Proteasome Inhibitor Research Articles

Navigating High-Risk and Ultrahigh-Risk Multiple Myeloma: Challenges and Emerging Strategies.

Despite significant improvement in the outcomes of patients with newly diagnosed multiple myeloma (NDMM) with novel therapies, there is still an underserved high-risk (HR) population that experiences early disease progression and death. With the median survival crossing 10 years, we defined ultrahigh-risk (uHR)MM as MM leading to death within 24-36 months of diagnosis and HRMM as MM leading to death within 36-60 months. Several features have emerged as markers of uHRMM: the co-occurrence of two or more high-risk cytogenetic abnormalities, extramedullary disease, plasma cell leukemia and a high-risk gene expression profiling signature. The heterogeneous risk definition across trials, the few trials available designed for HR patients, and the small HR subgroups in all-comers trials make it difficult to generate recommendations with high levels of evidence. Nevertheless, regardless of treatment administered, several studies consistently showed that achieving and maintaining measurable residual disease negativity is now considered the main factor able to mitigate the adverse prognosis related to baseline features. For fit patients with HR transplant-eligible (TE) NDMM, quadruplet induction/consolidation treatment with anti-CD38 monoclonal antibodies, immunomodulatory agents, proteasome inhibitors and dexamethasone, and autologous stem-cell transplant and maintenance with, if available, at least a doublet combination could be considered the option of choice. For non-TE NDMM, considering the recent data generated and carefully reviewing those upcoming, quadruplet treatment consisting of anti-CD38 monoclonal antibodies, immunomodulatory agents, proteasome inhibitors, and dexamethasone should also be considered. Future trials integrating BCMA-directed novel generation immunotherapies hold great potential for further advancing the treatment landscape in all NDMM patients with HR disease.

Decreased proteasome function increases oxidative stress in the early stage of pressure ulcer development

The aging process in the elderly results in heightened skin fragility associated with various disorders, including pressure ulcers (PUs). Despite the high incidence of PUs in the elderly population, there is a limited body of research specifically examining the impact of aging on the development of pressure ulcers. Therefore, investigating age-related physiological abnormalities is essential to elucidate the pathogenesis of PUs. Ischemia-reperfusion (I/R) injury and the subsequent oxidative stress caused by reactive oxygen species (ROS) play essential roles in the early stage of PUs. In this study, we used a mouse model of proteasomal dysfunction with an age-related phenotype to examine the role of proteasome activity in cutaneous I/R injury in vivo. Decreased proteasome function did not affect the expression of inflammatory cytokines and adhesion molecules in the I/R area in transgenic mice; however, proteasome inhibition increased oxidative stress that was not attenuated by activation of the oxidative stress response mediated by NF-E2-related factor 2 (Nrf2). In dermal fibroblasts (FCs) subjected to hypoxia-reoxygenation (H/R), proteasome inhibition induced oxidative stress and ROS production, and Nrf2 activation did not adequately upregulate antioxidant enzyme expression, possibly leading to antioxidant/oxidant imbalance. The free radical scavenger edaravone had protective effects against I/R injury in vivo and decreased oxidative stress in FCs treated with a proteasome inhibitor and subjected to H/R in vitro. The results suggest that the age-related decline in proteasome activity promotes cutaneous I/R injury-induced oxidative stress, and free radical scavengers may exert protective effects by preventing oxidative stress in the early stage of PUs in elderly patients with impaired proteasome function.

Protein homeostasis maintained by HOOK1 levels promotes the tumorigenic and stemness properties of ovarian cancer cells through reticulum stress and autophagy

BackgroundOvarian cancer has a high mortality rate mainly due to its resistance to currently used therapies. This resistance has been associated with the presence of cancer stem cells (CSCs), interactions with the microenvironment, and intratumoral heterogeneity. Therefore, the search for new therapeutic targets, particularly those targeting CSCs, is important for improving patient prognosis. HOOK1 has been found to be transcriptionally altered in a substantial percentage of ovarian tumors, but its role in tumor initiation and development is still not fully understood.MethodsThe downregulation of HOOK1 was performed in ovarian cancer cell lines using CRISPR/Cas9 technology, followed by growth in vitro and in vivo assays. Subsequently, migration (Boyden chamber), cell death (Western-Blot and flow cytometry) and stemness properties (clonal heterogeneity analysis, tumorspheres assay and flow cytometry) of the downregulated cell lines were analysed. To gain insights into the specific mechanisms of action of HOOK1 in ovarian cancer, a proteomic analysis was performed, followed by Western-blot and cytotoxicity assays to confirm the results found within the mass spectrometry. Immunofluorescence staining, Western-blotting and flow cytometry were also employed to finish uncovering the role of HOOK1 in ovarian cancer.ResultsIn this study, we observed that reducing the levels of HOOK1 in ovarian cancer cells reduced in vitro growth and migration and prevented tumor formation in vivo. Furthermore, HOOK1 reduction led to a decrease in stem-like capabilities in these cells, which, however, did not seem related to the expression of genes traditionally associated with this phenotype. A proteome study, along with other analysis, showed that the downregulation of HOOK1 also induced an increase in endoplasmic reticulum stress levels in these cells. Finally, the decrease in stem-like properties observed in cells with downregulated HOOK1 could be explained by an increase in cell death in the CSC population within the culture due to endoplasmic reticulum stress by the unfolded protein response.ConclusionHOOK1 contributes to maintaining the tumorigenic and stemness properties of ovarian cancer cells by preserving protein homeostasis and could be considered an alternative therapeutic target, especially in combination with inducers of endoplasmic reticulum or proteotoxic stress such as proteasome inhibitors.

Elranatamab in Japanese patients with relapsed/refractory multiple myeloma: results from MagnetisMM-2 and MagnetisMM-3.

Despite advances, most patients with multiple myeloma (MM) experience relapse and repeat multiple treatment lines, highlighting an unmet need for patients with relapsed or refractory MM (RRMM). Bispecific antibodies are a new option, but their efficacy and safety in Japanese patients are unknown. This was an analysis of Japanese patients receiving elranatamab monotherapy in MagnetisMM-2 (NCT04798586) and MagnetisMM-3 (NCT04649359). Both studies evaluated a priming dose regimen of elranatamab followed by weekly subcutaneous doses, in patients with disease progression while receiving or who were intolerant to ≥3 prior therapies (≥1 proteasome inhibitor, ≥1 immunomodulatory drug and≥1 anti-CD38 monoclonal antibody). The primary endpoints were dose limiting toxicities (DLTs) in MagnetisMM-2 and confirmed objective response rate (ORR) in MagnetisMM-3. In both, key secondary endpoints included safety, tolerability, duration of response, time to response, progression-free survival and overall survival. In MagnetisMM-2 (N=4) and MagnetisMM-3 (n=12), median ages were 68.5 and 66.5years, respectively. No DLTs were observed in MagnetisMM-2. ORRs were 50.0% (95% CI, 6.8-93.2) and 58.3% (95% CI, 27.7-84.8) in MagnetisMM-2 and MagnetisMM-3, respectively. All patients experienced treatment-emergent adverse events in MagnetisMM-2 (grade 3/4: 75.0%) and MagnetisMM-3 (grade 3/4: 100%); cytokine release syndrome occurred in 100% (grade 3/4: 25.0%) and 58.3% (no grade 3/4) of patients, respectively. Neither study reported immune effector cell-associated neurotoxicity syndrome. No new safety signals were observed, and ORRs were similar to that of the overall MagnetisMM-3 trial population, supporting further studies of elranatamab in Japanese patients with RRMM. ClinicalTrials.gov identifier: NCT04798586 (MagnetisMM-2), NCT04649359 (MagnetisMM-3).

Enhanced angiogenesis of human umbilical vein endothelial cells via THP-1-derived M2c-like macrophages and treatment with proteasome inhibitors 'bortezomib and ixazomib'.

The leading cause of cancer-related death is lung cancer, with metastasis being the most common cause of death. To elucidate the role of macrophages in lung cancer and angiogenesis processes, we established an in vitro co-culture model of A549 or HUVEC with THP-1 cells that polarized to M2c macrophages with hydrocortisone. The proteasome inhibitors bortezomib and ixazomib were investigated for their effects on proliferation, invasion, migration, metastasis, and angiogenesis pathways. The effects of bortezomib and ixazomib on gene expression in gene panels, including crucial genes related to angiogenesis and proteasomes, were investigated after the co-culture model to determine these effects at the molecular level. In conclusion, bortezomib and ixazomib showed antiproliferative effects in both cells, as well as in M2c macrophage co-culture. M2c macrophages also increased invasion in A549 cells and both invasion and migration in HUVEC. mRNA expression upregulation, specifically in the NFKB and VEGF genes, supported the metastatic and angiogenic effects found in A549 and HUVEC with M2c macrophage co-culture. Additionally, bortezomib inhibited the VEGFB pathway in HUVEC and NFKB1 in A549 cells. The significant findings obtained as a result of this study will provide information regarding angiogenesis induced by M2 macrophages.

Circadian regulation of macromolecular complex turnover and proteome renewal.

Although costly to maintain, protein homeostasis is indispensable for normal cellular function and long-term health. In mammalian cells and tissues, daily variation in global protein synthesis has been observed, but its utility and consequences for proteome integrity are not fully understood. Using several different pulse-labelling strategies, here we gain direct insight into the relationship between protein synthesis and abundance proteome-wide. We show that protein degradation varies in-phase with protein synthesis, facilitating rhythms in turnover rather than abundance. This results in daily consolidation of proteome renewal whilst minimising changes in composition. Coupled rhythms in synthesis and turnover are especially salient to the assembly of macromolecular protein complexes, particularly the ribosome, the most abundant species of complex in the cell. Daily turnover and proteasomal degradation rhythms render cells and mice more sensitive to proteotoxic stress at specific times of day, potentially contributing to daily rhythms in the efficacy of proteasomal inhibitors against cancer. Our findings suggest that circadian rhythms function to minimise the bioenergetic cost of protein homeostasis through temporal consolidation of protein turnover.

Valproate Mediated Proteasome Dysfunctions Induce Apoptosis

AbstractSeveral studies suggest Valproate's (VPA) therapeutic use in treating seizures, epilepsy, and bipolar disorder. Valproate is a class I histone deacetylases (HDACs) inhibitor and an attractive chemotherapeutic agent for targeting cancer. Few reports suggest that Valproate can suppress cell growth and cell differentiation and is linked with anti‐tumor activity. However, Valproate‐associated anti‐tumoral function and intracellular signaling cascade‐mediated anti‐cellular proliferation activities still need to be better understood. This current study suggests that Valproate can elevate proteasomal dysfunctions, resulting in misfolded protein accumulation and abnormal mitochondrial functions that successively induce apoptosis. Present findings indicate that treatment of Valproate inhibits Proteasome activities and also aggravates accumulation of expanded polyglutamine proteins and other proteasomal substrates. Overall, the aggregation of aberrant proteins and mitochondrial dysfunctions are observed, such as cytochrome c release, and disturbed mitochondrial membrane potential. Treatment of Valproate induces apoptotic morphological changes and cell death. These observations suggest that Valproate can cause mitochondrial abnormalities associated with apoptosis. These findings can provide new possible insights and suggest molecular approaches for developing better and specific Proteasome inhibitors that can be better useful with other anti‐tumor drugs for treatment of cancer and other complex diseases.

ACUTE MYOCARDIAL INFARCTION DURING VRD CHEMOTHERAPY IN A PATIENT WITH MULTIPLE MYELOMA: A CLINICAL CASE

Acute myocardial infarction is a critical condition associated with significant morbidity and mortality rates. Myocardial infarction-related acute myocardial injury is characterized by a rapid elevation and subsequent decline in cardiac troponin concentration. According to the relevant data patients with multiple myeloma are in a high-risk category for venous and arterial thrombosis. Therefore, the incidence of cardiovascular complications, which include myocardial infarction, in these patients is higher than in the general population. The development of metaplastic anemia further compounds this risk by diminishing myocardial oxygen supply. Moreover, chemotherapy for oncohematological diseases carries the potential for cardiotoxic cardiovascular complications. Immunomodulator drugs like Thalidomide and Lenalidomide, frequently utilized in multiple myeloma treatment, have been associated with Lenalidomide-induced myocardial infarction—a prevalent adverse effect. The use of proteasome inhibitors such as Bortezomib and Carfilzomib poses an increased risk for myocardial infarction development. This clinical case presents an instance of acute myocardial infarction in a multiple myeloma patient during low cumulative chemotherapy dosage, comprising Lenalidomide and Bortezomib. It underscores the necessity for enhanced clinical, instrumental, and laboratory monitoring before each specific chemotherapy course in high-risk multiple myeloma patients. Such monitoring facilitates the early detection of chemotherapy-induced cardiotoxic effects, allowing for timely intervention and management.

Single-center experience of patients with plasma cell leukemia in the era of new therapeutics.

Plasma cell leukemia (PCL) can occur de novo as primary PCL (pPCL), or in patients with prior diagnosis of multiple myeloma (MM) as secondary PCL (sPCL). In 2021, the diagnostic criteria have been revised, establishing a new cut-off of ≥ 5 % plasma cells in the peripheral blood. Lacking specific clinical trials, PCL is treated similarly to MM, however outcome for patients with PCL remains poor. Here, we report outcomes for patients with pPCL and sPCL in the era of novel agents. We performed a retrospective analysis and identified 19 patients (11 pPCL, 8 sPCL) who have been treated for PCL between 2010 and 2022 at University Hospital Essen. Patients with pPCL had a median overall survival (OS) of 37.8 months (95% CI: [15.4; 52.3] months) from diagnosis, with a median time to next treatment (TTNT) of 18.4 [2.0; 22.9] months. All patients were treated with a proteasome- inhibitor (PI)-based induction therapy and the majority was consolidated with an autologous stem cell transplantation (SCT). Five of these patients received a tandem transplantation. Patients with sPCL had a median OS of only 1.5 months after diagnosis of PCL. Only one patient achieved a remission with daratumumab and subsequent allogenic SCT. With our study, we add evidence for a PI-based induction therapy followed by a consolidating autologous stem cell transplantation for patients with pPCL and give further evidence that a tandem transplant concept might be beneficial. The diagnosis of sPCL remains devasting and needs new therapeutic approaches.

Reduction of Filamin C Results in Altered Proteostasis, Cardiomyopathy, and Arrhythmias.

Many cardiomyopathy-associated FLNC pathogenic variants are heterozygous truncations, and FLNC pathogenic variants are associated with arrhythmias. Arrhythmia triggers in filaminopathy are incompletely understood. We describe an individual with biallelic FLNC pathogenic variants, p.Arg650X and c.970-4A>G, with peripartum cardiomyopathy and ventricular arrhythmias. We also describe clinical findings in probands with FLNC variants including Val2715fs87X, Glu2458Serfs71X, Phe106Leu, and c.970-4A>G with hypertrophic and dilated cardiomyopathy, atrial fibrillation, and ventricular tachycardia. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated. The FLNC truncation, Arg650X/c.970-4A>G, showed a marked reduction in filamin C protein consistent with biallelic loss of function mutations. To assess loss of filamin C, gene editing of a healthy control iPSC line was used to generate a homozygous FLNC disruption in the actin binding domain. Because filamin C has been linked to protein quality control, we assessed the necessity of filamin C in iPSC-CMs for response to the proteasome inhibitor bortezomib. After exposure to low-dose bortezomib, FLNC-null iPSC-CMs showed an increase in the chaperone proteins BAG3, HSP70 (heat shock protein 70), and HSPB8 (small heat shock protein B8) and in the autophagy marker LC3I/II. FLNC null iPSC-CMs had prolonged electric field potential, which was further prolonged in the presence of low-dose bortezomib. FLNC null engineered heart tissues had impaired function after low-dose bortezomib. FLNC pathogenic variants associate with a predisposition to arrhythmias, which can be modeled in iPSC-CMs. Reduction of filamin C prolonged field potential, a surrogate for action potential, and with bortezomib-induced proteasome inhibition, reduced filamin C led to greater arrhythmia potential and impaired function.

Acetaminophen induces mitochondrial apoptosis through proteasome dysfunctions

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

Mutant dominant-negative rhodopsin∆I256 causes protein aggregates degraded via ERAD and prevents normal rhodopsin from proper membrane trafficking

Dominant mutations in the rhodopsin gene (Rho) contribute to 25% of autosomal dominant retinitis pigmentosa (adRP), characterized by photoreceptor loss and progressive blindness. One such mutation, Rho∆I256, carries a 3-bp deletion, resulting in the loss of one of two isoleucines at codons 255 and 256. Our investigation, using recombinant expression in HEK293 and COS-7 cells, revealed that Rho∆I256, akin to the known adRP mutation RhoP23H, induces the formation of rhodopsin protein (RHO) aggregates at the perinuclear region. Co-expression of Rho∆I256 or RhoP23H with wild-type RhoWT, mimicking the heterozygous genotype of adRP patients, demonstrated the dominant-negative effect, as all isoforms were retained in perinuclear aggregates, impeding membrane trafficking. In retinal explants from WT mice, mislocalization of labeled adRP isoforms at the outer nuclear layer was observed. Further analysis revealed that RHO∆I256 aggregates are retained at the endoplasmic reticulum (ER), undergo ER-associated degradation (ERAD), and colocalize with the AAA-ATPase escort chaperone valosin-containing protein (VCP). These aggregates are polyubiquitinated and partially colocalized with the 20S proteasome subunit beta-5 (PSMB5). Pharmacological inhibition of proteasome- or VCP activity increased RHO∆I256 aggregate size. In summary, RHO∆I256 exhibits dominant pathogenicity by sequestering normal RHOWT in ER aggregates, preventing its membrane trafficking and following the ERAD degradation.

The Synergistic Effect of Reduced Graphene Oxide and Proteasome Inhibitor in the Induction of Apoptosis through Oxidative Stress in Breast Cancer Cell Lines.

Reduced graphene oxide (rGO) and a proteasome inhibitor (MG-132) are some of the most commonly used compounds in various biomedical applications. However, the mechanisms of rGO- and MG-132-induced cytotoxicity remain unclear. The aim of this study was to investigate the anticancer effect of rGO and MG-132 against ZR-75-1 and MDA-MB-231 breast cancer cell lines. The results demonstrated that rGO, MG-132 or a mix (rGO + MG-132) induced time- and dose-dependent cytotoxicity in ZR-75-1 and MDA-MB-231 cells. Apart from that, we found that treatment with rGO and MG-132 or the mix increased apoptosis, necrosis and induction of caspase-8 and caspase-9 activity in both breast cancer cell lines. Apoptosis and caspase activation were accompanied by changes in the ultrastructure of mitochondria in ZR-75-1 and MDA-MB-231 cells incubated with rGO. Additionally, in the analyzed cells, we observed the induction of oxidative stress, accompanied by increased apoptosis and cell necrosis. In conclusion, oxidative stress induces apoptosis in the tested cells. At the same time, both mitochondrial and receptor apoptosis pathways are activated. These studies provided new information on the molecular mechanisms of apoptosis in the ZR-75-1 and MDA-MB-231 breast cancer cell lines.

The Proteasome Inhibitor CEP-18770 Induces Cell Death in Medulloblastoma.

