Bortezomib-resistant Multiple Myeloma Cells Research Articles

Targeting PARP14 with lomitapide suppresses drug resistance through the activation of DRP1-induced mitophagy in multiple myeloma

Multiple myeloma (MM) is a hematological malignancy that remains incurable, primarily due to the high likelihood of relapse or development of resistance to current treatments. To explore and discover new medications capable of overcoming drug resistance in MM, we conducted cell viability inhibition screens of 1504 FDA-approved drugs. Lomitapide, a cholesterol-lowering agent, was found to exhibit effective inhibition on bortezomib-resistant MM cells in vitro and in vivo. Our data also indicated that lomitapide decreases the permeability of the mitochondrial outer membrane and induces mitochondrial dysfunction in MM cells. Next, lomitapide treatment upregulated DRP1 and PINK1 expression levels, coupled with the mitochondrial translocation of Parkin, leading to MM cell mitophagy. Excessive mitophagy caused mitochondrial damage and dysfunction induced by lomitapide. Meanwhile, PARP14 was identified as a direct target of lomitapide by SPR-HPLC-MS, and we showed that DRP1-induced mitophagy was crucial in the anti-MM activity mediated by PARP14. Furthermore, PARP14 is overexpressed in MM patients, implying that it is a novel therapeutic target in MM. Collectively, our results demonstrate that DRP1-mediated mitophagy induced by PARP14 may be the cause for mitochondrial dysfunction and damage in response to lomitapide treatment.

Abstract 4670: KS18, an Mcl-1 inhibitor, triggers cell death and enhances the therapeutic efficacy of venetoclax in bortezomib-resistant multiple myeloma cells

Abstract A critical clinical challenge in the management of multiple myeloma (MM) is the development of both innate and acquired resistance to the treatment with bortezomib. Our prior research showed that the overexpression of the anti-apoptotic Bcl-2 family protein Mcl-1 can result in resistance to the chemotherapy drugs bortezomib and venetoclax. In order to overcome the issues posed by resistance, this study investigates the possibility of a small chemical called KS18, a novel Mcl-1 inhibitor. KS18 outperforms other Mcl-1 inhibitors such as S63845, VU661013, and AZD5991, according to the findings of our research, which shows that it is extraordinarily effective against MM cells that have become resistant to bortezomib. We establish the selectivity of KS18 through tests employing Mcl-1 knock-down (KD), and we find that it is both effective and efficient. In addition, we used immunoprecipitation (IP) and protein-protein interaction analysis (PPIs) to investigate the dynamic connections that exist between Mcl-1 and pro-apoptotic proteins. The KS18 therapy exhibits an outstanding ability to cause complete apoptosis, as seen by the remarkable 88.8% apoptosis rate recorded in MM patient samples. Not only does KS18 restore apoptosis in bortezomib-resistant MM cells, but it also synergizes with venetoclax to enhance the apoptotic response. This is an important finding. It has been demonstrated through both in vitro and in vivo research that KS18 can re-sensitize MM cells to the effects of bortezomib, which represents a potential step forward in the treatment of the disease. In bortezomib-resistant MM cells, treatment with KS18 led to a remarkable 92% reduction in colony formation compared to untreated controls. In vivo experiments that were performed on mice models that were resistant to bortezomib provide additional evidence that KS18 is effective. The extraordinary reduction in tumor weight of 55% that occurred as a direct result of treatment with KS18 at a dose of 1 mg/kg for a period of 15 days exemplifies the powerful anti-resistance characteristics of this compound. These intriguing findings highlight the potential value of KS18 as an adjunct to therapies aimed at overcoming bortezomib resistance in MM and other associated cancers. Bortezomib-resistant malignancies provide a challenge for patients, but additional research into the clinical value of KS18 holds the potential to improve treatment outcomes and broaden the range of therapeutic alternatives available to these patients. Citation Format: Omar S. Al Odat, Osama Aloudat, Emily Nelson, Tulin Budak-Alpogan, Subash Jonnalagadda, Yong Chen, Manoj Pandey. KS18, an Mcl-1 inhibitor, triggers cell death and enhances the therapeutic efficacy of venetoclax in bortezomib-resistant multiple myeloma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4670.

N6-methyladenosine-modified circ_0000337 sustains bortezomib resistance in multiple myeloma by regulating DNA repair.

Studies have shown that bortezomib resistance in multiple myeloma (MM) is mediated by the abnormalities of various molecules and microenvironments. Exploring these resistance mechanisms will improve the therapeutic efficacy of bortezomib. In this study, bone marrow tissues from three patients with MM, both sensitive and resistant to bortezomib, were collected for circRNA high-throughput sequencing analysis. The relationship between circ_0000337, miR-98-5p, and target gene DNA2 was analyzed by luciferase detection and verified by RT-qPCR. We first found that circ_0000337 was significantly upregulated in bortezomib-resistant MM tissues and cells, and overexpression of circ_0000337 could promote bortezomib resistance in MM cells. circ_0000337 may act as a miR-98-5p sponge to upregulate DNA2 expression, regulate DNA damage repair, and induce bortezomib resistance. Furthermore, it was determined that the increased circ_0000337 level in bortezomib-resistant cells was due to an increased N6-methyladenosine (m6A) level, resulting in enhanced RNA stability. In conclusion, the m6A level of circ_0000337 and its regulation may be a new and potential therapeutic target for overcoming bortezomib resistance in MM.

Identification of COQ2 as a regulator of proliferation and lipid peroxidation through genome-scale CRISPR-Cas9 screening in myeloma cells.

Multiple myeloma (MM) is the second most common malignant haematological disease with a poor prognosis. The limit therapeutic progress has been made in MM patients with cancer relapse, necessitating deeper research into the molecular mechanisms underlying its occurrence and development. A genome-wide CRISPR-Cas9 loss-of-function screening was utilized to identify potential therapeutic targets in our research. We revealed that COQ2 plays a crucial role in regulating MM cell proliferation and lipid peroxidation (LPO). Knockout of COQ2 inhibited cell proliferation, induced cell cycle arrest and reduced tumour growth invivo. Mechanistically, COQ2 promoted the activation of the MEK/ERK cascade, which in turn stabilized and activated MYC protein. Moreover, we found that COQ2-deficient MM cells increased sensitivity to the LPO activator, RSL3. Using an inhibitor targeting COQ2 by 4-CBA enhanced the sensitivity to RSL3 in primary CD138+ myeloma cells and in a xenograft mouse model. Nevertheless, co-treatment of 4-CBA and RSL3 induced cell death in bortezomib-resistant MM cells. Together, our findings suggest that COQ2 promotes cell proliferation and tumour growth through the activation of the MEK/ERK/MYC axis and targeting COQ2 could enhance the sensitivity to ferroptosis in MM cells, which may be a promising therapeutic strategy for the treatment of MM patients.

Drug Resistance Can be Overcome in Multiple Myeloma and Acute Myeloid Leukemia By Targeting Mcl-1 with the Small Chemical KS18

Drug resistance and patient recurrence are still key clinical difficulties in multiple myeloma (MM) treatment, despite the tremendous improvements provided by bortezomib therapy. In many cancers, Mcl-1, a member of the Bcl-2 protein family, helps keep cells alive by preventing their natural death process, apoptosis. The anti-cancer therapeutic promise of Mcl-1 inhibitors is highlighted by the fact that Mcl-1 overexpression increases carcinogenesis and medication resistance. Here, we provide KS18, a powerful pyoluteorin derivative with excellent effectiveness towards Mcl-1-dependent cancer cells, to address this unmet therapeutic need. Based on our results, we conclude that KS18 causes apoptosis in cancer cells through activating the mitochondrial outer membrane permeabilization (MOMP) pathway, with the participation of Bak and Bax, in particular in MM and acute myeloid leukemia (AML). With IC 50 values below 1.5µM, KS18 demonstrated efficacy against bortezomib-resistant MM cells, outperforming other Mcl-1 inhibitors in clinical trials such as S63845, VU661013, and AZD5991. Total apoptosis in MM patient samples treated with KS18 was an impressive 88.8 percent. After four weeks of treatment with a single tolerable dose each week, a model of bortezomib-resistant MM showed considerable tumor shrinkage, demonstrating the powerful anti-tumor efficacy of KS18. According to these results, KS18 may be able to overcome resistance by concentrating on Mcl-1. These encouraging findings have prompted the development of many models of drug-resistant MM and AML for in vivo evaluation of this potential chemical.

Synergistic Effects of Type I PRMT1 and Type II PRMT5 Inhibitors Against Multiple Myeloma

Multiple myeloma (MM) is a plasma cell malignancy characterized by the extensive expansion of monoclonal aberrant plasma cells in the bone marrow and the second most prevalent hematological malignancies worldwide. Despite the promising outcomes of advanced therapies, relapsed/refractory (RR) diseases remain incurable, highlighting an unmet clinical need to identify novel therapeutic targets. An emerging field of investigation is the role of aberrant post-translational modifications in multiple myeloma pathology. Arginine methylation is one of the most predominant post-translational modifications in cells, catalyzed by protein arginine methyltransferases (PRMTs) that plays a crucial role in multiple cellular processes. Type I PRMTs catalyze mono- (MMA) and asymmetric demethylation (ADMA) of arginine; Type II PRMTs catalyze mono- and symmetric demethylation (SDMA) of arginine on proteins; Type III PRMT mediates MMA only. Aberrant expression of PRMTs is strongly associated with poor prognosis of solid cancers and hematologic malignancies. Recently, we identified PRMT1 as a novel therapeutic vulnerability in MM cells. Among PRMTs, PRMT1 is the highest expressed gene in MM cell lines and patient cells. The elevation of PRMT1 expression is strongly associated with relapsed/refractory patients and poor clinical outcomes. Deletion of PRMT1 and suppression of the PRMT1's enzymatic activity exhibited a strong anti-MM in vitro via suppressing cell cycle and elevating the apoptosis. We also found that inhibition of PRMT1 boosts the T cell activation in the co-culture setup, indicating a potential enhancement of immunotherapy. Using a subcutaneous xenograft model, we showed that suppressing PRTM1 in vivo by either genetic or pharmaceutical approaches robustly inhibits MM tumor growth and extends survival of tumor-bearing mice. Our findings demonstrated that PRMT1 is indispensable in MM. PRMT5, a PRMT type II, is prognostically relevant and a known druggable target in MM. PRMT1 and PRMT5 inversely regulate post-transcription and have been implicated in human cancers. Recent studies in solid tumor showed a strong anti-tumor effect in vivo using the combinational inhibition of PRMT1 and PRMT5. We hypothesize that PRMT1 and PRMT5 might have a complementary function in MM cells. The combinational inhibition PRMT1 and PRTM5 will exhibit a synergistic anti-MM effect. To address this hypothesis, we treated MM cell lines with two clinical trial inhibitors: GSK3368715 (GSK) and EPZ 015666 (EPZ), suppressing PRMT type I and type II inhibitor, respectively. We first performed dose-dependent cell viability inhibition and selected effective doses for drug combination treatments in three different MM cell lines. The combination of GSK and EPZ demonstrated a strong synergistic effect in suppressing the viability of MM cells. Using the SynergyFinder algorithm, we found that the synergistic indexes (>10, synergism) for 3 MM cell lines JJN3, MM1S, and KMS11 were 33.5, 32.8, and 14.3, respectively. We next assessed the effects of combined treatment on the cell cycle and apoptosis of MM cells. We found that combination of GSK and EPZ strikingly elevated the apoptosis and suppressed cell cycle of MM cell lines compared single treatment and untreated control. Intriguingly, the combination treatment of two inhibitors significantly decreased MMA, SDMA, and ADMA, suggesting a robust suppression of global arginine methylation. Of note, we found a similar anti-MM effect when treating bortezomib-resistant MM cells with GSK and EPZ, indicating that PRMT type I and type II inhibitors potentially have a substantial clinical impact on relapsed MM. Of note, the same dose of GSK and EPZ that exhibits the synergistic anti-MM effect, didn't suppress the viability of healthy peripheral blood cells. In summary, our preliminary data suggest that suppression of both PRMT type I and type II might provide a potential effective combination treatment for both newly diagnosed and relapsed MM patients. We're currently investigating the underling mechanisms of how PRMTs regulate MM pathology and validating the in vivo efficacy of combination treatment using patient-derived xenograft.

STMN1 promotes cell malignancy and bortezomib resistance of multiple myeloma cell lines via PI3K/AKT signaling

ABSTRACT Background This study investigates the biological functions of Stathmin1 (STMN1) involving drug resistance and cell proliferation in multiple myeloma (MM) and its related mechanisms. Methods Bone marrow aspirates were collected from 20 MM patients, and the bone marrow mononuclear cells (BMMCs) were separated by Ficoll-Hypaque density gradient centrifugation. Blood samples of 20 patients with monoclonal gammopathy of undetermined significance (MGUS) and 20 healthy donors were collected. Normal plasma cells sorted from the peripheral blood of MGUS patients and healthy subject as controls. Two bortezomib (BTZ)-resistant MM cell lines were established, namely NCI-H929/BTZ and KM3/BTZ cells, and then transfected with lentiviruses packaging sh-STMN1 to knock down STMN1 level in BTZ-resistant cells. Expression of STMN1 was assessed by RT-qPCR and western blotting. CCK-8 assays were performed to assess 50% growth inhibition (IC50) values. Green fluorescent protein in BTZ-resistant cells infected with lentiviruses was observed by fluorescence microscopy. Cell viability, proliferation, cell cycle, and apoptosis were evaluated through MTT assays, colony formation assays, flow cytometry analyses, and TUNEL staining. Results STMN1 was upregulated in MM cells and bone marrow aspirates of MM patients. Additionally, STMN1 depletion attenuated BTZ resistance in MM cells. Moreover, downregulation of STMN1 limited the malignant phenotypes of BTZ-resistant cells. Mechanistically, the PI3K/Akt signaling was inactivated by STMN1 downregulation in BTZ-resistant cells. Conclusion STMN1 silencing inhibits cell proliferation and BTZ resistance in MM by inactivating the PI3K/Akt signaling.

GPER1 Activation Exerts Anti-Tumor Activity in Multiple Myeloma.

G protein-coupled estrogen receptor 1 (GPER1) activation is emerging as a promising therapeutic strategy against several cancer types. While GPER targeting has been widely studied in the context of solid tumors, its effect on hematological malignancies remains to be fully understood. Here, we show that GPER1 mRNA is down-regulated in plasma cells from overt multiple myeloma (MM) and plasma cell leukemia patients as compared to normal donors or pre-malignant conditions (monoclonal gammopathy of undetermined significance and smoldering MM); moreover, lower GPER1 expression associates with worse overall survival of MM patients. Using the clinically applicable GPER1-selective agonist G-1, we demonstrate that the pharmacological activation of GPER1 triggered in vitro anti-MM activity through apoptosis induction, also overcoming the protective effects exerted by bone marrow stromal cells. Noteworthy, G-1 treatment reduced in vivo MM growth in two distinct xenograft models, even bearing bortezomib-resistant MM cells. Mechanistically, G-1 upregulated the miR-29b oncosuppressive network, blunting an established miR-29b-Sp1 feedback loop operative in MM cells. Overall, this study highlights the druggability of GPER1 in MM, providing the first preclinical framework for further development of GPER1 agonists to treat this malignancy.

A novel alkaloid compound, DCZ0358, exerts significant antitumor activity in bortezomib-resistant multiple myeloma cells through inhibition of JAK2/STAT3 pathway.

Multiple myeloma (MM), the second most common haematological malignancy, is currently incurable because patients often develop multiple drug resistance and experience subsequent relapse of the disease. This study aims to identify a potential therapeutic agent that can counter bortezomib (BTZ) resistance in MM. DCZ0358, a novel alkaloid compound, is found to exert potent cytotoxic effects against BTZ-resistant MM cells in vivo and in vitro. The anti-myeloma activity of DCZ0358 is associated with inhibition of cell proliferation, promotion of cell apoptosis via caspase-mediated apoptotic pathways, and induction of G0/G1 phase arrest via downregulation of cyclin D1, CDK4, and CDK6. Further investigation of the molecular mechanism shows that DCZ0358 suppresses the JAK2/STAT3 signaling pathway. In conclusion, DCZ0358 can successfully counter BTZ resistance in MM cells. This study provides evidence that warrants future preclinical assessments of DCZ0358 as a therapeutic agent against BTZ resistance in MM.

DUT enhances drug resistance to proteasome inhibitors via promoting mitochondrial function in multiple myeloma.

Acquired chemoresistance to proteasome inhibitors (PIs), such as bortezomib (BTZ), becomes an intractable obstacle in the management of multiple myeloma (MM) in the clinic, but the underlying mechanisms are still not well elucidated. In the current study, we established bortezomib-resistant (BR) myeloma cells and performed stable isotope labeling by amino acids in cell culture (SILAC) assay to screen profiled protein expression. The level of deoxyuridine triphosphatase (DUT), an important enzyme of nucleotide metabolism, increased in the BR MM cells. Retrospective analysis indicated patients with higher DUT expression had poorer responses to PI-based treatment and clinical outcomes. DUT knockdown by RNAi effectively minimized BTZ resistance in MM cells. Moreover, DUT knockdown was accompanied with the downregulation of proliferating cell nuclear antigen (PCNA), contributing to decelerating cell growth, as well as augmented apoptosis due to bortezomib treatment. In contrast, DUT overexpression in parental MM.1S and LP-1 cells enhanced BTZ resistance. Furthermore, acquired resistance to BTZ could trigger the modulation of mitochondrial metabolism and function, as evidenced by elevated expression of genes associated with mitochondrial metabolism, as well as altered oxygen consumption rate and adenosine triphosphate (ATP) production in BR MM cells. DUT inhibition partially attenuated mitochondrial modulation, and instead favored an early impairment of mitochondrial integrity upon BTZ exposure so as to restrict MM progression and overcome drug resistance to BTZ treatment both in vitro and in vivo. In conclusion, we unveiled previously unrecognized effects of DUT on acquired drug resistance of MM, thus manipulating DUT may be efficacious for sensitizing MM cells to PIs.

β-catenin inhibitors ICG-001 and pyrvinium sensitize bortezomib-resistant multiple myeloma cells to bortezomib.

