Project description:Using ChIP-seq we identified the genome wide targets of BCL6 and LSD1 in lymhpoma cells (OCI-Ly1) with control siRNA or siRNA targeted to BCL6
Project description:BCL6 is a key oncogene in lymphoma pathogenesis. The expression of BCL6 in lymphoid cells can be deregulated by several mechanisms, including chromosomal translocations, somatic mutations in the promoter regulatory regions or reduced proteasome-mediated degradation. FBXO11 was recently identified as a major ubiquitin ligase involved in the degradation of BCL6 and is frequently inactivated in diffuse large B-cell lymphoma (DLBCL). In this work, we found that FBXO11 is frequently mutated in Burkitt lymphoma (BL) but rarely mutated in other BCL6-positive lymphomas, such as follicular lymphoma (FL). All mutations tested impaired FBXO11 mediated BCL6 degradation and FBXO11 knock-out completely stabilized BCL6 levels in human BL cell lines. Conditional deletion of one copy or both copies of FBXO11 in c-Myc-driven B cell lymphoma in mice accelerated lymphomagenesis, genetically confirming that FBXO11 is a haplo-insufficient oncosuppressor in lymphoma. In both FBOX11 WT and deficient BL mouse and human cell lines, blockade of BCL6 via a specific degrader or BCL6 inhibitors, impaired lymphoma growth in vitro and in vivo, an effect further enhanced by co-inhibition of c-Myc activity. Overall these findings not only establish FBXO11 as one of the most frequently mutated genes in BL, but also elucidate its biological functions in lymphomagenesis and thereby identify BCL6 as a specific therapeutic target in BL.
Project description:Using RNA-seq we identified the gene expression changes in GC B cells from LSD1 wild-type or LSD1-deficient mice immunized with T cell dependent antigens (Sheep Red Blood cells)
Project description:Using ChIP-seq, we identified the genome-wide targets of BCL6 and LSD1 in lymphoma cells SUDHL4 and performed H3K4me1 ChIP-seq in cells treated with control siRNA or siRNA targeted to BCL6.
Project description:The goal of this experiment is to measure the changes in gene expression induced by small molecules that either inhibit the interaction of the transcription factor BCL6 with co-repressor proteins, or that induce degradation of BCL6, in lymphoma cell lines.
Project description:The EZH2 histone methyltransferase mediates the humoral immune response and drives lymphomagenesis through de novo formation of bivalent chromatin domains at critical germinal center (GC) B cell promoters. Herein we show that the actions EZH2 in driving GC formation and lymphoma precursor lesions are dependent on the presence of the BCL6 transcriptional repressor, both of which are in turn dependent on the presence of non-canonical PRC1-BCOR complex. BCL6-BCOR complexes assemble preferentially at bivalent promoters in an H3K27me3-dependent manner. We observe specific induction of the CBX8 chromodomain protein in GC B cells. CBX8 binds to H3K27me3 at bivalent promoters and is required for stable association of BCOR complex and its histone modifications. CBX8 loss of function in B cells phenocopies loss of EZH2 and H3K27me3. Moreover, oncogenic BCL6 and EZH2 cooperate to accelerate diffuse large B cell lymphoma (DLBCL) development and combinatorial targeting of these repressors results in enhanced anti-lymphoma activity in vitro, in vivo and in primary human DLBCLs. KDM2B ChIP-sequencing of OCI-Ly1 cells
Project description:EZH2 mediates the humoral immune response and drives lymphomagenesis through de novo formation of bivalent chromatin domains and critical germinal center (GC) B cell promoters. We show that such formation is dependent on the presense of BCL6 and the presence of non-canonical PRC1-BCOR complex. We observe that BCL6 and EZH2 cooperate to accelerate diffuse large B cell lymphoma (DLBCL) development and combinatorial targeting of these repressors results in enhanced anti-lymphoma activity in vitro, in vivo, and in primary human DLBCLs. DLBCL cell lines treated with BCL6 inhibitor 79-6.1085
Project description:We have found that PRMT5 methylates BCL6 and is needed for its full transcriptional repressor activity. Concomitant inhibition of both BCL6 and PRMT5 exhibits synergistic killing of BCL6-expressing lymphoma cells.
Project description:Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphomas worldwide and is characterized by a high diversity of genetic and molecular alterations. Chromosomal translocations and mutations leading to deregulated expression of the transcriptional repressor BCL6 occur in a significant fraction of DLBCL patients. An oncogenic role of BCL6 in the initiation of DLBCL has been shown as the constitutive expression of BCL6 in mice recapitulates the pathogenesis of human DLBCL. However, the role of BCL6 in tumor maintenance remains poorly investigated due to the absence of suitable genetic models and limitations of pharmacological inhibitors. Here, we have utilized tetracycline-inducible CRISPR/Cas9 mutagenesis to study the consequences of BCL6 deletion in established DLBCL models in culture and in vivo. We show that BCL6 knock-out in SU-DHL-4 cells in vitro results in an anti-proliferative response 4-7 days after Cas9 induction that was characterized by cell cycle (G1) arrest. Conditional BCL6 deletion in established DLBCL tumors in vivo induced a significant tumor growth inhibition with initial tumor stasis followed by slow tumor growth kinetics. Our findings support a role of BCL6 in the maintenance of lymphoma growth and showcase the utility of inducible CRISPR/Cas9 systems for probing oncogene addiction.
Project description:The EZH2 histone methyltransferase mediates the humoral immune response and drives lymphomagenesis through de novo formation of bivalent chromatin domains at critical germinal center (GC) B cell promoters. Herein we show that the actions EZH2 in driving GC formation and lymphoma precursor lesions are dependent on the presence of the BCL6 transcriptional repressor, both of which are in turn dependent on the presence of non-canonical PRC1-BCOR complex. BCL6-BCOR complexes assemble preferentially at bivalent promoters in an H3K27me3-dependent manner. We observe specific induction of the CBX8 chromodomain protein in GC B cells. CBX8 binds to H3K27me3 at bivalent promoters and is required for stable association of BCOR complex and its histone modifications. CBX8 loss of function in B cells phenocopies loss of EZH2 and H3K27me3. Moreover, oncogenic BCL6 and EZH2 cooperate to accelerate diffuse large B cell lymphoma (DLBCL) development and combinatorial targeting of these repressors results in enhanced anti-lymphoma activity in vitro, in vivo and in primary human DLBCLs.