The PI3 Kinase δ Inhibitor, CAL-101 (GS-1101), Inhibits Chronic Lymphocytic Leukemia (CLL) Cell Survival in Endothelial and Marrow Stromal Cell Co-Cultures.

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1769-1769 ◽  
Author(s):  
Stefania Fiorcari ◽  
Wells S Brown ◽  
Bradley W McIntyre ◽  
Susan O'Brien ◽  
Mariela Sivina ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Endothelial Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Cell Survival ◽  
Stromal Cells ◽  
Lymphocytic Leukemia ◽  
Clinical Activity ◽  
Spontaneous Apoptosis ◽  
Cell Protection ◽  
Survival Signals

Abstract Abstract 1769 CLL cells are characterized by their ability to resist apoptosis in vivo, but in vitro they undergo spontaneous apoptosis. This suggests that interactions between CLL cells and accessory cells in the tissue microenvironments, such as mesenchymal stromal cells (MSC), nurselike cells (NLC), T-cells, and endothelial cells are critical for maintaining CLL cell survival. CLL cells display constitutive PI3K pathway activation, presumable due to CLL interactions with the microenvironment. CAL-101 is a potent and selective inhibitor of the p110d PI3K isoform and has shown promising clinical activity in chronic lymphocytic leukemia (CLL) in early stage clinical trials. Here, we investigated the ability of CAL-101 to disrupt interactions between CLL and endothelial cells (EC) or bone marrow stromal cells (BMSC). We tested two EC lines human umbilical vein endothelial cells (HUVEC) and UV-2 mouse vascular endothelial cells, and two BMSC lines, stroma-NKtert derived from human bone marrow, and KUSA-H1, a murine BMSC line. CLL cells were cultured for 72h in presence or absence of EC or BMSC. Fig A displays mean (±SEM) CLL cell viabilities of cells from 7 different patients. We found that both, EC and BMSC rescue CLL cells from spontaneous apoptosis with significantly higher CLL cell viabilities in the presence of EC and BMSC (*P< 0.05; **P< 0.01). For example, after 48h significantly higher CLL cell viabilities were noticed with HUVEC (53.2%±4.3%, p<0.05,), UV2 (61.8%±5.3%, p<0.01), stroma-NKtert (96.7%±5.3%, p<0.01) and KUSA-H1 (93.7%±0.95%, p<0.01), when compared to CLL cultured in medium alone (37.5%±4.1%). To test the effects of CAL-101 on EC- and BMSC-mediated CLL cell protection, CLL cells were cultured on ECs or BMSCs in presence or absence of CAL-101 (0.5μM and 5μM), and CLL cell viabilities were assessed at 24h, 48h and 72h. Viabilities of CAL-101 treated samples were normalized to the viabilities of control samples at the respective timepoints (100%). Fig B depicts the mean relative viabilities of CLL cells co-culture with ECs or BMCSs in presence of 5μM CAL-101, compared to CLL cells in the absence of CAL-101. We found a significant reduction of the viability of CLL cells in co-culture with EC and BMSC with both concentrations of CAL-101 (*P< 0.05; **P< 0.01; n=7). These data demonstrate that marrow stromal and endothelial cells both support the viability and protect CLL cells from apoptosis. When comparing BMSC with EC, we noticed that BMSC were more effective than EC in protecting CLL cells, which may explain why the marrow is a preferred site for residual disease and relapses in patients with CLL. CAL-101 can overcome both, BMSC- and EC-mediated CLL cell protection, indicating that CAL-101 inhibits BMSC- and EC-derived pro-survival signals. Ongoing experiments investigate the role of adhesion molecules on BMSC- and EC-derived survival signals and CLL cell adhesion to BMSC versus EC, and how adhesion molecule function is affected by CAL-101. These studies will give us better insight into the mechanism of action of this interesting new drug. Disclosures: O'Brien: Gilead: Consultancy, Research Support. Lannutti:Gilead Sciences: Employment.

Chronic Lymphocytic Leukemia-Exosomes Switch Endothelial and Mesenchymal Stromal Cells into Cancer-Associated Fibroblasts to Sustain Leukemic Cell Survival

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2927-2927 ◽  
Author(s):  
Jerome Paggetti ◽  
Franziska Haderk ◽  
Martina Seiffert ◽  
Bassam Janji ◽  
Yeoun Jin Kim ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Chronic Lymphocytic Leukemia ◽  
Cell Survival ◽  
B Lymphocytes ◽  
Stromal Cells ◽  
Leukemic Cell ◽  
Lymphoid Organs ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells

Abstract Chronic lymphocytic leukemia (CLL), the most common hematologic malignancy in Western countries, is mostly affecting the elderly over 65 year-old. CLL is characterized by the accumulation of mature but non-functional B lymphocytes of clonal origin in the blood and the primary lymphoid organs. CLL was previously considered as a relatively static disease resulting from the accumulation of apoptosis-resistant but quiescent B lymphocytes. However, recent studies using heavy water labeling indicated that CLL is in fact a very dynamic disease with alternation of proliferation phases and peripheral circulation. A focus on the trafficking of CLL cells in vivo has shown that leukemic cells circulate between the blood and the lymphoid organs but have a preference for the bone marrow. Recent next-generation sequencing of CLL cells indicated the presence of different genetic subclones. This intraclonal heterogeneity observed in CLL subpopulations may be in part determined by the interactions that leukemic cells entertain with their microenvironment when B cells migrate into the lymph nodes and the bone marrow. Indeed, tumor-stroma interactions are not only providing signals necessary for leukemic cells survival but may also influence the clonal architecture and evolution. One of these interactions involves CLL-derived exosomes. Here, we show that CLL-exosomes efficiently transfer nucleic acids, including functional microRNAs, and proteins, including MHC-Class II molecules and B-cell specific proteins, to bone marrow mesenchymal stem cells and endothelial cells. CLL-exosomes also activate signaling pathways, including PI3K and NF-κB pathways, in these stromal cells. As a consequence, gene expression is strongly modified indicating a switch towards a cancer-associated fibroblast phenotype. Functionally, exosome-stimulated stromal cells show a striking actin cytoskeleton remodeling characterized by the formation of stress fibers, and enhanced proliferation, motility and angiogenic properties. We also identified several proteins synthesized and secreted by stromal cells that promote leukemic cell adhesion and survival ex vivo. To confirm the involvement of CLL-exosomes in CLL pathology in vivo, MEC-1-eGFP cells were subcutaneously injected into immunocompromised NSG mice together with CLL-exosomes. We observed a significant increase in tumor size and a reduction in survival of exosome-treated animals. Flow cytometry analysis of selected organs indicated an enrichment in leukemic cells in the kidney, providing a potential explanation to the renal failures observed in CLL patients. In conclusion, the communication between CLL cells and stromal cells may be a critical factor influencing CLL progression by promoting leukemic cell survival. This study demonstrates the crucial role of exosomes as mediators of the communication between leukemic cells and their microenvironment. Exosomes could thus represent a suitable target for therapeutic intervention in CLL. Disclosures No relevant conflicts of interest to declare.

Increased Survival and Migration of CLL B-Cells in the Presence of Marrow Mesenchymal Stromal Cells: Novel Findings for Microenvironment-Targeted Therapies

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4571-4571
Author(s):  
Elisa Ave ◽  
Federica Frezzato ◽  
Cristina Gattazzo ◽  
Valentina Trimarco ◽  
Veronica Martini ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
B Cell ◽  
Stromal Cells ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Spontaneous Apoptosis ◽  
Parp 1 ◽  
Cells Cultured ◽  
Survival Signals

Abstract Abstract 4571 Background. The accumulation of CD19+/CD5+/CD23+ B cells with a prolonged lifespan in peripheral blood, secondary lymphoid organs and bone marrow (BM) is a peculiar feature of B-cell chronic lymphocytic leukemia (B-CLL). Since CLL cells removed from the in vivo microenvironment and in vitro cultured rapidly undergo spontaneous apoptosis, bidirectional interactions between malignant and by-stander cells may lead to an abnormal microenvironment that confers growth advantages to neoplastic clone. Mesenchymal Stromal Cells (MSCs) are the dominant marrow stromal population in indolent subtype of CLL/small lymphocytic leukemia (SLL) and follicular lymphoma (FL), rather than other aggressive B-cell lymphomas, and are involved in B-CLL cell survival. Despite the phenotypic and cytologic homogeneity, CLL is characterized by extremely variable clinical courses, suggesting that malignant B-cells hold variable degrees of dependency on pro-survival signals coming from the microenvironment. The aim of this study was to assess the role of MSCs in CLL B-cell localization and survival, defining the degree of dependency of leukemic B-cells from external pro-survival signals, with the ultimate goal of identifying patients that mostly benefit microenvironment-targeted therapies. Methods. MSCs isolated from the BM of 47 B-CLL patients were expanded ex vivo and characterized through flow cytometry analysis and differentiation cultures. Fresh isolated CLL peripheral blood mononuclear cells were co-cultured with CLL-MSCs or stromal cells and apoptosis were measured by Annexin V test and western blotting analysis (PARP-1 detection). Chemotactic assays were performed. Results. The survival of neoplastic cells ranged from 13.3% (±13.2) in leukemic cells cultured in medium alone to 58.5% (±17.2) when leukemic cells were cultured in presence of CLL-MSCs (p<0.01). Transwell experiments showed that the anti-apoptotic effect is mediated by soluble factors produced by MSCs. We investigated whether different CLL clones show a different susceptibility to spontaneous apoptosis when co-cultured in presence of MSCs recovered from B-CLL patients. The detection of the 85KDa cleaved PARP fragment in all CLL B-cells cultured in medium alone confirmed that they underwent spontaneous apoptosis. At the same time, the presence or the lacking of the cleaved fragment of PARP-1 on CLL B-cells after 7 day-co-cultures with MSCs discriminated patients into two groups: non-responder (89 kDa Parp fragment detectable) and responder (89 kDa Parp fragment not detectable) to microenvironment pro-survival signals. Finally, chemotaxis tests showed the ability of MSCs to produce and release molecules promoting the migration and the localization of neoplastic B-cells in bone marrow (Migration Index of leukemic cells: 5.1; Migration Index of normal B cells: 1.9; p<0.01). Conclusions. MSCs derived from patients with B-CLL provide survival signals to neoplastic cells, extending their lifespan and producing chemotactic factors that favour their accumulation into BM. On the other hand, CLL cells display heterogeneous responses to environmental pro-survival signals, suggesting that each CLL clone could differently react to the microenvironment protection. The blocking of the cross-talk between malignant clone and accessory cells within the microenvironment might represent an attractive novel strategy for CLL therapy. Our data provide the rationale for tailored therapies which powerfully target the cross-talk with marrow cells, particularly on patients carrying a clone more sensitive to anti-apoptotic signals coming from the microenvironment. Disclosures: No relevant conflicts of interest to declare.

PKC Inhibitor AEB071 Demonstrates Pre-Clinical Activity In Chronic Lymphocytic Leukemia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4187-4187
Author(s):  
Dalia ElGamal ◽  
Yiming Zhong ◽  
Katie Williams ◽  
Chia-Hsien Wu ◽  
Ching-Shih Chen ◽  
...  
Keyword(s):  
T Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Cell Survival ◽  
Stromal Cells ◽  
Lymphocytic Leukemia ◽  
Clinical Activity ◽  
Pkc Inhibitor ◽  
Pkc Β

Abstract Targeting B-cell receptor (BCR) downstream pathways is of therapeutic importance in eradicating chronic lymphocytic leukemia (CLL) cells. Members of the protein kinase C (PKC) family play an important role in B-cell activation. PKC-β has recently been shown to be over-expressed in CLL and essential to CLL development in the TCL1 mouse model. Mice deficient in PKC-β exhibit a survival defect in response to BCR stimulation, correlating with an inability to induce the NF-κB-dependent anti-apoptotic proteins as Bcl-xL and A1. Moreover, PKC-β-dependent activation of NF-κB in stromal cells is pivotal for the survival of B-CLL cells in vivo; wherein PKC-β inhibition was shown to prevent microenvironment protection of CLL. Additionally, PKC-β lies downstream of PLC-γ2 where activating mutations have been noted in BTK (ibrutinib) resistant patients, which conveys a potential mechanism to target resistance related to mutations in this target protein. Therefore exploration of a PCK-β inhibitor in CLL is highly justified and innovative. Sotrastaurin (AEB071) is an orally administered potent inhibitor of classical and novel PKC isotypes; with strong and specific activity on PKC-α, PKC-β and PKC-θ and lesser activity on PKC-δ, PKC-ε, and PKC-η. Pre-clinically, AEB071 has demonstrated in vivo pre-clinical activity in activated B-cell diffuse large B-cell lymphoma (DLBCL) models and is currently being tested for efficacy in CD79b mutated DLBCL. Since PKC-β is indispensable for BCR-induced NF-κB activation and B-cell survival, herein we evaluate the impact of AEB071 on CLL cell survival as a promising therapeutic to target this pathway. Our preliminary work demonstrated that AEB071 was markedly cytotoxic to CLL cells in a dose-dependent (≤6.25uM, p<0.001) and time-dependent manner (p=0.011) as measured by MTS analysis. In a whole blood assay, AEB071 exhibits a retained selective cytotoxicity against tumor cells with a modest reduction in B-CLL cells whereas no effect on T-cells or natural killer cells was detected in CLL patient samples. Notably, upon treatment of blood from healthy subjects, AEB071 showed no toxic effects on normal B-cells, T-cells and natural killer cells. AEB071 inhibits CPG-induced survival of CLL cells in vitro (p<0.01), and effectively blocks the protection induced by soluble factors such as CD40L, IL-4, and TNF (p<0.01), which are known to reduce the spontaneous apoptosis associated with CLL cells. Similar effects were observed with stromal cell contact; wherein AEB071 showed enhanced cytotoxic potency on CLL cells under co-culture conditions with stromal cells compared to CLL alone (p<0.05). Additionally, AEB071 attenuated anti-IgM-induced survival of CLL cells with a modest induction of apoptosis (p<0.001). Furthermore, treatment of PMA- or BCR-activated CLL cells with AEB071 could effectively abrogate downstream survival pathways including ERK1/2, p38MAPK, AKT, GSK3β, and NF-κB as revealed by immunoblot analysis. Collectively, this data indicate that therapeutic strategies to inhibit PKC-β have the potential to disrupt signaling from the microenvironment that lead to in vivo CLL cell survival and potentially drug resistance. Current studies are ongoing to evaluate the in vivo tolerability and therapeutic efficacy of AEB071 in the Eμ-TCL1 transgenic mouse model of CLL. In conclusion, PKC-β represents an innovative target for CLL and therefore, future efforts targeting PKC with the PKC inhibitor AEB071 as monotherapy in clinical trials of relapsed and refractory CLL patients may be warranted. Disclosures: No relevant conflicts of interest to declare.

