Proteasome inhibitors: antitumor effects and beyond

Effectiveness and infectious complications of BCMA T-cell engagers in treating multiple myeloma: Real-world evidence from Sweden

BACKGROUND

Multiple myeloma (MM), an incurable disease characterized by frequent relapses and a need for multiple treatments, often progresses to a relapse/refractory status resistant to all available drugs and drug classes. Bispecific antibodies, specifically BCMA T-cell engagers, have emerged as effective treatments for MM, demonstrating impressive efficacy. However, these treatments can adversely affect the immune system, increasing vulnerability to infections.

METHODS/RESULTS

This study evaluated the efficacy and safety of BCMA T-cell engagers in 58 Swedish patients with poor MM prognosis. The patients exhibited a 69% overall response rate, with 69% survival and 60% progression-free survival at 15 months.

CONCLUSIONS

Despite the risk of infectious complications, the prognosis of MM patients can be significantly improved with vigilant monitoring and proactive management of infections. This real-world data highlight the potential of BCMA T-cell engagers in treating MM, emphasizing the need for careful patient monitoring to mitigate infection risks.

A gain-of-function p53 mutant synergizes with oncogenic NRAS to promote acute myeloid leukemia in mice

We previously demonstrated that a subset of acute myeloid leukemia (AML) patients with concurrent RAS pathway and TP53 mutations have an extremely poor prognosis and that most of these TP53 mutations are missense mutations. Here, we report that, in contrast to the mixed AML and T cell malignancy that developed in NrasG12D/+ p53-/- (NP-/-) mice, NrasG12D/+ p53R172H/+ (NPmut) mice rapidly developed inflammation-associated AML. Under the inflammatory conditions, NPmut hematopoietic stem and progenitor cells (HSPCs) displayed imbalanced myelopoiesis and lymphopoiesis and mostly normal cell proliferation despite MEK/ERK hyperactivation. RNA-Seq analysis revealed that oncogenic NRAS signaling and mutant p53 synergized to establish an NPmut-AML transcriptome distinct from that of NP-/- cells. The NPmut-AML transcriptome showed GATA2 downregulation and elevated the expression of inflammatory genes, including those linked to NF-κB signaling. NF-κB was also upregulated in human NRAS TP53 AML. Exogenous expression of GATA2 in human NPmut KY821 AML cells downregulated inflammatory gene expression. Mouse and human NPmut AML cells were sensitive to MEK and NF-κB inhibition in vitro. The proteasome inhibitor bortezomib stabilized the NF-κB-inhibitory protein IκBα, reduced inflammatory gene expression, and potentiated the survival benefit of a MEK inhibitor in NPmut mice. Our study demonstrates that a p53 structural mutant synergized with oncogenic NRAS to promote AML through mechanisms distinct from p53 loss.

Priming Mesenchymal Stem/Stromal Cells with a Combination of a Low Dose of IFN-γ and Bortezomib Results in Potent Suppression of Pathogenic Th17 Immunity Through the IDO1-AHR Axis

Preconditioning of mesenchymal stem/stromal cells (MSCs) with the inflammatory cytokine IFN-γ enhances not only their immunosuppressive activity but also their expression of HLA and proinflammatory genes. We hypothesized that prevention of the upregulation of inflammatory cytokines and HLA molecules in IFN-γ-primed MSCs would render these cells more immunosuppressive and less immunogenic. In this study, we discovered the following findings supporting this hypothesis: (1) activated human T cells induced the expression of IDO1 in MSCs via IFN-γ secretion and those MSCs in turn inhibited T-cell proliferation in an AHR-dependent fashion; (2) there was no difference in the expression of IDO1 and HLA-DR in MSCs after priming with a low dose (25 IU/mL) versus a high dose (100 IU/mL) of IFN-γ; (3) the transient addition of bortezomib, a proteasome inhibitor, to culture MSCs after IFN-γ priming decreased the expression of HLA-DR, inflammatory cytokine genes and Vcam1 while increasing the expression of IDO1 and the production of L-kynurenine; finally, MSCs primed with a combination of a low dose of IFN-γ and bortezomib were more effective in inhibiting Th17-mediated idiopathic pneumonia syndrome (IPS) and chronic colitis than unprimed MSCs. Our results suggest that bortezomib significantly eliminates the unfavorable effects of IFN-γ priming of MSCs (increased expression of MHC molecules and inflammatory cytokines and cell aggregation genes) and simultaneously increases their immunosuppressive activity by upregulating IDO1. Taken together, our newly established MSC priming method may contribute to MSC-based cell therapy for inflammatory diseases.

B cells in systemic lupus erythematosus: Targets of new therapies and surveillance tools

B cell hyperactivity is a hallmark of the complex autoimmune disease systemic lupus erythematosus (SLE), which has justified drug development focusing on B cell altering agents during the last decades, as well as the off-label use of B cell targeting biologics. About a decade ago, the anti-B cell activating factor (BAFF) belimumab was the first biological agent to be licensed for the treatment of adult patients with active yet non-renal and non-neuropsychiatric SLE, to later be expanded to include treatment of pediatric SLE and, recently, lupus nephritis. B cell depletion is recommended as an off-label option in refractory cases, with the anti-CD20 rituximab having been the most used B cell depleting agent to date while agents with a slightly different binding specificity to CD20 such as obinutuzumab have also shown promise, forming a part of the current pipeline. In addition, terminally differentiated B cells have also been the targets of experimental therapies, with the proteasome inhibitor bortezomib being one example. Apart from being promising drug targets, B and plasma cells have also shown promise in the surveillance of patients with SLE, especially for monitoring B cell depleting or B cell altering therapies. Inadequate B cell depletion may signify poor expected clinical response to rituximab, for example, while prominent reductions in certain B cell subsets may signify a protection against flare development in patients treated with belimumab. Toward an era with a richer therapeutic armamentarium in SLE, including to a large extent B cell altering treatments, the challenge that emerges is to determine diagnostic means for evidence-based therapeutic decision-making, that uses clinical information, serological markers, and gene expression patterns to guide individualized precision strategies.

Novel immunotherapies in multiple myeloma

For a substantial period, options for the treatment of multiple myeloma (MM) were limited; however, the advent of novel therapies into clinical practice in the 1990s resulted in dramatic changes in the prognosis of the disease. Subsequently, new proteasome inhibitors and immunomodulators with innovations in efficacy and toxicity were introduced; yet there remains a spectrum of patients with poor outcomes with current treatment strategies. One of the causes of disease progression in MM is the loss of the ability of the dysfunctional immune environment to control virulent cell clones. In recent years, therapies to overcome the immunosuppressive tumor microenvironment and activate the host immune system have shown promise in MM, especially in relapsed and refractory disease. Clinical use of this approach has been approved for several immunotherapies, and a number of studies are currently underway in clinical trials. This review outlines three of the newest and most promising approaches being investigated to enhance the immune system against MM: (1) overcoming immunosuppression with checkpoint inhibitors, (2) boosting immunity against tumors with vaccines, and (3) enhancing immune effectors with adoptive cell therapy. Information on the latest clinical trials in each class will be provided, and further developments will be discussed.

Preceding bortezomib administration for a certain period reduces the risk of lenalidomide-induced skin rash

WHAT IS KNOWN AND OBJECTIVE

It was previously reported that the incidence of lenalidomide (LEN)-induced skin rash is reduced by administration of bortezomib (BOR) prior to LEN administration in patients with multiple myeloma (MM). Therefore, we investigated whether LEN-induced skin rash is affected by the duration of BOR administration and the dosing interval between BOR and LEN administration.

METHOD

A retrospective investigation was conducted among MM patients who received BOR treatment prior to LEN treatment in Eiju General Hospital from May 2010 to December 2020. We investigated whether the BOR administration duration and interval duration from the completion of BOR administration to the initial LEN administration affect the development of LEN-induced skin rash.

RESULT AND DISCUSSION

Twenty-eight of the 81 patients exhibited LEN-induced skin rash (34.6%). The administered duration, but not the interval, was significantly longer in the group without skin rash. Cut-off values were set for the duration of administration and interval, which were 35 days and 30 days, respectively. Multivariate analysis was performed on patients which are administered duration of more than 35 days and intervals of less than 30 days, and those who are not applicable. A significant difference was observed in the incidence of skin rash for each factor.

WHAT IS NEW AND CONCLUSION

The risk of reduced LEN-induced skin rash is affected not only by the presence of prior BOR administration, but also by the duration of BOR and the interval from the completion of BOR to the initial LEN administration.

Protein clearance strategies for disease intervention

Protein homeostasis, or proteostasis, is essential for cell function and viability. Unwanted, damaged, misfolded and aggregated proteins are degraded by the ubiquitin–proteasome system (UPS) and the autophagy-lysosome pathway. Growing evidence indicates that alterations in these major proteolytic mechanisms lead to a demise in proteostasis, contributing to the onset and development of distinct diseases. Indeed, dysregulation of the UPS or autophagy is linked to several neurodegenerative, infectious and inflammatory disorders as well as cancer. Thus, modulation of protein clearance pathways is a promising approach for therapeutics. In this review, we discuss recent findings and open questions on how targeting proteolytic mechanisms could be applied for disease intervention.

Lenalidomide, bortezomib and dexamethasone followed by tandem- autologous stem cell transplantation is an effective treatment modality for multi-hit multiple myeloma

In order to investigate the efficacy of lenalidomide, bortezomib and dexamethasone (VRD) induction chemotherapy regimen combined with tandem autologous stem cell transplantation (ASCT) in treating multi-hit multiple myeloma (MM), we analyzed 252 cases of newly diagnosed MM treated with the bortezomib-containing induction chemotherapy from June 2016 to June 2019. According to the fluorescence in situ hybridization (FISH) results on diagnosis, the patients were divided into multi-hit MM group (47 cases), single-hit MM group (81 cases), and standard-risk group (124 cases). Our analysis showed that R-ISS stageⅢ in transplantation group and R-ISS stageⅢ, multi-hit and VGPR or above was not achieved at the fourth cycle of chemotherapy in non-transplantation group were independent factors for poor prognosis by univariate and multivariate analyses. Moreover, the overall response rate (ORR) of VRD induction chemotherapy group was significantly higher than that of the non-VRD group in the single-hit and multi-hit groups (P = 0.021, P = 0.032); In terms of ASCT, tandem-ASCT can significantly improve the 2-year PFS (77.8 ± 3.9 %) and OS (83.3 ± 5.6 %) of multi-hit MM (P = 0.024, P = 0.037), while single-ASCT only has a limited effect on PFS (61.5 ± 3.0 %) and OS (71.9 ± 4.5 %) (P = 0.115, P = 0.155).

Marine Power on Cancer: Drugs, Lead Compounds, and Mechanisms

Worldwide, 19.3 million new cancer cases and almost 10.0 million cancer deaths occur each year. Recently, much attention has been paid to the ocean, the largest biosphere of the earth that harbors a great many different organisms and natural products, to identify novel drugs and drug candidates to fight against malignant neoplasms. The marine compounds show potent anticancer activity in vitro and in vivo, and relatively few drugs have been approved by the U.S. Food and Drug Administration for the treatment of metastatic malignant lymphoma, breast cancer, or Hodgkin's disease. This review provides a summary of the anticancer effects and mechanisms of action of selected marine compounds, including cytarabine, eribulin, marizomib, plitidepsin, trabectedin, zalypsis, adcetris, and OKI-179. The future development of anticancer marine drugs requires innovative biochemical biology approaches and introduction of novel therapeutic targets, as well as efficient isolation and synthesis of marine-derived natural compounds and derivatives.

The Role of the Proteasome in Platelet Function

Platelets are megakaryocyte-derived acellular fragments prepped to maintain primary hemostasis and thrombosis by preserving vascular integrity. Although they lack nuclei, platelets harbor functional genomic mediators that bolster platelet activity in a signal-specific manner by performing limited de novo protein synthesis. Furthermore, despite their limited protein synthesis, platelets are equipped with multiple protein degradation mechanisms, such as the proteasome. In nucleated cells, the functions of the proteasome are well established and primarily include proteostasis among a myriad of other signaling processes. However, the role of proteasome-mediated protein degradation in platelets remains elusive. In this review article, we recapitulate the developing literature on the functions of the proteasome in platelets, discussing its emerging regulatory role in platelet viability and function and highlighting how its functional coupling with the transcription factor NF-κB constitutes a novel potential therapeutic target in atherothrombotic diseases.

Inhibition of autophagy enhances apoptosis induced by bortezomib in AML cells

Bortezomib is a novel proteasome inhibitor, which has been successfully used to treat mantle cell lymphoma and multiple myeloma. However, the direct effects of bortezomib on acute promyelocytic leukaemia (APL) have not been fully investigated. In the present study, the WST-8 assay, western blotting, flow cytometry, monodansylcadaverine staining and transmission electron microscopy were performed. It was demonstrated that bortezomib treatment induced a time- and dose-dependent decrease in the viability of NB4 cells. Bortezomib treatment induced cell apoptosis in NB4 cells, as assessed by Annexin V/propidium iodide analysis, and the detection of cleaved caspase-3, cleaved poly(ADP-ribose) polymerase, Bax and Bcl-2 expression. Furthermore, bortezomib treatment induced autophagy in NB4 cells, as indicated by autophagosome formation, p62 degradation, LC3-I to LC3-II conversion and formation of acidic autophagic vacuoles. Notably, autophagy induced by bortezomib was initiated prior to apoptosis. Inhibition of autophagy by knocking down Beclin-1 expression increased bortezomib-induced apoptosis in NB4 cells. Therefore, the present study revealed that the combination of bortezomib and autophagy inhibition may be a potential treatment strategy for APL.

Serum and Glucocorticoid-Inducible Kinase 1 (SGK1) in NSCLC Therapy

Non-small cell lung cancer (NSCLC) remains the most prevalent and one of the deadliest cancers worldwide. Despite recent success, there is still an urgent need for new therapeutic strategies. It is also becoming increasingly evident that combinatorial approaches are more effective than single modality treatments. This review proposes that the serum and glucocorticoid-inducible kinase 1 (SGK1) may represent an attractive target for therapy of NSCLC. Although ubiquitously expressed, SGK1 deletion in mice causes only mild defects of ion physiology. The frequent overexpression of SGK1 in tumors is likely stress-induced and provides a therapeutic window to spare normal tissues. SGK1 appears to promote oncogenic signaling aimed at preserving the survival and fitness of cancer cells. Most importantly, recent investigations have revealed the ability of SGK1 to skew immune-cell differentiation toward pro-tumorigenic phenotypes. Future studies are needed to fully evaluate the potential of SGK1 as a therapeutic target in combinatorial treatments of NSCLC. However, based on what is currently known, SGK1 inactivation can result in anti-oncogenic effects both on tumor cells and on the immune microenvironment. A first generation of small molecules to inactivate SGK1 has already been already produced.

ADRM1 as a therapeutic target in hepatocellular carcinoma

Hepatocellular carcinoma (HCC), a primary liver tumor, is the third leading cause of cancer-related mortality worldwide. The proteasome system is overactivated in the majority of tumors, including HCC. However, targeting the proteasome system in HCC is not as effective as in other types of cancer. Therefore, a new target of HCC therapy needs to be identified, and the potential mechanism must be studied. Using the The Cancer Gene Genome Atlas and GEO datasets, the present investigation demonstrated for the first time that ADRM1 is overexpressed in HCC, and the high level of its expression predicts poor overall survival in HCC patients. The high expression of ADRM1 in HCC was verified using tumor tissue arrays. By comparing paired tumor and nontumor tissues, it was shown that the majority of HCC patients (76.25%) exhibited higher ADRM1 expression in the tumor than in normal tissues. in vitro experiments demonstrated that targeting ADRM1 with shRNAs significantly suppressed the proliferation of HCC cells. RA190, a specific inhibitor of ADRM1, suppressed cell proliferation and colony formation by HCC cells in a concentration-dependent manner. The study of the mechanism of the effects of RA190 revealed that targeting ADRM1 blocked the G2/M transition in the cell cycle and induced apoptosis of HCC cells. Together, the obtained results indicate that ADRM1 is a promising target for HCC therapy and suggest that ADRM1 inhibitors, such as RA190, have the potential for clinical application in the treatment of HCC.

Overview of the Side-Effects of FDA- and/or EMA-Approved Targeted Therapies for the Treatment of Hematological Malignancies

In the last decade there has been tremendous effort in offering better therapeutic management strategies to patients with hematologic malignancies. These efforts have ranged from biological to clinical approaches and resulted in the rapid development of new approaches. The main “problem” that comes with the high influx of newly approved drugs, which not only influences hematologists that frequently work with these drugs but also affects other healthcare professionals that work with hematologists in patient management, including intensive care unit (ICU) physicians, is they have to keep up within their specialty and, in addition, with the side-effects that can occur when encountering hematology-specific therapies. Nonetheless, there are few people that have an in-depth understanding of a specialty outside theirs. Thus, this manuscript offers an overview of the most common side-effects caused by therapies used in hematology nowadays, or that are currently being investigated in clinical trials, with the purpose to serve as an aid to other specialties. Nevertheless, because of the high amount of information on this subject, each chapter will offer an overview of the side-effects of a drug class with each reference of the section being intended as further reading.

NF-κB inhibitors in treatment and prevention of lung cancer

Intracellular signalling pathways have provided excellent resource for drug development particularly in the development of cancer therapeutics. A wide variety of malignancies common in human exhibit aberrant NF-κB constitutive expression which results in tumorigenic processes and cancer survival in a variety of solid tumour, including pancreatic cancer, lung, cervical, prostate, breast and gastric carcinoma. Numerous evidences indicate that NF-κB signalling mechanism is mainly involved in the progression of several cancers which may intensify an enhanced knowledge on its role in disease particularly lung tumorigenesis. This has led to tremendous research in designing a variety of NF-κB antagonists with enhanced clinical applications through different approaches the most common being suppression of IκB kinase (IKK) beta activity. Many NF-κB inhibitors for lung cancer are now under clinical trials. Preliminary results of clinical trials for several of these agents include small-molecule inhibitors and monoclonal antibodies. A few combinatorial treatment therapies are currently under investigation in the clinics and have shown promise, particularly NF-κB inhibition associated with lung cancer.

B Cell Therapy in Systemic Lupus Erythematosus: From Rationale to Clinical Practice

B cell hyperactivity and breach of tolerance constitute hallmarks of systemic lupus erythematosus (SLE). The heterogeneity of disease manifestations and relatively rare prevalence of SLE have posed difficulties in trial design and contributed to a slow pace for drug development. The anti-BAFF monoclonal antibody belimumab is still the sole targeted therapy licensed for SLE, lending credence to the widely accepted notion that B cells play central roles in lupus pathogenesis. However, more therapeutic agents directed toward B cells or B cell-related pathways are used off-label or have been trialed in SLE. The anti-CD20 monoclonal antibody rituximab has been used to treat refractory SLE during the last two decades, and the anti-type I IFN receptor anifrolumab is currently awaiting approval after one phase III clinical trial which met its primary endpoint and one phase III trial which met key secondary endpoints. While the latter does not directly affect the maturation and antibody production activity of B cells, it is expected to affect the contribution of B cells in proinflammatory cytokine excretion. The proteasome inhibitor bortezomib, primarily directed toward the plasma cells, has been used in few severe cases as an escape regimen. Collectively, current clinical experience and primary results of ongoing clinical trials prophesy that B cell therapies of selective targets will have an established place in the future personalized therapeutic management of lupus patients.

Autophagy protects HUVECs against ER stress-mediated apoptosis under simulated microgravity

Astronauts exposed to a gravity-free environment experience cardiovascular deconditioning that causes post-spaceflight orthostatic intolerance and other pathological conditions. Endothelial dysfunction is an important factor responsible for this alteration. Our previous study showed enhanced autophagy in endothelial cells under simulated microgravity. The present study explored the cytoprotective role of autophagy under microgravity in human umbilical vein endothelial cells (HUVECs). We found that clinorotation for 48 h induced apoptosis and endoplasmic reticulum (ER) stress in HUVECs. ER stress and the unfolded protein response (UPR) partially contributed to apoptosis under clinorotation. Autophagy partially reduced ER stress and restored UPR signaling by autophagic clearance of ubiquitin-protein aggregates, thereby reducing apoptosis. In addition, the ER stress antagonist 4-phenylbutyric acid upregulated autophagy in HUVECs. Taken together, these findings indicate that autophagy plays a protective role against apoptosis under clinorotation by clearing protein aggregates and partially restoring the UPR.

Discovery of a Small Molecule Probe of Rpn-6, an Essential Subunit of the 26S Proteasome

A considerable number of essential cellular proteins have no catalytic activity and serve instead as structural components to aid in assembling protein complexes. For example, the assembly and function of the 26S proteasome, the major enzymatic complex necessary for ubiquitin-dependent protein degradation, require a number of essential protein contacts to associate the 19S regulatory particle with the 20S core particle. Previously, small molecule inhibitors of the active sites of the 20S core particle have been developed, but the activity of the 26S proteasome could also be altered via the disruption of its assembly. We were interested in discovering a small molecule binder of Rpn-6, as it is among several essential proteins that facilitate 26S assembly, which could be used to further our understanding of the association of the 19S regulatory particle with the 20S core particle. Additionally, we were interested in whether a small molecule-Rpn-6 interaction could potentially be cytotoxic to cancer cells that rely heavily on proteasome activity for survival. A workflow for utilizing a one-bead, one-compound library and a thermal shift assay was developed to discover such a molecule. TXS-8, our lead hit, was discovered to have a low micromolar binding affinity for Rpn-6 as well as very limited binding to other proteins. The cytotoxicity of TXS-8 was evaluated in several cell lines, revealing increased cytotoxicity to hematological cancers. Discovery of this peptoid binder of Rpn-6 provides the initial evidence that Rpn-6 could be a druggable target to affect protein degradation and serves as a primary scaffold from which to design more potent binders. We suspect that Rpn-6 could have additional essential roles beyond that of a molecular clamp of the proteasome to help hematological cancer cells survive and that TXS-8 can serve as a useful tool for further elucidating its roles.

Targeting NF-κB-mediated inflammatory pathways in cisplatin-resistant NSCLC

OBJECTIVES

The majority of patients with non-small cell lung cancer (NSCLC) present with advanced stage disease, at which time chemotherapy is usually the most common treatment option. While somewhat effective, patients treated with platinum-based regimens will eventually develop resistance, with others presenting with intrinsic resistance. Multiple pathways have been implicated in chemo-resistance, however the critical underlying mechanisms have yet to be elucidated. The aim of this project was to determine the role of inflammatory mediators in cisplatin-resistance in NSCLC.

MATERIALS AND METHODS

Inflammatory mediator, NF-κB, and its associated pathways were investigated in an isogenic model of cisplatin-resistant NSCLC using age-matched parental (PT) and corresponding cisplatin-resistant (CisR) sublines. Pathways were assessed using mass spectrometry, western blot analysis and qRT-PCR. The cisplatin sensitizing potential of an NF-κB small molecule inhibitor, DHMEQ, was also assessed by means of viability assays and western blot analysis.

RESULTS

Proteomic analysis identified dysregulated NF-κB responsive targets in CisR cells when compared to PT cells, with increased NF-κB expression identified in four out of the five NSCLC sub-types examined (CisR versus PT). DHMEQ treatment resulted in reduced NF-κB expression in the presence of cisplatin, and re-sensitized CisR cells to the cytotoxic effects of the drug.

CONCLUSION

This study identified NF-ĸB as a potential therapeutic target in cisplatin-resistant NSCLC. Furthermore, inhibition of NF-ĸB using DHMEQ re-sensitized chemo-resistant cells to cisplatin treatment.

Bortezomib and Immune Globulin Have Limited Effects on Donor-Specific HLA Antibodies in Haploidentical Cord Blood Stem Cell Transplantation: Detrimental Effect of Persistent Haploidentical Donor-Specific HLA Antibodies

Donor-specific HLA antibodies (DSAs) have been associated with an increased risk of graft failure. To decrease DSA levels and reduce the risk of graft failure in haploidentical cord blood transplantation recipients, we studied the effect of bortezomib (BTZ) and i.v. immune globulin (IVIG) pretransplantation. Between 2012 and 2016, 14 patients with a DSA level >2000 mean fluorescence intensity (MFI) to 1 or more mismatched HLA alleles of haploidentical donors, cord blood donors, or both were treated with BTZ and IVIG. Fourteen patients received a median of 4 doses (range, 2 to 8 doses) of BTZ 1.3 mg/m² and a median total IVIG of 2 g/kg before transplantation. Only 2 of 14 patients attained a reduction in MFI to <2000 with this combination. After additional IVIG (n = 8), rituximab (n = 4), and/or plasmapheresis (n = 11), 12 of 14 patients were desensitized to a DSA level <2000 MFI at the time of engraftment. All obtained initial hematopoietic reconstitution, and no DSA rebound phenomenon was observed. Responders with DSA MFI <2000 to the haploidentical donor by transplantation engrafted at a rate comparable to that of historical controls, whereas engraftment in nonresponders took 3 times as long. BTZ and IVIG alone do not appear sufficient to rapidly induce DSA desensitization, and persistent DSAs to a haploidentical donor lead to delayed count recovery. Our data suggest that additional pretreatment with BTZ and IVIG in combination with the conditioning regimen may help abrogate the rebound phenomenon observed with plasmapheresis.

High chymotrypsin-like activity in the plasma of patients with newly diagnosed multiple myeloma treated with bortezomib is predictive of a better response and longer PFS

Proteasome inhibitors (PIs) such as bortezomib constitute an important part of the modern standard therapy for multiple myeloma (MM). In this study, we set out to assess whether proteasome concentration and chymotrypsin-like (ChT-L) activity could serve as potential biomarkers defining the likelihood of response to treatment with bortezomib, in order to identify patients who are more likely to respond to treatment with PI. We analysed proteasome concentration and ChT-L activity in the plasma of 78 patients with newly diagnosed MM during treatment with or without proteasome inhibitors. Values of all the studied parameters in the group of responders decreased sharply from the initial levels already after the third cycle of chemotherapy and remained significantly lower until the end of treatment. On the other hand, in the group of non-responders, there was an increase in the measured proteasome parameters already after the third cycle, and they remained high during the next cycles of therapy. We also showed that high baseline proteasome ChT-L activity values might prognosticate longer progression-free survival (PFS) in patients treated with PI. Our findings demonstrate that measuring plasma proteasome ChT-L activity can be used as a powerful biomarker for predicting clinical response to treatment and PFS in patients with newly diagnosed MM.

NF-κB Activation in Lymphoid Malignancies: Genetics, Signaling, and Targeted Therapy

The NF-κB transcription factor family plays a crucial role in lymphocyte proliferation and survival. Consequently, aberrant NF-κB activation has been described in a variety of lymphoid malignancies, including diffuse large B-cell lymphoma, Hodgkin lymphoma, and adult T-cell leukemia. Several factors, such as persistent infections (e.g., with Helicobacter pylori), the pro-inflammatory microenvironment of the cancer, self-reactive immune receptors as well as genetic lesions altering the function of key signaling effectors, contribute to constitutive NF-κB activity in these malignancies. In this review, we will discuss the molecular consequences of recurrent genetic lesions affecting key regulators of NF-κB signaling. We will particularly focus on the oncogenic mechanisms by which these alterations drive deregulated NF-κB activity and thus promote the growth and survival of the malignant cells. As the concept of a targeted therapy based on the mutational status of the malignancy has been supported by several recent preclinical and clinical studies, further insight in the function of NF-κB modulators and in the molecular mechanisms governing aberrant NF-κB activation observed in lymphoid malignancies might lead to the development of additional treatment strategies and thus improve lymphoma therapy.

