Arsenic Trioxide Enhances STI571-Induced Apoptosis of K562 Cells through Downregulating Bcl-XL and Bcr-Abl.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4449-4449
Author(s):  
Ri Zhang ◽  
Xuhui Zhang ◽  
YaJun Zhi ◽  
ZiLing Zhu ◽  
De Pei Wu
Keyword(s):  
Cytochrome C ◽  
Cell Line ◽  
Arsenic Trioxide ◽  
Drug Administration ◽  
Caspase 3 ◽  
K562 Cells ◽  
Myelogenous Leukemia ◽  
Mrna Levels ◽  
Down Regulation ◽  
Induced Apoptosis

Abstract We aimed to evaluate the effects of arsenic trioxide (ATO, Trisenox) on STI571 (Gleevec, imatinib mesylate)-induced apoptosis of a chronic myelogenous leukemia (CML) cell line, K562 cells. Cell prolifration and colony-forming assays were performed to determine the cytotoxicity of ATO alone and in combination with STI571. Apoptosis was analyzed by morphological changes, apoptosis rate and cell cycles. An Elisa assay was used to detect the levels of cytosolic cytochrome c (cyt c) and caspase-3 in K562 cells exposed to ATO and STI571 at graded concentrations. Semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was used to assay the transcriptional levels of Bcl-XL and Bcr-Abl genes in K562 cells. Results showed that both the colony-forming assay and cell proliferation assay demonstrated additive to synergistic effects of ATO on STI571-induced apoptosis in K562 cells, a Bcr-Abl positive cell line. Caspase-3 was activated during apoptosis and there was an increase in cytosolic accumulation of cytochrome c. Treatment of K562 cells with STI571 alone led to down-regulation of transcriptional levels of Bcl-XL at 12 hours and Bcr-Abl at 96 hours after drug administration. Treatment with ATO alone only led to reduce the mRNA levels of Bcl-XL, but not Bcr-Abl. Combined treatment with ATO and STI571 down regulated the transcripts of Bcl-XL at 12 hours and Bcr-Abl 72 hours after drug administration. We conclude that ATO enhanced cytotoxic and proapoptotic actions of STI571 could be mediated by the down-regulation of Bcr-Abl and Bcl-XL genes in K562 cells. Therefore ATO in combination with STI571 could be a promising therapy for CML.

Mcl-1 is downregulated in cisplatin-induced apoptosis, and proteasome inhibitors restore Mcl-1 and promote survival in renal tubular epithelial cells

2007 ◽  
Vol 292 (6) ◽  
pp. F1710-F1717 ◽  
Author(s):  
Cheng Yang ◽  
Varsha Kaushal ◽  
Sudhir V. Shah ◽  
Gur P. Kaushal
Keyword(s):  
Epithelial Cells ◽  
Cytochrome C ◽  
Caspase 3 ◽  
Proteasome Inhibitors ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Tubular Epithelial Cells ◽  
Renal Tubular Epithelial Cells ◽  
Renal Tubular ◽  
Induced Apoptosis

Mcl-1 is an antiapoptotic member of the Bcl-2 family that plays an important role in cell survival. We demonstrate that proteasome-dependent regulation of Mcl-1 plays a critical role in renal tubular epithelial cell injury from cisplatin. Protein levels of Mcl-1 rapidly declined in a time-dependent manner following cisplatin treatment of LLC-PK1cells. However, mRNA levels of Mcl-1 were not altered following cisplatin treatment. Expression of other antiapoptotic members of the Bcl-2 family such as Bcl-2 and BclxL was not affected by cisplatin treatment. Cisplatin-induced loss of Mcl-1 occurs at the same time as the mitochondrial release of cytochrome c, activation of caspase-3, and initiation of apoptosis. Treatment of cells with cycloheximide, a protein synthesis inhibitor, revealed rapid turnover of Mcl-1. In addition, treatment with cycloheximide in the presence or absence of cisplatin demonstrated that cisplatin-induced loss of Mcl-1 results from posttranslational degradation rather than transcriptional inhibition. Overexpression of Mcl-1 protected cells from cisplatin-induced caspase-3 activation and apoptosis. Preincubating cells with the proteasome inhibitor MG-132 or lactacystin not only restored cisplatin-induced loss of Mcl-1 but also resulted in an accumulation of Mcl-1 that exceeded basal levels; however, Bcl-2 and BclxL levels did not change in response to MG-132 or lactacystin. The proteasome inhibitors effectively blocked cisplatin-induced mitochondrial release of cytochrome c, caspase-3 activation, and apoptosis. These studies suggest that proteasome regulation of Mcl-1 is crucial in the cisplatin-induced apoptosis via the mitochondrial apoptotic pathway and that Mcl-1 is an important therapeutic target in cisplatin injury to renal tubular epithelial cells.

