Effects of interleukin-10 treated macrophages on bone marrow mesenchymal stem cells via signal transducer and activator of transcription 3 pathway

BACKGROUND Alveolar bone defects caused by inflammation are an urgent issue in oral implant surgery that must be solved.Regulating the various phenotypes of macrophages to enhance the inflammatory environment can significantly affect the progression of diseases and tissue engineering repair process.AIM To assess the influence of interleukin-10(IL-10)on the osteogenic differentiation of bone marrow mesenchymal stem cells(BMSCs)following their interaction with macrophages in an inflammatory environment.METHODS IL-10 modulates the differentiation of peritoneal macrophages in Wistar rats in an inflammatory environment.In this study,we investigated its impact on the proliferation,migration,and osteogenesis of BMSCs.The expression levels of signal transducer and activator of transcription 3(STAT3)and its activated form,phos-phorylated-STAT3,were examined in IL-10-stimulated macrophages.Subsequently,a specific STAT3 signaling inhibitor was used to impede STAT3 signal activation to further investigate the role of STAT3 signaling.RESULTS IL-10-stimulated macrophages underwent polarization to the M2 type through substitution,and these M2 macrophages actively facilitated the osteogenic differentiation of BMSCs.Mechanistically,STAT3 signaling plays a crucial role in the process by which IL-10 influences macrophages.Specifically,IL-10 stimulated the activation of the STAT3 signaling pathway and reduced the macrophage inflammatory response,as evidenced by its diminished impact on the osteogenic differentiation of BMSCs.CONCLUSION Stimulating macrophages with IL-10 proved effective in improving the inflammatory environment and promoting the osteogenic differentiation of BMSCs.The IL-10/STAT3 signaling pathway has emerged as a key regulator in the macrophage-mediated control of BMSCs’osteogenic differentiation.

Apigenin ameliorates imiquimod-induced psoriasis in C57BL/6J mice by inactivating STAT3 and NF-κB

Psoriasis is a chronic autoimmune disease featured by patches on the skin.It is caused by malfunction of immune cells and keratinocytes with inflammation as one of its key features.Apigenin(API)is a natural flavonoid with anti-inflammatory and immunoregulatory properties.Therefore,we speculated that API can ameliorate psoriasis,and determined its effect on the development of psoriasis by using imiquimod(IMQ)-induced psoriasis mouse model.Our results showed that API attenuated IMQ-induced phenotypic changes,such as erythema,scaling and epidermal thickening,and improved splenic hyperplasia.Abnormal differentiation of immune cells was restored in API-treated mice.Mechanistically,we revealed that API is a key regulator of signal transducer activator of transcription 3(STAT3).API regulated immune responses by reducing interleukin-23(IL-23)/STAT3/IL-17A axis.Moreover,it suppressed IMQ-caused cell hyperproliferation by inactivating STAT3 through regulation of extracellular signal-regulated kinase 1/2 and nuclear factor-κB(NF-κB)pathway.Furthermore,API reduced expression of inflammatory cytokines through inactivation of NF-κB.Taken together,our study demonstrates that API can ameliorate psoriasis and may be considered as a strategy for psoriasis treatment.

18β-glycyrrhetinic acid promotes gastric cancer cell autophagy and inhibits proliferation by regulating miR-328-3p/signal transducer and activator of transcription 3

