Induction of apoptosis by ProVP16-I and -II in resistant cells. The effect of ProVP16-I and -II (5 × 10^-7 M) on the cell cycle was analyzed in Molt-3 (A) and MOVP-3 (B) cells and results were compared with VP16 (5 × 10^-7 M). Cells were harvested at indicated time points (n = 3), fixed, stained with propidium iodide, and analyzed by FACS as described in “Materials and methods.” Percent cells in pre-G₁ (apoptotic cells) was calculated from DNA histograms.