scholarly journals Orlistatand and Rosuvastatin Suppressed Proliferation of K562 Human Myelogenous Leukemia Cell Line through AMPK/Akt/c-Myc Signaling

2020 ◽  
Author(s):  
Behnam Mojjarad ◽  
Yaghub Pazhang
Keyword(s):  
Cell Cycle ◽  
Chronic Myeloid Leukemia ◽  
Cell Line ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
K562 Cells ◽  
Myelogenous Leukemia ◽  
Leukemia Cell Line ◽  
Mrna Levels ◽  
Hsp 70

Abstract Background: Chronic myeloid leukemia is a myeloproliferative cancer with worldwide incidence, has become as a clinical concern due to chemoresistance in the patients received chemotherapy. Here, we investigated the effect of Orlistat and Rosuvastatin on K562 human myelogenous leukemia cell line in vitro and attempted to illuminate their possible underlying mechanisms. Methods: Cells were exposed to Orlistat and Rosuvastatin, the inhibitors of lipogenesis, then survival and apoptosis rate of K562 cells were examined by MTT assay and flow cytometric analysis respectively. The real time-PCR analysis was used to quantify mRNA levels of Bax, Bcl-2, and Hsp-70 genes. Cell cycle analysis was performed using flow cytometry, whereas the subcellular distribution of c-Myc was measured via immunofluorescence imaging technique. Additionally, the protein level of AMPK, p-AMPK Akt-1, and p-Akt-1 were studied by western blotting. Results: The results showed Orlistat and Rosuvastatin had synergistic anticancer effects on cells and in comparison with the control group, viability and apoptosis rate decreased and increased in treated cells respectively in a dose/time-dependent manner (P<0.05). The mRNA levels of Bax increased while expression of Hsp-70 decreased (P< 0.05). K562 cells treated with Orlistat and Rosuvastatin showed a cell cycle arrest in sub-G1 phase and a decreased level of c-Myc positive cells. Upon outlining the mechanism, it was revealed that AMPK/p-AMPK and p-Akt-1/Akt-1 ratio decreased in treated cells (P< 0.05). Conclusions: Data suggest Orlistat and Rosuvastatin could synergically suppress proliferation of K562 cells through AMPK/Akt/c-Myc axis, proposing a theoretical basis for upcoming application in the treatment of chronic myeloid leukemia

The Role of Peroxiredoxin III and Sulfiredoxin for Mitochondrial ROS Production to Arsenic Trioxide in Acute Promyelocytic Leukemia Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 5217-5217
Author(s):  
Yeung-Chul Mun ◽  
Jee-Young Ahn ◽  
Eun-Sun Yoo ◽  
Kyoung Min Cho ◽  
Kyoung Eun Lee ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Arsenic Trioxide ◽  
Acute Promyelocytic Leukemia ◽  
Caspase 3 ◽  
Promyelocytic Leukemia ◽  
Ros Generation ◽  
Down Regulation ◽  
Nb4 Cells ◽  
Mitochondrial Ros ◽  
Induced Apoptosis

Abstract Backgrounds: The Arsenic trioxide (ATO) is an effective cancer therapeutic drug for acute promyelocytic leukemia (APL), but in some cases, APL cells are resistant to ATO treatment. ATO exerts its effect mainly raising oxidative stress. However, not only the mechanisms of reactive oxygen species (ROS) generation by ATO but involvement of redox enzymes including peroxiredoxin (PRX) during ATO-induced apoptosis and its resistance remain elusive. Recently, Rhee et al had reported that PRX III and sufiredoxin together protect mice from pyrazole-induced oxidative liver injury was found (Antioxid & Redox Signal, 2012:17:1351-1361). Aims of current study are to elucidate that the changes of redox enzyme could be a mechanism of anti-leukemia effect in APL-derived NB4 cells during ATO treatment and to find ways to potentiate the anti-leukemic effects of ATO on APL cells. Methods: NB4, one of the human acute promyelocytic leukemia cell lines, was treated with 0~10 μM arsenic trioxide to induce apoptosis for 16-48 hours in RPMI-1640 medium supplemented with 10% FBS in CO2humidified atmosphere at 37°C. Apoptosis was measured by staining with 7-amino-actinomycin D (7-AAD) with flow cytometry. 2, 7-dichlrodihydro-fluorescein-diacetate (H2DCF-DA) and MitoSOX Red was used to detect cellular and mitochondrial ROS. SO2 form for PRX I, PRX II, and PRX III was detected by western blot assay using PRX SO2 form-specific antibody. Sulfiredoxin (SRX) and caspase 3, 9 were also detected by western blot analysis. To evaluate the effect of SRX depletion, NB4 cells were transfected with small interfering RNA (siRNA). Results: Intracellular ROS of NB4 cells was increased significantly after 16 hour of ATO treatment but decreased after 24 hour of ATO treatment. Mitochondrial ROS of NB4 cells was increased significantly after 39 hour of ATO treatment. Apoptosis of NB4 cell after ATO treatment was increased as time elapsed (24% on 16hr, 26% on 24hr, 48% on 39hr, and 60% on 48hr). Increased cysteine sulfinic acid (Cys–SO2H) PRX III, inactive and oxidized form, was observed as a hyperoxidation reaction in NB4 cells after ATO treatment in concordance with mitochondrial ROS increment of NB4 cells. Increased expressions of cleaved caspase-9 and cleaved caspase-3 were also observed during NB4 cell apoptosis by ATO treatment. Meanwhile, SRX expression was increased in NB4 cells after ATO treatment. Down regulation of SRX by siRNA promoted ROS generation and apoptosis in ATO-treated NB4 cells. Conclusions: Our data showed inactivation of PRX III by Cys–SO2H formation as hyperoxidation is developed during ATO-induced mitochondrial ROS generation and apoptosis process in APL cells. In addition, ATO promotes expression of SRX, which is known as reducing enzyme of Cys–SO2H PRX and which leads to down regulation of ROS accumulation in APL cells. These findings might be due to protective effect of SRX from ATO on mitochondrial oxidative stress. These findings suggest ATO-induced anti-leukemic activity could be down regulated by an enhancing PRX III reduction after ATO-induced SRX activation. Currently, the effect of down regulation of SRX by siRNA are being investigated to amplify the apoptosis in ATO-treated NB4 cells. Our study may provide the insights for finding novel targets in the development of new therapies, which potentiate ATO-induced apoptosis in APL cells. Disclosures No relevant conflicts of interest to declare.

Molecular Mechanism of Matrine-Induced Apoptosis in Leukemia K562 Cells

2006 ◽  
Vol 34 (06) ◽  
pp. 1095-1103 ◽  
Author(s):  
Xiao-Shan Liu ◽  
Jikai Jiang
Keyword(s):  
Cytochrome C ◽  
Caspase 3 ◽  
Chinese Herb ◽  
K562 Cells ◽  
Dependent Manner ◽  
Nih3t3 Cells ◽  
Proapoptotic Protein ◽  
General Caspase Inhibitor ◽  
Induced Apoptosis ◽  
Dose Dependent

Matrine, a low toxic alkaloid purified from the Chinese herb Kushen, has been reported to induce apoptosis in leukemia K562 cells. In this study, the mechanism underling this apoptotic event was investigated. Treatment of K562 cells with matrine resulted in inhibition of cell survival more significantly than treatment of non-cancer fibroblast NIH3T3 cells. When K562 cells were incubated with matrine in higher than 0.2 mg/ml doses for 48 hours, the apoptotic cells were increased and both poly (ADP-ribose) polymerase (PARP) and caspase-3 were cleaved in a dose dependent manner. General caspase inhibitor (z-VAD-fmk) or caspase-3 inhibitor (z-DEVD-fmk) almost completely suppressed matrine-induced apoptosis. In addition, matrine increased proapoptotic protein bax and caused the release of cytochrome C. Taken together, the results suggest that matrine induces a cytochrome C-mediated, caspase-dependent apoptosis.

scholarly journals Bcr-Abl Exerts Its Antiapoptotic Effect Against Diverse Apoptotic Stimuli Through Blockage of Mitochondrial Release of Cytochrome C and Activation of Caspase-3

Blood ◽  
1998 ◽  
Vol 91 (5) ◽  
pp. 1700-1705 ◽  
Author(s):  
Gustavo P. Amarante-Mendes ◽  
Caryn Naekyung Kim ◽  
Linda Liu ◽  
Yue Huang ◽  
Charles L. Perkins ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Dna Fragmentation ◽  
Caspase 3 ◽  
K562 Cells ◽  
Myelogenous Leukemia ◽  
Leukemic Cells ◽  
High Dose ◽  
Antiapoptotic Effect ◽  
Endogenous Expression ◽  
Cyt C

Abstract Bcr-Abl expression in leukemic cells is known to exert a potent effect against apoptosis due to antileukemic drugs, but its mechanism has not been elucidated. Recent reports have indicated that a variety of apoptotic stimuli cause the preapoptotic mitochondrial release of cytochrome c (cyt c) into cytosol, which mediates the cleavage and activity of caspase-3 involved in the execution of apoptosis. Whether Bcr-Abl exerts its antiapoptotic effect upstream to the cleavage and activation of caspase-3 or acts downstream by blocking the ensuing degradation of substrates resulting in apoptosis, has been the focus of the present studies. In these, we used (1) the human acute myelogenous leukemia (AML) HL-60 cells that are stably transfected with thebcr-abl gene (HL-60/Bcr-Abl) and express p185 Bcr-Abl; and (2) the chronic myelogenous leukemia (CML)-blast crisis K562 cells, which have endogenous expression of p210 Bcr-Abl. Exposure of the control AML HL-60 cells to high-dose Ara-C (HIDAC), etoposide, or sphingoid bases (including C2 ceramide, sphingosine, or sphinganine) caused the accumulation of cyt c in the cytosol, loss of mitochondrial membrane potential (MMP), and increase in the reactive oxygen species (ROS). These preapoptotic events were associated with the cleavage and activity of caspase-3, resulting in the degradation of poly (adenosine diphosphate [ADP]-ribose) polymerase (PARP) and DNA fragmentation factor (DFF), internucleosomal DNA fragmentation, and morphologic features of apoptosis. In contrast, in HL-60/Bcr-Abl and K562 cells, these apoptotic stimuli failed to cause the cytosolic accumulation of cyt c and other associated mitochondrial perturbations, as well as the failure to induce the activation of caspase-3 and apoptosis. While the control HL-60 cells showed high levels of Bcl-2 and barely detectable Bcl-xL, HL-60/Bcr-Abl cells expressed high levels of Bcl-xL and undetectable levels of Bcl-2, a pattern of expression similar to the one in K562 cells. Bax and caspase-3 expressions were not significantly different between HL-60/Bcr-Abl or K562 versus HL-60 cells. These findings indicate that Bcr-Abl expression blocks apoptosis due to diverse apoptotic stimuli upstream by preventing the cytosolic accumulation of cyt c and other preapoptotic mitochondrial perturbations, thereby inhibiting the activation of caspase-3 and execution of apoptosis.

scholarly journals Orlistatand and Rosuvastatin Suppressed Proliferation of K562 Human Myelogenous Leukemia Cell Line through AMPK/Akt/c-Myc Signaling

2020 ◽  
Author(s):  
Behnam Mojjarad ◽  
Yaghub Pazhang
Keyword(s):  
Cell Cycle ◽  
Chronic Myeloid Leukemia ◽  
Cell Line ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
K562 Cells ◽  
Myelogenous Leukemia ◽  
Leukemia Cell Line ◽  
Mrna Levels ◽  
Hsp 70

Abstract Background: Chronic myeloid leukemia is a myeloproliferative cancer with worldwide incidence, has become as a clinical concern due to chemoresistance in the patients received chemotherapy. Here, we investigated the effect of Orlistat and Rosuvastatin on K562 human myelogenous leukemia cell line in vitro and attempted to illuminate their possible underlying mechanisms. Methods: Cells were exposed to Orlistat and Rosuvastatin, the inhibitors of lipogenesis, then survival and apoptosis rate of K562 cells were examined by MTT assay and flow cytometric analysis respectively. The real time-PCR analysis was used to quantify mRNA levels of Bax, Bcl-2, and Hsp-70 genes. Cell cycle analysis was performed using flow cytometry, whereas the subcellular distribution of c-Myc was measured via immunofluorescence imaging technique. Additionally, the protein level of AMPK, p-AMPK Akt-1, and p-Akt-1 were studied by western blotting.Results: The results showed Orlistat and Rosuvastatin had synergistic anticancer effects on cells and in comparison with the control group, viability and apoptosis rate decreased and increased in treated cells respectively in a dose/time-dependent manner (P<0.05). The mRNA levels of Bax increased while expression of Hsp-70 decreased (P< 0.05). K562 cells treated with Orlistat and Rosuvastatin showed a cell cycle arrest in sub-G1 phase and a decreased level of c-Myc positive cells. Upon outlining the mechanism, it was revealed that AMPK/p-AMPK and p-Akt-1/Akt-1 ratio decreased in treated cells (P< 0.05).Conclusions: Data suggest Orlistat and Rosuvastatin could synergically suppress proliferation of K562 cells through AMPK/Akt/c-Myc axis, proposing a theoretical basis for upcoming application in the treatment of chronic myeloid leukemia.

In-Vitro Treatment of Lymphoma Cell Lines with BAY 43-9006 (Sorafenib) Is Followed by Typical Features of Apoptosis and Down-Regulation of MCL-1 Pointing to an Efficacy of Sorafenib in the Teatment of Lymphoma.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1392-1392
Author(s):  
Dirk Winkler ◽  
Christof Schneider ◽  
Annett Habermann ◽  
Hartmut Doehner ◽  
Stephan Stilgenbauer
Keyword(s):  
Cell Cycle ◽  
Cytochrome C ◽  
Map Kinase ◽  
Cell Lines ◽  
Caspase 3 ◽  
P53 Mutation ◽  
Down Regulation ◽  
Map Kinase Pathway ◽  
Induced Apoptosis ◽  
Kinase Pathway

