Nucleic Acid Sensors as Therapeutic Targets for Human Disease

Enhanced Cellular Immunity for Hepatitis B Virus Vaccine: A Novel Polyinosinic-Polycytidylic Acid-Incorporated Adjuvant Leveraging Cytoplasmic Retinoic Acid-Inducible Gene-Like Receptor Activation and Increased Antigen Uptake

Conventional aluminum adjuvants exhibit limited cellular immunity. Polyinosinic-polycytidylic acid (poly I:C) activates cytoplasmic retinoic acid-inducible gene-like receptor (RLR), triggering strong T cell activation and cellular responses. However, when applied as an adjuvant, its limited endocytosis and restricted cytoplasmic delivery diminish its effectiveness and increase its toxicity. Hybrid polymer-lipid nanoparticle (PLNP) possesses numerous benefits such as good stability, reduced drug leakage, simple fabrication, easy property modulation, and excellent reproducibility compared to the lipid nanoparticle or the polymeric vector. Here, we developed a novel cationic polymer-lipid hybrid adjuvant capable of incorporating poly I:C to enhance cellular immunity. The hepatitis B surface antigen (HBsAg) was immobilized onto poly I:C-incorprated PLNP (PPLNP) via electrostatic interactions, forming the HBsAg/PPLNP vaccine formulation. The PPLNP adjuvant largely enhanced the cellular endocytosis and cytoplasmic transport of poly I:C, activating RLR followed by promoting type I interferon (IFN) secretion. Meanwhile, PPLNP obviously enhanced the antigen uptake, prolonged antigen retention at the site of administration, and facilitated enhanced transport of antigens to lymph nodes. The HBsAg/PPLNP nanovaccine led to amplified concentrations of antigen-specific immunoglobulin G (IgG), IFN-γ, granzyme B, and an enhanced IgG2a/IgG1 ratio, alongside the FasL+/CD8+ T cell activation, favoring a T helper 1 (TH1)-driven immune response. PPLNP, distinguished by its biocompatibility, ease of fabrication, and effectiveness in augmenting cellular immunity, holds significant promise as a new adjuvant.

Association of hyperactivated transposon expression with exacerbated immune activation in systemic lupus erythematosus

BACKGROUND

Systemic Lupus Erythematosus (SLE) is a complex autoimmune disorder, and transposable elements (TEs) have been hypothesized to play a significant role in its development. However, limited research has explored this connection. Our study aimed to examine the relationship between TE expression and SLE pathogenesis.

METHODS

We analyzed whole blood RNA-seq datasets from 198 SLE patients and 84 healthy controls. The REdiscoverTE pipeline was employed to quantify TE and other gene expressions, identifying differentially expressed TEs. A TE score was calculated to measure overall TE expression for each sample. Gene ontology and gene set enrichment analyses were conducted to explore the functional implications of TE upregulation. Independent datasets were utilized to replicate the results and investigate cell type-specific TE expression.

RESULTS

Our analysis identified two distinct patient groups: one with high TE expression and another with TE expression comparable to controls. Patients with high TE expression exhibited upregulation of pathways involving nucleic acid sensors, and TE expression was strongly correlated with interferon (IFN) signatures. Furthermore, these patients displayed deregulated cell composition, including increased neutrophils and decreased regulatory T cells. Neutrophils were suggested as the primary source of TE expression, contributing to IFN production.

CONCLUSIONS

Our findings suggest that TE expression may serve as a crucial mediator in maintaining the activation of interferon pathways, acting as an endogenous source of nucleic acid stimulators in SLE patients.

Poxin-deficient poxviruses are sensed by cGAS prior to genome replication

Poxviruses are dsDNA viruses infecting a wide range of cell types, where they need to contend with multiple host antiviral pathways, including DNA and RNA sensing. Accordingly, poxviruses encode a variety of immune antagonists, most of which are expressed early during infection from within virus cores before uncoating and genome release take place. Amongst these antagonists, the poxvirus immune nuclease (poxin) counteracts the cyclic 2'3'-GMP-AMP (2'3'-cGAMP) synthase (cGAS)/stimulator of interferon genes DNA sensing pathway by degrading the immunomodulatory cyclic dinucleotide 2'3'-cGAMP, the product of activated cGAS. Here, we use poxviruses engineered to lack poxin to investigate how virus infection triggers the activation of STING and its downstream transcription factor interferon-responsive factor 3 (IRF3). Our results demonstrate that poxin-deficient vaccinia virus (VACV) and ectromelia virus (ECTV) induce IRF3 activation in primary fibroblasts and differentiated macrophages, although to a lower extent in VACV compared to ECTV. In fibroblasts, IRF3 activation was detectable at 10 h post-infection (hpi) and was abolished by the DNA replication inhibitor cytosine arabinoside (AraC), indicating that the sensing was mediated by replicated genomes. In macrophages, IRF3 activation was detectable at 4 hpi, and this was not affected by AraC, suggesting that the sensing in this cell type was induced by genomes released from incoming virions. In agreement with this, macrophages expressing short hairpin RNA (shRNA) against the virus uncoating factor D5 showed reduced IRF3 activation upon infection. Collectively, our data show that the viral genome is sensed by cGAS prior to and during genome replication, but immune activation downstream of it is effectively suppressed by poxin. Our data also support the model where virus uncoating acts as an immune evasion strategy to simultaneously cloak the viral genome and allow the expression of early immune antagonists.

Mechanoimmune-Driven Backpack Sustains Dendritic Cell Maturation for Synergistic Tumor Radiotherapy

Cell backpacks present significant potential in both therapeutic and diagnostic applications, making it essential to further explore their interactions with host cells. Current evidence indicates that backpacks can induce sustained immune responses. Our original objective was to incorporate a model antigen into the backpacks to promote dendritic cell maturation and facilitate antigen presentation, thereby inducing immune responses. However, we unexpectedly discovered that both antigen-loaded backpacks and empty backpacks demonstrated comparable abilities to induce dendritic cell maturation, resulting in nearly identical potency in T-cell proliferation. Our mechanistic studies suggest that the attachment of backpacks induces mechanical forces on dendritic cells via opening the PIEZO1 mechanical ion channel. This interaction leads to the remodeling of the intracellular cytoskeleton and facilitates the production of type I interferons by dendritic cells. Consequently, the mechano-immune-driven dendritic cell backpacks, when combined with radiotherapy, induce a robust antitumor effect. This research presents an avenue for leveraging mechanotransduction to enhance combination immunotherapeutic strategies, potentially leading to groundbreaking advancements in the field.

Therapeutic Targets in Innate Immunity to Tackle Alzheimer's Disease

There is an urgent need for effective disease-modifying therapeutic interventions for Alzheimer's disease (AD)-the most prevalent cause of dementia with a profound socioeconomic burden. Most clinical trials targeting the classical hallmarks of this disease-β-amyloid plaques and neurofibrillary tangles-failed, showed discrete clinical effects, or were accompanied by concerning side effects. There has been an ongoing search for novel therapeutic targets. Neuroinflammation, now widely recognized as a hallmark of all neurodegenerative diseases, has been proven to be a major contributor to AD pathology. Here, we summarize the role of neuroinflammation in the pathogenesis and progression of AD and discuss potential targets such as microglia, TREM2, the complement system, inflammasomes, and cytosolic DNA sensors. We also present an overview of ongoing studies targeting specific innate immune system components, highlighting the progress in this field of drug research while bringing attention to the delicate nature of innate immune modulations in AD.

Large-scale mutational analysis identifies UNC93B1 variants that drive TLR-mediated autoimmunity in mice and humans

Nucleic acid-sensing Toll-like receptors (TLR) 3, 7/8, and 9 are key innate immune sensors whose activities must be tightly regulated to prevent systemic autoimmune or autoinflammatory disease or virus-associated immunopathology. Here, we report a systematic scanning-alanine mutagenesis screen of all cytosolic and luminal residues of the TLR chaperone protein UNC93B1, which identified both negative and positive regulatory regions affecting TLR3, TLR7, and TLR9 responses. We subsequently identified two families harboring heterozygous coding mutations in UNC93B1, UNC93B1+/T93I and UNC93B1+/R336C, both in key negative regulatory regions identified in our screen. These patients presented with cutaneous tumid lupus and juvenile idiopathic arthritis plus neuroinflammatory disease, respectively. Disruption of UNC93B1-mediated regulation by these mutations led to enhanced TLR7/8 responses, and both variants resulted in systemic autoimmune or inflammatory disease when introduced into mice via genome editing. Altogether, our results implicate the UNC93B1-TLR7/8 axis in human monogenic autoimmune diseases and provide a functional resource to assess the impact of yet-to-be-reported UNC93B1 mutations.

Harnessing cGAS-STING axis for therapeutic benefits in systemic lupus erythematosus

The cyclic GMP-AMP synthase (cGAS), a prominent intracellular DNA sensor in mammalian cells, controls the innate immune response and the stimulator of interferon genes (STING)-mediated synthesis of pro-inflammatory cytokines, such as type-I interferon (IFN-I). For decades, IFN-I has been hypothesized to be essential in the development of systemic lupus erythematosus (SLE), a chronic multisystem autoimmunity characterized by immune complex (IC) deposition in small vessels. Recent findings revealed that the activation of the cGAS-STING pathway by self-DNA would propagate the autoimmune responses via upregulating IFN-I production in SLE. In this review, we aimed to provide a comprehensive outlook of the role of the cGAS-STING pathway in SLE pathobiology, as well as, a better understanding of current therapeutic opportunities targeting this axis.

Z-DNA binding protein 1 orchestrates innate immunity and inflammatory cell death

Innate immunity is not only the first line of host defense against microbial infections but is also crucial for the host responses against a variety of noxious stimuli. Z-DNA binding protein 1 (ZBP1) is a cytosolic nucleic acid sensor that can induce inflammatory cell death in both immune and nonimmune cells upon sensing of incursive virus-derived Z-form nucleic acids and self-nucleic acids via its Zα domain. Mechanistically, aberrantly expressed or activated ZBP1 induced by pathogens or noxious stimuli enables recruitment of TANK binding kinase 1 (TBK1), interferon regulatory factor 3 (IRF3), receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and RIPK3 to drive type I interferon (IFN-I) responses and activation of nuclear factor kappa B (NF-κB) signaling. Meanwhile, ZBP1 promotes the assembly of ZBP1- and absent in melanoma 2 (AIM2)-PANoptosome, which ultimately triggers PANoptosis through caspase 3-mediated apoptosis, mixed lineage kinase domain like pseudokinase (MLKL)-mediated necroptosis, and gasdermin D (GSDMD)-mediated pyroptosis. In response to damaged mitochondrial DNA, ZBP1 can interact with cyclic GMP-AMP synthase to augment IFN-I responses but inhibits toll like receptor 9-mediated inflammatory responses. This review summarizes the structure and expression pattern of ZBP1, discusses its roles in human diseases through immune-dependent (e.g., the production of IFN-I and pro-inflammatory cytokines) and -independent (e.g., the activation of cell death) functions, and highlights the attractive prospect of manipulating ZBP1 as a promising therapeutic target in diseases.

The promise, progress, and challenges of in situ immunization agents in cancer immunotherapy

In situ immunization (ISI) agents are an emerging and diverse class of locally acting cancer immunotherapeutic agents designed to promote innate immune activation in the early steps of the cancer immunity cycle to ultimately support development of a systemic tumor-specific immune response and protective immunologic memory. The aims of this review are to: (i) provide an introduction to ISI; (ii) summarize the history of ISI agents; (iii) expound upon the mechanism(s) and therapeutic objective(s) of ISI; (iv) compare the various approaches and therapeutic modalities developed and investigated to date; and (v) summarize clinical experiences in an effort to highlight the utility as well as the lessons and challenges of this promising approach. A prospective roadmap for future clinical development is provided that focuses on early and late-stage trial design considerations, the rationale and importance of investigating combination treatment, and the prospective use of ISI agents in the neoadjuvant setting.

DNA sensing of dendritic cells in cancer immunotherapy

Dendritic cells (DCs) are involved in the initiation and maintenance of immune responses against malignant cells by recognizing conserved pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) through pattern recognition receptors (PRRs). According to recent studies, tumor cell-derived DNA molecules act as DAMPs and are recognized by DNA sensors in DCs. Once identified by sensors in DCs, these DNA molecules trigger multiple signaling cascades to promote various cytokines secretion, including type I IFN, and then to induce DCs mediated antitumor immunity. As one of the potential attractive strategies for cancer therapy, various agonists targeting DNA sensors are extensively explored including the combination with other cancer immunotherapies or the direct usage as major components of cancer vaccines. Moreover, this review highlights different mechanisms through which tumor-derived DNA initiates DCs activation and the mechanisms through which the tumor microenvironment regulates DNA sensing of DCs to promote tumor immune escape. The contributions of chemotherapy, radiotherapy, and checkpoint inhibitors in tumor therapy to the DNA sensing of DCs are also discussed. Finally, recent clinical progress in tumor therapy utilizing agonist-targeted DNA sensors is summarized. Indeed, understanding more about DNA sensing in DCs will help to understand more about tumor immunotherapy and improve the efficacy of DC-targeted treatment in cancer.

N-MYC impairs innate immune signaling in high-grade serous ovarian carcinoma

High-grade serous ovarian cancer (HGSC) is a challenging disease, especially for patients with immunologically "cold" tumors devoid of tumor-infiltrating lymphocytes (TILs). We found that HGSC exhibits among the highest levels of MYCN expression and transcriptional signature across human cancers, which is strongly linked to diminished features of antitumor immunity. N-MYC repressed basal and induced IFN type I signaling in HGSC cell lines, leading to decreased chemokine expression and T cell chemoattraction. N-MYC inhibited the induction of IFN type I by suppressing tumor cell-intrinsic STING signaling via reduced STING oligomerization, and by blunting RIG-I-like receptor signaling through inhibition of MAVS aggregation and localization in the mitochondria. Single-cell RNA sequencing of human clinical HGSC samples revealed a strong negative association between cancer cell-intrinsic MYCN transcriptional program and type I IFN signaling. Thus, N-MYC inhibits tumor cell-intrinsic innate immune signaling in HGSC, making it a compelling target for immunotherapy of cold tumors.

Deubiquitinase USP4 suppresses antitumor immunity by inhibiting IRF3 activation and tumor cell-intrinsic interferon response in colorectal cancer

Despite the approval of immune checkpoint blockade (ICB) therapy for various tumor types, its effectiveness is limited to only approximately 15% of patients with microsatellite instability-high (MSI-H) or mismatch repair deficiency (dMMR) colorectal cancer (CRC). Approximately 80%-85% of CRC patients have a microsatellite stability (MSS) phenotype, which features a rare T-cell infiltration. Thus, elucidating the mechanisms underlying resistance to ICB in patients with MSS CRC is imperative. In this study, we demonstrate that ubiquitin-specific peptidase 4 (USP4) is upregulated in MSS CRC tumors and negatively regulates the immune response against tumors in CRC. Additionally, USP4 represses the cellular interferon (IFN) response and antigen presentation and impairs PRR signaling-mediated cell death. Mechanistically, USP4 impedes the nuclear localization of interferon regulator Factor 3 (IRF3) by deubiquitinating the K63-polyubiquitin chain of TRAF6 and IRF3. Knockdown of USP4 enhances the infiltration of T cells in CRC tumors and overcomes ICB resistance in an MC38 syngeneic mouse model. Moreover, published datasets revealed that patients showing higher USP4 expression exhibited decreased responsiveness to anti-PD-L1 therapy. These findings highlight an essential role of USP4 in the suppression of antitumor immunity in CRC.

Macrophage-Targeting DNA Nanomaterials: A Future Direction of Biological Therapy

DNA can be used for precise construction of complex and flexible micro-nanostructures, including DNA origami, frame nucleic acids, and DNA hydrogels. DNA nanomaterials have good biocompatibility and can enter macrophages via scavenger receptor-mediated endocytosis. DNA nanomaterials can be uniquely and flexibly designed to ensure efficient uptake by macrophages, which represents a novel strategy to regulate macrophage function. With the development of nanotechnology, major advances have been made in the design and manufacturing of DNA nanomaterials for clinical therapy. In diseases accompanied by macrophage disturbances including tumor, infectious diseases, arthritis, fibrosis, acute lung injury, and atherosclerosis, DNA nanomaterials received considerable attention as potential treatments. However, we lack sufficient information to guarantee precise targeting of macrophages by DNA nanomaterials, which precludes their therapeutic applications. In this review, we summarize recent studies of macrophage-targeting DNA nanomaterials and discuss the limitations and challenges of this approach with regard to its potential use as a biological therapy.

Expression of Toll-like receptors in the cerebellum during pathogenesis of prion disease

Prion diseases, such as scrapie, entail the accumulation of disease-specific prion protein (PrPSc) within the brain. Toll-like receptors (TLRs) are crucial components of the pattern recognition system. They recognize pathogen-associated molecular patterns (PAMPs) and play a central role in orchestrating host innate immune responses. The expression levels of Toll-like receptors (TLRs) in the central nervous system (CNS) were not well-defined. To establish a model of prion diseases in BALB/C mice, the 22L strain was employed. The features of the 22L strain were analyzed, and the cerebellum exhibited severe pathological changes. TLR1-13 levels in the cerebellum were measured using quantitative polymerase chain reaction (qPCR) at time points of 60, 90, 120, and the final end point (145 days post-infection). During the pathogenesis, the expression levels of Toll-like receptors (TLRs) 1, 2, 7, 8, and 9 increased in a time-dependent manner. This trend mirrored the expression patterns of PrPSc (the pathological isoform of the prion protein) and glial fibrillary acidic protein. Notably, at the end point, TLR1-13 levels were significantly elevated. Protein level of TLR7 and TLR9 showed increasing at the end point of the 22L-infected mice. A deeper understanding of the increased Toll-like receptors (TLRs) in prion diseases could shed light on their role in initiating immune responses at various stages during pathogenesis. This insight is particularly relevant when considering TLRs as potential therapeutic targets for prion diseases.

New frontiers in the cGAS-STING intracellular DNA-sensing pathway

The cGAS-STING intracellular DNA-sensing pathway has emerged as a key element of innate antiviral immunity and a promising therapeutic target. The existence of an innate immune sensor that can be activated by any double-stranded DNA (dsDNA) of any origin raises fundamental questions about how cGAS is regulated and how it responds to "foreign" DNA while maintaining tolerance to ubiquitous self-DNA. In this review, we summarize recent evidence implicating important roles for cGAS in the detection of foreign and self-DNA. We describe two recent and surprising insights into cGAS-STING biology: that cGAS is tightly tethered to the nucleosome and that the cGAMP product of cGAS is an immunotransmitter acting at a distance to control innate immunity. We consider how these advances influence our understanding of the emerging roles of cGAS in the DNA damage response (DDR), senescence, aging, and cancer biology. Finally, we describe emerging approaches to harness cGAS-STING biology for therapeutic benefit.

STING inhibition suppresses microglia-mediated synapses engulfment and alleviates motor functional deficits after stroke

Ischemic stroke is the leading cause of adult disability. Ischemia leads to progressive neuronal death and synapse loss. The engulfment of stressed synapses by microglia further contributes to the disruption of the surviving neuronal network and related brain function. Unfortunately, there is currently no effective target for suppressing the microglia-mediated synapse engulfment. Stimulator of interferon genes (STING) is an important participant in innate immune response. In the brain, microglia are the primary cell type that mediate immune response after brain insult. The intimate relationship between STING and microglia-mediated neuroinflammation has been gradually established. However, whether STING affects other functions of microglia remains elusive. In this study, we found that STING regulated microglial phagocytosis of synapses after photothrombotic stroke. The treatment of STING inhibitor H151 significantly improved the behavioral performance of injured mice in grid-walking test, cylinder test, and adhesive removal test after stroke. Moreover, the puncta number of engulfed SYP or PSD95 in microglia was reduced after consecutive H151 administration. Further analysis showed that the mRNA levels of several complement components and phagocytotic receptors were decreased after STING inhibition. Transcriptional factor STAT1 is known for regulating most of the decreased molecules. After STING inhibition, the nucleus translocation of phosphorylated STAT1 was also suppressed in microglia. Our data uncovered the novel regulatory effects of STING in microglial phagocytosis after stroke, and further emphasized STING as a potential drug-able target for post-stroke functional recovery.

Low molecular weight fucoidan LF2 improves the immunosuppressive tumor microenvironment and enhances the anti-pancreatic cancer activity of oxaliplatin

Chemotherapy remains the cornerstone of pancreatic cancer treatment. However, the dense interstitial and immunosuppressive microenvironment frequently render the ineffective anti-tumor activity of chemotherapeutic agents. Macrophages play a key role in the tumor immunomodulation. In this study, we found that low molecular weight of fucoidan (LF2) directly regulated the differentiation of mononuclear macrophages into the CD86+ M1 phenotype. LF2 significantly upregulated the expressions of M1 macrophage-specific cytokines, including iNOS, IL-6, TNFα and IL-12. LF2 modulated macrophage phenotypic transformation through activation of TLR4-NFκB pathway. Furthermore, we observed that LF2 enhanced the pro-apoptotic activity of oxaliplatin (OXA) in vitro by converting macrophages to a tumoricidal M1 phenotype. Meanwhile, LF2 increased intratumoral M1 macrophage infiltration and ameliorated the immunosuppressed tumor microenvironment, which in turn enhanced the anti-pancreatic ductal adenocarcinoma (PDAC) activity of OXA in vivo. Taken together, our results suggested that LF2 could act as a TLR4 agonist targeting macrophages and has a synergistic effect against PDAC when combined with OXA.

Harnessing anti-inflammatory pathways and macrophage nano delivery to treat inflammatory and fibrotic disorders

Targeting specific organs and cell types using nanotechnology and sophisticated delivery methods has been at the forefront of applicative biomedical sciences lately. Macrophages are an appealing target for immunomodulation by nanodelivery as they are heavily involved in various aspects of many diseases and are highly plastic in their nature. Their continuum of functional "polarization" states has been a research focus for many years yielding a profound understanding of various aspects of these cells. The ability of monocyte-derived macrophages to metamorphose from pro-inflammatory to reparative and consequently to pro-resolving effectors has raised significant interest in its therapeutic potential. Here, we briefly survey macrophages' ontogeny and various polarization phenotypes, highlighting their function in the inflammation-resolution shift. We review their inducing mediators, signaling pathways, and biological programs with emphasis on the nucleic acid sensing-IFN-I axis. We also portray the polarization spectrum of macrophages and the characteristics of their transition between different subtypes. Finally, we highlighted different current drug delivery methods for targeting macrophages with emphasis on nanotargeting that might lead to breakthroughs in the treatment of wound healing, bone regeneration, autoimmune, and fibrotic diseases.

Molecular determinants of immunogenic cell death elicited by radiation therapy

Cancer cells undergoing immunogenic cell death (ICD) can initiate adaptive immune responses against dead cell-associated antigens, provided that (1) said antigens are not perfectly covered by central tolerance (antigenicity), (2) cell death occurs along with the emission of immunostimulatory cytokines and damage-associated molecular patterns (DAMPs) that actively engage immune effector mechanisms (adjuvanticity), and (3) the microenvironment of dying cells is permissive for the initiation of adaptive immunity. Finally, ICD-driven immune responses can only operate and exert cytotoxic effector functions if the microenvironment of target cancer cells enables immune cell infiltration and activity. Multiple forms of radiation, including non-ionizing (ultraviolet) and ionizing radiation, elicit bona fide ICD as they increase both the antigenicity and adjuvanticity of dying cancer cells. Here, we review the molecular determinants of ICD as elicited by radiation as we critically discuss strategies to reinforce the immunogenicity of cancer cells succumbing to clinically available radiation strategies.

PARP7-mediated ADP-ribosylation of FRA1 promotes cancer cell growth by repressing IRF1- and IRF3-dependent apoptosis

PARP7 was reported to promote tumor growth in a cell-autonomous manner and by repressing the antitumor immune response. Nevertheless, the molecular mechanism of how PARP7-mediated ADP-ribosylation exerts these effects in cancer cells remains elusive. Here, we identified PARP7 as a nuclear and cysteine-specific mono-ADP-ribosyltransferase that modifies targets critical for regulating transcription, including the AP-1 transcription factor FRA1. Loss of FRA1 ADP-ribosylation via PARP7 inhibition by RBN-2397 or mutation of the ADP-ribosylation site C97 increased FRA1 degradation by the proteasome via PSMC3. The reduction in FRA1 protein levels promoted IRF1- and IRF3-dependent cytokine as well as proapoptotic gene expression, culminating in CASP8-mediated apoptosis. Furthermore, high PARP7 expression was indicative of the PARP7 inhibitor response in FRA1-positive lung and breast cancer cells. Collectively, our findings highlight the connected roles of PARP7 and FRA1 and emphasize the clinical potential of PARP7 inhibitors for FRA1-driven cancers.

Noncanonical MAVS signaling restrains dendritic cell-driven antitumor immunity by inhibiting IL-12

Mitochondrial antiviral signaling protein (MAVS)-mediated cytosolic RNA sensing plays a central role in tumor immunogenicity. However, the effects of host MAVS signaling on antitumor immunity remain unclear. Here, we demonstrate that the host MAVS pathway supports tumor growth and impairs antitumor immunity, whereas MAVS deficiency in dendritic cells (DCs) promotes tumor-reactive CD8+ T cell responses. Specifically, CD8+ T cell priming capacity was enhanced by MAVS ablation in a type I interferon-independent, but IL-12-dependent, manner. Mechanistically, loss of the RIG-I/MAVS cascade activated the noncanonical NF-κB pathway and in turn induced IL-12 production by DCs. MAVS-restrained IL-12 promoted cross-talk between CD8+ T cells and DCs, which was licensed by IFN-γ. Moreover, ablation of host MAVS sensitized tumors to immunotherapy and attenuated radiation resistance, thereby facilitating the maintenance of effector CD8+ T cells. These findings demonstrate that the host MAVS pathway acts as an immune regulator of DC-driven antitumor immunity and support the development of immunotherapies that antagonize MAVS signaling in DCs.

'From R-lupus to cancer': Reviewing the role of R-loops in innate immune responses

Cells possess an inherent and evolutionarily conserved ability to detect and respond to the presence of foreign and pathological 'self' nucleic acids. The result is the stimulation of innate immune responses, signalling to the host immune system that defence mechanisms are necessary to protect the organism. To date, there is a vast body of literature describing innate immune responses to various nucleic acid species, including dsDNA, ssDNA and ssRNA etc., however, there is limited information available on responses to R-loops. R-loops are 3-stranded nucleic acid structures that form during transcription, upon DNA damage and in various other settings. Emerging evidence suggests that innate immune responses may also exist for the detection of R-loop related nucleic acid structures, implicating R-loops as drivers of inflammatory states. In this review, we aim to summarise the evidence indicating that R-loops are immunogenic species that can trigger innate immune responses in physiological and pathological settings and discuss the implications of this in the study of various diseases and therapeutic development.

Understanding nucleic acid sensing and its therapeutic applications

Nucleic acid sensing is involved in viral infections, immune response-related diseases, and therapeutics. Based on the composition of nucleic acids, nucleic acid sensors are defined as DNA or RNA sensors. Pathogen-associated nucleic acids are recognized by membrane-bound and intracellular receptors, known as pattern recognition receptors (PRRs), which induce innate immune-mediated antiviral responses. PRR activation is tightly regulated to eliminate infections and prevent abnormal or excessive immune responses. Nucleic acid sensing is an essential mechanism in tumor immunotherapy and gene therapies that target cancer and infectious diseases through genetically engineered immune cells or therapeutic nucleic acids. Nucleic acid sensing supports immune cells in priming desirable immune responses during tumor treatment. Recent studies have shown that nucleic acid sensing affects the efficiency of gene therapy by inhibiting translation. Suppression of innate immunity induced by nucleic acid sensing through small-molecule inhibitors, virus-derived proteins, and chemical modifications offers a potential therapeutic strategy. Herein, we review the mechanisms and regulation of nucleic acid sensing, specifically covering recent advances. Furthermore, we summarize and discuss recent research progress regarding the different effects of nucleic acid sensing on therapeutic efficacy. This study provides insights for the application of nucleic acid sensing in therapy.

STING signaling promotes NK cell antitumor immunity and maintains a reservoir of TCF-1+ NK cells

Natural killer (NK) cells are cytotoxic innate lymphocytes that eradicate tumor cells. Inducing durable antitumor immune responses by NK cells represents a major priority of cancer immunotherapy. While cytosolic DNA sensing plays an essential role in initiating antitumor immunity, the role of NK cell-intrinsic STING signaling remains unclear. Here, we find that NK cell-intrinsic STING promotes antitumor responses and maintains a reservoir of TCF-1+ NK cells. In contrast, tumor cell-intrinsic cGAS and mtDNA are required for NK cell antitumor activity, indicating that tumor mtDNA recognition by cGAS partially triggers NK cell-intrinsic STING activation. Moreover, addition of cGAMP enables STING activation and type I interferon production in NK cells, thereby supporting the activation of NK cells in vitro. In humans, STING agonism promotes the expansion of TCF-1+ NK cells. This study provides insight into understanding how STING signaling drives NK cell antitumor immunity and the development of NK cell-based cancer immunotherapy.

