BCL-XL exerts a protective role against anemia caused by radiation-induced kidney damage.

Studies of gene-targeted mice identified the roles of the different pro-survival BCL-2 proteins during embryogenesis. However, little is known about the role(s) of these proteins in adults in response to cytotoxic stresses, such as treatment with anti-cancer agents. We investigated the role of BCL-XL in adult mice using a strategy where prior bone marrow transplantation allowed for loss of BCL-XL exclusively in non-hematopoietic tissues to prevent anemia caused by BCL-XL deficiency in erythroid cells.

Blood pressure changes after renal denervation are more pronounced in women and nondiabetic patients: findings from the Austrian Transcatheter Renal Denervation Registry.

Objectives: Three recently published sham-controlled studies proved the efficacy of renal denervation (RDN) in hypertensive patients. The study presented here analyzed a nationwide multicentre registry database to clarify which patient subgroups benefit most from radiofrequency RDN.

Methods: This is a post hoc analysis from the multicentre Austrian Transcatheter Renal Denervation Registry hosted by the Austrian Society of Hypertension.

Design, Synthesis, and Biological Activity of 1,2,3-Triazolobenzodiazepine BET Bromodomain Inhibitors.

A number of diazepines are known to inhibit bromo- and extra-terminal domain (BET) proteins. Their BET inhibitory activity derives from the fusion of an acetyl-lysine mimetic heterocycle onto the diazepine framework. Herein we describe a straightforward, modular synthesis of novel 1,2,3-triazolobenzodiazepines and show that the 1,2,3-triazole acts as an effective acetyl-lysine mimetic heterocycle.

Impact of loss of BH3-only proteins on the development and treatment of MLL-fusion gene-driven AML in mice.

Inhibition of the apoptosis pathway controlled by opposing members of the Bcl-2 protein family plays a central role in cancer development and resistance to therapy. To investigate how pro-apoptotic Bcl-2 homology domain 3 (BH3)-only proteins impact on acute myeloid leukemia (AML), we generated mixed lineage leukemia (MLL)-AF9 and MLL-ENL AMLs from BH3-only gene knockout mice. Disease development was not accelerated by loss of Bim, Puma, Noxa, Bmf, or combinations thereof; hence these BH3-only proteins are apparently ineffectual as tumor suppressors in this model.

Rapid Inflammation in Mice Lacking Both SOCS1 and SOCS3 in Hematopoietic Cells.

The Suppressors of Cytokine Signalling (SOCS) proteins are negative regulators of cytokine signalling required to prevent excess cellular responses. SOCS1 and SOCS3 are essential to prevent inflammatory disease, SOCS1 by attenuating responses to IFNγ and gamma-common (γc) cytokines, and SOCS3 via regulation of G-CSF and IL-6 signalling. SOCS1 and SOCS3 show significant sequence homology and are the only SOCS proteins to possess a KIR domain.

Eliminating Legionella by inhibiting BCL-XL to induce macrophage apoptosis.

Human pathogenic Legionella replicate in alveolar macrophages and cause a potentially lethal form of pneumonia known as Legionnaires' disease(1). Here, we have identified a host-directed therapeutic approach to eliminate intracellular Legionella infections. We demonstrate that the genetic deletion, or pharmacological inhibition, of the host cell pro-survival protein BCL-XL induces intrinsic apoptosis of macrophages infected with virulent Legionella strains, thereby abrogating Legionella replication.

MCL-1 is required throughout B-cell development and its loss sensitizes specific B-cell subsets to inhibition of BCL-2 or BCL-XL.

Pro-survival BCL-2 family members protect cells from programmed cell death that can be induced by multiple internal or external cues. Within the haematopoietic lineages, the BCL-2 family members BCL-2, BCL-XL and MCL-1 are known to support cell survival but the individual and overlapping roles of these pro-survival BCL-2 proteins for the persistence of individual leukocyte subsets in vivo has not yet been determined. By combining inducible knockout mouse models with the BH3-mimetic compound ABT-737, which inhibits BCL-2, BCL-XL and BCL-W, we found that dependency on MCL-1, BCL-XL or BCL-2 expression changes during B-cell development.

Effects of Renal Denervation Documented in the Austrian National Multicentre Renal Denervation Registry.