BACKGROUND Gastric cancer(GC)is one of the most common cancer types worldwide,and its prevention and treatment methods have garnered much attention.As the active ingredient of licorice,18β-glycyrrhetinic acid(18β-GRA)has a variety of pharmacological effects.The aim of this study was to explore the effective target of 18β-GRA in the treatment of GC,in order to provide effective ideas for the clinical prevention and treatment of GC.AIM To investigate the mechanism of 18β-GRA in inhibiting cell proliferation and promoting autophagy flux in GC cells.METHODS Whole transcriptomic analyses were used to analyze and screen differentially expressed microRNAs(miRNAs)in GC cells after 18β-GRA intervention.Lentivirus-transfected GC cells and the Cell Counting Kit-8 were used to detect cell proliferation ability,cell colony formation ability was detected by the clone formation assay,and flow cytometry was used to detect the cell cycle and apoptosis.A nude mouse transplantation tumor model of GC cells was constructed to verify the effect of miR-328-3p overexpression on the tumorigenicity of GC cells.Tumor tissue morphology was observed by hematoxylin and eosin staining,and microtubule-associated protein light chain 3(LC3)expression was detected by immunohistochemistry.TransmiR,STRING,and miRWalk databases were used to predict the relationship between miR-328-3p and signal transducer and activator of transcription 3(STAT3)-related information.Expression of STAT3 mRNA and miR-328-3p was detected by quantitative polymerase chain reaction(qPCR)and the expression levels of STAT3,phosphorylated STAT3(p-STAT3),and LC3 were detected by western blot analysis.The targeted relationship between miR-328-3p and STAT3 was detected using the dual-luciferase reporter gene system.AGS cells were infected with monomeric red fluorescent protein-green fluorescent protein-LC3 adenovirus double label.LC3 was labeled and autophagy flow was observed under a confocal laser microscope.RESULTS The expression of miR-328-3p was significantly upregulated after 18β-GRA intervention in AGS cells(P=4.51E-06).Overexpression of miR-328-3p inhibited GC cell proliferation and colony formation ability,arrested the cell cycle in the G0/G1 phase,promoted cell apoptosis,and inhibited the growth of subcutaneous tumors in BALB/c nude mice(P<0.01).No obvious necrosis was observed in the tumor tissue in the negative control group(no drug intervention or lentivirus transfection)and vector group(the blank vector for lentivirus transfection),and more cells were loose and necrotic in the miR-328-3p group.Bioinformatics tools predicted that miR-328-3p has a targeting relationship with STAT3,and STAT3 was closely related to autophagy markers such as p62.After overexpressing miR-328-3p,the expression level of STAT3 mRNA was significantly decreased(P<0.01)and p-STAT3 was downregulated(P<0.05).The dual-luciferase reporter gene assay showed that the luciferase activity of miR-328-3p and STAT33’untranslated regions of the wild-type reporter vector group was significantly decreased(P<0.001).Overexpressed miR-328-3p combined with bafilomycin A1(Baf A1)was used to detect the expression of LC3 II.Compared with the vector group,the expression level of LC3 II in the overexpressed miR-328-3p group was downregulated(P<0.05),and compared with the Baf A1 group,the expression level of LC3 II in the overexpressed miR-328-3p+Baf A1 group was upregulated(P<0.01).The expression of LC3 II was detected after intervention of 18β-GRA in GC cells,and the results were consistent with the results of miR-328-3p overexpression(P<0.05).Additional studies showed that 18β-GRA promoted autophagy flow by promoting autophagosome synthesis(P<0.001).qPCR showed that the expression of STAT3 mRNA was downregulated after drug intervention(P<0.05).Western blot analysis showed that the expression levels of STAT3 and p-STAT3 were significantly downregulated after drug intervention(P<0.05).CONCLUSION 18β-GRA promotes the synthesis of autophagosomes and inhibits GC cell proliferation by regulating the miR-328-3p/STAT3 signaling pathway.

Immunotherapeutic hydrogel for co-delivery of STAT3 siRNA liposomes and lidocaine hydrochloride for postoperative comprehensive management of NSCLC in a single application

Despite standard treatment for non-small cell lung cancer(NSCLC)being surgical resection,cancer recurrence and complications,such as induction of malignant pleural effusion(MPE)and significant postoperative pain,usually result in treatment failure.In this study,an alginate-based hybrid hydrogel(SOG)is developed that can be injected into the resection surface of the lungs during surgery.Briefly,endoplasmic reticulum-modified liposomes(MSLs)pre-loaded with the signal transducer and activator of transcription 3(STAT3)small interfering RNA and lidocaine hydrochloride are encapsulated in SOG.Once applied,MSLs strongly downregulated STAT3 expression in the tumor microenvironment,resulting in the apoptosis of lung cancer cells and polarization of tumor-associated macrophages towards the M1-like phenotype.Meanwhile,the release of lidocaine hydrochloride(LID)was beneficial for pain relief and natural killer cell activation.Our data demonstrated MSL@LID@SOG not only efficiently inhibited tumor growth but also potently improved the quality of life,including reduced MPE volume and pain relief in orthotopic NSCLC mouse models,even with a single administration.MSL@LID@SOG shows potential for comprehensive clinical management upon tumor resection in NSCLC,and may alter the treatment paradigms for other cancers.

STAT3-Dependent Effects of Polymeric Immunoglobulin Receptor in Regulating Interleukin-17 Signaling and Preventing Autoimmune Hepatitis

One-third of patients with autoimmune hepatitis(AIH)have cirrhosis at the time of diagnosis.The relevance of these variables,although unknown,is believed to be critical in AIH because of suspected interactions between the gut microbiome and genetic factors.Dysbiosis of the gut flora and elevated polymeric immunoglobulin receptor(pIgR)levels have been observed in both patients and mouse models.Moreover,there is a direct relationship between pIgR expression and transaminase levels in patients with AIH.In this study,we aimed to explore how pIgR influences the secretion of regenerating islet-derived 3 beta(Reg3b)and the flora composition in AIH using in vivo experiments involving patients with AIH and a concanavalin A-induced mouse model of AIH.Reg3b expression was reduced in pIgR gene(Pigr)-knockout mice compared to that in wild-type mice,leading to increased microbiota disruption.Conversely,exogenous pIgR supplementation increased Reg3b expression and maintained microbiota homeostasis.RNA sequencing revealed the participation of the interleukin(IL)-17 signaling pathway in the regulation of Reg3b through pIgR.Furthermore,the introduction of external pIgR could not restore the imbalance in gut microbiota in AIH,and the decrease in Reg3b expression was not apparent following the inhibition of signal transducer and activator of transcription 3(STAT3).In this study,pIgR facilitated the upregulation of Reg3b via the STAT3 pathway,which plays a crucial role in preserving the balance of the intestinal microbiota in AIH.Through this research,we discovered new molecular targets that can be used for the diagnosis and treatment of AIH.

Galectin 2 regulates JAK/STAT3 signaling activity to modulate oral squamous cell carcinoma proliferation and migration in vitro

Background:Galectin 2(LGALS2)is a protein previously reported to serve as a mediator of disease progression in a range of cancers.The function of LGALS2 in oral squamous cell carcinoma(OSCC),however,has yet to be explored,prompting the present study to address this literature gap.Methods:Overall,144 paired malignant tumor tissues and paracancerous OSCC patient samples were harvested and the LGALS2 expression levels were examined through qPCR and western immunoblotting.The LGALS2 coding sequence was introduced into the pcDNA3.0 vector,to enable the overexpression of this gene,while an LGALS2-specific shRNA and corresponding controls were also obtained.The functionality of LGALS2 as a regulator of the ability of OSCC cells to grow and undergo apoptotic death in vitro was assessed through EdU uptake and CCK-8 assays,and flow cytometer,whereas a Transwell system was used to assess migratory activity and invasivity.An agonist of the Janus Kinase 2(JAK2)/Signal Transducer and Activator of Transcription 3(STAT3)pathway was also used to assess the role of this pathway in the context of LGALS2 signaling.Results:Here,we found that lower LGALS2 protein and mRNA expression were evident in OSCC tumor tissue samples,and these expression levels were associated with clinicopathological characteristics and patient survival outcomes.Silencing LGALS2 enhanced proliferation in OSCC cells while rendering these cells better able to resist apoptosis.The opposite was instead observed after LGALS2 was overexpressed.Mechanistically,the ability of LGALS2 to suppress the progression of OSCC was related to its ability to activate the JAK/STAT3 signaling axis.Conclusion:Those results suggest a role for LGALS2 as a suppressor of OSCC progression through its ability to modulate JAK/STAT3 signaling,supporting the potential utility of LGALS2 as a target for efforts aimed at treating OSCC patients.

Gossypol acetic acid regulates leukemia stem cells by degrading LRPPRC via inhibiting IL-6/JAK1/STAT3 signaling or resulting mitochondrial dysfunction

BACKGROUND Leukemia stem cells(LSCs)are found to be one of the main factors contributing to poor therapeutic effects in acute myeloid leukemia(AML),as they are protected by the bone marrow microenvironment(BMM)against conventional therapies.Gossypol acetic acid(GAA),which is extracted from the seeds of cotton plants,exerts anti-tumor roles in several types of cancer and has been reported to induce apoptosis of LSCs by inhibiting Bcl2.AIM To investigate the exact roles of GAA in regulating LSCs under different microenvironments and the exact mechanism.METHODS In this study,LSCs were magnetically sorted from AML cell lines and the CD34+CD38-population was obtained.The expression of leucine-rich pentatricopeptide repeat-containing protein(LRPPRC)and forkhead box M1(FOXM1)was evaluated in LSCs,and the effects of GAA on malignancies and mitochondrial RESULTS LRPPRC was found to be upregulated,and GAA inhibited cell proliferation by degrading LRPPRC.GAA induced LRPPRC degradation and inhibited the activation of interleukin 6(IL-6)/janus kinase(JAK)1/signal transducer and activator of transcription(STAT)3 signaling,enhancing chemosensitivity in LSCs against conventional chemotherapies,including L-Asparaginase,Dexamethasone,and cytarabine.GAA was also found to downregulate FOXM1 indirectly by regulating LRPPRC.Furthermore,GAA induced reactive oxygen species accumulation,disturbed mitochondrial homeostasis,and caused mitochondrial dysfunction.By inhibiting IL-6/JAK1/STAT3 signaling via degrading LRPPRC,GAA resulted in the elimination of LSCs.Meanwhile,GAA induced oxidative stress and subsequent cell damage by causing mitochondrial damage.CONCLUSION Taken together,the results indicate that GAA might overcome the BMM protective effect and be considered as a novel and effective combination therapy for AML.

Inhibition of signal transducer and activator of transcription 3 expression by RNA interference suppresses invasion through inducing anoikis in human colon cancer cells

AIM:To investigate the roles and mechanism of signal transducer and activator of transcription 3 (STAT3) in invasion of human colon cancer cells by RNA interference. METHODS: Small interfering RNA (siRNA) targeting Signal transducer and activator of transcription 3 (STAT3) was transfected into HT29 colon cancer cells. STAT3 protein level and DNA-binding activity of STAT3 was evaluated by western blotting and electrophoretic mobility shift assay (EMSA), respectively. We studied the anchorage-independent growth using colony formation in soft agar, and invasion using the boyden chamber model, anoikis using DNA fragmentation assay and terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL), respectively. Western blot assay was used to observe the protein expression of Bcl-xL and survivin in colon cancer HT29 cells. RESULTS: RNA interference (RNAi) mediated by siRNA leads to suppression of STAT3 expression in colon cancer cell lines. Suppression of STAT3 expression by siRNA could inhibit anchorage-independent growth, and invasion ability, and induces anoikis in the colon cancer cell line HT29. It has been shown that knockdown of STAT3 expression by siRNA results in a reduction in expression of Bcl-xL and survivin in HT29 cells. CONCLUSION: These results suggest that STAT3 siRNA can inhibit the invasion ability of colon cancer cells through inducing anoikis, which antiapoptotic genes survivin and Bcl-xL contribute to regulation of anoikis.These studies indicate STAT3 siRNA could be a useful therapeutic tool for the treatment of colon cancer.

Silencing of signal transducer and activator of transcription 3 expression by RNA interference suppresses growth of human hepatocellular carcinoma in tumor-bearing nude mice

AIM： To explore the effect of silencing of signal transducer and activator of transcription 3 （STAT3） expression by RNA interference （RNAi） on growth of human hepatocellular carcinoma （HCC） in tumorbearing nude mice in vivo.METHODS： To construct the recombinant plasmid of pSilencer 3.0-H1-STAT3-siRNA-GFP （pSHI-siRNA- STAT3） and establish the tumor-bearing nude mouse model of the HCC cell line SMMC7721, we used intratumoral injection together with electroblotting to transfect the recombinant plasmid pSHI-siRNA- STAT3 into the transplanted tumor. The weight of the nude mice and tumor volumes were recorded. STAT3 gene transcription was detected by semi-quantitative reverse transcription polymerase chain reaction （RT- PCR）. Level of protein expression and location of STAT3 were determined by Western blotting and immunohistochemical staining. STAT3-related genes such as survivin, c-myc, VEGF, p53 and caspase3 mRNA and protein expression were detected in tumor tissues at the same time. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNEL） assay was used to detect apoptosis of tumor cells.RESULTS： The weight of the treated nude mice increased, and the tumor volume decreased markedly compared with those of the mock-treated and negative control groups （P 〈 0.01）. The results of RT-PCR and Western blotting showed that mRNA and protein levels of STAT3 declined markedly in the treated group. The change in STAT3-related gene expression in tumor tissues at the mRNA and protein level also varied, the expression of survivin, VEGF and c-myc were obviously reduced, and expression of p53 and caspase3 increased （P 〈 0.01）. Most of the tumor tissue ceils in the treated group developed apoptosis that was detected by TUNEL assay.CONCLUSION： Silencing of STAT3 expression by RNAi significantly inhibits expression of STAT3 mRNA and protein, and suppresses growth of human HCC in tumor-bearing nude mice. The mechanism may be related to down-regulation of survivin, VEGF and c-myc and up-regulation of p53 and caspase3 expression. Accordingly, the STAT3 gene may act as an important and effective target in gene therapy of HCC.

Downregulation of signal transducer and activator of transcription 3 by sorafenib:A novel mechanism for hepatocellular carcinoma therapy

Hepatocellular carcinoma is one of the most common cancers worldwide,and a leading cause of cancer-related death.Owing to unsatisfactory clinical outcomes under the current standard of care,there is a need to search for and identify novel and potent therapeutic targets to improve patient outcomes.Sorafenib is the first and only approved targeted therapy for the treatment of hepatocellular carcinoma.Besides functioning as a multiple tyrosine kinase,sorafenib also acts via a kinase-independent mechanism to target signal transducer and activator of transcription 3(STAT3) signaling in hepatocellular carcinoma cells.STAT3 is a key regulator of inflammation,cell survival,and tumorigenesis of liver cells,and the high percentage of hepatocellular carcinoma cells with constitutively active STAT3 justifies targeting it for the development of novel therapeutics.Sorafenib inactivates STAT3 and STAT3-related signaling by inducing a conformational change in and releasing the autoinhibition of Src homology region 2 domaincontaining phosphatase-1.This phosphatase negatively regulates STAT3 activity,which leads to the subsequent apoptosis of cancer cells.The novel anti-cancer property of sorafenib will be discussed in this review,not only adding information regarding its mechanism of action but also providing an innovative approach for the development of cancer therapeutics in the future.

Diffusion-weighted magnetic resonance imaging reflects activation of signal transducer and activator of transcription 3 during focal cerebral ischemia/reperfusion

Signal transducer and activator of transcription（STAT）is a unique protein family that binds to DNA,coupled with tyrosine phosphorylation signaling pathways,acting as a transcriptional regulator to mediate a variety of biological effects.Cerebral ischemia and reperfusion can activate STATs signaling pathway,but no studies have confirmed whether STAT activation can be verified by diffusion-weighted magnetic resonance imaging（DWI）in rats after cerebral ischemia/reperfusion.Here,we established a rat model of focal cerebral ischemia injury using the modified Longa method.DWI revealed hyperintensity in parts of the left hemisphere before reperfusion and a low apparent diffusion coefficient.STAT3 protein expression showed no significant change after reperfusion,but phosphorylated STAT3 expression began to increase after 30 minutes of reperfusion and peaked at 24 hours.Pearson correlation analysis showed that STAT3 activation was correlated positively with the relative apparent diffusion coefficient and negatively with the DWI abnormal signal area.These results indicate that DWI is a reliable representation of the infarct area and reflects STAT phosphorylation in rat brain following focal cerebral ischemia/reperfusion.

Glycine Attenuates Myocardial Fibrosis in Myocardial Infarction in Rats Partly through Modulating Signal Transducer and Activator of Transcription 3/Nuclear Factor-κB/Transforming Growth Factor-β axis

Objective: Inflammation and fibrosis are strongly associated with each other. Glycine is present in various traditional Chinese medicines and exhibits anti-inflammatory activity. However, the effects of glycine on myocardial fibrosis(MF) in rats with myocardial infarction(MI) have not been reported. The purpose of this study is to investigate the effects of glycine therapy on MF and comprehend its underlying mechanisms. Materials and Methods: Left anterior descending artery ligation-induced MI in Sprague Dawley rats was leveraged to assess the therapeutic effects of Glycine. Rats received either normal saline or glycine(0.5 mg/g bodyweight) for 7 days. Results: Glycine upregulated cardiac ejection fraction and fractional shortening to improve cardiac function, as evaluated by echocardiography. Histological and immunohistochemical analyses demonstrated that glycine could decrease inflammatory cell infiltration and alleviate collagen deposition. Western blotting revealed that nuclear factor-κB(NF-κB)-mediated inflammatory signaling was also downregulated by glycine treatment. The expression of signal transducer and activator of transcription 3(STAT3), tumor necrosis factor-α, and transforming growth factor-β(TGF-β) was decreased significantly in the glycine-treated group compared to the model group. Thus, glycine plays a protective role against myocardial ischemia and subsequent MF. Conclusion: The protective effects of glycine were achieved partly through STAT3/NF-κB/TGF-β signaling pathway.

(-)-Epigallocatechin-3-gallate inhibits growth of gastric cancer by reducing VEGF production and angiogenesis

AIM： To investigate the effect of （-）-epigallocatechin-3-gallate （EGCG） on growth of gastric cancer and its possible mechanism. METHODS： Heterotopic tumors were induced by subcutaneously injection of SGC-7901 cells in nude mice. Tumor growth was measured by calipers in two dimensions. Tumor angiogenesis was determined with tumor microvessel density （MVD） by immunohistology. Vascular endothelial growth factor （VEGF） protein level and activation of signal transducer and activator of transcription 3 （Star3） were examined by Western blotting. VEGF mRNA expression was determined by RT-PCR and VEGF release in tumor culture medium by ELISA. VEGF-induced cell proliferation was studied by MTT assay, cell migration by gelatin modified Boyden chamber （Transwell） and in vitro angiogenesis by endothelial tube formation in Matrigel. RESULTS： Intraperitoneal injection of EGCG inhibited the growth of gastric cancer by 60.4%. MVD in tumor tissues treated with EGCG was markedly reduced. EGCG treatment reduced VEGF protein level in vitro and in vivo. Secretion and mRNA expression of VEGF in tumor cells were also suppressed by EGCG in a dose-dependent manner. This inhibitory effect was associated with reduced activation of Star3, but EGCG treatment did not change the total Star3 expression. EGCG also inhibited VEGF-induced endothelial cell proliferation, migration and tube formation. CONCLUSION： EGCG inhibits the growth of gastric cancer by reducing VEGF production and angiogenesis, and is a promising candidate for anti-angiogenic treatment of gastric cancer.

