Involvement of EGF receptor and c-Src in the survival signals induced by TGF-β1 in hepatocytes

Relationship of Signaling Pathways between RKIP Expression and the Inhibition of EMT-Inducing Transcription Factors SNAIL1/2, TWIST1/2 and ZEB1/2

Untreated primary carcinomas often lead to progression, invasion and metastasis, a process that involves the epithelial-to-mesenchymal transition (EMT). Several transcription factors (TFs) mediate the development of EMT, including SNAIL1/SNAIL2, TWIST1/TWIST2 and ZEB1/ZEB2, which are overexpressed in various carcinomas along with the under expression of the metastasis suppressor Raf Kinase Inhibitor Protein (RKIP). Overexpression of RKIP inhibits EMT and the above associated TFs. We, therefore, hypothesized that there are inhibitory cross-talk signaling pathways between RKIP and these TFs. Accordingly, we analyzed the various properties and biomarkers associated with the epithelial and mesenchymal tissues and the various molecular signaling pathways that trigger the EMT phenotype such as the TGF-β, the RTK and the Wnt pathways. We also presented the various functions and the transcriptional, post-transcriptional and epigenetic regulations for the expression of each of the EMT TFs. Likewise, we describe the transcriptional, post-transcriptional and epigenetic regulations of RKIP expression. Various signaling pathways mediated by RKIP, including the Raf/MEK/ERK pathway, inhibit the TFs associated with EMT and the stabilization of epithelial E-Cadherin expression. The inverse relationship between RKIP and the TF expressions and the cross-talks were further analyzed by bioinformatic analysis. High mRNA levels of RKIP correlated negatively with those of SNAIL1, SNAIL2, TWIST1, TWIST2, ZEB1, and ZEB2 in several but not all carcinomas. However, in these carcinomas, high levels of RKIP were associated with good prognosis, whereas high levels of the above transcription factors were associated with poor prognosis. Based on the inverse relationship between RKIP and EMT TFs, it is postulated that the expression level of RKIP in various carcinomas is clinically relevant as both a prognostic and diagnostic biomarker. In addition, targeting RKIP induction by agonists, gene therapy and immunotherapy will result not only in the inhibition of EMT and metastases in carcinomas, but also in the inhibition of tumor growth and reversal of resistance to various therapeutic strategies. However, such targeting strategies must be better investigated as a result of tumor heterogeneities and inherent resistance and should be better adapted as personalized medicine.

Exploring the role of granzyme B in subretinal fibrosis of age-related macular degeneration

Age-related macular degeneration (AMD), a prevalent and progressive degenerative disease of the macula, is the leading cause of blindness in elderly individuals in developed countries. The advanced stages include neovascular AMD (nAMD), characterized by choroidal neovascularization (CNV), leading to subretinal fibrosis and permanent vision loss. Despite the efficacy of anti-vascular endothelial growth factor (VEGF) therapy in stabilizing or improving vision in nAMD, the development of subretinal fibrosis following CNV remains a significant concern. In this review, we explore multifaceted aspects of subretinal fibrosis in nAMD, focusing on its clinical manifestations, risk factors, and underlying pathophysiology. We also outline the potential sources of myofibroblast precursors and inflammatory mechanisms underlying their recruitment and transdifferentiation. Special attention is given to the potential role of mast cells in CNV and subretinal fibrosis, with a focus on putative mast cell mediators, tryptase and granzyme B. We summarize our findings on the role of GzmB in CNV and speculate how GzmB may be involved in the pathological transition from CNV to subretinal fibrosis in nAMD. Finally, we discuss the advantages and drawbacks of animal models of subretinal fibrosis and pinpoint potential therapeutic targets for subretinal fibrosis.

New and Old Key Players in Liver Cancer

Liver cancer represents a major health problem worldwide with growing incidence and high mortality, hepatocellular carcinoma (HCC) being the most frequent. Hepatocytes are likely the cellular origin of most HCCs through the accumulation of genetic alterations, although hepatic progenitor cells (HPCs) might also be candidates in specific cases, as discussed here. HCC usually develops in a context of chronic inflammation, fibrosis, and cirrhosis, although the role of fibrosis is controversial. The interplay between hepatocytes, immune cells and hepatic stellate cells is a key issue. This review summarizes critical aspects of the liver tumor microenvironment paying special attention to platelets as new key players, which exert both pro- and anti-tumor effects, determined by specific contexts and a tight regulation of platelet signaling. Additionally, the relevance of specific signaling pathways, mainly HGF/MET, EGFR and TGF-β is discussed. HGF and TGF-β are produced by different liver cells and platelets and regulate not only tumor cell fate but also HPCs, inflammation and fibrosis, these being key players in these processes. The role of C3G/RAPGEF1, required for the proper function of HGF/MET signaling in HCC and HPCs, is highlighted, due to its ability to promote HCC growth and, regulate HPC fate and platelet-mediated actions on liver cancer.

GPR56 signaling pathway network and its dynamics in the mesenchymal transition of glioblastoma

G protein-coupled receptor 56 (GPR56/ADGRG1) is a multifunctional adhesion GPCR involved in diverse biological processes ranging from development to cancer. In our earlier study, we reported that GPR56 is expressed heterogeneously in glioblastoma (GBM) and is involved in the mesenchymal transition, making it a promising therapeutic target (Ganesh et al., 2022). Despite its important role in cancer, its mechanism of action or signaling is not completely understood. Thus, based on transcriptomic, proteomic, and phosphoproteomic differential expression data of GPR56 knockdown U373-GBM cells included in our above study along with detailed literature mining of the molecular events plausibly associated with GPR56 activity, we have constructed a signaling pathway map of GPR56 as may be applicable in mesenchymal transition in GBM. The map incorporates more than 100 molecular entities including kinases, receptors, ion channels, and others associated with Wnt, integrin, calcium signaling, growth factors, and inflammation signaling pathways. We also considered intracellular and extracellular factors that may influence the activity of the pathway entities. Here we present a curated signaling map of GPR56 in the context of GBM and discuss the relevance and plausible cross-connectivity across different axes attributable to GPR56 function. GPR56 signaling and mesenchymal transition.

The type II TGF-β receptor phosphorylates Tyr 182 in the type I receptor to activate downstream Src signaling

Transforming growth factor–β (TGF-β) signaling has important roles during embryonic development and in tissue homeostasis. TGF-β ligands exert cellular effects by binding to type I (TβRI) and type II (TβRII) receptors and inducing both SMAD-dependent and SMAD-independent intracellular signaling pathways, the latter of which includes the activation of the tyrosine kinase Src. We investigated the mechanism by which TGF-β stimulation activates Src in human and mouse cells. Before TGF-β stimulation, inactive Src was complexed with TβRII. Upon TGF-β1 stimulation, TβRII associated with and phosphorylated TβRI at Tyr 182 . Binding of Src to TβRI involved the interaction of the Src SH2 domain with phosphorylated Tyr 182 and the interaction of the Src SH3 domain with a proline-rich region in TβRI and led to the activation of Src kinase activity and Src autophosphorylation. TGF-β1–induced Src activation required the kinase activities of TβRII and Src but not that of TβRI. Activated Src also phosphorylated TβRI on several tyrosine residues, which may stabilize the binding of Src to the receptor. Src activation was required for the ability of TGF-β to induce fibronectin production and migration in human breast carcinoma cells and to induce α–smooth muscle actin and actin reorganization in mouse fibroblasts. Thus, TGF-β induces Src activation by stimulating a direct interaction with TβRI that depends on tyrosine phosphorylation of TβRI by TβRII.

The Bright and the Dark Side of TGF-β Signaling in Hepatocellular Carcinoma: Mechanisms, Dysregulation, and Therapeutic Implications

Simple Summary

Transforming growth factor β (TGF-β) signaling is a preeminent regulator of diverse cellular and physiological processes. Frequent dysregulation of TGF-β signaling has been implicated in cancer. In hepatocellular carcinoma (HCC), the most prevalent form of primary liver cancer, the autocrine and paracrine effects of TGF-β have paradoxical implications. While acting as a potent tumor suppressor pathway in the early stages of malignancy, TGF-β diverts to a promoter of tumor progression in the late stages, reflecting its bright and dark natures, respectively. Within this context, targeting TGF-β represents a promising therapeutic option for HCC treatment. We discuss here the molecular properties of TGF-β signaling in HCC, attempting to provide an overview of its effects on tumor cells and the stroma. We also seek to evaluate the dysregulation mechanisms that mediate the functional switch of TGF-β from a tumor suppressor to a pro-tumorigenic signal. Finally, we reconcile its biphasic nature with the therapeutic implications.

Abstract

Hepatocellular carcinoma (HCC) is associated with genetic and nongenetic aberrations that impact multiple genes and pathways, including the frequently dysregulated transforming growth factor β (TGF-β) signaling pathway. The regulatory cytokine TGF-β and its signaling effectors govern a broad spectrum of spatiotemporally regulated molecular and cellular responses, yet paradoxically have dual and opposing roles in HCC progression. In the early stages of tumorigenesis, TGF-β signaling enforces profound tumor-suppressive effects, primarily by inducing cell cycle arrest, cellular senescence, autophagy, and apoptosis. However, as the tumor advances in malignant progression, TGF-β functionally switches to a pro-tumorigenic signal, eliciting aggressive tumor traits, such as epithelial–mesenchymal transition, tumor microenvironment remodeling, and immune evasion of cancer cells. On this account, the inhibition of TGF-β signaling is recognized as a promising therapeutic strategy for advanced HCC. In this review, we evaluate the functions and mechanisms of TGF-β signaling and relate its complex and pleiotropic biology to HCC pathophysiology, attempting to provide a detailed perspective on the molecular determinants underlying its functional diversion. We also address the therapeutic implications of the dichotomous nature of TGF-β signaling and highlight the rationale for targeting this pathway for HCC treatment, alone or in combination with other agents.

Comparative Metabolomics and Proteomics Reveal Vibrio parahaemolyticus Targets Hypoxia-Related Signaling Pathways of Takifugu obscurus

Coronavirus disease 2019 (COVID-19) raises the issue of how hypoxia destroys normal physiological function and host immunity against pathogens. However, there are few or no comprehensive omics studies on this effect. From an evolutionary perspective, animals living in complex and changeable marine environments might develop signaling pathways to address bacterial threats under hypoxia. In this study, the ancient genomic model animal Takifugu obscurus and widespread Vibrio parahaemolyticus were utilized to study the effect. T. obscurus was challenged by V. parahaemolyticus or (and) exposed to hypoxia. The effects of hypoxia and infection were identified, and a theoretical model of the host critical signaling pathway in response to hypoxia and infection was defined by methods of comparative metabolomics and proteomics on the entire liver. The changing trends of some differential metabolites and proteins under hypoxia, infection or double stressors were consistent. The model includes transforming growth factor-β1 (TGF-β1), hypoxia-inducible factor-1α (HIF-1α), and epidermal growth factor (EGF) signaling pathways, and the consistent changing trends indicated that the host liver tended toward cell proliferation. Hypoxia and infection caused tissue damage and fibrosis in the portal area of the liver, which may be related to TGF-β1 signal transduction. We propose that LRG (leucine-rich alpha-2-glycoprotein) is widely involved in the transition of the TGF-β1/Smad signaling pathway in response to hypoxia and pathogenic infection in vertebrates as a conserved molecule.

Hepatocarcinogenesis Prevention by Pirfenidone Is PPARγ Mediated and Involves Modification of Nuclear NF-kB p65/p50 Ratio

Targeted therapies for regulating processes such as inflammation, apoptosis, and fibrogenesis might modulate human HCC development. Pirfenidone (PFD) has shown anti-fibrotic and anti-inflammatory functions in both clinical and experimental studies. The aim of this study was to evaluate PPARγ expression and localization in samples of primary human tumors and assess PFD-effect in early phases of hepatocarcinogenic process. Human HCC tissue samples were obtained by surgical resection. Experimental hepatocarcinogenesis was induced in male Fischer-344 rats. TGF-β1 and α-SMA expression was evaluated as fibrosis markers. NF-kB cascade, TNFα, IL-6, and COX-2 expression and localization were evaluated as inflammation indicators. Caspase-3, p53, and PARP-1 were used as apoptosis markers, PCNA for proliferation. Finally, PPARα and PPARγ expression were evaluated to understand the effect of PFD on the activation of such pathways. PPARγ expression was predominantly localized in cytoplasm in human HCC tissue. PFD was effective to prevent histopathological damage and TGF-β1 and α-SMA overexpression in the experimental model. Anti-inflammatory effects of PFD correlate with diminished IKK and decrease in both IkB-phosphorylation/NF-kB p65 expression and p65-translocation into the nucleus. Pro-apoptotic PFD-induced effects are related with p53 expression, Caspase-3 p17 activation, and PARP-1-cleavage. In conclusion, PFD acts as a tumor suppressor by preventing fibrosis, reducing inflammation, and promoting apoptosis in MRHM.

The TGF-β/NADPH Oxidases Axis in the Regulation of Liver Cell Biology in Health and Disease

The Transforming Growth Factor-beta (TGF-β) pathway plays essential roles in liver development and homeostasis and become a relevant factor involved in different liver pathologies, particularly fibrosis and cancer. The family of NADPH oxidases (NOXs) has emerged in recent years as targets of the TGF-β pathway mediating many of its effects on hepatocytes, stellate cells and macrophages. This review focuses on how the axis TGF-β/NOXs may regulate the biology of different liver cells and how this influences physiological situations, such as liver regeneration, and pathological circumstances, such as liver fibrosis and cancer. Finally, we discuss whether NOX inhibitors may be considered as potential therapeutic tools in liver diseases.

Modulation of the TGF-β signaling pathway by long noncoding RNA in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a type of liver cancer with poor prognosis. There have been demonstrated to exist many possible mechanisms in HCC tumorigenesis, and recent investigations have provided some promising therapy targets. However, further mechanisms remain to be researched to improve the therapeutic strategy and diagnosis of HCC. Transforming growth factor-β (TGF-β) is a pleiotropic cytokine which plays critical roles in networks of different cellular processes, and TGF-β signaling has been found to participate in tumor initiation and development of HCC in recent years. Moreover, among the molecules and signaling pathways, researchers paid more attention to lncRNAs (long non-coding RNAs), but the connection between lncRNAs and TGF-βremain poorly understood. In this review, we conclude the malignant procedure which lncRNAs and TGF-β involved in, and summarize the mechanisms of lncRNAs and TGF-βin HCC initiation and development. Furthermore, the interaction between lncRNA and TGF-β are paid more attention, and the potential therapy targets are mentioned.

The dichotomous role of TGF-β in controlling liver cancer cell survival and proliferation

Hepatocellular carcinoma (HCC) is the major form of primary liver cancer and one of the most prevalent and life-threatening malignancies globally. One of the hallmarks in HCC is the sustained cell survival and proliferative signals, which are determined by the balance between oncogenes and tumor suppressors. Transforming growth factor beta (TGF-β) is an effective growth inhibitor of epithelial cells including hepatocytes, through induction of cell cycle arrest, apoptosis, cellular senescence, or autophagy. The antitumorigenic effects of TGF-β are bypassed during liver tumorigenesis via multiple mechanisms. Furthermore, along with malignant progression, TGF-β switches to promote cancer cell survival and proliferation. This dichotomous nature of TGF-β is one of the barriers to therapeutic targeting in liver cancer. Thereafter, understanding the underlying molecular mechanisms is a prerequisite for discovering novel antitumor drugs that may specifically disable the growth-promoting branch of TGF-β signaling or restore its tumor-suppressive arm. This review summarizes how TGF-β inhibits or promotes liver cancer cell survival and proliferation, highlighting the functional switch mechanisms during the process.

PTPRε Acts as a Metastatic Promoter in Hepatocellular Carcinoma by Facilitating Recruitment of SMAD3 to TGF-β Receptor 1

BACKGROUND AND AIMS

Transforming growth factor beta (TGF-β) suppresses early stages of tumorigenesis, but contributes to the migration and metastasis of cancer cells. However, the role of TGF-β signaling in invasive prometastatic hepatocellular carcinoma (HCC) is poorly understood. In this study, we investigated the roles of canonical TGF-β/mothers against decapentaplegic homolog 3 (SMAD3) signaling and identified downstream effectors on HCC migration and metastasis.

APPROACH AND RESULTS

By using in vitro trans-well migration and invasion assays and in vivo metastasis models, we demonstrated that SMAD3 and protein tyrosine phosphatase receptor epsilon (PTPRε) promote migration, invasion, and metastasis of HCC cells in vitro and in vivo. Further mechanistic studies revealed that, following TGF-β stimulation, SMAD3 binds directly to PTPRε promoters to activate its expression. PTPRε interacts with TGFBR1/SMAD3 and facilitates recruitment of SMAD3 to TGFBR1, resulting in a sustained SMAD3 activation status. The tyrosine phosphatase activity of PTPRε is important for binding with TGFBR1, recruitment and activation of SMAD3, and its prometastatic role in vitro. A positive correlation between pSMAD3/SMAD3 and PTPRε expression was determined in HCC samples, and high expression of SMAD3 or PTPRε was associated with poor prognosis of patients with HCC.

CONCLUSIONS

PTPRε positive feedback regulates TGF-β/SMAD3 signaling to promote HCC metastasis.

Downregulation of low-density lipoprotein receptor class A domain-containing protein 4 (Ldlrad4) in the liver of rats treated with nongenotoxic hepatocarcinogen to induce transforming growth factor β signaling promoting cell proliferation and suppressing apoptosis in early hepatocarcinogenesis

We previously found downregulation of low-density lipoprotein receptor class A domain-containing protein 4 (LDLRAD4), a negative regulator of transforming growth factor (TGF)-β signaling, in glutathione S-transferase placental form (GST-P) expressing (⁺ ) pre-neoplastic lesions produced by treatment with nongenotoxic hepatocarcinogens for up to 90 days in rats. Here, we investigated the relationship between LDLRAD4 downregulation and TGFβ signaling in nongenotoxic hepatocarcinogenesis. The transcripts of Tgfb and Hb-egf increased after ≥28 days of treatment. After 84 or 90 days, Snai1 increased transcripts and the subpopulation of GST-P⁺ foci downregulating LDLRAD4 co-expressed TGFβ1, phosphorylated EGFR, or phosphorylated AKT2, and downregulated PTEN, showing higher incidences than those in GST-P⁺ foci expressing LDLRAD4. The subpopulation of GST-P⁺ foci downregulating LDLRAD4 also co-expressed caveolin-1 or TACE/ADAM17, suggesting that disruptive activation of TGFβ signaling through a loss of LDLRAD4 enhances EGFR and PTEN/AKT-dependent pathways via caveolin-1-dependent activation of TACE/ADAM17 during nongenotoxic hepatocarcinogenesis. The numbers of c-MYC⁺ cells and PCNA⁺ cells were higher in LDLRAD4-downregulated GST-P⁺ foci than in LDLRAD4-expressing GST-P⁺ foci, suggesting a preferential proliferation of pre-neoplastic cells by LDLRAD4 downregulation. Nongenotoxic hepatocarcinogens markedly downregulated Nox4 after 28 days and later decreased cleaved caspase 3⁺ cells in LDLRAD4-downregulated GST-P⁺ foci, suggesting an attenuation of apoptosis by LDLRAD4 downregulation through activation of the EGFR pathway. At the late hepatocarcinogenesis stage in a two-stage model, LDLRAD4 downregulation was higher in adenoma and carcinoma than in pre-neoplastic cell foci, suggesting a role of LDLRAD4 downregulation in tumor development. Our results suggest that nongenotoxic hepatocarcinogens cause disruptive activation of TGFβ signaling through downregulating LDLRAD4 toward carcinogenesis in the rat liver.

Expression of TLR-2 in hepatocellular carcinoma is associated with tumour proliferation, angiogenesis and Caspase-3 expression

AIMS

Unlike other Toll-like receptors (TLRs), the role of toll like receptor 2 (TLR-2) in the pathogenesis of chronic liver disease and hepatocellular carcinoma (HCC) is not well studied. We, therefore, set out to investigate the expression of TLR-2 in different chronic liver disease states along with other markers of cell death, cellular proliferation and tissue vascularisation METHODS AND RESULTS: Immunohistochemistry was performed on liver tissue microarrays comprising hepatitis, cirrhosis and HCC patient samples using antibodies against TLR-2, Ki-67, Caspase-3 and VEGF. This was done in order to characterise receptor expression and translocation, apoptosis, cell proliferation and vascularisation. Cytoplasmic TLR-2 expression was found to be weak in 5/8 normal liver cases, 10/19 hepatitis cases and 8/21 cirrhosis patients. Moderate to strong TLR-2 expression was observed in some cases of hepatitis and cirrhosis. Both, nuclear and cytoplasmic TLR-2 expression was present in HCC with weak intensity in 11/41 cases, and moderate to strong staining in 19/41 cases. Eleven HCC cases were TLR-2 negative. Surprisingly, both cytoplasmic and nuclear TLR-2 expression in HCC were found to significantly correlate with proliferative index (r = 0.24 and 0.37), Caspase-3 expression (r = 0.27 and 0.38) and vascularisation (r = 0.56 and 0.23). Further, nuclear TLR-2 localisation was predominant in HCC, whereas cytoplasmic expression was more prevalent in hepatitis and cirrhosis. Functionally, treatment of HUH7 HCC cells with a TLR-2 agonist induced the expression of cellular proliferation and vascularisation markers CD34 and VEGF.

CONCLUSIONS

Our results demonstrate a positive correlation between the expression of TLR-2 and other markers of proliferation and vascularisation in HCC which suggests a possible role for TLR-2 in HCC pathogenesis.

Hepatitis C Virus and Hepatocellular Carcinoma: When the Host Loses Its Grip

Chronic infection with hepatitis C virus (HCV) is a major cause of hepatocellular carcinoma (HCC). Novel treatments with direct-acting antivirals achieve high rates of sustained virologic response; however, the HCC risk remains elevated in cured patients, especially those with advanced liver disease. Long-term HCV infection causes a persistent and accumulating damage of the liver due to a combination of direct and indirect pro-oncogenic mechanisms. This review describes the processes involved in virus-induced disease progression by viral proteins, derailed signaling, immunity, and persistent epigenetic deregulation, which may be instrumental to develop urgently needed prognostic biomarkers and as targets for novel chemopreventive therapies.

Th2 cells as an intermediate for the differentiation of naïve T cells into Th9 cells, associated with the Smad3/Smad4 and IRF4 pathway

Type 9 T-helper (Th9) cells are associated with atopic and inflammatory diseases. Their increased levels and functions contribute to a number of inflammatory disorders, where they are accompanied by enhanced Th2-cell activity. However, there is currently no consensus regarding the association between Th9 and Th2 cells. Th9 cells may be induced from naïve T (Th0) cells under specific polarization conditions in vitro, a process driven by the addition of specific cytokines. In the present study, Th0 cells were cultured under Th9-polarizing conditions to promote differentiation into interleukin (IL)-4⁺ IL-9^- or IL-4^- IL-9⁺ T cells after 3 or 5 days in culture, respectively; the mRNA expression levels of IL-9 and IL-4 were consistent with the induced cell types. Simultaneously, the levels of interferon-regulatory factor 4 (IRF-4) and Smad3/Smad4 were significantly increased following Th9-cell polarization. It was therefore proposed that Th2 cells may be generated in the early stages of Th9-cell differentiation, and then ultimately differentiate into Th9 cells via the Smad3/Smad4 and IRF-4 activation pathway.

Clathrin switches transforming growth factor-β role to pro-tumorigenic in liver cancer

BACKGROUND & AIMS

Upon ligand binding, tyrosine kinase receptors, such as epidermal growth factor receptor (EGFR), are recruited into clathrin-coated pits for internalization by endocytosis, which is relevant for signalling and/or receptor degradation. In liver cells, transforming growth factor-β (TGF-β) induces both pro- and anti-apoptotic signals; the latter are mediated by the EGFR pathway. Since EGFR mainly traffics via clathrin-coated vesicles, we aimed to analyse the potential role of clathrin in TGF-β-induced signalling in liver cells and its relevance in liver cancer.

METHODS

Real-Time PCR and immunohistochemistry were used to analyse clathrin heavy-chain expression in human (CLTC) and mice (Cltc) liver tumours. Transient knockdown (siRNA) or overexpression of CLTC were used to analyse its role on TGF-β and EGFR signalling in vitro. Bioinformatic analysis was used to determine the effect of CLTC and TGFB1 expression on prognosis and overall survival in patients with hepatocellular carcinoma (HCC).

RESULTS

Clathrin expression increased during liver tumorigenesis in humans and mice. CLTC knockdown cells responded to TGF-β phosphorylating SMADs (canonical signalling) but showed impairment in the anti-apoptotic signals (EGFR transactivation). Experiments of loss or gain of function in HCC cells reveal an essential role for clathrin in inhibiting TGF-β-induced apoptosis and upregulation of its pro-apoptotic target NOX4. Autocrine TGF-β signalling in invasive HCC cells upregulates CLTC expression, switching its role to pro-tumorigenic. A positive correlation between TGFB1 and CLTC was found in HCC cells and patients. Patients expressing high levels of TGFB1 and CLTC had a worse prognosis and lower overall survival.

CONCLUSIONS

This work describes a novel role for clathrin in liver tumorigenesis, favouring non-canonical pro-tumorigenic TGF-β pathways. CLTC expression in human HCC samples could help select patients that would benefit from TGF-β-targeted therapy.

