Induced Smad2 Phosphorylation Research Articles

PAR1 Scaffolds TGFβRII to Downregulate TGF-β Signaling and Activate ESC Differentiation to Endothelial Cells.

SummaryWe studied the function of the G-protein-coupled receptor PAR1 in mediating the differentiation of mouse embryonic stem cells (mESCs) to endothelial cells (ECs) that are capable of inducing neovascularization. We observed that either deletion or activation of PAR1 suppressed mouse embryonic stem cell (mESC) differentiation to ECs and neovascularization in mice. This was mediated by induction of TGFβRII/TGFβRI interaction, forming an active complex, which in turn induced SMAD2 phosphorylation. Inhibition of TGF-β signaling in PAR1-deficient mESCs restored the EC differentiation potential of mESCs. Thus, PAR1 in its inactive unligated state functions as a scaffold for TGFβRII to downregulate TGF-β signaling, and thereby promote ESC transition to functional ECs. The PAR1 scaffold function in ESCs is an essential mechanism for dampening TGF-β signaling and regulating ESC differentiation.

MYOSLID Is a Novel Serum Response Factor-Dependent Long Noncoding RNA That Amplifies the Vascular Smooth Muscle Differentiation Program.

Long noncoding RNAs (lncRNA) represent a growing class of noncoding genes with diverse cellular functions. We previously reported on SENCR, an lncRNA that seems to support the vascular smooth muscle cell (VSMC) contractile phenotype. However, information about the VSMC-specific lncRNAs regulated by myocardin (MYOCD)/serum response factor, the master switch for VSMC differentiation, is unknown. To define novel lncRNAs with functions related to VSMC differentiation, we performed RNA sequencing in human coronary artery SMCs that overexpress MYOCD. Several novel lncRNAs showed altered expression with MYOCD overexpression and one, named MYOcardin-induced Smooth muscle LncRNA, Inducer of Differentiation (MYOSLID), was activated by MYOCD and selectively expressed in VSMCs. MYOSLID was a direct transcriptional target of both MYOCD/serum response factor and transforming growth factor-β/SMAD pathways. Functional studies revealed that MYOSLID promotes VSMC differentiation and inhibits VSMC proliferation. MYOSLID showed reduced expression in failed human arteriovenous fistula samples compared with healthy veins. Although MYOSLID did not affect gene expression of transcription factors, such as serum response factor and MYOCD, its depletion in VSMCs disrupted actin stress fiber formation and blocked nuclear translocation of MYOCD-related transcription factor A (MKL1). Finally, loss of MYOSLID abrogated transforming growth factor-β1-induced SMAD2 phosphorylation. We have demonstrated that MYOSLID, the first human VSMC-selective and serum response factor/CArG-dependent lncRNA, is a novel modulator in amplifying the VSMC differentiation program, likely through feed-forward actions of both MKL1 and transforming growth factor-β/SMAD pathways.

English

Transforming growth factor-betas (TGF-βs) are elevated during menstruation and are involved in endometriosis. Similarly, matrix metalloproteinases like MMP-2 are also highly expressed in patients with endometriosis. Expression of gelatinases, MMP-2 and MMP-9, is increased by TGF-βs. TGF-βs bind and activate receptor-mediated Smad proteins to mediate gene expression, however, also non-Smad signaling pathways participate in signal transduction of the TGF-βs. In this study, we found that of MMP-2 and MMP-9 is higher in stromal cells especially in endometriotic cells compared to epithelial cells. Treatment of endometrial and endometriotic stromal and epithelial cells with TGF-β1 or TGF-β2 decreased cell numbers, induced Smad3 phosphorylation, and enhanced MMP-2 and MMP-9 secretion in all cell lines studied. Whereas a TGF-β receptor inhibitor (TβRI) inhibitor completely blocked the TGF-β-induced reduction in cell numbers, Smad3 phosphorylation, and MMP2 and MMP-9 secretion, a Smad3 inhibitor completely blocked Smad3 phosphorylation but only partly blocked the other TGFβ-induced responses. In summary, our results demonstrate that endometriotic cells showed reduced responsiveness upon TGFβ treatment compared to endometrial cells and thus we suggest that endometriotic cells are more resistant to TGF-β signals which resemble characteristics of tumour cells. Also, we suppose that TGF-β-induced increase in MMP-2 and MMP-9 might contribute to endometriosis by increasing tissue breakdown during menstruation and increased invasiveness of the endometrial tissues during implantation at ectopic sites.

Role of transforming growth factor-β1 in epithelial-mesenchymal transition of mesothelial cells and its effect on peritoneal metastasis of gastric cancer

To elucidate the role of transforming growth factor-beta1(TGF-β1) in epithelial-mesenchymal transition of mesothelial cells and peritoneal metastasis of gastric cancer. HMrSV5 cells, a human peritoneal mesothelial cell line, were incubated with TGF-β1, and their morphological changes were observed by phase contrast microscopy. Expressions of α-smooth muscle actin (α-SMA), vimentin, cytokeratin, E-cadherin, phosphorylated-Smad2 and Smad2 were examined by Western blotting. After fibroblastic-like mesothelial cells were co-incubate with HSC-39 cells(gastric cancer cell line), the adhesion and invasion potential of HSC-39 were evaluated by adhesion and invasion assay in vitro. Few mesothelial cells converted to spindle fibroblast-like morphology for 24 h, and remarkable phenotypic changes were observed at 72 h of TGF-β1 activation. TGF-β1 could induce α-SMA and vimentin expression, and down-regulate cytokeratin and E-cadherin expression in mesothelial cells (P<0.05). TGF-β1 induced phosphorylation of Smad2 within 15 min of stimulation, reached a maximum at 30 min after treatment and remained high level during the experiment without affecting total Smad2 expression(P>0.05). The percentage of HSC-39 gastric cancer cells adhered were significantly increased as compared to the control. When the mesothelial cells were treated by TGF-β1 for 72 h, the increased adhesion percentage was(146±17)%(P<0.05). After fibroblastic-like mesothelial cells co-incubated with HSC-39 cells for 48 h, more cancer cells [(61.1±11.4) cells/view field] invaded the coated membrane as compared to the control group [(31.9±8.1) cells/view field] (P<0.05). TGF-β1 can induce the transition of mesothelial cells into myofibroblasts and Smad2 signal pathway may play a role in this transition, which is associated with increased adhesion and invasiveness of gastric cancer cells, and provides favorable environment for the dissemination of gastric cancer.

Activin A balance regulates epithelial invasiveness and tumorigenesis

Activin A (Act A) is a member of the TGFβ superfamily. Act A and TGFβ have multiple common downstream targets and have been described to merge in their intracellular signaling cascades and function. We have previously demonstrated that coordinated loss of E-cadherin and TGFβ receptor II (TβRII) results in epithelial cell invasion. When grown in three-dimensional organotypic reconstruct cultures, esophageal keratinocytes expressing dominant-negative mutants of E-cadherin and TβRII showed activated Smad2 in the absence of functional TβRII. However, we could show that increased levels of Act A secretion was able to induce Smad2 phosphorylation. Growth factor secretion can activate autocrine and paracrine signaling, which affects crosstalk between the epithelial compartment and the surrounding microenvironment. We show that treatment with the Act A antagonist Follistatin or with a neutralizing Act A antibody can increase cell invasion in organotypic cultures in a fibroblast- and MMP-dependent manner. Similarly, suppression of Act A with shRNA increases cell invasion and tumorigenesis in vivo. Therefore, we conclude that maintaining a delicate balance of Act A expression is critical for homeostasis in the esophageal microenvironment.

Laminin α1 Regulates Age-Related Mesangial Cell Proliferation and Mesangial Matrix Accumulation through the TGF-β Pathway

Laminin α1 (LAMA1), a subunit of the laminin-111 basement membrane component, has been implicated in various biological functions in vivo and in vitro. Although LAMA1 is present in kidney, its roles in the kidney are unknown because of early embryonic lethality. Herein, we used a viable conditional knockout mouse model with a deletion of Lama1 in the epiblast lineage (Lama1(CKO)) to study the role of LAMA1 in kidney development and function. Adult Lama1(CKO) mice developed focal glomerulosclerosis and proteinuria with age. In addition, mesangial cell proliferation was increased, and the mesangial matrix, which normally contains laminin-111, was greatly expanded. In vitro, mesangial cells from Lama1(CKO) mice exhibited significantly increased proliferation compared with those from controls. This increased proliferation was inhibited by the addition of exogenous LAMA1-containing laminin-111, but not by laminin-211 or laminin-511, suggesting a specific role for LAMA1 in regulating mesangial cell behavior. Moreover, the absence of LAMA1 increased transforming growth factor (TGF)-β1-induced Smad2 phosphorylation, and inhibitors of TGF-β1 receptor I kinase blocked Smad2 phosphorylation in both control and Lama1(CKO) mesangial cells, indicating that the increased Smad2 phosphorylation occurred in the absence of LAMA1 via the TGF-β1 receptor. These findings suggest that LAMA1 plays a critical role in kidney function and kidney aging by regulating the mesangial cell population and mesangial matrix deposition through TGF-β/Smad signaling.

The Selective A3AR Antagonist LJ-1888 Ameliorates UUO-Induced Tubulointerstitial Fibrosis

Adenosine in the normal kidney significantly elevates in response to cellular damage. The renal A3 adenosine receptor (A3AR) is up-regulated under stress, but the therapeutic effects of A3AR antagonists on chronic kidney disease are not fully understood. The present study examined the effect of LJ-1888 [(2R,3R,4S)-2-[2-chloro-6-(3-iodobenzylamino)-9H-purine-9-yl]-tetrahydrothiophene-3,4-diol], a newly developed potent, selective, species-independent, and orally active A3AR antagonist, on unilateral ureteral obstruction (UUO)-induced renal fibrosis. Pretreatment with LJ-1888 inhibited UUO-induced fibronectin and collagen I up-regulation in a dose-dependent manner. Masson's trichrome staining confirmed that LJ-1888 treatment effectively reduced UUO-induced interstitial collagen accumulation. Furthermore, delayed administration of LJ-1888 showed an equivalent therapeutic effect on tubulointerstitial fibrosis to that of losartan. Small-interfering A3AR transfection effectively inhibited transforming growth factor-β1 (TGF-β1)-induced fibronectin and collagen I up-regulation in proximal tubular cells similar to LJ-1888, confirming that the renoprotective effect of LJ-1888 resulted from A3AR blockade. UUO- or TGF-β1-induced c-Jun N-terminal kinase and extracellular signal-regulated kinase phosphorylation decreased significantly after LJ-1888 administration. A3AR blockade reduced UUO- or TGF-β1-induced up-regulation of lysyl oxidase, which induces cross-linking of extracellular matrix, suggesting that LJ-1888 may also regulate extracellular matrix accumulation via post-translational regulation. In conclusion, the present data demonstrate that the A3AR antagonist, LJ-1888, blocked the development and attenuated the progression of renal fibrosis, and they suggest that LJ-1888 may become a new therapeutic modality for renal interstitial fibrosis.

Smad3 mediates cigarette smoke extract (CSE) induction of VEGF release by human fetal lung fibroblasts

Cigarette smoke is the major cause of chronic obstructive pulmonary disease (COPD), yet pathogenic mechanisms are not fully understood. Vascular endothelial growth factor (VEGF) is one of the major regulators of endothelial cell survival and is believed to play a role in the pathogenesis of COPD. Fibroblasts are a significant source of VEGF in the lungs; however the effect of cigarette smoke exposure on VEGF release by fibroblasts is not fully understood. We hypothesized that cigarette smoke-induced disturbed VEGF release by human lung fibroblasts is a potential pathogenic mechanism that could contribute to COPD. Cigarette smoke extract (CSE) was prepared by modification of the methods of Carp and Janoff (American Review of Respiratory Disease, 1978). Human fetal lung fibroblasts (HFL-1) were exposed to different concentrations of CSE and for different durations. VEGF release into the media was measured using ELISA. TGF-β1 receptor (TβR1)/Smad3 as a potential pathway for CSE modulated VEGF release was also investigated using biochemical analyses and siRNA inhibition of Smad3 and siRNA and pharmacologic inhibition of TβR1. CSE induced VEGF release by HFL-1 in concentration and time dependent manner. This was confirmed in two additional types of primary human fetal lung fibroblasts. CSE induced Smad3 phosphorylation and nuclear translocation in HFL-1 cells. Silencing of Smad3 by siRNA not only eliminated the stimulatory effect of CSE on VEGF release but also inhibited baseline VEGF production. Suppression of TβR1 by the pharmacological inhibitor (SB431542) markedly reduced VEGF release by HFL-1 in response to CSE and this effect was confirmed by TβR1 siRNA. In contrast, nicotine inhibited VEGF release by HFL-1 in a dose and time dependent manner. Our findings indicate that CSE stimulates Smad3-mediated VEGF release by lung fibroblasts. Nicotine does not account for the CSE stimulation of VEGF in HFL-1. The ability of lung fibroblasts to produce VEGF may play a role in pathogenesis of cigarette smoke induced lung disease.

SDF-1α reduces fibronectin expression in rat mesangial cells induced by TGF-β1 and high glucose through PI3K/Akt pathway

Stromal cell-derived factor-1 (SDF-1) is a chemokine and plays an important role in cell migration, whereas its role in diabetic nephropathy has not been illustrated distinctly. We hypothesized that SDF-1α may have an effect on extracellular matrix (ECM) accumulations in mesangial cells exposed to transforming growth factor-β1 (TGF-β1) or high glucose in vitro. The exogenous SDF-1α was added into rat mesangial cells incubated with TGF-β1 or high glucose in the medium. The expression of fibronectin (FN) was quantitated by real-time RT-PCR, and the change of Akt and Smad3 measured by western blotting. SDF-1α, its receptor C-X-C chemokine receptor type 4 (CXCR4) and FN mRNA were expressed in rat mesangial cells. Both TGF-β1 and high glucose raised the mRNA expressions of CXCR4 and FN in the cells. SDF-1α inhibited the elevated FN mRNA expression induced by TGF-β1 and high glucose through CXCR4 and PI3K/Akt signaling pathway, as the effect of SDF-1α was reversed by CXCR4 antagonist AMD3100 and PI3K inhibitor LY294002. Correspondingly, TGF-β1 induced Smad3 phosphorylation was suppressed when PI3K/Akt signaling pathway was activated by SDF-1α. Based on these findings, we conclude that SDF-1α ameliorates TGF-β1/high glucose induced ECM accumulations in mesangial cells, which may mediate through PI3K/Akt pathway. This novel mechanism may bring a new insight to our understandings of diabetic nephropathy.

Indoxyl Sulfate Enhances p53-TGF-β1-Smad3 Pathway in Proximal Tubular Cells

Background/Aim: Indoxyl sulfate-induced activation of nuclear factor (NF)-ĸB promotes transforming growth factor (TGF)-β₁ in human proximal tubular cells (HK-2 cells). The present study aimed to elucidate the cross talk among indoxyl sulfate, p53 and TGF-β₁-Smad3 signaling in proximal tubular cells. Methods: The effects of indoxyl sulfate on the expression of TGF-β₁, Smad3, and α-smooth muscle actin (α-SMA) were determined using HK-2 cells. As for in vivo experiments the following animals were used: Dahl salt-resistant normotensive rats (DN) and indoxyl sulfate-administered Dahl salt-resistant normotensive rats (DN+IS). Results: Both indoxyl sulfate and nutlin-3, a specific p53 inducer, stimulated TGF-β₁ expression, which was suppressed by pifithrin-α, p-nitro, a p53 inhibitor. Further, indoxyl sulfate stimulated TGF-β₁-induced expression of α-SMA by enhancing Smad3 expression and TGF-β₁-induced Smad3 phosphorylation. Indoxyl sulfate induced phosphorylation of extracellular signal-regulated kinase (ERK). U0126, an inhibitor of ERK pathway, prevented indoxyl sulfate-induced upregulation of Smad3 expression. Immunohistochemistry demonstrated that TGF-β₁ and Smad3 were localized in renal tubular cells, and that indoxyl sulfate increased the TGF-β₁ and Smad3-positive area in the kidney. Conclusion: Indoxyl sulfate stimulates p53-induced TGF-β₁ expression and TGF-β₁-induced α-SMA expression in proximal tubular cells. Indoxyl sulfate-induced Smad3 accelerates TGF-β₁-induced α-SMA expression through ERK activation. Thus, indoxyl sulfate enhances p53-TGF-β₁-Smad3 pathway in proximal tubular cells.

Suppression of activin A signals inhibits growth of malignant pleural mesothelioma cells

Background:Activins control the growth of several tumour types including thoracic malignancies. In the present study, we investigated their expression and function in malignant pleural mesothelioma (MPM).Methods:The expression of activins and activin receptors was analysed by quantitative PCR in a panel of MPM cell lines. Activin A expression was further analysed by immunohistochemistry in MPM tissue specimens (N=53). Subsequently, MPM cells were treated with activin A, activin receptor inhibitors or activin-targeting siRNA and the impact on cell viability, proliferation, migration and signalling was assessed.Results:Concomitant expression of activin subunits and receptors was found in all cell lines, and activin A was overexpressed in most cell lines compared with non-malignant mesothelial cells. Similarly, immunohistochemistry demonstrated intense staining of tumour cells for activin A in a subset of patients. Treatment with activin A induced SMAD2 phosphorylation and stimulated clonogenic growth of mesothelioma cells. In contrast, treatment with kinase inhibitors of activin receptors (SB-431542, A-8301) inhibited MPM cell viability, clonogenicity and migration. Silencing of activin A expression by siRNA oligonucleotides further confirmed these results and led to reduced cyclin D1/3 expression.Conclusion:Our study suggests that activin A contributes to the malignant phenotype of MPM cells via regulation of cyclin D and may represent a valuable candidate for therapeutic interference.

Abstract 4433: RB mediates TGF-β effects on growth inhibition and invasion in pancreatic cancer cells

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy that arises from precursor lesions, termed pancreatic intraepithelial neoplasia (PanIN). PDAC's aggressiveness derives from its advanced stage when patients present clinically, the high frequency of driver mutations (KRAS, INK4A, TP53 and SMAD4) and the heterogeneous distribution of low frequency driver mutations. To study the potential role of RB in PDAC pathobiology, we generated a novel mouse model with pancreatic RB deletion and oncogenic Kras expression (Rb/K mice). These mice rapidly developed highly proliferative PanIN that progress to PDAC with high frequency, underscoring RB's tumor suppressive role in the pancreas. RB deletion alone, however, did not alter pancreatic histology. Previously, we have demonstrated that Smad7-induced loss of TGF-β-mediated growth inhibition is due to functional inactivation of RB. To further examine RB's role in TGF-β action, we established pancreatic cancer cell lines from the Rb/K model. These cells were resistant to TGF-β1-mediated growth inhibition, whereas growth of murine cell lines that retained RB was markedly inhibited. RB loss also abolished TGF-β-induced cell invasion, but did not alter Smad-dependent TGF-β1 signaling since TGF-β1 induced Smad2 phosphorylation, Smad3/4 nuclear translocation, and transactivation of TGF-β1-dependent reporters. By contrast, RB loss did not affect TGF-β1-induced epithelial-to-mesenchymal transition. Array analysis revealed marked alterations in the gene expression profile of Rb/K cells. These data suggest that RB loss contributes to the dysregulation of TGF-β actions in PDAC and suggest that delineation of these perturbations may yield novel therapeutic approaches in this malignancy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4433. doi:1538-7445.AM2012-4433

PO-82 Hypoxia induces Smad2 phosphorylation signaling and increases stem cell-like properties and multi-drug resistance in K562 leukemic cells

PO-82 Hypoxia induces Smad2 phosphorylation signaling and increases stem cell-like properties and multi-drug resistance in K562 leukemic cells

Palm oil tocotrienol rich fraction reduces extracellular matrix production by inhibiting transforming growth factor-β1 in human intestinal fibroblasts

Extracellular matrix deposition is key event for the development of bowel stenosis in Crohn's disease patients. Transforming growth factor-β plays a key role in this process. We aimed at characterizing the effects of tocotrienol rich fraction on ECM proteins production and molecules that regulate the synthesis and degradation of extracellular matrix, matrix metalloproteinase-3 and tissue inhibitor of metalloproteinases-1, in human intestinal fibroblasts, and at elucidating whether the effects of tocotrienol rich fraction (TRF) are mediated through inhibition of TGF-β1. HIF were isolated from colonic or ileal tissue from Crohn's disease patients and control subjects, and were treated with TRF from palm oil either alone or in combination with TGF-β1. Procollagen 1, procollagen 3, TIMP-1 and MMP-3 production, and Smad3 phosphorylation were analyzed by Western-blotting. TRF significantly diminished procollagen 1 and 3 synthesis in HIF. Treatment of HIF with TRF increased MMP-3 production but did not modify TIMP-1. TGF-β1 induced Smad3 phosphorylation and enhanced procollagen 1 and 3 and TIMP-1 production. Pre-treatment of HIF with TRF prevented Smad3 phosphorylation and minimized the increase in collagen 1 and 3 production caused by TGF-β1. TRF has anti-fibrogenic effects on HIF, decreasing ECM production and increasing its degradation. This effect is mediated, at least in part, by inhibition of TGF-β1.

Activin A stimulates mouse macrophages to express APRIL via the Smad3 and ERK/CREB pathways

A proliferation-inducing ligand (APRIL) is primarily expressed by macrophages and dendritic cells, and stimulates B cell proliferation, differentiation, survival, and Ig production. In the present study, we investigated the role and signaling mechanisms of activin A in APRIL expression by mouse macrophages. Activin A markedly enhanced APRIL expression in mouse macrophages at both the transcriptional and protein levels. Overexpression of dominant-negative (DN)-Smad3 and SB431542 abrogated activin-induced APRIL transcription. Furthermore, activin A induced Smad3 phosphorylation. These results indicate that activin A enhances APRIL expression through both activin receptor-like kinase 4 (ALK4) and Smad3. In a subsequent analysis of activin A signaling, it was found that PD98059, an extracellular signal-related kinase (ERK) inhibitor, eliminated activin A-induced APRIL expression. On the other hand, overexpression of cAMP responsive element-binding protein (CREB), a molecule downstream of ERK, augmented activin A-induced APRIL expression, and this effect could be abolished by PD98059. This finding that activin A induces ERK and CREB phosphorylation suggests that ERK and CREB act as intermediates in APRIL expression. Taken together, these results demonstrate that activin A can enhance APRIL expression through two different pathways, Smad3 and ERK/CREB.

