scholarly journals Cannabidiol Induces Apoptosis and Perturbs Mitochondrial Function in Human and Canine Glioma Cells

2021 ◽  
Vol 12 ◽  
Author(s):  
Chase Gross ◽  
Dominique A. Ramirez ◽  
Stephanie McGrath ◽  
Daniel L. Gustafson
Keyword(s):  
Cell Death ◽  
Anticancer Agent ◽  
Glioma Cells ◽  
Fluorescent Imaging ◽  
Mitochondrial Activity ◽  
Dependent Manner ◽  
Trpv1 Channel ◽  
Pharmacologic Inhibitors ◽  
Dose Dependent

Cannabidiol (CBD), the major non-psychoactive compound found in cannabis, is frequently used both as a nutraceutical and therapeutic. Despite anecdotal evidence as an anticancer agent, little is known about the effect CBD has on cancer cells. Given the intractability and poor prognoses of brain cancers in human and veterinary medicine, we sought to characterize the in vitro cytotoxicity of CBD on human and canine gliomas. Glioma cells treated with CBD showed a range of cytotoxicity from 4.9 to 8.2 μg/ml; canine cells appeared to be more sensitive than human. Treatment with >5 μg/ml CBD invariably produced large cytosolic vesicles. The mode of cell death was then interrogated using pharmacologic inhibitors. Inhibition of apoptosis was sufficient to rescue CBD-mediated cytotoxicity. Inhibition of RIPK3, a classical necroptosis kinase, also rescued cells from death and prevented the formation of the large cytosolic vesicles. Next, cellular mitochondrial activity in the presence of CBD was assessed and within 2 hours of treatment CBD reduced oxygen consumption in a dose dependent manner with almost complete ablation of activity at 10 μg/ml CBD. Fluorescent imaging with a mitochondrial-specific dye revealed that the large cytosolic vesicles were, in fact, swollen mitochondria. Lastly, calcium channels were pharmacologically inhibited and the effect on cell death was determined. Inhibition of mitochondrial channel VDAC1, but not the TRPV1 channel, rescued cells from CBD-mediated cytotoxicity. These results demonstrate the cytotoxic nature of CBD in human and canine glioma cells and suggest a mechanism of action involving dysregulation of calcium homeostasis and mitochondrial activity.

scholarly journals TB-4 Antitumor effects of a novel curcumin derivative curcumin monoglucuronide on glioblastoma cells in vitro and in vivo

2021 ◽  
Vol 3 (Supplement_6) ◽  
pp. vi6-vi6
Author(s):  
Takashi Fujii ◽  
Shun Yamamuro ◽  
Masamichi Takahashi ◽  
Akihide Kondo ◽  
Yoshitaka Narita ◽  
...  
Keyword(s):  
Cell Death ◽  
Water Soluble ◽  
Dependent Manner ◽  
Antitumor Effects ◽  
Multiple Cell ◽  
Human Gbm ◽  
Dose Dependent ◽  
Novel Therapeutic

Abstract The therapeutic outcome of glioblastomas (GBMs) is still very poor. Therefore, invention of novel therapeutic methods against GBM cases is considered urgent. The antitumor effects of naturally-derived compounds are attracting attention recently, and therapeutic efficacy of curcumin, a plant-derived compound previously used for multiple purpose, has been indicated in many cancer systems; however, clinical application of curcumin is considered difficult because of its poor bioavailability (under 1 %). Curcumin monoglucuronide (CMG), a water-soluble prodrug of curcumin recently developed for overcoming this weakness, has been demonstrated excellent antitumor effects for several malignancies in vitro and in vivo; therefore, we investigated the effects of CMG against GBM cells. CMG induced cell death of human GBM cells lines (T98G, U251MG, and U87MG) by dose dependent manner by triggering multiple forms of cell death such as apoptosis and perthanatos. Immunoblotting of CMG-treated GBM cell lysates demonstrated activation of multiple cell death signaling. Furthermore, immunodeficiency mice harboring intracerebral U87MG cell xenografts systemically treated by CMG showed significantly prolonged survival compared with control mice. These results suggest CMG would be a novel therapeutic agent against GBM cases.

