title: Differential involvement of reactive oxygen species in apoptosis caused by the inhibition of protein phosphatase 2A in Jurkat and CCRF-CEM human T-leukemia cells.
abstract: A better understanding of dysregulated signaling pathways in cancer cells may suggest novel strategies to prevent tumor development and/or progression. Here we show that Jurkat and CCRF-CEM human T-leukemia cell lines were more sensitive than normal human T cells to the cytotoxic effect of inhibiting protein phosphatase 2A (PP2A). Inhibition of PP2A by okadaic acid (OA) caused T-leukemia cells to die by apoptosis, as indicated by DNA fragmentation, caspase-3 activation, loss of mitochondrial membrane potential (DeltaPsi(m)), and changes in nuclear morphology that were consistent with apoptosis. PP2A might therefore be a useful intracellular target for the treatment of T cell-derived leukemias. We also observed that reactive oxygen species (ROS) were generated in response to PP2A inhibition in T-leukemia cells. However, loss of DeltaPsi(m) that resulted from PP2A inhibition was not prevented by exogenous antioxidants (glutathione and N-acetyl-cysteine), indicating that OA-induced changes in mitochondrial membrane permeability were not a consequence of ROS production. Moreover, exogenous antioxidants protected CCRF-CEM T-leukemia cells from apoptosis caused by PP2A inhibition but failed to prevent OA-induced apoptosis in Jurkat T-leukemia cells, indicating a differential role for ROS in apoptosis caused by PP2A inhibition in two different human T-leukemia cell lines.
authors.affiliation: Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5.
authors.forename: Robert T M
authors.initials: RT
authors.lastname: Boudreau
authors.forename: David M
authors.initials: DM
authors.lastname: Conrad
authors.forename: David W
authors.initials: DW
authors.lastname: Hoskin
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D007938:Leukemia / Q000378:metabolism*; D015458:Leukemia, T-Cell / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D019319:Okadaic Acid / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D019319:Okadaic Acid; D054648:Protein Phosphatase 2; D053148:Caspase 3