Nucleic acid sensing pattern recognition receptors in the development of colorectal cancer and colitis

AIM2 enhances Candida albicans infection through promoting macrophage apoptosis via AKT signaling

Candida albicans is among the most prevalent invasive fungal pathogens for immunocompromised individuals and novel therapeutic approaches that involve immune response modulation are imperative. Absent in melanoma 2 (AIM2), a pattern recognition receptor for DNA sensing, is well recognized for its involvement in inflammasome formation and its crucial role in safeguarding the host against various pathogenic infections. However, the role of AIM2 in host defense against C. albicans infection remains uncertain. This study reveals that the gene expression of AIM2 is induced in human and mouse innate immune cells or tissues after C. albicans infection. Furthermore, compared to their wild-type (WT) counterparts, Aim2-/- mice surprisingly exhibit resistance to C. albicans infection, along with reduced inflammation in the kidneys post-infection. The resistance of Aim2-/- mice to C. albicans infection is not reliant on inflammasome or type I interferon production. Instead, Aim2-/- mice display lower levels of apoptosis in kidney tissues following infection than WT mice. The deficiency of AIM2 in macrophages, but not in dendritic cells, results in a phenocopy of the resistance observed in Aim2-/- mice against C. albican infection. The treatment of Clodronate Liposome, a reagent that depletes macrophages, also shows the critical role of macrophages in host defense against C. albican infection in Aim2-/- mice. Furthermore, the reduction in apoptosis is observed in Aim2-/- mouse macrophages following infection or treatment of DNA from C. albicans in comparison with controls. Additionally, higher levels of AKT activation are observed in Aim2-/- mice, and treatment with an AKT inhibitor reverses the host resistance to C. albicans infection. The findings collectively demonstrate that AIM2 exerts a negative regulatory effect on AKT activation and enhances macrophage apoptosis, ultimately compromising host defense against C. albicans infection. This suggests that AIM2 and AKT may represent promising therapeutic targets for the management of fungal infections.

The tRNAVal half: A strong endogenous Toll-like receptor 7 ligand with a 5'-terminal universal sequence signature

Toll-like receptors (TLRs) are crucial components of the innate immune system. Endosomal TLR7 recognizes single-stranded RNAs, yet its endogenous ssRNA ligands are not fully understood. We previously showed that extracellular (ex-) 5'-half molecules of tRNAHisGUG (the 5'-tRNAHisGUG half) in extracellular vesicles (EVs) of human macrophages activate TLR7 when delivered into endosomes of recipient macrophages. Here, we fully explored immunostimulatory ex-5'-tRNA half molecules and identified the 5'-tRNAValCAC/AAC half, the most abundant tRNA-derived RNA in macrophage EVs, as another 5'-tRNA half molecule with strong TLR7 activation capacity. Levels of the ex-5'-tRNAValCAC/AAC half were highly up-regulated in macrophage EVs upon exposure to lipopolysaccharide and in the plasma of patients infected with Mycobacterium tuberculosis. The 5'-tRNAValCAC/AAC half-mediated activation of TLR7 effectively eradicated bacteria infected in macrophages. Mutation analyses of the 5'-tRNAValCAC/AAC half identified the terminal GUUU sequence as a determinant for TLR7 activation. We confirmed that GUUU is the optimal ratio of guanosine and uridine for TLR7 activation; microRNAs or other RNAs with the terminal GUUU motif can indeed stimulate TLR7, establishing the motif as a universal signature for TLR7 activation. These results advance our understanding of endogenous ssRNA ligands of TLR7 and offer insights into diverse TLR7-involved pathologies and their therapeutic strategies.

GPR162 activates STING dependent DNA damage pathway as a novel tumor suppressor and radiation sensitizer

In the treatment of most malignancies, radiotherapy plays a significant role. However, the resistance of cancer cells to ionizing radiation (IR) is the main reason for the failure of radiotherapy, which causes tumor recurrence and metastasis. In this study, we confirmed that GPR162, an orphan receptor in the G-protein-coupled receptor family, acted as a novel radiotherapy sensitizer by interacting with the stimulator of interferon genes (STING), which targeted DNA damage responses, activated IRF3, accelerated the activation of type I interferon system, promoted the expression of chemokines including CXCL10 and CXCL4, and inhibited the occurrence and development of tumors. Interestingly, the activation of STING by overexpression of GPR162 was independent of the classical pathway of cGAS. STING inhibitors could resist the antitumor effect of overexpression of GPR162 in IR-induced mouse models. In addition, most solid tumors showed low expression of GPR162. And the higher expression of GPR162 indicated a better prognosis in patients with lung adenocarcinoma, liver cancer, breast cancer, etc. In summary, these results suggested that GPR162 may serve as a potential sensitizer of radiotherapy by promoting radiotherapy-induced STING-IFN production and increasing the expression of chemokines including CXCL10 and CXCL4 in DNA damage response, providing an alternative strategy for improving cancer radiotherapy.

The enigmatic helicase DHX9 as a candidate prognostic biomarker for resected pancreatic ductal adenocarcinoma

Background

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies, and current therapies have limited efficacy on PDAC. The DEAH-box helicase 9 (DHX9) is widely reported to influence cell biological behavior via regulating DNA replication, genomic stability, transcription, translation, and microRNA biogenesis. However, the prognostic role of DHX9 in PDAC remains unclear. Thus, the objective of this study is to investigate the prognostic value of DHX9 expression in PDAC patients.

Methods

Tumor specimens from PDAC patients with surgical resection were obtained, and DHX9 was stained and analyzed in this study. Univariate and multivariate Cox regression analyses were utilized to identify independent risk factors of overall survival (OS) and recurrence-free survival (RFS). The prognostic nomograms for predicting OS and RFS were established to obtain superior predictive power.

Results

Among the enrolled 110 patients, 61 patients were identified as having high expression of DHX9. The correlation analysis revealed that higher DHX9 expression in PDAC was prone to have advanced N stage (p = 0.010) and TNM stage (p = 0.017). For survival, the median OS (21.0 vs. 42.0 months, p < 0.001) and RFS (12.0 vs. 24.0 months, p < 0.001) of patients in the high DHX9 group were significantly shorter than those in the low DHX9 group. Within the univariate and multivariate analyses, American Joint Committee on Cancer (AJCC) N stage (p = 0.036) and DHX9 expression (p = 0.041) were confirmed as independent prognostic factors of OS, while nerve invasion (p = 0.031) and DHX9 expression (p = 0.005) were independent prognostic factors of RFS. Finally, the novel prognostic nomograms for OS and RFS were established and showed superior predictive accuracy.

Conclusion

This study identified the independent prognostic value of DHX9 for RFS and OS in resected PDAC patients, and higher DHX9 expression was prone to have an earlier recurrence and shorter OS. Therefore, DHX9 may be a promising and valuable biomarker and a potential target for treating PDAC. More accurate and promising predictive models would be achieved when DHX9 is incorporated into nomograms.

How Gut Microbiota Are Shaped by Pattern Recognition Receptors in Colitis and Colorectal Cancer

Simple Summary

The pathogenesis of intestinal inflammatory disorders such as colitis and colorectal cancer is complicated and dysregulation of gut microbiota is considered an important contributing factor. Inflammation is often initiated by the activation of pattern recognition receptors. However, the relationship between these innate immune receptors and gut microbiota is not fully understood. Here, we show that pattern recognition receptors not only recognize pathogens and initiate inflammatory signal transduction to induce immune responses, but also influence the composition of intestinal microorganisms, thus affecting the development of intestinal inflammation and cancer through various mechanisms. This suggests that the modification of innate immune receptors and relevant molecules could be therapeutic targets for the treatment of colitis and colorectal cancer by regulating gut microbiota.

Abstract

Disorders of gut microbiota have been closely linked to the occurrence of various intestinal diseases including colitis and colorectal cancer (CRC). Specifically, the production of beneficial bacteria and intestinal metabolites may slow the development of some intestinal diseases. Recently, it has been proposed that pattern recognition receptors (PRRs) not only recognize pathogens and initiate inflammatory signal transduction to induce immune responses but also influence the composition of intestinal microorganisms. However, the mechanisms through which PRRs regulate gut microbiota in the setting of colitis and CRC have rarely been systematically reviewed. Therefore, in this paper, we summarize recent advances in our understanding of how PRRs shape gut microbiota and how this influences the development of colitis and CRC.

Application and prospect of targeting innate immune sensors in the treatment of autoimmune diseases

Dysregulation of auto-reactive T cells and autoantibody-producing B cells and excessive inflammation are responsible for the occurrence and development of autoimmune diseases. The suppression of autoreactive T cell activation and autoantibody production, as well as inhibition of inflammatory cytokine production have been utilized to ameliorate autoimmune disease symptoms. However, the existing treatment strategies are not sufficient to cure autoimmune diseases since patients can quickly suffer a relapse following the end of treatments. Pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), Nod-like receptors (NLRs), RIG-I like receptors (RLRs), C-type lectin receptors (CLRs) and various nucleic acid sensors, are expressed in both innate and adaptive immune cells and are involved in the development of autoimmune diseases. Here, we have summarized advances of PRRs signaling pathways, association between PRRs and autoimmune diseases, application of inhibitors targeting PRRs and the corresponding signaling molecules relevant to strategies targeting autoimmune diseases. This review emphasizes the roles of different PRRs in activating both innate and adaptive immunity, which can coordinate to trigger autoimmune responses. The review may also prompt the formulation of novel ideas for developing therapeutic strategies against autoimmune diseases by targeting PRRs-related signals.

Molecular cloning and functional analysis of Macaca mulatta STING

Stimulator of interferon gene (STING), an adaptor molecule in the immune system, is involved in mediating the response to viral and bacterial infections, anti-tumor immunity, autoimmune diseases, and lipid metabolism. There have been reports on the cloning and function of STING in humans, pigs, chickens, and cats; however, STING has not been characterized in non-human primates or monkeys to date. Therefore, in this study, the rhesus macaque (Macaca mulata) STING gene was cloned, and we performed preliminary functional tests to examine its role in the interferon (IFN) pathway. The M. mulatta STING complementary DNA was 1140 bp in length and encoded 380 amino acid residues. Phylogenetic analysis showed that Homo sapiens and M. mulatta STING are closely related and clustered on the same branch. M. mulatta STING was confirmed to increase the promoter activities of IFN-β, nuclear factor-κB, and interferon-sensitive response element, and STING overexpression increased the mRNA levels of IFN-α, IFN-β, and interferon regulatory factor 3. Infection of Marc-145 cells with porcine reproductive and respiratory syndrome virus activated STING, and its expression increased along with increases in viral multiplicity of infection titer and time. Moreover, STING expression was time- and dose-dependently up-regulated by poly (I:C) and poly (dA:dT) treatments in Marc-145 cells. In summary, these results highlight STING as a vital immune system signal protein in the IFN pathway. This study provides a basis for understanding the immune characteristics of M. mulatta, and may have important implications for both monkey and human diseases.

DHX9 contributes to the malignant phenotypes of colorectal cancer via activating NF-κB signaling pathway

Colorectal cancer (CRC) is the leading cause of cancer-related mortality worldwide, which makes it urgent to identify novel therapeutic targets for CRC treatment. In this study, DHX9 was filtered out as the prominent proliferation promoters of CRC by siRNA screening. Moreover, DHX9 was overexpressed in CRC cell lines, clinical CRC tissues and colitis-associated colorectal cancer (CAC) mouse model. The upregulation of DHX9 was positively correlated with poor prognosis in patients with CRC. Through gain- and loss-of function experiments, we found that DHX9 promoted CRC cell proliferation, colony formation, apoptosis resistance, migration and invasion in vitro. Furthermore, a xenograft mouse model and a hepatic metastasis mouse model were utilized to confirm that forced overexpression of DHX9 enhanced CRC outgrowth and metastasis in vivo, while DHX9 ablation produced the opposite effect. Mechanistically, from one aspect, DHX9 enhances p65 phosphorylation, promotes p65 nuclear translocation to facilitate NF-κB-mediated transcriptional activity. From another aspect, DHX9 interacts with p65 and RNA polymerase II (RNA Pol II) to enhance the downstream targets of NF-κB (e.g., Survivin, Snail) expression to potentiate the malignant phenotypes of CRC. Together, our results suggest that DHX9 may be a potential therapeutic target for prevention and treatment of CRC patients.

Host-Viral Interactions in the Pathogenesis of Ulcerative Colitis

Ulcerative colitis is characterized by relapsing and remitting colonic mucosal inflammation. During the early stages of viral infection, innate immune defenses are activated, leading to the rapid release of cytokines and the subsequent initiation of downstream responses including inflammation. Previously, intestinal viruses were thought to be either detrimental or neutral to the host. However, persisting viruses may have a role as resident commensals and confer protective immunity during inflammation. On the other hand, the dysregulation of gut mucosal immune responses to viruses can trigger excessive, pathogenic inflammation. The purpose of this review is to discuss virus-induced innate immune responses that are at play in ulcerative colitis.

Monitoring the Activation of Caspases-1/3/4 for Describing the Pyroptosis Pathways of Cancer Cells

Pyroptosis is closely related to inhibiting the occurrence and development of tumors. However, the pyroptosis pathways (PPs) impacted by different stimulants are still unknown. To accurately understand the PP in cancer cells, we designed a multicolor fluorescent nanoprobe (Cas-NP) to monitor the activation of caspases-1/3/4 during pyroptosis. The Cas-NP was prepared by the assembly of three different fluorophores-labeled peptides, specific response to caspases-1/3/4 on Au nanoparticles via the Au-Se bond to in situ monitor caspase-1/3/4 with high selectivity and sensitivity. Moreover, the selenopeptide specific to caspase-4 (Cyanine-5-LEVD-SeH) was synthesized for the first time to overcome the difficulty in commercial synthesis. During the pyroptosis of cancer cells induced by adenosine triphosphate (ATP), only the fluorescence of caspase-1 significantly increases. When the cells are stimulated with lipopolysaccharide (LPS), the fluorescence signals corresponding to caspases-3 and 4 first appear and then the fluorescence of caspase-1 is observed. Furthermore, the inhibitor study indicates that the activated caspase-4 can lead to the activation of caspase-1 after the LPS treatment. We first discovered that caspase-3 is activated during the pyroptosis process stimulated by LPS and further verified the activation sequence of caspases-1/3/4 via visualized fluorescence detection. The study provides an effective tool for understanding complex signaling mechanisms in pyroptosis cells and new ideas to explore useful therapeutic inhibitors based on pyroptosis.

IFIH1 loss-of-function variants contribute to very early-onset inflammatory bowel disease

Genetic defects of innate immunity impairing intestinal bacterial sensing are linked to the development of Inflammatory Bowel Disease (IBD). Although much evidence supports a role of the intestinal virome in gut homeostasis, most studies focus on intestinal viral composition rather than on host intestinal viral sensitivity. To demonstrate the association between the development of Very Early Onset IBD (VEOIBD) and variants in the IFIH1 gene which encodes MDA5, a key cytosolic sensor for viral nucleic acids. Whole exome sequencing (WES) was performed in two independent cohorts of children with VEOIBD enrolled in Italy (n = 18) and USA (n = 24). Luciferase reporter assays were employed to assess MDA5 activity. An enrichment analysis was performed on IFIH1 comparing 42 VEOIBD probands with 1527 unrelated individuals without gastrointestinal or immunological issues. We identified rare, likely loss-of-function (LoF), IFIH1 variants in eight patients with VEOIBD from a combined cohort of 42 children. One subject, carrying a homozygous truncating variant resulting in complete LoF, experienced neonatal-onset, pan-gastrointestinal, IBD-like enteropathy plus multiple infectious episodes. The remaining seven subjects, affected by VEOIBD without immunodeficiency, were carriers of one LoF variant in IFIH1. Among these, two patients also carried a second hypomorphic variant, with partial function apparent when MDA5 was weakly stimulated. Furthermore, IFIH1 variants were significantly enriched in children with VEOIBD as compared to controls (p = 0.007). Complete and partial MDA5 deficiency is associated with VEOIBD with variable penetrance and expressivity, suggesting a role for impaired intestinal viral sensing in IBD pathogenesis.

Mechanisms of Immune Escape and Resistance to Checkpoint Inhibitor Therapies in Mismatch Repair Deficient Metastatic Colorectal Cancers

Simple Summary

A subset of colorectal cancers (CRCs) is characterized by a mismatch repair deficiency that is frequently associated with microsatellite instability (MSI). The compromised DNA repair machinery leads to the accumulation of tumor neoantigens affecting the sensitivity of MSI metastatic CRC to immune checkpoint inhibitors (CPIs), both upfront and in later lines of treatment. However, up to 30% of MSI CRCs exhibit primary resistance to frontline immune based therapy, and an additional subset develops acquired resistance. Here, we first discuss the clinical and molecular features of MSI CRCs and then we review how the loss of antigenicity, immunogenicity, and a hostile tumor microenvironment could influence primary and acquired resistance to CPIs. Finally, we describe strategies to improve the outcome of MSI CRC patients upon CPI treatment.

Abstract

Immune checkpoint inhibitors (CPIs) represent an effective therapeutic strategy for several different types of solid tumors and are remarkably effective in mismatch repair deficient (MMRd) tumors, including colorectal cancer (CRC). The prevalent view is that the elevated and dynamic neoantigen burden associated with the mutator phenotype of MMRd fosters enhanced immune surveillance of these cancers. In addition, recent findings suggest that MMRd tumors have increased cytosolic DNA, which triggers the cGAS STING pathway, leading to interferon-mediated immune response. Unfortunately, approximately 30% of MMRd CRC exhibit primary resistance to CPIs, while a substantial fraction of tumors acquires resistance after an initial benefit. Profiling of clinical samples and preclinical studies suggests that alterations in the Wnt and the JAK-STAT signaling pathways are associated with refractoriness to CPIs. Intriguingly, mutations in the antigen presentation machinery, such as loss of MHC or Beta-2 microglobulin (B2M), are implicated in initial immune evasion but do not impair response to CPIs. In this review, we outline how understanding the mechanistic basis of immune evasion and CPI resistance in MMRd CRC provides the rationale for innovative strategies to increase the subset of patients benefiting from CPIs.

Construction and validation of an RNA-binding protein-associated prognostic model for colorectal cancer

Colorectal cancer (CRC) is one of the most prevalent and fatal malignancies, and novel biomarkers for the diagnosis and prognosis of CRC must be identified. RNA-binding proteins (RBPs) are essential modulators of transcription and translation. They are frequently dysregulated in various cancers and are related to tumorigenesis and development. The mechanisms by which RBPs regulate CRC progression are poorly understood and no clinical prognostic model using RBPs has been reported in CRC. We sought to identify the hub prognosis-related RBPs and to construct a prognostic model for clinical use. mRNA sequencing and clinical data for CRC were obtained from The Cancer Genome Atlas database (TCGA). Gene expression profiles were analyzed to identify differentially expressed RBPs using R and Perl software. Hub RBPs were filtered out using univariate Cox and multivariate Cox regression analysis. We used functional enrichment analysis, including Gene Ontology and Gene Set Enrichment Analysis, to perform the function and mechanisms of the identified RBPs. The nomogram predicted overall survival (OS). Calibration curves were used to evaluate the consistency between the predicted and actual survival rate, the consistency index (c-index) was calculated, and the prognostic effect of the model was evaluated. Finally, we identified 178 differently expressed RBPs, including 121 up-regulated and 57 down-regulated proteins. Our prognostic model was based on nine RBPs (PNLDC1, RRS1, HEXIM1, PPARGC1A, PPARGC1B, BRCA1, CELF4, AEN and NOVA1). Survival analysis showed that patients in the high-risk subgroup had a worse OS than those in the low-risk subgroup. The area under the curve value of the receiver operating characteristic curve of the prognostic model is 0.712 in the TCGA cohort and 0.638 in the GEO cohort. These results show that the model has a moderate diagnostic ability. The c-index of the nomogram is 0.77 in the TCGA cohort and 0.73 in the GEO cohort. We showed that the risk score is an independent prognostic biomarker and that some RBPs may be potential biomarkers for the diagnosis and prognosis of CRC.

A STING-related prognostic score predicts high-risk patients of colorectal cancer and provides insights into immunotherapy

Background

Targeted therapeutic strategies for advanced colorectal cancer (CRC) have been limited. STING is crucial to the antitumor immunotherapy, for it stimulates IFN signaling to mediate the crosstalk between innate and adaptive immune responses. Emerging evidence suggests that STING also contributes to the prognosis of CRC. However, prognostic models relating to STING have not yet been explored.

Methods

A total of 431 CRC samples from the TCGA database were analyzed to explore the prognostic value of STING-related genes. We trained prognostic models using the multivariate Cox regression. A STING-related prognostic score (SPS) was calculated as the gene expression multiplied by the corresponding coefficients of the final model. A backward stepAIC strategy was adopted to select the optimal model. A nomogram was used to personalize medical decisions for CRC.

Results

The expression level of STING was upregulated in the CMS1 subtype (P=0.036). Among STING-related genes, DHX9 (HR =0.72, P=0.01), IRF2 (HR =1.34, P=0.022), and POLR1D (HR =1.23, P=0.038) showed significant prognostic value. The SPS was proven to be an independent risk factor (training: HR =2.9, P=0.00013; validation: HR =3.02, P=0.01), and outperformed random classifiers in identifying high-risk CRC. The high SPS group was characterized by less genomic aberrations, upregulated IL6-JAK-STAT3 and IL2-STAT5 signaling pathways, increased expression of TIM-3, increased infiltration of regulatory T (Treg) cells and T helper 17 (Th17) cells, and decreased infiltration of M0 macrophages. Finally, the nomogram based on the SPS and clinical factors showed good performance in CRC.

Conclusions

SPS is an independent risk factor that could identify high-risk CRC. While ICBs may benefit patients of the CMS1 subtype, for the CMS2, CMS3, and CMS4 subtypes in the high SPS group, STING agonists and immunotherapies targeting the Th17 axis may be beneficial. Finally, the SPS-based nomogram could help advance personalized medical decisions for CRC.

IRF3 prevents colorectal tumorigenesis via inhibiting the nuclear translocation of β-catenin

Occurrence of Colorectal cancer (CRC) is relevant with gut microbiota. However, role of IRF3, a key signaling mediator in innate immune sensing, has been barely investigated in CRC. Here, we unexpectedly found that the IRF3 deficient mice are hyper-susceptible to the development of intestinal tumor in AOM/DSS and Apcmin/+ models. Genetic ablation of IRF3 profoundly promotes the proliferation of intestinal epithelial cells via aberrantly activating Wnt signaling. Mechanically, IRF3 in resting state robustly associates with the active β-catenin in the cytoplasm, thus preventing its nuclear translocation and cell proliferation, which can be relieved upon microbe-induced activation of IRF3. In accordance, the survival of CRC is clinically correlated with the expression level of IRF3. Therefore, our study identifies IRF3 as a negative regulator of the Wnt/β-catenin pathway and a potential prognosis marker for Wnt-related tumorigenesis, and describes an intriguing link between gut microbiota and CRC via the IRF3-β-catenin axis.

Role of cGAS-STING signaling pathway in colon cancer

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) signaling pathway is an important immune response pathway in the cytoplasm, and it is an important mechanism that regulates innate immune and adaptive immune responses. As an important mechanism that detects and responds to pathogens, the cGAS-STING signaling pathway plays a key role in mediating immunity against DNA pathogens and the body's internal immunity against tumors. Clinically, STING activators are often used for tumor treatment. Also, cGAS can act as a tumor prognostic marker. At present, related agonists of cGAS and STING have been used in clinical treatment of colon cancer, but their effects in tumors from other tissues are not clear yet. Thus, their effectiveness and safety are still needed to be further studied.

DNA sensors, crucial receptors to resist pathogens, are deregulated in colorectal cancer and associated with initiation and progression of the disease

Background: DNA sensors are innate immune receptors that detect intracellular endogenous or exogenous DNA. They are critical to trigger immune response against DNA viral and intracellular bacterial infection, and are involved in inflammatory diseases and tumorigenesis. Recent accumulating evidences indicated that DNA sensors are also crucial for controlling the development of colorectal cancer (CRC). However, a systematic study on the expression profile of DNA sensors in CRC and their clinical significance are still lacking.

Methods: We investigated the expression profile of DNA sensors in CRC and their clinical significance by taking advantage of clinical CRC samples, mouse AOM/DSS treatment model, and Oncomine ® bioinformatics platform.

Results: Our study identified that the expression of DNA sensors, including AIM2, DAI, as well as inflammasome molecules ASC/IL-18, TLR9 and adaptor MyD88, and DDX60 decreased in human CRC, whereas the expression of DHX9, DHX36, and DDX41 significantly increased. Among them, the expression of AIM2/ASC/IL-18, MyD88, DAI, DHX36, and DDX60 were associated with cancer stages. In addition, we also performed correlation analysis between DNA sensors and their main signaling molecules to explore the possible mechanisms. The results showed that there were positive correlations between AIM2 and ASC/IL-18, DHX9 and MAVS, and TLR9 and MyD88 expression. In addition, the gene expression patterns of some DNA sensors were confirmed by Western-blot analysis.

Conclusions: Our study revealed that the expression of multiple DNA sensors was deregulated in CRC and might be involved in tumor development. More importantly, the study identified that, among all these DNA sensors, AIM2, DAI, and DDX60 could be potentially critical for diagnosis, prognosis, and therapy of CRC and deserve further investigation.

The role of pyroptosis in cancer: pro-cancer or pro-"host"?

Programmed cell death (PCD) refers to the way in which cells die depending on specific genes encoding signals or activities. Apoptosis, autophagy, and pyroptosis are all mechanisms of PCD. Among these mechanisms, pyroptosis is mediated by the gasdermin family, accompanied by inflammatory and immune responses. The relationship between pyroptosis and cancer is complex, and the effects of pyroptosis on cancer vary in different tissues and genetic backgrounds. On one hand, pyroptosis can inhibit the occurrence and development of tumors; on the other hand, as a type of proinflammatory death, pyroptosis can form a suitable microenvironment for tumor cell growth and thus promote tumor growth. In addition, the induction of tumor pyroptosis is also considered a potential cancer treatment strategy. Studies have shown that DFNA5 (nonsyndromic hearing impairment protein 5)/GSDME (Gasdermin-E) mRNA methylation results in lower expression levels of DFNA5/GSDME in most tumor cells than in normal cells, making it difficult to activate the pyroptosis in most tumor cells. During the treatment of malignant tumors, appropriate chemotherapeutic drugs can be selected according to the expression levels of DFNA5/GSDME, which can be upregulated in tumor cells, thereby increasing the sensitivity to chemotherapeutic drugs and reducing drug resistance. Therefore, induced pyroptosis may play a predominant role in the treatment of cancer. Here, we review the latest research on the anti- and protumor effects of pyroptosis and its potential applications in cancer treatment.

Mitochondria as playmakers of apoptosis, autophagy and senescence

Mitochondria are the key energy-producing organelles and cellular source of reactive species. They are responsible for managing cell life and death by a balanced homeostasis passing through a network of structures, regulated principally via fission and fusion. Herein we discuss about the most advanced findings considering mitochondria as dynamic biophysical systems playing compelling roles in the regulation of energy metabolism in both physiologic and pathologic processes controlling cell death and survival. Precisely, we focus on the mitochondrial commitment to the onset, maintenance and counteraction of apoptosis, autophagy and senescence in the bioenergetic reprogramming of cancer cells. In this context, looking for a pharmacological manipulation of cell death processes as a successful route for future targeted therapies, there is major biotechnological challenge in underlining the location, function and molecular mechanism of mitochondrial proteins. Based on the critical role of mitochondrial functions for cellular health, a better knowledge of the main molecular players in mitochondria disfunction could be decisive for the therapeutical control of degenerative diseases, including cancer.

Significance and Role of Pattern Recognition Receptors in Malignancy

Pattern recognition receptors (PRRs) are members of innate immunity, playing pivotal role in several immunological reactions. They are known to act as a bridge between innate and adaptive immunity. They are expressed on several normal cell types but have been shown with increasing frequency on/in tumor cells. Significance of this phenomenon is largely unknown, but it has been shown by several authors that they, predominantly Toll-like receptors (TLRs), act in the interest of tumor, by promotion of its growth and spreading. Preparation of artificial of TLRs ligands (agonists) paved the way to use them as a therapeutic agents for cancer, so far in a limited scale. Agonists may be combined with conventional anti-cancer modalities with apparently promising results. PRRs recognizing nucleic acids such as RIG-1 like receptors (sensing RNA) and STING (sensing DNA) constitute a novel promising approach for cancer immunotherapy.

The Role of Nucleic Acid Sensing in Controlling Microbial and Autoimmune Disorders

Innate immunity, the first line of defense against invading pathogens, is an ancient form of host defense found in all animals, from sponges to humans. During infection, innate immune receptors recognize conserved molecular patterns, such as microbial surface molecules, metabolites produces during infection, or nucleic acids of the microbe's genome. When initiated, the innate immune response activates a host defense program that leads to the synthesis proteins capable of pathogen killing. In mammals, the induction of cytokines during the innate immune response leads to the recruitment of professional immune cells to the site of infection, leading to an adaptive immune response. While a fully functional innate immune response is crucial for a proper host response and curbing microbial infection, if the innate immune response is dysfunctional and is activated in the absence of infection, autoinflammation and autoimmune disorders can develop. Therefore, it follows that the innate immune response must be tightly controlled to avoid an autoimmune response from host-derived molecules, yet still unencumbered to respond to infection. In this review, we will focus on the innate immune response activated from cytosolic nucleic acids, derived from the microbe or host itself. We will depict how viruses and bacteria activate these nucleic acid sensing pathways and their mechanisms to inhibit the pathways. We will also describe the autoinflammatory and autoimmune disorders that develop when these pathways are hyperactive. Finally, we will discuss gaps in knowledge with regard to innate immune response failure and identify where further research is needed.

DEAD-box helicases: the Yin and Yang roles in viral infections

Viruses hijack the host cell machinery and recruit host proteins to aid their replication. Several host proteins also play vital roles in inhibiting viral replication. Emerging class of host proteins central to both of these processes are the DEAD-box helicases: a highly conserved family of ATP-dependent RNA helicases, bearing a common D-E-A-D (Asp-Glu-Ala-Asp) motif. They play key roles in numerous cellular processes, including transcription, splicing, miRNA biogenesis and translation. Though their sequences are highly conserved, these helicases have quite diverse roles in the cell. Interestingly, often these helicases display contradictory actions in terms of the support and/or clearance of invading viruses. Increasing evidence highlights the importance of these enzymes, however, little is known about the structural basis of viral RNA recognition by the members of the DEAD-box family. This review summarizes the current knowledge in the field for selected DEAD-box helicases and highlights their diverse actions upon viral invasion of the host cell. We anticipate that through a better understanding of how these helicases are being utilized by viral RNAs and proteins to aid viral replication, it will be possible to address the urgent need to develop novel therapeutic approaches to combat viral infections.

The anticancer functions of RIG-I-like receptors, RIG-I and MDA5, and their applications in cancer therapy

Cancer is a major cause of death worldwide, and its incidence and mortality continuously increase in China. Nowadays, cancer heavily influences our health and constitutes enormous burden on society and families. Although there are many tools for cancer treatment, but the overall therapeutic effect is poor. In addition, cancer cells often develop resistance to therapy due to defective cell death or immune escape mechanisms. Therefore, it is a promising way for cancer treatment to effectively activate apoptosis and conquer immunosuppression. RIG-I-like receptors (RLRs) belong to RNA-sensing pattern recognition receptors (PRRs), one of the major subsets of PRRs, and play a critical role in sensing RNA viruses and initiate host antiviral responses such as the production of type I interferons (IFNs), proinflammatory cytokines, and other immune response molecules. Recent studies have demonstrated that tumor cells could mimic viral infection to activate viral recognition of immune system and the activation of interferon response pathway. RIG-I and MDA5, two members of RLRs family, could induce growth inhibition or apoptosis of multiple types of cancer cells on the activation by RNA ligands in IFN-dependent or IFN-independent approach. Previous studies have reviewed PRRs as promising immunotherapy targets for colorectal cancer and pancreatic cancer. However, until now, a comprehensive review on the role of RLRs in the development and treatment of various cancers is still lacking. In this article, we reviewed the latest studies on the roles as well as the mechanisms of RIG-I and MDA5 in the development of various cancers and therapeutic potentials of targeting RIG-I and MDA5 for cancer treatment.

Identification and function analysis of canine stimulator of interferon gene (STING)

Stimulator of interferon gene (STING) plays an important role in the cyclic GMP-AMP synthase (cGAS)-mediated activation of type I IFN responses. In this study, we identified and cloned canine STING gene. Full-length STING encodes a 375 amino acid product that shares the highest similarity with feline STING. Highest levels of mRNA of canine STING were detected in the spleen and lungs while the lowest levels in the heart and muscle. Analysis of its cellular localization showed that STING is localizes to the endoplasmic reticulum. STING overexpression induced the IFN response via the IRF3 and NF-κB pathways and up-regulated the expression of ISG15 and viperin. However, knockdown of STING did not inhibit the IFN-β response triggered by poly(dA:dT), poly(I:C), or SeV. Finally, overexpression of STING significantly inhibited the replication of canine influenza virus H3N2. Collectively, our findings indicate that STING is involved in the regulation of the IFN-β pathway in canine.

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Here we first identified and cloned canine STING gene.

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STING overexpression induced the IFN response via the IRF3 and NF-kB pathways.

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Overexpression of STING inhibited the replication of H3N2 CIV.