Nuclear Translocation Of Signal Transducer And Activator Of Transcription 3 Research Articles

Type I gamma phosphatidylinositol phosphate 5-kinase i5 controls cell sensitivity to interferon

The interferon signaling pathway is critical for host defense by serving diverse functions in both innate and adaptive immune responses. Here, we show that type I gamma phosphatidylinositol phosphate 5-kinase i5 (PIPKIγi5), an enzyme that synthesizes phosphatidylinositol-4,5-bisphosphate (PI4,5P2), controls the sensitivity to interferon in both human and mouse cells. PIPKIγi5 directly binds to the interferon-gamma (IFN-γ) downstream effector signal transducer and activator of transcription 1 (STAT1), which suppresses the STAT1 dimerization, IFN-γ-induced STAT1 nuclear translocation, and transcription of IFN-γ-responsive genes. Depletion of PIPKIγi5 significantly enhances IFN-γ signaling and strengthens an antiviral response. In addition, PIPKIγi5-synthesized PI4,5P2 can bind to STAT1 and promote the PIPKIγi5-STAT1 interaction. Similar to its interaction with STAT1, PIPKIγi5 is capable of interacting with other members of the STAT family, including STAT2 and STAT3, thereby suppressing the expression of genes mediated by these transcription factors. These findings identify the function of PIPKIγi5 in immune regulation.

Magnesium lithospermate B enhances the potential of human-induced pluripotent stem cell-derived cardiomyocytes for myocardial repair.

We previously reported that activation of the cell cycle in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) enhances their remuscularization capacity after human cardiac muscle patch transplantation in infarcted mouse hearts. Herein, we sought to identify the effect of magnesium lithospermate B (MLB) on hiPSC-CMs during myocardial repair using a myocardial infarction (MI) mouse model. In C57BL/6 mice, MI was surgically induced by ligating the left anterior descending coronary artery. The mice were randomly divided into five groups (n = 10 per group); a MI group (treated with phosphate-buffered saline only), a hiPSC-CMs group, a MLB group, a hiPSC-CMs + MLB group, and a Sham operation group. Cardiac function and MLB therapeutic efficacy were evaluated by echocardiography and histochemical staining 4 weeks after surgery. To identify the associated mechanism, nuclear factor (NF)-κB p65 and intercellular cell adhesion molecule-1 (ICAM1) signals, cell adhesion ability, generation of reactive oxygen species, and rates of apoptosis were detected in human umbilical vein endothelial cells (HUVECs) and hiPSC-CMs. After 4 weeks of transplantation, the number of cells that engrafted in the hiPSC-CMs + MLB group was about five times higher than those in the hiPSC-CMs group. Additionally, MLB treatment significantly reduced tohoku hospital pediatrics-1 (THP-1) cell adhesion, ICAM1 expression, NF-κB nuclear translocation, reactive oxygen species production, NF-κB p65 phosphorylation, and cell apoptosis in HUVECs cultured under hypoxia. Similarly, treatment with MLB significantly inhibited the apoptosis of hiPSC-CMs via enhancing signal transducer and activator of transcription 3 (STAT3) phosphorylation and B-cell lymphoma-2 (BCL2) expression, promoting STAT3 nuclear translocation, and downregulating BCL2-Associated X, dual specificity phosphatase 2 (DUSP2), and cleaved-caspase-3 expression under hypoxia. Furthermore, MLB significantly suppressed the production of malondialdehyde and lactate dehydrogenase and the reduction in glutathione content induced by hypoxia in both HUVECs and hiPSC-CMs in vitro. MLB significantly enhanced the potential of hiPSC-CMs in repairing injured myocardium by improving endothelial cell function via the NF-κB/ICAM1 pathway and inhibiting hiPSC-CMs apoptosis via the DUSP2/STAT3 pathway.

Natural bioactive compounds and STAT3 against hepatocellular carcinoma: An update

Hepatocellular carcinoma (HCC) is a challenging and very fatal liver cancer. The signal transducer and activator of transcription 3 (STAT3) pathway is a crucial regulator of tumor development and are ubiquitously active in HCC. Therefore, targeting STAT3 has emerged as a promising approach for preventing and treating HCC. Various natural bioactive compounds (NBCs) have been proven to target STAT3 and have the potential to prevent and treat HCC as STAT3 inhibitors. Numerous kinds of STAT3 inhibitors have been identified, including small molecule inhibitors, peptide inhibitors, and oligonucleotide inhibitors. Due to the undesirable side effects of the conventional therapeutic drugs against HCC, the focus is shifted to NBCs derived from plants and other natural sources. NBCs can be broadly classified into the categories of terpenes, alkaloids, carotenoids, and phenols. Most of the compounds belong to the family of terpenes, which prevent tumorigenesis by inhibiting STAT3 nuclear translocation. Further, through STAT3 inhibition, terpenes downregulate matrix metalloprotease 2 (MMP2), matrix metalloprotease 9 (MMP9) and vascular endothelial growth factor (VEGF), modulating metastasis. Terpenes also suppress the anti-apoptotic proteins and cell cycle markers. This review provides comprehensive information related to STAT3 abrogation by NBCs in HCC with in vitro and in vivo evidences.

Synthesis and Biological Evaluation of Novel 2-Amino-1,4-Naphthoquinone Amide-Oxime Derivatives as Potent IDO1/STAT3 Dual Inhibitors with Prospective Antitumor Effects.

Indoleamine-2,3-dioxygenase 1 (IDO1) and signal transducer and activator of transcription 3 (STAT3) have emerged as significant targets in the tumor microenvironment for cancer therapy. In this study, we synthesized three novel 2-amino-1,4-naphthoquinone amide-oxime derivatives and identified them as dual inhibitors of IDO1 and STAT3. The representative compound NK3 demonstrated effective binding to IDO1 and exhibited good inhibitory activity (hIDO1 IC50 = 0.06 μM), leading to its selection for further investigation. The direct interactions between compound NK3 and IDO1 and STAT3 proteins were confirmed through surface plasmon resonance analysis. A molecular docking study of compound NK3 revealed key interactions between NK3 and IDO1, with the naphthoquinone-oxime moiety coordinating with the heme iron. In the in vitro anticancer assay, compound NK3 displayed potent antitumor activity against selected cancer cell lines and effectively suppressed nuclear translocation of STAT3. Moreover, in vivo assays conducted on CT26 tumor-bearing Balb/c mice and an athymic HepG2 xenograft model revealed that compound NK3 exhibited potent antitumor activity with low toxicity relative to 1-methyl-L-tryptophan (1-MT) and doxorubicin (DOX). Overall, these findings provided evidence that the dual inhibitors of IDO1 and STAT3 may offer a promising avenue for the development of highly effective drug candidates for cancer therapy.

A traditional prescription comprising Astragali Radix and Schisandra chinensis Fructus induces apoptosis and protective autophagy in hepatocellular carcinoma cells

