• Toxicological Research
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• v.23 no.3
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• pp.197-205
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• 2007

Cancer metastasis is a major determinant of cancer patient mortality. Mounting evidence favors a strong positive role for $TGF-{\beta}$ in human cancer progression. The complex pattern on cross-talk of $TGF-{\beta}$ and the related other signaling pathways is an important area of investigation that will ultimately contribute to understanding of the bifunctional role of $TGF-{\beta}$ in cancer progression. This review summarizes some of the current understanding of $TGF-{\beta}$ signaling with a major focus in its contribution to the tumor cell invasion and metastasis. Five issues are addressed in this review: (1) $TGF-{\beta}$ signaling, (2) $TGF-{\beta}$ and EMT, (3) $TGF-{\beta}$ and MMP, (4) $TGF-{\beta}$ and Ras, and (5) Role of $TGF-{\beta}$ in invasion and metastasis. Due to the bifunctional cellular effects of $TGF-{\beta}$, as a tumor promoter and a tumor suppressor, more precisely defined $TGF-{\beta}$ signaling pathways need to be elucidated. According to the current literature, $TGF-{\beta}$ is clearly a major factor stimulating tumor progression through a complex spectrum of the interplay and cross-talk between various signaling molecules. Understanding the role of $TGF-{\beta}$ in invasion and metastasis will provide valuable information on establishing strategies to manipulate $TGF-{\beta}$ signaling which should be a high priority for the development of anti-metastatic therapeutics.

• BMB Reports
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• v.38 no.1
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• pp.9-16
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• 2005

Transforming Growth Factor (TGF)-$\beta$ family, including TGF-$\beta$, bone morphorgenic protein (BMP), and activn, plays an important role in essential cellular functions such as proliferation, differentiation, apoptosis, tissue remodeling, angiognesis, immune responses, and cell adhesions. TGF-$\beta$ predominantly transmits the signals through serine/threonine receptor kinases and cytoplasmic proteins called Smads. Since the discovery of TGF-$\beta$ in the early 1980s, the dysregulation of TGF-$\beta$/Smad signaling has been implicated in the pathogenesis of human diseases. Among signal transducers in TGF-$\beta$/Smad signaling, inhibitory Smads (I-Smads), Smad6 and Smad7, act as major negative regulators forming autoinhibitory feedback loops and mediate the cross-talking with other signaling pathways. Expressions of I-Smads are mainly regulated on the transcriptional levels and post-translational protein degradations and their intracellular levels are tightly controlled to maintain the homeostatic balances. However, abnormal levels of I-Smads in the pathological conditions elicit the altered TGF-$\beta$ signaling in cells, eventually causing TGF-$\beta$-related human diseases. Thus, exploring the molecular mechanisms about the regulations of I-Smads may provide the therapeutic clues for human diseases induced by the abnormal TGF-$\beta$ signaling.

• BMB Reports
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• v.50 no.12
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• pp.599-600
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• 2017

Many studies have focused on the tumor suppressive role of $TGF-{\beta}$ signaling during the early stages of tumorigenesis by activating the target genes involved in cytostasis and apoptosis. We investigated the effects of $TGF-{\beta}$ inhibition on early tumorigenesis in the liver, by employing diverse inhibitory methods. Strikingly, $TGF-{\beta}$ inhibition consistently suppressed hepatic tumorigenesis that was induced either by activated RAS plus p53 downregulation or by the co-activation of RAS and TAZ signaling; this demonstrates the requirements for canonical $TGF-{\beta}$ signaling in tumorigenesis. Moreover, we found that Snail is the target gene of the $TGF-{\beta}$ signaling pathway that promotes hepatic carcinogenesis. The knockdown of Snail suppressed the early tumorigenesis in the liver, as did the $TGF-{\beta}$ inhibition, while the ectopic expression of Snail restored tumorigenesis that was suppressed by the $TGF-{\beta}$ inhibition. Our findings establish the oncogenic $TGF-{\beta}$-Smad-Snail signaling axis during the early tumorigenesis in the liver.

• Biomedical Science Letters
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• v.24 no.4
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• pp.305-310
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• 2018

Microglia are emerging as critical regulators of innate immune responses in AD and other neurodegenerative disorders, highlighting the importance of understanding their molecular and cellular mechanisms. We attempted to determine the role of crosstalk signaling between $IFN-{\gamma}$ and $TGF-{\beta}$ in $A{\beta}$ clearance by microglia cells. We used in vitro and in vivo mouse models that recapitulated acute and chronic aspects of microglial responses to $A{\beta}$ peptides. We showed that crosstalk signaling between $TGF-{\beta}$ and Smad2 was an important mediator of neuro-inflammation. These findings suggest that microglial $TGF-{\beta}$ activity enhances the pathological progression to AD. As $TGF-{\beta}$ displays broad regulatory effects on beneficial microglial functions, the activation of inflammatory crosstalk signaling between $TGF-{\beta}$ and Smad2 may be a promising strategy to restore microglial functions, halt the progression of $A{\beta}$-driven pathology, and prevent AD development.

• Toxicological Research
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• v.27 no.4
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• pp.253-259
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• 2011

Transforming growth factor ${\beta}$ (TGF-${\beta}$) is involved in cellular processes including growth, differentiation, apoptosis, migration, and homeostasis. Generally, TGF-${\beta}$ is the inhibitor of cell cycle progression and plays a role in enhancing the antagonistic effects of many growth factors. Unlike the antiproliferative effect of TGF-${\beta}$, E2, an endogeneous estrogen, is stimulating cell proliferation in the estrogen-dependent organs, which are mediated via the estrogen receptors, $ER{\alpha}$ and $ER{\beta}$, and may be considered as a critical risk factor in tumorigenesis of hormone-responsive cancers. Previous researches reported the cross-talk between estrogen/$ER{\alpha}$ and TGF-${\beta}$ pathway. Especially, based on the E2-mediated inhibition of TGF-${\beta}$ signaling, we examined the inhibition effect of 4-tert-octylphenol (OP) and 4-nonylphenol (NP), which are well known xenoestrogens in endocrine disrupting chemicals (EDCs), on TGF-${\beta}$ signaling via semi-quantitative reverse-transcription PCR. The treatment of E2, OP, or NP resulted in the downregulation of TGF-${\beta}$ receptor2 (TGF-${\beta}$ R2) in TGF-${\beta}$ signaling pathway. However, the expression level of TGF-${\beta}1$ and TGF-${\beta}$ receptor1 (TGF-${\beta}$ R1) genes was not altered. On the other hand, E2, OP, or NP upregulated the expression of a cell-cycle regulating gene, c-myc, which is a oncogene and a downstream target gene of TGF-${\beta}$ signaling pathway. As a result of downregulation of TGF-${\beta}$ R2 and the upregulation of c-myc, E2, OP, or NP increased cell proliferation of BG-1 ovarian cancer cells. Taken together, these results suggest that E2 and these two EDCs may mediate cancer cell proliferation by inhibiting TGF-${\beta}$ signaling via the downregulation of TGF-${\beta}$ R2 and the upregulation of c-myc oncogene. In addition, it can be inferred that these EDCs have the possibility of tumorigenesis in estrogen-responsive organs by certainly representing estrogenic effect in inhibiting TGF-${\beta}$ signaling.

• Molecules and Cells
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• v.38 no.1
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• pp.20-25
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• 2015

TGF-${\beta}$ regulates pleiotropic cellular responses including cell growth, differentiation, migration, apoptosis, extracellular matrix production, and many other biological processes. Although non-Smad signaling pathways are being increasingly reported to play many roles in TGF-${\beta}$-mediated biological processes, Smads, especially receptor-regulated Smads (R-Smads), still play a central mediatory role in TGF-${\beta}$ signaling for epithelial-mesenchymal transition. Thus, the biological activities of R-Smads are tightly regulated at multiple points. Inhibitory Smad (I-Smad also called Smad7) acts as a critical endogenous negative feedback regulator of Smad-signaling pathways by inhibiting R-Smad phosphorylation and by inducing activated type I TGF-${\beta}$ receptor degradation. Roles played by Smad7 in health and disease are being increasingly reported, but the molecular mechanisms that regulate Smad7 are not well understood. In this study, we show that E3 ubiquitin ligase Itch acts as a positive regulator of TGF-${\beta}$ signaling and of subsequent EMT-related gene expression. Interestingly, the Itch-mediated positive regulation of TGF-${\beta}$ signaling was found to be dependent on Smad7 ubiquitination and its subsequent degradation. Further study revealed Itch acts as an E3 ubiquitin ligase for Smad7 polyubiquitination, and thus, that Itch is an important regulator of Smad7 activity and a positive regulator of TGF-${\beta}$ signaling and of TGF-${\beta}$-mediated biological processes. Accordingly, the study uncovers a novel regulatory mechanism whereby Smad7 is controlled by Itch.

• Journal of Cancer Prevention
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• v.23 no.4
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• pp.162-169
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• 2018

$TGF-{\beta}$ signaling plays a tumor suppressive role in normal and premalignant cells but promotes tumor progression during the late stages of tumor development. The $TGF-{\beta}$ signaling pathway is tightly regulated at various levels, including transcriptional and post-translational mechanisms. Ubiquitination of signaling components, such as receptors and Smad proteins is one of the key regulatory mechanisms of $TGF-{\beta}$ signaling. Tripartite motif (TRIM) family of proteins is a highly conserved group of E3 ubiquitin ligase proteins that have been implicated in a variety of cellular functions, including cell growth, differentiation, immune response, and carcinogenesis. Recent emerging studies have shown that some TRIM family proteins function as important regulators in tumor initiation and progression. This review summarizes current knowledge of TRIM family proteins regulating the $TGF-{\beta}$ signaling pathway with relevance to cancer.

• Biomolecules & Therapeutics
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• v.21 no.5
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• pp.323-331
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• 2013

TGF-${\beta}$ pathway is being extensively evaluated as a potential therapeutic target. The transforming growth factor-${\beta}$ (TGF-${\beta}$) signaling pathway has the dual role in both tumor suppression and tumor promotion. To design cancer therapeutics successfully, it is important to understand TGF-${\beta}$ related functional contexts. This review discusses the molecular mechanism of the TGF-${\beta}$ pathway and describes the different ways of tumor suppression and promotion by TGF-${\beta}$. In the last part of the review, the data on targeting TGF-${\beta}$ pathway for cancer treatment is assessed. The TGF-${\beta}$ inhibitors in pre-clinical studies, and Phase I and II clinical trials are updated.

• Molecules and Cells
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• v.40 no.3
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• pp.211-221
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• 2017

Transforming growth factor ${\beta}1$ $(TGF{\beta}1)/Smad4$ signaling plays a pivotal role in maintenance of the dynamic balance between bone formation and resorption. The microRNA miR-155 has been reported to exert a significant role in the differentiation of macrophage and dendritic cells. The goal of this study was to determine whether miR-155 regulates osteoclast differentiation through $TGF{\beta}1/Smad4$ signaling. Here, we present that $TGF{\beta}1$ elevated miR-155 levels during osteoclast differentiation through the stimulation of M-CSF and RANKL. Additionally, we found that silencing Smad4 attenuated the upregulation of miR-155 induced by $TGF{\beta}1$. The results of luciferase reporter experiments and ChIP assays demonstrated that $TGF{\beta}1$ promoted the binding of Smad4 to the miR-155 promoter at a site located in 454 bp from the transcription start site in vivo, further verifying that miR-155 is a transcriptional target of the $TGF{\beta}1/Smad4$ pathway. Subsequently, TRAP staining and qRT-PCR analysis revealed that silencing Smad4 impaired the $TGF{\beta}1$-mediated inhibition on osteoclast differentiation. Finally, we found that miR-155 may target SOCS1 and MITF to suppress osteoclast differentiation. Taken together, we provide the first evidence that $TGF{\beta}1/Smad4$ signaling affects osteoclast differentiation by regulation of miR-155 expression and the use of miR-155 as a potential therapeutic target for osteoclast-related diseases shows great promise.

• IMMUNE NETWORK
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• v.14 no.5
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• pp.237-240
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• 2014

Endoglin (also known as CD105 or TGF-${\beta}$ type III receptor) is a co-receptor involved in TGF-${\beta}$ signaling. In atherosclerosis, TGF-${\beta}$ signaling is crucial in regulating disease progression owing to its anti-inflammatory effects as well as its inhibitory effects on smooth muscle cell proliferation and migration. Endoglin is a regulator of TGF-${\beta}$ signaling, but its role in atherosclerosis has yet to be defined. This review focuses on the roles of the various forms of endoglin in atherosclerosis. The expression of the two isoforms of endoglin (long-form and short-form) is increased in atherosclerotic lesions, and the expression of the soluble forms of endoglin is upregulated in sera of patients with hypercholesterolemia and atherosclerosis. Interestingly, long-form endoglin shows an atheroprotective effect via the induction of eNOS expression, while short-form and soluble endoglin enhance atherogenesis by inhibiting eNOS expression and TGF-${\beta}$ signaling. This review summarizes evidence suggesting that the different forms of endoglin have distinct roles in atherosclerosis.