bay-11-7082 and Leukemia

A growing body of evidence suggests the inhibition of NFkappaB as a strategy to induce cell death in tumor cells. In this work, we evaluated the effects of the pharmacological NFkappaB inhibitors BAY117082 and MG132 on leukemia cells apoptosis. BAY117082 and MG132 presented potent apoptotic effects compared to inhibitors of MAPKs, EGFR, PI3K/Akt, PKC and PKA signaling pathways. Non-tumor peripheral blood cells were insensitive to BAY117082 and MG132 apoptotic effects. BAY117082 and MG132-induced apoptosis was dependent on their ability to increase ROS as a prelude to mitochondria membrane potential (MMP) depolarization, permeability transition pore opening and cytochrome c release. Antioxidants blocked MG132 and BAY117082 effects on ROS, MMP and cell death. Although apoptotic markers as phosphatidylserine externalization, chromatin condensation and sub-G1 were detected in BAY117082-treated cells, caspases activation did not occur and apoptosis was insensitive to caspase inhibitors, suggesting a caspase-independent mechanism. In contrast, MG132 induced classical apoptosis through ROS-mitochondria and subsequent caspase-9/caspase-3 activation. At sub-apoptotic concentrations, BAY117082 and MG132 arrested cells in G2/M phase of the cell cycle and blocked doxorubicin-induced NFkappaB, which sensitized doxorubicin-resistant cells. Data suggest that the NFkappaB inhibitors MG132 and BAY117082 are potential anti-leukemia agents.

Topics: Antibiotics, Antineoplastic; Antineoplastic Agents; Apoptosis; Caspases; Cell Proliferation; Cytochromes c; Dose-Response Relationship, Drug; Doxorubicin; Drug Resistance, Neoplasm; Enzyme Activation; Humans; Jurkat Cells; K562 Cells; Leukemia; Leupeptins; Membrane Potential, Mitochondrial; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; NF-kappa B; Nitriles; Reactive Oxygen Species; Sulfones; Time Factors; U937 Cells

NF-kappaB activation is reciprocally regulated by RelA/p65 acetylation and deacetylation, which are mediated by histone acetyltransferases (HATs) and deacetylases (HDACs). Here we demonstrate that in leukemia cells, NF-kappaB activation by the HDAC inhibitors (HDACIs) MS-275 and suberoylanilide hydroxamic acid was associated with hyperacetylation and nuclear translocation of RelA/p65. The latter events, as well as the association of RelA/p65 with IkappaBalpha, were strikingly diminished by either coadministration of the IkappaBalpha phosphorylation inhibitor Bay 11-7082 (Bay) or transfection with an IkappaBalpha superrepressor. Inhibition of NF-kappaB by pharmacological inhibitors or genetic strategies markedly potentiated apoptosis induced by HDACIs, and this was accompanied by enhanced reactive oxygen species (ROS) generation, downregulation of Mn-superoxide dismutase and XIAP, and c-Jun N-terminal kinase 1 (JNK1) activation. Conversely, N-acetyl L-cysteine blocked apoptosis induced by Bay/HDACIs by abrogating ROS generation. Inhibition of JNK1 activation attenuated Bay/HDACI lethality without affecting NF-kappaB inactivation and ROS generation. Finally, XIAP overexpression dramatically protected cells against the Bay/HDACI regimen but failed to prevent ROS production and JNK1 activation. Together, these data suggest that HDACIs promote the accumulation of acetylated RelA/p65 in the nucleus, leading to NF-kappaB activation. Moreover, interference with these events by either pharmacological or genetic means leads to a dramatic increase in HDACI-mediated lethality through enhanced oxidative damage, downregulation of NF-kappaB-dependent antiapoptotic proteins, and stress-related JNK1 activation.

Topics: Acetylation; Apoptosis; Benzamides; Down-Regulation; Enzyme Activation; Enzyme Inhibitors; Gene Expression Regulation, Enzymologic; Histone Deacetylase Inhibitors; HL-60 Cells; Humans; Hydroxamic Acids; JNK Mitogen-Activated Protein Kinases; Jurkat Cells; Leukemia; NF-kappa B; Nitriles; Oxidative Stress; Proteins; Pyridines; Reactive Oxygen Species; Sulfones; Superoxide Dismutase; Transcription Factor RelA; U937 Cells; Vorinostat; X-Linked Inhibitor of Apoptosis Protein

Glutathione S-transferases (GSTs) play an important role in the protection of cells against xenobiotics and lipid hydroperoxides generated by oxidative stress. In human, the GSTP1-1 expression is commonly increased in many tumors and involved in the development of antineoplastic drug resistance. Reactive oxygen species are released at inflammation sites and oxidative stress conditions enhance the expression of genes encoding antioxidant enzymes such as GSTs. Here we investigated the regulation of the GSTP1-1 gene expression in the K562 cell line by nuclear factor kappaB (NF-kappaB) and the pro-inflammatory cytokine tumor necrosis factor alpha (TNFalpha). By studying GSTP1-1 mRNA expression and NF-kappaB/GSTP1-1 promoter interactions, we showed the implication of NF-kappaB in the GSTP1-1 gene expression and we described a new specific TNFalpha-inducible NF-kappaB binding site upstream of the minimal promoter. Moreover, TNFalpha treatment as well as cotransfection of NF-kappaB signaling pathway intermediates induced an activation of the GSTP1-1 gene promoter in K562 cells. Site-directed mutagenesis of the NF-kappaB site strongly inhibited TNFalpha- and NF-kappaBp65-induced promoter activation. Altogether, we showed that a sequence located at -323/-314 within the GSTP1-1 promoter bound NF-kappaB p50/65 and p65/p65 dimers and that this kappaB site was involved in the regulation of the gene by TNFalpha.

Topics: Binding Sites; Gene Expression Regulation, Neoplastic; Glutathione S-Transferase pi; Glutathione Transferase; Humans; Isoenzymes; Leukemia; NF-kappa B; Nitriles; Organic Chemicals; Promoter Regions, Genetic; Signal Transduction; Sulfones; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha