TGF-beta autocrine loop regulates cell growth and myogenic differentiation in human rhabdomyosarcoma cells

Trastuzumab Decreases the Expression of G1/S Regulators and Syndecan-4 Proteoglycan in Human Rhabdomyosarcoma

Rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children, arises from skeletal muscle cells that fail to differentiate terminally. Two subgroups of RMS, fusion-positive and fusion-negative RMS (FPRMS and FNRMS, respectively), are characterized by the presence or absence of the PAX3/7-FOXO1 fusion gene. RMSs frequently exhibit increased expression of human epidermal growth factor receptor-2 (HER2). Trastuzumab is a humanized monoclonal antibody targeting HER2, and its potential role in RMS treatment remains to be elucidated. Syndecan-4 (SDC4) is a heparan sulfate proteoglycan (HSPG) affecting myogenesis via Rac1-mediated actin remodeling. Previously, we demonstrated that the SDC4 gene is amplified in 28% of human FNRMS samples, associated with high mRNA expression, suggesting a tumor driver role. In this study, after analyzing the copy numbers and mRNA expressions of other HSPGs in human RMS samples, we found that in addition to SDC4, syndecan-1, syndecan-2, and glypican-1 were also amplified and highly expressed in FNRMS. In RD (human FNRMS) cells, elevated SDC4 expression was accompanied by low levels of phospho-Ser179 of SDC4, leading to high Rac1-GTP activity. Notably, this high SDC4 expression in RD cells decreased following trastuzumab treatment. Trastuzumab decreased the levels of G1/S checkpoint regulators cyclin E and cyclin D1 and reduced the cell number; however, it also downregulated the cyclin-dependent kinase inhibitor p21. The level of MyoD, a transcription factor essential for RMS cell survival, also decreased following trastuzumab administration. Our findings contribute to the understanding of the role of SDC4 in FNRMS. Since HER2 is expressed in about half of RMSs, the trastuzumab-mediated changes observed here may have therapeutic implications.

Smad7 Controls Immunoregulatory PDL2/1-PD1 Signaling in Intestinal Inflammation and Autoimmunity

Smad7, a negative regulator of TGF-β signaling, has been implicated in the pathogenesis and treatment of inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC). Here, we found that Smad7 mediates intestinal inflammation by limiting the PDL2/1-PD1 axis in dendritic cells (DCs) and CD4+T cells. Smad7 deficiency in DCs promotes TGF-β responsiveness and the co-inhibitory molecules PDL2/1 on DCs, and it further imprints T cell-PD1 signaling to promote Treg differentiation. DC-specific Smad7 deletion mitigates DSS-induced colitis by inducing CD103+PDL2/1+DCs and Tregs. In addition, Smad7 deficiency in CD4+T cells promotes PD1 and PD1-induced Tregs in vitro. The transfer of Smad7-deficient CD4+T cells enhances Tregs in vivo and protects against T cell-mediated colitis. Furthermore, Smad7 antisense ameliorates DSS-induced UC, increasing TGF-β and PDL2/1-PD1 signaling. Enhancing PD1 signaling directly via Fc-fused PDL2/1 is also beneficial. Our results identify how Smad7 mediates intestinal inflammation and leverages these pathways therapeutically, providing additional strategies for IBD intervention.

Inhibitory Antibodies against Activin A and TGF-β Reduce Self-Supported, but Not Soluble Factors-Induced Growth of Human Pulmonary Arterial Vascular Smooth Muscle Cells in Pulmonary Arterial Hypertension

Increased growth and proliferation of distal pulmonary artery vascular smooth muscle cells (PAVSMC) is an important pathological component of pulmonary arterial hypertension (PAH). Transforming Growth Factor-β (TGF-β) superfamily plays a critical role in PAH, but relative impacts of self-secreted Activin A, Gremlin1, and TGF-β on PAH PAVSMC growth and proliferation are not studied. Here we report that hyper-proliferative human PAH PAVSMC have elevated secretion of TGF-β1 and, to a lesser extent, Activin A, but not Gremlin 1, and significantly reduced Ser^465/467-Smad2 and Ser^423/425-Smad3 phosphorylation compared to controls. Media, conditioned by PAH PAVSMC, markedly increased Ser^465/467-Smad2, Ser^423/425-Smad3, and Ser^463/465-Smad1/5 phosphorylation, up-regulated Akt, ERK1/2, and p38 MAPK, and induced significant proliferation of non-diseased PAVSMC. Inhibitory anti-Activin A antibody reduced PAH PAVSMC growth without affecting canonical (Smads) or non-canonical (Akt, ERK1/2, p38 MAPK) effectors. Inhibitory anti-TGF-β antibody significantly reduced P-Smad3, P-ERK1/2 and proliferation of PAH PAVSMC, while anti-Gremlin 1 had no anti-proliferative effect. PDGF-BB diminished inhibitory effects of anti-Activin A and anti-TGF-β antibodies. None of the antibodies affected growth and proliferation of non-diseased PAVSMC induced by PAH PAVSMC-secreted factors. Together, these data demonstrate that human PAH PAVSMC have secretory, proliferative phenotype that could be targeted by anti-Activin A and anti-TGF-β antibodies; potential cross-talk with PDGF-BB should be considered while developing therapeutic interventions.

Sphingosine-1-phosphate induced epithelial-mesenchymal transition of hepatocellular carcinoma via an MMP-7/ syndecan-1/TGF-β autocrine loop

Sphingosine-1-phosphate (S1P) induces epithelial–mesenchymal transition (EMT) in hepatocellular carcinoma (HCC). However, its underlying mechanism remains largely unknown. In the present study, we investigated the correlation between S1P and syndecan-1 in HCC, the molecular mechanism involved, as well as their roles in EMT of HCC. Results revealed a high serum S1P level presents in patients with HCC, which positively correlated with the serum syndecan-1 level. A significant inverse correlation existed between S1P₁ and syndecan-1 in HCC tissues. S1P elicits activation of the PI3K/AKT signaling pathways via S1P₁, which triggers HPSE, leading to increases in expression and activity of MMP-7 and leading to shedding and suppression of syndecan-1. The loss of syndecan-1 causes an increase in TGF-β1 production. The limited chronic increase in TGF-β1 can convert HCC cells into a mesenchymal phenotype via establishing an MMP-7/Syndecan-1/TGF-β autocrine loop. Finally, TGF-β1 and syndecan-1 are essential for S1P-induced epithelial to mesenchymal transition. Taken together, our study demonstrates that S1P induces advanced tumor phenotypes of HCC via establishing an MMP-7/syndecan-1/TGF-β1 autocrine loop, and implicates targetable S1P₁-PI3K/AKT-HPSE-MMP-7 signaling axe in HCC metastasis.

Sphingosine 1-phosphate regulates proliferation, cell cycle and apoptosis of hepatocellular carcinoma cells via syndecan-1

Sphingosine 1-phosphate (S1P) plays an important role in hepatocarcinogenesis. We previously demonstrated that S1P induced epithelial-mesenchymal transition of hepatocellular carcinoma (HCC) cells via an MMP-7/Syndecan-1/TGF-β autocrine loop. In the present study, we investigated the regulative role of S1P in cell survival and progression of HCC cells, and tested whether syndecan-1 is required in the S1P action. After transfected with syndecan-1 shRNA, HepG2 and SMMC7721 cells were treated with S1P for 72 h, and then cell proliferation was detected by CCK8 assay, and cell cycle progression and cell apoptosis were detected by flow cytometry. The levels of apoptosis markers including cleaved-Caspase-3 and cleaved-PARP in SMMC7721 cells were examined by western blotting. Results showed that S1P significantly enhanced cell proliferation in HCC cells, which was significantly inhibited by syndecan-1 shRNA. S1P induced the cell proportion in S phase in HCC cells, whereas S1P decreased the proportion of cells in both early and late apoptosis. Syndecan-1 shRNA induced the G2/M arrest in the presence of S1P. In the syndecan-1 shRNA transfected HCC cells, the proportions of late and early apoptotic cells, and levels of cleaved-Caspase-3 and cleaved-PARP were significantly increased in cells with or without S1P treatment. Thus, S1P augments the proportion of cells in S phase of the cell cycle that might translate to enhance HCC cell proliferation and inhibit the cell apoptosis via syndecan-1.

TGF-β Inhibition Improves Oncolytic Herpes Viroimmunotherapy in Murine Models of Rhabdomyosarcoma

Oncolytic viruses are an emerging class of cancer therapeutics that couple cytotoxicity with the induction of an anti-tumor immune response. Host-virus interactions are complex and modulated by a tumor microenvironment whose immunosuppressive activities can limit the effectiveness of cancer immunotherapies. In an effort to improve this aspect of oncolytic virotherapy, we combined the oncolytic herpes virus HSV1716 with the transforming growth factor beta receptor 1 (TGF-βR1) inhibitor A8301 to treat syngeneic models of murine rhabdomyosarcoma. Mice that received HSV1716 or A8301 alone showed little to no benefit in efficacy and survival over controls. Conversely, mice given combination therapy exhibited tumor stabilization throughout the treatment regimen, which was reflected in significantly prolonged survival times including some complete responses. In vitro cell viability and virus replication assays showed that the rhabdomyosarcoma cell lines were generally insensitive to HSV1716 and A8301. Likewise, in vivo virus replication assays showed that HSV1716 titers moderately decreased in the presence of A8301. The enhanced efficacy instead appears to be dependent on the generation of an improved anti-tumor T cell response as determined by its loss in athymic nude mice and following in vivo depletion of either CD4⁺ or CD8⁺ cells. These data suggest TGF-β inhibition can augment the immunotherapeutic efficacy of oncolytic herpes virotherapy.

Obesity-associated extracellular mtDNA activates central TGFβ pathway to cause blood pressure increase

Hypothalamic inflammation was recently found to mediate obesity-related hypertension, but the responsible upstream mediators remain unexplored. In this study, we show that dietary obesity is associated with extracellular release of mitochondrial DNA (mtDNA) into the cerebrospinal fluid and that central delivery of mtDNA mimics transforming growth factor-β (TGFβ) excess to activate downstream signaling pathways. Physiological study reveals that central administration of mtDNA or TGFβ is sufficient to cause hypertension in mice. Knockout of the TGFβ receptor in proopiomelanocortin neurons counteracts the hypertensive effect of not only TGFβ but also mtDNA excess, while the hypertensive action of central mtDNA can be blocked pharmacologically by a TGFβ receptor antagonist or genetically by TGFβ receptor knockout. Finally, we confirm that obesity-induced hypertension can be reversed through central treatment with TGFβ receptor antagonist. In conclusion, circulating mtDNA in the brain employs neural TGFβ pathway to mediate a central inflammatory mechanism of obesity-related hypertension.

Effects of transforming growth factor on the developing embryonic ureter: An in-vitro megaureter model in mice

INTRODUCTION

It is generally agreed that the cause of a megaureter is narrowing at the vesicoureteral junction, with a functional obstruction arising from an aperistaltic, juxtavesical segment that is unable to transport urine at an acceptable rate. Histological examinations of megaureter specimens have reported several histological analyses, and the pathogenic role of transforming growth factor is still a matter of speculation.

OBJECTIVE

To evaluate whether transforming growth factor-beta (TGF-β) and its receptors (TGFRs) are expressed during ureterovesical junction (UVJ) and lower ureter development in mice, and whether exogenous TGF-β might postpone the maturation of smooth muscle cells, in the pathogenesis of megaureter using an embryonic organ-culture model.

METHODS

Expression of TGF-β and TGFRs on the lower ureter and UVJ were determined at different embryonic days (E) (E16, 18, 20 and postnatal day 1). The functional studies were performed by harvesting ureters from wild-type mice at embryonic day 16 (E16), which were grown in serum-free organ-culture; some cultures were supplemented with TGF-β (2 and 20 ng/ml) and/or with soluble TGFR, which blocks bioactivity. Organs were harvested after 6 days and the expression of CD31 and Ki67 were assessed using immunohistochemistry. The muscle content of the UVJ and ureter were analyzed by flowcytometry.

RESULTS

The TGF-β and TGFR positive cells were immune detected in embryonic ureters. The TGF-β expression was highest on E18 and decreased postnatally. Exogenous TGF-β decreased ureterovesical (UV) muscle differentiation and proliferation. The longitudinal muscle fibers were significantly less in TGF-β explants. The TGF-β also decreased the proportions of cells expressing α smooth muscle actin (α-SMA). Soluble TGFR blocked the effects of exogenous TGF-β.

CONCLUSIONS

In organ culture, exogenous TGF-β postpones the UV smooth muscle proliferation and affects the muscular structure. Whether the effects of TGF-β are direct or indirect, these form an in-vitro megaureter model. The finding that TGF-β is highest in embryonic ureters in vivo and decreased postnatally suggests that a pathological persistence might potentially explain the pathogenesis of primary megaureters.

