Project description:High expression of the FOXP1 transcription factor distinguishes the highly aggressive Activated B Cell (ABC) type of Diffuse Large B Cell Lymphoma (DLBCL) from the more indolent Germinal Center (GCB) DLBCL subtype and is correlated with poor prognosis. A genetic or functional role for FOXP1 in lymphomagenesis and/or tumor maintenance, however, remains unknown. Here, we report that sustained expression of FOXP1 is necessary for ABC DLBCL cell line survival. Genome-wide transcript profiling reveals that FOXP1 acts directly and indirectly by enforcing expression of known ABC DLBCL hallmarks, including the classical NF-kappaB survival pathway. Our data further suggest that FOXP1 maintains the ABC subtype distinction by repressing gene expression programs dominant in GCB DLBCL and supports a model in which the target of ABC DLBCL transformation is a transitory cell type en route from the germinal center B cell to the terminally differentiated plasma cell.
Project description:ChIP-Sequencing of 4 diffuse large B-cell lymphoma cell lines expressing different amounts of FOXP1 was performed in order to identify target genes bound by the transcription factor FOXP1.
Project description:Diffuse large B-cell lymphoma (DLBCL) represents the most common form of lymphoma. We could show that in DLBCL cell lines the transcription factor NFAT is constitutively activated and drives the survival of a DLBCL subset. Aim of the analysis was to identify NFAT target genes in a NFAT-dependent (HBL-1) or -independent (HT) DLBCL cell line. To block NFAT activity, the DLBCL cells were treated with the calcineurin inhibitor cyclosporin A (CsA) up to 48 h. With this approach, we identified several survival-related NFAT target genes in HBL-1 cells that might explain the toxic effects of calcineurin inhibitors.
Project description:Expression of the forkhead transcription factor FOXP1 is essential for early B cell development, whereas downregulation of FOXP1 at the germinal center (GC) stage is required for GC B cell function. Aberrantly high FOXP1 expression is frequently observed in diffuse large B cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue (MALT) lymphoma, being associated with poor prognosis. Here, by gene expression microarray [GSE51382] and quantitative RT-PCR analysis upon ectopic overexpression of FOXP1 in primary human memory B cells (MBCs) and B-cell lines, combined with chromatin immunoprecipitation-sequencing (ChIP-seq), we established that FOXP1 directly represses expression of PRDM1, IRF4, and XBP1, transcriptional master regulators of plasma cell (PC) differentiation. In accordance, FOXP1 is prominently expressed in primary human naive and MBCs but expression strongly decreases during plasma PC differentiation. Moreover, as compared to IgM+ MBCs, IgG+ MBCs combine lower expression of FOXP1 with an enhanced intrinsic PC differentiation propensity, and constitutive (over)expression of FOXP1 in B cell lines and primary human MBCs represses their ability to differentiate into PCs. Taken together, our data indicate that proper control of FOXP1 expression plays a critical role in PC differentiation, whereas aberrant overexpression of FOXP1 might contribute to lymphomagenesis by blocking terminal B cell differentiation. OXP1 ChIP-seq profile in primary human memory B cells (MBCs) and B-cell lines
Project description:Genomic profiles of DLBCL (Diffuse Large B-cell Lymphoma) patients 20 DLBCL patients were selected for detection of genomic aberrations
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.
Project description:Expression of the forkhead transcription factor FOXP1 is essential for early B cell development, whereas downregulation of FOXP1 at the germinal center (GC) stage is required for GC B cell function. Aberrantly high FOXP1 expression is frequently observed in diffuse large B cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue (MALT) lymphoma, being associated with poor prognosis. Here, by gene expression microarray [GSE51382] and quantitative RT-PCR analysis upon ectopic overexpression of FOXP1 in primary human memory B cells (MBCs) and B-cell lines, combined with chromatin immunoprecipitation-sequencing (ChIP-seq), we established that FOXP1 directly represses expression of PRDM1, IRF4, and XBP1, transcriptional master regulators of plasma cell (PC) differentiation. In accordance, FOXP1 is prominently expressed in primary human naive and MBCs but expression strongly decreases during plasma PC differentiation. Moreover, as compared to IgM+ MBCs, IgG+ MBCs combine lower expression of FOXP1 with an enhanced intrinsic PC differentiation propensity, and constitutive (over)expression of FOXP1 in B cell lines and primary human MBCs represses their ability to differentiate into PCs. Taken together, our data indicate that proper control of FOXP1 expression plays a critical role in PC differentiation, whereas aberrant overexpression of FOXP1 might contribute to lymphomagenesis by blocking terminal B cell differentiation.
Project description:Transformation of Follicular Lymphoma to Diffuse Large Cell Lymphoma: Alternative Patterns with Increased or Decreased Expression of c-myc and its Regulated genes The natural history of follicular lymphoma (FL) is frequently characterized by transformation to a more aggressive diffuse large B cell lymphoma (DLBCL). We compared the gene expression profiles between transformed DLBCL and their antecedent FL. No genes were observed to increase or decrease their expression in all the cases of histological transformation. However, two different gene expression profiles associated with the transformation process were defined, one in which c-myc and genes regulated by c-myc showed increased expression and one in which these same genes showed decreased expression. Further, there was a striking difference in gene expression profiles between transformed DLBCL and de novo DLBCL, since the gene expression profile of transformed DLBCL was more similar to their antecedent FL than to de novo DLBCL. The study demonstrates that transformation from FL to DLBCL can occur by alternative pathways and that transformed DLBCL and de novo DLBCL have very different gene expression profiles that may underlie the different clinical behaviors of these two types of morphologically similar lymphomas.
Project description:Large cell lymphomas of the gastrointestinal tract are currently regarded as diffuse large B-cell lymphomas despite a more favourable clinical outcome and a lower aggressiveness compared to other nodal and extranodal DLBCL. We compared gene expression profiles of 28 gastrointestinal marginal zone B-cell lymphomas and variants with several other B-cell lymphoma entities such as Burkitt’s lymphoma, nodal DLBCL, follicular lymphoma, mantle cell lymphoma, primary mediastinal B-cell lymphoma and normal B-cell populations. Based on a subset of NF-kappaB target genes, partitioning and hierarchical cluster algorithms were used which led to comparable results. The different B-cell subsets, the Burkitt’s lymphoma, and the small cell lymphomas formed distinct groups, respectively. The DLBCL were subdivided into one group containing only DLBCL samples, one subset clustered together with the PMBL samples, and another one together with the blastic variants of MZBL. These results implicate that extranodal blastic MZBL represent a distinct subgroup of DLBCL.