Generation of Fibrodysplasia ossificans progressiva and control integration free iPSC lines from periodontal ligament fibroblasts.

Fibrodysplasia ossificans progressiva (FOP) is a very rare devastating heterotopic ossification disorder, classically caused by a heterozygous single point mutation (c.617G>A) in the ACVR1gene, encoding the Bone morphogenetic protein (BMP) type I receptor, also termed activin receptor-like kinase (ALK)2. FOP patients develop heterotopic ossification episodically in response to inflammatory insults, thereby compromising tissue sampling and the development of in vitro surrogate models for FOP. Here we describe the generation and characterization of a control and a classical FOP induced pluripotent stem cell (iPSC) line derived from periodontal ligament fibroblast cells using Sendai virus vectors.

Hepatocyte-specific Smad7 deletion accelerates DEN-induced HCC via activation of STAT3 signaling in mice.

TGF-ß signaling in liver cells has variant roles in the dynamics of liver diseases, including hepatocellular carcinoma (HCC). We previously found a correlation of high levels of the important endogenous negative TGF-ß signaling regulator SMAD7 with better clinical outcome in HCC patients. However, the underlying tumor-suppressive molecular mechanisms are still unclear. Here, we show that conditional (TTR-Cre) hepatocyte-specific SMAD7 knockout (KO) mice develop more tumors than wild-type and corresponding SMAD7 transgenic mice 9 months after diethylnitrosamine (DEN) challenge, verifying SMAD7 as a tumor suppressor in HCC. In line with our findings in patients, Smad7 levels in both tumor tissue as well as surrounding tissue show a significant inverse correlation with tumor numbers. SMAD7 KO mice presented with increased pSMAD2/3 levels and decreased apoptosis in the tumor tissue. Higher tumor incidence was accompanied by reduced P21 and upregulated c-MYC expression in the tumors. Activation of signal transducer and activator of transcription factor 3 signaling was found in Smad7-deficient mouse tumors and in patients with low tumoral SMAD7 expression as compared with surrounding tissue. Together, our results provide new mechanistic insights into the tumor-suppressive functions of SMAD7 in hepatocarcinogenesis.

Expression of TGFß-family signalling components in ageing cartilage: age-related loss of TGFß and BMP receptors.

OBJECTIVE: Ageing is the main risk factor for osteoarthritis (OA). We investigated if expression of transforming growth factor ß (TGFß)-family components, a family which is crucial for the maintenance of healthy articular cartilage, is altered during ageing in cartilage. Moreover, we investigated the functional significance of selected age-related changes. DESIGN: Age-related changes in expression of TGFß-family members were analysed by quantitative PCR in healthy articular cartilage obtained from 42 cows (age: ¾-10 years). To obtain functional insight of selected changes, cartilage explants were stimulated with TGFß1 or bone morphogenetic protein (BMP) 9, and TGFß1 and BMP response genes were measured. RESULTS: Age-related cartilage thinning and loss of collagen type 2a1 expression (∼256-fold) was observed, validating our data set for studying ageing in cartilage. Expression of the TGFß-family type I receptors; bAlk2, bAlk3, bAlk4 and bAlk5 dropped significantly with advancing age, whereas bAlk1 expression did not. Of the type II receptors, expression of bBmpr2 decreased significantly. Type III receptor expression was unaffected by ageing. Expression of the ligands bTgfb1 and bGdf5 also decreased with age. In explants, an age-related decrease in TGFß1-response was observed for the pSmad3-dependent gene bSerpine1 (P = 0.016). In contrast, ageing did not affect BMP9 signalling, an Alk1 ligand, as measured by expression of the pSmad1/5 dependent gene bId1. CONCLUSIONS: Ageing negatively affects both the TGFß-ALK5 and BMP-BMPR signalling routes, and aged chondrocytes display a lowered pSmad3-dependent response to TGFß1. Because pSmad3 signalling is essential for cartilage homeostasis, we propose that this change contributes to OA development.

Fibulin-4 deficiency increases TGF-ß signalling in aortic smooth muscle cells due to elevated TGF-ß2 levels.

Fibulins are extracellular matrix proteins associated with elastic fibres. Homozygous Fibulin-4 mutations lead to life-threatening abnormalities such as aortic aneurysms. Aortic aneurysms in Fibulin-4 mutant mice were associated with upregulation of TGF-ß signalling. How Fibulin-4 deficiency leads to deregulation of the TGF-ß pathway is largely unknown. Isolated aortic smooth muscle cells (SMCs) from Fibulin-4 deficient mice showed reduced growth, which could be reversed by treatment with TGF-ß neutralizing antibodies. In Fibulin-4 deficient SMCs increased TGF-ß signalling was detected using a transcriptional reporter assay and by increased SMAD2 phosphorylation. Next, we investigated if the increased activity was due to increased levels of the three TGF-ß isoforms. These data revealed slightly increased TGF-ß1 and markedly increased TGF-ß2 levels. Significantly increased TGF-ß2 levels were also detectable in plasma from homozygous Fibulin-4(R/R) mice, not in wild type mice. TGF-ß2 levels were reduced after losartan treatment, an angiotensin-II type-1 receptor blocker, known to prevent aortic aneurysm formation. In conclusion, we have shown increased TGF-ß signalling in isolated SMCs from Fibulin-4 deficient mouse aortas, not only caused by increased levels of TGF-ß1, but especially TGF-ß2. These data provide new insights in the molecular interaction between Fibulin-4 and TGF-ß pathway regulation in the pathogenesis of aortic aneurysms.

Disorganised stroma determined on pre-treatment breast cancer biopsies is associated with poor response to neoadjuvant chemotherapy: Results from the NEOZOTAC trial.

INTRODUCTION: The tumor-associated stroma is of importance for tumor progression and is generally accepted to have a significant influence on patient prognosis. However, little is known regarding specific features of tumor-associated stromal tissues and response to (neoadjuvant) chemotherapy. This study investigated the predictive value of extracellular matrix organization on response to chemotherapy in patients treated in the NEOZOTAC trial. METHODS: Stromal organisation was analyzed via a simple method using image analysis software on hematoxylin and eosin (H&E)-stained slides from primary tumor biopsies collected as part of the NEOZOTAC trial. Heidenhain's AZAN trichrome-stained slides were also analyzed for comparison of collagen evaluation. Sections were stained for phospho-Smad2 (pS2) in order to determine the relationship of TGF-ß signaling with stromal organization. RESULTS: A statistically significant relationship was observed between stroma consisting of organised collagen and pathological response to neoadjuvant chemotherapy (Odds Ratio 0.276, 95%CI 0.124-0.614, P = 0.002). This parameter was also related to ER-status (P = 0.003), clinical tumor -status (P = 0.041), nodal status (P = 0.029) and pS2 status (P = 0.025). Correlation between stromal organisation determined on H&E-stained and AZAN-stained tissue sections was high (Pearson's correlation coefficient = 0.806). CONCLUSION: Intratumoral stromal organisation determined using pre-treatment breast cancer biopsies was related to pathological response to chemotherapy. This parameter might play a role in the management of breast cancer for identifying those patients that are likely to benefit from neoadjuvant chemotherapy.

The high affinity ALK1-ligand BMP9 induces a hypertrophy-like state in chondrocytes that is antagonized by TGFß1.

OBJECTIVE: In osteoarthritic cartilage, expression of the receptor ALK1 correlates with markers of deleterious chondrocyte hypertrophy. Recently, bone morphogenetic protein 9 (BMP9) was identified as a high affinity ligand for ALK1. Therefore, we studied if BMP9 signaling results in expression of hypertrophy markers in chondrocytes. Furthermore, because transforming growth factorß1 (TGFß1) is a well known anti-hypertrophic factor, the interaction between BMP9 and TGFß1 signaling was also studied. DESIGN: Primary chondrocytes were isolated from bovine cartilage and stimulated with BMP9 and/or TGFß1 to measure intracellular signaling via pSmads with the use of Western blot. Expression of Smad-responsive genes or hypertrophy-marker genes was measured using qPCR. To confirm observations on TGFß/Smad3 responsive genes, a Smad3-dependent CAGA12-luc transcriptional reporter assay was performed in the chondrocyte G6 cell line. RESULTS: In primary chondrocytes, BMP9 potently induced phosphorylation of Smad1/5 and Smad2 to a lesser extent. BMP9-induced Smad1/5 phosphorylation was rapidly (2 h) reflected in gene expression, whereas Smad2 phosphorylation was not. Remarkably, BMP9 and TGFß1 dose-dependently synergized on Smad2 phosphorylation, and showed an additive effect on expression of Smad3-dependent genes like bSerpine1 after 24 h. The activation of the TGFß/Smad3 signaling cascade was confirmed using the CAGA12-luc transcriptional reporter. BMP9 selectively induced bAlpl and bColX expression, which are considered early markers of cellular hypertrophy, but this was potently antagonized by addition of a low dose of TGFß1. CONCLUSIONS: This study shows that in vitro in chondrocytes, BMP9 potently induces pSmad1/5 and a chondrocyte hypertrophy-like state, which is potently blocked by TGFß1. This observation underlines the importance of TGFß1 in maintenance of chondrocyte phenotype.