Nanoparticle Delivery of Immunostimulatory Alu RNA for Cancer Immunotherapy

It was recently found that patients with relapsing remitting multiple sclerosis exhibit widespread loss of adenosine-to-inosine (A-to-I) RNA editing, which contributes to the accumulation of immunostimulatory double-stranded Alu RNA in circulating leukocytes and an attendant increase in levels of proinflammatory cytokines (e.g., type I IFNs). A specific Alu RNA (i.e., AluJb RNA) was implicated in activating multiple RNA-sensing pathways and found to be a potent innate immune agonist. Here, we have performed a bioinformatic analysis of A-to-I RNA editing in human melanoma samples and determined that pre-therapy levels of A-to-I RNA editing negatively correlate with survival times, suggesting that an accumulation of endogenous double-stranded Alu RNA might contribute to cancer patient survival. Furthermore, we demonstrated that immunostimulatory Alu RNA can be leveraged pharmacologically for cancer immunotherapy. AluJb RNA was in vitro transcribed and then formulated with endosome-destabilizing polymer nanoparticles to improve intracellular delivery of the RNA and enable activation of RNA-sensing pathways. AluJb RNA/polymer complexes (i.e., Alu-NPs) were engineered to form colloidally stable nanoparticles that exhibited immunostimulatory activity in vitro and in vivo. Finally, the therapeutic potential of Alu-NPs for the treatment of cancer was demonstrated by attenuated tumor growth and prolonged survival in the B16.F10 murine melanoma tumor model. Thus, these data collectively implicate intratumoral Alu RNA as a potentiator of antitumor innate immunity and identify AluJb RNA as a novel nucleic acid immunotherapeutic for cancer.

Significance

Loss of A-to-I editing leads to accumulation of unedited Alu RNAs that activate innate immunity via RNA-sensing pattern recognition receptors. When packaged into endosome-releasing polymer nanoparticles, AluJB RNA becomes highly immunostimulatory and can be used pharmacologically to inhibit tumor growth in mouse melanoma models. These findings identify Alu RNAs as a new class of nucleic acid innate immune agonists for cancer immunotherapy.

T-cell derived extracellular vesicles prime macrophages for improved STING based cancer immunotherapy

A key phenomenon in cancer is the establishment of a highly immunosuppressive tumour microenvironment (TME). Despite advances in immunotherapy, where the purpose is to induce tumour recognition and hence hereof tumour eradication, the majority of patients applicable for such treatment still fail to respond. It has been suggested that high immunological activity in the tumour is essential for achieving effective response to immunotherapy, which therefore have led to exploration of strategies that triggers inflammatory pathways. Here activation of the stimulator of interferon genes (STING) signalling pathway has been considered an attractive target, as it is a potent trigger of pro-inflammatory cytokines and types I and III interferons. However, immunotherapy combined with targeted STING agonists has not yielded sustained clinical remission in humans. This suggests a need for exploring novel adjuvants to improve the innate immunological efficacy. Here, we demonstrate that extracellular vesicles (EVs), derived from activated CD4+ T cells (T-EVs), sensitizes macrophages to elevate STING activation, mediated by IFNγ carried on the T-EVs. Our work support that T-EVs can disrupt the immune suppressive environment in the tumour by reprogramming macrophages to a pro-inflammatory phenotype, and priming them for a robust immune response towards STING activation.

DNA Nanomaterials-Based Platforms for Cancer Immunotherapy

The past few decades have witnessed the evolving paradigm for cancer therapy from nonspecific cytotoxic agents to selective, mechanism-based therapeutics, especially immunotherapy. In particular, the integration of nanomaterials with immunotherapy is proven to improve the therapeutic outcome and minimize off-target toxicity in the treatment. As a novel nanomaterial, DNA-based self-assemblies featuring uniform geometries, feasible modifications, programmability, surface addressability, versatility, and intrinsic biocompatibility, are extensively exploited for innovative and effective cancer immunotherapy. In this review, the successful employment of DNA nanoplatforms for cancer immunotherapy, including the delivery of immunogenic cell death inducers, adjuvants and vaccines, immune checkpoint blockers as well as the application in immune cell engineering and adoptive cell therapy is summarized. The remaining challenges and future perspectives regarding the pharmacokinetics/pharmacodynamics, in vivo fate and immunogenicity of DNA materials, and the design of intelligent DNA nanomedicine for individualized cancer immunotherapy are also discussed.

Targeting STING Activation by Antigen-Inspired MnO2 Nanovaccines Optimizes Tumor Radiotherapy

Immune checkpoint blockers therapy can improve the radiotherapy-induced immunosuppression by enhancing interferon secretion, but still suffer from low clinical response rate and potential adverse effects. Mn²⁺ -mediated activation of interferon gene stimulator (STING) pathway provides an alternative for combination radioimmunotherapy of tumor. However, it is still a challenge for specific delivery of Mn²⁺ to innate immune cells and targeting activation of STING pathway. Herein, a novel antigen-inspired MnO₂ nanovaccine is fabricated as Mn²⁺ source and functionalized with mannose, enabling it to target innate immune cells to activate the STING pathway. Meanwhile, the release of Mn²⁺ in the intracellular lysosomes can also be for magnetic resonance imaging to monitor the dynamic distribution of nanovaccines in vivo. The targeting activation of STING pathway can enhance radiotherapy-induced immune responses for inhibiting local and distant tumors, and resisting tumor metastasis. The study proposes an optimized radiotherapy strategy through targeting STING activation of antigen-inspired nanovaccines.

Liposomal Delivery of MIW815 (ADU-S100) for Potentiated STING Activation

Stimulator of interferon genes (STING) agonists can improve the anticancer efficacy of immune checkpoint blockade by amplifying tumor immunogenicity. However, the clinical translation of cyclic dinucleotides (CDNs) as STING agonists is hindered by their poor drug-like properties. In this study, we investigated the design criteria for DOTAP/cholesterol liposomes for the systemic delivery of ADU-S100 and delineated the impact of key formulation factors on the loading efficiency, serum stability, and STING agonistic activity of ADU-S100. Our findings demonstrate that the cationic liposomal formulation of ADU-S100 can be optimized to greatly potentiate STING activation in antigen-presenting cells.

SAMHD1 expression modulates innate immune activation and correlates with ovarian cancer prognosis

Purpose

SAMHD1 is a deoxynucleotide triphosphate (dNTP) triphosphohydrolase which has been proposed as a putative prognostic factor in haematological cancers and certain solid tumours, although with controversial data. Here, we evaluate SAMHD1 function in ovarian cancer, both in vitro and in ovarian cancer patients.

Methods

SAMHD1 expression was downregulated in ovarian cancer cell lines OVCAR3 and SKOV3 by RNA interference. Gene and protein expression changes in immune signalling pathways were assessed. SAMHD1 expression in ovarian cancer patients was evaluated by immunohistochemistry and survival analysis was performed according to SAMHD1 expression.

Results

SAMHD1 knockdown induced a significant upregulation of proinflammatory cytokines concomitant to increased expression of the main RNA-sensors, MDA5 and RIG-I, and interferon-stimulated genes, supporting the idea that the absence of SAMHD1 promotes innate immune activation in vitro. To assess the contribution of SAMHD1 in ovarian cancer patients, tumours were stratified in SAMHD1-low and SAMHD1-high expressing tumours, resulting in significantly shorter progression free survival (PFS) and overall survival (OS) in SAMHD1-high expression subgroup (p=0.01 and 0.04, respectively).

Conclusions

SAMHD1 depletion correlates with increased innate immune cell signalling in ovarian cancer cells. In clinical samples, SAMHD1-low expressing tumors showed increased progression free survival and overall survival irrespective of BRCA mutation status. These results point towards SAMHD1 modulation as a new therapeutic strategy, able to enhance innate immune activation directly in tumour cells, leading to improved prognosis in ovarian cancer.

