Decreased PU.1 expression in mature B cells induces lymphomagenesis.

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of lymphoma, accounting for 30% of non-Hodgkin lymphomas. Although comprehensive analysis of genetic abnormalities has led to the classification of lymphomas, the exact mechanism of lymphomagenesis remains elusive. The Ets family transcription factor, PU.1, encoded by Spi1, is essential for the development of myeloid and lymphoid cells. Our previous research illustrated the tumor suppressor function of PU.1 in classical Hodgkin lymphoma and myeloma cells. In the current study, we found that patients with DLBCL exhibited notably reduced PU.1 expression in their lymphoma cells, particularly in the non-germinal center B-cell-like (GCB) subtype. This observation suggests that downregulation of PU.1 may be implicated in DLBCL tumor growth. To further assess PU.1's role in mature B cells in vivo, we generated conditional Spi1 knockout mice using Cγ1-Cre mice. Remarkably, 13 of the 23 knockout mice (56%) showed splenomegaly, lymphadenopathy, or masses, with some having histologically confirmed B-cell lymphomas. In contrast, no wild-type mice developed B-cell lymphoma. In addition, RNA-seq analysis of lymphoma cells from Cγ1-Cre Spi1F/F mice showed high frequency of each monoclonal CDR3 sequence, indicating that these lymphoma cells were monoclonal tumor cells. When these B lymphoma cells were transplanted into immunodeficient recipient mice, all mice died within 3 weeks. Lentiviral-transduced Spi1 rescued 60% of the recipient mice, suggesting that PU.1 has a tumor suppressor function in vivo. Collectively, PU.1 is a tumor suppressor in mature B cells, and decreased PU.1 results in mature B-cell lymphoma development.

Serum monoclonal immunoglobulin light-chain detection differs between immunofixation electrophoresis methods in patients with AL amyloidosis.

Serum immunofixation electrophoresis (IFE) is often performed for screening monoclonal proteins (M proteins) in immunoglobulin light-chain amyloidosis (AL amyloidosis). However, the performance of serum IFE for detecting M protein in AL amyloidosis patients is often insufficient. In this study, we examined the detection rate of serum M protein in newly diagnosed AL amyloidosis patients and analyzed differences in M protein detection between IFE methods. Among 60 patients newly diagnosed with AL amyloidosis, 22 had undetectable serum M protein by IFE with the Epalyzer2 system. Samples with undetectable M protein had significantly lower involved serum-free light-chain (iFLC) and a smaller difference between involved and uninvolved serum-free light-chain (dFLC) values than samples with IFE-detectable monoclonal light chains. When samples that tested negative for M protein by the Epalyzer2 system were retested by IFE with the HYDRASYS 2 system, 50% had IFE-detectable monoclonal light chains. The IFE system and reagents used may affect serum monoclonal immunoglobulin light-chain detection in AL amyloidosis patients, especially those with low iFLC or low dFLC samples. More attention should be paid to the performance of IFE systems, since it may affect the diagnostic and therapeutic evaluation of AL amyloidosis patients.

A new staging system using right atrial strain in patients with immunoglobulin light-chain cardiac amyloidosis.

AIMS: There are minimal data on the prognostic impact of right atrial strain during the reservoir phase (RASr) in patients with immunoglobulin light-chain (AL) cardiac amyloidosis. METHODS AND RESULTS: Among 78 patients who were diagnosed with AL cardiac amyloidosis at Kumamoto University Hospital from 2007 to 2022, 72 patients with sufficient two-dimensional speckle tracking imaging data without chemotherapy before the diagnosis were retrospectively analysed. During a median follow-up of 403 days, 31 deaths occurred. Age and the rate of male sex were not significantly different between the all-cause death group and the survival group (age, 70.4 ± 8.8 years vs. 67.0 ± 10.0 years, P = 0.14, male sex, 65% vs. 66%, P = 0.91). The estimated glomerular filtration rate (eGFR) was significantly lower, and B-type natriuretic peptide (BNP) and high sensitivity cardiac troponin T (hs-cTnT) were significantly higher, in the all-cause death group versus the survival group (eGFR, 48.2 ± 21.0 mL/min/1.73 m2 vs. 59.4 ± 24.4 mL/min/1.73 m2, P < 0.05, BNP, 725 [360-1312] pg/mL vs. 123 [81-310] pg/mL, P < 0.01, hs-cTnT, 0.12 [0.07-0.18] ng/mL vs. 0.05 [0.03-0.08] ng/mL, P < 0.01). Left ventricular (LV) global longitudinal strain (GLS) (LV-GLS), left atrial strain during the reservoir phase (LASr), right ventricular GLS (RV-GLS), and RASr were significantly lower in the all-cause death group versus the survival group (LV-GLS, 8.5 ± 4.3% vs. 11.8 ± 3.8%, P < 0.01, LASr, 8.8 ± 7.1% vs. 14.3 ± 8.1%, P < 0.01, RV-GLS, 11.6 ± 5.1% vs. 16.4 ± 3.9%, P < 0.01, RASr, 10.2 ± 7.3% vs. 20.7 ± 9.5%, P < 0.01). RASr was significantly associated with all-cause death after adjusting for RV-GLS, LV-GLS and LASr (hazard ratio [HR]: 0.91, 95% confidence interval [95% CI]: 0.83-0.99, P < 0.05). RASr and log-transformed BNP were significantly associated with all-cause death after adjusting for log-transformed troponin T and eGFR (RASr, HR: 0.93, 95% CI: 0.87-1.00, P < 0.05; log-transformed BNP, HR: 2.10, 95% CI: 1.17-3.79, P < 0.05). The optimal cut-off values were RASr: 16.4% (sensitivity: 66%, specificity: 84%, area under curve [AUC]: 0.81) and BNP: 311.2 pg/mL (sensitivity: 83%, specificity: 78%, AUC: 0.82) to predict all-cause mortality using ROC analysis. Kaplan-Meier analysis revealed that patients with low RASr (<16.4%) or high BNP (>311.2 pg/mL) had a significantly high probability of all-cause death (both, P < 0.01). We devised a new staging score by adding 1 point if RASr decreased or BNP levels increased more than each cut-off value. The HR for all-cause death using score 0 as a reference was 5.95 (95% CI: 1.19-29.79; P < 0.05) for score 1 and 23.29 (95% CI: 5.37-100.98; P < 0.01) for score 2. CONCLUSIONS: The new staging system using RASr and BNP predicted prognosis in patients with AL cardiac amyloidosis.

Waldenstrom's macroglobulinemia-like B cell lymphoma with MYD88 L265P mutation and t(14;18)(q32;q21) involving IGH-MALT1.

A 65-year-old woman was referred to the hospital for further investigation of weight loss, hyperproteinemia, and anemia. Serum immunofixation electrophoresis revealed IgM-κ M protein. Bone marrow examination revealed an increase in the number of B -cells with immunoglobulin kappa light-chain restriction. Although the MYD88 L265P mutation was identified in bone marrow mononuclear cells, which suggested the diagnosis of Waldenstrom's macroglobulinemia (WM), a fusion signal of IgH-MALT1, which is commonly observed in extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) lymphoma, was also identified. Here, we describe a rare case of low-grade B-cell lymphoma with MYD88 L265P mutations accompanying IgH-MALT1.

Isatuximab Plus Carfilzomib and Dexamethasone in East Asian Patients With Relapsed Multiple Myeloma: Updated IKEMA Subgroup Analysis.