The BMP pathway either enhances or inhibits the Wnt pathway depending on the SMAD4 and p53 status in CRC.

BACKGROUND: Constitutive Wnt activation is essential for colorectal cancer (CRC) initiation but also underlies the cancer stem cell phenotype, metastasis and chemosensitivity. Importantly Wnt activity is still modulated as evidenced by higher Wnt activity at the invasive front of clonal tumours termed the ß-catenin paradox. SMAD4 and p53 mutation status and the bone morphogenetic protein (BMP) pathway are known to affect Wnt activity. The combination of SMAD4 loss, p53 mutations and BMP signalling may integrate to influence Wnt signalling and explain the ß-catenin paradox. METHODS: We analysed the expression patterns of SMAD4, p53 and ß-catenin at the invasive front of CRCs using immunohistochemistry. We activated BMP signalling in CRC cells in vitro and measured BMP/Wnt activity using luciferase reporters. MTT assays were performed to study the effect of BMP signalling on CRC chemosensitivity. RESULTS: Eighty-four percent of CRCs with high nuclear ß-catenin staining are SMAD4 negative and/or p53 aberrant. BMP signalling inhibits Wnt signalling in CRC only when p53 and SMAD4 are unaffected. In the absence of SMAD4, BMP signalling activates Wnt signalling. When p53 is lost or mutated, BMP signalling no longer influences Wnt signalling. The cytotoxic effects of 5-FU are influenced in a similar manner. CONCLUSIONS: The BMP signalling pathway differentially modulates Wnt signalling dependent on the SMAD4 and p53 status. The use of BMPs in cancer therapy, as has been proposed by previous studies, should be targeted to individual cancers based on the mutational status of p53 and SMAD4.

Interaction with colon cancer cells hyperactivates TGF-ß signaling in cancer-associated fibroblasts.

The interaction between epithelial cancer cells and cancer-associated fibroblasts (CAFs) has a major role in cancer progression and eventually in metastasis. In colorectal cancer (CRC), CAFs are present in high abundance, but their origin and functional interaction with epithelial tumor cells has not been elucidated. In this study we observed strong activation of the transforming growth factor-ß (TGF-ß)/Smad signaling pathway in CRC CAFs, accompanied by decreased signaling in epithelial tumor cells. We evaluated the TGF-ß1 response and the expression of target genes including matrix metalloproteinases (MMPs) and plasminogen activator inhibitor (PAI)-1 of various epithelial CRC cell lines and primary CAFs in vitro. TGF-ß1 stimulation caused high upregulation of MMPs, PAI-1 and TGF-ß1 itself. Next we showed that incubation of CAFs with conditioned medium (CM) from epithelial cancer cells led to hyperactivation of the TGF-ß signaling pathway, enhanced expression of target genes like PAI-1, and the expression of α-smooth muscle actin (α-SMA). We propose that the interaction of tumor cells with resident fibroblasts results in hyperactivated TGF-ß1 signaling and subsequent transdifferentiation of the fibroblasts into α-SMA-positive CAFs. In turn this leads to cumulative production of TGF-ß and proteinases within the tumor microenvironment, creating a cancer-promoting feedback loop.

Specific interactions between Smad proteins and AP-1 components determine TGFß-induced breast cancer cell invasion.

