Prognostic value of CPSS cytogenetic risk classification in patients with CMML after allogeneic hematopoietic cell transplantation : a retrospective multicenter study of the Chronic Malignancies Working Party of the EBMT

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Graft-versus-host disease and relapse/rejection-free survival after allogeneic transplantation for idiopathic severe aplastic anemia: a comprehensive analysis from the SAAWP of the EBMT

Survival after allogeneic hematopoietic stem cell transplantation (allo-HSCT) for severe idiopathic aplastic anemia (SAA) has improved in recent years, approaching 75% at 5 years. However, an SAA-adapted composite endpoint, graft-versus-host disease (GvHD) and relapse/rejection-free survival (GRFS), may more accurately assess patient outcomes beyond survival. We analyzed GRFS to identify risk factors and specific causes of GRFS failure. Our retrospective analysis from the Severe Aplastic Anemia Working Party of the European Society for Blood and Marrow Transplantation included 479 patients with idiopathic SAA who underwent allo-HSCT in two conventional situations: i) upfront allo-HSCT from a matched related donor (MRD) (upfront cohort), and ii) allo-HSCT for relapsed or refractory SAA (rel/ref cohort). Relevant events for GRFS calculation included graft failure, grade 3-4 acute GvHD, extensive chronic GvHD, and death. In the upfront cohort (n=209), 5-year GRFS was 77%. Late allo-HSCT (i.e., >6 months after SAA diagnosis) was the main poor prognostic factor, specifically increasing the risk of death as the cause of GRFS failure (hazard ratio [HR]=4.08; 95% confidence interval [CI]: 1.41-11.83; P=0.010). In the rel/ref cohort (n=270), 5-year GRFS was 61%. Age was the main factor significantly increasing the risk of death (HR=1.04; 95% CI: 1.02-1.06; P</p

Differences in the Localization of Receptor Tyrosine Kinase FLT3 in Human Hematopoietic Stem and Progenitor Cells and Leukemic Blasts.

Abstract Activation of type III receptor tyrosine kinase FLT3 by its ligand controls cell proliferation and differentiation in normal hematopoiesis. Constitutively activating mutations of FLT3 are common abnormalities in acute myeloid leukemia. Internal tandem duplication (ITD) mutations of the FLT3 receptor are found in approximately one third of patients with AML and normal karyotype and have been shown to be associated with inferior response towards chemotherapy. One possible way how mutant FLT3 receptors may be mediating its pathological effects is by altering the normal localization of the receptor protein. To determine the intracellular localization of wild type and mutant FLT3 receptors, confocal laser scanning microscopy was performed in cultured leukemic cell lines (THP-1, EOL-1, MV4-11) and primary hematopoietic stem cells (HSC) from healthy donors. HSC (CD34+) cells were prepared from human bone marrow and leukapheresis products of healthy donors by MACS technique using CD34 and CD135 (FLT3) coupled microbeads. Additionally, different leukemic cell lines were transduced with retroviral vectors encoding FLT3wt or FLT3-ITD receptors. In normal HSC, only 4–13% are expressing FLT3, and unexpectedly FLT3 staining was observed both in the plasma membrane and evenly distributed in the cytoplasm. The intracellular FLT3wt was not localized to the endoplasmic reticulum (ER), but part of it co-localized with the Trans-Golgi-network (TGN) and early endosomes. In leukemic cell lines endogenously expressing either wt or mutant FLT3, wtFLT3 localized to the plasma membrane and uniformly to the cytoplasm whereas mutant FLT3 strongly accumulated in a perinuclear region but did not localize to the plasma membrane. Stable transfection of leukemic cell lines with wt or mutant FLT3 confirmed this localization pattern. In leukemic cell lines neither FLT3wt nor FLT3-ITD accumulated in the ER or in the Golgi apparatus, but instead FLT3wt and FLT3-ITD seem to reside in the TGN and in early endosomes as shown by immunofluorescence costaining with the organelle markers. These data indicate that although perinuclear accumulation of mutant FLT3 is observed in all cells analyzed, wtFLT3 is also found intracellularly. FLT3-ITD might reside in a different state concerning glycosylation and/or phosphorylation (Schmidt-Arras et al., Mol Cell Biol, 2005) and therefore it may activate alternative or additional signaling cascades by having access to different or additional substrates. Further studies will clarify, whether intracellularly located wtFLT3 in healthy HSC and FLT3wt-expressing leukemic cells is also involved in FLT3 signaling.</jats:p

Hypoxia Increases IL-8 Secretion of Mesenchymal Stroma Cells Affecting Migratory Capacity in An Autocrine Manner

Abstract Hypoxia increases IL-8 secretion of mesenchymal stroma cells affecting migratory capacity in an autocrine manner Manja Wobus, Katrin Müller, Gerhard Ehninger, Martin Bornhäuser Department of Hematology/Oncology, University Hospital Dresden, Fetscherstr. 74, 01307 Dresden, Germany Adult bone marrow-derived stem cells represent an important source of cells for regeneration and repair of a number of damaged tissues. Mesenchymal stromal cells (MSCs) give rise to the cellular components of the bone marrow microenvironment and support expansion and differentiation of hematopoeitic stem cells in the respective niche. Low oxygen tension is thought to be an integral component of the endosteal niche microenvironment. When used for therapeutic purposes, MSCs cultured in standard conditions must adapt from 21% oxygen to less than 1% oxygen in the ischemic tissue. Understanding the mechanisms by which the production of cytokines and growth factors by MSCs is regulated may represent an important way to optimize their beneficial paracrine and autocrine effects. Human primary MSCs were incubated under normoxic (20% O2) and hypoxic (0.5% O2) conditions over five days and the pattern of released cytokines in the cell culture supernatants was compared using a human cytokine array (R &amp; D Systems). Amongst others, we found upregulated IL-8 levels under hypoxic conditions leading us to further investigation of IL-8 expression in MSCs and its role for in-vitro migration. As expected, IL-8 mRNA levels were significantly higher in hypoxic MSCs. The result of the cytokine array was confirmed by examination of secreted IL-8 in the cell culture supernatant by ELISA (PeproTech). The migration capacity was investigated in a 24-well transwell chamber assay with 8 μm pore size. Using recombinant IL-8 as a chemoattractant in the lower chamber, we detected an almost twofold enhanced MSC migration rate after 24 hours under hypoxic conditions. As a different approach to investigate the migratory capacity, we used an in-vitro scratch assay. A wound was applied to a MSC monolayer in absence or presence of IL-8 which clearly enhanced the migration of MSCs into the wound area after 24 hours. In summary, IL-8 secretion by human primary MSCs is clearly increased under hypoxic conditions. IL-8 in turn seems to be a chemotactic factor for MSCs and enhances their migratory capacity in an autocrine manner.</jats:p

Histone Deacetylase Inhibitors As Enhancers of Human Hematopoietic Stem Cell Activity

Abstract Introduction The identification of compounds which increase the number but also keep or enhance the activity of hematopoietic stem and progenitor cells (HSPCs) could improve the clinical outcome after autologous and allogeneic hematopoietic stem cell transplantation (HSCT). So far, most attempts to increase HSPC numbers ex vivo have been unsuccessful because of either inadequate cell numbers and/or loss of engraftment capacity and HSPC quality during expansion. Executing drug discovery screens in vertebrate systems is generally expensive, technically challenging and time consuming. Therefore, the zebrafish represents a versatile vertebrate model allowing HSPC regulation and development studies during embryogenesis and adulthood. Methods We used a semi-automated chemical screen to identify modulators of HSPC activity by transgenic (cmyb:EGFP) zebrafish embryos. Verification of identified histone deacetylase (HDAC) inhibitor candidates was carried out in vitro using human CD34+ HSPCs which were isolated from apharesis samples of healthy donors after mobilization with G-CSF by anti-CD34 coupled magnetic beads. The influence of HDAC inhibitors on HSPC phenotype, gene expression pattern as well as adhesion and migration capacity was analyzed after 5 days of treatment either in single or in co-culture with bone marrow-derived mesenchymal stromal cells (MSCs). Results The HDAC inhibitors valproic acid (VPA), resminostat and entinostat were shown to significantly amplify the number of hematopoietic precursors in a chemical in vivo zebrafish embryo screen (Arulmozhivarman et al. 2016). Treatment of human CD34+ HSPCs with these compounds in vitro resulted in a significantly increased percentage of CD34+CD90+ cells up to 60% compared to controls which showed only 2% of double positive cells as well as in 3-fold higher CD34+ and about 12-fold higher CD34+CD90+ absolute cell numbers. CD34 is a well-known surface marker for human immature HSPCs and in combination with CD90 it defines a potentially pluripotent subpopulation. In a co-culture setting, we found that VPA treated cells showed 2 to 3-fold higher attachment capacity on MSCs compared to the control cells. This finding led us to quantify the adhesive capacity of cells using static adhesion assay and atomic force microscopy based single-cell force spectroscopy (AFM-SCFS). Interestingly, detachment forces of VPA treated HSPCs were 3 times increased on MSCs compared to control cells and a similar phenotype was observed by static adhesion assay. Accordingly, the chemokine-mediated migration of VPA treated HSPCs towards SDF-1/CXCL12 was inhibited. To reveal underlying downstream molecules and mechanisms mediating the modified cellular characteristics, a whole genome expression array was carried out for HSPCs treated with VPA in comparison to untreated controls. Amongst a panel of regulated genes, the melanoma cell adhesion molecule (MCAM/CD146), Notch 3 and its downstream effector Hes-1 as well as the SDF-1 receptor CXCR-4 were found to be significantly changed. Whereas the decreased expression of CXCR4 correlates with the inhibited migration potential of VPA-treated HSPCs and Notch-3/Hes-1 have a known role in normal and malignant hematopoiesis (Gu et al. 2016), the induced expression of MCAM on HSPCs was not described so far. The result was confirmed by flow cytometry which revealed a 40% MCAM-positive cell population when treated with VPA, whereas the control showed only negative cells. Additionally, significant higher transcript levels were detected for MCAM by quantitative real-time PCR in VPA expanded cells. Recently, we described a role of MCAM in MSCs for the hematopoietic support (Stopp et al. 2013). The inducible expression in HSPCs may reflect homotypic interactions which preserve a more immature subpopulation with high stem cell activity. Conclusion We describe for the first time the ability of the HDAC inhibitors VPA, resminostat and entinostat to efficiently expand CD34+ HSPCs ex vivo especially supporting a CD34+CD90+ subpopulation with potentially high stem cell activity. Moreover, a potential role of MCAM in this context may offer new perspectives of the HSPC expansion ex vivo for the improvement of HSCT. Disclosures No relevant conflicts of interest to declare. </jats:sec

High Prevalence of Functional Laa Specific Cytotoxic T Lymphocytes in Healthy Individuals-Implications for Strategies in Adoptive T Cell Therapies of Relapsed Leukemia

Abstract While adoptive transfer of virus antigen specific T cells has shown to be effective in therapy of resistant recurrent viremia which is frequently associated with the lack of protective immunity following hematopoietic stem cell transplantation, the transfer of leukemia associated antigen specific (LAA) T cells is less implemented and appears to depend on factors that hamper a successful translation into the clinic. Among them are low frequencies and low antigen affinity of LAA specific T cells which currently mandate laborious in vitro expansion protocols. Moreover, screening of healthy individuals with regard to the presence of LAA specific T cells revealed contradictory results. Since we failed to detect LAA specific T cells in healthy donors using single peptide specificities to known LAA epitopes coupled to MHC Streptamers, here we asked if the use of peptide mixes comprising 15mers overlapping by 11 amino acids and spanning the entire LAA protein could elicit in vitro T cell responses in healthy donors, otherwise undetectable by single peptide staining. A cohort of 48 HLA A*0201 healthy individuals was screened using intracellular cytokine staining (ICS) after stimulation with tumor specific peptide mixes representing well known LAAs (WT1, PRAME, NY-ESO, Survivin and p53). While distinct T-helper cell responses were not observed in either of the specimen tested, cytotoxic T lymphocytes could be elicited and measured after incubation with peptide mixes for 5 hours and subsequent CD8+ IFNγ+ staining in 12 out of 48 healthy subjects. Only one individual displayed specifies against multiple antigens (WT1:0,1%; PRAME:0,5%; NY-ESO:0,1%; p53:0.06%), while the remaining responses were directed to one single antigen per individual. Most prevalent and highest T cell frequencies were found against PRAME in 5 out of all screened subjects (mean 0.4±0.3%; max. 0.8%), followed by WT1 in 4 (mean 0.07±0.03%; max. 0.1%) and NY-ESO in 3 individuals (mean 0,07±0,04%; max. 0,1%); one showed CD8 T cells specific against Survivin (0,03%) and 2 individuals had CD8 frequencies specific against p53 (0,05±0,01; max. 0,06%), respectively. The calculated limit of detection (LOD) for the enumeration of LAA specific T cells was 0,02%. In contrary, testing LAA positive individuals with according MHC Streptamers presenting single peptides of previously described epitopes showed no frequencies exceeding LOD. Further analysis showed LAA specific CD8+ IFNγ+ T cells exhibit mainly a less differentiated phenotype (CD45RA+, CCR7+/-, TNFα+, IL-2+/-) and could be immune-magnetically isolated to purities of 94.5±0.7% using a PRAME-specific IFN-γ capture assay yielding 1*104 antigen specific T cells out of 4*107 PBMCs. Simultaneous enrichment of helper T cells to a purity of 73.0±7.6% proofed their existence, despite no CD4+ response could be detected via ICS in the first place. The cytotoxic potential of the cell product was confirmed in an Europium assay using T2 cells loaded with PRAME peptide mix. The specific lysis accounted to 19.3% at an E:T ratio of 1:1 after 90 minutes of co-incubation. In conclusion, using LAA specific peptide mixes in combination with ICS we were able to show a relatively high prevalence of LAA specific T cells, especially for PRAME, in healthy donors. These LAA specific T cells can be enriched without the need of in vitro expansion culturing ex vivo using the IFN-γ capture assay with regard to achieving a functional LAA specific T cell product for adoptive T cell transfer. Furthermore, a less differentiated phenotype exhibited by a large proportion of LAA specific T cells might contribute to their long term survival in a patient after transplantation. Disclosures No relevant conflicts of interest to declare. </jats:sec

Engineering Biomimetic Culture Systems: Impact On Human Bone Marrow-Derived Stem Cells.

Abstract Abstract 3628 Poster Board III-564 The bone marrow (BM) harbours haematopoietic stem/progenitor cells (HSCs) in anatomically distinct sites (niches) where HSCs are subjected to regulatory cues such as cytokines, cell-cell contacts and extra-cellular matrix (ECM) all of which control stem cell fate. In particular mesenchymal stromal cells (MSCs) are an integral part of the bone marrow and are known to be key regulators of the HSC niche. We have previously shown that bio-artificial scaffolds can have a significant impact on the in vitro behaviour of MSCs. Here, we are therefore focussing on the role of (native) ECM within the MSC-HSC microenvironment by building on our previous findings and published data (Seib et al.,Tissue Eng Part A., 2009 in press). Thus the aim of the current study is (a) to identify niche-specific ECM components and (b) the use of such ECMs for in vitro culture of BM-derived stem cells. To mimic the natural ECM composition of the BM, different ECM types were generated from BM-derived cells using (a) Dexter cultures, (b) standard MSC cultures, (c) MSCs subjected to osteogenic differentiation. After 10 days of culture those MSC-derived ECMs were decellularised using 0.5% Triton-X and 20mM NH4OH leaving only the ECM behind (verified by scanning electron microscopy). Those ECMs were used as a substrate for a second culture of MSCs, which were analysed for their proliferation and differentiation potential. Cell-free ECM from standard MSC cultures improved MSC proliferation compared to cells grown on regular tissue culture plastic (TCP) over the period of 8 days. Most notably, all cell-free ECM preparations lead to a significant difference in the cytoskeletal arrangement of MSCs during the first 2 days of culture compared to TCP controls. Cultivation of MSCs on native ECM provided a guiding structure for those cells to grow into, and helped to maintain an elongated cell shape compared to substantial cell spreading on TCP (roundness 0.2 versus 0.5 and cell area of 2.2 versus 8.2mm2, respectively, p&lt;0.001, n=60. A factor of 1 was set to equate to a perfect circle). Next, we investigate if native ECM could either directly improve HSC cultures or maximise MSC feeder characteristics. For the latter set of studies MSCs were initially cultured for 7 days on cell-free ECM (from standard MSC cultures) and subsequently co-cultured with human peripheral blood CD34+ HSCs in serum free medium supplemented with cytokines (Tpo, Flt3, and SCF at 10ng/ml). Following a 14 day culture period up to 3.5-fold more CD34+ cells were present in ECM co-cultures compared to TCP co-cultures that was accompanied with an overall expansion of CD45+ cells of 109-fold versus 35-fold, respectively. Our data suggest that ECM preparations derived from MSCs might be useful to accomplish better expansion of HSCs under defined culture conditions. In addition, this system permits the identification of bimolecular key components that can be utilized in the future design of simple and robust carrier systems for improved HSC maintenance in vitro. Figure HSC-MSC co-culture on preformed ECM substrates. (A) MSC-derived ECM (from standard MSC culture) following cell lysis (complete absence of cells). (B) Growth of a new set of MSCs on ECM substrates as shown in (A). (C) HSC-MSC co-culture on ECM substrates. Scale bars at 2μm. Arrow heads point out ECM structures. Figure HSC-MSC co-culture on preformed ECM substrates. (A) MSC-derived ECM (from standard MSC culture) following cell lysis (complete absence of cells). (B) Growth of a new set of MSCs on ECM substrates as shown in (A). (C) HSC-MSC co-culture on ECM substrates. Scale bars at 2μm. Arrow heads point out ECM structures. Disclosures: No relevant conflicts of interest to declare. </jats:sec

The Calcineurin/NFAT Signaling Pathway Is a Target for the Collagen Type I-Induced Calcium Response in Megakaryocytes and Mediates Expression of Megakaryocytic Genes.

Abstract Megakaryocytes, as precursor cells of platelets, comprise a cell population crucial for the maintenance of adult hematopoiesis. Since platelets are anuclear cellular fragments, the platelet transcriptome as well as the proteome are largely determined by the megakaryocyte. Calcium signaling in response to agonists such as collagen or thrombin has a central function in platelet activation and therefore likely represents an important signaling pathway in megakaryocytes as well. Indeed, megakaryocytes show considerable elevation of intracellular calcium levels in response to selected platelet agonists, but the downstream effector molecules of calcium signaling in these cells or the transcriptional responses induced are unknown. We here establish calcineurin and the NFAT (Nuclear Factor of Activated T cells) family of transcription factors as components of a calcium-induced signaling cascade in megakaryocytes. In resting megakaryocytes, NFAT is cytoplasmic and inactive, but can be activated by fibrillar collagen type 1, a physiological agonist of platelets and megakaryocytes known to induce a sustained increase in intracellular calcium levels in these cells. In contrast, treatment with SDF-1a, thrombopoietin, or VEGF remained without noticeable effect, presumably because of the short duration of the calcium transients induced by these agents. Collagen-induced NFAT activation in megakaryocytes requires dephosphorylation by calcineurin and is completely sensitive to the calcineurin inhibitor cyclosporin A. Activation of NFAT by collagen was paralleled by the induction of the expression of Down Syndrome Critical Region I (DSCR1) and Fas Ligand (FasL), two genes recently identified as NFAT targets in megakaryocytes. Collagen-induced expression of DSCR1 and FasL occurred in a calcineurin- and NFAT-dependent manner, as it was blocked by both cyclosporin A as well as the specific peptide inhibitor of NFAT, VIVIT. These experiments show that the calcineurin pathway is a target for selected physiological ligands capable of inducing sustained calcium mobilization in megakaryocytes and regulates megakaryocyte gene expression in a cyclosporin A- and NFAT-dependent manner.</jats:p

Reciprocal Regulation of DSCR1 (Down Syndrome Critical Region 1) Expression and NFAT (Nuclear Factor of Activated T Cells) Activation in Megakaryocytes.

Abstract NFAT (Nuclear Factor of Activated T cells) is a family of calcium-induced, calcineurin-dependent transcription factors, well characterized as central regulators of inducible gene expression in T lymphocytes but now known to function also in several other cell types in various adaptation and differentiation processes. Activation of NFAT by the phosphatase calcineurin is counteracted by several inhibitory kinases and can be completely blocked by the immunosuppressant Cyclosporin A. The Down syndrome critical region 1 (DSCR1; also termed CSP1, MCIP1 or RCAN1) gene belongs to the calcipressin family of endogenous calcineurin inhibitors and is expressed in several isoforms, one of which (isoform C, coded by exons 4–7) has been described to be a transcriptional target for NFAT in striated muscle, endothelial, and neural cells. The DSCR1 gene is located within the Down syndrome critical region of human chromosome 21 and is, together with 200–300 other genes, overexpressed about 1.5-fold in patients with Down syndrome (DS). Previously, dysregulation of NFAT signaling by overexpression of DSCR1 has been implicated in causing various of the pathophysiological features observed in DS patients. Children with DS also suffer from an about 500-fold increased incidence of acute megakaryocytic leukemia; the respective roles of NFAT or DSCR1 in megakaryocytes of either normal individuals or those with DS, however, has not yet been established. Here we show that DSCR1 is upregulated during megakaryocytic differentiation in a lineage-specific manner, and in mature megakaryocytes is further strongly induced by calcineurin stimulation. DSCR1 expression in megakaryocytes is regulated by NFAT, since overexpression of NFATc2 enhances, while overexpression of the specific inhibitor of NFAT activation, VIVIT, suppresses expression of the gene. We further demonstrate that DSCR1 does not only represent an NFAT target in megakaryocytes, but itself acts an inhibitor of NFAT signaling in these cells. Overexpression of DSCR1 in CMK cells as well as in primary megakaryocytes by retroviral transduction profoundly suppressed ionomycin-induced dephosphorylation and nuclear translocation of NFATc2, as well as transactivation of an NFAT-dependent promoter construct. Finally, overexpression of DSCR1 in megakaryocytes markedly downregulated both the constitutive and induced expression of Fas Ligand, a pro-apoptotic gene recently established as a NFAT target in megakaryocytes. Together, these results suggest that DSCR1 acts as an NFAT-induced NFAT inhibitor in megakaryocytes and, when overexpressed, interferes with the expression of NFAT-dependent megakaryocytic genes.</jats:p

Role of Jagged/Notch Signaling in the Cell Fate Determination of Bone Marrow Human Mesenchymal Stem Cells.

Abstract Notch, expressed on hematopoietic progenitors plays a crucial role in hematopoiesis. Mesenchymal stem cells (MSC) express both, Notch and its ligand Jagged and are known to support self renewal of hematopoietic progenitors via cell-cell contact and cytokine secretion. The Jagged/Notch signaling pathway has been implicated in the differentiation process of MSC, however it is not completely understood and current observations are contradictory. In order to analyze the effect of Notch signaling on human MSC differentiation we constructed lentiviral vectors that contained either the GFP-marker gene, hJagged1 IRES GFP, hNotch1 intracellular domain (NICD) IRES GFP or a gene fusion between dominant negative Mastermind1 (MAML1dn - inhibitor of Notch signaling) and the Cherry reporter gene. Primary hMSC that were obtained from bone marrow of 3 different donors were transduced with respective lentivirus vectors to greater than 98%. After exposure to adipogenic and osteogenic differentiation stimuli hMSC differentiation was quantified by Alizarin red or oil red staining, alkaline phosphatase (AP) activity and expression levels of adipogenic or osteogenic markers by Real-time PCR. Jagged1 transduced hMSC demonstrated enhanced calcium phosphate deposits and enhanced AP activity and expression levels in osteogenic differentiation medium, while adipogenic differentiation was strongly inhibited as quantified by oil red staining and low mRNA expression of genes upregulated during adipogenic differentiation (pprY, Fabp4). Similarly, overexpression of NICD induced strong and rapid osteogenic differentiation while inhibiting adipogenic differentiation and reducing cell viability. Moreover, NICD overexpression upregulates the expression of endogenous Jagged1 up to 5-fold. Inhibition of Notch signaling via overexpression of MAML1dn partially blocked the effect of hJagged1 and NICD in co-transduction experiments. In another approach MSC samples obtained from 20 donors with various osteogenic differentiation potential as measured by AP activity were analyzed for Notch1 and Jagged1 expression. While there was no correlation between AP activity and Notch1 levels we observed a significant positive correlation for AP activity and Jagged1 expression. In summary, our data strongly suggest that increased Jagged/Notch signaling enhances the osteogenic differentiation of hMSC while inhibiting their adipogenic fate.</jats:p