Survival and cell-cycle effects. (A) Induction of apoptotic cell death in CD138⁺ Ocy-My5 MM cells after 48 hours of exposure to 10 nM B-B4–DM1. Cells were stained with PI and annexin V and then analyzed by flow cytometry. Percentages of stained cells are reported in each quadrant. (B) Effects of B-B4–DM1 treatment on the cell cycle. Ocy-My5 MM cells were exposed to 13.3 μg/mL (83 nM) B-B4 mAb or 10 nM B-B4–DM1 for 48 hours. Cell-cycle profile was analyzed using PI staining, and percentages of cells in S phase (S) and G₂/M phase are indicated in each quadrant. Data are representative of 3 experiments.