Proteasome Inhibitor Bortezomib Research Articles

Comparative Analysis of Acquired Resistance to Bortezomib in Prostate Cancer Cells Using Proteomic and Bioinformatic Tools.

Chemotherapy is a potent tool against cancer, but drug resistance remains a major obstacle. To combat this, understanding the molecular mechanisms behind resistance in cancer cells and the protein expression changes driving these mechanisms is crucial. Targeting the Ubiquitin-Proteasome System (UPS) has proven effective in treating multiple myeloma and shows promise for solid tumours. Despite initial success with the proteasome inhibitor bortezomib, acquired resistance soon after treatment poses a significant challenge to its efficacy. In this study, we explored proteins potentially involved in acquired resistance to bortezomib using label-free nLC-MS/MS proteomic analysis. The investigation revealed 299 proteins with notable differences in expression levels in the bortezomib-resistant PC3 prostate cancer cell line. Using bioinformatics tools, we illustrated the top 10 gene ontology (GO) processes [e.g., translational initiation (p = 5.964E-10), CRD-mediated mRNA stabilisation (p = 1.636E-5), and hydrogen ion transmembrane transport (p = 6.46E-5)] and the top 20 KEGG [e.g., metabolic pathways (p = 7.601E-13), biosynthesis of amino acids (p = 3.834E-12), and chemical carcinogenesis-reactive oxygen species (p = 1.891E-4)] and REACTOME [e.g., metabolism (p = 4.182E-21), translation (p = 9.484E-18), and Nonsense-Mediated Decay (NMD) (p = 1.829E-8)] pathways in the PC3-resistant cells. We further refined our results by comparing them with globally validated TCGA datasets. We correlated the 299 proteins identified through proteomic analysis with tumour aggressiveness and resistance by comparing them with the TCGA nodal metastasis N0 vs. N1 datasets using the UALCAN portal and identified 37 proteins consistent with our results. We believe that a combination of bortezomib with chemotherapeutics targeting these proteins could be effective in overcoming the resistance developed against bortezomib.

The effective multiplicity of infection for HCMV depends on the activity of the cellular 20S proteasome.

Human cytomegalovirus (HCMV) is a betaherpesvirus capable of infecting numerous cell types and persisting throughout an infected individual's life. Disease usually occurs in individuals with compromised or underdeveloped immune systems. Several antivirals exist but have limitations relating to toxicity and resistance. HCMV replication involves upregulation of host proteasomal activities, which play important roles in the temporal stages of replication. Here, we defined the impact on replication kinetics of the proteasome inhibitor, bortezomib. We demonstrate that bortezomib significantly reduces levels of viral genomes and infectious virions produced from a population of cells. Inhibition reduced expression of viral proteins that are influenced by genome synthesis. When added prior to 24 hpi, we observe decreases in PCNA and Cdk1 while increases in p21 whose regulations contribute to efficient replication. This response synergized with an antiviral, maribavir. Since some replication occurred, we tested the hypothesis that a subset of infected cells might break through inhibition. Initially, we simulated bortezomib activities using a mechanistic computational model of late-lytic replication. Upon reducing multiplicity of infection (MOI) in silico, we observed near-identical simulated results compared to experimental data. Next, we analyzed replication using live-cell imaging. This revealed treated cultures do contain a population of cells with fully developed late-stage cytoplasmic assembly compartments but at significantly lower numbers. We refer to this as the effective MOI. Overall, our studies support a hypothesis in which 20S proteasome inhibition disrupts HCMV replication by reducing the MOI to an effective MOI, defined by a fraction of infected cells capable of progressing to fulminant infection.IMPORTANCEHuman cytomegalovirus (HCMV) infection and reactivation continues to contribute to morbidity and mortality around the world. Antiviral compounds are available but have limitations. Here, we have defined the impact of the proteasome inhibitor bortezomib on HCMV replication. Proteasomal activities play a critical role in temporal changes required for replication. We demonstrate that disrupting these activities inhibits viral replication while likely supporting increased antiviral activity of the anti-HCMV agent, maribavir. Using a combination of live-cell imaging and computational tools, we discover that a subset of infected cells progresses to fulminant infection, which we define as the effective multiplicity of infection, and this subset would otherwise be missed when analyzing the average of the population.

