of PM2.5-induced lung injury and its potential mechanisms. The expression levels of cGAS in lung tissues and different types of cells isolated from murine lungs were detected. We generated a PM2.5-induced lung injury model with cGAS conditional knockout mice in type II alveolar epithelial (AT2) cells and investigated the roles of cGAS in ferroptosis in PM2.5-treated AT2 cells. The results demonstrated that PM2.5 could upregulate the expression of cGAS in lung tissues and AT2 cells. cGAS deficiency in AT2 cells not only improved pulmonary function, including lung compliance and oxygen saturation, but also relieved lung pathological injury in mice. In terms of mechanism, the absence of cGAS in AT2 cells notably reduced lipid peroxidation and ferroptosis in lungs exposed to PM2.5, achieved by increasing the protein level of ferritin. Meanwhile, cGAS deficiency also blocked the interaction between NCOA4 and ferritin, thus decreasing ferritinophagy. Additionally, periillaldehyde, one of the cGAS inhibitors, could protect against PM2.5-induced inflammation, oxidative stress, and edema in lung tissues by downregulating cGAS. Overall, cGAS promotes ferroptosis in PM2.5-induced lung injury by enhancing NCOA4-mediated ferritinophagy and shows promise as a therapeutic option for diseases associated with PM2.5 exposure.

Engineered low-pathogenic Helicobacter pylori as orally tumor immunomodulators for the stimulation of systemic immune response

Gastric cancer constitutes a malignant neoplasm characterized by heightened invasiveness, posing significant global health threat. Inspired by the analysis that gastric cancer patients with Helicobacter pylori (H. pylori) infection have higher overall survival, whether H. pylori can be used as therapeutics agent and oral drug delivery system for gastric cancer. Hence, we constructed engineered H. pylori for gastric cancer treatment. A type Ⅱ H. pylori with low pathogenicity, were conjugated with photosensitizer to develop the engineered living bacteria NIR-triggered system (Hp-Ce6). Hp-Ce6 could maintain activity in stomach acid, quickly infiltrate through mucus layer and finally migrate to tumor region owing to the cell morphology and urease of H. pylori. H. pylori, accumulated in the tumor site, severed as vaccine to activate cGAS-STING pathway, and synergistically remodel the macrophages phenotype. Upon irradiation within stomach, Hp-Ce6 directly destroyed tumor cells via photodynamic effect inherited by Ce6, companied by inducing immunogenic tumor cell death. Additionally, Hp-Ce6 exhibited excellent biosafety with fecal elimination and minimal blood absorption. This work explores the feasibility and availability of H. pylori-based oral delivery platforms for gastric tumor and further provides enlightening strategy to utilize H. pylori invariably presented in the stomach as in-situ immunomodulator to enhance antitumor efficacy.

pH and Redox Dual-Responsive Nanoparticle with Enhanced Dendritic Cell Maturation for Cancer Therapy

Type I interferons (IFNs) are essential for activating dendritic cells (DCs) and presenting tumor-associated antigens to T cells. IFNs are primarily produced from DCs among immune cells. A combination of chemotherapy and metalloimmunotherapy induces IFN production by activating the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway. However, chemotherapeutic agents deplete DC populations, suppressing immunostimulatory activities, despite their potent anticancer activities. Furthermore, an optimal ratio between chemotherapeutic agents and metal for activating DCs at the highest level has not been reported, and evidence for ensuring DC survival is lacking. In this study, we hypothesized that there is an optimal ratio to yield the highest DC maturation and anticancer activity with minimal DC depletion. To demonstrate it, we have designed a pH and redox dual-responsive nanoparticle, MnO2@BSA@DOX (MD), to prevent DCs from depleting and activate the cGAS-STING pathway both in cancer cells and DCs, inducing considerable levels of IFNs and maturation. MD consists of a core-layer structure, a manganese dioxide (MnO2) core, and a cross-linked layer with bovine serum albumin (BSA) and doxorubicin (DOX), with a specific ratio of DOX to manganese. MD exhibits structure-based selectivity between cancer cells and DCs by targeting the extracellular pH of the tumor microenvironment and intracellular redox reactions in cancer cells. Among various formulations, the 1:1 ratio shows the highest maturation with no significant depletion. Moreover, it induces distinct cytotoxicity in cancer cells through apoptosis and cGAS-STING activation, leading to increased calreticulin expression and enhanced DC phagocytosis. Consequently, it results in superior tumor suppression and prolonged survival with the high accumulation of MD in the tumor and no observed systemic toxicities, highlighting its potential as a therapeutic agent in cancer treatments.

PRKDC regulates cGAMP to enhance immune response in lung cancer treatment

Background

Despite its involvement in nucleotide metabolism, tumor immune landscape, and immunotherapy response, the role of 2'-3'-cyclic guanosine monophosphate-adenosine monophosphate (2',3'-cGAMP) in lung adenocarcinoma (LUAD) remails unelucidated. This study aimed to investigate the antitumor effects of 2',3'-cGAMP in LUAD.

Method

Herein, patients with LUAD were screened for prognostic biomarkers, which were then assessed for sensitivity to immunotherapy and chemotherapy utilizing the "TIDE" algorithm and CellMiner database. The results were validated using a mouse xenograft model. Additionally, macrophages and lung cancer cells were co-cultured, and macrophage polarization and apoptosis levels in the lung cancer cells were detected through flow cytometry. Protein levels were analyzed through western blotting and immunofluorescence. Finally, drug-encapsulated nanoparticles were designed to systematically examine the antitumor efficacy of the treatment against LUAD.

Result

Notably, 2',3'-cGAMP-mediated protein kinase, DNA-activated, catalytic subunit (PRKDC) inhibition induced macrophage polarization toward the M1 phenotype, thereby triggering apoptosis in LUAD cells. Furthermore, in vivo experiments showed that M1 macrophage infiltration enhancement and apoptosis induction in lung cancer cells were achieved by suppressing PRKDC expression via 2',3'-cGAMP, which inhibited lung cancer growth. The machine-learning approaches revealed SB505124 to be an effective antitumor agent in LUAD cells with high PRKDC levels owing to its ability to promote 2',3'-cGAMP-mediated apoptosis. Encapsulation of 2',3'-cGAMP, and SB505124 within a nano-delivery system markedly reduced tumor volumes in murine lung cancer tissues compared with that by individual agents.

Conclusion

The findings of this study reveal that PRKDC can predict poor survival of patients with LUAD. Additionally, SB505124 enhances the efficacy of 2',3'-cGAMP-based immunotherapy in patients exhibiting a high PRKDC expression.

Multifaceted roles of cGAS-STING pathway in the lung cancer: from mechanisms to translation

Lung cancer (LC) remains one of the most prevalent and lethal malignancies globally, with a 5-year survival rate for advanced cases persistently below 10%. Despite the significant advancements in immunotherapy, a substantial proportion of patients with advanced LC fail to respond effectively to these treatments, highlighting an urgent need for novel immunotherapeutic targets. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway has gained prominence as a potential target for improving LC immunotherapy due to its pivotal role in enhancing anti-tumor immune responses, augmenting tumor antigen presentation, and promoting T cell infiltration. However, emerging evidence also suggests that the cGAS-STING pathway may have pro-tumorigenic effects in the context of LC. This review aims to provide a comprehensive analysis of the cGAS-STING pathway, including its biological composition, activation mechanisms, and physiological functions, as well as its dual roles in LC and the current and emerging LC treatment strategies that target the pathway. By addressing these aspects, we intend to highlight the potential of the cGAS-STING pathway as a novel immunotherapeutic target, while also considering the challenges and future directions for its clinical application.

Nucleus-Targeted Sonosensitizer Activates the cGAS-STING Pathway for Tumor Sonodynamic Immunotherapy

A nucleus is crucial for both sonodynamic therapy (SDT) and antitumor immunity. However, how to burst ROS generation in situ, accurately damage a nucleus, and meanwhile activate a cGAS-STING pathway-induced innate immune response are still a great challenge. Here, we present TBzT-CPi, a small molecule with a D-A-π-A1 structure that simultaneously amplifies nucleus-targeted SDT and cGAS-STING pathway-dependent immune stimulation. TBzT-CPi could accumulate in the nucleus upon ultrasound irradiation and generate ROS in situ, which damages DNA and simultaneously triggers immunogenic cell death (ICD). Stirringly, nucleus-targeting SDT not only efficiently induces apoptosis in tumor cells but also modifies the immunosuppressive tumor microenvironment by activating cytotoxic T lymphocytes, maturing dendritic cells, and secreting cytokines. These findings pave the way for developing nucleus-targeting sonosensitizers for sonodynamic immunotherapy of cancer.

The emerging field of viroimmunotherapy for pediatric brain tumors

Pediatric brain tumors are the most common solid tumors in children. Even to date, with the advances in multimodality therapeutic management, survival outcomes remain dismal in some types of tumors, such as pediatric-type diffuse high-grade gliomas or central nervous system embryonal tumors. Failure to understand the complex molecular heterogeneity and the elusive tumor and microenvironment interplay continues to undermine therapeutic efficacy. Developing a strategy that would improve survival for these fatal tumors remains unmet in pediatric neuro-oncology. Oncolytic viruses (OVs) are emerging as a feasible, safe, and promising therapy for brain tumors. The new paradigm in virotherapy implies that the direct cytopathic effect is followed, under certain circumstances, by an antitumor immune response responsible for the partial or complete debulking of the tumor mass. OVs alone or combined with other therapeutic modalities have been primarily used in adult neuro-oncology. A surge in encouraging preclinical studies in pediatric brain tumor models recently led to the clinical translation of OVs with encouraging results in these tumors. In this review, we summarize the different virotherapy tested in preclinical and clinical studies in pediatric brain tumors, and we discuss the limitations and future avenues necessary to improve the response of these tumors to this type of therapy.

A Highly Charged Positive Cage Causes Simultaneous Enhancement of Type-II and O2-Independent-Type-I Photodynamic Therapy via One-/Two-Photon Stimulation and Tumor Immunotherapy via PANoptosis and Ferroptosis

To solve the oxygen dependence problem of photodynamic therapy (PDT), it is critical to explore photosensitizers that do not rely on O2 molecule to generate reactive oxygen species (ROS). Herein, a stable cationic metal-organic cage [Pd6(RuLoz 3)8](BF4)28 (MOC-88) that possesses high +28 charges is designed. The cage-confined positive microenvironment enables efficient generation of hydroxyl radicals and improved yield of the singlet oxygen under one-/two-photon excitation, showing excellent performance to concurrently enhance Type-II and O2-independent-Type-I PDT. Moreover, the effective ROS production and robust lipid peroxidation trigger a series of signaling pathways (inflammasome, cyclic guanosine monophosphate-adenosine monophosphate synthase stimulator of interferon genes, and NF-κB) to evoke PANoptosis and ferroptosis in tumor cells, enabling MOC-88 to simultaneously cause the loss of cell membrane integrity, release a series of inflammatory cytokines and damage-associated molecular patterns, stimulate the maturation and antigen presentation ability of dendritic cells, and ultimately activate T-cell-dependent adaptive immunity in vivo to inhibit tumor growth.

Copper-Based Composites Nanoparticles Improve Triple-Negative Breast Cancer Treatment with Induction of Apoptosis-Cuproptosis and Immune Activation

The synergistic effect of apoptosis and cuproptosis, along with the activation of the immune system, presents a promising approach to enhance the efficacy against triple-negative breast cancer (TNBC). Here, two prodrugs are synthesized: a reactive oxygen species (ROS)-responsive prodrug PEG-TK-DOX and a glutathione (GSH)-responsive prodrug PEG-DTPA-SS-CPT. These prodrugs are self-assembled and chelated Cu2+ to prepare nanoparticle PCD@Cu that simultaneously loaded doxorubicin (DOX), camptothecin (CPT), and Cu2+. The elevated levels of ROS and GSH in TNBC cells disrupted the PCD@Cu structure, leading to the release of Cu+, DOX, and CPT and the depletion of GSH. DOX and CPT triggered apoptosis with immunogenic cell death (ICD) in TNBC cells. Simultaneously, PCD@Cu downregulated the expression of copper transporting ATPase 2 (ATP7B), causing a significant accumulation of copper ions in TNBC cells. This further induced the aggregation of lipoylated dihydrolipoamide S-acetyltransferase (DLAT) and downregulation of iron-sulfur (Fe-S) cluster proteins, ultimately leading to cuproptosis and ICD in TNBC. In vitro and in vivo experiments confirmed that PCD@Cu induced apoptosis and cuproptosis in TNBC and activated the immune system, demonstrating strong anti-tumor capabilities. Moreover, PCD@Cu exhibited an excellent biosafety profile. Overall, this study provides a promising strategy for effective TNBC therapy.

