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Published December 2003 | Published
Journal Article Open

Development of Protacs to Target Cancer-promoting Proteins for Ubiquitination and Degradation


The proteome contains hundreds of proteins that in theory could be excellent therapeutic targets for the treatment of human diseases. However, many of these proteins are from functional classes that have never been validated as viable candidates for the development of small molecule inhibitors. Thus, to exploit fully the potential of the Human Genome Project to advance human medicine, there is a need to develop generic methods of inhibiting protein activity that do not rely on the target protein's function. We previously demonstrated that a normally stable protein, methionine aminopeptidase-2 or MetAP-2, could be artificially targeted to an Skp1-Cullin-F-box (SCF) ubiquitin ligase complex for ubiquitination and degradation through a chimeric bridging molecule or Protac (proteolysis targeting chimeric molecule). This Protac consisted of an SCFß-TRCP-binding phosphopeptide derived from I{kappa}B{alpha} linked to ovalicin, which covalently binds MetAP-2. In this study, we employed this approach to target two different proteins, the estrogen (ER) and androgen (AR) receptors, which have been implicated in the progression of breast and prostate cancer, respectively. We show here that an estradiol-based Protac can enforce the ubiquitination and degradation of the {alpha} isoform of ER in vitro, and a dihydroxytestosterone-based Protac introduced into cells promotes the rapid disappearance of AR in a proteasome-dependent manner. Future improvements to this technology may yield a general approach to treat a number of human diseases, including cancer.

Additional Information

© 2003 The American Society for Biochemistry and Molecular Biology, Inc. Received, September 15, 2003, and in revised form, September 30, 2003. Published, MCP Papers in Press, October 2, 2003, DOI 10.1074/mcp.T3000009-MCP200. We thank Charles Sawyers for providing the GFP-AR expression plasmid and Eric Davidson (Division of Biology, Caltech, La Jolla, CA) for use of the microinjection equipment and microscope. We are also grateful to Frank Mercurio (Signal Division, Celgene Pharmaceuticals, Warren, NJ) for help obtaining GA-1-monosuccinimidyl suberate.

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