Transforming growth factor-beta: latent forms, binding proteins and receptors

Advances and Challenges in Targeting TGF-β Isoforms for Therapeutic Intervention of Cancer: A Mechanism-Based Perspective

The TGF-β family is a group of 25 kDa secretory cytokines, in mammals consisting of three dimeric isoforms (TGF-βs 1, 2, and 3), each encoded on a separate gene with unique regulatory elements. Each isoform plays unique, diverse, and pivotal roles in cell growth, survival, immune response, and differentiation. However, many researchers in the TGF-β field often mistakenly assume a uniform functionality among all three isoforms. Although TGF-βs are essential for normal development and many cellular and physiological processes, their dysregulated expression contributes significantly to various diseases. Notably, they drive conditions like fibrosis and tumor metastasis/progression. To counter these pathologies, extensive efforts have been directed towards targeting TGF-βs, resulting in the development of a range of TGF-β inhibitors. Despite some clinical success, these agents have yet to reach their full potential in the treatment of cancers. A significant challenge rests in effectively targeting TGF-βs' pathological functions while preserving their physiological roles. Many existing approaches collectively target all three isoforms, failing to target just the specific deregulated ones. Additionally, most strategies tackle the entire TGF-β signaling pathway instead of focusing on disease-specific components or preferentially targeting tumors. This review gives a unique historical overview of the TGF-β field often missed in other reviews and provides a current landscape of TGF-β research, emphasizing isoform-specific functions and disease implications. The review then delves into ongoing therapeutic strategies in cancer, stressing the need for more tools that target specific isoforms and disease-related pathway components, advocating mechanism-based and refined approaches to enhance the effectiveness of TGF-β-targeted cancer therapies.

Multifaceted TGF-β signaling, a master regulator: From bench-to-bedside, intricacies, and complexities

Physiological embryogenesis and adult tissue homeostasis are regulated by transforming growth factor-β (TGF-β), an evolutionarily conserved family of secreted polypeptide factors, acting in an autocrine and paracrine manner. The role of TGF-β in inflammation, fibrosis, and cancer is complex and sometimes even contradictory, exhibiting either inhibitory or promoting effects depending on the stage of the disease. Under pathological conditions, especially fibrosis and cancer, overexpressed TGF-β causes extracellular matrix deposition, epithelial-mesenchymal transition, cancer-associated fibroblast formation, and/or angiogenesis. In this review article, we have tried to dive deep into the mechanism of action of TGF-β in inflammation, fibrosis, and carcinogenesis. As TGF-β and its downstream signaling mechanism are implicated in fibrosis and carcinogenesis blocking this signaling mechanism appears to be a promising avenue. However, targeting TGF-β carries substantial risk as this pathway is implicated in multiple homeostatic processes and is also known to have tumor-suppressor functions. There is a need for careful dosing of TGF-β drugs for therapeutic use and patient selection.

Mutual regulation between glycosylation and transforming growth factor-β isoforms signaling pathway

Transforming growth factor-beta (TGF-β) superfamily members orchestrate a wide breadth of biological processes. Through Sma and Mad (Smad)-related dependent or noncanonical pathways, TGF-β members involve in the occurrence and development of many diseases such as cancers, fibrosis, autoimmune diseases, cardiovascular diseases and brain diseases. Glycosylation is one kind of the most common posttranslational modifications on proteins or lipids. Abnormal protein glycosylation can lead to protein malfunction and biological process disorder, thereby causing serious diseases. Previously, researchers commonly make comprehensive systematic overviews on the roles of TGF-β signaling in a specific disease or biological process. In recent years, more and more evidences associate glycosylation modification with TGF-β signaling pathway, and we can no longer disengage and ignore the roles of glycosylation from TGF-β signaling to make investigation. In this review, we provide an overview of current findings involved in glycosylation within TGF-βs and theirs receptors, and the interaction effects between glycosylation and TGF-β subfamily signaling, concluding that there is an intricate mutual regulation between glycosylation and TGF-β signaling, hoping to present the glycosylation regulatory patterns that concealed in TGF-βs signaling pathways.

Activated CTLA-4-independent immunosuppression of Treg cells disturbs CTLA-4 blockade-mediated antitumor immunity

Combination therapy with anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and anti-programmed death-1 (PD-1) monoclonal antibodies (mAbs) has dramatically improved the prognosis of patients with multiple types of cancer, including renal cell carcinoma (RCC). However, more than half of RCC patients fail to respond to this therapy. Regulatory T cells (Treg cells) are a subset of highly immunosuppressive CD4⁺ T cells that promote the immune escape of tumors by suppressing effector T cells in the tumor microenvironment (TME) through various mechanisms. CTLA-4 is constitutively expressed in Treg cells and is regarded as a key molecule for Treg-cell-mediated immunosuppressive functions, suppressing antigen-presenting cells by binding to CD80/CD86. Reducing Treg cells in the TME with an anti-CTLA-4 mAb with antibody-dependent cellular cytotoxicity (ADCC) activity is considered an essential mechanism to achieve tumor regression. In contrast, we demonstrated that CTLA-4 blockade without ADCC activity enhanced CD28 costimulatory signaling pathways in Treg cells and promoted Treg-cell proliferation in mouse models. CTLA-4 blockade also augmented CTLA-4-independent immunosuppressive functions, including cytokine production, leading to insufficient antitumor effects. Similar results were also observed in human peripheral blood lymphocytes and tumor-infiltrating lymphocytes from patients with RCC. Our findings highlight the importance of Treg-cell depletion to achieve tumor regression in response to CTLA-4 blockade therapies.

Diacerein ameliorates kidney injury induced by cisplatin in rats by activation of Nrf2/Ho-1 pathway and Bax down-regulation

Cisplatin is an antineoplastic medicine used for solid tumor treatment. The main side effect that limits its dose is nephrotoxicity. Diacerein has been used for the treatment of joint diseases like osteoarthritis. It also has exhibited analgesic effects and antipyretic activities in animal models so this study targets to indicate the diacerein effect on nephrotoxicity induced by cisplatin in rats. Rats were distributed into four groups: normal healthy control; diacerein, which received diacerein daily by gastric gavage (50 mg/kg/day); cisplatin, which received only one intraperitoneal injection of cisplatin (6 mg/kg) and cisplatin and diacerein, which received diacerein daily after the cisplatin injection till 7th and 12th days, respectively. Diacerein treatment decreased kidney function markers so the cisplatin effect was reversed. Also, diacerein increased the renal antioxidants and decreased oxidative stress. Diacerein up-regulated Ho-1 (heme oxygenase 1), Nrf2 (Nuclear factor erythroid 2–related factor 2) and endothelial nitric oxide synthase (eNOS) genes expression, while down-regulated Bcl-2-associated X protein (Bax) gene expression. Furthermore, the renal transforming growth factor beta-1 (TGF-β1) decreased by the diacerein effect. Consequently, diacerein has a curative effect against cisplatin due to its anti-inflammatory, antioxidant, and antiapoptotic properties.

Reprogramming oral epithelial keratinocytes into a pluripotent phenotype for tissue regeneration

Objectives

We set out to reprogram adult somatic oral epithelial keratinocytes into pluripotent cells for regenerative dentistry.

Setting and Sample population

Immortalized murine oral keratinocyte cell (IMOK) line raised from adult mouse mucosa were cultured in vitro in our studies.

Materials and Methods

Adult murine oral epithelial keratinocytes were chronically treated with TGF‐β1 in vitro, and the expression of Oct4, Nanog, Sox2 and Nestin, as well as specific homeobox Gata and Pax gene family members were investigated.

Results

We documented the induction of stem factors linked with pluripotency and/or the maintenance and regulation of stem‐cell self‐renewal in oral epithelial keratinocytes by TGFβ1. Moreover, we discovered that this TGF‐β1‐induced increase in Oct4, Nanog, Sox2 and Nestin was inhibited by SB431542, suggesting that TGF‐β1 signals via the TGF‐βRI receptor to induce pluripotency and stemness.

Conclusions

Adult oral epithelial keratinocytes treated chronically with TGF‐β1 acquired phenotypic characteristics consistent with pluripotent stem cells, highlighting the facileness of reprogramming adult oral keratinocytes into an unlimited supply of pluripotent stem cells.

Interaction Networks Converging on Immunosuppressive Roles of Granzyme B: Special Niches Within the Tumor Microenvironment

Granzyme B is a renowned effector molecule primarily utilized by CTLs and NK cells against ill-defined and/or transformed cells during immunosurveillance. The overall expression of granzyme B within tumor microenvironment has been well-established as a prognostic marker indicative of priming immunity for a long time. Until recent years, increasing immunosuppressive effects of granzyme B are unveiled in the setting of different immunological context. The accumulative evidence confounded the roles of granzyme B in immune responses, thereby arousing great interests in characterizing detailed feature of granzyme B-positive niche. In this paper, the granzyme B-related regulatory effects of major suppressor cells as well as the tumor microenvironment that defines such functionalities were longitudinally summarized and discussed. Multiplex networks were built upon the interactions among different transcriptional factors, cytokines, and chemokines that regarded to the initiation and regulation of granzyme B-mediated immunosuppression. The conclusions and prospect may facilitate better interpretations of the clinical significance of granzyme B, guiding the rational development of therapeutic regimen and diagnostic probes for anti-tumor purposes.

TGFB1/INHBA Homodimer/Nodal-SMAD2/3 Signaling Network: A Pivotal Molecular Target in PDAC Treatment

Pancreatic cancer remains a grueling disease that is projected to become the second-deadliest cancer in the next decade. Standard treatment of pancreatic cancer is chemotherapy, which mainly targets the differentiated population of tumor cells; however, it paradoxically sets the roots of tumor relapse by the selective enrichment of intrinsically chemoresistant pancreatic cancer stem cells that are equipped with an indefinite capacity for self-renewal and differentiation, resulting in tumor regeneration and an overall anemic response to chemotherapy. Crosstalk between pancreatic tumor cells and the surrounding stromal microenvironment is also involved in the development of chemoresistance by creating a supportive niche, which enhances the stemness features and tumorigenicity of pancreatic cancer cells. In addition, the desmoplastic nature of the tumor-associated stroma acts as a physical barrier, which limits the intratumoral delivery of chemotherapeutics. In this review, we mainly focus on the transforming growth factor beta 1 (TGFB1)/inhibin subunit beta A (INHBA) homodimer/Nodal-SMAD2/3 signaling network in pancreatic cancer as a pivotal central node that regulates multiple key mechanisms involved in the development of chemoresistance, including enhancement of the stem cell-like properties and tumorigenicity of pancreatic cancer cells, mediating cooperative interactions between pancreatic cancer cells and the surrounding stroma, as well as regulating the deposition of extracellular matrix proteins within the tumor microenvironment.

Proprotein convertases: Key players in inflammation-related malignancies and metastasis

Many cancers occur from locations of inflammation due to chronic irritation and/or infection. Tumor microenvironment contains various different inflammatory cells and mediators that orchestrate diverse neoplastic processes, including proliferation, survival, adhesion and migration. In parallel, tumor cells have adapted some of the signaling molecules used by inflammatory cells, such as selectins and chemokines as well as their receptors for invasion, extravasation and subsequently metastasis. Expression and/or activation of the majority of these molecules is mediated by the proprotein convertases (PCs); proteases expressed by both tumor cells and inflammatory cells. This review analyzes the potential role of these enzymatic system in inflammation-associated cancer impacting on the malignant and metastatic potential of cancer cells, describing the possible use of PCs as a new anti-inflammatory therapeutic approach to tumor progression and metastasis.

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Proteins maturation by the proprotein convertases plays important role in inflammation-related cancer and metastasis.

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Protein precursors require the proprotein convertases for the induction of inflammation.

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Understanding of the molecular mechanism linking the proprotein convertases to inflammation will allow novel therapies.

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Inhibitors of the proprotein convertases constitute great potential for cancer treatment.

Role of Matrix Metalloproteinase-2 in Eosinophil-Mediated Airway Remodeling

Airway remodeling is responsible for the progressive decline of lung function in bronchial asthma. Matrix metalloproteinase-2 and fibroblast-to-myofibroblast transition are involved in tissue remodeling. Here we evaluated whether eosinophils play a role in fibroblasts-to-myofibroblasts transition and in the expression of matrix metalloproteinase-2. We co-cultured human eosinophils with human fetal lung fibroblast-1 cells, assessed the expression of remodeling-associated molecules by immunoassays and polymerase-chain reaction, and eosinophils-mediated migration of human fetal lung fibroblast-1 cells using a Boyden chamber. To clarify the participation of matrix metalloproteinase-2 in airway remodeling we administered bone marrow-derived eosinophils by intra-tracheal route to transgenic mice overexpressing the human matrix metalloproteinase-2. The expression of α-smooth muscle actin significantly increased in human fetal lung fibroblast-1 cells co-cultured with human eosinophils compared to controls. There was enhanced expression of matrix metalloproteinase-2 during fibroblast-to-myofibroblast transition. An inhibitor of matrix metalloproteinases blocked eosinophils-associated fibroblast-to-myofibroblast transition and increased migration of fibroblasts. The human matrix metalloproteinase-2 transgenic mice receiving adoptive transfer of mouse eosinophils exhibited increased inflammation and advanced airway remodeling compared to wild type mice. This study demonstrated that eosinophils induce fibroblast-to-myofibroblast transition, secretion of matrix metalloproteinase-2, accelerated migration of fibroblasts, and promote matrix metalloproteinase-2-related airway remodeling. These findings provide a novel mechanistic pathway for eosinophil-associated airway remodeling in bronchial asthma.

LAP+CD4+ T cells are elevated among the peripheral blood mononuclear cells and tumor tissue of patients with hepatocellular carcinoma

The purpose of the present study was to investigate the role of latency-associated peptide (LAP)⁺CD4⁺T cells in hepatocellular carcinoma (HCC) immunity. Flow cytometric analysis was performed to detect the proportion of LAP⁺CD4⁺ T cells among the peripheral blood mononuclear cells (PBMCs) of 30 HBV-infected HCC patients at the pre-operative and post-operative stages, as well as 30 hepatitis B virus (HBV)-infected volunteers as a control group. Furthermore, tumor tissues and peri-tumor tissues from 28 patients with HCC, as well as hepatic tissues from 28 HBV-infected patients with benign lesions were subjected to immunohistochemical analysis with double staining for LAP and CD4, and the average number of the LAP⁺CD4⁺T cells in each visual field was quantified. The results indicated that the proportion of LAP+CD4+ T cells in the PBMCs of patients with HCC was significantly higher than that in the control group (1.84±0.85 vs. 0.73±0.39%, P=0.019), while it was significantly reduced after the operation (1.07±0.35, P=0.021), but still slightly, if not significantly, higher compared with that in the control group (P=0.342). Furthermore, the number of LAP⁺CD4⁺ T cells per high-magnification microscopic field (magnification, ×400) in the HCC tissues was 11.25±3.00, which was significantly higher than that in the peri-cancer tissues (5.75±1.00) and that in the HBV-infected hepatic tissues around benign lesions (2.61±0.83). In peri-cancer tissues, LAP⁺CD4⁺ T cells were also significantly more abundant than in control tissues. Furthermore, in the HCC tissues, LAP⁺CD4⁺ T cells were present as clusters in the tumor stroma and closely associated with CD4⁺ T lymphocytes. By contrast, in the peri-cancer liver tissues and HBV-infected hepatic tissues around benign lesions, LAP⁺CD4⁺ T cells were sparsely distributed. LAP⁺CD4⁺ T cells have marked inhibitory effects, and in the peripheral blood and tumor tissues of patients with HCC, they have an important role in the suppression of anti-tumor immunity and in the immune evasion of tumor cells.

CD4⁺ T cells expressing latency-associated peptide and Foxp3 are an activated subgroup of regulatory T cells enriched in patients with colorectal cancer

Latency-associated peptide (LAP) - expressing regulatory T cells (Tregs) are important for immunological self-tolerance and immune homeostasis. In order to investigate the role of LAP in human CD4⁺Foxp3⁺ Tregs, we designed a cross-sectional study that involved 42 colorectal cancer (CRC) patients. The phenotypes, cytokine-release patterns, and suppressive ability of Tregs isolated from peripheral blood and tumor tissues were analyzed. We found that the population of LAP-positive CD4⁺Foxp3⁺ Tregs significantly increased in peripheral blood and cancer tissues of CRC patients as compared to that in the peripheral blood and tissues of healthy subjects. Both LAP⁺ and LAP⁻ Tregs had a similar effector/memory phenotype. However, LAP⁺ Tregs expressed more effector molecules, including tumor necrosis factor receptor II, granzyme B, perforin, Ki67, and CCR5, than their LAP⁻ negative counterparts. The in vitro immunosuppressive activity of LAP⁺ Tregs, exerted via a transforming growth factor-β–mediated mechanism, was more potent than that of LAP⁻ Tregs. Furthermore, the enrichment of LAP⁺ Treg population in peripheral blood mononuclear cells (PBMCs) of CRC patients correlated with cancer metastases. In conclusion, we found that LAP⁺ Foxp3⁺ CD4⁺ Treg cells represented an activated subgroup of Tregs having more potent regulatory activity in CRC patients. The increased frequency of LAP⁺ Tregs in PBMCs of CRC patients suggests their potential role in controlling immune response to cancer and presents LAP as a marker of tumor-specific Tregs in CRC patients.

TGF-β-dependent induction of CD4⁺CD25⁺Foxp3⁺ Tregs by liver sinusoidal endothelial cells

BACKGROUND & AIMS

CD4(+) CD25(+) Foxp3(+) regulatory T cells (Tregs) have a profound ability to control immune responses. We have previously shown that the liver is a major source of peripherally induced Tregs. Here, we investigate the liver cell types and molecular mechanisms responsible for hepatic Treg induction.

METHODS

To assess the Treg-inducing potential of liver resident antigen-presenting cell types, we studied the conversion of Foxp3(-) non-Tregs into Foxp3(+) Tregs induced by liver dendritic cells (DCs), liver sinusoidal endothelial cells (LSECs), or Kupffer cells (KCs). The dependency of Treg induction on TGF-β was tested in Treg conversion assays using T cells with reduced TGF-β sensitivity. The suppressive potential of liver cell-induced Tregs was assessed by an in vitro suppression assay and in vivo, in the model of experimental autoimmune encephalomyelitis (EAE).

RESULTS

All tested liver cell types were capable of inducing Foxp3(+) Tregs; however, LSECs were most efficient in inducing Tregs. Treg-induction was antigen-specific and depended on TGF-β. LSECs featured membrane-bound LAP/TGF-β and the anchor molecule GARP, which is required for tethering LAP/TGF-β to the cell membrane. LSEC-induced Tregs suppressed proliferation and cytokine secretion of effector T cells in vitro. LSEC-induced Tregs were also functional suppressors in vivo, as neuroantigen-specific Tregs induced by LSECs were able to suppress EAE.

CONCLUSIONS

We demonstrate that LSECs are the major liver cell type responsible for TGF-β dependent hepatic Treg induction. The extraordinary capacity of LSECs to induce Tregs was associated with their unique ability to tether TGF-β to their membrane.

Endothelial cell TIMP-1 is upregulated by shear stress via Sp-1 and the TGFβ1 signaling pathways

Laminar shear stress promotes vascular integrity by inhibiting proteolysis of the extracellular matrix (ECM) surrounding the microvasculature. We hypothesized that the matrix metalloproteinase inhibitor TIMP-1 would be upregulated in endothelial cells exposed to shear stress. Microvascular endothelial cells isolated from rat or mouse skeletal muscles were exposed to laminar shear stress for 2, 4, or 24 h. A biphasic increase in TIMP-1 protein was observed at 2 and 24 h of shear stress exposure. Sp-1 siRNA prevented the increase in TIMP-1 after 2, but not 24, hours of shear exposure. TGFβ production and Smad2/3 phosphorylation are increased by shear stress. Inhibition of TGFβ signaling, either by use of the TGFβ receptor 1 inhibitor SB-431542 or with Smad 2/3 siRNA, abrogated the shear stress-induced increase in TIMP-1 mRNA after 24 h of shear stress exposure. These results suggest that both acute and chronic elevated laminar shear stress act to maintain vessel integrity through increasing TIMP-1 production, but that the TGFβ signaling pathway is essential to maintain TIMP-1 expression during chronic shear stress.

Transforming growth factor-beta 1 (TGF-B1) liberation from its latent complex during embryo implantation and its regulation by estradiol in mouse

Transforming growth factor-beta (TGF-B) plays an important role in embryo implantation; however, TGF-B requires liberation from its inactive latent forms (i.e., large latent TGF-B complex [LLC] and small latent TGF-B complex [SLC]) to its biologically active (i.e., monomer or dimer) forms in order to act on its receptors (TGF-BRs), which in turn activate SMAD2/3. Activation of TGF-B1 from its latent complexes in the uterus is not yet deciphered. We investigated uterine latent TGF-B1 complex and its biologically active form during implantation, decidualization, and delayed implantation. Our study, utilizing nonreducing SDS-PAGE followed by Western blotting and immunoblotting with TGF-B1, LTBP1, and latency-associated peptide, showed the presence of LLC and SLC in the uterine extracellular matrix and plasma membranous protein fraction during stages of the implantation period. A biologically active form of TGF-B1 (~17-kDa monomer) was highly elevated in the uterine plasma membranous compartment at the peri-implantation stage (implantation and nonimplantation sites). Administration of hydroxychloroquine (an inhibitor of pro-TGF-B processing) at the preimplantation stage was able to block the liberation of biologically active TGF-B1 from its latent complex at the postimplantation stage; as a consequence, the number of implantation sites was reduced at Day 5 (1000 h), as was the number of fetuses at Day 13. The inhibition of TGF-B1 showed reduced levels of phosphorylated SMAD3. Further, the delayed-implantation mouse model showed progesterone and estradiol coordination to release the active TGF-B1 form from its latent complex in the receptive endometrium. This study demonstrates the importance of liberation of biologically active TGF-B1 during the implantation period and its regulation by estradiol.

The Dual Role of TGFβ in Human Cancer: From Tumor Suppression to Cancer Metastasis

The transforming growth factor-beta (TGFβ) superfamily encompasses widespread and evolutionarily conserved polypeptide growth factors that regulate and orchestrate growth and differentiation in all cell types and tissues. While they regulate asymmetric cell division and cell fate determination during early development and embryogenesis, TGFβ family members play a major regulatory role in hormonal and immune responses, cell growth, cell death and cell immortalization, bone formation, tissue remodeling and repair, and erythropoiesis throughout adult life. The biological and physiological functions of TGFβ, the founding member of this family, and its receptors are of central importance to human diseases, particularly cancer. By regulating cell growth, death, and immortalization, TGFβ signaling pathways exert tumor suppressor effects in normal cells and early carcinomas. Thus, it is not surprising that a high number of human tumors arise due to mutations or deletions in the genes coding for the various TGFβ signaling components. As tumors develop and progress, these protective and cytostatic effects of TGFβ are often lost. TGFβ signaling then switches to promote cancer progression, invasion, and tumor metastasis. The molecular mechanisms underlying this dual role of TGFβ in human cancer will be discussed in depth in this paper, and it will highlight the challenge and importance of developing novel therapeutic strategies specifically aimed at blocking the prometastatic arm of the TGFβ signaling pathway without affecting its tumor suppressive effects.

Shearing of synovial fluid activates latent TGF-β

OBJECTIVE

TGF-β is synthesized in an inactive latent complex that is unable to bind to membrane receptors, thus unable to induce a cellular biological response until it has been activated. In addition to activation by chemical mediators, recent studies have demonstrated that mechanical forces may activate latent TGF-βvia integrin-mediated cellular contractions, or mechanical shearing of blood serum. Since TGF-β is present in synovial fluid in latent form, and since normal diarthrodial joint function produces fluid shear, this study tested the hypothesis that the native latent TGF-β1 of synovial fluid can be activated by shearing.

DESIGN

Synovial fluid from 26 bovine joints and three adult human joints was sheared at mean shear rates up to 4000 s(-1) for up to 15 h.

RESULTS

Unsheared synovial fluid was found to contain high levels of latent TGF-β1 (4.35 ± 2.02 ng/mL bovine, 1.84 ± 0.89 ng/mL human; mean ± radius of 95% confidence interval) and low amounts (<0.05 ng/mL) of the active peptide. Synovial fluid concentrations of active TGF-β1 increased monotonically with shear rate and shearing duration, reaching levels of 2.64 ± 1.22 ng/mL for bovine and 0.60 ± 0.39 ng/mL for human synovial fluid. Following termination of shearing, there was no statistical change in these active levels over the next 8 h for either species, demonstrating long-term stability of the activated peptide. The unsheared control group continued to exhibit negligible levels of active TGF-β1 at all times.

CONCLUSIONS

Results confirmed the hypothesis of this study and suggest that shearing of synovial fluid might contribute an additional biosynthetic effect of mechanical loading of diarthrodial joints.

LAP+CD4+ T cells are suppressors accumulated in the tumor sites and associated with the progression of colorectal cancer

PURPOSE

Suppressor T cells are one of the determinants of colorectal cancer (CRC) clinical outcome. LAP(+)CD4(+) T cell is a recently identified subset of suppressor T cells. This study was designed to investigate their clinical relevance in patients with CRC.

EXPERIMENTAL DESIGN

Sixty patients with CRC and 24 healthy donors (HD) were enrolled in this study. The percentages of LAP(+)CD4(+) T cells in peripheral blood and tumor tissue were measured. The phenotype and functional relevance of LAP(+)CD4(+) T cells were analyzed subsequently.

RESULTS

The percentages of LAP(+)CD4(+) T cells in peripheral blood of patients with CRC were significantly higher than HD (HD vs. CRC: 3.1% ± 0.78% vs. 8.8% ± 5.8%, P < 0.0001) and in tumor tissue when compared with nontumor tissue (nontumor vs. tumor: 3.2% ± 1.1% vs. 9.5% ± 5.5%, P = 0.0002). In addition, LAP(+)CD4(+) T cells with effector memory (EM) phenotype were more likely to accumulate in the tumor sites than in peripheral blood. These LAP(+)CD4(+) T cells produced significantly higher levels of IFN-γ, IL-17 and comparatively lower IL-2 and very few IL-10. LAP(+)CD4(+) T cells could suppress the proliferation of LAP(-)CD4(+) T cells that were partially mediated by TGF-β. Furthermore, these LAP(+)CD4(+) T cells accumulated in tumor site and increased further in the peripheral blood in patients with metastasis.

CONCLUSIONS

LAP(+)CD4(+) T cells as a suppressor subset could accumulate in the tumor microenvironment and circulated more in the peripheral blood with tumor progression in patients with CRC.

T cell- but not tumor cell-produced TGF-β1 promotes the development of spontaneous mammary cancer

During their development, tumors acquire multiple capabilities that enable them to proliferate, disseminate and evade immunosurveillance. A putative mechanism is through the production of the cytokine TGF-β1. We showed in our recent studies that T cell-produced TGF-β1 inhibits antitumor T cell responses to foster tumor growth raising the question of the precise function of TGF-β1 produced by tumor cells in tumor development. Here, using a transgenic model of mammary cancer, we report that deletion of TGF-β1 from tumor cells did not protect mice from tumor development. However, ablation of TGF-β1 from T cells significantly inhibited mammary tumor growth. Additionally, absence of TGF-β1 in T cells prevented tumors from advancing to higher pathological grades and further suppressed secondary tumor development in the lungs. These findings reveal T cells but not tumor cells as a critical source of TGF-β1 that promotes tumor development.

Murine CD4 T cells produce a new form of TGF-β as measured by a newly developed TGF-β bioassay

BACKGROUND

It is generally assumed that T cells do not produce active TGF-β since active TGF-β as measured in supernatants by ELISA without acidification is usually not detectable. However, it is possible that active TGF-β from T cells may take a special form which is not detectable by ELISA.

METHODOLOGY/PRINCIPAL FINDINGS

We constructed a TGF-β bioassay which can detect both soluble and membrane-bound forms of TGF-β from T cells. For this bioassay, 293T cells were transduced with (caga)(12) Smad binding element-luciferase along with CD32 (Fc receptor) and CD86. The resulting cells act as artificial antigen presenting cells in the presence of anti-CD3 and produce luciferase in response to biologically active TGF-β. We co-cultured pre-activated murine CD4(+)CD25(-) T cells or CD4(+)CD25(+) T cells with the 293T-caga-Luc-CD32-CD86 reporter cells in the presence of anti-CD3 and IL-2. CD4(+)CD25(-) T cells induced higher luciferase in the reporter cells than CD4(+)CD25(+) T cells. This T cell-produced TGF-β is in a soluble form since T cell culture supernatants contained the TGF-β activity. The TGF-β activity was neutralized with an anti-mouse LAP mAb or an anti-latent TGF-β/pro-TGF-β mAb, but not with anti-active TGF-β Abs. An anti-mouse LAP mAb removed virtually all acid activatable latent TGF-β from the T cell culture supernatant, but not the ability to induce TGF-β signaling in the reporter cells. The induction of TGF-β signaling by T cell culture supernatants was cell type-specific.

CONCLUSIONS/SIGNIFICANCE

A newly developed 293T-caga-Luc-CD32-CD86 reporter cell bioassay demonstrated that murine CD4 T cells produce an unconventional form of TGF-β which can induce TGF-β signaling. This new form of TGF-β contains LAP as a component. Our finding of a new form of T cell-produced TGF-β and the newly developed TGF-β bioassay system will provide a new avenue to investigate T cell function of the immune system.

TGF-β induces surface LAP expression on murine CD4 T cells independent of Foxp3 induction

Background

It has been reported that human FOXP3⁺ CD4 Tregs express GARP-anchored surface latency-associated peptide (LAP) after activation, based on the use of an anti-human LAP mAb. Murine CD4 Foxp3⁺ Tregs have also been reported to express surface LAP, but these studies have been hampered by the lack of suitable anti-mouse LAP mAbs.

Methodology/Principal Findings

We generated anti-mouse LAP mAbs by immunizing TGF-β^−/− animals with a mouse Tgfb1-transduced P3U1 cell line. Using these antibodies, we demonstrated that murine Foxp3⁺ CD4 Tregs express LAP on their surface. In addition, retroviral transduction of Foxp3 into mouse CD4⁺CD25⁻ T cells induced surface LAP expression. We then examined surface LAP expression after treating CD4⁺CD25⁻ T cells with TGF-β and found that TGF-β induced surface LAP not only on T cells that became Foxp3⁺ but also on T cells that remained Foxp3⁻ after TGF-β treatment. GARP expression correlated with the surface LAP expression, suggesting that surface LAP is GARP-anchored also in murine T cells.

Conclusions/Significance

Unlike human CD4 T cells, surface LAP expression on mouse CD4 T cells is controlled by Foxp3 and TGF-β. Our newly described anti-mouse LAP mAbs will provide a useful tool for the investigation and functional analysis of T cells that express LAP on their surface.

Depletion of TGF-β from fetal bovine serum

TGF-β is one of the key cytokines controlling immune responses. Measuring TGF-β from culture supernatants in vitro is an important index of immune function. However, fetal bovine serum (FBS) contains a high level of latent TGF-β that often hampers measuring T cell-derived TGF-β in culture using FBS-supplemented medium. In this report, we generated anti-latency associated peptide (LAP) monoclonal antibodies which cross-react with bovine LAP, and developed a protocol to deplete TGF-β from FBS. This provides the ability to reliably quantify TGF-β in vitro without relying on serum-free media which do not support growth of murine T cells.