Intrinsic TGF-β signaling promotes age-dependent CD8+ T cell polyfunctionality attrition

Advanced age is associated with immune system deficits that result in an increased susceptibility to infectious diseases; however, specific mediators of age-dependent immune dysfunction have not been fully elucidated. Here we demonstrated that aged mice exhibit poor effector CD8+ T cell polyfunctionality, primarily due to CD8+ T cell-extrinsic deficits, and that reduced CD8+ T cell polyfunctionality correlates with increased susceptibility to pathogenic diseases. In aged animals challenged with the parasite Encephalitozoon cuniculi, effector CD8+ T cell survival and polyfunctionality were suppressed by highly elevated TGF-β1. Furthermore, TGF-β depletion reduced effector CD8+ T cell apoptosis in both young and aged mice and enhanced effector CD8+ T cell polyfunctionality in aged mice. Surprisingly, intrinsic blockade of TGF-β signaling in CD8+ T cells was sufficient to rescue polyfunctionality in aged animals. Together, these data demonstrate that low levels of TGF-β1 promote apoptosis of CD8+ effector T cells and high TGF-β1 levels associated with age result in both CD8+ T cell apoptosis and an altered transcriptional profile, which correlates with loss of polyfunctionality. Furthermore, elevated TGF-β levels are observed in the elderly human population and in aged Drosophila, suggesting that TGF-β represents an evolutionarily conserved negative regulator of the immune response in aging organisms.

Lactate-modulated induction of THBS-1 activates transforming growth factor (TGF)-beta2 and migration of glioma cells in vitro

Background

An important phenomenon observed in glioma metabolism is increased aerobic glycolysis in tumor cells, which is generally referred to as the Warburg effect. Transforming growth factor (TGF)-beta2, which we previously showed to be induced by lactic acid, is a key pathophysiological factor in glioblastoma, leading to increased invasion and severe local immunosuppression after proteolytic cleavage from its latency associated peptide. In this study we tested the hypothesis, that lactate regulates TGF-beta2 expression and glioma cell migration via induction of Thrombospondin-1 (THBS-1), a TGF-beta activating protein.

Methods

Lactate levels were reduced by knockdown of LDH-A using specific small interfering RNA (siRNA) and competitive inhibition of LDH-A by sodium oxamate. Knockdown of THBS-1 was performed using specific siRNA. Western Blot, qRT-PCR, and ELISA were used to investigate expression levels of LDH-A, LDH-B, TGF-beta2 and THBS-1. Migration of cells was examined by Spheroid, Scratch and Boyden Chamber assays.

Results

Knockdown of LDH-A with subsequent decrease of lactate concentration leads to reduced levels of THBS-1 and TGF-beta2 in glioma cells. Lactate addition increases THBS-1 protein, leading to increased activation of TGF-beta2. Inhibition of THBS-1 reduces TGF-beta2 protein and migration of glioma cells. Addition of synthetic THBS-1 can rescue reduced TGF-beta2 protein levels and glioma cell migration in siLDH-A treated cells.

Conclusion

We define a regulatory cascade between lactate, THBS-1 and TGF-beta2, leading to enhanced migration of glioma cells. Our results demonstrate a specific interaction between tumor metabolism and migration and provide a better understanding of the mechanisms underlying glioma cell invasion.

Myotonic dystrophy protein kinase (DMPK) prevents ROS-induced cell death by assembling a hexokinase II-Src complex on the mitochondrial surface

The biological functions of myotonic dystrophy protein kinase (DMPK), a serine/threonine kinase whose gene mutations cause myotonic dystrophy type 1 (DM1), remain poorly understood. Several DMPK isoforms exist, and the long ones (DMPK-A/B/C/D) are associated with the mitochondria, where they exert unknown activities. We have studied the isoform A of DMPK, which we have found to be prevalently associated to the outer mitochondrial membrane. The kinase activity of mitochondrial DMPK protects cells from oxidative stress and from the ensuing opening of the mitochondrial permeability transition pore (PTP), which would otherwise irreversibly commit cells to death. We observe that DMPK (i) increases the mitochondrial localization of hexokinase II (HK II), (ii) forms a multimeric complex with HK II and with the active form of the tyrosine kinase Src, binding its SH3 domain and (iii) it is tyrosine-phosphorylated by Src. Both interaction among these proteins and tyrosine phosphorylation of DMPK are increased under oxidative stress, and Src inhibition selectively enhances death in DMPK-expressing cells after HK II detachment from the mitochondria. Down-modulation of DMPK abolishes the appearance of muscle markers in in vitro myogenesis, which is rescued by oxidant scavenging. Our data indicate that, together with HK II and Src, mitochondrial DMPK is part of a multimolecular complex endowed with antioxidant and pro-survival properties that could be relevant during the function and differentiation of muscle fibers.

TGF-β1 suppression of microRNA-450b-5p expression: a novel mechanism for blocking myogenic differentiation of rhabdomyosarcoma

Transforming growth factor beta 1 (TGF-β1) is the most potent inhibitor of myogenic differentiation (MyoD) of rhabdomyosarcoma (RMS); however, the underlying mechanisms of this inhibition remain unclear. In this study, we identified novel TGF-β1-related microRNAs (miRNAs); among these, miR-450b-5p is significantly regulated by TGF-β1. We provide evidence that TGF-β1 exerts it function by suppressing miR-450b-5p. Both in cultured cells and tumor implants, miR-450b-5p significantly arrested the growth of RMS and promoted its MyoD. Utilizing a bioinformatics approach, we identified miR-450b-5p target mRNAs. Among these candidates, only the expression of ecto-NOX disulfide-thiol exchanger 2 (ENOX2) and paired box 9 (PAX9) was augmented by miR-450b-5p knockdown examined by western blot; the engineered inhibition antagonized TGF-β1-mediated differentiation inhibition. Furthermore, we found that the Smad3 and Smad4 pathways, but not Smad2, are the principal mediator of TGF-β1 suppression of miR-450b-5p. Taken together, these results suggest that disrupting the TGF-β1 suppression of miR-450b-5p, or knockdown of ENOX2 and PAX9, are effective approaches in inducing RMS MyoD.

Krüppel-like factor 6 (KLF6) promotes cell proliferation in skeletal myoblasts in response to TGFβ/Smad3 signaling

Background

Krüppel-like factor 6 (KLF6) has been recently identified as a MEF2D target gene involved in neuronal cell survival. In addition, KLF6 and TGFβ have been shown to regulate each other’s expression in non-myogenic cell types. Since MEF2D and TGFβ also fulfill crucial roles in skeletal myogenesis, we wanted to identify whether KLF6 functions in a myogenic context.