TBK1-Zyxin signaling controls tumor-associated macrophage recruitment to mitigate antitumor immunity

Mechanical control is fundamental for cellular localization within a tissue, including for tumor-associated macrophages (TAMs). While the innate immune sensing pathways cGAS-STING and RLR-MAVS impact the pathogenesis and therapeutics of malignant diseases, their effects on cell residency and motility remain incompletely understood. Here, we uncovered that TBK1 kinase, activated by cGAS-STING or RLR-MAVS signaling in macrophages, directly phosphorylates and mobilizes Zyxin, a key regulator of actin dynamics. Under pathological conditions and in STING or MAVS signalosomes, TBK1-mediated Zyxin phosphorylation at S143 facilitates rapid recruitment of phospho-Zyxin to focal adhesions, leading to subsequent F-actin reorganization and reduced macrophage migration. Intratumoral STING-TBK1-Zyxin signaling was evident in TAMs and critical in antitumor immunity. Furthermore, myeloid-specific or global disruption of this signaling decreased the population of CD11b+ F4/80+ TAMs and promoted PD-1-mediated antitumor immunotherapy. Thus, our findings identify a new biological function of innate immune sensing pathways by regulating macrophage tissue localization, thus providing insights into context-dependent mitigation of antitumor immunity.

DNA-sensing pathways in health, autoinflammatory and autoimmune diseases

Detection of microbial DNA is a primary means of host defense. In mammalian cells, DNA-sensing pathways induce robust anti-microbial responses and initiation of adaptive immunity, leading to the eventual clearance of the infectious agent. However, while conferring the advantage of broad detection capability, the sequence-independent recognition mechanisms of most DNA sensors pose a significant challenge for mammalian cells to maintain ignorance to self-DNA under homeostatic conditions. In this Review, we summarize the fundamentals of DNA-sensing pathways and the intricate regulatory networks that keep these pathways in check. In addition, we describe how regulatory restraints can be defective and underlie human autoinflammatory and autoimmune diseases. Further, we discuss therapies in development that limit inflammation fueled by self-DNA or inappropriate activation of DNA-sensing pathways.

Novel Photo-STING Agonists Delivered by Erythrocyte Efferocytosis-Mimicking Pattern to Repolarize Tumor-Associated Macrophages for Boosting Anticancer Immunotherapy

Immunotherapy has emerged as a highly effective therapeutic strategy for cancer treatment. Cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon gene (STING) pathway activation facilitates tumor-associated macrophage (TAM) polarization toward M1 phenotype, and Mn2+ are effective agents for this pathway activation. However, the high in vivo degradation rate and toxicity of Mn2+ hamper clinical application of immunotherapy. Here, this work has newly synthesized and screened manganese porphyrins for Mn2+ transport, referred to as photo-STING agonists (PSAs), and further encapsulate them into core-shell nanoparticles named Rm@PP-GA with dual specificity for tumor tissue and TAMs. Not only do PSAs achieve higher Mn2+ delivery efficiency compared to Mn2+, but they also generate reactive oxygen species under light exposure, promoting mitochondrial DNA release for cGAS-STING pathway activation. In Rm@PP-GA, globin and red blood cell membranes (Rm) are used for erythrocyte efferocytosis-mimicking delivery. Rm can effectively prolong the in vivo circulation period while globin enables PSAs to be taken up by TAMs via CD163 receptors. After Rm rupture mediated by perfluorohexane in nanoparticles under ultrasonication, drugs are specifically released for TAM repolarization. Further, dendritic cells mature, as well as T lymphocyte infiltrate, both of which favor tumor eradication. Therefore, cancer immunotherapy is optimized by novel PSAs delivered by erythrocyte efferocytosis-mimicking delivery pattern.

Recent advances in nanoadjuvant-triggered STING activation for enhanced cancer immunotherapy

The development of effective cancer treatments is a popular in contemporary medical research. Immunotherapy, the fourth most common cancer treatment method, relies on activating autoimmune function to eradicate tumors and exhibits advantages such as a good curative effect and few side effects. In recent years, tumor vaccines that activate the stimulator of interferon genes (STING) pathway are being actively researched in the field of immunotherapy; however, their application is still limited because of the rapid clearance rate of tumor-related lymph nodes and low efficiency of antigen presentation. The rise of nanomedicine has provided new opportunities for solving these problems. By preparing materials with adjuvant effects nanoparticles, the small size of nanoparticles can be exploited to enable the entry of vaccines into tumor-related lymph nodes to accurately deliver STING agonists and activate the immune response. Based on this, this paper reviews various types of nano-adjuvants based on metals, platinum chemotherapy drugs, camptothecin derivatives, deoxyribonucleic acid, etc. and highlights the transformation prospects of these nano-adjuvants in tumor vaccines to provide a reference for promoting the development of nano-medicine and tumor vaccinology.

Robust and Sustained STING Pathway Activation via Hydrogel-Based In Situ Vaccination for Cancer Immunotherapy

The stimulator of interferon genes (STING) pathway is crucial for tumor immunity, leading to the exploration of STING agonists as potential immunotherapy adjuvants. However, their clinical application faces obstacles including poor pharmacokinetics, transient activation, and an immunosuppressive tumor microenvironment (TME). Addressing these limitations, our study aims to develop an injectable silk fibroin hydrogel-based in situ vaccine. It incorporates a nanoscale STING agonist, an immunogenic cell death (ICD) inducer, and an immunomodulator to ensure their controlled and sustained release. cGAMP nanoparticles (cGAMPnps) with a core-shell structure ensure optimal delivery of cGAMP to dendritic cells (DCs), thereby activating the STING pathway and fostering DC maturation. ICD-associated damage-associated molecular patterns amplify and prolong STING activation via enhanced type I IFN and other inflammatory pathways, along with delayed degradation of cGAMP and STING. Furthermore, the STING-driven vascular normalization by cGAMPnps and ICD, in conjunction with immunomodulators like antiprogrammed cell death protein 1 antibody (anti-PD-1 Ab) or OX40 ligand (OX40L), effectively remodels the immunosuppressive TME. This in situ gel vaccine, when used independently or with surgery as neoadjuvant/adjuvant immunotherapy, enhances DC and CD8+ T-cell activation, suppressing tumor progression and recurrence across various immunologically cold tumor models. It revolutionizes the application of STING agonists in cancer immunotherapy, offering substantial promise for improving outcomes across a broad spectrum of malignancies.

Discovery of Imidazo[1,2-a]pyrazine Derivatives as Potent ENPP1 Inhibitors

ENPP1 acts as a negative regulator of the cGAS-STING pathway through the hydrolysis of 2'3'-cGAMP. Inhibitors of ENPP1 are regarded as promising agents for stimulating the immune response in cancer immunotherapy. This study describes the identification and optimization of imidazo[1,2-a]pyrazine derivative 7 as a highly potent and selective ENPP1 inhibitor. Compound 7 demonstrated substantial inhibitory activity against ENPP1 with an IC50 value of 5.70 or 9.68 nM while showing weak inhibition against ENPP2 and ENPP3. Furthermore, compound 7 was shown to enhance the mRNA expression of cGAMP-induced STING pathway downstream target genes, such as IFNB1, CXCL10, and IL6. In vivo pharmacokinetic and antitumor studies showed promising results, with 7 not only exhibiting efficient pharmacokinetic properties but also enhancing the antitumor efficacy of the anti-PD-1 antibody. Treatment with 7 (80 mg/kg) combined with anti-PD-1 antibody achieved a tumor growth inhibition rate of 77.7% and improved survival in a murine model.

Immunomodulatory effects of trastuzumab deruxtecan through the cGAS-STING pathway in gastric cancer cells

Although the efficacy of trastuzumab deruxtecan (T-DXd) against HER2-positive gastric cancers (GCs) has driven its clinical application, the precise mechanisms governing its immunomodulatory role remain unclear. In this study, we examined the immune-related mechanisms of action of T-DXd in GC cells. T-DXd exhibited potent antitumor effects in GC cells across diverse HER2 expression levels by inducing DNA damage and apoptosis. Activation of the DNA damage response by T-DXd led to increased PD-L1 expression. RNA-Seq analysis revealed that T-DXd modulated immune-related pathways, resulting in the upregulation of genes associated with inflammation and IFN signaling. Importantly, T-DXd activated the cGAS-STING pathway, inducing an IFN-I response in HER2-positive GC cells. Furthermore, T-DXd activated dendritic cells via the cancer cell-intrinsic cGAS-STING-IFN axis and enhanced PBMC-mediated tumor cell killing by activating CD8+ T cells. These findings provide valuable insights into the role of the cytosolic DNA sensing pathway in the action of T-DXd and offer a compelling rationale for combining T-DXd with immune checkpoint blockade therapies in GC treatment.

The Role of STING-Mediated Activation of Dendritic Cells in Cancer Immunotherapy

The signaling pathway that comprises cyclic guanosine monophosphate-adenosine monophosphate (cGAMP or GMP-AMP) synthase (cGAS) and Stimulator of Interferon Genes (STING) is emerging as a druggable target for immunotherapy, with tumor-resident dendritic cells (DC) playing a critical role in mediating its effects. The STING receptor is part of the DNA-sensing cellular machinery, that can trigger the secretion of pro-inflammatory mediators, priming effector T cells and initiating specific antitumor responses. Yet, recent studies have highlighted the dual role of STING activation in the context of cancer: STING can either promote antitumor responses or enhance tumor progression. This dichotomy often depends on the cell type in which cGAS-STING signaling is induced and the activation mode, namely acute versus chronic. Of note, STING activation at the DC level appears to be particularly important for tumor eradication. This review outlines the contribution of the different conventional and plasmacytoid DC subsets and describes the mechanisms underlying STING-mediated activation of DCs in cancer. We further highlight how the STING pathway plays an intricate role in modulating the function of DCs embedded in tumor tissue. Additionally, we discuss the strategies being employed to harness STING activation for cancer treatment, such as the development of synthetic agonists and nano-based delivery systems, spotlighting the current techniques used to prompt STING engagement specifically in DCs.

Cold and hot tumors: from molecular mechanisms to targeted therapy

Immunotherapy has made significant strides in cancer treatment, particularly through immune checkpoint blockade (ICB), which has shown notable clinical benefits across various tumor types. Despite the transformative impact of ICB treatment in cancer therapy, only a minority of patients exhibit a positive response to it. In patients with solid tumors, those who respond well to ICB treatment typically demonstrate an active immune profile referred to as the "hot" (immune-inflamed) phenotype. On the other hand, non-responsive patients may exhibit a distinct "cold" (immune-desert) phenotype, differing from the features of "hot" tumors. Additionally, there is a more nuanced "excluded" immune phenotype, positioned between the "cold" and "hot" categories, known as the immune "excluded" type. Effective differentiation between "cold" and "hot" tumors, and understanding tumor intrinsic factors, immune characteristics, TME, and external factors are critical for predicting tumor response and treatment results. It is widely accepted that ICB therapy exerts a more profound effect on "hot" tumors, with limited efficacy against "cold" or "altered" tumors, necessitating combinations with other therapeutic modalities to enhance immune cell infiltration into tumor tissue and convert "cold" or "altered" tumors into "hot" ones. Therefore, aligning with the traits of "cold" and "hot" tumors, this review systematically delineates the respective immune characteristics, influencing factors, and extensively discusses varied treatment approaches and drug targets based on "cold" and "hot" tumors to assess clinical efficacy.

Intratumoral STING agonist reverses immune evasion in PD-(L)1-refractory Merkel cell carcinoma: mechanistic insights from detailed biomarker analyses

BACKGROUND

Antibodies blocking programmed death (PD)-1 or its ligand (PD-L1) have revolutionized cancer care, but many patients do not experience durable benefits. Novel treatments to stimulate antitumor immunity are needed in the PD-(L)1 refractory setting. The stimulator of interferon genes (STING) protein, an innate sensor of cytoplasmic DNA, is a promising target with several agonists in development. However, response rates in most recent clinical trials have been low and mechanisms of response remain unclear. We report detailed biomarker analyses in a patient with anti-PD-L1 refractory, Merkel cell polyomavirus (MCPyV)-positive, metastatic Merkel cell carcinoma (MCC) who was treated with an intratumoral (IT) STING agonist (ADU-S100) plus intravenous anti-PD-1 antibody (spartalizumab) and experienced a durable objective response with regression of both injected and non-injected lesions.

METHODS

We analyzed pretreatment and post-treatment tumor and peripheral blood samples from our patient with single-cell RNA sequencing, 30-parameter flow cytometry, T cell receptor sequencing, and multiplexed immunohistochemistry. We analyzed cancer-specific CD8 T cells using human leukocyte antigen (HLA)-I tetramers loaded with MCPyV peptides. We also analyzed STING expression and signaling in the tumor microenvironment (TME) of 88 additional MCC tumor specimens and in MCC cell lines.

RESULTS

We observed high levels of MCPyV-specific T cells (12% of T cells) in our patient's tumor at baseline. These cancer-specific CD8 T cells exhibited characteristics of exhaustion including high TOX and low TCF1 proteins. Following treatment with STING-agonist plus anti-PD-1, IT CD8 T cells expanded threefold. We also observed evidence of likely improved antigen presentation in the MCC TME (greater than fourfold increase of HLA-I-positive cancer cells). STING expression was not detected in any cancer cells within our patient's tumor or in 88 other MCC tumors, however high STING expression was observed in immune and stromal cells within all 89 MCC tumors.

