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    Luteolin selectively kills STAT3 highly activated gastric cancer cells through enhancing the binding of STAT3 to SHP-1. Song Shiyu,Su Zhonglan,Xu Hui,Niu Mengyuan,Chen Xiufang,Min Haiyan,Zhang Bin,Sun Guibo,Xie Sijing,Wang Hongwei,Gao Qian Cell death & disease The antitumor effect of luteolin, a plant flavonoid, in gastric cancer (GC) cells has not been fully understood. Here we show that luteolin selectively kills STAT3 overactivated GC cells that are often drug resistant. The treatment of luteolin in these GC cells significantly inhibited STAT3 phosphorylation and reduced the expression of STAT3 targeting gene Mcl-1, Survivin and Bcl-xl. Silencing of SHP-1, a protein tyrosine phosphatase, abolished the inhibitory effect of luteolin on STAT3 and cell apoptosis, suggesting that SHP-1 is crucial in luteolin-mediated cellular function. Moreover, this luteolin effect of STAT3 dephosphorylation by SHP-1 involved in HSP-90, which protected STAT3 phosphorylation by forming HSP-90/STAT3 complex. Thus, luteolin inhibited STAT3 activation through disrupting the binding of HSP-90 to STAT3, which promoted its interaction to SHP-1, resulted in the dephosphorylation of STAT3. The GC cell xenograft mouse model confirmed the effectiveness of luteolin induced inhibition of tumor growth in vivo. 10.1038/cddis.2017.38
    Meta-analysis of STAT3 and phospho-STAT3 expression and survival of patients with breast cancer. Liu Ya,Huang Jie,Li Wen,Chen Yujuan,Liu Xuejuan,Wang Jing Oncotarget Objective:The prognostic value of signal transducer and activator of transcription 3 (STAT3) and phospho-STAT3 in breast cancer remains controversial in heterogeneous. The objective of this meta-analysis was to evaluate STAT3 and phospho-STAT3 expression on the prognosis of breast cancer patients. Materials and Methods:PubMed, Cochrane Central Register of Controlled Trials, Embase, Web of Science, Chinese CNKI, and Wan Fang were searched up to 19th June 2017. Studies which investigated the STAT3 or phospho-STAT3 expression of patients with breast cancer on the basis of patient survival data or survival curve were eligible. Results:This meta-analysis involves 12 studies and 4513 female patients with breast cancer. No clear relationship exists between overall survival (OS) and high expression of STAT3 and p-STAT3 (hazard ratio [HR] = 0.95, 95% confidence interval [CI]: 0.62-1.46, > 0.05). p-STAT3 expression is unrelated to disease-free survival (HR = 0.69, 95% CI: 0.18-2.55, = 0.573). Notably, the pooled effect predicts better breast cancer-specific survival with p-STAT3 overexpression (HR = 0.68, 95% CI: 0.59-0.78, = 30.9%, < 0.001). Results of subgroup analyses show that STAT3 overexpression indicates shorter OS (HR = 1.87, 95% CI: 1.42-2.45, < 0.001) when excluding the heterogeneity test. Meanwhile, p-STAT3-positive patients have a significantly higher OS than their counterparts (HR = 0.72, 95% CI: 0.57-0.91, < 0.01). Conclusions:Positive STAT3 expression may indicate poor OS. However, p-STAT3, as a potential molecular biomarker for predicting chemotherapeutic effect, appears to have better prognostic value than STAT3. 10.18632/oncotarget.23962
    Differential roles of STAT3 depending on the mechanism of STAT3 activation in gastric cancer cells. Okamoto W,Okamoto I,Arao T,Yanagihara K,Nishio K,Nakagawa K British journal of cancer BACKGROUND:Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that is activated in response to growth factors and cytokines, and which contributes to the regulation of cell proliferation, apoptosis, and motility in many human tumour types. METHODS:We investigated the mechanisms of STAT3 activation and the function of STAT3 depending on its mechanism of activation in gastric cancer cells. RESULTS:The MET-tyrosine kinase inhibitor (TKI) and cell transfection with a small interfering RNA (siRNA) specific for MET mRNA inhibited STAT3 phosphorylation in MET-activated cells, indicating that STAT3 activation is linked to MET signalling. Forced expression of a constitutively active form of STAT3 also attenuated MET-TKI-induced apoptosis, suggesting that inhibition of STAT3 activity contributes to MET-TKI-induced apoptosis. MKN1 and MKN7 cells, both of which are negative for MET activation, produced interleukin-6 (IL-6) that activated STAT3 through the Janus kinase pathway. Depletion of STAT3 by siRNA inhibited migration and invasion of these cells, suggesting that STAT3 activated by IL-6 contributes to regulation of cell motility. CONCLUSION:Our data thus show that activated STAT3 contributes to either cell survival or motility in gastric cancer cells, and that these actions are related to different mechanisms of STAT3 activation. 10.1038/bjc.2011.246
    A STAT3-decoy oligonucleotide induces cell death in a human colorectal carcinoma cell line by blocking nuclear transfer of STAT3 and STAT3-bound NF-κB. Souissi Inès,Najjar Imen,Ah-Koon Laurent,Schischmanoff Pierre Olivier,Lesage Denis,Le Coquil Stéphanie,Roger Claudine,Dusanter-Fourt Isabelle,Varin-Blank Nadine,Cao An,Metelev Valeri,Baran-Marszak Fanny,Fagard Remi BMC cell biology BACKGROUND:The transcription factor STAT3 (signal transducer and activator of transcription 3) is frequently activated in tumor cells. Activated STAT3 forms homodimers, or heterodimers with other TFs such as NF-κB, which becomes activated. Cytoplasmic STAT3 dimers are activated by tyrosine phosphorylation; they interact with importins via a nuclear localization signal (NLS) one of which is located within the DNA-binding domain formed by the dimer. In the nucleus, STAT3 regulates target gene expression by binding a consensus sequence within the promoter. STAT3-specific decoy oligonucleotides (STAT3-decoy ODN) that contain this consensus sequence inhibit the transcriptional activity of STAT3, leading to cell death; however, their mechanism of action is unclear. RESULTS:The mechanism of action of a STAT3-decoy ODN was analyzed in the colon carcinoma cell line SW 480. These cells' dependence on activated STAT3 was verified by showing that cell death is induced by STAT3-specific siRNAs or Stattic. STAT3-decoy ODN was shown to bind activated STAT3 within the cytoplasm, and to prevent its translocation to the nucleus, as well as that of STAT3-associated NF-κB, but it did not prevent the nuclear transfer of STAT3 with mutations in its DNA-binding domain. The complex formed by STAT3 and the STAT3-decoy ODN did not associate with importin, while STAT3 alone was found to co-immunoprecipitate with importin. Leptomycin B and vanadate both trap STAT3 in the nucleus. They were found here to oppose the cytoplasmic trapping of STAT3 by the STAT3-decoy ODN. Control decoys consisting of either a mutated STAT3-decoy ODN or a NF-κB-specific decoy ODN had no effect on STAT3 nuclear translocation. Finally, blockage of STAT3 nuclear transfer correlated with the induction of SW 480 cell death. CONCLUSIONS:The inhibition of STAT3 by a STAT3-decoy ODN, leading to cell death, involves the entrapment of activated STAT3 dimers in the cytoplasm. A mechanism is suggested whereby this entrapment is due to STAT3-decoy ODN's inhibition of active STAT3/importin interaction. These observations point to the high potential of STAT3-decoy ODN as a reagent and to STAT3 nucleo-cytoplasmic shuttling in tumor cells as a potential target for effective anti-cancer compounds. 10.1186/1471-2121-12-14
    Clinicopathological and Prognostic Role of STAT3/p-STAT3 in Breast Cancer Patients in China: A Meta-Analysis. Li Yang,Wang Yue,Shi Zhixiang,Liu Jinghan,Zheng Shuyun,Yang Jinsong,Liu Yi,Yang Yuhua,Chang Feng,Yu Wenying Scientific reports In order to explore the important factors in the diagnosis of breast cancer in China, meta-analysis of previous studies was performed to understand the association between STAT3/p-STAT3 and breast cancer. Information about STAT3/p-STAT3 expression and clinical data about breast cancer in China in particular were gathered from PubMed, Web of Science, CNKI and WanFang databases. RevMan 5.3 and STATA 14.0 were used to analyze the occurrence, development and metastasis of breast cancer for 2818 patients in 18 studies. STAT3/p-STAT3 expression was higher in breast cancer tissue than in normal ones (OR = 7.48, 95% CI = 5.64-9.94), in highly differentiated breast cancer tissue than in lowly differentiated cancer tissues (OR = 2.13, 95% CI = 1.53-2.98), in III/IV stage breast cancer than in I/II stage breast cancer (OR = 3.58, 95% CI = 2.44-5.25), and in tissue with lymphatic metastasis than in normal tissues (OR = 3.72, 95% CI = 2.59-5.35), respectively. Thus, the expression of STAT3/p-STAT3 plays a clinicopathological and prognostic role in the diagnosis and treatment of Chinese breast cancer patients. 10.1038/s41598-019-47556-z
    Eriocalyxin B Inhibits STAT3 Signaling by Covalently Targeting STAT3 and Blocking Phosphorylation and Activation of STAT3. Yu Xiaokui,He Li,Cao Peng,Yu Qiang PloS one Activated STAT3 plays an important role in oncogenesis by stimulating cell proliferation and resisting apoptosis. STAT3 therefore is an attractive target for cancer therapy. We have screened a traditional Chinese herb medicine compound library and found Eriocalyxin B (EB), a diterpenoid from Isodon eriocalyx, as a specific inhibitor of STAT3. EB selectively inhibited constitutive as well as IL-6-induced phosphorylation of STAT3 and induced apoptosis of STAT3-dependent tumor cells. EB did not affect the upstream protein tyrosine kinases or the phosphatase (PTPase) of STAT3, but rather interacted directly with STAT3. The effects of EB could be abolished by DTT or GSH, suggesting a thiol-mediated covalent linkage between EB and STAT3. Site mutagenesis of cysteine in and near the SH2 domain of STAT3 identified Cys712 to be the critical amino acid for the EB-induced inactivation of STAT3. Furthermore, LC/MS/MS analyses demonstrated that an α, β-unsaturated carbonyl of EB covalently interacted with the Cys712 of STAT3. Computational modeling analyses also supported a direct interaction between EB and the Cys712 of STAT3. These data strongly suggest that EB directly targets STAT3 through a covalent linkage to inhibit the phosphorylation and activation of STAT3 and induces apoptosis of STAT3-dependent tumor cells. 10.1371/journal.pone.0128406
    Dynamic Mitochondrial Localisation of STAT3 in the Cellular Adipogenesis Model 3T3-L1. Kramer Adam H,Edkins Adrienne L,Hoppe Heinrich C,Prinsloo Earl Journal of cellular biochemistry A mechanistic relationship exists between protein localisation, activity and cellular differentiation. Understanding the contribution of these molecular mechanisms is required for elucidation of conditions that drive development. Literature suggests non-canonical translocation of the Signal Transducer and Activator of Transcription 3 (STAT3) to the mitochondria contributes to the regulation of the electron transport chain, cellular respiration and reactive oxygen species production. Based on this we investigated the role of mitochondrial STAT3, specifically the serine 727 phosphorylated form, in cellular differentiation using the well-defined mouse adipogenic model 3T3-L1. Relative levels of reactive oxygen species (ROS) and the levels and dynamic localization of pSTAT3S727 were investigated during the initiation of adipogenesis. As a signalling entity, ROS is known to regulate the activation of C/EBPβ to stimulate a critical cascade of events prior to differentiation of 3T3-L1. Results indicate that upon induction of the differentiation programme, relative levels of mitochondrial pSTAT3S727 dramatically decrease in the mitochondria; in contrast the total cellular pSTAT3S727 levels increase. A positive correlation between increasing levels of ROS and dynamic changes in C/EBPβ indicate that mitochondrial STAT3 plays a potential critical role as an initiator of the process. Based on these findings we propose a model for mitochondrial STAT3 as a regulator of ROS in adipogenesis. 10.1002/jcb.25076
