REST promotes ETS1-dependent vascular growth in medulloblastoma.

Expression of the RE1-silencing transcription factor (REST), a master regulator of neurogenesis, is elevated in medulloblastoma (MB) tumors. A cell-intrinsic function for REST in MB tumorigenesis is known. However, a role for REST in the regulation of MB tumor microenvironment has not been investigated. Here, we implicate REST in remodeling of the MB vasculature and describe underlying mechanisms. Using RESTTG mice, we demonstrate that elevated REST expression in cerebellar granule cell progenitors, the cells of origin of sonic hedgehog (SHH) MBs, increased vascular growth. This was recapitulated in MB xenograft models and validated by transcriptomic analyses of human MB samples. REST upregulation was associated with enhanced secretion of proangiogenic factors. Surprisingly, a REST-dependent increase in the expression of the proangiogenic transcription factor E26 oncogene homolog 1, and its target gene encoding the vascular endothelial growth factor receptor-1, was observed in MB cells, which coincided with their localization at the tumor vasculature. These observations were confirmed by RNA-Seq and microarray analyses of MB cells and SHH-MB tumors. Thus, our data suggest that REST elevation promotes vascular growth by autocrine and paracrine mechanisms.

RNA-Seq analysis on ets1 mutant embryos of Xenopus tropicalis identifies microseminoprotein beta gene 3 as an essential regulator of neural crest migration.

The proto-oncogene ets1 is highly expressed in the pre-migratory and migratory neural crest (NC), and has been implicated in the delamination and migration of the NC cells. To identify the downstream target genes of Ets1 in this process, we did RNA sequencing (RNA-Seq) on wild-type and ets1 mutant X. tropicalis embryos. A list of genes with significantly differential expression was obtained by analyzing the RNA-Seq data. We validated the RNA-Seq data by quantitative PCR, and examined the expression pattern of the genes identified from this assay with whole mount in situ hybridization. A majority of the identified genes showed expression in migrating NC. Among them, the expression of microseminoprotein beta gene 3 (msmb3) was positively regulated by Ets1 in both X. laevis and X. tropicalis. Knockdown of msmb3 with antisense morpholino oligonucleotides or disruption of msmb3 by CRISPR/Cas9 both impaired the migratory streams of NC. Our study identified msmb3 as an Ets1 target gene and uncovered its function in maintaining neural crest migration pattern.

ETS-1 induces Sorafenib-resistance in hepatocellular carcinoma cells via regulating transcription factor activity of PXR.

Transcription factor E26 transformation specific sequence 1 (ETS-1) is a primary regulator in the metastasis of human cancer cells, especially hepatocellular carcinoma (HCC) cells; and it would affect the prognosis of HCC patients who received chemotherapies. However, the regulatory role of ETS-1 in the resistance of HCC cells to molecular-targeting agent remains poorly understood. In the present work, we demonstrate that high ETS-1 expression correlates with poor prognosis of advanced HCC patients received Sorafenib treatment. Mechanistically, ETS-1 binds to nuclear Pregnane X receptor (PXR) directly and enhances PXR's transcription factor activity, which further leads to the induction of the PXR's downstream multi-drug resistance related genes. Overexpression of ETS-1 accelerates the metabolic clearance of Sorafenib in HCC cells and leads to the better survival and faster migration of those cells. The therapeutic studies show that ETS-1 promotes the Sorafenib-resistance of HCC tumor models and ETS-1 blockade enhances the anti-tumor capacity of Sorafenib by decreasing PXR activation. Thus, our study suggests that ETS-1 could enhance the activation of PXR and be a potential therapeutic target for overcoming Sorafenib resistance in HCC treatment.

Experimental and integrative analyses identify an ETS1 network downstream of BCR-ABL in chronic myeloid leukemia (CML).

The BCR-ABL oncogene, the hallmark of chronic myeloid leukemia (CML), has been shown to activate several signaling pathways in leukemic cells. The natural history of this disease has been radically modified by tyrosine kinase inhibitors (TKIs). However, resistance to several lines of TKI therapies and progression to blast crisis (BC) remain significant concerns. To identify novel signaling pathways induced by BCR-ABL, we performed a transcriptome analysis in a BCR-ABL-expressing UT-7 cell line. More than 2000 genes differentially expressed between BCR-ABL-expressing and parental UT-7 cells were identified and ETS1 was found to be the most upregulated. ETS1 protein expression was also shown to be highly increased in UT-7 cells expressing BCR-ABL either constitutively or under the control of TET-inducible promoters. ETS1 expression is tyrosine-kinase dependent because it was reduced by TKIs. A significant increase of ETS1 messenger RNA (mRNA) expression was observed in blood cells from CML patients at diagnosis compared with healthy controls. Integration of publicly available chromatin immunoprecipitation sequencing and transcriptomic data with our results allowed us to identify potential ETS1 targets, some of which are involved in the progression of CML. The messenger RNA expression of two of these genes (DNM3 and LIMS1) was found to be associated with the absence of major cytogenetic response after 1 year of imatinib therapy. The present work demonstrates for the first time the involvement of the ETS1 transcriptional program in the experimental UT-7 model and a large cohort of CML patients.

DOT1L promotes angiogenesis through cooperative regulation of VEGFR2 with ETS-1.

Histone methyltransferase DOT1L is implicated in various biological processes including cell proliferation, differentiation and embryogenesis. Gene ablation of Dot1l results in embryonic lethality and cardiovascular defects including decreased vasculature. However, how DOT1L might contribute to the development of vasculature is not clear. Here, we report that DOT1L is required for angiogenesis. We demonstrated that silencing of DOT1L in human umbilical vein endothelial cells (HUVECs) leads to decreased cell viability, migration, tube formation, and capillary sprout formation in vitro, as well as reduced formation of functional vascular networks in matrigel plugs in vivo. Genome-wide analysis of DOT1L targets via H3K79me2 ChIP-seq annotation in HUVECs identified a number of genes including VEGFR2 that are critically involved in angiogenesis. We showed that DOT1L cooperates with transcription factor ETS-1 to stimulate the expression of VEGFR2, thereby activating ERK1/2 and AKT signaling pathways and promoting angiogenesis. Our study revealed a mechanistic role for DOT1L in the promotion of angiogenesis, adding to the understanding of the biological function of this histone methyltransferase.

Enhanced MAPK signaling drives ETS1-mediated induction of miR-29b leading to downregulation of TET1 and changes in epigenetic modifications in a subset of lung SCC.

Non-small-cell lung cancer is the leading cause of cancer death worldwide and is comprised of several histological subtypes, the two most common being adenocarcinoma (AC) and squamous cell carcinoma (SCC). Targeted therapies have successfully improved response rates in patients with AC tumors. However, the majority of SCC tumors lack specific targetable mutations, making development of new treatment paradigms for this disease challenging. In the present study, we used iterative non-negative matrix factorization, an unbiased clustering method, on mRNA expression data from the cancer genome atlas (TCGA) and a panel of 24 SCC cell lines to classify three disease segments within SCC. Analysis of gene set enrichment and drug sensitivity identified an immune-evasion subtype that showed increased sensitivity to nuclear factor-κB and mitogen-activated protein kinase (MAPK) inhibition, a replication-stress associated subtype that showed increased sensitivity to ataxia telangiectasia inhibition, and a neuroendocrine-associated subtype that showed increased sensitivity to phosphoinositide 3-kinase and fibroblast growth factor receptor inhibition. Additionally, each of these subtypes exhibited a unique microRNA expression profile. Focusing on the immune-evasion subtype, bioinformatic analysis of microRNA promoters revealed enrichment for binding sites for the MAPK-driven ETS1 transcription factor. Indeed, we found that knockdown of ETS1 led to upregulation of eight microRNAs and downregulation of miR-29b in the immune-evasion subtype. Mechanistically, we found that miR-29b targets the DNA-demethylating enzyme, TET1, for downregulation resulting in decreased 5-hmC epigenetic modifications. Moreover, inhibition of MAPK signaling by gefitinib led to decreased ETS1 and miR-29b expression with a corresponding increase in TET1 expression and increase in 5-hmC. Collectively, our work identifies three subtypes of lung SCC that differ in drug sensitivity and shows a novel mechanism of miR-29b regulation by MAPK-driven ETS1 expression which leads to downstream changes in TET1-mediated epigenetic modifications.

Transcription factor Ets-1 links glucotoxicity to pancreatic beta cell dysfunction through inhibiting PDX-1 expression in rodent models.

AIMS/HYPOTHESIS: 'Glucotoxicity' is a term used to convey the negative effect of hyperglycaemia on beta cell function; however, the underlying molecular mechanisms that impair insulin secretion and gene expression are poorly defined. Our objective was to define the role of transcription factor v-ets avian erythroblastosis virus E26 oncogene homologue 1 (Ets-1) in beta cell glucotoxicity. METHODS: Primary islets and Min6 cells were exposed to high glucose and Ets-1 expression was measured. Recombinant adenovirus and transgenic mice were used to upregulate Ets-1 expression in beta cells in vitro and in vivo, and insulin secretion was assessed. The binding activity of H3/H4 histone on the Ets-1 promoter, and that of forkhead box (FOX)A2, FOXO1 and Ets-1 on the Pdx-1 promoter was measured by chromatin immunoprecipitation and quantitative real-time PCR assay. RESULTS: High glucose induced upregulation of Ets-1 expression and hyperacetylation of histone H3 and H4 at the Ets-1 gene promoter in beta cells. Ets-1 overexpression dramatically suppressed insulin secretion and biosynthesis both in vivo and in vitro. Besides, Ets-1 overexpression increased the activity of FOXO1 but decreased that of FOXA2 binding to the pancreatic and duodenal homeobox 1 (PDX-1) homology region 2 (PH2), resulting in inhibition of Pdx-1 promoter activity and downregulation of PDX-1 expression and activity. In addition, high glucose promoted the interaction of Ets-1 and FOXO1, and the activity of Ets-1 binding to the Pdx-1 promoter. Importantly, PDX-1 overexpression reversed the defect in pancreatic beta cells induced by Ets-1 excess, while knockdown of Ets-1 prevented hyperglycaemia-induced dysfunction of pancreatic beta cells. CONCLUSIONS/INTERPRETATION: Our observations suggest that Ets-1 links glucotoxicity to pancreatic beta cell dysfunction through inhibiting PDX-1 expression in type 2 diabetes.

Association of E26 Transformation Specific Sequence 1 Variants with Rheumatoid Arthritis in Chinese Han Population.

OBJECTIVE: E26 transformation specific sequence 1 (ETS-1) belongs to the ETS family of transcription factors that regulate the expression of various immune-related genes. Increasing evidence indicates that ETS-1 could contribute to the pathogenesis of autoimmune disease. Recent research has provided evidence that ETS-1 might correlate with rheumatoid arthritis (RA), but it's not clearly defined. In this study, we aimed to identify whether polymorphisms of ETS-1 play a role in Rheumatoid arthritis (RA) susceptibility and development in Chinese Han population. METHODS: Four single nucleotide polymorphisms (SNPs) within ETS-1 were selected based on HapMap data and previous associated studies. Whole blood and serum samples were obtained from 158 patients with RA and 192 healthy subjects. Genotyping was performed with polymerase chain reaction-high resolution melting (PCR-HRM) assay and the data was analyzed using SPSS17.0. RESULTS: A significantly positive correlation was observed between the SNP rs73013527 of ETS-1 and RA susceptibility, DAS28 and CRP (P<0.001, P = 0.001, and P = 0.028, respectively). Carriers of the haplotype CCT or TCT for rs4937333, rs11221332 and rs73013527 were associated with decreased risk of RA as compared to controls. No statistical significant difference was observed in the distribution of rs10893872, rs4937333 and rs11221332 genotypes between RA patients and controls. CONCLUSIONS: Our data further supports that ETS-1 has a relevant role in the pathogenesis and development of RA. Allele T of rs73013527 plays a protective role in occurrence of RA but a risk factor in the high disease activity. Rs10893872, rs11221332 and rs4937333 are not associated with RA susceptibility and clinical features.

ETS1 induces human trophoblast differentiation.

A possible role for the transcription factor v-ets avian erythroblastosis virus E26 oncogene homolog 1 (ETS1) in human trophoblast cell differentiation was examined using a highly enriched fraction of human mononuclear cytotrophoblast cells (CTBs) that differentiate spontaneously in vitro to a multinucleated syncytiotrophoblast cell (STB) phenotype. ETS1 mRNA and protein levels were abundant in freshly isolated CTBs and decreased as the cells differentiated. Silencing of ETS1 expression in freshly prepared CTBs markedly attenuated syncytialization, as demonstrated by desmoplakin staining, and blocked the induction of syncytin, the transcription factor activator protein-2α, placental lactogen, and other STB-specific genes. Conversely, overexpression of ETS1 in primary trophoblast cells induced STB marker gene mRNAs and transactivated each of the gene proximal promoters. Taken together, these findings strongly suggest a critical role for ETS1 in the induction of human villus CTB differentiation. The effect of ETS1 on syncytialization likely results, at least in part, from inhibition of syncytin expression, whereas the induction of STB marker genes likely results in part from transactivation by activator protein-2α.

Dual developmental role of transcriptional regulator Ets1 in Xenopus cardiac neural crest vs. heart mesoderm.

AIMS: Ets1 is an important transcription factor that is expressed in both the cardiac neural crest (NC) and heart mesoderm of vertebrate embryos. Moreover, Ets1 deletion in humans results in congenital heart abnormalities. To clarify the functional contributions of Ets1 in cardiac NC vs. heart mesoderm, we performed tissue-targeted loss-of-function analysis to compare the relative roles of Ets1 in these two tissues during heart formation using Xenopus embryos as a model system. METHODS AND RESULTS: We confirmed by in situ hybridization analysis that Ets1 is expressed in NC and heart mesoderm during embryogenesis. Using a translation-blocking antisense morpholino to knockdown Ets1 protein selectively in the NC, we observed defects in NC delamination from the neural tube, collective cell migration, as well as segregation of NC streams in the cranial and cardiac regions. Many cardiac NC cells failed to reach their destination in the heart, resulting in defective aortic arch artery formation. A different set of defects was noted when Ets1 knockdown was targeted to heart mesoderm. The formation of the primitive heart tube was dramatically delayed and the endocardial tissue appeared depleted. As a result, the conformation of the heart was severely disrupted. In addition, the outflow tract septum was missing, and trabeculae formation in the ventricle was abolished. CONCLUSION: Our study shows that Ets1 is required in both the cardiac NC and heart mesoderm, albeit for different aspects of heart formation. Our results reinforce the suggestion that proper interaction between these tissues is critical for normal heart development.

ETS1 is a genome-wide effector of RAS/ERK signaling in epithelial cells.

The RAS/ERK pathway is commonly activated in carcinomas and promotes oncogenesis by altering transcriptional programs. However, the array of cis-regulatory elements and trans-acting factors that mediate these transcriptional changes is still unclear. Our genome-wide analysis determined that a sequence consisting of neighboring ETS and AP-1 transcription factor binding sites is enriched near cell migration genes activated by RAS/ERK signaling in epithelial cells. In vivo screening of candidate ETS proteins revealed that ETS1 is specifically required for migration of RAS/ERK activated cells. Furthermore, both migration and transcriptional activation through ETS/AP-1 required ERK phosphorylation of ETS1. Genome-wide mapping of multiple ETS proteins demonstrated that ETS1 binds specifically to enhancer ETS/AP-1 sequences. ETS1 occupancy, and its role in cell migration, was conserved in epithelial cells derived from multiple tissues, consistent with a chromatin organization common to epithelial cell lines. Genome-wide expression analysis showed that ETS1 was required for activation of RAS-regulated cell migration genes, but also identified a surprising role for ETS1 in the repression of genes such as DUSP4, DUSP6 and SPRY4 that provide negative feedback to the RAS/ERK pathway. Consistently, ETS1 was required for robust RAS/ERK pathway activation. Therefore, ETS1 has dual roles in mediating epithelial-specific RAS/ERK transcriptional functions.

Additive effects of microRNAs and transcription factors on CCL2 production in human white adipose tissue.

Adipose tissue inflammation is present in insulin-resistant conditions. We recently proposed a network of microRNAs (miRNAs) and transcription factors (TFs) regulating the production of the proinflammatory chemokine (C-C motif) ligand-2 (CCL2) in adipose tissue. We presently extended and further validated this network and investigated if the circuits controlling CCL2 can interact in human adipocytes and macrophages. The updated subnetwork predicted that miR-126/-193b/-92a control CCL2 production by several TFs, including v-ets erythroblastosis virus E26 oncogene homolog 1 (avian) (ETS1), MYC-associated factor X (MAX), and specificity protein 12 (SP1). This was confirmed in human adipocytes by the observation that gene silencing of ETS1, MAX, or SP1 attenuated CCL2 production. Combined gene silencing of ETS1 and MAX resulted in an additive reduction in CCL2 production. Moreover, overexpression of miR-126/-193b/-92a in different pairwise combinations reduced CCL2 secretion more efficiently than either miRNA alone. However, although effects on CCL2 secretion by co-overexpression of miR-92a/-193b and miR-92a/-126 were additive in adipocytes, the combination of miR-126/-193b was primarily additive in macrophages. Signals for miR-92a and -193b converged on the nuclear factor-κB pathway. In conclusion, TF and miRNA-mediated regulation of CCL2 production is additive and partly relayed by cell-specific networks in human adipose tissue that may be important for the development of insulin resistance/type 2 diabetes.

Autocrine GM-CSF transcription in the leukemic progenitor cell line KG1a is mediated by the transcription factor ETS1 and is negatively regulated through SECTM1 mediated ligation of CD7.

BACKGROUND: CD7 expression is found on ~30% of acute myeloblastic leukemias (AML). The leukemic progenitor cell line KG1a (CD7+) constitutively expresses GM-CSF while the parental KG1 (CD7-) cell line does not. This study focuses on the molecular basis of CD7 mediated GM-CSF regulation. METHODS: KG1a cells were treated with recombinant SECTM1-Fc protein, the PI3K kinase inhibitors wortmannin, LY292004, or PI4K activator spermine. Stable KG1-CD7+, KG1a-shCD7, KG1a-shETS1 as well as KG1a-GFP, KG1a-PKCßII-GFP cell lines were generated and the levels of CD7, GM-CSF and ETS-1 mRNA and protein were compared by real-time-PCR, western blotting, flow cytometry and ELISA. RESULTS: SECTM1 is expressed in Human Bone Marrow Endothelial Cells (HBMEC) and its expression can be upregulated by both IFN-γ. KG1a cells demonstrated high expression levels of CD7 and ETS-1 allowing a constitutative signaling through the PI3K/Atk pathway to promote GM-CSF expression, while KG1 cells with low expression of CD7 and ETS-1 showed low GM-CSF expression. On KG1a cells GM-CSF expression could be negatively regulated by PI3K inhibitors or by recombinant SECTM1-Fc. Overexpression of CD7 in KG1 cells was insufficient to promote GM-CSF expression, while silencing of CD7 or ETS-1 resulted in reduced GM-CSF expression levels. Differentiation capable KG1a cells overexpressing PKCßII illustrated complete loss of CD7, but maintained normal levels of both ETS-1 and GM-CSF expression. CONCLUSION: These findings add an additional layer to the previously described autocrine/paracrine signaling between leukemic progenitor cells and the bone marrow microenvironment and highlight a role for SECTM1 in both normal and malignant hematopoiesis. GENERAL SIGNIFICANCE: This work shows that SECTM1 secreted from bone marrow stromal cells may interact with CD7 to influence GM-CSF expression in leukemic cells.

Ets-1 regulates intracellular glutathione levels: key target for resistant ovarian cancer.

BACKGROUND: Ovarian cancer is characterized by high rates of metastasis and therapeutic resistance. Many chemotherapeutic agents rely on the induction of oxidative stress to cause cancer cell death, thus targeting redox regulation is a promising strategy to overcome drug resistance. METHODS: We have used a tetracycline-inducible Ets-1 overexpression model derived from 2008 ovarian cancer cells in the present study. To examine the role of Ets-1 in glutathione regulation we have measured intracellular reactive oxygen species and glutathione levels, as well as glutathione peroxidase enzyme activity. Glutathione synthesis was limited using transsulfuration or Sx(c)- pathway blocking agents, and glutamate release was measured to confirm Sx(c)- blockade. Cell viability following drug treatment was assessed via crystal violet assay. Oxidative stress was induced through glucose oxidase treatment, which produces hydrogen peroxide by glucose oxidation. The protein expressions of redox-related factors were measured through western blotting. RESULTS: Overexpression of Ets-1 was associated with decreased intracellular ROS, concomitantly with increased intracellular GSH, GPX antioxidant activity, and Sx(c)- transporter activity. Under basal conditions, inhibition of the transsulfuration pathway resulted in decreased GSH levels and GPX activity in all cell lines, whereas inhibition of Sx(c)- by sulfasalazine decreased GPX activity in Ets-1-expressing cells only. However, under oxidative stress the intracellular GSH levels decreased significantly in correlation with increased Ets-1 expression following sulfasalazine treatment. CONCLUSIONS: In this study we have identified a role for proto-oncogene Ets-1 in the regulation of intracellular glutathione levels, and examined the effects of the anti-inflammatory drug sulfasalazine on glutathione depletion using an ovarian cancer cell model. The findings from this study show that Ets-1 mediates enhanced Sx(c)- activity to increase glutathione levels under oxidative stress, suggesting that Ets-1 could be a promising putative target to enhance conventional therapeutic strategies.

