Regulation of the transforming growth factor-beta 1 and -beta 3 promoters by transcription factor Sp1

VPAC2 Receptor Signaling Promotes Growth and Immunosuppression in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) harbors a complex tumor microenvironment, and cross-talk among cells in the tumor microenvironment can contribute to drug resistance and relapse. Vasoactive intestinal peptide (VIP) is overexpressed in PDAC, and VIP receptors expressed on T cells are a targetable pathway that sensitizes PDAC to immunotherapy. In this study, we showed that pancreatic cancer cells engage in autocrine VIP signaling through VIP receptor 2 (VPAC2). High coexpression of VIP with VPAC2 correlated with reduced relapse-free survival in patients with PDAC. VPAC2 activation in PDAC cells upregulated Piwi-like RNA-mediated gene silencing 2, which stimulated cancer cell clonogenic growth. In addition, VPAC2 signaling increased expression of TGFβ1 to inhibit T-cell function. Loss of VPAC2 on PDAC cells led to reduced tumor growth and increased sensitivity to anti-PD-1 immunotherapy in mouse models of PDAC. Overall, these findings expand our understanding of the role of VIP/VPAC2 signaling in PDAC and provide the rationale for developing potent VPAC2-specific antagonists for treating patients with PDAC. Significance: Autocrine VIP signaling via VPAC2 promotes cancer cell growth and inhibits T-cell function in pancreatic ductal adenocarcinoma, highlighting its potential as a therapeutic target to improve pancreatic cancer treatment.

Autocrine TGFβ1 Opposes Exogenous TGFβ1-Induced Cell Migration and Growth Arrest through Sustainment of a Feed-Forward Loop Involving MEK-ERK Signaling

Simple Summary

Transforming growth factor (TGF) β signaling is intimately involved in nearly all aspects of tumor development and is known for its role as both a tumor suppressor in benign tissues and a tumor promoter in advanced cancers. This dual role is also reflected by cancer cell-produced TGFβ that eventually acts on the same cell(s) in an autocrine fashion. Recently, we observed that endogenous TGFB1 can inhibit rather than stimulate cell motility in cell lines with high autocrine TGFβ production. The unexpected anti-migratory role prompted us to evaluate how autocrine TGFβ1 impacts the cells’ migratory and proliferative responses to exogenous (recombinant human) TGFβ. Surprisingly, endogenous TGFB1 opposed the migratory and growth-inhibitory responses induced by exogenous TGFβ1 by driving a self-perpetuating feedforward loop involving MEK-ERK signaling. Our observation has implications for the use of TGFβ signaling inhibitors in cancer therapy.

Abstract

Autocrine transforming growth factor β (aTGFβ) has been implicated in the regulation of cell invasion and growth of several malignant cancers such as pancreatic ductal adenocarcinoma (PDAC) or triple-negative breast cancer (TNBC). Recently, we observed that endogenous TGFB1 can inhibit rather than stimulate cell motility in cell lines with high aTGFβ production and mutant KRAS, i.e., Panc1 (PDAC) and MDA-MB-231 (TNBC). The unexpected anti-migratory role prompted us to evaluate if aTGFβ1 may be able to antagonize the action of exogenous (recombinant human) TGFβ (rhTGFβ), a well-known promoter of cell motility and growth arrest in these cells. Surprisingly, RNA interference-mediated knockdown of the endogenous TGFB1 sensitized genes involved in EMT and cell motility (i.e., SNAI1) to up-regulation by rhTGFβ1, which was associated with a more pronounced migratory response following rhTGFβ1 treatment. Ectopic expression of TGFB1 decreased both basal and rhTGFβ1-induced migratory activities in MDA-MB-231 cells but had the opposite effect in Panc1 cells. Moreover, silencing TGFB1 reduced basal proliferation and enhanced growth inhibition by rhTGFβ1 and induction of cyclin-dependent kinase inhibitor, p21^WAF1. Finally, we show that aTGFβ1 promotes MEK-ERK signaling and vice versa to form a self-perpetuating feedforward loop that is sensitive to SB431542, an inhibitor of the TGFβ type I receptor, ALK5. Together, these data suggest that in transformed cells an ALK5-MEK-ERK-aTGFβ1 pathway opposes the promigratory and growth-arresting function of rhTGFβ1. This observation has profound translational implications for TGFβ signaling in cancer.

Elucidating the cellular mechanism for E2-induced dermal fibrosis

BACKGROUND

Both TGFβ and estradiol (E2), a form of estrogen, are pro-fibrotic in the skin. In the connective tissue disease, systemic sclerosis (SSc), both TGFβ and E2 are likely pathogenic. Yet the regulation of TGFβ in E2-induced dermal fibrosis remains ill-defined. Elucidating those regulatory mechanisms will improve the understanding of fibrotic disease pathogenesis and set the stage for developing potential therapeutics. Using E2-stimulated primary human dermal fibroblasts in vitro and human skin tissue ex vivo, we identified the important regulatory proteins for TGFβ and investigated the extracellular matrix (ECM) components that are directly stimulated by E2-induced TGFβ signaling.

METHODS

We used primary human dermal fibroblasts in vitro and human skin tissue ex vivo stimulated with E2 or vehicle (ethanol) to measure TGFβ1 and TGFβ2 levels using quantitative PCR (qPCR). To identify the necessary cell signaling proteins in E2-induced TGFβ1 and TGFβ2 transcription, human dermal fibroblasts were pre-treated with an inhibitor of the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway, U0126. Finally, human skin tissue ex vivo was pre-treated with SB-431542, a TGFβ receptor inhibitor, and ICI 182,780, an estrogen receptor α (ERα) inhibitor, to establish the effects of TGFβ and ERα signaling on E2-induced collagen 22A1 (Col22A1) transcription.

RESULTS

We found that expression of TGFβ1, TGFβ2, and Col22A1, a TGFβ-responsive gene, is induced in response to E2 stimulation. Mechanistically, Col22A1 induction was blocked by SB-431542 and ICI 182,780 despite E2 stimulation. Additionally, inhibiting E2-induced ERK/MAPK activation and early growth response 1 (EGR1) transcription prevents the E2-induced increase in TGFβ1 and TGFβ2 transcription and translation.

CONCLUSIONS

We conclude that E2-induced dermal fibrosis occurs in part through induction of TGFβ1, 2, and Col22A1, which is regulated through EGR1 and the MAPK pathway. Thus, blocking estrogen signaling and/or production may be a novel therapeutic option in pro-fibrotic diseases.

Anti-IL-20 Antibody Protects against Ischemia/Reperfusion-Impaired Myocardial Function through Modulation of Oxidative Injuries, Inflammation and Cardiac Remodeling

Acute myocardial infarction (AMI) is the most critical event in the disease spectrum of coronary artery disease. To rescue cardiomyocytes in AMI, it is important to restore blood supply as soon as possible to reduce ischemia-induced injury. However, worse damage can occur during the reperfusion phase, called the reperfusion injury. Under ischemia/reperfusion (I/R) injury, elevated oxidative stress plays a critical role in regulation of apoptosis, inflammation and remodeling of myocardium. Our previous study has demonstrated that interleukin (IL)-20 is increased during hypoxia/reoxygenation stimulation and promotes apoptosis in cardiomyocytes. This study was, therefore, designed to investigate whether IL-20 antibody could reduce I/R-induced myocardial dysfunction. Results from this study revealed that IL-20 antibody treatment significantly suppressed I/R-induced nicotinamide adenine dinucleotide phosphate oxidase, oxidative stress, apoptosis, proinflammatory responses, cardiac fibrosis, and expression of cardiac remodeling markers in Sprague-Dawley rats. Plasma B-type natriuretic peptide level was also reduced by IL-20 antibody injection. IL-20 antibody treatment appeared to restore cardiac function under the I/R injury in terms of greater values of ejection fraction and fractional shortening compared to the control group. Two commonly used indicators of cardiac injury, lactate dehydrogenase and creatine kinase-MB, were also lower in the IL-20 antibody injection group. Taken together, our results suggested that IL-20 antibody holds the potential to reduce the I/R-elicited cardiac dysfunction by preventing cardiac remodeling.

Early Moderate Intensity Aerobic Exercise Intervention Prevents Doxorubicin-Caused Cardiac Dysfunction Through Inhibition of Cardiac Fibrosis and Inflammation

Doxorubicin (DOX) is known as an effective drug in the fight against various cancers. However, one of the greatest impediments is DOX-induced cardiomyopathy, which may potentially lead to heart failure. Accumulating evidence has shed light on the pathological mechanism of DOX-induced cardiotoxicity, but treatments to mitigate the cardiac damage are still required. In an attempt to address this issue, we evaluated whether exercise provides cardioprotective effects on the DOX-induced cardiotoxicity. We showed that treadmill exercise (3 times/week; 1-week of exercise acclimatization and 4-weeks of endurance exercise) during the DOX treatment successfully prevented the cardiac dysfunction. The DOX-stimulated expression of IκBα, NF-κB, COX-2, and IL-8 were all downregulated by exercise as well as the fibrosis factors (TGF-β1, phosphorylated ERK, Sp1, and CTGF). Moreover, we showed that treadmill exercise diminished the expression of several cardiac remodeling-associated factors, such as FGF2, uPA, MMP2, and MMP9. These results were in line with the finding that exercise intervention reduced cardiac fibrosis and restored cardiac function, with higher values of ejection fraction and fractional shortening compared to the DOX-treated group. Two commonly used indicators of cardiac injury, lactate dehydrogenase, and creatine kinase-MB, were also decreased in the exercise group. Collectively, our results suggested that it may be beneficial to prescribe treadmill exercise as an adjunct therapy to limit cardiac damage caused by DOX.