Therapeutic immunomodulation by rationally designed nucleic acids and nucleic acid nanoparticles

The immune system has evolved to defend organisms against exogenous threats such as viruses, bacteria, fungi, and parasites by distinguishing between "self" and "non-self". In addition, it guards us against other diseases, such as cancer, by detecting and responding to transformed and senescent cells. However, for survival and propagation, the altered cells and invading pathogens often employ a wide range of mechanisms to avoid, inhibit, or manipulate the immunorecognition. As such, the development of new modes of therapeutic intervention to augment protective and prevent harmful immune responses is desirable. Nucleic acids are biopolymers essential for all forms of life and, therefore, delineating the complex defensive mechanisms developed against non-self nucleic acids can offer an exciting avenue for future biomedicine. Nucleic acid technologies have already established numerous approaches in therapy and biotechnology; recently, rationally designed nucleic acids nanoparticles (NANPs) with regulated physiochemical properties and biological activities has expanded our repertoire of therapeutic options. When compared to conventional therapeutic nucleic acids (TNAs), NANP technologies can be rendered more beneficial for synchronized delivery of multiple TNAs with defined stabilities, immunological profiles, and therapeutic functions. This review highlights several recent advances and possible future directions of TNA and NANP technologies that are under development for controlled immunomodulation.

Selecting Therapeutic Antisense Oligonucleotides with Gene Targeting and TLR8 Potentiating Bifunctionality

A growing body of preclinical evidence has led to the hypothesis that human Toll-like receptor 8 (hTLR8) activation in the tumor microenvironment (TME) could have potent anticancer effects through its action on monocytes, myeloid dendritic cells (mDCs), and natural killer (NK) cells. This has motivated the initiation of several clinical trials for chemical hTLR8 agonists in a variety of cancers. Concurrently, a growing number of synthetic antisense oligonucleotides (ASOs) are being developed as cancer therapeutics. We have recently reported that 2'-O-methyl (2'OMe)-modified ASOs can potentiate sensing of hTLR8 chemical agonists in a sequence-dependent manner. This suggests that select gene-targeting ASOs with anticancer activity may synergize with low-dose hTLR8 agonists in the TME. Here, we provide a detailed protocol to rapidly screen and identify such synthetic bifunctional oligonucleotides with synergistic activity on hTLR8 sensing.

The Role of Nucleases Cleaving TLR3, TLR7/8 and TLR9 Ligands, Dicer RNase and miRNA/piRNA Proteins in Functional Adaptation to the Immune Escape and Xenophagy of Prostate Cancer Tissue

The prototypic sensors for the induction of innate and adaptive immune responses are the Toll-like receptors (TLRs). Unusually high expression of TLRs in prostate carcinoma (PC), associated with less differentiated, more aggressive and more propagating forms of PC, changed the previous paradigm about the role of TLRs strictly in immune defense system. Our data reveal an entirely novel role of nucleic acids-sensing Toll-like receptors (NA-TLRs) in functional adaptation of malignant cells for supply and digestion of surrounding metabolic substrates from dead cells as specific mechanism of cancer cells survival, by corresponding ligands accelerated degradation and purine/pyrimidine salvage pathway. The spectrophotometric measurement protocols used for the determination of the activity of RNases and DNase II have been optimized in our laboratory as well as the enzyme-linked immunosorbent method for the determination of NF-κB p65 in prostate tissue samples. The protocols used to determine Dicer RNase, AGO2, TARBP2 and PIWIL4 were based on enzyme-linked immunosorbent assay. The amount of pre-existing acid-soluble oligonucleotides was measured and expressed as coefficient of absorbance. The activities of acid DNase II and RNase T2, and the activities of nucleases cleaving TLR3, TLR7/8 and TLR9 ligands (Poly I:C, poly U and unmethylated CpG), increased several times in PC, compared to the corresponding tumor adjacent and control tissue, exerting very high sensitivity and specificity of above 90%. Consequently higher levels of hypoxanthine and NF-κB p65 were reported in PC, whereas the opposite results were observed for miRNA biogenesis enzyme (Dicer RNase), miRNA processing protein (TARB2), miRNA-induced silencing complex protein (Argonaute-AGO) and PIWI-interacting RNAs silence transposon. Considering the crucial role of purine and pyrimidine nucleotides as energy carriers, subunits of nucleic acids and nucleotide cofactors, future explorations will be aimed to design novel anti-cancer immune strategies based on a specific acid endolysosomal nuclease inhibition.

Fucoidan, as an immunostimulator promotes M1 macrophage differentiation and enhances the chemotherapeutic sensitivity of capecitabine in colon cancer

Chemotherapy resistance is one of the most critical challenges in colorectal cancer (CRC) treatment. The occurrence and development of chemotherapy resistance closely related to the tumor immune microenvironment (TIME). As the most important immunosuppressive immune cells infiltrating into the TIME, macrophages are essential for chemotherapy resistance in CRC treatment. In this study, we found that a kind of fucoidan (FPS1M) induced macrophages differentiation to the M1 phenotype, and this transformation promoted cancer cells apoptosis both in vitro and in vivo. TNFα is a key mediator of FPS1M-induced tumorcidal activity of macrophages. Mechanistically, as a stimulator of TLR4, FPS1M enhanced macrophages glycolysis and regulated macrophages differentiation to the M1 phenotype by the activation of TLR4 mediated PI3K/AKT/mTOR signaling axis. In addition, FPS1M improved the immunosuppressed tumor microenvironment by increasing the infiltration of M1 macrophages in tumor tissue, which was conducive to improving the sensitivity of tumor to chemotherapy. Collectively, our findings demonstrated that FPS1M has the great potential to be used in tumor immunotherapy. The results also suggested that the combination of FPS1M with capecitabine is an alternative therapy method for colon cancer.

Macrophages as tools and targets in cancer therapy

Tumour-associated macrophages are an essential component of the tumour microenvironment and have a role in the orchestration of angiogenesis, extracellular matrix remodelling, cancer cell proliferation, metastasis and immunosuppression, as well as in resistance to chemotherapeutic agents and checkpoint blockade immunotherapy. Conversely, when appropriately activated, macrophages can mediate phagocytosis of cancer cells and cytotoxic tumour killing, and engage in effective bidirectional interactions with components of the innate and adaptive immune system. Therefore, they have emerged as therapeutic targets in cancer therapy. Macrophage-targeting strategies include inhibitors of cytokines and chemokines involved in the recruitment and polarization of tumour-promoting myeloid cells as well as activators of their antitumorigenic and immunostimulating functions. Early clinical trials suggest that targeting negative regulators (checkpoints) of myeloid cell function indeed has antitumor potential. Finally, given the continuous recruitment of myelomonocytic cells into tumour tissues, macrophages are candidates for cell therapy with the development of chimeric antigen receptor effector cells. Macrophage-centred therapeutic strategies have the potential to complement, and synergize with, currently available tools in the oncology armamentarium.

Macrophages can promote tumorigenesis and enhance the antitumour response. This Review discusses the molecular mechanisms underlying the reprogramming of macrophages in the tumour microenvironment and provides an overview of macrophage-targeted therapies for the treatment of cancer.

Sex bias in systemic lupus erythematosus: a molecular insight

Acknowledging sex differences in immune response is particularly important when we consider the differences between men and women in the incidence of disease. For example, over 80% of autoimmune disease occurs in women, whereas men have a higher incidence of solid tumors compared to women. In general women have stronger innate and adaptive immune responses than men, explaining their ability to clear viral and bacterial infections faster, but also contributing to their increased susceptibility to autoimmune disease. The autoimmune disease systemic lupus erythematosus (SLE) is the archetypical sexually dimorphic disease, with 90% of patients being women. Various mechanisms have been suggested to account for the female prevalence of SLE, including sex hormones, X-linked genes, and epigenetic regulation of gene expression. Here, we will discuss how these mechanisms contribute to pathobiology of SLE and how type I interferons work with them to augment sex specific disease pathogenesis in SLE.

