Plasma Cells Of Multiple Myeloma Patients Research Articles

HDAC Inhibition Induces CD26 Expression on Multiple Myeloma Cells via the c-Myc/Sp1-mediated Promoter Activation.

There is a desire to induce and sustain CD26 expression on multiple myeloma cells to elicit superior anti-myeloma response by humanized anti-CD26 mAb therapy. HDACi upregulates the expression levels of CD26 on myeloma cells via the increased acetylation of c-MycK323 on the CD26 promoter, leading to initiation of CD26 transcription, thereby synergistically augments the efficacy of CD26mAb against CD26neg myeloma cells.

BR109, a Novel Fully Humanized T-Cell-Engaging Bispecific Antibody with GPRC5D Binding, Has Potent Antitumor Activities in Multiple Myeloma.

At present, multiple myeloma (MM) is still an essentially incurable hematologic malignancy. Although BCMA-targeted therapies have achieved remarkable results, BCMA levels were found to be downregulated in patients with MM who relapsed after these treatments. Therefore, the search for other antigens specific to MM has become a priority. Independently of BCMA expression, G-protein-coupled receptor family C group 5 member D (GPRC5D) is mainly expressed in the plasma cells of MM patients, while it is expressed in a limited number of normal tissues. Combining MM-specific antigen GPRC5D and T-cell-mediated therapies would be a promising therapeutic strategy for MM. Recently, we constructed a new anti-GPRC5D × anti-CD3 T-cell-engaging bispecific antibody (TCB), BR109, which was capable of binding to human GPRC5D and human CD3ε. Moreover, BR109 was proven to have relatively good stability and antitumor activity. BR109 could specifically trigger T-cell-mediated cytotoxicity against many GPRC5D-positive MM cells in vitro. Meanwhile, antitumor activity was demonstrated in MM cell line xenograft mouse models with human immune cell reconstitution. These preclinical studies have formed a solid foundation for the evaluation of MM treatment efficacy in clinical trials.

A Functional Genomic Screen to Identify Novel Genes Involved in Multiple Myeloma Tumour Development

Multiple myeloma (MM) is an incurable malignancy characterised by uncontrolled proliferation of plasma cells (PCs) in the bone marrow (BM). MM is a genetically heterogeneous disease with each patient's PCs harbouring unique genetic mutations, however the development of MM tumours is not only dependent on the underlying genetics but also on the selective pressures applied by the BM microenvironment. Hence, we hypothesise that identifying the dependencies which promote MM cell outgrowth in the BM microenvironment will allow for the identification of new drug targets. This project aims to use an in vivo functional screen, combining CRISPR-Cas9 gene editing, using a single guide RNA (sgRNA) library targeting thousands of genes, with a murine model of MM, to identify novel genes involved in MM tumour development. The Bassik human apoptosis and cancer CRISPR knockout library (Addgene #101926) was used to transduce MM cells with 31,324 unique sgRNAs targeting 3,015 genes and 1,500 control regions. The human MM cell line OPM2 was transduced with the Cas9 transgene (FuCas9GFP), followed by the sgRNA expression vector (pMCB320) generating OPM2-Cas9-sgRNA cells. These cells were then injected (5x10 5 cells/mouse, n=8 mice + 1 tumour-naive control) into the tibiae of immunodeficient NOD.Cg-Prkdc scid Il2rg tm1Wjl/SzJ (NSG) mice. Four weeks post-injection, the primary tumour within the injected tibia was isolated and sgRNA frequencies were assessed via next generation sequencing and compared with that of the initial library and the injected cells using the MAGeCK algorithm. To identify genes that play roles in MM tumour formation in patients, we assessed the expression of our identified genes in CD138-selected BM PCs from newly diagnosed MM patients (n=155) when compared with normal PCs from healthy donors (n=5) in microarray dataset E-MTAB-363 (ArrayExpress). Furthermore, to identify potential pathway involvement of our identified genes we performed gene set enrichment analysis (GSEA) using the University of California San Diego and Broad Institute developed GSEA software, comparing to Hallmark Gene Sets. Comparison of the in vitro cultured cells with the initial library identified 34 genes with undetectable (p<0.05) sgRNAs post in vitro culture, suggesting these genes play key roles in the survival of OPM2 cells. This list contained a number of genes known to control MM cell survival, such as IRF4 and CCND2. Additionally, sgRNAs targeting a further 115 genes were significantly depleted (p<0.05) in vitro and were completely undetectable in vivo, suggesting that these are implicated in cell proliferation and tumour formation in vivo. This gene list contained some already known MM drivers such as MYC, KRAS and DIS3. Furthermore, we identified 28 genes where CRISPR knockout had no significant effect in vitro but were critical dependencies for tumour development, with sgRNAs being undetectable (p<0.05) in vivo. This list contained genes known to be important for MM and BM stromal cell interaction such as ALCAM and SPP1. Notably, 25% of the genes identified as critical dependencies for OPM2 cells in vitro and/or in vivo are significantly upregulated >2-fold (p<0.05; limma) in MM patient PCs when compared with normal PCs (E-MTAB-363), suggesting these may play a role in tumour development in patients. Gene set enrichment analysis revealed that the genes that were essential in vitro were predominantly involved in cell survival related pathways such as cell cycle regulation (G2M checkpoint) and DNA replication/repair; however, the uniquely in vivo genes are predominantly involved in cell metabolism pathways such as MTORC1 signalling, oxidative phosphorylation and glycolysis. Overall, this study has successfully used a functional genetic screen to identify novel gene dependencies required for in vitro MM cell growth and in vivo MM tumour development. A secondary genetic screen will be performed in vivo to validate and refine this list of candidate genes. These validated genes will be further investigated using patient derived data sets to determine if they represent common vulnerabilities in patients and in multiple MM cell lines to investigate their specific mechanistic and pathway involvement. Identification and understanding the driving dependencies which promote MM cell outgrowth in the BM microenvironment will allow for the identification and development of new drug targets to improve patient outcomes.