Renal denervation (RDN) is a new procedure for treatment-resistant hypertensive patients. In order to monitor all procedures undergone in Austria, the Austrian Society of Hypertension established the investigator-initiated Austrian Transcatheter Renal Denervation (TREND) Registry. From April 2011 to September 2014, 407 procedures in 14 Austrian centres were recorded.

Site-specific recombinatorics: in situ cellular barcoding with the Cre Lox system.

Background: Cellular barcoding is a recently developed biotechnology tool that enables the familial identification of progeny of individual cells in vivo. In immunology, it has been used to track the burst-sizes of multiple distinct responding T cells over several adaptive immune responses. In the study of hematopoiesis, it revealed fate heterogeneity amongst phenotypically identical multipotent cells.

The caspase-8 inhibitor emricasan combines with the SMAC mimetic birinapant to induce necroptosis and treat acute myeloid leukemia.

Resistance to chemotherapy is a major problem in cancer treatment, and it is frequently associated with failure of tumor cells to undergo apoptosis. Birinapant, a clinical SMAC mimetic, had been designed to mimic the interaction between inhibitor of apoptosis proteins (IAPs) and SMAC/Diablo, thereby relieving IAP-mediated caspase inhibition and promoting apoptosis of cancer cells. We show that acute myeloid leukemia (AML) cells are sensitive to birinapant-induced death and that the clinical caspase inhibitor emricasan/IDN-6556 augments, rather than prevents, killing by birinapant.

Targeting p38 or MK2 Enhances the Anti-Leukemic Activity of Smac-Mimetics.

Birinapant is a smac-mimetic (SM) in clinical trials for treating cancer. SM antagonize inhibitor of apoptosis (IAP) proteins and simultaneously induce tumor necrosis factor (TNF) secretion to render cancers sensitive to TNF-induced killing. To enhance SM efficacy, we screened kinase inhibitors for their ability to increase TNF production of SM-treated cells.

Acute myeloid leukemia requires Hhex to enable PRC2-mediated epigenetic repression of Cdkn2a.

Unlike clustered HOX genes, the role of nonclustered homeobox gene family members in hematopoiesis and leukemogenesis has not been extensively studied. Here we found that the hematopoietically expressed homeobox gene Hhex is overexpressed in acute myeloid leukemia (AML) and is essential for the initiation and propagation of MLL-ENL-induced AML but dispensable for normal myelopoiesis, indicating a specific requirement for Hhex for leukemic growth. Loss of Hhex leads to expression of the Cdkn2a-encoded tumor suppressors p16(INK4a) and p19(ARF), which are required for growth arrest and myeloid differentiation following Hhex deletion.

Innate immunodeficiency following genetic ablation of Mcl1 in natural killer cells.

The cytokine IL-15 is required for natural killer (NK) cell homeostasis; however, the intrinsic mechanism governing this requirement remains unexplored. Here we identify the absolute requirement for myeloid cell leukaemia sequence-1 (Mcl1) in the sustained survival of NK cells in vivo. Mcl1 is highly expressed in NK cells and regulated by IL-15 in a dose-dependent manner via STAT5 phosphorylation and subsequent binding to the 3'-UTR of Mcl1.

Targeting of MCL-1 kills MYC-driven mouse and human lymphomas even when they bear mutations in p53.

The transcriptional regulator c-MYC is abnormally overexpressed in many human cancers. Evasion from apoptosis is critical for cancer development, particularly c-MYC-driven cancers. We explored which anti-apoptotic BCL-2 family member (expressed under endogenous regulation) is essential to sustain c-MYC-driven lymphoma growth to reveal which should be targeted for cancer therapy.

Enhanced stability of Mcl1, a prosurvival Bcl2 relative, blunts stress-induced apoptosis, causes male sterility, and promotes tumorigenesis.

The B-cell CLL/lymphoma 2 (Bcl2) relative Myeloid cell leukemia sequence 1 (Mcl1) is essential for cell survival during development and for tissue homeostasis throughout life. Unlike Bcl2, Mcl1 turns over rapidly, but the physiological significance of its turnover has been unclear. We have gained insight into the roles of Mcl1 turnover in vivo by analyzing mice harboring a modified allele of Mcl1 that serendipitously proved to encode an abnormally stabilized form of Mcl1 due to a 13-aa N-terminal extension.

HoxA9 regulated Bcl-2 expression mediates survival of myeloid progenitors and the severity of HoxA9-dependent leukemia.