Methods

KLF6 protein expression levels and promoter activity were analyzed using standard cellular and molecular techniques in cell culture.

Results

We found that KLF6 and MEF2D are co-localized in the nuclei of mononucleated but not multinucleated myogenic cells and, that the MEF2 cis element is a key component of the KLF6 promoter region. In addition, TGFβ potently enhanced KLF6 protein levels and this effect was repressed by pharmacological inhibition of Smad3. Interestingly, pharmacological inhibition of MEK/ERK (1/2) signaling resulted in re-activation of the differentiation program in myoblasts treated with TGFβ, which is ordinarily repressed by TGFβ treatment. Conversely, MEK/ERK (1/2) inhibition had no effect on TGFβ-induced KLF6 expression whereas Smad3 inhibition negated this effect, together supporting the existence of two separable arms of TGFβ signaling in myogenic cells. Loss of function analysis using siRNA-mediated KLF6 depletion resulted in enhanced myogenic differentiation whereas TGFβ stimulation of myoblast proliferation was reduced in KLF6 depleted cells.

Conclusions

Collectively these data implicate KLF6 in myoblast proliferation and survival in response to TGFβ with consequences for our understanding of muscle development and a variety of muscle pathologies.

Distinct effects of ligand-induced PDGFRα and PDGFRβ signaling in the human rhabdomyosarcoma tumor cell and stroma cell compartments

Platelet-derived growth factor receptors (PDGFR) α and β have been suggested as potential targets for treatment of rhabdomyosarcoma, the most common soft tissue sarcoma in children. This study identifies biologic activities linked to PDGF signaling in rhabdomyosarcoma models and human sample collections. Analysis of gene expression profiles of 101 primary human rhabdomyosarcomas revealed elevated PDGF-C and -D expression in all subtypes, with PDGF-D as the solely overexpressed PDGFRβ ligand. By immunohistochemistry, PDGF-CC, PDGF-DD, and PDGFRα were found in tumor cells, whereas PDGFRβ was primarily detected in vascular stroma. These results are concordant with the biologic processes and pathways identified by data mining. While PDGF-CC/PDGFRα signaling associated with genes involved in the reactivation of developmental programs, PDGF-DD/PDGFRβ signaling related to wound healing and leukocyte differentiation. Clinicopathologic correlations further identified associations between PDGFRβ in vascular stroma and the alveolar subtype and with presence of metastases. Functional validation of our findings was carried out in molecularly distinct model systems, where therapeutic targeting reduced tumor burden in a PDGFR-dependent manner with effects on cell proliferation, vessel density, and macrophage infiltration. The PDGFR-selective inhibitor CP-673,451 regulated cell proliferation through mechanisms involving reduced phosphorylation of GSK-3α and GSK-3β. Additional tissue culture studies showed a PDGFR-dependent regulation of rhabdosphere formation/cancer cell stemness, differentiation, senescence, and apoptosis. In summary, the study shows a clinically relevant distinction in PDGF signaling in human rhabdomyosarcoma and also suggests continued exploration of the influence of stromal PDGFRs on sarcoma progression.

Rhabdomyosarcomas: an overview on the experimental animal models

Rhabdomyosarcomas (RMS) are aggressive childhood soft-tissue malignancies deriving from mesenchymal progenitors that are committed to muscle-specific lineages. Despite the histopathological signatures associated with three main histological variants, termed embryonal, alveolar and pleomorphic, a plethora of genetic and molecular changes are recognized in RMS. Over the years, exposure to carcinogens or ionizing radiations and gene-targeting approaches in vivo have greatly contributed to disclose some of the mechanisms underlying RMS onset. In this review, we describe the principal distinct features associated with RMS variants and focus on the current available experimental animal models to point out the molecular determinants cooperating with RMS development and progression.

Caveolins in rhabdomyosarcoma

Caveolins are scaffolding proteins that play a pivotal role in numerous processes, including caveolae biogenesis, vesicular transport, cholesterol homeostasis and regulation of signal transduction. There are three different isoforms (Cav-1, -2 and -3) that form homo- and hetero-aggregates at the plasma membrane and modulate the activity of a number of intracellular binding proteins. Cav-1 and Cav-3, in particular, are respectively expressed in the reserve elements (e.g. satellite cells) and in mature myofibres of skeletal muscle and their expression interplay characterizes the switch from muscle precursors to differentiated elements. Recent findings have shown that caveolins are also expressed in rhabdomyosarcoma, a group of heterogeneous childhood soft-tissue sarcomas in which the cancer cells seem to derive from progenitors that resemble myogenic cells. In this review, we will focus on the role of caveolins in rhabdomyosarcomas and on their potential use as markers of the degree of differentiation in these paediatric tumours. Given that the function of Cav-1 as tumour conditional gene in cancer has been well-established, we will also discuss the relationship between Cav-1 and the progression of rhabdomyosarcoma.

Differentiation of human rhabdomyosarcoma RD cells is regulated by reciprocal, functional interactions between myostatin, p38 and extracellular regulated kinase signalling pathways

Rhabdomyosarcoma (RMS) includes heterogeneous tumours of mesenchymal derivation which are genetically committed to the myogenic lineage, but fail to complete terminal differentiation. Previous works have reported on deregulated myostatin, p38 and extracellular regulated kinase (ERK) signalling in RMS cell lines; however, the functional link between these pathways and their relative contribution to RMS pathogenesis and/or maintenance of the transformed phenotype in vitro are unclear. Herein we show that the constitutive expression of a dominant-negative form of activin receptor type IIb (dnACTRIIb), which inhibits myostatin signalling, decreased proliferation and promoted differentiation of the human RMS RD cell line. DnACTRIIb-dependent differentiation of RD cells correlated with a reduced SMAD2/3 (small mother against decapentaplegic) and ERK signalling and the activation of p38 pathway. Conversely, the expression of a constitutively activated ALK5 (activin receptor-like kinase) (caALK5) form, activating SMAD3 and ERK pathways, led to further impairment of RD differentiation. Pharmacological blockade of ERK pathway in RD cells was sufficient to replicate the biological phenotype observed in dnACTRIIb-expressing RD cells, and also recovered the differentiation of caALK5-expressing RD cells. Conversely, deliberate activation of p38 signalling mimics the effect of dnActRIIb and overcame the differentiation block in RD cells. These data indicate the existence of a network formed by myostatin/SMAD2/3, ERK and p38 pathways that, when deregulated, might contribute to the pathogenesis of RMS. The components of this network might, therefore, be a valuable target for interventions towards correcting the malignant phenotype of RMS.

TGF-beta1 signal pathway may contribute to rhabdomyosarcoma development by inhibiting differentiation

Overexpression of transforming growth factor-beta1 (TGF-beta1) and its downstream molecules in the rhabdomyosarcoma (RMS) RD cell line has been reported previously, but the regulatory role of TGF-beta1 on RMS has not been studied extensively. In the present study, we showed that expression of TGF-beta1 and its downstream molecules type II TGF-beta receptor (TbetaRII) and Smad4 was significantly higher in RMS than in normal skeletal muscle, and there was a significant relationship between TGF-beta1 expression and histological grade. Gene silencing with TGF-beta1 short-hairpin RNA (shRNA)-expressing vectors significantly decreased the growth of RD cells, which was confirmed by caspase-3 (in vitro) and TUNEL (in vivo) assays. Moreover, a proportion of treated rhabdomyosarcoma (RD) cells changed to a round shape from the normal fusiform or polygonal shape and expressed myofilaments. Myogenin is one of the myogenic differentiation genes (MyoD) family of myogenic regulators, and was obviously higher in TGF-beta1-shRNA-treated tumors than it in control at the mRNA and protein level. Immunohistochemical staining with myogenic differentiation markers such as myosin and desmin in subcutaneous RMS tissue showed that TGF-beta1 shRNA increased staining for myosin. These results provide new insight into the biological function of TGF-beta1 in malignant tumors, and imply that the TGF-beta1 signal pathway is a potential therapeutic target for drugs that induce differentiation of RMS.

Efficient lysis of rhabdomyosarcoma cells by cytokine-induced killer cells: implications for adoptive immunotherapy after allogeneic stem cell transplantation

BACKGROUND

Rhabdomyosarcoma is the most common soft tissue sarcoma in childhood and has a poor prognosis. Here we assessed the capability of ex vivo expanded cytokine-induced killer cells to lyse both alveolar and embryonic rhabdomyosarcoma cell lines and investigated the mechanisms involved.

DESIGN AND METHODS

Peripheral blood mononuclear cells from six healthy donors were used to generate and expand cytokine-induced killer cells. The phenotype and composition of these cells were determined by multiparameter flow cytometry, while their cytotoxic effect against rhabdomyosarcoma cells was evaluated by a europium release assay.

RESULTS

Cytokine-induced killer cells efficiently lysed cells from both rhabdomyosarcoma cell lines. Antibody-mediated masking of either NKG2D molecule on cytokine-induced killer cells or its ligands on rhabdomyosarcoma cells (major histocompatibility antigen related chain A and B and UL16 binding protein 2) diminished this effect by 50%, suggesting a major role for the NKG2D molecule in rhabdomyosarcoma cell killing. No effect was observed after blocking CD11a, CD3 or TCRalphabeta molecules on cytokine-induced killer cells or CD1d on rhabdomyosar-coma cells. Remarkably, cytokine-induced killer cells used tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to activate caspase-3, as the main caspase responsible for the execution of apoptosis. Accordingly, blocking TRAIL receptors on embryonic rhabdomyosarcoma cell lines significantly reduced the anti-tumor effect of cytokine-induced killer cells. About 50% of T cells within the cytokine-induced killer population had an effector memory phenotype, 20% had a naïve phenotype and approximately 30% of the cells had a central memory phenotype. In addition, cytokine-induced killer cells expressed low levels of activation-induced markers CD69 and CD137 and demonstrated a low alloreactive potential.

CONCLUSIONS

Our data suggest that cytokine-induced killer cells may be used as a novel adoptive immunotherapy for the treatment of patients with rhabdomyosarcoma after allogeneic stem cell transplantation.

Identification of novel genes expressed during rhabdomyosarcoma differentiation using cDNA microarrays

Rhabdomyosarcomas (RMS) are highly aggressive tumors that are thought to arise as a consequence of the regulatory disruption of the growth and differentiation of skeletal muscle progenitor cells. Normal myogenesis is characterized by the expression of the myogenic regulatory factor gene family but, despite their expression in RMS, these tumor cells fail to complete the latter stages of myogenesis. The RMS cell line RD-A was treated with 12-O-tetradecanoylphorbol-13-acetate to induce differentiation and cultured for 10 days. RNA was extracted on days 1, 3, 6, 8 and 10. A human skeletal muscle cDNA microarray was developed and used to analyze the global gene expression of RMS tumors over the time-course of differentiation. As a comparison, the genes identified were subsequently examined during the differentiated primary human skeletal muscle cultures. Prothymosin alpha (PTMA), and translocase of inner mitochondrial membrane 10 (Tim10), two genes not previously implicated in RMS, showed reduced expression during differentiation. Marked differences in the expression of PTMA and Tim10 were observed during the differentiation of human primary skeletal muscle cells. These results identify several new genes with potential roles in the myogenic arrest present in rhabdomyosarcoma. PTMA expression in RMS biopsy samples might prove to be an effective diagnostic marker for this disease.

Endothelin-3 production by human rhabdomyosarcoma: a possible new marker with a paracrine role

Several autocrine and paracrine growth factor circuits have been found in human rhabdomyosarcoma cells. In this study we show that endothelin-3 (ET-3), a vasoactive peptide, is produced by human rhabdomyosarcoma cell lines, whereas it is not expressed by human sarcoma cell lines of non-muscle origin. We did not find evidence of a significant autocrine loop; nevertheless ET-3 produced by rhabdomyosarcoma cells can act as a paracrine factor, since it promotes migration of endothelial cells. Moreover ET-3 is present in plasma of mice bearing xenografts of human rhabdomyosarcoma cells, and may be potential new marker of the human rhabdomyosarcoma to be studied further.

Late relapse of myelodysplasia after allogeneic transplantation concomitant with new presentation of invasive liposarcoma as a secondary neoplasm

Second malignancies are uncommon events in the survivors of allogeneic transplant procedures, although they are increased compared to normal control populations. Among these malignancies, sarcomas are exceedingly rare. In addition, relapse of primary myelodysplasia rarely occurs after 5 years from the time of allogeneic transplantation. This report describes an unusual presentation of liposarcoma with concomitant relapse of underlying myelodysplasia developing in a patient 9 years after the first of two allogeneic transplantations.

Effects of interleukin-1beta, interleukin-13 and transforming growth factor-beta on gene expression in human airway smooth muscle using gene microarrays

Inflammatory gene expression in airway smooth muscle may be influenced by its inflammatory milieu. We analysed the gene expression profile of airway smooth muscle cells cultured from human airways exposed to a pro-inflammatory cytokine, interleukin-1beta, a T helper-2 cytokine, interleukin-13, and to a growth factor, transforming growth factor (TGF)beta1 (10 ng/ml each) after 4 and 24 h using the Affymetrix GeneChip 95A array which detects approximately 12,500 genes and expression sequence tags (ESTs). Airway smooth muscle cells were responsive to each cytokine with distinctive patterns of gene expression for cytokines, chemokines, adhesion and signalling proteins, and transcription factors. Interleukin-1beta induced the highest number of genes such as cytokines/chemokines including interleukin-8, growth-related oncogene (GRO)-alpha, -beta and -gamma, epithelial neutrophil activating protein (ENA)-78, monocyte chemotactic protein (MCP)-1, -2 and -3 and eotaxin. Using quantitative real-time reverse transcription-polymerase chain reaction, the expression of GRO-alpha, -beta and -gamma, interleukin-8 and eotaxin by interleukin-1beta was confirmed, with good correlation with microarray data. Transforming growth factor (TGF)beta1 induced other growth factors such as connective tissue growth factor (CTGF), vascular endothelial growth factor (VEGF), insulin growth factor (IGF) and many structural and extracellular matrix proteins. Interleukin-13 was the weakest inducer, with stimulation of eotaxin and genes of unknown function. While many genes were co-regulated at 4 and 24 h, there were also differences in expression patterns. Interleukin-1beta induces a predominantly pro-inflammatory profile while TGFbeta1 can be linked to proliferative and matrix changes. The rich profile of mediators, growth factors and signalling molecules released from airway smooth muscle depends on the inflammatory milieu.

Terminal differentiation of Sol 8 myoblasts is retarded by a transforming growth factor-beta autocrine regulatory loop

In DM (differentiation medium), Sol 8 myoblasts spontaneously form myotubes and express the betaMHC (beta-myosin heavy chain), their main marker of terminal differentiation. This marker is detectable at 24 h, and increases up to 72 h. Our aim was to define temporal effects of TGFbeta (transforming growth factor beta) on betaMHC expression in Sol 8 cells. TGFbeta1 (1 ng/ml) added at time zero to DM decreased MyoD expression and completely inhibited betaMHC expression in Sol 8 cells. This inhibition of betaMHC expression was progressively lost when TGFbeta1 was added from 8 to 34 h. After 34 h, the cells were irreversibly differentiated, and TGFbeta1 did not inhibit betaMHC accumulation any longer. Two independent approaches showed that a TGFbeta autocrine regulatory loop retarded and partially impaired Sol 8 cell terminal differentiation. First, permanent immunoneutralization of the active TGFbetas released by the cells into DM increased betaMHC levels at 72 h compared with controls. Secondly, a dominant-negative mutant of the TGFbeta type II receptor was overexpressed in Sol 8 cells under the control of the betaMHC promoter. Both the dominant-negative receptor and the betaMHC gene were expressed after 24 h in DM. The delayed blocking of the TGFbeta signalling pathway by the dominant-negative receptor was as effective as permanent immunoneutralization to promote betaMHC expression. To conclude, TGFbeta inhibits Sol 8 cell terminal differentiation within a narrow time interval (24-34 h) that coincides with the onset of betaMHC expression.

Inhibition of Connective Tissue Growth Factor (CTGF/CCN2) Expression Decreases the Survival and Myogenic Differentiation of Human Rhabdomyosarcoma Cells

Connective tissue growth factor (CTGF/CCN2), a cysteine-rich protein of the CCN (Cyr61, CTGF, Nov) family of genes, emerged from a microarray screen of genes expressed by human rhabdomyosarcoma cells. Rhabdomyosarcoma is a soft tissue sarcoma of childhood deriving from skeletal muscle cells. In this study, we investigated the role of CTGF in rhabdomyosarcoma. Human rhabdomyosarcoma cells of the embryonal (RD/12, RD/18, CCA) and the alveolar histotype (RMZ-RC2, SJ-RH4, SJ-RH30), rhabdomyosarcoma tumor specimens, and normal skeletal muscle cells expressed CTGF. To determine the function of CTGF, we treated rhabdomyosarcoma cells with a CTGF antisense oligonucleotide or with a CTGF small interfering RNA (siRNA). Both treatments inhibited rhabdomyosarcoma cell growth, suggesting the existence of a new autocrine loop based on CTGF. CTGF antisense oligonucleotide-mediated growth inhibition was specifically due to a significant increase in apoptosis, whereas cell proliferation was unchanged. CTGF antisense oligonucleotide induced a strong decrease in the level of myogenic differentiation of rhabdomyosarcoma cells, whereas the addition of recombinant CTGF significantly increased the proportion of myosin-positive cells. CTGF emerges as a survival and differentiation factor and could be a new therapeutic target in human rhabdomyosarcoma.

Myostatin inhibits rhabdomyosarcoma cell proliferation through an Rb-independent pathway

Rhabdomyosarcoma (RMS) tumors are the most common soft-tissue sarcomas in childhood. In this investigation, we show that myostatin, a skeletal muscle-specific inhibitor of growth and differentiation is expressed and translated in the cultured RMS cell line, RD. The addition of exogenous recombinant myostatin inhibits the proliferation of RD cells cultured in growth media, consistent with the role of myostatin in normal myoblast proliferation inhibition. However, unlike normal myoblasts, upregulation of p21 was not observed. Rather, myostatin signalling resulted in the specific downregulation of both Cdk2 and its cognate partner, cyclin-E. The analysis of Rb reveals that there was no change in its phosphorylation status with myostatin treatment, consistent with D-type-cyclin-Cdk4/6 complexes being active in the absence of p21. Moreover, the activity of Rb appeared to be unchanged between treated and nontreated RD cells, as determined by the ability of Rb to bind E2F1. The examination of NPAT, a substrate of cyclin-E-Cdk2 involved in the transcriptional activation of replication-dependent histone gene expression, revealed that it undergoes a loss of phosphorylation with myostatin treatment. Supporting this, a downregulation in H4-histone gene expression was observed. These results suggest that myostatin could potentially be used as an inhibitor of RMS proliferation and define a previously uncharacterized, Rb-independent mechanism for the inhibition of muscle precursor cell proliferation by myostatin.

Variation in cadherins and catenins expression is linked to both proliferation and transformation of Rhabdomyosarcoma

Cadherins are a family of transmembrane glycoproteins that mediate Ca(2+)-dependent homophilic cell-cell adhesion and play a crucial role in cell differentiation. E-cadherin-mediated cell-cell adhesion is lost during the development of most epithelial cancers. This study examines cadherin-dependent adhesion in cell lines derived from rhabdomyosarcoma (RMS), a highly malignant soft-tissue tumor committed to the myogenic lineage, but arrested prior to terminal differentiation. We analysed the expression of cadherins and associated catenins at the mRNA and protein levels as well as their localization in nine RMS-derived cell lines relative to normal myoblasts. We show a decrease in the expression of cadherins and catenins in all RMS-derived cell lines compared to control cells. This decrease in the expression of N- and M-cadherin was confirmed in RMS biopsies. In contrast, R-cadherin is found expressed in RMS, whereas it is normally absent in normal myoblasts. We show that a decrease of R-cadherin expression using RNA interference inhibits cell proliferation of the RD cell line. In addition to their diminished expression, cadherins and catenins do not localize to intercellular contacts in embryonal RMS (ERMS), whereas specific persistent localization is seen in alveolar RMS (ARMS)-derived cell lines. Thus, RMS exhibit defects in the expression of molecules of the cadherin family. Defects in the localization of these adhesion molecules at the sites of cell-cell contact are specifically observed in the ERMS subtype. In addition, our data suggest that R-cadherin is a specific diagnostic marker for RMS and is also an important factor of RMS cell proliferation.

Inhibition of autocrine secretion of myostatin enhances terminal differentiation in human rhabdomyosarcoma cells

Rhabdomyosarcomas (RMSs) are one of the most common solid tumor of childhood. Rhabdomyosarcoma (RMS) cells fail to both complete the skeletal muscle differentiation program and irreversibly exit the cell cycle as a consequence of an active repression exerted on the muscle-promoting factor MyoD. Myostatin is a negative regulator of normal muscle growth, we have thus studied its possible role in RMS cells. Here, we present evidence that overexpression of myostatin is a common feature of RMS since both subtypes of RMS (embryonal RD and alveolar Rh30 cells) express high levels of myostatin when compared to nontumoral skeletal muscle cells. Interestingly, we found that inactivation of myostatin through overexpression of antisense myostatin or of follistatin (a myostatin antagonist) constructs enhanced differentiation of RD cells. In addition, RD and Rh30 cells treated with blocking antimyostatin antibodies progress into the myogenic terminal differentiation program. Finally, our results suggest that high levels of myostatin could impair MyoD function in RMS cells. These results show that an autocrine myostatin loop contributes to maintain RMS cells in an undifferentiating stage and suggest that new therapeutic approaches could be exploited for the treatment of RMS based on inactivation of myostatin protein.

Transforming growth factor beta1 is up-regulated by activated Raf in skeletal myoblasts but does not contribute to the differentiation-defective phenotype

The Raf/MEK/MAPK signaling module elicits a strong negative impact on skeletal myogenesis that is reflected by a complete loss of muscle gene transcription and differentiation in multinucleated myocytes. Recent evidence indicates that Raf signaling also may contribute to myoblast cell cycle exit and cytoprotection. To further define the mechanisms by which Raf participates in cellular responses, a stable line of myoblasts expressing an estrogen receptor-Raf chimeric protein was created. The cells (23A2RafER(DD)) demonstrate a strict concentration-dependent increase in chimeric Raf protein synthesis and downstream phosphoMAPK activation. Initiation of low-level Raf activity in these cells augments contractile protein expression and myocyte fusion. By contrast, induction of high level Raf activity in 23A2RafER(DD) myoblasts inhibits the formation of myocytes and muscle reporter gene expression. Interestingly, treatment of myoblasts with conditioned medium isolated from Raf-repressive cells inhibits all of the aspects of myogenesis. Closer examination indicates that the transforming growth factor-beta(1) (TGF-beta(1)) gene is up-regulated in Raf-repressive myoblasts. The cells also direct elevated levels of Smad transcriptional activity, suggesting the existence of a TGF-beta(1) autocrine loop. However, extinguishing the biological activity of TGF-beta(1) does not restore the myogenic program. Our results provide evidence for the involvement of Raf signal transmission during myocyte formation as well as during inhibition of myogenesis.

Systematic analysis of the TGF-beta/Smad signalling pathway in the rhabdomyosarcoma cell line RD

Transforming growth factor-beta (TGF-beta) is a multifunctional regulator of cell growth and differentiation, whose actions are highly cell type specific. To study the role of the TGF-beta1 autocrine loop in regulating growth and myogenic differentiation in the human rhabdomyosarcoma cell line, RD, an attempt was made to establish a framework for the expression of several components of TGF-beta1/Smad signalling pathway at the mRNA and protein levels by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis in RD cells compared with the normal myoblasts. Higher exogenous concentration of TGF-beta1 was necessary to reach a growth-inhibition effect, whereas TGF-beta1 downregulated the expression of myosin heavy-chain mRNA at lower concentrations than that was required for growth inhibition. Treatment with TGF-beta1 significantly decreased the number of sarcomeric actin and myosin-expressing cells. In this study, we have shown that RD cells displayed higher expression of TbetaRI, TbetaRII, Smad2 and Smad4 at both the mRNA and protein levels than myoblasts. Smad3 and Smad7 mRNA were expressed at higher level in RD cells than in myoblasts. The staining patterns of TbetaR and Smads suggest that they may transduce different TGF-beta1 signalling in RD cells than in myoblasts. TGF-beta1 signalling induced a rapid relocation of Smad2 to the nucleus; in contrast, Smad4 remained localized to the cytoplasm unless it was coexpressed with Smad2. These studies suggest that signalling from the cell surface to the nucleus through Smad proteins is a required component of TGF-beta1-induced cell response in RD cells. The RD cell line is a suitable model to study the TGF-beta autocrine loop involved in growth and differentiation of RMS.

