Sp1-dependent regulation of the RTP801 promoter and its application to hypoxia-inducible VEGF plasmid for ischemic disease

Purpose. Gene therapy using vascular endothelial growth factor ( VEGF) is a new potential treatment of ischemic disease. To be safe and effective, VEGF expression should be enhanced locally in ischemic tissue. In this study, we identified the cis-regulatory element for the hypoxia induction of the RTP801 promoter. In addition, pRTP801-VEGF was evaluated as a therapeutic plasmid in vitro. Methods. The cis-regulatory element for hypoxia induction was identified by deletion and mutation analyses. Antisense oligonucleotide co-transfection assay was performed to evaluate the role of Sp1. pRTP801-VEGF was constructed by the insertion of the RTP801 promoter into the VEGF plasmid. The hypoxia-inducible expression of VEGF was evaluated by in vitro transfection assay. Results. In luciferase assay, the region between -495 and -446 was responsible for the hypoxia-induced transcription. The mutation of the Sp1 site in this region reduced hypoxia-induced transcription. In addition, co-transfection with antisense Sp1 oligonucleotide suggests that hypoxia induction of the RTP801 promoter is mediated by Sp1. In vitro transfection showed that pRTP801-VEGF had higher VEGF expression than pEpo-SV-VEGF. In addition, VEGF expression by pRTP801-VEGF was induced under hypoxia. Conclusions. With strong basal promoter activity and induction under hypoxia, pRTP801-VEGF may be useful for gene therapy for ischemic disease.