title: Proteasome inhibition in cancer: development of PS-341.
abstract: The 26S proteasome regulates protein turnover in eukaryotic cells. This is relevant in human cancer because the cell cycle, tumor growth, and survival are governed by a large repertoire of intracellular proteins that are regulated by the ubiquitin-mediated proteasome degradative pathway. In the development of new antitumor agents whose mechanisms are distinct from currently available therapies, we have discovered a potent, selective inhibitor of the proteasome: PS-341, a dipeptide boronic acid. Compared with normal cells, cancer cells--and specifically myeloma--treated with PS-341 are differentially sensitive to proteasome inhibition and apoptosis. A unique feature of PS-341 involves the inhibition of nuclear factor (NF)-kappaB activation through stabilization of the inhibitor protein IkappaB. Myeloma cells depend on NF-kappaB-mediated transcription of cytokine growth factor interleukin-6, angiogenesis through vascular endothelial growth factor, and the cell adhesion molecule VCAM-1 for adherence of the plasma cells to the stromal tissue in bone marrow. At low nanomolar concentrations, PS-341 is highly effective in abrogating the transcription of these genes, which are under the direct regulation of NF-kappaB. Moreover, PS-341 appears to synergize with dexamethasone in myeloma cell culture, which may prove to be of additional benefit clinically. The safety profile in phase I trials of PS-341 in patients with cancer appears encouraging. Because proteasome inhibition with PS-341 results in potent antitumor activity in vitro, PS-341 may offer a promising new approach to treating otherwise fatal malignancy.
authors.affiliation: Millennium Pharmaceuticals, Inc., 75 Sydney Street, Cambridge, MA 02139, USA.
authors.forename: J
authors.initials: J
authors.lastname: Adams
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001897:Boronic Acids / Q000494:pharmacology* / Q000627:therapeutic use; D000069286:Bortezomib; D002453:Cell Cycle / Q000187:drug effects; D002986:Clinical Trials as Topic; D003546:Cysteine Endopeptidases; D004354:Drug Screening Assays, Antitumor; D019337:Hematologic Neoplasms / Q000188:drug therapy*; D006801:Humans; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D009101:Multiple Myeloma / Q000188:drug therapy*; D010447:Peptide Hydrolases; D011480:Protease Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D046988:Proteasome Endopeptidase Complex; D011719:Pyrazines / Q000494:pharmacology* / Q000627:therapeutic use; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D011719:Pyrazines; D000069286:Bortezomib; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease