miR-17-92 cluster-BTG2 axis regulates B-cell receptor signaling in mantle cell lymphoma.

B-cell receptor (BCR) signaling is critically activated and stable for mantle cell lymphoma (MCL), but the underlying mechanism of the activated BCR signaling pathway is not clear. The pathogenic basis of miR-17-92 cluster remains unclear although the oncogenic microRNA (miRNA) miR-17-92 cluster is highly expressed in patients with MCL. We revealed that miR-17-92 cluster overexpression is partly dependent on SOX11 expression and chromatin acetylation of MIR17HG enhancer regions. Moreover, miR-17-92 cluster regulates not only cell proliferation but BCR signaling activation in MCL cell lines. To comprehensively identify miR-17-92 cluster target genes, we performed pulldown-seq, where target RNA of miRNA was captured using the biotinylated miRNA mimics and magnetic bead-coated streptavidin, and quantified using next-generation sequencing. The pulldown-seq identified novel miRNA target genes, including tumor suppressors such as BTG2 (miR-19b), CDKN2A (miR-17), SYNE1 (miR-20a), TET2 (miR-18, miR-19b, and miR-92a), TNFRSF10A (miR-92a), and TRAF3 (miR-17). Notably, the gene expression profile data of patients with MCL revealed that BTG2 expression was negatively associated with that of BCR signature genes, and low BTG2 expression was associated with poor overall survival. Moreover, BTG2 silencing in MCL cell lines significantly induced BCR signaling overactivation and cell proliferation. Our results suggest an oncogenic role of miR-17-92 cluster-activating BCR signaling throughout BTG2 deregulation in MCL. Furthermore, this may contribute to the prediction of the therapeutic efficacy and improved outcomes of MCL.

The Rationale for the Dual-Targeting Therapy for RSK2 and AKT in Multiple Myeloma.

Multiple myeloma (MM) is characterized by remarkable cytogenetic/molecular heterogeneity among patients and intraclonal diversity even in a single patient. We previously demonstrated that PDPK1, the master kinase of series of AGC kinases, is universally active in MM, and plays pivotal roles in cell proliferation and cell survival of myeloma cells regardless of the profiles of cytogenetic and genetic abnormalities. This study investigated the therapeutic efficacy and mechanism of action of dual blockade of two major PDPK1 substrates, RSK2 and AKT, in MM. The combinatory treatment of BI-D1870, an inhibitor for N-terminal kinase domain (NTKD) of RSK2, and ipatasertib, an inhibitor for AKT, showed the additive to synergistic anti-tumor effect on human MM-derived cell lines (HMCLs) with active RSK2-NTKD and AKT, by enhancing apoptotic induction with BIM and BID activation. Moreover, the dual blockade of RSK2 and AKT exerted robust molecular effects on critical gene sets associated with myeloma pathophysiologies, such as those with MYC, mTOR, STK33, ribosomal biogenesis, or cell-extrinsic stimuli of soluble factors, in HMCLs. These results provide the biological and molecular rationales for the dual-targeting strategy for RSK2 and AKT, which may overcome the therapeutic difficulty due to cytogenetic/molecular heterogeneity in MM.

Lenalidomide and pomalidomide potently interfere with induction of myeloid-derived suppressor cells in multiple myeloma.

An increase in immunosuppressive myeloid-derived suppressor cells (MDSCs) is associated with disease progression and treatment resistance in multiple myeloma (MM). We investigated the mechanisms underlying MDSC induction, and sought to discover a strategy for prevention of MDSC induction in MM. Using a transwell co-culture system, four of nine examined human myeloma-derived cell lines (HMCLs) were potent in inducing monocytic (M)-MDSCs from normal peripheral blood mononuclear cells (PBMCs). As the results, we identified that secretion of C-C motif chemokine ligand 5 (CCL5) and macrophage migration inhibitory factor (MIF) by myeloma cells is a prerequisite for induction of MDSCs in MM. The immunomodulatory drug (IMiD) compounds, such as lenalidomide (LEN) and pomalidomide (POM), were identified as potent inhibitors of MDSC induction through bidirectional molecular effects of cereblon (CRBN)-dependent and -independent downregulation of CCL5 and MIF in myeloma cells; and downregulation of C-C motif chemokine receptor 5, a receptor for CCL5, and induction of interferon regulatory factor 8, a critical transcription factor for monocytic differentiation, in PBMCs. In the present study of the molecular mechanisms underlying MDSC induction, we identified a novel effect of LEN and POM of inhibiting MDSC induction via overlapping regulatory effects in myeloma cells and normal PBMCs.

Dual targeting of bromodomain-containing 4 by AZD5153 and BCL2 by AZD4320 against B-cell lymphomas concomitantly overexpressing c-MYC and BCL2.

Despite the recent therapeutic progress, the prognoses of diffuse large B-cell lymphomas (DLBCLs) that concomitantly overexpress c-MYC and BCL2, i.e., double hit lymphoma (DHL) and double expressing lymphoma (DEL), remain poor. This study examined triple targeting of c-MYC, BCL2 and the B-cell receptor (BCR) signaling pathway for DHL and DEL. We first used AZD5153, a novel bivalent inhibitor for bromodomain-containing 4 (BRD4), in DHL- and DEL-derived cell lines, because BRD4 regulates disease type-oriented key molecules for oncogenesis. AZD5153 was more effective than conventional monovalent BRD4 inhibitors, JQ1 and I-BET151, in inhibiting cell proliferation of a DHL-derived cell line and two DEL-derived cell lines, with at least 10-fold lower half growth inhibitory concentrations. AZD5153 caused G1/S cell cycle blockade, while the apoptosis-inducing effect was relatively modest. At the molecular level, AZD5153 was potent in downregulating various molecules for oncogenesis, such as c-MYC, AKT2 and MAP3K; those involved in the BCR signaling pathway, such as CD19, BLNK and CD79B; and those associated with B-cell development, such as IKZF1, IKZF3, PAX5, POU2AF1 and EBF1. In contrast, AZD5153 did not decrease anti-apoptotic BCL2 proteins, and did not activate pro-apoptotic BH3-only proteins, except BAD. To augment cell death induction, we added a novel BH3-mimicking BCL2 inhibitor AZD4320 to AZD5153, and found that these two agents had a mostly synergistic antitumor effect by increasing cells undergoing apoptosis in all three cell lines. These results provide a rationale for dual targeting of BRD4 and BCL2 using AZD5153 and AZD4320 as a therapeutic strategy against DHL and DEL.

Epigenetic repression of miR-375 is the dominant mechanism for constitutive activation of the PDPK1/RPS6KA3 signalling axis in multiple myeloma.

Cytogenetic/molecular heterogeneity is the hallmark of multiple myeloma (MM). However, we recently showed that the serine/threonine kinase PDPK1 and its substrate RPS6KA3 (also termed RSK2) are universally active in MM, and play pivotal roles in myeloma pathophysiology. In this study, we assessed involvement of aberrant miR-375 repression in PDPK1 overexpression in MM. An analysis of plasma cells from 30 pre-malignant monoclonal gammopathies of undetermined significance and 73 MM patients showed a significant decrease in miR-375 expression in patient-derived plasma cells regardless of the clinical stage, compared to normal plasma cells. Introduction of miR-375 reduced PDPK1 expression in human myeloma cell lines (HMCLs), indicating that miR-375 is the dominant regulator of PDPK1 expression. In addition, miR-375 introduction also downregulated IGF1R and JAK2 in HMCLs. CpG islands in the MIR375 promoter were pathologically hypermethylated in all 8 HMCLs examined and in most of 58 patient-derived myeloma cells. Treatment with SGI-110, a hypomethylating agent, and/or trichostatin A, a histone deacetylase inhibitor, increased miR-375 expression, but repressed PDPK1, IGF1R and JAK2 in HMCLs. Collectively, these results show the universal involvement of overlapping epigenetic dysregulation for abnormal miR-375 repression in MM, which is likely to contribute to myelomagenesis and to subsequent myeloma progression by activating oncogenic signalling pathways.

Association of Cumulative Steroid Dose with Risk of Infection after Treatment for Severe Acute Graft-versus-Host Disease.

This study aimed to characterize the incidence and risk factors of invasive fungal disease, cytomegalovirus infection, other viral diseases, and gram-negative rod infection after glucocorticoid treatment for severe acute graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation and to elucidate the associations of cumulative steroid dose with the risks of individual infections. The study cohort included 91 consecutive patients who developed maximum grades III and IV acute GVHD at our center. The mean cumulative prednisolone-equivalent dose was 41 mg/kg during the first 4 weeks. The cumulative incidence rates of fungal disease, cytomegalovirus disease, other viral diseases, and gram-negative rod infection at 6 months after glucocorticoid treatment were remarkably high, at 14%, 21%, 28%, and 20%, respectively. GVHD within 26 days after transplantation and low lymphocyte count at GVHD treatment were associated with increased risks of several infections. Cumulative prednisolone-equivalent steroid doses ≥ 55 mg/kg during the first 4 weeks were associated with an increased risk of fungal disease (hazard ratio, 3.65; P = .03) and cumulative doses ≥ 23 mg/kg were associated with an increased risk of non-cytomegalovirus viral diseases (hazard ratio, 4.14; P = .02). Strategies to reduce the risk of infectious complications are needed, particularly for patients who have risk factors and those who receive high cumulative steroid doses.

Negative impact of immunoparesis in response to anti-SARS-CoV-2 mRNA vaccination of patients with multiple myeloma.

Multiple myeloma reduces cellular and humoral immunity. Optimal prediction of antibody response to anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine in patients with MM and related disorders is essential to prevent coronavirus disease 2019 (COVID-19) during the SARS-CoV-2 pandemic. This study analyzed the humoral response to the anti-SARS-CoV-2 messenger ribonucleic acid (mRNA) vaccine and its associated factor in 83 patients from June to November 2021 at seven member institutions of the Kyoto Clinical Hematology Study Group. SARS-CoV-2 neutralizing antibody (nAb) was measured from 12 to 210 days. The result revealed that 40 (48.2%) patients with MM and 59 (100%) healthy controls became seropositive after vaccination. Receiver operating characteristic curve analysis identified serum immunoglobulin (Ig) M of > 18 mg/dL at vaccination as the optimal threshold level associated with seropositivity in the whole cohort. Moreover, the multivariate analysis identified serum IgM of > 18 mg/dL as the independent predictor for a favorable response. Serum IgA level was positively associated with vaccine response in a sub-cohort. Our findings indicate a significant association between immunoparesis and impaired humoral response against mRNA vaccination, including that against SARS-CoV-2, and that serum non-M-protein Ig levels can serve as surrogate biomarkers of nAb production ability.

Impact of Treatment with Anti-CD20 Monoclonal Antibody on the Production of Neutralizing Antibody Against Anti-SARS-CoV-2 Vaccination in Mature B-Cell Neoplasms.

Background and Purpose: Anti-CD20 monoclonal antibodies (MoAbs), rituximab (RIT), and obinutuzumab (OBZ) are the central components of immunochemotherapy for B-cell lymphoma (BCL). However, these agents potentially cause B-cell depletion, resulting in the impairment of antibody (Ab) production. During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, the optimal prediction of Ab response against anti-SARS-CoV-2 vaccination is critically important in patients with BCL treated by B-cell depletion therapeutics to prevent coronavirus disease 2019 (COVID-19). Patients and Methods:  We investigated the effect of using RIT and/or OBZ on the Ab response in 131 patients with various types of BCL who received the second SARS-CoV-2 mRNA vaccine either after, during, or before immunochemotherapy containing B-cell-depleting moiety between June and November 2021 at seven institutes belonging to the Kyoto Clinical Hematology Study Group. The SARS-Cov-2 neutralizing Ab (nAb) was measured from 14 to 207 days after the second vaccination dose using the iFlash3000 automatic analyzer and the iFlash-2019-nCoV Nab kit. Results: Among 86 patients who received the vaccine within 12 months after B-cell depletion therapy, 8 (9.3%) were seropositive. In 30 patients who received the vaccine after 12 months from B-cell depletion therapy, 22 (73%) were seropositive. In 15 patients who were subjected to B-cell depletion therapy after vaccination, 2 (13%) were seropositive. The multivariate analysis indicated that an interval of 12 months between B-cell depletion therapy and the subsequent vaccination was significantly associated with effective Ab production. Receiver operating characteristic curve analysis identified the optimal threshold period after anti-CD20 MoAb treatment, which determines the seropositivity against SARS-CoV-2, to be 342 days. Conclusion: The use of anti-CD20 MoAb within 12 months before vaccination is a critical risk for poor Ab response against anti-SARS-CoV-2 vaccination in patients with BCL.

Gastric Myeloid Sarcoma Mimicking a Scirrhous Gastric Cancer.

Myeloid sarcoma (MS) is a relatively rare manifestation of myeloid neoplasms at sites other than the bone marrow. The rarity of gastrointestinal (GI) MS is attributed to certain factors, such as misdetection due to insufficient endoscopic assessments at the initial presentation with acute myeloid leukemia (AML) as well as the difficulty of making a histologic assessment of leukemic involvement of the GI tract. We herein report a case of AML with gastric involvement and discuss the importance of screening examinations and therapies considering the location of MS and the data of cytogenetic and molecular mutation.

Prognostic impact of resistance to bortezomib and/or lenalidomide in carfilzomib-based therapies for relapsed/refractory multiple myeloma: The Kyoto Clinical Hematology Study Group, multicenter, pilot, prospective, observational study in Asian patients.

BACKGROUND: Combinatory strategies with carfilzomib (CFZ), a second-generation proteasome inhibitor, plus dexamethasone (DEX) with or without lenalidomide (LEN) have shown promising efficacy for patients with relapsed/refractory multiple myeloma (RRMM) in pivotal clinical trials. However, their effects on patients who were resistance to bortezomib (BTZ) and/or LEN have not been fully evaluated in a daily practice setting. AIMS: To evaluate the real-world efficacy and safety of CFZ-based treatments; that is, CFZ with LEN plus DEX (KRD therapy) and CFZ with DEX (KD therapy), in Asian patients, we conducted a multicenter pilot prospective observational study in the Kyoto Clinical Hematology Study Group. METHODS AND RESULTS: All 50 patients with RRMM enrolled in this study were treated with CFZ-based treatments between 2017 and 2019. KRD and KD were administered to 31 and 19 patients, respectively. The overall response rates (ORRs) were 80.6% with KRD and 73.7% with KD. Two-year progression-free survival (PFS) and overall survival (OS) were 58.5% and 79.7% with KRD, and 23.1% and 52.6% with KD. By multivariate analysis, refractoriness to BTZ and to LEN were identified as independent unfavorable factors for both PFS and OS. The common non-hematologic AEs included hypertension (42.0%), fever (24.0%), fatigue (24.0%), and infection (16.0%). No serious heart failure was observed. This study is registered as UMIN000025108. CONCLUSION: This study suggests the need of the development of novel CFZ-containing strategy which can overcome the refractoriness to BTZ and/or LEN, while both KRD and KD were shown to be mostly feasible in Asian patients in a daily practice setting.

Clinical impacts of frailty, poor performance status, and advanced age in carfilzomib-containing treatment for relapsed/refractory multiple myeloma: post hoc investigation of the KOTOSG multicenter pilot prospective observational study.

We conducted a post hoc analysis of our previous pilot observational study on the efficacy and safety of carfilzomib (CFZ)-containing therapy in 50 patients with relapsed/refractory multiple myeloma in routine practice to clarify the relationships between three major criteria for vulnerability (frailty, poor performance status [PS], and advanced age [≥ 75 years]) and their clinical impact on efficacy and adverse events (AEs). Sixteen patients fulfilled at least one and five patients fulfilled all three criteria. The overall response rate was not significantly affected by frailty, poor PS, and/or advanced age; however, frailty and advanced age were significantly associated with shorter progression-free survival (PFS). In contrast, no significant difference in PFS was observed between patients with PS0-1 or PS2-4. The three criteria for vulnerability were associated with more frequent hematologic AEs: frailty, poor PS, and/or advanced age significantly increased the risk of grade 3-4 anemia and lymphopenia. However, these criteria were not associated with increased risk of other non-hematologic AEs except infection. Collectively, these results demonstrate the need to carefully manage severe hematologic AEs in vulnerable patients and perform disease-specific assessment of frailty to predict prognosis.

Combination of Bone Marrow Biopsy and Flow Cytometric Analysis: The Prognostically Relevant Central Approach for Detecting Bone Marrow Invasion in Diffuse Large B-Cell Lymphoma.

