scholarly journals c-Myb expression is critical to maintain proliferation and glucose metabolism of large pre-B cells

2020 ◽  
Author(s):  
Andrea R. Daamen ◽  
Rowena B. Crittenden ◽  
Timothy P. Bender
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
B Cells ◽  
Glucose Metabolism ◽  
B Cell ◽  
Cell Survival ◽  
Myb Transcription Factor ◽  
Cell Cycle Exit ◽  
Cell Stage ◽  
B Cell Survival

AbstractThe c-Myb transcription factor is required for the differentiation of CD19+ B-lineage cells and plays significant roles from the specification of the B cell lineage to the survival of pro-B cells. c-Myb coordinates the survival of pro-B cells with the expression of genes required for transition to the large pre-B cell stage of differentiation. However, it is not known if c-Myb is important for the proliferative expansion or subsequent differentiation into small pre-B cells. Here we demonstrate that c-Myb expression is important for large pre-B cell survival, proliferation, and differentiation into small pre-B cells. Utilizing genome-wide analysis, we found that c-Myb was important for maintaining glucose uptake and utilization and exogenous expression of Glut1 and Hk1 rescued large pre-B cell recovery and survival. Furthermore, we found that c-Myb is important for repression of Ikaros and Aiolos and our c-Myb-dependent gene signature was enriched in an Ikaros footprint of genes that drive cell cycle exit and the large to small pre-B cell transition. However, upon loss of c-Myb expression, inhibition of Ikaros activity was able to restore certain Ikaros-mediated gene expression changes but was insufficient to rescue recovery of large pre-B cell numbers. We found that c-Myb regulates glucose utilization and glucose-dependent survival through Hk1 in an Ikaros-independent manner. Thus, c-Myb regulation of glucose metabolism is critical to maintain large pre-B cell survival while repression of the Ikaros-mediated gene expression program is critical to prevent premature cell cycle exit and premature differentiation into small pre-B cells.

scholarly journals Ras Mediates Effector Pathways Responsible for Pre-B Cell Survival, Which Is Essential for the Developmental Progression to the Late Pre-B Cell Stage

2000 ◽  
Vol 192 (2) ◽  
pp. 171-182 ◽  
Author(s):  
Hitoshi Nagaoka ◽  
Yoshimasa Takahashi ◽  
Reiko Hayashi ◽  
Tohru Nakamura ◽  
Kumiko Ishii ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Chain Gene ◽  
B Cell Differentiation ◽  
Antigen Receptors ◽  
Cell Stage ◽  
Light Chain Gene ◽  
B Cell Survival ◽  
Effector Pathways

Ras is essential for the transition from early B cell precursors to the pro-B stage, and is considered to be involved in the signal cascade mediated by pre-B cell antigen receptors. To examine the role of p21ras in the late stage of B cell differentiation, we established transgenic mice (TG) expressing a dominant-inhibitory mutant of Ha-ras (Asn-17 Ha-ras) in B lineage cells at high levels after the early B cell precursor stage. Expression of p21Asn-17 Ha-ras was associated with a prominent reduction in the number of late pre-B cells, but had little effect on proliferation of early pre-B cells. Inhibition of p21ras activity markedly reduced the life span of pre-B cells, due, at least in part, to downregulation of the expression of an antiapoptotic protein, Bcl-xL. Thus, the apparent role for p21ras activity in pre-B cell survival may explain the decreased numbers of late pre-B cells in Asn-17 Ha-ras TG. Consistent with this possibility, overexpression of Bcl-2 in Asn-17 Ha-ras TG reversed the reduction in the number of late pre-B cells undergoing immunoglobulin light chain gene (IgL) rearrangement and progressing to immature B cells. These results suggest that p21ras mediates effector pathways responsible for pre-B cell survival, which is essential for progression to the late pre-B and immature B stages.

scholarly journals B Cell–Activating Factor Promotes B Cell Survival in Ectopic Lymphoid Tissues in Nasal Polyps

2021 ◽  
Vol 11 ◽  
Author(s):  
Zhe-Zheng Wang ◽  
Jia Song ◽  
Hai Wang ◽  
Jing-Xian Li ◽  
Qiao Xiao ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Stromal Cells ◽  
Caspase 3 ◽  
Lymphoid Tissues ◽  
B Cell Activating Factor ◽  
B Cell Survival ◽  
Active Caspase

Ectopic lymphoid tissues (eLTs) characterized by B cell aggregation contribute to the local immunoglobulin production in nasal polyps (NPs). B cell-activating factor (BAFF) is vital for B cell survival, proliferation, and maturation. The purpose of this study is to investigate whether BAFF is involved in the B cell survival and eLT formation in NPs. The mRNA and protein levels of BAFF in NP tissues with and without eLTs were detected by PCR and ELISA assay, respectively. The cellular sources of BAFF and active caspase-3-positive B cells in NPs were studied by immunofluorescence staining. B cells purified from NP tissues were stimulated with BAFF and were analyzed by flow cytometry. Stromal cells purified from NP tissues were stimulated with lymphotoxin (LT) α1β2, and BAFF levels in culture supernatants were analyzed by ELISA. Compared with those in control tissues and NPs without eLTs, the BAFF levels were elevated in NPs with eLTs. Abundant BAFF-positive cells and few active caspase-3-positive apoptotic B cells were found in NPs with eLTs, in contrast to those in NPs without eLTs. There was a negative correlation between the numbers of BAFF-positive cells and frequencies of apoptotic B cells in total B cells in NP tissues. BAFF protected nasal polyp B cells from apoptosis in vitro. Stromal cells were an important cellular source of BAFF in NPs with eLTs. LTα1β2 induced BAFF production from nasal stromal cells in vitro. We propose that BAFF contribute to eLT formation in NPs by promoting B cell survival.

scholarly journals Attenuation of Apoptosis Underlies B Lymphocyte Stimulator Enhancement of Humoral Immune Response

2000 ◽  
Vol 192 (7) ◽  
pp. 953-964 ◽  
Author(s):  
Richard K.G. Do ◽  
Eunice Hatada ◽  
Hayyoung Lee ◽  
Michelle R. Tourigny ◽  
David Hilbert ◽  
...  
Keyword(s):  
Immune Response ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
B Lymphocyte ◽  
Humoral Immune ◽  
B Cell Survival ◽  
B Lymphocyte Stimulator

B lymphocyte stimulator (BLyS) is a newly identified monocyte-specific TNF family cytokine. It has been implicated in the development of autoimmunity, and functions as a potent costimulator with antiimmunoglobulin M in B cell proliferation in vitro. Here we demonstrate that BLyS prominently enhances the humoral responses to both T cell–independent and T cell–dependent antigens, primarily by attenuation of apoptosis as evidenced by the prolonged survival of antigen-activated B cells in vivo and in vitro. BLyS acts on primary splenic B cells autonomously, and directly cooperates with CD40 ligand (CD40L) in B cell activation in vitro by protecting replicating B cells from apoptosis. Moreover, although BLyS alone cannot activate the cell cycle, it is sufficient to prolong the survival of naive resting B cells in vitro. Attenuation of apoptosis by BLyS correlates with changes in the ratios between Bcl-2 family proteins in favor of cell survival, predominantly by reducing the proapoptotic Bak and increasing its prosurvival partners, Bcl-2 and Bcl-xL. In either resting or CD40L-activated B cells, the NF-κB transcription factors RelB and p50 are specifically activated, suggesting that they may mediate BLyS signals for B cell survival. Together, these results provide direct evidence for BLyS enhancement of both T cell–independent and T cell–dependent humoral immune responses, and imply a role for BLyS in the conservation of the B cell repertoire. The ability of BLyS to increase B cell survival indiscriminately, at either a resting or activated state, and to cooperate with CD40L, further suggests that attenuation of apoptosis underlies BLyS enhancement of polyclonal autoimmunity as well as the physiologic humoral immune response.

scholarly journals Plasma cells induce apoptosis of pre-B cells by interacting with bone marrow stromal cells

Blood ◽  
1996 ◽  
Vol 87 (8) ◽  
pp. 3375-3383 ◽  
Author(s):  
T Tsujimoto ◽  
IA Lisukov ◽  
N Huang ◽  
MS Mahmoud ◽  
MM Kawano
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Cell Lines ◽  
Stromal Cells ◽  
Plasma Cells ◽  
Myeloma Cell ◽  
Myeloma Cells ◽  
B Cell Survival

By using two-color phenotypic analysis with fluorescein isothiocyanate- anti-CD38 and phycoerythrin-anti-CD19 antibodies, we found that pre-B cells (CD38+CD19+) signifcantly decreased depending on the number of plasma cells (CD38++CD19+) in the bone marrow (BM) in the cases with BM plasmacytosis, such as myelomas and even polyclonal gammopathy. To clarify how plasma cells suppress survival of pre-B cells, we examined the effect of plasma cells on the survival of pre-B cells with or without BM-derived stromal cells in vitro. Pre-B cells alone rapidly entered apoptosis, but interleukin-7 (IL-7), a BM stromal cell line (KM- 102), or culture supernatants of KM-102 cells could support pre-B cell survival. On the other hand, inhibitory factors such as transforming growth factor-beta1 (TGF-beta1) and macrophage inflammatory protein- 1beta (MIP-1beta) could suppress survival of pre-B cells even in the presence of IL-7. Plasma cells alone could not suppress survival of pre- B cells in the presence of IL-7, but coculture of plasma cells with KM- 102 cells or primary BM stromal cells induced apoptosis of pre-B cells. Supernatants of coculture with KM-102 and myeloma cell lines (KMS-5) also could suppress survival of pre-B cells. Furthermore, we examined the expression of IL-7, TGF-beta1, and MIP-1beta mRNA in KM-102 cells and primary stromal cells cocultured with myeloma cell lines (KMS-5). In these cells, IL-7 mRNA was downregulated, but the expression of TGF- beta1 and MIP-1beta mRNA was augmented. Therefore, these results suggest that BM-derived stromal cells attached to plasma (myeloma) cells were modulated to secrete lesser levels of supporting factor (IL- 7) and higher levels of inhibitory factors (TGF-beta1 and MIP-1beta) for pre-B cell survival, which could explain why the increased number of plasma (myeloma) cells induced suppression of pre-B cells in the BM. This phenomenon may represent a feedback loop between pre-B cells and plasma cells via BM stromal cells in the BM.

The Akt/Mcl-1 Pathway Plays a Prominent Role in Mediating Pro-Survival Signals Derived from the B-Cell Receptor in Chronic Lymphocytic Leukemia B-Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 341-341
Author(s):  
Pablo G. Longo ◽  
Luca Laurenti ◽  
Stefania Gobessi ◽  
Simona Sica ◽  
Giuseppe Leone ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Igm Antibodies ◽  
B Cell Survival ◽  
Sustained Activation ◽  
Constitutively Active

Abstract Studies of the immunoglobulin variable region gene repertoire have provided compelling evidence that antigen-stimulation through the B-cell receptor (BCR) plays a crucial role in the pathogenesis and progression of chronic lymphocytic leukemia (CLL). In addition, previous studies from our lab have shown that CLL B-cells become more resistant to spontaneous and chemotherapy-induced apoptosis following sustained engagement of the BCR with immobilized anti-IgM antibodies, which mimic stimulation with membrane-bound antigens. Investigation of downstream signaling pathways revealed that sustained BCR engagement induces prolonged activation of the PI3K/Akt and MEK/ERK pathways, which are key regulators of survival and proliferation in various cell types. To further define the role of sustained activation of the Akt and ERK kinases in regulating CLL growth and survival, we transfected constitutively active mutants of Akt (myr.Akt) and MEK2 in primary leukemic cells and evaluated changes in the expression of relevant apoptosis- and cell-cycle regulatory proteins. Introduction of constitutively active MEK2 resulted in activation of ERK, but did not induce significant changes in the levels of most investigated proteins (Bcl-2, Bcl-xL, Bim, Bax or Mcl-1). The only exception was the inhibitor of apoptosis protein XIAP, which showed increased expression in most but not all experiments. In contrast, transfection of myr.Akt showed a consistent increase in the levels of the antiapoptotic protein Mcl-1, which ranged from 1.5 to more than 4-fold higher levels with respect to cells transfected with control vectors. Increased expression of Mcl-1 was observed in all experiments and paralleled the rise in Mcl-1 that occurred following stimulation of CLL B-cells with immobilized anti-IgM antibodies. The increase in Mcl-1 protein levels was entirely due to post-transcriptional mechanisms, since quantification by real-time PCR did not show an increase in Mcl-1 mRNA levels. Constitutively active Akt also upregulated Bcl-xL and XIAP, although this increase was lower than the increase in Mcl-1. In addition, CLL cells transfected with myr.Akt showed induction of cyclin D3 and an increase in cell size and viability, indicating that sustained activation of Akt is required for both leukemic cell survival and cell cycle progression. To determine the relative importance of Mcl-1, Bcl-xL and XIAP in CLL B-cell survival, we downregulated expression of these proteins in primary CLL B-cells by RNA interference. Surprisingly, downregulation of Bcl-xL and XIAP had no effect on CLL B-cell survival. In contrast, silencing of Mcl-1 induced rapid and potent apoptosis in all investigated cases and abrogated the prosurvival effect of stimulation with immobilized anti-IgM antibodies. Together, these data provide direct evidence that pro-survival BCR signaling in CLL B-cells is mediated, at least in part, through the Akt/Mcl-1 pathway. In addition, they suggest that Mcl-1 could be an attractive candidate for targeting, either with small molecule inhibitors or with pharmacological agents that interfere with BCR signals propagated by the Akt kinase.

Sensitivity to Wnt Pathway Inhibition in CLL Is Associated with Specific Gene Expression Signatures

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 801-801
Author(s):  
Lili Wang ◽  
Alex K Shalek ◽  
Jellert Gaublomme ◽  
Nir Yosef ◽  
Jennifer R Brown ◽  
...  
Keyword(s):  
Gene Expression ◽  
B Cells ◽  
Cell Viability ◽  
B Cell ◽  
Cell Survival ◽  
Wnt Pathway ◽  
Differentially Expressed ◽  
Differential Sensitivity ◽  
Specific Gene ◽  
Disease Heterogeneity

Abstract Abstract 801 We have recently found that the Wnt/b-catenin signaling pathway plays a key role in chronic lymphocytic leukemia (CLL). We were, however, intrigued by the question of whether this aberrant pathway may function differently in independent leukemias, and contribute to disease heterogeneity. To assess differential activity of the Wnt pathway across patients, we tested the effects of blocking Wnt activation on CLL cell survival. We knocked down a key downstream gene, LEF1, which is the most differentially expressed gene in CLL compared to normal B cells (based on gene expression microarrays). Addressing this question requires genetic manipulation of primary normal and malignant human B cells, and yet these cells are notoriously difficult to transfect. We therefore focused on developing a method for introducing siRNAs into normal and malignant B cells. We adapted a novel delivery system consisting of vertical silicon nanowires (SiNWs, Shalek et al PNAS 2010) that penetrate the plasma membrane in a minimally invasive fashion and deliver biomolecular cargo directly into the cytoplasm. We achieved consistent and reliable delivery of fluorescently labeled siRNAs (at 50–200 pmol) into normal and CLL B cells. siRNA was delivered to >90% of cells with >85% cell viability remaining after 48 hours. We used this platform to knockdown LEF1 in 20 CLL-B and 5 normal CD19+ B cell samples, and examined cell survival 48 hours after siRNA delivery using an ATP-based CellTiter-Glo assay. Indeed, our studies revealed a heterogeneous response among CLL-B cells to LEF1 inhibition. As a group, CLL-B cells were significantly more sensitive to LEF1 knockdown with a survival rate of 77% (12% s.e.m) compared to 97% (13% s.e.m) in normal B cells. CLL B cells from different patients showed differential sensitivity to LEF1 knockdown, with 8 non-responders, 8 intermediate responders and 4 strong responders (i.e. significant death). Sensitivity to LEF1 inhibition did not correlate with known CLL cytogenetic prognostic factors. To determine if the differential response to LEF1 knockdown was associated with specific gene signatures, we examined gene expression data generated from CLL-B cells from 12 (4 strong, 3 intermediate, and 5 non-responders) of the 20 CLLs tested (using the Affymetrix U133 Plus 2 Array). To increase statistical power, we used each CLL's expression profile (using only genes that showed variability across samples) to create clusters of ∼19 CLLs that showed similar expression profiles (using microarray data from our compendium of 177 additional CLLs). We further reduced the number of genes to ∼4000 genes by retaining only those whose expression levels were significantly different in at least one associated cluster relative to normal CD19+ B cell controls (T-test, FDR<10−4; p-values converted using the Benjamini-Hochberg method). These analyses led to the identification of several hundred genes whose expression correlated significantly with LEF1 knockdown's effect on cell viability. Analysis of these differentially expressed genes identified several potentially important pathways. Ongoing analyses include the identification and validation of a molecular signature for this effect. This signature could enable rapid identification of patients who would be most responsive to therapy with LEF1 inhibitors, which are under development along with other Wnt pathway inhibitors. Disclosures: No relevant conflicts of interest to declare.

scholarly journals The BAFFling persistence of memory B cells

2020 ◽  
Vol 218 (2) ◽  
Author(s):  
Jeremy F. Brooks ◽  
Julie Zikherman
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Essential Role ◽  
Memory B Cells ◽  
B Cell Survival

Although BAFF/BLyS and its receptor, BAFFR, play critical roles in naive B cell survival, the pathways involved in the persistence of memory B cells are largely unknown. In this issue of JEM, two groups, Müller-Winkler et al. (https://doi.org/10.1084/jem.20191393) and Lau et al. (https://doi.org/10.1084/jem.20191167), take complementary approaches to identify an essential role for BAFFR in the survival of memory B cells.

scholarly journals TRAF3 regulates the oncogenic proteins Pim2 and c-Myc to restrain survival in normal and malignant B cells

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Amy L. Whillock ◽  
Nurbek Mambetsariev ◽  
Wai W. Lin ◽  
Laura L. Stunz ◽  
Gail A. Bishop
Keyword(s):  
Cell Death ◽  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Cell Lines ◽  
Adapter Protein ◽  
Protein Levels ◽  
B Cell Survival ◽  
Multiple Context ◽  
Context Specific

Abstract TRAF3 is a versatile intracellular adapter protein with multiple context-specific roles. Uniquely in B cells, TRAF3 deficiency enhances survival and increases the risk of transformation, as loss of TRAF3 is observed in several types of B cell cancers. Here, we report a new mechanism for TRAF3 in the restraint of B cell survival. We found that TRAF3 deficiency was associated with induction of the pro-survival kinase Pim2 in mouse primary B cells and human malignant B cell lines. The increase in Pim2 was independent of NF-κB2 activation but was ameliorated with inhibition of STAT3 expression or function. TRAF3 deficiency also led to a Pim2-dependent increase in c-Myc protein levels and was associated with reduced c-Myc ubiquitination. TRAF3-deficient primary B cells were less sensitive to cell death induced by the Pim inhibitors SGI-1776 and TP-3654. Interestingly, human malignant B cell lines with low expression of TRAF3 were more sensitive to Pim inhibition-induced cell death. Combination treatment of TRAF3-deficient B cells and B cell tumor lines with c-Myc inhibitors enhanced their sensitivity to Pim inhibition, suggesting a possible therapeutic strategy. TRAF3 thus suppresses a Pim2-mediated B cell survival axis, which can be a potential target for treatment of B cell malignancies.

