The development of proteasome inhibitors as anticancer drugs

Proteasome inhibition induces apoptosis through simultaneous inactivation of MCL-1/BCL-XL by NOXA independent of CHOP and JNK pathways

Proteasome inhibitors have been employed in the treatment of relapsed multiple myeloma and mantle cell lymphoma. The observed toxicity caused by proteasome inhibitors is a universal phenotype in numerous cancer cells with different sensitivity. In this study, we investigate the conserved mechanisms underlying the toxicity of the proteasome inhibitor bortezomib using gene editing approaches. Our findings utilizing different caspase knocking out cells reveal that bortezomib induces classic intrinsic apoptosis by activating caspase-9 and caspase-3/7, leading to pore-forming protein GSDME cleavage and subsequent lytic cell death or called secondary necrosis, a phenotype also observed in many apoptosis triggers like TNFα plus CHX, DTT and tunicamycin treatment in HeLa cells. Furthermore, through knocking out of nearly all BH3-only proteins including BIM, BAD, BID, BMF and PUMA, we demonstrate that NOXA is the sole BH3-only protein responsible for bortezomib-induced apoptosis. Of note, NOXA is well known for selectively binding to MCL-1 and A1, but our studies utilizing different BH3 mimetics as well as immunoprecipitation assays indicate that, except for the constitutive interaction of NOXA with MCL-1, the accumulation of NOXA after bortezomib treatment allows it to interact with BCL-XL, then simultaneous relieving suppression on apoptosis by both anti-apoptotic proteins BCL-XL and MCL-1. In addition, though bortezomib-induced significant ER stress and JNK activation were observed in the study, further genetic depletion experiments prove that bortezomib-induced apoptosis occurs independently of ER stress-related apoptosis factor CHOP and JNK. In summary, these results provide a solid conclusion about the critical role of NOXA in inactivation of BCL-XL except MCL-1 in bortezomib-induced apoptosis.

The Ubiquitin Tale: Current Strategies and Future Challenges

Ubiquitin (Ub) is often considered a structurally conserved protein. Ubiquitination plays a prominent role in the regulation of physiological pathways. Since the first mention of Ub in protein degradation pathways, a plethora of nonproteolytic functions of this post-translational modification have been identified and investigated in detail. In addition, several other structurally and functionally related proteins have been identified and investigated for their Ub-like structures and functions. Ubiquitination and Ub-like modifications play vital roles in modulating the pathways involved in crucial biological processes and thus affect the global proteome. In this Review, we provide a snapshot of pathways, substrates, diseases, and novel therapeutic targets that are associated with ubiquitination or Ub-like modifications. In the past few years, a large number of proteomic studies have identified pools of ubiquitinated proteins (ubiquitylomes) involved or induced in healthy or stressed conditions. These comprehensive studies involving identification of new ubiquitination substrates and sites contribute enormously to our understanding of ubiquitination in more depth. However, with the current tools, there are certain limitations that need to be addressed. We review recent technological advancements in ubiquitylomic studies and their limitations and challenges. Overall, large-scale ubiquitylomic studies contribute toward understanding global ubiquitination in the contexts of normal and disease conditions.

The Role of S-Glutathionylation in Health and Disease: A Bird's Eye View

Protein glutathionylation is a reversible post-translational modification that involves the attachment of glutathione to cysteine residues. It plays a role in the regulation of several cellular processes and protection against oxidative damage. Glutathionylation (GS-ylation) modulates protein function, inhibits or enhances enzymatic activity, maintains redox homeostasis, and shields several proteins from irreversible oxidative stress. Aberrant GS-ylation patterns are thus implicated in various diseases, particularly those associated with oxidative stress and inflammation, such as cardiovascular diseases, neurodegenerative disorders, cancer, and many others. Research in the recent years has highlighted the potential to manipulate protein GS-ylation for therapeutic purposes with strategies that imply both its enhancement and inhibition according to different cases. Moreover, it has become increasingly evident that monitoring the GS-ylation status of selected proteins offers diagnostic potential in different diseases. In this review, we try to summarize recent research in the field with a focus on our current understanding of the molecular mechanisms related to aberrant protein GS-ylation.

Clickable Probes for Pathogen Proteasomes: Synthesis and Applications

The 20S proteasome is a multimeric protease complex that is essential for proteostasis in the cell. Small molecule proteasome inhibitors are approved drugs for various cancers and are advancing clinically as antiparasitics. Although tools and technologies to study the 20S proteasome have advanced, only one probe is commercially available to image proteasome activity. This probe consists of a fluorescently labeled, peptidyl vinyl sulfone that binds to one or more of the catalytic proteasome subunits. Here, we synthesized two, active site-directed epoxyketone probes, LJL-1 and LJL-2, that were based on the peptidyl backbones of the anticancer drugs, carfilzomib and bortezomib, respectively. Each probe was conjugated, via click chemistry, to a bifunctional group comprising 5-carboxytetramethylrhodamine (TAMRA) and biotin to, respectively, visualize and enrich the 20S proteasome from protein extracts of two eukaryotic pathogens, Leishmania donovani and Trichomonas vaginalis. Depending on species, each probe generated a different subunit-binding profile by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), and the biotin tag enabled the enrichment of the bound subunits which were then formally identified by proteomics. Species differences in the order of electrophoretic migration by the β subunits were also noted. Finally, both probes reacted specifically with the 20S subunits in contrast to the commercial vinyl sulfone probe that cross reacted with cysteine proteases. LJL-1 and LJL-2 should find general utility in the identification and characterization of pathogen proteasomes, and serve as reagents to evaluate the specificity and mechanism of binding of new antiparasitic proteasome inhibitors.

Acetaminophen induces mitochondrial apoptosis through proteasome dysfunctions

Acetaminophen is a known antipyretic and non-opioid analgesic for mild pain and fever. Numerous studies uncover their hidden chemotherapeutics applications, including chronic cancer pain management. Acetaminophen also represents an anti-proliferative effect in some cancer cells. Few studies also suggest that the use of Acetaminophen can trigger apoptosis and impede cellular growth. However, Acetaminophen's molecular potential and precise mechanism against improper cellular proliferation and use as an effective anti-proliferative agent still need to be better understood. Here, our current findings show that Acetaminophen induces proteasomal dysfunctions, resulting in aberrant protein accumulation and mitochondrial abnormalities, and consequently induces cell apoptosis. We observed that the Acetaminophen treatment leads to improper aggregation of ubiquitylated expanded polyglutamine proteins, which may be due to the dysfunctions of proteasome activities. Our in-silico analysis suggests the interaction of Acetaminophen and proteasome. Furthermore, we demonstrated the accumulation of proteasome substrates and the depletion of proteasome activities after treating Acetaminophen in cells. Acetaminophen induces proteasome dysfunctions and mitochondrial abnormalities, leading to pro-apoptotic morphological changes and apoptosis successively. These results suggest that Acetaminophen can induce cell death and may retain a promising anti-proliferative effect. These observations can open new possible molecular strategies in the near future for developing and designing specific and effective proteasome inhibitors, which can be helpful in conjugation with other anti-tumor drugs for their better efficiency.

Exploring the origins of neurodevelopmental proteasomopathies associated with cardiac malformations: are neural crest cells central to certain pathological mechanisms?

Neurodevelopmental proteasomopathies constitute a recently defined class of rare Mendelian disorders, arising from genomic alterations in proteasome-related genes. These alterations result in the dysfunction of proteasomes, which are multi-subunit protein complexes essential for maintaining cellular protein homeostasis. The clinical phenotype of these diseases manifests as a syndromic association involving impaired neural development and multisystem abnormalities, notably craniofacial anomalies and malformations of the cardiac outflow tract (OFT). These observations suggest that proteasome loss-of-function variants primarily affect specific embryonic cell types which serve as origins for both craniofacial structures and the conotruncal portion of the heart. In this hypothesis article, we propose that neural crest cells (NCCs), a highly multipotent cell population, which generates craniofacial skeleton, mesenchyme as well as the OFT of the heart, in addition to many other derivatives, would exhibit a distinctive vulnerability to protein homeostasis perturbations. Herein, we introduce the diverse cellular compensatory pathways activated in response to protein homeostasis disruption and explore their potential implications for NCC physiology. Altogether, the paper advocates for investigating proteasome biology within NCCs and their early cranial and cardiac derivatives, offering a rationale for future exploration and laying the initial groundwork for therapeutic considerations.

The role of proteasomes in tumorigenesis

Protein homeostasis is the basis of normal life activities, and the proteasome family plays an extremely important function in this process. The proteasome 20S is a concentric circle structure with two α rings and two β rings overlapped. The proteasome 20S can perform both ATP-dependent and non-ATP-dependent ubiquitination proteasome degradation by binding to various subunits (such as 19S, 11S, and 200 PA), which is performed by its active subunit β1, β2, and β5. The proteasome can degrade misfolded, excess proteins to maintain homeostasis. At the same time, it can be utilized by tumors to degrade over-proliferate and unwanted proteins to support their growth. Proteasomes can affect the development of tumors from several aspects including tumor signaling pathways such as NF-κB and p53, cell cycle, immune regulation, and drug resistance. Proteasome-encoding genes have been found to be overexpressed in a variety of tumors, providing a potential novel target for cancer therapy. In addition, proteasome inhibitors such as bortezomib, carfilzomib, and ixazomib have been put into clinical application as the first-line treatment of multiple myeloma. More and more studies have shown that it also has different therapeutic effects in other tumors such as hepatocellular carcinoma, non-small cell lung cancer, glioblastoma, and neuroblastoma. However, proteasome inhibitors are not much effective due to their tolerance and singleness in other tumors. Therefore, further studies on their mechanisms of action and drug interactions are needed to investigate their therapeutic potential.

Targeted Therapies in the Treatment of Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is a rare, heterogeneous B-cell non-Hodgkin's lymphoma. The standard front-line treatment utilizes chemotherapy, often followed by consolidation with an autologous hematopoietic cell transplant; however, in most patients, the lymphoma will recur and require subsequent treatments. Additionally, mantle cell lymphoma primarily affects older patients and is frequently chemotherapy-resistant, which has further fostered the necessity for new, chemotherapy-free treatment options. In the past decade, targeted therapies in mantle cell lymphoma have been practice-changing as the treatment paradigm shifts further away from relying primarily on cytotoxic agents. Here, we will review the pathophysiology of mantle cell lymphoma and discuss the emergence of targeted, chemotherapy-free treatments aimed at disrupting the abnormal biology driving its lymphomagenesis. Treatments targeting the constitutive activation of NF-kB, Bruton's Tyrosine Kinase signaling, and anti-apoptosis will be the primary focus as we discuss their clinical data and toxicities. Our review will also focus primarily on the emergence and use of targeted therapies in the relapsed/refractory setting but will also discuss the emergence of their use in front-line therapy and in combination with other agents.

Expression of the chemokine receptor CCR1 decreases sensitivity to bortezomib in multiple myeloma cell lines

BACKGROUND

The proteasome inhibitor bortezomib is one of the primary therapies used for the haematological malignancy multiple myeloma (MM). However, intrinsic or acquired resistance to bortezomib, via mechanisms that are not fully elucidated, is a barrier to successful treatment in many patients. Our previous studies have shown that elevated expression of the chemokine receptor CCR1 in MM plasma cells in newly diagnosed MM patients is associated with poor prognosis. Here, we hypothesised that the poor prognosis conferred by CCR1 expression is, in part, due to a CCR1-mediated decrease in MM plasma cell sensitivity to bortezomib.

METHODS

In order to investigate the role of CCR1 in MM cells, CCR1 was knocked out in human myeloma cell lines OPM2 and U266 using CRISPR-Cas9. Additionally, CCR1 was overexpressed in the mouse MM cell line 5TGM1. The effect of bortezomib on CCR1 knockout or CCR1-overexpressing cells was then assessed by WST-1 assay, with or without CCL3 siRNA knockdown or addition of recombinant human CCL3. NSG mice were inoculated intratibially with OPM2-CCR1KO cells and were treated with 0.7 mg/kg bortezomib or vehicle twice per week for 3 weeks and GFP+ tumour cells in the bone marrow were quantitated by flow cytometry. The effect of CCR1 overexpression or knockout on unfolded protein response pathways was assessed using qPCR for ATF4, HSPA5, XBP1, ERN1 and CHOP and Western blot for IRE1α and p-Jnk.

RESULTS

Using CCR1 overexpression or CRIPSR-Cas9-mediated CCR1 knockout in MM cell lines, we found that CCR1 expression significantly decreases sensitivity to bortezomib in vitro, independent of the CCR1 ligand CCL3. In addition, CCR1 knockout rendered the human MM cell line OPM2 more sensitive to bortezomib in an intratibial MM model in NSG mice in vivo. Moreover, CCR1 expression negatively regulated the expression of the unfolded protein response receptor IRE1 and downstream target gene XBP1, suggesting this pathway may be responsible for the decreased bortezomib sensitivity of CCR1-expressing cells.

CONCLUSIONS

Taken together, these studies suggest that CCR1 expression may be associated with decreased response to bortezomib in MM cell lines.

Induction of proteasomal activity in mammalian cells by lifespan-extending tRNA synthetase inhibitors

We have recently shown that multiple tRNA synthetase inhibitors can greatly increase lifespan in multiple models by acting through the conserved transcription factor ATF4. Here, we show that these compounds, and several others of the same class, can greatly upregulate mammalian ATF4 in cells in vitro, in a dose dependent manner. Further, RNASeq analysis of these cells pointed toward changes in protein turnover. In subsequent experiments here we show that multiple tRNA synthetase inhibitors can greatly upregulate activity of the ubiquitin proteasome system (UPS) in cells in an ATF4-dependent manner. The UPS plays an important role in the turnover of many damaged or dysfunctional proteins in an organism. Increasing UPS activity has been shown to enhance the survival of Huntington's disease cell models, but there are few known pharmacological enhancers of the UPS. Additionally, we see separate ATF4 dependent upregulation of macroautophagy upon treatment with tRNA synthetase inhibitors. Protein degradation is an essential cellular process linked to many important human diseases of aging such as Alzheimer's disease and Huntington's disease. These drugs' ability to enhance proteostasis more broadly could have wide-ranging implications in the treatment of important age-related neurodegenerative diseases.

The Rise of Boron-Containing Compounds: Advancements in Synthesis, Medicinal Chemistry, and Emerging Pharmacology

Boron-containing compounds (BCC) have emerged as important pharmacophores. To date, five BCC drugs (including boronic acids and boroles) have been approved by the FDA for the treatment of cancer, infections, and atopic dermatitis, while some natural BCC are included in dietary supplements. Boron's Lewis acidity facilitates a mechanism of action via formation of reversible covalent bonds within the active site of target proteins. Boron has also been employed in the development of fluorophores, such as BODIPY for imaging, and in carboranes that are potential neutron capture therapy agents as well as novel agents in diagnostics and therapy. The utility of natural and synthetic BCC has become multifaceted, and the breadth of their applications continues to expand. This review covers the many uses and targets of boron in medicinal chemistry.

Optimal strategies of oncolytic virus-bortezomib therapy via the apoptotic, necroptotic, and oncolysis signaling network

Bortezomib and oncolytic virotherapy are two emerging targeted cancer therapies. Bortezomib, a proteasome inhibitor, disrupts protein degradation in cells, leading to the accumulation of unfolded proteins that induce apoptosis. On the other hand, virotherapy uses genetically modified oncolytic viruses (OVs) to infect cancer cells, trigger cell lysis, and activate anti-tumor response. Despite progress in cancer treatment, identifying administration protocols for therapeutic agents remains a significant concern, aiming to strike a balance between efficacy, minimizing toxicity, and administrative costs. In this work, optimal control theory was employed to design a cost-effective and efficient co-administration protocols for bortezomib and OVs that could significantly diminish the population of cancer cells via the cell death program with the NF$ \kappa $B-BAX-RIP1 signaling network. Both linear and quadratic control strategies were explored to obtain practical treatment approaches by adapting necroptosis protocols to efficient cell death programs. Our findings demonstrated that a combination therapy commencing with the administration of OVs followed by bortezomib infusions yields an effective tumor-killing outcome. These results could provide valuable guidance for the development of clinical administration protocols in cancer treatment.

Recent developments in the total synthesis of natural products using the Ugi multicomponent reactions as the key strategy

The total syntheses of selected natural products using different versions of the Ugi multicomponent reaction is reviewed on a case-by-case basis. The revision covers the period 2008-2023 and includes detailed descriptions of the synthetic sequences, the use of state-of-the-art chemical reagents and strategies, as well as the advantages and limitations of the transformation and some remedial solutions. Relevant data on the isolation and bioactivity of the different natural targets are also briefly provided. The examples clearly evidence the strategic importance of this transformation and its key role in the modern natural products synthetic chemistry toolbox. This methodology proved to be a valuable means for easily building molecular complexity and efficiently delivering step-economic syntheses even of intricate structures, with a promising future.

A review of progress in o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities for cancer therapy

Histone deacetylases, as a new class of anticancer targets, could maintain homeostasis by catalyzing histone deacetylation and play important roles in regulating the expression of target genes. Due to the fact that simultaneous intervention with dual tumor related targets could improve treatment effects, researches on innovative design of dual-target drugs are underway. HDAC is known as a "sensitizer" for the synergistic effects with other anticancer-target drugs because of its flexible structure design. The synergistic effects of HDAC inhibitor and other target inhibitors usually show enhanced inhibitory effects on tumor cells, and also provide new strategies to overcome multidrug resistance. Many research groups have reported that simultaneously inhibiting HDAC and other targets, such as tubulin, EGFR, could enhance the therapeutic effects. The o-aminobenzamide group is often used as a ZBG group in the design of HDAC inhibitors with potent antitumor effects. Given the prolonged inhibitory effects and reduced toxic side effects of HDAC inhibitors using o-aminobenzamide as the ZBG group, the o-aminobenzamide group is expected to become a more promising alternative to hydroxamic acid. In fact, o-aminobenzamide-based dual inhibitors of HDAC with different chemical structures have been extensively prepared and reported with synergistic and enhanced anti-tumor effects. In this work, we first time reviewed the rational design, molecular docking, inhibitory activities and potential application of o-aminobenzamide-based HDAC inhibitors with dual targeting capabilities in cancer therapy, which might provide a reference for developing new and more effective anticancer drugs.

Proteasome inhibitors in the treatment of nonsmall cell lung cancer: A systematic review of clinical evidence

Background and Aims

Nonsmall cell lung cancer accounts for over 85% of lung cancer incidences worldwide, and often has a poor prognosis. Proteasome inhibitors, such as bortezomib, have previously demonstrated evidence in preclinical and clinical models in the treatment of NSCLC both alone and as part of chemotherapeutic regimens.

Methods

Five databases were searched from inception to February 2023 to identify published clinical trial data and ongoing clinical trials on the use of proteasome inhibitors in treatment of NSCLC with a comprehensive search strategy.

Results

This review examines the clinical evidence from 21 completed and published phase I and II trials studying the use of bortezomib monotherapy and combination therapy in the treatment of NSCLC. Bortezomib/docetaxel combination resulted in longer median time-to-progression (TTP), median duration of response, median duration of disease control and median progression-free survival (PFS) than bortezomib monotherapy, with concurrent administration having greater 6-month PFS and median overall survival (OS) than sequential administration. Bortezomib/vorinostat with chemotherapy was well tolerated and effective. Bortezomib/gemcitabine/carboplatin, bortezomib/bevacizumab/carboplatin and bortezomib/paclitaxel/carboplatin combinations showed promising results and were of further investigational value.

Conclusion

Bortezomib showed some clinical promise in combination therapy but not monotherapy. It also demonstrated a manageable side effect profile. Combination regimens are of further investigation value in Phase II trials.

Boron in cancer therapeutics: An overview

Boron has become a crucial weapon in anticancer research due to its significant intervention in cell proliferation. Being an excellent bio-isosteric replacement of carbon, it has modulated the anticancer efficacy of various molecules in the development pipeline. It has elicited promising results through interactions with various therapeutic targets such as HIF-1α, steroid sulfatase, arginase, proteasome, etc. Since boron liberates alpha particles, it has a wide-scale application in Boron Neutron Capture therapy (BNCT), a radiotherapy that demonstrates selectivity towards cancer cells due to high boron uptake capacity. Significant advances in the medicinal chemistry of boronated compounds, such as boronated sugars, natural/unnatural amino acids, boronated DNA binders, etc., have been reported over the past few years as BNCT agents. In addition, boronated nanoparticles have assisted the field of bio-nano medicines by their usage in radiotherapy. This review exclusively focuses on the medicinal chemistry aspects, radiotherapeutic, and chemotherapeutic aspects of boron in cancer therapeutics. Emphasis is also given on the mechanism of action along with advantages over conventional therapies.

New lead compounds identification against KRas mediated cancers through pharmacophore-based virtual screening and in vitro assays

Cancer remains the leading cause of mortality and morbidity in the world, with 19.3 million new diagnoses and 10.1 million deaths in 2020. Cancer is caused due to mutations in proto-oncogenes and tumor-suppressor genes. Genetic analyses found that Ras (Rat sarcoma) is one of the most deregulated oncogenes in human cancers. The Ras oncogene family members including NRas (Neuroblastoma ras viral oncogene homolog), HRas (Harvey rat sarcoma) and KRas are involved in different types of human cancers. The mutant KRas is considered as the most frequent oncogene implicated in the development of lung, pancreatic and colon cancers. However, there is no efficient clinical drug even though it has been identified as an oncogene for 30 years. Therefore there is an emerging need to develop potent, new anticancer drugs. In this study, computer-aided drug designing approaches as well as experimental methods were employed to find new and potential anti-cancer drugs. The pharmacophore model was developed from an already known FDA approved anti-cancer drug Bortezomib using the software MOE. The validated pharmacophore model was then used to screen the in-house and commercially available databases. The pharmacophore-based virtual screening resulted in 26 and 86 hits from in-house and commercial databases respectively. Finally, 6/13 (in-house database) and 24/64 hits (commercial databases) were selected with different scaffolds having good interactions with the significant active residues of KRasG12D protein that were predicted as potent lead compounds. Finally, the results of pharmacophore-based virtual screening were further validated by molecular dynamics simulation analysis. The 6 hits of the in-house database were further evaluated experimentally. The experimental results showed that these compounds have good anti-cancer activity which validate the protocol of our in silico studies. KRasG12D protein is a very important anti-cancer target and potent inhibitors for this target are still not available, so small lead compound inhibitors were identified to inhibit the activity of this protein by blocking the GTP-binding pocket.Communicated by Ramaswamy H. Sarma.

Sequential Ubiquitination and Phosphorylation Epigenetics Reshaping by MG132-Loaded Fe-MOF Disarms Treatment Resistance to Repulse Metastatic Colorectal Cancer

Abnormal epigenetic regulation is identified to correlate with cancer progression and renders tumor refractory and resistant to reactive oxygen species (ROS)-based anti-tumor actions. To address it, a sequential ubiquitination and phosphorylation epigenetics modulation strategy is developed and exemplified by the well-established Fe-metal-organic framework (Fe-MOF)-based chemodynamic therapy (CDT) nanoplatforms that load the 26S proteasome inhibitor (i.e., MG132). The encapsulated MG132 can blockade 26S proteasome, terminate ubiquitination, and further inhibit transcription factor phosphorylation (e.g., NF-κB p65), which can boost pro-apoptotic or misfolded protein accumulations, disrupt tumor homeostasis, and down-regulate driving genes expression of metastatic colorectal cancer (mCRC). Contributed by them, Fe-MOF-unlocked CDT is magnified to considerably elevate ROS content for repulsing mCRC, especially after combining with macrophage membrane coating-enabled tropism accumulation. Systematic experiments reveal the mechanism and signaling pathway of such a sequential ubiquitination and phosphorylation epigenetics modulation and explain how it could blockade ubiquitination and phosphorylation to liberate the therapy resistance to ROS and activate NF-κB-related acute immune responses. This unprecedented sequential epigenetics modulation lays a solid foundation to magnify oxidative stress and can serve as a general method to enhance other ROS-based anti-tumor methods.

Proteasome Inhibitor-Based Regimens in the Frontline Management of Waldenström Macroglobulinemia

Proteasome inhibitors (PIs) have long been used in myeloma therapy but also for Waldenström macroglobulinemia. Their use has been successful and has also been investigated for the frontline management of the disease. Bortezomib was effective either as a single agent or in combination with other regimens with high response rates observed in most studies, despite its adverse effects, especially neurotoxicity, which remains a major concern. Clinical trials with second-generation PIs such as carfilzomib and ixazomib have also been conducted, always in combination with immunotherapy in previously untreated patients. They have been shown to be active and neuropathy-sparing treatment options.

RNF4 and USP7 cooperate in ubiquitin-regulated steps of DNA replication

DNA replication requires precise regulation achieved through post-translational modifications, including ubiquitination and SUMOylation. These modifications are linked by the SUMO-targeted E3 ubiquitin ligases (STUbLs). Ring finger protein 4 (RNF4), one of only two mammalian STUbLs, participates in double-strand break repair and resolving DNA-protein cross-links. However, its role in DNA replication has been poorly understood. Using CRISPR/Cas9 genetic screens, we discovered an unexpected dependency of RNF4 mutants on ubiquitin specific peptidase 7 (USP7) for survival in TP53-null retinal pigment epithelial cells. TP53-/-/RNF4-/-/USP7-/- triple knockout (TKO) cells displayed defects in DNA replication that cause genomic instability. These defects were exacerbated by the proteasome inhibitor bortezomib, which limited the nuclear ubiquitin pool. A shortage of free ubiquitin suppressed the ataxia telangiectasia and Rad3-related (ATR)-mediated checkpoint response, leading to increased cell death. In conclusion, RNF4 and USP7 work cooperatively to sustain a functional level of nuclear ubiquitin to maintain the integrity of the genome.

Molecular Mechanisms Driving and Regulating the AAA+ ATPase VCP/p97, an Important Therapeutic Target for Treating Cancer, Neurological and Infectious Diseases

p97/VCP, a highly conserved type II ATPase associated with diverse cellular activities (AAA+ ATPase), is an important therapeutic target in the treatment of neurodegenerative diseases and cancer. p97 performs a variety of functions in the cell and facilitates virus replication. It is a mechanochemical enzyme that generates mechanical force from ATP-binding and hydrolysis to perform several functions, including unfolding of protein substrates. Several dozens of cofactors/adaptors interact with p97 and define the multifunctionality of p97. This review presents the current understanding of the molecular mechanism of p97 during the ATPase cycle and its regulation by cofactors and small-molecule inhibitors. We compare detailed structural information obtained in different nucleotide states in the presence and absence of substrates and inhibitors. We also review how pathogenic gain-of-function mutations modify the conformational changes of p97 during the ATPase cycle. Overall, the review highlights how the mechanistic knowledge of p97 helps in designing pathway-specific modulators and inhibitors.

Triazole-fused pyrimidines in target-based anticancer drug discovery

In recent decades, the development of targeted drugs has featured prominently in the treatment of cancer, which is among the major causes of mortality globally. Triazole-fused pyrimidines, a widely-used class of heterocycles in medicinal chemistry, have attracted considerable interest as potential anticancer agents that target various cancer-associated targets in recent years, demonstrating them as valuable templates for discovering novel anticancer candidates. The current review concentrates on the latest advancements of triazole-pyrimidines as target-based anticancer agents, including works published between 2007 and the present (2007-2022). The structure-activity relationships (SARs) and multiple pathways are also reviewed to shed light on the development of more effective and biotargeted anticancer candidates.

Inhibitors of the ATPase p97/VCP: From basic research to clinical applications

Protein homeostasis deficiencies underlie various cancers and neurodegenerative diseases. The ubiquitin-proteasome system (UPS) and autophagy are responsible for most of the protein degradation in mammalian cells and, therefore, represent attractive targets for cancer therapy and that of neurodegenerative diseases. The ATPase p97, also known as VCP, is a central component of the UPS that extracts and disassembles its substrates from various cellular locations and also regulates different steps in autophagy. Several UPS- and autophagy-targeting drugs are in clinical trials. In this review, we focus on the development of various p97 inhibitors, including the ATPase inhibitors CB-5083 and CB-5339, which reached clinical trials by demonstrating effective anti-tumor activity across various tumor models, providing an effective alternative to targeting protein degradation for cancer therapy. Here, we provide an overview of how different p97 inhibitors have evolved over time both as basic research tools and effective UPS-targeting cancer therapies in the clinic.

Insights of metal 8-hydroxylquinolinol complexes as the potential anticancer drugs

8-Hydroxyquinoline and its derivatives, which belong to a well-known class of quinoline based drugs with varied biological activities, have been extensively explored for the treatments of cancer, Alzheimer's disease, neurodegenerative diseases and other life-threatening diseases. In virtue of the existence of bicyclic heterocyclic scaffold, their bidentate chelators can further bind to metal ions via O- and N-donors from 8-hydroxylquinolinol skeletons to yield a variety of metal 8-hydroxylquinolinol complexes appealing as the anticancer drugs with low toxicity, due to their better biological effects and higher anticancer activities than free 8-hydroxylquinolinol ligands and cis-diammine-dichloro-platinum. The present review summarizes the recent developments in the syntheses, crystal structures, and anticancer activities of metal 8-hydroxylquinolinol complexes, attempting to discover a correlation between their structures and anticancer activities, and to provide an evidence for their potential application perspectives. It means to offer the helpful and meaningful guidance for the researchers in the future syntheses of new and highly efficient anticancer metal 8-hydroxylquinolinol complexes based drugs.

Complexity in radiological morphology predicts worse prognosis and is associated with an increase in proteasome component levels in clear cell renal cell carcinoma

Background

We previously reported preoperative radiological morphology (RM) as an independent predictor for pathological upstaging after partial nephrectomy in patients with T1 renal cell carcinoma (RCC).

Purpose

To investigate the prognostic importance of RM in all stages and the molecular characteristics underlying the differences between each type of RM in patients with clear cell RCC (ccRCC).

Design setting and participants

The Cancer Imaging Archive datasets (TCIA), comprising CT images and RNA-sequencing data, were used (n = 163). Specimens from 63 patients with ccRCC at our institution and their CT images were used. All images were divided into three types according to RM classification.

Outcome measurements and statistical analysis

Relationships with outcome were analyzed using Cox regression analysis and log-rank test.

Results and limitations

The irregular type was a significant independent predictor of worse disease-free survival (odds ratio: 2.22, p = 0.037) compared to round and lobular types in TCIA datasets. The irregular type showed a significant increase in both mRNA and protein expression of proteasome components, PSMB1 and PSMB3. Moreover, high expression of their coding genes shortened the progression-free survival of the patients with ccRCC who received sunitinib or avelumab plus axitinib therapy. The study limitations include the qualitative classification of RM and the need for novel radiomics and texture analysis techniques.

Conclusions

Investigating RM on pre-treatment CT scans can effectively predict worse prognosis. Increased RM complexity may indirectly predict drug sensitivity via increased expression of PSMB1 and PSMB3 in patients with ccRCC. Specific targeting of the ubiquitin-proteasome system might be a novel treatment strategy for ccRCC with increased RM complexity.

Patient summary

The clinical and morphological characteristics of patients with ccRCC vary greatly according to cancer staging. In this study, we built upon our prior findings of the prognostic importance of RM in T1 RCC and expanded it to encompass all stages of RCC, using a series of patients from a Japanese hospital.

Quaternary nanoparticles enable sustained release of bortezomib for hepatocellular carcinoma

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) represents the third leading cause of cancer-related mortality in the world. Over the past two decades, there has been minimal improvement in therapies as well as clinical outcomes for patients with Barcelona Clinic Liver Cancer (BCLC)-B. These patients are treated with local interventions, including transarterial chemoembolization. Current methodologies only allow sustained intratumoral release measured in hours. Methodologies to allow sustained local release of the drug cargo over days to weeks are acutely needed. We hypothesize that tumor response as well as outcomes of patients with BCLC-B can be improved through utilization of a highly cytotoxic agent delivered with a sustained release platform.

APPROACH AND RESULTS

High-throughput drug screening across 40 HCC patient-derived organoids identified bortezomib (BTZ) as a highly cytotoxic small molecule for HCC. We designed and manufactured sustained release BTZ nanoparticles (BTZ-NP) using a flash nanocomplexation/nanoprecipitation process. We quantified the release profile and tested the anti-tumoral effects in vivo. The BTZ-NP formulation demonstrated a sustained release of BTZ of 30 days. This BTZ-NP formulation was highly effective in controlling tumor size and improved survival in vivo in three animal models of HCC, including when delivered via the hepatic artery, as we envision its delivery in patients. In addition, the BTZ-NP formulation was superior to treatment with doxorubicin-drug eluting beads.

CONCLUSIONS

The BTZ-NP formulation provides a potent and safe treatment of HCC via a localized delivery approach. These results warrant additional preclinical studies to advance this technology to human clinical trials.

Polystyrene nanoplastics affect the human ubiquitin structure and ubiquitination in cells: a high-resolution study

Humans are estimated to consume several grams per week of nanoplastics (NPs) through exposure to a variety of contamination sources. Nonetheless, the effects of these polymeric particles on living systems are still mostly unknown. Here, by means of CD, NMR and TEM analyses, we describe at an atomic resolution the interaction of ubiquitin with polystyrene NPs (PS-NPs), showing how a hard protein corona is formed. Moreover, we report that in human HeLa cells exposure to PS-NPs leads to a sensible reduction of ubiquitination. Our study overall indicates that PS-NPs cause significant structural effects on ubiquitin, thereby influencing one of the key metabolic processes at the base of cell viability.

MLN2238 exerts its anti-tumor effects via regulating ROS/JNK/mitochondrial signaling pathways in intrahepatic cholangiocarcinoma

Background: Intrahepatic Cholangiocarcinoma (iCCA) is a highly malignant tumor with limited treatment options that contributes largely to cancer-related deaths worldwide. Compared with traditional transcriptomic analysis, single-cell RNA sequencing (scRNA-seq) is emerging as a more advanced and popular tool for the in-depth exploration of cellular diversity and molecular complexity. As a next-generation proteasome inhibitor, MLN2238 presents better pharmacodynamics, pharmacokinetics, and therapeutic responses in various cancers. However, its effects and mechanisms of action in iCCA remain unknown. Methods: iCCA tumor heterogeneity was determined based on 4,239 qualified scRNA-seq data from 10 iCCA samples. The potential biological roles of proteasome-related genes in iCCA were investigated using a pseudo-trajectory reconstruction. The effect of MLN2238 on iCCA cell proliferation was estimated using the CCK-8, EdU, and clone formation assays. Flow cytometry was used to examine the effect of added MLN2238 on cell cycle and apoptosis levels. Autophagic flux was detected using AdPlus-mCherry-GFP-LC3B cells. ROS levels and mitochondrial membrane potential were determined using DCFH-DA probing and JC-1 staining. JNK activation and mitochondrial apoptosis were observed using western blotting and immunofluorescence microscopy, respectively. Finally, we used a tumor-bearing mouse model to validate its efficacy in vivo for iCCA treatment. Results: Proteasome-related genes were dysregulated in iCCA progression and expressed at higher levels in tumor tissues. MLN2238 suppressed cell proliferation, blocked the cell cycle in the G2/M phase, promoted apoptosis, and induced cytoprotective autophagy in iCCA cells. Furthermore, MLN2238 increased ROS levels and activated the JNK signaling pathway. Inhibition of ROS and JNK activation by NAC and SP600125 significantly reversed MLN2238-induced apoptosis. MLN2238 also suppressed the growth of iCCA tumors in vivo. Conclusion: Proteasome-related genes play pivotal roles in iCCA development. MLN2238, as a proteasome inhibitor, induces apoptosis in iCCA cells through ROS/JNK/mitochondrial signaling pathways, and hence, making MLN2238 a potential therapeutic choice for iCCA.

Molecular Mechanism of Pathogenesis and Treatment Strategies for AL Amyloidosis

In amyloid light-chain (AL) amyloidosis, small B-cell clones (mostly plasma cell clones) present in the bone marrow proliferate and secrete unstable monoclonal free light chains (FLCs), which form amyloid fibrils that deposit in the interstitial tissue, resulting in organ injury and dysfunction. AL amyloidosis progresses much faster than other types of amyloidosis, with a slight delay in diagnosis leading to a marked exacerbation of cardiomyopathy. In some cases, the resulting heart failure is so severe that chemotherapy cannot be administered, and death sometimes occurs within a few months. To date, many clinical studies have focused on therapeutics, especially chemotherapy, to treat this disease. Because it is necessary to promptly lower FLC, the causative protein of amyloid, to achieve a hematological response, various anticancer agents targeting neoplastic plasma cells are used for the treatment of this disease. In addition, many basic studies using human specimens to elucidate the pathophysiology of AL have been conducted. Gene mutations associated with AL, the characteristics of amyloidogenic LC, and the structural specificity of amyloid fibrils have been clarified. Regarding the mechanism of cellular and tissue damage, the mass effect due to amyloid deposition, as well as the toxicity of pre-fibrillar LC, is gradually being elucidated. This review outlines the pathogenesis and treatment strategies for AL amyloidosis with respect to its molecular mechanisms.

The aspartyl protease DDI2 drives adaptation to proteasome inhibition in multiple myeloma

Proteasome inhibitors, such as bortezomib, are first-line therapy against multiple myeloma (MM). Unfortunately, patients frequently become refractory to this treatment. The transcription factor NRF1 has been proposed to initiate an adaptation program that regulates proteasome levels. In the context of proteasome inhibition, the cytosolic protease DDI2 cleaves NRF1 to release an active fragment that translocates to the nucleus to promote the transcription of new proteasome subunits. However, the contribution of the DDI2-NRF1 pathway to bortezomib resistance is poorly understood. Here we show that upon prolonged bortezomib treatment, MM cells become resistant to proteasome inhibition by increasing the expression of DDI2 and consequently activation of NRF1. Furthermore, we found that many MM cells became more sensitive to proteasome impairment in the context of DDI2 deficiency. Mechanistically, we demonstrate that both the protease and the HDD domains of DDI2 are required to activate NRF1. Finally, we show that partial inhibition of the DDI2-protease domain with the antiviral drug nelfinavir increased bortezomib susceptibility in treated MM cells. Altogether, these findings define the DDI2-NRF1 pathway as an essential program contributing to proteasome inhibition responses and identifying DDI2 domains that could be targets of interest in bortezomib-treated MM patients.

Site-Specific Proteasome Inhibitors

Proteasome is a multi-subunit protein degradation machine, which plays a key role in the maintenance of protein homeostasis and, through degradation of regulatory proteins, in the regulation of numerous cell functions. Proteasome inhibitors are essential tools for biomedical research. Three proteasome inhibitors, bortezomib, carfilzomib, and ixazomib are approved by the FDA for the treatment of multiple myeloma; another inhibitor, marizomib, is undergoing clinical trials. The proteolytic core of the proteasome has three pairs of active sites, β5, β2, and β1. All clinical inhibitors and inhibitors that are widely used as research tools (e.g., epoxomicin, MG-132) inhibit multiple active sites and have been extensively reviewed in the past. In the past decade, highly specific inhibitors of individual active sites and the distinct active sites of the lymphoid tissue-specific immunoproteasome have been developed. Here, we provide a comprehensive review of these site-specific inhibitors of mammalian proteasomes and describe their utilization in the studies of the biology of the active sites and their roles as drug targets for the treatment of different diseases.

Progress on the Application of Bortezomib and Bortezomib-Based Nanoformulations

Bortezomib (BTZ) is the first proteasome inhibitor approved by the Food and Drug Administration. It can bind to the amino acid residues of the 26S proteasome, thereby causing the death of tumor cells. BTZ plays an irreplaceable role in the treatment of mantle cell lymphoma and multiple myeloma. Moreover, its use in the treatment of other hematological cancers and solid tumors has been investigated in numerous clinical trials and preclinical studies. Nevertheless, the applications of BTZ are limited due to its insufficient specificity, poor permeability, and low bioavailability. Therefore, in recent years, different BTZ-based drug delivery systems have been evaluated. In this review, we firstly discussed the functions of proteasome inhibitors and their mechanisms of action. Secondly, the properties of BTZ, as well as recent advances in both clinical and preclinical research, were reviewed. Finally, progress in research regarding BTZ-based nanoformulations was summarized.

Protein Kinase A (PRKA) Activity Is Regulated by the Proteasome at the Onset of Human Sperm Capacitation

The proteasome increases its activity at the onset of sperm capacitation due to the action of the SACY/PRKACA pathway; this increase is required for capacitation to progress. PRKA activity also increases and remains high during capacitation. However, intracellular levels of cAMP decrease in this process. Our goal was to evaluate the role of the proteasome in regulating PRKA activity once capacitation has started. Viable human sperm were incubated in the presence and absence of epoxomicin or with 0.1% DMSO. The activity of PRKA; the phosphorylation pattern of PRKA substrates (pPRKAs); and the expression of PRKAR1, PRKAR2, and AKAP3 were evaluated by Western blot. The localization of pPRKAs, PRKAR1, PRKAR2, and AKAP3 was evaluated by immunofluorescence. Treatment with epoxomicin changed the localization and phosphorylation pattern and decreased the percentage of pPRKAs-positive sperm. PRKA activity significantly increased at 1 min of capacitation and remained high throughout the incubation. However, epoxomicin treatment significantly decreased PRKA activity after 30 min. In addition, PRKAR1 and AKAP3 were degraded by the proteasome but with a different temporal kinetic. Our results suggest that PRKAR1 is the target of PRKA regulation by the proteasome.

Carfilzomib: A Promising Proteasome Inhibitor for the Treatment of Relapsed and Refractory Multiple Myeloma

The proteasome is crucial for the degradation of intracellular proteins and plays an important role in mediating a number of cell survival and progression events by controlling the levels of key regulatory proteins such as cyclins and caspases in both normal and tumor cells. However, compared to normal cells, cancer cells are more dependent on the ubiquitin proteasome pathway (UPP) due to the accumulation of proteins in response to uncontrolled gene transcription, allowing proteasome to become a potent therapeutic target for human cancers such as multiple myeloma (MM). Up to date, three proteasome inhibitors namely bortezomib (2003), carfilzomib (2012) and ixazomib (2015) have been approved by the US Food and Drug Administration (FDA) for the treatment of patients with relapsed and/or refractory MM. This review mainly focuses on the biochemical properties, mechanism of action, toxicity profile and pivotal clinical trials related to carfilzomib, a second-generation proteasome inhibitor that binds irreversibly with proteasome to overcome the major toxicities and resistance associated with bortezomib.

Overcoming drug resistance by targeting protein homeostasis in multiple myeloma

Multiple myeloma (MM) is a plasma cell disorder typically characterized by abundant synthesis of clonal immunoglobulin or free light chains. Although incurable, a deeper understanding of MM pathobiology has fueled major therapeutical advances over the past two decades, significantly improving patient outcomes. Proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies are among the most effective anti-MM drugs, targeting not only the cancerous cells, but also the bone marrow microenvironment. However, de novo resistance has been reported, and acquired resistance is inevitable for most patients over time, leading to relapsed/refractory disease and poor outcomes. Sustained protein synthesis coupled with impaired/insufficient proteolytic mechanisms makes MM cells exquisitely sensitive to perturbations in protein homeostasis, offering us the opportunity to target this intrinsic vulnerability for therapeutic purposes. This review highlights the scientific rationale for the clinical use of FDA-approved and investigational agents targeting protein homeostasis in MM.

Inhibition of the ubiquitin-proteasome system by an NQO1-activatable compound

Malignant cells display an increased sensitivity towards drugs that reduce the function of the ubiquitin-proteasome system (UPS), which is the primary proteolytic system for destruction of aberrant proteins. Here, we report on the discovery of the bioactivatable compound CBK77, which causes an irreversible collapse of the UPS, accompanied by a general accumulation of ubiquitylated proteins and caspase-dependent cell death. CBK77 caused accumulation of ubiquitin-dependent, but not ubiquitin-independent, reporter substrates of the UPS, suggesting a selective effect on ubiquitin-dependent proteolysis. In a genome-wide CRISPR interference screen, we identified the redox enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1) as a critical mediator of CBK77 activity, and further demonstrated its role as the compound bioactivator. Through affinity-based proteomics, we found that CBK77 covalently interacts with ubiquitin. In vitro experiments showed that CBK77-treated ubiquitin conjugates were less susceptible to disassembly by deubiquitylating enzymes. In vivo efficacy of CBK77 was validated by reduced growth of NQO1-proficient human adenocarcinoma cells in nude mice treated with CBK77. This first-in-class NQO1-activatable UPS inhibitor suggests that it may be possible to exploit the intracellular environment in malignant cells for leveraging the impact of compounds that impair the UPS.

Natural compounds in the regulation of proteostatic pathways: An invincible artillery against stress, ageing, and diseases

Cells have different sets of molecules for performing an array of physiological functions. Nucleic acids have stored and carried the information throughout evolution, whereas proteins have been attributed to performing most of the cellular functions. To perform these functions, proteins need to have a unique conformation and a definite lifespan. These attributes are achieved by a highly coordinated protein quality control (PQC) system comprising chaperones to fold the proteins in a proper three-dimensional structure, ubiquitin-proteasome system for selective degradation of proteins, and autophagy for bulk clearance of cell debris. Many kinds of stresses and perturbations may lead to the weakening of these protective cellular machinery, leading to the unfolding and aggregation of cellular proteins and the occurrence of numerous pathological conditions. However, modulating the expression and functional efficiency of molecular chaperones, E3 ubiquitin ligases, and autophagic proteins may diminish cellular proteotoxic load and mitigate various pathological effects. Natural medicine and small molecule-based therapies have been well-documented for their effectiveness in modulating these pathways and reestablishing the lost proteostasis inside the cells to combat disease conditions. The present article summarizes various similar reports and highlights the importance of the molecules obtained from natural sources in disease therapeutics.

The role of the ubiquitin-proteasome pathway in skin cancer development: 26S proteasome-activated NF-κB signal transduction

The Ubiquitin-Proteasome System plays a central role in signal transduction associated with stress, in the skin in particular by the control of NF-κB pathways. Under normal conditions, the inhibitory protein IκB is phosphorylated by kinases, then ubiquitinated and ends up at the proteasome to be degraded. The present short review discusses recent progress in the inhibition of NF-κB activation by proteasome inhibitors prevents the degradation of protein IκB, which accumulates in the cytosol, and there by the activation of NF-κB. Moreover, would not only limit the expression of adhesion molecules and cytokines involved in metastatic processes, but also increase the sensitivity of cancer cells to apoptosis. Considering this fact, the activity of NF-κB is regulated by the phosphorylation and proteasome-dependent degradation of its inhibitor Iκb. In this scenario, the use of a proteasome inhibitor might be an effective strategy in the treatment of skin cancer with constitutive activation of NF-κB.

Automating UbiFast for High-throughput and Multiplexed Ubiquitin Enrichment

Robust methods for deep-scale enrichment and site-specific identification of ubiquitylation sites are necessary for characterizing the myriad roles of protein ubiquitylation. To this end we previously developed UbiFast, a sensitive method for highly multiplexed ubiquitylation profiling where K-ϵ-GG peptides are enriched with anti-K-ε-GG antibody and labeled on-antibody with isobaric labeling reagents for sample multiplexing. Here, we present robotic automation of the UbiFast method using a magnetic bead-conjugated K-ε-GG antibody (mK-ε-GG) and a magnetic particle processor. We report the identification of ∼20,000 ubiquitylation sites from a TMT10-plex with 500 μg input per sample processed in ∼2 h. Automation of the UbiFast method greatly increased the number of identified and quantified ubiquitylation sites, improved reproducibility, and significantly reduced processing time. The automated method also significantly reduced variability across process replicates compared with the manual method. The workflow enables processing of up to 96 samples in a single day making it suitable to study ubiquitylation in large sample sets. Here we demonstrate the applicability of the method to profile small amounts of tissue using breast cancer patient–derived xenograft (PDX) tissue samples.

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HS mag anti-K-ε-GG antibody increases sensitivity of ubiquitylation site detection.

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Automated UbiFast increases reproducibility and sample processing throughput.

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The automated UbiFast workflow enables processing of up to 96 samples in one day.

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UbiFast can be employed to profile ubiquitylomes from small amounts of tumor tissue.

Proteasome inhibition by bortezomib parallels a reduction in head and neck cancer cells growth, and an increase in tumor-infiltrating immune cells

Head and neck cancer (HNC) has frequently an aggressive course for the development of resistance to standard chemotherapy. Thus, the use of innovative therapeutic drugs is being assessed. Bortezomib is a proteasome inhibitor with anticancer effects. In vitro antitumoral activity of Bortezomib was investigated employing human tongue (SCC-15, CAL-27), pharynx (FaDu), salivary gland (A-253) cancer cell lines and a murine cell line (SALTO-5) originated from a salivary gland adenocarcinoma arising in BALB-neuT male mice transgenic for the oncogene neu. Bortezomib inhibited cell proliferation, triggered apoptosis, modulated the expression and activation of pro-survival signaling transduction pathways proteins activated by ErbB receptors and inhibited proteasome activity in vitro. Intraperitoneal administration of Bortezomib delayed tumor growth of SALTO-5 cells transplanted in BALB-neuT mice, protracted mice survival and adjusted tumor microenvironment by increasing tumor-infiltrating immune cells (CD4⁺ and CD8⁺ T cells, B lymphocytes, macrophages, and Natural Killer cells) and by decreasing vessels density. In addition, Bortezomib modified the expression of proteasome structural subunits in transplanted SALTO-5 cells. Our findings further support the use of Bortezomib for the treatment of HNC and reveal its ineffectiveness in counteracting the activation of deregulated specific signaling pathways in HNC cell lines when resistance to proteasome inhibition is developed.

Sensitivity of Acute Myelocytic Leukemia Cells to the Dienone Compound VLX1570 Is Associated with Inhibition of the Ubiquitin-Proteasome System

Dienone compounds with a 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore have been widely reported to show tumor cell selectivity. These compounds target the ubiquitin-proteasome system (UPS), known to be essential for the viability of tumor cells. The induction of oxidative stress, depletion of glutathione, and induction of high-molecular-weight (HMW) complexes have also been reported. We here examined the response of acute myeloid leukemia (AML) cells to the dienone compound VLX1570. AML cells have relatively high protein turnover rates and have also been reported to be sensitive to depletion of reduced glutathione. We found AML cells of diverse cytogenetic backgrounds to be sensitive to VLX1570, with drug exposure resulting in an accumulation of ubiquitin complexes, induction of ER stress, and the loss of cell viability in a dose-dependent manner. Caspase activation was observed but was not required for the loss of cell viability. Glutathione depletion was also observed but did not correlate to VLX1570 sensitivity. Formation of HMW complexes occurred at higher concentrations of VLX1570 than those required for the loss of cell viability and was not enhanced by glutathione depletion. To study the effect of VLX1570 we developed a zebrafish PDX model of AML and confirmed antigrowth activity in vivo. Our results show that VLX1570 induces UPS inhibition in AML cells and encourage further work in developing compounds useful for cancer therapeutics.

A simplified method for bortezomib determination using dried blood spots in combination with liquid chromatography/tandem mass spectrometry

Bortezomib, a proteinase inhibitor currently used to treat multiple myeloma and mantle cell lymphoma, has a high incidence of adverse reactions and large inter-individual differences in plasma concentrations. A simple, validated LC-MS/MS method for the quantitative analysis of bortezomib in dried blood spot (DBS) samples was developed to provide support for determining the effective concentration range of bortezomib for clinical use. Fifty (i50) μL of spiked blood were added onto Whatman protein saver cards to prepare the DBS samples. Circular cards of 6 mm diameter were punched, extracted by methanol containing the internal standard (apatinib), and injected into the LC-MS/MS system. The method validation included selectivity, linearity, accuracy and precision, stability, matrix effect, recovery and hematocrit. The calibration curve showed correlation coefficient values higher than 0.999 in the range of 0.2 - 20.0 ng/mL for bortezomib. The acceptance criteria of accuracy (relative error < 12.5%) and precision (coefficient of variation < 10.7%) were met in all cases. The matrix effect was<13.2%, and the recovery was between 87.3 and 100.2%. DBS samples were shown to be stable when stored in cold conditions or at room temperature. Different hematocrit values did not significantly affect the accuracy of the measured concentrations. And there are no significant differences between bortezomib concentrations in DBS samples and plasma samples. This new method was successfully used for clinical concentration determinations of bortezomib and can be applied in future therapeutic drug monitoring and pharmacokinetic studies of bortezomib especially in pediatric patients.

Valosin-containing Protein in Psoriasis: A Clinical and Immunohistochemical Study

Psoriasis is a chronic immune-mediated inflammatory skin disease, affects about 2% to 3% of the world population. Valosin-containing protein (VCP) is one of the newly discovered markers that is highly expressed in neoplasms and hyperproliferative lesions. This work aimed to study the role of VCP in psoriasis vulgaris by immunohistochemical study and correlate its expression with the available clinicopathologic data. This prospective case-control study was conducted on 25 patients with psoriasis vulgaris and 25 age-matched and sex-matched healthy individuals as a control group. Skin biopsies were taken under local anesthesia from cases and controls. VCP immunoreactivity showed that epidermal VCP expression had a significant stepwise increase (P=0.002) from control to lesional psoriatic sections. Epidermal VCP H-score was significantly associated with the progressive course (P=0.037). Similarly, VCP in the dermis showed a significant expression in lesional psoriatic skin (P≤0.001). Higher VCP in the dermis in cases with a history of joint affection (P<0.05) was detected. We concluded that VCP is a promising marker for follow-up and monitoring of psoriatic patients and may play a role as a therapeutic target.

Hypomethylating Chemotherapeutic Agents as Therapy for Myelodysplastic Syndromes and Prevention of Acute Myeloid Leukemia

Myelodysplastic Syndromes (MDSs) affect the elderly and can progress to Acute Myeloid Leukemia (AML). Epigenetic alterations including DNA methylation and chromatin modification may contribute to the initiation and progression of these malignancies. DNA hypomethylating agents such as decitabine and azacitidine are used as therapeutic treatments and have shown to promote expression of genes involved in tumor suppression, apoptosis, and immune response. Another anti-cancer drug, the proteasome inhibitor bortezomib, is used as a chemotherapeutic treatment for multiple myeloma (MM). Phase III clinical trials of decitabine and azacitidine used alone and in combination with other chemotherapeutics demonstrated their capacity to treat hematological malignancies and prolong the survival of MDS and AML patients. Although phase III clinical trials examining bortezomib's role in MDS and AML patients are limited, its underlying mechanisms in MM highlight its potential as a chemotherapeutic for such malignancies. Further research is needed to better understand how the epigenetic mechanisms mediated by these chemotherapeutic agents and their targeted gene networks are associated with the development and progression of MDS into AML. This review discusses the mechanisms by which decitabine, azacitidine, and bortezomib alter epigenetic programs and their results from phase III clinical trials.

The relationship between gut microbiota and proteolytic activity in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disease that affects 3.8-9.2% of the world population. It affects the physiology and psychology of patients and increases the burden on families, the healthcare system, society, and economic development. Presently, a large number of studies have shown that compared to healthy individuals, the composition and diversity of gut microbiota in IBS patients have changed, and the proteolytic activity (PA) in fecal supernatant and colonic mucosa of IBS patients has also increased. These findings indicate that the imbalance of intestinal microecology and intestinal protein hydrolysis is closely related to IBS. Furthermore, the intestinal flora is a key substance that regulates the PA and is associated with IBS. The current review described the intestinal microecology and intestinal proteolytic activity of patients with IBS and also discussed the effect of intestinal flora on PA. In summary, this study proposed a pivotal role of gut microbiota and PA in IBS, respectively, and provided an in-depth insight into the diagnosis and treatment targets of IBS as well as the formulation of new treatment strategies for other digestive diseases and protease-related diseases.

Bortezomib induces methylation changes in neuroblastoma cells that appear to play a significant role in resistance development to this compound

The anticancer activity of bortezomib (BTZ) has been increasingly studied in a number of indications and promising results for the use of this treatment have been shown in neuroblastoma. As BTZ treatment is usually administered in cycles, the development of resistance and side effects in patients undergoing therapy with BTZ remains a major challenge for the clinical usage of this compound. Common resistance development also means that certain cells are able to survive BTZ treatment and bypass molecular mechanisms that render BTZ anticancer activity. We studied the methylome of neuroblastoma cells that survived BTZ treatment. Our results indicate that BTZ induces pronounced genome wide methylation changes in cells which recovered from the treatment. Functional analyses of identified methylation changes demonstrated they were involved in key cancer pathology pathways. These changes may allow the cells to bypass the primary anticancer activity of BTZ and develop a treatment resistant and proliferative phenotype. To study whether cells surviving BTZ treatment acquire a proliferative phenotype, we repeatedly treated cells which recovered from the first round of BTZ treatment. The repetitive treatment led to induction of the extraordinary proliferative potential of the cells, that increased with subsequent treatments. As we did not observe similar effects in cells that survived treatment with lenalidomide, and non-treated cells cultured under the same experimental conditions, this phenomenon seems to be BTZ specific. Overall, our results indicate that methylation changes may play major role in the development of BTZ resistance.

Dysregulation of the Ubiquitin Proteasome System in Human Malignancies: A Window for Therapeutic Intervention

Simple Summary

The ubiquitin proteasome system (UPS) governs the non-lysosomal degradation of oxidized, damaged, or misfolded proteins in eukaryotic cells. Dysregulation of the UPS results in loss of ability to maintain protein quality through proteolysis, and is closely related to the development of various malignancies and tumorigenesis. Here, we provide a comprehensive general overview on the regulation and roles of UPS and discuss the mechanisms linking dysregulated UPS to human malignancies. Inhibitors developed against components of the UPS, which include U.S. Food and Drug Administration FDA-approved and those currently undergoing clinical trials, are also presented in this review.

Abstract

The ubiquitin proteasome system (UPS) governs the non-lysosomal degradation of oxidized, damaged, or misfolded proteins in eukaryotic cells. This process is tightly regulated through the activation and transfer of polyubiquitin chains to target proteins which are then recognized and degraded by the 26S proteasome complex. The role of UPS is crucial in regulating protein levels through degradation to maintain fundamental cellular processes such as growth, division, signal transduction, and stress response. Dysregulation of the UPS, resulting in loss of ability to maintain protein quality through proteolysis, is closely related to the development of various malignancies and tumorigenesis. Here, we provide a comprehensive general overview on the regulation and roles of UPS and discuss functional links of dysregulated UPS in human malignancies. Inhibitors developed against components of the UPS, which include U.S. Food and Drug Administration FDA-approved and those currently undergoing clinical trials, are also presented in this review.

Pyrrolidinedithiocarbamic Acid Ammonium Salt Inhibits Apoptosis and Phenotypic Transformation of Co-Culture of Myeloma Cells and Renal Tubular Epithelial Cells by Reducing the Secretion of Light Chain Protein

Background:

We investigate the effects of NFϰB inhibitor pyrrolidinedithiocarbamic acid ammonium salt (PDTC) on the viability, apoptosis and cell phenotype of HK-2 cells in the co-culture system of myeloma cells in renal tubular epithelial cells.

Methods:

This study was performed in Qiqihar Medical University, Qiqihar, China from Jun 2018 to Jan 2019. RPMI-8226 cells and HK-2 cells were inoculated in the co-culture chamber and cultured to establish the co-culture system. An immunoturbidimetric assay was performed to detect ϰ light chain and λ light chain in RPMI-8226 cells. The effect of PDTC on the secretion of ϰ light chain and λ light chain of RPMI-8226 cells was detected by immunoturbidimetry and the ratio was calculated.

Results:

PDTC significantly increased the viability of HK-2 cells. PDTC reduced the apoptosis of renal tubular epithelial cells. After PDTC treatment, the expression of cell surface marker E-cadherin decreased, and the expression of α-SMA increased, which induced the renal interstitial fibrosis. The secretion of ϰ light chain and λ light chain of RPMI-8226 cells was significantly decreased after the addition of PDTC, but the ratio was not changed.

Conclusion:

PDTC can inhibit the cell activity, promote apoptosis, and reduce the secretion of secretion of ϰ light chain and λ light chain through inhibiting the NF-ϰB pathway activation of myeloma cell RPMI-8226.