Role Of Smad3 Research Articles

SMAD3 mediates the specification of human induced pluripotent stem cell-derived epicardium into progenitors for the cardiac pericyte lineage

Understanding the molecular mechanisms of epicardial epithelial-to-mesenchymal transition (EMT), particularly in directing cell fate toward epicardial derivatives, is crucial for regenerative medicine using human induced pluripotent stem cell (iPSC)-derived epicardium. Although transforming growth factor β (TGF-β) plays a pivotal role in epicardial biology, orchestrating EMT during embryonic development via downstream signaling through SMAD proteins, the function of SMAD proteins in the epicardium in maintaining vascular homeostasis or mediating the differentiation of various epicardial-derived cells (EPDCs) is not yet well understood. Our study reveals that TGF-β-independent SMAD3 expression autonomously predicts epicardial cell specification and lineage maintenance, acting as a key mediator in promoting the angiogenic-oriented specification of the epicardium into cardiac pericyte progenitors. This finding uncovers a novel role for SMAD3 in the human epicardium, particularly in generating cardiac pericyte progenitors that enhance cardiac microvasculature angiogenesis. This insight opens new avenues for leveraging epicardial biology in developing more effective cardiac regeneration strategies.

The Role of Smad3 in the Realization of the Growth Potential of Different Types of Neural Progenitor Cells and the Secretory Function of Neuroglia.

The features of the participation of Smad3 in the functioning of neural stem cells (NSC), neuronal committed precursors (NCP), and neuroglial elements were studied in vitro. It was found that this intracellular signaling molecule enhances the clonogenic and proliferative activities of NCP and inhibits specialization of neuronal precursors. At the same time, Smad3 does not participate in the realization of the growth potential of NSC. With regard to the secretory function (production of neurotrophic growth factors) of neuroglial cells, the stimulating role of Smad3-mediated signaling was shown. These results indicate the promise of studying the possibility of using Smad3 as a fundamentally new target for neuroregenerative agents.

The Snail signaling branch downstream of the TGF-β/Smad3 pathway mediates Rho activation and subsequent stress fiber formation

Cancer cells acquire malignant phenotypes through an epithelial-mesenchymal transition, which is induced by environmental factors or extracellular signaling molecules, including transforming growth factor-β (TGF-β). Among epithelial-mesenchymal transition-associated cell responses, cell morphological changes and cell motility are closely associated with remodeling of the actin stress fibers. Here, we examined the TGF-β signaling pathways leading to these cell responses. Through knockdown experiments in A549 lung adenocarcinoma cells, we found that Smad3-mediated induction of Snail, but not that of Slug, is indispensable for morphological changes, stress fiber formation, and enhanced motility in cells stimulated with TGF-β. Ectopic expression of Snail in SMAD3-knockout cells rescued the defect in morphological changes and stress fiber formation by TGF-β, indicating that the role of Smad3 in these responses is to upregulate Snail expression. Mechanistically, Snail is required for TGF-β-induced upregulation of Wnt5b, which in turn activates RhoA and subsequent stress fiber formation in cooperation with phosphoinositide 3-kinase. However, ectopic expression of Snail in SMAD3-knockout cells failed to rescue the defect in cell motility enhancement by TGF-β, indicating that activation of the Smad3/Snail/Wnt5b axis is indispensable but not sufficient for enhancing cell motility; a Smad3-dependent but Snail-independent pathway to activate Rac1 is additionally required. Therefore, the Smad3-dependent pathway leading to enhanced cell motility has two branches: a Snail-dependent branch to activate RhoA and a Snail-independent branch to activate Rac1. Coordinated activation of these branches, together with activation of non-Smad signaling pathways, mediates enhanced cell motility induced by TGF-β.

Smad3 Mediates Diabetic Dyslipidemia and Fatty Liver in db/db Mice by Targeting PPARδ

Transforming growth factor-β (TGF-β)/Smad3 signaling has been shown to play important roles in fibrotic and inflammatory diseases. However, the role of Smad3 in dyslipidemia and non-alcoholic fatty liver disease (NAFLD) in type 2 diabetes remains unclear, and whether targeting Smad3 has a therapeutic effect on these metabolic abnormalities remains unexplored. These topics were investigated in this study in Smad3 knockout (KO)-db/db mice and by treating db/db mice with a Smad3-specific inhibitor SIS3. Compared to Smad3 wild-type (WT)-db/db mice, Smad3 KO-db/db mice were protected against dyslipidemia and NAFLD. Similarly, treatment of db/db mice with SIS3 at week 4 before the onset of type 2 diabetes until week 12 was capable of lowering blood glucose levels and improving diabetic dyslipidemia and NAFLD. In addition, using RNA-sequencing, the potential Smad3-target genes related to lipid metabolism was identified in the liver tissues of Smad3 KO/WT mice, and the regulatory mechanisms were investigated. Mechanistically, we uncovered that Smad3 targeted peroxisome proliferator-activated receptor delta (PPARδ) to induce dyslipidemia and NAFLD in db/db mice, which was improved by genetically deleting and pharmacologically inhibiting Smad3.

Large-Scale Proteomics Data Reveal Integrated Prognosis-Related Protein Signatures and Role of SMAD4 and RAD50 in Prognosis and Immune Infiltrations of Prostate Cancer Microenvironment.

The online version contains supplementary material available at 10.1007/s43657-022-00070-1.

Smad7 Is Highly Expressed in Human Degenerative Discs and Participates in IL-1β-Induced Apoptosis of Rat AF Cells via the Mitochondria Pathway.

Background Abnormal Smad7 expression can lead to apoptosis in different cell types. Previously, we found high expression of Smad7 in rat degenerative discs. However, the exact role of Smad7 in the apoptosis of disc cells and the possible underlying mechanism remain unclear. Methods Degenerative and nondegenerative human lumbar intervertebral discs were collected from patients during operation. The expressions of SMAD7 mRNA and protein in the different components of these discs were measured with real-time PCR and Western blotting, respectively. Annulus fibrosus (AF) cells were isolated and cultivated from the discs of young healthy rats. Smad7 in the AF cells was overexpressed with adenovirus and knocked down with siRNA. IL-1β was used to induce apoptosis in the AF cells. Loss-and-gain cell function experiments were performed to show the effect of Smad7 on the apoptosis of AF cells. The function recovery experiments were performed to verify whether Smad7 regulates the apoptosis of AF cells through the mitochondria-mediated pathway. Results Both the mRNA and protein expressions of Smad7 were significantly higher in the different components of human degenerative discs than in those of the nondegenerative discs. IL-1β stimulated apoptosis while upregulating the Smad7 expression in the AF cells in vitro. Overexpression of Smad7 in AF cells exaggerated the IL-1β-induced apoptosis in the cells while knockdown of Smad7 expression suppressed this apoptosis. With the exaggerated apoptosis in the AF cells with Smad7 overexpression, both active cleaved caspase-3 and cleaved caspase-9, the ratio of Bax/Bcl-2, and Cyt-c increased significantly. However, the inhibitor of caspase-9, Z-LEHD-FMK, significantly diminished the apoptosis in these cells. Conclusion Smad7 is highly expressed in human degenerative discs and participates in IL-1β-induced apoptosis of rat AF cells via the mitochondria pathway. Smad7 may be a potential target for the prevention and treatment of degenerative disc disease.

Abstract 2402: SMAD4 represses PDAC metastatic colonization through binding FOSL1 enhancer regions

Abstract Less than 5% of patients diagnosed with pancreatic ductal adenocarcinomas (PDAC) survive more than 5 years, largely due to therapeutic resistance and metastatic disease. Half of all PDAC patients have been shown to have loss of SMAD4, which has been shown to correlate with metastasis. Here we functionally demonstrate that SMAD4 is a key suppressor of metastatic colonization of PDAC. Using an in vitro and in vivo multi-component RNA-seq analysis on isogenic human PDAC cell lines, we defined SMAD4-dependent gene expression changes. Specifically, we identified genes that were suppressed in the presence of SMAD4. These genes could contribute to tumor metastasis. To test this, we performed a pooled open reading frame (ORF) overexpression lung colonization assay with the identified genes. We found that expression of the transcription factor FOSL1 is sufficient for metastatic colonization. Mechanistically, SMAD4 directly binds and modulates the activity of the FOSL1 enhancer. Taken together, these studies demonstrate a direct role for SMAD4 in regulating metastatic colonization and identify FOSL1 as a direct SMAD4-regulated gene involved in distant site colonization. Citation Format: Jonathan P. Rennhack, Chao Dai, Andrew Aguirre, John Doench, David Root, William C. Hahn. SMAD4 represses PDAC metastatic colonization through binding FOSL1 enhancer regions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2402.

