Effects of cAC10-vcMMAE on cell cycle and apoptosis. CD30⁺, L540 cells were cultured in complete media containing a saturating level (1 μg/mL) of cAC10, cAC10-vcMMAE, or an isotype-matched irrelevant cIgG-vcMMAE. At 12, 24, and 48 hours after exposure, cells were labeled with bromodeoxyuridine for 30 minutes to detect nascent DNA synthesis and with propidium iodine to detect total DNA content, and they were analyzed for active DNA synthesis and cell cycle position at the time of harvest by flow cytometry. Quadrants R2 to R4 correspond to G₁, S-phase, and G₂/M-phase cells, respectively. R1 and R5 correspond to sub-G₁ fragmented DNA typical of apoptotic cells.