Spleen tyrosine kinase inhibition prevents chemokine- and integrin-mediated stromal protective effects in chronic lymphocytic leukemia

Blood ◽  
2010 ◽  
Vol 115 (22) ◽  
pp. 4497-4506 ◽  
Author(s):  
Maike Buchner ◽  
Constance Baer ◽  
Gabriele Prinz ◽  
Christine Dierks ◽  
Meike Burger ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Tyrosine Kinase ◽  
Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Cytotoxic Agents ◽  
Protective Effects ◽  
Spleen Tyrosine Kinase ◽  
Growth And Survival ◽  
Akt Phosphorylation ◽  
Bcr Signaling

Abstract The microenvironment provides essential growth and survival signals to chronic lymphocytic leukemia (CLL) cells and contributes to their resistance to cytotoxic agents. Pharmacologic inhibition of spleen tyrosine kinase (SYK), a key mediator of B-cell receptor (BCR) signaling, induces apoptosis in primary CLL cells and prevents stroma contact-mediated cell survival. This report demonstrates a role of SYK in molecularly defined pathways that mediate the CLL-microenvironmental crosstalk independent from the BCR. Chemokine and integrin stimulation induced SYK phosphorylation, SYK-dependent Akt phosphorylation, and F-actin formation in primary CLL cells. Inhibition of SYK by 2 pharmacologic inhibitors and siRNA-knockdown abrogated downstream SYK signaling and morphologic changes induced by these stimuli. CLL cell migration toward CXCL12, the major homing attractor, and CLL cell adhesion to VCAM-1, a major integrin ligand expressed on stromal cells, were markedly reduced by SYK inhibition. In combination with fludarabine, the SYK inhibitor R406 abrogated stroma-mediated drug resistance by preventing up-regulation of the antiapoptotic factor Mcl-1 in CLL cells. SYK blockade in CLL is a promising therapeutic principle not only for its inhibition of the BCR signaling pathway, but also by inhibiting protective stroma signals in a manner entirely independent of BCR signaling.

Spleen Tyrosine Kinase Inhibition Prevents Chemokine- and Integrin-Mediated Stromal Protective Effects in Chronic Lymphocytic Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2356-2356
Author(s):  
Maike Buchner ◽  
Constance Baer ◽  
Gabriele Prinz ◽  
Hassan Jumaa ◽  
Hendrik Veelken ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Adhesion ◽  
Chronic Lymphocytic Leukemia ◽  
Tyrosine Kinase ◽  
Cell Survival ◽  
Lymphocytic Leukemia ◽  
Akt Phosphorylation ◽  
High Affinity ◽  
Bcr Signaling ◽  
Integrin Ligand

Abstract Abstract 2356 Poster Board II-333 B cell chronic lymphocytic leukemia (CLL) remains incurable despite recent therapeutic advances, and identification of novel molecular targets in CLL is highly desirable. The microenvironment provides essential growth and survival signals to CLL cells and confers resistance to cytotoxic agents, a phenomenon termed cell adhesion-mediated drug resistance (CAM-DR). The chemokine CXCL12 and the integrin ligand VCAM have been identified as important microenvironmental pathways that mediate CLL cell survival and CAM-DR. We have previously demonstrated that inhibition of spleen tyrosine kinase (SYK), a key component of the BCR signaling pathway, induces apoptosis in primary CLL cells when cultured alone or supported by stroma (Buchner et al., Cancer Res. 2009). In this study, we investigated SYK inhibition with regard to the interaction between CLL cells and the microenvironment. Stromal cell coculture resulted in SYK activation in primary CLL cells as indicated by phospho-protein analysis by flow cytometry (p<0.001) and immunoblotting. In vitro stimulation with 20 ng/ml recombinant CXCL12 or VLA-4 integrin ligation by contact to VCAM-1 precoated wells (10 μg/ml) for 15 sec had equivalent effects. SYK inhibition by the pharmacological SYK inhibitor R406 significantly reduced F-actin polymerization and Akt phosphorylation induced by CXCL12, integrin ligand, or stromal contact. In functional experiments, migration of CLL cells towards CXCL12 was reduced to 77% (p<0.001) by R406 in transwell culture. Likewise, CLL cell adhesion to VCAM was limited by SYK inhibition to 50% (p<0.01) compared to control cells in flow chamber experiments. In response to a number of physiological stimuli, including BCR ligation, integrins are activated through the modulation of their conformation to mediate high-affinity adhesion. Analysis of the expression of a high affinity epitope of CD29, the β1 chain of VLA-4, on CLL cells by flow cytometry with and without SYK inhibition revealed a significant decrease of 31% (p<0.0001), while the expression of total CD29 decreased only by 10% (p<0.01). To verify the specificity of the effects of pharmacological SYK inhibitors, we performed siRNA mediated silencing of SYK in primary CLL cells. 48 h after transfection, we observed a downregulation of SYK protein expression by flow cytometry by 27% (p<0.05), while the viability of the cells was not significantly affected for 72 h. Stimulation of control- and SYK-siRNA treated cells with VCAM significantly increased Akt phosphorylation in control but not in SYK-siRNA transfected cells. Furthermore, SYK-silenced CLL cells adhered significantly less to VCAM-coated surfaces than control-silenced CLL cells. Beyond inhibition of these defined pathways, R406 abrogated the protective effect of stromal coculture on CLL cell survival. The anti-apoptotic factor Mcl-1 was upregulated in CLL cells cultured with stroma compared to those cultured alone (mean MFI ± SEM: 144 ± 21 vs. 182 ± 23, p<0.001). SYK inhibition almost completely abolished the upregulation of Mcl-1 in stroma-cocultured CLL cells (mean MFI ± SEM: 182 ± 23 vs. 130 ± 15, p<0.001). Finally, SYK inhibition also prevented CAM-DR against fludarabine in stroma coculture. Taken together, our data demonstrate direct effects of SYK inhibition on chemokine and integrin-mediated CLL-stroma interactions and establish a novel therapeutic mechanism of action for SYK inhibitors in CLL. Indeed, a promising clinical activity in patients with relapsed/refractory CLL/SLL with an overall response rate of 54% has been reported for the oral prodrug of R406, fostamatinib disodium in CLL patients (Friedmann et al, ASH 2008). Of note, an unexplained transient but dramatic leukocyte flare during lymph node regression was reported in several of these patients. Our results offer a convincing explanation for this phenomenon and may even suggest that SYK blockade in CLL is a promising therapeutic principle not only due to inhibition of BCR signaling, but perhaps even more importantly by disrupting the contact of CLL cells with their protective microenvironment. Disclosures: No relevant conflicts of interest to declare.

ZAP-70 enhances B-cell–receptor signaling despite absent or inefficient tyrosine kinase activation in chronic lymphocytic leukemia and lymphoma B cells

Blood ◽  
2006 ◽  
Vol 109 (5) ◽  
pp. 2032-2039 ◽  
Author(s):  
Stefania Gobessi ◽  
Luca Laurenti ◽  
Pablo G. Longo ◽  
Simona Sica ◽  
Giuseppe Leone ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Tyrosine Kinase ◽  
B Cell ◽  
Antigen Receptor ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Tcr Signaling ◽  
Bcr Signaling

Abstract Expression of ZAP-70 is an important negative prognostic factor in chronic lymphocytic leukemia (CLL). This protein tyrosine kinase is a key mediator of T-cell receptor (TCR) signaling and is structurally homologous to Syk, which plays an analogous role in B-cell receptor (BCR) signaling. Recent studies indicate that ZAP-70 may participate in BCR signaling as well, but the mechanism of action is not completely understood. We have now compared antigen receptor-induced activation of ZAP-70 in B cells and T cells by analyzing phosphorylation of critical regulatory tyrosine residues. We show that BCR-mediated activation of ZAP-70 is very inefficient in CLL and lymphoma B cells and is negligible when compared to activation of Syk. Despite the inefficient catalytic activation, the ability of ZAP-70 to recruit downstream signaling molecules in response to antigen receptor stimulation appeared relatively preserved. Moreover, ectopic expression of ZAP-70 enhanced and prolonged activation of several key mediators of BCR signaling, such as the Syk, ERK, and Akt kinases, and decreased the rate of ligand-mediated BCR internalization. We conclude that the role of ZAP-70 in BCR signaling is quite distinct from its role in TCR signaling and is likely mediated by inhibition of events that terminate the signaling response.

Nurture versus Nature: The Microenvironment in Chronic Lymphocytic Leukemia

Hematology ◽  
2011 ◽  
Vol 2011 (1) ◽  
pp. 96-103 ◽  
Author(s):  
Jan A. Burger
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Tyrosine Kinase ◽  
B Cell ◽  
Disease Progression ◽  
Drug Testing ◽  
Cell Receptor ◽  
Lymphocytic Leukemia ◽  
In Vivo Models

Abstract Intrinsic factors such as genetic lesions, anti-apoptotic proteins, and aberrant signaling networks within leukemia cells have long been the main focus of chronic lymphocytic leukemia (CLL) research. However, over the past decade, it became increasingly clear that external signals from the leukemia microenvironment make pivotal contributions to disease progression in CLL and other B-cell malignancies. Consequently, increasing emphasis is now placed on exploring and targeting the CLL microenvironment. This review highlights critical cellular and molecular pathways of CLL-microenvironment cross-talk. In vitro and in vivo models for studying the CLL microenvironment are discussed, along with their use in searching for therapeutic targets and in drug testing. Clinically, CXCR4 antagonists and small-molecule antagonists of B cell receptor (BCR)-associated kinases (spleen tyrosine kinase [Syk], Bruton's tyrosine kinase [Btk], and PI3Kδ) are the most advanced drugs for targeting specific interactions between CLL cells and the miocroenvironment. Preclinical and first clinical evidence suggests that high-risk CLL patients can particularly benefit from these alternative agents. These findings indicate that interplay between leukemia-inherent and environmental factors, nature and nurture determines disease progression in CLL.

B-Cell Receptor Signaling Enhances Migration of B-Cell Chronic Lymphocytic Leukemia Cells in Response to the Chemokine Stromal Cell-Derived Factor-1 (SDF-1/CXCL12).

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1187-1187
Author(s):  
Jan A. Burger ◽  
Myriam Krome ◽  
Andrea Bürkle ◽  
Tanja N. Hartmann
Keyword(s):  
Dendritic Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Stromal Cells ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Follicular Dendritic Cells ◽  
Accessory Cells ◽  
Bcr Signaling

Abstract There is growing evidence that the microenvironment confers survival signals to Chronic Lymphocytic Leukemia (CLL) B-cells that may result in disease progression and resistance to therapy. In the marrow or secondary lymphoid tissues, CLL cells are in close contact with non-tumoral accessory cells, such as mesenchymal stromal cells or nurselike cells. We previously characterized SDF-1 (CXCL12) as a central mediator for CLL cell migration and interaction with the protective microenvironment. Constitutive secretion of CXCL12 attracts CLL cells to stroma or NLC through its cognate receptor, CXCR4. These accessory cells protect CLL cells from spontaneous or drug-induced apoptosis, which is contact-dependent and partially mediated by CXCL12. B-cell receptor (BCR) signaling has been considered another important regulator of CLL cell survival. Typically, CLL cell that lack somatic mutations in the immunoglobulin (Ig) variable region (V) genes and display high levels of the tyrosine kinase ZAP-70 strongly responds to anti-IgM stimulation. Because both, CXCL12 stimulation and BCR signaling may represent important mechanism for maintenance of CLL cell within the microenvironment, we examined whether anti-IgM stimulation affects CXCL12 responses in correlation with the ZAP-70 status. BCR signaling was modulated either by crosslinking the BCR with IgM or by blocking the tyrosine kinase Syk. Effective BCR cross-linking with anti-IgM antibodies was demonstrated by phosphorylation of Syk and p44/42 MAP kinase. In ZAP-70 positive cells, BCR crosslinking resulted in a robust activation of Syk, p44/42 MAP kinases, and protein kinase B (Akt). ZAP-70 negative CLL cells displayed a weaker activation of p44/42 upon IgM crosslinking. Pretreatment of CLL cells with anti-IgM resulted in an enhanced calcium mobilization upon CXCL12 stimulation. This was not due to changes in surface expression of CXCR4. Accordingly, Syk inhibition by piceatannol resulted in a loss of calcium response upon CXCL12 stimulation. Furthermore, anti-IgM stimulation significantly increased CLL cell chemotaxis towards CXCL12 1.4 ± 1.2fold (n=9, p=0.027), and Syk inhibition by piceatannol decreased chemotaxis to 0.6 ± 0.2fold of controls (n=8). In these experiments, we could not detect differences between ZAP-70 positive or negative cells. However, there was a strong difference regarding the spontaneous, CXCL12-dependent migration of CLL cells beneath marrow stromal cells (pseudoemperipolesis). BCR crosslinking significantly increased pseudoemperipolesis of ZAP-70 expressing CLL cells 13.4 ± 21.0fold (n=7, p=0.043), whereas there was no significant increase in pseudoemperipolesis of ZAP-70 negative cells (1.4 ± 0.2fold increase, n=8). Syk inhibition by piceatannol significantly decreased the pseudoemperipolesis of ZAP-70 positive as well as ZAP-70 negative CLL cells to 0.4 ± 0.07 of controls (n=5, p=0.043). Interestingly, spontaneous migration of CLL cells beneath follicular dendritic cells (HK cells) was also significantly enhanced by anti-IgM stimulation, in particular in ZAP-70 positive cases. In summary, BCR signaling enhances calcium mobilization, CLL cell migration to CXCL12, and pseudoemperipolesis beneath marrow stroma or follicular dendritic cells. These data suggest that BCR stimulation co-operates with CXCL12 for localization and/or maintenance of CLL cells within distinct tissue microenvironments.

ZAP-70 Is Not Phosphorylated on the Activating Tyrosine Residue (Tyr319) in Chronic Lymphocytic Leukemia and B-Cell Lymphoma Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 178-178
Author(s):  
Stefania Gobessi ◽  
Aleksandar Petlickovski ◽  
Luca Laurenti ◽  
Dimitar G. Efremov
Keyword(s):  
T Cells ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Progressive Disease ◽  
Cell Receptor ◽  
Kinase Domain ◽  
Lymphocytic Leukemia ◽  
Bcr Signaling ◽  
Cell Receptor Signaling

Abstract The protein tyrosine kinase ZAP-70 is expressed at high levels in leukemic B-cells from chronic lymphocytic leukemia (CLL) patients with progressive disease and short survival. ZAP-70 is a key component of the proximal T-cell receptor signaling pathway and is highly homologous to Syk, an important B-cell receptor signaling (BCR) molecule. Recent studies indicate that ZAP-70 may participate in BCR signaling as well, but the mechanism of action is still not well understood. In T-cells, upon TCR stimulation ZAP-70 becomes phosphorylated on Tyr319 by the Src-like kinase Lck, which results in the release of the ZAP-70 kinase domain from an autoinhibited state to a fully active conformation. The Tyr319 site in ZAP-70 corresponds to the Tyr352 site in Syk, which is phosphorylated in B-cells following BCR stimulation. We therefore investigated the activation status of ZAP-70 and Syk in BCR stimulated CLL B-cells, using phosphorylation of Tyr319 and Tyr352 as markers of their activation. Analysis of 10 ZAP-70-positive CLL samples by immunoblotting with the phospho-ZAP70Tyr319/SykTyr352 antibody revealed that ZAP-70 is not phosphorylated at this site either before or after BCR stimulation, although in control experiments with Jurkat T-cells ZAP-70 became phosphorylated on Tyr319 upon TCR stimulation. Moreover, the Tyr352 site in Syk was phosphorylated following BCR stimulation in 6 of the 10 CLL B-cell samples. To further investigate the reasons for the unexpected lack of ZAP-70 activation in CLL B-cells, we produced stable transfectants of the BJAB lymphoma B-cell line that expressed ZAP-70 at levels similar to those found in CLL cases with progressive disease. In agreement with the CLL B-cell experiments, the Tyr319 site in ZAP-70 was not phosphorylated either before or after BCR stimulation. Since phosphorylation of Tyr319 is Lck-dependent in T-cells, and this kinase is expressed also in CLL B-cells, we ectopically expressed Lck in the ZAP-70-positive BJAB clones. Again, the Tyr319 site was not phosphorylated, indicating that ZAP-70 does not undergo activation of the kinase domain also in this cellular system. In contrast, BCR crosslinking in BJAB cells induced significant phosphorylation of Tyr352 in Syk, which was further enhanced in the clones that coexpressed ZAP-70. Furthermore, analysis of downstream signaling pathways following BCR stimulation showed stronger and prolonged activation of ERK and to a lesser extent Akt in the ZAP-70 positive clones, whereas no difference was observed in terms of activation of PLC-γ 2, JNK and degradation of the NF-kB inhibitor IkB. These data indicate that ZAP-70 does not undergo full activation in B-cells, but can still enhance activation of certain downstream BCR signaling pathways, possibly by affecting the activity of the related PTK Syk.

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.

Anergic Response to B-Cell Receptor Signaling in Chronic Lymphocytic Leukemia: The Differing Roles of IgD and IgM in the Microenvironment and Peripheral Blood.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2889-2889
Author(s):  
Tom Butler ◽  
Alexander Montoya ◽  
Andrew James Clear ◽  
Rita Coutinho ◽  
David C Taussig ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Bcr Signaling ◽  
B Cell Receptor Signaling ◽  
Cell Receptor Signaling

Abstract Abstract 2889 Chronic Lymphocytic Leukemia (CLL) cells depend on B cell receptor signaling as well as other microenvironmental survival signals (1). Drugs targeting the BCR signaling pathways are showing exciting results in CLL clinical trials. A peculiarity of CLL is that IgD signaling is generally preserved, whilst IgM signaling is decreased and it has been suggested that this pattern mimics anergic B-cells, and might be consistent with chronic autoantigen exposure. We examined the differing roles of IgM and IgD signaling in CLL using a theoretical framework of anergy. Peripheral blood (PB) CLL cells exhibited higher IgD expression, as compared to IgM (n=204, p<0.0001), but this did not have prognostic impact. When we examined IgM and IgD expression in LN biopsies compared to paired PB (n=10) expression, IgM expression was lower in LN (p=0.002) whilst IgD expression was unchanged. Although the number of these paired samples is small, cases with lower LN IgM levels had poorer prognosis, and we are investigating this further with a larger cohort. We hypothesize that reduced LN IgM expression reflects antigen engagement and an anergic response in the microenvironment. We sought to replicate Mockridge et al' s model of reversible anergy (2) by monitoring the dynamic changes in IgM/D expression after in vitro incubation. Most (18/20) PB CLL samples underwent calcium (Ca) flux after IgD crosslinking, whereas only 13/20 cases underwent IgM Ca flux, and the level of Ca flux was less than with IgD, a well recognized anergic pattern. Incubation for 24h in vitro led to partial restoration of IgM Ca flux and some improvement in IgD Ca flux. This was impaired by treatment with anti-IgD or IgM F(ab)2 fragments, mimicking antigen exposure, and in keeping with a model of CLL cells engaging autoantigen in vivo. Further support for the pro-survival role of the BCR in CLL was demonstrated by the finding that both IgD and IgM ligation was associated with reduced apoptosis in vitro, with a significant decrease in apoptosis with IgD ligation as compared to IgM. To examine the mechanistic differences of signaling via IgM and IgD further, we used high-throughput mass-spectrometry based phosphoproteomics. This allows analysis of multiple active signaling pathways without a priori knowledge of which pathways to investigate. 6 CLL samples were compared to 5 tonsil controls. 4,575 unique phosphopeptides were identified using MASCOT proteomics software and quantified using a label-free technique based on extracted ion currents. 174 phosphoproteins (p<0.001, fold change up to >4000-fold) were over-expressed in CLL relative to healthy B-cells. These included components of RNA processing complexes, cytoskeletal regulators and MAPK signaling pathway components. Kinase prediction based on phosphoprotein substrates confirmed activation of kinases known to be active in CLL (such as AKT1, ERK1/2, CK2), but several novel kinases (such as CaMK1, CRIK, ROCK1 and BCKDK) were also active in CLL relative to healthy controls. Evaluation of differentially expressed phosphoproteins after BCR ligation included components of the spliceosome, regulators of the cytoskeleton, as well as known BCR signaling components. BCR-induced kinase activities included mTOR, CDK family members, MAPKs, BCKDK and others. There was much overlap between kinases active after IgM and IgD ligation, but also marked differences in CLL and tonsil BCR signaling. CONCLUSIONS Anergic IgM signaling is contrasted with IgD as a dynamic and plastic process that appears different in the LN and PB compartments in CLL. Mass-spectrometry based phosphoproteomics offers a powerful tool for interrogating intracellular signaling, with networks of phosphorylation characterizing the topology of pathways. BCR signaling in healthy B-cells has not previously been studied using this approach and comparisons with CLL highlight known pathways as well as suggesting novel treatment targets. The ultimate goal is to identify kinases active in CLL that will provide rational and effective drug combinations. Disclosures: Gribben: Celgene: Honoraria; Roche: Honoraria; Pharmacyclics: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria.

