Biomedical subjects

Dennis K Watson

Publications and source records attributed to Dennis K Watson.

At least 19 recordsLinked to original sources

PubMed2006

Maturation stage-specific regulation of megakaryopoiesis by pointed-domain Ets proteins.

Numerous megakaryocyte-specific genes contain signature Ets-binding sites in their regulatory regions. Fli-1 (friend leukemia integration 1), an Ets transcription factor, is required for the normal maturation of megakaryocytes and controls the expression of multiple megakaryocyte-specific genes. However, in Fli-1-/- mice, early megakaryopoiesis persists, and the expression of the early megakaryocyte-specific genes, alphaIIb and cMpl, is maintained, consistent with functional compensation by a related Ets factor(s). Here we identify the Ets protein GABPalpha (GA-binding protein alpha) as a regulator of early megakaryocyte-specific genes. Notably, GABPalpha preferentially occupies Ets elements of early megakaryocyte-specific genes in vitro and in vivo, whereas Fli-1 binds both early and late megakaryocyte-specific genes. Moreover, the ratio of GABPalpha/Fli-1 expression declines throughout megakaryocyte maturation. Consistent with this expression pattern, primary fetal liver-derived megakaryocytes from Fli-1-deficient murine embryos exhibit reduced expression of genes associated with late stages of maturation (glycoprotein [GP] Ibalpha, GPIX, and platelet factor 4 [PF4]), whereas GABPalpha-deficient megakaryocytes were mostly impaired in the expression of early megakaryocyte-specific genes (alphaIIb and cMpl). Finally, mechanistic experiments revealed that GABPalpha, like Fli-1, can impart transcriptional synergy between the hematopoietic transcription factor GATA-1 and its cofactor FOG-1 (friend of GATA-1). In concert, these data reveal disparate, but overlapping, functions of Ets transcription factors at distinct stages of megakaryocyte maturation.

Animals↗

PubMed2006

Transcription factor Ets-1 regulates fibroblast growth factor-1-mediated angiogenesis in vivo: role of Ets-1 in the regulation of the PI3K/AKT/MMP-1 pathway.

We previously demonstrated that a modified secreted form of fibroblast growth factor 1 (FGF-1), a prototypic member of the FGF family, has the ability to stimulate angiogenesis in an in vivo model of angiogenesis, the so-called chick chorioallantoic membrane assay or CAM. We recently defined the importance of the phosphatidylinositol 3-kinase/AKT pathway in FGF-1-mediated angiogenesis in this model using specific pharmacological inhibitors. In our continuing efforts to define the molecular signaling pathway regulating FGF-1-induced angiogenesis in vivo, we utilized a transcription factor activity assay and identified transcription factor Ets-1 as a critical effector of FGF-1-induced angiogenesis. Both activity and mRNA expression levels of the Ets-1 molecule were increased in response to FGF-1 overexpression in CAMs, as documented by electrophoretic mobility shift assay (gel shift) and reverse transcription real-time PCR techniques, respectively. Furthermore, the delivery of Ets-1 antisense (AS) into CAM tissues effectively reduced angiogenesis in the CAM assay. In addition, both Ets-1 AS-treated chicken CAMs and cultured endothelial cells exhibited a reduction in matrix metalloproteinase 1 gene expression levels. The Ets-1 AS-treated endothelial cells also demonstrated a reduction in migration. These data suggest that Ets-1 activation is a requisite for FGF-1-mediated angiogenesis in vivo. Therefore, Ets-1 might be a potential target for the generation of inhibitor drugs for the treatment of FGF-dependent pathological angiogenesis such as metastatic tumors, rheumatoid arthritis and diabetic retinopathy.

Animals↗

PubMed2006

Evaluation of survivin reverse transcriptase-polymerase chain reaction for noninvasive detection of bladder cancer.

PURPOSE: Survivin, a member of the inhibitor of apoptosis gene family, is expressed in most common cancers. We investigated the expression pattern of survivin in the tumors of patients with bladder cancer and assessed the diagnostic potential of RT-PCR detection of survivin mRNA in urine. MATERIALS AND METHODS: RT-PCR was used to analyze mRNA expression of survivin in 161 cases of bladder cancer, including TCC in 97, SCC in 53 and adenocarcinoma in 11, and their matched nontumor tissues. Urine specimens (50 ml) were collected from 84 patients in whom bladder cancer was documented by transurethral resection or biopsy, 41 with nonbladder cancer urological diseases and 42 healthy volunteers. Total RNA was extracted from urine sediments and RT-PCR was performed for survivin. RESULTS: Survivin expression was detected in all bladder cancer tissues. In contrast, survivin was not detectable in normal urothelium specimens. Urinary survivin was detected in urine samples from 51 of 53 patients with TCC, 22 of 25 with SCC and 6 of 6 with adenocarcinoma. Overall sensitivity was 94%. Survivin mRNA was not detected in any healthy volunteers. Positive results were obtained in 2 patients with renal cell carcinoma, 1 with hematuria and 1 with a contracted bladder but in none with other urological diseases. Overall specificity was 95%. CONCLUSIONS: Survivin mRNA detection in urine sediment using RT-PCR shows high sensitivity and specificity for bladder cancer. It may prove useful for the routine screening and monitoring of patients.

Gene Expression Regulation, Neoplastic↗

PubMed2005

Prognostic and functional significance of thromboxane synthase gene overexpression in invasive bladder cancer.

Thromboxane synthase (TXAS) is one of the enzymes downstream from cyclooxygenase-2 and catalyzes the synthesis of thromboxane A(2) (TXA(2)). TXAS was among the genes we identified based on its overexpression in invasive bladder tumors. TXAS is overexpressed in common forms of bladder tumors: 69 of 97 (71.1%) transitional cell carcinoma (TCC), 38 of 53 (71.6%) squamous cell carcinoma, and 5 of 11 (45.5%) adenocarcinoma relative to nontumor tissue. Overall, 112 of 161 (69.5%) invasive tumors exhibited elevated expression. Significantly, patients with tumors having >4-fold levels of TXAS expression showed significant statistical evidence of lower overall survival expressed by the estimated hazard ratio of 2.74 with P = 0.009 in Cox's regression analysis. TXAS mRNA expression was found to be an independent prognostic marker for patients with bladder cancer. Treatment of bladder cancer cell lines (T24 and TCC-SUP) with TXAS inhibitors and TXA(2) (TP) receptor antagonists reduced cell growth, migration, and invasion, whereas TP agonists stimulated cell migration and invasion. The positive correlation between elevated TXAS expression and shorter patient survival supports a potential role for TXAS-regulated pathways in tumor invasion and metastases and suggests that modulation of the TXAS pathway may offer a novel therapeutic approach.

Adenocarcinoma↗

PubMed2005

Bystander effect contributes to the antitumor efficacy of CaSm antisense gene therapy in a preclinical model of advanced pancreatic cancer.

Pancreatic adenocarcinoma (PC) is an aggressive malignancy resistant to standard treatment modalities. Previously, we have reported that cancer-associated Sm-like protein (CaSm) contributes to the neoplastic transformation of PC. In this study, we utilized a recently established preclinical model of PC to determine if molecular targeting of CaSm can serve as the basis for a novel PC therapy. In a subcutaneous tumor model, intratumoral administration of an adenoviral vector encoding CaSm antisense RNA (Ad-alphaCaSm) significantly inhibited Panc02 tumor growth. Furthermore, in a metastatic tumor model, systemic administration of Ad-alphaCaSm resulted in a significant decrease in the number of hepatic metastases and increased survival time. We assessed the efficiency of in vivo delivery and observed significant levels of vector transduction in tissues containing PC, as well as a bystander effect that was amplifying the efficacy of CaSm gene therapy. This bystander effect was also active in vitro and was shown to be at least partially independent of host-related mechanisms. We conclude that CaSm antisense gene therapy is an effective novel therapy for PC and that the antitumor efficacy is dependent on both direct and bystander mechanisms.

Adenoviridae↗

PubMed2005

ETS transcription factors and their emerging roles in human cancer.

Cancer can be defined as a genetic disease, resulting as a consequence of multiple events associated with initiation, promotion and metastatic growth. Cancer results from the loss of control of cellular homeostasis. Cell homeostasis is the result of the balance between proliferation and cell death, while cellular transformation can be viewed as a loss of relationship between these events. Oncogenes and tumour suppressor genes act as modulators of cell proliferation, while the balance of apoptotic and anti-apoptotic genes controls cell death. All cancer cells acquire similar sets of functional capacities: (1) independence from mitogenic/growth signals; (2) loss of sensitivity to "anti-growth" signals; (3) evade apoptosis; (4) Neo-angiogenic conversion; (5) release from senescence; and (6) invasiveness and metastasis. One of the goals of molecular biology is to elucidate the mechanisms that contribute to the development and progression of cancer. Such understanding of the molecular basis of cancer will provide new possibilities for: (1) earlier detection as well as better diagnosis and staging of disease with detection of minimal residual disease recurrences and evaluation of response to therapy; (2) prevention; and (3) novel treatment strategies. We feel that increased understanding of ETS-regulated biological pathways will directly impact these areas. ETS proteins are transcription factors that activate or repress the expression of genes that are involved in various biological processes, including cellular proliferation, differentiation, development, transformation and apoptosis. Identification of target genes that are regulated by a specific transcription factor is one of the most critical areas in understanding the molecular mechanisms that control transcription. Furthermore, identification of target gene promoters for normal and oncogenic transcription factors provides insight into the regulation of genes that are involved in control of normal cell growth, and differentiation, as well as provide information critical to understanding cancer development. This review will highlight the current understanding of ETS genes and their role in cancer.

Genes, Tumor Suppressor↗

PubMed2005

Caspase-1 is a direct target gene of ETS1 and plays a role in ETS1-induced apoptosis.

ETS1, the founding member of Ets transcriptional factor family, plays an important role in cell proliferation, differentiation, lymphoid cell development, transformation, angiogenesis, and apoptosis. Previous work has shown that ETS1 represses tumorigenicity of colon carcinoma cells in vivo, and that the p42-ETS1 protein bypasses a defect in apoptosis in colon carcinoma cells through the up-regulation of caspase-1 expression. In this report, we show that expression of p42-ETS1 inhibits tumorigenicity of colon cancer DLD-1 cells through induction of apoptosis in vivo. In support of the hypothesis that caspase-1 might be a target involved in the sensitization of DLD-1 cells to Fas-induced apoptosis by ETS1, overexpression of caspase-1 bypasses Fas-induced apoptosis in these cells as well. Furthermore, ETS1-mediated apoptosis was observed in MOP8 cells, a transformed mouse NIH3T3 cell line. To determine whether ETS1 activates the transcription of caspase-1, luciferase reporters driven by the wild-type and mutant caspase-1 promoters were generated. Both p51-ETS1 and p42-ETS1 transactivated the caspase-1 transcription and a functional Ets binding site is identified in the caspase-1 promoter. Wild-type caspase-1 promoter (pGL3-ICE) was strongly transactivated by ETS1 and this transactivation was dramatically diminished by the mutation of the potential Ets binding site (-525 bp). In addition, electrophoretic mobility shift assay and chromatin immunoprecipitation assay showed complex formation between this binding site and ETS1 proteins. Taken together, ETS1 transcriptionally induces the expression of caspase-1; as such, the regulatory control of caspase-1 expression by ETS1 may underlie the apoptotic susceptibility modulated by ETS1 in specific tumor cells.

Animals↗

PubMed2005

CaSm-mediated cellular transformation is associated with altered gene expression and messenger RNA stability.

CaSm (cancer-associated Sm-like) was originally identified based on elevated expression in pancreatic cancer and in several cancer-derived cell lines. CaSm encodes a 133 amino acid protein that contains two Sm motifs found in the common small nuclear RNA proteins and the LSm (like-Sm) family of proteins. Compared with normal human prostate tissue and primary prostate epithelial cells, some primary prostate tumors and prostate cancer-derived cell lines have elevated CaSm expression. Expression of antisense CaSm RNA in DU145 cells results in reduced CaSm protein levels and less transformed phenotype, measured by anchorage-independent growth in vitro and tumor formation in severe combined immunodeficient mice in vivo. Additional data shows that adenoviral delivery of antisense CaSm inhibits the growth of prostate cancer cell lines by altering cell cycle progression, and is associated with reduced expression of cyclin B1 and CDK1 proteins. Consistent with failure of antisense-treated cells to enter mitosis, microarray analysis identified altered expression of NEK2 and nucleophosmin/B23. Although the mechanisms by which CaSm contributes to neoplastic transformation and cellular proliferation are unknown, it has been shown that the yeast homologue (spb8/LSm1) of CaSm is required for 5' to 3' degradation of specific mRNAs. We provide data consistent with a similar role for CaSm in human cells, supporting the hypothesis that elevated CaSm expression observed in cancer leads to destabilization of multiple gene transcripts, contributing to the mutator phenotype of cancer cells.

Adenoviridae↗

PubMed2005

SP100 inhibits ETS1 activity in primary endothelial cells.

SP100 was first identified as a nuclear autoimmune antigen and is a constituent of the nuclear body. SP100 interacts with the ETS1 transcription factor, and we have previously shown that SP100 reduces ETS1-DNA binding and inhibits ETS1 transcriptional activity on the MMP1 and uPA promoters. We now demonstrate that SP100 expression is upregulated by interferons, which have been shown to be antiangiogenic, in primary endothelial cells. As ETS1 is functionally important in promoting angiogenesis, we tested the hypothesis that ETS1 activity is negatively modulated by SP100 in endothelial cells. SP100 directly antagonizes ETS1-mediated morphological changes in human umbilical vein endothelial cell (HUVEC) network formation and reduces HUVEC migration and invasion. To further understand the functional relationship between ETS1 and SP100, cDNA microarray analysis was utilized to assess reprogramming of gene expression by ETS1 and SP100. A subset of the differentially regulated genes, including heat-shock proteins (HSPs) H11, HSPA1L, HSPA6, HSPA8, HSPE1 and AXIN1, BRCA1, CD14, CTGF (connective tissue growth factor), GABRE (gamma-aminobutyric acid A receptor epsilon), ICAM1, SNAI1, SRD5A1 (steroid-5-alpha-reductase 1) and THY1, were validated by real-time PCR and a majority showed reciprocal expression in response to ETS1 and SP100. Interestingly, genes that are negatively regulated by ETS1 and upregulated by SP100 have antimigratory or antiangiogenic properties. Collectively, these data indicate that SP100 negatively modulates ETS1-dependent downstream biological processes.

Antigens, Nuclear↗

PubMed2005

Establishing a murine pancreatic cancer CaSm model: up-regulation of CaSm is required for the transformed phenotype of murine pancreatic adenocarcinoma.

We have recently shown that the cancer-associated Sm-like protein (CaSm) is overexpressed in human pancreatic adenocarcinoma (PC). However, the role of CaSm in the process of neoplastic transformation remains unclear. To define further the role of CaSm in PC transformation, we have established a murine model based on the murine pancreatic cancer cell lines Panc02 and Panc03. CaSm is overexpressed in the aggressive Panc02 cells and expressed at much lower levels in the more indolent Panc03 cells. Up-regulation of CaSm in Panc03 cells increased in vitro proliferation and anchorage-independent growth and promoted subcutaneous tumor establishment and growth in syngeneic mice. Conversely, adenoviral down-regulation of CaSm in Panc02 led to significant inhibition of cellular proliferation and anchorage-independent growth in vitro and complete abolition of tumor growth and metastasis in vivo. Up-regulation of CaSm in NIH3T3 resulted in loss of contact inhibition and increased soft agar colony formation in vitro. The requirement for CaSm overexpression for neoplastic transformation confirms the concept that CaSm is a critical oncogene and potential target for molecular intervention. Furthermore, establishment of the murine clinically relevant model of pancreatic metastases provides a framework for the generation of preclinical data to support the development of novel molecular therapies targeting CaSm.

