scholarly journals A novel 3D culture model recapitulates primary FL B cell features and promotes their survival

2021 ◽  
Author(s):  
Claire Lamaison ◽  
Simon Latour ◽  
Nelson Hélaine ◽  
Valérie Le Morvan ◽  
Julien Saint-Vanne ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
3D Model ◽  
3D Culture ◽  
Cell Encapsulation ◽  
Primary Lymphoma ◽  
B Cell Lymphomas ◽  
Dynamic Relationship ◽  
Biomechanical Forces

Non-Hodgkin B-cell lymphomas (B-NHL) mainly develop within lymph nodes (LN) as densely packed aggregates of tumor cells and their surrounding microenvironment, creating a tumor niche specific to each lymphoma subtypes. In vitro preclinical models mimicking biomechanical forces, cellular microenvironment, and 3D organization of B-cell lymphomas remain scarce, while all these parameters constitute key determinants of lymphomagenesis and drug resistance. Using a microfluidic method based on cell encapsulation inside permeable, elastic, and hollow alginate microspheres, we developed a new tunable 3D-model incorporating lymphoma B cells, extracellular matrix (ECM), and/or tonsil stromal cells (TSC). We revealed that under 3D confinement lymphoma B cells were able to form cohesive spheroids resulting from overexpression of ECM components. Moreover, lymphoma B cells and TSC dynamically formed self-organized 3D spheroids favoring spheroid growth. 3D culture induced resistance to classical chemotherapeutic agent doxorubicin, but not to BCL2 inhibitor ABT-199, identifying this approach as a relevant in vitro model to assess the activity of therapeutic agents in B-NHL. RNAseq analysis highlighted the synergy of 3D, ECM, and TSC in upregulating similar pathways in malignant B cells in vitro than those overexpressed in primary lymphoma cells in situ. Finally, our 3D model including ECM and TSC allowed long-term in vitro survival of primary follicular lymphoma B cells. In conclusion, we propose a new high throughput 3D model mimicking lymphoma tumor niche and making it possible to study the dynamic relationship between lymphoma B cells and their microenvironment and to screen new anti-cancer drugs.

Pathologic Co-Expression and Physical Interaction of c-MYC and BCL6 in B-Cell Lymphomas.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2-2 ◽  
Author(s):  
Masumichi Saito ◽  
Ryan T. Phan ◽  
Herbert C. Morse ◽  
Laura Pasqualucci ◽  
Riccardo Dalla-Favera
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Lymphoma ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Transgenic Animals ◽  
Primary Lymphoma ◽  
Physical Interaction

Abstract Deregulated expression of the proto-oncogenes BCL6 and c-MYC caused by chromosomal translocation or somatic hypermutation is common in non-Hodgkin B cell lymphoma derived from germinal center (GC) B cells, including diffuse large cell lymphoma (DLBCL) and Burkitt lymphoma (BL). Normal GC B cells express BCL6, whereas, surprisingly, they do not express c-MYC, suggesting that the expression of this oncogene in BL and DLBCL (20% of cases) is ectopic (Klein, U. et al. Proc Natl Acad Sci U S A100, 2639–2644, 2003). Here we report that c-MYC is absent in proliferating GC B cells because it is transcriptionally suppressed by BCL6, as demonstrated by the presence of specific BCL6 binding sites in the c-MYC promoter region and by chromatin immunoprecipitation experiments showing that BCL6 is bound to these sites in vivo. Thus, c-MYC escapes BCL6-mediated suppression in lymphoma leading to the co-expression of the two transcription factors, an event never observed in immunohistochemical and gene expression profile analysis of normal GC B cells. Surprisingly, co-immunoprecipitation experiments and in vitro binding experiments indicate that, when co-expressed, BCL6 and c-MYC are physically bound in a novel complex detectable in DLBCL and BL cell lines as well as in primary lymphoma cases. The formation of the BCL6/c-MYC complex has several significant functional consequences on the function of both c-MYC and BCL6: 1) a two fold, BCL6-binding dependent increase in c-MYC half-life, an event that has been shown to contribute to its oncogenic activation; 2) a synergistic increase in the ability of both BCL6 and c-MYC to suppress MIZ1-activated transcription of the p21CIP cell cycle arrest gene; 3) MYC-dependent inhibition of BCL6 acetylation by p300, an event that physiologically inactivates BCL6 via c-MYC-mediated recruitment of HDAC. Notably, the pathologic co-expression of c-MYC and BCL6 was shown to have pathologic consequences in vivo, since double transgenic BCL6/c-MYC mice display accelerated lymphoma development and the appearance of a novel GC-derived tumor phenotype not recognizable in single transgenic animals and containing the pathologic c-MYC/BCL6 complex. Thus, the pathologic co-expression and illegitimate physical interaction of BCL6 and c-MYC leads to an increase in the constitutive activity of both oncogenes. These results identify a novel mechanism of oncogenic function for BCL6 and c-MYC and a novel tumor-specific protein complex of potential therapeutic interest.

scholarly journals TC-PTP is required for the maintenance of MYC-driven B-cell lymphomas

Blood ◽  
2009 ◽  
Vol 114 (24) ◽  
pp. 5016-5023 ◽  
Author(s):  
Ryan M. Young ◽  
Avital Polsky ◽  
Yosef Refaeli
Keyword(s):  
B Cells ◽  
B Cell ◽  
Protein Tyrosine Phosphatases ◽  
Molecular Target ◽  
Cell Tumor ◽  
Tumor Proliferation ◽  
B Cell Lymphomas ◽  
Tumor Maintenance

Abstract We sought to determine the contributions of protein tyrosine phosphatases (PTPs) to the pathogenesis of B-cell lymphomas. We found that T-cell PTP (TC-PTP) was overexpressed in transformed B cells. We hypothesized that TC-PTP may be a tumor-promoting gene that is regulated by MYC overexpression in B cells. Knockdown of TC-PTP in murine tumors resulted in decreased cell viability in vitro because of an arrest in the G1 phase of the cell cycle. Furthermore, cells with reduced TC-PTP expression were unable to either engraft or expand in vivo. Taken together, these data indicate that TC-PTP is required for B-cell tumor maintenance. Our data also suggested a correlation between TC-PTP expression and MYC overexpression. To investigate this further, we used malignant murine B cells that contain a doxycycline-repressible MYC transgene. We found that repression of MYC overexpression with doxycycline reduced TC-PTP expression. Moreover, enforced expression of TC-PTP showed partial rescue of the expansion of tumor cells after suppression of MYC overexpression. These results suggest that MYC overexpression induces TC-PTP overexpression, which in turn promotes tumor proliferation, implicating TC-PTP as an important effector of the MYC-driven proliferation program in B-cell lymphomas. Thus, TC-PTP may be a suitable molecular target for the treatment of B-cell lymphomas.

GX15-070 and Bortezomib Induce Up-Regulation of BH3 Single Domain Pro-Apoptotic Proteins Puma and Noxa and Is Associated with Synergistic Anti-Tumor Activity in Rituximab-Sensitive, Rituximab-Resistant Cell Lines (RSCL and RRCL), and Primary Lymphoma Patient Specimens.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1389-1389 ◽  
Author(s):  
Elizabeth A. Gruber ◽  
Myron S. Czuczman ◽  
Scott H. Olejniczak ◽  
Joy Knight ◽  
Francisco J. Hernandez-Ilizaliturri
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
B Cell Lymphoma ◽  
Resistant Cell ◽  
Single Domain ◽  
Primary Lymphoma ◽  
B Cell Lymphomas ◽  
Bh3 Domain ◽  
In Vitro Exposure

