Expression and induction of cathepsins B and D in K562 cells

Three distinct lysosomal protease activities have been identified in the human leukemia cell line, K562. These include cathepsin D, the classic protease of the mature red blood cell, as well as two proteases, cathepsins B and H, which have been associated with development and differentiation in a variety of tissues. Each of these three lysosomal proteases was expressed in a specific fashion during hemoglobin induction in K562 cells. Both cathepsin B and cathepsin D activities could be induced by growth of K562 cells in medium containing either hemin or heat-treated serum or by increasing the concentrations of untreated serum in the medium. Cathepsin H activity in the same cells remained unchanged. This is the first report of inducible protease activities in K562 cells. Our identification of specific well-characterized protease activities that change differentially during K562 induction provides a framework for additional studies on the role of proteases in hematopoietic differentiation.     

Induction of B-lymphocyte antigens on the chronic myeloid leukemic cell line K562 using sodium butyrate

Chronic myeloid leukemia (CML) is a disorder arising from a defect in the hemopoietic stem cell. Consequently, the malignant clone can involve all cells within the stem cell's capacity for differentiation, including erythrocytes, granulocytes, monocytes, megakaryocytes, and lymphocytes. Similarly, the K562 cell line, which was derived from a patient with CML, has been shown to be capable of differentiation towards erythrocytes, granulocytes, monocytes, and megakaryocytes, and in this respect may represent a model of the hemopoietic stem cell. However, although K562 shows properties of a myeloid stem cell, no lymphocyte-specific features or differentiation have yet been described. In the present study, K562 cells have been induced to differentiate by culture in the presence of sodium butyrate. The direction and extent of induced differentiation over 12 days were determined with a panel of monoclonal antibodies and with cytochemical stains. This treatment consistently induced expression of pre-B-cell markers, including B-lymphocyte-specific B4 and B1, and of the common acute lymphoblastic leukemia antigen (CALLA), recognized by J5. In addition to the increased expression of B-lymphocyte markers, butyrate induction of K562 resulted in a decrease in granulocyte markers, increases in certain monocyte and platelet markers, and an increase in beta 2 microglobulin expression. Butyrate-induced expression of B-lymphocyte markers was not observed with the myelomonocytic cell line U937. The expression of B-lymphocyte-specific antigens on butyrate-induced K562 may result from the relaxed control of gene expression, but alternatively these observations may indicate the lymphoid-myeloid stem cell nature of K562.     

Amplified C lambda and c-abl genes are on the same marker chromosome in K562 leukemia cells.

The human leukemia cell line K562, derived from a patient with Philadelphia chromosome-positive chronic myelogenous leukemia, contains amplified c-abl oncogenes and unrearranged C lambda genes. Using in situ hybridization techniques, we have determined that the amplified c-abl and C lambda DNA sequences of K562 cells are both located on the same abnormal acrocentric marker chromosome, which may represent an altered Philadelphia chromosome.     

HC56基因转染对淋巴瘤或白血病细胞株活力的作用

目的：探讨外源HC56基因产物对B淋巴瘤细胞株Raji和髓系白血病细胞株K562细胞活力的作用。方法：应用脂质体介导的基因转染方法，将外源基因HC56分别导入Raji和K562细胞，用苔盼兰拒染试验，观察外源基因的瞬时表达对细胞活力的作用。结果：Raji和K562细胞转染HC56基因后，与转染PBK／CMV空载体的实验对照组比较，细胞的活力明显受到抑制(P＜0.05)。结论：外源HC56基因产物可明显抑制淋巴瘤或白血病细胞株的活力。     

Proteasome inhibitor bortezomib overcomes P-gp-mediated multidrug resistance in resistant leukemic cell lines

Introduction: To study the effect of bortezomib alone or in combination with daunorubicin (DNR) on an mdr1 single‐factor drug‐resistant leukemia cell line K562/MDR1, a multifactor‐resistant cell line K562/A02, a drug‐sensitive cell line K562, and primary cells from acute myeloid leukemia patients. Methods: The cell lines were exposed to bortezomib, DNR, and bortezomib plus DNR, and cell proliferation, cell cycle, apoptosis rate, and expression of MDR1/BCL2 were analyzed. Results: Bortezomib potently inhibited growth and increased the apoptosis rate in the cell lines. In K562/MDR1 and K562/A02, the calcium channel blocker verapamil reduced the 50% inhibitory concentration and apoptosis rate of DNR, a P‐gp protein substrate, but not of bortezomib. Bortezomib plus DNR had synergistic effect on antiproliferation (synergistic ratio > 1). Apoptosis was substantially more increased by the combination of two drugs than by bortezomib alone. Bortezomib arrested the cell cycles of three cell lines at the G2/M stage, decreased BCL2 mRNA expression, but did not affect MDR1 mRNA levels. The antiproliferative role of bortezomib was also confirmed in primary leukemia cells. Conclusion: Bortezomib is a promising potential therapy for acute leukemia, especially mdr1 drug‐resistant leukemia.     

Dup-697, a specific COX-2 inhibitor,suppresses growth and induces apoptosis on K562 leukemia cells by cell-cycle arrest and caspase-8 activation

This investigation was designed to assess the effect of DuP-697 on growth and apoptosis in a human chronic myeloid leukemia (CML) cell line (K562 cells) and primary CML cells from CML patient bone marrow. DuP-697 significantly suppressed K562 cells and primary CML cells growth and induced apoptosis in a concentration-dependent manner and the growth-inhibiting effect was independent on Philadelphia chromosome. The IC50 of DuP-697 at 36 h was 31.7 μM. It arrested G1-S phase transmit on cell cycle and its apoptosis activity was partially abrogated by pretreating K562 cells with Z-IETD-fmk, a specific inhibitor of caspase-8. This study suggested that Dup-697 suppresses growth and induces apoptosis on K562 leukemia cells by cell-cycle arrest and caspase-8 activation.     

白血病细胞系WT1的表达及反义核苷酸对其的抑制作用

目的:探讨RT-PCR方法测定白血病细胞系WT1基因的表达以及WT1反义寡核苷酸对白血病细胞系增殖的抑制作用。方法:应用RT-PCR方法测定K562、HL-60、TF-1及U937 4株白血病细胞系WT1基因的表达,然后应用针对WT1翻译起始位点的反义寡核苷酸(WT1 ASO)处理K562细胞系、U937细胞系,采用锥虫蓝拒染法确定白血病细胞的增殖。结果:K562、HL-60及TF-1 3株白血病细胞系均高度表达WT1,而U937细胞系未测到WT1。WT1 ASO能够抑制WT1表达阳性的K562细胞的生长,对WT1表达阴性的U937则无抑制作用;而WT1有义寡核苷酸对K562细胞系、U937细胞系均无抑制作用。结论:RT-PCR测定方法可以检测WT1基因在白血病细胞系表达,WT1反义寡核苷酸对白血病细胞有特异的抑制作用。WT1基因在白血病细胞增殖过程中起一定作用。     

The role of folates in the development of methotrexate resistance in human leukemia cell line K562

The effect of reduced and oxidized folates on the development of methotrexate (MTX) resistance has been examined in human leukemia cell line K562 (K562/S). K562/S cells were made resistant to MTX by soft-agar cloning either in RPMI-1640 medium (K562/MTX-PGA) or in folic-acid-free RPMI-1640 medium containing 10 nM leucovorin (K562/MTX-LV). The optimal concentrations of leucovorin for the growth of K562/S, K562/MTX-PGA and K562/MTX-LV cells were 1 nM, 5 nM and 10 nM respectively. K562/MTX-PGA cells were 24-fold resistant to MTX as noted by impaired MTX transport. In contrast, K562/MTX-LV cells were 26-fold resistant to MTX as noted by gene amplification of dihydrofolate reductase. Furthermore cross-resistance to cytosine arabinoside was only demonstrated in K562/MTX-PGA, while the K562/MTX-LV cells showed no significant cross-resistance to cytosine arabinoside. These results suggest that the type and level of folates used during the development of MTX resistance may play a role in the mechanism for MTX resistance. Leukemia cells that are grown in leucovorin might serve as a model for acquired MTX resistance in vivo.     

Induction of erythropoietic colonies in a human chronic myelogenous leukemia cell line.

The ability of cells derived from the K562 cell line to generate erythropoietic colonies was studied. The K562 cell line was derived from a patient with chronic myelogenous leukemia 8 yr ago by Lozzio and Lozzio. Rare benzidine-positive colonies formed when these cells were cloned in plasma clots (3 +/- 1/10(4) cells), and their number was not substantially increased by the addition of erythropoietin (9.5 +/- 1/10(4) cells). Sodium butyrate was capable of markedly enhancing the number of benzidine-positive colonies (19.5 +/- 1/10(4) cells) formed, while the combination of sodium butyrate plus erythropoietin exerted a synergistic effect on erythropoietic colony formation (57 +/- 4/10(4) cells). The K562 cell line is a long-term culture system that contains human erythropoietic stem cells. This cell line should be useful in future studies on the cellular and molecular events associated with human erythroid cell differentiation.     

白血病细胞色素P4503A亚家族多肽5与耐药的相关研究

目的　探讨细胞色素P4 5 0 3A亚家族多肽 5 (CYP3A5 )与白血病耐药是否相关。方法逆转录 PCR、免疫组化、高压液相色谱法检测白血病细胞系CYP3A5基因的转录、表达及活性 ,四氮唑蓝法检测细胞系对柔红霉素 (DNR)IC50 值、流式细胞仪 (FCM )检测细胞周期及DNR诱导凋亡能力。结果　K5 6 2、U937、HL 6 0、NB4、Jurkat 5种细胞株仅K5 6 2、U937细胞转录CYP3A5基因。 5种细胞株对DNR敏感性 (IC50 ,mg/L)依次为NB4 (0 0 6 8± 0 0 36 ) >Jurkat(0 0 76± 0 0 13) >HL 6 0(0 0 92± 0 0 16 ) >K5 6 2 (0 14 8± 0 0 4 1) >U937(0 15 0± 0 0 35 ) ,K5 6 2、U937细胞与NB4、Jurkat、HL 6 0细胞相比 ,对DNR显著耐受 (P <0 0 1)。K5 6 2与NB4细胞相比 ,前者表达CYP3A5蛋白 ,并具有显著高的CYP3A5活性 (3 0 75± 0 0 36 )× 10 -3 、(1 6 35± 0 196 )× 10 -3 ,P <0 0 5。FCM显示K5 6 2与NB4细胞二者S期比例相近 ,经 1mg/LDNR诱导 6h后NB4细胞出现明显的凋亡峰 (凋亡比 18 4 % ) ,而K5 6 2细胞则无 (凋亡比 0 8% )。结论　CYP3A5基因的转录、表达及活性与白血病耐药相关。     

Cyclosporin A induces erythroid differentiation of K562 cells through p38 MAPK and ERK pathways

We studied the effects of cyclosporin A (CsA) on the erythroid differentiation of human erythroid leukemia cell line K562. After K562 was treated with CsA for 4 days, the percentage of hemoglobinized cells was increased by 3.3 times. Because it was reported p38 MAPK (p38) and ERK are involved in erythropoietin-induced erythroid differentiation, we studied their roles using specific inhibitors. p38 inhibitor (SB203580) prevented CsA-induced hemoglobin synthesis in K562 cells, although MEK/ERK inhibitor (U0126) enhanced it by 3.3 times in K562 cells. These results indicate activation of p38 and inactivation of ERK are involved in CsA-induced erythroid differentiation of K562 cells.     

Anti-K562 cell monoclonal antibodies recognize hematopoietic progenitors.

The K562 leukemia cell has properties of self-renewal and pluripotency similar to those of the hematopoietic stem cell. Monoclonal antibodies to K562 cells have been produced by using hybridoma technology. By radioimmunoassay, some anti-K562 cell antibodies also bind to erythrocyte antigens or peripheral blood mononuclear cells; others are more specific for K562 cells. Antibody binding to hematopoietic progenitors was assayed by using the ability of these cells to form colonies in vitro. After exposure of human bone marrow cells to anti-K562 antibodies and complement, myeloid or erythroid colony formation was inhibited. Some of the inhibitory antibodies showed little binding to mature blood cells by radioimmunoassay, immunofluorescence, and complement cytotoxicity, suggesting that they recognize antigens specific to undifferentiated cells. With the fluorescence-activated cell sorter, one inhibitory antibody was shown to stain only 3% of bone marrow cells. Inhibitory anti-K562 antibodies also bind to myelogenous leukemia cells and virus-transformed lymphocytes. Thus, these antibodies appear to recognize antigens shared by normal hematopoietic progenitors, leukemic cells, and transformed lymphocytes.     

Doxorubicin induces the DNA damage response in cultured human mesenchymal stem cells

Anthracyclines, including doxorubicin, are widely used in the treatment of leukemia. While the effects of doxorubicin on hematopoietic cells have been characterized, less is known about the response of human mesenchymal stem cells (hMSCs) in the bone marrow stroma to anthracyclines. We characterized the effect of doxorubicin on key DNA damage responses in hMSCs, and compared doxorubicin sensitivity and DNA damage response activation between isolated hMSCs and the chronic myelogenous leukemia cell line, K562. Phosphorylation of H2AX, Chk1, and RPA2 was more strongly activated in K562 cells than in hMSCs, at equivalent doses of doxorubicin. hMSCs were relatively resistant to doxorubicin such that, following exposure to 15???M doxorubicin, the level of cleaved caspase-3 detected by western blotting was lower in hMSCs compared to K562 cells. Flow cytometric analysis of cell cycle progression demonstrated that exposure to doxorubicin induced G2/M phase arrest in hMSCs, while 48?h after exposure, 15.6?% of cells were apoptotic, as determined from the percentage of cells having sub-G1 DNA content. We also show that the doxorubicin sensitivity of hMSCs isolated from a healthy donor was comparable to that of hMSCs isolated from a chronic lymphocytic leukemia patient. Overall, our results demonstrate that high doses of doxorubicin induce the DNA damage response in hMSCs, and that cultured hMSCs are relatively resistant to doxorubicin.     

Increased sensitivity of myeloid leukemia cell lines: potential of lovastatin as bone-marrow-purging agent

Lovastatin reduces the isoprenylation of p21ras via suppression of mevalonic acid generation. Lovastatin has been shown to reduce tumor cell proliferation in a dose-dependent manner. Here, the potential of lovastatin for purging leukemia cells from bone marrow was investigated using the myeloblastic cell lines K562 and KG-1 as a model system, derived from an erythroleukemia and an acute myelogenous leukemia, respectively. Optimal purging conditions were determined using an MTT proliferation and a leukemia colony assay. Elimination of leukemia cells was time- and dose-dependent. Depletion of K562 was 2.5 logs for 100 microM of lovastatin at 72 h of incubation. Compared to another purging agent, 100 microg/ml mafosfamide had an activity comparable to 100 mM lovastatin. Interestingly, KG-1 acute myelogenous leukemia cells were even more sensitive to lovastatin than K562 cells. In clonogenic assays, 100 microM of lovastatin resulted in a 3- to 4-log reduction of K562 colonies. Lovastatin had a progressive effect on normal hematopoietic progenitor cells. At a concentration of 100 microM of lovastatin, CFU-GM colonies were reduced by 1-2 logs. In conclusion, a differential effect on leukemia and normal progenitor cells could be detected in a clonogenic assay. These results suggest that lovastatin deserves further study as an agent for ex vivo marrow purging.     

Antibodies to myeloid precursor cells in autoimmune neutropenia

Antibodies to mature blood neutrophils and to bone marrow myeloid cells have been described in the sera of some patients with apparent autoimmune neutropenia. To further explore the prevalence and specificities of antibodies to myeloid precursor cells, we evaluated sera from 148 patients with suspected autoimmune neutropenia for the presence of antibodies to neutrophils, to cultured myeloid cell lines, and to highly purified bone marrow myeloid progenitor cells. Using an immunofluorescence flow cytometric assay, we identified IgG antibodies in 42 (28%) of these sera that bound specifically to K562 cells, a multilineage cell line originally derived from a patient with chronic myelogenous leukemia. Twenty-two (15%) of the sera also contained IgG antibodies that bound specifically to the primitive myelomonocytic leukemia cell line KG1a. Twenty-five (17%) of the sera had IgG antibodies to myeloid cell lines in the absence of antibodies to mature neutrophils. There was a trend toward more severe neutropenia in patients with antibodies to K562 cells, without antineutrophil antibodies. In further studies, antibodies from 12 sera bound to mononuclear CD34+ cells that had been purified from normal human bone marrow by an immunomagnetic separation procedure. Moreover, two of these sera suppressed the growth of granulocyte-macrophage colony- forming units (CFU-GM) in methylcellulose cultures. The presence of antibodies to primitive hematopoietic cells in the sera of some patients with suspected immune neutropenia suggests that these antibodies may have a role in the pathogenesis of the neutropenia observed.     