Ethnopharmacological relevanceHepatocellular carcinoma (HCC) poses a growing challenge to global health efforts. The 5-year survival rate of HCC patients is still dismal. A traditional prescription Qi-Wei-Wan (QWW) comprising Astragali Radix and Schisandra chinensis Fructus has traditionally been used for HCC treatment according to traditional Chinese medicine theory, but the pharmacological basis is not clear. Aim of the studyThis study aims to investigate the anti-HCC effects of an ethanolic extract of QWW (hereafter, QWWE) and the mechanism of action. Materials and methodsAn UPLC-Q-TOF-MS/MS method was developed to control the quality of QWWE. Two human HCC cell lines (HCCLM3 and HepG2) and a HCCLM3 xenograft mouse model were employed to investigate the anti-HCC effects of QWWE. The anti-proliferative effect of QWWE in vitro was determined by MTT, colony formation and EdU staining assays. Apoptosis and protein levels were examined by flow cytometry and Western blotting, respectively. Nuclear presence of signal transducer and activator of transcription 3 (STAT3) was examined by immunostaining. Transient transfection of pEGFP-LC3 and STAT3C plasmids was performed to assess autophagy and determine the involvement of STAT3 signaling in QWWE’s anti-HCC effects, respectively. ResultsWe found that QWWE inhibited the proliferation of and triggered apoptosis in HCC cells. Mechanistically, QWWE inhibited the activation of SRC and STAT3 at Tyr416 and Tyr705, respectively; inhibited the nuclear translocation of STAT3; lowered Bcl-2 protein levels, while increased Bax protein levels in HCC cells. Over-activating STAT3 attenuated the cytotoxic and apoptotic effects of QWWE in HCC cells. Moreover, QWWE induced autophagy in HCC cells by inhibiting mTOR signaling. Blocking autophagy with autophagy inhibitors (3-methyladenine and chloroquine) enhanced the cytotoxicity, apoptotic effect and the inhibitory effect on STAT3 activation of QWWE. Intragastric administration of QWWE at 10 mg/kg and 20 mg/kg potently repressed tumor growth and inhibited STAT3 and mTOR signaling in tumor tissues, but did not significantly affect mouse body weight. ConclusionQWWE exhibited potent anti-HCC effects. Inhibiting the STAT3 signaling pathway is involved in QWWE-mediated apoptosis, while blocking mTOR signaling contributes to QWWE-mediated autophagy induction. Blockade of autophagy enhanced the anti-HCC effects of QWWE, indicating that the combination of an autophagy inhibitor and QWWE might be a promising therapeutic strategy for HCC management. Our findings provide pharmacological justifications for the traditional use of QWW in treating HCC.

Loss of miR-26b-5p promotes gastric cancer progression via miR-26b-5p-PDE4B/CDK8-STAT3 feedback loop

BackgroundChronic inflammation is a well-known risk factor for the development of gastric cancer (GC). Nevertheless, the molecular mechanisms underlying inflammation-related GC progression are incompletely defined.MethodsBioinformatic analysis was performed based on data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO), and the expression of miR-26b-5p in GC cells and tissues was validated by quantitative real-time PCR (qRT-PCR). Cell proliferation was examined through Cell Counting Kit-8 (CCK8), 5-Ethynyl-2’-deoxyuridine (EdU), colony formation, flow cytometry, and tumor xenografts. Correlation between miR-26b-5p and Cyclin dependent kinase 8 (CDK8) or Phosphodiesterase 4B (PDE4B) was analyzed by dual-luciferase reporter assays, qRT-PCR, and Western blot. The effect of miR-26b-5p on the Signal transducer and activator of transcription 3 (STAT3) pathway was investigated using Western blot, immunofluorescence (IF), and immunohistochemistry (IHC). The impact of STAT3 on miR-26b-5p was determined by dual-luciferase reporter assays and qRT-PCR.ResultsThe expression of miR-26b-5p was significantly downregulated in Helicobacter Pylori (H. pylori)-infected GC cells. The decreased expression of miR-26b-5p was also detected in GC cells and tissues compared to normal gastric epithelium cells (GES1) and normal adjacent gastric tissues. The low expression of miR-26b-5p promoted GC proliferation in vitro and in vivo and was related to the poor outcome of GC patients. In terms of mechanism, miR-26b-5p directly targeted PDE4B and CDK8, resulting in decreased phosphorylation and nuclear translocation of STAT3, which was associated with the regulation of GC proliferation by miR-26b-5p. Notably, miR-26b-5p was transcriptionally suppressed by STAT3, thus forming the miR-26b-5p-PDE4B/CDK8-STAT3 positive feedback loop.ConclusionThe newly identified miR-26b-5p-PDE4B/CDK8-STAT3 feedback loop plays an important role in inflammation-related GC progression and may serve as a promising therapeutic target for GC.

096 IL23-induced STAT3 nuclear translocation in MAIT cells at baseline is a candidate biomarker of response to biologics targeting the IL23/IL17 axis

The role of the interleukin (IL)23/IL17 axis in psoriasis is well-established and has led to the development of biologics targeting IL23 and IL17A. Ustekinumab, targets the IL12/23p40 shared subunit and blocks IL23-receptor interactions, restricting the activation of Signal Transducer and Activator of Transcription 3 (STAT3) in T cells, and IL17A production. Secukinumab blocks IL17A binding to its receptor, preventing keratinocyte activation. Although both biologics are effective, clinical response varies, highlighting the need to identify biomarkers predictive of response.

Atorvastatin ameliorates lipid overload-induced mitochondrial dysfunction and myocardial hypertrophy by decreasing fatty acid oxidation through inactivation of the p-STAT3/CPT1 pathway

Although statins are shown to have cardiac pleiotropic effects independent of lowering cholesterol, the underlying mechanism remains unclear. Mitochondrial dysfunction induced by increased fatty acid oxidation (FAO) is the culprit in the development of cardiac hypertrophy and dysfunction. This study was to explore whether the cardiac pleiotropic effects of atorvastatin were associated with FAO regulation, with a specific focus on carnitine palmitoyltransferase 1 (CPT1). High-fat diet (HFD)-fed mice and palmitic acid (PA)-stimulated neonatal rat primary cardiomyocytes (NRCMs) were treated with atorvastatin, with or without FAO modulators, signal transducer and activator of transcription 3 (STAT3) agonist, and inhibitor. Atorvastatin (3 mg/kg) did not reduce serum cholesterol levels in HFD-fed mice but ameliorated mitochondrial dysfunction and cardiac hypertrophy. In vitro, atorvastatin and the FAO inhibitor alleviated PA-induced mitochondrial dysfunction and cardiomyocyte hypertrophy. However, the FAO enhancer eliminated atorvastatin’s protective effects. Furthermore, atorvastatin decreased CPT1 and FAO levels and prevented STAT3 phosphorylation and nuclear translocation. STAT3 inhibitor had the same inhibitory effects as atorvastatin on CPT1, FAO levels, and cardiomyocyte hypertrophy, whereas STAT3 agonist disrupted these effects of atorvastatin. Our results demonstrate that atorvastatin decreases myocardial FAO by inactivating the p-STAT3/CPT1 signaling pathway, which improves lipid overload-induced mitochondrial dysfunction and cardiac hypertrophy in a cholesterol-independent manner. This is the first study to explore the cardiac pleiotropic effects of atorvastatin with respect to FAO. However, whether atorvastatin regulates FAO in the cardiac hypertrophy model induced by other variables has not been investigated in this work, and this is expected to be performed in the future.

SENP1 Protects Against Pressure Overload-Induced Cardiac Remodeling and Dysfunction Via Inhibiting STAT3 Signaling.

Background SENP1 (sentrin/small ubiquitin-like modifier-specific protease 1) has emerged as a significant modulator involved in the pathogenesis of a variety of human diseases, especially cancer. However, the regulatory roles of SENP1 in cardiovascular biology and diseases remain controversial. Our current study aims to clarify the function and regulation of SENP1 in pressure overload-induced cardiac remodeling and dysfunction. Methods and Results We used a preclinical mouse model of transverse aortic constriction coupled with in vitro studies in neonatal rat cardiomyocytes to study the role of SENP1 in cardiac hypertrophy. Gene delivery system was used to knockdown or overexpress SENP1 in vivo. Here, we observed that SENP1 expression was significantly augmented in murine hearts following transverse aortic constriction as well as neonatal rat cardiomyocytes treated with phenylephrine or angiotensin II. Cardiac-specific SENP1 knockdown markedly exacerbated transverse aortic constriction-induced cardiac hypertrophy, systolic dysfunction, fibrotic response, and cellular apoptosis. In contrast, adenovirus-mediated SENP1 overexpression in murine myocardium significantly attenuated cardiac remodeling and dysfunction following chronic pressure overload. Mechanistically, JAK2 (Janus kinase 2) and STAT3 (signal transducer and activator of transcription 3) acted as new interacting partners of SENP1 in this process. SENP1-JAK2/STAT3 interaction suppressed STAT3 nuclear translocation and activation, ultimately inhibiting the transcription of prohypertrophic genes and the initiation of hypertrophic response. Furthermore, cardiomyocyte-specific STAT3 knockout mice were generated to validate the underlying mechanisms, and the results showed that STAT3 ablation blunted the cardiac hypertrophy-promoting effects of SENP1 deficiency. Additionally, pharmacological inhibition of SENP1 by Momordin Ic amplified cardiac remodeling post-transverse aortic constriction. Conclusions Our study provided evidence that SENP1 protected against pressure overload-induced cardiac remodeling and dysfunction via inhibiting STAT3 signaling. SENP1 supplementation might constitute a new promising treatment against cardiac hypertrophy. Notably, cardiovascular side effects should be seriously considered while applying systemic SENP1 blockers to suppress tumors.

Exposure to short-chain chlorinated paraffins induces astrocyte activation via JAK2/STAT3 signaling pathway

In the last few decades, short-chain chlorinated paraffins (SCCPs) have become the most heavily produced monomeric organohalogen compounds, and have been reported to induce multiple organ toxicity. However, the effects of SCCPs on the central nervous system are unknown. In the present study, we show that SCCP exposure induced astrocyte proliferation and increased the expression of two critical markers of astrocyte activation, glial fibrillary acidic protein and inducible nitric oxide synthase, in vivo and in vitro. SCCP exposure also increased inflammatory factory gene expression. Moreover, SCCP treatment triggered Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signalling, as shown by increased phosphorylation and STAT3 translocation to the nucleus. Both JAK2 and STAT3 inhibition effectively attenuated SCCP-induced astrocyte activation. Finally, JAK2 inhibition significantly rescued STAT3 phosphorylation and nuclear translocation. Taken together, JAK2/STAT3 pathway activation contributed to SCCP-induced astrocyte activation. These data will help elucidate the molecular mechanism underlying SCCP-induced neurotoxicity.

High-fat diet induced cyclophilin B enhances STAT3/lncRNA-PVT1 feedforward loop and promotes growth and metastasis in colorectal cancer

High-fat diet (HFD) has been implicated to promote colorectal cancer (CRC). Recently, oncogene Cyclophilin B (CypB) is reported to be induced by cholesterol. However, the role of CypB in CRC carcinogenesis and metastasis associated with HFD remains unknown. In the present study, we showed that HFD-induced CypB enhances proliferation and metastasis through an inflammation-driven circuit, including Signal Transducer and Activator of Transcription 3 (STAT3)-triggered transcription of lncRNA-PVT1, and its binding with CypB that promotes activation of STAT3. CypB was found to be upregulated in CRC, which was correlated with elevated body mass index and poor prognosis. HFD induced CypB expression and proinflammatory cytokines in colon of mice. Besides, CypB restoration facilitated growth, invasion and metastasis in CRC cells both in vitro and in vivo. Moreover, RIP sequencing data identified lncRNA-PVT1 as a functional binding partner of CypB. Mechanistically, PVT1 increased the phosphorylation and nuclear translocation of STAT3 in response to IL-6, through directly interaction with CypB, which impedes the binding of Suppressors Of Cytokine Signalling 3 (SOCS3) to STAT3. Furthermore, STAT3 in turn activated PVT1 transcription through binding to its promoter, forming a regulatory loop. Finally, this CypB/STAT3/PVT1 axis was verified in TCGA datasets and CRC tissue arrays. Our data revealed that CypB linked HFD and CRC malignancy by enhancing the CypB/STAT3/PVT1 feedforward axis and activation of STAT3.

Cirsiliol regulates mitophagy in colon cancer cells via STAT3 signaling

BackgroundMitophagy is a type of selective autophagy for dysfunctional mitochondria and plays a key role in tumorigenesis and cancer progression. However, whether mitophagy plays a role in colon cancer remains unclear. Cirsiliol is a natural product and has been found to exert anti-cancer effects in multiple tumors. The effects of cirsiliol in the tumorigenesis and progression of colon cancer remain unknown.MethodsCCK8 assay, plate cloning assay, and cell scratch assay were performed to determine cell viability, colony formation, and wound healing abilities of HCT116 and SW480 cells. JC-1 staining, H2DCFDA staining, and Mito-Tracker Red staining were carried out to evaluate mitochondrial membrane potential (Δψm), intracellular reactive oxygen species (ROS) level, and mitochondrial morphology. Molecular docking technology was utilized to predict interaction of cirsiliol and signal transducer and activator of transcription 3 (STAT3). Immunofluorescence staining was used to measure nuclear translocation of STAT3. The protein levels of phosphorylated STAT3 (Y705), total STAT3, and mitophagy proteins were detected by western blot.ResultsIn this study, we first found that cirsiliol inhibited cell viability, colony formation, and wound healing abilities of HCT116 and SW480 colon cancer cells. Moreover, cirsiliol suppressed Δψm, increased ROS production, and disrupted mitochondrial morphology via inhibiting the levels of mitophagy proteins including PINK1, Parkin, BNIP3, and FUNDC1. Application of mitophagy activator improved the levels of mitophagy-related proteins, and ameliorated Δψm and ROS levels. According to the result of molecular docking, we found that cirsiliol potentially bound to the SH2 domain of STAT3, the key domain for the functional activation of STAT3. Moreover, it was found that cirsiliol inhibited constitutive and IL‑6‑induced STAT3 phosphorylation and nuclear translocation by western blot and immunofluorescence analysis. Comparing with cirsiliol group, we found that overexpression of STAT3 restored the expressions of mitophagy proteins.ConclusionsCirsiliol targets STAT3 to inhibit colon cancer cell proliferation by regulating mitophagy.

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.

Pulsed Electromagnetic Fields Protect Against Brain Ischemia by Modulating the Astrocytic Cholinergic Anti-inflammatory Pathway.

Neuroinflammation is one of the most important pathological processes following brain ischemia. Pulsed electromagnetic fields (PEMFs) protect against brain ischemia, but their role in regulating neuroinflammation remains unclear. In the present study, we investigated the biological effects of PEMF exposure on brain ischemia-induced neuroinflammation through the astrocytic cholinergic anti-inflammatory pathway. PEMF exposure reduced the activation of astrocytes and neuroinflammation following brain ischemia by directly modulating astrocytic injury and inflammatory cytokine release. Inhibition of nicotinic acetylcholine receptor alpha 7 subunit (α7nAChR) by a specific antagonist reversed the regulatory effects of PEMF on astrocytes. Furthermore, negative regulation of signal transducer and activator of transcription 3 (STAT3) by α7nAChR was found to be an important downstream mechanism through which PEMF regulates astrocyte-related neuroinflammation. PEMF suppressed STAT3 phosphorylation and nuclear translocation by activating α7nAChR. These results demonstrate that PEMF exerts anti-inflammatory effects in the context of brain ischemia by modulating astrocytic α7nAChR/STAT3 signaling.

The antimicrobial drug pyrimethamine inhibits STAT3 transcriptional activity by targeting the enzyme dihydrofolate reductase

Cancer is often characterized by aberrant gene expression patterns caused by the inappropriate activation of transcription factors. Signal transducer and activator of transcription 3 (STAT3) is a key transcriptional regulator of many protumorigenic processes and is persistently activated in many types of human cancer. However, like many transcription factors, STAT3 has proven difficult to target clinically. To address this unmet clinical need, we previously developed a cell-based assay of STAT3 transcriptional activity and performed an unbiased and high-throughput screen of small molecules known to be biologically active in humans. We identified the antimicrobial drug pyrimethamine as a novel and specific inhibitor of STAT3 transcriptional activity. Here, we show that pyrimethamine does not significantly affect STAT3 phosphorylation, nuclear translocation, or DNA binding at concentrations sufficient to inhibit STAT3 transcriptional activity, suggesting a potentially novel mechanism of inhibition. To identify the direct molecular target of pyrimethamine and further elucidate the mechanism of action, we used a new quantitative proteome profiling approach called proteome integral solubility alteration coupled with a metabolomic analysis. We identified human dihydrofolate reductase as a target of pyrimethamine and demonstrated that the STAT3-inhibitory effects of pyrimethamine are the result of a deficiency in reduced folate downstream of dihydrofolate reductase inhibition, implicating folate metabolism in the regulation of STAT3 transcriptional activity. This study reveals a previously unknown regulatory node of the STAT3 pathway that may be important for the development of novel strategies to treat STAT3-driven cancers.

Magnolol Induces the Extrinsic/Intrinsic Apoptosis Pathways and Inhibits STAT3 Signaling-Mediated Invasion of Glioblastoma Cells.

Glioblastoma multiforme (GBM) is the most common form of malignant brain tumor, with poor prognosis; the efficacy of current standard therapy for GBM remains unsatisfactory. Magnolol, an herbal medicine from Magnolia officinalis, exhibited anticancer properties against many types of cancers. However, whether magnolol suppresses GBM progression as well as its underlying mechanism awaits further investigation. In this study, we used the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay, apoptosis marker analysis, transwell invasion and wound-healing assays to identify the effects of magnolol on GBM cells. We also validated the potential targets of magnolol on GBM with the GEPIA (Gene Expression Profiling Interactive Analysis) and Western blotting assay. Magnolol was found to trigger cytotoxicity and activate extrinsic/intrinsic apoptosis pathways in GBM cells. Both caspase-8 and caspase-9 were activated by magnolol. In addition, GEPIA data indicated the PKCδ (Protein kinase C delta)/STAT3 (Signal transducer and activator of transcription 3) signaling pathway as a potential target of GBM. Magnolol effectively suppressed the phosphorylation and nuclear translocation of STAT3 in GBM cells. Meanwhile, tumor invasion and migration ability and the associated genes, including MMP-9 (Matrix metalloproteinase-9) and uPA (Urokinase-type plasminogen activator), were all diminished by treatment with magnolol. Taken together, our results suggest that magnolol-induced anti-GBM effect may be associated with the inactivation of PKCδ/STAT3 signaling transduction.

Protective effects of progesterone on pulmonary artery smooth muscle cells stimulated with Interleukin 6 via blocking the shuttling and transcriptional function of STAT3

BackgroundSex hormone paradox is a crucial but unresolved issue in the field of pulmonary artery hypertension (PAH), and is thought to be related to different pathogenic factors. Inflammation is one of pathological mechanisms of PAH development. However, effects of sex hormones on the pulmonary vasculature under the condition of inflammation are still elusive. MethodsInterleukin-6 (IL-6) was used as a representative inflammatory stimulator. Effects of 17β-estradiol or progesterone on human pulmonary artery smooth muscle cells (PASMCs) were measured under the condition of IL-6. Cell functions of proliferation and migration were measured by Alarmar Blue, EdU assay, wound-healing assay and transwell chambers. We explored further mechanisms using western blot, immunofluorescence, co-immunoprecipitation, qPCR and chromatin immunoprecipitation. ResultsOur results revealed that IL-6 promoted the proliferation of PASMCs, but progesterone could reverse the adverse effect of IL-6. The protective effect was dependent on progesterone receptor (PGR). By interacting with signal transducer and activator of transcription 3 (STAT3), activated PGR could reduce the IL-6-induced nuclear translocation of STAT3 and prevent STAT3-chromatin binding in PASMCs, leading to the decreased transcription of downstream CCND1 and BCL2. Alternatively, progesterone slightly decreased the phosphorylation of pro-proliferative Erk1/2 and Akt kinases and upregulated the anti-proliferative pSmad1-Id1/2 axis in IL-6-incubated PASMCs. ConclusionsProgesterone played a protective role on PASMCs in the context of IL-6, by blocking the functions of STAT3. Our findings might assist in explaining the clinical phenomenon of better prognosis for women with PAH.

