Abstract-The success of therapeutic vascularization and tissue engineering will rely on our ability to create vascular networks using human cells that can be obtained readily, can be expanded safely ex vivo, and can produce robust vasculogenic activity in vivo. Here we describe the formation of functional microvascular beds in immunodeficient mice by coimplantation of human endothelial and mesenchymal progenitor cells isolated from blood and bone marrow.

We report here the isolation of a novel, highly tissue-restricted member of the ets transcription factor/ oncogene family, ESE-1 (for epithelium-specific Ets), which has features distinct from those of any other ets-related factor. ESE-1 contains two putative DNA binding domains: an ETS domain, which is unique in that the 5 half shows relatively weak homology to known ets factors, and an A/T hook domain, found in HMG proteins and various other nuclear factors. In contrast to any known ets factors, ESE-1 is expressed exclusively in epithelial cells. ESE-1 expression is induced during terminal differentiation of the epidermis and in a primary human keratinocyte differentiation system. The keratinocyte terminal differentiation marker gene, SPRR2A, is a putative target for ESE-1, since SPRR2A expression during keratinocyte differentiation correlates with induction of ESE-1 expression, and ESE-1 binds with high affinity to and transactivates the ets binding site in the SPRR2A promoter. ESE-1 also binds to and transactivates the enhancer of the Endo A gene, a potential target for ESE-1 in simple epithelia. Due to the important role that other ets factors play in cellular differentiation, ESE-1 is expected to be a critical regulator of epithelial cell differentiation.Although several aspects of epithelium-specific gene expression have been recently elucidated, very few distinctly epithelial cell-restricted transcription factors have been characterized. This is in striking contrast to the identification of a vast number of genes transcribed exclusively in epithelial cells. Epithelium-specific gene regulation plays a critical role during embryogenesis, and the epithelial cell lineage is the first differentiated cell type to appear after fertilization. Differentiation of epithelial cells proceeds along a tightly controled pathway towards cell cycle arrest and terminal differentiation, characterized by precisely timed regulation of specific sets of genes. The majority of epithelial cancers originate as a result of aberrant gene expression leading to defects in epithelial cell differentiation and proliferation.In search of transcriptional regulators of cell differentiation, we have focused on members of the ets transcription factor/ oncogene family (26,42,54). All members of the ets family share a highly conserved DNA binding domain, the ETS domain (81). Outside the DNA binding domain, very little homology is common to all members of the ets family (81). However, ets-related proteins can be grouped into subclasses based on additional homologous domains shared by particular members of the ets family (26). The involvement of ets factors in human carcinogenesis has recently been highlighted by the discovery of several distinct chromosomal translocations involving specific members of the ets family in different cancer types (10,19,20,27,57,85). ets factors play a critical role in transcriptional control of stringently regulated genes, such as genes involved in tissue development, differentiation, angiogenesis, cell cycle contro...

Prostate cancer, the most frequent solid cancer in older men, is a leading cause of cancer deaths. Although proliferation and differentiation of normal prostate epithelia andtheinitialgrowthofprostatecancercellsareandrogendependent, prostate cancers ultimately become androgen-independent and refractory to hormone therapy. The prostate-specific antigen (PSA) gene has been widely used as a diagnostic indicator for androgen-dependent and -independent prostate cancer. Androgen-induced and prostate epithelium-specific PSA expression is regulated by a proximal promoter and an upstream enhancer via several androgen receptor binding sites. However, little progress has been made in identifying androgen-independent regulatory elements involved in PSA gene regulation. We report the isolation of a novel, prostate epithelium-specific Ets transcription factor, PDEF (prostate-derived Ets factor), that among the Ets family uniquely prefers binding to a GGAT rather than a GGAA core. PDEF acts as an androgen-independent transcriptional activator of the PSA promoter. PDEF also directly interacts with the DNA binding domain of androgen receptor and enhances androgen-mediated activation of the PSA promoter. Our results, as well as the critical roles of other Ets factors in cellular differentiation and tumorigenesis, strongly suggest that PDEF is an important regulator of prostate gland and/or prostate cancer development.

Summary Vegf signaling specifies arterial fate during early vascular development by inducing the transcription of Delta-like 4 (Dll4), the earliest Notch ligand gene expressed in arterial precursor cells (aPCs). Dll4 expression precedes that of Notch receptors in arteries, and factors that direct its arterial-specific expression are not known. To identify the transcriptional program that initiates arterial Dll4 expression we characterized an arterial-specific and Vegf-responsive enhancer of Dll4. Our findings demonstrate that Notch signaling is not required for initiation of Dll4 expression in arteries, and suggest that Notch instead functions as a maintenance factor. Importantly, we find that Vegf signaling activates MAP kinase (MAPK)-dependent ETS factors in the arterial endothelium to drive expression of Dll4, as well as Notch4. These findings identify a Vegf/MAPK-dependent transcriptional pathway that specifies arterial identity by activating Notch signaling components, and illustrate how signaling cascades can modulate broadly expressed transcription factors to achieve tissue-specific transcriptional outputs.