Abstract BAY 43-9006 (sorafenib) is a multikinase inhibitor that has shown efficacy against a variety of malignancies in preclinical models. In the treatment of lymphoma, however, its place is still to be determined. We treated 7 lymphoma cell lines with sorafenib (10μM) over 24h and 48h respectively: EHEB (B-CLL), JVM-2 (MCL), GRANTA-519 (MCL), JURKAT (T-ALL with p53 mutation), BL-60, NAMALWA and BJAB (all Burkitt’s lymphoma with del 17p and p53 mutation). To determine the rates and type of sorafenib induced apoptosis, 4-colour FACS analyses (CD19, 7AAD, active caspase-3, cytochrome c) were performed. The expression of the following proteins involved in apoptosis, cell cycle regulation and the MAP-kinase pathway was studied by Western blotting: BAX, BCL-2, MCL-1, p53, p21, p27, procaspase-3, procaspase-8, procaspase-9, PARP, ERK, JNK and p38. The posphorylation status of ERK, JNK, and p38 was investigated after 5–120 minutes of treatment. Significant rates of sorafenib induced apoptosis as detected by 7AAD-FACS were seen in EHEB (46% apoptotic rate), JVM-2 (36%), GRANTA (75%), JURKAT (85%) and BL-60 (84%) after 48 hours. Cytochrome c releases, BAX cleavage as well as a down-regulation of MCL-1 and p27 were seen in all cell lines after 48 hours independent of their p53 status (no expression of p27 was detected in JVM-2). No activation of caspase-3 was seen by FACS and no cleavage product of caspase-3 could be detected by Western blotting. However, reduced levels of procaspase-3 were detected for EHEB, BL-60, NAMALWA and JURKAT. A decrease of expression of procaspase 3/8/9 was seen in NAMALWA, BL60 and JURKAT. No regulation of caspases was seen in the MCL cell lines, despite significant rates of sorafenib induced apoptosis. In BL-60 and NAMALWA, both showing a deletion of TP53 and a p53 mutation in the remaining allele, sorafenib treatment resulted in down-regulation of all proteins studied except for BCL-2 that did not show expression change; BJAB also showed reduced levels of p21, JNK and ERK after treatment, but responded with up-regulation of p53 and BCL-2 and unchanged levels for caspases. Down-regulation of BCL-2 was only seen in GRANTA, whereas EHEB responded with an up-regulation. All cell lines except for JURKAT, the only T-cell line, exhibited declining expression of proteins of the MAP-kinase pathway. Sorafenib inhibited the posphorylation of ERK in BL60, NAMALWA and JURKAT at a concentration of 1 and 10μM after 120 minutes of treatment. No change in posphorylation status was seen in the other cell lines. Although the effects of sorafenib on caspases, cell cycle regulating proteins, downstream proteins of the MAP-kinase pathway and their posphorylation status differed among the lymphoma cell lines studied, sorafenib treatment was consistently followed by typical features of apoptosis such as BAX cleavage and cytochrome c release. Induction of cell death did not depend on functional p53 gene. Furthermore, all cell lines investigated responded with down-regulation of the anti-apoptotic protein MCL-1 and the cell cycle regulator p27. Interestingly, not all cell lines responded with activation of caspases. A central role of MCL-1 operating upstream of cytochrome c release and caspase activation as well as induction of cell death by sorafenib through both caspase-dependent and -independent pathways are in line with earlier reports on other malignancies, and point to an efficacy of sorafenib in the treatment of lymphoma.

Downregulation of Peroxiredoxin III Contributes to Arsenic Trioxide-Induced Apoptosis in APL.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4322-4322
Author(s):  
Pablo Vivas-Mejia ◽  
Bulent Ozpolat ◽  
Xian Chen ◽  
Gabriel Lopez-Berestein
Keyword(s):  
Arsenic Trioxide ◽  
Caspase 3 ◽  
Mrna Levels ◽  
Oxygen Species ◽  
Caspase 9 ◽  
Cytochrome C Release ◽  
Nb4 Cells ◽  
Low Levels ◽  
Induced Apoptosis

