Refractoriness of STING therapy is relieved by AKT inhibitor through effective vascular disruption in tumour

Hypocrellin B Exerts Its Antitumor Effect on Colorectal Cancer by Inhibiting the AKT Pathway

Colorectal cancer is the fourth most common malignant cancer worldwide, with limited treatment options for advanced cases. The natural compound hypocrellin B has been shown to inhibit tumor growth, but its effects and specific mechanisms of action in colorectal cancer remain unclear. Here, we explore the anti-tumor effect of hypocrellin B on human colorectal cancer cells and identify molecular targets. We found that hypocrellin B significantly inhibits proliferation and migration and promotes apoptosis of colorectal cancer cells in vitro by targeting the AKT/STING signaling pathway. Hypocrellin B also inhibited tumor growth in vivo in a mouse xenograft model. In summary, hypocrellin B exerts an anticolorectal cancer effect by inhibiting the phosphorylation of AKT, thus blocking a key pathway of tumor growth and survival. These results indicate that hypocrellin B is a promising candidate for the treatment of colorectal cancer, warranting further investigation.

Carvedilol sensitizes chemotherapy by targeting STING to boost anti-tumor immunity

The stimulator of interferon genes (STING)-mediated type I interferon (IFN) response is critical for mounting anti-tumor immunity and sensitizing chemotherapy by remodeling the tumor immune microenvironment. However, no clinically available drugs have been applied for STING activation. Based on high-throughput screening of small-molecule microarrays, we found that carvedilol, an adrenergic receptor blocker used to treat essential hypertension and symptomatic heart failure, is a STING activator. Mechanistically, carvedilol interacts with STING at threonine 263 and enhances its dimerization. Importantly, carvedilol enhances the therapeutic effect of etoposide in both the allografted tumor model and patient-derived tumor-like cell clusters (PTCs) by promoting etoposide-induced STING activation. Our findings identify carvedilol as a STING activator and provide a theoretical basis for combining carvedilol and etoposide in cancer therapy.

Distinct oligomeric assemblies of STING induced by non-nucleotide agonists

STING plays essential roles coordinating innate immune responses to processes that range from pathogenic infection to genomic instability. Its adaptor function is activated by cyclic dinucleotide (CDN) secondary messengers originating from self (2'3'-cGAMP) or bacterial sources (3'3'-CDNs). Different classes of CDNs possess distinct binding modes, stabilizing STING's ligand-binding domain (LBD) in either a closed or open conformation. The closed conformation, induced by the endogenous ligand 2'3'-cGAMP, has been extensively studied using cryo-EM. However, significant questions remain regarding the structural basis of STING activation by open conformation-inducing ligands. Using cryo-EM, we investigate potential differences in conformational changes and oligomeric assemblies of STING for closed and open conformation-inducing synthetic agonists. While we observe a characteristic 180° rotation for both classes, the open-LBD inducing agonist diABZI-3 uniquely induces a quaternary structure reminiscent but distinct from the reported autoinhibited state of apo-STING. Additionally, we observe slower rates of activation for this ligand class in functional assays, which collectively suggests the existence of a potential additional regulatory mechanism for open conformation-inducing ligands that involves head-to-head interactions and restriction of curved oligomer formation. These observations have potential implications in the selection of an optimal class of STING agonist in the context of a defined therapeutic application.

Targeting tumor monocyte-intrinsic PD-L1 by rewiring STING signaling and enhancing STING agonist therapy

STING is an important DNA sensing machinery in initiating immune response, yet therapies targeting STING have shown poor outcomes in clinical trials. Here, we reveal that STING signaling induces PD-L1hi tumor monocytes (Tu.Mons) that dominate the resistance against STING agonist therapy. Cell-intrinsic PD-L1, induced by the STING-IRF3-IFN-I axis, is identified as the driving factor for protumoral PD-L1hi Tu.Mons. Notably, TLR2-activated Tu.Mons resist STING-induced upregulation of cell-intrinsic PD-L1 and the associated protumoral functions. Mechanistically, TLR2 stimulation remodels STING signaling by facilitating STING and TRAF6 interaction, which suppresses the IRF3-IFN-I response and enhances NF-κB activation. Moreover, we demonstrate that combining STING agonists with TLR2 agonist pretreatment significantly improves antitumor efficacy in murine syngeneic and humanized models. Our findings uncover a protumoral aspect of STING activation mediated by cell-intrinsic PD-L1 and propose a promising strategy to boost antitumor immunity by fine-tuning STING signaling outputs.

