Leukemic Cell Apoptosis Caused by Constitutively Active Mutant Glucocorticoid Receptor Fragments

1995 ◽  
pp. 417-421
Author(s):  
LYNNE V. NAZARETH ◽  
E. BRAD THOMPSON
Keyword(s):  
Glucocorticoid Receptor ◽  
Cell Apoptosis ◽  
Leukemic Cell ◽  
Receptor Fragments ◽  
Constitutively Active

scholarly journals Neutrophil elastase produces 52-kD and 30-kD glucocorticoid receptor fragments in the cytosol of human leukemia cells

Blood ◽  
1987 ◽  
Vol 70 (3) ◽  
pp. 860-868
Author(s):  
CW Distelhorst ◽  
KE Janiga ◽  
KJ Howard ◽  
SE Strandjord ◽  
EJ Campbell
Keyword(s):  
Glucocorticoid Receptor ◽  
Neutrophil Elastase ◽  
Glucocorticoid Receptors ◽  
Leukemia Cell ◽  
Specific Inhibitor ◽  
Leukemia Cells ◽  
Human Leukemia ◽  
Receptor Fragments ◽  
Limited Digestion

Characterization of glucocorticoid receptors in leukemia cells is important to understand mechanisms of glucocorticoid resistance but has been impeded by receptor fragmentation in cytosol extracts. We recently found that formation of 52- and 30-kilodalton (kD) glucocorticoid receptor fragments in cytosol of leukemia cells is due to proteolysis and is blocked by diisopropylfluorophosphate (DFP). In the present study, we identify a 28-kD serine protease in cytosol of leukemia cells that binds [3H]DFP and correlates with the formation of 52- and 30-kD receptor fragments. This protease is immunoprecipitated by antiserum to neutrophil elastase. Limited digestion of [3H]dexamethasone-21-mesylate- labeled receptors by purified neutrophil elastase produces 52- and 30- kD receptor fragments. Receptor fragmentation in the cytosol of leukemia cells in inhibited by methoxysuccinyl-alanyl-alanyl-prolyl- valyl-chloromethylketone, a highly specific inhibitor of neutrophil elastase. The addition of as few as 5% neutrophils to a lymphoid cell suspension provides sufficient elastase to produce receptor fragmentation. Our findings indicate that neutrophil elastase is responsible for receptor fragmentation in the cytosol of leukemia cells. The neutrophil elastase may be endogenous to the leukemia cells or may come from neutrophils that contaminate leukemia cell suspensions.

Introduction of Constitutivelly Active Akt in Primary CLL B-Cells Results in Upregulation of Mcl-1, Bcl-XL and Cyclin D3 and Promotes Leukemic Cell Survival.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2805-2805
Author(s):  
Pablo Longo ◽  
Stefania Gobessi ◽  
Luca Laurenti ◽  
Simona Sica ◽  
Giuseppe Leone ◽  
...  
Keyword(s):  
B Cells ◽  
Cell Survival ◽  
Leukemic Cell ◽  
Lymphocytic Leukemia ◽  
Cyclin D3 ◽  
Leukemic Cells ◽  
Interleukin 4 ◽  
Antiapoptotic Proteins ◽  
Sustained Activation ◽  
Constitutively Active

Abstract The PI3K/Akt and Raf/MEK/ERK pathways are key regulators of various cellular responses, including proliferation, survival, differentiation, migration and malignant transformation. These pathways are activated in chronic lymphocytic leukemia B-cells by a number of survival or growth stimulatory signals, such as immobilized anti-IgM antibodies, interleukin-4, phorbol-ester, CXCL12, or stimulatory CpG oligonucleotides. Moreover, enhanced activation of Akt has been implicated in the pathogenesis of the CLL-like disorder that develops in mice transgenic for the TCL1 oncogene. To further delineate the relative contribution of the PI3K/Akt and Raf/MEK/ERK pathways in regulating leukemic cell growth and survival, we introduced constitutively active Akt or constitutively active MEK2 in primary CLL B-cells by nucleofection. Expression of constitutively active Akt consistently promoted survival, as evidenced by a higher percentage of Annexin V/PI negative cells after 48 hours in culture (median 52%) compared to samples transfected with control vector (median 31%). Immunoblot analysis of several important antiapoptotic proteins revealed that enforced activation of Akt upregulates Mcl-1 and Bcl-xL, whereas no changes were observed in the levels of Bcl-2. Expression of constitutively active Akt also induced an increase in size and granularity of the leukemic cells, indicating increased metabolic activity. These changes were associated with significant induction of cyclin D3, indicating that activation of Akt is required for both leukemic cell survival and cell cycle progression. In contrast, introduction of constitutively active MEK2 induced sustained activation of ERK, but showed only a modest increase in the percentage of viable CLL B-cells (median 36%) and no significant changes in the levels of any of the investigated antiapoptotic proteins. These experiments provide direct evidence that sustained activation of Akt promotes leukemic cell survival and upregulates Mcl-1, an antiapoptotic protein that has been associated with resistance to chemotherapy in patients with CLL.

Role of hERG1 K+ Channels as a Positive Regulator In SDF-1alpha-Mediated Proliferation of Leukemia Cells and Leukemia Stem/Progenitor Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4786-4786
Author(s):  
Fang Zheng ◽  
Huiyu Li ◽  
Fang Liu ◽  
Wen Du ◽  
Shiang Huang
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Proliferation ◽  
Progenitor Cells ◽  
Signaling Pathway ◽  
Cell Apoptosis ◽  
Leukemic Cell ◽  
Bone Marrow Microenvironment ◽  
Leukemic Cells ◽  
K Channels

Abstract Abstract 4786 Background: Mounting evidence that leukemia stem cells (LSCs) occupy and receive important signals from specialized areas (“niches”) that alter the stromal microenvironment and disrupt normal hematopoiesis. The innovative therapeutic strategies focus on targeting of microenvironmental interactions in leukemia. Therefore, it is important to fully elaborate the mechanisms of microenvironment- mediated leukemogenesis. Stromal-cell derived factor-1alpha (SDF-1à) is the main cytokine produced by bone marrow stromal cells. The SDF-1à/CXCR4 axis specifically mediates homing and migration of leukemic blasts. While our previous work has shown that SDF-1à significantly increases hERG1 K+ tail current and a specific hERG1 K+ channels inhibitor significantly blocks SDF-1à- induced migration of leukemic cells. In fact, recent studies suggested that the human ether à-go-go-related gene (HERG) K+ channels are constitutively expressed in AML stem/progenitor cells, and regulate cell proliferation as well as clinical prognosis. Here we investigate the hypothesis that a new leukemic blast–stromal interaction is mediate by hERG1 K+ channels and SDF-1à. Methods: Proliferation assay, apoptosis and cell cycle analysis were used to analyze effects of E-4031(a specific hERG1 K+ channels inhibitor) in the presence of SDF-1à on leukemia cell lines HL-60. RT–PCR and western blot analysis were used to determine changes in herg1 expression and Wnt/β-catenin signaling pathway in response to SDF-1à in the presence and absence of E-4031. Primary leukemias obtained from the bone marrow of de novo AML patients (n=6) at diagnosis. Mononuclear cells were isolated from the samples using Ficoll-Paque density gradient separation, and cultured with SDF-1à in the presence and absence of E-4031. AML colony-forming cell (CFC) assays and flow cytometry were performed to assess the effects of E-4031 in the presence of SDF-1à on LSCs. Results: SDF-1a enhanced cell proliferation in a dose-dependent manner. The maximal increase by 1.6 times was obtained for 100ng/ml. While this effect was impaired by E-4031, which significantly impaired cell proliferation induced by SDF-1a with a concentration of 100ng/mL by (40.3±8.4)%. In addition, E-4031 inhibited SDF-1a-stimulated leukemic cell proliferation by inducing G0/G1 arrest. Cell apoptosis analysis revealed that either E-4031 or SDF-1a has direct effect on HL-60 cell apoptosis. Unexpected, there was no significant synergistic effect upon apoptosis. After exposures to 100ng/ml SDF-1à, hERG1 mRNA and protein levels increased significantly, by approximately 1.5-fold above control levels. Moreover, SDF-1a increased the expression of Wnt/β-catenin target genes, including β-catenin, cyclin-D1, and c-myc. Interestingly, this manner was abolished by E-4031. The presence of progenitor cells was evaluated by plating suspension cells cultured with SDF-1a in CFC assays. E-4031 decreased numbers of CFC in suspension to 77.3%. Upon expansion with SDF-1a, E-4031 resulted in a significant reduction in the number of progenitors to 31.8%. The effects on LSCs were determined on phenotypically described stem cells from AML. Treatment with 1μ M E-4031 for 48 hours inhibited the proliferation of LCSs compared with untreated controls, a mean viability of 11.8% for CD34+CD38- and 10.4% for CD34+CD38+. In contrast, a significant decrease in the viability of stem cells after E-4031 in the present of SDF-1a treatment, with only 9.6% for CD34+CD38- and 9.5% for CD34+CD38+. Conclusions: Initial studies provided evidence that the hERG1 K+ channels and SDF-1 emerged as mediators of stromal/leukemic cell interactions, which largely contribute to the proliferation mediated by the microenvironment. Likewise, other components of bone marrow microenvironment, such as Wnt/β-catenin signaling pathway, may modulate hERG1 K+ channels in leukemic cells. Taken together, these results provided rationale for studies of new molecular events involved in bone marrow microenvironment and leukemogenesis. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Phosphorylation of β-actin by protein kinase C-delta in camptothecin analog-induced leukemic cell apoptosis

