Combined Inhibition of p 97 and the Proteasome Causes Lethal Disruption of the Secretory Apparatus in Multiple Myeloma Cells (original) (raw)
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Inhibition of the AAA ATPase, p97, was recently shown to be a novel method for targeting the ubiquitin proteasome system (UPS) and CB-5083, a first in class inhibitor of p97, has demonstrated broad antitumor activity in a range of both hematological and solid tumor models. Here, we show that CB-5083 has robust activity against multiple myeloma (MM) cell lines and a number of in vivo MM models. Treatment with CB-5083 is associated with accumulation of ubiquitinated proteins, induction of the unfolded protein response (UPR) and apoptosis. CB-5083 decreases viability in MM cell lines and patient derived MM cells, including those with background proteasome inhibitor (PI) resistance. CB-5083 has a unique mechanism of action that combines well with PIs which is likely owing to the p97-dependent retro-translocation of the transcription factor, Nrf1, which transcribes proteasome subunit genes following exposure to a PI. In vivo studies using clinically relevant MM models demonstrate that s...
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The proteasome inhibitor PS-341 inhibits IB degradation, prevents NF-B activation, and induces apoptosis in several types of cancer cells, including chemoresistant multiple myeloma (MM) cells. PS-341 has marked clinical activity even in the setting of relapsed refractory MM. However, PS-341-induced apoptotic cascade(s) are not yet fully defined. By using gene expression profiling, we characterized the molecular sequelae of PS-341 treatment in MM cells and further focused on molecular pathways responsible for the anticancer actions of this promising agent. The transcriptional profile of PS-341-treated cells involved down-regulation of growth͞survival signaling pathways, and up-regulation of molecules implicated in proapoptotic cascades (which are both consistent with the proapoptotic effect of proteasome
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The ubiquitin-proteasome pathway is the major cellular degradative system for various proteins critical for proliferation, survival and homing of myeloma cells. Bortezomib is the first specific and reversible proteasome inhibitor for clinical application in humans.
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Since the early 1990s, the synthesis and subsequent clinical application of small molecule inhibitors of the ubiquitin proteasome pathway (UPP) has revolutionized the treatment and prognosis of multiple myeloma. In this review, we summarize important aspects of the biology of the UPP with a focus on its structure and key upstream/downstream regulatory components. We then review current knowledge of plasma cell sensitivity to proteasome inhibition and highlight new proteasome inhibitors that have recently entered clinical development. Lastly, we address the putative role of circulating proteasomes as a novel biomarker in multiple myeloma and provide guidance for future clinical trials using proteasome inhibitors.
The Landscape of Signaling Pathways and Proteasome Inhibitors Combinations in Multiple Myeloma
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Multiple myeloma is a malignancy of terminally differentiated plasma cells, characterized by an extreme genetic heterogeneity that poses great challenges for its successful treatment. Due to antibody overproduction, MM cells depend on the precise regulation of the protein degradation systems. Despite the success of PIs in MM treatment, resistance and adverse toxic effects such as peripheral neuropathy and cardiotoxicity could arise. To this end, the use of rational combinatorial treatments might allow lowering the dose of inhibitors and therefore, minimize their side-effects. Even though the suppression of different cellular pathways in combination with proteasome inhibitors have shown remarkable anti-myeloma activities in preclinical models, many of these promising combinations often failed in clinical trials. Substantial progress has been made by the simultaneous targeting of proteasome and different aspects of MM-associated immune dysfunctions. Moreover, targeting deranged metabo...
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Multiple myeloma (MM) accounts for 10% of hematological cancers. Stem cell transplantation remains the cornerstone of first-line treatment for eligible patients, but historically, pharmaceutical treatment options for MM have been limited. The proteasome was identified as a target for MM therapy in the early 2000s and, in 2004, the boronic acid proteasome inhibitor bortezomib gained European approval. Bortezomib now plays a major role in MM treatment, but the duration of its use can be limited by toxicities such as peripheral neuropathy and the development of resistance. A new generation of proteasome inhibitors has since entered the treatment landscape: carfilzomib, an epoxyketone-based agent with a distinct mode of action, high clinical efficacy, and lower levels of peripheral neuropathy compared with bortezomib, received approval in 2015 for use in patients with relapsed and/or refractory MM (RRMM). Ixazomib, a second-generation, orally administered, boronic acid proteasome inhibi...
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Introduction of bortezomib, the first generation of proteasome inhibitor, has significantly improved the median overall survival of patients with multiple myeloma (MM). However, the dose-limiting adverse events and acquired drug resistance limit its long-term usage. Here, we report in vitro and in vivo anti-MM activity of the irreversible proteasome inhibitor BSc2118. BSc2118 inhibited the chymotrypsin-like (CT-L) proteasome activity, accompanied by accumulation of ubiquitinated proteins. BSc2118 suppressed tumor cell growth through induction of G2/M phase arrest and induced apoptosis via activation of the apoptotic signaling cascade, in association with up-regulation of p53 and p21. Importantly, BSc2118 was active in vitro against MM cells' acquired bortezomib resistance. Of note, BSc2118 also displayed a novel anti-angiogenesis activity both in vitro and in vivo. Lastly, BSc2118 exhibited a broader safety dose range and higher anti-tumor efficacy in vivo in a human MM xenograf...
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The proteasome is the key player in targeted degradation of cellular proteins and serves as a therapeutic target for treating several blood malignancies. Although in general, degradation of proteins via the proteasome requires their ubiquitination, a subset of proteins can be degraded independently of their ubiquitination by direct interaction with subunits of the 20S proteasome core. Thus, investigation of the proteasome-associated proteins may help identify novel targets of proteasome degradation and provide important insights into the mechanisms of malignant cell proteostasis. Here, using biochemical purification of proteasomes from multiple myeloma (MM) cells followed by mass-spectrometry we have uncovered 77 proteins in total that specifically interacted with the 20S proteasome via its PSMA3 subunit. Our GST pull-down assays followed by western blots validated the interactions identified by mass-spectrometry. Eleven proteins were confirmed to bind PSMA3 only upon apoptotic cond...