Characterization of T-PLL antiapoptotic dependencies at baseline. (A) We subjected single-cell suspensions of blood samples to baseline BH3 profiling. In parallel, we cocultured primary T-PLL cells with the stromal cell line NKTert and exposed them to ruxolitinib, PRN694, ibrutinib, belinostat, or DMSO. Then, we performed a DBP to measure early drug-induced changes in net proapoptotic signaling and examined whether the findings with DBP could be corroborated with the results of cell viability assays. (B) Heat map of the percentage of cyt c loss, as quantified by flow cytometry on 24 T-PLL patient samples at baseline (green, lowest value; red, highest value). Each row is a sample, with the corresponding number, and each column refers to a BH3-only peptide or a tool compound with which the gently permeabilized cells were incubated for 60 minutes. (C-E) The percentage of cyt c loss for each of the 24 CLL (open circles) and 24 T-PLL (solid circles) samples. Unpaired Student t test; means ± standard error of the mean. The title of each panel denotes the parameter measured (overall priming and specific dependencies), as well as the peptide or tool compound used to probe it. **P < .01; ****P < .0001.