Drug-elimination activity of HA117 and MDR1 as analyzed using the DNR efflux assay. The fluorescence intensity of DNR in 4T1/MDR1 cells (C) was much lower than that of 4T1 (A) and 4T1/HA117 (B) cells (P < 0.05). There was no statistically significant difference in the DNR fluorescence intensity between 4T1 and 4T1/HA117 cells (P > 0.05). The bar graphs represent the quantification and comparison of the fluorescence intensity of the cells. P > 0.05* vs. control cells (4T1), P < 0.05 ** vs. control cells (4T1). R1: Percent of all cells. R2: Percent of cells with no or low DNR fluorescence. This experiment was repeated at least 3 times with the same results.