ABCG2 protein expression and function in cell lines.

ABCG2 protein expression and function measured in cell lines using (A) mitoxantrone efflux and anti-ABCG2 monoclonal antibody 5D3, (B) SP analysis and antibody inhibition, and (C) idarubicin efflux. Panel A shows results of flow cytometry for mitoxantrone, in which higher fluorescence levels indicate higher intracellular retention of the fluorescent antitumor agent mitoxantrone. Results also are shown for anti-ABCG2 monoclonal antibody 5D3–labeling of the cell lines. Panel B shows an SP analysis of the cell lines after incubation with either the 5D3 antibody (bottom row), which inhibits ABCG2 function, or an isotype control antibody (top row). The percentage of cells within the SP gate is shown in the upper left corner of each analysis. Panel C represents the results of flow cytometry for idarubicin in the parental cell line AML3 and clone 6.2.