Smad4-mediated TGF-beta signaling in tumorigenesis

Roles of TGFβ signaling Smads in squamous cell carcinoma

Smad proteins are classified in different groups based on their functions in mediating transforming growth factor β (TGFβ) superfamily components. Smad1/5/8 mainly mediate bone morphogenetic proteins (BMP) pathway and Smad2/3 mainly mediate TGFβ pathway. Smad4 functions as common Smad to mediate both pathways. Previous studies showed many members of TGFβ superfamily play a role in carcinogenesis. The current review focuses on the role of TGFβ signaling Smads in squamous cell carcinomas (SCCs). TGFβ signaling inhibits early tumor development, but promotes tumor progression in the late stage. Although Smad2, Smad3 and Smad4 are all TGFβ signaling Smads, they play different roles in SCCs. Genetically, Smad2 and Smad4 are frequently mutated or deleted in certain human cancers whereas Smad3 mutation or deletion is infrequent. Genetically engineered mouse models with these individual Smad deletions have provided important tools to identify their diversified roles in cancer. Using these models, we have shown that Smad4 functions as a potent tumor suppressor and its loss causes spontaneous SCCs development; Smad2 functions as a tumor suppressor and its loss promotes SCC formation initiated by other genetic insults but is insufficient to initiate tumor formation. In contrast, Smad3 primarily mediates TGFβ-induced inflammation. The functions of each Smad also depends on the presence/absence of its Smad partner, thus need to be interpreted in a context-specific manner.

Expression and clinical significance of the transforming growth factor-β signalling pathway in endometrial cancer

AIMS

To evaluate the components of the transforming growth factor (TGF)-β-Smad signalling pathway in human endometrial cancer (EC).

METHODS AND RESULTS

TGF-β1, TGF-β receptor type I, TGF-β receptor type II, Smad2, Smad3, Smad4, Skil and Disabled-2 (DAB2) mRNA levels were determined by reverse transcriptase polymerase chain reaction on EC cell lines and in 70 EC tissues. Immunohistochemistry for Skil and DAB2 antibodies was performed on 362 EC cases. Decreased mRNA levels of all eight components of the TGF-β pathway tested were found in the majority of 70 cases. For DAB2, the mRNA level was correlated with protein expression level (P = 0.04). The Skil mRNA level was associated with tumour stage (P = 0.03), and the Smad2/3/4 mRNA level with tumour grade (P = 0.03, P = 0.02, and P = 0.00, respectively). The Smad4 mRNA level was also associated with tumour size (P = 0.05), subtype (P = 0.04), and disease-free survival (DFS) (P = 0.05). The TGF-β1 mRNA level was associated with DFS (P = 0.04). Finally, tumours with positive Skil protein expression had a shorter recurrence time, whereas, those with positive DAB2 protein expression had a longer recurrence time.

CONCLUSIONS

Down-regulation of the TGF-β-Smad signalling pathway might be responsible for the pathogenesis of human EC, and some of its components appeared to be prognostic factors. Exploration of future therapy targeting the TGF-β-Smad pathway is warranted in EC.

Computational analysis of expression of human embryonic stem cell-associated signatures in tumors

Background

The cancer stem cell model has been proposed based on the linkage between human embryonic stem cells and human cancer cells. However, the evidences supporting the cancer stem cell model remain to be collected. In this study, we extensively examined the expression of human embryonic stem cell-associated signatures including core genes, transcription factors, pathways and microRNAs in various cancers using the computational biology approach.

Results

We used the class comparison analysis and survival analysis algorithms to identify differentially expressed genes and their associated transcription factors, pathways and microRNAs among normal vs. tumor or good prognosis vs. poor prognosis phenotypes classes based on numerous human cancer gene expression data. We found that most of the human embryonic stem cell- associated signatures were frequently identified in the analysis, suggesting a strong linkage between human embryonic stem cells and cancer cells.

Conclusions

The present study revealed the close linkage between the human embryonic stem cell associated gene expression profiles and cancer-associated gene expression profiles, and therefore offered an indirect support for the cancer stem cell theory. However, many interest issues remain to be addressed further.

miR-146a suppresses the sensitivity to interferon-α in hepatocellular carcinoma cells

BACKGROUND

Interferon-based (IFN-based) therapy is effective in the treatment of advanced hepatocellular carcinoma (HCC). However, the issue of resistance to this therapy remains to be solved. The aim of this study was to identify microRNAs (miRNAs) that govern the sensitivity to IFN-α in HCC cells.

METHODS

miRNA microarray analysis using IFN-α-resistant clones of PLC/PRF/5 (PLC-Rs) and their parental cells (PLC-P) was conducted. Changes in the anti-cancer effects of IFN-α were studied after gain-of-function and loss-of-function of the candidate miRNA.

RESULTS

miR-146a expression was significantly higher in PLC-Rs than in PLC-P. miR-146a decreased the sensitivity to IFN-α through the suppression of apoptosis. Further experiments showed that miR-146a-related resistance to IFN-α was mediated through SMAD4.

CONCLUSIONS

The results indicated that miR-146a regulated the sensitivity of HCC cells to the cytotoxic effects of IFN-α through SMAD4, suggesting that this miRNA could be suitable for prediction of the clinical response and potential therapeutic target in HCC patients on IFN-based therapy.

Transforming growth factor beta signaling in adult cardiovascular diseases and repair

The majority of children with congenital heart disease now live into adulthood due to the remarkable surgical and medical advances that have taken place over the past half century. Because of this, adults now represent the largest age group with adult cardiovascular diseases. It includes patients with heart diseases that were not detected or not treated during childhood, those whose defects were surgically corrected but now need revision due to maladaptive responses to the procedure, those with exercise problems and those with age-related degenerative diseases. Because adult cardiovascular diseases in this population are relatively new, they are not well understood. It is therefore necessary to understand the molecular and physiological pathways involved if we are to improve treatments. Since there is a developmental basis to adult cardiovascular disease, transforming growth factor beta (TGFβ) signaling pathways that are essential for proper cardiovascular development may also play critical roles in the homeostatic, repair and stress response processes involved in adult cardiovascular diseases. Consequently, we have chosen to summarize the current information on a subset of TGFβ ligand and receptor genes and related effector genes that, when dysregulated, are known to lead to cardiovascular diseases and adult cardiovascular deficiencies and/or pathologies. A better understanding of the TGFβ signaling network in cardiovascular disease and repair will impact genetic and physiologic investigations of cardiovascular diseases in elderly patients and lead to an improvement in clinical interventions.

Transcriptional control of gene expression in pancreatic cancer: from sequence-specific transcription factors to nuclear architecture

Transcription plays a central role in the regulation of gene expression during neoplastic transformation in different tissues. Using this nuclear process as a common topic in this special issue of the Journal of Gastrointestinal Cancer we have covered with five review articles key aspects of gene transcription and its impact in pancreatic carcinogenesis. We are confident that the knowledge included in these review articles will help understand the contribution of this molecular event to the pathogenesis of this devastating disease and serve as foundation for the development of new therapeutic tools.

Lysophosphatidic acid-induced p21Waf1 expression mediates the cytostatic response of breast and ovarian cancer cells to TGFβ

Lysophosphatidic acid (LPA) is a multifunctional intercellular phospholipid mediator present in blood and other biological fluids. In cancer cells, LPA stimulates expression or activity of inflammatory cytokines, angiogenic factors, matrix metalloproteinases, and other oncogenic proteins. In this study, we showed that LPA upregulated expression of the cyclin-dependent kinase inhibitor p21(Waf1) in TGFβ-sensitive breast and ovarian cancer cells, but not in TGFβ-resistant ones. We examined the possibility that LPA-induced p21 might contribute to the cytostatic response to TGFβ. In serum-free conditions, TGFβ alone induced p21 expression weakly in TGFβ-sensitive cells. Serum or serum-borne LPA cooperated with TGFβ to elicit the maximal p21 induction. LPA stimulated p21 via LPA(1) and LPA(2) receptors and Erk-dependent activation of the CCAAT/enhancer binding protein beta transcription factor independent of p53. Loss or gain of p21 expression led to a shift between TGFβ-sensitive and -resistant phenotypes in breast and ovarian cancer cells, indicating that p21 is a key determinant of the growth inhibitory activity of TGFβ. Our results reveal a novel cross-talk between LPA and TGFβ that underlies TGFβ-sensitive and -resistant phenotypes of breast and ovarian cancer cells.

The relationship between fibrogenic TGFβ1 signaling in the joint and cartilage degradation in post-injury osteoarthritis

OBJECTIVE

To review the literature on modulation of chondrocyte activities in the osteoarthritic joint, and to discuss these changes in relation to established hard and soft tissue repair paradigms, with an emphasis on transforming growth factor beta (TGFβ1)-mediated signaling which can promote either a chondrogenic or fibrogenic phenotype.

METHODS

Papers addressing the close relationship between repair in general, and the specific post-injury response of joint tissues are summarized. Different interpretations of the role of TGFβ1 in the emergence of an "osteoarthritic" chondrocyte are compared and the phenotypic plasticity of "reparative" progenitor cells is examined. Lastly, emerging data on a central role for A-Disintegrin-And-Metalloproteinase-with-Thrombospondin-like-Sequences-5 (ADAMTS5) activity in modulating TGFβ1 signaling through activin receptor-like kinase 1 (ALK1) and activin receptor-like kinase 5 (ALK5) pathways is discussed.

RESULTS

The review illustrates how a transition from ALK5-mediated fibrogenic signaling to ALK1-mediated chondrogenic signaling in joint cells represents the critical transition from a non-reparative to a reparative cell phenotype. Data from cell and in vivo studies illustrates the mechanism by which ablation of ADAMTS5 activity allows the transition to reparative chondrogenesis. Multiple large gene expression studies of normal and osteoarthritis (OA) human cartilages (CAs) also support an important role for TGFβ1-mediated pro-fibrogenic activities during disease progression.

CONCLUSIONS

We conclude that progressive articular CA damage in post-injury OA results primarily from biomechanical, cell biologic and mediator changes that promote a fibroblastic phenotype in joint cells. Since ADAMTS5 and TGFβ1 appear to control this process, agents which interfere with their activities may not only enhance endogenous CA repair in vivo, but also improve the properties of tissue-engineered CA for implantation.

MicroRNA miR-146b-5p regulates signal transduction of TGF-β by repressing SMAD4 in thyroid cancer

MicroRNAs (miRNA) are small non-coding RNAs involved in post-transcriptional gene regulation that have crucial roles in several types of tumors, including papillary thyroid carcinoma (PTC). miR-146b-5p is overexpressed in PTCs and is regarded as a relevant diagnostic marker for this type of cancer. A computational search revealed that miR-146b-5p putatively binds to the 3' untranslated region (UTR) of SMAD4, an important member of the transforming growth factor β (TGF-β) signaling pathway. The TGF-β pathway is a negative regulator of thyroid follicular cell growth, and the mechanism by which thyroid cancer cells evade its inhibitory signal remains unclear. We questioned whether the modulation of the TGF-β pathway by miR-146b-5p can contribute to thyroid tumorigenesis. Luciferase reporter assay confirmed the direct binding of miR-146b-5p on the SMAD4 3'UTR. Specific inhibition of miR-146b-5p with a locked nucleic acid-modified anti-miR-146b oligonucleotide significantly increased SMAD4 levels in the human papillary carcinoma cell lines, TPC-1 and BCPAP. Moreover, suppression of miR-146b-5p increased the cellular response to the TGF-β anti-proliferative signal, significantly decreasing the proliferation rate. The overexpression of miR-146b-5p in normal rat follicular PCCL3 cells decreased SMAD4 levels and disrupted TGF-β signal transduction. MiR-146b-5p overexpression in PCCL3 cells also significantly increased cell proliferation in the absence of thyroid-stimulating hormone and conferred resistance to TGF-β-mediated cell-cycle arrest. Additionally, the activation of thyroid most common oncogenes RET/PTC3 and BRAF in PCCL3 cells upregulated miR-146b-5p expression. Our results confirm the oncogenic role of miR-146b-5p in thyroid follicular cells and contribute to knowledge regarding the modulation of TGF-β signal transduction by miRNAs in PTCs.

SMAD4 mutation segregating in a family with juvenile polyposis, aortopathy, and mitral valve dysfunction

Juvenile polyposis syndrome (JPS) is caused by heterozygous mutations in either SMAD4 or BMPR1A. Individuals with JPS due to mutations in SMAD4 are at greater risk to manifest signs of hereditary hemorrhagic telangiectasia (HHT). HHT is caused by either mutations in SMAD4 or other genes that modulate transforming growth factor-beta (TGFβ) signaling. Additional genes in the TGFβ network include FBN1, TGFBR1, and TGFBR2, mutations of which cause either Marfan syndrome (MFS) or Loeys-Dietz syndrome (LDS), respectively. As SMAD4, FBN1, and TGFBR1/2 map to different regions of the genome, disorders associated with mutations in these genes are not expected to co-segregate in a family. We report an individual whose family history was positive for aortopathy, mitral valve dysfunction, and JPS. Mutation analysis of SMAD4 implicates this gene for these phenotypes in this family. Although SMAD4 is among several genes in the TGFβ network, and although prior single case reports have described large vessel aneurysms in HHT, this is the first description of aortic and mitral disease presenting with JPS. This observation suggests that, in addition to HHT, individuals with SMAD4 mutations may be at risk for aortic dilation and mitral valve dysfunction. We emphasize the importance of comprehensive review of the medical history prior to molecular testing, especially in an asymptomatic patient.

Genetic variation in the TGF-β signaling pathway and colon and rectal cancer risk

BACKGROUND

The TGF-β signaling pathway is an essential regulator of many cellular process involved in carcinogenesis. Smad proteins are central to the function of TGF-β signaling. In this study, we evaluated genetic variation in TGFβ1, TGFβR1, Smad1, Smad2, Smad3, and Smad4 and risk of colon and rectal cancer.

METHODS

Data are from a large case-control study of colon (n = 1,444 cases, 1,841 controls) and rectal (n = 754 cases, 856 controls) cancer participants with DNA.

RESULTS

Both TGFβ1 rs1800469 and rs4803455 were associated with colon cancer [odds ratio (OR) = 0.65 and 1.43, 95% CI = 0.51-0.84 and 1.18-1.73, respectively) but not rectal cancer. Likewise, 1 of 3 tagSNPs for TGFβR1, 2 of the 4 tagSNPs for Smad2, and 4 of 37 Smad3 tagSNPs were associated with colon cancer. Fewer significant associations were observed for rectal cancer, with only 1 tagSNP in Smad2 and 3 tagSNP in Smad3 having 95% CIs excluding 1.0. Several Smad3 tagSNPs were only associated with CpG island methylator phenotype. We observed several statistically significant interactions between genetic variation in the TGF-β signaling pathway and NFκB1, further illustrating its involvement in proposed mechanisms. In addition, we observed statistically significant interaction between TGFβ1, TGFβR1, and Smad3 and cigarette smoking, aspirin use, and estrogen status for both colon and rectal cancers. Variation in TGFβ1, TGFβR1, and Smad3 seemed to influence survival after diagnosis of colon and rectal cancer.

CONCLUSIONS

These findings provide further support for genetic variation in the TGF-β signaling pathway and risk of developing both colon and rectal cancers.

IMPACT

Insight into biological pathways is provided.

Anterior visceral endoderm SMAD4 signaling specifies anterior embryonic patterning and head induction in mice

SMAD4 serves as a common mediator for signaling of TGF-β superfamily. Previous studies illustrated that SMAD4-null mice die at embryonic day 6.5 (E6.5) due to failure of mesoderm induction and extraembryonic defects; however, functions of SMAD4 in each germ layer remain elusive. To investigate this, we disrupted SMAD4 in the visceral endoderm and epiblast, respectively, using a Cre-loxP mediated approach. We showed that mutant embryos lack of SMAD4 in the visceral endoderm (Smad4^Co/Co;TTR-Cre) died at E7.5-E9.5 without head-fold and anterior embryonic structures. We demonstrated that TGF-β regulates expression of several genes, such as Hex1, Cer1, and Lim1, in the anterior visceral endoderm (AVE), and the failure of anterior embryonic development in Smad4^Co/Co;TTR-Cre embryos is accompanied by diminished expression of these genes. Consistent with this finding, SMAD4-deficient embryoid bodies showed impaired responsiveness to TGF-β-induced gene expression and morphological changes. On the other hand, embryos carrying Cre-loxP mediated disruption of SMAD4 in the epiblasts exhibited relatively normal mesoderm and head-fold induction although they all displayed profound patterning defects in the later stages of gastrulation. Cumulatively, our data indicate that SMAD4 signaling in the epiblasts is dispensable for mesoderm induction although it remains critical for head patterning, which is significantly different from SMAD4 signaling in the AVE, where it specifies anterior embryonic patterning and head induction.

