Detection of human leukemia cells with multidrug-resistance phenotype using multilabeling with fluorescent dyes

Reduced accumulation of multiple drugs is a characteristic of cells overexpressing P-glycoprotein. This phenotype is referred to as multidrug-resistance (MDR). A protocol based on reduced accumulation of fluorescent dyes is proposed for discriminating MDR cells in cell populations. The combination of three fluorescent dyes, Hoechst 33342, rhodamine 123 and Nile red, with different intracellular targets, has been designed to characterize cells with different levels of resistance, using image cytometry. The fluorescence intensity of each dye was quantified in living cells. The protocol was applied to human leukemia cell lines, (K562, K562/ADR, CCRF-CEM, CEM/VLB100, CEM/VM-1). The effect of verapamil on dye accumulation is emphasized.