Critical interactions between TGF-beta signaling/ELF, and E-cadherin/beta-catenin mediated tumor suppression

βII spectrin (SPTBN1): biological function and clinical potential in cancer and other diseases

βII spectrin, the most common isoform of non-erythrocyte spectrin, is a cytoskeleton protein present in all nucleated cells. Interestingly, βII spectrin is essential for the development of various organs such as nerve, epithelium, inner ear, liver and heart. The functions of βII spectrin include not only establishing and maintaining the cell structure but also regulating a variety of cellular functions, such as cell apoptosis, cell adhesion, cell spreading and cell cycle regulation. Notably, βII spectrin dysfunction is associated with embryonic lethality and the DNA damage response. More recently, the detection of altered βII spectrin expression in tumors indicated that βII spectrin might be involved in the development and progression of cancer. Its mutations and disorders could result in developmental disabilities and various diseases. The versatile roles of βII spectrin in disease have been examined in an increasing number of studies; nonetheless, the exact mechanisms of βII spectrin are still poorly understood. Thus, we summarize the structural features and biological roles of βII spectrin and discuss its molecular mechanisms and functions in development, homeostasis, regeneration and differentiation. This review highlight the potential effects of βII spectrin dysfunction in cancer and other diseases, outstanding questions for the future investigation of therapeutic targets. The investigation of the regulatory mechanism of βII spectrin signal inactivation and recovery may bring hope for future therapy of related diseases.

The Novel Histone Deacetylase Inhibitor, OBP-801, Induces Apoptosis in Rhabdoid Tumors by Releasing the Silencing of NOXA

Rhabdoid tumor is an aggressive, early childhood tumor. Biallelic inactivation of the SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 (SMARCB1)/integrase interactor 1 (INI1) gene is the only common genetic feature in rhabdoid tumors. Loss of SMARCB1 function results in downregulation of several tumor suppressor genes including p16, p21, and NOXA The novel histone deacetylase inhibitor, OBP-801, induces p21 and has shown efficacy against various cancers. In our study, OBP-801 strongly inhibited the cell growth of all rhabdoid tumor cell lines in WST-8 assay. However, Western blotting and cell-cycle analysis revealed that OBP-801 did not activate the P21-RB pathway in some cell lines. p21 knockout indicated that p21 did not dominate the OBP-801 antitumor effect in rhabdoid tumor cell lines. We discovered that OBP-801 induced NOXA expression and caspase-dependent apoptosis in rhabdoid tumor cell lines independent of TP53. Chromatin immunoprecipitation assay showed that OBP-801 acetylated histone proteins and recruited RNA polymerase II to the transcription start site (TSS) of the NOXA promotor. Moreover, OBP-801 recruited BRG1 and BAF155, which are members of the SWI/SNF complex, to the TSS of the NOXA promotor. These results suggest that OBP-801 epigenetically releases the silencing of NOXA and induces apoptosis in rhabdoid tumors. OBP-801 strongly inhibited tumor growth in human rhabdoid tumor xenograft mouse models in vivo Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and cleaved caspase-3 were stained in tumors treated with OBP-801. In conclusion, OBP-801 induces apoptosis in rhabdoid tumor cells by epigenetically releasing the silencing of NOXA, which is a key mediator of rhabdoid tumor apoptosis. The epigenetic approach for NOXA silencing with OBP-801 is promising for rhabdoid tumor treatment.

SPTBN1 suppresses the progression of epithelial ovarian cancer via SOCS3-mediated blockade of the JAK/STAT3 signaling pathway

SPTBN1 plays an anticancer role in many kinds of tumors and participates in the chemotherapeutic resistance of epithelial ovarian cancer (EOC). Here, we reported that lower SPTBN1 expression was significantly related to advanced EOC stage and shorter progression-free survival. SPTBN1 expression was also higher in less invasive EOC cell lines. Moreover, SPTBN1 decreased the migration ability of the EOC cells A2780 and HO8910 and inhibited the growth of EOC cells in vitro and tumor xenografts in vivo. SPTBN1 suppression increased the epithelial mesenchymal transformation marker Vimentin while decreasing E-cadherin expression. By analyzing TCGA data and immunohistochemistry staining of tumor tissue, we found that SPTBN1 and SOCS3 were positively coexpressed in EOC patients. SOCS3 overexpression or JAK2 inhibition decreased the proliferation and migration of EOC cells as well as the expression of p-JAK2, p-STAT3 and Vimentin, which were enhanced by the downregulation of SPTBN1, while E-cadherin expression was also reversed. It was also verified in mouse embryonic fibroblasts (MEFs) that loss of SPTBN1 activated the JAK/STAT3 signaling pathway with suppression of SOCS3. Our results suggest that SPTBN1 suppresses the progression of epithelial ovarian cancer via SOCS3-mediated blockade of the JAK/STAT3 signaling pathway.

Enteral Nutrition Supplemented with Transforming Growth Factor-β, Colostrum, Probiotics, and Other Nutritional Compounds in the Treatment of Patients with Inflammatory Bowel Disease

Enteral nutrition seems to play a significant role in the treatment of both adults and children with active Crohn's disease, and to a lesser degree in the treatment of patients with active ulcerative colitis. The inclusion of some special factors in the enteral nutrition formulas might increase the rate of the efficacy. Actually, enteral nutrition enriched in Transforming Growth Factor-β reduced the activity index and maintained remission in patients with Crohn's disease. In addition, a number of experimental animal studies have shown that colostrum exerts a significantly positive result. Probiotics of a special type and a certain dosage could also reduce the inflammatory process in patients with active ulcerative colitis. Therefore, the addition of these factors in an enteral nutrition formula might increase its effectiveness. Although the use of these formulas is not supported by large clinical trials, it could be argued that their administration in selected cases as an exclusive diet or in combination with the drugs used in patients with inflammatory bowel disease could benefit the patient. In this review, the authors provide an update on the role of enteral nutrition, supplemented with Transforming Growth Factor-β, colostrum, and probiotics in patients with inflammatory bowel disease.

Administration of Steamed and Freeze-Dried Mature Silkworm Larval Powder Prevents Hepatic Fibrosis and Hepatocellular Carcinogenesis by Blocking TGF-β/STAT3 Signaling Cascades in Rats

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths worldwide and the majority of HCC patients occur with a background of hepatic fibrosis and cirrhosis. We have previously reported the hepatoprotective effects of steamed and freeze-dried mature silkworm larval powder (SMSP) in a chronic ethanol-treated rat model. Here, we assessed the anti-fibrotic and anti-carcinogenic effects of SMSP on diethylnitrosamine (DEN)-treated rats. Wistar rats were intraperitoneally injected with DEN once a week for 12 or 16 weeks with or without SMSP administration (0.1 and 1 g/kg). SMSP administration significantly attenuated tumor foci formation and proliferation in the livers of the rats treated with DEN for 16 weeks. SMSP administration also inhibited hepatic fibrosis by decreasing the levels of collagen fiber and the expression of pro-collagen I and alpha-smooth muscle actin (α-SMA). Moreover, SMSP supplementation improved the major parameters of fibrosis such as transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), tumor necrosis factor-alpha (TNF-α), plasminogen activator inhibitor-1 (PAI-1), and collagen type I (Col1A1) in the livers from the rats treated with DEN for 16 weeks. As s possible mechanisms, we investigated the effects of SMSP on the TGF-β and signal transducer and activator of transcription 3 (STAT3)-mediated signaling cascades, which are known to promote hepatic fibrosis. We found that SMSP treatment inhibited the activation of TGF-β and the phosphorylation of STAT3 pathway in DEN-treated rats. Moreover, SMSP administration suppressed the expressions of the target genes of TGF-β and STAT3 induced by DEN treatment. Our findings provide experimental evidences that SMSP administration has inhibitory effects of hepatic fibrosis and HCC induced by DEN in vivo and could be a promising strategy for the prevention or treatment of hepatic fibrosis and hepatocellular carcinogenesis.

The role of spectrin in cell adhesion and cell-cell contact

Spectrins are proteins that are responsible for many aspects of cell function and adaptation to changing environments. Primarily the spectrin-based membrane skeleton maintains cell membrane integrity and its mechanical properties, together with the cytoskeletal network a support cell shape. The occurrence of a variety of spectrin isoforms in diverse cellular environments indicates that it is a multifunctional protein involved in numerous physiological pathways. Participation of spectrin in cell–cell and cell–extracellular matrix adhesion and formation of dynamic plasma membrane protrusions and associated signaling events is a subject of interest for researchers in the fields of cell biology and molecular medicine. In this mini-review, we focus on data concerning the role of spectrins in cell surface activities such as adhesion, cell–cell contact, and invadosome formation. We discuss data on different adhesion proteins that directly or indirectly interact with spectrin repeats. New findings support the involvement of spectrin in cell adhesion and spreading, formation of lamellipodia, and also the participation in morphogenetic processes, such as eye development, oogenesis, and angiogenesis. Here, we review the role of spectrin in cell adhesion and cell–cell contact.

Impact statement

This article reviews properties of spectrins as a group of proteins involved in cell surface activities such as, adhesion and cell–cell contact, and their contribution to morphogenesis. We show a new area of research and discuss the involvement of spectrin in regulation of cell–cell contact leading to immunological synapse formation and in shaping synapse architecture during myoblast fusion. Data indicate involvement of spectrins in adhesion and cell–cell or cell–extracellular matrix interactions and therefore in signaling pathways. There is evidence of spectrin’s contribution to the processes of morphogenesis which are connected to its interactions with adhesion molecules, membrane proteins (and perhaps lipids), and actin. Our aim was to highlight the essential role of spectrin in cell–cell contact and cell adhesion.

SPTBN1 and cancer, which links?

SPTBN1 is a dynamic intracellular nonpleckstrin homology-domain protein, functioning as a transforming growth factor-β signal transducing adapter protein which is necessary to form Smad3/Smad4 complex. Recently SPTBN1 is considered to be associated with many kinds of cancers. SPTBN1 expression and function differ between different tumor states or types. This review summarizes the recent advances in the expression patterns of SPTBN1 in cancers, and in understanding the mechanisms by which SPTBN1 affects the occurrence, progression, and metastasis of cancer. Identifying SPTBN1 expression and function in cancers will contribute to the clinical diagnosis and treatment of cancer and the investigation of anticancer drugs.

The Molecular Mechanism of Transforming Growth Factor-β Signaling for Intestinal Fibrosis: A Mini-Review

Inflammatory bowel disease is known as the most chronic inflammatory disorder in colon, which subsequently progresses to intestinal obstruction and fistula formation. Many studies to date for the treatment of IBD have been focused on inflammation. However, most of the anti-inflammatory agents do not have anti-fibrotic effects and could not relieve intestinal stricture in IBD patients. Because preventing or reversing intestinal fibrosis in IBD is a major therapeutic target, we analyzed the papers focusing on TGF-β signaling in intestinal fibrosis. TGF-β is a good candidate to treat the intestinal fibrosis in IBD which involves TGF-β signaling pathway, EMT, EndMT, ECM, and other regulators. Understanding the mechanism involved in TGF-β signaling will contribute to the treatment and diagnosis of intestinal fibrosis occurring in IBD as well as the understanding of the molecular mechanisms underlying the pathogenesis.

Role of TGF-β in Alcohol-Induced Liver Disease

Over 90% of hepatocellular carcinoma (HCC) occurs against a background of chronic liver disease or cirrhosis induced from viral hepatitis to alcohol injury. One third of patients with cirrhosis will develop HCC during their lifetime, with a 3-5% annual incidence. However, little is known about the key mechanisms by which toxins mediate DNA damage in the liver. Recent studies support a central role for TGF-β signaling in conferring genomic stability yet the precise mechanism of action and the specific stages of tumor suppression remain unclear (Bornstein S, White R, Malkoski S, Oka M, Han G, Cleaver T, Reh D, Andersen P, Gross N, Olson S, Deng C, Lu SL, Wang XJ. J Clin Invest 119:3408-3419 (2009); Korc M. J Clin Invest 119:3208-3211 (2009); Glick A, Popescu N, Alexander V, Ueno H, Bottinger E, Yuspa SH. Proc Natl Acad Sci U S A 96:14949-14954 (1999)). Furthermore, it has recently been shown that β2SP^+/- and β2SP^+/-/Smad3^+/- mice phenocopy a hereditary human cancer syndrome, the Beckwith-Wiedemann syndrome (BWS), which has an 800 fold risk of cancers including HCC, hepatoblastoma, and a range of liver disorders. Identifying key biological pathways and mechanisms for suppressing alcohol-induced stem cell injury and HCC will be critical for enhancing patient care and the employment of new therapeutic approaches.

Analysis of Genomes and Transcriptomes of Hepatocellular Carcinomas Identifies Mutations and Gene Expression Changes in the Transforming Growth Factor-β Pathway

BACKGROUND & AIMS

Development of hepatocellular carcinoma (HCC) is associated with alterations in the transforming growth factor-beta (TGF-β) signaling pathway, which regulates liver inflammation and can have tumor suppressor or promoter activities. Little is known about the roles of specific members of this pathway at specific of HCC development. We took an integrated approach to identify and validate the effects of changes in this pathway in HCC and identify therapeutic targets.

METHODS

We performed transcriptome analyses for a total of 488 HCCs that include data from The Cancer Genome Atlas. We also screened 301 HCCs reported in the Catalogue of Somatic Mutations in Cancer and 202 from Cancer Genome Atlas for mutations in genome sequences. We expressed mutant forms of spectrin beta, non-erythrocytic 1 (SPTBN1) in HepG2, SNU398, and SNU475 cells and measured phosphorylation, nuclear translocation, and transcriptional activity of SMAD family member 3 (SMAD3).

RESULTS

We found somatic mutations in at least 1 gene whose product is a member of TGF-β signaling pathway in 38% of HCC samples. SPTBN1 was mutated in the largest proportion of samples (12 of 202, 6%). Unsupervised clustering of transcriptome data identified a group of HCCs with activation of the TGF-β signaling pathway (increased transcription of genes in the pathway) and a group of HCCs with inactivation of TGF-β signaling (reduced expression of genes in this pathway). Patients with tumors with inactivation of TGF-β signaling had shorter survival times than patients with tumors with activation of TGF-β signaling (P = .0129). Patterns of TGF-β signaling correlated with activation of the DNA damage response and sirtuin signaling pathways. HepG2, SNU398, and SNU475 cells that expressed the D1089Y mutant or with knockdown of SPTBN1 had increased sensitivity to DNA crosslinking agents and reduced survival compared with cells that expressed normal SPTBN1 (controls).

CONCLUSIONS

In genome and transcriptome analyses of HCC samples, we found mutations in genes in the TGF-β signaling pathway in almost 40% of samples. These correlated with changes in expression of genes in the pathways; up-regulation of genes in this pathway would contribute to inflammation and fibrosis, whereas down-regulation would indicate loss of TGF-β tumor suppressor activity. Our findings indicate that therapeutic agents for HCCs can be effective, based on genetic features of the TGF-β pathway; agents that block TGF-β should be used only in patients with specific types of HCCs.

Genomic landscape of gastric cancer: molecular classification and potential targets

Gastric cancer imposes a considerable health burden worldwide, and its mortality ranks as the second highest for all types of cancers. The limited knowledge of the molecular mechanisms underlying gastric cancer tumorigenesis hinders the development of therapeutic strategies. However, ongoing collaborative sequencing efforts facilitate molecular classification and unveil the genomic landscape of gastric cancer. Several new drivers and tumorigenic pathways in gastric cancer, including chromatin remodeling genes, RhoA-related pathways, TP53 dysregulation, activation of receptor tyrosine kinases, stem cell pathways and abnormal DNA methylation, have been revealed. These newly identified genomic alterations await translation into clinical diagnosis and targeted therapies. Considering that loss-of-function mutations are intractable, synthetic lethality could be employed when discussing feasible therapeutic strategies. Although many challenges remain to be tackled, we are optimistic regarding improvements in the prognosis and treatment of gastric cancer in the near future.

TGF-β signaling in liver and gastrointestinal cancers

Transforming Growth Factor-β (TGF-β) plays crucial and complex roles in liver and gastrointestinal cancers. These include a multitude of distinct functions, such as maintaining stem cell homeostasis, promoting fibrosis, immune modulating, as a tumor suppressor and paradoxically, as a tumor progressor. However, key mechanisms for the switches responsible for these distinct actions are poorly understood, and remain a challenge. The Cancer Genome Atlas (TCGA) analyses and genetically engineered mouse models now provide an integrated approach to dissect these multifaceted and context-dependent driving roles of the TGF-β pathway. In this review, we will discuss the molecular mechanisms of TGF-β signaling, focusing on colorectal, gastric, pancreatic, and liver cancers. Novel drugs targeting the TGF-β pathway have been developed over the last decade, and some have been proven effective in clinical trials. A better understanding of the TGF-β pathway may improve our ability to target it, thus providing more tools to the armamentarium against these deadly cancers.

Hepatic Premalignant Alterations Triggered by Human Nephrotoxin Aristolochic Acid I in Canines

Aristolochic acid I (AAI) existing in plant drugs from Aristolochia species is an environmental human carcinogen associated with urothelial cancer. Although gene association network analysis demonstrated gene expression profile changes in the liver of human TP53 knock-in mice after acute AAI exposure, to date, whether AAI causes hepatic tumorigenesis is still not confirmed. Here, we show that hepatic premalignant alterations appeared in canines after a 10-day AAI oral administration (3 mg/kg/day). We observed c-Myc oncoprotein and oncofetal RNA-binding protein Lin28B overexpressions accompanied by cancer progenitor-like cell formation in the liver by AAI exposure. Meanwhile, we found that forkhead box O1 (FOXO1) was robustly phosphorylated, thereby shuttling into the cytoplasm of hepatocytes. Furthermore, utilizing microarray and qRT-PCR analysis, we confirmed that microRNA expression significantly dysregulated in the liver treated with AAI. Among them, we particularly focused on the members in let-7 miRNAs and miR-23a clusters, the downstream of c-Myc and IL6 receptor (IL6R) signaling pathway linking the premalignant alteration. Strikingly, when IL6 was added in vitro, IL6R/NF-κB signaling activation contributed to the increase of FOXO1 phosphorylation by the let-7b inhibitor. Therefore, it highlights the new insight into the interplay of the network in hepatic tumorigenesis by AAI exposure, and also suggests that anti-premalignant therapy may be crucial for preventing AAI-induced hepatocarcinogenesis.

Caspase-3/7-mediated Cleavage of β2-spectrin is Required for Acetaminophen-induced Liver Damage

The ubiquitously expressed β2-spectrin (β2SP, SPTBN1) is the most common non-erythrocytic member of the β-spectrin gene family. Loss of β2-spectrin leads to defects in liver development, and its haploinsufficiency spontaneously leads to chronic liver disease and the eventual development of hepatocellular cancer. However, the specific role of β2-spectrin in liver homeostasis remains to be elucidated. Here, we reported that β2-spectrin was cleaved by caspase-3/7 upon treatment with acetaminophen which is the main cause of acute liver injury. Blockage of β2-spectrin cleavage robustly attenuated β2-spectrin-specific functions, including regulation of the cell cycle, apoptosis, and transcription. Cleaved fragments of β2-spectrin were physiologically active, and the N- and C-terminal fragments retained discrete interaction partners and activity in transcriptional regulation and apoptosis, respectively. Cleavage of β2-spectrin facilitated the redistribution of the resulting fragments under conditions of liver damage induced by acetaminophen. In contrast, downregulation of β2-spectrin led to resistance to acetaminophen-induced cytotoxicity, and its insufficiency in the liver promoted suppression of acetaminophen-induced liver damage and enhancement of liver regeneration.

CONCLUSIONS

β2-Spectrin, a TGF-β mediator and signaling molecule, is cleaved and activated by caspase-3/7, consequently enhancing apoptosis and transcriptional control to determine cell fate upon liver damage. These findings have extended our knowledge on the spectrum of β2-spectrin functions from a scaffolding protein to a target and transmitter of TGF-β in liver damage.

βII-Spectrin (SPTBN1) suppresses progression of hepatocellular carcinoma and Wnt signaling by regulation of Wnt inhibitor kallistatin

βII-Spectrin (SPTBN1) is an adapter protein for Smad3/Smad4 complex formation during transforming growth factor beta (TGF-β) signal transduction. Forty percent of SPTBN1(+/-) mice spontaneously develop hepatocellular carcinoma (HCC), and most cases of human HCC have significant reductions in SPTBN1 expression. In this study, we investigated the possible mechanisms by which loss of SPTBN1 may contribute to tumorigenesis. Livers of SPTBN1(+/-) mice, compared to wild-type mouse livers, display a significant increase in epithelial cell adhesion molecule-positive (EpCAM(+)) cells and overall EpCAM expression. Inhibition of SPTBN1 in human HCC cell lines increased the expression of stem cell markers EpCAM, Claudin7, and Oct4, as well as decreased E-cadherin expression and increased expression of vimentin and c-Myc, suggesting reversion of these cells to a less differentiated state. HCC cells with decreased SPTBN1 also demonstrate increased sphere formation, xenograft tumor development, and invasion. Here we investigate possible mechanisms by which SPTBN1 may influence the stem cell traits and aggressive behavior of HCC cell lines. We found that HCC cells with decreased SPTBN1 express much less of the Wnt inhibitor kallistatin and exhibit decreased β-catenin phosphorylation and increased β-catenin nuclear localization, indicating Wnt signaling activation. Restoration of kallistatin expression in these cells reversed the observed Wnt activation.

CONCLUSION

SPTBN1 expression in human HCC tissues is positively correlated with E-cadherin and kallistatin levels, and decreased SPTBN1 and kallistatin gene expression is associated with decreased relapse-free survival. Our data suggest that loss of SPTBN1 activates Wnt signaling, which promotes acquisition of stem cell-like features, and ultimately contributes to malignant tumor progression.

CEACAM1 long cytoplasmic domain isoform is associated with invasion and recurrence of hepatocellular carcinoma

BACKGROUND

The two isoforms of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), 1 with a long cytoplasmic domain (CEACAM1-L) and 1 with a short (CEACAM1-S), are involved in different signaling pathways. β2-spectrin (β2SP) is an adaptor protein that plays critical roles in the proper control of Smad access to activate receptors involved in regulation of TGF-β signaling. In this study, we examined the association between CEACAM1 isoform balance and hepatocellular carcinoma (HCC) malignant potential and investigated the possibility of a molecular interaction between CEACAM1 and β2SP.

METHODS

Immunohistochemical analysis was carried out with CEACAM1-L or CEACAM1-S antibodies on 154 HCC tissues to correlate with the factors of malignancy. Invasion assay was performed for the effect of CEACAM1 expression on HCC cell lines. Moreover, immunohistochemical analysis and immunoprecipitation analysis were performed to investigate the association between CEACAM1 isoform balance and β2SP.

RESULTS

In immunohistochemical analysis, CEACAM1-L expression dominance was a risk factor for HCC recurrence (p = 0.04) and was significantly associated with a shorter survival compared with CEACAM1-S expression dominance. Invasion assay indicated that CEACAM1-4L-transfected HLF and PLC/PRF/5 cells showed significantly increased invasion (p < 0.0001) and CEACAM1-4S-transfected HLF cells showed significantly decreased invasion. Immunohistochemical analysis of β2SP suggested that the HCCs with CEACAM1-L-dominant expression were more strongly stained with β2SP than the HCCs with CEACAM1-S-dominant expression (p = 0.013), and coprecipitation assays indicated that CEACAM1-L could bind to β2SP.

CONCLUSIONS

CEACAM1-L may enhance the HCC invasiveness through an interaction with β2SP and subsequent effects on TGF-β signaling.

Targeting TGF-β signaling in cancer

INTRODUCTION

The transforming growth factor-β (TGF-β) signaling pathway has a pivotal role in tumor suppression and yet, paradoxically, in tumor promotion. Functional context dependent insights into the TGF-β pathway are crucial in developing TGF-β-based therapeutics for cancer.

AREAS COVERED

This review discusses the molecular mechanism of the TGF-β pathway and describes the different ways of tumor suppression by TGF-β. It is then explained how tumors can evade these effects and how TGF-β contributes to further growing and spreading of some of the tumors. In the last part of the review, the data on targeting TGF-β pathway for cancer treatment is assessed. This review focuses on anti-TGF-β based treatment and other options targeting activated pathways in tumors where the TGF-β tumor suppressor pathway is lost. Pre-clinical as well up to date results of the most recent clinical trials are given.

EXPERT OPINION

Targeting the TGF-β pathway can be a promising direction in cancer treatment. However, several challenges still exist, the most important are differentiating between the carcinogenic effects of TGF-β and its other physiological roles, and delineating the tumor suppressive versus the tumor promoting roles of TGF-β in each specific tumor. Future studies are needed in order to find safer and more effective TGF-β-based drugs.

Loss of TGF-β adaptor β2SP activates notch signaling and SOX9 expression in esophageal adenocarcinoma

TGF-β and Notch signaling pathways play important roles in regulating self-renewal of stem cells and gastrointestinal carcinogenesis. Loss of TGF-β signaling components activates Notch signaling in esophageal adenocarcinoma, but the basis for this effect has been unclear. Here we report that loss of TGF-β adapter β2SP (SPNB2) activates Notch signaling and its target SOX9 in primary fibroblasts or esophageal adenocarcinoma cells. Expression of the stem cell marker SOX9 was markedly higher in esophageal adenocarcinoma tumor tissues than normal tissues, and its higher nuclear staining in tumors correlated with poorer survival and lymph node invasion in esophageal adenocarcinoma patients. Downregulation of β2SP by lentivirus short hairpin RNA increased SOX9 transcription and expression, enhancing nuclear localization for both active Notch1 (intracellular Notch1, ICN1) and SOX9. In contrast, reintroduction into esophageal adenocarcinoma cells of β2SP and a dominant-negative mutant of the Notch coactivator mastermind-like (dnMAN) decreased SOX9 promoter activity. Tumor sphere formation and invasive capacity in vitro and tumor growth in vivo were increased in β2SP-silenced esophageal adenocarcinoma cells. Conversely, SOX9 silencing rescued the phenotype of esophageal adenocarcinoma cells with loss of β2SP. Interaction between Smad3 and ICN1 via Smad3 MH1 domain was also observed, with loss of β2SP increasing the binding between these proteins, inducing expression of Notch targets SOX9 and C-MYC, and decreasing expression of TGF-β targets p21(CDKN1A), p27 (CDKN1B), and E-cadherin. Taken together, our findings suggest that loss of β2SP switches TGF-β signaling from tumor suppression to tumor promotion by engaging Notch signaling and activating SOX9.

TGF-β signaling in onset and progression of hepatocellular carcinoma

Transforming growth factor (TGF)-β is a central regulator in chronic liver disease, contributing to all stages of disease progression from initial liver injury through inflammation and fibrosis to cirrhosis and hepatocellular carcinoma. Liver damage-induced levels of active TGF-β enhance hepatocyte destruction and mediate hepatic stellate cell and fibroblast activation resulting in a wound-healing response, including myofibroblast generation and extracellular matrix deposition. Further evidence points to a decisive role of cytostatic and apoptotic functions mediated on hepatocytes, which is critical for the control of liver mass, with loss of TGF-β activities resulting in hyperproliferative disorders and cancer. This concept is based on studies that describe a bipartite role of TGF-β with tumor suppressor functions at early stages of liver damage and regeneration, whereas during cancer progression TGF-β may turn from a tumor suppressor into a tumor promoter that exacerbates invasive and metastatic behavior. We have delineated this molecular switch of the pathway from cytostatic to tumor promoting in further detail and identify activation of survival signaling pathways in hepatocytes as a most critical requirement. Targeting the TGF-β signaling pathway has been explored to inhibit liver disease progression. While interfering with TGF-β signaling in various short-term animal models has demonstrated promising results, liver disease progression in humans is a process of decades with different phases in which TGF-β or its targeting may have both beneficial and adverse outcomes. We emphasize that, in order to achieve therapeutic effects, targeting TGF-β signaling in the right cell type at the right time is required.

Wnt/beta-catenin signaling in hepatic organogenesis

Wnt/beta-catenin signaling has come to the forefront of liver biology in recent years. This pathway regulates key pathophysiological events inherent to the liver including development, regeneration and cancer, by dictating several biological processes such as proliferation, apoptosis, differentiation, adhesion, zonation and metabolism in various cells of the liver. This review will examine the studies that have uncovered the relevant roles of Wnt/beta-catenin signaling during the process of liver development. We will discuss the potential roles of Wnt/beta-catenin signaling during the phases of development, including competence, hepatic induction, expansion and morphogenesis. In addition, we will discuss the role of negative and positive regulation of this pathway and how the temporal expression of Wnt/beta-catenin can direct key processes during hepatic development. We will also identify some of the major deficits in the current understanding of the role of Wnt/beta-catenin signaling in liver development in order to provide a perspective for future studies. Thus, this review will provide a contextual overview of the role of Wnt/beta-catenin signaling during hepatic organogenesis.

Dysfunctional transforming growth factor-β signaling with constitutively active Notch signaling in Barrett's esophageal adenocarcinoma

BACKGROUND

Esophageal adenocarcinoma is often considered to arise from a clonal stem-like population of cells, which is potentially responsible for its poor prognosis. Transforming growth factor β (TGF-β) and Notch signaling pathways play important roles in regulating self-renewal of stem cells and cell-fate determination. Both pathways are frequently implicated in gastrointestinal carcinogenesis. However, their contributions to esophageal adenocarcinoma remain unclear.

METHODS

We evaluated TGF-β and Notch signaling components in normal esophagus, Barrett's esophagus, and adenocarcinoma tissues and cell lines via immunohistochemical analysis and immunoblotting; Hes-1 transcription was assayed using a Hes-1 luciferase reporter.

RESULTS

We observed loss of Smad4 (P<.05) and β2 spectrin (β2SP) (P<.01) in 5/10 Barrett's esophagus and 17/22 adenocarcinoma tissue sections. Concomitantly, dramatically raised levels of Notch signaling components Hes1 and Jagged1 occurred in adenocarcinoma tissues and cell lines compared with normal tissues. In normal esophagus, Oct3/4-positive cells are located in the basal layer (2-3 per cluster), representing a pool of progenitor cells. We observed an expansion of this pool of Oct3/4 positive cells in esophageal adenocarcinoma (15 per cluster). Furthermore, a panel of SOXs proteins documented for stem cell markers exhibit increased expression in tumor cells, indicating expansion of putative cancer stem cells. Finally, we observed growth inhibition in BE3 cells with a γ-secretase inhibitor, but not in SKGT-4 cells. Unlike SKGT-4 cells, BE3 cells have activated Notch signaling with disruption of TGF-β signaling.

CONCLUSIONS

Our findings demonstrated a potential therapeutic value for targeted therapy in esophageal adenocarcinoma in the setting of loss of β2SP/TGF-β with concomitant constitutively active Notch signaling.

