The nature of the endonucleases responsible for DNA fragmentation in apoptosis has not yet been clearly defined. The intracellular acidity has been known to greatly affect apoptosis probably by affecting the activity of the endonucleases. In this study, the implication of pH in the apoptosis was investigated through the use of human HL-60 leukemia cells. The cells were incubated in media with different pH ranging from 3.5 to 7.5 for 4 hrs and the mode of cell death was investigated. The trypan blue exclusion assay showed that close to 25% and 90% of the cells were dead when incubated in pH 6.4 and pH 5.0 media, respectively. The agarose gel electrophoresis of DNA demonstrated that significant DNA fragmentation occurred in the HL-60 cells incubated in the pH 6.2-6.4 media for 4 hr indicating cell death by apoptosis. The electron microscopy study also demonstrated that many of the cells incubated in the pH 6.4 medium were in the process of apoptosis while the cells maintained in the pH 5.0 medium were dying by necrosis. The intracellular pH (pHi) of HL-60 cells was 6.6-6.9 when the extracellular pH (pHe) was 6.2-6.4. These results demonstrated that DNase I which has a maximal endonuclease activity near pH 7.0 may be responsible for the apoptosis accompanied by DNA fragmentation in HL-60 cells in the pH 6.4 medium. This observation is at variance with the previous reports that DNase II mediate the DNA fragmentation in apoptosis. The cell death at extremely low pH (pH 5.0) appeared to be due mainly to necrosis.
*Apoptosis ; DNA Damage ; HL-60 Cells/metabolism/*pathology ; Human ; Hydrogen-Ion Concentration ; Support, Non-U.S. Gov't

OBJECTIVETo study the effect of reactive oxygen species (ROS) during the leukemogenic process associated with exposure to benzene.

METHODSHL-60 was treated with 3 micromol/L benzoquinone (BQ). Generation of ROS in cells was measured by DCFH-DA method. For proliferation assays,cells were stained with alamar blue dye and counted.

RESULTSROS production and the proliferation of cell were all increased in BQ-treated cells (13.10 +/- 0.15, 185% +/- 30.00%) as compared with control cells (11.32 +/- 0.09, 100% +/- 0.00%) (P < 0.05); The addition of catalase just before BQ addition reduced ROS generation to basal levels and decreased the growth of cell (P < 0.05).

CONCLUSIONROS may play an important role in the process of proliferation of HL-60 cells induced by BQ.

Benzoquinones ; toxicity ; Cell Proliferation ; drug effects ; HL-60 Cells ; drug effects ; metabolism ; pathology ; Humans ; Reactive Oxygen Species ; metabolism

To investigate the effect of a microsomal prostaglandin E synthase-1 (mPGES-1) inhibitor MK886 on cell cycle of the human acute myeloid leukemia HL-60 cells. HL-60 cells were treated with different concentration of MK886 (10, 25, 50 µmol/L) for 24 h. Flow cytometry, Western blot and ELISA were used to measure cell cycle, cyclin D1, mPGES-1, PGE(2), Akt, P-Akt and C-MYC. The results indicated that after treated with MK886, the percentage of HL-60 cells decreased in G(0)/G(1) phase and increased in S phase, and expressions of mPGES-1, cyclin D1, P-Akt and C-MYC and synthesis of PGE(2) decreased significantly. It is concluded that MK886 can arrest HL-60 cells in G(0)/G(1) phase, the mechanism of which is possibly associated to inhibition of mPGES-1 expression, reduction of PGE(2) synthesis, suppression of Akt phosphorylation and C-MYC expression, down-regulation of cyclin D1 expression.
Cell Cycle ; drug effects ; HL-60 Cells ; Humans ; Indoles ; pharmacology ; Intramolecular Oxidoreductases ; antagonists & inhibitors ; Leukemia ; metabolism ; pathology ; Prostaglandin-E Synthases

The purpose of this study was to investigate the expression feature of a human tumor related gene chp2 in leukemia primary cells and leukemia cell lines, real-time quantitative PCR (RQ-PCR) was performed to detect the expression level of chp2 gene in peripheral blood mononuclear cells from 10 healthy individuals (as control) and 24 cases of leukemia, and in 4 kinds of leukemia cell lines. The results showed that the detection rate of chp2 gene in 10 normal controls was 80%, positive expression was (0.744 +/- 0.682) x 10(5) cps/microl. The expression levels of chp2 mRNA leukemia primary cells and leukemia cell lines were significantly higher than that in the normal control (p < 0.05). The expression levels of chp2 mRNA were higher in AML cells (7 cases), CML cells (6 cases), ALL cells (7 cases) and CLL cells (4 cases), and their expression levels were (11.637 +/- 5.588), (6.122 +/- 3.785), (4.262 +/- 2.561) and (3.434 +/- 1.974) x 10(5) cps/microl respectively. Gene chp2 positively expressed in four kinds of leukemia cell lines, and the expression levels in K562 cells, Jurkat cells, HL-60 cells and M07e cells were (5.243 +/- 1.852), (4.463 +/- 1.621), (4.137 +/- 1.837) and (2.578 +/- 1.137) x 10(6) cps/microl respectively. The expression level in leukemia cell lines was higher than that in primary cells. It is concluded that the human tumor related gene chp2 expression in leukemia primary cells and leukemia cell lines significantly increase, which may play an important role in growth process of leukemia cells.
Calcium-Binding Proteins ; genetics ; metabolism ; HL-60 Cells ; Humans ; Jurkat Cells ; K562 Cells ; Leukemia ; genetics ; metabolism ; pathology ; Neoplasm Proteins ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism

In order to establish a new more rapid, safe and sensitive colorimetric assay for the proliferation of leukemic cells, MTS/pms has been developed. This automated colorimetric assay is based on the characteristic of viable and metabolically active leukemic cells to cleave MTS/pms into a water-soluble product whose optical density is determined at 492 nm by an automated microtiter-plate reader photometer. The results indicated that only active leukemic cells cleaved MTS/pms into product measured, and dead cells did not reduce MTS/pms. A linear relations hip were found between the viable cell number and optical density of MTS/pms cleaved by HL-60 and K562 cell (r = 0.963). Compared with MTT and INT assays, the reduced product of MTS/pms is water-soluble. It is concluded that MTS/pms colorimetric assay is more rapid, accurate and sensitive for the bioassay of proliferation of leukemic cells.
Cell Division ; Colorimetry ; methods ; Formazans ; metabolism ; HL-60 Cells ; Humans ; K562 Cells ; Leukemia ; pathology ; Methylphenazonium Methosulfate ; metabolism ; Tetrazolium Salts ; metabolism ; Thiazoles ; metabolism

OBJECTIVETo explore ZO-1 gene expression and methylation in leukemia cells and the involvement of ZO-1 gene in leukemogenesis.

METHODSRestriction landmark genomic scanning (RLGS) was used to identify new leukemia related gene, and methylation specific PCR (MSP) for ZO-1 methylation status. ZO-1 specific siRNA was designed and prepared by in vitro transcription and transfected into K562 cells, the transfected cells were cultured for 48 hours before harvesting. The effect of ZO-1 siRNA was monitored by Northern blot. Cellular proliferation capacity was assayed by CCK-8, cell apoptosis by Annexin V-fluorescence in isothiocyanate (FITC) assay, and cell cycle by phosphatidylinositol (PI).

RESULTSThe intensified spots in RLGS gel were subjected to bioinformatics analysis and one of the candidate spots was proved to be ZO-1 gene. In fresh leukemia cells, Molt4 cells and HL-60 cells, ZO-1 was hypermethylated, causing it reduced or silenced. ZO-1 gene was highly expressed with no methylation in normal peripheral blood MNC and K562 cells. There was a good correlation between promoter methylation and the gene silence. The silenced gene can be re-activated by demethylation treatment with 5-AZA-dC in most leukemia cell lines. RNA interference for ZO-1 gene in K562 cells did not interfere with cell proliferation, cell cycle and apoptosis.

CONCLUSIONZO-1 gene methylation might be involved in the tumorigenesis of acute leukemia.

Animals ; DNA Methylation ; HL-60 Cells ; Humans ; K562 Cells ; Leukemia ; genetics ; pathology ; Membrane Proteins ; genetics ; metabolism ; Mice ; Phosphoproteins ; genetics ; metabolism ; Zonula Occludens-1 Protein

OBJECTIVETo investigate miR-181a function and regulation mechanism by identifying miR-181a target genes in acute myeloid leukemia (AML).

METHODSThe HL-60 cells of human AML was transfected by small molecular analog miR-181a, the cell proliferation was detected by CCK-8 method after electroporation in HL-60 cell lines. Target genes of miR-181a were predicted and analyzed by the bioinformatics software and database. Target genes were confirmed by HL-60 cell line and the patient leukemia cells.

RESULTSOverexpressed miR-181a in HL-60 cell line significantly enhanced cell proliferation compared with that in control (P < 0.05). Dual luciferase reporter gene assay showed that miR-181a significantly suppressed the reporter gene activity containing ATM 3'-UTR by about 56.8% (P < 0.05), but it didn't suppress the reporter gene activity containing 3'-UTR ATM mutation. Western blot showed that miR-181a significantly downregulated the expression of ATM in human leukemia cells. It is also found that miR-181a was significantly increased in AML, which showed a negative correlation with ATM expression.

CONCLUSIONmiR-181a promotes cell proliferation in AML by regulating the tumor suppressor ATM, thus it plays the role as oncogene in pathogenesis of AML.

Ataxia Telangiectasia Mutated Proteins ; metabolism ; Cell Proliferation ; Down-Regulation ; HL-60 Cells ; Humans ; Leukemia, Myeloid, Acute ; metabolism ; pathology ; MicroRNAs ; genetics ; metabolism ; Transfection

OBJECTIVETo study the effect of glycyrrhetinic acid (GA) on the invasive capacity of leukemic cells and the activity of intracellular gelatinase.

METHODSThe effect of GA, in different concentrations, on the proliferation of cultured K562 and HL-60 leukemic cells in vitro was determined by MTT assay; that on cell invasive capacity was tested by Transwell cubicle matrigel invasion assay; and that on the activity of gelatinase in cells was detected by gelatin zymography.

RESULTSGA showed significant inhibitory effect on the proliferation of K562 and HL-60 leukemic cells; it inhibited the invasive capacity of cells in concentration-dependent manner; and significantly down-regulated the activity of gelatinase A and B in cells.

CONCLUSIONSGA can inhibit invasive capacity of K562 and HL-60 leukemia cells by way of suppressing the activity of gelatinase A and B. This study provides an experimental evidence for preventing extra-medullary infiltration of leukemic cells.

Cell Proliferation ; drug effects ; Down-Regulation ; Gelatinases ; metabolism ; Glycyrrhetinic Acid ; pharmacology ; HL-60 Cells ; Humans ; K562 Cells ; Leukemia ; drug therapy ; enzymology ; pathology ; physiopathology ; Neoplasm Invasiveness

Tanshinone II-A is a derivative of phenanthrene-quinone isolated from Salvia miltiorrhiza BUNGE, a traditional herbal medicine that is known to induce antiinflammatory, anti-oxidative and cytotoxic activity. We have examined cellular effects of Tanshione II-A on HL60 human promyelocytic leukemic cells and K562 human erythroleukemic cells. Tanshione II-A induced a dose- and time-dependent DNA fragmentation into the multiples of 180 bp and specific proteolytic cleavage of poly(ADP-ribose) polymerase in both cell lines. PI-staining and flow cytometry analysis of K562 cells following Tanshione II-A treatment showed an increase of the cells possessing hypodiploid DNA indicative of apoptotic state of cells. Caspase-3 activity was significantly increased during Tanshinone II-A treatment of both HL60 and K562 cells, whereas caspase-1 activity was not changed. These results suggest that Tanshione II-A induced HL60 and K562 cellular apoptosis that may be associated with the selective members of caspase family. Copyright 2000 Academic Press.
Antineoplastic Agents, Phytogenic/pharmacology* ; Antineoplastic Agents, Phytogenic/chemistry ; Apoptosis/physiology* ; Caspases/metabolism* ; Caspases/drug effects* ; Cell Cycle/drug effects ; DNA Fragmentation/drug effects ; Dose-Response Relationship, Drug ; Drugs, Chinese Herbal/pharmacology* ; Drugs, Chinese Herbal/chemistry ; Enzyme Activation/drug effects ; HL-60 Cells/pathology ; HL-60 Cells/metabolism ; HL-60 Cells/drug effects ; Human ; Lamiaceae/chemistry ; Leukemia/pathology* ; Leukemia/metabolism ; Leukemia/drug therapy ; Leukemia, Erythroblastic, Acute/pathology ; Leukemia, Erythroblastic, Acute/metabolism ; Leukemia, Erythroblastic, Acute/drug therapy ; Phenanthrenes/pharmacology* ; Phenanthrenes/chemistry ; Tumor Cells, Cultured

The objective of study was to explore the role of vascular endothelial growth factor (VEGF) and its receptor-2 in pathogenesis of acute myeloid leukemia. The acute myeloid leukemia model was established on 20 mice with severe combined immunodeficiency (SCID) transplanted by HL-60 cells. The mice were divided into the normal control and test group randomly. The expression of VEGF was detected by enzyme linked immunosorbent assay (ELISA). The expression of VEGFR-2 mRNA was detected by RT-PCR. The results showed that the establishment of acute myeloid leukemia model was succeeded on all SCID mice by HL-60 cell transplantation. The expressions of VEGF and VEGFR-2 mRNAs could be determined on all mice. As compared with the normal control group, the expressions of VEGF and VEGFR-2 mRNAs in the test group significantly increased, but gradually increased during the course of disease. It is concluded that the abnormal expressions of VEGF and VEGFR-2 exist in mice with acute myeloid leukemia, which may be involved in the pathogenesis of AML.
Animals ; Bone Marrow ; pathology ; HL-60 Cells ; Humans ; Mice ; Mice, SCID ; Neoplasm Transplantation ; Vascular Endothelial Growth Factor A ; metabolism ; Vascular Endothelial Growth Factor Receptor-2 ; metabolism