MDR properties of H-FT–transfected MEL. Left: CAAM uptake into MEL cells and its reversal by verapamil (VP) and cyclosporin (CS). Cells (1 × 106/mL) were suspended in MEM medium at 37°C, supplemented with CA-AM (125 nmol/L) and fluorescence recorded in parallel with time. Verapamil 15 μmol/L (ver) or cyclosporin 6 μmol/L addition is indicated by the arrow. The relative rates of CA-AM entry into cells after and before addition of verapamil were: wt: 1.2; cl-6: 2.8; cl-12: 1.8; cl-16: 1.6. Cl-6 displayed ×3 and ×5 higher IC50 towards vinblastine and colchicine, respectively. Right: viability profiles. The plots depict the fluorescence intensity (540 to greater than 590 nm) of Alamar Blue (AB = 5%) for each cell system at the indicated concentration of the drug (total exposure time to drug: 48 hours and to Alamar Blue: 4 hours; 7 × 103 cells/well; n = 3). The average of n = 3 ± SE was plotted against the respective inhibitor concentration and analyzed by NLSQ (best fits depicted over the experimental points) yielding the following IC50 (μmol/L) for colchicine and vinblastine, respectively: wt (150 ± 47 and 8 ± 1.5); cl-6 (700 ± 23 and 23 ± 1); cl-12 (230 ± 14 and 12 ± 1); and cl-16 (100 ± 23 and 8 ± 1).