Myocardial deletion of Smad4 using a novel α skeletal muscle actin Cre recombinase transgenic mouse causes misalignment of the cardiac outflow tract

SMAD4 acts as the converging point for TGFβ and BMP signaling in heart development. Here, we investigated the role of SMAD4 in heart development using a novel α skeletal muscle actin Cre recombinase (MuCre) transgenic mouse strain. Lineage tracing using MuCre/ROSA26^LacZ reporter mice indicated strong Cre-recombinase expression in developing and adult heart and skeletal muscles. In heart development, significant MuCre expression was noted at E11.5 in the atrial, ventricular, outflow tract and atrioventricular canal myocardium, but not in the endocardial cushions. MuCre-driven conditional deletion of Smad4 in mice caused double outlet right ventricle (DORV), ventricular septal defect (VSD), impaired trabeculation and thinning of ventricular myocardium, and mid-gestational embryonic lethality. In conclusion, MuCre mice effectively delete genes in both heart and skeletal muscles, thus enabling the discovery that myocardial Smad4 deletion causes misalignment of the outflow tract and DORV.

SMAD4--molecular gladiator of the TGF-beta signaling is trampled upon by mutational insufficiency in colorectal carcinoma of Kashmiri population: an analysis with relation to KRAS proto-oncogene

BACKGROUND

The development and progression of colorectal cancer has been extensively studied and the genes responsible have been well characterized. However the correlation between the SMAD4 gene mutations with KRAS mutant status has not been explored by many studies so far. Here, in this study we aimed to investigate the role of SMAD4 gene aberrations in the pathogenesis of CRC in Kashmir valley and to correlate it with various clinicopathological variables and KRAS mutant genotype.

METHODS

We examined the paired tumor and normal tissue specimens of 86 CRC patients for the occurrence of aberrations in MCR region of SMAD4 and exon 1 of KRAS by PCR-SSCP and/or PCR-Direct sequencing.

RESULTS

The overall mutation rate of mutation cluster region (MCR) region of SMAD4 gene among 86 patients was 18.6% (16 of 86). 68.75% (11/16) of the SMAD4 gene mutants were found to have mutations in KRAS gene as well. The association between the KRAS mutant genotype with SMAD4 mutants was found to be significant (P = or < 0.05). Further more, we found a significant association of tumor location, tumor grade, node status, occupational exposure to pesticides and bleeding PR/Constipation with the mutation status of the SMAD4 gene (P = or < 0.05).

CONCLUSION

Our study suggests that SMAD4 gene aberrations are the common event in CRC development but play a differential role in the progression of CRC in higher tumor grade (C+D) and its association with the KRAS mutant status suggest that these two molecules together are responsible for the progression of the tumor to higher/advanced stage.

The effect of transforming growth factor-beta1 on nasopharyngeal carcinoma cells: insensitive to cell growth but functional to TGF-beta/Smad pathway

Objectives

This study explored the response of nasopharyngeal carcinoma cells to TGF-β1-induced growth suppression and investigated the roles of the TGF-β/Smad signaling pathway in nasopharyngeal carcinoma cells.

Methods

The cells of nasopharyngeal carcinoma cell line CNE2 were treated with TGF-β1. The growth responses of CNE2 cells were analyzed by MTT assay. The mRNA expression and protein subcellular localization of the TGF-β/Smad signaling components in the CNE2 were determined by real time RT-PCR and immunocytochemical analysis.

Results

We found that the growth of CNE2 cells was not suppressed by TGF-β1. The signaling proteins TβRII, Smad 7 were expressed normally, while Smad2, Smad3, and Smad4 increased significantly at the mRNA level. TGF-β type II receptor and Smad7 had no change compared to the normal nasopharyngeal epithelial cells. In addition, Smad2 was phosphorylated to pSmad2, and the activated pSmad2 translocated into the nucleus from the cytoplasm, while the inhibitory Smad-Smad7 translocated from the nucleus to the cytoplasm after TGF-β1 stimulation.

Conclusion

The results suggested that CNE2 cells are not sensitive to growth suppression by TGF-β1, but the TGF-β/Smad signaling transduction is functional. Further work is needed to address a more detailed spectrum of the TGF-β/Smad signaling pathway in CNE2 cells.

Advances in pancreatic cancer detection

Pancreatic cancer represents a major challenge for research studies and clinical management. No specific tumor marker for the diagnosis of pancreatic cancer exists. Therefore, extensive genomic, transcriptomic, and proteomic studies are being developed to identify candidate markers for use in high-throughput systems capable of large cohort screening. Understandably, the complex pathophysiology of pancreatic cancer requires sensitive and specific biomarkers that can improve both early diagnosis and therapeutic monitoring. The lack of a single diagnostic marker makes it likely that only a panel of biomarkers is capable of providing the appropriate combination of high sensitivity and specificity. Biomarker discovery using novel technology can improve prognostic upgrading and pinpoint new molecular targets for innovative therapy.