Exploring anti-TGF-β therapies in cancer and fibrosis

Transforming growth factor-β (TGF-β) is a multifunctional cytokine, with important roles in maintaining tissue homeostasis. TGF-β signals via transmembrane serine/threonine kinase receptors and intracellular Smad transcriptional regulators. Perturbed TGF-β signaling has been implicated in a large variety of pathological conditions. Increased TGF-β levels have been found in patients with cancer, fibrosis, and systemic sclerosis, and were correlated with disease severity. In cancer, TGF-β mediates tumor invasion and metastasis by affecting both tumor cells and the tumor microenvironment including fibroblast activation and immune suppression. Furthermore, TGF-β is a strong stimulator of extracellular matrix deposition. On the basis of these observations, small molecule inhibitors of the TGF-β receptor kinases, neutralizing antibodies that interfere with ligand?receptor interactions, antisense oligonucleotides reducing TGF-β expression, and soluble receptor ectodomains that sequester TGF-β have been developed to intervene with excessive TGF-β signaling activity in the aforementioned disorders. Here, we review the current state of anti-TGF-β therapy in clinical trials.

Stromal upregulation of lateral epithelial adhesions: gene expression analysis of signalling pathways in prostate epithelium

Background

Stromal signalling increases the lateral cell adhesions of prostate epithelial cells grown in 3D culture. The aim of this study was to use microarray analysis to identify significant epithelial signalling pathways and genes in this process.

Methods

Microarray analysis was used to identify genes that were differentially expressed when epithelial cells were grown in 3D Matrigel culture with stromal co-culture compared to without stroma. Two culture models were employed: primary epithelial cells (ten samples) and an epithelial cell line (three experiments). A separate microarray analysis was performed on each model system and then compared to identify tissue-relevant genes in a cell line model.

Results

TGF beta signalling was significantly ranked for both model systems and in both models the TGF beta signalling gene SOX4 was significantly down regulated. Analysis of all differentially expressed genes to identify genes that were common to both models found several morphology related gene clusters; actin binding (DIAPH2, FHOD3, ABLIM1, TMOD4, MYH10), GTPase activator activity (BCR, MYH10), cytoskeleton (MAP2, MYH10, TMOD4, FHOD3), protein binding (ITGA6, CD44), proteinaceous extracellular matrix (NID2, CILP2), ion channel/ ion transporter activity (CACNA1C, CACNB2, KCNH2, SLC8A1, SLC39A9) and genes associated with developmental pathways (POFUT1, FZD2, HOXA5, IRX2, FGF11, SOX4, SMARCC1).

Conclusions

In 3D prostate cultures, stromal cells increase lateral epithelial cell adhesions. We show that this morphological effect is associated with gene expression changes to TGF beta signalling, cytoskeleton and anion activity.

Transforming growth factor-β adaptor, β2-spectrin, modulates cyclin dependent kinase 4 to reduce development of hepatocellular cancer

Transforming growth factor beta (TGF-β) is an important regulator of cell growth, and loss of TGF-β signaling is a hallmark of carcinogenesis. The Smad3/4 adaptor protein β2-spectrin (β2SP) is emerging as a potent regulator of tumorigenesis through its ability to modulate the tumor suppressor function of TGF-β. However, to date the role of the TGF-β signaling pathway at specific stages of the development of hepatocellular carcinoma (HCC), particularly in relation to the activation of other oncogenic pathways, remains poorly delineated. Here we identify a mechanism by which β2SP, a crucial Smad3 adaptor, modulates cyclin dependent kinase 4 (CDK4), cell cycle progression, and suppression of HCC. Increased expression of β2SP inhibits phosphorylation of the retinoblastoma gene product (Rb) and markedly reduces CDK4 expression to a far greater extent than other CDKs and cyclins. Furthermore, suppression of CDK4 by β2SP efficiently restores Rb hypophosphorylation and cell cycle arrest in G(1) . We further demonstrate that β2SP interacts with CDK4 and Smad3 in a competitive and TGF-β-dependent manner. In addition, haploinsufficiency of cdk4 in β2sp(+/-) mice results in a dramatic decline in HCC formation compared to that observed in β2sp(+/-) mice.

CONCLUSION

β2SP deficiency leads to CDK4 activation and contributes to dysregulation of the cell cycle, cellular proliferation, oncogene overexpression, and the formation of HCCs. Our data highlight CDK4 as an attractive target for the pharmacologic inhibition of HCC and demonstrate the importance of β2sp(+/-) mice as a model of preclinical efficacy in the treatment of HCC.

Epithelial-mesenchymal interactions in biliary diseases

In most cholangiopathies, liver diseases of different etiologies in which the biliary epithelium is the primary target in the pathogenic sequence, the central mechanism involves inflammation. Inflammation, characterized by pleomorphic peribiliary infiltrate containing fibroblasts, macrophages, lymphocytes, as well as endothelial cells and pericytes, is associated to the emergence of "reactive cholangiocytes." These biliary cells do not possess bile secretory functions, are in contiguity with terminal cholangioles, and are of a less-differentiated phenotype. They have acquired several mesenchymal properties, including motility and ability to secrete a vast number of proinflammatory chemo/cytokines and growth factors along with de novo expression of a rich receptor machinery. These functional properties enable reactive cholangiocytes to establish intimate contacts and to mutually exchange a variety of paracrine signals with the different mesenchymal cell types populating the portal infiltrate. The extensive crosstalk between the epithelial and mesenchymal compartments is the driver of liver repair mechanisms in cholangiopathies, ultimately evolving toward portal fibrosis. Herein, the authors first review the properties of the different cell types involved in their interaction, and then analyze the underlying molecular mechanisms as they relate to liver repair in cholangiopathies.

