Activation Of Signal Transducer And Activator Of Transcription 3 Signaling Pathway Research Articles

Glaucocalyxin A suppresses multiple myeloma progression in vitro and in vivo through inhibiting the activation of STAT3 signaling pathway

BackgroundMultiple myeloma (MM) is the most common malignant hematological disease in the people worldwide. Glaucocalyxin A (GLA) is a bioactive ent-kauranoid diterpenoid, that is derived from Rabdosia japonica var. GLA has been demonstrated that it had various pharmacological activities, such as anti-coagulation, anti-bacterial, anti-tumor, anti-inflammation, antioxidant activities. Although GLA has effective anti-tumor properties, its effects on multiple myeloma remain unclear. The aim of this study was to examine the possible anti-cancer effects of GLA and their molecular mechanisms on MM cells in vitro and in vivo.MethodsTo evaluate the role of GLA on the proliferation of MM cells in vitro and in vivo, we used MTT method to detect the role of GLA on the proliferation of MM cells. Cell apoptosis and cell cycle assay were evaluated by flow cytometry. Protein expressions in GLA-treated and untreated MM cells were evaluated by western blot analyses. MM xenograft nude mice model was used to investigate the role of GLA on the proliferation of MM cells in vivo. IHC assay was used to examine the role of GLA on the MM xenograft model in vivo.ResultsIn the present study, we firstly reported the potent anti-myeloma activity of GLA on MM cells. We found that GLA could induce apoptosis in vitro and in vivo. GLA could inhibit the phosphorylation of the signal transducer and activator of transcription 3 (STAT3) and downregulate interleukin IL-6 induced STAT3 phosphorylation in MM. Overexpression of STAT3 could significantly prevent apoptosis induced by GLA; while knockdown of STAT3 enhanced it. Moreover, GLA could inhibit cell proliferation by inducing the cell cycle arrest. GLA reduced the expression of cell cycle-related proteins CCNB1, CCND1, CCND2, and CCND3 and increased the expression of p21 in MM cell lines. In addition, in the MM xenograft nude mice model, GLA exhibited very good anti-myeloma activity. Administration of GLA almost completely inhibited tumor growth within 19 days without physical toxicity. And the IHC results showed GLA significantly inhibited cell proliferation and interfered STAT3 pathway on MM xenograft model tumor tissues.ConclusionsTaken together, our present research indicated that GLA inhibits the MM cell proliferation, induces MM cell apoptosis and cell cycle arrest through blocking the activation of STAT3 pathway. Thus, GLA may be a potential therapeutic candidate for MM patients in the future.

Krupple-Like Factor 5 is a Potential Therapeutic Target and Prognostic Marker in Epithelial Ovarian Cancer.

Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy. Despite current therapeutic and surgical options, advanced EOC shows poor prognosis. Identifying novel molecular therapeutic targets is highly needed in the management of EOC. Krupple-like factor 5 (KLF5), a zinc-finger transcriptional factor, is highly expressed in a variety of cancer types. However, its role and expression in EOC is not fully illustrated. Immunohistochemical analysis was performed to assess KLF5 protein expression in 425 primary EOC samples using tissue microarray. We also addressed the function of KLF5 in EOC and its interaction with signal transducer and activator of transcription 3 (STAT3) signaling pathway. We found that KLF5 overexpressed in 53% (229/425) of EOC samples, and is associated with aggressive markers. Forced expression of KLF5 enhanced cell growth in low expressing EOC cell line, MDAH2774. Conversely, knockdown of KLF5 reduced cell growth, migration, invasion and progression of epithelial to mesenchymal transition in KLF5 expressing cell lines, OVISE and OVSAHO. Importantly, silencing of KLF5 decreased the self-renewal ability of spheroids generated from OVISE and OVSAHO cell lines. In addition, downregulation of KLF5 potentiated the effect of cisplatin to induce apoptosis in these cell lines. These data reveals the pro-tumorigenic role of KLF5 in EOC and uncover its role in activation of STAT3 signaling pathway, suggesting the importance of KLF5 as a potential therapeutic target for EOC therapy.

