title: Efficacy and mechanism of action of the proteasome inhibitor PS-341 in T-cell lymphomas and HTLV-I associated adult T-cell leukemia/lymphoma.
abstract: HTLV-I associated adult T-cell leukemia (ATL) and HTLV-I-negative peripheral T-cell lymphomas are associated with poor prognosis. Using pharmacological concentrations of the proteasome inhibitor PS-341, we demonstrate inhibition of cell proliferation and induction of apoptosis in fresh ATL cells, HTLV-I transformed and HTLV-I-negative malignant T cells, while normal resting or activated T lymphocytes were resistant. Combination of PS-341 and doxorubicin or etoposide resulted in an additive growth inhibition. In HTLV-I-negative malignant cells, PS-341 treatment significantly downregulated the antiapoptotic protein X-IAP and to a lesser extent c-IAP-1 and bcl-X(L) and resulted in caspase-dependent apoptosis. In HTLV-I transformed cells, the inhibition of the proteasomal degradation of Tax by PS-341 likely explains the relative protection of HTLV-I infected cells against caspase-dependent apoptosis. PS-341 treatment of these cells stabilized IkappaBalpha, IkappaBbeta, IkappaBvarepsilon, p21, p27 and p53 proteins and selectively inhibited Rel-A DNA binding NF-kappaB complexes. In both HTLV-I-positive and -negative cells, PS-341 treatment induced ceramide accumulation that correlated with apoptosis. We conclude that PS-341 affects multiple pathways critical for the survival of HTLV-I-positive and -negative malignant T cells supporting a potential therapeutic role for PS-341 in both ATL and HTLV-I-negative T-cell lymphomas, whether alone or in combination with chemotherapy.
authors.affiliation: Department of Internal Medicine, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
authors.forename: Rihab
authors.initials: R
authors.lastname: Nasr
authors.forename: Marwan E
authors.initials: ME
authors.lastname: El-Sabban
authors.forename: José-Antonio
authors.initials: JA
authors.lastname: Karam
authors.forename: Ghassan
authors.initials: G
authors.lastname: Dbaibo
authors.forename: Youmna
authors.initials: Y
authors.lastname: Kfoury
authors.forename: Bertrand
authors.initials: B
authors.lastname: Arnulf
authors.forename: Yves
authors.initials: Y
authors.lastname: Lepelletier
authors.forename: Françoise
authors.initials: F
authors.lastname: Bex
authors.forename: Hugues
authors.initials: H
authors.lastname: de Thé
authors.forename: Olivier
authors.initials: O
authors.lastname: Hermine
authors.forename: Ali
authors.initials: A
authors.lastname: Bazarbachi
mesh_terms: D000328:Adult; D000970:Antineoplastic Agents / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D001897:Boronic Acids / Q000633:toxicity*; D000069286:Bortezomib; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000473:pathology*; D016399:Lymphoma, T-Cell / Q000473:pathology*; D011480:Protease Inhibitors / Q000633:toxicity*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000633:toxicity*
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D002518:Ceramides; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D000069286:Bortezomib