scholarly journals In Vitro Activity and Target Modulation of PV-10 Against Relapsed and Refractory Pediatric Leukemia

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 5207-5207
Author(s):  
Lucy Swift ◽  
Chunfen Zhang ◽  
Ravi Shah ◽  
Tanya Trippett ◽  
Aru Narendran
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Phase Contrast ◽  
Leukemia Cell ◽  
Time Lapse ◽  
Video Microscopy ◽  
Dependent Manner ◽  
Pediatric Leukemia ◽  
Leukemia Cell Lines ◽  
Time Lapse Video

Abstract Introduction: Leukemias are the most common childhood cancers, accounting for 30% of all pediatric cancer diagnoses. Although the survival rate for pediatric leukemia has greatly improved, relapse is a major cause of treatment failure. Approximately 15-20% of pediatric acute lymphoblastic leukemia (ALL) patients and 30-40% of acute myeloid leukemia (AML) patients relapse, with relapsed ALL identified as the fourth most common malignancy in children. Treatment of relapsed pediatric leukemia includes intensification of chemotherapeutic regimens and use of bone marrow transplantation (BMT). However, increasing the intensity of combination chemotherapies and introduction of second-line drugs is often accompanied by cumulative toxicity with marginal incremental benefits. Therefore, research to identify and develop novel tolerable and effective agents is urgently needed. PV-10 (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) is a novel therapeutic that induces direct cytotoxicity in adult and pediatric solid tumors and stimulates tumor specific immune activation through immunogenic cell death. Our studies aim to identify the potential of PV-10 in future clinical trials for relapsed and refractory pediatric leukemias. Methods: A panel of eleven cell lines derived from patients with either primary or relapsed pediatric leukemia (CEM-C1, CCRF-SB, Kasumi-1, KOPN8, Molm-13, Molt-3, Molt-4, MV4-11, SEM, SUP-B15 and TIB-202) and cells from three primary leukemia patient specimens (T-ALL, AML, Infant AML) were treated with increasing concentrations of PV-10 and cell viability was measured by alamar blue assay, 96 h post-treatment. Target modulation and induction of cell death pathways were investigated by western blot, phase-contrast microscopy and time-lapse video microscopy. Analysis of cell cycle alterations and induction of apoptosis were measured by flow cytometry. Combination studies will be performed to identify anti-cancer agents that are synergistic with PV-10 and animal models of pediatric leukemia used to identify the activity of PV-10 against pediatric leukemia in vivo. Results: PV-10 decreased cell viability in a concentration and time dependent manner in the eleven pediatric leukemia cell lines (mean IC50 93 µM), and three primary leukemia samples (mean IC50 122 µM) tested. Observation of four different leukemia cell lines (Molm-13, MV4-11, SEM, TIB-202) by phase-contrast and time-lapse video microscopy indicated that PV-10 was cytotoxic and not cytostatic to cells. Quantification of dead cells from time-lapse video microscopy experiments showed that PV-10 was cytotoxic in a cell line and concentration dependent manner. At 24 h post-treatment with 100 µM PV-10, 88% of MV4-11 cells, 69% of Molm-13 cells, 27% of TIB-202 cells and 25% of SEM cells had undergone cell death. When the concentration of PV-10 was increased to 200 µM, 100% of MV4-11 and Molm13 cells, 94% of SEM cells and 60% of TIB-202 cells had undergone cell death, 24 h after treatment. Additionally, observation by time-lapse video microscopy suggested that cells were dying by apoptosis, as treatment with PV-10 led to cell shrinkage. Induction of apoptosis by PV-10 was confirmed by dose and time dependent PARP cleavage, detected by western blot. Conclusions: Our studies provide first proof-of-concept pre-clinical data for the activity and mechanisms of action of PV-10 in pediatric leukemia. These data provide the rationale for additional studies and the formulation of an early-phase clinical trial for patients with relapsed and refractory pediatric leukemia. Disclosures No relevant conflicts of interest to declare.

Preclinical Evaluation of Oncolytic Reovirus in Targeted Therapeutics for High-Risk Pediatric Leukemia

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3571-3571
Author(s):  
Matthew F. Clarkson ◽  
Aru Narendran ◽  
Randal N. Johnston
Keyword(s):  
Cell Death ◽  
High Risk ◽  
Cell Viability ◽  
Cell Lines ◽  
Leukemia Cell ◽  
Treatment Strategies ◽  
Leukemia Cells ◽  
Western Blots ◽  
Pediatric Leukemia ◽  
Leukemia Cell Lines

Abstract Abstract 3571 Purpose: Leukemia is the most common malignancy in children. Improved treatment strategies in recent decades have yielded substantially enhanced outcomes for children with leukemia, reaching survival rates >80%. However, there remain significant issues with current treatment. Certain subgroups of patients who are resistant to or relapse from current treatments have a dismal prognosis. Furthermore, there are significant late effects of intensive treatments, including secondary cancers, neurocognitive defects, cardiotoxicity, obesity and infertility. For these reasons, novel treatment strategies are urgently needed for high-risk leukemia in children. Reovirus type 3 Dearing is a wild-type double-stranded RNA virus that has shown great promise as a selective oncolytic agent by its ability to replicate in transformed cells but not in normal cells. Although a number of early phase clinical studies have been completed in patients with advanced, refractory solid tumors in adults, systematic evaluation of this agent in the treatment of refractory pediatric leukemia has not been reported. As an initial step towards developing an oncolytics based treatment approach, we report preclinical data with respect to the activity, target validation, target modulation and drug combinability of reovirus in childhood leukemia cells. Experimental Design: A panel of pediatric leukemia cell lines representing high-risk molecular features such as Bcr-Abl, MLL rearranged and mixed lineage was used (n =6). Expression of JAM-A, the cell surface receptor for reovirus, was assessed by flow cytometry. The Ras Activation Assay Kit (EMD Millipore) was used to assess activity of the RAS protein. Western Blots were used to assess the activation (phosphorylation) of the signaling partners downstream of RAS. Cells treated with reovirus, chemotherapy drugs, or both for distinct treatment schedules were assessed for cell viability by the CellTiter-Glo© Luminescent Cell Viability Assay (Promega), and cell death by apoptosis was confirmed by cleavage of PARP. Productive viral infection was assessed by measuring reoviral protein synthesis by Western Blots, and reoviral replication was assessed by virus plaque titration assay. Drug synergies were calculated according to the method of Chou and Talalay. Results: Target validation assays showed the expression of JAM-A, which facilitates effective viral entry into malignant cells, in five of six cell lines. These cell lines also demonstrated differential activation of RAS and downstream kinases, suggesting targeted susceptibility of these cells to reovirus oncolysis. To further test this, we infected cells with reovirus for 1–4 days and assessed cytopathic effects. Using phase contrast microscopy, we observed the virus treated cell lines to demonstrate morphological changes characteristic of cell death following infection. Cell viability assays were used to quantify this effect, and the mechanism of cell death was determined to be apoptotic as evidenced by caspase-dependent cleavage of PARP. Reovirus-induced cell death was correlated with viral protein production and replication. Next, we screened for the ability of reovirus to induce synergistic activity in a panel of conventional and novel targeted therapeutic agents. Our studies showed that, in contrast to the current antileukemic agents, the Bcl-2 inhibitor BH3 mimetic ABT-737 was able to significantly synergize with reovirus in all cell lines tested. Conclusions: In our in vitro studies, oncolytic reovirus as a single agent showed potent oncolytic activity against all pediatric leukemia cell lines tested that express the receptor for reovirus, regardless of the status of the RAS signaling pathway. Further, we found reovirus-induced oncolysis can be enhanced by combination with Bcl-2 inhibition but was unaltered or antagonized by the other drugs indicating a key relationship between the two pathways. As such, our data for the first time, show that pediatric leukemia cells carry the potential to be targeted by reovirus induced oncolysis and the identification of drug synergy and the biomarkers of target modulation provide the basis for further studies to develop this novel therapeutic approach for clinical studies in the near future. Disclosures: No relevant conflicts of interest to declare.

