BCL2-Family Dysregulation in B-Cell Malignancies: From Gene Expression Regulation to a Targeted Therapy Biomarker

BCL2-family proteins have a central role in the mitochondrial apoptosis machinery and their expression is known to be deregulated in many cancer types. Effort in the development of small molecules that selectively target anti-apoptotic members of this family i.e., Bcl-2, Bcl-xL, Mcl-1 recently opened novel therapeutic opportunities. Among these apoptosis-inducing agents, BH3-mimetics (i.e., venetoclax) led to promising preclinical and clinical activity in B cell malignancies. However, several mechanisms of intrinsic or acquired resistance have been described ex vivo therefore predictive markers of response as well as mechanism-based combinations have to be designed. In the present study, we analyzed the expression of the BCL2-family genes across 10 mature B cell malignancies through computational normalization of 21 publicly available Affimetrix datasets gathering 1,219 patient samples. To better understand the deregulation of anti- and pro-apoptotic members of the BCL2-family in hematological disorders, we first compared gene expression profiles of malignant B cells to their relative normal control (naïve B cell to plasma cells, n = 37). We further assessed BCL2-family expression according to tissue localization i.e., peripheral blood, bone marrow, and lymph node, molecular subgroups or disease status i.e., indolent to aggressive. Across all cancer types, we showed that anti-apoptotic genes are upregulated while pro-apoptotic genes are downregulated when compared to normal counterpart cells. Of interest, our analysis highlighted that, independently of the nature of malignant B cells, the pro-apoptotic BH3-only BCL2L11 and PMAIP1 are deeply repressed in tumor niches, suggesting a central role of the microenvironment in their regulation. In addition, we showed selective modulations across molecular subgroups and showed that the BCL2-family expression profile was related to tumor aggressiveness. Finally, by integrating recent data on venetoclax-monotherapy clinical activity with the expression of BCL2-family members involved in the venetoclax response, we determined that the ratio (BCL2+BCL2L11+BAX)/BCL2L1 was the strongest predictor of venetoclax response for mature B cell malignancies in vivo

Role of the tumor microenvironment in B cell lymphomas

Le lymphome à cellules du manteau (LCM) est un lymphome non-hodgkinien agressif associé à un mauvais pronostic. Malgré des améliorations récentes dans les stratégies thérapeutiques pour traiter le LCM, sa prise en charge demeure difficile. Des progrès technologiques dans le séquençage de nouvelle génération ont amélioré notre compréhension des anomalies intrinsèques de cellules de LCM mais le rôle des signauxextrinsèques reste largement inconnu. Des études récentes ont souligné le rôle central du microenvironnement du LCM dans la survie, la prolifération et la chimiorésistance des cellules tumorales. La caractérisation des niches tumorales du LCM et la compréhension des dialogues entre les cellules tumorales et les cellules environnantes au sein de leurmicroenvironnement sont nécessaires pour améliorer l’efficacité des traitements. Dans ce travail de thèse, nous présentons une revue de la littérature des niches tumorales du LCM ainsi que nos travaux sur le rôle du microenvironnement dans les lymphomes B. Ces connaissances apportent un rationnel pour l’élaboration de nouvelles stratégies thérapeutiques pour pallier à la chimiorésistance durant le traitement du LCM.Mantle cell lymphoma (MCL) is an aggressive non-Hodgkin lymphoma associated with poor prognosis, and despite recent improvements in the therapeutic strategies for treating MCL, its management remains challenging. While improvements in next generation sequencing technologyhave greatly increased our understanding of the intrinsic abnormalities of MCL, the role of extrinsic signaling remains largely unknown. Recent studies have highlighted the central role of the MCLmicroenvironment in tumor cell survival, drug resistance and proliferation. Characterization of the diverse MCL tumoral niches and comprehension of the crosstalk between tumor cells and surrounding cells within the MCL microenvironment are needed to increase treatment efficacy. In this work, we present a revue of MCL microenvironment and our results on the role of tumoral niches in B lymphomas. This knowledge could be rapidly translated into new therapeuticstrategies to overcome drug resistance during MCL treatment

Rationale for targeting tumor cells in their microenvironment for mantle cell lymphoma treatment

International audienceMantle cell lymphoma (MCL) is an aggressive non-Hodgkin lymphoma associated with poor prognosis, and despite recent improvements in the therapeutic strategies for treating MCL, its management remains challenging. While improvements in next generation sequencing technology have greatly increased our understanding of the intrinsic abnormalities of MCL, the role of extrinsic signaling remains largely unknown. Recent studies have highlighted the central role of the MCL microenvironment in tumor cell survival, drug resistance and proliferation. Characterization of the diverse MCL tumoral niches and comprehension of the crosstalk between tumor cells and surrounding cells within the MCL microenvironment are needed to increase treatment efficacy. Here, we reviewed the recent findings regarding the MCL microenvironment that could be rapidly translated into new therapeutic strategies to overcome drug resistance during MCL treatment

BCL2-Family Dysregulation in B-Cell Malignancies: From Gene Expression Regulation to a Targeted Therapy Biomarker