Abstract 5081: Anti-tumor activity of HPN217, a BCMA-targeting tri-specific T cell engager, is enhanced by γ-secretase inhibitors in preclinical models

Abstract HPN217 is a Tri-specific T Cell-Activating Construct (TriTAC) currently being evaluated in a phase 1 clinical trial for relapsed or refractory multiple myeloma (MM) (NCT04184050). It consists of a single domain antibody (sdAb) specific for B-cell maturation antigen (BCMA), a serum albumin-specific sdAb for half-life extension, and a single chain Fv (scFv) specific for the CD3ε subunit of the T cell receptor (TCR) complex for T cell engagement. BCMA is a cell surface receptor highly expressed on malignant plasma cells in MM patients and plays an important role in B-cell proliferation and survival. Soluble BCMA (sBCMA) is produced when the extracellular domain of BCMA is cleaved by γ-secretase and enters circulation. sBCMA may act as a sink for BCMA targeted therapies, potentially decreasing anti-tumor efficacy. Previous studies have shown γ-secretase inhibitors (GSIs) can increase membrane bound BCMA expression on MM cells and decrease sBCMA concentrations, providing a rationale for combining GSIs with HPN217. Here we describe preclinical studies evaluating that combination in vitro and in vivo. To evaluate the effects of GSIs on BCMA expression, MM cell lines MOLP8, KMS-12-BM, and MM.1S were incubated with GSIs LY3039478, PF03084014, or RO4929097overnight. GSI treatment led to a 3-7-fold increase in BCMA expression on MM cell surface. To determine the effects of increased BCMA expression mediated by GSIs on the activity of HPN217, an in vitro T cell dependent cell cytotoxicity assay (TDCC) was conducted. GSIs enhanced the activity of HPN217, in some cases leading to a 3.5-fold increase in potency compared to HPN217 alone. Next, the impact of the combination was tested in vivo using a disseminated MOLP-8 xenograft model engrafted with T cells from a healthy human donor. Vehicle treated mice succumbed to disease burden with a median survival of 23 days as assessed by body weight loss and clinical observations. A suboptimal dose of 4 ug/kg HPN217 protected mice from disease burden for an additional 3 days. By contrast, the combination of HPN217 and LY3039478 led to a significant increase in survival compared to vehicle or either monotherapy, with a median survival of 43 days. Taken together these results demonstrate the potential utility of GSIs to enhance the anti-tumor activity of HPN217 and supports further investigation of this combinatorial approach in patients. Citation Format: Payton C. Laurie, Mary Ellen Molloy, Patrick P. Ng, Banmeet S. Anand. Anti-tumor activity of HPN217, a BCMA-targeting tri-specific T cell engager, is enhanced by γ-secretase inhibitors in preclinical models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5081.

Identification a Novel Molecular Mechanism Underlying the Anti-CD38-Based Treatment Resistance in Multiple Myeloma Patients

Introduction: Anti-CD38 antibody (Daratumumab (DARA)/Isatuximab (ISA))-mediated therapy is now used in combination therapies to treat both newly diagnosed and relapsed/refractory multiple myeloma (MM). Despite a high extent and frequency of response to DARA/ISA containing therapy, MM patient relapse is still common. Several resistance mechanisms to DARA/ISA have been reported including MM cell clonal selection towards reduced CD38 expression; loss of MM cell surface CD38 upon the formation of a CD38-DARA complex leading to immunosuppression; and immunomodulatory effects after the DARA/ISA treatment via the downregulation of intracellular signaling pathways in bone marrow stromal cells. Given the widespread use of anti-CD38-directed treatment in MM, the identification of anti-CD38 based treatment resistance is an urgent clinical need. Methods/results: To understand the underlying molecular mechanism of anti-CD38-based treatment resistance, we assessed post-transcriptional alterations on CD38 transcripts. We performed total and single-cell RNA sequencing of six samples from MM patients treated with DARA/ISA in combination with other MM drugs. Specifically, we examined mRNA splicing aberrations on the CD38 transcripts in 44 MM patient plasma cells (PCs). Four CD38 splice variants (CD38-Va, -Vb, -Vc, and Vd (CD38 SpVs)) were identified in CD138+PCs from DARA-resistant patient samples. These CD38-SpVs are the result of one or more cassette-exon splicing. Some of these splicing events cause in-frame shifts, which lead to the activation of a cryptic stop codon on the CD38 transcript and encode truncated proteins. The cryptic stop codon location at the specific proximity of the exon-intron junction, allowing these transcripts escaping degradation via non-sense mediated decay. In MM PCs, CD38 splice variant transcripts were overexpressed at different levels (2-4 fold) in various combinations with one or more novel splice variants and CD38 full-length (CD38-FL) transcripts. These splice variants were absent in MM PCs from BM aspirates from age-matched healthy donors. Next, we evaluated the expression of the CD38 SpVs and FL transcripts in PCs from MM patients at the time they were sensitive to DARA/ISA treatment and when resistance developed. We identified CD38 splice variant transcripts that were selectively expressed MM PCs at the time of resistance to DARA/ISA treatment. We also identified CD38 splice variant transcripts that are overexpressed in DARA/ISA treatment-sensitive patient samples. Our findings were further validated in DARA resistant patient sample by single-cell RNA-seq analysis, which showed overexpression of CD38Vb in >80% of PCs. We identified splice site mutations that contribute to the expression of CD38 SpVs. To evaluate whether CD38 aberrant splicing is associated with DARA resistance, we generated a KMS11 DARA-resistant cell line (KMS11 DARA-Res) and evaluated the expression of splice variants in these cells. This analysis demonstrated that KMS11DARA-Res over-express CD38 SpVs. To determine whether CD38 splice variants encode functional proteins, we cloned, sequenced, and stably expressed CD38 SpVs transcripts into H929 cells (H929-CD38 SpVs). CD38 SpVs expressions were evaluated by flow cytometry and live cell imaging. These analyses demonstrated that CD38 SpVs encode proteins. Importantly, CD38 splice variant protein folding analyses showed that splicing alterations abrogate DARA/ISA binding sites. Then, to evaluate the functional effects of aberrant splicing of CD38 in MM cells, we carried out DARA/ISA binding assays and evaluated cell killing with ADCC assays in H929- CD38SpV cells. Importantly, these analyses showed that both DARA/ISA binding and ADCC was lost in H929-CD38SpV cells. Conclusions: We identified a novel molecular mechanism that underlies the resistance to anti-CD38-based treatment, both DARA and ISA. By this mechanism, CD38 cognate epitopes are removed from the cell surface of MM cells without an entire disposal of the target protein. The existence of such splicing-based mechanisms of resistance indicates that other antibody-based therapeutics or future CARs should be developed against CD38 epitopes that are created as a result of splicing. This approach may allow for selective targeting of MM PCs while spearing other CD38 expressing normal cells, enhancing cytotoxicity and improving therapeutic index.

A Cancer-Related microRNA Signature Shows Biomarker Utility in Multiple Myeloma.

Multiple myeloma (MM) is the second most common hematological malignancy, arising from terminally differentiated B cells, namely plasma cells. miRNAs are small non-coding RNAs that participate in the post-transcriptional regulation of gene expression. In this study, we investigated the role of nine miRNAs in MM. CD138+ plasma cells were selected from bone marrow aspirates from MM and smoldering MM (sMM) patients. Total RNA was extracted and in vitro polyadenylated. Next, first-strand cDNA synthesis was performed using an oligo-dT–adapter primer. For the relative quantification of the investigated miRNAs, an in-house real-time quantitative PCR (qPCR) assay was developed. A functional in silico analysis of the miRNAs was also performed. miR-16-5p and miR-155-5p expression was significantly lower in the CD138+ plasma cells of MM patients than in those of sMM patients. Furthermore, lower levels of miR-15a-5p, miR-16-5p, and miR-222-3p were observed in the CD138+ plasma cells of MM patients with osteolytic bone lesions, compared to those without. miR-125b-5p was also overexpressed in the CD138+ plasma cells of MM patients with bone disease that presented with skeletal-related events (SREs). Furthermore, lower levels of miR-223-3p were associated with significantly worse overall survival in MM patients. In conclusion, we propose a miRNA signature with putative clinical utility in MM.

Bone Marrow Neutrophils of Multiple Myeloma Patients Exhibit Myeloid-Derived Suppressor Cell Activity.

Activated normal density granulocytes (NDGs) can suppress T-cell responses in a similar way as myeloid-derived suppressor cells (MDSCs). In this study, we tested the hypothesis that NDGs from blood and bone marrow of multiple myeloma (MM) patients have the ability to suppress T-cells, as MDSC. MM is an incurable plasma cell malignancy of the bone marrow. Like most malignancies, myeloma cells alter its microenvironment to promote tumor growth, including inhibition of the immune system. We found that MM NDG from the bone marrow suppressed proliferation of T-cells, in contrast to healthy donors. The inhibitory effect could not be explained by changed levels of mature or immature NDG in the bone marrow. Moreover, NDG isolated from the blood of both myeloma patients and healthy individuals could inhibit T-cell proliferation and IFN-γ production. On the contrary to previous studies, blood NDGs did not have to be preactivated to mediate suppressive effects. Instead, they became activated during coculture, indicating that contact with activated T-cells is important for their ability to regulate T-cells. The inhibitory effect was dependent on the production of reactive oxygen species and could be reverted by the addition of its inhibitor, catalase. Our findings suggest that blood NDGs from MM patients are suppressive, but no more than NDGs from healthy donors. However, only bone marrow NDG from MM patients exhibited MDSC function. This MDSC-like suppression mediated by bone marrow NDG could be important for the growth of malignant plasma cells in MM patients.

The Significance of CD319 and CD269 in the Detection of Immunophenotyping and Minimal Residual Disease in Multiple Myeloma Patients

To investigate the expression of CD319 and CD269 in plasma cells of patients with multiple myeloma (MM) and the feasibility of using CD319 instead of CD38 as a gating antigen in immunophenotyping and minimal residual disease (MRD) monitoring. The expression levels of CD319 and CD269 antigens in clonal bone marrow plasma cells of 387 patients were detected by CD38/CD138 gating strategy with 8-color flow cytometry, and the stability of antigens was also analyzed, and the sensitivity and correlation of two different gating strategies employing CD319/CD138 and CD38/CD138 were compared as well. The control group consisted of 53 cases with non-malignant blood disease matched by age and sex. Monoclonal plasma cells were detected in 303 of 387 MM patients, among which 277 cases (91.42%) were positive for CD269, and all cases were positive for CD319 (100%). In newly diagnosed MM (NDMM) and recurrent refractory MM (RRMM) patients, the expression levels of CD269 were 97.53% (0-99.92%) and 94.96% (0.22%-99.99%), respectively, while levels of CD319 were 99.90% (87.77%-100%) and 99.78% (63.12%-100%), respectively. The expression levels of CD269 and CD319 in the control group were 97.00% (77.00%-100%) and 100% (89.00%-100%), respectively. There were no significant differences in the expression levels of CD269 and CD319 among NDMM, RRMM and the control group. Patients acquiring therapeutic effects were divided into complete remission (CR) group, very good partial response (VGPR) group and partial response (PR) group. Gating with CD38/CD138, median MRD values were 0.76% (0-1.88%), 0.77% (0-4.96%) and 1.75% (0.09%-10.90%) in the three groups, respectively, while gating with CD319/CD138, median MRD values were 0.57% (0.18%-1.96%), 1.07% (0.12%-4.85%) and 1.77% (0.08%-8.22%), respectively. There was no significant difference in MRD level by the two gating strategies, but a good correlation between the two (r=0.808, P<0.05). In addition, in 4 patients treated by CD38 monoclonal antibody (DARA), the expression level of CD38 was observed to be down-regulated or even negative after treatment. When the MRD level was very low, CD38/CD138 gating resulted in false MRD-, while CD319/CD138 gating resulted in MRD+. CD319 and CD269 express stably and continuously in plasma cells of MM patients at different disease stages. CD319 can be used as an alternative of CD38 for immunophenotyping and MRD detection, especially for MRD detection after DARA treatment, while CD269 is suitable for detection before BCMA-CAR-T treatment.

The Role and Therapeutic Target of Base Excision Repair Genes in Multiple Myeloma (MM)

Background: Dysregulated DNA repair genes play a pathological role in diverse forms of malignancies, including multiple myeloma (MM). High expression of some DNA repair enzymes has been reported in various tumors and associated with their progression and drug resistance. Here, we investigated the association between MM and base excision repair (BER) system, which is known as a DNA repair pathway for the processing of small base lesions derived from oxidation and alkylation damages. To elucidate the roles of BER in the pathogenesis of MM, we investigated the distribution of functional polymorphisms of BER, the expression level of BER genes, and the effectiveness of BER inhibitors and knockdown BER genes for MM cell lines.Material and methods: Genotyping of OGG1 Ser326Cys, MUTYH Gln324His, APE1 Asp148Glu, XRCC1 Arg399Gln, and PARP1 Val762Ala in 146 MM patients and 202 race-matched healthy controls was determined by using the PCR-restriction fragment length polymorphism (PCR-RFLP) method. Mononuclear cells were separated from bone marrow aspirates and CD138+ cells were collected using EasySep. The mRNA expression of BER genes in MM cell lines (KMM1, KMS12PE, KMSE12BM, KMS11, RPMI8226, and OPM2), primary MM cells, and normal plasma cells was assessed by real-time PCR method. The protein level of BER genes was assessed by western blot analysis. BER inhibitors, including APE1 inhibitor and PARP inhibitor were used. Inducible knockdown system was used for suppressed OGG1 expression. Genotype and allele frequencies were compared between the study groups using Χ2-test. Probability values <0.05 were considered statistically significant. This study was approved by the Institutional Review Board of Gunma University Hospital.Results: The PARP1 Val762Ala single nucleotide polymorphism, which is reported to increase cancer risk, was associated with susceptibility to MM. In the patient group, the Val/Val genotype frequency was lower (32.9% compared with 43.6%, P = 0.044) and the Val/Ala genotype frequency was higher (56.8% compared with 43.1%, P = 0.011) than those in the control groups. In contrast to PARP1 polymorphism, the distributions of other BER polymorphisms, including OGG1 Ser326Cys, MUTYH Gln324His, APE1 Asp148Glu, and XRCC1 Arg399Gln, showed no significant difference between MM patients and control groups. Next, we examined the association between the polymorphisms and the clinical characteristics of MM patients. No significant difference was observed in the allele frequency as well as in sex, age, other clinical settings, and overall survival. The BER genes, such as OGG1, APE1, and PARP1, were detected in all MM cell lines. Protein expression of OGG1, APE1, and PARP1 correlated with mRNA expression in MM cell lines. The mRNA levels of OGG1, APE1, and PARP1 of malignant plasma cells of MM patients were significantly higher than those of normal plasma cells (p < 0.05). The mRNA levels of OGG1, APE1, and PARP1 genesof plasma cells of newly diagnosed MM patients were significantly higher than those of refractory or relapsed MM patients. We exposed MM cell lines to increasing concentrations of APE-1 inhibitor, methoxamine, and PARP1-selective inhibitor, BYK204165, which demonstrated potent and selective growth inhibition in vitro. To determine the role of OGG1 gene in MM growth and survival, we suppressed its expression using an inducible knockdown system and observed significant inhibition of MM cell lines (KMS11 and KMM1) proliferation.Conclusion: The PARP1 Val762Ala polymorphism may be associated with the susceptibility to MM. High expression of BER genes such as OGG1, APE1, and PARP1 was detected in malignant plasma cells, and the inhibition of these BER genes reduced MM cell growth. According to these results, inhibition of BER genes may be a potential therapeutic target of MM. DisclosuresMurakami:Sanofi: Honoraria; Fujimoto: Honoraria; BMS: Honoraria; Ono: Honoraria; Takeda: Honoraria; Celgene: Honoraria.

The long non-coding RNA CRNDE regulates growth of multiple myeloma cells via an effect on IL6 signalling

Multiple myeloma (MM) is a currently incurable malignancy of antibody-secreting plasma cells. Long non-coding RNAs (lncRNAs) have been recognised as an important class of regulatory molecules which are increasingly implicated in tumorigenesis. While recent studies have demonstrated changes in expression of lncRNAs in MM, the functional significance and molecular pathways downstream of these changes remain poorly characterised. In this study, we have performed CRISPR-mediated deletion of the locus encoding the lncRNA Colorectal Neoplasia Differentially Expressed (CRNDE), a known oncogenic lncRNA that is overexpressed in plasma cells of MM patients and is a marker of poor prognosis. We found that CRISPR-mediated deletion of the CRNDE locus in MM cells decreases proliferation and adhesion properties, increases sensitivity to Dexamethasone and reduces tumour growth in an in vivo xenograft model. Transcriptomic profiling in CRNDE-deleted MM cells demonstrated that CRNDE activates expression of a number of genes previously implicated in the aetiology of MM, including IL6R. We further demonstrate that deletion of the CRNDE locus diminishes IL6 signalling and proliferative responses in MM cells. Altogether this study reveals the IL6 signalling pathway as a novel mechanism by which CRNDE impacts upon MM cell growth and disease progression.

Abstract 4556: Preclinical pharmacology and safety of RO7297089, a novel anti-BCMA/CD16a bispecific antibody for the treatment of multiple myeloma

Abstract RO7297089 is a bispecific antibody (IgG-scFv) targeting Bcell maturation antigen (BCMA) and CD16a (FcγRIIIA) that is being developed for the treatment of multiple myeloma (MM). BCMA is exclusively expressed on plasmablasts and differentiated plasma cells (PCs), and is overexpressed on malignant PCs in MM patients. CD16a is expressed on natural killer (NK) cells, monocytes, mast cells, and macrophages. Herein, we characterized the mode of action and safety profile of RO7297089 in vitro and in vivo. RO7297089 showed potent cell killing when using BCMA+ MM tumor cell lines as target cells and human peripheral blood mononuclear cells, NK cells or macrophages as effector cells. Minimal increases in TNFα (2x) and IFNγ (4x), but not other cytokines/chemokines, were observed compared to the vehicle control treatment only in the presence of the BCMA+ MM tumor cell line up to the concentration tested. This suggests that, unlike T-cell engagers, the risk of cytokine release syndrome in patients receiving RO7297089 is low. Cynomolgus monkey is the only relevant nonclinical species for RO7297089 as it showed binding to both recombinant CD16 and BCMA with comparable affinity to human antigens. Following five weekly intravenous administrations to monkeys at 0, 15, and 50 mg/kg, RO7297089 was well tolerated. In line with the mechanism of action, there were no test article-related cytokine increases or adverse findings observed in both dose levels. Systemic exposure of RO7297089 was approximately dose proportional from 15 to 50 mg/kg. Anti-drug antibodies (ADA) were observed in some animals at both dose levels, and ADA-related decreases in concentrations were observed at only 15 mg/kg. To evaluate in vivo activity, RO7297089-related effects on total plasma sBCMA and PCs were assessed. Elevations of sBCMA levels (100x) were observed post dose at both dose levels, and these effects returned to predose levels in animals that did not maintain concentrations at 15 mg/kg, suggesting that RO7297089 bound to and stabilized circulating cynomolgus sBCMA. Time- and dose-dependent reductions in serum IgM levels were observed at both dose levels. Changes in PC numbers were not detected by immunophenotyping; however, gene expression analysis of PC markers was included and demonstrated clear reductions in mRNA expression levels of PC markers including BCMA and J-chain in blood at both dose levels, suggesting reductions in BCMA+ cells. Collectively, these studies suggest that RO7297089 selectively kills BCMA+ cells by engaging CD16a-positive immune cells and has a favorable safety profile. Citation Format: Satoko Kakiuchi-Kiyota, Melissa M. Schutten, Adeyemi O. Adedeji, Hao Cai, Robert Hendricks, Luna Liu, Sivan Cohen, Aaron M. Fullerton, Nicholas Corr, Lanlan Yu, Denise de Almeida Nagata, Shelly Zhong, Michael Dillon, Christoph Spiess, Steve R. Leong, Bing Zheng, Susanne Wingert, Uwe Reusch, Stefan Knackmuss, Thorsten Ross, Andrew Polson, Ayse M. Ovacik. Preclinical pharmacology and safety of RO7297089, a novel anti-BCMA/CD16a bispecific antibody for the treatment of multiple myeloma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4556.

Circ_0007841 promotes the progression of multiple myeloma through targeting miR-338-3p/BRD4 signaling cascade

BackgroundThe pathogenesis of multiple myeloma (MM) is not completely known. Uncovering the potential mechanism of MM initiation and progression is essential for identifying novel diagnostic and therapeutic targets. Herein, we explored the function and the working mechanism of circular RNA circ_0007841 in MM progression.MethodsQuantitative real-time polymerase chain reaction (qRT-PCR) was employed to detect the expression of circ_0007841, microRNA-338-3p (miR-338-3p) and bromodomain containing 4 (BRD4). Cell proliferation ability was analyzed through cell counting kit-8 (CCK8) assay, colony formation assay and flow cytometry. Transwell assays were conducted to measure the migration and invasion abilities of MM cells. Cell apoptosis was also assessed by flow cytometry. The interaction between miR-338-3p and circ_0007841 or BRD4 was confirmed by dual-luciferase reporter assay and RNA-pull down assay.ResultsCirc_0007841 was highly expressed in bone marrow (BM)-derived plasma cells of MM patients and MM cell lines than that in healthy volunteers and normal plasma cell line nPCs. Circ_0007841 promoted the proliferation, cell cycle and metastasis and impeded the apoptosis of MM cells. miR-338-3p was a direct target of circ_0007841 in MM cells and circ_0007841 accelerated the progression of MM through targeting miR-338-3p. BRD4 could directly bind to miR-338-3p in MM cells and miR-338-3p exerted an anti-tumor role through targeting BRD4. Circ_0007841 promoted the activation of PI3K/AKT signaling via miR-338-3p/BRD4 axis. Exosomes generated from mesenchymal stromal cells (MSCs) elevated the malignant behaviors of MM cells via circ_0007841.ConclusionCirc_0007841 acted as an oncogene to promote the proliferation, cell cycle and motility and restrain the apoptosis of MM cells through sequestering miR-338-3p to up-regulate the expression of BRD4.

A T-cell–redirecting bispecific G-protein–coupled receptor class 5 member D x CD3 antibody to treat multiple myeloma

AbstractT-cell–mediated approaches have shown promise in myeloma treatment. However, there are currently a limited number of specific myeloma antigens that can be targeted, and multiple myeloma (MM) remains an incurable disease. G-protein–coupled receptor class 5 member D (GPRC5D) is expressed in MM and smoldering MM patient plasma cells. Here, we demonstrate that GPRC5D protein is present on the surface of MM cells and describe JNJ-64407564, a GPRC5DxCD3 bispecific antibody that recruits CD3+ T cells to GPRC5D+ MM cells and induces killing of GPRC5D+ cells. In vitro, JNJ-64407564 induced specific cytotoxicity of GPRC5D+ cells with concomitant T-cell activation and also killed plasma cells in MM patient samples ex vivo. JNJ-64407564 can recruit T cells and induce tumor regression in GPRC5D+ MM murine models, which coincide with T-cell infiltration at the tumor site. This antibody is also able to induce cytotoxicity of patient primary MM cells from bone marrow, which is the natural site of this disease. GPRC5D is a promising surface antigen for MM immunotherapy, and JNJ-64407564 is currently being evaluated in a phase 1 clinical trial in patients with relapsed or refractory MM (NCT03399799).

The Role of PHF19 As a Promoter of Tumorigenicity and Therapeutic Target in Multiple Myeloma

Introduction - Multiple Myeloma (MM) is a hematologic malignancy characterized by clonal growth of differentiated plasma cells (PCs). Despite improvement in MM therapy, the disease remains mostly incurable and is characterized by recurrent relapses with development of resistant clones that eventually lead to patient death. The pathways that lead to resistant and aggressive MM are not fully understood highlighting the need to improve our understanding of MM biology to identify potential new pathways and therapeutical targets. PHD Finger Protein 19 (PHF19) is a regulator of Polycomb Repressive Complex 2 (PRC2), the sole methyltransferase complex capable of catalyzing H3K27me3 to induce and enforce gene repression. PRC2 employs enhancer of zeste homolog 1 and 2 (EZH1/EZH2) as enzymatic subunits to hypermethylate H3K27. While overexpression and gain of function mutations of EZH1/2 have been observed in many cancers the role of this particular pathway in MM remains poorly understood. In the present study, we report on PHF19 as a new candidate gene to play a potential crucial role in MM oncogenesis. Methods- Gene expression profiling (GEP; Affymetrix U133 Plus 2.0) was performed on 739 MM patients (from total therapy trials [TT] 3-5; low risk MM n=636, high risk MM n=103), 42 patients with monoclonal gammopathy of undetermined significance (MGUS), 73 smoldering MM patients, 42 patients with primary plasma cell leukemia and 34 healthy donors. Myeloma risk was determined by the GEP 70 signature as previously defined. To test the implications of functional PHF19 knock down (KD) we used TRIPZ inducible PHF19 shRNA vs. scrambled control (Dharmacon) in two MM cell lines (JJN3 and ARP1). Real time PCR as well as western blotting was used to confirm PHF19 KD as well as to elucidate the effect on H3K27me3 (Cell Signaling). Functional in vitro studies included proliferation (Promega), clonogenic assays (StemCell), cell cycle and apoptosis assays (both Invitrogen). In vivo studies were performed using SCID mice that were subjected to tail vain injection with PHF19 KD JJN3 cells (n=10) or scrambled shRNA control (n=10). Weekly ELISA (Bethyl) and in vivo imaging (Xenogen) were performed and survival was recorded. Results- GEP of the previously mentioned patient populations and healthy controls identified PHF19 (chr9q33.2) as a candidate gene that was consistently dysregulated in MM patients. Mean expression levels at different MM stages correlated with disease aggressiveness (ANOVA, p&amp;lt;0.0001), Figure 1. High expression of PHF19 (log2&amp;gt;10.46) at diagnosis correlated significantly with adverse clinical parameters, including ISS III, anemia and elevated LDH, as well as worse overall survival (5 yr OS = 29% for patients with high PHF19 expression vs 77% for patients with low PHF19 expression [log2&amp;lt;10.46], p&amp;lt; 0.0001). These results led us to test the implications of functional PHF19 KD using TRIPZ inducible PHF19 shRNA vs. scrambled control in the JJN3 and ARP1 MM cell lines. PHF19 KD led to a drastic reduction of H3K27me3 thereby resulting in significantly reduced proliferation via cell cycle arrest, while apoptosis was not substantially altered. Clonogenic assays showed a significant reduction in colony numbers and size of MM cells with PHF19 KD compared to the control (&amp;gt;75% reduction in both cell lines, p&amp;lt;0.05). Xenograft studies showed consistently less tumor burden in the mice injected with PHF19 KD cells compared to scrambled control, evident through ELISA testing for IgG Kappa (Median =180 mg/ml for scrambled control vs 80 mg/ml for PHF19 KD at week 8, p=0.07) and bioimaging (Median bioilumisence 2.1x108 p/s for scrambled control vs. 0.8x108 p/s for PHF19 KD at week 8, non-significant). Median OS in mice injected with PHF19 KD cell was substantially longer (66 days) compared to mice subjected to scrambled control cells (54 days), p=0.052. Conclusion- In summary we show that PHF19 is upregulated in malignant plasma cells of MM patients and that PHF19 expression levels increase with advanced MM stages. High PHF19 expression was a marker of adverse prognosis in our total therapy (TT 3-5) cohort. Most importantly, in-vitro and in-vivo functional studies showed that PHF19 has important biological functions in MM. These results suggest that epigenetic regulation through histone methylation, in particular, H3K27 trimethylation, plays a crucial role in MM and the affected downstream pathways should be further elucidated. Disclosures Boyle: Janssen: Honoraria, Other: Travel; Abbvie: Honoraria; Amgen: Honoraria, Other: travel; Takeda: Honoraria, Other: travel; Celgene Corporation: Honoraria, Other: Travel. van Rhee:Kite Pharma: Consultancy; Adicet Bio: Consultancy; Karyopharm Therapeutics: Consultancy; Takeda: Consultancy; Sanofi Genzyme: Consultancy; Castleman Disease Collaborative Network: Consultancy; EUSA: Consultancy. Walker:Celgene: Research Funding.

Clinical effects of CD45 on the prognosis of extramedullary myeloma relapse.

The incidence of extramedullary relapse (EMR) arising during the clinical course of multiple myeloma (MM) has increased in recent years. Therefore, we herein investigated the effects of immunophenotyping on the prognosis of MM patients with EMR. We conducted a retrospective review on data collected from MM patients with EMR between January 2007 and December 2018 at the Japanese Red Cross Society Wakayama Medical Center. Patient characteristics at the diagnosis of EMR, the prognostic significance of immunophenotyping and other factors were evaluated. Extramedullary relapse was detected in 55 of 231 patients (23.8%). At the diagnosis of EMR, CD45, the leucocyte common antigen, was detected in 54.5% of cases. CD45 negativity in bone marrow correlated with thrombocytopenia and higher serum LDH levels. Moreover, high-risk cytogenetics was more frequently observed in CD45- than in CD45+patients. A univariate analysis showed that overall survival (OS) was significantly shorter in CD45- than in CD45+patients. Thrombocytopenia, higher serum LDH levels and high-risk cytogenesis were also associated with shorter OS. A multivariate analysis confirmed that CD45 negativity, higher serum LDH levels and high-risk cytogenesis were independent adverse prognostic factors for OS. A Kaplan-Meier analysis revealed the potential of CD45- as a prognostic factor in patients with EMR and that it correlated with shorter survival. The present results showed that the expression of CD45 in the neoplastic plasma cells of MM patients with EMR was associated with patient prognosis independent of other prognostic factors. The establishment of a treatment strategy for EMR patients with CD45- MM cells is needed to improve poor outcomes.

Citron Rho-interacting kinase silencing causes cytokinesis failure and reduces tumor growth in multiple myeloma

AbstractCitron Rho-interacting serine/threonine kinase (CIT) is a serine/threonine kinase that acts as a key component of the midbody and is essential for cytokinesis. CIT has been reported to be highly expressed in some tumor tissues and to play a role in cancer proliferation; however, the significance of CIT has not been investigated in multiple myeloma (MM). Here, we identified, by protein microarray and immunohistochemistry, that CIT is 1 of the upregulated proteins in the plasma cells of MM patients compared with healthy controls. Analysis of a gene expression profile data set showed that MM patients with high CIT gene expression had significantly worse overall survival compared with MM patients with low CIT gene expression. CIT silencing in MM cell lines induced cytokinesis failure and resulted in decreased MM cell proliferation in vitro and in vivo. TP53 expression was found to be an independent predictor of CIT dependency, with low-TP53 cell lines exhibiting a strong dependency on CIT. This study provides the rationale for CIT being a potential therapeutic target in MM in future trials.

Outcome of Multiple Myeloma with Chromosome 1q Gain and 1p Deletion after High-Dose Therapy and Autologous Hematopoietic Stem Cell Transplantation

Background and AimThe gain/amplification CKS1B gene at chromosome region 1q21 (1q+) is one of the most common genetic aberrations in multiple myeloma (MM). CKS1Bamplification and overexpression contribute to increased p27Kip1 degradation, cell cycle upregulation and poor outcomes in MM patients. Amplification of CKS1B is frequently associated with the deletion of CDKN2C gene at chromosome region 1p32 (1p-). Deletion of CDKN2C, a tumor suppressor gene, leads to an increased proliferative rate of plasma cells in MM patients and is also associated with inferior outcomes. There are limited data on the impact of 1q+/1p- on the outcomes after high-dose therapy and autologous stem cell transplantation (auto-HCT).MethodsIn this retrospective study, we evaluated outcomes of patients with 1q+ and/or 1p- after high-dose therapy and auto-HCT. From 2007 to 2015, 1365 MM patients underwent high-dose therapy and auto-HCT at our institution. We identified 100 patients with 1q+ and/or 1p- by fluorescent in situ hybridization (FISH) from that cohort. The cut off value used for gain/amplification of a 1q21/CKS1B was 7.9%; gain/amplification of two 1q21/CKS1B was 4.4%; and deletion of a 1p32.3/CDKN2C was 6.8%. A control group (N=287) with diploid cytogenetics and normal FISH panel with no high risk abnormalities was selected from the same cohort. From the above two cohorts, using a 1:1 propensity score-matched analysis without replacement, we were able to identify a matched control for 85 patients with 1q+/1p-.ResultsBaseline characteristics of the 1q+/1p- and control groups are summarized in table 1. Sixty-seven (79%), 4 (5%) and 14 (16%) patients had 1q+, 1p- or both 1q+ and 1p-, respectively. There was no significant difference in induction therapy, preparative regimen, or maintenance therapy between the two groups. The median follow-up time for all patients was 29.2 months (range: 0.29 -84.96). The cumulative incidence of 100-day nonrelapse mortality was 1.1% and 0% for the 1q+/1p- and the control groups, respectively. Forty-two patients (51%) in the 1q+/1p- group achieved a CR compared to 40 patients (49%) in the control group (P=0.6). VGPR rates in the 1q+/1p- and controls groups were 47% and 53% (P=0.5) respectively. The overall response rate for the 1q+/1p-and controls group was 96% and 100%, respectively (P=0.3). Median PFS for the 1q+/1p- and the controls groups were 26.5 months and 38.8 months, respectively. The estimated 3-year PFS for the 1q+/1p- and the control groups were 41% and 56%, respectively (HR 2.2, CI 1.18-4.16, P=0.01) (Figure 1A). The 3-year OS for the 1q+/1p- and the control groups were 79% and 86%, respectively (HR 1.5, CI 0.61-4.05, P=0.34) (Figure 1B).Conclusion1q+/1p- abnormalities with amplification CKS1B and deletion of CDKN2C genes were seen in approximately 7% of MM patients undergoing auto-HCT between 2007 and 2015. They were associated with a shorter PFS when compared to a propensity matched group of patients with diploid cytogenetics and normal FISH panel. Patients with 1q+/1p- may need more aggressive therapeutic approaches. DisclosuresThomas:Amgen Inc: Research Funding; Bristol Myers Squibb Inc.: Research Funding; Array Pharma: Research Funding; Acerta Pharma: Research Funding; Celgene: Research Funding. Lee:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies Corporation: Consultancy; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Chugai Biopharmaceuticals: Consultancy; Takeda Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees. Patel:Poseida Therapeutics, Inc.: Research Funding; Takeda: Research Funding; Abbvie: Research Funding; Celgene: Research Funding. Shpall:Affirmed GmbH: Research Funding. Orlowski:Bristol-Myers Squibb: Consultancy; Kite Pharma: Consultancy; Celgene: Consultancy; Amgen: Consultancy, Research Funding; Sanofi-Aventis: Consultancy; Janssen: Consultancy; Spectrum Pharma: Research Funding; BioTheryX: Research Funding; Takeda: Consultancy. Champlin:Otsuka: Research Funding; Sanofi: Research Funding.

Combining Next Generation Proteomics Platforms with Drug Sensitivity Resistance Testing Allows Identification of Physiologically Distinct Sub-Clones That Can Inform Therapeutic and Drug Development Strategies

Introduction: A hallmark of Multiple Myeloma (MM) is the sequel development of drug resistant phenotypes, which may be present initially or emerge during the course of treatment. These drug resistant phenotypes reflect the intra-tumor and inter-patient heterogeneity of this cancer. Most MM cells are sensitive to proteasome inhibitors (PIs), which have become the standard of care in the treatment of newly diagnosed and relapsed MM. However, resistance develops (intrinsic/acquired). Although several novel drugs have recently been approved or are in development for MM, there are few molecular indicators to guide treatment selection. To address this limitation we have combined mass spectrometry-based proteomics analysis together with ex vivo drug response profiles and clinical outcome to elucidate a best possible accurate phenotype of the resistant sub-clones, thus yielding a theranostic profile that will inform therapeutic and drug development strategies.Methods: We performed mass spectrometry-based proteomics analysis on plasma cells isolated from 38 adult MM patient bone marrow aspirates (CD138+). Samples were obtained at diagnosis or prior to commencing therapy. The participating subjects gave written informed consent in accordance with the Declaration of Helsinki that was approved by local ethics committees. For the proteomics analysis, peptides were purified using the filtered aided sample preparation (FASP) method. Subsequently, samples were prepared for label-free liquid chromatography mass spectrometry (LC-MS/MS) using a Thermo Scientific Q-Exactive MS mass spectrometer. Proteins were analysed using the MaxQuant and Perseus software for mass-spectrometry (MS)-based proteomics data analysis, UniProtKB-Swiss Prot database and KEGG Pathway database. In parallel, we undertook a comprehensive functional strategy to directly determine the drug dependency of myeloma plasma cells based on ex vivo drug sensitivity and resistance testing (DSRT)as previously described (1).Results: Our initial proteomic analysis was generated by examining MM patient plasma cells, grouped based on DSRT to 142 anticancer drugs including standard of care and investigational drugs. Each of the 142 drugs was tested over a 10,000-fold concentration range, allowing for the establishment of accurate dose-response curves for each drug in each patient. MM patients were stratified into four distinct subgroups as follows: highly sensitive (Group I), sensitive (Group II), resistant (Group III) or highly resistant (Group IV) to the panel of drugs tested. We then performed blinded analysis on the 4 groups of CD138+ plasma cells divided based on the ex vivo sensitivity profile, identifying a highly significant differential proteomic signature between the 4-chemosensitivity profiles, with Cell Adhesion Mediated-Drug Resistance (CAM-DR) related proteins (e.g. integrins αIIb and β3) significantly elevated in the highly resistant phenotype (Group IV). In addition our results showed that Group I patients displayed significant upregulation of cell proliferation proteins including: MCM2, FEN1, PCNA and RRM2. Furthermore, Group I patients have shorter Progression Free Survival (PFS) as well as Overall Survival (OS) compared to the other subgroups. Figure 1 shows the Heatmap summarizing the expression of proteins (log2 fold change) in the four distinct MM patient subgroups.Conclusions:Our findings suggest that combining a proteomics based study together with drug sensitivity and resistance testing allows for an iterative adjustment of therapies for patients with MM, one patient at a time, thus providing a theranostic approach. Our results suggest that the disease driving mechanisms in the patient subgroups are distinct, with highly resistant patients exhibiting cell adhesion mediated cytoprotection, while highly sensitive patients show an increased cell proliferation protein profile with shorter PFS and OS. Our study aims to guide treatment decisions for individual cancer patients coupled with monitoring of subsequent responses in patients to measure and understand the efficacy and mechanism of action of the drugs. Future work will include the establishment of flow cytometry-based screening assays to identify the different resistant phenotypes at diagnosis/relapse.

Diagnostic Value of CD27 Antigen in Patients with Multiple Myeloma

To explore the expression of CD27 antigen in patients with multiple myeloma(MM), and its clinical diagnostic value, as well as the correlation of CD27 with clinical features and genetic abnormalities. Using 8 color flow cytometry, the immunophenotype of 123 MM patients' marrow cells was examined, while 51 cases of normal plasma cell reactive prolieration were used as control. Antibodies are as follows:ckappa-FITC/clambda-PE/ CD38-ECD/CD45-PERCP/CD19-PC7/ CD27-APC/CD138-BV421/ CD56-BV510. For differentiation of abnormal plasma cells from normal or reactive plasma cells, FS INT /FS PEAK with CD138/CD38 gating strategy was used to measure cell markers CD138,CD38, CD56, CD19, ckappa, clambda and CD45, then the expression rate of CD27 and mean fluorescence intensity(MFI) were analyzed for its diagnostic value in MM. At the same time, the laboratory data of 107 cases of MM patients were analyzed and the fluorescence in situ hybridization (FISH) was used to detecte 1q21 amplification, 13q14 deletion, p53 deletion and IGH rearrangement in 34 cases, then the clinical features and genetic abnormalities were compared between CD27- and CD27+ MM patients. The CD27 positive rate of abnormal plasma cells in MM patients was 48% (59/123) (percentage ≥20% as positive criterion), MFI was 31.3±35.6; while the positive rate of normal or reactive plasma cells were 100% (51/51), the MFI was 93.7±6.3. The positive rate and MFI of CD27 in MM patients were significantly lower than that in normal or reactive plasma cells (P<0.01). Laboratory examination of 58 cases of CD27 negative and 49 cases of CD27 positive MM patients indicated that no significant differences were shown on disease progress parameter, such as hemoglobin, albumin, serum calcium, serum creatinine,and no notable differences were involved in the analysis of prognostic factors between the 2 groups, such as β2-MG microglobulin and LDH levels (P<0.05). The 1q21 amplification, 13q14 deletion, p53 deletion, and IGH rearrangement results all were not significantly different between 17 cases of CD27 negative and 17 cases of CD27 positive MM patients(P<0.05). CD27 has a unique expression profile, and its negative or weak expression is highly suggestive for MM. The 8 color flow cytometry can be used to analyze the expression of multiple antigens, which can provide a reliable evidence for the diagnosis and differential diagnosis of MM disease.

DEK protein level is a biomarker of CD138positive normal and malignant plasma cells.

Overexpression of DEK oncogene is associated with increased proliferation of carcinoma cells and it is observed in several solid tumors due to the amplification of the 6p22.3 chromosomal region where DEK locates. Although the same chromosomal amplification occurs in multiple myeloma (MM), a plasma cell neoplasm, whether the expression and the copy number of the DEK gene are affected in MM remains elusive. We show that despite the increased copy number in CD138positive MM cells (4 out of 41 MM samples), DEK mRNA expression was down-regulated compared with that in CD138negative bone marrow (BM) cells of the same patients (P<0.0001). DEK protein was not detectable by immunohistochemistry (IHC) in CD138positive normal plasma cells or in malignant plasma cells of MM patients (n = 56) whereas it was widely expressed in normal and neoplastic B-cells. Stable knockdown or overexpression of DEK in CD138positive MM cell lines did not affect the proliferation and viability of the cells profoundly in the presence or absence of chemotherapeutic agent melphalan whereas knockdown of DEK moderately but significantly increased the expression level of CD138 (p<0.01). Decreased DEK expression in plasma cells suggests a potential role of this gene in plasma cell development and lack of detectable DEK protein by IHC could be used as a biomarker for normal and malignant plasma cells.