Smad4-mediated TGF-beta signaling in tumorigenesis

Transforming growth factor-β (TGF-β) family members exert their function via specific type I and type II serine/threonine kinase receptors and intracellular Smad transcription factors, including the common mediator Smad4. The dual effects of TGF-β signaling on tumor initiation and progression are cell-specific and yet to be determined under distinct contexts. A number of genetically manipulated mouse models with alterations in the TGF-β pathway genes, particularly the pivotal Smad4, revealed that these genes play crucial functions in maintaining tissue homeostasis and suppressing tumorigenesis. Loss of Smad4 plays a causal role in initiating squamous cell carcinomas of skin and upper digestive tract as well as adenocarcinomas of gastrointestinal tract. However, for some cancers like pancreatic and cholangiocellular carcinomas, Smad4 deficiency does not initiate the tumorigenesis but acts as a promoter to accelerate or synergize the development and progression of cancers that are started by other oncogenic pathways. Intriguingly, emerging evidences from mouse models have highlighted the important roles of non-cell autonomous effects of Smad4-mediated TGF-β signaling in the inhibition of oncogenesis. All these data have greatly deepened our understanding of molecular mechanisms of cell-autonomous and non-cell autonomous effect of Smad4-mediated TGF-β signaling in suppressing carcinogenesis, which may facilitate the development of successful therapies targeting TGF-β signaling for the treatment of human cancers.

Smad4-mediated TGF-beta signaling in tumorigenesis

Transforming growth factor-beta (TGF-beta) family members exert their function via specific type I and type II serine/threonine kinase receptors and intracellular Smad transcription factors, including the common mediator Smad4. The dual effects of TGF-beta signaling on tumor initiation and progression are cell-specific and yet to be determined under distinct contexts. A number of genetically manipulated mouse models with alterations in the TGF-beta pathway genes, particularly the pivotal Smad4, revealed that these genes play crucial functions in maintaining tissue homeostasis and suppressing tumorigenesis. Loss of Smad4 plays a causal role in initiating squamous cell carcinomas of skin and upper digestive tract as well as adenocarcinomas of gastrointestinal tract. However, for some cancers like pancreatic and cholangiocellular carcinomas, Smad4 deficiency does not initiate the tumorigenesis but acts as a promoter to accelerate or synergize the development and progression of cancers that are started by other oncogenic pathways. Intriguingly, emerging evidences from mouse models have highlighted the important roles of non-cell autonomous effects of Smad4-mediated TGF-beta signaling in the inhibition of oncogenesis. All these data have greatly deepened our understanding of molecular mechanisms of cell-autonomous and non-cell autonomous effect of Smad4-mediated TGF-beta signaling in suppressing carcinogenesis, which may facilitate the development of successful therapies targeting TGF-beta signaling for the treatment of human cancers.

Runx3 expression in gastrointestinal tract epithelium: resolving the controversy

We reported earlier that RUNX3 is expressed in human and mouse gastrointestinal tract (GIT) epithelium and that it functions as a tumor suppressor in gastric and colorectal tissues. However, there have been conflicting reports describing the absence of Runx3 in GIT epithelial cells. A part of the controversy may be derived from the use of a specific antibody by other groups (referred to as G-poly). Here, we show further evidence to support our earlier observations and provide a possible explanation for this apparent controversy. We generated multiple anti-RUNX3 monoclonal antibodies and found that RUNX3 antibodies recognizing the RUNX3 N-terminal region (residues 1-234) react with RUNX3 in gastric epithelial cells, whereas those recognizing the C-terminal region (beyond residue 234) did not. G-poly primarily recognizes the region beyond 234 and hence, is unable to detect Runx3 in this tissue.

Hepatocellular cancer arises from loss of transforming growth factor beta signaling adaptor protein embryonic liver fodrin through abnormal angiogenesis

We have previously demonstrated that 40%-70% of elf(+/-) mice spontaneously develop hepatocellular cancer (HCC) within 15 months, revealing the importance of the transforming growth factor-beta (TGF-beta) signaling pathway in suppressing tumorigenesis in the liver. The current study was carried out to investigate mechanisms by which embryonic liver fodrin (ELF), a crucial Smad3/4 adaptor, suppresses liver tumor formation. Histological analysis of hyperplastic liver tissues from elf(+/-) mice revealed abundant newly formed vascular structures, suggesting aberrant angiogenesis with loss of ELF function. In addition, elf(+/-) mice displayed an expansion of endothelial progenitor cells. Ectopic ELF expression in fetal bovine heart endothelial (FBHE) cells resulted in cell cycle arrest and apoptosis. Further analysis of developing yolk sacs of elf(-/-) mice revealed a failure of normal vasculature and significantly decreased endothelial cell differentiation with embryonic lethality. Immunohistochemical analysis of hepatocellular cancer (HCC) from the elf(+/-) mice revealed an abnormal angiogenic profile, suggesting the role of ELF as an angiogenic regulator in suppressing HCC. Lastly, acute small interfering RNA (siRNA) inhibition of ELF raised retinoblastoma protein (pRb) levels nearly fourfold in HepG2 cells (a hepatocellular carcinoma cell line) as well as in cow pulmonary artery endothelial (CPAE) cells, respectively.

CONCLUSION

Taken together these results, ELF, a TGF-beta adaptor and signaling molecule, functions as a critical adaptor protein in TGF-beta modulation of angiogenesis as well as cell cycle progression. Loss of ELF in the liver leads the cancer formation by deregulated hepatocyte proliferation and stimulation of angiogenesis in early cancers. Our studies propose that ELF is potentially a powerful target for mimetics enhancing the TGF-beta pathway tumor suppression of HCC.

What lurks beneath: IL-11, via Stat3, promotes inflammation-associated gastric tumorigenesis

Chronic inflammation in the stomach induces cellular transformation and gastric cancer primarily in the distal stomach or antrum. In this issue of the JCI, a study in mice by Ernst et al. provides new insight into the role of IL-11 and its glycoprotein 130 (gp130) receptor in inflammation-associated gastric epithelial cell oncogenic transformation, which they show is mediated by and dependent on increased activation of Stat3 and, to a lesser extent, Stat1 (see the related article beginning on page 1727). Prior studies from this group have shown that Stat3 hyperactivity stimulates the TGF-beta inhibitor Smad7. Collectively, the studies suggest that an important pathway of oncogenic transformation in the stomach is through suppression of growth inhibitory signals, such as members of the TGF-beta family, that originate from the stroma.

Progenitor/stem cells give rise to liver cancer due to aberrant TGF-beta and IL-6 signaling

Cancer stem cells (CSCs) are critical for the initiation, propagation, and treatment resistance of multiple cancers. Yet functional interactions between specific signaling pathways in solid organ "cancer stem cells," such as those of the liver, remain elusive. We report that in regenerating human liver, two to four cells per 30,000-50,000 cells express stem cell proteins Stat3, Oct4, and Nanog, along with the prodifferentiation proteins TGF-beta-receptor type II (TBRII) and embryonic liver fodrin (ELF). Examination of human hepatocellular cancer (HCC) reveals cells that label with stem cell markers that have unexpectedly lost TBRII and ELF. elf(+/-) mice spontaneously develop HCC; expression analysis of these tumors highlighted the marked activation of the genes involved in the IL-6 signaling pathway, including IL-6 and Stat3, suggesting that HCC could arise from an IL-6-driven transformed stem cell with inactivated TGF-beta signaling. Similarly, suppression of IL-6 signaling, through the generation of mouse knockouts involving a positive regulator of IL-6, Inter-alpha-trypsin inhibitor-heavy chain-4 (ITIH4), resulted in reduction in HCC in elf(+/-) mice. This study reveals an unexpected functional link between IL-6, a major stem cell signaling pathway, and the TGF-beta signaling pathway in the modulation of mammalian HCC, a lethal cancer of the foregut. These experiments suggest an important therapeutic role for targeting IL-6 in HCCs lacking a functional TGF-beta pathway.

Transforming growth factor beta controls the directional migration of hepatocyte cohorts by modulating their adhesion to fibronectin

Transforming growth factor beta (TGF-beta) has a strong impact on liver development and physiopathology, exercised through its pleiotropic effects on growth, differentiation, survival, and migration. When exposed to TGF-beta, the mhAT3F cells, immortalized, highly differentiated hepatocytes, maintained their epithelial morphology and underwent dramatic alterations of adhesion, leading to partial or complete detachment from a culture plate, followed by readhesion and spreading. These alterations of adhesive behavior were caused by sequential changes in expression of the alpha5beta1 integrin and of its ligand, the fibronectin. The altered specificity of anchorage to the extracellular matrix gave rise to changes in cells' collective motility: cohorts adhering to fibronectin maintained a persistent, directional motility, with ezrin-rich pathfinder cells protruding from the tips of the cohorts. The absence of adhesion to fibronectin prevented the appearance of polarized pathfinders and lead to random, oscillatory motility. Our data suggest a novel role for TGF-beta in the control of collective migration of epithelial cohorts.

Inactivation of TGF-β signaling in lung cancer results in increased CDK4 activity that can be rescued by ELF

Escape from TGF-beta inhibition of proliferation is a hallmark of multiple cancers including lung cancer. We explored the role of ELF, crucial TGF-beta adaptor protein identified from endodermal progenitor cells, in lung carcinogenesis and cell-cycle regulation. Interestingly, elf-/- mice develop multiple defects that include lung, liver, and cardiac abnormalities. Four out of 6 lung cancer and mesothelioma cell lines displayed deficiency of ELF expression with increased CDK4 expression. Immunohistochemistry and Western blot analysis of primary human lung cancers also showed decreased ELF expression and overexpression of CDK4. Moreover, rescue of ELF in ELF-deficient cell lines decreased the expression of CDK4 and resulted in accumulation of G1/S checkpoint arrested cells. These results suggest that disruption in TGF-beta signaling mediated by loss of ELF in lung cancer leads to cell-cycle deregulation by modulating CDK4 and ELF highlights a key role of TGF-beta adaptor protein in suppressing early lung cancer.

Actions of TGF-beta as tumor suppressor and pro-metastatic factor in human cancer

Transforming growth factor-beta (TGF-beta) is a secreted polypeptide that signals via receptor serine/threonine kinases and intracellular Smad effectors. TGF-beta inhibits proliferation and induces apoptosis in various cell types, and accumulation of loss-of-function mutations in the TGF-beta receptor or Smad genes classify the pathway as a tumor suppressor in humans. In addition, various oncogenic pathways directly inactivate the TGF-beta receptor-Smad pathway, thus favoring tumor growth. On the other hand, all human tumors overproduce TGF-beta whose autocrine and paracrine actions promote tumor cell invasiveness and metastasis. Accordingly, TGF-beta induces epithelial-mesenchymal transition, a differentiation switch that is required for transitory invasiveness of carcinoma cells. Tumor-derived TGF-beta acting on stromal fibroblasts remodels the tumor matrix and induces expression of mitogenic signals towards the carcinoma cells, and upon acting on endothelial cells and pericytes, TGF-beta regulates angiogenesis. Finally, TGF-beta suppresses proliferation and differentiation of lymphocytes including cytolytic T cells, natural killer cells and macrophages, thus preventing immune surveillance of the developing tumor. Current clinical approaches aim at establishing novel cancer drugs whose mechanisms target the TGF-beta pathway. In conclusion, TGF-beta signaling is intimately implicated in tumor development and contributes to all cardinal features of tumor cell biology.

TGF-beta signaling pathway inactivation and cell cycle deregulation in the development of gastric cancer: role of the beta-spectrin, ELF

We have shown that loss of ELF, a stem cell adaptor protein, disrupts TGF-beta signaling through Smad3 and Smad4 localization. Notably elf(+/-)/smad4(+/-) mice develop gastric cancer presenting this as an important model for analyzing molecular event in gastric carcinogenesis. To gain further insight into the functional role of ELF in gastric cancer suppression, we carried out a detailed characterization of cell cycle events leading to gastric tumorigenesis. elf(-/-) cells and elf(+/-)/smad4(+/-) mice demonstrate a marked alteration of cell cycle regulators, such as Cdk4, K-Ras, and p21. Levels of Cdk4 increased compared to normal controls, suggesting loss of ELF results in functional abnormalities in cell cycle regulation. We further demonstrate that the elf(-/-) MEFs show a disruption of G1/S cell cycle transition and a significant reduction in senescence. Thus, in response to ELF deficiency, the abnormalities of G1/S checkpoint and senescence contribute their increment of susceptibility to malignant transformation.

TGF-beta receptor-binding proteins: complex interactions

Members of the Smad protein family are fundamental downstream mediators of TGF-beta signals. However, the basic, linear Smad signaling pathway is unlikely to be the sole contributor to the plethora of cell type-specific TGF-beta responses. Investigators have identified a number of molecules that interact with the TGF-beta receptors (TbetaRs) and may explain, at least in part, the tight regulation of TGF-beta effects. Understanding these TbetaR-interacting molecules is thus a matter of great potential significance for elucidating TGF-beta-family signal transduction. The present article reviews our current understanding of the roles and mechanisms of action of this relatively understudied group of molecules.