benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and Leukemia

Tropolones, such as β-thujaplicin, are small lead-like natural products that possess a variety of biological activities. While the β-substituted natural products and their synthetic analogs are potent inhibitors of human cancer cell growth, less is known about their α-substituted counterparts. Recently, we synthesized a series of α-substituted tropolones including 2-hydroxy-7-(naphthalen-2-yl)cyclohepta-2,4,6-trien-1-one (α-naphthyl tropolone). Here, we evaluate the antiproliferative mechanisms of α-naphthyl tropolone and the related α-benzodioxinyl analog. The α-substituted tropolones inhibit growth of lymphocytic leukemia cells, but not healthy blood cells, with nanomolar potency. Treatment of leukemia cell lines with the tropolone dose-dependently induces apoptosis as judged by staining with annexin V and propidium iodide and Western blot analysis of cleaved caspase 3 and 7. Moreover, pre-treatment of cells with the caspase inhibitor Z-VAD-FMK inhibited the apoptotic effects of the tropolone in two lymphocytic lines. Caspase inhibition also blocked elevated histone acetylation caused by the tropolone, indicating that its effects on histone acetylation are potentiated by caspases. In contrast, α-naphthyl tropolone upregulated p53 expression and phosphorylation of Akt and mTOR in a manner that was not rescued by caspase inhibition. The effects of tropolone were blocked by co-incubation with high levels of free extracellular iron but not by pre-loading with iron. Additionally, dose and time dependent reduction in ex vivo viability of cells from leukemia patients was observed. Taken together, we demonstrate that α-substituted tropolones upregulate DNA damage repair pathways leading to caspase-dependent apoptosis in malignant lymphocytes.

Topics: Acetylation; Amino Acid Chloromethyl Ketones; Apoptosis; Caspases; Cell Line; Cell Proliferation; Cell Survival; DNA Repair; Histones; Humans; Leukemia; Leukocytes, Mononuclear; Monoterpenes; Proto-Oncogene Proteins c-akt; TOR Serine-Threonine Kinases; Tropolone; Tumor Suppressor Protein p53; Up-Regulation

Heat shock protein 90 (HSP90) is a molecular chaperone that supports stability of client proteins. We found that HSP90 was cleaved to 55 kDa protein after treatment with histone deacetylase (HDAC) inhibitors including suberoylanilide hydroxamic acid (SAHA) in several leukemia cell lines. We further analyzed molecular changes induced by SAHA in K562 cells. The SAHA-induced cleavage of HSP90 was blocked by a pan-caspase inhibitor, z-VAD-fmk, implying that the process is dependent on caspase activity. However, the experiments using antagonistic and agonistic Fas antibodies revealed that the cleavage of HSP90 was not dependent on Fas signaling. SAHA induced generation of reactive oxygen species (ROS), and the cleavage of HSP90 was blocked by a ROS scavenger N-acetylcystein (NAC). We also confirmed that hydrogen peroxide (H2O2) induced cleavage of HSP90 in a similar manner. Caspase 2, 3, 4, 6, 8, and 10 were activated by treatment with SAHA, and the activities were reduced by the pretreatment of NAC. Treatment of the cells with caspase 10 inhihitor, but not other inhibitors of caspases activated by SAHA, prevented cleavage of HSP90 by SAHA. SAHA-induced ROS generation and HSP90 cleavage were dependent on newly synthesized unknown proteins. Taken together, our results suggest that the cleavage of HSP90 by SAHA is mediated by ROS generation and caspase 10 activation. HSP90 cleavage may provide an additional mechanism involved in anti-cancer effects of HDAC inhibitors.

Topics: Acetylcysteine; Amino Acid Chloromethyl Ketones; Caspase 10; Caspase Inhibitors; Caspases; fas Receptor; Histone Deacetylase Inhibitors; HSP90 Heat-Shock Proteins; Humans; Hydrogen Peroxide; Hydroxamic Acids; K562 Cells; Leukemia; Proteolysis; Reactive Oxygen Species; Signal Transduction; Vorinostat

