Abstract
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. Consequently, there is considerable interest in developing chemotherapeutic drugs that specifically disrupt the function of Hsp90. Here, we investigated the extent to which a novel novobiocin-derived C-terminal Hsp90 inhibitor, designated KU135, induced antiproliferative effects in Jurkat T-lymphocytes. The results indicated that KU135 bound directly to Hsp90, caused the degradation of known Hsp90 client proteins, and induced more potent antiproliferative effects than the established N-terminal Hsp90 inhibitor 17-allylamino-demethoxygeldanamycin (17-AAG). Closer examination of the cellular response to KU135 and 17-AAG revealed that only 17-AAG induced a strong up-regulation of Hsp70 and Hsp90. In addition, KU135 caused wild-type cells to undergo G2/M arrest, whereas cells treated with 17-AAG accumulated in G1. Furthermore, KU135 but not 17-AAG was found to be a potent inducer of mitochondria-mediated apoptosis as evidenced, in part, by the fact that cell death was inhibited to a similar extent by Bcl-2/Bcl-xL overexpression or the depletion of apoptotic protease-activating factor-1 (Apaf-1). Together, these data suggest that KU135 inhibits cell proliferation by regulating signaling pathways that are mechanistically different from those targeted by 17-AAG and as such represents a novel opportunity for Hsp90 inhibition.
Footnotes
This work was supported by the National Institutes of Health National Cancer Institute [Grants R01-CA125392 and R01-CA120458]; the National Institutes of Health National Institute of Environmental Health Sciences [Grant T32-ES007079]; the National Institutes of Health National Center for Research Resources [Grant P20-RR016443]; the American Cancer Society [Grant IRG-09-062-01]; Oklahoma Agricultural Experiment Station [Project 1975]; and the Kansas Technology Enterprise Corporation through the Centers of Excellence Program.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.109.058545
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ABBREVIATIONS:
- Hsp
- heat shock protein
- MOMP
- mitochondrial outer membrane permeabilization
- Apaf-1
- apoptotic protease activating factor-1
- 17-AAG
- 17-allylamino-demethoxygeldanamycin
- MTS
- 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt
- FITC
- fluorescein isothiocyanate
- DMSO
- dimethyl sulfoxide
- SPR
- surface plasmon resonance
- Δψ
- mitochondrial membrane potential
- PBS
- phosphate-buffered saline
- PAGE
- polyacrylamide gel electrophoresis
- Pipes
- piperazine-N,N′-bis(2-ethanesulfonic acid)
- TRAP
- tumor necrosis factor receptor-associated protein
- KU135
- 3-(3′,6-dimethoxybiphenyl-3-ylcarboxamido)-6-methoxy-8-methyl-2-oxo-2H-chromen-7-yl acetate.
- Received June 11, 2009.
- Accepted September 9, 2009.
- © 2009 The American Society for Pharmacology and Experimental Therapeutics
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