Next-generation sequencing in two cases of de novo acute basophilic leukaemia.

Acute basophilic leukaemia (ABL) is a rare subtype of acute myeloid leukaemia (AML); therefore, few data are available about its biology. Herein, we analysed two ABL patients using flow cytometry and next-generation sequencing (NGS). Two cell populations were detected by flow cytometry in both patients. In Case no. 1, blasts (CD34+ , CD203c- , CD117+ , CD123dim+ ) and basophils (CD34- , CD203c+ , CD117± , CD123+ ) were identified, both of which were found by NGS to harbour the 17p deletion and have loss of heterozygosity of TP53. In Case no. 2, blasts (CD33+ , CD34+ , CD123- ) and basophils (CD33+ , CD34+ , CD123+ ) were identified. NGS detected NPM1 mutations in either blasts or basophils, and TET2 in both. These data suggest an overlap of the mutational landscape of ABL and AML, including TP53 and TET2 mutations. Moreover, additional mutations or epigenetic factors may contribute for the differentiation into basophilic blasts.

Characterization of human FcεRIα chain expression and gene copy number in humanized rat basophilic leukaemia (RBL) reporter cell lines.

Several laboratories have created rat basophil leukemia (RBL) cell lines stably transfected with the human high affinity IgE receptor (FcεRIH). More recently, humanized RBL cell lines saw the introduction of reporter genes such as luciferase (RS-ATL8) and DsRed (RBL NFAT-DsRed). These reporters are more sensitive than their parental non-reporter humanized RBL cell lines. However, no studies so far have addressed the levels of FcεRIH surface expression on humanized RBL cell lines. This is a critical parameter, as it determines the ability of these cells to be efficiently sensitized with human IgE, hence it should affect the sensitivity of the cell assay-a critical parameter for any diagnostic application. Our purpose was to assess and compare the levels of expression of the transfected FcεRIH chain in humanized RBL cell lines. We compared surface levels of FcεRIαH by flow cytometry, using a fluorescently labelled monoclonal antibody (CRA-1/AER-37) and determined receptor numbers using calibration microspheres. FcεRIαH copy numbers were assessed by qPCR, and the sequence verified. Transfection with FcεRIγH cDNA was assessed for its ability to increase FcεRIαH expression in the NFAT-DsRed reporter. While both SX-38 and RS-ATL8 expressed about 500.000 receptors/cell, RBL 703-21 and NFAT-DsRed had approximately 10- to 30-fold lower FcεRIαH expression, respectively. This was neither related to FcεRIH gene copy numbers, nor to differences in steady state mRNA levels, as determined by qPCR and RT-qPCR, respectively. Instead, FcεRIαH surface expression appeared to correlate with the co-expression of FcεRIγH. Stable transfection of NFAT-DsRed cells with pBJ1 neo-huFcεRI gamma, which constitutively expresses FcεRIγH, increased FcεRIαH chain expression levels. Levels of FcεRIαH surface expression vary greatly between humanized RBL reporter cell lines. This difference will affect the sensitivity of the reporter system when used for diagnostic purposes.

Construction and identification of the recombinant hFcεRIα/RBL-2H3 cells.

IgE/FcεRI signal pathway plays a crucial role in triggering allergic reactions, and there is no cross-recognition between IgE and FcεRI in human and rats. In order to obtain the hFcεRIα/ RBL-2H3 cell line, total RNA was extracted from U937 cells, and the human FcεRIα gene was obtained by RT-PCR technology. Then the amplified product was digested and inserted into the pIRES2-EGFP vector. After the plasmid was transfected into the RBL-2H3 cells using lipofectamine, and the RBL-2H3 cell lines of stable expression were screened by G418. The transfection efficiency reached 60.45% with optimizing transfection parameters. The last the expression of hFcεRIα was detected by RT-PCR, western blotting and fluorescent microscopy. The present results demonstrated that the pIRES2-EGFP-hFcεRIα vector was constructed and a stable cell line of hFcεRIα/ RBL-2H3 cells was established successfully. This cell line is promising tools for further research on the pathogenesis and drug development of allergic diseases.

Immobilized fibrinogen activates human platelets through glycoprotein VI.

Glycoprotein VI, a major platelet activation receptor for collagen and fibrin, is considered a particularly promising, safe antithrombotic target. In this study, we show that human glycoprotein VI signals upon platelet adhesion to fibrinogen. Full spreading of human platelets on fibrinogen was abolished in platelets from glycoprotein VI- deficient patients suggesting that fibrinogen activates platelets through glycoprotein VI. While mouse platelets failed to spread on fibrinogen, human-glycoprotein VI-transgenic mouse platelets showed full spreading and increased Ca2+ signaling through the tyrosine kinase Syk. Direct binding of fibrinogen to human glycoprotein VI was shown by surface plasmon resonance and by increased adhesion to fibrinogen of human glycoprotein VI-transfected RBL-2H3 cells relative to mock-transfected cells. Blockade of human glycoprotein VI with the Fab of the monoclonal antibody 9O12 impaired platelet aggregation on preformed platelet aggregates in flowing blood independent of collagen and fibrin exposure. These results demonstrate that human glycoprotein VI binds to immobilized fibrinogen and show that this contributes to platelet spreading and platelet aggregation under flow.

Development of an in vitro model system for studying the interaction of Equus caballus IgE with its high-affinity receptor FcεRI.

The interaction of IgE with its high-affinity Fc receptor (FcεRI) followed by an antigenic challenge is the principal pathway in IgE mediated allergic reactions. As a consequence of the high affinity binding between IgE and FcεRI, along with the continuous production of IgE by B cells, allergies usually persist throughout life, with currently no permanent cure available. Horses, especially race horses, which are commonly inbred, are a species of mammals that are very prone to the development of hypersensitivity responses, which can seriously affect their performance. Physiological responses to allergic sensitization in horses mirror that observed in humans and dogs. In this paper we describe the development of an in situ assay system for the quantitative assessment of the release of mediators of the allergic response pertaining to the equine system. To this end, the gene encoding equine FcεRIα was transfected into and expressed onto the surface of parental Rat Basophil Leukemia (RBL-2H3.1) cells. The gene product of the transfected equine α-chain formed a functional receptor complex with the endogenous rat ß- and γ-chains. The resultant assay system facilitated an assessment of the quantity of mediator secreted from equine FcεRIα transfected RBL-2H3.1 cells following sensitization with equine IgE and antigenic challenge using ß-hexosaminidase release as a readout. Mediator release peaked at 36.68% ± 4.88% at 100 ng ml(-1) of antigen. This assay was modified from previous assays used to study human and canine allergic responses. We have also shown that this type of assay system has multiple applications for the development of diagnostic tools and the safety assessment of potential therapeutic intervention strategies in allergic disease.

Mitochondrial calcium uniporter MCU supports cytoplasmic Ca2+ oscillations, store-operated Ca2+ entry and Ca2+-dependent gene expression in response to receptor stimulation.

Ca2+ flux into mitochondria is an important regulator of cytoplasmic Ca2+ signals, energy production and cell death pathways. Ca2+ uptake can occur through the recently discovered mitochondrial uniporter channel (MCU) but whether the MCU is involved in shaping Ca2+ signals and downstream responses to physiological levels of receptor stimulation is unknown. Here, we show that modest stimulation of leukotriene receptors with the pro-inflammatory signal LTC4 evokes a series of cytoplasmic Ca2+ oscillations that are rapidly and faithfully propagated into mitochondrial matrix. Knockdown of MCU or mitochondrial depolarisation, to reduce the driving force for Ca2+ entry into the matrix, prevents the mitochondrial Ca2+ rise and accelerates run down of the oscillations. The loss of cytoplasmic Ca2+ oscillations appeared to be a consequence of enhanced Ca2+-dependent inactivation of InsP3 receptors, which arose from the loss of mitochondrial Ca2+ buffering. Ca2+ dependent gene expression in response to leukotriene receptor activation was suppressed following knockdown of the MCU. In addition to buffering Ca2+ release, mitochondria also sequestrated Ca2+ entry through store-operated Ca2+ channels and this too was prevented following loss of MCU. MCU is therefore an important regulator of physiological pulses of cytoplasmic Ca2+.

