The PIM family kinases promote growth and survival of tumor cells and are expressed in a wide variety of human cancers. Their potential as therapeutic targets, however, is complicated by overlapping activities with multiple other pathways and remains poorly defined in most clinical scenarios. Here we explore activity of the new pan-PIM inhibitor PIM447 in a variety of lymphoid-derived tumors. We find strong activity in cell lines derived from the activated B-cell subtype of diffuse large B-cell lymphoma (ABC-DLBCL). Sensitive lines show lost activation of the mTORC1 signaling complex and subsequent lost activation of cap-dependent protein translation. In addition, we characterize recurrent PIM1 protein-coding mutations found in DLBCL clinical samples and find most preserve the wild-type protein's ability to protect cells from apoptosis but do not bypass activity of PIM447. Pan-PIM inhibition therefore may have an important role to play in the therapy of selected ABC-DLBCL cases.

No description available.

The most common human leukemia is B-cell chronic lymphocytic leukemia (B-CLL), which is characterized by a progressive accumulation of abnormal B-lymphocytes in blood, bone marrow and secondary lymphoid organs. Typically disease progression is slow, but as the number of leukemic cells increases, they interfere with the production of other important blood cells, causing the patients to be in an immunosuppressive state. To study the basis of this immunoregulation, we used cells from the transgenic Eμ-TCL1 mouse, which spontaneously develop B-CLL due to a B-cell specific expression of the oncogene, TCL1. Previously we showed that Eμ-TCL1 CLL cells constitutively produce an anti-inflammatory cytokine, IL-10. Here we studied the role of IL-10 in CLL cell survival in vitro and the development of CLL in vivo. We found that neutralization of IL-10 using anti-IL-10 antibodies or blocking the IL-10 receptor (IL-10R) using anti-IL-10R antibodies did not affect the survival of CLL cells in vitro. On the other hand, adoptively transferred Eμ-TCL1 cells grew at a slower rate in IL-10R KO mice vs. wild type (WT) mice. There was a significant reduction in CLL cell engraftment in the spleen, bone marrow, peritoneal cavity and liver of the IL-10R KO compared to WT mice. Further studies revealed that IL-10 could be playing a role in the tumor microenvironment possibly by affecting anti-tumor immunity. This was seen by a reduction in the activation of CD8+ T cells as well as a significantly lower production of IFN-γ by CD4+ T cells purified from CLL-injected WT mice compared to those purified from CLL-injected IL-10R KO mice. Also CLL-primed IL-10R null T cells were more effective than those from similarly CLL-primed wild type mice in controlling CLL growth in immunodeficient recipient mice. These studies demonstrate that CLL cells suppress host anti-tumor immunity via IL-10 production. This led us to investigate possible mechanisms by which IL-10 is produced. We found a novel role of B-cell receptor (BCR) signaling pathway in constitutive IL-10 secretion. Inhibition of Src or Syk family kinases reduces the constitutive IL-10 production by Eμ-TCL1 cells in a dose dependent manner. We identified the transcription factor Sp1 as a novel regulator of IL-10 production by CLL cells and that it is regulated by BCR signaling via the Syk/MAPK pathway.

Die systemische Autoimmunerkrankung Systemischer Lupus Erythematodes (SLE) ist durch die Produktion von autoreaktiven Antikörpern charakterisiert. In wie weit veränderte B-Zellrezeptor (BZR) Signalwege oder Co-Rezeptoren in diesem Prozess involviert sind, ist noch nicht ausreichend im humanen SLE untersucht worden. Aus diesem Grund wurde in der vorliegenden Arbeit eine detaillierte Analyse des inhibitorischen Co-Rezeptors CD22, der Kinase Syk und Akt in B-Zellen des peripheren Blutes von SLE Patienten durchgeführt. SLE Patienten zeigten eine Dysbalance in BZR abhängigen Signalwegen, welche eine B-Zellsubpopulationen unabhängige Reduktion der p-Syk/p-Akt Ratio versursacht. Diese Verschiebung könnte zu einer defekten negativen Selektion und somit zur Bildung von autoreaktiven Zellen führen, die wiederum durch Überlebensvorteile persistieren könnten. Zusätzlich wurde im peripheren Blut von SLE Patienten eine bislang nicht bekannte CD27 Syk++ B-Zellpopulation nachgewiesen. Diese wies, trotz des fehlenden Gedächtnismarkers CD27, Gedächtnismerkmale auf und könnte für die bekannte erhöhte Plasmazell-induktion in SLE Patienten verantwortlich sein. Somit konnte Syk als intrazellulärer Marker einer Gedächtnispopulation identifiziert werden. Des Weiterem stellt die Wiederherstellung der Balance von Syk- und Akt Phosphorylierung nach BZR Aktivierung einen erfolgsversprechenden Therapieansatz bei SLE Patienten dar, um die Entstehung und das Überleben von autoreaktiven B- und Plasmazellen besser kontrollieren zu können. / Systemic lupus erythematosus (SLE) is a severe systemic autoimmune disease in which loss of tolerance to nucleic acids results into the production of autoreactive antibodies (Ab) Therefore, B cells might play a key role in the pathogenesis of this disease. However, abnormalities of BCR associated co receptors and downstream kinases with potential implications in selection processes are rare for human SLE. Thus, a comprehensive analysis of the inhibitory BCR co-receptor CD22, the spleen tyrosine kinase (Syk) and the pro-survival serine kinase Akt has been undertaken to gain new insights into potential BCR signaling disturbances in this autoimmune disease. This data indicate that B cells from SLE patients display an intrinsically disturbed balance of BCR related signaling pathways, resulting in a B cell subset independent reduced p-Syk/p-Akt ratio. This may lead to a diminished BCR dependent negative selection and enhanced survival of SLE B cells, permitting the emergence of autoreactive B and plasma cells. Furthermore, SLE patients exhibit an increased frequency of a novel CD27-Syk++ B cell subset with memory features, enhanced tonic BCR signaling and the capacity to differentiate in auto-Ab secreting cells. The current study provides evidence that the use of intracellular markers, such as Syk, could permit a more precise delineation of CD27- memory B cell subsets in autoimmune diseases since the conventional used memory marker CD27 has some limitations. In addition, the balance between the BCR associated kinases Syk and Akt might be a promising therapeutic target to reduce the occurrence of autoreactive B and plasma cells.