Reappearance of Bcl-2 members upon ibrutinib relapse. (A) Summary of Bcl-2 member expression in LN emigrants before and during ibrutinib treatment (n = 16). Ibrutinib T1 represents an early time point showing clinical response to ibrutinib, and T2 represents a later time point upon ibrutinib treatment. Red lines indicate patients who relapsed on ibrutinib (n = 9), and black lines indicate patients who stayed in remission (n = 7). Geometric mean fluorescence intensities were normalized by setting the baseline LN immigrant population at 100%. The paired-sample Student t test was used for statistical analysis for all patients to compare expression at baseline with expression upon ibrutinib treatment. Subsequently, patients were divided into remission or relapse groups, after which 1-way analysis of variance was used to compare Bcl-2 member expression between groups during follow-up. (B) Western blot of peripheral blood collected from 2 patients who relapsed on ibrutinib. Samples were collected at baseline, after 0.5 to 1.5 years of ibrutinib treatment, and during relapse on ibrutinib after 4 years (patient #9) and 1 year (patient #10) of treatment. Protein lysates were probed for Mcl-1, Bcl-XL, and Bcl-2; actin was used as loading control. B, baseline.