The effect of forskolin on BCP-ALL blasts is mediated through cAMP signaling. Freshly isolated BCP-ALL blasts from 2 patients (ALL5 and ALL9) were cultured in the presence or absence of 60 µM forskolin or 200 µM 8-CPT-cAMP for 45 min prior to treatment with IR as indicated. Cells were analyzed for cell death as in Figure 1A. The histogram shows mean values with error bars indicating the range of values.