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HSP90 promotes Burkitt lymphoma cell survival by maintaining tonic B cell receptor signaling

ABSTRACT: Burkitt’s lymphoma (BL) is an aggressive B-cell neoplasm that is currently treated by intensive chemotherapy in combination with anti-CD20 antibodies. Because of their toxicity, current treatment regimens are often not suitable for elderly patients or for patients in developing countries where BL is endemic. Hence, there is a need for targeted therapies. In this study, we performed a compound screen in 17 BL cell lines to identify small molecule inhibitors affecting cell survival. We observed that, among other compounds, inhibitors of heat shock protein 90 (HSP90) induce apoptosis in BL cells in vitro at concentrations that did not affect normal B cells. By global proteomic and phosphoproteomic profiling, we found that in BL, HSP90 inhibition compromises activity of the pivotal B cell antigen receptor (BCR)-proximal effector spleen tyrosine kinase (SYK), which we identified as an HSP90 client protein. Consistently, expression of constitutively active TEL-SYK counteracted the apoptotic effect of HSP90 inhibition. Hence, our study provides a molecular rationale for the use of HSP90 inhibitors in the treatment of BL by demonstrating that HSP90 inhibition interferes with tonic BCR signaling and thus impairs BL cell survival.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Henning Urlaub

PROVIDER: MSV000080781 | MassIVE | Wed Mar 29 13:55:00 BST 2017

SECONDARY ACCESSION(S): PXD004181

REPOSITORIES: MassIVE

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HSP90 promotes Burkitt lymphoma cell survival by maintaining tonic B-cell receptor signaling.

Walter Roland R Pan Kuan-Ting KT Doebele Carmen C Comoglio Federico F Tomska Katarzyna K Bohnenberger Hanibal H Young Ryan M RM Jacobs Laura L Keller Ulrich U Bönig Halvard H Engelke Michael M Rosenwald Andreas A Urlaub Henning H Staudt Louis M LM Serve Hubert H Zenz Thorsten T Oellerich Thomas T

Blood 20161115 5

Burkitt lymphoma (BL) is an aggressive B-cell neoplasm that is currently treated by intensive chemotherapy in combination with anti-CD20 antibodies. Because of their toxicity, current treatment regimens are often not suitable for elderly patients or for patients in developing countries where BL is endemic. Targeted therapies for BL are therefore needed. In this study, we performed a compound screen in 17 BL cell lines to identify small molecule inhibitors affecting cell survival. We found that i ...[more]

PMID: 28064214

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Project description:The B cell receptor (BCR) signaling, required for the survival and maturation of B cells, is a major deregulated pathway in B cell lymphomas. Several mutations are known to enhance the tonic BCR signal in Burkitt lymphomas (BL) or to mimic an activated receptor in some diffuse large B cell lymphomas (DLBCL). While the proximal events and kinases of the BCR signaling are well studied, less is known about the interactions of downstream effector pathways. In order to reach a less abstract description of this pathway we decided to employ the Modular Response Analysis-based modelling approach STASNet on more directly connected phosphorylation data. Using a Luminex proteomics platform we measured the phosphorylation of fourteen signaling and effector proteins after activating the B cell receptor (BCR) signaling and/or using inhibitors directed against seven intracellular signaling molecules in two independent Burkitt lymphoma cells (BL-2, BL-41). Application of a novel two step STASNet modelling pipeline unveiled novel feedback and crosstalk structures in the BCR-driven signaling network, including a crosstalk from p38 which negatively regulates MEK/ERK-activity in the presence of active BCR. Using Western Blot measurements, we verified and further characterized the p38-MEK/ERK crosstalk and demonstrated that it is a general mechanism in BL cells. Global Tandem Mass Tag (TMT) phosphoproteomic analysis on BL-2 cells found PI3K to be a major mediator of B-cell receptor signaling and manifested the p38-ERK crosstalk directly on ERK phosphosites and indirectly on seven bona fide ERK targets. We also noticed that the BL-2-learned pathway network structure was transferable to perturbation data from closely related BL-41 cells. Moreover, - compared to a literature-derived network - the BL-2-developed predictive pathway proved also to be a better starting point for network development in cells with aberrant BCR signaling in two representative cell lines derived from Diffuse large B cells (HBL-1, OCI-LY3). This indicates that models trained on activated B-cells are highly informative to be transferred to closely related cancer signaling network.

Project description:Aggressive double and triple hit (DH/TH) DLBCL feature activation of Hsp90 stress pathways. Herein, we show that Hsp90 controls post-transcriptional dynamics of key mRNA species including those encoding BCL6, MYC and BCL2. Using a proteomics approach, we found that Hsp90 binds to and maintains activity of eIF4E (eukaryotic translation initiation factor 4E). EIF4E drives nuclear export and translation of BCL6, MYC and BCL2 mRNA. eIF4E RIP-sequencing in DLBCL suggests that nuclear eIF4E controls an extended program that includes BCR signaling, cellular metabolism and epigenetic regulation. Accordingly, eIF4E was required for survival of DLBCL including the most aggressive subtypes DH/TH lymphomas. Indeed, eIF4E inhibition induces tumor regression in cell line and patient-derived tumorgrafts of TH-DLBCL, even in the presence of elevated Hsp90 activity. Targeting Hsp90 is typically limited by counter-regulatory elevation of Hsp70B, which induces resistance to Hsp90 inhibitors. Surprisingly, we identify Hsp70 mRNA as an eIF4E target. In this way, eIF4E inhibition can overcome drug resistance to Hsp90 inhibitors. Accordingly, rational combinatorial inhibition of eIF4E and Hsp90 inhibitors resulted in cooperative anti-lymphoma activity in DH/TH DLBCL in vitro and in vivo. We found that eIF4E activity regulates the nuclear export of BCL6, MYC, and BCL2 in DH/TH DLBCLs. To determine the extent of nuclear eIF4E activity in DH/TH DLBCLs and how these programs can support the oncogenic activity of BCL6, MYC and/or BCL2 transcripts, we conducted eIF4E-RIP of nuclear RNA followed by RNA-sequencing in OCI-Ly1 cells in triplicates. To understand the changes in gene expression after ribavarin in a clinically relevant sample, we generated a patient-derived xenograft (PDX) in NSG mice from a de-identified specimen isolated from a patient prior to treatment harboring a triple-hit ABC-type DLBCL. PDX cells from passage four (PDX-4) were implanted into NSG mice. When tumors were palpable, mice were randomized to receive vehicle or 80 mg/kg/b.i.d. ribavarin intraperitoneally for 10 days. We isolated RNA from tumors treated with vehicle (n=2) or ribavarin (n=2) and performed mRNA-seq.

Project description:Background. Heat shock protein 90 (Hsp90) is essential for the stability and the function of many client proteins, such as ERB2, C-RAF, CDK4, HIF-1 aplha and AKT. Recent reports demonstrated that inhibition of Hsp90 modulates multiple functions required for survival of human cancer, such as myeloma (Mitsiades et al, Blood:107, 1092, 2006), however, the precise mechanism of anti-cancer effect of Hsp90 inhibition is still uncertain. Aim. The aim of this study is evaluate the effect of Hsp90 inhibition, and to identify molecular pathways responsible for anti-proliferative effect on ATL cells. Method. For Hsp90 inhibition, Geldanamycin derivates, 17AAG (17-allylamino -17-demethoxygeldanamycin) and 17DMAG (17-(dimethylaminoethylamino) 17-demethoxygeldanamycin) were used in this study. Interleukin 2-independent ATL cell lines (MT-2 and MT-4) and an interleukin 2-dependent ATL cell line (TaY) were incubated, with or without Hsp90 inhibitors. Fresh ATL cells obtained from patients were also used after obtaining informed consent. Cell numbers at 48 h after incubation with or without Hsp90 inhibitors were assessed with the Cell Counting Kit-8 assay (Dojindo Molecular Technologies, Gaithersburg, MD, USA). For detection of apoptosis, we used Annexin V-biotin apoptosis detection kit (Calbiochem, La Jolla, CA, USA). Gene expression analysis was done using a DNA microarray (NCBI Gene expression omnibus; GPL 2531) and statistical analysis was done by a GeneSifter (VizXlabs, Seattle, WA, USA). Results. We found cell death induced by Hsp90 inhibitors in all the 3 ATL cell lines as well as patient specimens. Inhibitory concentration (IC50) of 17AAG in 3 ATL cell lines was 300 to 700 nM, and that of 17DMAG was 150 to 200 nM. Fresh ATL cells obtained from patients were more sensitive for either 17AAG or 17DMAG. Gene expression analysis of ATL cells revealed that up-regulation of HSPA1A encoding Hsp70, and genes related to cell cycle arrest (i.e. CDKN1A). Genes regulating cell proliferation or anti-apoptosis (i.e. MYC, BCL2 and Cyclin C), genes related to cytokine or chemokine (i.e. IL9, CCL 17, and CCL27), and notably, genes involved in Wnt/-catenin signaling pathway (i.e.TCF7L2 and TCF4), were remarkably repressed. Inhibition of AKT at the protein level was also evident, suggesting the possibility that AKT may down-regulates -catenin/ TCF7L2 pathways in response to Hsp90 inhibitors in ATL cells. Conclusion. Our results have provided new insights into the complex molecular pharmacology of Hsp90 inhibitors, and suggest that Hsp90 inhibitors might be beneficial as anti-proliferative agent in treating ATL patients. Six samples treated with Hsp90 inhibitors (17-AAG or 17-DMAG) were analyzed in biological duplicate.