title: Functional blocks in caspase activation pathways are common in leukemia and predict patient response to induction chemotherapy.
abstract: Defects in apoptosis mechanisms contribute to chemoresistance in malignancy. However, correlations of apoptosis-regulating proteins with clinical outcome in cancer patients are variable, presumably reflecting the difficulty of using static tests of gene expression in a scenario influenced by a dynamic interplay of multiple pro- and antiapoptotic molecules. Therefore, we assessed the functional integrity of apoptosis pathways in intact primary leukemia cells and correlated the functional status of these pathways with clinical outcome. Active apoptogenic proteins were introduced into primary leukemia cells by electroporation followed by measurement of active caspases by flow cytometric techniques. Cytochrome c was introduced to activate the intrinsic (mitochondrial) pathway, whereas caspase-8 was introduced to activate the extrinsic (death receptor) pathway. In a series of 24 patients with acute myeloid leukemia, 79% had a block in at least one pathway, indicating that defects in caspase activation mechanisms are common in patients with leukemia. Simultaneous blocks in both pathways correlated with chemoresistant disease (92% of patients with chemoresistant disease versus 33% of patients with chemosensitive disease; P = 0.005) and decreased overall patient survival (35% versus 89% 1-year survival; P = 0.02). Simultaneous blockage of the intrinsic and extrinsic pathways could be explained by a defect located at a point of convergence of the two pathways, probably related to overexpression of endogenous inhibitors of the effector-caspases, rather than decreased levels of these proteases. This study supports the importance of apoptosis pathways in determining response to chemotherapy and suggests that functional defects in caspase activation are prognostic in patients with leukemia.
authors.affiliation: The Burnham Institute, La Jolla, California 92037, USA.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Schimmer
authors.forename: Irene Munk
authors.initials: IM
authors.lastname: Pedersen
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kitada
authors.forename: Emel
authors.initials: E
authors.lastname: Eksioglu-Demiralp
authors.forename: Mark D
authors.initials: MD
authors.lastname: Minden
authors.forename: Ryan
authors.initials: R
authors.lastname: Pinto
authors.forename: Ken
authors.initials: K
authors.lastname: Mah
authors.forename: Michael
authors.initials: M
authors.lastname: Andreeff
authors.forename: Youngsoo
authors.initials: Y
authors.lastname: Kim
authors.forename: Won Suk
authors.initials: WS
authors.lastname: Suh
authors.forename: John C
authors.initials: JC
authors.lastname: Reed
mesh_terms: D000328:Adult; D000368:Aged; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000008:administration & dosage* / Q000378:metabolism; D003574:Cytochrome c Group / Q000008:administration & dosage* / Q000037:antagonists & inhibitors / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D018274:Electroporation; D004789:Enzyme Activation; D053804:Granzymes; D006801:Humans; D020014:K562 Cells; D007951:Leukemia, Myeloid / Q000188:drug therapy* / Q000201:enzymology*; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D010047:Ovalbumin / Q000008:administration & dosage / Q000031:analogs & derivatives*; D012697:Serine Endopeptidases / Q000008:administration & dosage
chemical_list: D061945:Caspase Inhibitors; D003574:Cytochrome c Group; C042851:fluorescein-ovalbumin; D010047:Ovalbumin; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases