Phosphorylation Of IRF3 Research Articles

93 (PB083) - Preclinical Profile of RP14042, a novel, selective, and potent small molecule inhibitor of PARP7

Background: Poly (ADP-ribose) polymerase (PARP)-7 is a member of PARP family and is classified as monoPARP as it catalyzes the transfer of single units of ADP-ribose (MARylation) onto its substrates to exert its physiological functions. It is involved in several cellular processes, including responses to hypoxia, innate immunity, and regulation of nuclear receptors. In addition, PARP7 is overexpressed/amplified in variety of cancers including Ovarian, Breast, Pancreatic ductal adenocarcinoma (PDAC), Non-small cell lung carcinoma (NSCLC) and Squamous cancers. PARP-7 acts as a negative regulator of nucleic acid sensing in tumor cells leading to suppression of Type I interferon (IFN) response. Preclinical studies have demonstrated that inhibition of PARP-7 restores Type I interferon (IFN) signaling leading to tumor cell growth inhibition and activation of the immune system, thereby contributing to tumor regression. Herein, we describe the preclinical profile of RP14042, a novel, selective, and potent small molecule inhibitor of PARP7. Material & Methods: Enzymatic potency was evaluated using a PARP Chemiluminescent Activity Assay Kit (BPS biosciences). Cell growth was determined following incubation with RP14042 as a single agent in various solid tumor cell lines. Cell cycle was evaluated following incubation of cells with compound for 72 h, subsequent staining with Propidium Iodide, and analysis by flow cytometry. Expression of p-STAT1 and p-IRF3 were determined in NCI-H1373 cell line by Western blotting. Pharmacokinetic properties of the molecule were also evaluated. Results: RP14042 inhibited PARP7 with an IC50 of 10.2 nM with selectivity over other members of the PARP family. Compound caused a dose-dependent growth inhibition of NCI-H1373, a PARP-7 overexpressing, cell line with an GI50 of 0.5 μM without any effect on the growth in low PARP-7 expressing cell lines. Incubation of NCI-H1373 cells with RP14042 caused G0/G1 cell cycle arrest. Inhibition of PARP7 by RP14042 in NCI-H1373 induced STAT1 and IRF3 phosphorylation suggesting restoration of Type I IFN signaling. Pharmacokinetic studies in rodents indicated high oral bioavailability with favorable plasma concentrations relevant for efficacy. Conclusion: Data demonstrate the therapeutic potential of RP14042 in PARP7 overexpressing tumors No conflict of interest.

Berberine inhibits low shear stress-induced vascular endothelial inflammation via decreasing phosphorylation of Akt and IRF3

BackgroundLow shear stress (LSS) is closely related to vascular endothelial inflammation and the development of atherosclerosis. Berberine (BBR), a natural compound isolated from Coptis chinensis, has been reported to exert anti-inflammatory and antiatherosclerotic effects. However, the role of berberine in low shear stress-induced endothelial inflammation remains unclear. MethodsThe role of berberine in low shear stress-induced vascular endothelial inflammation was investigated in human umbilical vein endothelial cells (HUVECs) using a plate flow chamber in vitro and in mice with an established LSS model by partial ligation of the carotid artery in vivo. ResultsFirst, in vitro experiments demonstrated that BBR significantly decreased the expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) and the phosphorylation of Akt in HUVECs induced by low shear stress. Moreover, BBR significantly inhibited the low shear stress-mediated phosphorylation of IRF3 and its translocation to the nucleus. Notably, Akt overexpression markedly reversed the inhibitory effects of BBR on LSS-induced IRF3 activation and ICAM-1 expression. Moreover, in vivo experiments showed that BBR markedly decreased intimal ICAM-1 and IRF3 in the LSS areas of partially ligated carotid arteries in mice; however, EC-specific Akt overexpression mediated by adeno-associated viruses abolished the anti-inflammatory effect of BBR. ConclusionTaken together, our findings suggest that BBR treatment attenuates LSS-induced vascular endothelial inflammation by decreasing the activation of the Akt/IRF3 signalling pathway.

Middle East respiratory syndrome coronavirus ORF4b protein inhibits TLR7- and TLR9-dependent alpha interferon induction.

The Toll-like receptor (TLR)7- and TLR9-dependent signalling cascade is responsible for production of a large amount of alpha interferon by plasmacytoid dendritic cells upon viral infection. Here, we show that Middle East respiratory syndrome coronavirus (MERS-CoV) accessory protein ORF4b has the most potential among the MERS-CoV accessory proteins to inhibit the TLR7/9-signaling-dependent alpha interferon production. ORF4b protein, which has a bipartite nuclear localization signal, was found to bind to IKKα, a kinase responsible for phosphorylation of interferon regulatory factor (IRF)7. This interaction caused relocation of a large proportion of IKKα from the cytoplasm to the nucleus. Studies using ORF4b and IKKα mutants demonstrated that ORF4b protein inhibited IKKα-mediated IRF7 phosphorylation by sequestering IKKα in the nucleus and by impeding the phosphorylation process of cytoplasmic IKKα.

Transcription-independent regulation of STING activation and innate immune responses by IRF8 in monocytes

Sensing of cytosolic DNA of microbial or cellular/mitochondrial origin by cGAS initiates innate immune responses via the adaptor protein STING. It remains unresolved how the activity of STING is balanced between a productive innate immune response and induction of autoimmunity. Here we show that interferon regulatory factor 8 (IRF8) is essential for efficient activation of STING-mediated innate immune responses in monocytes. This function of IRF8 is independent of its transcriptional role in monocyte differentiation. In uninfected cells, IRF8 remains inactive via sequestration of its IRF-associated domain by its N- and C-terminal tails, which reduces its association with STING. Upon triggering the DNA sensing pathway, IRF8 is phosphorylated at Serine 151 to allow its association with STING via the IRF-associated domain. This is essential for STING polymerization and TBK1-mediated STING and IRF3 phosphorylation. Consistently, IRF8-deficiency impairs host defense against the DNA virus HSV-1, and blocks DNA damage-induced cellular senescence. Bone marrow-derived mononuclear cells which have an autoimmune phenotype due to deficiency of Trex1, respond to IRF-8 deletion with reduced pro-inflammatory cytokine production. Peripheral blood mononuclear cells from systemic lupus erythematosus patients are characterized by elevated phosphorylation of IRF8 at the same Serine residue we find to be important in STING activation, and in these cells STING is hyper-active. Taken together, the transcription-independent function of IRF8 we describe here appears to mediate STING activation and represents an important regulatory step in the cGAS/STING innate immune pathway in monocytes.

DDX56 inhibits PRV replication through regulation of IFN-β signaling pathway by targeting cGAS.

Pseudorabies virus (PRV) is an agent of Aujeszky's disease, and causes great economic losses to pig farming. Re-outburst of pseudorabies implies that new control measures are urgently needed. We show here that DDX56 possesses the ability to inhibit PRV replication in vitro, which may be an important factor for PRV infection. Overexpression of DDX56 inhibited PRV genomic DNA transcription and lower titers of PRV infection in PK15 cells, whereas down-regulation of the DDX56 expression had a promotion role on virus replication. Further study demonstrated that DDX56 exerted its proliferation-inhibitory effects of PRV through up-regulating cGAS-STING-induced IFN-β expression. Moreover, we found that DDX56 could promote cGAS expression and direct interaction also existed between DDX56 and cGAS. Based on this, DDX56-regulated IFN-β pathway may be targeted at cGAS. To verify this, down-regulated cGAS expression in DDX56 over-expression cells was performed. Results indicated that knockdown of cGAS expression could abrogate the inhibition role of DDX56 on PRV proliferation and weaken the effect of DDX56 on IFN-β expression. In addition, DDX56 played a promotion role in IRF3 phosphorylation and nucleus translocation. Altogether, our results highlight DDX56's antiviral role in PRV infection, and our findings contribute to a better understanding of host factors controlling PRV replication.

Grass Carp Mex3A Promotes Ubiquitination and Degradation of RIG-I to Inhibit Innate Immune Response.

As one of the Mex3 family members, Mex3A is crucial in cell proliferation, migration, and apoptosis in mammals. In this study, a novel gene homologous to mammalian Mex3A (named CiMex3A, MW368974) was cloned and identified in grass carp, which is 1,521 bp in length encoding a putative polypeptide of 506 amino acids. In CIK cells, CiMex3A is upregulated after stimulation with LPS, Z-DNA, and especially with intracellular poly(I:C). CiMex3A overexpression reduces the expressions of IFN1, ISG15, and pro-inflammatory factors IL8 and TNFα; likewise, Mex3A inhibits IRF3 phosphorylation upon treatment with poly(I:C). A screening test to identify potential targets suggested that CiMex3A interacts with RIG-I exclusively. Co-localization analysis showed that Mex3A and RIG-I are simultaneously located in the endoplasmic reticulum, while they rarely appear in the endosome, mitochondria, or lysosome after exposure to poly(I:C). However, RIG-I is mainly located in the early endosome and then transferred to the late endosome following stimulation with poly(I:C). Moreover, we investigated the molecular mechanism underlying CiMex3A-mediated suppression of RIG-I ubiquitination. The results demonstrated that Mex3A truncation mutant (deletion in the RING domain) can still interact physically with RIG-I, but fail to degrade it, suggesting that Mex3A also acts as a RING-type E3 ubiquitin ligase. Taken together, this study showed that grass carp Mex3A can interact with RIG-I in the endoplasmic reticulum following poly(I:C) stimulation, and then Mex3A facilitates the ubiquitination and degradation of RIG-I to inhibit IRF3-mediated innate antiviral immune response.

TRIM25 inhibits spring viraemia of carp virus replication by positively regulating RIG-I signaling pathway in common carp (Cyprinus carpio L.)

Common carp (Cyprinus carpio L.) is one of the most widely cultivated fish in China. Spring viraemia of carp virus (SVCV) is a highly pathogenic virus and has often caused excessive losses in carp pond fisheries. Innate immune play important roles against virus infection. To better understand the immune response of common carp against SVCV infection, transcriptome analysis was performed using the Illumina Novaseq 6000 platform. It was showed that a total of 3953 differentially expressed unigenes were identified, and the RLR signaling pathway were significantly enriched after SVCV infection. Subsequently, the role of RLR signaling pathway in SVCV infection was studied. The results showed that common carp RIG-I (CcRIG-I) and TRIM25 (CcTRIM25) significantly decreased the replication of SVCV by inducing the phosphorylation of TBK1, IRF3 and p65 and the expression of ifn-1, viperin, isg15 and mx. Further studies illustrated that CcTRIM25 could positive regulate CcRIG-I mediated downstream signaling pathway. Finally, the mechanism of CcTRIM25 promoting CcRIG-I-mediated signaling was investigated. CcTRIM25 could interact with the caspase activation and recruitment domain (CARD) of CcRIG-I and promoted K63-linked polyubiquitination of CcRIG-I. Altogether, the study revealed a mechanism of CcTRIM25 regulating CcRIG-I mediated immune response in SVCV infection.

African swine fever virus MGF505-3R inhibits cGAS-STING-mediated IFN-β pathway activation by degrading TBK1

African swine fever virus (ASFV) is an important pathogen causing acute infectious disease in domestic pigs and wild boars that seriously endangers the global swine industry. As ASFV is structurally complex and encodes a large number of functional proteins, no effective vaccine has been developed to date. Thus, dissecting the mechanisms of immune escape induced by ASFV proteins is crucial. A previous study showed that the ASFV-encoded protein is an important factor in host immunity. In this study, we identified a negative regulator, MGF505-3R, that significantly downregulated cGAS/STING- and poly (dG:dC)-mediated IFN-β and interferon stimulation response element (ISRE) reporter activity and suppressed IFNB1 and IFIT2 mRNA levels. In addition, TBK1, IRF3 and IκBα phosphorylation levels were also inhibited. Mechanistically, MGF505-3R interacted with cGAS/TBK1/IRF3 and targeted TBK1 for degradation, thereby disrupting the cGAS-STING-mediated IFN-β signaling pathway, which appears to be highly correlated with autophagy. Knockdown MGF505-3R expression enhanced IFN-β and IL-1β production. Taken together, our study revealed a negative regulatory mechanism involving the MGF505-3R-cGAS-STING axis and provided insights into an evasion strategy employed by ASFV that involves autophagy and innate signaling pathways.