Abstract The interactions between the members of the BH3 domain family of proteins play an important role in the development, progression, and prognosis in various subtypes of B-cell lymphomas. Therapies that selectively favor a pro-apoptotic environment are attractive strategies to overcome chemotherapy resistance in B-cell lymphomas. We previously reported that by targeting Bcl-2 family proteins with either Bcl-2 anti-sense oligonucleotides or GX15-070, a novel pan-inhibitor of the Bcl-2 family members, improved rituximab and/or chemotherapy activity in vitro and/or in vivo (Ramanarayanan J, et al, BJH2004; 127:519–30 and Hernandez-Ilizaliturri F, et al, Blood2006; 108:2502a/2523a). Recently, investigators have demonstrated that the proteasome is an important regulator of various members of Bcl-2 family proteins. In our efforts to increase the therapeutic options for B-cell lymphoma patients we studied the biological effects of GX15-070 in combination with the proteosome inhibitor bortezomib in a panel of rituximab-sensitive (RSCL) and rituximab-resistant cell lines (RRCL). Resistant clones were generated by chronic exposure of Raji, RL, or DHL-4 cells to escalating doses of rituximab with (4RH) or without (2R) human complement. In addition, we utilized lymphoma cells isolated from patients with treatment-naïve or refractory/relapsed diffuse large B-cell lymphomas (DLBCL). NHL cells were exposed in vitro to escalating doses of GX15-070 (0, 2, 5, 10 and 20μM) and/or Bortezomib (0, 2, 10 and 20nM) for 24 and 48 hrs. Changes in the expression of BH3 domain Bcl-2 proteins were studied by Western blot (i.e. Bcl-2, Mcl-1, Bcl-XL, Bad, Bid, Bax, Bak, Puma, and Noxa). NHL cell lines and DLBCL cells isolated from patients were exposed to different concentrations of GX15-070 (0 to 20μM) with or without Bortezomib (0 to 20nM). Cell viability was determined by the Cell Titer-Glow luminescent assay, and DNA synthesis was evaluated by standard [3H]-Thymidine incorporation assays at 24 and 48 hrs. Statistical differences were analyzed by Chi-square test. In vitro exposure of RRCL and RSCL to GX15-070 resulted in a significant up-regulation of Puma while in vitro exposure of the same cells to bortezomib led to a dose- and time-dependent up-regulation of Noxa and Bak. In vitro exposure of RRCL, RSCL, and primary lymphoma specimens to GX15-070 and bortezomib resulted in significant synergistic activity compared to controls. In summary, deregulation of apoptosis by BH3 inhibition with GX15-070 and bortezomib: induces the expression of BH3 single domain proteins Puma and Noxa; results in cell death and antiproliferation not only in RSCL and RRCL, but also from “treatment-refractory” primary DLBCL patient samples. Our findings strongly suggest that GX15-070 added to bortezomib may result in a novel and potent therapeutic strategy against aggressive B-cell lymphomas.

Direct Growth Inhibition of Both Mouse and Human B Cell Lymphomas by CpG Oligodeoxynucleotides

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2854-2854
Author(s):  
Reiko E Yamada ◽  
David J Betting ◽  
Michael Ahdoot ◽  
Kristopher K Steward ◽  
John M Timmerman
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
B Cell Lymphoma ◽  
B Cell Lymphomas ◽  
Cpg Oligodeoxynucleotides ◽  
Mantle Cell ◽  
Class B ◽  
Human B Cell

Abstract Abstract 2854 Immunostimulatory CpG oligodeoxynucleotides (ODN) are potent activators of T cell immunity and antibody-dependent cellular cytotoxicity (ADCC), and under study as immunotherapeutic agents for a variety of cancers, including B cell lymphomas. Recently, anti-CD20 antibody-CpG conjugates have been shown to eradicate rituximab-resistant B cell lymphoma in a syngeneic murine lymphoma model (D. Betting et al, ASH 2009). CpG is known to strongly stimulate the proliferation of normal B cells. Paradoxically, CpG has been reported to markedly inhibit the in vitro growth of the murine B cell lymphoma A20 (J. Li et al, J. Immunol. 2007), thereby prompting us to investigate the direct effects of CpGs on the growth of human B cell lymphomas. We first demonstrated that CpGs, especially those of the B class, potently inhibited proliferation of the A20 mouse B cell line in vitro by up to 81.5% (class A 58.7% and class C 52.7%). Moreover, in non-tumor bearing mice intratumoral injections of CpG activated normal B cells, while mice bearing subcutaneous A20 tumors showed suppressed tumor growth after CpG injections. Similarly, in humans, CpGs strongly stimulated the proliferation of normal peripheral blood B cells (stimulation index for class B 27.5 at 5 μg/ml). A panel of 12 human lymphoma cell lines (DLBCL, Burkitt's, mantle cell) were cultured in the presence or absence of varying concentrations of CpGs of A, B, or C classes (50, 10, or 2 μg/ml) or control ODN. Proliferation was measured by [3H]-thymidine incorporation in quadruplicate 72 hour cultures, and apoptosis measured by Annexin-V and PI flow cytometry. In contrast to the stimulation observed with normal human B cells, the proliferation of all 12 lymphoma lines were inhibited by CpGs. The strongest inhibitory effects were seen with CpG 7909, a class B CpG under clinical development for cancer therapy (Pfizer, PF-3512676). Raji cells were inhibited by 77.9%, 40.7%, and 8.8% at CpG concentrations of 50, 10, and 2 μg/ml, respectively (p≤0.01 for all comparisons vs. media alone). Among the 12 tested cell lines, the percentage growth inhibition using 50 μg/ml CpG 7909 was 61.2–80.4% for germinal center-type DLBCL (SUDHL-4, SUDHL-6, OCI-Ly19), 50–59.5% for activated B cell-type DLBCL (SUDHL-2, OCI-Ly3, OCI-Ly10), 56.4–79.3% for Burkitt's lymphomas (Raji, Ramos, Daudi, BJAB), and 69.6–69.9% for mantle cell lymphomas (Jeko-1, Granta-519). Interestingly, although all of the human cell lines expressed TLR9 by semi-quantitative RT-PCR, inhibition in the proliferation levels did not correlate with TLR9 expression levels. CpG 7909 also induced significant levels of apoptosis in Raji and Jeko-1 cells, 10.1% and 27.6% respectively at 50 μg/ml. In conclusion, we have demonstrated that CpGs have divergent effects on normal versus malignant B cells in both mouse and human systems. Delivery of CpG to mouse lymphoma cells inhibited their growth in vivo, while normal mouse B cells were activated. Furthermore, CpGs directly inhibit the proliferation of a large panel of human B cell lymphomas representing the majority of aggressive histologies. These results provide a novel mechanism of action for CpGs as therapeutic agents for B cell lymphomas. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Addition of constitutive c-myc expression to Abelson murine leukemia virus changes the phenotype of the cells transformed by the virus from pre-B-cell lymphomas to plasmacytomas.

1993 ◽  
Vol 13 (4) ◽  
pp. 2578-2585 ◽  
Author(s):  
E M Weissinger ◽  
H Mischak ◽  
J Goodnight ◽  
W F Davidson ◽  
J F Mushinski
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocytes ◽  
Leukemia Virus ◽  
B Cell Lymphomas ◽  
Immature B Cells ◽  
Abelson Murine Leukemia Virus ◽  
Murine Leukemia

Abelson murine leukemia virus (A-MuLV), a retrovirus that expresses the v-abl oncogene, characteristically induces pre-B-cell lymphomas following in vivo infection of BALB/c mice or in vitro infection of suspensions of fetal liver or bone marrow cells. ABL-MYC, a retrovirus that expresses both v-abl and c-myc, induces solely plasmacytomas in BALB/c mice. To investigate how the addition of overexpression of c-myc to that of v-abl accomplishes this dramatic change in the phenotype of the cells transformed by these closely related retroviruses, we utilized helper-free A-MuLV (psi 2) and ABL-MYC (psi 2) in vitro to infect suspensions of cells from different lymphoid tissues and purified immature and purified mature B cells. As expected, A-MuLV(psi 2) induced only pre-B-cell lymphomas in vivo and in vitro when immature B cells were present. ABL-MYC(psi 2), on the other hand, produced only plasmacytomas, even when purified immature B lymphocytes were infected in vitro. Although the A-MuLV(psi 2)-induced pre-B-cell lymphomas express easily detectable levels of c-myc mRNA, maturation into more-mature forms of B lymphocytes is blocked. The constitutively overexpressed c-myc in the ABL-MYC retrovirus abrogates this block, permits maturation of infected immature B cells, and yields transformed plasma cells.

Addition of constitutive c-myc expression to Abelson murine leukemia virus changes the phenotype of the cells transformed by the virus from pre-B-cell lymphomas to plasmacytomas

1993 ◽  
Vol 13 (4) ◽  
pp. 2578-2585
Author(s):  
E M Weissinger ◽  
H Mischak ◽  
J Goodnight ◽  
W F Davidson ◽  
J F Mushinski
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocytes ◽  
Leukemia Virus ◽  
B Cell Lymphomas ◽  
Immature B Cells ◽  
Abelson Murine Leukemia Virus ◽  
Murine Leukemia

Abelson murine leukemia virus (A-MuLV), a retrovirus that expresses the v-abl oncogene, characteristically induces pre-B-cell lymphomas following in vivo infection of BALB/c mice or in vitro infection of suspensions of fetal liver or bone marrow cells. ABL-MYC, a retrovirus that expresses both v-abl and c-myc, induces solely plasmacytomas in BALB/c mice. To investigate how the addition of overexpression of c-myc to that of v-abl accomplishes this dramatic change in the phenotype of the cells transformed by these closely related retroviruses, we utilized helper-free A-MuLV (psi 2) and ABL-MYC (psi 2) in vitro to infect suspensions of cells from different lymphoid tissues and purified immature and purified mature B cells. As expected, A-MuLV(psi 2) induced only pre-B-cell lymphomas in vivo and in vitro when immature B cells were present. ABL-MYC(psi 2), on the other hand, produced only plasmacytomas, even when purified immature B lymphocytes were infected in vitro. Although the A-MuLV(psi 2)-induced pre-B-cell lymphomas express easily detectable levels of c-myc mRNA, maturation into more-mature forms of B lymphocytes is blocked. The constitutively overexpressed c-myc in the ABL-MYC retrovirus abrogates this block, permits maturation of infected immature B cells, and yields transformed plasma cells.

EBV MicroRNA Expression in Virus Driven B-Cell Differentiation and Lymphomagenesis.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 93-93
Author(s):  
Jamie P Nourse ◽  
Pauline Crooks ◽  
Do Nguyen Van ◽  
Kimberley Jones ◽  
Nathan Ross ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Phase 1 ◽  
Differentiation Process ◽  
B Cell Differentiation ◽  
B Cell Lymphomas