Deregulated expression of Hox genes such as HoxA9 is associated with development of myeloproliferative disorders and leukemia and indicates a poor prognosis. To investigate the molecular mechanisms by which HoxA9 promotes immortalization of hematopoietic cells, we generated growth factor dependent myeloid cells in which HoxA9 expression is regulated by administration of 4-hydroxy-tamoxifen. Maintenance of HoxA9 overexpression is required for continued cell survival and proliferation, even in the presence of growth factors.

Reversible growth factor dependency and autonomy during murine myelomonocytic leukemia induced by oncogenes.

When murine fetal liver cells were transduced with either of the human acute myeloid leukemia fusion oncogenes MLL-ENL or MLL-AF9 and then transplanted to irradiated recipient mice, myelomonocyte leukemias rapidly developed from the transplanted cells. Analysis of initial events following transduction showed that both oncogenes immediately induced a wide range of enhanced proliferative states, the most extreme of which could generate continuous lines of cells. Maturation defects accompanied the enhanced proliferative states.

Targeting acute myeloid leukemia by dual inhibition of PI3K signaling and Cdk9-mediated Mcl-1 transcription.

Resistance to cell death is a hallmark of cancer and renders transformed cells resistant to multiple apoptotic triggers. The Bcl-2 family member, Mcl-1, is a key driver of cell survival in diverse cancers, including acute myeloid leukemia (AML). A screen for compounds that downregulate Mcl-1 identified the kinase inhibitor, PIK-75, which demonstrates marked proapoptotic activity against a panel of cytogenetically diverse primary human AML patient samples.

Mcl-1 is essential for the survival of plasma cells.

The long-term survival of plasma cells is entirely dependent on signals derived from their environment. These extrinsic factors presumably induce and sustain the expression of antiapoptotic proteins of the Bcl-2 family. It is uncertain whether there is specificity among Bcl-2 family members in the survival of plasma cells and whether their expression is linked to specific extrinsic factors.

Bcl-2, Bcl-x(L), and Bcl-w are not equivalent targets of ABT-737 and navitoclax (ABT-263) in lymphoid and leukemic cells.

The BH3-mimetic ABT-737 and an orally bioavailable compound of the same class, navitoclax (ABT-263), have shown promising antitumor efficacy in preclinical and early clinical studies. Although both drugs avidly bind Bcl-2, Bcl-x(L), and Bcl-w in vitro, we find that Bcl-2 is the critical target in vivo, suggesting that patients with tumors overexpressing Bcl-2 will probably benefit. In human non-Hodgkin lymphomas, high expression of Bcl-2 but not Bcl-x(L) predicted sensitivity to ABT-263.

Anti-apoptotic Mcl-1 is essential for the development and sustained growth of acute myeloid leukemia.

Acute myeloid leukemia (AML) frequently relapses after initial treatment. Drug resistance in AML has been attributed to high levels of the anti-apoptotic Bcl-2 family members Bcl-x(L) and Mcl-1. Here we report that removal of Mcl-1, but not loss or pharmacological blockade of Bcl-x(L), Bcl-2, or Bcl-w, caused the death of transformed AML and could cure disease in AML-afflicted mice.

Mcl-1 is essential for germinal center formation and B cell memory.

Lymphocyte survival during immune responses is controlled by the relative expression of pro- and anti-apoptotic molecules, regulating the magnitude, quality, and duration of the response. We investigated the consequences of deleting genes encoding the anti-apoptotic molecules Mcl1 and Bcl2l1 (Bcl-x(L)) from B cells using an inducible system synchronized with expression of activation-induced cytidine deaminase (Aicda) after immunization. This revealed Mcl1 and not Bcl2l1 to be indispensable for the formation and persistence of germinal centers (GCs).

MLL2 is required in oocytes for bulk histone 3 lysine 4 trimethylation and transcriptional silencing.

During gametogenesis and pre-implantation development, the mammalian epigenome is reprogrammed to establish pluripotency in the epiblast. Here we show that the histone 3 lysine 4 (H3K4) methyltransferase, MLL2, controls most of the promoter-specific chromatin modification, H3K4me3, during oogenesis and early development. Using conditional knockout mutagenesis and a hypomorph model, we show that Mll2 deficiency in oocytes results in anovulation and oocyte death, with increased transcription of p53, apoptotic factors, and Iap elements.