Notch-Regulated Enhancers in B-Cell Lymphoma Activate MYC and Potentiate B-Cell Receptor Signaling

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 457-457
Author(s):  
Russell J.H. Ryan ◽  
Jelena Petrovic ◽  
Dylan Rausch ◽  
Caleb Lareau ◽  
Winston Lee ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Target Gene ◽  
Target Genes ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
Rna Seq ◽  
Bcr Signaling ◽  
Notch Activation

Abstract Gain-of-function mutations in Notch receptor genes occur in 10-15% of cases of chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL), and are associated with inferior clinical outcomes. Nearly all Notch mutations reported in B cell tumors lead to loss of the C-terminal negative regulatory PEST domain and result in stabilization of the activated form of Notch (intracellular Notch [ICN]), whereas mutations that lead to ligand-independent Notch activation (which are common in T cell acute lymphoblastic leukemia [T-ALL]) are rare. ICN can be detected in tumor cells within lymph nodes of >80% of patients with CLL, suggesting that Notch may have a broader oncogenic role than the incidence of Notch mutations would suggest. However, the downstream targets of Notch in B-cell tumors have not been identified. We used a gamma-secretase inhibitor (GSI) washout strategy to determine the immediate, direct effects of Notch activation in three MCL cell lines with Notch gain-of-function mutations, including two cell lines with unusual Notch gene rearrangements that lead to ligand-independent Notch activation, as well as a third line with a Notch PEST domain mutation in which signaling was activated with recombinant Notch ligand. Using these models, we identified likely direct target genes and their associated genomic Notch response elements using RNA-seq and ChIP-Seq in the Notch-on and Notch-off states. Most of these response elements corresponded to long-range enhancers that showed Notch-dependent changes in H3K27 acetylation, and were bound by components of the Notch transcription complex (NTC) in both cell lines. We confirmed these associations by performing ChIP-Seq on primary CLL and MCL biopsies, and by identifying specific looping interactions with Notch target gene promoters in public genome-wide proximity ligation datasets (RNA Pol2 ChIA-PET) from a lymphoblastoid cell line expressing the EBV-encoded Notch surrogate protein EBNA2. MYC was among the most strongly Notch-activated genes in Notch-dependent MCL cell lines and was associated with NTC binding at two B cell-specific 5' enhancers distinct from the Notch-dependent MYC enhancer previously identified in T-ALL. MCL cell line proliferation was blocked by Cas9 nuclease or epigenetic repressors targeting the 5' MYC enhancers, whereas cells were rescued from Notch inhibition by GSI via transduction with MYC. Gene set enrichment analysis of other direct Notch target genes identified in MCL models showed enrichment for regulators of B cell receptor (BCR) signaling, including the Src family kinase genes FYN, LYN, and BLK, and the signaling complex adaptor BLNK, as well as regulators of CD40 and cytokine signaling. RNA-seq analysis of primary CLL lymph node biopsies revealed significantly higher expression of many Notch target genes in biopsies with high levels of ICN. To functionally validate Notch target genes in primary tumors, we co-cultured CLL and MCL cells obtained from peripheral blood with Notch ligand-expressing stromal cells in the presence ("notch off") or absence ("notch on") of GSI, and demonstrated increased expression of Notch target genes, including MYC, in the "notch-on" cells. Furthermore, "notch-on" CLL cells showed increased phosphorylation of the BCR signaling intermediates SYK and PLCg2 upon BCR crosslinking compared to GSI-treated cells. Finally, we validated Notch-dependent regulation of target genes in vivo in a patient-derived xenograft model of NOTCH1-mutant MCL. Notch target gene expression was significantly higher in MCL cells within the spleen versus bone marrow or blood, but was markedly reduced in animals treated for five days with GSI. Additional xenograft studies are ongoing, and will be described at the meeting. Our data link active Notch signaling to two well-characterized oncogenic drivers in B cell lymphoma, MYC and BCR signaling, and may have important implications for the development of treatment strategies involving Notch antagonists and other targeted therapeutics, such as BCR targeting agents. Disclosures Weinstock: Novartis: Consultancy, Research Funding.

High Density Lipoprotein-like Nanoparticles Synergize with Akt and Btk Inhibitors to Induce Cell Death in Diffuse Large B Cell Lymphomas

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3022-3022
Author(s):  
Jonathan Scott Rink ◽  
Sol Misener ◽  
Osman Cen ◽  
Shuo Yang ◽  
Leo I. Gordon ◽  
...  
Keyword(s):  
Cell Death ◽  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Density Lipoprotein ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
Cholesterol Homeostasis ◽  
B Cell Lymphomas ◽  
Bcr Signaling

Abstract Introduction: We previously reported that our bio-inspired, synthetic high-density lipoprotein-like nanoparticles (HDL NP) induced apoptosis in B cell lymphoma cells expressing scavenger receptor type B1 (SCARB1), the high-affinity receptor for cholesterol-rich HDLs. HDL NPs consist of a 5nm gold nanoparticle core surface functionalized with the HDL-defining apolipoprotein A1 and a phospholipid bilayer, and bind specifically to SCARB1, inducing the efflux of free cholesterol and inhibiting cholesteryl ester influx. SCARB1 is overexpressed in a subset of follicular and diffuse large B cell lymphomas (DLBCL), and resides in cholesterol-rich plasma membrane microdomains called lipid rafts, similar to the B cell receptor (BCR) and its associated signaling kinases. Upon binding to natural HDL, SCARB1 activates a number of pro-survival signaling kinases, including Akt and PI3K. Both Akt and PI3K are also involved in B cell receptor-mediated signaling in germinal center-derived (GC) DLBCL, through tonic BCR signaling, and activated B cell (ABC) DLBCL, through chronic active BCR signaling. Additionally, PI3K was recently shown to play a role in recruitment and activation of Btk, a crucial survival kinase downstream of the BCR. We hypothesized that small molecule inhibitors against pro-survival kinases, specifically Akt and Btk, will synergize with HDL NPs against B cell lymphomas. Methods: Burkitt's lymphoma (Ramos), GC DLBCL (SUDHL4) and ABC DLBCL (TMD8 and HBL-1) cell lines were treated with the Akt inhibitor GDC-0068 or the Btk inhibitor Ibrutinib, in the absence or presence of HDL NPs, and synergy was calculated using the Calcusyn software. Phos-flow was used to assay for changes in the phosphorylation status of Akt and Btk. Results: The Burkitt's lymphoma and GC DLBCL cell lines were more sensitive to HDL NP induced cell death compared to the ABC DLBCL cell lines (Ramos HDL NP IC50 = 1.5nM; SUDHL4 HDL NP IC50 = 2.1nM; TMD8 HDL NP IC50 = 31.4nM; HBL-1 HDL NP IC50 = 89nM). HDL NPs synergized with GDC-0068 in the Ramos, SUDHL4 and TMD8 cell lines (all combination indexes < 1). Correspondingly, HDL NPs dose-dependently decreased phosphorylation of Akt in Ramos and TMD8 cells. Ibrutinib synergized with the HDL NPs in all cell lines tested (all combination indexes < 1). In TMD8 cells, HDL NPs decreased p-Btk levels comparable to treatment with 10nM Ibrutinib. Addition of the PI3K inhibitor Pilaralisib (XL147) demonstrated mild synergy in the Ramos cell line, but not the SUDHL4, TMD8 or HBL-1 cell lines (all combination index values >1). Treatment of Ramos and SUDHL4 cells with an inhibitor of PTEN, a phosphatase responsible for acting in opposition to PI3K leading to inactivation of Akt, rescued the cells from HDL NP-induced cell death. TMD8 cells treated with the PTEN inhibitor demonstrated a smaller increase in survival when HDL NPs were applied, suggesting that PI3K may not play a major role in HDL NP-induced cell death in activated B cell DLBCLs. PTEN activity is influenced by the level of cholesterol and cholesteryl esters present in the cell, with increasing levels correlating with decreased PTEN activity. Cholesterol levels were higher in the ABC DLBCL cell lines compared to the other B cell lymphoma cell lines. HDL NPs significantly reduced the cholesterol content of Ramos cells, but not the TMD8 or HBL-1 cells, suggesting that the ability of the HDL NPs to alter cellular cholesterol homeostasis correlates with their ability to induce lymphoma cell death. Conclusion: HDL NPs demonstrated synergy with inhibitors to the pro-survival kinases Akt and Btk, suggesting that HDL NPs act to disrupt second messenger signaling pathways in lymphoma cells by directly altering signaling through SCARB1, modulating cellular cholesterol homeostasis, and/or through disruption of membrane raft organization. HDL NPs represent an innovative, targeted therapeutic, with great potential, to add to existing combination chemotherapy regimens. Disclosures Thaxton: Aurasense: Equity Ownership, Patents & Royalties: The patent for the HDL NPs has been licensed to Aurasense, a biotech company co-founded by C. Shad Thaxton..