Abstract Abstract 93 Lymphomagenesis is a complex process, in part reflecting the nature of the transforming event, as well as the developmental stage of the cell. In the B-cell differentiation represents a continuum that is initiated when a naïve B-cell encounters antigen, undergoes a germinal centre (GC) reaction and ends with terminal differentiation into either a memory or plasma B-cell. Interruption of this process by a transforming event may result in a clonal proliferation where differentiation of the cell is blocked at this stage. The majority of B-cell lymphomas are derived from GC or post-GC B-cells. As physiologically relevant human models that emulate the various stages of B-cell differentiation are lacking we rationalized that in-vitro utilization of the B-cell lymphotrophic Epstein-Barr virus (EBV) would provide insights into this process. In one scenario, EBV infects naïve B-cells and drives a differentiation process paralleling the GC reaction through a well-characterized series of latency gene expression programs. EBV is also implicated in a range of GC and post-GC derived B-cell lymphomas (including Burkitt's, Hodgkin's, PTLD and DLBCL). Using high efficiency EBV infection of isolated naïve B-cells from EBV seronegative subjects, we have demonstrated that EBV infection provides a highly relevant in-vitro model that accurately reflects three distinct phases in the GC differentiation process. Alterations in the expression of a broad range of genes associated with the differentiation of the naïve B-cell were observed within 24 hours of infection and within four days of infection a process exhibiting many similarities to the GC reaction had taken place. These included BCL6, the levels of which were rapidly down-regulated within 24 hours indicating activation of the naïve B-cell. Levels of the memory cell marker CD27 steadily increased over 24 to 96 hours, while BLIMP1 expression increased, peaking at 48 hours. An increase in AID expression over 8 to 48 hours was consistent with somatic hypermutation and isotype switching. Finally a dramatic elevation in expression of the GC associated oncogene LMO2 was observed after two days followed by an equally dramatic downregulation after two weeks. Within two weeks of infection (phase 1), B-cells progressed through a GC-like phase followed by a one week transition state (phase 2) after which continued culture resulted in further differentiation to cells with the phenotypic hallmarks of post-GC cells (phase 3). MicroRNAs (miRNAs) are small non-coding RNAs, which act as negative regulators of gene expression. miRNA expression reflects the developmental lineage and differentiation state of several human cancers and over-expression is implicated in lymphomagenesis. They are also associated with the development of the GC reaction. EBV expresses at least 39 unique miRNAs from the BART and BHRF1 clusters within the viral genome. These EBV miRNAs are differentially expressed in tumour cell lines, suggesting roles during EBV-driven B-cell differentiation and lymphomagenesis. The relationship between EBV miRNAs and the kinetics of EBV driven B-cell differentiation has not been characterized. In our model we find distinct miRNA expression kinetics, coincidental with gene expression changes during B-cell differentiation, suggesting that these regulatory molecules may be involved in the GC process. Although a small number of EBV miRNAs were expressed at low levels early in the GC-like phase 1, the majority were up-regulated during the transition phase 2, exhibiting a subsequent partial down-regulation in the post-GC-like phase 3. The three phases were coincident with differential BART and BHRF1 promoter usage and alternate splicing. Strikingly, application of the infection model to primary patient samples and lymphoma cell-lines revealed that lymphomas clustered within distinct phases, reflecting the full continuum of the B-cell differentiation process. Interestingly, the majority of PTLD samples clustered within the transition phase, whereas Burkitt's and Hodgkin's lymphoma sample segregated with the GC stage. Application of our gene expression and miRNA data to cell-lines and a range of GC and post-GC EBV-positive lymphomas of various histological types indicate that our B-cell differentiation model can be used to accurately classify B-cell lymphomas in a physiologically relevant manner according to the stage of arrested B-cell differentiation. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Stromal cells regulate malignant B-cell spatial organization, survival, and drug response in a new 3D model mimicking lymphoma tumor niche

2020 ◽  
Author(s):  
Claire Lamaison ◽  
Simon Latour ◽  
Nelson Hélaine ◽  
Valérie Le Morvan ◽  
Céline Monvoisin ◽  
...  
Keyword(s):  
B Cell ◽  
Stromal Cells ◽  
Drug Response ◽  
Spatial Organization ◽  
3D Model ◽  
Cell Types ◽  
Self Organized ◽  
Biomechanical Forces ◽  
3D Spheroids

ABSTRACTNon-Hodgkin B-cell lymphomas (B-NHL) mainly develop within lymph nodes as densely packed aggregates of tumor cells and their surrounding microenvironment, creating a tumor niche specific to each lymphoma subtypes. Until now, in vitro preclinical models mimicking biomechanical forces, cellular microenvironment, and 3D organization of B lymphomas remain scarce while all these parameters constitute key determinants of lymphomagenesis and drug resistance. Using a microfluidic method based on the encapsulation of cells inside permeable, elastic, and hollow alginate microspheres, we developed a new tunable 3D-model incorporating extracellular matrix and/or stromal cells. Lymphoma B cells and stromal cells dynamically formed self-organized 3D spheroids, thus initiating a coevolution of these two cell types, reflecting their bidirectional crosstalk, and recapitulating the heterogeneity of B-NHL subtypes. In addition, this approach makes it suitable to assess in a relevant in vitro model the activity of new therapeutic agents in B-NHL.

Proteinkinase C-β Inhibitors Mitigate Microenvironment-Mediated Survival Of CLL Cells and Sensitise Malignant B Cells To Cytotoxic Drugs

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 669-669
Author(s):  
Gloria Lutzny ◽  
Zhoulei Li ◽  
Madlen Oelsner ◽  
Jolanta Slawska ◽  
Thomas Kocher ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Stromal Cells ◽  
Cytotoxic Drugs ◽  
B Cell Lymphomas ◽  
Cytotoxic Effects ◽  
Pkc Β ◽  
Apoptotic Proteins

Abstract Heterotypic interactions between bone marrow stromal cells (BMSCs) and malignant B cells contribute to apoptosis-resistance of tumour cells, based on the provision of anti-apoptotic factors by stromal cells. For this reason, interference with the microenvironment may offer an alternative approach to chemotherapy to target B cell lymphomas/ leukaemias. However, the success of such treatments critically relies on specific targets expressed in the lymphoma microenvironment. We have previously reported that monoclonal B cells from patients with CLL, MCL und ALL activate and reprogram BMSCs. This activation of stromal cells is an essential prerequisite for microenvironment-mediated survival of malignant B cells and requires the induction and activation of protein-kinase C-β in stromal cells in vitro and in vivo. This is underscored by a complete resistance of PKC-β knockout mice to adoptively transferred B cell lymphomas from TCL1 transgenic mice (Lutzny et al. Cancer Cell. 2013 Jan 14; 23(1):77-92.). Analyses of primary CLL cells co-cultured on human or mouse BMSCs indicate that stromal cells protect malignant B cells from apoptosis primarily by enhancing the expression of the anti-apoptotic proteins Mcl1, XIAP, BclXL and Bcl2A1. Knockdown of Mcl1 expressed in CLL cells further demonstrates that its expression is crucial for stroma-mediated survival even in the presence of BMSCs. Since BMSC-mediated survival and propagation of CLL depends on the kinase activity of PKC-β, we hypothesized that pharmacological inhibition of the activation of stromal cells using small molecule inhibitors against PKC-β may display anti-leukemic effects. Here we report that the PKC-β inhibitor enzastaurin enhances the cytotoxic effects of standard chemotherapeutic drugs and of the BCL2-inhibitor ABT737. Dose-response analyses indicate that enzastaurin potentiates the cytotoxic effects of ABT737 in a synergistic manner, rapidly causing caspase-mediated apoptosis of malignant B cells. This drug-sensitising effect of enzastaurin is mediated by inhibition of PKC-β induced and expressed in activated stromal cells and not related to a direct cytotoxic effect on malignant B cells: PKC-β deficient BMSCs fail to maintain high expression levels of the anti-apoptotic proteins Mcl1, XIAP and Bcl2A1 in CLL cells, which show a significantly enhanced sensitivity to ABT737 compared to CLL cells cultured on PKC-β proficient stromal cells. These data provide evidence that PKC-β inhibitors can therapeutically be used to abolish microenvironment-mediated survival of malignant B cells. In order to assess whether drug combinations of enzastaurin and BCL2 inhibitors demonstrate synergistic anti-lymphoma effects in vivo, we adoptively transferred malignant B cells from diseased TCL1 mice into wild-type recipient mice. Tumour-bearing mice were treated with enzastaurin, ABT199 or a combination of both drugs. Response to treatment, assessed by PET-CT scan, indicates that the combination of enzastaurin and ABT199 is superior to single agent treatment. These data indicate that malignant B cells can be sensitized to cytotoxic drugs by inhibiting the tumour-promoting effects of the lymphoma microenvironment with PKC-β inhibitors. Our preclinical in vitro and in vivo experiments justify testing this drug combination as a new approach to leukaemia/ lymphoma therapy in a phase I/II clinical trial. Disclosures: No relevant conflicts of interest to declare.

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