Levels of Bcl-2 members collapse upon ibrutinib treatment. (A) FACS analysis showing overlays of Mcl-1, Bcl-XL, and Bcl-2 expression for LN immigrants and emigrants. Data are from a representative patient at baseline and after 4 and 10 weeks of ibrutinib treatment. (B) Summary of Bcl-2 member expression in LN emigrants before and after ibrutinib treatment (n = 14). Geometric mean fluorescence intensities were normalized by setting the baseline LN immigrant population at 100%. Black lines indicate unmutated IgHV CLL samples (um-CLL), red lines indicate mutated IgHV CLL samples (m-CLL), and gray lines indicate patient samples for whom the mutation status was not determined (ND). A paired-sample Student t test was used for statistical analyses. (C-D) Western blots of peripheral blood collected from 8 patients treated with ibrutinib. Samples were collected at baseline and after 6 to 17 days of ibrutinib treatment (patients #1 and #2) or after 3 months of ibrutinib treatment (patients #3-8). Protein lysates were probed for Mcl-1, Bcl-XL, and Bcl-2; actin was used as loading control. B, baseline; ns, not significant.