Although bortezomib (BTZ) displays efficacy in treating multiple myeloma (MM), BTZ resistance in MM patients has been reported. Meanwhile, treating BTZ resistant MM cells with β-catenin inhibitors have demonstrated the ability to reserve BTZ resistance. Thus, the present study aimed to investigate the synergistic effect of the β-catenin inhibitors, ICG-001 and pyrvinium (PP), with BTZ in the treatment of BTZ-resistant MM cells. Different concentrations of ICG-001 (0–32 µM) or PP (0–32 nM) were used to treat the BTZ-resistant RPMI-8226 (RPMI-8226BR) and BTZ-resistant KMS-11 (KMS-11BR) cell lines, followed by a BTZ combination treatment. Subsequently, cell viability and apoptosis in these two cell lines were determined by CCK-8 assay and flow cytometry, respectively. The proteins involved in the Wnt/β-catenin signaling pathway were detected using western blotting. The Wnt/β-catenin signaling pathway was activated in the RPMI-8226BR and the KMS-11BR cells. In addition, the cell viability of RPMI-8226BR and KMS-11BR cells were decreased following β-catenin inhibitor (ICG-001 and PP) treatment alone. Furthermore, the β-catenin inhibitors, ICG-001 and PP, plus BTZ combination treatment revealed a notable decrease in cell viability and a marked increase in cell apoptosis rate, compared with that in cells treated with ICG-001, PP or BTZ alone in the RPMI-8226BR and KMS-11BR cell lines. In conclusion, the β-catenin inhibitors, ICG-001 and PP not only increased apoptosis, but also sensitized BTZ-resistant MM cells to BTZ, indicating their potential therapeutic application in MM.

SHP2 Inhibitors Show Anti-Myeloma Activity and Synergize With Bortezomib in the Treatment of Multiple Myeloma.

Multiple myeloma (MM) is a plasma cell malignancy that remains incurable. The protein tyrosine phosphatase SHP2 is a central node regulating RAS/mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK) signaling pathway which plays a crucial role in the pathogenesis and proteasome inhibitor (PI) resistance of MM. Several preclinical studies have demonstrated that SHP2 inhibitors exerted antitumor activity in cancer-harboring diverse mutations in the RAS pathway, offering the potential for targeting myeloma. In this study, we showed that pharmacological inhibition of SHP2 activity using SHP099 and RMC-4550 efficiently inhibited the proliferation of MM cells by inducing apoptosis and cell cycle arrest. As per the mechanism, SHP2 inhibitors activated the level of cleaved caspase3, BAK, and P21 and downregulated ERK phosphorylation in MM cells. Moreover, the blockade of SHP2 exhibited anti-myeloma effect in vivo in a mouse xenograft model. In addition, SHP2 inhibitors synergized the antineoplastic effect of bortezomib in bortezomib-sensitive MM cells and showed identical efficacy in targeting bortezomib-resistant MM cells. Overall, our findings suggest that SHP2-specific inhibitors trigger anti-myeloma activity in vitro and in vivo by regulating the ERK pathway and enhancing cytotoxicity of bortezomib, providing therapeutic benefits for both bortezomib naïve and resistant MM.

System Xc− inhibition blocks bone marrow-multiple myeloma exosomal crosstalk, thereby countering bortezomib resistance

Multiple myeloma (MM) cells derive proliferative signals from the bone marrow (BM) microenvironment via exosomal crosstalk. Therapeutic strategies targeting this crosstalk are still lacking. Bortezomib resistance in MM cells is linked to elevated expression of xCT (the subunit of system Xc−). Extracellular glutamate released by system Xc− can bind to glutamate metabotropic receptor (GRM) 3, thereby upregulating Rab27-dependent vesicular trafficking. Since Rab27 is also involved in exosome biogenesis, we aimed to investigate the role of system Xc− in exosomal communication between BM stromal cells (BMSCs) and MM cells. We observed that expression of xCT and GRMs was increased after bortezomib treatment in both BMSCs and MM cells. Secretion of glutamate and exosomes was simultaneously enhanced which could be countered by inhibition of system Xc− or GRMs. Moreover, glutamate supplementation increased exosome secretion by increasing expression of Alix, TSG101, Rab27a/b and VAMP7. Importantly, the system Xc− inhibitor sulfasalazine reduced BMSC-induced resistance to bortezomib in MM cells in vitro and enhanced its anti-MM effects in vivo. These findings suggest that system Xc− plays an important role within the BM and could be a potential target in MM.

Epigenomic reprogramming via HRP2-MINA dictates response to proteasome inhibitors in multiple myeloma with t(4;14) translocation.

