Ets Related Gene and Smad3 Proteins Collaborate to Activate Transforming Growth Factor-Beta Mediated Signaling Pathway in ETS Related Gene-Positive Prostate Cancer Cells

Abstract

TGF-β/Smads signaling plays a significant role in the regulation of growth of normal and prostate cancer cells. Smad proteins function as important mediators of intracellular signal transduction of transforming growth factor-β (TGF-β). TGF-β signaling pathway is known to regulate cell proliferation, differentiation, apoptosis and play a major role in some human diseases and cancers. Following their phosphorylation by TGF-β receptor-I, Receptor-regulated Smads (including Smad2 and Smad3 proteins) form a heteromeric complex with co-Smad (Smad4) and then translocate into the nucleus where they bind and regulate the expression of target genes. ERG (Ets Related Gene) belongs to the ETS family of transcriptional factors. Chromosomal rearrangement of TMPRSS2 gene and ERG gene has been found in majority of prostate cancers. Over-expression of full length or truncated ERG proteins have been shown to associate with a higher rate of recurrent and unfavorable prognosis of prostate cancer. In order to understand how ERG oncoprotein regulates TGF-β/Smads signaling pathway, we have studied the effect of ERG on TGF-β/Smad3 signaling pathway. In this study, we demonstrate that ERG oncoprotein physically interacts with Smad3 protein and stabilizes phospho-Smad3 protein and thereby enhance TGF-β/Smad3 signaling pathway in prostate cells. Thus, ERG oncoprotein plays an important role in prostate tumorigenesis by using a novel mechanism to activate TGF-β/Smad3 signaling pathway.

Dynamic regulation of canonical TGFβ signalling by endothelial transcription factor ERG protects from liver fibrogenesis

“…We demonstrate that ERG directly represses SMAD2/3 transcriptional activity, independently of expression of SMAD2/3 or its receptor ALK5. We find that ERG can interact with SMAD2/3 in HUVEC and in HSEC in agreement with studies that show overexpression of exogenous ERG and SMAD3 results in protein interaction 36, 37 . ERG and SMAD3 both bind to the promoters of target genes, indicating that ERG acts as a co-repressor for SMAD3.…”

“…Cells were collected in lysis buffer (50 mM Tris, pH 7.5, 150 mM NaCl, 0.1% Igepal, 1 mM EDTA, 0.25% sodium deoxycholate) 37 supplemented with 1 mM phenylmethylsufony fluoride (PMSF), protease inhibitor cocktail, and phosphatase inhibitor cocktail 2 and 3 (Sigma). Endonuclease treatment was conducted with the addition of 500 units of Benzonase (Sigma-Aldrich, UK) for 1 h at room temperature.…”

Up-regulation of Biglycan is Associated with Poor Prognosis and PTEN Deletion in Patients with Prostate Cancer

“…It is well known that about 50% of all prostate cancers carry a gene fusion linking the androgen-regulated serine protease TMPRSS2 with the ETS-transcription factor ERG resulting in an androgen-related overexpression of ERG with subsequent transcriptional deregulation of more than 1600 ERG target genes [21] , [43] , [44] . Others and we have shown that activation of the TGF-ß signaling pathway is one important consequence of ERG fusion in prostate cancer [44] , [45] , [46] . That the extracellular matrix modulator TGF-β1 is an important stimulator of BGN transcriptional and post translational modifications [47] , [48] provides a mechanistic explanation for the higher fraction of cancers with BGN up-regulation in ERG-positive as compared to ERG-negative cancers.…”

Relationship between ETS Transcription Factor ETV1 and TGF-β-regulated SMAD Proteins in Prostate Cancer

“…This implies that ETV1 overexpression restrains its own oncogenic impact, at least during the initial PIN phase of prostate tumorigenesis, by causing SMAD3/4 overexpression. Although we have not investigated the mechanism, one speculation is that interaction with ETV1 might stabilize SMAD proteins, similar as has been observed for SMAD3 and another ETS transcription factor, the ERG oncoprotein 46 . However, in contradiction to this hypothesis, we observed no alteration of SMAD3/4 protein levels in PC3 prostate cancer cells upon ETV1 downregulation (see Fig.…”