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Transcriptional profiling of murine germinal center (GC) B cells from GC-specific conditional Crebbp and Ep300 knock-out mice

ABSTRACT: Inactivating mutations of the CREBBP acetyltransferase and, at lower frequencies, its paralogue EP300 are among the most common genetic alterations in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL), the two most frequent B cell malignancies. Here we uncover unexpected distinct functions for CREBBP and EP300 in the germinal center (GC), i.e. the target structure for most human B cell lymphomas. We show that these proteins modulate non-overlapping transcriptional programs that are preferentially enriched in biological functions associated with the separate anatomic compartments of the GC. Consistently, deletion of CREBBP or EP300 have opposing effects on GC formation in vivo. Nonetheless, these proteins partially compensate for each other to maintain a minimal threshold of acetyltransferase activity and guarantee homeostatic control of the GC, which is completely abrogated by their combined loss. This synthetic lethal interaction is retained in DLBCL cells, identifying an Achille’s heel in CREBBP-mutant lymphomas that could be pharmacologically targeted by using a novel, selective small molecule inhibitor of the CREBBP/EP300 bromodomain. These data shed light on the unique roles of CREBBP and EP300 in the physiology and pathology of GC B cells, and provide a proof-of-principle for the development and testing of EP300 inhibition as a therapeutic strategy in these diseases.

ORGANISM(S): Mus musculus

PROVIDER: GSE124192 | GEO | 2021/06/01

REPOSITORIES: GEO

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H3K27Ac mapping in isogenic CREBBP-WT, CREBBP-KO and EP300-KO SUDHL4 cell lines

Project description:Inactivating mutations of the CREBBP acetyltransferase and, at lower frequencies, its paralogue EP300 are among the most common genetic alterations in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL), the two most frequent B cell malignancies. Here we uncover unexpected distinct functions for CREBBP and EP300 in the germinal center (GC), i.e. the target structure for most human B cell lymphomas. We show that these proteins modulate non-overlapping transcriptional programs that are preferentially enriched in biological functions associated with the separate anatomic compartments of the GC. Consistently, deletion of CREBBP or EP300 have opposing effects on GC formation in vivo. Nonetheless, these proteins partially compensate for each other to maintain a minimal threshold of acetyltransferase activity and guarantee homeostatic control of the GC, which is completely abrogated by their combined loss. This synthetic lethal interaction is retained in DLBCL cells, identifying an Achille’s heel in CREBBP-mutant lymphomas that could be pharmacologically targeted by using a novel, selective small molecule inhibitor of the CREBBP/EP300 bromodomain. These data shed light on the unique roles of CREBBP and EP300 in the physiology and pathology of GC B cells, and provide a proof-of-principle for the development and testing of EP300 inhibition as a therapeutic strategy in these diseases.

2020-02-19 | GSE132365 | GEO

Transcriptomic profile of germinal center B cells from conditional GC-specific (Cg1-Cre) Crebbp-HET, Kmt2d-HET, and compound Crebbp-HET/Kmt2d-HET mice, with littermate controls

Project description:Inactivating mutations of the KMT2D methyltransferase and the CREBBP acetyltransferase are among the most common genetic alterations in B-cell lymphoma and co-occur in 40-60% of follicular lymphoma (FL) and diffuse large B cell lymphoma (DLBCL) cases, suggesting they may be co-selected. Here we show that combined germinal center (GC)-specific haploinsufficiency of Crebbp and Kmt2d synergize in vivo to promote the expansion of abnormal GCs, a common pre-neoplastic event. These enzymes form a biochemical complex on selected enhancers/super-enhancers that are critical for the delivery of signals in the GC light-zone and are only corrupted upon dual Crebbp/Kmt2d loss, both in mouse GC B cells and in human DLBCLs. Moreover, we find that CREBBP directly acetylates KMT2D in GC-derived B cells. Accordingly, inactivation of CREBBP by FL/DLBCL-associated truncating and/or missense mutations abrogates its ability to catalyze KMT2D acetylation. Importantly, genetic and pharmacologic loss of CREBBP and the consequent decrease in KMT2D acetylation leads to reduced levels of H3K4me1, supporting a role for acetylation in modulating KMT2D activity. These data identify a direct biochemical and functional interaction between CREBBP and KMT2D, with implications for their role as tumor suppressors in FL/DLBCL and for the development of combinatorial therapies targeting enhancer defects induced by their loss.

2023-02-28 | GSE220255 | GEO

CARM1 inhibition reduces histone acetyltransferase activity causing synthetic lethality in CREBBP/EP300 mutated lymphomas [RNA-seq_Toledo]

Project description:Somatic mutations affecting CREBBP and EP300 are a hallmark of Diffuse Large B Cell Lymphoma (DLBCL). These mutations are frequently monoallelic, within the histone acetyltransferase (HAT) domain and usually mutually exclusive, suggesting that they might affect a common pathway and their residual WT expression is required for cell survival. Using in vitro and in vivo models, we found that inhibition of CARM1 activity (CARM1i) slows DLBCL growth and that the levels of sensitivity are positively correlated with the CREBBP/EP300 mutation load. Conversely, treatment of DLBCLs that do not have CREBBP/EP300 mutations with CARM1i and a CBP/p300 inhibitor revealed a strong synergistic effect. Our mechanistic data show that CARM1i further reduces the HAT activity of CBP genome wide and downregulates CBP target genes in DLBCL cells, resulting in a synthetic lethality that leverages the mutational status of CREBBP/EP300 as a biomarker for the use of small molecule inhibitors of CARM1 in DLBCL and other cancers.

2020-06-18 | GSE152667 | GEO

CARM1 inhibition reduces histone acetyltransferase activity causing synthetic lethality in CREBBP/EP300 mutated lymphomas [RNA-seq_MEF]

2020-06-18 | GSE152666 | GEO

CARM1 inhibition reduces histone acetyltransferase activity causing synthetic lethality in CREBBP/EP300 mutated lymphomas [ChIP-seq]

2020-06-18 | GSE152665 | GEO

Identification of CREBBP bound genes in germinal center B cells

Project description:Inactivating mutations of the gene encoding for the CREBBP acetyltransferase are highly frequent in diffuse large B cell lymphoma (DLBCL, 30% of cases) and follicular lymphoma (FL, 60% of cases), the two most common cancers derived from the germinal-center (GC). However, the role of CREBBP inactivation in lymphomagenesis remains unclear. Using functional epigenomics and mouse genetics, here we define the program modulated by CREBBP in primary human GC B cells and show that CREBBP regulates enhancer/super-enhancer networks, with specific roles in GC/post-GC cell fate decisions. Conditional GC-specific deletion of Crebbp in the mouse perturbs the expression of a limited set of genes involved in the regulation of signal transduction (BCR, TLR and CD40), lineage specification (NF-κB and BCL6) and terminal B cell differentiation (PRDM1, IRF4). Consistently, Crebbp-deficient B cells exhibit proliferative advantage and show impaired plasma cell differentiation. While GC-specific loss of Crebbp was not sufficient to initiate malignant transformation, compound Crebbp-haploinsufficient/BCL2-transgenic mice, mimicking the genetics ofFL and DLBCL, display an increased incidence of clonal lymphoid malignancies recapitulating the features of the human diseases. These findings establish CREBBPas a haploinsufficient tumor suppressor gene in GC B cells and provide insights into the mechanisms and targets by which loss of CREBBP contributes to lymphomagenesis.

2017-01-11 | GSE89688 | GEO

Gene expression profile analysis of germinal center B cells from conditional Crebbp knockout mice and littermate controls

Project description:Inactivating mutations of the gene encoding for the CREBBP acetyltransferase are highly frequent in diffuse large B cell lymphoma (DLBCL, 30% of cases) and follicular lymphoma (FL, 60% of cases), the two most common cancers derived from thegerminal-center (GC). However, the role of CREBBP inactivation in lymphomagenesisremains unclear. Using functional epigenomics and mouse genetics, here we definethe program modulated by CREBBP in primary human GC B cells and show thatCREBBP regulates enhancer/super-enhancer networks, with specific roles in GC/post-GC cell fate decisions. Conditional GC-specific deletion of Crebbp in the mouseperturbs the expression of a limited set of genes involved in the regulation of signaltransduction (BCR, TLR and CD40), lineage specification (NF-κB and BCL6) andterminal B cell differentiation (PRDM1, IRF4). Consistently, Crebbp-deficient B cellsexhibit proliferative advantage and show impaired plasma cell differentiation. WhileGC-specific loss of Crebbp was not sufficient to initiate malignant transformation,compound Crebbp-haploinsufficient/BCL2-transgenic mice, mimicking the genetics ofFL and DLBCL, display an increased incidence of clonal lymphoid malignanciesrecapitulating the features of the human diseases. These findings establish CREBBPas a haploinsufficient tumor suppressor gene in GC B cells and provide insights intothe mechanisms and targes by which loss of CREBBP contributes to lymphomagenesis.

2017-01-11 | GSE88799 | GEO

Array based comparative genomic hybridisation analysis of 1 Mb resolution of 21 follicular lymphomas (FL), 31 transformed diffuse large B-cells lymphomas (DLBCL), 29 de novo DLBCL (10 of GC and 19 non-GC related immunophenotype).

Project description:Follicular lymphoma (FL) is one of the most common types of indolent B-cell lymphoma in Western countries. FL commonly transforms to more aggressive diffuse large B-cell lymphoma (DLBCL) at reported frequencies between 15 - 60%. We have used microarray comparative genomic hybridisation (aCGH) at 1 Mb resolution to study copy number changes in paired tumor samples (primary FL and a subsequent tDLBCL) as well as de novo DLBCL cases to outline genetic mechanisms of transformation from follicular lymphoma to diffuse large B-cell lymphoma. Single hybridization per case. 21 FL, 31 transformed DLBCL, 29 de novo DLBCL (10 GC and 19 non-GC DLBCL). Tumor labelled with Cy5 and reference with Cy3. Mixture of 20 normal male or female genomic DNA was used in sex-mismatched hybridization.

2014-04-18 | E-GEOD-56884 | biostudies-arrayexpress

BCL6 repression of EP300 provides a basis for rational combinatorial therapy in diffuse large B cell lymphomas.

Project description:The BCL6 transcriptional repressor is a critical oncogene in diffuse large B-cell lymphomas (DLBCL). The specific BCL6 inhibitor RI-BPI potently kills DLBCL cells. We find that RI-BPI induces a particular gene expression signature in DLBCL. In order to identify classes of drugs that might synergize with RIBPI we examined the connectivity of this signature and found a strong association with HDAC and Hsp90 inhibitors. This was explained by the discovery that BCL6 directly represses the p300 lysine acetyltransferase and its co-factor BAT3. RI-BPI induced expression of p300 and BAT3, and p300 acetyltransferase activity, resulting in acetylation of p300 targets like p53 and Hsp90. As a consequence, RI-BPI could attenuate Hsp90 chaperone function, similar to the effect of Hsp90 and HDAC inhibitors. Induction of p300 and BAT3 was required for the anti-lymphoma effects of RI-BPI since specific blockade of either protein rescued DLBCL cells from the BCL6 inhibitor. RI-BPI synergistically killed DLBCL cells in combination with HDAC inhibitors (SAHA, TSA and VPA) and Hsp90 inhibitors (17-DMAG and PUH71). The combination of RI-BPI and SAHA, or RI-BPI and PU-H71 potently suppressed or even eradicated human DLBCL in mice. BCL6 repression of EP300 thus provides a basis for rational targeted combinatorial therapy for patients with DLBCL. Direct comparison of gene expression levels in DLBCL cell lines after 24hs of treatment with either a Bcl6 inhibitor peptide or control peptide

2010-09-21 | E-GEOD-24236 | biostudies-arrayexpress

Selective inhibition of HDAC3 targets synthetic vulnerabilities and activates immune surveillance in lymphoma

Project description:CREBBP mutations are highly recurrent in B-cell lymphomas and either inactivate its histone acetyltransferase (HAT) domain or truncate the protein. Herein, we show that these two classes of mutations yield different degrees of disruption of the epigenome, with HAT mutations being more severe and associated with inferior clinical outcome. Genes perturbed by CREBBP mutation are direct targets of the BCL6/HDAC3 onco-repressor complex. Accordingly, we show that HDAC3 selective inhibitors reverse CREBBP mutant aberrant epigenetic programming resulting in: a) growth inhibition of lymphoma cells through induction of BCL6 target genes such as CDKN1A and b) restoration of immune surveillance due to induction of BCL6-repressed IFN pathway and antigen presentation genes. By reactivating these genes, exposure to HDAC3-i restored the ability of tumor infiltrating lymphocytes to kill DLBCL cells in an MHC II and MHC I dependent manner, and synergized with PD-L1 blockade in a syngeneic model in vivo. Hence HDAC3-i represents a novel mechanism-based immune-epigenetic therapy for CREBBP mutant lymphomas.

2020-06-12 | GSE142357 | GEO

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