Abstract Arsenic trioxide (ATO) induces differentiation and apoptosis in acute promyelocytic leukemia (APL). Compared with other leukemia cells, the APL-derived NB4 cells are particularly sensitive to ATO-induced apoptosis. Several reports indicate that in NB4 cells, apoptosis occurs in part by a mechanism that involves the inhibition of glutathione peroxidase, one of the enzymes that regulate the levels of H2O2 in the mitochondria, and that is present only at low levels in NB4 cells. Peroxirredoxin III (Prx III) is a mitochondria-specific H2O2-scavenger member of the thioredoxin-dependent peroxidases. NB4 cells express high levels of Prx III; however the role of Prx III in ATO-induced apoptosis in NB4 cells has not been investigated. We studied here whether Prx III is regulated during ATO-induced apoptosis in NB4 cells and whether the depletion of Prx III further sensitized these cells to ATO-induced apoptosis. The protein and mRNA levels of Prx III were decreased during ATO-induced apoptosis of NB4 cells. The down-regulation of Prx III occurred prior to the accumulation of reactive oxygen species, reduction in the mitochondrial membrane potential and apoptosis. Depletion of Prx III enhanced the ATO-induced mitochondrial damage, and also promoted cytochrome-c release, and caspase-3 and caspase-9 activation. Prx III is downregulated early during ATO-induced apoptosis, facilitating in this way the mitochondria-depending apoptotic events triggered by the accumulation of H2O2.

scholarly journals Bcr-Abl Exerts Its Antiapoptotic Effect Against Diverse Apoptotic Stimuli Through Blockage of Mitochondrial Release of Cytochrome C and Activation of Caspase-3

Blood ◽  
1998 ◽  
Vol 91 (5) ◽  
pp. 1700-1705 ◽  
Author(s):  
Gustavo P. Amarante-Mendes ◽  
Caryn Naekyung Kim ◽  
Linda Liu ◽  
Yue Huang ◽  
Charles L. Perkins ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Dna Fragmentation ◽  
Caspase 3 ◽  
K562 Cells ◽  
Myelogenous Leukemia ◽  
Leukemic Cells ◽  
High Dose ◽  
Antiapoptotic Effect ◽  
Endogenous Expression ◽  
Cyt C

Bcr-Abl expression in leukemic cells is known to exert a potent effect against apoptosis due to antileukemic drugs, but its mechanism has not been elucidated. Recent reports have indicated that a variety of apoptotic stimuli cause the preapoptotic mitochondrial release of cytochrome c (cyt c) into cytosol, which mediates the cleavage and activity of caspase-3 involved in the execution of apoptosis. Whether Bcr-Abl exerts its antiapoptotic effect upstream to the cleavage and activation of caspase-3 or acts downstream by blocking the ensuing degradation of substrates resulting in apoptosis, has been the focus of the present studies. In these, we used (1) the human acute myelogenous leukemia (AML) HL-60 cells that are stably transfected with thebcr-abl gene (HL-60/Bcr-Abl) and express p185 Bcr-Abl; and (2) the chronic myelogenous leukemia (CML)-blast crisis K562 cells, which have endogenous expression of p210 Bcr-Abl. Exposure of the control AML HL-60 cells to high-dose Ara-C (HIDAC), etoposide, or sphingoid bases (including C2 ceramide, sphingosine, or sphinganine) caused the accumulation of cyt c in the cytosol, loss of mitochondrial membrane potential (MMP), and increase in the reactive oxygen species (ROS). These preapoptotic events were associated with the cleavage and activity of caspase-3, resulting in the degradation of poly (adenosine diphosphate [ADP]-ribose) polymerase (PARP) and DNA fragmentation factor (DFF), internucleosomal DNA fragmentation, and morphologic features of apoptosis. In contrast, in HL-60/Bcr-Abl and K562 cells, these apoptotic stimuli failed to cause the cytosolic accumulation of cyt c and other associated mitochondrial perturbations, as well as the failure to induce the activation of caspase-3 and apoptosis. While the control HL-60 cells showed high levels of Bcl-2 and barely detectable Bcl-xL, HL-60/Bcr-Abl cells expressed high levels of Bcl-xL and undetectable levels of Bcl-2, a pattern of expression similar to the one in K562 cells. Bax and caspase-3 expressions were not significantly different between HL-60/Bcr-Abl or K562 versus HL-60 cells. These findings indicate that Bcr-Abl expression blocks apoptosis due to diverse apoptotic stimuli upstream by preventing the cytosolic accumulation of cyt c and other preapoptotic mitochondrial perturbations, thereby inhibiting the activation of caspase-3 and execution of apoptosis.

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