Pseudokinase TRIB3 stabilizes SSRP1 via USP10-mediated deubiquitination to promote multiple myeloma progression.

Multiple myeloma (MM), the world's second most common hematologic malignancy, poses considerable clinical challenges due to its aggressive progression and resistance to therapy. Addressing these challenges requires a detailed understanding of the mechanisms driving MM initiation, progression, and therapeutic resistance. This study identifies the pseudokinase tribble homolog 3 (TRIB3) as a high-risk factor that promotes MM malignancy in vitro and in vivo. Mechanistically, TRIB3 directly interacts with structure-specific recognition protein 1 (SSRP1) and ubiquitin-specific peptidase 10 (USP10), facilitating the formation of a TRIB3/USP10/SSRP1 ternary complex. This complex stabilizes SSRP1 via USP10-mediated deubiquitination, thereby driving MM cell proliferation. Furthermore, a stapled peptide, SP-A, was developed, which effectively disrupts the TRIB3/USP10/SSRP1 complex, leading to a decrease in SSRP1 levels by inhibiting its stabilization through USP10. Notably, SP-A exhibits strong synergistic effects when combined with the proteasome inhibitor bortezomib. Given the critical role of the TRIB3/USP10/SSRP1 complex in MM pathophysiology, it represents a promising therapeutic target for MM treatment. In MM cells, TRIB3, USP10 and SSRP1 form a ternary complex and TRIB3 enhances the deubiquitinating effect of USP10 on SSRP1, leading to malignant progression of MM. In the case of drug intervention, SP-A attenuates the binding of SSRP1 and USP10 by inhibiting protein interactions between TRIB3 and SSRP1 and promoted SSRP1 protein degradation, leading to significant inhibition of MM development. Visual abstract created with Biorender.

CTNI-36. THE FEASIBILITY OF USING BORTEZOMIB WITH CHEMOTHERAPY IN ATYPICAL TERATOID/RHABDOID TUMORS

Abstract Atypical teratoid/rhabdoid tumors (ATRTs) are highly aggressive pediatric brain tumors with sensitivity to proteasome inhibitors in preclinical models. We evaluated the feasibility of combining the proteasome inhibitor bortezomib with chemotherapy. Patients aged 0-20 years with newly diagnosed ATRT were enrolled from January 2022 through December 2023. A modified Medical University of Vienna (MUV)-ATRT regimen was used. They were treated with bortezomib of 1.3 mg/m2/dose given intravenously or subcutaneously twice a week for 2 weeks concurrently with 6 cycles of chemotherapy and 2 additional cycles after high-dose chemotherapy. Radiation therapy was given prior to or at the end of chemotherapy. A total of 36 chemotherapy cycles with bortezomib in 6 patients were evaluated. The primary endpoint was grade 3 or higher non-hematologic toxicities. Numbers of cycles with grade 3+ toxicities included: AST/ALT elevation (1), hypokalemia (2), peripheral neuropathy (1), subdural hemorrhage (2), vomiting (2), oral mucositis (3), lung infection (2), urinary tract infection (8), sepsis (3), febrile neutropenia (20). No grade 3+ toxicities were considered bortezomib-related. Three patients completed 8 cycles of bortezomib treatment; 2 patients discontinued the study due to progressive disease after 2 and 4 cycles respectively; 1 patient completed 6 cycles of bortezomib and died of septic shock in complete remission after high-dose chemotherapy. Two patients had a surgical complete resection. Three patients were evaluable for response after bortezomib: 1 partial response and 2 stable disease. Two patients had progression-free survival for 16+ and 22+ months after diagnosis, respectively. Among the 3 patients with progressive disease, 2 had metastatic relapse and 1 had primary and metastatic relapse. There were 4 deaths due to metastatic PD (n=2), septic shock after high-dose chemotherapy (n=1), and septic shock after 2nd line treatment for PD (n=1). We conclude that adding bortezomib to standard and high-dose chemotherapy of ATRT was feasible with the occurrence of grade 3/4 toxicities no more than what was expected with chemotherapy alone. Metastatic relapse remains the major challenge of ATRT treatment.

Visualization of Bortezomib Induced Peripheral Neuropathy By Dorsal Root Ganglion MRI in Patients with Multiple Myeloma

Background: Whereas most treatments in multiple myeloma (MM) are stopped due to their inefficiency over time and the development of drug resistance, the use of the proteasome inhibitor bortezomib (BTZ) is mainly limited by its neurotoxic effects and the induction of BTZ induced neuropathy (BIPN). Of particular pathophysiological importance is the dorsal root ganglion (DRG), which plays a central role in the development of BIPN (Argyriou et al. Blood 2008). As early BIPN diagnosis and treatment adjustment is critical, we here investigated the predictive potential of DRG MRI and measured the DRG T2 signal intensity as a biomarker of inflammation in BTZ treated MM patients. Methods: We recruited a total of 112 MM patients receiving BTZ either currently or in the past. Of these, 92 (82 %) had BIPN, which was painful in 37% (n=41) and mild and only detectable by sophisticated clinical-neurological diagnostics in 52% of patients (n = 58, severity Grade 1 with/without pain). DRG MRI was performed in a subset of 54 patients, including 45 of them with detectable BIPN (all grades), and additionally in 12 healthy controls. Using high-resolution three-dimensional T2-weighted fast spin-echo DRG MRI, we evaluated the lumbosacral DRG Th12-S2 bilaterally in all patients. Comparative analyses were performed using one-way ANOVA with Bonferroni correction. Pearson's Rho was used for the correlation analyses. Results: Analysis revealed a significant increase in DRG T2 signal intensity in MM patients with BIPN compared to MM patients without BIPN (p= 0.005) and healthy controls (p= 0.003). Furthermore, an inverse correlation was found between DRG T2 signal intensity and intraepidermal nerve fiber density (IENFD) (p= 0.035). The mean DRG volume on L5+S1 level (in mm³) did not differ significantly between the groups, however, IENFD was significantly decreased in BIPN MM patients (n=26; 3.41 fibers/mm) compared to the healthy controls (n=12, 5.28 fibers/mm; p = 0.031), MM patients without BIPN showed no difference in IENFD (4.45 fibers/mm) compared to healthy controls. Conclusion: DRG T2 signal intensity is a surrogate marker of inflammation, and our observations suggest that inflammatory changes at the DRG level underlie BIPN in MM patients. Our imaging holds potential to be used as a non-invasive biomarker for early BIPN detection and to define patients at risk. This is an ongoing study, and imaging from the full cohort and from additional longitudinal assessment will be presented at the meeting.

The effective multiplicity of infection for HCMV depends on activity of the cellular 20S proteasome.

HCMV infection and reactivation continues to contribute to morbidity and mortality around the world. Antiviral compounds are available but have limitations. Here, we have defined the impact of the proteasome inhibitor bortezomib on HCMV replication. Proteasomal activities play a critical role in temporal changes required for replication. We demonstrate that disrupting these activities inhibits viral replication while likely supporting increased antiviral activity of the anti-HCMV agent, maribavir. Using a combination of live cell imaging and computational tools, we discover that a subset of infected cells progresses to fulminant infection which we define as the effective MOI, and this subset would otherwise be missed when analyzing the average of the population.