Establishment of an Arsenic Trioxide—Resistant Human Leukemia Cell Line That Shows Multidrug Resistance

We have established an arsenic trioxide (As2O3)-resistant cell line (K562/AS-3) derived from the human leukemia cell line K562. K562/AS-3 was sequentially cultured with increasing concentrations of As2O3 up to 3.5 microM and then cloned by the limiting dilution method. K562/AS-3 was found to be about 7-fold more resistant to As2O3 than the parent cells (IC50=12.9 microM for K562/AS-3 and 1.8 microM for K562), and also showed cross resistance to VP-16 and vincristine. The multidrug resistance-associated protein (MRP1) gene was found to be overexpressed, but the MDR gene was not detected. MRP1 function was evaluated by measuring calcein acetoxymethyl ester (calcein-AM) efflux, and by verifying its inhibition by MK571, a potent MRP inhibitor. In addition, an increase of the total intracellular glutathione content was found in K562/AS-3. The resistance of K562/AS-3 to As2O3 was reversed by the addition of MK571, but not by verapamil. K562/AS-3 may be useful for studying the mechanism of the anticancer effect of As2O3 and how to overcome As2O3-resistance.     

Transfected leukocyte integrin CD11b/CD18 (Mac-1) mediates phorbol ester-activated, homotypic cell:cell adherence in the K562 cell line

The CD11b/CD18 leukocyte integrin molecule mediates diverse neutrophil adherence-related functions, including cell:cell and cell:extracellular matrix attachments. To study the individual role of this leukocyte integrin in cell adherence in hematopoietic cells, we expressed the CD11b/CD18 complex on the surface of K562 cells, a cell line derived from an individual with chronic myelogenous leukemia in blast crisis. We used an amphotrophic retroviral vector designated LCD18SN, harboring the complete coding sequence for the CD18 subunit, to transfer the CD18 cDNA into K562 cells and select stable cell lines. The CD11b subunit in the expression plasmid pREP4 was transfected into these K562/CD18 cells by electroporation and stable cell clones were selected. These K562 cells possessed RNA and intracellular protein for each subunit, and they expressed the CD11b/CD18 heterodimer on the cell surface. When CD11b/CD18 expressing K562 cells were stimulated with phorbol myristate acetate (50 ng/mL) for 24 to 48 hours, these K562 cells formed dense cell:cell aggregates. This homotypic aggregation required both activation of the CD11b/CD18 complex and the induction of the counter- receptor for CD11b/CD18 on the conjugate cell. This cell line will (1) enable the structure-function relationships between cell activation and homotypic adherence to be assessed, (2) provide the opportunity to identify accessory molecules required for activation of the CD11b/CD18 complex, and (3) facilitate the identification of novel ligands for the CD11b/CD18 complex.     

Monoclonal antibodies against the human leukemia cell line K 562

Three monoclonal antibodies raised against K 562, a cell line originally established from a patient with chronic myeloid leukemia (CML) in terminal blast crisis, were selected according to their distinct reaction pattern. Whereas two antibodies (ZIK-C1-A/C5 and ZIK-C1-A/H5 also designated C and H) recognized antigens, present on K 562 cells and other immature and mature hematopoietic cells (cell lines and normal blood and bone marrow cells), antibody ZIK-C1-A/D9 also designated Y showed an exclusive binding to K 562 cells. The results obtained (here and in the following paper) indicate, that antibody ZIK-C1-A/D9 defines an early differentiation antigen of hematopoiesis or a leukemia-associated antigen.