Interleukin-6 induces transcriptional activation of vascular endothelial growth factor (VEGF) in astrocytes in vivo and regulates VEGF promoter activity in glioblastoma cells via direct interaction between STAT3 and Sp1

IL-6 Trans-Signaling Links Inflammation with Angiogenesis in the Peritoneal Membrane

Vascular endothelial growth factor (VEGF) is implicated in the peritoneal membrane remodeling that limits ultrafiltration in patients on peritoneal dialysis (PD). Although the exact mechanism of VEGF induction in PD is unclear, VEGF concentrations in drained dialysate correlate with IL-6 levels, suggesting a link between these cytokines. Human peritoneal mesothelial cells (HPMCs), the main source of IL-6 and VEGF in the peritoneum, do not bear the cognate IL-6 receptor and are thus unable to respond to classic IL-6 receptor signaling. Here, we investigated whether VEGF release by HPMCs is controlled by IL-6 in combination with its soluble receptor (IL-6 trans-signaling). Although treatment with either IL-6 or soluble IL-6 receptor (sIL-6R) alone had no effect on VEGF production, stimulation of HPMCs with IL-6 in combination with sIL-6R promoted VEGF expression and secretion through a transcriptional mechanism involving STAT3 and SP4. Conditioned medium from HPMCs cultured with IL-6 and sIL-6R promoted angiogenic endothelial tube formation, which could be blocked by silencing SP4. In vivo, induction of peritoneal inflammation in wild-type and IL-6-deficient mice showed IL-6 involvement in the control of Sp4 and Vegf expression and new vessel formation, confirming the role of IL-6 trans-signaling in these processes. Taken together, these findings identify a novel mechanism linking IL-6 trans-signaling and angiogenesis in the peritoneal membrane.

Role of STAT3 in Genesis and Progression of Human Malignant Gliomas

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.

Ribosomal Protein Rpl22 Controls the Dissemination of T-cell Lymphoma

Mutations in ribosomal proteins cause bone marrow failure syndromes associated with increased cancer risk, but the basis by which they do so remains unclear. We reported previously that the ribosomal protein Rpl22 is a tumor suppressor in T-cell acute lymphoblastic leukemia/lymphoma (T-ALL), and that loss of just one Rpl22 allele accelerates T-cell lymphomagenesis by activating NF-κB and inducing the stem cell factor Lin28B. Here, we show that, paradoxically, loss of both alleles of Rpl22 restricts lymphoma progression through a distinct effect on migration of malignant cells out of the thymus. Lymphoma-prone AKT2-transgenic or PTEN-deficient mice on an Rpl22(-/-) background developed significantly larger and markedly more vascularized thymic tumors than those observed in Rpl22(+/+) control mice. But, unlike Rpl22(+/+) or Rpl22(+/-) tumors, Rpl22(-/-) lymphomas did not disseminate to the periphery and were retained in the thymus. We traced the defect in the Rpl22(-/-) lymphoma migratory capacity to downregulation of the KLF2 transcription factor and its targets, including the key migratory factor sphingosine 1-phosphate receptor 1 (S1PR1). Indeed, reexpression of S1PR1 in Rpl22-deficient tumor cells restores their migratory capacity in vitro The regulation of KLF2 and S1PR1 by Rpl22 appears to be proximal as Rpl22 reexpression in Rpl22-deficient lymphoma cells restores expression of KLF2 and S1P1R, while Rpl22 knockdown in Rpl22-sufficient lymphomas attenuates their expression. Collectively, these data reveal that, while loss of one copy of Rpl22 promotes lymphomagenesis and disseminated disease, loss of both copies impairs responsiveness to migratory cues and restricts malignant cells to the thymus. Cancer Res; 76(11); 3387-96. ©2016 AACR.

RARα mediates all-trans-retinoic acid-induced VEGF-C, VEGF-D, and VEGFR3 expression in lung cancer cells

The regulation of vascular endothelial growth factors C (VEGF-C) and D (VEGF-D), and their receptor VEGFR3 gene and protein expression by all-trans-retinoic acid (atRA) in A549 lung cancer cells, was investigated. We showed that atRA treatment increased VEGF-C, VEGF-D, and VEGFR3 protein and mRNA contents in dose-dependent manner. atRA-mediated increase of both ligands and receptor expression correlated with the elevated level of retinoic acid receptor α (RARα) expression, while the level of another atRA receptor, peroxisome proliferator-activated receptor β/δ (PPARβ/δ), was decreased. We demonstrated that the classical counterpart of RARα, retinoid X receptor α (RXRα), was down-regulated in both cytoplasm and nucleus of A549 cells upon atRA addition. On the contrary, the nuclear quantity of another possible RARα counterpart, transcription factor Sp1, was increased after atRA treatment.

IL-1alpha induces angiogenesis in brain endothelial cells in vitro: implications for brain angiogenesis after acute injury

Inflammation is a major contributor to neuronal injury and is associated with poor outcome after acute brain injury such as stroke. The pro-inflammatory cytokine interleukin (IL)-1 is a critical regulator of cerebrovascular inflammation after ischemic injury, mainly through action of both of its isoforms, IL-1α and IL-1β, at the brain endothelium. In contrast, the differential action of these ligands on endothelial activation and post-stroke angiogenesis is largely unknown. Here, we demonstrate that IL-1α is chronically elevated in the brain after experimental stroke suggesting that it is present during post-stroke angiogenic periods. Furthermore, we demonstrate that IL-1α is a potent mediator of endothelial activation and inducer of angiogenic markers in endothelial cells in vitro. Using brain endothelial cell lines, we found that IL-1α was significantly more potent than IL-1β at inducing endothelial cell activation, as measured by expression of the pro-angiogenic chemokine CXCL-1. IL-1α also induced strong expression of the angiogenic mediator IL-6 in a concentration-dependent manner. Furthermore, IL-1α induced significant proliferation and migration of endothelial cells, and promoted formation of tube-like structures that are established key hallmarks of angiogenesis in vitro. Finally, all of those responses were blocked by the IL-1 receptor antagonist (IL-1RA). In conclusion, our data highlights a potential new role for IL-1 in brain repair mechanisms and identifies IL-1α as a potential new therapy to promote post-stroke angiogenesis. Inflammation is a major contributor to neuronal injury and is associated with poor outcome after neurotrauma. We demonstrate that cytokine IL-1α is chronically elevated in the brain after experimental stroke suggesting that it is present chronically post-stroke. We demonstrate that IL-1α is a potent mediator of endothelial activation and inducer of angiogenic markers in endothelial cells. Our data highlights a new role for IL-1 in brain repair mechanisms and identifies IL-1α as a potential therapy to promote post-stroke angiogenesis.

Nuclear factor-κB in glioblastoma: insights into regulators and targeted therapy

Nuclear factor-κB (NF-κB) is a ubiquitous transcription factor that regulates multiple aspects of cancer formation, growth, and treatment response. Glioblastoma (GBM), the most common primary malignant tumor of the central nervous system, is characterized by molecular heterogeneity, resistance to therapy, and high NF-κB activity. In this review, we examine the mechanisms by which oncogenic pathways active in GBM impinge on the NF-κB system, discuss the role of NF-κB signaling in regulating the phenotypic properties that promote GBM and, finally, review the components of the NF-κB pathway that have been targeted for treatment in both preclinical studies and clinical trials. While a direct role for NF-κB in gliomagenesis has not been reported, the importance of this transcription factor in the overall malignant phenotype suggests that more rational and specific targeting of NF-κB-dependent pathways can make a significant contribution to the management of GBM.

Increased CSF biomarkers of angiogenesis in Parkinson disease

Objective:

To study biomarkers of angiogenesis in Parkinson disease (PD), and how these are associated with clinical characteristics, blood–brain barrier (BBB) permeability, and cerebrovascular disease.

Methods:

In this cross-sectional analysis, 38 elderly controls and 100 patients with PD (82 without dementia and 18 with dementia) were included from the prospective Swedish BioFinder study. CSF samples were analyzed for the angiogenesis biomarkers vascular endothelial growth factor (VEGF); its receptors, VEGFR-1 and VEGFR-2; placental growth factor (PlGF); angiopoietin 2 (Ang2); and interleukin-8. BBB permeability, white matter lesions (WMLs), and cerebral microbleeds (CMB) were assessed. CSF angiogenesis biomarkers were also measured in 2 validation cohorts: (1) 64 controls and 87 patients with PD with dementia; and (2) 35 controls and 93 patients with neuropathologically confirmed diagnosis of PD with and without dementia.

Results:

Patients with PD without dementia displayed higher CSF levels of VEGF, PlGF, and sVEGFR-2, and lower levels of Ang2, compared to controls. Similar alterations in VEGF, PlGF, and Ang2 levels were observed in patients with PD with dementia. Angiogenesis markers were associated with gait difficulties and orthostatic hypotension as well as with more pronounced BBB permeability, WMLs, and CMB. Moreover, higher levels of VEGF and PlGF levels were associated with increased CSF levels of neurofilament light (a marker of neurodegeneration) and monocyte chemotactic protein–1 (a marker of glial activation). The main results were validated in the 2 additional cohorts.

Conclusions:

CSF biomarkers of angiogenesis are increased in PD, and they are associated with gait difficulties, BBB dysfunction, WMLs, and CMB. Abnormal angiogenesis may be important in PD pathogenesis and contribute to dopa-resistant symptoms.

FT011, a Novel Cardiorenal Protective Drug, Reduces Inflammation, Gliosis and Vascular Injury in Rats with Diabetic Retinopathy

Diabetic retinopathy features inflammation as well as injury to glial cells and the microvasculature, which are influenced by hypertension and overactivity of the renin-angiotensin system. FT011 is an anti-inflammatory and anti-fibrotic agent that has been reported to attenuate organ damage in diabetic rats with cardiomyopathy and nephropathy. However, the potential therapeutic utility of FT011 for diabetic retinopathy has not been evaluated. We hypothesized that FT011 would attenuate retinopathy in diabetic Ren-2 rats, which exhibit hypertension due to an overactive extra-renal renin-angiotensin system. Diabetic rats were studied for 8 and 32 weeks and received intravitreal injections of FT011 (50 μM) or vehicle (0.9% NaCl). Comparisons were to age-matched controls. In the 8-week study, retinal inflammation was examined by quantitating vascular leukocyte adherence, microglial/macrophage density and the expression of inflammatory mediators. Macroglial Müller cells, which exhibit a pro-inflammatory and pro-angiogenic phenotype in diabetes, were evaluated in the 8-week study as well as in culture following exposure to hyperglycaemia and FT011 (10, 30, 100 μM) for 72 hours. In the 32-week study, severe retinal vasculopathy was examined by quantitating acellular capillaries and extracellular matrix proteins. In diabetic rats, FT011 reduced retinal leukostasis, microglial density and mRNA levels of intercellular adhesion molecule-1 (ICAM-1). In Müller cells, FT011 reduced diabetes-induced gliosis and vascular endothelial growth factor (VEGF) immunolabeling and the hyperglycaemic-induced increase in ICAM-1, monocyte chemoattractant protein-1, CCL20, cytokine-induced neutrophil chemoattractant-1, VEGF and IL-6. Late intervention with FT011 reduced acellular capillaries and the elevated mRNA levels of collagen IV and fibronectin in diabetic rats. In conclusion, the protective effects of FT011 in cardiorenal disease extend to key elements of diabetic retinopathy and highlight its potential as a treatment approach.

STAT3 Serine 727 Phosphorylation: A Relevant Target to Radiosensitize Human Glioblastoma

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.

Ebselen by modulating oxidative stress improves hypoxia-induced macroglial Müller cell and vascular injury in the retina

Oxidative stress is an important contributor to glial and vascular cell damage in ischemic retinopathies. We hypothesized that ebselen via its ability to reduce reactive oxygen species (ROS) and augment nuclear factor-like 2 (Nrf2) anti-oxidants would attenuate hypoxia-induced damage to macroglial Müller cells and also lessen retinal vasculopathy. Primary cultures of rat Müller cells were exposed to normoxia (21% O2), hypoxia (0.5% O2) and ebselen (2.5 μM) for up to 72 h. Oxygen-induced retinopathy (OIR) was induced in C57BL/6J mice while control mice were housed in room air. Mice received vehicle (saline, 5% dimethyl sulfoxide) or ebselen (10 mg/kg) each day between postnatal days 6-18. In cultured Müller cells, flow cytometry for dihydroethidium revealed that ebselen reduced the hypoxia-induced increase in ROS levels, whilst increasing the expression of Nrf2-regulated anti-oxidant genes, heme oxygenase 1, glutathione peroxidase-1, NAD(P)H dehydrogenase quinone oxidoreductase 1 and glutamate-cysteine ligase. Moreover, in Müller cells, ebselen reduced the hypoxia-induced increase in protein levels of pro-angiogenic and pro-inflammatory factors including vascular endothelial growth factor, interleukin-6, monocyte chemoattractant-protein 1 and intercellular adhesion molecule-1, and the mRNA levels of glial fibrillary acidic protein (GFAP), a marker of Müller cell injury. Ebselen improved OIR by attenuating capillary vaso-obliteration and neovascularization and a concomitant reduction in Müller cell gliosis and GFAP. We conclude that ebselen protects against hypoxia-induced injury of retinal Müller cells and the microvasculature, which is linked to its ability to reduce oxidative stress, vascular damaging factors and inflammation. Agents such as ebselen may be potential treatments for retinopathies that feature oxidative stress-mediated damage to glia and the microvasculature.

Emerging translational approaches to target STAT3 signalling and its impact on vascular disease

Acute and chronic inflammation responses characterize the vascular remodelling processes in atherosclerosis, restenosis, pulmonary arterial hypertension, and angiogenesis. The functional and phenotypic changes in diverse vascular cell types are mediated by complex signalling cascades that initiate and control genetic reprogramming. The signalling molecule's signal transducer and activator of transcription 3 (STAT3) plays a key role in the initiation and continuation of these pathophysiological changes. This review highlights the pivotal involvement of STAT3 in pathological vascular remodelling processes and discusses potential translational therapies, which target STAT3 signalling, to prevent and treat cardiovascular diseases. Moreover, current clinical trials using highly effective and selective inhibitors of STAT3 signalling for distinct diseases, such as myelofibrosis and rheumatoid arthritis, are discussed with regard to their vascular (side-) effects and their potential to pave the way for a direct use of these molecules for the prevention or treatment of vascular diseases.

IL-1β induces IL-6 production in retinal Müller cells predominantly through the activation of p38 MAPK/NF-κB signaling pathway

IL-6 plays an important role in various inflammatory ocular diseases, including diabetic retinopathy. Müller cells are the major source of inflammatory mediators, including IL-6, in the retina. However, the mechanism of regulating IL-6 production in these cells remains unclear. Examination of signaling pathways in human retinal Müller cells (MIO-M1 cell line) cultured with IL-1β, TNF-α, IL-6, IL-8, VEGF, IFN-γ, glucose or mannitol showed that IL-1β was the most potent stimulator of IL-6 production. In addition, IL-1 β also increased NF-κB p50 protein level and phosphorylation of p38 MAPK, ERK1/2 and c-Jun. Induction of IL-6 production by IL-1β was significantly reduced by addition of p38 MAPK (SB203580), MEK1/2 (U0126) or NF-κB (BAY11-7082) inhibitors, with the highest effect being observed with SB203580. To explore the specific elements in IL-6 promoter responsible for IL-1β-induction of IL-6 expression, a series of plasmids bearing various IL-6 promoter mutations were transiently expressed in MIO-MI cells cultured in the presence or absence of IL-1β (10ng/ml) and/or SB203580 (10µM). Results showed that IL-6 promoter activity of the parent pIL-6-Luc651 was significantly enhanced by IL-1β, but the level was significantly attenuated by SB203580. Furthermore, the IL-6 promoter activity was also reduced upon deletion of NF-κB, AP-1 or C/EBP binding sites, with NF-κB deletion being the greatest. These results are the first demonstration that IL-1β induces IL-6 production in Müller cells by activation of IL-6 promoter activity predominantly through the p38 MAPK/NF-κB pathway.

Angiogenesis in the placenta: the role of reactive oxygen species signaling

Proper placental development and function are central to the health of both the mother and the fetus during pregnancy. A critical component of healthy placental function is the proper development of its vascular network. Poor vascularization of the placenta can lead to fetal growth restriction, preeclampsia, and in some cases fetal death. Therefore, understanding the mechanisms by which uterine stressors influence the development of the placental vasculature and contribute to placental dysfunction is of central importance to ensuring a healthy pregnancy. In this review we discuss how oxidative stress observed in maternal smoking, maternal obesity, and preeclampsia has been associated with aberrant angiogenesis and placental dysfunction resulting in adverse pregnancy outcomes. We also highlight that oxidative stress can influence the expression of a number of transcription factors important in mediating angiogenesis. Therefore, understanding how oxidative stress affects redox-sensitive transcription factors within the placenta may elucidate potential therapeutic targets for correcting abnormal placental angiogenesis and function.

Pathophysiological mechanisms regulated by cytokines in gliomas

Glioma, a neuroglia originated malignancy, consists of one of the most aggressive primary tumors of the central nervous system with poor prognosis and lack of efficient treatment strategy. Cytokines have been implicated in several stages of glioma progression, participating in tumor onset, growth enhancement, angiogenesis and aggressiveness. Interestingly, cytokines have also the ability to inhibit glioma growth upon specific regulation or interplay with other molecules. This review addresses the dual role of major cytokines implicated in glioma pathology, pointing toward promising therapeutic approaches.

Phase II trial of bortezomib plus doxorubicin in hepatocellular carcinoma (E6202): a trial of the Eastern Cooperative Oncology Group

PURPOSE

To evaluate the efficacy and tolerability of bortezomib in combination with doxorubicin in patients with advanced hepatocellular carcinoma, and to correlate pharmacodynamic markers of proteasome inhibition with response and survival.

EXPERIMENTAL DESIGN

This phase II, open-label, multicenter study examined the efficacy of bortezomib (1.3 mg/m(2) IV on d1, 4, 8, 11) and doxorubicin (15 mg/m(2) IV on d1, 8) in 21-day cycles. The primary endpoint was objective response rate.

RESULTS

Best responses in 38 treated patients were 1 partial response (2.6 %), 10 (26.3 %) stable disease, and 17 (44.7 %) progressive disease; 10 patients were unevaluable. Median PFS was 2.2 months. Median OS was 6.1 months. The most common grade 3 to 4 toxicities were hypertension, glucose intolerance, ascites, ALT elevation, hyperglycemia and thrombosis/embolism. Worse PFS was seen in patients with elevated IL-6, IL-8, MIP-1α and EMSA for NF-κB at the start of treatment. Worse OS was seen in patients with elevated IL-8 and VEGF at the start of treatment. Patients had improved OS if a change in the natural log of serum MIP-1α/CCL3 was seen after treatment. RANTES/CCL5 levels decreased significantly with treatment.

CONCLUSIONS

The combination of doxorubicin and bortezomib was well-tolerated in patients with hepatocellular carcinoma, but the primary endpoint was not met. Exploratory analyses of markers of proteasome inhibition suggest a possible prognostic and predictive role and should be explored further in tumor types for which bortezomib is efficacious.

Identification of transcription factors involved in the transcriptional regulation of the CXCL12 gene in rat pancreatic insulinoma Rin-5F cell line

Diabetes is characterized by a deficit in the number of functional pancreatic β-cells. Understanding the mechanisms that stimulate neogenesis of β-cells should contribute to improved maintenance of β-cell mass. Chemokine CXCL12 has recently become established as a novel β-cell growth factor, however the mechanisms controlling its expression require clarification. We investigated the proteins involved in the transcriptional regulation of the rat β-cell CXCL12 gene (Cxcl12). Using the electrophoretic mobility shift assay and chromatin immunoprecipitation, we established the in vitro and in vivo binding of C/EBPβ, C/EBPα, STAT3, p53, FOXO3a, and HMG I/Y to the Cxcl12 promoter. Co-immunoprecipitation experiments revealed protein-protein interactions between YY1 and PARP-1, FOXO3a and PARP-1, Sp1 and PARP-1, p53 and PARP-1, C/EBPβ and PARP-1, YY1 and p53, YY1 and FOXO3a, p53 and FOXO3a, Sp1 and FOXO3a, C/EBPβ and FOXO3a, C/EBPα and FOXO3a, Sp1 and STAT3. Our data lay the foundation for research into the interplay of signaling pathways that determine the β-cell Cxcl12 expression profile.

Cytokines: shifting the balance between glioma cells and tumor microenvironment after irradiation

Malignant gliomas invariably recur after irradiation, showing radioresistance. Meanwhile, cranial irradiation can bring some risk for developing cognitive dysfunction. There is increasing evidence that cytokines play their peculiar roles in these processes. On the one hand, cytokines directly influence the progression of malignant glioma, promoting or suppressing tumor progression. On the other hand, cytokines indirectly contribute to the immunologic response against gliomas, exhibiting pro-inflammatory or immunosuppressive activities. We propose that cytokines are not simply unregulated products from tumor cells or immune cells, but mediators finely adjust the balance between glioma cells and tumor microenvironment after irradiation. The paper, therefore, focuses on the changes of cytokines after irradiation, analyzing how these mediate the response of tumor cells and normal cells to irradiation. In addition, cytokine-based immunotherapeutic strategies, accompanied with irradiation, for the treatment of gliomas are also discussed.

Cerebral microdialysis in glioma studies, from theory to application

Despite recent advances in the treatment of solid tumors, there are few effective treatments for malignant gliomas due to the infiltrative nature, and the protective shield of blood-brain barrier or blood-tumor barriers that restrict the passage of chemotherapy drugs into the brain. Imaging techniques, such as PET and MRI, have allowed the assessment of tumor function in vivo, but they are indirect measures of activity and do not easily allow continuous repeated evaluations. Because the biology of glioma on a cellular and molecular level is fairly unknown, especially in relation to various treatments, the development of novel therapeutic approaches to this devastating condition requires a strong need for a deeper understanding of the tumor's pathophysiology and biochemistry. Cerebral microdialysis, a probe-based sampling technique, allows a discrete volume of the brain to be sampled for neurochemical analysis of neurotransmitters, metabolites, biomarkers, and chemotherapy drugs, which has been employed in studying brain tumors, and is significant for improving the treatment of glioma. In this review, the current concepts of cerebral microdialysis for glioma are elucidated, with a special emphasis on its application to neurochemistry and pharmacokinetic studies.

Transcription factor C/EBP-β mediates downregulation of dipeptidyl-peptidase III expression by interleukin-6 in human glioblastoma cells

Dipeptidyl-peptidase III (DPP III) is a cytosolic metallo-aminopeptidase implicated in various physiological and pathological processes. A previous study from our laboratory indicated an elevated expression of DPP III in glioblastoma (U87MG) cells. In the present study we investigated the role of interleukin-6 (IL-6), a pleiotropic cytokine produced by glial tumors, in the regulation of DPP III expression. Immunohistochemistry, western blotting and quantitative RT-PCR were used for quantitation of DPP III and IL-6 in human glioblastoma cells and tumors. Cell transfections and DPP III promoter reporter assays were performed to study the transcriptional regulation of DPP III by IL-6. Promoter deletion analysis, site directed mutagenesis, chromatin immunoprecipitation assays and small interfering RNA (siRNA) technology was employed to elucidate the molecular mechanism of IL-6 mediated regulation of DPP III expression in glioblastoma cells. Our results for the first time demonstrate a negative correlation (r = 0.632, P = 0.01) between DPP III and IL-6 in both human tumors and cultured glioblastoma cells. Treatment of U87MG cells with IL-6 significantly decreased DPP III expression with a concomitant increase in the levels of transcription factor CCAAT/enhancer binding protein beta (C/EBP-β). Deletion/mutagenesis of C/EBP-β binding motif of DPP III promoter significantly increased its activity and abolished its responsiveness to IL-6. This effect could also be mimicked by C/EBP-β siRNA. In conclusion our study for the first time demonstrates C/EBP-β mediated transcriptional downregulation of DPP III by IL-6. Our results demonstrating a negative correlation between IL-6 and DPP III taken together with the previously reported prognostic significance of this cytokine in glioblastoma suggests that DPP III may prove useful as a prognostic marker.

SH2B1β interacts with STAT3 and enhances fibroblast growth factor 1-induced gene expression during neuronal differentiation

Neurite outgrowth is an essential process during neuronal differentiation as well as neuroregeneration. Thus, understanding the molecular and cellular control of neurite outgrowth will benefit patients with neurological diseases. We have previously shown that overexpression of the signaling adaptor protein SH2B1β promotes fibroblast growth factor 1 (FGF1)-induced neurite outgrowth (W. F. Lin, C. J. Chen, Y. J. Chang, S. L. Chen, I. M. Chiu, and L. Chen, Cell. Signal. 21:1060-1072, 2009). SH2B1β also undergoes nucleocytoplasmic shuttling and regulates a subset of neurotrophin-induced genes. Although these findings suggest that SH2B1β regulates gene expression, the nuclear role of SH2B1β was not known. In this study, we show that SH2B1β interacts with the transcription factor, signal transducer, and activator of transcription 3 (STAT3) in neuronal PC12 cells, cortical neurons, and COS7 fibroblasts. By affecting the subcellular distribution of STAT3, SH2B1β increased serine phosphorylation and the concomitant transcriptional activity of STAT3. As a result, overexpressing SH2B1β enhanced FGF1-induced expression of STAT3 target genes Egr1 and Cdh2. Chromatin immunoprecipitation assays further reveal that, in response to FGF1, overexpression of SH2B1β promotes the in vivo occupancy of STAT3-Sp1 heterodimers at the promoter of Egr1 and Cdh2. These findings establish a central role of SH2B1β in orchestrating signaling events to transcriptional activation through interacting and regulating STAT3-containing complexes during neuronal differentiation.

Targeting tumor micro-environment for design and development of novel anti-angiogenic agents arresting tumor growth

Angiogenesis: a process of generation of new blood vessels has been proved to be necessary for sustained tumor growth and cancer progression. Inhibiting angiogenesis pathway has long been remained a significant hope for the development of novel, effective and target orientated antitumor agents arresting the tumor proliferation and metastasis. The process of neoangiogenesis as a biological process is regulated by several pro- and anti-angiogenic factors, especially vascular endothelial growth factor, fibroblast growth factor, epidermal growth factor, hypoxia inducible factor 1 and transforming growth factor. Every endothelial cell destined for vessel formation is equipped with receptors for these angiogenic peptides. Moreover, numerous other angiogenic cytokines such as platelet derived growth factor (PGDF), placenta growth factor (PGF), nerve growth factor (NGF), stem-cell factor (SCF), and interleukins-2, 4, 6 etc. These molecular players performs critical role in regulating the angiogenic switch. Couple of decade's research in molecular aspects of tumor biology has unraveled numerous structural and functional mysteries of these angiogenic peptides. In present article, a detailed update on the functional and structural peculiarities of the various angiogenic peptides is described focusing on structural opportunities made available that has potential to be used to modulate function of these angiogenic peptides in developing therapeutic agents targeting neoplastic angiogenesis. The data may be useful in the mainstream of developing novel anticancer agents targeting tumor angiogenesis. We also discuss major therapeutic agents that are currently used in angiogenesis associated therapies as well as those are subject of active research or are in clinical trials.

Targeting interleukin-6 in inflammatory autoimmune diseases and cancers

Interleukin-6 (IL-6) is a pleiotropic cytokine with significant functions in the regulation of the immune system. As a potent pro-inflammatory cytokine, IL-6 plays a pivotal role in host defense against pathogens and acute stress. However, increased or deregulated expression of IL-6 significantly contributes to the pathogenesis of various human diseases. Numerous preclinical and clinical studies have revealed the pathological roles of the IL-6 pathway in inflammation, autoimmunity, and cancer. Based on the rich body of studies on biological activities of IL-6 and its pathological roles, therapeutic strategies targeting the IL-6 pathway are in development for cancers, inflammatory and autoimmune diseases. Several anti-IL-6/IL-6 receptor monoclonal antibodies developed for targeted therapy have demonstrated promising results in both preclinical studies and clinical trials. Tocilizumab, an anti-IL-6 receptor antibody, is effective in the treatment of various autoimmune and inflammatory conditions notably rheumatoid arthritis. It is the only IL-6 pathway targeting agent approved by the regulatory agencies for clinical use. Siltuximab, an anti-IL-6 antibody, has been shown to have potential benefits treating various human cancers either as a single agent or in combination with other chemotherapy drugs. Several other anti-IL-6-based therapies are also under clinical development for various diseases. IL-6 antagonism has been shown to be a potential therapy for these disorders refractory to conventional drugs. New strategies, such as combination of IL-6 blockade with inhibition of other signaling pathways, may further improve IL-6-targeted immunotherapy of human diseases.

A membrane penetrating peptide aptamer inhibits STAT3 function and suppresses the growth of STAT3 addicted tumor cells

Cancer cells are characterized by the aberrant activation of signaling pathways governing proliferation, survival, angiogenesis, migration and immune evasion. These processes are partially regulated by the transcription factor STAT3. This factor is inappropriately activated in diverse tumor types. Since tumor cells can become dependent on its persistent activation, STAT3 is a favorable drug target. Here, we describe the functional characterization of the recombinant STAT3 inhibitor, rS3-PA. This inhibitor is based on a 20 amino acid peptide which specifically interacts with the dimerization domain of STAT3. It is integrated into a thioredoxin scaffold and fused to a protein transduction domain. Protein gel blot and immunofluorescence analyses showed that rS3-PA is efficiently taken up by cells via an endocytosis independent mechanism. Intracellularly, it reduces the phosphorylation of STAT3 and enhances its degradation. This leads to the downregulation of STAT3 target gene expression on the mRNA and protein levels. Subsequently, tumor cell proliferation, survival and migration and the induction of angiogenesis are inhibited. In contrast, normal cells remain unaffected. Systemic administration of rS3-PA at doses of 7.5 mg/kg reduced P-STAT3 levels and significantly inhibited tumor growth up to 35% in a glioblastoma xenograft mouse model.

Transgenic analysis of GFAP promoter elements

Transcriptional regulation of the glial fibrillary acidic protein gene (GFAP) is of interest because of its astrocyte specificity and its upregulation in response to CNS injuries. We have used a transgenic approach instead of cell transfection to identify promoter elements of the human GFAP gene, since previous observations show that GFAP transcription is regulated differently in transfected cultured cells from in the mouse. We previously showed that block mutation of enhancer regions spanning from bp -1488 to -1434 (the C1.1 segment) and -1443 to -1399 (C1.2) resulted in altered patterns of expression and loss of astrocyte specificity, respectively. This analysis has now been extended upstream to bp -1612 to -1489 (the B region), which previously has been shown especially important for expression. Block mutation of each of four contiguous sequences, which together span the B region, each decreased the level of transgene activity by at least 50%, indicating that multiple sites contribute to the transcriptional activity in a cooperative manner. Several of the block mutations also altered the brain region pattern of expression, astrocyte specificity and/or the developmental time course. Transgenes were then analyzed in which mutations were limited to specific transcription factor binding sites in each of the 4 B block segments as well as in C1.1 and C1.2. Whereas mutation of the conserved consensus AP-1 site unexpectedly had little effect on transgene expression; NFI, SP1, STAT3, and NF-κB were identified as having important roles in regulating the strength of GFAP promoter activity and/or its astrocyte specificity.

The radio-sensitizing effect of xanthohumol is mediated by STAT3 and EGFR suppression in doxorubicin-resistant MCF-7 human breast cancer cells

BACKGROUND

Chemotherapeutic drug resistance remains a clinical obstacle in cancer management. Drug-resistant cancer cells usually exhibit cross-resistance to ionizing radiation, which has devastating consequences for patients. With a better understanding of the molecular mechanisms, it will be possible to develop strategies to overcome this cross-resistance and to increase therapeutic sensitivity.

METHODS

Natural and synthetic flavonoid compounds including xanthohumol, the principal flavonoid in hops, were investigated for its radio-sensitizing activity on human breast cancer MCF-7 and adriamycin-resistant MCF-7 (MCF-7/ADR) cells. Chemo-sensitizing or radio-sensitizing effect was analyzed by tetrazolium-based colorimetric assay and flow cytometry. Western blot analysis, confocal microscopy, gene silencing with siRNA transfection and luciferase reporter gene assay were performed to examine signaling molecule activation.

RESULTS

Among the tested flavonoid compounds, pretreatment of the cells with xanthohumol significantly sensitized MCF-7/ADR cells to the radiation treatment by inducing apoptosis. In MCF-7/ADR cells, treatment with xanthohumol alone or with gamma-rays significantly decreased levels of anti-apoptotic proteins. Multi-drug resistance 1 (MDR1), epidermal growth factor receptor (EGFR) and signal transducer and activator of transcription 3 (STAT3) expression levels in MCF-7/ADR cells were suppressed by xanthohumol treatment. In addition, xanthohumol treatment increased death receptor (DR)-4 and DR5 expression. The xanthohumol-induced changes of these resistance-related molecules in MCF-7/ADR cells were synergistically increased by gamma-ray treatment.

CONCLUSIONS

Xanthohumol restored sensitivity of MCF-7/ADR cells to doxorubicin and radiation therapies.

GENERAL SIGNIFICANCE

Our results suggest that xanthohumol may be a potent chemo- and radio-sensitizer, and its actions are mediated through STAT3 and EGFR inhibition.

c-myc but not Hif-1α-dependent downregulation of VEGF influences the proliferation and differentiation of HL-60 cells induced by ATRA

Vascular endothelial growth factor (VEGF) plays an important role in solid tumor growth, progression and metastasis as well as in the proliferation and differentiation of hematological malignancies. However, the molecular mechanism that modulates VEGF expression and secretion in leukemia cells has not yet to be elucidated. The purpose of the present study was to investigate the role of the signal pathway in modulating the expression of VEGF in HL-60 cells. Specific siRNAs targeting VEGF were transfected into HL-60 cells and the VEGF expression was measured with reverse transcription-polymerase chain reaction (RT-PCR) and western blot assay. The cell proliferation of HL-60 cells was detected by the cell counting kit-8 (CCK-8) assay and the differentiation of HL-60 cells induced by all-trans-retinoic acid (ATRA) was detected by the RT-PCR assay and flow cytometry assay for CD11b. The upstream transcription factors that were related to VEGF expression such as P53, SP-1, c-jun, VHL, cox-2, c-myc and stat3 were detected by RT-PCR assay. In addition, the chromatin immunoprecipitation (ChIP) assay was used to reveal the role of c-myc by binding the target gene VEGF. The results demonstrated the hypoxia-inducible factor 1α-related signaling pathway, not the same as in solid tumors, might not play a key role in modulating VEGF expression. c-myc contributes to the modulation of VEGF expression by targeting the promoter of VEGF, which was indicated by the ChIP assay. In conclusion, our data demonstrate that VEGF plays an important role in the differentiation and proliferation of HL-60 cells; c-myc-dependent downregulation of VEGF induced by ATRA contributes to the differentiation of HL-60 cells.

Angiogenic inhibition in high-grade gliomas: past, present and future

High-grade gliomas, especially glioblastoma (GBM), are among the most aggressive and vascularized tumors. Angiogenesis plays a significant role in tumor growth and survival, and thus offers a target for anticancer treatment. Bevacizumab, a humanized monoclonal antibody against VEGF, was approved by the US FDA as a single agent for the treatment of recurrent glioblastoma. Significant radiographic response and progression-free survival were seen with bevacizumab treatment. However, benefits to overall survival remain undetermined. Other antiangiogenic strategies targeting VEGF, VEGF receptor (VEGFR) and other angiogenic factors have also been examined. Tumor progression after antiangiogenic treatment is inevitable, and effective salvage therapy is yet to be identified. Mechanisms of resistance to antiangiogenic therapy include activation of alternative proangiogenic pathways and increased tumor invasion. Strategies targeting these escape mechanisms are currently being investigated. The use of antiangiogenic drugs is generally well tolerated, although rare and potentially life-threatening adverse effects have been identified. With the striking antipermeability effect of anti-VEGF inhibitors, assessment of true tumor response has become a challenge. The Response Assessment in Neuro-Oncology Working Group has developed new criteria for clinical trials in patients with high-grade glioma. Identification of neuroimaging advances and biologic markers will greatly enhance treatment strategies for these patients.

IL-6 promotes the expression of vascular endothelial growth factor through the p38 signalling pathway in hypertrophied adenoids in children

OBJECTIVES

To examine the expression of vascular endothelial growth factor (VEGF) in hypertrophied adenoids in children and investigate the possible regulatory mechanism.

METHODS

Thirty-eight children with hypertrophied adenoids (moderate, 16; severe, 22) were enrolled to investigate the VEGF expression in the adenoid tissues using immunohistochemistry (IHC) and quantitative reverse transcription polymerase chain reaction (qRT-PCR). The IL-6 concentration in the nasopharyngeal secretions was measured using an enzyme-linked immunosorbent assay (ELISA). VEGF mRNA expression was further measured in isolated adenoidal cells in vitro after IL-6 stimulation, and the activation of the p38 signalling pathway was determined by Western blot analysis.

RESULTS

Our findings showed extensive immunoreactivity of VEGF in the hypertrophied adenoids in children. The levels of VEGF protein and mRNA were significantly higher in severely hypertrophied adenoids than in moderately hypertrophied adenoids (P<0.05). The expression of IL-6 was detectable in the nasopharyngeal secretions, which was significantly associated with the severity of the hypertrophied adenoid. VEGF mRNA expression was upregulated in isolated adenoidal cells in vitro after IL-6 stimulation, and the p38 signalling pathway was activated.

CONCLUSIONS

The increased expression of VEGF in adenoid tissues suggests a possible role of the IL-6/VEGF axis in the pathogenesis of hypertrophied adenoids in children.

The microRNA-27a: ZBTB10-specificity protein pathway is involved in follicle stimulating hormone-induced VEGF, Cox2 and survivin expression in ovarian epithelial cancer cells

Previously, we demonstrated that follicle stimulating hormone (FSH) enhanced VEGF expression and facilitated ovarian cancer angiogenesis via the PI3K/AKT signaling pathway. In this study, we further investigated the involvement of microRNA-27a: ZBTB10‑specificity protein pathway in the mechanism of FSH-induced VEGF, Cox2 and survivin expression. Treatment with FSH resulted in significant increase in the expression of VEGF, Cox2, survivin, Sp1 proteins and microRNA-27a in a dose-dependent manner, whereas reverse protein expression pattern was observed in ZBTB10. Downregulation of microRNA-27a using antisense microRNA-27a blocked FSH-induced VEGF, Cox2 and survivin expression. Overexpression of ZBTB10 also attenuated the FSH-induced expression of these molecules. The enhanced expression of VEGF, Cox2 and survivin was also abolished by knocking down Sp1 using small interfering RNA. Collectively, these results indicated that stimulation of ovarian cancer cell VEGF, Cox2 and survivin expression by FSH involves the microRNA‑27a: ZBTB10-specificity protein pathway.

Opposing roles of STAT-1 and STAT-3 in regulating vascular endothelial growth factor expression in vascular smooth muscle cells

Increased microvessel density in atherosclerotic plaques plays a major role in promoting plaque destabilization resulting in increased risk of stroke and myocardial infarction. Previously we have shown that expression of the inflammatory cytokine, Oncostatin-M (OSM), in human atherosclerotic plaques correlated with increased microvessel density, indicating a role for OSM in promoting plaque angiogenesis. The purpose of this study was to determine the mechanism by which OSM regulates Vascular Endothelial Growth Factor (VEGF) expression in human coronary artery smooth muscle cells. Using shRNA and overexpression studies, we have shown that the transcription factor, STAT-1 inhibited VEGF expression, while STAT-3 promoted the expression of VEGF. We further show that the mechanism by which STAT-1 and STAT-3 regulates VEGF expression is through modulation of Hypoxia Inducible Factor-1α (HIF-1α). STAT-1 suppresses HIF-1α expression, whereas STAT-3 positively regulates HIF-1α expression. These results provide evidence that activated STAT-1 and STAT-3 regulate VEGF expression indirectly, by modulating HIF-1α activity.

Endothelins reciprocally regulate VEGF-A and angiopoietin-1 production in cultured rat astrocytes: implications on astrocytic proliferation

Vascular endothelial growth factors (VEGFs) and angiopoietins (ANGs) are involved in pathophysiological responses in damaged nerve tissues. Astrocytes produce VEGFs and ANGs upon brain ischemia and traumatic injury. To clarify the extracellular signals regulating VEGF and ANG production, effects of endothelins (ETs), a family of endothelium-derived peptides, were examined in cultured rat astrocytes. ET-1 (100 nM) and Ala(1,3,11,15)-ET-1 (100 nM), an ET(B) receptor agonist, increased VEGF-A mRNA levels in cultured astrocytes, while ANG-1 mRNA was decreased by ETs. ET-1 did not affect astrocytic VEGF-B, placental growth factor (PLGF), and ANG-2 mRNA levels. The effects of ET-1 on VEGF-A and ANG-1 mRNAs were inhibited by BQ788, an ET(B) antagonist. Release of VEGF-A proteins from cultured astrocytes was increased by ET-1. In contrast, ET-1 reduced release of astrocytic ANG-1. Exogenous ET-1 (100 nM) and VEGF(165) (100 ng/mL), an isopeptide of VEGF-A, stimulated bromodeoxyuridine (BrdU) incorporation into cultured astrocytes. Treatment with ET-1 and VEGF(165) increased the numbers of cyclin D1-positive astrocytes. Exogenous ANG-1 (250 ng/mL) did not stimulate the BrdU incorporation. Increases in BrdU incorporation by ET-1 and VEGF(165) were not affected by ANG-1. In 60-70% confluent cultures, SU4312 (10 μM), a VEGF receptor tyrosine kinase inhibitor, partially reduced the effects of ET-1 on BrdU incorporation and cyclin D1 expression. ET-induced BrdU incorporation and cyclin D1 expression were reduced by a neutralizing antibody against VEGF-A. Our findings suggest that ET-1 is a factor regulating astrocytic VEGF-A and ANG-1, and that increased VEGF-A production potentiates ET-induced astrocytic proliferation by an autocrine mechanism.