scholarly journals Ivermectin induces autophagy-mediated cell death through the AKT/mTOR signaling pathway in glioma cells

2019 ◽  
Vol 39 (12) ◽  
Author(s):  
Jingjing Liu ◽  
Hongsheng Liang ◽  
Chen Chen ◽  
Xiaoxing Wang ◽  
Faling Qu ◽  
...  
Keyword(s):  
Cell Death ◽  
Molecular Mechanisms ◽  
Anticancer Agent ◽  
Glioma Cells ◽  
Mtor Signaling ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Transmission Electron ◽  
Diphenyltetrazolium Bromide

Abstract Glioma is one of the most common types of primary brain tumors. Ivermectin (IVM), a broad-spectrum antiparasitic drug, has been identified as a novel anticancer agent due to its inhibitory effects on the proliferation of glioma cells in vitro and in vivo. However, the ability of IVM to induce autophagy and its role in glioma cell death remains unclear. The main objective of the present study was to explore autophagy induced by IVM in glioma U251 and C6 cells, and the deep underlying molecular mechanisms. In addition, we examined the effects of autophagy on apoptosis in glioma cells. In the present study, transmission electron microscopy (TEM), immunofluorescence, Western blot and immunohistochemistry were used to evaluate autophagy activated by IVM. Cell viability was measured by 3-(4,5-dimethylthiazol2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and colony formation assay. The apoptosis rate was detected by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Meanwhile, autophagy inhibition was achieved by using chloroquine (CQ). U251-derived xenografts were established for examination of IVM-induced autophagy on glioma in vivo. Taken together, the results of the present study showed that autophagy induced by IVM has a protective effect on cell apoptosis in vitro and in vivo. Mechanistically, IVM induced autophagy through AKT/mTOR signaling and induced energy impairment. Our findings show that IVM is a promising anticancer agent and may be a potential effective treatment for glioma cancers.

scholarly journals Enhanced Malignant Phenotypes of Glioblastoma Cells Surviving NPe6-Mediated Photodynamic Therapy are Regulated via ERK1/2 Activation

Cancers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3641
Author(s):  
Tatsuya Kobayashi ◽  
Makoto Miyazaki ◽  
Nobuyoshi Sasaki ◽  
Shun Yamamuro ◽  
Eita Uchida ◽  
...  
Keyword(s):  
Cell Death ◽  
Photodynamic Therapy ◽  
Migration And Invasion ◽  
Dependent Manner ◽  
Potential Therapeutic Target ◽  
Talaporfin Sodium ◽  
Polymerase Inhibitor ◽  
Human Gbm ◽  
Dose Dependent

To manage refractory and invasive glioblastomas (GBM)s, photodynamic therapy (PDT) using talaporfin sodium (NPe6) (NPe6-PDT) was recently approved in clinical practice. However, the molecular machineries regulating resistance against NPe6-PDT in GBMs and mechanisms underlying the changes in GBM phenotypes following NPe6-PDT remain unknown. Herein, we established an in vitro NPe6-mediated PDT model using human GBM cell lines. NPe6-PDT induced GBM cell death in a NPe6 dose-dependent manner. However, this NPe6-PDT-induced GBM cell death was not completely blocked by the pan-caspase inhibitor, suggesting NPe6-PDT induces both caspase-dependent and -independent cell death. Moreover, treatment with poly (ADP-ribose) polymerase inhibitor blocked NPe6-PDT-triggered caspase-independent GBM cell death. Next, it was also revealed resistance to re-NPe6-PDT of GBM cells and GBM stem cells survived following NPe6-PDT (NPe6-PDT-R cells), as well as migration and invasion of NPe6-PDT-R cells were enhanced. Immunoblotting of NPe6-PDT-R cells to assess the behavior of the proteins that are known to be stress-induced revealed that only ERK1/2 activation exhibited the same trend as migration. Importantly, treatment with the MEK1/2 inhibitor trametinib reversed resistance against re-NPe6-PDT and suppressed the enhanced migration and invasion of NPe6-PDT-R cells. Overall, enhanced ERK1/2 activation is suggested as a key regulator of elevated malignant phenotypes of GBM cells surviving NPe6-PDT and is therefore considered as a potential therapeutic target against GBM.

scholarly journals P.042 Raloxifene sensitizes glioblastoma cells to hypoxia-induced death through inhibition of stress granule dissolution

2018 ◽  
Vol 45 (s2) ◽  
pp. S27-S27
Author(s):  
A Robichaud ◽  
K Attwood ◽  
A Balgi ◽  
M Roberge ◽  
A Weeks
Keyword(s):  
Cell Death ◽  
Glioma Cells ◽  
Treatment Resistance ◽  
Cell Counting ◽  
Dependent Manner ◽  
Treatment Results ◽  
Malignant Brain Tumour ◽  
Cytoplasmic Rna ◽  
Dose Dependent ◽  
Tumour Cell Death

Background: Glioblastoma (GBM) is the most common primary malignant brain tumour. Despite aggressive therapy, median survival is only 14 months. Death typically results from treatment failure and local recurrence. The GBM microenvironment is highly hypoxic, which correlates with treatment resistance. Cytoplasmic RNA stress granules (SGs) form in response to hypoxic stress and act as sights of mRNA triage, allowing preferential translation of pro-survival mRNA during stress. We hypothesize that SGs may play a role in hypoxia-induced resistance to therapy, and may be targetable by chemotherapeutics to improve outcomes. Methods: We screened 1280 approved compounds to identify drugs that inhibited formation or dissolution of SGs in U251 glioma cells. Raloxifene inhibited SG dissolution in a dose dependent manner. We treated cells with raloxifene and incubated them in hypoxia, and then measured rates of cell death using cell counting and Presto blue. Results: Cell death rates were synergistically higher in cells treated with the combination of raloxifene and hypoxia compared to either treatment alone. Conclusions: Raloxifene inhibits the dissolution of SGs in glioma cells, and combination treatment results in synergistic tumour cell death. Taken together, this provides evidence that inhibition of SG dissolution may be a viable target for future GBM chemotherapeutics.

In Vitro Activity of a Novel Fully Human Anti-CD40 Antibody CHIR-12.12 in Chronic Lymphocytic Leukemia: Blockade of CD40 Activation and Induction of ADCC.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2504-2504 ◽  
Author(s):  
Xia Tong ◽  
Georgios V. Georgakis ◽  
Long Li ◽  
O’Brien Susan ◽  
Younes Anas ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Cell Death ◽  
Chronic Lymphocytic Leukemia ◽  
Cell Line ◽  
Blood Donors ◽  
Lymphocytic Leukemia ◽  
Dependent Manner ◽  
Dose Dependent

Abstract B-cell chronic lymphocytic leukemia (CLL) is characterized by in vivo accumulation of long-lived CD5+ B cells. However when cultured in vitro CLL cells die quickly by apoptosis. Protection from apoptosis in vivo is believed to result from supply of survival signals provided by cells in the microenvironment. We and others have previously reported that CLL cells express CD40 receptor, and that CD40 stimulation of CLL cells may rescue CLL cells from spontaneous and drug-induced apoptosis in vitro. These observations suggested that blocking CD40-CD40L pathway might deprive CLL cells from survival signals and induce apoptosis. To test this hypothesis, we have generated a fully human anti-CD40 blocking monoclonal antibody in XenoMousemice (Abgenix, Inc.). The antibody CHIR-12.12 was first evaluated for its effect on normal human lymphocytes. Lymphocytes from all 10 healthy blood donors did not proliferate in response to CHIR-12.12 at any concentration tested (0.0001 mg/ml to 10 mg/ml range). In contrast, activating CD40 on normal B-lymphocytes by CD40L induced their proliferation in vitro. Importantly, CHIR-12.12 inhibited CD40L- induced proliferation in a dose dependent manner with an average IC50 of 51 ± 26 pM (n=10 blood donors). The antagonistic activity of CHIR-12.12 was then tested in primary CLL samples from 9 patients. CHIR-12.12 alone did not induce CLL cell proliferation. In contrast, primary CLL cells incubated with CD40L, either resisted spontaneous cell death or proliferated. This effect was reversed by co-incubation with CHIR-12.12 antibody, restoring CLL cell death (n=9). CHIR-12.12 was then examined for its ability to lyse CLL cell line EHEB by antibody dependent cell mediated cytotoxicity (ADCC). Freshly isolated human NK cells from normal volunteer blood donors were used as effector cells. CHIR-12.12 showed lysis activity in a dose dependent manner and produced maximum lysis levels at 0.1 mg/ml. When compared with rituximab, CHIR-12.12 mediated greater maximum specific lysis (27.2 % Vs 16.2 %, p= 0.007). The greater ADCC by CHIR-12.12 was not due to higher density of CD40 molecules on CLL cell line compared to CD20 molecules. The CLL target cells expressed 509053 ±13560 CD20 molecules compared to 48416 ± 584 CD40 molecules. Collectively, these preclinical data suggest that CHIR-12.12 monoclonal antibody may have a therapeutic role in patients with CLL.

Protective effect of chloroform extract of Stereospermum chelonoides bark against amyloid beta42 induced cell death in SH-SY5Y cells and against inflammation in Swiss albino mice

2018 ◽  
Vol 29 (6) ◽  
pp. 621-630
Author(s):  
Md. Imamul Islam ◽  
Meena Afroze Shanta ◽  
Milon Mondal ◽  
Nazia Hoque ◽  
Senjuti Majumder ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Death ◽  
Protective Effect ◽  
Antioxidant Capacity ◽  
Caspase 3 ◽  
Radical Scavenging ◽  
Chloroform Extract ◽  
Dependent Manner ◽  
Dose Dependent

Abstract Background This study was designed to evaluate the free radical scavenging property of chloroform extract of the bark of Stereospermum chelonoides (SCBC) and to investigate its potential in Alzheimer’s disease and inflammation, two oxidative stress related disorders. Methods Preliminary phytochemical analysis and in vitro antioxidant potential of SCBC were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, ferric reducing antioxidant power (FRAP) assay, cupric reducing antioxidant capacity (CUPRAC) and total antioxidant capacity determination assay. Total phenol and total flavonoid contents were also determined. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) based cytotoxicity and cyto-protective assays were performed on human neuroblastoma SH-SY5Y cells. Thioflavin-T assay and caspase activation measurement assay were carried out to elucidate the mechanism of cytoprotection of SCBC observed here. In vivo anti-inflammatory potential was measured using croton oil and xylene induced ear edema tests. Results Phytochemical screening of SCBC revealed the presence of various phytoconstituents. Dose-dependent in vitro antioxidant activity was observed. The extract was enriched in flavonoids and polyphenolic compounds too. SCBC was found to inhibit amyloid-β peptide 1-42 (Aβ42) induced cell death in a dose-dependent manner. Encouraged by the cyto-protective effect, its effects on Aβ42 fibrillogenesis and caspase-3 activated apoptosis were observed. SCBC significantly slowed down the Aβ42 fibrillogenesis and caspase-3 activation in a concentration-dependent manner indicating its probable mechanism of rendering cyto-protection. SCBC has been able to reduce inflammation significantly in croton oil induced ear edema in both doses. Conclusions Thus, this study could form the basis for further study for the potential use of SCBC in oxidative stress associated cell death and inflammation.

scholarly journals EXTH-62. PRECLINICAL EFFICACY OF THE IMIPRIDONE ONC-206 AGAINST MEDULLOBLASTOMA

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii100-ii101
Author(s):  
Tobey MacDonald ◽  
Anshu Malhotra ◽  
Jingbo Liu ◽  
Hongying Zhang ◽  
Matthew Schneiderjan ◽  
...  
Keyword(s):  
Cell Death ◽  
Malignant Glioma ◽  
Ex Vivo ◽  
Clinical Results ◽  
Normal Brain ◽  
Dependent Manner ◽  
Group 3 ◽  
Dose Dependent

