Effect of forodesine on dNTP pools. Accumulation of dGTP (A) and all 4 dNTPs (B) with the incubation of forodesine in primary CLL cells. The primary CLL cells from 11 patients were incubated with 2 μM forodesine and 10 μM dGuo at 4 and 8 hours, and the nucleotides in the leukemia cells were extracted by 60% methanol and dNTPs were measured by DNA polymerase assay. The data of accumulation of dGTP for all patients (A) and the 4 dNTPs (▪, dGTP; ▴, dATP; ▾, dCTP; and ♦, dTTP) for one patient (B) are plotted.