A novel drug-regulated gene expression system based on the nuclear receptor constitutive androstane receptor (CAR)

Purpose. To develop and characterize a new drug-regulated gene expression s ystem based on the nuclear receptor constitutive androstane receptor (CAR). Methods. Both transient and stable transfection into HEK293 cells of lucife rase plasmids under the control of either drug- and steroid-responsive nucl ear receptor CAR or the tetracycline-sensitive transactivator tTA were used in development of stable cell lines. Results. A stable first-generation cell line that expresses luciferase gene under the control of nuclear receptor CAR was developed. The luciferase ex pression in CAR-producing cells could be suppressed by androstanes and reac tivated by structurally unrelated drugs chlorpromazine, metyrapone, phenoba rbital, and clotrimazole. The kinetics of luciferase expression in CAR-prod ucing cells and the tTA system were comparable. The overall regulation of C AR system was improved by modifications to the DNA binding domain and site. Conclusions. Because of its wide ligand selectivity and transferable ligand binding domain, CAR expands the repertoire of regulated gene expression sy stems.