Georg-Speyer-Haus
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Newly emerging influenza A viruses (IAV) pose a major threat to human health by causing seasonal epidemics and/or pandemics, the latter often facilitated by the lack of pre-existing immunity in the general population. Early recognition of candidate pandemic influenza viruses (CPIV) is of crucial importance for restricting virus transmission and developing appropriate therapeutic and prophylactic strategies including effective vaccines. Often, the pandemic potential of newly emerging IAV is only fully recognized once the virus starts to spread efficiently causing serious disease in humans. Here, we used a novel phylogenetic algorithm based on the informational spectrum method (ISM) to identify potential CPIV by predicting mutations in the viral hemagglutinin (HA) gene that are likely to (differentially) affect critical interactions between the HA protein and target cells from bird and human origin, respectively. Predictions were subsequently validated by generating pseudotyped retrovirus particles and genetically engineered IAV containing these mutations and characterizing potential effects on virus entry and replication in cells expressing human and avian IAV receptors, respectively. Our data suggest that the ISM-based algorithm is suitable to identify CPIV among IAV strains that are circulating in animal hosts and thus may be a new tool for assessing pandemic risks associated with specific strains.
IKKβ acts as a tumor suppressor in cancer-associated fibroblasts during intestinal tumorigenesis
(2015)
Cancer-associated fibroblasts (CAFs) comprise one of the most important cell types in the tumor microenvironment. A proinflammatory NF-κB gene signature in CAFs has been suggested to promote tumorigenesis in models of pancreatic and mammary skin cancer. Using an autochthonous model of colitis-associated cancer (CAC) and sporadic cancer, we now provide evidence for a tumor-suppressive function of IKKβ/NF-κB in CAFs. Fibroblast-restricted deletion of Ikkβ stimulates intestinal epithelial cell proliferation, suppresses tumor cell death, enhances accumulation of CD4+Foxp3+ regulatory T cells, and induces angiogenesis, ultimately promoting colonic tumor growth. In Ikkβ-deficient fibroblasts, transcription of negative regulators of TGFβ signaling, including Smad7 and Smurf1, is impaired, causing up-regulation of a TGFβ gene signature and elevated hepatocyte growth factor (HGF) secretion. Overexpression of Smad7 in Ikkβ-deficient fibroblasts prevents HGF secretion, and pharmacological inhibition of Met during the CAC model confirms that enhanced tumor promotion is dependent on HGF–Met signaling in mucosa of Ikkβ-mutant animals. Collectively, these results highlight an unexpected tumor suppressive function of IKKβ/NF-κB in CAFs linked to HGF release and raise potential concerns about the use of IKK inhibitors in colorectal cancer patients.
Haematopoietic stem cells (HSCs) require the right composition of microRNAs (miR) for proper life-long balanced blood regeneration. Here we show a regulatory circuit that prevents excessive HSC self-renewal by upregulation of miR-193b upon self-renewal promoting thrombopoietin (TPO)-MPL-STAT5 signalling. In turn, miR-193b restricts cytokine signalling, by targeting the receptor tyrosine kinase c-KIT. We generated a miR-193b knockout mouse model to unravel the physiological function of miR-193b in haematopoiesis. MiR-193b−/− mice show a selective gradual enrichment of functional HSCs, which are fully competent in multilineage blood reconstitution upon transplantation. The absence of miR-193b causes an accelerated expansion of HSCs, without altering cell cycle or survival, but by decelerating differentiation. Conversely, ectopic miR-193b expression restricts long-term repopulating HSC expansion and blood reconstitution. MiR-193b-deficient haematopoietic stem and progenitor cells exhibit increased basal and cytokine-induced STAT5 and AKT signalling. This STAT5-induced microRNA provides a negative feedback for excessive signalling to restrict uncontrolled HSC expansion.
Background/Aims: Middle East respiratory syndrome coronavirus (MERS-CoV) and Marburg virus (MARV) are among the World Health Organization’s top 8 emerging pathogens. Both zoonoses share nonspecific early symptoms, a high lethality rate, and a reduced number of specific treatment options. Therefore, we evaluated extracorporeal virus and glycoprotein (GP) elimination by lectin affinity plasmapheresis (LAP).
Methods: For both MERS-CoV (pseudovirus) as well as MARV (GPs), 4 LAP devices (Mini Hemopurifiers, Aethlon Medical, San Diego, CA, USA) and 4 negative controls were tested. Samples were collected every 30 min and analyzed for reduction in virus infectivity by a flow cytometry-based infectivity assay (MERS-CoV) and in soluble GP content (MARV) by an immunoassay.
Results: The experiments show a time-dependent clearance of MERS-CoV of up to 80% within 3 h (pseudovirus). Up to 70% of MARV-soluble GPs were eliminated at the same time. Substantial saturation of the binding resins was detected within the first treatment hour.
Conclusion: MERS-CoV (pseudovirus) and MARV soluble GPs are eliminated by LAP in vitro. Considering the high lethality and missing established treatment options, LAP should be evaluated in vivo. Especially early initiation, continuous therapy, and timed cartridge exchanges could be of importance.
The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points.
During erythropoiesis, haematopoietic stem cells (HSCs) differentiate in successive steps of commitment and specification to mature erythrocytes. This differentiation process is controlled by transcription factors that establish stage- and cell type-specific gene expression. In this study, we demonstrate that FUSE binding protein 1 (FUBP1), a transcriptional regulator important for HSC self-renewal and survival, is regulated by T-cell acute lymphocytic leukaemia 1 (TAL1) in erythroid progenitor cells. TAL1 directly activates the FUBP1 promoter, leading to increased FUBP1 expression during erythroid differentiation. The binding of TAL1 to the FUBP1 promoter is highly dependent on an intact GATA sequence in a combined E-box/GATA motif. We found that FUBP1 expression is required for efficient erythropoiesis, as FUBP1-deficient progenitor cells were limited in their potential of erythroid differentiation. Thus, the finding of an interconnection between GATA1/TAL1 and FUBP1 reveals a molecular mechanism that is part of the switch from progenitor- to erythrocyte-specific gene expression. In summary, we identified a TAL1/FUBP1 transcriptional relationship, whose physiological function in haematopoiesis is connected to proper erythropoiesis.
Runt-related transcription factor 1 (RUNX1) is a well-known master regulator of hematopoietic lineages but its mechanisms of action are still not fully understood. Here, we found that RUNX1 localizes on active chromatin together with Far Upstream Binding Protein 1 (FUBP1) in human B-cell precursor lymphoblasts, and that both factors interact in the same transcriptional regulatory complex. RUNX1 and FUBP1 chromatin localization identified c-KIT as a common target gene. We characterized two regulatory regions, at +700 bp and +30 kb within the first intron of c-KIT, bound by both RUNX1 and FUBP1, and that present active histone marks. Based on these regions, we proposed a novel FUBP1 FUSE-like DNA-binding sequence on the +30 kb enhancer. We demonstrated that FUBP1 and RUNX1 cooperate for the regulation of the expression of the oncogene c-KIT. Notably, upregulation of c-KIT expression by FUBP1 and RUNX1 promotes cell proliferation and renders cells more resistant to the c-KIT inhibitor imatinib mesylate, a common therapeutic drug. These results reveal a new mechanism of action of RUNX1 that implicates FUBP1, as a facilitator, to trigger transcriptional regulation of c-KIT and to regulate cell proliferation. Deregulation of this regulatory mechanism may explain some oncogenic function of RUNX1 and FUBP1.
Background & Aims: Microvillus inclusion disease (MVID) is a congenital intestinal malabsorption disorder caused by defective apical vesicular transport. Existing cellular models do not fully recapitulate this heterogeneous pathology. The aim of this study was to characterize 3-dimensional intestinal organoids that continuously generate polarized absorptive cells as an accessible and relevant model to investigate MVID.
Methods: Intestinal organoids from Munc18-2/Stxbp2-null mice that are deficient for apical vesicular transport were subjected to enterocyte-specific differentiation protocols. Lentiviral rescue experiments were performed using human MUNC18-2 variants. Apical trafficking and microvillus formation were characterized by confocal and transmission electron microscopy. Spinning disc time-lapse microscopy was used to document the lifecycle of microvillus inclusions.
Results: Loss of Munc18-2/Stxbp2 recapitulated the pathologic features observed in patients with MUNC18-2 deficiency. The defects were fully restored by transgenic wild-type human MUNC18-2 protein, but not the patient variant (P477L). Importantly, we discovered that the MVID phenotype was correlated with the degree of enterocyte differentiation: secretory vesicles accumulated already in crypt progenitors, while differentiated enterocytes showed an apical tubulovesicular network and enlarged lysosomes. Upon prolonged enterocyte differentiation, cytoplasmic F-actin–positive foci were observed that further progressed into classic microvillus inclusions. Time-lapse microscopy showed their dynamic formation by intracellular maturation or invagination of the apical or basolateral plasma membrane.
Conclusions: We show that prolonged enterocyte-specific differentiation is required to recapitulate the entire spectrum of MVID. Primary organoids can provide a powerful model for this heterogeneous pathology. Formation of microvillus inclusions from multiple membrane sources showed an unexpected dynamic of the enterocyte brush border.
Adult neurogenesis is regulated by stem cell niche-derived extrinsic factors and cell-intrinsic regulators, yet the mechanisms by which niche signals impinge on the activity of intrinsic neurogenic transcription factors remain poorly defined. Here, we report that MEIS2, an essential regulator of adult SVZ neurogenesis, is subject to posttranslational regulation in the SVZ olfactory bulb neurogenic system. Nuclear accumulation of MEIS2 in adult SVZ-derived progenitor cells follows downregulation of EGFR signaling and is modulated by methylation of MEIS2 on a conserved arginine, which lies in close proximity to nested binding sites for the nuclear export receptor CRM1 and the MEIS dimerization partner PBX1. Methylation impairs interaction with CRM1 without affecting PBX1 dimerization and thereby allows MEIS2 nuclear accumulation, a prerequisite for neuronal differentiation. Our results describe a form of posttranscriptional modulation of adult SVZ neurogenesis whereby an extrinsic signal fine-tunes neurogenesis through posttranslational modification of a transcriptional regulator of cell fate.
New technologies and therapies designed to facilitate development of personalized treatments are rapidly emerging in the field of biomedicine. Strikingly, the goal of personalized medicine refined the concept of therapy by developing cell-based therapies, the so-called “living drugs”. Breakthrough advancements were achieved in this regard in the fields of gene therapy, cell therapy, tissue-engineered products and advanced therapeutic techniques. The Advanced Therapies in Healthcare symposium, organized by the Clinical Research Center Department of Sidra Medicine, in Doha, Qatar (October 2017), brought together world-renowned experts from the fields of oncology, hematology, immunology, inflammation, autoimmune disorders, and stem cells to offer a comprehensive picture of the status of worldwide advanced therapies in both pre-clinical and clinical development, providing insights to the research phase, clinical data and regulatory aspects of these therapies. Highlights of the meeting are provided in this meeting report.
Site-specific recombinases (SSR) are utilized as important genome engineering tools to precisely modify the genome of mice and other model organisms. Reporter mice that mark cells that at any given time had expressed the enzyme are frequently used for lineage tracing and to characterize newly generated mice expressing a recombinase from a chosen promoter. With increasing sophistication of genome alteration strategies, the demand for novel SSR systems that efficiently and specifically recombine their targets is rising and several SSR-systems are now used in combination to address complex biological questions in vivo. Generation of reporter mice for each one of these recombinases is cumbersome and increases the number of mouse lines that need to be maintained in animal facilities. Here we present a multi-reporter mouse line for loci-of-recombination (X) (MuX) that streamlines the characterization of mice expressing prominent recombinases. MuX mice constitutively express nuclear green fluorescent protein after recombination by either Cre, Flp, Dre or Vika recombinase, rationalizing the number of animal lines that need to be maintained. We also pioneer the use of the Vika/vox system in mice, illustrating its high efficacy and specificity, thereby facilitating future designs of sophisticated recombinase-based in vivo genome engineering strategies.
A point mutation in the Ncr1 signal peptide impairs the development of innate lymphoid cell subsets
(2018)
NKp46 (CD335) is a surface receptor shared by both human and mouse natural killer (NK) cells and innate lymphoid cells (ILCs) that transduces activating signals necessary to eliminate virus-infected cells and tumors. Here, we describe a spontaneous point mutation of cysteine to arginine (C14R) in the signal peptide of the NKp46 protein in congenic Ly5.1 mice and the newly generated NCRB6C14R strain. Ly5.1C14R NK cells expressed similar levels of Ncr1 mRNA as C57BL/6, but showed impaired surface NKp46 and reduced ability to control melanoma tumors in vivo. Expression of the mutant NKp46C14R in 293T cells showed that NKp46 protein trafficking to the cell surface was compromised. Although Ly5.1C14R mice had normal number of NK cells, they showed an increased number of early maturation stage NK cells. CD49a+ILC1s were also increased but these cells lacked the expression of TRAIL. ILC3s that expressed NKp46 were not detectable and were not apparent when examined by T-bet expression. Thus, the C14R mutation reveals that NKp46 is important for NK cell and ILC differentiation, maturation and function.
Background and aims: Expression of carbonic anhydrase IX (CA9), an enzyme expressed in response to hypoxia, acidosis and oncogenic alterations, is reported to be a prognostic factor in HCC patients. Here we evaluated serum CA9 levels in HCC and cirrhosis patients.
Methods: HCC and cirrhosis patients were prospectively recruited and CA9 levels were determined. CA9 levels were compared to stages of cirrhosis and HCC stages. The association of the CA9 levels and overall survival (OS) was assessed. Furthermore, immunohistochemical CA9 expression in HCC and cirrhosis was evaluated.
Results: 215 patients with HCC were included. The median serum CA9 concentration in patients with HCC was 370 pg/ml and significantly higher than in a healthy cohort. Patients with advanced cancer stages (BCLC and ALBI score) had hid significant higher levels of CA9 in the serum. HCC patients with high serum CA9 concentrations (>400 pg/ml) had an increased mortality risk (hazard ratio (HR) 1.690, 95% confidence interval (CI) 1.017–2.809, P = 0.043). Serum CA9 concentration in cirrhotic patients did not differ significantly from HCC patients. Higher CA9 levels in cirrhotic patients correlated with portal hypertension and esophageal varices. Patients with ethanol induced cirrhosis had the highest CA9 levels in both cohorts. Levels of CA9 did not correlate with immunohistochemical expression.
Conclusions: We conclude that a high CA9 level is a possible prognostic indicator for a poor outcome in HCC patients. The high CA9 levels are probably mainly associated with portal hypertension. Ductular reactions might be a possible source of serum CA9.
Recent studies have suggested increased plasticity of differentiated cells within the intestine to act both as intestinal stem cells (ISCs) and tumour-initiating cells. However, little is known of the processes that regulate this plasticity. Our previous work has shown that activating mutations of Kras or the NF-κB pathway can drive dedifferentiation of intestinal cells lacking Apc. To investigate this process further, we profiled both cells undergoing dedifferentiation in vitro and tumours generated from these cells in vivo by gene expression analysis. Remarkably, no clear differences were observed in the tumours; however, during dedifferentiation in vitro we found a marked upregulation of TGFβ signalling, a pathway commonly mutated in colorectal cancer (CRC). Genetic inactivation of TGFβ type 1 receptor (Tgfbr1/Alk5) enhanced the ability of KrasG12D/+ mutation to drive dedifferentiation and markedly accelerated tumourigenesis. Mechanistically this is associated with a marked activation of MAPK signalling. Tumourigenesis from differentiated compartments is potently inhibited by MEK inhibition. Taken together, we show that tumours arising in differentiated compartments will be exposed to different suppressive signals, for example, TGFβ and blockade of these makes tumourigenesis more efficient from this compartment.
UPF1 regulates myeloid cell functions and S100A9 expression by the hnRNP E2/miRNA-328 balance
(2016)
UPF1 is a key player in nonsense mediated mRNA decay (NMD) but also involved in posttranscriptional gene regulation. In this study we found that UPF1 regulates the expression of genes with functions in inflammation and myeloid cell differentiation via hnRNP E2. The majority of the UPF1-regulated genes identified in monocytic cells contain a binding site for hnRNP E2 within 5′ UTR located introns with hnRNP E2 acting here as splicing regulator. We found that miRNA-328 which is significantly induced during monocytic cell differentiation acts independently from its gene silencing function as RNA decoy for hnRNP E2. One representative gene controlled by the hnRNP E2/miRNA-328 balance is S100A9 which plays an important role in cell differentiation and oxidative stress response of monocytes. Induction of miRNA-328 expression during cell differentiation antagonizes the blockade by hnRNP E2 which results in the upregulation of CD11b expression and ROS production in monocytic cells. Taken together, our data indicate that upregulation of miR-328 is responsible for the induction of hnRNP E2 target genes during myeloid cell differentiation.
Although effective antibody-based vaccines have been developed against multiple viruses, such approaches have so far failed for the human immunodeficiency virus type 1 (HIV-1). Despite the success of anti-retroviral therapy (ART) that has turned HIV-1 infection into a chronic disease and has reduced the number of new infections worldwide, a vaccine against HIV-1 is still urgently needed. We discuss here the major reasons for the failure of “classical” vaccine approaches, which are mostly due to the biological properties of the virus itself. HIV-1 has developed multiple mechanisms of immune escape, which also account for vaccine failure. So far, no vaccine candidate has been able to induce broadly neutralizing antibodies (bnAbs) against primary patient viruses from different clades. However, such antibodies were identified in a subset of patients during chronic infection and were shown to protect from infection in animal models and to reduce viremia in first clinical trials. Their detailed characterization has guided structure-based reverse vaccinology approaches to design better HIV-1 envelope (Env) immunogens. Furthermore, conserved Env epitopes have been identified, which are promising candidates in view of clinical applications. Together with new vector-based technologies, considerable progress has been achieved in recent years towards the development of an effective antibody-based HIV-1 vaccine.
Hypoxia-induced long non-coding RNA Malat1 is dispensable for renal ischemia/reperfusion-injury
(2018)
Renal ischemia-reperfusion (I/R) injury is a major cause of acute kidney injury (AKI). Non-coding RNAs are crucially involved in its pathophysiology. We identified hypoxia-induced long non-coding RNA Malat1 (Metastasis Associated Lung Adenocarcinoma Transcript 1) to be upregulated in renal I/R injury. We here elucidated the functional role of Malat1 in vitro and its potential contribution to kidney injury in vivo. Malat1 was upregulated in kidney biopsies and plasma of patients with AKI, in murine hypoxic kidney tissue as well as in cultured and ex vivo sorted hypoxic endothelial cells and tubular epithelial cells. Malat1 was transcriptionally activated by hypoxia-inducible factor 1-α. In vitro, Malat1 inhibition reduced proliferation and the number of endothelial cells in the S-phase of the cell cycle. In vivo, Malat1 knockout and wildtype mice showed similar degrees of outer medullary tubular epithelial injury, proliferation, capillary rarefaction, inflammation and fibrosis, survival and kidney function. Small-RNA sequencing and whole genome expression analysis revealed only minor changes between ischemic Malat1 knockout and wildtype mice. Contrary to previous studies, which suggested a prominent role of Malat1 in the induction of disease, we did not confirm an in vivo role of Malat1 concerning renal I/R-injury.
The signal transducer and activator of transcription 5 (STAT5) regulates differentiation, survival, proliferation and transformation of hematopoietic cells. Upon cytokine stimulation, STAT5 tyrosine phosphorylation (pYSTAT5) is transient, while in diverse neoplastic cells persistent overexpression and enhanced pYSTAT5 are frequently found. Post-translational modifications might contribute to enhanced STAT5 activation in the context of transformation, but the strength and duration of pYSTAT5 are incompletely understood. We found that O-GlcNAcylation and tyrosine phosphorylation act together to trigger pYSTAT5 levels and oncogenic transcription in neoplastic cells. The expression of a mutated hyperactive gain-of-function (GOF) STAT5 without O-GlcNAcylation resulted in decreased tyrosine phosphorylation, oligomerization and transactivation potential and complete loss of oncogenic transformation capacity. The lack of O-GlcNAcylation diminished phospho-ERK and phospho-AKT levels. Our data show that O-GlcNAcylation of STAT5 is an important process that contributes to oncogenic transcription through enhanced STAT5 tyrosine phosphorylation and oligomerization driving myeloid transformation. O-GlcNAcylation of STAT5 could be required for nutrient sensing and metabolism of cancer cells.
Mammalian oocytes are arrested in the dictyate stage of meiotic prophase I for long periods of time, during which the high concentration of the p53 family member TAp63α sensitizes them to DNA damage-induced apoptosis. TAp63α is kept in an inactive and exclusively dimeric state but undergoes rapid phosphorylation-induced tetramerization and concomitant activation upon detection of DNA damage. Here we show that the TAp63α dimer is a kinetically trapped state. Activation follows a spring-loaded mechanism not requiring further translation of other cellular factors in oocytes and is associated with unfolding of the inhibitory structure that blocks the tetramerization interface. Using a combination of biophysical methods as well as cell and ovary culture experiments we explain how TAp63α is kept inactive in the absence of DNA damage but causes rapid oocyte elimination in response to a few DNA double strand breaks thereby acting as the key quality control factor in maternal reproduction.
Inhibition of the IκB kinase complex (IKK) has been implicated in the therapy of several chronic inflammatory diseases including inflammatory bowel diseases. In this study, using mice with an inactivatable IKKα kinase (IkkαAA/AA), we show that loss of IKKα function markedly impairs epithelial regeneration in a model of acute colitis. Mechanistically, this is caused by compromised secretion of cytoprotective IL-18 from IKKα-mutant intestinal epithelial cells because of elevated caspase 12 activation during an enhanced unfolded protein response (UPR). Induction of the UPR is linked to decreased ATG16L1 stabilization in IkkαAA/AA mice. We demonstrate that both TNF-R and nucleotide-binding oligomerization domain stimulation promote ATG16L1 stabilization via IKKα-dependent phosphorylation of ATG16L1 at Ser278. Thus, we propose IKKα as a central mediator sensing both cytokine and microbial stimulation to suppress endoplasmic reticulum stress, thereby assuring antiinflammatory function during acute intestinal inflammation.