Bone marrow (BM) involvement is associated with prognosis in diffuse large B-cell lymphoma (DLBCL), the most prevalent disease subtype of malignant lymphoma. We conducted this multi-institutional retrospective study to investigate the functional association and prognostic values of four BM tests (BM biopsy, BM clot, flow cytometry (FCM), and BM smear). A total of 221 DLBCL patients were enrolled. BM involvement was detected in 17 (7.7%), 16 (7.2%), 27 (12.2%), and 34 (15.4%) patients by BM biopsy, BM clot, FCM, and BM smear, respectively. The consistency between BM biopsy and clot examination was favorable, with a κ coefficient of 0.705, whereas the consistencies among other modalities were poor. In 184 patients treated with the first-line R-CHOP (-like) regimen, BM involvement was associated with shorter progression-free survival (PFS) irrespective of the type of modality for a positive result. Intriguingly, among various single and combinatory modalities, the combination of BM biopsy and FCM had the highest hazard ratio of 3.33 and a c-index of 0.712. In conclusion, our study suggested that the combination of BM biopsy and FCM is the prognostically relevant central approach for BM involvement detection. The other BM examinations also may provide complementary information in clinical settings.

EWSR1 overexpression is a pro-oncogenic event in multiple myeloma.

Multiple myeloma (MM) is cytogenetically, genetically and molecularly heterogenous even among subclones in one patient, therefore, it is essential to identify both frequent and patient-specific drivers of molecular abnormality. Following previous molecular investigations, we in this study investigated the expression patterns and function of the Ewing sarcoma breakpoint region 1 (EWSR1) gene in MM. The EWSR1 transcriptional level in CD138-positive myeloma cells was higher in 36.4% of monoclonal gammopathy of undetermined significance, in 67.4% of MM patients compared with normal plasma cells, and significantly higher in ten human myeloma-derived cell lines (HMCLs) examined. EWSR1 gene knockdown caused growth inhibition with an increase of apoptotic cells in NCI-H929 and KMS-12-BM cells. Gene expression profiling using microarray analysis suggested EWSR1 gene knockdown caused transcriptional modulation of several genes associated with processes such as cell proliferation, cell motility, cell metabolism, and gene expression. Of particular, EWSR1 gene knockdown caused upregulation of let-7c and downregulation of its known targets K-RAS and AKT. Finally, our analysis using community database suggested that high EWSR1 expression positively associates with poor prognosis and advanced disease stage in MM. These findings suggest that EWSR1 overexpression is a pro-oncogenic molecular abnormality that may participate in MM progression.

Serine-227 in the N-terminal kinase domain of RSK2 is a potential therapeutic target for mantle cell lymphoma.

RSK2 is a serine/threonine kinase downstream signaling mediator in the RAS/ERK signaling pathway and may be a therapeutic target in mantle cell lymphoma (MCL), an almost incurable disease subtype of non-Hodgkin lymphoma. In this study, serine-227 (RSK2Ser227 ) in the N-terminal kinase domain (NTKD) of RSK2 was found to be ubiquitously active in five MCL-derived cell lines and in tumor tissues derived from five MCL patients. BI-D1870, an inhibitor specific to RSK2-NTKD, caused RSK2Ser227 dephosphorylation, and thereby, induced dose-dependent growth inhibition via G2 /M cell cycle blockade and apoptosis in four of the five cell lines, while one cell line showed only modest sensitivity. In addition, RSK2 gene knockdown caused growth inhibition in the four BI-D1870-sensitive cell lines. Comparative gene expression profiling of the MCL-derived cell lines showed that inhibition of RSK2Ser227 by BI-D1870 caused downregulation of oncogenes, such as c-MYC and MYB; anti-apoptosis genes, such as BCL2 and BCL2L1; genes for B cell development, including IKZF1, IKZF3, and PAX5; and genes constituting the B cell receptor signaling pathway, such as CD19, CD79B, and BLNK. These findings show that targeting of RSK2Ser227 enables concomitant blockade of pathways that are critically important in B cell tumorigenesis. In addition, we found favorable combinatory growth inhibitory effects of BI-D1870 with inhibitors of BTK (ibrutinib), AKT (ipatasertib), and BCL2 (venetoclax) in cell characteristic-dependent manners. These results provide a rationale for RSK2Ser227 in the NTKD as a potential therapeutic target in MCL and for future development of a novel bioavailable RSK2 NTKD-specific inhibitor.

