Smad7 induces hepatic metastasis in colorectal cancer

SETD5 regulates the OGT-catalyzed O-GlcNAcylation of RNA polymerase II, which is involved in the stemness of colorectal cancer cells

The dosage-dependent recruitment of RNA polymerase II (Pol II) at the promoters of genes related to neurodevelopment and stem cell maintenance is required for transcription by the fine-tuned expression of SET-domain-containing protein 5 (SETD5). Pol II O-GlcNAcylation by O-GlcNAc transferase (OGT) is critical for preinitiation complex formation and transcription cycling. SETD5 dysregulation has been linked to stem cell-like properties in some cancer types; however, the role of SETD5 in cancer cell stemness has not yet been determined. We here show that aberrant SETD5 overexpression induces stemness in colorectal cancer (CRC) cells. SETD5 overexpression causes the upregulation of PI3K-AKT pathway-related genes and cancer stem cell (CSC) markers such as CD133, Kruppel-like factor 4 (KLF4), and estrogen-related receptor beta (ESRRB), leading to the gain of stem cell-like phenotypes. Our findings also revealed a functional relationship between SETD5, OGT, and Pol II. OGT-catalyzed Pol II glycosylation depends on SETD5, and the SETD5-Pol II interaction weakens in OGT-depleted cells, suggesting a SETD5-OGT-Pol II interdependence. SETD5 deficiency reduces Pol II occupancy at PI3K-AKT pathway-related genes and CD133 promoters, suggesting a role for SETD5-mediated Pol II recruitment in gene regulation. Moreover, the SETD5 depletion nullified the SETD5-induced stemness of CRC cells and Pol II O-GlcNAcylation. These findings support the hypothesis that SETD5 mediates OGT-catalyzed O-GlcNAcylation of RNA Pol II, which is involved in cancer cell stemness gain via CSC marker gene upregulation.

Tetrahydrocurcumin (THC) enhanced the clearance of Cryptococcus deneoformans during infection in vivo

Cryptococcal species often cause lung infections and are the main cause of fungal meningitis. Claudin-4 appears to be a major structural component that maintains a tight alveolar barrier and prevents fluid and electrolyte leakage into the alveolar space. We aimed to determine whether S7-tetrahydrocurcumin (THC) could clearance of C. deneoformans and regulate claudin-4 expression during C. deneoformans infection. We investigated the effect of THC on C. deneoformans infection and its possible mechanism in vivo. Transmission electron microscopy was used to observe the ultrastructure of the lung tissue and the invasion of Cryptococcus. To clarify the effect of THC, we examined claudin-4, c-Jun, and Smad2 expression. We also measured claudin-4 expression in pulmonary specimens from clinical patients. THC reduced cryptococcal cell invasion in the lungs, improved alveolar exudation, and reduced inflammation. Pretreatment with THC suppressed c-Jun and Smad2 expression, resulting in significantly increased claudin-4 levels. In contrast, the expression of claudin-4 in clinical specimens from patients with cryptococcal infection was higher than that in normal specimens. THC enhanced the clearance of C. deneoformans during infection in vivo. We investigated the expression of claudin-4 and the possible mechanism of THC against C. deneoformans infection.

TGFβ and the Tumor Microenvironment in Colorectal Cancer

Growing evidence supports an important role of the tumor microenvironment (TME) in the pathogenesis of colorectal cancer (CRC). Resident cells such as fibroblasts or immune cells infiltrating into the TME maintain continuous crosstalk with cancer cells and thereby regulate CRC progression. One of the most important molecules involved is the immunoregulatory cytokine transforming growth factor-β (TGFβ). TGFβ is released by various cells in the TME, including macrophages and fibroblasts, and it modulates cancer cell growth, differentiation, and cell death. Mutations in components of the TGF pathway, including TGFβ receptor type 2 or SMAD4, are among the most frequently detected mutations in CRC and have been associated with the clinical course of disease. Within this review, we will discuss our current understanding about the role of TGFβ in the pathogenesis of CRC. This includes novel data on the molecular mechanisms of TGFβ signaling in TME, as well as possible strategies for CRC therapy targeting the TGFβ pathway, including potential combinations with immune checkpoint inhibitors.

Genetic analysis and allele-specific expression of SMAD7 3'UTR variants in human colorectal cancer reveal a novel somatic variant exhibiting allelic imbalance

BACKGROUND

Considering the impact of SMAD7 deregulation in colorectal cancer (CRC) progression and the significance of single nucleotide variant (SNV)-mediated disruptions of microRNA (miRNA)-dependent regulation for cancer susceptibility, our study aimed to analyze genetic variation in the SMAD7 3' untranslated region ( 3'UTR) in CRC, measure differences in allelic mRNA expression, and evaluate its interference with miRNA-mediated post-transcriptional regulation.

PATIENTS AND METHODS

This study included 80 patients with different CRC stages and six human colon cancer cell lines of various histological origins. SMAD7 3'UTR was analyzed by direct sequencing, followed by the relative quantification of differential allelic expression of detected variants by allele-specific qRT-PCR. In silico tools were employed for predictions of regulatory consequences of detected variants.

RESULTS

A total of four different SNVs in one cell line and nine patients were found, among which were a novel somatic point variant and three already known germline variants (rs16950113, rs1050799536, and rs1043778717). All evaluated SNVs exhibited variable extents of allelic imbalance in expression. In silico analysis predicted significant effects of SNVs on miRNA binding efficiency, with each SNV disrupting existing and creating new target sites for one or more miRNAs.

CONCLUSION

Imbalance observed in the expression of SNV alleles altering miRNA binding suggests that all investigated SNVs are potential contributing factors impacting SMAD7 expression regulation in CRC that further studies should investigate.

TGF-β Signaling in Metastatic Colorectal Cancer (mCRC): From Underlying Mechanism to Potential Applications in Clinical Development

Colorectal cancer (CRC) is a serious public health issue, and it has the leading incidence and mortality among malignant tumors worldwide. CRC patients with metastasis in the liver, lung or other distant sites always have poor prognosis. Thus, there is an urgent need to discover the underlying mechanisms of metastatic colorectal cancer (mCRC) and to develop optimal therapy for mCRC. Transforming growth factor-β (TGF-β) signaling plays a significant role in various physiologic and pathologic processes, and aberrant TGF-β signal transduction contributes to mCRC progression. In this review, we summarize the alterations of the TGF-β signaling pathway in mCRC patients, the functional mechanisms of TGF-β signaling, its promotion of epithelial-mesenchymal transition, its facilitation of angiogenesis, its suppression of anti-tumor activity of immune cells in the microenvironment and its contribution to stemness of CRC cells. We also discuss the possible applications of TGF-β signaling in mCRC diagnosis, prognosis and targeted therapies in clinical trials. Hopefully, these research advances in TGF-β signaling in mCRC will improve the development of new strategies that can be combined with molecular targeted therapy, immunotherapy and traditional therapies to achieve better efficacy and benefit mCRC patients in the near future.

Identification and Validation of a Four-Gene Ferroptosis Signature for Predicting Overall Survival of Lung Squamous Cell Carcinoma

Background

Lung squamous cell carcinoma (LUSC) represents 30% of all non-small cell lung carcinoma. Targeted therapy is not sufficient for LUSC patients because of the low frequency of targeted-effective mutation in LUSC whereas immunotherapy offers more options for patients with LUSC. We explored a ferroptosis-related prognostic signature that can potentially assess the prognosis and immunotherapy efficacy of LUSC patients.

