scholarly journals Lw-213 Synergizes with Rituximab to Inhibit Diffuse Large B-Cell Lymphomas By Upregulating CD20

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4366-4366
Author(s):  
Yuchen Li ◽  
Hui Li ◽  
Hui Hui ◽  
Jingyan Xu
Keyword(s):  
Cell Death ◽  
B Cell ◽  
Cell Lines ◽  
B Cell Lymphoma ◽  
Cell Counting ◽  
Mrna Levels ◽  
Sox2 Expression ◽  
Cd20 Expression ◽  
Large B Cell

Abstract Background：Downregulation of CD20, a molecular target for monoclonal antibodies (mAbs), is a clinical problem leading to decreased efficacy of anti-CD20-based therapeutic regimens.Up to one-third of diffuse large B cell lymphoma (DLBCL) patients eventually develop resistance to R-CHOP regimen, since the remaining therapeutic options are limited. LW-213, a derivative of wogonin, is reported to possess antineoplastic properties in a variety of cancers, but whether it has effects on DLBCL is n-ot known. Studies have reported that upregulation of CD20 expression b-y either HDACi or silenced SOX2 expression showed sensitizing potential in Rituximab-induced cell death in malignant B cells. Our study was to explore whether LW-213 could sensitize DLBCL to Rixutimab thus improve therapeutic efficacy. Methods： Two DLBCL cell lines, RI-1 (ABC subtype) and Su-DHL -8 (GCB subtype), were used in our study. RI-1 and Su-DHL-8 cells were treated with LW-213 at different doses and for different times, and their proliferation and viability were detected by Cell counting kit-8 (CCK8).Flow cytometry was used to determine surface CD20 expression. Western blotting and q-PCR were applied to examine the protein and mRNA levels of CD20, SOX2, Ace-H3 and Ace-H3K27. CDC assay was used to evaluate the synergistic effects of LW-213 and Rixutimab. Results：We showed that LW-213 inhibited the proliferation of human DLBCL cell lines (Su-DHL-8、RI-1 ) in dose-and time-dependent manners with IC 50 values at the low μmol/L levels, meanwhile it potently inhibited primary lymphoma cells derived from peripheral blood of B-cel-l lymphoma patients. Furthermore, LW-213 significantly increased CD20 surface expression and the acetylation level of histone in DLBCL cell li-nes. Inversely，the SOX2 expression level remarkably decreased. Finally,Combination with LW-213 significantly synergized Rituximab-induced cell death in vitro. Conclusion： The results demonstrate that LW-213 sensitizes DLBCL cells to Rituximab in vitro by upregulating CD20 expression and the SOX2/ace-H3K27/ace-H3 axis may plays a critical role in CD20 upregulation processing. Even though this strategy is important in vitro models,the upregulating CD20 expression therapy against DLBCL proposed in this study warrants further study in vivo and clinical trials . Keywords：CD20 DLBCL Rituximab SOX2 Histone Deacetylation Disclosures No relevant conflicts of interest to declare.

PDK4-Mediated Metabolic Reprogramming Promotes Rituximab Resistance in Diffuse Large B-Cell Lymphoma Via Negative Regulation of MS4A1/CD20

2021 ◽  
Author(s):  
Duanfeng Jiang ◽  
Qiuyu Mo ◽  
Xiaoying Sun ◽  
Xiaotao Wang ◽  
Min Dong ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Metabolic Reprogramming ◽  
Cell Counting ◽  
Expression Levels ◽  
Large B Cell Lymphoma ◽  
Cd20 Expression ◽  
Large B Cell

