Background: E-selectin expression is very low in normal adult blood vessels, but is significantly elevated in newly formed tumor capillaries. We hypothesized that a viral vector which has transcriptional specificity for the tumor vasculature may be a tool for angiogenesis-targeted gene therapy. We therefore designed an adenoviral vector which would only be expressed in cells that transcribe the E-selectin gene.
Materials and methods: The E-selectin promoter was inserted into an adenoviral vector driven by the luciferase reporter gene. The resulting AdV-Esel-Luc vector was then used to transduce endothelial cells as well as other cell types, and luciferase activity measured with a luminometric assay.
Results: Exposure of transduced endothelial cells to TNF-alpha (tumor necrosis factor-alpha), a known inducer of the E-selectin promoter, generated a 30-fold increase in luciferase expression compared to untreated cells (p = 0.01). Endothelial cells cultured in tumor conditioned media as an in vitro recreation of the tumor environment resulted in even higher induction of luciferase (p = 0.0001). Furthermore, many non-endothelial cell lines expressed minimal levels of luciferase when transduced with the AdV-Esel-Luc vector under identical conditions.
Conclusions: We conclude that the E-selectin promoter can be used in order to confer transcriptional specificity to an adenoviral vector. This transcriptional specificity may in the future enable us to deliver the specific expression of therapeutic genes to the tumor vasculature.