Adenocarcinoma↗

PubMed2005

The FLI-1 transcription factor is a short-lived phosphoprotein in T cells.

The FLI-1 transcription factor is a member of the ETS gene family, most closely related to ERG. In this study, the FLI-1 protein products were characterized using a specific monoclonal antibody previously developed against bacterially expressed protein. In the human T-cell line Jurkat, both isoforms of FLI-1, p51 and p48, are phosphorylated, primarily on serine residues. FLI-1 phosphorylation is increased by a Ca(2+)-mediated process, and inhibitor studies indicate that protein phosphatase 2A, at least in part, controls FLI-1 phosphorylation level. FLI-1 phosphorylation is not stimulated by phorbal 12-myristate 13-acetate (PMA), a protein kinase C activator, and in this it differs from ERG protein phosphorylation. The p51 isoform has a half-life of 105 min, and p48 has a half-life of 80 min; in contrast, the ERG protein is much more stable with a half-life of 21 h. Newly synthesized FLI-1 protein decreased during human T cell activation. Our data suggest that although the FLI-1 and ERG genes are highly homologous, their distinct properties may contribute to their different roles in gene regulation.

Antibodies, Monoclonal↗

PubMed2004

Interleukins 2 and 15 regulate Ets1 expression via ERK1/2 and MNK1 in human natural killer cells.

Interleukins (IL)-2 and IL-15 regulate natural killer (NK) cell proliferation, survival, and cytolytic activity. Ets1 is a transcription factor expressed early in NK cell differentiation. Because IL-2Rbeta, IL-2Rgamma, IL-15, and Ets1 knock-out mice similarly lack NK cells, we explored a molecular connection between IL-2R signaling and Ets1. Here we report the post-transcriptional regulation of Ets1 by IL-2R signaling in human NK cells. IL-2 and IL-15 stimulation leads to increased Ets1 protein levels with no significant change in mRNA levels. Pulse and pulse-chase experiments show that IL-2 stimulation results in both a marked increase in the nascent translation of Ets1 and an increased protein half-life. Pharmacological inhibition of MEK specifically blocks IL-2- and IL-15-induced translation, whereas p38, phosphatidylinositol 3-kinase, and mTOR inhibitors had no effect on Ets1 levels. Fli1, an Ets family member, exhibited a different mechanism of regulation, illustrating the specificity of IL-2R beta and gamma subunit signaling on the regulation of Ets1 expression. Expression of a dominant negative form of MNK1, a regulator of the translation initiation factor eIF4E, blocks the expression of Ets1 as do the dominant negative forms of the common IL-2R beta and gamma chains. Expression of Ets1 is regulated similarly in normal peripheral human NK cells. Taken together, our findings provide a direct link between IL-2R subunit signaling and Ets1 expression and helps to explain the interdependence of the IL-2R subunits and Ets1 for NK cell development and function.

Androstadienes↗

PubMed2004

Decreased expression of the Ets family transcription factor Fli-1 markedly prolongs survival and significantly reduces renal disease in MRL/lpr mice.

Increased Fli-1 mRNA is present in PBLs from systemic lupus erythematosus patients, and transgenic overexpression of Fli-1 in normal mice leads to a lupus-like disease. We report in this study that MRL/lpr mice, an animal model of systemic lupus erythematosus, have increased splenic expression of Fli-1 protein compared with BALB/c mice. Using mice with targeted gene disruption, we examined the effect of reduced Fli-1 expression on disease development in MRL/lpr mice. Complete knockout of Fli-1 is lethal in utero. Fli-1 protein expression in heterozygous MRL/lpr (Fli-1(+/-)) mice was reduced by 50% compared with wild-type MRL/lpr (Fli-1(+/+)) mice. Fli-1(+/-) MRL/lpr mice had significantly decreased serum levels of total IgG and anti-dsDNA Abs as disease progressed. Fli-1(+/-) MRL/lpr mice had significantly increased splenic CD8(+) and naive T cells compared with Fli-1(+/+) MRL/lpr mice. Both in vivo and in vitro production of MCP-1 were significantly decreased in Fli-1(+/-) MRL/lpr mice. The Fli-1(+/-) mice had markedly decreased proteinuria and significantly lower pathologic renal scores. At 48 wk of age, survival was significantly increased in the Fli-1(+/-) MRL/lpr mice, as 100% of Fli-1(+/-) MRL/lpr mice were alive, in contrast to only 27% of Fli-1(+/+) mice. These findings indicate that Fli-1 expression is important in lupus-like disease development, and that modulation of Fli-1 expression profoundly decreases renal disease and improves survival in MRL/lpr mice.

Animals↗

PubMed2004

Ets-dependent regulation of target gene expression during megakaryopoiesis.

Megakaryopoiesis is the process by which hematopoietic stem cells in the bone marrow differentiate into mature megakaryocytes. The expression of megakaryocytic genes during megakaryopoiesis is controlled by specific transcription factors. Fli-1 and GATA-1 transcription factors are required for development of megakaryocytes and promoter analysis has defined in vitro functional binding sites for these factors in several megakaryocytic genes, including GPIIb, GPIX, and C-MPL. Herein, we utilize chromatin immunoprecipitation to examine the presence of Ets-1, Fli-1, and GATA-1 on these promoters in vivo. Fli-1 and Ets-1 occupy the promoters of GPIIb, GPIX, and C-MPL genes in both Meg-01 and CMK11-5 cells. Whereas GPIIb is expressed in both Meg-01 and CMK11-5 cells, GPIX and C-MPL are only expressed in the more differentiated CMK11-5 cells. Thus, in vivo occupancy by an Ets factor is not sufficient to promote transcription of some megakaryocytic genes. GATA-1 and Fli-1 are both expressed in CMK11-5 cells and co-occupy the GPIX and C-MPL promoters. Transcription of all three megakaryocytic genes is correlated with the presence of acetylated histone H3 and phosphorylated RNA polymerase II on their promoters. We also show that exogenous expression of GATA-1 in Meg-01 cells leads to the expression of endogenous c-mpl and gpIX mRNA. Whereas GPIIb, GPIX, and C-MPL are direct target genes for Fli-1, both Fli-1 and GATA-1 are required for formation of an active transcriptional complex on the C-MPL and GPIX promoters in vivo. In contrast, GPIIb expression appears to be independent of GATA-1 in Meg-01 cells.

Base Sequence↗

PubMed2004

Dysregulation of granulocyte, erythrocyte, and NK cell lineages in Fli-1 gene-targeted mice.

Targeted disruption of the Friend leukemia integration 1 (Fli-1) proto-oncogene results in severe dysmegakaryopoiesis and embryonic lethality. We used morula-stage aggregation as a strategy to further clarify the hematopoietic defects of the Fli-1 gene-targeted mice. Analyses of lineage expression of Fli-1(+/-) and Fli-1(-/-) cells in the peripheral blood and bone marrow of chimeric mice consistently demonstrated reduced numbers of neutrophilic granulocytes and monocytes and increased numbers of natural killer (NK) cells. Transplantation studies using sorted Fli-1 mutant cells produced similar findings. Clonal culture studies of bone marrow cells revealed increased numbers of granulocytic and early erythroid progenitors in the Fli-1(+/-) cells. The sorted Fli-1(-/-) bone marrow cells revealed specific down-regulation of CCAAT/enhancer binding protein-alpha (C/EBPalpha) and C/EBPepsilon, and the receptors for granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage CSF (GM-CSF), consistent with their critical roles in granulopoiesis. Collectively, these observations suggest previously unknown physiologic roles for Fli-1 in granulocytic, erythroid, and NK cell proliferation and differentiation. Production of chimeras by morula-stage embryo aggregation is an effective way to unravel cell-autonomous hematopoietic defects in gene-targeted mice.

