Ca2+ and phorbol ester synergistically induce HL-60 differentiation

Enhancement of ATRA-induced cell differentiation by inhibition of calcium accumulation into the endoplasmic reticulum: cross-talk between RAR alpha and calcium-dependent signaling

Sarco-endoplasmic reticulum calcium ATPase (SERCA) enzymes control calcium-induced cellular activation by accumulating calcium from the cytosol into the endoplasmic reticulum (ER). To better understand the role of SERCA proteins and cellular calcium homeostasis in all-trans retinoic acid (ATRA)-induced differentiation, we investigated the effect of pharmacologic inhibition of SERCA-dependent calcium uptake into the ER on ATRA-induced differentiation of the HL-60 myelogenous and the NB4 promyelocytic cell lines. SERCA inhibitors di-tert-butyl-benzohydroquinone (tBHQ), thapsigargin, and cyclopiazonic acid significantly enhanced the induction of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and CD11b marker expression induced by suboptimal concentrations of ATRA (50 nM) in both cell lines. Analysis of cellular calcium homeostasis revealed that a 60% mobilization of the total SERCA-dependent intracellular calcium pool was necessary to obtain enhancement of ATRA-dependent differentiation by tBHQ. Moreover, after 3 days of ATRA treatment in combination with tBHQ, NB4 cells showed a significantly decreased calcium mobilization compared with treatments with tBHQ or ATRA alone, suggesting that enhanced differentiation and calcium mobilization are causally related. Interestingly, several ATRA-resistant NB4-derived cell lines were partially responsive to the differentiation-inducing effect of the combination of the 2 drugs. In addition, we found that retinoic acid receptor alpha (RAR alpha) and PML-RAR alpha proteins are protected from ATRA-induced proteolytic degradation by SERCA inhibition, indicating that cellular calcium homeostasis may interact with signaling systems involved in the control of ATRA-dependent transcriptional activity. By linking calcium to ATRA-dependent signaling, our data open new avenues in the understanding of the mechanisms of differentiation-induction therapy of leukemia.

Inhibition of H2 histamine receptor-mediated cation channel opening by protein kinase C in human promyelocytic cells

Histamine, through H(2) receptors, triggers a prominent rise in intracellular free Ca(2+) concentration ([Ca(2+)](i)) in addition to an elevation of cAMP level in HL-60 promyelocytes. Here we show that the histamine-induced [Ca(2+)](i) rise was due to influx of Ca(2+) from the extracellular space, probably through nonselective cation channels, as incubation of the cells with SKF 96365 abolished the histamine-induced [Ca(2+)](i) rise, Na(+) influx, and membrane depolarization. The Ca(2+) influx was specifically inhibited by pretreatment of the cells with PMA or extracellular ATP with 50% inhibitory concentrations of 0.12 +/- 0.03 nM and 185 +/- 17 microM, respectively. Western blot analysis of protein kinase C (PKC) isoforms revealed that PMA (< or =1 nM) and ATP (300 microM) caused selective translocation of PKC-delta to the particulate/membrane fraction. Costimulation of the cells with histamine and SKF 96365 partially reduced histamine-induced granulocytic differentiation, which was evaluated by looking at the extent of fMet-Leu-Phe-induced [Ca(2+)](i) rise and superoxide generation. In conclusion, nonselective cation channels are opened by stimulation of the H(2) receptor, and the channels are at least in part involved in the induction of histamine-mediated differentiation processes. Both effects of histamine were selectively inhibited probably by the delta isoform of PKC in HL-60 cells.

Stimulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) production and its role as an autocrine inducer of CD14 upregulation in human myeloid leukemia cells

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic cytokine that takes part in the growth and differentiation of normal and leukemic hematopoietic cells. Because of its potential significance in the etiopathogenesis of myeloid leukemia, we have studied the extracellular stimuli leading to GM-CSF secretion from a human myeloid leukemia cell line, K-562, and have demonstrated an important role for the cytokine in the differentiation process of this cell line. TNF-alpha, IL-1 beta, phorbol ester (PMA), and calcium ionophore A23187 were found to stimulate GM-CSF production from K-562 cells. PMA caused the cells to differentiate into megakaryocytic lineage, whereas treatment with A23187 resulted in increased expression of monocyte/macrophage marker CD14. Neutralization of the GM-CSF activity in the culture medium, as well as blocking of its receptors, resulted in suppression of the increase in CD14 expression and partially restored the proliferative capacity in cells exposed to A23187. Autocrine GM-CSF secretion did not appear to play an important role in PMA-induced megakaryocytic differentiation. These results suggest that autocrine GM-CSF secretion may be associated with differentiation of myeloid leukemic cells without any significant growth stimulatory activity.

Studies on the role of protein kinases in the TNF-mediated enhancement of murine tumor cell-endothelial cell interactions

We have previously demonstrated that the exposure of mouse microvascular endothelium (MME) to tumor necrosis factor-alpha (TNF) led to the increased binding of mouse mastocytoma cells (P815) to endothelial monolayers (Bereta et al., in press). In the current study we examined the possible involvement of protein kinases in TNF signal transduction in the endothelial cells. PKA does not appear to play a role in the potentiation of binding by TNF. We found that the TNF-generated signal is inhibited by H-7 and sangivamycin, but not by staurosporine. TNF did not cause translocation of PKC to the cell membrane and its effect could not be completely mimicked by PMA nor by PMA in the presence of calcium-raising agents. Thus, we concluded that the "classical" PKC pathway is not completely responsible for TNF signalling in this system. We also found that staurosporine itself strongly enhanced adhesion of tumor cells to endothelium, utilizing a mechanism distinct from that of TNF. Although the data provide evidence for the role of kinases in the effect of TNF on binding of tumor cells to MME, this role appears to be a complex one.

The bistratenes: new cytotoxic marine macrolides which induce some properties indicative of differentiation in HL-60 cells

The biological effects of cytotoxic macrolide polyethers, the bistratenes, isolated from the ascidian Lissoclinum bistratum, have been examined. Bistratene A was toxic to HL-60 human promyelocytic leukemia cells with an IC50 value of 424 nM. At lower concentrations (10-100 nM), bistratene A induced the incomplete differentiation of these cells along the monocyte/macrophage pathway. These effects were not due to inhibition of DNA synthesis. Bistratene B had similar effects to bistratene A. At micromolar concentrations these compounds enhance the phospholipid-dependent activity of type II protein kinase C from bovine spleen. The bistratenes provide new probes for studying the molecular mechanisms governing cell growth and differentiation.

Intranuclear distribution of the human myeloid cell nuclear differentiation antigen in HL-60 cells

Based on solubility properties, the human myeloid cell nuclear differentiation antigen exists as at least two distinct populations. Most is easily extracted from isolated nuclei in 0.35 M NaCl, while 20 percent resists such treatment. Compared to undigested nuclei, both the amount of myeloid cell nuclear differentiation antigen (MNDA) released from nuclei after DNase I treatment and the amount resisting further extraction in 0.35 M NaCl increased after DNA was digested with DNase I. Under these conditions, there was a concomitant decrease in the amount of MNDA that was extractable with 0.35 M NaCl. Mixing nuclear protein extracts that contain MNDA with nuclei from cells that do not express this protein demonstrated that the MNDA redistributes from the freely soluble form to the nuclear residual fraction as a consequence of DNase I digestion. These data are consistent with a model in which the amount of MNDA that is tightly bound to salt-washed nuclei is held constant in the presence of an excess of unassociated MNDA in the nucleus, and that the level of MNDA binding to this nuclear fraction increases in proportion to the extent of DNA damage resulting from DNase I digestion.

Molecular analysis of pleckstrin: the major protein kinase C substrate of platelets

Activation of protein kinase C (PKC) in platelets causes the immediate phosphorylation of pleckstrin, an apparent Mr 40-47,000 protein previously called 40K or P47. Pleckstrin presumably plays an important but as yet unknown role in mediating cellular responses evoked by agonist-induced phosphoinositide turnover. We have cloned the cDNA for pleckstrin from the HL-60 human promyelocytic leukemia cell line by immunological screening of a lambda gt11 expression library (Tyers et al.: Nature 333:470-473, 1988) and now report further analysis of the pleckstrin sequence. Pleckstrin has a deduced Mr of 40,087 and is encoded by a 1,050-bp open reading frame which is preceded by a short open reading frame that terminates before the correct initiator methionine. A single polymorphic site was found in the coding region. An unusual pattern of sequence heterogeneity occurred about a poly(A) tract in the 3' untranslated region. The 3.0-kb pleckstrin mRNA induced upon differentiation of HL-60 cells apparently has heterogeneous 5' ends which undergo differential regulation during HL-60 cell maturation. Analysis by multiple sequence alignment with known PKC substrates identified a strong candidate site for phosphorylation by PKC and a potential Ca2+-binding EF-hand motif. No other similarities to proteins in current databases were found.

Synergistic inhibition of metabolic cooperation by oleic acid or 12-0-tetradecanoylphorbol-13-acetate and dichlorodiphenyltrichlorethane (DDT) in Chinese hamster V79 cells: implication of a role for protein kinase C in the regulation of gap junctional intercellular communication

The effects of TPA and/or DDT and oleic acid and/or DDT on gap junction-mediated intercellular communication (i.e. metabolic cooperation) between Chinese hamster V79 cells was examined. Addition of TPA, DDT or oleic acid alone to cocultures of 6-thioguanine-resistant (6-TGR) and 6-thioguanine-sensitive (6-TGS) V79 cells significantly increased the recovery of 6-TGR cells indicating inhibition of metabolic cooperation. In the presence of TPA and DDT or oleic acid and DDT the observed recovery of 6-TGR cells was significantly greater than the expected (calculated) additive 6-TGR cell recovery. No synergistic increases in 6-TGR cell recovery were observed when co-cultures of V79 cells were exposed to dieldrin and DDT. These results indicate that TPA and DDT or oleic acid and DDT can act synergistically to inhibit metabolic cooperation. These data suggest a role for protein kinase C in the regulation of gap junction-mediated intercellular communication.

Metallothionein RNA levels in HL-60 cells. Effect of cadmium, differentiation, and protein kinase C activation

Metallothionein (MT) gene transcription is regulated in a developmental and tissue-specific manner by metal ions and other agents. We examined MT expression in the human promyelocytic leukemia cell line HL-60 during differentiation along macrophage and neutrophil lineages. All HL-60 phenotypes showed similar basal levels of MT RNA with significant induction following exposure to Cd2+ but not activators of PKC. MT RNA did not correlate with growth state or with known levels of PKC activity, thus our data do not support a role for MT in HL-60 differentiation or for PKC in MT expression.

Immunocytochemical evidence for translocation of protein kinase C in human megakaryoblastic leukemic cells: synergistic effects of Ca2+ and activators of protein kinase C on the plasma membrane association

Immunological analysis using monoclonal antibodies against subspecies of protein kinase C revealed the predominant expression of the isozyme, type II, in human megakaryoblastic leukemic cells. We investigated the effects of phorbol diester 12-O-tetradecanoyl phorbol-13-acetate (TPA), the Ca2+ ionophore ionomycin and synthetic diacylglycerol 1-oleoyl-2-acetylglycerol (OAG) on the immunocytochemical localization of protein kinase C in these cells. Indirect immunofluorescence techniques revealed the enzyme to be located in a diffuse cytosolic pattern, in the intact cells. When the cells were exposed to 100 nM TPA, the immunofluorescent staining was translocated from the cytoplasm to the plasma membrane. The translocation was protracted and staining on the membrane decreased in parallel with the Ca2+, phospholipid-dependent protein kinase activity. Treatment of the cells with 500 nM ionomycin caused an apparent translocation comparable with that seen with TPA, however, this translocation was transient and most of the cytosolic staining was within 60 min. We also found that 30 micrograms/ml OAG did not have significant effects on distribution of the staining, but rather acted synergistically on the translocation with the suboptimal concentration of 100 nM ionomycin. A similar synergism was also observed with 10 nM TPA and 100 nM ionomycin. These results obtained in situ provide evidence that intracellular Ca2+ and diacylglycerol regulate membrane binding of the enzyme in vivo.

Early steps in interferon-gamma production: possible involvement of Ca2+-calmodulin-dependent enzymes

A23187 in combination with phorbol myristate acetate (PMA) strongly induces production of interferon-gamma (IFN-gamma) by human peripheral blood mononuclear cells (PBMC) and even by murine PBMC, which respond poorly to A23187 alone. Macrophage depletion of PBMC strongly reduces IFN-gamma production induced by several mitogens, but does not affect IFN-gamma production induced by A23187 and PMA. In addition the same stimuli are able in combination to induce strong amounts of IFN-gamma, even in the Jurkat T cell line. The protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H-7) and the calmodulin antagonist N-(6-aminoehexyl)-5-chloro-1-naphthalenesulfonamide (W-7) were examined for their ability to inhibit IFN-gamma production induced by PMA and A23187. At concentrations near the Ki for protein kinase C, H-7 failed to inhibit PMA- and A23187-induced IFN-gamma production. In contrast, W-7 at low concentrations inhibited IFN-gamma production induced by the same stimuli. In addition OAG, which is known to directly activate protein kinase C, failed to act synergistically with A23187 in the induction of IFN-gamma. On the basis of these results we propose that A23187 and PMA may mimic the early steps of lymphocyte activation, without the requirement of macrophage, bypassing antigen-, or lectin-induced signal. Our results suggest that Ca2+-calmodulin-dependent reactions other than protein kinase C activation may be essential for IFN-gamma production, at least at level of the producing cells.

Induction of the 47 kDa platelet substrate of protein kinase C during differentiation of HL-60 cells

Immunoblot analysis showed that the 47 kDa platelet substrate of protein kinase C (P47) was expressed at low levels in undifferentiated HL-60 leukaemia cells. Treatment of these cells with dimethyl sulphoxide, 1 alpha,25-dihydroxycholecalciferol or retinoic acid caused progressive increases in P47 content. Retinoic acid (1 microM) elicited the largest response, a 4-fold increase in P47 protein after 7 days that was accompanied by an increase in translatable P47 mRNA. The induction of P47 by retinoic acid preceded cessation of cell proliferation and development of the capacity to reduce Nitro Blue Tetrazolium, indicating that its expression is an early event in the myeloid differentiation of HL-60 cells.

Platelet-derived growth factor. Phorbol ester induces the expression of the B-chain but not of the A-chain in HEL cells

It was shown previously [(1984) EMBO J. 3, 453-459] that after treatment of the human erythroleukemia cell line HEL with phorbol ester and dimethyl sulfoxide there was a marked increase in the amounts of megakaryocytic markers, especially of platelet alpha-granule proteins and platelet glycoproteins. In order to investigate this differentiation process further we have studied the expression of the mRNA encoding PDGF-A and PDGF-B (c-sis). Upon addition of the phorbol ester to the culture medium the expression of the c-sis transcript was enhanced about 7-fold over a period of 4 days. With dimethyl sulfoxide there was no significant stimulation of the expression. Addition of cycloheximide to HEL cells treated for a short period with phorbol ester superinduced the expression of the c-sis gene. The HEL cells did not express the A-chain mRNA even in the presence of phorbol ester or dimethyl sulfoxide. This leads us to propose that synthesis of the PDGF-A chain and PDGF-B chain is differentially regulated in the megakaryocytic-like HEL cell line.