BCL3 Translocation Research Articles

Abstract P13: Genetic and epigenetic characterization of B-cell chronic lymphocytic leukemia with IG::BCL3-translocation provides evidence for a distinct biological entity

Abstract IG translocations occur in various B-cell neoplasms and result in the deregulation of (onco)genes due to their juxtaposition with regulatory elements in the immunoglobulin loci, predominantly the immunoglobulin heavy chain (IGH) locus (14q32). Some of these IGH translocations are pathognomonic for distinct disease entities, like those involving MYC, BCL2 or CCND1 in Burkitt, Follicular or Mantle Cell Lymphomas, respectively. In Chronic Lymphocytic Leukemia (CLL), the BCL3 gene (19q13), a transcriptional coactivator of the nuclear factor-kappaB (NF-κB) family, is a known partner gene in these translocations. Two subsets of IG::BCL3 translocation-positive B-cell neoplasms have been described that exhibit differences in chromosomal aberrations, IGHV mutation status, and histopathology [Martín-Subero et al. 2007]. In CLL, IG::BCL3 translocation is linked to a younger age at diagnosis, a more aggressive clinical course, and an atypical tumor cell phenotype [Michaux et al. 1997; Au et al. 2002]. A total of 89 B-cell neoplasms, primarily diagnosed as CLL, displaying IG::BCL3 translocation detected by fluorescence in situ hybridization (FISH), were examined. Analysis of DNA methylation and copy number aberrations (CNA) was conducted for 86 IGH::BCL3-translocated B-cell neoplasms using 850K EPIC BeadChip array data. Evaluation of chromosomal aberrations typical for CLL was moreover performed by FISH and the IGHV mutation status was determined. IGH::BCL3 breakpoint junctions were sequenced in 23 samples using targeted capture and whole-genome sequencing approaches. RNA expression of BCL3 was assessed using the HTG mRNA pan B-cell panel. In UMAP analysis of DNA methylation, CLLs with IG::BCL3 translocation exhibited segregation from other CLLs, irrespective of IGH translocations. Supervised analysis revealed global hypomethylation of B-cell neoplasms with IG::BCL3 translocation compared to other CLL. A total of 66/69 CLLs with IG::BCL3 translocation showed an unmutated IGHV status (96%). Copy number determination using BeadChip data (n=86) and FISH analysis (n=85) showed a significantly higher incidence of trisomy 12 in IG::BCL3-translocated cases compared to the general CLL population (p=0.011). Breakpoint sequencing indicated IG::BCL3 junctions to be recurrently associated with aberrant class-switch recombination at the IGH locus, involving IGHA (n=11/23), IGHG (n=5/23) and IGHM segments (n=5/23). Breakpoints at the BCL3 locus displayed two groups. 80 cases (all CLL) were located upstream of BCL3 and two other B-cell neoplasms (NHL, DLBCL) were located downstream of BCL3. BCL3 expression analysis in 15 IG::BCL3-translocated CLLs confirmed its transcriptional upregulation compared to the general CLL population. Our genetic and epigenetic analyses support the view that CLL with IG::BCL3 translocation may constitute a genetically and epigenetically distinct subtype of B-cell neoplasms, diverging from the typical CLL. Citation Format: Cosima Drewes, Cristina López, Nnamdi Okeke, Sina Hillebrecht, Petra Schütz, Anja Fischer, Anja Mottok, Susanne Bens, Christof Schneider, Stephan Stilgenbauer, Eugen Tausch, Reiner Siebert. Genetic and epigenetic characterization of B-cell chronic lymphocytic leukemia with IG::BCL3-translocation provides evidence for a distinct biological entity [abstract]. In: Proceedings of the Blood Cancer Discovery Symposium; 2024 Mar 4-6; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5(2_Suppl):Abstract nr P13.

Characterization of the genetic and epigenetic landscape of B‐cell neoplasms with IG::BCL3‐translocation

Introduction: The BCL3 gene (19q13) encodes a transcriptional coactivator of the nuclear factor-kappaB (NF-κB) family. It is recurrently deregulated in B-cell neoplasms by a juxtaposition to regulatory elements of one of the immunoglobulin loci, mostly the immunoglobulin heavy chain (IGH) locus (14q32). Two distinct subsets of IG::BCL3 translocation-positive B-cell neoplasms, differing in the number of chromosomal aberrations, IGHV mutation status and histopathology, have been described [Martín-Subero et al., 2007]. In B-cell chronic lymphocytic leukaemia (CLL), the IG::BCL3 translocation has been associated with younger age at diagnosis, a more aggressive clinical course and an atypical tumour cell phenotype [Michaux et al., 1997; Au et al., 2002]. Methods: A total of 89 B-cell neoplasms with IG::BCL3 translocation detected by fluorescence in situ hybridisation (FISH), including predominately cases diagnosed as CLL, were studied. Breakpoints at the BCL3 and IGH loci were sequenced in a subset of samples using targeted capture and breakpoint-spanning PCR approaches. Chromosomal aberrations detected by FISH as well as the IGHV mutation status were analysed. In addition, DNA methylation and copy number aberration (CNA) analyses were performed for 48 samples with CLL using the 850K EPIC BeadChip array. Results: Targeted capture-based sequencing data showed that in the majority of cases BCL3 translocations are associated with aberrant class-switch recombination at the IGH locus, often involving IGHA segments (n = 4/10). From the 69 IG::BCL3-translocated cases with available IGHV mutation status, a total of 51 (74%) were classified as unmutated and 18 (26%) as mutated. This indicates an overrepresentation of cases with unmutated IGHV status among the IG::BCL3-translocated cases compared to the general CLL population. Based on EPIC BeadChip data (total n = 48) 25 (52%) IG::BCL3-translocated cases carried a trisomy 12, 11 cases (23%) a deletion 13q, 7 cases (15%) a deletion 17p and 3 cases (6%) a deletion 11q. FISH analysis of a partially overlapping set of neoplasms (n = 54) was in line with the EPIC BeadChip data and revealed 17 IG::BCL3-translocated cases (32%) with trisomy 12, 7 cases (13%) with deletion 17p and deletion 13q each, and 4 cases (7%) with deletion 11q. Thus, IG::BCL3-translocated cases showed a striking skewing towards the presence of trisomy 12 compared to the general CLL population (p = 0.011). In the DNA methylation analyses, the IG::BCL3-translocated CLLs segregated separately from other CLLs with and without IGH translocations. Conclusions: Our large multi-OMICs study of IG::BCL3-translocated B-cell neoplasms corroborates previous reports on the pathogenetic heterogeneity of these lymphomas and moreover provides evidence that IG::BCL3-translocated CLL might form a genetically and epigenetically distinct subtype of B-cell neoplasms distinct from common CLL. Keywords: Chronic Lymphocytic Leukemia (CLL), Genomics, Epigenomics, and Other -Omics No conflicts of interests pertinent to the abstract.

Bcl-3 promotes Wnt signaling by maintaining the acetylation of \u03b2-catenin at lysine 49 in colorectal cancer

Wnt/β-catenin signaling plays a critical role in colorectal cancer (CRC) tumorigenesis and the homeostasis of colorectal cancer stem cells (CSCs), but its molecular mechanism remains unclear. B-cell lymphoma 3 (Bcl-3), a member of the IκB family, is overexpressed in CRC and promotes tumorigenicity. Here, we report a novel function of Bcl-3 in maintaining colorectal CSC homeostasis by activating Wnt/β-catenin signaling. Silencing Bcl-3 suppresses the self-renewal capacity of colorectal CSCs and sensitizes CRC cells to chemotherapeutic drugs through a decrease in Wnt/β-catenin signaling. Moreover, our data show that Bcl-3 is a crucial component of Wnt/β-catenin signaling and is essential for β-catenin transcriptional activity in CRC cells. Interestingly, Wnt3a increases the level and nuclear translocation of Bcl-3, which binds directly to β-catenin and enhances the acetylation of β-catenin at lysine 49 (Ac-K49-β-catenin) and transcriptional activity. Bcl-3 depletion decreases the Ac-K49-β-catenin level by increasing the level of histone deacetylase 1 to remove acetyl groups from β-catenin, thus interrupting Wnt/β-catenin activity. In CRC clinical specimens, Bcl-3 expression negatively correlates with the overall survival of CRC patients. A significantly positive correlation was found between the expression of Bcl-3 and Ac-K49-β-catenin. Collectively, our data reveal that Bcl-3 plays a crucial role in CRC chemoresistance and colorectal CSC maintenance via its modulation of the Ac-K49-β-catenin, which serves as a promising therapeutic target for CRC.