Methods

A total of 502 LUSC patients were downloaded from The Cancer Genome Atlas (TCGA). The external validation data were obtained from the Gene Expression Omnibus (GEO): GSE73403. Then, we identified the candidate genes and constructed the prognostic signature through the Cox survival regression analyses and least absolute shrinkage and selection operator (LASSO). Risk score plot, Kaplan–Meier curve, and ROC curve were used to assess the prognostic power and performance of the model. The CIBERSORT algorithm estimated the fraction of immune cell types. TIDE was utilized to predict the response to immunotherapy. IMvigor210 was used to explore the association between the risk scores and immunotherapy outcomes. A nomogram combined selected clinical characteristics, and the risk scores were constructed.

Results

We screened 132 differentially expressed ferroptosis-related genes. According to KEGG and GO pathway analyses, these genes were mainly engaged in the positive regulation of cytokine production, cytokine metabolic process, and oxidoreductase activity. We then constructed a prognostic model via LASSO regression. The proportions of CD8+ T cells, CD4+ activated T cells, and follicular helper T cells were significantly different between low-risk and high-risk groups. TIDE algorithm indicated that low-risk LUSC patients might profit more from immune checkpoint inhibitors. The predictive value of the ferroptosis gene model in immunotherapy response was further confirmed in IMvigor210. Finally, we combined the clinical characteristics with a LASSO regression model to construct a nomogram that could be easily applied in clinical practice.

Conclusion

We identified a prognostic model that provides an accurate and objective basis for guiding individualized treatment decisions for LUSC.

Genome-Wide Analysis of Smad7-Mediated Transcription in Mouse Embryonic Stem Cells

Smad7 has been identified as a negative regulator of the transforming growth factor TGF-β pathway by direct interaction with the TGF-β type I receptor (TβR-I). Although Smad7 has also been shown to play TGF-β unrelated functions in the cytoplasm and in the nucleus, a comprehensive analysis of its nuclear function has not yet been performed. Here, we show that in ESCs Smad7 is mainly nuclear and acts as a general transcription factor regulating several genes unrelated to the TGF-β pathway. Loss of Smad7 results in the downregulation of several key stemness master regulators, including Pou5f1 and Zfp42, and in the upregulation of developmental genes, with consequent loss of the stem phenotype. Integrative analysis of genome-wide mapping data for Smad7 and ESC self-renewal and pluripotency transcriptional regulators revealed that Smad7 co-occupies promoters of highly expressed key stemness regulators genes, by binding to a specific consensus response element NCGGAAMM. Altogether, our data establishes Smad7 as a new, integral component of the regulatory circuitry that controls ESC identity.

SMAD7 and SMAD4 expression in colorectal cancer progression and therapy response

Inhibitory SMAD7 and common mediator SMAD4 play crucial roles in SMAD-dependent TGF-β signaling that is often disrupted in colorectal cancer (CRC). This study aimed to profile the expression of SMAD7 and SMAD4 in primary and metastatic CRC and to evaluate their significance in disease progression and therapy response. The expression of SMAD7 and SMAD4 genes was analyzed by quantitative real-time PCR in tissues from 35 primary and metastatic CRC patients and in vitro in 7 human cell lines originating from colon tissue. Expression levels of SMAD7 and SMAD4, as well as their ratio, were determined and their association with tumor characteristics and response to therapy were evaluated. SMAD4 level was significantly lower in tumors compared to non-tumor tissues in both primary (p = 0.001) and metastatic (p = 0.001) CRC patients, while tumor expression of SMAD7 was significantly lower from non-tumor tissue only in metastatic patients (p = 0.017). SMAD7/SMAD4 ratio was elevated in CRC primary tumor tissues and cell lines compared to corresponding non-tumor tissues and cell line, respectively (p = 0.003). SMAD7 expression was significantly elevated in primary tumor tissues obtained from responders to neoadjuvant chemoradiotherapy (nCRT) compared to non-responders (p = 0.014). Alterations of expression and ratio of SMAD7 and SMAD4 in CRC cell lines, primary rectal cancer, and liver metastasis emphasize the importance of these genes in different stages of disease progression. Differential expression of SMAD7 in responders versus non-responders to nCRT should be further investigated for its potential predictive value.

TGF-β Signaling in Liver, Pancreas, and Gastrointestinal Diseases and Cancer

Genetic alterations affecting transforming growth factor-β (TGF-β) signaling are exceptionally common in diseases and cancers of the gastrointestinal system. As a regulator of tissue renewal, TGF-β signaling and the downstream SMAD-dependent transcriptional events play complex roles in the transition from a noncancerous disease state to cancer in the gastrointestinal tract, liver, and pancreas. Furthermore, this pathway also regulates the stromal cells and the immune system, which may contribute to evasion of the tumors from immune-mediated elimination. Here, we review the involvement of the TGF-β pathway mediated by the transcriptional regulators SMADs in disease progression to cancer in the digestive system. The review integrates human genomic studies with animal models that provide clues toward understanding and managing the complexity of the pathway in disease and cancer.

miR-21-5p/SMAD7 axis promotes the progress of lung cancer

Background

Lung cancer is one of the most common malignant tumors threatening human health. The aim of this study was to investigate the function of miR‐21‐5p in lung cancer progression.

Methods

We analyzed the expression levels of miR‐21‐5p in lung cancer tissues and cell lines. The qRT‐PCR and MTT assays were performed after transfection with miR‐21‐5p mimic, inhibitor and negative control into lung cancer cells.

Results

Luciferase reporter assays showed miR‐21‐5p directly target SMAD7. The miR‐21‐5p inhibitor significantly suppressed lung cancer cell proliferation, invasion and migration. We found that SMAD7 was upregulated in lung cancer tissue. In addition, we found that SMAD7 inhibited lung cancer cell proliferation and miR‐21‐5p mimic damaged the inhibitory effect of SMAD7.

Conclusions

miRNA‐21‐5p may promote cell proliferation, migration and invasion by spoiling SMAD7 expression in lung cancer cells.

Expression and function of Smad7 in autoimmune and inflammatory diseases

Transforming growth factor-β (TGF-β) plays a critical role in the pathological processes of various diseases. However, the signaling mechanism of TGF-β in the pathological response remains largely unclear. In this review, we discuss advances in research of Smad7, a member of the I-Smads family and a negative regulator of TGF-β signaling, and mainly review the expression and its function in diseases. Smad7 inhibits the activation of the NF-κB and TGF-β signaling pathways and plays a pivotal role in the prevention and treatment of various diseases. Specifically, Smad7 can not only attenuate growth inhibition, fibrosis, apoptosis, inflammation, and inflammatory T cell differentiation, but also promotes epithelial cells migration or disease development. In this review, we aim to summarize the various biological functions of Smad7 in autoimmune diseases, inflammatory diseases, cancers, and kidney diseases, focusing on the molecular mechanisms of the transcriptional and posttranscriptional regulation of Smad7.

Role of TGF-Beta and Smad7 in Gut Inflammation, Fibrosis and Cancer

The human gastrointestinal tract contains the largest population of immune cells in the body and this is a reflection of the fact that it is continuously exposed to a myriad of dietary and bacterial antigens. Although these cells produce a variety of inflammatory cytokines that could potentially promote tissue damage, in normal conditions the mucosal immune response is tightly controlled by counter-regulatory factors, which help induce and maintain gut homeostasis and tolerance. One such factor is transforming growth factor (TGF)-β1, a cytokine produced by multiple lineages of leukocytes, stromal cells and epithelial cells, and virtually targets all the gut mucosal cell types. Indeed, studies in animals and humans have shown that defects in TGF-β1 production and/or signaling can lead to the development of immune-inflammatory pathologies, fibrosis and cancer in the gut. Here, we review and discuss the available evidence about the role of TGF-β1 and Smad7, an inhibitor of TGF-β1 activity, in gut inflammation, fibrosis and cancer with particular regard to the contribution of these two molecules in the pathogenesis of inflammatory bowel diseases and colon cancer.

Current perspectives on inhibitory SMAD7 in health and disease

Transforming growth factor β (TGF-β) family members play an extensive role in cellular communication that orchestrates both early development and adult tissue homeostasis. Aberrant TGF-β family signaling is associated with a pathological outcome in numerous diseases, and in-depth understanding of molecular and cellular processes could result in therapeutic benefit for patients. Canonical TGF-β signaling is mediated by receptor-regulated SMADs (R-SMADs), a single co-mediator SMAD (Co-SMAD), and inhibitory SMADs (I-SMADs). SMAD7, one of the I-SMADs, is an essential negative regulator of the pleiotropic TGF-β and bone morphogenetic protein (BMP) signaling pathways. In a negative feedback loop, SMAD7 inhibits TGF-β signaling by providing competition for TGF-β type-1 receptor (TβRI), blocking phosphorylation and activation of SMAD2. Moreover, SMAD7 recruits E3 ubiquitin SMURF ligases to the type I receptor to promote ubiquitin-mediated proteasomal degradation. In addition to its role in TGF-β and BMP signaling, SMAD7 is regulated by and implicated in a variety of other signaling pathways and functions as a mediator of crosstalk. This review is focused on SMAD7, its function in TGF-β and BMP signaling, and its role as a downstream integrator and crosstalk mediator. This crucial signaling molecule is tightly regulated by various mechanisms. We provide an overview of the ways by which SMAD7 is regulated, including noncoding RNAs (ncRNAs) and post-translational modifications (PTMs). Finally, we discuss its role in diseases, such as cancer, fibrosis, and inflammatory bowel disease (IBD).

Exosomal miR-106a derived from gastric cancer promotes peritoneal metastasis via direct regulation of Smad7

Peritoneal metastasis develops in more than half of patients with gastric cancer but influencing factors are poorly characterized. Exosomes are increasingly recognized as a new mediator in cancer directional metastasis through the transfer of nucleic acids or proteins to neighboring or distant cells. The role of exosomes in peritoneal metastasis and whether it could establish pre-metastatic milieu are largely unknown. Here, we assessed the migration of gastric cancer (GC) cells and identified that PKH26-labeled exosomes from GC cells can be ingested by peritoneal mesothelial cells (MCs). Additionally, miRNA (miR-106a) that highly enriched in GC-derived exosomes (GC-exos) and essential for destroying the mesothelial barrier was demonstrated through the observation of the injury of the MCs including migratory enhancement and imbalance of apoptosis and proliferation. Moreover, either stimulating miR-106a or treatment with GC-exos could inhibit the expression of Smad7, accompanied by the concurrent elevated α-SMA and fibronectin in MCs. Silencing of miR-106a abolished GC-exos-induced gene expression in MCs. The MCs regain the viability, apoptosis reduction and Smad7 expression after rescue experiment conducted in miR-106a-enriched GC-exos. Xenograft model suggested that exosomal miR-106a had a potential to promote tumor growth through targeting Smad7. Collectively, we revealed that the delivery of miR-106a from GC-exos plays a crucial role in gastric cancer peritoneal metastasis.Abbreviations: MiR-106a: microRNA-106a; Smad7: small mothers against decapentaplegic 7; GC: gastric cancer; MCs: mesothelial cells; Exos: exosomes; HG: high-differentiated gastric cancer cells; LG: low-differentiated gastric cancer cells.

The association between SMAD7 polymorphisms and colorectal cancer susceptibility as well as clinicopathological features in the Iranian population

AIM

Our aim was to investigate the association between two single nucleotide polymorphisms (SNPs) of SMAD7 and the risk of CRC among Iranian individuals.

BACKGROUND

Genome-wide association studies (GWAS) have identified 18q21 as a risk locus for colorectal cancer (CRC), which maps to the SMAD7 gene.

METHODS

This case-control study was conducted on 109 CRC cases and 109 controls in the Iranian population to evaluate the influence of two SNPs of SMAD7, rs2337106 and rs6507874, on the risk of CRC as well as on clinicopathological features. Genotype determination was performed by TaqMan assay via an ABI 7500 Real Time PCR System (Applied Biosystems) for the DNA of peripheral blood. Descriptive analysis and logistic regression model were used for statistical analyses.

RESULTS

Genotyping of the SNPs in the SMAD7 gene revealed that the frequency of G allele of rs2337106 was 53.7% in controls and 56.4% in cases (p-value=0.564) while the frequency of C allele of rs6507874 was 55.5% in controls and 56.3% in cases (p-value=0.772). Further, there were no significant differences in genotype frequencies of these SNPs between CRC patients and controls. The SMAD7 genotypes were not associated with the risk of CRC or with any clinicopathological characteristics such as tumor site, tumor grade, and stage TNM in CRC patients (p-value>0.05), even after adjustment for sex, age, and smoking status.

CONCLUSION

Our results provided the first evidence that SMAD7 genotypes, rs2337106 and rs6507874, could not be predisposing markers in genetic susceptibility to CRC in an Iranian population, at least in the studied population.

Smad7 Controls Immunoregulatory PDL2/1-PD1 Signaling in Intestinal Inflammation and Autoimmunity

Smad7, a negative regulator of TGF-β signaling, has been implicated in the pathogenesis and treatment of inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC). Here, we found that Smad7 mediates intestinal inflammation by limiting the PDL2/1-PD1 axis in dendritic cells (DCs) and CD4+T cells. Smad7 deficiency in DCs promotes TGF-β responsiveness and the co-inhibitory molecules PDL2/1 on DCs, and it further imprints T cell-PD1 signaling to promote Treg differentiation. DC-specific Smad7 deletion mitigates DSS-induced colitis by inducing CD103+PDL2/1+DCs and Tregs. In addition, Smad7 deficiency in CD4+T cells promotes PD1 and PD1-induced Tregs in vitro. The transfer of Smad7-deficient CD4+T cells enhances Tregs in vivo and protects against T cell-mediated colitis. Furthermore, Smad7 antisense ameliorates DSS-induced UC, increasing TGF-β and PDL2/1-PD1 signaling. Enhancing PD1 signaling directly via Fc-fused PDL2/1 is also beneficial. Our results identify how Smad7 mediates intestinal inflammation and leverages these pathways therapeutically, providing additional strategies for IBD intervention.

Smad7 and Colorectal Carcinogenesis: A Double-Edged Sword

Colorectal carcinogenesis is a complex process in which many immune and non-immune cells and a huge number of mediators are involved. Among these latter factors, Smad7, an inhibitor of the transforming growth factor (TGF)-β1 signaling that has been involved in the amplification of the inflammatory process sustaining chronic intestinal inflammation, is supposed to make a valid contribution to the growth and survival of colorectal cancer (CRC) cells. Smad7 is over-expressed by tumoral cells in both sporadic CRC and colitis-associated CRC, where it sustains neoplastic processes through activation of either TGFβ-dependent or non-dependent pathways. Consistently, genome-wide association studies have identified single nucleotide polymorphisms of the Smad7 gene associated with CRC and shown that either amplification or deletion of the Smad7 gene associates with a poor prognosis or better outcome, respectively. On the other hand, there is evidence that over-expression of Smad7 in immune cells infiltrating the inflamed gut of patients with inflammatory bowel disease can elicit anti-tumor responses, with the down-stream effect of attenuating CRC cell growth. Taken together, these observations suggest a double role of Smad7 in colorectal carcinogenesis, which probably depends on the cell subset and the biological context analyzed. In this review, we summarize the available evidences about the role of Smad7 in both sporadic and colitis-associated CRC.

Epithelial Claudin Proteins and Their Role in Gastrointestinal Diseases

Our bodies are protected from the external environment by mucosal barriers that are lined by epithelial cells. The epithelium plays a critical role as a highly dynamic, selective semipermeable barrier that separates luminal contents and pathogens from the rest of the body and controlling the absorption of nutrients, fluid and solutes. A series of protein complexes including the adherens junction, desmosomes, and tight junctions function as the principal barrier in paracellular diffusion and regulators of intracellular solute, protein, and lipid transport. Tight junctions are composed of a series of proteins called occludins, junctional adhesion molecules, and claudins that reside primarily as the most apical intercellular junction. Here we will review one of these protein families, claudins, and their relevance to gastrointestinal and liver diseases.

Role of the transforming growth factor-β signaling pathway in the pathogenesis of colorectal cancer

The transforming growth factor-β (TGF-β) signaling pathway plays an important role in cancer cell proliferation, growth, metastasis, and apoptosis. It has been shown that TGF-β acts as a tumor suppressor in the early stages of the disease, and as a tumor promoter in its late stages. Mutations in the TGF-β signaling components, the TGF-β receptors and cytoplasmic signaling transducers, are frequently observed in colorectal carcinomas. Exploiting specific TGF-β receptor agonist and antagonist with antitumor properties may be a way of controlling cancer progression. This review summarizes the regulatory role of TGF-β signaling in the pathogenesis of colorectal cancer.

Deregulation of Negative Controls on TGF-β1 Signaling in Tumor Progression

The multi-functional cytokine transforming growth factor-β1 (TGF-β1) has growth inhibitory and anti-inflammatory roles during homeostasis and the early stages of cancer. Aberrant TGF-β activation in the late-stages of tumorigenesis, however, promotes development of aggressive growth characteristics and metastatic spread. Given the critical importance of this growth factor in fibrotic and neoplastic disorders, the TGF-β1 network is subject to extensive, multi-level negative controls that impact receptor function, mothers against decapentaplegic homolog 2/3 (SMAD2/3) activation, intracellular signal bifurcation into canonical and non-canonical pathways and target gene promotor engagement. Such negative regulators include phosphatase and tensin homologue (PTEN), protein phosphatase magnesium 1A (PPM1A), Klotho, bone morphogenic protein 7 (BMP7), SMAD7, Sloan-Kettering Institute proto-oncogene/ Ski related novel gene (Ski/SnoN), and bone morphogenetic protein and activin membrane-bound Inhibitor (BAMBI). The progression of certain cancers is accompanied by loss of expression, overexpression, mislocalization, mutation or deletion of several endogenous repressors of the TGF-β1 cascade, further modulating signal duration/intensity and phenotypic reprogramming. This review addresses how their aberrant regulation contributes to cellular plasticity, tumor progression/metastasis and reversal of cell cycle arrest and discusses the unexplored therapeutic value of restoring the expression and/or function of these factors as a novel approach to cancer treatment.

TGFβ and IGF1R signaling activates protein kinase A through differential regulation of ezrin phosphorylation in colon cancer cells

Aberrant cell survival plays a critical role in cancer progression and metastasis. We have previously shown that ezrin, a cAMP-dependent protein kinase A-anchoring protein (AKAP), is up-regulated in colorectal cancer (CRC) liver metastasis. Phosphorylation of ezrin at Thr-567 activates ezrin and plays an important role in CRC cell survival associated with XIAP and survivin up-regulation. In this study, we demonstrate that in FET and GEO colon cancer cells, knockdown of ezrin expression or inhibition of ezrin phosphorylation at Thr-567 increases apoptosis through protein kinase A (PKA) activation in a cAMP-independent manner. Transforming growth factor (TGF) β signaling inhibits ezrin phosphorylation in a Smad3-dependent and Smad2-independent manner and regulates pro-apoptotic function through ezrin-mediated PKA activation. On the other hand, ezrin phosphorylation at Thr-567 by insulin-like growth factor 1 receptor (IGF1R) signaling leads to cAMP-dependent PKA activation and enhances cell survival. Further studies indicate that phosphorylated ezrin forms a complex with PKA RII, and dephosphorylated ezrin dissociates from the complex and facilitates the association of PKA RII with AKAP149, both of which activate PKA yet lead to either cell survival or apoptosis. Thus, our studies reveal a novel mechanism of differential PKA activation mediated by TGFβ and IGF1R signaling through regulation of ezrin phosphorylation in CRC, resulting in different cell fates. This is of significance because TGFβ and IGF1R signaling pathways are well-characterized tumor suppressor and oncogenic pathways, respectively, with important roles in CRC tumorigenesis and metastasis. Our studies indicate that they cross-talk and antagonize each other's function through regulation of ezrin activation. Therefore, ezrin may be a potential therapeutic target in CRC.

SMAD7 polymorphisms and colorectal cancer risk: a meta-analysis of case-control studies

Mothers against decapentaplegic homolog 7 (SMAD7) inhibits the transforming growth factor-β (TGF-β) signaling pathway, which regulates carcinogenesis and cancer progression. A number of studies have reported that SMAD7 polymorphisms (rs4464148, rs4939827, and rs12953717) are associated with colorectal cancer (CRC) risk, but the results from these studies remain conflicting. To determine a more precise estimation of the relationship between SMAD7 and CRC, we undertook a large-scale meta-analysis of 63 studies, which included a total of 187,181 subjects (86,585 cases and 100,596 controls). The results of our meta-analysis revealed that the C allele of rs4464148 [CC vs. TT+TC, odds ratio (OR) =1.23, 95% confidence interval (CI): 1.14–1.33, P < 0.01], the T allele of rs4939827 [TT vs. CC+TC, odds ratio OR=1.15, 95%CI:1.07–1.22, P < 0.01] and the T allele of rs12953717 [TT vs. CC+TC, OR =1.22, 95%CI:1.16–1.29, P < 0.01] were all associated with the increased CRC risk. Subgroup analysis according to ethnicity showed rs4464148 and rs12953717 were associated with the risk of CRC in both Caucasians and Asians, whereas rs4939827 was a risk polymorphism for CRC specifically in Caucasians. In summary, this large-scale meta-analysis indicated that SMAD7 polymorphisms (rs4464148, rs4939827, and rs12953717) correlate with CRC.

TGFβ1 Promotes Breast Cancer Local Invasion and Liver Metastasis by Increasing the CD44high/CD24- Subpopulation

OBJECTIVE

Previous studies have shown that the transforming growth factor β1 pathway plays an important role in breast cancer metastasis to the liver. However, the mechanism of this metastasis has not been fully clarified. Cancer stem cells are essential for the initiation and propagation of tumor metastasis. The objective of our current study was to define the role of cancer stem cells in transforming growth factor β1-mediated breast cancer hepatic metastases.

METHOD

Hematoxylin and eosin staining was used to assess the formation of breast cancer liver metastases and local invasion. Cancer stem cells surface markers (CD44, CD24, and Epithelial cell adhesion molecule [EpCAM]), luminal/mesenchymal markers (keratin8 and alpha smooth muscle actin), and proliferation markers (Ki-67 and cyclinD1) were detected by immunohistochemistry assays. Flow cytometry was used to evaluate the effect of transforming growth factor β1 on the CD44+/CD24- cancer stem cell population. Quantitative real-time polymerase chain reaction was employed to assess the gene expression of the stem cell self-renewal markers nanog, pou5f1 (coding for Oct4), and sox2.

RESULTS

Transforming growth factor β1 increased the formation of liver metastases by the MDA-MB231 (MDA) breast cancer cell line but did not affect the liver metastasis of CD44+/CD24+ noncancer stem cells. Transforming growth factor β1 treatment did not significantly affect tumor proliferation in vitro or in vivo. Transforming growth factor β1 promoted mammary tumor local invasion. Furthermore, the CD44high/CD24- cancer stem cell population was also significantly increased by transforming growth factor β1 treatment. Besides, the gene expression of the stem cell self-renewal markers (nanog, pou5f1, and sox2) and another stem cell surface marker (EpCAM) was increased by transforming growth factor β1 treatment. Finally, clusters of CD44-positive breast cancer cells were observed in the livers of mice from the control and transforming growth factor β1 pretreatment groups.

CONCLUSION

Our results indicate that transforming growth factor β1 increases the local invasive capacity and liver metastasis of breast cancer cells by inducing the CD44high/CD24- cancer stem cell population.

TGF-β Family Signaling in Tumor Suppression and Cancer Progression

Transforming growth factor-β (TGF-β) induces a pleiotropic pathway that is modulated by the cellular context and its integration with other signaling pathways. In cancer, the pleiotropic reaction to TGF-β leads to a diverse and varied set of gene responses that range from cytostatic and apoptotic tumor-suppressive ones in early stage tumors, to proliferative, invasive, angiogenic, and oncogenic ones in advanced cancer. Here, we review the knowledge accumulated about the molecular mechanisms involved in the dual response to TGF-β in cancer, and how tumor cells evolve to evade the tumor-suppressive responses of this signaling pathway and then hijack the signal, converting it into an oncogenic factor. Only through the detailed study of this complexity can the suitability of the TGF-β pathway as a therapeutic target against cancer be evaluated.

Colorectal cancer susceptibility loci as predictive markers of rectal cancer prognosis after surgery

To understand the molecular mechanism of rectal cancer and develop markers for disease prognostication, we generated and explored a dataset from 243 rectal cancer patients by gene expression microarray analysis of cancer samples and matched controls, and SNP-arrays of germline DNA. We found that two of the loci most strongly linked with colorectal cancer (CRC) risk, 8q24 (upstream of MYC) and 18q21 (in the intron of SMAD7), as well as 20q13 (in the intron of LAMA5), are tightly associated with the prognosis of rectal cancer patients. For SNPs on 18q21 (rs12953717 and rs4464148) and 20q13 (rs4925386), alleles that correlate with higher risk for the development of CRC are associated with shorter disease free survival (DFS). However, for rs6983267 on 8q24, the low risk allele is associated with a higher risk for recurrence and metastasis after surgery, and importantly, is strongly correlated with the resistance of CRC cell lines to chemoradiotherapy (CRT). We also found that although MYC expression is dramatically increased in cancer, patients with higher levels of MYC have a better prognosis. The expression of SMAD7 is weakly correlated with DFS. Notably, the presence of the 8q24 and 18q21 SNP alleles is not correlated with expression levels of MYC and SMAD7. rs4464148, and probably rs6983267 and rs4925386, are linked with overall survival time of patients. In conclusion, we show that several CRC risk SNPs detect subpopulations of rectal cancer patients with poor prognosis, and that rs6983267 probably affects prognosis through interfering with the resistance of cancer cells to CRT.

A low-frequency variant in SMAD7 modulates TGF-β signaling and confers risk for colorectal cancer in Chinese population

The TGF-β pathway plays an essential role in regulating cell proliferation and differentiation. GWASs and candidate approaches have identified a battery of genetic variants in the TGF-β pathway contributing to colorectal cancer (CRC). However, most of the significant variants are common variants and their functions remain ambiguous. To identify causal variants with low-frequency in the TGF-β pathway contributing to CRC susceptibility in Chinese population, we performed targeted sequencing of 12 key genes in TGF-β signaling in CRC patients followed by a two-stage case-control study with a total of 5109 cases and 5169 controls. Bioinformatic annotations and biochemical experiments were applied to reveal the potential functions of significant variants. Seven low-frequency genetic variants were captured through targeted sequencing. The two stage association studies showed that missense variant rs3764482 (c. 83C>T; p. S28F) in the gene SMAD7 was consistently and significantly associated with CRC risk. Compared with the wild type, the ORs for variant allele were 1.37 (95%CI: 1.10-1.70, P = 0.005), 1.55 (95%CI: 1.30-1.86, P = 1.15 × 10⁶ ), and 1.48 (1.29-1.70, P = 2.44 × 10^;8 ) in stage 1, stage 2, and the combined analyses, respectively. Functional annotations revealed that the minor allele T of rs3764482 was more effective than the major allele C in blocking the TGF-β signaling and inhibiting the phosphorylation of receptor-regulated SMADs (R-SMADs). In conclusion, low-frequency coding variant rs3764482 in SMAD7 is associated with CRC risk in Chinese population. The rs3764482 variant may block the TGF-β signaling via impeding the activation of downstream genes, leading to cancer cell proliferation, thus contributing to CRC pathogenesis.

MicroRNA-182 targets SMAD7 to potentiate TGFβ-induced epithelial-mesenchymal transition and metastasis of cancer cells

The transforming growth factor β (TGFβ) pathway plays critical roles during cancer cell epithelial-mesenchymal transition (EMT) and metastasis. SMAD7 is both a transcriptional target and a negative regulator of TGFβ signalling, thus mediating a negative feedback loop that may potentially restrain TGFβ responses of cancer cells. Here, however, we show that TGFβ treatment induces SMAD7 transcription but not its protein level in a panel of cancer cells. Mechanistic studies reveal that TGFβ activates the expression of microRNA-182 (miR-182), which suppresses SMAD7 protein. miR-182 silencing leads to SMAD7 upregulation on TGFβ treatment and prevents TGFβ-induced EMT and invasion of cancer cells. Overexpression of miR-182 promotes breast tumour invasion and TGFβ-induced osteoclastogenesis for bone metastasis. Furthermore, miR-182 expression inversely correlates with SMAD7 protein in human tumour samples. Therefore, our data reveal the miR-182-mediated disruption of TGFβ self-restraint and provide a mechanism to explain the unleashed TGFβ responses in metastatic cancer cells.

SMAD7 is a transcriptional target and a negative regulator of TGFβ signalling forming a negative feedback loop. Here the authors show that in cancer cells TGFβ activates the expression of microRNA-182 that suppresses SMAD7 protein, promoting TGFβ-mediated breast tumour invasion and bone metastasis.

Expression of VEGF-D, SMAD4, and SMAD7 and Their Relationship with Lymphangiogenesis and Prognosis in Colon Cancer

AIM

The vascular endothelial growth factor (VEGF) and TGF-β1 pathways play important roles in cancer. However, few studies have evaluated the expression and roles of VEGF-D, SMAD4, and SMAD7 in colon cancer, and the conclusions remain controversial. To clarify the roles of VEGF-D, SMAD4, and SMAD7 in colon cancer, we examined their expression and evaluated correlations with lymphangiogenesis, prognosis, and chemotherapeutic outcome.

METHODS

The expression of VEGF-D, SMAD4, and SMAD7 was immunohistochemically examined in 251 primary colon cancer samples obtained from the Harbin Medical University.

RESULTS

The expression of VEGF-D, SMAD4, and SMAD7 was identified in 71.7, 41.0, and 69.7 % of samples, respectively. Positive expression of VEGF-D and SMAD7 and lost expression of SMAD4 were significantly correlated with lymph node metastasis and high lymphatic vessel density. VEGF-D and SMAD7 were found to be independent indicators of prognosis and chemotherapy outcome, and positive expression of either VEGF-D or SMAD7 was associated with significantly shorter overall survival and disease-free survival (OS and DFS) than negative expression in all 251 patients (P < 0.001 for OS and DFS) and patients following chemotherapy (P < 0.001 for OS and DFS).

CONCLUSION

VEGF-D, SMAD4, and SMAD7 were involved in lymphangiogenesis and lymph node metastasis. VEGF-D and SMAD7 can serve as predictors of prognosis and chemotherapeutic outcome in colon cancer.

