Relationship between intracellular dGTP and activation of caspases in primary CLL cells with forodesine. CLL cells were incubated with 2 μM forodesine and 10 μM dGuo at different time points, and the activation of caspases 8, 9, and 3 were measured by fluorometric assay. Data from 2 patients for caspases 8 and 9 (A-B) and the relationship between accumulation of dGTP and the activation of caspase 3 (C) for 11 patients are plotted.