CONCLUSIONS

Our results suggest that STING agonists may be able to work indirectly in MCC via signaling through immune and stromal cells in the TME, and may not necessarily need STING expression in the cancer cells. This approach may be particularly effective in tumors that are already infiltrated by inflammatory cells in the TME but are evading immune detection via HLA-I downregulation.

A prospective study of neoadjuvant pembrolizumab plus chemotherapy for resectable esophageal squamous cell carcinoma: The Keystone-001 trial

In this phase II study, 47 patients with locally advanced, resectable esophageal squamous cell carcinoma (ESCC) received three cycles of pembrolizumab plus chemotherapy, followed by Da Vinci robot-assisted surgery. The primary endpoints were safety and major pathological response (MPR). Key secondary endpoints included complete pathological response (pCR) and survival. No grade ≥3 adverse events or surgical delays occurred during neoadjuvant therapy. Among 46 patients studied for efficacy, the MPR and pCR rates were 72% and 41%, respectively. After a median follow-up of 27.2 months, the 2-year overall survival (OS) and disease-free survival (DFS) rates were 91% and 89%, respectively. Expansion of TRGC2+ NKT cells in peripheral blood correlated with neoadjuvant treatment effectiveness, which was validated by in vitro organoid experiments and external cancer datasets, and its functional classification and mechanism of action were further explored. These findings show preoperative pembrolizumab plus chemotherapy is a promising therapeutic strategy for resectable ESCC.

Co-delivery of SN38 and MEF2D-siRNA via tLyp-1-modified liposomes reverses PD-L1 expression induced by STING activation in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) exhibits an immunosuppressive tumor microenvironment, leading to a low objective response rate when immune checkpoint inhibitors (ICIs) are utilized. The cGAS-STING pathway demonstrates a powerful immune stimulatory effect, nevertheless, activation of this pathway triggers an upregulation of PD-L1, which inhibits the anti-tumor function of immune cells. The present study discovered that knockdown of MEF2D by a siRNA in H22 cells decreases the expression of PD-L1. Subsequently, tLyp-1-modified liposomes were developed for the delivery of SN38 and MEF2D-siRNA. The outcomes indicated that the modification of tLyp-1 could enhance the uptake of liposomes by tumor cells. tLip/siMEF2D/SN38 liposomes can effectively knockdown the expression of MEF2D in HCC cells and reduce the expression of PD-L1 in vitro and in vivo, thereby enhancing proliferation inhibition and apoptosis induction, and effectively suppressing the growth of tumors. SN38 treatment elevated the expression of p-TBK1 and p-IRF3 in tumor tissue, signifying the activation of the cGAS-STING pathway and facilitating the maturation of dendritic cells in vitro and in vivo. At the same time, the co-delivery of MEF2D-siRNA reduced the expression of PD-L1, thereby decreasing the quantity of M2 macrophages and myeloid-derived suppressor cells (MDSCs) in tumors, increasing the number of CD4+ T cells within the tumor, and strengthening the anti-tumor immune efficacy. In conclusion, our results suggest that tLyP-1 modified, SN38- and MEF2D siRNA-loaded liposomes have the potential for the treatment of HCC and optimize the immunotherapy of HCC via STING activation.

Bidirectional regulation of the cGAS-STING pathway in the immunosuppressive tumor microenvironment and its association with immunotherapy

Adaptive anti-tumor immunity is currently dependent on the natural immune system of the body. The emergence of tumor immunotherapy has improved prognosis and prolonged the survival cycle of patients. Current mainstream immunotherapies, including immune checkpoint blockade, chimeric antigen receptor T-cell immunotherapy, and monoclonal antibody therapy, are linked to natural immunity. The cGAS-STING pathway is an important natural immunity signaling pathway that plays an important role in fighting against the invasion of foreign pathogens and maintaining the homeostasis of the organism. Increasing evidence suggests that the cGAS-STING pathway plays a key role in tumor immunity, and the combination of STING-related agonists can significantly enhance the efficacy of immunotherapy and reduce the emergence of immunotherapeutic resistance. However, the cGAS-STING pathway is a double-edged sword, and its activation can enhance anti-tumor immunity and immunosuppression. Immunosuppressive cells, including M2 macrophages, MDSC, and regulatory T cells, in the tumor microenvironment play a crucial role in tumor escape, thereby affecting the immunotherapy effect. The cGAS-STING signaling pathway can bi-directionally regulate this group of immunosuppressive cells, and targeting this pathway can affect the function of immunosuppressive cells, providing new ideas for immunotherapy. In this study, we summarize the activation pathway of the cGAS-STING pathway and its immunological function and elaborate on the key role of this pathway in immune escape mediated by the tumor immunosuppressive microenvironment. Finally, we summarize the mainstream immunotherapeutic approaches related to this pathway and explore ways to improve them, thereby providing guidelines for further clinical services.

Genomic instability as a driver and suppressor of anti-tumor immunity

Genomic instability is a driver and accelerator of tumorigenesis and influences disease outcomes across cancer types. Although genomic instability has been associated with immune evasion and worsened disease prognosis, emerging evidence shows that genomic instability instigates pro-inflammatory signaling and enhances the immunogenicity of tumor cells, making them more susceptible to immune recognition. While this paradoxical role of genomic instability in cancer is complex and likely context-dependent, understanding it is essential for improving the success rates of cancer immunotherapy. In this review, we provide an overview of the underlying mechanisms that link genomic instability to pro-inflammatory signaling and increased immune surveillance in the context of cancer, as well as discuss how genomically unstable tumors evade the immune system. A better understanding of the molecular crosstalk between genomic instability, inflammatory signaling, and immune surveillance could guide the exploitation of immunotherapeutic vulnerabilities in cancer.

Nanomaterial-based cancer immunotherapy: enhancing treatment strategies

Cancer immunotherapy has emerged as a pivotal approach for treating various types of cancer, incorporating strategies such as chimeric antigen receptor T-cell (CAR-T) therapy, immune checkpoint blockade therapy, neoantigen peptides, mRNA vaccines, and small molecule modulators. However, the clinical efficacy of these therapies is frequently constrained by significant adverse effects and limited therapeutic outcomes. In recent years, the integration of nanotechnology into cancer immunotherapy has gained considerable attention, showcasing notable advantages in drug delivery, targeted accumulation, controlled release, and localized administration. This review focuses on nanomaterial-based immunotherapeutic strategies, particularly the development and application of nanocarriers such as liposomes, lipid nanoparticles, polymeric nanoparticles, and self-assembling scaffolds. We examine how these strategies can enhance the efficacy of cancer immunotherapy while minimizing adverse effects and analyze their potential for clinical translation.

