Tumor-targeted delivery of a STING agonist improvescancer immunotherapy

C176-loaded and phosphatidylserine-modified nanoparticles treat retinal neovascularization by promoting M2 macrophage polarization

Retinal neovascularization (RNV), a typical pathological manifestation involved in most neovascular diseases, causes retinal detachment, vision loss, and ultimately irreversible blindness. Repeated intravitreal injections of anti-VEGF drugs were developed against RNV, with limitations of incomplete responses and adverse effects. Therefore, a new treatment with a better curative effect and more prolonged dosage is demanding. Here, we induced macrophage polarization to anti-inflammatory M2 phenotype by inhibiting cGAS-STING signaling with an antagonist C176, appreciating the role of cGAS-STING signaling in the retina in pro-inflammatory M1 polarization. C176-loaded and phosphatidylserine-modified dendritic mesoporous silica nanoparticles were constructed and examined by a single intravitreal injection. The biosafe nanoparticles were phagocytosed by retinal macrophages through a phosphatidylserine-mediated "eat me" signal, which persistently release C176 to suppress STING signaling and thereby promote macrophage M2 polarization specifically. A single dosage can effectively alleviate pathological angiogenesis phenotypes in murine oxygen-induced retinopathy models. In conclusion, these C176-loaded nanoparticles with enhanced cell uptake and long-lasting STING inhibition effects might serve as a promising way for treating RNV.

When DNA damage responses meet tumor immunity: From mechanism to therapeutic opportunity

DNA damage is a prevalent phenomenon in the context of cancer progression. Evidence suggests that DNA damage responses (DDR) are pivotal in overcoming tumor immune evasion. Alternatively, traditional radiotherapy and chemotherapy operate by inducing DNA damage, consequently stimulating the immune system to target tumors. The intricate interplay between signaling pathways involved in DDR and immune activation underscores the significance of considering both factors in developing improved immunotherapies. By delving deeper into the mechanisms underlying immune activation brought on by DNA damage, it becomes possible to identify novel treatment approaches that boost the anticancer immune response while minimizing undesirable side effects. This review explores the mechanisms behind DNA damage-induced antitumor immune responses, the importance of DNA damage in antitumor immunity, and potential therapeutic approaches for cancer immunotherapy targeting DDR. Additionally, we discuss the challenges of combination therapy and strategies for integrating DNA damage-targeting therapies with current cancer immunotherapy. In summary, this review highlights the critical role of DNA damage in tumor immunology, underscoring the potential of DDR inhibitors as promising therapeutic modalities for cancer treatment.

New immune cell engagers for cancer immunotherapy

There have been major advances in the immunotherapy of cancer in recent years, including the development of T cell engagers - antibodies engineered to redirect T cells to recognize and kill cancer cells - for the treatment of haematological malignancies. However, the field still faces several challenges to develop agents that are consistently effective in a majority of patients and cancer types, such as optimizing drug dose, overcoming treatment resistance and improving efficacy in solid tumours. A new generation of T cell-targeted molecules was developed to tackle these issues that are potentially more effective and safer. In addition, agents designed to engage the antitumour activities of other immune cells, including natural killer cells and myeloid cells, are showing promise and have the potential to treat a broader range of cancers.

Cell Membrane Hybrid Lipid Nanovesicles Enhance Innate Immunity for Synergistic Immunotherapy by Promoting Immunogenic Cell Death and cGAS Activation

Immunotherapy shows great therapeutic potential for long-term protection against tumor relapse and metastasis. Innate immune sensors, such as cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING), dissolve DNA and induce type I interferon. Through activation of the cGAS/STING pathway, chemotherapy drugs and reversine (REV) may provide synergetic anti-tumor effects. Here, we prepared drug-loaded cell membrane hybrid lipid nanovesicles (LEVs) (designated LEV@DOX@REV) by fusion of cell membranes, phospholipids, doxorubicin (DOX), and REV, to realize accurate delivery to tumors and chemo-immunotherapy. The cell membranes of LEVs confer "homing" abilities. DOX can induce immunogenic cell death as a result of its specific immunomodulatory effects, which promotes the maturation of immune cells and improves the microenvironment of the immune system. REV is proven to efficiently activate cGAS/STING signaling, thereby enhancing the immune system. The antitumor efficacy of LEV@DOX@REV was evaluated in a 4T1 subcutaneous tumor xenograft model, a distant metastatic tumor model, and a liver metastatic tumor model. LEV@DOX@REV facilitated the infiltration of cytotoxic T lymphocytes within tumors, increased the secretion of proinflammatory cytokines, and modified the tumor microenvironment. In conclusion, LEV@DOX@REV displayed favorable antitumor effects and extended the survival of tumor-bearing mice. We therefore successfully developed nanoparticles capable of enhancing immune activation that have potential therapeutic applications for cancer immunotherapy.

Pharmaceutical innovation and advanced biotechnology in the biotech-pharmaceutical industry for antibody-drug conjugate development

Antibody-drug conjugates (ADCs), from prototypes in the 1980s to first- and second-generation products in the 2000s, and now in their multiformats, have progressed tremendously to meet oncological challenges. Currently, 13 ADCs have been approved for medical practice, with over 200 candidates in clinical trials. Moreover, ADCs have evolved into different formats, including bispecific ADCs, probody-drug conjugates, pH-responsive ADCs, target-degrading ADCs, and immunostimulating ADCs. Technologies from biopharmaceutical industries have a crucial role in the clinical transition of these novel biotherapeutics. In this review, we highlight several features contributing to the prosperity of bioindustrial ADC development. Various proprietary technologies from biopharmaceutical companies are discussed. Such advances in biopharmaceutical industries are the backbone for the success of ADCs in development and clinical application.

Delivery of STING agonists for cancer immunotherapy

Agonists of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway, a critical mediator of innate immune response to foreign invaders with DNA, have gained significant interest in cancer immunotherapy. STING agonists are envisioned as a way of complementing the antitumor activity of the patient's immune system and immune checkpoint blockade therapy. However, their clinical development has been challenging due to the poor pharmacokinetic and physicochemical properties. This review discusses drug delivery efforts to circumvent the challenges, their accomplishment, and unmet needs based on the last five years of literature.

The Evolution of Antibody-Drug Conjugates: Toward Accurate DAR and Multi-specificity

Antibody-drug conjugates (ADCs) consist of antibodies, linkers and payloads. They offer targeted delivery of potent cytotoxic drugs to tumor cells, minimizing off-target effects. However, the therapeutic efficacy of ADCs is compromised by heterogeneity in the drug-to-antibody ratio (DAR), which impacts both cytotoxicity and pharmacokinetics (PK). Additionally, the emergence of drug resistance poses significant challenges to the clinical advancement of ADCs. To overcome these limitations, a variety of strategies have been developed, including the design of multi-specific drugs with accurate DAR. This review critically summarizes the current challenges faced by ADCs, categorizing key issues and evaluating various innovative solutions. We provide an in-depth analysis of the latest methodologies for achieving homogeneous DAR and explore design strategies for multi-specific drugs aimed at combating drug resistance. Our discussion offers a current perspective on the advancements made in refining ADC technologies, with an emphasis on enhancing therapeutic outcomes.

Enhancing immunotherapy outcomes by targeted remodeling of the tumor microenvironment via combined cGAS-STING pathway strategies

Immune checkpoint inhibitors (ICIs) represent a groundbreaking advance in the treatment of malignancies such as melanoma and non-small cell lung cancer, showcasing substantial therapeutic benefits. Nonetheless, the efficacy of ICIs is limited to a small subset of patients, primarily benefiting those with "hot" tumors characterized by significant immune infiltration. The challenge of converting "cold" tumors, which exhibit minimal immune activity, into "hot" tumors to enhance their responsiveness to ICIs is a critical and complex area of current research. Central to this endeavor is the activation of the cGAS-STING pathway, a pivotal nexus between innate and adaptive immunity. This pathway's activation promotes the production of type I interferon (IFN) and the recruitment of CD8+ T cells, thereby transforming the tumor microenvironment (TME) from "cold" to "hot". This review comprehensively explores the cGAS-STING pathway's role in reconditioning the TME, detailing the underlying mechanisms of innate and adaptive immunity and highlighting the contributions of various immune cells to tumor immunity. Furthermore, we delve into the latest clinical research on STING agonists and their potential in combination therapies, targeting this pathway. The discussion concludes with an examination of the challenges facing the advancement of promising STING agonists in clinical trials and the pressing issues within the cGAS-STING signaling pathway research.

IGF2 promotes alveolar bone regeneration in murine periodontitis via inhibiting cGAS/STING-mediated M1 macrophage polarization

Periodontitis is a chronic inflammatory disease with the destruction of supporting periodontal tissue. This study evaluated the role of insulin-like growth factor 2 (IGF2) in periodontitis by inhibiting the polarization of M1 macrophages via the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway. IGF2 was enriched in the gingival tissue of murine periodontitis model identified by RNA sequencing. IGF2 application alleviated the expression of pro-inflammatory factors and promoted osteogenesis and the expression of related genes and proteins in a dose-dependent manner in periodontitis. The result of micro-CT verified this finding. Both in vivo and in vitro results revealed that IGF2 decreased the polarization of M1 macrophages and pro-inflammatory factors by immunofluorescence staining, flow cytometry, western blotting and RT-PCR. IGF2 application promoted the osteogenic ability of periodontal ligament fibroblasts (PDLFs) indirectly via its inhibition of M1 polarization evaluated by alkaline phosphatase and alizarin red staining. Then, the cGAS/STING pathway was upregulated in periodontitis and macrophages challenged by LPS, the inhibition of which led to downregulation of M1 polarization. Furthermore, IGF2 could downregulate cGAS, STING and the phosphorylation of P65. Collectively, our study indicates IGF2 can regulate the polarization of M1 macrophages via the cGAS/STING pathway and highlights the promising future of IGF2 as a therapeutic treatment for periodontitis.

The STING agonist IMSA101 enhances chimeric antigen receptor T cell function by inducing IL-18 secretion

As a strategy to improve the therapeutic success of chimeric antigen receptor T cells (CART) directed against solid tumors, we here test the combinatorial use of CART and IMSA101, a newly developed stimulator of interferon genes (STING) agonist. In two syngeneic tumor models, improved overall survival is observed when mice are treated with intratumorally administered IMSA101 in addition to intravenous CART infusion. Transcriptomic analyses of CART isolated from tumors show elevated T cell activation, as well as upregulated cytokine pathway signatures, in particular IL-18, in the combination treatment group. Also, higher levels of IL-18 in serum and tumor are detected with IMSA101 treatment. Consistent with this, the use of IL-18 receptor negative CART impair anti-tumor responses in mice receiving combination treatment. In summary, we find that IMSA101 enhances CART function which is facilitated through STING agonist-induced IL-18 secretion.

Programable Albumin-Hitchhiking Nanobodies Enhance the Delivery of STING Agonists to Potentiate Cancer Immunotherapy

Stimulator of interferon genes (STING) is a promising target for potentiating antitumor immunity, but multiple pharmacological barriers limit the clinical utility, efficacy, and/or safety of STING agonists. Here we describe a modular platform for systemic administration of STING agonists based on nanobodies engineered for in situ hitchhiking of agonist cargo on serum albumin. Using site-selective bioconjugation chemistries to produce molecularly defined products, we found that covalent conjugation of a STING agonist to anti-albumin nanobodies improved pharmacokinetics and increased cargo accumulation in tumor tissue, stimulating innate immune programs that increased the infiltration of activated natural killer cells and T cells, which potently inhibited tumor growth in multiple mouse tumor models. We also demonstrated the programmability of the platform through the recombinant integration of a second nanobody domain that targeted programmed cell death ligand-1 (PD-L1), which further increased cargo delivery to tumor sites while also blocking immunosuppressive PD-1/PD-L1 interactions. This bivalent nanobody carrier for covalently conjugated STING agonists stimulated robust antigen-specific T cell responses and long-lasting immunological memory, conferred enhanced therapeutic efficacy, and was effective as a neoadjuvant treatment for improving responses to adoptive T cell transfer therapy. Albumin-hitchhiking nanobodies thus offer an enabling, multimodal, and programmable platform for systemic delivery of STING agonists with potential to augment responses to multiple immunotherapeutic modalities.

Tumor Exosomal ENPP1 Hydrolyzes cGAMP to Inhibit cGAS-STING Signaling

To evade immune surveillance, tumor cells express ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1) on the surface of their membrane, which degrades extracellular cyclic GMP-AMP (cGAMP), thereby inhibiting the cyclic GMP-AMP synthase (cGAS) stimulator of interferon gene (STING) DNA-sensing pathway. To fully understand this tumor stealth mechanism, it is essential to determine whether other forms of ENPP1 with hydrolytic cGAMP activity also are present in the tumor microenvironment to regulate this innate immune pathway. Herein, it is reported that various tumor-derived exosomes carry ENPP1, and can hydrolyze synthetic 2'3'-cGAMP and endogenous 2'3'-cGAMP produced by cells to inhibit cGAS-STING pathway in immune cells. Moreover, tumor exosomal ENPP1 also can hydrolyze 2'3'-cGAMP bound to LL-37 (an effective transporter of 2'3'-cGAMP) to inhibit STING signaling. Furthermore, high expression of ENPP1 in exosomes is observed isolated from human breast and lung cancer tissue, and tumor exosomal ENPP1 inhibited the immune infiltration of CD8+ T cells and CD4+ T cells. The results elucidate the essential function of tumor exosomal ENPP1 in the cGAS-STING pathway, furthering understanding of the crosstalk between the tumor cells and immune system.

Branched glycopolymer prodrug-derived nanoassembly combined with a STING agonist activates an immuno-supportive status to boost anti-PD-L1 antibody therapy

Despite the great potential of anti-PD-L1 antibodies for immunotherapy, their low response rate due to an immunosuppressive tumor microenvironment has hampered their application. To address this issue, we constructed a cell membrane-coated nanosystem (mB4S) to reverse an immunosuppressive microenvironment to an immuno-supportive one for strengthening the anti-tumor effect. In this system, Epirubicin (EPI) as an immunogenic cell death (ICD) inducer was coupled to a branched glycopolymer via hydrazone bonds and diABZI as a stimulator of interferon genes (STING) agonist was encapsulated into mB4S. After internalization of mB4S, EPI was acidic-responsively released to induce ICD, which was characterized by an increased level of calreticulin (CRT) exposure and enhanced ATP secretion. Meanwhile, diABZI effectively activated the STING pathway. Treatment with mB4S in combination with an anti-PD-L1 antibody elicited potent immune responses by increasing the ratio of matured dendritic cells (DCs) and CD8+ T cells, promoting cytokines secretion, up-regulating M1-like tumor-associated macrophages (TAMs) and down-regulating immunosuppressive myeloid-derived suppressor cells (MDSCs). Therefore, this nanosystem for co-delivery of an ICD inducer and a STING agonist achieved promotion of DCs maturation and CD8+ T cells infiltration, creating an immuno-supportive microenvironment, thus potentiating the therapy effect of the anti-PD-L1 antibody in both 4T1 breast and CT26 colon tumor mice.

Synthetic cationic helical polypeptides for the stimulation of antitumour innate immune pathways in antigen-presenting cells

Intracellular DNA sensors regulate innate immunity and can provide a bridge to adaptive immunogenicity. However, the activation of the sensors in antigen-presenting cells (APCs) by natural agonists such as double-stranded DNAs or cyclic nucleotides is impeded by poor intracellular delivery, serum stability, enzymatic degradation and rapid systemic clearance. Here we show that the hydrophobicity, electrostatic charge and secondary conformation of helical polypeptides can be optimized to stimulate innate immune pathways via endoplasmic reticulum stress in APCs. One of the three polypeptides that we engineered activated two major intracellular DNA-sensing pathways (cGAS-STING (for cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes) and Toll-like receptor 9) preferentially in APCs by promoting the release of mitochondrial DNA, which led to the efficient priming of effector T cells. In syngeneic mouse models of locally advanced and metastatic breast cancers, the polypeptides led to potent DNA-sensor-mediated antitumour responses when intravenously given as monotherapy or with immune checkpoint inhibitors. The activation of multiple innate immune pathways via engineered cationic polypeptides may offer therapeutic advantages in the generation of antitumour immune responses.

Harnessing the cGAS-STING pathway to potentiate radiation therapy: current approaches and future directions

In this review, we cover the current understanding of how radiation therapy, which uses ionizing radiation to kill cancer cells, mediates an anti-tumor immune response through the cGAS-STING pathway, and how STING agonists might potentiate this. We examine how cGAS-STING signaling mediates the release of inflammatory cytokines in response to nuclear and mitochondrial DNA entering the cytoplasm. The significance of this in the context of cancer is explored, such as in response to cell-damaging therapies and genomic instability. The contribution of the immune and non-immune cells in the tumor microenvironment is considered. This review also discusses the burgeoning understanding of STING signaling that is independent of inflammatory cytokine release and the various mechanisms by which cancer cells can evade STING signaling. We review the available data on how ionizing radiation stimulates cGAS-STING signaling as well as how STING agonists may potentiate the anti-tumor immune response induced by ionizing radiation. There is also discussion of how novel radiation modalities may affect cGAS-STING signaling. We conclude with a discussion of ongoing and planned clinical trials combining radiation therapy with STING agonists, and provide insights to consider when planning future clinical trials combining these treatments.

Macrophages: plastic participants in the diagnosis and treatment of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) rank among the most prevalent types of head and neck cancer globally. Unfortunately, a significant number of patients receive their diagnoses at advanced stages, limiting the effectiveness of available treatments. The tumor microenvironment (TME) is a pivotal player in HNSCC development, with macrophages holding a central role. Macrophages demonstrate diverse functions within the TME, both inhibiting and facilitating cancer progression. M1 macrophages are characterized by their phagocytic and immune activities, while M2 macrophages tend to promote inflammation and immunosuppression. Striking a balance between these different polarization states is essential for maintaining overall health, yet in the context of tumors, M2 macrophages typically prevail. Recent efforts have been directed at controlling the polarization states of macrophages, paving the way for novel approaches to cancer treatment. Various drugs and immunotherapies, including innovative treatments based on macrophages like engineering macrophages and CAR-M cell therapy, have been developed. This article provides an overview of the roles played by macrophages in HNSCC, explores potential therapeutic targets and strategies, and presents fresh perspectives on the future of HNSCC treatment.

Discovery of a triphenylamine-based ligand that targets mitochondrial DNA G-quadruplexes and activates the cGAS-STING immunomodulatory pathway

Stabilization of G-quadruplex (G4) structures in mitochondria leads to the damage of mitochondrial DNA (mtDNA), making mtDNA G4s a promising target in the field of cancer therapy in recent years. Damaged mtDNA released into the cytosol can stimulate cytosolic DNA-sensing pathways, and cGAS-STING pathway is a typical one with potent immunostimulatory effects. A few small molecule ligands of mtDNA G4s are identified with antitumor efficacy, but little is known about their results and mechanisms on immunomodulation. In this study, we engineered a series of triphenylamine-based analogues targeting mtDNA G4s, and A6 was determined as the most promising compound. Cellular studies indicated that A6 caused severe mtDNA damage. Then, damaged mtDNA stimulated cGAS-STING pathway, resulting in the following cytokine production of tumor cells and the maturation of DCs. In vivo experiments certified that A6 exerted suppressive influences on tumor growth and metastasis in 4T1 cell-bearing mice by the regulation of TME, including the remodeling of macrophages and the activation of T cells. To our knowledge, it is the first time to report a ligand targeting mtDNA G4s to activate the cGAS-STING immunomodulatory pathway, providing a novel strategy for the future development of mtDNA G4-based antitumor agents.

PBMCs as Tool for Identification of Novel Immunotherapy Biomarkers in Lung Cancer

BACKGROUND

Lung cancer (LC), including both non-small (NSCLC) and small (SCLC) subtypes, is currently treated with a combination of chemo- and immunotherapy. However, predictive biomarkers to identify high-risk patients are needed. Here, we explore the role of peripheral blood mononuclear cells (PBMCs) as a tool for novel biomarkers searching.

METHODS

We analyzed the expression of the cGAS-STING pathway, a key DNA sensor that activates during chemotherapy, in PBMCs from LC patients divided into best responders (BR), responders (R) and non-responders (NR). The PBMCs were whole exome sequenced (WES).

RESULTS

PBMCs from BR and R patients of LC cohorts showed the highest levels of STING (p < 0.0001) and CXCL10 (p < 0.0001). From WES, each subject had at least 1 germline/somatic alteration in a DDR gene and the presence of more DDR gene mutations correlated with clinical responses, suggesting novel biomarker implications. Thus, we tested the effect of the pharmacological DDR inhibitor (DDRi) in PBMCs and in three-dimensional spheroid co-culture of PBMCs and LC cell lines; we found that DDRi strongly increased cGAS-STING expression and tumor infiltration ability of immune cells in NR and R patients. Furthermore, we performed FACS analysis of PBMCs derived from LC patients from the BR, R and NR cohorts and we found that cytotoxic T cell subpopulations displayed the highest STING expression.

CONCLUSIONS

cGAS-STING signaling activation in PBMCs may be a novel potential predictive biomarker for the response to immunotherapy and high levels are correlated with a better response to treatment along with an overall increased antitumor immune injury.

Tumor associated macrophages as key contributors and targets in current and future therapies for melanoma

INTRODUCTION

Despite the success of immunotherapies for melanoma in recent years, there remains a significant proportion of patients who do not yet derive benefit from available treatments. Immunotherapies currently licensed for clinical use target the adaptive immune system, focussing on Tcell interactions and functions. However, the most prevalent immune cells within the tumor microenvironment (TME) of melanoma are macrophages, a diverse immune cell subset displaying high plasticity, to which no current therapies are yet directly targeted. Macrophages have been shown not only to activate the adaptive immune response, and enhance cancer cell killing, but, when influenced by factors within the TME of melanoma, these cells also promote melanoma tumorigenesis and metastasis.

AREAS COVERED

We present a review of the most up-to-date literatureavailable on PubMed, focussing on studies from within the last 10 years. We also include data from ongoing and recent clinical trials targeting macrophages in melanoma listed on clinicaltrials.gov.

EXPERT OPINION

Understanding the multifaceted role of macrophages in melanoma, including their interactions with immune and cancer cells, the influence of current therapies on macrophage phenotype and functions and how macrophages could be targeted with novel treatment approaches, are all critical for improving outcomes for patients with melanoma.

