Smad3 Is Overexpressed in Advanced Human Prostate Cancer and Necessary for Progressive Growth of Prostate Cancer Cells in Nude Mice

Abstract

Purpose: The purpose of this study was to investigate the potential role of Smad3, a key mediator of transforming growth factor-h signaling, in progression of prostate cancer. Experimental Design: Expression of Smad proteins was determined in human prostate cancer tissue array and cell lines. Growth and metastasis of cells overexpressing dominant-negative Smad3 (Smad3D) were studied to determine its role in tumor progression in mice. Cell growth, apoptosis, and expression of angiogenic molecules in tumor lesions were studied to determine potential pathways that Smad3 promotes tumor progression. Results: Smad3 was overexpressed in human prostate cancer, which correlated with Gleason score and expression of proliferating cell nuclear antigen. Androgen-independent PC-3MM2 and DU145 cells expressed much higher levels of Smad3 than did androgen-dependent LNCaP, 22Rv1, and LAPC-4 cells. Overexpression of Smad3D in PC-3MM2 cells (PC-3MM2-Smad3D) had minimal direct effects on cell growth but attenuated effects of transforming growth factor-h1 on gene expression and cell growth. Overexpression of Smad3D did not significantly alter tumor incidence but reduced tumor growth rate and metastasis incidence. Most cells in the control tumors, but not PC-3MM2-Smad3D tumors, were positively stained by an antibody to proliferating cell nuclear antigen. Microvessels and expression of angiogenic molecule interleukin-8 were significantly reduced in tumors from PC-3MM2-Smad3D cells. PC-3MM2-Smad3D tumors also expressed lower levels of vascular endothelial growth factor and platelet-derived growth factor. Conclusions: These data suggest that Smad3, through regulating angiogenic molecule expression in tumor cells, is critical for progression of human prostate cancer.Transforming growth factor-h1 (TGF-h1) is overexpressed in prostate cancer, especially in advanced disease. It has been shown that overexpression of TGF-h1 in prostate cancer tissues and high urinary and serum levels of TGF-h1 are associated with enhanced tumor angiogenesis and tumor metastasis, and poor clinical outcome (1 -3). TGF-h1 induces biological effects through a family of type I and type II transmembrane serine/ threonine kinase receptors. On interaction with TGF-h1, TGF-h receptor (ThR) II recruits ThRI, leading to phosphorylation and activation of ThRI. With the assistance of adapter proteins, ThRI binds the receptor-regulated Smads (Smad2 and/or Smad3) and phosphorylates the Smads at their COOH-terminal SSXS motif. The phosphorylated Smad2 or Smad3 will then associate with the common Smad4, translocate into the nucleus, bind to concatamers of a CAGA sequence (Smadbox), and activate target gene expression through interaction with other transcription factors, such as activator protein-1 and forkhead activin signal transducers (4, 5). TGF-h1 also induces gene transcription through Smad-independent pathways (6). As such, TGF-h1 stimulates TGF-h -activated kinase 1, via TGF-h -activated kinase 1 binding protein 1, and leads to the activation of transcription ...

MED12 overexpression is a frequent event in castration-resistant prostate cancer

“…Recent studies have reported that SMAD3 is overexpressed in PCa tissues and is necessary for progressive growth of PCa cells in nude mice (Lu et al 2007). On the basis of these results and results from other studies showing that MED12 is implicated in TGFb-receptor regulation (Huang et al 2012) and our findings that MED12 has increased expressed in castration-resistant PCa tissues, we aimed to investigate whether MED12 is implicated in TGFb signaling in PCa.…”

“…In addition, activation of TGFb signaling has been shown to increase the invasive and migratory behavior of PCa cells (Walker et al 2013), and inhibition of TGFb signaling reduced tumor growth and/or invasiveness in vivo (Gaspar et al 2007, Moore et al 2008. Furthermore, a study in 2007 has shown that SMAD-dependent TGFb signaling is critical for PCa growth and progression in nude mice (Lu et al 2007). The response of metastatic PCa cell lines to TGFb depends on the cellular microenvironment.…”

Opposite functions of HIF-α isoforms in VEGF induction by TGF-β1 under non-hypoxic conditions

“…TGF-b1 functions as a paracrine growth inhibitor in normal cells of the epithelial lineage by inducing cell cycle arrest and apoptosis, and many human cancers escape from TGF-b1-mediated growth suppression by mutational alterations of its receptors or Smads (Markowitz et al, 1995). Unlikely normal epithelial cells, carcinoma cells produce active TGF-b1, which promotes tumor growth, migration and metastasis (Stearns et al, 1999;Zhu and Kyprianou, 2005;Lu et al, 2007;Pu et al, 2009). In prostate tumorigenesis, TGF-b1 has biphasic functions, having a growth inhibitory effect at early stages, but at later stages enhancing the malignant properties of tumors.…”

“…However, both intracellular and serum TGF-b1 levels are elevated in cancer patients and further increased in patients with metastatic carcinoma (Truong et al, 1993). Several studies have shown that prostate cancer cells are resistant to TGF-b1-induced growth inhibition, and TGF-b1 actually promotes tumor growth, migration and metastasis, indicating that TGF-b1 action is oncogenically conversed in the process of tumorigenesis (Stearns et al, 1999;Zhu and Kyprianou, 2005;Lu et al, 2007;Pu et al, 2009). We reported that TGF-b1 promotes cellular proliferation of prostate carcinomas through the activation of Ras/MAPK signaling and induction of tumor-promoting genes, such as interleukin-6, indicating that prostate cancers have a selective growth advantage by autocrine TGF-b1 production (Park et al, 2000(Park et al, , 2003.…”

Argonaute-1 Machinery Silent Cancer Noises

“…Many proliferation promoting and protooncogenes are illustrated in these pathways including serine/threonine/ tyrosine kinases, G-protein coupled receptors (GPCs), membrane associated G-proteins, growth factors; DNA-binding protein factors and transcription factors as well. A large number of genes grouped under AbG-0.5 kb gene group such as CDC20 (Cell Division Cycle 20), SMC1A (Structural Maintenance of Chromosomes 1A), BUB1 (budding uninhibited by benzimidazoles 1) and SMAD3 (Mothers against Decapentaplegic Homolog 3) are known to promote cell cycle progression and proliferation in different cancer types [80][81][82][83]. Gene Ontology (GO) classification and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis also reported that AGO1-regulated genes (ArGs), regulate various cancer related pathways and they shared this with AbGs-5 kb genes including cell cycle regulation, MAPK signalling pathway, p53 signaling pathway in various cancers Regulation of pre-mRNAs by MALAT (Metastasis Associated Lung Adenocarcinoma Transcript 1) was the first demonstration of the regulation of alternative splicing by endogenous sRNA pathways [63].…”