Distinct B-Cell Specific Transcriptional Contexts of the BCL2 Oncogene Impact Pre-Malignant Development in Mouse Models (original) (raw)
Related papers
bioRxiv (Cold Spring Harbor Laboratory), 2021
Follicular lymphoma (FL) is the most common indolent form of non-Hodgkin lymphoma arising from malignant germinal center (GC) B-cells. The genetic hallmark that leads to the development of FL is the t(14:18) which occurs early in the bone marrow during B cell development, thereby placing the anti-apoptotic BCL2 gene under the direct control of the transcriptional enhancers in 3' of immunoglobulin heavy chain locus (IgH 3'RR) and leading to the constitutive expression of the BCL2 protein. To assess the impact of the BCL2 deregulation on B-cell fate and try to reproduce FL development in mice, two models were designed: the Igκ-BCL2 (Knock in of the BCL2 in the light chain Ig kappa locus) and the 3'RR-BCL2 (Transgene containing BCL2 and a micro-3'RR), both containing the full BCL2 promoter region.
American Journal of Pathology, 2004
mediastinal large B-cell lymphoma. The t(14;18)(q32; q21) has been reported previously to define a unique subset within the GCB-DLBCL. We evaluated for the translocation in 141 cases of DLBCL that were successfully gene expression profiled. Using a dual-probe fluorescence in situ hybridization assay, we detected the t(14;18) in 17% of DLBCLs and in 34% of the GCB subgroup which contained the vast majority of positive cases. In addition, 12 t(14;18)-positive cases de-tected by polymerase chain reaction assays on additional samples were added to the fluorescence in situ hybridization-positive cases for subsequent analysis. Immunohistochemical data indicated that BCL2, BCL6, and CD10 protein were preferentially expressed in the t(14;18)-positive cases as compared to t(14;18)-negative cases. Within the GCB subgroup, the expression of BCL2 and CD10, but not BCL6, differed significantly between cases with or without the t(14; 18): 88% versus 24% for BCL2 and 72% versus 32% for CD10, respectively. In the GCB-DLBCL subgroup, a heterogeneous group of genes is overexpressed in the t(14;18)-positive subset, among which BCL2 is a significant discriminator. Interestingly, the t(14;18)-negative subset is dominated by overexpression of cell cycle-associated genes, indicating that these tumors are significantly more proliferative, suggesting distinctive pathogenetic mechanisms. However, despite this higher proliferative activity, there was no significant difference in overall or failure-free survival between the t(14;18)-positive and -negative subsets within the GCB subgroup. Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy of mature B cells with an annual incidence of ϳ25,000 cases in the United States. DLBCL is a heterogeneous entity both clinically and morphologically. We have recently shown by gene expression profiling that DLBCL can be classified into two major subgroups. 1 The germinal center B-cell-like (GCB) subgroup expresses genes characteristic of normal GC B cells and is associated with a good outcome after multiagent chemotherapy, whereas the activated B-cell-like (ABC) subgroup expresses genes characteristic of activated blood B cells and is associated with a poor clinical outcome. Nonetheless, considerable molecular heterogeneity exists within each subgroup. A small number of DLBCL cases are unclassifiable and do not express the GCB or ABC sig-
Growth- and Tumor-Promoting Effects of Deregulated BCL2 in Human B-Lymphoblastoid Cells
Pnas, 1989
Human follicular B-cell lymphomas possess a t(14;18) that translocates a putative protooncogene, BCL2, into the immunoglobulin heavy chain locus. The normal BCL2 gene is quiescent in resting B cells, expressed in proliferating, but down-regulated in differentiated B cells. Inappropriately high levels of BCL2-immunoglobulin chimeric RNA are present in t(14;18) lymphomas for their mature B-cell stage. We examined the biologic effects of BCL2 deregulation in human B cells by introducing BCL2 into human B-lymphoblastoid cell lines (LCLs) with retroviral gene transfer. Although deregulated BCL2 expression as a single agent was not sufficient to confer tumorigenicity to LCLs, it consistently produced a 3- to 4-fold increment in LCL clonogenicity in soft agar. In addition, BCL2 deregulation complements the transforming effects of the MYC oncogene in LCLs. BCL2 augmented the clonogenicity of LCLs bearing exogenous MYC and increased the frequency and shortened the latency of tumor induction in immunodeficient mice. These results demonstrate a role for BCL2 as a protooncogene that affects B-cell growth and enhances B-cell neoplasia.
Blood, 1998
Although highly responsive, advanced stage follicular lymphoma (FL) is not curable with conventional treatment. This relative resistance is thought to be due to the t(14;18) that results in the constitutive overexpression of the death-inhibiting protein bcl-2. However, the observation that FL cells are sensitive to treatment in vivo and prone to apoptosis on in vitro culture questions whether bcl-2 alone is responsible for the pathogenesis and clinical behavior of this disease. Therefore, multiple genes are likely to be involved in both the lymphomagenesis and the clinical course of FL. We examined whether expression of other bcl-2 family genes might also be operative. Here, we show that FL cells display a different pattern of expression of bcl-2 family proteins from normal germinal center (GC) B cells that are thought to be their normal counterpart. FL cells express the death-suppressor proteins bcl-2, bcl-xL, and mcl-1; whereas GC B cells express bcl-xL and mcl-1 but also the proa...
Blood, 2003
The BCL6 proto-oncogene encodes a transcriptional repressor whose expression is deregulated by chromosomal translocations in approximately 40% of diffuse large B-cell lymphomas (DLBCLs). The BCL6 regulatory sequences are also targeted by somatic hypermutation in germinal center (GC) B cells and in a fraction of all GC-derived lymphomas. However, the functional consequences of these mutations are unknown. Here we report that a subset of mutations specifically associated with DLBCL causes deregulated BCL6 transcription. These mutations affect 2 adjacent BCL6 binding sites located within the first noncoding exon of the gene, and they prevent BCL6 from binding its own promoter, thereby disrupting its negative autoregulatory circuit. These alterations were found in approximately 16% of DLBCLs devoid of chromosomal translocations involving the BCL6 locus, but they were not found in normal GC B cells. This study establishes a novel mechanism for BCL6 deregulation and reveals a broader invo...
BCL-2 overexpression overcomes cell of origin stratification in diffuse large B-cell lymphoma
Hematology/Oncology and Stem Cell Therapy, 2018
To the Editor Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with variable clinical and pathologic presentations. The prognosis of DLBCL patients can be estimated using the International Prognostic Index (IPI) or its revised variant (R-IPI) [1]. Furthermore, using gene expression profiling, DLBCL can be divided based on its cell of origin (COO) into germinal center type (GCB), activated B-cell, or Type 3 with the latter two collectively known as nongerminal center type (non-GCB) with poor prognosis relative to the former type [2]. However, such complementary DNA (cDNA)based assays needed for classification remain prohibitive for routine clinical use almost two decades after the initial report. Immunohistochemical (IHC) algorithms, such as the one proposed by Hans et al., [3] are rapid alternatives that are readily available and have demonstrated reasonable concordance to gene expression profiling. 35 The antiapoptotic B-cell lymphoma 2 (BCL-2) oncogene 36 confers a negative prognostic impact in GCB DLBCL when 37 overexpressed irrespective of the MYC status [4]. Non-GCB 38 DLBCL appears to arise from postgerminal center B cells 39 and involves activation of the nuclear factor signaling path-40 way (NHB). BCL-2 overexpression can also be seen in con-41 junction with MYC, resulting in the entity called ''double 42 expressing lymphoma'' [5]. Our aim with this analysis was 43 twofold: first, to assess the prognostic impact of COO 44 assignment using the Hans algorithm in DLBCL patients from 45 the Middle East and North Africa (MENA) region; and second, 46 to examine whether BCL-2 overexpression alters the 47
New concepts in follicular lymphoma biology: From BCL2 to epigenetic regulators and non-coding RNAs
The molecular pathogenesis of follicular lymphoma (FL) was partially revealed 3 decades ago, with the discovery of the translocation that brings BCL2 under the influence of immunoglobulin heavy chain en-hancers in a vast majority of cases. Despite the importance of this seminal observation, it has become increasingly clear that additional genetic alterations need to occur to trigger neoplastic transformation and disease progression. The evolution of FL involves developmental arrest and disruption of the normal function of one or more of epigenetic regulators including KMT2D/MLL2, EZH2 , CBP/ CREBBP , p300/ EP300 , and HIST1H1 in > 95% of cases. B-cells "arrested" in germinal centers acquire dozens of additional genetic aberrations that influence key pathways controlling their physiological development including B Cell Receptor (BCR) signaling, PI3K/AKT, TLR, mTOR, NF-κB, JAK/STAT, MAPK, CD40/CD40L, chemokine, and interleukin signaling. Additionally, most cases of FL do not result from linear accumulation of ge-nomic aberrations, but rather evolve from a common progenitor cell population by diverse evolution, creating multiple FL subclones in one patient. Moreover, one of the subclones might acquire a combination of aberrations involving genes controlling cell survival and proliferation including MDM2, CDKN2A/B, BCL6, MYC, TP53, β2M, FOXO1, MYD88, STAT3, or miR-17-92 , and this can lead to the transformation of an initially indolent FL to an aggressive lymphoma (2%-3% risk per year). The complexity of the disease is also underscored by the importance of its interactions with the microenvironment that can substantially influence disease development and prognosis. Interpreting individual aberrations in relation to their impact on normal processes, their frequency, position in the disease evolution, and the consequences of their (co)occurrence, are the basis for understanding FL pathogenesis. This is necessary for the identification of patients with risk of early progression or transformation, for the development of novel targeted therapies, and for personalized treatment approaches. In this review, we summarize recent knowledge of molecular pathways and microenvironmental components involved in FL biology, and discuss them in the context of physiological B-cell development, FL evolution, and targeted therapies.