NOTCH2 Contributes to Venetoclax Resistance in Chronic Lymphocytic Leukemia

BACKGROUND: Chronic lymphocytic leukemia (CLL) has recently experienced an unprecedented revolution thanks to the discovery of crucial pathogenetic mechanisms. Despite considerable therapeutic advancements, the eradication of the disease is not complete and resistance and transformation may occur. Venetoclax is a small-molecule BH3 mimetic that competes for binding in the hydrophobic groove of Bcl-2, a key protein involved in CLL cells survival. Venetoclax was shown to have an excellent antitumor activity in patients with relapsed CLL including those with high risk features. However, venetoclax monotherapy shows an overall response rate of 79% and complete response rates of 16% and leave some open questions mainly related to intrinsic features of CLL patients that may guide a pattern of resistance. A recent work shows that durable response to venetoclax based therapy is more likely in patients having minimal adenopathy, mutated IGHV gene, wild type TP53 and Notch1 genes. AIM OF THE WORK: We hypothesize that specific intrinsic features of CLL cells may contribute to drive possible mechanisms of resistance to venetoclax (ABT-199) treatment. METHODS: Notch2 expression was monitored by western blot in purified CLL cells. Modulation of Notch2 expression in vitro was performed by using siRNA strategy. ABT-199 was used at doses of 0.1 nM or 1 nM. RESULTS: Notch signaling is relevant in CLL pathogenesis. We detected a peculiar high expression of Notch2 in a subgroup of CLL patients carrying trisomy 12. The high expression of Notch2 correlated with high levels of Mcl-1, CD23 and Hes1. Interfering with Notch2 expression in trisomy 12 CLL patients, by siRNA silencing, was able to affect leukemic cells viability, reducing CD23 and Mcl-1 expression. Since Mcl-1 is involved in ABT-199 resistance, we wondered if ABT-199 may have a different effect in CLL cells isolated from patients carrying trisomy 12 comparing to no trisomy 12 cases. After 24h of culture in complete medium, trisomy 12 CLL cells showed a gain in survival rate of 10% during treatment with both 0.1 nM or 1 nM in comparison to no trisomy 12 cases. This advantage in viability reflected the maintenance of Notch2 and Mcl-1 expression in trisomy 12 both at 0.1 nM and 1 nM of ABT-199 compared to control. Conversely, a reduction of Notch2 and consequently Mcl-1 levels were observed in no trisomy 12 cases at both doses of ABT-199. We did not detect any variation in Bcl-2 levels. We wondered if Notch2 expression may reduce the response to ABT-199 in trisomy 12 CLL. To demonstrate this hypothesis, we interfered with Notch2 by silencing strategy. Treatment with Notch2 siRNA decreased the expression of Notch2 and Mcl-1 in combination with ABT-199 as shown in Figure 1A. We also found that Notch2 down-regulation cooperated with ABT-199 decreasing CLL cells viability (Figure 1B). CONCLUSIONS: Collectively, our results show a novel mechanism that may compromise the clinical response to venetoclax in CLL patients. Although the excellent mechanism of action of venetoclax, Bcl-XL and Mcl-1, two major anti-apoptotic proteins of Bcl-2 family not inhibited by venetoclax, are key determinants of both acquired and intrinsic resistance to treatment. The possibility to identify patients with more pronounced expression of Mcl-1 may help to optimize the treatment. The expression of Notch2 identify a subset of CLL patients, mainly harboring trisomy 12 aberration, that through the maintenance of high levels of Mcl-1, may be involved in a reduced response to ABT-199. Disclosures Luppi: Gilead Sci., MSD, Pfizer, Novartis, Abbvie, Sanofi, Daiichi Sankyo, Jazz Pharmaceuticals: Honoraria. Marasca:Janssen and Gilead Sci, Abbvie, Roche and Shire: Honoraria, Research Funding.

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

Blood ◽

10.1182/blood.v116.21.4627.4627 ◽

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.

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Aberrant expression of B-lymphocyte stimulator by B chronic lymphocytic leukemia cells: a mechanism for survival

Blood ◽

10.1182/blood-2002-02-0558 ◽

2002 ◽

Vol 100 (8) ◽

pp. 2973-2979 ◽

Cited By ~ 164

Author(s):

Anne J. Novak ◽

Richard J. Bram ◽

Neil E. Kay ◽

Diane F. Jelinek

Keyword(s):

B Cells ◽

Chronic Lymphocytic Leukemia ◽

B Cell ◽

B Lymphocyte ◽

Leukemic Cell ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Aberrant Expression ◽

B Lymphocyte Stimulator

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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High incidence of monoclonal proteins in the serum and urine of chronic lymphocytic leukemia patients

Blood ◽

10.1182/blood.v64.6.1207.1207 ◽

1984 ◽

Vol 64 (6) ◽

pp. 1207-1211 ◽

Cited By ~ 49

Author(s):

MJ Deegan ◽

JP Abraham ◽

M Sawdyk ◽

EJ Van Slyck

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Membrane Immunoglobulin ◽

High Incidence ◽

Secretory Products ◽

Monoclonal Proteins ◽

Chain Type ◽

Serum And Urine

Abstract Chronic lymphocytic leukemia (CLL) is generally considered a nonsecretory B cell immunoproliferative disorder. Conventional electrophoretic and immunoelectrophoretic methods have revealed serum monoclonal proteins in less than 10% of these patients. However, there is increasing experimental evidence from in vitro studies demonstrating that CLL cells may secrete immunoglobulins, particularly free light chains. We examined the serum and urine of 36 consecutive CLL patients for monoclonal proteins using sensitive immunochemical methods (high resolution agarose gel electrophoresis combined with immunofixation). The results obtained were correlated with the Rai stage, quantitative immunoglobulin levels, and lymphocyte membrane immunoglobulin phenotype of the leukemic cells. Twenty-three monoclonal proteins were identified in the serum or urine of 22 patients, an incidence of 61%. Six patients had serum monoclonal proteins, seven had only urinary monoclonal proteins, and nine had monoclonal proteins in serum and urine. In every instance the monoclonal protein was the same light chain type as expressed on the leukemic cells. Our findings suggest that the monoclonal proteins observed in the serum or urine of CLL patients are secretory products of the tumor cells and that their discovery is a function of the sensitivity of the method used for their detection.

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Complement alternative pathway activation by chronic lymphocytic leukemia cells: its role in their hepatosplenic localization

Blood ◽

10.1182/blood.v63.2.463.463 ◽

1984 ◽

Vol 63 (2) ◽

pp. 463-467 ◽

Cited By ~ 12

Author(s):

F Praz ◽

G Karsenty ◽

JL Binet ◽

P Lesavre

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Alternative Pathway ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Complement Alternative Pathway ◽

Acetylneuraminic Acid ◽

Pathway Activation ◽

Do So

Abstract Using affinity-purified 125I-F(ab')2 anti-human C3, we have investigated the ability of various leukemic cells to activate complement. Lymphocytes from patients with chronic lymphocytic leukemia (CLL) activated the alternative pathway, but cells from patients with other forms of leukemia or normal lymphocytes did not do so. The amount of C3 deposited on the CLL cells was significantly higher in patients with organomegaly (i.e., splenomegaly and/or hepatomegaly). Activation of complement by CLL cells as assessed by C3 deposition on the membrane occurred both in vivo and in vitro and was not related to the N- acetylneuraminic acid content of the membrane.

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ZAP-70 Expression Is Associated with Increased Migration to SDF-1 in Chronic Lymphocytic Leukemia.

Blood ◽

10.1182/blood.v108.11.587.587 ◽

2006 ◽

Vol 108 (11) ◽

pp. 587-587

Author(s):

Yuji Miura ◽

Elinor Lee ◽

Federica Gibellini ◽

Therese White ◽

Gerald Marti ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Cxcr4 Expression ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Short Exposure ◽

Mrna Levels ◽

Dependent Manner ◽

Western Blots ◽

Stroma Cell

Abstract Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of mature B lymphocytes in the peripheral blood (PB), lymph nodes (LN) and bone marrow (BM). Increasing evidence suggests that CLL cells depend on survival and proliferation signals provided by stroma cells in LN and BM. The chemokine receptor CXCR4 (CD184) and its ligand stromal cell-derived factor-1 (SDF-1) play an important role in trafficking of lymphocytes and may guide CLL cells to stroma cell niches. ZAP70 expression has prognostic value in CLL but the functional consequences of ZAP70 expression remain incompletely defined. Given that ZAP70 has been implicated in CXCR4 signaling its expression could enhance migration to SDF-1 and thereby promote interactions with stroma cells. As measured by flow cytometry, CXCR4 expression on leukemic cells obtained from different anatomic sites differed; cells from the PB (n=24, median 71% above isotype control) expressed CXCR4 more strongly than cells from BM (n=21, median 39%) and from LN (n=9, median 24%). Expression of CD69, an activation marker, followed a reverse pattern with cells from LN and BM typically showing higher expression than cells from PB, albeit with not detectable difference in expression in several patients. In vitro CLL cells from PB migrated in a dose dependent manner to SDF-1, and cells that had migrated down-modulated CXCR4 expression (89% before migration - 54% after migration). After exposure to SDF-1 CXCR4 expression decreased rapidly and remained virtually absent for at least 24 hours. Several mechanisms apparently decrease CXCR4 expression after contact with SDF-1, including internalization (given rapid re-expression of CXCR4 when SDF-1 is washed off after short exposure), protein degradation or inhibition of translation (evidenced by a decrease in total CXCR4 protein on Western blots), and mRNA degradation or transcriptional inhibition (decrease in mRNA levels more than 6 hours from SDF-1 exposure). In vitro migration of ZAP70(+) CLL cells toward SDF-1 through a 5μm membrane (Migration Index [MI] of 12.0, n=5) was significantly increased compared to ZAP70(−) CLL cells (MI of 2.9, n=4, p<0.05). To exclude effects of contaminating cells we repeated these assays with purified CLL cells (negative selection) with similar results. To model the complex interactions of CLL cells with stroma, we cultured PB derived leukemic cells with or without murine marrow stroma cells (S17). CXCR4 expression on CD19+ cells decreased from 90% without S17 to 50% when cultured on S17 cells, consistent with the known SDF-1 secretion by the murine stroma cell line. Conversely, CD69 expression increased from 58% without S17 to 71% with S17 cells. In addition, culturing of CLL cells on an S17 stroma cell layer extended their survival by several weeks when compared to cultures without S17 cells. Our data is consistent with a model in which CLL cells migrate along an SDF-1 gradient to stroma cell niches in BM and LN where they are activated. ZAP70 expression is associated with more effective migration in an SDF-1 gradient and thereby may facilitate access to growth and survival signals which then could contribute to the more progressive nature of ZAP70(+) CLL. The interaction between leukemic cells and stroma may represent a novel target for therapy of patients with CLL.

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Influence of Chromosomal Aberrations on Response to First Line Therapy in B-Cell Chronic Lymphocytic Leukemia: Interim Analysis of PALG-CLL3 Randomized Study Comparing Cladribine Plus Cyclophosphamide vs Fludarabine Plus Cyclophosphamide.

Blood ◽

10.1182/blood.v110.11.2046.2046 ◽

2007 ◽

Vol 110 (11) ◽

pp. 2046-2046

Author(s):

Tadeusz Robak ◽

Jerzy Z. Blonski ◽

Ewa Wawrzyniak ◽

Aleksandra Palacz ◽

Joanna Gora-Tybor ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

B Cell ◽

Chromosomal Aberrations ◽

Interim Analysis ◽

Chromosomal Abnormalities ◽

Complete Response ◽

Lymphocytic Leukemia ◽

Lower Probability ◽

Trisomy 12 ◽

Cell Chronic Lymphocytic Leukemia

Abstract Impact of cytogenetic abnormalities on treatment with different purine nucleoside analogs in patients (pts) with B-cell chronic lymphocytic leukemia (B-CLL) is largely unknown. One of objectives of PALG-CLL3 trial, comparing cladribine plus cyclophosphamide (CC) with fludarabine plus cyclophosphamide (FC) in previously untreated progressive B-CLL, was to verify the response to treatment in subsets of pts characterized by common cytogenetic abberrations. Chromosomal abnormalities were assessed using fluorescence in situ hybridization (FISH) on interphase nuclei of lymphocytes on whole blood smears prior to the start of the study treatment. Pts were screened for trisomy 12, deletions (del) 11q, del 13q and del 17p using DNA probes: CEP12, LSI: ATM, D13S319 and p53 (Vysis), respectively. For the purpose of the present interim analysis complete cytogenetic results were available in 133 pts out of 423 pts included to the study. In this group the chromosomal aberrations were detected in 102 pts (77%) including single abnormalities observed in 69 pts (52%) and two or more aberrations in 33 pts (25%). Thirty-one pts (23%) exhibited a normal interphase FISH pattern. The most frequent single abnormality was del 13q found in 38 pts (29%), while del 17p, trisomy 12 and del 11q were identified in 14 pts (11%), 11 pts (8%), and 6 pts, (5%), respectively. The most frequently observed associations of chromosomal aberrations were: del 13q with del 11q (11 pts, 8%) and del 13q with del 17p (10 pts, 8%). Four pts (3%) revealed three chromosomal abnormalities including association of trisomy 12/del 11q/del 13q in two pts, trisomy 12/del 11q/del 17p in one pt and del 11q/del 13q/del 17p in one pt. Overall, treatment was completed and response assessed in 113 out of 133 pts with known FISH pattern. In this group of pts del 17p was the only chromosomal abnormality that correlated significantly with treatment outcome. Pts with del 17p (21, 19%) had lower probability to achieve a complete response (CR) (0.044). Interestingly, in independent analyses of both treatment arms, the negative impact of 17p was seen in pts treated with FC (p=0.002), but not in pts treated with CC (p=0.6). Moreover, comparing response rates between treatment arms we found that CC was superior to FC in terms of complete response in pts with del 17p (57% CR in CC v 14% CR in FC arm, p=0.04). In conclusion, chromosomal abnormalities can be detected in majority B-CLL pts requiring treatment. Our preliminary results suggest that CC combination may have some advantage in terms of CR achievement in B-CLL pts harboring del 17p.

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Increased CD39 Expression on CD4+ T-Lymphocytes Has Clinical and Prognostic Significance in Chronic Lymphocytic Leukemia,

Blood ◽

10.1182/blood.v118.21.3895.3895 ◽

2011 ◽

Vol 118 (21) ◽

pp. 3895-3895

Author(s):

Yair Herishanu ◽

Inbal Hazan-Hallevi ◽

Sigi Kay ◽

Varda Deutsch ◽

Aaron Polliack ◽

...

Keyword(s):

T Cells ◽

Chronic Lymphocytic Leukemia ◽

T Lymphocytes ◽

Peripheral Blood ◽

Conflicts Of Interest ◽

Prognostic Significance ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Anti Inflammatory

Abstract Abstract 3895 Chronic lymphocytic leukemia (CLL) cells depend on their microenvironment for proliferation and survival. Ectonucleotidase CD39 has anti-inflammatory properties as it hydrolyzes pro-inflammatory extra-cellular ATP, generates anti-inflammatory adenosine and also protects regulatory T cells from ATP-induced cell death. In this study we investigated the clinical significance of CD39 expression on CD4+T-cells in 45 patients with CLL as well as its compartmental regulation and explored the possible mechanisms for its induction. Compared to healthy individuals, CD4+CD39+ lymphocytes were increased in the peripheral blood of patients with CLL (4.6%±2.28 vs. 17.3%±12.49, respectively, p=0.004), and correlated with advanced stage of disease (9.72%±5.76, 18.15%±12.03 and 25.90%±16.34, of CD4+ lymphocytes, in patients with Rai stages 0, 1+2 and 3+4, respectively, p=0.019). CD4+CD39+ cells were also higher in patients with CLL who needed therapeutic intervention (untreated; 12.99%±10.63 vs treated; 22.21%±12.88, p=0.01) and in those who were ZAP70+ or had b2-microglobulin levels>3g/L. There were more CD4+CD39+ lymphocytes in the bone marrow compartment (22.25%±16.16) than in the peripheral blood (16.60%±15.84, p=0.009). In-vitro studies showed that CD39 can be induced on CD4+cells by exposure to ATP or indirectly, following B-cell receptor (BCR) engagement (CD4+CD39+ lymphocytes increased by 1.56 fold, in the BCR engaged samples compared to their paired controls; 20.27%±11.3 vs. 13%±9.42, respectively, p=0.0006). Conclusions: Increased CD39 expression on CD4+ T-lymphocytes in CLL associates with an aggressive disease. This may reflect the ability of the leukemic cells to suppress the surrounding immune environment, and contribute to a poorer prognosis. CD39+ may also serve as a future target for the development of novel therapies with immune modulating anti–tumor agents in CLL. Disclosures: No relevant conflicts of interest to declare.

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Preclinical Testing of a Novel Axl-Kinase Inhibitor in Chronic Lymphocytic Leukemia

Blood ◽

10.1182/blood.v120.21.1799.1799 ◽

2012 ◽

Vol 120 (21) ◽

pp. 1799-1799

Author(s):

Maria Göbel ◽

Michael Möllmann ◽

Andre Görgens ◽

Ulrich Dührsen ◽

Andreas Hüttmann ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Tyrosine Kinase ◽

Receptor Tyrosine Kinase ◽

Cell Polarization ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Blue Staining ◽

Nsg Mice

Abstract Abstract 1799 The receptor tyrosine kinase Axl belongs to the TAM (Tyro-3, Axl and Mer) family and is involved in the progression of several human malignancies including chronic lymphocytic leukemia (CLL), where it is has been found to be overexpressed in comparison to normal B-cells. An increasing body of evidence suggests that Axl acts as an oncogene which increases the survival, proliferation, metastatic potential and chemotherapy resistance of tumor cells. Hence, it has been recently identified as a potential therapeutic target in a wide range of tumor entities with deregulated Axl expression including prostate cancer, glioma, lung cancer and CLL. Here, we investigated two different Axl inhibitors for their potential to inhibit the migratory capacity and survival of leukemic cells in preclinical CLL models. In vitro studies: Freshly isolated PBMC (>90% CD5+CD19+) from CLL patients were incubated in serum free medium for 48h containing concentrations series of 2 different Axl inhibitors: BMS777607, a previously published inhibitor of the MET kinase family, and LDC2636, a novel inhibitor of the TAM receptor tyrosine kinase (RTK) family with high affinity to Axl. Viability of CLL cells was assessed by trypan blue staining and flow cytometry employing annexin V staining. Since a polarized phenotype is required for migration, cell polarization was analyzed by time-lapse video-microscopy. We detected cytotoxic effects in a patient dependent manner that were more prevalent in LDC2636 as compared to BMS777607 treated cells (LD50= 1.4 μM vs. 5.2 μM, p<0.004, n=5). Cell polarization of the remaining viable cells was significantly reduced in a dose dependent fashion in comparison to vehicle only controls (LDC2636 IC50 = 7.2 μM, p<0.00001; BMS777607: IC50=6.2μM; p=0.0004). Of note, both Axl inhibitors exhibited significantly weaker effects on both, the viability and cell polarization of normal PBMC over the whole concentration range tested (p<0.05, n=5). In vivo studies: To verify our hypothesis that reduced cell polarization results in decreased homing of leukemic cells in vivo we employed a recently developed adoptive transfer model of CLL. In this model NOD/SCID/gcnull(NSG) mice were pre-treated with a single intraperitoneal bolus of LDC2636 or BMS777607 (20 mg/kg) and subsequently transplanted with primary CLL cells. Both Axl inhibitors significantly reduced the homing capacity of CLL cells to the bone marrow of NSG mice by 43% and 59%, respectively, compared to vehicle treated controls (LDC2636: p=0.046, BMS777607 p=0.0077; n=3). These data demonstrate that Axl inhibitors exert potent in vitro and in vivo activity against human CLL cells, which is caused at least in part by the suppression of CLL homing to their supportive stromal niches. Disclosures: No relevant conflicts of interest to declare.

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Chronic Lymphocytic Leukemia Cells With Trisomy 12 Home To The Bone Marrow In a CXCR4-Independent Manner and Are Prone To Proliferate In Vitro

Blood ◽

10.1182/blood.v122.21.870.870 ◽

2013 ◽

Vol 122 (21) ◽

pp. 870-870

Author(s):

Evelyn Hutterer ◽

Elisabeth Hinterseer ◽

Sylvia Ganghammer ◽

Gabriele Brachtl ◽

Daniela Asslaber ◽

...

Keyword(s):

Bone Marrow ◽

Chronic Lymphocytic Leukemia ◽

Research Funding ◽

Lymphocytic Leukemia ◽

Dependent Manner ◽

Independent Manner ◽

Atypical Cell ◽

Trisomy 12 ◽

Inside Out

Abstract Trisomy 12 (tri12) is a frequent chromosomal aberration in chronic lymphocytic leukemia (CLL) associated with atypical cell morphology, high in vivo tumor proliferation activity and a predisposition to Richter’s transformation. Tri12 harboring CLL cells express increased levels of the negative prognostic marker CD49d, the α4 subunit of the integrin very late antigen 4 (VLA-4), which we previously identified as a key regulator of CLL cell homing to bone marrow (BM). During this process, inside-out activation of VLA-4 upon CXCR4 binding to endothelially displayed CXCL12 is thought to upregulate the adhesive properties of VLA-4 and augment the arrest of CLL cells on the VCAM-1 presenting vessels. Here, we investigated the functional interplay of VLA-4 and CXCR4 in CLL carrying tri12. We first found that the upregulation of CD49d expression in this subset (MFIR CD49d 9.8±5.3 (n=22) vs. 2.7±3.9 (n=126), p<0.0001) was paralleled by their reduced CXCR4 expression (MFIR CXCR4 11.8±7.2 (n=22) vs. 22.7±14.2 (n=126), p=0.0003). Using short term adoptive transfers, we compared the ability of tri12 and no tri12 CLL cells to home to the BM of NOD/SCID mice. 5-10x106 CLL cells were injected into tail vein and homing was evaluated after 3 hours. Based on their more frequent CD49d high phenotype, we observed increased homing rates (homed human CLL cells per 106 injected cells per 106 acquired murine cells) of tri12 compared to no tri12 CLL (225±160 (n=7) vs. 90±117 (n=20), p=0.025). However, when comparing CD49d+ tri12 and CD49d+ no tri12 subsets, we did not observe any significant differences in their homing capacity. To further study CXCL12/CXCR4 function in BM homing, we pretreated mice with either the novel CXCL12 antagonist NOX-A12 or the CXCR4 inhibitor AMD3100 prior to CLL cell injection. While homing of no tri12 CLL cells (n=3, in duplicates) was reduced by both pretreatments (homing rates 137 vs 38 vs 30), the homing capacity of tri12 CLL cells (n=3, in duplicates) was not affected. We next tested whether VLA-4 expressed on these cells was able to undergo CXCL12-induced activation and support cell arrest under shear conditions. To this end, we perfused CLL cells over VCAM-1 or VCAM-1/CXCL12 substrates and analyzed rates and categories of cell tethering at a single cell level by videomicroscopy. CXCL12 induced the arrests of no tri12 CLL cells (n=3) on VCAM-1 under shear flow in a CXCR4 and VLA-4 dependent manner. In contrast, tri12 CLL cells (n=3) robustly tethered to VCAM-1 in the absence of the chemokine, and interactions could not be further enhanced by additional CXCL12 nor could they be abrogated by use of AMD3100. This failure of CXCR4-induced adhesion was not based on a general defect in CXCR4 functionality as in vitro chemotaxis of tri12 CLL cells (n=5) towards CXCL12 was fully maintained. To detect potential differences in VLA-4 affinity regulation, we used a conformationally sensitive antibody that recognizes epitopes induced by VLA-4 ligation, and an LDV-containing VLA-4 specific ligand to probe resting integrin affinity. Also, we used a small fluorescent ligand to study rapid VLA-4 affinity changes during inside-out chemokine induced activation. On resting tri12 CLL, VLA-4 exhibited an affinity state similar to that observed on circulating lymphocytes, and tri12 CLL cells failed to undergo the rapid affinity up-regulation triggered by CXCL12 pretreatment, in keeping with tethering experiments. Next, we investigated whether the tumor microenvironment has a different influence on the behavior of the tri12 subset. Therefore we subjected the cells to in vitro co-cultures mimicking the lymphoid proliferation centers. Basal levels of the early activation marker CD69 were similar in tri12 CLL compared to no tri12 cases. Tri12 CLL, however, underwent stronger activation when cultured in presence of accessory cells (%CD69+ cells 60.0±18.5 (n=4) vs. 17.7±20.1 (n=19), p=0.008). Moreover, in several setups, proliferation rates of these cells were increased, irrespective of the proliferative stimulus and detection method used. In summary, our results provide a mechanistical basis at least in part explaining the peculiar and clinical features of the tri12 CLL subset. In light of the specific migratory and proliferative properties of tri12 cells and novel agents targeting particularly these functions, our findings may also imply therapeutical consequences. Disclosures: Greil: NOXXON Pharma AG: Research Funding. Hartmann:NOXXON Pharma AG: Research Funding.

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Induction of apoptotic cell death in chronic lymphocytic leukemia by 2- chloro-2'-deoxyadenosine and 9-beta-D-arabinosyl-2-fluoroadenine

Blood ◽

10.1182/blood.v81.1.143.143 ◽

1993 ◽

Vol 81 (1) ◽

pp. 143-150 ◽

Cited By ~ 213

Author(s):

LE Robertson ◽

S Chubb ◽

RE Meyn ◽

M Story ◽

R Ford ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Dna Fragmentation ◽

Dna Cleavage ◽

Light And Electron Microscopy ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Dna Integrity ◽

Drug Induced ◽

Prolonged Incubation

Abstract 2-Chloro-2′-deoxyadenosine (CldAdo) and 9-beta-D-arabinosyl-2- fluoroadenine (F-ara-A) have shown marked activity in the treatment of indolent lymphoid malignancies. Based on the susceptibility of various lymphocyte populations to apoptosis, we investigated whether CldAdo or F-ara-A would induce this process in lymphocytes from patients with chronic lymphocytic leukemia (CLL). In vitro exposure of leukemic lymphocytes to CldAdo or F-ara-A for 24 to 72 hours elicited features of apoptosis visible by light and electron microscopy. Analysis of DNA integrity showed DNA cleavage into nucleosomal-sized multimers. Using a quantitative assay, drug-induced DNA fragmentation was both time and dose dependent. Inhibition of active macromolecular synthesis did not prevent drug-induced fragmentation; however, both drug-induced and spontaneous DNA fragmentation were prevented by intracellular calcium chelation. In vitro culture with phorbol ester generally decreased drug- induced DNA cleavage. After prolonged incubation, CLL cells exhibited spontaneous cleavage; albeit, at significantly lower rates than drug- treated cells. Heterogeneity was observed for spontaneous and drug- induced DNA fragmentation and was significantly lower in B-leukemic cells obtained from patients with high-risk and refractory disease. We conclude that CldAdo and F-ara-A are potent inducers of apoptotic death in CLL and that this feature correlates with the disease status.

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