A major pathogenetic mechanism in classical Hodgkin lymphoma (cHL) is constitutive activation of canonical nuclear factor-κB (NF-κB) p50/p65 signaling, controlling lymphoma cell proliferation and ...survival. Recently, we demonstrated that aberrant Notch1 activity is a negative regulator of the B cell program in B cell-derived Hodgkin and Reed-Sternberg (HRS) cells. Despite abundant evidence for a complex context-dependent cross talk between Notch and NF-κB signaling in hematopoietic cells, it is unknown whether these pathways interact in HRS cells. Here, we show that Notch-signaling inhibition in HRS cells by the γ-secretase inhibitor (GSI) XII results in decreased alternative p52/RelB NF-κB signaling, interfering with processing of the NF-κB2 gene product p100 into its active form p52. As a result, expression of Notch and NF-κB target genes is reduced, and survival of HRS cells is impaired. Stimulation of alternative NF-κB signaling in the Hodgkin cell line L540cy by activation of the CD30 receptor rescued GSI-mediated loss of cell viability and apoptosis induction. Our data reveal that Notch is an essential upstream regulator of alternative NF-κB signaling and indicate cross talk between both the pathways in HRS cells. Therefore, we suggest that targeting the Notch pathway is a promising therapeutic option in cHL.
We review the main results obtained by the BRAHMS Collaboration on the properties of hot and dense hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A ...particular focus of this paper is to discuss to what extent the results collected so far by BRAHMS, and by the other three experiments at RHIC, can be taken as evidence for the formation of a state of deconfined partonic matter, the so-called quark–gluon plasma (QGP). We also discuss evidence for a possible precursor state to the QGP, i.e., the proposed color glass condensate.
Classical Hodgkin lymphoma (cHL) is now recognized as a B-cell-derived lymphoma which is characterized by only about 1% malignant pathognomonic Hodgkin and Reed-Sternberg (HRS) cells and an abundant ...infiltrate of reactive bystander cells. HRS cells are unique with respect to their lost B-cell-specific gene expression pattern and recurrent genetic lesions. Aberrant activity of Notch signaling, a highly conserved developmental pathway, acts as a negative regulator of the B cell program in HRS cells and thereby contributes to their reprogramming. Another striking feature and the major pathogenetic mechanism in HRS cells is constitutive NF-κB activation. A number of aberrations that contribute to canonical NF-κB activity in HRS cells have been described such as genetic lesions, deregulated receptor signaling and Epstein-Barr virus (EBV) infection. The importance of Notch and NF-κB signaling for cHL pathogenesis, their potential cross-talk and implications for future therapeutic applications are being discussed.
Inappropriate activation of the NOTCH signaling pathway, for example, by activating mutations, contributes to the pathogenesis of various human malignancies. Here, we demonstrate that aberrant ...expression of an essential NOTCH coactivator of the Mastermind-like (MAML) family provides an alternative mechanism to activate NOTCH signaling in human lymphoma cells. We detected high-level MAML2 expression in several B cell-derived lymphoma types, including classical Hodgkin lymphoma (cHL) cells, relative to normal B cells. Inhibition of MAML-protein activity by a dominant negative form of MAML or by small hairpin RNAs targeting MAML2 in cHL cells resulted in downregulation of the NOTCH target genes HES7 and HEY1, which we identified as overexpressed in cHL cells, and in reduced proliferation. Furthermore, a NOTCH gene-expression signature in cHL cells confirmed their cell-autonomous NOTCH activity. Finally, in line with the essential role of MAML proteins for assembly and activity of the NOTCH transcriptional complex (NTC), we show that MAML-derived small-peptide constructs block NOTCH activity and disrupt NTC formation in vitro. These data strongly suggest direct targeting of the NTC as treatment strategy for NOTCH-dependent malignancies.
Despite evidence that deregulated Notch signalling is a master regulator of multiple myeloma (MM) pathogenesis, its contribution to myeloma bone disease remains to be resolved. Notch promotes ...survival of human MM cells and triggers human osteoclast activity in vitro. Here, we show that inhibition of Notch through the γ-secretase inhibitor XII (GSI XII) induces apoptosis of murine MOPC315.BM myeloma cells with high Notch activity. GSI XII impairs murine osteoclast differentiation of receptor activator of NF-κB ligand (RANKL)-stimulated RAW264.7 cells in vitro. In the murine MOPC315.BM myeloma model GSI XII has potent anti-MM activity and reduces osteolytic lesions as evidenced by diminished myeloma-specific monoclonal immunoglobulin (Ig)-A serum levels and quantitative assessment of bone structure changes via high-resolution microcomputed tomography scans. Thus, we suggest that Notch inhibition through GSI XII controls myeloma bone disease mainly by targeting Notch in MM cells and possibly in osteoclasts in their microenvironment. We conclude that Notch inhibition is a valid therapeutic strategy in MM.
Plasticity of committed mouse B cells has been demonstrated by inactivation of the B-cell commitment transcription factor PAX5, resulting in loss of the B-cell phenotype and differentiation into ...various hematopoietic lineages. Furthermore, mature mouse B cells could be reprogrammed into macrophages by overexpression of myeloid-specific transcription factors. Here, we report that aberrant activity of the transmembrane receptor, Notch1, interferes with the B-lymphoid phenotype of mature human germinal center-derived B cells in Hodgkin lymphoma, so called Hodgkin and Reed-Sternberg cells. They have lost the B-cell phenotype despite their mature B-cell origin. Notch1 remodels the B-cell transcription factor network by antagonizing the key transcription factors E2A and early B-cell factor (EBF). Through this mechanism, B lineage-specific genes were suppressed and B lineage-inappropriate genes were induced. We provide evidence that absence of the Notch inhibitor Deltex1 contributes to deregulated Notch activity in Hodgkin and Reed-Sternberg cells. These data suggest that Notch activation interferes with dedifferentiation of neoplastic B cells in Hodgkin lymphoma.
Multiple myeloma (MM) is a lethal human cancer characterized by a clonal expansion of malignant plasma cells in bone marrow. Mouse models of human MM are technically challenging and do not always ...recapitulate human disease. Therefore, new mouse models for MM are needed. Mineral-oil induced plasmacytomas (MOPC) develop in the peritoneal cavity of oil-injected BALB/c mice. However, MOPC typically grow extramedullary and are considered poor models of human MM. Here we describe an in vivo-selected MOPC315 variant, called MOPC315.BM, which can be maintained in vitro. When injected i.v. into BALB/c mice, MOPC315.BM cells exhibit tropism for bone marrow. As few as 10(4) MOPC315.BM cells injected i.v. induced paraplegia, a sign of spinal cord compression, in all mice within 3-4 weeks. MOPC315.BM cells were stably transfected with either firefly luciferase (MOPC315.BM.Luc) or DsRed (MOPC315.BM.DsRed) for studies using noninvasive imaging. MOPC315.BM.Luc cells were detected in the tibiofemoral region already 1 hour after i.v. injection. Bone foci developed progressively, and as of day 5, MM cells were detected in multiple sites in the axial skeleton. Additionally, the spleen (a hematopoietic organ in the mouse) was invariably affected. Luminescent signals correlated with serum myeloma protein concentration, allowing for easy tracking of tumor load with noninvasive imaging. Affected mice developed osteolytic lesions. The MOPC315.BM model employs a common strain of immunocompetent mice (BALB/c) and replicates many characteristics of human MM. The model should be suitable for studies of bone marrow tropism, development of osteolytic lesions, drug testing, and immunotherapy in MM.