Smurf2-induced degradation of SMAD2 causes inhibition of hair follicle stem cell differentiation

Hair follicle stem cells (HFSCs) are implicated in the formation of hair follicles and epidermis. This study aims to clarify the role of SMAD2 in regulating the differentiation of HFSCs, which is involved with Smurf2. Functional assays were carried out in human HFSCs to assess the effect of SMAD2 and Smurf2 with altered expression on growth dynamics of HFSCs. Ubiquitination of SMAD2 and its protein stability were assessed. The binding relationship between NANOG and DNMT1 was assessed. A mouse skin wound model was induced to verify the effects of Smurf2/SMAD2/NANOG/DNMT1 on wound healing. SMAD2 overexpression was observed in HFSCs during differentiation and its ectopic expression contributed to promotion of differentiation and apoptosis of HFSCs while arresting cell proliferation. Mechanistic investigations indicated that Smurf2 promoted the ubiquitination and degradation of SMAD2, thus causing downregulation of SMAD2 expression. By this mechanism, NANOG expression was reduced and the subsequent DNMT1 transcriptional expression was also diminished, leading to suppression of differentiation and apoptosis of HFSCs while stimulating cell proliferation. Moreover, in vivo data showed that Smurf2 upregulation limited epidermal wound healing in mice by inhibiting the SMAD2/NANOG/DNMT1 axis. Our work proposed a potential target regarding SMAD2 restoration in promoting HFSC differentiation and skin wound healing.

814 SMAD4 AS A POTENTIAL GATEKEEPER FOR GENOMIC INSTABILITY AND MTOR-MEDIATED TUMORIGENESIS IN ESOPHAGEAL ADENOCARCINOMA

Abstract Extensive genomic analysis of patient samples has identified genes whose mutation or loss map malignant progression from Barrett’s metaplasia, through low- (CDKN2A) and high-grade dysplasia (TP53), to invasive adenocarcinoma (SMAD4). Interestingly, loss of SMAD4 has been found to occur exclusively in the invasive disease stage, but the reason for this is unknown. This work aimed to characterise the role of SMAD4 in esophageal adenocarcinoma (EAC) tumorigenesis and identify novel therapeutic targets for SMAD4-deficient EAC. Methods We developed a novel in vivo tumorigenesis model that demonstrates progression of dysplastic Barrett’s esophagus (BE) to invasive EAC upon knockout of SMAD4. We conducted parallel genome-wide CRISPR-Cas9 knockout screens, both in vitro and in vivo, on a background of either wildtype-SMAD4 or SMAD4-knockout dysplastic BE cells to identify co-operative drivers of tumorigenesis in vivo, as well as synthetic lethal interactions to identify potential therapeutic targets in SMAD4-deficient EAC. Functional validation of hits was performed using cell-based assays and drugs targeting candidate molecular targets. Results We identified a synthetic lethal relationship between SMAD4-deficiency and cell cycle checkpoint inhibition, suggesting a role for SMAD4 in maintaining genomic stability and a potential novel therapeutic avenue for SMAD4-deficient EAC. A concurrent in vivo CRISPR-Cas9 tumorigenesis screen produced tumors 4-fold faster than loss of SMAD4 alone and identified regulators of mTOR signalling and SMAD4 as co-operative drivers of tumorigenesis in EAC. Interestingly, these tumorigenic cells exhibited an inherent dependency on specific translation mechanisms downstream of mTOR. Meanwhile, wildtype-SMAD4 BE cells failed to thrive in vivo with mTOR modifications alone, indicating a true co-operative effect at play with SMAD4 loss. Conclusion This study uncovered a potential gatekeeping role of SMAD4 in maintaining genomic stability and inhibiting mTOR-mediated EAC tumorigenesis. In sum, loss of SMAD4 was found to increase genomic instability, thereby rendering EAC cells sensitive to cell cycle checkpoint impediment, whilst simultaneously co-operating with modulated mTOR signalling to promote tumorigenesis in EAC xenograft models.

Involvement of Smad7 in Inflammatory Diseases of the Gut and Colon Cancer.

In physiological conditions, the human intestinal mucosa is massively infiltrated with various subsets of immune cells, the activity of which is tightly regulated by several counter-regulatory factors. One of these factors is transforming growth factor-β1 (TGF-β1), a cytokine produced by multiple cell types and targeting virtually all the intestinal mucosal cells. Binding of TGF-β1 to its receptors triggers Smad2/3 signaling, thus culminating in the attenuation/suppression of immune–inflammatory responses. In patients with Crohn’s disease and patients with ulcerative colitis, the major human inflammatory bowel diseases (IBD), and in mice with IBD-like colitis, there is defective TGF-β1/Smad signaling due to high levels of the intracellular inhibitor Smad7. Pharmacological inhibition of Smad7 restores TGF-β1 function, thereby reducing inflammatory pathways in patients with IBD and colitic mice. On the other hand, transgenic over-expression of Smad7 in T cells exacerbates colitis in various mouse models of IBD. Smad7 is also over-expressed in other inflammatory disorders of the gut, such as refractory celiac disease, necrotizing enterocolitis and cytomegalovirus-induced colitis, even though evidence is still scarce and mainly descriptive. Furthermore, Smad7 has been involved in colon carcinogenesis through complex and heterogeneous mechanisms, and Smad7 polymorphisms could influence cancer prognosis. In this article, we review the data about the expression and role of Smad7 in intestinal inflammation and cancer.

The Role of Smad2 in Transforming Growth Factor β1–Induced Hypertrophy of Ligamentum Flavum

Hypertrophy of the ligamentum flavum (LF) contributes to the development of spinal stenosis. Smad proteins can mediate the fibrogenesis activity through the transforming growth factor β1 (TGF-β1) pathway, but which Smad protein plays a more important role in the hypertrophy process of LF is unclear. The LF samples were obtained from 50 patients. After the LF cells (LFCs) were cultured, small interfering ribonucleic acid (siRNA) that target human phosphorylated-Smad2, 3, or 4 (p-Smad2,3,4) genes was transfected into LFCs. Next, proteins from cells were extracted and the protein levels of Smad2, Smad3, and Smad4 were detected by Western blot. The messenger ribonucleic acid level of TGF-β1 was measured by real-time polymerase chain reaction (PCR). Furthermore, an enzyme-linked immunosorbent assay was performed to test the impact of Smad2 downstream of the TGF-β1 signaling pathway. Degeneration of the LF was characterized by an increase in disorganized elastic fibers and fibrotic transformation by extracellular collagen deposition. The gene expression analysis of fibrotic genes in LFCs showed that knockdown of phosphorylated-Smad2 by siRNA significantly reduced the protein expression level of TGF-β1 compared with other groups. The enzyme-linked immunosorbent assay suggested that the protein expression level of Smad2 can influence the downstream events of TGF-β1 signaling pathway in the LFCs. Our findings suggest that Smad2 plays a potential role in the pathologic development of hypertrophy of LF. We also found that Smad2 knockdown by Smad-siRNA can influence the TGF-β1 signaling pathway through decreasing expression of TGF-β1, tumor necrosis factor α, and nuclear factor κb.

LncRNA MCTP1-AS1 Regulates EMT Process in Endometrial Cancer by Targeting the miR-650/SMAD7 Axis.

