Figure 5.

P-gp affects caspase-dependent DNA fragmentation in drug-resistant K562 cell lines. K562 cell lines [K562 (P-gp^low) or KVIN (P-gp^high)] were labeled with ⁵¹Cr (a and c) and/or ¹²⁵IUdR (b and d) for 1 h, washed in growth media, and incubated for 4–48 h in 96-well plates (2 × 10⁴ cells/well) with cell death stimuli at final concentrations as follows: (a and b) VIN (0.1 μg/ml, 48 h) and (c and d) pfp (60 units) and gB (0.5 μg/ml, 4 h). In some wells cells were preincubated for 30 min with anti-P-gp mAb (MRK-16) (50 μg/ml, final concentration) and/or followed by 20 μM (final concentration) ZVAD-fmk or control ZFA-fmk inhibitor for 30 min. Cell death stimuli then were added as indicated for 4–48 h. These data are calculated as the mean ± SE of duplicate samples and are representative of at least two different experiments.