Depletion of intracellular glutathione (GSH) is the prime hallmark of the progression of apoptosis. Previously, we reported that curcumin induces reactive oxygen species (ROS)-mediated depletion of GSH, which leads to caspase-dependent and independent apoptosis in mouse fibroblast cells (F. Thayyullathil et al., Free Radic. Biol. Med.45, 1403-1412, 2008). In this study, we investigated the antileukemic potential of curcumin in vitro, and we further examined the molecular mechanisms of curcumin-induced apoptosis in human leukemic cells. Curcumin suppresses the growth of human leukemic cells via ROS-independent GSH depletion, which leads to caspase activation, inhibition of sphingomyelin synthase (SMS) activity, and induction of ceramide (Cer) generation. Pretreatment of leukemic cells with carbobenzoxy-Val-Ala-Asp fluoromethylketone, a universal inhibitor of caspases, abrogates the SMS inhibition and Cer generation, and in turn prevents curcumin-induced cell death. Curcumin treatment of leukemic cells also downregulates the expression of the inhibitor of apoptosis proteins (IAPs), phospho-Akt, c-Myc, and cyclin D1. Extracellular supplementation with GSH attenuates curcumin-induced depletion of GSH, caspase-dependent inhibition of SMS, Cer generation, and downregulation of IAPs, whereas, L-D-buthionine sulfoximine, a widely used inhibitor of GSH synthesis, potentiates GSH depletion, Cer generation, and apoptosis induced by curcumin. Taken together, our findings provide evidence suggesting for the first time that GSH regulates caspase-dependent inhibition of SMS activity, Cer generation, and apoptosis induced by curcumin in human leukemic cells.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Blotting, Western; Caspases; Cell Line; Ceramides; Curcumin; Glutathione; Humans; Leukemia

A series of alkyl α/β-(1→6)-diglucopyranosides 1-12 were synthesized and assessed for cytotoxicity against HL-60, U937, Molt-3 and MCF-7 cancer cell lines. The menthyl derivatives displayed strong cytotoxic properties showing IC(50) values between 6 and 16 μM. Furthermore, we demonstrated that the selected synthetic (+)-menthyl β-(1→6)-diglucopyranoside 5 induces apoptotic cell death in human leukemia cells through a mechanism that involves activation of multiple caspases. Cell death was completely prevented by the non-specific caspase inhibitor z-VAD-fmk and found to be associated with the release of cytochrome c, an increase in the expression of Bax levels and a decrease in the generation of reactive oxygen species.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; bcl-2-Associated X Protein; Caspases; Cell Line, Tumor; Cytochromes c; Disaccharides; HL-60 Cells; Humans; Leukemia; Reactive Oxygen Species

Flavonoids are naturally occurring polyphenolic compounds and are among the most promising anticancer agents. Here we demonstrate that the flavonoid derivative astragalin heptaacetate (AHA) induces cell death. This was prevented by the non-specific caspase inhibitors z-VAD-fmk and Q-VD-OPH, and reduced by the selective caspase-4 inhibitor z-LEVD-fmk. AHA-induced cell death was found to be: (i) associated with the release of cytochrome c, (ii) suppressed by the overexpression of Bcl-x(L), (iii) amplified by inhibition of extracellular signal-regulated kinases (ERKs) 1/2 and c-jun NH(2)-terminal kinases/stress activated protein kinases (JNK/SAPK) signaling, and (iv) completely abrogated by the free-radical scavenger N-acetyl-l-cysteine.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Caspase Inhibitors; Caspases; Cell Death; Cell Proliferation; Cysteine Proteinase Inhibitors; Cytochromes c; Glycosides; HL-60 Cells; Humans; Kaempferols; Leukemia; MAP Kinase Signaling System; Proto-Oncogene Proteins c-bcl-2; Quinolines

Ceramide can be converted into sphingomyelin by sphingomyelin synthases (SMS) 1 and 2. In this study, we show that in human leukemia Jurkat cells, which express mainly SMS1, Fas ligand (FasL) treatment inhibited SMS activity in a dose- and time-dependent manner before nuclear fragmentation. The SMS inhibition elicited by FasL (1) was abrogated by benzyloxycarbonyl valyl-alanyl-aspartyl-(O-methyl)-fluoromethylketone (zVAD-fmk), a broad-spectrum caspase inhibitor; (2) did not occur in caspase-8-deficient cells and (3) was not affected in caspase-9-deficient cells. Western blot experiments showed SMS1 cleavage in a caspase-dependent manner upon FasL treatment. In a cell-free system, caspase-2, -7, -8 and -9, but not caspase-3 and -10, cleaved SMS1. In HeLa cells, SMS1 was Golgi localized and relocated throughout the cytoplasm in cells exhibiting an early apoptotic phenotype on FasL treatment. zVAD-fmk prevented FasL-induced SMS1 relocation. Thus, FasL-mediated SMS1 inhibition and relocation depend on caspase activation and likely represent proximal events in Fas signaling. FasL-induced ceramide production and cell death were enhanced in cells stably expressing an siRNA against SMS1. Conversely, in cells stably overexpressing SMS1, FasL neither increased ceramide generation nor efficiently induced cell death. Altogether, our data show that SMS1 is a novel caspase target that is functionally involved in the regulation of FasL-induced apoptosis.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Caspases; Ceramides; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fas Ligand Protein; Golgi Apparatus; HeLa Cells; Humans; Jurkat Cells; Leukemia; Membrane Proteins; Nerve Tissue Proteins; RNA Interference; RNA, Small Interfering; Signal Transduction; Sphingomyelins; Transferases (Other Substituted Phosphate Groups)

