scholarly journals Antileukemic Activity and Mechanism of Drug Resistance to the Marine Salinispora tropica Proteasome Inhibitor Salinosporamide A (Marizomib)

2014 ◽  
Vol 86 (1) ◽  
pp. 12-19 ◽  
Author(s):  
Denise Niewerth ◽  
Gerrit Jansen ◽  
Lesley F. V. Riethoff ◽  
Johan van Meerloo ◽  
Andrew J. Kale ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Proteasome Inhibitor ◽  
Antileukemic Activity ◽  
Salinosporamide A ◽  
Salinispora Tropica

Exploration and engineering of biosynthetic pathways in the marine actinomycete Salinispora tropica

2009 ◽  
Vol 81 (6) ◽  
pp. 1075-1084 ◽  
Author(s):  
Markus Nett ◽  
Bradley S. Moore
Keyword(s):  
Natural Products ◽  
Metabolic Pathways ◽  
Anticancer Agent ◽  
Complex Molecules ◽  
Dna Cleaving ◽  
Metabolic Plasticity ◽  
Salinosporamide A ◽  
Salinispora Tropica ◽  
Marine Actinomycete ◽  
Key Genes

In recent years, members of the marine actinomycete genus Salinispora have proven to be a precious source of structurally diverse secondary metabolites, including the potent anticancer agent salinosporamide A and the enediyne-derived sporolides. The tremendous potential of these marine-dwelling microbes for natural products biosynthesis, however, was not fully realized until sequencing of the Salinispora tropica genome revealed the presence of numerous orphan biosynthetic loci besides a plethora of rare metabolic pathways. This contribution summarizes the biochemical exploration of this prolific organism, highlighting studies in which genome-based information was exploited for the discovery of new enzymatic processes and the engineering of unnatural natural products. Inactivation of key genes within the salinosporamide pathway has expanded its inherent metabolic plasticity and enabled access to various salinosporamide derivatives by mutasynthesis. New insights into the biosynthesis of the sporolides allowed us to increase production titers of these structurally complex molecules, thereby providing the means to search for the DNA cleaving presporolide enediyne.

scholarly journals Coupled Biosynthesis of Volatiles and Salinosporamide A in Salinispora tropica

ChemBioChem ◽  
2016 ◽  
Vol 17 (20) ◽  
pp. 1978-1985 ◽  
Author(s):  
Ulrike Groenhagen ◽  
Ana Ligia Leandrini De Oliveira ◽  
Elisha Fielding ◽  
Bradley S. Moore ◽  
Stefan Schulz
Keyword(s):  
Salinosporamide A ◽  
Salinispora Tropica

scholarly journals Salinosporamide A: A Highly Cytotoxic Proteasome Inhibitor from a Novel Microbial Source, a Marine Bacterium of the New Genus Salinospora

2003 ◽  
Vol 42 (3) ◽  
pp. 355-357 ◽  
Author(s):  
Robert H. Feling ◽  
Greg O. Buchanan ◽  
Tracy J. Mincer ◽  
Christopher A. Kauffman ◽  
Paul R. Jensen ◽  
...  
Keyword(s):  
Proteasome Inhibitor ◽  
Marine Bacterium ◽  
New Genus ◽  
Salinosporamide A

scholarly journals The Contribution of Proteasome Subunits to Myeloma Cell Viability and Proteasome Inhibitor Sensitivity

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4337-4337
Author(s):  
Chang-Xin Shi ◽  
Yuan Xiao Zhu ◽  
Laura Ann Bruins ◽  
Cecilia Bonolo De Campos ◽  
William Stewart ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Drug Resistance ◽  
Cell Viability ◽  
Cell Lines ◽  
Proteasome Inhibitor ◽  
Conflicts Of Interest ◽  
Myeloma Cell ◽  
Resistance Function ◽  
Proteasome Subunits ◽  
Underlying Mechanisms

Background Bortezomib (BTZ) is highly effective in the treatment of multiple myeloma; however, emergent drug resistance is common. The underlying mechanisms of such proteasome inhibitor resistance are still incompletely understood. Methods To further understand its resistant mechanism, we generated eight multiple myeloma (MM) cell lines resistant to bortezomib (BTZ) by exposure to increasing drug concentration: five of them acquired novel PSMB5 mutations. Given the rarity of similar mutations in over 1,500 analyzed MM patients, we explored in depth the role of the proteasome on MM cell viability and BTZ sensitivity by systematically deleting the major proteasome targets of BTZ by CRISPR. Results We demonstrated that MM cell lines without PSMB5 were surprisingly viable (mutation corresponding yeast gene pre2 is lethal). PSMB5 mutated, BTZ resistant, MM cell lines were re-sensitized to BTZ when PSMB5 was experimentally deleted, implying that this mutation is activating in its drug resistance function. In contrast PSMB6 knockout was lethal to MM cell lines, which were efficiently rescued by re-introduction of wild type PSMB6. Interestingly, reduction in PSMB6 levels also prevented the splicing of the major catalytic subunits PSMB5, PSMB7, PSMB8 and PSMB10. PSMB6 engineered with no splicing function or catalytic activity, also restored viability, inferring that the contribution of PSMB6 to proteasome structure is more important than functional activity. Supporting this observation, BTZ sensitivity was restored in resistant MM cells line by introducing low level expression of mutated PSMB6 lacking splicing function. As with PSMB6, PSMB7 knockout was lethal to MM cell lines. In contrast, loss of immunoproteasome subunits PSMB8 and PSMB9 was neither lethal nor restored sensitivity to BTZ. Our results demonstrate that expression of the three constitutive proteasome subunits PSMB5, PSMB6 and PSMB7 is highly co-dependent. This dependence is relying on the structure, but not the function, of PSMB5 and PSMB6. Conclusions In summary, PSMB5 and PSMB6, but not PSMB8 and PSMB9, are highly relevant for BTZ sensitivity in MM. Absence of PSMB6 or PSMB7, but not PSMB5, was lethal in MM cell lines. Expression of PSMB5, PSMB6 and PSMB7 was highly co-dependent. Together these findings suggest that the modulation of expression rather than function of PSMB5, PSMB6 or PSMB7 may be a new therapeutic strategy. Disclosures No relevant conflicts of interest to declare.

scholarly journals Glucocorticoids enhance the antileukemic activity of FLT3 inhibitors in FLT3-mutant acute myeloid leukemia

Blood ◽  
2020 ◽  
Vol 136 (9) ◽  
pp. 1067-1079 ◽  
Author(s):  
Melat T. Gebru ◽  
Jennifer M. Atkinson ◽  
Megan M. Young ◽  
Lijun Zhang ◽  
Zhenyuan Tang ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Drug Exposure ◽  
Residual Disease ◽  
Initial Response ◽  
Antileukemic Activity ◽  
Proapoptotic Protein ◽  
Flt3 Inhibitors ◽  
Acute Myeloid

Abstract FLT3 is a frequently mutated gene that is highly associated with a poor prognosis in acute myeloid leukemia (AML). Despite initially responding to FLT3 inhibitors, most patients eventually relapse with drug resistance. The mechanism by which resistance arises and the initial response to drug treatment that promotes cell survival is unknown. Recent studies show that a transiently maintained subpopulation of drug-sensitive cells, so-called drug-tolerant "persisters" (DTPs), can survive cytotoxic drug exposure despite lacking resistance-conferring mutations. Using RNA sequencing and drug screening, we find that treatment of FLT3 internal tandem duplication AML cells with quizartinib, a selective FLT3 inhibitor, upregulates inflammatory genes in DTPs and thereby confers susceptibility to anti-inflammatory glucocorticoids (GCs). Mechanistically, the combination of FLT3 inhibitors and GCs enhances cell death of FLT3 mutant, but not wild-type, cells through GC-receptor–dependent upregulation of the proapoptotic protein BIM and proteasomal degradation of the antiapoptotic protein MCL-1. Moreover, the enhanced antileukemic activity by quizartinib and dexamethasone combination has been validated using primary AML patient samples and xenograft mouse models. Collectively, our study indicates that the combination of FLT3 inhibitors and GCs has the potential to eliminate DTPs and therefore prevent minimal residual disease, mutational drug resistance, and relapse in FLT3-mutant AML.

RFWD2 Induces Cellular Proliferation and Proteasome Inhibitor Resistance By Mediating p27 Ubiqutinaiton in Multiple Myeloma

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3068-3068
Author(s):  
Ye Yang ◽  
Mengjie Guo ◽  
Chunyan Gu
Keyword(s):  
Multiple Myeloma ◽  
Cell Proliferation ◽  
Drug Resistance ◽  
Proteasome Inhibitor ◽  
Cellular Proliferation ◽  
Conflicts Of Interest ◽  
Scid Mice ◽  
Rpmi 8226

Purpose: In recent years, with the emergence of targeted proteasome inhibitors (PIs), the treatment of multiple myeloma (MM) has made great progress and significantly improves the survival rate of patients. However, MM remains an incurable disease, mainly due to the recurrence of drug resistance. The constitutive photomorphogenic 1 (RFWD2, also known as COP1), is closely related to the occurrence and development of tumors, but its role in MM is largely unknown. This study was aimed to explore the mechanism of RFWD2 on cell proliferation and resistance to proteasome inhibitor in MM. Experimental Design: Using gene expression profiling (GEP) samples, we verified the relation of RFWD2 to MM patients' survival and drug-resistance. The effect of RFWD2 on cell proliferation was confirmed by MTT and cell cycle analysis in RFWD2-overexpressed and RFWD2-knockdown MM cells. MTT and apoptosis experiments were performed to evaluate whether RFWD2 influenced the sensitivity of MM cells to several chemotherapy drugs. MM xenografts were established in immunodeficient NOD/SCID mice by injecting wild-type or RFWD2 over-expression MM cells with drug intervention. The mechanism of drug resistance was elucidated by analyzing the association of RFWD2 with E3 ligase of p27. Bortezomib-resistant RPMI 8226 cells were used to construct RFWD2 knockdown cells, which were injected into NOD/SCID mice to assess the effect of RFWD2 on bortezomib resistance in vivo. Results: RFWD2 expression was closely related to poor outcome, relapse and bortezomib resistance in MM patients' GEP cohorts. Elevated RFWD2 induced cell proliferation, while decreased RFWD2 inhibited cell proliferation and induced apoptosis in MM cells. RFWD2-overexpression MM cells resulted in PIs resistance, however, no chemotherapy resistance to adriamycin and dexamethasone was observed in vitro. In addition, overexpressing RFWD2 in MM cells led to bortezomib resistance rather than adriamycin resistance in myeloma xenograft mouse model. RFWD2 regulated the ubiquitination degradation of P27 by interacting with RCHY1 ubiquitin ligase. The knockdown of RFWD2 in bortezomib-resistant RPMI 8226 cells overcame bortezomib resistance in vivo. Conclusions: Our data demonstrate that elevated RFWD2 induces MM cell proliferation and resistance to PIs, but not to adriamycin and dexamethasone both in vitro and in vivo through mediating the ubiquitination of p27. Collectively, RFWD2 is a novel promising therapeutic target in MM. Disclosures No relevant conflicts of interest to declare.

Modeling Proteasome Inhibition in Lymphoma

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4946-4946
Author(s):  
Linda B. Baughn ◽  
Holly Stessman ◽  
Aatif Mansoor ◽  
Brian Van Ness
Keyword(s):  
Drug Resistance ◽  
Genomic Instability ◽  
Proteasome Inhibitor ◽  
Research Funding ◽  
Proteasome Inhibitors ◽  
Fold Increase ◽  
Proteasome Inhibition ◽  
Burkitt’S Lymphoma ◽  
Model System ◽  
Burkitt's Lymphoma

Abstract Abstract 4946 The proteasome inhibitor Bortezomib (Bz) has been widely used to treat multiple myeloma, relapsed mantle cell lymphoma and is undergoing clinical evaluation for other B cell malignancies including non-Hodgkin lymphoma. Despite its initial success, patients treated with Bz eventually relapse due to the development of drug resistance. Therefore, understanding the basis of drug resistance is a critical component for improved therapy. The acquisition of Bz resistance in lymphomas, particularly those with constitutive expression of the B cell-specific DNA mutator, activation-induced cytidine deaminase (AID), has not been previously characterized. We have utilized the AID-expressing human non-Hodgkin Burkitt's lymphoma as a model system for this study. Burkitt's lymphoma lines (Ramos and BL-2) are suitable because they are highly sensitive to Bz induced apoptosis with an IC50 of approximately 11 nM after 48 hrs of treatment. In order to generate Bz resistant Burkitt's lymphoma lines, Ramos cells were treated weekly with increasing concentrations of Bz for 3 months. Compared to the parental line, this newly formed line displayed an approximately 2.5–3-fold increase in IC50 to Bz as well as to three other proteasome inhibitors (next-generation proteasome inhibitor, MLN 2238, epoxomicin and carfilzomib), while maintaining sensitivity to different chemotherapeutic agents (PD 0332991 cyclin 4/6 dependent kinase inhibitor and melphalan). In this model system, resistance to Bz conferred a general cross-resistance to other proteasome inhibitors, a phenotype that has been stably maintained for 5 months. We next asked whether AID plays a role in the acquisition of Bz resistance in Ramos cells by promoting hypermutation and genomic instability. In support of this hypothesis, the G322A and C326T mutations in the gene encoding the proteasome subunit and target of Bz, psmb5, occur within AID hotspots raising the possibility that AID could directly mutate psmb5. Furthermore, like many proteins, AID is degraded by the proteasome arguing that proteasome inhibition further stabilizes AID protein resulting in aberrant hypermutation. Consistent with this, we detected by flow cytometry (intracellular staining) a 2-fold increase in AID protein following a 24-hour, 20 nM Bz treatment of Ramos cells. AID normally mutates immunoglobulin (Ig) genes and these mutations are necessary for the production of protective antibodies, while aberrant AID activity leads to mutations in non-Ig genes. Surprisingly, despite the increase in AID protein, we observe reduced mutation frequency within the functional IgH gene following 3-month Bz treatment compared to untreated controls. Despite this reduction, array comparative genomic hybridization (a-CGH) studies indicate copy number abnormalities in Bz resistant cells and details of the chromosomal abnormalities and target genes deregulated will be presented. These data demonstrate that Burkitt's lymphoma cells are sensitive to Bz and drug resistance can be readily achieved in vitro. Furthermore, Bz treatment stabilizes AID protein and promotes increased genomic instability. Disclosures: Stessman: Millennium: The Takeda Oncology Company: Research Funding. Mansoor:Millennium: The Takeda Oncology Company: Research Funding. Van Ness:Millennium: The Takeda Oncology Company: Research Funding.

scholarly journals Selective Overproduction of the Proteasome Inhibitor Salinosporamide A via Precursor Pathway Regulation

2011 ◽  
Vol 18 (12) ◽  
pp. 1527-1536 ◽  
Author(s):  
Anna Lechner ◽  
Alessandra S. Eustáquio ◽  
Tobias A.M. Gulder ◽  
Mathias Hafner ◽  
Bradley S. Moore
Keyword(s):  
Proteasome Inhibitor ◽  
Salinosporamide A ◽  
Pathway Regulation
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