Targeting CK2 overexpression and hyperactivation as a novel therapeutic tool in chronic lymphocytic leukemia

Blood ◽  
2010 ◽  
Vol 116 (15) ◽  
pp. 2724-2731 ◽  
Author(s):  
Leila R. Martins ◽  
Paulo Lúcio ◽  
Milene C. Silva ◽  
Kenna L. Anderes ◽  
Paula Gameiro ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Cell Survival ◽  
Clinical Stage ◽  
Critical Role ◽  
Serum Levels ◽  
Therapeutic Strategies ◽  
Lymphocytic Leukemia ◽  
Downstream Target ◽  
Stage Disease

Abstract Expression of protein kinase CK2 is frequently deregulated in cancer and mounting evidence implicates CK2 in tumorigenesis. Here, we show that CK2 is overexpressed and hyperactivated in chronic lymphocytic leukemia (CLL). Inhibition of CK2 induces apoptosis of CLL cells without significantly affecting normal B and T lymphocytes. Importantly, this effect is not reversed by coculture with OP9 stromal cells, which are otherwise capable of rescuing CLL cells from in vitro spontaneous apoptosis. CLL cell death upon CK2 inhibition is mediated by inactivation of PKC, a PI3K downstream target, and correlates with increased PTEN activity, indicating that CK2 promotes CLL cell survival at least in part via PI3K-dependent signaling. Although CK2 antagonists induce significant apoptosis of CLL cells in all patient samples analyzed, sensitivity to CK2 blockade positively correlates with the percentage of CLL cells in the peripheral blood, β2 microglobulin serum levels and clinical stage. These data suggest that subsets of patients with aggressive and advanced stage disease may especially benefit from therapeutic strategies targeting CK2 function. Overall, our study indicates that CK2 plays a critical role in CLL cell survival, laying the groundwork for the inclusion of CK2 inhibitors into future therapeutic strategies.

Activation of NFAT and NFkB Transcription Factors upon B Cell Receptor (BCR) Stimulation Is Restricted to Evolutive Chronic Lymphocytic Leukemia (CLL) Cases.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2803-2803
Author(s):  
Nathalie S. Chevallier ◽  
Pierre-Antoine Deglesne ◽  
Taoufik Beitar ◽  
Fanny Baran-Marszak ◽  
Remi Letestu ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Chronic Lymphocytic Leukemia ◽  
Cell Survival ◽  
Binding Capacity ◽  
Clinical Stage ◽  
Peptide Inhibitors ◽  
Lymphocytic Leukemia ◽  
Cyclin D2 ◽  
Bcr Signaling

Abstract Chronic lymphocytic leukemia (CLL) is a highly heterogeneous disease in which BCR signaling capacity plays a central role in disease progression. Previously, we have shown that BCR engagement allows the identification of two groups of patients with a strong correlation between the in vitro cell survival response and the biological criteria (IgVH somatic hypermutations, ZAP 70 expression ) or the clinical stage. One group, corresponding to non evolutive patients, showed absence of a substantial BCR signaling (Non responder). In contrast, BCR signaling promoted in vitro cell survival in the group of Responder cases corresponding to evolutive patients. In the latter only, response to BCR ligation was associated with induction of NFkB and NFAT regulated genes, such as Cyclin D2 and CD23. Since NFAT and NFkB transcription factors, regardless of the patients clinical status, have been described as constitutively nuclear in B-CLL cells, the aim of our study was to investigate whether the functional implication of these factors was different between our two groups. First, we confirmed by confocal microscopy and band shift analysis that localization of NFAT and NFkB was uniformely nuclear independently of the CLL status and the BCR response capacity. By RQ-PCR , we also investigated the expression of the various isoforms of NFAT (NFAT1, 2, 3 and 4) and showed that their expression profile was similar to normal B cells. Despite the nuclear localization of NFkB and NFAT, DNA binding capacity was only enhanced in cases responsive to BCR stimulation. Finally, using specific Tat-peptide inhibitors of NFAT and NFkB nuclear transport upregulation of cyclin D2 and CD23 was abrogated and survival advantage was lost in responder cases thereby confirming the crucial role of these factors upon BCR stimulation. However, in non responder cases in which no CD23 or cyclin D2 induction was present, this inhibition had no impact on cell survival upon BCR stimulation . Nonetheless, these cells retained the ability to respond to ionomycin or PMA reflecting functional PKC/calcium-calcineurin signaling pathways. Altogether, our results showed that NFAT and NFkB were activated in responder cells only despite their homogenous expression in all cases. In conclusion, the inability of the cells from stable B-CLL cases to activate the NFAT and NFkB pathways upon BCR signaling is not related to a functional defect or abnormal expression of these factors but likely reflects an early signaling defect. Moreover, our results show that the use of peptide inhibitors may restore a stable profile in B-CLL cells from evolutive patients.

Lenalidomide Abrogates the Protective Influence of Nurse-Like Cells on Primary Chronic Lymphocytic Leukemia Cells In Vitro.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3116-3116 ◽  
Author(s):  
Danelle F. James ◽  
Maryann R. Betty ◽  
Ruzbeh Mosadeghi ◽  
Thomas J. Kipps
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Cell Viability ◽  
Cell Survival ◽  
Leukemia Cell ◽  
Lymphocytic Leukemia ◽  
Response To Treatment ◽  
Leukemia Cells ◽  
High Dependency ◽  
Cells Cultured

Abstract Lenalidomide (3-(4-amino-1-oxo-3H-isoindol-2-yl)piperidine-2,6-dione)) is an agent approved for treatment of patients with del 5q myelodysplastic syndromes and previously treated multiple myeloma. Lenalidomide has been found in early clinical trials to have potential therapeutic activity in patients with relapsed chronic lymphocytic leukemia (CLL). The mechanism(s) whereby this drug is active in CLL is unknown. In particular, studies to date have not found lenalidomide to have any direct cytotoxic activity on CLL cells in vitro. This has stimulated speculation that this agent might adversely affect the positive influence of the microenvironment on leukemia-cell survival. We and others have observed that cells found in the leukemia microenvironment can support CLL-cell survival in vitro. One such type of cells are nurse-like cells (NLC), which can differentiate from the CD14-positive blood mononuclear cells of CLL patients into large, round adherent cells that can attract and support CLL cell survival in vitro for weeks, if not longer. We evaluated the effects of lenalidomide on primary leukemia-cell survival in vitro when the CLL cells from different patients (N=21) were cultured alone or together with NLC generated as previously described [Tsukada Blood 2002]. We assessed the in-vitro activity of lenalidomide on primary CLL cells from 21 patients, in duplicate in a series of 6 experiments. Lenalidomide at concentrations of 0.1μM-200μM did not significantly impact the survival of CLL cells that were cultured alone for up to 12 days. Analysis of cell surface markers revealed increased expression of CD38 at 36 hours in 5/5 lenalidomide treated CLL samples compared with untreated cells (MFIR 5.7 +/− .86 vs. 3.4 +/− .83 p=.003). We observed sustained upregualtion of CD40 and regulation of CXCR4 in the majority of cells treated with lenalidomide. When cultured with NLC, the survival of CLL cells was comparable to or significantly higher than that of CLL cells cultured alone 62.4% vs. 51% (+/−3% SEM n=21 p [<] 0.0005). The addition of lenalidomide at concentrations of 0.1μM and greater to co-cultures of NLC and CLL cells caused specific reductions in CLL cell survival to levels similar to or lower than that of CLL cells cultured without NLC. In the presence of NLC, lenalidomide at 1μM reduced CLL cell viability compared to control (41.5% vs. 56% +/−4% p [<] 0.0005 paired student t test n=13). For most patients the levels of CLL cell viability on days 4 through 8 in the co-cultures with lenalidomide was significantly lower than those of CLL cells co-cultured with NLC in the absence of lenalidomide. As such, this study reveals that physiologic concentrations of lenalidomide might abrogate the protective influence of NLC on CLL cell survival in vitro and potentially in vivo. Conceivably, those patients who have leukemia cells displaying a high dependency on NLC for survival in vitro also might be most likely to experience a favorable clinical response to treatment with lenalidomide. This hypothesis will be tested in a prospective manner with a planned clinical trial evaluating lenalidomide for treatment of CLL through the CLL Research Consortium.

scholarly journals The degree of BCR and NFAT activation predicts clinical outcomes in chronic lymphocytic leukemia

Blood ◽  
2012 ◽  
Vol 120 (2) ◽  
pp. 356-365 ◽  
Author(s):  
Christine Le Roy ◽  
Pierre-Antoine Deglesne ◽  
Nathalie Chevallier ◽  
Taoufik Beitar ◽  
Virginie Eclache ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Binding Capacity ◽  
Critical Role ◽  
Lymphocytic Leukemia ◽  
Protein Levels ◽  
Intracellular Calcium Mobilization ◽  
Bcr Signaling ◽  
Nfat Activation

Abstract B-cell antigen receptor (BCR)–mediated signaling plays a critical role in chronic lymphocytic leukemia (CLL) pathogenesis and gives an in vitro survival advantage to B cells isolated from patients with unfavorable prognostic factors. In this study, we undertook to elucidate the signaling intermediates responsible for this biologic alteration. In responding cells only, in vitro BCR engagement triggers global phosphorylation of Syk, activation of phospholipase Cγ2, and intracellular calcium mobilization, reflecting competency of BCR signaling. The calcium–calcineurin-dependent transcription factor NFAT2 is up-regulated and to some extent constitutively activated in all CLL B cells. In contrast, its DNA-binding capacity is enhanced on IgM stimulation in responding cells only. NFAT inhibition using the VIVIT peptide prevents induction of CD23 target gene and IgM-induced survival, converting responding cells to unresponsive status. At the opposite, ionomycin-induced NFAT activity allows survival of nonresponding cells. These results demonstrate that the functional heterogeneity relies on variability of protein levels establishing BCR-dependent thresholds and NFAT-dependent activation. Finally, status of the BCR-NFAT pathway for each patient reveals its relevance for CLL clinical outcome and points out to BCR-NFAT intermediates as promising functional therapeutic targets.

scholarly journals High TCL1 levels are a marker of B-cell receptor pathway responsiveness and adverse outcome in chronic lymphocytic leukemia

Blood ◽  
2009 ◽  
Vol 114 (21) ◽  
pp. 4675-4686 ◽  
Author(s):  
Marco Herling ◽  
Kaushali A. Patel ◽  
Nicole Weit ◽  
Nils Lilienthal ◽  
Michael Hallek ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Clinical Stage ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Advanced Clinical Stage ◽  
Therapy Regimen ◽  
Cell Counts

Abstract Although activation of the B-cell receptor (BCR) signaling pathway is implicated in the pathogenesis of chronic lymphocytic leukemia (CLL), its clinical impact and the molecular correlates of such response are not clearly defined. T-cell leukemia 1 (TCL1), the AKT modulator and proto-oncogene, is differentially expressed in CLL and linked to its pathogenesis based on CD5+ B-cell expansions arising in TCL1-transgenic mice. We studied here the association of TCL1 levels and its intracellular dynamics with the in vitro responses to BCR stimulation in 70 CLL cases. The growth kinetics after BCR engagement correlated strongly with the degree and timing of induced AKT phospho-activation. This signaling intensity was best predicted by TCL1 levels and the kinetics of TCL1-AKT corecruitment to BCR membrane activation complexes, which further included the kinases LYN, SYK, ZAP70, and PKC. High TCL1 levels were also strongly associated with aggressive disease features, such as advanced clinical stage, higher white blood cell counts, and shorter lymphocyte doubling time. Higher TCL1 levels independently predicted an inferior clinical outcome (ie, shorter progression-free survival, P < .001), regardless of therapy regimen, especially for ZAP70+ tumors. We propose TCL1 as a marker of the BCR-responsive CLL subset identifying poor prognostic cases where targeting BCR-associated kinases may be therapeutically useful.

Serum Tumor Markers in Non-Hodgkin's Lymphomas and Chronic Lymphocytic Leukemia

1993 ◽  
Vol 8 (1) ◽  
pp. 14-20 ◽  
Author(s):  
A.N. Pavlidis ◽  
J. Kalef-Ezra ◽  
L.C. Bourantas ◽  
A. Lambrou ◽  
A. Mavridis
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Tumor Markers ◽  
Clinical Stage ◽  
Prognostic Significance ◽  
Interleukin 2 ◽  
Serum Levels ◽  
Lymphocytic Leukemia ◽  
Mean Values ◽  
Hodgkin's Lymphomas ◽  
Normal Controls

The levels of soluble interleukin-2 receptors (sIL-2R), beta-2 microglobulin (β-2M), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were measured in the serum of 50 previously untreated patients with non-Hodgkin's lymphoma (NHL) and chronic lymphocytic leukemia (CLL) as well as in 25 age and sex-matched normal controls. Compared to normal controls, mean serum levels of sIL-2R and β-2M were significantly increased in both NHL and CLL (p < 0.001) while the increase in ESR and CRP was less marked (p < 0.01 and p < 0.05, respectively). Comparison of these tumor markers with histologic grading showed statistically significant differences only for CRP between low, intermediate and high-grade lymphomas (p < 0.001 and p < 0.05). More advanced stages exhibited higher mean values of all serum markers than early stages (p < 0.001 for sIL-2R, β-2M and ESR and p < 0.05 for CRP). An association with the presence of b-symptoms was observed only for sIL-2R (p < 0.05). In addition, sIL-2R as well as β-2M were able to predict time to progression in patients with diffuse large-cell lymphomas. We conclude that of the four tumor markers tested sIL-2R and β-2M more frequently showed increased serum levels and were associated with clinical stage and/or presence of b-symptoms. Both sIL-2R and β-2M were also found to have prognostic significance for survival.

scholarly journals High serum levels of soluble interleukin 2 receptor in patients with B chronic lymphocytic leukemia

Blood ◽  
1987 ◽  
Vol 70 (2) ◽  
pp. 396-400 ◽  
Author(s):  
G Semenzato ◽  
R Foa ◽  
C Agostini ◽  
R Zambello ◽  
L Trentin ◽  
...  
Keyword(s):  
T Cell ◽  
Chronic Lymphocytic Leukemia ◽  
Interleukin 2 ◽  
Serum Levels ◽  
High Serum ◽  
Lymphocytic Leukemia ◽  
Soluble Form ◽  
Enzyme Linked Immunosorbent Assay ◽  
Interleukin 2 Receptor

Abstract By using an enzyme-linked immunosorbent assay, the presence of the soluble form of the interleukin-2 receptor (sIL-2R) was evaluated in the peripheral blood of 54 patients with B cell chronic lymphocytic leukemia (B-CLL). Serum levels of sIL-2R were correlated with clinical features, relevant hematologic and immunological data, and in some cases, with in vitro functional studies. In 51 patients (94.4%), the levels of sIL-2R were increased as compared with normal age-matched controls (1,781 U/mL +/- 231 v 276 U/mL +/- 26, respectively; P less than .001). Although this increase was observed in all stages of the disease and independently of several hematologic and immunologic parameters, a trend toward lower levels of sIL-2R was documented in patients with a less-invasive disease. When the values were correlated with the functional status of the residual T cell population, it was found that patients with the lowest levels of sIL-2R showed the best mitogenic response and helper capacity. It is suggested that in B-CLL patients the high levels of serum sIL-2R, capable of binding to its ligand, may block the T cell-produced IL-2, thus contributing toward a defective physiological action by this lymphokine. In turn, this defective availability of IL-2 may play a part in the abnormal immunoregulation that is implicated in the hypogammaglobulinemia, susceptibility to infections, and incidence of second neoplasias often observed in this disease.

