Maximal activation of transcription by Stat1 and Stat3 requires both tyrosine and serine phosphorylation

Harmine Inhibits Multiple TLR-Induced Inflammatory Expression through Modulation of NF-κB p65, JNK, and STAT1

Harmine is a beta-carboline alkaloid present in various plants, including in the seeds of Peganum harmala L. This study aimed to investigate the anti-inflammatory activity and mechanism of harmine using macrophages stimulated with various toll-like receptor (TLR) agonists and a model of endotoxemia. The expression of inflammatory mediators induced by ligands of TLRs 2, 3, 4, and 9 were examined in thioglycollate-elicited peritoneal macrophages isolated from BALB/c and C57BL/6 mouse strains. Further, the activation of NF-κB, MAPK, AP-1, and STAT1 was explored using lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly(I:C)). Finally, the liver inflammatory response during endotoxemia was examined. Harmine inhibited inducible nitric oxide synthase, cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-12, and other markers induced by various TLR agonists. The inhibition of NF-κB activity by harmine occurred via the modulation of p65 phosphorylation, independent of IκBα degradation. The inhibition of AP-1 activity by harmine was associated with the modulation of JNK. Harmine inhibited the LPS-induced serine and tyrosine phosphorylation of STAT1, but only affected serine phosphorylation by poly(I:C) treatment. In vivo, harmine inhibited iNOS and COX-2 expression during endotoxemia. Collectively, the results show that harmine can be effective against infectious inflammation through modulation of NF-κB, JNK, and STAT1.

Virus-host interactions during tick-borne bunyavirus infection

The Bunyavirales order is the largest grouping of RNA viruses, comprising emerging and re-emerging human, plant and animal pathogens. Bunyaviruses have a global distribution and many members of the order are transmitted by arthropods. They have evolved a plethora of mechanisms to manipulate the regulatory processes of the infected cell to facilitate their own replicative cycle, in hosts of disparate phylogenies. Interest in virus-vector interactions is growing rapidly. However, current understanding of tick-borne bunyavirus cellular interaction is heavily biased to studies conducted in mammalian systems. In this short review, we summarise current understandings of how tick-borne bunyaviruses utilise major cellular pathways (innate immunity, apoptosis and RNAi responses) in mammalian or tick cells to facilitate virus replication.

Evaluation of the putative lymphoma-associated point mutation D427H in the STAT3 transcription factor

Background

Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor that promotes cell proliferation and immunomodulation in untransformed cells and maintains stemness of transformed cells, facilitating invasion and metastasis. Numerous point mutations in the STAT3 protein have been identified that drive malignancy in various tumor entities. The missense mutation D427H localized in the STAT3 DNA-binding domain has been previously reported in patients with NK/T cell lymphomas. To assess the biological activity of this missense mutation, we compared the STAT3-D427H mutant to wild-type (WT) protein as well as the known hyper-active mutant F174A.

Results

Although previously reported as an activating mutation, the STAT3-D427H mutant neither showed elevated cytokine-induced tyrosine phosphorylation nor altered nuclear accumulation, as compared to the WT protein. However, the D427H mutant displayed enhanced binding to STAT-specific DNA-binding sites but a reduced sequence specificity and dissociation rate from DNA, which was demonstrated by electrophoretic mobility shift assays. This observation is consistent with the phenotype of the homologous E421K mutation in the STAT1 protein, which also displayed enhanced binding to DNA but lacked a corresponding increase in transcriptional activity.

Conclusions

Based on our data, it is unlikely that the D427H missense mutation in the STAT3 protein possesses an oncogenic potential beyond the WT molecule.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-022-00422-9.

Five Rutaceae family ethanol extracts alleviate H2O2 and LPS-induced inflammation via NF-κB and JAK-STAT3 pathway in HaCaT cells

This study was designed to investigate the effects of five Rutaceae family ethanol extracts (FRFEE): Citrus medica Linn (CML), Citrus aurantium L. Cv. Daidai (CAD), Citrus medica Linn. var. sarcodactylis (Noot.) Swingle (CMS),Citrus sinensis L. Osbeck (CSO) and Zanthoxylum bungeanum Maxim (ZBM) on retarding the progression of H₂O₂ and LPS-induced HaCaT cells. Cell inflammatory injury model was established by H₂O₂ and LPS. The alleviative effects of FRFEE were evaluated by detecting the activity of superoxide dismutase (SOD), glutathione (GSH) and the generation of reactive oxygen species (ROS). The inflammatory signaling pathways of NF-κB and JAK-STAT3 were detected by Western blotting, the mRNA expression levels of inflammatory factors and skin barrier factors were detected by RT-PCR. 50% ethanol extracts of five medicinal and food homologous herbs of Rutaceae family showed different levels of anti-oxidant and anti-inflammatory activities. The FRFEE effectively improved SOD and GSH content and decreased ROS levels. Meanwhile, FRFEE strongly suppressed two inflammatory signaling pathways NF-κB and JAK-STAT3. The RT-PCR examination of inflammatory factors and skin barrier factor revealed significant anti-inflammatory effects of FRFEE. It was worth noting that among the five extracts, Zanthoxylum bungeanum Maxim extract had the best anti-inflammatory and anti-oxidation effects. In addition, it could strongly inhibit the expression of psoriasis factor CCL20. In summary, these results suggested that Zanthoxylum bungeanum Maxim extract could be used as an anti-psoriatic agent in the treatment of psoriasis among FRFEE.

NUSAP1, a novel stemness-related protein, promotes early recurrence of hepatocellular carcinoma

Early recurrence (within 2 years after resection) is the primary cause of poor outcomes among hepatocellular carcinoma (HCC) patients, and liver cancer stem cells are the main contributors to postsurgical HCC recurrence. Nucleolar and spindle-associated protein 1 (NUSAP1) has been reported to be involved in tumor progression. We investigated the function and clinical value of NUSAP1 in early recurrence of HCC. Data from public datasets and our cohort were used to assess the association between NUSAP1 expression and early HCC recurrence. Gain- and loss-of-function experiments were carried out in vivo and in vitro. The predictive effect of NUSAP1 on early HCC recurrence was further evaluated by a validation cohort. We found that elevated NUSAP1 expression in HCC specimens was correlated with poor outcome, especially in cases with postoperative early recurrence. Functional studies indicated that NUSAP1 significantly promotes HCC progression. A postsurgical recurrence murine model further revealed that upregulated NUSAP1 dramatically increased the likelihood of HCC early recurrence. RNA sequencing data revealed that the gene sets of cancer stemness and the signal transducer and activator of transcription 3 (STAT3) pathway were enriched by NUSAP1 overexpression. Mechanistically, NUSAP1 enhanced cancer stemness through stimulating STAT3 nuclear translocation and activation through receptor of activated protein C kinase 1 (RACK1). In a validation cohort with 112 HCC patients, NUSAP1 effectively predicted HCC early recurrence. Our results indicated that NUSAP1 promotes early recurrence of HCC by sustaining cancer stemness and could serve as a valuable predictive indicator for postsurgical intervention in HCC patients.

Reactive astrocytes transduce inflammation in a blood-brain barrier model through a TNF-STAT3 signaling axis and secretion of alpha 1-antichymotrypsin

Astrocytes are critical components of the neurovascular unit that support blood-brain barrier (BBB) function. Pathological transformation of astrocytes to reactive states can be protective or harmful to BBB function. Here, using a human induced pluripotent stem cell (iPSC)-derived BBB co-culture model, we show that tumor necrosis factor (TNF) transitions astrocytes to an inflammatory reactive state that causes BBB dysfunction through activation of STAT3 and increased expression of SERPINA3, which encodes alpha 1-antichymotrypsin (α1ACT). To contextualize these findings, we correlated astrocytic STAT3 activation to vascular inflammation in postmortem human tissue. Further, in murine brain organotypic cultures, astrocyte-specific silencing of Serpina3n reduced vascular inflammation after TNF challenge. Last, treatment with recombinant Serpina3n in both ex vivo explant cultures and in vivo was sufficient to induce BBB dysfunction-related molecular changes. Overall, our results define the TNF-STAT3-α1ACT signaling axis as a driver of an inflammatory reactive astrocyte signature that contributes to BBB dysfunction.

SENP3 affects the expression of PYCR1 to promote bladder cancer proliferation and EMT transformation by deSUMOylation of STAT3

Abnormal activation of signal transducer and activator of transcription 3 (STAT3) has been found in various types of human cancers, including bladder cancer (BC). In our study, we examined the regulation of STAT3 post-translational modifications (PTMs) and found that SENP3 is high in bladder cancer. Sentrin/SUMO-specific protease3 (SENP3) and STAT3 were highly expressed in BC tissues when compared with tissue adjacent to carcinoma. SENP3 induced STAT3 protein level and p-STAT3 translocating into nuclear through deSUMOylation of STAT3. Further, nuclear STAT3, as a transcriptional activity factor, promoted pyrroline-5-carboxylate reductase 1 PYCR1 gene and protein level by interacting with the promoter of (PYCR1). Next, we found that knockdown of PYCR1 inhibited Epithelial to mesenchymal transition of bladder cancer, and simultaneously mitigated the carcinogenic effects of STAT3. In vitro, STAT3 knockdown in bladder cancer cells inhibited cell proliferation, migration, and invasion. In contrast, SENP3 overexpression reversed these effects. In all, results lend novel insights into the regulation of STAT3, which has key roles in bladder cancer progression.

Identification of four STAT3 isoforms and functional investigation of IL-6/JAK2/STAT3 pathway in blunt snout bream (Megalobrama amblycephala)

Signal transducer and activator of transcription 3 (STAT3) is a major regulator of immune response and chronic inflammatory, which can be activated by interleukin-6 (IL-6). In mammals, STAT3 has multiple isoforms, and its function has been well studied. In teleost, a single stat3 has been cloned and identified in several species, but studies on its function are limited. In the present study, four stat3 isoforms including mastat3α1, mastat3α2, mastat3β1 and mastat3β2 were identified from blunt snout bream (Megalobrama amblycephala). The results of quantitative PCR (qPCR) showed that four mastat3 transcripts were ubiquitously expressed in all 10 tissues examined. After Aeromonas hydrophila challenge, the expression patterns of mastat3a1, mastat3a2 and mastat3β2 were similar, but significantly different from that of mastat3β1. In addition, western blot showed that rmaIL-6+rmasIL-6R (IL-6 trans-signaling) significantly up-regulated phosphorylation levels of the four maSTAT3 isoforms and mRNA levels of the il-10, il-11, tnf-a, socs3a and socs3b genes, while rmaIL-6 (IL-6 classical signaling) only significantly up-regulated phosphorylation levels of the two maSTAT3α isoforms and mRNA levels of the il-10, socs3a and socs3b genes. Meanwhile, overexpression or inhibition of JAK2 could significantly change the STAT3 phosphorylation. Finally, JAK2 and STAT3 inhibitors could significantly inhibit the up-regulation of il-10, il-11, tnf-a, socs3a and socs3b induced by rmaIL-6+rmasIL-6R or rmaIL-6. To sum up, this study reveals the functional distinctions and overlaps among the four maSTAT3 isoforms in blunt snout bream and reveals the differential regulation of IL-6 classical signaling and trans-signaling on downstream immune genes via the JAK2/STAT3 pathway, enriching our knowledge of fish's defense mechanisms against pathogens.

Status of the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) pathway in liver and skin of the freeze tolerant wood frog

The wood frog (Rana sylvatica) has adapted full-body freezing and thawing as a means of sub-zero winter survival and early-breeding in ephemeral pools. One such protective process implicated recently in freeze-thaw tolerance is that of anti-apoptotic signaling, which has been proposed to play a cytoprotective role by modulating stress-induced death signals. This study employed the use of immunoblotting to examine response of a potent cell cycle and apoptosis regulator, known as the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway, to freezing and thawing in the liver and skin of the wood frog. This pathway demonstrably exhibits factor- and tissue-specific changes between non-frozen, 24 h-frozen, and 8 h-thawed conditions. There were few changes in JAK-STAT proteins in frozen frogs, but protective changes were observed upon thaw: Elevated levels of pJAK3 and nuclear localization of pSTAT3 and pSTAT5 suggested an increase in anti-apoptotic signaling after thaw. By contrast, both STAT1 and STAT3 signaling appeared to increase in frozen skin, suggesting frogs use homeostatic regulation of apoptotic- and anti-apoptotic signals, in an antagonistic and compensatory manner. As such, these findings support that JAK-STAT pathway signaling modulation is a plausible adaptation that contributes to fast and reversible manipulation of anti-apoptotic signals, thus assisting in freeze survival of the wood frog.

Leishmania intercepts IFN-γR signaling at multiple levels in macrophages

IFN-γ, a type 2 interferon and a cytokine, is critical for both innate and adaptive immunity. IFN-γ binds to the IFN-γRs on the cell membrane of macrophages, signals through JAK1-STAT-1 pathway and induces IFN-γ-stimulated genes (ISGs). As Leishmania amastigotes reside and replicate within macrophages, IFN-γ mediated macrophage activation eventuate in Leishmania elimination. As befits the principle of parasitism, the impaired IFN-γ responsiveness in macrophages ensures Leishmania survival. IFN-γ responsiveness is a function of integrated molecular events at multiple levels in the cells that express IFN-γ receptors. In Leishmania-infected macrophages, reduced IFN-γRα expression, impaired IFN-γRα and IFN-γRβ hetero-dimerization due to altered membrane lipid composition, reduced JAK-1 and STAT-1 phosphorylation but increased STAT-1 degradation and impaired ISGs induction collectively determine the IFN-γ responsiveness and the efficacy of IFN-γ induced antileishmanial function of macrophages. Therefore, parasite load is not only decided by the levels of IFN-γ produced but also by the IFN-γ responsiveness. Indeed, in Leishmania-infected patients, IFN-γ is produced but IFN-γ signalling is downregulated. However, the molecular mechanisms of IFN-γ responsiveness remain unclear. Therefore, we review the current understanding of IFN-γ responsiveness of Leishmania-infected macrophages.

IFNγ-induced PD-L1 expression in ovarian cancer cells is regulated by JAK1, STAT1 and IRF1 signaling

Expression of the immune checkpoint programmed death ligand-1 (PD-L1) is increased in ovarian cancer (OC) and correlates with poor prognosis. Interferon-γ (IFNγ) induces PD-L1 expression in OC cells, resulting in their increased proliferation and tumor growth, but the mechanisms that regulate the PD-L1 expression in OC remain unclear. Here, we show that the IFNγ-induced PD-L1 expression in OC cells is associated with increased levels of STAT1, Tyr-701 pSTAT1 and Ser-727 pSTAT1. Suppression of JAK1 and STAT1 significantly decreases the IFNγ-induced PD-L1 expression in OC cells, and STAT1 overexpression increases the IFNγ-induced PD-L1 expression. In addition, IFNγ induces expression of the transcription factor interferon regulatory factor 1 (IRF1) and IRF1 suppression attenuates the IFNγ-induced gene and protein levels of PD-L1. Chromatin immunoprecipitation results show that IFNγ induces PD-L1 promoter acetylation and recruitment of STAT1, Ser-727 pSTAT1 and IRF1 in OC cells. Together, these findings demonstrate that the IFNγ-induced PD-L1 expression in OC cells is regulated by JAK1, STAT1, and IRF1 signaling, and suggest that targeting the JAK1/ STAT1/IRF1 pathway may provide a leverage to regulate the PD-L1 levels in ovarian cancer.

Neuropilin-2 promotes lineage plasticity and progression to neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC), a lethal subset of prostate cancer, is characterized by loss of AR signaling and resulting resistance to AR-targeted therapy during neuroendocrine transdifferentiation, for which the molecular mechanisms remain unclear. Here, we report that neuropilin 2 (NRP2) is upregulated in both de novo and therapy-induced NEPC, which induces neuroendocrine markers, neuroendocrine cell morphology, and NEPC cell aggressive behavior. NRP2 silencing restricted NEPC tumor xenograft growth. Mechanistically, NRP2 engages in reciprocal crosstalk with AR, where NRP2 is transcriptionally inhibited by AR, and in turn suppresses AR signaling by downregulating the AR transcriptional program and confers resistance to enzalutamide. Moreover, NRP2 physically interacts with VEGFR2 through the intracellular SEA domain to activate STAT3 phosphorylation and subsequently SOX2, thus driving NEPC differentiation and growth. Collectively, these results characterize NRP2 as a driver of NEPC and suggest NRP2 as a potential therapeutic target in NEPC.

Stat3 Tyrosine 705 and Serine 727 Phosphorylation Associate With Clinicopathological Characteristics and Distinct Tumor Cell Phenotypes in Triple-Negative Breast Cancer

Signal transducer and activator of transcription 3 (Stat3) is responsible for many aspects of normal development and contributes to the development and progression of cancer through regulating epithelial cell identity and cancer stem cells. In breast cancer, Stat3 is associated with triple-negative breast cancers (TNBC) and its function has been related to the activation of p63, itself a marker of basal-like TNBC and a master regulator of stem cell activities. Stat3 activation is controlled by dual phosphorylation at tyrosine 705 (pTyr705) and serine 727 (pSer727), although it is unclear whether these have equivalent effects, and whether they are related or independent events. To address these issues, we investigated Stat3 phosphorylation at the two sites by immunohistochemistry in 173 patients with TNBC. Stat3 phosphorylation was assessed by automated quantitative measurements of digitized scanned images and classified into four categories based on histoscore. The results were analyzed for associations with multiple markers of tumor phenotype, proliferation, BRCA status, and clinicopathological characteristics. We show that the levels of pTyr705- and pSer727-Stat3 were independent in 34% of tumors. High pTyr705-Stat3 levels were associated with the luminal differentiation markers ERβ/AR and MUC1, whereas tumors with high levels of pSer727-Stat3 were more likely to be positive for the basal marker CK5/6, but were independent of p63 and were EGFR negative. Combined high pSer727- and low Tyr705-Stat3 phosphorylation associated with basal-like cancer. Although high Stat3 phosphorylation levels were associated with less aggressive tumor characteristics, they did not associate with improved survival, indicating that Stat3 phosphorylation is an unfavorable indicator for tumors with an otherwise good prognosis according to clinicopathological characteristics. These findings also show that pTyr705-Stat3 and pSer727-Stat3 associate with specific breast tumor phenotypes, implying that they exert distinct functional activities in breast cancer.

Genomic profiling identifies distinct genetic subtypes in extra-nodal natural killer/T-cell lymphoma

Extra-nodal NK/T-cell lymphoma, nasal type (ENKTCL) is a highly aggressive Epstein-Barr virus associated lymphoma, typically presenting in the nasal and paranasal areas. We assembled a large series of ENKTCL (n = 209) for comprehensive genomic analysis and correlative clinical study. The International Lymphoma Prognostic Index (IPI), site of disease, stage, lymphadenopathy, and hepatomegaly were associated with overall survival. Genetic analysis revealed frequent oncogenic activation of the JAK/STAT3 pathway and alterations in tumor suppressor genes (TSGs) and genes associated with epigenomic regulation. Integrated genomic analysis including recurrent mutations and genomic copy number alterations using consensus clustering identified seven distinct genetic clusters that were associated with different clinical outcomes, thus constituting previously unrecognized risk groups. The genetic profiles of ENTKCLs from Asian and Hispanic ethnic groups showed striking similarity, indicating shared pathogenetic mechanism and tumor evolution. Interestingly, we discovered a novel functional cooperation between activating STAT3 mutations and loss of the TSG, PRDM1, in promoting NK-cell growth and survival. This study provides a genetic roadmap for further analysis and facilitates investigation of actionable therapeutic opportunities in this aggressive lymphoma.

p53 Isoforms as Cancer Biomarkers and Therapeutic Targets

Simple Summary

The well-known tumor suppressor protein p53 plays important roles in tumor prevention through transcriptional regulation of its target genes. Reactivation of p53 activity has been a potent strategy for cancer treatment. Accumulating evidences indicate that p53 isoforms truncated/modified in the N- or C-terminus can modulate the p53 pathway in a p53-dependent or p53-independent manner. It is thus imperative to characterize the roles of the p53 isoforms in cancer development. This review illustrates how p53 isoforms participate in tumor development and/or suppression. It also summarizes the knowledge about the p53 isoforms as promising cancer biomarkers and therapeutic targets.

Abstract

This review aims to summarize the implications of the major isoforms of the tumor suppressor protein p53 in aggressive cancer development. The current knowledge of p53 isoforms, their involvement in cell-signaling pathways, and their interactions with other cellular proteins or factors suggests the existence of an intricate molecular network that regulates their oncogenic function. Moreover, existing literature about the involvement of the p53 isoforms in various cancers leads to the proposition of therapeutic solutions by altering the cellular levels of the p53 isoforms. This review thus summarizes how the major p53 isoforms Δ40p53α/β/γ, Δ133p53α/β/γ, and Δ160p53α/β/γ might have clinical relevance in the diagnosis and effective treatments of cancer.

SOCS3 gene silencing does not occur through methylation and mutations in gastric cancer

Gastric cancer (GC) is ranked the third leading cause of cancer-related deaths worldwide. Mutations and epigenetic alterations in several essential genes, including p53, KRAS, PIK3CA, FAT4 and ARID1A, are often reported. Furthermore, loss of SOCS3 expression was reported in GC, suggesting its tumor suppressor role. To assess the mutational and methylation status of SOCS3, we performed gene panel exome sequencing on 47 human GC samples. The SOCS3 gene was rarely mutated, suggesting alternative regulation mechanisms, such as promoter hypermethylation and/or long non-coding RNAs (lncRNAs). We first explored SOCS3 promoter methylation status in 44 human GC samples by methylation-specific PCR (MS-PCR). Thirteen out of forty-four patients (29.5%) displayed a methylation pattern. Then, to see whether SOCS3 expression is silenced by CpG methylation, we examined publicly available databases (cbioportal and The Cancer Genome Atlas (TCGA)). The analysis revealed β values lower than 0.1, indicating hypo-methylation in healthy and GC samples. Moreover, moderate methylation (β < 0.4) and high methylation (β > 0.4) did not affect the free survival, suggesting that methylation is unlikely to be the mechanism ruling SOCS3 silencing in GC. Next, to assess the regulatory effects of lncRNAs on SOCS3, we silenced the AC125807.2-lncRNA and quantified the SOCS3 gene expression in AGS and NCI-N87 gastric cancer cell line. SOCS3 was found to be downregulated following AC125807.2-lncRNA silencing in AGS cells, suggesting the potential implication of lncRNA AC125807.2 in SOCS3 regulation. However, in NCI-N87 cells, there was no significant change in SOCS3 expression. In conclusion, neither mutations nor hypermethylation was associated with the SOCS3 downregulation in GC, and alternative mechanisms, including non-coding RNAs-mediated gene silencing, may be proposed.

The cytokines interleukin-6 and interferon-α induce distinct microglia phenotypes

Background

Elevated production of the cytokines interleukin (IL)-6 or interferon (IFN)-α in the central nervous system (CNS) is implicated in the pathogenesis of neurological diseases such as neuromyelitis optica spectrum disorders or cerebral interferonopathies, respectively. Transgenic mice with CNS-targeted chronic production of IL-6 (GFAP-IL6) or IFN-α (GFAP-IFN) recapitulate important clinical and pathological features of these human diseases. The activation of microglia is a prominent manifestation found both in the human diseases and in the transgenic mice, yet little is known about how this contributes to disease pathology.

Methods

Here, we used a combination of ex vivo and in situ techniques to characterize the molecular, cellular and transcriptomic phenotypes of microglia in GFAP-IL6 versus GFAP-IFN mice. In addition, a transcriptomic meta-analysis was performed to compare the microglia response from GFAP-IL6 and GFAP-IFN mice to the response of microglia in a range of neurodegenerative and neuroinflammatory disorders.

Results

We demonstrated that microglia show stimulus-specific responses to IL-6 versus IFN-α in the brain resulting in unique and extensive molecular and cellular adaptations. In GFAP-IL6 mice, microglia proliferated, had shortened, less branched processes and elicited transcriptomic and molecular changes associated with phagocytosis and lipid processing. In comparison, microglia in the brain of GFAP-IFN mice exhibited increased proliferation and apoptosis, had larger, hyper-ramified processes and showed transcriptomic and surface marker changes associated with antigen presentation and antiviral response. Further, a transcriptomic meta-analysis revealed that IL-6 and IFN-α both contribute to the formation of a core microglia response in animal models of neurodegenerative and neuroinflammatory disorders, such as Alzheimer’s disease, tauopathy, multiple sclerosis and lipopolysaccharide-induced endotoxemia.

Conclusions

Our findings demonstrate that microglia responses to IL-6 and IFN-α are highly stimulus-specific, wide-ranging and give rise to divergent phenotypes that modulate microglia responses in neuroinflammatory and neurodegenerative diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02441-x.

LATS1 is a central signal transmitter for achieving full type-I interferon activity

Interferons (IFNs) have broad-spectrum antiviral activity to resist virus epidemic. However, IFN antiviral efficacy needs to be greatly improved. Here, we reveal that LATS1 is a vital signal transmitter governing full type-I IFN (IFN-I) signaling activity. LATS1 constitutively binds with the IFN-I receptor IFNAR2 and is rapidly tyro-phosphorylated by Tyk2 upon IFN-I engagement. Tyro-phosphorylation of LATS1 promotes LATS1 activation and YAP degradation, thereby promoting IFN-mediated antiproliferation activity. Moreover, activated LATS1 translocates into the nucleus and induces CDK8-Ser62 phosphorylation, which in turn phosphorylates STAT1 at Ser⁷²⁷ and induces full IFN-I antiviral activity. LATS1 deficiency restricts in vivo IFN-I signaling and attenuates host antiviral immune response. Our study identifies IFN-I as a previously unidentified extracellular diffusible ligand signal for activation of the Hippo core LATS1 pathway and reveals Tyk2-LATS1-CDK8 as a complete signaling cascade controlling full IFN-I activity.

