PKA inhibition potentiates IR-induced cell death in BCP-ALL blasts. (A) Frozen aliquots of BCP-ALL blasts from ALL5 were thawed and cultured in the presence or absence of 1 mM Rp-8-Br-cAMPS 45 min prior to treatment with 2 Gy of IR with subsequent cell death analysis by fluorescence-activated cell sorter 20 h after irradiation as described in Figure 1A (n = 7, error bars = SEM; *P < .05 by paired samples t test). (B) Cells treated as in panel 5A were harvested 4 h after irradiation and subjected to immunoblot analysis using antibodies against p53 and actin. The immunoblot shows 1 representative experiment of 3. A vertical division line has been inserted to mark the site where the picture file has been cut and repositioned to remove lanes of intervening samples. (C) Freshly isolated normal BCPs from 2 donors were treated and analyzed as described in Figure 5A. The histogram shows mean values with error bars indicating the range of values.