CDK10 suppresses metastasis of lung adenocarcinoma through inhibition of the ETS2/c-Raf/p-MEK/p-ERK signaling loop

The repertoire of aberrant signaling underlying the pathogenesis of lung adenocarcinoma remains largely uncharacterized, which precludes an efficient therapy for these patients, especially when distant metastasis occurs. Cyclin-dependent kinase 10 (CDK10) has been reported to modulate the progression of malignant tumors; however, contradictory effects have been found among different types of malignant tumors. In the present study, we found that CDK10 was downregulated in lung adenocarcinoma compared with the paired adjacent normal lung tissue, and lower expression level of CDK10 was associated with more frequent N2 staged lymph node and distant metastasis, higher TNM stage, and shorter overall survival. Further study indicated that CDK10 inhibited the migration and invasion abilities with no impact on the proliferation of lung adenocarcinoma cells. Mechanistically, CDK10 could bind to and promote the degradation of ETS2, a transcription factor for C-RAF and MMP2/9, thereby inactivating the downstream c-Raf/p-MEK/p-ERK pathway that drives epithelial-mesenchymal transition and impairing the expression of matrix metalloproteinases involved in cell invasion. In addition, the p-MEK/p-ERK pathway conducts a positive feedback regulation on the expression of ETS2. Knockdown of CDK10 in human lung adenocarcinoma cells significantly promoted the formation of metastatic foci in lungs in a xenograft mouse model. In conclusion, CDK10 suppresses metastasis of lung adenocarcinoma by disrupting the ETS2/c-Raf/p-MEK/p-ERK/ETS2 signaling and MMP2/9, providing a new therapeutic target for the treatment of lung adenocarcinoma with metastasis.

USP39-Mediated Non-Proteolytic Control of ETS2 Suppresses Nuclear Localization and Activity

ETS2 is a member of the ETS family of transcription factors and has been implicated in the regulation of cell proliferation, differentiation, apoptosis, and tumorigenesis. The aberrant activation of ETS2 is associated with various human cancers, highlighting its importance as a therapeutic target. Understanding the regulatory mechanisms and interacting partners of ETS2 is crucial for elucidating its precise role in cellular processes and developing novel strategies to modulate its activity. In this study, we conducted binding assays using a human deubiquitinase (DUB) library and identified USP39 as a novel ETS2-binding DUB. USP39 interacts with ETS2 through their respective amino-terminal regions, and the zinc finger and PNT domains are not required for this binding. USP39 deubiquitinates ETS2 without affecting its protein stability. Interestingly, however, USP39 significantly suppresses the transcriptional activity of ETS2. Furthermore, we demonstrated that USP39 leads to a reduction in the nuclear localization of ETS2. Our findings provide valuable insights into the intricate regulatory mechanisms governing ETS2 function. Understanding the interplay between USP39 and ETS2 may have implications for therapeutic interventions targeting ETS2-related diseases, including cancer, where the dysregulation of ETS2 is frequently observed.

A distal super-enhancer activates oncogenic ETS2 via recruiting MECOM in inflammatory bowel disease and colorectal cancer

Abnormal activities of distal cis-regulatory elements (CREs) contribute to the initiation and progression of cancer. Gain of super-enhancer (SE), a highly active distal CRE, is essential for the activation of key oncogenes in various cancers. However, the mechanism of action for most tumor-specific SEs still largely remains elusive. Here, we report that a candidate oncogene ETS2 was activated by a distal SE in inflammatory bowel disease (IBD) and colorectal cancer (CRC). The SE physically interacted with the ETS2 promoter and was required for the transcription activation of ETS2. Strikingly, the ETS2-SE activity was dramatically upregulated in both IBD and CRC tissues when compared to normal colon controls and was strongly correlated with the level of ETS2 expression. The tumor-specific activation of ETS2-SE was further validated by increased enhancer RNA transcription from this region in CRC. Intriguingly, a known IBD-risk SNP resides in the ETS2-SE and the genetic variant modulated the level of ETS2 expression through affecting the binding of an oncogenic transcription factor MECOM. Silencing of MECOM induced significant downregulation of ETS2 in CRC cells, and the level of MECOM and ETS2 correlated well with each other in CRC and IBD samples. Functionally, MECOM and ETS2 were both required for maintaining the colony-formation and sphere-formation capacities of CRC cells and MECOM was crucial for promoting migration. Taken together, we uncovered a novel disease-specific SE that distantly drives oncogenic ETS2 expression in IBD and CRC and delineated a mechanistic link between non-coding genetic variation and epigenetic regulation of gene transcription.

Direct Reprogramming of Mouse Embryonic Fibroblasts to Induced Trophoblast Stem Cells

Trophoblast cells are the first committed lineage to emerge during mammalian preimplantation embryo development. Trophoblast stem (TS) cells can be derived from the trophectoderm (TE) of blastocyst-stage embryos and differentiate into extraembryonic trophoblast cells of the placenta. While mouse TS cells are an indispensable tool to study placental development, and reproductive diseases such as implantation failure and recurrent miscarriage, human TS cells have not been isolated. To model human trophoblast development and to investigate trophoblast-specific causes of reproductive diseases, it will be important to derive human induced trophoblast stem (iTS) cells. Recent studies have shown that fibroblasts can be reprogrammed to iTS cells by overexpressing four transcription factors (TFs) including TFAP2C, GATA3, EOMES, and ETS2. Here, we describe a protocol to directly convert mouse embryonic fibroblasts (MEFs) to iTS cells following overexpression of 10 TFs. iTS cells are capable of self-renewing using conventional TS cell culture media supplemented with the external signal FGF4 and heparin. iTS cells are also able to differentiate into trophoblast lineages.

Integration of Wnt and FGF signaling in the Xenopus gastrula at TCF and Ets binding sites shows the importance of short-range repression by TCF in patterning the marginal zone

During Xenopus gastrulation, Wnt and FGF signaling pathways cooperate to induce posterior structures. Wnt target expression around the blastopore falls into two main categories: a horseshoe shape with a dorsal gap, as in Wnt8 expression; or a ring, as in FGF8 expression. Using ChIP-seq, we show, surprisingly, that the FGF signaling mediator Ets2 binds near all Wnt target genes. However, β-catenin preferentially binds at the promoters of genes with horseshoe patterns, but further from the promoters of genes with ring patterns. Manipulation of FGF or Wnt signaling demonstrated that 'ring' genes are responsive to FGF signaling at the dorsal midline, whereas 'horseshoe' genes are predominantly regulated by Wnt signaling. We suggest that, in the absence of active β-catenin at the dorsal midline, the DNA-binding protein TCF binds and actively represses gene activity only when close to the promoter. In contrast, genes without functional TCF sites at the promoter may be predominantly regulated by Ets at the dorsal midline and are expressed in a ring. These results suggest recruitment of only short-range repressors to potential Wnt targets in the Xenopus gastrula.

Single CpG site methylation controls estrogen receptor gene transcription and correlates with hormone therapy resistance

Hormone therapy is the most effective treatment for patients with estrogen receptor α-positive breast cancers. However, although resistance occurs during treatment in some cases and often reflects changed estrogen receptor α status, the relationship between changes in estrogen receptor α expression and resistance to therapy are poorly understood. In this study, we identified a mechanism for altered estrogen receptor α expression during disease progression and acquired hormone therapy resistance in aromatase inhibitor-resistant breast cancer cell lines. Subsequently, we investigated promoter switching and DNA methylation status of the estrogen receptor α promoter, and found marked changes of methylation at a single CpG site (CpG4) in resistant cells. In addition, luciferase reporter assays showed reduced transcriptional activity from this methylated CpG site. This CpG region was also completely conserved among species, suggesting that it acts as a methylation-sensitive Ets-2 transcription factor binding site, as confirmed using chromatin immunoprecipitation assays. In estrogen receptor α-positive tumors, CpG4 methylation levels were inversely correlated with estrogen receptor α expression status, suggesting that single CpG site plays an important role in the regulation of estrogen receptor α transcription.

The C-ETS2-TFEB Axis Promotes Neuron Survival under Oxidative Stress by Regulating Lysosome Activity

Excessive reactive oxygen species/reactive nitrogen species (ROS/RNS) produced as a result of ageing causes damage to macromolecules and organelles or leads to interference of cell signalling pathways, which in turn results in oxidative stress. Oxidative stress occurs in many neurodegenerative diseases (e.g., Parkinson's disease) and contributes to progressive neuronal loss. In this study, we show that cell apoptosis is induced by oxidative stress and that lysosomes play an important role in cell survival under oxidative stress. As a compensatory response to this stress, lysosomal genes were upregulated via induction of transcription factor EB (TFEB). In addition, localization of TFEB to the nucleus was increased by oxidative stress. We also confirmed that TFEB protects cells from oxidative stress both in vitro and in vivo. Finally, we found that C-ETS2 senses oxidative stress, activates TFEB transcription, and mediates the upregulation of lysosomal genes. Our results demonstrate a mechanistic pathway for inducing lysosomal activity during ageing and neurodegeneration.

Systems Analysis of Adaptive Responses to MAP Kinase Pathway Blockade in BRAF Mutant Melanoma

Fifty percent of cutaneous melanomas are driven by activated BRAF^V600E, but tumors treated with RAF inhibitors, even when they respond dramatically, rapidly adapt and develop resistance. Thus, there is a pressing need to identify the major mechanisms of intrinsic and adaptive resistance and develop drug combinations that target these resistance mechanisms. In a combinatorial drug screen on a panel of 12 treatment-naïve BRAF^V600E mutant melanoma cell lines of varying levels of resistance to mitogen-activated protein kinase (MAPK) pathway inhibition, we identified the combination of PLX4720, a targeted inhibitor of mutated BRaf, and lapatinib, an inhibitor of the ErbB family of receptor tyrosine kinases, as synergistically cytotoxic in the subset of cell lines that displayed the most resistance to PLX4720. To identify potential mechanisms of resistance to PLX4720 treatment and synergy with lapatinib treatment, we performed a multi-platform functional genomics analysis to profile the genome as well as the transcriptional and proteomic responses of these cell lines to treatment with PLX4720. We found modest levels of resistance correlated with the zygosity of the BRAF V600E allele and receptor tyrosine kinase (RTK) mutational status. Layered over base-line resistance was substantial upregulation of many ErbB pathway genes in response to BRaf inhibition, thus generating the vulnerability to combination with lapatinib. The transcriptional responses of ErbB pathway genes are associated with a number of transcription factors, including ETS2 and its associated cofactors that represent a convergent regulatory mechanism conferring synergistic drug susceptibility in the context of diverse mutational landscapes.

Transcriptional Regulation of the p16 Tumor Suppressor Gene

The p16 tumor suppressor gene encodes a specific inhibitor of cyclin-dependent kinase (CDK) 4 and 6 and is found altered in a wide range of human cancers. p16 plays a pivotal role in tumor suppressor networks through inducing cellular senescence that acts as a barrier to cellular transformation by oncogenic signals. p16 protein is relatively stable and its expression is primary regulated by transcriptional control. Polycomb group (PcG) proteins associate with the p16 locus in a long non-coding RNA, ANRIL-dependent manner, leading to repression of p16 transcription. YB1, a transcription factor, also represses the p16 transcription through direct association with its promoter region. Conversely, the transcription factors Ets1/2 and histone H3K4 methyltransferase MLL1 directly bind to the p16 locus and mediate p16 induction during replicative and premature senescence. In the present review, we discuss the molecular mechanisms by which these factors regulate p16 transcription.