STING1 targets MYH9 to drive adipogenesis through the AKT/GSK3β/β-catenin pathway

Stimulator of interferon response cGAMP interactor 1 (STING1), as an innate immune adaptor protein that mediates DNA sensing, has attracted tremendous biomedical interest. However, several recent researches have revealed the key role of STING1 in regulating the metabolic pathway. Here, we investigated its role in adipocyte differentiation. Preadipocytes with lentivirus-mediated Sting1 knockdown or overexpression were constructed to examine the effect of STING1 on adipocyte differentiation in vitro. Proteomics was performed in adipocytes to explore the mechanisms by which STING1 exerts pro-adipogenesis effects. Coimmunoprecipitation (CoIP)/mass spectrometry (MS) assay were used to identify the interacting partners of STING1. Our results showed that STING1 was upregulated during adipogenic differentiation of 3T3-L1 and white adipose tissue-derived stromal vascular precursor cells (WAT-SVF), accompanied by upregulation of adipocyte marker genes, peroxisome proliferator-activated receptor gamma (Pparg) and CCAAT/enhancer-binding protein beta (Cebpβ). Knockdown or overexpression of Sting1 altered adipogenesis in adipocytes. Mechanistically, proteomics and CoIP/MS assay revealed that STING1 targets non-muscle myosin protein (MYH9) to block its expression, which enhances AKT/GSK3β signaling and mediates β-catenin accumulation, affecting adipogenesis-related genes in adipocytes. These findings suggest that STING1 targeting combined with MYH9 regulates adipocyte differentiation through the AKT/GSK3β/β-catenin pathway. This is a new potential target for the treatment of hypertrophic adipose tissue, or obesity.

Endothelial STING-JAK1 interaction promotes tumor vasculature normalization and antitumor immunity

Stimulator of interferon genes (STING) agonists have been developed and tested in clinical trials for their antitumor activity. However, the specific cell population(s) responsible for such STING activation-induced antitumor immunity have not been completely understood. In this study, we demonstrated that endothelial STING expression was critical for STING agonist-induced antitumor activity. STING activation in endothelium promoted vessel normalization and CD8+ T cell infiltration - which required type I IFN (IFN-I) signaling- but not IFN-γ or CD4+ T cells. Rather than an upstream adaptor for inducing IFN-I signaling, STING acted downstream of interferon-α/β receptor (IFNAR) in endothelium for the JAK1-STAT signaling activation. Mechanistically, IFN-I stimulation induced JAK1-STING interaction and promoted JAK1 phosphorylation, which involved STING palmitoylation at the Cysteine 91 site but not its C-terminal tail (CTT) domain. Endothelial STING and JAK1 expression was significantly associated with immune cell infiltration in patients with cancer, and STING palmitoylation level correlated positively with CD8+ T cell infiltration around STING-positive blood vessels in tumor tissues from patients with melanoma. In summary, our findings uncover a previously unrecognized function of STING in regulating JAK1/STAT activation downstream of IFN-I stimulation and provide a new insight for future design and clinical application of STING agonists for cancer therapy.

Differential Response to Local Stimulator of Interferon Genes Agonist Administration in Tumors with Various Stimulator of Interferon Genes Statuses

Background/Objectives: The stimulator of interferon genes (STING) is currently accepted as a relevant target for anti-cancer therapies. Besides encouraging results showing STING agonist-induced tumor growth inhibition, in some types of tumors the effect is less prominent. We hypothesized that higher STING levels in cancer cells and the possibility of its activation determine a greater anti-cancer response. As the local administration of STING agonists induces a systemic reaction, we emphasized the importance of host tumor-induced hematological disruption in the efficiency of the therapeutic response. Methods: We investigated the response to STING stimulation in murine cancer cell lines-melanoma (B16-F10) and breast carcinoma (4T1)-and murine normal cell lines: fibroblast cells (NIH/3T3), endothelial cells (H5V), and macrophages (J774A.1). We assessed STING agonist-induced tumor growth inhibition and the therapy's impact on the hematological system parameters and systemic cytokine release. Results: Our results underlined the improved therapeutic effect of STING activation in melanoma (B16-F10) over breast carcinoma (4T1) tumors. The outcomes reflected a high dysregulation of the hematological system in mice with developed 4T1 tumors, which may support persistent inflammation and impede STING-induced therapeutic effects. Moreover, among typical cytokines produced following STING activation, CCL2 fold change was the one that increased the most in the serum of B16-F10-bearing mice and differentiated the observed response to the STING agonist between investigated tumor models. Conclusions: The current study provides new evidence of the different responses to STING activation among two poorly immunogenic tumor models. The high abundance of STING in B16-F10 cells and the possibility of its activation is linked with improved therapeutic response in vivo compared to 4T1. The effect also seems to be connected with a less dysregulated hematological system in mice with B16-F10 tumors over mice with 4T1 tumors. This highlighted the need for general insight into tumor-induced local and systemic responses to the efficiency of the proposed therapy.

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.

