dGTP accumulation. (A) Basal dGTP levels after 24 hours of 10μM dGuo exposure and (B) dGTP accumulation after 24 hours of 10μM dGuo and 1μM forodesine exposure in 22 T-ALL and 6 BCP-ALL patient samples. Undetectable dGTP levels have been assigned a value of 1. (C) Intracellular dGTP levels after 24 hours 10μM dGuo and 1μM forodesine exposure in forodesine-sensitive versus -resistant patients (22 T-ALL, 6 BCP-ALL, and 2 AML samples). Horizontal lines represent median values. **P < .01.