2008 ◽  
Vol 29 (1) ◽  
pp. 135-142 ◽  
Author(s):  
Shuang Wang ◽  
Ying Zheng ◽  
Yun Yu ◽  
Li Xia ◽  
Guo-qiang Chen ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cell Apoptosis ◽  
Leukemic Cell ◽  
Protein Kinase C Delta ◽  
Kinase C

Regulative function of telomerase and extracelluar regulated protein kinases to leukemic cell apoptosis

2002 ◽  
Vol 22 (4) ◽  
pp. 292-294
Author(s):  
Dengju Li ◽  
Yaozhen Zhang ◽  
Wenjing Cao ◽  
Lan Sun ◽  
Huizhen Xu ◽  
...  
Keyword(s):  
Protein Kinases ◽  
Cell Apoptosis ◽  
Leukemic Cell ◽  
Regulative Function

scholarly journals Characterization of glucocorticoid receptors and glucocorticoid receptor mRNA in human leukemia cells: stabilization of the receptor by diisopropylfluorophosphate

Blood ◽  
1987 ◽  
Vol 69 (3) ◽  
pp. 750-756
Author(s):  
CW Distelhorst ◽  
R Miesfeld
Keyword(s):  
Glucocorticoid Receptor ◽  
Glucocorticoid Receptors ◽  
Leukemia Cell ◽  
Leukemia Cells ◽  
Human Leukemia ◽  
Lymphoma Cells ◽  
Human Leukemia Cells ◽  
Mouse Lymphoma Cells ◽  
Receptor Fragments ◽  
Mouse Lymphoma

We have shown that cytosol samples from human leukemia cells frequently contain glucocorticoid receptor fragments that have a mol wt (Mr) of approximately 52,000. In the present study we demonstrate that the Mr approximately 52,000-receptor fragments are derived from intact glucocorticoid receptors (Mr approximately 97,000) by the action of a serine protease. Mr approximately 52,000-receptor fragments were present in cytosol from 24 of 52 leukemia cell samples. Only normal size glucocorticoid receptors were present in cytosol samples if diisopropylfluorophosphate (DFP), a potent inhibitor of serine proteases, was added to the hypotonic buffer used for cytosol preparation. Receptor proteolysis was not inhibited by hydrolyzed DFP, benzamidine, phenylmethylsulfonylfluoride, aprotinin, iodoacetamide, or mercuric chloride. The leukemia cell protease digests the receptor at a different site than chymotrypsin, which digests the intact receptor to produce a Mr approximately 40,000 receptor fragment. Receptor messenger RNA (mRNA) in S49 mouse lymphoma cells and in human leukemia cells was analyzed by Northern hybridization with a cDNA for the normal glucocorticoid receptor. Mutant S49 mouse lymphoma cells that have abnormally small glucocorticoid receptors (Mr approximately 48,000) make a 5.0-kilobase receptor transcript in addition to the normal size 6.5-kilobase receptor transcript. A normal size receptor transcript of 6.5 kilobases was present in all of the human leukemia cells whether or not Mr approximately 52,000-receptor fragments were present. Therefore, abnormalities of glucocorticoid receptor mRNA, which may give rise to the synthesis of foreshortened receptors in certain mutant mouse lymphoma cells, are apparently absent from human leukemia cells.

Cell cycle regulation of membrane glucocorticoid receptor in CCRF-CEM human ALL cells: correlation to apoptosis.

1997 ◽  
Vol 273 (3) ◽  
pp. E571 ◽  
Author(s):  
F N Sackey ◽  
C S Watson ◽  
B Gametchu
Keyword(s):  
Cell Cycle ◽  
Glucocorticoid Receptor ◽  
Fluorescent Microscopy ◽  
Leukemic Cell ◽  
Leukemic Cell Line ◽  
Trypan Blue Exclusion ◽  
Second Growth ◽  
Human Leukemic Cell Line ◽  
And Function ◽  
Cycle Regulation

The human leukemic cell line (CCRF-CEM) and a subline enriched for the plasma membrane-resident glucocorticoid receptor (mGR) were studied for the influence of the cell cycle on the expression and function of mGR. Three synchronization procedures (double thymidine, colcemid, and combined thymidine-colcemid blocks) were used. Fluorescent microscopy and flow cytometry simultaneously assessed antibody-tagged mGR and DNA. In addition, mGR was quantitated and characterized by immunoprecipitation and immunoblotting. Apoptosis was assayed by DNA fragmentation (TUNEL assay) and by cell survival (trypan blue exclusion). All synchronization procedures demonstrated that progression from DNA replication (S) to the second growth phase and mitosis (G2/M) leads to cells having the highest levels of mGR expression and being highly glucocorticoid sensitive in the apoptosis assays: 32 and 80% sensitivity of wild type and mGR-enriched cells, respectively, compared with 12 and 30% sensitivity in asynchronous cells. Therefore, mGR expression appears to be cell cycle regulated, with its highest expression at late S-G2/M, when the cells are most sensitive to the lymphocytolytic effects of glucocorticoids.

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