Hepatocyte growth factor-mediated gastrin-releasing peptide induces IL-8 expression through Ets-1 in gastric cancer cells.

Gastric cancer cells secrete a variety of proangiogenic molecules, including IL-8 and VEGF. However, factors regulating the expression of proangiogenic genes for gastric cancer remain largely undefined. We investigated the role of HGF-induced activation of GRP and Ets-1 transcription factor in expression of the proangiogenic factor IL-8. The genes associated with angiogenesis induced by HGF were screened using cDNA micro-array technology in two gastric cancer cell lines (NUGC-3 and MKN-28). First, GRP RNA and protein were confirmed to be upregulated. Then, expression of GRP, Ets-1, and IL-8 were further estimated by Western blot analysis. A role for Ets-1 in HGF-induced upregulation of IL-8 was determined by knockdown of Ets-1 with Ets-1 sh-RNA and a chromatin immune precipitation assay. The levels of GRP, Ets-1, and IL-8 were upregulated in cells treated with HGF in a dose-dependent manner. HGF-induced expression of Ets-1 and IL-8 was increased more by GRP treatment and inhibited by pretreatment with an ERK 1/2 inhibitor (PD098059). HGF-induced upregulation of IL-8 was repressed by Ets-1 knockdown. HGF enhanced the binding activity of Ets-1 to the IL-8 promoter in control cells, but not in the Ets-1 shRNA cells. We confirmed the functional role of HGF-induced Ets-1 in activation of the IL-8 promoter by the reporter gene assay. Downregulation of IL-8 also decreased in vitro cell invasion. In conclusion, HGF mediated the GRP induction of IL-8 expression through Ets-1, which thus might serve as a promising target for gastric cancer therapy.

hypoxia-inducible factors activate CD133 promoter through ETS family transcription factors.

CD133 is a cellular surface protein that has been reported to be a cancer stem cell marker, and thus it is considered to be a potential target for cancer treatment. However, the mechanism regulating CD133 expression is not yet understood. In this study, we analyzed the activity of five putative promoters (P1-P5) of CD133 in human embryonic kidney (HEK) 293 cells and colon cancer cell line WiDr, and found that the activity of promoters, particularly of P5, is elevated by overexpression of hypoxia-inducible factors (HIF-1α and HIF-2α). Deletion and mutation analysis identified one of the two E-twenty six (ETS) binding sites (EBSs) in the P5 region as being essential for its promoter activity induced by HIF-1α and HIF-2α. In addition, a chromatin imunoprecipitation assay demonstrated that HIF-1α and HIF-2α bind to the proximal P5 promoter at the EBSs. The immunoprecipitation assay showed that HIF-1α physically interacts with Elk1; however, HIF-2α did not bind to Elk1 or ETS1. Furthermore, knockdown of both HIF-1α and HIF-2α resulted in a reduction of CD133 expression in WiDr. Taken together, our results revealed that HIF-1α and HIF-2α activate CD133 promoter through ETS proteins.

Understanding the role of ETS-mediated gene regulation in complex biological processes.

Ets factors are members of one of the largest families of evolutionarily conserved transcription factors, regulating critical functions in normal cell homeostasis, which when perturbed contribute to tumor progression. The well-documented alterations in ETS factor expression and function during cancer progression result in pleiotropic effects manifested by the downstream effect on their target genes. Multiple ETS factors bind to the same regulatory sites present on target genes, suggesting redundant or competitive functions. The anti- and prometastatic signatures obtained by examining specific ETS regulatory networks will significantly improve our ability to accurately predict tumor progression and advance our understanding of gene regulation in cancer. Coordination of multiple ETS gene functions also mediates interactions between tumor and stromal cells and thus contributes to the cancer phenotype. As such, these new insights may provide a novel view of the ETS gene family as well as a focal point for studying the complex biological control involved in tumor progression. One of the goals of molecular biology is to elucidate the mechanisms that contribute to the development and progression of cancer. Such an understanding of the molecular basis of cancer will provide new possibilities for: (1) earlier detection, as well as better diagnosis and staging of disease; (2) detection of minimal residual disease recurrences and evaluation of response to therapy; (3) prevention; and (4) novel treatment strategies. Increased understanding of ETS-regulated biological pathways will directly impact these areas.