Animals↗

PubMed2004

SP100 expression modulates ETS1 transcriptional activity and inhibits cell invasion.

The ETS1 transcription factor is a member of the Ets family of conserved sequence-specific DNA-binding proteins. ETS1 has been shown to play important roles in various cellular processes such as proliferation, differentiation, lymphoid development, motility, invasion and angiogenesis. These diverse roles of ETS1 are likely to be dependent on specific protein interactions. To identify proteins that interact with ETS1, a yeast two-hybrid screen was conducted. Here, we describe the functional interaction between SP100 and ETS1. SP100 protein interacts with ETS1 both in vitro and in vivo. SP100 is localized to nuclear bodies and ETS1 expression alters the nuclear body morphology in living cells. SP100 negatively modulates ETS1 transcriptional activation of the MMP1 and uPA promoters in a dose-dependent manner, decreases the expression of these endogenous genes, and reduces ETS1 DNA binding. Expression of SP100 inhibits the invasion of breast cancer cells and is induced by Interferon-alpha, which has been shown to inhibit the invasion of cancer cells. These data demonstrate that SP100 modulates ETS1-dependent biological processes.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Triplex DNA-mediated downregulation of Ets2 expression results in growth inhibition and apoptosis in human prostate cancer cells.

Ets2 is a member of the Ets family of transcription factors that in humans comprise 25 distinct members. Various Ets-domain transcription factors have been implicated in cancer development. Ets2 is expressed in prostate and breast cancer cells and is thought to have a role in promoting growth and survival in these cell types. However, a definitive role and the mechanisms whereby Ets2 acts in cancer cells are still unclear. Structural and functional similarities as well as overlapping DNA binding specificities complicate the identification of the specific roles of the various Ets factors. In this study, we used a triplex-forming oligonucleotide (TFO) to selectively inhibit Ets2 transcription in prostate cancer cells. We had previously shown that the Ets2-targeting TFO, which was directed to a unique purine-rich sequence critical for Ets2 promoter activity, acted with a high degree of sequence-specificity and target selectivity. TFO-mediated downregulation of Ets2 in prostate cancer cells induced important phenotypic changes, including inhibition of anchorage-dependent and anchorage -independent growth, cell cycle alterations and induction of apoptotic cell death. Expression of Ets2 under the control of a heterologous promoter abolished the anti-proliferative effects of the TFO in both short- and long-term assays, suggesting that these effects were a direct result of downregulation of Ets2 transcription and confirming target selectivity of the TFO. Furthermore, normal human fibroblasts, which expressed low levels of Ets2, were not affected by the Ets2-targeting TFO. Downregulation of Ets2 in prostate cancer cells was associated with reduced levels of the anti-apoptotic protein bcl-x(L) and growth regulatory factors cyclin D1 and c-myc. These data revealed a specific role of this transcription factor in promoting growth and survival of prostate cancer cells. Furthermore, the activity and selectivity of the Ets2-targeting TFO suggest that it might represent a valid approach to prostate cancer therapy.

Apoptosis↗

PubMed2004

Ets proteins in biological control and cancer.

The Ets family consists of a large number of evolutionarily conserved transcription factors, many of which have been implicated in tumor progression. Extensive studies on this family of proteins have focused so far mainly on the biochemical properties and cellular functions of individual factors. Since most of the Ets factors can bind to the core consensus DNA sequence GGAA/T in vitro, it has been a challenge to differentiate redundant from specific functions of various Ets proteins in vivo. Recent findings, however, suggest that such apparent redundancy may in fact be a central component of a network of differentially regulated specific Ets factors, resulting in distinct biological and pathological consequences. The programmed "Ets conversion" appears to play a critical role during tumor progression, especially in control of cellular changes during epithelial-mesenchymal transition and metastasis. Coordination of multiple Ets gene functions also mediates interactions between tumor and stromal cells. 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.

Animals↗