Abnormal histone methylation is responsible for increased vascular endothelial growth factor 165a secretion from airway smooth muscle cells in asthma

Vascular endothelial growth factor (VEGF), a key angiogenic molecule, is aberrantly expressed in several diseases including asthma where it contributes to bronchial vascular remodeling and chronic inflammation. Asthmatic human airway smooth muscle cells hypersecrete VEGF, but the mechanism is unclear. In this study, we defined the mechanism in human airway smooth muscle cells from nonasthmatic and asthmatic patients. We found that asthmatic cells lacked a repression complex at the VEGF promoter, which was present in nonasthmatic cells. Recruitment of G9A, trimethylation of histone H3 at lysine 9 (H3K9me3), and a resultant decrease in RNA polymerase II at the VEGF promoter was critical to repression of VEGF secretion in nonasthmatic cells. At the asthmatic promoter, H3K9me3 was absent because of failed recruitment of G9a; RNA polymerase II binding, in association with TATA-binding protein-associated factor 1, was increased; H3K4me3 was present; and Sp1 binding was exaggerated and sustained. In contrast, DNA methylation and histone acetylation were similar in asthmatic and nonasthmatic cells. This is the first study, to our knowledge, to show that airway cells in asthma have altered epigenetic regulation of remodeling gene(s). Histone methylation at genes such as VEGF may be an important new therapeutic target.

Potential role for STAT3 inhibitors in glioblastoma

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor. Signal transducers and activators of transcription 3 (STAT3) is a transcription factor that translocates to the nucleus to modulate the expression of a variety of genes associated with cell survival, differentiation, proliferation, angiogenesis, and immune function. Several cancers induce constitutive STAT3 activation. Most studies have reported that STAT3 inhibition has antineoplastic activity; however, emerging evidence suggests that the role of STAT3 activity in GBM may be more nuanced than initially appreciated. The authors review the roles of STAT3 in GBM and discuss potential strategies for targeting STAT3.

The Stat3/GR interaction code: predictive value of direct/indirect DNA recruitment for transcription outcome

Transcription factor recruitment to genomic sites of action is primarily due to direct protein:DNA interactions. The subsequent recruitment of coregulatory complexes leads to either transcriptional activation or repression. In contrast to this canonical scheme, some transcription factors, such as the glucocorticoid receptor (GR), behave as transcriptional repressors when recruited to target genes through protein tethering. We have investigated the genome-wide prevalence of tethering between GR and Stat3 and found nonreciprocal interactions, namely that GR tethering to DNA-bound Stat3 results in transcriptional repression, whereas Stat3 tethering to GR results in synergism. Further, other schemes of GR and Stat3 corecruitment to regulatory modules result in transcriptional synergism, including neighboring and composite binding sites. The results indicate extensive transcriptional interactions between Stat3 and GR; further, they provide a genome-wide assessment of transcriptional regulation by tethering and a molecular basis for integration of signals mediated by GR and Stats in health and disease.

The molecular profile of microglia under the influence of glioma

Microglia, which contribute substantially to the tumor mass of glioblastoma, have been shown to play an important role in glioma growth and invasion. While a large number of experimental studies on functional attributes of microglia in glioma provide evidence for their tumor-supporting roles, there also exist hints in support of their anti-tumor properties. Microglial activities during glioma progression seem multifaceted. They have been attributed to the receptors expressed on the microglia surface, to glioma-derived molecules that have an effect on microglia, and to the molecules released by microglia in response to their environment under glioma control, which can have autocrine effects. In this paper, the microglia and glioma literature is reviewed. We provide a synopsis of the molecular profile of microglia under the influence of glioma in order to help establish a rational basis for their potential therapeutic use. The ability of microglia precursors to cross the blood-brain barrier makes them an attractive target for the development of novel cell-based treatments of malignant glioma.

Impact of vegf on astrocytes: analysis of gap junctional intercellular communication, proliferation, and motility

The purpose of the present study was to investigate the effects of vascular endothelial growth factor (VEGF) on gap junctional intercellular communication (GJIC), cell proliferation, and cell dynamics in primary astrocytes. VEGF is known as a dimeric polypeptide that potentially binds to two receptors, VEGFR-1 and VEGFR-2, however many effects are mediated by VEGFR-2, for example, actin polymerization, forced cell migration, angiogenesis, and cell proliferation. Recently it has been shown that in case of hypoxia, ischemia or injury VEGF is upregulated to stimulate angiogenesis and cell proliferation. Besides this, VEGF reveals a potent therapeutical target for averting tumor vascularization, emerging in bevacizumab, the first humanized anti-VEGF-A antibody for treating recurrent Glioblastoma multiforme. To expand our knowledge about VEGF effects in glial cells, we cultivated rat astrocytes in medium containing VEGF for 1 and 2 days. To investigate the effects of VEGF on GJIC, we microinjected neurobiotin into a single cell and monitored dye-spreading into adjacent cells. These experiments showed that VEGF significantly enhances astrocytic GJIC compared with controls. Cell proliferation measured by BrdU-labeling also revealed a significant increase of astrocytic mitose rates subsequent to 1 day of VEGF exposure, whereas longer VEGF treatment for 2 days did not have additive effects. To study cell-dynamics of astrocytes subsequent to VEGF treatment, we additionally transfected astrocytes with LifeAct-RFP. Live-cell imaging and quantitative analysis of these cells with aid of confocal laser scanning microscopy revealed higher process movement of VEGF-treated astrocytes. In conclusion, VEGF strongly affects cell proliferation, GJIC, and motility in astrocytes.

High-dose siRNAs upregulate mouse Eri-1 at both transcription and posttranscription levels

The eri-1 gene encodes a 3′ exonuclease that can negatively regulate RNA interference via siRNase activity. High-dose siRNAs (hd-siRNAs) can enhance Eri-1 expression, which in return degrade siRNAs and greatly reduces RNAi efficiency. Here we report that hd-siRNAs induce mouse Eri-1 (meri-1) expression through the recruitment of Sp1, Ets-1, and STAT3 to the meri-1 promoter and the formation of an Sp1-Ets-1-STAT3 complex. In addition, hd-siRNAs also abolish the 3′ untranslated region (UTR) mediated posttranscriptional repression of meri-1. Our findings demonstrate the molecular mechanism underlying the upregulation of meri-1 by hd-siRNA.