Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Smad4 Protein”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2003

Mechanism of a transcriptional cross talk between transforming growth factor-beta-regulated Smad3 and Smad4 proteins and orphan nuclear receptor hepatocyte nuclear factor-4.

We have shown previously that the transforming growth factor-beta (TGFbeta)-regulated Sma-Mad (Smad) protein 3 and Smad4 proteins transactivate the apolipoprotein C-III promoter in hepatic cells via a hormone response element that binds the nuclear receptor hepatocyte nuclear factor 4 (HNF-4). In the present study, we show that Smad3 and Smad4 but not Smad2 physically interact with HNF-4 via their Mad homology 1 domains both in vitro and in vivo. The synergistic transactivation of target promoters by Smads and HNF-4 was shown to depend on the specific promoter context and did not require an intact beta-hairpin/DNA binding domain of the Smads. Using glutathione S-transferase interaction assays, we established that two regions of HNF-4, the N-terminal activation function 1 (AF-1) domain (aa 1-24) and the C-terminal F domain (aa 388-455) can mediate physical Smad3/HNF-4 interactions in vitro. In vivo, Smad3 and Smad4 proteins enhanced the transactivation function of various GAL4-HNF-4 fusion proteins via the AF-1 and the adjacent DNA binding domain, whereas a single tyrosine to alanine substitution in AF-1 abolished coactivation by Smads. The findings suggest that the transcriptional cross talk between the TGFbeta-regulated Smads and HNF-4 is mediated by specific functional domains in the two types of transcription factors. Furthermore, the specificity of this interaction for certain target promoters may play an important role in various hepatocyte functions, which are regulated by TGFbeta and the Smads.

Animals↗
PubMed2005

SCF(beta-TrCP1) controls Smad4 protein stability in pancreatic cancer cells.

Smad4, also known as deleted in pancreatic carcinoma locus 4 (DPC4), is a critical co-factor in signal transduction pathways activated by transforming growth factor (TGF)-beta-related ligands that regulate cell growth and differentiation. Mutations in Smad4/DPC4 have been identified in approximately 50% of pancreatic adenocarcinomas. Here we report that SCF(beta-TrCP1), a ubiquitin (E3) ligase, is a critical determinant for Smad4 protein degradation in pancreatic cancer cells. We found that F-box protein beta-TrCP1 in this E3 ligase interacted with Smad4 and that SCF(beta-TrCP1) inhibited TGF-beta biological activity in pancreatic cancer cells by decreasing Smad4 stability. Very low Smad4 protein levels in human pancreatic ductal adenocarcinoma cells were observed by immunohistochemistry. By analyzing pancreatic tumor-derived Smad4 mutants, we found that most point-mutated Smad4 proteins, except those within or very close to a mutation cluster region, exhibited higher interaction affinity with beta-TrCP1 and significantly elevated protein ubiquitination by SCF(beta-TrCP1). Furthermore, AsPC-1 and Caco-2, two cancer cell lines harboring Smad4 point mutations, exhibited rapid Smad4 protein degradation due to the effect of SCF(beta-TrCP1). Both Smad4 levels and TGF-beta signaling were elevated by retrovirus-delivered beta-TrCP1 siRNA in pancreatic cancer cells. Therefore, inhibition of Smad4-specific E3 ligase might be a target for therapeutic intervention in pancreatic cancer.

Adenocarcinoma↗
PubMed2006

Chromosome 18q deletion and Smad4 protein inactivation correlate with liver metastasis: A study matched for T- and N- classification.

Smad4 protein, whose gene is coded at chromosome 18q21.1, is an important tumour suppressor that mediates transforming growth factor-beta. It has been reported that inactivation of the Smad4 gene and allelic loss of chromosome 18q correlate with liver metastasis and poorer prognosis in colorectal cancers. Utilising a recently developed method of immunohistochemical staining for Smad4 protein, we focused on the specific impact of Smad4 protein expression on liver metastasis in colorectal cancer. We also evaluated the association between chromosome18q deletion and liver metastasis. We selected 20 colorectal cancers with liver metastasis for the experimental group, and 20 cases without liver metastasis for the control. In order to exclude the influence of lymph node metastasis, all cases were lymph node negative. In addition, the two groups were matched for tumour depth, tumour differentiation and tumour location. We compared the expression level of Smad4 protein immunohistochemically in these 20 matched pairs. We also compared the loss of heterozygosity status at chromosome 18q in these 20 matched pairs. Immunohistochemical staining revealed a significant difference (P = 0.024) in the level of Smad4 protein between the two groups. We also observed a significantly different (P=0.0054) ratio of allelic deletion at chromosome 18q21. Smad4 protein expression level and allelic loss at 18q21 are associated with the process of liver metastasis in colorectal cancers evaluated when excluding clinical and pathological features except for liver metastasis.

Adenocarcinoma↗
PubMed2001

The SMAD4 protein and prognosis of pancreatic ductal adenocarcinoma.

PURPOSE: SMAD4 (also called Dpc4) is a tumor suppressor in the TGF-beta signaling pathway that is genetically inactivated in approximately 55% of all pancreatic adenocarcinomas. We investigated whether prognosis after surgical resection for invasive pancreatic adenocarcinoma is influenced by SMAD4 status. EXPERIMENTAL DESIGN: Using immunohistochemistry, we characterized the SMAD4 protein status of 249 pancreatic adenocarcinomas resected from patients who underwent pancreaticoduodenectomy (Whipple resection) at The Johns Hopkins Hospital, Baltimore, MD, between 1990 and 1997. The SMAD4 gene status of 56 of 249 (22%) pancreatic carcinomas was also determined. A multivariate Cox proportional hazards model assessed the relative risk of mortality associated with SMAD4 status, adjusting for known prognostic variables. RESULTS: Patients with pancreatic adenocarcinomas with SMAD4 protein expression had significantly longer survival (unadjusted median survival was 19.2 months as compared with 14.7 months in patients with pancreatic cancers lacking SMAD4 protein expression; P = 0.03). This SMAD4 survival benefit persisted after adjustment for prognostic factors including tumor size, margins, lymph node status, pathological stage, blood loss, and use of adjuvant chemoradiotherapy. The relative hazard of mortality for cancers lacking SMAD4 after adjusting for other prognostic factors was 1.36 (95% confidence interval, 1.01-1.83; P = 0.04). CONCLUSION: Patients undergoing Whipple resection for pancreatic adenocarcinoma survive longer if their cancers express SMAD4.

Adenocarcinoma↗
PubMed2002

[Location studies of Smad4 protein in the rat testis during postnatal development].

In order to shed light on the mechanisms of TGF-beta action in the testis,we examined the expression and function of Smad4 protein, the common-mediator Smads, which is one of intracellular signaling molecules of TGF-beta superfamily members, in rat testis during postnatal development. Whole testes were collected from SD rats aged 3 days, 7 days, 14 days and 28 days, and adult. In this study, we examined, by means of western blots, the protein expression of Smad4 during rat testicular development and its cellular localization by immunohistochemical ABC method with glucose oxidase-DAB-nickel enhancement technique. The results showed that the protein of Smad4 was present in rats from 3 days of age to adulthood, and the immunoreactivity for Smad4 was exclusively localized to the cytoplasm of Leydig cells with negative nuclei in the interstitial tissue at any time point. No expression was detected in germ cells. Therefore, our data provide evidence for the molecular mechanism of TGF-beta action in rat testes during postnatal development and spermatogenesis of rats.

Animals↗
PubMed2003

Expression and localization of Smad1, Smad2 and Smad4 proteins in rat testis during postnatal development.

AIM: To study the expression and regulation of Smad1, Smad2 and Smad4 proteins (intracellular signaling molecules of transforming growth factor-b family) in rat testis during postnatal development. METHODS: The whole testes were collected from SD rats aged 3, 7, 14, 28 and 90 (adult) days. The cellular localization and developmental changes were examined by immunohistochemistry ABC method with the glucose oxidase-DAB-nickel enhancement technique. Quantitative analysis of the immunostaining was made by the image analysis system. The Smads proteins coexistence in the adult rat testis was tested by the double immune staining for CD14-Smad4 and Smad2-Smad4. The protein expression of Smad during rat testicular development was examined by means of Western blots. RESULTS: Smad1, Smad2 and Smad4 were present throughout testicular development. The immunostaining of Smad1 and Smad2 were present in spermatogenic cells. A positive immunoreactivity was located at the cytoplasm, but the nucleus was negative. Smad1 was immunolocalized at the d14, d28 and adult testes, while Smad2, at the d7, d14, d28 and adult testis. There was positive immunoreaction in the Sertoli cells and Leydig cells as well. The immunolocalization of Smad4 was exclusively at the cytoplasm of Leydig cells and the nuclei were negative throughout the testicular development. No expression was detected in the germ cells. The results of image and statistical analysis showed that generally the expression of Smad1, Smad2 and Smad4 in the testis tended to increase gradually with the growth of the rat. CONCLUSION: The present data provide direct evidences for the molecular mechanism of TGF-bgr action in rat testes during postnatal development and spermatogenesis.

Animals↗
PubMed2004

Smad4 protein stability is regulated by ubiquitin ligase SCF beta-TrCP1.

Smad4 is a key intracellular mediator for the transforming growth factor-beta (TGF-beta) superfamily of growth factors and is also an important tumor suppressor. The receptor-regulated Smad (R-Smad) proteins are regulated by ubiquitin-mediated degradation, yet the precise control of Smad4 protein stability is unclear. We have identified SCF(beta-TrCP1), a ubiquitin (E3) ligase, as a critical determinant for the protein degradation of Smad4 protein. F-box protein beta-TrCP1 in this E3 ligase interacts with Smad4 both in yeast and in mammalian cells, but has no interaction with Smad2 and has weak interaction with Smad3. The beta-TrCP1/Smad3 interaction was abolished by Smad4 gene silencing, indicating the interaction is indirect and is through Smad4. Ectopic expression of SCF complex containing beta-TrCP1 is sufficient to induce the ubiquitination and degradation of Smad4. Furthermore, small interfering RNA-triggered endogenous beta-TrCP1 suppression increases the expression of Smad4 protein. Consistent with these results, cells that overexpress the SCF complex display an inhibited TGF-beta-dependent transcriptional activity and an impaired cell cycle arrest function. Thus, SCF(beta-TrCP1) abrogates TGF-beta function in vivo by decreasing Smad4 stability.

Blotting, Western↗
PubMed2003

Loss of Smad4 protein expression occurs infrequently in endometrial carcinomas.

Smad4 is a member of the Smad proteins, which are needed for mediating signals of transforming growth factor beta from the cell surface to the nucleus. Smad4 is also a tumor suppressor gene for cancers of the pancreas, colon, and lung. The aim of this study was to investigate the expression and prognostic significance of this gene product in endometrial cancer. Immunohistochemical staining for Smad4 was performed on formalin-fixed, paraffin-embedded specimens of endometrial tumors with an anti-Smad4 monoclonal antibody (clone B8): 97 primary endometrial carcinomas, 20 cases of endometrial hyperplasia, and 26 cases of metastases from endometrial carcinoma. The immunoreactivity of each tumor was correlated with the clinical and histopathologic parameters of the patients. Diffusely positive expression of Smad4 protein was detected in all 20 cases of endometrial hyperplasia and in most of the primary and metastatic endometrial cancers. The frequency of positive expression decreased progressively with tumor grade. Clinically, however, it was not associated with tumor progression, nor did it predict patient outcome. Although loss of heterozygosity at chromosome 18q21 (the location of the Smad4 gene) is frequent in endometrial carcinomas, the authors show in this immunohistochemical study that inactivation of this gene occurs infrequently in this tumor.

Biomarkers, Tumor↗
PubMed2005

Smad4 protein expression correlates with grade, stage, and DNA ploidy in prostatic adenocarcinomas.

The tumor suppressor gene Smad4 (DPC4) has been localized to chromosome 18q21.1 and is a member of the Smad family that mediates the transforming growth factor beta signaling pathway suppressing epithelial cell growth. However, variable expression of this protein has been reported, with a loss in some cancers and increased expression in others. Given both the variability and lack of consensus reported regarding Smad4 expression in prostate cancer, we assessed Smad4 immunoreactivity in prostatic adenocarcinomas (PACs). Formalin-fixed, paraffin-embedded tissue sections from 133 PACs were immunostained by a manual method using indirect biotin streptavidin horseradish peroxidase and diaminobenzidine detection using a monoclonal mouse antihuman Smad4 antibody (sc-7966; Santa Cruz Biotechnology Inc, Santa Cruz, Calif). Nuclear immunoreactivity and cytoplasmic immunoreactivity were each semiquantitatively scored based on intensity and percentage of positive cells. Deoxyribonucelic acid ploidy was determined on Feulgen-stained tissue sections by static image analysis. Results were correlated with morphological and prognostic variables. Variable nuclear and cytoplasmic Smad4 positivity was noted in the adjacent benign glands in all cases. Of 133 PACs, 64 (48%) featured increased nuclear and 68 (51%) featured increased cytoplasmic protein expression. Nuclear Smad4 overexpression correlated with tumor grade (P = .02), stage (P = .04), and DNA ploidy (P = .04). Cytoplasmic overexpression correlated with tumor grade (P = .04) and DNA ploidy (P = .04) while showing a trend for correlation with tumor stage (P = .08). Neither nuclear nor cytoplasmic Smad4 overexpression correlated with postsurgical biochemical disease recurrence. Smad4 protein expression persists in PACs compared with benign glands, with both nuclear and cytoplasmic overexpression correlating with prognostic variables indicative of aggressive tumor behavior. Given the significant reported variability of Smad4 in several different cancers, further studies in prostate and other tumors are warranted to elucidate its role in tumorigenesis.

Adenocarcinoma↗
PubMed1999

Identification of two Smad4 proteins in Xenopus. Their common and distinct properties.

Smad family proteins have been identified as mediators of intracellular signal transduction by the transforming growth factor-beta (TGF-beta) superfamily. Each member of the pathway-restricted, receptor-activated Smad family cooperates and synergizes with Smad4, called co-Smad, to transduce the signals. Only Smad4 has been shown able to function as a common partner of the various pathway-restricted Smads in mammals. Here we have identified a novel Smad4-like molecule in Xenopus (XSmad4beta) as well as a Xenopus homolog of a well established Smad4 (XSmad4alpha). XSmad4beta is 70% identical to XSmad4alpha in amino acid sequence. Both of the Xenopus Smad4s can cooperate with Smad1 and Smad2, the pathway-restricted Smads specific for bone morphogenetic protein and TGF-beta, respectively. However, they show distinct properties in terms of their developmental expression patterns, subcellular localizations, and phosphorylation states. Moreover, XSmad4beta, but not XSmad4alpha, has the potent ability to induce ventralization when microinjected into the dorsal marginal region of the 4-cell stage of the embryos. These results suggest that the two Xenopus Smad4s have overlapping but distinct functions.

Amino Acid Sequence↗
PubMed2002

Role of Smad1 and Smad4 proteins in the induction of p21WAF1,Cip1 during bone morphogenetic protein-induced growth arrest in human breast cancer cells.

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta family of cytokines. The recent observation that BMPs can inhibit breast cancer cell proliferation in vitro suggests that BMPs or the BMP pathway may hold promise as therapeutic targets for the control of breast tumor growth in women. Better to understand the mechanism of BMP-induced growth arrest we examined the effect of BMP-2 and mediators of BMP-2 action on cell proliferation and p21(Cip1) expression in breast cancer cell lines. We show here that BMP-2 potently inhibited the proliferation of breast cancer cell lines that express both Smad1 and Smad4 (CAMA-1, MCF7, MDA-MB-231, T-47D, ZR-75-1), but not that of cells that only express Smad1 (MDA-MB-468). Growth inhibition correlated with up-regulation of p21 mRNA and protein levels. Up-regulation of p21 was resistant to cycloheximide but not to actinomycin D, suggesting that it occurred at the transcriptional level. Using p21 promoter-luciferase reporter constructs we mapped the BMP-responsive region of the p21 promoter to within 211 base pairs of the transcription start site. Induction of p21 promoter activity was rapid and coincided with up-regulation of p21 mRNA and protein levels. p21 promoter activity required both Smad1 and Smad4 and was induced by either BMP-2 or constitutively active type I BMP receptors. Moreover, the C-terminal SSVS region of Smad1 was necessary for activation of the p21 promoter by BMP-2. Taken together, these results indicate that the mechanism of BMP-induced p21 promoter activation involves BMP receptors and BMP Smads.

Blotting, Northern↗
PubMed2001

[Deletion mapping of chromosome 18q and Smad proteins expression analysis in urinary bladder carcinomas].

OBJECTIVE: To investigate the role of loss of heterozygosity (LOH) on chromosome 18q in the carcinogenesis and progression of urinary bladder cancer and to provide clues for early detection and positional cloning of related genes. METHODS: Deletion mapping was performed on 18q using 12 microsatellite markers. Immunohistochemistry staining was used to evaluate the expression level of two tumor suppressor candidates Smad 2 and Smad 4 in this region. RESULTS: LOH in at least one of the 12 microsatellites on 18q was detected in 84.2% (32/38) of patients with bladder cancer. The minimal deletion region included tumor suppressor candidate Smad 4. Immunohistochemical study revealed that 21.1% (8/38) of the cases had up-regulated Smad 2 protein and 34.2% (13/38) of the cases had down-regulated Smad 2 protein. Smad4 protein expression was down-regulated in 68.4% (26/38) of the cases but up-regulated Smad 4 expression was seen in only one case. CONCLUSIONS: LOH on 18q was closely linked with bladder cancer. The irregular expression of tumor suppressor candidates Smad 2 and Smad 4 may play important role in the initiation and progression of bladder neoplasms.

Adolescent↗
PubMed2006

A novel mouse Smad4 mutation reduces protein stability and wild-type protein levels.

Smad4 is a key signal transducer of the transforming growth factor-beta (TGF-beta) superfamily of growth factors that are critical regulators of embryonic patterning and adult tissue homeostasis. The biological activity of the TGF-beta signaling is tightly controlled at multiple levels, including the abundance of SMAD4 proteins. We previously recovered a novel allele of Smad4 in a gene-based screen in N-ethyl-N-nitrosourea (ENU)-mutagenized mouse embryonic stem cells. The mutation resulted in an unstable truncated protein that is degraded through proteasomal pathways. In the heterozygous state, this allele acts in a dominant negative fashion to reduce the wild-type protein level as well as signaling output. Biochemical characterization indicated that the truncated protein is able to form a complex with the wild-type protein, thus targeting it for proteasomal degradation as well. Phenotypic analyses of the heterozygous animals provided insight into the threshold requirement of Smad4-dependent signaling in vivo.

Alleles↗
PubMedDate not supplied

Expression of Smad4 and TGF-beta2 in colorectal carcinoma.

BACKGROUND: TGF-beta, a potent natural antiproliferative agent, is believed to play an important role in suppressing tumorigenicity. This effect is mediated through Smad4, a tumour-suppressor gene, at chromosome 18q21, which affects gene transcription and controls cell growth. The aim of the study was to investigate the expression of Smad4 and TGF-beta2 in colorectal carcinomas and to correlate them with pathological parameters and patient survival. MATERIALS AND METHODS: Formalin-fixed paraffin-embedded tissue from 49 cases of colon carcinoma was stained by immunohistochemistry for TGF-beta2 and Smad4 protein. RESULTS: Smad4 nuclear and cytoplasmic staining was absent in 9/49 (18.3%) or reduced in 18/49 (36. 7%) colorectal carcinoma, while in the remaining 22 (44.8%) Smad4 expression comparable with colonic mucosa was observed. TGF-P2 cytoplasmic staining was expressed in all cases and was overexpressed in 24/49 (48.9%) carcinoma. A statistically significant correlation was found between Smad4 expression and tumour grade (p =0.02) and between TGF-beta2 expression and Dukes' stage (p=0.03). A slight tendency for a relationship between Smad4 and TGF-beta2 (p=0.25) was also observed. No statistically significant relationship between the above markers and survival was detected. CONCLUSION: In poorly-differentiated carcinoma, Smad4 protein expression was retained and may be linked to TGF-beta2 overexpression, due to the activation or deregulation of the TGF-fl signalling pathway. Inactivation of the TGF-beta gene occurs at an early stage of colorectal carcinogenesis, while inactivation of Smad4 is probably a late event.

Colorectal Neoplasms↗
PubMed2000

Expression of Smad4 Gene in Pichia pastoris and Identification of the Protein.

Smad4 is a novel tumor suppressor gene which is mutated or deleted in about 50% of pancreatic carcinoma and 30% of colon cancer. SMAD4 was expressed in Pichia pastoris and was characterized. The molecular weight of the expression product was shown to be about 67 kD, and 13 amino acids in N terminal were determined and were identical with the putative sequence from Smad4 cDNA, and it was able to specifically react with the antibody against SMAD4.

Journal Article↗
PubMed2006

Disruption of transforming growth factor beta-Smad signaling pathway in head and neck squamous cell carcinoma as evidenced by mutations of SMAD2 and SMAD4.

The role of the TGF-beta-Smad signaling pathway in the carcinogenesis of head and neck cancer has not been fully evaluated genetically. In this study, we screened for mutation in the five main members of the TGF-beta -Smad signaling pathway, TGF-beta type I receptor (TGFBRI), TGF-beta type II receptor (TGFBRII), SMAD2, SMAD3 and SMAD4, in eight human head and neck squamous cell carcinoma (HNSCC) cell lines. Two mutations with presumed loss of heterozygosity (LOH) were identified. A novel missense mutation of SMAD2, located in exon 8 at codon 276 TCG (ser) -->TTG (leu), was identified in cell line SCC-15. This is the first report of a biallelic mutation of the SMAD2 gene in HNSCC. A nonsense mutation of the SMAD4 gene in exon 5 codon 245 CAG (glut) -->TAG (stop) was found in cell line CAL27. Western blotting verified that this nonsense mutation gives rise to the complete loss of the Smad4 protein in the cells. While the down-regulation and loss of expressions of the TGF-beta-Smad signaling pathway have been described frequently in HNSCC, here we offer further genetic evidence that the pathway is directly targeted for mutation during the HNSCC tumorigenesis.

Activin Receptors, Type I↗
PubMed2000

Synergistic cooperation between Sp1 and Smad3/Smad4 mediates transforming growth factor beta1 stimulation of alpha 2(I)-collagen (COL1A2) transcription.

Transforming growth factor-beta1 (TGFbeta) is a strong activator of extracellular matrix accumulation. TGFbeta stimulates the gene coding for human alpha2(I)-collagen (COL1A2) by inducing binding of an Sp1-containing complex to an upstream promoter element (TGFbeta responsive element or TbRE) that contains a CAGA box. Here we report that the CAGA box of the TbRE is the binding site of the Smad3/Smad4 complex, and that the binding of the complex is required for TGFbeta-induced COL1A2 up-regulation. Recombinant Smad3 and Smad4 bind in vitro to the CAGA box of COL1A2; TGFbeta treatment of cultured fibroblasts induces Smad3/Smad4 binding to the TbRE; transient overexpression of Smad3 and Smad4 in fibroblasts transactivates TbRE-driven transcription; and COL1A2 gene up-regulation by TGFbeta is abolished in cells stably transfected with plasmids that express dominant negative forms of Smad3 or Smad4. In Sp1-deficient Drosophila Schneider cells, there was cooperative synergy between Smad3/Smad4 and Sp1 at the TbRE site. The analysis also emphasized the requirement of both Sp1- and Smad-binding sites for optimal promoter transactivation. In cells stably transfected with a plasmid expressing a dominant negative form of Sp1, the synergy was shown to be promoter-specific and dependent on the binding of Sp1 to the TbRE. Interestingly, overexpression of dominant negative Sp1 was found to block the antagonistic signal of tumor necrosis factor-alpha on COL1A2 transcription, as well. These results provide the first linkage between the Smad3 and Smad4 proteins and TGFbeta stimulation of type I collagen biosynthesis.

3T3 Cells↗