LAY SUMMARY

Clathrin heavy-chain expression increases during liver tumorigenesis in humans (CLTC) and mice (Cltc), altering the cellular response to TGF-β in favour of anti-apoptotic/pro-tumorigenic signals. A positive correlation between TGFB1 and CLTC was found in HCC cells and patients. Patients expressing high levels of TGFB1 and CLTC had a worse prognosis and lower overall survival. CLTC expression in HCC human samples could help select patients that would benefit from therapies targeting TGF-β.

Downregulation of Epidermal Growth Factor Receptor in hepatocellular carcinoma facilitates Transforming Growth Factor-β-induced epithelial to amoeboid transition

The Epidermal Growth Factor Receptor (EGFR) and the Transforming Growth Factor-beta (TGF-β) are key regulators of hepatocarcinogenesis. Targeting EGFR was proposed as a promising therapy; however, poor success was obtained in human hepatocellular carcinoma (HCC) clinical trials. Here, we describe how EGFR is frequently downregulated in HCC patients while TGF-β is upregulated. Using 2D/3D cellular models, we show that after EGFR loss, TGF-β is more efficient in its pro-migratory and invasive effects, inducing epithelial to amoeboid transition. EGFR knock-down promotes loss of cell-cell and cell-to-matrix adhesion, favouring TGF-β-induced actomyosin contractility and acquisition of an amoeboid migratory phenotype. Moreover, TGF-β upregulates RHOC and CDC42 after EGFR silencing, promoting Myosin II in amoeboid cells. Importantly, low EGFR combined with high TGFB1 or RHOC/CDC42 levels confer poor patient prognosis. In conclusion, this work reveals a new tumour suppressor function for EGFR counteracting TGF-β-mediated epithelial to amoeboid transitions in HCC, supporting a rational for targeting the TGF-β pathway in patients with low EGFR expression. Our work also highlights the relevance of epithelial to amoeboid transition in human tumours and the need to better target this process in the clinic.

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EGFR expression is low and heterogeneous in a great percentage of HCC patients.

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EGFR loss in HCC cells facilitates TGF-β pro-migratory and invasive functions.

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EGFR silenced HCC cells respond to TGF-β inducing epithelial-amoeboid transition.

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TGF-β upregulates RHOC and CDC42 and actomyosin contractility in EGFR silenced cells.

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Low EGFR combined with high TGFB1 or RHOC/CDC42 levels confer poor HCC prognosis.

Transforming Growth Factor-β and Axl Induce CXCL5 and Neutrophil Recruitment in Hepatocellular Carcinoma

Transforming growth factor (TGF)-β suppresses early hepatocellular carcinoma (HCC) development but triggers pro-oncogenic abilities at later stages. Recent data suggest that the receptor tyrosine kinase Axl causes a TGF-β switch toward dedifferentiation and invasion of HCC cells. Here, we analyzed two human cellular HCC models with opposing phenotypes in response to TGF-β. Both HCC models showed reduced proliferation and clonogenic growth behavior following TGF-β stimulation, although they exhibited differences in chemosensitivity and migratory abilities, suggesting that HCC cells evade traits of anti-oncogenic TGF-β. Transcriptome profiling revealed differential regulation of the chemokine CXCL5, which positively correlated with TGF-β expression in HCC patients. The expression and secretion of CXCL5 was dependent on Axl expression, suggesting that CXCL5 is a TGF-β target gene collaborating with Axl signaling. Loss of either TGF-β or Axl signaling abrogated CXCL5-dependent attraction of neutrophils. In mice, tumor formation of transplanted HCC cells relied on CXCL5 expression. In HCC patients, high levels of Axl and CXCL5 correlated with advanced tumor stages, recruitment of neutrophils into HCC tissue, and reduced survival. Conclusion: The synergy of TGF-β and Axl induces CXCL5 secretion, causing the infiltration of neutrophils into HCC tissue. Intervention with TGF-β/Axl/CXCL5 signaling may be an effective therapeutic strategy to combat HCC progression in TGF-β-positive patients.

ERK1/2-mediated EGFR-signaling is required for TGFβ-induced lens epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) plays a critical role in the pathogenesis of fibrotic cataract. Transforming growth factor-beta (TGFβ) is a potent inducer of this fibrotic process in lens. Recent studies in cancer progression have shown that in addition to activating the canonical Smad signaling pathway, TGFβ can also transactivate the epidermal growth factor receptor (EGFR) to enhance invasive cell migration. The present study aims to elucidate the involvement of EGFR-signaling in TGFβ-induced EMT in LECs. Treatment with TGFβ2 induced transdifferentiation of LECs into myofibroblastic cells, typical of an EMT. TGFβ2 induced the phosphorylation of the EGFR and upregulation of Egfr and Hb-egf gene expression. Pharmacologic inhibition of EGFR-signaling using PD153035 inhibited TGFβ-induced EMT, including the upregulation of mesenchymal markers and downregulation of epithelial markers. Crosstalk between TGFβ2-induced EGFR and ERK1/2 was evident, with both pathways impacting on Smad2/3-signaling. Our finding that TGFβ2 transactivates downstream EGFR-signaling reveals a previously unknown mechanism in the pathogenesis of cataract. Understanding the complex interplay between divergent canonical and non-canonical signaling pathways, as well as downstream target genes involved in TGFβ-induced EMT, will enable the development of more effective targeted therapies in the pharmacological treatment of cataract.

Foxf2 plays a dual role during transforming growth factor beta-induced epithelial to mesenchymal transition by promoting apoptosis yet enabling cell junction dissolution and migration

Background

The most life-threatening step during malignant tumor progression is reached when cancer cells leave the primary tumor mass and seed metastasis in distant organs. To infiltrate the surrounding tissue and disseminate throughout the body, single motile tumor cells leave the tumor mass by breaking down cell-cell contacts in a process called epithelial to mesenchymal transition (EMT). An EMT is a complex molecular and cellular program enabling epithelial cells to abandon their differentiated phenotype, including cell-cell adhesion and cell polarity, and to acquire mesenchymal features and invasive properties.

Methods

We employed gene expression profiling and functional experiments to study transcriptional control of transforming growth factor (TGF)β-induced EMT in normal murine mammary gland epithelial (NMuMG) cells.

Results

We identified that expression of the transcription factor forkhead box protein F2 (Foxf2) is upregulated during the EMT process. Although it is not required to gain mesenchymal markers, Foxf2 is essential for the disruption of cell junctions and the downregulation of epithelial markers in NMuMG cells treated with TGFβ. Foxf2 is critical for the downregulation of E-cadherin by promoting the expression of the transcriptional repressors of E-cadherin, Zeb1 and Zeb2, while repressing expression of the epithelial maintenance factor Id2 and miRNA 200 family members. Moreover, Foxf2 is required for TGFβ-mediated apoptosis during EMT by the transcriptional activation of the proapoptotic BH3-only protein Noxa and by the negative regulation of epidermal growth factor receptor (EGFR)-mediated survival signaling through direct repression of its ligands betacellulin and amphiregulin. The dual function of Foxf2 during EMT is underscored by the finding that high Foxf2 expression correlates with good prognosis in patients with early noninvasive stages of breast cancer, but with poor prognosis in advanced breast cancer.

Conclusions

Our data identify the transcription factor Foxf2 as one of the important regulators of EMT, displaying a dual function in promoting tumor cell apoptosis as well as tumor cell migration.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-1043-6) contains supplementary material, which is available to authorized users.

Transforming Growth Factor-β-Induced Cell Plasticity in Liver Fibrosis and Hepatocarcinogenesis

The Transforming Growth Factor-beta (TGF-β) family plays relevant roles in the regulation of different cellular processes that are essential for tissue and organ homeostasis. In the case of the liver, TGF-β signaling participates in different stages of disease progression, from initial liver injury toward fibrosis, cirrhosis and cancer. When a chronic injury takes place, mobilization of lymphocytes and other inflammatory cells occur, thus setting the stage for persistence of an inflammatory response. Macrophages produce profibrotic mediators, among them, TGF-β, which is responsible for activation -transdifferentiation- of quiescent hepatic stellate cells (HSC) to a myofibroblast (MFB) phenotype. MFBs are the principal source of extracellular matrix protein (ECM) accumulation and prominent mediators of fibrogenesis. TGF-β also mediates an epithelial-mesenchymal transition (EMT) process in hepatocytes that may contribute, directly or indirectly, to increase the MFB population. In hepatocarcinogenesis, TGF-β plays a dual role, behaving as a suppressor factor at early stages, but contributing to later tumor progression, once cells escape from its cytostatic effects. As part of its potential pro-tumorigenic actions, TGF-β induces EMT in liver tumor cells, which increases its pro-migratory and invasive potential. In parallel, TGF-β also induces changes in tumor cell plasticity, conferring properties of a migratory tumor initiating cell (TIC). The main aim of this review is to shed light about the pleiotropic actions of TGF-β that explain its effects on the different liver cell populations. The cross-talk with other signaling pathways that contribute to TGF-β effects, in particular the Epidermal Growth Factor Receptor (EGFR), will be presented. Finally, we will discuss the rationale for targeting the TGF-β pathway in liver pathologies.

Lysosomal acid lipase promotes cholesterol ester metabolism and drives clear cell renal cell carcinoma progression

OBJECTIVES

Clear cell renal cell carcinoma (ccRCC) is characterized histologically by accumulation of cholesterol esters, cholesterol and other neutral lipids. Lysosomal acid lipase (LAL) is a critical enzyme involved in the cholesterol ester metabolism. Here, we sought to determine whether LAL could orchestrate metabolism of cholesterol esters in order to promote ccRCC progression.

MATERIALS AND METHODS

Quantitative reverse-transcription PCR and western blots were conducted to assess the expression of LAL in human ccRCC tissues. We analysed the relationship between LAL levels and patient survival using tissue microarrays. We used cell proliferation assays, colony formation assays, cell death assays, metabolic assays and xenograft tumour models to evaluate the biological function and underlying mechanisms.

RESULTS

LAL was up-regulated in ccRCC tissue. Tissue microarray analysis revealed higher levels of LAL in advanced grades of ccRCC, and high LAL expression indicated lower patient survival. Suppressing LAL expression not only blocked the utilization of cholesterol esters but also impaired proliferation and cellular survival. Furthermore, immunohistochemistry staining showed that LAL expression was correlated with Akt phosphorylation. Suppressing LAL expression decreased the phosphorylation level of Akt and Src and reduced the level of 14,15-epoxyeicosatrienoic acids in ccRCC cells. Supplement of 14,15-epoxyeicosatrienoic acids rescued proliferation in vitro and in vivo.

CONCLUSIONS

LAL promoted cell proliferation and survival via metabolism of epoxyeicosatrienoic acids and activation of the Src/Akt pathway.

The level of caveolin-1 expression determines response to TGF-β as a tumour suppressor in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a heterogeneous tumour associated with poor prognostic outcome. Caveolin-1 (CAV1), a membrane protein involved in the formation of caveolae, is frequently overexpressed in HCC. Transforming growth factor-beta (TGF-β) is a pleiotropic cytokine having a dual role in hepatocarcinogenesis: inducer of apoptosis at early phases, but pro-tumourigenic once cells acquire mechanisms to overcome its suppressor effects. Apoptosis induced by TGF-β is mediated by upregulation of the NADPH oxidase NOX4, but counteracted by transactivation of the epidermal growth factor receptor (EGFR) pathway. Previous data suggested that CAV1 is required for the anti-apoptotic signals triggered by TGF-β in hepatocytes. Whether this mechanism is relevant in hepatocarcinogenesis has not been explored yet. Here we analysed the TGF-β response in HCC cell lines that express different levels of CAV1. Accordingly, stable CAV1 knockdown or overexpressing cell lines were generated. We demonstrate that CAV1 is protecting HCC cells from TGF-β-induced apoptosis, which attenuates its suppressive effect on clonogenic growth and increases its effects on cell migration. Downregulation of CAV1 in HLE cells promotes TGF-β-mediated induction of the pro-apoptotic BMF, which correlates with upregulation of NOX4, whereas CAV1 overexpression in Huh7 cells shows the opposite effect. CAV1 silenced HLE cells show attenuation in TGF-β-induced EGFR transactivation and activation of the PI3K/AKT pathway. On the contrary, Huh7 cells, which do not respond to TGF-β activating the EGFR pathway, acquire the capacity to do so when CAV1 is overexpressed. Analyses in samples from HCC patients revealed that tumour tissues presented higher expression levels of CAV1 compared with surrounding non-tumoural areas. Furthermore, a significant positive correlation among the expression of CAV1 and TGFB1 was observed. We conclude that CAV1 has an essential role in switching the response to TGF-β from cytostatic to tumourigenic, which could have clinical meaning in patient stratification.

YAP modulates TGF-β1-induced simultaneous apoptosis and EMT through upregulation of the EGF receptor

YAP is a transcriptional co-regulator that plays important roles in various patho-physiological processes, including the survival and death of cells. However, the effect of YAP on apoptosis and EMT, simultaneously mediated by TGF-β1, is not known. In this study, we demonstrate that YAP can modulate cell fate of apoptosis versus EMT by acting as a surviving factor. Overexpression of YAP in mouse mammary epithelial (NMuMG) cells suppressed TGF-β1-induced apoptosis, which shifted the cellular response predominantly toward EMT. In contrast, knockdown of YAP induced spontaneous apoptosis and enhanced TGF-β1-induced apoptosis, leading to a sharp decrease in the proportion of surviving cells that underwent EMT. These data suggest that YAP is an essential factor for modulating cellular responses to TGF-β1. Further investigation showed that YAP could regulate the expression level and activation of EGFR. Knockdown or inhibition of EGFR abolished the suppressive effect of YAP on apoptosis, whereas activation of EGFR by EGF significantly reduced apoptosis caused by the knockdown of YAP. The results indicate that EGFR and its activation are critical for YAP-mediated suppression of TGF-β1-induced apoptosis. This study provides a new understanding of the regulatory mechanism underlying the determination of cell fate in response to TGF-β1-mediated simultaneous apoptosis and EMT.

Induction of Apoptosis in Human Cancer Cells Through Extrinsic and Intrinsic Pathways by Balanites aegyptiaca Furostanol Saponins and Saponin-Coated SilverNanoparticles

The aim of this investigation is to examine the anticancer activities of Balanites aegyptiaca fruit extract with its biogenic silver nanoparticles (AgNPs) against colon and liver cancer cells. B. aegyptiaca aqueous extract was fractionated according to polarity and by biosynthesized AgNP. The cytotoxicity of the extract, semi-purified fractions, and the AgNPs was examined on noncancerous cell lines. The safer fraction was subjected to ultra-performance liquid chromatography-MS to identify the major active constituents. The anticancer activities of the nontoxic doses of all the used treatments were tested against HepG2 and CaCo2 cells. The nontoxic dose of the B. aegyptiaca (0.63 mg/ml) extract showed high anti-proliferative activities against HepG2 and CaCo2 with a percentage of 81 and 77%, respectively. The butanol fraction was safer than the other two fractions with 46.3 and 90.35% anti-proliferative activity against Caco2 and HepG2 cells, respectively. The nontoxic dose of AgNPs (0.63 mg/ml) inhibits both HepG2 and Caco2 cells with a percentage of 84.5 and 83.4%, respectively. In addition, AgNPs regulate the expression of certain genes with folding higher than that of crude extract. Saponin-coated AgNPs showed great abilities to select the most anticancer ingredient(s) from the B. aegyptiaca extract with a more safety pattern than the polarity gradient fractionation.

Epithelial-mesenchymal transition in tissue repair and fibrosis

The epithelial-mesenchymal transition (EMT) describes the global process by which stationary epithelial cells undergo phenotypic changes, including the loss of cell-cell adhesion and apical-basal polarity, and acquire mesenchymal characteristics that confer migratory capacity. EMT and its converse, MET (mesenchymal-epithelial transition), are integral stages of many physiologic processes and, as such, are tightly coordinated by a host of molecular regulators. Converging lines of evidence have identified EMT as a component of cutaneous wound healing, during which otherwise stationary keratinocytes (the resident skin epithelial cells) migrate across the wound bed to restore the epidermal barrier. Moreover, EMT plays a role in the development of scarring and fibrosis, as the matrix-producing myofibroblasts arise from cells of the epithelial lineage in response to injury but are pathologically sustained instead of undergoing MET or apoptosis. In this review, we summarize the role of EMT in physiologic repair and pathologic fibrosis of tissues and organs. We conclude that further investigation into the contribution of EMT to the faulty repair of fibrotic wounds might identify components of EMT signaling as common therapeutic targets for impaired healing in many tissues. Graphical Abstract Model for injury-triggered EMT activation in physiologic wound repair (left) and fibrotic wound healing (right).

The rationale for targeting TGF-β in chronic liver diseases

BACKGROUND

Transforming growth factor (TGF)-β is a pluripotent cytokine that displays several tissue-specific biological activities. In the liver, TGF-β is considered a fundamental molecule, controlling organ size and growth by limiting hepatocyte proliferation. It is involved in fibrogenesis and, therefore, in worsening liver damage, as well as in triggering the development of hepatocellular carcinoma (HCC). TGF-β is known to act as an oncosuppressor and also as a tumour promoter in HCC, but its role is still unclear.

DESIGN

In this review, we discuss the potential role of TGF-β in regulating the tumoural progression of HCC, and therefore the rationale for targeting this molecule in patients with HCC.

RESULTS

A considerable amount of experimental preclinical evidence suggests that TGF-β is a promising druggable target in patients with HCC. To support this hypothesis, a phase II clinical trial is currently ongoing using a TGF-β pathway inhibitor, and results will soon be available.

CONCLUSIONS

The identification of new TGF-β related biomarkers will help to select those patients most likely to benefit from therapy aimed at inhibiting the TGF-β pathway. New formulations that may provide a more controlled and sustained delivery of the drug will improve the therapeutic success of such treatments.

Caveolin-1-dependent activation of the metalloprotease TACE/ADAM17 by TGF-β in hepatocytes requires activation of Src and the NADPH oxidase NOX1

Transforming growth factor-β (TGF-β) plays a dual role in hepatocytes, inducing both pro- and anti-apoptotic responses, the balance between which decides cell fate. Survival signals are mediated by the epidermal growth factor receptor (EGFR) pathway, which is activated by TGF-β. We have previously shown that caveolin-1 (CAV1) is required for activation of the metalloprotease tumour necrosis factor (TNF)-α-converting enzyme/a disintegrin and metalloproteinase 17 (TACE/ADAM17), and hence transactivation of the EGFR pathway. The specific mechanism by which TACE/ADAM17 is activated has not yet been determined. Here we show that TGF-β induces phosphorylation of sarcoma kinase (Src) in hepatocytes, a process that is impaired in Cav1(-/-) hepatocytes, coincident with a decrease in phosphorylated Src in detergent-resistant membrane fractions. TGF-β-induced activation of TACE/ADAM17 and EGFR phosphorylation were blocked using the Src inhibitor PP2. Cav1(+/+) hepatocytes showed early production of reactive oxygen species (ROS) induced by TGF-β, which was not seen in Cav1(-/-) cells. Production of ROS was inhibited by both the NADPH oxidase 1 (NOX1) inhibitor STK301831 and NOX1 knock-down, which also impaired TACE/ADAM17 activation and thus EGFR phosphorylation. Finally, neither STK301831 nor NOX1 silencing impaired Src phosphorylation, but PP2 blocked early ROS production, showing that Src is involved in NOX1 activation. As expected, inhibition of Src or NOX1 increased TGF-β-induced cell death in Cav1(+/+) cells. In conclusion, CAV1 is required for TGF-β-mediated activation of TACE/ADAM17 through a mechanism that involves phosphorylation of Src and NOX1-mediated ROS production.

Dissecting the role of epidermal growth factor receptor catalytic activity during liver regeneration and hepatocarcinogenesis

Different data support a role for the epidermal growth factor receptor (EGFR) pathway during liver regeneration and hepatocarcinogenesis. However, important issues, such as the precise mechanisms mediating its actions and the unique versus redundant functions, have not been fully defined. Here, we present a novel transgenic mouse model expressing a hepatocyte-specific truncated form of human EGFR, which acts as negative dominant mutant (ΔEGFR) and allows definition of its tyrosine kinase-dependent functions. Results indicate a critical role for EGFR catalytic activity during the early stages of liver regeneration. Thus, after two-thirds partial hepatectomy, ΔEGFR livers displayed lower and delayed proliferation and lower activation of proliferative signals, which correlated with overactivation of the transforming growth factor-β pathway. Altered regenerative response was associated with amplification of cytostatic effects of transforming growth factor-β through induction of cell cycle negative regulators. Interestingly, lipid synthesis was severely inhibited in ΔEGFR livers after partial hepatectomy, revealing a new function for EGFR kinase activity as a lipid metabolism regulator in regenerating hepatocytes. In spite of these profound alterations, ΔEGFR livers were able to recover liver mass by overactivating compensatory signals, such as c-Met. Our results also indicate that EGFR catalytic activity is critical in the early preneoplastic stages of the liver because ΔEGFR mice showed a delay in the appearance of diethyl-nitrosamine-induced tumors, which correlated with decreased proliferation and delay in the diethyl-nitrosamine-induced inflammatory process.

CONCLUSION

These studies demonstrate that EGFR catalytic activity is critical during the initial phases of both liver regeneration and carcinogenesis and provide key mechanistic insights into how this kinase acts to regulate liver pathophysiology. (Hepatology 2016;63:604-619).

Apoptosis in liver carcinogenesis and chemotherapy

Hepatocellular carcinoma (HCC) is a major health problem. In human hepatocarcinogenesis, the balance between cell death and proliferation is deregulated, tipping the scales for a situation where antiapoptotic signals are overpowering the death-triggering stimuli. HCC cells harbor a wide variety of mutations that alter the regulation of apoptosis and hence the response to chemotherapeutical drugs, making them resistant to the proapoptotic signals. Considering all these modifications found in HCC cells, therapeutic approaches need to be carefully studied in order to specifically target the antiapoptotic signals. This review deals with the recent relevant contributions reporting molecular alterations for HCC that lead to a deregulation of apoptosis, as well as the challenge of death-inducing chemotherapeutics in current HCC treatment.

EGF augments TGFβ-induced epithelial-mesenchymal transition by promoting SHP2 binding to GAB1

In many epithelial cells, epidermal growth factor (EGF) augments the epithelial-mesenchymal transition (EMT) that occurs when cells are treated with transforming growth factor β (TGFβ). We demonstrate that this augmentation requires activation of SH2 domain-containing phosphatase-2 (SHP2; also known as PTPN11), a proto-oncogene. In lung and pancreatic cancer cell lines, reductions in E-cadherin expression, increases in vimentin expression and increases in cell scatter rates were larger when cells were treated with TGFβ and EGF versus TGFβ or EGF alone. SHP2 knockdown promoted epithelial characteristics basally and antagonized EMT in response to TGFβ alone or in combination with EGF. Whereas EGF promoted SHP2 binding to tyrosine phosphorylated GAB1, which promotes SHP2 activity, TGFβ did not induce SHP2 association with phosphotyrosine-containing proteins. Knockdown of endogenous SHP2 and reconstitution with an SHP2 mutant with impaired phosphotyrosine binding ability eliminated the EGF-mediated EMT augmentation that was otherwise restored with wild-type SHP2 reconstitution. These results demonstrate roles for basal and ligand-induced SHP2 activity in EMT and further motivate efforts to identify specific ways to inhibit SHP2, given the role of EMT in tumor dissemination and chemoresistance.

Transmembrane 4 L Six Family Member 5 (TM4SF5)-Mediated Epithelial-Mesenchymal Transition in Liver Diseases

The membrane protein TM4SF5, a member of the transmembrane 4L six family, forms a tetraspanin-enriched microdomain (TEM) on the cell surface, where many different membrane proteins and receptors form a massive protein-protein complex to regulate cellular functions including transdifferentiation, migration, and invasion. We recently reported that TM4SF5 causes epithelial-mesenchymal transition (EMT), eventually contributing to aberrant multilayer cellular growth, drug resistance, enhanced migration, invasion, its circulation in the blood, tumor initiation for successful metastasis, and muscle development in zebrafish. In this review, I summarize the information on the role of TM4SF5 in EMT-related functions at TM4SF5-enriched microdomain (T5EM) on cell surface, where proteins such as TM4SF5, CD151, CD44, integrins, and epidermal growth factor receptor (EGFR) can form numerous protein complexes. TM4SF5-mediated EMT contributes to diverse cellular functions, leading to fibrotic phenotypes and initiating and maintaining tumors in primary and/or metastatic regions, in addition to its role in muscle development in zebrafish. Anti-TM4SF5 strategies for addressing the protein networks can lead to regulation of the fibrotic, tumorigenic, and tumor-maintaining functions of TM4SF5-positive hepatic cells. This review is for us to (re)consider the antifibrotic or antitumorigenic (i.e., anti-EMT-related diseases) strategies of dealing with protein networks that would be involved in cross-talks to regulate various cellular functions during TM4SF5-dependent progression from fibrotic to cancerous hepatic cells.

Axl activates autocrine transforming growth factor-β signaling in hepatocellular carcinoma

In hepatocellular carcinoma (HCC), intrahepatic metastasis frequently correlates with epithelial to mesenchymal transition (EMT) of malignant hepatocytes. Several mechanisms have been identified to be essentially involved in hepatocellular EMT, among them transforming growth factor (TGF)-β signaling. Here we show the up-regulation and activation of the receptor tyrosine kinase Axl in EMT-transformed hepatoma cells. Knockdown of Axl expression resulted in abrogation of invasive and transendothelial migratory abilities of mesenchymal HCC cells in vitro and Axl overexpression-induced metastatic colonization of epithelial hepatoma cells in vivo. Importantly, Axl knockdown severely impaired resistance to TGF-β-mediated growth inhibition. Analysis of the Axl interactome revealed binding of Axl to 14-3-3ζ, which is essentially required for Axl-mediated cell invasion, transendothelial migration, and resistance against TGF-β. Axl/14-3-3ζ signaling caused phosphorylation of Smad3 linker region (Smad3L) at Ser213, resulting in the up-regulation of tumor-progressive TGF-β target genes such as PAI1, MMP9, and Snail as well as augmented TGF-β1 secretion in mesenchymal HCC cells. Accordingly, high Axl expression in HCC patient samples correlated with elevated vessel invasion of HCC cells, higher risk of tumor recurrence after liver transplantation, strong phosphorylation of Smad3L, and lower survival. In addition, elevated expression of both Axl and 14-3-3ζ showed strongly reduced survival of HCC patients.

CONCLUSION

Our data suggest that Axl/14-3-3ζ signaling is central for TGF-β-mediated HCC progression and a promising target for HCC therapy.

PI3K signalling is required for a TGFβ-induced epithelial-mesenchymal-like transition (EMT-like) in human melanoma cells

Epithelial to mesenchymal transition (EMT) is a programme defined in epithelial cells and recognized as playing a critical role in cancer progression. Although melanoma is not a cancer of epithelial cells, hallmarks of EMT have been described to play a critical role in melanoma progression. Here, we demonstrate that long-term TGFβ exposure can induce a dedifferentiated EMT-like state resembling a previously described invasive phenotype (EMT-like). TGFβ-induced EMT-like is marked by the downregulation of melanocyte differentiation markers, such as MITF, and the upregulation of mesenchymal markers, such as N-cadherin, and an increase in melanoma cell migration and cell invasion. Pharmacological interference shows the dependency of TGFβ-induced EMT-like on the activation of the PDGF signalling pathway and the subsequent activation of PI3K in human melanoma cells. Together, the data provide novel insights into the transcriptional plasticity of melanoma cells that might contribute to tumor progression in patients and propose avenues to therapeutic interventions.

Oncocytoma-like renal tumor with transformation toward high-grade oncocytic carcinoma: a unique case with morphologic, immunohistochemical, and genomic characterization

Renal oncocytoma is a benign tumor with characteristic histologic findings. We describe an oncocytoma-like renal tumor with progression to high-grade oncocytic carcinoma and metastasis. A 74-year-old man with no family history of cancer presented with hematuria. Computed tomography showed an 11 cm heterogeneous multilobulated mass in the right kidney lower pole, enlarged aortocaval lymph nodes, and multiple lung nodules. In the nephrectomy specimen, approximately one third of the renal tumor histologically showed regions classic for benign oncocytoma transitioning to regions of high-grade carcinoma without sharp demarcation. With extensive genomic investigation using single nucleotide polymorphism-based array virtual karyotyping, multiregion sequencing, and expression array analysis, we were able to show a common lineage between the benign oncocytoma and high-grade oncocytic carcinoma regions in the tumor. We were also able to show karyotypic differences underlying this progression. The benign oncocytoma showed no chromosomal aberrations, whereas the high-grade oncocytic carcinoma showed loss of the 17p region housing FLCN (folliculin [Birt-Hogg-Dubé protein]), loss of 8p, and gain of 8q. Gene expression patterns supported dysregulation and activation of phosphoinositide 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homolog (Akt), mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK), and mechanistic target of rapamycin (serine/threonine kinase) (mTOR) pathways in the high-grade oncocytic carcinoma regions. This was partly attributable to FLCN underexpression but further accentuated by overexpression of numerous genes on 8q. In the high-grade oncocytic carcinoma region, vascular endothelial growth factor A along with metalloproteinases matrix metallopeptidase 9 and matrix metallopeptidase 12 were overexpressed, facilitating angiogenesis and invasiveness. Genetic molecular testing provided evidence for the development of an aggressive oncocytic carcinoma from an oncocytoma, leading to aggressive targeted treatment but eventual death 39 months after the diagnosis.

Signaling mechanisms of the epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) is an essential mechanism in embryonic development and tissue repair. EMT also contributes to the progression of disease, including organ fibrosis and cancer. EMT, as well as a similar transition occurring in vascular endothelial cells called endothelial-mesenchymal transition (EndMT), results from the induction of transcription factors that alter gene expression to promote loss of cell-cell adhesion, leading to a shift in cytoskeletal dynamics and a change from epithelial morphology and physiology to the mesenchymal phenotype. Transcription program switching in EMT is induced by signaling pathways mediated by transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP), Wnt-β-catenin, Notch, Hedgehog, and receptor tyrosine kinases. These pathways are activated by various dynamic stimuli from the local microenvironment, including growth factors and cytokines, hypoxia, and contact with the surrounding extracellular matrix (ECM). We discuss how these pathways crosstalk and respond to signals from the microenvironment to regulate the expression and function of EMT-inducing transcription factors in development, physiology, and disease. Understanding these mechanisms will enable the therapeutic control of EMT to promote tissue regeneration, treat fibrosis, and prevent cancer metastasis.

Roxithromycin treatment inhibits TGF-β1-induced activation of ERK and AKT and down-regulation of caveolin-1 in rat airway smooth muscle cells

BACKGROUND

Roxithromycin (RXM) has been widely used in asthma treatment; however, the mechanism has not been fully understood. The aim of our study was to investigate the underlying mechanism of RXM treatment in mediating the effect of transforming growth factor (TGF)-β1 on airway smooth muscle cells (ASMCs) proliferation and caveolinn-1 expression.

METHODS

Firstly, the rat ovalbumin (OVA) model was built according to the previous papers. Rat ASMCs were prepared and cultured, and then TGF-β1 production in ASMCs was measured by enzyme-linked immunosorbent assay (ELISA). Moreover, the proliferation of ASMCs was determined using cell counting kit (CCK-8) assay. Additionally, the expressions of caveolin-1, phosphorylated-ERK1/2 (p-ERK1/2) and phosphorylated-AKT (p-AKT) in ASMCs treated with or without PD98059 (an ERK1/2 inhibitor), wortannin (a PI3K inhibitor), β-cyclodextrin (β-CD) and RXM were measured by Western blot. Finally, data were evaluated using t-test or one-way ANOVA, and then a P value < 0.05 was set as a threshold.

RESULTS

Compared with normal control, TGF-β1 secretion was significantly increased in asthmatic ASMCs; meanwhile, TGF-β1 promoted ASMCs proliferation (P < 0.05). However, ASMCs proliferation was remarkably inhibited by RXM, β-CD, PD98059 and wortmannin (P < 0.05). Moreover, the expressions of p-ERK1/2 and p-AKT were increased and peaked at 20 min after TGF-β1 stimulation, and then suppressed by RXM. Further, caveolin-1 level was down-regulated by TGF-β1 and up-regulated by inhibitors and RXM.

CONCLUSION

Our findings demonstrate that RXM treatment inhibits TGF-β1-induced activation of ERK and AKT and down-regulation of caveolin-1, which may be the potential mechanism of RXM protection from chronic inflammatory diseases, including bronchial asthma.

Caveolin-1 is required for TGF-β-induced transactivation of the EGF receptor pathway in hepatocytes through the activation of the metalloprotease TACE/ADAM17

Transforming growth factor-beta (TGF-β) plays a dual role in hepatocytes, inducing both pro- and anti-apoptotic responses, whose balance decides cell fate. Survival signals are mediated by the epidermal growth factor receptor (EGFR) pathway, which is activated by TGF-β in these cells. Caveolin-1 (Cav1) is a structural protein of caveolae linked to TGF-β receptors trafficking and signaling. Previous results have indicated that in hepatocytes, Cav1 is required for TGF-β-induced anti-apoptotic signals, but the molecular mechanism is not fully understood yet. In this work, we show that immortalized Cav1(-/-) hepatocytes were more sensitive to the pro-apoptotic effects induced by TGF-β, showing a higher activation of caspase-3, higher decrease in cell viability and prolonged increase through time of intracellular reactive oxygen species (ROS). These results were coincident with attenuation of TGF-β-induced survival signals in Cav1(-/-) hepatocytes, such as AKT and ERK1/2 phosphorylation and NFκ-B activation. Transactivation of the EGFR pathway by TGF-β was impaired in Cav1(-/-) hepatocytes, which correlated with lack of activation of TACE/ADAM17, the metalloprotease responsible for the shedding of EGFR ligands. Reconstitution of Cav1 in Cav1(-/-) hepatocytes rescued wild-type phenotype features, both in terms of EGFR transactivation and TACE/ADAM17 activation. TACE/ADAM17 was localized in detergent-resistant membrane (DRM) fractions in Cav1(+/+) cells, which was not the case in Cav1(-/-) cells. Disorganization of lipid rafts after treatment with cholesterol-binding agents caused loss of TACE/ADAM17 activation after TGF-β treatment. In conclusion, in hepatocytes, Cav1 is required for TGF-β-mediated activation of the metalloprotease TACE/ADAM17 that is responsible for shedding of EGFR ligands and activation of the EGFR pathway, which counteracts the TGF-β pro-apoptotic effects. Therefore, Cav1 contributes to the pro-tumorigenic effects of TGF-β in liver cancer cells.

Role of the tissue microenvironment as a therapeutic target in hepatocellular carcinoma

Hepatocellular carcinoma is difficult to treat, primarily because the underlying molecular mechanisms driving clinical outcome are still poorly understood. Growing evidence suggests that the tissue microenvironment has a role in the biological behavior of the tumor. The main clinical issue is to identify the best target for therapeutic approaches. Here, we discuss the hypothesis that the entire tissue microenvironment might be considered as a biological target. However, the tissue microenvironment consists of several cellular and biochemical components, each of which displays a distinct biological activity. We discuss the major components of this environment and consider how they may interact to promote tumor/host crosstalk.

Hepatitis C virus and microRNAs: miRed in a host of possibilities

It is well-established that the host microRNA (miRNA) milieu has a significant influence on the etiology of disease. In the context of viruses, such as hepatitis C virus (HCV), microRNAs have been shown to influence viral life cycles both directly, through interactions with the viral genome, and indirectly, through regulation of critical virus-associated host pathways. Several miRNA profiling studies have demonstrated that HCV infection aberrantly regulates a significant number of human miRNA. However, the biological relevance of these modulations remains poorly understood. In this review, we summarize recent research that has shed light on the pro-viral and anti-viral roles of HCV-induced changes in human miRNA expression and their significance in the development of HCV related sequelae and response to therapy.

The NADPH oxidase NOX4 inhibits hepatocyte proliferation and liver cancer progression

The NADPH oxidase NOX4 has emerged as an important source of reactive oxygen species in signal transduction, playing roles in physiological and pathological processes. NOX4 mediates transforming growth factor-β-induced intracellular signals that provoke liver fibrosis, and preclinical assays have suggested NOX4 inhibitors as useful tools to ameliorate this process. However, the potential consequences of sustained treatment of liver cells with NOX4 inhibitors are yet unknown. The aim of this work was to analyze whether NOX4 plays a role in regulating liver cell growth either under physiological conditions or during tumorigenesis. In vitro assays proved that stable knockdown of NOX4 expression in human liver tumor cells increased cell proliferation, which correlated with a higher percentage of cells in S/G2/M phases of the cell cycle, downregulation of p21(CIP1/WAF1), increase in cyclin D1 protein levels, and nuclear localization of β-catenin. Silencing of NOX4 in untransformed human and mouse hepatocytes also increased their in vitro proliferative capacity. In vivo analysis in mice revealed that NOX4 expression was downregulated under physiological proliferative situations of the liver, such as regeneration after partial hepatectomy, as well as during pathological proliferative conditions, such as diethylnitrosamine-induced hepatocarcinogenesis. Xenograft experiments in athymic mice indicated that NOX4 silencing conferred an advantage to human hepatocarcinoma cells, resulting in earlier onset of tumor formation and increase in tumor size. Interestingly, immunochemical analyses of NOX4 expression in human liver tumor cell lines and tissues revealed decreased NOX4 protein levels in liver tumorigenesis. Overall, results described here strongly suggest that NOX4 would play a growth-inhibitory role in liver cells.

TGF-β Mediated Crosstalk Between Malignant Hepatocyte and Tumor Microenvironment in Hepatocellular Carcinoma

In this article, we have reviewed current literature regarding the regulation of hepatocellular carcinoma (HCC) by the interaction of malignant hepatocytes and their tissue environment through cytokine signaling, here represented by transforming growth factor-beta (TGF-β) signaling. We have discussed responses of TGF-β signaling in transition of hepatic stellate cells to myofibroblasts (MFBs), recruitment of tumor-associated macrophages (TAMs), and enrichment of tumor-associated endothelial cells (TECs). The malignant hepatocytes also secrete various factors such as platelet-derived growth factors (PDGFs), vascular endothelial growth factor (VEGF), and TGF-β. TGF-β, a super-family of cytokines, creates tumor microenvironment by interacting through other growth factors (epidermal growth factor receptor (EGFR), PDGF, fibroblast growth factor (FGF), hepatocyte growth factor (HGF), VEGF), cytokines and chemokines, and extracellular matrix (ECM) remodeling. Hence, the HCC tumor microenvironment may now be recognized as an important participant of tumor progression to act as potential target to systemic therapies compared to targeted therapies.

Overactivation of the TGF-β pathway confers a mesenchymal-like phenotype and CXCR4-dependent migratory properties to liver tumor cells

Transforming growth factor-beta (TGF-β) is an important regulatory suppressor factor in hepatocytes. However, liver tumor cells develop mechanisms to overcome its suppressor effects and respond to this cytokine by inducing other processes, such as the epithelial-mesenchymal transition (EMT), which contributes to tumor progression and dissemination. Recent studies have placed chemokines and their receptors at the center not only of physiological cell migration but also of pathological processes, such as metastasis in cancer. In particular, CXCR4 and its ligand, stromal cell-derived factor 1α (SDF-1α) / chemokine (C-X-C motif) ligand 12 (CXCL12) have been revealed as regulatory molecules involved in the spreading and progression of a variety of tumors. Here we show that autocrine stimulation of TGF-β in human liver tumor cells correlates with a mesenchymal-like phenotype, resistance to TGF-β-induced suppressor effects, and high expression of CXCR4, which is required for TGF-β-induced cell migration. Silencing of the TGF-β receptor1 (TGFBR1), or its specific inhibition, recovered the epithelial phenotype and attenuated CXCR4 expression, inhibiting cell migratory capacity. In an experimental mouse model of hepatocarcinogenesis (diethylnitrosamine-induced), tumors showed increased activation of the TGF-β pathway and enhanced CXCR4 levels. In human hepatocellular carcinoma tumors, high levels of CXCR4 always correlated with activation of the TGF-β pathway, a less differentiated phenotype, and a cirrhotic background. CXCR4 concentrated at the tumor border and perivascular areas, suggesting its potential involvement in tumor cell dissemination.

CONCLUSION

A crosstalk exists among the TGF-β and CXCR4 pathways in liver tumors, reflecting a novel molecular mechanism that explains the protumorigenic effects of TGF-β and opens new perspectives for tumor therapy.

Hepatitis C virus induced miR200c down modulates FAP-1, a negative regulator of Src signaling and promotes hepatic fibrosis

Hepatitis C virus (HCV) induced liver disease is the leading indication for liver transplantation (LTx). Reinfection and accelerated development of fibrosis is a universal phenomenon following LTx. The molecular events that lead to fibrosis following HCV infection still remains poorly defined. In this study, we determined microRNA (miRNA) and mRNA expression profiles in livers from chronic HCV patients and normals using microarrays. Using Genego software and pathway finder we performed an interactive analysis to identify target genes that are modulated by miRNAs. 22 miRNAs were up regulated (>2 fold) and 35 miRNAs were down regulated (>2fold) compared to controls. Liver from HCV patients demonstrated increased expression of 306 genes (>3 fold) and reduced expression of 133 genes (>3 fold). Combinatorial analysis of the networks modulated by the miRNAs identified regulation of the phospholipase C pathway (miR200c, miR20b, and miR31through cellular proto-oncogene tyrosine-protein kinase Src (cSrc)), response to growth factors and hormones (miR141, miR107 and miR200c through peroxisome proliferator-activated receptor alpha and extracellular-signal-regulated kinases, and regulation of cellular proliferation (miR20b, miR10b, and miR141 through cyclin-dependent kinase inhibitor 1 or CDK-interacting protein 1 p21). Real time PCR (RT-PCR) validation of the miRNA in HCV infected livers demonstrated a 3.3 ±0.9 fold increase in miR200c. In vitro transfection of fibroblasts with miR200c resulted in a 2.2 fold reduction in expression of tyrosine-protein phosphatase non-receptor type 13 or FAS associated phosphatase 1 (FAP-1) and 2.3 fold increase in expression of cSrc. miR200c transfection resulted in significant increases in expression of collagen and fibroblast growth factor (2.8 and 3.4 fold, p<0.05). Therefore, we propose that HCV induced increased expression of miR200c can down modulate the expression of FAP1, a critical regulator of Src and MAP kinase pathway that play an important role in the production of fibrogenic growth factors and development of fibrosis.