Overexpression of TGF-ß 1 gene induces cell surface localized glucose-regulated protein 78-associated latency-associated peptide/TGF-ß

TGF-beta plays a crucial role in immune regulation. It has been reported that pro-TGF-beta, latency-associated peptide (LAP), latent TGF-beta and/or active TGF-beta (LAP/TGF-beta) is localized on the cell surface of Foxp3(+) regulatory T cells. However, the molecular mechanism(s) of how LAP/TGF-beta is anchored on the cell membrane is unknown. In this study, we show that forced expression of human TGF-beta(1) gene by retrovirus transduction into P3U1 mouse myeloma cells, and other cell types including murine CD4(+)CD25(-) T cells, makes these cells surface LAP/TGF-beta-positive. The surface LAP/TGF-beta contains high-glycosylated, furin-processed latent TGF-beta, which is different from the low-glycosylated, furin-unprocessed intracellular form or the high-glycosylated, furin-unprocessed secreted form. Furthermore, surface LAP/TGF-beta forms a complex with the molecular chaperone glucose-regulated protein 78 (GRP78, also known as BiP), and knockdown of GRP78 reduced the expression levels of surface LAP/TGF-beta. GRP78, however, is not involved in GARP-mediated surface LAP/TGF-beta. Our results suggest that GRP78 provides an additional surface localization mechanism for LAP/TGF-beta, which may play an important role in controlling TGF-beta activity.

Potential role of multiple members of the kallikrein-related peptidase family of serine proteases in activating latent TGF beta 1 in semen

Transforming growth factor beta1 (TGF beta 1) has been implicated as a key contributor of immunosuppression in seminal plasma. The biochemical mechanisms that lead to production of active seminal TGF beta 1 are not fully understood. It is plausible that TGF beta 1 activation is partly induced simultaneously with the release of motile spermatozoa following liquefaction of the semen coagulum. Several members of the kallikrein-related peptidase (KLK) family are involved in the regulation of semen liquefaction. This study examines the involvement of these KLKs in TGF beta 1 activation in vitro and ex vivo, in seminal plasma. Latent TGF beta 1 was rapidly activated by KLK14. The latency-associated propeptide (LAP) was shown to be cleaved by KLK14 into small peptide fragments, providing a possible mechanism for TGF beta 1 activation. KLK14 also cleaved the latent TGFbeta binding protein 1 (LTBP1). KLK1, 2, and 5 might also contribute to TGF beta 1 activation by nicking the LAP motif and inducing conformational changes that aid in subsequent processing of LAP or through LTBP1 cleavage. Our study provides strong evidence for the involvement of multiple members of the seminal KLK cascade in activation of latent TGF beta 1 in seminal plasma. These findings might have clinical implications in infertility treatment of cases with concurrent delayed liquefaction and TGF beta 1-related semen antigenicity.

The Family of IL-10-secreting CD4+ T cells

Regulatory T cells (Treg cells) play critical roles in the induction of peripheral tolerance to self- and foreign antigens. Naturally occurring CD4(+)CD25(+) Treg cells, which characteristically express the transcription factor forkhead box protein P3 (Foxp3), have been studied intensively because their deficiency abrogates self-tolerance and causes autoimmune disease. However, several lines of evidence suggest that additional important mechanisms other than the Foxp3 system are required to enforce immunological self-tolerance in the periphery. Interleukin-10 (IL-10) is a regulatory cytokine that plays a central role in controlling inflammatory processes, and IL-10-secreting T cells may constitute an additional mechanism that are responsible for peripheral tolerance. Type-1 T regulatory (Tr1) cells, CD46-stimulated IL-10-secreting T cells, and IL-10-secreting T cells induced by vitamin D3 (VitD3) and dexamethasone (Dex) are induced populations with significant regulatory activities. However, assessing the detailed physiological function of these cells is difficult, because of the lack of specific markers that can reliably differentiate the population of IL-10-secreting Treg cells from other T cells. Recently, CD4(+)CD25(-)LAP(+) T cells, CD4(+)NKG2D(+) T cells, CD4(+)IL-7R(-) T cells, and CD4(+)CD25(-)LAG3(+) T cells have been reported as naturally present IL-10-secreting Treg cells. Although the relationship between these induced and naturally present IL-10-secreting Treg cells is unclear, elucidation of their respective roles in modulating immune responses is crucial to understand T cell-mediated tolerance. Furthermore, the identification of specific markers and molecular signatures will enable the purification or induction of IL-10-secreting Treg cells for the treatment of patients having inflammatory diseases.

Novel CD8+ Treg suppress EAE by TGF-beta- and IFN-gamma-dependent mechanisms

Although CD8+ Treg-mediated suppression has been described, CD8+ Treg remain poorly characterized. Here we identify a novel subset of CD8+ Treg that express latency-associated peptide (LAP) on their cell surface (CD8+LAP+ cells) and exhibit regulatory activity in vitro and in vivo. Only a small fraction of CD8+LAP+ cells express Foxp3 or CD25, although the expression levels of Foxp3 for these cells are higher than their LAP- counterparts. In addition to TGF-beta, CD8+LAP+ cells produce IFN-gamma, and these cells suppress EAE that is dependent on both TGF-beta and IFN-gamma. In an adoptive co-transfer model, CD8+LAP+ cells suppress myelin oligodendrocyte glycoprotein (MOG)-specific immune responses by inducing or expanding Foxp3+ cells and by inhibiting proliferation and IFN-gamma production in vivo. Furthermore, in vivo neutralization of IFN-gamma and studies with IFN-gamma-deficient mice demonstrate an important role for IFN-gamma production in the function of CD8+LAP+ cells. Our findings identify the underlying mechanisms that account for the immunoregulatory activity of CD8+ T cells and suggest that induction or amplification of CD8+LAP+ cells may be a therapeutic strategy to help control autoimmune processes.

TGF-beta/extracellular matrix interactions in dentin matrix: a role in regulating sequestration and protection of bioactivity

TGF-beta isoforms sequestrated in dentin matrix potentially provide a reservoir of bioactive molecules that may influence cell behavior in the dentin-pulp complex following tissue injury. The association of these growth factors with dentin matrix and the influence of such associations on the bioactivity of growth factors are still unclear. We used surface plasmon resonance technology in the BIAcore 3000 system to investigate the binding of TGF-beta isoforms 1 and 3 to purified decorin, biglycan, and EDTA soluble dentin matrix components. TGF-beta isoforms 1 and 3 were immobilized on sensorchips CM4 through amine coupling. For kinetic studies of protein binding, purified decorin and biglycan, isolated EDTA soluble dentin matrix, and dentin matrix immunodepleted of decorin and/or biglycan were injected over TGF-beta isoforms and allowed to interact. Programmed kinetic analysis software provided sensorgrams for each concentration of proteoglycan or dentin matrix extract injected. Purified decorin and biglycan and dentin matrix extract bound to the TGF-beta isoforms. However, the association with TGF-beta3 was much weaker than that with TGF-beta1. After immunoaffinity depletion of the dentin matrix extract, the level of interaction between the dentin matrix extract and TGF-beta was significantly reduced. These results suggest isoform-specific interactions between decorin/biglycan and TGF-beta isoforms 1 and 3, which may explain why TGF-beta3 is not detected in the dentin matrix despite being expressed at higher levels than TGF-beta1 in odontoblasts. These proteoglycans appear to play a significant role in TGF-beta/extracellular matrix interactions and may be important in the sequestration of these growth factors in the dentin matrix.

Keloid scarring: bench and bedside

Wound healing is a fundamental complex-tissue reaction leading to skin reconstitution and thereby ensuring survival. While, fetal wounds heal without scarring, a normal "fine line" scar is the clinical outcome of an undisturbed wound healing in adults. Alterations in the orchestrated wound healing process result in hypertrophic or keloid scarring. Research in the past decades attempted to identify genetic, cellular, and molecular factors responsible for these alterations. These attempts lead to several new developments in treatments for keloids, such as, imiquimod, inhibition of transforming growth factor beta, and recombinant interleukin-10. The urgent need for better therapeutics is underlined by recent data substantiating an impaired quality of life in keloid and hypertrophic scar patients. Despite the increasing knowledge about the molecular regulation of scar formation no unifying theory explaining keloid development has been put forward until today. This review aims to give an overview about the genetic and molecular background of keloids and focus of the current research on keloid scarring with special emphasis on new forthcoming treatments. Clinical aspects and the spectrum of scarring are summarized.

Latency-associated peptide identifies a novel CD4+CD25+ regulatory T cell subset with TGFbeta-mediated function and enhanced suppression of experimental autoimmune encephalomyelitis

CD4(+)CD25(+) regulatory T cells (Tregs) are essential for maintaining self-tolerance and immune homeostasis. Here we characterize a novel subset of CD4(+)CD25(+) Tregs that express latency-associated peptide (LAP) on their cell surface (CD4(+)CD25(+)LAP(+) cells). CD4(+)CD25(+)LAP(+) cells express elevated levels of Foxp3 and Treg-associated molecules (CTLA4, glucocorticoid-induced TNFR-related gene), secrete TGFbeta, and express both cell surface TGFbeta and surface receptors for TGFbeta. In vitro, the suppressive function of CD4(+)CD25(+)LAP(+) cells is both cell contact and soluble factor dependent; this contrasts with CD4(+)CD25(+)LAP(-) cells, which are mainly cell contact dependent. In a model of experimental autoimmune encephalomyelitis, CD4(+)CD25(+)LAP(+) cells exhibit more potent suppressive activity than CD4(+)CD25(+)LAP(-) cells, and the suppression is TGFbeta dependent. We further show that CD4(+)CD25(+)LAP(+) cells suppress myelin oligodendrocyte glycoprotein-specific immune responses by inducing Foxp3 and by inhibiting IL-17 production. Our findings demonstrate that CD4(+)CD25(+) Tregs are a heterogeneous population and that the CD4(+)CD25(+) subset that expresses LAP functions in a TGFbeta-dependent manner and has greater in vivo suppressive properties. Our work helps elucidate the ambiguity concerning the role of TGFbeta in CD4(+)CD25(+) Treg-mediated suppression and indicates that LAP is an authentic marker able to identify a TGFbeta-expressing CD4(+)CD25(+) Treg subset.

Noggin blocks invasive growth of murine B16-F1 melanoma cells in the optic cup of the chick embryo

Melanoma cells originate from the neural crest and are characterized by high migratory potential and invasive growth. After transplantation into the neural tube of the chick embryo, melanoma cells spontaneously emigrate along the neural crest pathways without tumor formation or malignant growth. This emigration depends on the constitutive over-expression of bone morphogenetic protein-2 (BMP-2) and can be ablated by the BMP-antagonist noggin. When transplanted into the embryonic optic cup, melanoma cells invade the host tissue and form malignant tumors. Here, we asked if the invasive growth of melanoma cells in the optic cup could be influenced by BMP-2 or noggin. Mouse B16-F1 cells were grown as aggregates, treated with BMP-2 or noggin during aggregation and transplanted into the optic cup of 3-day chick embryos. After 3 days of subsequent incubation, embryos were evaluated for melanoma cell invasiveness. Immunohistochemical examination revealed that untreated and BMP-2-treated melanoma cells had grown malignantly into the host tissue. However, noggin pretreatment of the aggregates had blocked melanoma cell invasiveness and tumor formation. We conclude that invasive growth of melanoma cells in vivo is BMP-dependent and can be ablated by noggin, thus rendering noggin a promising agent for the treatment of BMP-over-expressing melanoma.

Transfer of maternal cytokines to suckling piglets: in vivo and in vitro models with implications for immunomodulation of neonatal immunity

Maternal cytokines may play instructive roles in development of the neonatal immune system. However, cytokines in colostrum and milk and their transfer from mothers to neonates have not been well documented, except for TGF-beta. Swine provide a unique model to study lactogenic cytokines because the sow's impermeable placenta prohibits transplacental passage. We investigated IL-6 and TNF-alpha (pro-inflammatory), IFN-gamma and IL-12 (Th1), IL-10 and IL-4 (Th2) and TGF-beta1 (Th3) concentrations in sow serum and colostrum/milk and serum of their suckling and weaned piglets and in age-matched colostrum-deprived gnotobiotic piglets. All cytokines were detected in colostrum/milk and correlated with concentrations in sow serum except for mammary-derived TNF-alpha and TGF-beta1. Detection of IL-12 and TGF-beta1 in pre-suckling and colostrum-deprived gnotobiotic piglet serum suggests constitutive production: other cytokines were undetectable confirming absence of transplacental transfer. Peak median cytokine concentrations in suckling piglet serum occurred at post-partum days 1-2 (IL-4>IL-6>IFN-gamma>IL-10). The effects in vitro of physiologically relevant concentrations of the two predominant lactogenic cytokines (TGF-beta1 and IL-4) on porcine naive B cell responses to lipopolysaccharide (LPS) and rotavirus (RV) were investigated. High (10 ng/ml) TGF-beta1 suppressed immunoglobulin secreting cell responses to LPS and rotavirus; low concentrations (0.1 ng/ml) promoted isotype switching to IgA antibody. Interleukin-4 induced inverse dose-dependent (0.1 ng>10 ng/ml) isotype switching to IgA and enhanced IgM secreting cell responses to LPS and rotavirus. In summary, we documented the transfer and persistence of maternal cytokines from colostrum/milk to neonates and their potential role in Th-2 biased IgA responses and reduced immunologic responsiveness of neonates.

LTBP-1 blockade in dioxin receptor-null mouse embryo fibroblasts decreases TGF-beta activity: Role of extracellular proteases plasmin and elastase

In mouse embryonic fibroblasts (MEF) lacking dioxin receptor (AhR), high levels of latent transforming growth factor-beta (TGF-beta)-binding protein-1 (LTBP-1) correlated with increased TGF-beta1 activity, an observation suggesting that LTBP-1 could contribute to maintain TGF-beta1 levels. Here, using small interfering RNAs (siRNA), we have first analyzed if LTBP-1 expression affected TGF-beta1 activity in MEF cells. We have then determined how LTBP-1 levels could alter the activity of extracellular proteases known to activate TGF-beta1, and finally, whether protease inhibition could reduce TGF-beta1 activation. LTBP-1 inhibition by siRNA in AhR-/- MEF decreased the amount of active TGF-beta1 and reduced plasminogen activators (PA)/plasmin and elastase activities and thrombospondin-1 (TSP-1) expression, without significantly affecting their mRNA levels. On the contrary, LTBP-1 siRNA restored matrix metalloproteinase-2 (MMP-2) activity in AhR-/- MEF. Interestingly, whereas a TGF-beta1 neutralizing antibody mimicked many of the LTBP-1 siRNA effects on extracellular proteases, addition of recombinant TGF-beta1 protein increased proteases activity over basal levels in AhR-/- MEF. These proteases contributed to TGF-beta activation since their specific inhibitors reduced active TGF-beta levels in these cells. These results suggest that LTBP-1 contributes to TGF-beta1 activation in MEF, possibly by influencing the activities of PA/plasmin, elastase, TSP-1, and MMP-2. TGF-beta1, on the other hand, could be also involved in maintaining the activity of these extracellular proteases. Thus, LTBP-1 appears to play a role in TGF-beta1 activation through a process involving extracellular protease activities, which, in turn, could be affected by TGF-beta1 levels.

Coordinate expression of BMP-2, BMP receptors and Noggin in normal mouse spine

The purpose of this study was to determine the localization of bone morphogenetic protein-2 (BMP-2), BMP receptors (BMPRs) and Noggin in mouse spinal tissues. The coordinate expression of these positive and negative regulators of BMP signaling may elucidate regulatory mechanisms for bone induction in the spine. Whole spines from 3-week-old mice were used and the spatial expression profiles of BMP-2, BMPR-1a, -1b, -2 and Noggin were examined using in situ hybridization. BMP-2, BMPR-1b and -2 were observed in bone marrow cells in the vertebrae, chondrocytes, hyaline cartilage cells and fibrous cells in the intervertebral discs and neurons of the spinal cord in the entire spine. BMPR-1a was also observed in these cells, but only in the cervical spine. Noggin was expressed in bone marrow cells in the vertebrae, chondrocytes and hyaline cartilage cells and fibrous cells in the intervertebral discs in the entire spine and in neurons in the spinal cord in the cervical and thoracic regions. Noggin was also expressed in the anterior longitudinal, posterior longitudinal and yellow ligaments in the cervical spine, and in the fibrous cells in the anterior longitudinal and yellow ligaments of the lumbar spine.

Understanding heart development and congenital heart defects through developmental biology: a segmental approach

ABSTRACT The heart is the first organ to form and function during development. In the pregastrula chick embryo, cells contributing to the heart are found in the postero-lateral epiblast. During the pregastrula stages, interaction between the posterior epiblast and hypoblast is required for the anterior lateral plate mesoderm (ALM) to form, from which the heart will later develop. This tissue interaction is replaced by an Activin-like signal in culture. During gastrulation, the ALM is committed to the heart lineage by endoderm-secreted BMP and subsequently differentiates into cardiomyocyte. The right and left precardiac mesoderms migrate toward the ventral midline to form the beating primitive heart tube. Then, the heart tube generates a right-side bend, and the d-loop and presumptive heart segments begin to appear segmentally: outflow tract (OT), right ventricle, left ventricle, atrioventricular (AV) canal, atrium and sinus venosus. T-box transcription factors are involved in the formation of the heart segments: Tbx5 identifies the left ventricle and Tbx20 the right ventricle. After the formation of the heart segments, endothelial cells in the OT and AV regions transform into mesenchyme and generate valvuloseptal endocardial cushion tissue. This phenomenon is called endocardial EMT (epithelial-mesenchymal transformation) and is regulated mainly by BMP and TGFbeta. Finally, heart septa that have developed in the OT, ventricle, AV canal and atrium come into alignment and fuse, resulting in the completion of the four-chambered heart. Altered development seen in the cardiogenetic process is involved in the pathogenesis of congenital heart defects. Therefore, understanding the molecular nature regulating the 'nodal point' during heart development is important in order to understand the etiology of congenital heart defects, as well as normal heart development.

Positive and negative regulation of the transforming growth factor beta/activin target gene goosecoid by the TFII-I family of transcription factors

Goosecoid (Gsc) is a homeodomain-containing transcription factor present in a wide variety of vertebrate species and known to regulate formation and patterning of embryos. Here we show that in embryonic carcinoma P19 cells, the transcription factor TFII-I forms a complex with Smad2 upon transforming growth factor beta (TGFbeta)/activin stimulation, is recruited to the distal element (DE) of the Gsc promoter, and activates Gsc transcription. Downregulation of endogenous TFII-I by small inhibitory RNA in P19 cells abolishes the TGFbeta-mediated induction of Gsc. Similarly, Xenopus embryos with endogenous TFII-I expression downregulated by injection of TFII-I-specific antisense oligonucleotides exhibit decreased Gsc expression. Unlike TFII-I, the related factor BEN (binding factor for early enhancer) is constitutively recruited to the distal element in the absence of TGFbeta/activin signaling and is replaced by the TFII-I/Smad2 complex upon TGFbeta/activin stimulation. Overexpression of BEN in P19 cells represses the TGFbeta-mediated transcriptional activation of Gsc. These results suggest a model in which TFII-I family proteins have opposing effects in the regulation of the Gsc gene in response to a TGFbeta/activin signal.

Low dose fibroblast growth factor-2 (FGF-2) enhances bone morphogenetic protein-2 (BMP-2)-induced ectopic bone formation in mice

To examine how fibroblast growth factor-2 (FGF-2) affects the BMP signaling pathway during bone morphogenetic protein-2 (BMP-2)-induced ectopic bone formation, we implanted type I collagen disks containing constant amounts of BMP-2 (5 micrograms) and varying amounts of FGF-2 onto the back muscles of adult male mice. We then performed histological analyses and histomorphometry, and measured bone mineral density and radiopaque area on the discs 1, 2, and 3 weeks after implantation. We also determined the expression profiles of several genes involved in bone formation and the BMP signaling pathway in the muscle that had been adjacent to the implanted disc and in muscle-derived primary culture cells that had similarly been treated with a constant concentration of BMP-2 and a varying concentration of FGF-2. In the presence of a constant amount of BMP-2, we confirmed that low doses of FGF-2 increased ectopic bone formation in vivo and high doses inhibited bone formation. Northern and/or Western blots of recovered muscle from the in vivo experiment and treated muscle-derived primary culture cells from the in vitro experiment revealed that low doses of FGF-2, but not high doses, increased the expression BMP receptor (BMPR)-1B, phosphorylated Smad1, Noggin, and Osteocalcin. Our results indicate that low-dose FGF-2 may facilitate BMP-2-induced ectopic bone formation by altering the expression of BMPRs on the surface of bone forming progenitor cells. They also indicate that the inhibitory effect of high-dose FGF-2 is not mediated via increased expression of the BMP inhibitor Noggin.

Expression profiles of BMP-related molecules induced by BMP-2 or -4 in muscle-derived primary culture cells

The formation of ectopic bone in muscle following the implantation of decalcified bone matrix led to the search and eventual discovery of bone morphogenetic proteins (BMPs) in bone matrix. The precise sequence of molecular events that underpin the cellular transformation of undifferentiated mesenchymal cells into bone has not been established, and is the subject of this study. Northern and Western blot analyses were used to examine changes in gene expression of cells treated with BMP-2 or -4. The molecules, which included BMP receptors (BMPRs), Noggin (a BMP-specific antagonist), osteocalcin (OC), Smad-4, and MyoD, were examined at messenger RNA (mRNA) and protein levels. The changes in expression of these molecules were followed in mouse muscle-derived primary culture cells, and osteoblastic or nonosteoblastic embryonic cell lines. We show the early up-regulation of BMPR-1A, -2, Noggin, OC, and Smad-4 in muscle-derived primary culture cells in a dose-dependent manner in response to BMP-2 or -4. MyoD expression was not detected after BMP stimulation. The differential expression of these positive and negative regulators of BMP signaling points to a potential regulatory mechanism for bone induction in mesenchymal cells.

Effects of TGF-beta s on the growth, collagen synthesis and collagen lattice contraction of human dental pulp fibroblasts in vitro

Transforming growth factor-beta (TGF-beta) is important in regulating the repair and regeneration of damaged dental pulp. For further elucidating the roles of different isoforms of TGF-beta in the healing and inflammatory processes of human dental pulp, we found that TGF-beta1, TGF-beta2 and TGF-beta3 inhibited the growth of two human dental pulp cell strains in vitro by 19-29, 18-25 and 23-26%, respectively, at a concentration of 0.5 ng/ml. TGF-beta also differentially stimulated the collagen synthesis of pulp cells. Collagen synthesis increased by 1 ng/ml of TGF-beta1 and TGF-beta2 by 42 and 51%, respectively. TGF-beta3 (0.1-1 ng/ml) lacked of stimulatory effect on collagen synthesis of pulp cells. Pulp cells have the intrinsic capacity to contract collagen lattice, leading to decreasing of lattice diameter. An 8 h exposure to TGF-beta1 and TGF-beta2 enhanced the pulp cell-populated collagen lattice contraction at concentrations ranging from 0.2 to 3 ng/ml. At similar concentrations, TGF-beta3 lacked of this stimulatory effect. When collagen lattice were detached after 24 h of exposure, TGF-beta1 and TGF-beta2 (0.6-3 ng/ml) induced the pulp cells-populated collagen lattice contraction within 4-8h of gel detachment. These results indicate that TGF-beta-induced collagen lattice contraction is a late cellular event. These in vitro results indicate that effects of TGF-beta isoforms on the growth, collagen synthesis and collagen lattice contraction of pulp cells may play crucial roles in the pathobiological processes of dental pulp.

Overexpression of TGF-beta by infiltrated granulocytes correlates with the expression of collagen mRNA in pancreatic cancer

Pancreatic cancer is often associated with an intense production of interstitial collagens, known as the desmoplastic reaction. To understand more about desmoplasia in pancreatic cancer, the expression of mRNA for type I and III collagens and potent desmoplastic inducing growth factors transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), acidic and basic fibroblast growth factor (FGF), platelet-derived growth factor (PDGF) A and C and epidermal growth factor (EGF) was analysed by quantitative RT–PCR. Expression of both collagens in 23 frozen primary pancreatic cancer nodules was significantly higher than that in 15 non-neoplastic pancreatic tissues. The expressions of mRNAs for TGF-β, acidic FGF, basic FGF and PDGF C were likewise higher in surgical cancer nodules, while that of CTGF, PDGF A and EGF were not. Among these growth factors, the expression of TGF-β mRNA showed the most significant correlation with that of collagens (P<0.0001). By immunohistochemistry, TGF-β showed faint cytoplasmic staining in cancer cells. In contrast, isolated cells, mainly located on the invasive front surrounding cancerous nests, were prominently and strongly stained. These TGF-β-positive cells contained a segmented nucleus, were negative for anti-macrophage (CD68) and positive for anti-granulocyte antibodies, indicating their granulocytic nature. In conclusion, TGF-β seemed to play a major role among the various growth factors in characteristic overproduction of collagens in pancreatic cancer. Moreover, the predominant cells that express TGF-β were likely to be infiltrated granulocytes (mostly are neutrophils) and not pancreatic cancer cells.