Cpg Oligodeoxynucleotide-Mediated Effects on B-Cell Chronic Lymphocytic Leukemia In Vitro Are Influenced by Cytogenetic Status and the Presence of Serum.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4828-4828
Author(s):  
Bernd Jahrsdorfer ◽  
Sue E. Blackwell ◽  
James E. Wooldridge ◽  
Christiana M. Taylor ◽  
George J. Weiner
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Cell Survival ◽  
Poor Prognosis ◽  
Good Prognosis ◽  
Lymphocytic Leukemia ◽  
Autologous Serum ◽  
Cpg Odn ◽  
Mediated Effects ◽  
Cell Chronic Lymphocytic Leukemia

Abstract Immunostimulatory CpG-containing oligodeoxynucleotides (CpG ODN) are TLR9 agonists that mediate a number of immunologic effects in normal and malignant B cells including upregulation of immunogenic molecules. They are therefore felt to be attractive as potential components of immunotherapy for B cell chronic lymphocytic leukemia (B-CLL). The cytogenetic status of B-CLL is predictive of clinical prognosis, but little is known about how CpG ODN-mediated effects on B-CLL cells correlate with cytogenetic status. The present study was designed to explore the impact cytogenetic status has on in vitro B-CLL cell survival and immunogenicity. Since most in vitro studies to date have been performed under serum-low conditions, we also evaluated how the presence of autologous serum or plasma impacts on CpG ODN-mediated effects on B-CLL cells. B-CLL cytogenetic status by interphase FISH, as well as immunophenotype and cell survival in the absence or presence of CpG ODN was determined in 23 samples. CpG ODN decreased in vitro survival of B-CLL cells with good prognosis cytogenetics, but had little effect on cells with poor prognosis cytogenetics. In contrast, CpG ODN upregulated costimulatory and antigen-presenting molecules and enhanced allogeneic T cell response in samples with good and poor prognosis cytogenetics. The optimal concentration for CpG ODN-mediated effects in the presence of 100% autologous serum or plasma was higher (10–20 micrograms/ml ODN) than for serum-low conditions (2.5–5 micrograms/ml ODN). The observed inhibition of CpG ODN-mediated effects by serum directly correlated with a lower uptake of ODN into B-CLL cells in the presence of serum. In conclusion, CpG ODN induced changes in B-CLL consistent with enhanced immunogenicity in all samples studied, but induced apoptosis most effectively in the subset of B-CLL cells with good prognosis cytogenetics. Approximately 4-fold more CpG ODN was needed to induce these changes when serum was present as compared to low serum conditions due to decreased ODN uptake by the cells in the presence of serum. These studies suggest CpG ODN may be useful as immunotherapeutic agents for B-CLL irrespective of cytogenetic status because of their potential effects on immunogenicity. Higher systemic doses of CpG ODN than previously thought might be necessary to induce these changes because of the effect of serum proteins on ODN uptake.

CXCL12 Enhances Survival of Chronic Lymphocytic Leukemia Cells Via a RAF-Dependent Pathway That Can Be Inhibited by Sorafenib

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2445-2445
Author(s):  
Davorka Messmer ◽  
Jessie-F Fecteau ◽  
Morgan O'Hayre ◽  
Tracy Handel ◽  
Thomas J. Kipps
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Cell Survival ◽  
Small Molecule ◽  
Kinase Inhibitor ◽  
Conflicts Of Interest ◽  
Growth Factor Receptor ◽  
Lymphocytic Leukemia ◽  
Increased Risk ◽  
Dependent Pathway

Abstract Abstract 2445 The cellular microenvironment is critical for the survival of Chronic Lymphocytic Leukemia (CLL) cells. CLL cells die rapidly in vitro unless they receive survival signals from stromal cells or “nurse-like” cells (NLCs). CLL cell survival is in part mediated by the stromal cell-derived factor-1 (SDF-1alpha, designated as CXCL12), which is expressed by NLCs. CXCL12 is a highly conserved chemokine that can promote CLL-cell survival through its receptor CXCR4. Prior studies showed that treatment of CLL cells with CXCL12 induced activation of Extracellular Signal-Regulated Kinase (ERK). In this study, we examined CXCL12 signaling in CLL cells to characterize the mechanism (s) accounting for its ability to enhance CLL-cell survival. For this we examined CLL cells with high- or low- level expression of the zeta-associated protein of 70 kD (ZAP-70), a tyrosine kinase that is expressed by CLL cells of patients who have an increased risk for early disease progression and short survival. We found that CXCL12 induced a robust intracellular Ca2+ flux in ZAP-70+ CLL cells but only modest-to-poor Ca2+ flux in ZAP-70-negative CLL cells. Furthermore, ZAP-70+ CLL cells (n=10) responded to CXCL12 stimulation with increased and prolonged phosphorylation of ERK and MEK compared to ZAP-70-negative CLL cells (n=9). To investigate the underlying mechanism for MEK activation in ZAP-70+ CLL, we used small molecule inhibitors and found that CXCL12-induced phosphorylation of ERK and MEK could be blocked by sorafenib, a small molecule inhibitor of RAF. The role of RAF was further supported using KG5, a kinase inhibitor of RAF signaling through B-RAF and C-RAF in addition to platelet-derived-growth-factor-receptor (PDGFR) alpha and beta, Flt3, and Kit. As a control, we used a kinase inhibitor that targets all of these kinases except B- and C-RAF (KG1) and found it could not inhibit MEK activation. The involvement of Raf was further substantiated using GW5074, an inhibitor of B-RAF and C-RAF. Both KG5 and GW5074 could inhibit CXCL12-induced MEK activation in ZAP-70+ CLL samples. CXCL12-induced activation of MEK/ERK was not affected by sunitinib, an inhibitor of non-RAF kinases that also are inhibited by sorafenib, including VEGFR, PDGFR, Flt3, and c-Kit. Sorafenib not only inhibited MEK/ERK activation but also caused apoptosis of CLL cells whereby ZAP-70+ CLL cells showed incresed sensitivity to lower doses of sorafenib. Consistent with these results we found that ZAP-70+ CLL cells had a greater responsiveness to CXCL12 for survival in vitro than did ZAP-70-negative CLL cells. We conclude that CXCL12 can enhance survival particularly of ZAP-70+ CLL cells via a RAF dependent pathway, which can be targeted by the kinase inhibitor sorafenib. As such, sorafenib might be effective in blocking the protective influence of the microenvironment on CLL cells, suggesting that this drug could have activity in the treatment of patients with this disease. Disclosures: No relevant conflicts of interest to declare.

Nicotinamide Promotes Apoptosis In Chronic Lymphocytic Leukemia through Activation of the p53/Mir-34a/SIRT1 Tumor Suppressor Network

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4627-4627
Author(s):  
Valentina Audrito ◽  
Tiziana Vaisitti ◽  
Sara Serra ◽  
Davide Rossi ◽  
Daniela Gottardi ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Lymphocytes ◽  
Conflicts Of Interest ◽  
Therapeutic Potential ◽  
Critical Role ◽  
Disease Model ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Intrinsic Resistance

Abstract Abstract 4627 Nicotinamide (Nam), is the main precursor of nicotinamide adenine dinucleotide (NAD+). It regulates intracellular levels of NAD+ and consequently activities of four classes of NAD+-consuming enzymes, including NADases, mono-ADP-ribosyl transferases (ARTs), poly-ADP-ribose polymerases (PARPs) and sirtuins. Pharmacological doses of Nam inhibit the physiological activation and proliferation of mouse B lymphocytes, suggesting that this agent might affect also human B cell homeostasis. We approaches this issue by comparing the effects of Nam on normal vs. leukemic B lymphocytes. Chronic lymphocytic leukemia (CLL) was selected as disease model, for testing in vitro the therapeutic potential of Nam, due its intrinsic resistance to apoptosis, mediated by an imbalance in the mechanisms regulating cell death, mainly regulated through the activities of NAD+-dependent enzymes. This study shows that pharmacological doses of Nam (5-10 mM) significantly inhibit proliferation and induce apoptosis of CLL cells. At earlier time points, Nam markedly reduces phosphorylation of multiple intracellular substrates, including ERK1/2. Normal B lymphocytes, used as control, were significantly less sensitive to the action of Nam. We hypothesized that these effects could be explained at least in part as a consequence of the inhibitory effects of Nam on NAD+-consuming enzymes. Attention was focused on SIRT1, a deacetylase that plays a critical role in cancer and that acts as a longevity factor. The results demonstrate that Nam exposure inhibits the activity, and also the expression of SIRT1. This effect is apparent only in leukemic cells, where SIRT1 protein levels are significantly higher than in normal B lymphocytes, obtained from spleen or tonsils, markedly less sensitive to Nam effects. The functional block of SIRT1 induced by Nam is followed by activation of p53, transcription of miR-34a and translational repression of SIRT1 mRNA (p53/miR-34a/SIRT1 functional loop). The endpoint is the activation of apoptosis. The same loop is the target of conventional DNA-damaging drugs, such as etoposide. Thus, addition of Nam to conventional DNA-damaging chemotherapeutics agents, leads to an inhibition of SIRT1 through two independent and synergic pathways, resulting in additive effects on apoptosis. In conclusion this work suggests that Nam represents a potentially useful non-chemotherapeutic agent, characterized by a known and established safety profile, to be associated to conventional cytotoxic drugs in the treatment of selected forms of CLL. Disclosures: No relevant conflicts of interest to declare.

scholarly journals RhoH is critical for cell-microenvironment interactions in chronic lymphocytic leukemia in mice and humans

Blood ◽  
2012 ◽  
Vol 119 (20) ◽  
pp. 4708-4718 ◽  
Author(s):  
Anja Troeger ◽  
Amy J. Johnson ◽  
Jenna Wood ◽  
William G. Blum ◽  
Leslie A. Andritsos ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Critical Role ◽  
Disease Onset ◽  
Lymphocytic Leukemia ◽  
Cell Contact ◽  
Cell Microenvironment ◽  
The Impact ◽  
Cell Cell

Abstract Trafficking of B-cell chronic lymphocytic leukemia (CLL) cells to the bone marrow and interaction with supporting stromal cells mediates important survival and proliferation signals. Previous studies have demonstrated that deletion of Rhoh led to a delayed disease onset in a murine model of CLL. Here we assessed the impact of RhoH on homing, migration, and cell-contact dependent interactions of CLL cells. Rhoh−/− CLL cells exhibited reduced marrow homing and subsequent engraftment. In vitro migration toward the chemokines CXCL12 and CXCL13 and cell-cell interactions between Rhoh−/− CLL cells and the supporting microenvironment was reduced. In the absence of RhoH the distribution of phosphorylated focal adhesion kinase, a protein known to coordinate activation of the Rho GTPases RhoA and Rac, appeared less polarized in chemokine-stimulated Rhoh−/− CLL cells, and activation and localization of RhoA and Rac was dysregulated leading to defective integrin function. These findings in the Rhoh−/− CLL cells were subsequently demonstrated to closely resemble changes in GTPase activation observed in human CLL samples after in vitro and in vivo treatment with lenalidomide, an agent with known influence on microenvironment protection, and suggest that RhoH plays a critical role in prosurvival CLL cell-cell and cell-microenvironment interactions with this agent.

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