Understanding of molecular mechanisms underlying the effects of cell cycle proteins in response to the chemotherapeutic agents is of great importance for improving the efficacy of targeted therapeutics and overcoming resistance to chemotherapeutic agents. Staurosporine and tumor necrosis factor alpha (TNFalpha) are the therapeutic agents that inhibit tumor cell growth by inducing cell death. Staurosporine induces apoptosis through the intrinsic pathway, while TNFalpha trigger the cell death via the extrinsic apoptotic pathway. We have previously demonstrated that the cell cycle regulatory protein, cyclin A1 played an important role in the development of acute myeloid leukemia (AML), and cyclin A1 expression correlated with disease characteristics and patient outcome in leukemia. However, it remains unknown how cyclin A1 expression is regulated in leukemic cells treated with the therapeutic agents. Here, we demonstrate that cyclin A1 protein is regulated by proteasome-mediated ubiquitination and degradation in untreated U-937 cells. Interestingly, ubiquitination- and proteasomal-mediated degradation of cyclin A1 is prevented in cells treated with staurosporine or TNFalpha. Induction of apoptosis in U-937 cells by staurosporine or TNFalpha resulted in an increase in cyclin A1 protein expression, which correlated well with cyclin A1 protein modification and the activation of caspase-3. Blocking caspases activity by Z-VAD-FMK had no effect on the increased cyclin A1 expression, suggesting that cyclin A1 might be regulated by caspase-3 independent pathways. We further propose that CDC25C may be associated with cyclin A1 protein modification in response to staurosporine or TNFalpha treatment. Our results suggest that cyclin A1 protein is stabilized via post-transcriptional modification in response to apoptosis induced by staurosporine or TNFalpha.

Topics: Acetylcysteine; Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Caspase 3; Caspase Inhibitors; cdc25 Phosphatases; Cell Line, Tumor; Cyclin A1; Cyclin-Dependent Kinase 2; Cysteine Proteinase Inhibitors; Enzyme Inhibitors; Humans; Leukemia; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Protein Processing, Post-Translational; Staurosporine; Tumor Necrosis Factor-alpha; Ubiquitination

Platonin is a photosensitizer used for photodynamic therapy. In this study, we tested the effect of platonin on human leukemic cells. Treatment with platonin in the dark markedly reduced cell membrane integrity, and induced significant G(0)/G(1) arrest of a panel of human leukemic cell lines, including U937, HL-60, K562, NB4 and THP-1. Development of hypodiploid cells was not evident in these cell lines within 24 h, but was noted in U937, HL-60 and NB4 cells after 24 h. No myeloid differentiation of these cells was noted after five-day treatment. Intriguingly, exposure of monoblastic U937 cells to platonin caused changes characteristic of autophagy, including appearance of cytoplasmic membranous vacuoles and formation of acidic vesicular organelles (AVO) in more than 95% of cells. The platonin-induced autophagy was accompanied by localization of microtubule-associated protein 1 light chain 3 to autophagosomes. Pretreatment with pancaspase inhibitor Z-VAD-fmk abrogated the platonin-induced hypodiploidity, but had no effect on growth inhibition and formation of AVO, indicating a caspase-independent autophagy-associated cell death. Pretreatment of cells with 3-methyladenine attenuated platonin-mediated growth inhibition and formation of AVO. Platonin augmented the expression of BNIP3 in both U937 and K562 cells, whereas had an opposite effect on phosphorylation of mTOR downstream molecule p70S6K. Platonin, at the condition inducing autophagy, induced the mitochondrial membrane permeation. These results suggest that the platonin is capable of inhibiting growth as well as inducing cell death, mainly autophagy-associated, in leukemic cells via a mitochondria-mediated and caspase-independent pathway. A markedly less viability inhibition was noted to human monocytes, the normal counterpart of these myeloid leukemic cells. Platonin, other than a photodynamic agent, may offer significant promise as a therapeutic agent against leukemia.

