Telomerase Activity and Microgravity-Dependent Apoptosis in Human Leukemia HL-60 Cells

Mammalian cells subjected to conditions of spaceflight and the microgravity environment ofspace; manifest a number of alterations in structure and function. Among the most notable changes incells flown on the Space Shuttle are reduced growth activation and decline in growth rate in the totalpopulation. Other changes include chromosomal aberrations, inhibited locomotion, alteredcytokine production, changes in PKC distribution, and increased apoptos.

Impact du statut de différenciation des cellules promyélocytaires HL-60 sur l’efficacité anticancéreuse et antiinflammatoire de l’EGCG

L’altération de la barrière hématoencéphalique (BHE) par les cellules tumorales et les cellules immunes circulantes peut mener à la neuroinflammation. Les cellules leucémiques promyélocytaires HL-60 sont un excellent modèle pour étudier et comprendre les mécanismes de signalisation moléculaires qui caractérisent le développement tumoral et métastatique. La cancérogenèse peut s’accompagner de modulations de l’expression de biomarqueurs tels que la cyclooxygénase-2 et la métalloprotéase-9. Les recherches décrites dans ce mémoire relatent l’analyse des biomarqueurs inflammatoires et invasifs régulés lors de la différenciation induite par le PMA des cellules HL-60 en macrophages. Le statut de différenciation cellulaire pourrait avoir un impact sur les gènes cibles de la voie NF-κB. Nous émettons l’hypothèse que le PMA active la voie NF-κB et que cette signalisation peut être renversée par l’(-)-épigallocatéchine-gallate (EGCG). En effet, une régulation à la hausse de l’expression de plusieurs gènes combinée à la diminution de l’expression d’IκB mettent en évidence l’implication de la voie NF-κB dans l’activation des mécanismes pro-inflammatoires et pro-invasifs. Les mêmes observations sont faites dans les cellules différenciées appelées «macrophages-like». L’EGCG, un polyphénol dérivé du thé vert, a un potentiel chimiopréventif. Il est capable d’inhiber la signalisation moléculaire passant par la voie NF-κB dans les cellules HL-60 traitées simultanément par l’EGCG et le PMA, mais pas dans les cellules «macrophages-like». Cette différence peut s’expliquer par une modulation de l’expression du récepteur de surface cellulaire de l’EGCG, le récepteur à la laminine de 67 kDa, et de son précurseur de 37 kDa. Collectivement, nos résultats montrent que le statut de différenciation des cellules promyélocytaires HL-60 concorde avec l’activation des mécanismes favorisant le développement d’un cancer et des métastases. Cet effet peut être prévenu par l’utilisation d’agents naturels tel l’EGCG. Le ciblage de biomarqueurs liés au statut de différenciation des cellules tumorales impliquées dans la perturbation de la barrière hématoencéphalique qui cause la neuroinflammation permettrait l’avancement des connaissances dans la prévention de la cancérogenèse.

Antiproliferative activity of pristimerin isolated from Maytenus ilicifolia (Celastraceae) in human HL-60 cells

Pristimerin has been shown to be cytotoxic to several cancer cell lines. In the present work, the cytotoxicity of pristimerin was evaluated in human tumor cell lines and in human peripheral blood mononuclear cells (PBMC). This work also examined the effects of pristimerin (0.4; 0.8 and 1.7 mu M) in HL-60 cells, after 6, 12 and 24 h of exposure. Pristimerin reduced the number of viable cells and increased number of non-viable cells in a concentration-dependent manner by tripan blue test showing morphological changes consistent with apoptosis. Nevertheless, pristimerin was not selective to cancer cells, since it inhibited PBMC proliferation with an IC50 of 0.88 PM. DNA synthesis inhibition assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation in HL-60 cells was 70% and 83% for the concentrations of 0.4 and 0.8 mu M, respectively. Pristimerin (10 and 20 mu M) was not able to inhibit topoisomerase 1. In AO/EB (acridine orange/ethidium bromide) staining, all tested concentrations reduced the number of HL-60 viable cells, with the occurrence of necrosis and apoptosis in a concentration-dependent manner, results in agreement with trypan blue exclusion findings. The analysis of membrane integrity and internucleosomal DNA fragmentation by flow cytometry in the presence of pristimerin indicated that treated cells underwent apoptosis. The present data point to the importance of pristimerin as representative of an emerging class of potential anticancer chemicals, exhibiting an antiproliferative effect by inhibiting DNA synthesis and triggering apoptosis. (c) 2008 Elsevier Ltd. All rights reserved.

The silent survival of Staphylococcus aureus phagocyted by HL-60 derived neutrophils

Staphylococcus aureus is a Gram positive pathogen that causes various human infections and represents one of the most common causes of bacteremia. S. aureus is able to invade a variety of non-professional phagocytes and that can survive engulfment by neutrophils, producing both secreted and surface components that compromise innate immune responses. In the contest of our study we evaluated the functional activity of vaccine specific antibodies by opsonophagocytosis killing assay (OPKA). Interestingly a low level of killing of the staphylococcal cells has been observed. In the meanwhile intracellular survival studies showed that S. aureus persisted inside phagocytes for several hours until a burst of growth after 5 hours in the supernatant. These data suggest that the strong ability of S. aureus to survive in the phagocytes could be the cause of the low killing measured by OPKA. Moreover parallel studies on HL-60 cells infected with S. aureus done by using transmission electron microscopy (TEM) interestingly showed that staphylococcal cells have an intracellular localization (endosomal vacuoles) and that they are able not only to maintain the integrity of their membrane but also to replicate inside vacuolar compartments. Finally in order to generate 3D volume of whole bacteria when present inside neutrophilic vacuoles, we collected a series of tomographic two-dimensional (2D) images by using a transmission electron microscope, generating 5 different tomograms. The three-dimensional reconstruction reveals the presence of intact bacteria within neutrophil vacuoles. The S. aureus membrane appears completely undamaged and integral in contrast with the physiological process of phagosytosis through vacuoles progression. S. aureus bacteria show a homogenous distribution of the density in all the three dimensions (X, Y, Z). All these evidences definitely explain the ability of the pathogen to survive inside the endosomal vacuoles and should be the cause of the low killing level.

UV irradiation-induced apoptosis leads to activation of a 36-kDa myelin basic protein kinase in HL-60 cells.

UV irradiation induces apoptosis (or programmed cell death) in HL-60 promyelocytic leukemia cells within 3 h. UV-induced apoptosis is accompanied by activation of a 36-kDa myelin basic protein kinase (p36 MBP kinase). This kinase is also activated by okadaic acid and retinoic acid-induced apoptosis. Irrespective of the inducing agent, p36 MBP kinase activation is restricted to the subpopulation of cells actually undergoing apoptosis. Activation of p36 MBP kinase occurs in enucleated cytoplasts, indicating no requirement for a nucleus or fragmented DNA in signaling. We also demonstrate the activation of p36 kinase in tumor necrosis factor-alpha- and serum starvation-induced cell death using the human prostatic tumor cell line LNCap and NIH 3T3 fibroblasts, respectively. We postulate that p36 MBP kinase is a common component in diverse signaling pathways leading to apoptosis.

Targeting of proteins to granule subsets is determined by timing and not by sorting: The specific granule protein NGAL is localized to azurophil granules when expressed in HL-60 cells.

