title: Proteasome inhibitor PS-341 (VELCADE) induces stabilization of the TRAIL receptor DR5 mRNA through the 3'-untranslated region.
abstract: Addition of proteasome inhibitor PS-341 (VELCADE, bortezomib) to prostate cancer cells enhances cell death mediated by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). PS-341 sensitizes prostate cancer cells to TRAIL-induced apoptosis by increasing TRAIL receptors (DR5), inhibiting protein degradation, and elevating DR5 mRNA. Investigations into how PS-341 regulates the stability of DR5 mRNA revealed that PS-341 increased DR5 mRNA by extending its half-life from 4 to 10 h. The 2.5-kb 3'-untranslated region of the DR5 gene stabilized a heterologous gene in LNCaP human prostate cancer cells, suggesting the importance of this mRNA sequence. In contrast, human prostate cancer cell lines PC-3 and DU145 do not show this stabilization, suggesting cell specificity. PS-341 treatment of LNCaP cells increases the level of specific cytoplasmic mRNA-binding proteins, including AUF-1 isoforms, hnRNP C1/C2, and HuR proteins. In UV cross-linking experiments, after PS-341 treatment, the HuR protein markedly increases binding to specific sequences in the DR5 3'-untranslated region. In LNCaP cells treated with PS-341, small interfering RNA-mediated knockdown of HuR markedly decreases the half-life of DR5 mRNA, indicating that HuR is essential for mRNA stabilization. HuR protein is ubiquitinated, suggesting that PS-341 increases this protein by preventing its degradation. These experiments implicate modulation of mRNA stability as a novel mechanism by which proteasome inhibitors function, sensitizing cancer cells to antineoplastic agents.
authors.affiliation: Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Suite 124, Charleston, SC 29425, USA.
authors.forename: Karthikeyan
authors.initials: K
authors.lastname: Kandasamy
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Kraft
mesh_terms: D020413:3' Untranslated Regions / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D006801:Humans; D008297:Male; D011480:Protease Inhibitors / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D000970:Antineoplastic Agents; D001897:Boronic Acids; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D025801:Ubiquitin; D000069286:Bortezomib