V600E B-Raf requires the Hsp90 chaperone for stability and is degraded in response to Hsp90 inhibitors.
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.
Grbovic
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OM
Program in Molecular Pharmacology and Chemistry and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Basso
A D
AD
Sawai
A
A
Ye
Q
Q
Friedlander
P
P
Solit
D
D
Rosen
N
N
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D045744:Cell Line, Tumor; D018833:Chaperonins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D047029:Lactams, Macrocyclic; D008545:Melanoma / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D020125:Mutation, Missense / Q000235:genetics*; D048491:Proto-Oncogene Proteins A-raf / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D017828:Rifabutin / Q000031:analogs & derivatives / Q000494:pharmacology
D016227:Benzoquinones; C498362:CDC37 protein, human; D018797:Cell Cycle Proteins; D047029:Lactams, Macrocyclic; D017828:Rifabutin; C112765:tanespimycin; C482119:BRAF protein, human; D048491:Proto-Oncogene Proteins A-raf; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D018833:Chaperonins