Carnosol, a Natural Polyphenol, Inhibits Migration, Metastasis, and Tumor Growth of Breast Cancer via a ROS-Dependent Proteasome Degradation of STAT3.

We have previously demonstrated that carnosol, a naturally occurring diterpene, inhibited in vitro cell viability and colony growth, as well as induced cell cycle arrest, autophagy and apoptosis in human triple negative breast cancer (TNBC) cells. In the present study, we evaluated the ability of carnosol to inhibit tumor growth and metastasis in vivo. We found that non-cytotoxic concentrations of carnosol inhibited the migration and invasion of MDA-MB-231 cells in wound healing and matrigel invasion assays. Furthermore, gelatin zymography, ELISA, and RT-PCR assays revealed that carnosol inhibited the activity and downregulation the expression of MMP-9. Mechanistically, we demonstrated that carnosol suppressed the activation of STAT3 signaling pathway through a ROS-dependent targeting of STAT3 to proteasome-degradation in breast cancer cells (MDA-MB-231, Hs578T, MCF-7, and T47D). We show that blockade of proteasome activity, by MG-132 and bortezomib, or ROS accumulation, by N-acetylcysteine (NAC), restored the level of STAT3 protein. In addition, using chick embryo tumor growth assay, we showed that carnosol significantly and markedly suppressed tumor growth and metastasis of breast cancer xenografts. To the best of our knowledge, this is the first report which shows that carnosol specifically targets signal transducer and activator of transcription 3 (STAT3) for proteasome degradation in breast cancer. Our study further provide evidence that carnosol may represent a promising therapeutic candidate that canmodulate breast cancer growth and metastasis.

Glaucocalyxin A-induced oxidative stress inhibits the activation of STAT3 signaling pathway and suppresses osteosarcoma progression in vitro and in vivo

Osteosarcoma (OS) is ranked as the most common primary bone malignancy in children and adolescents worldwide, and the 5-year overall survival rate of OS is not optimistic. Constitutive activation of signal transducer and activator of transcription 3 (STAT3) has been implicated in tumor cell growth, proliferation, and anti-apoptosis in OS. Therefore, the discovery of novel molecular compounds that can effectively block STAT3 activation, is essential for the treatment of OS and improving prognosis. Here, we investigate whether Glaucocalyxin A (GLA), derived from Rabdosia japonica, exhibit the potential anticancer effects in OS. First of all, we identify that GLA potently suppressed cell proliferation, induced G2/M phase arrest and promoted substantial apoptosis in OS. Next, we conclude that GLA could induce Reactive oxygen species (ROS)-mediated oxidative stress via an imbalance of GSH and GSSG. Then, we elucidate for the first time that GLA could significantly inhibit both constitutive and IL-6-inducible activation of STAT3 (Tyr705) and JAK2, the upstream regulator of STAT3. Furthermore, we elucidate that the inhibition of STAT3 is mainly induced by ROS-mediated oxidative stress. Overall, our findings demonstrate that GLA could exhibit potent anticancer effects through effectively blocking the STAT3 signaling pathway, which was induced by ROS-mediated oxidative stress in OS in vitro and in vivo.

Silicon dioxide nanoparticles induce COX-2 expression through activation of STAT3 signaling pathway in HaCaT cells

Silicon dioxide nanoparticles (SiO2-NPs) are widely used in biomedicines and consumer products, such as sunscreens and cosmetics. However, SiO2-NPs can cause adverse effects on human health, depending on the size and concentration of nanoparticles. The present study was aimed at investigating the molecular mechanism underlying SiO2-NPs-induced inflammation in human keratinocyte (HaCaT) cells. Incubation of HaCaT cells with SiO2-NPs induced the expression of cyclooxygenase-2 (COX-2) mRNA and protein. Treatment of cells with SiO2-NPs also induced the phosphorylation, DNA binding and the reporter gene activity of signal transducer and activator of transcription 3 (STAT3). Transfection of cells with STAT3 siRNA abrogated SiO2-NPs-induced COX-2 expression. Moreover, SiO2-NPs enhanced the phosphorylation of Janus kinase2 (JAK2), Src and Akt. Pharmacological inhibition of either JAK2, Src or Akt abrogated SiO2-NPs-induced STAT3 transcriptional activity and the expression of COX-2. Treatment with LY294002 also attenuated SiO2-NPs-induced Src phosphorylation, while, JAK2 phosphorylation was not changed. In addition, SiO2-NPs generated reactive oxygen species (ROS) and treatment of N-acetyl cysteine (NAC) attenuated the phosphorylation of JAK2, Src, Akt and STAT3, as well as the expression of COX-2 in SiO2-NPs-treated HaCaT cells. Taken together, our study provides the first report that SiO2-NPs induce COX-2 expression in HaCaT cells by activating the STAT3 signaling through ROS-mediated phosphorylation of upstream kinases, Akt/Src and JAK2.

Primary study of the effects of ursolic acid on colorectal tumor and tumor microenvironment in mice

Objective To investigate the effect of ursolic acid (UA) on the colorectal tumor and microenvironment in mice, and to provide a theoretical basis for the clinical application of UA. Methods The models of subcutaneous transplanted tumor of mouse CT26 cells was established. The models were divided into four groups: control group, tumor bearing group, tumor bearing dimethyl sulfoxide (DMSO) group and tumor bearing UA group. The serum levels of interleukin-6 (IL-6) were detected by enzyme linked immunosorbent assay (ELISA). The number and percentage of myeloid-derived suppressor cell (MDSC) in the spleen of mice were analyzed by flow cytometry. The mRNA levels of IL-6 and signal transducer and activator of transcription 3 (STAT3) in tumor were examined by real-time quantitative polymerase chain reaction (RT-PCR). The protein levels of STAT3 and p-STAT3 in tumor were detected by Western blotting. Results The results showed that UA could significantly decrease the number of spleen MDSC. The accounts of spleen MDSC of tumor bearing UA group (249.60±17.12) was lower than that of tumor bearing DMSO group (366.40±34.08), and the difference was statistically significant (P=0.021). The serum level of IL-6 in tumor bearing UA group [(46.40±17.05) pg/ml] was decreased than that in tumor bearing DMSO group [(94.27±21.51) pg/ml], and the difference was statistically significant (P=0.012). The expression levels of IL-6 and STAT3 mRNA in tumor tissues of tumor bearing UA group (0.12±0.01, 0.21±0.08) were lower than those of tumor bearing DMSO group (0.69±0.14, 0.79±0.06), and the differences were statistically significant (P=0.008; P=0.003). The protein expression levels of STAT3 and p-STAT3 in tumor tissues of tumor bearing UA group (0.81±0.02, 0.28±0.04) were lower than those of tumor bearing DMSO group (0.98±0.02, 0.91±0.22), and the differences were statistically significant (P=0.027; P=0.029) . Conclusion UA may inhibit the activation of STAT3 signaling pathway and the amplification of MDSC in microenvironment by redu-cing IL-6, thus to enhance the function of immune-killing tumor cells to regulate tumor immune microenvironment and inhibit the immune escape of mouse colorectal cancer cells. Key words: Ursolic acid; Colorectal neoplasms; Tumor microenvironment; Myeloid-derived suppre-ssor cells

Arresting effect of AG490 inhibiting activation of STAT3 signaling pathway on sclera remodeling in guinea pigs with form-deprived myopia

Background JAK/ signal transducer and activator of transcription 3 (STAT3) signal pathway plays a critical role during the sclera remodeling of experimental myopia.As a tyrosine kinase inhibitor, AG490 can inhibit the activation of this pathway.But whether AG490 plays a role in delaying the development of myopia is not completely clear. Objective This study was to investigate the inhibition of AG490 to activation of STAT3 signaling pathway and the sequential arresting effect on the sclera remodeling in form-deprived myopia (FDM) models. Methods Forty guinea pigs were randomly divided into the normal control group, model control group, PBS control group and AG490 treatment group.FDM models were established by the occlusion of the right eyes of guinea pigs for consecutive 4 weeks using translucent goggles in the model control group, PBS control group and AG490 treated group, and 25 μl PBS or AG490 were respectively injected into vitreous since the first day of modeling in two-day interval till the fourth week in the PBS control group and AG490 treated group.Refractive state and axial length were examined with retinoscopy and A-scan ultrasonography before and 4 weeks after experiment.The experimental eyes were extracted in the fourth week, and the expressions of scleral STAT3, p-STAT3, metal matrix proteinase-2 (MMP-2) proteins and STAT3 mRNA, MMP-2 mRNA were detected by immunocytochemstry and semi-quantitative reverse transcription PCR (RT-PCR) respectively.The use and care of experimental animals followed ARVO. Results Compared to the normal control group, the negative refraction power and axial length were significantly increased in the model control group, PBS control group and AG490 treated group, and the axial length in the AG490 treated group was smaller than those in the model control group and PBS control group, showing significant differences among the 4 groups (refraction: F=89.063, P=0.000; axial length: F=96.145, P=0.000). The expressions of STAT3, MMP-2 and p-STAT3 in scleral tissue were weaker in the normal control group.The expressional values (A values) of STAT3, p-STAT3 and MMP-2 were 0.064±0.016, 0.019±0.002 and 0.155±0.052 in the AG490 treated group, which were lower than 0.129±0.008, 0.071±0.021, 0.425±0.004 of the model control group and 0.130±0.004, 0.069±0.002, 0.421±0.042 of the PBS control group (STAT3: t=4.641, 9.364, both at P<0.01; p-STAT3: t=4.638, 4.488, both at P<0.05; MMP-2: t=9.123, 9.029, both at P<0.05), however, these expressions were still higher than those of the normal control group (t=2.674, 2.251, 2.682, all at P <0.05). The expressional levels (A values) of STAT3 mRNA and MMP-2 mRNA in the AG490 treated group were 0.295±0.032 and 0.569±0.019, which were significantly lower than 0.547±0.015 and 0.782±0.051 in the model group as well as 0.544±0.015 and 0.779±0.048 in the PBS control group (STAT3 mRNA: t=10.115, 11.703, both at P<0.01; MMP-2 mRNA: t=9.218, 9.494, both at P<0.01). The expressional levels (A values) of STAT3 mRNA and MMP-2 mRNA in the AG490 treated group were still higher than those in the normal control group (t=2.576, 3.565, both at P<0.05). Conclusions AG490 can ultimately inhibit the development of axial myopia by arresting the activation of STAT3 signaling pathway in the FDM eyes and further regulating the expression of MMP-2 in sclera and delaying the remodeling of sclera. Key words: Myopia/prevention & control; Sclera; Eye/growth & development; Form deprivation; Janus kinase 2/antagonists & inhibitors; STAT3 transcription factor/antagonists & inhibitors; Signal transduction/drug effects; Disease models, animal; Guinea pig

Inhibition of STAT3 acetylation is associated with angiotesin renal fibrosis in the obstructed kidney.

To explore the relationship between the signal transducer and activator of transcription 3 (STAT3) signaling and renal fibrosis. Rat renal tubular epithelial NRK-52E cells were treated with angiotesin II (Ang II), nicotinamide (an inhibitor of NAD+-dependent class III protein deacetylases, SIRT1-7), or resveratrol (an activator of SIRT1). Mice underwent unilateral ureteral obstruction (UUO) were used for in vivo studies. Renal interstitial fibrosis was observed with HE and Masson's trichrome staining. STAT3 acetylation and phosphorylation, fibronectin, collagen I, collagen IV, and α-smooth muscle actin (α-SMA) levels were examined using Western blotting. Nicotinamide (0.625-10 mmol/L) dose-dependently increased STAT3 acetylation on Lys685 and phosphorylation on Tyr705 in NRK-52E cells, accompanied by accumulation of fibronectin and collagen IV. Ang II increased STAT3 phosphorylation on Tyr705 and the expression of fibronectin, collagen IV and α-SMA in the cells. Pretreatment with resveratrol (12.5 μmol/L) blocked Ang II-induced effects in the cells. UUO induced marked STAT3 phosphorylation, fibronectin, collagen IV and α-SMA accumulation, and renal interstitial fibrosis in the obstructed kidneys, which were significantly attenuated by daily administration of resveratrol (100 mg/kg). STAT3 acetylation plays an important role in activation of STAT3 signaling pathway and consequent renal fibrosis.