Caspase-3 activity and formation of acidic vesicular organelles (AVOs) after treatment with patupilone. Caspase-3 activity in patupilone-treated medulloblastoma cells (D341Med [A], D425Med [B], and DAOY [C]) was determined at the indicated time points. (D–F) AVO formation was determined in patupilone-treated medulloblastoma cells ([D] D341Med, 1 nM; [E] D425Med, 0.5 nM; [F] DAOY, 1 nM). Green (510–530 nm) and red (465 nm) fluorescence emission from 5 × 105 cells illuminated with blue (488 nm) excitation light was measured with a FACSCalibur at the indicated time points.