The chromosomal t(4;14) (p16;q32) translocation drives high expression of histone methyltransferase nuclear SET domain–containing 2 (NSD2) and plays vital roles in multiple myeloma (MM) evolution and progression. However, the mechanisms of NSD2-driven epigenomic alterations in chemoresistance to proteasome inhibitors (PIs) are not fully understood. Using a CRISPR/Cas9 sgRNA library in a bone marrow–bearing MM model, we found that hepatoma-derived growth factor 2 (HRP2) was a suppressor of chemoresistance to PIs and that its downregulation correlated with a poor response and worse outcomes in the clinic. We observed suppression of HRP2 in bortezomib-resistant MM cells, and knockdown of HRP2 induced a marked tolerance to PIs. Moreover, knockdown of HRP2 augmented H3K27me3 levels, consequentially intensifying transcriptome alterations promoting cell survival and restriction of ER stress. Mechanistically, HRP2 recognized H3K36me2 and recruited the histone demethylase MYC-induced nuclear antigen (MINA) to remove H3K27me3. Tazemetostat, a highly selective epigenetic inhibitor that reduces H3K27me3 levels, synergistically sensitized the anti-MM effects of bortezomib both in vitro and in vivo. Collectively, these results provide a better understanding of the origin of chemoresistance in patients with MM with the t(4;14) translocation and a rationale for managing patients with MM who have different genomic backgrounds.

P-088: Indirubin-3’-monoxime acts as an alternative proteasome inhibitor and confers new regimens for the treatment of Multiple Myeloma

<h3>Background</h3> Multiple myeloma (MM) is still an incurable malignancy of plasma cells. Despite the therapeutic benefit of the proteasome inhibitor (PI) bortezomib, drug resistance still accounts for majority of tumor relapses and cancer-related death in MM patients. Thus, exploring the mechanism underlying BTZ resistance and investigating a novel treatment strategy are urgent requisites for clinical practise. Indirubin-3'-monoxime (Id-3) is an active ingredient of a traditional Chinese medicine. <h3>Method</h3> In the present study, we firstly investigated Id-3 effects on myeloma treatment in patient primary samples and myeloma cell lines. We also investigated the molecular mechanism of Id-3 treatment on MM cells via in vivo and in vitro study. <h3>Results</h3> We first reported that Id-3 is an effective cytotoxicity agentia against MM cells growth by inducing the MM cells apoptosis. Id-3 treatment also effectively induces the cell death in bortezomib-resistant MM cell lines and primary myeloma patient samples. Stringently, we found there is a synergistic anti-MM effect between Id-3 and bortezomib. The treatment with lower dosage combination of Id-3 and bortezomib exhibited a notably inhibition of the growth of myeloma cells both in xenograft mouse model and MM-PDX model. Mechanism study revealed that Id-3 treatment efficiently inhibited the chymotrypsin-like and caspase-like activity of proteasome in MM cells. The level of the proteasome 11s activator, PA200 (PSME4) and PA28y (PSME3) was significantly down-regulated both in mRNA and protein level. GEO datasets analysis showed that the high levels of PSME4 and PSME3 were over-expressed in relapsed patients and MM cell lines which correlated with the drug-resistance of MM cells. Kaplan-Meier analysis showed that patients with high-levels of PSME3 or PSME4 had the shortened survival. Knocking-down the level of PSME4 or PSME3 by shRNA noteworthy inhibited the cell growth and enhanced the sensitivity to bortezomib of MM cells. In vivo study also found that down-regulated the level of PSME3 or PSME4 can suppress the proliferation of MM cells and prolong the survival of MM-bearing mouse. <h3>Conclusions</h3> Taken together, our study supported that Id-3 is an effective agentia against the survival of MM cells both in bortezomib-sensitive and -resistance ones. We further identified that the 11s proteasome activators, PSME3 and PSME4, were down-regulated effectively by Id-3 treatment. High-levels of PSME3 or PSME4 were correlated with the inferior outcome of MM patients. Down-regulating PSME3 and PSME4 by Id-3 or shRNA could efficiently suppressed the growth of MM cells and improve the survival of MM-bearing mice. Our study provides the rational evidence for the clinical application of Id-3 in the treatment of MM.

OAB-021: BCMA-specific ADC MEDI2228 and Daratumumab induce synergistic myeloma cytotoxicity via enhanced IFN-driven innate immune responses and expression of CD38 and NKG2D ligands

<h3>Background</h3> Efforts are required to improve potency and durability of CD38- and BCMA-based immunotherapies in human multiple myeloma (MM). <h3>Methods</h3> We here delineated the molecular and cellular mechanisms underlying novel immunomodulatory effects triggered by BCMA pyrrolobenzodiazepine (PBD) antibody drug conjugate MEDI2228 which may augment efficacy of these immunotherapies. RNA sequencing followed by gene set enrichment analysis showed that MEDI2228 significantly enriched IFN I-signaling and induced type I interferon (IFN I)-stimulated genes (ISGs) in MM cell lines. The most MEDI2228-enhanced IFN-driven genes include chemokines/cytokines and receptors (i.e., CXCL9/10, CCL4L1/2, CCL22, CCL1/3/4/5, CCL3L1/3, TNFSF9/10, CSF2 (GM-CSF), CCR7), RSAD2, CASP1, ISGs (i.e., XAF1, TRIMs, IFITs, ISG15, GBP2/3, OAS1/2/L, RNASEL, MX1/2, FAS), RUNX3, GZMB, IKBKE, IRF1/6/7/9, STAT1/2/4/6, MB21D1(CGAS), TMEM173 (STING), IFIT1/2/3/5, and SOCS1/2/3. <h3>Results</h3> Regardless of genetic heterogeneity and resistance to current anti-MM therapies, MEDI2228 induced dose- and time-dependent DNA damage-ATM/ATR-CHK1/2 pathways, activation of cGAS-STING-TBK1-IRF3 and STAT1-IRF1-signaling cascades, as well as increased CD38 expression. It overcame CD38 downregulation triggered by IL6 and bone marrow stromal cell culture supernatant (BMSC-sup), via activation of STAT1-IRF1 without phosphorylation of STAT3 in immunomodulatory drugs (IMiDs)- and bortezomib-resistant MM cell lines. In contrast, MEDI2228 did not change CD38 expression and survival in BCMA-negative NK effector cells. Significantly, MEDI2228 with anti-CD38 monoclonal antibody Daratumumab (Dara) synergistically induced NK-mediated lysis of MM cell lines and autologous resistant patient MM cells, even in the presence of BMSC-sup and BMSCs. In parallel, MEDI2228 increased membrane expression of NKG2D ligands (NKG2DLs), i.e., MICA/B and ULBPs, in all MM cells tested, including Dara-resistant patient cells, correlating with enhanced MM cell susceptibility to NK cell killing. Since MEDI2228, but not its MMAF-ADC homolog M3 even used at >1-log higher concentrations enhanced surface expression of CD38 and NKG2DLs on MM cells, the potent DDR-mediated immunomodulation triggered by MEDI2228 vs M3 is critical in rendering MM cells more susceptible to Dara-induced NK cell killing. Importantly, M2 still activated STAT1/IRF1 signaling to induce CD38 and MICA/B expression in MM tumors grown in mice. All MM1S tumor-bearing NSG mice reconsituted with human NK cells became tumor-free following a single low dose M2 with Dara treatment, with 100% host survival. <h3>Conclusions</h3> Taken together, our data showed that MEDI2228 restored MM sensitivity to CD38 targeting by Dara without depleting NK cells and potentiated immunogenic cell death of MM cells. These results therefore provide the mechanistic rationale for clinical evaluation of combination CD38- and BCMA-directed immunotherapies to further improve patient outcome in MM.

DKK1 activates noncanonical NF-κB signaling via IL-6–induced CKAP4 receptor in multiple myeloma

AbstractProteasome inhibitors, such as bortezomib (BTZ), represent the key elements in chemotherapy regimens for multiple myeloma (MM), whereas acquired chemoresistance and ultimately relapse remain a major obstacle. In the current study, we screened differently expressed cytokines in bortezomib-resistant MM cells and found that Dickkopf-1 (DKK1) level was remarkably augmented, whereas CD138 level was significantly suppressed. DKK1 in vitro specifically enhanced the resistance of myeloma cells to bortezomib treatment, and excessive DKK1 drove CD138 downregulation via inhibition of canonical Wnt signaling. Notably, DKK1 mainly induced drug resistance in MM cells via the receptor of CKAP4. Mechanistically, CKAP4 transduced DKK1 signal and evoked NF-κB pathway through recruiting and preventing cullin associated and neddylation dissociated 1 from hampering the assembly of E3 ligase-mediated ubiquitination of IκBα. In addition, we found that interleukin-6 (IL-6) stimulated CKAP4 expression to generate drug resistance, and disturbance of DKK1-CKAP4 axis improved sensitivity to BTZ treatment of MM and attenuated bone destruction in a mouse model. Collectively, our study revealed the previously unidentified role of DKK1 in myeloma drug resistance via Wnt signaling dependent and independent manners, and clarified the importance of antagonism of DKK1-IL-6 loop in bone marrow microenvironment.

Omega-3 Fatty Acids DHA and EPA Reduce Bortezomib Resistance in Multiple Myeloma Cells by Promoting Glutathione Degradation.