Tumor-specific transcript variants of cyclin D1 in mantle cell lymphoma and multiple myeloma with chromosome 11q13 abnormalities.

Cyclin D1 (CCND1) overexpression is an early and unifying oncogenic event in mantle cell lymphoma (MCL) and multiple myeloma (MM) with chromosome 11q13 abnormalities. Herein, we report newly discovered transcript variants of the CCND1 gene in MCL and MM cells with chromosome 11q13 abnormalities. These transcript variants, designated CCND1.tv., covered the full-length coding region of CCND1 with longer 5'-untranslated regions (5'-UTRs) of CCND1 and occasionally contained a novel exon. CCND1.tv. was specifically detectable in patient-derived primary MCL or MM cells with chromosomal translocation t(11;14)(q13;q32), but not in t(11;14)-negative cells. The lengths of the 5'-UTR sequences of CCND1.tv. differed among patients and cell lines. Introduction of CCND1.tv. led to increased expression of normal-sized CCND1 protein in HEK293 cells. Furthermore, mTOR inhibition by rapamycin or serum starvation reduced ectopic expression of CCND1.tv.-derived CCND1 protein, but not 5'-UTR less CCND1-derived CCND1 protein in HEK293 cells, suggesting that the protein expression of CCND1.tv. is regulated by the mTOR pathway. Our results suggest that the aberrant expression of CCND1.tv. may contribute to the understanding of the pathogenesis of MCL and MM with 11q13 abnormalities.

Tuberculosis Peritonitis During Treatment of Polycythemia Vera with Ruxolitinib.

Ruxolitinib is a selective JAK1/2 inhibitor that is widely used for the treatment of myeloproliferative neoplasms (MPNs), including myelofibrosis and polycythemia vera (PV). Despite its clinical efficacy for MPNs, ruxolitinib possesses immunosuppressive properties that potentially increase the risks for opportunistic infection, such as mycobacterium tuberculosis (MTB) infection, and reactivation of occult viral infection. Herein, we report the case of a 76-year-old male with PV who developed tuberculosis peritonitis under ruxolitinib therapy for 28 weeks. While previous studies and case reports have suggested an increased risk of MTB infection of various organs during ruxolitinib treatment of MPNs, this case is apparently the first of tuberculosis peritonitis in a patient with MPN treated with ruxolitinib. A review of previous case reports suggests the need for careful observation for MTB from the relatively early phase of ruxolitinib treatment, given that the median duration from the start of ruxolitinib treatment to the emergence of MTB was 20 weeks (range: 3-88 weeks). Clinicians should consider tuberculosis peritonitis as a differential diagnosis when patients with MPN treated with ruxolitinib develop infectious abdominal symptoms.

Aberrant BUB1 Overexpression Promotes Mitotic Segregation Errors and Chromosomal Instability in Multiple Myeloma.

Chromosome instability (CIN), the hallmarks of cancer, reflects ongoing chromosomal changes caused by chromosome segregation errors and results in whole chromosomal or segmental aneuploidy. In multiple myeloma (MM), CIN contributes to the acquisition of tumor heterogeneity, and thereby, to disease progression, drug resistance, and eventual treatment failure; however, the underlying mechanism of CIN in MM remains unclear. Faithful chromosomal segregation is tightly regulated by a series of mitotic checkpoint proteins, such as budding uninhibited by benzimidazoles 1 (BUB1). In this study, we found that BUB1 was overexpressed in patient-derived myeloma cells, and BUB1 expression was significantly higher in patients in an advanced stage compared to those in an early stage. This suggested the involvement of aberrant BUB1 overexpression in disease progression. In human myeloma-derived cell lines (HMCLs), BUB1 knockdown reduced the frequency of chromosome segregation errors in mitotic cells. In line with this, partial knockdown of BUB1 showed reduced variations in chromosome number compared to parent cells in HMCLs. Finally, BUB1 overexpression was found to promote the clonogenic potency of HMCLs. Collectively, these results suggested that enhanced BUB1 expression caused an increase in mitotic segregation errors and the resultant emergence of subclones with altered chromosome numbers and, thus, was involved in CIN in MM.

BRD4-Regulated Molecular Targets in Mantle Cell Lymphoma: Insights into Targeted Therapeutic Approach.

BACKGROUND: Since bromodomain-containing protein 4 (BRD4) facilitates the transcription of genes important for neoplastic cells in a cancer-type specific manner, BRD4-regulated molecules may also include therapeutic targets for mantle cell lymphoma (MCL), a treatment-refractory subtype of malignant lymphoma. MATERIALS AND METHODS: In order to uncover direct BRD4-regulated targets in MCL, we performed integrated analysis using the pathway database and the results of both gene-expression profiling and chromatin immunoprecipitation with parallel sequencing for BRD4. RESULTS: Treatment with BRD4 inhibitor I-BET151 exerted a dose-dependent inhibitory effect on cell proliferation in MCL cell lines. BRD4 was found to directly regulate series of genes involved in the B-cell receptor (BCR) signaling pathway, including B-cell linker (BLNK), paired box 5 (PAX5), and IKAROS family zinc finger 3 (IKZF3), and several oncogenes, such as MYB. Indeed, the combinatory inhibition of BCR pathway and IKZF showed an additive antitumor effect. CONCLUSION: Concomitant targeting multiple BRD4-regulated molecules may constitute a rational therapeutic strategy for MCL.

A novel method of amplified fluorescent in situ hybridization for detection of chromosomal microdeletions in B cell lymphoma.

Chromosomal microdeletions frequently cause loss of prognostically relevant tumor suppressor genes in hematologic malignancies; however, detection of minute deletions by conventional methods for chromosomal analysis, such as G-banding and fluorescence in situ hybridization (FISH), is difficult due to their low resolution. Here, we describe a new diagnostic modality that enables detection of chromosomal microdeletions, using CDKN2A gene deletion in B cell lymphomas (BCLs) as an example. In this method, which we refer to as amplified-FISH (AM-FISH), a 31-kb fluorescein isothiocyanate (FITC)-conjugated DNA probe encoding only CDKN2A was first hybridized with the chromosome, and then labeled with Alexa Fluor 488-conjugated anti-FITC secondary antibody to increase sensitivity. CDKN2A signals were equally identifiable by AM-FISH and conventional FISH in normal mononuclear blood cells. In contrast, when two BCL cell lines lacking CDKN2A were analyzed, CDKN2A signals were not detected by AM-FISH, whereas conventional FISH yielded false signals. Furthermore, AM-FISH detected CDKN2A deletions in two BCL patients with 9p21 microdeletions, which were not detected by conventional FISH. These results suggest that AM-FISH is a highly sensitive, specific, and simple method for diagnosis of chromosomal microdeletions.

Phosphoinositide-dependent protein kinase 1 is a potential novel therapeutic target in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a relatively rare subtype of B-cell non-Hodgkin lymphoma (NHL) that has a poor prognosis despite recent advances in immunochemotherapy and molecular targeted therapeutics against NHL. Therefore, the development of a new therapeutic strategy for MCL is urgently needed. In this study, we show for the first time that 3-phosphoinositide-dependent protein kinase 1 (PDPK1), an oncogenic serine-threonine protein kinase, is commonly expressed in its phosphorylated active form in patient-derived tumor cells of various types of B-cell NHL cells, including diffuse large B-cell lymphoma, follicular lymphoma, and MCL. Blockade of PDPK1 activity by small-molecule inhibitors specific for PDPK1 (BX-912 and GSK2334470) or by RNA interference exerted antiproliferative effects in all four MCL-derived cell lines examined and these growth-inhibitory effects were mediated by both induction of apoptosis and G2/M cell cycle blockade. In addition, blockade of PDPK1 led to inactivation of its downstream effector kinase RSK2, but not AKT, suggesting the importance of the PDPK1/RSK2 signaling pathway in the proliferation and survival of MCL cells. Finally, when combined with anticancer agents, including genotoxic agents, a proteasome inhibitor, and a BH3 mimetic in vitro, the PDPK1 inhibitor BX-912 showed additive growth-inhibitory effects against MCL-derived cell lines in most settings. In particular, the combination of BX-912 and ABT-263, a BH3 mimetic, resulted in the enhancement of the induction of apoptosis. In conclusion, our results suggest that PDPK1 is a potential novel therapeutic target in MCL and indicate that clinical development of PDPK1-targeted therapy for MCL is desirable.