IRF1 supports DNA binding of STAT1 by promoting its phosphorylation

Atherosis-associated lnc_000048 activates PKR to enhance STAT1-mediated polarization of THP-1 macrophages to M1 phenotype

JOURNAL/nrgr/04.03/01300535-202419110-00029/figure1/v/2024-03-08T184507Z/r/image-tiff Our previous study has demonstrated that lnc_000048 is upregulated in large-artery atherosclerotic stroke and promotes atherosclerosis in ApoE-/- mice. However, little is known about the role of lnc_000048 in classically activated macrophage (M1) polarization. In this study, we established THP-1-derived testing state macrophages (M0), M1 macrophages, and alternately activated macrophages (M2). Real-time fluorescence quantitative PCR was used to verify the expression of marker genes and the expression of lnc_000048 in macrophages. Flow cytometry was used to detect phenotypic proteins (CD11b, CD38, CD80). We generated cell lines with lentivirus-mediated upregulation or downregulation of lnc_000048. Flow cytometry, western blot, and real-time fluorescence quantitative PCR results showed that down-regulation of lnc_000048 reduced M1 macrophage polarization and the inflammation response, while over-expression of lnc_000048 led to the opposite effect. Western blot results indicated that lnc_000048 enhanced the activation of the STAT1 pathway and mediated the M1 macrophage polarization. Moreover, catRAPID prediction, RNA-pull down, and mass spectrometry were used to identify and screen the protein kinase RNA-activated (PKR), then catRAPID and RPIseq were used to predict the binding ability of lnc_000048 to PKR. Immunofluorescence (IF)-RNA fluorescence in situ hybridization (FISH) double labeling was performed to verify the subcellular colocalization of lnc_000048 and PKR in the cytoplasm of M1 macrophage. We speculate that lnc_000048 may form stem-loop structure-specific binding and activate PKR by inducing its phosphorylation, leading to activation of STAT1 phosphorylation and thereby enhancing STAT1 pathway-mediated polarization of THP-1 macrophages to M1 and inflammatory factor expression. Taken together, these results reveal that the lnc_000048/PKR/STAT1 axis plays a crucial role in the polarization of M1 macrophages and may be a novel therapeutic target for atherosclerosis alleviation in stroke.

ΔNp63-restricted viral mimicry response impedes cancer cell viability and remodels tumor microenvironment in esophageal squamous cell carcinoma

Tumor protein p63 isoform ΔNp63 plays roles in the squamous epithelium and squamous cell carcinomas (SCCs), including esophageal SCC (ESCC). By integrating data from cell lines and our latest patient-derived organoid cultures, derived xenograft models, and clinical sample transcriptomic analyses, we identified a novel and robust oncogenic role of ΔNp63 in ESCC. We showed that ΔNp63 maintains the repression of cancer cell endogenous retrotransposon expression and cellular double-stranded RNA sensing. These subsequently lead to a restricted cancer cell viral mimicry response and suppressed induction of tumor-suppressive type I interferon (IFN-I) signaling through the regulations of Signal transducer and activator of transcription 1, Interferon regulatory factor 1, and cGAS-STING pathway. The cancer cell ΔNp63/IFN-I signaling axis affects both the cancer cell and tumor-infiltrating immune cell (TIIC) compartments. In cancer cells, depletion of ΔNp63 resulted in reduced cell viability. ΔNp63 expression is negatively associated with the anticancer responses to viral mimicry booster treatments targeting cancer cells. In the tumor microenvironment, cancer cell TP63 expression negatively correlates with multiple TIIC signatures in ESCC clinical samples. ΔNp63 depletion leads to increased cancer cell antigen presentation molecule expression and enhanced recruitment and reprogramming of tumor-infiltrating myeloid cells. Similar IFN-I signaling and TIIC signature association with ΔNp63 were also observed in lung SCC. These results support the potential application of ΔNp63 as a therapeutic target and a biomarker to guide candidate anticancer treatments exploring viral mimicry responses.