BACKGROUND: The Phase 3 IKEMA study (NCT03275285) demonstrated isatuximab (Isa) in combination with carfilzomib (K) and dexamethasone (d) significantly improved progression-free survival (PFS) in patients with relapsed multiple myeloma (MM) compared with Kd. A post-hoc analysis of East Asian patients in IKEMA evaluated the efficacy and safety of Isa-Kd versus Kd in this population and was previously published. PATIENTS AND METHODS: Patients with relapsed MM who had received 1 to 3 prior lines of therapy were randomized 3:2 to receive Isa-Kd or Kd. The primary endpoint was PFS, and key secondary endpoints included rate of very good partial response or better (≥VGPR), complete response (CR) rate, and minimal residual disease (MRD) negativity. Of the IKEMA overall population, 46 patients were of East Asian descent. This is an updated analysis of the efficacy and safety of Isa-Kd in East Asian patients, including data through 14 January 2022. RESULTS: Isa-Kd continued to demonstrate improved efficacy and safety versus Kd in East Asian patients with relapsed MM, with improved PFS, rate of ≥VGPR, CR rate, and MRD negativity, that was consistent with the overall IKEMA population. The rate of Grade ≥3 treatment-emergent adverse events was also consistent with the prior analysis and overall IKEMA population. CONCLUSION: Based on the results of this analysis, Isa-Kd is a novel treatment option for East Asian patients with relapsed MM.

Prognostic value of right ventricular global longitudinal strain in patients with immunoglobulin light-chain cardiac amyloidosis.

Aims: Left ventricular (LV) global longitudinal strain (GLS) (LV-GLS) is a strong and independent predictor of outcomes in patients with immunoglobulin light-chain (AL) cardiac amyloidosis. This study was performed to investigate whether right ventricular (RV) GLS (RV-GLS) provides prognostic information in patients with AL amyloidosis. Methods and results: Among 74 patients who were diagnosed with AL cardiac amyloidosis at Kumamoto University Hospital from December 2005 to December 2022, 65 patients who had enough information for two-dimensional speckle tracking imaging and did not receive chemotherapy before the diagnosis of cardiac amyloidosis were retrospectively analysed. During a median follow-up of 359 days, 29 deaths occurred. In two-dimensional echocardiographic findings, LV-GLS, left atrium reservoir strain (LASr), and RV-GLS were significantly lower in the all-cause death group than in the survival group (LV-GLS: 8.9 ± 4.2 vs. 11.7 ± 3.9, P < 0.01; LASr: 9.06 ± 7.28 vs. 14.09 ± 8.32, P < 0.05; RV-GLS: 12.0 ± 5.1 vs. 16.8 ± 4.0, P < 0.01). Multivariable Cox proportional hazard analysis showed RV-GLS was significantly and independently associated with all-cause death in patients with AL cardiac amyloidosis (hazard ratio 0.85; 95% confidence interval, 0.77-0.94; P < 0.01). Receiver operating characteristic analysis showed that the area under the curve of RV-GLS for all-cause death was 0.774 and that the best cut-off value of RV-GLS was 14.5% (sensitivity, 75%; specificity, 72%). In the Kaplan-Meier analysis, patients with AL cardiac amyloidosis who had low RV-GLS (<14.5%) had a significantly higher probability of all-cause death (P < 0.01). Conclusion: RV-GLS has prognostic value in patients with AL cardiac amyloidosis and provides greater prognostic power than LV-GLS and LASr.

Cardiac MRI-derived Extracellular Volume Fraction versus Myocardium-to-Lumen R1 Ratio at Postcontrast T1 Mapping for Detecting Cardiac Amyloidosis.

Purpose: To evaluate the diagnostic performance of myocardium-to-lumen R1 (1/T1) ratio on postcontrast T1 maps for the detection of cardiac amyloidosis in a large patient sample. Materials and Methods: This retrospective study included consecutive patients who underwent MRI-derived extracellular volume fraction (MRI ECV) analysis between March 2017 and July 2021 because of known or suspected heart failure or cardiomyopathy. Pre- and postcontrast T1 maps were generated using the modified Look-Locker inversion recovery sequence. Diagnostic performances of MRI ECV and myocardium-to-lumen R1 ratio on postcontrast T1 maps (a simplified index not requiring a native T1 map and hematocrit level data) for detecting cardiac amyloidosis were evaluated using the area under the receiver operating characteristic curve (AUC), sensitivity, and specificity. Results: Of 352 patients (mean age, 63 years ± 16 [SD]; 235 men), 136 had cardiac amyloidosis. MRI ECV showed 89.0% (121 of 136; 95% CI: 82%, 94%) sensitivity and 98.6% (213 of 216; 95% CI: 96%, 100%) specificity for helping detect cardiac amyloidosis (cutoff value of 40% [AUC, 0.99 {95% CI: 0.97, 1.00}; P < .001]). Postcontrast myocardium-to-lumen R1 ratio showed 92.6% (126 of 136; 95% CI: 89%, 96%) sensitivity and 93.1% (201 of 216; 95% CI: 89%, 96%) specificity (cutoff value of 0.84 [AUC, 0.98 {95% CI: 0.95, 0.99}; P < .001]). There was no evidence of a difference in AUCs for each parameter (P = .10). Conclusion: Postcontrast myocardium-to-lumen R1 ratio showed excellent diagnostic performance comparable to that of MRI ECV in the detection of cardiac amyloidosis.Keywords: MR Imaging, Cardiac, Heart, Cardiomyopathies Supplemental material is available for this article. © RSNA, 2023.