Topics: Amino Acid Chloromethyl Ketones; Autophagy; Caspases; Cell Cycle; Cell Differentiation; Cell Line, Tumor; Cell Membrane; Cell Proliferation; Cell Survival; Cytoplasm; Diploidy; Humans; Leukemia; Membrane Potential, Mitochondrial; Microtubule-Associated Proteins; Mitochondria; Monocytes; Thiazoles; Time Factors; Vacuoles

To improve our understanding of ionizing radiation effects on immune cells, we investigated steps leading to radiation-induced cell death in MOLT-4, a thymus-derived human leukemia cell. After exposure of MOLT-4 cells to 4 Gy of X-rays, irradiated cells sequentially showed increase in intracellular reactive oxygen species (ROS), decrease in mitochondrial membrane potential, and eventually apoptotic cell death. In the presence of the caspase inhibitor z-VAD-fmk, irradiated cells exhibited necrotic characteristics such as mitochondrial swelling instead of apoptosis. ROS generation was not detected during this necrotic cell death process. These results indicate that radiation-induced apoptosis in MOLT-4 cells requires elevation of intracellular ROS as well as activation of a series of caspases, whereas the cryptic necrosis program--which is independent of intracellular ROS generation and caspase activation--is activated when the apoptosis pathway is blocked.

Topics: Amino Acid Chloromethyl Ketones; Caspase Inhibitors; Caspases; Cell Death; Cell Line, Tumor; Cell Shape; Cytochromes c; Humans; Leukemia; Membrane Potential, Mitochondrial; Mitochondria; Reactive Oxygen Species; X-Rays

Combined treatment with the medicinal mushroom Ganoderma lucidum and the herb Duchesnea chrysantha extracts (GDE) causes a synergistic induction of mitochondrial damage and apoptosis in HL-60 cells. GDE treatment is selectively toxic to HL-60 leukemia cells whereas no cytotoxic effect is observed in normal peripheral blood mononuclear cells. GDE-induced apoptosis is associated with Bcl-2 down-regulation, Bax translocation, mitochondrial cytochrome c release and caspase-3 activation, suggesting that apoptosis by this combination occurs through the mitochondria-dependent pathway. The present findings suggest that this combination merits further investigation as a potential therapeutic agent for the treatment of cancer.

Topics: Amino Acid Chloromethyl Ketones; Antineoplastic Agents; Apoptosis; Basidiomycota; bcl-2-Associated X Protein; Blotting, Western; Caspase 3; Caspase Inhibitors; Cell Survival; Cytochromes c; Dose-Response Relationship, Drug; Enzyme Activation; Flow Cytometry; Growth Inhibitors; HL-60 Cells; Humans; Leukemia; Mitochondria; Mitochondrial Membranes; Plant Extracts; Protein Transport; Rosaceae; Time Factors

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine having potent cytotoxic activity specifically to tumor cells. Agonistic antibodies against TRAIL receptors are currently being explored as anti-cancer therapeutics. Here, we report studies on JKTR-18, a monovalent human monoclonal antibody Fab selected against human recombinant TRAIL receptor 2 (DR5) by phage display technology. It induced cell death in Jurkat and HL60 leukemia cell lines without the need for secondary crosslinkers in vitro. It did not compete with soluble TRAIL (sTRAIL) for binding to DR5, and its combination with sTRAIL resulted in greater cell death than either agent alone. The cell death induced by JKTR-18 included a caspase-independent mechanism. This is the first report of a monovalent antibody fragment against TRAIL receptor that can induce tumor cell death in the absence of a crosslinker.

Topics: Amino Acid Chloromethyl Ketones; Amino Acid Sequence; Antibodies, Monoclonal; Apoptosis; Caspase 3; Caspase 7; Caspase Inhibitors; Cell Survival; Cysteine Proteinase Inhibitors; DNA Fragmentation; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; HL-60 Cells; Humans; Immunoglobulin Fab Fragments; Jurkat Cells; Leukemia; Molecular Sequence Data; Protein Binding; Receptors, TNF-Related Apoptosis-Inducing Ligand; Time Factors

The mechanism of apoptosis induced by treatment with As(2)O(3) alone or in combination with buthionine sulfoximine (BSO) was studied in NB4, U937, Namalwa, and Jurkat cells. As(2)O(3) at concentrations <2 micromol/L induced apoptosis in NB4 cells and Namalwa cells but not in U937 and Jurkat cells. As(2)O(3)-induced apoptosis in NB4 cells and Namalwa cells correlated with increase of H(2)O(2) and caspase activation without activation of c-Jun NH(2)-terminal kinase (JNK). BSO (10 micromol/L) depleted the reduced form of intracellular glutathione without inducing apoptosis but synergized with 1 micromol/L As(2)O(3) to induce apoptosis in all four cell lines. This synergy correlated with JNK activation. Treatment with As(2)O(3) plus BSO, but not with As(2)O(3) alone, increased the levels of death receptor (DR) 5 protein and caspase-8 cleavage. The JNK inhibitor SP600125 inhibited the increase in DR5 protein and attenuated apoptosis induced by treatment with As(2)O(3) plus BSO. These observations suggest that a DR-mediated pathway activated by JNK is involved in apoptosis induced by treatment with As(2)O(3) plus BSO.

Topics: Amino Acid Chloromethyl Ketones; Anthracenes; Apoptosis; Arsenic Trioxide; Arsenicals; Blotting, Western; Buthionine Sulfoximine; Caspase 3; Caspase Inhibitors; Cell Proliferation; Dose-Response Relationship, Drug; Drug Synergism; Enzyme Activation; Glutathione; Humans; Hydrogen Peroxide; JNK Mitogen-Activated Protein Kinases; Jurkat Cells; Leukemia; Lymphoma; Oxides; Receptors, TNF-Related Apoptosis-Inducing Ligand; Time Factors; U937 Cells

We have previously shown that actinonin causes inhibition of cellular proliferation in U937 leukemia cells. In this report we demonstrate that the inhibition of cell growth by actinonin occurs through the induction of apoptosis. Signs of apoptosis at high actinonin concentration included DNA fragmentation, exposure of phosphatidylserine and condensation of cell nuclei. Apoptosis caused by actinonin was inhibited by Z-VAD-FMK, a broad specificity inhibitor of caspases, implicating the caspase pathway of apoptosis. Further, apoptosis was associated with a large increase in intracellular caspase-3 and -7 activities.

Topics: Amino Acid Chloromethyl Ketones; Anti-Bacterial Agents; Apoptosis; Caspase 3; Caspase 7; Caspase Inhibitors; Caspases; Cysteine Proteinase Inhibitors; DNA Damage; Humans; Hydroxamic Acids; Leukemia; Lymphoma, Large B-Cell, Diffuse; Tumor Cells, Cultured

Paclitaxel, an antineoplastic drug, inhibits cell growth and cell cycle progression and induces apoptosis in human leukemia HL-60 cells. Caspase-3 plays a direct role in proteolytic cleavage of cellular proteins responsible for progression to apoptosis.. We examined the cell morphology and apoptosis in HL-60 cells after exposure to paclitaxel and measured caspase-3 activities with or without z-VAD-fmk (a broad-spectrum caspase inhibitor) pretreatment by flow cytometric analysis and Western blotting.. Together, our results were (1) paclitaxel mainly induced G2/M cell cycle arrest in HL-60 cells (p<0.001); (2) time (p<0.001)- and dose-dependent (p<0.001) apoptosis of HL-60 cells was induced by paclitaxel; (3) in HL-60 cells, z-VAD-fmk blocked paclitaxel-induced apoptosis (12 h: p<0.001; 24 h: p<0.01; 48 h: p<0.01; 72 h: p<0.001) and caspase-3 activation (12 h: p<0.05; 24 h: p<0.01; 48 h: p<0.01; 72 h: p<0.01).. These results suggest that paclitaxel can induce G2/M cell cycle transition and apoptosis via caspase-3 activity in HL-60 cells.

Topics: Amino Acid Chloromethyl Ketones; Antineoplastic Agents; Apoptosis; Blotting, Western; Caspase 3; Caspases; Cell Division; Dose-Response Relationship, Drug; Flow Cytometry; HL-60 Cells; Humans; Leukemia; Paclitaxel; Protease Inhibitors

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) might represent a future cytotoxic drug to treat cancer as it induces apoptosis in tumor cells without toxicity in animal trials. We recently described that in contrast to apoptosis, TRAIL mediates tumor cell survival and proliferation in certain tumor cells. Here we studied the effect of TRAIL on 18 cell lines and 53 primary leukemia cells and classified these tumor cells into four groups: TRAIL, anti-DR4 or anti-DR5 induced apoptosis in group A cells, whereas they had no effect on group 0 cells and mediated proliferation in group P cells. To our surprise, TRAIL induced simultaneous apoptosis and proliferation in group AP cells. More than 20% of all cells tested belonged to group P and showed TRAIL-mediated proliferation even in the presence of certain cytotoxic drugs but not inhibitors of nuclear factor-kappaB. Transfection with B-cell leukemia/lymphoma protein 2 transformed group A cells into group 0 cells, whereas transfection with Fas-associated polypeptide with death domain (FADD)-like interleukin-1-converting enzyme-inhibitory protein (FLIP) transformed them into group AP cells. Loss of caspase-8 or transfection of dominant-negative FADD transformed group A cells into group P cells. Taken together, our data suggest that proliferation is a frequent effect of TRAIL on tumor cells, which is related to receptor-proximal apoptosis defects at the level of the death-inducing signaling complex and should be prevented during antitumor therapy with TRAIL.