Transcriptional (ChIP-Chip) Analysis of ELF1, ETS2, RUNX1 and STAT5 in Human Abdominal Aortic Aneurysm

We investigated transcriptional control of gene expression in human abdominal aortic aneurysm (AAA). We previously identified 3274 differentially expressed genes in human AAA tissue compared to non-aneurysmal controls. Four expressed transcription factors (ELF1, ETS2, STAT5 and RUNX1) were selected for genome-wide chromatin immunoprecipitation. Transcription factor binding was enriched in 4760 distinct genes (FDR < 0.05), of which 713 were differentially expressed in AAA. Functional classification using Gene Ontology (GO), KEGG, and Network Analysis revealed enrichment in several biological processes including “leukocyte migration” (FDR = 3.09 × 10⁻⁰⁵) and “intracellular protein kinase cascade” (FDR = 6.48 × 10⁻⁰⁵). In the control aorta, the most significant GO categories differed from those in the AAA samples and included “cytoskeleton organization” (FDR = 1.24 × 10⁻⁰⁶) and “small GTPase mediated signal transduction” (FDR = 1.24 × 10⁻⁰⁶). Genes up-regulated in AAA tissue showed a highly significant enrichment for GO categories “leukocyte migration” (FDR = 1.62 × 10⁻¹¹), “activation of immune response” (FDR = 8.44 × 10⁻¹¹), “T cell activation” (FDR = 4.14 × 10⁻¹⁰) and “regulation of lymphocyte activation” (FDR = 2.45 × 10⁻⁰⁹), whereas the down-regulated genes were enriched in GO categories “cytoskeleton organization” (FDR = 7.84 × 10⁻⁰⁵), “muscle cell development” (FDR = 1.00 × 10⁻⁰⁴), and “organ morphogenesis” (FDR = 3.00 × 10⁻⁰⁴). Quantitative PCR assays confirmed a sub-set of the transcription factor binding sites including those in MTMR11, DUSP10, ITGAM, MARCH1, HDAC8, MMP14, MAGI1, THBD and SPOCK1.

Phosphorylation of ETS1 by Src family kinases prevents its recognition by the COP1 tumor suppressor

Oncoproteins and tumor suppressors antagonistically converge on critical nodes governing neoplastic growth, invasion, and metastasis. We discovered that phosphorylation of the ETS1 and ETS2 transcriptional oncoproteins at specific serine or threonine residues creates binding sites for the COP1 tumor suppressor protein, which is an ubiquitin ligase component, leading to their destruction. In the case of ETS1, however, phosphorylation of a neighboring tyrosine residue by Src family kinases disrupts COP1 binding, thereby stabilizing ETS1. Src-dependent accumulation of ETS1 in breast cancer cells promotes anchorage-independent growth in vitro and tumor growth in vivo. These findings expand the list of potential COP1 substrates to include proteins whose COP1-binding sites are subject to regulatory phosphorylation and provide insights into transformation by Src family kinases.

MicroRNA 17-92 cluster mediates ETS1 and ETS2-dependent RAS-oncogenic transformation

The ETS-family transcription factors Ets1 and Ets2 are evolutionarily conserved effectors of the RAS/ERK signaling pathway, but their function in Ras cellular transformation and biology remains unclear. Taking advantage of Ets1 and Ets2 mouse models to generate Ets1/Ets2 double knockout mouse embryonic fibroblasts, we demonstrate that deletion of both Ets1 and Ets2 was necessary to inhibit Hras^G12V induced transformation both in vitro and in vivo. Hras^G12V expression in mouse embryonic fibroblasts increased ETS1 and ETS2 expression and binding to cis-regulatory elements on the c-Myc proximal promoter, and consequently induced a robust increase in MYC expression. The expression of the oncogenic microRNA 17-92 cluster was increased in Hras^G12V transformed cells, but was significantly reduced when ETS1 and ETS2 were absent. MYC and ETS1 or ETS2 collaborated to increase expression of the oncogenic microRNA 17-92 cluster in Hras^G12V transformed cells. Enforced expression of exogenous MYC or microRNA 17-92 rescued Hras^G12V transformation in Ets1/Ets2-null cells, revealing a direct function for MYC and microRNA 17-92 in ETS1/ETS2-dependent Hras^G12V transformation.

MiR-126 promotes coxsackievirus replication by mediating cross-talk of ERK1/2 and Wnt/β-catenin signal pathways

Coxsackievirus B3 (CVB3) is one of the most prevalent causes of viral myocarditis and is associated with many other pathological conditions. CVB3 replication relies on host cellular machineries and causes direct damage to host cells. MicroRNAs have been found to regulate viral infections but their roles in CVB3 infection are still poorly understood. Here we describe a novel mechanism by which miR-126 regulates two signal pathways essential for CVB3 replication. We found that CVB3-induced ERK1/2 activation triggered the phosphorylation of ETS-1 and ETS-2 transcription factors, which induced miR-126 upregulation. By using both microRNA mimics and inhibitors, we proved that the upregulated miR-126 suppressed sprouty-related, EVH1 domain containing 1 (SPRED1) and in turn enhanced ERK1/2 activation. This positive feedback loop of ERK1/2-miR-126-ERK1/2 promoted CVB3 replication. Meanwhile, miR-126 expression stimulated GSK-3β activity and induced degradation of β-catenin through suppressing LRP6 and WRCH1, two newly identified targets in the Wnt/β-catenin pathway, which sensitized the cells to virus-induced cell death and increased viral progeny release to initiate new infections. Our results demonstrate that upregulated miR-126 upon CVB3 infection targets SPRED1, LRP6, and WRCH1 genes, mediating cross-talk between ERK1/2 and Wnt/β-catenin pathways, and thus promoting viral replication and contributes to the viral cytopathogenicity.

Ets-2 regulates cell apoptosis via the Akt pathway, through the regulation of urothelial cancer associated 1, a long non-coding RNA, in bladder cancer cells

The majority of the human genome is transcribed and generates non-coding RNAs (ncRNAs) that fail to encode protein information. Long non-coding RNAs (lncRNAs) are emerging as a novel class of ncRNAs, but our knowledge about these ncRNAs is limited. Previously, our laboratory has identified that a lncRNA, Urothelial cancer associated 1 (UCA1), played an important role in bladder cancer. Despite the recent interest in UCA1 as a diagnostic marker for bladder cancer, little is known about its transcriptional regulation. To elucidate the regulation of UCA1 gene expression, we have characterized the human UCA1 gene promoter. A 2.0-kb fragment of its 5' flanking region was cloned into a luciferase reporter vector. Deletion and mutation analysis suggested that an Ets-2 binding site was critical for UCA1 gene promoter activity. Further analysis of this site by gel shifting, chromatin immune precipitation (ChIP), and co-transfection experiments showed that transcription factor Ets-2 directly bound to the UCA1 promoter region and stimulated UCA1 promoter activity in bladder cancer cells. Taking into account the anti-apoptosis function of Ets-2, our data suggested that Ets-2 regulates apoptosis process by regulating the expression of UCA1, moreover UCA1 may be involved in the activation of Akt signaling pathway by Ets-2 in bladder cancer cells.

Ets2 in tumor fibroblasts promotes angiogenesis in breast cancer

Tumor fibroblasts are active partners in tumor progression, but the genes and pathways that mediate this collaboration are ill-defined. Previous work demonstrates that Ets2 function in stromal cells significantly contributes to breast tumor progression. Conditional mouse models were used to study the function of Ets2 in both mammary stromal fibroblasts and epithelial cells. Conditional inactivation of Ets2 in stromal fibroblasts in PyMT and ErbB2 driven tumors significantly reduced tumor growth, however deletion of Ets2 in epithelial cells in the PyMT model had no significant effect. Analysis of gene expression in fibroblasts revealed a tumor- and Ets2-dependent gene signature that was enriched in genes important for ECM remodeling, cell migration, and angiogenesis in both PyMT and ErbB2 driven-tumors. Consistent with these results, PyMT and ErbB2 tumors lacking Ets2 in fibroblasts had fewer functional blood vessels, and Ets2 in fibroblasts elicited changes in gene expression in tumor endothelial cells consistent with this phenotype. An in vivo angiogenesis assay revealed the ability of Ets2 in fibroblasts to promote blood vessel formation in the absence of tumor cells. Importantly, the Ets2-dependent gene expression signatures from both mouse models were able to distinguish human breast tumor stroma from normal stroma, and correlated with patient outcomes in two whole tumor breast cancer data sets. The data reveals a key function for Ets2 in tumor fibroblasts in signaling to endothelial cells to promote tumor angiogenesis. The results highlight the collaborative networks that orchestrate communication between stromal cells and tumor cells, and suggest that targeting tumor fibroblasts may be an effective strategy for developing novel anti-angiogenic therapies.

Involvement of V-Ets erythroblastosis virus E26 oncogene homolog 2 in regulation of transcription activity of MDR1 gene

Over-expression of MDR1 confers multidrug resistance (MDR) in cancers and remains a major cause for the failure of chemotherapy. In the present study, we found that V-Ets erythroblastosis virus E26 oncogene homolog 2 (ETS2) could activate MDR1 transcription and P-glycoprotein (P-gp) expression in SGC7901 cells. Knockdown of ETS2 attenuated MDR1 transcription and P-gp expression, and increased the sensitivity of MDR cancer cells to cytotoxic drugs that were transported by P-gp in SGC7901/VCR cells. ETS2 could bind to the ETS2 sites on the MDR1 promoter and activate its transcription. The regulation of MDR1 expression by ETS2 may provide potential ways to overcome MDR in cancer treatment.

The SAM domain of human TEL2 can abrogate transcriptional output from TEL1 (ETV-6) and ETS1/ETS2

Regulation of gene expression downstream of the Receptor Tyrosine Kinase signaling pathway in Drosophila relies on a transcriptional effector network featuring two conserved Ets family proteins, Yan and Pointed, known as TEL1 (ETV6) and ETS1/ETS2, respectively, in mammals. As in Drosophila, both TEL1 and ETS1/ETS2 operate as Ras pathway transcriptional effectors and misregulated activity of either factor has been implicated in many human leukemias and solid tumors. Providing essential regulation to the Drosophila network, direct interactions with the SAM domain protein Mae attenuate both Yan-mediated repression and PointedP2-mediated transcriptional activation. Given the critical contributions of Mae to the Drosophila circuitry, we investigated whether the human Ets factors TEL1 and ETS1/ETS2 could be subject to analogous regulation. Here we demonstrate that the SAM domain of human TEL2 can inhibit the transcriptional activities of ETS1/2 and TEL1. Drosophila Mae can also attenuate human ETS1/ETS2 function, suggesting there could be cross-species conservation of underlying mechanism. In contrast, Mae is not an effective inhibitor of TEL1, suggesting the mode of TEL2SAM-mediated inhibition of TEL1 may be distinct from how Drosophila Mae antagonizes Yan. Together our results reveal both further similarities and new differences between the mammalian and Drosophila networks and more broadly suggest that SAM domain-mediated interactions could provide an effective mechanism for modulating output from the TEL1 and ETS1/2 oncogenes.

Gene expression changes in peripheral blood mononuclear cells in occupational exposure to nickel

Allergic contact dermatitis is preceded by a clinically silent phase of sensitisation. In this study, we investigated whether the expression levels of six genes were related to nickel exposure and/or nickel sensitisation, and whether they could predict allergic manifestations to nickel. The mRNA expression level of six genes involved in cell growth (PIM1 and ETS2), metabolism/synthesis (HSD11B1 and PRDX4), apoptosis (CASP8) and signal transduction (CISH) was investigated by means of quantitative real-time RT-PCR in a cohort of 110 subjects, including healthy controls (n=51), nickel-exposed workers (n=23) and patients allergic to nickel (n=36). Our findings show that the expression levels of the analysed genes did not differ between allergic patients and healthy controls, while higher expression levels of ETS2 and CASP8 were detected in the nickel-exposed workers. Changes in ETS2 and CASP8 expression are likely to be related to nickel exposure rather than to allergy.

Ets-2 and p53 mediate cAMP-induced MMP-2 expression, activity and trophoblast invasion

BACKGROUND

We have previously shown that Matrix metalloproteinase (MMP) -2 is a key-enzyme in early trophoblast invasion and that Protein Kinase A (PKA) increases MMP-2 expression and trophoblast invasion. The aim of this study was to examine MMP -2 regulation by PKA in invasive trophoblasts: JAR choriocarcinoma cell-line and 6-8 w first trimester trophoblasts.

METHODS

The effect of Forskolin (PKA) on MMP-2 expression was assessed by Northern Blot and RT-PCR. Possible transcription factors binding to consensus MMP-2 promoter sequences in response to Forskolin, were detected by EMSA binding assay and their expression assessed by western blot analysis. Antisense transfection of relevant transcription factors was performed and the inhibitory effect assessed on MMP-2 expression (RT-PCR), secretion (zymography) and trophoblast invasiveness (transwell migration assay).

RESULTS

We found that Forskolin increased MMP-2 mRNA in JAR cells within 24 hours, and induced binding to p53, Ets, C/EBP and AP-2. Transcription factors Ets-2, phospho- p53, C/EBP epsilon, C/EBP lambda and AP-2 alpha bound to their respective binding sequences in response to Forskolin and the expressions of these transcription factors were all elevated in Forskolin- treated cells. Inhibition of Ets-2 and p53 reduced MMP-2 expression, secretion and invasiveness of Forskolin treated cells.

CONCLUSION

MMP-2 is regulated by PKA through several binding sites and transcription factors including Ets-2, p53, C/EBP, C/EBP lambda and AP-2 alpha. Ets-2 and p53 mediate cAMP- induced trophoblast invasiveness, through regulation of MMP-2.

Pten in stromal fibroblasts suppresses mammary epithelial tumours

The tumour stroma is believed to contribute to some of the most malignant characteristics of epithelial tumours. However, signalling between stromal and tumour cells is complex and remains poorly understood. Here we show that the genetic inactivation of Pten in stromal fibroblasts of mouse mammary glands accelerated the initiation, progression and malignant transformation of mammary epithelial tumours. This was associated with the massive remodelling of the extracellular matrix (ECM), innate immune cell infiltration and increased angiogenesis. Loss of Pten in stromal fibroblasts led to increased expression, phosphorylation (T72) and recruitment of Ets2 to target promoters known to be involved in these processes. Remarkably, Ets2 inactivation in Pten stroma-deleted tumours ameliorated disruption of the tumour microenvironment and was sufficient to decrease tumour growth and progression. Global gene expression profiling of mammary stromal cells identified a Pten-specific signature that was highly represented in the tumour stroma of patients with breast cancer. These findings identify the Pten-Ets2 axis as a critical stroma-specific signalling pathway that suppresses mammary epithelial tumours.

Transcription of the putative tumor suppressor gene HCCS1 requires binding of ETS-2 to its consensus near the transcription start site

The hepatocellular carcinoma suppressor 1 (HCCS1) gene was identified by both positional cloning from a predominant region of loss of heterozygosity (17p13.3) in liver cancer and by functional screening for genes affecting cell proliferation in large-scale transfection assays. Its overexpression results in inhibition of cell proliferation in cell culture and tumor growth in nude mice. To understand its transcription regulation, the promoter architecture has been dissected in detail. The major start of transcription was mapped by primer extension to a C residue, 177 nucleotides upstream of the ATG codon. By assessing the promoter activity of a set of linker-scanning mutants of the minimal promoter (-60 to +148 region) in a transient transfection assay, we found that the +1 to + 40 region is critical to HCCS1 gene transcription, containing binding sites for transcription factors NF-kappaB (-21 to +7 and +40 to +26), p53 (+29 to +9) and ETS (+4 to +20 and +23 to +39). Biochemical and molecular analyses revealed that the ETS transcription factors ETS-2 and Elf-1 bind to the two ETS sites in situ and contribute significantly to the transcriptionally active state of the HCCS1 gene, while NF-kappaB, p53 and two other members of the ETS family (ETS-1 and NERF2) appear to play little role. Our observations provide insight into the mechanistic aspects of HCCS1 transcription regulation.

Differential regulation of NAB corepressor genes in Schwann cells

BACKGROUND

Myelination of peripheral nerves by Schwann cells requires not only the Egr2/Krox-20 transactivator, but also the NGFI-A/Egr-binding (NAB) corepressors, which modulate activity of Egr2. Previous work has shown that axon-dependent expression of Egr2 is mediated by neuregulin stimulation, and NAB corepressors are co-regulated with Egr2 expression in peripheral nerve development. NAB corepressors have also been implicated in macrophage development, cardiac hypertrophy, prostate carcinogenesis, and feedback regulation involved in hindbrain development.

RESULTS

To test the mechanism of NAB regulation in Schwann cells, transfection assays revealed that both Nab1 and Nab2 promoters are activated by Egr2 expression. Furthermore, direct binding of Egr2 at these promoters was demonstrated in vivo by chromatin immunoprecipitation analysis of myelinating sciatic nerve, and binding of Egr2 to the Nab2 promoter was stimulated by neuregulin in primary Schwann cells. Although Egr2 expression activates the Nab2 promoter more highly than Nab1, we surprisingly found that only Nab1 - but not Nab2 - expression levels were reduced in sciatic nerve from Egr2 null mice. Analysis of the Nab2 promoter showed that it is also activated by ETS proteins (Ets2 and Etv1/ER81) and is bound by Ets2 in vivo.

CONCLUSION

Overall, these results indicate that induction of Nab2 expression in Schwann cells involves not only Egr2, but also ETS proteins that are activated by neuregulin stimulation. Although Nab1 and Nab2 play partially redundant roles, regulation of Nab2 expression by ETS factors explains several observations regarding regulation of NAB genes. Finally, these data suggest that NAB proteins are not only feedback inhibitors of Egr2, but rather that co-induction of Egr2 and NAB genes is involved in forming an Egr2/NAB complex that is crucial for regulation of gene expression.

CD13/APN transcription is regulated by the proto-oncogene c-Maf via an atypical response element

Angiogenic growth factors induce the transcription of the cell surface peptidase CD13/APN in activated endothelial cells of the tumor vasculature. Inhibition of CD13/APN abrogates endothelial invasion and morphogenesis in vitro and tumor growth in vivo suggesting a critical functional role for CD13 in angiogenesis. Experiments to identify the transcription factors responsible for this regulation demonstrated that exogenous expression of the proto-oncogene c-Maf, but not other bZip family members tested, potently activates transcription from a critical regulatory region of the CD13 proximal promoter between -115 and -70 bp which is highly conserved among mammalian species. Using promoter mutation, EMSA and ChIP analyses we established that both endogenous and recombinant c-Maf directly interact with an atypical Maf response element contained within this active promoter region via its basic DNA/leucine zipper domain. However full activity of c-Maf requires the amino-terminal transactivation domain, and site-directed mutation of putative phosphorylation sites within the transactivation domain (serines 15 and 70) shows that these sites behave in a dramatic cell type-specific manner. Therefore, this atypical response element predicts a broader range of c-Maf target genes than previously appreciated and thus impacts its regulation of multiple myeloma as well as endothelial cell function and angiogenesis.

Expression patterns of Ets2 protein correlate with bone-specific proteins in cell-seeded three-dimensional bone constructs

The transcription factor Ets2 and its transcriptional targets osteopontin (OPN) and osteocalcin (OC) are expressed in tissue-engineered bone constructs in vitro. Up to now little is known about the role of Ets2 in tissue-engineering applications. This study was intended to investigate the hypothesis that protein expression of Ets2 is correlated with the expression of bone-specific proteinsin tissue-engineeredbone constructs. Cell-seeded three-dimensional bone constructs manufactured with osteoblastic cells and poly(lactic-co-glycolic acid) polymer fleeces over a period of 21 days were analyzed by SDS-PAGE and Western blotting. The protein expression of OPN, OC, osteonectin and collagen type I was analyzed. Cellularity, alkaline phosphatase-specific activity and histology confirmed the osteoblastic phenotype of the constructs. Correlations between Ets2 expression and OPN and Ets2 and collagen type I expression could be detected during the phase of late osteoblastic differentiation between days 9 and 21. The correlation between OC and collagen type I was significant in this late stage of osteoblastic differentiation. These results suggest that there is a strong interplay of Ets2 with bone-specific proteins in cell-seeded three-dimensional bone constructs. This study is a crucial step to elucidate the complex interplay of bone-related proteins in the application of bone tissue engineering.

Identification of murine cdk10: association with Ets2 transcription factor and effects on the cell cycle

Cyclin-dependent kinases (cdks) are the catalytic subunits of a large family of serine/threonine protein kinases whose best-characterized members are key regulators of eukaryotic cell cycle progression. They are activated by binding to regulatory subunits generally termed as cyclins. Cdk10 is a cdc2-related kinase that contains the canonical regulatory Tyr and Thr residues present in all protein kinases and a PSTAIRE-like motif named PISSLRE. Although little is known about this protein, human cdk10 has been shown to encode two different isoforms, each having a distinct function. They differ at both the carboxy- and amino-terminals, although most of the amino acid sequence is predicted to be identical for the two isoforms. A role at the G2/M transition has been suggested for an isoform of cdk10, while the alternative splicing form interacts with the N-terminus of the Ets2 transcription factor. Here we report the cloning and the functional characterization of a cDNA encoding the murine homologue of cdk10. Unlike its human counterpart, only one murine cdk10 protein has been identified, and this unique murine cdk10 cDNA encodes a putative protein of 360 amino acids. Comparison of the amino acid sequences of murine and human cdk10 shows high homology. Murine cdk10 binds Ets2 transcription factors in vitro, does not show a direct involvement in the G2/M transition and, therefore, does not affect the proliferation rate of the cell lines analyzed.

CENP-F expression is associated with poor prognosis and chromosomal instability in patients with primary breast cancer

DNA microarrays have the potential to classify tumors according to their transcriptome. Tissue microarrays (TMAs) facilitate the validation of biomarkers by offering a high-throughput approach to sample analysis. We reanalyzed a high profile breast cancer DNA microarray dataset containing 96 tumor samples using a powerful statistical approach, between group analyses. Among the genes we identified was centromere protein-F (CENP-F), a gene associated with poor prognosis. In a published follow-up breast cancer DNA microarray study, comprising 295 tumour samples, we found that CENP-F upregulation was significantly associated with worse overall survival (p<0.001) and reduced metastasis-free survival (p<0.001). To validate and expand upon these findings, we used 2 independent breast cancer patient cohorts represented on TMAs. CENP-F protein expression was evaluated by immunohistochemistry in 91 primary breast cancer samples from cohort I and 289 samples from cohort II. CENP-F correlated with markers of aggressive tumor behavior including ER negativity and high tumor grade. In cohort I, CENP-F was significantly associated with markers of CIN including cyclin E, increased telomerase activity, c-Myc amplification and aneuploidy. In cohort II, CENP-F correlated with VEGFR2, phosphorylated Ets-2 and Ki67, and in multivariate analysis, was an independent predictor of worse breast cancer-specific survival (p=0.036) and overall survival (p=0.040). In conclusion, we identified CENP-F as a biomarker associated with poor outcome in breast cancer and showed several novel associations of biological significance.

Curcumin, a Dietary Component, Has Anticancer, Chemosensitization, and Radiosensitization Effects by Down-regulating the MDM2 Oncogene through the PI3K/mTOR/ETS2 Pathway

The oncoprotein MDM2, a major ubiquitin E3 ligase of tumor suppressor p53, has been suggested as a novel target for human cancer therapy based on its p53-dependent and p53-independent activities. We have identified curcumin, which has previously been shown to have anticancer activity, as an inhibitor of MDM2 expression. Curcumin down-regulates MDM2, independent of p53. In a human prostate cancer cell lines PC3 (p53(null)), curcumin reduced MDM2 protein and mRNA in a dose- and time-dependent manner, and enhanced the expression of the tumor suppressor p21(Waf1/CIP1). The inhibitory effects occur at the transcriptional level and seem to involve the phosphatidylinositol 3-kinase/mammalian target of rapamycin/erythroblastosis virus transcription factor 2 pathway. Curcumin induced apoptosis and inhibited proliferation of PC3 cells in culture, but both MDM2 overexpression and knockdown reduced these effects. Curcumin also inhibited the growth of these cells and enhanced the cytotoxic effects of gemcitabine. When it was administered to tumor-bearing nude mice, curcumin inhibited growth of PC3 xenografts and enhanced the antitumor effects of gemcitabine and radiation. In these tumors, curcumin reduced the expression of MDM2. Down-regulation of the MDM2 oncogene by curcumin is a novel mechanism of action that may be essential for its chemopreventive and chemotherapeutic effects. Our observations help to elucidate the process by which mitogens up-regulate MDM2, independent of p53, and identify a mechanism by which curcumin functions as an anticancer agent.