Matrix metalloprotease-9 induces transforming growth factor-β 1 production in airway epithelium via activation of epidermal growth factor receptors

Aims Matrix metalloprotease (MMP)-9 is present in abundance in various chronic airway disorders and is involved in lung remodeling. MMP may cleave membrane-bound precursor proteins and release epidermal growth factor-like ligands that subsequently bind to epidermal growth factor receptor (EGFR). We hypothesized that MMP-9 may stimulate the airway epithelium to produce fibrogenic mediators through activation of membrane-bound receptors. Main methods Human airway epithelial cells were grown on air–liquid interface culture inserts. MMP-9 was employed to stimulate the cells. Conditioned medium following MMP-9 stimulation was co-incubated with human lung fibroblasts. Key findings MMP-9 stimulated human airway epithelial cells to produce transforming growth factor (TGF)-β 1 at both the mRNA and protein level. Using a microarray, increased phosphorylation of EGFR tyrosine kinase (TK) was identified and further confirmed by immunoprecipitation and Western blot analysis. A significant increase in EGF and TGF-α release was observed after MMP-9 had been added for 30 min. Protease inhibitor, EGFR monoclonal antibody and EGFR-TK inhibitor blocked this action and subsequent TGF-β 1 production. Neutralizing antibodies against EGF and TGF-α substantially inhibited TGF-β 1 production following MMP-9 stimulation. MMP-9-induced TGF-β 1 production occurred through MAP kinase p44/42 phosphorylation. Selective p44/42 kinase inhibitor UO126 successfully inhibited TGF-β 1 production. Conditioned medium from epithelial cells treated with MMP-9 significantly induced Smad3 phosphorylation and subsequent fibroblast proliferation after 24 h culture. Significance These data indicate that MMP-9 induces TGF-β 1 production in the airway epithelium through the cleavage of EGF and EGF-like ligands and activating EGFR, suggesting potential targets of therapeutic intervention in airway fibrotic disorders.

TGF-β–Exposed Plasmacytoid Dendritic Cells Participate in Th17 Commitment

TGF-β is required for both Foxp3(+) regulatory T cell (Treg) and Th17 commitment. Plasmacytoid DCs (pDC) have been shown to participate to both Treg and Th17 commitment as well. However, few studies have evaluated the direct effect of TGF-β on pDC, and to our knowledge, no study has assessed the capacity of TGF-β-exposed pDC to polarize naive CD4(+) T cells. In this paper, we show that TGF-β-treated pDC favor Th17 but not Treg commitment. This process involves a TGF-β/Smad signal, because TGF-β treatment induced Smad2 phosphorylation in pDC and blockade of TGF-β signaling with the SD208 TGF-βRI kinase inhibitor abrogated Th17 commitment induced by TGF-β-treated pDC. Moreover, TGF-β mRNA synthesis and active TGF-β release were induced in TGF-β-treated pDC and anti-TGF-β Ab blocked Th17 commitment. Unexpectedly, TGF-β treatment also induced increased IL-6 production by pDC, which serves as the other arm for Th17 commitment driven by TGF-β-exposed pDC, because elimination of IL-6-mediated signal with either IL-6- or IL-6Rα-specific Abs prevented Th17 commitment. The in vivo pathogenic role of TGF-β-treated pDC was further confirmed in the Th17-dependent collagen-induced arthritis model in which TGF-β-treated pDC injection significantly increased arthritis severity and pathogenic Th17 cell accumulation in the draining lymph nodes. Thus, our data reveal a previously unrecognized effect of TGF-β-rich environment on pDC ability to trigger Th17 commitment. Such findings have implications in the pathogenesis of autoimmune diseases or immune responses against mucosal extracellular pathogens.

