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Cells Sep 2023Aging is associated with the disruption of protein homeostasis and causally contributes to multiple diseases, including amyotrophic lateral sclerosis (ALS). One strategy...
Aging is associated with the disruption of protein homeostasis and causally contributes to multiple diseases, including amyotrophic lateral sclerosis (ALS). One strategy for restoring protein homeostasis and protecting neurons against age-dependent diseases such as ALS is to de-repress autophagy. BECN1 is a master regulator of autophagy; however, is repressed by BCL2 via a BH3 domain-mediated interaction. We used an induced pluripotent stem cell model of ALS caused by mutant FUS to identify a small molecule BH3 mimetic that disrupts the BECN1-BCL2 interaction. We identified obatoclax as a brain-penetrant drug candidate that rescued neurons at nanomolar concentrations by reducing cytoplasmic FUS levels, restoring protein homeostasis, and reducing degeneration. Proteomics data suggest that obatoclax protects neurons via multiple mechanisms. Thus, obatoclax is a candidate for repurposing as a possible ALS therapeutic and, potentially, for other age-associated disorders linked to defects in protein homeostasis.
Topics: Humans; Amyotrophic Lateral Sclerosis; Motor Neurons; Induced Pluripotent Stem Cells; Mutation; Autophagy; Phenotype; Proto-Oncogene Proteins c-bcl-2; RNA-Binding Protein FUS
PubMed: 37759469
DOI: 10.3390/cells12182247 -
International Journal of Molecular... Mar 2020Colorectal cancer (CRC) is a highly prevailing cancer and the fourth leading cause of cancer mortality worldwide. Aberrant expression of antiapoptotic BCL-2 family...
Colorectal cancer (CRC) is a highly prevailing cancer and the fourth leading cause of cancer mortality worldwide. Aberrant expression of antiapoptotic BCL-2 family proteins is closely linked to neoplastic progression and chemoresistance. Obatoclax is a clinically developed drug, which binds antiapoptotic BCL-2, BCL-xL, and MCL-1 for inhibition to elicit apoptosis. Survivin is an antiapoptotic protein, whose upregulation correlates with pathogenesis, therapeutic resistance, and poor prognosis in CRC. Herein, we provide the first evidence delineating the functional linkage between Obatoclax and survivin in the context of human CRC cells. In detail, Obatoclax was found to markedly downregulate survivin. This downregulation was mainly achieved via transcriptional repression, as Obatoclax lowered the levels of both mRNA and promoter activity, while blocking proteasomal degradation failed to prevent survivin from downregulation by Obatoclax. Notably, ectopic survivin expression curtailed Obatoclax-induced apoptosis and cytotoxicity, confirming an essential role of survivin downregulation in Obatoclax-elicited anti-CRC effect. Moreover, Obatoclax was found to repress hyperactive WNT/β-catenin signaling activity commonly present in human CRC cells, and, markedly, ectopic expression of dominant-active β-catenin mutant rescued the levels of survivin along with elevated cell viability. We further revealed that, depending on the cell context, Obatoclax suppresses WNT/β-catenin signaling in HCT 116 cells likely via inducing β-catenin destabilization, or by downregulating LEF1 in DLD-1 cells. Collectively, we for the first time define survivin downregulation as a novel, pro-apoptotic mechanism of Obatoclax as a consequence of Obatocalx acting as an antagonist to WNT/β-catenin signaling.
Topics: Apoptosis; Biomarkers, Tumor; Cell Proliferation; Colorectal Neoplasms; Enzyme Inhibitors; Gene Expression Regulation, Neoplastic; Humans; Indoles; Proto-Oncogene Proteins c-bcl-2; Pyrroles; Survivin; Tumor Cells, Cultured; Wnt Proteins; beta Catenin
PubMed: 32150830
DOI: 10.3390/ijms21051773 -
Emerging Microbes & Infections Dec 2022(COVID-19) caused by the emerging (SARS-CoV-2) has set off a global pandemic. There is an urgent unmet need for safe, affordable, and effective therapeutics against...
(COVID-19) caused by the emerging (SARS-CoV-2) has set off a global pandemic. There is an urgent unmet need for safe, affordable, and effective therapeutics against COVID-19. In this regard, drug repurposing is considered as a promising approach. We assessed the compounds that affect the endosomal acidic environment by applying human angiotensin-converting enzyme 2 (hACE2)- expressing cells infected with a SARS-CoV-2 spike (S) protein-pseudotyped HIV reporter virus and identified that obatoclax resulted in the strongest inhibition of S protein-mediated virus entry. The potent antiviral activity of obatoclax at nanomolar concentrations was confirmed in different human lung and intestinal cells infected with the SARS-CoV-2 pseudotype system as well as clinical virus isolates. Furthermore, we uncovered that obatoclax executes a double-strike against SARS-CoV-2. It prevented SARS-CoV-2 entry by blocking endocytosis of virions through diminished endosomal acidification and the corresponding inhibition of the enzymatic activity of the endosomal cysteine protease cathepsin L. Additionally, obatoclax impaired the SARS-CoV-2 S-mediated membrane fusion by targeting the MCL-1 protein and reducing furin protease activity. In accordance with these overarching mechanisms, obatoclax blocked the virus entry mediated by different S proteins derived from several SARS-CoV-2 variants of concern such as, Alpha (B.1.1.7), Beta (B.1.351), and Delta (B.1.617.2). Taken together, our results identified obatoclax as a novel effective antiviral compound that keeps SARS-CoV-2 at bay by blocking both endocytosis and membrane fusion. Our data suggested that obatoclax should be further explored as a clinical drug for the treatment of COVID-19.
Topics: COVID-19; Cathepsins; Furin; Humans; Hydrogen-Ion Concentration; Indoles; Pyrroles; SARS-CoV-2; Spike Glycoprotein, Coronavirus; Virus Internalization
PubMed: 34989664
DOI: 10.1080/22221751.2022.2026739 -
Expert Opinion on Investigational Drugs Mar 2012Augmentation and acceleration of apoptosis for cancer therapy are logical therapeutic strategies given the increasing body of data suggesting the dysregulation of... (Review)
Review
INTRODUCTION
Augmentation and acceleration of apoptosis for cancer therapy are logical therapeutic strategies given the increasing body of data suggesting the dysregulation of control of cell death in many neoplasms. Apoptosis is particularly well studied in hematological neoplasms, thus these varied diseases present opportunities for pro-apoptotic drug development both as single agents and in combination with established therapies. Accordingly, several agents targeting function of anti-apoptotic Bcl-2 family members have entered clinical trials in the last decade and are discussed.
AREAS COVERED
The pan Bcl-2 family member BH3 domain mimetic obatoclax (GX15-070) is currently under clinical evaluation in solid tumors and hematological neoplasms. This agent offers the attractive property of uniformly inhibiting all of the anti-apoptotic members of the Bcl-2 protein family. Its chemistry and preclinical development and activity are reviewed. Pharmacology, pharmacodynamics, drug resistance and clinical use of this agent in leukemias and lymphomas are discussed. The prospects for obatoclax in changing clinical practice are addressed.
EXPERT OPINION
Obatoclax may not prove to have dramatic single agent activity for hematological neoplasms. It seems more likely that its activity will be manifest in combination therapy with other agents, particularly cytotoxic chemotherapies. Results of ongoing studies are awaited.
Topics: Antineoplastic Agents; Apoptosis; Clinical Trials as Topic; Drug Delivery Systems; Drug Resistance, Neoplasm; Humans; Indoles; Leukemia; Lymphoma; Proto-Oncogene Proteins c-bcl-2; Pyrroles
PubMed: 22324354
DOI: 10.1517/13543784.2012.652302 -
Journal of Cellular Biochemistry Sep 2014Pan-Bcl-2 family inhibitor obatoclax has been demonstrated to be effective against various cancers, of which the mechanism of action is not fully understood. In this...
Pan-Bcl-2 family inhibitor obatoclax has been demonstrated to be effective against various cancers, of which the mechanism of action is not fully understood. In this study, we demonstrate that obatoclax suppressed esophageal cancer cell viability with concomitant G1/G0-phase cell cycle arrest. At the tested concentrations (1/2 IC50 and IC50), obatoclax neither induced PARP cleavage nor increased the Annexin V-positive population, suggesting G1/G0-phase arrest rather than apoptosis accounts for most of the reduction of cell viability produced by obatoclax. Double knockdown of Bak and Bax by small interference RNA failed to block obatoclax-induced G1/G0-phase arrest, implying its role in cell cycle progression is Bak/Bax-independent. The cell cycle arresting effect of obatoclax was associated with up-regulation of p21(waf1/Cip1). Knockdown of p21(waf1/Cip1) significantly attenuated obatoclax-induced G1/G0-phase arrest. Although obatoclax stimulated phosphorylation of Erk, p38, and JNK, pharmacological inhibition of p38 but not Erk or JNK blocked obatoclax-induced G1/G0-phase arrest. Moreover, knockdown of p38 abolished the cell cycle arresting effect of obatoclax. In consistent with this finding, inhibition of p38 blocked obatoclax-induced p21(waf1/Cip1) expression while inhibition of Erk or JNK failed to exert similar effect. To conclude, these findings suggest that obatoclax induced cell cycle arrest via p38/p21(waf1/Cip1) signaling pathway. This study may shed a new light on the anti-cancer activity of obatoclax in relation to cell cycle arrest.
Topics: Antineoplastic Agents; Cell Cycle; Cell Line, Tumor; Cell Survival; Cyclin-Dependent Kinase Inhibitor p21; Esophageal Neoplasms; Humans; Indoles; MAP Kinase Signaling System; Phosphorylation; Pyrroles; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein; p38 Mitogen-Activated Protein Kinases
PubMed: 24788582
DOI: 10.1002/jcb.24829 -
Translational Oncology Aug 2021Bcl-2 family proteins play critical roles in regulating lymphocyte development and maintain homeostasis, and have also been proved to be involved in various cancer types...
Bcl-2 family proteins play critical roles in regulating lymphocyte development and maintain homeostasis, and have also been proved to be involved in various cancer types development. However, the role of Bcl-2 in hepatocellular carcinoma (HCC) development has not been clearly studied. Here, we reported the pan-Bcl-2 inhibitor, obatoclax could directly inhibit HCC growth in vitro. We further demonstrated in murine HCC model that obatoclax also suppressed HCC development in vivo. We also proved that although obatoclax inhibited T cells expansion, it had no influence on T cells activation in vivo. Mechanism study revealed that obatoclax sensitized HCC cells to T cell-mediated killing. Combination therapy of obatoclax with anti-PD-1 antibody synergistically suppressed HCC development and prolonged the survival rate of tumor-bearing mice. The combination therapy promoted T cells activation and effector cytokines expression both in spleen and tumor. In summary, our results proved that obatoclax sensitized HCC cells to T cell -mediated killing. Combination of obatoclax with immune checkpoint blockade served as a promising therapeutic strategy for HCC treatment.
PubMed: 33975180
DOI: 10.1016/j.tranon.2021.101116 -
PloS One 2016Obatoclax belongs to a class of compounds known as BH3 mimetics which function as antagonists of Bcl-2 family apoptosis regulators. It has undergone extensive...
Obatoclax belongs to a class of compounds known as BH3 mimetics which function as antagonists of Bcl-2 family apoptosis regulators. It has undergone extensive preclinical and clinical evaluation as a cancer therapeutic. Despite this, it is clear that obatoclax has additional pharmacological effects that contribute to its cytotoxic activity. It has been claimed that obatoclax, either alone or in combination with other molecularly targeted therapeutics, induces an autophagic form of cell death. In addition, obatoclax has been shown to inhibit lysosomal function, but the mechanism of this has not been elucidated. We have evaluated the mechanism of action of obatoclax in eight ovarian cancer cell lines. Consistent with its function as a BH3 mimetic, obatoclax induced apoptosis in three cell lines. However, in the remaining cell lines another form of cell death was evident because caspase activation and PARP cleavage were not observed. Obatoclax also failed to show synergy with carboplatin and paclitaxel, chemotherapeutic agents which we have previously shown to be synergistic with authentic Bcl-2 family antagonists. Obatoclax induced a profound accumulation of LC-3 but knockdown of Atg-5 or beclin had only minor effects on the activity of obatoclax in cell growth assays suggesting that the inhibition of lysosomal function rather than stimulation of autophagy may play a more prominent role in these cells. To evaluate how obatoclax inhibits lysosomal function, confocal microscopy studies were conducted which demonstrated that obatoclax, which contains two basic pyrrole groups, accumulates in lysosomes. Studies using pH sensitive dyes demonstrated that obatoclax induced lysosomal alkalinization. Furthermore, obatoclax was synergistic in cell growth/survival assays with bafilomycin and chloroquine, two other drugs which cause lysosomal alkalinization. These studies explain, for the first time, how obatoclax inhibits lysosomal function and suggest that lysosomal alkalinization contributes to the cytotoxic activity of obatoclax.
Topics: Biological Transport; Biomimetic Materials; Cathepsins; Cell Death; Cell Line, Tumor; Humans; Hydrogen-Ion Concentration; Indoles; Lysosomes; Proto-Oncogene Proteins c-bcl-2; Pyrroles
PubMed: 26950068
DOI: 10.1371/journal.pone.0150696 -
Hematology, Transfusion and Cell Therapy 2022
PubMed: 33753045
DOI: 10.1016/j.htct.2021.01.004 -
ACS Infectious Diseases Nov 2023The implementation of combined antiretroviral therapy (cART) has rendered HIV-1 infection clinically manageable and efficiently improves the quality of life for patients...
The implementation of combined antiretroviral therapy (cART) has rendered HIV-1 infection clinically manageable and efficiently improves the quality of life for patients with AIDS. However, the persistence of a latent HIV-1 reservoir is a major obstacle to achieving a cure for AIDS. A "shock and kill" strategy aims to reactivate latent HIV and then kill it by the immune system or cART drugs. To date, none of the LRA candidates has yet demonstrated effectiveness in achieving a promising functional cure. Interestingly, the phosphorylation and activation of antiapoptotic Bcl-2 protein induce resistance to apoptosis during HIV-1 infection and the reactivation of HIV-1 latency in central memory CD4 T cells from HIV-1-positive patients. Therefore, a Bcl-2 antagonist might be an effective LRA candidate for HIV-1 cure. In this study, we reported that a pan-Bcl-2 antagonist obatoclax induces HIV-1 reactivation in latently infected cell lines and in PBMCs/CD4 T cells of HIV-infected individuals . Obatoclax promotes HIV-1 transcriptional initiation and elongation by regulating the NF-κB pathway. Obatoclax activates caspase 8 and does not induce the phosphorylation of the antiapoptotic protein Bcl-2 in latent HIV-1 infected cell lines. More importantly, it preferentially induces apoptosis in latently infected cells. In addition, obatoclax exhibited potent anti-HIV-1 activity on target cells. The abilities to reactivate latent HIV-1 reservoirs, inhibit HIV-1 infection, and induce HIV-1 latent cell apoptosis make obatoclax worth investigating for development as an ideal LRA for use in the "shock and kill" approach.
Topics: Humans; NF-kappa B; HIV Infections; Virus Activation; Virus Latency; HIV-1; Acquired Immunodeficiency Syndrome; Quality of Life; CD4-Positive T-Lymphocytes; Apoptosis
PubMed: 37796279
DOI: 10.1021/acsinfecdis.3c00218 -
BMC Cancer Aug 2015Obatoclax is a clinical stage drug candidate that has been proposed to target and inhibit prosurvival members of the Bcl-2 family, and thereby contribute to cancer cell...
BACKGROUND
Obatoclax is a clinical stage drug candidate that has been proposed to target and inhibit prosurvival members of the Bcl-2 family, and thereby contribute to cancer cell lethality. The insolubility of this compound, however, has precluded the use of many classical drug-target interaction assays for its study. Thus, a direct demonstration of the proposed mechanism of action, and preferences for individual Bcl-2 family members, remain to be established.
METHODS
Employing modified proteins and lipids, we recapitulated the constitutive association and topology of mitochondrial outer membrane Mcl-1 and Bak in synthetic large unilamellar liposomes, and measured bakdependent bilayer permeability. Additionally, cellular and tumor models, dependent on Mcl-1 for survival, were employed.
RESULTS
We show that regulation of bilayer permeabilization by the tBid - Mcl-1 - Bak axis closely resemblesthe tBid - Bcl-XL - Bax model. Obatoclax rapidly and completely partitioned into liposomal lipid but also rapidly exchanged between liposome particles. In this system, obatoclax was found to be a direct and potent antagonist of liposome-bound Mcl-1 but not of liposome-bound Bcl-XL, and did not directly influence Bak. A 2.5 molar excess of obatoclax relative to Mcl-1 overcame Mcl-1-mediated inhibition of tBid-Bak activation. Similar results were found for induction of Bak oligomers by Bim. Obatoclax exhibited potent lethality in a cellmodel dependent on Mcl-1 for viability but not in cells dependent on Bcl-XL. Molecular modeling predicts that the 3-methoxy moiety of obatoclax penetrates into the P2 pocket of the BH3 binding site of Mcl-1. A desmethoxy derivative of obatoclax failed to inhibit Mcl-1 in proteoliposomes and did not kill cells whose survival depends on Mcl-1. Systemic treatment of mice bearing Tsc2(+) (/) (-) Em-myc lymphomas (whose cells depend on Mcl-1 for survival) with obatoclax conferred a survival advantage compared to vehicle alone (median 31 days vs 22 days, respectively; p=0.003). In an Akt-lymphoma mouse model, the anti-tumor effects of obatoclax synergized with doxorubicin. Finally, treatment of the multiple myeloma KMS11 cell model (dependent on Mcl-1 for survival) with dexamethasone induced Bim and Bim-dependent lethality. As predicted for an Mcl-1 antagonist, obatoclax and dexamethasone were synergistic in this model.
CONCLUSIONS
Taken together, these findings indicate that obatoclax is a potent antagonist of membranerestricted Mcl-1. Obatoclax represents an attractive chemical series to generate second generation Mcl-1 inhibitors.
Topics: Animals; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Cell Line, Tumor; Disease Models, Animal; Doxorubicin; Drug Synergism; Humans; Indoles; Lymphoma; Membrane Proteins; Mice; Myeloid Cell Leukemia Sequence 1 Protein; Proto-Oncogene Proteins; Pyrroles; Xenograft Model Antitumor Assays
PubMed: 26231047
DOI: 10.1186/s12885-015-1582-5