Combination screen in multi-cell type tumor spheroids reveals interaction between aryl hydrocarbon receptor antagonists and E1 ubiquitin-activating enzyme inhibitor

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates genes of drug transporters and metabolic enzymes to detoxify small molecule xenobiotics. It has a complex role in cancer biology, influencing both the progression and suppression of tumors by modulating malignant properties of tumor cells and anti-tumor immunity, depending on the specific tumor type and developmental stage. This has led to the discovery and development of selective AhR modulators, including BAY 2416964 which is currently in clinical trials. To identify small molecule anticancer agents that might be combined with AhR antagonists for cancer therapy, a high-throughput combination screen was performed using multi-cell type tumor spheroids grown from malignant cells, endothelial cells, and mesenchymal stem cells. The AhR selective antagonists BAY 2416964, GNF351, and CH-223191 were tested individually and in combination with twenty-five small molecule anticancer agents. As single agents, BAY 2416964 and CH-223191 showed minimal activity, whereas GNF351 reduced the viability of some spheroid models at concentrations greater than 1 µM. The activity of most combinations aligned well with the single agent activity of the combined agent, without apparent contributions from the AhR antagonist. All three AhR antagonists sensitized tumor spheroids to TAK-243, an E1 ubiquitin-activating enzyme inhibitor. These combinations were active in spheroids containing bladder, breast, ovary, kidney, pancreas, colon, and lung tumor cell lines. The AhR antagonists also potentiated pevonedistat, a selective inhibitor of the NEDD8-activating enzyme E1 regulatory subunit, in several tumor spheroid models. In contrast, the AhR antagonists did not enhance the cytotoxicity of the proteasome inhibitor bortezomib.

An automated positive selection screen in yeast provides support for boron-containing compounds as inhibitors of SARS-CoV-2 main protease.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus continues to cause severe disease and deaths in many parts of the world, despite massive vaccination efforts. Antiviral drugs to curb an ongoing infection remain a priority. The virus-encoded 3C-like main protease (MPro; nsp5) is seen as a promising target. Here, with a positive selection genetic system engineered in Saccharomyces cerevisiae using cleavage and release of MazF toxin as an indicator, we screened in a robotized setup small molecule libraries comprising ~2,500 compounds for MPro inhibitors. We detected eight compounds as effective against MPro expressed in yeast, five of which are characterized proteasome inhibitors. Molecular docking indicates that most of these bind covalently to the MPro catalytically active cysteine. Compounds were confirmed as MPro inhibitors in an in vitro enzymatic assay. Among those were three previously only predicted in silico; the boron-containing proteasome inhibitors bortezomib, delanzomib, and ixazomib. Importantly, we establish reaction conditions in vitro preserving the MPro-inhibitory activity of the boron-containing drugs. These differ from the standard conditions, which may explain why boron compounds have gone undetected in screens based on enzymatic in vitro assays. Our screening system is robust and can find inhibitors of a specific protease that are biostable, able to penetrate a cell membrane, and are not generally toxic. As a cellular assay, it can detect inhibitors that fail in a screen based on an in vitro enzymatic assay using standardized conditions, and now give support for boron compounds as MPro inhibitors. This method can also be adapted for other viral proteases.IMPORTANCEThe coronavirus disease 2019 (COVID-19) pandemic triggered the realization that we need flexible approaches to find treatments for emerging viral threats. We implemented a genetically engineered platform in yeast to detect inhibitors of the virus's main protease (MPro), a promising target to curb severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Screening molecule libraries, we identified candidate inhibitors and verified them in a biochemical assay. Moreover, the system detected boron-containing molecules as MPro inhibitors. Those were previously predicted computationally but never shown effective in a biochemical assay. Here, we demonstrate that they require a non-standard reaction buffer to function as MPro inhibitors. Hence, our cell-based method detects protease inhibitors missed by other approaches and provides support for the boron-containing molecules. We have thus demonstrated that our platform can screen large numbers of chemicals to find potential inhibitors of a viral protease. Importantly, the platform can be modified to detect protease targets from other emerging viruses.

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

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

Association of KRAS Mutation and Gene Pathways in Colorectal Carcinoma: A Transcriptome- and Methylome-Wide Study and Potential Implications for Therapy.

Kirsten Rat Sarcoma (KRAS) is the most commonly mutated oncogene in colorectal carcinoma (CRC). We have previously reported the interactions between microsatellite instability (MSI), DNA promoter methylation, and gene expression. In this study, we looked for associations between KRAS mutation, gene expression, and methylation that may help with precision medicine. Genome-wide gene expression and DNA methylation were done in paired CRC tumor and surrounding healthy tissues. The results suggested that (a) the magnitude of dysregulation of many major gene pathways in CRC was significantly greater in patients with the KRAS mutation, (b) the up- and down-regulation of these dysregulated gene pathways could be correlated with the corresponding hypo- and hyper-methylation, and (c) the up-regulation of CDKN2A was more pronounced in tumors with the KRAS mutation. A recent cell line study showed that there were higher CDKN2A levels in 5-FU-resistant CRC cells and that these could be down-regulated by Villosol. Our findings suggest the possibility of a better response to anti-CDKN2A therapy with Villosol in KRAS-mutant CRC. Also, the more marked up-regulation of genes in the proteasome pathway in CRC tissue, especially with the KRAS mutation and MSI, may suggest a potential role of a proteasome inhibitor (bortezomib, carfilzomib, or ixazomib) in selected CRC patients if necessary.

Mantle Cell Lymphoma- A Rare Occurrence: Case Report

Mantle Cell Lymphoma (MCL) is a relatively uncommon yet distinct type of malignant lymphoma whose clinical and pathological characterization has been limited by the small numbers of cases published to date. It comprises 3-7% of all Hodgkin’s lymphoma cases, with a median diagnosis age of 68 years. Based on immunophenotypic and molecular data, MCL is a neoplasm composed of cells resembling those residing in follicular mantle zones. Although MCL usually presents as advanced disease some patients may present with more limited (stages I-I) disease. We present the case of a 41-year-old male who exhibited generalized lymphadenopathy and hepatosplenomegaly. Peripheral smear showed absolute lymphocytosis and the bone marrow biopsy and flow cytometry identified the condition as mantle cell lymphoma. The patient’s management required a multidisciplinary approach, incorporating haematological, molecular, and genetic evaluations. Treatment included hyper-CVAD chemotherapy. Proteasome inhibitors (Bortezomib), mTOR inhibitors (Temsirolimus), and immunomodulatory drugs (Lenalidomide) have recently been added to the treatment options in MCL.This case underscores the significance of comprehensive evaluation and customized therapeutic strategies and re looking an old diagnosis in managing complex haematological disorders.

Actinomycin D and bortezomib disrupt protein homeostasis in Wilms tumor.

Wilms tumor is the most common kidney cancer in children, and diffusely anaplastic Wilms tumor is the most chemoresistant histological subtype. Here we explore how Wilms tumor cells evade the common chemotherapeutic drug actinomycin D, which inhibits ribosomal RNA biogenesis. Using ribosome profiling, protein arrays, and a genome-wide knockout screen, we describe how actinomycin D disrupts protein homeostasis and blocks cell cycle progression. We found that, when ribosomal capacity is limited by actinomycin D treatment, anaplastic Wilms tumor cells preferentially translate proteasome components and upregulate proteasome activity. Furthermore, the proteasome inhibitor bortezomib sensitizes cells to actinomycin D treatment by inducing apoptosis both in vitro and in vivo. Lastly, we show that increased levels of proteasome components are associated with anaplastic histology and with worse prognosis in non-anaplastic Wilms tumor. In sum, maintaining protein homeostasis is critical for Wilms tumor proliferation, and it can be therapeutically disrupted by blocking protein synthesis or turnover.