Multicenter double-blind randomized controlled trial to evaluate the effectiveness and safety of bortezomib as a treatment for refractory systemic lupus erythematosus

OBJECTIVES

The objective of this study is to evaluate the efficacy and safety of bortezomib for treating systemic lupus erythematosus (SLE), in patients whose disease activity could not be controlled.

METHODS

Fourteen SLE patients with persistent disease activity were selected, who required prednisolone doses of >10 mg/d despite concomitant immunosuppressive therapy. Patients were randomly administered either bortezomib or a placebo, eight times. The primary and secondary end-points were a change in anti-dsDNA antibody titer at week 24 and the SLE Responder Index (SRI), respectively.

RESULTS

In the bortezomib group, four out of eight patients discontinued the trial; three others failed to complete the minimum protocol treatment due to adverse reactions. The changes in anti-dsDNA antibody titers at week 24 were 4.24% and -1.96%, for the bortezomib and placebo groups, respectively, disconfirming bortezomib's efficacy. In contrast, the corresponding SRI at week 12 was 75% and 40%.

CONCLUSIONS

As bortezomib therapy for SLE is associated with many adverse reactions, treatment indications should be selected carefully, and protocols should aim to prevent these occurrences. Although the change in anti-dsDNA antibody titer did not support the efficacy of bortezomib as a treatment for SLE, high SRI in the treatment group suggests bortezomib may utilize mechanisms other than inhibition of anti-dsDNA antibody production.

Proteasome inhibition and mechanism of resistance to a synthetic, library-based hexapeptide

Background The hexapeptide 4A6 (Ac-Thr(tBu)-His(Bzl)-Thr(Bzl)-Nle-Glu(OtBu)-Gly-Bza) was isolated from a peptide library constructed to identify peptide-based transport inhibitors of multidrug resistance (MDR) efflux pumps including P-glycoprotein and Multidrug Resistance-associated Protein 1. 4A6 proved to be a substrate but not an inhibitor of these MDR efflux transporters. In fact, 4A6 and related peptides displayed potent cytotoxic activity via an unknown mechanism. Objective To decipher the mode of cytotoxic activity of 4A6. Methods Screening of 4A6 activity was performed against the NCI60 panel of cancer cell lines. Possible interactions of 4A6 with the 26S proteasome were assessed via proteasome activity and affinity labeling, and cell growth inhibition studies with leukemic cells resistant to the proteasome inhibitor bortezomib (BTZ). Results The NCI60 panel COMPARE analysis revealed that 4A6 had an activity profile overlapping with BTZ. Consistently, 4A6 proved to be a selective and reversible inhibitor of β5 subunit (PSMB5)-associated chymotrypsin-like activity of the 26S proteasome. This conclusion is supported by several lines of evidence: (i) inhibition of chymotrypsin-like proteasome activity by 4A6 and related peptides correlated with their cell growth inhibition potencies; (ii) 4A6 reversibly inhibited functional β5 active site labeling with the affinity probe BodipyFL-Ahx₃L₃VS; and (iii) human myeloid THP1 cells with acquired BTZ resistance due to mutated PSMB5 were highly (up to 287-fold) cross-resistant to 4A6 and its related peptides. Conclusion 4A6 is a novel specific inhibitor of the β5 subunit-associated chymotrypsin-like proteasome activity. Further exploration of 4A6 as a lead compound for development as a novel proteasome-targeted drug is warranted.

Positioning of proteasome inhibitors in therapy of solid malignancies

Targeting of the protein degradation pathway, in particular, the ubiquitin-proteasome system, has emerged as an attractive novel cancer chemotherapeutic modality. Although proteasome inhibitors have been most successfully applied in the treatment of hematological malignancies, they also received continuing interest for the treatment of solid tumors. In this review, we summarize the current positioning of proteasome inhibitors in the treatment of common solid malignancies (e.g., lung, colon, pancreas, breast, and head and neck cancer), addressing topics of their mechanism(s) of action, predictive factors and molecular mechanisms of resistance.

Designing Dietary Recommendations Using System Level Interactomics Analysis and Network-Based Inference

Background: A range of computational methods that rely on the analysis of genome-wide expression datasets have been developed and successfully used for drug repositioning. The success of these methods is based on the hypothesis that introducing a factor (in this case, a drug molecule) that could reverse the disease gene expression signature will lead to a therapeutic effect. However, it has also been shown that globally reversing the disease expression signature is not a prerequisite for drug activity. On the other hand, the basic idea of significant anti-correlation in expression profiles could have great value for establishing diet-disease associations and could provide new insights into the role of dietary interventions in disease. Methods: We performed an integrated analysis of publicly available gene expression profiles for foods, diseases and drugs, by calculating pairwise similarity scores for diet and disease gene expression signatures and characterizing their topological features in protein-protein interaction networks. Results: We identified 485 diet-disease pairs where diet could positively influence disease development and 472 pairs where specific diets should be avoided in a disease state. Multiple evidence suggests that orange, whey and coconut fat could be beneficial for psoriasis, lung adenocarcinoma and macular degeneration, respectively. On the other hand, fructose-rich diet should be restricted in patients with chronic intermittent hypoxia and ovarian cancer. Since humans normally do not consume foods in isolation, we also applied different algorithms to predict synergism; as a result, 58 food pairs were predicted. Interestingly, the diets identified as anti-correlated with diseases showed a topological proximity to the disease proteins similar to that of the corresponding drugs. Conclusions: In conclusion, we provide a computational framework for establishing diet-disease associations and additional information on the role of diet in disease development. Due to the complexity of analyzing the food composition and eating patterns of individuals our in silico analysis, using large-scale gene expression datasets and network-based topological features, may serve as a proof-of-concept in nutritional systems biology for identifying diet-disease relationships and subsequently designing dietary recommendations.

Bax is involved in the anticancer activity of Velcade in colorectal cancer

Numerous chemotherapeutic agents promote tumor cell death by activating the intrinsic apoptosis signaling pathway. This pathway is regulated by mitochondrial dysfunction, which occurs through an intricate process controlled by complex interactions between B-cell lymphoma 2 (Bcl-2) family members and other cellular proteins. Bcl-2-associated X protein (Bax) is a proapoptotic protein that is an essential component of the intrinsic apoptosis signaling pathway. Patients lacking Bax may be less sensitive to chemotherapy due to an impaired intrinsic apoptosis signaling pathway. The present study demonstrated that Bax expression in colorectal cancer (CRC) tissues was typically increased compared with that in adjacent normal tissues. Furthermore, Bax^-/- HCT-116 cells exhibited reduced proliferation and colony formation ability compared with Bax^+/+ HCT116 cells, although the rate of apoptosis of these cells remained unchanged. However, Bax^-/- HCT116 cells became more resistant to apoptosis when treated with Velcade. The results of the present study provide novel insights into the relevance of Bax expression to the prognosis of CRC.

Body fat composition as predictive factor for treatment response in patients with newly diagnosed multiple myeloma - subgroup analysis of the prospective GMMG MM5 trial

INTRODUCTION/BACKGROUND

Obesity is a well-known risk factor for malignant tumors and increased body mass index (BMI) is correlated to the risk of developing multiple myeloma (MM). The correlation of body fat composition with disease activity, adverse events and treatment response of MM patients has not been investigated yet.

PATIENTS AND METHODS

A subgroup of 108 patients from a single institution enrolled in the prospective GMMG-MM5 trial, who received a whole-body low-dose computed tomography (WBLDCT) before induction therapy, were included in this study. Body fat composition was measured in WBLDCT for each patient, divided in the compartments abdomen, pelvis, thigh and further categorized in subcutaneous (SAT) and visceral adipose tissue (VAT). The correlation of these parameters with disease activity (M protein, plasma cell count, LDH, CRAB-criteria), adverse cytogenetics, adverse events and treatment response were evaluated.

RESULTS

Significant reciprocal correlation was found between adverse cytogenetics and VAT of the abdomen and pelvis, respectively (gain 1q21: p=0.009 and p=0.021; t(4;14): p=0.038 and p=0.042). No correlation of VAT or SAT with adverse events was observed. Significant reciprocal correlation was observed between abdominal (p=0.03) and pelvic (p=0.035) VAT and treatment response. Abdominal VAT remains significant (p=0.034) independently of revised ISS stage and treatment. The BMI did not show a significant correlation with treatment response or investigated cytogenetics.

CONCLUSION

Based on the clinically relevant difference in treatment outcome depending on VAT and SAT, excessive body fat of abdomen and pelvis might be a predictive factor for poor treatment response. Further influences in this context should be considered as well, e.g. chemotherapy dosing and body fat metabolism. Further studies are necessary to investigate this hypothesis.

Neurophysiological and clinical outcomes in chemotherapy-induced neuropathy in cancer

Chemotherapy induced peripheral neuropathy (CIPN) is a significant toxicity of cancer treatment, with the potential to affect long-term function and quality of life in cancer survivors. There remains a lack of consensus around optimal assessment techniques. While current approaches to CIPN assessment are focused on clinical grading scales, it is becoming increasingly evident that a more comprehensive multimodal assessment package is necessary to accurately characterise the impact of CIPN as well as gauge the utility of neuroprotective mechanisms. Neurophysiological techniques provide objective biomarkers and may enable early detection of toxicity while patient reported outcomes are necessary to determine the significance of symptoms to individual patients. In addition to providing an objective assessment, clinical neurophysiological techniques provide important insights into the contributory pathophysiological mechanisms of CIPN with different chemotherapy agents. There is a paucity of implementation of these techniques in the clinical trial setting. The present Review aims to facilitate the use of neurophysiological studies as part of comprehensive assessment packages for the monitoring of CIPN by summarising current understanding of neurophysiological changes that underlie the development of neuropathy, clinical presentations and patient reported outcomes as well as advantages and limitations of current techniques for the neurophysiological assessment of CIPN.

Novel Proteasome Inhibitors and Histone Deacetylase Inhibitors: Progress in Myeloma Therapeutics

The unfolded protein response is responsible for the detection of misfolded proteins and the coordination of their disposal and is necessary to maintain the cellular homoeostasis. Multiple myeloma cells secrete large amounts of immunoglobulins, proteins that need to be correctly folded by the chaperone system. If this process fails, the misfolded proteins have to be eliminated by the two main garbage-disposal systems of the cell: proteasome and aggresome. The blockade of either of these systems will result in accumulation of immunoglobulins and other toxic proteins in the cytoplasm and cell death. The simultaneous inhibition of the proteasome, by proteasome inhibitors (PIs) and the aggresome, by histone deacetylase inhibitors (HDACi) results in a synergistic increase in cytotoxicity in myeloma cell lines. This review provides an overview of mechanisms of action of second-generation PIs and HDACi in multiple myeloma (MM), the clinical results currently observed with these agents and assesses the potential therapeutic impact of the different agents in the two classes. The second-generation PIs offer benefits in terms of increased efficacy, reduced neurotoxicity as off-target effect and may overcome resistance to bortezomib because of their different chemical structure, mechanism of action and biological properties. HDACi with anti-myeloma activity in clinical development discussed in this review include vorinostat, panobinostat and selective HDAC6 inhibitor, ricolinostat.

The proteasome regulates collagen-induced platelet aggregation via nuclear-factor-kappa-B (NFĸB) activation

INTRODUCTION

Platelets possess critical hemostatic functions in the system of thrombosis and hemostasis, which can be affected by a multitude of external factors. Previous research has shown that platelets have the capacity to synthesize proteins de novo and more recently a multicatalytic protein complex, the proteasome, has been discovered in platelets. Due to its vital function for cellular integrity, the proteasome has become a therapeutic target for anti-proliferative drug therapies in cancer. Clinically thrombocytopenia is a frequent side-effect, but the aggregatory function of platelets also appears to be affected. Little is known however about underlying regulatory mechanisms and functional aspects of proteasome inhibition on platelets. Our study aims to investigate the role of the proteasome in regulating collagen-induced platelet aggregation and its interaction with NFkB in this context.

MATERIAL AND METHODS

Using fluorescence activity assays, platelet aggregometry and immunoblotting, we investigate regulatory interactions of the proteasome and Nuclear-factor-kappa-B (NFkB) in collagen-induced platelet aggregation.

RESULTS

We show that collagen induces proteasome activation in platelets and collagen-induced platelet aggregation can be reduced with proteasome inhibition by the specific inhibitor epoxomicin. This effect does not depend on Rho-kinase/ROCK activation or thromboxane release, but rather depends on NFkB activation. Inhibition of the proteasome prevented cleavage of NFκB-inhibitor protein IκBα and decreased NFκB activity after collagen stimulation. Inhibition of the NFκB-pathway in return reduced collagen-induced platelet proteasome activity and cleavage of proteasome substrates.

CONCLUSIONS

This work offers novel explanations how the proteasome influences collagen-dependent platelet aggregation by involving non-genomic functions of NFkB.

TRIB2 and the ubiquitin proteasome system in cancer

Tribbles family of pseudokinase proteins are known to mediate the degradation of target proteins in Drosophila and mammalian systems. The main protein proteolysis pathway in eukaryotic cells is the ubiquitin proteasome system (UPS). The tribbles homolog 2 (TRIB2) mammalian family member has been well characterized for its role in murine and human leukaemia, lung and liver cancer. One of the most characterized substrates for TRIB2-mediated degradation is the myeloid transcription factor CCAAT enhancer binding protein α (C/EBPα). However, across a number of cancers, the molecular interactions that take place between TRIB2 and factors involved in the UPS are varied and have differential downstream effects. This review summarizes our current knowledge of these interactions and how this information is important for our understanding of TRIB2 in cancer.

Innovation in non-Hodgkin lymphoma drug discovery: what needs to be done?

INTRODUCTION

A new generation of anticancer agents called target drugs has been recently developed for the treatment of non-Hodgkin lymphomas. Current recovery rates in these diseases are up to 70% with immunotherapy based on the anti-CD20 monoclonal antibody combined with standard chemotherapeutics. However, there are still refractory or relapsed patients. Recently, several novel anti-lymphoma agents have been developed. Choosing the most effective personalized therapy still remains a crucial challenge in hematology. Areas covered: New drugs can specifically target malignant cells and inhibit cancer cell growth, proliferation and survival by specific interactions with one or more target proteins. Recent clinical studies have illustrated promising outcomes for novel drugs used as single agents and in combination with traditional therapeutics. In this article, the authors discuss novel targeted therapies with a promising outcome in NHL patients that are becoming integrated into treatment paradigms. Expert opinion: The development of new treatment options may help to avoid cytotoxic chemotherapy entirely in some clinical settings. Multicenter studies should be continued to investigate small agents and pathways inhibitors as this will enable us to enhance not only the duration of the treatment response but also the quality of the extended survival.

Substituted quinolines as noncovalent proteasome inhibitors

Screening of a library of diverse heterocyclic scaffolds identified substituted quinolines as inhibitors of the human proteasome. The heterocyclic library was prepared via a novel titanium-catalyzed multicomponent coupling reaction, which rendered a diverse set of isoxazoles, pyrimidines, pyrroles, pyrazoles and quinolines. SAR of the parent lead compound indicated that hydrophobic residues on the benzo-moiety significantly improved potency. Lead compound 25 inhibits the chymotryptic-like proteolytic activity of the proteasome (IC50 5.4μM), representing a new class of nonpeptidic, noncovalent proteasome inhibitors.

Immune responses in multiple myeloma: role of the natural immune surveillance and potential of immunotherapies

Multiple myeloma (MM) is a tumor of terminally differentiated B cells that arises in the bone marrow. Immune interactions appear as key determinants of MM progression. While myeloid cells foster myeloma-promoting inflammation, Natural Killer cells and T lymphocytes mediate protective anti-myeloma responses. The profound immune deregulation occurring in MM patients may be involved in the transition from a premalignant to a malignant stage of the disease. In the last decades, the advent of stem cell transplantation and new therapeutic agents including proteasome inhibitors and immunoregulatory drugs has dramatically improved patient outcomes, suggesting potentially key roles for innate and adaptive immunity in disease control. Nevertheless, MM remains largely incurable for the vast majority of patients. A better understanding of the complex interplay between myeloma cells and their immune environment should pave the way for designing better immunotherapies with the potential of very long term disease control. Here, we review the immunological microenvironment in myeloma. We discuss the role of naturally arising anti-myeloma immune responses and their potential corruption in MM patients. Finally, we detail the numerous promising immune-targeting strategies approved or in clinical trials for the treatment of MM.

BOK Is a Non-canonical BCL-2 Family Effector of Apoptosis Regulated by ER-Associated Degradation

The mitochondrial pathway of apoptosis is initiated by mitochondrial outer membrane permeabilization (MOMP). The BCL-2 family effectors BAX and BAK are thought to be absolutely required for this process. Here, we report that BCL-2 ovarian killer (BOK) is a bona fide yet unconventional effector of MOMP that can trigger apoptosis in the absence of both BAX and BAK. However, unlike the canonical effectors, BOK appears to be constitutively active and unresponsive to antagonistic effects of the antiapoptotic BCL-2 proteins. Rather, BOK is controlled at the level of protein stability by components of the endoplasmic reticulum (ER)-associated degradation pathway. BOK is ubiquitylated by the AMFR/gp78 E3 ubiquitin ligase complex and targeted for proteasomal degradation in a VCP/p97-dependent manner, which allows survival of the cell. When proteasome function, VCP, or gp78 activity is compromised, BOK is stabilized to induce MOMP and apoptosis independently of other BCL-2 proteins.

Bortezomib regulates NF-κB and TGF-β1 expression in hepatic fibrosis in a rat model

AIM: To assess the protective effect of the proteasome inhibitor bortezomib on liver fibrosis in rats and to explore the possible mechanism.

METHODS: Thirty SD rats were randomized into three groups: a normal diet group (ND group), a liver fibrosis group (LF group) and a bortezomib group (Bor group). After treatment, the rats in each group were sacrificed. Hepatic fibrosis was assessed by HE and Masson trichrome staining. The expression of nuclear factor-kappa B (NF-κB) p65 was assessed by immunohistochemistry. Real-time PCR was employed to detect the transforming growth factor β1 (TGF-β1) mRNA level in liver samples. The expression of TGF-β1 protein was determined by Western blot analysis.

RESULTS: The hepatic fibrosis level in the Bor group was significantly lower than that in the LF group as revealed by HE and Masson staining. The positive rate of NF-κB p65 subunit was significantly lower in the Bor group than in the LF group (4.72 vs 9.05, P < 0.05). The expression of TGF-β1 mRNA was significantly lower in the Bor group than in the LF group (0.96 vs 1.64, P < 0.05). The expression of TGF-β1 protein was also significantly lower in the Bor group than in the LF group (1.34 vs 1.72, P < 0.05).

CONCLUSION: These findings suggest that bortezomib reduces hepatocyte injury in rats with hepatic fibrosis possibly by suppression of NF-κB activation and TGF-β1 expression.

Sugar-boronate ester scaffold tethered pyridyl-imine palladium(ii) complexes: synthesis and their in vitro anticancer evaluation

The anticancer activity of sugar-boronate ester containing palladium(ii) complexes is reported.

Toward understanding induction of oxidative stress and apoptosis by proteasome inhibitors

SIGNIFICANCE

Proteasome inhibitors (PIs) are used in the clinic for the treatment of hematopoietic malignancies. PI inhibitors induce endoplasmatic reticulum (ER) stress and oxidative stress, disruption of signaling pathways, mitochondrial dysfunction, and, eventually, cell death by apoptosis. PIs designated as clinical candidates include natural product derivatives and compounds developed by rational design and feature a wide diversity of structural elements. The vast amount of literature on this topic underscores PIs significance in driving basic research alongside therapeutic benefit.

RECENT ADVANCES

Research in recent years has brought an in-depth insight into the molecular mechanisms of PI-induced apoptosis. However, there are some paradoxes and controversies in the literature. In this review, the advances and uncertainties, in particular on the time course events that make cells commit to apoptosis, are discussed. In addition, some mechanisms of evolved PI resistance are presented, and speculations on the difference in sensitivity between cell or tumor types are brought forward. The review concludes by giving an outlook of recent methods that may be employed to describe the system biology of how PIs impact cell survival decisions.

CRITICAL ISSUES

The biology of ER stress, reactive oxygen species (ROS) production, and apoptosis as induced by PIs is not well understood. Absorbed by the strong focus on PIs, one might overlook the importance of proteasome activity activators or modulators and the study of enzymatic pathways that lie up- or downstream from the proteasome function.

