Aberrant Expression of the NF-κB and IκB Proteins in B Cells from Viable Motheaten Mice

B-cell chronic lymphocytic leukemia (B-CLL) is defined by the accumulation of CD5+ B cells in the periphery and bone marrow. This disease is not characterized by highly proliferative cells but rather by the presence of leukemic cells with significant resistance to apoptosis and, therefore, prolonged survival. B-lymphocyte stimulator (BLyS) is a newly identified tumor necrosis factor (TNF) family member shown to be critical for maintenance of normal B-cell development and homeostasis and it shares significant homology with another TNF superfamily member, APRIL. The striking effects of BLyS on normal B-cell maintenance and survival raises the possibility that it may be involved in pathogenesis and maintenance of hematologic malignancies, including B-CLL. In this study, we investigated the status of APRIL and BLyS expression, as well as their receptors, in this disease. All B-CLL patient cells studied expressed one or more of 3 known receptors for BLyS; however, the pattern of expression was variable. In addition, we demonstrate for the first time that B-CLL cells from a subset of patients aberrantly express BLyS and APRIL mRNA, whereas these molecules were not detectable in normal B cells. Furthermore, we provide in vitro evidence that BLyS protects B-CLL cells from apoptosis and enhances cell survival. Because these molecules are key regulators of B-cell homeostasis and tumor progression, leukemic cell autocrine expression of BLyS and APRIL may be playing an important role in the pathogenesis of this disease.

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Ataxin-1 regulates B cell function and the severity of autoimmune experimental encephalomyelitis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2003798117 ◽

2020 ◽

Vol 117 (38) ◽

pp. 23742-23750 ◽

Cited By ~ 1

Author(s):

Alessandro Didonna ◽

Ester Canto Puig ◽

Qin Ma ◽

Atsuko Matsunaga ◽

Brenda Ho ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Cell Function ◽

Cell Activity ◽

Cell Polarization ◽

Spinocerebellar Ataxia Type ◽

Loss Of Function ◽

Th1 Cell ◽

Aberrant Expression

Ataxin-1 (ATXN1) is a ubiquitous polyglutamine protein expressed primarily in the nucleus where it binds chromatin and functions as a transcriptional repressor. Mutant forms of ataxin-1 containing expanded glutamine stretches cause the movement disorder spinocerebellar ataxia type 1 (SCA1) through a toxic gain-of-function mechanism in the cerebellum. Conversely, ATXN1 loss-of-function is implicated in cancer development and Alzheimer’s disease (AD) pathogenesis.ATXN1was recently nominated as a susceptibility locus for multiple sclerosis (MS). Here, we show thatAtxn1-null mice develop a more severe experimental autoimmune encephalomyelitis (EAE) course compared to wildtype mice. The aggravated phenotype is mediated by increased T helper type 1 (Th1) cell polarization, which in turn results from the dysregulation of B cell activity. Ataxin-1 ablation in B cells leads to aberrant expression of key costimulatory molecules involved in proinflammatory T cell differentiation, including cluster of differentiation (CD)44 and CD80. In addition, comprehensive phosphoflow cytometry and transcriptional profiling link the exaggerated proliferation of ataxin-1 deficient B cells to the activation of extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription (STAT) pathways. Lastly, selective deletion of the physiological binding partner capicua (CIC) demonstrates the importance of ATXN1 native interactions for correct B cell functioning. Altogether, we report a immunomodulatory role for ataxin-1 and provide a functional description of theATXN1locus genetic association with MS risk.

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TRAF3 Over-Expression Contributes to the Enhanced Alternative NF-κB Activity in Hodgkin's Lymphoma Cells.