Reversal of Sp1 transactivation and TGFβ1/SMAD1 signaling by H2S prevent nickel-induced fibroblast activation

Nickel as a heavy metal is known to bring threat to human health, and nickel exposure is associated with changes in fibroblast activation which may contribute to its fibrotic properties. H₂S has recently emerged as an important gasotransmitter involved in numerous cellular signal transduction and pathophysiological responses. Interaction of nickel and H₂S on fibroblast cell activation has not been studied so far. Here, we showed that a lower dose of nickel (200 μM) induced the activation of human fibroblast cells, as evidenced by increased cell growth, migration and higher expressions of α-smooth muscle actin (αSMA) and fibronectin, while high dose of nickel (1 mM) inhibited cell viability. Nickel reduced intracellular thiol contents and stimulated oxidative stress. Nickel also repressed the mRNA and protein expression of cystathionine gamma-lyase (CSE, a H₂S-generating gene) and blocked the endogenous production of H₂S. Exogenously applied NaHS (a H₂S donor) had no effect on nickel-induced cell viability but significantly attenuated nickel-stimulated cell migration and the expression of αSMA and fibronectin. In contrast, CSE deficiency worsened nickel-induced αSMA expression. Moreover, H₂S incubation reversed nickel-stimulated TGFβ1/SMAD1 signal and blocked TGFβ1-initiated expressions of αSMA and fibronectin. Nickel inhibited the interaction of Sp1 with CSE promoter but strengthened the binding of Sp1 with TGFβ1 promoter, which was reversed by exogenously applied NaHS. These data reveal that H₂S protects from nickel-stimulated fibroblast activation and CSE/H₂S system can be a potential target for the treatment of tissue fibrosis induced by nickel.

Butyrate produced by gut commensal bacteria activates TGF-beta1 expression through the transcription factor SP1 in human intestinal epithelial cells

The intestinal microbiota contributes to the global wellbeing of their host by their fundamental role in the induction and maintenance of a healthy immune system. Commensal bacteria shape the mucosal immune system by influencing the proportion and the activation state of anti-inflammatory regulatory T cells (Treg) by metabolites that are still only partially unravelled. Microbiota members such as Clostridiales provide a transforming growth factor β (TGFβ)-rich environment that promotes the accumulation of Treg cells in the gut. The intestinal epithelial cells (IECs) take a central part in this process, as they are a major source of TGFβ1 upon bacterial colonisation. In this study, we investigated which gut commensal bacteria were able to regulate the TGFB1 human promoter in IECs using supernatants from cultured bacteria. We reported that Firmicutes and Fusobacteria supernatants were the most potent TGFB1 modulators in HT-29 cells. Furthermore, we demonstrated that butyrate was the main metabolite in bacterial supernatants accounting for TGFβ1 increase. This butyrate-driven effect was independent of the G-protein coupled receptors GPR41, GPR43 and GPR109a, the transporter MCT1 as well as the transcription factors NF-κB and AP-1 present on TGFB1 promoter. Interestingly, HDAC inhibitors were inducing a similar TGFB1 increase suggesting that butyrate acted through its HDAC inhibitor properties. Finally, our results showed that SP1 was the main transcription factor mediating the HDAC inhibitor effect of butyrate on TGFB1 expression. This is, to our knowledge, the first characterisation of the mechanisms underlying TGFB1 regulation in IEC by commensal bacteria derived butyrate.

Cancer upregulated gene 2 induces epithelial-mesenchymal transition of human lung cancer cells via TGF-β signaling

Cancer upregulated gene 2 (CUG2) enhances cell migration and invasion, but the underlying mechanism has not been revealed. Herein, CUG2 decreased the expression of E-cadherin and increased the expression of N-cadherin and vimentin, characteristics of the epithelial-mesenchymal transition (EMT). A CUG2 deletion mutant, lacking interaction with nucleophosmin 1 (NPM1), or suppression of NPM1 reduced wound healing and cell invasion, indicating that CUG2-mediated EMT requires NPM1. CUG2 enhanced activation of Smad2/3 and expression of Snail and Twist, while the CUG2 silence decreased these TGF-β signaling pathways, leading to suppression of EMT. NPM silence also inhibited the CUG2-induced TGF-β signaling. These results suggest that TGF-β signaling is involved in CUG2-induced EMT. Treatment with EW-7197, a novel inhibitor of TGF-β signaling, diminished CUG2-mediated EMT and inhibition of Akt, ERK, JNK, and p38 MAPK, non-canonical TGF-β signaling molecules, also decreased expression of Smad2/3, Snail and Twist, leading to inhibition of EMT. The results confirm that TGF-β signaling is essential for CUG2-mediated EMT. Interestingly, TGF-β enhanced CUG2 expression. We further found that both CUG2-induced TGF-β production and TGF-β-induced CUG2 up-regulation required a physical interaction between Sp1 and Smad2/3 in the CUG2 and TGF-β promoter, as demonstrated by a promoter reporter assay, immunoprecipitation, and ChIP assay. These results indicated close crosstalk between CUG2 and TGF-β. Conversely, suppression of CUG2 or NPM1 did not completely inhibit TGF-β-induced EMT, indicating that the effect of TGF-β on EMT is dominant over the effect of CUG2 on EMT. Collectively, our findings suggest that CUG2 induces the EMT via TGF-β signaling.

Dysregulation of TGFβ1 Activity in Cancer and Its Influence on the Quality of Anti-Tumor Immunity

TGFβ1 is a pleiotropic cytokine that exhibits a variety of physiologic and immune regulatory functions. Although its influence on multiple cell types is critical for the regulation of numerous biologic processes in the host, dysregulation of both TGFβ1 expression and activity is frequently observed in cancer and contributes to various aspects of cancer progression. This review focuses on TGFβ1’s contribution to tumor immune suppression and escape, with emphasis on the influence of this regulatory cytokine on the differentiation and function of dendritic cells and T cells. Clinical trials targeting TGFβ1 in cancer patients are also reviewed, and strategies for future therapeutic interventions that build on our current understanding of immune regulation by TGFβ1 are discussed.

Small-nucleic-acid-based therapeutic strategy targeting the transcription factors regulating the vascular inflammation, remodeling and fibrosis in atherosclerosis

Atherosclerosis arises when injury to the arterial wall induces an inflammatory cascade that is sustained by a complex network of cytokines, together with accumulation of lipids and fibrous material. Inflammatory cascades involve leukocyte adherence and chemotaxis, which are coordinated by the local secretion of adhesion molecules, chemotactic factors, and cytokines. Transcription factors are critical to the integration of the various steps of the cascade response to mediators of vascular injury, and are induced in a stimulus-dependent and cell-type-specific manner. Several small-nucleic-acid-based therapeutic strategies have recently been developed to target transcription factors: antisense oligodeoxynucleotides, RNA interference, microRNA, and decoy oligodeoxynucleotides. The aim of this review was to provide an overview of these particular targeted therapeutic strategies, toward regulation of the vascular inflammation, remodeling and fibrosis associated with atherosclerosis.

Antifibrotic effect of synthetic Smad/Sp1 chimeric decoy oligodeoxynucleotide through the regulation of epithelial mesenchymal transition in unilateral ureteral obstruction model of mice

Renal tubulointerstitial fibrosis is considered to be a common final pathway related to the progressive loss of renal function in chronic kidney disease. It is characterized by the excessive accumulation of extracellular matrix through the pivotal role of epithelial-mesenchymal transition. Transforming growth factor-β1 is postulated to play a central role in renal fibrosis via a downstream pathway such as Smad. Specificity protein 1 (Sp1), which is another transcription factor, is also involved in the basal expression of extracellular matrix. In this study, we investigate the effect of Smad decoy oligodeoxynucleotides (ODN) and Sp1 decoy ODN in unilateral ureteral obstruction induced renal fibrosis in mice. Furthermore, the effectiveness of the newly designed chimeric decoy ODN, which contains both Smad and Sp1 binding sequences in one decoy molecule (Smad/Sp1 chi decoy ODN), was demonstrated. The expression of fibrosis and inflammatory related cytokines and products of fibrosis were ameliorated in the Smad, Sp1 and chimeric decoy ODN treated groups compared with the scrambled decoy ODN treated group. Epithelial-mesenchymal transition was suppressed by the Smad, Sp1 and Smad/Sp1 chi decoy ODN. Immunohistochemistry and Western-blot analysis revealed that Smad/Sp1 chi decoy ODN showed a more significant inhibitory effect on fibrosis and EMT compared with Smad and Sp1 decoy ODNs. These results support the efficacy of Smad/Sp1 chi decoy compared with a single Smad or Sp1 decoy ODNs in preventing renal fibrosis induced by unilateral ureteral obstruction.

Lipid Peroxidation and Transforming Growth Factor-β1 Levels in Gastric Cancer at Pathologic Stages

OBJECTIVE

High levels of TGF-β1 and enhanced TGF-β1 receptor signaling are related to the pathology of gastric cancer. This effect is caused by oxidative stress and lipid peroxidation products. The aim of this study was to investigate the levels of TGF-β1 and lipid peroxidation products in gastric cancer patients and their correlation with pathologic stage.

MATERIAL AND METHODS

Lipid peroxidation products and TGF-β1 levels were studied in the serum samples of 50 gastric cancer patients and 18 control subjects.

RESULTS

HNE-protein adducts and TGF-β1 levels were significantly higher in T2, T3 and T4 gastric cancers than in either the T1 stage or controls (p<0.001). Pathologic stage was correlated with TGF-β1 levels (r=0.702, p<0.05).

CONCLUSION

These markers production may contribute to tumor angiogenesis and aid in the prognosis of the gastric cancer.

Anti-fibrotic effects via regulation of transcription factor Sp1 on hepatic stellate cells

BACKGROUND

Hepatic stellate cells (HSCs), the central cells in hepatic fibrosis, are characterized by sustaining activation, a process that consists in increased proliferation and over-expression of fibrotic genes. Transcription factor Sp1 mediates the expression of a variety of fibrotic genes expression and thereby play an important role in fibrosis. In addition, previous reports have indicated that Sp1 binding activity is greatly increased in activated HSCs. Thus, our aim was to investigate the anti-proliferative and anti-fibrotic effects of the oligonuceotide decoy of the transcription factor Sp1, ODN, a potent inhibitor of Sp1-activated transcription.

METHODS

We optimized Lipofectamin 2000 (LF2000):ODN DNA ratio for the transfection of hepatic stellate cells HSC-T6. Then we measure the effect of transfected ODN on HSC-T6 cells' proliferation and fibrotic gene expression, and study the mechanism involved.

RESULTS

At a DNA concentration of 1 μM and a ratio ODN DNA:LF2000 of 1:3, HSC-T6 cells have the maximal transfection efficiency with the lowest toxicity. Transfected ODN effectively blocks Sp1 binding to the promoter regions of cell cycle regulatory proteins cyclin D1, p27(KIP1) and fibrotic genes, including transforming growth factor (TGF)-β1, Platelet-derived growth factor (PDGF)-BB, α-SMA, α1 (I) collagen and tissue inhibitor of metalloproteinases-1 (TIMP-1). ODN inhibits HSC-T6 proliferation and fibrotic genes expression in vitro.

CONCLUSION

Sp1 is a key transcription factor that mediates proliferation and fibrotic gene synthesis of HSC-T6, inhibition of Sp1 with decoy ODN may be an effective approach to prevent the progression of hepatic fibrosis.

Palifermin induces alveolar maintenance programs in emphysematous mice

RATIONALE

Emphysema is characterized by destruction of alveoli with ensuing airspace enlargement and loss of alveoli. Induction of alveolar regeneration is still a major challenge in emphysema therapy.

OBJECTIVES

To investigate whether therapeutic application of palifermin (DeltaN23-KGF) is able to induce a regenerative response in distal lung parenchyma after induction of pulmonary emphysema.

METHODS

Mice were therapeutically treated at three occasions by oropharyngeal aspiration of 10 mg DeltaN23-KGF per kg body weight after induction of emphysema by porcine pancreatic elastase.

MEASUREMENTS AND MAIN RESULTS

Airflow limitation associated with emphysema was largely reversed as assessed by noninvasive head-out body plethysmography. Porcine pancreatic elastase-induced airspace enlargement and loss of alveoli were partially reversed as assessed by design-based stereology. DeltaN23-KGF induced proliferation of epithelium, endothelium, and fibroblasts being associated with enhanced differentiation as well as increased expression of vascular endothelial growth factor, vascular endothelial growth factor receptors, transforming growth factor (TGF)-beta1, TGF-beta2, (phospho-) Smad2, plasminogen activator inhibitor-1, and elastin as assessed by quantitative reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry. DeltaN23-KGF induced the expression of TGF-beta1 in and release of active TGF-beta1 from primary mouse alveolar epithelial type 2 (AE2) cells, murine AE2-like cells LA-4, and cocultures of LA-4 and murine lung fibroblasts (MLF), but not in MLF cultured alone. Recombinant TGF-beta1 but not DeltaN23-KGF induced elastin gene expression in MLF. Blockade of TGF-signaling by neutralizing antibody abolished these effects of DeltaN23-KGF in LA-4/MLF cocultures.

CONCLUSIONS

Our data demonstrate that therapeutic application of DeltaN23-KGF has the potential to induce alveolar maintenance programs in emphysematous lungs and suggest that the regenerative effect on interstitial tissue is linked to AE2 cell-derived TGF-beta1.

Antifibrotic effect through the regulation of transcription factor using ring type-Sp1 decoy oligodeoxynucleotide in carbon tetrachloride-induced liver fibrosis

BACKGROUND

Liver fibrosis is characterized by the excessive accumulation of extracellular matrix (ECM). Recent advances in the knowledge about the cellular, molecular and genetic aspects of fibrosis have opened a new era of research on liver cirrhosis. A transcription factor, Sp1, originally described as a ubiquitous transcription factor, is involved in the basal expression of ECM genes and may be important in the fibrotic processes.

METHODS

The chronic hepatic damage received intraperitoneal injection of carbon tetrachloride (2 mg/kg) dissolved in corn oil (1 : 3 ratio) three times a weekly for 8 weeks. The delivery of decoy oligodeoxynucleotide (ODN) was performed by injection of 10 microg of scrambled decoy ODN or 10 microg of ring type (R)-Sp1 decoy ODN through the mouse tail vein. All animals of each group were sacrificed, DNA binding activity, expression of cytokines and histological analysis were measured.

RESULTS

We have generated a R-Sp1 decoy ODN that effectively blocks Sp1 binding to the promoter region for transcription regulation of transforming growth factor (TGF)-beta1. The expression of fibrotic cytokines and inflammatory cytokines was decreased by using the R-Sp1 decoy ODN in liver cirrhosis.

CONCLUSIONS

The present study demonstrates that the R-Sp1 decoy ODN inhibits TGF-beta1 expression in liver cirrhosis. These results indicate that targeting Sp1 can efficiently block ECM expression, and suggest that such an approach may represent an interesting therapeutic alternative towards the treatment of cirrhosis.

Dual role of Sp3 transcription factor as an inducer of apoptosis and a marker of tumour aggressiveness

BACKGROUND

The ambiguous role of transcription factor Sp3 for tumour progression is still debated since it was described as a transcriptional repressor or activator. Here we tried to decipher the molecular mechanisms implicated in Sp3 accumulation observed in aggressive tumours.

METHODOLOGY

We generated normal and tumour cell lines conditionally expressing Sp3. Cell growth was analyzed in vitro and after inoculation in nude mice. Apoptosis was assessed by pan- caspase activity assays, by counting fragmented nuclei and by determination of caspase 9 cleavage. Gene expression was determined by quantitative PCR. Cleavage by different caspases was performed after in vitro translation of the Sp3 cDNA in the presence of [S(35)] labelled methionine. Different tumour cell lines and head and neck tumour samples were tested for the presence of Sp3 by western blots. Correlation between Sp3 expression and overall survival has been statistically determined.

PRINCIPAL FINDINGS

Conditional over-expression of Sp3 induces apoptosis and modifies expression of genes implicated in the regulation of cell cycle and pro and anti apoptotic genes. Sp3 over-expression strongly reduces the development of tumours in nude mice confirming its pro-apoptotic potential in vivo. However, cells can survive to apoptosis through selective Sp3 cleavage by caspase. Sp3 induction in established tumours resulted in transient regression then progression. Progression coincides with re-accumulation of the full length form of Sp3. Sp3 is over-expressed in tumour cell lines of different origins. The presence of high levels of the full-length form of Sp3 indicates a poor prognosis for overall survival of patients with head and neck tumours.

CONCLUSIONS

Full length Sp3 accumulation highlights bypass of tumour cell apoptotic capacities and is indicative of head and neck tumours aggressiveness.

Transforming growth factor beta isoforms (TGF-beta1, TGF-beta2, TGF-beta3) messenger RNA expression in laryngeal cancer

PURPOSE

Cancerogenesis is a multistage process controlled by many cytokines, including growth factors. The aim of the study was the comparison of transcriptional activity of transforming growth factor beta (TGF-beta) genes in laryngeal squamous cell carcinomas and adjacent nonneoplastic tissues.

MATERIALS AND METHODS

Tissues samples were obtained from 32 patients with laryngeal squamous cell carcinoma in histologic grades G1 to G3 who underwent surgical treatment at the ENT Clinics of Medical University of Silesia in Katowice, Poland. Quantification of gene expression was performed by real-time quantitative reverse transcriptase polymerase chain reaction technique.

RESULTS

In tumor cells, expression of TGF-beta1 and TGF-beta2 isoforms (P < .001) was higher than in normal tissues. There was a positive correlation between the expression of TGF-beta1 and TGF-beta2 genes in tumors (R = 0.78, P = .0000) and adjacent normal tissues (R = 0.77, P = .0000).

CONCLUSIONS

The results suggest that TGF-beta1 and TGF-beta2 messenger RNAs may be useful as molecular markers in distinguishing cancer from nonneoplastic tissues in laryngeal area.

NFkappaB mediates IL-1beta-induced down-regulation of TbetaRII through the modulation of Sp3 expression

We previously showed that interleukin-1beta (IL-1beta) down-regulation of type II TGFbeta receptor (TbetaRII) involves NFkappaB pathway and requires de novo synthesis of a yet unknown protein. Here, we demonstrate that this effect is mediated through Sp1 site located at position -25 of human TbetaRII promoter. Inhibition of transcription factors binding (decoy oligonucleotides or mithramycin) abolished IL-1beta effect. EMSA and ChIP revealed that this treatment induced Sp3 binding to cis-sequence whereby IL-1beta exerts its transcriptional effects whereas it decreased that of Sp1. Moreover, although the cytokine did not modulate Sp1 expression, it increased that of Sp3 via NFkappaB pathway. Experiments of gain and loss of function clearly showed that Sp3 inhibited TbetaRII expression whereas its silencing abolished IL-1beta effect. In addition, both Sp1 and Sp3 were found to interact with NFkappaB, which therefore may indirectly interact with TbetaRII pro moter. Altogether, these data suggest that IL-1beta decreases TbetaRII expression by inducing Sp3 via NFkappaB and its binding on core promote at the expense of Sp1, which could explain the loss of cell responsiveness in certain conditions. These findings bring new insights in the knowledge of the interference between two antagonistic transduction pathways involved in multiple physiopathological processes.

