AZT but not GCV induces apoptosis and is phosphorylated in EBV⁺ BL cell lines. (A) EBV⁺ BL (BL-5, BL-8) and EBV^- BL (BL-9, Ramos) cells were treated with either [methyl-³H]-AZT (5 μg/mL; A) or [8-³H]-GCV (5 μg/mL; G) for 1, 4, 8, and 16 hours. Methanol extracts were then subjected to HPLC fractionation to purify the different phosphorylated forms of the nucleosides. The figure shows the relative amounts of the monophosphorylated nucleosides. (B) EBV⁺ BL (BL-5, BL-8) and EBV^- BL (Ramos, BL-9) cells were treated with medium, AZT (10 μg/mL), or GCV (10 μg/mL) for 36 hours and analyzed for apoptosis by Annexin/PI staining and FACS analysis. Bars represent the percentage of apoptotic cells in a triplicate experiment. The results are shown as the mean ± standard deviation.