Mannosylated STING Agonist Drugamers for Dendritic Cell-Mediated Cancer Immunotherapy

The Stimulator of Interferon Genes (STING) pathway is a promising target for cancer immunotherapy. Despite recent advances, therapies targeting the STING pathway are often limited by routes of administration, suboptimal STING activation, or off-target toxicity. Here, we report a dendritic cell (DC)-targeted polymeric prodrug platform (polySTING) that is designed to optimize intracellular delivery of a diamidobenzimidazole (diABZI) small-molecule STING agonist while minimizing off-target toxicity after parenteral administration. PolySTING incorporates mannose targeting ligands as a comonomer, which facilitates its uptake in CD206+/mannose receptor+ professional antigen-presenting cells (APCs) in the tumor microenvironment (TME). The STING agonist is conjugated through a cathepsin B-cleavable valine-alanine (VA) linker for selective intracellular drug release after receptor-mediated endocytosis. When administered intravenously in tumor-bearing mice, polySTING selectively targeted CD206+/mannose receptor+ APCs in the TME, resulting in increased cross-presenting CD8+ DCs, infiltrating CD8+ T cells in the TME as well as maturation across multiple DC subtypes in the tumor-draining lymph node (TDLN). Systemic administration of polySTING slowed tumor growth in a B16-F10 murine melanoma model as well as a 4T1 murine breast cancer model with an acceptable safety profile. Thus, we demonstrate that polySTING delivers STING agonists to professional APCs after systemic administration, generating efficacious DC-driven antitumor immunity with minimal side effects. This new polymeric prodrug platform may offer new opportunities for combining efficient targeted STING agonist delivery with other selective tumor therapeutic strategies.

cGAS-STING pathway mediates activation of dendritic cell sensing of immunogenic tumors

Type I interferons (IFN-I) play pivotal roles in tumor therapy for three decades, underscoring the critical importance of maintaining the integrity of the IFN-1 signaling pathway in radiotherapy, chemotherapy, targeted therapy, and immunotherapy. However, the specific mechanism by which IFN-I contributes to these therapies, particularly in terms of activating dendritic cells (DCs), remains unclear. Based on recent studies, aberrant DNA in the cytoplasm activates the cyclic GMP-AMP synthase (cGAS)- stimulator of interferon genes (STING) signaling pathway, which in turn produces IFN-I, which is essential for antiviral and anticancer immunity. Notably, STING can also enhance anticancer immunity by promoting autophagy, inflammation, and glycolysis in an IFN-I-independent manner. These research advancements contribute to our comprehension of the distinctions between IFN-I drugs and STING agonists in the context of oncology therapy and shed light on the challenges involved in developing STING agonist drugs. Thus, we aimed to summarize the novel mechanisms underlying cGAS-STING-IFN-I signal activation in DC-mediated antigen presentation and its role in the cancer immune cycle in this review.

The efficient synthesis and purification of 2'3'- cGAMP from Escherichia coli

Agonists of the stimulator of interferon genes (STING) pathway are being explored as potential immunotherapeutics for the treatment of cancer and as vaccine adjuvants for infectious diseases. Although chemical synthesis of 2'3' - cyclic Guanosine Monophosphate-Adenosine Monophosphate (cGAMP) is commercially feasible, the process results in low yields and utilizes organic solvents. To pursue an efficient and environmentally friendly process for the production of cGAMP, we focused on the recombinant production of cGAMP via a whole-cell biocatalysis platform utilizing the murine cyclic Guanosine monophosphate-Adenosine monophosphate synthase (mcGAS). In E. coli BL21(DE3) cells, recombinant expression of mcGAS, a DNA-dependent enzyme, led to the secretion of cGAMP to the supernatants. By evaluating the: (1) media composition, (2) supplementation of divalent cations, (3) temperature of protein expression, and (4) amino acid substitutions pertaining to DNA binding; we showed that the maximum yield of cGAMP in the supernatants was improved by 30% from 146 mg/L to 186 ± 7 mg/mL under optimized conditions. To simplify the downstream processing, we developed and validated a single-step purification process for cGAMP using anion exchange chromatography. The method does not require protein affinity chromatography and it achieved a yield of 60 ± 2 mg/L cGAMP, with <20 EU/mL (<0.3 EU/μg) of endotoxin. Unlike chemical synthesis, our method provides a route for the recombinant production of cGAMP without the need for organic solvents and supports the goal of moving toward shorter, more sustainable, and more environmentally friendly processes.

Aryl hydrocarbon receptor suppresses STING-mediated type I IFN expression in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is one of the most aggressive types of cancer. Despite decades of intense investigation, treatment options remain limited, and rapid recurrence with distant metastases remains a significant challenge. Cancer cell-intrinsic production of cytokines such as type I interferons (IFN-I) is a known potent modulator of response to therapy in many cancers, including TNBC, and can influence therapeutic outcome. Here, we report that, in TNBC systems, the aryl hydrocarbon receptor (AhR) suppresses IFN-I expression via inhibition of STImulator of Interferon Genes (STING), a key mediator of interferon production. Intratumoral STING activity is essential in mediating the efficacy of PARP inhibitors (PARPi) which are used in the treatment of cancers harboring BRCA1 deficiency. We find that, in TNBC cells, PARPi treatment activates AhR in a BRCA1 deficiency-dependent manner, thus suggesting the presence of a negative feedback loop aimed at modulating PARPi efficacy. Importantly, our results indicate that the combined inhibition of PARP and AhR is superior in elevating IFN-I expression as compared to PARPi-alone. Thus, AhR inhibition may allow for enhanced IFN-I production upon PARPi in BRCA1-deficient breast cancers, most of which are of TNBC origin, and may represent a therapeutically viable strategy to enhance PARPi efficacy.

Exploring the next generation of antibody-drug conjugates

Antibody-drug conjugates (ADCs) are a promising cancer treatment modality that enables the selective delivery of highly cytotoxic payloads to tumours. However, realizing the full potential of this platform necessitates innovative molecular designs to tackle several clinical challenges such as drug resistance, tumour heterogeneity and treatment-related adverse effects. Several emerging ADC formats exist, including bispecific ADCs, conditionally active ADCs (also known as probody-drug conjugates), immune-stimulating ADCs, protein-degrader ADCs and dual-drug ADCs, and each offers unique capabilities for tackling these various challenges. For example, probody-drug conjugates can enhance tumour specificity, whereas bispecific ADCs and dual-drug ADCs can address resistance and heterogeneity with enhanced activity. The incorporation of immune-stimulating and protein-degrader ADCs, which have distinct mechanisms of action, into existing treatment strategies could enable multimodal cancer treatment. Despite the promising outlook, the importance of patient stratification and biomarker identification cannot be overstated for these emerging ADCs, as these factors are crucial to identify patients who are most likely to derive benefit. As we continue to deepen our understanding of tumour biology and refine ADC design, we will edge closer to developing truly effective and safe ADCs for patients with treatment-refractory cancers. In this Review, we highlight advances in each ADC component (the monoclonal antibody, payload, linker and conjugation chemistry) and provide more-detailed discussions on selected examples of emerging novel ADCs of each format, enabled by engineering of one or more of these components.