Regulation of TGF-beta1 gene transcription in human prostate cancer cells by nitric oxide

BACKGROUND

Overexpression of transforming growth factor (TGF)-beta1 is associated with advanced prostate cancer. Our previous studies showed an inverse correlation between the expressions of TGF-beta1 and inducible nitric oxide synthase (iNOS) in prostatic tumors in mice. The purpose of this study was to investigate regulation of TGF-beta1 expression in human prostate cancer cells by nitric oxide (NO).

METHODS

Expression of TGF-beta1 in the three well-characterized lines of human prostate cancer cells (PC-3MM2, LNCaP, and DU145) was determined by using the enzyme-linked immunoabsorbance assay (ELISA), real-time reverse-transcriptase PCR (RT-PCR), nuclear run-on, and promoter activity analyses.

RESULTS

Expression of both TGF-beta1 protein and mRNA was inhibited in both dose- and time-dependent manners by NO donors sodium nitroprusside (SNP), S-nitroso-N-acetylpenicilamine (SNAP), S-nitrosoglutathione (GSNO), and (+/-)-(E)-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexeneamide (NOR-1) and by transfection of iNOS. The inhibitory effects of SNP and iNOS on TGF-beta1 expression were reduced in cells treated with NO scavengers N-dithiocarboxysarcosine (DTCS), 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), and hemoglobin, or with the iNOS inhibitor N-methyl-arginine (NMA). SNP downregulated the in vitro transcription of TGF-beta1 mRNA, inhibited TGF-beta1 promoter activity, but had no significant effects on TGF-beta1 mRNA stability.

CONCLUSION

These results show that NO downregulates TGF-beta1 expression in prostate cancer cells at transcription level by suppressing the de novo synthesis of TGF-beta1 mRNA.

Antifibrotic effect via the regulation of transcription factor Sp1 in lung fibrosis

The aim of this study is to evaluate the antifibrotic effect of ring-type Sp1 decoy oligonucleotides (ODNs) through blocking the transcription of transforming growth factor (TGF)-beta1 and its downstream target genes. In this experiment, the expression of TGF-beta1, metalloproteinase (MMP)-13, and fibronectin was decreased in the group with the treatment of the ring-type Sp1 decoy ODNs. Also, alpha-smooth muscle actin positive bronchial lining cells and alveolar epithelial cells were observed, especially around the lesions of extracellular matrix (ECM) deposition. These findings provide evidences for the finding of pulmonary epithelial-mesenchymal transition (EMT) and the effectiveness of Sp1 transcription factor as a target for the gene therapy on lung fibrosis.

A novel functional polymorphism in the transforming growth factor-beta2 gene promoter and tumor progression in breast cancer

Transforming growth factor-beta (TGF-beta), a multifunctional growth factor, plays an important role in breast cancer. There is increasing evidence that enhanced expression of TGF-beta promotes breast cancer progression contributing to metastasis and invasiveness of the tumor. We identified a functional polymorphism in the TGFB2 promoter, a 4-bp insertion at position -246 relative to the transcriptional start site (-246ins). Transient transfection experiments showed that the -246ins polymorphism significantly increased TGFB2 promoter activity in breast cancer cells. Electrophoretic mobility shift assays revealed binding of the transcription factor Sp1 to the -246ins allele. Overexpression of Sp1 enhanced promoter activity of the -246ins allele, demonstrating that Sp1 mediates transcriptional activation. Furthermore, the -246ins allele was associated with enhanced TGF-beta(2) expression in breast cancer tissue (P = 0.0005). To evaluate the role of the polymorphism in breast cancer, frequency of the -246ins allele was determined in breast cancer patients (n = 78) and healthy female controls (n = 143). No significant differences were found. However, the presence of the -246ins allele was associated with lymph node metastasis (P = 0.003). The -246ins allele was a significant predictor for lymph node metastasis independent of estrogen and progesterone receptor status in a multivariate logistic regression analysis (P = 0.0118, odds ratio, 5.18; 95% confidence interval, 1.44-18.62). We provide evidence that the TGFB2 -246ins polymorphism leads to enhanced TGF-beta(2) expression levels in vivo and might thereby contribute to tumor progression and development of metastases.

Ring-Sp1 decoy oligonucleotide effectively suppresses extracellular matrix gene expression and fibrosis of rat kidney induced by unilateral ureteral obstruction

Tubulointerstitial fibrosis is the consequence of an injury characterized by the accumulation of excess collagen and other extracellular matrix components, resulting in the destruction of the normal kidney architecture and subsequent loss of function. A transcription factor Sp1, originally described as a ubiquitous transcription factor, is involved in the basal expression of extracellular matrix genes and may, therefore, be important in fibrotic processes. Here, we report on the design of a ring-Sp1 decoy oligonucleotide, containing the consensus Sp1 binding sequence in a single decoy molecule without an open end, to create a novel therapeutic strategy for fibrosis. The ring-Sp1 decoy oligonucleotide is highly resistant to degradation by nucleases or serum compared to the conventional phosphorothioated double-stranded Sp1 decoy oligonucleotide, and effectively suppressed the expression of transforming growth factor-beta1 and fibronectin, the binding of Sp1 to the promoter region of these genes, and proliferation in response to serum in normal rat kidney fibroblasts. Moreover, treatment with the ring-Sp1 decoy in vivo significantly attenuates extracellular matrix gene expression in the rat kidney in which a unilateral ureteral obstruction had been induced. These results suggest that the ring-Sp1 decoy oligonucleotide represents promising therapeutic alternative to the conventional treatment of fibrotic disorders.

NF-kappaB and activator protein 1 response elements and the role of histone modifications in IL-1beta-induced TGF-beta1 gene transcription

Abnormal expression of TGF-beta1 is believed to play an important role in the pathogenesis of a number of chronic inflammatory and immune lung diseases, including asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis. Gene activation in eukaryotes requires coordinated use of specific cell signals, chromatin modifications, and chromatin remodeling. We studied the roles of the ubiquitous inflammatory transcription factors, NF-kappaB and AP-1, in activation of the TGF-beta1 gene and histone acetylation at the TGF-beta1 promoter. IL-1beta-induced TGF-beta1 protein secretion and mRNA expression were prevented by actinomycin D and were attenuated by the inhibitor of kappaB kinase 2 inhibitor AS602868 and the JNK inhibitor SP600125, suggesting a degree of transcriptional regulation mediated by the NF-kappaB and AP-1 pathways. We demonstrated that IL-1beta activated the p65 subunit of NF-kappaB and the c-Jun subunit of AP-1. Using chromatin immunoprecipitation assays, we observed a sequential recruitment of p65 and c-Jun, accompanying ordered elevation of the levels of histone H4 and H3 acetylation and recruitment of RNA polymerase II at distinct regions in the native TGF-beta1 promoter. The specific NF-kappaB and AP-1 binding sites in the TGF-beta1 promoter were confirmed by an ELISA-based binding assay, and evidence for histone hyperacetylation in TGF-beta1 induction was supported by the observation that the histone deacetylase inhibitor trichostatin A enhanced basal and IL-1beta-induced TGF-beta1 mRNA expression. Our results suggest that IL-1beta-stimulated transcription of TGF-beta1 is temporally regulated by NF-kappaB and AP-1 and involves histone hyperacetylation at distinct promoter sites.

Allelic diversity in the TGFB1 regulatory region: characterization of novel functional single nucleotide polymorphisms

Altered TGF-beta1 expression due to polymorphisms affects a wide variety of normal cellular and disease processes such as T cell activation and proliferation, tumor progression, and asthma. In this study, a comprehensive examination of function and diversity was undertaken for the TGFB1 promoter region and exon 1 (-2,665 to +423). The known TGF-beta1 promoter was extended to encompass 463 bases by the identification of a strong enhancer activity for a distal segment (-2,665 to -2,204). Ten novel polymorphisms and 14 novel alleles were identified. Most single nucleotide polymorphisms (SNPs) appear to be randomly associated except c.-768_-769insC and c.+74G > C and a set of five novel polymorphisms present in a single allele in persons of African descent. The TGFB1 alleles clustered into three phylogenetic groups based on the common functional SNPs c.-1347C > T (commonly known as -509C-T) and c.+29T > C (commonly known as +869T-C) suggesting three phenotypic groups. Two SNPs unique to African-Americans affect the TGFB1 regulatory region. The c.-1287G > A SNP in the promoter alters the binding affinity of two unidentified transcription factor complexes which translates into a significant difference in reporter gene expression and the c.-387C > T SNP in the 5' UTR alters the binding of Stimulating protein 1 and 3. Thus, TGFB1 possesses a highly polymorphic, extensive regulatory region that likely impacts the pathogenesis of numerous TGF-beta1 related diseases.

Ah receptor signals cross-talk with multiple developmental pathways

For many years, the Ah receptor (AHR) has been a favorite of toxicologists and molecular biologists studying the connections between genes and the changes in the control of gene expression resulting from environmental exposures. Much of the attention given to the Ah receptor has focused on the nature of its ligands, many of which are known or suspected carcinogens, and on the role that its best studied regulatory product, the CYP1A1 enzyme, plays in toxic responses and carcinogen activation. This understandable bias has resulted in a disproportionate amount of Ah receptor research being directed at toxicological or adaptive end points. In recent times, it has become evident that Ah receptor functions are also involved in molecular cascades that lead to inhibition of proliferation, promotion of differentiation, or apoptosis, with an important bearing in development. Developmental and toxicological AHR functions may not always be related. The ancestral AHR protein in invertebrates directs the developmental fate of a few specific neurons and does not bind xenobiotic ligands. The mammalian AHR maintains normal liver function in the absence of exogenous ligands and, when activated by dioxin, cross-talks with morphogenetic and developmental signals. Toxic end points, such as the induction of cleft palate by dioxin in mice embryos, might be at the crossroads of these signals and provide important clues as to the developmental role of the AHR.

Nkx2.1 transcription factor in lung cells and a transforming growth factor-beta1 heterozygous mouse model of lung carcinogenesis

The Nkx2.1 homeobox gene and transforming growth factor-beta1 (TGF-beta1) are essential for organogenesis and differentiation of the mouse lung. NKX2.1 is a marker of human lung carcinomas, but it is not known whether this gene participates in early tumorigenesis. Addition of TGF-beta1 to TGF-beta1-responsive nontumorigenic mouse lung cells cotransfected with a NKX2.1Luc luciferase reporter and either a Sp1 or Sp3 plasmid showed a significant increase or decrease, respectively, in NKX2.1Luc transcription. Cotransfection of Sp3 and dominant-negative TGF-beta type II receptor plasmids negated the effect of Sp1. Cotransfected Sp1 plasmid with either dominant-negative Smad2 or Smad3 or Smad4 plasmids significantly decreased NKX2.1Luc transcription. Electrophoretic mobility shift assays revealed binding of Sp1 and Smad4 to the NKX2.1 promoter. With a TGF-beta1 heterozygous mouse model, Nkx2.1 mRNA and protein in lungs of TGF-beta1 heterozygous mice were significantly lower compared to wildtype (WT) littermates. Competitive reverse transcription (RT)-polymerase chain reaction (PCR) and immunostaining showed that Nkx2.1 mRNA and protein decreased significantly in adenomas and adenocarcinomas compared to normal lung tissue. Our in vitro data showed that regulation of Nkx2.1 by TGF-beta1 occurs through TGF-beta type II receptor and Smad signaling, with Sp1 and Sp3 in lung cells. Our in vivo data showed reduced Nkx2.1 in lungs of TGF-beta1 heterozygous mice compared to WT mice, that is detectable in adenomas, and that is further reduced in carcinogenesis, and that correlates with reduction of Sp1, Sp3, and Smads in lung adenocarcinomas. Our findings suggest that reduced Nkx2.1 and TGF-beta1 signaling components may contribute to tumorigenesis in the lungs of TGF-beta1 heterozygous mice.

Regulation of Fgf10 gene expression in the prostate: identification of transforming growth factor-beta1 and promoter elements

Fibroblast growth factor 10 (FGF10) is a mesenchymal paracrine-acting factor that plays a key role in the organogenesis of the prostate, and Fgf10 transcripts exhibit a highly restricted expression pattern within prostatic mesenchyme. To study the regulation of Fgf10 we have used organ rudiments grown in vitro as well as a primary stromal cell system derived from the ventral mesenchymal pad (VMP), a condensed area of mesenchyme known to induce prostatic organogenesis. Characterization of VMP cells (VMPCs) showed that they retained expression of AR as well as transcripts for FGF10 and TGFbeta1, -2, and -3. We propose that VMPCs are a good model of specialized mesenchyme involved in prostatic organogenesis and are distinct from general urogenital sinus mesenchyme/stroma. Treatment of VMPCs with TGFbeta1 resulted in a rapid and transient decrease in Fgf10 transcript levels, which were reduced 9-fold at 3 h. TGFbeta1 also inhibited Fgf10 expression in VMP organ rudiments grown in vitro. To further analyze Fgf10 regulation, 6 kb of mouse genomic sequence 5' to the translation start site was characterized by promoter analysis. Deletion analysis of the Fgf10 promoter in VMPCs identified a region of the promoter that mediated a significant proportion of promoter activity as well as mediating promoter down-regulation by TGFbeta1. This element was located between nucleotides -182 and -172 and contained a consensus Sp1 binding site. Taken together, our data suggest that TGFbeta1 is a regulator of Fgf10 expression in prostatic mesenchyme and that a proximal element within the Fgf10 promoter plays an important role in its regulation and expression.

Downregulation of TNF-alpha and VEGF expression by Sp1 decoy oligodeoxynucleotides in mouse melanoma tumor

Melanoma tumor growth and progression are highly dependent on adequate blood supply through angiogenesis. Since several genes involved in angiogenesis revealed potential binding sites for the transcription factor Sp1, we have examined the effects of local inoculation of Sp1 decoy oligodeoxynucleotides (ODNs) on the growth of transplanted murine melanoma tumors and the expression of VEGF and TNF-alpha within these tumors. Treatment with Sp1 decoy ODNs, but not their mutated form, led to a significant increase (P=0.041) of the tumor necrotic area, as evaluated morphometrically. Tumor necrosis was associated with a significant decrease of microvascular density (P=0.012) and relative vascular area (P=0.026), as determined by counting CD34-positive vascular structures within the tumor microenvironment of Sp1 decoy ODNs and control ODN-treated tumors. RT-PCR experiments showed a strong decrease in the levels of VEGF188 and VEGF164 isoforms and a moderate decrease of TNF-alpha in Sp1 decoy-treated tumors. Taken together, our results indicate that Sp1 decoy ODNs may inhibit angiogenesis by affecting the gene expression of key players in angiogenesis such as TNF-alpha and VEGF. These findings indicate that Sp1 decoy ODNs may be a potential new therapeutic tool in antiangiogenic therapy.

Ecteinascidin-743 drug resistance in sarcoma cells: transcriptional and cellular alterations

A human chondrosarcoma cell line, CS-1, was treated successively with increasing concentrations of the marine chemotherapeutic Ecteinascidin-743 (ET-743), yielding a variant cell line displaying a significant degree of resistance to the cytotoxic action of this drug. Various experiments were performed to discern molecular aberrations between the parent and resistant cell line, and also identify potential molecular markers indicative of drug resistance. Although no significant differences in the levels of membrane transporters such as P-glycoprotein or multidrug resistance protein 1 (MRP1) were detected, the cell migratory ability of the ET-743-resistant cell variant was reduced, as was its attachment capability to gelatin-coated cell culture dishes. Staining of the actin-containing cytoskeleton with fluorescent-labeled phalloidin revealed marked differences in the cytoskeleton architecture between the parent and ET-743-resistant CS-1 cell lines. Comparison of serum-free conditioned medium from both cell lines showed conspicuous differences in the levels of several proteins, including a quartet of high molecular weight proteins (> or =140 kDa). The protein sequences of two of these high molecular weight proteins, present at significantly higher concentrations in conditioned medium obtained from the parent cell line, corresponded to subunits of types I and IV collagen. Analysis of type I collagen alpha1 chain mRNA revealed a significantly lower level in the ET-743-resistant CS-1 cell line. Thus, prolonged exposure to ET-743 may cause changes in cell function through cytoskeleton rearrangement and/or modulation of collagen levels.

Comparative functional analysis of rat TGF-beta1 and Xenopus laevis TGF-beta5 promoters suggest differential regulations

We have carried out a comparative functional analysis of the rat TGF-beta1 and Xenopus laevis TGF-beta5 promoters across several mammalian and amphibian cell lines. Progressive deletion constructs of both the promoters have been made using a PCR based approach and the basal promoter activities studied in Xenopus tadpole cell line (XTC), Xenopus adult kidney fibroblast cell line (A6), human hepatoma cell line (HepG2), normal rat kidney cell line (NRK), and Chinese hamster ovary cell line (CHO). Data suggests that the basal promoter activity of TGF-beta1 is low as compared to TGF-beta5 promoter in XTC cells but comparable in A6 cells, while TGF-beta5 promoter shows nearly negligible activity as compared to TGF-beta5 promoter in all the tested mammalian cell lines. Moreover, TGF-beta5 promoter is found to be repressed in XTC cells on treatment with TGF-beta5 protein. Thus, the regulation of TGF-beta1 and TGF-beta5 promoters is distinct in amphibian and mammalian species. We therefore suggest that contrary to the suggested functional equivalence of TGF-beta1 and TGF-beta5 proteins, TGF-beta1 and TGF-beta5 genes have distinct functions in their respective species.

High-throughput single-nucleotide polymorphism analysis of the IL1RN locus in patients with ankylosing spondylitis by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry

OBJECTIVE

To examine single-nucleotide polymorphisms (SNPs) in the 3' region of the IL1RN gene in a large Caucasoid case-control series and in ankylosing spondylitis (AS) families from Western Canada by use of high-throughput MassArray matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry SNP typing.

METHODS

An association analysis was performed in a case-control cohort of 394 AS cases and 500 controls. Family-based association analysis was performed in 58 simplex and 13 multiplex families. Three SNPs located in the 3' region of the IL1RN gene (T/C at position 27810 in exon 4, T/C at position 30735 in exon 6, and G/C at position 31017 in exon 6) were examined by high-throughput MassArray MALDI-TOF mass spectrometry. Haplotype inference software programs were used to infer the most likely haplotypes and to compare haplotype frequencies, which were then further analyzed in family-based association studies by transmission disequilibrium tests.

RESULTS

The frequency of allele C at SNP position 30735 in exon 6 was significantly increased in AS cases (35.1%) versus controls (27.8%), as was the phenotype frequency (61.7% versus 48.6%). A significantly increased frequency of SNP allele G at position 31017 in exon 6 in cases (32.9%) versus controls (28.3%) was also noted. A highly significant difference in the overall distribution of haplotype frequencies was evident between cases and controls, with significant increases in the frequencies of the 27810C/30735C/31017C and 27810C/30735T/31017G haplotypes, but a significant reduction in the estimated frequency of the 27810C/30735T/31017C haplotype, in the AS cases. Estimation of haplotype frequencies based on 2 SNP markers indicated a highly significant increase in the 30735C/31017C haplotype and a highly significant decrease in the 30735T/31017C haplotype in cases compared with controls. Preliminary evidence for reduced transmission of the 27810C/30735T/31017C 3-marker haplotype was also found in family-based association analyses.

CONCLUSION

Our data establish a highly significant disease association with markers in the IL1RN gene. In the absence of nonsynonymous coding sequence substitutions, it is possible that the primary disease-associated locus regulates gene expression. Association with specific haplotypes raises the possibility that the primary disease locus is in linkage disequilibrium with a specific combination(s) of markers in the IL1RN gene.

P38 mitogen-activated protein kinase mediates hexosamine-induced TGFbeta1 mRNA expression in human mesangial cells

AIMS/HYPOTHESIS

The hexosamine pathway has been implicated in the induction of TGFbeta1 expression and in the pathophysiology of diabetic glomerulopathy. Glucose-induced TGFbeta1 expression is mediated by p38 mitogen-activated-protein-kinase (p38-MAPK) and this kinase is activated in the diabetic glomeruli. We examined whether the p38-MAPK is implicated in hexosamine-induced TGFbeta1 mRNA expression in human mesangial cells. GFAT overexpression induced an increase in p38-MAPK activation after 6 and 12 h incubation in normal glucose, and this was prevented by the GFAT inhibitor azaserine. Furthermore, high glucose enhanced p38-MAPK activation in GFAT tranfected cells ( p</=0.04). P38-MAPK inhibition using SB202190 (1 micro mol/l) reduced hexosamine-induced TGFbeta1 expression in normal and high glucose. The activation of the p38-MAPK was dependent on protein kinase-C.

METHODS

The products of the hexosamine biosynthetic pathway were increased by the addition of glucosamine or by the overexpression of the rate-limiting enzyme of the hexosamine pathway, glutamine: fructose-6-phosphate amidotransferase (GFAT).

RESULTS

Glucosamine addition resulted in cell death. UDP-N-Acetylglucosamine, one of the major hexosamine end-products, was increased in normal (7 mmol/l) and high (25 mmol/l) glucose conditions in GFAT-transfected cells compared to control transfected cells by twofold and 1.7-fold respectively ( p</=0.04) and this was accompanied by a 1.6- and 2.3-fold increase ( p</=0.02) in TGFbeta1 mRNA expression. Addition of the GFAT inhibitor azaserine (10 micro mol/l) prevented the induction of TGFbeta1 in GFAT transfected cells.

CONCLUSION/INTERPRETATION

Overexpression of GFAT increases hexosamine accumulation which mediates TGFbeta1 expression via a protein kinase-C and p38-MAPK dependent mechanism. Increased glucose concentrations magnify these effects.

Ultraviolet irradiation alters transforming growth factor beta/smad pathway in human skin in vivo

Solar ultraviolet irradiation damages human skin and causes premature skin aging and skin cancer. As transforming growth factor beta plays an important role in regulating cell growth and extracellular matrix synthesis, we investigated expression of transforming growth factor beta isoforms, transforming growth factor beta receptors, and transforming growth factor beta regulated Smad transcription factors following irradiation with an ultraviolet B source and solar-simulated ultraviolet irradiation of human skin in vivo. Full-thickness, sun-protected adult human skin expressed transforming growth factor beta1, beta2, and beta3 transcripts in a ratio of 1:5:3, as determined by quantitative real-time reverse transcription polymerase chain reaction. Northern analysis demonstrated that the ultraviolet irradiation (2 minimal erythema dose) caused moderate (2-3-fold) gradual increases of transforming growth factor beta1 and beta3 mRNA expression during 3 d post exposure. In contrast, expression of transforming growth factor beta2 mRNA, the predominant form of transforming growth factor beta in human skin, decreased within 4 h after ultraviolet irradiation. In situ hybridization revealed transforming growth factor beta1, beta2, and beta3 mRNA expression in cells throughout the epidermis and the dermis in nonirradiated skin. Following ultraviolet or solar-simulated ultraviolet irradiation, transforming growth factor beta1 and beta3 mRNA were increased and transforming growth factor beta2 mRNA was reduced throughout the epidermis and dermis. No significant changes were observed in transforming growth factor beta type I receptor mRNA expression after ultraviolet irradiation. In contrast, transforming growth factor beta type II receptor mRNA expression was reduced 60% within 4 h following ultraviolet exposure in human skin in vivo. Transforming growth factor beta type II receptor mRNA levels remained reduced for 8 h and recovered by 24 h post ultraviolet. In situ hybridization revealed that ultraviolet or solar-simulated ultraviolet irradiation caused loss of transforming growth factor beta type II receptor mRNA in basal and suprabasal cells in the epidermis and dermal cells. In addition, no significant changes were observed in Smad2, Smad3, and Smad4 expression after ultraviolet irradiation. In contrast, ultraviolet and solar-simulated ultraviolet irradiation rapidly induced gene expression of Smad7, which antagonizes the actions of the transforming growth factor beta/Smad pathway. Smad7 mRNA induction occurred throughout the epidermis and dermal cells as determined by in situ hybridization. Ultraviolet irradiation also caused reduced DNA binding of Smad3/4 in human skin in vivo. Reduced Smad3/4 DNA binding was observed within 4 h following irradiation. Taken together, these results demonstrate that ultraviolet and solar-simulated ultraviolet irradiation alter the transforming growth factor beta/Smad pathway in human skin in vivo. Ultraviolet induction of Smad7 and reduction of transforming growth factor beta2 and transforming growth factor beta type II receptor should diminish transforming growth factor beta signaling, and probably contribute to the decrease of transforming growth factor beta regulated type I and type III procollagen gene expression observed in ultraviolet and solar-simulated ultraviolet irradiated human skin in vivo.

Expression of TGF-betas and their receptors is differentially modulated by reactive oxygen species and nitric oxide in human articular chondrocytes

OBJECTIVES

To study the effects exerted by two antioxidants, N-monomethyl-L-arginine (L-NMMA), as an inhibitor of nitric oxide (NO) synthesis, and N-acetylcysteine (NAC), a reactive oxygen species (ROS) scavenger, on the expression of the major growth factor involved in cartilage repair, TGF-beta, under the three isoforms beta1, beta2 and beta3, and the receptors I and II of this factor, using lipopolysaccharide (LPS)-treated human chondrocytes in culture.

METHODS

Suspension cultures of human chondrocytes derived from the knee of osteoarthritic patients were treated for 48 h with lipopolysaccharide (LPS) (10 microg/ml), L-NMMA (0.5 mM) or NAC (1 mM). Nitrite levels were assayed on the culture media using the Griess spectrophotometric method. After total RNA extraction, the expression of inducible NO synthase (iNOS), TGF-beta1, TGF-beta2, TGF-beta3, TGF-beta receptors I and II, was determined by semi-quantitative polymerase chain-reaction (RT-PCR).

RESULTS

LPS induced a dramatic increase of both NO production and iNOS mRNA level. The addition of L-NMMA (0.5 mM) abolished NO production without affecting iNOS mRNA levels. In contrast NAC (1 mM) strongly synergized with LPS to stimulate NO synthesis. LPS treatment did not significantly alter TGF-beta1 expression whereas L-NMMA inhibited its production. TGF-beta2 mRNA level was decreased by LPS and was not changed in the presence of L-NMMA. On the other hand, NAC was capable of counteracting the LPS-induced inhibition of TGF-beta2 expression. TGFbeta3 mRNA level was markedly reduced by LPS alone, or with both L-NMMA and NAC. Finally, the expression of TGF-betaRI was slightly increased in the presence of combined LPS and L-NMMA or NAC whereas that of TGFbeta-RII was reduced in the same conditions.

CONCLUSIONS

The modulation of TGF-beta system was found to be differentially controlled by NO and ROS productions. Indeed, the control exerted on TGF-beta expression varied according to the isoform: TGF-beta1 mRNA level depends on NO whereas that of TGF-beta2 is regulated by ROS and TGF-beta3 seems to be unaffected by both of them. The expression of TGF-beta receptors appeared to be modulated by NO and ROS levels. The relevance of the present findings to osteoarthritis (OA) physiopathology and the potential use of antioxidant therapy to treat this disease are discussed.

Control of connective tissue gene expression by TGF beta: role of Smad proteins in fibrosis

Transforming growth factor-beta (TGF beta) plays a critical role in the development of tissue fibrosis. Its expression is consistently elevated in affected organs and correlates with increased extracellular matrix deposition. During the last few years, tremendous progress has been made in understanding the molecular aspects of intracellular signaling downstream of the TGF beta receptors. In particular, Smad proteins--TGF beta receptor kinase substrates that translocate into the cell nucleus to act as transcription factors--have been studied extensively. Their role in the modulation of extracellular matrix gene expression is discussed in this review.

Transforming growth factor-beta signaling through the Smad pathway: role in extracellular matrix gene expression and regulation

Transforming growth factor (TGF)-beta represents a prototype of multifunctional cytokine. Its broad activities include, among others, context-specific inhibition or stimulation of cell proliferation, control of extracellular matrix (ECM) synthesis and degradation, control of mesenchymal-epithelial interactions during embryogenesis, mediation of cell and tissue responses to injury, control of carcinogenesis, and modulation of immune functions. Regulation of production and turnover of ECM components is essential for tissue homeostasis and function. TGF-beta exerts its effects on cell proliferation, differentiation, and migration in part through its capacity to modulate the deposition of ECM components. Specifically, TGF-beta isoforms have the ability to induce the expression of ECM proteins in mesenchymal cells, and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the ECM. Deregulation of these functions is associated with abnormal connective tissue deposition, as observed, for example, during scarring or fibrotic processes. In this review we discuss the current understanding of the signaling mechanisms used by TGF-beta to elicit its effects on target genes, focusing primarily on Smad proteins and their role in the transcriptional regulation of ECM gene expression. Other signaling mechanisms, such as the MAP/SAP kinase or Ras pathways, although potentially important for transmission of some of the TGF-beta signals, will not be described. Transforming growth factor-beta (TGF-beta) plays a critical role in the regulation of extracellular matrix gene expression. Its overexpression is believed to contribute to the development of tissue fibrosis. The recent identification of Smad proteins, TGF-beta receptor kinase substrates that translocate into the cell nucleus to act as transcription factors, has increased our understanding of the molecular mechanisms underlying TGF-beta action. This review focuses primarily on the mechanisms underlying Smad modulation of gene expression and how they relate to wound healing. Potential implications for the development of therapeutic approaches against tissue fibrosis are discussed.

Beyond Mitomycin: TGF-beta and wound healing

The introduction of the anti-cancer drugs Mitomycin and 5-fluorouracil as anti-scarring agents within the last decade, has greatly improved surgical results of glaucoma filtration surgery. However, a number of problems associated with their use have emerged. At the same time, the transforming growth factor-beta (TGF-beta) has been identified as an important component of wound healing, particularly in the conjunctival scarring response. Recent developments in molecular therapy offer exciting prospects for the modulation of wound healing, specifically those targeting TGF-beta. As TGF-beta is such a potent stimulant of scarring, this review examines its biology and role in ocular wound healing and repair, and discusses promising new approaches to modifying its activity.

Blocking sp1 transcription factor broadly inhibits extracellular matrix gene expression in vitro and in vivo: implications for the treatment of tissue fibrosis

Fibrosis is a consequence of injury characterized by accumulation of excess collagen and other extracellular matrix components, resulting in the destruction of normal tissue architecture and loss of function. Sp1 was originally described as a ubiquitous transcription factor. It is involved in the basal expression of extracellular matrix genes and may, therefore, be important in fibrotic processes. To evaluate the effect of Sp1 blockade on the expression of extracellular matrix genes, clones of NIH 3T3 fibroblasts stably transfected with an anti-sense Sp1 expression vector. Simultaneously reduced expression of several extracellular matrix genes as compared with mock-transfected clones was noted using differential hybridization of cDNA microarrays, without significant alteration in cell growth. Transfection of human dermal fibroblasts with several extracellular matrix gene (COL1A1, COL1A2, COL3A1, COL5A2, COL7A1, TIMP-1, and decorin) promoter/reporter constructs demonstrated that anti-sense Sp1-induced reduction of extracellular matrix gene mRNA steady-state levels results from transcriptional repression, consistent with the role of Sp1 as a transcription factor. Decoy Sp1 binding oligonucleotides inhibited COL1A2 promoter activity both in cultured fibroblasts and in vivo, in the skin of transgenic mice, which have integrated a mouse COL1A2 promoter/luciferase reporter gene construct. These results indicate that targeting Sp1 efficiently blocks extracellular matrix gene expression, and suggest that such an approach may represent an interesting therapeutic alternative toward the treatment of fibrotic disorders.

Smad2, Smad3 and Smad4 cooperate with Sp1 to induce p15(Ink4B) transcription in response to TGF-beta

Transforming growth factor-beta (TGF-beta) arrests growth of epithelial cells by inducing the transcription of p15(Ink4B), a cyclin-dependent kinase inhibitor. In this study, we demonstrate that p15(Ink4B) induction was mediated by a TGF-beta-induced complex of Smad2, Smad3, Smad4 and Sp1. Mutations in the Sp1- or Smad-binding sequences decreased or abolished the TGF-beta responsiveness of the p15(Ink4B) promoter. Interference with, or deficiency in, Smad2, Smad3 or Smad4 functions also reduced or abolished the TGF-beta-dependent p15(Ink4B) induction, whereas the absence of Sp1 reduced the basal and TGF-beta-induced p15(Ink4B) transcription. In the nucleoprotein complex, Smad2 interacted through its C-domain with Sp1 and enhanced the DNA binding and transcriptional activity of Sp1. Smad3 interacted indirectly with Sp1 through its association with Smad2 and/or Smad4, and bound directly to the p15(Ink4B) promoter. Finally, Smad4 interacted through its N-domain with Sp1. Our data demonstrate the physical interactions and functional cooperativity of Sp1 with a complex of Smad2, Smad3 and Smad4 in the induction of the p15(Ink4B) gene. These findings explain the tumor suppressor roles of Smad2 and Smad4 in growth arrest signaling by TGF-beta.

Overexpression of GFAT activates PAI-1 promoter in mesangial cells

Effects of hyperglycemia on glomerular cells may be mediated by glucose entry into the hexosamine pathway, and mesangial cell (MC) expression of the hexosamine pathway rate-limiting enzyme glutamine:fructose-6-phosphate amidotransferase (GFAT) is increased in diabetic glomerulosclerosis. We hypothesized that GFAT activity would be an important determinant of gene expression in glomerular MC. When overexpressed in primary MC, GFAT produced a two- to threefold increase in the activity of plasminogen activator inhibitor-1 (PAI-1) promoter. There was a 1.4-fold increase in PAI-1 promoter activity in cells exposed to high glucose (20 mM), whereas in MC overexpressing GFAT, exposure to high glucose caused a 3.5- to 4-fold increase in promoter activity. PAI-1 promoter activation was dependent on GFAT enzyme activity because o-diazoacetyly-L-serine and 6-diazo-5-oxonorleucine, inhibitors of GFAT enzyme activity, abrogated the activation of PAI-1 promoter in MC overexpressing GFAT. Glucosamine, which is downstream of GFAT in the hexosamine pathway, produced a 2.5-fold increase in the PAI-1 promoter activity. In addition to increasing the mRNA levels for transforming growth factor-beta1 (TGF-beta1), GFAT overexpression also increased mRNA levels for the TGF-beta type I and type II receptors. TGF-beta-neutralizing antibody did not normalize PAI-1 promoter activity in MC exposed to glucosamine or those overexpressing GFAT. We conclude that GFAT expression and activity are important determinants of gene expression in MC and that flux through the hexosamine pathway activates expression of genes implicated in vascular injury pathways.

Effect of lovastatin on small GTP binding proteins and on TGF-beta1 and fibronectin expression

We have shown that lovastatin, an inhibitor of 3 hydroxy-3-methylglutary coenzyme A (HMG CoA) reductase, delays development and progression of diabetic nephropathy in streptozotocine-induced diabetic rats through suppression of glomerular transforming growth factor (TGF)-beta1 mRNA expression. We have also shown that lovastatin suppresses both control and high glucose (HG)-induced TGF-beta1 and fibronectin mRNA expression and protein synthesis by rat mesangial cell (RMC) and that this down-regulation by lovastatin is reversed by mevalonate. It was postulated that this down-regulation may be linked to signaling of small guanine triphosphate (GTP)-binding proteins and mediated by the limitation of isoprenoids such as farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP) in RMC. To determine the isoprenoid and small GTP-binding proteins involved in TGF-beta1 and fibronectin expression. FPP or GGPP was added alone or in combination to RMC treated with lovastatin cultured under normal or high glucose condition. Suppression of TGF-beta1 and fibronectin expression by lovastatin was reversed effectively when GGPP was added alone. Partial reversal of lovastatin effect on fibronectin and TGF-beta1 expression was found when FPP was added alone. Adding both GGPP and FPP resulted in complete reversal of lovastatin effect on fibronectin but not TGF-beta1 suggesting that fibronectin and TGF-beta1 are regulated differently. Furthermore, luciferase activity of RMC cotransfected with fibronectin promoter reporter system and plasmid-expressing C3 exoenzyme (a specific inactivator of Rho family GTP binding proteins, pEFC3) was completely suppressed when compared with RMC cotransfected with empty vector, pEF. Because geranylgeranylation is usually involved in post-translational modification and membrane targeting of Rho family small GTP binding proteins, these data indicate that Rho family small GTP-binding proteins rather than Ras family small GTP binding proteins may play a key role in the TGF-beta1 and fibronectin expression in RMC.

