Electroporation of Molm-14 cells and Ba/F3 FLT3-ITD transfectants with FLT3 siRNA results in down-regulation of FLT3, decreased activation of downstream signaling molecules, and induction of apoptosis. (A) siRNA-induced silencing of FLT3 was assessed by immunoblot of whole cell lysates 24 hours after siRNA transfection. RNAi-induced down-regulation of FLT3 also resulted in decreased phosphorylation of STAT5, MAPkinase, and Akt in both Ba/F3 FLT3-ITD transfectants and Molm-14 cells. NS indicates nonspecific. (B) Ba/F3 FLT3-ITD transfectants and Molm-14 cells demonstrate an increase in apoptosis (annexin/PI-positive cells indicated by ▦; viable cells indicated by ▪) over time when treated with FLT3 siRNA (n = 3 ± SE). (C) Treatment of Ba/F3 FLT3-ITD transfectants and Molm-14 cells (n = 5 ± SE) with FLT3-specific siRNA (▴) results in an overall decrease of proliferation (n = 8 ± SE). indicates mock; ▪, nonspecific siRNA.