all-trans-Retinoic acid-induced expression and regulation of retinoic acid 4-hydroxylase (CYP26) in human promyelocytic leukemia

all-trans-Retinoic acid (ATRA) induces complete remission in majority of patients with acute promyelocytic leukemia (APL). However, accelerated metabolism of ATRA that is induced by chronic daily administration of oral ATRA has been implicated as one of the mechanisms leading to a reduced sensitivity or resistance to ATRA therapy. We investigated the expression and regulation of CYP26, a novel p450 enzyme, which is highly specific for ATRA, in promyelocytic leukemia cells (NB4 and HL-60). We found that treatment of NB4 cells with a pharmacological concentration of ATRA (1 microM) induced rapid and dose-dependent expression of CYP26 mRNA. The CYP26 expression returned to pretreatment levels in both cells after ATRA was removed from the media. Retinoic acid receptor-alpha (RARalpha) specific antagonist (CD2503) totally abolished the ATRA-induced expression of CYP26 mRNA in HL-60 and NB4 cells. Furthermore, HL-60R, a HL-60 subclone expressing nonfunctional RAR because of a point mutation in the ligand-binding domain of RARalpha, failed to show CYP26 mRNA expression in response to ATRA. ATRA-induced expression of CYP26 was restored in HL-60R cells retrovirally transduced with RARalpha, but not in those cells transduced with the other retinoid receptors. In conclusion, ATRA induces expression of CYP26 in myeloid and promyelocytic leukemia cells and this expression is modulated by RARalpha. The induction of CYP26 expression by ATRA treatment might be related to a substrate-driven feedback mechanism to regulate intracellular concentrations of ATRA and its over expression in some clones may be partly responsible for reduced sensitivity or resistance to ATRA therapy.

Induction of apoptosis by momordin I in promyelocytic leukemia (HL-60) cells

We studied the effect of momordin I, a compound purified from a plant, Ampelopsis japonica, on cell proliferation and induction of apoptosis in human promyelocytic leukemia (HL-60) cells. Momordin I was cytotoxic to HL-60 cells with an IC50 of 19.0 microg/ml. The antiproliferative effects of momordin I appear to be attributable to its induction of apoptotic cell death, as momordin I induced nuclear morphology changes and internucleosomal DNA fragmentation and it increased the proportion of hypodiploid cells. Momordin I treatment also gradually decreased the expression of.the anti-apoptotic protein Bcl-2, but increased the expression of the pro-apoptotic protein Bax. In addition, momordin I treatment increased the activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase. In this study we showed that momordin I induced apoptosis of HL-60 cells by reduction of the Bcl-2:Bax ratio and by activation of caspase-3. These results provide important information towards understanding the mechanism by which momordin I induces apoptosis.

The expression of vimentin in HL-60 cells induced with etoposide using immunofluorescence and immunogold methods

HL-60 leukemic cells were treated with 6 different doses of etoposide for 72 hours. Changes in the distribution of vimentin were found to be dependent on the concentration of etoposide. As compared with control cells there were distinct changes in cells incubated with 100 and 200 microM/L of the drug. The size of cells treated with 100 microM/L and especially with 200 microM/L increased, but the number of cells decreased. In control cells and those treated with 0.02, 0.2 and 2 microM/L etoposide, vimentin was seen rather as a ring often with the increased concentration near one pole of the cells. Cells at 20 microM/L etoposide showed the same staining pattern but more brighter cells were found. The addition of 100 microM/L and 200 microM/L etoposide to cells resulted in diffusely distributed fluorescence staining, which often appeared as a quite dense network around the nucleus. Immunogold labelling was observed in cells treated with all doses of etoposide and control cells. Labelling was localized in the nucleus but also in the cytoplasm but rather in the area of the nucleus.

A 28-kDa glycoprotein functions as a platelet ligand for P-selectin (CD62P)

P-selectin (CD62P) is expressed on activated platelets and on stimulated endothelial cells. It interacts with P-selectin glycoprotein ligand-1 (PSGL-1; CD162) for adhesion of activated platelets on leukocytes and for rolling of leukocytes on stimulated endothelial cells. Recently, resting and activated platelets have been shown to roll on endothelial P-selectin, indicating that platelets express (a) ligand(s) for P-selectin. Here we show that P-selectin specifically precipitated one 28-kDa glycoprotein from the whole cell lysates and the membrane lysates of human platelets in a Ca2+-dependent manner. Further, the purified 28-kDa molecule could inhibit the binding of P-selectin to human resting and activated platelets. In contrast, KPLI (a leukocyte adhesion blocking MoAb to PSGL-1) did not neutralize the binding of P-selectin to human platelets, even though it abolished the binding of P-selectin to human promyeloid HL-60 cells. Our results thus indicate that the 28-kDa glycoprotein may function as an important platelet ligand for P-selectin.

Sulfhydryl binding and topoisomerase inhibition by PCB metabolites

Polychlorinated biphenyls (PCBs) are highly persistent contaminants in our environment. Their persistence is due to a general resistance to metabolic attack. Lower halogenated PCBs, however, are metabolized to mono- and dihydroxy compounds, and the latter may be further oxidized to quinones with the formation of reactive oxygen species (ROS). We have shown that PCB metabolism generates ROS in vitro and in cells in culture and this leads to oxidative DNA damage, like DNA strand breaks and 8-oxo-dG formation. In the present study, we have evaluated the reactivity of PCB metabolites with other nucleophiles, like glutathione (GSH), by assessing (1) quantitative GSH binding in vitro, (2) GSH and thiol (sulfhydryl) depletion in HL-60 cells, (3) the associated cytotoxicity, and (4) the inhibition of topoisomerase II activity in vitro. PCB quinones were found to bind GSH in vitro at a ratio of 1:1.5 and to deplete GSH in HL-60 cells as measured by both spectrophotometric and spectrofluorometric methods. By flow cytometry analysis, we confirmed that there was intracellular GSH depletion in HL-60 cells by PCB quinones and this is associated with cytotoxicity. On the other hand, the PCB hydroquinone metabolites did not bind GSH or other thiols within 1 h of exposure. However, by spectral analyses we found that the PCB hydroquinones could be oxidized enzymatically to the quinones, which could then bind GSH. The resulting hydroquinone-glutathione addition product(s) could undergo a second and third cycle of oxidation and GSH addition with the formation of di- and tri-GSH-PCB adducts. The effect of the PCB metabolites was also tested on a sulfhydryl-containing enzyme, topoisomerase II. PCB quinones inhibited topoisomerase II activity while the PCB hydroquinone metabolites did not. Hence, the oxidation of PCB hydroquinone metabolites to quinones in cells followed by the binding of quinones to GSH and to protein sulfhydryl groups and the resulting oxidative stress may be important aspects of the toxicity of these compounds.

Design and synthesis of a novel and potent series of inhibitors of cytosolic phospholipase A(2) based on a 1,3-disubstituted propan-2-one skeleton

Using knowledge of the substrate specificity of cPLA(2) (phospholipases A(2)), a novel series of inhibitors of this enzyme were designed based upon a three point model of inhibitor binding to the enzyme active site comprising a lipophilic anchor, an electrophilic serine "trap", and an acidic binding moiety. The resulting 1,3-diheteroatom-substituted propan-2-ones were evaluated as inhibitors of cPLA(2) in both aggregated bilayer and soluble substrate assays. Systematic variation of the lipophilic, electrophilic, and acidic groups revealed a well-defined structure-activity relationship against the enzyme. Optimization of each group led to compound 22 (AR-C70484XX), which contains a decyloxy lipophilic side chain, a 1,3-diaryloxypropan-2-one moiety as a unique serine trap, and a benzoic acid as the acidic binding group. AR-C70484XX was found to be among the most potent in vitro inhibitors of cPLA(2) described to date being more than 20-fold more active against the isolated enzyme (IC(50) = 0.03 microM) than the standard cPLA(2) inhibitor, arachidonyl trifluoromethyl ketone (AACOCF(3)), and also greater than 10-fold more active than AACOCF(3) against the cellular production of arachidonic acid by HL60 cells (IC(50) = 2.8 microM).

