PDEF is a negative regulator of colon cancer cell growth and migration.

ETS is a family of transcriptional regulators with functions in most biological processes. Dysregulated ETS factor function leads to altered expression of multiple genes that play critical roles in many of the processes required for cancer progression. While the Ets family gene, prostate-derived ETS factor (PDEF), is expressed in epithelial tissues including prostate, breast, and colon, PDEF protein expression has been found to be reduced or lost during prostate and breast cancer progression. The goal of this study was to examine the expression and biologic impact of altered PDEF expression in colon cancer. PDEF mRNA and protein are not detectable in several colon-cancer-derived cell lines. Re-expression of PDEF in colon cancer cells inhibits growth and migration. Growth affects are due to altered cellular proliferation, indicated by increased altered cell population in G(1) and S phases of the cell cycle, as well as increased apoptosis. Relevant to its modulation of growth and migration phenotypes, PDEF expression resulted in altered expression of genes with established roles in cell cycle, motility, and invasion. Furthermore, chromatin immunoprecipitation studies show that p21 and urokinase plasminogen activator (uPA) are direct PDEF transcriptional targets. While non-tumor colon epithelium expresses PDEF mRNA and protein, the majority of tumors showed decreased mRNA and/or protein expression. In human tumor tissue samples, PDEF expression was inversely correlated with the expression levels of uPA. Collectively, the data support the model that PDEF is a negative regulator of tumor progression by modulating the expression of growth and migration promoting genes.

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.

Pdef expression in human breast cancer is correlated with invasive potential and altered gene expression.

Ets transcription factors control multiple biological processes, including cell proliferation, differentiation, apoptosis, angiogenesis, transformation, and invasion. Pdef is an Ets transcription factor originally identified in prostate tissue. We demonstrate that human Pdef is expressed at high levels primarily in tissues with high epithelial cell content, including prostate, colon, and breast. We also determined that Pdef protein is reduced in human invasive breast cancer and is absent in invasive breast cancer cell lines. We next assessed the functional consequences of these observations. Significantly, expression of Pdef in breast cancer cells leads to inhibition of invasion, migration, and growth. Expression of Pdef also results in the down-regulation of urokinase-type plasminogen activator and activation of the promoter of the tumor suppressor gene, MASPIN: Growth-suppressive effects of Pdef expression are mediated in part by a G(0)-G(1) cell cycle arrest associated with elevated p21 levels. Collectively, these results indicate that Pdef loss may alter the expression of genes controlling progression to invasive breast cancer.

The epithelial-specific Ets factors occupy a unique position in defining epithelial proliferation, differentiation and carcinogenesis.

The Ets family of transcription factors regulates many biological processes. Within the Ets family are a subset of proteins that have epithelial restricted expression patterns, both in tissues and cell lines. These Epithelial-specific Ets (Ese) factors, cluster into two groups based on the sequence of the Ets DNA binding domain: (i) Ese1, Ese2 and Ese3, and (ii) the more divergent, Pdef. Gene targeting and cell culture studies have demonstrated that Ese factors are important for cellular differentiation. Furthermore, the ability of Ese factors to regulate expression of genes that are markers of differentiation supports this model. Significantly, the expression profile of these Ese factors is altered in epithelial cancers relative to the respective normal tissues. It is likely that this variation in expression affects downstream target genes important for carcinogenesis such as oncogenes and tumor suppressor genes. Understanding the role of these Ese factors in normal cellular differentiation may elucidate specific mechanisms by which cancer cells can become undifferentiated.

Beyond expression profiling: next generation uses of high density oligonucleotide arrays.

In the past decade, microarray technology has become a major tool for high-throughput comprehensive analysis of gene expression, genotyping and resequencing applications. Currently, the most widely employed application of high-density oligonucleotide arrays (HDOAs) involves monitoring changes in gene expression. This application has been carried out in a variety of organisms ranging from Escherichia coli to humans. The recent near completion of the human and mouse genome sequences, however, as well as the genomes of other model experimental species, has allowed for novel applications of HDOAs, such as: the discovery of novel transcripts, mapping functionally important genomic regions and identifying functional domains in RNA molecules. Integrating all this information will provide novel global views of the locations of RNA transcription, DNA replication and the protein nucleic acid interactions that regulate these processes.

Ets1 is an effector of the transforming growth factor beta (TGF-beta ) signaling pathway and an antagonist of the profibrotic effects of TGF-beta.

Extracellular matrix (ECM) production and turnover are tightly controlled under normal physiological conditions. Ets factors regulate matrix turnover by activating transcription of several metalloproteinases (MMPs) and are frequently overexpressed in aggressive tumors and arthritis. Because of the prominent role of transforming growth factor beta (TGF-beta) in ECM synthesis, this study was undertaken to determine the possible interactions between Ets1 and the TGF-beta pathway. Experiments using adenoviral delivery of Ets1 in human fibroblasts have established that Ets1 strongly suppresses TGF-beta induction of collagen type I and other matrix-related genes and reverses TGF-beta-dependent inhibition of MMP-1. Subsequent experiments utilizing COL1A2 promoter demonstrated that Ets1 in the presence of TGF-beta signaling interferes with the stimulatory role of p300. To gain further insight into the mechanism of Ets1 inhibition of the TGF-beta signaling, the protein levels and post-translational modifications of Ets1 after TGF-beta treatment were analyzed. The level of total Ets1 protein was not affected after 24 h of TGF-beta stimulation. Moreover, TGF-beta did not affect either serine or threonine phosphorylation levels of Ets1. However, TGF-beta induced rapid and prolonged lysine acetylation of Ets1. In addition, analyses of endogenous p300.Ets1 complexes revealed that acetylated Ets1 is preferentially associated with the p300/CBP complexes. TGF-beta treatment leads to dissociation of Ets1 from the CBP/p300 complexes. Together, these findings suggest that elevated expression of Ets1 in fibroblasts fundamentally alters their responses to TGF-beta in favor of matrix degradation and away from matrix deposition as exemplified by arthritis and cancer.