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.

cGAS/STING in skin melanoma: from molecular mechanisms to therapeutics

Melanoma, recognized as the most aggressive type of skin cancer, has experienced a notable increase in cases, especially within populations with fair skin. This highly aggressive cancer is largely driven by UV radiation exposure, resulting in the uncontrolled growth and malignant transformation of melanocytes. The cGAS-STING pathway, an immune signaling mechanism responsible for detecting double-stranded DNA in the cytoplasm, is essential for mediating the immune response against melanoma. This pathway serves a dual purpose: it enhances antitumor immunity by activating immune cells, but it can also promote tumor growth when chronically activated by creating an immunosuppressive environment. This review comprehensively examines the multifaceted implication of the cGAS-STING pathway in melanoma pathogenesis and treatment. We explore its molecular mechanisms, including epigenetic regulation, interaction with signaling pathways such as AR signaling, and modulation by various cellular effectors like TG2 and activin-A. The therapeutic potential of modulating the cGAS-STING pathway is highlighted, with promising results from STING agonists, combination therapies with immune checkpoint inhibitors, and novel drug delivery systems, including nanoparticles and synthetic drugs. Our findings underscore the importance of the cGAS-STING pathway in melanoma, presenting it as a critical target for enhancing anti-tumor immunity. By leveraging this pathway, future therapeutic strategies can potentially convert 'cold' tumors into 'hot' tumors, making them more susceptible to immune responses.

High-performance self-cascade nanoreactors for combined ferroptosis, photothermal therapy, and starving therapy

Despite the great potential of starving therapy caused by nanoreactor based on glucose oxidase (GOX) in tumor therapy, efficiency and uncontrolled reaction rates in vivo lead to inevitable toxicity to normal tissues, which seriously hindering their clinical conversion. Herein, a cascade nanoreactor (GOX/Mn/MPDA) was constructed by coating mesoporous polydopamine nanoparticles (MPDA) with MnO2 shell and then depositing GOX into honeycomb-shaped manganese oxide nanostructures to achieve a combination of ferroptosis, photothermal therapy and starving therapy. Upon uptake of nanodrugs to cancer cells, the MnO2 shell would deplete glutathione (GSH) and produce Mn2+, while a large amount of H2O2 generated from the catalytic oxidation of glucose by GOX would accelerate the Fenton-like reaction mediated by Mn2+, producing high toxic •OH. More importantly, the cascade reaction between GOX and MnO2 would be further strengthened by localized hyperthermia caused by irradiated by near-infrared laser (NIR), inducing significant anti-tumor effects in vitro and in vivo. Regarding the effectiveness of tumor treatment in vivo, the tumor inhibition rate achieved an impressive 64.33%. This study provided a new strategy for anti-tumor therapeutic by designing a photothermal-enhanced cascade catalytic nanoreactor.

The multiple faces of cGAS-STING in antitumor immunity: prospects and challenges

As a key sensor of double-stranded DNA (dsDNA), cyclic GMP-AMP synthase (cGAS) detects cytosolic dsDNA and initiates the synthesis of 2'3' cyclic GMP-AMP (cGAMP) that activates the stimulator of interferon genes (STING). This finally promotes the production of type I interferons (IFN-I) that is crucial for bridging innate and adaptive immunity. Recent evidence show that several antitumor therapies, including radiotherapy (RT), chemotherapy, targeted therapies and immunotherapies, activate the cGAS-STING pathway to provoke the antitumor immunity. In the last decade, the development of STING agonists has been a major focus in both basic research and the pharmaceutical industry. However, up to now, none of STING agonists have been approved for clinical use. Considering the broad expression of STING in whole body and the direct lethal effect of STING agonists on immune cells in the draining lymph node (dLN), research on the optimal way to activate STING in tumor microenvironment (TME) appears to be a promising direction. Moreover, besides enhancing IFN-I signaling, the cGAS-STING pathway also plays roles in senescence, autophagy, apoptosis, mitotic arrest, and DNA repair, contributing to tumor development and metastasis. In this review, we summarize the recent advances on cGAS-STING pathway's response to antitumor therapies and the strategies involving this pathway for tumor treatment.

Second messenger 2'3'-cyclic GMP-AMP (2'3'-cGAMP): the cell autonomous and non-autonomous roles in cancer progression

Cytosolic double-stranded DNA (dsDNA) is frequently accumulated in cancer cells due to chromosomal instability or exogenous stimulation. Cyclic GMP-AMP synthase (cGAS) acts as a cytosolic DNA sensor, which is activated upon binding to dsDNA to synthesize the crucial second messenger 2'3'-cyclic GMP-AMP (2'3'-cGAMP) that in turn triggers stimulator of interferon genes (STING) signaling. The canonical role of cGAS-cGAMP-STING pathway is essential for innate immunity and viral defense. Recent emerging evidence indicates that 2'3'-cGAMP plays an important role in cancer progression via cell autonomous and non-autonomous mechanisms. Beyond its role as an intracellular messenger to activate STING signaling in tumor cells, 2'3'-cGAMP also serves as an immunotransmitter produced by cancer cells to modulate the functions of non-tumor cells especially immune cells in the tumor microenvironment by activating STING signaling. In this review, we summarize the synthesis, transmission, and degradation of 2'3'-cGAMP as well as the dual functions of 2'3'-cGAMP in a STING-dependent manner. Additionally, we discuss the potential therapeutic strategies that harness the cGAMP-mediated antitumor response for cancer therapy.

Harnessing innate immune pathways for therapeutic advancement in cancer

The innate immune pathway is receiving increasing attention in cancer therapy. This pathway is ubiquitous across various cell types, not only in innate immune cells but also in adaptive immune cells, tumor cells, and stromal cells. Agonists targeting the innate immune pathway have shown profound changes in the tumor microenvironment (TME) and improved tumor prognosis in preclinical studies. However, to date, the clinical success of drugs targeting the innate immune pathway remains limited. Interestingly, recent studies have shown that activation of the innate immune pathway can paradoxically promote tumor progression. The uncertainty surrounding the therapeutic effectiveness of targeted drugs for the innate immune pathway is a critical issue that needs immediate investigation. In this review, we observe that the role of the innate immune pathway demonstrates heterogeneity, linked to the tumor development stage, pathway status, and specific cell types. We propose that within the TME, the innate immune pathway exhibits multidimensional diversity. This diversity is fundamentally rooted in cellular heterogeneity and is manifested as a variety of signaling networks. The pro-tumor effect of innate immune pathway activation essentially reflects the suppression of classical pathways and the activation of potential pro-tumor alternative pathways. Refining our understanding of the tumor's innate immune pathway network and employing appropriate targeting strategies can enhance our ability to harness the anti-tumor potential of the innate immune pathway and ultimately bridge the gap from preclinical to clinical application.

Non-Interferon-Dependent Role of STING Signaling in Pulmonary Hypertension

BACKGROUND

Patients with constitutive activation of DNA-sensing pathway through stimulator of IFN (interferon) genes (STING), such as those with STING-associated vasculopathy with onset in infancy, develop pulmonary hypertension (PH). However, the role of STING signaling in general PH patients is heretofore undescribed. Here, we seek to investigate the role of STING in PH development.

METHODS

STING expression in patient lung samples was examined. PH was induced in global STING-deficient mice and global type I IFN receptor 1-deficient mice using bleomycin or chronic hypoxia exposure. PH development was evaluated by right ventricular systolic pressure and Fulton index, with additional histological and flow cytometric analysis. VEGF (vascular endothelial growth factor) expression on murine immune cells was quantified and evaluated with multiplex and flow cytometry. Human myeloid-derived cells were differentiated from peripheral blood mononuclear cells and treated with either STING agonist or STING antagonist for evaluation of VEGF secretion.

RESULTS

Global STING deficiency protects mice from PH development, and STING-associated PH seems independent of type I IFN signaling. Furthermore, a role for STING-VEGF signaling pathway in PH development was demonstrated, with altered VEGF secretion in murine pulmonary infiltrated myeloid cells in a STING-dependent manner. In addition, pharmacological manipulation of STING in human myeloid-derived cells supports in vivo findings. Finally, a potential role of STING-VEGF-mediated apoptosis in disease development and progression was illustrated, providing a roadmap toward potential therapeutic applications.

CONCLUSIONS

Overall, these data provide concrete evidence of STING involvement in PH, establishing biological plausibility for STING-related therapies in PH treatment.

Harnessing the innate immune system by revolutionizing macrophage-mediated cancer immunotherapy

Immunotherapy is a promising and safer alternative to conventional cancer therapies. It involves adaptive T-cell therapy, cancer vaccines, monoclonal antibodies, immune checkpoint blockade (ICB), and chimeric antigen receptor (CAR) based therapies. However, most of these modalities encounter restrictions in solid tumours owing to a dense, highly hypoxic and immune-suppressive microenvironment as well as the heterogeneity of tumour antigens. The elevated intra-tumoural pressure and mutational rates within fastgrowing solid tumours present challenges in efficient drug targeting and delivery. The tumour microenvironment is a dynamic niche infiltrated by a variety of immune cells, most of which are macrophages. Since they form a part of the innate immune system, targeting macrophages has become a plausible immunotherapeutic approach. In this review, we discuss several versatile approaches (both at pre-clinical and clinical stages) such as the direct killing of tumour-associated macrophages, reprogramming pro-tumour macrophages to anti-tumour phenotypes, inhibition of macrophage recruitment into the tumour microenvironment, novel CAR macrophages, and genetically engineered macrophages that have been devised thus far. These strategies comprise a strong and adaptable macrophage-toolkit in the ongoing fight against cancer and by understanding their significance, we may unlock the full potential of these immune cells in cancer therapy.

The Multifunctional Nature of the MicroRNA/AKT3 Regulatory Axis in Human Cancers

Serine/threonine kinase (AKT) signaling regulates diverse cellular processes and is one of the most important aberrant cell survival mechanisms associated with tumorigenesis, metastasis, and chemoresistance. Targeting AKT has become an effective therapeutic strategy for the treatment of many cancers. AKT3 (PKBγ), the least studied isoform of the AKT family, has emerged as a major contributor to malignancy. AKT3 is frequently overexpressed in human cancers, and many regulatory oncogenic or tumor suppressor small non-coding RNAs (ncRNAs), including microRNAs (miRNAs), have recently been identified to be involved in regulating AKT3 expression. Therefore, a better understanding of regulatory miRNA/AKT3 networks may reveal novel biomarkers for the diagnosis of patients with cancer and may provide invaluable information for developing more effective therapeutic strategies. The aim of this review was to summarize current research progress in the isoform-specific functions of AKT3 in human cancers and the roles of dysregulated miRNA/AKT3 in specific types of human cancers.

Antitumor effect of anti-vascular therapy with STING agonist depends on the tumor microenvironment context

Introduction

Targeting tumor vasculature is an efficient weapon to fight against cancer; however, activation of alternative pathways to rebuild the disrupted vasculature leads to rapid tumor regrowth. Immunotherapy that exploits host immune cells to elicit and sustain potent antitumor response has emerged as one of the most promising tools for cancer treatment, yet many treatments fail due to developed resistance mechanisms. Therefore, our aim was to examine whether combination of immunotherapy and anti-vascular treatment will succeed in poorly immunogenic, difficult-to-treat melanoma and triple-negative breast tumor models.

Methods

Our study was performed on B16-F10 melanoma and 4T1 breast tumor murine models. Mice were treated with the stimulator of interferon genes (STING) pathway agonist (cGAMP) and vascular disrupting agent combretastatin A4 phosphate (CA4P). Tumor growth was monitored. The tumor microenvironment (TME) was comprehensively investigated using multiplex immunofluorescence and flow cytometry. We also examined if such designed therapy sensitizes investigated tumor models to an immune checkpoint inhibitor (anti-PD-1).

Results

The use of STING agonist cGAMP as monotherapy was insufficient to effectively inhibit tumor growth due to low levels of STING protein in 4T1 tumors. However, when additionally combined with an anti-vascular agent, a significant therapeutic effect was obtained. In this model, the obtained effect was related to the TME polarization and the stimulation of the innate immune response, especially activation of NK cells. Combination therapy was unable to activate CD8+ T cells. Due to the lack of PD-1 upregulation, no improved therapeutic effect was observed when additionally combined with the anti-PD-1 inhibitor. In B16-F10 tumors, highly abundant in STING protein, cGAMP as monotherapy was sufficient to induce potent antitumor response. In this model, the therapeutic effect was due to the infiltration of the TME with activated NK cells. cGAMP also caused the infiltration of CD8+PD-1+ T cells into the TME; hence, additional benefits of using the PD-1 inhibitor were observed.

Conclusion

The study provides preclinical evidence for a great influence of the TME on the outcome of applied therapy, including immune cell contribution and ICI responsiveness. We pointed the need of careful TME screening prior to antitumor treatments to achieve satisfactory results.

Functional tumor cell-intrinsic STING, not host STING, drives local and systemic antitumor immunity and therapy efficacy following cryoablation

BACKGROUND

Despite its potential utility in delivering direct tumor killing and in situ whole-cell tumor vaccination, tumor cryoablation produces highly variable and unpredictable clinical response, limiting its clinical utility. The mechanism(s) driving cryoablation-induced local antitumor immunity and the associated abscopal effect is not well understood.

METHODS

The aim of this study was to identify and explore a mechanism of action by which cryoablation enhances the therapeutic efficacy in metastatic tumor models. We used the subcutaneous mouse model of the rhabdomyosarcoma (RMS) cell lines RMS 76-9STINGwt or RMS 76-9STING-/-, along with other murine tumor models, in C57BL/6 or STING-/- (TMEM173-/- ) mice to evaluate local tumor changes, lung metastasis, abscopal effect on distant tumors, and immune cell dynamics in the tumor microenvironment (TME).

RESULTS

The results show that cryoablation efficacy is dependent on both adaptive immunity and the STING signaling pathway. Contrary to current literature dictating an essential role of host-derived STING activation as a driver of antitumor immunity in vivo, we show that local tumor control, lung metastasis, and the abscopal effect on distant tumor are all critically dependent on a functioning tumor cell-intrinsic STING signaling pathway, which induces inflammatory chemokine and cytokine responses in the cryoablated TME. This reliance extends beyond cryoablation to include intratumoral STING agonist therapy. Additionally, surveys of gene expression databases and tissue microarrays of clinical tumor samples revealed a wide spectrum of expressions among STING-related signaling components.

CONCLUSIONS

Tumor cell-intrinsic STING pathway is a critical component underlying the effectiveness of cryoablation and suggests that expression of STING-related signaling components may serve as a potential therapy response biomarker. Our data also highlight an urgent need to further characterize tumor cell-intrinsic STING pathways and the associated downstream inflammatory response evoked by cryoablation and other STING-dependent therapy approaches.

Biomaterial-enabled therapeutic modulation of cGAS-STING signaling for enhancing antitumor immunity

cGAS-STING signaling is a central component in the therapeutic action of most existing cancer therapies. The accumulated knowledge of tumor immunoregulatory network in recent years has spurred the development of cGAS-STING agonists for tumor treatment as an effective immunotherapeutic strategy. However, the clinical translation of these agonists is thus far unsatisfactory because of the low immunostimulatory efficacy and unrestricted side effects under clinically relevant conditions. Interestingly, the rational integration of biomaterial technology offers a promising approach to overcome these limitations for more effective and safer cGAS-STING-mediated tumor therapy. Herein, we first outline the cGAS-STING signaling axis and generally discuss its association with tumors. We then symmetrically summarize the recent progress in those biomaterial-based cGAS-STING agonism strategies to generate robust antitumor immunity, categorized by the chemical nature of those cGAS-STING stimulants and carrier substrates. Finally, a perspective is provided to discuss the existing challenges and potential opportunities in cGAS-STING modulation for tumor therapy.

Light-Driven Self-Recruitment of Biomimetic Semiconducting Polymer Nanoparticles for Precise Tumor Vascular Disruption

Tumor vascular disrupting therapy has offered promising opportunities to treat cancer in clinical practice, whereas the overall therapeutic efficacy is notably limited due to the off-target effects and repeated dose toxicity of vascular disrupting agents (VDAs). To tackle this problem, a VDA-free biomimetic semiconducting polymer nanoparticle (SPN_P ) is herein reported for precise tumor vascular disruption through two-stage light manipulation. SPN_P consists of a semiconducting polymer nanoparticle as the photothermal agent camouflaged with platelet membranes that specifically target disrupted vasculature. Upon the first photoirradiation, SPN_P administered in vivo generates mild hyperthermia to trigger tumor vascular hemorrhage, which activates the coagulation cascade and recruits more SPN_P to injured blood vessels. Such enhanced tumor vascular targeting of photothermal agents enables intense hyperthermia to destroy the tumor vasculature during the second photoirradiation, leading to complete tumor eradication and efficient metastasis inhibition. Intriguingly, the mechanism study reveals that this vascular disruption strategy alleviates splenomegaly and reverses the immunosuppressive tumor microenvironment by reducing myeloid-derived suppressor cells. Therefore, this study not only illustrates a light-driven self-recruitment strategy to enhance tumor vascular disruption via a single dose of biomimetic therapeutics but also deciphers the immunotherapeutic role of vascular disruption therapy that is conducive to clinical studies.

The impact of hypoxia on tumor-mediated bypassing anti-PD-(L)1 therapy

Extending the durability of response is the current focus in cancer immunotherapy with immune checkpoint inhibitors (ICIs). However, factors like non-immunogenic tumor microenvironment (TME) along with aberrant angiogenesis and dysregulated metabolic systems are negative contributors. Hypoxia is a key TME condition and a critical promoter of tumor hallmarks. It acts on immune and non-immune cells within TME in order for promoting immune evasion and therapy resistance. Extreme hypoxia is a major promoter of resistance to the programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitor therapy. Hypoxia inducible factor-1 (HIF-1) acts as a key mediator of hypoxia and a critical promoter of resistance to the anti-PD-(L)1. Targeting hypoxia or HIF-1 can thus be an effective strategy for reinvigoration of cellular immunity against cancer. Among various strategies presented so far, the key focus is over vascular normalization, which is an approach highly effective for reducing the rate of hypoxia, increasing drug delivery into the tumor area, and boosting the efficacy of anti-PD-(L)1.

STING-activating nanoparticles normalize the vascular-immune interface to potentiate cancer immunotherapy

The tumor-associated vasculature imposes major structural and biochemical barriers to the infiltration of effector T cells and effective tumor control. Correlations between stimulator of interferon genes (STING) pathway activation and spontaneous T cell infiltration in human cancers led us to evaluate the effect of STING-activating nanoparticles (STANs), which are a polymersome-based platform for the delivery of a cyclic dinucleotide STING agonist, on the tumor vasculature and attendant effects on T cell infiltration and antitumor function. In multiple mouse tumor models, intravenous administration of STANs promoted vascular normalization, evidenced by improved vascular integrity, reduced tumor hypoxia, and increased endothelial cell expression of T cell adhesion molecules. STAN-mediated vascular reprogramming enhanced the infiltration, proliferation, and function of antitumor T cells and potentiated the response to immune checkpoint inhibitors and adoptive T cell therapy. We present STANs as a multimodal platform that activates and normalizes the tumor microenvironment to enhance T cell infiltration and function and augments responses to immunotherapy.

Unlocking the promise of systemic STING agonist for cancer immunotherapy

Stimulator of interferon genes (STING) pathway is the key innate immune pathway involving in cancer immunity. Emerging new molecules and drug delivery systems have made systemic STING agonist immunotherapy possible and demonstrated efficient tumor eradication in preclinical studies. In this perspective, we will discuss the potential mechanisms of STING agonism as a multifaceted anti-cancer therapy and the pharmacological challenges associated with systemic delivery of STING agonists on the level of organs, tissues, cells, and intracellular compartments. We will present and discuss drug delivery strategies to address these challenges. New advances in the field can unlock the promise of systemic STING agonist as effective and safe cancer immunotherapy.

Thymidine phosphorylase facilitates retinoic acid inducible gene-I induced endothelial dysfunction

Activation of nucleic acid sensors in endothelial cells (ECs) has been shown to drive inflammation across pathologies including cancer, atherosclerosis and obesity. We previously showed that enhancing cytosolic DNA sensing by inhibiting three prime exonuclease 1 (TREX1) in ECs led to EC dysfunction and impaired angiogenesis. Here we show that activation of a cytosolic RNA sensor, Retinoic acid Induced Gene 1 (RIG-I) diminishes EC survival, angiogenesis and triggers tissue specific gene expression programs. We discovered a RIG-I dependent 7 gene signature that affects angiogenesis, inflammation and coagulation. Among these, we identified the thymidine phosphorylase TYMP as a key mediator of RIG-I induced EC dysfunction via its regulation of a subset of interferon stimulated genes. Our RIG-I induced gene signature was also conserved in the context of human diseases - in lung cancer vasculature and herpesvirus infection of lung endothelial cells. Pharmacological or genetic inhibition of TYMP rescues RIG-I induced EC death, migration arrest and restores sprouting angiogenesis. Interestingly, using RNAseq we identified a gene expression program that was RIG-I induced but TYMP dependent. Analysis of this dataset indicated that IRF1 and IRF8 dependent transcription is diminished in RIG-I activated cells when TYMP is inhibited. Functional RNAi screen of our TYMP dependent EC genes, we found that a group of 5 genes - Flot1, Ccl5, Vars2, Samd9l and Ube2l6 are critical for endothelial cell death mediated by RIG-I activation. Our observations identify mechanisms by which RIG-I drives EC dysfunction and define pathways that can be pharmacologically targeted to ameliorate RIG-I induced vascular inflammation.

Targeting STING to promote antitumor immunity

Pharmacology-based methods that promote antitumor immunity have the potential to be highly efficacious while avoiding the systemic cytotoxicity associated with traditional chemotherapies. Activation of type I interferon (IFN) signaling in antigen-presenting cell types [e.g., macrophages and dendritic cells (DCs)] is critical, if not essential, for inducing a tumor-specific adaptive immune response, including the activation of cytolytic CD8 T cells. In the context of promoting antitumor immunity, the cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING) pathway has emerged as a principal regulator of essential type I IFN signaling. As such, STING represents a highly attractive target for developing a first-in-class immunotherapy, albeit one with a potential for significant cell type- and downstream pathway-dependent on-target toxicities, as well as conceivable pharmacogenomic liabilities.

Selective STING stimulation in dendritic cells primes antitumor T cell responses

T cells that recognize tumor antigens are crucial for mounting antitumor immune responses. Induction of antitumor T cells in immunogenic tumors depends on STING, the intracellular innate immune receptor for cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) and related cyclic dinucleotides (CDNs). However, the optimal way to leverage STING activation in nonimmunogenic tumors is still unclear. Here, we show that cGAMP delivery by intratumoral injection of virus-like particles (cGAMP-VLP) led to differentiation of circulating tumor-specific T cells, decreased tumor regulatory T cells (T_regs), and antitumoral responses that synergized with PD1 blockade. By contrast, intratumoral injection of the synthetic CDN ADU-S100 led to tumor necrosis and systemic T cell activation but simultaneously depleted immune cells from injected tumors and induced minimal priming of circulating tumor-specific T cells. The antitumor effects of cGAMP-VLP required type 1 conventional dendritic cells (cDC1), whereas ADU-S100 eliminated cDC1 from injected tumors. cGAMP-VLP preferentially targeted STING in dendritic cells at a 1000-fold smaller dose than ADU-S100. Subcutaneous administration of cGAMP-VLP showed synergy when combined with PD1 blockade or a tumor T_reg-depleting antibody to elicit systemic tumor-specific T cells and antitumor activity, leading to complete and durable tumor eradication in the case of tumor T_reg depletion. These findings show that cell targeting of STING stimulation shapes the antitumor T cell response and identify a therapeutic strategy to enhance T cell-targeted immunotherapy.

Multifaceted functions of STING in human health and disease: from molecular mechanism to targeted strategy

Since the discovery of Stimulator of Interferon Genes (STING) as an important pivot for cytosolic DNA sensation and interferon (IFN) induction, intensive efforts have been endeavored to clarify the molecular mechanism of its activation, its physiological function as a ubiquitously expressed protein, and to explore its potential as a therapeutic target in a wide range of immune-related diseases. With its orthodox ligand 2'3'-cyclic GMP-AMP (2'3'-cGAMP) and the upstream sensor 2'3'-cGAMP synthase (cGAS) to be found, STING acquires its central functionality in the best-studied signaling cascade, namely the cGAS-STING-IFN pathway. However, recently updated research through structural research, genetic screening, and biochemical assay greatly extends the current knowledge of STING biology. A second ligand pocket was recently discovered in the transmembrane domain for a synthetic agonist. On its downstream outputs, accumulating studies sketch primordial and multifaceted roles of STING beyond its cytokine-inducing function, such as autophagy, cell death, metabolic modulation, endoplasmic reticulum (ER) stress, and RNA virus restriction. Furthermore, with the expansion of the STING interactome, the details of STING trafficking also get clearer. After retrospecting the brief history of viral interference and the milestone events since the discovery of STING, we present a vivid panorama of STING biology taking into account the details of the biochemical assay and structural information, especially its versatile outputs and functions beyond IFN induction. We also summarize the roles of STING in the pathogenesis of various diseases and highlight the development of small-molecular compounds targeting STING for disease treatment in combination with the latest research. Finally, we discuss the open questions imperative to answer.

Chemical regulation of the cGAS-STING pathway

Nucleic acids represent a major class of pathogen and damage signatures, recognized by a variety of host sensors to initiate signaling cascades and immune responses, such as mechanisms of RLR-MAVS, cGAS-STING, TLR-TRIF, and AIM2 inflammasome. Yet, an outstanding challenge is understanding how nucleic acid sensing initiates immune responses and its tethering in various infectious, cancerous, autoimmune, and inflammatory diseases. However, the discovery and application of a plethora of small molecule compounds have substantially facilitated this process. This review provides an overview and recent development of the innate DNA-sensing pathway of cGAS-STING and highlights the multiple agonists and inhibitors in fine-tuning the pathway that can be exploited to improve disease treatment, focusing primarily on crucial pathway components and regulators.

Gatekeeping role of Nf2/Merlin in vascular tip EC induction through suppression of VEGFR2 internalization

In sprouting angiogenesis, the precise mechanisms underlying how intracellular vascular endothelial growth factor receptor 2 (VEGFR2) signaling is higher in one endothelial cell (EC) compared with its neighbor and acquires the tip EC phenotype under a similar external cue are elusive. Here, we show that Merlin, encoded by the neurofibromatosis type 2 (NF2) gene, suppresses VEGFR2 internalization depending on VE-cadherin density and inhibits tip EC induction. Accordingly, endothelial Nf2 depletion promotes tip EC induction with excessive filopodia by enhancing VEGFR2 internalization in both the growing and matured vessels. Mechanistically, Merlin binds to the VEGFR2-VE-cadherin complex at cell-cell junctions and reduces VEGFR2 internalization-induced downstream signaling during tip EC induction. As a consequence, nonfunctional excessive sprouting occurs during tumor angiogenesis in EC-specific Nf2-deleted mice, leading to delayed tumor growth. Together, Nf2/Merlin is a crucial molecular gatekeeper for tip EC induction, capillary integrity, and proper tumor angiogenesis by suppressing VEGFR2 internalization.

Crosstalk between circRNAs and the PI3K/AKT signaling pathway in cancer progression

Circular RNAs (circRNAs), covalently closed noncoding RNAs, are widely expressed in eukaryotes and viruses. They can function by regulating target gene expression, linear RNA transcription and protein generation. The phosphoinositide 3-kinase (PI3K)/AKT signaling pathway plays key roles in many biological and cellular processes, such as cell proliferation, growth, invasion, migration, and angiogenesis. It also plays a pivotal role in cancer progression. Emerging data suggest that the circRNA/PI3K/AKT axis modulates the expression of cancer-associated genes and thus regulates tumor progression. Aberrant regulation of the expression of circRNAs in the circRNA/PI3K/AKT axis is significantly associated with clinicopathological characteristics and plays an important role in the regulation of biological functions. In this review, we summarized the expression and biological functions of PI3K-AKT-related circRNAs in vitro and in vivo and assessed their associations with clinicopathological characteristics. We also further discussed the important role of circRNAs in the diagnosis, prognostication, and treatment of cancers.