Lentivirus-mediated shRNA interference targeting STAT3 inhibits human pancreatic cancer cell invasion

AIM： To investigate RNA interference targeting signal transducer and activator of transcription-3 （STAT3） on invasion of human pancreatic cancer cells.METHODS： We constructed three plasmids of RNA interference targeting the STAT3 gene. After LV （lentivirus）-STAT3siRNA （STAT3 small interfering RNA） the vector was transfected into the human pancreatic cell line, SW1990 and cell proliferation was measured by the MTT assay. Flow cytometry was used to assess cell cycle. Vascular endothelial growth favor （VEGF） and matrix metalloproteinase-2 （MMP-2） mRNA and protein expression were examined by quantitative PCR and western blotting, respectively. The invasion ability of SW1990 cells was determined by cell invasion assay.RESULTS： We successfully constructed the LVSTAT3siRNA lentivirus vector and proved that it can suppress expression of STAT3 gene in SW1990 cells. RNA interference of STAT3 by the LV-STAT3siRNA construct significantly inhibited the growth of SW1990 cells, in addition to significantly decreasing both VEGF and MMP-2 mRNA and protein expression. Moreover, suppression of STAT3 by LV-STAT3siRNA decreased the invasion ability of SW1990 cells.CONCLUSION： The STAT3 signaling pathway may provide a novel therapeutic target for the treatment of pancreatic cancer since it inhibits the invasion ability of pancreatic cancer cells.

(-)-Epigallocatechin-3-gallate inhibits VEGF expression induced by IL-6 via Stat3 in gastric cancer

AIM: To demonstrate that (-)-Epigallocatechin-3-gallate (EGCG) inhibits vascular endothelial growth factor (VEGF) expression and angiogenesis induced by interleukin-6 (IL-6) via suppressing signal transducer and activator of transcription 3 (Stat3) activity in gastric cancer. METHODS: Human gastric cancer (AGS) cells were treated with IL-6 (50 ng/mL) and EGCG at different concentrations. VEGF, total Stat3 and activated Stat3 protein levels in the cell lyses were examined by Western blotting, VEGF protein level in the conditionedmedium was measured by enzyme-linked immunosorbent assay, and the level of VEGF mRNA was evaluated by reverse transcription polymerase chain reaction (RTPCR). Stat3 nuclear translocation was determined by Western blotting with nuclear extract, and Stat3-DNA binding activity was examined with Chromatin immunoprecipitation (ChIP) assay. IL-6 induced endothelial cell proliferation was measured with 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazoliumbromide assay, in vitro angiogenesis was determined with endothelial cell tube formation assay in Matrigel, and IL-6-induced angiogenesis in vitro was measured with Matrigel plug assay. RESULTS: There was a basal expression and secretion of VEGF in AGS cells. After stimulation with IL-6, VEGF expression was apparently up-regulated and a 2.4-fold increase was observed. VEGF secretion in the conditioned medium was also increased by 2.8 folds. When treated with EGCG, VEGF expression and secretion were dose-dependently decreased. IL-6 also increased VEGF mRNA expression by 3.1 folds. EGCG treatment suppressed VEGF mRNA expression in a dose-dependent manner. EGCG dose-dependently inhibited Stat3 activation induced by IL-6, but did not change the total Stat3 expression. When treated with EGCG or AG490, VEGF expressions were reduced to the level or an even lower level in the tumor cells not stimulated with IL-6. However, PD98059 and LY294002 did not change VEGF expression induced by IL-6. EGCG inhibited Stat3 nucleus translocation, and Stat3-DNA binding activity was also markedly decreased by EGCG. Furthermore, EGCG inhibited IL-6 induced vascular endothelial cell proliferation and tube formation in vitro and angiogenesis in vitro . CONCLUSION: EGCG inhibits IL-6-induced VEGF expression and angiogenesis via suppressing Stat3 activity in gastric cancer, which has provided a novel mechanistic insight into the anti-angiogenic activity of EGCG.

Expression of p-STAT3 and vascular endothelial growth factor in MNNG-induced precancerous lesions and gastric tumors in rats

AIM: To investigate the dynamic expression of p-signal transducer and activator of transcription 3 (STAT3) and vascular endothelial growth factor (VEGF) in the formation of gastric tumors induced by drinking water containing N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) in Wistar rats. METHODS: One hundred and twenty Wistar rats were randomly divided into two groups (60 in each group): Control group and Model group. The rats in each group were then randomly divided into three groups (20 in each group): C/M15, C/M25 and C/M40 (15, 25 and 40 represent the number of feeding weeks from termination). Rats in the control group received normal drinking water and rats in the model group received drinking water containing 100 μg/mL MNNG. Stomach tissues were collected at the end of the 15th, 25th and 40th week, respectively, for microscopic measurement using hematoxylin and eosin staining. The expression of p-STAT3 and VEGF in different pathological types of gastric tissue, including normal, inflammation, atrophy, hyperplasia and gastric stromal tumor, was observed by immunohistochemistry and Western blot, and the corelation between p-STAT3 and VEGF was analyzed. RESULTS: (1) The expression of p-STAT3 in tissue with gastritis, atrophy, dysplasia and gastric stromal tumor were significantly increased in the model group compared with the control group (2.5 ± 1.0, 2.75 ± 0.36, 6.2 ± 0.45, 5.67 ± 0.55 vs 0.75 ± 0.36, P = 0.026, 0.035, 0.001, 0.002, respectively); the expression of p-STAT3 in tissue with dysplasia was higher than that in samples with gastritis or atrophy (6.2 ± 0.45 vs 2.5 ± 1.0, P = 0.006; 6.2 ± 0.45 vs 2.75 ± 0.36, P = 0.005, respectively); however, the expression of p-STAT3 in gastritis and atrophy was not significantly different (P > 0.05); (2) the expression of VEGF in tissue with gastritis, atrophy, dysplasia and gastric stromal tumor was significantly increased in the model group compared with normal gastric mucosa; and the expression of VEGF in tissue with dysplasia was higher than that in tissue with inflammation and atrophy (10.8 ± 1.96 vs 7.62 ± 0.25, P = 0.029; 10.8 ± 1.96 vs 6.26 ± 0.76, P = 0.033, respectively); similarly, the expression of VEGF in tissue with gastritis and atrophy was not significantly different (P > 0.05); and (3) the expression of VEGF was positively correlated with p-STAT3. CONCLUSION: p-STAT3 plays an important role in gastric cancer formation by regulating the expression of VEGF to promote the progression of gastric tumor from gastritis.

STAT3 and sphingosine-1-phosphate in inflammation-associated colorectal cancer

Accumulated evidences have demonstrated that signal transducer and activator of transcription 3(STAT3)is a critical link between inflammation and cancer.Multiple studies have indicated that persistent activation of STAT3 in epithelial/tumor cells in inflammation-associated colorectal cancer(CRC)is associated with sphingosine-1-phosphate(S1P)receptor signaling.In inflammatory response whereby interleukin(IL)-6 production is abundant,STAT3-mediated pathways were found to promote the activation of sphingosine kinases(SphK1and SphK2)leading to the production of S1P.Reciprocally,S1P encourages the activation of STAT3 through a positive autocrine-loop signaling.The crosstalk between IL-6,STAT3 and sphingolipid regulated pathways may play an essential role in tumorigenesis and tumor progression in inflamed intestines.Therapeutics targeting both STAT3 and sphingolipid are therefore likely to contribute novel and more effective therapeutic strategies against inflammation-associated CRC.

STAT3 Correlates with Stem Cell-related Transcription Factors in Cervical Cancer

Summary： Cancer stem cells （CSCs） are considered responsible for the high recurrence rate in cervical carcinoma. It has been demonstrated that the signal transducer and activator of transcription 3 （STAT3） is involved in the oncogenesis and takes part in mediating the effects of maintaining stem cell phenotype and pluripotency by regulating the expression of stem cell-related transcription factors. However, the correlation between STAT3 and stem cell-related transcription factors in cervical cancer has not been elucidated. In this study, we established overexpressing plasmid （GV316-STAT3） and siRNA-STAT3 for transfecting Siha cells. Cells negative or positive for Nanog, Oct4, or Sox2 were selected by flow cytometry. Proliferation and differentiation rate of Siha cells was determined by detecting the efficiency of tumor sphere formation. The expression of Nanog, Oct4 and Sox2 （cancer stem cell markers） and STAT3 was detected by quantitative real-time PCR and immunoblotting for Siha cells and by immuno- histochemistry （IHC） for cervical tissues, respectively. The results showed that Nanog＋, Oct4＋, and Sox2＋ Siha-STAT3 over-expressing cells displayed the typical non-adherent spheres. The sphere for- mation efficiency was significantly different between Siha-STAT3 overexpressing cells and siRNA-STAT3 cells （P〈0.05）. Meanwhile, the expression levels of Oct4, Nanog and Sox2 rrtRNA and protein were significantly higher in Siha-STAT3 overexprssing cells than in siRNA-STAT3 cells （P〈0.05）. In addition, the positive rate of STAT3, Nanog, Oct4 and Sox2 in cervical cancer tissues was higher than that in chronic cervicitis group （P〈0.05）. There was a significantly positive relationship between STAT3 and Nanog or Oct4 or Sox2 expression （all P〈0.001）. These results suggested that Oct4＋, Sox2＋, and Nanog＋ cell population possesses stem cell properties in cervical cancer, which may contribute to cervical carcinogenesis and be regulated by STAT3.