    Blockage of STAT3 Signaling Pathway by Morusin Induces Apoptosis and Inhibits Invasion in Human Pancreatic Tumor Cells. Kim Chulwon,Kim Jin Ho,Oh Eun Young,Nam Dongwoo,Lee Seok Geun,Lee Junhee,Kim Sung-Hoon,Shim Bum Sang,Ahn Kwang Seok Pancreas OBJECTIVES:Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor implicated in carcinogenesis. Here, we investigated the role of morusin, the major prenylflavonoid, isolated from Chinese herbal medicine in abrogating the constitutive STAT3 activation in human pancreatic tumor cells. METHODS:The effect of morusin on STAT3 activation, associated protein kinases, STAT3-regulated gene products, cellular proliferation, and apoptosis was examined. RESULTS:Morusin specifically inhibited constitutive STAT3 activation both at tyrosine residue 705 and serine residue 727 in 4 pancreatic tumor cells. The inhibition of STAT3 was mediated through the suppression of activation of upstream JAK1, JAK2, and c-Src kinases. Morusin led to the accumulation of the cells in different phases of the cell cycle and caused induction of apoptosis and loss of mitochondrial membrane potential. Morusin downregulated the expression of various STAT3-regulated gene products; this correlated with induction of caspase-3 activation and anti-invasive effects. Treatment with the protein tyrosine phosphatase inhibitor pervanadate reversed the morusin-induced downregulation of STAT3, thereby suggesting the involvement of a protein tyrosine phosphatase. CONCLUSIONS:Morusin is a novel blocker of STAT3 activation and thus may have potential in negative regulation of growth and metastasis of pancreatic tumor cells. 10.1097/MPA.0000000000000496
    Mitochondrial STAT3 plays a major role in IgE-antigen-mediated mast cell exocytosis. Erlich Tal Hadad,Yagil Zohar,Kay Gillian,Peretz Alona,Migalovich-Sheikhet Helena,Tshori Sagi,Nechushtan Hovav,Levi-Schaffer Francesca,Saada Ann,Razin Ehud The Journal of allergy and clinical immunology BACKGROUND:The involvement of mitochondrial oxidative phosphorylation (OXPHOS) in mast cell exocytosis was recently suggested by the finding that mitochondria translocate to exocytosis sites upon mast cell activation. In parallel, mitochondrial signal transducer and activator of transcription 3 (STAT3) was found to be involved in ATP production. However, the regulation of mitochondrial STAT3 function and its connection to mast cell exocytosis is unknown. OBJECTIVE:We sought to explore the role played by mitochondrial STAT3 in mast cell exocytosis. METHODS:Experiments were performed in vitro with human and mouse mast cells and rat basophilic leukemia (RBL) cells and in vivo in mice. OXPHOS activity was measured after immunologic activation. The expression of STAT3, extracellular signal-regulated kinase 1/2, and protein inhibitor of activated STAT3 in the mitochondria during mast cell activation was determined, as was the effect of STAT3 inhibition on OXPHOS activity and mast cell function. RESULTS:Here we show that mitochondrial STAT3 is essential for immunologically mediated degranulation of human and mouse mast cells and RBL cells. Additionally, in IgE-antigen-activated RBL cells, mitochondrial STAT3 was phosphorylated on serine 727 in an extracellular signal-regulated kinase 1/2-dependent manner, which was followed by induction of OXPHOS activity. Furthermore, the endogenous inhibitor of STAT3, protein inhibitor of activated STAT3, was found to inhibit OXPHOS activity in the mitochondria, resulting in inhibition of mast cell degranulation. Moreover, mice injected with Stattic, a STAT3 inhibitor, had a significant decrease in histamine secretion. CONCLUSION:These results provide the first evidence of a regulatory role for mitochondrial STAT3 in mast cell functions, and therefore mitochondrial STAT3 could serve as a new target for the manipulation of allergic diseases. 10.1016/j.jaci.2013.12.1075
    Resveratrol inhibits STAT3 signaling pathway through the induction of SOCS-1: Role in apoptosis induction and radiosensitization in head and neck tumor cells. Baek Seung Ho,Ko Jeong-Hyeon,Lee Hanwool,Jung Jinhong,Kong Moonkyoo,Lee Jung-woo,Lee Junhee,Chinnathambi Arunachalam,Zayed M E,Alharbi Sulaiman Ali,Lee Seok-Geun,Shim Bum Sang,Sethi Gautam,Kim Sung-Hoon,Yang Woong Mo,Um Jae-Young,Ahn Kwang Seok Phytomedicine : international journal of phytotherapy and phytopharmacology BACKGROUND:Signal transducer and activator of transcription 3 (STAT3) is persistently activated in squamous cell carcinoma of the head and neck (SCCHN) and can cause uncontrolled cellular proliferation and division. HYPOTHESIS:Thus, its targeted abrogation could be an effective strategy to reduce the risk of SCCHN. Resveratrol is known for its anti-cancer efficacy in a variety of cancer models. STUDY DESIGN:The effect resveratrol on STAT3 activation, associated protein kinases, phosphatases, cellular proliferation and apoptosis was investigated. METHODS:We evaluated the effect of resveratrol on STAT3 signaling cascade and its regulated functional responses in SCCHN cells. RESULTS:We found that HN3 and FaDu cells expressed strongly phosphorylated STAT3 on both tyrosine 705 and serine 727 residues as compared to other SCCHN cells. The phosphorylation was completely suppressed by resveratrol in FaDu cells, but not substantially in HN3 cells. STAT3 suppression was mediated through the inhibition of activation of upstream JAK2, but not of JAK1 and Src kinases. Treatment with the protein tyrosine phosphatase (PTP) inhibitor pervanadate reversed the resveratrol-induced down-regulation of STAT3, thereby indicating a critical role for a PTP. We also found that resveratrol induced the expression of the SOCS-1 protein and mRNA. Further, deletion of SOCS-1 gene by siRNA suppressed the induction of SOCS-1, and reversed the inhibition of STAT3 activation. Resveratrol down-regulated various STAT3-regulated gene products, inhibited proliferation, invasion, as well as induced the cell accumulation in the sub-G1 phase and caused apoptosis. Beside, this phytoalexin also exhibited the enhancement of apoptosis when combined with ionizing radiation treatment. CONCLUSION:Our results suggest that resveratrol blocks STAT3 signaling pathway through induction of SOCS-1, thus attenuating STAT3 phosphorylation and proliferation in SCCHN cells. 10.1016/j.phymed.2016.02.011
    Kaposi's sarcoma-associated herpesvirus kaposin B induces unique monophosphorylation of STAT3 at serine 727 and MK2-mediated inactivation of the STAT3 transcriptional repressor TRIM28. King Christine A Journal of virology Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of primary effusion lymphoma (PEL), multicentric Castleman's disease (MCD), and the inflammation-driven neoplasm Kaposi's sarcoma (KS). A triad of processes, including abnormal proliferation of endothelial cells, aberrant angiogenesis, and chronic inflammation, characterize KS lesions. STAT3 is a key transcription factor governing these processes, and deregulation of STAT3 activity is linked to a wide range of cancers, including PEL and KS. Using primary human endothelial cells (ECs), I demonstrate that KSHV infection modulated STAT3 activation in two ways: (i) KSHV induced uncoupling of canonical tyrosine (Y) and serine (S) phosphorylation events while (ii) concomitantly inducing the phosphorylation and inactivation of TRIM28 (also known as KAP-1 or TIF-1β), a newly identified negative regulator of STAT3 activity. KSHV infection of primary ECs induced chronic STAT3 activation characterized by a shift from the canonical dual P-STAT3 Y705 S727 form to a mono P-STAT3 S727 form. Expression of the latent protein kaposin B promoted the unique phosphorylation of STAT3 at S727, in the absence of Y705, activated the host kinase mitogen-activated protein kinase-activated protein (MAPKAP) kinase 2 (MK2), and stimulated increased expression of STAT3-dependent genes, including CCL5, in ECs. TRIM28-mediated repression of STAT3 is relieved by phosphorylation of S473, and in vitro kinase assays identified TRIM28 S473 as a bona fide target of MK2. Together, these data suggest that kaposin B significantly contributes to the chronic inflammatory environment that is a hallmark of KS by unique activation of the proto-oncogene STAT3, coupled with MK2-mediated inactivation of the STAT3 transcriptional repressor TRIM28. 10.1128/JVI.02976-12
    STAT3 is constitutively phosphorylated on serine 727 residues, binds DNA, and activates transcription in CLL cells. Hazan-Halevy Inbal,Harris David,Liu Zhiming,Liu Jie,Li Ping,Chen Xiaomin,Shanker Sreejesh,Ferrajoli Alessandra,Keating Michael J,Estrov Zeev Blood Chronic lymphocytic leukemia (CLL) is the most common leukemia in the Western hemisphere, but its pathogenesis is still poorly understood. Constitutive tyrosine phosphorylation (p) of signal transducer and activator of transcription (STAT) 3 occurs in several solid tumors and hematologic malignancies. In CLL, however, STAT3 is constitutively phosphorylated on serine 727, not tyrosine 705, residues. Because the biologic significance of serine pSTAT3 in CLL is not known, we studied peripheral blood cells of 106 patients with CLL and found that, although tyrosine pSTAT3 was inducible, serine pSTAT3 was constitutive in all patients studied, regardless of blood count, disease stage, or treatment status. In addition, we demonstrated that constitutive serine pSTAT3 translocates to the nucleus by the karyopherin-beta nucleocytoplasmic system and binds DNA. Dephosphorylation of inducible tyrosine pSTAT3 did not affect STAT3-DNA binding, suggesting that constitutive serine pSTAT3 binds DNA. Furthermore, infection of CLL cells with lentiviral STAT3-small hairpin RNA reduced the expression of several STAT3-regulated survival and proliferation genes and induced apoptosis, suggesting that constitutive serine pSTAT3 initiates transcription in CLL cells. Taken together, our data suggest that constitutive phosphorylation of STAT3 on serine 727 residues is a hallmark of CLL and that STAT3 be considered a therapeutic target in this disease. 10.1182/blood-2009-10-230060
    Stress-induced dynamic regulation of mitochondrial STAT3 and its association with cyclophilin D reduce mitochondrial ROS production. Meier Jeremy A,Hyun Moonjung,Cantwell Marc,Raza Ali,Mertens Claudia,Raje Vidisha,Sisler Jennifer,Tracy Erin,Torres-Odio Sylvia,Gispert Suzana,Shaw Peter E,Baumann Heinz,Bandyopadhyay Dipankar,Takabe Kazuaki,Larner Andrew C Science signaling Signal transducer and activator of transcription 3 (STAT3) is associated with various physiological and pathological functions, mainly as a transcription factor that translocates to the nucleus upon tyrosine phosphorylation induced by cytokine stimulation. In addition, a small pool of STAT3 resides in the mitochondria, where it serves as a sensor for various metabolic stressors including reactive oxygen species (ROS). Mitochondrially localized STAT3 largely exerts its effects through direct or indirect regulation of the activity of the electron transport chain (ETC). It has been assumed that the amounts of STAT3 in the mitochondria are static. We showed that various stimuli, including oxidative stress and cytokines, triggered a signaling cascade that resulted in a rapid loss of mitochondrially localized STAT3. Recovery of the mitochondrial pool of STAT3 over time depended on phosphorylation of Ser in STAT3 and new protein synthesis. Under these conditions, mitochondrially localized STAT3 also became competent to bind to cyclophilin D (CypD). Binding of STAT3 to CypD was mediated by the amino terminus of STAT3, which was also important for reducing mitochondrial ROS production after oxidative stress. These results outline a role for mitochondrially localized STAT3 in sensing and responding to external stimuli. 10.1126/scisignal.aag2588