The chromosome 21 kinase DYRK1A: emerging roles in cancer biology and potential as a therapeutic target

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) is a serine/threonine kinase that belongs to the DYRK family of proteins, a subgroup of the evolutionarily conserved CMGC protein kinase superfamily. Due to its localization on chromosome 21, the biological significance of DYRK1A was initially characterized in the pathogenesis of Down syndrome (DS) and related neurodegenerative diseases. However, increasing evidence has demonstrated a prominent role in cancer through its ability to regulate biologic processes including cell cycle progression, DNA damage repair, transcription, ubiquitination, tyrosine kinase activity, and cancer stem cell maintenance. DYRK1A has been identified as both an oncogene and tumor suppressor in different models, underscoring the importance of cellular context in its function. Here, we review mechanistic contributions of DYRK1A to cancer biology and its role as a potential therapeutic target.

An inhibitory effect on the nuclear accumulation of phospho-STAT1 by its unphosphorylated form

BACKGROUND

Unphosphorylated signal transducer and activator of transcription 1 (U-STAT1) has been reported to elicit a distinct gene expression profile as compared to tyrosine-phosphorylated STAT1 (P-STAT1) homodimers. However, the impact of U-STAT1 on the IFNγ-induced immune response mediated by P-STAT1 is unknown. By generating a double mutant of STAT1 with mutation R602L in the Src-homology 2 (SH2) domain and Y701F in the carboxy-terminal transactivation domain mimicking U-STAT1, we investigated the effects of U-STAT1 on P-STAT1-mediated signal transduction.

RESULTS

In this study, we discovered a novel activity of U-STAT1 that alters the nucleo-cytoplasmic distribution of cytokine-stimulated P-STAT1. While the dimerization-deficient mutant R602L/Y701F was not able to display cytokine-induced nuclear accumulation, it inhibited the nuclear accumulation of co-expressed IFNγ-stimulated wild-type P-STAT1. Disruption of the anti-parallel dimer interface in the R602L/Y701F mutant via additional R274W and T385A mutations did not rescue the impaired nuclear accumulation of co-expressed P-STAT1. The mutant U-STAT1 affected neither the binding of co-expressed P-STAT1 to gamma-activated sites in vitro, nor the transcription of reporter constructs and the activation of STAT1 target genes. However, the nuclear accumulation of P-STAT1 was diminished in the presence of mutant U-STAT1, which was not restored by mutations reducing the DNA affinity of mutant U-STAT1. Whereas single mutations in the amino-terminus of dimerization-deficient U-STAT1 similarly inhibited the nuclear accumulation of co-expressed P-STAT1, a complete deletion of the amino-terminus restored cytokine-stimulated nuclear accumulation of P-STAT1. Likewise, the disruption of a dimer-specific nuclear localization signal also rescued the U-STAT1-mediated inhibition of P-STAT1 nuclear accumulation.

CONCLUSION

Our data demonstrate a novel role of U-STAT1 in affecting nuclear accumulation of P-STAT1, such that a high intracellular concentration of U-STAT1 inhibits the detection of nuclear P-STAT1 in immunofluorescence assays. These observations hint at a possible physiological function of U-STAT1 in buffering the nuclear import of P-STAT1, while preserving IFNγ-induced gene expression. Based on these results, we propose a model of a hypothetical import structure, the assembly of which is impaired under high concentrations of U-STAT1. This mechanism maintains high levels of cytoplasmic STAT1, while simultaneously retaining signal transduction by IFNγ. Video Abstract.

DYRK1B-STAT3 Drives Cardiac Hypertrophy and Heart Failure by Impairing Mitochondrial Bioenergetics

BACKGROUND

Heart failure is a global public health issue that is associated with increasing morbidity and mortality. Previous studies have suggested that mitochondrial dysfunction plays critical roles in the progression of heart failure; however, the underlying mechanisms remain unclear. Because kinases have been reported to modulate mitochondrial function, we investigated the effects of DYRK1B (dual-specificity tyrosine-regulated kinase 1B) on mitochondrial bioenergetics, cardiac hypertrophy, and heart failure.

METHODS

We engineered DYRK1B transgenic and knockout mice and used transverse aortic constriction to produce an in vivo model of cardiac hypertrophy. The effects of DYRK1B and its downstream mediators were subsequently elucidated using RNA-sequencing analysis and mitochondrial functional analysis.

RESULTS

We found that DYRK1B expression was clearly upregulated in failing human myocardium and in hypertrophic murine hearts, as well. Cardiac-specific DYRK1B overexpression resulted in cardiac dysfunction accompanied by a decline in the left ventricular ejection fraction, fraction shortening, and increased cardiac fibrosis. In striking contrast to DYRK1B overexpression, the deletion of DYRK1B mitigated transverse aortic constriction-induced cardiac hypertrophy and heart failure. Mechanistically, DYRK1B was positively associated with impaired mitochondrial bioenergetics by directly binding with STAT3 to increase its phosphorylation and nuclear accumulation, ultimately contributing toward the downregulation of PGC-1α (peroxisome proliferator-activated receptor gamma coactivator-1α). Furthermore, the inhibition of DYRK1B or STAT3 activity using specific inhibitors was able to restore cardiac performance by rejuvenating mitochondrial bioenergetics.

CONCLUSIONS

Taken together, the findings of this study provide new insights into the previously unrecognized role of DYRK1B in mitochondrial bioenergetics and the progression of cardiac hypertrophy and heart failure. Consequently, these findings may provide new therapeutic options for patients with heart failure.

Effects of Dexamethasone on DNA Synthesis in Lens Epithelial Cells are Dependent on Cell Type and Growth Factor

PURPOSE

To determine the factors that influence the ability of dexamethasone (dex) to inhibit or stimulate the growth of lens epithelial cells.

METHOD

Different growth factors with or without dex (10^-6 M) were added to quiescent cultures of two clones of Nakano mouse lens epithelial cells (NK11) in serum-free medium. DNA synthesis was then measured after 8 to 12 hours by the incorporation of tritiated thymidine.

RESULTS

Dex was found to both stimulate and inhibit mitogen-induced ³H-thymidine incorporation into the DNA of cultured mouse lens epithelial cells. Enhancement or repression by dex was found to depend on the growth factor used to stimulate the quiescent cell. EGF and insulin were consistently inhibited with dex. Basic fibroblast growth factor (bFGF) and retinoblastoma-derived growth factor (RbDGF) were both enhanced and inhibited by dex, depending on the growth factor concentration and the cell clone used for the experiment. Additionally, RbDGF protects against the dex inhibition of insulin stimulation, but not the inhibition of EGF stimulation. Progesterone, an inhibitor of the activation of the glucocorticoid receptor, blocks the dex inhibitory effect on the EGF and insulin stimulation of DNA synthesis.The ability of progesterone to affect the dex inhibition is consistent with the dex receptor modulating DNA synthesis. The dex effect on DNA synthesis, either stimulatory or inhibitory, was still seen if dex was added as late as 10 hours after the growth factor.

CONCLUSIONS

The study demonstrated that dex reduces the overall growth and activity of lens epithelial cells in vitro. This result provides insight into the risk of developing posterior subcapsular cataracts (PSC) in patients on oral glucocorticoid therapy. Understanding the basic mechanisms by which steroids mediate lens cell growth may provide the ability to more accurately predict who will develop PSC. The present studies show the difference in the effect of dex from lens cell to lens cell, but, more importantly, suggest a pattern of dependent variables that might prove useful in such predictions.

STAT3 Role in T-Cell Memory Formation

Along with the clinical success of immuno-oncology drugs and cellular therapies, T-cell biology has attracted considerable attention in the immunology community. Long-term immunity, traditionally analyzed in the context of infection, is increasingly studied in cancer. Many signaling pathways, transcription factors, and metabolic regulators have been shown to participate in the formation of memory T cells. There is increasing evidence that the signal transducer and activator of transcription-3 (STAT3) signaling pathway is crucial for the formation of long-term T-cell immunity capable of efficient recall responses. In this review, we summarize what is currently known about STAT3 role in the context of memory T-cell formation and antitumor immunity.

Oncogenic dependency on STAT3 serine phosphorylation in KRAS mutant lung cancer

The oncogenic potential of the latent transcription factor signal transducer and activator of transcription (STAT)3 in many human cancers, including lung cancer, has been largely attributed to its nuclear activity as a tyrosine-phosphorylated (pY705 site) transcription factor. By contrast, an alternate mitochondrial pool of serine phosphorylated (pS727 site) STAT3 has been shown to promote tumourigenesis by regulating metabolic processes, although this has been reported in only a restricted number of mutant RAS-addicted neoplasms. Therefore, the involvement of STAT3 serine phosphorylation in the pathogenesis of most cancer types, including mutant KRAS lung adenocarcinoma (LAC), is unknown. Here, we demonstrate that LAC is suppressed in oncogenic KrasG12D-driven mouse models engineered for pS727-STAT3 deficiency. The proliferative potential of the transformed KrasG12D lung epithelium, and mutant KRAS human LAC cells, was significantly reduced upon pS727-STAT3 deficiency. Notably, we uncover the multifaceted capacity of constitutive pS727-STAT3 to metabolically reprogramme LAC cells towards a hyper-proliferative state by regulating nuclear and mitochondrial (mt) gene transcription, the latter via the mtDNA transcription factor, TFAM. Collectively, our findings reveal an obligate requirement for the transcriptional activity of pS727-STAT3 in mutant KRAS-driven LAC with potential to guide future therapeutic targeting approaches.

Sepsis induces interleukin 6, gp130/JAK2/STAT3, and muscle wasting

BACKGROUND

Sepsis and inflammation can cause intensive care unit-acquired weakness (ICUAW). Increased interleukin-6 (IL-6) plasma levels are a risk factor for ICUAW. IL-6 signalling involves the glycoprotein 130 (gp130) receptor and the JAK/STAT-pathway, but its role in sepsis-induced muscle wasting is uncertain. In a clinical observational study, we found that the IL-6 target gene, SOCS3, was increased in skeletal muscle of ICUAW patients indicative for JAK/STAT-pathway activation. We tested the hypothesis that the IL-6/gp130-pathway mediates ICUAW muscle atrophy.

METHODS

We sequenced RNA (RNAseq) from tibialis anterior (TA) muscle of cecal ligation and puncture-operated (CLP) and sham-operated wildtype (WT) mice. The effects of the IL-6/gp130/JAK2/STAT3-pathway were investigated by analysing the atrophy phenotype, gene expression, and protein contents of C2C12 myotubes. Mice lacking Il6st, encoding gp130, in myocytes (cKO) and WT controls, as well as mice treated with the JAK2 inhibitor AG490 or vehicle were exposed to CLP or sham surgery for 24 or 96 h.

RESULTS

Analyses of differentially expressed genes in RNAseq (≥2-log2-fold change, P < 0.01) revealed an activation of IL-6-signalling and JAK/STAT-signalling pathways in muscle of septic mice, which occurred after 24 h and lasted at least for 96 h during sepsis. IL-6 treatment of C2C12 myotubes induced STAT3 phosphorylation (three-fold, P < 0.01) and Socs3 mRNA expression (3.1-fold, P < 0.01) and caused myotube atrophy. Knockdown of Il6st diminished IL-6-induced STAT3 phosphorylation (-30.0%; P < 0.01), Socs3 mRNA expression, and myotube atrophy. JAK2 (- 29.0%; P < 0.01) or STAT3 inhibition (-38.7%; P < 0.05) decreased IL-6-induced Socs3 mRNA expression. Treatment with either inhibitor attenuated myotube atrophy in response to IL-6. CLP-operated septic mice showed an increased STAT3 phosphorylation and Socs3 mRNA expression in TA muscle, which was reduced in septic Il6st-cKO mice by 67.8% (P < 0.05) and 85.6% (P < 0.001), respectively. CLP caused a loss of TA muscle weight, which was attenuated in Il6st-cKO mice (WT: -22.3%, P < 0.001, cKO: -13.5%, P < 0.001; WT vs. cKO P < 0.001). While loss of Il6st resulted in a reduction of MuRF1 protein contents, Atrogin-1 remained unchanged between septic WT and cKO mice. mRNA expression of Trim63/MuRF1 and Fbxo32/Atrogin-1 were unaltered between CLP-treated WT and cKO mice. AG490 treatment reduced STAT3 phosphorylation (-22.2%, P < 0.05) and attenuated TA muscle atrophy in septic mice (29.6% relative reduction of muscle weight loss, P < 0.05). The reduction in muscle atrophy was accompanied by a reduction in Fbxo32/Atrogin-1-mRNA (-81.3%, P < 0.05) and Trim63/MuRF1-mRNA expression (-77.6%, P < 0.05) and protein content.

CONCLUSIONS

IL-6 via the gp130/JAK2/STAT3-pathway mediates sepsis-induced muscle atrophy possibly contributing to ICUAW.

STAT3 mediated regulation of glucose metabolism in leukemia cells

Cancer cells rewire metabolic pathways as they demand more ATP and building blocks for proliferation. Glucose is the most consumed nutrient by cancer cells and metabolized to lactate even in the presence of oxygen. This phenomenon is called 'aerobic glycolysis'. Also, glucose level is found lower in tumor environment. Leukemia is characterized by abnormal proliferation of hematopoietic cells. STAT3 a transcription factor and an oncogene is upregulated in many tumor types. Despite its well-defined functions, STAT3 has also been proposed as a metabolic regulator. In this study, we aimed to determine the role STAT3 activation in glucose limitation, in leukemia cell lines. K562, NB-4 and HL-60 cells were found sensitive to glucose limitation. In low glucose conditions, total and nuclear STAT3 protein was decreased in all cells. In mitochondria, S727 phosphorylated STAT3 (mitochondrial form) was determined slightly increased in K562 and NB-4 cells. On the other side, ectopically STAT3 expressing cells had increased glucose consumption and less proliferated in low glucose medium. This data suggests that aerobic glycolysis might be upregulated upon STAT3 expression in leukemia cells, in glucose limitation. Furthermore, in this study, it was found that GLUT3 expressing cells did not reduce STAT3 expression in low glucose medium. GLUT3 was previously determined as a molecular marker for cell sensitivity to glucose limitation, therefore, it could be hypothesized as GLUT3 expressing cells might not need to alter STAT3 expression in low glucose level. Overall, our data suggest that leukemia cells rewire glucose metabolism via STAT3 expression in glucose limitation. Elucidating pathways that cause differential phosphorylation of STAT3 and its interaction with other energy regulating pathways in cellular response to glucose limitation might be beneficial to design new drug targets such as STAT3 inhibitors for leukemia treatment.

Long non-coding RNAs in gastrointestinal cancers: implications for protein phosphorylation

Phosphorylation of proteins is one of the most extensively investigated post-translational protein modifications. Threonine, serine and tyrosine in proteins are the most commonly phosphorylated amino acids. Dysregulated cancer-related signaling pathways due to aberrant phosphorylation status of the key protein(s) in these pathways exist in most malignancies. Intensive studies in the recent decade have implicated long non-coding RNAs (lncRNAs) in the precise regulation of protein phosphorylation in cancers. In this review, we systematically delve into recent advance that underlines the multidimensional role of lncRNAs in modulating protein phosphorylation, regulating cancerous signaling and impacting prognosis of gastrointestinal (GI) cancers including hepatocellular carcinoma, colorectal cancer, gastric cancer, esophageal cancer, and pancreatic cancer. LncRNAs regulate protein phosphorylation via directly binding to the target protein(s), interacting with the partner protein(s) of the target protein(s) or lncRNAs-encoded small peptides. Although there are still extensive studies on disclosing the intricate interactions between lncRNAs and proteins and their impacts on protein phosphorylation, we believe that targeting lncRNAs controlling phosphorylation of key protein(s) in cancerous signaling pathways might provide novel paths for precision therapeutics of GI cancers in the future.

Functional analysis and regulation mechanism of interferon gamma in macrophages of large yellow croaker (Larimichthys crocea)

Interferon gamma (IFN-γ) is a widely expressed cytokine that has potent antiviral and immunomodulatory effects. The expression and bioactivity of IFN-γ have been reported in several fish species. However, the molecular mechanism mediated by IFN-γ in fish macrophages has not been completely elucidated. This study used the macrophage cell line to investigate the functional activities and regulation mechanism of large yellow croaker IFN-γ (LcIFN-γ). Herein, the mRNA expression of Lcifn-γ was significantly upregulated in macrophages after LPS and poly(I:C) treatment. Recombinant LcIFN-γ protein (rLcIFN-γ) significantly enhanced the phagocytic ability and respiratory burst activity of macrophages. Meanwhile, rLcIFN-γ induced M1 phenotype polarization of macrophages with the upregulated expressions of pro-inflammatory gene. Moreover, rLcIFN-γ upregulated the IFN-stimulated genes (ISGs) expression and activated JAK (Janus tyrosine kinases)-STAT (signal transducer and activator of transcription) signaling pathway by causing the phosphorylation of JAK1 and STAT1^Tyr701. Furthermore, the promoter activity of IFN-regulatory factor 1 (IRF1) was significantly upregulated by the phosphorylated transcription factor STAT1 through binding to its promoter region. In addition to the classical JAK-STAT pathway, rLcIFN-γ also activated multiple distinct signaling cascades such as mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) pathways. Overall, this study indicated the powerful effects of LcIFN-γ on macrophage activation of large yellow croaker and its molecular mechanism.

Multicellular Effects of STAT3 in Non-small Cell Lung Cancer: Mechanistic Insights and Therapeutic Opportunities

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and accounts for 85% of lung cancer cases. Aberrant activation of the Signal Transducer and Activator of Transcription 3 (STAT3) is frequently observed in NSCLC and is associated with a poor prognosis. Pre-clinical studies have revealed an unequivocal role for tumor cell-intrinsic and extrinsic STAT3 signaling in NSCLC by promoting angiogenesis, cell survival, cancer cell stemness, drug resistance, and evasion of anti-tumor immunity. Several STAT3-targeting strategies have also been investigated in pre-clinical models, and include preventing upstream receptor/ligand interactions, promoting the degradation of STAT3 mRNA, and interfering with STAT3 DNA binding. In this review, we discuss the molecular and immunological mechanisms by which persistent STAT3 activation promotes NSCLC development, and the utility of STAT3 as a prognostic and predictive biomarker in NSCLC. We also provide a comprehensive update of STAT3-targeting therapies that are currently undergoing clinical evaluation, and discuss the challenges associated with these treatment modalities in human patients.

Exploiting the STAT3 Nexus in Cancer-Associated Fibroblasts to Improve Cancer Therapy

The tumor microenvironment (TME) is composed of a heterogenous population of cells that exist alongside the extracellular matrix and soluble components. These components can shape an environment that is conducive to tumor growth and metastatic spread. It is well-established that stromal cancer-associated fibroblasts (CAFs) in the TME play a pivotal role in creating and maintaining a growth-permissive environment for tumor cells. A growing body of work has uncovered that tumor cells recruit and educate CAFs to remodel the TME, however, the mechanisms by which this occurs remain incompletely understood. Recent studies suggest that the signal transducer and activator of transcription 3 (STAT3) is a key transcription factor that regulates the function of CAFs, and their crosstalk with tumor and immune cells within the TME. CAF-intrinsic STAT3 activity within the TME correlates with tumor progression, immune suppression and eventually the establishment of metastases. In this review, we will focus on the roles of STAT3 in regulating CAF function and their crosstalk with other cells constituting the TME and discuss the utility of targeting STAT3 within the TME for therapeutic benefit.

BUB1 drives the occurrence and development of bladder cancer by mediating the STAT3 signaling pathway

Background

The incidence of bladder urothelial carcinoma (UC), a common malignancy of the urinary tract, is approximately three times higher in men than in women. High expression of the mitotic kinase BUB1 is associated with the occurrence and development of several cancers, although the relationship between BUB1 and bladder tumorigenesis remains unclear.

Methods

Using a microarray approach, we found increased BUB1 expression in human BCa. The association between BUB1 and STAT3 phosphorylation was determined through molecular and cell biological methods. We evaluated the impact of pharmacologic inhibition of BUB1 kinase activity on proliferation and BCa progression in vitro and in vivo.

Results

In this study, we found that BUB1 expression was increased in human bladder cancer (BCa). We further identified through a series of molecular and cell biological approaches that BUB1 interacted directly with STAT3 and mediated the phosphorylation of STAT3 at Ser727. In addition, the findings that pharmacologic inhibition of BUB1 kinase activity significantly suppressed BCa cell proliferation and the progression of bladder cancer in vitro and in vivo were further verified. Finally, we found that the BUB1/STAT3 complex promoted the transcription of STAT3 target genes and that depletion of BUB1 and mutation of the BUB1 kinase domain abrogated this transcriptional activity, further highlighting the critical role of kinase activity in the activation of STAT3 target genes. A pharmacological inhibitor of BUB1 (2OH-BNPP1) was able to significantly inhibit the growth of BCa cell xenografts.

Conclusion

This study showed that the BUB1 kinase drives the progression and proliferation of BCa by regulating the transcriptional activation of STAT3 signaling and may be an attractive candidate for therapeutic targeting in BCa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02179-z.

The Crosstalk Between Signaling Pathways and Cancer Metabolism in Colorectal Cancer

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers worldwide. Metabolic reprogramming represents an important cancer hallmark in CRC. Reprogramming core metabolic pathways in cancer cells, such as glycolysis, glutaminolysis, oxidative phosphorylation, and lipid metabolism, is essential to increase energy production and biosynthesis of precursors required to support tumor initiation and progression. Accumulating evidence demonstrates that activation of oncogenes and loss of tumor suppressor genes regulate metabolic reprogramming through the downstream signaling pathways. Protein kinases, such as AKT and c-MYC, are the integral components that facilitate the crosstalk between signaling pathways and metabolic pathways in CRC. This review provides an insight into the crosstalk between signaling pathways and metabolic reprogramming in CRC. Targeting CRC metabolism could open a new avenue for developing CRC therapy by discovering metabolic inhibitors and repurposing protein kinase inhibitors/monoclonal antibodies.

Prenatal interleukin 6 elevation increases glutamatergic synapse density and disrupts hippocampal connectivity in offspring

Early prenatal inflammatory conditions are thought to be a risk factor for different neurodevelopmental disorders. Maternal interleukin-6 (IL-6) elevation during pregnancy causes abnormal behavior in offspring, but whether these defects result from altered synaptic developmental trajectories remains unclear. Here we showed that transient IL-6 elevation via injection into pregnant mice or developing embryos enhanced glutamatergic synapses and led to overall brain hyperconnectivity in offspring into adulthood. IL-6 activated synaptogenesis gene programs in glutamatergic neurons and required the transcription factor STAT3 and expression of the RGS4 gene. The STAT3-RGS4 pathway was also activated in neonatal brains during poly(I:C)-induced maternal immune activation, which mimics viral infection during pregnancy. These findings indicate that IL-6 elevation at early developmental stages is sufficient to exert a long-lasting effect on glutamatergic synaptogenesis and brain connectivity, providing a mechanistic framework for the association between prenatal inflammatory events and brain neurodevelopmental disorders.

STAT3 as a mediator of oncogenic cellular metabolism: Pathogenic and therapeutic implications

The oncogenic transcription factor signal transducer and activator of transcription 3 (STAT3) is activated constitutively in a wide array of human cancers. It is an appealing molecular target for novel therapy as it directly regulates expression of genes involved in cell proliferation, survival, angiogenesis, chemoresistance and immune responsiveness. In addition to these well-established oncogenic roles, STAT3 has also been found to mediate a wide array of functions in modulating cellular behavior. The transcriptional function of STAT3 is canonically regulated through tyrosine phosphorylation. However, STAT3 phosphorylated at a single serine residue can allow incorporation of this protein into the inner mitochondrial membrane to support oxidative phosphorylation (OXPHOS) and maximize the utility of glucose sources. Conflictingly, its canonical transcriptional activity suppresses OXPHOS and favors aerobic glycolysis to promote oncogenic behavior. Apart from mediating the energy metabolism and controversial effects on ATP production, STAT3 signaling modulates lipid metabolism of cancer cells. By mediating fatty acid synthesis and beta oxidation, STAT3 promotes employment of available resources and supports survival in the conditions of metabolic stress. Thus, the functions of STAT3 extend beyond regulation of oncogenic genes expression to pleiotropic effects on a spectrum of essential cellular processes. In this review, we dissect the current knowledge on activity and mechanisms of STAT3 involvement in transcriptional regulation, mitochondrial function, energy production and lipid metabolism of malignant cells, and its implications to cancer pathogenesis and therapy.