Yeast large ribosomal subunit (LSU) precursors are subject to substantial changes in protein composition during their maturation due to coordinated transient interactions with a large number of ribosome biogenesis factors and due to the assembly of ribosomal proteins. These compositional changes go along with stepwise processing of LSU rRNA precursors and with specific rRNA folding events, as revealed by recent cryo-electron microscopy analyses of late nuclear and cytoplasmic LSU precursors. Here we aimed to analyze changes in the spatial rRNA surrounding of selected ribosomal proteins during yeast LSU maturation. For this we combined a recently developed tethered tertiary structure probing approach with both targeted and high throughput readout strategies. Several structural features of late LSU precursors were faithfully detected by this procedure. In addition, the obtained data let us suggest that early rRNA precursor processing events are accompanied by a global transition from a flexible to a spatially restricted rRNA conformation. For intermediate LSU precursors a number of structural hallmarks could be addressed which include the fold of the internal transcribed spacer between 5.8S rRNA and 25S rRNA, the orientation of the central protuberance and the spatial organization of the interface between LSU rRNA domains I and III.
Hematopoietic differentiation is controlled by key transcription factors, which regulate stem cell functions and differentiation. TAL1 is a central transcription factor for hematopoietic stem cell development in the embryo and for gene regulation during erythroid/megakaryocytic differentiation. Knowledge of the target genes controlled by a given transcription factor is important to understand its contribution to normal development and disease. To uncover direct target genes of TAL1 we used high affinity streptavidin/biotin-based chromatin precipitation (Strep-CP) followed by Strep-CP on ChIP analysis using ChIP promoter arrays. We identified 451 TAL1 target genes in K562 cells. Furthermore, we analysed the regulation of one of these genes, the catalytic subunit beta of protein kinase A (PRKACB), during megakaryopoiesis of K562 and primary human CD34+ stem cell/progenitor cells. We found that TAL1 together with hematopoietic transcription factors RUNX1 and GATA1 binds to the promoter of the isoform 3 of PRKACB (Cβ3). During megakaryocytic differentiation a coactivator complex on the Cβ3 promoter, which includes WDR5 and p300, is replaced with a corepressor complex. In this manner, activating chromatin modifications are removed and expression of the PRKACB-Cβ3 isoform during megakaryocytic differentiation is reduced. Our data uncover a role of the TAL1 complex in controlling differential isoform expression of PRKACB. These results reveal a novel function of TAL1, RUNX1 and GATA1 in the transcriptional control of protein kinase A activity, with implications for cellular signalling control during differentiation and disease.
Background: Legionella pneumophila (L. pneumophila) is a causative agent of severe pneumonia. It is highly adapted to intracellular replication and manipulates host cell functions like vesicle trafficking and mRNA translation to its own advantage. However, it is still unknown to what extent microRNAs (miRNAs) are involved in the Legionella-host cell interaction.
Methods: WT and MyD88-/- murine bone marrow-derived macrophages (BMM) were infected with L. pneumophila, the transcriptome was analyzed by high throughput qPCR array (microRNAs) and conventional qPCR (mRNAs), and mRNA-miRNA interaction was validated by luciferase assays with 3´-UTR mutations and western blot.
Results: L. pneumophila infection caused a pro-inflammatory reaction and significant miRNA changes in murine macrophages. In MyD88-/- cells, induction of inflammatory markers, such as Ccxl1/Kc, Il6 and miR-146a-5p was reduced. Induction of miR-125a-3p was completely abrogated in MyD88-/- cells. Target prediction analyses revealed N-terminal asparagine amidase 1 (NTAN1), a factor from the n-end rule pathway, to be a putative target of miR-125a-3p. This interaction could be confirmed by luciferase assay and western blot.
Conclusion: Taken together, we characterized the miRNA regulation in L. pneumophila infection with regard to MyD88 signaling and identified NTAN1 as a target of miR-125a-3p. This finding unravels a yet unknown feature of Legionella-host cell interaction, potentially relevant for new treatment options.
Gallbladder cancer (GBC) is a lethal cancer with poor prognosis associated with high invasiveness and poor response to chemotherapy and radiotherapy. New therapeutic approaches are urgently needed in order to improve survival and response rates of GBC patients. We screened 130 small molecule inhibitors on a panel of seven GBC cell lines and identified the HSP90 inhibitor 17-AAG as one of the most potent inhibitory drugs across the different lines. We tested the antitumor efficacy of 17-AAG and geldanamycin (GA) in vitro and in a subcutaneous preclinical tumor model NOD-SCID mice. We also evaluated the expression of HSP90 by immunohistochemistry in human GBC tumors.
In vitro assays showed that 17-AAG and GA significantly reduced the expression of HSP90 target proteins, including EGFR, AKT, phospho-AKT, Cyclin B1, phospho-ERK and Cyclin D1. These molecular changes were consistent with reduced cell viability and cell migration and promotion of G2/M cell cycle arrest and apoptosis observed in our in vitro studies.
In vivo, 17-AAG showed efficacy in reducing subcutaneous tumors size, exhibiting a 69.6% reduction in tumor size in the treatment group compared to control mice (p < 0.05).
The HSP90 immunohistochemical staining was seen in 182/209 cases of GBC (87%) and it was strongly expressed in 70 cases (33%), moderately in 58 cases (28%), and weakly in 54 cases (26%).
Our pre-clinical observations strongly suggest that the inhibition of HSP90 function by HSP90 inhibitors is a promising therapeutic strategy for gallbladder cancer that may benefit from new HSP90 inhibitors currently in development.
Es war kein Aprilscherz, als das »Time Magazine« am 1. April 2013 auf der Titelseite ankündigte, wie man Krebs heilen kann. Anlass war die Gründung einer Initiative zur besseren Vernetzung von klinischen Forschern und Grundlagenwissenschaftlern, um so neue Therapieansätze wie »Checkpoint-Inhibitoren« bei malignem Melanom (schwarzem Hautkrebs), auch auf andere Krebserkrankungen übertragen zu können. Checkpoint-Inhibitoren sind der erste echte Durchbruch in der Therapie von fortgeschrittenen Krebserkrankungen.
Background: Due to the steadily increasing number of cancer patients worldwide the early diagnosis and treatment of cancer is a major field of research. The diagnosis of cancer is mostly performed by an experienced pathologist via the visual inspection of histo-pathological stained tissue sections. To save valuable time, low quality cryosections are frequently analyzed with diagnostic accuracies that are below those of high quality embedded tissue sections. Thus, alternative means have to be found that enable for fast and accurate diagnosis as the basis of following clinical decision making.
Methods: In this contribution we will show that the combination of the three label-free non-linear imaging modalities CARS (coherent anti-Stokes Raman-scattering), TPEF (two-photon excited autofluorescence) and SHG (second harmonic generation) yields information that can be translated into computational hematoxylin and eosin (HE) images by multivariate statistics. Thereby, a computational HE stain is generated resulting in pseudo-HE overview images that allow for identification of suspicious regions. The latter are analyzed further by Raman-spectroscopy retrieving the tissue’s molecular fingerprint.
Results: The results suggest that the combination of non-linear multimodal imaging and Raman-spectroscopy possesses the potential as a precise and fast tool in routine histopathology.
Conclusions: As the key advantage, both optical methods are non-invasive enabling for further pathological investigations of the same tissue section, e.g. a direct comparison with the current pathological gold-standard.
Cancer research has become a global enterprise, and the number of researchers, as well as the cost for their activities, has skyrocketed. The budget for the National Cancer Institute of the United States National Institutes of Health alone was US$5.2 billion in 2015. Since most of the research is funded by public money, it is perfectly legitimate to ask if these large expenses are worth it. In this brief commentary, we recapitulate some of the breakthroughs that mark the history of breast cancer research over the past decades and emphasize the resulting benefits for afflicted women. In 1971, only 40% of women diagnosed with breast cancer would live another 10 years. Today, nearly 80% of women reach that significant milestone in most developed countries. This dramatic change has afforded breast cancer patients many productive years and a better quality of life. Progress resulted largely from advances in the understanding of the molecular details of the disease and their translation into innovative, rationally designed therapies. These developments are founded on the revolution in molecular and cellular biology, an entirely new array of methods and technologies, the enthusiasm, optimism, and diligence of scientists and clinicians, and the considerable funding efforts from public and private sources. We were lucky to be able to spend our productive years in a period of scientific upheaval in which methods and concepts were revolutionized and that allowed us to contribute, within the global scientific community, to the progress in basic science and clinical practice.
Gallbladder cancer (GBC) is a highly malignant tumor characterized by a poor response to chemotherapy and radiotherapy. We evaluated the in vitro and in vivo antitumor efficacy of mTOR inhibitors, rapamycin and WYE-354. In vitro assays showed WYE-354 significantly reduced cell viability, migration and invasion and phospho-P70S6K expression in GBC cells. Mice harboring subcutaneous gallbladder tumors, treated with WYE-354 or rapamycin, exhibited a significant reduction in tumor mass. A short-term treatment with a higher dose of WYE-354 decreased the tumor size by 68.6% and 52.4%, in mice harboring G-415 or TGBC-2TKB tumors, respectively, compared to the control group. By contrast, treatment with a prolonged-low-dose regime of rapamycin almost abrogated tumor growth, exhibiting 92.7% and 97.1% reduction in tumor size, respectively, compared to control mice. These results were accompanied by a greater decrease in the phosphorylation status of P70S6K and a lower cell proliferation Ki67 index, compared to WYE-354 treated mice, suggesting a more effective mTOR pathway inhibition. These findings provide a proof of concept for the use of rapamycin or WYE-354 as potentially good candidates to be studied in clinical trials in GBC patients.
MiR144/451 expression is repressed by RUNX1 during megakaryopoiesis and disturbed by RUNX1/ETO
(2016)
Abstract: A network of lineage-specific transcription factors and microRNAs tightly regulates differentiation of hematopoietic stem cells along the distinct lineages. Deregulation of this regulatory network contributes to impaired lineage fidelity and leukemogenesis. We found that the hematopoietic master regulator RUNX1 controls the expression of certain microRNAs, of importance during erythroid/megakaryocytic differentiation. In particular, we show that the erythorid miR144/451 cluster is epigenetically repressed by RUNX1 during megakaryopoiesis. Furthermore, the leukemogenic RUNX1/ETO fusion protein transcriptionally represses the miR144/451 pre-microRNA. Thus RUNX1/ETO contributes to increased expression of miR451 target genes and interferes with normal gene expression during differentiation. Furthermore, we observed that inhibition of RUNX1/ETO in Kasumi1 cells and in RUNX1/ETO positive primary acute myeloid leukemia patient samples leads to up-regulation of miR144/451. RUNX1 thus emerges as a key regulator of a microRNA network, driving differentiation at the megakaryocytic/erythroid branching point. The network is disturbed by the leukemogenic RUNX1/ETO fusion product.
Author Summary: The regulatory network between transcription factors, epigenetic cofactors and microRNAs is decisive for normal hematopoiesis. The transcription factor RUNX1 is important for the establishment of a megakaryocytic gene expression program and the concomitant repression of erythroid genes during megakaryocytic differentiation. Gene regulation by RUNX1 is frequently disturbed by mutations and chromosomal translocations, such as the t(8;21) translocation, which gives rise to the leukemogenic RUNX1/ETO fusion protein. We found that RUNX1 regulates microRNAs, which are of importance at the megakaryocytic/erythroid branching point. Specifically, RUNX1 down-regulates expression of the microRNA cluster miR144/451 during megakaryocytic differentiation by changing the epigenetic histone modification pattern at the locus. We could show that miR451, one of the micorRNAs of the miR144/451 cluster, supports erythroid differentiation. We found that expression of miR451 is repressed by the RUNX1/ETO fusion protein, resulting in up regulation of miR451 target genes. Our data support the notion that RUNX1 suppresses the erythroid gene expression program including the erythroid microRNA miR451 and that the RUNX1/ETO fusion protein interferes with normal gene regulation by RUNX1.
The transcription factor Tal1 is a critical activator or repressor of gene expression in hematopoiesis and leukaemia. The mechanism by which Tal1 differentially influences transcription of distinct genes is not fully understood. Here we show that Tal1 interacts with the peptidylarginine deiminase IV (PADI4). We demonstrate that PADI4 can act as an epigenetic coactivator through influencing H3R2me2a. At the Tal1/PADI4 target gene IL6ST the repressive H3R2me2a mark triggered by PRMT6 is counteracted by PADI4, which augments the active H3K4me3 mark and thus increases IL6ST expression. In contrast, at the CTCF promoter PADI4 acts as a repressor. We propose that the influence of PADI4 on IL6ST transcription plays a role in the control of IL6ST expression during lineage differentiation of hematopoietic stem/progenitor cells. These results open the possibility to pharmacologically influence Tal1 in leukaemia.
Immunohistochemical assessment of phosphorylated mTORC1-pathway proteins in human brain tumors
(2015)
Background: Current pathological diagnostics include the analysis of (epi-)genetic alterations as well as oncogenic pathways. Deregulated mammalian target of rapamycin complex 1 (mTORC1) signaling has been implicated in a variety of cancers including malignant gliomas and is considered a promising target in cancer treatment. Monitoring of mTORC1 activity before and during inhibitor therapy is essential. The aim of our study is to provide a recommendation and report on pitfalls in the use of phospho-specific antibodies against mTORC1-targets phospho-RPS6 (Ser235/236; Ser240/244) and phospho-4EBP1 (Thr37/46) in formalin fixed, paraffin embedded material.
Methods and findings: Primary, established cell lines and brain tumor tissue from routine diagnostics were assessed by immunocyto-, immunohistochemistry, immunofluorescent stainings and immunoblotting. For validation of results, immunoblotting experiments were performed. mTORC-pathway activation was pharmacologically inhibited by torin2 and rapamycin. Torin2 treatment led to a strong reduction of signal intensity and frequency of all tested antibodies. In contrast phospho-4EBP1 did not show considerable reduction in staining intensity after rapamycin treatment, while immunocytochemistry with both phospho-RPS6-specific antibodies showed a reduced signal compared to controls. Staining intensity of both phospho-RPS6-specific antibodies did not show considerable decrease in stability in a timeline from 0–230 minutes without tissue fixation, however we observed a strong decrease of staining intensity in phospho-4EBP1 after 30 minutes. Detection of phospho-signals was strongly dependent on tissue size and fixation gradient. mTORC1-signaling was significantly induced in glioblastomas although not restricted to cancer cells but also detectable in non-neoplastic cells.
Conclusion: Here we provide a recommendation for phospho-specific immunohistochemistry for patient-orientated therapy decisions and monitoring treatment response.
Background: The complex cellular networks within tumors, the cytokine milieu, and tumor immune escape mechanisms affecting infiltration and anti-tumor activity of immune cells are of great interest to understand tumor formation and to decipher novel access points for cancer therapy. However, cellular in vitro assays, which rely on monolayer cultures of mammalian cell lines, neglect the three-dimensional architecture of a tumor, thus limiting their validity for the in vivo situation.
Methods: Three-dimensional in vivo-like tumor spheroid were established from human cervical carcinoma cell lines as proof of concept to investigate infiltration and cytotoxicity of NK cells in a 96-well plate format, which is applicable for high-throughput screening. Tumor spheroids were monitored for NK cell infiltration and cytotoxicity by flow cytometry. Infiltrated NK cells, could be recovered by magnetic cell separation.
Results: The tumor spheroids were stable over several days with minor alterations in phenotypic appearance. The tumor spheroids expressed high levels of cellular ligands for the natural killer (NK) group 2D receptor (NKG2D), mediating spheroid destruction by primary human NK cells. Interestingly, destruction of a three-dimensional tumor spheroid took much longer when compared to the parental monolayer cultures. Moreover, destruction of tumor spheroids was accompanied by infiltration of a fraction of NK cells, which could be recovered at high purity.
Conclusion: Tumor spheroids represent a versatile in vivo-like model system to study cytotoxicity and infiltration of immune cells in high-throughput screening. This system might proof useful for the investigation of the modulatory potential of soluble factors and cells of the tumor microenvironment on immune cell activity as well as profiling of patient-/donor-derived immune cells to personalize cellular immunotherapy.
Epigenetic silencing of transgene expression represents a major obstacle for the efficient genetic modification of multipotent and pluripotent stem cells. We and others have demonstrated that a 1.5 kb methylation-free CpG island from the human HNRPA2B1-CBX3 housekeeping genes (A2UCOE) effectively prevents transgene silencing and variegation in cell lines, multipotent and pluripotent stem cells, and their differentiated progeny. However, the bidirectional promoter activity of this element may disturb expression of neighboring genes. Furthermore, the epigenetic basis underlying the anti-silencing effect of the UCOE on juxtaposed promoters has been only partially explored. In this study we removed the HNRPA2B1 moiety from the A2UCOE and demonstrate efficient anti-silencing properties also for a minimal 0.7 kb element containing merely the CBX3 promoter. This DNA element largely prevents silencing of viral and tissue-specific promoters in multipotent and pluripotent stem cells. The protective activity of CBX3 was associated with reduced promoter CpG-methylation, decreased levels of repressive and increased levels of active histone marks. Moreover, the anti-silencing effect of CBX3 was locally restricted and when linked to tissue-specific promoters did not activate transcription in off target cells. Thus, CBX3 is a highly attractive element for sustained, tissue-specific and copy-number dependent transgene expression in vitro and in vivo.
IKKα promotes intestinal tumorigenesis by limiting recruitment of M1-like polarized myeloid cells
(2014)
The recruitment of immune cells into solid tumors is an essential prerequisite of tumor development. Depending on the prevailing polarization profile of these infiltrating leucocytes, tumorigenesis is either promoted or blocked. Here, we identify IκB kinase α (IKKα) as a central regulator of a tumoricidal microenvironment during intestinal carcinogenesis. Mice deficient in IKKα kinase activity are largely protected from intestinal tumor development that is dependent on the enhanced recruitment of interferon γ (IFNγ)-expressing M1-like myeloid cells. In IKKα mutant mice, M1-like polarization is not controlled in a cell-autonomous manner but, rather, depends on the interplay of both IKKα mutant tumor epithelia and immune cells. Because therapies aiming at the tumor microenvironment rather than directly at the mutated cancer cell may circumvent resistance development, we suggest IKKα as a promising target for colorectal cancer (CRC) therapy.
Myelodysplastic syndromes (MDSs) represent clonal disorders mainly of the elderly that are characterized by ineffective hematopoiesis and an increased risk of transformation into acute myeloid leukemia. The pathogenesis of MDS is thought to evolve from accumulation and selection of specific genetic or epigenetic events. Emerging evidence indicates that MDS is not solely a hematopoietic disease but rather affects the entire bone marrow microenvironment, including bone metabolism. Many of these cells, in particular mesenchymal stem and progenitor cells (MSPCs) and osteoblasts, express a number of adhesion molecules and secreted factors that regulate blood regeneration throughout life by contributing to hematopoietic stem and progenitor cell (HSPC) maintenance, self-renewal and differentiation. Several endocrine factors, such as erythropoietin, parathyroid hormone and estrogens, as well as deranged iron metabolism modulate these processes. Thus, interactions between MSPC and HSPC contribute to the pathogenesis of MDS and associated pathologies. A detailed understanding of these mechanisms may help to define novel targets for diagnosis and possibly therapy. In this review, we will discuss the scientific rationale of "osteohematology" as an emerging research field in MDS and outline clinical implications.
The metastasis-associated lung adenocarcinoma transcript 1, MALAT1, is a long non-coding RNA (lncRNA) that has been discovered as a marker for lung cancer metastasis. It is highly abundant, its expression is strongly regulated in many tumor entities including lung adenocarcinoma and hepatocellular carcinoma as well as physiological processes, and it is associated with many RNA binding proteins and highly conserved throughout evolution. The nuclear transcript MALAT-1 has been functionally associated with gene regulation and alternative splicing and its regulation has been shown to impact proliferation, apoptosis, migration and invasion.
Here, we have developed a human and a mouse knockout system to study the loss-of-function phenotypes of this important ncRNA. In human tumor cells, MALAT1 expression was abrogated using Zinc Finger Nucleases. Unexpectedly, the quantitative loss of MALAT1 did neither affect proliferation nor cell cycle progression nor nuclear architecture in human lung or liver cancer cells. Moreover, genetic loss of Malat1 in a knockout mouse model did not give rise to any obvious phenotype or histological abnormalities in Malat1-null compared with wild-type animals. Thus, loss of the abundant nuclear long ncRNA MALAT1 is compatible with cell viability and normal development.
DNA damage in oocytes induces a switch of the quality control factor TAp63α from dimer to tetramer
(2011)
TAp63a, a homolog of the p53 tumor suppressor, is a quality control factor in the female germline. Remarkably, already undamaged oocytes express high levels of the protein, suggesting that TAp63a’s activity is under tight control of an inhibitory mechanism. Biochemical studies have proposed that inhibition requires the C-terminal transactivation inhibitory domain. However, the structural mechanism of TAp63a inhibition remains unknown. Here, we show that TAp63a is kept in an inactive dimeric state. We reveal that relief of inhibition leads to tetramer formation with ~20-fold higher DNA affinity. In vivo, phosphorylation-triggered tetramerization of TAp63a is not reversible by dephosphorylation. Furthermore, we show that a helix in the oligomerization domain of p63 is crucial for tetramer stabilization and competes with the transactivation domain for the same binding site. Our results demonstrate how TAp63a is inhibited by complex domain-domain interactions that provide the basis for regulating quality control in oocytes.