Leptin Activates STAT3 and ERK1/2 Pathways and Induces Endometrial Cancer Cell Proliferation

Obesity is an established risk factor for endometrial cancer.Leptin,a secreted protein of the ob gene by white adipose tissue,plays an important role in the regulation of food intake and energy consumption in the brain and acts as a potential growth stimulator in normal and neoplastic cancer cells.However,a direct role for leptin in endometrial cancer has not been demonstrated.In the present study,the effect of leptin on the proliferation of Ishikawa endometrial cancer cells was investigated as well as the possible mechanism（s） underlying this action in endometrial cancers which express both short and long isoforms of leptin receptors.The expression of leptin receptor（ObRb） in Ishikawa cells was detected by RT-PCR and Western blotting.The cells after serum starvation,were treated by leptin with various concentrations（0,10,50,100,150 ng/mL） for different durations（6,12,24 h）.The effect of leptin treatment on cell proliferation was examined by MTT assay.Meanwhile,inhibitory effect of Janus tyrosine kinase 2（JAK2）/signal transducer and activator of transcription 3（STAT3） inhibitor AG490 or extracellular signal-regulated kinase 1/2（ERK1/2） inhibitor PD98059 on the proliferation of Ishikawa cells induced by leptin was also studied.Ishikawa cells were treated with 100 ng/mL leptin for various periods（0,20,40,60 min）,and the levels of STAT3 phosphorylation and ERK1/2 phosphorylation were examined by Western blotting.The results showed that leptin induced the phosphorylation of STAT3 and the activation of ERK1/2 in a time-and dose-dependent manner in the Ishikawa endometrial cancer cells.Blocking STAT3 phosphorylation with the inhibitor AG490,or blocking ERK1/2 activation by the specific ERK1/2 kinase inhibitor,PD98059,abolished leptin-induced proliferation of Ishikawa cells.In addition,leptin was found to potently induce the invasion of endometrial cancer cells in a Matrigel invasion assay.Leptin-stimulated invasion was effectively blocked by pharmacological inhibitors of STAT3（AG490） and ERK1/2 kinase（PD98059）.These results suggested that leptin promotes endometrial cancer growth and invasiveness by activating STAT3 and ERK1/2 signaling pathways and therefore blocking its action at the receptor level can be a rational therapeutic strategy.

Sorafenib inhibits growth and metastasis of hepatocellular carcinoma by blocking STAT3

AIM: To investigate the inhibitory role and the underlying mechanisms of sorafenib on signal transducer and activator of transcription 3 (STAT3) activity in hepatocellular carcinoma (HCC).METHODS: Human and rat HCC cell lines were treated with sorafenib. Proliferation and STAT3 dephosphorylation were assessed. Potential molecular mechanisms of STAT3 pathway inhibition by sorafenib were evaluated. In vivo antitumor action and STAT3 inhibition were investigated in an immunocompetent orthotopic rat HCC model.RESULTS: Sorafenib decreased STAT3 phosphorylationat the tyrosine and serine residues (Y705 and S727), but did not affect Janus kinase 2 (JAK2) and phosphatase shatterproof 2 (SHP2), which is associated with growth inhibition in HCC cells. Dephosphorylation of S727 was associated with attenuated extracellular signal-regulated kinase (ERK) phosphorylation, similar to the effects of a mitogen-activated protein kinase (MEK) inhibitor U0126, suggesting that sorafenib induced S727 dephosphorylation by inhibiting MEK/ERK signaling. Meanwhile, sorafenib could also inhibit Akt phosphorylation, and both the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 and Akt knockdown resulted in Y705 dephosphorylation, indicating that Y705 dephosphorylation by sorafenib was mediated by inhibiting the PI3K/Akt pathway. Finally, in the rat HCC model, sorafenib signifi cantly inhibited STAT3 activity, reducing tumor growth and metastasis.CONCLUSION: Sorafenib inhibits growth and metastasis of HCC in part by blocking the MEK/ERK/STAT3 and PI3K/Akt/STAT3 signaling pathways, but independent of JAK2 and SHP2 activation.