The mechanism of protein targeting to individual granules in cells that contain different subsets of storage granules is poorly understood. The neutrophil contains two highly distinct major types of granules, the peroxidase positive (azurophil) granules and the peroxidase negative (specific and gelatinase) granules. We hypothesized that targeting of proteins to individual granule subsets may be determined by the stage of maturation of the cell, at which the granule proteins are synthesized, rather than by individual sorting information present in the proteins. This was tested by transfecting the cDNA of the specific granule protein, NGAL, which is normally synthesized in metamyelocytes, into the promyelocytic cell line HL-60, which is developmentally arrested at the stage of formation of azurophil granules, and thus does not contain specific and gelatinase granules. Controlled by a cytomegalovirus promoter, NGAL was constitutively expressed in transfected HL-60 cells. This resulted in the targeting of NGAL to azurophil granules as demonstrated by colocalization of NGAL with myeloperoxidase, visualized by immunoelectron microscopy. This shows that targeting of proteins into distinct granule subsets may be determined solely by the time of their biosynthesis and does not depend on individual sorting information present in the proteins.

The yeast and mammalian isoforms of phosphatidylinositol transfer protein can all restore phospholipase C-mediated inositol lipid signaling in cytosol-depleted RBL-2H3 and HL-60 cells.

The mammalian phosphatidylinositol transfer proteins (PITP) and the yeast Saccharomyces cerevisiae PITP (SEC14p) that show no sequence homology both catalyze exchange of phosphatidylinositol (PI) between membranes compartments in vitro. In HL-60 cells where the cytosolic proteins are depleted by permeabilization, exogenously added PITPalpha is required to restore G protein-mediated phospholipase Cbeta (PLCbeta) signaling. Recently, a second mammalian PITPbeta form has been described that shows 77% identity to rat PITPalpha. We have examined the ability of the two mammalian PITPs and SEC14p to restore PLC-mediated signaling in cytosol-depleted HL-60 and RBL-2H3 cells. Both PITPalpha and PITPbeta isoforms as well as SEC14p restore G protein-mediated PLCbeta signaling with a similar potency. In RBL-2H3 cells, crosslinking of the IgE receptor by antigen stimulates inositol lipid hydrolysis by tyrosine phosphorylation of PLCgamma1. Permeabilization of RBL cells leads to loss of PLCgamma1 as well as PITP into the extracellular medium and this coincides with loss of antigen-stimulated lipid hydrolysis. Both PLCgamma1 and PITP were required to restore inositol lipid signaling. We conclude that (i) because the PI binding/transfer activities of PITP/SEC14p is the common feature shared by all three transfer proteins, it must be the relevant activity that determines their abilities to restore inositol lipid-mediated signaling and (ii) PITP is a general requirement for inositol lipid hydrolysis regardless of how and which isoform of PLC is activated by the appropriate agonist.

Regulation of glycolipid synthesis in HL-60 cells by antisense oligodeoxynucleotides to glycosyltransferase sequences: effect on cellular differentiation.

Treatment of the human promyelocytic leukemia cell line HL-60 with antisense oligodeoxynucleotides to UDP-N-acetylgalactosamine:beta-1,4-N-acetylgalactosaminyl-transferase (GM2-synthase; EC 2.4.1.92) and CMP-sialic acid:alpha-2,8-sialyltransferase (GD3-synthase; EC 2.4.99.8) sequences effectively down-regulated the synthesis of more complex gangliosides in the ganglioside synthetic pathways after GM3, resulting in a remarkable increase in endogenous GM3 with concomitant decreases in more complex gangliosides. The treated cells underwent monocytic differentiation as judged by morphological changes, adherent ability, and nitroblue tetrazolium staining. These data provide evidence that the increased endogenous ganglioside GM3 may play an important role in regulating cellular differentiation and that the antisense DNA technique proves to be a powerful tool in manipulating glycolipid synthesis in the cell.

Étude des voies de signalisation et des mécanismes moléculaires impliqués dans [l']apoptose des cellules leucémiques HL-60 traitées avec des inhibiteurs de topoisomérases I et II

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Étude des voies de signalisation et des mécanismes moléculaires impliqués dans [l']apoptose des cellules leucémiques HL-60 traitées avec des inhibiteurs de topoisomérases I et II

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Protein Kinase C and Anaplastic Lymphoma Kinase Targeted Compounds

The protein kinases (PKs) belong to the largest single family of enzymes, phosphotransferases, which catalyze the phosphorylation of other enzymes and proteins and function primarily in signal transduction. Consequently, PKs regulate cell mechanisms such as growth, differentiation, and proliferation. Dysfunction of these cellular mechanisms may lead to cancer, a major predicament in health care. Even though there is a range of clinically available cancer-fighting drugs, increasing number of cancer cases and setbacks such as drug resistance, constantly keep cancer research active. At the commencement of this study an isophthalic acid derivative had been suggested to bind to the regulatory domain of protein kinase C (PKC). In order to investigate the biological effects and structure-activity relationships (SARs) of this new chemical entity, a library of compounds was synthesized. The best compounds induced apoptosis in human leukemia HL-60 cells and were not cytotoxic in Swiss 3T3 fibroblasts. In addition, the best apoptosis inducers were neither cytotoxic nor mutagenic. Furthermore, results from binding affinity assays of PKC isoforms revealed the pharmacophores of these isophthalic acid derivatives. The best inhibition constants of the tested compounds were measured to 210 nM for PKCα and to 530 nM for PKCδ. Among natural compounds targeting the regulatory domain of PKC, the target of bistramide A has been a matter of debate. It was initially found to activate PKCδ; however, actin was recently reported as the main target. In order to clarify and to further study the biological effects of bistramide A, the total syntheses of the natural compound and two isomers were performed. Biological assays of the compounds revealed accumulation of 4n polyploid cells as the primary mode of action and the compounds showed similar overall antiproliferative activities. However, each compound showed a distinct distribution of antimitotic effect presumably via actin binding, proapoptotic effect presumably via PKCδ, and pro-differentiation effect as evidenced by CD11b expression. Furthermore, it was shown that the antimitotic and proapoptotic effects of bistramide A were not secondary effects of actin binding but independent effects. The third aim in this study was to synthesize a library of a new class of urea-based type II inhibitors targeted at the kinase domain of anaplastic lymphoma kinase (ALK). The best compounds in this library showed IC50 values as low as 390 nM for ALK while the initial low cellular activities were successfully increased even by more than 70 times for NPM-ALK- positive BaF3 cells. More importantly, selective antiproliferative activity on ALK-positive cell lines was achieved; while the best compound affected the BaF3 and SU-DHL-1 cells with IC50 values of 0.5 and 0.8 μM, respectively, they were less toxic to the NPM-ALK-negative human leukemic cells U937 (IC50 = 3.2 μM) and BaF3 parental cells (IC50 = 5.4 μM). Furthermore, SAR studies of the synthesized compounds revealed functional groups and positions of the scaffold, which enhanced the enzymatic and cellular activities.

Kinetic measurements of cell surface E-selectin/carbohydrate ligand interactions

Selectin/ligand interactions initiate the multistep adhesion and signaling cascades in the recruitment of leukocytes from circulation to inflamed tissues and may also play a role in tumor metastasis. Kinetic properties of these interactions are essential determinants governing blood-borne cells' tethering to and rolling on the vessel wall. Extending our recently developed micropipette method, we have measured the kinetic rates of E-selectin/ligand interactions. Red cells coated with an E-selectin construct were allowed to bind HL-60 or Colo-205 cells bearing carbohydrate ligands. Specific adhesions were observed to occur at isolated points, the frequency of which followed a Poisson distribution. These point attachments were formed at the same rate with both the HL-60 and Colo-205 cells (0.14 +/- 0.04 and 0.13 +/- 0.03 mum(2) s(-1) per unit density of E-selectin, respectively) but dissociated from the former at a rate twice as fast as did from the latter (0.92 +/- 0.23 and 0.44 +/- 0.10 s(-1), respectively). The reverse rates agree well with those measured by the flow chamber. The forward rates are orders of magnitude higher than those of Fc gamma receptors interacting with IgG measured under similar conditions, consistent with the rapid kinetics requirement for the function of E-selectin/ligand binding, which is to capture leukocytes on endothelial surfaces from flow.