Keratinocyte gene therapy: inducible promoters and in vivo control of transgene expression.

Modulation of transgene expression by exogenous agents is an optimal goal in gene therapy. Successful keratinocyte gene therapy requires a promoter-enhancer cassette to regulate expression of the therapeutic gene in vivo. In this study, we first transferred plasmids, constructed by introducing inducible promoters fused to the beta-galactosidase gene (LAC Z), into keratinocytes in vitro. Metallothionein (MT) and 1,24-vitamin D(3)(OH)(2) dehydroxylase (VDH) promoters responded to the inducing agents, Cadmium and 1,25-vitamin D(3)(OH)(2) (VitD(3)), respectively. The plasmids were then introduced in vivo using a naked DNA method and the inducible promoters were evaluated by measuring beta-gal activity in rat keratinocytes. Zinc induced the transferred MT promoter activity by approximately 2-fold or 10-fold when administered systemically and topically, respectively. In addition, VitD(3) induced the transferred VDH promoter activity approximately 10-fold when administered topically. These data are useful for developing inducible promoters for keratinocyte gene therapy.