Medulloblastomas (MBs) represent the most prevalent malignant solid tumors in kids. The conventional treatment regimen for MBs includes surgical removal of the tumor, followed by radiation and chemotherapy. However, this approach is associated with significant morbidity and detrimental side effects. Consequently, there is a critical demand for more precise and less harmful treatments to enhance the quality of life for survivors. CEP-18770, a novel proteasome inhibitor that targets the 20S subunit, has emerged as a promising candidate, due to its anticancer activity in metastatic solid tumors and multiple myeloma, coupled with an acceptable safety profile. In this study, we aimed to assess the anticancer efficacy of CEP-18770 by employing a variety of MB patient-derived cells and cell lines. Our preclinical investigations revealed that CEP-18770 effectively inhibits proteasome activity and induces apoptosis in MBs cells. Furthermore, we discovered that CEP-18770 and cisplatin, a current component of MB therapy, exhibit a synergistic apoptotic effect. This paper shows that CEP-18770 holds potential as an adjunctive treatment for MB tumors, thereby paving the way for more targeted and less toxic therapeutic strategies.

Bortezomib Inhibits Open Configurations of the 20S Proteasome.

Bortezomib, a small dipeptide-like molecule, is a proteasome inhibitor used widely in the treatment of myeloma and lymphoma. This molecule reacts with threonine side chains near the center of the 20S proteasome and disrupts proteostasis by blocking enzymatic sites that are responsible for protein degradation. In this work, we use novel mass-spectrometry-based techniques to examine the influence of bortezomib on the structures and stabilities of the 20S core particle. These studies indicate that bortezomib binding dramatically favors compact 20S structures (in which the axial gate is closed) over larger structures (in which the axial gate is open)─suppressing gate opening by factors of at least ∼400 to 1300 over the temperature range that is studied. Thus, bortezomib may also restrict degradation in the 20S proteasome by preventing substrates from entering the catalytic pore. That bortezomib influences structures at the entrance region of the pore at such a long distance (∼65 to 75 Å) from its binding sites raises a number of interesting biophysical issues.

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.

Anti-Melanogenic Effects of Cnidium monnieri Extract via p38 Signaling-Mediated Proteasomal Degradation of Tyrosinase.

Cnidium monnieri fructus is widely used in traditional Oriental medicine for treating female genital disorders, male impotence, frigidity, and skin-related conditions in East Asia. However, the role of C. monnieri fructus extract (CMFE) in melanin synthesis is not well elucidated. This study aimed to investigate the anti-melanogenesis effect and mechanism of action of CMFE in α-MSH-stimulated B16F10 cells. Intracellular melanin content and tyrosinase activity were measured in α-MSH-stimulated B16F10 cells treated with various concentrations of CMFE (0.5-5 μg/mL). mRNA and protein levels of tyrosinase and MITF were evaluated using qRT-PCR and ting. CMFE's effect on the proteasomal degradation of tyrosinase was confirmed using a proteasomal degradation inhibitor, MG132. CMFE treatment activated p38, a protein associated with proteasomal degradation. Treatment with CMFE at up to 5 μg/mL showed no significant cytotoxicity. CMFE significantly reduced α-MSH-stimulated melanin production (43.29 ± 3.55% decrease, p < 0.05) and cellular tyrosinase activity (31.14 ± 3.15% decrease, p < 0.05). Although mRNA levels of MITF and tyrosinase increased, CMFE suppressed tyrosinase protein levels. The suppressive effect of CMFE on tyrosinase protein was blocked by MG132. CMFE inhibited melanogenesis by promoting the proteasome degradation of tyrosinase through p38 activation. These findings suggest that CMFE has the potential to be a natural whitening agent for inhibiting melanogenesis.

Multikinase inhibitors modulate non-constitutive proteasome expression in colorectal cancer cells.

