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

BCLXL PROTAC degrader DT2216 targets secondary plasma cell leukemia addicted to BCLXL for survival

Secondary plasma cell leukemia (sPCL) is a rare form of aggressive plasma cell malignancy arising mostly at end-stage refractory multiple myeloma and consequently presenting limited therapeutic options. We analyzed 13 sPCL for their sensitivity to BH3 mimetics targeting either BCL2 (venetoclax) or BCLXL (A1155463) and showed that 3 sPCL were efficiently killed by venetoclax and 3 sPCL by A1155463. Accordingly, BH3 profiling of 2 sPCL sensitive to BCLXL inhibition confirmed their high BCLXL primed profile. While targeting BCLXL using BH3 mimetics induces platelets on-target drug toxicity, the recent development of DT2216, a clinical-stage BCLXL proteolysis targeting chimera PROTAC compound, provides an alternative strategy to target BCLXL. Indeed, DT2216 specifically degrades BCLXL via VHL E3 ligase, without inducing thrombocytopenia. We demonstrated in human myeloma cell lines and sPCL that sensitivity to DT2216 strongly correlated with the sensitivity to A1155463. Interestingly, we showed that low doses of DT2216 (nM range) were sufficient to specifically degrade BCLXL after 48 hours of treatment, consistent with VHL expression, in all cell lines but irrespectively to DT2216 sensitivity. In myeloma cells, DT2216 induced apoptotic cell death and triggered BAX and BAK activation. In conclusion, our study demonstrated that patients with sPCL addicted to BCLXL, a small but a very challenging group, could potentially receive therapeutic benefit from DT2216. Clinical trials of DT2216 in this subset of sPCL patients are warranted

Le rôle du complexe Mcl-1/Bim dans la régulation de l'apoptose des cellules de myélome multiple

Le myélome multiple est une tumeur plasmocytaire maligne. L'IL-6 est essentielle pour la survie de ces cellules, elle régule positivement une protéine anti-apoptotique primordiale: Mcl-1. La protéine pro-apoptotique Bim a été décrite par son interaction avec Mcl-1 et est impliquée dans l'initiation de l'apoptose. Nous montrons que les trois isoformes de Bim sont exprimées dans les cellules de myélome comme dans les lymphocytes B. Elles sont localisées à la mitochondrie, associées à Mcl-1 et Bcl-2 qui la neutraliseraient. Il n'y a pas de Bim libre. La privation en IL-6 induit l'apoptose associée à l'augmentation de Bim et à la diminution de Mcl-1. Dans les cellules apoptotiques, Bim reste lié à Bcl-2 alors qu'il est libéré de Mcl-1 pour activer Bax. Mcl-1L et BimEL sont clivées par les caspases générant des formes pro-apoptotiques qui amplifient l'apopotose. Ainsi le complexe Bim/Mcl-1 est essentiel dans la régulation de l'apoptose des ces cellules.Multiple myeloma is a plasma cell malignancy. IL-6 is essential for survival of myeloma cells, it up-regulates Mcl-1. Mcl-1 has a major role in myeloma cell survival. The pro-apoptotic protein Bim has an important role as an initiator of apoptosis. We show that the three Bim isoforms are expressed on myeloma cells as well as on B cells. They are endogenously associated to Mcl-1 and Bcl-2. Bim is preferentially co-localised in mitochondria along with the anti-apoptotic counterparts. They neutralise Bim since there is no free Bim. IL-6 starvation induces apoptosis associated to the simultaneous Bim up-regulation and Mcl-1 diminution. Upon apoptosis induction Bim/Bcl-2 complex is not modified whereas Bim/Mcl-1 complex is nearly abolished leading to Bim release and to Bax activation. Mcl-1L and BimEL are cleaved by caspases giving rise to pro-apototic fragments that contribute to the apoptosis amplification loop. Indeed, Bim/Mcl-1 complex is essential for apoptosis regulation of those cells.NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Restoring Apoptosis with BH3 Mimetics in Mature B-Cell Malignancies

International audienceApoptosis is a highly conserved mechanism enabling the removal of unwanted cells. Mitochondrial apoptosis is governed by the B-cell lymphoma (BCL-2) family, including anti-apoptotic and pro-apoptotic proteins. Apoptosis evasion by dysregulation of anti-apoptotic BCL-2 members (BCL-2, MCL-1, BCL-XL) is a common hallmark in cancers. To divert this dysregulation into vulnerability, researchers have developed BH3 mimetics, which are small molecules that restore effective apoptosis in neoplastic cells by interfering with anti-apoptotic proteins. Among them, venetoclax is a potent and selective BCL-2 inhibitor, which has demonstrated the strongest clinical activity in mature B-cell malignancies, including chronic lymphoid leukemia, mantle-cell lymphoma, and multiple myeloma. Nevertheless, mechanisms of primary and acquired resistance have been recently described and several features such as cytogenetic abnormalities, BCL-2 family expression, and ex vivo drug testing have to be considered for predicting sensitivity to BH3 mimetics and helping in the identification of patients able to respond. The medical need to overcome resistance to BH3 mimetics supports the evaluation of innovative combination strategies. Novel agents including MCL-1 targeting BH3 mimetics are currently evaluated and may represent new therapeutic options in the field. The present review summarizes the current knowledge regarding venetoclax and other BH3 mimetics for the treatment of mature B-cell malignancies

Repression of Mcl-1 and disruption of the Mcl-1/Bak interaction in myeloma cells couple ER stress to mitochondrial apoptosis

International audienceAs myeloma cells actively produce and secrete immunoglobulins, they are prone to ER stress, which if unresolved leads to apoptosis. We found that myeloma cell death induced by the ER stressor Thapsi-gargin was highly variable, ranging from 2 to 89%. Induction of ATF4 and CHOP was observed in myeloma cells under Thapsigargin independently of cell death. The decrease in Mcl-1 was associated with protein translation inhibition and identified as a crucial factor in Thapsigargin sensitivity, since it was the only Bcl-2 family protein differentially modified between sensitive and resistant myeloma cells. Bak but not Bax was found to contribute to Thapsigargin-induced apoptosis. Appropriately, a basal Mcl-1/Bak interaction was demonstrated in Thapsigargin-sensitive cells. Of note, the only pro-apoptotic protein freed from Mcl-1 under Thapsigargin was Bak, whereas Mcl-1/Noxa or Mcl-1/Bim complexes were simultaneously increased. Thus, the disruption of the basal Mcl-1/Bak complex in Thapsigargin-sensitive cells seemed to be an essential event in cell death induction, probably favored by the induced Noxa and Bim BH3-only proteins. These findings underscore the implication of the Mcl-1/Bak axis in myeloma cell death triggered by Thapsigargin

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

Curcumin induces cell death of the main molecular myeloma subtypes, particularly the poor prognosis subgroups

International audienceMultiple myeloma (MM), a plasma cell malignancy, remains incurable despite the development of new therapies. Curcumin anti-tumor effects were previously characterized in multiple myeloma, however only few MM cell lines were included in these studies. Since myeloma is a heterogeneous disease it is important to address the impact of myeloma molecular heterogeneity in curcumin cell death induction. In the present study, a large panel of human myeloma cell lines (HMCLs) (n = 29), representing the main molecular MM subgroups, was screened for curcumin sensitivity. We observed that curcumin cell death induction was heterogeneous, of note 16 HMCLs were highly sensitive to curcumin (LD50 < 20.5 μM), 6 HMCLs exhibited intermediate LD50 values (20.5 μM ≤ LD50 < 32.2 μM) and only 7 HMCLs were weakly sensitive (35 < LD50 < 56 μM). Cell lines harboring the t(11;14) translocation were less sensitive (median LD50 32.9 μM) than non-t(11;14) (median LD50 17.9 μM), which included poor prognosis t(4;14) and t(14;16) cells. Interestingly, curcumin sensitivity was not dependent on TP53 status. For the first time we showed that primary myeloma cells were also sensitive, even those displaying del(17p), another poor prognosis factor. We also unravel the contribution of anti-apoptotic Bcl-2 family molecules in curcumin response. We found that down-regulation of Mcl-1, an essential MM survival factor, was associated with curcumin-induced cell death and its knockdown sensitized myeloma cells to curcumin, highlighting Mcl-1 as an important target for curcumin-induced apoptosis. Altogether, these results support clinical trials including curcumin in association with standard therapy