title: Bortezomib inhibits docetaxel-induced apoptosis via a p21-dependent mechanism in human prostate cancer cells.
abstract: Bortezomib (PS-341, Velcade) is a peptide boronate inhibitor of the 20S proteasome that is currently being combined with taxanes in several clinical trials in patients with prostate cancer. Here, we report that bortezomib inhibited docetaxel-induced M-phase arrest and apoptosis in androgen-dependent LNCaP-Pro5 cells. Direct analysis of kinase activity in immune complex kinase assays revealed that docetaxel activated cyclin-dependent kinase (CDK) 1 (CDC2) and that bortezomib blocked this activation. The effects of bortezomib were associated with accumulation of p21 and mimicked by chemical CDK inhibitors or by transfecting cells with a small interfering RNA construct specific for CDK1. Transient transfection with p21 also inhibited docetaxel-induced apoptosis; conversely, p21 silencing reversed the antagonistic effects of bortezomib on docetaxel-induced apoptosis. Together, our data show that bortezomib interferes with docetaxel-induced apoptosis via a p21-dependent mechanism that is associated with CDK1 inhibition. These observations may have important implications for the ongoing bortezomib-docetaxel combination trials as well as trials using bortezomib and other cell cycle-sensitive agents.
authors.affiliation: Department of Urology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, 77030, USA.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Canfield
authors.forename: Keyi
authors.initials: K
authors.lastname: Zhu
authors.forename: Simon A
authors.initials: SA
authors.lastname: Williams
authors.forename: David J
authors.initials: DJ
authors.lastname: McConkey
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D016203:CDC2 Protein Kinase / Q000187:drug effects / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D000077143:Docetaxel; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D011719:Pyrazines / Q000494:pharmacology*; D043823:Taxoids / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D050759:Cyclin-Dependent Kinase Inhibitor p21; D011719:Pyrazines; D043823:Taxoids; D000077143:Docetaxel; D000069286:Bortezomib; D016203:CDC2 Protein Kinase