scholarly journals Critical role of PI3K signaling for NF-κB–dependent survival in a subset of activated B-cell–like diffuse large B-cell lymphoma cells

2010 ◽  
Vol 108 (1) ◽  
pp. 272-277 ◽  
Author(s):  
Bernhard Kloo ◽  
Daniel Nagel ◽  
Matthias Pfeifer ◽  
Michael Grau ◽  
Michael Düwel ◽  
...  
Keyword(s):  
B Cell ◽  
Target Genes ◽  
Cell Lymphoma ◽  
Critical Role ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
Critical Function ◽  
Large B Cell Lymphoma ◽  
Bcr Signaling ◽  
Large B Cell

The activated B-cell–like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) represents a very aggressive human lymphoma entity. Constitutive NF-κB activation caused by chronic active B-cell receptor (BCR) signaling is common feature of many ABC DLBCL cells; however, the pathways linking BCR signaling to the NF-κB prosurvival network are largely unknown. Here we report that constitutive activity of PI3K and the downstream kinase PDK1 are essential for the viability of two ABC DLBCL cell lines that carry mutations in the BCR proximal signaling adaptor CD79B. In these cells, PI3K inhibition reduces NF-κB activity and decreases the expression of NF-κB target genes. Furthermore, PI3K and PDK1 are required for maintaining MALT1 protease activity, which promotes survival of the affected ABC DLBCL cells. These results demonstrate a critical function of PI3K-PDK1 signaling upstream of MALT1 protease and NF-κB in distinct ABC DLBCL cells and provide a rationale for the pharmacologic use of PI3K inhibitors in DLBCL therapy.

A BCL6 Target Gene Signature Predicts the Biological Behavior and Classification of Diffuse Large B-Cell Lymphoma.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 616-616
Author(s):  
Jose M. Polo ◽  
Przemyslaw Juszczynski ◽  
Leandro Cerchietti ◽  
Stefano Monti ◽  
Kenny Ye ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Target Gene ◽  
Target Genes ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Gene Signature ◽  
Transcriptional Profiles ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Abstract Diffuse large B-cell lymphoma (DLBCL), the most common lymphoid malignancy, is a heterogeneous disease. These tumors are thought to arise from normal antigen-exposed B-cells that have migrated to or through the germinal center (GC). Structural abnormalities of the BCL6 locus (chromosomal translocation and aberrant somatic hypermutation) are the most common genetic abnormalities in DLBCL, occurring in over a third of these tumors. We recently developed a potent and specific BCL6 peptide inhibitor (BPI) that disrupts the interaction between BCL6 and the SMRT co-repressor complex. BPI was cytotoxic against some, but not all, BCL6 positive primary DLBCLs and DLBCL cell lines, indicating that a subset of DLBCLs was particularly dependent on BCL6 for their survival. We predicted that such cases might be identified through a specific BCL6-dependent gene signature and utilized ChIP on chip and a 24,000 promoter genomic microarray to identify BCL6 target genes. In these studies, BCL6 bound to 431 loci. Eighty percent of these candidate target genes contained a canonical BCL6 binding site and 85% of analyzed candidates were confirmed using quantitative single-locus CHIP. GO term enrichment revealed that BCL6 targets were significantly more likely to be genes associated with transcription, ubiquitylation, response to DNA damage, cell cycle and chromatin assembly/disassembly (FDR &lt;.05). We predicted that coordinate regulation of the BCL6 targets would serve as a signature of BCL6 activity. For this reason, we asked whether the BCL6 target gene set was differentially expressed in the recently described DLBCL comprehensive clusters, “B-cell Receptor/Proliferation (BCR),” “Oxidative Phosphorylation (OxPhos),” and Host Response (HR),” using 2 large series of primary DLBCLs with available transcriptional profiles. Since HR tumors are largely defined by infiltrating host inflammatory cells, we focused on BCR and OxPhos DLBCLs. Of interest, BCR tumors more frequently exhibit BCL6 chromosomal translocations and increased BCL6 expression. Consistent with these observations, gene set enrichment analysis (GSEA) revealed highly significant differential expression of BCL6 target genes in BCR vs. OxPhos tumors (p &lt;.0001). In contrast, GSEA of the BCL6 targets in the same DLBCLs sorted into developmental cell-of-origin groups was not significant (“GC” vs. “ABC”/”Other”, p =.25 and “GC” vs. “ABC” only, p =.082). To assess the functional significance of the BCL6 signature in the DLBCL consensus clusters, we generated a predictive algorithm based on the transcriptional profiles of a series of DLBCL cell lines to assign the lines to BCR, OxPhos or HR comprehensive clusters. Five BCR and 3 OxPhos DLBCL cell lines were selected for additional blinded functional analyses. BPI treatment upregulated BCL6 target gene expression in BCR, but not OxPhos, DLBCLs. Furthermore, BPI was significantly more effective in BCR lines than OxPhos DLBCLs (BPI IC50s of BCR vs. Ox Phos lines, 12.7±1.7 μM vs 48.9±2.6 μM, respectively, p&lt;. 0001). Taken together, the data indicate that BCR DLBCLs are significantly more dependent on BCL6 transcriptional repression and more sensitive to targeted BCL6 inhibition. More generally, these studies suggest that DLBCL comprehensive cluster designation will help guide the targeted therapy of biologically discrete DLBCL subsets.

scholarly journals SYK-dependent tonic B-cell receptor signaling is a rational treatment target in diffuse large B-cell lymphoma

Blood ◽  
2008 ◽  
Vol 111 (4) ◽  
pp. 2230-2237 ◽  
Author(s):  
Linfeng Chen ◽  
Stefano Monti ◽  
Przemyslaw Juszczynski ◽  
John Daley ◽  
Wen Chen ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
Primary Tumors ◽  
Large B Cell Lymphoma ◽  
Bcr Signaling ◽  
Survival Signals

The role of B-cell receptor (BCR)–mediated survival signals in diffuse large B-cell lymphoma (DLBCL) remains undefined. Ligand-induced BCR signaling induces receptor oligomerization, Igα/β immunoreceptor tyrosine-based activation motif (ITAM) phosphorylation, and activation of the spleen tyrosine kinase (SYK), which initiates downstream events and amplifies the initial BCR signal. BCRs also transmit low-level tonic survival signals in the absence of receptor engagement. Herein, we assess the role of SYK-dependent tonic BCR survival signals in DLBCL cell lines and primary tumors and evaluate the efficacy of an ATP-competitive inhibitor of SYK, R406, in vitro. R406 induced apoptosis of the majority of examined DLBCL cell lines. In R406-sensitive DLBCL cell lines, R406 specifically inhibited both tonic- and ligand-induced BCR signaling (autophosphorylation of SYK525/526 and SYK-dependent phosphorylation of the B-cell linker protein [BLNK]). The majority of examined primary DLBCLs also exhibited tonic- and ligand-induced BCR signaling; in these primary tumors, BCR signaling was also inhibited by R406. Of note, BCR-dependent and R406-sensitive DLBCL cell lines were independently identified as “BCR-type” tumors by transcriptional profiling. Therefore, SYK-dependent tonic BCR signaling is an important and potentially targetable survival pathway in some, but not all, DLBCLs. In addition, R406-sensitive DLBCLs can be identified by their transcriptional profiles.

scholarly journals The B-Cell Receptor Is Required for Optimal Viability, Growth, and Chemotherapy Resistance of Diffuse Large B-Cell Lymphoma Cell Lines of the Germinal Center B-Cell Subtype

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 493-493 ◽  
Author(s):  
Ondrej Havranek ◽  
Stefan Koehrer ◽  
Justin M Comer ◽  
Zhiqiang Wang ◽  
Jingda Xu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
B Cell ◽  
Signaling Pathways ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Chemotherapy Resistance ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
Bcr Signaling ◽  
Relative Decline

Abstract Introduction. An essential role for the B-cell receptor (BCR) has been shown in multiple types of B-cell lymphoma by studies of cell lines and clinical responses to inhibitors of SYK or BTK. Diffuse large B-cell lymphoma (DLBCL) lines of the germinal center B-cell (GCB) type express a BCR, which can signal after crosslinking, but are unaffected by BCR pathway targeting toxic to lines of the activated B-cell (ABC) DLBCL subtype: knockdown of BCR signaling mediators (BTK, CD79A, and CD79B) by shRNA, and small-molecule inhibition of BTK by ibrutinib. GCB-DLBCL lines (and primary samples) also lack constitutive NF-kB activity and mutations in ITAM domains of CD79A or CD79B, BCR-related features of ABC-DLBCL. Most GCB-DLBCL patients resist BTK inhibition by ibrutinib, further suggesting that BCR signaling is not a feature of GCB-DLBCL. Methods. In 8 GCB-DLBCL lines (OCI-Ly7, OCI-Ly19, SUDHL-4, SUDHL-6, SUDHL-10, DB, BJAB, and HT) and one ABC-DLBCL line (HBL-1), we used electroporation to deliver a plasmid expressing Cas9 protein and a guide RNA (gRNA) targeting one of these: constant exons of IGHM, IGHG, or Igκ; the cell line-specific IgH hypervariable region (HVR); or CXCR4. Knock-in (KI) of mouse CD8a (mCD8a), after the HVR V segment leader sequence and followed by a polyA signal, was used as a positive marker of BCR knockout (KO) in HBL-1 and OCI-Ly19 cell lines. Surface BCR, CXCR4, and mCD8a were detected by flow cytometry (FACS). BCR KO cells were viably sorted 4-6 days after electroporation, cultured 1-3 days more, and studied by whole-genome gene expression profiling (GEP) on Illumina HT12v4 arrays and Western blotting. Results. Only 2 days after electroporation, FACS showed cells with correlated loss of surface BCR proteins (IgH, Igκ or Igl, and CD79B), which eventually declined to undetectable levels. Forward and side scatter showed that BCR KO cells were smaller. The proportion of BCR KO (or mCD8a KI/KO) cells declined over time, steadily after complete BCR elimination (Fig. 1A). BCR KO cells in GCB-DLBCL lines grew more slowly than BCR-replete cells but variably, from almost no difference in BJAB to growth cessation in SUDHL-4, SUDHL-10 and HBL-1 (Fig. 1B). CXCR4 KO cells were a stable proportion (Fig. 1A) with a normal growth rate (Fig. 1B), indicating that growth reduction by BCR KO is specific. Continued expression of mCD8a indicated viability and sustained IgH transcription in BCR KO cells. Cell cycle analysis showed lower proportions of S and G2/M phases in BCR KO cells, proportional to growth retardation, and sub-G1 cells in OCI-Ly7 (Fig. 2), SUDHL-4 and SUDHL-10. Apoptosis in OCI-Ly7 BCR KO cells was confirmed with a caspase-3 fluorogenic substrate. Igκ KO similarly caused complete BCR loss and growth retardation, in OCI-Ly7 cells even more than with IgH KO. In the HT cell line, which lacked BCR expression due to a single-nucleotide deletion in its IgH HVR, KI repaired the HVR and caused expression of surface BCR (IgM with Igκ and CD79B) but no change in growth rate, suggesting BCR-proximal activators of BCR signaling pathways. Targeted BCR KO is not currently a therapeutic option, but BCR KO cells were relatively more sensitive to an in vitro regimen modeling the non-prednisone drugs of CHOP. No change in drug sensitivity was observed with BCR KO in BJAB, or in CXCR4 KO cells. GEP showed that BCR KO downregulated several genes characteristically expressed by GCB-DLBCL, and genes associated with negative regulation of BCR signaling. Pathway analysis with Gene Set Enrichment Analysis (GSEA) showed that BCR KO reduced expression of proliferation-related signatures, and produced changes associated with B-cell differentiation stages lacking a mature BCR, either early (pre-B cells) or late (plasma cells). GSEA implicated loss of MAPK/ERK and PI3K/AKT signaling pathways as mediators of BCR KO-induced changes, confirmed by Western blotting showing loss of phosphorylation of SYK, AKT and ERK after BCR KO. Conclusions. Complete BCR KO by Cas9/gRNA showed that GCB-DLBCL lines require the BCR for optimal viability, cell growth, and chemotherapy resistance. BCR KO-induced changes are mediated by MAPK/ERK and PI3K/AKT signaling pathways. Table A. B. Figure 1. Figure 1A. BCR KO cells (distinguished from BCR-replete cells by FACS), but not CXCR4 KO cells, show relative decline (A) and slower absolute growth (B) in mixed cultures. Figure 1A. BCR KO cells (distinguished from BCR-replete cells by FACS), but not CXCR4 KO cells, show relative decline (A) and slower absolute growth (B) in mixed cultures. Figure 1B Figure 1B. Figure 2 Cell cycle changes with BCR KO in OCI-Ly7. Figure 2. Cell cycle changes with BCR KO in OCI-Ly7. Disclosures No relevant conflicts of interest to declare.

scholarly journals Ibrutinib in B-cell lymphoma: single fighter might be enough?

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Chao Xue ◽  
Xin Wang ◽  
Lingyan Zhang ◽  
Qingyuan Qu ◽  
Qian Zhang ◽  
...  
Keyword(s):  
B Cell ◽  
Signaling Pathway ◽  
Cell Lymphoma ◽  
Critical Role ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
High Response Rate ◽  
Main Body ◽  
Combination Strategies ◽  
Bcr Signaling

Abstract Background In recent years, the B cell receptor (BCR) signaling pathway has become a “hot point” because it plays a critical role in B-cell proliferation and function. Bruton’s tyrosine kinase (BTK) is overexpressed in many subtypes of B-cell lymphoma as a downstream kinase in the BCR signaling pathway. Ibrutinib, the first generation of BTK inhibitor, has shown excellent antitumor activity in both indolent and aggressive B-cell lymphoma. Main body Ibrutinib monotherapy has been confirmed to be effective with a high response rate (RR) and well-tolerated in many B-cell lymphoma subgroups. To achieve much deeper and faster remission, combination strategies contained ibrutinib were conducted to evaluate their synergistic anti-tumor effect. Conclusions For patients with indolent B-cell lymphoma, most of them respond well with ibrutinib monotherapy. Combination strategies contained ibrutinib might be a better choice to achieve deeper and faster remission in the treatment of aggressive subtypes of B-cell lymphoma. Further investigations on the long-term efficacy and safety of the ibrutinib will provide novel strategies for individualized treatment of B-cell lymphoma.

Targeting B-cell receptor and PI3K signaling in diffuse large B-cell lymphoma

Blood ◽  
2021 ◽  
Author(s):  
Wendan Xu ◽  
Philipp Berning ◽  
Georg Lenz
Keyword(s):  
B Cell ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
Genetic Alterations ◽  
B Cell Receptor ◽  
Special Focus ◽  
Large B Cell Lymphoma ◽  
Bcr Signaling ◽  
Large B Cell

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous diagnostic category comprising distinct molecular subtypes characterized by diverse genetic aberrations that dictate patient outcome. As roughly one-third of DLBCL patients are not cured by current standard chemo-immunotherapy a better understanding of the molecular pathogenesis is warranted to improve outcome. B-cell receptor (BCR) signaling is crucial for the development, growth and survival of both normal and a substantial fraction of malignant B-cells. Various analyses revealed genetic alterations of central components of the BCR or its downstream signaling effectors in some subtypes of DLBCL. Thus, BCR signaling and the downstream NF-κB and PI3K cascades have been proposed as potential targets for the treatment of DLBCL patients. As one of the main effectors of BCR activation, PI3K mediated signals play a crucial role in the pathogenesis and survival of DLBCL. In this review, we summarize our current understanding of BCR signaling with a special focus on the PI3K pathway in DLBCL and how to utilize this knowledge therapeutically.

scholarly journals Establishment of two Epstein-Barr virus negative Burkitt cell lines from a patient with AIDS and B-cell lymphoma

Blood ◽  
1988 ◽  
Vol 72 (4) ◽  
pp. 1255-1260 ◽  
Author(s):  
A Ganser ◽  
C Carlo-Stella ◽  
CR Bartram ◽  
T Boehm ◽  
G Heil ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Epstein Barr Virus ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Cell Receptor ◽  
Immunoglobulin Gene ◽  
Barr Virus ◽  
Epstein Barr ◽  
Immunodeficiency Syndrome

Abstract To analyze the pathogenesis of B-cell lymphomas in patients with acquired immunodeficiency syndrome (AIDS), we studied two cell lines, Es I and Es III, established from one such lymphoma for the presence of sequences of the Epstein-Barr virus (EBV) and the human immunodeficiency virus [HIV; lymphadenopathy-associated virus (LAV/HTLV- III)] as well as for the presence of cytogenetic abnormalities and monoclonal rearrangements of immunoglobulin and T-cell receptor genes. Both cell lines expressed the same IgM, kappa phenotype as the original lymphoma. The karyotype of Es I was 46, XY, t(8;14), 2 p+, inv (6p), 17p-, and the cells of Es III had an additional i(7q). Immunoglobulin gene studies demonstrated the identical monoclonal rearrangements in both cell lines. Neither EBV nor HIV sequences were detectable in the malignant B cells at the genomic level, leading to the conclusion that mechanisms other than transformation by EBV or HIV may have contributed to the B-cell lymphoma in this patient and possibly also to the generally increased frequency in patients with AIDS.

Signatures of Response to the Proteasome Inhibitor Bortezomib in Diffuse Large B-Cell Lymphoma.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 608-608
Author(s):  
Friedrich Feuerhake ◽  
Stefano Monti ◽  
Jonathan Blank ◽  
Erxi Wu ◽  
Wen Chen ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Proteasome Inhibitor ◽  
Target Genes ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Rank Test ◽  
Bortezomib Treatment ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Abstract The proteasome inhibitor, bortezomib (VELCADE®, formerly PS341), has significant anti-tumor activity in several lymphoid malignancies. Reported targets of this broad-based inhibitor include the NF K B pathway (I K B A). Recently defined subtypes of large B-cell lymphoma (LBCL) exhibit constitutive activation of NF K B, prompting us to analyze the efficacy of bortezomib in a panel of 10 DLBCL cell lines. Six of the diffuse LBCL cell lines were sensitive to bortezomib treatment at doses below 10 nM (range IC50 = 2.9 to 6.9 nM) whereas 4 cell lines were resistant at 10 nM (IC50 = 14.8 to 70.2 nM). Baseline proteasomal function, as defined by cleavage of the 20S proteasome-specific fluorogenic peptide LLVY-AMC, was similar in sensitive and resistant DLBCLs; however, the IC50 for bortezomib proteasomal inhibition was somewhat lower in sensitive vs. resistant lines (sens. vs res., p = .04, one-sided t test). Baseline NF K B activity varied widely in the DLBCL cell lines and did not differ in cell lines that were sensitive vs. resistant to bortezomib. Ten nM bortezomib did not inhibit NF K B activity in resistant DLBCL cell lines whereas the same dose reduced NF K B activity in sensitive DLBCL cell lines (sens. vs. res., p &lt; .005, rank test [Mann-Whitney]). However, 5 of 6 sensitive DLBCL cell lines had very low baseline NF K B levels (&lt; 0.5 relative absorbance units) suggesting that NF K B inhibition was not a major factor in bortezomib response and prompting further analysis of additional bortezomib targets. Three sensitive and 1 resistant DLBCL cell line were selected for detailed analyses of transcriptional profiles following bortezomib treatment. We developed an algorithm for identifying genes that were significantly up- or down-regulated in the bortezomib-sensitive cell lines but unchanged in the resistant line. In addition, we utilized gene set enrichment analysis (GSEA) and gene ontogeny (GO) termed enrichment to interpret the molecular signatures of response. Genes down-regulated in response to bortezomib included critical B-cell transcription factors, components of the B-cell receptor signaling cascade and genes regulating mitosis and cell cycle control; up-regulated genes included heat shock proteins (HSP) and multiple proteasomal components. Consistent with the functional data, down-regulation of NF K B target genes was not a common feature in all bortezomib-sensitive cell lines. In contrast, target genes of the c-MYC transcription factor were significantly down-regulated and c-MYC activity was decreased in sensitive (but not resistant) DLBCL cell lines following bortezomib treatment (sens. vs. res., p &lt; .005, rank test). Taken together, the results provide insights into likely mechanisms of action of bortezomib in DLBCL, highlighting c-MYC as a potentially important target and identifying HSP as a complementary target to overcome bortezomib resistance.

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