Down-regualtion of miR-106b induces epithelial-mesenchymal transition but suppresses metastatic colonization by targeting Prrx1 in colorectal cancer

Accumulating evidence identified that epithelial-mesenchymal transition (EMT) is acquired during progression to metastatic, but whether it is an absolute requirement is still controversial. MiR-106b has been confirmed to promote cancer cell proliferation; however few studies are available on its functions in EMT and metastasis in colorectal cancer (CRC). In this study, we found that knocking down miR-106b induced EMT conferring migratory and invasive properties. MiR-106b knockdown induced cytoskeletal reorganization through staining intracellular F-actin. The expression of Rho GTPases (Rac1 and Cdc42) and Tiam1 was significantly enforced after miR-106b down-regulation. However, miR-106b knocking down could suppress metastatic colonization in vivo. Correspondingly, over expression of miR-106b obtained an opposite effect. We identified Prrx1 was a direct target of miR-106b through using target prediction algorithms and dual-Luciferase reporter assay. Moreover, Moreover, we also found TGF-β1 could down-regulate miR-106b, and simultaneously miR-106b also influences the expression of TGF-β1, establishing a negative feedback loop to regulate the expression of Prrx1 together. Taken together, these findings demonstrated that miR-106b knockdown could induce EMT which conferring cells migratory and invasive properties but could not accomplish distant metastatic colonization efficiently.

Lack of influence of the SMAD7 gene rs2337107 polymorphism on risk of colorectal cancer in an Iranian population

SMAD7 has been identified as a functional candidate gene for colorectal cancer (CRC). SMAD7 protein is a known antagonist of the transforming growth factor beta (TGF-β) signaling pathway which is involved in tumorigenesis. Polymorphisms in SMAD7 may thus alter cancer risk. The aim of this study was to investigate the influence of a SMAD7 gene polymorphism (rs2337107) on risk of CRC and clinicopathological features in an Iranian population. In total, 210 subjects including 105 patients with colorectal cancer and 105 healthy controls were recruited in our study. All samples were genotyped by TaqMan assay via an ABI 7500 Real Time PCR System (Applied Biosystems) with DNA from peripheral blood. The polymorphism was statistically analyzed to investigate the relationship with the risk of colorectal cancer and clinicopathological properties. Logistic regression analysis revealed that there was no significant association between rs2337107 and the risk of colorectal cancer. In addition, no significant association between genotypes and clinicopathological features was observed (p value>0.05). Although there was not any association between genotypes and disorder, CT was the most common genotype in this population. This genotype prevalence was also higher in the patients with well grade (54.9%) and colon (72.0%) tumors. Our results provide the first evidence that this polymorphism is not a potential contributor to the risk of colorectal cancer and clinicopathological features in an Iranian population, and suggests the need of a large-scale case-control study to validate our results.

MicroRNA-93 suppress colorectal cancer development via Wnt/β-catenin pathway downregulating

MicroRNA-93 (miR-93) is involved in several carcinoma progressions. It has been reported that miR-93 acts as a promoter or suppressor in different tumors. However, till now, the role of miR-93 in colon cancer is unclear. Herein, we have found that expression of miR-93 was lower in human colon cancer tissue and colorectal carcinoma cell lines compared with normal colon mucosa. Forced expression of miR-93 in colon cancer cells inhibits colon cancer invasion, migration, and proliferation. Furthermore, miR-93 may downregulate the Wnt/β-catenin pathway, which was confirmed by measuring the expression level of the β-catenin, axin, c-Myc, and cyclin-D1 in this pathway. Mothers against decapentaplegic homolog 7 (Smad7), as an essential molecular protein for nuclear accumulation of β-catenin in the canonical Wnt signaling pathway, is predicted as a putative target gene of miR-93 by the silico method and demonstrated that it may be suppressed by targeting its 3'UTR. These findings showed that miR-93 suppresses colorectal cancer development via downregulating Wnt/β-catenin, at least in part, by targeting Smad7. This study revealed that miR-93 is an important negative regulator in colon cancer and suggested that miR-93 may serve as a novel therapeutic agent that offers benefits for colon cancer treatment.

Partial loss of Smad7 function impairs bone remodeling, osteogenesis and enhances osteoclastogenesis in mice

Smad7 is well demonstrated as a negative regulator of TGF-β signaling. Its alteration in expression often results in diseases such as cancer and fibrosis. However, the exact role of Smad7 in regulating bone remodeling during mammalian development has not been properly delineated. In this study we performed experiments to clarify the involvement of Smad7 in regulating osteogenesis and osteoclastogenesis both invivo and invitro. Genetically engineered Smad7(ΔE1) (KO) mice were used, whereby partial functional of Smad7 is lost by deleting exon I of the Smad7 gene and the truncated proteins cause a hypomorphic allele. Analysis with μCT imagery and bone histomorphometry showed that the KO mice had lower TbN, TbTh, higher TbSp in the metaphysic region of the femurs at 6, 12, 24weeks from birth, as well as decreased MAR and increased osteoclast surface compared with the WT mice. In vitro BM-MSC multi-lineage differentiation evaluation showed that the KO group had reduced osteogenic potential, fewer mineralized nodules, lower ALP activity, and reduced gene expression of Col1A1, Runx2 and OCN. The adipogenic potential was elevated in the KO group with more formation of lipid droplets, and increased gene expression of Adipsin and C/EBPα. The osteoclastogenic potential of KO mice BMMs was elevate, with emergence of more osteoclasts, larger resorptive areas, and increased gene expression of TRAP and CTR. Our results indicate that partial loss of Smad7 function in mice leads to compromised bone formation and enhanced bone resorption. Thus, Smad7 is acknowledged as a novel key regulator between osteogenesis and osteoclastogenesis.

STAT1 drives tumor progression in serous papillary endometrial cancer

Recent studies of the interferon-induced transcription factor STAT1 have associated its dysregulation with poor prognosis in some cancers, but its mechanistic contributions are not well defined. In this study, we report that the STAT1 pathway is constitutively upregulated in type II endometrial cancers. STAT1 pathway alteration was especially prominent in serous papillary endometrial cancers (SPEC) that are refractive to therapy. Our results defined a "SPEC signature" as a molecular definition of its malignant features and poor prognosis. Specifically, we found that STAT1 regulated MYC as well as ICAM1, PD-L1, and SMAD7, as well as the capacity for proliferation, adhesion, migration, invasion, and in vivo tumorigenecity in cells with a high SPEC signature. Together, our results define STAT1 as a driver oncogene in SPEC that modulates disease progression. We propose that STAT1 functions as a prosurvival gene in SPEC, in a manner important to tumor progression, and that STAT1 may be a novel target for molecular therapy in this disease.

Identification of microRNA-214 as a negative regulator of colorectal cancer liver metastasis by way of regulation of fibroblast growth factor receptor 1 expression

The purpose of this study was to identify microRNAs (miRNAs) involved in the pathology of colorectal cancer (CRC) liver metastasis and investigate their underlying mechanisms. A total of 39 miRNAs were identified to be differentially expressed between 16 primary CRC tissues with liver metastases and 16 CRC tissues without liver metastases from 32 patients by Affymetric miRNA microarrays. A panel of eight miRNAs were confirmed to be significantly and differentially expressed between CRC tissues with and without liver metastases through quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis in the 32 patients. In a validated cohort of 99 CRC patients (44 with and 55 without liver metastases), only miR-214 was validated to be significantly down-regulated in CRC with liver metastases, which was associated with an unfavorable prognosis. Ectopic expression of miR-214 suppressed proliferation, migration, and invasion in vitro, tumor growth and liver metastasis in an in vivo xenograft mouse model, whereas miR-214 knockdown promoted proliferation, migration, and invasion in CRC cell lines. Further studies indicated that fibroblast growth factor receptor 1 (FGFR1) was a potential target of miR-214. Restoring miR-214 expression in CRC cells decreased endogenous FGFR1 messenger RNA (mRNA) and protein levels. FGFR1 knockdown mimicked the tumor suppressive effect of miR-214 on CRC cells, while reintroduction of FGFR1 abolished the tumor suppressive effect of miR-214 on CRC cells. Moreover, miR-214 expression levels were inversely correlated with FGFR1 in CRC patients.

CONCLUSION

Down-regulation of miR-214 expression was correlated with increased FGFR1 expression levels, which may contribute to increased CRC liver metastasis. miR-214 may serve as a potential marker to predict survival, and the miR-214-FGFR1 axis may be a therapeutic target in CRC patients.

SMAD7: a timer of tumor progression targeting TGF-β signaling

In the context of cancer, transforming growth factor β (TGF-β) is a cell growth suppressor; however, it is also a critical inducer of invasion and metastasis. SMAD is the important mediator of TGF-β signaling pathway, which includes receptor-regulated SMADs (R-SMADs), common-mediator SMADs (co-SMADs), and inhibitory SMADs (I-SMADs). I-SMADs block the activation of R-SMADs and co-SMADs and thus play important roles especially in the SMAD-dependent signaling. SMAD7 belongs to the I-SMADs. As an inhibitor of TGF-β signaling, SMAD7 is overexpressed in numerous cancer types and its abundance is positively correlated to the malignancy. Emerging evidence has revealed the switch-in-role of SMAD7 in cancer, from a TGF-β inhibiting protein at the early stages that facilitates proliferation to an enhancer of invasion at the late stages. This role change may be accompanied or elicited by the tumor microenvironment and/or somatic mutation. Hence, current knowledge suggests a tumor-favorable timer nature of SMAD7 in cancer progression. In this review, we summarized the advances and recent findings of SMAD7 and TGF-β signaling in cancer, followed by specific discussion on the possible factors that account for the functional changes of SMAD7.

The expression of TGF-β1, Smad3, phospho-Smad3 and Smad7 is correlated with the development and invasion of nonfunctioning pituitary adenomas

Background

Transforming growth factor β (TGF-β) signaling functions as a suppressor or a promoter in tumor development, depending on the tumor stage and type. However, the role of TGF-β signaling in nonfunctioning pituitary adenomas (NFPAs) has not been explored.

Methods

TGF-β1, Smad2, phospho-Smad2 (p-Smad2), Smad3, phospho-Smad3 (p-Smad3), Smad4, and Smad7 were detected in 5 cases of normal anterior pituitaries, 29 cases of invasive NFPAs, and 21 cases of noninvasive NFPAs by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blot, and immunohistochemical analysis.

Results

The Smad3 and p-Smad3 protein levels gradually decreased from normal anterior pituitaries, noninvasive NFPAs, to invasive NFPAs. However, there were no significant differences in Smad2 (P = 0.122) and p-Smad2 protein levels (P = 0.101) or Smad2 mRNA level (P = 0.409). In addition, the TGF-β1 mRNA level gradually decreased while the Smad7 mRNA level gradually increased from normal anterior pituitaries, noninvasive NFPAs, to invasive NFPAs. Furthermore, proliferating cell nuclear antigen (PCNA) mRNA level was markedly increased in invasive NFPAs compared to noninvasive ones (P < 0.01), and its level was negatively correlated with Smad3 mRNA level (P < 0.01).

Conclusion

The activity of TGF-β signaling may be restrained in NFPAs and is correlated with the development and invasion of NFPAs.

MiR-181c modulates the proliferation, migration, and invasion of neuroblastoma cells by targeting Smad7

MicroRNAs (miRNAs) function as key regulators of gene expression in various cancers. In this study, the aim is to explore the roles and regulation mechanism of miR-181c in neuroblastoma (NB) cells. We found that miR-181c was downregulated in metastatic NB tissues, compared with primary NB tissues. Then functional studies indicated that miR-181c overexpression inhibited NB cell proliferation, migration, and invasion, while miR-181c inhibition increased cell proliferation, migration, and invasion. EGFP reporter assay, real-time polymerase chain reaction and western blot analysis validated that Smad7 was a direct target of miR-181c. MiR-181c reduced Smad7 expression at both mRNA and protein levels. Finally, functional assays showed that the effect of Smad7 knockdown on cells was similar to that of miR-181c overexpression. Importantly, Smad7 overexpression could restore the antitumor effects that were induced by miR-181c. In conclusion, our results demonstrated that miR-181c inhibits NB cell growth and metastasis-related traits through the suppression of Smad7, functioning as a tumor suppressor. Moreover, our results suggested that miR-181c may serve as an important therapeutic target for NB patients.

The dual role of Smad7 in the control of cancer growth and metastasis

Smad7 was initially identified as an inhibitor of Transforming growth factor (TGF)-β due mainly to its ability to bind TGF-β receptor type I and prevent TGF-β-associated Smad signaling. More recently, it has been demonstrated that Smad7 can interact with other intracellular proteins and regulate also TGF-β-independent signaling pathways thus making a valid contribution to the neoplastic processes in various organs. In particular, data emerging from experimental studies indicate that Smad7 may differently modulate the course of various tumors depending on the context analyzed. These observations, together with the demonstration that Smad7 expression is deregulated in many cancers, suggest that therapeutic interventions around Smad7 can help interfere with the development/progression of human cancers. In this article we review and discuss the available data supporting the role of Smad7 in the modulation of cancer growth and progression.

Relationship of TGF-β1 and Smad7 expression with decreased dendritic cell infiltration in liver gastrointestinal cancer metastasis

Immune responses and their modulation within the liver are critical to the outcome of liver malignancies. In late-stage tumors, secreted TGF-β promotes oncogenic functions and can confer tolerogenicity to some immune cells like DCs. The TGF-β signaling pathway is involved in the control of several biological processes, including immunosurveillance. The aim of the present study was to assess CD1a(+) and CD83(+) DCs and to evaluate the impact of TGF-β pathway on DCs maturation and distribution in the liver metastases from gastric and colorectal tumors. The percentage of CD83(+) DCs in the liver tissue, surrounding metastasis and in the metastasis-free liver was measured by flow cytometry, and TGF-β levels were assessed in the tissue supernatant from the peritumoral liver after mononuclear cell isolation and in the sera of the same patients. CD1a(+) and CD83(+) DCs were observed in the tumor stroma and border. Out of 73 patients, there was cytoplasmic reactivity: of TGF-β1 in 37 (50.7%); of Smad4 in 62 (84.9%); of Smad7 in 46 (63%), and of TGFβRII in 39 (53.4%) of the metastases. The TGF-β1 expression in tumor cell cytoplasm correlated with low CD1a(+) and low CD83(+) DCs infiltration. The tissue levels of TGF-β1, measured by ELISA in the supernatant were significantly increased in metastases than in normal liver. Using a two-color FACS analysis, we found that the percentage of HLA-DR(+) CD83(+) DCs in metastases was significantly decreased as compared with metastasis-free liver tissue. In conclusion, the positive and negative correlations between the mediators from the TGF-β pathway implied the existence of imbalance and suppression of this cytokine activity. The presence of increased TGF-β expression by immunohistochemistry in tumor cells was confirmed by detection of increased TGF-β tissue level in the supernatant from the tissue homogenate. The observation of low numbers of CD1a(+) and CD83(+) DCs in tumor stroma correlated with TGF-β overexpression in tumor cells, a fact that well documents the immunosuppressive role of TGF-β in metastasis development. The increased percentage of CD83(+) DCs in the peritumoral tissue supposes that there could be active recruitment or local differentiation of DCs in the metastasis border, but inside the tumor the immune cells recruitment and activity are suppressed by TGF-β and by other cytokines.

MiR-20a triggers metastasis of gallbladder carcinoma

BACKGROUND & AIMS

The dysfunction of miRNAs has been demonstrated to participate in the development of various tumors. However, whether miRNAs are involved in metastasis and progression of gallbladder carcinoma (GBC) remains unknown.

METHODS

A new designed gain-of-function miRNA screening technology was applied to filter out pro-metastatic miRNAs in GBC. Their expression in GBC tissues was validated by real-time PCR. The biological functions of miRNAs were intensively studied by transwell, immunoblot, immunohistochemical, and in situ hybridization assays. Tumorigenicity and liver metastasis were further examined in nude mice.

RESULTS

Of 880 miRNAs, 17 were filtered out as the prominent metastatic inducers of GBCs. Among them, the upregulation of pro-metastatic miR-20a was closely associated with local invasion, distant metastasis, and poor prognosis of 67 followed-up GBC patients, clinically. Patients with higher miR-20a expression exhibited worse overall survival (OS and median OS time was 5 and 20 months, respectively) than the lower expression group. A dramatically increased TGF-β1 level was found in GBC patients, which was responsible for the elevation of miR-20a. The ectopic expression of miR-20a could induce epithelial-mesenchymal transition and enhance metastasis of GBC cells in vitro and in vivo, by directly targeting the 3' UTR of Smad7, and subsequently promoting nuclear translocation of β-catenin. Conversely, the blockage of miR-20a by specific antagomir effectively restored the expression of Smad7 and attenuated TGF-β-induced cell metastasis.

CONCLUSIONS

TGF-β1-mediated activation of the miR-20a/Smad7/β-catenin axis plays a pivotal role in the pathogenesis and worse prognosis of GBCs and may serve as a potential therapeutic target in the future.

Claudins and the modulation of tight junction permeability

Claudins are tight junction membrane proteins that are expressed in epithelia and endothelia and form paracellular barriers and pores that determine tight junction permeability. This review summarizes our current knowledge of this large protein family and discusses recent advances in our understanding of their structure and physiological functions.

MicroRNA-25 functions as a potential tumor suppressor in colon cancer by targeting Smad7

Because it is a member of the miR-106b~25 cluster, microRNA-25 (miR-25) is known to be dysregulated in human cancers. However, the expression and role of miR-25 in colon cancer remain unclear. In this study, miR-25 was found to be down-regulated in human colon cancer tissues when compared to those in matched, non-neoplastic mucosa tissues. Functional studies revealed that restoration of miR-25 expression inhibited cell proliferation and migration. In contrast, miR-25 inhibition could promote the proliferation and migratory ability of cells. Stable over-expression of miR-25 also suppressed the growth of colon cancer-cell xenografts in vivo. Furthermore, bioinformatic predictions and experimental validation were used to identify Smad7 as a direct target of miR-25. Functional reverse experiments indicated that the antitumor effects of miR-25 were probably mediated by its repression of Smad7. These results suggest that miR-25 may function as a tumor suppressor by targeting Smad7 in colon cancer. Thus, miR-25 may serve as a potential therapeutic agent or target for cancer therapy.

A novel method to analyze nucleocytoplasmic transport in vivo by using short peptide tags

Regulated nucleocytoplasmic transport is of vital importance for maintaining the physiology of the cell, and disturbed nucleocytoplasmic shuttling of certain proteins has been found in a variety of diseases including cancer. The most frequently used procedure to analyze those processes is to fuse the protein of interest to a fluorescent protein such as GFP (green fluorescent protein)--a technique that is prone to impair normal protein function and subcellular localization. We report a novel approach to monitor nucleocytoplasmic transport processes in vivo by combining short TetR inducing peptide tags (TIP) with a TetR-controlled reporter gene in a human cell line. The technology is exemplified by demonstrating nucleocytoplasmic shuttling of the glucocorticoid receptor and activity of two further TIP fusions to cancer-related proteins. The technology presented provides the basis for efficient screening systems to isolate compounds altering the nucleocytoplasmic distribution of a protein of interest.

Claudins and alveolar epithelial barrier function in the lung

The alveolar epithelium of the lung constitutes a unique interface with the outside environment. This thin barrier must maintain a surface for gas transfer while being continuously exposed to potentially hazardous environmental stimuli. Small differences in alveolar epithelial barrier properties could therefore have a large impact on disease susceptibility or outcome. Moreover, recent work has focused attention on the alveolar epithelium as central to several lung diseases, including acute lung injury and idiopathic pulmonary fibrosis. Although relatively little is known about the function and regulation of claudin tight junction proteins in the lung, new evidence suggests that environmental stimuli can influence claudin expression and alveolar barrier function in human disease. This review considers recent advances in the understanding of the role of claudins in the breakdown of the alveolar epithelial barrier in disease and in epithelial repair.

TGF-β1, Smad-2/-3, Smad-1/-5/-8, and Smad-4 signaling factors are expressed in ameloblastomas, adenomatoid odontogenic tumors, and calcifying cystic odontogenic tumors: an immunohistochemical study

OBJECTIVES

The TGF-β/Smad signaling pathway regulates diverse cellular functions, including tooth development, and is involved in numerous pathological processes such as tumorigenesis. The aim of this study was to investigate the immunoexpression of the TGF-β/Smad signaling pathway members in ameloblastoma (AM), calcifying cystic odontogenic tumor (CCOT), and adenomatoid odontogenic tumor (AOT).

MATERIALS AND METHODS

This retrospective cross-sectional study included 65 tissue specimens: 34 AMs, 13 CCOTs, and 18 AOTs. Serial sections were immunohistochemically stained with TGF-β1, Smad-4, Smad-1/-5/-8, and Smad-2/-3 antibodies, and a semiquantitative measurement of the positive cells was carried out by two oral pathologists using a 0-3 scale (0: no immunoreactivity, 1: <20% positive cells, 2: 20-50% positive cells, 3: >50% positive cells).

RESULTS

All biomarkers studied were found significantly decreased in AM compared to CCOT and AOT. AOT and CCOT expressed Smad-1/-5/-8 more strongly compared to AM (OR = 11.66, P < 0.001 and OR = 5.34, P = 0.013, respectively), and Smad-2/-3 immunostaining was found significantly increased in CCOT (OR = 10.42, P = 0.001) and AOT (OR = 5.16, P < 0.004) compared to AM. Similarly, Smad-4 was expressed more strongly in AOT and CCOT compared to AM (P = 0.001), while AOT demonstrated a fivefold higher chance to express TGF-β1 compared to AM (P = 0.011).

CONCLUSION

TGF-β/Smad signaling pathway is activated in AM, AOT, and CCOT. The statistically significant reduced TGF-β1/Smad immunoexpression in AM compared to AOT/CCOT could be associated with the more aggressive biological behavior of AM including increased cell proliferation and reduced apoptosis and differentiation. Thus, the biomarkers TGF-β, Smad-4, Smad-1/-5/-8, and Smad-2/-3 could serve as supplementary diagnostic indices between odontogenic tumors of high and low neoplastic dynamics.

Role of Smad7 in inflammatory bowel diseases

Crohn's disease and ulcerative colitis, the major forms of inflammatory bowel diseases (IBD) in man, are complex diseases in which genetic and environmental factors interact to promote an excessive mucosal immune response directed against normal components of the bacterial microflora. There is also evidence that the pathologic process is due to defects in counter-regulatory mechanisms, such as those involving the immunosuppressive cytokine transforming growth factor (TGF)-β1. Indeed, studies in human IBD tissues and murine models of colitis have documented a disruption of TGF-β1 signalling marked by a block in the phosphorylation of Smad3, a signalling molecule associated with the activated TGF-β receptor, due to up-regulation of Smad7, an intracellular inhibitor of Smad3 phosphorylation. Knock-down of Smad7 with a specific antisense oligonucleotide restores TGF-β1/Smad3 signalling, thus resulting in a marked suppression of inflammatory cytokine production and attenuation of murine colitis. These findings together with the demonstration that Smad7 antisense oligonucleotide is not toxic when administered in mice have paved the way for the development of a Smad7 antisense oligonucleotide-based pharmaceutical compound that is now ready to enter the clinics. In this article we review the available data supporting the pathogenic role of Smad7 in IBD and discuss whether and how Smad7 antisense therapy could help dampen the ongoing inflammation in IBD.