title: Lactacystin, a proteasome inhibitor, potentiates the apoptotic effect of parthenolide, an inhibitor of NFkappaB activation, on drug-resistant mouse leukemia L1210 cells.
abstract: An L1210 cell line (Y8) selected for resistance to deoxyadenosine does not express p53 mRNA or protein but expresses WAF1/p21 even under basal conditions. The Y8 cell line had been previously shown to have an increased apoptotic response to a variety of agents that included DNA damaging agents, kinase inhibitors and drugs directed at NFkappa B activation. In this study we show that lactacystin (LC, an inhibitor of proteasome activity) in combination with parthenolide (PA) caused a synergistic increase in the apoptotic fraction of the Y8 cells. LC (2.5 microM) alone and PA (5.0 microM) caused less than 20% of the Y8 cells to undergo apoptosis. However, the combination of LC (2.5 microM) plus PA (5.0 microM) caused 60% of the Y8 cells to undergo apoptosis. The combination of drugs had no effects on the parental wild-type L1210 cells. Pretreatment of the intact Y8 cells with the caspase-3 inhibitor, Ac-DEVD-CHO, resulted in a marked decrease in the apoptosis caused by the LC plus PA combination. Cell-free extracts prepared from the LC plus PA combination-treated cells had activated caspase activities in the caspase cascade: caspase-3 >> caspase-8 > caspase-6 and caspase-10. These results suggest that there are interacting pathways involving aspects of NFkappa B activation and proteasome activity that could be exploited in therapy directed at p53-deficient tumor cells that would lead to caspase-3 activation and apoptosis bypassing the p53-dependent chemotherapy insensitivity.
authors.affiliation: Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA.
authors.forename: Ann H
authors.initials: AH
authors.lastname: Cory
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Cory
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D007939:Leukemia L1210 / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D046988:Proteasome Endopeptidase Complex; D012717:Sesquiterpenes / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis
chemical_list: D061945:Caspase Inhibitors; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D015853:Cysteine Proteinase Inhibitors; D009097:Multienzyme Complexes; D016328:NF-kappa B; D012717:Sesquiterpenes; D016159:Tumor Suppressor Protein p53; C067713:lactacystin; C002669:parthenolide; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine