scholarly journals ZAP-70 enhances IgM signaling independent of its kinase activity in chronic lymphocytic leukemia

Blood ◽  
2008 ◽  
Vol 111 (5) ◽  
pp. 2685-2692 ◽  
Author(s):  
Liguang Chen ◽  
Lang Huynh ◽  
John Apgar ◽  
Li Tang ◽  
Laura Rassenti ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Intracellular Calcium ◽  
Kinase Activity ◽  
Cell Receptor ◽  
Sh2 Domain ◽  
Lymphocytic Leukemia ◽  
Calcium Flux ◽  
Response To Treatment ◽  
Intracellular Calcium Flux

We transduced chronic lymphocytic leukemia (CLL) cells lacking ZAP-70 with vectors encoding ZAP-70 or various mutant forms of ZAP-70 and monitored the response of transduced CLL cells to treatment with F(ab)2 anti-IgM (anti-μ). CLL cells made to express ZAP-70, a kinase-defective ZAP-70 (ZAP-70-KA369), or a ZAP-70 unable to bind c-Cbl (ZAP-YF292) experienced greater intracellular calcium flux and had greater increases in the levels of phosphorylated p72Syk, B-cell linker protein (BLNK), and phospholipase C-γ, and greater activation of the Ig accessory molecule CD79b in response to treatment with anti-μ than did mock-transfected CLL cells lacking ZAP-70. Transfection of CLL cells with vectors encoding truncated forms of ZAP-70 revealed that the SH2 domain, but not the SH1 domain, was necessary to enhance intracellular calcium flux in response to treatment with anti-μ. We conclude that ZAP-70 most likely acts as an adapter protein that facilitates B-cell receptor (BCR) signaling in CLL cells independent of its tyrosine kinase activity or its ability to interact with c-Cbl.

Influence of Mir-155 On B-Cell Receptor Signaling in Chronic Lymphocytic Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2343-2343
Author(s):  
Liguang Chen ◽  
Bing Cui ◽  
George Chen ◽  
Michelle Salcedo ◽  
Carlo M. Croce ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Calcium Influx ◽  
Critical Role ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Calcium Flux ◽  
Expression Levels ◽  
Bcr Signaling

Abstract Abstract 2343 Poster Board II-320 B-cell receptor (BCR) signaling arguably plays an important role in the pathogenesis and/or progression of chronic lymphocytic leukemia. Ligation of the BCR by F(ab)2 anti-μ can induce phosphorylation of p72Syk, BLNK, phospholipase C-gamma (PLCγ) and other downstream adapter/signaling molecules, inducing intracellular calcium flux and cellular activation. Prior studies found that CLL cells that expressed unmutated Ig heavy-chain variable region genes (IGHV) and the zeta-associated protein of 70 kD (ZAP-70) generally experienced greater levels of activation following treatment with anti-μ than did CLL cells that lacked expression of ZAP-70. However, we found unusual cases that lacked expression of ZAP-70 that also responded vigorously to treatment with anti-μ, suggesting that other factors contribute to the noted differences in BCR-signaling. Analyses for expression of microRNAs by microarray revealed that CLL cells that used unmutated IGHV and that expressed ZAP-70 expressed higher levels of certain microRNAs than did cases that used mutated IGHV and that lacked expression of ZAP-70. One of such microRNA, miR-155, was found to target mRNA encoding SHIP-1, a phosphatase that plays a critical role in modulating the level of BCR signaling in normal B cells. Using quantitative assays for miR-155 we found high-level expression of this microRNA was associated with proficient BCR signaling in CLL. To examine whether miR-155 could modulate the levels of SHIP-1 and/or BCR signaling in CLL cells we transfected primary leukemia cells from each of multiple patients with control oligo-RNAs, miR-155, or a specific inhibitor of miR-155 (miR-155 inhibitor). Twenty-four hours later the cells were stimulated with anti-μ or control antibody and then examined 10 minutes later for expression of SHIP-1, induced calcium influx, or phosphorylation of kinases and adapter proteins that are involved in BCR signaling. CLL cells that had low expression levels of miR-155 and that were poorly responsive BCR had significantly higher levels of calcium influx and phosphorylated p72Syk, BLNK, and PLCγ in response to anti-μ following transfection with miR-155 than following mock transfection or transfection with control oligo-RNA. Conversely, CLL cells that had high expression levels of miR-155 and highly responsive BCR were made to have significantly higher amounts of SHIP-1 protein and to have significantly lower relative levels of phosphorylated protein and calcium influx in response to anti-μ following transfection with the miR-155 inhibitor than did mock transfected CLL cells. These results identify miR-155 as a factor that can modulate BCR signaling in CLL in part by regulating the relative expression level of SHIP-1. These results demonstrate that differential expression of microRNAs in CLL can influence physiologic features that potentially contribute to disease progression. Disclosures: No relevant conflicts of interest to declare.

Association Between the Proficiency of B-Cell Receptor Signaling and the Relative Expression Levels of ZAP-70, SHIP-1, and Mir-155 in Chronic Lymphocytic Leukemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3155-3155 ◽  
Author(s):  
Liguang Chen ◽  
Bing Cui ◽  
Suping Zhang ◽  
George Chen ◽  
Carlo M. Croce ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Calcium Flux ◽  
Expression Levels ◽  
Relative Expression ◽  
Bcr Signaling

Abstract The immunoglobulin (Ig) repertoire expressed in chronic lymphocytic leukemia (CLL) appears highly selected, suggesting that stimulation of the B-cell receptor (BCR) by unknown self or environmental antigen(s) likely contributes to the pathogenesis and/or progression of this disease. Ligation of the BCR by F(ab)2 anti-μ can induce phosphorylation of p72Syk, BLNK, phospholipase Cgamma and other downstream adapter/signaling molecules, inducing intracellular calcium flux and cellular activation. Prior studies found that CLL cells that expressed unmutated Ig heavy-chain variable region genes (IGHV) and/or the zeta-associated protein of 70 kD (ZAP-70) generally experienced greater levels of activation following treatment with anti-μ than did CLL cells that use mutated IGHV and/or that lacked expression of ZAP-70. However, unusual cases that expressed mutated IGHV or that lack expression of ZAP-70 also were well stimulated by treatment with anti-μ, suggesting that other factors contribute to the noted differences in BCR-signaling observed between cases of CLL. We found that cases that used unmutated IGHV and that expressed ZAP-70 could be distinguished from cases that used mutated IGHV and that lacked expression of ZAP-70 by interrogating for differences in expression of selected microRNA, which are short non-coding RNA that each govern the post-transcriptional expression of a discrete set of genes. We focused attention on expression of miR-155, which generally is expressed at higher levels in CLL cells that express unmutated IGHV and ZAP-70 than CLL cells that use mutated IGHV and that lack ZAP-70. One of the putative target genes regulated by this microRNA is SHIP-1, a phosphatase that plays a critical role in modulating BCR signaling. We examined the MicroRNA-155 expression in CLL B cells and compared these values with the relative expression levels of SHIP-1 protein or ZAP-70 and use of unmutated IGHV. The relative levels of miR-155 were determined by real-time PCR. CLL B cells were stimulated with anti-μ or control Ig for 10 minutes and then examined for relative protein phosphorylation by flow cytometric and immunoblot analyses. CLL cases were segregated into groups with high-BCR signaling versus low BCR-signaling based on the relative levels of phosphorylation observed on signaling/adapter proteins following treatment with anti-μ. CLL cells with high-BCR signaling potential expressed significantly higher levels of miR-155 (1.62±0.33) than did CLL cells with low-BCR signaling potential (0.42±0.13, p<0.05). We also examined for SHIP-1 protein by flow cytometry and phosphorylated SHIP-1 by immunoblot analyses. These analyses revealed that the expression levels of SHIP-1 protein inversely correlated with the expression levels of miR-155 in CLL and the proficiency of BCR-signaling. Moreover, CLL cells with high BCR-signaling potential had significantly lower amounts of SHIP-1 protein, and significantly higher relative levels of phosphorylated SHIP-1 following treatment with anti-μ, than did CLL cells with low BCR-signaling potential. Although SHIP-1 protein was significantly more abundant in cases that lacked ZAP-70 than in cases that expressed ZAP-70, we identified cases that lacked ZAP-70 and had low levels of SHIP-1 that also experienced high-levels of BCRsignaling following treatment with anti-μ. These results indicate that the proficiency of BCR-signaling in CLL could be influenced by the relative levels of ZAP-70 and SHIP-1, at least the latter of which appears regulated by microRNA that are differentially expressed in aggressive versus indolent cases of CLL.

Geldanamycin-induced Lyn dissociation from aberrant Hsp90-stabilized cytosolic complex is an early event in apoptotic mechanisms in B-chronic lymphocytic leukemia

Blood ◽  
2008 ◽  
Vol 112 (12) ◽  
pp. 4665-4674 ◽  
Author(s):  
Livio Trentin ◽  
Martina Frasson ◽  
Arianna Donella-Deana ◽  
Federica Frezzato ◽  
Mario A. Pagano ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Molecular Mechanisms ◽  
Catalytic Domain ◽  
Cell Receptor ◽  
Hsp90 Inhibitor ◽  
Lymphocytic Leukemia ◽  
Early Event ◽  
Downstream Signaling ◽  
Transient Interactions

Abstract Lyn, a tyrosine kinase belonging to the Src family, plays a key role as a switch molecule that couples the B-cell receptor to downstream signaling. In B-CLL cells, Lyn is overexpressed, anomalously present in the cytosol, and displays a high constitutive activity, compared with normal B lymphocytes. The aim of this work was to gain insights into the molecular mechanisms underlying these aberrant properties of Lyn, which have already been demonstrated to be related to defective apoptosis in B-cell chronic lymphocytic leukemia (B-CLL) cells. Herein, Lyn is described to be in an active conformation as integral component of an aberrant cytosolic 600-kDa multiprotein complex in B-CLL cells, associated with several proteins, such as Hsp90 through its catalytic domain, and HS1 and SHP-1L through its SH3 domain. In particular, Hsp90 appears tightly bound to cytosolic Lyn (CL), thus stabilizing the aberrant complex and converting individual transient interactions into stable ones. We also demonstrate that treatment of B-CLL cells with geldanamycin, an Hsp90 inhibitor already reported to induce cell death, is capable of dissociating the CL complex in the early phases of apoptosis and thus inactivating CL itself. These data identify the CL complex as a potential target for therapy in B-CLL.

scholarly journals Targeted inhibition of eIF4A suppresses B-cell receptor-induced translation and expression of MYC and MCL1 in chronic lymphocytic leukemia cells

2021 ◽  
Author(s):  
Sarah Wilmore ◽  
Karly-Rai Rogers-Broadway ◽  
Joe Taylor ◽  
Elizabeth Lemm ◽  
Rachel Fell ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Mrna Translation ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Mrna Levels ◽  
Mrna Stabilization

AbstractSignaling via the B-cell receptor (BCR) is a key driver and therapeutic target in chronic lymphocytic leukemia (CLL). BCR stimulation of CLL cells induces expression of eIF4A, an initiation factor important for translation of multiple oncoproteins, and reduces expression of PDCD4, a natural inhibitor of eIF4A, suggesting that eIF4A may be a critical nexus controlling protein expression downstream of the BCR in these cells. We, therefore, investigated the effect of eIF4A inhibitors (eIF4Ai) on BCR-induced responses. We demonstrated that eIF4Ai (silvestrol and rocaglamide A) reduced anti-IgM-induced global mRNA translation in CLL cells and also inhibited accumulation of MYC and MCL1, key drivers of proliferation and survival, respectively, without effects on upstream signaling responses (ERK1/2 and AKT phosphorylation). Analysis of normal naïve and non-switched memory B cells, likely counterparts of the two main subsets of CLL, demonstrated that basal RNA translation was higher in memory B cells, but was similarly increased and susceptible to eIF4Ai-mediated inhibition in both. We probed the fate of MYC mRNA in eIF4Ai-treated CLL cells and found that eIF4Ai caused a profound accumulation of MYC mRNA in anti-IgM treated cells. This was mediated by MYC mRNA stabilization and was not observed for MCL1 mRNA. Following drug wash-out, MYC mRNA levels declined but without substantial MYC protein accumulation, indicating that stabilized MYC mRNA remained blocked from translation. In conclusion, BCR-induced regulation of eIF4A may be a critical signal-dependent nexus for therapeutic attack in CLL and other B-cell malignancies, especially those dependent on MYC and/or MCL1.

Chronic lymphocytic leukemia: revelations from the B-cell receptor

Blood ◽  
2004 ◽  
Vol 103 (12) ◽  
pp. 4389-4395 ◽  
Author(s):  
Freda K. Stevenson ◽  
Federico Caligaris-Cappio
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Cell Of Origin ◽  
Regulatory B Cell ◽  
V Genes

Abstract The finding that chronic lymphocytic leukemia (CLL) consists of 2 clinical subsets, distinguished by the incidence of somatic mutations in the immunoglobulin (Ig) variable region (V) genes, has clearly linked prognosis to biology. Antigen encounter by the cell of origin is indicated in both subsets by selective but distinct expression of V genes, with evidence for continuing stimulation after transformation. The key to distinctive tumor behavior likely relates to the differential ability of the B-cell receptor (BCR) to respond. Both subsets may be undergoing low-level signaling in vivo, although analysis of blood cells limits knowledge of critical events in the tissue microenvironment. Analysis of signal competence in vitro reveals that unmutated CLL generally continues to respond, whereas mutated CLL is anergized. Differential responsiveness may reflect the increased ability of post-germinal center B cells to be triggered by antigen, leading to long-term anergy. This could minimize cell division in mutated CLL and account for prognostic differences. Unifying features of CLL include low responsiveness, expression of CD25, and production of immunosuppressive cytokines. These properties are reminiscent of regulatory T cells and suggest that the cell of origin of CLL might be a regulatory B cell. Continuing regulatory activity, mediated via autoantigen, could suppress Ig production and lead to disease-associated hypogammaglobulinemia. (Blood. 2004;103:4389-4395)

scholarly journals Silenced B-cell receptor response to autoantigen in a poor-prognostic subset of chronic lymphocytic leukemia

