title: p53-Independent up-regulation of a TRAIL receptor DR5 by proteasome inhibitors: a mechanism for proteasome inhibitor-enhanced TRAIL-induced apoptosis.
abstract: Gliomas are the most common brain tumors in adults and account for more than half of all brain tumors. Despite intensive clinical investigations, average survival for the patients harboring the malignancy has not been significantly improved. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), shown to have potent and cancer-selective killing activity, has drawn considerable attention as a promising anti-cancer therapy. In an attempt to develop TRAIL as an anti-cancer therapy for gliomas, tumor suppressor activity of TRAIL was assessed using human glioma cell lines such as U373MG, U343MG, U87MG and LN18. U343MG, U87MG and LN18 cells were susceptible to TRAIL; however, U373MG cells were completely refractory to TRAIL. Resistance to the applied therapies is a key issue in cancer treatment; thus, various combination treatments were evaluated using U373MG cells to identify a better regimen. Unlike Doxorubicin, Etoposide, Actinomycin D and Wortmannin, a proteasome inhibitor MG132 significantly enhanced TRAIL-induced apoptosis. Similarly, other proteasome inhibitors, including Lactacystin, Proteasome inhibitor I and Velcade (Bortezomib), also enhanced apoptotic activity of TRAIL. Among these proteasome inhibitors, Velcade, the only approved drug, was as effective as MG132 in enhancing TRAIL-induced apoptosis. Both Velcade and MG132 increased the protein levels of DR5, a TRAIL receptor known to be up-regulated by p53, in U373MG cells where p53 is mutated. Our data indicate that proteasome inhibitors up-regulate DR5 in a p53-independent manner and a combination therapy comprising TRAIL and Velcade become a better treatment regimen for gliomas.
authors: Faculty of Pharmacy, College of Pharmacy, Chung-Ang University, Seoul 156-756, Republic of Korea. seold@cau.ac.kr
authors: Dai-Wu
authors: DW
authors: Seol
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols; D017209:Apoptosis / Q000187:drug effects; D001897:Boronic Acids / Q000627:therapeutic use*; D000069286:Bortezomib; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D015853:Cysteine Proteinase Inhibitors / Q000627:therapeutic use*; D005910:Glioma / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D007976:Leupeptins / Q000627:therapeutic use; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000627:therapeutic use*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000627:therapeutic use*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D001897:Boronic Acids; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D061988:Proteasome Inhibitors; D011719:Pyrazines; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D016159:Tumor Suppressor Protein p53; D000069286:Bortezomib; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde