Bortezomib-induced FLT3 down-regulation via interaction with the SP1/NF-κB(p65) complex. (A) SiRNA mediated knock-down of SP1 or NFκ-B(p65) down-regulates FLT3 expression in MV4-11 cells that harbor a FLT3-ITD and express FLT3 at high levels. (B) Overexpression of SP1 or NF-κB(p65) increases the expression of FLT3 in the KG1 cell line that usually has low expression of FLT3. (C) Increasing miR-29b in the MV4-11 cell line decreases FLT3 expression in MV4-11 cells. (D) Bortezomib treatment decreases FLT3 expression in a time- and dose-dependent manner in the MV4-11 cell line and in primary patient blasts (obtained from patients not enrolled on the current clinical trial; samples were procured in the OSU Leukemia Tissue Bank).