Epigenetic regulation of major histocompatibility complexes in gastrointestinal malignancies and the potential for clinical interception

BACKGROUND

Gastrointestinal malignancies encompass a diverse group of cancers that pose significant challenges to global health. The major histocompatibility complex (MHC) plays a pivotal role in immune surveillance, orchestrating the recognition and elimination of tumor cells by the immune system. However, the intricate regulation of MHC gene expression is susceptible to dynamic epigenetic modification, which can influence functionality and pathological outcomes.

MAIN BODY

By understanding the epigenetic alterations that drive MHC downregulation, insights are gained into the molecular mechanisms underlying immune escape, tumor progression, and immunotherapy resistance. This systematic review examines the current literature on epigenetic mechanisms that contribute to MHC deregulation in esophageal, gastric, pancreatic, hepatic and colorectal malignancies. Potential clinical implications are discussed of targeting aberrant epigenetic modifications to restore MHC expression and 0 the effectiveness of immunotherapeutic interventions.

CONCLUSION

The integration of epigenetic-targeted therapies with immunotherapies holds great potential for improving clinical outcomes in patients with gastrointestinal malignancies and represents a compelling avenue for future research and therapeutic development.

Interferon-regulatory factor-1 boosts bevacizumab cardiotoxicity by the vascular endothelial growth factor A/14-3-3γ axis

AIM

Myocardial injury is a significant cause of death. This study investigated the role and underlying mechanism of interferon-regulatory factor-1 (IRF1) in bevacizumab (BVZ)-induced cardiomyocyte injury.

METHODS AND RESULTS

HL-1 cells and C57BL/6 mice receiving BVZ treatment were used to establish in vitro and in vivo models of myocardial injury. The relationship between VEGFA and 14-3-3γ was verified through co-immunoprecipitation and Glutathione S Transferase (GST) pull-down assay. Cell viability and apoptosis were analysed by MTT, propidium iodide (PI) staining and flow cytometry. The release of lactate dehydrogenase (LDH), cardiac troponins T (cTnT), and creatine kinase MB (CK-MB) was measured using the enzyme linked immunosorbent assay. The effects of knocking down IRF1 on BVZ-induced mice were analysed in vivo. IRF1 levels were increased in BVZ-treated HL-1 cells. BVZ treatment induced apoptosis, inhibited cell viability, and promoted the release of LDH, cTnT, and CK-MB. IRF1 silencing suppressed BVZ-induced myocardial injury, whereas IRF1 overexpression had the opposite effect. IRF1 regulated VEGFA expression by binding to its promoter, with the depletion of VEGFA or 14-3-3γ reversing the effects of IRF1 knockdown on the cell viability and apoptosis of BVZ-treated HL-1 cells. 14-3-3γ overexpression promoted cell proliferation, inhibited apoptosis, and reduced the release of LDH, cTnT, and CK-MB, thereby alleviating BVZ-induced HL-1 cell damage. In vivo, IRF1 silencing alleviated BVZ-induced cardiomyocyte injury by regulating the VEGFA/14-3-3γ axis.

CONCLUSION

The IRF1-mediated VEGFA/14-3-3γ signalling pathway promotes BVZ-induced myocardial injury. Our study provides evidence for potentially new target genes for the treatment of myocardial injury.

Molecular Atlas of HER2+ Breast Cancer Cells Treated with Endogenous Ligands: Temporal Insights into Mechanisms of Trastuzumab Resistance

Trastuzumab therapy in HER2+ breast cancer patients has mixed success owing to acquired resistance to therapy. A detailed understanding of downstream molecular cascades resulting from trastuzumab resistance is yet to emerge. In this study, we investigate the cellular mechanisms underlying acquired resistance using trastuzumab-sensitive and -resistant cancer cells (BT474 and BT474R) treated with endogenous ligands EGF and HRG across time. We probe early receptor organization through microscopy and signaling events through multiomics measurements and assess the bioenergetic state through mitochondrial measurements. Integrative analyses of our measurements reveal significant alterations in EGF-treated BT474 HER2 membrane dynamics and robust downstream activation of PI3K/AKT/mTORC1 signaling. EGF-treated BT474R shows a sustained interferon-independent activation of the IRF1/STAT1 cascade, potentially contributing to trastuzumab resistance. Both cell lines exhibit temporally divergent metabolic demands and HIF1A-mediated stress responses. BT474R demonstrates inherently increased mitochondrial activity. HRG treatment in BT474R leads to a pronounced reduction in AR expression, affecting downstream lipid metabolism with implications for treatment response. Our results provide novel insights into mechanistic changes underlying ligand treatment in BT474 and BT474R and emphasize the pivotal role of endogenous ligands. These results can serve as a framework for furthering the understanding of trastuzumab resistance, with therapeutic implications for women with acquired resistance.

N-MYC-interacting protein enhances type II interferon signaling by inhibiting STAT1 sumoylation

Signaling desensitization is key to limiting signal transduction duration and intensity. Signal transducer and activator of transcription 1 (STAT1) can mediate type II interferon (IFNγ)-induced immune responses, which are enhanced and inhibited by STAT1 phosphorylation and sumoylation, respectively. Here, we identified an N-MYC interacting protein, NMI, which can enhance STAT1 phosphorylation and STAT1-mediated IFNγ immune responses by binding and sequestering the E2 SUMO conjugation enzyme, UBC9, and blocking STAT1 sumoylation. NMI facilitates UBC9 nucleus-to-cytoplasm translocation in response to IFNγ, thereby inhibiting STAT1 sumoylation. STAT1 phosphorylation at Y701 and sumoylation at K703 are mutually exclusive modifications that regulate IFNγ-dependent transcriptional responses. NMI could not alter the phosphorylation level of sumoylation-deficient STAT1 after IFNγ treatment. Thus, IFNγ signaling is modulated by NMI through sequestration of UBC9 in the cytoplasm, leading to inhibition of STAT1 sumoylation. Hence, NMI functions as a switch for STAT1 activation/inactivation cycles by modulating an IFNγ-induced desensitization mechanism.

Hypergraph factorization for multi-tissue gene expression imputation

Integrating gene expression across tissues and cell types is crucial for understanding the coordinated biological mechanisms that drive disease and characterise homeostasis. However, traditional multitissue integration methods cannot handle uncollected tissues or rely on genotype information, which is often unavailable and subject to privacy concerns. Here we present HYFA (Hypergraph Factorisation), a parameter-efficient graph representation learning approach for joint imputation of multi-tissue and cell-type gene expression. HYFA is genotype-agnostic, supports a variable number of collected tissues per individual, and imposes strong inductive biases to leverage the shared regulatory architecture of tissues and genes. In performance comparison on Genotype-Tissue Expression project data, HYFA achieves superior performance over existing methods, especially when multiple reference tissues are available. The HYFA-imputed dataset can be used to identify replicable regulatory genetic variations (eQTLs), with substantial gains over the original incomplete dataset. HYFA can accelerate the effective and scalable integration of tissue and cell-type transcriptome biorepositories.

IFN-γ enhances the efficacy of mesenchymal stromal cell-derived exosomes via miR-21 in myocardial infarction rats

Background

Mesenchymal stromal cells (MSCs) activated with IFN-γ elicit stronger physical effects. Exosomes (Exos) secreted from MSCs show protective effects against myocardial injury. This study aimed to determine whether Exos derived from IFN-γ-treated MSCs exhibit more potent cardioprotective function and the underlying mechanisms.

Methods

H9c2 cells or human umbilical vein endothelial cells (HUVECs) were treated with Exos isolated from MSCs (Ctrl-Exo) or IFN-γ-primed MSCs (IFN-γ-Exo) under oxygen and glucose deprivation (OGD) conditions in vitro and in vivo in an infarcted rat heart. RNA sequencing was used to identify differentially expressed functional transcription factors (TFs). Quantitative reverse transcription-PCR (qPCR) was used to confirm the upregulated TFs and miRNA in IFN-γ-primed MSCs. Dual-luciferase reporter gene assay was used to analyze the transcriptional regulation of miRNAs by STAT1. The target of miR-21-5p (miR-21) was determined by luciferase reporter assays and qPCR. The function of BTG2 was verified in vitro under OGD conditions.

Result

IFN-γ-Exo accelerated migration and tube-like structure formation and prevented OGD-induced apoptosis in H9c2. Similarly, IFN-γ-Exo treatment caused a decrease in fibrosis, reduced cardiomyocyte apoptosis, and improved cardiac function compared to Ctrl-Exo treatment. MiR-21 was significantly upregulated in IFN-γ-primed MSCs and IFN-γ-Exo. STAT1 transcriptionally induced miR-21 expression. Up-regulated miR-21 could inhibit BTG anti-proliferation factor 2 (BTG2) expressions. BTG2 promoted H9c2 cell apoptosis and reversed the protective effects of miR-21 under OGD conditions.

Conclusion

IFN-γ-Exo showed enhanced therapeutic efficacy against acute MI, possibly by promoting angiogenesis and reducing apoptosis by upregulating miR-21, which directly targeted BTG2.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02984-z.

Host-Level Susceptibility and IRF1 Expression Influence the Ability of IFN-γ to Inhibit KSHV Infection in B Lymphocytes

Kaposi's sarcoma-associated herpesvirus (KSHV) is associated with vascular endothelial cell tumor, Kaposi's sarcoma (KS) and lymphoproliferative disorder, multicentric Castleman's disease (MCD), primary effusion lymphoma (PEL) and KSHV inflammatory cytokine syndrome (KICS). Dysregulation of proinflammatory cytokines is found in most KSHV associated diseases. However, little is known about the role of host microenvironment in the regulation of KSHV establishment in B cells. In the present study, we demonstrated that IFN-γ has a strong inhibitory effect on KSHV infection but only in a subset of tonsil-derived lymphocyte samples that are intrinsically more susceptible to infection, contain higher proportions of naïve B cells, and display increased levels of IRF1 and STAT1-pY701. The effect of IFN-γ in responsive samples was associated with increased frequencies of germinal center B cells (GCB) and decreased infection of plasma cells, suggesting that IFN-γ-mediated modulation of viral dynamics in GC can inhibit the establishment of KSHV infection.

Down-regulating HK2 inhibits proliferation of endometrial stromal cells through a noncanonical pathway involving phosphorylation of STAT1 in endometriosis

BACKGROUND

Endometriosis is a benign gynecologic disease that causes chronic pelvic pain, dysmenorrhea and infertility and shares several characteristics with malignant tumors, afflicting women of reproductive age. Hexokinase 2 (HK2) plays an essential role as the first rate-limiting enzyme in the metabolic glycolysis pathway, and its abnormal elevation in tumors is associated with tumor genesis and metastasis. However, the expression and role of HK2 in endometriosis remain unclear.

METHODS

We sequenced the primary endometrial stromal cells from patients with endometrioma and utilized immunohistochemistry, quantitative real-time PCR and western blot to determine the expression of HK2. Then wound healing assays, cell invasion assays, cell proliferation assays were performed to explore the functions of HK2 in endometrial stromal cells. Furthermore, mice models of endometriosis were used to observe the effects of HK2 inhibitors in vivo. Lastly, glycolysis metabolism detection and transcriptome sequencing were carried out in HK2-knockdown endometrial stromal cells to analyze the mechanism of HK2 affecting cell function.

RESULTS

Endometrial stromal cells of endometrioma displayed active glycolysis metabolism and elevated expression of HK2. Downregulating HK2 reduced the migration, invasion and proliferation capacity of endometrial stromal cells. Knockdown of HK2 induced upregulation of signal transducer and activator of transcription 1 (STAT1) and their phosphorylation to attenuate the proliferation of endometrial stromal cells.

CONCLUSIONS

HK2 is associated with the migration, invasion and proliferation of endometrial stromal cells, which might provide new insights into the pathogenesis and treatment of endometriosis.

IRF1 Inhibits Autophagy-Mediated Proliferation of Colorectal Cancer via Targeting ATG13

IRF1 is a nuclear transcription factor that mediates interferon effects and appears to have anti-tumor activity. To determine the roles of IRF1 in colorectal cancer (CRC), we investigated the effects of IRF1 in CRC cells. We found that IRF1 inhibit cell proliferation and tumor growth. Under starvation conditions, IRF1 enhanced apoptosis and reduced autophagic flux. ATG13, an important factor of autophagy complex, was confirmed as a target of IRF1. These findings indicated that IRF1 function as a tumor suppressor in CRC and inhibit autophagy through ATG13, targeting this pathway may provide new insights into the molecular mechanisms of CRC progression.

