NFkB in multiple myeloma - EJM IkBa super-repressor
Ontology highlight
ABSTRACT: Mechanisms of constitutive NF-kappaB signaling in multiple myeloma are unknown. An inhibitor of IkappaB kinase beta (IKKbeta), targeting the classical NF-kappaB pathway, was lethal to many myeloma cell lines. Several had elevated expression of NIK due to genomic alterations or enhanced protein stability while others had inactivating mutations or deletion of TRAF3. Both abnormalities triggered the classical and alternative NF-kappaB pathways. A majority of primary myeloma patient samples and cell lines had elevated NF-kappaB target gene expression, often associated with genetic and epigenetic alteration of NIK, TRAF3, CYLD, BIRC2/BIRC3, CD40, NFKB1, and NFKB2. These genetic and functional data demonstrate that addiction to the NF-kappaB pathway is a frequent feature of myeloma and suggest that IKKbeta inhibitors hold promise for the treatment of this disease. Keywords: time series design
Project description:Mechanisms of constitutive NF-kappaB signaling in multiple myeloma are unknown. An inhibitor of IkappaB kinase beta (IKKbeta), targeting the classical NF-kappaB pathway, was lethal to many myeloma cell lines. Several had elevated expression of NIK due to genomic alterations or enhanced protein stability while others had inactivating mutations or deletion of TRAF3. Both abnormalities triggered the classical and alternative NF-kappaB pathways. A majority of primary myeloma patient samples and cell lines had elevated NF-kappaB target gene expression, often associated with genetic and epigenetic alteration of NIK, TRAF3, CYLD, BIRC2/BIRC3, CD40, NFKB1, and NFKB2. These genetic and functional data demonstrate that addiction to the NF-kappaB pathway is a frequent feature of myeloma and suggest that IKKbeta inhibitors hold promise for the treatment of this disease. Keywords: time series design
Project description:Mutations involving the NFKB pathway are present in at least 17% of multiple myeloma (MM) tumors and 40% of MM cell lines (MMCL). These mutations, which are thought to be progression events, enable MM tumors to become less dependent on extrinsic bone marrow signals that activate NFKB. Studies on a panel of 50 MMCL provide some clarification of the mechanisms through which these mutations act and the significance of classical vs alternative activation of NFKB. First, only one mutation (NFKB2) selectively activates the alternative pathway, whereas several mutations (CYLD, NFKB1, TACI) selectively activate the classical pathway. However, most mutations affecting NIK level (NIK, TRAF2, TRAF3, cIAP1&2, CD40) activate the alternative but often both pathways. Second, we confirm the critical role of TRAF2 in regulating NIK degradation, whereas TRAF3 enhances but is not essential for cIAP1/2-mediated proteosomal degradation of NIK in MM. Third, using transfection to selectively activate the classical or alternative NFKB pathways, we show virtually identical changes in gene expression in one MMCL, whereas the changes are similar albeit non-identical in a second MMCL. Together, our results suggest that MM tumors can achieve increased autonomy from the bone marrow microenvironment by mutations that activate either NFKB pathway.
Project description:Inflammation is beneficial when it is part of the innate immune response, but harmful when it occurs in an unregulated, chronic manner. We now report that IkappaB-beta, a member of the classical IkappaB family, serves a dual role of both inhibiting and facilitating the inflammatory response. IkappaB-beta degradation releases NF-kappaB dimers which upregulate proinflammatory target genes such as TNF-alpha. Suprisingly absence of IkappaB-beta results in a dramatic reduction of TNF-alpha in response to LPS even though the activation of NF-kappaB is normal. The inhibition of TNF-alpha mRNA expression can be correlated to the absence of nuclear, hypophosphorylated-IkappaB-beta bound to p65:cRel heterodimers at a specific kappaB site on the TNF-alpha promoter. Therefore IkappaB-beta acts through p65:cRel dimers to maintain prolonged expression of TNF-alpha. As a result, IkappaB-beta knockout mice are resistant to LPS induced septic shock and collagen-induced arthritis, and therefore blocking IkappaB-beta might be a promising new strategy for selectively inhibiting the chronic phase of TNF-alpha producting during the inflammatory response.
Project description:NF-kB pathway activation is the hallmark of hematological malignancies. In multiple myeloma (MM), a large variety of genomic alterations leading to either inactivation of repressor such as TRAF3, CYLD or cIAP1/2 or amplification of activators such as CD40 or NIK collectively contribute to frequently deregulate NF-kB signaling. In order to evaluate the prognostic impact of NF-kB mutations in MM, we performed a comprehensive analysis of a panel of newly diagnosed patients with cIAP1/2 biallelic deletion. We found that all patients have dysregulated NF-kB pathway and the majority of them presented t(4;14). Then we analyzed clinical outcome of 37 MM at presentation with t(4;14) and treated with bortezomib according to their NF-kB status. We showed that increase of NF-kB activity confers prolonged event-free survival. Altogether, our data suggest that NF-kB activation resulting from NF-kB mutations (ie cIAP1/2 deletion) or other mechanisms improves outcome of t(4;14)-positive MM treated with bortezomib.
Project description:Inflammation is beneficial when it is part of the innate immune response, but harmful when it occurs in an unregulated, chronic manner. We now report that IkappaB-beta, a member of the classical IkappaB family, serves a dual role of both inhibiting and facilitating the inflammatory response. IkappaB-beta degradation releases NF-kappaB dimers which upregulate proinflammatory target genes such as TNF-alpha. Suprisingly absence of IkappaB-beta results in a dramatic reduction of TNF-alpha in response to LPS even though the activation of NF-kappaB is normal. The inhibition of TNF-alpha mRNA expression can be correlated to the absence of nuclear, hypophosphorylated-IkappaB-beta bound to p65:cRel heterodimers at a specific kappaB site on the TNF-alpha promoter. Therefore IkappaB-beta acts through p65:cRel dimers to maintain prolonged expression of TNF-alpha. As a result, IkappaB-beta knockout mice are resistant to LPS induced septic shock and collagen-induced arthritis, and therefore blocking IkappaB-beta might be a promising new strategy for selectively inhibiting the chronic phase of TNF-alpha producting during the inflammatory response. Wild type and IkappaB-beta knockout BMDM cells were stimulated with LPS(1ug/ml) for 0, 1, and 5 hours. RNA isolated from the cells was analyzed on Affymetrix Mouse Genome 430A 2.0 gene expression chip.
Project description:Classical Hodgkin lymphoma (cHL) is one of the most common malignant lymphomas. It is characterized by the presence of rare Hodgkin and Reed/Sternberg (HRS) cells embedded in an extensive inflammatory infiltrate. Constitutive activation of nuclear factor-kappaB (NF-kappaB) in HRS cells which transcriptionally regulates expression of multiple anti-apoptotic factors and pro-inflammatory cytokines plays a central role in the pathogenesis of cHL (1, 2). In non-stimulated condition, NF-kappaB proteins are rendered inactive by binding to their inhibitors (IkappaB s), which sequester them in the cytoplasm. Stimulation of multiple receptors activates the IkappaB kinase (IKK) complex that phosphorylates IkappaB at two specific serine residues, followed by its ubiquitination and proteasomal degradation, thereby releasing NF-kappaB proteins and allowing their nuclear translocation (3). Recently, two studies provided further insights into the molecular mechanisms of IKK activation upon TNF stimulation (4, 5). Activation of the IKK complex and subsequent NF-kappaB activation requires Lys63 polyubiquitination of RIP1, a kinase which is recruited to the receptor upon TNF stimulation. IKK-gamma (NEMO), the regulatory subunit of the IKK complex, specifically recognizes these Lys63-linked polyubiquitins attached to RIP1 and thereby activates IKK and NF-kappaB (4, 5). A20 is an ubiquitin-modifying enzyme that inhibits NF-kappaB activation in succession of tumor necrosis factor (TNF) receptor and Toll-like receptor induced signals (6-8). This enzyme removes Lys63 linked ubiquitin chains from RIP1 and adds Lys48 polyubiquitins to RIP1, thereby targeting this factor for proteasomal degradation, thus explaining the molecular mechanism of NF-kappaB inhibition by A20 (6). A20 likely inhibits NF-kappaB acitivity also by additional means, including interaction with TRAF1 and TRAF2 (9).
Project description:Classical Hodgkin lymphoma (cHL) is one of the most common malignant lymphomas. It is characterized by the presence of rare Hodgkin and Reed/Sternberg (HRS) cells embedded in an extensive inflammatory infiltrate. Constitutive activation of nuclear factor-kappaB (NF-kappaB) in HRS cells which transcriptionally regulates expression of multiple anti-apoptotic factors and pro-inflammatory cytokines plays a central role in the pathogenesis of cHL (1, 2). In non-stimulated condition, NF-kappaB proteins are rendered inactive by binding to their inhibitors (IkappaB s), which sequester them in the cytoplasm. Stimulation of multiple receptors activates the IkappaB kinase (IKK) complex that phosphorylates IkappaB at two specific serine residues, followed by its ubiquitination and proteasomal degradation, thereby releasing NF-kappaB proteins and allowing their nuclear translocation (3). Recently, two studies provided further insights into the molecular mechanisms of IKK activation upon TNF stimulation (4, 5). Activation of the IKK complex and subsequent NF-kappaB activation requires Lys63 polyubiquitination of RIP1, a kinase which is recruited to the receptor upon TNF stimulation. IKK-ï§ï (NEMO), the regulatory subunit of the IKK complex, specifically recognizes these Lys63-linked polyubiquitins attached to RIP1 and thereby activates IKK and NF-kappaB (4, 5). A20 is an ubiquitin-modifying enzyme that inhibits NF-kappaB activation in succession of tumor necrosis factor (TNF) receptor and Toll-like receptor induced signals (6-8). This enzyme removes Lys63 linked ubiquitin chains from RIP1 and adds Lys48 polyubiquitins to RIP1, thereby targeting this factor for proteasomal degradation, thus explaining the molecular mechanism of NF-kappaB inhibition by A20 (6). A20 likely inhibits NF-kappaB acitivity also by additional means, including interaction with TRAF1 and TRAF2 (9). SNP 6.0 array (Affymetrix) analyses were performed according to the manufacturer's directions on DNA extracted from three Hodgkin cell lines (L1236, HDLM-2, U-HO1), HapMap samples included in the Genotyping Console Software 3.0 were used as references.
Project description:Treatment of diffuse large B-cell lymphoma (DLBCL) remains challenging due to extensive molecular, clinical, and pathological heterogeneity. Here, we report recurrent focal deletions of the chr14q32.31-32 locus, including TRAF3, a negative regulator of NF-κB signaling, in a cohort of uniformly-treated de novo DLBCL (24/324 cases). Integrative analysis uncovered a correlation between TRAF3 copy number loss and TRAF3 reduced expression. CRISPR-mediated TRAF3 loss-of-function (LOF) in DLBCL cell lines enhanced non-canonical NF-κB (NC NF-κB) signaling, rendering cells sensitive to shRNA-induced knockdown of the central NC NF-κB kinase, NIK. NIK pharmacological inhibitors differentially impaired proliferation, and induced apoptosis of TRAF3 LOF cells, further suggesting an acquired onco-addiction to NC NF-κB. Beyond these cell-intrinsic effects, co-culturing of TRAF3 LOF DLBCL cells with primary human CD8+ T-cells revealed an impairment in effector marker induction (Granzyme B, IFNγ) and proliferation in the latter. Accordingly, a reduction in T-cell infiltrates was observed in the microenvironment of TRAF3-low expressing primary DLBCL tumor samples. Neutralization of IL10 produced by TRAF3 LOF cells restored and enhanced GZMB and IFNγ expression in co-cultured CD8+ T-cells. Our findings demonstrate a direct relationship between TRAF3 genetic alterations and NC NF-κB activation, favoring pro-oncogenic cell-intrinsic effects and immune-evasive mechanisms, and highlight NIK as a therapeutic target in defined subset of DLBCL.
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.
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.