The cGAS-cGAMP-STING pathway connects DNA damage to inflammation, senescence, and cancer

Lysophosphatidic acid receptor LPA3 prevents oxidative stress and cellular senescence in Hutchinson-Gilford progeria syndrome

Hutchinson–Gilford progeria syndrome (HGPS) is a rare laminopathy that produces a mutant form of prelamin A, known as Progerin, resulting in premature aging. HGPS cells show morphological abnormalities of the nuclear membrane, reduced cell proliferation rates, accumulation of reactive oxygen species (ROS), and expression of senescence markers. Lysophosphatidic acid (LPA) is a growth factor‐like lipid mediator that regulates various physiological functions via activating multiple LPA G protein‐coupled receptors. Here, we study the roles of LPA and LPA receptors in premature aging. We report that the protein level of LPA₃ was highly downregulated through internalization and the lysosomal degradation pathway in Progerin‐transfected HEK293 cells. By treating Progerin HEK293 cells with an LPA₃ agonist (OMPT, 1‐Oleoyl‐2‐O‐methyl‐rac‐glycerophosphothionate) and performing shRNA knockdown of the Lpa3r transcript in these cells, we showed that LPA₃ activation increased expression levels of antioxidant enzymes, consequently inhibiting ROS accumulation and ameliorating cell senescence. LPA₃ was shown to be downregulated in HGPS patient fibroblasts through the lysosomal pathway, and it was shown to be crucial for ameliorating ROS accumulation and cell senescence in fibroblasts. Moreover, in a zebrafish model, LPA₃ deficiency was sufficient to cause premature aging phenotypes in multiple organs, as well as a shorter lifespan. Taken together, these findings identify the decline of LPA₃ as a key contributor to the premature aging phenotypes of HGPS cells and zebrafish.

The Differentiation of Human Cytomegalovirus Infected-Monocytes Is Required for Viral Replication

Viral dissemination is a key mechanism responsible for persistence and disease following human cytomegalovirus (HCMV) infection. Monocytes play a pivotal role in viral dissemination to organ tissue during primary infection and following reactivation from latency. For example, during primary infection, infected monocytes migrate into tissues and differentiate into macrophages, which then become a source of viral replication. In addition, because differentiated macrophages can survive for months to years, they provide a potential persistent infection source in various organ systems. We broadly note that there are three phases to infection and differentiation of HCMV-infected monocytes: (1) Virus enters and traffics to the nucleus through a virus receptor ligand engagement event that activates a unique signalsome that initiates the monocyte-to-macrophage differentiation process. (2) Following initial infection, HCMV undergoes a "quiescence-like state" in monocytes lasting for several weeks and promotes monocyte differentiation into macrophages. While, the initial event is triggered by the receptor-ligand engagement, the long-term cellular activation is maintained by chronic viral-mediated signaling events. (3) Once HCMV infected monocytes differentiate into macrophages, the expression of immediate early viral (IE) genes is detectable, followed by viral replication and long term infectious viral particles release. Herein, we review the detailed mechanisms of each phase during infection and differentiation into macrophages and discuss the biological significance of the differentiation of monocytes in the pathogenesis of HCMV.

Cellular senescence and senescence-associated secretory phenotype via the cGAS-STING signaling pathway in cancer

Cellular senescence is historically regarded as a tumor suppression mechanism to prevent damaged cells from aberrant proliferation in benign and premalignant tumors. However, recent findings have suggested that senescent cells contribute to tumorigenesis and age‐associated pathologies through the senescence‐associated secretory phenotype (SASP). Therefore, to control age‐associated cancer, it is important to understand the molecular mechanisms of the SASP in the cancer microenvironment. New findings have suggested that the cyclic GMP‐AMP synthase (cGAS)‐stimulator of interferon genes (STING) signaling pathway, a critical indicator of innate immune response, triggers the SASP in response to accumulation of cytoplasmic DNA (cytoplasmic chromatin fragments, mtDNA and cDNA) in senescent cells. Notably, the cGAS‐STING signaling pathway promotes or inhibits tumorigenesis depending on the biological context in vivo, indicating that it may be a potential therapeutic target for cancer. Herein, we review the regulatory machinery and biological function of the SASP via the cGAS‐STING signaling pathway in cancer.

Combination of STING Pathway Agonist With Saponin Is an Effective Adjuvant in Immunosenescent Mice

There is an urgent need to improve protective responses to influenza vaccination in the elderly population, which is at especially high risk for adverse outcomes from influenza infection. Currently available inactivated vaccines provide limited protection, even when a 4-fold higher dose of the vaccine is administered. Adjuvants are often added to vaccines to boost protective efficacy. Here we describe a novel combination of an activator of the STING pathway, 2′,3′-cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) with a saponin adjuvant, that we found to be highly effective in boosting protective immunity from vaccination in an aged mouse model. Using this combination with a subunit influenza vaccine, we observed that survival of vaccinated 20 month-old mice after lethal challenge increased from 0 to 20% with unadjuvanted vaccine to 80–100%, depending on the vaccination route. Compared to unadjuvanted vaccine, the levels of vaccine-specific IgG and IgG2a increased by almost two orders of magnitude as early as 2 weeks after a single immunization with the adjuvanted formulation. By analyzing phosphorylation of interferon regulatory factor 3 (IRF3) in cell culture, we provide evidence that the saponin component increases access of exogenous cGAMP to the intracellular STING pathway. Our findings suggest that combining a STING activator with a saponin-based adjuvant increases the effectiveness of influenza vaccine in aged hosts, without having to increase dose or perform additional vaccinations. This study reports a novel adjuvant combination that (a) is more effective than current methods of boosting vaccine efficacy, (b) can be used to enhance efficacy of licensed influenza vaccines, and (c) results in effective protection using a single vaccine dose.

Tight nuclear tethering of cGAS is essential for preventing autoreactivity

cGAS is an intracellular innate immune sensor that detects double-stranded DNA. The presence of billions of base pairs of genomic DNA in all nucleated cells raises the question of how cGAS is not constitutively activated. A widely accepted explanation for this is the sequestration of cGAS in the cytosol, which is thought to prevent cGAS from accessing nuclear DNA. Here, we demonstrate that endogenous cGAS is predominantly a nuclear protein, regardless of cell cycle phase or cGAS activation status. We show that nuclear cGAS is tethered tightly by a salt-resistant interaction. This tight tethering is independent of the domains required for cGAS activation, and it requires intact nuclear chromatin. We identify the evolutionarily conserved tethering surface on cGAS and we show that mutation of single amino acids within this surface renders cGAS massively and constitutively active against self-DNA. Thus, tight nuclear tethering maintains the resting state of cGAS and prevents autoreactivity.

Uncoupled turnover disrupts mitochondrial quality control in diabetic retinopathy

Mitochondrial quality control (MQC) is crucial for regulating CNS homeostasis, and its disruption has been implicated in the pathogenesis of some of the most common neurodegenerative diseases. In healthy tissues, the maintenance of MQC depends upon an exquisite balance between mitophagy (removal of damaged mitochondria by autophagy) and biogenesis (de novo synthesis of mitochondria). Here, we show that mitophagy is disrupted in diabetic retinopathy (DR) and decoupled from mitochondrial biogenesis during the progression of the disease. Diabetic retinas from human postmortem donors and experimental mice exhibit a net loss of mitochondrial contents during the early stages of the disease process. Using diabetic mitophagy-reporter mice (mitoQC-Ins2^Akita) alongside pMitoTimer (a molecular clock to address mitochondrial age dynamics), we demonstrate that mitochondrial loss arose due to an inability of mitochondrial biogenesis to compensate for diabetes-exacerbated mitophagy. However, as diabetes duration increases, Pink1-dependent mitophagy deteriorates, leading to the build-up of mitochondria primed for degradation in DR. Impairment of mitophagy during prolonged diabetes is linked with the development of retinal senescence, a phenotype that blunted hyperglycemia-induced mitophagy in mitoQC primary Müller cells. Our findings suggest that normalizing mitochondrial turnover may preserve MQC and provide therapeutic options for the management of DR-associated complications.

Uncoupled mitophagy and mitochondrial biogenesis leads to mitochondrial damage in the retina during the progression of diabetes.

Targeting senescent cells in translational medicine

Organismal ageing is a complex process driving progressive impairment of functionality and regenerative potential of tissues. Cellular senescence is a state of stable cell cycle arrest occurring in response to damage and stress and is considered a hallmark of ageing. Senescent cells accumulate in multiple organs during ageing, contribute to tissue dysfunction and give rise to pathological manifestations. Senescence is therefore a defining feature of a variety of human age-related disorders, including cancer, and targeted elimination of these cells has recently emerged as a promising therapeutic approach to ameliorate tissue damage and promote repair and regeneration. In addition, in vivo identification of senescent cells has significant potential for early diagnosis of multiple pathologies. Here, we review existing senolytics, small molecules and drug delivery tools used in preclinical therapeutic strategies involving cellular senescence, as well as probes to trace senescent cells. We also review the clinical research landscape in senescence and discuss how identifying and targeting cellular senescence might positively affect pathological and ageing processes.

The Rho GTPase RND3 regulates adipocyte lipolysis

BACKGROUND

Adipose tissue plays a crucial role in diet- and obesity-related insulin resistance, with implications for several metabolic diseases. Identification of novel target genes and mechanisms that regulate adipocyte function could lead to improved treatment strategies. RND3 (RhoE/Rho8), a Rho-related GTP-binding protein that inhibits Rho kinase (ROCK) signaling, has been linked to diverse diseases such as apoptotic cardiomyopathy, heart failure, cancer and type 2 diabetes, in part by regulating cytoskeleton dynamics and insulin-mediated glucose uptake.

RESULTS

We here investigated the expression of RND3 in adipose tissue in human obesity, and discovered a role for RND3 in regulating adipocyte metabolism. In cross-sectional and prospective studies, we observed 5-fold increased adipocyte levels of RND3 mRNA in obesity, reduced levels after surgery-induced weight loss, and positive correlations of RND3 mRNA with adipocyte size and surrogate measures of insulin resistance (HOMA2-IR and circulating triglyceride/high-density lipoprotein cholesterol (TAG/HDL-C) ratio). By screening for RND3-dependent gene expression following siRNA-mediated RND3 knockdown in differentiating human adipocytes, we found downregulation of inflammatory genes and upregulation of genes related to adipocyte ipolysis and insulin signaling. Treatment of adipocytes with tumor necrosis factor alpha (TNFα), lipopolysaccharide (LPS), hypoxia or cAMP analogs increased RND3 mRNA levels 1.5-2-fold. Functional assays in primary human adipocytes confirmed that RND3 knockdown reduces cAMP- and isoproterenol-induced lipolysis, which were mimicked by treating cells with ROCK inhibitor. This effect could partly be explained by reduced protein expression of adipose triglyceride lipase (ATGL) and phosphorylated hormone-sensitive lipase (HSL).

CONCLUSION

We here uncovered a novel differential expression of adipose RND3 in obesity and insulin resistance, which may at least partly depend on a causal effect of RND3 on adipocyte lipolysis.

Interrupting cyclic dinucleotide-cGAS-STING axis with small molecules

The cyclic dinucleotide-cGAS-STING axis plays important roles in host immunity. Activation of this signaling pathway, via cytosolic sensing of bacterial-derived c-di-GMP/c-di-AMP or host-derived cGAMP, leads to the production of inflammatory interferons and cytokines that help resolve infection. Small molecule activators of the cGAS-STING axis have the potential to augment immune response against various pathogens or cancer. The aberrant activation of this pathway, due to gain-of-function mutations in any of the proteins that are part of the signaling axis, could lead to various autoimmune diseases. Inhibiting various nodes of the cGAS-STING axis could provide relief to patients with autoimmune diseases. Many excellent reviews on the cGAS-STING axis have been published recently, and these have mainly focused on the molecular details of the cGAS-STING pathway. This review however focuses on small molecules that can be used to modulate various aspects of the cGAS-STING pathway, as well as other parallel inflammatory pathways.

miR29a and miR378b Influence CpG-Stimulated Dendritic Cells and Regulate cGAS/STING Pathway

The Cytosine–phosphate–guanosine (CpG) motif, which is specifically recognized intracellularly by dendritic cells (DCs), plays a crucial role in regulating the innate immune response. MicroRNAs (miRNAs) can strongly influence the antigen-presenting ability of DCs. In this study, we examine the action of miRNAs on CpG-stimulated and control DCs, as well as their effect on cyclic guanosine monophosphate-adenosine monophosphate (GMP–AMP) synthase (cGAS) and the stimulator of interferon genes (STING) signal pathway. Firstly, we selected miRNAs (miR-29a and miR-378b) based on expression in CpG-stimulated mouse bone marrow-derived dendritic cells (BMDCs). Secondly, we investigated the functions of miR-29a and miR-378b on CpG-stimulated and unstimulated BMDCs. The results showed that miR-29a and miR-378b increased expression of both the immunoregulatory DC surface markers (CD86 and CD40) and the immunosuppressive molecule CD273 by DCs. Thirdly, cytokine detection revealed that both miR-29a and miR-378b enhanced interferon-β (IFN-β) expression while suppressing tumor necrosis factor-α (TNF-α) production. Finally, our results suggest that miR-378b can bind TANK-binding kinase binding protein 1 (TBKBP1) to activate the cGAS/STING signaling pathway. By contrast, miR-29a targeted interferon regulatory factor 7 (IRF7) and promoted the expression of STING. Together, our results provide insight into the molecular mechanism of miRNA induction by CpG to regulate DC function.

After Nf1 loss in Schwann cells, inflammation drives neurofibroma formation

Plexiform neurofibromas (PNF) are peripheral nerve tumors caused by bi-allelic loss of NF1 in the Schwann cell (SC) lineage. PNF are common in individuals with Neurofibromatosis type I (NF1) and can cause significant patient morbidity, spurring research into potential therapies. Immune cells are rare in peripheral nerve, whereas in PNF 30% of the cells are monocytes/macrophages. Mast cells, T cells, and dendritic cells (DCs) are also present. NF1 mutant neurofibroma SCs with elevated Ras-GTP signaling resemble injury-induced repair SCs, in producing growth factors and cytokines not normally present in SCs. This provides a cytokine-rich environment facilitating PNF immune cell recruitment and fibrosis. We propose a model based on genetic and pharmacologic evidence in which, after loss of Nf1 in the SC lineage, a lag occurs. Then, mast cells and macrophages are recruited to nerve. Later, T cell/DC recruitment through CXCL10/CXCR3 drives neurofibroma initiation and sustains PNF macrophages and tumor growth. Stat3 signaling is an additional critical mediator of neurofibroma initiation, cytokine production, and PNF growth. At each stage of PNF development therapeutic benefit should be achievable through pharmacologic modulation of leukocyte recruitment and function.

Bioactive modulators targeting STING adaptor in cGAS-STING pathway

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-pathway triggers innate immune responses by recognizing cytosolic DNA. Recent studies revealed that STING adaptor associates with various diseases, and several modulators targeting STING have been identified including three agonists that have entered clinical trials for treating cancer over the past 2 years. In particular, the efficacy of STING agonists and/or antagonists suggests adaptor STING as a potential therapeutic target for diverse diseases. Herein, we summarize the latest advances in understanding STING functioning and provide an overview of recent STING modulator discoveries, including structural details and the potential therapeutic applications of these modulators.

The cGAS-STING pathway is a therapeutic target in a preclinical model of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer, and the incidence of HCC is increasing. Recently, cancer immunotherapy has emerged as an efficient treatment against some cancers. Here we have used a mouse model of mutagen-induced HCC to explore the therapeutic usefulness of targeting the DNA-activated STING pathway in HCC. STING-deficient mice exhibited unaltered initial development of HCC, but had higher number of large tumors at late stages of disease. In the liver of STING-deficient HCC mice, we observed reduced levels of phospho-STAT1, autophagy, and cleaved caspase3. These responses were activated in the liver by treatment with a cyclic dinucleotide (CDN) STING agonist. Importantly, CDN treatment of mice after HCC development efficiently reduced tumor size. Initiation of CDN treatment at an even later stage of disease to allow HCC detection by MR scanning revealed that the majority of tumors regressed in response to CDN, but new tumors were also detected, which were unresponsive to CDN treatment. Overall, the modulation of the STING pathway affects the development of HCC, and holds promise for a use as a treatment of this disease, most likely in combination with other immunomodulatory treatments such as PD1 inhibitors or with standard of care.

PROPERTIES AND FUNCTIONS OF THE NOVEL TYPE I INTERFERON EPSILON

Interferon epsilon (IFNε) is a type I IFN with unusual patterns of expression and therefore, function. It is constitutively expressed by reproductive tract epithelium and regulated by hormones during estrus cycle, reproduction, and menopause and by exogenous hormones. The IFNe protein is encoded by a gene in the type I IFN locus, binds to IFNAR1 and 2 which are required for signaling via the JAK STAT pathway. Its affinity for binding receptors and transducing signals is less potent than IFNα or β subtypes in vitro. Nevertheless, in vivo experiments indicate its efficacy in regulating mucosal immune responses and protecting from bacterial and viral infections. These studies demonstrate a different mechanism of action to type I IFNs. In this organ system with dynamic fluxes in cellularity, requirement to tolerate an implanted fetus, and be protected from disease, there is co-option of a special IFN from a family of effective immunoregulators, with unique controls and modified potency to make it a safe and effective constitutive reproductive tract cytokine.

Induction of pro-inflammatory cytokines by 29-kDa FN-f via cGAS/STING pathway

The cGAS-STING pathway plays an important role in pathogen-induced activation of the innate immune response. The 29-kDa amino-terminal fibronectin fragment (29-kDa FN-f) found predominantly in the synovial fluid of osteoarthritis (OA) patients increases the expression of catabolic factors via the toll-like receptor-2 (TLR-2) signaling pathway. In this study, we investigated whether 29-kDa FN-f induces inflammatory responses via the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon gene (STING) pathway in human primary chondrocytes. The levels of cGAS and STING were elevated in OA cartilage compared with normal cartilage. Long-term treatment of chondrocytes with 29-kDa FN-f activated the cGAS/STING pathway together with the increased level of gamma-H2AX, a marker of DNA breaks. In addition, the expression of pro-inflammatory cytokines, including granulocyte-macrophage colony-stimulating factor (GM-CSF/CSF-2), granulocyte colony-stimulating factor (G-CSF/CSF-3), and type I interferon (IFN-α), was increased more than 100-fold in 29-kDa FN-f-treated chondrocytes. However, knockdown of cGAS and STING suppressed 29-kDa FN-f-induced expression of GM-CSF, G-CSF, and IFN-α together with the decreased activation of TANK-binding kinase 1 (TBK1), interferon regulatory factor 3 (IRF3), and inhibitor protein κBα (IκBα). Furthermore, NOD2 or TLR-2 knockdown suppressed the expression of GM-CSF, G-CSF, and IFN-α as well as decreased the activation of the cGAS/STING pathway in 29-kDa FN-f-treated chondrocytes. These data demonstrate that the cGAS/STING/TBK1/IRF3 pathway plays a critical role in 29-kDa FN-f-induced expression of pro-inflammatory cytokines.

Cerpegin-derived furo[3,4-c]pyridine-3,4(1H,5H)-diones enhance cellular response to interferons by de novo pyrimidine biosynthesis inhibition

There is an increasing interest in the field of cancer therapy for small compounds targeting pyrimidine biosynthesis, and in particular dihydroorotate dehydrogenase (DHODH), the fourth enzyme of this metabolic pathway. Three available DHODH structures, featuring three different known inhibitors, were used as templates to screen in silico an original chemical library from Erevan University. This process led to the identification of P1788, a compound chemically related to the alkaloid cerpegin, as a new class of pyrimidine biosynthesis inhibitors. In line with previous reports, we investigated the effect of P1788 on the cellular innate immune response. Here we show that pyrimidine depletion by P1788 amplifies cellular response to both type-I and type II interferons, but also induces DNA damage as assessed by γH2AX staining. Moreover, the addition of inhibitors of the DNA damage response led to the suppression of the P1788 stimulatory effects on the interferon pathway. This demonstrates that components of the DNA damage response are bridging the inhibition of pyrimidine biosynthesis by P1788 to the interferon signaling pathway. Altogether, these results provide new insights on the mode of action of novel pyrimidine biosynthesis inhibitors and their development for cancer therapies.

The Next Generation of Immunotherapy for Cancer: Small Molecules Could Make Big Waves

After decades of intense effort, therapeutics that leverage the immune system to fight cancer have now been conclusively demonstrated to be effective. Immuno-oncology has arrived and will play a key role in the treatment of cancer for the foreseeable future. However, the search for novel methods to improve immune responses to cancer continues unabated. Toward this end, small molecules that can either reduce immune suppression in the tumor milieu or enhance activation of cytotoxic lymphocyte responses to the tumor are actively being pursued. Such novel treatment strategies might be used as monotherapies or combined with other cancer therapies to increase and broaden their efficacy. In this article, we provide an overview of small molecule immunotherapeutic approaches for the treatment of cancer. Over the next decade and beyond, these approaches could further enhance our ability to harness the immune system to combat cancer and thus become additional weapons in the oncologist's armory.

Cellular Senescence: Defining a Path Forward

Cellular senescence is a cell state implicated in various physiological processes and a wide spectrum of age-related diseases. Recently, interest in therapeutically targeting senescence to improve healthy aging and age-related disease, otherwise known as senotherapy, has been growing rapidly. Thus, the accurate detection of senescent cells, especially in vivo, is essential. Here, we present a consensus from the International Cell Senescence Association (ICSA), defining and discussing key cellular and molecular features of senescence and offering recommendations on how to use them as biomarkers. We also present a resource tool to facilitate the identification of genes linked with senescence, SeneQuest (available at http://Senequest.net). Lastly, we propose an algorithm to accurately assess and quantify senescence, both in cultured cells and in vivo.

Interferon γ and α Have Differential Effects on SAMHD1, a Potent Antiviral Protein, in Feline Lymphocytes

Sterile alpha motif and histidine/aspartic domain-containing protein 1 (SAMHD1) is a protein with anti-viral, anti-neoplastic, and anti-inflammatory properties. By degrading cellular dNTPs to constituent deoxynucleoside and free triphosphate, SAMHD1 limits viral DNA synthesis and prevents replication of HIV-1 and some DNA viruses such as HBV, vaccinia, and HSV-1. Recent findings suggest SAMHD1 is broadly active against retroviruses in addition to HIV-1, such as HIV-2, FIV, BIV, and EIAV. Interferons are cytokines produced by lymphocytes and other cells that induce a wide array of antiviral proteins, including some with activity again lentiviruses. Here we evaluated the role of IFNs on SAMHD1 gene expression, transcription, and post-translational modification in a feline CD4⁺ T cell line (FeTJ) and in primary feline CD4⁺ T lymphocytes. SAMHD1 mRNA in FetJ cells increased in a dose-related manner in response to IFNγ treatment concurrent with increased nuclear localization and phosphorylation. IFNα treatment induced SAMHD1 mRNA but did not significantly alter SAMHD1 protein detection, phosphorylation, or nuclear translocation. In purified primary feline CD4⁺ lymphocytes, IL2 supplementation increased SAMHD1 expression, but the addition of IFNγ did not further alter SAMHD1 protein expression or nuclear localization. Thus, the effect of IFNγ on SAMHD1 expression is cell-type dependent, with increased translocation to the nucleus and phosphorylation in FeTJ but not primary CD4⁺ lymphocytes. These findings imply that while SAMH1 is inducible by IFNγ, overall activity is cell type and compartment specific, which is likely relevant to the establishment of lentiviral reservoirs in quiescent lymphocyte populations.

Immune effector monocyte-neutrophil cooperation induced by the primary tumor prevents metastatic progression of breast cancer

Metastatic behavior varies significantly among breast cancers. Mechanisms explaining why the majority of breast cancer patients never develop metastatic outgrowth are largely lacking but could underlie the development of novel immunotherapeutic target molecules. Here we show interplay between nonmetastatic primary breast cancer and innate immune response, acting together to control metastatic progression. The primary tumor systemically recruits IFNγ-producing immune effector monocytes to the lung. IFNγ up-regulates Tmem173/STING in neutrophils and enhances their killing capacity. The immune effector monocytes and tumoricidal neutrophils target disseminated tumor cells in the lungs, preventing metastatic outgrowth. Importantly, our findings could underlie the development of immunotherapeutic target molecules that augment the function of immune effector monocytes and neutrophils.

Phagocytosis checkpoints as new targets for cancer immunotherapy

Cancer immunotherapies targeting adaptive immune checkpoints have substantially improved patient outcomes across multiple metastatic and treatment-refractory cancer types. However, emerging studies have demonstrated that innate immune checkpoints, which interfere with the detection and clearance of malignant cells through phagocytosis and suppress innate immune sensing, also have a key role in tumour-mediated immune escape and might, therefore, be potential targets for cancer immunotherapy. Indeed, preclinical studies and early clinical data have established the promise of targeting phagocytosis checkpoints, such as the CD47-signal-regulatory protein α (SIRPα) axis, either alone or in combination with other cancer therapies. In this Review, we highlight the current understanding of how cancer cells evade the immune system by disrupting phagocytic clearance and the effect of phagocytosis checkpoint blockade on induction of antitumour immune responses. Given the role of innate immune cells in priming adaptive immune responses, an improved understanding of the tumour-intrinsic processes that inhibit essential immune surveillance processes, such as phagocytosis and innate immune sensing, could pave the way for the development of highly effective combination immunotherapy strategies that modulate both innate and adaptive antitumour immune responses.

Topoisomerases and cancer chemotherapy: recent advances and unanswered questions

DNA topoisomerases are enzymes that catalyze changes in the torsional and flexural strain of DNA molecules. Earlier studies implicated these enzymes in a variety of processes in both prokaryotes and eukaryotes, including DNA replication, transcription, recombination, and chromosome segregation. Studies performed over the past 3 years have provided new insight into the roles of various topoisomerases in maintaining eukaryotic chromosome structure and facilitating the decatenation of daughter chromosomes at cell division. In addition, recent studies have demonstrated that the incorporation of ribonucleotides into DNA results in trapping of topoisomerase I (TOP1)–DNA covalent complexes during aborted ribonucleotide removal. Importantly, such trapped TOP1–DNA covalent complexes, formed either during ribonucleotide removal or as a consequence of drug action, activate several repair processes, including processes involving the recently described nuclear proteases SPARTAN and GCNA-1. A variety of new TOP1 inhibitors and formulations, including antibody–drug conjugates and PEGylated complexes, exert their anticancer effects by also trapping these TOP1–DNA covalent complexes. Here we review recent developments and identify further questions raised by these new findings.

DAMP-sensing receptors in sterile inflammation and inflammatory diseases

The innate immune system has the capacity to detect 'non-self' molecules derived from pathogens, known as pathogen-associated molecular patterns, via pattern recognition receptors. In addition, an increasing number of endogenous host-derived molecules, termed damage-associated molecular patterns (DAMPs), have been found to be sensed by various innate immune receptors. The recognition of DAMPs, which are produced or released by damaged and dying cells, promotes sterile inflammation, which is important for tissue repair and regeneration, but can also lead to the development of numerous inflammatory diseases, such as metabolic disorders, neurodegenerative diseases, autoimmune diseases and cancer. Here we examine recent discoveries concerning the roles of DAMP-sensing receptors in sterile inflammation and in diseases resulting from dysregulated sterile inflammation, and then discuss insights into the cross-regulation of these receptors and their ligands.

Hepatic senescence, the good and the bad

Gradual alterations of cell’s physiology and functions due to age or exposure to various stresses lead to the conversion of normal cells to senescent cells. Once becoming senescent, the cell stops dividing permanently but remains metabolically active. Cellular senescence does not have a single marker but is characterized mainly by a combination of multiple markers, such as, morphological changes, expression of cell cycle inhibitors, senescence associated β-galactosidase activity, and changes in nuclear membrane. When cells in an organ become senescent, the entire organism can be affected. This may occur through the senescence-associated secretory phenotype (SASP). SASP may exert beneficial or harmful effects on the microenvironment of tissues. Research on senescence has become a very exciting field in cell biology since the link between age-related diseases, including cancer, and senescence has been established. The loss of regenerative and homeostatic capacity of the liver over the age is somehow connected to cellular senescence. The major contributors of senescence properties in the liver are hepatocytes and cholangiocytes. Senescent cells in the liver have been implicated in the etiology of chronic liver diseases including cirrhosis and hepatocellular carcinoma and in the interference of liver regeneration. This review summarizes recently reported findings in the understanding of the molecular mechanisms of senescence and its relationship with liver diseases.

Lipopolysaccharide enhances DNA-induced IFN-β expression and autophagy by upregulating cGAS expression in A549 cells

Cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) is a newly identified cytosolic DNA sensor, but its function in lung epithelial cells is relatively unknown. In the present study, the effects of lipopolysaccharide (LPS) on the expression and function of cGAS in the A549 lung epithelial cell line was investigated. The cells were treated with LPS at different concentrations (e.g., 100, 200, 400 and 800 ng/ml), and the cGAS expression levels were examined via western blot analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The cells were pretreated with LPS, followed by E. coli DNA transfection using Lipofectamine^® 3000. After 24 h, interferon (IFN)-β production was measured using ELISA and the expression of the autophagic markers, microtubule-associated proteins 1A/1B light chain 3 and sequestosome-1, were determined using western blot analysis. The cells were also pretreated with either a toll-like receptor (TLR) 4 inhibitor, a serine/threonine-protein kinase TBK1 (TBK1) inhibitor or an nuclear factor (NF)-κB inhibitor, followed by LPS treatment, and the cGAS expression levels were examined via western blot analysis and RT-qPCR. The result showed that LPS treatment upregulated cGAS expression in a dose-dependent manner. E. coli DNA treatment could induce IFN-β production and autophagy via cGAS, which was enhanced by LPS pretreatment. The effect of LPS on cGAS expression was suppressed by treatment with a TLR4 inhibitor, a TBK1 inhibitor and an NF-κB inhibitor. In conclusion, LPS enhances DNA-induced IFN-β production and autophagy by upregulating cGAS expression through the myeloid differentiation primary response protein MyD88-independent TLR4 signaling pathway in A549 cells.

Ageing as a risk factor for neurodegenerative disease

Ageing is the primary risk factor for most neurodegenerative diseases, including Alzheimer disease (AD) and Parkinson disease (PD). One in ten individuals aged ≥65 years has AD and its prevalence continues to increase with increasing age. Few or no effective treatments are available for ageing-related neurodegenerative diseases, which tend to progress in an irreversible manner and are associated with large socioeconomic and personal costs. This Review discusses the pathogenesis of AD, PD and other neurodegenerative diseases, and describes their associations with the nine biological hallmarks of ageing: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, mitochondrial dysfunction, cellular senescence, deregulated nutrient sensing, stem cell exhaustion and altered intercellular communication. The central biological mechanisms of ageing and their potential as targets of novel therapies for neurodegenerative diseases are also discussed, with potential therapies including NAD⁺ precursors, mitophagy inducers and inhibitors of cellular senescence.

SLC19A1 transports immunoreactive cyclic dinucleotides

The accumulation of DNA in the cytosol serves as a key immunostimulatory signal associated with infections, cancer and genomic damage^1,2. Cytosolic DNA triggers immune responses by activating the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway³. The binding of DNA to cGAS activates its enzymatic activity, leading to the synthesis of a second messenger, cyclic guanosine monophosphate-adenosine monophosphate (2'3'-cGAMP)^4-7. This cyclic dinucleotide (CDN) activates STING⁸, which in turn activates the transcription factors interferon regulatory factor 3 (IRF3) and nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), promoting the transcription of genes encoding type I interferons and other cytokines and mediators that stimulate a broader immune response. Exogenous 2'3'-cGAMP produced by malignant cells⁹ and other CDNs, including those produced by bacteria^10-12 and synthetic CDNs used in cancer immunotherapy^13,14, must traverse the cell membrane to activate STING in target cells. How these charged CDNs pass through the lipid bilayer is unknown. Here we used a genome-wide CRISPR-interference screen to identify the reduced folate carrier SLC19A1, a folate-organic phosphate antiporter, as the major transporter of CDNs. Depleting SLC19A1 in human cells inhibits CDN uptake and functional responses, and overexpressing SLC19A1 increases both uptake and functional responses. In human cell lines and primary cells ex vivo, CDN uptake is inhibited by folates as well as two medications approved for treatment of inflammatory diseases, sulfasalazine and the antifolate methotrexate. The identification of SLC19A1 as the major transporter of CDNs into cells has implications for the immunotherapeutic treatment of cancer¹³, host responsiveness to CDN-producing pathogenic microorganisms¹¹ and-potentially-for some inflammatory diseases.

Mitochondria in the signaling pathways that control longevity and health span

Genetic and pharmacological intervention studies have identified evolutionarily conserved and functionally interconnected networks of cellular energy homeostasis, nutrient-sensing, and genome damage response signaling pathways, as prominent regulators of longevity and health span in various species. Mitochondria are the primary sites of ATP production and are key players in several other important cellular processes. Mitochondrial dysfunction diminishes tissue and organ functional performance and is a commonly considered feature of the aging process. Here we review the evidence that through reciprocal and multilevel functional interactions, mitochondria are implicated in the lifespan modulation function of these pathways, which altogether constitute a highly dynamic and complex system that controls the aging process. An important characteristic of these pathways is their extensive crosstalk and apparent malleability to modification by non-invasive pharmacological, dietary, and lifestyle interventions, with promising effects on lifespan and health span in animal models and potentially also in humans.

Topoisomerase inhibitors promote cancer cell motility via ROS-mediated activation of JAK2-STAT1-CXCL1 pathway

Background

Topoisomerase inhibitors (TI) can inhibit cell proliferation by preventing DNA replication, stimulating DNA damage and inducing cell cycle arrest. Although these agents have been commonly used in the chemotherapy for the anti-proliferative effect, their impacts on the metastasis of cancer cells remain obscure.

Methods

We used the transwell chamber assay to test effects of Topoisomerase inhibitors Etoposide (VP-16), Adriamycin (ADM) and Irinotecan (CPT-11) on the migration and invasion of cancer cells. Conditioned medium (CM) from TI-treated cells was subjected to Mass spectrometry screening. Gene silencing, neutralizing antibody, and specific chemical inhibitors were used to validate the roles of signaling molecules.

Results

Our studies disclosed that TI could promote the migration and invasion of a subset of cancer cells, which were dependent on chemokine (C-X-C motif) ligand 1 (CXCL1). Further studies disclosed that TI enhanced phosphorylation of Janus kinase 2 (JAK2) and Signal transducers and activators of transcription 1 (STAT1). Silencing or chemical inhibition of JAK2 or STAT1 abrogated TI-induced CXCL1 expression and cell motility. Moreover, TI increased cellular levels of reactive oxygen species (ROS) and promoted oxidation of Protein Tyrosine Phosphatase 1B (PTP1B), while reduced glutathione (GSH) reversed TI-induced JAK2-STAT1 activation, CXCL1 expression, and cell motility.

Conclusions

Our study demonstrates that TI can promote the expression and secretion of CXCL1 by elevating ROS, inactivating PTP1B, and activating JAK2-STAT1 signaling pathway, thereby promoting the motility of cancer cells.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1353-2) contains supplementary material, which is available to authorized users.

Fatigue, Sleep, and Autoimmune and Related Disorders

Profound and debilitating fatigue is the most common complaint reported among individuals with autoimmune disease, such as systemic lupus erythematosus, multiple sclerosis, type 1 diabetes, celiac disease, chronic fatigue syndrome, and rheumatoid arthritis. Fatigue is multi-faceted and broadly defined, which makes understanding the cause of its manifestations especially difficult in conditions with diverse pathology including autoimmune diseases. In general, fatigue is defined by debilitating periods of exhaustion that interfere with normal activities. The severity and duration of fatigue episodes vary, but fatigue can cause difficulty for even simple tasks like climbing stairs or crossing the room. The exact mechanisms of fatigue are not well-understood, perhaps due to its broad definition. Nevertheless, physiological processes known to play a role in fatigue include oxygen/nutrient supply, metabolism, mood, motivation, and sleepiness-all which are affected by inflammation. Additionally, an important contributing element to fatigue is the central nervous system-a region impacted either directly or indirectly in numerous autoimmune and related disorders. This review describes how inflammation and the central nervous system contribute to fatigue and suggests potential mechanisms involved in fatigue that are likely exhibited in autoimmune and related diseases.

Progressing from Recurring Tissue Injury to Genomic Instability: A New Mechanism of Neutrophil Pathogenesis

Aberrant neutrophil (PMN) infiltration of the intestinal mucosa is a hallmark of inflammatory bowel diseases, including Crohn's disease and ulcerative colitis. While the genotoxic function of PMNs and its implications in carcinogenesis have been primarily associated with oxidative stress, recent work by Butin-Israeli and colleagues has defined a novel mechanism where PMN-derived microparticles through the delivery and activity of specific miRNAs promoted formation of double-strand breaks (DSBs), and in parallel, suppressed DSB repair through the downregulation of lamin B1 and Rad51. Respective downregulation of these two proteins compromised the nuclear envelope and high-fidelity repair by homologous recombination, increasing DSB accumulation and aneuploidy. This discovery defined a novel mode of action where PMN-mediated suppression of DSB repair leading to genomic instability in the injured mucosa may facilitate progression toward colorectal cancer.

Regulation of signaling mediated by nucleic acid sensors for innate interferon-mediated responses during viral infection

Type I and type III interferons are important anti-viral cytokines that are massively induced during viral infection. This dynamic process is regulated by many executors and regulators for efficient eradication of invading viruses and protection from harmful, excessive responses. An array of innate sensors recognizes virus-derived nucleic acids to activate their downstream signaling to evoke cytokine responses including interferons. In particular, a cytoplasmic RNA sensor RIG-I (retinoic acid-inducible gene I) is involved in the detection of multiple types of not only RNA viruses but also DNA viruses. Accumulating findings have revealed that activation of nucleic acid sensors and the related signaling mediators is regulated on the basis of post-translational modification such as ubiquitination, phosphorylation and ADP-ribosylation. In addition, long non-coding RNAs (lncRNAs) have been implicated as a new class of regulators in innate signaling. A comprehensive understanding of the regulatory mechanisms of innate sensor activation and its signaling in host-virus interaction will provide a better therapeutic strategy to efficiently control viral infection and maintain immune homeostasis.

DNA sensing by the cGAS-STING pathway in health and disease

The detection of pathogens through nucleic acid sensors is a defining principle of innate immunity. RNA-sensing and DNA-sensing receptors sample subcellular compartments for foreign nucleic acids and, upon recognition, trigger immune signalling pathways for host defence. Over the past decade, our understanding of how the recognition of nucleic acids is coupled to immune gene expression has advanced considerably, particularly for the DNA-sensing receptor cyclic GMP-AMP synthase (cGAS) and its downstream signalling effector stimulator of interferon genes (STING), as well as the molecular components and regulation of this pathway. Moreover, the ability of self-DNA to engage cGAS has emerged as an important mechanism fuelling the development of inflammation and implicating the cGAS-STING pathway in human inflammatory diseases and cancer. This detailed mechanistic and biological understanding is paving the way for the development and clinical application of pharmacological agonists and antagonists in the treatment of chronic inflammation and cancer.

Inflammatory signaling in genomically instable cancers

Recent studies have shown that genomic instability in tumor cells leads to activation of inflammatory signaling through the cGAS/STING pathway. In this review, we describe multiple ways by which genomic instability leads to cGAS/STING-mediated inflammatory signaling, as well as the consequences for tumor development and the tumor microenvironment. Also, we elaborate on how tumor cells have apparently evolved to escape the immune surveillance mechanisms that are triggered by cGAS/STING signaling. Finally, we describe how cGAS/STING-mediated inflammatory signaling can be therapeutically targeted to improve therapy responses.

Self-DNA Sensing Fuels HIV-1-Associated Inflammation

Inflammation, over-reacting innate immunity, and CD4⁺ T cell depletion are hallmarks of HIV-1 infection. Self-DNA is usually not considered in the context of HIV-1-associated inflammation, although self-DNA contributes to inflammation in diverse pathologies, including autoimmune diseases, cancer, multiorgan failure after trauma, and even virus infections. Cells undergoing HIV-1-associated pyroptotic bystander cell death release self-DNA and other damage-associated molecular patterns (DAMPs), including chaperones and histones. In complexes with such DAMPs or extracellular vesicles, self-DNA gains immunogenic potential and becomes accessible to intracellular DNA sensors. Therefore, we hypothesize that self-DNA can contribute to HIV-1-associated inflammation. Self-DNA might not only drive HIV-1-associated 'inflamm-ageing' but also provide new opportunities for 'shock and kill' strategies aimed at eliminating latent HIV-1.

Genomic instability and innate immune responses to self-DNA in progeria

In the last decade, we have seen increasing evidence of the importance of structural nuclear proteins such as lamins in nuclear architecture and compartmentalization of genome function and in the maintenance of mechanical stability and genome integrity. With over 400 mutations identified in the LMNA gene (encoding for A-type lamins) associated with more than ten distinct degenerative disorders, the role of lamins as genome caretakers and the contribution of lamins dysfunction to disease are unarguable. However, the molecular mechanisms whereby lamins mutations cause pathologies remain less understood. Here, we review pathways and mechanisms recently identified as playing a role in the pathophysiology of laminopathies, with special emphasis in Hutchinson Gilford Progeria Syndrome (HGPS). This devastating incurable accelerated aging disease is caused by a silent mutation in the LMNA gene that generates a truncated lamin A protein "progerin" that exerts profound cellular toxicity and organismal decline. Patients usually die in their teens due to cardiovascular complications such as myocardial infarction or stroke. To date, there are no efficient therapies that ameliorate disease progression, stressing the need to understand molecularly disease mechanisms that can be targeted therapeutically. We will summarize data supporting that replication stress is a major cause of genomic instability in laminopathies, which contributes to the activation of innate immune responses to self-DNA that in turn accelerate the aging process.

A pyrophosphatase-coupled assay to monitor the NTase activity of cGAS

Cyclic GMP-AMP synthase, cGAS, converts ATP and GTP into a cyclic dinucleotide second messenger, cyclic GMP-AMP or cGAMP, through its enzymatic, nucleotidyl transferase (NTase) activity. Although many methods are available to directly measure cGAMP production, these assays often have high cost of implementation and/or experimental limitations. This chapter details how to implement an alternative approach that is relatively inexpensive, accurate and medium-throughput. The assay measures cGAS NTase activity by quantifying pyrophosphate production, a byproduct of the cGAS reaction. A coupling enzyme, pyrophosphatase, catalyzes the hydrolysis of pyrophosphate into inorganic phosphate, which enables facile detection of cGAS activity through conventional phosphomolybdate-malachite green absorbance methodology. This method is amenable for conventional steady-state kinetic measurements as well as high-throughput compound screening.

Homeostatic Roles of STING in Cell Proliferation and Chromosomal Instability

In this issue of Cancer Research, Ranoa and colleagues report on the role of STING (stimulator of IFN genes, TMEM173) in regulating critical tumor cell-intrinsic functions including cell-cycle progression, chromosomal stability, and cellular response to therapeutic ionizing radiation. The authors used multiple methods including RNA expression profiling, molecular and biochemical techniques, cell biology, and reagents from genetically modified murine models to test their hypothesis that downregulating the STING pathway in cancer cells promotes cellular transformation through accumulation of chromosomal instability and premature progression of the cell cycle. Their findings demonstrate that STING is a tumor suppressor that inhibits cell proliferation by restricting entry to mitosis as well as protecting cells against aneuploidy. These findings significantly advance our understanding of the role of STING as a tumor gate keeper.See related article by Ranoa et al., p. 1465.

Immunosurveillance of cancer cell stress

Cancer development is tightly controlled by effector immune responses that recognize and eliminate malignantly transformed cells. Nonetheless, certain immune subsets, such as tumor-associated macrophages, have been described to promote tumor growth, unraveling a double-edge role of the immune system in cancer. Cell stress can modulate the crosstalk between immune cells and tumor cells, reshaping tumor immunogenicity and/or immune function and phenotype. Infiltrating immune cells are exposed to the challenging conditions typically present in the tumor microenvironment. In return, the myriad of signaling pathways activated in response to stress conditions may tip the balance toward stimulation of antitumor responses or immune-mediated tumor progression. Here, we explore how distinct situations of cellular stress influence innate and adaptive immunity and the consequent impact on cancer establishment and progression.

Genome and transcriptome analyses providing insight into the immune response of pearl oysters after allograft and xenograft transplantations

The immune response after allograft or xenograft transplantation in the pearl oyster is a major factor that cause its nucleus rejection and death. To determine the mechanism underlying the immune response after allograft and xenograft transplantations in the pearl oyster Pinctada fucata martensii, we constructed two sets of transcriptomes of hemocytes at different times (6 and 12 h; 1, 3, 6, 12, and 30 d) after allograft and xenograft transplantations, in which the xenografted mantle tissue was from Pinctada maxima. The transcriptomic analysis reveals many genes are involved in the immune response to transplantation, such as transient receptor potential cation channel (TRP), calmodulin (CaM), DNA replication-related genes, and sugar and lipid metabolism-related genes. The expression of these identified genes was higher in the host pearl oyster transplanted with xenograft than that by allograft. The histological analysis of the pearl sac also confirmed that many hemocytes were still gathered around the transplanted nucleus, and no pearl sac was formed in the host pearl oysters at 30 d after xenograft transplantation. The genomic analysis indicated that pearl oysters evolved many copies of genes, such as TRP, CaM, and GST, to sense and cope with the immune response after transplantation. "Ribosome" and "Cytosolic DNA-sensing pathway" were specifically induced in the xenograft group, whereas "Notch signaling pathway" specifically responded to the allograft transplantation. These results can improve our understanding of the mechanism underlying the immune response of pearl oysters after allograft and xenograft transplantations.

DNA Repair Deficiency in Breast Cancer: Opportunities for Immunotherapy

Historically the development of anticancer treatments has been focused on their effect on tumor cells alone. However, newer treatments have shifted attention to targets on immune cells, resulting in dramatic responses. The effect of DNA repair deficiency on the microenvironment remains an area of key interest. Moreover, established therapies such as DNA damaging treatments such as chemotherapy and PARP inhibitors further modify the tumor microenvironment. Here we describe DNA repair pathways in breast cancer and activation of innate immune pathways in DNA repair deficiency, in particular, the STING (STimulator of INterferon Genes) pathway. Breast tumors with DNA repair deficiency are associated with upregulation of immune checkpoints including PD-L1 (Programmed Death Ligand-1) and may represent a target population for single agent or combination immunotherapy treatment.

Fcmr regulates mononuclear phagocyte control of anti-tumor immunity

Myeloid cells contribute to tumor progression, but how the constellation of receptors they express regulates their functions within the tumor microenvironment (TME) is unclear. We demonstrate that Fcmr (Toso), the putative receptor for soluble IgM, modulates myeloid cell responses to cancer. In a syngeneic melanoma model, Fcmr ablation in myeloid cells suppressed tumor growth and extended mouse survival. Fcmr deficiency increased myeloid cell population density in this malignancy and enhanced anti-tumor immunity. Single-cell RNA sequencing of Fcmr-deficient tumor-associated mononuclear phagocytes revealed a unique subset with enhanced antigen processing/presenting properties. Conversely, Fcmr activity negatively regulated the activation and migratory capacity of myeloid cells in vivo, and T cell activation by bone marrow-derived dendritic cells in vitro. Therapeutic targeting of Fcmr during oncogenesis decreased tumor growth when used as a single agent or in combination with anti-PD-1. Thus, Fcmr regulates myeloid cell activation within the TME and may be a potential therapeutic target.

Myeloid cells modulate the immune response within the tumour microenvironment, but the underlying mechanisms remain largely unknown. Here, the authors show that Fcmr – the putative receptor for soluble IgM – is a potent negative regulator of anti-tumour immunity.

DNA released from neutrophil extracellular traps (NETs) activates pancreatic stellate cells and enhances pancreatic tumor growth

Neutrophil extracellular trap (NET) formation results in the expulsion of granulocyte proteins and DNA into the extracellular space. This process is mediated by the enzyme peptidyl arginine deiminase 4 (PADI4) and translocation of elastase to the nucleus. NET formation, marked by increased levels of extracellular DNA, promotes pancreatic cancer proliferation and metastasis. Mice deficient in Padi4 demonstrate decreased pancreatic tumor growth, associated with a reduction in circulating extracellular DNA levels, diminished pancreatic stromal activation and improved survival in murine orthotopic pancreatic adenocarcinoma. Transplantation of Padi4-/- bone marrow into genetically engineered mice with Kras driven pancreatic adenocarcinoma (Pdx1-Cre:KrasG12D/+, KC mice) limits the frequency of invasive cancers when compared with syngeneic controls. DNA from neutrophils activates pancreatic stellate cells that form dense, fibrous stroma which can promote and enable tumor proliferation. DNase treatment diminishes murine tumor growth and stromal activation to reverse the effect of NETs within the tumor microenvironment. Furthermore, deletion of the receptor for advanced glycation end products (RAGE) in pancreatic stellate cells abrogates the effects of DNA in promoting stellate cell proliferation and decreases tumor growth. Circulating neutrophil-derived DNA correlates with the stage in patients with pancreatic ductal adenocarcinoma, confirming the role of NETs in human pancreatic cancer. These findings support further investigation into targeting of NETs, PADI4 and extracellular DNA as a potential treatment strategy in patients with pancreatic cancer. Trial Registration: This study reports correlative data from a clinical trial registered with clinicaltrials.gov, NCT01978184 (November 7, 2013).

The cGAS-cGAMP-STING Pathway: A Molecular Link Between Immunity and Metabolism

It has been appreciated for many years that there is a strong association between metabolism and immunity in advanced metazoan organisms. Distinct immune signatures and signaling pathways have been found not only in immune but also in metabolic cells. The newly discovered DNA-sensing cGAS-cGAMP-STING pathway mediates type I interferon inflammatory responses in immune cells to defend against viral and bacterial infections. Recent studies show that this pathway is also activated by host DNA aberrantly localized in the cytosol, contributing to increased sterile inflammation, insulin resistance, and the development of nonalcoholic fatty liver disease (NAFLD). Potential interactions of the cGAS-cGAMP-STING pathway with mTORC1 signaling, autophagy, and apoptosis have been reported, suggesting an important role of the cGAS-cGAMP-STING pathway in the networking and coordination of these important biological processes. However, the regulation, mechanism of action, and tissue-specific role of the cGAS-cGAMP-STING signaling pathway in metabolic disorders remain largely elusive. It is also unclear whether targeting this signaling pathway is effective for the prevention and treatment of obesity-induced metabolic diseases. Answers to these questions would provide new insights for developing effective therapeutic interventions for metabolic diseases such as insulin resistance, NAFLD, and type 2 diabetes.

Chromatin's physical properties shape the nucleus and its functions

The cell nucleus encloses, organizes, and protects the genome. Chromatin maintains nuclear mechanical stability and shape in coordination with lamins and the cytoskeleton. Abnormal nuclear shape is a diagnostic marker for human diseases, and it can cause nuclear dysfunction. Chromatin mechanics underlies this link, as alterations to chromatin and its physical properties can disrupt or rescue nuclear shape. The cell can regulate nuclear shape through mechanotransduction pathways that sense and respond to extracellular cues, thus modulating chromatin compaction and rigidity. These findings reveal how chromatin's physical properties can regulate cellular function and drive abnormal nuclear morphology and dysfunction in disease.