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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 -
Lung Cancer (Amsterdam, Netherlands) Dec 2011We previously reported data on the safety, tolerability, and recommended phase II dose of obatoclax mesylate in conjunction with topotecan in patients with advanced...
INTRODUCTION
We previously reported data on the safety, tolerability, and recommended phase II dose of obatoclax mesylate in conjunction with topotecan in patients with advanced solid tumor malignancies. Preliminary efficacy data suggested activity in patients with recurrent small cell lung cancer (SCLC). Based on these data, we performed a phase II study of obatoclax mesylate plus topotecan in patients with relapsed SCLC to assess efficacy.
METHODS
This was an open-label, single-arm, phase II extension of obatoclax mesylate plus topotecan in patients with relapsed SCLC. Obatoclax mesylate was given intravenously (IV) at a dose of 14mg/m(2) on days 1 and 3 with IV topotecan at 1.25mg/m(2) on days 1-5 of an every 3-week cycle. The primary end-point of this study was overall response rate.
RESULTS
Nine patients with recurrent SCLC were enrolled into the first stage of the study. Patients received a median of 2 cycles of treatment. All patients were evaluable for the primary end-point of overall response. There were no partial or complete responses. Five patients (56%) had stable disease. The remaining four patients (44%) developed progressive disease. The most common grade 3 or 4 adverse events included thrombocytopenia (22%), anemia (11%), neutropenia (11%), and ataxia (11%).
CONCLUSION
Obatoclax mesylate added to topotecan does not exceed the historic response rate seen with topotecan alone in patients with relapsed SCLC following the first-line platinum-based therapy.
Topics: Aged; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Small Cell; Disease Progression; Female; Humans; Indoles; Lung Neoplasms; Middle Aged; Proto-Oncogene Proteins c-bcl-2; Pyrroles; Recurrence; Thrombocytopenia; Topotecan
PubMed: 21620511
DOI: 10.1016/j.lungcan.2011.05.005 -
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 -
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 -
Drug News & Perspectives Mar 2008
Topics: Antineoplastic Agents; Controlled Clinical Trials as Topic; Humans; Hydrazines; Indoles; Melanoma; Neoplasm Metastasis; Neoplasms; Pyrroles
PubMed: 18389103
DOI: No ID Found -
Chemico-biological Interactions Feb 2015Obatoclax is an indole-pyrrole compound that induces cancer cell apoptosis through targeting the anti-apoptotic Bcl-2 protein family. Previously, we developed a series...
Obatoclax is an indole-pyrrole compound that induces cancer cell apoptosis through targeting the anti-apoptotic Bcl-2 protein family. Previously, we developed a series of obatoclax derivatives and studied their STAT3 inhibition-dependent activity against cancer cell lines. The obatoclax analog, prodigiosin, has been reported to mediate DNA cleavage in cancer cells by coordinating with copper complexes. To gain an understanding of copper-obatoclax complex activity, we applied obatoclax derivatives to examine their copper-mediated nuclease activity as a means to establish a basis for structure activity relationship. Replacement of the indole ring of obatoclax with furanyl, thiophenyl or Boc-indolyl rings reduced the DNA cleavage ability. The same effect was achieved through the replacement of the obatoclax pyrrolyl ring with thiazolidinedione and thioacetal. Among the compounds tested, we demonstrated that the complex of obatoclax or compound 7 with copper exhibited potent DNA strand scission which correlated with HCC cell growth inhibition.
Topics: Antineoplastic Agents; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Proliferation; Cell Survival; Copper; DNA Cleavage; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Humans; Indoles; Liver Neoplasms; Molecular Structure; Organometallic Compounds; Pyrroles; Structure-Activity Relationship
PubMed: 25598309
DOI: 10.1016/j.cbi.2014.12.026 -
Molecules and Cells Mar 2015Obatoclax, a pan-Bcl2 inhibitor, shows antitumor activities in various solid malignancies. Bcl2-deficient mice have shown the importance of Bcl2 in osteoclasts, as the...
Obatoclax, a pan-Bcl2 inhibitor, shows antitumor activities in various solid malignancies. Bcl2-deficient mice have shown the importance of Bcl2 in osteoclasts, as the bone mass of the mice was increased by the induced apoptosis of osteoclasts. Despite the importance of Bcl2, the effects of obatoclax on the proliferation and differentiation of osteoclast precursors have not been studied extensively. Here, we describe the anti-proliferative effects of obatoclax on osteoclast precursors and its negative role on fusion of the cells. Stimulation with low doses of obatoclax significantly suppressed the proliferation of osteoclast precursors in a dose-dependent manner while the apoptosis was markedly increased. Its stimulation was sufficient to block the activation of ERK MAP kinase by RANKL. The same was true when PD98059, an ERK inhibitor, was administered to osteoclast precursors. The activation of JNK1/2 and p38 MAP kinase, necessary for osteoclast differentiation, by RANKL was not affected by obatoclax. Interestingly, whereas the number of TRAP-positive mononuclear cells was increased by both obatoclax and PD98059, fused, multinucleated cells larger than 100 μm in diameter containing more than 20 nuclei were completely reduced. Consistently, obatoclax failed to regulate the expression of osteoclast marker genes, including c-Fos, TRAP, RANK and CtsK. Instead, the expression of DC-STAMP and Atp6v0d2, genes that regulate osteoclast fusion, by RANKL was significantly abrogated by both obatoclax and PD98059. Taken together, these results suggest that obatoclax down-regulates the proliferation and fusion of osteoclast precursors through the inhibition of the ERK1/2 MAP kinase pathway.
Topics: Animals; Apoptosis; Cell Fusion; Cell Proliferation; Cells, Cultured; Down-Regulation; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Gene Expression; Gene Silencing; Indoles; MAP Kinase Signaling System; Membrane Proteins; Mice, Inbred C57BL; Nerve Tissue Proteins; Osteoclasts; Pyrroles; RANK Ligand; Vacuolar Proton-Translocating ATPases
PubMed: 25666350
DOI: 10.14348/molcells.2015.2340 -
PloS One 2014An open-label phase I/II study of single-agent obatoclax determined a maximum tolerated dose (MTD) and schedule, safety, and efficacy in older patients (≥ 70 yr) with... (Randomized Controlled Trial)
Randomized Controlled Trial
PURPOSE
An open-label phase I/II study of single-agent obatoclax determined a maximum tolerated dose (MTD) and schedule, safety, and efficacy in older patients (≥ 70 yr) with untreated acute myeloid leukemia (AML).
EXPERIMENTAL DESIGN
Phase I evaluated the safety of obatoclax infused for 3 hours on 3 consecutive days (3 h × 3 d) in 2-week cycles. Initial obatoclax dose was 30 mg/day (3 h × 3 d; n = 3). Obatoclax was increased to 45 mg/day (3 h × 3 d) if ≤ 1 patient had a dose-limiting toxicity (DLT) and decreased to 20 mg/day (3 h × 3 d) if DLT occurred in ≥ 2 patients. In the phase II study, 12 patients were randomized to receive obatoclax at the dose identified during phase I (3 h × 3 d) or 60 mg/day administered by continuous infusion over 24 hours for 3 days (24 h × 3 d) to determine the morphologic complete response rate.
RESULTS
In phase I, two of three patients receiving obatoclax 30 mg/day (3 h × 3 d) experienced grade 3 neurologic DLTs (confusion, ataxia, and somnolence). Obatoclax was decreased to 20 mg/day (3 h × 3 d). In phase II, no clinically relevant safety differences were observed between the 20 mg/day (3 h × 3 d; n = 7) and 60 mg/day (24 h × 3 d; n = 5) arms. Neurologic and psychiatric adverse events were most common and were generally transient and reversible. Complete response was not achieved in any patient.
CONCLUSIONS
Obatoclax 20 mg/day was the MTD (3 h × 3 d) in older patients with AML. In the schedules tested, single-agent obatoclax was not associated with an objective response. Evaluation in additional subgroups or in combination with other chemotherapy modalities may be considered for future study.
TRIAL REGISTRATION
ClinicalTrials.gov NCT00684918.
Topics: Aged; Aged, 80 and over; Blast Crisis; Demography; Drug Administration Schedule; Female; Humans; Indoles; Leukemia, Myeloid, Acute; Male; Neutrophils; Platelet Count; Pyrroles; Treatment Outcome
PubMed: 25285531
DOI: 10.1371/journal.pone.0108694 -
Cell Death & Disease Dec 2010Direct pharmacological targeting of the anti-apoptotic B-cell lymphoma-2 (BCL-2) family is an attractive therapeutic strategy for treating cancer. Obatoclax is a...
Direct pharmacological targeting of the anti-apoptotic B-cell lymphoma-2 (BCL-2) family is an attractive therapeutic strategy for treating cancer. Obatoclax is a pan-BCL-2 family inhibitor currently in clinical development. Here we show that, although obatoclax can induce mitochondrial apoptosis dependent on BCL-2 associated x protein/BCL-2 antagonist killer (BAX/BAK) consistent with its on-target pharmacodynamics, simultaneous silencing of both BAX and BAK did not abolish acute toxicity or loss of clonogenicity. This is despite complete inhibition of apoptosis. Obatoclax dramatically reduced viability without inducing loss of plasma membrane integrity. This was associated with rapid processing of light chain-3 (LC3) and reduction of S6 kinase phosphorylation, consistent with autophagy. Dramatic ultrastructural vacuolation, not typical of autophagy, was also induced. Silencing of beclin-1 failed to prevent LC3 processing, whereas knockout of autophagy-related (Atg)7 abolished LC3 processing but failed to prevent obatoclax-induced loss of clonogenicity or ultrastructural changes. siRNA silencing of Atg7 in BAX/BAK knockout mouse embryonic fibroblasts did not prevent obatoclax-induced loss of viability. Cells selected for obatoclax resistance evaded apoptosis independent of changes in BCL-2 family expression and displayed reduced LC3 processing. In summary, obatoclax exhibits BAX- and BAK-dependent and -independent mechanisms of toxicity and activation of autophagy. Mechanisms other than autophagy and apoptosis are blocked in obatoclax resistant cells and contribute significantly to obatoclax's anticancer efficacy.
Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; Autophagy; Autophagy-Related Protein 7; Beclin-1; Cell Line, Tumor; Cell Membrane; Drug Resistance, Neoplasm; Humans; Indoles; Membrane Proteins; Mice; Myeloid Cell Leukemia Sequence 1 Protein; Proto-Oncogene Proteins c-bcl-2; Pyrroles; Ubiquitin-Activating Enzymes; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein
PubMed: 21368880
DOI: 10.1038/cddis.2010.86 -
Blood Jan 2009Obatoclax mesylate is a small molecule pan-Bcl-2 antagonist with in vitro activity against chronic lymphocytic leukemia (CLL) cells. Obatoclax was administered to...
Obatoclax mesylate is a small molecule pan-Bcl-2 antagonist with in vitro activity against chronic lymphocytic leukemia (CLL) cells. Obatoclax was administered to patients with advanced CLL at doses ranging from 3.5 to 14 mg/m(2) as a 1-hour infusion and from 20 to 40 mg/m(2) as a 3-hour infusion every 3 weeks. Twenty-six patients received a total of 74 cycles. Dose-limiting reactions were neurologic (somnolence, euphoria, ataxia) and associated with the infusion. The maximum tolerated dose (MTD) was 28 mg/m(2) over 3 hours every 3 weeks. One (4%) of 26 patients achieved a partial response. Patients with anemia (3/11) or thrombocytopenia (4/14) experienced improvements in hemoglobin and platelet counts. Circulating lymphocyte counts were reduced in 18 of 26 patients with a median reduction of 24%. Overall, the maximum plasma concentration (C(max)) and area under the curve (AUC) values of obatoclax were dose proportional. Activation of Bax and Bak was demonstrated in peripheral blood mononuclear cells, and induction of apoptosis was related to overall obatoclax exposure, as monitored by the plasma concentration of oligonucleosomal DNA/histone complexes. Obatoclax mesylate has biologic activity and modest single-agent activity in heavily pretreated patients with advanced CLL. Further evaluation in less heavily pretreated patients and in combination with other therapeutic agents is warranted. This trial has been registered with http://clinicaltrials.gov under identifier NCT00600964.
Topics: Aged; Anemia; Apoptosis; Female; Humans; Indoles; Leukemia, Lymphocytic, Chronic, B-Cell; Lymphocyte Count; Male; Maximum Tolerated Dose; Middle Aged; Platelet Count; Proto-Oncogene Proteins c-bcl-2; Pyrroles; Thrombocytosis; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein
PubMed: 18931344
DOI: 10.1182/blood-2008-02-137943