Role Of Ets Factors Research Articles

BRAF-induced EHF expression affects TERT in aggressive papillary thyroid cancer.

BRAFV600E and TERT promoter mutations in papillary thyroid carcinoma (PTC) have a synergistic effect on prognosis. This effect is believed to arise from MAPK activation triggered by BRAFV600E, leading to the upregulation of ETS transcription factors that bind to the mutant TERT promoter. To explore the role of ETS factors in relation to clinical features, BRAFV600E and TERT promoter mutations in PTC. Transcriptomic data for 28 ETS factors were analyzed in the PTC cohort of The Cancer Genome Atlas (TCGA, n=399) and subsequently validated in a local cohort (n=93). In vitro experiments were performed to investigate the regulatory role in relation to BRAFV600E and TERT expression. TCGA identified ETS1, ERG, FLI1, GABPA, EHF, ETV6 and SPDEF as differentially expressed genes between stages I+II and III+IV. In both cohorts, EHF was consistently associated with adverse clinical features, BRAFV600E and TERT promoter mutation/expression. Notably, in BRAFV600E mutated PTC, high EHF expression was associated with shorter disease-free survival. Cases harboring concurrent BRAFV600E, TERT promoter mutations and high EHF expression exhibited the shortest disease-free survival. In cells harboring concurrent BRAFV600E and TERT promoter mutation, over-expression of EHF significantly increased TERT expression while knockdown or pharmacological inhibition of BRAF significantly decreased both EHF and TERT expression. In addition, ChIP-qPCR analysis suggested a potential binding of EHF in TERT promoter mutant cells but not in TERT promoter wild-type cells. The ETS transcription factor EHF is associated with poor prognosis in PTC. This is potentially mediated by BRAF-induced upregulation of EHF which in turn increases TERT expression in TERT promoter mutated cells.

Abstract PR1: Oncogenic ETS over-expression mimics RAS/MAPK signaling in prostate cells

Abstract The aberrant expression of an oncogenic ETS transcription factor is implicated in the progression of the majority of prostate cancers. The prostate cancer chromosomal rearrangements that drive over-expression are associated with one of four ETS genes, ERG, ETV1, ETV4 and ETV5. It is not clear how these four oncogenic ETS genes differ from the numerous other ETS genes expressed in normal prostate. We report that these oncogenic ETS proteins, but not other ETS factors, enhance prostate cell migration. Genome-wide binding analysis matched this specific biological function to occupancy of a unique set of genomic sites highlighted by the presence of ETS and AP-1 binding sequences. ETS/AP-1 binding sequences are prototypical RAS-responsive elements, but oncogenic ETS proteins activated a RAS/MAPK transcriptional program in the absence of MAPK activation. Thus, overexpression of oncogenic ETS proteins can replace RAS/MAPK pathway activation in prostate cells. The genomic description of this ETS/AP-1 regulated, RAS-responsive, gene expression program provides a resource for understanding the role of ETS factors in both prostate cancer and other cancers with either ETS or RAS pathway mutations. This abstract is also presented as Poster B26. Citation Format: Peter C. Hollenhorst, Mary W. Ferris, Megan A. Hull, Heejoon Chae, Sun Kim, Barbara J. Graves. Oncogenic ETS overexpression mimics RAS/MAPK signaling in prostate cells [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr PR1.

Abstract 3492: NET as a repressor on transcriptional regulation of MT1-MMP in endothelial cells

Abstract In mice deficient for the Ets family genes, disrupted angiogenesis and malformed vascular system inform critical role of Ets factors in vasculogenesis and angiogenesis. NET is a member of ETS transcription factors and acts as a repressor of transcription. To find role of NET in angiogenesis, angiogenesis related assay were carried out using NET specific siRNA. In addition, it was confirmed regulation of NET on transcription of angiogenesis-regulated genes. Our results showed that suppression of NET expression result in buildup of VEGF-induced tube formation. In addition, suppressed expression of NET induced expression of MT1-MMP. Induction of MT1-MMP expression by knock down of NET expression was not result direct effect of NET on transcription of MT1-MMP in endothelial cells. In endothelial cell, NET suppressed ETS-1 induced-transcriptional activity of MT1-MMP. Our results suggest that NET is a negative regulator of angiogenesis on indirect regulation of MT1-MMP and induction of tube formation by its expressional suppression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3492. doi:10.1158/1538-7445.AM2011-3492

ETS Transcription Factors in the Tumor Microenvironment

ETS factors are involved in cancer progression through transcriptional regulation of factors mediating cell cycle, cell growth, apoptosis, cell adhesion and migration. The biological processes regulated by ETS factors are important not only in tumor cells, but also in the surrounding cells comprising the tumor microenvironment. Additionally, ETS factors can serve as transcriptional activators and repressors to regulate gene expression in a cell context-specific fashion. Here we discuss recent advances in which the regulatory roles of ETS factors in stromal cells are critical during both development and cancer. These new findings uncover the importance of ETS signaling in the stromal compartment of tumors and shed light on new potential mechanisms of ETS factors.

ETS‐family genes in pancreatic development

ETS-family factors play major roles in development and cancer, notably as critical targets for extra-cellular signaling pathways, including MAPK-signaling. Given the presently limited knowledge on the role of ETS-factors in pancreatic development, we here sought to characterize all 26 individual members of the ETS-family in relation to pancreatic development using a combination of genomics, RT-PCR, and histological techniques. This analysis uncovers 22 ETS family genes displaying select spatial and temporal expression patterns in the developing pancreas. Highly specific expression of ETS-family components is observed in pancreatic progenitor cells or the associated embryonic mesenchyme. Other members are linked to the differentiation of more mature pancreatic cells, including exocrine and endocrine cell types. We find that two members of the Etv subfamily, Etv4 and Etv5, are expressed in cells proximal to pancreatic mesenchyme, and, furthermore, induced in FGF10-arrested pancreatic progenitors suggesting that these factors mediate mesenchymal-to-epithelial signaling.

ETS transcription factors and regulation of immunity

The ETS family is a diverse group of transcription factors that control the expressions of genes that participate in an array of cellular activities, ranging from mitosis to apoptosis. As a consequence of regulating these processes, most ETS factors are oncogenic. However, there is growing evidence that ETS factors are also essential to regulation of the immune system. Of the 29 recognized ETS factors, nine are known to regulate genes involved in immunity, including Ets1, Ets2, GABP, Fli1, Elf1, MEF, ESE1, PU.1, and SpiB. These ETS factors typically activate the transcription of genes associated with pathogen and tumor defense, but several also demonstrate ability to repress transcription. Ets1 and PU.1 appear to have the greatest impact on immunity, primarily through their control of immune cell development. Alterations of Fli1 and Elf1 expression are associated with autoimmunity, emphasizing the role of ETS factors as not only positive, but also negative regulators of immunity. This review summarizes the roles of ETS factors in development of the immune system, defense against pathogens and malignancies, and self-tolerance.

Selective repression of rat prolactin gene by stable expression of dominant-negative Ets in GH4 pituitary cells.

Members of the Ets family of transcription factors are key regulators controlling prolactin (PRL) gene expression. Utilizing a transient transfection approach and the GH4 rat pituitary cell line, we have shown that Ets- 1 acts synergistically with the pituitary-specific POU homeodomain transcription factor, Pit-1, to mediate basal and Ras-induced regulation of the proximal (-425) rat PRL (rPRL) promoter. Although the transient transfection approach has provided important information regarding rPRL proximal promoter regulation, the role of Ets factors in the regulation of the intact, endogenous PRL promoter has not been explored. To address this area of question, we created several clonal GH4 cell lines that stably express either dominant-negative Ets (dn-EtsZ) or dominant-active Ets (VP16 Ets) constructs and used these cell lines as a model system to analyze the role of Ets factors on endogenous PRL gene expression. Northern blot analysis of these cells showed that PRL mRNA levels were dramatically reduced, by an average of 80%, in the cell lines expressing dn-Ets compared to vector-only controls. Conversely, stable expression of the dominant-active VP16 Ets led to an average threefold increase in PRL mRNA. GH4 cells expressing dn-EtsZ displayed significantly lower levels of intracellular PRL protein content and greatly diminished secretion of PRL into the cell culture medium, compared to vector-only controls. Consistent with our previous observations, the mRNA levels for growth hormone were unaffected by either dn-EtsZ or VP16 Ets expression. Expression of dn-EtsZ reduced Pit-1 mRNA levels by about 30%; however, the intracellular levels of Pit-1 protein were unchanged. Taken together, these results verify and strengthen the view that Ets factors play a critical role in the regulation of endogenous PRL gene expression and PRL protein production.

