Effects of Bcr-Abl expression on apoptosis and intracellular calcium changes after VP-16 treatment. (A) Cytosolic and (B) mitochondrial calcium level measured by flow cytometry. Cells were treated with VP-16 for 14 hours, loaded with 1 μM CaGreen-1 or 1 μM Rhod-2, and analyzed on the FL-1 or FL-2 channel, respectively. Untreated cells are shown as filled histograms, and VP-16–treated cells as black-line histograms. (C) Percentage of apoptotic cells quantified by TUNEL assay. Cells were incubated with VP-16 for 14 hours, fixed, incubated with TdT/dUTPs-FITC, and analyzed on the FL-1 channel. Cells with higher fluorescence correspond to cells with fragmented DNA. Untreated cells are shown as filled histograms and VP-16–treated cells as black-line histograms. Representative histograms are shown.