title: Synergistic interaction of the histone deacetylase inhibitor SAHA with the proteasome inhibitor bortezomib in mantle cell lymphoma.
abstract: OBJECTIVE
  Mantle cell lymphoma (MCL) is an incurable B cell lymphoma, and novel treatment strategies are urgently needed. We evaluated the effects of combined treatment with the proteasome inhibitor bortezomib and the histone deacetylase inhibitor (HDACi) suberoylanilide hydroxamic acid (SAHA) on MCL. Bortezomib acts by targeting the proteasome, and--among other mechanisms--results in a reduced nuclear factor-kappa B (NF-kappaB) activity. HDACi promote histone acetylation, and also interfere with NF-kappaB signaling.
  
  
  METHODS
  Human MCL cell lines (JeKo-1, Granta-519 and Hbl-2) were exposed to bortezomib and/or SAHA. Cell viability and apoptosis were quantified by the MTT and annexin-V assay, respectively. Reactive oxygen species (ROS) were analyzed using the fluorophore H2DCFDA. In addition, activated caspases, proteasome- and NF-kappaB activity were quantified.
  
  
  RESULTS
  Combined incubation with bortezomib and SAHA resulted in synergistic cytotoxic effects, as indicated by combination index values <1 using the median effect method of Chou and Talalay. The combination of both inhibitors led to a strong increase in apoptosis as compared to single agents and was accompanied by enhanced ROS generation, while each agent alone only modestly induced ROS. The free radical scavenger N-acetyl-L-cysteine blocked the ROS generation and reduced the apoptosis significantly. In addition, coexposure of bortezomib and SAHA led to increased caspase-3, -8 and -9 activity, marked reduction of proteasome activity and decrease of NF-kappaB activity.
  
  
  CONCLUSIONS
  This is the first report giving evidence that SAHA and bortezomib synergistically induce apoptosis in MCL cells. These data build the framework for clinical trials using combined proteasome and histone deacetylase inhibition in the treatment of MCL.
authors.affiliation: Department of Haematology and Oncology, Charité Universitätsmedizin Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Heider
authors.forename: Ivana
authors.initials: I
authors.lastname: von Metzler
authors.forename: Martin
authors.initials: M
authors.lastname: Kaiser
authors.forename: Marleen
authors.initials: M
authors.lastname: Rosche
authors.forename: Jan
authors.initials: J
authors.lastname: Sterz
authors.forename: Susanne
authors.initials: S
authors.lastname: Rötzer
authors.forename: Jessica
authors.initials: J
authors.lastname: Rademacher
authors.forename: Christian
authors.initials: C
authors.lastname: Jakob
authors.forename: Claudia
authors.initials: C
authors.lastname: Fleissner
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kuckelkorn
authors.forename: Peter-Michael
authors.initials: PM
authors.lastname: Kloetzel
authors.forename: Orhan
authors.initials: O
authors.lastname: Sezer
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis; D001897:Boronic Acids / Q000737:chemistry / Q000494:pharmacology*; D000069286:Bortezomib; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000737:chemistry / Q000494:pharmacology*; D020522:Lymphoma, Mantle-Cell / Q000188:drug therapy*; D016328:NF-kappa B / Q000378:metabolism; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000737:chemistry / Q000494:pharmacology*; D017382:Reactive Oxygen Species; D016896:Treatment Outcome; D000077337:Vorinostat
chemical_list: D001897:Boronic Acids; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D016328:NF-kappa B; D061988:Proteasome Inhibitors; D011719:Pyrazines; D017382:Reactive Oxygen Species; D000077337:Vorinostat; D000069286:Bortezomib; D020169:Caspases