Belinostat-resistant TCL cells do not undergo apoptosis and exhibit reduced histone acetylation after belinostat treatment. (A) Generation of novel belinostat-resistant TCL models. HuT-78 and Karpas-299 parental and belinostat-resistant cells were treated with the indicated concentrations of belinostat for 72 hours. Cell viability was measured by 3-MTT assay. Data are shown as mean ± standard deviation (SD) (n = 3). (B-C) Measurement of apoptosis in TCL parental and belinostat-resistant cells. Induction of apoptosis was measured by active caspase-3 assay (B) and propidium iodide–fluorescence-activated cell sorting (PI-FACS) (C) analysis after treatment with the indicated concentrations of belinostat for 48 hours. Data are shown as mean ± SD (n = 3). *P < .05 indicates a significant difference from parental cells treated with the same concentration of belinostat. (D) Belinostat-resistant TCL cells display reduced histone acetylation after belinostat treatment. Acetylation of histones was measured in parental and resistant cells by immunoblotting after 24 hours of belinostat treatment.