INHBA gene silencing inhibits gastric cancer cell migration and invasion by impeding activation of the TGF-β signaling pathway

Gastric cancer (GC) is the fourth largest cancer in the world, with a 5-year survival rate of <30%. Thus, this study intends to investigate the effects of inhibin βA (INHBA) gene silencing on the migration and invasion of GC cells via the transforming growth factor-β (TGF-β) signaling pathway. Initially, this study determined the expression of INHBA and the TGF-β signaling pathway-related genes in GC tissues. After that, to assess the effect of INHBA silencing on GC progression, GC cells were transfected with short hairpin RNAs that targeted INHBA in order to detect the expression of INHBA and the TGF-β signaling pathway-related genes, as well as cell migration, invasion, and proliferation abilities. Finally, a tumor xenograft model in nude mice was constructed to verify the effect that the silencing of INHBA had on tumor growth. Highly expressed INHBA and activated TGF-β signaling pathways were observed in GC tissues. In response to shINHBA-1 and shINHBA-2, the TGF-β signaling pathway was inhibited in GC cells, whereas the GC cell migration, invasion, proliferation, and tumor growth were significantly dampened. On the basis of the observations and findings of this study, INHBA gene silencing inhibited the progression of GC by inactivating the TGF-β signaling pathway, which provides a potential target in the treatment of GC.     

Tumor-associated microglia/macrophages enhance the invasion of glioma stem-like cells via TGF-β1 signaling pathway

The invasion of malignant glioma cells into the surrounding normal brain tissues is crucial for causing the poor outcome of this tumor type. Recent studies suggest that glioma stem-like cells (GSLCs) mediate tumor invasion. However, it is not clear whether microenvironment factors, such as tumor-associated microglia/macrophages (TAM/Ms), also play important roles in promoting GSLC invasion. In this study, we found that in primary human gliomas and orthotopical transplanted syngeneic glioma, the number of TAM/Ms at the invasive front was correlated with the presence of CD133(+) GSLCs, and these TAM/Ms produced high levels of TGF-β1. CD133(+) GSLCs isolated from murine transplanted gliomas exhibited higher invasive potential after being cocultured with TAM/Ms, and the invasiveness was inhibited by neutralization of TGF-β1. We also found that human glioma-derived CD133(+) GSLCs became more invasive upon treatment with TGF-β1. In addition, compared with CD133(-) committed tumor cells, CD133(+) GSLCs expressed higher levels of type II TGF-β receptor (TGFBR2) mRNA and protein, and downregulation of TGFBR2 with short hairpin RNA inhibited the invasiveness of GSLCs. Mechanism studies revealed that TGF-β1 released by TAM/Ms promoted the expression of MMP-9 by GSLCs, and TGFBR2 knockdown reduced the invasiveness of these cells in vivo. These results demonstrate that TAM/Ms enhance the invasiveness of CD133(+) GSLCs via the release of TGF-β1, which increases the production of MMP-9 by GSLCs. Therefore, the TGF-β1 signaling pathway is a potential therapeutic target for limiting the invasiveness of GSLCs.     

TGF-β family signaling in stem cells

Background

The diversity of cell types and tissue types that originate throughout development derives from the differentiation potential of embryonic stem cells and somatic stem cells. While the former are pluripotent, and thus can give rise to a full differentiation spectrum, the latter have limited differentiation potential but drive tissue remodeling. Additionally cancer tissues also have a small population of self-renewing cells with stem cell properties. These cancer stem cells may arise through dedifferentiation from non-stem cells in cancer tissues, illustrating their plasticity, and may greatly contribute to the resistance of cancers to chemotherapies.

Scope of review

The capacity of the different types of stem cells for self-renewal, the establishment and maintenance of their differentiation potential, and the selection of differentiation programs are greatly defined by the interplay of signaling molecules provided by both the stem cells themselves, and their microenvironment, the niche. Here we discuss common and divergent roles of TGF-β family signaling in the regulation of embryonic, reprogrammed pluripotent, somatic, and cancer stem cells.

Major conclusions

Increasing evidence highlights the similarities between responses of normal and cancer stem cells to signaling molecules, provided or activated by their microenvironment. While TGF-β family signaling regulates stemness of normal and cancer stem cells, its effects are diverse and depend on the cell types and physiological state of the cells.

General significance

Further mechanistic studies will provide a better understanding of the roles of TGF-β family signaling in the regulation of stem cells. These basic studies may lead to the development of a new therapeutic or prognostic strategies for the treatment of cancers. This article is part of a Special Issue entitled Biochemistry of Stem Cells.     

USP15 stabilizes TGF-β receptor I and promotes oncogenesis through the activation of TGF-β signaling in glioblastoma

In advanced cancer, including glioblastoma, the transforming growth factor β (TGF-β) pathway acts as an oncogenic factor and is considered to be a therapeutic target. Using a functional RNAi screen, we identified the deubiquitinating enzyme ubiquitin-specific peptidase 15 (USP15) as a key component of the TGF-β signaling pathway. USP15 binds to the SMAD7-SMAD specific E3 ubiquitin protein ligase 2 (SMURF2) complex and deubiquitinates and stabilizes type I TGF-β receptor (TβR-I), leading to an enhanced TGF-β signal. High expression of USP15 correlates with high TGF-β activity, and the USP15 gene is found amplified in glioblastoma, breast and ovarian cancer. USP15 amplification confers poor prognosis in individuals with glioblastoma. Downregulation or inhibition of USP15 in a patient-derived orthotopic mouse model of glioblastoma decreases TGF-β activity. Moreover, depletion of USP15 decreases the oncogenic capacity of patient-derived glioma-initiating cells due to the repression of TGF-β signaling. Our results show that USP15 regulates the TGF-β pathway and is a key factor in glioblastoma pathogenesis.     

Abnormal activation of the Akt-GSK3β signaling pathway in peripheral blood T cells from patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease accompanied by the activation and proliferation of T cells and B cells. In this study, we found that the distributions of lymphocytes obtained from patients with SLE or SLE with renal disease (RSLE) were reduced in the G₀/G₁ phase and were elevated in the S phase after phytohemagglutinin treatment. Increased expression of CDK2 and decreased expression of cyclin-dependent kinase inhibitors p27^Kip1 and p21^WAF1/CIP1 were observed in RSLE and SLE lymphocytes. The phosphorylation levels of Akt473 and GSK3β (ser9) were increased in lymphocytes from the patients. Moreover, inhibition of GSK3β with lithium chloride or SB216763 induced T cell proliferation, and the most significant effects were observed in RSLE lymphocytes. These results indicate that upregulation of CDKs and downregulation of p27^Kip1 and p21^WAF1/CIP1 increased the proliferation of T lymphocytes in SLE patients. Abnormal activation of the Akt–GSK3β signaling pathway increased the proliferation of lupus lymphocytes.     

Evolution of the TGF-β signaling pathway and its potential role in the ctenophore, Mnemiopsis leidyi

The TGF-β signaling pathway is a metazoan-specific intercellular signaling pathway known to be important in many developmental and cellular processes in a wide variety of animals. We investigated the complexity and possible functions of this pathway in a member of one of the earliest branching metazoan phyla, the ctenophore Mnemiopsis leidyi. A search of the recently sequenced Mnemiopsis genome revealed an inventory of genes encoding ligands and the rest of the components of the TGF-β superfamily signaling pathway. The Mnemiopsis genome contains nine TGF-β ligands, two TGF-β-like family members, two BMP-like family members, and five gene products that were unable to be classified with certainty. We also identified four TGF-β receptors: three Type I and a single Type II receptor. There are five genes encoding Smad proteins (Smad2, Smad4, Smad6, and two Smad1s). While we have identified many of the other components of this pathway, including Tolloid, SMURF, and Nomo, notably absent are SARA and all of the known antagonists belonging to the Chordin, Follistatin, Noggin, and CAN families. This pathway likely evolved early in metazoan evolution as nearly all components of this pathway have yet to be identified in any non-metazoan. The complement of TGF-β signaling pathway components of ctenophores is more similar to that of the sponge, Amphimedon, than to cnidarians, Trichoplax, or bilaterians. The mRNA expression patterns of key genes revealed by in situ hybridization suggests that TGF-β signaling is not involved in ctenophore early axis specification. Four ligands are expressed during gastrulation in ectodermal micromeres along all three body axes, suggesting a role in transducing earlier maternal signals. Later expression patterns and experiments with the TGF-β inhibitor SB432542 suggest roles in pharyngeal morphogenesis and comb row organization.     

Ubiquitin removal in the TGF-β pathway

The transforming growth factor (TGF-β) pathway is regulated by ubiquitin-mediated proteolysis at different levels. Two studies now identify deubiquitinating enzymes (DUBs) for the TGF-β type I receptor. Both ubiquitin-specific peptidase-4 (USP4) and -15 (USP15) extend the life of activated receptors against the negative pressure of receptor-ubiquitinating complexes, but through distinct modes of action.     