    Modulation of allergic responses by mitochondrial STAT3 inhibitors. Erlich T H,Sharkia I,Landolina N,Assayag M,Goldberger O,Berkman N,Levi-Schaffer F,Razin E Allergy BACKGROUND:Recently, we have shown that mast cell mitochondrial STAT3 could serve as a new target for the regulation of the allergic response as it plays an essential role in immunologically mediated degranulation of mast cells. In the present work, we explored how two recently developed mitochondrial STAT3 inhibitors (Mitocur-1 and Mitocur-3) modulate the allergic response. METHODS:Experiments were performed both in vitro in cultured human/mouse mast cells and with rat basophilic leukemia (RBL) cells and also in vivo in mice. The effect of mitochondrial STAT3 inhibition on mast cell function was determined via checking degranulation and several cytokines secretion levels. RESULTS:Here, we show that treatment of rodent and human cultured mast cells with low concentrations of mitochondrial STAT3 inhibitors had no effect on STAT3 target gene expression. However, these inhibitors caused a significant reduction in mast cell exocytosis and cytokine release, due to a decrease in OXPHOS activity and STAT3 serine 727 phosphorylation. It was also observed in an OVA mouse model of allergic asthma that one of the inhibitors used significantly reduced eosinophilia and neutrophilia compared to the control mice group. Furthermore, it was observed that treatment with this inhibitor resulted in a significant reduction in blood histamine levels in mice after IgE-Ag challenge. CONCLUSION:The present data strongly suggest that the development of mitochondrial STAT3 inhibitors could serve as a potential treatment for allergy-associated diseases. 10.1111/all.13467
    Role of STAT3 in Genesis and Progression of Human Malignant Gliomas. Ouédraogo Zangbéwendé Guy,Biau Julian,Kemeny Jean-Louis,Morel Laurent,Verrelle Pierre,Chautard Emmanuel Molecular neurobiology Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in glioblastoma and has been identified as a relevant therapeutic target in this disease and many other human cancers. After two decades of intensive research, there is not yet any approved STAT3-based glioma therapy. In addition to the canonical activation by tyrosine 705 phosphorylation, concordant reports described a potential therapeutic relevance of other post-translational modifications including mainly serine 727 phosphorylation. Such reports reinforce the need to refine the strategy of targeting STAT3 in each concerned disease. This review focuses on the role of serine 727 and tyrosine 705 phosphorylation of STAT3 in glioma. It explores their contribution to glial cell transformation and to the mechanisms that make glioma escape to both immune control and standard treatment. 10.1007/s12035-016-0103-0
    Formononetin-induced oxidative stress abrogates the activation of STAT3/5 signaling axis and suppresses the tumor growth in multiple myeloma preclinical model. Kim Chulwon,Lee Seok-Geun,Yang Woong Mo,Arfuso Frank,Um Jae-Young,Kumar Alan Prem,Bian Jinsong,Sethi Gautam,Ahn Kwang Seok Cancer letters Aberrant reactions of signal transducer and transcriptional activator (STAT) are frequently detected in multiple myeloma (MM) cancers and can upregulate the expression of multiple genes related to cell proliferation, survival, metastasis, and angiogenesis. Therefore, agents capable of inhibiting STAT activation can form the basis of novel therapies for MM patients. In the present study, we investigated whether the potential anti-cancer effects of Formononetin (FT), a naturally occurring isoflavone derived from Astragalus membranaceus, Trifolium pratense, Glycyrrhiza glabra, and Pueraria lobata, against MM cell lines and human multiple myeloma xenograft tumors in athymic nu/nu mice model are mediated through the negative regulation of STAT3 and STAT5 pathways. Data from the in vitro studies indicated that FT could significantly inhibit cell viability, and induce apoptosis. Interestingly, FT also suppressed constitutive STAT3 (tyrosine residue 705 and serine residue 727) and STAT5 (tyrosine residue 694/699) activation, which correlated with the suppression of the upstream kinases (JAK1, JAK2, and c-Src) in MM cells, and this effect was found to be mediated via an increased production of reactive oxygen species (ROS) due to GSH/GSSG imbalance. Also, FT abrogated STAT3 and STAT5 DNA binding capacity and nuclear translocation. FT induced cell cycle arrest, downregulated the expression of STAT3-regulated anti-apoptotic, angiogenetic, and proliferative gene products; and this correlated with induction of caspase-3 activation and cleavage of PARP. Intraperitoneal administration of FT significantly suppressed the tumor growth in the multiple myeloma xenograft mouse model without exhibiting any significant adverse effects. Overall, our findings indicate that FT exhibits significant anti-cancer effects in MM that may be primarily mediated through the ROS-regulated inhibition of the STAT3 and STAT5 signaling cascade. 10.1016/j.canlet.2018.05.038
    STAT3 serine 727 phosphorylation influences clinical outcome in glioblastoma. Lin Guo-Shi,Chen Yu-Peng,Lin Zhi-Xiong,Wang Xing-Fu,Zheng Zong-Qing,Chen Long International journal of clinical and experimental pathology Besides STAT3 tyrosine 705 phosphorylation (pTyr705-STAT3), phosphorylation of STAT3 at serine 727 (pSer727-STAT3) is shown to contribute to tumorigenesis and be closely related with resistance to radiotherapy and chemotherapy in glioma, but there is currently no study regarding its relevance to prognosis in glioblastoma (GBM). Here, the expression of phosphorylated STAT3 was detected in tumor specimens from 88 patients with newly diagnosed GBM by immunohistochemistry, the Kaplan-Meier survival curve and COX proportional hazards regression model were applied to estimate its influences on progression-free survival (PFS) and overall survival (OS). Immunohistochemical assay showed elevated expression of pSer727-STAT3 in GBM compared with normal brain tissue. Univariate analysis indicated significant correlations of high percentage of pSer727-STAT3 positive tumor cells with shorter PFS (P = 0.006) and OS (P = 0.002). In multivariate analysis, high pSer727-STAT3 expression was demonstrated as an independent unfavorable prognostic indicator for PFS (HR 1.830, P = 0.022) and OS (HR 1.797, P = 0.040). And patients with high expression of both pTyr705-STAT3 and pSer727-STAT3 had a poorer prognosis compared with the remainder (P < 0.005). In conclusion, the high proportion of pSer727-STAT3 positive neoplastic cells in GBM is an independent unfavorable prognostic factor, and increased expression of both pTyr705-STAT3 and pSer727-STAT3 is predictive of poorer clinical outcome, thereby adding to the growing evidence that STAT3 inhibition may be a potential therapeutic strategy in glioblastoma.
    Neuronal activity-dependent STAT3 localization to nucleus is dependent on Tyr-705 and Ser-727 phosphorylation in rat hippocampal neurons. Murase Sachiko,McKay Ronald D The European journal of neuroscience Signal transducer and activator of transcription 3 (STAT3) dramatically increases during the first post-natal week, and supports the survival of mature hippocampal neurons. Recently, we reported that chronic elevation of excitability leads to a loss of STAT3 signal, inducing vulnerability in neurons. The loss of STAT3 signal was due to impaired Erk1/2 activation. While overnight elevation of activity attenuated STAT3 signal, brief low-frequency stimuli, which induce long-term depression, have been shown to activate STAT3. Here we investigated how STAT3 responds to depolarization in mature neurons. A brief depolarization results in the transient activation of STAT3: it induces calcium influx through L-type voltage-gated calcium channels, which triggers activation of Src family kinases. Src family kinases are required for phosphorylation of STAT3 at Tyr-705 and Ser-727. PTyr-705 is Janus kinase (JAK)-dependent, while PSer-727 is dependent on Akt, the Ser/Thr kinase. Both PTyr-705 and PSer-727 are necessary for nuclear translocation of STAT3 in these neurons. Chronic elevation of spontaneous activity by an A-type potassium blocker, 4-aminopyridine (4-AP), also induced the transient phosphorylation of STAT3, which after 4 h fell to basal levels despite the presence of 4-AP. These results suggest that phasic and chronic neuronal activation induce distinct molecular pathways, resulting in opposing regulation of STAT3 signal. 10.1111/ejn.12412
    Convallatoxin promotes apoptosis and inhibits proliferation and angiogenesis through crosstalk between JAK2/STAT3 (T705) and mTOR/STAT3 (S727) signaling pathways in colorectal cancer. Zhang Zhi Hong,Li Ming Yue,Wang Zhe,Zuo Hong Xiang,Wang Jing Ying,Xing Yue,Jin Chenghua,Xu Guanghua,Piao Lianxun,Piao Hongxin,Ma Juan,Jin Xuejun Phytomedicine : international journal of phytotherapy and phytopharmacology BACKGROUND:Aberrant activation of STAT3 is frequently encountered and promotes survival, cellular proliferation, migration, invasion and angiogenesis in tumor cell. Convallatoxin, triterpenoid ingredient, exhibits anticancer pharmacological properties. PURPOSE:In this work, we investigated the anticancer potential of convallatoxin and explored whether convallatoxin mediates its effect through interference with the STAT3 activation in colorectal cancer cells. METHODS:In vitro, the underlying mechanisms of convallatoxin at inhibiting STAT3 activation were investigated by homology modeling and molecular docking, luciferase reporter assay, MTT assay, RT-PCR, Western blotting and immunofluorescence assays. Changes in cellular proliferation, apoptosis, migration, invasion and angiogenesis were analyzed by EdU labeling assay, colony formation assay, flow cytometry assay, wound-healing assay, matrigel transwell invasion assay and tube formation assays. And in vivo, antitumor activity of convallatoxin was assessed in a murine xenograft model of HCT116 cells. RESULTS:Convallatoxin decreased the viability of colorectal cancer lines. Moreover, convallatoxin reduced the P-STAT3 (T705) via the JAK1, JAK2, and Src pathways and inhibited serine-727 phosphorylation of STAT3 via the PI3K-AKT-mTOR-STAT3 pathways in colorectal cancer cells. Interestingly, we discovered the crosstalk between mTOR and JAK2 in mTOR/STAT3 and JAK/STAT3 pathways, which collaboratively regulated STAT3 activation and convallatoxin play a role in it. Convallatoxin also downregulated the expression of target genes involved cell survival (e.g., Survivin, Bcl-xl, Bcl-2), proliferation (e.g., Cyclin D1), metastasis (e.g., MMP-9), and angiogenesis (e.g., VEGF). Indeed, we found that convallatoxin inhibited tube formation, migration, and invasion of endothelial cells, and inhibited the proliferation. Finally, in vivo observations were confirmed by showing antitumor activity of convallatoxin in a murine xenograft model. CONCLUSION:The result of the current study show that convallatoxin promotes apoptosis and inhibits proliferation and angiogenesis through crosstalk between JAK2/STAT3 (T705) and mTOR/STAT3 (S727) signaling pathways in colorectal cancer cells and indicate that convallatoxin could be a valuable candidate for the development of colorectal cancer therapeutic. 10.1016/j.phymed.2020.153172
    Zinc improves mitochondrial respiratory function and prevents mitochondrial ROS generation at reperfusion by phosphorylating STAT3 at Ser. Zhang Ge,Sheng Mingwei,Wang Jiannan,Teng Tianming,Sun Yuemin,Yang Qing,Xu Zhelong Journal of molecular and cellular cardiology Serine 727 (Ser) phosphorylation of STAT3 plays a role in the regulation of mitochondrial respiration. This study aimed to test if zinc could regulate mitochondrial respiration through phosphorylation of STAT3 at Ser in the setting of ischemia/reperfusion in the heart. Under normoxic conditions, treatment of isolated rat hearts with ZnCl increased cytosolic STAT3 phosphorylation at Ser followed by phospho-STAT3 translocation to mitochondria. In isolated rat hearts subjected to 30 min regional ischemia followed by 20 min of reperfusion, ZnCl given 5 min before the onset of reperfusion also increased mitochondrial phospho-STAT3. ZnCl enhanced ERK phosphorylation and PD98059 reversed the effect of ZnCl on STAT3 phosphorylation. ZnCl improved the mitochondrial oxidative phosphorylation at reperfusion. This effect was abolished by STAT3S727A, a mutant in which Ser is replaced with alanine, in H9c2 cells subjected to hypoxia/reoxygenation. In addition, ZnCl increased the mRNA level of the complex I subunit ND6, which was also reversed by STAT3S727A. Moreover, ZnCl attenuated mitochondrial ROS generation and dissipation of mitochondrial membrane potential (ΔΨm) at reoxygenation through Ser phosphorylation. Finally, ZnCl suppression of succinate dehydrogenase (SDH) activity upon the onset of reperfusion was nullified by the Ser mutation. In conclusion, zinc improves cardiac oxidative phosphorylation and inhibits mitochondrial ROS generation at reperfusion by increasing mitochondrial STAT3 phosphorylation at Ser via ERK. The preservation of ND6 mtDNA and the inhibition of SDH activity may account for the role of STAT3 in the beneficial action of zinc on the mitochondrial oxidative phosphorylation and ROS generation at reperfusion. 10.1016/j.yjmcc.2018.03.019
    STAT3 Serine 727 Phosphorylation: A Relevant Target to Radiosensitize Human Glioblastoma. Ouédraogo Zangbéwendé Guy,Müller-Barthélémy Mélanie,Kemeny Jean-Louis,Dedieu Véronique,Biau Julian,Khalil Toufic,Raoelfils Lala Ines,Granzotto Adeline,Pereira Bruno,Beaudoin Claude,Guissou Innocent Pierre,Berger Marc,Morel Laurent,Chautard Emmanuel,Verrelle Pierre Brain pathology (Zurich, Switzerland) Radiotherapy is an essential component of glioma standard treatment. Glioblastomas (GBM), however, display an important radioresistance leading to tumor recurrence. To improve patient prognosis, there is a need to radiosensitize GBM cells and to circumvent the mechanisms of resistance caused by interactions between tumor cells and their microenvironment. STAT3 has been identified as a therapeutic target in glioma because of its involvement in mechanisms sustaining tumor escape to both standard treatment and immune control. Here, we studied the role of STAT3 activation on tyrosine 705 (Y705) and serine 727 (S727) in glioma radioresistance. This study explored STAT3 phosphorylation on Y705 (pSTAT3-Y705) and S727 (pSTAT3-S727) in glioma cell lines and in clinical samples. Radiosensitizing effect of STAT3 activation down-modulation by Gö6976 was explored. In a panel of 15 human glioma cell lines, we found that the level of pSTAT3-S727 was correlated to intrinsic radioresistance. Moreover, treating GBM cells with Gö6976 resulted in a highly significant radiosensitization associated to a concomitant pSTAT3-S727 down-modulation only in GBM cell lines that exhibited no or weak pSTAT3-Y705. We report the constitutive activation of STAT3-S727 in all GBM clinical samples. Targeting pSTAT3-S727 mainly in pSTAT3-Y705-negative GBM could be a relevant approach to improve radiation therapy. 10.1111/bpa.12254
    Mitochondrial localized Stat3 promotes breast cancer growth via phosphorylation of serine 727. Zhang Qifang,Raje Vidisha,Yakovlev Vasily A,Yacoub Adly,Szczepanek Karol,Meier Jeremy,Derecka Marta,Chen Qun,Hu Ying,Sisler Jennifer,Hamed Hossein,Lesnefsky Edward J,Valerie Kristoffer,Dent Paul,Larner Andrew C The Journal of biological chemistry Signal transducer and activator of transcription 3 (Stat3) is a key mediator in the development of many cancers. For 20 years, it has been assumed that Stat3 mediates its biological activities as a nuclear localized transcription factor activated by many cytokines. However, recent studies from this laboratory and others indicate that Stat3 has an independent function in the mitochondria (mitoStat3) where it controls the activity of the electron transport chain (ETC) and mediates Ras-induced transformation of mouse embryo fibroblasts. The actions of mitoStat3 in controlling respiration and Ras transformation are mediated by the phosphorylation state of serine 727. To address the role of mitoStat3 in the pathogenesis of cells that are transformed, we used 4T1 breast cancer cells, which form tumors that metastasize in immunocompetent mice. Substitution of Ser-727 for an alanine or aspartate in Stat3 that has a mitochondrial localization sequence, MLS-Stat3, has profound effects on tumor growth, complex I activity of the ETC, and accumulation of reactive oxygen species (ROS). Cells expressing MLS-Stat3(S727A) display slower tumor growth, decreased complex I activity of the ETC, and increased ROS accumulation under hypoxia compared with cells expressing MLS-Stat3. In contrast, cells expressing MLS-Stat3(S727D) show enhanced tumor growth and complex I activity and decreased production of ROS. These results highlight the importance of serine 727 of mitoStat3 in breast cancer and suggest a novel role for mitoStat3 in regulation of ROS concentrations through its action on the ETC. 10.1074/jbc.M113.505057
    Phospho-valproic acid (MDC-1112) suppresses glioblastoma growth in preclinical models through the inhibition of STAT3 phosphorylation. Luo Dingyuan,Fraga-Lauhirat Magdalena,Millings Jonathan,Ho Cristella,Villarreal Emily M,Fletchinger Teresa C,Bonfiglio James V,Mata Leyda,Nemesure Matthew D,Bartels Lauren E,Wang Ruixue,Rigas Basil,Mackenzie Gerardo G Carcinogenesis New therapeutic strategies against glioblastoma multiforme (GBM) are urgently needed. Signal transducer and activator of transcription 3 (STAT3), constitutively active in many GBM tumors, plays a major role in GBM tumor growth and represents a potential therapeutic target. We have documented previously that phospho-valproic acid (MDC-1112), which inhibits STAT3 activation, possesses strong anticancer properties in multiple cancer types. In this study, we explored the anticancer efficacy of MDC-1112 in preclinical models of GBM, and evaluated its mode of action. MDC-1112 inhibited the growth of multiple human GBM cell lines in a concentration- and time-dependent manner. Normal human astrocytes were resistant to MDC-1112, indicating selectivity. In vivo, MDC-1112 reduced the growth of subcutaneous GBM xenografts in mice by up to 78.2% (P < 0.01), compared with the controls. Moreover, MDC-1112 extended survival in an intracranial xenograft model. Although all vehicle-treated mice died by 19 days of treatment, 7 of 11 MDC-1112-treated mice were alive and healthy by the end of 5 weeks, with many showing tumor regression. Mechanistically, MDC-1112 inhibited STAT3 phosphorylation at the serine 727 residue, but not at tyrosine 705, in vitro and in vivo. STAT3 overexpression rescued GBM cells from the cell growth inhibition by MDC-1112. In addition, MDC-1112 reduced STAT3 levels in the mitochondria and enhanced mitochondrial levels of reactive oxygen species, which triggered apoptosis. In conclusion, MDC-1112 displays strong efficacy in preclinical models of GBM, with the serine 727 residue of STAT3 being its key molecular target. MDC-1112 merits further evaluation as a drug candidate for GBM. New therapeutic options are needed for glioblastoma. The novel agent MDC-1112 is an effective anticancer agent in multiple animal models of glioblastoma, and its mechanism of action involves the inhibition of STAT3 phosphorylation, primarily at its Serine 727 residue. 10.1093/carcin/bgz069
    The role of STAT3 protein as a prognostic factor in the clear cell renal carcinoma. Systematic review. Lorente D,Trilla E,Meseguer A,Arevalo J,Nemours S,Planas J,Placer J,Celma A,Salvador C,Regis L,Schwartzmann I,Morote J Actas urologicas espanolas CONTEXT AND OBJECTIVE:There have been significant advances in the knowledge of renal carcinogenesis n the last years. Nowadays, renal tumors are classified according to their genetic profile and specific treatments based on the identification of therapeutic targets have also been developed. However, no prognostic markers have yet been identified. The aim of this review is to analyse literature that has evaluated the expression of the STAT3 protein as a molecular marker in clear cell renal carcinoma (ccRCC). EVIDENCE ACQUISITION:In January 2018 a systematic review was conducted in Pubmed, Cochrane library and Sciencedirect databases, from papers published from 1990. Search terms were"renal cell carcinoma"and"STAT3"or"STAT-3"and"prognostic factor. Following the principles of the PRISMA declaration and the PICO selection strategy, original articles with series of patients diagnosed with localized or metastatic ccRCC, and where the activity of STAT3 is analysed as a prognostic marker, were selected. A total of 132 publications were identified, of which 10 were finally revised, for they met the inclusion criteria. EVIDENCE SYNTHESIS:STAT3 activation (phosphorylation) through Ser727 is important during ccRCC development and progression. PSTAT3 expression seems to be a prognostic marker and an antiangiogenic-resistance marker in metastatic patients. There is little evidence as prognostic marker in patients with localized disease. CONCLUSIONS:STAT3 (Ser 727) expression in the nucleus of the ccRCC cells can be a prognostic marker and an antiangiogenic-resistance marker. Current scientific evidence is limited and more studies are needed to demonstrate its usefulness. 10.1016/j.acuro.2018.08.003
    Reduced phosphorylation of Stat3 at Ser-727 mediated by casein kinase 2 - protein phosphatase 2A enhances Stat3 Tyr-705 induced tumorigenic potential of glioma cells. Mandal Tapashi,Bhowmik Arijit,Chatterjee Anirban,Chatterjee Uttara,Chatterjee Sandip,Ghosh Mrinal Kanti Cellular signalling Signal transducer and activator of transcription 3 (Stat3) is a transcription factor that is involved in cell survival and proliferation and has been found to be persistently activated in most human cancers mainly through its phosphorylation at Tyr-705. However, the role and regulation of Stat3 Ser-727 phosphorylation in cancer cells have not been clearly evaluated. In our findings, correlation studies on the expression of CK2 and Stat3 Ser-727 phosphorylation levels in human glioma patient samples as well as rat orthotopic tumor model show a degree of negative correlation. Moreover, brain tumor cell lines were treated with various pharmacological inhibitors to inactivate the CK2 pathway. Here, increased Stat3 Ser-727 phosphorylation upon CK2 inhibition was observed. Overexpression of CK2 (α, α' or β subunits) by transient transfection resulted in decreased Stat3 Ser-727 phosphorylation. Stat3 Tyr-705 residue was conversely phosphorylated in similar situations. Interestingly, we found PP2A, a protein phosphatase, to be a mediator in the negative regulation of Stat3 Ser-727 phosphorylation by CK2. In vitro assays prove that Ser-727 phosphorylation of Stat3 affects the transcriptional activity of its downstream targets like SOCS3, bcl-xl and Cyclin D1. Stable cell lines constitutively expressing Stat3 S727A mutant showed increased survival, proliferation and invasion which are characteristics of a cancer cell. Rat tumor models generated with the Stat3 S727A mutant cell line formed more aggressive tumors when compared to the Stat3 WT expressing stable cell line. Thus, in glioma, reduced Stat3 Ser-727 phosphorylation enhances tumorigenicity which may be regulated in part by CK2-PP2A pathway. 10.1016/j.cellsig.2014.04.003