MDM2 Inhibitor Nutlin-3a Triggers Autophagic Cell Death In Addition to Apoptosis In Leukemia Cell Lines with Wild-Type p53

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3300-3300
Author(s):  
Seshagiri Duvvuri ◽  
Vivian Ruvolo ◽  
Duncan H. Mak ◽  
Kensuke Kojima ◽  
Marina Konopleva ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Death ◽  
Western Blot ◽  
Cell Lines ◽  
Research Funding ◽  
Leukemia Cell ◽  
Annexin V ◽  
Dependent Manner ◽  
Autophagic Vacuoles ◽  
Leukemia Cell Lines

Abstract Abstract 3300 Background: Nutlin-3a is a small molecule inhibitor of MDM2 and has been shown to induce apoptosis and cell cycle arrest in various cancer models in a p53 dependent manner. Autophagy is a programmed cell death that can occur concurrently with apoptosis or in its absence. There is significant debate whether autophagy is a protective mechanism or a bona fide mechanism of cell death. While autophagy can function as tumor cell defense mechanism against cellular stress induced death, mutation/loss of alleles of certain genes regulating autophagy have been associated with development of cancer (e.g. Beclin-1 in breast cancer [Nature, 1999, 402: 672–676]). Multiple proteins involved in autophagy are transcriptional targets of p53 but Nutlin-3a has not been evaluated for its role in inducing autophagy. Here we present data suggesting that low dose Nutlin-3a induces autophagy in addition to apoptosis in leukemia cell lines in a p53 dependent manner. Methods and results: OCI-AML-3 cells (p53-WT) treated with Nutlin-3a (2.5 and 5.0μM for 48, 72 and 96 hrs) were stained with mono-dansyl-cadaverine (MDC), a dye that accumulates in acidic autophagic vacuoles. OCI-AML-3 cells showed increasing staining with MDC in a dose and time dependent fashion by both flow cytometry (54%, 57% and 51% MDC positive after treatment with Nutlin-3a 5.0μM for 48, 72 and 96 hrs) and by confocal microscopy. Nutlin-3a treated cells also were positive for Annexin-V (flow cytometry 22%, 26% and 36% at 48, 72 and 96 hrs time points), and some of the cells were double-positive for Annexin-V and MDC (9.2%, 5% and 7% at 48, 72 and 96 hrs) suggesting that both apoptosis and autophagy can occur simultaneously. Autophagy induction was confirmed by Transmission Electron Microscopy (TEM). Large, multiple autophagic vacuoles were observed in OCI-AML-3 cells treated with Nutlin-3a. OCI-AML-3 cells with stable p53 knockdown by shRNA or HL-60 cells (p53-null) did not show increased MDC staining by flow cytometry (both cell lines) or autophagic vacuoles by TEM (HL-60) after similar treatment. Western blot analysis showed increases in LC3-II and in conjugation of Atg5/12, early and late autophagy markers respectively, in OCI-AML-3 cells after treatment with Nutlin-3a. Increased expression of the autophagy markers (LC3-II and Atg 5/12 conjugate) were also seen by Western blot analysis in the ALL cell lines REH and NALM-6 (both p53-WT) after treatment with Nutlin-3a. Western blot and/or RT-PCR analysis showed upregulation of other p53 related proteins involved in autophagy e.g. DRAM, AMPK-β, LKB1, pLKB1 in OCI-AML-3 cells treated with Nutlin-3a. As mTOR/Akt pathway inhibits autophagy, analysis of mTOR targets showed downregulation of the total and phospho-ribosomal-S6-protein levels, whereas there was no change in total or phospho-4-EBP-1 levels. Knockdown of Beclin-1 (ATG6), one of the proteins required for initiation of the formation of autophagic vacuoles, caused reduction in autophagic vacuoles (MDC staining by confocal microscopy) in OCI-AML-3 and REH cells without affecting apoptosis induction (Annexin V by flow cytometry). Pharmacologic inhibition of late autophagy by Bafilomycin (10nM for 2 hours) reduced MDC staining in OCI-AML-3 cells treated with Nutlin-3a for 48 hrs (32% without and 9% with Bafilomycin) while having limited inhibition of apoptosis (Annexin V positive 42% without and 33% with Bafilomycin). Conclusion: Nutlin-3a induces autophagy in leukemia cells by a p53 dependent manner. We also demonstrate that autophagy could go hand-in-hand with apoptosis and in a fraction of cells both processes may occur concomitantly. Inhibition of autophagy does not necessarily enhance apoptosis. Disclosures: Andreeff: Roche: Research Funding. Borthakur:ASCO: Research Funding.

Catha edulis(Khat) Induces Cell Death by Apoptosis in Leukemia Cell Lines

2003 ◽  
Vol 1010 (1) ◽  
pp. 384-388 ◽  
Author(s):  
E DIMBA ◽  
B T. GJERTSEN ◽  
G W. FRANCIS ◽  
A C. JOHANNESSEN ◽  
O K. VINTERMYR
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Leukemia Cell ◽  
Catha Edulis ◽  
Leukemia Cell Lines

Combination of Farnesyl Transferase Inhibitor (Tipifarnib) with Perifosine Induces Apoptosis through phos-PDK1 in Human Lymphoma and Leukemia Cell Lines.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1488-1488 ◽  
Author(s):  
Ebenezer David ◽  
Rajni Sinha ◽  
Claire Torre ◽  
Jonathan L. Kaufman ◽  
Sagar Lonial
Keyword(s):  
Cell Death ◽  
Western Blot ◽  
Cell Lines ◽  
Blot Analysis ◽  
Leukemia Cell ◽  
Human Leukemia ◽  
Targeted Agents ◽  
Leukemia Cell Lines ◽  
Targeted Agent ◽  
The Impact

Abstract Introduction: Novel agents as anti-cancer therapy are used in the setting of specific molecular abnormalities that provide a survival advantage for malignant cells. One such agent, tipifarnib, is theoretically targeted at Ras mutations which are present in a number of different human cancers. Our previous experience with the FTIs (David et al, in press Blood) has demonstrated that they are ideal agents to combine with other targeted agents. We have investigated the combination of the AKT inhibitor perifosine with tipifarnib in human leukemia and lymphoma cell lines with the hypothesis that the combination of 2 targeted agents will disrupt separate survival pathways and ultimately result in synergistic tumor cell death. Methods: In this study we used the human leukemia cell lines HL-60, Jurkat, and the lymphoma cell line HT. Western blot analysis was used to assess for the effect of either single agent perifosine, tipifarnib, or the combination on AKT, p-AKT, PDK-1, and caspase cleavage. Flow cytometry was utilized to assess for Annexin V staining following combination therapy. Results:Dose escalation studies demonstrated that doses of tipifarnib up to 5μm demonstrated a significant cell death in HL-60 and HT cells. Perifosine doses of 1–5uM also induced cell death in both HL-60 and HT cells. When apoptosis was assessed using western blot analysis of caspase 3 activity and cleavage, the combination of perifosine and tipifarnib demonstrated significant apoptosis using low doses of both agents. The apoptosis was associated with downregulation of phos-PDK1, with a resultant downregulation in p-AKT. The level of phos-PDK1 was completely inhibited in less than 24 hrs in both the HL-60 and HT cell lines in combination than when either agent was given alone. Conclusion: The combination of perifosine, and AKT targeted agent, with tipifarnib, a Ras targeted agent, appear to induce significant cell death in lymphoma and leukemia cell lines with rapid downregulation of p-AKT via the PDK-1 pathway. This apoptosis occurs in vitro using concentrations well below those that have been achieved in current clinical trials using these agents. Additional studies are being carried out to further delineate the mechanism of synergy as well as to further explore the impact of sequence of administration using this combination. Further studies are also planned to xplore the impact of the combination on primary human leukemia and lymphoma cells from the blood and bone marrow.

The Acrylonitrile Analog, VJ-289 Ablates Acute Myelogenous Leukemia Blast, Progenitor and Stem Cell Populations by Inducing Tubulin Acetylation and Caspase Activation

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2496-2496
Author(s):  
Hongliang Zong ◽  
Narsimha Reddy Penthala ◽  
Siddhartha Sen ◽  
Sarah Brennan ◽  
Vijayakumar Sonar ◽  
...  
Keyword(s):  
Cell Lines ◽  
Leukemia Cell ◽  
Leukemic Cell ◽  
Dependent Manner ◽  
Caspase Activation ◽  
Tubulin Acetylation ◽  
Leukemia Cell Lines ◽  
Cord Blood Cells ◽  
Stem Cell Populations ◽  
Dose Dependent

Abstract Abstract 2496 Combretastatin A-4, a derivative of combretastatin, a natural product of the South African tree Combretum caffrum, has been reported to have anti-angiogenic and anti-tubulin effects in different cancer cell lines. We synthesized 48 novel combretastatin analogs to assess anti-leukemia activity in a panel of 12 leukemia cell lines. We identified an analog, VJ-289 [(Z)-3-(1H-indol-2-yl)-2-(3,4,5-trimethoxyphenyl)acrylonitrile] with robust anti-leukemic activity. VJ-289 showed a dose-dependent toxicity to most of the leukemic cell lines tested. The average LD50 for the 12 different leukemia cell lines was 132 nM (95% CI, 91.8–170.5). Specifically, MV4-11 cells demonstrated the most sensitivity to VJ-289 (LD50 = 66 nM), whereas THP-1 was the most resistant (LD50 = 227 nM). Furthermore, when the activity of VJ-289 was tested, five out of 14 primary AML samples demonstrated resistance to VJ-289 with an LD50 > 300nM. The average LD50 for the sensitive primary AML samples was 64.06 nM (95% CI, 35.36–92.76; N=9). Most importantly, normal CD34+ cord blood cells were significantly less affected by VJ-289 (LD50 > 500 nM). Furthermore, VJ-289 was capable of eliminating AML progenitor/stem cells as determined by phenotypic analysis in 15 primary AML samples, colonies forming ability (N=6) and xenotransplant assays (N=6). Overall, we observed a 90.3% decrease in colony formation after treatment with 150 nM VJ-289 relative to untreated control. In contrast, VJ-289 had less impact on colony forming ability of normal hematopoietic stem/progenitor cells from cord blood cells (66.1% decrease relative to untreated; p=0.013). To investigate the role of VJ-289 in leukemic cell apoptosis, various cell survival signaling pathways were examined. Western blotting and intracellular staining/flow cytometry data showed that caspases, including caspase 3 and 8, were activated alongside the cleavage of PARP in a dose-dependent manner. Caspase activation was observed as early as 4 h after treatment with 100 nM VJ-289. PI3K/AKT, MAPK and NF-κB were decreased upon VJ-289 treatment. Moreover, the degradation of MCL1 and the cleavage of Bcl2, two anti-apoptotic Bcl2 family members, were decreased by VJ-289 in a dose- and time-dependent manner. Interestingly, the acetylation of α-tubulin, which is critical for microtubule stabilization, and is involved in multiple cellular functions, ranging from cell motility, cell cycle progression or cell differentiation to intracellular trafficking and signaling, was transiently induced by VJ-289 within 2 hours, and was inhibited dramatically after 4 hours. In summary, we have identified a combrestastatin A-4 analog, VJ-289, as a new anti-leukemia agent with the ability to ablate blast, progenitor and stem cell populations via induction of caspase activation and α-tubulin acetylation. Studies are underway to determine what modulates sensitivity to VJ-289 across AML specimens. Disclosures: No relevant conflicts of interest to declare.

Uncovering Cardioprotective Strategies For Anthracycline Therapy By Analysis Of Redox and Apoptotic Effects

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1293-1293
Author(s):  
Daniela E. Egas Bejar ◽  
Joy M. Fulbright ◽  
Fernando F. Corrales-Medina ◽  
Mary E. Irwin ◽  
Blake Johnson ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Death ◽  
Vitamin E ◽  
Acute Leukemia ◽  
Cell Lines ◽  
Leukemia Cell ◽  
Cell Types ◽  
Leukemia Cells ◽  
Soluble Form ◽  
Leukemia Cell Lines

Abstract Anthracyclines are among the most powerful drugs used for the treatment of leukemia, however their use has been associated with cardiotoxicity. Reactive oxygen species (ROS) are generated in both cancer and normal cells after anthracycline exposure and have been implicated in both early and late onset cardiotoxicity. Counteracting this ROS generation are intracellular antioxidants such as the ubiquitous antioxidant glutathione (GSH), levels of which are depleted upon anthracycline exposure. Basal expression of GSH pathway components and other antioxidants vary greatly between different cell types. Due to this differential expression of cellular antioxidants in cardiomyocytes versus leukemia cells, we posit that anthracyclines exert distinct effects on oxidative stress and consequent apoptosis induction in leukemia cells and nontransformed hematopoietic cells (PBMC) relative to cardiomyocytes. As a result, we expect potentially varied mechanisms of cell death induction in these cell lines after anthracycline treatment. To test this hypothesis, the acute leukemia cell lines Jurkat and ML-1 and the cardiomyocyte line H9C2 were used. Dose responses with the anthracyclines, doxorubicin and daunorubicin, were carried out and trypan blue exclusion and propidium iodide staining followed by flow cytometry were used to assess viability and DNA fragmentation respectively. Cardiomyocytes had a 25-150 fold higher IC50 value than the acute leukemia cell lines, indicating selectivity. To assess whether apoptosis was induced by anthracyclines, caspase 3 activity was measured and found to be increased at 24 hours in Jurkat cells which preceded decreases in viability, supporting an apoptotic mechanism of cell death. GSH levels also decreased markedly after 24 hours of treatment with anthracyclines in this cell line, however, a pan-caspase inhibitor did not block GSH depletion, indicating that these events occur independent of each other. To evaluate whether antioxidants conferred protection against loss of viability in all cell types, cells were pretreated for at least 30 minutes with antioxidants and then treated with doxorubicin and daunorubicin for 24 hours. Antioxidants used were N-acetylcysteine (NAC, a GSH precursor and amino acid source), GSH ethyl ester (cell permeable form of GSH), tiron (free radical scavenger) and trolox (a water soluble form of vitamin E). GSH ethylester did not prevent cytotoxicity of anthracyclines in acute leukemia lines or cardiomyocytes. Therefore boosting GSH levels in leukemia cells does not reverse cytotoxicity. Trolox, however, did block anthracycline induced cell death in ML-1 cells, suggesting that vitamin E supplementation would counteract leukemia cell specific effects of anthracyclines on AML cells. Tiron protected PBMC from doxorubicin cytotoxicity but did not protect leukemia cells or cardiomyocytes, hinting at a protective strategy for normal non-leukemia blood cells. Interestingly, NAC did not interfere with the cytotoxic effects of anthracyclines on acute leukemia cells or PBMC, but protected H9C2 cells from daunorubicin cytotoxicity. Taken together, these data reveal differential protective effects of antioxidants in cardiomyocytes and PBMCs relative to ALL and AML cells. Our work indicates that NAC can protect cardiomyocytes without interfering with anthracycline cytotoxicity in acute leukemia cells. In humans, one randomized control trial tested the addition of NAC to doxorubicin therapy, detecting no evidence of cardioprotective activity by chronic administration of NAC. However, the schedule used for administration of NAC in that study may not have been optimal, and biomarkers for oxidative stress reduction by NAC were not incorporated into the trial. Previously, other antioxidants have been used with very limited clinical success and possible contributing factors include inadequate sample size, choice of agent, dose used, duration of intervention and the lack of biomarker endpoints. Designing a cardioprotective and antioxidant strategy with attention to these factors may prove to be efficacious in protecting cardiac cells without interfering with the antitumoral effect of anthracyclines. To this end, our data suggests that trolox and vitamin E analogues should not be used in acute leukemia as they may interfere with the cytotoxic action of anthracyclines but NAC or cysteine may be used as cardioprotectants. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Endoplasmic Reticulum Stress Signaling Comprises a G9a Inhibitor Tolerance Pathway and PERK Inhibition Increases Anti-Leukemia Activity of G9a Inhibitor in Leukemia Cells and Leukemia Stem-like Cells

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1360-1360
Author(s):  
Jieun Jang ◽  
Ju-In Eom ◽  
Hoi-kyung Jeung ◽  
So-Young Seol ◽  
Haerim Chung ◽  
...  
Keyword(s):  
Cell Death ◽  
Er Stress ◽  
Cell Lines ◽  
Apoptotic Cell ◽  
Leukemia Cell ◽  
Apoptotic Cell Death ◽  
Leukemia Cells ◽  
Dependent Manner ◽  
Eif2α Phosphorylation ◽  
Kg1 Cells

Abstract Background: Histone methyltransferase (HMTase) G9a regulates the transcription of multiple genes by primarily catalyzing dimethylation of histone H3 lysine 9 (H3K9me2), as well as several non-histone lysine sites. Recently, pharmacological and genetic targeting of the G9a was shown to be efficient in slowing down acute myeloid leukemia (AML) cell proliferation in a mouse model and human AML cell lines thus making this HMTase potential target for epigenetic therapy of AML. Activation of adaptive mechanisms to drug plays a crucial role in drug resistance and relapse by allowing cell survival under stressful conditions. Therefore, inhibition of the adaptive response is considered as a prospective therapeutic strategy. The tolerance mechanism to HMTase regulation in leukemia cell is unclear yet. The PERK-eIF2α phosphorylation pathway is an important arm of the unfolded protein response (UPR), which is induced under conditions of endoplasmic reticulum (ER) stress. Recent previous studies showed that pro-survival ER stress is induced in cancer cells and contributes to development of drug resistance. Methods: We investigated the levels of apoptosis and ER stress by G9a inhibitor BIX-01294 in leukemia cell lines. U937, cytarabine-resistant U937 (U937/AR) and KG1 were used. U937/AR cell line was established in our laboratory by exposing parental U937 cells to stepwise increasing concentrations of cytarabine. Results: We initially examined the expression of G9a in leukemia cell lines and the primary AML cells obtained from a patient at the different time point. In U937/AR cells and primary AML cells obtained at relapse, G9a expression was increased compare to that in U937 cells and primary AML cells obtained at diagnosis, respectively. G9a expression was also increased in KG1 cells. In both of U937 and U937/AR, apoptotic cell death was induced by BIX-01294 in a dose-dependent manner. In contrast, apoptotic cell death was minimal in KG1 cells which are enriched in cells expressing a leukemia stem cell phenotype (CD34+CD38-). To address the activation of ER stress response by BIX-01294 in leukemia cells, we examined the effect of BIX-01294 treatment on PERK and eIF2α protein expression and phosphorylation levels. We found that treatment of U937, U937/AR, KG1 cells with 3μM of BIX-01294 for 24h caused an upregulation of phosphorylated PERK and eIF2α. The upregulation of PERK phosphorylation was associated with a decrease in PERK protein levels after treatment. To further address the role of the PERK-eIF2α phosphorylation in BIX-01294 sensitivity, we examined whether PERK inhibition using small interfering RNA (siRNA) or specific inhibitor could sensitize cells to BIX-01294-mediated death. The siRNA against PERK effectively inhibited BIX-01294-mediated phosphorylation of PERK and eIF2α in U937 and U937/AR cells. The addition of PERK siRNA led to a significant increase in the extent of BIX-01294-induced apoptotic cell death in U937 (P = 0.0003) and U937/AR (P < 0.0001) as compared with that of BIX-01294 treatment alone. PERK inhibitor GSK260641 significantly increased BIX-01294-induced apoptotic cell death in U937 (P < 0.0001) and U937/AR (P = 0.006) cells. To our surprise, addition of PERK siRNA or GSK260641 increased the sensitivity of KG1 cells to BIX-01294-mediated death in a dose-dependent manner (P = 0.0003 for siRNA, P = 0.0053 for GSK260641). Conclusion: These data demonstrated that PERK-eIF2α activation has a pro-survival function to G9a inhibitor in leukemia cells and mediates resistance of AML stem cells to G9a inhibitor treatment. The PERK-eIF2α phosphorylation arm may represent a suitable target for combating resistance to G9a inhibitor in AML. The mechanisms underlying the increased sensitivity of AML cells with PERK inhibition to G9a inhibitor are unclear at present and are needed to define in further studies. Disclosures No relevant conflicts of interest to declare.

Sodium Salicylate Activates Caspases and Induces Apoptosis of Myeloid Leukemia Cell Lines

Blood ◽  
1999 ◽  
Vol 93 (7) ◽  
pp. 2386-2394 ◽  
Author(s):  
Lidija Klampfer ◽  
Jörg Cammenga ◽  
Hans-Georg Wisniewski ◽  
Stephen D. Nimer
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Sodium Salicylate ◽  
Leukemia Cell ◽  
Human Leukemia ◽  
Leukemia Cell Lines ◽  
Induced Apoptosis ◽  
Chemopreventive Activity ◽  
Myeloid Leukemia Cell

Abstract Nonsteroidal antiinflammatory agents (NSAIA) have been shown to exert potent chemopreventive activity against colon, lung, and breast cancers. In this study, we show that at pharmacological concentrations (1 to 3 mmol/L) sodium salicylate (Na-Sal) can potently induce programmed cell death in several human myeloid leukemia cell lines, including TF-1, U937, CMK-1, HL-60, and Mo7e. TF-1 cells undergo rapid apoptosis on treatment with Na-Sal, as indicated by increased annexin V binding capacity, cpp-32 (caspase-3) activation, and cleavage of poly (ADP-ribose) polymerase (PARP) and gelsolin. In addition, the expression of MCL-1, an antiapoptotic member of the BCL-2 family, is downregulated during Na-Sal–induced cell death, whereas the expression of BCL-2, BAX, and BCL-XL is unchanged. Z-VAD, a potent caspase inhibitor, prevents the cleavage of PARP and gelsolin and rescues cells from Na-Sal–induced apoptosis. In addition, we show that Na-Sal accelerates growth factor withdrawal-induced apoptosis and synergizes with daunorubicin to induce apoptosis in TF-1 cells. Thus, our data provide a potential mechanism for the chemopreventive activity of NSAIA and suggest that salicylates may have therapeutic potential for the treatment of human leukemia.

scholarly journals Apoptosis induced by erythroid differentiation of human leukemia cell lines is inhibited by Bcl-XL

Blood ◽  
1996 ◽  
Vol 87 (9) ◽  
pp. 3837-3843 ◽  
Author(s):  
A Benito ◽  
M Silva ◽  
D Grillot ◽  
G Nunez ◽  
JL Fernandez-Luna
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Leukemia Cell ◽  
K562 Cells ◽  
Erythroid Differentiation ◽  
Leukemia Cells ◽  
Human Leukemia ◽  
Human Leukemia Cells ◽  
Leukemia Cell Lines ◽  
Wide Range

The induction of tumor cell differentiation represents an attractive strategy for the treatment of a wide range of malignancies. Differentiation of HL-60 promyelocytic leukemia cells towards neutrophils or monocytes has been shown to induce apoptotic cell death, which is inhibited by bcl-2 over-expression. However, the role of the bcl-2 gene family during erythroid differentiation of human leukemia cells remains unknown. We found that human erythroleukemia (HEL) and K562, two leukemia cell lines that undergo erythroid differentiation do not express Bcl-2, but express Bcl-XL, a related protein that functions as an inhibitor of apoptosis. Differentiation of HEL or K562 cells with inducers of erythroid differentiation (hemin, retinoic acid, or transforming growth factor-beta) was accompanied by progressive cell death and degradation of genomic DNA into oligonucleosomal fragments. The loss of cellular viability was associated with downregulation of bcl-xL mRNA and protein. In contrast, the levels of Bax, another Bcl-2 family member implicated in apoptosis remained unaltered. Constitutive expression of Bcl-XL by gene transfer inhibited apoptosis triggered by erythroid differentiation of HEL K562 cells. Yet, Bcl-XL did not alter the expression of epsilon-globin, which is induced during erythoid differentiation of HEL and K562 cells, arguing that apoptosis and differentiation can be uncoupled by Bcl-XL. These results indicate that Bcl-XL acts as an antiapoptosis protein in leukemia cells that undergo erythroid differentiation and that downregulation of bcl-x is a component of the apoptotic response that is coupled to differentiation in human leukemia cells.

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