Eriocitrin, a dietary flavonoid suppressed cell proliferation, induced apoptosis through modulation of JAK2/STAT3 and JNK/p38 MAPKs signaling pathway in MCF-7 cells.

Eriocitrin, a lemons flavanone, exhibits several biological properties, antiproliferative, and proapoptotic effects. However,its molecular mechanical action is not entirely clarified. Oxidative stress causes abnormal stimulation of signal transducer and activator of transcription 3 (STAT3) and c-Jun NH2-terminal kinase (JNK), p38 mitogen-activated protein kinases (MAPKs) signaling has been strongly connected with the ruling of cell survival and apoptosis of cancer cells. Herein, we investigated an antiproliferative and proapoptotic effect that Eriocitrin modulates STAT3/MAPKs signaling activation in MCF-7 cells. We noticed that Eriocitrin strongly enhances reactive oxygen species (ROS) generation, alteration of mitochondrial outer membrane potential, and enhances apoptotic morphological changes. Furthermore, Eriocitrin suppressed STAT3 phosphorylation via inhibiting an upstream molecule of JAK2 and Src kinase activation, thereby blocking STAT3 nuclear translocation. Similarly, Eriocitrin causes oxidative stress-mediated JNK/p38 MAPK signaling activation. We confirmed that Eriocitrin induced ROS-mediated apoptosis inhibited by the antioxidant substance of N-acetylcysteine. Eriocitrin induced apoptosis via suppression of STAT3 signaling regulated proteins, activating proapoptotic factors Bax, caspase 7, 8, 9 and suppressing Bcl-2, Bcl-x expression in MCF-7 cells. Overall, these results evidenced that Eriocitrin can affect multiple signaling events associated with tumorigenesis. From this evidence, Eriocitrin, a novel chemotherapeutic agent, can be used to treat breast cancer.

051 STAT3 nuclear translocation in circulating MAIT cells is a potential biomarker of clinical outcome to ustekinumab in psoriasis

Biologic drugs, such as ustekinumab, have significantly transformed psoriasis treatment. Ustekinumab targets the shared interleukin (IL)-12/23p40 subunit, preventing IL-23 from binding to its receptor and blocking translocation of Signal Transducer and Activator of Transcription 3 (STAT3). Although ustekinumab is highly effective, clinical response is variable and there is an unmet need for the identification of biomarkers predictive of response. Here we monitor IL-23-induced STAT3 activation in peripheral blood mononuclear cells (PBMCs) to identify predictive biomarkers of outcome to ustekinumab.

Circ-E2F3 promotes cervical cancer progression by inhibiting microRNA-296-5p and increasing STAT3 nuclear translocation.

Circular RNA E2F transcription factor 3 (circ-E2F3) has been demonstrated to be differentially expressed in some diseases and cancers. However, the role of circ-E2F3 in cervical cancer (CC) progression remains unclear. Therefore, we aimed to elucidate the mechanism of circ-E2F3 regulation of CC progression. Circ-E2F3 expression was determined in CC samples, and its correlation with the clinicopathological characteristics of CC patients and cell biological processes was examined. The interaction among circ-E2F3, microRNA-296-5p (miR-296-5p), and signal transducer and activator of transcription 3 (STAT3) was analyzed by dual luciferase reporter gene and fluorescence in situ hybridization assays. Circ-E2F3-depleted CaSki cells were implanted into nude mice to verify the function of circ-E2F3 in vivo. Circ-E2F3 was upregulated in both CC tissues and cell lines, and this correlated with the clinicopathological features and poor prognosis of CC patients. Moreover, circ-E2F3 promoted the proliferation, invasion, and migration of CC cells and tumor growth in vivo. It was also observed that circ-E2F3 promoted the nuclear translocation of STAT3 through inhibition of miR-296-5p, thus affecting the expression of cyclin D1. Taken together, the key findings of our study demonstrate that circ-E2F3 induces inhibition of miR-296-5p, which triggers activation and nuclear translocation of STAT3 that then upregulates cyclin D1 expression.