TTRAP is a novel component of the non-canonical TRAF6-TAK1 TGF-β signaling pathway

Transforming growth factor-β (TGF-β) principally relays its effects through the Smad pathway however, accumulating evidence indicate that alternative signaling routes are also employed by this pleiotropic cytokine. For instance recently, we have demonstrated that ligand occupied TGF-β receptors can directly trigger the TRAF6-TAK1 signaling module, resulting in MAP kinase activation. Here we report identification of the adaptor molecule TTRAP as a novel component of this non-canonical TGF-β pathway. We show that the protein associates with TGF-β receptors and components of the TRAF6-TAK1 signaling module, resulting in differential regulation of TGF-β activated p38 and NF-κB responses. Modulation of cellular TTRAP level affects cell viability in the presence of TGF-β, suggesting that the protein is an important component of the TGF-β induced apoptotic process.     

Role of TGF-β signaling in the mechanisms of tamoxifen resistance

The transforming growth factor beta (TGF-β) signaling pathway plays complex role in the regulation of cell proliferation, apoptosis and differentiation in breast cancer. TGF-β activation can lead to multiple cellular responses mediating the drug resistance evolution, including the resistance to antiestrogens. Tamoxifen is the most commonly prescribed antiestrogen that functionally involved in regulation of TGF-β activity. In this review, we focus on the role of TGF-β signaling in the mechanisms of tamoxifen resistance, including its interaction with estrogen receptors alfa (ERα) pathway and breast cancer stem cells (BCSCs). We summarize the current reported data regarding TGF-β signaling components as markers of tamoxifen resistance and review current approaches to overcoming tamoxifen resistance based on studies of TGF-β signaling.     

Regulation of the TGF-β pathway by deubiquitinases in cancer

The transforming growth factor-β (TGF-β) pathway regulates diverse cellular processes. It signals via serine/threonine kinase receptors and intracellular Smad and non-Smad effector proteins. In cancer cells, aberrant TGF-β signalling can lead to loss of growth inhibition and an increase in invasion, epithelial-to-mesenchymal transition (EMT) and metastasis. Therapeutic targeting of the pro-oncogenic TGF-β responses is currently being explored as a potential therapy against certain invasive and metastatic cancer types. The ubiquitin post-translational regulation system is emerging as a key regulatory mechanism for the control of TGF-β pathway components. In this review, we focus on the role of deubiquitinases (DUBs), which counteract the activity of E3 ubiquitin ligases. We will discuss the mechanisms by which specific DUBs control Smad and non-Smad TGF-β signalling routes, and how perturbation of the expression and function of DUBs contributes to misregulation of TGF-β signalling in cancer.     

MicroRNA-101 protects cardiac fibroblasts from hypoxia-induced apoptosis via inhibition of the TGF-β signaling pathway

Cardiac fibroblasts (CFs) are the most numerous cells in the heart and are recognized primarily for their ability to maintain both the structural integrity and the physiological functions of the heart. The transforming growth factor beta (TGF-β) signaling pathway is reportedly involved in the modulation of CF functions, including apoptosis. Recent studies have indicated that microRNA-101 (miR-101) attenuates the TGF-β signaling pathway, either by inhibiting the expression of TGFβ1 or by targeting transforming growth factor-β receptor type I (TGFβRI). The present study aimed to determine whether miR-101 protects CFs from hypoxia-induced apoptosis and to investigate the mechanisms underlying its protective effects. The CCK-8 test, electron microscopy and TUNEL assay results demonstrated that miR-101a/b significantly inhibited hypoxia-induced CF apoptosis. The results of Western blotting, quantitative RT-PCR and immunofluorescence assays indicated that miR-101a dramatically inhibited the hypoxia-induced up-regulation of both TGFβRI and p-Smad 3 but not TGFβ1 in CFs. Additionally, miR-101a significantly reversed the hypoxia-induced up-regulation of Bax and Caspase-3, the down-regulation of Bcl-2 and the activation of Caspase-3 in CFs. Moreover, miR-101a markedly inhibited the intracellular Ca²⁺ ([Ca²⁺]_i) overload caused by hypoxia. Taken together, our results suggest that miR-101a protects CFs against hypoxia-induced apoptosis by inhibiting the TGF-β signaling pathway, which may be a potential therapeutic target for heart injury.     

Induction of primitive streak and mesendoderm formation in monolayer hESC culture by activation of TGF-β signaling pathway by Activin B

Human embryonic stem cells (hESCs) have the ability to differentiate into all human cells, however controlling the differentiation has always been a challenge. In the present study we have investigated the direct differentiation of hESCs on MEFs by using TGF-β signaling pathway activators Activin A and Activin B. Activation of the TGF-β pathway with Activin B in low serum highly induced primitive streak and mesendoderm formation after 24 h, which included up-regulation of SOX 17 and BRACHYURY protein and gene expression. Continuous stimulation with Activin B in 2% serum further induced mesendoderm formation by increased gene expression of Brachyury, SOX17, MEOX and FOX at the same time we found down-regulation of neuroectodermal marker genes. Further, by stimulating the mesodermal cells by BMP-2 we succeeded to induce mesenchymal like cells with high expression of mesenchymal markers including; MEOX, FOX, RUNX2, COL1 and OSTEOPONTIN. In conclusion we have directed the differentiation of hESCs as monolayer to primitive streak like cells with Activin B and further into pure mesoderm and mesenchymal like cells by BMP-2.     

The cell sorting process of Xenopus gastrula cells involves the acto-myosin system and TGF-β signaling

We have previously shown that the cell sorting process of animal pole cells (AC) and vegetal pole cells (VC) from Xenopus gastrulae is considered to involve two steps: concentrification and polarization. In this study, we addressed the question of what specified the spatial relationship of the AC and VC clusters during the process. First, we examined the inhibitory or facilitatory treatment for myosin 2 activity during each of the two steps. The aggregates treated with Y27632 or blebbistatin during the concentrification step showed a cluster random arrangement, suggesting the prevention of the cell sorting by inhibition of myosin 2. Meanwhile, the treatment with a Rac1 inhibitor, NSC23766, during the same step resulted in promotion of the fusion of the AC clusters and the progression of the cell sorting, presumably by an indirect activation of myosin 2. On the other hand, the treatments with any of the three drugs during the polarization step showed that the two clusters did not appose, and their array remained concentric. Thus, the modulation of cell contraction might be indispensable to each of the two steps. Next, the activin/nodal TGF-β signaling was perturbed by using a specific activin receptor-like kinase inhibitor, SB431542. The results revealed a bimodal participation of the activin/nodal TGF-β signaling, i.e., suppressive and promotive effects on the concentrification and the polarization, respectively. Thus, the present in vitro system, which permits not only the cell contraction-mediated cell sorting but also the TGF-β-directed mesodermal induction such as cartilage formation, may fairly reflect the embryogenesis in vivo.     

Invasion of breast cancer cells into collagen matrix requires TGF-α and Cdc42 signaling

Invasion of MDA-MB-231 breast cancer cells into three-dimensional (3-D) type I-collagen matrices depends on TGF-α. We characterized the steps of invasion mediated by TGF-α. Cell migration, as observed by videomicroscopy, was effectively stimulated by collagen, suggesting that TGF-α may specifically participate in the invasion of a 3-D collagen matrix. We assessed the role of small GTPases of the Rho family in the invasion. Cdc42 was found to be necessary for invasion but dispensable for cell migration. These results suggest that TGF-α mediates invasion into 3-D collagen matrices by initiating the formation of protrusions into collagen, likely through activation of Cdc42.

Structured summary

PAKphysically interacts with Rac1 by pull down (View interaction)PAKphysically interacts with CDC42 by pull down (View interaction)     

Interplay of cysteinyl leukotrienes and TGF-β in the activation of hepatic stellate cells from Schistosoma mansoni granulomas

Hepatic stellate cells (HSCs) have a critical role in liver physiology, and in the pathogenesis of liver inflammation and fibrosis. Here, we investigated the interplay between leukotrienes (LT) and TGF-β in the activation mechanisms of HSCs from schistosomal granulomas (GR-HSCs). First, we demonstrated that GR-HSCs express 5-lipoxygenase (5-LO), as detected by immunolocalization in whole cells and confirmed in cell lysates through western blotting and by mRNA expression through RT-PCR. Moreover, mRNA expression of 5-LO activating protein (FLAP) and LTC₄-synthase was also documented, indicating that GR-HSCs have the molecular machinery required for LT synthesis. Morphological analysis of osmium and Oil-Red O-stained HSC revealed large numbers of small lipid droplets (also known as lipid bodies). We observed co-localization of lipid droplet protein marker (ADRP) and 5-LO by immunofluorescence microscopy. We demonstrated that GR-HSCs were able to spontaneously release cysteinyl-LTs (CysLTs), but not LTB_4, into culture supernatants. CysLT production was highly enhanced after TGF-β-stimulation. Moreover, the 5-LO inhibitor zileuton and 5-LO gene deletion were able to inhibit the TGF-β-stimulated proliferation of GR-HSCs, suggesting a role for LTs in HSC activation. Here, we extend the immunoregulatory function of HSC by demonstrating that HSC from liver granulomas of schistosome-infected mouse are able to release Cys-LTs in a TGF-β-regulated manner, potentially impacting pathogenesis and liver fibrosis in schistosomiasis.