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Within the EURO-SKI trial, 132 chronic phase CML patients discontinued imatinib treatment. RNA was isolated from peripheral blood in order to analyze the expression of MDR1, ABCG2 and OCT1. ABCG2 was predictive for treatment-free remission in Cox regression analysis. High transcript levels of the ABCG2 efflux transporter (>4.5 parts per thousand) were associated with a twofold higher risk of relapse. Introduction: Tyrosine kinase inhibitors (TKIs) can safely be discontinued in chronic myeloid leukemia (CML) patients with sustained deep molecular response. ABCG2 (breast cancer resistance protein), OCT1 (organic cation transporter 1), and ABCB1 (multidrug resistance protein 1) gene products are known to play a crucial role in acquired pharmacogenetic TKI resistance. Their influence on treatment-free remission (TFR) has not yet been investigated. Materials and Methods: RNA was isolated on the last day of TKI intake from peripheral blood leukocytes of 132 chronic phase CML patients who discontinued TKI treatment within the European Stop Tyrosine Kinase Inhibitor Study trial. Plasmid standards were designed including subgenic inserts of OCT1, ABCG2, and ABCB1 together with GUSB as reference gene. For expression analyses, quantitative real-time polymerase chain reaction was used. Multiple Cox regression analysis was performed. In addition, gene expression cutoffs for patient risk stratification were investigated. Results: The TFR rate of 132 patients, 12 months after TKI discontinuation, was 54% (95% confidence interval [CI], 46%-62%). ABCG2 expression (parts per thousand) was retained as the only significant variable (P=.02; hazard ratio, 1.04; 95% CI, 1.01-1.07) in multiple Cox regression analysis. Only for the ABCG2 efflux transporter, a significant cutoff was found (P=.04). Patients with an ABCG2/GUSB transcript level >4.5 parts per thousand (n=93) showed a 12-month TFR rate of 47% (95% CI, 37%-57%), whereas patients with low ABCG2 expression (

The diagnosis of acute promyelocytic leukemia (APL) in pregnancy is an uncommon, life-threatening emergency. Choice of treatment and management of complications are challenging. We report the case of a patient with diagnosis of APL at gestational age (GA) 24 + 4. We describe the interdisciplinary management during pregnancy and delivery and provide a 2-year follow-up. Existing reports on APL in pregnancy are summarized. Single-agent induction therapy with all-trans retinoic acid (ATRA) was started and resulted in normalization of blood cell counts after 32 days. Vaginal delivery of a healthy baby occurred at GA 34 + 4. Consolidation therapy consisted of four courses of ATRA and arsenic trioxide (ATO). Less than 100 cases of APL in pregnancy are published. Misdiagnosis as HELLP syndrome with fatal outcome may occur. Combination therapies (ATRA-plus anthracyclines) were used in the majority of reports. Diagnosis and treatment of APL during pregnancy continues to be a challenge requiring interdisciplinary team work. Single-agent ATRA therapy may evolve as a safe and less-toxic treatment modality.

© 2018 The Authors., [Background]: The present prospective, multinational, noninterventional study aimed to document and describe real-world treatment regimens and disease progression in multiple myeloma (MM) patients. [Patients and Methods]: Adult patients initiating any new MM therapy from October 2010 to October 2012 were eligible. A multistage patient/site recruitment model was applied to minimize the selection bias; enrollment was stratified by country, region, and practice type. The patient medical and disease features, treatment history, and remission status were recorded at baseline, and prospective data on treatment, efficacy, and safety were collected electronically every 3 months., [Results]: A total of 2358 patients were enrolled. Of these patients, 775 and 1583 did and did not undergo stem cell transplantation (SCT) at any time during treatment, respectively. Of the patients in the SCT and non-SCT groups, 49%, 21%, 14%, and 15% and 57%, 20%, 12% and 10% were enrolled at treatment line 1, 2, 3, and ≥ 4, respectively. In the SCT and non-SCT groups, 45% and 54% of the patients had received bortezomib-based therapy without thalidomide/lenalidomide, 12% and 18% had received thalidomide/lenalidomide-based therapy without bortezomib, and 30% and 4% had received bortezomib plus thalidomide/lenalidomide-based therapy as frontline treatment, respectively. The corresponding proportions of SCT and non-SCT patients in lines 2, 3, and ≥ 4 were 45% and 37%, 30% and 37%, and 12% and 3%, 33% and 27%, 35% and 32%, and 8% and 2%, and 27% and 27%, 27% and 23%, and 6% and 4%, respectively. In the SCT and non-SCT patients, the overall response rate was 86% to 97% and 64% to 85% in line 1, 74% to 78% and 59% to 68% in line 2, 55% to 83% and 48% to 60% in line 3, and 49% to 65% and 36% and 45% in line 4, respectively, for regimens that included bortezomib and/or thalidomide/lenalidomide., [Conclusion]: The results of our prospective study have revealed great diversity in the treatment regimens used to manage MM in real-life practice. This diversity was linked to factors such as novel agent accessibility and evolving treatment recommendations. Our results provide insight into associated clinical benefits., Writing support during the development of our report was provided by Laura Mulcahy and Catherine Crookes of FireKite, an Ashfield company, a part of UDG Healthcare plc, which was funded by Millennium Pharmaceuticals, Inc, and Janssen Global Services, LLC. The EMMOS study was supported by research funding from Janssen Pharmaceutical NV and Millennium Pharmaceuticals, Inc.

Cultivation of A549 non-small-cell lung carcinoma (NSCLC) cells in the presence of staurosporine (SSP) leads to a reduction or a lack of proliferation in a concentration-dependent manner. This inhibition of proliferation is accompanied by the generation of polyploid giant cancer cells (PGCCs) that are characterized by cell flattening, increased cell size, polyploidy, and polynucleation as determined by crystal violet staining, BrdU and DiI labelling, and flow cytometry as well as video time-lapse analysis. Continuous SSP treatment of A549 cells can preserve PGCCs for at least two months in a resting state. Upon removal of SSP, A549 PGCCs restart to divide and exhibit a proliferation pattern and cellular morphology indistinguishable from cells where PGCCs originally derived from. Thus, SSP-treated A549 cells represent a simple and reliable experimental model for the reversible generation of PGCCs and their subsequent experimental analysis.

We have recently shown that staurosporine mediates the conversion of small cell lung carcinoma (SCLC) cells into a neuron-like process-bearing phenotype. Here, we have extended these studies to the staurosporine analogs K252a, lestaurtinib, PKC412, stauprimide, and UCN-01 and analyzed their influence on process extension, cell cycle distribution, and induction of polyploidy in four SCLC cell lines. In GLC-2 cells, all compounds provoked extensive process formation with the exception of PKC412 that showed no response. In H1184 cells, process formation was predominantly induced by staurosporine and, to lesser extent, in lestaurtinib-, stauprimide-, and UCN-01-treated cells. In the presence of K252a or PKC412, cells became bipolar and spindle shaped or showed pronounced cell flattening. In GLC-36 and SCLC-24H cells, only cell flattening was detectable. Process formation was reversible upon drug removal as shown for GLC-2 and H1184 cells. Fluorescence-activated cell sorting (FACS) and fluorescence in situ hybridization (FISH) analysis indicated the induction of polyploidy in all staurosporine and in two out of four stauprimide-treated SCLC cell lines. For other staurosporine analogs, polyploidy was observed only in UCN-01-treated GLC-36 cells and in K252a-treated H1184 and GLC-36 cells. The presence of staurosporine or its analogs did not alter the constitutive activation pattern of the canonical Akt/PI3K or MEK/extracellular signal-regulated kinase (ERK)1/2 signaling pathways nor could we detect an influence of stauprimide application on the expression level of the c-Myc oncogene. These data demonstrate that in SCLC cells, albeit a higher substrate specificity, staurosporine analogs can induce staurosporine-comparable effects.

Signaling by the stem cell factor receptor Kit in hematopoietic stem and progenitor cells is functionally associated with the regulation of cellular proliferation, differentiation and survival. Expression of the receptor is downregulated upon terminal differentiation in most lineages, including red blood cell terminal maturation, suggesting that omission of Kit transduced signals is a prerequisite for the differentiation process to occur. However, the molecular mechanisms by which Kit signaling preserves the undifferentiated state of progenitor cells are not yet characterized in detail. In this study, we generated a mouse model for inducible expression of a Kit receptor carrying an activating mutation and studied its effects on fetal liver hematopoiesis. We found that sustained Kit signaling leads to expansion of erythroid precursors and interferes with terminal maturation beyond the erythroblast stage. Primary KIT(D816V) erythroblasts stimulated to differentiate fail to exit cell cycle and show elevated rates of apoptosis because of insufficient induction of survival factors. They further retain expression of progenitor cell associated factors c-Myc, c-Myb and GATA-2 and inefficiently upregulate erythroid transcription factors GATA-1, Klf1 and Tal1. In KIT(D816V) erythroblasts we found constitutive activation of the mitogen-activated protein kinase (MAPK) pathway, elevated expression of the src kinase family member Lyn and impaired Akt activation in response to erythropoietin. We demonstrate that the block in differentiation is partially rescued by MAPK inhibition, and completely rescued by the multikinase inhibitor Dasatinib. These results show that a crosstalk between Kit and erythropoietin receptor signaling cascades exists and that continuous Kit signaling, partly mediated by the MAPK pathway, interferes with this crosstalk.

Scientific reports 7, 41427 (2017). doi:10.1038/srep41427, Published by Nature Publishing Group, London

Epithelial-to-mesenchymal-transition (EMT) is critical for normal embryogenesis and effective postnatal wound healing, but is also associated with cancer metastasis. SNAIL, ZEB, and TWIST families of transcription factors are key modulators of the EMT process, but their precise roles in adult hematopoietic development and homeostasis remain unclear. Here we report that genetic inactivation of Zeb2 results in increased frequency of stem and progenitor subpopulations within the bone marrow (BM) and spleen and that these changes accompany differentiation defects in multiple hematopoietic cell lineages. We found no evidence that Zeb2 is critical for hematopoietic stem cell self-renewal capacity. However, knocking out Zeb2 in the BM promoted a phenotype with several features that resemble human myeloproliferative disorders, such as BM fibrosis, splenomegaly, and extramedullary hematopoiesis. Global gene expression and intracellular signal transduction analysis revealed perturbations in specific cytokine and cytokine receptor-related signaling pathways following Zeb2 loss, especially the JAK-STAT and extracellular signal-regulated kinase pathways. Moreover, we detected some previously unknown mutations within the human Zeb2 gene (ZFX1B locus) from patients with myeloid disease. Collectively, our results demonstrate that Zeb2 controls adult hematopoietic differentiation and lineage fidelity through widespread modulation of dominant signaling pathways that may contribute to blood disorders.

Activating mutations leading to ligand-independent signaling of the stem cell factor receptor KIT are associated with several hematopoietic malignancies. One of the most common alterations is the D816V mutation. In this study, we characterized mice, which conditionally express the humanized KITD816V receptor in the adult hematopoietic system to determine the pathological consequences of unrestrained KIT signaling during blood cell development. We found that KITD816V mutant animals acquired a myeloproliferative neoplasm similar to polycythemia vera, marked by a massive increase in red blood cells and severe splenomegaly caused by excessive extramedullary erythropoiesis. Moreover, we found mobilization of stem cells from bone marrow to the spleen. Splenectomy prior to KITD816V induction prevented expansion of red blood cells, but rapidly lead to a state of aplastic anemia and bone marrow fibrosis, reminiscent of post polycythemic myeloid metaplasia, the spent phase of polycythemia vera. Our results show that the extramedullary hematopoietic niche microenvironment significantly influences disease outcome in KITD816V mutant mice, turning this model a valuable tool for studying the interplay between functionally abnormal hematopoietic cells and their microenvironment during development of polycythemia vera-like disease and myelofibrosis.

Zeb2 (Sip1/Zfhx1b) is a member of the zinc-finger E-box-binding (ZEB) family of transcriptional repressors previously demonstrated to regulate epithelial-to-mesenchymal transition (EMT) processes during embryogenesis and tumor progression. We found high Zeb2 mRNA expression levels in HSCs and hematopoietic progenitor cells (HPCs), and examined Zeb2 function in hematopoiesis through a conditional deletion approach using the Tie2-Cre and Vav-iCre recombination mouse lines. Detailed cellular analysis demonstrated that Zeb2 is dispensable for hematopoietic cluster and HSC formation in the aorta-gonadomesonephros region of the embryo, but is essential for normal HSC/HPC differentiation. In addition, Zeb2-deficient HSCs/HPCs fail to properly colonize the fetal liver and/or bone marrow and show enhanced adhesive properties associated with increased β1 integrin and Cxcr4 expression. Moreover, deletion of Zeb2 resulted in embryonic (Tie2-Cre) and perinatal (Vav-icre) lethality due to severe cephalic hemorrhaging and decreased levels of angiopoietin-1 and, subsequently, improper pericyte coverage of the cephalic vasculature. These results reveal essential roles for Zeb2 in embryonic hematopoiesis and are suggestive of a role for Zeb2 in hematopoietic-related pathologies in the adult. ispartof: Blood vol:117 issue:21 pages:5620-5630 ispartof: location:United States status: published

SummaryStem cell population size is highly regulated across species and tissue types, and alterations are associated with premature tissue failure or cancer. We assessed whether the tumor suppressor and mediator of cell contact inhibition Nf2/merlin plays a role in governing the hematopoietic stem cell pool by stem cell-autonomous or niche-determined processes. Hematopoietic stem cells in Nf2-deficient mice were increased in number and demonstrated a marked shift in location to the circulation. These changes were entirely dependent on changes in the microenvironment, with a marked increase in trabecular bone and marrow vascularity associated with increased VEGF, but without cell-autonomous alterations in stem cell characteristics. Nf2/merlin is critical for maintaining normal structure and function of the hematopoietic stem cell niche. It limits both bone and vascular components, and our model suggests that it thereby constrains stem cell number and position.

Summary Throughout development, cell fate decisions are converted into epigenetic information that determines cellular identity. Covalent histone modifications are heritable epigenetic marks and are hypothesized to play a central role in this process. In this report, we assess the concordance of histone H3 lysine 4 dimethylation (H3K4me2) and trimethylation (H3K4me3) on a genome-wide scale in erythroid development by analyzing pluripotent, multipotent, and unipotent cell types. Although H3K4me2 and H3K4me3 are concordant at most genes, multipotential hematopoietic cells have a subset of genes that are differentially methylated (H3K4me2+/me3−). These genes are transcriptionally silent, highly enriched in lineage-specific hematopoietic genes, and uniquely susceptible to differentiation-induced H3K4 demethylation. Self-renewing embryonic stem cells, which restrict H3K4 methylation to genes that contain CpG islands (CGIs), lack H3K4me2+/me3− genes. These data reveal distinct epigenetic regulation of CGI and non-CGI genes during development and indicate an interactive relationship between DNA sequence and differential H3K4 methylation in lineage-specific differentiation.

SummaryWingless (Wnt) is a potent morphogen demonstrated in multiple cell lineages to promote the expansion and maintenance of stem and progenitor cell populations. Wnt effects are highly context dependent, and varying effects of Wnt signaling on hematopoietic stem cells (HSCs) have been reported. We explored the impact of Wnt signaling in vivo, specifically in the context of the HSC niche by using an osteoblast-specific promoter driving expression of the paninhibitor of canonical Wnt signaling, Dickkopf1 (Dkk1). Here we report that Wnt signaling was markedly inhibited in HSCs and, unexpectedly given prior reports, reduction in HSC Wnt signaling resulted in reduced p21Cip1 expression, increased cell cycling, and a progressive decline in regenerative function after transplantation. This effect was microenvironment determined, but irreversible if the cells were transferred to a normal host. Wnt pathway activation in the niche is required to limit HSC proliferation and preserve the reconstituting function of endogenous hematopoietic stem cells.

Stem-cell ageing is thought to contribute to altered tissue maintenance and repair. Older humans experience increased bone marrow failure and poorer haematologic tolerance of cytotoxic injury. Haematopoietic stem cells (HSCs) in older mice have decreased per-cell repopulating activity, self-renewal and homing abilities, myeloid skewing of differentiation, and increased apoptosis with stress. Here we report that the cyclin-dependent kinase inhibitor p16INK4a, the level of which was previously noted to increase in other cell types with age, accumulates and modulates specific age-associated HSC functions. Notably, in the absence of p16INK4a, HSC repopulating defects and apoptosis were mitigated, improving the stress tolerance of cells and the survival of animals in successive transplants, a stem-cell-autonomous tissue regeneration model. Inhibition of p16INK4a may ameliorate the physiological impact of ageing on stem cells and thereby improve injury repair in aged tissue.

Specialized blood cells are generated through the entire life of an organism by differentiation of a small number of hematopoietic stem cells (HSC). There are strictly regulated mechanisms assuring a constant and controlled production of mature blood cells. Although such mechanisms are not completely understood, some factors regulating cell cycle and differentiation have been identified. We have previously shown that Caspase-3 is an important regulator of HSC homeostasis and cytokine responsiveness. p21cip1/waf1 is a known cell cycle regulator, however its role in stem cell homeostasis seems to be limited. Several reports indicate interactions between p21cip1/waf1 and Caspase-3 in a cell type dependent manner. Here we studied the impact of simultaneous depletion of both factors on HSC homeostasis. Depletion of both Caspase-3 and p21cip1/waf1 resulted in an even more pronounced increase in the frequency of hematopoietic stem and progenitor cells. In addition, simultaneous deletion of both genes revealed a further increase of cell proliferation compared to single knock-outs and WT control mice, while apoptosis or self-renewal ability were not affected in any of the genotypes. Upon transplantation, p21cip1/waf1-/- bone marrow did not reveal significant alterations in engraftment of lethally irradiated mice, while Caspase-3 deficient HSPC displayed a significant reduction of blood cell production. However, when both p21cip1/waf1 and Caspase-3 were eliminated this differentiation defect caused by Caspase-3 deficiency was abrogated.

