Abstract
Heat shock protein (HSP) 90 regulates client oncoprotein maturation. The chaperone function of HSP90 is blocked by 17-N-allylamino-17-demethoxygeldanamycin (17-AAG), although it results in transcription and translation of antiapoptotic HSP proteins. Using three myeloma cell lines, we tested whether inhibition of transcription/translation of HSP or client proteins will enhance 17-AAG-mediated cytotoxicity. 8-Chloro-adenosine (8-Cl-Ado), currently in clinical trials, inhibits bioenergy production, mRNA transcription, and protein translation and was combined with 17-AAG. 17-AAG treatment resulted in HSP transcript and protein level elevation. In the combination, 8-Cl-Ado did not abrogate HSP mRNA and protein induction. HSP90 requires ATP to stabilize client proteins; hence, expression of signal transducer and activator of transcription 3 (STAT3), Raf-1, and Akt was analyzed. 17-AAG alone resulted in <10% change in STAT3, Raf-1, and Akt protein levels, whereas no change was observed for 4E-BP1. In contrast, the combination treatment resulted in a >50% decrease in client protein levels and marked hypophosphorylation of 4E-BP1. 8-Cl-Ado alone resulted in a <30% decrease of client proteins and 4E-BP1 hypophosphorylation. 8-Cl-Ado combined with 17-AAG resulted in more than additive cytotoxicity. In conclusion, 8-Cl-Ado, which targets transcription, translation, and cellular bioenergy, enhanced 17-AAG-mediated cytotoxicity in myeloma cells.
Footnotes
This work was supported by the National Institutes of Health National Cancer Institute [Grants Lymphoma SPORE CA136411, Myeloma SPORE CA142509].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.111.184903.
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ABBREVIATIONS:
- HSP
- heat shock protein
- 17-AAG
- 17-N-allylamino-17-demethoxygeldanamycin
- HSF-1
- heat shock factor
- MM
- multiple myeloma
- 8-Cl-Ado
- 8-chloro-adenosine
- RT
- reverse transcription
- PCR
- polymerase chain reaction
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- STAT
- signal transducer and activator of transcription
- mTor
- mammalian target of rapamycin.
- Received June 22, 2011.
- Accepted August 3, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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