CP-09. HTDS ON NOVEL CELL LINES IDENTIFIED BETA-CATENIN INHIBITOR TEGATRABETAN AND PROTEASOME INHIBITOR BORTEZOMIB AS TWO NOVEL POTENTIAL AGENTS AGAINST ADAMANTINOMATOUS CRANIOPHARYNGIOMA

Abstract BACKGROUND Adamantinomatous craniopharyngiomas (ACPs) are rare intracranial suprasellar tumors, primarily affecting pediatric population. ACPs are histologically benign but their location makes them highly debilitating and clinically challenging with no standard of care available. Mutations in exon 3 of the CTNNB1 gene, codifying for β-catenin, are pathognomonic hallmark of ACPs. Although several cell lines and patient-derived models have been sporadically described, no reproducible pre-clinical models are available for these tumors. METHODS Eight ACP patients underwent gross total resections and we were able to generate novel cell lines from four of them. The lines, named CBTP-77, CBTP-97, CBTP-101 and CBTP-119, grow consistently and have been passaged more than 15 times. Immunocytochemistry and RNA sequencing were performed, highlighting inter- and intra-line heterogeneity, typical of ACP tumors. To identify new therapeutic targets, High Throughput Drug Screening (HTDS) was performed on two lines. RESULTS β-catenin inhibitor tegatrabetan, FGFR inhibitor erdafitinib, and the proteasome inhibitor bortezomib resulted as top effective agents. In vitro validation of the three agents confirmed strong cytotoxicity and on target activity shown by downregulation of the WNT and PI3K/AKT/mTOR pathways. The limited CNS permeability of these agents, makes them great candidates for local intra-cystic delivery, as described for other therapeutic options for ACP. CONCLUSIONS Our study represents the first large scale screening for new therapeutic agents for ACP, highlighting the importance of establishing consistent cell lines and preclinical models for these rare and devastating tumors.

Abstract A012: Targeting proteasome vulnerabilities for the treatment of monosomy 7 associated blood disorders

Abstract Monosomy 7 is among the most frequent cytogenetic abnormalities in hematological disorders and is associated with short survival and drug resistance. Despite its high prevalence and detrimental impact, the therapeutic vulnerabilities underlying monosomy 7-associated blood disorders remain largely elusive, impeding progress toward improved patient care. The homeostatic cellular requirement for a normal dosage of essential genes creates an opportunity to target vulnerabilities that arise due to reduced levels of proteins encoded by a haploinsufficient essential gene. Briefly, the loss of one copy of a dosage-sensitive essential gene (gene X), in combination with the inhibition of itself or a related gene (gene Y), or an associated pathway results in lethal consequences for cells. The remarkable and selective clinical efficacy of lenalidomide for the treatment of del(5q) MDS has demonstrated how allelic haploinsufficiency underlies the sensitivity to this drug by synthetic lethality. Differential expression analysis of gene and protein expression in primary AML samples with monosomy 7 revealed significant downregulation of multiple proteasome pathway members at the protein level, but not at the RNA level. Primary AML samples with -7/del(7q) exhibited increased sensitivity (low IC50) to the proteasome inhibitor bortezomib, as evidenced by two independent ex vivo drug screening cohorts (the Beat AML and the FIMM study). Chromosome 7 harbors four proteasome subunits, PSMA2, PSMC2, PSMG3, and SEM1. We performed gene expression, protein expression, copy number analysis, and individual gene knockout experiments. The results have revealed PSMA2 to be a haploinsufficient essential gene on chromosome 7. PSMA2 knockout confers leukemia a growth disadvantage for multiple AML cell clines in both TP53 wild-type and knockout backgrounds. We generated PSMA2 isogenic hemizygous deletion and diploid single-cell clones. PSMA2 hemizygous deletion cells exhibited approximately half the protein expression compared to diploid controls, confirming that PSMA2 is a haploinsufficient gene. PSMA2hemizygous deletion single-cell clones showed significantly enhanced sensitivity to all three evaluated proteasome inhibitors (bortezomib, ixazomib, and carfilzomib), aligning with the sensitivity observed in primary -7/del(7q) leukemia samples. PSMA2 hemizygous deletion cell clones displayed increased p38 and decreased pERK levels upon treatment with proteasome inhibitors, potentially contributing to their increased sensitivity to proteasome inhibitors. Proteomics analysis and in vivo validation is ongoing. As such, we have identified haploinsufficient essential gene PSMA2 mediated proteasome pathway vulnerability in monosomy 7 associated leukemia and further showed that proteasome inhibitors as promising therapeutic approaches for treating hematological disorders associated with monosomy 7. Citation Format: Haijiao Zhang, Basil Allen, Daniel Bottomly, Peter Ryabinin, Schannon K. Targeting proteasome vulnerabilities for the treatment of monosomy 7 associated blood disorders [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr A012.