Small cell lung carcinomas (SCLCs) represent highly aggressive tumors with an overall five-year survival rate in the range of 5 to 10%. Here, we show that four out of five SCLC cell lines reversibly develop a neuron-like phenotype on extracellular matrix constituents such as fibronectin, laminin or thrombospondin upon staurosporine treatment in an RGD/integrin-mediated manner. Neurite-like processes extend rapidly with an average speed of 10 µm per hour. Depending on the cell line, staurosporine treatment affects either cell cycle arrest in G2/M phase or induction of polyploidy. Neuron-like conversion, although not accompanied by alterations in the expression pattern of a panel of neuroendocrine genes, leads to changes in protein expression as determined by two-dimensional gel electrophoresis. It is likely that SCLC cells already harbour the complete molecular repertoire to convert into a neuron-like phenotype. More extensive studies are needed to evaluate whether the conversion potential of SCLC cells is suitable for therapeutic interventions.

Ovarian cancers are heterogeneous and contain stemlike cells that are able to self-renew and are responsible for sustained tumor growth. Metastasis in the peritoneal cavity occurs more frequently in ovarian cancer than in other malignancies, but the underlying mechanism remains largely unknown. We have identified that ovarian cancer stemlike cells (CSCs), which were defined as side population (SP) cells, were present in patients’ ascitic fluid and mesenchymally transformed cell lines, ES-2 and HO-8910PM. SP cells, which were sorted from both cell lines and implanted into immunocompromised mice, were localized to the xenografted tumor boundary. In addition, SP cells exhibited an epithelial phenotype and showed a distinct gene expression profile with reduced expression of cell adhesion molecules (CAMs), indicating that SP cells exert an important role in ovarian cancer progression on the basis of their delicate interaction with the surrounding microenvironment and anatomical localization in tumors. In contrast, non-SP cells exhibited a more mesenchymal phenotype and showed more increased invasive potential than SP cells. This heterogeneity was observed as an endogenous transformation via the epithelial-mesenchymal transition (EMT) process. Inhibition of the EMT process by Snail1 silencing reduced the SP cell frequency, and affected their invasive capacity and engraftment. These findings illustrate the interplay between epithelial ovarian CSCs and the EMT, and exert a link to explain tumor heterogeneity and its necessity for ovarian cancer maintenance, metastasis and progression.

The functional decline in hematopoietic function seen during aging involves a progressive reduction in the immune response and an increased incidence of myeloid malignancy, and has been linked to aging of hematopoietic stem cells (HSCs). The molecular mechanisms underlying HSC aging remain unclear. Here we demonstrate that elevated activity of the small RhoGTPase Cdc42 in aged HSCs is causally linked to HSC aging and correlates with a loss of polarity in aged HSCs. Pharmacological inhibition of Cdc42 activity functionally rejuvenates aged HSCs, increases the percentage of polarized cells in an aged HSC population, and restores the level and spatial distribution of histone H4 lysine 16 acetylation to a similar status as seen in young HSCs. Our data therefore suggest a mechanistic role for Cdc42 activity in HSC biology and epigenetic regulation, and identify Cdc42 activity as a pharmacological target for ameliorating stem cell aging.

To the editor: Recently, inhibition of lysine-specific demethylase 1 (LSD1) has gained attention as a potential novel treatment in acute myeloid leukemia (AML).[1][1][⇓][2]-[3][3] However, expression in other hematologic neoplasms has not been examined. LSD1 is a central epigenetic regulator of

SummaryLimited responsiveness to inflammatory cytokines is a feature of adult hematopoietic stem cells and contributes to the relative quiescence and durability of the stem cell population in vivo. Here we report that the executioner Caspase, Caspase-3, unexpectedly participates in that process. Mice deficient in Caspase-3 had increased numbers of immunophenotypic long-term repopulating stem cells in association with multiple functional changes, most prominently cell cycling. Though these changes were cell autonomous, they reflected altered activation by exogenous signals. Caspase-3−/− cells exhibited cell type-specific changes in phosphorylated members of the Ras-Raf-MEK-ERK pathway in response to specific cytokines, while notably, members of other pathways, such as pSTAT3, pSTAT5, pAKT, pp38 MAPK, pSmad2, and pSmad3, were unaffected. Caspase-3 contributes to stem cell quiescence, dampening specific signaling events and thereby cell responsiveness to microenvironmental stimuli.

The molecular mechanisms that regulate human blood vessel formation during early development are largely unknown. Here we used human ESCs (hESCs) as an in vitro model to explore early human vasculogenesis. We demonstrated that stromal cell-derived factor-1 (SDF-1) and CXCR4 were expressed concurrently with hESC-derived embryonic endothelial differentiation. Human ESC-derived embryonic endothelial cells underwent dose-dependent chemotaxis to SDF-1, which enhanced vascular network formation in Matrigel. Blocking of CXCR4 signaling abolished capillary-like structures induced by SDF-1. Inhibition of the SDF-1/CXCR4 signaling pathway by AMD3100, a CXCR4 antagonist, disrupted the endothelial sprouting outgrowth from human embryoid bodies, suggesting that the SDF-1/CXCR4 axis plays a critical role in regulating initial vessel formation, and may function as a morphogen during human embryonic vascular development.

Bone-marrow-derived cells can contribute nuclei to skeletal muscle fibers. However, serial sectioning of muscle in mdx mice implanted with GFP-labeled bone marrow reveals that only 20% of the donor nuclei chronically incorporated in muscle fibers show dystrophin (or GFP) expression, which is still higher than the expected frequency of “revertant” fibers, but there is no overall increase above controls over time. Obviously, the vast majority of incorporated nuclei either never or only temporarily turn on myogenic genes; also, incorporated nuclei eventually loose the activation of the β-actin::GFP transgene. Consequently, we attempted to enhance the expression of dystrophin. In vivo application of the chromatin-modifying agents 5-azadeoxycytidine and phenylbutyrate as well as local damage by cardiotoxin injections caused a small increase in dystrophin-positive fibers without abolishing the appearance of “silent” nuclei. The results thus confirm that endogenous repair processes and epigenetic modifications on a small-scale lead to dystrophin expression from donor nuclei. Both effects, however, remain below functionally significant levels.

The zinc finger transcription factor GATA-2 plays a fundamental role in generating hematopoietic stem-cells in mammalian development. Less well defined is whether GATA-2 participates in adult stem-cell regulation, an issue we addressed using GATA-2 heterozygote mice that express reduced levels of GATA-2 in hematopoietic cells. While GATA-2+/- mice demonstrated decreases in some colony-forming progenitors, the most prominent changes were observed within the stem-cell compartment. Heterozygote bone marrow had a lower abundance of Lin(-)c-kit(+)Sca-1(+)CD34- cells and performed poorly in competitive transplantation and quantitative week-5 cobblestone area-forming cell (CAFC) assays. Furthermore, a stem-cell-enriched population from GATA1+/- marrow was more quiescent and exhibited a greater frequency of apoptotic cells associated with decreased expression of the anti-apoptotic gene Bcl-xL. Yet the self-renewal potential of the +/- stem-cell compartment, as judged by serial transplantations, was unchanged. These data indicate compromised primitive cell proliferation and survival in the setting of a lower GATA-2 gene dose without a change in the differentiation or self-renewal capacity of the stem-cells that remain. Thus, GATA-2 dose regulates adult stem-cell homeostasis by affecting select aspects of stem cell function.

Laser-assisted microdissection (LAM) allows isolation of specific cell populations for molecular studies. The combination of LAM and of real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) enables generation of quantitative cell-specific gene expression data. Histochemical stains used to identify cells desired for LAM should provide acceptable morphology and not interfere with RNA or with subsequent molecular analysis techniques. To determine a reliable stain for analysing RNA, using the housekeeping gene, RPL13A, we performed quantitative gene expression analysis of laser microdissected cells from prostatic frozen tissues. The frozen sections were histochemically stained with hematoxylin, methyl green, toluidine blue O and May-Grunwald. After laser microdissection real-time quantitative RT-PCR was performed. Methyl green yielded more RT-PCR product than did the other dyes. The lowest yield of amplification was obtained after May-Grunwald staining. Therefore we recommend methyl green for general use in gene expression analysis, especially when handling small amounts of RNA.

The ability of stem cells to continuously supply vast numbers of cells is magnificent, but it can be devastating if it runs amok, as in some tumours. So what makes a normal stem cell turn bad, and can it be redeemed?

The regulation of cell cycle activity, differentiation and self-renewal of stem cells are dependent on accurate processing of intrinsic and extrinsic signals. Traditionally, signaling pathway activation has been detected by immunobloting using phospho-specific antibodies. However, detection of signal transduction in rare cells within heterogeneous populations, such as hematopoietic stem and progenitor cells (HSC) has been difficult to achieve. In a recently reported approach to visualize signaling in selected single c-Kit+ Sca-1+ Lin− (KSL) bone marrow cells, cells were sorted onto glas slides by flow cytometry and signaling was detected by confocal fluorescence microscopy, a very time consuming method that thus restricts the number of cells that can be analysed simultaneously. Moreover it permits only qualitative, but not quantitative signaling evaluation (Yamazaki et al., EMBO J. 2006). Here, we report a new protocol allowing quantitative measurement of signaling activity in large numbers of defined murine and human hematopoietic cells. The cells are stained with established surface markers and then phospho-specific antibodies are used to detect the levels of active intracellular signaling molecules. Signals are quantified by flow cytometry fluorescence measurement. Importantly, the protocol developed in our laboratory enables preservation of surface marker staining identifying the cells of interest inspite the fixation and permeabilization procedures necessary for intracellular signaling detection. This applies also for antigens previously reported to be particularly vulnerable to standard fixation and permeabilization approaches (e.g. the murine stem cell markers c-Kit and Sca1). Thus, our protocol provides an easy and reliable method for quantifying the activation degree of several intracellular signaling pathways on single cell level in defined hematopoietic (stem) cells within the heterogeous bone marrow (BM) compartment. Using cytokines known to exert a biological effect on HSCs, we have examined the susceptibility of KSL murine BM cells and human BM CD34+ cells to cytokine-induced signaling. We have performed extensive dosage titration and time course analysis for multiple cytokines (SCF, TPO, Flt-3, IL-3, IL-6, Ang-1, SDF-1α, TGF-β, and BMP-4) and signaling pathways (ERK, Akt, p38MAPK, Jak-Stat, TGF-β/BMP-Smad) in murine KSL BM cells. The activation intensity and the duration of signal activity as measured by the expression of corresponding phosphorylated proteins were cytokine specific. The obtained results can be used as a platform to explore signaling alterations in distinct compartments of the hematopoietic system, and may provide mechanistical insights for observed bone marrow defects (e.g impaired ERK signaling pathway has been detected as a possible cause of hematopoietic defects in Caspase-3 mutant murine HSCs, Janzen et al, Cell Stem Cell 2008). Furthermore, we could show that the technique is also applicable to human BM cells and that the human hematopoietic stem cell marker CD34 is also preserved by our fixation and permeabilization protocol. Preliminary results suggest that cytokines induce similar signaling activation in human CD34+BM cells collected from healthy donors. As observed in mouse KSL BM cells, stimulation of human CD34+cells with human stem cell factor (hSCF) induced activation of the ERK but not the Akt pathway. Ongoing experiments analyse the stimulatory effects of other cytokines such as thrombopoietin (TPO) and fms-related tyrosine kinase 3 (Flt-3) and their corresponding pathways. Moreover, comparative studies are underway analyzing cross-reactivity between mouse and human cytokines, aiming to provide insights into cytokine-induced biases in commonly used xenotransplantation models.

P2 receptors are functionally diverse cell surface receptors that bind nucleotides adenine (ADP, ATP) and uridine (UDP, UTP). P2Y receptors are metabotropic G protein-coupled receptors that mediate vascular and immune responses to injury. We previously reported the differential expression cloning of the UTP-glycoconjugate receptor, P2Y14 from quiescent primary human bone marrow (BM) hematopoietic stem cells (HSCs). Using P2Y14−/− mice, we now report that the presence of P2Y14 protects HSCs from apoptosis in the face of cytotoxic chemical injury. P2Y14 null mice develop normally and showed no significant differences in peripheral blood cell counts, BM cellularity or the absolute number/proportion of lin−cKit+Sca1+ (LKS+) and CD34−/lowLKS+ (34-LKS+) cells compared to their wildtype littermates. Similarly, cell cycle status, in vitro colony-forming cell (CFC) capacity, in vivo homing and in vivo colony-forming unit-spleen (CFU-S) function were unaffected. Since the role of nucleotide receptors in injury response have been reported, we examined BM HSC content following IP injection of 200mg/kg cyclophosphamide (CTX) and found that the relative protection of LKS+ and 34-LKS+ cells from CTX-induced apoptosis was lost in P2Y14 null animals (WT LKS+: 12.7% AnnexinV+7AAD-, KO LKS+ 36.8% AnnexinV+7AAD−, n=5 each, p=0.004; WT 34-LKS+: 13.2% AnnexinV+7AAD−, KO LKS+ 38.7% AnnexinV+7AAD−, n=5 each, p=0.007). In addition, the kinetics of long-term myeloid recovery after a single injection of 5-Fluorouracil (5FU) IP 150mg/kg was significantly more accentuated in P2Y14 null animals, with significantly greater peripheral blood Gr-1+ cell count at days 21–56 post-injection (n=10 each, p=0.009). When sorted BM LKS+ cells were exposed in vitro to UDP-glucose, a putative P2Y14 ligand known to be released from cytoplasm during cellular injury, BrDU incorporation was significantly reduced (n=3 each, p

The processes of cell cycle control, differentiation and apoptosis are closely intertwined in controlling cell fate during development and in adult homeostasis. Molecular pathways connecting these events in stem cells are poorly defined and we were particularly interested in the cysteine-aspartic acid protease, Caspase-3, an ‘executioner’ caspase also implicated in the regulation of the cyclin dependent kinase inhibitors, p21Cip1 and p27Kip1. These latter proteins are known to participate in primitive hematopoietic cell cycling and self-renewal. We demonstrated high levels of Caspase-3 mRNA and protein in immunophenotypically defined mouse hematopoietic stem cells (HSC). Using mice engineered to be deficient in Caspase-3, we observed a consistent reduction of lymphocytes in peripheral blood counts and a slight reduction in bone marrow cellularity. Notably, knockout animals had an increase in the stem cell enriched Lin−cKit+Sca1+Flk2low (LKSFlk2lo) cell fraction. The apoptotic rates of LKS cells under homeostatic conditions as assayed by the Annexin V assay were not significantly different from controls. However, in-vitro analysis of sorted LKS cells revealed a reduced sensitivity to apoptotic cell death in absence of Caspase-3 under conditions of stress (cytokine withdrawal or gamma irradiation). Primitive hematopoietic cells displayed a higher proliferation rate as demonstrated by BrdU incorporation and a significant reduction in the percentage of cells in the quiescent stage of the cell cycle assessed by the Pyronin-Y/Hoechst staining. Upon transplantation, Caspase-3−/− stem cells demonstrated marked differentiation abnormalities with significantly reduced ability to differentiate into multiple hematopoietic lineages while maintaining an increased number of primitive cells. In a competitive bone marrow transplant using congenic mouse stains Capase-3 deficient HSC out-competed WT cells at the stem cell level, while giving rise to comparable number of peripheral blood cells as the WT controls. Transplant of WT BM cells into Caspase-3 deficient mice revealed no difference in reconstitution ability, suggesting negligible effect of the Caspase-3−/− niche microenvironment to stem cell function. These data indicate that Caspase-3 is involved in the regulation of differentiation and proliferation of HSC as a cell autonomous process. The molecular bases for these effects remain to be determined, but the multi-faceted nature of the changes seen suggest that Caspase-3 is central to multiple regulatory pathways in the stem cell compartment.

The processes of cell cycle control, differentiation and apoptosis are closely intertwined in controlling cell fate during development and in adult homeostasis. Much emphasis has been placed on differentiation and proliferation in hematopoiesis, but little is known about control of the stem cell pool by mediators of apoptosis. We are particularly interested in the cysteine-aspartic acid protease, Caspase-3, an ‘executioner’ caspase also implicated in the regulation of the cyclin dependent kinase inhibitor, p21Cip1. p21 is known to regulate hematopoietic stem cell (HSC) cycling and we demonstrated high levels of Caspase-3 mRNA and protein in immunophenotypically defined mouse HSC. Using mice engineered to be deficient in Caspase-3, we observed no difference from wild-type in blood counts. However, knock-out animals had reduced bone marrow cellularity and an increase in the stem cell enriched lin-kit+Sca-1+ CD34 low (LKS-CD34lo) cell fraction. The apoptotic rates of LKS cells under homeostatic conditions were minimally different from controls. However, under conditions of stress (gamma irradiation, heat shock or cytokine withdrawal), Caspase-3 deficient LKS cells demonstrated reduced sensitivity to apoptotic cell death as measured by TUNEL or Annexin-V assay. Primitive hematopoietic cells from these animals in vivo also had reduced BrdU incorporation reflecting decreased proliferation and, upon transplantation, demonstrated marked differentiation abnormalities. Caspase-3−/− marrow cells had significantly reduced ability to differentiate into lymphoid and myeloid lineages 12 weeks after transplantation. Similarly, WT bone marrow cells treated prior to transplantation with a selective Caspase-3 inhibitor, z-DEVD.fmk, displayed a significant disadvantage in peripheral blood reconstitution, compared with a mock control. These data indicate that Caspase-3 is involved in the regulation of apoptosis, differentiation and proliferation of HSC. The molecular bases for these effects remain to be determined, but the multi-faceted nature of the changes seen suggest that Caspase-3 is central to multiple regulatory pathways in the stem cell compartment.