Abstract Treatment for medulloblastoma (MB) is typically ineffective for MYC amplified or metastatic SHH, Group 3 and 4 subgroups. Promising preclinical and clinical results have been obtained for adult and pediatric malignant glioma treated with ONC-201, a selective antagonist of DRD2, a G-protein coupled receptor that regulates prosurvival pathways. Herein, we report the activity of ONC-201 and ONC-206, which has increased non-competitive antagonism of DRD2, against MB. We treated three different MB cell types representative of SHH- and Group 3-like cells, with varied levels of DRD2 expression, and consistently observed increased cell death in a dose-dependent manner at lower doses of ONC-206 compared to ONC-201. We also evaluated ClpP as an additional drug target in MB. ClpP is a mitochondrial protease that has been shown to directly bind and be activated by ONC 201, and is highly expressed at the protein level across pediatric MB, malignant glioma and ATRT, but not normal brain. We observed that similar to ONC-201, ONC-206 treatment of MB cells induces the restoration of mitochondrial membrane potential to the non-proliferative state, degradation of the mitochondrial substrate SDHB, reduction in survivin and elevation in ATF4 (integrated stress response). Importantly, ONC-206 treatment induced significant cell death of patient-derived SHH, WNT, and Group 3 tumors ex vivo and Group 4 cells in vitro, while having no observable toxicity in normal brain. ONC-206 treatment of a transgenic mouse model of Shh MB in vivo significantly reduces tumor growth and doubles survival time in a dose-dependent manner following 2 weeks of therapy. Additional in vivo data will be reported in preparation for a planned Phase I study of ONC-206 in children with malignant brain tumors.

scholarly journals Okadaic acid–induced apoptosis in malignant glioma cells

2003 ◽  
Vol 14 (2) ◽  
pp. 1-7 ◽  
Author(s):  
Bimal G. Rami ◽  
Lawrence S. Chin ◽  
Barbara E. Lazio ◽  
Satyendra K. Singh
Keyword(s):  
Cell Death ◽  
Okadaic Acid ◽  
Cellular Proliferation ◽  
Fluorescent Microscopy ◽  
Glioma Cells ◽  
Mitogen Activated Protein Kinase ◽  
Dependent Manner ◽  
Mobility Shift ◽  
Cell Counts

Object Okadaic acid (OA), a potent protein phosphatase inhibitor, has been known to induce apoptosis in a variety of cell types. The authors attempted to characterize further this model by identifying proteins involved in this form of programmed cell death. Methods Cellular proliferation was assessed using a colorimetric nonradioactive proliferation assay and cell counts. Apoptosis was determined by fluorescent microscopy. Activation of the mitogen-activated protein kinase (MAPK) pathways was determined by immunoprecipitation of extracellular signal–regulated kinase (ERK), c-Jun-n-terminal kinase (JNK), and p38 followed by in vitro kinase assays. Western blot analyses were conducted to show inhibitory-κB (IκB) phosphorylation and degradation as well as Bax upregulation. The binding of nuclear factor–κB (NFκB) was shown by electrophoretic mobility shift assay. Okadaic acid induced cell death in T98G human malignant cell lines (50% inhibiting concentration = 20–25 nM). In T98G cells YO-PRO fluorescent staining was identified, thus indicating an apoptotic mechanism with a smaller percentage of cells undergoing necrotic cell death. Additionally OA induced JNK and MAPK activities in a time-dependent manner, increased the expression of Bax, and increased IκB phosphorylation and NFκB activation. There was a temporal correlation between these subcellular events and the detection of apoptosis morphology in glioma cells. Conclusions The authors believe that OA acts by blocking dephosphorylation events, thus activating apoptotic pathways through ERK and JNK activity. Additionally Bax, IκB and NFκB may also play a role in regulating these pathways.

