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Biotech / Medical : Kosan BioSciences -- KOSN -- Ignore unavailable to you. Want to Upgrade?

To: Icebrg who wrote (636)	12/23/2005 3:28:04 PM
From: tuck	Respond to of 933

[V600E B-Raf requires the Hsp90 chaperone for stability and is degraded in response to Hsp90 inhibitors ] >>Published online before print December 21, 2005 Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0609973103 Biochemistry V600E B-Raf requires the Hsp90 chaperone for stability and is degraded in response to Hsp90 inhibitors ( 17-allylamino-17-demethoxygeldanamycin \| cdc37 \| melanoma ) O. M. Grbovic, A. D. Basso *, A. Sawai, Q. Ye, P. Friedlander, D. Solit, and N. Rosen Program in Molecular Pharmacology and Chemistry and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 Communicated by Samuel J. Danishefsky, Memorial Sloan-Kettering Cancer Center, New York, NY, November 16, 2005 (received for review May 25, 2005) The Raf family includes three members, of which B-Raf is frequently mutated in melanoma and other tumors. We show that Raf-1 and A-Raf require Hsp90 for stability, whereas B-Raf does not. In contrast, mutated, activated B-Raf binds to an Hsp90-cdc37 complex, which is required for its stability and function. Exposure of melanoma cells and tumors to the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin results in the degradation of mutant B-Raf, inhibition of mitogen-activated protein kinase activation and cell proliferation, induction of apoptosis, and antitumor activity. These data suggest that activated mutated B-Raf proteins are incompetent for folding in the absence of Hsp90, thus suggesting that the chaperone is required for the clonal evolution of melanomas and other tumors that depend on this mutation. Hsp90 inhibition represents a therapeutic strategy for the treatment of melanoma.<< Cheers, Tuck