Fli-1 Inhibits Collagen Type I Production in Dermal Fibroblasts via an Sp1-dependent Pathway

Fibrosis is characterized by the excessive deposition of extracellular matrix (ECM), especially collagen. Because Ets factors are implicated in physiological and pathological ECM remodeling, the aim of this study was to investigate the role of Ets factors in collagen production. We demonstrate that the expression of collagenous proteins and collagen alpha2(I) (COL1A2) mRNA was inhibited following stable transfection of Fli-1 in dermal fibroblasts. Subsequent analysis of the COL1A2 promoter identified a critical Ets binding site that mediates Fli-1 inhibition. In contrast, Ets-1 stimulates COL1A2 promoter activity. In vitro binding assays demonstrate that both Fli-1 and Ets-1 form DNA-protein complexes with sequences present in COL1A2 promoter. Furthermore, Fli-1 binding to the COL1A2 is enhanced via Sp1-dependent interaction. Studies using Fli-1 dominant interference and DNA binding mutants indicate that Fli-1 inhibition is mediated by both direct (DNA binding) and indirect (via protein-protein interaction) mechanisms and that Sp1 is an important mediator of the Fli-1 function. Furthermore, experiments using the Gal4 system in the context of different cell types as well as experiments with the COL1A2 promoter in different cell lines demonstrate that the direction and magnitude of the effect of Fli-1 is promoter- and cell context-specific. We propose that Fli-1 inhibits COL1A2 promoter activity by competition with Ets-1. In addition, we postulate that another factor (co-repressor) may be required for maximal inhibition after recruitment to the Fli-1-Sp1 complex. We conclude that the ratio of Fli-1 to Ets-1 and the presence of co-regulatory proteins ultimately control ECM production in fibroblasts.

Ets factors and regulation of the extracellular matrix.

Ets factors are critical mediators of extracellular matrix (ECM) remodelling. As the spectrum of Ets-regulated target genes widens, so does their role in various pathological and physiological processes. Regulation of matrix degrading proteases by Ets factors in tumor invasion and metastasis is well established. Emerging evidence suggests that they may also play a role in the pathology of autoimmune diseases. Newly characterized Ets target genes such as tenascin-C and collagen type I suggest their role in diseases characterized by aberrant collagen deposition (fibrosis). Ets function is also critical in bone and cartilage development. There is increasing knowledge of the complex regulatory mechanisms involved in transcription of Ets target genes. Ets factors may function as activators or as repressors via association with specific cofactors depending on the promoter context. Signaling pathways can modulate the activation status of Ets factors and their transcriptional partners. Precise understanding of the role of Ets factors in the complex cellular network governing the expression of ECM proteins and the enzymes that degrade them will be a focus of future studies.

Role of ets factors in the activity and endothelial cell specificity of the mouse Tie gene promoter.

The Tie gene encodes an endothelial cell receptor tyrosine kinase necessary for normal vascular development. The Tie gene promoter targets expression of heterologous genes specifically to endothelial cells in transgenic mice. Here we have characterized the promoter sequences critical for endothelial cell-specific activity in cultured cells and transgenic mice. Progressive deletions and site-directed mutations of the promoter showed that the critical endothelial cell-specific elements are an octamer transcription factor binding site and several Ets binding sites located in two clusters within 300 bp upstream of the major transcription initiation site. Among members of the Ets transcription factor family tested, NERF-2 (a novel transcription factor related to the ets factor ELF-1), which is expressed in endothelial cells, and ETS2 showed the strongest transactivation of the Tie promoter; ETS1 gave lower levels of stimulation and the other Ets factors gave little or no transactivation. Furthermore, the Tie promoter directed the production of high amounts of human growth hormone into the circulation of transgenic mice. The secreted amounts correlated with transgene copy number, being relatively insensitive to the effects of the transgene integration site. These properties suggest that Tie promoter activity is controlled by endothelial cell Ets factors and that it has potential for use in vectors for endothelial cell-specific gene expression.