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:Primary bone diffuse large B-cell lymphoma (PB-DLBCL) is a rare extranodal lymphoma subtype. This retrospective study elucidates the currently unknown genetic background of a large clinically well-annotated cohort of DLBCL with osseous localizations (O-DLBCL), including PB-DLBCL. 103 O-DLBCL patients were included and compared with 63 (extra)nodal non-osseous (NO)-DLBCLs with germinal center B-cell phenotype (NO-DLBCL-GCB). Cell-of-origin (COO) was determined by immunohistochemistry and gene-expression-profiling (GEP) using (extended)-NanoString/Lymph2Cx. Mutational profiles were identified with targeted next-generation deep-sequencing, including 52 B-cell lymphoma-relevant genes. O-DLBCLs, including 34 PB-DLBCL, were predominantly classified as GCB-phenotype based on immunohistochemistry (74%) and NanoString analysis (88%). Unsupervised hierarchical clustering of an extended-NanoString/Lymph2Cx demonstrated significantly different GEP-clusters for PB-DLBCL as opposed to NO-DLBCL-GCB (P<0.001). Expression levels of 23 genes of two different targeted GEP-panels, indicated a centrocyte–like phenotype for PB-DLBCL, whereas NO-DLBCL-GCB showed a centroblast-like constitution. PB-DLBCL had significantly more frequent mutations in four GCB-associated genes, i.e. B2M, EZH2, IRF8, and TNFRSF14, compared to NO-DLBCL-GCB (P=0.031, P=0.010, P=0.047, and P=0.003). PB-DLBCL with its corresponding specific mutational profile were significantly associated with a superior overall survival compared to equivalent Ann Arbor limited-stage I/II NO-DLBCL-GCB (P=0.011). This study is the first to demonstrate that PB-DLBCL is characterized by a GCB-phenotype, with a centrocyte-like GEP-pattern and a GCB-associated mutational profile (both involved in immune surveillance) and a favorable prognosis. These novel biology-associated features provide evidence that PB-DLBCL represents a distinct extranodal DLBCL entity and its specific mutational landscape holds potential for targeted therapies (e.g. EZH2-inhibitors). The NanoString analsyis consisted out of 219 probes for Lymph2Cx classifier (COO), MYC-activity GEP score, CNV-associated GEP signature, consensus clustering, and immune-ratio signature. This custome probeset was used to differentiate GEPs between osseous and non-osseos DLBCL of the GCB-phenotype.
Project description:Genome wide transcript and target gene profiling reveal that FOXP1 acts directly and indirectly by enforcing known ABC-DLBCL hallmarks, including Chronically Activated B cell receptor Signaling (CABS) and the classical NF-κB survival pathway. Our data further suggest that FOXP1 maintains ABC-subtype distinction by repressing gene expression programs dominant in GCB-DLBCL and support a model in which the normally transitory B cell plasmablast is the target of ABC-DLBCL transformation. ChIP sequenicng was performed for the FOXP1 transcription factor in DLBCL cell lines. Input was sequenced and used as a control.
Project description:Diffuse large B-cell lymphoma (DLBCL) represents a heterogeneous diagnostic category with distinct molecular subtypes that can be defined by gene expression profiling. However, even within these defined subtypes, heterogeneity prevails. To further elucidate the pathogenesis of these entities, we determined the expression of the tumor suppressor phosphatase and tensin homolog (PTEN) in 248 primary DLBCL patient samples. These analyses revealed that loss of PTEN was detectable in 55% of germinal center B-cell-like (GCB) DLBCLs, whereas this abnormality was found in only 14% of non-GCB DLBCL patient samples. In GCB DLBCL, the PTEN status was inversely correlated with activation of the oncogenic PI3K/ protein kinase B (AKT) pathway in both DLBCL cell lines and primary patient samples. Re-expression of PTEN induced cytotoxicity in PTEN-deficient GCB DLBCL cell line models by inhibiting PI3K/AKT signaling, indicating an addiction to this pathway in this subset of GCB DLBCLs. PI3K/AKT inhibition induced down-regulation of the transcription factor MYC. Re-expression of MYC rescued GCB DLBCL cells from PTEN-induced toxicity, identifying a regulatory mechanism of MYC expression in DLBCL. Finally, pharmacologic PI3K inhibition resulted in toxicity selectively in PTEN-deficient GCB DLBCL lines. Collectively, our results indicate that PTEN loss defines a PI3K/ AKT-dependent GCB DLBCL subtype that is addicted to PI3K and MYC signaling and suggest that pharmacologic inhibition of PI3K might represent a promising therapeutic approach in these lymphomas.
Project description:Diffuse large B-cell lymphoma (DLBCL) represents a heterogeneous diagnostic category with distinct molecular subtypes that can be deM-oM-,M-^Aned by gene expression proM-oM-,M-^Aling. However, even within these deM-oM-,M-^Aned subtypes, heterogeneity prevails. To further elucidate the pathogenesis of these entities, we determined the expression of the tumor suppressor phosphatase and tensin homolog (PTEN) in 248 primary DLBCL patient samples. These analyses revealed that loss of PTEN was detectable in 55% of germinal center B-cell-like (GCB) DLBCLs, whereas this abnormality was found in only 14% of non-GCB DLBCL patient samples. In GCB DLBCL, the PTEN status was inversely correlated with activation of the oncogenic PI3K/ protein kinase B (AKT) pathway in both DLBCL cell lines and primary patient samples. Reexpression of PTEN induced cytotox- icity in PTEN-deM-oM-,M-^Acient GCB DLBCL cell line models by inhibiting PI3K/AKT signaling, indicating an addiction to this pathway in this subset of GCB DLBCLs. PI3K/AKT inhibition induced down-regulation of the transcription factor MYC. Reexpression of MYC rescued GCB DLBCL cells from PTEN-induced toxicity, identifying a regulatory mechanism of MYC expression in DLBCL. Finally, pharmacologic PI3K inhibition resulted in toxicity selectively in PTEN-deM-oM-,M-^Acient GCB DLBCL lines. Collectively, our results indicate that PTEN loss deM-oM-,M-^Anes a PI3K/ AKT-dependent GCB DLBCL subtype that is addicted to PI3K and MYC signaling and suggest that pharmacologic inhibition of PI3K might represent a promising therapeutic approach in these lymphomas. This GEO dataset is comprised of a) GEP measurements for 34 primary DLBCL patient samples plus two reference samples, b) 8 paired GEP measurements of the HT DLBCL cell line and c) aCGH measurements for two DLBCL cell lines in addition to previously published cell lines in GSE43272 (i.e., Sample GSM1059798). All of these data were used in the paper cited below.
Project description:Diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) are the most prevalent B-lymphocyte neoplasms in which abnormal activation of the Bruton’s tyrosine kinase (BTK)–mediated B-cell receptor (BCR) signaling pathway contributes to pathogenesis. Ibrutinib is an oral covalent BTK inhibitor that has shown some efficacy in both indications. To improve ibrutinib efficacy through combination therapy, we first investigated differential gene expression in parental and ibrutinib-resistant cell lines to better understand the mechanisms of resistance. Ibrutinib-resistant TMD8 cells had higher BCL2 gene expression and increased sensitivity to ABT-199, a BCL-2 inhibitor. Consistently, clinical samples from ABC-DLBCL patients who experienced poorer response to ibrutinib had higher BCL2 gene expression. We further demonstrated synergistic growth suppression by ibrutinib and ABT-199 in multiple ABC-DLBCL, GCB-DLBCL, and FL lymphoma cell lines. The combination of both drugs also reduced colony formation, increased apoptosis, and inhibited tumor growth in a TMD8 xenograft model. A synergistic combination effect was also found in ibrutinib-resistant cells generated by either genetic mutation or drug treatment. Together, these findings suggest a potential clinical benefit from ibrutinib and ABT-199 combination therapy.
Project description:We studied 498 de-novo adult DLBCL cases, which had been diagnosed between January 2002 and October 2009, as part of the International DLBCL Rituximab-CHOP Consortium Program Study We perform global gene expression profiling from formalin fixed paraffin embedded 498 DLBCL tissues RNA by SPIA mediated microarray detection and identified the distinct subgroups of the disease within DLBCL, known as germinal-center-B-cell-like (GCB), activated B-cell-like (ABC), and unclassified DLBCL (UC).
Project description:Copy number analysis can be useful for assessing prognosis in diffuse large B cell lymphoma (DLBCL). We analyzed copy number data from tumor samples of 60 patients diagnosed with DLBCL de novo and their matched normal samples. We detected a total of 63 recurrent copy number alterations (CNAs), including 33 gains, 30 losses, and nine recurrent acquired copy number neutral loss of heterozygosity (CNN-LOH). Interestingly, 20% of cases acquired CNN-LOH of 6p21 locus, which involves the HLA region. In normal cells there were no CNAs but we observed CNN-LOH involving some key lymphoma regions such as 6p21 and 9p24.1 (5%) and 17p13.1 (2.5%) in DLBCL patients. Furthermore, a model with some specific CNA was able to predict the subtype of DLBCL, 1p36.32 and 10q23.31 losses being restricted to germinal center B cell-like (GCB) DLBCL. In contrast, 8p23.3 losses and 11q24.3 gains were strongly associated with the non-GCB subtype. A poor prognosis was associated with biallelic inactivation of TP53 or 18p11.32 losses, while prognosis was better in cases carrying 11q24.3 gains, which includes ETS1 and FLI1 genes. In summary, CNA abnormalities identify specific DLBCL groups, and we describe CN-LOH in germline cells from DLBCL patients that are associated with genes that probably play a key role in DLBCL development.
Project description:Mutations in genes encoding the various subunits of the SWI/SNF chromatin remodeling complex are frequently observed in different human cancers. In diffuse large B-cell lymphoma (DLBCL), genetic changes in BCL7A, a subunit of the SWI/SNF complex, have been recently reported but the functional role of such genetic changes remains unknown. BCL7A mutations concentrate at the first exon and the most frequently mutated hotspot is the splice donor site of the first intron. By using in vitro and in vivo analyses, we show that restoration of BCL7A drives a tumor suppressor-like phenotype. Further, we found that splice site mutations block the tumor suppressor phenotype and prevent BCL7A from binding to the SWI/SNF complex. Finally, we identified that the SWI/SNF complex accumulates mutations in a third of DLBCL tumors, especially in the GCB subtype. These discoveries highlight the tumor suppressor role of BCL7A mutations in DLBCL, and suggest that the SWI/SNF complex is involved in DLBCL pathogenesis.