Proliferating or differentiating stimuli act on different lipid-dependent signaling pathways in nuclei of human leukemia cells

Previous results have shown that the human promyelocytic leukemia HL-60 cell line responds to either proliferating or differentiating stimuli. When these cells are induced to proliferate, protein kinase C (PKC)-beta II migrates toward the nucleus, whereas when they are exposed to differentiating agents, there is a nuclear translocation of the alpha isoform of PKC. As a step toward the elucidation of the early intranuclear events that regulate the proliferation or the differentiation process, we show that in the HL-60 cells, a proliferating stimulus (i.e., insulin-like growth factor-I [IGF-I]) increased nuclear diacylglycerol (DAG) production derived from phosphatidylinositol (4,5) bisphosphate, as indicated by the inhibition exerted by 1-O-octadeyl-2-O-methyl-sn-glycero-3-phosphocholine and U-73122 (1-[6((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione), which are pharmacological inhibitors of phosphoinositide-specific phospholipase C. In contrast, when HL-60 cells were induced to differentiate along the granulocytic lineage by dimethyl sulfoxide, we observed a rise in the nuclear DAG mass, which was sensitive to either neomycin or propranolol, two compounds with inhibitory effect on phospholipase D (PLD)-mediated DAG generation. In nuclei of dimethyl sulfoxide-treated HL-60 cells, we observed a rise in the amount of a 90-kDa PLD, distinct from PLD1 or PLD2. When a phosphatidylinositol (4,5) bisphosphate-derived DAG pool was generated in the nucleus, a selective translocation of PKC-beta II occurred. On the other hand, nuclear DAG derived through PLD, recruited PKC-alpha to the nucleus. Both of these PKC isoforms were phosphorylated on serine residues. These results provide support for the proposal that in the HL-60 cell nucleus there are two independently regulated sources of DAG, both of which are capable of acting as the driving force that attracts to this organelle distinct, DAG-dependent PKC isozymes. Our results assume a particular significance in light of the proposed use of pharmacological inhibitors of PKC-dependent biochemical pathways for the therapy of cancer disease.

Kinetics of HL-60 cell entry to apoptosis during treatment with TNF-alpha or camptothecin assayed by the stathmo-apoptosis method

BACKGROUND

Duration of apoptosis, from onset to final disintegration of the cell, is often short and variable. The apoptotic index (AI), as a snapshot of a transient event of variable length, does not truly represent incidence of apoptosis in the studied cell population. We recently proposed to estimate the cumulative apoptotic index (CAI) by inducing stathmo-apoptosis. A fluorescent inhibitor of caspases (FLICA) FAM-VAD-FMK is used to arrest the process of apoptosis and thereby prevent cell disintegration. Simultaneously, the arrested/apoptotic cells become FLICA-labeled. In the present study, this approach was applied to measure kinetics of HL-60 cell entrance into apoptosis induced via cell surface death receptor or a mitochondria-initiated pathway. Materials and Methods Cultures of HL-60 cells were treated with either TNF-alpha or camptothecin (CPT) in the absence or constant presence of 10-50 microM FLICA. The CAI was measured at different time points for up to 48 h by flow cytometry. Bivariate analysis of DNA content and cell labeling with FLICA was used to correlate apoptosis with the cell-cycle position.

RESULTS

Selective loss of apoptotic cells seen in HL-60 cell cultures exposed to either TNF-alpha or CPT alone was prevented in cultures containing FLICA. Addition of FLICA alone had no effect on cell viability. The percentage of FLICA-labeled cells was plotted as a function of time after addition of TNF-alpha or CPT. The rate of cell entry to apoptosis was subsequently estimated from the slopes of the stathmo-apoptotic plot. The slopes revealed that the TNF-alpha or CPT-treated cells asynchronously underwent apoptosis with a stochastic-like kinetics and at two different rates. About 50% of cells in the TNF-alpha-treated cultures underwent apoptosis during the initial 6 h at a rate of approximately 8% of cells per hour; the remaining cells were undergoing apoptosis at a rate of approximately 2.5% of cells per hour for up to 24 h. Also, about 50% of the CPT-treated cells, predominantly those in S phase of the cell cycle, underwent apoptosis within the initial 8 h of CPT exposure, at a rate of approximately 7% of cells per hour. Remaining cells were undergoing apoptosis at a rate of approximately 1% of cells per hour during up to 48 h exposure to CPT. Spontaneous apoptosis in the untreated cultures occurred at a rate of 0.2% of cells per hour.

CONCLUSIONS

This approach provides a means for measuring the kinetics of cell entrance to apoptosis (caspase activation) in large populations of cells in relation to the cell-cycle position.

Activation of caspase-3, proteolytic cleavage of DFF and no oligonucleosomal DNA fragmentation in apoptotic Molt-4 cells

A variety of endonucleases has been implicated in apoptotic DNA fragmentation. DNA fragmentation factor (DFF) is one of the endonucleases responsible for DNA fragmentation. Since an oligonucleosomal DNA ladder is not induced in apoptotic Molt-4 cells, we investigated whether or not the absence of ladder formation is related to an inability of DFF endonuclease in the cells. Semiquantitative RT-PCR analysis showed that the mRNA level of DFF-40 and DFF-45 in Molt-4 cells was approximately the same, compared with in other cells, which exhibit different levels of the fragmentation in apoptosis. When Molt-4 cells were induced to undergo apoptosis by neocarzinostatin (NCS) treatment, both caspase-3 activation and DFF-45 cleavage were observed. Furthermore, DFF immunoprecipitated from Molt-4 cells exhibited DNA degradation activity. These results suggest that functional expression of DFF is not sufficient for the induction of DNA fragmentation in Molt-4 cells.

In vitro studies of gadolinium-DTPA conjugated with monoclonal antibodies as cancer-specific magnetic resonance imaging contrast agents

The monoclonal antibodies, 9.2.27 against human melanoma cell lines and WM53 against leukemia cell lines, were conjugated with cyclic anhydride gadolinium-diethylenetriaminepenta-acetic acid (Gd-cDTPAa) and used as tumor-specific contrast agents in magnetic resonance imaging (MRI). The data indicate that Gd-DTPA-9.2.27 in solution decreased the T1 relaxation of water protons at 7.0 Tesla (300 MHz) in direct proportion to the gadolinium concentration, and this effect was greater than in Gd-DTPA solutions. These conjugates show high specificity for melanoma and leukemia cell lines. T1 relaxation time at 7.0 Tesla, measured for the melanoma cell line (MM-138) and leukemia cell line (HL-60) after incubation at 37 degrees C for 4 hr, were significantly decreased (approximately 25%) relative to controls. The gadolinium concentration in cells and washing solutions was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). A linear relationship was observed between T1 relaxation rates and gadolinium concentrations obtained by ICP-AES. The ICP-AES results showed no gadolinium uptake in the non-targeted HT-29 colorectal cancer cells.

Cell adhesion regulates the plasminogen activator inhibitor-1 gene expression in anchorage-dependent cells

Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor of both tissue- and urokinase-type plasminogen activators (t-PA, u-PA). PAI-1 also regulates the attachment of cells to the adhesive glycoprotein vitronectin (VN). PAI-1 gene expression has been observed in various cell types, and many regulatory factors have been identified to play a role in PAI-1 gene transcription. The complete picture of how the PAI-1 gene is expressed when cells adhere to a culture plate has not been fully elucidated. We found that in anchorage-dependent cells, PAI-1 gene was up-regulated when cells were beginning to attach to a culture dish and was down-regulated when cells had attached completely. The PAI-1 gene expression was induced only in adhered cells but not in non-adhered cells. The regulation of PAI-1 protein was also found in both culture medium and cell lysate when cells were attached to a culture dish. Our experiment indicates that vitronectin and fibronectin, as components of ECM, may be the factors involved in the regulation of PAI-1 gene expression. PAI-1, as an inhibitor of the interaction between vitronectin and integrin alphavbeta3, may also be a regulator of its own expression.

Regulation of cell cycle progression and apoptosis by beta-carotene in undifferentiated and differentiated HL-60 leukemia cells: possible involvement of a redox mechanism

Although epidemiologic studies have demonstrated that a high intake of vegetables containing beta-carotene lowers the risk of cancer, recent intervention studies have revealed that beta-carotene supplementation to smokers resulted in a high incidence of lung cancer. We hypothesized that beta-carotene may act as a pro- or anticancerogenic agent by modulating pathways involved in cell growth and that such a modulation may involve a redox mechanism. To test this hypothesis, cell proliferation, apoptosis and redox status were evaluated in undifferentiated and dimethylsulfoxide-differentiated HL-60 cells exposed to beta-carotene. The carotenoid modified cell cycle progression and induced apoptosis in a dose-dependent manner. These effects were more remarkable in undifferentiated cells than in differentiated cells. In accord with these findings, in undifferentiated cells, beta-carotene was more effective in decreasing cyclin A and Bcl-2 expression and in increasing p21 and p27 expression. Neither Bcl-xL nor Bax expression were significantly modified by the carotenoid. From a mechanistic point of view, the delay in cell growth by beta-carotene was highly coincident with the increased intracellular reactive oxygen species production and oxidized glutathione content induced by the carotenoid. Moreover, alpha-tocopherol minimized the effects of beta-carotene on cell growth. These data provide evidence that beta-carotene modulates molecular pathways involved in cell cycle progression and apoptosis and support the hypothesis that a redox mechanism may be implicated. They also suggest that differentiated cells may be less susceptible to the carotenoid than highly neoplastic undifferentiated cells.

Induction of apoptosis by 3,4'-dimethoxy-5-hydroxystilbene in human promyeloid leukemic HL-60 cells

3, 4'-Dimethoxy-5-hydroxystilbene (DMHS) is a hydroxystilbene compound obtained by methylation and acid hydrolysis of piceid (resveratrol-3-O-glucoside) from Polygonum cuspidatum. Herein, we report that DMHS induces programmed cell death or apoptosis in human promyelocytic leukemic HL-60 cells. We found that treatment of HL-60 cells with DMHS suppressed the cell growth in a concentration-dependent manner with an IC50 value of 25 microM. DMHS increased internucleosomal DNA fragmentation in a time-dependent manner. The cell death by DMHS was partially prevented by the caspase inhibitor, zVAD-fmk. DMHS caused activation of caspases such as caspase-3, -8, and -9. Immunoblot experiments revealed that DMHS-induced apoptosis was associated with the induction of Bax expression. The release of cytochrome c from mitochondria into the cytosol was increased in response to DMHS. Taken together, our present results indicated that DMHS leads to apoptotic cell death in HL-60 cells through increased Bax expression and release of cytochrome c into cytosol and may be considered as a good candidate for a cancer chemopreventive agent in humans.

Enzymatic regional methylation assay: a novel method to quantify regional CpG methylation density

We have developed a novel quantitative method for rapidly assessing the CpG methylation density of a DNA region in mammalian cells. After bisulfite modification of genomic DNA, the region of interest is PCR amplified with primers containing two dam sites (GATC). The purified PCR products are then incubated with 14C-labeled S-adenosyl-L-methionine (SAM) and dam methyltransferase as an internal control to standardize DNA quantity. This is followed by an incubation with 3H-labeled SAM and SssI methyltransferase for methylation quantification. By use of standard mixtures of cell line DNA with a defined methylation status in every assay, the ratio (3H/14C signal) of each sample can be converted into percentage values to assess the methylation density of the amplified sequence. This methylation-sensitive technique, termed ERMA (Enzymatic Regional Methylation Assay) provides several advantages over existing methods used for methylation analysis as it determines an exact measurement of the methylation density of the region studied. We demonstrate a use of this technique in determining the methylation density of the promoter region of the tumor suppressor gene p15INK4B and changes that occur after treatment with demethylating agents.

Ajoene, an experimental anti-leukemic drug: mechanism of cell death

The organosulfur compound ajoene, a constitutent of garlic, has been shown to induce apoptosis in a leukemic cell line as well as in blood cells of a leukemic patient. The mechanisms of action of ajoene, however, are unknown. The present study aims to characterize the molecular events leading to ajoene-triggered apoptosis. We show here that ajoene (20 microM) leads to a time-dependent activation of caspase-3-like activity as well as to the proteolytic processing of procaspase-3 and -8. Activation of caspases was necessary for ajoene-induced apoptosis since the broad-range caspase inhibitor zVAD-fmk completely abrogated ajoene-mediated DNA fragmentation. Although the initiator caspase-8 was activated, the CD95 death receptor was not involved in death signaling since the HL-60 clone used was shown to express a functionally inactive CD95 receptor. Furthermore, ajoene induced the release of cytochrome c, which was not inhibited by zVAD-fmk indicating that cytochrome c release precedes caspase activation. Ajoene also led to a dissipation of the mitochondrial transmembrane potential. Overexpression of Bcl-x(L) clearly diminished ajoene-induced caspase activation as well as apoptosis. These results indicate that apoptosis in leukemia cells triggered by ajoene is based on the activation of a mitochondria-dependent caspase cascade which includes also the activation of the initiator caspase-8.

Induction of cell death by pro-oxidant action of Moxa smoke

Moxa smoke induced internucleosomal DNA fragmentation in human promyelocytic leukemic HL-60 cells, but not in other cell lines. The cytotoxic activity of Moxa smoke was significantly reduced by a popular antioxidant, N-acetyl-L-cysteine (NAC). Moxa smoke showed oxidation potential (measured by NO monitor) and produced carbon radical (measured by ESR spectroscopy). The addition of NAC significantly reduced both the oxidation potential and carbon radical intensity of Moxa smoke. Activity staining of polyacryamide gel electrophoresis of MnSOD revealed the possible modification of the conformation and/or activity of this enzyme at an early stage of HL-60 cell death. These data suggest that Moxa smoke induces cytotoxicity by its pro-oxidant action.

Intracellular uptake and trafficking of Pluronic micelles in drug-sensitive and MDR cells: effect on the intracellular drug localization

The intracellular uptake and localization of a fluorescently labeled Pluronic P-105 in HL-60 leukemia cells and in A2780 drug-sensitive and A2780/ADR MDR ovarian carcinoma cells were characterized by flow cytometry and fluorescence microscopy. Pluronic P-105 molecules were labeled with a pH-sensitive fluorescent label, 5-(and 6-)carboxy-2'7'-dichlorofluorescein. The fluorescence intensity of labeled Pluronic was about twofold higher at pH 7.4 than at pH 5.5. At Pluronic concentrations exceeding the critical micelle concentration (cmc), flow cytometry histograms manifested bimodal distribution of cell fluorescence for all types of cells. Cell population characterized by higher fluorescence intensity presumably resulted from Pluronic transfer from the acidic environment of cytoplasmic vesicles (endosomes or lysosomes) into the neutral environment of the cytoplasm and cell nuclei, which suggested the permeabilization of the membranes of acidic vesicle by Pluronic molecules. For the MDR cells, the bimodal distribution of cell fluorescence was already observed at very low Pluronic concentrations in the incubation medium (i.e., below the cmc). The data suggest that the membranes of acidic vesicles of MDR cells are more susceptible to the action of polymeric surfactants than those of drug-sensitive cells. Permeabilization of acidic vesicles had a dramatic effect on the intracellular trafficking of drugs: when delivered in PBS, the anthracyclin drug ruboxyl (Rb) sequestered in cytoplasmic vesicles and was excluded from cell nuclei; however, when delivered in Pluronic micelles, drug accumulated in cell nuclei. Drug uptake from/with Pluronic micelles was substantially enhanced by ultrasound. These findings suggest that the nuclear accumulation of drugs internalized via fluid-phase endocytosis can be enhanced by the application of Pluronic micelles and can be further augmented by ultrasonic irradiation.

A role for the subcellular localization of Bax in differentiation-induced resistance to apoptosis in HL-60 cells

The promyelocytic leukemia cell line HL-60 was induced to undergo granulocytic differentiation by treatment with dimethyl sulphoxide (DMSO). The differentiated HL-60 cells were resistant to apoptosis induction by etoposide treatment. The resistant cells did not show evidence of cytochrome c release from the mitochondria or cleavage of caspase-3. Because of the important role of Bax in the regulation of apoptosis in HL-60 cells and neutrophils, we studied its levels and sub-cellular localization in susceptible and resistant HL-60 cells. Although, there was no significant change in Bax levels as a result of DMSO treatment, resistance to apoptosis was associated with lack of Bax translocation from the cytosol to the mitochondria-containing fraction. These results emphasize the role of Bax in apoptosis and point out the importance of studying not only its level, but also its sub-cellular localization.

Transforming growth factor-beta1 transcriptionally activates CD34 and prevents induced differentiation of TF-1 cells in the absence of any cell-cycle effects

A number of cytokines modulate self-renewal and differentiation of hematopoietic elements. Among these is transforming growth factor beta1 (TGF-beta1), which regulates cell cycle and differentiation of hematopoietic cells, but has pleiotropic activities depending on the state of responsiveness of the target cells. It has been previously shown by us and other authors that TGF-beta1 maintains human CD34(+) hematopoietic progenitors in an undifferentiated state, independently of any cell cycle effects, and that depletion of TGF-beta1 triggers differentiation accompanied by a decrease in CD34 antigen expression. In the present work, we show that exogenous TGF-beta1 upregulates the human CD34 antigen in the CD34(+) cell lines TF-1 and KG-1a, but not in the more differentiated CD34(-) cell lines HL-60 and K-562. We further studied this effect in the pluripotent erythroleukemia cell line TF-1. Here, TGF-beta1 did not effect cell growth, but induced transcriptional activation of full-length CD34 and prevented differentiation induced by differentiating agents. This effect was associated with nuclear translocation of Smad-2, activation of TAK-1, and with a dramatic decrease in p38 phosphorylation. In other systems TGF-beta1 has been shown to activate a TGF-beta-activated kinase 1 (TAK1), which in turn, activates p38. The specific inhibitor of p38 phosphorylation, SB202190, also increased CD34 RNA expression, indicating the existence of a link between p-38 inhibition by TGF-beta1 and CD34 overexpression. Our data demonstrate that TGF-beta1 transcriptionally activates CD34 and prevents differentiation of TF-1 cells by acting independently through the Smad, TAK1 and p38 pathways, and thus provide important clues for the understanding of hematopoietic development and a potential tool to modify response of hematopoietic cells to mitogens or differentiating agents.

c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) is required for mitoxantrone- and anisomycin-induced apoptosis in HL-60 cells

Programmed cell death, or apoptosis, has emerged as a common mechanism by which cells respond to chemotherapeutic drugs. However, the signaling mechanisms that mediate drug-induced apoptosis are still widely unknown. Mitogen-activated protein kinase (MAPK) signaling cascades trigger stimulus-specific responses in cells with ERK being associated with proliferation and differentiation, and JNK/SAPK and p38 mediating stress and apoptotic responses. Here, we found that mitoxantrone and anisomycin stimulated a dose- and time-dependent induction of JNK/SAPK activity, and to a lesser extent p38 activity, that preceded the appearance of apoptosis as measured by internucleosomal DNA fragmentation. These compounds did not induce ERK activity. We further demonstrated that p38 activity was not involved in the induction of apoptosis since the use of the p38 inhibitor, SB203580, did not prevent drug-induced apoptotic DNA fragmentation. Additionally, direct inhibition of JNK/SAPK signaling through the use of dominant-negative MKK4/SEK1 (SEK-AL) inhibited mitoxantrone- and anisomycin-induced apoptosis. These results suggest that mitoxantrone- and anisomycin-induced apoptosis is dependent on JNK/SAPK, but not p38, activity.

Action of (E)-2'-deoxy-2'-(fluoromethylene)cytidine on DNA metabolism: incorporation, excision, and cellular response

(E)-2'-deoxy-2'-(fluoromethylene)cytidine (FMdC) is a new analog of deoxycytidine with promising anticancer activity. We investigated the action of FMdC on DNA metabolism by evaluating its incorporation into DNA, its excision from DNA in vitro, and the role of the incorporation of FMdC into DNA in causing cytotoxicity. In vitro DNA primer extension demonstrated that FMdC nucleotides were incorporated with relatively high substrate efficiency into the C sites of the elongating DNA strand. Once incorporated, FMdC became a poor substrate for further chain elongation by DNA polymerases, resulting in a termination of DNA synthesis at the sites of incorporation. Furthermore, the 3' --> 5' exonuclease activity of DNA polymerase epsilon or wild-type p53 protein was ineffective in removing the incorporated FMdC from DNA in vitro. FMdC also showed potent cytotoxic activity against human leukemia and solid tumor cells. Incubation with a low concentration of FMdC (10 nM) induced cell cycle arrest at S or G1 phases, but the cells eventually died as the time of incubation increased. Compared with HL-60 cells, human myeloid ML-1 cells with wild-type p53 were more sensitive to FMdC, but the S or G1 phase arrest did not seem to depend on the presence or absence of p53. Inhibiting the incorporation of FMdC into cellular DNA by aphidicolin suppressed the cytotoxic effect of the compound. We conclude that the incorporated FMdC nucleotide profoundly disrupts DNA synthesis and resists excision by exonucleases, and that incorporation of this analog into DNA is a key molecular event responsible for the drug's cytotoxicity.

Cell death-inducing activity of opiates in human oral tumor cell lines

In screening cytotoxic agents in morphine alkaloids [TE1-10], codeinone [TE8] was cytotoxic against two human oral tumor cells lines (HSC-2 and HSG). The cytotoxic activity of codeinone (CC50=1.0-1.2 microg/mL) against HSC-2 or HSG cells was higher than that of doxorubicin (CC50=1.9-2.0 microg/mL). Human oral gingival fibroblasts (HGF) were relatively resistant to codeinone, as judged by higher SI ratio (3.7) suggesting the tumor-selective cytotoxicity of codeinone. The cytotoxic activity of morphine (CC50=221 microg/mL) against HSC-2 was slightly lower than that of codeine (CC50=186 microg/mL), thebaine (CC50=125 microg/mL), etorphine (CC50=94 microg/mL) or dihydroetorphine (CC50=60 microg/mL). A study of structurally-related compounds suggested that the alpha,beta-unsaturated ketone group of codeinone was responsible for its antitumor cytotoxicity. The cytotoxic activity of codeinone was significantly reduced by N-acetylcysteine, but not affected by FeCl3, CuCl2, CoCl2, sodium ascorbate or catalase. Neither codeinone nor morphine inhibited P-glycoprotein-mediated rhodamine-123 efflux in multidrug resistant mouse T lymphoma L5178 transfected with human MDR 1 gene. These data suggest that codeinone induces cytotoxicity in oral tumor cell lines, possibly by a Michael-like addition of a protein SH or of an amino group to the bouble bond of codeinone.

Baicalin is a major component of PC-SPES which inhibits the proliferation of human cancer cells via apoptosis and cell cycle arrest

BACKGROUND

PC-SPES is an eight-herb mixture that was shown to have activity against prostate cancer. Recently, we isolated a major component (6% of the total ethanolic extract) known as baicalin from PC-SPES by high performance liquid chromatography (HPLC).

METHODS

Baicalin was evaluated for its ability to inhibit clonal growth, and to induce cell cycle arrest of various cancer types (PC-3, DU145, LNCaP prostate cancer cell lines, MCF-7 breast cancer cell line, HL-60 myeloblastic leukemia cell line, and NB4 promyelocytic leukemia cell line). The ability of baicalin to induce apoptosis of cancer cells was examined by both staining with Annexin V and detection of cleavage of Poly (ADP-ribose) polymerase (PARP)(3). Western blot analysis examined the effect of baicalin on levels of p21(waf1) and p27(kip1) in those cells. Futhermore, induction of differentiation in HL-60 cells was measured by expression of CD11b.

RESULTS

Baicalin inhibited the clonal proliferation of LNCaP and PC3 prostate cancer cell lines, and the HL-60 and NB4 myeloblastic/promyelocytic leukemia cell lines with a 50% inhibition (ED(50)) that ranged between 6.4 x 10(-6) to 12 x 10(-6) mol/L. Cell cycle analysis showed that baicalin (2 x 10(-5) mol/L, 4 days) caused a G(0)/G(1) and G(2)/M accumulation of LNCaP and HL-60 cells, respectively. Concomitantly, differentiation and apoptosis were induced in HL-60 cells, as measured by expression of CD11b antigen, staining with annexin V, and detection of cleavage of PARP. Moreover, baicalin enhanced the expression of the cyclin-dependent kinase inhibitor, p27(kip1) in LNCaP and HL-60 cells.

CONCLUSIONS

Baicalin inhibited the proliferation of cancer cells via apoptosis and cell cycle arrest, in which p27(kip1) may play a role. Baicalin may be a novel, adjunctive therapy for selected malignancies including prostate cancer.

The constitutive photomorphogenesis 9 signalosome directs vascular endothelial growth factor production in tumor cells

Angiogenesis is a prerequisite for solid tumor growth and metastasis. Elucidation of the signaling pathways that control tumor angiogenesis constitutes the basis for a rational antiangiogenic tumor therapy. Here we show that the production of vascular endothelial growth factor (VEGF) in HeLa and HL-60 cells is directed by the constitutive photomorphogenesis 9 signalosome (CSN). The CSN is a kinase complex that cooperates with the ubiquitin/26S proteasome system in regulating the stability of proteins involved in signal transduction. VEGF expression is controlled by the transcription factors activator protein (AP)-1, AP-2, SP-1, and hypoxia-inducible factor 1. Inhibition of CSN kinase activity by 50 microM curcumin for 2 h decreases the cellular c-Jun concentration, resulting in a reduction of the VEGF production by approximately 75%. The removal of the inhibitor from the cells led to a time-dependent recovery of endogenous c-Jun that is paralleled by increasing VEGF production. Elevated cellular CSN activity induced by CSN subunit 2 overexpression causes increased VEGF production in HeLa cells. A competitor of CSN-dependent c-Jun phosphorylation, the NH(2)-terminal c-Jun fragment Deltac-Jun(1-226), inhibits VEGF production in HeLa cells. The transcription factors AP-2 and SP-1 act independently of the CSN. They contribute less than a quarter to basal VEGF production. Under our experimental conditions, hypoxia-inducible factor 1alpha protein was not detected. Overexpression of the tumor suppressor p53 reduces VEGF production in HeLa cells. p53 competes with c-Jun for CSN-specific phosphorylation with the consequence of c-Jun destabilization. We conclude that CSN-directed c-Jun signaling mediates high VEGF production in HeLa and HL-60 cells. The data provide an explanation for the known antiangiogenic and antitumorigenic activities of curcumin. Because the CSN regulates the major part of VEGF production in the tested tumor cells, it constitutes a potentially important target for tumor therapy.

Synergistic interaction of lovastatin and paclitaxel in human cancer cells

The hydroxymethylglutaryl-CoA reductase inhibitor lovastatin is used widely to treat hypercholesterolemia and has been shown to have cell cycle-specific effects. In these studies, we have examined the effects of combining lovastatin and paclitaxel (Taxol), a microtubule-stabilizing agent, in the human leukemia K562 and HL-60 cell lines. Isobologram analysis of cytotoxicity assays revealed that there is a synergistic interaction between the two agents in both cell lines. Cell cycle analyses showed that lovastatin enhances paclitaxel-induced G2-M arrest in both cell lines. In addition, Annexin V apoptotic studies revealed that lovastatin enhances paclitaxel-induced apoptosis in HL-60 cells. Lovastatin did not affect levels of [3H]paclitaxel in cells. Whereas lovastatin induced an accumulation of unmodified Ras and caused an up-regulation of both RhoB and Rap1A, paclitaxel was found to have no effect on the isoprenylated proteins. Studies of the centromere-associated protein mitosin revealed that treatment with lovastatin and paclitaxel resulted in increased mitosin levels and that lovastatin altered the association of mitosin with condensed chromosomes. These findings provide insight into the mechanisms underlying the cell cycle effects of lovastatin and support the development of a novel therapeutic strategy directed toward altering deleterious cell proliferation.

Characterization of nuclear factors that bind to the human thymidylate synthase gene in HL-60 cells differentiated by all-trans retinoic acid treatment

HL-60 cells differentiate into granulocyte-like cells by all-trans retinoic acid (ATRA) treatment, and the cellular proliferation is markedly reduced during the differentiation. To elucidate the molecular mechanisms of the growth arrest during the cellular differentiation, we examined the regulated expression of the thymidylate synthase (TS) gene. Northern blot analysis revealed that the expression of the TS gene was almost suppressed in the differentiated HL-60 cells. The change in the levels of nuclear factors, NF-TS2 and NF-TS3, that bind to the 5'-terminal regulatory region of the human TS gene was examined during the differentiation of the HL-60 cells. The amount of NF-TS2 did not change significantly during the differentiation, whereas that of NF-TS3 clearly increased as the cells differentiated. We previously reported that NF-TS2 and NF-TS3 bind to the sequence around the initiation codon ATG of the human TS gene. Further analyses revealed that the DNA sequences of NF-TS2 and NF-TS3 are very similar, and the first and second positions of the ATG triplet codon are important for the formation of rigid DNA-protein complexes. The present findings concerning the binding site and changes during the differentiation induced by ATRA treatment are very similar to those previously reported on the differentiation induced by 1,25-dihydroxyvitamin D3 treatment. These findings suggest that NF-TS3 is involved in regulating the expression of the human TS gene during the differentiation of HL-60 cells, regardless of the terminal cell type: macrophage-like cells or granulocyte-like cells.

Pro-oxidant and antioxidant mechanisms of etoposide in HL-60 cells: role of myeloperoxidase

Etoposide is an effective anticancer agent whose antitumor activity is associated with its phenolic E-ring, which can participate in intracellular redox cycling reactions. Myeloperoxidase (MPO)-catalyzed one-electron oxidation of the etoposide phenolic ring and/or interaction of this phenolic moiety with reactive radicals yields its phenoxyl radical, whose reactivity may determine the pro- or antioxidant effects of this molecule in cells. Using MPO-rich HL-60 cells, we directly demonstrated that both anti- and pro-oxidant activities of etoposide are realized in cells. Etoposide acted as an effective radical scavenger and antioxidant protector of phosphatidylethanolamine, phosphatidylcholine, and other intracellular phospholipids against H2O2-induced oxidation in HL-60 cells with constitutively high MPO activity and in HL-60 cells depleted of MPO by an inhibitor of heme synthesis, succinyl acetone. MPO-catalyzed production of etoposide phenoxyl radicals observed directly in HL-60 cells by electron paramagnetic resonance (EPR) did not result in oxidation of these membrane phospholipids, suggesting that the radicals were not reactive enough to trigger lipid oxidation. MPO-dependent pro-oxidant activity of etoposide was directly demonstrated by (a) the ability of intracellular reduced glutathione (GSH) to eliminate EPR-detectable etoposide phenoxyl radicals, (b) the ability of etoposide phenoxyl radicals to oxidize GSH and protein thiols (after preliminary depletion of intracellular GSH with a maleimide reagent, ThioGlo-1), and (c) the disappearance of these effects after depletion of MPO by pretreatment of cells with succinyl acetone. In addition, titration of intracellular GSH (in intact cells) using the maleimide reagent ThioGlo-1 resulted in remarkably augmented EPR-detectable etoposide phenoxyl radicals and enhanced etoposide-induced topoisomerase II-DNA covalent complexes. In conclusion, the phenolic moiety of etoposide acts as an effective free radical scavenger, accounting for its antioxidant action. Whereas one-electron oxidation of etoposide by free radical scavenging and/or by MPO results in a phenoxyl radical with low reactivity toward lipids, its high reactivity toward thiols is a determinant of its pro-oxidant effects in HL-60 cells.

Expression profiling of sulfotransferases in human cell lines derived from extra-hepatic tissues

To explore the physiological roles of sulfotransferases (SULTs) in extra-hepatic tissues, we examined the expression of eight SULT genes by reverse transcription (RT)-PCR in human cell lines that were established from various tissues. Expression levels of SULTs were low in neural cell lines such as NB-1 and GI-1, and high in epithelial cell lines, such as Caco-2 and BeWo. SULT1C2 expression was abundant in all cell types, whereas that of SULT1E1, SULTIBI or SULT2B1 was restricted to a specific cell type. SULT1C1, which can catalyze the sulfation of N-hydroxy-2-acetylaminofluorene, was expressed in Caco-2, BeWo and KB562. Induction of differentiation did not generally affect SULT expression, although that of SULT1C2 was reduced after differentiation of the neuroblastoma cell line, NB-1, was induced. The profile of SULT expression in the culture cells obtained here gives clues to understanding the physiological roles of SULT enzymes in extra-hepatic tissues or organs.

Cationic lipids enhanced cellular uptake and activity of bcl-2 antisense oligodeoxynucleotide G3139 in HL-60 cells

AIM

To explore the effect of cationic lipid 1,3-di-oleoyloxy-2-(6-carboxy-spermyl)-propylamid (DOSPER) on cellular uptake and activity of bcl-2 antisense oligodeoxynucleotide G3139 in HL-60 cells.

METHODS

The cell-associated mean fluorescence intensity and the percentage of cells with positive staining for Bcl-2 were measured by flow cytometry. The subcellular distribution of fluorescein isothiocyanate (FITC)-labeled G3139 was observed by fluorescence microscope and the bcl-2 mRNA level was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

(1) DOSPER increased cellular uptake of G3139 into HL-60 cells greatly. When DOSPER/G3139 (microg : microg) was 2 : 1, the uptake of G3139 reached top after treatment for 2 h and increased about 20 times compared with application of G3139 alone. In the presence of DOSPER, G3139 was localized in nucleus and cytosol with a bright spotted fluorescence staining. However, G3139 was localized in cytoplasm with faint fluorescence in the absence of DOSPER. (2) Cell-associated G3139 could be effluxed out of cells. After treated with G3139 in the presence of DOSPER for 4 h, the cell-associated G3139 could be fitted by C(t)=68.2e(-0.60) t+31.8e(-0.02) t (% of initial value), with a half-life of approximately 1.1 h. In the absence of DOSPER, the cell-associated G3139 could be fitted by C(t)=64.8e(-2.27) t+35.2e(-0.04) t, with a half-life of about 18 min. (3) In the presence of DOSPER, G3139 1.0 micromol/L specially reduced bcl-2 mRNA level, and Bcl-2 protein decreased from 97 % +/- 4 % to 70.6 % +/- 2.1 %.

CONCLUSION

DOSPER enhanced the activity of G3139 and it might be attributed to increase of the cellular uptake and change of the subcellular distribution of G3139.

beta(2)-microglobulin induces apoptosis in HL-60 human leukemia cell line and its multidrug resistant variants overexpressing MRP1 but lacking Bax or overexpressing P-glycoprotein

In this study, we examined whether exogenous beta(2)-microglobulin (beta(2)m) can induce apoptosis in the drug sensitive HL-60 leukemia cell line and its drug resistant variants and investigated the molecular mechanism of beta(2)m-induced apoptosis. Our data revealed that beta(2)m is very significantly down-regulated in two multidrug resistant variants of the HL-60 cells: (a) the MRP1-bearing, Bax-deficient HL-60/ADR cell line, and (b) the P-glycoprotein (P-gp) overexpressing HL-60/VCR cell line. However, exogenous beta(2)m induced similar levels of apoptosis in HL-60 cells and these drug resistant variants. beta(2)m-induced apoptosis in HL-60 and HL-60/VCR cells was associated with decreased mitochondrial membrane potential (Deltapsim) but did not affect Deltapsim in HL-60/ADR cells. Surprisingly, cyclosporin A (CsA), a known inhibitor of the mitochondrial permeability transition (MPT) pore, inhibited beta(2)m-induced apoptosis in HL-60/ADR cells but not in HL-60 and HL-60/VCR cells, suggesting that the pro-apoptotic effect of beta(2)m in these cells is not through MPT pore formation. Furthermore, beta(2)m induced the release of cytochrome c and the apoptosis-inducing factor (AIF) from mitochondria in HL-60 and HL-60/VCR cells, but not in HL-60/ADR cells. Additionally, Z-VAD-fmk, a general inhibitor of caspases which inhibited cytochrome c release in HL-60 and HL-60/VCR cells, had no effect on AIF release in any of these cell lines, but inhibited beta(2)m-induced apoptosis in all three cell lines. However, Western blot analysis revealed that caspases-1, -3, -6, -8, and -9 are not activated during beta(2)m-induced apoptosis in these cells. Therefore, beta(2)m-induces apoptosis through an unknown caspase-dependent mitochondrial pathway in HL-60 and HL-60/VCR cells and by a Bax-independent, non-mitochondrial, caspase-dependent pathway in HL-60/ADR cells.

Genomic structure, chromosomal localization and expression profile of a novel melanoma differentiation associated (mda-7) gene with cancer specific growth suppressing and apoptosis inducing properties

Abnormalities in cellular differentiation are frequent occurrences in human cancers. Treatment of human melanoma cells with recombinant fibroblast interferon (IFN-beta) and the protein kinase C activator mezerein (MEZ) results in an irreversible loss in growth potential, suppression of tumorigenic properties and induction of terminal cell differentiation. Subtraction hybridization identified melanoma differentiation associated gene-7 (mda-7), as a gene induced during these physiological changes in human melanoma cells. Ectopic expression of mda-7 by means of a replication defective adenovirus results in growth suppression and induction of apoptosis in a broad spectrum of additional cancers, including melanoma, glioblastoma multiforme, osteosarcoma and carcinomas of the breast, cervix, colon, lung, nasopharynx and prostate. In contrast, no apparent harmful effects occur when mda-7 is expressed in normal epithelial or fibroblast cells. Human clones of mda-7 were isolated and its organization resolved in terms of intron/exon structure and chromosomal localization. Hu-mda-7 encompasses seven exons and six introns and encodes a protein with a predicted size of 23.8 kDa, consisting of 206 amino acids. Hu-mda-7 mRNA is stably expressed in the thymus, spleen and peripheral blood leukocytes. De novo mda-7 mRNA expression is also detected in human melanocytes and expression is inducible in cells of melanocyte/melanoma lineage and in certain normal and cancer cell types following treatment with a combination of IFN-beta plus MEZ. Mda-7 expression is also induced during megakaryocyte differentiation induced in human hematopoietic cells by treatment with TPA (12-O-tetradecanoyl phorbol-13-acetate). In contrast, de novo expression of mda-7 is not detected nor is it inducible by IFN-beta+MEZ in a spectrum of additional normal and cancer cells. No correlation was observed between induction of mda-7 mRNA expression and growth suppression following treatment with IFN-beta+MEZ and induction of endogenous mda-7 mRNA by combination treatment did not result in significant intracellular MDA-7 protein. Radiation hybrid mapping assigned the mda-7 gene to human chromosome 1q, at 1q 32.2 to 1q41, an area containing a cluster of genes associated with the IL-10 family of cytokines. Mda-7 represents a differentiation, growth and apoptosis associated gene with potential utility for the gene-based therapy of diverse human cancers.

Synthesis and purine receptor affinity of 6-oxopurine nucleosides and nucleotides containing (N)-methanocarba-pseudoribose rings

6-Oxopurine derivatives containing a northern (N) methanocarba modification (i.e., fused cyclopropane and cyclopentane rings in place of the ribose) were synthesized and the adenosine receptor affinity measured. Guanine or hypoxanthine was coupled at the 7-position, or 1,3-dibutylxanthine was coupled at the 9-position. The pseudoribose ring was also substituted at the 5'-position with an N-methyluronamide or with phosphate groups.

Synthesis and bioactivities of novel 5,6-bis(4-methoxyphenyl)-2H-pyridazin-3-one derivatives: inhibitors of interleukin-1 beta (IL-1beta) production

New 5,6-bis(4-methoxyphenyl)-2H-pyridazin-3-one derivatives were prepared, and their abilities to inhibit IL-1beta production were evaluated. Some compounds showed potent inhibitory activity against IL-1beta production in HL-60 cells stimulated with lipopolysaccharide (LPS). The synthesis and structure-activity relationships of these compounds are described.

Synthesis and bioactivities of novel pyridazine derivatives: inhibitors of interleukin-1 beta (IL-1beta) production

New pyridazine derivatives were prepared, and their abilities to inhibit IL-1beta production were evaluated. Some compounds showed potent inhibitory activity against IL-1beta production in HL-60 cells stimulated with lipopolysaccharide (LPS). The synthesis and structure-activity relationships of these compounds are described.

Promyelocytic HL-60 cells induce apoptosis selectively in transformed cells: involvement of myeloperoxidase, nitric oxide and target cell-derived superoxide anions

Promyelocytic HL-60 cells induced apoptosis selectively in transformed fibroblasts, but not in nontransformed parental cells or in revertants. Apoptosis induction was independent of direct cell-to-cell contact. It depended on the number of effector and target cells, pointing to the role of factors derived from both cell populations. Inhibitor studies allowed the establishment of the following model for intercellular signalling during apoptosis induction: target cell-derived superoxide anions spontaneously dismutate and form hydrogen peroxide. HL-60 effector cells release MPO which converts hydrogen peroxide into hypochlorous acid. Hypochlorous acid then may interact with target-cell-derived superoxide anions to yield apoptosis-inducing hydroxyl radicals. In addition, effector-cell-derived NO reacts with target-cell-derived superoxide anions and forms apoptosis-inducing peroxynitrite. These data explain the selective apoptosis induction in transformed cells by effector cells of the granulocyte lineage.

Effects of histamine and related compounds on the differentiation of HL-60-Eo cells into eosinophils

The effects of histamine and related compounds on the differentiation of HL-60-Eo cells into eosinophils were studied. The histamine and H2 agonists impromidine and 4-methylhistamine caused concentration-related increases in the number of differentiated cells. On the other hand, the H1 agonists 2-methylhistamine and 2-pyndylethylamine showed no such effect. Histamine-induced eosinophil differentiation was antagonized by the H2 antagonists cimetidine and ranitidine. Histamine and H2 agonists inhibited (3H)-thymidine uptake, suggesting that these compounds caused a decrease in proliferation. Histamine as well as the H2 agonists impromidine and 4-methythistamine caused increases in cAMP level, and this effect was antagonized by ranitidine. From these findings, we concluded that both the differentiation of HL-60-Eo cells into eosinophils and proliferation of HL-60-Eo cells were mediated via H2 receptors.

Bromodeoxyuridine increases keratin 19 protein expression at a posttranscriptional level in two human lung tumor cell lines

Keratins form the largest subfamily of intermediate filament proteins and show strict lineage- and differentiation-associated expression in epithelial cells. Little is known about the mechanisms that control keratin protein synthesis in these cells. We have examined the effect of the differentiation-modulating agent, 5'-bromo-2'-deoxyuridine (BrdU), on keratin 19 (K19) expression in two human lung carcinoma cell lines, DLKP and A549. Treatment of both cell lines with 10 microM BrdU for 7 d induced the expression of K19 protein in keratin-negative DLKP cells, and significantly increased K19 protein expression in A549 cells. K19 messenger ribonucleic acids (mRNAs) were detected by Northern blot and reverse transcriptase-polymerase chain reaction analyses in both cell lines, but no increase in K19 mRNA levels was detected in either cell line, even with treatment with BrdU for up to 21 d. This suggests that K19 protein synthesis is normally blocked at a posttranscriptional level in DLKP cells, and BrdU can somehow reverse this block, resulting in the induction of K19 protein synthesis. Treatment of HL60, a leukemic cell line, with BrdU, resulted in noninduction of K19 protein synthesis, and no K19 mRNA transcripts were detected before and after BrdU treatment, possibly suggesting that BrdU is acting in an epithelial-specific manner to reverse a block in K19 protein synthesis in DLKP keratin-negative lung cancer cells. Therefore, DLKP (and A549) may be useful cellular models to investigate if this represents a regulatory step in early lung development or a mechanism whereby tumor cells possess the ability to down-regulate the expression of a more-differentiated phenotype.

Cross-resistance to cytosine arabinoside in a multidrug-resistant human promyelocytic cell line selected for resistance to doxorubicin: implications for combination chemotherapy

The pyrimidine analogue cytosine arabinoside (AraC) is one of the most effective drugs used in the treatment of acute leukaemia. Overexpression of the multidrug resistance (MDR-1) gene and its product, P-glycoprotein (P-gp), is associated with cellular resistance to drugs, such as anthracyclines and vinca alkaloids. This resistance can be reversed by cyclosporine analogues or verapamil (ver). We investigated the in vitro cross-resistance to AraC in a doxorubicin-resistant HL60 cell line, with an elevated expression of the MDR-1 gene. The resistant clone showed an eightfold increased resistance to AraC and a two- to fourfold resistance to the other analogues, as measured by cytotoxicity test. There was no significant increase in the activity of 5'-nucleotidase or in the amount of deoxyribonucleotide pools between cell lines. We could, however, detect a reduction in deoxycytidine kinase (dCK) activity (30%, P = 0.021, using deoxycytidine as substrate) and the level of AraC triphosphates was significantly reduced in the resistant cells (70%, P = 0.009). When the cells were exposed to cyclosporin A (CsA) or the cyclosporine analogue PSC 833 (PSC) in combination with AraC, there was more extensive apoptosis, as measured by formation of oligonucleosomal DNA fragmentation and caspase-3-like activity, than with exposure to AraC alone. We also found an increased retention of AraC in the resistant cells when incubated with AraC in combination with CsA. Ver in combination with AraC, failed to increase apoptosis for the resistant cell line. Our data suggests that the resistance to AraC for the P-gp-expressing cells is a result of a reduction of dCK activity and an increase in efflux, the latter possibly depending on P-gp. A combination of CsA or PSC with AraC may improve the effect of AraC in vivo.

Improved safety, pharmacokinetics and therapeutic efficacy profiles of a novel liposomal formulation of mitoxantrone

We describe here the preclinical studies of a novel formulation of liposome-entrapped mitoxantrone (LEM). The liposome entrapment efficiency of mitoxantrone was 93.4 +/- 2.8%. In vitro cytotoxicity studies in HL60 cells comparing LEM with conventional mitoxantrone (MTO) showed IC50 values of 0.31 +/- 0.05 ng/ml and 0.48 +/- 0.06 ng/ml for LEM and MTO, respectively. In CD2F1 mice, LEM was significantly less toxic as compared with MTO. A single intravenous (i.v.) dose of 15 mg/kg MTO produced 100% mortality in CD2F1 mice by Day 10, whereas a single i.v. dose as high as 35 mg/kg LEM caused no mortality for at least up to Day 60 post-treatment. Multiple doses of MTO (i.v., 5.0 mg/kg, 1x daily, x5) caused 100% mortality by Day 10, whereas a similar dose regimen of LEM caused no mortality in CD2F1 mice. Clinical and histopathology evaluations indicated long-term normal tissue protection in mice treated with relatively high single dose (i.v., 35 mg/kg) or multiple doses of LEM (i.v., 5.0 mg/kg, 1x daily, x5). LEM also demonstrated favourable pharmacokinetic profiles. CD2F1 mice injected with 5 mg/kg i.v. dose of LEM showed plasma levels 51-fold higher than with an equivalent dose of MTO. The area under the plasma concentration-time curve was 200-fold greater with LEM as compared to MTO. The plasma half-lives were 0.96 hours and 0.11 hours for LEM and MTO, respectively. An altered tissue distribution was observed with LEM; cardiac tissue demonstrating at least 2.6-fold lower levels of mitoxantrone with LEM vs. MTO. LEM exhibited significant anti-tumor activity against murine ascitic L1210 leukemia in CD2F1 mice. Treatment with a single dose of 20.0 mg/kg LEM resulted in 100% long-term survivors. LEM 2.5 mg/kg (i.v., x4) had antitumor activity against a human hormone-independent prostate carcinoma (PC-3) grown in athymic mice, while a comparable dose of MTO was too toxic. A significant decrease in toxicity, altered pharmacokinetics, and enhanced efficacy of LEM suggest that LEM may provide a viable alternative to the clinical use of conventional mitoxantrone.

Synergistic cytotoxic action of vitamin C and vitamin K3

We investigated the combination effect of sodium ascorbate (vitamin C) and menadione (vitamin K3) on the viability of various cultured cells. Human oral squamous cell carcinoma (HSC-2, HSC-3) and human promyelocytic leukemia (HL-60) cells were more sensitive to these vitamins as compared to normal cells (human gingival fibroblast HGF, human periodontal ligament fibroblast HPLF, human pulp cell HPC). The combination of vitamin C and vitamin K3 produced synergistic cytotoxicity against all these 6 cell lines. Treatment with vitamin C or vitamin K3, or their combination, induced internucleosomal DNA fragmentation only in HL-60 cells, but not in the oral tumor cell lines (HSC-2, HSC-3, HSG). ESR spectroscopy showed that vitamins C and K3 produce radicals under alkaline conditions and that the combination of these two vitamins synergistically enhanced their respective radical intensities.

Synthesis and biological activities of novel structural analogues of 2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand

Novel analogues of 2-arachidonoylglycerol (2-AG), an endogenous cannabinoid receptor ligand, were developed. Chemical synthesis of these analogues (2-AGA105 and 2-AGA109) was accomplished starting from 2-octyn-1-ol and diethyl malonate and employing Wittig coupling of triene phosphonate with an aldehyde intermediate in a convergent and stereoselective manner. These analogues should be useful lead compounds for the development of novel 2-AG mimetics.

Proteomic analysis of apoptosis initiation induced by all-trans retinoic acid in human acute promyelocytic leukemia cells

The irreversible destiny of apoptosis in its early stage might play a critical role in the apoptosis of human acute promyelocytic leukemia (APL) cell line induced by all-trans retinoic acid (ATRA). To characterize protein alterations during the apoptosis-initiation phase and to understand the metabolic status at that time, we investigated the protein profiles in the apoptosis-initiation phase of APL cell line HL-60 by proteomic analysis. ATRA-withdrawal was conducted to demonstrate that there was committed initiation phase of apoptosis triggered by 10(-6) M ATRA at day 3. Only after that time point, ATRA-treated cells irreversibly went to apoptosis. Also at that time point, the positive regulators of apoptosis such as STAT3 increased at protein level, whereas negative regulators (Bcl-2 and p-STAT3) decreased. In addition, caspase-3 also increased after that time. Furthermore, comparative proteomic analysis was utilized to examine the protein expression profiles during the initiation stage of apoptosis. Our results showed 12 upregulated and 7 downregulated proteins experiencing twofold alteration, including key regulators of signal transduction such as G-proteins and nucleic receptors, proteins related with metabolism, oxidation and reduction, proteins associated with the nucleus and cytoskeleton-related proteins. Some of them could be positive modulators to trigger apoptosis, whereas others could contribute to intracellular defense against apoptosis induced by exogenous triggers. The results above suggest that there is a subtle balance between apoptosis and the intracellular defense against apoptosis. Once the balance is disturbed, cells would irreversibly initiate to undergo the execution of apoptosis.

Resistance of human leukemic cell lines to 1-beta-D-arabinofuranosylcytosine: characterization of an experimental model

1-beta-D-arabinofuranosylcytosine (ara-C) is an antimetabolite used for the treatment of acute myelogenous leukemia. The ability of ara-C to kill neoplastic cells has been correlated to the induction of apoptosis. The clinical use of ara-C is limited by the development of drug resistance. Alterations in drug-induced apoptosis play a critical role in ara-C resistance. In particular, the proto-oncogene bcl-2 has been implicated in this phenomenon. To better understand the molecular basis of the role of bcl-2 in ara-C resistance, we investigated the relationship between the cytotoxic effect of ara-C, the expression levels and the subcellular localization of bcl-2 in three human leukemic cell lines (HL-60, KG1, J111). We have also evaluated the effects of ara-C on the J111 leukemic cell line (showing the lowest levels of Bcl-2 and the highest sensitivity to ara-C) overexpressing the bcl-2 oncogene. The model we developed here will allow further studies on the role of post-translational events involving bcl-2 (such as translocation and/or phosphorylation) in the cellular response to ara-C treatment.

Interactions of PC/Chol and PS/Chol liposomes with human cells in vitro

Interactions between phosphatidylcholine (PC) or phosphatidylserine (PS) liposomes and human umbilical vein endothelial cells (HUVEC) or human promyelocytic leukemia cells (HL60) were investigated. Pyramine encapsulating or rhodamine incorporating small unilamellar liposomes with mean diameters around 80 nm (demonstrated to retain encapsulated material and to be nontoxic under experimental conditions) were used. Liposome uptake by both types of cells increased when increasing amounts of vesicles were co-incubated. For both lipid compositions, the interaction with HUVEC was very fast (association reached a plateau within 5 min) and so was the release of internalized vesicles (90% within 10 min at 37 degrees C). The reduced association values at 4 degrees C and the punctuate fluorescence observed in the cell cytoplasm after interaction, were indicative of whole liposome internalization. This internalization was clathrin-independent, since it was not inhibited by sodium azide and deoxyglucose. Pre-treatment of HUVEC with filipin or NEM resulted in modification of the interaction, something that could be due to alterations in the biochemical characteristics of HUVEC membranes that inhibit vesicular processes. In HL-60 cells, a slower association and faster release of PC/Chol liposomes was demonstrated, while association of both liposomes with these cells was energy-and temperature-independent. Nevertheless, morphological studies revealed differences in the interactions: A bright fluorescent rim observed after interaction with PC/Chol liposomes, suggests that these liposomes were adsorbed on the surface of HL60 cells, while the uniform cytoplasmic fluorescence observed after incubation with PS/Chol liposomes was indicative of fusion as the interaction mechanism.

Quantitation of interferon regulatory factor transcripts in patients with acute myeloid leukemia

Interferon regulatory factors IRF-1 and IRF-2, the two mutually antagonistic factors, fluctuate during the cell cycle and play an important role in normal and neoplastic growth processes. The relative levels of these two transcripts were analyzed in 5 normal and 43 acute myeloid leukemia (AML) bone marrow (BM) specimens by a semiquantitative RT-PCR method. IRF-1 and IRF-2 cDNA sequences were coamplified using primers that were designed to span regions of high homology between the genes. Each primer can anneal equally to both IRF-1 and IRF-2 sequences. Hence, the relative amount of amplified products from each cDNA species provides an estimation of proportional concentration of the RNA transcripts in the test sample. Results indicate expression of both the transcripts on all the leukemia and lymphoma cell lines tested, normal and AML BM. Significantly higher IRF-1:IRF-2 ratio was observed in normal as compared to AML BM (p = 0.007). There was no correlation with clinical factors such as FAB subtype. A single dose of amifostine or three daily doses of recombinant IL-4 were administered to 5 and 8 AML patients, respectively. The changes in the expression of these transcripts were studied prior to administration of the agent (d0) and after 3 days (d3). IL-4 treatment showed significant increase in the IRF-1:IRF-2 ratio in 4 of 8 patients (p = 0.05); amifostine treatment did not show any appreciable change.

Pharmacologic or genetic manipulation of glutathione S-transferase P1-1 (GSTpi) influences cell proliferation pathways

Glutathione S-transferase P1-1 (GSTpi) is an abundant and ubiquitously expressed protein in normal and malignant mammalian tissues and possesses catalytic and ligand binding properties. Our present data suggest that the protein contributes to the regulation of cell proliferation. Mouse embryo fibroblasts (MEFs) isolated from mice with a GSTP1-1 [glutathione S-transferase P1-1 (isozyme in nonhepatic tissue)] null genotype (GSTpi(-/-)) doubled their population in 26.2 h versus 33.6 h for the wild type (GSTpi(+/+)). Retroviral transfection of GSTP1-1 into GSTpi(-/-) MEF cells slowed the doubling time to 30.4 h. Both early passage and immortalized MEF cells from GSTpi(-/-) animals expressed significantly elevated activity of extracellular signal-regulated kinases ERK1/ERK2, kinases linked to cell proliferation pathways. In vivo, GSTpi(-/-) mice had higher basal levels of circulating white blood cells compared with GSTpi(+/+). Administration of a peptidomimetic inhibitor of GSTP1-1, TLK199, (gamma-glutamyl-S-(benzyl)cysteinyl-R-phenyl glycine diethyl ester), stimulated both lymphocyte production and bone marrow progenitor (colony-forming unit-granulocyte macrophage) proliferation, but only in GSTpi(+/+) and not in GSTpi(-/-) animals. Selection of a resistant clone of an HL60 tumor cell line through chronic exposure to TLK199 resulted in cells with elevated activities of c-Jun NH2 terminal kinase (JNK1) and ERK1/ERK2, and allowed the cells to proliferate under stress conditions that induced high levels of apoptosis in the wild type cells. The in vitro and in vivo data are consistent with the principle that GSTP1-1 influences cell proliferation.

Induction of apoptosis by a ribosome-inactivating protein from Agrostemma githago is associated with down-regulation of anti-apoptotic bcl-2 protein expression

Agrostin is a type 1 ribosome-inactivating protein (RIP) isolated from the seeds of Agrostemma githago. 3[H]-thymidine incorporation in human leukemic HL-60 cells was significantly reduced after incubation with agrostin showing that the RIP was inhibitory on the cell proliferation. Results from flow cytometric studies illustrated that apoptosis was induced by agrostin, which was associated with activation of endonucleases and DNA fragmentation of the leukemic cells. Anti-apoptotic bcl-2 protein level was also reduced by agrostin showing that the associated apoptotic pathway might involve down-regulation of the intracellular bcl-2 protein level.

Production of hydrogen peroxide and methionine sulfoxide by epigallocatechin gallate and antioxidants

Epigallocatechin gallate (EGCG) induced apoptosis-associated characteristics in human oral tumor cell lines more efficiently than ascorbates, gallic acid, vitamin K, flavonoids or steroidal saponins. Since catalase partially inhibited the cytotoxic activity of EGCG, the possible involvement of hydrogen peroxide (H2O2) in cell death induction was investigated, using TCPO chemiluminescence method. Production of H2O2 by EGCG, sodium ascorbate, gallic acid or catechin reached a maximum level within 30 minutes, and was increased up to a plateau level above pH 8. Under optimal conditions, 1 mM EGCG was converted to 1 mM H2O2. At neutral pH, EGCG produced the highest amount of H2O2, followed by gallic acid, sodium ascorbate and catechin. EGCG produced methionine sulfoxide from methionine in the culture medium, while the methionine oxidation by EGCG was significantly reduced in the presence of serum. ESR spectroscopy showed that EGCG, gallic acid and sodium ascorbate, but not catechin, produced radicals under alkaline condition and that all these compounds scavenged superoxide anion, produced by hypoxanthine-xanthine oxidase reaction. EGCG also effectively scavenged the ascorbate and gallate radicals, more efficiently than other compounds. These data suggest that the apoptosis induction by EGCG may be mediated by H2O2 produced in the culture medium.

Changes in amino acid pool and utilization during apoptosis in HL-60 cells induced by epigallocatechin gallate or gallic acid

Recent studies have demonstrated the apoptosis-inducing potential of epigallocatechin gallate (EGCG), a major component of green tea, against various cultured cell lines. By using an amino acid analyzer, we investigated here the possible changes in the amino acid pool and utilization during the apoptosis of HL-60 cells induced by EGCG or gallic acid, a structural unit of tannin. Sublethal concentrations of EGCG initially elevated and then reduced the intracellular concentrations of most of amino acids except for glutamic acid and aspartic acid, whereas lethal concentrations of EGCG continuously reduced these amino acid pools during 6 hours. Both sublethal and lethal concentrations of gallic acid initially elevated and then reduced these amino acid pools. Both inducers elevated the intracellular accumulation and production of arginine and extensively reduced the utilization of other amino acids. These data demonstrate that EGCG showed more severe effects on the amino acid pool and utilization than gallic acid, which may explain, at least in part, the difference in apoptosis-inducing potential between these inducers.

Antitumor effect of beta2-microglobulin in leukemic cell-bearing mice via apoptosis-inducing activity: activation of caspase-3 and nuclear factor-kappaB

We have reported previously that beta2-microglobulin (beta2m) induces apoptosis in leukemic cells in vitro, and that an interaction between beta2m and HLA class I antigen induces apoptosis. Here we examined whether beta2m can induce apoptosis in leukemic cells in vivo and whether it has an antitumor effect in tumor-bearing mice. Daily administration of 50 or 250 microg of beta2m induced apoptosis and an antitumor effect on K562 leukemia cell-bearing mice in the same manner as tumor necrosis factor-alpha. In tumor tissues in beta2m-treated mice, both caspase-3 and nuclear factor-kappaB (NF-kappaB) were stained more strongly than in control mice by anti-caspase-3 and anti-NF-kappaB p65/Rel A polyclonal antibodies. We also observed the in vivo immunological effects of beta2m on lymphoid and hematopoietic organs, such as thymus, bone marrow, Peyer's patches, liver, and spleen in normal mice. Using antibodies against caspase-3 and NF-kappaB, immunohistochemical staining showed that no specific tissues were damaged or stained in normal mice. We conclude that beta2m stimulates caspase-3 and NF-kappaB pathways to induce apoptosis, making it a useful approach to a new therapy for leukemia.