ATRT-01. Reconstitution of cGAS/ STING pathway via epigenetic reprogramming leads to anti-viral inflammatory signaling in Atypical teratoid rhabdoid tumors (ATRTs)

BACKGROUND: Atypical teratoid rhabdoid tumors (ATRTs) are highly aggressive brain tumors that affect young children characterized by biallelic inactivation of the SMARCB1 gene. Though patients benefit from multimodal therapy, there is no improvement in overall survival which necessitates the exploration of alternative approaches. Innate-based immune and epigenetic therapies have shown benefits in several cancers. The role of innate immune signaling has not been investigated in ATRTs. Our previous data from several ATRT cell lines showed loss of expression of key innate signaling components, like cGAS and STING that are needed for sensing extracellular dsDNA. Additionally, ATRT cell lines do not respond to STING agonists, like cGAMP or ISD. RESULTS: Co-treatment of ATRT cell lines, BT-12 and BT-16 with two epigenetic modulators, panobinostat and decitabine, leads to re-expression of cGAS and STING in a time-dependent manner. Furthermore, treatment with decitabine alone leads to demethylation of several CpG sites on the STING promoter and increased expression of STING mRNA. Panobinostat and decitabine co-treatment reconstitute STING-mediated innate signaling, as measured by IRF-3 and STAT1 phosphorylation and production of ISG-15 and IFIT-1 after treatment with cGAMP, a STING agonist. Co-treatment with panobinostat and decitabine also induced expression of antiviral pro-inflammatory chemokines/cytokines in ATRT cell lines, including type III IFN, IL-6, IL-8, IL-28, and IL-29. CONCLUSION: Our data suggest that ATRT cell lines are unresponsive to innate agonists possibly due to the loss of expression of key innate immune components. However, the cGAS/STING pathway is reactivated by epigenetic drugs, specifically the combination of panobinostat and decitabine. This is further potentiated by treating with STING agonists like cGAMP. Combination treatment of ATRT cell lines with panobinostat and decitabine also induced antiviral inflammatory signaling. This response could be a potential treatment modality to inhibit tumor growth and/or mediate cancer immunotherapy in these aggressive tumors.

TRIM56 overexpression restricts porcine epidemic diarrhoea virus replication in Marc-145 cells by enhancing TLR3-TRAF3-mediated IFN-β antiviral response.

Infection with the porcine epidemic diarrhoea virus (PEDV) causes severe enteric disease in suckling piglets, causing massive economic losses in the swine industry worldwide. Tripartite motif-containing 56 (TRIM56) has been shown to augment type I IFN response, but whether it affects PEDV replication remains uncharacterized. Here we investigated the role of TRIM56 in Marc-145 cells during PEDV infection. We found that TRIM56 expression was upregulated in cells infected with PEDV. Overexpression of TRIM56 effectively reduced PEDV replication, while knockdown of TRIM56 resulted in increased viral replication. TRIM56 overexpression significantly increased the phosphorylation of IRF3 and NF-κB P65, and enhanced the IFN-β antiviral response, while silencing TRIM56 did not affect IRF3 activation. TRIM56 overexpression increased the protein level of TRAF3, the component of the TLR3 pathway, thereby significantly activating downstream IRF3 and NF-κB signalling. We demonstrated that TRIM56 overexpression inhibited PEDV replication and upregulated expression of IFN-β, IFN-stimulated genes (ISGs) and chemokines in a dose-dependent manner. Moreover, truncations of the RING domain, N-terminal domain or C-terminal portion on TRIM56 were unable to induce IFN-β expression and failed to restrict PEDV replication. Together, our results suggested that TRIM56 was upregulated in Marc-145 cells in response to PEDV infection. Overexpression of TRIM56 inhibited PEDV replication by positively regulating the TLR3-mediated antiviral signalling pathway. These findings provide evidence that TRIM56 plays a positive role in the innate immune response during PEDV infection.

STING is an intrinsic checkpoint inhibitor that restrains the TH17 cell pathogenic program.

SUMMARYExternal and intrinsic factors regulate the transcriptional profile of T helper 17 (TH17) cells, thereby affecting their pathogenic potential and revealing their context-dependent plasticity. The stimulator of interferon genes (STING), a component of the intracellular DNA-sensing pathway, triggers immune responses but remains largely unexplored in T cells. Here, we describe an intrinsic role of STING in limiting the TH17 cell pathogenic program. We demonstrate that non-pathogenic TH17 cells express higher levels of STING than those activated under pathogenic conditions. Activation of STING induces interleukin-10 (IL-10) production in TH17 cells, decreasing IL-17A and IL-23R expression in a type I interferon (IFN)-independent manner. Mechanistically, STING-induced IL-10 production partially requires aryl hydrocarbon receptor (AhR) signaling, while the decrease of IL-17A expression occurs due to a reduction of Rorγt transcriptional activity. Our findings reveal a regulatory function of STING in the TH17 cell activation program, proposing it as a valuable target to limit TH17-cell-mediated inflammation.

The impact of lipid nanoparticles (LNP) on anti-viral pathways and immune function in aged individuals

Abstract Aging leads to increased morbidity and mortality posing a big challenge to societies as the world population shifts to an increased proportion of aged individuals. Immunosenescence, a condition of chronic increased level of basal inflammation and immune system dysregulation, is suspected to decrease vaccine efficacy and enhance COVID-19 complications in older individuals. Current vaccination efforts like mRNA vaccines utilize lipid nanoparticle (LNP) platforms that elicit the immune response however, little is known about how LNP adjuvantation affects anti-viral pathways and immune function in aged individuals. We have previously shown that type I IFN production including the phosphorylation of IRF7 and TBK-1 in the TLR 7/8, RIG-I or cGAS-STING pathways and phagocytosis is dysregulated in innate immune cells (i.e., cDC1s, cDC2s, and CD14dimCD16+ monocytes) from healthy older adults (n=11). Our preliminary data utilizing LNP show that in response to LNP stimulus at 4 and 24 hours, older adults have decreased IFNy output. Thus, we further hypothesize that cDC1, cDC2, and CD14dim CD16+ monocytes from healthy, older adults (n=11) will have dysregulated anti-viral signaling and antigen presentation in response to LNP stimulation as measured by the defect in type I IFN production, phosphorylation of IRF7, TBK-1, and immune function like phagocytosis and antigen presentation via flow cytometry. These data support our previous reports of a delayed/decreased proinflammatory output following stimulation and demonstrate potential targets of antiviral pathways that can resolve dysfunctions of the aging immune system for an effective vaccination response. Supported by NIH (U19 AI128910-04S1)

Suppression of local IFN-I by commensal microbiota-derived butyrate impairs antitumor effects of ionizing radiation

Abstract The antitumor effects of ionizing radiation (IR) are mediated in part through activation of innate and adaptive immunity. Here, we report that gut microbiota influences tumor control following IR. Vancomycin decreased the abundance of butyrate-producing gut bacteria, accompanied with reduction of butyric acid in circulation and tumor tissues, and enhanced antitumor responses to IR. Oral administration of Lachnospiraceae, a family of vancomycin-sensitive bacteria, associated with increased systemic and intratumoral butyric acid levels and impaired the efficacy of IR in germ-free (GF) mice. Local butyrate inhibited STING-activated type I IFN expression in dendritic cells (DCs) through blockade of TBK 1 and IRF3 phosphorylation, which abrogated IR-induced tumor-specific cytotoxic T cell immune responses without directly protecting tumor cells from radiation. Our findings demonstrate that the selective targeting of butyrate-producing microbiota may provide a novel therapeutic option to enhance tumor radiation sensitivity. This work was supported by a grant from the Ludwig Foundation to R.R. Weichselbaum, and National Institutes of Health/National Cancer Institute Provocative Questions grants R21 CA227528 and R21 CA231273-01 (R.R. Weichselbaum).

Leptospira spp. are a potent activator of Type I IFN responses via the cGAS-STING pathway

Abstract Leptospirosis is a widespread zoonotic disease which can be potentially fatal in infected humans and dogs. The spirochetal bacteria Leptospira interrogans is the major causative agent of leptospirosis. Rodents serve as reservoir hosts for L. interrogans and once colonized they continue to shed bacteria in their urine. The host immune response to Leptospira spp. remains poorly defined. Leptospiral lipopolysaccharide and lipoproteins can activate TLR4 and TLR2. In addition, leptospires have been shown to activate the NLRP3 inflammasome in macrophages. We observed that when compared to other Gram-negative bacteria, L. interrogans induced a poor inflammasome response with little or no notable pyroptosis. In contrast, L. interrogans induced a robust type I IFN responses in both mouse macrophages and human monocytes. The L. interrogans-induced type I IFN response was dependent on both cGAS and STING and resulted in rapid phosphorylation of TBK1 and IRF3. Furthermore, supernatants from infected macrophages were capable of inducing IFNβ expression in uninfected macrophages, suggesting paracrine signaling from infected cells. These studies demonstrate that L. interrogans can drive a cGAS-STING dependent type I IFN response that may contribute to the host defense against this pathogen.

SARS-CoV-2 spike protein-induced cell fusion activates the cGAS-STING pathway and the interferon response.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the unprecedented coronavirus disease 2019 (COVID-19) pandemic. Critical cases of COVID-19 are characterized by the production of excessive amounts of cytokines and extensive lung damage, which is partially caused by the fusion of SARS-CoV-2-infected pneumocytes. Here, we found that cell fusion caused by the SARS-CoV-2 spike (S) protein induced a type I interferon (IFN) response. This function of the S protein required its cleavage by proteases at the S1/S2 and the S2' sites. We further showed that cell fusion damaged nuclei and resulted in the formation of micronuclei that were sensed by the cytosolic DNA sensor cGAS and led to the activation of its downstream effector STING. Phosphorylation of the transcriptional regulator IRF3 and the expression of IFNB, which encodes a type I IFN, were abrogated in cGAS-deficient fused cells. Moreover, infection with VSV-SARS-CoV-2 also induced cell fusion, DNA damage, and cGAS-STING-dependent expression of IFNB. Together, these results uncover a pathway underlying the IFN response to SARS-CoV-2 infection. Our data suggest a mechanism by which fused pneumocytes in the lungs of patients with COVID-19 may enhance the production of IFNs and other cytokines, thus exacerbating disease severity.

Effect of Berberine on the Inflammatory Response of ANA-1 Cells Induced by Angiotensin Ⅱ Based on TLR4 Signaling Pathway

Effect of Berberine on the Inflammatory Response of ANA-1 Cells Induced by Angiotensin Ⅱ Based on TLR4 Signaling Pathway

The Role of Long Noncoding RNA BST2-2 in the Innate Immune Response to Viral Infection.

Long noncoding RNAs (lncRNAs) widely exist in the cells and play important roles in various biological processes. The role of lncRNAs in immunity remains largely unknown. lncRNA BST2-2 (lncBST2-2) was upregulated upon viral infection and dependent on the interferon (IFN)/JAK/STAT signaling pathway. There was no coding potential found in the lncBST2-2 transcript. Overexpression of lncBST2-2 inhibited the replication of hepatitis C virus (HCV), Newcastle disease virus (NDV), vesicular stomatitis virus (VSV), and herpes simplex virus (HSV), while knockdown of lncBST2-2 facilitated viral replication. Further studies showed that lncBST2-2 promoted the phosphorylation, dimerization, and nuclear transport of IRF3, promoting the production of IFNs. Importantly, lncBST2-2 interacted with the DNA-binding domain of IRF3, which augmented TBK1 and IRF3 interaction, thereby inducing robust production of IFNs. Moreover, lncBST2-2 impaired the interaction between IRF3 and PP2A-RACK1 complex, an essential step for the dephosphorylation of IRF3. These data shown that lncBST2-2 promotes the innate immune response to viral infection through targeting IRF3. Our study reveals the lncRNA involved in the activation of IRF3 and provides a new insight into the role of lncRNA in antiviral innate immunity. IMPORTANCE Innate immunity is an important part of the human immune system to resist the invasion of foreign pathogens. IRF3 plays a critical role in the innate immune response to viral infection. In this study, we demonstrated that lncBST2-2 plays an important role in innate immunity. Virus-induced lncBST2-2 positively regulates innate immunity by interacting with IRF3 and blocking the dephosphorylation effect of RACK1-PP2A complex on IRF3, thus inhibiting viral infection. Our study provides a new insight into the role of lncBST2-2 in the regulation of IRF3 signaling activation.

HPV E5 Mediates Resistance to PD-1 Checkpoint Blockade Via Inhibition of MHC and IFN Pathway

<h3>Purpose/Objective(s)</h3> Objective response rates to PD-1 blockade in human papillomavirus (HPV) mediated Head and Neck Squamous cell carcinoma (HNSCC) are low and resistance mechanisms are unclear. HPV oncogenes are known to modulate immune responses; however, the role that they play in limiting responses to PD-1 blockade is poorly understood. Here we investigated HPV oncogenes and uncovered a novel mechanism by which HPV E5 suppresses immune responses and diminishes the activity of PD-1 blockade in HNSCC. <h3>Materials/Methods</h3> Human cell lines were engineered to express HPV E5 and RNAseq was performed to elucidate E5 mediated alterations in transcriptome. MHC class I pull downs and tandem MS/MS was performed to characterize the immunopeptidome and investigate the effect of HPV E5 on the repertoire of presented tumor antigens. Syngeneic murine models were used to dissect molecular mechanisms by which E5 modulates antigen presentation and IFN signaling pathways. Finally, a curated database of tumor RNAseq from 35 HPV-positive HNSCC patients was analyzed to determine the impact of E5 on HLA expression and patient outcomes. <h3>Results</h3> RNAseq revealed dramatic downregulation of antigen processing and type I interferon pathways in E5-expressing human cell lines. Immunopeptidome analysis revealed that E5-expressing cells have a significantly restricted antigen repertoire, indicating that E5 may help HPV mediated tumors escape from host immune surveillance. Remarkably, syngeneic murine tumors expressing HPV E5 were rendered entirely resistant to PD-1 blockade compared to responding parental lines without E5 expression. Mechanistically HPV E5 was demonstrated to suppress phosphorylation of IRF3 and type I interferon production, while directly binding MHC and preventing translocation to the cell surface. Ultimately, we observed a striking improvement in disease free survival (DFS) and overall survival (OS) in patients with low E5 and high HLA expression [Median DFS 50mo in E5 high/HLA-A low versus not reached in E5 low/HLA-A high; p=0.039]. <h3>Conclusion</h3> Our findings establish HPV E5 as a mediator of resistance to PD-1 checkpoint blockade via inhibition of HLA expression and IFN response pathways. These results have broad clinical relevance beyond HNSCC to other HPV-associated malignancies and reveal a powerful mechanism of HPV E5-mediated immunosuppression which can be exploited to improve response rates to PD-1 checkpoint blockade.

The RNA helicase DDX3 promotes IFNB transcription via enhancing IRF-3/p300 holocomplex binding to the IFNB promoter

The human DEAD-box protein 3 (DDX3) has been reported as a positive regulator and functions in the induction of type I interferon signaling. We elucidated the function of DDX3 in the positive regulation of IFNB production in non-pDC cells. We found that DDX3 regulates virus-induced activation of IFNB at the level of IRF-3. However, it does not affect conventional innate signaling, including IRF-3 phosphorylation, dimerization, or nuclear translocation of IRF-3, but has some downstream events after IRF-3 phosphorylation. Co-immunoprecipitation analyses revealed that DDX3 interacts with IRF-3 through its DNA-binding domain and promotes IRF-3-mediated IFNB promoter activation. DDX3 does not affect the formation of the IRF-3/p300/CBP complex. Instead, ChIP and EMSA assay revealed that DDX3 promotes the recruitment of IRF-3 and transcriptional co-activator p300/CBP to the IFNB promoter. The ATP binding pocket of DDX3 is involved in this association and is essential for the transcriptional activation. Taken together, our study demonstrates that DDX3 plays an important role in guiding a transcription factor complex formed by antiviral signaling to the target gene promoter.

STING agonist enhances the efficacy of programmed death-ligand 1 monoclonal antibody in breast cancer immunotherapy by activating the interferon-β signalling pathway

ABSTRACT This study aimed to explore the role of a stimulator of interferon (IFN) gene (STING) agonist in breast cancer (BCa) immunotherapy. Clinical samples were collected from 37 patients with BCa. A tumor-bearing mouse model was established by injecting 4T1 cells into the mammary fat pad of mice. STING agonist and atezolizumab were injected in the mice twice a week for 2 weeks. Peripheral blood, tumor mass, lung, liver, brain cortex and kidney samples of the tumor-bearing mice were collected. Anti-IFN alpha receptor subunit 1 (IFNAR1) was used to treat 4T1 cells. Tumor tissues of patients with BCa exhibited lower STING and high programmed cell death protein 1 and programmed death-ligand 1 protein expressions. The STING agonist inhibited 4T1 cell growth in mice (P < 0.001) and increased the IFN-β level and phosphorylation of STING, TBK1, IRF3 and STAT1 in tumor mass of tumor-bearing mice (P < 0.001). It synergized with atezolizumab to inhibit 4T1 cell growth in mice and increased tumor necrosis factor-α, IFN-β, interleukin-10 and IFN-γ levels in the peripheral blood and tumor mass (P < 0.01). It synergized with atezolizumab to increase CD8+ cytotoxic T cells and decrease FOXP3+ Treg cells in the tumor-bearing mouse model. The STING agonist was nontoxic to the lung, liver, brain cortex and kidney. Anti-IFNAR1 reversed the STING agonist promotion on TBK1, IRF3 and STAT1 phosphorylation in 4T1 cells (P < 0.01). STING agonists enhance the efficacy of atezolizumab in BCa immunotherapy by activating the IFN-β signaling pathway.