Abstract Background: Diffuse large B cell lymphoma (DLBCL) heterogeneity promotes the recurrence and anti-CD20-based therapeutic resistance. In previous studies, it has been demonstrated that the downregulation of MS4A1/CD20 expression after chemoimmunotherapy with rituximab can lead to rituximab resistance. However, the the mechanisms of CD20-loss remains unknown. Methods: The expression levels of PDK4 were investigated in DLBCL patients and cell lines by RNA-seq, qRT-PCR, western blotting and immunofluorescence analysis. Lentiviral infection was used to regulate the level of PDK4 in DLBCL cells. The effects of PDK4 on apoptosis, drug sensitivity and proliferation of DLBCL cells were evaluated by flow cytometry and cell-counting kit-8 (CCK-8) assay, as well as being assessed in a murine model. Cell metabolism was conducted by measurement of glucose consumption, lactate production, ATP levels, ECAR and OCR with corresponding assay kit. Results: Our data showed that PDK4 expression levels elevated significantly in DLBCL cells derived from both the patients and cell lines with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone regimen) resistant. We further found that the overexpression of PDK4 in DLBCL cells can lead to cell proliferation and rituximab resistance both in vitro and in vivo. Furthermore, the loss of PDK4 expression or treatment with the PDK4 inhibitor dichloroacetate is effective in increasing the rituximab-induced cell apoptosis in DLBCL cells. According to the mechanism studies, PDK4 mediated a metabolic shift that the main energy source was changed from OXPHOS to glycolysis. More importantly, with the knockdown or overexpression of PDK4 in DLBCL cells leads to a reverse MS4A1/CD20 expression. Conclusion: Our data identify a metabolic reprogramming role of PDK4 in rituximab resistance of DLBCL and highlight the unique function of PDK4 as an attractive therapeutic target.

scholarly journals Repurposing dasatinib for diffuse large B cell lymphoma

2019 ◽  
Vol 116 (34) ◽  
pp. 16981-16986 ◽  
Author(s):  
Claudio Scuoppo ◽  
Jiguang Wang ◽  
Mirjana Persaud ◽  
Sandeep K. Mittan ◽  
Katia Basso ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Kinase Inhibitor ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Multikinase Inhibitor ◽  
Large B Cell Lymphoma ◽  
Large B Cell

To repurpose compounds for diffuse large B cell lymphoma (DLBCL), we screened a library of drugs and other targeted compounds approved by the US Food and Drug Administration on 9 cell lines and validated the results on a panel of 32 genetically characterized DLBCL cell lines. Dasatinib, a multikinase inhibitor, was effective against 50% of DLBCL cell lines, as well as against in vivo xenografts. Dasatinib was more broadly active than the Bruton kinase inhibitor ibrutinib and overcame ibrutinib resistance. Tumors exhibiting dasatinib resistance were commonly characterized by activation of the PI3K pathway and loss of PTEN expression as a specific biomarker. PI3K suppression by mTORC2 inhibition synergized with dasatinib and abolished resistance in vitro and in vivo. These results provide a proof of concept for the repurposing approach in DLBCL, and point to dasatinib as an attractive strategy for further clinical development in lymphomas.

IL-4 Affects Proliferation, Chemosensitivity-and Rituximab Sensitivity of Germinal Center B-Cell like (GCB) and Activated B-Cell like (ABC) Diffuse Large B-Cell Lymphoma Differently.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 242-242 ◽  
Author(s):  
Hovav Nechushtan ◽  
Joseph D. Rosenblatt ◽  
Izidore S. Lossos
Keyword(s):  
Cell Death ◽  
B Cell ◽  
Cell Lines ◽  
Germinal Center ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Cell Lysis ◽  
Large B Cell Lymphoma ◽  
Expression Of Genes ◽  
Large B Cell

Abstract Diffuse Large B-cell Lymphoma (DLBCL) represent a diverse group of lymphoid neoplasms with heterogeneous clinical, histological, immunophenotypic, cytogenetic and molecular genetic features. Approximately 50% of DLBCL patients are not cured by the standard combination chemotherapy regimens. DLBCL can be subclassified into GCB-like DLBCL which are characterized by expression of genes normally expressed in germinal center B cells, and having a significantly better overall survival (OS) than the ABC-like DLBCL, which are characterized by expression of genes induced during in vitro activation of normal B cells. At least two markers of the GCB-phenotype - BCL6 and HGAL - are IL-4 target genes, increased expression of which independently predicts better OS. These observations suggest that endogenous or exogenously administered IL-4 may influence behavior of DLBCL. IL-4 mRNA was detected at low levels in 5 of 7 GCB-like and in all 4 ABC-like DLBCL tumor specimens. Two of 7 GCB-like tumors showed high expression levels of IL-4 as determined by real-time RT-PCR. Examination of the effects of IL-4 on proliferation of GCB-like (SUDHL6, SUDHL4 and OCILY19) and ABC-like (OCILY10 and OCILY3) DLBCL cell lines showed that IL-4 mildly increased DNA synthesis, as assessed by thymidine incorporation, in all the GCB-like DLBCL. Conversely, IL-4 markedly decreased proliferation in the ABC-like DLBCL cell lines by inducing G1 arrest. IL-4 also differently affected the sensitivity of GCB-like and ABC-like DLBCL to doxorubicin. IL-4 reduced doxorubicin-induced cell death of ABC-like cell lines (20–50% reduction) while it markedly increased the killing of the GCB-like cells (40–80% induction). IL-4 also prevented serum starvation-induced cell death of the ABC-like DLBCL, but it increased cell death of the GCB-like DLBCL cell lines. Recently, Rituximab was shown to improve survival of DLBCL patients when added to the CHOP regimen. The precise mechanisms of its action are unknown; however present data suggest that it may affect lymphoma cells either by activation of complement lysis or by mediating ADCC. IL-4 reduced the complement mediated Rituximab cell lysis of the ABC-like cell lines, while it increased the complement mediated Rituximab cell lysis of the GCB-like DLBCL cell lines. Expression levels of surface markers that modulate complement cell lysis (CD46, CD55 and CD59) were not affected by IL-4 exposure. In contrast, IL-4 did not affect killing of GCB-like and ABC-like cells by ADCC. These observations suggest that DLBCL subtypes may respond differently to the in vivo cytokine milieu of the tumor. Different responsiveness to IL-4 may modulate tumor sensitivity to the current therapeutic modalities and can potentially be explored to augment response to chemotherapy and Rituximab.

scholarly journals Targeting Positive Cofactor 4 induces autophagic cell death in MYC-expressing diffuse large B cell lymphoma

2021 ◽  
Author(s):  
Le Ma ◽  
Qiang Gong ◽  
Zelin Chen ◽  
Yu Wang ◽  
Xu Tan ◽  
...  
Keyword(s):  
Cell Death ◽  
B Cell ◽  
Molecular Mechanisms ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Autophagic Cell Death ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Abstract Background: The MYC-expressing diffuse large B-cell lymphoma (DLBCL) is one of the refractory lymphomas. The pathogenesis of MYC-expressing DLBCL is still unclear, and there is a lack of effective therapy. In this study, we have explored the clinical significance and the molecular mechanisms of transcription co-activator 4 (PC4) in MYC-expressing DLBCL.Methods: We investigated PC4 expression in 54 cases of DLBCL patients’ tissues and matched normal specimens, and studied the molecular mechanisms of PC4 in MYC-expressing DLBCL both in vitro and in vivo.Results: We reported for the first time that targeting c-Myc could induce autophagic cell death in MYC-expressing DLBCL cell lines. We next characterized that PC4 was an upstream regulator of c-Myc, and PC4 was overexpressed in DLBCL and was closely related to clinical staging, prognosis and c-Myc expression. Further, our in vivo and in vitro studies revealed that PC4 knockdown could induce autophagic cell death of MYC-expressing DLBCL. And inhibition of c-Myc mediated aerobic glycolysis and activation of AMPK / mTOR signaling pathway were responsible for the autophagic cell death induced by PC4 knockdown in MYC-expressing DLBCL. Through the CHIP, DLRTM and EMSA assay, we also found that PC4 exerted its oncogenic functions by directly binding to c-Myc promoters.Conclusions: PC4 exerts its oncogenic functions by directly binding to c-Myc promoters. Inhibition of PC4 can induce autophagic cell death of MYC-expressing DLBCL. Our study provides novel insights into the functions and mechanisms of PC4 in MYC-expressing DLBCL, and suggests that PC4 might be a promising therapeutic target for MYC-expressing DLBCL.

scholarly journals The bromodomain and extra-terminal domain degrader MZ1 exhibits preclinical anti-tumoral activity in diffuse large B-cell lymphoma of the activated B cell-like type

2021 ◽  
Vol 2 (6) ◽  
pp. 586-601
Author(s):  
Chiara Tarantelli ◽  
Eleonora Cannas ◽  
Hillarie Ekeh ◽  
Carmelo Moscatello ◽  
Eugenio Gaudio ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Bet Inhibitor ◽  
Terminal Domain ◽  
Large B Cell Lymphoma ◽  
Bet Inhibitors ◽  
Large B Cell

Aim: Bromodomain and extra-terminal domain (BET) proteins are epigenetic readers that play a fundamental role in transcription regulation. Preclinical and early clinical evidence sustain BET targeting as an anti-cancer approach. BET degraders are chimeric compounds comprising of a BET inhibitor, which allows the binding to BET bromodomains, linked to a small molecule, binder for an E3 ubiquitin ligase complex, triggering BET proteins degradation via the proteasome. These degraders, called proteolysis-targeting chimeras (PROTACs), can exhibit greater target specificity compared to BET inhibitors and overcome some of their limitations, such as the upregulation of the BET proteins themselves. Here are presented data on the anti-tumor activity and the mechanism of action of the BET degrader MZ1 in diffuse large B cell lymphoma (DLBCL) of the activated B-cell like (ABC, ABC DLBCL), using a BET inhibitor as a comparison. Methods: Established lymphoma cell lines were exposed for 72 h to increasing doses of the compounds. Cell proliferation was evaluated by using an 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazoliumbromide (MTT) assay. Fluorescent-Activated Cell Sorter (FACS) analysis was performed to measure apoptotic activation and RNA sequencing (RNA-Seq) to study the transcriptional changes induced by the compounds. Results: MZ1, and not its negative control epimer cisMZ1, was very active with a median half maximal inhibitory concentration (IC50) of 49 nmol/L. MZ1 was more in vitro active than the BET inhibitor birabresib (OTX015). Importantly, MZ1 induced cell death in all the ABC DLBCL cell lines, while the BET inhibitor was cytotoxic only in a fraction of them. BET degrader and inhibitor shared partially similar changes at transcriptome level but the MZ1 effect was stronger and overlapped with that caused cyclin-dependent kinase 9 (CDK9) inhibition. Conclusions: The BET degrader MZ1 had strong cytotoxic activity in all the ABC DLBCL cell lines that were tested, and, at least in vitro, it elicited more profound effects than BET inhibitors, and encourages further investigations.

Vav-1 expression correlates with NFκB activation and CD40-mediated cell death in diffuse large B-cell lymphoma cell lines

2010 ◽  
pp. n/a-n/a ◽  
Author(s):  
Annette Hollmann ◽  
Raquel Aloyz ◽  
Kristi Baker ◽  
Stephan Dirnhofer ◽  
Trevor Owens ◽  
...  
Keyword(s):  
Cell Death ◽  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Lymphoma Cell ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Cyclin-Dependent Kinase Inhibitor Seliciclib Shows In Vitro Activity in Diffuse Large B Cell Lymphomas.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4738-4738
Author(s):  
Francesco Bertoni ◽  
Katia Lacrima ◽  
Andrea Rinaldi ◽  
Sara Vignati ◽  
Vittoria Martin ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Active Agent ◽  
B Cell Lymphoma ◽  
Lymphocytic Leukemia ◽  
Vitro Activity ◽  
In Vitro Activity ◽  
Large B Cell

Abstract Background. Despite recent improvements in treatment, a significant fraction of patients with diffuse large B cell lymphoma (DLBCL) still fail therapy. Therefore, new therapeutic modalities are needed to advance the cure rate. Seliciclib (CYC202, R-roscovitine) is a purine analogue developed as an inhibitor of CDK2/cyclin E CDK7/cyclin H and CDK9/cyclin T. Seliciclib has been shown to be active in B cell neoplasms, such as mantle cell lymphoma, chronic lymphocytic leukemia and in multiple myeloma in vitro. The aim of this study was to assess the in vitro activity of seliciclib in DLBCL. Materials and methods. The anti-proliferative activity of seliciclib was tested in nine human DLBCL cell lines and six DLBCL primary cell cultures. The effects of seliciclib on the cell cycle and on apoptosis, as well as on transcription-related proteins were assessed. Results. The cell viability of all DLBCL cell lines and primary cells was reduced by seliciclib treatment. The IC50 for the cell lines ranged from 13 to 36 μM. The effect of seliciclib was independent of the genetic aberrations characterizing the cell lines. After seliciclib exposure cells accumulated in G2/M or in G1 phase, with most of the cells showing signs of apoptosis. Despite the clear cytotoxic effect and induction of apoptosis, we could not identify a unique mechanism of action. Conclusions. Our in vitro data suggest that seliciclib is an active agent in DLBCL. Its efficacy is apparently independent of the underlying chromosomal translocations characteristic of DLBCL. The drug might represent a new therapeutic agent in this lymphoma subtype.

scholarly journals The Novel HDAC Inhibitor Chidamide Synergizes with Rituximab to Inhibit DLBCL Tumor Growth in Vitro and In Vivo By up-Regulating CD20 Expression

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 2947-2947
Author(s):  
Xu-Wen Guan ◽  
Wang Hua-Qing ◽  
Li Jia ◽  
Feng-Ting Liu
Keyword(s):  
Cell Death ◽  
Tumor Growth ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Combined Treatment ◽  
B Cell Lymphoma ◽  
Surface Expression ◽  
Cd20 Expression

Abstract Background: Histone deacetylases (HDACs) are crucial proteins for supporting tumorigenesis. HDACs reverse chromatin acetylation and alter transcription of oncogenes and tumor suppressor genes by removing acetyl groups from histones. HDAC inhibitors are considered as promising anti-cancer drugs, particularly in combination with other standard treatment regimens. Chidamide is the world first oral HDAC inhibitor which selectively inhibits class I HDAC1, HDAC2, and HDAC3 as well as class IIb HDAC10. Chidamide has been approved by China FDA in 2015 for the treatment of relapsed or refractory peripheral T-cell lymphoma. Diffuse large B-cell lymphoma (DLBCL) is the most aggressive form of B-cell lymphoma. Treatment with R-CHOP i.e. Rituximab (the anti-CD20 monoclonal antibody) plus CHOP (Cyclophosphamide, doxorubicin, vincristine, and prednisone) has significantly improved clinical outcome for DLBCL patients. However, treatment-induced deacetylation of CD20 gene and consequently down-regulation of CD20 protein expression causes an acquired resistance to further treatment with R-CHOP. We hypothesize that inhibition of HDACs by Chidamide could overcome Rituximab-mediated down-regulation of CD20 and facilitate Rituximab-induced DLBCL tumor growth inhibition. The aim of this study is to determine the synergistic effect of Chidamide and Rituximab in the treatment of DLBCL in vitro and in vivo. Methods: The levels of CD20 (MS4A1) mRNA expression and clinical outcomes in patients with DLBCL treated either with R-CHOP or CHOP were obtained from the Gene Expression Omnibus (GEO) repository (NCBI GSE 10846). The association of CD20 expression with overall survival (OS) was analyzed by Cox regression analysis and the cut-off point was calculated by the X-tile software. CD20 protein surface expression and Rituximab-induced cell death were analyzed by flow cytometry. The IC50s of Chidamide and the synergisms with Rituximab (10 µg/ml) on five DLBCB cell lines (OCI-LY3, OCI-LY7, Su-DHL6, Su-DHL8, and Su-DLH10) were determined by MTT test after cells were treated with a range of concentrations of Chidamide with or without Rituximab for 24 hours. The synergism was calculated using ComboSyn software to obtain the combination index (CI). For in vivo experiments, the human DLBCL cell line OCI-LY7 were injected to 6 weeks BALB/C nude mice to develop xenograft DLBCL mice models. After tumors were palpable, mice were divided into four groups and injected with NaCl (control), Rituximab, Chidamide and Rituximab plus Chidamide daily for three weeks. The tumor volumes were monitored frequently during the treatment. Results: In R-CHOP treated cohort (n=233), higher expression of CD20 expression (n=137) is significantly associated with superior clinical outcomes compared with lower CD20 expression (n=96) with P=0.0038, HR=0.4753, 95% CI=0.274-0.779. However, the levels of CD20 have no effect on clinical outcome in DLBCL patients treated with CHOP (n=183). The levels of CD20 protein surface expression on five DLBCL cell lines were significantly and positively correlated with the sensitivities of cells to Rituximab-induced cell death (P=0.0018, R=0.88). HDAC1, HDCA2 and HDCA3 proteins were detected in these DLBCL cell lines. Treatment with Rituximab significantly reduced CD20 surface expression but treatment with Chidamide significantly increased CD20 surface expression in DLBCL cells. The CI numbers for combined treatment with Chidamide and Rituximab were either <0.01 (very strong synergism) or <0.3 (strong synergism), indicating that Chidamide significantly synergized Rituximab-induced cell death. For in vivo assay, treatment with either Rituximab or Chidamide alone slightly but not significantly reduced tumor volume. Combination with Chidamide and Rituximab significantly inhibited tumor growth in DLBCL xenograft mice (P<0.0001). Mice with combined treatment showed significantly prolonged survival compared with other groups. Conclusions: our data demonstrate for the first time that inhibition of HDACs by Chidamide significantly synergized Rituximab-induced tumor growth inhibition in vitro and in vivo. We propose that CD20 surface expression should be used clinically to evaluate treatment response in patients with DLBCL. Chidamide is a promising sensitizer for the treatment of DLBCL with R-CHOP. Disclosures No relevant conflicts of interest to declare.

scholarly journals MYC-Dependent PI3K and MCL-1 Feedbacks Attenuate BET Inhibitors Activity in Diffuse Large B-Cell Lymphoma

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 294-294
Author(s):  
Enrico Derenzini ◽  
Patrizia Mondello ◽  
Yuxuan Liu ◽  
Mary Scallion ◽  
Zahra Asgari ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Pi3k Pathway ◽  
Combination Strategies ◽  
Large B Cell Lymphoma ◽  
Bet Inhibitors ◽  
Large B Cell

Abstract MYC overexpression is a poor prognostic predictor in Diffuse Large B-Cell Lymphoma (DLBCL). MYC-targeting with bromodomain and extraterminal protein family (BET) inhibitors is a promising strategy for the treatment of MYC-driven cancers, including lymphomas. However, preclinical and emerging data from early clinical trials demonstrated a modest antiproliferative activity in vitro and in vivo. We hypothesized that BET inhibition may induce feedback survival mechanisms preventing or attenuating cell death that could be exploited for designing future, more effective, combination strategies. In a high-throughput combinatorial drug screening experiment, we found that phosphatidylinositol 3-kinase (PI3K) pathway inhibitors enhanced the antiproliferative effects of BET inhibitors (JQ1, I-BET 151, CPI-203) with a strong class effect. JQ1 upregulated the mRNA expression of several upstream components of the PI3K pathway, including PIK3CA, PIK3R1, PDK1 in a large panel of DLBCL and Burkitt lymphoma cell lines. These effects translated in increased pathway activation as demonstrated by increased levels of the phosphorylated forms of downstream targets GSK3α/β, TSC2, P70S6K, and by increased concentrations of chemokines known to be regulated by PI3K in cell culture supernatants (CCL3 and CCL4). This effect was reversed by submicromolar doses of the PI3K inhibitor BKM-120. MYC silencing recapitulated the effects of BET inhibitors on PI3K pathway gene expression, activation and chemokine secretion. These data indicate that BET inhibition induces PI3K activation by a MYC-dependent feedback. We also observed transcriptional upregulation of the antiapoptotic gene Myeloid Leukemia 1 (MCL-1) following BET inhibition or MYC depletion, suggesting a second MYC-dependent mechanism. RNAi-mediated MCL-1 silencing or co-treatment with a small molecule MCL-1 inhibitor (UMI-77) enhanced the effects of BET inhibitors in DLBCL cell lines by inducing apoptosis. Using SILAC-based quantitative mass spectrometry, we found that BET inhibitors at submicromolar doses downregulated several E2 ubiquitin conjugating enzymes including UBE2C. RNAi mediated UBE2C knockdown induced MCL-1 upregulation in DLBCL cells. The enhanced in vitro effect of combining BETi and PI3Ki was reproduced in TMD8 mouse xenografts. To our knowledge, this is the first study demonstrating MYC-dependent regulation of the PI3K pathway, MCL-1 and the ubiquitin system upon BET inhibition. Our study revealed previously unknown mechanisms of action of BET inhibitors uncovering novel MYC-dependent survival feedback loops, and providing a framework for future combination strategies. Disclosures Zelenetz: Gilead Sciences: Research Funding.

Constitutive STAT6 activation in primary mediastinal large B-cell lymphoma

Blood ◽  
2004 ◽  
Vol 104 (2) ◽  
pp. 543-549 ◽  
Author(s):  
Chrystelle Guiter ◽  
Isabelle Dusanter-Fourt ◽  
Christiane Copie-Bergman ◽  
Marie-Laure Boulland ◽  
Sabine le Gouvello ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Janus Kinase ◽  
Interleukin 4 ◽  
Mrna Levels ◽  
Primary Tumors ◽  
Large B Cell Lymphoma ◽  
Large B Cell

Abstract Primary mediastinal large B-cell lymphoma (PMBL), currently recognized as a diffuse large B-cell lymphoma (DLBCL) subtype, shows increased expression of interleukin 4 (IL-4)/IL-13 signaling effectors and targets, suggesting constitutive activation of these pathways. We therefore investigated the functional state of the signal transducer and activator of transcription 6 (STAT6), mediating IL-4/IL-13 transcriptional effects. Constitutive STAT6 phosphorylation and DNA-binding activity were detected in PMBL cell lines but not DLBCL cell lines. Moreover, immunohistochemical analysis revealed nuclear phosphorylated STAT6 (P-STAT6) in 8 of 11 PMBL, compared with 1 of 10 DLBCL primary tumors (P = .01). IL-4 and IL-13 transcripts were absent in PMBL cell lines and expressed at low levels in tumors, indicating that, contrary to classical Hodgkin lymphoma (cHL), STAT6 activation is not due to an autocrine IL-4/IL-13 secretion. We demonstrated an amplification of the JAK2 gene in 2 of 6 PMBL cases, and showed higher JAK2 mRNA levels in PMBL compared with DLBCL (P = .005). The Janus kinase 2 (JAK2) was constitutively phosphorylated in the PMBL MedB1 cell line. MedB1 treatment with JAK2 inhibitor AG490 partially decreased STAT6 phosphorylation, suggesting that JAK2 is partially involved in STAT6 activation in these cells. Our findings highlight phosphorylated STAT6 as a characteristic distinguishing PMBL from DLBCL, but a common feature to PMBL and cHL, supporting the hypothesis of common pathogenic events in these 2 lymphomas. (Blood. 2004;104: 543-549)

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