Abstract 1967: Ligand-dependent TGFβ signalling potential

Abstract Transforming growth factor beta (TGFβ) is a cytokine which regulates many normal biological processes such as organogenesis and cell cycle control. Its signaling pathway is under intense study as it is commonly dysregulated in pathophysiological conditions such as cancer and fibrosis. The TGFβ signalling cascade is initiated by the binding of ligand to cell-surface serine-threonine kinase receptors. Binding of ligand to the TGFβ receptors initiates phosphorylation of intracellular signalling proteins called Smads, which can then enter the nucleus and initiate specific transcriptional programs. There are three TGFβ ligands which can activate canonical Smad signalling: TGFβ1, TGFβ2 and TGFβ3. These ligands share significant sequence homology (70-80%) but have different spatial and temporal patterns of expression in development. Although TGFβ1 and TGFβ3 are highly expressed in the tumour microenvironment, the role of TGFβ3 has been largely over-looked and thought to be the same as TGFβ1. The objective of the present study is to evaluate the signalling capacity of TGFβ1 and TGFβ3 in non-small cell lung cancer cells. Using dose response studies, we show that TGFβ1 ligand induces Smad2 phosphorylation to a greater extent than TGFβ3. We also show that TGFβ3 induces a lower reduction in steady-state levels of E-cadherin, a protein involved in cell-cell adhesion, compared to TGFβ1. To evaluate the transcriptional programs of both ligands, we used microarray technology to assess gene transcription in non-small cell lung cancer cells treated with TGFβ1 or TGFβ3. Consistent with our signalling data, we found that TGFβ3 induces far fewer genes than TGFβ1. Future studies will evaluate the differential roles of TGFβ1 and TGFβ3 in cancer cell migration and epithelial-to-mesenchymal transition. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1967. doi:10.1158/1538-7445.AM2011-1967

TGF-β1 Promotes Migration and Invasion of Salivary Adenoid Cystic Carcinoma

Salivary adenoid cystic carcinoma (SACC) is one of the most common subtypes of salivary gland carcinomas and frequently metastasizes to distant organs. However, little is known about the molecular mechanisms that promote SACC metastasis. In this study, we report that transforming growth factor (TGF)-β1 was highly expressed in the highly metastatic SACC-LM cell line as compared with its parental low-metastatic SACC-83 cell line. Exogenous addition of TGF-β1 induced Smad2 phosphorylation and promoted the migration and invasion of SACC-83 cells. Consistently, the inhibition of endogenous TGF-β1 signaling in SACC-LM cells by an inhibitor specific to the type I TGF-β1 receptor (TβRI) suppressed cell migration and invasion. Moreover, we found that TGF-β1 expression was significantly increased in human primary SACC samples with metastasis. Taken together, our results suggest that TGF-β1 may play a crucial role in SACC metastasis.

TGFβ1 induces IL‐6 and inhibits IL‐8 release in human bronchial epithelial cells: The role of Smad2/3

Human bronchial epithelial (HBE) cells contribute to asthmatic airway inflammation by secreting cytokines, chemokines, and growth factors, including interleukin (IL)-6, IL-8 and transforming growth factor (TGF) β1, all of which are elevated in asthmatic airways. This study examines the signaling pathways leading to TGFβ1 induced IL-6 and IL-8 in primary HBE cells from asthmatic and non-asthmatic volunteers. HBE cells were stimulated with TGFβ1 in the presence or absence of signaling inhibitors. IL-6 and IL-8 protein and mRNA were measured by ELISA and real-time PCR respectively, and cell signaling kinases by Western blot. TGFβ1 increased IL-6, but inhibited IL-8 production in both asthmatic and non-asthmatic cells; however, TGF induced significantly more IL-6 in asthmatic cells. Inhibition of JNK MAP kinase partially reduced TGFβ1 induced IL-6 in both cell groups. TGFβ1 induced Smad2 phosphorylation, and blockade of Smad2/3 prevented both the TGFβ1 modulated IL-6 increase and the decrease in IL-8 production in asthmatic and non-asthmatic cells. Inhibition of Smad2/3 also increased basal IL-8 release in asthmatic cells but not in non-asthmatic cells. Using CHIP assays we demonstrated that activated Smad2 bound to the IL-6, but not the IL-8 promoter region. We conclude that the Smad2/3 pathway is the predominant TGFβ1 signaling pathway in HBE cells, and this is altered in asthmatic bronchial epithelial cells. Understanding the mechanism of aberrant pro-inflammatory cytokine production in asthmatic airways will allow the development of alternative ways to control airway inflammation.