Tumor cell plasticity is an event that has been observed in several malignancies. In fact, most of the solid tumors are characterized by cellular heterogeneity and undergo constant changes as the tumor develops. The increased plasticity displayed by these cells allows them to acquire additional properties, enabling epithelial-mesenchymal transitions, dedifferentiation and the acquisition of stem cell-like properties. Here we discuss the particular importance of an inflammatory microenvironment for the bidirectional control of cellular plasticity and the potential for therapeutic intervention.
Immunotherapy of cancer utilizes dendritic cells (DCs) for antigen presentation and the induction of tumor-specific immune responses. However, the therapeutic induction of anti-tumor immunity is limited by tumor escape mechanisms. In this study, immortalized dendritic D2SC/1 cells were transduced with a mutated version of the p53 tumor suppressor gene, p53M234I, or p53C132F/E168G, which are overexpressed in MethA fibrosarcoma tumor cells. In addition, D2SC/1 cells were fused with MethA tumor cells to generate a vaccine that potentially expresses a large repertoire of tumor-antigens. Cellular vaccines were transplanted onto Balb/c mice and MethA tumor growth and anti-tumor immune responses were examined in vaccinated animals. D2SC/1-p53M234I and D2SC/1-p53C132F/E168G cells induced strong therapeutic and protective MethA tumor immunity upon transplantation in Balb/c mice. However, in a fraction of immunized mice MethA tumor growth resumed after an extended latency period. Analysis of these tumors indicated loss of p53 expression. Mice, pre-treated with fusion hybrids generated from D2SC/1 and MethA tumor cells, suppressed MethA tumor growth and averted adaptive immune escape. Polyclonal B-cell responses directed against various MethA tumor proteins could be detected in the sera of D2SC/1-MethA inoculated mice. Athymic nude mice and Balb/c mice depleted of CD4(+) or CD8(+) T-cells were not protected against MethA tumor cell growth after immunization with D2SC/1-MethA hybrids. Our results highlight a potential drawback of cancer immunotherapy by demonstrating that the induction of a specific anti-tumor response favors the acquisition of tumor phenotypes promoting immune evasion. In contrast, the application of DC/tumor cell fusion hybrids prevents adaptive immune escape by a T-cell dependent mechanism and provides a simple strategy for personalized anti-cancer treatment without the need of selectively priming the host immune system.
Survivin is a well-established target in experimental cancer therapy. The molecule is over-expressed in most human tumors, but hardly detectable in normal tissues. Multiple functions in different subcellular compartments have been assigned. It participates in the control of cell division, apoptosis, the cellular stress response, and also in the regulation of cell migration and metastasis. Survivin expression has been recognized as a biomarker: high expression indicates an unfavorable prognosis and resistance to chemotherapeutic agents and radiation treatment. Survivin is an unconventional drug target and several indirect approaches have been exploited to affect its function and the phenotype of survivin-expressing cells. Interference with the expression of the survivin gene, the utilization of its messenger RNA, the intracellular localization, the interaction with binding partners, the stability of the survivin protein, and the induction of survivin-specific immune responses have been taken into consideration. A direct strategy to inhibit survivin has been based on the identification of a specifically interacting peptide. This peptide can recognize survivin intracellularly and cause the degradation of the ligand–survivin complex. Technology is being developed that might allow the derivation of small molecular-weight, drug-like compounds that are functionally equivalent to the peptide ligand.
Gene therapy on the move
(2013)
The first gene therapy clinical trials were initiated more than two decades ago. In the early days, gene therapy shared the fate of many experimental medicine approaches and was impeded by the occurrence of severe side effects in a few treated patients. The understanding of the molecular and cellular mechanisms leading to treatment- and/or vector-associated setbacks has resulted in the development of highly sophisticated gene transfer tools with improved safety and therapeutic efficacy. Employing these advanced tools, a series of Phase I/II trials were started in the past few years with excellent clinical results and no side effects reported so far. Moreover, highly efficient gene targeting strategies and site-directed gene editing technologies have been developed and applied clinically. With more than 1900 clinical trials to date, gene therapy has moved from a vision to clinical reality. This review focuses on the application of gene therapy for the correction of inherited diseases, the limitations and drawbacks encountered in some of the early clinical trials and the revival of gene therapy as a powerful treatment option for the correction of monogenic disorders.
HIV neutralizing antibodies (nAbs) represent an important tool in view of prophylactic and therapeutic applications for HIV-1 infection. Patients chronically infected by HIV-1 represent a valuable source for nAbs. HIV controllers, including long-term non-progressors (LTNP) and elite controllers (EC), represent an interesting subgroup in this regard, as here nAbs can develop over time in a rather healthy immune system and in the absence of any therapeutic selection pressure. In this study, we characterized two particular antibodies that were selected as scFv antibody fragments from a phage immune library generated from an LTNP with HIV neutralizing antibodies in his plasma. The phage library was screened on recombinant soluble gp140 envelope (Env) proteins. Sequencing the selected peptide inserts revealed two major classes of antibody sequences. Binding analysis of the corresponding scFv-Fc derivatives to various trimeric and monomeric Env constructs as well as to peptide arrays showed that one class, represented by monoclonal antibody (mAb) A2, specifically recognizes an epitope localized in the pocket binding domain of the C heptad repeat (CHR) in the ectodomain of gp41, but only in the trimeric context. Thus, this antibody represents an interesting tool for trimer identification. MAb A7, representing the second class, binds to structural elements of the third variable loop V3 and neutralizes tier 1 and tier 2 HIV-1 isolates of different subtypes with matching critical amino acids in the linear epitope sequence. In conclusion, HIV controllers are a valuable source for the selection of functionally interesting antibodies that can be selected on soluble gp140 proteins with properties from the native envelope spike.
Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by impaired antimicrobial activity in phagocytic cells. As a monogenic disease affecting the hematopoietic system, CGD is amenable to gene therapy. Indeed in a phase I/II clinical trial, we demonstrated a transient resolution of bacterial and fungal infections. However, the therapeutic benefit was compromised by the occurrence of clonal dominance and malignant transformation demanding alternative vectors with equal efficacy but safety-improved features. In this work we have developed and tested a self-inactivating (SIN) gammaretroviral vector (SINfes.gp91s) containing a codon-optimized transgene (gp91(phox)) under the transcriptional control of a myeloid promoter for the gene therapy of the X-linked form of CGD (X-CGD). Gene-corrected cells protected X-CGD mice from Aspergillus fumigatus challenge at low vector copy numbers. Moreover, the SINfes.gp91s vector generates substantial amounts of superoxide in human cells transplanted into immunodeficient mice. In vitro genotoxicity assays and longitudinal high-throughput integration site analysis in transplanted mice comprising primary and secondary animals for 11 months revealed a safe integration site profile with no signs of clonal dominance.