Epicardium-derived cells are important for correct development of the Purkinje fibers in the avian heart

During embryonic development, the proepicardial organ (PEO) grows out over the heart surface to form the epicardium. Following epithelial-mesenchymal transformation, epicardium-derived cells (EPDCs) migrate into the heart and contribute to the developing coronary arteries, to the valves, and to the myocardium. The peripheral Purkinje fiber network develops from differentiating cardiomyocytes in the ventricular myocardium. Intrigued by the close spatial relationship between the final destinations of migrating EPDCs and Purkinje fiber differentiation in the avian heart, that is, surrounding the coronary arteries and at subendocardial sites, we investigated whether inhibition of epicardial outgrowth would disturb cardiomyocyte differentiation into Purkinje fibers. To this end, epicardial development was inhibited mechanically with a membrane, or genetically, by suppressing epicardial epithelial-to-mesenchymal transformation with antisense retroviral vectors affecting Ets transcription factor levels (n=4, HH39-41). In both epicardial inhibition models, we evaluated Purkinje fiber development by EAP-300 immunohistochemistry and found that restraints on EPDC development resulted in morphologically aberrant differentiation of Purkinje fibers. Purkinje fiber hypoplasia was observed both periarterially and at subendocardial positions. Furthermore, the cells were morphologically abnormal and not aligned in orderly Purkinje fibers. We conclude that EPDCs are instrumental in Purkinje fiber differentiation, and we hypothesize that they cooperate directly with endothelial and endocardial cells in the development of the peripheral conduction system.

The Transcriptional ETS2 Repressor Factor Associates with Active and Inactive Erks through Distinct FXF Motifs

The transcriptional ETS2 repressor factor (ERF) is phosphorylated by Erks both in vivo and in vitro. This phosphorylation determines the subcellular localization and biological function of ERF. Here, we show that active and inactive Erk2 proteins bind ERF with high affinity through a hydrophobic pocket formed by the alphaF and alphaG helices and the activation loop of Erk2. We have identified two FXF motifs on ERF that mediate the specific interaction with Erks. One of these motifs is utilized only by active Erks, whereas the other mediates the association with inactive Erks but also contributes to interaction with active Erks. Mutation of the phenylalanines of these motifs to alanines resulted in decreased association and phosphorylation of ERF by Erks both in cells and in vitro. ERF proteins carrying these mutations exhibited increased nuclear accumulation and increased inhibition of cellular proliferation. Expression of ERF regions harboring these motifs could inhibit Erk activity in cells. Our data suggest that, in the proper context, FXF motifs can mediate a strong and specific interaction not only with active but also inactive Erks and that these interactions determine protein function in vivo.

Post-implantation mouse conceptuses produce paracrine signals that regulate the uterine endometrium undergoing decidualization

The uterus undergoes a series of dramatic changes in response to an implanting conceptus that, in some mammalian species, includes differentiation of the endometrial stroma into decidual tissue. This process, called decidualization, can be induced artificially in rodents indicating that the conceptus may not be essential for a proper maternal response in early pregnancy. In order to test this hypothesis, we determined if and how the conceptus affects uterine gene expression. We identified 5 genes (Angpt1, Angpt2, Dtprp, G1p2 and Prlpa) whose steady-state levels in the uterus undergoing decidualization depends on the presence of a conceptus. In situ hybridization revealed region-specific effects which suggested that various components of the conceptus and more than one signal from the conceptus are likely responsible for altering decidual cell function. Using cell culture models we found that trophoblast giant cells secrete a type I interferon-like molecule which can induce G1p2 expression in endometrial stromal cells. Finally, decidual Prlpa expression was reduced in the uterus adjacent to Hand1- and Ets2-deficient embryos, suggesting that normal trophoblast giant cells in the placenta are required for the conceptus-dependent effects on Prlpa expression in the mesometrial decidua. Overall, these results provide support for the hypothesis that molecular signals from the mouse conceptus have local effects on uterine gene expression during decidualization.

Expression of genes involved in the regulation of p16 in psoriatic involved skin

It has been suggested that the up-regulation of the tumour suppressor p16 gene and induction of senescence protect the phenotype of psoriatic involved skin from malignant transformation. On the other hand, Id1, which is inversely correlated with p16 has been shown to be up-regulated in psoriatic involved skin. To test the hypothesis that there may be an altered regulation of p16 in psoriatic involved skin, we have measured genes involved in the Igf-1 receptor signalling through the Ras/MAPK cascade. Igf-1R, IGFBP3, hRas, Ets2, JunB, Egr-1, Id1, MIDA1 and p16 gene expressions were measured using quantitative real-time PCR in total RNA isolated from punch biopsies from psoriatic involved (n = 9) and uninvolved skin (n = 9) and from cutaneous squamous cell cancer (SCC) involved (n = 8) and uninvolved skin (n = 8). The IGFBP3, hRas, JunB, Egr-1, Id1 and MIDA1 genes were up-regulated in psoriatic involved skin compared with uninvolved skin. The p16, JunB and MIDA1 genes were up-regulated in SCC involved skin compared with uninvolved skin. Our results indicate that there may be a balance between the proliferation and induction of senescence in psoriasis. This balance may vary and the psoriatic involved skin represented in this study appears to be in a proliferative state rather than senescence. Furthermore, we suggest that the noted up-regulation of JunB, which has been shown to up-regulate p16, in combination with the previously reported elevation of p16 expression in psoriatic involved skin, may indicate activation of a pathway by which JunB may protect the psoriatic plaque by inducing p16 in an event of malignant stress.

Ets2 is necessary in trophoblast for normal embryonic anteroposterior axis development

Although the trophoblast is necessary for the growth, viability and patterning of the mammalian embryo, understanding of its patterning role is still rudimentary. Expression of the transcription factor Ets2 is restricted to the trophoblast in early postimplantation stages and Ets2 mutants have been previously shown to have defects in trophoblast development. We show here that Ets2 is necessary in the trophoblast for fundamental aspects of anteroposterior (AP) epiblast axis initiation, including mesoderm initiation at the primitive streak,establishment of posterior character in the epiblast and appropriate spatial restriction of the anterior visceral endoderm (AVE). Most homozygous Ets2 mutants also show highly reduced development of the trophoblast with an absence of extraembryonic ectoderm (EXE) markers. Embryos in which the EXE has been physically removed before culture in vitro phenocopy the patterning defects of Ets2 mutants. These defects cannot be rescued by providing Ets2 mutants with wild-type epiblast in tetraploid aggregations. Thus, EXE-derived signals are necessary for normal embryonic patterning. Ets2 is likely to be required in the EXE downstream of epiblast signals, such as Fgf, and, in turn, helps to regulate signals from the EXE that signal back to the epiblast to promote proper primitive streak and AVE development. This study provides new insights about the genetic and cellular basis of the patterning role and development of the early trophoblast.

Transcription factors Ets2 and Sp1 act synergistically with histone acetyltransferase p300 in activating human interleukin-12 p40 promoter

There has been considerable interest in researching the regulatory mechanisms that control the synthesis of interleukin (IL)-12, which plays a central role in the differentiation of T-helper-1 cells. In this study, we performed a series of transient transfection experiments designed to elucidate the functional relationship between the IL-12 promoter-specific transcription factors (Ets2 and Sp1) and histone acetylation modification in IL-12 regulation mediated by p300 and various histone deacetylases (HDACs). Results presented in this report demonstrated that the transcription factors Ets2 and Sp1 acted synergistically with p300 to activate the human IL-12 promoter. The histone acetyltransferase (HAT) activity of p300 was required for this synergic effect, because the adenovirus E1A protein inhibited the synergy. Conversely, HDACs repressed the synergic effect of transcription factors and histone acetylation on the activation of IL-12, while p300 was able to rectify it. These data indicated that Ets2 and Sp1 worked concertedly and synergistically with p300 in the regulation of human IL-12 expression.

Ets2-dependent microenvironmental support of mouse mammary tumors

Decreasing the amount of active mouse Ets2 transcription factor by half in mice or use of a MAP kinase insensitive hypomorphic targeted Ets2 allele restricts the appearance of transgenic mammary tumors caused by either Polyoma middle T antigen (PyMT) or activated Neu/ErbB2. In addition, the early growth of transplanted mammary tumors is limited by restricted Ets2 activity of the host. Here we have tested genetically, with the use of a conditional Ets2flox allele and tissue specific Cre recombinase expression, whether Ets2 also functions within tumor cells by inactivating Ets2 within mammary luminal epithelial cells from which transgenic PyMTY315/322F tumors arise. We find that inactivation of Ets2 within tumor cells has no effect on tumor appearance or growth. By contrast, complete inactivation of Ets2 in both epithelial and stromal cells moderates the early hyperplastic phase of tumor development and the time of tumor appearance but does not prevent tumor occurrence and has no detectable effect on tumor growth. Thus, Ets2 supports mammary tumors exclusively through their microenvironment.

The effect of nimesulide, a selective cyclooxygenase-2 inhibitor, on Ets-1 and Ets-2 expression in head and neck cancer cell lines

BACKGROUND

The protooncogenes Ets-1 and Ets-2 are involved in carcinogenesis of different tumors. Nimesulide, a selective cyclooxygenase-2 (COX-2) inhibitor, has antiproliferative effects on tumor cells. The question arises whether nimesulide influences Ets-1 and Ets-2 synthesis in head and neck tumors.

METHODS

Expression of Ets-1 and Ets-2 was analyzed in tumor tissues by immunohistochemistry. The influence of nimesulide and an extracellular signal-regulated kinase (ERK) inhibitor on cell proliferation of two head and neck cancer cell lines and Ets-1 and Ets-2 expression was determined by automated cell counting and Western blotting, respectively.

RESULTS

Immunohistochemistry showed a high expression of Ets-1 and Ets-2 in tumor tissues. In both cell lines, Ets-1 and Ets-2 expression were reduced after 24 and 48 hours by nimesulide.

CONCLUSION

Both Ets-1 and Ets-2 are overexpressed in head and neck cancer specimens. Inhibition of Ets-1 and Ets-2 expression in head and neck cancer cell lines by nimesulide might explain the proapoptotic property of this COX-2 inhibitor.

Molecular evidence for a critical period in mural trophoblast development in bovine blastocysts

Embryonic and extra-embryonic lineages are separated at the blastocyst stage in the mouse at the onset of implantation but well ahead of implantation in most mammals. To provide information on the development of the trophoblast lineage in late-implanting bovine embryos, we combined the use of molecular markers defining embryonic and extra-embryonic lineages in the mouse with a transcriptomic approach dedicated to the early steps of the elongation process, a characteristic feature of blastocyst development in ruminants. In this study, we present molecular evidence for differences between the cow and the mouse in the programming of trophoblast differentiation. This different programming encompasses: (i) the expression of epiblast specifying genes (Oct-4, Nanog) in bovine trophoblast cells at the onset of elongation, (ii) the transcription of proliferation markers in early elongating blastocysts, (iii) the early detection of trophoblast-specific transcripts related to extra-embryonic tissue's differentiation (Hand1, Ets2, IFN-tau) and (iv) the identification of a new transcript (c12) which displays a reciprocal pattern to that of Oct-4 and Nanog genes in the embryonic cells and for which no equivalent has thus far been found in the mouse. Altogether, these results tended to show that early elongation is a critical transition in bovine trophoblast development.

Increased Dosage of the RUNX1/AML1 Gene: A Third Mode of RUNX Leukemia?

RUNX1/AML1, located on chromosome 21, is a key factor in the generation and maintenance of hematopoietic stem cells and the gene most frequently implicated in human leukemias. Chromosome translocations and point mutations are well-documented genetic alterations in RUNX leukemia (also known as CBF leukemia). In addition, overdosage or overexpression of RUNX1 is suspected to be a third mode of RUNX1 involvement in leukemogenesis. The possibility that this mode might underlie Down syndrome-related leukemias caused by trisomy of chromosome 21 is discussed.