Targeted intracellular delivery of dimeric STINGa by two pHLIP peptides for treatment of solid tumors

Introduction: We have developed a delivery approach that uses two pHLIP peptides that collaborate in the targeted intracellular delivery of a single payload, dimeric STINGa (dMSA). Methods: dMSA was conjugated with two pHLIP peptides via S-S cleavable self-immolating linkers to form 2pHLIP-dMSA. Results: Biophysical studies were carried out to confirm pH-triggered interactions of the 2pHLIP-dMSA with membrane lipid bilayers. The kinetics of linker self-immolation and dMSA release, the pharmacokinetics, the binding to plasma proteins, the stability of the agent in plasma, the targeting and resulting cytokine activation in tumors, and the biodistribution of the construct was investigated. This is the first study demonstrating that combining the energy of the membrane-associated folding of two pHLIPs can be utilized to enhance the targeted intracellular delivery of large therapeutic cargo payloads. Discussion: Linking two pHLIPs to the cargo extends blood half-life, and targeted delivery of dimeric STINGa induces tumor eradication and the development of robust anti-cancer immunity.

Locoregional drug delivery for cancer therapy: Preclinical progress and clinical translation

Systemic drug delivery is the current clinically preferred route for cancer therapy. However, challenges associated with tumor localization and off-tumor toxic effects limit the clinical effectiveness of this route. Locoregional drug delivery is an emerging viable alternative to systemic therapies. With the improvement in real-time imaging technologies and tools for direct access to tumor lesions, the clinical applicability of locoregional drug delivery is becoming more prominent. Theoretically, locoregional treatments can bypass challenges faced by systemic drug delivery. Preclinically, locoregional delivery of drugs has demonstrated enhanced therapeutic efficacy with limited off-target effects while still yielding an abscopal effect. Clinically, an array of locoregional strategies is under investigation for the delivery of drugs ranging in target and size. Locoregional tumor treatment strategies can be classified into two main categories: 1) direct drug infusion via injection or implanted port and 2) extended drug elution via injected or implanted depot. The number of studies investigating locoregional drug delivery strategies for cancer treatment is rising exponentially, in both preclinical and clinical settings, with some approaches approved for clinical use. Here, we highlight key preclinical advances and the clinical relevance of such locoregional delivery strategies in the treatment of cancer. Furthermore, we critically analyze 949 clinical trials involving locoregional drug delivery and discuss emerging trends.

Therapeutic synthetic and natural materials for immunoengineering

Immunoengineering is a rapidly evolving field that has been driving innovations in manipulating immune system for new treatment tools and methods. The need for materials for immunoengineering applications has gained significant attention in recent years due to the growing demand for effective therapies that can target and regulate the immune system. Biologics and biomaterials are emerging as promising tools for controlling immune responses, and a wide variety of materials, including proteins, polymers, nanoparticles, and hydrogels, are being developed for this purpose. In this review article, we explore the different types of materials used in immunoengineering applications, their properties and design principles, and highlight the latest therapeutic materials advancements. Recent works in adjuvants, vaccines, immune tolerance, immunotherapy, and tissue models for immunoengineering studies are discussed.

The cGAS-STING pathway: a therapeutic target in diabetes and its complications

Diabetic wound healing (DWH) represents a major complication of diabetes where inflammation is a key impediment to proper healing. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway has emerged as a central mediator of inflammatory responses to cell stress and damage. However, the contribution of cGAS-STING activation to impaired healing in DWH remains understudied. In this review, we examine the evidence that cGAS-STING-driven inflammation is a critical factor underlying defective DWH. We summarize studies revealing upregulation of the cGAS-STING pathway in diabetic wounds and discuss how this exacerbates inflammation and senescence and disrupts cellular metabolism to block healing. Partial pharmaceutical inhibition of cGAS-STING has shown promise in damping inflammation and improving DWH in preclinical models. We highlight key knowledge gaps regarding cGAS-STING in DWH, including its relationships with endoplasmic reticulum stress and metal-ion signaling. Elucidating these mechanisms may unveil new therapeutic targets within the cGAS-STING pathway to improve healing outcomes in DWH. This review synthesizes current understanding of how cGAS-STING activation contributes to DWH pathology and proposes future research directions to exploit modulation of this pathway for therapeutic benefit.

Applications of cryo-EM in drug development for STING

STING is a critical adaptor protein in the cGAS-mediated DNA-sensing innate immune pathway. Binding of the second messenger cGAMP generated by cGAS to STING induces the high-order oligomerization and activation of the STING dimer. STING is a promising target for diseases associated with the cGAS/STING pathway such as cancer and autoimmune diseases. Recent applications of cryo-EM to STING have led to exciting progress in the understanding of its regulatory mechanism. Cryo-EM structures of STING bound to either cGAMP mimetics or novel small molecule ligands not only revealed the action mechanisms of these ligands but also suggested new ways to modulate the activity of STING for therapeutic purposes. Some of these recent studies are highlighted here.

Novel tumor-associated macrophage populations and subpopulations by single cell RNA sequencing

Tumor-associated macrophages (TAMs) are present in almost all solid tumor tissues. 16They play critical roles in immune regulation, tumor angiogenesis, tumor stem cell activation, tumor invasion and metastasis, and resistance to therapy. However, it is unclear how TAMs perform these functions. With the application of single-cell RNA sequencing (scRNA-seq), it has become possible to identify TAM subpopulations associated with distinct functions. In this review, we discuss four novel TAM subpopulations in distinct solid tumors based on core gene signatures by scRNA-seq, including FCN1 +, SPP1 +, C1Q + and CCL18 + TAMs. Functional enrichment and gene expression in scRNA-seq data from different solid tumor tissues found that FCN1 + TAMs may induce inflammation; SPP1 + TAMs are potentially involved in metastasis, angiogenesis, and cancer cell stem cell activation, whereas C1Q + TAMs participate in immune regulation and suppression; And CCL18 + cells are terminal immunosuppressive macrophages that not only have a stronger immunosuppressive function but also enhance tumor metastasis. SPP1 + and C1Q + TAM subpopulations can be further divided into distinct populations with different functions. Meanwhile, we will also present emerging evidence highlighting the separating macrophage subpopulations associated with distinct functions. However, there exist the potential disconnects between cell types and subpopulations identified by scRNA-seq and their actual function.

Cell-to-cell communications of cGAS-STING pathway in tumor immune microenvironment

Targeting cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway is a promising strategy for tumor treatment. The pattern recognition receptor cGAS identifies dsDNA and catalyzes the formation of a second messenger 2'3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), activating the downstream interferons and pro-inflammatory cytokines through the adaptor protein STING. Notably, in tumor immune microenvironment, key components of cGAS-STING pathway are transferred among neighboring cells. The intercellular transmission under these contexts serves to sustain and amplify innate immune responses while facilitating the emergence of adaptive immunity. The membrane-based system, including extracellular vesicles transport, phagocytosis and membrane fusion transmit dsDNA, cGAMP and activated STING, enhances the immune surveillance and inflammatory responses. The membrane proteins, including a specific protein channel and intercellular gap junctions, transfer cGAMP and dsDNA, which are crucial to regulate immune responses. The ligand-receptor interactions for interferon transmission amplifies the anti-tumor response. This review elaborates on the regulatory mechanisms of cell-to-cell communications of cGAS-STING pathway in tumor immune microenvironment, explores how these mechanisms modulate immunological processes and discusses potential interventions and immunotherapeutic strategies targeting these signaling cascades.

Orthogonal Hydroxyl Functionalization of cGAMP Confers Metabolic Stability and Enables Antibody Conjugation

cGAMP is a signaling molecule produced by the cGAS-DNA complex to establish antimicrobial and antitumor immunity through STING. Whereas STING activation holds potential as a new strategy to treat cancer, cGAMP is generally considered unsuitable for in vivo use because of the rapid cleavage of its phosphodiester linkages and the limited cellular uptake under physiological conditions. Consequently, phosphorothioation and fluorination are commonly used to improve the metabolic stability and permeability of cGAMP and its synthetic analogues. We now show that methylation of the 3'-hydroxyl group of cGAMP also confers metabolic stability and that acylation of the 2'-hydroxyl group can be achieved directly and selectively to enable receptor-mediated intracellular delivery. Unlike phosphorothioation and fluorination, these modifications do not create a new stereogenic center and do not require laborious building block synthesis. As such, orthogonal hydroxyl functionalization is a simple solution to issues associated with the in vivo use of cGAMP.