Im Jahre 2004 sind am Universitätsklinikum Frankfurt zwei Patienten mit X-CGD gentherapeutisch behandelt worden. Nach einer initialen Phase mit Nachweis ausreichender Mengen Oxidase-positiver Zellen im Blut der Patienten und einer deutlichen klinischen Besserung vorbestehender Infektionsherde kam es zu einem Verlust der Transgenexpression durch epigenetische Veränderungen des viralen Promotors. Ferner entwickelte sich durch Insertionsmutagenese eine klonale Expansion in der Hämatopoese und schließlich ein myelodysplastisches Syndrom mit Monosomie 7 bei beiden Patienten. In der Zusammenschau mit anderen Gentherapiestudien zur X-CGD zeigt sich, dass bislang ein langanhaltendes Engraftment funktionierender genkorrigierter Zellen nur im Zusammenhang mit einer Insertionsmutagenese beobachtet wurde. Zukünftige gentherapeutische Strategien zur Behandlung der X-CGD müssen das Risiko einer Insertionsmutagenese minimieren und gleichzeitig die Effektivität des Engraftments genkorrigierter Zellen steigern. Dies soll durch den Einsatz von SIN-Vektoren sowie einer Intensivierung der Konditionierung der Patienten erreicht werden.
Gene-modified autologous hematopoietic stem cells (HSC) can provide ample clinical benefits to subjects suffering from X-linked chronic granulomatous disease (X-CGD), a rare inherited immunodeficiency characterized by recurrent, often life-threatening bacterial and fungal infections. Here we report on the molecular and cellular events observed in two young adults with X-CGD treated by gene therapy in 2004. After the initial resolution of bacterial and fungal infections, both subjects showed silencing of transgene expression due to methylation of the viral promoter, and myelodysplasia with monosomy 7 as a result of insertional activation of ecotropic viral integration site 1 (EVI1). One subject died from overwhelming sepsis 27 months after gene therapy, whereas a second subject underwent an allogeneic HSC transplantation. Our data show that forced overexpression of EVI1 in human cells disrupts normal centrosome duplication, linking EVI1 activation to the development of genomic instability, monosomy 7 and clonal progression toward myelodysplasia.
The leukemia-associated fusion protein RUNX1/ETO is generated by the chromosomal translocation t(8;21) which appears in about 12% of all de novo acute myeloid leukemias (AMLs). Essential for the oncogenic potential of RUNX1/ETO is the oligomerization of the chimeric fusion protein through the nervy homology region 2 (NHR2) within ETO. In previous studies, we have shown that the intracellular expression of peptides containing the NHR2 domain inhibits RUNX1/ETO oligomerization, thereby preventing cell proliferation and inducing differentiation of RUNX1/ETO transformed cells. Here, we show that introduction of a recombinant TAT-NHR2 fusion polypeptide into the RUNX1/ETO growth-dependent myeloid cell line Kasumi-1 results in decreased cell proliferation and increased numbers of apoptotic cells. This effect was highly specific and mediated by binding the TAT-NHR2 peptide to ETO sequences, as TAT-polypeptides containing the oligomerization domain of BCR did not affect cell proliferation or apoptosis in Kasumi-1 cells. Thus, the selective interference with NHR2-mediated oligomerization by peptides represents a challenging but promising strategy for the inhibition of the leukemogenic potential of RUNX1/ETO in t(8;21)-positive leukemia.
Transcription factors play a crucial role in regulating differentiation processes during human life and are important in disease. The basic helix-loop-helix transcription factors Tal1 and Lyl1 play a major role in the regulation of gene expression in the hematopoietic system and are involved in human leukemia. Tal2, which belongs to the same family of transcription factors as Tal1 and Lyl1, is also involved in human leukaemia. However, little is known regarding the expression and regulation of Tal2 in hematopoietic cells. Here we show that Tal2 is expressed in hematopoietic cells of the myeloid lineage. Interestingly, we found that usage of the Tal2 promoter is different in human and mouse cells. Two promoters, hP1 and hP2 drive Tal2 expression in human erythroleukemia K562 cells, however in mouse RAW cells only the mP1 promoter is used. Furthermore, we found that Tal2 expression is upregulated during oesteoclastogenesis. We show that Tal2 is a direct target gene of the myeloid transcription factor PU.1, which is a key transcription factor for osteoclast gene expression. Strikingly, PU.1 binding to the P1 promoter is conserved between mouse and human, but PU.1 binding to P2 was only detected in human K562 cells. Additionally, we provide evidence that Tal2 influences the expression of the osteoclastic differentiation gene TRACP. These findings provide novel insight into the expression control of Tal2 in hematopoietic cells and reveal a function of Tal2 as a regulator of gene expression during osteoclast differentiation.
Human endogenous retrovirus (HERV) genomes are chromosomally integrated in all cells of an individual. They are normally transcriptionally silenced and transmitted only vertically. Enhanced expression of HERV-K accompanied by the emergence of anti-HERV-K-directed immune responses has been observed in tumor patients and HIV-infected individuals. As HERV-K is usually not expressed and immunological tolerance development is unlikely, it is an appropriate target for the development of immunotherapies. We generated a recombinant vaccinia virus (MVA-HKenv) expressing the HERV-K envelope glycoprotein (ENV), based on the modified vaccinia virus Ankara (MVA), and established an animal model to test its vaccination efficacy. Murine renal carcinoma cells (Renca) were genetically altered to express E. coli beta-galactosidase (RLZ cells) or the HERV-K ENV gene (RLZ-HKenv cells). Intravenous injection of RLZ-HKenv cells into syngenic BALB/c mice led to the formation of pulmonary metastases, which were detectable by X-gal staining. A single vaccination of tumor-bearing mice with MVA-HKenv drastically reduced the number of pulmonary RLZ-HKenv tumor nodules compared to vaccination with wild-type MVA. Prophylactic vaccination of mice with MVA-HKenv precluded the formation of RLZ-HKenv tumor nodules, whereas wild-type MVA-vaccinated animals succumbed to metastasis. Protection from tumor formation correlated with enhanced HERV-K ENV-specific killing activity of splenocytes. These data demonstrate for the first time that HERV-K ENV is a useful target for vaccine development and might offer new treatment opportunities for diverse types of cancer.
Rückschläge werfen eine neue Technologie um Jahrzehnte zurück – besonders, wenn Menschenleben zu beklagen sind. Bei der Gentherapie wird aber oft vergessen, dass sie nur bei Patienten angewendet wird, für die es keine konventionelle Therapie mehr gibt. Nach der Euphorie und den Rückschlägen der Anfangsjahre können Forscher nun die ersten Erfolge vorweisen.
Yeast cells can be killed upon expression of pro-apoptotic mammalian proteins. We have established a functional yeast survival screen that was used to isolate novel human anti-apoptotic genes overexpressed in treatment-resistant tumors. The screening of three different cDNA libraries prepared from metastatic melanoma, glioblastomas and leukemic blasts allowed for the identification of many yeast cell death-repressing cDNAs, including 28% of genes that are already known to inhibit apoptosis, 35% of genes upregulated in at least one tumor entity and 16% of genes described as both anti-apoptotic in function and upregulated in tumors. These results confirm the great potential of this screening tool to identify novel anti-apoptotic and tumor-relevant molecules. Three of the isolated candidate genes were further analyzed regarding their anti-apoptotic function in cell culture and their potential as a therapeutic target for molecular therapy. PAICS, an enzyme required for de novo purine biosynthesis, the long non-coding RNA MALAT1 and the MAST2 kinase are overexpressed in certain tumor entities and capable of suppressing apoptosis in human cells. Using a subcutaneous xenograft mouse model, we also demonstrated that glioblastoma tumor growth requires MAST2 expression. An additional advantage of the yeast survival screen is its universal applicability. By using various inducible pro-apoptotic killer proteins and screening the appropriate cDNA library prepared from normal or pathologic tissue of interest, the survival screen can be used to identify apoptosis inhibitors in many different systems.