Targeting the immune microenvironment in Waldenström macroglobulinemia via halting the CD40/CD40-ligand axis.

Recent investigations have improved our understanding of the molecular aberrations supporting Waldenström macroglobulinemia (WM) biology; however, whether the immune microenvironment contributes to WM pathogenesis remains unanswered. First, we showed how a transgenic murine model of human-like lymphoplasmacytic lymphoma/WM exhibits an increased number of regulatory T cells (Tregs) relative to control mice. These findings were translated into the WM clinical setting, in which the transcriptomic profiling of Tregs derived from patients with WM unveiled a peculiar WM-devoted messenger RNA signature, with significant enrichment for genes related to nuclear factor κB-mediated tumor necrosis factor α signaling, MAPK, and PI3K/AKT, which was paralleled by a different Treg functional phenotype. We demonstrated significantly higher Treg induction, expansion, and proliferation triggered by WM cells, compared with their normal cellular counterpart; with a more profound effect within the context of CXCR4C1013G-mutated WM cells. By investigating the B-cell-to-T-cell cross talk at single-cell level, we identified the CD40/CD40-ligand as a potentially relevant axis that supports WM cell-Tregs interaction. Our findings demonstrate the existence of a Treg-mediated immunosuppressive phenotype in WM, which can be therapeutically reversed by blocking the CD40L/CD40 axis to inhibit WM cell growth.

CT Extracellular Volume Fraction versus Myocardium-to-Lumen Signal Ratio for Cardiac Amyloidosis.

Background Large studies on the diagnostic performance of CT-derived myocardial extracellular volume fraction (ECV) for detecting cardiac amyloidosis are lacking. A simple and practical index as a surrogate for CT ECV would be clinically useful. Purpose To compare the diagnostic performances between CT-derived myocardial ECV and myocardium-to-lumen signal ratio for the detection of cardiac amyloidosis in a large patient sample. Materials and Methods This retrospective study included patients who underwent CT ECV analysis because of suspected heart failure or cardiomyopathy between January 2018 and July 2021. CT ECV was quantified using routine pre-transcatheter aortic valve replacement planning cardiac CT, pre-atrial fibrillation ablation planning cardiac CT, or coronary CT angiography with the addition of unenhanced and delayed phase cardiac CT scans. The diagnostic performances of CT ECV and myocardium-to-lumen signal ratio in delayed phase cardiac CT (a simplified index not requiring unenhanced CT and hematocrit) for detecting cardiac amyloidosis were evaluated using the area under the receiver operating characteristic curve (AUC), sensitivity, and specificity. Results Of 552 patients (mean age, 69 years ± 14 [SD]; 295 men), 41 had cardiac amyloidosis. The sensitivity of CT ECV for amyloidosis was 90% (37 of 41 patients [95% CI: 77, 97]), with a specificity of 92% (472 of 511 patients [95% CI: 90, 95]) and optimal ECV cutoff value of 37% (AUC, 0.97 [95% CI: 0.96, 0.99]). The sensitivity of myocardium-to-lumen signal ratio was 88% (36 of 41 patients [95% CI: 74, 96]), with a specificity of 92% (469 of 511 patients [95% CI: 89, 94]) and optimal myocardium-to-lumen signal ratio cutoff value of 0.87 (AUC, 0.96 [95% CI: 0.94, 0.97]; P = .27 for comparison with ECV). Conclusion CT-derived myocardial extracellular volume fraction and myocardium-to-lumen signal ratio showed comparable and excellent diagnostic performance in detecting cardiac amyloidosis in a large patient sample. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Williams in this issue.

Assessing the treatment effect of daratumumab by serial measurements of cardiac biomarkers and imaging parameters in light-chain cardiac amyloidosis.

Daratumumab, an anti-human CD38 monoclonal antibody, has become the standard of care in patients with systemic light-chain (AL) amyloidosis and multiple myeloma (MM). Herein, we report two cases of AL cardiac amyloidosis with MM who were treated with daratumumab, lenalidomide, and dexamethasone (DRd). Serial evaluation of cardiac biomarkers, echocardiography, and cardiac magnetic resonance imaging (CMR) were performed during 12 months of DRd treatment. A complete hematologic response was achieved three months after treatment initiation and sustained during the observation period. Twelve months after DRd treatment, we found improvements in levels (values for case 1 and case 2, respectively) of B-type natriuretic peptide (593.2 → 312.2 pg/mL and 202.4 → 104.3 pg/mL), N-terminal pro-brain natriuretic peptide (4005 → 1800 pg/mL and 2576 → 1170 pg/mL), high-sensitivity cardiac troponin T (0.156 → 0.072 ng/mL and 0.0678 → 0.0467 ng/mL), and global longitudinal strain (-6.8 → -10.4 % and -11.8 → -14.8 %). CMR revealed no noticeable changes in native T1 value or extracellular volume fraction. However, one case showed decreased native T2 value (61 → 55 ms). In conclusion, DRd treatment improved heart failure and cardiac function, relieved myocardial damage, and prevented amyloid deposition progression in the patients with AL cardiac amyloidosis. Cardiac biomarkers and imaging findings may be useful for monitoring the therapeutic effects of daratumumab-containing regimens. Learning objective: Daratumumab-containing regimens led to a rapid complete hematologic response, improvements in heart failure symptoms, cardiac function, and regression of myocardial damage in light-chain cardiac amyloidosis. This treatment prevents additional amyloid deposition and suppresses the direct cardiotoxic effects of amyloidogenic immunoglobulin light-chains. Serial assessments of cardiac biomarkers and imaging findings are useful for evaluating the therapeutic effect of daratumumab-containing regimens.

Water Droplet-in-Oil Digestion Method for Single-Cell Proteomics.

Recent advances in single-cell proteomics highlight the promise of sensitive analyses in limited cell populations. However, technical challenges remain for sample recovery, throughput, and versatility. Here, we first report a water droplet-in-oil digestion (WinO) method based on carboxyl-coated beads and phase transfer surfactants for proteomic analysis using limited sample amounts. This method was developed to minimize the contact area between the sample solution and the container to reduce the loss of proteins and peptides by adsorption. This method increased protein and peptide recovery 10-fold. The proteome profiles obtained from 100 cells using the WinO method highly correlated with those from 10,000 cells using the in-solution digestion method. We successfully applied the WinO method to single-cell proteomics and quantified 462 proteins. Using the WinO method, samples can be easily prepared in a multi-well plate, making it a widely applicable and suitable method for single-cell proteomics.

Isatuximab plus carfilzomib and dexamethasone in East Asian patients with relapsed multiple myeloma: IKEMA subgroup analysis.

In the phase 3 IKEMA study (NCT03275285), isatuximab (Isa) plus carfilzomib (K) and dexamethasone (d) significantly improved progression-free survival (PFS) in relapsed multiple myeloma (MM), compared with Kd. This IKEMA subgroup analysis evaluated efficacy and safety of Isa-Kd versus Kd among East Asian patients. Eligible patients had 1-3 prior lines of therapy and were stratified by number of prior lines and revised International Staging System. The primary endpoint was PFS. Key secondary endpoints included overall response, very good partial response or better (≥VGPR), minimal residual disease (MRD) negativity, and complete response (CR) rate. Forty-six East Asian patients (19 Japanese, 27 South Korean) were randomized to Isa-Kd (n = 25) or Kd (n = 21). Isa-Kd improved PFS (HR 0.64; 95% CI 0.23-1.76), ≥VGPR (80.0% vs 52.4%), MRD negativity rate (44.0% vs 9.5%), and CR (44.0% vs 23.8%). The rate of grade ≥ 3 treatment-emergent adverse events (TEAEs) was 79% for Isa-Kd versus 55% for Kd. The rate of serious TEAEs was 46% versus 50%, and the rate of TEAEs leading to treatment discontinuation was 4% versus 10%. Overall, Isa-Kd improved efficacy and safety versus Kd in East Asian patients with relapsed MM, consistent with the overall IKEMA population.

A novel PDK1 inhibitor, JX06, inhibits glycolysis and induces apoptosis in multiple myeloma cells.

Pyruvate dehydrogenase kinase 1 (PDK1) is a Ser/Thr kinase that inactivates mitochondrial pyruvate dehydrogenase (PDH), leading to switch of glucose metabolism from mitochondrial oxidation to aerobic glycolysis. We previously reported that PDK1 inhibition is a potent therapeutic strategy in multiple myeloma (MM). However, availability of PDK1 inhibitors, which are effective at low concentrations, are limited at present, making PDK1 inhibition difficult to apply in the clinic. In the present study, we examined the efficacy and mechanism of action of JX06, a novel PDK1 inhibitor, against MM cells. We confirmed that PDK1 is highly expressed in normal plasma cells and MM cells using publicly available gene expression datasets. JX06 suppressed cell growth and induced apoptosis against MM cells from approximately 0.5 µM JX06 treatment reduced PDH phosphorylation, suggesting that JX06 is indeed inhibiting PDK1. Intracellular metabolite analysis revealed that JX06 treatment reduced metabolites associated with glucose metabolism of MM cells. Additionally, JX06 in combination with a well-known proteasome inhibitor, bortezomib, significantly increased MM cell death, which raises the possibility of combination use of JX06 with proteasome inhibitors in the clinic. These findings demonstrate that PDK1 can be potentially targeted by JX06 in MM through glycolysis inhibition, leading to a novel therapeutic strategy in MM.

Relationship between Serum Bortezomib Concentration and Emergence of Diarrhea in Patients with Multiple Myeloma and/or AL Amyloidosis.

(1) Background: multiple myeloma patients have benefited from bortezomib therapy, though it has often been discontinued owing to diarrhea. The objective of this study was to verify serum bortezomib concentration in the emergence of diarrhea. (2) Methods: this prospective, observational case-control, and monocentric study was performed with an approval by the Ethics Committee of Kumamoto University Hospital in 2015 (No. 1121) from February 2015 to April 2017. (3) Results: twenty-four patients with bortezomib therapy were recruited; eight patients (33.3%) developed diarrhea at day 3 as median. Median measured trough bortezomib concentration at 24 h after first or second dose for patients with or without diarrhea was 0.87 or 0.48 ng/mL, respectively (p = 0.04, Wilcoxon signed rank test). Receiver operation characteristic (ROC) analysis produced the cut-off concentration of 0.857 ng/mL (area under the ROC curve of 0.797, sensitivity of 0.625, specificity of 0.875). The survival curves between patients with and without diarrhea were similar (p = 0.667); those between patients with higher and lower concentration than median value (0.61 ng/mL) were also similar (p = 0.940). (4) Conclusions: this study indicated the possible involvement of serum bortezomib concentration in the emergence of diarrhea in bortezomib therapy in patients with multiple myeloma.

ROBO1 Promotes Homing, Dissemination, and Survival of Multiple Myeloma within the Bone Marrow Microenvironment.

