title: Molecular pathways that modify tumor radiation response.
abstract: Aberrant expression of signal transduction molecules in pathways controlling cell survival, proliferation, death, or differentiation are a common feature of all tumors. The identification of the molecules that are involved allows the development of novel tumor-specific strategies. Not surprisingly, targeting these pathways often also results in radiosensitization. The efficacy of such directed therapies may, however, be limited by the heterogeneity and the multiple mutations that are associated with the cancerous state. A more robust alternative may be to target global mechanisms of cellular control. The ubiquitin/proteasome degradation pathway is one candidate for such therapeutic intervention. This pathway is the main posttranscriptional mechanism that controls levels of many short-lived proteins involved in regulation of cell cycle progression, DNA transcription, DNA repair, and apoptosis. Many of these proteins are involved in various malignancies and/or radiation responses. In recent years, proteasome inhibitors have gained interest as a promising new group of antitumor drugs. PS-341, a reversible inhibitor of proteasome chymotryptic activity, is currently being tested in phase I clinical trials. In this study, we show that proteasome inhibition by PS-341 can alter cellular radiosensitivity in vitro and in vivo, in addition to having direct antitumor effects.
authors.affiliation: Department of Radiation Oncology, Roy E. Coats Research Laboratories and Jonsson Comprehensive Cancer Center, UCLA School of Medicine, Los Angeles, CA 90095-1714, USA.
authors.forename: M
authors.initials: M
authors.lastname: Pervan
authors.forename: F
authors.initials: F
authors.lastname: Pajonk
authors.forename: J R
authors.initials: JR
authors.lastname: Sun
authors.forename: H R
authors.initials: HR
authors.lastname: Withers
authors.forename: W H
authors.initials: WH
authors.lastname: McBride
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004357:Drug Synergism; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex; D011719:Pyrazines / Q000494:pharmacology*; D011836:Radiation Tolerance; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D007976:Leupeptins; D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D011719:Pyrazines; D014452:Ubiquitins; D000069286:Bortezomib; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde