Bortezomib in multiple myeloma: systematic review and clinical considerations

Targeting UBE2T suppresses breast cancer stemness through CBX6-mediated transcriptional repression of SOX2 and NANOG

Breast cancer stem cells (BCSCs) are the main cause of breast cancer recurrence and metastasis. While the ubiquitin-proteasome system contributes to the regulation of BCSC stemness, the underlying mechanisms remain unclear. Here, we identified ubiquitin-conjugating enzyme E2T (UBE2T) as a pivotal ubiquitin enzyme regulating BCSC stemness through systemic screening assays, including single-cell RNA sequencing (scRNA-seq) and stemness-index analysis. We found that patients with high UBE2T expression exhibited worse prognosis than those with low expression (10-year PFS: 55.95 % vs. 85.08 %), which are consistent across various subtypes of breast cancers. Genetic ablation of UBE2T suppresses BCSC stemness and tumor progression in organoids and spontaneous MMTV-PyMT mice, dependent on the transcriptional inactivation of pluripotency genes SOX2 and NANOG. Mechanically, UBE2T collaborates with the E3 ligase TRIM25 to perform K48-linked polyubiquitination and degradation of CBX6 at K214, which deficiency helps to promote the transcription of SOX2 and NANOG and enhances BCSC stemness. The pharmacological inhibitor of UBE2T significantly reduced the expression of NANOG and SOX2, suppressed tumor progression, and demonstrated synergistic effects when combined with chemotherapeutics, but not with other treatments. Collectively, our study revealed that the UBE2T-TRIM25-CBX6 axis can regulate BCSC stemness and offers a potentially therapeutic strategy to combat breast cancer in a clinical translation setting.

Recent advancements in nanomedicine as a revolutionary approach to treating multiple myeloma

Multiple myeloma, the second most common hematological malignancy, remains incurable with a 5-year survival rate of approximately 50 % and recurrence rates near 100 %, despite significant attempts to develop effective medicines. Therefore, there is a pressing demand in the medical field for innovative and more efficient treatments for MM. Currently, the standard approach for treating MM involves administering high-dose chemotherapy, which frequently correlates with improved results; however, one major limiting factor is the significant side effects of these medications. Furthermore, the strategies used to deliver medications to tumors limit their efficacy, whether by rapid clearance from circulation or an insufficient concentration in cancer cells. Cancer treatment has shifted from cytotoxic, nonspecific chemotherapy regimens to molecularly targeted, rationally developed drugs with improved efficacy and fewer side effects. Nanomedicines may provide an effective alternative way to avoid these limits by delivering drugs into the complicated bone marrow microenvironment and efficiently reaching myeloma cells. Putting drugs into nanoparticles can make their pharmacokinetic and pharmacodynamic profiles much better. This can increase the drug's effectiveness in tumors, extend its time in circulation in the blood, and lower its off-target toxicity. In this review, we introduce several criteria for the rational design of nanomedicine to achieve the best anti-tumoral therapeutic results. Next, we discuss recent advances in nanomedicine for MM therapy.

Deubiquitinase JOSD1 tempers hepatic proteotoxicity

Derangements in protein homeostasis and associated proteotoxicity mark acute, chronic, and drug-induced hepatocellular injury. Metabolic dysfunction-associated proteasomal inhibition and the use of proteasome inhibitors often underlie such pathological hepatic proteotoxicity. In this study, we sought to identify a candidate deubiquitinating enzyme (DUB) responsible for reversing the proteotoxic damage. To this end, we performed a siRNA screening wherein 96 DUBs were individually knocked down in HepG2 cells under proteasomal inhibitor-induced stress for dual readouts, apoptosis, and cell viability. Among the putative hits, we chose JOSD1, a member of the Machado-Josephin family of DUBs that reciprocally increased cell viability and decreased cell death under proteotoxicity. JOSD1-mediated mitigation of proteotoxicity was further validated in primary mouse hepatocytes by gain and loss of function studies. Marked plasma membrane accumulation of monoubiquitinated JOSD1 in proteotoxic conditions is a prerequisite for its protective role, while the enzymatically inactive JOSD1 C36A mutant was conversely polyubiquitinated, does not have membrane localisation and fails to reverse proteotoxicity. Mechanistically, JOSD1 physically interacts with the suppressor of cytokine signalling 1 (SOCS1), deubiquitinates it and enhances its stability under proteotoxic stress. Indeed, SOCS1 expression is necessary and sufficient for the hepatoprotective function of JOSD1 under proteasomal inhibition. In vivo, adenovirus-mediated ectopic expression or depletion of JOSD1 in mice liver respectively protects or aggravates hepatic injury when challenged with proteasome blocker Bortezomib. Our study thus unveils JOSD1 as a potential candidate for ameliorating hepatocellular damage in liver diseases.

Novel treatments for immune thrombocytopenia: targeting platelet autoantibodies

INTRODUCTION

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by low platelets and an increased risk of bleeding. Platelet autoantibodies target major platelet glycoproteins and cause Fc-mediated platelet destruction in the spleen and reticuloendothelial systems. As mechanisms of disease, platelet autoantibodies are important therapeutic targets. Neonatal Fc receptor (FcRn) antagonists are a new class of therapeutics that reduce the half-life of immunoglobulin G including pathogenic platelet autoantibodies. Spleen tyrosine kinase (Syk) inhibitors interfere with Fc-mediated platelet clearance. Bruton's tyrosine kinase (BTK) inhibitors and B-cell activating factor (BAFF) inhibitors reduce antibody production. The efficacy of these targeted therapies provides new support for the role of platelet autoantibodies in pathogenesis of ITP even these antibodies can be difficult to detect.

AREAS COVERED

This review includes an in-depth exploration of the pathophysiologic mechanisms of ITP, focusing on autoantibodies. Treatments outlined in this review include a) FcRn antagonists, b) complement inhibitors, c) B-cell directed therapies such as BTK inhibitors, and anti-BAFF agents, d) Syk inhibitors, e) plasma-cell directed therapies, and f) novel cellular therapeutic products.

EXPERT OPINION

Platelet autoantibodies are often elusive in ITP, yet novel treatments targeting this pathway reinforce their role in the pathogenesis of this autoimmune platelet disorder.

Integrative Analysis of Multi-Omics Data to Identify Deregulated Molecular Pathways and Druggable Targets in Chronic Lymphocytic Leukemia

Chronic Lymphocytic Leukemia (CLL) is the most common B-cell malignancy in the Western world, characterized by frequent relapses despite temporary remissions. Our study integrated publicly available proteomic, transcriptomic, and patient survival datasets to identify key differences between healthy and CLL samples. We exposed approximately 1000 proteins that differentiate healthy from cancerous cells, with 608 upregulated and 415 downregulated in CLL cases. Notable upregulated proteins include YEATS2 (an epigenetic regulator), PIGR (Polymeric immunoglobulin receptor), and SNRPA (a splicing factor), which may serve as prognostic biomarkers for this disease. Key pathways implicated in CLL progression involve RNA processing, stress resistance, and immune response deficits. Furthermore, we identified three existing drugs-Bosutinib, Vorinostat, and Panobinostat-for potential further investigation in drug repurposing in CLL. We also found limited correlation between transcriptomic and proteomic data, emphasizing the importance of proteomics in understanding gene expression regulation mechanisms. This generally known disparity highlights once again that mRNA levels do not accurately predict protein abundance due to many regulatory factors, such as protein degradation, post-transcriptional modifications, and differing rates of translation. These results demonstrate the value of integrating omics data to uncover deregulated proteins and pathways in cancer and suggest new therapeutic avenues for CLL.

Ubiquitination and deubiquitination in cancer: from mechanisms to novel therapeutic approaches

Ubiquitination, a pivotal posttranslational modification of proteins, plays a fundamental role in regulating protein stability. The dysregulation of ubiquitinating and deubiquitinating enzymes is a common feature in various cancers, underscoring the imperative to investigate ubiquitin ligases and deubiquitinases (DUBs) for insights into oncogenic processes and the development of therapeutic interventions. In this review, we discuss the contributions of the ubiquitin-proteasome system (UPS) in all hallmarks of cancer and progress in drug discovery. We delve into the multiple functions of the UPS in oncology, including its regulation of multiple cancer-associated pathways, its role in metabolic reprogramming, its engagement with tumor immune responses, its function in phenotypic plasticity and polymorphic microbiomes, and other essential cellular functions. Furthermore, we provide a comprehensive overview of novel anticancer strategies that leverage the UPS, including the development and application of proteolysis targeting chimeras (PROTACs) and molecular glues.

Bortezomib exerts its anti-cancer activity through the regulation of Skp2/p53 axis in non-melanoma skin cancer cells and C. elegans

Non-melanoma skin cancer (NMSC), encompassing basal and squamous cell carcinoma, is the most prevalent cancer in the United States. While surgical removal remains the conventional therapy with a 95% 5-year cure rate, there is a growing interest in exploring alternative treatment strategies. In this study, we investigated the role of Bortezomib (BTZ), a proteasome inhibitor, in NMSC. Using two NMSC cell lines (A431 and A388), we examined the effects of BTZ treatment. Our results demonstrated that 48 h of BTZ treatment led to downregulating Skp2 expression in both A431 and A388 cells while upregulating p53 expression, specifically in A388 cells. These alterations resulted in impaired cellular growth and caspase-dependent cell death. Silencing Skp2 in A388 cells with siRNA confirmed the upregulation of p53 as a direct target. Furthermore, BTZ treatment increased the Bax to Bcl-2 ratio, promoting mitochondrial permeability and the subsequent release of cytochrome C, thereby activating caspases. We also found that BTZ exerted its antitumor effects by generating reactive oxygen species (ROS), as blocking ROS production significantly reduced BTZ-induced apoptotic cell death. Interestingly, BTZ treatment induced autophagy, which is evident from the increased expression of microtubule-associated proteins nucleoporin p62 and LC-3A/B. In addition to cell lines, we assessed the impact of BTZ in an in vivo setting using Caenorhabditis elegans (C. elegans). Our findings demonstrated that BTZ induced germline apoptosis in worms even at low concentrations. Notably, this increased apoptosis was mediated through the activity of CEP-1, the worm's counterpart to mammalian p53. In summary, our study elucidated the molecular mechanism underlying BTZ-induced apoptosis in NMSC cell lines and C. elegans. By targeting the skp2/p53 axis, inducing mitochondrial permeability, generating ROS, and promoting autophagy, BTZ demonstrates promising anti-cancer activity in NMSC. These findings provide novel insights into potential therapeutic strategies for controlling the unregulated growth of NMSC.

Liquid Overlay and Collagen-Based Three-Dimensional Models for In Vitro Investigation of Multiple Myeloma

Multiple myeloma (MM) clones reside in the bone marrow (BM), which plays a role in its survival and development. The interactions between MM and their neighboring mesenchymal stromal cells (MSCs) have been shown to promote MM growth and drug resistance. However, those interactions are often missing or misrepresented in traditional two-dimensional (2D) culture models. Application of novel three-dimensional (3D) models might recapitulate the BM niche more precisely, which will offer new insights into MM progression and survival. Here, we aimed to establish two 3D models, based on MSC spheroids and collagen droplets incorporating both MM cells and MSCs with the goal of replicating the native myeloma context of the BM niche. This approach revealed that although MSCs can spontaneously assemble spheroids with altered metabolic traits, MSC spheroid culture does not support the integration of MM cells. On the contrary, collagen-droplet culture supported the growth of both cell types. In collagen, MSC proliferation was reduced, with the correlating decrease in ATP production and Ki-67 expression, which might resemble in vivo conditions, rather than 2D abundance of nutrients and space. MSCs and MMs were distributed homogenously throughout the collagen droplet, with an apparent CXCL12 expression in MSCs. In addition, the response of MM cells to bortezomib was substantially reduced in collagen, indicating the importance of 3D culture in the investigation of myeloma cell behavior, as drug resistance is one of the most pertinent issues in cancer therapy.

The Efficacy of Carfilzomib Treatment in Bortezomib-Refractory Patients-Real Life Experience in a Tertiary Romanian Hospital

Background: Proteasome inhibitors (PIs) represent one of the most effective classes of therapy for patients with multiple myeloma (MM) and are incorporated in many of the current treatment regimens. The first-generation PI, bortezomib, has shown impressive results in patients with either newly diagnosed or relapsed/refractory MM, but once patients become resistant, treatment is increasingly challenging. Although the existing data show that the second-generation PI, carfilzomib, is highly efficient, there is still limited knowledge regarding the response to carfilzomib-based therapy in bortezomib-resistant patients. The aim of this study was to evaluate carfilzomib treatment performance in bortezomib-sensitive versus -refractory patients, in a real-life eastern European country setting. Methods: We retrospectively evaluated 127 adult patients exposed to bortezomib with relapsed or refractory MM, that subsequently received a carfilzomib-based therapy. We investigated the differences in the overall response rate (ORR), progression-free survival (PFS), and overall survival (OS) after carfilzomib-based therapy between the two patient groups. Results: The ORR in the bortezomib-sensitive group was significantly higher than that in the refractory group, leading to a superior PFS in this category of patients. For patients presenting with a high cytogenetic risk, we observed a significant difference in PFS between the bortezomib-sensitive and -refractory group, while standard cytogenetic risk patients presented a similar PFS regardless of the bortezomib sensitivity status. In addition, in patients with ISS (International Staging System) stage I or II, the previous sensitivity to bortezomib correlated with an improved PFS, while for patients with ISS stage III, both groups had a comparable PFS. No significant differences in OS were observed between the two groups. Conclusions: In countries where novel or experimental therapies are not readily available, carfilzomib-based therapy can still be a viable therapy option for patients presenting with bortezomib-refractory status, an ISS stage III, and standard cytogenetic risk.

Role of Immune Cells and Immunotherapy in Multiple Myeloma

The clinical signs of multiple myeloma, a plasma cell (PC) dyscrasia, include bone loss, renal damage, and paraproteinemia. It can be defined as the uncontrolled growth of malignant PCs within the bone marrow. The distinctive bone marrow milieu that regulates the progression of myeloma disease involves interactions between plasma and stromal cells, and myeloid and lymphoid cells. These cells affect the immune system independently or because of a complicated web of interconnections, which promotes disease development and immune evasion. Due to the importance of these factors in the onset of disease, various therapeutic strategies have been created that either target or improve the immunological processes that influence disease progression. The immune system has a role in the mechanism of action of multiple myeloma treatments. The main contributions of immune cells to the bone marrow microenvironment, as well as how they interact and how immune regulation might lead to therapeutic effects, are covered in this study.

Design, Synthesis, and Antifungal Activity of 3-Substituted-2(5H)-Oxaboroles

Next generation antimicrobial therapeutics are desperately needed as new pathogens with multiple resistance mechanisms continually emerge. Two oxaboroles, tavaborole and crisaborole, were recently approved as topical treatments for onychomycosis and atopic dermatitis, respectively, warranting further studies into this privileged structural class. Herein, we report the antimicrobial properties of 3-substituted-2(5H)-oxaboroles, an unstudied family of medicinally relevant oxaboroles. Our results revealed minimum inhibitory concentrations as low as 6.25 and 5.20 μg/mL against fungal (e.g., Penicillium chrysogenum) and yeast (Saccharomyces cerevisiae) pathogens, respectively. These oxaboroles were nonhemolytic and nontoxic to rat myoblast cells (H9c2). Structure-activity relationship studies suggest that planarity is important for antimicrobial activity, possibly due to the effects of extended conjugation between the oxaborole and benzene rings.

A glimpse into relapsed refractory multiple myeloma treatment in real-world practice in Spain: the GeminiS study

OBJECTIVES

To describe the incorporation of monoclonal antibodies (mAb) in real-world (RW) practice for the treatment of patients with relapsed refractory multiple myeloma (RRMM) in a setting with other treatment alternatives.

METHODS

This was an observational, multicenter, ambispective study of RRMM treated with or without a mAb.

RESULTS

A total of 171 patients were included. For the group treated without mAb, the median (95% CI) progression-free survival (PFS) to relapse was 22.4 (17.8-27.0) months; partial response or better (≥PR) and complete response or better (≥CR) was observed in 74.1% and 24.1% of patients, respectively; and median time to first response in first relapse was 2.0 months and in second relapse was 2.5 months. For the group of patients treated with mAb in first or second relapse, the median PFS was 20.9 (95% CI, could not be evaluated) months; the ≥ PR and ≥ CR rates were 76,2% and 28.6%, respectively; and the median time to first response in first relapse was 1.2 month and in second relapse was 1.0 months. The safety profiles for the combinations were consistent with those expected.

CONCLUSIONS

The incorporation of mAb in RW practice for the treatment of RRMM has shown good quality and speed of response with a similar safety profile shown in randomized clinical trials.

Natural Products-Pyrazine Hybrids: A Review of Developments in Medicinal Chemistry

Pyrazine is a six-membered heterocyclic ring containing nitrogen, and many of its derivatives are biologically active compounds. References have been downloaded through Web of Science, PubMed, Science Direct, and SciFinder Scholar. The structure, biological activity, and mechanism of natural product derivatives containing pyrazine fragments reported from 2000 to September 2023 were reviewed. Publications reporting only the chemistry of pyrazine derivatives are beyond the scope of this review and have not been included. The results of research work show that pyrazine-modified natural product derivatives have a wide range of biological activities, including anti-inflammatory, anticancer, antibacterial, antiparasitic, and antioxidant activities. Many of these derivatives exhibit stronger pharmacodynamic activity and less toxicity than their parent compounds. This review has a certain reference value for the development of heterocyclic compounds, especially pyrazine natural product derivatives.

Clinical perspectives on the optimal use of lenalidomide plus bortezomib and dexamethasone for the treatment of newly diagnosed multiple myeloma

To improve the outcomes of patients with the otherwise incurable hematologic malignancy of multiple myeloma (MM), a key paradigm includes initial treatment to establish disease control rapidly followed by maintenance therapy to ensure durability of response with manageable toxicity. However, patients' prognosis worsens after relapse, and the disease burden and drug toxicities are generally more challenging with subsequent lines of therapy. It is therefore particularly important that patients with newly diagnosed multiple myeloma (NDMM) receive optimal frontline therapy. The combination of lenalidomide, bortezomib, and dexamethasone (RVd) has consistently demonstrated a tolerable safety profile with significant and clinically relevant benefit, including deep and durable responses with improved survival in patients with NDMM regardless of their transplant eligibility. Furthermore, comparative studies evaluating this triplet regimen against both doublet and other triplet regimens have established RVd as a standard of care in this setting based upon its remarkable and concordant efficacy. Given the breadth of clinical data, physician familiarity, inclusion in treatment guidelines, and the emerging potential of RVd-containing quadruplet regimens, RVd will likely continue as a key cornerstone of the treatment of NDMM, and its role will therefore likely continue to grow as a therapeutic backbone in the initial treatment of MM.

Calcium silicate/bortezomib combinatory therapy for multiple myeloma

Multiple myeloma (MM) is the second most common hematologic malignancy. Bortezomib (BOR), a first-generation proteasome inhibitor, is the basic agent for the treatment of MM and has greatly improved the survival of patients with MM. However, the side effects of BOR (e.g. peripheral neuropathy) occur frequently and almost all MM patients eventually develop resistance to BOR and go on to develop refractory relapsed multiple myeloma (RRMM). Therefore, it is of great significance to find a method to increase the sensitivity of MM to BOR to reduce toxicity and drug resistance. Herein, we found that calcium silicate (CS), a silicate bioceramic that releases Si ions (SIs), enhanced the BOR anti-myeloma effect in vitro in human myeloma cell lines (HMCLs), including BOR-resistant cell lines (U266/BOR). The enhanced anti-myeloma effect of these two agents was demonstrated in primary MM cells regardless of disease status and in MM xenograft mice. Mechanistically, SI enhanced G2/M cell cycle arrest and the inhibition of the NF-κB pathway induced by BOR. These results imply that the combination of SI and BOR (SI/BOR) is a promising way to overcome BOR resistance in MM and RRMM. The future use of nanotechnology to prepare CS nanomaterials as BOR carriers for the treatment of MM and RRMM is a very promising clinical application.

JQ-1/bortezomib combination strongly impairs MM and PEL survival by inhibiting c-Myc and mTOR despite the activation of prosurvival mechanisms

Multiple myeloma (MM) and primary effusion lymphoma (PEL) are two aggressive hematologic cancers against which bortezomib and JQ-1, proteasome and bromodomain and extraterminal domain (BET) inhibitors, respectively, have been shown to have a certain success. However, the combination of both seems to be more promising than the single treatments against several cancers, including MM. Indeed, in the latter, proteasome inhibition upregulated nuclear respiratory factor 1 (NRF1), and such a prosurvival effect was counteracted by BET inhibitors. In the present study, we found that JQ-1/bortezomib induced a strong cytotoxic effect against PEL and discovered new insights into the cytotoxic mechanisms induced by such a drug combination in PEL and MM cells. In particular, a stronger c-Myc downregulation, leading to increased DNA damage, was observed in these cells after treatment with JQ-1/bortezomib than after treatment with the single drugs. Such an effect contributed to mechanistic target of rapamycin (mTOR)-phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 (p-4EBP1) axis inhibition, also occurring through c-Myc downregulation. However, besides the prodeath effects, JQ-1/bortezomib activated unfolded protein response (UPR) and autophagy as prosurvival mechanisms. In conclusion, this study demonstrated that JQ-1/bortezomib combination could be a promising treatment for MM and PEL, unveiling new molecular mechanisms underlying its cytotoxic effect, and suggested that UPR and autophagy inhibition could be exploited to further potentiate the cytotoxicity of JQ-1/bortezomib.

Novel Local "Off-the-Shelf" Immunotherapy for the Treatment of Myeloma Bone Disease

Myeloma bone disease (MBD) is one of the major complications in multiple myeloma (MM)-the second most frequent hematologic malignancy. It is characterized by the formation of bone lesions due to the local action of proliferating MM cells, and to date, no effective therapy has been developed. In this study, we propose a novel approach for the local treatment of MBD with a combination of natural killer cells (NKs) and mesenchymal stem cells (MSCs) within a fibrin scaffold, altogether known as FINM. The unique biological properties of the NKs and MSCs, joined to the injectable biocompatible fibrin, permitted to obtain an efficient "off-the-shelf" ready-to-use composite for the local treatment of MBD. Our in vitro analyses demonstrate that NKs within FINM exert a robust anti-tumor activity against MM cell lines and primary cells, with the capacity to suppress osteoclast activity (~60%) within in vitro 3D model of MBD. Furthermore, NKs' post-thawing cytotoxic activity is significantly enhanced (~75%) in the presence of MSCs, which circumvents the decrease of NKs cytotoxicity after thawing, a well-known issue in the cryopreservation of NKs. To reduce the tumor escape, we combined FINM with other therapeutic agents (bortezomib (BZ), and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)), observing a clear therapeutic synergistic effect in vitro. Finally, the therapeutic efficacy of FINM in combination with BZ and TRAIL was assessed in a mouse model of MM, achieving 16-fold smaller tumors compared to the control group without treatment. These results suggest the potential of FINM to serve as an allogeneic "off-the-shelf" approach to improve the outcomes of patients suffering from MBD.

DRPreter: Interpretable Anticancer Drug Response Prediction Using Knowledge-Guided Graph Neural Networks and Transformer

Some of the recent studies on drug sensitivity prediction have applied graph neural networks to leverage prior knowledge on the drug structure or gene network, and other studies have focused on the interpretability of the model to delineate the mechanism governing the drug response. However, it is crucial to make a prediction model that is both knowledge-guided and interpretable, so that the prediction accuracy is improved and practical use of the model can be enhanced. We propose an interpretable model called DRPreter (drug response predictor and interpreter) that predicts the anticancer drug response. DRPreter learns cell line and drug information with graph neural networks; the cell-line graph is further divided into multiple subgraphs with domain knowledge on biological pathways. A type-aware transformer in DRPreter helps detect relationships between pathways and a drug, highlighting important pathways that are involved in the drug response. Extensive experiments on the GDSC (Genomics of Drug Sensitivity and Cancer) dataset demonstrate that the proposed method outperforms state-of-the-art graph-based models for drug response prediction. In addition, DRPreter detected putative key genes and pathways for specific drug-cell-line pairs with supporting evidence in the literature, implying that our model can help interpret the mechanism of action of the drug.

A Journey through the Inter-Cellular Interactions in the Bone Marrow in Multiple Myeloma: Implications for the Next Generation of Treatments

Tumors are composed of a plethora of extracellular matrix, tumor and non-tumor cells that form a tumor microenvironment (TME) that nurtures the tumor cells and creates a favorable environment where tumor cells grow and proliferate. In multiple myeloma (MM), the TME is the bone marrow (BM). Non-tumor cells can belong either to the non-hematological compartment that secretes soluble mediators to create a favorable environment for MM cells to grow, or to the immune cell compartment that perform an anti-MM activity in healthy conditions. Indeed, marrow-infiltrating lymphocytes (MILs) are associated with a good prognosis in MM patients and have served as the basis for developing different immunotherapy strategies. However, MM cells and other cells in the BM can polarize their phenotype and activity, creating an immunosuppressive environment where immune cells do not perform their cytotoxic activity properly, promoting tumor progression. Understanding cell-cell interactions in the BM and their impact on MM proliferation and the performance of tumor surveillance will help in designing efficient anti-MM therapies. Here, we take a journey through the BM, describing the interactions of MM cells with cells of the non-hematological and hematological compartment to highlight their impact on MM progression and the development of novel MM treatments.

Pyrazine and Phenazine Heterocycles: Platforms for Total Synthesis and Drug Discovery

There are numerous pyrazine and phenazine compounds that demonstrate biological activities relevant to the treatment of disease. In this review, we discuss pyrazine and phenazine agents that have shown potential therapeutic value, including several clinically used agents. In addition, we cover some basic science related to pyrazine and phenazine heterocycles, which possess interesting reactivity profiles that have been on display in numerous cases of innovative total synthesis approaches, synthetic methodologies, drug discovery efforts, and medicinal chemistry programs. The majority of this review is focused on presenting instructive total synthesis and medicinal chemistry efforts of select pyrazine and phenazine compounds, and we believe these incredible heterocycles offer promise in medicine.

Herpesviral encephalitis associated with bortezomib use in a patient with multiple myeloma and associated light-chain amyloidosis

INTRODUCTION

Bortezomib is proteasome inhibitor used in multiple myeloma treatment. The reactivation of herpes simplex virus (HSV) and varicella-zoster virus (VZV) during bortezomib-based therapy is a well-known adverse event. Antiviral prophylaxis is mandatory. Nevertheless, reports of herpesviral encephalitis are scarce.

CASE REPORT

A 57-year-old multiple myeloma patient who during CyBorD protocol (Bortezomib, cyclophosphamide, and dexamethasone), after a transient suspension of antiviral prophylaxis presented progressive headaches unresponsive to conventional analgesics, asthenia, fever, episodic visual hallucinations, and vesicular lesions in the right supraorbital and frontal region. Herpetic encephalitis was diagnosed after detecting herpes zoster in cerebrospinal fluid.

MANAGEMENT & OUTCOME

The patient was treated with acyclovir 500mg every 6 hours for 21 days, and subsequent valacyclovir prophylaxis achieving an excellent clinical evolution. Anti-myeloma treatment was changed to lenalidomide and dexamethasone achieving a durable complete response. Herpesviral encephalitis is a rare but severe complication associated with the use of Bortezomib, especially when patients did not receive acyclovir prophylaxis. However, a rapid detection based on the clinical suspicion, and the prompt start of treatment, may lead to overcome this adverse event.

The Sec61 translocon is a therapeutic vulnerability in multiple myeloma

Multiple myeloma (MM) is an incurable malignancy characterized by the uncontrolled expansion of plasma cells in the bone marrow. While proteasome inhibitors like bortezomib efficiently halt MM progression, drug resistance inevitably develop, and novel therapeutic approaches are needed. Here, we used a recently discovered Sec61 inhibitor, mycolactone, to assess the interest of disrupting MM proteostasis via protein translocation blockade. In human MM cell lines, mycolactone caused rapid defects in secretion of immunoglobulins and expression of pro‐survival interleukin (IL)‐6 receptor and CD40, whose activation stimulates IL‐6 production. Mycolactone also triggered pro‐apoptotic endoplasmic reticulum stress responses synergizing with bortezomib for induction of MM cell death and overriding acquired resistance to the proteasome inhibitor. Notably, the mycolactone–bortezomib combination rapidly killed patient‐derived MM cells ex vivo, but not normal mononuclear cells. In immunodeficient mice engrafted with MM cells, it demonstrated superior therapeutic efficacy over single drug treatments, without inducing toxic side effects. Collectively, these findings establish Sec61 blockers as novel anti‐MM agents and reveal the interest of targeting both the translocon and the proteasome in proteostasis‐addicted tumors.

Chemical reagents modulate nucleic acid-activated toll-like receptors

Nucleic acid-mediated interferon signaling plays a pivotal role in defense against microorganisms, especially during viral infection. Receptors sensing exogenous nucleic acid molecules are localized in the cytosol and endosomes. Cytosolic sensors, including cGAS, RIG-I, and MDA5, and endosome-anchored receptors are toll-like receptors (TLR3, TLR7, TLR8, and TLR9). These TLRs share the same domain architecture and have similar structures, facing the interior of endosomes so their binding to nucleic acids of invading pathogens via endocytosis is possible. The correct function of these receptors is crucial for cell homeostasis and effective response against pathogen invasion. A variety of endogenous mechanisms modulates their activities. Nevertheless, naturally occurring mutations lead to aberrant TLR-mediated interferon (IFN) signaling. Furthermore, certain pathogens require a more robust defense against control. Thus, manipulating these TLR activities has a profound impact. High-throughput virtual screening followed by experimental validation led to the discovery of numerous chemicals that can change these TLR-mediated IFN signaling activities. Many of them are unique in selectivity, while others regulate more than one TLR due to commonalities in these receptors. We summarized these nucleic acid-sensing TLR-mediated IFN signaling pathways and the corresponding chemicals activating or deactivating their signaling.

Systematic Profiling of DNMT3A Variants Reveals Protein Instability Mediated by the DCAF8 E3 Ubiquitin Ligase Adaptor

Clonal hematopoiesis is a prevalent age-related condition associated with a greatly increased risk of hematologic disease; mutations in DNA methyltransferase 3A (DNMT3A) are the most common driver of this state. DNMT3A variants occur across the gene with some particularly associated with malignancy, but the functional relevance and mechanisms of pathogenesis of the majority of mutations are unknown. Here, we systematically investigated the methyltransferase activity and protein stability of 253 disease-associated DNMT3A mutations, and found that 74% were loss-of-function mutations. Half of these variants exhibited reduced protein stability and, as a class, correlated with greater clonal expansion and acute myeloid leukemia development. We investigated the mechanisms underlying the instability using a CRISPR screen and uncovered regulated destruction of DNMT3A mediated by the DCAF8 E3 ubiquitin ligase adaptor. We establish a new paradigm to classify novel variants that has prognostic and potential therapeutic significance for patients with hematologic disease. SIGNIFICANCE: DNMT3A has emerged as the most important epigenetic regulator and tumor suppressor in the hematopoietic system. Our study represents a systematic and high-throughput method to characterize the molecular impact of DNMT3A missense mutations and the discovery of a regulated destruction mechanism of DNMT3A offering new prognostic and future therapeutic avenues.See related commentary by Ma and Will, p. 23.This article is highlighted in the In This Issue feature, p. 1.

Ubiquitin-specific peptidase 37: an important cog in the oncogenic machinery of cancerous cells

Protein ubiquitination is one of the most crucial posttranslational modifications responsible for regulating the stability and activity of proteins involved in homeostatic cellular function. Inconsistencies in the ubiquitination process may lead to tumorigenesis. Ubiquitin-specific peptidases are attractive therapeutic targets in different cancers and are being evaluated for clinical development. Ubiquitin-specific peptidase 37 (USP37) is one of the least studied members of the USP family. USP37 controls numerous aspects of oncogenesis, including stabilizing many different oncoproteins. Recent work highlights the role of USP37 in stimulating the epithelial-mesenchymal transition and metastasis in lung and breast cancer by stabilizing SNAI1 and stimulating the sonic hedgehog pathway, respectively. Several aspects of USP37 biology in cancer cells are yet unclear and are an active area of research. This review emphasizes the importance of USP37 in cancer and how identifying its molecular targets and signalling networks in various cancer types can help advance cancer therapeutics.

In vivo quantitative assessment of therapeutic response to bortezomib therapy in disseminated animal models of multiple myeloma with [18F]FDG and [64Cu]Cu-LLP2A PET

Background

Multiple myeloma (MM) is a disease of cancerous plasma cells in the bone marrow. Imaging-based timely determination of therapeutic response is critical for improving outcomes in MM patients. Very late antigen-4 (VLA4, CD49d/CD29) is overexpressed in MM cells. Here, we evaluated [¹⁸F]FDG and VLA4 targeted [⁶⁴Cu]Cu-LLP2A for quantitative PET imaging in disseminated MM models of variable VLA4 expression, following bortezomib therapy.

Methods

In vitro and ex vivo VLA4 expression was evaluated by flow cytometry. Human MM cells, MM.1S-CG and U266-CG (C: luciferase and G: green fluorescent protein), were injected intravenously in NOD-SCID gamma mice. Tumor progression was monitored by bioluminescence imaging (BLI). Treatment group received bortezomib (1 mg/kg, twice/week) intraperitoneally. All cohorts (treated, untreated and no tumor) were longitudinally imaged with [¹⁸F]FDG (7.4–8.0 MBq) and [⁶⁴Cu]Cu-LLP2A (2–3 MBq; Molar Activity: 44.14 ± 1.40 MBq/nmol) PET, respectively.

Results

Flow cytometry confirmed high expression of CD49d in U266 cells (> 99%) and moderate expression in MM.1S cells (~ 52%). BLI showed decrease in total body flux in treated mice. In MM.1S-CG untreated versus treated mice, [⁶⁴Cu]Cu-LLP2A localized with a significantly higher SUV_mean in spine (0.58 versus 0.31, p < 0.01) and femur (0.72 versus 0.39, p < 0.05) at week 4 post-tumor inoculation. There was a four-fold higher uptake of [⁶⁴Cu]Cu-LLP2A (SUV_mean) in untreated U266-CG mice compared to treated mice at 3 weeks post-treatment. Compared to [⁶⁴Cu]Cu-LLP2A, [¹⁸F]FDG PET detected treatment-related changes at later time points.

Conclusion

[⁶⁴Cu]Cu-LLP2A is a promising tracer for timely in vivo assessment of therapeutic response in disseminated models of MM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00840-4.

The Synergistic Activity of Bortezomib and TIC10 against A2058 Melanoma Cells

Combination antitumor treatments are essential parts of modern tumor therapy as—compared to monotherapies—(i) they are more effective; (ii) the dose of the compounds can be reduced; and (iii) therefore the side effects are improved. Our research group previously demonstrated the antitumor character of bortezomib (BOZ) in A2058 melanoma cells. Unfortunately, dose-related side effects are common during BOZ therapy, which could be prevented by reducing the dose of BOZ. This study aimed to characterize synergistic combinations of BOZ with a TRAIL (TNF-related apoptosis-inducing ligand) -inducing compound (TIC10), where the doses can be cut down but the efficacy is preserved. Endpoint cell viability assays were performed on A2058 cells, and synergism of BOZ and TIC10 was observed after 72 h. Synergism was further validated in a real-time impedimetric assay, and our results showed that BOZ-treated melanoma cells survived the treatment, an effect not registered in the co-treatments. Treatment with the combinations resulted in increased apoptosis, which was not accompanied by enhanced LDH release. Nevertheless, the expression of death receptor 5 (DR5) was increased on the cell surface without transcriptional regulation. In summary, our findings support the theory that the application of BOZ and TIC10 in combination could provide higher efficacy in vitro.

Emerging New Approaches in Desensitization: Targeted Therapies for HLA Sensitization

There is an urgent need for therapeutic interventions for desensitization and antibody-mediated rejection (AMR) in sensitized patients with preformed or de novo donor-specific HLA antibodies (DSA). The risk of AMR and allograft loss in sensitized patients is increased due to preformed DSA detected at time of transplant or the reactivation of HLA memory after transplantation, causing acute and chronic AMR. Alternatively, de novo DSA that develops post-transplant due to inadequate immunosuppression and again may lead to acute and chronic AMR or even allograft loss. Circulating antibody, the final product of the humoral immune response, has been the primary target of desensitization and AMR treatment. However, in many cases these protocols fail to achieve efficient removal of all DSA and long-term outcomes of patients with persistent DSA are far worse when compared to non-sensitized patients. We believe that targeting multiple components of humoral immunity will lead to improved outcomes for such patients. In this review, we will briefly discuss conventional desensitization methods targeting antibody or B cell removal and then present a mechanistically designed desensitization regimen targeting plasma cells and the humoral response.

Pegfilgrastim for primary prophylaxis of febrile neutropenia in multiple myeloma

Multiple myeloma (MM) survival rates have been substantially increased thanks to novel agents that have improved survival outcomes and shown better tolerability than treatments of earlier years. These new agents include immunomodulating imide drugs (IMiD) thalidomide and lenalidomide, the proteasome inhibitor bortezomib (PI), recently followed by new generation IMID pomalidomide, monoclonal antibodies daratumumab and elotuzumab, and next generation PI carfilzomib and ixazomib. However, even in this more promising scenario, febrile neutropenia remains a severe side effect of antineoplastic therapies and can lead to a delay and/or dose reduction in subsequent cycles. Supportive care has thus become key in helping patients to obtain the maximum benefit from novel agents. Filgrastim is a human recombinant subcutaneous preparation of G-CSF, largely adopted in hematological supportive care as "on demand" (or secondary) prophylaxis to recovery from neutropenia and its infectious consequences during anti-myeloma treatment. On the contrary, pegfilgrastim is a pegylated long-acting recombinant form of granulocyte colony-stimulating factor (G-CSF) that, given its extended half-life, can be particularly useful when adopted as "primary prophylaxis," therefore before the onset of neutropenia, along chemotherapy treatment in multiple myeloma patients. There is no direct comparison between the two G-CSF delivery modalities. In this review, we compare data on the two administrations' modality, highlighting the efficacy of the secondary prophylaxis over multiple myeloma treatment. Advantage of pegfilgrastim could be as follows: the fixed administration rather than multiple injections, reduction in neutropenia and febrile neutropenia rates, and, finally, a cost-effectiveness advantage.

Cytotoxicity and Target Modulation in Pediatric Solid Tumors by the Proteasome Inhibitor Carfilzomib

BACKGROUND

Most children with recurrent metastatic solid tumors have high mortality rates. Recent studies have shown that proteasome inhibition leads to effective tumor killing in cells that have acquired treatment resistance and metastatic properties.

OBJECTIVE

The purpose of this study was to test the potential of Carfilzomib (CFZ), a proteasome inhibitor, in refractory pediatric solid tumors, which is currently unknown.

METHODS

A panel of pediatric solid tumor cell lines, including neuroblastoma, Ewing's sarcoma, osteosarcoma, rhabdomyosarcoma, and atypical teratoid rhabdoid tumor (ATRT), was used to evaluate the cytotoxic and proteasomal inhibitory effects of CFZ. A drug scheduling experiment was performed to determine the optimal dose and time to obtain effective cell killing. Combination studies of CFZ with chemotherapeutic drugs of different classes were performed to determine the extent of synergy.

RESULTS

CFZ showed effective cytotoxicity against all cell lines tested (mean IC50 = 7nM, range = 1-20nM) and activity in a fluorophore-tagged cell-based proteasome assay. Drug scheduling experiments showed that the minimum exposure of 4-8 hours/day is needed for effective cumulative killing. CFZ, when combined with chemotherapeutic drugs of different classes, synergistically enhanced the extent of cell death.

CONCLUSIONS

CFZ showed cytotoxic activity against all the solid pediatric cancer cell lines tested. This study provides initial in vitro data on the potential of CFZ to treat pediatric solid tumors and supports further investigations into the components of drug scheduling, biological correlates, and drug combinations for future early phase clinical trials in children.

Photoinduced Borylation for the Synthesis of Organoboron Compounds

Organoboron compounds have important synthetic value and can be applied in numerous transformations. The development of practical and convenient ways to synthesize boronate esters has thus attracted significant interest. Photoinduced borylations originated from stoichiometric reactions of alkanes and arenes with well-defined metal-boryl complexes. Now, photoredox-initiated borylations, catalyzed by either transition metal or organic photocatalysts, and photochemical borylations with high efficiency have become a burgeoning area of research. In this Focus Review, we summarize research on photoinduced borylations, especially emphasizing recent developments and trends. This includes the photoinduced borylation of arenes, alkanes, aryl/alkyl halides, activated carboxylic acids, amines, alcohols, and so on based on transition metal catalysis, metal-free organocatalysis, and direct photochemical activation. We focus on reaction mechanisms involving single-electron transfer, triplet-energy transfer, and other radical processes.

Ubiquitination of Nonhistone Proteins in Cancer Development and Treatment

Ubiquitination, a crucial post-translation modification, regulates the localization and stability of the substrate proteins including nonhistone proteins. The ubiquitin-proteasome system (UPS) on nonhistone proteins plays a critical role in many cellular processes such as DNA repair, transcription, signal transduction, and apoptosis. Its dysregulation induces various diseases including cancer, and the identification of this process may provide potential therapeutic targets for cancer treatment. In this review, we summarize the regulatory roles of key UPS members on major nonhistone substrates in cancer-related processes, such as cell cycle, cell proliferation, apoptosis, DNA damage repair, inflammation, and T cell dysfunction in cancer. In addition, we also highlight novel therapeutic interventions targeting the UPS members (E1s, E2s, E3s, proteasomes, and deubiquitinating enzymes). Furthermore, we discuss the application of proteolysis-targeting chimeras (PROTACs) technology as a novel anticancer therapeutic strategy in modulating protein target levels with the aid of UPS.

Chemokine receptor CXCR4: An important player affecting the molecular-targeted drugs commonly used in hematological malignancies

INTRODUCTION

A variety of molecular-targeted drugs have been widely used in hematological malignancies and have shown great advances. Nevertheless, as the use of drugs in clinical practice increases, the problem of relapse or of the disease being refractory to treatment is becoming apparent. This problem is closely related to the C-X-C chemokine receptor 4 (CXCR4).

AREAS COVERED

This review focuses mainly on the effect of CXCR4 on molecular-targeted drug resistance in hematological malignancies as well as the clinical efficacy of CXCR4 antagonists combined with molecular-targeted drugs. Relevant literatures published between 2006 and 2020 were searched using PubMed/Medline for this review.

EXPERT OPINION

Monoclonal antibodies and non-antibody molecular-targeted drugs provide new therapeutic approaches for B-lineage malignancies and leukemia, but the clinical activity of these drugs is affected by CXCR4. In general, high CXCR4 expression or mutation inhibits the effects of molecular-targeted drugs, but there are exceptions, and in studies of proteasome inhibitors bortezomib (Bz) in multiple myeloma (MM), low CXCR4 expression or loss of CXCR4 was associated with Bz resistance (BzR) and poor treatment outcomes. Given that CXCR4 is a critical mediator of molecular-targeted drug resistance, numerous studies have combined molecular-targeted drugs with CXCR4 antagonists, which synergistically enhance the anti-proliferative/pro-apoptotic effect of molecular-targeted drugs.

The MUK eight protocol: a randomised phase II trial of cyclophosphamide and dexamethasone in combination with ixazomib, in relapsed or refractory multiple myeloma (RRMM) patients who have relapsed after treatment with thalidomide, lenalidomide and a proteasome inhibitor

BACKGROUND

Multiple myeloma is a plasma cell tumour with approximately 5500 new cases in the UK each year. Ixazomib is a next generation inhibitor of the 20S proteasome and is thought to be an effective treatment for those who have relapsed from bortezomib. The combination of cyclophosphamide and dexamethasone (CD) is a recognised treatment option for patients with relapsed refractory multiple myeloma (RRMM) who have relapsed after treatment with bortezomib and lenalidomide, whilst also often being combined with newer proteasome inhibitors. The most apparent combination for ixazomib is therefore with CD.

METHODS

MUK eight is a randomised, controlled, open, parallel group, multi-centre phase II trial that will recruit patients with RRMM who have relapsed after treatment with thalidomide, lenalidomide, and a proteasome inhibitor. The primary objective of the trial is to evaluate whether ixazomib in combination with cyclophosphamide and dexamethasone (ICD) has improved clinical activity compared to CD in terms of progression-free survival (PFS). Secondary objectives include comparing toxicity profiles and the activity and cost-effectiveness of both treatments. Since opening, the trial has been amended to allow all participants who experience disease progression (as per the IMWG criteria) on the CD arm to subsequently switch to receive ICD treatment, once progression has been confirmed with two clinical members of the Trial Management Group (TMG). This 'switch' phase of the study is exploratory and will assess second progression-free survival measured from randomisation to second disease progression (PFS2) and progression-free survival from the point of switching to second disease progression (PFS Switch) in participants who switch from CD to ICD treatment.

DISCUSSION

Development of ixazomib offers the opportunity to further investigate the value of proteasome inhibition through oral administration in the treatment of RRMM. Previous studies investigating the safety and efficacy of ICD in patients with RRMM demonstrate a toxicity profile consistent with ixazomib in combination with lenalidomide and dexamethasone, whilst the combination showed possible activity in RRMM patients. Further investigation of the anti-tumour effect of this drug in RRMM patients is therefore warranted, especially since no trials comparing CD with ICD have been completed at present.

TRIAL REGISTRATION

ISRCTN number: ISRCTN58227268 . Registered on 26 August 2015.

Proteasome Subunits Differentially Control Myeloma Cell Viability and Proteasome Inhibitor Sensitivity

We generated eight multiple myeloma cell lines resistant to bortezomib; five acquired PSMB5 mutations. In 1,500 patients such mutations were rare clinically. To better understand disruption of proteasomes on multiple myeloma viability and drug sensitivity, we systematically deleted the major proteasome catalytic subunits. Multiple myeloma cells without PSMB5 were viable. Drug-resistant, PSMB5-mutated cell lines were resensitized to bortezomib by PSMB5 deletion, implying PSMB5 mutation is activating in its drug resistance function. In contrast, PSMB6 knockout was lethal to multiple myeloma cell lines. Depleting PSMB6 prevented splicing of the major catalytic subunits PSMB5, PSMB7, PSMB8, and PSMB10; however, PSMB6 engineered without splicing function or catalytic activity, also restored viability, inferring the contribution of PSMB6 to proteasome structure to be more important than functional activity. Supporting this, bortezomib sensitivity was restored in drug-resistant multiple myeloma cell lines by low level expression of mutated PSMB6 lacking splicing function. Loss of PSMB8 and PSMB9 was neither lethal nor restored bortezomib sensitivity. Significant codependency of PSMB5, PSMB6, and PSMB7 expression was observed. We demonstrated elevated levels of PSMB6 and 7, but not 8 and 9, in some, but not all, serial patient samples exposed to proteasome inhibitors. In summary, we show PSMB6 and PSMB7, but not PSMB5, to be essential for multiple myeloma cell survival, this dependency is structural and that upregulation or activating mutation of PSMB5, 6, and 7 confers proteasome inhibitor resistance, while depletion confers sensitivity. IMPLICATIONS: These findings support modulation of PSMB5, PSMB6, or PSMB7 expression as a new therapeutic strategy.

Real-world treatment patterns and outcomes in non-transplant newly diagnosed multiple Myeloma in France, Germany, Italy, and the United Kingdom

OBJECTIVES

The treatment paradigm in newly diagnosed multiple myeloma (NDMM) is evolving toward individualized, risk-directed, and longer duration of therapy (DOT). The objective of this study was to describe treatment patterns and outcomes in non-transplant NDMM in four European countries.

METHODS

This retrospective chart review included adults with NDMM diagnosed between January 1, 2012, and December 31, 2013 (early cohort), or April 1, 2016, and March 31, 2017 (recent cohort).

RESULTS

Among 836 patients, molecular testing was performed in 21% and 35% patients of early vs recent cohorts; proteasome inhibitor (PI)/alkylator combinations were the principal first-line (1 L) therapy (39% vs 43%). Use of immunomodulatory drug (IMID)/alkylator combinations declined from early to recent cohort (26% vs 13%) but IMID (7% vs 16%) use increased. Few patients (5%) received 1 L maintenance therapy. Two-thirds of patients were treated with a fixed duration intent, with a median 7-month 1 L DOT and progression-free survival (PFS) of 32.8 months in the early cohort. Both 1 L DOT and PFS were longer with oral compared to injectable regimens.

CONCLUSIONS

Although frontline treatment patterns changed significantly, 1 L DOT is short. The uptake of molecular testing and 1 L maintenance is low. These results highlight areas of unmet need in NDMM.

Final analysis of a phase 1/2b study of ibrutinib combined with carfilzomib/dexamethasone in patients with relapsed/refractory multiple myeloma

Patients with multiple myeloma (MM) inevitably relapse on initial treatment regimens, and novel combination therapies are needed. Ibrutinib is a first‐in‐class, once‐daily inhibitor of Bruton's tyrosine kinase, an enzyme implicated in growth and survival of MM cells. Preclinical data suggest supra‐additivity or synergy between ibrutinib and proteasome inhibitors (PIs) against MM. This phase 1/2b study evaluated the efficacy and safety of ibrutinib plus the PI carfilzomib and dexamethasone in patients with relapsed/refractory MM (RRMM). In this final analysis, we report results in patients who received the recommended phase 2 dose (RP2D; ibrutinib 840 mg and carfilzomib 36 mg/m² with dexamethasone), which was determined in phase 1. The primary efficacy endpoint was overall response rate (ORR). Fifty‐nine patients with RRMM received the RP2D (18 in phase 1 and 41 in phase 2b). These patients had received a median of three prior lines of therapy; 69% were refractory to bortezomib, and 90% were refractory to their last treatment. ORR in the RP2D population was 71% (stringent complete response and complete response: 3% each). Median duration of clinical benefit and median duration of response were both 6.5 months. Median progression‐free survival (PFS) was 7.4 months, and median overall survival (OS) was 35.9 months. High‐risk patients had comparable ORR and median PFS (67% and 7.7 months, respectively) to non–high‐risk patients, whose ORR was 73% and median PFS was 6.9 months, whereas median OS in high‐risk patients was 13.9 months and not reached in non–high‐risk patients. The most common grade ≥3 hematologic treatment‐emergent adverse events (TEAEs) were anemia and thrombocytopenia (17% each); the most common grade ≥3 non‐hematologic TEAE was hypertension (19%). In patients with RRMM treated with multiple previous lines of therapy, ibrutinib plus carfilzomib demonstrated anticancer activity within the expected efficacy range. No new safety signals were identified and the combination was well‐tolerated.

Cdc37 suppression induces plasma cell immaturation and bortezomib resistance in multiple myeloma via Xbp1s

Multiple myeloma (MM) is the second most prevalent hematologic malignancy. Although the use of bortezomib (BTZ) significantly improves MM therapy, intrinsic and acquired drug resistance to BTZ remains a major clinical problem. In this study, we find that Cdc37, a key co-chaperone of Hsp90, is downregulated in relapsed MM patients, especially after BTZ treatment, suggesting a link between Cdc37 and BTZ resistance. Suppression of Cdc37 or inhibition of Cdc37/Hsp90 association induces plasma cell dedifferentiation, quiescence of MM cells, and BTZ resistance in MM. Furthermore, we discover that Cdc37 expression correlates positively with Xbp1s, a critical transcription factor for plasma cell differentiation in MM samples. Depletion/inhibition of Cdc37 downregulates Xbp1s, while overexpression of Xbp1s in MM cell lines partially rescues plasma immaturation and BTZ resistance. It is suggested that Xbp1s may act as a key downstream effector of Cdc37. Experiments with a mouse model also demonstrate that Cdc37 inhibition promotes plasma cell immaturation, confers BTZ resistance, and increases MM progression in vivo. Together, we identify a critical factor and a new signaling mechanism that regulate plasma cell immaturation and BTZ resistance in MM cells. Our findings may constitute a novel strategy that overcomes BTZ resistance in MM therapy.

The role of ubiquitination in tumorigenesis and targeted drug discovery

Ubiquitination, an important type of protein posttranslational modification (PTM), plays a crucial role in controlling substrate degradation and subsequently mediates the "quantity" and "quality" of various proteins, serving to ensure cell homeostasis and guarantee life activities. The regulation of ubiquitination is multifaceted and works not only at the transcriptional and posttranslational levels (phosphorylation, acetylation, methylation, etc.) but also at the protein level (activators or repressors). When regulatory mechanisms are aberrant, the altered biological processes may subsequently induce serious human diseases, especially various types of cancer. In tumorigenesis, the altered biological processes involve tumor metabolism, the immunological tumor microenvironment (TME), cancer stem cell (CSC) stemness and so on. With regard to tumor metabolism, the ubiquitination of some key proteins such as RagA, mTOR, PTEN, AKT, c-Myc and P53 significantly regulates the activity of the mTORC1, AMPK and PTEN-AKT signaling pathways. In addition, ubiquitination in the TLR, RLR and STING-dependent signaling pathways also modulates the TME. Moreover, the ubiquitination of core stem cell regulator triplets (Nanog, Oct4 and Sox2) and members of the Wnt and Hippo-YAP signaling pathways participates in the maintenance of CSC stemness. Based on the altered components, including the proteasome, E3 ligases, E1, E2 and deubiquitinases (DUBs), many molecular targeted drugs have been developed to combat cancer. Among them, small molecule inhibitors targeting the proteasome, such as bortezomib, carfilzomib, oprozomib and ixazomib, have achieved tangible success. In addition, MLN7243 and MLN4924 (targeting the E1 enzyme), Leucettamol A and CC0651 (targeting the E2 enzyme), nutlin and MI-219 (targeting the E3 enzyme), and compounds G5 and F6 (targeting DUB activity) have also shown potential in preclinical cancer treatment. In this review, we summarize the latest progress in understanding the substrates for ubiquitination and their special functions in tumor metabolism regulation, TME modulation and CSC stemness maintenance. Moreover, potential therapeutic targets for cancer are reviewed, as are the therapeutic effects of targeted drugs.

Therapeutic targets in myeloma bone disease

Multiple myeloma (MM) is the second most common haematological malignancy and is characterized by a clonal proliferation of neoplastic plasma cells within the bone marrow. MM is the most frequent cancer involving the skeleton, causing osteolytic lesions, bone pain and pathological fractures that dramatically decrease MM patients' quality of life and survival. MM bone disease (MBD) results from uncoupling of bone remodelling in which excessive bone resorption is not compensated by new bone formation, due to a persistent suppression of osteoblast activity. Current management of MBD includes antiresorptive agents, bisphosphonates and denosumab, that are only partially effective due to their inability to repair the existing lesions. Thus, research into agents that prevent bone destruction and more importantly repair existing lesions by inducing new bone formation is essential. This review discusses the mechanisms regulating the uncoupled bone remodelling in MM and summarizes current advances in the treatment of MBD. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

The impact of multiple myeloma induction therapy on hematopoietic stem cell mobilization and collection: 25-year experience

While first-line induction therapy for patients with multiple myeloma has changed over the years, autologous hematopoietic stem cell transplantation still plays a significant role, improving both depth of response and progression-free survival of myeloma patients. Our 25-year experience in mobilizing hematopoietic stem and progenitor cells for 472 transplant-eligible myeloma patients was retrospectively reviewed. Patients were stratified according to the remission induction therapy received, and the outcomes were compared among the cohorts that received vincristine, adriamycin and dexamethasone (VAD) (n = 232), bortezomib and dexamethasone (BD) (n = 86), cyclophosphamide, bortezomib and dexamethasone (CyBorD) (n = 82) and other regimens (n = 67). Cyclophosphamide plus granulocyte colony-stimulating factor was the predominant mobilization regimen given. A greater number of CD34⁺ cells (9.9 × 10E6/kg, p = 0.026) was collected with less hospital admissions in BD patients (13%, p = 0.001), when compared to those receiving VAD (7.5 × 10E6/kg, 29%), CyBorD (7.6 × 10E6/kg, 19%), or other regimens (7.9 × 10E6/kg, 36%). Induction therapy did not influence the overall rate of unscheduled visits or the length of hospitalization because of complications following mobilization. The myeloma response was not significantly deepened following the cyclophosphamide administered for mobilization. This analysis demonstrates the importance of monitoring the impact of initial treatment on downstream procedures such as stem cell mobilization and collection.

Capsaicinoids enhance chemosensitivity to chemotherapeutic drugs

Cytotoxic chemotherapy is the mainstay of cancer treatment. Conventional chemotherapeutic agents do not distinguish between normal and neoplastic cells. This leads to severe toxic side effects, which may necessitate the discontinuation of treatment in some patients. Recent research has identified key molecular events in the initiation and progression of cancer, promoting the design of targeted therapies to selectively kill tumor cells while sparing normal cells. Although, the side effects of such drugs are typically milder than conventional chemotherapies, some off-target effects still occur. Another serious challenge with all chemotherapies is the acquisition of chemoresistance upon prolonged exposure to the drug. Therefore, identifying supplementary agents that sensitize tumor cells to chemotherapy-induced apoptosis and help minimize drug resistance would be valuable for improving patient tolerance and response to chemotherapy. The use of effective supplementary agents provides a twofold advantage in combination with standard chemotherapy. First, by augmenting the activity of the chemotherapeutic drug it can lower the dose needed to kill tumor cells and decrease the incidence and severity of treatment-limiting side effects. Second, adjuvant therapies that lower the effective dose of chemotherapy may delay/prevent the development of chemoresistance in tumors. Capsaicinoids, a major class of phytochemical compounds isolated from chili peppers, have been shown to improve the efficacy of several anti-cancer drugs in cell culture and animal models. The present chapter summarizes the current knowledge about the chemosensitizing activity of capsaicinoids with conventional and targeted chemotherapeutic drugs, highlighting the potential use of capsaicinoids in novel combination therapies to improve the therapeutic indices of conventional and targeted chemotherapeutic drugs in human cancers.

High numbers of CD163+ tumor-associated macrophages correlate with poor prognosis in multiple myeloma patients receiving bortezomib-based regimens

The prognostic significance of tumor-associated macrophages (TAMs) in multiple myeloma (MM) in the era of novel drugs remains unclear. CD163 expression was detected by immunohistochemistry to determine the number of TAMs in 198 MM patients receiving bortezomib-based regimens and the data were used to evaluate its relevance with clinical characteristics, treatment response, and prognosis. Patients with high levels of infiltrated CD163+ TAMs (>55/HPF) at diagnosis tended to have more adverse clinical characteristics. Patients with high CD163+ TAM content (>55/HPF) at diagnosis had worse progression-free survival (PFS) (P<0.001) and overall survival (OS) (P<0.001),and achieved lower complete remission (CR)/near-CR rate (P<0.001), than patients with low CD163+ TAM levels. Multivariate analysis revealed that CD163+ TAM content was an independent adverse prognostic factor for PFS and OS. Our data indicated that CD163+ TAM content at diagnosis is a powerful predictor of prognosis for MM in the era of novel drugs, and this discovery offers new insight into potential therapeutic strategies.

E3 ubiquitin ligases in B-cell malignancies

Ubiquitylation is a post-translational modification (PTM) that controls various cellular signaling pathways. It is orchestrated by a three-step enzymatic cascade know as the ubiquitin proteasome system (UPS). E3 ligases dictate the specificity to the substrates, primarily leading to proteasome-dependent degradation. Deregulation of the UPS components by various mechanisms contributes to the pathogenesis of cancer. This review focuses on E3 ligase-substrates pairings that are implicated in B-cell malignancies. Understanding the molecular mechanism of specific E3 ubiquitin ligases will present potential opportunities for the development of targeted therapeutic approaches.

A Phase Ib/II Study of Oprozomib in Patients with Advanced Multiple Myeloma and Waldenström Macroglobulinemia

PURPOSE

The oral proteasome inhibitor oprozomib has shown preclinical antitumor activity. Here, we report phase Ib/II study results investigating single-agent oprozomib in patients with relapsed multiple myeloma and Waldenström macroglobulinemia.

PATIENTS AND METHODS

The primary objectives were to determine the MTD, safety, and tolerability of oprozomib (phase Ib) as well as overall response rate (ORR; phase II). Oprozomib was administered once daily on days 1, 2, 8, and 9 (2/7 schedule) or days 1 to 5 (5/14 schedule) of a 14-day cycle.

RESULTS

In patients with multiple myeloma or Waldenström macroglobulinemia (n = 71), the determined MTDs were 300 mg/day (2/7 schedule) and 240 mg/day (5/14 schedule). Median oprozomib treatment duration for patients with multiple myeloma was 11.4 weeks (2/7 schedule, 240/300 mg/day), 5.4 weeks (5/14, 240 mg/day), and 10.1 weeks (5/14, 150/180 mg/day). For patients with Waldenström macroglobulinemia, these values were 34.6 weeks (2/7 schedule, 240/300 mg/day) and 8.1 weeks (5/14 schedule, 240 mg/day). The most common grade ≥3 adverse events (AE) in phase Ib included gastrointestinal and hematologic AEs. Three AE-related deaths in phase II prompted enrollment into 2/7 and 5/14 step-up dosing schedules (240/300 mg/day and 150/180 mg/day, respectively). In phase II, ORRs in 95 response-eligible multiple myeloma patients were 41.0%, 28.1%, and 25.0% in the 2/7, 240/300-mg/day; 5/14, 150/180-mg/day; and 5/14, 240-mg/day cohorts, respectively. ORRs in 31 response-eligible Waldenström macroglobulinemia patients were 71.4% and 47.1% for the 2/7 and 5/14 cohorts, respectively.

CONCLUSIONS

This study demonstrated promising efficacy of single-agent oprozomib in patients with relapsed multiple myeloma and Waldenström macroglobulinemia.

The lncRNA BORG facilitates the survival and chemoresistance of triple-negative breast cancers

Disseminated breast cancer cells employ adaptive molecular responses following cytotoxic therapeutic insult which promotes their survival and subsequent outgrowth. Here we demonstrate that expression of the pro-metastatic lncRNA BORG (BMP/OP-Responsive Gene) is greatly induced within triple-negative breast cancer (TNBC) cells subjected to environmental and chemotherapeutic stresses commonly faced by TNBC cells throughout the metastatic cascade. This stress-mediated induction of BORG expression fosters the survival of TNBC cells and renders them resistant to the cytotoxic effects of doxorubicin both in vitro and in vivo. The chemoresistant traits of BORG depend upon its robust activation of the NF-κB signaling axis via a novel BORG-mediated feed-forward signaling loop, and via its ability to bind and activate RPA1. Indeed, genetic and pharmacologic inhibition of NF-κB signaling or the DNA-binding activity of RPA1 abrogates the pro-survival features of BORG and renders BORG-expressing TNBCs sensitive to doxorubicin-induced cytotoxicity. These findings suggest that therapeutic targeting of BORG or its downstream molecular effectors may provide a novel means to alleviate TNBC recurrence.

Overcoming Biological Barriers in Neuroblastoma Therapy: The Vascular Targeting Approach with Liposomal Drug Nanocarriers

Neuroblastoma is a rare pediatric cancer characterized by a wide clinical behavior and adverse outcome despite aggressive therapies. New approaches based on targeted drug delivery may improve efficacy and decrease toxicity of cancer therapy. Furthermore, nanotechnology offers additional potential developments for cancer imaging, diagnosis, and treatment. Following these lines, in the past years, innovative therapies based on the use of liposomes loaded with anticancer agents and functionalized with peptides capable of recognizing neuroblastoma cells and/or tumor-associated endothelial cells have been developed. Studies performed in experimental orthotopic models of human neuroblastoma have shown that targeted nanocarriers can be exploited for not only decreasing the systemic toxicity of the encapsulated anticancer drugs, but also increasing their tumor homing properties, enhancing tumor vascular permeability and perfusion (and, consequently, drug penetration), inducing tumor apoptosis, inhibiting angiogenesis, and reducing tumor glucose consumption. Furthermore, peptide-tagged liposomal formulations are proved to be more efficacious in inhibiting tumor growth and metastatic spreading of neuroblastoma than nontargeted liposomes. These findings, herein reviewed, pave the way for the design of novel targeted liposomal nanocarriers useful for multitargeting treatment of neuroblastoma.