l-663536 and Leukemia--Myelogenous--Chronic--BCR-ABL-Positive

Micromolar MK886, a selective inhibitor of 5-lipoxygenase at nanomolar concentration, induces physiologic cell death in U937 and chronic myelogenous leukemia blast cells. When U937 cells were challenged with 10 microM MK886, an acute, biphasic and sustained rise in intracellular Ca2+ occurred, as determined with Fura-2. The initial increase was followed by a transient decline and a larger rise due to an influx of external Ca2+. The first increase and part of the subsequent rise also developed in Ca(2+)-free medium, identifying their origin from intracellular stores. The intracellular Ca2+ concentration of U937 cells that remained after culture for 24 or 48 h with 5 or 10 microM MK886 was not reliably altered from the control values of 130 +/- 8.3 nM. Under similar conditions MK886 did not increase cytosol Ca2+ of a human prostate (PC3) cell line examined in suspension. The increase in intracellular Ca2+ in response to MK886 in calcium-containing medium was confirmed with an ACAS laser spectrometer. U937 cytosol pH was measured with the fluorescent probe BCECF, but not persistent acute or chronic change was induced by MK886. The rapid and sustained rise in Ca2+ induced by MK886 is an early event in U937 cells which subsequently undergo physiologic cell death characterized in many by apoptosis.

Topics: Amiloride; Apoptosis; Calcium; Cell Survival; DNA; Fluoresceins; Fura-2; Humans; Hydrogen-Ion Concentration; Indoles; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Lipoxygenase Inhibitors; Male; Prostate; Trypsin; Tumor Cells, Cultured

Inhibitors of the arachidonic acid metabolizing enzyme, 5-lipoxygenase, reduce the rate of proliferation of chronic myelogenous leukemia blast cells. The inhibitory agents studied were ETYA, A63162 and SC41661A. These reagents induced differentiation of cultured chronic myelogenous leukemia cells from blast to promyelocytic morphology. Promyelocytic cells then underwent apoptosis, which was identified by nuclear and cytoplasmic morphological features and by DNA laddering. Proliferation of monoblastoid U937 and myelomonocytic HL60 cell lines, known to contain 5-lipoxygenase and synthesize leukotrienes, was reduced by these inhibitors. U937 cells cultured with ETYA, A63162 or SC41661A for 48 h exhibited apoptosis as assessed by DNA laddering and morphology. Characteristic ultrastructural changes of apoptosis were seen at 120 h. MK886, an inhibitor of 5-lipoxygenase with a mechanism of action distinct from oxidation/reduction reagents, at 20-40 microM also inhibited CML and U937 cell proliferation and induced apoptosis, as shown by DNA laddering and ultrastructure.

Topics: 5,8,11,14-Eicosatetraynoic Acid; Acetamides; Amides; Antineoplastic Agents; Apoptosis; Blast Crisis; Cell Differentiation; Cell Division; DNA, Neoplasm; Humans; Indoles; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Lipoxygenase Inhibitors; Phenyl Ethers; Pyridines; Tumor Cells, Cultured

The proliferation of malignant hemopoietic cell lines is inhibited by antagonists of 5-lipoxygenase, suggesting that the endogenous generation of leukotrienes via the action of this enzyme may play some role in the proliferation of these cells (Snyder D. S., Castro R. & Desforges J. F. (1989), Expl Hemat. 17, 6). Here we have confirmed that the lipoxygenase inhibitors piriprost, nordihydroguiaretic acid and BW755C decreased DNA synthesis and proliferation of leukemic cell lines. However, the concentrations of these drugs required for half-maximal inhibition of proliferation were significantly greater than their IC50 values for 5-lipoxygenase inhibition. We therefore studied the actions of two novel, potent lipoxygenase inhibitors, BWA4C and MK886, on proliferation (as measured by estimating the number of viable, trypan blue-excluding cells) and DNA synthesis (measured by the incorporation of radiolabeled thymidine) in the leukemia cell lines HL60, K562 and Jurkat. Neither parameter was affected by concentrations of these drugs which were shown in parallel studies to substantially inhibit leukotriene generation in whole blood. The data show that endogenous leukotriene generation does not play a significant role in the regulation of proliferation of these leukemic cell lines and suggest that conclusions about leukotriene involvement in the control of cellular metabolic pathways based on the use of lipoxygenase inhibitors should be re-assessed.

Topics: 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; Benzeneacetamides; Blast Crisis; Burkitt Lymphoma; Cell Division; Epoprostenol; Hematopoietic System; Humans; Hydroxamic Acids; Indoles; Leukemia; Leukemia-Lymphoma, Adult T-Cell; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Leukemia, Promyelocytic, Acute; Leukotriene Antagonists; Leukotrienes; Lipoxygenase Inhibitors; Masoprocol; Tumor Cells, Cultured