FIGURE 4.
Characteristics of drug-selected cells. A, MCF-7 and T47D cells and drug-escaped clones from a paclitaxel-treated population were stained for the rhodamine 123 dye efflux assay as described. Drug efflux was analyzed by FACS. Drug-selected cells generated a significant rhodamine 123low fraction when compared with the parental cell line. B, MCF-7 and MCF-7 drug-escaped cells after treatment with nocodazole were analyzed for side population. An increase in side population cells is evident in the surviving clones. C, MCF-7 SCAT3 cells and MCF-7 SCAT3 vincristine-resistant clones were exposed to different drugs and imaged by FRET microscopy. The percentage of cells with loss of FRET is calculated for each drug, and the histogram is shown. D, MCF-7 SCAT3 cells and MCF-7 SCAT3 vincristine-resistant clones were exposed to camptothecin. After 12 h of drug treatment, the cells were placed in a live cell incubation chamber, and FRET imaging was carried out for an additional 12 h for MCF-SCAT3 cells and 48 h for vincristine-resistant cells at an interval of 10 min. Representative time lapse images of MCF7 SCAT3 cells (D) and vincristine-resistant cells (E) are shown. By 24 h of drug treatment, most parent cells showed an increase in ECFP fluorescence, indicating caspase activation (blue cells); the percentage of FRET lost cells is significantly less in drug-resistant clone even at 48 h of camptothecin treatment. F, breast tissue from surgical margin and from tumor with and without adjuvant chemotherapy was stained for SA-β-gal as described. Representative images are given. Strong positive staining for SA-β-gal is evident in the tumor samples. G, the respective parental cells and respective drug-surviving cells were evaluated for an in vitro Matrigel invasion assay as described. Each experiment was performed in triplicate, and the number of cells invaded across the membrane is presented. Error bars, S.D.