DNA fragmentation after exposure to flavopiridol. (A) Exponentially growing SUDHL4, SUDHL6, MOLT4, and Jurkat cells were exposed to the indicated concentrations of flavopiridol for 14 hours and genomic DNA extracted as described in Materials and Methods before electrophoresis in a 1.6% agarose gel. (B) SUDHL4 cells were exposed to the following concentrations of flavopiridol for the indicated periods after prelabelling DNA with [¹⁴C]-thymidine. The fraction of DNA eluting from filters is indicated. Untreated control (▵); 100 nmol/L (▪); 300 nmol/L (▴); 500 nmol/L (□); 1,000 nmol/L (•). (C) PC-3 cells were exposed to either untreated control (○); 1,000 nmol/L (•), or 3,000 nmol/L (▿) flavopiridol-containing medium for 24 or 48 hours. Each symbol represents the mean of three independent experiments.