Blood ◽

10.1182/blood.v114.22.3665.3665 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3665-3665

Author(s):

Feng Guo ◽

Peng Zhou ◽

Liang Ma

Keyword(s):

B Cells ◽

B Cell ◽

Expression Vector ◽

Conflicts Of Interest ◽

Negative Regulator ◽

Activity Assay ◽

Lymphoma Cells ◽

Aberrant Expression ◽

Wide Range ◽

P100 Processing

Abstract Abstract 3665 Poster Board III-601 Introduction Hodgkin and Reed-Sternberg (H-RS) cells are originated from germinal center B cells. Constitutive nuclear factor κB (NF-κB) activation is one of the molecular characteristic futures of H-RS cells. TNFR-associated factors (TRAFs) participate in a wide range of biological processes, such as adaptive and innate immunity, stress response, and bone metabolism, which are mediated by the induction of cell survival, proliferation, and differentiation. Among those, TRAF3 are reported as a negative regulator of the alternative NF-κB signaling pathway in B cells. How TRAF3 functions in H-RS cells is currently unclear. Methods Electromobility shift assay (EMSA) was performed to examine the NF-κB activity in B cell-derived Hodgkin's cells (L428 and KM-H2). An ELISA-based NF-κB family transcription factor activity assay was performed to quantify NF-κB DNA-binding in nuclear extracts from L428 cells. p100 processing, the expression of other NF-κB family members in the cytoplasm, and TRAF3 expression were detected by Western blot analysis. The effects of TRAF3 in L428 cells were studied by transient expression of TRAF3 expression vector. Results In this study, we found that TRAF3 was minimally detected in B cell-derived Hodgkin's cell lines (L428 and KM-H2) either in mRNA or protein levels. Both the classical (p50-RelA) and the alternative (p52-RelB) NF-kB activity were consistently activated in L428 cells, measured by EMSA and TransAM NF-kB activity assay. The enhanced alternative NF-κB activity, accompanied by increased p100 processing and RelB accumulation in the cytoplasm were detected in L428 cells. Transient transfection of TRAF3-expression vector enforced the expression of TRAF3 and blocked the p100 processing in L428 cells. The alternative NF-kB activity was partially decreased whereas the classical NF-kB activity remained intact. In addition, the increased TRAF3 expression did not affect the anti-apoptotic effects in L428 cells. Conclusions Not only the classical NF-κB activity but also the alternative NF-κB activity characterized by p100 processing and p52-RelB nuclear localization is constitutively activated in B cell-derived lymphoma cells. Lack of TRAF3 expression might be one of the reasons for the aberrant expression of alternative NF-κB activity. TRAF3 is indeed an important molecule regulating the activation of the alternative NF-kB activity but not the classical NF-kB activity in H-RS cells. Disclosures: No relevant conflicts of interest to declare.

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Overexpression of the Protein Tyrosine Phosphatase Lyp Reduces the Responsiveness of Chronic Lymphocytic Leukemia B-Cells to B-Cell Receptor Ligation.

Blood ◽

10.1182/blood.v114.22.800.800 ◽

2009 ◽

Vol 114 (22) ◽

pp. 800-800

Author(s):

Roberto Negro ◽

Pablo G Longo ◽

Michela Tarnani ◽

Stefania Gobessi ◽

Luca Laurenti ◽

...

Keyword(s):

Signal Transduction ◽

B Cells ◽

Autoimmune Diseases ◽

B Cell ◽

Conflicts Of Interest ◽

Signaling Molecules ◽

Negative Regulator ◽

Nucleotide Sequence Analysis ◽

Aberrant Expression ◽

Bcr Signaling

Abstract Abstract 800 CLL B cells display many features that suggest a role for antigen stimulation in the development and progression of the disease. These include the expression of stereotyped B-cell receptors (BCRs), the association between IgVH gene mutation status and prognosis, and the gene-expression profile of antigen-stimulated B cells. In addition, CLL B cells have other BCR-related features that distinguish them from normal B lymphocytes, such as lower levels of surface Ig, less efficient BCR signal transduction and increased basal activity of the proximal BCR signaling molecules Lyn and Syk. We have now investigated whether any of these features are related to aberrant expression or function of the phosphatases SHP-1, SHP-2 and Lyp (PTPN22), which regulate the amplitude and duration of the BCR signal by dephosphorylating various components of the BCR signal transduction unit. These phosphatases are also interesting because mutated or polymorphic variants have been linked to various malignant or autoimmune diseases. We started our study by performing nucleotide sequence analysis of the complete coding region of SHP1, SHP2 and Lyp in 8, 21 and 29 CLL B cell samples, respectively. Overall, only two mutations were identified (an R527C substitution in SHP2 and a Q456E substitution in Lyp, each in a single patient), suggesting that these phosphatases are infrequently mutated in CLL. The previously reported Lyp polymorphisms R620W and R263Q were observed in 2 additional cases. We next investigated expression of these phosphatases in purified CLL and normal B cells by immunoblotting. Expression of SHP1 and SHP2 was relatively uniform in the different CLL B-cells samples (n=42) and was not different from normal B cells (n=4). In contrast, expression of Lyp was markedly higher in most CLL samples, with 35 of the 49 investigated cases exhibiting 2 to more than 10 fold higher levels than normal B cells (n=5) (CLL, mean Lyp levels 4.7, SD +/−3.7; normal B cells, mean Lyp levels 0.9, SD +/−0.1, P=0.022). The mean Lyp levels were somewhat higher in U-CLL than M-CLL (6.0 vs. 3.9) and ZAP-70-positive than ZAP-70-negative cases (5.6 vs. 4.7), but these differences were not statistically significant. Analysis of Lyp expression in various lymphoma B-cell lines (n=9) also did not reveal significant differences with respect to normal B-cells, suggesting that Lyp overexpression is a specific feature of CLL. To determine what are the consequences of Lyp overexpression on BCR signaling, we downregulated Lyp in primary CLL B-cells by RNA interference and investigated activation of BCR signaling molecules following sIgM crosslinking. Downregulation of Lyp resulted in a substantial increase in BCR-induced phosphorylation of Lyn (Y397), Syk (Y352), BLNK (Y84) and ERK (T202/Y204), suggesting that overexpression of this phosphatase may be at least partially responsible for the lower BCR signaling capacity of CLL B-cells. Since Lyp expression can be induced in resting T cells by activation with anti-CD3, we investigated whether BCR stimulation will have a similar effect on CLL B-cells. A two-fold increase in Lyp levels was observed after 24 hours of sustained BCR stimulation with immobilized anti-IgM, whereas transient stimulation with soluble anti-IgM resulted in a 20% decrease in Lyp levels. These effects were specific for Lyp, since no such changes were observed in the expression of SHP1 and SHP2. In summary, this study shows that CLL B-cells specifically overexpress the phosphatase Lyp, and important negative regulator of BCR signaling that has been implicated in the pathogenesis of several common autoimmune diseases. Given the observation that Lyp can be induced by sustained BCR engagement and in view of recent findings that Lyp is also overexpressed in anergic B cells, these data further support the notion that CLL cells are continuously exposed to (auto)antigen in vivo. Disclosures: No relevant conflicts of interest to declare.

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Aberrant expression and reverse signalling of CD70 on malignant B cells

British Journal of Haematology ◽

10.1046/j.1365-2141.1999.01573.x ◽

1999 ◽

Vol 106 (2) ◽

pp. 491-503 ◽

Cited By ~ 90

Author(s):

Susanne M. A. Lens ◽

Paul Drillenburg ◽

Bianca F. A. den Drijver ◽

Gijs van Schijndel ◽

Steven T. Pals ◽

...

Keyword(s):

B Cells ◽

Aberrant Expression

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Notch2 is involved in the overexpression of CD23 in B-cell chronic lymphocytic leukemia

Blood ◽

10.1182/blood.v99.10.3742 ◽

2002 ◽

Vol 99 (10) ◽

pp. 3742-3747 ◽

Cited By ~ 93

Author(s):

Rainer Hubmann ◽

Josef D. Schwarzmeier ◽

Medhat Shehata ◽

Martin Hilgarth ◽

Markus Duechler ◽

...

Keyword(s):

B Cells ◽

Chronic Lymphocytic Leukemia ◽

B Cell ◽

Core Promoter ◽

Lymphocytic Leukemia ◽

Mobility Shift ◽

Aberrant Expression ◽

Barr Virus ◽

Epstein Barr ◽

Cell Chronic Lymphocytic Leukemia

Members of the Notch family encode transmembrane receptors that modulate differentiation, proliferation, and apoptotic programs of many precursor cells, including hematopoietic progenitors. Stimulation of Notch causes cleavage followed by translocation of the intracellular domain (NotchIC) to the nucleus, where it activates transcription of CBF1 responsive genes. The aim of this study was to elucidate the mechanisms leading to the overexpression of CD23, a striking feature of B-cell chronic lymphocytic leukemia (B-CLL) cells. By electrophoretic mobility shift assays, we identified a transcription factor complex (C1) that binds sequence specific to one known and 4 newly identified putative CBF1 recognition sites in the CD23a core promoter region. With the use of Epstein-Barr virus (EBV)–infected B cells as a model for CBF1 mediated CD23a expression, C1 was found to be EBV inducible. Supershift assays revealed that the nuclear form of Notch2 is a component of C1 in B-CLL cells, supporting a model in which NotchIC activates transcription by binding to CBF1 tethered to DNA. Transient transfection of REH pre–B cells with an activated form of Notch2 induced endogenous CD23a, confirming thatCD23a is a target gene of Notch2 signaling. Finally, reverse transcription-polymerase chain reaction and kinetic analysis demonstrated that the Notch2 oncogene is not only overexpressed in B-CLL cells but might also be related to the failure of apoptosis characteristic for this disease. In conclusion, these data suggest that deregulation of Notch2 signaling is involved in the aberrant expression of CD23 in B-CLL.

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Aberrant Expression of a Proliferation-Inducing Ligand Underlies Autoimmune Mechanisms in Immune Thrombocytopenia

Blood ◽

10.1182/blood-2018-99-111743 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 3763-3763

Author(s):

Yunfeng Hao ◽

Renchi Yang ◽

Zeping Zhou

Keyword(s):

T Cells ◽

B Cells ◽

B Cell ◽

Normal Control ◽

Normal Control Group ◽

Autoimmune Response ◽

Control Group ◽

Aberrant Expression ◽

Platelet Surface ◽

B10 Cells

Abstract Background: Immunological thrombocytopenia (ITP) is an antibody-mediated autoimmune disease characterized by accelerated platelet destruction and suboptimal platelet production. The proliferation-inducing ligand (APRIL or TNFSF13), a member of the TNF superfamily, is structurally and functionally related to the TNF family of B cell activating factors (BAFF, TNFSF13b) and has been shown to regulate lymphocyte survival by interacting with its receptors. And activation. Transmembrane activators and calcium regulate cyclophilin ligand interactors (TACI) and B cell mature antigens (BCMA). APRIL is secreted by various cells as soluble factors, including inactive B cells, T cells, monocytes, neutrophils, macrophages and dendritic cells, as well as epithelial cells, osteoclasts and megakaryocytes. Recent studies have shown that APRIL not only participates in normal immune responses, but also plays an important role in the establishment and/or maintenance of autoimmune and inflammatory diseases. Aims: Based on the relationship between APRIL, which promotes proliferation and regulates immunity, and the development of autoimmunity, we hypothesize that APRIL may play a role in the pathogenesis of ITP. Methods:1. The EDTA anticoagulated whole blood was collected, and peripheral blood mononuclear cells (PBMC) were separated by Ficoll density gradient centrifugation. The APRIL levels on the surface of T cells, B cells, DC cells and platelets were detected by flow cytometry.Detection of plasma APRIL levels in patients with ITP by ELISA.Real time quantitative PCR were used for detecting the level of APRIL and its receptors BCMA and TACI from PBMC of healthy controls and ITP patients.Use soluble APRIL or BLyS protein and APRIL inhibitors to examine the effect of APRIL inhibition on IL-10 secretion by B cells. Flow cytometry and intracellular staining were used to evaluate B10 cells. Resoult: 1. The APRIL on the platelet surface of patients with ITP was significantly lower than that of the normal control group (p<0.01). In the ITP patients of 10 patients with complete remission, the content of APRIL on the platelet surface was significantly increased after treatment (p=0.02), and there was no significant change in the treatment-ineffective group. . The levels of APRIL and its receptors BCMA and TACI on B cells and DC cells in ITP patients were higher than those in normal controls, and the difference was statistically significant. APRIL is not expressed on CD4 + T cells, CD8 + T cells.The expression of APRIL mRNA in PBMNCs was significantly higher in ITP patients than in the normal control group (p <0.01). There was no difference in BCMA and TACI expression in PBMNC of ITP patients compared to normal controls.Plasma APRIL levels were significantly higher in ITP patients than in the normal control group, p = 0.04, and negatively correlated with platelet count, p = 0.029.In 10 patients with ITP, the percentage of CD19 + B cells remained similar between patients, and the results showed that the amount of B10 cells in the medium supplemented with APRIL was greater than that of B10 cells containing BLyS and control medium (p<0.01; p= 0.01), and the use of APRIL inhibitors resulted in a decrease in B10 cells. Conclusion: Our study shows that aberrant expression of APRIL is involved in the autoimmune response of ITP, and the effect of treatment can be assessed by measuring changes in the level of APRIL on the platelet surface. We also speculate that APRIL inhibits, rather than promotes, an immune-mediated inflammatory response in the pathogenesis of ITP. Our current observations support that the immunomodulatory effects of APRIL may be due, at least in part, to stimulation of IL-10 producing B cells. Disclosures No relevant conflicts of interest to declare.

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Gene Expression Profiling of Mantle Cell Lymphoma in the Leukemic Phase Reveals Aberrant Expression of Genes from the TGF-β Signaling Pathway.

Blood ◽

10.1182/blood.v104.11.2048.2048 ◽

2004 ◽

Vol 104 (11) ◽

pp. 2048-2048

Author(s):

Edgar G. Rizzatti ◽

Rodrigo A. Panepucci ◽

Rodrigo Proto-Siqueira ◽

Wilma T. Anselmo-Lima ◽

Oswaldo K. Okamoto ◽

...

Keyword(s):

Gene Expression ◽

B Cells ◽

Cyclin D1 ◽

Signaling Pathway ◽

Peripheral Blood ◽

Cell Lymphoma ◽

Aberrant Expression ◽

Mantle Cell ◽

Leukemic Phase ◽

Activin Receptors

Abstract Mantle cell lymphoma (MCL) is a distinctive subtype of B-cell lymphoma associated with the t(11;14)(q13;32) and consequent ectopic overexpression of cyclin D1 in the tumor cells. Disease is predominantly disseminated at diagnosis and a frank leukemic phase is detected in one fourth of patients. Ontogenetically, MCL is considered the malignant counterpart of pre-germinal-center naive B-cells. Although the overexpression of cyclin D1 plays a pivotal role on the pathogenesis of MCL, studies with transgenic mice have shown that it is not sufficient by itself to cause lymphoma, and a better understanding of the molecular genetics of this disease may provide insights toward a potentially curable therapy. To address this issue, we compared the gene expression profile of MCL and normal naive B-cells using oligonucleotide microarrays representing 10,000 genes. MCL cells and naive B-cells (IgD+CD38±CD27−) were highly purified, by magnetic activated cell sorting, from the peripheral blood of patients with MCL in the leukemic phase and from tonsils of normal controls, respectively (purity > 95% in all samples). Three individuals were selected for each group and experiments were performed in replicates using the Amersham CodeLink Human UniSet I Bioarrays. For validation purposes, the expression of 10 selected genes (6 overexpressed and 4 underexpressed in lymphoma cells) was quantified by TaqMan real-time RT-PCR in non-purified peripheral blood samples from 25 patients with MCL in the leukemic phase and compared with normal naive B-cells, with fully concordant results. Data mining from our microarray results revealed an aberrant expression of several genes from the TGF-β signaling pathway in MCL (p<0.01): ACVR1 (fold change = 2.5), ACVR2 (2.9), ACVR2B (16.3), BMP4 (11.8), TGIF (4.0), Smad2 (3.4) and Smad6 (0.6). Except for TGIF and Smad6, all other genes induce the TGF-β signaling pathway. Although TGIF was overexpressed, it depends on the relative levels of Smad co-repressors or co-activators to exert its inhibitory activity; whereas Smad6, which is also an inhibitory mediator, was underexpressed. The activin receptors ACVR1, ACVR2 and ACVR2B are receptors of the TGF-β superfamily, which consists of TGF-β, activins, bone morphogenic proteins (BMPs) and others. Upon ligand binding, activin receptors induce anti-proliferative and pro-apoptotic responses, acting as tumor suppressors in early tumorigenesis. In advanced cancer, however, there is a loss of growth-inhibitory responsiveness downstream the core TGF-β signaling pathway, and it may be used as a tumor-progression factor by inducing immune supression, angiogenesis, epithelial-mesenchymal transdifferentiation and increased potential for metastasis. Interestingly, the cyclin D1/TGF-β double transgenic liver model in mice (Deane et al. Cancer Res.2004; 64:1315) showed enhanced tumor formation when compared with its single transgenic littermates. Our results suggest an activation of the TGF-β signaling pathway in MCL, and point toward potential new therapeutic targets for this yet incurable lymphoma.

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HDAC Profiling In Mantle Cell Lymphoma Unveils HDAC11 and HDAC10 as Potential Molecular Targets

Blood ◽

10.1182/blood.v116.21.2506.2506 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2506-2506

Author(s):

Bijal D. Shah ◽

Alejandro Villagra ◽

Oscar Merino ◽

Jennifer Rock-Klotz ◽

Karrune Woan ◽

...

Keyword(s):

Cell Cycle ◽

Cell Proliferation ◽

B Cells ◽

B Lymphocytes ◽

Cell Lines ◽

Class Ii ◽

Class I ◽

Cell Cycle Analysis ◽

Malignant Cells ◽

Aberrant Expression

Abstract Abstract 2506 Background: Epigenetic changes in chromatin structure involving histone modifications have been recently implicated in the deregulated expression of critical genes in MCL, including cyclin D1 and some tumor suppressor genes. Special emphasis has been given therefore to the assessment of the therapeutic role of epigenetic modifiers in MCL. Among these, a family of compounds known as histone deacetylase inhibitors (HDI) display antitumor activity both in experimental models as well as in recently completed clinical trials in MCL patients. Given that aberrant expression of histone deacetylases (HDACs) has been shown to influence disease aggressiveness and response to treatment in several malignancies1,2,3, we seek to determine the expression of specific HDACs in human MCL. Methods: Expression of HDAC class I (HDAC1, 2, 3, 8), class II (HDAC4, 5, 6, 9, 10) and Class IV (HDAC11) was determined by quantitative real-time RT-PCR using specific HDAC primers in four human MCL cell lines (JEKO, Z138, MINO, SP53), primary malignant cells from lymph nodes of patients with MCL and in B-lymphocytes isolated from normal donors (Control). Protein expression of selected HDACs was evaluated by western blot. Knocking down of specific HDACs was performed using shRNAs lentiviruses targeting specific human HDAC sequences. Cell proliferation and cell cycle analysis of MCL cells lacking a specific HDAC were performed using standard techniques. Results: No significant differences in class I HDAC expression was found among normal B-lymphocytes, MCL cell lines and malignant B-cells from MCL patients. In contrast, the expression all class II HDACs, but HDAC9, was reduced in MCL cell lines and primary human MCL cells relative to normal B-cells. Of note, HDAC10 expression was consistently absent or significantly decreased in all MCL cell lines and primary MCL cells. Analysis of HDAC11 revealed interesting findings: increased expression of HDAC11 mRNA was observed in human MCL cell lines and primary human MCL cells, with the highest expression among two patients with the blastoid variant of MCL and the lowest expression in cells from two patients with a clinically indolent MCL. Next, we knocked-down HDAC11 in Z138 MCL cells and generated two stable clones (HDAC11KD) that displayed a slower cell proliferation relative to non-target shRNA control cells. Cell cycle analysis revealed that HDAC11KD clones are cycling at a significantly lower rate than control cells. Conclusion: HDAC11 over-expression in MCL seems to confer a proliferation/survival advantage to malignant cells. This finding provides a rationale to selectively disrupt this HDAC in MCL. Given that decreased HDAC10 expression is associated with a more aggressive behavior in other malignancies1, our findings of diminished HDAC10 expression in MCL warrant further investigation. Disclosures: Leonard: Hospira: Consultancy, Honoraria; Cell Therapeutics: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Biogen IDEC: Consultancy, Honoraria; Calistoga: Consultancy, Honoraria; Johnson and Johnson: Consultancy, Honoraria; EMD Serono: Consultancy, Honoraria; Sanofi Aventis: Consultancy, Honoraria; Millenium: Consultancy, Honoraria; Biotest: Consultancy, Honoraria; Cephalon: Consultancy, Honoraria; Pharmion: Consultancy, Honoraria; Eisai: Consultancy, Honoraria; Cougar Biotechnology: Consultancy, Honoraria; Immunomedics: Honoraria; Genentech: Consultancy, Honoraria; Novartis: Consultancy, Honoraria.