Synergistic Effects of a Novel Water-Soluble Small Molecule, ON 013105, and Rituximab on Mantle Cell Lymphoma In Vitro and In Vivo

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 771-771
Author(s):  
Anil Prasad ◽  
Ashutosh Shrivastava ◽  
Ramana Reddy ◽  
Amanda M. Gillum ◽  
E. Premkumar Reddy ◽  
...  
Keyword(s):  
Cell Death ◽  
Tumor Volume ◽  
Cell Lymphoma ◽  
Single Agent ◽  
Dependent Manner ◽  
Mantle Cell ◽  
Dose Dependent ◽  
Efficacy Studies

Abstract Abstract 771 Mantle cell lymphoma (MCL) is a well-defined subtype of B-cell non-Hodgkin's lymphoma characterized by a t(11;14)(q13;q32) chromosomal translocation, and associated with constitutive over-expression of cyclin D1. MCL generally has poor clinical outcome marked by relapse. There is considerable need for novel and more effective agents against MCL. ON 013105 belongs to the styryl benzylsulfones, a novel family of non-ATP competitive kinase inhibitors with potent antitumor activity. Here, we report that ON 013105 induced cell death in a dose-dependent manner in two well-characterized MCL cell lines, Granta 519 and Z138C. In vitro cell death was preceded by the activation of caspases 3 and 9 and cleavage of PARP, indicating induction of apoptosis. In addition, ON 013105-treated cells exhibited reduced expression of cyclin D1 and c-myc. These effects on expression and apoptosis were not evident in cells treated with ON 013101, an inactive (non-cytotoxic) isomer of ON 013105. Since it is common clinical practice to combine Rituximab (RTX) with chemotherapy regimens in treating CD20+ B cell-lymphoma, we studied ON 013105 combined with rituximab, and found ON 013105-induced apoptosis more efficiently than when employed as a single agent. The combination effect on cell death was synergistic in nature. To further study this activity, we focused on Mcl-1, a member of the anti-apoptotic Bcl-2 family known to inhibit apoptosis induced by cytotoxic stimuli through antagonizing pro-apoptotic Bcl-2 family members. We observed a dramatic decrease in Mcl-1 expression in cells treated with ON 013105 (but not with ON 013101) in combination with RTX, compared to ON 013105 alone. We also evaluated the effects of ON 013105 in combination with Doxorubicin or Vincristine and found that both these compounds also significantly enhanced the cytotoxic effects of ON 013105. In vivo pharmacokinetics studies in a mouse model system revealed that plasma concentrations up to 50 μM could be safely achieved by administering ON 013105 at 100 mg/kg via i.v or i.p routes. Significant levels of ON 013100 (30-40% of the peak levels of ON 013105), an active metabolite, were also detected in the circulation, presumably due to the in vivo dephosphorylation of ON 013105 by phosphatase action. ON 013105 was well tolerated in mice, both as a single agent and when used in combination with rituximab, and there were no systemic toxic effects to the host and no loss in body weight. In vivo efficacy studies in mouse xenograft models employing transplanted MCL cells demonstrated that ON 013105 effectively inhibited tumor growth in a dose-dependent manner. ON 013015 at 25 mg/kg (Q2D) and 75mg/kg (Q7D) induced 46% and 80 % reduction of tumor volume, respectively, compared to controls, over 4 weeks of treatment. Moreover, ON 013105 at 25 mg/kg (Q2D) in a combination regimen with RTX (2.5 mg/kg, Q3D) induced over 85% reduction of tumor volume. Though in vivo efficacy studies of ON013015 (25 mg/kg, Q2D) in combination with Doxorubicin (3.5mg/kg, Q7D) or Vincristine (0.3mg/kg, Q2D) showed drastic decrease in tumor growth in mouse models, this effect was accompanied by severe side effects to the host, including mortality. In sum, ON 013105, alone and in combination with RTX may be a potent therapeutic agent against MCL. A Phase I dose escalation trial of ON 013105 as a single agent is underway in patients with relapsed/refractory lymphoma including MCL. Disclosures: No relevant conflicts of interest to declare.

