Role of SMAD proteins in colitis-associated cancer: from known to the unknown

The Interaction Between SMAD1 and YAP1 Is Correlated with Increased Resistance of Gastric Cancer Cells to Cisplatin

Drug resistance is a major obstacle leading to treating failure and poor outcome in gastric cancer (GC). This study explores the interaction between SMAD family member 1 (SMAD1) and Yes1-associated transcriptional regulator (YAP1) and their roles in cisplatin (DDP) resistance in GC. Transcriptome analysis predicted that SMAD1 is highly expressed in DDP-resistant cells. Elevated SMAD1 expression was detected in GC tissue and cells, especially in DDP-resistant cells (MKN-45/DDP and AGS/DDP). SMAD1 downregulation in cells decreased 50% inhibition value of DDP, reduced proliferation, migration, and invasion, and promoted cell cycle arrest and apoptosis. A protein-protein interaction network suggested a possible SMAD1 and YAP1 interaction in GC. The SMAD1 and YAP1 interaction was validated by chromatin immunoprecipitation (ChIP), co-immunoprecipitation (Co-IP), and luciferase assays. SMAD1 bound to YAP1 and activated its transcription. SMAD1 formed complexes with YAP1 in nucleus, and YAP1 upregulation enhanced SMAD1 activity as well. Upregulation of YAP1 restored the malignant behaviors of GC cells suppressed by SMAD1 silencing. In vivo, SMAD1 silencing suppressed growth and DDP resistance of xenograft tumors in nude mice, and this suppression was blocked by YAP1 overexpression again. In conclusion, this study demonstrates that SMAD1 can interact with YAP1 to enhance the DDP resistance of GC cells.

Transforming Growth Factor Beta Promotes Inflammation and Tumorigenesis in Smad4-Deficient Intestinal Epithelium in a YAP-Dependent Manner

Transforming growth factor beta (TGF-β), a multifunctional cytokine, plays critical roles in immune responses. However, the precise role of TGF-β in colitis and colitis-associated cancer remains poorly defined. Here, it is demonstrated that TGF-β promotes the colonic inflammation and related tumorigenesis in the absence of Smad family member 4 (Smad4). Smad4 loss in intestinal epithelium aggravates colitis and colitis-associated neoplasia induced by dextran sulfate sodium (DSS) and azoxymethane/dextran sulfate sodium (AOM/DSS), leading to over-activated immune responses and increased TGF-β1 levels. In Smad4-deficient organoids, TGF-β1 stimulates spheroid formation and impairs intestinal stem cell proliferation and lineage specification. YAP, whose expression is directly upregulated by TGF-β1 after Smad4 deletion, mediates the effect of TGF-β1 by interacting with Smad2/3. Attenuation of YAP/TAZ prevents TGF-β1-induced spheroid formation in Smad4-/- organoids and alleviates colitis and colitis-associated cancer in Smad4-deficient mice. Collectively, these results highlight an integral role of the TGF-β/Smad4 axis in restraining intestinal inflammation and tumorigenesis and suggest TGF-β or YAP signaling as therapeutic targets for these gastrointestinal diseases intervention.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.

The comprehensive detection of miRNA and circRNA in the regulation of intramuscular and subcutaneous adipose tissue of Laiwu pig

circRNAs, as miRNA sponges, participate in many important biological processes. However, it remains unclear whether circRNAs can regulate lipid metabolism. This study aimed to explore the competing endogenouse RNA (ceRNA) regulatory network that affects the difference between intramuscular fat (IMF) and subcutaneous fat (SCF) deposition, and to screen key circRNAs and their regulatory genes. In this experiment, we identified 265 differentially expressed circRNAs, of which 187 up-regulated circRNA and 78 down-regulated circRNA in IMF. Subsequently, we annotated the function of DEcircRNA's host genes, and found that DEcircRNA's host genes were mainly involved in GO terms (including cellular response to fatty acids, lysophosphatidic acid acyltransferase activity, R-SMAD binding, etc.) and signaling pathways (fatty acid biosynthesis, Citrate cycle, TGF- β Signal pathway) related to adipogenesis, differentiation and lipid metabolism. By constructing a circRNA-miRNA network, we screened out DEcircRNA that can competitively bind to more miRNAs as key circRNAs (circRNA_06424 and circRNA_08840). Through the functional annotation of indirect target genes and protein network analysis, we found that circRNA_06424 affects the expression of PPARD, MMP9, UBA7 and other indirect target genes by competitively binding to miRNAs such as ssc-miR-339-5p, ssc-miR-744 and ssc-miR-328, and participates in PPAR signaling pathway, Wnt signaling pathway, unsaturated fatty acid and other signaling pathways, resulting in the difference of fat deposition between IMF and SCF. This study provide a theoretical basis for further research investigating the differences of lipid metabolism in different adipose tissues, providing potential therapeutic targets for ectopic fat deposition and lipid metabolism diseases.

Inflammatory bowel disease and carcinogenesis

Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer mortality worldwide. Colitis-associated colorectal cancer (CAC) is a subtype of CRC associated with inflammatory bowel disease (IBD). It is well known that individuals with IBD have a 2-3 times higher risk of developing CRC than those who do not, rendering CAC a major cause of death in this group. Although the etiology and pathogenesis of CAC are incompletely understood, animal models of chronic inflammation and human cohort data indicate that changes in the intestinal environment, including host response dysregulation and gut microbiota perturbations, may contribute to the development of CAC. Genomic alterations are a hallmark of CAC, with patterns that are distinct from those in sporadic CRC. The discovery of the biological changes that underlie the development of CAC is ongoing; however, current data suggest that chronic inflammation in IBD increases the risk of developing CAC. Therefore, a deeper understanding of the precise mechanisms by which inflammation triggers genetic alterations and disrupts intestinal homeostasis may provide insight into novel therapeutic strategies for the prevention of CAC.

From inflammatory bowel disease to colorectal cancer: what's the role of miRNAs?

Inflammatory Bowel Disease (IBD) is a chronic inflammatory disease with relapse and remission periods. Ulcerative colitis and Crohn's disease are two major forms of the disease. IBD imposes a lot of sufferings on the patient and has many consequences; however, the most important is the increased risk of colorectal cancer, especially in patients with Ulcerative colitis. This risk is increased with increasing the duration of disease, thus preventing the progression of IBD to cancer is very important. Therefore, it is necessary to know the details of events contributed to the progression of IBD to cancer. In recent years, the importance of miRNAs as small molecules with 20-22 nucleotides has been recognized in pathophysiology of many diseases, in which IBD and colorectal cancer have not been excluded. As a result, the effectiveness of these small molecules as therapeutic target is hopefully confirmed. This paper has reviewed the related studies and findings about the role of miRNAs in the course of events that promote the progression of IBD to colorectal carcinoma, as well as a review about the effectiveness of some of these miRNAs as therapeutic targets.

SMAD1 as a biomarker and potential therapeutic target in drug-resistant multiple myeloma

BACKGROUND

SMAD1, a central mediator in TGF-β signaling, is involved in a broad range of biological activities including cell growth, apoptosis, development and immune response, and is implicated in diverse type of malignancies. Whether SMAD1 plays an important role in multiple myeloma (MM) pathogenesis and can serve as a therapeutic target are largely unknown.

METHODS

Myeloma cell lines and primary MM samples were used. Cell culture, cytotoxicity and apoptosis assay, siRNA transfection, Western blot, RT-PCR, Soft-agar colony formation, and migration assay, Chromatin immunoprecipitation (Chip), animal xenograft model studies and statistical analysis were applied in this study.

RESULTS

We demonstrate that SMAD1 is highly expressed in myeloma cells of MM patients with advanced stages or relapsed disease, and is associated with significantly shorter progression-free and overall survivals. Mechanistically, we show that SMAD1 is required for TGFβ-mediated proliferation in MM via an ID1/p21/p27 pathway. TGF-β also enhanced TNFα-Induced protein 8 (TNFAIP8) expression and inhibited apoptosis through SMAD1-mediated induction of NF-κB1. Accordingly, depletion of SMAD1 led to downregulation of NF-κB1 and TNFAIP8, resulting in caspase-8-induced apoptosis. In turn, inhibition of NF-κB1 suppressed SMAD1 and ID1 expression uncovering an autoregulatory loop. Dorsomorphin (DM), a SMAD1 inhibitor, exerted a dose-dependent cytotoxic effect on drug-resistant MM cells with minimal cytotoxicity to normal hematopoietic cells, and further synergized with the proteasomal-inhibitor bortezomib to effectively kill drug-resistant MM cells in vitro and in a myeloma xenograft model.

CONCLUSIONS

This study identifies SMAD1 regulation of NF-κB1/TNFAIP8 and ID1-p21/p27 as critical axes of MM drug resistance and provides a potentially new therapeutic strategy to treat drug resistance MM through targeted inhibition of SMAD1.

TRIM21 Is Decreased in Colitis-associated Cancer and Negatively Regulates Epithelial Carcinogenesis

BACKGROUND

Tripartite motif-containing (TRIM)21 is reported to be associated with the regulation of immune response in gut mucosa. Here we studied the underlying mechanisms of TRIM21 in the pathogenesis of colitis-associated cancer (CAC).

METHODS

We analyzed TRIM21 expression in tumor tissues from patients with colorectal cancer (CRC) and ulcerative colitis (UC)-associated cancer by immunohistochemistry and real-time polymerase chain reaction and established a CAC model in TRIM21-∕- and wild type mice by azoxymethane (AOM) and dextran sodium sulfate (DSS). Associated gene expression of tumor cell proliferation, adhesion, tissue remodeling and angiogenesis, and inflammatory cytokines were examined in normal colon and CAC by immunohistochemistry and real-time polymerase chain reaction.

RESULTS

Expression of TRIM21 was found to be decreased in tumor tissues from patients with CRC and UC-associated cancer than that in controls, and TRIM21-∕- deficiency promoted AOM/DSS-induced CAC, characterized by more weight loss and multiple, large colon tumors in TRIM21-∕- mice. Moreover, associated gene expression of tumor cell proliferation (eg, Ki67), tissue remodeling and angiogenesis (eg, MMP10, HIF1-α, COX2, Ang4), and pro-inflammatory cytokines (eg, IL-6, TNF-α, IL-1β) markedly upregulated, whereas associated gene expression of tumor cell adhesion (E-cadherin) and inflammatory cytokines (eg, IL-10, TGF-β, Foxp3, IFN-γ) downregulated in tumor tissues from TRIM21-/- mice compared with controls.

CONCLUSIONS

TRIM21 is decreased in colitis-associated cancer and negatively regulates intestinal epithelial carcinogenesis by modulating epithelial cell proliferation, adhesion, tissue remodeling and angiogenesis, and pro-inflammatory responses. Therefore, TRIM21 may serve as a novel therapeutic target for CAC therapy.

Molecular genetic study on GATA5 gene promoter in acute myocardial infarction

Background

Acute myocardial infarction (AMI) is a severe type of coronary artery disease, caused by coronary occlusion and followed by cardiac ischaemia. GATA binding protein 5 (GATA5) is an important member of GATA family and plays an important role in vascular inflammation, endothelial function, oxidative stress and cell metabolism. Previous studies have shown that the DNA sequence variants (DSVs) in GATA4 and GATA6 promoter can increase susceptibility to AMI. In this study, we explored the relationship between GATA5 promoter and AMI for the first time, hoping to provide a new genetic basis for understanding the pathogenesis of AMI.

Methods

GATA5 promoter was sequenced in 683 individuals (332 AMI patients and 351 controls). The transcriptional activity of the GATA5 promoter with or without DSVs in HEK-293 cells, H9c2 cells and primary neonatal rat cardiomyocytes were examined by Promega Dual-Luciferase® Reporter Assay system. Electrophoretic mobility shift assay (EMSA) was performed to explore whether the DSVs interfered with the binding of transcription factors (TFs).

Results

Nine mutations have been found in GATA5 promoter, eight of them evidently altered the transcriptional activity of the GATA5 promoter, five of them disrupted the binding of TFs (such as farnesoid X receptor). Furthermore, haplotype AT (across rs80197101 and rs77067995) is a dangerous haplotype of AMI. Genotype GA and allele A of rs80197101 and genotype CT and allele T of rs77067995 are the risk factors of AMI.

Conclusions

DSVs in GATA5 promoter can increase susceptibility to AMI. But the mechanism remains to be verified in vivo.

Diminution of microRNA-98 alleviates renal fibrosis in diabetic nephropathy by elevating Nedd4L and inactivating TGF-β/Smad2/3 pathway

MicroRNAs (miRNAs) have already been documented to function in diabetic nephropathy (DN), yet little research has focused on the role of miR-98 in this disease. Here, we discuss the mechanism of miR-98 on the renal fibrosis in DN. Recombinant adeno-associated virus carrying miR-98 inhibitor or Nedd4L overexpression plasmid was injected into DN modeled rats to explore their roles in DN. Renal tubular epithelial cell injury models (NRK-52E cells) were induced by high glucose (HG). HG-treated NRK-52E cells were transfected with miR-98 inhibitor or Nedd4L overexpression plasmid for further verification. MiR-98 was upregulated, Nedd4L was downregulated and TGF-β/Smad2/3 signaling was activated in kidney tissues of DN rats and HG-treated NRK-52E cells. miR-98 targeted Nedd4L mRNA 3'UTR. MiR-98 depletion and Nedd4L overexpression inactivated TGF-β/Smad2/3 signaling pathway, alleviated pathological damage and fibrosis, ameliorated inflammation, and depressed cell apoptosis of kidney tissues of DN rats. MiR-98 depletion and Nedd4L overexpression inactivated TGF-β/Smad2/3 signaling pathway, strengthened viability, and limited apoptosis of HG-treated renal tubular epithelial cells. Nedd4L overexpression reversed the effect of up-regulating miR-98 on DN rats and HG-treated renal tubular epithelial cells. Altogether, we find that miR-98 is upregulated in kidney tissues of DN rats, and miR-98 diminution and Nedd4L elevation attenuate renal fibrosis through inactivation of the TGF-β/Smad2/3 pathway, which provides a novel therapy for DN.

Variants of SMAD1 gene increase the risk of colorectal cancer in the Bangladeshi population

Colorectal cancer is the fourth most common type of malignancy worldwide that may develop due to the accumulation of several genetic variations. Different single nucleotide polymorphisms of SMAD1 gene are assumed to be linked with increased colorectal cancer risk. The current case-control study was conducted to verify the association of genetic polymorphisms of SMAD1 (rs11100883 and rs7661162) with colorectal cancer in the Bangladeshi population. This study was performed on 275 colorectal cancer patients and 300 healthy volunteers using polymerase chain reaction-restriction fragment length polymorphism method. The odds ratios were adjusted for age and sex with logistic regression analysis. In case of SMAD1 rs11100883 polymorphism, GA heterozygous genotype, GA + AA (dominant model), and minor allele "A" were significantly associated with colorectal cancer (adjusted odds ratio = 1.55, 95% confidence interval = 1.09-2.20, p = 0.014; adjusted odds ratio = 1.59, 95% confidence interval = 1.13-2.23, p = 0.008; and odds ratio = 1.35, 95% confidence interval = 1.06-1.73, p = 0.015, respectively) and the significance exists after the Bonferroni correction. Again, single nucleotide polymorphism rs7661162 showed significant association with an elevated colorectal cancer risk for AG heterozygous genotype, AG + GG (dominant model), AG versus AA + GG (overdominant model), and minor allele "G" (adjusted odds ratio = 1.78, 95% confidence interval = 1.24-2.56, p = 0.002; adjusted odds ratio = 1.68, 95% confidence interval = 1.18-2.39, p = 0.004; adjusted odds ratio = 1.76, 95% confidence interval = 1.23-2.53, p = 0.002; and odds ratio = 1.47, 95% confidence interval = 1.08-2.00, p = 0.014, respectively) and significance withstands after the Bonferroni correction. No significant age and gender differences between cases and controls were observed. In silico, gene expression analysis showed that the SMAD1 mRNA level was downregulated in the colon and rectal cancer tissues compared to healthy tissues. In conclusion, our findings indicate that SMAD1 rs11100883 and rs7661162 polymorphisms are responsible for increasing the susceptibility of colorectal cancer development in the Bangladeshi population.

Molecular Pathogenesis and Classification of Colorectal Carcinoma

Purpose of review

Molecular pathways in colorectal carcinogenesis involve several complex genetic and epigenetic modulations that cause normal colonic mucosa to metamorphose into a benign polyp and subsequently into a malignant tumor. Our purpose is to recapitulate historical and recent genomic research in order to augment the understanding of colorectal cancer pathogenesis.

Recent Findings

In 2015, the molecular classification for colorectal cancers was unified into one system with four distinct groups, also called as consensus molecular subtypes. This led to an enhanced understanding of molecular and immune signatures which has implications on predicting the clinical behavior as well as response to different therapeutic agents.

Summary

In this review, we expound on the current literature as well as draw on our own experience to present the important molecular pathogenesis pathways, key genetic mutations, differences in pathogenesis of left versus right sided tumors as well as the molecular classification of colorectal cancers.

SMADs binding site polymorphisms rs9911630 is associated with susceptibility but not prognosis of gastric cancer: a case control study

Background: Single nucleotide polymorphisms (SNPs) in transcription factor binding sites (TFBS) can change their binding strength, affecting the function of transcription factors (TFs). Small mother against decapentaplegic (SMAD) proteins are known as a family of TFs involved in tumorigenesis. We performed this study to investigate whether SNPs in SMADs binding sites affect the susceptibility or prognosis of gastric cancer (GC).

Methods: Using bioinformatics tools, we focused on the association between rs9911630 polymorphism and GC. We performed this case-control study in 1275 GC patients and 1426 cancer-free subjects using TaqMan allelic discrimination method.

Results: We found that rs9911630 A>G polymorphism was associate to an increased risk of gastric cancer (adjusted OR for additive model = 1.16; 95% CI = 1.03-1.30). Furthermore, we assess whether rs9911630 polymorphism affected the prognosis of GC. However, no significant association was discovered between rs9911630 A>G polymorphism and overall survival time of GC patients (HR for addictive model = 1.01; 95%CI = 0.88-1.15).

Conclusions: Our results suggested that rs9911630 polymorphism in SMADs target site might influence susceptibility but not prognosis of gastric cancer.

1,25(OH)2D3 improves blood lipid metabolism, liver function, and atherosclerosis by constraining the TGF-β/Smad signaling pathway in rats with hyperlipidemia

1,25(OH)₂D₃ has already been reported to function in some diseases. However, its role in hyperlipidemia (HLP) remains unknown. This study aims to investigate the effect of 1,25(OH)₂D₃ on HLP rats. Rat models were established by high-fat diet feeding, perfusion of different doses of 1,25-(OH)₂D₃ and injection of TGF-β1 siRNA. Whole blood viscosity, plasma viscosity, hematocrit, and erythrocyte aggregation index were detected, together with levels of biochemical indexes, 6-keto-PGF1α, and TXB2 in serum. Levels of oxidative stress indexes and inflammatory factors in serum and liver tissues were determined. TGF-β1 and Smad3 expression in serum, liver tissues, and aorta was detected. 1,25(OH)₂D₃ lowered HLP-induced rise of whole blood viscosity, red blood cell aggregation index, plasma viscosity, and hematocrit, TC, TG, LDL-C, apoB, ALT, AST, TXB2, MDA, IL-1β, TNF-α, and increased HLP-induced decrease of HDL-C, apoAI, 6-keto-PGF1α, SOD, GSH-Px, CAT, and T-AOC. TGF-β1 and Smad3 expression in serum, liver tissue, and aorta of 1,25(OH)₂D₃-treated rats reduced. High 1,25(OH)₂D₃ dose and inhibited TGF-β/Smad signaling pathway alleviated lipid metabolism, liver function, and atherosclerotic injury in HLP rats. Our study found that 1,25(OH)₂D₃ improves blood lipid metabolism, liver function, and atherosclerosis injury by constraining the TGF-β/Smad signaling pathway in rats with HLP.

Transcription factor KLF4 modulates microRNA-106a that targets Smad7 in gastric cancer

Mounting evidence has revealed that microRNAs (miRNAs, miRNA) play oncogenic or anti-oncogenic roles in many cancer types. Our previous studies have found the ectopic expression of miR-106a in gastric cancer. However, its deregulation and some potential targets have not yet been fully explored. In this investigation, we identified that the upstream transcriptional factor krüppel-like factor 4 (KLF4), a novel regulator, directly bound to the promoter sequence of miR-106a and was responsible for its deregulation. Using real-time PCR and immunohistochemistry, we further verified that the expression level of KLF4 was negatively correlated with the miR-106a expression in tissue samples. Moreover, the downstream locus was also screened and small mothers against decapentaplegic 7 (Smad7) was revealed to be a direct target of miR-106a, with its 3'-UTR region complementarily bound to miR-106a and the protein expression was mediated by miR-106a in gastric cancer cells, which was confirmed by luciferase assay and Western blot. The role of KLF4-miR-106a-Smad7 in gastric cancer invasion was assessed by real-time PCR and transwell assay. The promoting effect of miR-106a on gastric cancer invasion was significantly abolished by the overexpression of KLF4. The silencing of Smad7 partially promoted the cell invasion when miR-106a was suppressed. In conclusion, we suggest that the ectopic expression of miR-106a is modulated by the upstream transcriptional factor KLF4, which influences the invasive ability of gastric cancer through the downstream target Smad7. MiR-106a should, therefore, be considered as a potential molecular phenotype in gastric cancer.

HLTF suppresses the migration and invasion of colorectal cancer cells via TGF‑β/SMAD signaling in vitro

Helicase‑like transcription factor (HLTF) has been identified as a tumor suppressor gene. The hypermethylation of HTLF is frequently observed in various types of cancer, including colorectal cancer (CRC). However, the mechanisms through which HLTF suppresses CRC progression remain unclear. Thus, the aim of the present study was to explore the biological function of HLTF in CRC cells and the underlying mechanisms. CRC tissues and cells were used to detect the expression of HLTF. Wound‑healing and Transwell assays were performed to assess the motility of CRC cells. The results revealed that HLTF expression was significantly associated with the differentiation status, invasion depth, lymph node metastasis and distant metastasis. A low HLTF expression was significantly associated with a poor survival. Furthermore, HTLF knockdown or ectopic overexpression significantly promoted or suppressed the motility of CRC cells, respectively. With regard to the underlying molecular mechanisms, the protein expression of HTLF was upregulated when the CRC cells were stimulated with transforming growth factor (TGF)‑β, and HLTF upregulation induced an increase in SMAD4 and p‑SMAD2/3 expression and a decrease in levels of the TGF‑β/SMAD pathway downstream genes, Vimentin and zinc finger e‑box binding homeobox 1 (ZEB1). On the whole, the findings of this study suggest that HLTF is negatively associated with the progression of CRC, and its overexpression suppresses the migration and invasion of CRC cells by targeting the TGF‑β/SMAD pathway.

New insights into TGF-β/Smad signaling in tissue fibrosis

Transforming growth factor-β1 (TGF-β1) is considered as a crucial mediator in tissue fibrosis and causes tissue scarring largely by activating its downstream small mother against decapentaplegic (Smad) signaling. Different TGF-β signalings play different roles in fibrogenesis. TGF-β1 directly activates Smad signaling which triggers pro-fibrotic gene overexpression. Excessive studies have demonstrated that dysregulation of TGF-β1/Smad pathway was an important pathogenic mechanism in tissue fibrosis. Smad2 and Smad3 are the two major downstream regulator that promote TGF-β1-mediated tissue fibrosis, while Smad7 serves as a negative feedback regulator of TGF-β1/Smad pathway thereby protects against TGF-β1-mediated fibrosis. This review presents an overview of the molecular mechanisms of TGF-β/Smad signaling pathway in renal, hepatic, pulmonary and cardiac fibrosis, followed by an in-depth discussion of their molecular mechanisms of intervention effects both in vitro and in vivo. The role of TGF-β/Smad signaling pathway in tumor or cancer is also discussed. Additionally, the current advances also highlight targeting TGF-β/Smad signaling pathway for the prevention of tissue fibrosis. The review reveals comprehensive pathophysiological mechanisms of tissue fibrosis. Particular challenges are presented and placed within the context of future applications against tissue fibrosis.