Expression of transforming growth factor beta in renal cell carcinoma and matched non-involved renal tissue

TGFbeta1 is one of several cytokines produced by proximal tubular and renal cancer cells. Previous studies have been mainly focused on determining plasma or serum TGFbeta levels, its effect on RCC cultures, and the expression of TGFbeta mRNA. Cancerous and autologous normal kidney samples were obtained from 24 patients treated by radical nephrectomy. TGFbeta1 expression was determined using a semi quantitative Western blot analysis and immunohistochemistry. Blot densities and immunohistochemical expression intensities in normal and neoplastic tissue were compared, and subsequently correlated to tumor stage, histological type and nuclear grade. All tissue samples examined expressed TGFbeta1; mean tumor to non-involved kidney spot density ratio correlated with advancing stage and higher nuclear grade. The overexpression of TGFbeta1 in certain RCCs may partially explain their resistance to the growth suppression action of TGFbeta. The correlation with tumor stage and grade indicates a possible role in the development of metastatic potential as well as in host's immune response modulation.

Transforming growth factor-beta and its role in asthma

Transforming growth factor-beta (TGF-beta) is an important fibrogenic and immunomodulatory factor that may play a role in the structural changes observed in the asthmatic airways. In vitro as well as in vivo studies have evidenced a dual role for TGF-beta: it can either function as a pro- or anti-inflammatory cytokine on inflammatory cells, participating into the initiation and resultion of inflammatory and immune responses in the airways. TGF-beta is also involved in the remodelling of the airway wall, and has in particular been related to the subepithelial fibrosis. TGF-beta is produced in the airways by inflammatory cells infiltrated in the bronchial mucosa, as well as by structural cells of the airway wall including fibroblasts, epithelial, endothelial and smooth muscle cells. By releasing TGF-beta, these different cell types may then participate into the increased levels of TGF-beta observed in bronchoalveolar lavage fluid from asthmatic patients. Taken together, these results suggest that TGF-beta may play a role in inflammation in asthma. However, as its role is dual in the modulation of inflammation, further studies are needed to elucidate the precise role of TGF-beta in the airways.

Temporal and spatial expression profiles of BMP receptors and noggin during BMP-2-induced ectopic bone formation

The mechanism of ectopic bone formation has not been clear. After BMP-2 implantation into the back muscles of 198 mice, expression of BMPR-1A, -2, and Noggin was increased during the early phase of the reaction. The results suggest that positive and negative feedback mechanisms modulate ectopic osteogenesis induced by this growth factor.

INTRODUCTION

The expression of bone morphogenetic protein receptors (BMPRs) and Noggin during ectopic bone formation after implantation of BMP-2 into the back muscles of adult mice was investigated in this study.

METHODS

One hundred ninety-eight male ddy mice were divided into groups and received either collagen disks containing BMP-2, collagen disks alone, or sham surgery with no disk implantation. Changes in the temporal and spatial expression profiles of BMPRs and Noggin were examined by Northern blotting, in situ hybridization, Western blotting, and immunohistochemistry.

RESULTS AND CONCLUSIONS

In the BMP group, expression of BMPR-1A, -2, and Noggin mRNA and protein was enhanced 2-4 days after implantation in undifferentiated mesenchymal cells and regenerating muscle fibers located close to the BMP-retaining implants. On day 7, the expression was also observed in cartilage cells, and after day 14, in the osteoblastic cells around bone tissue. The level of expression peaked at day 4 after implantation and persisted at a much lower level during the bone forming process. No significant expression of BMPR-1B was detected at the mRNA and protein levels during the bone-forming reaction. In the BMP free control groups, a mild enhancement of BMPR-2 expression was also noted around the implant, but this was not observed for BMPR-1A, -1B, or Noggin. Upregulated expression of BMPR-1A, -2, and Noggin in undifferentiated mesenchymal cells and regenerating muscle fibers occurs during the early phase of BMP-2-induced bone formation. The coordinate expression of these positive and negative regulators of BMP signaling points to a potential regulatory mechanism for bone induction.

Angiogenesis factors in gliomas: a new key to tumour therapy?

Angiogenesis, the formation of new blood vessels, is required for the growth and expansion of tumours. Gliomas, the most common brain tumours, are particularly highly vascularized and, therefore, serve as a model to elucidate the process of tumour angiogenesis and to investigate new anti-angiogenic therapies. This review describes the role of angiogenic factors in glioma angiogenesis and new strategies to inhibit glioma growth by application of anti-angiogenic substances. We focus on vascular endothelial growth factor (VEGF), but also examine the role of angiopoietin and pleiotropic factors such as platelet-derived growth factor (PDGF), pleiotrophin and transforming growth factor-beta (TGF-beta). Strategies to inhibit glioma growth by reducing the action of angiogenic factors, by the application of anti-angiogenic substances such as angiostatin or endostatin, or inactivation of endothelial cells, are discussed. These new anti-angiogenic therapies appear to have a high potential not only for the treatment of gliomas, but also of other tumours.

Transforming growth factor-beta1 and renal cell cancer: cell growth, mRNA expression and protein production of cytokines

PURPOSE

We evaluated the effects of transforming growth factor-beta1 (TGF-beta1) on growth activity, cytokine mRNA expression and cytokine protein production by renal cancer cells.

MATERIALS AND METHODS

Exogenous continuous exposure of biologically active TGF-beta1 was performed on ACHN cells at various concentrations of 0.1 to 30 ng./ml. and the number of cells was counted each culture day. To determine the index of S-phase cells the bromodeoxyuridine pulse labeling method was used. Reverse transcriptase-polymerase chain reaction (PCR) was done and PCR products were quantified. Each supernatant cytokine level was measured using an enzyme-linked immunosorbent assay.

RESULTS

TGF-beta1 significantly inhibited the growth activities of ACHN cells compared with controls. Bromodeoxyuridine labeling indexes after treating ACHN cells with TGF-beta1 (10 ng./ml.) showed that it began to decrease gradually after 24 hours and after 72 hours it was inhibited to approximately 40% compared with controls. The mRNA of TGF-beta1, TGF-beta types 1 and 2 receptors, interleukin-6 (IL-6) and granulocyte-macrophage colony-stimulating factor (GM-CSF) from ACHN cells was detected by reverse transcriptase-PCR assay. IL-6 and GM-CSF proteins were produced constitutively from ACHN cells but other cytokines were not. Adding TGF-beta1 to the cell culture medium did not influence mRNA expression, or the protein production of IL-6 or GM-CSF.

CONCLUSIONS

The inhibition of growth activities of ACHN cells by TGF-beta1 are mediated by its direct binding to specific receptors on ACHN cells followed by cell cycle inhibition, while TGF-beta1 seems to have no effect on the production of the cytokines studied.

Roles of TGFbeta signaling in epidermal/appendage development

The transforming growth factor beta (TGFbeta) superfamily encompasses a number of structurally related proteins that can be divided into several subfamilies including TGFbetas, activins/inhibins and bone morphogenetic proteins (BMPs). The Smads are major intracellular mediators in transducing the signals of TGFbeta superfamily members, and are abundantly expressed in the developing epidermis and epidermal appendages. Moreover, the phenotypes of transgenic/knockout mice with altered components of the TGFbeta superfamily signaling pathway suggest that TGFbeta superfamily signaling is required for epidermal/appendage development. TGFbeta superfamily members are involved in most events during epidermal/appendage development through the TGFbeta signal transduction pathway and through cross talk with other signaling pathways. Future studies will be instrumental in defining the precise roles for TGFbeta superfamily signaling in epidermal/appendage development.