The Novel Proteasome Inhibitor MLN2238 (Ixazomib) Induces Death In CLL Cells In Vitro and Potentiates Lethality Of Fludarabine and The BCL2 Inhibitor At-101

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4189-4189
Author(s):  
Kasyapa S. Chitta ◽  
Aneel Paulus ◽  
Sharoon Akhtar ◽  
Maja Kuranz ◽  
Kena Miller ◽  
...  
Keyword(s):  
Cell Death ◽  
Annexin V ◽  
Inhibitory Effect ◽  
Lymphocytic Leukemia ◽  
Dose Effect ◽  
Response To Treatment ◽  
Dependent Manner ◽  
Proteasomal Activity ◽  
Dose Dependent

Abstract Background Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of clonal B cells in the peripheral blood, bone marrow, lymph nodes, and spleen. This is due to a combined effect of deferred apoptosis with slow, but persistent proliferation of malignant cells. In CLL, tumor-sustaining homeostasis is critically maintained by the ubiquitin proteasome system. The proteasome mediates degradation of various transcription factors such as TP53 as well as upholding a balance between the anti and pro apoptotic proteins of the BCL2 family. Previous studies have demonstrated that the clinical course of the disease is negatively associated with malfunctioning apoptotic pathways that result in increased levels of BCL2. Thus, identification and correction of defects that affect programmed cell death offer therapeutic vantage to reset and engage cell death pathways in CLL. Aim Examination of the anti-CLL properties of the investigational agent MLN2238 (Millennium Pharmaceuticals, Inc., Cambridge, MA) and its ability to inhibit the proteasomal machinery; induce CLL cell death and downregulate BCL2. MLN2238 activity was also investigated in conjunction with anti-CLL therapies such as fludarabine and dexamethasone along with the BH3 mimetic BCL2 inhibitor, AT-101 (Ascenta Pharmaceuticals, Malvern, PA). Methods CLL cells with >90% CD19+ tumor population were obtained from 28 patients with a confirmed diagnosis of CLL. Proteasomal activity was measured using synthetic fluorogenic peptide substrates. Apoptosis was measured by annexin-v/PI staining, and mitochondrial membrane permeability (MOMP) was assessed using TMRM followed by flow cytometry. Protein profiles were ascertained by western blot. Results MLN2238 inhibited the chymotrypsin-like proteasomal activity by more than 90% (p<0.005) in all patient samples without altering PSMB5 protein levels. Moderate to minimal inhibitory effect on caspase-like and trypsin-like proteasomal activities, respectively, was also noted. CLL cells showed a concentration dependent decrease in viability in response to treatment with MLN2238 at an IC50 of 50 nM. MLN2238 treated cells underwent apoptosis in a dose dependent manner with a median dose effect (cell death) observed in 42% of cells at 25 nM (range 10% - 54%) and 60% of cells at a 50 nM concentration (range, 25% - 73%). PARP-1 and caspase-3 cleavage along with an increase in MOMP was also noted after CLL cells were treated with MLN2238; however, apoptosis was only partially blocked by the pan-caspase inhibitor z-VAD.fmk. BCL2 downregulation was dose-dependent and was observed as early as 12 hours. We sought to determine whether directly disrupting BCL2 function with AT-101 could enhance the anti-CLL effects of MLN2238. When used at sub-IC50 concentrations, AT1-10 synergized with MLN2238 to induce CLL cell death. Synergy was also observed when MLN2238 was paired with the cytotoxic agent fludarabine, whereas the combination of MLN2238 and dexamethasone resulted in additive anti-CLL activity. Conclusion While PI have made an important impact in various B cell cancers, their role in CLL has not been well established. We investigated preclinically, a novel PI and noted that targeting the proteasome with MLN2238 resulted in lethal events in CLL cells, which were further enhanced by disruption of the BCL2 prosurvival pathway. Moreover, proteasome disruption sensitized CLL cells to the cytotoxic effect of fludarabine, an important therapeutic in CLL. These data provides the mechanistic basis for evaluation of MLN2238 in CLL through rationale design of drug combination strategies based on CLL biology. We would like to acknowledge the Leukemia and Lymphoma Society (A.C.-K. is a Leukemia and Lymphoma Scholar in Clinical Research) for their ongoing support. We are also grateful to Mary Ella Mahoney Davidson (Millennium Pharmaceuticals) for providing logistical support. Disclosures: Foran: Celgene: Research Funding.

Sign in / Sign up

Export Citation Format

Share Document