Method for screening ecdysone-inducible stable cell lines

Ecdysone-inducible systems are useful tools to study the function of variou s genes in different types of mammalian cells. However it is technically di fficult to establish stable cell lines, This is partly because the conditio nal expression system requires the expression of two or more components dri ven by different kinds of promoters. In this paper we describe the use of a luciferase reporter gene system for rapid screening of cell lines that exp ress the ecdysone and retinoid X receptors. Using this system, two human st able colon cancer cell lines, SW480/VgRXR and HCT116/VgRXR, were successful ly generated. The expression of these receptors remained high after six mon ths of continuous culturing. A tight regulation of gene induction in SW480/ VgRXR was observed using 2 muM Ponasterone A. The gene induction was rapid and persistent. Our results demonstrated the advantage of establishing cell lines that continuously express high levels of ecdysone receptor proteins.