Introduction: Proteasomes are multi-subunit protein complexes responsible for protein degradation in cells. Immunoproteasomes and intermediate proteasomes (together non-constitutive proteasomes) are specific forms of proteasomes frequently associated with immune response, antigen presentation, inflammation and stress. Expression of non-constitutive proteasome subunits has a prognostic value in several types of cancer. Thus, factors that modulate non-constitutive proteasome expression in tumors are of particular interest. Multikinase inhibitors (MKIs) demonstrate promising results in treatment of cancer. At the same time, their immunomodulatory properties and effects on non-constitutive proteasome expression in colorectal cancer cells are poorly investigated. Methods: Proteasome subunit expression in colorectal cancer was evaluated by bioinformatic analysis of available datasets. Two colorectal cancer cell lines, expressing fluorescent non-constitutive proteasomes were treated with multikinase inhibitors: regorafenib and sorafenib. The proteasome subunit expression was assessed by real-time PCR, Western blotting and flow cytometry. The proteasome activity was studied using proteasome activity-based probe and fluorescent substrates. Intracellular proteasome localization was revealed by confocal microscopy. Reactive oxygen species levels following treatment were determined in cells. Combined effect of proteasome inhibition and treatment with MKIs on viability of cells was estimated. Results: Expression of non-constitutive proteasomes is increased in BRAF-mutant colorectal tumors. Regorafenib and sorafenib stimulated the activity and synthesis of non-constitutive proteasomes in examined cell lines. MKIs induced oxidative stress and redistribution of proteasomes within cells. Sorafenib stimulated formation of cytoplasmic aggregates, containing proteolyticaly active non-constitutive proteasomes, while regorafenib had no such effect. MKIs caused no synergistic action when were combined with the proteasome inhibitor. Discussion: Obtained results indicate that MKIs might affect the crosstalk between cancer cells and immune cells via modulation of intracellular proteasome pool. Observed phenomenon should be considered when MKI-based therapy is applied.

FDA Approval Summary: Ciltacabtagene Autoleucel for Relapsed or Refractory Multiple Myeloma.

In February 2022, the U.S. Food and Drug Administration approved ciltacabtagene autoleucel, a chimeric antigen receptor (CAR) T cell therapy targeting the B-cell maturation antigen (BCMA), for adult patients with relapsed/refractory multiple myeloma (RRMM) after ≥4 lines of therapy including an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 monoclonal antibody. Approval was based on overall response rate (ORR), complete response (CR) rate and duration of response (DOR) in 97 adult patients in a single-arm, open-label, multicenter phase 2 trial (CARTITUDE-1 [NCT03548207]). Patients received a single infusion of ciltacabtagene autoleucel, preceded by lymphodepleting chemotherapy. Of the 97 patients evaluable, ORR was 97.9% (95% CI: 92.7, 99.7) with stringent CR rate of 78.4% (95% CI: 68.8, 86.1). After median follow-up of 18 months, median DOR was 21.8 months (95% CI: 21.8, not estimable [NE]) in responders (PR or better) and NE (95% CI: 21.8 months, NE) in patients who achieved stringent CR. Serious adverse reactions occurred in 55% of 97 patients evaluated for safety. Grade 3 or higher cytokine release syndrome and neurologic toxicities occurred in 5% and 11%, respectively, leading to a Risk Evaluation and Mitigation Strategy. Neurologic toxicities included immune effector cell associated neurologic syndrome (ICANS) typically seen with CAR-T products, Parkinsonism, peripheral neuropathy, cranial nerve palsies and Guillain-Barre Syndrome (GBS). One fatal case of hemophagocytic lymphohistiocytosis/macrophage activation syndrome occurred. Prolonged and recurrent grade 3 or 4 cytopenias occurred; a single patient required hematopoietic stem cell rescue.

A new mutation in the Parkinson's-related FBXO7 gene impairs mitochondrial and proteasomal function.

Around 10% of Parkinson's disease (PD) cases are associated with mutations in various genes, including FBXO7, which encodes the substrate-recognition component for the Skp1-Cullin-F-box (SCF) class of ubiquitin E3 ligases that target proteins for proteasomal degradation. In their recent study, Al Rawi etal. characterized a new mutation in FBXO7, L250P, in a pediatric patient. Their findings reveal that the L250P mutation abolishes Fbxo7 interaction with the proteasome regulator, proteasome inhibitor 31kD (PI31), affecting proteasomal activity and the ubiquitination of some of the ligase's targets. Furthermore, the authors show that this previously undescribed mutation impairs mitochondrial function and mitophagy, emphasizing the importance of mitochondrial and proteasomal dysfunction in PD pathogenesis.