FUTURE DIRECTIONS

An increased understanding of the systems biology at mRNA and protein levels and the kinetics behind the interaction between PIs and cells is imperative. The design and synthesis of subunit specific inhibitors for each of the seven known proteasome activities and for the enzymes associated to proteasomes will aid in unraveling biology of the ubiquitin-proteasome system in relation to ER stress, ROS production, and apoptosis and will generate leads for therapeutic intervention.

Treating rare lymphoproliferative malignancies: a focus on indolent large granular lymphocytic leukemia

SUMMARY 

Large granular lymphocyte leukemia is a heterogeneous group of lymphoproliferative disorders that arises from mature T cells or NK cells. These disorders are relatively uncommon and usually present with cytopenias and/or autoimmune disorders. As patients often do not have symptoms warranting therapy upfront, surveillance is often employed. Common frontline therapies include cyclosphosphamide, methotrexate or cyclosporine A, however, no controlled trials or retrospective analyses have demonstrated one superior therapeutic strategy. Mechanisms of pathogenesis and survival have been identified that include abnormalities in the cell surface receptors halting apoptotic signals, dysregulation of prosurvival and apoptotic signaling pathways, and somatic mutations of the STAT3 and STAT5b genes, among others. Investigating novel therapies that target pathways shared by other neoplastic processes, as well as the identification of new agents directed toward the aberrant cellular mechanisms of large granular lymphocyte leukemia, are fundamental to moving from empiric chemotherapy to targeted therapies in the future.

Patterns of cardiac toxicity associated with irreversible proteasome inhibition in the treatment of multiple myeloma

Carfilzomib is a novel irreversible proteasome inhibitor (PI) used with increasing frequency to treat patients with relapsed and/or refractory multiple myeloma (RRMM). This agent is an effective treatment for this challenging population, but proteasome inhibition has the potential of significant cardiac toxicity via the accumulation of intracellular protein aggregates. Although large clinical trials have not suggested an excess of heart failure with PI therapy, nonhuman animal studies and case reports in humans with the PI bortezomib have suggested otherwise. We describe the clinical presentation and management of 6 patients with RRMM who experienced significant cardiac toxicity associated with carfilzomib treatment. A common clinical syndrome of dyspnea associated with left ventricular systolic and/or diastolic dysfunction was identified. These abnormalities were largely reversible with prompt cessation of PI therapy and initiation of traditional heart failure treatments. Safe readministration of carfilzomib with dose modification was possible in some cases.

Synthesis and activity of isoxazoline vinyl ester pseudopeptides as proteasome inhibitors

The ubiquitin–proteasome pathway (UPP) influences essential cellular functions including cell growth, differentiation, apoptosis, signal transduction, antigen processing and inflammatory responses. The main proteolytic component of the UPP is the 26S proteasome, which is responsible for the turnover of many cellular proteins and represents an attractive target for the treatment of pathologies such as cancer, as well as inflammatory, immune and neurodegenerative diseases. Natural and synthetic proteasome inhibitors having different chemical structures and potency have been discovered. We report herein the synthesis, proteasome inhibition and modelling studies of novel C-terminal isoxazoline vinyl ester pseudopeptides. Some new compounds that contain a C-terminal extended conjugation inhibit β1 and especially β5 proteasomal catalytic subunits with IC50 values ranging from 10 to 100 µm. These results will permit further optimization based on these structural moieties to develop more active and selective molecules.

Discovery of novel covalent proteasome inhibitors through a combination of pharmacophore screening, covalent docking, and molecular dynamics simulations

The ubiquitin-proteasome pathway plays a pivotal role in the regulation of cellular protein processing and degradation. Proteasome inhibitors (PIs) have enormous potential to treat multiple myeloma, solid tumors, parasites, inflammation, and immune diseases, which is spurring the development of new types of PIs with enhanced efficacy, fewer side effects, and reduced drug resistance. Nevertheless, virtual screening for covalent PIs has rarely been reported because calculating the covalent binding energy is a challenging task. The aim of this study was to discover new covalent inhibitors of the 20S proteasome. The structures of PIs were manually divided into two parts: a noncovalent binding part resulting from virtual screening, and an epoxyketone group that was pre-selected as a covalent binding part. The SPECS database was screened by noncovalent docking and a pharmacophore model built with the 20S proteasome. After validating the covalent conjugation, 88 hits with epoxyketone were covalently docked into the 20S proteasome to analyze the intermolecular interactions. Four compounds were selected after multiple filtration and validations. Molecular dynamics simulations were performed to check the stability of the noncovalent and covalent docked ligand-enzyme complexes and investigate the interaction patterns of the screened inhibitors. Finally, two compounds with novel aromatic backbones, reasonable interactions, and stable covalent binding modes were retained. These compounds can serve as potential hits for further biological evaluation.

Bortezomib and IL-12 produce synergetic anti-multiple myeloma effects with reduced toxicity to natural killer cells

The aim of this study was to examine the hypothesis that a combination of proteasome inhibition by bortezomib and immune therapy with interleukin-12 (IL-12) can produce enhanced antitumor efficacy relative to the effects of either of these agents alone. A mouse xenograft model of myeloma was developed. The mice were randomly divided into saline control (NS), IL-12 (0.4 µg/animal; intraperitoneal), bortezomib (0.75 mg/kg; intravenous), and bortezomib+IL-12 groups. Effects of treatments on tumor growth were assessed by before and after treatment comparisons and group comparisons. The effects of various treatments on the number of peripheral blood lymphocytes and natural killer (NK) cells were assessed by complete blood count and flow cytometry analysis. The cell-killing function of NK cells in splenocytes was evaluated using the lactate dehydrogenase release assay. IL-12 treatment alone produced a mild decrease in tumor volume compared with control (P>0.05). Bortezomib alone resulted in substantial inhibition of tumor growth at varying time points, reaching ~65 and ~60% reduction in tumor volume after 15 and 21 days of therapy, respectively. At the same time points, the combination therapy produced ~75 and ~84% decreases in tumor growth, respectively, which were significantly greater than the reduction produced by bortezomib monotherapy. Tumors resumed growth upon termination of bortezomib treatment at 2 weeks, although the tumor volume was still significantly smaller than that in the time-matched NS and IL-12 animals. This rebound of tumor growth was completely prevented with the combination therapy, and tumor volume continued to decrease throughout the time course. The percentage and total number of NK cells were significantly decreased after bortezomib monotherapy and combination therapy; however, they remained unaltered after IL-12 treatment compared with no treatment. Further, combination therapy significantly restored the bortezomib-induced functional impairment of the cell-killing capability of NK cells, relative to bortezomib alone. We conclude that the bortezomib-IL-12 combination therapy offers superior antitumor efficacy over monotherapy with either bortezomib or IL-12 in a mouse model of myeloma. Restoration of bortezomib-induced functional impairment of NK cells by IL-12 may be a mechanism for the synergetic effects of the two agents. Therefore, a combination of the two agents may represent a more rational therapeutic approach for myeloma.