The Y-box binding protein YB-1 is associated with progressive disease and mediates survival and drug resistance in multiple myeloma

Current knowledge about molecular mechanisms underlying disease progression and drug resistance in multiple myeloma (MM) is still limited. Here, we analyzed the potential pathogenetic role of the Y-box binding protein YB-1 in MM. YB-1 is a member of the cold-shock domain protein superfamily and involved in various cellular functions such as proliferation. Immunohistochemical analyses revealed that neither normal bone marrow (BM) plasma cells (PCs), premalignant PCs of patients with monoclonal gammopathy of unknown significance (MGUS), nor MM cells with a mature morphology showed expression of YB-1 in situ. In contrast, YB-1 was strongly expressed in situ in normal PC precursor blasts as well as in a MM subset and in vitro in all of the evaluated MM cell lines. The YB-1-expressing MM cells were characterized by an immature morphology and a highly proliferative phenotype as defined by Ki 67 expression. We observed that siRNA-mediated knockdown of YB-1 decreased proliferation and induced apoptosis in MM cells even in the presence of BM stromal cells. Furthermore, we found that overexpression of YB-1 mediated resistance toward doxorubicin-induced apoptosis in MM cells. Thus, YB-1 contributes to disease progression, survival, and drug resistance in MM and might therefore provide an attractive therapeutic target.     

CD38 low IgG-secreting cells are precursors of various CD38 high-expressing plasma cell populations

Despite the important role immunoglobulin G (IgG)-secreting plasma cells play in memory immune responses, the differentiation and homeostasis of these cells are not completely understood. Here, we studied the differentiation of human IgG-secreting cells ex vivo and in vitro, identifying these cells by the cellular affinity matrix technology. Several subpopulations of IgG-secreting cells were identified among the cells isolated from tonsils and bone marrow, particularly differing in the expression levels of CD9, CD19, and CD38. CD38 low IgG-secreting cells were present exclusively in the tonsils. A major fraction of these cells appeared to be early plasma cell precursors, as upon activation of B cells in vitro, IgG secretion preceded up-regulation of CD38, and on tonsillar sections, IgG-containing, CD38 low cells with a plasmacytoid phenotype were found in follicles, where plasma cell differentiation starts. A unitary phenotype of migratory peripheral blood IgG-secreting cells suggests that all bone marrow plasma cell populations share a common precursor cell. These data are compatible with a multistep model for plasma cell differentiation and imply that a common CD38 low IgG-secreting precursor gives rise to a diverse plasma cell compartment.     

Bispezifische Antikörper in der Hämatologie und Onkologie

Zum Thema Für ausgew?hlte Tumorpatienten stellen monoklonale Antik?rper heute eine neue, klinisch gut vertr?gliche Therapieoption dar. Bispezifische Antik?rper – mit einer Spezifit?t gegen ein zytotoxisches Triggermolekül auf Immuneffektorzellen und einer zweiten gegen ein Zielantigen auf Tumorzellen – bieten die M?glichkeit, die therapeutische Effizienz von Antik?rpern weiter zu steigern. In Abh?ngigkeit von dem gew?hlten Triggermolekül k?nnen zytotoxische T-Zellen durch Aktivierung über CD3, NK-Zellen über CD16 und myeloische Zellen über CD64 und CD89 Lyse von Tumorzellen vermitteln. W?hrend bislang bispezifische Antik?rper mit hohem Produktionsaufwand durch chemische Kopplung oder Fusion zweier Hybridome generiert wurden, k?nnten rekombinante Technologien künftig eine breitere klinische Erprobung erm?glichen. In diesem Artikel geben wir einen überblick über die experimentellen Grundlagen sowie über erste klinische Erfahrungen mit bispezifischen Antik?rpern.     

Macrophage inflammatory protein 1-alpha (MIP-1 alpha ) triggers migration and signaling cascades mediating survival and proliferation in multiple myeloma (MM) cells

Recently, it has been demonstrated that macrophage inflammatory protein 1- alpha (MIP-1 alpha) is crucially involved in the development of osteolytic bone lesions in multiple myeloma (MM). The current study was designed to determine the direct effects of MIP-1 alpha on MM cells. Thus, we were able to demonstrate that MIP-1 alpha acts as a potent growth, survival, and chemotactic factor in MM cells. MIP-1 alpha-induced signaling involved activation of the AKT/protein kinase B (PKB) and the mitogen-activated protein kinase (MAPK) pathway. In addition, inhibition of AKT activation by phosphatidylinositol 3- kinase (PI3-K) inhibitors did not influence MAPK activation, suggesting that there is no cross talk between MIP-1 alpha-dependent activation of the PI3-K/AKT and extracellular-regulated kinase (ERK) pathway. Our data suggest that besides its role in development of osteolytic bone destruction, MIP-1 alpha also directly affects cell signaling pathways mediating growth, survival, and migration in MM cells and provide evidence that MIP-1 alpha might play a pivotal role in the pathogenesis of MM.     

Preclinical anti‐myeloma activity of the novel HDAC‐inhibitor JNJ‐26481585

Pharmacological inhibitors of histone deacetylases (HDACs) are currently being developed and tested as anti‐cancer agents and may be useful to enhance the therapeutic efficiency of established anti‐myeloma treatments. This study preclinically evaluated the effects of the ‘second generation’ pan‐HDAC inhibitor JNJ‐26481585 on human multiple myeloma (MM) cells from established cell lines and primary MM samples (n = 42). Molecular responses in both groups of MM cells included histone acetylation, a shift in Bcl2‐family members towards proapoptotic bias, attenuation of growth and survival pathway activity and Hsp72 induction. Mcl‐1 depletion and Hsp72 induction were the most reliable features observed in JNJ‐26481585‐treated primary MM samples. The drug alone effectively induced myeloma cell death at low nanomolar concentrations. In vitro combination of JNJ‐26481585 with anti‐myeloma therapeutic agents generally resulted In effects close to additivity. In view of the favourable activity of this novel HDAC‐inhibitor towards primary myeloma cells further evaluation in a clinical setting is warranted.     

A novel recombinant bispecific single-chain antibody, bscWue-1 x CD3, induces T-cell-mediated cytotoxicity towards human multiple myeloma cells.

The development of antibody-based strategies for the treatment of multiple myeloma (MM) has been hampered so far by the fact that suitable plasma cell-specific surface antigens have been missing. However, recently a novel monoclonal antibody, designated Wue-1, has been generated that specifically recognizes normal and malignant human plasma cells. Therefore, Wue-1 is an interesting and promising candidate to develop novel immunotherapeutic strategies for the treatment of MM. One variant for an antibody-based strategy is the bispecific antibody approach. Recombinant bispecific single-chain (bsc) antibodies are especially interesting candidates because they show exceptional biological properties. We have generated a novel MM-directed recombinant bsc antibody, bscWue-1 x CD3, and analyzed the biological properties of this antibody using the MM cell line NCI-H929 and primary cells from the bone marrow of patients with MM. We were able to show that bscWue-1 x CD3 induces efficient and selective T-cell-mediated cell death of NCI-H929 cells and primary myeloma cells in nine out of 11 cases. The bscWue-1 x CD3 Ab is efficacious even at low E:T ratios, and with or without additional T-cell pre- or costimulation. Target cell lyses were specific for Wue-1 antigen-positive cells and could be blocked by the Wue-1 monoclonal antibody.     

Mutated RAS and constitutively activated Akt delineate distinct oncogenic pathways, which independently contribute to multiple myeloma cell survival

We have recently shown that approximately half of primary multiple myeloma (MM) samples display constitutive Akt activity, which disposes them for sensitivity to Akt inhibition. The Akt pathway counts among the signaling conduits for oncogenic RAS and activating mutations of K- and N-RAS frequently occur in MM. We therefore analyzed the relation between RAS mutation and Akt dependency in biopsies and CD138-purified cells from MM patients (n = 65) and the function of oncogenic RAS for MM cell survival in a range of MM cell lines with differing RAS status. Whereas RAS mutations do not predict Akt dependency, oncogenic RAS retains an important role for MM cell survival. Knockdown of either K- or N-RAS strongly decreased the viability of MM cells that harbored the respective oncogenic isoform, whereas ablation of wild-type RAS isoforms had little or no effect. Silencing of oncogenic RAS did not affect the Akt pathway, again indicating lack of a direct link. Combined inhibition of RAS and Akt strongly enhanced MM cell death. These data suggest that oncogenic RAS and Akt may independently contribute to MM cell survival. Targeting of both pathways could provide an attractive therapeutic strategy for patients with oncogenic RAS and dysregulated Akt signaling.