Essential role of MALT1 protease activity in activated B cell-like diffuse large B-cell lymphoma
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ABSTRACT: A key element for the development of suitable anti-cancer drugs is the identification of cancer-specific enzymatic activities that can be therapeutically targeted. Mucosa-associated lymphoid tissue transformation protein 1 (MALT1) is a proto-oncogene that contributes to tumorigenesis in diffuse large B-cell lymphoma (DLBCL) of the activated B-cell (ABC) subtype, the least curable subtype of DLBCL. Recent data suggest that MALT1 has proteolytic activity, but it is unknown whether this activity is relevant for tumor growth. Here we report that MALT1 is constitutively active in DLBCL lines of the ABC but not the GCB subtype. Inhibition of the MALT1 proteolytic activity led to reduced expression of growth factors and apoptosis inhibitors, and specifically affected the growth and survival of ABC DLBCL lines. These results demonstrate a key role for the proteolytic activity of MALT1 in DLBCL of the ABC subtype, and provide a rationale for the development of pharmacological inhibitors of MALT1 in DLBCL therapy.
Project description:A key element for the development of suitable anti-cancer drugs is the identification of cancer-specific enzymatic activities that can be therapeutically targeted. Mucosa-associated lymphoid tissue transformation protein 1 (MALT1) is a proto-oncogene that contributes to tumorigenesis in diffuse large B-cell lymphoma (DLBCL) of the activated B-cell (ABC) subtype, the least curable subtype of DLBCL. Recent data suggest that MALT1 has proteolytic activity, but it is unknown whether this activity is relevant for tumor growth. Here we report that MALT1 is constitutively active in DLBCL lines of the ABC but not the GCB subtype. Inhibition of the MALT1 proteolytic activity led to reduced expression of growth factors and apoptosis inhibitors, and specifically affected the growth and survival of ABC DLBCL lines. These results demonstrate a key role for the proteolytic activity of MALT1 in DLBCL of the ABC subtype, and provide a rationale for the development of pharmacological inhibitors of MALT1 in DLBCL therapy. HBL-1 cells (n=8) were treated with IkB kinase beta inhibitor MLN120B (25 micromolar; Calbiochem) for 2h, 3h, 4h, 6h, 8h, 12h, 16h, and 24h (Cy5) and their gene expression compared to vehicle-treated cells (DMSO, Cy3). HBL-1 cells (n=4) and OCI-Ly3 cells (n=4) were treated with MALT1 inhibitor z-VRPR-fmk (50 micromolar; Alexis Biochemicals) for 6h, 12h, 24h, and 30h (Cy5) and their gene expression compared to vehicle-treated cells (DMSO, Cy3).
Project description:The MALT1 paracaspase plays an essential role in Activated B-cell like Diffuse Large B-cell Lymphoma (ABC DLBCL) downstream of B-cell and Toll-like receptor pathway genes mutated in these tumors. Although MALT1 is considered to be a compelling therapeutic target, development of tractable and specific MALT1 protease inhibitors has thus far been elusive. Herein, we developed a target engagement assay that provides a quantitative readout for specific MALT1 inhibitory effects in living cells. This enabled a structure-guided medicinal chemistry effort culminating in a novel class of substrate-mimetic compounds that bind MALT1 active site and, constitute the first pharmacologically tractable irreversible MALT1 inhibitor. We confirmed MALT1 targeting is effective at suppressing ABC DLBCL cells in vitro and in vivo. We show that reduction in serum IL10 levels exquisitely correlates with drug PK and degree of MALT1 inhibition in vitro and in vivo and constitutes a useful pharmacodynamic biomarker to evaluate these compounds in clinical trials. Our new inhibitor revealed insights into the biology of MALT1 in ABC DLBCL, such as driving JAK-STAT signaling and suppressing type I interferon (IFN) response and MHC class II expression, suggesting that MALT1 inhibition could prime lymphomas for immune recognition by cytotoxic immune cells.
Project description:The activated B-cell–like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) represents a very aggressive human lymphoma entity. Constitutive NF-κB activation caused by chronic active B-cell receptor (BCR) signaling is common feature of many ABC DLBCL cells; however, the pathways linking BCR signaling to the NF-κB prosurvival network are largely unknown. Here we report that constitutive activity of PI3K and the downstream kinase PDK1 are essential for the viability of two ABC DLBCL cell lines that carry mutations in the BCR proximal signaling adaptor CD79B. In these cells, PI3K inhibition reduces NF-κB activity and decreases the expression of NF-κB target genes. Furthermore, PI3K and PDK1 are required for maintaining MALT1 protease activity, which promotes survival of the affected ABC DLBCL cells. These results demonstrate a critical function of PI3K-PDK1 signaling upstream of MALT1 pro- tease and NF-κB in distinct ABC DLBCL cells and provide a rationale for the pharmacologic use of PI3K inhibitors in DLBCL therapy.
Project description:Constitutive MALT1 activity drives survival of malignant lymphomas addicted to chronic B-cell receptor (BCR) signaling, oncogenic CARD11, or the API2-MALT1 fusion oncoprotein. While MALT1 scaffolding induces NF-kB-dependent survival signaling, MALT1 protease function is thought to augment NF-kB activation by cleaving signaling mediators and transcriptional regulators in B-cell lymphomas. However, the pathological role of MALT1 protease function in lymphomagenesis is not well understood. Here, we show that TRAF6 controls MALT1-dependent activation of NF-kB transcriptional responses, but is dispensable for MALT1 protease activation driven by oncogenic CARD11. To uncouple enzymatic and non-enzymatic functions of MALT1, we analyzed TRAF6-dependent and -independent as well as MALT1 protease-dependent gene expression profiles downstream of oncogenic CARD11 and API2-MALT1. By cleaving and inactivating the RNA binding proteins Regnase-1 and Roquin-1/2, MALT1 protease induces post-transcriptional upregulation of genes like NFKBIZ/IkBz, NFKBID/IkBNS and ZC3H12A/Regnase-1 in activated B-cell-like diffuse large B-cell lymphoma (ABC DLBCL). We demonstrate that oncogene-driven MALT1 activity in ABC DLBCL cells regulates NFKBIZ and NFKBID induction on mRNA level via releasing a brake imposed by Regnase-1 and Roquin-1/2. Furthermore, MALT1 protease drives post-transcriptional gene induction in the context of the API2-MALT1 fusion created by the recurrent t(11;18)(q21;q21) translocation in mucosa-associated lymphoid tissue (MALT) lymphoma. Thus, MALT1 paracaspase acts as a bifurcation point for enhancing transcriptional and post-transcriptional gene expression in malignant lymphomas. Moreover, the identification of MALT1 protease selective target genes will provides specific biomarkers for the clinical evaluation of MALT1 inhibitors.
Project description:Chronic active B cell receptor (BCR) signaling, a hallmark of the ABC subtype of diffuse large B cell lymphoma (DLBCL), engages the CARD11-MALT1-BCL10 (CBM) adapter complex to activates IkappaB kinase (IKK) and the classical NF-kappaB pathway. Here we show that the CBM complex includes the E3 ubiquitin ligases cIAP1 and cIAP2, which are essential mediators of BCR-dependent NF-kappaB activity in ABC DLBCL. cIAP1/2 attach K63-linked polyubiquitin chains on themselves and on BCL10, resulting in the recruitment of IKK and the linear ubiquitin chain ligase LUBAC, which is essential for IKK activation. SMAC mimetic drugs target cIAP1/2 for destruction, and consequently suppress NF-kappaB and selectively kill BCR-dependent ABC DLBCL lines, supporting their clinical evaluation in patients with ABC DLBCL. Four ABC DLBCL tumor biopsy samples and one ABC DLBCL cell line (YM) (n=5) were analysed for copy number gains using the Affymetrix Genome-Wide Human SNP 6.0 Array. CEL files are being made available through dbGaP
Project description:Attempts at modeling chromosomal translocations involving MALT1 gene, hallmarks of human mucosa-associated lymphoid tissue (MALT) lymphoma, have failed to reproduce the disease in mice. Here we describe a transgenic model in which MALT1 expression was targeted to mouse hematopoietic stem/progenitor cells. In Sca1-MALT1 mice, MALT1 deregulation activated the NF-kappaB pathway in Sca1+ cells, promoting selective B-cell differentiation and mature lymphocyte accumulation in extranodal tissues, progressively leading to the development of clonal B-cell lymphomas. These tumors recapitulated the histopathological features of human MALT lymphomas, presenting typical lymphoepithelial lesions and plasmacytic differentiation. Transcriptional profiling of Sca1-MALT1 murine lymphomas revealed overlapping molecular signatures with human MALT lymphomas, including MALT1-mediated NF-kappaB activation, pro-inflammatory signaling and XBP1-induced plasmacytic differentiation. Moreover, murine Malt1 showed proteolytic activity by cleaving Bcl10 in Sca1-MALT1 lymphomas. Our novel technological approach has allowed modeling human MALT lymphoma in mice, which represent unique tools study MALT lymphoma biology and evaluate anti-MALT1 therapies. Keywords: lymphoma profiling, MALT lymphoma 97 samples were analized of which 13 were normal B-cell purified subpopulations and 84 lymphoma samples (31 MALT lymphomas, 26 DLBCL, 15 FCL and 12 SMZL)
Project description:Chronic active B cell receptor (BCR) signaling, a hallmark of the ABC subtype of diffuse large B cell lymphoma (DLBCL), engages the CARD11-MALT1-BCL10 (CBM) adapter complex to activates IkappaB kinase (IKK) and the classical NF-kappaB pathway. Here we show that the CBM complex includes the E3 ubiquitin ligases cIAP1 and cIAP2, which are essential mediators of BCR-dependent NF-kappaB activity in ABC DLBCL. cIAP1/2 attach K63-linked polyubiquitin chains on themselves and on BCL10, resulting in the recruitment of IKK and the linear ubiquitin chain ligase LUBAC, which is essential for IKK activation. SMAC mimetic drugs target cIAP1/2 for destruction, and consequently suppress NF-kappaB and selectively kill BCR-dependent ABC DLBCL lines, supporting their clinical evaluation in patients with ABC DLBCL. Samples from four ABC DLBCL cell lines (HBL1, TMD8, OCILY3, and OCILY10) were exposed to 2.5 uM birinapant for 2, 4, 6, and 24 hours (n=16). Samples from 2 ABC DLBCL cell lines (HBL1 and TMD8) were transduced with shRNA and induced with doxycycline for 3 and 4 days (n=4).
Project description:The paracaspase Malt1 is a central regulator of antigen receptor signaling that is frequently mutated in human lymphoma. As a scaffold, it assembles protein complexes for NF-kB activation, and its proteolytic domain cleaves negative NF-kB regulators for signal enforcement. Still, the physiological functions of Malt1-protease are unknown. We demonstrate that targeted Malt1-paracaspase inactivation induces a lethal inflammatory syndrome with lymphocyte-dependent neurodegeneration in vivo. Paracaspase activity is essential for regulatory T-cell and innate-like B-cell development, but it is largely dispensable for overcoming Malt1-dependent thresholds for lymphocyte activation. In addition to NF-kB inhibitors, Malt1 cleaves an entire set of mRNA stability regulators, including Roquin-1, Roquin-2 and Regnase-1, and paracaspase inactivation results in excessive IFNγ production by effector lymphocytes that drives pathology. Together, our results reveal distinct threshold and modulatory functions of Malt1 that differentially control lymphocyte differentiation and activation pathways and demonstrate that selective paracaspase blockage skews systemic immunity towards destructive autoinflammation.
Project description:Chronic active B cell receptor (BCR) signaling, a hallmark of the ABC subtype of diffuse large B cell lymphoma (DLBCL), engages the CARD11-MALT1-BCL10 (CBM) adapter complex to activates IkappaB kinase (IKK) and the classical NF-kappaB pathway. Here we show that the CBM complex includes the E3 ubiquitin ligases cIAP1 and cIAP2, which are essential mediators of BCR-dependent NF-kappaB activity in ABC DLBCL. cIAP1/2 attach K63-linked polyubiquitin chains on themselves and on BCL10, resulting in the recruitment of IKK and the linear ubiquitin chain ligase LUBAC, which is essential for IKK activation. SMAC mimetic drugs target cIAP1/2 for destruction, and consequently suppress NF-kappaB and selectively kill BCR-dependent ABC DLBCL lines, supporting their clinical evaluation in patients with ABC DLBCL.