KU675, a Concomitant Heat-Shock Protein Inhibitor of Hsp90 and Hsc70 that Manifests Isoform Selectivity for Hsp90α in Prostate Cancer Cells.
The 90-kDa heat-shock protein (Hsp90) assists in the proper folding of numerous mutated or overexpressed signal transduction proteins that are involved in cancer. Inhibiting Hsp90 consequently is an attractive strategy for cancer therapy as the concomitant degradation of multiple oncoproteins may lead to effective antineoplastic agents. Here we report a novel C-terminal Hsp90 inhibitor, designated KU675, that exhibits potent antiproliferative and cytotoxic activity along with client protein degradation without induction of the heat-shock response in both androgen-dependent and -independent prostate cancer cell lines. In addition, KU675 demonstrates direct inhibition of Hsp90 complexes as measured by the inhibition of luciferase refolding in prostate cancer cells. In direct binding studies, the internal fluorescence signal of KU675 was used to determine the binding affinity of KU675 to recombinant Hsp90α, Hsp90β, and Hsc70 proteins. The binding affinity (Kd) for Hsp90α was determined to be 191 μM, whereas the Kd for Hsp90β was 726 μM, demonstrating a preference for Hsp90α. Western blot experiments with four different prostate cancer cell lines treated with KU675 supported this selectivity by inducing the degradation of Hsp90α -: dependent client proteins. KU675 also displayed binding to Hsc70 with a Kd value at 76.3 μM, which was supported in cellular by lower levels of Hsc70-specific client proteins on Western blot analyses. Overall, these findings suggest that KU675 is an Hsp90 C-terminal inhibitor, as well as a dual inhibitor of Hsc70, and may have potential use for the treatment of cancer.
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.).
Weiya
W
Liu
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.).
George A
GA
Vielhauer
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.) jholzbeierlein@kumc.edu bblagg@ku.edu.
Jeffrey M
JM
Holzbeierlein
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.).
Huiping
H
Zhao
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.).
Suman
S
Ghosh
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.).
Douglas
D
Brown
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.).
Eugene
E
Lee
Department of Urology, University of Kansas Medical Center, Kansas City, Kansas (W.L., G.A.V., J.M.H., D.B., E.L.); and Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas (H.Z., S.G., B.S.J.B.) jholzbeierlein@kumc.edu bblagg@ku.edu.
Brian S J
BS
Blagg
D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003374:Coumarins / Q000138:chemical synthesis / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D050883:HSC70 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006801:Humans; D008297:Male; D009675:Novobiocin / Q000031:analogs & derivatives*; D010671:Phenylurea Compounds / Q000138:chemical synthesis / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000378:metabolism*; D011485:Protein Binding
D000970:Antineoplastic Agents; D003374:Coumarins; D050883:HSC70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C533585:HSP90AA2P protein, human; C000600174:KU675 compound; D010671:Phenylurea Compounds; D009675:Novobiocin