Oncogenic KRAS-Induced Feedback Inflammatory Signaling in Pancreatic Cancer: An Overview and New Therapeutic Opportunities

Pancreatic ductal adenocarcinoma (PDAC) remains highly refractory to treatment. While the KRAS oncogene is present in almost all PDAC cases and accounts for many of the malignant feats of PDAC, targeting KRAS or its canonical, direct effector cascades remains unsuccessful in patients. The recalcitrant nature of PDAC is also heavily influenced by its highly fibro-inflammatory tumor microenvironment (TME), which comprises an acellular extracellular matrix and various types of non-neoplastic cells including fibroblasts, immune cells, and adipocytes, underscoring the critical need to delineate the bidirectional signaling interplay between PDAC cells and the TME in order to develop novel therapeutic strategies. The impact of tumor-cell KRAS signaling on various cell types in the TME has been well covered by several reviews. In this article, we critically reviewed evidence, including work from our group, on how the feedback inflammatory signals from the TME impact and synergize with oncogenic KRAS signaling in PDAC cells, ultimately augmenting their malignant behavior. We discussed past and ongoing clinical trials that target key inflammatory pathways in PDAC and highlight lessons to be learned from outcomes. Lastly, we provided our perspective on the future of developing therapeutic strategies for PDAC through understanding the breadth and complexity of KRAS and the inflammatory signaling network.

Second-Generation Jak2 Inhibitors for Advanced Prostate Cancer: Are We Ready for Clinical Development?

Simple Summary

Prostate Cancer (PC) is currently estimated to affect 1 in 9 men and is the second leading cause of cancer in men in the US. While androgen deprivation therapy, which targets the androgen receptor, is one of the front-line therapies for advanced PC and for recurrence of organ-confined PC treated with surgery, lethal castrate-resistant PC develops consistently in patients. PC is a multi-focal cancer with different grade carcinoma areas presenting simultaneously. Jak2-Stat5 signaling pathway has emerged as a potentially highly effective molecular target in PCs with positive areas for activated Stat5 protein. Activated Jak2-Stat5 signaling can be readily targeted by the second-generation Jak2-inhibitors that have been developed for myeloproliferative and autoimmune disorders and hematological malignancies. In this review, we analyze and summarize the Jak2 inhibitors that are currently in preclinical and clinical development.

Abstract

Androgen deprivation therapy (ADT) for metastatic and high-risk prostate cancer (PC) inhibits growth pathways driven by the androgen receptor (AR). Over time, ADT leads to the emergence of lethal castrate-resistant PC (CRPC), which is consistently caused by an acquired ability of tumors to re-activate AR. This has led to the development of second-generation anti-androgens that more effectively antagonize AR, such as enzalutamide (ENZ). However, the resistance of CRPC to ENZ develops rapidly. Studies utilizing preclinical models of PC have established that inhibition of the Jak2-Stat5 signaling leads to extensive PC cell apoptosis and decreased tumor growth. In large clinical cohorts, Jak2-Stat5 activity predicts PC progression and recurrence. Recently, Jak2-Stat5 signaling was demonstrated to induce ENZ-resistant PC growth in preclinical PC models, further emphasizing the importance of Jak2-Stat5 for therapeutic targeting for advanced PC. The discovery of the Jak2V617F somatic mutation in myeloproliferative disorders triggered the rapid development of Jak1/2-specific inhibitors for a variety of myeloproliferative and auto-immune disorders as well as hematological malignancies. Here, we review Jak2 inhibitors targeting the mutated Jak2V617F vs. wild type (WT)-Jak2 that are currently in the development pipeline. Among these 35 compounds with documented Jak2 inhibitory activity, those with potency against WT-Jak2 hold strong potential for advanced PC therapy.

A novel phosphoproteomic landscape evoked in response to type I interferon in the brain and in glial cells

BACKGROUND

Type I interferons (IFN-I) are key responders to central nervous system infection and injury and are also increased in common neurodegenerative diseases. Their effects are primarily mediated via transcriptional regulation of several hundred interferon-regulated genes. In addition, IFN-I activate several kinases including members of the MAPK and PI3K families. Yet, how changes to the global protein phosphoproteome contribute to the cellular response to IFN-I is unknown.

METHODS

The cerebral phosphoproteome of mice with brain-targeted chronic production of the IFN-I, IFN-α, was obtained. Changes in phosphorylation were analyzed by ontology and pathway analysis and kinase enrichment predictions. These were verified by phenotypic analysis, immunohistochemistry and immunoblots. In addition, primary murine microglia and astrocytes, the brain's primary IFN-I-responding cells, were acutely treated with IFN-α and the global phosphoproteome was similarly analyzed.

RESULTS

We identified widespread protein phosphorylation as a novel mechanism by which IFN-I mediate their effects. In our mouse model for IFN-I-induced neurodegeneration, protein phosphorylation, rather than the proteome, aligned with the clinical hallmarks and pathological outcome, including impaired development, motor dysfunction and seizures. In vitro experiments revealed extensive and rapid IFN-I-induced protein phosphorylation in microglia and astrocytes. Response to acute IFN-I stimulation was independent of gene expression and mediated by a small number of kinase families. The changes in the phosphoproteome affected a diverse range of cellular processes and functional analysis suggested that this response induced an immediate reactive state and prepared cells for subsequent transcriptional responses.

CONCLUSIONS

Our studies reveal a hitherto unappreciated role for changes in the protein phosphorylation landscape in cellular responses to IFN-I and thus provide insights for novel diagnostic and therapeutic strategies for neurological diseases caused by IFN-I.

The spliceosome factor sart3 regulates hematopoietic stem/progenitor cell development in zebrafish through the p53 pathway

Hematopoietic stem cells (HSCs) possess the potential for self-renew and the capacity, throughout life, to differentiate into all blood cell lineages. Yet, the mechanistic basis for HSC development remains largely unknown. In this study, we characterized a zebrafish smu471 mutant with hematopoietic stem/progenitor cell (HSPC) defects and found that sart3 was the causative gene. RNA expression profiling of the sart3^smu471 mutant revealed spliceosome and p53 signaling pathway to be the most significantly enriched pathways in the sart3^smu471 mutant. Knock down of p53 rescued HSPC development in the sart3^smu471 mutant. Interestingly, the p53 inhibitor, mdm4, had undergone an alternative splicing event in the mutant. Restoration of mdm4 partially rescued HSPC deficiency. Thus, our data suggest that HSPC proliferation and maintenance require sart3 to ensure the correct splicing and expression of mdm4, so that the p53 pathway is properly inhibited to prevent definitive hematopoiesis failure. This study expands our knowledge of the regulatory mechanisms that impact HSPC development and sheds light on the mechanistic basis and potential therapeutic use of sart3 in spliceosome-mdm4-p53 related disorders.

Out of Control: The Role of the Ubiquitin Proteasome System in Skeletal Muscle during Inflammation

The majority of critically ill intensive care unit (ICU) patients with severe sepsis develop ICU-acquired weakness (ICUAW) characterized by loss of muscle mass, reduction in myofiber size and decreased muscle strength leading to persisting physical impairment. This phenotype results from a dysregulated protein homeostasis with increased protein degradation and decreased protein synthesis, eventually causing a decrease in muscle structural proteins. The ubiquitin proteasome system (UPS) is the predominant protein-degrading system in muscle that is activated during diverse muscle atrophy conditions, e.g., inflammation. The specificity of UPS-mediated protein degradation is assured by E3 ubiquitin ligases, such as atrogin-1 and MuRF1, which target structural and contractile proteins, proteins involved in energy metabolism and transcription factors for UPS-dependent degradation. Although the regulation of activity and function of E3 ubiquitin ligases in inflammation-induced muscle atrophy is well perceived, the contribution of the proteasome to muscle atrophy during inflammation is still elusive. During inflammation, a shift from standard- to immunoproteasome was described; however, to which extent this contributes to muscle wasting and whether this changes targeting of specific muscular proteins is not well described. This review summarizes the function of the main proinflammatory cytokines and acute phase response proteins and their signaling pathways in inflammation-induced muscle atrophy with a focus on UPS-mediated protein degradation in muscle during sepsis. The regulation and target-specificity of the main E3 ubiquitin ligases in muscle atrophy and their mode of action on myofibrillar proteins will be reported. The function of the standard- and immunoproteasome in inflammation-induced muscle atrophy will be described and the effects of proteasome-inhibitors as treatment strategies will be discussed.

A Novel Regulatory Player in the Innate Immune System: Long Non-Coding RNAs

Long non-coding RNAs (lncRNAs) represent crucial transcriptional and post-transcriptional gene regulators during antimicrobial responses in the host innate immune system. Studies have shown that lncRNAs are expressed in a highly tissue- and cell-specific- manner and are involved in the differentiation and function of innate immune cells, as well as inflammatory and antiviral processes, through versatile molecular mechanisms. These lncRNAs function via the interactions with DNA, RNA, or protein in either cis or trans pattern, relying on their specific sequences or their transcriptions and processing. The dysregulation of lncRNA function is associated with various human non-infectious diseases, such as inflammatory bowel disease, cardiovascular diseases, and diabetes mellitus. Here, we provide an overview of the regulation and mechanisms of lncRNA function in the development and differentiation of innate immune cells, and during the activation or repression of innate immune responses. These elucidations might be beneficial for the development of therapeutic strategies targeting inflammatory and innate immune-mediated diseases.

