FLT3 inhibition induces HDAC8 upregulation. MV4-11 cells (A) and MOLM-13 cells (B) were treated with AC220 (5 nM) for 24 hours. The transcription of 11 HDACs was analyzed by quantitative real-time polymerase chain reaction (PCR). MV4-11 cells (C) and MOLM-13 cells (D) were treated with different concentrations of AC220 for 24 hours. The transcription of HDAC8 was analyzed by quantitative real-time PCR. MV4-11 cells (E) and MOLM-13 cells (F) were treated with different concentrations of AC220 for 24 hours and then subjected to western blot to detect the indicated proteins. MV4-11 cells (G) and MOLM-13 cells (H) cells were transfected with FLT3 siRNA (siFLT3-1 and siFLT3-2) and control siRNA (siCtrl). The transcription of HDAC8 was analyzed by quantitative real-time PCR. MV4-11 cells (I) and MOLM-13 cells (J) were transfected with FLT3 siRNA and control siRNA and then subjected to western blot to detect the indicated proteins. (K) Primary AML blasts from 12 FLT3-ITD⁺ AML patients were treated with AC220 (20 nM) for 24 hours and then analyzed by immunoblot for HDAC8. (L) Primary AML blasts from 12 FLT3-ITD⁺ AML patients were treated with AC220 (20 nM) for 24 hours. The transcription of HDAC8 was analyzed by quantitative real-time PCR. Data are mean ± standard error of the mean. *P < .05, **P < .01, ***P < .001, ****P < .0001.