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PU.1 and Spi-B Oppose Transformation Of Pre-B Cells Through Activation Of Key Genes Involved In B Cell Receptor Signalling

Blood ◽

10.1182/blood.v122.21.3737.3737 ◽

2013 ◽

Vol 122 (21) ◽

pp. 3737-3737

Author(s):

Darah A. Christie ◽

Shereen A. Turkistany ◽

Li S. Xu ◽

Stephen K. H. Li ◽

Ian Welch ◽

...

Keyword(s):

Bone Marrow ◽

Transcription Factors ◽

B Cells ◽

B Cell ◽

Cell Receptor ◽

B Cell Receptor ◽

Cell Phenotype ◽

Aberrant Expression ◽

Receptor Signalling ◽

Key Genes

Abstract B cell development is controlled by stage-specific expression of transcription factors. Aberrant expression of such factors can lead to B cell acute lymphoblastic leukemia (B-ALL). Deletion of genes encoding the E26 transformation-specific (ETS) transcription factors, PU.1 and Spi-B, in B cells (CD19+/CreSfpi1lox/loxSpib-/- mice, abbreviated to CD19-CreΔPB) leads to B-ALL at 100% incidence and with a median survival of 21 weeks. However, little is known about the target genes of PU.1 and Spi-B that explain leukemic transformation in these mice. In the current study, we investigated the developmental origins and mechanisms of leukemogenesis in CD19-CreΔPB mice. We found that B-ALL cells in CD19-CreΔPB mice had frequently rearranged both their heavy and light chain genes, but retained cell surface expression of interleukin-7 receptor (IL-7R), suggesting aberrant pre-B cell differentiation. Preleukemic CD19-CreΔPB mice had increased frequencies of pre-B cells compared to wild type mice. Pre-B cells, but not mature B cells, purified from the bone marrow of preleukemic CD19-CreΔPB mice could rapidly transfer disease to transplanted recipient mice. B-ALL cells from established tumors had uniform expression of markers indicating a pre-B cell phenotype and contained a high-frequency of leukemia-initiating cells as measured by transplantation assays. Genome-wide analysis of gene expression showed that B cell receptor signalling was the top impaired pathway in B-ALL cells from CD19-CreΔPB mice. Bone marrow cells from CD19-CreΔPB mice had increased responsiveness to IL-7R signalling and could be cultured as IL-7-dependent cell lines. Preleukemic or leukemic cells from CD19-CreΔPB mice expressed reduced levels of the gene encoding Bruton’s tyrosine kinase (Btk), which we show is a target gene of PU.1 and/or Spi-B that in combination with reduced BLNK is sufficient to explain increased IL-7R responsiveness. We conclude that mutation of PU.1 and Spi-B predispose developing B cells to leukemogenesis by impairing expression of key genes, such as Btk, that are required for BCR signalling and are involved in attenuation of IL-7 receptor signaling. Disclosures: No relevant conflicts of interest to declare.

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