Ets1 and heat shock factor 1 regulate transcription of the Transformer 2ß gene in human colon cancer cells.

BACKGROUND: Transformer (Tra) 2ß is a member of the serine/arginine-rich (SR)-like protein family that regulates alternative splicing of numerous genes in a concentration-dependent manner. Several types of cancer cells up-regulate Tra2ß expression, while the regulatory mechanism of Tra2ß expression remains to be elucidated. In this study, we examined the transcriptional regulation and possible functions of Tra2ß in human colon cancer cells. METHODS: We cloned 959 bp-upstream of the human TRA2ß 5'-flank into luciferase constructs. Chromatin immunoprecipitation (ChIP) was employed to identify crucial cis element(s) and trans activator(s) of the TRA2ß promoter. Tra2ß expression in the human colon and colon cancer tissues was examined by immunohistochemistry. RESULTS: In response to sodium arsenite, colon cancer cells (HCT116) increased levels of TRA2ß1 mRNA encoding a functional, full-length Tra2ß with a peak around 6 h without changing its mRNA stability. Transient expression assays using a reporter gene driven by serially truncated TRA2ß promoters and Chip assay demonstrated that an Ets1-binding site present at -64 to -55 bp was crucial for basal transcription, while three heat shock elements (HSEs) located at -145 to -99 bp mediated the oxidant-induced transactivation of TRA2ß. Tra2ß knockdown caused apoptosis of HCT116 cells. Tra2ß were preferentially expressed in proliferative compartment of normal human colonic glands and adenocarcinomas, where Ets1 and heat shock factor 1 were also highly expressed. CONCLUSIONS: Our results suggest that oxidative stress-responsive Tra2ß may play an important role in colon cancer growth.

Review of Ets1 structure, function, and roles in immunity.

The Ets1 transcription factor is a member of the Ets gene family and is highly conserved throughout evolution. Ets1 is known to regulate a number of important biological processes in normal cells and in tumors. In particular, Ets1 has been associated with regulation of immune cell function and with an aggressive behavior in tumors that express it at high levels. Here we review and summarize the general features of Ets1 and describe its roles in immunity and autoimmunity, with a focus on its roles in B lymphocytes. We also review evidence that suggests that Ets1 may play a role in malignant transformation of hematopoietic malignancies including B cell malignancies.

Involvement of transcription factor Ets-1 in the expression of the α3 integrin subunit gene.

The α3ß1 integrin is an adhesion receptor for extracellular matrix proteins, and plays crucial roles in cell motility, proliferation, and differentiation. The aberrant expression of this adhesion molecule on tumor cells is frequently associated with their malignant behaviors. We previously reported that the Ets transcription factor-binding consensus sequence 133 bp upstream of the mouse α3 integrin gene is an important element for its expression in various tumor cell lines. In the present study, we attempted to identify a transcription factor bound to the Ets-consensus sequence, and found that Ets-1 bound to this sequence in an electrophoretic mobility shift assay, chromatin immunoprecipitation assay, and pull-down assay with a tandem repeat of the sequence as adsorbent. We next examined the role of Ets-1 in α3 integrin gene expression by use of a luciferase assay with a reporter plasmid containing the 5'-flanking region of the α3 integrin gene. Cotransfection of HEK293T cells with an Ets-1 expression construct and the reporter plasmid increased luciferase activity. By contrast, transfection of HT1080 cells (high α3 integrin expresser) with a dominant-negative mutant of Ets-1 decreased luciferase activity. Overexpression of Ets-1 in HepG2 hepatocellular carcinoma cells (low α3 integrin expresser) upregulated α3 integrin expression as assessed by immunoprecipitation. Finally, the induction of α3 integrin gene expression in HepG2 cells after transforming growth factor-ß1 treatment was abrogated by the dominant-negative mutant of Ets-1. These results suggest that Ets-1 is involved in transcriptional activation of the α3 integrin gene through its binding to the Ets-consensus sequence at -133 bp.