Caspase-9 inhibition triggers Hsp90-based chemotherapy-mediated tumor intrinsic innate sensing and enhances antitumor immunity

BACKGROUND

Antineoplastic chemotherapies are dramatically efficient when they provoke immunogenic cell death (ICD), thus inducing an antitumor immune response and even tumor elimination. However, activated caspases, the hallmark of most cancer chemotherapeutic agents, render apoptosis immunologically silent. Whether they are dispensable for chemotherapy-induced cell death and the apoptotic clearance of cells in vivo is still elusive.

METHODS

A rational cell-based anticancer drug library screening was performed to explore the immunogenic apoptosis pathway and therapeutic targets under apoptotic caspase inhibition. Based on this screening, the potential of caspase inhibition in enhancing chemotherapy-induced antitumor immunity and the mechanism of actions was investigated by various cells and mouse models.

RESULTS

Heat shock protein 90 (Hsp90) inhibition activates caspases in tumor cells to produce abundant genomic and mitochondrial DNA fragments and results in cell apoptosis. Meanwhile, it hijacks Caspase-9 signaling to suppress intrinsic DNA sensing. Pharmacological blockade or genetic deletion of Caspase-9 causes tumor cells to secrete interferon (IFN)-β via tumor intrinsic mitochondrial DNA/the second messenger cyclic GMP-AMP (cGAS) /stimulator of interferon genes (STING) pathway without impairing Hsp90 inhibition-induced cell death. Importantly, both Caspase-9 and Hsp90 inhibition triggers an ICD, leading to the release of numerous damage-associated molecular patterns such as high-mobility group box protein 1, ATP and type I IFNs in vitro and remarkable antitumor effects in vivo. Moreover, the combination treatment also induces adaptive resistance by upregulating programmed death-ligand 1 (PD-L1). Additional PD-L1 blockade can further overcome this acquired immune resistance and achieve complete tumor regression.

CONCLUSIONS

Blockade of Caspase-9 signaling selectively provokes Hsp90-based chemotherapy-mediated tumor innate sensing, leading to CD8+ T cell-dependent tumor control. Our findings implicate that pharmacological modulation of caspase pathway increases the tumor-intrinsic innate sensing and immunogenicity of chemotherapy-induced apoptosis, and synergizes with immunotherapy to overcome adaptive resistance.

Targeting mitotic regulators in cancer as a strategy to enhance immune recognition

Eukaryotic DNA has evolved to be enclosed within the nucleus to protect the cellular genome from autoinflammatory responses driven by the immunogenic nature of cytoplasmic DNA. Cyclic GMP-AMP Synthase (cGAS) is the cytoplasmic dsDNA sensor, which upon activation of Stimulator of Interferon Genes (STING), mediates production of pro-inflammatory interferons (IFNs) and interferon stimulated genes (ISGs). However, although this pathway is crucial in detection of viral and microbial genetic material, cytoplasmic DNA is not always of foreign origin. It is now recognised that specifically in genomic instability, a hallmark of cancer, extranuclear material in the form of micronuclei (MN) can be generated as a result of unresolved DNA lesions during mitosis. Activation of cGAS-STING in cancer has been shown to regulate numerous tumour-immune interactions such as acquisition of 'immunologically hot' phenotype which stimulates immune-mediated elimination of transformed cells. Nonetheless, a significant percentage of poorly prognostic cancers is 'immunologically cold'. As this state has been linked with low proportion of tumour-infiltrating lymphocytes (TILs), improving immunogenicity of cold tumours could be clinically relevant by exhibiting synergy with immunotherapy. This review aims to present how inhibition of vital mitotic regulators could provoke cGAS-STING response in cancer and improve the efficacy of current immunotherapy regimens.

Overcoming challenges in the delivery of STING agonists for cancer immunotherapy: A comprehensive review of strategies and future perspectives

STING (Stimulator of Interferon Genes) agonists have emerged as promising agents in the field of cancer immunotherapy, owing to their excellent capacity to activate the innate immune response and combat tumor-induced immunosuppression. This review provides a comprehensive exploration of the strategies employed to develop effective formulations for STING agonists, with particular emphasis on versatile nano-delivery systems. The recent advancements in delivery systems based on lipids, natural/synthetic polymers, and proteins for STING agonists are summarized. The preparation methodologies of nanoprecipitation, self-assembly, and hydrogel, along with their advantages and disadvantages, are also discussed. Furthermore, the challenges and opportunities in developing next-generation STING agonist delivery systems are elaborated. This review aims to serve as a reference for researchers in designing novel and effective STING agonist delivery systems for cancer immunotherapy.

cGAS-STING signaling in the tumor microenvironment

The cGAS-STING signaling is an important pathway involved in the regulation of tumor microenvironment, which affects many cellular functions including immune activation. Its role in combating tumor progression is widely recognized, especially with its function in inducing innate and adaptive immune responses, on which many immunotherapies have been developed. However, a growing number of findings also suggest a diversity of its roles in shaping tumor microenvironment, including functions that promote tumor progression. Here, we summarize the functions of the cGAS-STING signaling in tumor microenvironment to maintain tumor survival and proliferation through facilitating the forming of an immunosuppressive tumor microenvironment and discuss the current advances of STING-related immunotherapies.

Antibody drug conjugates beyond cytotoxic payloads

For many years, antibody drug conjugates (ADC) have teased with the promise of targeted payload delivery to diseased cells, embracing the targeting of the antibody to which a cytotoxic payload is conjugated. During the past decade this promise has started to be realised with the approval of more than a dozen ADCs for the treatment of various cancers. Of these ADCs, brentuximab vedotin really laid the foundations of a template for a successful ADC with lysosomal payload release from a cleavable dipeptide linker, measured DAR by conjugation to the Cys-Cys interchain bonds of the antibody and a cytotoxic payload. Using this ADC design model oncology has now expanded their repertoire of payloads to include non-cytotoxic compounds. These new payload classes have their origins in prior medicinal chemistry programmes aiming to design selective oral small molecule drugs. While this may not have been achieved, the resulting compounds provide excellent starting points for ADC programmes with some compounds amenable to immediate linker attachment while for others extensive SAR and structural information offer invaluable design insights. Many of these new oncology payload classes are of interest to other therapeutic areas facilitating rapid access to drug-linkers for exploration as non-oncology ADCs. Other therapeutic areas have also pursued unique payload classes with glucocorticoid receptor modulators (GRM) being the most clinically advanced in immunology. Here, ADC payloads come full circle, as oncology is now investigating GRM payloads for the treatment of cancer. This chapter aims to cover all these new ADC approaches while describing the medicinal chemistry origins of the new non-cytotoxic payloads.

The common H232 STING allele shows impaired activities in DNA sensing, susceptibility to viral infection, and in monocyte cell function, while the HAQ variant possesses wild-type properties

Different innate immune pathways converge to Stimulator of interferon genes (STING) and trigger type I interferon responses after recognition of abnormal nucleic acids in the cells. This non-redundant function renders STING a major player in immunosurveillance, and an emerging target for cancer and infectious diseases therapeutics. Beyond somatic mutations that often occur in cancer, the human gene encoding STING protein, TMEM173 (STING1), holds great genetic heterogeneity; R232, HAQ (R71H-G230A-R293Q) and H232 are the most common alleles. Although some of these alleles are likely to be hypomorphic, their function is still debated, due to the available functional assessments, which have been performed in biased biological systems. Here, by using genetic background-matched models, we report on the functional evaluation of R232, HAQ and H232 variants on STING function, and on how these genotypes affect the susceptibility to clinically relevant viruses, thus supporting a potential contributing cause to differences in inter-individual responses to infections. Our findings also demonstrate a novel toll-like receptor-independent role of STING in modulating monocytic cell function and differentiation into macrophages. We further supported the interplay of STING1 variants and human biology by demonstrating how monocytes bearing the H232 allele were impaired in M1/M2 differentiation, interferon response and antigen presentation. Finally, we assessed the response to PD-1 inhibitor in a small cohort of melanoma patients stratified according to STING genotype. Given the contribution of the STING protein in sensing DNA viruses, bacterial pathogens and misplaced cancer DNA, these data may support the development of novel therapeutic options for infectious diseases and cancer.

Bioactivable STING Nanoagonists to Synergize NIR-II Mild Photothermal Therapy Primed Robust and Long-Term Anticancer Immunity

Pharmacological activation of the stimulator of interferon genes (STING) pathway has become a promising strategy for cancer immunotherapy. However, the insufficient tumorous accumulation, rapid clearance, and short duration of drug efficacy in the tumor microenvironment of small structural STING agonists greatly compromise the therapeutic efficacy. Herein, a tumorous extracellular matrix (ECM) is presented anchoring STING agonist-based photoimmunothernostic nanomedicine (SAPTN) that can be activated by mild-temperature photothermal therapy (mild PTT) induced neutrophilic inflammation. The SAPTN owns second window near-infrared (NIR-II) photonics properties fitting for NIR-II fluorescence and photoacoustic imaging-guided cancer therapy. The aggregates SAPTN targeting to the ECM provide slow and continuous release of potent STING agonists diABZIs. The mild PTT and long-lasting STING agonists released in the ECM synergistically prime systematic, robust, and long-term anticancer immunity. In a tumor model, this approach leads to complete tumor eradication in about 100% of mice with orthotopic breast tumors, and the mice regained tumor-free survival of at least 2 months. In addition, the immune-mediated abscopal effect shows inhibition of the distant solid tumor growth by intratumoral administration of SAPTN with laser irradiation. Overall, this approach represents a generalized photoactivable nanomedicine to prime anticancer immunity for improved cancer theranostics.

GAS-STING: a classical DNA recognition pathways to tumor therapy

Cyclic GMP-AMP synthetase (cGAS), recognized as the primary DNA sensor within cells, possesses the capability to identify foreign DNA molecules along with free DNA fragments. This identification process facilitates the production of type I IFNs through the activator of the interferon gene (STING) which induces the phosphorylation of downstream transcription factors. This action characterizes the most archetypal biological functionality of the cGAS-STING pathway. When treated with anti-tumor agents, cells experience DNA damage that triggers activation of the cGAS-STING pathway, culminating in the expression of type I IFNs and associated downstream interferon-stimulated genes. cGAS-STING is one of the important innate immune pathways,the role of type I IFNs in the articulation between innate immunity and T-cell antitumour immunity.type I IFNs promote the recruitment and activation of inflammatory cells (including NK cells) at the tumor site.Type I IFNs also can promote the activation and maturation of dendritic cel(DC), improve the antigen presentation of CD4+T lymphocytes, and enhance the cross-presentation of CD8+T lymphocytes to upregulating anti-tumor responses. This review discussed the cGAS-STING signaling and its mechanism and biological function in traditional tumor therapy and immunotherapy.

Metal-Organic Frameworks Nucleated by Silk Fibroin and Modified with Tumor-Targeting Peptides for Targeted Multimodal Cancer Therapy

Multimodal therapy requires effective drug carriers that can deliver multiple drugs to specific locations in a controlled manner. Here, the study presents a novel nanoplatform constructed using zeolitic imidazolate framework-8 (ZIF-8), a nanoscale metal-organic framework nucleated under the mediation of silk fibroin (SF). The nanoplatform is modified with the newly discovered MCF-7 breast tumor-targeting peptide, AREYGTRFSLIGGYR (AR peptide). Indocyanine green (ICG) and doxorubicin (DOX) are loaded onto the nanoplatform with high drug encapsulation efficiency (>95%). ICG enables the resultant nanoparticles (NPs), called AR-ZS/ID-P, to release reactive oxygen species for photodynamic therapy (PDT) and heat for photothermal therapy (PTT) under near-infrared (NIR) irradiation, promoting NIR fluorescence and thermal imaging to guide DOX-induced chemotherapy. Additionally, the controlled release of both ICG and DOX at acidic tumor conditions due to the dissolution of ZIF-8 provides a drug-targeting mechanism in addition to the AR peptide. When intravenously injected, AR-ZS/ID-P NPs specifically target breast tumors and exhibit higher anticancer efficacy than other groups through ICG-enabled PDT and PTT and DOX-derived chemotherapy, without inducing side effects. The results demonstrate that AR-ZS/ID-P NPs are a promising multimodal theranostic nanoplatform with maximal therapeutic efficacy and minimal side effects for targeted and controllable drug delivery.

Antibody-drug conjugates in breast cancer: overcoming resistance and boosting immune response

Antibody-drug conjugates (ADCs) have emerged as a revolutionary therapeutic class, combining the precise targeting ability of monoclonal antibodies with the potent cytotoxic effects of chemotherapeutics. Notably, ADCs have rapidly advanced in the field of breast cancer treatment. This innovative approach holds promise for strengthening the immune system through antibody-mediated cellular toxicity, tumor-specific immunity, and adaptive immune responses. However, the development of upfront and acquired resistance poses substantial challenges in maximizing the effectiveness of these therapeutics, necessitating a deeper understanding of the underlying mechanisms. These mechanisms of resistance include antigen loss, derangements in ADC internalization and recycling, drug clearance, and alterations in signaling pathways and the payload target. To overcome resistance, ongoing research and development efforts are focused on urgently identifying biomarkers, integrating immune therapy approaches, and designing novel cytotoxic payloads. This Review provides an overview of the mechanisms and clinical effectiveness of ADCs, and explores their unique immune-boosting function, while also highlighting the complex resistance mechanisms and safety challenges that must be addressed. A continued focus on how ADCs impact the tumor microenvironment will help to identify new payloads that can improve patient outcomes.

Optogenetic engineering of STING signaling allows remote immunomodulation to enhance cancer immunotherapy

The cGAS-STING signaling pathway has emerged as a promising target for immunotherapy development. Here, we introduce a light-sensitive optogenetic device for control of the cGAS/STING signaling to conditionally modulate innate immunity, called 'light-inducible SMOC-like repeats' (LiSmore). We demonstrate that photo-activated LiSmore boosts dendritic cell (DC) maturation and antigen presentation with high spatiotemporal precision. This non-invasive approach photo-sensitizes cytotoxic T lymphocytes to engage tumor antigens, leading to a sustained antitumor immune response. When combined with an immune checkpoint blocker (ICB), LiSmore improves antitumor efficacy in an immunosuppressive lung cancer model that is otherwise unresponsive to conventional ICB treatment. Additionally, LiSmore exhibits an abscopal effect by effectively suppressing tumor growth in a distal site in a bilateral mouse model of melanoma. Collectively, our findings establish the potential of targeted optogenetic activation of the STING signaling pathway for remote immunomodulation in mice.

Blocking Tim-3 enhances the anti-tumor immunity of STING agonist ADU-S100 by unleashing CD4+ T cells through regulating type 2 conventional dendritic cells

Rationale: An immunosuppressive tumor microenvironment (TME) is a major obstacle in tumor immunotherapy. Stimulator of interferon genes (STING) agonists trigger an inflammatory innate immune response to potentially overcome tumor immunosuppression. While STING agonists may hold promise as potential cancer therapy agents, tumor resistance to STING monotherapy has emerged in clinical trials, and the mechanisms remain unclear. Methods: The in vivo anti-tumor immunity of STING agonist ADU-S100 (S100), plus anti-T cell immunoglobulin and mucin-domain containing-3 antibody (αTim-3) were measured using murine tumor models. Tumor-specific T cell activation and alterations in the TME were detected using flow cytometry. The maturation and function of dendritic cells (DC) were also measured using flow cytometry, and the importance of CD4+ T cells in combination therapy was measured by blocking antibodies. Additionally, the effect of S100 on CD4+ T was verified via in vitro assays. Lastly, the impact of conventional dendritic cells (cDC) 2 with a high expression of Tim-3 on survival or therapeutic outcomes was further evaluated in human tumor samples. Results: S100 boosted CD8+ T by activating cDC1 but failed to initiate cDC2. Mechanistically, the administration of S100 results in an upregulation of Tim-3 expressed in cDC2 (Tim-3+cDC2) in both mice and humans, which is immunosuppressive. Tim-3+cDC2 restrained CD4+ T and attenuated the CD4+ T-driven anti-tumor response. Combining S100 with αTim-3 effectively promoted cDC2 maturation and antigen presentation, releasing CD4+ T cells, thus reducing tumor burden while prolonging survival. Furthermore, high percentages of Tim-3+cDC2 in the human TME predicted poor prognosis, whereas the abundance of Tim-3+cDC2 may act as a biomarker for CD4+ T quality and a contributing indicator for responsiveness to immunotherapy. Conclusion: This research demonstrated that blocking Tim-3 could enhance the anti-tumor immunity of STING agonist ADU-S100 by releasing CD4+ T cells through regulating cDC2. It also revealed an intrinsic barrier to ADU-S100 monotherapy, besides providing a combinatorial strategy for overcoming immunosuppression in tumors.

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.

Photoactivated DNA Assembly and Disassembly for On-Demand Activation and Termination of cGAS-STING Signaling

Despite significant progress in DNA self-assembly for interfacing with biology, spatiotemporally controlled regulation of biological process via in situ dynamic DNA assembly remains an outstanding challenge. Here, we report an optically triggered DNA assembly and disassembly strategy that enables on-demand activation and termination of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway. In the design, an activatable DNA hairpin is engineered with a photocleavable group at defined site to modulate its self-assembly activity. Light activation induces the configurational switching and consequent self-assembly of the DNA hairpins to form long linear double-stranded structures, allowing to stimulate cGAS protein to synthesize 2',3'-cyclic-GMP-AMP (cGAMP) for STING stimulation. Furthermore, by endowing the pre-assembled DNA scaffold with a built-in photolysis feature, we demonstrate that the cGAS-STING stimulation can be efficiently terminated through remote photo-triggering, providing for the first time a route to control the temporal "dose" on-demand for such a stimulation. We envision that this regulation strategy will benefit and inspire both fundamental research and therapeutic applications regarding the cGAS-STING pathway.

The battle between the innate immune cGAS-STING signaling pathway and human herpesvirus infection

The incidence of human herpesvirus (HHVs) is gradually increasing and has affected a wide range of population. HHVs can result in serious consequences such as tumors, neonatal malformations, sexually transmitted diseases, as well as pose an immense threat to the human health. The cGAS-STING pathway is one of the innate immune pattern-recognition receptors discovered recently. This article discusses the role of the cGAS-STING pathway in human diseases, especially in human herpesvirus infections, as well as highlights how these viruses act on this pathway to evade the host immunity. Moreover, the author provides a comprehensive overview of modulators of the cGAS-STING pathway. By focusing on the small molecule compounds based on the cGAS-STING pathway, novel targets and concepts have been proposed for the development of antiviral drugs and vaccines, while also providing a reference for the investigation of disease models related to the cGAS-STING pathway. HHV is a double-stranded DNA virus that can trigger the activation of intracellular DNA sensor cGAS, after which the host cells initiate a cascade of reactions that culminate in the secretion of type I interferon to restrict the viral replication. Meanwhile, the viral protein can interact with various molecules in the cGAS-STING pathway. Viruses can evade immune surveillance and maintain their replication by inhibiting the enzyme activity of cGAS and reducing the phosphorylation levels of STING, TBK1 and IRF3 and suppressing the interferon gene activation. Activators and inhibitors of the cGAS-STING pathway have yielded numerous promising research findings in vitro and in vivo pertaining to cGAS/STING-related disease models. However, there remains a dearth of small molecule modulators that have been successfully translated into clinical applications, which serves as a hurdle to be overcome in the future.

Lipid-based nanoparticles as drug delivery systems for cancer immunotherapy

Immune checkpoint inhibitors (ICIs) have shown remarkable success in cancer treatment. However, in cancer patients without sufficient antitumor immunity, numerous data indicate that blocking the negative signals elicited by immune checkpoints is ineffective. Drugs that stimulate immune activation-related pathways are emerging as another route for improving immunotherapy. In addition, the development of nanotechnology presents a promising platform for tissue and cell type-specific delivery and improved uptake of immunomodulatory agents, ultimately leading to enhanced cancer immunotherapy and reduced side effects. In this review, we summarize and discuss the latest developments in nanoparticles (NPs) for cancer immuno-oncology therapy with a focus on lipid-based NPs (lipid-NPs), including the characteristics and advantages of various types. Using the agonists targeting stimulation of the interferon genes (STING) transmembrane protein as an exemplar, we review the potential of various lipid-NPs to augment STING agonist therapy. Furthermore, we present recent findings and underlying mechanisms on how STING pathway activation fosters antitumor immunity and regulates the tumor microenvironment and provide a summary of the distinct STING agonists in preclinical studies and clinical trials. Ultimately, we conduct a critical assessment of the obstacles and future directions in the utilization of lipid-NPs to enhance cancer immunotherapy.

Bacterial cGAS-like enzymes produce 2',3'-cGAMP to activate an ion channel that restricts phage replication

The mammalian innate immune system uses cyclic GMP-AMP synthase (cGAS) to synthesize the cyclic dinucleotide 2',3'-cGAMP during antiviral and antitumor immune responses. 2',3'-cGAMP is a nucleotide second messenger that initiates inflammatory signaling by binding to and activating the stimulator of interferon genes (STING) receptor. Bacteria also encode cGAS/DncV-like nucleotidyltransferases (CD-NTases) that produce nucleotide second messengers to initiate antiviral (antiphage) signaling. Bacterial CD-NTases produce a wide range of cyclic oligonucleotides but have not been documented to produce 2',3'-cGAMP. Here we discovered bacterial CD-NTases that produce 2',3'-cGAMP to restrict phage replication. Bacterial 2',3'-cGAMP binds to CD-NTase associated protein 14 (Cap14), a transmembrane protein of unknown function. Using electrophysiology, we show that Cap14 is a chloride-selective ion channel that is activated by 2',3'-cGAMP binding. Cap14 adopts a modular architecture, with an N-terminal transmembrane domain and a C-terminal nucleotide-binding SAVED domain. Domain-swapping experiments demonstrated the Cap14 transmembrane region could be substituted with a nuclease, thereby generating a biosensor that is selective for 2',3'-cGAMP. This study reveals that 2',3'-cGAMP signaling extends beyond metazoa to bacteria. Further, our findings suggest that transmembrane proteins of unknown function in bacterial immune pathways may broadly function as nucleotide-gated ion channels.