Multiple myeloma (MM) is a hematological malignancy that exhibits aberrantly high levels of proteasome activity. While treatment with the proteasome inhibitor bortezomib substantially increases overall survival of MM patients, acquired drug resistance remains the main challenge for MM treatment. Using a combination treatment of docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) and bortezomib, it was demonstrated previously that pretreatment with DHA/EPA significantly increased bortezomib chemosensitivity in MM cells. In the current study, both transcriptome and metabolome analysis were performed to comprehensively evaluate the underlying mechanism. It was demonstrated that pretreating MM cells with DHA/EPA before bortezomib potently decreased the cellular glutathione (GSH) level and altered the expression of the related metabolites and key enzymes in GSH metabolism, whereas simultaneous treatment only showed minor effects on these factors, thereby suggesting the critical role of GSH degradation in overcoming bortezomib resistance in MM cells. Moreover, RNA-seq results revealed that the nuclear factor erythroid 2-related factor 2 (NRF2)-activating transcription factor 3/4 (ATF3/4)-ChaC glutathione specific gamma-glutamylcyclotransferase 1 (CHAC1) signaling pathway may be implicated as the central player in the GSH degradation. Pathways of necroptosis, ferroptosis, p53, NRF2, ATF4, WNT, MAPK, NF-κB, EGFR, and ERK may be connected to the tumor suppressive effect caused by pretreatment of DHA/EPA prior to bortezomib. Collectively, this work implicates GSH degradation as a potential therapeutic target in MM and provides novel mechanistic insights into its significant role in combating bortezomib resistance.

Circular RNA circ-CCT3 promotes bortezomib resistance in multiple myeloma via modulating miR-223-3p/BRD4 axis.

Multiple myeloma is a frequent hematologic malignancy. Bortezomib is the first-line drug for multiple myeloma chemotherapy. The present study aimed to investigate the potential role and mechanism of circular RNA chaperonin containing TCP1 subunit 3 (circ-CCT3) in bortezomib resistance of multiple myeloma. The levels of circ-CCT3, microRNA-223-3p (miR-223-3p), and bromodomain-containing 4 (BRD4) were detected by quantitative real-time PCR or western blot. Cell Counting Kit-8 (CCK-8) method was used to measure the half-inhibitory concentration of bortezomib and cell viability. Cell cycle distribution, apoptosis, proliferation and migration were determined by flow cytometry, 5-ethynyl-2'-deoxyuridine, and wound healing assay. The levels of relevant proteins were checked via western blot. The binding association between miR-223-3p and circ-CCT3/BRD4 was validated via a dual-luciferase reporter assay. Circ-CCT3 and BRD4 were upregulated, while miR-223-3p was downregulated in bortezomib-resistant multiple myeloma patients and cells. Silencing of circ-CCT3 enhanced the sensitivity of bortezomib-resistant multiple myeloma cells to bortezomib. Circ-CCT3 knockdown weakened bortezomib resistance via modulating miR-223-3p. Moreover, miR-223-3p increased bortezomib sensitivity by inhibiting BRD4. Downregulation of circ-CCT3 attenuated bortezomib resistance of multiple myeloma via regulating miR-223-3p/BRD4 pathway, which provided a new potential target for multiple myeloma chemoresistance.

BCMA-Specific ADC MEDI2228 and Daratumumab Induce Synergistic Myeloma Cytotoxicity via IFN-Driven Immune Responses and Enhanced CD38 Expression.

Efforts are required to improve the potency and durability of CD38- and BCMA-based immunotherapies in human multiple myeloma. We here delineated the molecular and cellular mechanisms underlying novel immunomodulatory effects triggered by BCMA pyrrolobenzodiazepine (PBD) antibody drug conjugate (ADC) MEDI2228 which can augment efficacy of these immunotherapies. MEDI2228-induced transcriptional and protein changes were investigated to define significantly impacted genes and signaling cascades in multiple myeloma cells. Mechanisms whereby MEDI2228 combination therapies can enhance cytotoxicity or overcome drug resistance in multiple myeloma cell lines and patient multiple myeloma cells were defined using in vitro models of tumor in the bone marrow (BM) microenvironment, as well as in human natural killer (NK)-reconstituted NOD/SCID gamma (NSG) mice bearing MM1S tumors. MEDI2228 enriched IFN I signaling and enhanced expression of IFN-stimulated genes in multiple myeloma cell lines following the induction of DNA damage-ATM/ATR-CHK1/2 pathways. It activated cGAS-STING-TBK1-IRF3 and STAT1-IRF1-signaling cascades and increased CD38 expression in multiple myeloma cells but did not increase CD38 expression in BCMA-negative NK effector cells. It overcame CD38 downregulation on multiple myeloma cells triggered by IL6 and patient BM stromal cell-culture supernatant via activation of STAT1-IRF1, even in immunomodulatory drug (IMiD)- and bortezomib-resistant multiple myeloma cells. In vitro and in vivo upregulation of NKG2D ligands and CD38 in MEDI2228-treated multiple myeloma cells was further associated with synergistic daratumumab (Dara) CD38 MoAb-triggered NK-mediated cytotoxicity of both cell lines and autologous drug-resistant patient multiple myeloma cells. These results provide the basis for clinical evaluation of combination MEDI2228 with Dara to further improve patient outcome in multiple myeloma.