scholarly journals Acalabrutinib in the treatment of chronic lymphocytic leukemia: a review of recent evidence

2021 ◽  
Vol 23 (2) ◽  
pp. 332-338
Author(s):  
Andrei A. Petrenko ◽  
Maria I. Kislova ◽  
Elena A. Dmitrieva ◽  
Eugene A. Nikitin
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitor ◽  
Kinase Inhibitor ◽  
Real Life ◽  
Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Phase Iii ◽  
Multicenter Studies ◽  
Bruton Tyrosine Kinase

Chronic lymphocytic leukemia (CLL) treatment landscape has changed dramatically with the recently developed drugs targeting the B-cell receptor (BCR) signalling pathway. Acalabrutinib, a second generation Bruton tyrosine kinase inhibitor, was approved in 2020 in Russia for the treatment of patients with CLL. Acalabrutinib was developed as a more selective Bruton tyrosine kinase inhibitor then ibrutinib. This drug is aimed at reducing the adverse events that limit the use of ibrutinib, such as atrial fibrillation and bleeding. Phase I/II multicenter studies have demonstrated the efficacy and safety of acalabrutinib monotherapy in untreated CLL patients and in patients with relapsed/refractory CLL and ibrutinib intolerance. Phase III trials, ASCEND and ELEVATE-TN, compared acalabrutinib monotherapy and a combination of acalabrutinib and obinutuzumab versus standard therapies and demonstrated improved efficacy and tolerability of acalabrutinib. A phase III trial comparing acalabrutinib and ibrutinib monotherapy (ELEVATE-RR) is ongoing. The results of this study along with real-life clinical data could determine the place of acalabrutinib in CLL treatment.

Activation of AKT and Enhanced Resistance to Apoptosis Induced by Surface IgM Ligation in ZAP-70-Positive Chronic Lymphocytic Leukemia B Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2940-2940
Author(s):  
Liguang Chen ◽  
Gabriel A. Meraz ◽  
Thomas J. Kipps
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Tyrosine Kinase ◽  
Protein Tyrosine Kinase ◽  
Leukemia Cell ◽  
Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Experimental Conditions ◽  
V Genes ◽  
Over Time

Abstract Signaling through the B-cell receptor (BCR) for antigen has been implicated to play a role in the pathogenesis and/or progression of chronic lymphocytic leukemia (CLL). Previously we found that BCR ligation on CLL cells that expressed ZAP-70 induced significantly higher levels of phosphorylation in p72Syk, BLNK, and phospholipase C-gamma than did BCR ligation on CLL cells that lacked expression of this protein tyrosine kinase. We hypothesized that CLL B cells that express ZAP-70 also may have enhanced levels of AKT activation following BCR ligation that is associated with increased resistance to apoptosis. CLL B cells were stimulated via surface IgM ligation and monitored at various time points for phosphorylation of cytoplasmic signaling molecules via immunoblot analyses and for viability by flow cytometry after staining with propidium iodide and DiOC6 to detect changes in mitochondrial membrane potential associated with apoptosis. We found that CLL cells that expressed ZAP-70 experienced significantly higher levels of AKT phosphorylation within 10 minutes following BCR-ligation than did ZAP-70-negative CLL cells. Over time a significantly higher proportion of ZAP-70-negative CLL cells were induced to undergo apoptosis by BCR-ligation than similarly treated CLL cells that were ZAP-70 positive. The differences between these two groups in leukemia cell viability over time after BCR ligation could be abrogated by addition of LY294002, a PI3-K inhibitor, to the CLL cell cultures 30 minutes prior to surface IgM ligation. We conclude that ZAP-70-positive CLL cells are relatively resistant to apoptosis induced by surface IgM ligation under the experimental conditions used, a characteristic that is associated with enhanced phosphorylation of AKT and activation of AKT-dependent pathways following BCR ligation. These studies support a model proposing that BCR ligation induces signaling that results in enhanced growth and/or survival of CLL cells that express ZAP-70 relative to that of leukemia cells that lack expression of this tyrosine kinase. Because expression of ZAP-70 typically is associated with expression of unmutated Ig V genes in CLL, the improved signaling afforded by expression of this tyrosine kinase may account in part for the greater tendency for disease progression observed in patients with CLL cells that use unmutated Ig V genes.

Sign in / Sign up

Export Citation Format

Share Document