Rare double-hit with two translocations involving IGH both, with BCL2 and BCL3, in a monoclonal B-cell lymphoma/leukemia

BackgroundChronic Lymphocytic Leukemia (CLL) is a lymphoproliferative disease characterized by multiple recurring clonal cytogenetic anomalies and is the most common leukemia in adults. Chromosomal abnormalities associated with CLL include trisomy 12 and IGH;BCL3 rearrangement [t(14;19)(q32;q13)] that juxtaposes a proto-oncogenic gene BCL3 and an immunoglobulin heavy chain, a translocation that may be associated with shorter survival. In addition to the IGH;BCL3 rearrangement, other translocations involving 14q32 locus are involved in various lymphoproliferative pathologies pointing toward the significance of IGH locus in oncogenic progression. Significantly, in the majority of B-cell neoplasms that carry an IGH;BCL3 rearrangement, it is a sole translocation involving an IGH locus.Case PresentationWe report a patient who, in addition to trisomy 12, carried a rare double-hit translocation characterized by the IGH;BCL3 translocation and an additional clonal IGH;BCL2 translocation involving IGH and another proto-oncogene BCL2, t(14;18)(q32;q21), commonly found in follicular lymphoma. Further single nucleotide polymorphism (SNP) array-based analysis detected a duplication of the 58.8 kb region at 19q13.32 adjacent to the BCL3 translocation junction on chromosome 19q13. Interestingly, the duplicated region contained ERCC2 gene, which encodes a DNA excision repair protein involved in the cancer-prone syndrome, xeroderma pigmentosum.ConclusionsTaken together our findings indicate the existence of double-translocation driven oncogenic events involving both IGH loci and proto-oncogenes BCL2 and BCL3. Importantly, the IGH;BCL3 translocation was characterized by the duplication of the genomic region adjacent to BCL3, containing a major DNA repair factor, ERCC2.Electronic supplementary materialThe online version of this article (doi:10.1186/s13039-015-0203-y) contains supplementary material, which is available to authorized users.

Functional nature of a novel mutant CYLD observed in pediatric lymphoblastic B‐cell leukemia

The Deubiquitinating enzyme, Cylindromatosis (CYLD), has been established as a crucial regulator of B-cells. The present study was addressed to identify the nature of CYLD-dependent RNomics in patients of pediatric age group with B-ALL. The study revealed the presence of a novel mutant CYLD of 55 kDa in these patients. The mutant CYLD displayed its ability to restrict the cells in G2 phase of cell cycle, down-regulate PLK-1 and block the nuclear translocation of BCL3. Based upon these results, we propose that this mutant CYLD has the capacity to act as a differential marker characteristic of B-cell lymphoblastic leukemia. Pediatr Blood Cancer 2015;62:1066-1069. © 2015 Wiley Periodicals, Inc.

Abstract 4217: Nuclear expression of BCL10 has a role in the regulation of cell growth and progression of pancreatic cancer through the activation of NF-κB-related signaling

Abstract Background: We previously reported that activation of TNF-α results in upregulation of NF-κB and nuclear translocation of BCL3 and BCL10 in breast cancer cell line and lymphoma cell line (J Biol Chem 2006;281:167-75, Blood 2008;112:2927-34). Furthermore, we recently demonstrated that BCL10 plays an important role in controlling the growth of cervical cancer cells through NF-κB dependent cyclin D1 regulation (Gynecol Oncol 2012;126:245-51). Since NF-κB activation has been shown to occur in the pathogenesis of pancreatic cancer, we sought to investigate whether BCL10-signaling possesses clinical significance in relation to pancreatic cancer. Methods: Three pancreatic cancer cell lines (PANC-1, AsPC-1, and BxPC-3) were used in this study. Cell cycle was analyzed by flow cytometry. The expression of protein and mRNA of BCL10- and NF-κB- related signaling was assessed by immunoblotting and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. The DNA-binding activity of NF-κB was determined by the luciferase assay. The expression of BCL10, and NF-κB in tumor cells from recurrent, locally advanced, and metastatic pancreatic patients who received chemotherapy was examined using immunohistochemical staining. Results: We transfected three pancreatic cancer cell lines with BCL10 small interfering RNA (siRNA), and discovered that the down-regulation of BCL10 inhibited the viability of these pancreatic cancer cells through the G1 arrest. BCL10 siRNA treatment inhibited the expression of p-IKKβ and p-IκB, and nuclear BCL3 translocation, and also down-regulated NF-κB activation and its downstream cell cycle proteins, c-Myc, and cyclin B1. The results of qRT-PCR showed that BCL10 siRNA treatment inhibited the mRNA expression levels of BCL10, BCL3, c-Myc, and cyclin B1. Our results reveal that patients with nuclear BCL10 expression had a worse median overall survival than those without (7.9 months versus 16.9 months, p = 0.007). Furthermore, nuclear expression of BCL10 was closely associated with nuclear BCL3 expression (p < 0.001), and NF-κB activation (p < 0.001). Conclusions: Our findings indicate that nuclear BCL10 plays an important role in controlling the growth and progression of pancreatic cancer cells through NF-κB-related signaling pathway. Citation Format: Sung-Hsin Kuo, Shih-Hung Yang, Kun-Huei Yeh, Pei-Yen Yeh, Yu-Wen Tien, Hsiao-Wei Lee, Li-Tzong Chen, Ann-Lii Cheng. Nuclear expression of BCL10 has a role in the regulation of cell growth and progression of pancreatic cancer through the activation of NF-κB-related signaling. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4217. doi:10.1158/1538-7445.AM2014-4217

Acquisition of t(11;14) in a patient with chronic lymphocytic leukemia carrying both t(14;19)(q32;q13.1) and +12

A rare recurrent chromosomal translocation, t(14;19)(q32;q13), has been identified in a variety of B-cell malignancies, including chronic lymphocytic leukemia (CLL). We report a unique case of CLL in a patient carrying both trisomy 12 and t(14;19) (q32;q13.1), in whom t(11;14)(q13;q32) developed at relapse. The patient was a 77-yr-old woman, and her lymphoma cells at presentation showed CD5(+), CD10(-), CD19(+), CD20(+)(dim), CD23(+), CD38(+), and CD11c(+). At relapse, the patient's lymphoma cells showed positive staining for cyclin D1 in addition to CD5, CD20, and CD23. Lymphoma cells in specimens at both presentation and relapse were positive for lymphoid enhancer factor 1 (LEF1) and negative for sex-determining region Y-box 11 (SOX11). IGH-BCL1 FISH became positive at relapse. Split FISH assay using BCL1, BCL3, IGH, and CCND1 probes on lymph node specimens obtained at presentation and at autopsy confirmed that the translocation of BCL3 was solely detected in the lymph node at presentation and detected BCL3 and CCND1 translocations in the specimen at autopsy. These observations indicated that IGH-BCL3 and IGH-CCND1 had occurred in the same clone after treatment of the disease. In line with immunohistochemical and cytogenetic studies, additional PCR analysis of the FR3-JH region showed the same sequence derived from IGHV4-34 in specimens obtained at disease onset and relapse.

Interleukin‐2 induces NF‐κB activation through BCL10 and affects its subcellular localization in natural killer lymphoma cells

Deregulation of nuclear factor (NF)-kappaB signalling is common in cancers and is essential for tumourigenesis. Constitutive NF-kappaB activation in extranodal natural killer (NK)-cell lymphoma, nasal type (ENKL) is known to be associated with aberrant nuclear translocation of BCL10. Here we investigated the mechanisms leading to NF-kappaB activation and BCL10 nuclear localization in ENKLs. Given that ENKLs are dependent on T-cell-derived interleukin-2 (IL2) for cytotoxicity and proliferation, we investigated whether IL2 modulates NF-kappaB activation and BCL10 subcellular localization in ENKLs. In the present study, IL2-activated NK lymphoma cells were found to induce NF-kappaB activation via the PI3K/Akt pathway, leading to an increase in the entry of G(2)/M phase and concomitant transcription of NF-kappaB-responsive genes. We also found that BCL10, a key mediator of NF-kappaB signalling, participates in the cytokine receptor-induced activation of NF-kappaB. Knockdown of BCL10 expression resulted in deficient NF-kappaB signalling, whereas Akt activation was unaffected. Our results suggest that BCL10 plays a role downstream of Akt in the IL2-triggered NF-kappaB signalling pathway. Moreover, the addition of IL2 to NK cells led to aberrant nuclear translocation of BCL10, which is a pathological feature of ENKLs. We further show that BCL10 can bind to BCL3, a transcriptional co-activator and nuclear protein. Up-regulation of BCL3 expression was observed in response to IL2. Similar to BCL10, the expression and nuclear translocation of BCL3 were induced by IL2 in an Akt-dependent manner. The nuclear translocation of BCL10 was also dependent on BCL3 because silencing BCL3 by RNA interference abrogated this translocation. We identified a critical role for BCL10 in the cytokine receptor-induced NF-kappaB signalling pathway, which is essential for NK cell activation. We also revealed the underlying mechanism that controls BCL10 nuclear translocation in NK cells. Our findings provide insight into a molecular network within the NF-kappaB signalling pathway that promotes the pathogenesis of NK cell lymphomas.

TP53 Mutations, the Most Frequent Genetic Lesion in Richter Syndrome, Represent An Independent Predictor of Survival Post Transformation.

Abstract 670Richter syndrome (RS) represents the transformation of chronic lymphocytic leukemia (CLL) to aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL). Knowledge of the genetic lesions associated with RS is scant and represents the aim of this study. The study was based on 47 RS cases (all DLBCL). In 32 cases, paired CLL/RS samples were available (28 clonally related and 4 clonally unrelated). In 15 cases, the sole RS sample was analysed. According to CD10/BCL6/MUM1 immunohistochemistry expression pattern, 43/47 (91.5%) RS were classified as non-germinal center DLBCL. At diagnosis, 37.8% RS showed ECOG PS >1, 77.8% Binet stage B-C, 95.7% Ann Arbor stage III-IV, 44.4% B symptoms, 45.7% tumor size >5 cm, 32.6% involvement of >1 extranodal site, 66.7% LDH elevation, and 28.9% platelets <100 × 10e(9)/l. RS treatment included CHOP-like regimens in 71.1% cases, rituximab-based immunochemotherapy in 44.4%, and allogeneic stem cell transplant in 8.9%. Candidate genetic lesions were selected among those recurrently affecting: i) de novo DLBCL; and ii) CLL. Mutational analysis of the TNFAIP3/A20, CARD11, BLIMP1, and TP53 genes was performed by direct DNA sequencing. Probes used for FISH analysis were: i) LSI13, LSID13S319, CEP12, LSIp53, LSIATM, LSI IGH/BCL2, LSI BCL6, LSI IGH/c-MYC/CEP8, LSI N-MYC (Abbott); BCL3 split signal (Dako): iii) 6q21/alpha-satellite (Kreatech Biotechnology); iv) BAC clones 373L24-rel and 440P05-BCL11A. Clonal relationship between CLL and RS samples was assessed by immunoglobulin gene rearrangement analysis. Among gene mutations that are associated with de novo DLBCL, TP53 mutations (exons 4-8) were identified in 18/46 (39.1%) RS, and CARD11 mutations (exons 5-9) in 3/44 (6.8%). Neither TNFAIP3/A20 (exons 2-9) nor BLIMP1 (exons 2-4) mutations were identified in RS. Among chromosomal abnormalities that are associated with de novo DLBCL, c-MYC translocation was observed in 2/17 (11.8%) RS, c-MYC amplification in 2/17 (11.8%), BCL6 amplification in 2/17 (11.8%), REL amplification in 1/10 (10.0%), and BCL2 amplification in 1/17 (5.9%). Neither BCL6 translocation, nor BCL2 translocation or BLIMP1 deletion were observed in RS. Among chromosomal abnormalities that are associated with CLL, 17p13 deletion (TP53) was observed in 5/17 (29.4%) RS, 11q22-q23 deletion (ATM) in 5/17 (29.4%), +12 in 4/17 (23.5%), 13q14 deletion (MIR15A/16B) in 2/17 (11.8%), BCL11A amplification in 1/10 (10.0%), BCL3 amplification in 2/17 (11.8%), BCL3 translocation in 1/17 (5.9%), and N-MYC amplification in 1/17 (5.9%). Analysis of paired clonally related CLL/RS samples showed that TP53 mutations and CARD11 mutations are acquired at RS transformation. Chromosomal abnormalities acquired at RS transformation included TP53 deletion (3/10, 30.0%), c-MYC translocation (2/10, 20.0%), BCL3 amplification (2/10, 20.0%), c-MYC amplification (1/10, 10.0%), BCL6 amplification (1/10, 10.0%), BCL2 amplification (1/10, 10.0%), and ATM deletion (1/10, 10.0%). To date, the sole tool for predicting RS survival is represented by the RS score, that is based on clinical variables (Tsimberidou et al, J Clin Oncol 2006; 24:2343). The notion that TP53 status predict survival in both CLL (Zenz et al, Blood 2008; 112: 3322; Rossi et al, Clin Cancer Res 2009; 15: 995) and de novo DLBCL (Young et al, Blood 2008; 112: 3088) prompted investigation of the impact of TP53 mutations on survival post RS transformation. Survival post transformation was significantly longer in RS devoid of TP53 mutations (27.0 months) compared to RS with TP53 mutations (9.4 months) (p=.023) (Fig. 1). Other variables associated with RS survival were age (p<.001), ECOG PS (p<.001), tumor size (p=.001), B symptoms (p=.001), platelet count (p=.002), Binet stage (p=.001), Rai stage (p=.001), and IPI (p=.008). Treatment strategy did not affect RS survival. Multivariate analysis selected TP53 mutations (HR:2.34; p=.028) as an independent predictor of RS survival along with variables identified by the RS score, including ECOG PS (p=.008), tumor size (p<.001), and platelet count (p=.004) . The conclusions of our study are multifold: i) the genetic profile of RS differs from that of de novo DLBCL; ii) few lesions are shared by RS and de novo DLBCL, including CARD11 mutations, c-MYC translocation and REL amplification; iii) TP53 mutations are the most frequent genetic lesion in RS; iv) TP53 mutations are an independent prognostic factor in RS. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Activation of nuclear factor‐κB signaling pathway by interleukin‐1 after hypoxia/ischemia in neonatal rat hippocampus and cortex

Perinatal hypoxia/ischemia (HI) is a common cause of neurological deficits in children. Interleukin-1 (IL-1) activity has been implicated in HI-induced brain damage. However, the mechanisms underlying its action in HI have not been characterized. We used a 7-day-old rat model to elucidate the role of nuclear factor-kappaB (NF-kappaB) activation in HI stimulation of IL-1 signaling. HI was induced by permanent ligation of the left carotid artery followed by 90 min of hypoxia (7.8% O(2)). Using ELISA assays, we observed increased cell death and caspase 3 activity in hippocampus and cortex 3, 6, 12, 24 and 48 h post-HI. IL-1beta protein expression increased, beginning at 3 h after HI and lasting until 24 h post-HI in hippocampus and 12 h post-HI in cortex. Intracerebroventricular injection of 2 microg IL-1 receptor antagonist (IL-1Ra) 2 h after HI significantly reduced cell death and caspase 3 activity. Electrophoretic mobility shift assay analyses of hippocampus and cortex after HI for NF-kappaB activity showed increased p65/p50 DNA-binding activity at 24 h post-HI. Western blot analyses showed significant nuclear translocation of p65. Protein expression levels of two known inflammatory agents, inducible nitric oxide synthase and cycloxygenase 2, known to be transcriptionally regulated by NF-kappaB, also increased at 24 h after HI. All these HI-induced changes were reversed by IL-1Ra blockade of IL-1 signaling, consistent with IL-1 triggering of inflammatory apoptotic outcomes via NF-kappaB transcriptional activation. The observed increase in cytoplasmic phosphorylated inhibitor kappaBalpha (IkappaBalpha) and nuclear translocation of Bcl-3 24 h after HI was also significantly attenuated by IL-1Ra blockade, suggesting that HI-induced IL-1 activation of NF-kappaB is via both the degradation of IkappaBalpha and the nuclear translocation of Bcl-3.

Bcl-3 Expression and Nuclear Translocation Are Induced by Granulocyte-Macrophage Colony-Stimulating Factor and Erythropoietin in Proliferating Human Erythroid Precursors

AbstractBcl-3 is a proto-oncogene involved in the chromosomal translocation t(14;19) found in some patients with chronic lymphocytic leukemia. It shares structural similarities with and is a member of the IκB family of proteins. In this report, involvement of Bcl-3in hematopoietic growth factor-stimulated erythroid proliferation and differentiation was examined. In TF-1 cells, an erythroleukemia cell line, granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (Epo) greatly enhanced Bcl-3 expression at both the protein and mRNA levels in association with stimulation of proliferation. Bcl-3 protein was also highly expressed in early burst-forming unit-erythroid (BFU-E)–derived erythroid precursors (day 7) and decreased during maturation (days 10 and 14), suggesting that Bcl-3 is involved in normal erythroid proliferation. In these hematopoietic cells, Bcl-3 was hyperphosphorylated. GM-CSF and Epo modulated the subcellular localization of Bcl-3. Upon stimulation of TF-1 cells with GM-CSF or Epo, the nuclear translocation ofBcl-3 was dramatically enhanced. Overexpression of Bcl-3 in TF-1 cells by transient transfection along with the NF-κB factors p50 or p52 resulted in significant induction of an human immunodeficiency virus–type 1 (HIV-1) κB-TATA-luceriferase reporter plasmid, demonstrating that Bcl-3 has a positive role in transactivation of κB-containing genes in erythroid cells. Stimulation with GM-CSF enhanced c-myb mRNA expression in these cells. Bcl-3 in nuclear extracts of TF-1 cells bound to a κB enhancer in the c-mybpromoter together with NF-κB2/p52 and this binding activity was enhanced by GM-CSF stimulation. Furthermore, cotransfection of Bcl-3 with p52 or p50 in TF-1 cells resulted in significant activation of ac-myb κB-TATA-luceriferase reporter plasmid. These findings suggest that Bcl-3 may participate in the transcriptional regulation of certain κB-containing genes involved in hematopoiesis, includingc-myb.© 1998 by The American Society of Hematology.

Bcl-3 Expression and Nuclear Translocation Are Induced by Granulocyte-Macrophage Colony-Stimulating Factor and Erythropoietin in Proliferating Human Erythroid Precursors

Bcl-3 is a proto-oncogene involved in the chromosomal translocation t(14;19) found in some patients with chronic lymphocytic leukemia. It shares structural similarities with and is a member of the IkappaB family of proteins. In this report, involvement of Bcl-3 in hematopoietic growth factor-stimulated erythroid proliferation and differentiation was examined. In TF-1 cells, an erythroleukemia cell line, granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (Epo) greatly enhanced Bcl-3 expression at both the protein and mRNA levels in association with stimulation of proliferation. Bcl-3 protein was also highly expressed in early burst-forming unit-erythroid (BFU-E)-derived erythroid precursors (day 7) and decreased during maturation (days 10 and 14), suggesting that Bcl-3 is involved in normal erythroid proliferation. In these hematopoietic cells, Bcl-3 was hyperphosphorylated. GM-CSF and Epo modulated the subcellular localization of Bcl-3. Upon stimulation of TF-1 cells with GM-CSF or Epo, the nuclear translocation of Bcl-3 was dramatically enhanced. Overexpression of Bcl-3 in TF-1 cells by transient transfection along with the NF-kappaB factors p50 or p52 resulted in significant induction of an human immunodeficiency virus-type 1 (HIV-1) kappaB-TATA-luceriferase reporter plasmid, demonstrating that Bcl-3 has a positive role in transactivation of kappaB-containing genes in erythroid cells. Stimulation with GM-CSF enhanced c-myb mRNA expression in these cells. Bcl-3 in nuclear extracts of TF-1 cells bound to a kappaB enhancer in the c-myb promoter together with NF-kappaB2/p52 and this binding activity was enhanced by GM-CSF stimulation. Furthermore, cotransfection of Bcl-3 with p52 or p50 in TF-1 cells resulted in significant activation of a c-myb kappaB-TATA-luceriferase reporter plasmid. These findings suggest that Bcl-3 may participate in the transcriptional regulation of certain kappaB-containing genes involved in hematopoiesis, including c-myb.