BackgroundLong noncoding RNAs (lncRNAs) play critical roles in the pathogenesis of several diseases, especially some kinds of cancer. This study aimed to investigate the expression of MTCP1-AS1 and its effects on endometrial cancer (EC).MethodsMTCP1-AS1 expression level was determined in human EC tissues and cell lines by qRT-PCR. The role of MTCP1-AS1 on EC cell proliferation, migration, invasion and epithelial to mesenchymal transition (EMT) was detected by CCK8, wound-healing assay, transwell assay and Western blot, respectively. Moreover, luciferase reporter assay and RNA-binding protein immunoprecipitation (RIP) assay were performed to verify the targeting relationship between miR-650, MCTP1-AS1 and SMAD7 in EC cells.ResultsOur data showed that MCTP1-AS1 expression was downregulated in EC tissues and cell lines. Overexpression of MCTP1-AS1 inhibited cell proliferation, migration, invasion and EMT process of EC cells. Moreover, MCTP1-AS1 was proved to be the target of miR-650 and reversely correlated with its expression. In addition, MCTP1-AS1 reversed the effect of miR-650 on the EC cells, which might be associated with the role of SMAD7. Moreover, Western blot showed siRNA-SMAD7 transfection could rescue the repressed TGF-β/SMAD pathway induced by MCTP1-AS1 in EC cells.ConclusionTaken together, these data suggested that lncRNA MCTP1-AS1 inhibited cell proliferation, migration, invasion and EMT process of EC cells via targeting the miR-650/SMAD7 axis and it has the potential to be explored as a therapeutic target for the treatment of EC in the future.

Smad4 deficiency substitutes Cdkn2b but not Cdkn2a downregulation in pancreatic cancer following induction of genetic events in adult mice

BackgroundMinor progress in pancreatic cancer treatment and prognosis implies that more reliable animal models are urgently needed to decipher its molecular mechanisms and preclinical research. We recently reported a genetically engineered adult mouse model where Cdkn2b downregulation was required together with Cdkn2a downregulation to inactivate the Rb pathway. Besides, the role of Smad4, which is mutated more frequently than Cdkn2b in human pancreatic cancer, was determined critical on the development of the pancreas tumor by some reports. However, the impact of Smad4 deficiency in combination with PDAC-relevant mutations, such as Cdkn2a when induced in adult pancreas has not been completely elucidated in mice. MethodsLentiviral delivered oncogene/tumor suppressors in adult pancreas. The development of pancreatic cancer was monitored. Hematoxylin and eosin staining and immunofluorescence were performed for pathological identification of the pancreatic cancer. Real-time polymerase chain reaction, immunofluorescence and western blot were used to test gene expression. ResultsLoss of Smad4 could cooperate with alterations of KRAS, Trp53, and Cdkn2a to induce pancreatic cancer in adult mice. The role of Smad4 was mainly in downregulating the expression of Cdkn2b and further inducing phosphorylation of the Rb1 protein. ConclusionsThese findings show an essential role of Smad4 deficiency in pancreatic ductal adenocarcinoma (PDAC) formation. This model better recapitulates the adult onset, clonal origin, and genetic alterations in human PDAC and can be simply generated on a large-scale.

The role of Smad4 in the regulation of insulin resistance, inflammation and cell proliferation in HTR8-Svneo cells.

Gestational diabetes mellitus (GDM) is a metabolic disorder whose major pathophysiological basis is demonstrated as placental insulin resistance (IR), while Smad4 always functions in the signal transduction of transforming growth factor beta (TGF-β) pathway. Our study aims to figure out the role of Smad4 in an insulin resistance (IR) cellular model using placental trophoblast cell line. Importantly, HTR8-Svneo cells, in the status of IR, indicated a significant increase in the expression of Smad4. Subsequently, the HTR8-Svneo cell line with up-regulated or depleted Smad4 was respectively achieved by the effective over-expressed plasmid or siRNA of Smad4. We found out that the deficiency of Smad4 could promote the insulin sensitivity and restrict the inflammatory response in IR group of cells with significant augment in glucose uptake, up-regulation of insulin signalling-related molecules and attenuation in inflammatory biomarker expressions. On the contrary, the over-expression of Smad4 showed a reversal effect on these alterations in IR group of cells. Besides, the positive effect of Smad4 on cell viability was also observed in our study. SIGNIFICANCE OF THE STUDY: Gestational diabetes mellitus (GDM) is a metabolic disorder whose major pathophysiological basis is demonstrated as insulin resistance (IR). Importantly, our findings indicate that the deficiency of Smad4 significantly improves the insulin sensitivity and relieves the inflammation in the cellular model of IR. Besides, the positive effect of Smad4 on cell viability was also observed in our study. Our present findings provide novel insights for the investigation on molecular details about the GDM pathogenesis.

The role of Smad7 in cutaneous wound healing.

Chronic refractory wounds are generally caused by local tissue defects and necrosis, and they are characterized by delayed wound healing as well as high recurrence, which seriously affects life quality. However, effective therapeutics to treat wounds are currently unavailable. Therapy primarily aims to accelerate generation of granulation tissue and decrease recurrence. The pathogenesis of chronic refractory wounds is closely related to multiple complex signaling pathways and a series of cytokines. Among these signaling pathways, TGF-β/Smad7 axis plays a critical role. Specifically, Smad7 is an antagonist of TGF-β that inhibits activation of TGF-β. Moreover, Smad7 promotes wound healing by regulating cytokines and controlling growth, differentiation and apoptosis of cells, which may be exploited to cure the disease. This review aims to reveal the exact functions and mechanisms of Smad7 in regulation of wound healing.

Abstract 5173: Identification of new targets in SMAD4-deficient cancers by whole genome CRISPR screening

Abstract The TGF-β signaling mediator SMAD4 is frequently mutated or deleted in colorectal cancer (CRC) and pancreatic cancers (PC) and is associated with poorer prognosis. This makes SMAD4 loss interesting to harness for synthetic lethality-based therapy. In this study, we first restored SMAD4 in SMAD4-deficient cell lines (HT29 and SW620) and showed that SMAD4 restoration reestablished the TGF-β-induced growth inhibition in vitro and in vivo, thereby confirming the tumor suppressive role of SMAD4 in these cell lines. In order to identify genetic vulnerabilities of SMAD4-deficient cells, we conducted pooled genome-wide loss-of-function CRISPR/Cas9 screens across four non-isogenic cell lines harboring altered (HT29 and SW620) or wild-type (DLD1 and MIAPACA2) SMAD4. We identified candidate genes, including the Krüppel-like factor 5 (KLF5), which has already been suggested as a potentially interesting target for drug therapy in SMAD4-deficient cancers. Novel candidates that might be interesting synthetic lethal targets in SMAD4-negative cancers will be presented. Citation Format: Christophe Marcireau, Hélène Erasimus, Vanessa Kolnik, Frederic Lacroix, Stéphane D'agostino, Olivier Lemaitre, Alexandre Rohaut, Isabelle Sanchez, Sukhvinder Sidhu, Gilbert Thill, Michel Didier, Laurent Debussche. Identification of new targets in SMAD4-deficient cancers by whole genome CRISPR screening [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5173.

MicroRNA-148a-3p inhibits progression of hepatocelluar carcimoma by repressing SMAD2 expression in an Ago2 dependent manner

BackgroundHepatocellular carcinoma (HCC) is one of the most prevalent common cancer worldwide with high mortality. Transforming growth factor-β (TGF-β) signaling pathway was reported dysregulated during liver cancer formation and progression. As a key component of TGF-β signaling, the role of SMAD2 and its regulatory mechanisms in HCC remain unclear.MethodsSMAD2 expression in paired HCC specimens were determined by western blot and immunohistochemistry (IHC). quantitative real-time PCR (qRT-PCR) was used to measure mRNA and microRNA (miRNA) expression level. Cell migration, invasion and proliferation ability were evaluated by transwell, CCK8 and EdU assay. In silico websites were used to manifest overall survival rates of HCC patients or to predict miRNAs targeting SMAD2. Dual luciferase reporter assay and anti-Ago2 immunoprecipitation assay were performed to confirm the binding between SMAD2 mRNA and miRNA-148a-3p (miR-148a). Tumorigenesis and lung metastasis mouse model were used to explore the role of miR-148a in vivo. In situ hybridization (ISH) was conducted to determine the expression of miR-148a in liver tissues.ResultsIn this study, we found that SMAD2 was highly expressed in HCC and elevated SMAD2 expression predicted shorter overall survival (OS) time for HCC patients. SMAD2 promoted mobility and proliferation of HCC cells in vitro. We further revealed that the expression of miR-148a was negatively correlated with SMAD2 and found that miR-148a repressed SMAD2 expression by downregulating its mRNA through binding with Argonaute 2 (Ago2) in HCC. Transwell, CCK8 and animal experiments exhibited miR-148a inhibited metastasis and proliferation of HCC in vitro and in vivo. Moreover, the phenotype changes caused by miR-148a manipulation were recovered by rescuing SMAD2 expression in HCC cells. ISH assay indicated miR-148a was downregulated in HCC and low expression of miR-148a associated with more aggressive clinic features and poor prognosis.ConclusionmiR-148a was identified as a repressor of HCC progression by downregulating SMAD2 in an Ago2 dependent manner.

Smad3 Regulates Neuropilin 2 Transcription by Binding to its 5' Untranslated Region.

BackgroundVascular smooth muscle cell phenotypic change and consequential intimal hyperplasia (IH) cause arterial stenosis and posttreatment restenosis. Smad3 is a master transcription factor, yet its underlying functional mechanisms in this disease context are not well defined.Methods and ResultsIn cultured smooth muscle cells, Smad3 silencing and overexpression respectively reduced and increased the mRNA and protein of NRP2 (neuropilin 2), a recently reported pro‐IH signaling factor. Smad3 silencing attenuated pro‐IH smooth muscle cell phenotypes including proliferation, migration, and dedifferentiation (reduced smooth muscle α‐actin). While increased Smad3 enhanced these phenotypes, NRP2 silencing abolished this enhancement. Interestingly, the 5′ untranslated region but not the promoter of NRP2 was indispensable for Smad3‐enhanced transcriptional activity (luciferase assay); both chromatin immunoprecipitation and electrophoretic mobility shift assay showed predominant Smad3 binding in the +51 to +78 bp region of NRP2′s 5′ untranslated region. In vivo, Smad3 haploinsufficiency reduced NRP2 (immunostaining) and IH (by 47%) in wire‐injured mouse femoral arteries.ConclusionsSmad3 controls NRP2 expression by occupying its 5′ untranslated region in promoting smooth muscle cell phenotypic change in vitro. This and in vivo results shed new light on the long‐debated role of Smad3 in IH.

Smad4 induces cell death in HO-8910 and SKOV3 ovarian carcinoma cell lines via PI3K-mTOR involvement.

This study investigated the effect and mechanism of Smad4 in ovarian carcinoma (OC) cell viability and demonstrated that Smad4 acted as a tumor suppressor in OC, which may contribute to the understanding of molecular mechanisms underlying OC occurrence and progression. Smad4 expression was decreased in the OC specimens, but Smad4 recovery in the OC cell lines impaired the survival and viability of OC cells by increasing autophagy and apoptosis. Further investigation showed that Smad4 interacted with the P85 subunit of PI3K and caused deactivation of the PI3K/mTOR pathway. Therefore, Smad4 could be considered as a target in cancer therapy due to its regulatory effect in OC carcinogenesis.

The role of Smad2 and Smad3 in regulating homeostatic functions of fibroblasts in vitro and in adult mice

The heart contains an abundant fibroblast population that may play a role in homeostasis, by maintaining the extracellular matrix (ECM) network, by regulating electrical impulse conduction, and by supporting survival and function of cardiomyocytes and vascular cells. Despite an explosion in our understanding of the role of fibroblasts in cardiac injury, the homeostatic functions of resident fibroblasts in adult hearts remain understudied. TGF-β-mediated signaling through the receptor-activated Smads, Smad2 and Smad3 critically regulates fibroblast function. We hypothesized that baseline expression of Smad2/3 in fibroblasts may play an important role in cardiac homeostasis. Smad2 and Smad3 were constitutively expressed in normal mouse hearts and in cardiac fibroblasts. In cultured cardiac fibroblasts, Smad2 and Smad3 played distinct roles in regulation of baseline ECM gene synthesis. Smad3 knockdown attenuated collagen I, collagen IV and fibronectin mRNA synthesis and reduced expression of the matricellular protein thrombospondin-1. Smad2 knockdown on the other hand attenuated expression of collagen V mRNA and reduced synthesis of fibronectin, periostin and versican. In vivo, inducible fibroblast-specific Smad2 knockout mice and fibroblast-specific Smad3 knockout mice had normal heart rate, preserved cardiac geometry, ventricular systolic and diastolic function, and normal myocardial structure. Fibroblast-specific Smad3, but not Smad2 loss modestly but significantly reduced collagen content. Our findings suggest that fibroblast-specific Smad3, but not Smad2, may play a role in regulation of baseline collagen synthesis in adult hearts. However, at least short term, these changes do not have any impact on homeostatic cardiac function.