International audienceBCL2-family proteins have a central role in the mitochondrial apoptosis machinery and their expression is known to be deregulated in many cancer types. Effort in the development of small molecules that selectively target anti-apoptotic members of this family i.e., Bcl-2, Bcl-xL, Mcl-1 recently opened novel therapeutic opportunities. Among these apoptosis-inducing agents, BH3-mimetics (i.e., venetoclax) led to promising preclinical and clinical activity in B cell malignancies. However, several mechanisms of intrinsic or acquired resistance have been described ex vivo therefore predictive markers of response as well as mechanism-based combinations have to be designed. In the present study, we analyzed the expression of the BCL2-family genes across 10 mature B cell malignancies through computational normalization of 21 publicly available Affimetrix datasets gathering 1,219 patient samples. To better understand the deregulation of anti-and pro-apoptotic members of the BCL2-family in hematological disorders, we first compared gene expression profiles of malignant B cells to their relative normal control (naïve B cell to plasma cells, n = 37). We further assessed BCL2-family expression according to tissue localization i.e., peripheral blood, bone marrow, and lymph node, molecular subgroups or disease status i.e., indolent to aggressive. Across all cancer types, we showed that anti-apoptotic genes are upregulated while pro-apoptotic genes are downregulated when compared to normal counterpart cells. Of interest, our analysis highlighted that, independently of the nature of malignant B cells, the pro-apoptotic BH3-only BCL2L11 and PMAIP1 are deeply repressed in tumor niches, suggesting a central role of the microenvironment in their regulation. In addition, we showed selective modulations across molecular subgroups and showed that the BCL2-family expression profile was related to tumor aggressiveness. Finally, by integrating recent data on venetoclax-monotherapy clinical activity with the expression of BCL2-family members involved in the venetoclax response, we determined that the ratio (BCL2+BCL2L11+BAX)/BCL2L1 was the strongest predictor of venetoclax response for mature B cell malignancies in vivo. Q1

Pannexin‐1 limits the production of proinflammatory cytokines during necroptosis

International audienceThe activation of mixed lineage kinase-like (MLKL) by receptor-interacting protein kinase-3 (RIPK3) controls the execution of necroptosis, a regulated form of necrosis that occurs in apopto-sis-deficient conditions. Active oligomerized MLKL triggers the exposure of phosphatidylserine residues on the cell surface and disrupts the plasma membrane integrity by forming lytic pores. MLKL also governs endosomal trafficking and biogenesis of small extracellular vesicles as well as the production of proin-flammatory cytokines during the early steps of necroptosis; however, the molecular basis continues to be elucidated. Here, we find that MLKL oligomers activate Pannexin-1 (PANX1) channels , concomitantly to the loss of phosphatidylserine asymmetry. This plasma membrane "leakiness" requires the small GTPase RAB27A and RAB27B isoforms, which regulate intracellu-lar vesicle trafficking, docking, and fusion with the plasma membrane. Although cells in which PANX1 is silenced or inhibited normally undergo necroptotic death, they display enhanced production of cytokines such as interleukin-8, indicating that PANX1 may tamper with inflammation. These data identify a novel signaling nexus between MLKL, RAB27, and PANX1 and propose ways to interfere with inflammation associated with necroptosis

CSF1R and BTK inhibitions as novel strategies to disrupt the dialogue between mantle cell lymphoma and macrophages: MCL/macrophage protumoral interplay

International audienceThe microenvironment strongly influences mantle cell lymphoma (MCL) survival, proliferation and chemoresistance. However, little is known regarding the molecular characterization of lymphoma niches. Here, we focused on the interplay between MCL cells and associated monocytes/macrophages. Using circulating MCL cells (n=58), we showed that, through the secretion of CSF1 and, to a lesser extent, IL-10, MCL polarized monocytes into specific CD163+ M2-like macrophages (MϕMCL). In turn, MϕMCL favored lymphoma survival and proliferation ex vivo. We next demonstrated that BTK inhibition abrogated CSF1 and IL-10 production in MCL cells leading to the inhibition of macrophage polarization and consequently resulting in the suppression of microenvironment-dependent MCL expansion. In vivo, we showed that CSF1 and IL-10 plasma concentrations were higher in MCL patients than in healthy donors, and that monocytes from MCL patients overexpressed CD163. Further analyses of serial samples from ibrutinib-treated patients (n=8) highlighted a rapid decrease of CSF1, IL-10 and CD163 in responsive patients. Finally, we showed that targeting the CSF1R abrogated MϕMCL-dependent MCL survival, irrespective of their sensitivity to ibrutinib. These data reinforced the role of the microenvironment in lymphoma and suggested that macrophages are a potential target for developing novel therapeutic strategies in MCL

CSF1R and BTK inhibitions as novel strategies to disrupt the dialogue between mantle cell lymphoma and macrophages: MCL/macrophage protumoral interplay

International audienceThe microenvironment strongly influences mantle cell lymphoma (MCL) survival, proliferation and chemoresistance. However, little is known regarding the molecular characterization of lymphoma niches. Here, we focused on the interplay between MCL cells and associated monocytes/macrophages. Using circulating MCL cells (n=58), we showed that, through the secretion of CSF1 and, to a lesser extent, IL-10, MCL polarized monocytes into specific CD163+ M2-like macrophages (MϕMCL). In turn, MϕMCL favored lymphoma survival and proliferation ex vivo. We next demonstrated that BTK inhibition abrogated CSF1 and IL-10 production in MCL cells leading to the inhibition of macrophage polarization and consequently resulting in the suppression of microenvironment-dependent MCL expansion. In vivo, we showed that CSF1 and IL-10 plasma concentrations were higher in MCL patients than in healthy donors, and that monocytes from MCL patients overexpressed CD163. Further analyses of serial samples from ibrutinib-treated patients (n=8) highlighted a rapid decrease of CSF1, IL-10 and CD163 in responsive patients. Finally, we showed that targeting the CSF1R abrogated MϕMCL-dependent MCL survival, irrespective of their sensitivity to ibrutinib. These data reinforced the role of the microenvironment in lymphoma and suggested that macrophages are a potential target for developing novel therapeutic strategies in MCL

Rational targeted therapies to overcome microenvironment-dependent expansion of mantle cell lymphoma

International audienceKey Points • CD40L plus cytokines induces cell-cycle progression and loss of mitochondrial priming, leading to drug resistance in MCL. • CD40L plus cytokines mimics in situ molecular profiles and allows the development of new approaches by integrating the role of the microenvironment. Mantle cell lymphoma (MCL) accumulates in lymphoid organs, but disseminates early on in extranodal tissues. Although proliferation remains located in lymphoid organs only, suggesting a major role of the tumor ecosystem, few studies have assessed MCL microenvironment. We therefore cocultured primary circulating MCL cells from 21 patients several weeks ex vivo with stromal or lymphoid-like (CD40L) cells to determine which interactions could support their proliferation. We showed that coculture with lymphoid-like cells, but not stromal cells, induced cell-cycle progression, which was amplified by MCL-specific cytokines (insulin Q : 5-like growth factor-1, B-cell activating factor, interleukin-6, interleukin-10). Of interest, we showed that our model recapitulated the MCL in situ molecular signatures (ie, proliferation, NF-kB, and survival signatures). We further demonstrated that proliferating MCL harbored an imbalance in Bcl-2 family expression, leading to a consequent loss of mitochondrial priming. Of interesting, this loss of priming was overcome by the type II anti-CD20 antibody obinutuzumab, which counteracted Bcl-x L induction through NF-kB inhibition. Finally, we showed that the mitochondrial priming directly correlated with the sensitivity toward venetoclax and alkylating drugs. By identifying the microenvironment as the major support for proliferation and drug resistance in MCL, our results highlight a selective approach to target the lymphoma niche. (Blood. 2016;00(00):1-11

The IL32/BAFF axis supports prosurvival dialogs in the lymphoma ecosystem and is disrupted by NIK inhibition

International audienceAggressive B-cell malignancies, such as mantle cell lymphoma (MCL), are microenvironment-dependent tumors and a better understanding of the dialogs occurring in lymphoma protective ecosystems will provide new perspectives to increase treatment efficiency. To identify novel molecular regulations, we performed a transcriptomic analysis based on the comparison of circulating (n=77) versus MCL lymph nodes (n=107) together with RNA sequencing of malignant (n=8) versus normal B-cell (n=6) samples. This integrated analysis led to the discovery of microenvironment-dependent and tumor-specific secretion of the interleukin-32 beta (IL32β), whose expression was confirmed in situ within MCL lymph nodes by multiplex immunohistochemistry. Using ex vivo models of primary MCL cells (n=23), we demonstrated that, through the secretion of IL32β, the tumor was able to polarize monocytes into specific MCL-associated macrophages, which in turn favor tumor survival. We highlighted that while IL32β-stimulated macrophages secreted several protumoral factors, they supported tumor survival through a soluble dialog, mostly driven by BAFF. Finally, we demonstrated the efficacy of selective NIK/alternative-NFNB inhibition to counteract microenvironment-dependent induction of IL32β and BAFF-dependent survival of MCL cells. This data uncovered the IL32β/BAFF axis as a previously undescribed pathway involved in lymphoma-associated macrophages polarization and tumor survival, which could be counteracted through selective NIK inhibition

BTG1 mutation yields supercompetitive B cells primed for malignant transformation.

Multicellular life requires altruistic cooperation between cells. The adaptive immune system is a notable exception, wherein germinal center B cells compete vigorously for limiting positive selection signals. Studying primary human lymphomas and developing new mouse models, we found that mutations affecting BTG1 disrupt a critical immune gatekeeper mechanism that strictly limits B cell fitness during antibody affinity maturation. This mechanism converted germinal center B cells into supercompetitors that rapidly outstrip their normal counterparts. This effect was conferred by a small shift in MYC protein induction kinetics but resulted in aggressive invasive lymphomas, which in humans are linked to dire clinical outcomes. Our findings reveal a delicate evolutionary trade-off between natural selection of B cells to provide immunity and potentially dangerous features that recall the more competitive nature of unicellular organisms