Pharmacologic inhibition of Hsp90 down-regulates WT1 protein. (A) K562 and (B) KG-1 leukemia cells were treated with the Hsp90 inhibitor 17-AAG for 24 hours. The cells were lysed, and protein extracts were subjected to SDS-PAGE and analyzed by Western blotting for WT1, Hsp90, and/or the WT1-regulated protein c-Myc. β-actin was used as loading control. (C) K562, (D) KG1, (E) Kasumi-1, and (F) MV4-11 leukemia cells were treated with the Hsp90 inhibitor STA-9090 for 24 hours and analyzed for WT1 expression by Western blotting. (G) Primary myeloid leukemia blasts from 5 AML patients (PS#1-5) were isolated, treated with STA-9090 for 24 hours, and analyzed for WT1 and β-actin by Western blotting.