Reconstitution of PTEN activity by CK2 inhibitors and interference with the PI3-K/Akt cascade counteract the antiapoptotic effect of human stromal cells in chronic lymphocytic leukemia

Blood ◽  
2010 ◽  
Vol 116 (14) ◽  
pp. 2513-2521 ◽  
Author(s):  
Medhat Shehata ◽  
Susanne Schnabl ◽  
Dita Demirtas ◽  
Martin Hilgarth ◽  
Rainer Hubmann ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Chronic Lymphocytic Leukemia ◽  
Stromal Cells ◽  
Molecular Mechanisms ◽  
Mononuclear Cells ◽  
Lymphocytic Leukemia ◽  
Therapeutic Concept ◽  
Antiapoptotic Effect ◽  
Human Stromal Cells ◽  
Ck2 Inhibitors

Abstract Evidence suggests that tumor microenvironment is critically involved in supporting survival of chronic lymphocytic leukemia (CLL) cells. However, the molecular mechanisms of this effect and the clinical significance are not fully understood. We applied a microenvironment model to explore the interaction between CLL cells and stromal cells and to elucidate the role of phosphatidylinositol 3 kinase (PI3-K)/Akt/phosphatase and tensin homolog detected on chromosome 10 (PTEN) cascade in this process and its in vivo relevance. Primary human stromal cells from bone marrow, lymph nodes, and spleen significantly inhibited spontaneous apoptosis of CLL cells. Pan–PI3-K inhibitors (LY294002, wortmannin, PI-103), isotype-specific inhibitors of p110α, p110β, p110γ, and small interfering RNA against PI3-K and Akt1 counteracted the antiapoptotic effect of the stromal cells. Induction of apoptosis was associated with a decrease in phosphatidylinositol-3,4,5-triphosphate, PI3-K–p85, and dephosphorylation of phosphatidylinositol-dependent kinase-1 (PDK-1), Akt1, and PTEN. Freshly isolated peripheral blood mononuclear cells from patients with CLL (n = 44) showed significantly higher levels of phosphorylated Akt1, PDK-1, PTEN, and CK2 than healthy persons (n = 8). CK2 inhibitors (4,5,6,7-tetrabromo-1H-benzotriazole, apigenin, and 5,6-dichloro-1-β-D-ribofuranosylbenzimidazol) decreased phosphorylation of PTEN and Akt, induced apoptosis in CLL cells, and enhanced the response to fludarabine. In conclusion, bone marrow microenvironment modulates the PI3-K/Akt/PTEN cascade and prevents apoptosis of CLL cells. Combined inhibition of PI3-K/Akt and recovery of PTEN activity may represent a novel therapeutic concept for CLL.

Chronic Lymphocytic Leukemia (CLL) Cells Require Microenvironmental Stimuli to Resist Apoptosis through Activation of STAT3 Mediated by VEGF.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1069-1069
Author(s):  
Iris Gehrke ◽  
Julian Paesler ◽  
Rajesh Kumar Gandhirajan ◽  
Regina Razavi ◽  
Alexandra Filipovich ◽  
...  
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Cell Survival ◽  
Lymphocytic Leukemia ◽  
Vegf Receptor ◽  
Mrna Levels ◽  
Activated State ◽  
Survival Effect

Abstract B-cell chronic lymphocytic leukemia (CLL) is characterized by an accumulation of mature, but incompetent B-cells due to a decrease of apoptosis rather than an increase in proliferation. Vascular endothelial growth factor (VEGF) has been suggested to play an important role in this so called apoptotic block. However, so far little is understood whether VEGF is acting mainly as a microenvironmental stimulus and/or whether CLL cells themselves contribute to the enhanced apoptotic resistance by maintaining an autocrine VEGF loop. Moreover, it is unknown by which mechanisms VEGF prevents apoptosis and whether this can be circumvented by inhibition of VEGF signaling. By quantitative real time PCR we found no significant difference in mRNA VEGF levels in B-cells from CLL patients and healthy donors after isolation from blood. In contrast, ELISA revealed clearly increased levels of secreted VEGF in plasma of CLL patients and in the supernatant under culture conditions compared to healthy individuals. In addition, we found the VEGF receptor 2 (VEGFR2), which is existent in CLL and healthy B-cells, in a phosphorylated, hence activated state, to a significantly higher extent in CLL cells as assessed by intracellular phospho flow cytometry. In conclusion, despite its expression in healthy B-cells VEGF does not seem to be secreted and therefore, no VEGF receptor phosphorylation takes place. Whereas CLL cells exhibit a long life span in vivo, they die rapidly in vitro, suggesting major survival factors being existent in the CLL cells microenvironment. We found levels of secreted VEGF in supernatant decreasing with time in culture, going along with decreasing levels of phosphorylated VEGFR2 and increasing cell death as assessed by Annexin V-FITC/PI staining. This further supports the role of VEGF in CLL cell survival. Coculturing primary CLL cells with the bone marrow stromal derived cell line HS5 dramatically increased VEGF transcription and secretion and improved cell survival. Hence, VEGF expression in CLL cells is not only mediated by autocrine, but also paracrine stimuli involving bone marrow stromal. Knocking down VEGF in HS5 cells and subsequent coculture with CLL cells might prove the major role of VEGF in this survival supporting coculture setting. Besides coculturing also supplement of culture medium with recombinant human VEGF (rhVEGF) increased survival, but to a lesser extent than coculture, indicating a direct cell-cell interaction as advantageous. Furthermore, we found a downregulation of anti apoptotic proteins, such as X-linked inhibitor of apoptosis protein (XIAP), myeloid cell leukemia 1 (MCL1) and BclXL upon VEGF stimulation. Also cyclinD1 was upregulated as seen by immunoblotting. We further tried to discover the underlying mechanism of how VEGF mediates its pro survival effect and found STAT3 to become phosphorylated on tyrosine 705 upon VEGF stimulation. In CLL STAT3 is known to be constitutively phosphorylated on serine 727. This phosphorylation is not sufficient to induce target gene expression though. We could show that Y705 phosphorylation of STAT3 is responsible for upregulation of anti apoptotic BCLXL and cyclinD1. A PCR array detecting mRNA levels of 84 transcription factors in untreated and VEGF stimulated CLL cells shall provide more information about mechanistical details how VEGF mediates it pro survival effect. Since VEGF seems to be a major player in CLL cell survival it might be a suitable target to overcome the apoptotic block. In first experiments we found an induction of apoptosis after neutralization of VEGF or inhibition of the VEGF receptor. This additionally highlights the severe importance of VEGF in the apoptotic block in CLL cells. Therefore, VEGF might serve as an excellent therapeutic target in CLL.

Standardizing Co-Culture Conditions Between Chronic Lymphocytic Leukemia Cells and Marrow Stromal Cells: Towards a Reliable and Reproducible System to Assess Cell Adhesion-Mediated Drug Resistance

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3149-3149
Author(s):  
Antonina Kurtova ◽  
Maite P. Quiroga ◽  
William G. Wierda ◽  
Michael Keating ◽  
Jan A. Burger
Keyword(s):  
Bone Marrow ◽  
Drug Resistance ◽  
Cell Adhesion ◽  
Chronic Lymphocytic Leukemia ◽  
Stromal Cells ◽  
Lymphocytic Leukemia ◽  
Marrow Stromal Cells ◽  
Hpv E6 ◽  
Induced Apoptosis

Abstract Contact between chronic lymphocytic leukemia (CLL) cells and accessory stromal cells in tissue microenvironments is considered to play a major role in regulating CLL cell survival and disease progression. Stromal cells of various origins and species, and variable stromal-CLL cell ratios have been used in the past to study CLL-stromal cell interactions and to assess cell-adhesion mediated drug resistance (CAM-DR). Because of the heterogeneity of the currently used in vitro systems to study CLL-MSC interactions, and the importance of these co-culture systems for development and testing of novel agents, we tested a panel of murine and human MSC lines for their capacities to support CLL cell survival and CAM-DR, using various CLL-MSC ratios and fludarabine (F-ara-A) to induce CLL cell apoptosis. We tested four murine, non-transformed MSC lines derived from bone marrow: M210B4, KUM4, ST-2 and KUSA-H1. Also, we tested three human transformed cell lines: Stroma-NKtert, derived from bone marrow and immortalized by human telomerase reverse transcriptase (hTERT), UE6E7-T2 derived from bone marrow and transformed with human papilloma viruses (HPV) E6, E7 and hTERT, and UCB408E6E7Tert33 derived from umbilical cord blood and transformed with hTERT and HPV E6, E7. CLL cells were isolated from peripheral blood of untreated patients and each cell line was tested with at least three different patients according to the following protocol: viability of CLL was tested after 24, 48 and 72 hours by flow cytometry after staining with DiOC6 and propidium iodide. The following conditions were assayed on each of the MSC lines: CLL cells in suspension culture, CLL cells in suspension culture with 10 mM F-ara-A, CLL cells in co-culture with MSC, and CLL cells in co-culture with MSC and with 10 mM F-ara-A. Firstly, we performed titration experiments in order to identify the most appropriate ratio between stromal and CLL cells, using CLL-MSC ratios of 5:1, 10:1, 20:1, 50:1 and 100:1. We found a decline in MSC-derived CLL cell protection at the highest ratio of 100:1, suggesting that ratios of 50:1 or lower provide optimal conditions for in vitro assays. Results shown in Table 1 were assayed using a 20:1 ratio and represented relative viabilities when compared to untreated controls (mean±SEM). Regarding the protective effect of different MSC, we found that all MSC lines demonstrated remarkable protection of CLL cells from spontaneous and F-ara-A-induced apoptosis. We also found that stromal cells that had round shape morphology and easily formed confluent monolayer (M210B4, KUSA-H1, Stroma-NKTert) showed more prolonged protective effect in comparison to cell lines with more spindle shaped morphology (ST-2, KUM4, UE6E7-T2). The failure of UE6E7-T2 and UCB408E6E7Tert33 to demonstrate long-term protection of CLL cells could be related to their own sensitivity to F-ara-A. In this comparative study we demonstrated that both murine and human MSC provide substantial and comparable levels of protection from spontaneous and drug-induced apoptosis. CLL:MSC ratios of 50:1 or lower can be considered ideal for co-culture experiments. Further experiments have to be done to determine the levels of MSC-derived protection in a larger series of CLL samples and in different laboratories for validation. Collectively, in these co-culture assays we can study CLL-MSC interactions and CLL drugs under more standardized conditions that may allow us to evaluate the efficacy of new treatments that target the CLL microenvironment. Time points 24 hours 48 hours 72 hours +Flu + MSC + MSC +Flu +Flu + MSC + MSC +Flu +Flu +MSC + MSC +Flu M210B4 85.2±2.4 117.2±5.0 110.5±4.9 30.8±12.6 138.1±9.5 113.0±2.2 5.2±3.1 138.1±5.1 120.4±3.4 ST-2 93.6±3.0 99.9±2.6 103.1±0.5 51.6±9.4 111.9±2.6 89.8±8.7 13.9±6.3 112.6±5.7 87.0±16.4 KUM-4 93.6±3.0 106.4±1.8 104.2±1.9 51.6±9.4 112.4±2.6 100.8±2.8 13.9±6.3 111.8±6.7 88.5±11.4 KUSA-H1 79.4±7.4 125.1±3.7 118.2±2.0 33.9±10.9 136.0±3.6 107.2±7.0 11.3±6.1 133.6±5.4 84.9±7.6 Stroma-NKTert 79.3±7.0 118.6±7.0 111.0±7.0 30.5±9.5 130.7±9.5 115.6±8.0 7.1±4.3 133.0±11.5 122.7±9.0 UE6E7-T2 79.3±7.0 113.4±3.9 109.3±3.0 30.5±9.5 118.4±4.8 85.0±7.1 7.1±4.3 119.2±6.9 51.0±10.1 UCB408 E6E7Tert33 81.5±7.2 120.2±5.4 111.8±2.7 36.7±9.4 123.7±6.3 86.7±7.7 8.5±6.7 119.7±6.1 50.8±13.0 Table 1. Flu: fludarabine (10mM/ml), MSC: marrow stromal cells

Erythroid Differentiation Regulator 1 (ERDR1) From Nurse-Like Cells Promotes the Survival of Chronic Lymphocytic Leukemia Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1372-1372
Author(s):  
Hendrik W. Van Deventer ◽  
Robert Mango ◽  
Jonathan Serody
Keyword(s):  
Bone Marrow ◽  
Chronic Lymphocytic Leukemia ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Conflicts Of Interest ◽  
Erythroid Differentiation ◽  
Mesenchymal Cells ◽  
Lymphocytic Leukemia ◽  
Leukemia Cells ◽  
Wild Type

Abstract Abstract 1372 Background: Chemotherapy resistance in chronic lymphocytic leukemia (CLL) can be mediated by anti-apoptotic signals produced by stromal or nurse-like cells. Developing strategies to overcome this resistance is hindered by the lack of suitable “stromal” targets responsible for these signals. We have discovered that erythroid differentiation regulator 1 (ERDR1) may be a candidate target for such a strategy. In this study, we show Erdr1 is generated by several stromal cell types including bone marrow stromal cells, fibrocytes, and nurse-like cells. Furthermore, inhibition of stroma-generated Erdr1 results in increased apoptosis of co-cultured CLL cells. Methods/Results: We initially identified Erdr1 on an Affymetrix array that compared the gene expression of wild type and CCR5-/- mice with pulmonary metastasis. The increased expression of Erdr1 in the wild type mice was particularly pronounced in the pulmonary mesenchymal cells. Therefore, these cells were transfected with one of two shRNAs (shRNA #9 or shRNA#11) and the survival of these cells was compared with mesenchymal cells transfected with a non-targeted control vector. After 15 days in culture, the control cells expanded normally; however, no significant expansion was seen in either the shRNA#9 or shRNA#11 transfected cells. These differences in cellular expansion were associated with differences in apoptosis. 21.4+1.6% of the Erdr1 knockdown cells were annexin V+ compared to 11.2+1.9% of the non-targeted control (p<0.03). Using GFP as a marker for transfection, we were also able to show that knockdown of Erdr1 increased the apoptosis of surrounding non-transfected mesenchymal cells. Thus, Erdr1 is a critical protein for the survival of stromal cells. Further analysis of the mesenchymal cell subpopulations revealed the greatest expression of Erdr1 in the CD45+, thy1.1+/− fibrocytes. When compared to CD45- fibroblasts, the fibrocytes expressed CCR5 and increased Erdr1 expression by 14.2+/−2.9 fold when treated with the CCR5 ligand CCL4. Given the similarities between fibrocytes and nurse-like cells, we went on to measure the effect of Erdr1 inhibition on CLL cells. In these experiments, stable Erdr1 knockdown and control clones were selected after the transfection of the bone marrow stromal cell line M2-10B4. These clones were then co-cultured with primary CLL cells. At 96 hours, leukemia cells co-cultured with the control lines had expanded by 1.33 + 0.9 compared to 0.74 + 0.22 fold in the knock-down lines (p<0.03). As before, the lack of cellular expansion was associated with an increase in apoptosis. To further show the relevance of these findings to CLL, we demonstrated that human fibrocytes and nurse-like cells expressed mRNA and protein for ERDR1 in all patient samples tested. Implications for the treatment of human disease: Our data demonstrate that ERDR1 is a critically important protein for the survival of nurse-like cells. These data suggest that targeting ERDR1 or the upstream pathway through CCR5 might be a novel approach for the treatment of CLL. Disclosures: No relevant conflicts of interest to declare.

Mode of Action of the SDF-1/CXCL12 Inhibiting Spiegelmer® Nox-A12 and Its Impact On Chronic Lymphocytic Leukemia (CLL) Cell Motility and Chemosensitization

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 318-318
Author(s):  
Dirk Zboralski ◽  
Julia Hoellenriegel ◽  
Christian Maasch ◽  
Anna Kruschinski ◽  
Jan A. Burger
Keyword(s):  
Bone Marrow ◽  
Chronic Lymphocytic Leukemia ◽  
Stromal Cells ◽  
Mode Of Action ◽  
Leukemia Cell ◽  
Lymphocytic Leukemia ◽  
Lymphoid Tissues ◽  
Cell Trafficking ◽  
Dependent Manner

Abstract Abstract 318 NOX-A12 is a novel Spiegelmer®-based antagonist of SDF-1/CXCL12, a chemokine involved in the regulation of chronic lymphocytic leukemia (CLL) cell trafficking. Spiegelmers® are mirror-image oligonucleotides that are identified to specifically bind to proteins in a manner conceptually similar to antibodies. Unlike aptamers, however, Spiegelmers® are built from the non-natural L-isomer form of nucleotides which confers resistance to the action of nucleases and avoids potential immunogenicity. CXCL12 is constitutively secreted and presented by bone marrow stromal cells (BMSC) via glycosaminoglycans (GAG) and acts as a homing factor for normal and malignant hematopoietic cells to the bone marrow (BM) and secondary lymphoid tissues via CXCR4 receptors that are expressed at high levels on circulating CLL cells. The microenvironment in the BM and secondary lymphoid tissues, in particular the CXCL12-CXCR4 axis, favors survival and chemotherapy-resistance of leukemic cells. We therefore investigated the effects of NOX-A12 in an in vitro co-culture system to model the interaction of CLL cells with their microenvironment. Surprisingly we observed that NOX-A12 increased pseudoemperipolesis in vitro, i.e. spontaneous leukemia cell migration beneath BMSC. Interestingly, this NOX-A12 induced trans-migration of CLL cells was completely inhibited by the CXCR4 antagonist AMD3100, suggesting a CXCL12/CXCR4 dependent mechanism. We postulated that this observation might result from a direct effect of NOX-A12 on CXCL12 release by the stromal cells. Therefore, we investigated this hypothesis in different BMSC lines (MS-5, R15C, and TSt-4) and we found that NOX-A12 induced a significant CXCL12 release in all three tested cell lines. We asked whether this NOX-A12 dependent increase of CXCL12 of BMSCs is due to release from either intracellular or extracellular storages. Intracellular staining of CXCL12 using flow cytometry did not reveal significant changes when BMSCs were incubated with NOX-A12. Furthermore, the transcription of CXCL12 was not found to be altered after NOX-A12 incubation over a period of three days as shown by quantitative RT-PCR. Rather, CXCL12 is released from extracellular storages of BMSCs. First hints were obtained through a rapid CXCL12 release within five minutes of incubation with NOX-A12. To confirm that CXCL12 is bound to the extracellular surface (by GAGs like heparin) and is being detached by NOX-A12 we first incubated BMSCs with NOX-A12, followed by a wash step and the addition of recombinant CXCL12. Recombinant CXCL12 was bound by BMSCs that were pre-incubated with NOX-A12 but not with a non-functional control (revNOX-A12), indicating that NOX-A12 strips off CXCL12. To corroborate the findings we incubated the BMSCs with heparin which also led to the release of CXCL12 in a dose dependent manner. Of note, the EC50 of heparin regarding CXCL12 release was much higher compared to the EC50 of NOX-A12 (≈ 12 μM vs. 5 nM) revealing the high affinity of NOX-A12 to CXCL12. The competition of NOX-A12 with heparin regarding CXCL12 binding was confirmed by Biacore experiments. Based on these findings, we developed a novel adapted co-culture approach to examine the ability of NOX-A12 to chemosensitize CLL cells. In this setting, we first strip off CXCL12 from BMSCs by NOX-A12 and subsequently add CLL cells which will be either non-treated or treated with chemotherapy (fludarabine combined with bendamustine). We found that NOX-A12 slightly decreased CLL cell viability. As expected, a strong viability decrease was observed with chemotherapy, which could be even further decreased by the combination with NOX-A12, suggesting synergistic effects. In conclusion, we propose that NOX-A12's mode of action is the release of extracellular bound CXCL12 and its subsequent inhibition. Since CXCL12 induces leukemia cell trafficking and homing to tissue microenvironment and also favors leukemia cell survival, we believe that targeting CXCL12 is an attractive approach to remove the protective effects of CXCL12-secreting BMSCs in order to sensitize CLL cells for subsequent chemotherapy. Thus, NOX-A12 represents a very promising agent to significantly improve the treatment of CLL. The compound is currently being tested in a Phase IIa study in relapsed CLL patients. Disclosures: Zboralski: NOXXON Pharma AG, Berlin, Germany: Employment. Maasch:NOXXON Pharma AG: Employment. Kruschinski:NOXXON Pharma AG: Employment. Burger:NOXXON Pharma AG: Consultancy, Research Funding.

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