IRF2BP2 Mutation Is Associated with Increased STAT1 and STAT5 Activation in Two Family Members with Inflammatory Conditions and Lymphopenia

Interferon regulatory factor 2 binding protein 2 (IRF2BP2) is a transcriptional coregulator that has an important role in the regulation of the immune response. IRF2BP2 has been associated with the Janus kinase (JAK)-signal transducers and activators of transcription (STAT) pathway, but its exact role remains elusive. Here, we identified a novel clinical variant, IRF2BP2 c.625_665del, from two members of a family with inflammatory conditions and investigated the function of IRF2BP2 and c.625_665del mutation in JAK-STAT pathway activation and inflammatory signaling. The levels of constitutive and cytokine-induced phosphorylation of STATs and total STAT1 in peripheral blood monocytes, T cells, and B cells from the patients and four healthy controls were measured by flow cytometry. Inflammation-related gene expression was studied in peripheral blood mononuclear cells using direct digital detection of mRNA (NanoString). Finally, we studied the relationship between IRF2BP2 and STAT1 activation using a luciferase reporter system in a cell model. Our results show that patients having the IRF2BP2 c.625_665del mutation presented overexpression of STAT1 protein and increased constitutive activation of STAT1. In addition, interferon-induced JAK-STAT signaling was upregulated, and several interferon-inducible genes were overexpressed. Constitutive phosphorylation of STAT5 was also found to be upregulated in CD4⁺ T cells from the patients. Using a cell model, we show that IRF2BP2 was needed to attenuate STAT1 transcriptional activity and that IRF2BP2 c.625_665del mutation failed in this. We conclude that IRF2BP2 has an important role in suppressing immune responses elicited by STAT1 and STAT5 and suggest that aberrations in IRF2BP2 can lead to abnormal function of intrinsic immunity.

Genetic disruption of zebrafish mab21l1 reveals a conserved role in eye development and affected pathways

BACKGROUND

The male-abnormal 21 like (MAB21L) genes are important in human ocular development. Homozygous loss of MAB21L1 leads to corneal dystrophy in all affected individuals along with cataracts and buphthalmos in some. The molecular function and downstream pathways of MAB21L factors are largely undefined.

RESULTS

We generated the first mab21l1 zebrafish mutant carrying a putative loss-of-function allele, c.107delA p.(Lys36Argfs*7). At the final stages of embryonic development, homozygous mab21l1c.107delA fish displayed enlarged anterior chambers and corneal thinning which progressed with age. Additional studies revealed increased cell death in the mutant corneas, transformation of the cornea into a skin-like epithelium, and progressive lens degeneration with development of fibrous masses in the anterior chamber. RNA-seq of wild-type and mutant ocular transcriptomes revealed significant changes in expression of several genes, including irf1a and b, stat1, elf3, krt17, tlr9, and loxa associated with immunity and/or corneal function. Abnormal expression of lysyl oxidases have been previously linked with corneal thinning, fibrosis, and lens defects in mammals, suggesting a role for loxa misexpression in the progressive mab21l1c.107delA eye phenotype.

CONCLUSIONS

Zebrafish mab21l1 is essential for normal corneal development, similar to human MAB21L1. The identified molecular changes in mab21l1c.107delA mutants provide the first clues about possible affected pathways.

Effects of 17β-Estradiol on Monocyte/Macrophage Response to Staphylococcus aureus: An In Vitro Study

To describe how 17β-estradiol (E2) influence in the monocyte/macrophage response induced by S. aureus in in vitro models of murine peritoneal macrophages (MPMs) and human peripheral blood monocytes (HPBM). MPMs (2 x 10⁵/ml) were isolated from sham (n=3) and ovariectomized (OVX) females (n = 3) and males (n = 3) after induction by thioglycolate. The MPMs obtained from OVX females and males were treated for 24 hours with 17β-estradiol (E2) (10^-7 M), and after that, inoculation with S. aureus was carried out for 6 hours. The macrophages were collected and destined to evaluate the relative gene expression of TNF-α, IL-1β, IL-6, IL-8 and TLR2. For the in vitro model of HPBMs, six men and six women of childbearing age were selected and HPBMs were isolated from samples of the volunteers’ peripheral blood. In women, blood was collected both during menstruation and in the periovulatory period. HPBMs were inoculated with S. aureus for 6 hours and the supernatant was collected for analysis of cytokines by Luminex and the HPBMs were removed for analysis of 84 genes involved in the host’s response to bacterial infections by RT-PCR array. Previous treatment with E2 decreased the gene expression and production of proinflammatory cytokines, such as TNF-α, IL-1β and IL-6 and decreased the expression of TLR2 tanto em MPMs quanto em HPBMs. The analysis of gene expression shows that E2 inhibited the NFκB pathway. It is suggested that 17β-estradiol acts as an immunoprotective in the monocyte/macrophage response induced by S. aureus.

Immunity Depletion, Telomere Imbalance, and Cancer-Associated Metabolism Pathway Aberrations in Intestinal Mucosa upon Short-Term Caloric Restriction

Systems cancer biology analysis of calorie restriction (CR) mechanisms and pathways has not been carried out, leaving therapeutic benefits unclear. Using metadata analysis, we studied gene expression changes in normal mouse duodenum mucosa (DM) response to short-term (2-weeks) 25% CR as a biological model. Our results indicate cancer-associated genes consist of 26% of 467 CR responding differential expressed genes (DEGs). The DEGs were enriched with over-expressed cell cycle, oncogenes, and metabolic reprogramming pathways that determine tissue-specific tumorigenesis, cancer, and stem cell activation; tumor suppressors and apoptosis genes were under-expressed. DEG enrichments suggest telomeric maintenance misbalance and metabolic pathway activation playing dual (anti-cancer and pro-oncogenic) roles. The aberrant DEG profile of DM epithelial cells is found within CR-induced overexpression of Paneth cells and is coordinated significantly across GI tract tissues mucosa. Immune system genes (ISGs) consist of 37% of the total DEGs; the majority of ISGs are suppressed, including cell-autonomous immunity and tumor-immune surveillance. CR induces metabolic reprogramming, suppressing immune mechanics and activating oncogenic pathways. We introduce and argue for our network pro-oncogenic model of the mucosa multicellular tissue response to CR leading to aberrant transcription and pre-malignant states. These findings change the paradigm regarding CR's anti-cancer role, initiating specific treatment target development. This will aid future work to define critical oncogenic pathways preceding intestinal lesion development and biomarkers for earlier adenoma and colorectal cancer detection.

Dexmedetomidine Exerts Renal Protective Effect by Regulating the PGC-1α/STAT1/IRF-1 Axis

BACKGROUND

Ischemia-reperfusion (I/R) injury is the main cause of acute kidney injury (AKI), and its incidence and mortality increase year by year in the population. Dexmedetomidine (DEX) can improve AKI by regulating inflammation and oxidative stress, but its mechanism is still unclear.

METHODS

A hypoxia/reoxygenation (H/R) model of HK-2 cells and a kidney I/R model of C57BL/6J mice were established. In the experiment, cells were transfected with sh-PGC-1α to inhibit PGC-1α expression. The changes of ROS level and mitochondrial membrane potential (MMP) were analyzed. HE staining was used to assess kidney damage in mice. Concentration of kidney injury markers serum creatinine and blood urea nitrogen and expression of inflammatory factors were detected by ELISA. qPCR analysis was used to detect mRNA levels of related proteins in cells and mouse kidney tissues. The protein intracellular content and phosphorylation levels were determined by Western blotting.

RESULT

The production of inflammatory factors and ROS was increased in HK-2 cells treated with H/R, while MMP, cell viability, and mitochondrial-related protein levels were decreased. DEX attenuated pathological changes induced by H/R, while knockdown of PGC-1α eliminated the mitigation effect. DEX inhibited the damage of I/R to the kidneys of mice and increased the expression of mitochondrial-related proteins and PGC-1α in the kidneys, while inhibiting the phosphorylation of STAT1 and the expression of IRF-1.

CONCLUSIONS

DEX appears to inhibit mitochondrial damage and cellular inflammation by upregulating PGC-1α to affect STAT1 phosphorylation level and IRF-1 expression, thereby preventing AKI.

Competitive binding of STATs to receptor phospho-Tyr motifs accounts for altered cytokine responses

Cytokines elicit pleiotropic and non-redundant activities despite strong overlap in their usage of receptors, JAKs and STATs molecules. We use IL-6 and IL-27 to ask how two cytokines activating the same signaling pathway have different biological roles. We found that IL-27 induces more sustained STAT1 phosphorylation than IL-6, with the two cytokines inducing comparable levels of STAT3 phosphorylation. Mathematical and statistical modeling of IL-6 and IL-27 signaling identified STAT3 binding to GP130, and STAT1 binding to IL-27Rα, as the main dynamical processes contributing to sustained pSTAT1 levels by IL-27. Mutation of Tyr613 on IL-27Rα decreased IL-27-induced STAT1 phosphorylation by 80% but had limited effect on STAT3 phosphorgylation. Strong receptor/STAT coupling by IL-27 initiated a unique gene expression program, which required sustained STAT1 phosphorylation and IRF1 expression and was enriched in classical Interferon Stimulated Genes. Interestingly, the STAT/receptor coupling exhibited by IL-6/IL-27 was altered in patients with systemic lupus erythematosus (SLE). IL-6/IL-27 induced a more potent STAT1 activation in SLE patients than in healthy controls, which correlated with higher STAT1 expression in these patients. Partial inhibition of JAK activation by sub-saturating doses of Tofacitinib specifically lowered the levels of STAT1 activation by IL-6. Our data show that receptor and STATs concentrations critically contribute to shape cytokine responses and generate functional pleiotropy in health and disease.

m6 A RNA methyltransferases METTL3/14 regulate immune responses to anti-PD-1 therapy

An impressive clinical success has been observed in treating a variety of cancers using immunotherapy with programmed cell death-1 (PD-1) checkpoint blockade. However, limited response in most patients treated with anti-PD-1 antibodies remains a challenge, requiring better understanding of molecular mechanisms limiting immunotherapy. In colorectal cancer (CRC) resistant to immunotherapy, mismatch-repair-proficient or microsatellite instability-low (pMMR-MSI-L) tumors have low mutation burden and constitute ~85% of patients. Here, we show that inhibition of N⁶ -methyladenosine (m⁶ A) mRNA modification by depletion of methyltransferases, Mettl3 and Mettl14, enhanced response to anti-PD-1 treatment in pMMR-MSI-L CRC and melanoma. Mettl3- or Mettl14-deficient tumors increased cytotoxic tumor-infiltrating CD8⁺ T cells and elevated secretion of IFN-γ, Cxcl9, and Cxcl10 in tumor microenvironment in vivo. Mechanistically, Mettl3 or Mettl14 loss promoted IFN-γ-Stat1-Irf1 signaling through stabilizing the Stat1 and Irf1 mRNA via Ythdf2. Finally, we found a negative correlation between METTL3 or METTL14 and STAT1 in 59 patients with pMMR-MSI-L CRC tumors. Altogether, our findings uncover a new awareness of the function of RNA methylation in adaptive immunity and provide METTL3 and METTL14 as potential therapeutic targets in anticancer immunotherapy.

How microRNAs affect the PD-L1 and its synthetic pathway in cancer

Programmed cell death-ligand 1 (PD-L1) is a glycoprotein that is expressed on the cell surface of both hematopoietic and nonhematopoietic cells. PD-L1 play a role in the immune tolerance and protect self-tissues from immune system attack. Dysfunction of this molecule has been highlighted in the pathogenesis of tumors, autoimmunity, and infectious disorders. MicroRNAs (miRNAs) are endogenous molecules that are classified as small non-coding RNA with approximately 20-22 nucleotides (nt) length. The function of miRNAs is based on complementary interactions with target mRNA via matching completely or incompletely. The result of this function is decay of the target mRNA or preventing mRNA translation. In the past decades, several miRNAs have been discovered which play an important role in the regulation of PD-L1 in various malignancies. In this review, we discuss the effect of miRNAs on PD-L1 expression and consider the effect of miRNAs on the synthetic pathway of PD-L1, especially during cancers.

STAT1 transcriptionally regulates the expression of S1PR1 by binding its promoter region

Sphingosine 1-phosphate receptor 1 (S1PR1) plays a pivotal role in mediating trafficking and migration of immune cells. Previous reports also identify S1PR1 as an important susceptibility gene of asthma and other autoimmune disorders. However, little has been known about the regulatory mechanism of S1PR1 expression. Thus we systematically investigated the transcriptional regulation of S1PR1 in this study. Promoter activity of S1PR1 gene was carefully screened using series of pGL3-Basic reporter vectors, containing full length (range from transcription start site to upstream -1 kb region) or several truncated fragments of S1PR1 promoter. We identified an area (from -29 to -12 bp) of the S1PR1 promoter as the minimal promoter region. Bioinformatics prediction results showed that several transcription factors were recruited to these sites. EMSA and ChIP assays demonstrated the transcriptional factor STAT1 could bind to the region. We also found that the level of S1PR1 level was significantly reduced when STAT1 was knocked-down. Consistent with the reduction of S1PR1 caused by depletion of STAT1, overexpression of STAT1 resulted in up-regulation of S1PR1. In addition, both mRNA and protein levels of S1PR1 were increased when STAT1 was activated by IFN-γ, and decreased when STAT1 was inhibited by fludarabine. Besides, the levels of STAT1 and S1PR1 expression were positively correlated in peripheral blood leukocytes derived from 41 healthy individuals. Our study showed that transcription factor STAT1 could bind to upstream region of -29 bp to -12 bp of the S1PR1 promoter and stimulate the expression of S1PR1.

Single-Cell RNA-Sequencing Identifies Activation of TP53 and STAT1 Pathways in Human T Lymphocyte Subpopulations in Response to Ex Vivo Radiation Exposure

Detrimental health consequences from exposure to space radiation are a major concern for long-duration human exploration missions to the Moon or Mars. Cellular responses to radiation are expected to be heterogeneous for space radiation exposure, where only high-energy protons and other particles traverse a fraction of the cells. Therefore, assessing DNA damage and DNA damage response in individual cells is crucial in understanding the mechanisms by which cells respond to different particle types and energies in space. In this project, we identified a cell-specific signature for radiation response by using single-cell transcriptomics of human lymphocyte subpopulations. We investigated gene expression in individual human T lymphocytes 3 h after ex vivo exposure to 2-Gy gamma rays while using the single-cell sequencing technique (10X Genomics). In the process, RNA was isolated from ~700 irradiated and ~700 non-irradiated control cells, and then sequenced with ~50 k reads/cell. RNA in each of the cells was distinctively barcoded prior to extraction to allow for quantification for individual cells. Principal component and clustering analysis of the unique molecular identifier (UMI) counts classified the cells into three groups or sub-types, which correspond to CD4+, naïve, and CD8+/NK cells. Gene expression changes after radiation exposure were evaluated using negative binomial regression. On average, BBC3, PCNA, and other TP53 related genes that are known to respond to radiation in human T cells showed increased activation. While most of the TP53 responsive genes were upregulated in all groups of cells, the expressions of IRF1, STAT1, and BATF were only upregulated in the CD4+ and naïve groups, but were unchanged in the CD8+/NK group, which suggests that the interferon-gamma pathway does not respond to radiation in CD8+/NK cells. Thus, single-cell RNA sequencing technique was useful for simultaneously identifying the expression of a set of genes in individual cells and T lymphocyte subpopulation after gamma radiation exposure. The degree of dependence of UMI counts between pairs of upregulated genes was also evaluated to construct a similarity matrix for cluster analysis. The cluster analysis identified a group of TP53-responsive genes and a group of genes that are involved in the interferon gamma pathway, which demonstrate the potential of this method for identifying previously unknown groups of genes with similar expression patterns.