Toll-like receptor signaling in multiple myeloma cells promotes the expression of pro-survival genes B-cell lymphoma 2 and MYC and modulates the expression of B-cell maturation antigen.

Infections are common in plasma cell cancer multiple myeloma (MM) due to disease-related immune deficiencies and cancer treatment. Myeloma cells express Toll-like receptors (TLRs), and TLR activation has been shown to induce proliferative and pro-survival signals in cancer cells. MM is a complex and heterogeneous disease, and expression levels of TLRs as well as downstream signaling components are likely to differ between patients. Here, we show that in a large cohort of patients, TLR1, TLR4, TLR6, TLR9, and TLR10 are the most highly expressed in primary CD138+ cells. Using an MM cell line expressing TLR4 and TLR9 as a model, we demonstrate that TLR4 and TLR9 activation promoted the expression of well-established pro-survival and oncogenes in MM such as MYC, IRF4, NFKB, and BCL2. TLR4 and TLR9 activation inhibited the efficacy of proteasome inhibitors bortezomib and carfilzomib, drugs used in the treatment of MM. Inhibiting the autophagosome-lysosome protein degradation pathway by hydroxychloroquine (HCQ) diminished the protective effect of TLR activation on proteasome inhibitor-induced cytotoxicity. We also found that TLR signaling downregulated the expression of TNFRSF17, the gene encoding for B-cell maturation antigen (BCMA). MYC, BCL2, and BCL2L1 were upregulated in approximately 50% of primary cells, while the response to TLR signaling in terms of TNFRSF17 expression was dichotomous, as an equal fraction of patients showed upregulation and downregulation of the gene. While proteasome inhibitors are part of first-line MM treatment, several of the new anti-MM immune therapeutic drugs target BCMA. Thus, TLR activation may render MM cells less responsive to commonly used anti-myeloma drugs.

The efficacy of Bortezomib-based regimens on survival state in newly diagnosed multiple myeloma patients.

The prognosis of patients with multiple myeloma (MM) has significantly improved over the past ten years because of several innovative treatments, including the proteasome inhibitor Bortezomib and immunomodulatory drugs (IMiDs) like Thalidomide and Lenalidomide. The present study aimed to determine the effectiveness of Bortezomib-based regimens on survival state of MM patients. This retrospective study included 204 newly diagnosed MM patients who were registered at Nanakali Hospital for Blood Diseases and Cancer, Erbil- Iraq, between April 2008 and April 2022. The patients were split into two primary groups: those receiving treatment with Bortezomib and those not. Clinical and laboratory data, treatment type, responsiveness to induction therapy, and survival results were examined in the enrolled patients' medical records. The mean patient age was 60 years, males constituted 55.8% of the included patients. At the time of diagnosis, 98 individuals (48%) had stage 3 illness. Except for the LDH, which was noticeably higher in the non-Bortezomib group, the patients laboratory results did not substantially change between the Bortezomib and non-Bortezomib groups (p = 0.001). In patients treated with Bortezomib, the complete response (CR) rate following induction was substantially greater (35.2%) than in those treated without Bortezomib (9.1%). Compared to the non-Bortezomib group, the median survival time of the Bortezomib group was considerably greater (p < 0.001). Bortezomib has a significant role in inducing a CR before bone marrow (BM) transplantation, and it has a significant role in the survival outcome in MM.