The Cyclin-Dependent Kinase 8 (CDK8) Inhibitor DCA Promotes a Tolerogenic Chemical Immunophenotype in CD4+ T Cells via a Novel CDK8-GATA3-FOXP3 Pathway

Immune health requires innate and adaptive immune cells to engage precisely balanced pro- and anti-inflammatory forces. We employ the concept of chemical immunophenotypes to classify small molecules functionally or mechanistically according to their patterns of effects on primary innate and adaptive immune cells. The high-specificity, low-toxicity cyclin-dependent kinase 8 (CDK8) inhibitor 16-didehydro-cortistatin A (DCA) exerts a distinct tolerogenic profile in both innate and adaptive immune cells. DCA promotes regulatory T cells (Treg) and Th2 differentiation while inhibiting Th1 and Th17 differentiation in both murine and human cells. This unique chemical immunophenotype led to mechanistic studies showing that DCA promotes Treg differentiation in part by regulating a previously undescribed CDK8-GATA3-FOXP3 pathway that regulates early pathways of Foxp3 expression. These results highlight previously unappreciated links between Treg and Th2 differentiation and extend our understanding of the transcription factors that regulate Treg differentiation and their temporal sequencing. These findings have significant implications for future mechanistic and translational studies of CDK8 and CDK8 inhibitors.

DUOX2, a New Biomarker for Disseminated Gastric Cancer's Response to Low Dose Radiation in Mice

Treatment options are rather limited for gastrointestinal cancer patients whose disease has disseminated into the intra-abdominal cavity. Here, we designed pre-clinical studies to evaluate the potential application of chemopotentiation by Low Dose Fractionated Radiation Therapy (LDFRT) for disseminated gastric cancer and evaluate the role of a likely biomarker, Dual Oxidase 2 (DUOX2). Nude mice were injected orthotopically with human gastric cancer cells expressing endogenous or reduced levels of DUOX2 and randomly assigned to four treatment groups: 1; vehicle alone, 2; modified regimen of docetaxel, cisplatin and 5'-fluorouracil (mDCF) for three consecutive days, 3; Low Dose- Whole Abdomen Radiation Therapy (LD-WART) (5 fractions of 0.15 Gy in three days), 4; mDCF and LD-WART. The combined regimen increased the odds of preventing cancer dissemination (mDCF + LD-WART OR = 4.16; 80% CI = 1.0, 17.29) in the DUOX2 positive tumors, while tumors expressing lower DUOX2 levels were more responsive to mDCF alone with no added benefit from LD-WART. The molecular mechanisms underlying DUOX2 effects in response to the combined regimen include NF-κB upregulation. These data are particularly important since our study indicates that about 33% of human stomach adenocarcinoma do not express DUOX2. DUOX2 thus seems a likely biomarker for potential clinical application of chemopotentiation by LD-WART.

Channeling macrophage polarization by rocaglates increases macrophage resistance to Mycobacterium tuberculosis

Macrophages contribute to host immunity and tissue homeostasis via alternative activation programs. M1-like macrophages control intracellular bacterial pathogens and tumor progression. In contrast, M2-like macrophages shape reparative microenvironments that can be conducive for pathogen survival or tumor growth. An imbalance of these macrophages phenotypes may perpetuate sites of chronic unresolved inflammation, such as infectious granulomas and solid tumors. We have found that plant-derived and synthetic rocaglates sensitize macrophages to low concentrations of the M1-inducing cytokine IFN-gamma and inhibit their responsiveness to IL-4, a prototypical activator of the M2-like phenotype. Treatment of primary macrophages with rocaglates enhanced phagosome-lysosome fusion and control of intracellular mycobacteria. Thus, rocaglates represent a novel class of immunomodulators that can direct macrophage polarization toward the M1-like phenotype in complex microenvironments associated with hypofunction of type 1 and/or hyperactivation of type 2 immunity, e.g., chronic bacterial infections, allergies, and, possibly, certain tumors.

Post-translational modifications in T cells in systemic erythematosus lupus

Systemic erythematosus lupus (SLE) is a classic autoimmune disease characterized by multiple autoantibodies and immune-mediated tissue damage. The aetiology of this disease is still unclear. A new drug, belimumab, which acts against the B-lymphocyte stimulator (BLyS), can effectively improve the condition of SLE patients, but it cannot resolve all SLE symptoms. The discovery of novel, precise therapeutic targets is urgently needed. It is well known that abnormal T-cell function is one of the most crucial factors contributing to the pathogenesis of SLE. Protein post-translational modifications (PTMs), including phosphorylation, glycosylation, acetylation, methylation, ubiquitination and SUMOylation have been emphasized for their roles in activating protein activity, maintaining structural stability, regulating protein-protein interactions and mediating signalling pathways, in addition to other biological functions. Summarizing the latest data in this area, this review focuses on the potential roles of diverse PTMs in regulating T-cell function and signalling pathways in SLE pathogenesis, with the goal of identifying new targets for SLE therapy.

A Michael Acceptor Analogue, SKSI-0412, Down-Regulates Inflammation and Proliferation Factors through Suppressing Signal Transducer and Activator of Transcription 3 Signaling in IL-17A-Induced Human Keratinocyte

The activation of signal transducer and activator of transcription 3 (STAT3), as well as up-regulation of cytokines and growth factors to promote STAT3 activation, have been found in the epidermis of psoriatic lesions. Recently, a series of synthetic compounds possessing the Michael acceptor have been reported as STAT3 inhibitors by covalently binding to cysteine of STAT3. We synthesized a Michael acceptor analog, SKSI-0412, and confirmed the binding affinity between STAT3 and SKSI-0412. We hypothesized that the SKSI-0412 can inhibit interleukin (IL)-17A-induced inflammation in keratinocytes. The introduction of IL-17A increased the phosphorylation of STAT3 in keratinocytes, whereas the inactivation of STAT3 by SKSI-0412 reduced IL-17A-induced STAT3 phosphorylation and IκBζ expression. In addition, human β defensin-2 and S100A7, which are regulated by IκBζ, were significantly decreased with SKSI-0412 administration. We also confirmed that SKSI-0412 regulates cell proliferation, which is the major phenotype of psoriasis. Based on these results, we suggest targeting STAT3 with SKSI-0412 as a novel therapeutic strategy to regulate IL-17A-induced psoriatic inflammation in keratinocytes.

The anti-parallel dimer binding interface in STAT3 transcription factor is required for the inactivation of cytokine-mediated signal transduction

Signal transducer and activator of transcription 3 (STAT3) gain-of-function mutations have been widely reported in patients with tumors and haematological malignancies. However, the molecular mechanisms of these pathogenic mutations remain largely uninvestigated. In this study, we have extensively characterized two STAT3 missense mutations, namely a valine-to-alanine exchange in the amino-terminal region (V77A) and a phenylalanine-to-alanine substitution (F174A) in the coiled-coil domain. The two mutants displayed elevated levels of tyrosine phosphorylation, premature nuclear accumulation, and differential transcriptional responses following stimulation of cells with interleukin-6 and interferon-ɣ. In line with their hyper-phosphorylated status, a greater fraction of V77A and F174A proteins was bound to DNA on high-affinity binding sites termed sis-inducible elements (SIE) as compared to the wild-type (WT) protein. Unexpectedly, these STAT3 variants displayed similar kinetics using in vitro kinase and dephosphorylation assays performed with recombinant Janus kinase 2 (JAK2) and Tc45 phosphatase, respectively. This indicates that the two mutations neither affected the susceptibility of STAT3 to the enzymatic activity of the inactivating tyrosine phosphatase nor to the activating kinase. However, experiments triggering intracellular dephosphorylation by the addition of the tyrosine-kinase inhibitor staurosporine to cytokine-pretreated cells showed that the two mutants partially resisted dephosphorylation. From these data, we propose that the F174A missense mutation hinders the exchange from a parallel to an anti-parallel dimer conformation, thereby increasing the ratio of tyrosine-phosphorylated molecules bound to DNA and enhancing gene-dependent transcription. Our data point to the physiological importance of the anti-parallel dimer conformation in the inactivation of the cytokine-induced STAT3 signalling pathway.