Involvement of retroelements in the autoimmune response in humans

Retroelements are mobile genomic components requiring an RNA intermediate which is reverse-transcribed into complementary DNA for transposition. Human genome contains a vast amount of retroelements including retrotransposons and endogenous retroviruses. These elements are categorized according to presence or absence of long terminal repeats, LTRs or non-LTRs, as well as autonomous and non-autonomous according to involvement of reverse transcriptase. The retroelements have been accumulated in mammalian genomes over all evolutionary times through vertical transmission, and many of them were inactivated through accumulation of mutations. However, the retroelements entered into genome within the last 200,000 years are mostly functional. Some of the active retroelements are associated with varying autoimmune diseases because anti-retroelement antibodies might cross-react with other proteins in the human body. For instance, autoimmunity and inflammation could be stimulated by increased expression of long interspersed element 1 (LINE-1 or L1) or decreased L1 degradation. Different regulation of L1 expression might be related to the genetic and sex-related variations or environmental factors. Activation of retroelements is also controlled by epigenetic silencing mechanisms such as histone modification. Elevated levels of L1 retroelements could trigger the production of type I interferon, a crucial innate defense mechanism in mammals against viruses, and systemic autoimmune response is induced. Loss-of-function in some deoxyribonucleases (DNases) such as three prime repair exonuclease 1 that degrades reverse-transcribed DNA is also related to autoimmune diseases. Additionally, human endogenous retroviruses also play a role in autoimmune diseases. Involvement of retroelements in autoimmune disorders is exemplified with three diseases, i.e. systemic lupus erythematosus, Aicardi–Goutières syndrome, and multiple sclerosis.

Macrophages Are a Double-Edged Sword: Molecular Crosstalk between Tumor-Associated Macrophages and Cancer Stem Cells

Cancer stem cells (CSCs) are a subset of highly tumorigenic cells in tumors. They have enhanced self-renewal properties, are usually chemo-radioresistant, and can promote tumor recurrence and metastasis. They can recruit macrophages into the tumor microenvironment and differentiate them into tumor-associated macrophages (TAMs). TAMs maintain CSC stemness and construct niches that are favorable for CSC survival. However, how CSCs and TAMs interact is not completely understood. An understanding on these mechanisms can provide additional targeting strategies for eliminating CSCs. In this review, we comprehensively summarize the reported mechanisms of crosstalk between CSCs and TAMs and update the related signaling pathways involved in tumor progression. In addition, we discuss potential therapies targeting CSC–TAM interaction, including targeting macrophage recruitment and polarization by CSCs and inhibiting the TAM-induced promotion of CSC stemness. This review also provides the perspective on the major challenge for developing potential therapeutic strategies to overcome CSC-TAM crosstalk.

Synergy of a STING agonist and an IL-2 superkine in cancer immunotherapy against MHC I-deficient and MHC I+ tumors

Cyclic dinucleotides (CDN) and Toll-like receptor (TLR) ligands mobilize antitumor responses by natural killer (NK) cells and T cells, potentially serving as complementary therapies to immune checkpoint therapy. In the clinic thus far, however, CDN therapy targeting stimulator of interferon genes (STING) protein has yielded mixed results, perhaps because it initiates responses potently but does not provide signals to sustain activation and proliferation of activated cytotoxic lymphocytes. To improve efficacy, we combined CDN with a half life-extended interleukin-2 (IL-2) superkine, H9-MSA (mouse serum albumin). CDN/H9-MSA therapy induced dramatic long-term remissions of the most difficult to treat major histocompatibility complex class I (MHC I)–deficient and MHC I+ tumor transplant models. H9-MSA combined with CpG oligonucleotide also induced potent responses. Mechanistically, tumor elimination required CD8 T cells and not NK cells in the case of MHC I+ tumors and NK cells but not CD8 T cells in the case of MHC-deficient tumors. Furthermore, combination therapy resulted in more prolonged and more intense NK cell activation, cytotoxicity, and expression of cytotoxic effector molecules in comparison with monotherapy. Remarkably, in a primary autochthonous sarcoma model that is refractory to PD-1 checkpoint therapy, the combination of CDN/H9-MSA with checkpoint therapy yielded long-term remissions in the majority of the animals, mediated by T cells and NK cells. This combination therapy has the potential to activate responses in tumors resistant to current therapies and prevent MHC I loss accompanying acquired resistance of tumors to checkpoint therapy.

A nanovaccine for enhancing cellular immunity via cytosolic co-delivery of antigen and polyIC RNA

Traditional approaches to cancer vaccines elicit weak CD8+ T cell responses and have largely failed to meet clinical expectations. This is in part due to inefficient antigen cross-presentation, inappropriate selection of adjuvant and its formulation, poor vaccine pharmacokinetics, and/or suboptimal coordination of antigen and adjuvant delivery. Here, we describe a nanoparticle vaccine platform for facile co-loading and dual-delivery of antigens and nucleic acid adjuvants that elicits robust antigen-specific cellular immune responses. The nanovaccine design is based on diblock copolymers comprising a poly(ethylene glycol)-rich first block that is functionalized with reactive moieties for covalent conjugation of antigen via disulfide linkages, and a pH-responsive second block for electrostatic packaging of nucleic acids that also facilitates endosomal escape of associated vaccine cargo to the cytosol. Using polyIC, a clinically-advanced nucleic acid adjuvant, we demonstrated that endosomolytic nanoparticles promoted the cytosolic co-delivery of polyIC and protein antigen, which acted synergistically to enhance antigen cross-presentation, co-stimulatory molecule expression, and cytokine production by dendritic cells. We also found that the vaccine platform increased the accumulation of antigen and polyIC in the local draining lymph nodes. Consequently, dual-delivery of antigen and polyIC with endsomolytic nanoparticles significantly enhanced the magnitude and functionality of CD8+ T cell responses relative to a mixture of antigen and polyIC, resulting in inhibition of tumor growth in a mouse tumor model. Collectively, this work provides a proof-of-principle for a new cancer vaccine platform that strongly augments anti-tumor cellular immunity via cytosolic co-delivery of antigen and nucleic acid adjuvant.

Phase I Dose-Escalation Trial of MIW815 (ADU-S100), an Intratumoral STING Agonist, in Patients with Advanced/Metastatic Solid Tumors or Lymphomas

PURPOSE

This phase I study assessed the safety, pharmacokinetics (PKs), and efficacy of MIW815 (ADU-S100), a novel synthetic cyclic dinucleotide that activates the stimulator of IFN genes (STING) pathway, in patients with advanced/metastatic cancers.

PATIENTS AND METHODS

Patients (n = 47) received weekly i.t. injections of MIW815, 50 to 6,400 μg, on a 3-weeks-on/1-week-off schedule.

RESULTS

A maximum tolerated dose was not reached. Most common treatment-related adverse events were pyrexia (17%), chills, and injection-site pain (each 15%). MIW815 was rapidly absorbed from the injection site with dose-proportional PK, a rapid terminal plasma half-life (approximately 24 minutes), and high interindividual variability. One patient had a partial response (PR; Merkel cell carcinoma); two patients had unconfirmed PR (parotid cancer, myxofibrosarcoma). Lesion size was stable or decreased in 94% of evaluable, injected lesions. RNA expression and immune infiltration assessments in paired tumor biopsies did not reveal significant on-treatment changes. However, increases in inflammatory cytokines and peripheral blood T-cell clonal expansion suggested systemic immune activation.

CONCLUSIONS

MIW815 was well tolerated in patients with advanced/metastatic cancers. Clinical activity of single-agent MIW815 was limited in this first-in-human study; however, evidence of systemic immune activation was seen.

