Effect of abexinostat combined with ibrutinib on BTK protein, signaling, and CLL survival. (A) Induction of miR-147b, miR-210, miR-425, miR-1253, miR-4269, and miR-4667-3p in CLL cells left untreated and exposed to abexinostat (Abex), ibrutinib (IB), or abexinostat and ibrutinib combined. Data represent mean ± SEM of 18 CLL samples. After abexinostat: P < .001 for miR-210 and miR-4667-3p; P < .05 for miR-147b, miR1253, and miR-4269; after abexinostat and ibrutinib combined: P = .001 for miR-210; P < .05 for miR-4269 and miR-4667-3p mixed effects model. (B) BTK mRNA in cells left untreated and exposed to abexinostat, ibrutinib, or abexinostat and ibrutinib combined. Data represent the mean ± SEM of 10 CLL samples (P < .01 for BTK expression after exposure to either abexinostat or abexinostat plus ibrutinib, mixed effects model). (C) Action of abexinostat alone or combined with ibrutinib on p-Y223-BTK, total BTK, p-PLCγ2, total PLCγ2, p-ERK, total ERK, p-AKT, total AKT, and H3K9Ac. GAPDH was assayed as a loading control, and H3 was assayed as a control for H3K9Ac. (D) Effect of abexinostat, ibrutinib, or combined abexinostat and ibrutinib on the induction of apoptosis (Annexin V–positive cells) in primary CLL samples. Data represent the mean ± SEM of 13 CLL samples (P < .05, interaction test of synergy from a mixed effects model). *P ≤ .05; **P ≤ .01; ***P ≤ .001.