Ligand-dependent regulation of vascular endothelial growth factor and erythropoietin expression by a plasmid-based autoinducible GeneSwitch system

We investigated the ability of an improved mifepristone-dependent GeneSwitc h system to regulate the expression of genes for two therapeutic proteins: vascular endothelial growth factor (VEGF) and erythropoietin. The GeneSwitc h system consisted of two plasmids, one encoding the chimeric GeneSwitch pr otein, the other an inducible transgene. When the constitutive CMV promoter of the GeneSwitch plasmid was replaced by an autoinducible promoter consis ting of; four copies of GAL4 DNA binding sites linked to a minimal thymidin e kinase promoter, the tightness of transgene regulation was improved by an order of magnitude. Quantitative RT-PCR analysis of GeneSwitch mRNA confir med that the autoinducible promoter was responsive to mifepristone. We demo nstrated the ability of the improved GeneSwitch system to regulate the expr ession of VEGF or erythropoietin in a biologically relevant manner after de livery of plasmids to the hindlimb muscle of adult mice. This ability of th e autoinducible GeneSwitch system to regulate the expression of therapeutic proteins in mice indicates its potential for use in human gene therapy app lications.