Haematologica ◽  
2014 ◽  
Vol 99 (11) ◽  
pp. 1722-1730 ◽  
Author(s):  
A.-C. Bergh ◽  
C. Evaldsson ◽  
L. B. Pedersen ◽  
C. Geisler ◽  
K. Stamatopoulos ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Receptor Response

scholarly journals Role of NFAT in Chronic Lymphocytic Leukemia and Other B-Cell Malignancies

2021 ◽  
Vol 11 ◽  
Author(s):  
Ilenia Sana ◽  
Maria Elena Mantione ◽  
Piera Angelillo ◽  
Marta Muzio
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Therapeutic Potential ◽  
Cell Receptor ◽  
Distinct Pattern ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
B Cell Malignancies ◽  
Activated T Cells ◽  
Inflammatory Microenvironment

In recent years significant progress has been made in the clinical management of chronic lymphocytic leukemia (CLL) as well as other B-cell malignancies; targeting proximal B-cell receptor signaling molecules such as Bruton Tyrosine Kinase (BTK) and Phosphoinositide 3-kinase (PI3Kδ) has emerged as a successful treatment strategy. Unfortunately, a proportion of patients are still not cured with available therapeutic options, thus efforts devoted to studying and identifying new potential druggable targets are warranted. B-cell receptor stimulation triggers a complex cascade of signaling events that eventually drives the activation of downstream transcription factors including Nuclear Factor of Activated T cells (NFAT). In this review, we summarize the literature on the expression and function of NFAT family members in CLL where NFAT is not only overexpressed but also constitutively activated; NFAT controls B-cell anergy and targeting this molecule using specific inhibitors impacts on CLL cell viability. Next, we extend our analysis on other mature B-cell lymphomas where a distinct pattern of expression and activation of NFAT is reported. We discuss the therapeutic potential of strategies aimed at targeting NFAT in B-cell malignancies not overlooking the fact that NFAT may play additional roles regulating the inflammatory microenvironment.

scholarly journals B-cell receptor stereotyped subsets and outcome for patients with chronic lymphocytic leukemia in the HOVON 68 trial

2021 ◽  
Author(s):  
Fie J. Vojdeman ◽  
Lone B. Pedersen ◽  
Doreen te Raa ◽  
Vesa Juvonen ◽  
Yvette van Norden ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia

scholarly journals Phosphoinositide 3-Kinase Signaling in the Tumor Microenvironment: What Do We Need to Consider When Treating Chronic Lymphocytic Leukemia With PI3K Inhibitors?

2021 ◽  
Vol 11 ◽  
Author(s):  
Ebru Aydin ◽  
Sebastian Faehling ◽  
Mariam Saleh ◽  
Laura Llaó Cid ◽  
Martina Seiffert ◽  
...  
Keyword(s):  
Tumor Microenvironment ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Treatment Strategies ◽  
Cell Receptor ◽  
Pi3k Pathway ◽  
Lymphocytic Leukemia ◽  
Pi3k Signaling ◽  
Extracellular Signals ◽  
Pi3k Inhibition

Phosphoinositide 3-kinases (PI3Ks) and their downstream proteins constitute a signaling pathway that is involved in both normal cell growth and malignant transformation of cells. Under physiological conditions, PI3K signaling regulates various cellular functions such as apoptosis, survival, proliferation, and growth, depending on the extracellular signals. A deterioration of these extracellular signals caused by mutational damage in oncogenes or growth factor receptors may result in hyperactivation of this signaling cascade, which is recognized as a hallmark of cancer. Although higher activation of PI3K pathway is common in many types of cancer, it has been therapeutically targeted for the first time in chronic lymphocytic leukemia (CLL), demonstrating its significance in B-cell receptor (BCR) signaling and malignant B-cell expansion. The biological activity of the PI3K pathway is not only limited to cancer cells but is also crucial for many components of the tumor microenvironment, as PI3K signaling regulates cytokine responses, and ensures the development and function of immune cells. Therefore, the success or failure of the PI3K inhibition is strongly related to microenvironmental stimuli. In this review, we outline the impacts of PI3K inhibition on the tumor microenvironment with a specific focus on CLL. Acknowledging the effects of PI3K inhibitor-based therapies on the tumor microenvironment in CLL can serve as a rationale for improved drug development, explain treatment-associated adverse events, and suggest novel combinatory treatment strategies in CLL.

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