Intratumoral cancer immunotherapy exploiting anti-viral immunity

After a long period of endeavor, immunotherapy has become the mainstream of cancer therapies. This success is mostly ascribed to immune checkpoint blockade, chimeric antigen receptor-transduced T cell therapies, and bispecific antibodies. However, these methods have been effective or applicable to only a limited proportion of patients so far. Thus, further development of broadly applicable and effective immunotherapies is eagerly anticipated. Given that innate immunity is key to the induction of robust adaptive immunity and that the immunosuppressive tumor microenvironment is a major hurdle to overcome, intratumoral immunotherapy in which delivery of immunostimulatory microbial agents to the tumor site triggers innate immunity in situ is a rational strategy. There has been a plethora of preclinical and clinical trials conducted involving the delivery of either mimetics of viral nucleic acids or oncolytic viruses intratumorally to trigger innate immunity via various nucleic acid sensors in the tumor site. Many of these have shown significant antitumor effects in mice, particularly in combination with immune checkpoint blockade. Oncolytic herpes simplex virus type 1 has been approved for the treatment of advanced melanoma in the United States and Europe and of glioblastoma in Japan. Whereas direct intratumoral administration has mainly been chosen as a delivery route, several promising compounds amenable to systemic administration have been developed. Intratumoral delivery of immunostimulatory agents will become an important option for cancer immunotherapy as an off-the-shelf, broadly applicable, and rational strategy that exploits the physiology of immunity, namely anti-microbial immunity.

Macrophages and cancer stem cells: a malevolent alliance

Myeloid cells infiltrating tumors are gaining ever growing attention in the last years because their pro-tumor and immunosuppressive functions are relevant for disease progression and therapeutic responses. The functional ambiguity of tumor-associated macrophages (TAMs), mostly promoting tumor evolution, is a challenging hurdle. This is even more evident in the case of cancer stem cells (CSCs); as active participants in the specialized environment of the cancer stem cell niche, TAMs initiate a reciprocal conversation with CSCs. TAMs contribute to protect CSCs from the hostile environment (exogenous insults, toxic compounds, attacks from the immune cells), and produce several biologically active mediators that modulate crucial developmental pathways that sustain cancer cell stemness. In this review, we have focused our attention on the interaction between TAMs and CSCs; we describe how TAMs impact on CSC biology and, in turn, how CSCs exploit the tissue trophic activity of macrophages to survive and progress. Since CSCs are responsible for therapy resistance and tumor recurrence, they are important therapeutic targets. In view of the recent success in oncology obtained by stimulating the immune system, we discuss some macrophage-targeted therapeutic strategies that may also affect the CSCs and interrupt their malevolent alliance.

Regulation of cGAS-STING pathway - Implications for systemic lupus erythematosus

Type I interferon (IFN-I) is implicated in the pathogenesis of systemic lupus erythematosus (SLE) and the closely associated monogenic autoinflammatory disorders termed the “interferonopathies.” Recently, the cytosolic DNA sensor cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) and its downstream signaling adaptor stimulator of interferon genes (STING) have been identified as having important, if not central, roles in driving IFN-I expression in response to self-DNA. This review highlights the many ways in which this pathway is regulated in order to prevent self-DNA recognition and underlines the importance of maintaining tight control in order to prevent autoimmune disease. We will discuss the murine and human studies that have implicated the cGAS-STING pathway as being an important contributor to breakdown in tolerance in SLE and highlight the potential therapeutic application of this knowledge for the treatment of SLE.

Regulation of the nucleic acid-sensing Toll-like receptors

Many of the ligands for Toll-like receptors (TLRs) are unique to microorganisms, such that receptor activation unequivocally indicates the presence of something foreign. However, a subset of TLRs recognizes nucleic acids, which are present in both the host and foreign microorganisms. This specificity enables broad recognition by virtue of the ubiquity of nucleic acids but also introduces the possibility of self-recognition and autoinflammatory or autoimmune disease. Defining the regulatory mechanisms required to ensure proper discrimination between foreign and self-nucleic acids by TLRs is an area of intense research. Progress over the past decade has revealed a complex array of regulatory mechanisms that ensure maintenance of this delicate balance. These regulatory mechanisms can be divided into a conceptual framework with four categories: compartmentalization, ligand availability, receptor expression and signal transduction. In this Review, we discuss our current understanding of each of these layers of regulation.

Activation of nucleic acid-sensing Toll-like receptors is finely tuned to limit self-reactivity while maintaining recognition of foreign microorganisms. The authors describe recent progress made in defining the regulatory mechanisms that facilitate this delicate balance.

Sequence-dependent inhibition of cGAS and TLR9 DNA sensing by 2'-O-methyl gapmer oligonucleotides

Oligonucleotide-based therapeutics have the capacity to engage with nucleic acid immune sensors to activate or block their response, but a detailed understanding of these immunomodulatory effects is currently lacking. We recently showed that 2′-O-methyl (2′OMe) gapmer antisense oligonucleotides (ASOs) exhibited sequence-dependent inhibition of sensing by the RNA sensor Toll-Like Receptor (TLR) 7. Here we discovered that 2′OMe ASOs can also display sequence-dependent inhibitory effects on two major sensors of DNA, namely cyclic GMP-AMP synthase (cGAS) and TLR9. Through a screen of 80 2′OMe ASOs and sequence mutants, we characterized key features within the 20-mer ASOs regulating cGAS and TLR9 inhibition, and identified a highly potent cGAS inhibitor. Importantly, we show that the features of ASOs inhibiting TLR9 differ from those inhibiting cGAS, with only a few sequences inhibiting both pathways. Together with our previous studies, our work reveals a complex pattern of immunomodulation where 95% of the ASOs tested inhibited at least one of TLR7, TLR9 or cGAS by ≥30%, which may confound interpretation of their in vivo functions. Our studies constitute the broadest analysis of the immunomodulatory effect of 2′OMe ASOs on nucleic acid sensing to date and will support refinement of their therapeutic development.

Therapeutic Manipulation of Tumor-associated Macrophages: Facts and Hopes from a Clinical and Translational Perspective

The stroma of most solid tumors is populated by myeloid cells, which mostly represent macrophages. Tumor-associated macrophages (TAMs), strongly influenced by cancer cell-derived factors, are key drivers of immunosuppression and support tumor growth and spread to distant sites. Their accurate quantification and characterization in the tumor microenvironment are gaining prognostic value: increasing evidence demonstrates their ability to hamper cancer patients' response to chemotherapy, as well as to immunotherapies based on checkpoint inhibition. Therefore, strategies to counteract their negative effects are nowadays gaining momentum at preclinical, translational, and clinical levels. Our knowledge of the biology of TAMs has greatly advanced in the last years; several strategies to target and reprogram their functions to become antitumor effectors have proven successful in experimental preclinical tumor models; on the other hand, few approaches have so far been effectively translated into clinic practice. A growing interest in the therapeutic manipulation of TAMs is evidenced by numerous early-phase clinical trials, which are continuously fueled by new discoveries from basic research. This gives us hope that the targeting and sustained reprogramming of TAMs will be more specific to synergize with current therapies and maximize antitumor responses in patients.

Cytosolic sensor STING in mucosal immunity: a master regulator of gut inflammation and carcinogenesis

The stimulator of interferon genes (STING) connects microbial cytosolic sensing with host cell effector functions. STING signaling plays a central role in cyclic dinucleotides (CDNs) and DNA sensing to induce secretion of interferons and pro-inflammatory mediators. Although activated STING signaling favors antimicrobial progress and facilitates mucosal would healing, its role in mucosal immunity and gut homeostasis is paradoxical, ranging from positive and negative effects within the gut. In our review, we summarize recent advance of STING signaling in gut homeostasis and inflammation, especially focusing on its molecular basis in mucosal immune response. Deep understanding of the regulatory mechanisms of intestinal STING pathway could promote clinical manipulation of this fundamental signaling as a promising immunomodulatory therapy.