The bone marrow (BM) microenvironment actively promotes multiple myeloma (MM) pathogenesis and therapies targeting both cancer cells and the niche are highly effective. We were interested in identifying novel signaling pathways supporting MM-BM crosstalk. Mutations in the transmembrane receptor Roundabout 1 (ROBO1) were recently identified in MM patients, however their functional consequences are uncertain. Through protein structure-function studies, we discovered that ROBO1 is necessary for MM adhesion to BM stromal and endothelial cells and ROBO1 knock out (KO) compromises BM homing and engraftment in a disseminated mouse model. ROBO1 KO significantly decreases MM proliferation in vitro and intra- and extramedullary tumor growth, in vivo. Mechanistically, ROBO1 C-terminus is cleaved in a ligand-independent fashion and is sufficient to promote MM proliferation. Viceversa, mutants lacking the cytoplasmic domain, including the human-derived G674* truncation, act dominantly negative. Interactomic and RNA sequencing studies suggest ROBO1 may be involved in RNA processing, supporting further studies.

Lysine Demethylase 5A is Required for MYC Driven Transcription in Multiple Myeloma.

Lysine demethylase 5A (KDM5A) is a negative regulator of histone H3K4 trimethylation, a histone mark associated with activate gene transcription. We identify that KDM5A interacts with the P-TEFb complex and cooperates with MYC to control MYC targeted genes in multiple myeloma (MM) cells. We develop a cell-permeable and selective KDM5 inhibitor, JQKD82, that increases histone H3K4me3 but paradoxically inhibits downstream MYC-driven transcriptional output in vitro and in vivo. Using genetic ablation together with our inhibitor, we establish that KDM5A supports MYC target gene transcription independent of MYC itself, by supporting TFIIH (CDK7)- and P-TEFb (CDK9)-mediated phosphorylation of RNAPII. These data identify KDM5A as a unique vulnerability in MM functioning through regulation of MYC-target gene transcription, and establish JQKD82 as a tool compound to block KDM5A function as a potential therapeutic strategy for MM.

[The role of regulatory T cells in multiple myeloma progression].

Regulatory T cells (Tregs) are a subset of CD4+ T lymphocytes that suppress the functions of antigen-presenting cells and effector T cells, characterized by the expression of transcription factor forkhead box P3 (FOXP3). Recent studies have reported an increase in the number of Tregs in the bone marrow (BM) of multiple myeloma (MM) patients. However, the role and mechanisms of Treg accumulation in the BM of MM patients remain debatable. Here, we present our data demonstrating the significance of Tregs in the context of MM disease progression. Using the transplantable MM mouse model, we observed a significant increase in Tregs in the BM of MM-injected mice from the early disease stage. We observed extended survival in MM-injected mice with Treg depletion than in mice without Treg depletion, demonstrating direct in vivo evidence that Tregs enhance disease progression in MM. It is noteworthy that type 1 interferon (IFN) signaling is activated in MM-associated Tregs. By using type 1 IFN receptor blocking antibody treatment and type 1 IFN receptor knockout Tregs, we demonstrated a significant decrease in MM-associated Treg proliferation, which was associated with longer survival in MM-injected mice. Thus, we have demonstrated that Tregs play a significant role in MM progression; the function and homeostasis of Tregs are regulated by type 1 IFN secreted in the BM microenvironment.

Expression of activated integrin ß7 in multiple myeloma patients.

Multiple myeloma (MM) is still extremely difficult to cure, and new therapeutic drugs are needed. We recently found that integrin ß7 is constitutively activated in MM cells, and chimeric antigen receptor (CAR) T cells targeting activated integrin ß7 have a significant anti-MM effect. In this study, we performed flow cytometry analysis of the expression of activated integrin ß7 in bone marrow cells from 137 symptomatic MM patients. In 60/137 (44%) MM patients, activated integrin ß7 was detected in most MM cells (> 80% of MM cells were in the positive gate). Activated integrin ß7 was highly expressed in MM cells even in heavily treated patients. It also showed high expression in many CD38lo/-CD138-CD19+B cells, which reportedly include clonotypic B cells, in the bone marrow of MM patients. Taken together, these results suggest that CAR T-cell therapy targeting activated integrin ß7 has the potential to benefit many patients with relapsed or refractory MM.