Deregulation of the transforming growth factor ß (TGFß) signal transduction cascade is functionally linked to cancer. In early phases, TGFß acts as a tumor suppressor by inhibiting tumor cell proliferation, whereas in late phases, it can act as a tumor promoter by stimulating tumor cell invasion and metastasis. Smad transcriptional effectors mediate TGFß responses, but relatively little is known about the Smad-containing complexes that are important for epithelial-mesenchymal transition and invasion. In this study, we have tested the hypothesis that specific members of the AP-1 transcription factor family determine TGFß signaling specificity in breast cancer cell invasion. Using a 3D model of collagen-embedded spheroids of MCF10A-MII premalignant human breast cancer cells, we identified the AP-1 transcription factor components c-Jun, JunB, c-Fos and Fra1 as essential factors for TGFß-induced invasion and found that various mesenchymal and invasion-associated TGFß-induced genes are co-regulated by these proteins. In situ proximity ligation assays showed that TGFß signaling not only induces complexes between Smad3 and Smad4 in the nucleus but also complexes between Smad2/3 and Fra1, whereas complexes between Smad3, c-Jun and JunB could already be detected before TGFß stimulation. Finally, chromatin immunoprecipitations showed that c-Jun, JunB and Fra1, but not c-Fos, are required for TGFß-induced binding of Smad2/3 to the mmp-10 and pai-1 promoters. Together these results suggest that in particular formation of Smad2/3-Fra1 complexes may reflect activation of the Smad/AP-1-dependent TGFß-induced invasion program.

The prognostic role of TGF-ß signaling pathway in breast cancer patients.

BACKGROUND: The transforming growth factor-ß (TGF-ß) pathway has dual effects on tumor growth. Seemingly, discordant results have been published on the relation between TGF-ß signaling markers and prognosis in breast cancer. Improved prognostic information for breast cancer patients might be obtained by assessing interactions among TGF-ß signaling biomarkers. PATIENTS AND METHODS: The expression of nuclear Smad4, nuclear phosphorylated-Smad2 (p-Smad2), and the membranous expression of TGF-ß receptors I and II (TßRI and TßRII) was determined on a tissue microarray of 574 breast carcinomas. Tumors were stratified according to the Smad4 expression in combination with p-Smad2 expression or Smad4 in combination with the expression of both TGF-ß receptors. RESULTS: Tumors with high expression of TßRII, TßRI and TßRII, and p-Smad2 (P = 0.018, 0.005, and 0.022, respectively), and low expression of Smad4 (P = 0.005) had an unfavorable prognosis concerning progression-free survival. Low Smad4 expression combined with high p-Smad2 expression or low expression of Smad4 combined with high expression of both TGF-ß receptors displayed an increased hazard ratio of 3.04 [95% confidence interval (CI) 1.390-6.658] and 2.20 (95% CI 1.464-3.307), respectively, for disease relapse. CONCLUSIONS: Combining TGF-ß biomarkers provides prognostic information for patients with stage I-III breast cancer. This can identify patients at increased risk for disease recurrence that might therefore be candidates for additional treatment.

Visualizing TGF-ß and BMP signaling in human atherosclerosis: a histological evaluation based on Smad activation.

BACKGROUND: The TGF-ß superfamily members transforming growth factor-ß (TGF-ß/Activin) and bone morphogenetic proteins (BMP) have been implicated in the pathogenesis of atherosclerosis. However, their role in human disease remains controversial. In this study we used Smad phosphorylation as a read out for TGF-ß and BMP signaling during the initiation, progression and (de)stabilization of human atherosclerotic disease. MATERIAL AND METHODS: A systematic analysis was performed in 114 peri-renal aortic patches (stained with Movat Pentachrome, H&E, pSmad2, pSmad1,5,8 and PAI-1) covering the entire atherosclerotic spectrum (van Dijk, 2010). Immunostaining against T-cells (CD3) and monocytes and macrophages (CD68) was used to explore a putative association between TGF-ß and BMP signaling and vascular inflammation. RESULTS: Smad phosphorylation was present within the normal arterial wall in approximately 10% of the endothelial cells and intimal smooth muscle cells. A significant increase in pSmad2 and pSmad1,5,8 positivity was found in non-progressive lesions (>50% positivity). No further increase or decrease was found in the progressive atherosclerotic lesions, vulnerable and stabilized lesions. No association was found between TGF-ß and BMP signaling and CD3 and CD68 expression, nor cap thickness. CONCLUSION: Activation of the TGF-ß and BMP pathways is an early event in atherosclerotic lesion formation. No significant relationships were found between Smad phosphorylation and vessel wall inflammation or plaque vulnerability.

Critical role of endoglin in tumor cell plasticity of Ewing sarcoma and melanoma.

Tumor cell plasticity enables certain types of highly malignant tumor cells to dedifferentiate and engage a plastic multipotent embryonic-like phenotype, which enables them to 'adapt' during tumor progression and escape conventional therapeutic strategies. This plastic phenotype of aggressive cancer cells enables them to express endothelial cell-specific markers and form tube-like structures, a phenotype that has been linked to aggressive behavior and poor prognosis. We demonstrate here that the transforming growth factor (TGF)-ß co-receptor endoglin, an endothelial cell marker, is expressed by tumor cells and its expression correlates with tumor cell plasticity in two types of human cancer, Ewing sarcoma and melanoma. Moreover, endoglin expression was significantly associated with worse survival of Ewing sarcoma patients. Endoglin knockdown in tumor cells interferes with tumor cell plasticity and reduces invasiveness and anchorage-independent growth in vitro. Ewing sarcoma and melanoma cells with reduced endoglin levels showed reduced tumor growth in vivo. Mechanistically, we provide evidence that endoglin, while interfering with TGF-ß signaling, is required for efficient bone morphogenetic protein, integrin, focal adhesion kinase and phosphoinositide-3-kinase signaling in order to maintain tumor cell plasticity. The present study delineates an important role of endoglin in tumor cell plasticity and progression of aggressive tumors.

Smad2 and Smad3 have opposing roles in breast cancer bone metastasis by differentially affecting tumor angiogenesis.

Transforming growth factor (TGF)-beta can suppress and promote breast cancer progression. How TGF-beta elicits these dichotomous functions and which roles the principle intracellular effector proteins Smad2 and Smad3 have therein, is unclear. Here, we investigated the specific functions of Smad2 and Smad3 in TGF-beta-induced responses in breast cancer cells in vitro and in a mouse model for breast cancer metastasis. We stably knocked down Smad2 or Smad3 expression in MDA-MB-231 breast cancer cells. The TGF-beta-induced Smad3-mediated transcriptional response was mitigated and enhanced by Smad3 and Smad2 knockdown, respectively. This response was also seen for TGF-beta-induced vascular endothelial growth factor (VEGF) expression. TGF-beta induction of key target genes involved in bone metastasis, were found to be dependent on Smad3 but not Smad2. Strikingly, whereas knockdown of Smad3 in MDA-MB-231 resulted in prolonged latency and delayed growth of bone metastasis, Smad2 knockdown resulted in a more aggressive phenotype compared with control MDA-MB-231 cells. Consistent with differential effects of Smad knockdown on TGF-beta-induced VEGF expression, these opposing effects of Smad2 versus Smad3 could be directly correlated with divergence in the regulation of tumor angiogenesis in vivo. Thus, Smad2 and Smad3 differentially affect breast cancer bone metastasis formation in vivo.

Role of TGF-beta in the tumor stroma.

Recent findings have demonstrated that the tumor stroma actively contributes to tumorigenesis. The communication of malignant cells and tumor stromal components is orchestrated in part by a network of growth factors. One of these growth factors is transforming growth factor-beta (TGF-beta), a secreted multifunctional protein that acts in a highly cellular contextual manner. TGF-beta can either stimulate or inhibit the tumor-promoting effects of the different components of the tumor stroma. In this review, we discuss our current understanding on how TGF-beta influences different stromal compartments.

Oral administration of GW788388, an inhibitor of TGF-beta type I and II receptor kinases, decreases renal fibrosis.

Progressive kidney fibrosis precedes end-stage renal failure in up to a third of patients with diabetes mellitus. Elevated intra-renal transforming growth factor-beta (TGF-beta) is thought to underlie disease progression by promoting deposition of extracellular matrix and epithelial-mesenchymal transition. GW788388 is a new TGF-beta type I receptor inhibitor with a much improved pharmacokinetic profile compared with SB431542. We studied its effect in vitro and found that it inhibited both the TGF-beta type I and type II receptor kinase activities, but not that of the related bone morphogenic protein type II receptor. Further, it blocked TGF-beta-induced Smad activation and target gene expression, while decreasing epithelial-mesenchymal transitions and fibrogenesis. Using db/db mice, which develop diabetic nephropathy, we found that GW788388 given orally for 5 weeks significantly reduced renal fibrosis and decreased the mRNA levels of key mediators of extracellular matrix deposition in kidneys. Our study shows that GW788388 is a potent and selective inhibitor of TGF-beta signalling in vitro and renal fibrosis in vivo.

BMP-9 signals via ALK1 and inhibits bFGF-induced endothelial cell proliferation and VEGF-stimulated angiogenesis.

Genetic studies in mice and humans have shown that the transforming growth factor-beta (TGF-beta) type-I receptor activin receptor-like kinase 1 (ALK1) and its co-receptor endoglin play an important role in vascular development and angiogenesis. Here, we demonstrate that ALK1 is a signalling receptor for bone morphogenetic protein-9 (BMP-9) in endothelial cells (ECs). BMP-9 bound with high affinity to ALK1 and endoglin, and weakly to the type-I receptor ALK2 and to the BMP type-II receptor (BMPR-II) and activin type-II receptor (ActR-II) in transfected COS cells. Binding of BMP-9 to ALK2 was greatly facilitated when BMPR-II or ActR-II were co-expressed. Whereas BMP-9 predominantly bound to ALK1 and BMPR-II in ECs, it bound to ALK2 and BMPR-II in myoblasts. In addition, we observed binding of BMP-9 to ALK1 and endoglin in glioblastoma cells. BMP-9 activated Smad1 and/or Smad5, and induced ID1 protein and endoglin mRNA expression in ECs. Furthermore, BMP-9 was found to inhibit basic fibroblast growth factor (bFGF)-stimulated proliferation and migration of bovine aortic ECs (BAECs) and to block vascular endothelial growth factor (VEGF)-induced angiogenesis. Taken together, these results suggest that BMP-9 is a physiological ALK1 ligand that plays an important role in the regulation of angiogenesis.

Reversible ubiquitination regulates the Smad/TGF-beta signalling pathway.

TGF-beta (transforming growth factor-beta) signals through serine/threonine kinase receptors and intracellular Smad transcription factors. An important regulatory step involves specific ubiquitination by Smurfs (Smad-ubiquitin regulatory factors), members of the HECT (homologous to E6-associated protein C-terminus) ubiquitin ligase family, which mediate the proteasomal degradation of Smads and/or receptors. Recently, we have defined a novel interaction between Smads and UCH37 (ubiquitin C-terminal hydrolase 37), a DUB (de-ubiquitinating enzyme) that could potentially counteract Smurf-mediated ubiquitination. We have demonstrated specific interactions between UCH37 and inhibitory Smad7, as well as weaker associations with Smad2 and Smad3. Importantly, Smad7 can act as an adaptor able to recruit UCH37 to the type I TGF-beta receptor. Consequently, UCH37 dramatically up-regulates TGF-beta-dependent gene expression by de-ubiquitinating and stabilizing the type I TGF-beta receptor. Our findings suggest that competing effects of ubiquitin ligases and DUBs in complex with Smad7 can serve to fine-tune responses to TGF-betas under various physiological and pathological conditions. Studies are currently under way using activity-based HA (haemagglutinin)-tagged ubiquitin probes to identify the full spectrum of DUBs that impact on Smad/TGF-beta signalling activity.

Bone morphogenetic protein signal transduction in bone.

Bone morphogenetic proteins (BMPs) promote bone formation by stimulating the proliferation and differentiation of osteoblasts. It has been suggested that non-union of the bone, and delayed healing, may be the result of decreased levels of BMP activity. Activation of BMP receptors initiates phosphorylation of the downstream effector proteins, known as receptor-regulated Smads, leading to signal transduction. Receptor-regulated Smads form a hetero-oligomeric complex with a common mediator Smad, which translocates into the nucleus and regulates target gene transcription. The BMP signalling cascade is closely regulated, with the inhibitory Smads blocking the intracellular signal cascade. Extracellular antagonists, such as noggin, inhibit binding to BMP receptors. BMP-2 and BMP-7 have demonstrated clinical utility for bone regeneration, and are commercially available through the use of recombinant DNA technology.