The role of Sp1 in the differential expression of transforming growth factor-beta receptor type II in human breast adenocarcinoma MCF-7 cells

Progression of MCF-7 cells from early passage (MCF-7E, <200 passage) to late passage (MCF-7L, >500 passage) correlates with a loss of sensitivity to exogenous TGFbeta1. We have previously shown that loss of TGFbeta sensitivity is due to decreased expression of the transforming growth factor receptor type II (TbetaRII) and is associated with increased tumorigenicity in nude mice. Reduced TbetaRII expression in MCF-7L cells is caused by decreased TbetaRII promoter activity in this cell line. Our previous studies using 5' deletion constructs of this promoter revealed that MCF-7L cells were unable to support transcription of the minimal promoter (-47 to +2) to the same levels as the MCF-7E cells. This region of the promoter contains an Sp1 element at position -25 from the major transcription start site. In this study, we investigated the role of Sp1 in TbetaRII transcription. Mutation of the Sp1 site resulted in decreased transcription of TbetaRII in MCF-7E and MCF-7L cells, indicating that this site played a role in transcription of this promoter. Gel shift assays using the proximal Sp1 site from the TbetaRII promoter showed enhanced DNA:protein complex formation with nuclear proteins isolated from MCF-7E cells compared with MCF-7L cells. Supershift analysis identified this binding activity as Sp1. Western blot analysis of Sp1 levels demonstrated that MCF-7E cells contain increased Sp1 protein compared with MCF-7L cells, paralleling the increased binding activity. Differential Sp1 activity was also demonstrated by higher levels of transcription of an Sp1-dependent insulin-like growth factor II promoter construct in MCF-7E cells compared with MCF-7L cells. Co-transfection of an Sp1 expression vector with a TbetaRII promoter construct in MCF-7L cells induced the expression from the promoter-CAT constructs and resulted in an increase of endogenous TbetaRII protein levels. These results demonstrate that the transcriptional repression of TbetaRII in MCF-7L cells is caused, in part, by lower Sp1 levels.

TIEG proteins join the Smads as TGF-beta-regulated transcription factors that control pancreatic cell growth

The control of epithelial cell proliferation, differentiation, and apoptosis requires a balance between signaling and transcriptional regulation. Recent developments in pancreatic cell research have revealed that transforming growth factor-beta (TGF-beta) signaling is important for the regulation of each of these phenomena. More importantly, perturbations in this pathway are associated with pancreatic cancer. A chief example of these alterations is the mutation in the TGF-beta-regulated transcription factor Smad4/DPC4 that is found in a large percentage of pancreatic tumors. Surprisingly, studies on transcription factors have remained an underrepresented area of pancreatic research. However, the discovery of Smad4/DPC4 as a transcription factor fueled further studies aimed at characterizing transcription factors involved in normal and neoplastic pancreatic cell growth. Our laboratory recently described the existence of a novel family of zinc finger transcription factors, TGF-beta-inducible early-response gene (TIEG)1 and TIEG2, from the exocrine pancreas that, similarly to Smads, participate in the TGF-beta response and inhibit epithelial cell proliferation. This review therefore focuses on describing the structure and function of these two families of transcription factor proteins that are becoming key players in the regulation of pancreatic cell growth.

Cloning of the Promoter Region of Human Endoglin, the Target Gene for Hereditary Hemorrhagic Telangiectasia Type 1

Endoglin (CD105) is a cell surface component of the transforming growth factor-β (TGF-β) receptor complex highly expressed by endothelial cells. Mutations in the endoglin gene are responsible for the hereditary hemorrhagic telangiectasia type 1 (HHT1), also known as Osler-Weber-Rendu syndrome (OMIM 187300). This is an autosomal dominant vascular disorder probably caused by a haploinsufficiency mechanism displaying low levels of the normal protein. To understand the mechanisms underlying the regulated expression of endoglin, a genomic DNA clone containing 3.3 kb of the 5′-flanking sequence of the human endoglin gene has been isolated. The 5′-flanking region of the endoglin gene lacks consensus TATA and CAAT boxes, but contains two GC-rich regions and consensus motifs for Sp1, ets, GATA, AP-2, NFκB, and Mad, as well as TGF-β–, glucocorticoid-, vitamin D-, and estrogen-responsive elements. As determined by primer extension and 5′ RACE experiments, a cluster of transcriptional start sites was found to be located 350 bp upstream from the translation initiation codon. To analyze the endoglin promoter activity, the upstream −400/+341 fragment was fused to the luciferase gene and transient transfections were conducted in several cell types. This construct displayed a tissue-specific activity in human and bovine endothelial cells. Analysis of various deletion constructs showed the existence of a basal promoter region within the −81/+350 fragment as well as major transcriptional regulatory elements within the −400/−141 fragment. Electrophoretic mobility shift assays demonstrated the specific interaction of a member of the ets family with a consensus motif located at position −68. A promoter construct mutated at this ets sequence showed a much reduced activity as compared with the wild-type construct, supporting the involvement of this ets motif in the basal activity of the promoter. The endoglin promoter exhibited inducibility in the presence of TGF-β1, suggesting possible therapeutic treatments in HHT1 patients, in which the expression level of the normal endoglin allele might not reach the threshold required for its function. Isolation and characterization of the human endoglin promoter represents an initial step in elucidating the controlled expression of the endoglin gene.

Cloning of the Promoter Region of Human Endoglin, the Target Gene for Hereditary Hemorrhagic Telangiectasia Type 1

Endoglin (CD105) is a cell surface component of the transforming growth factor-β (TGF-β) receptor complex highly expressed by endothelial cells. Mutations in the endoglin gene are responsible for the hereditary hemorrhagic telangiectasia type 1 (HHT1), also known as Osler-Weber-Rendu syndrome (OMIM 187300). This is an autosomal dominant vascular disorder probably caused by a haploinsufficiency mechanism displaying low levels of the normal protein. To understand the mechanisms underlying the regulated expression of endoglin, a genomic DNA clone containing 3.3 kb of the 5′-flanking sequence of the human endoglin gene has been isolated. The 5′-flanking region of the endoglin gene lacks consensus TATA and CAAT boxes, but contains two GC-rich regions and consensus motifs for Sp1, ets, GATA, AP-2, NFκB, and Mad, as well as TGF-β–, glucocorticoid-, vitamin D-, and estrogen-responsive elements. As determined by primer extension and 5′ RACE experiments, a cluster of transcriptional start sites was found to be located 350 bp upstream from the translation initiation codon. To analyze the endoglin promoter activity, the upstream −400/+341 fragment was fused to the luciferase gene and transient transfections were conducted in several cell types. This construct displayed a tissue-specific activity in human and bovine endothelial cells. Analysis of various deletion constructs showed the existence of a basal promoter region within the −81/+350 fragment as well as major transcriptional regulatory elements within the −400/−141 fragment. Electrophoretic mobility shift assays demonstrated the specific interaction of a member of the ets family with a consensus motif located at position −68. A promoter construct mutated at this ets sequence showed a much reduced activity as compared with the wild-type construct, supporting the involvement of this ets motif in the basal activity of the promoter. The endoglin promoter exhibited inducibility in the presence of TGF-β1, suggesting possible therapeutic treatments in HHT1 patients, in which the expression level of the normal endoglin allele might not reach the threshold required for its function. Isolation and characterization of the human endoglin promoter represents an initial step in elucidating the controlled expression of the endoglin gene.

Serum responsive gene expression mediated by Sp1

We compared the Sp1 binding activity of Rat2 fibroblasts in nuclear extracts prepared from quiescent cells and cells stimulated with 20% serum. Increased DNA-binding activity was observed in extracts from serum-stimulated cells when an Sp1 oligonucleotide was used as radiolabeled probe in electrophoretic mobility shift assays. This increase in Sp1 DNA-binding activity is not due to changes in the amount of Sp1 in the nucleus as shown by immunoblot analysis. The transcriptional activity of a reporter construct containing six Sp1 sites upstream of a minimal adenovirus promoter or an Sp1-dependent promoter such as ornithine decarboxylase (ODC) containing Sp1 sites was enhanced following serum stimulation in transient transfection assays. Dephosphorylation of the nuclear extracts with potato acid phosphatase abolished the Sp1 DNA-binding activity, demonstrating a possible correlation between phosphorylation of Sp1 and DNA-binding activity. These results implicate a potential role for Sp1 in mediating signal transduction pathways in response to mitogenic signals.

Molecular cloning and characterization of TIEG2 reveals a new subfamily of transforming growth factor-beta-inducible Sp1-like zinc finger-encoding genes involved in the regulation of cell growth

Sp1-like zinc finger transcription factors are involved in the regulation of cell growth and differentiation. Recent evidence demonstrating that mammalian cells express novel, yet uncharacterized, Sp1-like proteins has stimulated a search for new members of this family. We and others have recently reported that the transforming growth factor (TGF)-beta-regulated gene TIEG encodes a new Sp1-like protein that inhibits cell growth in cultured cells. Here we report the identification, nuclear localization, DNA binding activity, transcriptional repression activity, and growth inhibitory effects of TIEG2, a novel TGF-beta-inducible gene related to TIEG. TIEG2 is ubiquitously expressed in human tissues, with an enrichment in pancreas and muscle. TIEG2 shares 91% homology with TIEG1 within the zinc finger region and 44% homology within the N terminus. Biochemical characterization reveals that TIEG2 is a nuclear protein, which, as predicted from the primary structure, specifically binds to an Sp1-like DNA sequence in vitro and can repress a promoter containing Sp1-like binding sites in transfected Chinese hamster ovary epithelial cells. Furthermore, functional studies using [3H]thymidine uptake and MTS (3-(4, 3-dimethyltiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-su lfophenyl)-2 H-tetrazolium) assays demonstrate that the overexpression of TIEG2 in Chinese hamster ovary cells inhibits cell proliferation. Thus, TIEG2, together with TIEG1, defines a new subfamily of TGF-beta-inducible Sp1-like proteins involved in the regulation of cell growth.