Inhibition of skeletal muscle development: less differentiation gives more muscle

The fact that stem cells have to be protected from premature differentiation is true for many organs in the developing embryo and the adult organism. However, there are several arguments that this is particularly important for (skeletal) muscle. There are some evolutionary arguments that muscle is a "default" pathway for mesodermal cells, which has to be actively prevented in order to allow cells to differentiate into other tissues. Myogenic cells originate from very small areas of the embryo where only a minor portion of these cells is supposed to differentiate. Differentiated muscle fibres are unconditionally post-mitotic, leaving undifferentiated stem cells as the only source of regeneration. The mechanical usage of muscle and its superficial location in the vertebrate body makes regeneration a frequently used mechanism. Looking at the different inhibitory mechanisms that have been found within the past 10 or so years, it appears as if evolution has taken this issue very serious. At all possible levels we find regulatory mechanisms that help to fine tune the differentiation of myogenic cells. Secreted molecules specifying different populations of somitic cells, diffusing or membrane-bound signals among fellow myoblasts, modulating molecules within the extracellular matrix and last, but not least, a changing set of activating and repressing cofactors. We have come a long way from the simple model of MyoD just to be turned on at the right time in the right cell.

Intraosseous rhabdomyosarcoma of the mandible: a case report

Rhabdomyosarcoma is the most common soft-tissue sarcoma of the head and neck region in children and adolescents. Oral cavity involvement is relatively uncommon, with tongue, soft palate, hard palate, and buccal mucosa being the sites of predilection. This report presents a rare case of intraosseous oral rhabdomyosarcoma arising in the mandibular bone of a 6-year-old child. Clinical, radiologic, and histopathologic features and possible pathogenesis are discussed.

PKCalpha-mediated ERK, JNK and p38 activation regulates the myogenic program in human rhabdomyosarcoma cells

We have previously suggested that PKCalpha has a role in 12-O-Tetradecanoylphorbol-13-acetate (TPA)-mediated growth arrest and myogenic differentiation in human embryonal rhabdomyosarcoma cells (RD). Here, by monitoring the signalling pathways triggered by TPA, we demonstrate that PKCalpha mediates these effects by inducing transient activation of c-Jun N-terminal protein kinases (JNKs) and sustained activation of both p38 kinase and extracellular signal-regulated kinases (ERKs) (all referred to as MAPKs). Activation of MAPKs following ectopic expression of constitutively active PKCalpha, but not its dominant-negative form, is also demonstrated. We investigated the selective contribution of MAPKs to growth arrest and myogenic differentiation by monitoring the activation of MAPK pathways, as well as by dissecting MAPK pathways using MEK1/2 inhibitor (UO126), p38 inhibitor (SB203580) and JNK and p38 agonist (anisomycin) treatments. Growth-arresting signals are triggered either by transient and sustained JNK activation (by TPA and anisomycin, respectively) or by preventing both ERK and JNK activation (UO126) and are maintained, rather than induced, by p38. We therefore suggest a key role for JNK in controlling ERK-mediated mitogenic activity. Notably, sarcomeric myosin expression is induced by both TPA and UO126 but is abrogated by the p38 inhibitor. This finding indicates a pivotal role for p38 in controlling the myogenic program. Anisomycin persistently activates p38 and JNKs but prevents myosin expression induced by TPA. In accordance with this negative role, reactivation of JNKs by anisomycin, in UO126-pre-treated cells, also prevents myosin expression. This indicates that, unlike the transient JNK activation that occurs in the TPA-mediated myogenic process, long-lasting JNK activation supports the growth-arrest state but antagonises p38-mediated myosin expression. Lastly, our results with the MEK inhibitor suggest a key role of the ERK pathway in regulating myogenic-related morphology in differentiated RD cells.

Subset-specific reductions in lung lymphocyte accumulation following intratracheal antigen challenge in endothelial selectin-deficient mice

We previously demonstrated induction and expression of CD62E and CD62P in the lungs of mice primed and then challenged with intratracheal (i.t.) SRBC. The current study examined accumulation of endogenous lymphocytes in the lungs of endothelial E- and P-selectin-deficient (E(-)P(-)) mice after i.t. SRBC challenge. Compared with syngeneic wild-type (wt) mice, E(-)P(-) mice showed an 85-95% decrease in CD8(+) T cells and B cells in the lungs at both early and late time points. In contrast, CD4(+) T cell accumulation was reduced by approximately 60% early, but equivalent to wt levels later. Surprisingly, many gammadelta T cells were found in lungs and blood of E(-)P(-) mice but were undetectable in the lungs and blood of wt mice. Absolute numbers of peripheral blood CD4, CD8, and B lymphocytes in E(-)P(-) mice equaled or exceeded the levels in wt mice, particularly after challenge. Trafficking studies using alphabeta T lymphoblasts confirmed that the recruitment of circulating cells after challenge was markedly reduced in E(-)P(-) mice. Furthermore, Ag priming occurred normally in both the selectin-deficient and wt mice, because primed lymphocytes from both groups transferred Ag sensitivity into naive wt mice. Lung production of mRNA for six CC and two CXC chemokines after challenge was equivalent by RT-PCR analysis in wt and E(-)P(-) mice. Therefore, reduced lung accumulation of alphabeta T cells and B cells in E(-)P(-) mice did not result from reduced delivery of circulating lymphocytes to the lungs, unsuccessful Ag priming, or defective pulmonary chemokine production. Selectin-dependent lymphocyte recruitment into the lungs following i.t.-SRBC challenge is subset specific and time dependent.

TGFbeta1 -mediated epithelial to mesenchymal transition is accompanied by invasion in the SiHa cell line

It has recently been suggested by several investigators that the epithelial-mesenchymal transition-inducing capacity of TGFbetas contributes to invasive transition of tumors at later stages of carcinogenesis. In the present study, we examined the possibility of TGFbeta1-stimulated epithelial-mesenchymal transition in SiHa cell line, detailed molecular events in the process, and its possible contribution to the invasive transition of tumors. TGFbeta1-induced epithelial-mesenchymal transition of SiHa cells was based on morphological and biochemical criteria; actin stress fiber formation, focal translocalization of integrin alphav, talin, and vinculin, fibronectin-based matrix assembly at the cell periphery, and translocalization and down-regulation of E-cadherin. TGFbeta1 also stimulated surface expression of integrin alphavbeta3 and FAK activation. Focal translocalization of integrin alphav preceded actin reorganization and fibronectin matrix assembly, and functional blocking of the integrin suppressed actin stress fiber formation. Furthermore, induction of actin reorganization and fibronectin matrix assembly by TGFbeta1 were shown to be mutually independent events. These changes were irreversible because 5 minutes pulse exposure to TGFbeta1 was sufficient to stimulate progress of actin reorganization and fibronectin matrix assembly. In further studies with raft culture, TGFbeta1 was found to stimulate invasion of SiHa cells into a type I collagen gel matrix. In conclusion, TGFbeta1 stimulated epithelial-mesenchymal transition of SiHa cells, indicating a positive role in the invasive transition of tumors.