Regulation of vascular endothelial growth factor (VEGF) gene transcription by estrogen receptors α and β

Vascular endothelial growth factor (VEGF) mediates angiogenic activity in a variety of estrogen target tissues. To determine whether estrogen has a direct transcriptional effect on VEGF gene expression, we developed a model system by transiently transfecting human VEGF promoter-luciferase reporter constructs into primary human endometrial cells and into Ishikawa cells, derived from a well-differentiated human endometrial adenocarcinoma. In primary endometrial epithelial cells, treatment with 17β-estradiol (E₂) resulted in a 3.8-fold increase in luciferase activity, whereas a 3.2-fold induction was demonstrated for stromal cells. Our Ishikawa cells had less than 100 functional estrogen receptors (ER)/cell and were therefore cotransfected with expression vectors encoding either the α- or the β-form of the human ER. In cells cotransfected with ERα, E₂ induced 3,2-fold induction in VEGF-promoter luciferase activity. A 2.3-fold increase was observed in cells cotransfected with ERβ. Through specific deletions, the E₂ response was restricted to a single 385-bp Pvull-Sstl fragment in the 5' flanking DNA. Cotransfection of this upstream region with a DNA binding domain ER mutant, or site-directed mutagenesis of a variant ERE within this fragment, resulted in the loss of the E₂ response. Electromobility shift assays demonstrated that this same ERE sequence specifically binds estradiol-ER complexes. These studies demonstrate that E₂-regulated VEGF gene transcription requires a variant ERE located 1.5 kb upstream from the transcriptional start site. Site-directed mutagenesis of this ERE abrogated E₂-induced VEGF gene expression.