Targeting STING signaling for the optimal cancer immunotherapy

Despite the transformative impact of anti-PD-1/PD-L1 therapies, challenges such as low response rates persist. The stimulator of interferon genes (STING) pathway, a crucial element of innate immunity, emerges as a strategic target to overcome these limitations. Understanding its multifaceted functions in cancer, including antigen presentation and response to DNA damage, provides valuable insights. STING agonists, categorized into cyclic dinucleotides (CDNs) and non-CDNs, exhibit promising safety and efficacy profiles. Innovative delivery systems, including antibody-drug conjugates, nanocarriers, and exosome-based therapies, address challenges associated with systemic administration and enhance targeted tumor delivery. Personalized vaccines, such as DT-Exo-STING, showcase the adaptability of STING agonists for individualized treatment. These advancements not only offer new prospects for combination therapies but also pave the way for overcoming resistance mechanisms. This review focuses on the potential of targeting STING pathway to enhance cancer immunotherapy. The integration of STING agonists into cancer immunotherapy holds promise for more effective, personalized, and successful approaches against malignancies, presenting a beacon of hope for the future of cancer treatment.

Two-dimensional coordination risedronate-manganese nanobelts as adjuvant for cancer radiotherapy and immunotherapy

The irradiated tumor itself represents an opportunity to establish endogenous in situ vaccines. However, such in situ cancer vaccination (ISCV) triggered by radiation therapy (RT) alone is very weak and hardly elicits systemic anticancer immunity. In this study, we develop two-dimensional risedronate-manganese nanobelts (RMn-NBs) as an adjuvant for RT to address this issue. RMn-NBs exhibit good T2 magnetic resonance imaging performance and enhanced Fenton-like catalytic activity, which induces immunogenic cell death. RMn-NBs can inhibit the HIF-1α/VEGF axis to empower RT and synchronously activate the cGAS/STING pathway for promoting the secretion of type I interferon, thereby boosting RT-triggered ISCV and immune checkpoint blockade therapy against primary and metastatic tumors. RMn-NBs as a nano-adjuvant for RT show good biocompatibility and therapeutic efficacy, presenting a promising prospect for cancer radiotherapy and immunotherapy.

A Photoactivatable Self-Assembled Nanoagonist for Synergistic Therapy against Pancreatic Ductal Adenocarcinoma

Immunotherapy has revolutionized the cancer treatment paradigm, yet efficient immunotherapeutic responses against immune-cold/desert cancers remain challenging. Herein, we report that photoactivatable nanoagonists yield a potent antitumor synergy of photoimmunotherapy against pancreatic ductal adenocarcinoma (PDAC). The nanoagonist was fabricated by assembling an amphiphilic boron dipyrromethene-derived polymer conjugated with a Toll-like receptor agonist via a photocleavable linker and stimulator of interferon genes agonist. The nanoagonist enables light-induced generation of reactive oxygen species and on-demand release of the agonists to yield synergistic photoimmunotherapy. The produced tumor antigens promote dendritic cell maturation, which is further amplified by these agonists for eliciting adaptive immunity, accompanied by apparently abscopal and long-term memory effects. The nanoagonist further alleviates the fibrosis of tumor stroma and the immunosuppressive microenvironment, leading to the deep infiltrations of clinically used therapeutics and immune cells to yield preferable combinational treatments against PDAC models. These results provide valuable insights into activatable nanoparticles for cancer therapy against immune-desert cancers.

Clinical applications of STING agonists in cancer immunotherapy: current progress and future prospects

The STING (Stimulator of Interferon Genes) pathway is pivotal in activating innate immunity, making it a promising target for cancer immunotherapy. STING agonists have shown potential in enhancing immune responses, particularly in tumors resistant to traditional therapies. This scholarly review examines the diverse categories of STING agonists, encompassing CDN analogues, non-CDN chemotypes, CDN-infused exosomes, engineered bacterial vectors, and hybrid structures of small molecules-nucleic acids. We highlight their mechanisms, clinical trial progress, and therapeutic outcomes. While these agents offer significant promise, challenges such as toxicity, tumor heterogeneity, and delivery methods remain obstacles to their broader clinical use. Ongoing research and innovation are essential to overcoming these hurdles. STING agonists could play a transformative role in cancer treatment, particularly for patients with hard-to-treat malignancies, by harnessing the body's immune system to target and eliminate cancer cells.

γ-Butyrolactone Derivatives of MSA-2 are STING Prodrugs

STING agonists are potent enhancers of a pro-inflammatory response and, thus, potentially useful therapeutics. Unfortunately, many agonists developed to date require complex drug delivery formulations and often have poor water solubility, limiting their use for systemic administration. Here, we report the discovery and chemical characterization of lactones of MSA-2 as new STING prodrugs with enhanced properties. We show that these prodrugs form efficient inclusion complexes with tumor myeloid cell targeting cyclodextrin nanoparticles and propose a new mechanism of formation and hydrolysis.

Engineered extracellular vesicles enable high-efficient delivery of intracellular therapeutic proteins

Developing an intracellular delivery system is of key importance in the expansion of protein-based therapeutics acting on cytosolic or nuclear targets. Recently, extracellular vesicles (EVs) have been exploited as next-generation delivery modalities due to their natural role in intercellular communication and biocompatibility. However, fusion of protein of interest to a scaffold represents a widely used strategy for cargo enrichment in EVs, which could compromise the stability and functionality of cargo. Herein, we report intracellular delivery via EV-based approach (IDEA) that efficiently packages and delivers native proteins both in vitro and in vivo without the use of a scaffold. As a proof-of-concept, we applied the IDEA to deliver cyclic GMP-AMP synthase (cGAS), an innate immune sensor. The results showed that cGAS-carrying EVs activated interferon signaling and elicited enhanced antitumor immunity in multiple syngeneic tumor models. Combining cGAS EVs with immune checkpoint inhibition further synergistically boosted antitumor efficacy in vivo. Mechanistically, scRNA-seq demonstrated that cGAS EVs mediated significant remodeling of intratumoral microenvironment, revealing a pivotal role of infiltrating neutrophils in the antitumor immune milieu. Collectively, IDEA, as a universal and facile strategy, can be applied to expand and advance the development of protein-based therapeutics.

Reuterin promotes pyroptosis in hepatocellular cancer cells through mtDNA-mediated STING activation and caspase 8 expression

Hepatocellular carcinoma (HCC) is the most common form of liver cancer with poor prognosis. The available drugs for advanced HCC are limited and substantial therapeutic advances including new drugs and new combination therapies are still in urgent need. In this study, we found that the major metabolite of Lactobacillus reuteri (L. reuteri), reuterin showed great anti-HCC potential and could help in sorafenib treatment. Reuterin treatment impaired mitophagy and caused the aberrant clustering of mitochondrial nucleoids to block mitochondrial DNA (mtDNA) replication and mitochondrial fission, which could promote mtDNA leakage and subsequent STING activation in HCC cells. STING could activate pyroptosis and necroptosis, while reuterin treatment also induced caspase 8 expression to inhibit necroptosis through cleaving RIPK3 in HCC cells. Thus, pyroptosis was the main death form in reuterin-treated HCC cells and STING suppression remarkably rescued the growth inhibitory effect of reuterin and concurrently knockdown caspase 8 synergized to restrain the induction of pyroptosis. In conclusion, our study explains the detailed molecular mechanisms of the antitumor effect of reuterin and reveals its potential to perform as a combinational drug for HCC treatment.

STING-Activating Small Molecular Therapeutics for Cancer Immunotherapy

Immuno-oncology has become a revolutionary strategy for cancer treatment. Therapeutic interventions based on adaptive immunity through immune checkpoint therapy or chimeric antigen receptor (CAR) T cells have received clinical approval for monotherapy and combination treatment in various cancers. Although these treatments have achieved clinical successes, only a minority of cancer patients show a response, highlighting the urgent need to discover new therapeutic molecules that could be exploited to improve clinical outcomes and pave the way for the next generation of immunotherapy. Given the critical role of the innate immune system against infection and cancer, substantial efforts have been dedicated to developing novel anticancer therapeutics that target these pathways. Targeting the stimulator of interferon genes (STING) pathway is a powerful strategy to generate a durable antitumor response, and activation of the adaptor protein STING induces the initiation of transcriptional cascades, thereby producing type I interferons, pro-inflammatory cytokines and chemokines. Various STING agonists, including natural or synthetic cyclic dinucleotides (CDNs), have been developed as anticancer therapeutics. However, since most CDNs are confined to intratumoral administration, there has been a great interest in developing non-nucleotide agonists for systemic treatment. Here, we review the current development of STING-activating therapeutics in both preclinical and clinical stages.

Make it STING: nanotechnological approaches for activating cGAS/STING as an immunomodulatory node in osteosarcoma

Osteosarcoma is a highly aggressive bone cancer primarily affecting children, adolescents, and young adults. The current gold standard for treatment of osteosarcoma patients consists of two to three rounds of chemotherapy, followed by extensive surgical intervention from total limb reconstruction to amputation, followed by additional rounds of chemotherapy. Although chemotherapy has advanced the treatment of osteosarcoma significantly, the overall 5-year survival rate in resistant forms of osteosarcoma is still below 20%. The interaction between cancer and the immune system has long been recognized as a critical aspect of tumour growth. Tumour cells within the tumour microenvironment (TME) suppress antitumour immunity, and immunosuppressive cells and cytokines provide the extrinsic factors of tumour drug resistance. Emerging research demonstrates an immunostimulatory role for the cGAS/STING pathway in osteosarcoma, typically considered an immune-cold or immunosuppressed cancer type. cGAS/STING signalling appears to drive an innate immune response against tumours and potentiates the efficacy of other common therapies including chemo and radiotherapy. Nanotechnological delivery systems for improved therapy delivery for osteosarcoma have also been under investigation in recent years. This review provides an overview of cGAS/STING signalling, its divergent roles in the context of cancer, and collates current research which activates cGAS/STING as an adjuvant immunomodulatory target for the treatment of osteosarcoma. It will also discuss current nanotechnological delivery approaches that have been developed to stimulate cGAS/STING. Finally, it will highlight the future directions that we believe will be central to the development of this transformative field.

A Novel Manganese Ion Delivery Carrier Promotes Immune Cell Proliferation and Enhances Innate Immune Responses

Manganese is a transition metal that is an essential trace element for human health. Manganese ions (Mn2+), which serve as one of the most common transition metal ions, play vital roles in enhancing innate immune responses. However, immune agonists based on Mn2+ are poorly utilized in clinical trials due to poor chemodynamics and adverse events. In this work, we designed a novel delivery carrier for loading manganese ions by constructing hFn-MT3(Mn2+) protein nanoparticles (termed as NPs(Mn2+)), which contained human ferritin heavy chain (hFn) and metallothionein-3 (MT3), induced by isopropyl β-d-thiogalactoside (IPTG) and manganese ions in the prokaryotic expression system. The NPs(Mn2+) protein nanoparticles could not only stimulate immune cell proliferation but also activate innate immune responses via the cGAS-STING-IRF3 signaling pathway. Collectively, our results unveil a candidate strategy for delivering metal ions beyond Mn2+ and may broaden metal ion clinical use in the field of immunotherapies.

The common Sting1 HAQ, AQ alleles rescue CD4 T cellpenia, restore T-regs, and prevent SAVI (N153S) inflammatory disease in mice

The significance of STING1 gene in tissue inflammation and cancer immunotherapy has been increasingly recognized. Intriguingly, common human STING1 alleles R71H-G230A-R293Q (HAQ) and G230A-R293Q (AQ) are carried by ~60% of East Asians and ~40% of Africans, respectively. Here, we examine the modulatory effects of HAQ, AQ alleles on STING-associated vasculopathy with onset in infancy (SAVI), an autosomal dominant, fatal inflammatory disease caused by gain-of-function human STING1 mutations. CD4 T cellpenia is evident in SAVI patients and mouse models. Using Sting1 knock-in mice expressing common human STING1 alleles HAQ, AQ, and Q293, we found that HAQ, AQ, and Q293 splenocytes resist STING1-mediated cell death ex vivo, establishing a critical role of STING1 residue 293 in cell death. The HAQ/SAVI(N153S) and AQ/SAVI(N153S) mice did not have CD4 T cellpenia. The HAQ/SAVI(N153S), AQ/SAVI(N153S) mice have more (~10-fold, ~20-fold, respectively) T-regs than WT/SAVI(N153S) mice. Remarkably, while they have comparable TBK1, IRF3, and NFκB activation as the WT/SAVI, the AQ/SAVI mice have no tissue inflammation, regular body weight, and normal lifespan. We propose that STING1 activation promotes tissue inflammation by depleting T-regs cells in vivo. Billions of modern humans have the dominant HAQ, AQ alleles. STING1 research and STING1-targeting immunotherapy should consider STING1 heterogeneity in humans.

Nuclear translocation of nucleotide enzyme Phosphoglucomutase 2 governs DNA damage response and anti-tumor immunity

Targeting nucleotide enzymes emerges as a promising avenue for impeding tumor proliferation and fortifying anti-tumor immunogenicity. The non-canonical role of nucleotide enzymes remains poorly understood. In this study, we have identified that Phosphoglucomutase 2 (PGM2) rapidly accumulates at the DNA damage site to govern the DNA damage response mediated by the phosphorylation at Serine 165 and by forming a complex with Rho-associated coiled-coil-containing protein kinase 2 (ROCK2). Silencing PGM2 in Glioblastoma Multiforme (GBM) cells heightens DNA damage in vitro and enhances the sensitivity of temozolomide (TMZ) treatment by activating anti-tumor immunity in vivo. Furthermore, we demonstrate that pharmacological inhibition of ROCK2 synergistically complements TMZ treatment and pembrolizumab (PD-L1) checkpoint immunotherapy, augmenting anti-tumor immunity. This study reveals the non-canonical role of the nucleotide enzyme PGM2 in the regulation of DNA damage response and anti-tumor immunity, with implications for the development of therapeutic approaches in cancer treatment.

Small molecule innate immune modulators in cancer therapy

Immunotherapy has proved to be a breakthrough in cancer treatment. So far, a bulk of the approved/late-stage cancer immunotherapy are antibody-based. Although these antibody-based drugs have demonstrated great promise, a majority of them are limited due to their access to extracellular targets, lack of oral bioavailability, tumor microenvironment penetration, induction of antibody dependent cytotoxicity etc. In recent times, there has been an increased research focus on the development of small molecule immunomodulators since they have the potential to overcome the aforementioned limitations posed by antibodies. Furthermore, while most biologics based therapeutics that are in clinical use are limited to modulating the adaptive immune system, very few clinically approved therapeutic modalities exist that modulate the innate immune system. The innate immune system, which is the body's first line of defense, has the ability to turn cold tumors hot and synergize strongly with existing adaptive immune modulators. In preclinical studies, small molecule innate immune modulators have demonstrated synergistic efficacy as combination modalities with current standard-of-care immune checkpoint antibodies. In this review, we highlight the recent advances made by small molecule innate immunomodulators in cancer immunotherapy.

Self-assembly of a ruthenium-based cGAS-STING photoactivator for carrier-free cancer immunotherapy

The cGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) pathway promotes antitumor immune responses by sensing cytosolic DNA fragments leaked from nucleus and mitochondria. Herein, we designed a highly charged ruthenium photosensitizer (Ru1) with a β-carboline alkaloid derivative as the ligand for photo-activating of the cGAS-STING pathway. Due to the formation of multiple non-covalent intermolecular interactions, Ru1 can self-assemble into carrier-free nanoparticles (NPs). By incorporating the triphenylphosphine substituents, Ru1 can target and photo-damage mitochondrial DNA (mtDNA) to cause the cytoplasmic DNA leakage to activate the cGAS-STING pathway. Finally, Ru1 NPs show potent antitumor effects and elicit intense immune responses in vivo. In conclusion, we report the first self-assembling mtDNA-targeted photosensitizer, which can effectively activate the cGAS-STING pathway, thus providing innovations for the design of new photo-immunotherapeutic agents.

PTPRT loss enhances anti-PD-1 therapy efficacy by regulation of STING pathway in non-small cell lung cancer

With the revolutionary progress of immune checkpoint inhibitors (ICIs) in non-small cell lung cancer, identifying patients with cancer who would benefit from ICIs has become critical and urgent. Here, we report protein tyrosine phosphatase receptor type T (PTPRT) loss as a precise and convenient predictive marker independent of PD-L1 expression for anti-PD-1/PD-L1 axis therapy. Anti-PD-1/PD-L1 axis treatment markedly increased progression-free survival in patients with PTPRT-deficient tumors. PTPRT-deficient tumors displayed cumulative DNA damage, increased cytosolic DNA release, and higher tumor mutation burden. Moreover, the tyrosine residue 240 of STING was identified as a direct substrate of PTPRT. PTPRT loss elevated phosphorylation of STING at Y240 and thus inhibited its proteasome-mediated degradation. PTPRT-deficient tumors released more IFN-β, CCL5, and CXCL10 by activation of STING pathway and increased immune cell infiltration, especially of CD8 T cells and natural killer cells, ultimately enhancing the efficacy of anti-PD-1 therapy in multiple subcutaneous and orthotopic tumor mouse models. The response of PTPRT-deficient tumors to anti-PD-1 therapy depends on the tumor-intrinsic STING pathway. In summary, our findings reveal the mechanism of how PTPRT-deficient tumors become sensitive to anti-PD-1 therapy and highlight the biological function of PTPRT in innate immunity. Considering the prevalence of PTPRT mutations and negative expression, this study has great value for patient stratification and clinical decision-making.

Inactivated cGAS-STING Signaling Facilitates Endocrine Resistance by Forming a Positive Feedback Loop with AKT Kinase in ER+HER2- Breast Cancer

Endocrine-resistant ER+HER2- breast cancer (BC) is particularly aggressive and leads to poor clinical outcomes. Effective therapeutic strategies against endocrine-resistant BC remain elusive. Here, analysis of the RNA-sequencing data from ER+HER2- BC patients receiving neoadjuvant endocrine therapy and spatial transcriptomics analysis both show the downregulation of innate immune signaling sensing cytosolic DNA, which primarily occurs in endocrine-resistant BC cells, not immune cells. Indeed, compared with endocrine-sensitive BC cells, the activity of sensing cytosolic DNA through the cGAS-STING pathway is attenuated in endocrine-resistant BC cells. Screening of kinase inhibitor library show that this effect is mainly mediated by hyperactivation of AKT1 kinase, which binds to kinase domain of TBK1, preventing the formation of a trimeric complex TBK1/STING/IRF3. Notably, inactivation of cGAS-STING signaling forms a positive feedback loop with hyperactivated AKT1 to promote endocrine resistance, which is physiologically important and clinically relevant in patients with ER+HER2- BC. Blocking the positive feedback loop using the combination of an AKT1 inhibitor with a STING agonist results in the engagement of innate and adaptive immune signaling and impairs the growth of endocrine-resistant tumors in humanized mice models, providing a potential strategy for treating patients with endocrine-resistant BC.