Functional Investigation of IGF1R Mutations in Multiple Myeloma.

High expression of the receptor tyrosine kinase (RTK) insulin-like growth factor-1 receptor (IGF1R) and RTK mutations are associated with high-risk/worse prognosis in multiple myeloma (MM). Combining the pIGF1R/pINSR inhibitor linsitinib with the proteasome inhibitor (PI) bortezomib seemed promising in a clinical trial, but IGF1R expression was not associated with therapy response. Because the oncogenic impact of IGF1R mutations is so far unknown, we investigated the functional impact of IGF1R mutations on survival signaling, viability/proliferation and survival response to therapy. We transfected four human myeloma cell lines (HMCLs) with IGF1RWT, IGF1RD1146N and IGF1RN1129S (Sleeping Beauty), generated CRISPR-Cas9 IGF1R knockouts in the HMCLs U-266 (IGF1RWT) and L-363 (IGF1RD1146N) and tested the anti-MM activity of linsitinib alone and in combination with the second-generation PI carfilzomib in seven HMCLs. IGF1R knockout entailed reduced proliferation. Upon IGF1R overexpression, survival signaling was moderately increased in all HCMLs and slightly affected by IGF1RN1129S in one HMCL, whereby the viability remained unaffected. Expression of IGF1RD1146N reduced pIGF1R-Y1135, especially under serum reduction, but did not impact downstream signaling. Linsitinib and carfilzomib showed enhanced anti-myeloma activity in six out of seven HMCL irrespective of the IGF1R mutation status. In conclusion, IGF1R mutations can impact IGF1R activation and/or downstream signaling, and a combination of linsitinib with carfilzomib might be a suitable therapeutic approach for MM patients potentially responsive to IGF1R blockade.

Association of posterior reversible encephalopathy syndrome with proteasome inhibitors approved for multiple myeloma: Analysis of FAERS database.

e19515 Background: Proteasome inhibitors (PI) are a class of drugs that are used in the treatment of Multiple Myeloma. There are currently three PIs (Bortezomib, Carfilzomib, and Ixazomib) approved by FDA for this indication. Peripheral neuropathy has been described as one of their most common side effects but the association with another life-threatening neurological disorder, Posterior Reversible Encephalopathy Syndrome (PRES), remains poorly understood. Methods: We conducted a retrospective pharmacovigilance study using the FDA Adverse Event Reporting System database to analyze the risk of PRES associated with various Proteasome Inhibitors. We employed disproportionality signal analysis and calculated the reporting odds ratio with a 95% confidence interval. Results: A total of 79,450 adverse events were found within the FAERS database that were associated with the three FDA approved PIs. PRES accounted for 274 cases, of which 165 cases were in females and 71 cases in males. Majority of patients were adults, with 119 cases between 18-64 years of age, 88 cases above 65 years, and 50 cases with age not specified. Death was reported in 70 cases while 74 cases were marked as having life threatening illness, and 152 cases needed hospitalization. Bortezomib accounted for most cases (202 cases, ROR 6.03, 95% CI 5.3-7.1), followed by Carfilzomib (68 cases, ROR 7.2, 95% CI 5.7-9.1), and Ixazomib (9 cases, ROR 0.99, 95% CI 0.5-1.7). Conclusions: The study helps to shed light on the incidence, and hospital outcomes of PRES associated with various proteasome inhibitors. Significant safety signals were found for Bortezomib, and Carfilzomib. Females were almost 2.5 times more likely to develop PRES compared to males. These findings highlight the importance of keeping a high index of suspicion for PRES while evaluating patients on PIs who present with concerning neurological symptoms.

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.

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.