Project description:Gene expression profiling (GEP) divides DLBCL according to the cell of origin into GCB, ABC and unclassifiable, exhibiting different mutational profiles. The Hans algorithm, a surrogate of GEP, classifies cases expressing CD10, BCL6 and MUM1 as GCB but it is not clear whether all these cases correspond to GCB-type. Accordingly, LBCL with IRF4 rearrangement usually expresses GCB phenotype (CD10+, BCL6+) together with strong MUM1/IRF4.
Project description:Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease, with at least one-third of its patients not responding to the current chemotherapy regimen, R-CHOP. By gene expression profiling, patients with DLBCL can be categorized into two clinically relevant subtypes: activated B-cell (ABC) DLBCL and germinal center B-cell (GCB). Patients with ABC DLBCL have a worse prognosis, and are defined by chronic, overactive signaling through the B-cell receptor and NF-κB pathways. We examined the effects of the Src family kinase (SFK) inhibitor dasatinib in a panel of ABC and GCB DLBCL cell lines, and found that the ABC DLBCL cell lines are much more sensitive to dasatinib than the GCB DLBCL cell lines. However, using multiplexed inhibitor bead coupled to mass spectrometry (MIB/MS) kinome profiling competition and western blot analysis, both subtypes display inhibition of the SFKs in response to dasatinib after both short- and long-term treatment. MIB/MS analyses revealed several cell cycle kinases, including CDK4, CDK6, and the Aurora kinases, are inhibited by dasatinib treatment in the ABC DLBCL subtype, but not in the GCB DLBCL subtype. The present findings have important implications for the clinical use of dasatinib for the treatment of ABC DLBCL, either alone or in combination with other agents.
Project description:Rationale: The BCL6 oncogene is constitutively activated by chromosomal translocations and amplification in ABC-DLBCLs, a class of DLBCLs that respond poorly to current therapies. Yet the role of BCL6 in maintaining these lymphomas has not been investigated. BCL6 mediates its effects by recruiting corepressors to an extended groove motif. Development of effective BCL6 inhibitors requires compounds exceeding the binding affinity of these corepressors. Objectives: To design small molecule inhibitors with superior potency vs. endogenous BCL6 ligands for unmet putative therapeutic needs such as targeting ABC-DLBCL. Findings: We used an in silico drug design functional-group mapping approach called SILCS to create a specific BCL6 inhibitor with 10-fold greater potency than endogenous corepressors. The compound, called FX1, binds in such a way as to occupy an essential region of the BCL6 lateral groove. FX1 disrupts BCL6 repression complex formation, reactivates BCL6 target genes, and mimics the phenotype of mice engineered to express BCL6 with lateral groove mutations. This compound eradicated established DLBCLs xenografts at low doses. Most strikingly, FX1 suppressed ABC-DLBCL cells as well as primary human ABC-DLBCL specimens ex vivo. Conclusions: ABC-DLBCL is a BCL6 dependent disease that can be targeted by novel inhibitors able to exceed the binding affinity of natural BCL6 ligands.
Project description:To identify differentially expressed genes regulated by FOXP1 in DLBCL cells via gene expression profiling of GCB-DLBCL (DB, K422) and ABC-DLBCL (OCI-Ly3, HBL-1) cell lines treated with siRNA targeting FOXP1 or non-silencing siRNA control. Two GCB-DLBCL (DB, K422) and two ABC-DLBCL (OCI-Ly3, HBL-1) cell lines were each treated separately with two independent siRNA oligonucleotides targeting FOXP1 (siFOXP1_308, siFOXP1_309) or non-silencing siRNA (siCtrl). Biological replicates derived from three independent experiments were obtained, RNA-extracted and subsequently hybridized into a human microarray platform for gene expression profiling.
Project description:Multi-agent chemotherapy still represents the first-line standard-of-care treatment for diffuse large B-cell lymphoma (DLBCL), the most common form of lymphoma in adults. However, the clinicopathological and molecular heterogeneity of DLBCLs poses a major challenge in their successful therapy. At least two major subtypes, i.e. germinal center B-cell-like (GCB) and the aggressive activated B-cell-like (ABC) DLBCL, which differ both in their gene expression profile and in their mutation patterns, have been identified. Here we demonstrate a broad inhibitory effect of dimethyl fumarate (DMF) on the outgrowth of both DLBCL subtypes, even though the molecular basis for its efficacy differs between GCB and ABC DLBCL. Due to high expression of arachidonate 5-lipoxygenase in concert with low glutathione and glutathione peroxidase 4 levels, DMF induced lipid peroxidation and thus ferroptotic cell death in GCB DLBCL. In contrast, in ABC DLBCL inhibition of NF-κB and STAT3 activity essentially contributed to DMF-dependent cytotoxicity. Interestingly, the BCL-2 specific BH3 mimetic ABT-199 or an inhibitor of the ferroptosis suppressor protein 1 synergized with DMF treatment in inducing cell death in DLBCL cell lines. Collectively, our findings identify the established and approved drug DMF as a promising novel therapeutic option in the treatment of both GCB and ABC DLBCL.
Project description:To identify differentially expressed genes regulated by FOXP1 in DLBCL cells via gene expression profiling of GCB-DLBCL (DB, K422) and ABC-DLBCL (OCI-Ly3, HBL-1) cell lines treated with siRNA targeting FOXP1 or non-silencing siRNA control.
Project description:B cell receptor (BCR) signaling has emerged as a therapeutic target in B cell lymphomas, but the precise deployment of inhibitors to target oncogenic BCR signaling requires detailed knowledge of the signaling cascades that the BCR triggers in individual tumors. Here, we have used CRISPR-Cas9 screens to investigate whether the ABC and GCB molecular subtypes of diffuse large B cell lymphoma (DLBCL) utilize distinct BCR signaling modes to sustain their proliferation and survival. Constitutive germinal center (GC) BCR signaling in GCB DLBCLs requires the BCR, CD19 and SYK engaging PI(3) kinase for survival. In ABC DLBCLs with oncogenic mutations in the BCR and MYD88, a novel BCR-TLR9-MYD88 signaling supercomplex is assembled on endolysosomal membranes that engages NF-kB. Our data explain why this subset of ABC DLBCL tumors respond frequently to ibrutinib, an inhibitor of BCR-dependent NF- kB activation, while GCB DLBCLs are insensitive, and thus provide a roadmap for the rational development of BCR pathway inhibitors in molecular subtypes of DLBCL.
Project description:The ABC subtype of diffuse large B cell lymphoma (DLBCL) remains the least curable form of this lymphoma despite recent advances in therapy. We have combined structural and functional genomics to triangulate on new oncogenic mechanisms and devise new therapeutic strategies. RNA interference screen revealed a dependence of ABC DLBCL cell lines on MYD88 and IRAK1. High throughput resequencing of RNA (RNA-Seq) revealed frequent somatic mutations in MYD88 that preferentially occurred in the ABC DLBCL subtype. Remarkably, one third of ABC DLBCL tumor samples harbored the same amino acid substitution, L265P, in the MYD88 TIR domain at an evolutionarily invariant residue in its hydrophobic core. This mutation was rare or absent in two other DLBCL subtypes, but was observed in 9% of MALT lymphomas. At a lower frequency, multiple other mutations were observed in the MYD88 TIR domain, occurring in both the ABC and GCB subtypes of DLBCL. Survival of ABC DLBCL lines bearing the L265P mutation was sustained by the mutant but not wild type MYD88 isoform, demonstrating that this MYD88 mutant is oncogenic and gain-of-function. The MYD88 L265P mutant assembled a protein complex that spontaneous triggers the phosphorylation of IRAK1, leading to NF-kB signaling, secretion of the cytokines IL-6, IL-10 and interferon-b, and JAK kinase signaling. These findings demonstrate that the MYD88 signaling pathway is integral to the pathogenesis of ABC DLBCL, providing a genetic rationale for therapeutic targeting of the MYD88 signaling pathway in this lymphoma subtype. To generate a gene expression signature of MYD88 signaling in ABC DLBCL, the HBL-1 cell line was transduced with retroviral vectors expressing either shMYD88-4 or shMYD88-7. Following puromycin selection, shRNA expression was induced for 24 or 48 hours and gene expression was measured, comparing uninduced (Cy3) to induced (Cy5) cells, using genome-wide Agilent 4x44K oligonucleotide microarrays. A signature of NF-kB signaling in ABC DLBCL was generated by treating HBL-1 cells with the IkB kinase beta inhibitor MLN120B for 2h, 3h, 4h, 6h, 8h, 12h, 16h, and 24h (Cy5), and comparing their gene expression to untreated cells (Cy3). A signature of JAK signaling in ABC DLBCL was generated by treating HBL-1 cells with JAK inhibitor I (5 micromolar; Calbiochem) for 2h, 4h, 6h, and 8h (Cy5) and comparing their gene expression to vehicle-treated cells (DMSO, Cy3). RNA-Seq data not provided.
Project description:Refractory/relapsed diffuse large B-cell lymphoma (DLBCL) has a poor prognosis. Novel drugs targeting the constitutively activated NF- B pathway characteristic of ABC-DLBCL are promising, but evaluation depends on accurate activated B cell-like (ABC)/germinal center B cell-like (GCB) molecular classification. This is traditionally performed on gene microarray expression profiles of fresh biopsies, which are not routinely collected, or by immunohistochemistry on formalin-fixed, paraffin-embedded (FFPE) tissue, which lacks reproducibility and classification accuracy. We explored the possibility of using routine archival FFPE tissue for gene microarray applications. We examined Affymetrix HG U133 Plus 2.0 gene expression profiles from paired archival FFPE and fresh-frozen tissues of 40 ABC/GCB-classified DLBCL cases to compare classification accuracy and test the potential for this approach to aid the discovery of therapeutic targets and disease classifiers in DLBCL. Unsupervised hierarchical clustering of unselected present probe sets distinguished ABC/GCB in FFPE with remarkable accuracy, and a Bayesian classifier correctly assigned 32 of 36 cases with >90% probability. Enrichment for NF- B genes was appropriately seen in ABC-DLBCL FFPE tissues. The top discriminatory genes expressed in FFPE separated cases with high statistical significance and contained novel biology with potential therapeutic insights, warranting further investigation. These results support a growing understanding that archival FFPE tissues can be used in microarray experiments aimed at molecular classification, prognostic biomarker discovery, and molecular exploration of rare diseases.