scholarly journals Concurrent engagement of CD40 and the antigen receptor protects naive and memory human B cells from APO-1/Fas-mediated apoptosis.

1996 ◽  
Vol 183 (4) ◽  
pp. 1377-1388 ◽  
Author(s):  
C Lagresle ◽  
P Mondière ◽  
C Bella ◽  
P H Krammer ◽  
T Defrance
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
Antigen Receptor ◽  
Cell Types ◽  
Memory B Cells ◽  
Apoptotic Pathway ◽  
Cell Responses ◽  
Human B Cells ◽  
B Cell Survival

Naive and memory B cells were isolated from human tonsils and examined for expression of APO-1/Fas and for their sensitivity to the APO-1-dependent apoptosis. APO-1 was found to be constitutively expressed on memory but not on naive B cells. The susceptibility of both cell types to the APO-1 apoptotic pathway was acquired upon CD40 triggering and was correlated with increased expression of the APO-1 receptor. Both naive and memory B cells were protected from the APO-1-mediated death signal after dual ligation of the Ag receptor adn CD40. Our findings suggest that the APO-1 pathway controls the specificity of B cell responses to T-dependent Ags and that occupancy of the Ag receptor dictates the outcome of APO-1-ligation on B cell survival.

scholarly journals Constitutive NF-κB and NFAT activation leads to stimulation of the BLyS survival pathway in aggressive B-cell lymphomas

Blood ◽  
2006 ◽  
Vol 107 (11) ◽  
pp. 4540-4548 ◽  
Author(s):  
Lingchen Fu ◽  
Yen-Chiu Lin-Lee ◽  
Lan V. Pham ◽  
Archito Tamayo ◽  
Linda Yoshimura ◽  
...  
Keyword(s):  
Gene Expression ◽  
B Cells ◽  
B Cell ◽  
Cell Survival ◽  
B Lymphocyte ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Non Hodgkin Lymphoma ◽  
Survival Pathway ◽  
Differentiation And Proliferation

AbstractB-lymphocyte stimulator (BLyS), a relatively recently recognized member of the tumor necrosis factor ligand family (TNF), is a potent cell-survival factor expressed in many hematopoietic cells. BLyS binds to 3 TNF-R receptors, TACI, BCMA, BAFF-R, to regulate B-cell survival, differentiation, and proliferation. The mechanisms involved in BLYS gene expression and regulation are still incompletely understood. In this study, we examined BLYS gene expression, function, and regulation in B-cell non-Hodgkin lymphoma (NHL-B) cells. Our studies indicate that BLyS is constitutively expressed in aggressive NHL-B cells, including large B-cell lymphoma (LBCL) and mantle cell lymphoma (MCL), playing an important role in the survival and proliferation of malignant B cells. We found that 2 important transcription factors, NF-κB and NFAT, are involved in regulating BLyS expression through at least one NF-κB and 2 NFAT binding sites in the BLYS promoter. We also provide evidence suggesting that the constitutive activation of NF-κB and BLyS in NHL-B cells forms a positive feedback loop associated with lymphoma cell survival and proliferation. Our findings indicate that constitutive NF-κB and NFAT activations are crucial transcriptional regulators of the BLyS survival pathway in malignant B cells that could be therapeutic targets in aggressive NHL-B.

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