Expression Of B-cell Lymphoma 6 Research Articles

Hypoxic stress caused apoptosis of MDBK cells by p53/BCL6-mitochondrial apoptosis pathway

Hypoxia is an important characteristic of Tibetan plateau environment. It can lead to apoptosis, but the mechanism of apoptosis caused by hypoxic stress needs further clarification. Here, cattle kidney cell MDBK were used as cell model. The effect of hypoxic stress on apoptosis and its molecular mechanism were explored. MDBK cells were treated with hypoxic stress, apoptosis and mitochondrial apoptotic pathway were significantly increased, and the expression of B-cell lymphoma 6 (BCL6) was significantly decreased. Overexpressing or inhibiting BCL6 demonstrated that BCL6 inhibited the apoptosis. And the increase of apoptosis controlled by hypoxic stress was blocked by BCL6 overexpressing. MDBK cells were treated with hypoxic stress, the expression and the nuclear localization of p53 were significantly increased. Overexpressing or inhibiting p53 demonstrated that hypoxic stress suppressed the expression of BCL6 through p53. Together, these results indicated that hypoxic stress induced the apoptosis of MDBK cells, and BCL6 was an important negative factor for this regulation process. In MDBK cells, hypoxic stress suppressed the expression of BCL6 through p53/BCL6-mitochondrial apoptotic pathway. This study enhanced current understanding of the molecular mechanisms underlying the regulation of apoptosis by hypoxic stress in MDBK cells.

Correlation between B-cell lymphoma 6 with the balance of T helper-1/2 and severity of allergic rhinitis.

Allergic rhinitis (AR) is a prevailing immune disorder affecting the nasal mucosa. B-cell lymphoma 6 (BCL6) imposes essential roles in immunity. This study probed into the serum expression of BCL6 and its effect on AR diagnosis and patients' quality of life (QOL). A total of 113 patients with AR including 38 cases with mild AR (MAR) and 75 cases with moderate-severe AR (MSAR) were enrolled, with 101 healthy people enrolled as control. Serum expression of BCL6 was detected by RT-qPCR and the diagnostic efficacy of BCL6 for AR was analyzed using the receiver operating characteristic curve. The proportion of T helper-1/2 (Th1/Th2) cells in CD4+ T cells in peripheral blood mononuclear cells was detected using flow cytometry. The correlation between BCL6 and Th1/Th2 cells and the effects of BCL6 expression on patients' QOL were assessed by Pearson analysis and Mini-RQLQ questionnaire. BCL6 was downregulated in patients with AR, serum BCL6 level < 0.8450 had certain auxiliary diagnostic values for AR, and serum BCL6 level < 0.5400 could assist the diagnosis of AR severity. Th1 cell proportion in CD4+ T cells was decreased, whereas Th2 cell proportion was increased with AR severity. BCL6 was positively-linked with Th1 cells but inversely-correlated with Th2 cells in patients with AR. Patients with AR with low BCL6 expression had a poorer QOL compared with high BCL6 expression. The domains most affected by BCL6 expression were practical problems, nasal symptoms, and lacrimation. Serum BCL6 is downregulated and low BCL6 expression greatly deteriorates QOL in patients with AR.

Comparison of Morphological and Digital-Assisted Analysis for BCL6 Endometrial Expression in Women with Endometriosis.

BCL6 (B-cell lymphoma 6) is a proto-oncogene and transcriptional repressor initially described as being involved in B-cell lymphoma. Recently, this factor has been identified as a promising tissue biomarker which could be used to diagnose women affected by endometriosis. Previous studies used HSCORE for BCL6 staining quantification in the endometrium. However, this semi-quantitative technique of analysis has some limitations, including a lack of objectivity, robustness, and reproducibility that may lead to intra- and inter-observer variability. Our main goal was to develop an original computer-assisted method to quantify BCL6 staining from whole-slide images reliably. In order to test the efficiency of our new digital method of quantification, we compared endometrial BCL6 expression between fertile and infertile women without or with different stages of endometriosis by using the widely used HSCORE analysis and our new automatic digital image analysis. We find a higher expression of BCL6 in the endometrium of infertile women with endometriosis and women with stage IV endometriosis. Furthermore, we demonstrate a significant correlation between the two types of independent measurements, indicating the robustness of results and also the reliability of our computer-assisted method for BCL6 quantification. In conclusion, our work, by using this original computer-assisted method, enables BCL6 quantification more objectively, reliably, robustly, and promptly compared to HSCORE analysis.

The oncoprotein BCL6 enables solid tumor cells to evade genotoxic stress

Genotoxic agents remain the mainstay of cancer treatment. Unfortunately, the clinical benefits are often countered by a rapid tumor adaptive response. Here, we report that the oncoprotein B cell lymphoma 6 (BCL6) is a core component that confers solid tumor adaptive resistance to genotoxic stress. Multiple genotoxic agents promoted BCL6 transactivation, which was positively correlated with a weakened therapeutic efficacy and a worse clinical outcome. Mechanistically, we discovered that treatment with the genotoxic agent etoposide led to the transcriptional reprogramming of multiple pro-inflammatory cytokines, among which the interferon-α and interferon-γ responses were substantially enriched in resistant cells. Our results further revealed that the activation of interferon/signal transducer and activator of transcription 1 axis directly upregulated BCL6 expression. The increased expression of BCL6 further repressed the tumor suppressor PTEN and consequently enabled resistant cancer cell survival. Accordingly, targeted inhibition of BCL6 remarkably enhanced etoposide-triggered DNA damage and apoptosis both in vitro and in vivo. Our findings highlight the importance of BCL6 signaling in conquering solid tumor tolerance to genotoxic stress, further establishing a rationale for a combined approach with genotoxic agents and BCL6-targeted therapy.

Tnfaip6 Secreted by Bone Marrow-Derived Mesenchymal Stem Cells Attenuates TNBS-Induced Colitis by Modulating Follicular Helper T Cells and Follicular Regulatory T Cells Balance in Mice.

Objective: To investigate the immunological mechanism of bone marrow–derived mesenchymal stem cells (BM-MSCs) in inflammatory bowel disease (IBD). Methods: Mice with 2,4,6-trinitrobenzene sulfonic acid (TNBS)–induced colitis were intraperitoneally injected with phosphate-buffered saline, BM-MSCs, BM-MSCs with tumor necrosis factor–induced protein 6 (Tnfaip6) knockdown mediated by RNA interference recombinant adenovirus, and BM-MSCs–infected with control adenovirus or recombinant mouse Tnfaip6. The disease activity index, weight loss, and histological scores were recorded. Serum levels of Tnfaip6 and pro- and anti-inflammatory cytokines, including interleukin (IL)-21, tumor necrosis factor-alpha (TNF-α), IL-10 were measured by enzyme-linked immunosorbent assay. The relative expression levels of these cytokines, B-cell lymphoma 6 (BCL-6) and fork-like transcription factor p3 (Foxp3) in the colon were determined by real-time quantitative PCR (RT-qPCR). BCL-6 and Foxp3 are the master regulators of follicular helper T cells (Tfh) and follicular regulatory T cells (Tfr), respectively. The infiltration of Tfh and Tfr in mesenteric lymph nodes (MLNs) and spleens was analyzed by flow cytometry. Results: Compared to the normal control group, the expression levels of BCL-6 and IL-21 in the colon, Tfh infiltration, and ratios of Tfh/Tfr in the MLNs and spleen, and the serum concentrations of IL-21 and TNF-α increased significantly in the colitis model group (p < 0.05). Intraperitoneal injection of BM-MSCs or Tnfaip6 ameliorated weight loss and clinical and histological severity of colitis, downregulated the expression of BCL-6, IL-21, and TNF-α, upregulated the expression of Foxp3, IL-10, and Tnfaip6 (p < 0.05), increased Tfr and reduced the infiltration of Tfh in the MLNs and spleen, and downregulated the Tfh/Tfr ratio (p < 0.05). On the other hand, BM-MSCs lost the therapeutic effect and immune regulatory functions on Tfh and Tfr after Tnfaip6 knockdown. Conclusion: Tfh increase in the inflamed colon, Tfh decrease and Tfr increase during the colitis remission phase, and the imbalance of the Tfh/Tfr ratio is closely related to the progression of IBD. Tnfaip6 secreted by BM-MSCs alleviates IBD by inhibiting Tfh differentiation, promoting Tfr differentiation, and improving the imbalance of Tfh/Tfr in mice.

Expression of BCL6 in paediatric B-cell acute lymphoblastic leukaemia and association with prognosis.

B-cell lineage acute lymphoblastic leukaemia (B-ALL) is the most common paediatric malignancy. Transcription factor B-cell lymphoma 6 (BCL6) is essential to germinal centre formation and antibody affinity maturation and plays a major role in mature B-cell malignancies. More recently, it was shown to act as a critical downstream regulator in pre-BCR+ B-ALL. We investigated the expression of the BCL6 protein in a population-based cohort of paediatric B-ALL cases and detected moderate to strong positivity through immunohistochemistry in 7% of cases (8/117); however, only two of eight BCL6 cases (25%) co-expressed the ZAP70 protein. In light of these data, the subtype with active pre-BCR signalling constitutes a rare entity in paediatric B-ALL. In three independent larger cohorts with gene expression data, high BCL6 mRNA levels were associated with the TCF3-PBX1, Ph-like, NUTM1, MEF2D and PAX5-alt subgroups and the 'metagene' signature for pre-BCR-associated genes. However, higher-than-median BCL6 mRNA level alone was associated with favourable event free survival in the Nordic paediatric cohort, indicating that using BCL6 as a diagnostic marker requires careful design, and evaluation of protein level is needed alongside the genetic or transcriptomic data.

SAT-LB056 Is AIP a Tumor Suppressor or an Oncogene? AIP as a Novel Regulator of the Oncogene BCL6 in Diffuse Large B Cell Lymphoma

Background: Heterozygous germline loss-of-function mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene are usually associated with acromegaly or gigantism due to a young-onset somatotropinoma. AIP functions as a tumor suppressor gene in the pituitary, while its role in other tumours is unknown. AIP is highly expressed in patients with Diffuse Large B Cell Lymphoma (DLBCL) compared to any other tumor type. DLBCL arises from germinal centre B cells which characteristically express the transcriptional repressor B cell lymphoma-6 (BCL6), key for germinal centre formation. Increased expression of BCL6 can lead to the development of DLBCL. Despite the obvious importance of BCL6 expression in GC B cells, the mechanisms by which it is regulated are still poorly understood. Aim: The aim of this study was to investigate the relationship of the high AIP expression, BCL6 and the pathobiology of DLBCL. Methods: We generated mice carrying a conditional homozygous deletion of Aip in T and B cells (Aipfl/fl;Rag1Cre/+). Co-localization of AIP and members of the BCL6 ubiquitination/proteasome pathway by immunofluorescence analysis. Ubiquitin-mediated proteasomal degradation study was done by immuno-precipitation (IP). Results: Our study found that AIP is highly expressed in DLBCL. Genetic deletion of Aip revealed that AIP supported BCL6 expression in mice. The ubiquitin E3 ligase FBXO11 has been previously shown to add ubiquitin to BCL6. We found that AIP could bind to the deubiquitinase UCHL1 and that UCHL1 could remove ubiquitin from BCL6 thereby supporting BCL6 expression by preventing FBXO11 mediated degradation of BCL6 recapitulating what we observed in Aip deficient B cells. Conclusions: The data presented here reveal AIP to be a novel positive regulator of BCL6 protein expression which is commonly up-regulated in DLBCL and prevents FBXO11 degradation of BCL6 by enabling the UCHL1 to remove ubiquitin from BCL6. Therefore, AIP is a potential novel therapeutic target to treat DLBCL. It appears that AIP function as a tumor suppressor in the pituitary and as an oncogene to the pathobiology of DLBCL. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

MiR-519d-3p Inhibits Cell Proliferation and Invasion of Gastric Cancer by Downregulating B-Cell Lymphoma 6

miR-519d inhibits cell growth, migration, and invasion, but its role in gastric cancer (GC) cells is obscure. We showed that miR-519d-3p was lowly expressed in GC tissues and was associated with the clinical stage and lymph node metastasis of GC tissues. We found that miR-519d-3p repressed cell proliferation and invasion of MGC803 cells and delayed the G1/S phase transition, resulting in decreased cyclin B1 and MMP2 and increased E-cadherin levels. Furthermore, miR-519d-3p targeted and downregulated B-cell lymphoma 6 (BCL6) expression. BCL6 overexpression partially abrogated the suppressive function of miR-519d in MGC803 cells. In conclusion, our study demonstrated that miR-519d-3p functions as a tumor suppressor by targeting and downregulating the expression of BCL6 in GC cells.

Expression of and correlation between BCL6 and ZEB family members in patients with breast cancer.

B-cell lymphoma 6 (BCL6), a proto-oncogene, is an evolutionarily conserved zinc finger protein that functions as a transcriptional repressor. BCL6 is the master regulator of B-lymphocyte development, and it has been reported that BCL6 may serve an important role in breast cancer progression. The aim of the present study was to investigate the expression of BCL6, zinc finger E-box-binding homeobox (ZEB)1 and ZEB2 and their associations in breast cancer. The mRNA and protein expression of BCL6, ZEB1 and ZEB2 was assessed using in situ hybridization and immunohistochemistry, respectively, in 228 patients with breast cancer and 80 patients with benign breast disease. In addition, the association between BCL6, ZEB1 and ZEB2 expression and the clinicopathological characteristics and survival of patients with breast cancer were analyzed. The mRNA and protein expression of BCL6, ZEB1 and ZEB2 were significantly higher in breast cancer tissues compared with benign breast disease tissues (P<0.05). The expression of BCL6, ZEB1 and ZEB2 were significantly positively correlated with tumor size, lymph node metastasis and a higher tumor stage (P<0.05). Furthermore, patients with BCL6, ZEB1 and ZEB2 protein-positive primary tumors had significantly lower overall survival (P=0.001, 0.002 and 0.001, respectively) and relapse-free survival (P=0.002, 0.001 and 0.003, respectively) rates. The mRNA expressions of ZEB1 (rs=0.326, P<0.001) and ZEB2 (rs=0.382, P<0.001) were significantly positively correlated with BCL6 mRNA expression, and the protein expressions of ZEB1 ((rs=0.449, P<0.001) and ZEB2 (rs=0.669, P<0.001) were significantly positively correlated with BCL6 protein expression. These results suggest that BCL6, ZEB1 and ZEB2 are potential biomarkers for the invasion, metastasis and prognosis of breast cancer, and that BCL6 may be a regulator of the ZEB family.

Involvement of the oncogene B-cell lymphoma 6 in the fusion and differentiation process of trophoblastic cells of the placenta.

The oncogene B-cell lymphoma 6 (BCL6) is associated with lymphomagenesis. Intriguingly, its expression is increased in preeclamptic placentas. Preeclampsia is one of the leading causes of maternal and perinatal mortality and morbidity. Preeclamptic placentas are characterized by various defects like deregulated differentiation and impaired fusion of trophoblasts. Its pathogenesis is however not totally understood. We show here that BCL6 is present throughout the cell fusion process in the fusogenic trophoblastic cell line BeWo. Suppression of BCL6 promotes trophoblast fusion, indicated by enhanced levels of fusion-related β-hCG, syncytin 1 and syncytin 2. Increased mRNA levels of these genes could also be observed in primary term cytotrophoblasts depleted of BCL6. Conversely, stable overexpression of BCL6 reduces the fusion capacity of BeWo cells. These data suggest that an accurately regulated expression of BCL6 is important for proper differentiation and successful syncytialization of trophoblasts. While deregulated BCL6 is linked to lymphomagenesis by blocking lymphocyte terminal differentiation, increased BCL6 in the placenta contributes to the development of preeclampsia by impairing trophoblast differentiation and fusion.