Topics: Adaptor Proteins, Signal Transducing; Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Apoptosis Regulatory Proteins; CASP8 and FADD-Like Apoptosis Regulating Protein; Caspase 8; Caspase Inhibitors; Caspases; Cell Line, Tumor; Cell Proliferation; Fas-Associated Death Domain Protein; HT29 Cells; Humans; Intracellular Signaling Peptides and Proteins; Leukemia; Membrane Glycoproteins; Mice; Neoplasms; TNF-Related Apoptosis-Inducing Ligand; Tumor Necrosis Factor-alpha

The role of p53 in apoptosis and the contrasting p53 status in tumors prompted us to investigate the bleomycin-induced apoptosis in p53-null human leukemia HL-60 cells (bleomycin at 160 microM for 7.5 h). Cells with apoptotic phenotype increased from 0.87% in controls to 9.40% in bleomycin-treated cells. Both the enzymes, caspase-3 and -8, were activated. Furthermore, the apoptotic phenotypes totally disappeared with zVAD-fmk, a caspase inhibitor. Besides, cytochrome c release from mitochondria happened simultaneously to apoptotic phenotypes, shrinkage of mitochondria but being independent of the mitochondrial permeability transition, since cyclosporine A and bongkrekic acid were inefficient on induced apoptosis. On the other hand, incubations with bleomycin (BLM) did not result in detectable changes in the expression of Bcl-2- and Bax-mRNA neither Bcl-2- or Bax-proteins. In conclusion, we suggest that BLM can produce apoptosis independently of p53 through three mechanisms: i) at the nuclear level by its endonuclease activities; ii) at the cell membrane, by activating caspases; and iii) at the mitochondria by releasing cytochrome c. These results indicate that BLM-induced apoptosis in HL-60 cells results from the activation of a mitochondria-dependent caspase cascade which includes also the activation of the initiator caspase-8.

Topics: Amino Acid Chloromethyl Ketones; Antimetabolites, Antineoplastic; Apoptosis; bcl-2-Associated X Protein; Bleomycin; Blotting, Western; Bongkrekic Acid; Caspase 3; Caspase 8; Caspases; Cell Line; Cyclosporine; Cytochromes c; DNA Fragmentation; Enzyme Activation; Genes, p53; HL-60 Cells; Humans; Leukemia; Microscopy, Electron; Mitochondria; Phenotype; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Reverse Transcriptase Polymerase Chain Reaction; RNA; RNA, Messenger; Time Factors; Tumor Suppressor Protein p53

Khat chewing is a widespread habit that has a deep-rooted sociocultural tradition in Africa and the Middle East. The biological effects of khat are inadequately investigated and controversial. For the first time, we show that an organic extract of khat induces a selective type of cell death having all morphological and biochemical features of apoptotic cell death. Khat extract was shown to contain the major alkaloid compounds cathinone and cathine. The compounds alone and in combination also induced apoptosis. Khat-induced apoptosis occurred synchronously in various human cell lines (HL-60, NB4, Jurkat) within 8 h of exposure. It was partially reversed after removal of khat and the effect was dependent on de novo protein synthesis, as demonstrated by cotreatment with cycloheximide. The cell death was blocked by the pan-caspase inhibitor Z-VAD-fmk, and also by submicromolar concentrations of Z-YVAD-fmk and Z-IETD-fmk, inhibitors of caspase-1 and -8, respectively. The 50% inhibition constant (IC(50)) for khat (200 microg ml(-1))-induced apoptosis by Z-VAD-fmk, Z-YVAD-fmk and Z-IETD-fmk was 8 x 10(-7) M as compared to 2 x 10(-8) M and 8 x 10(-8) M, respectively. Western blot analysis showed a specific cleavage of procaspase-3 in apoptotic cells, which was inhibited by Z-VAD-fmk. The cell death by khat was more sensitively induced in leukaemia cell lines than in human peripheral blood leukocytes. It is concluded that khat induces a rather swift and sensitive cell death by apoptosis through mechanisms involving activation of caspase-1, -3 and -8.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Caspase 1; Caspase 3; Caspase 8; Caspase Inhibitors; Caspases; Catha; Cell Line, Tumor; Cycloheximide; Cysteine Proteinase Inhibitors; Enzyme Activation; Enzyme Inhibitors; Humans; Leukemia; Oligopeptides; Plant Extracts; Propylamines; Protein Synthesis Inhibitors; Tumor Cells, Cultured

We previously found that dibutyl phthalate (DBP) had a pharmacological activity in eliminating tumor cells and could be used as a purging agent in autologous bone marrow transplantation. In this study, we show that DBP can induce apoptosis in MO7e and U937 leukemia cell lines. Treatment of these cells with DBP up-regulates cellular activity of caspase-3/CPP32 and causes apoptosis rapidly as determined by cell viability and dUTP nick end labeling assay. Activation of caspase-3/CPP32 and cleavage of poly(ADP-ribose) polymerase were determined in DBP-induced apoptosis of leukemia cells. However, DBP treatment did not induce the expression of fas. Two caspase inhibitors, z-VAD-fmk and N-acetyl-Asp-Glu-Val-Asp-aldehyde partly blocked the cell death of MO7e cells induced by DBP. These results suggest that fas-independent activation of caspase-3 protease plays important roles in the purging effect of DBP on leukemia cells.

Topics: Amino Acid Chloromethyl Ketones; Amino Acids; Apoptosis; Blotting, Western; Caspase 3; Caspases; Cell Line; Cell Survival; Dibutyl Phthalate; Dose-Response Relationship, Drug; Enzyme Activation; fas Receptor; Humans; In Situ Nick-End Labeling; Leukemia; Tumor Cells, Cultured; U937 Cells; Up-Regulation

We previously showed that cepharanthine (CEP), a biscoclaurine alkaloid, induces caspase-dependent and Fas-independent apoptosis in Jurkat and K562 human leukemia cells. In the present study, we investigated the effect of CEP on three groups of human mitogen-activated protein kinases (MAPKs) in relation to CEP-induced apoptosis. CEP, at the concentration required for and at the time of induction of apoptosis, activated MAPKs p38 in both Jurkat and K562 cells and activated extracellular signal-regulated kinases (ERKs) only in K562 cells. However, CEP treatment did not trigger c-Jun NH(2)-terminal kinases (JNKs) activation. CEP increased the expression and phosphorylation levels of c-Jun and ATF-2 transcription factors. zVAD-fmk, a general caspase inhibitor, did not inhibit CEP-triggered p38 activation in Jurkat and K562 cells or ERK activation in K562 cells. Unexpectedly, pretreatment with a specific p38 inhibitor, SB203580, promoted CEP-induced apoptosis and caspase activation in Jurkat and K562 cells, whereas pretreatment with an MEK-1 inhibitor PD98059 inhibited CEP-induced apoptosis and caspase activation in K562 cells. A selective tyrosine kinase inhibitor, herbimycin A, which completely inhibited CEP-triggered ERKs activation, clearly promoted CEP-induced c-Jun expression and phosphorylation. Our results suggest that each of the three groups of MAP family members is uniquely involved in the CEP-mediated signal cascades in two different leukemia cell lines for inducing/regulating caspase activation and DNA fragmentation.

Topics: Alkaloids; Amino Acid Chloromethyl Ketones; Antineoplastic Agents, Phytogenic; Apoptosis; Benzylisoquinolines; Caspase Inhibitors; Cysteine Proteinase Inhibitors; Enzyme Activation; Enzyme Inhibitors; Humans; Jurkat Cells; K562 Cells; Kinetics; Leukemia; MAP Kinase Signaling System; Mitogen-Activated Protein Kinases; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Protein-Tyrosine Kinases; Transcription Factors

We investigated the effects of valproic acid (VPA) on the growth and survival of human leukemia cell lines. VPA induced cell death in all of the nine cell lines tested in a dose dependent manner. VPA-treatment induced apoptotic changes in MV411 cells including DNA fragmentation, phosphatidylserine externalization, cytochrome c release from mitochondria, and activation of caspases-3, -8, and -9. A caspase inhibitor, zVAD-FMK, inhibited the DNA fragmentation induced by VPA but not cell death. These findings suggest that VPA exerts an anti-leukemic effect by both caspase-dependent and -independent apoptotic signaling pathways.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Caspases; Cytochrome c Group; Dose-Response Relationship, Drug; Enzyme Activation; Humans; Leukemia; Tumor Cells, Cultured; Valproic Acid

4-Hydroxynonenal (HNE), a reactive and cytotoxic end-product of lipid peroxidation, has been suggested to be a key mediator of oxidative stress-induced cell death and in various cell types has been shown to induce apoptosis. We have demonstrated that HNE, at micromolar concentrations, induces dose- and time-dependent apoptosis in a leukemic cell line (CEM-C7). Interestingly, much higher concentrations of HNE (> 15-fold) were required to induce apoptosis in leukocytes obtained from normal individuals. We also demonstrate that HNE causes a decrease in clonogenicity of CEM-C7 cells. Furthermore, our data characterize the caspase cascade involved in HNE-induced apoptosis in CEM-C7 cells. Using specific fluorogenic substrates and irreversible peptide inhibitors, we demonstrate that caspase 2, caspase 3, and caspase 8 are involved in HNE-induced apoptosis, and that caspase 2 is the first initiator caspase that activates the executioner caspase 3, either directly or via activation of caspase 8. Our studies also suggest the involvement of another executioner caspase, which appears to be similar to caspase 8 but not caspases 2 and 3, in its specificity. The demonstration of decreased clonogenicity by HNE in the leukemic cells, and their higher susceptibility to HNE-induced apoptosis as compared to the normal cells, suggests that such compounds may have potential for leukemia chemotherapy.

Topics: Aldehydes; Amino Acid Chloromethyl Ketones; Antineoplastic Agents; Apoptosis; Caspase Inhibitors; Caspases; Cell Survival; Cysteine Proteinase Inhibitors; DNA Fragmentation; Dose-Response Relationship, Drug; Enzyme Activation; Humans; Leukemia; Models, Biological; Oxidative Stress; Proto-Oncogene Proteins c-myc; Time Factors; Tumor Cells, Cultured

The recombinant immunotoxins anti-Tac(Fv)-PE38 (LMB-2), targeting the interleukin-2 receptor alpha subunit (IL-2Ralpha, Tac or CD25), and RFB4(dsFv)-PE38 (BL22), targeting CD22, are being evaluated in clinical trials as treatment for hematologic malignancies. The toxin moiety Pseudomonas exotoxin A (PE) of these recombinant molecules leads to the arrest of protein synthesis due to inactivation of elongation factor 2. Here, we provide evidence that cell lines derived from patients with hematologic malignancies react to immunotoxins not only with inhibition of protein synthesis but also with characteristic hallmarks of apoptosis such as caspase activation, cleavage of the "death substrate poly(ADP)-ribose polymerase and DNA laddering. Anti-Tac(Fv)-PE38 leads to a 10-fold increase in the cleavage of the fluorescent substrate DEVD-AFC, suggesting that a caspase-3-like enzyme is involved. This was verified by cleavage of caspase-3 (CPP32). MT1 cells exhibited DNA laddering after treatment with immunotoxin, which was reversed by pre-treatment with the protease inhibitor zVAD-fmk. This caspase inhibitor led to an at least 5-fold improvement in cell viability without altering inhibition of protein synthesis. Interestingly, HUT-102 cells did not undergo programmed cell death after exposure to immunotoxins that kill these cells. We conclude that immunotoxins may be valuable in the treatment of cancers that are resistant toward apoptosis because their targeted killing is often facilitated by, but not completely dependent on, programmed cell death. Int. J. Cancer 87:86-94, 2000. Published 2000 Wiley-Liss, Inc.

Topics: Amino Acid Chloromethyl Ketones; Antibodies; Antigens, CD; Antigens, Differentiation, B-Lymphocyte; Apoptosis; Burkitt Lymphoma; Caspase 3; Caspases; Cell Adhesion Molecules; Cell Survival; Coumarins; DNA Fragmentation; Dose-Response Relationship, Drug; Hematologic Neoplasms; Immunoblotting; Immunotoxins; Lectins; Leucine; Leukemia; Lymphoma, T-Cell; Oligopeptides; Protease Inhibitors; Recombinant Proteins; Sialic Acid Binding Ig-like Lectin 2; Tetrazolium Salts; Tumor Cells, Cultured

The caspase-mediated cleavage of a limited number of cellular proteins is a common feature of apoptotic cell death. This cleavage usually inhibits the function of the target protein or generates peptides that actively contribute to the death process. In the present study, we demonstrate that the cyclin-dependent kinase inhibitor p27Kip1 is cleaved by caspases in human leukemic cells exposed to apoptotic stimuli. We have shown recently that p27Kip1 overexpression delayed leukemic cell death in response to cytotoxic drugs. In transient transfection experiments, the p23 and the p15 N-terminal peptides generated by p27Kip1 proteolysis demonstrate an anti-apoptotic effect similar to that induced by the wild-type protein, whereas cleavage-resistant mutants have lost their protective effect. Moreover, stable transfection of a cleavage-resistant mutant of p27Kip1 sensitizes leukemic cells to drug-induced cell death. Altogether, these results indicate that proteolysis of p27Kip1 triggered by caspases mediates the anti-apoptotic activity of the protein.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Base Sequence; Calpain; Caspase 3; Caspase 6; Caspase 8; Caspase 9; Caspase Inhibitors; Caspases; CDC2-CDC28 Kinases; Cell Cycle Proteins; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinase Inhibitor p27; Cyclin-Dependent Kinases; Cysteine Proteinase Inhibitors; Etoposide; Humans; Leukemia; Leupeptins; Microtubule-Associated Proteins; Molecular Sequence Data; Mutation; Nucleic Acid Synthesis Inhibitors; Oligopeptides; Protein Serine-Threonine Kinases; Thimerosal; Tumor Cells, Cultured; Tumor Suppressor Protein p53; Tumor Suppressor Proteins