BCL6-targeted peptide inhibitors induced significant apoptosis associated with differential expression of BCL6 genes in primary AML cells. (A) Fifty-five different AML cells were subjected to ex vivo treatment with 10 μM RI-BPI for 48 hours. The relative percentage of live cells (annexin V negative/7-AAD negative) were plotted and sorted from lowest (left) to highest (right) sensitivity to RI-BPI. Dotted line indicates 50% of relative live cell percentage with RI-BPI treatment. Profiles of each of the primary cells used in the analysis are provided in supplemental Table 1. (B) Representative flow cytometry data to show how dead cells were detected, with a comparison between untreated and RI-BPI–treated cells. (C) Based on mutational profiles of the 55 primary AML cells, normalized percent live cells after RI-BPI (10 mM, 48 hours) treatment was compared between subgroups with different molecular markers. Linear regression analysis showing a correlation between sensitivity to RI-BPI and expression level of BCL6 in 6 different primary AML cells (D) and in 11 different AML cell lines (E). MFI, mean fluorescence intensity.