Abstract 2430: The expression of BCL6 and ZEB family transcription factors and their correlation in breast cancers

Abstract The proto-oncogene B-cell lymphoma 6 (BCL6) is an evolutionarily conserved zinc finger protein and a potent transcriptional repressor. It is also the master regulator of B-lymphocyte development. Emerging evidence indicates that BCL6 may play an important role in breast cancer progression. In this study, we investigated the expression of BCL6 and tis correlation with the expression of epithelial-mesenchymal transition (EMT)-associated transcription factors zinc finger E-box-binding homeobox 1 (ZEB1) and ZEB2 in invasive breast cancers. The mRNA and protein expression of BCL6, ZEB1 and ZEB2 were examined using in situ hybridization and immunohistochemistry, respectively, in 228 breast cancer patients and 80 patients with breast benign diseases. The association of BCL6, ZEB1 and ZEB2 expression with clinicopathological parameters and patient survival were analyzed. We found that the expression of BCL6, ZEB1 and ZEB2 protein and mRNA were significantly higher in breast cancer tissues than in breast benign disease tissues (P&amp;lt;0.05). The expression levels of BCL6, ZEB1 and ZEB2 were all positively correlated with the tumor size, lymph node metastasis and higher tumor stages (P&amp;lt;0.05). Furthermore, patients with BCL6, ZEB1 and ZEB2 protein-positive primary tumors were associated with a significant lower overall survival (OS) rate (P=0.001, 0.002 and 0.001, respectively) and post-operative relapse-free survival (RFS) rate (P=0.002, 0.001 and 0.003 for the expression of BCL6, ZEB1 and ZEB2, respectively). The mRNA expression of ZEB1 and ZEB2 were positively correlated with BCL6 mRNA expression (rs=0.326, P&amp;lt;0.001; and rs=0.382, P&amp;lt;0.001, respectively); the protein expression of ZEB1 and ZEB2 were also positively correlated with BCL6 protein expression (rs=0.449, P&amp;lt;0.001; and rs=0.669, P&amp;lt;0.001, respectively). These results indicate that BCL6, ZEB1 and ZEB2 may be as potential biomarkers for predicting invasion, metastasis and prognosis of breast cancer and that BCL6 may be a regulator of ZEB family transcription factors (ZEB1 and ZEB2). Note: This abstract was not presented at the meeting. Citation Format: Min Zhao, Lin Ang, Li Zheng, Jin Wang, Jin Huang, Hongguang Hu, Qiang Zou. The expression of BCL6 and ZEB family transcription factors and their correlation in breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2430. doi:10.1158/1538-7445.AM2017-2430

P 9 Involvement of B-cell lymphoma 6 in the fusion process of trophoblastic cells of the placenta

Introduction Preeclampsia (PE) is one of the leading causes of maternal and perinatal mortality and morbidity and despite intensive research its pathogenesis is not totally understood. In a previous study, we evaluated the gene expression of placental samples from PE patients and controls using a self-designed gene array that targeted critical signaling pathways. Interestingly, the gene of B-cell lymphoma 6 (BCL6), a transcriptional repressor and key regulator of B-lymphocyte development, is increased in preeclamptic placentas. It is expressed in villous cytotrophoblasts (vCTBs), promotes proliferation and survival of trophoblastic cells and is a promising target to decipher the molecular mechanisms behind the pathogenesis of PE in more detail. Objectives The cell-cell fusion of mononuclear vCTBs forms the continuous syncytiotrophoblast (STB) layer. This process is critical for the placental development and is known to be deregulated in preeclamptic placenta. In this work, we have investigated the potential role of BCL6 in the fusion process of trophoblastic cells. Materials and methods Various molecular biological methods were used for this study including Western blotting, quantitative real-time PCR, immunofluorescence staining and ELISA to explore the function of BCL6 in the fusion process of trophoblastic cell lines and vCTBs isolated from term placentas. Cell lines were stimulated with forskolin to induce cell fusion. Results We show that BCL6 is present throughout the whole fusion process. We also demonstrate that the fusion capability of the investigated cells is affected by BCL6, as knockdown of BCL6 results in a considerable enhanced fusion rate of BeWo cells. Furthermore, increased mRNA expression of fusion-related proteins is also observable in JEG-3 cells as well as vCTBs. Conversely, stable overexpression of BCL6 impairs the process of fusion in BeWo cells. Conclusion Our data indicate that an accurately regulated expression of BCL6 is important for proper differentiation and successful syncytialization of trophoblasts in the placenta. Increased BCL6 impairs trophoblast fusion, contributing to the development of PE. Further work is required to detail the molecular mechanisms whereby BCL6 affects the fusion. It also warrants investigations in vivo and in vitro to clarify the correlation between elevated BCL6 and deregulated cytokines, hypoxia and oxidative stress in the preeclamptic placenta.

Overexpression of B-cell lymphoma 6 alters gene expression profile in a myeloma cell line and is associated with decreased DNA damage response.

B‐cell lymphoma 6 (BCL6) attenuates DNA damage response (DDR) through gene repression and facilitates tolerance to genomic instability during immunoglobulin affinity maturation in germinal center (GC) B cells. Although BCL6 expression is repressed through normal differentiation of GC B cells into plasma cells, a recent study showed the ectopic expression of BCL6 in primary multiple myeloma (MM) cells. However, the functional roles of BCL6 in MM cells are largely unknown. Here, we report that overexpression of BCL6 in a MM cell line, KMS12PE, induced transcriptional repression of ataxia telangiectasia mutated (ATM), a DDR signaling kinase, which was associated with a reduction in γH2AX formation after DNA damage. In contrast, transcription of known targets of BCL6 in GC B cells was not affected, suggesting a cell type‐specific function of BCL6. To further investigate the effects of BCL6 overexpression on the MM cell line, we undertook mRNA sequence analysis and found an upregulation in the genomic mutator activation‐induced cytidine deaminase (AID) with alteration in the gene expression profile, which is suggestive of de‐differentiation from plasma cells. Moreover, interleukin‐6 exposure to KMS12PE led to upregulation of BCL6 and AID, downregulation of ATM, and attenuation of DDR, which were consistent with the effects of BCL6 overexpression in this MM cell line. Taken together, these results indicated that overexpression of BCL6 alters gene expression profile and confers decreased DDR in MM cells. This phenotypic change could be reproduced by interleukin‐6 stimulation, suggesting an important role of external stimuli in inducing genomic instability, which is a hallmark of MM cells.

A Critical Role of miR-144 in Diffuse Large B-cell Lymphoma Proliferation and Invasion.

MicroRNAs are endogenous noncoding RNAs that play important roles in a wide variety of biologic processes such as apoptosis, development, aging, and tumorigenesis. The B-cell lymphoma 6 (BCL6) transcriptional repressor has emerged as a critical therapeutic target in diffuse large B-cell lymphomas (DLBCL), but the mechanisms regulating BCL6 are still unclear. In the current study, we screened the microRNA expression profiles in DLBCL specimens and cell lines by qRT-PCR and found that the expression of miR-144 was significantly downregulated in DLBCL tissues and cell lines and negatively correlated with BCL6 expression. We further demonstrated that BCL6 was the direct target gene of miR-144, and miR-144 suppressed the expression of BCL6 via binding the 3'untranslated region of BCL6 mRNA. Biologically, forced expression of miR-144 significantly attenuated cell proliferation and invasion of OCI-Ly3 cells in vitro, and the tumor-suppressor effect of miR-144 was also confirmed using a xenograft mouse model in vivo Taken together, our results reveal that miR-144 regulates BCL6 in DLBCL and provide a rationale for developing strategies that target miR-144 as a therapeutic intervention for DLBCL.

MicroRNA-187 induces diffuse large B-cell lymphoma cell apoptosis via targeting BCL6.

MicroRNAs (miRs) are endogenous non-coding RNAs that serve key functions in a wide range of biological processes, including cell growth, development, apoptosis and carcinogenesis. However, the association between miR-187 and B-cell lymphoma 6 (BCL6) has yet to be fully investigated in lymphoma cell apoptosis. The present study hypothesized that a post-translational mechanism may exist for BCL6 expression, which is regulated by miR-187 in lymphoma cells. The present study demonstrated that the expression of miR-187 in diffuse large B-cell lymphoma (DLBCL) cells was significantly decreased, and its expression was negatively correlated with BCL6 expression. It was also observed that miR-187 directly binds to the 3'-untranslated region of BCL6 mRNA and subsequently suppresses the expression of BCL6. Additionally, the induced expression of miR-187 significantly promoted DLBCL cell apoptosis in vitro. The drug sensitivity of human DLBCL SUDHL2 cells was increased following induction of miR-187 overexpression via an miR-187 mimic. In conclusion, the results of the present study suggest that the modulation of miR-187 expression in DLBCL cells may improve the sensitivity of chemotherapy through BCL6 targeting.

BCL6 mRNA Expression Level in Invasive Duct Carcinoma not otherwise Specified.

B-Cell Lymphoma 6 (BCL6) has an oncogenic role in tumourigenesis of various malignancies. It represses genes involved in terminal differentiation and plays complementary role with Signal Transducer and Activator of Transcription 3 (STAT3) in triple-negative breast cancer cellular function. To evaluate the expression of BCL6 in cancer breast and determine its correlation with the clinico-pathological features including the molecular subtype of breast carcinoma. This prospective case control study was carried out on 150 patients, divided into 100 cases of invasive duct carcinoma not otherwise specified and 50 benign breast lesions including fibroadenoma and fibrocystic disease. Fresh tissues were excised, which were then subjected to RNA extraction. The BCL6 mRNA level was assessed using real-time reverse transcription Polymerase Chain Reaction (PCR). There was a significant higher levels of BCL6 mRNA in malignant cases compared to benign ones (p<0.001). The level of BCL6 mRNA was higher in cases showing advanced tumor stage (p<0.04), triple negative subtype and associated in situ component (p<0.001) compared to cases with an early stage, luminal or Her 2-neu positive subtypes and those lacking in situ component. BCL6 is up-regulated in breast cancer and is associated with poor prognostic features such as advanced stage and triple negative molecular subtype. BCL6 inhibitors might be considered as targeted therapy for breast cancer.

Early Growth Response Genes 2 and 3 Regulate the Expression of Bcl6 and Differentiation of T Follicular Helper Cells

T follicular helper (Tfh) cells support differentiation of B cells to plasma cells and high affinity antibody production in germinal centers (GCs), and Tfh differentiation requires the function of B cell lymphoma 6 (BCL6). We have now discovered that early growth response gene 2 (EGR2) and EGR3 directly regulate the expression of Bcl6 in Tfh cells, which is required for their function in regulation of GC formation. In the absence of EGR2 and -3, the expression of BCL6 in Tfh cells is defective, leading to impaired differentiation of Tfh cells, resulting in a failure to form GCs following virus infection and defects in production of antiviral antibodies. Enforced expression of BCL6 in EGR2/3-deficient CD4 T cells partially restored Tfh differentiation and GC formation in response to virus infection. Our findings demonstrate a novel function of EGR2/3 that is important for Tfh cell development and Tfh cell-mediated B cell immune responses.

Abstract 4944: Identification of B-cell lymphoma 6 as a novel therapeutic target in glioblastoma

Abstract Background Glioblastoma multiforme (GBM) is one of the most aggressive cancers in humans. Identification and characterization of the GBM-promoting factors is imperative for the development of novel and effective clinical interventions. We recently discovered that the expression of B-cell lymphoma 6 (BCL6), a gene involved in the development of B cell lymphoma, is up-regulated in GBM. This study aims to explore the functional implications of BCL6 in this disease. Methods We analysed the transcriptional level of BCL6 in primary glioma samples, and screened the protein expression in a panel of human GBM cell lines as well as primary GBM explants. cDNA microarray analysis was conducted to identify the potential downstream targets of BCL6 in GBM. Small-interfering RNA (siRNA), small hairpin RNA (shRNA), and CRISPR-mediated gene silencing strategies were applied to examine the biological function of BCL6. Finally, inhibitors targeting BCL6 were tested in glioma cells. Results In silico analysis revealed elevated BCL6 mRNA levels in both primary GBM samples and cell lines when compared with neural stem cell or non-tumor brain tissues. Western blot confirmed the prevalent expression of BCL6 in GBM cell lines as well as primary GBM explants. Functional studies showed that BCL6 played an important role in promoting cell growth. Depletion of endogenous BCL6 through siRNA, shRNA or CRISPR in GBM cells led to marked inhibition of cell proliferation both in vitro and in vivo. Transcriptome analysis showed that BCL6 is an important regulator of TP53 signaling pathway. Knockdown of BCL6 increased the expression of p53, p21CIP and p27KIP. CHIP-qPCR further confirmed that BCL6 interacted directly to the TP53 promoter and suppressed its expression. Moreover, BCL6 negatively regulated MEK-ERK activation in GBM cells. BCL6 depletion reduced the phosphorylation levels of both MEK1/2 and ERK1/2, but had little effect on AKT phosphorylation. Our further investigations uncovered that BCL6 modulated the expression of several key regulators of MEK-ERK pathway, such as SPRY1, SPRY2 and AXL. Finally, BCL6 inhibitor showed marked anti-proliferation activity in GBM cells, suggesting that targeting BCL6 may serve as a new strategy to treat GBM. Conclusion Our data suggest that BCL6 is involved in glioma tumorigenesis through regulating both the TP53 and MEK-ERK pathways, and that BCL6 is a potential therapeutic target for glioma treatment. Citation Format: Ye Chen, Liang Xu, Masaharu Hazawa, Anand M. Thippeswamy, Henry Yang, Markus Müschen, De-Chen Lin, Phillip Koeffler. Identification of B-cell lymphoma 6 as a novel therapeutic target in glioblastoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4944. doi:10.1158/1538-7445.AM2015-4944

BCL6 controls Th9 cell development by repressing Il9 transcription.

The transcriptional repressor B cell lymphoma 6 (BCL6) is required for the development of Th follicular cells, and it has been shown to suppress Th2 cell differentiation. We demonstrate that BCL6 is a key regulator of Th9 cell development. BCL6 expression is transiently downregulated in polarized Th9 cells, and forced expression of BCL6 in Th9 cells impairs Th9 cell differentiation. In contrast, BCL6 knockdown upregulated IL-9 production in Th9 cells. The function of BCL6 in Th9 cells is under the control of IL-2/JAK3/STAT5 signaling pathway. Using chromatin immunoprecipitation, we show that, in Th9 cells, BCL6 and STAT5 bind to adjacent motifs in the Il9 promoter. Furthermore, we found that STAT5 binding was associated with the abundance of a permissive histone mark at the Il9 promoter, whereas under conditions in which BCL6 binding was predominant, a repressive histone mark was prevalent. The effects of STAT5 and BCL6 on IL-9 transcription were further demonstrated using an IL-9 luciferase reporter assay in which BCL6 repressed STAT5-mediated Il9 transactivation. In experimental autoimmune encephalomyelitis, forced expression of BCL6 in myelin oligodendrocyte glycoprotein35-55-specific Th9 cells resulted in decreased IL-9 production and induction of IFN-γ, causing an exacerbation of the clinical disease. Our findings demonstrate a novel role of BCL6 in the regulation of Th9 cell development and their encephalitogenicity.

B-cell lymphoma 6 protein stimulates oncogenicity of human breast cancer cells.

BackgroundB-cell lymphoma 6 (BCL6) protein, an evolutionarily conserved zinc finger transcription factor, showed to be highly expressed in various human cancers in addition to malignancies in the lymphoid system. This study investigated the role of BCL6 expression in breast cancer and its clinical significance in breast cancer patients.MethodsExpression of BCL6 protein was assessed using in situ hybridization and immunohistochemistry in 127 breast cancer patients and 50 patients with breast benign disease as well as in breast cell lines. Expression of BCL6 was restored or knocked down in two breast cancer cell lines (MCF-7 and T47D) using BCL6 cDNA and siRNA, respectively. The phenotypic change of these breast cancer cell lines was assessed using cell viability MTT, Transwell invasion, colony formation, and flow cytometry assays and in a xenograft mice model. Luciferase reporter gene, immunoblot, and qRT-PCR were used to investigate the molecular events after manipulated BCL6 expression in breast cancer cells.ResultsBCL6 protein was highly expressed in breast cancer cell lines and tissue specimens and expression of BCL6 protein was associated with disease progression and poor survival of breast cancer patients. In vitro, the forced expression of BCL6 results in increased proliferation, anchorage-independent growth, migration, invasion and survival of breast cancer cell lines, whereas knockdown of BCL6 expression reduced these oncogenic properties of breast cancer cells. Moreover, forced expression of BCL6 increased tumor growth and invasiveness in a nude mouse xenograft model. At the gene level, BCL6 was a target gene of miR-339-5p. Expression of BCL6 induced expression of CXCR4 and cyclinD1 proteins.ConclusionsThe current study demonstrated the oncogenic property of BCL6 in breast cancer and further study could target BCL6 as a novel potential therapeutic strategy for breast cancer.