Eicosapentaenoic acid and docosahexaenoic acid suppress Th2 cytokine expression in RBL-2H3 basophilic leukemia cells.

It is known that the intake of omega-3 fatty acids, such as eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), is beneficial for preventing and/or treating allergic diseases. The pathogenesis of allergic diseases is associated with overactivation of Th2-skewed immunity. Basophils generate large amounts of Th2 cytokines such as interleukin (IL)-4 and IL-13, which are critically involved in allergic inflammation. We investigated how EPA and DHA affect Th2 cytokine expression in phorbol 12-myristate 13-acetate- and ionomycin (PI)-activated RBL-2H3 basophilic leukemia cells. EPA and DHA induced a dramatic decrease in the production of IL-4 and IL-13 and their transcription in a dose-dependent manner. Luciferase assays of RBL-2H3 cells stably expressing Il4 and Il13 promoter-reporter plasmids demonstrated a significant suppression of PI-induced promoter activation. Analysis of certain transcription factors revealed that nuclear expression of c-Fos and the mRNA expression were suppressed by EPA and DHA. Furthermore, they significantly inhibited the nuclear expression and translocation of nuclear factor of activated T cells (NF-AT)1. In contrast, the expression levels of nuclear factor kappa-B (NF-κB), GATA-binding proteins (GATAs), and CCAAT/enhancer binding protein alpha (C/EBPα) were not significantly affected by EPA and DHA. Phosphorylation of extracellular signal-related kinase was inhibited by EPA and DHA, and phosphorylation of p38 mitogen-activated protein kinase was decreased by DHA, but not by EPA. Taken together, our data suggest that EPA and DHA may suppress Th2-skewed allergic immune responses by inhibiting the expression of basophilic IL-4 and IL-13.

Down-regulation of S100A9 and S100A10 in manganese-resistant RBL-2H3 cells.

Exposure to excess amounts of manganese causes toxic effects, including neurological symptoms such as Parkinsonism. However, endogenous factors involved in the protection against manganese toxicity remain unclear. Previously, we showed that rat basophilic leukemia RBL-2H3 cells are highly sensitive to MnCl2 compared with other rat cell lines. To identify the genes involved in resistance to manganese toxicity, two lines of Mn-resistant cells showing resistance to 300 µM MnCl2 (RBL-Mnr300) and 1200 µM MnCl2 (RBL-Mnr1200) were developed from RBL-2H3 cells by a stepwise increase in MnCl2 concentration in the medium. Microarray analyses were carried out to compare gene expression between parental RBL-2H3 cells and RBL-Mnr300 or RBL-Mnr1200 cells. Five genes exhibited more than 10-fold up-regulation in both RBL-Mnr300 and RBL-Mnr1200 cells, and 24 genes exhibited less than 0.1-fold down-regulation in both Mn-resistant cell lines. The S100a9 and S100a10 genes, encoding the calcium-binding S100A9 and S100A10 proteins, respectively, were found among the three most down-regulated genes in both Mn-resistant cell lines. The marked decreases in mRNA levels of S100a9 and S100a10 were confirmed by real-time RT-PCR analyses. Further characterization and comparison of these Mn-resistant cells may enable the identification of novel genes that play important roles in the modification of manganese toxicity.

Fc receptor-γ subunits with both polar or non-polar amino acids at position of T22 are capable of restoring surface expression of the high-affinity IgE receptor and degranulation in γ subunit-deficient rat basophilic leukemia cells.

The high-affinity IgE receptor (FcɛRI) is formed by the IgE-binding α subunit, ß subunit and γ subunits homodimer. All three subunits are required for proper expression of the receptor on the plasma membrane of mast cells and basophils. However, the exact molecular mechanism of inter-subunit interactions required for correct expression and function of the FcɛRI complex remains to be identified. A recent study suggested that polar aspartate at position 194 within the transmembrane domain of the α subunit could interact by hydrogen bonding with polar threonine at position 22 in the transmembrane domains of the γ subunits. To verify this, we used previously isolated rat basophilic leukemia (RBL)-2H3 variant cells deficient in the expression of the FcɛRI-γ subunit (FcR-γ), and transfected them with DNA vectors coding for FcR-γ of the wild-type or mutants in which T22 was substituted for nonpolar alanine (T22A mutant) or polar serine (T22S mutant). Analysis of the transfectants showed that both T22A and T22S mutants were capable to restore surface expression of the FcɛRI similar to wild-type FcR-γ. Furthermore, cells transfected with wild-type, T22A or T22S FcR-γ showed comparably enhanced FcɛRI-mediated degranulation. Our data indicate that substitution of FcR-γ T22 with non-polar amino acid does not interfere with surface expression of the FcɛRI and its signaling capacity.

The chemokine receptors CXCR1 and CXCR2 couple to distinct G protein-coupled receptor kinases to mediate and regulate leukocyte functions.

The chemokine receptors, CXCR1 and CXCR2, couple to Gαi to induce leukocyte recruitment and activation at sites of inflammation. Upon activation by CXCL8, these receptors become phosphorylated, desensitized, and internalized. In this study, we investigated the role of different G protein-coupled receptor kinases (GRKs) in CXCR1- and CXCR2-mediated cellular functions. To that end, short hairpin RNA was used to inhibit GRK2, 3, 5, and 6 in RBL-2H3 cells stably expressing CXCR1 or CXCR2, and CXCL8-mediated receptor activation and regulation were assessed. Inhibition of GRK2 and GRK6 increased CXCR1 and CXCR2 resistance to phosphorylation, desensitization, and internalization, respectively, and enhanced CXCL8-induced phosphoinositide hydrolysis and exocytosis in vitro. GRK2 depletion diminished CXCR1-induced ERK1/2 phosphorylation but had no effect on CXCR2-induced ERK1/2 phosphorylation. GRK6 depletion had no significant effect on CXCR1 function. However, peritoneal neutrophils from mice deficient in GRK6 (GRK6(-/-)) displayed an increase in CXCR2-mediated G protein activation but in vitro exhibited a decrease in chemotaxis, receptor desensitization, and internalization relative to wild-type (GRK6(+/+)) cells. In contrast, neutrophil recruitment in vivo in GRK6(-/-) mice was increased in response to delivery of CXCL1 through the air pouch model. In a wound-closure assay, GRK6(-/-) mice showed enhanced myeloperoxidase activity, suggesting enhanced neutrophil recruitment, and faster wound closure compared with GRK6(+/+) animals. Taken together, the results indicate that CXCR1 and CXCR2 couple to distinct GRK isoforms to mediate and regulate inflammatory responses. CXCR1 predominantly couples to GRK2, whereas CXCR2 interacts with GRK6 to negatively regulate receptor sensitization and trafficking, thus affecting cell signaling and angiogenesis.

Anti-inflammatory effects of low-molecular weight chitosan oligosaccharides in IgE-antigen complex-stimulated RBL-2H3 cells and asthma model mice.

The anti-inflammatory effects of low-molecular weight chitosan oligosaccharides (LM-COS) prepared from high-molecular weight chitosan by enzymatic digestion were investigated against allergic reaction and allergic asthma in vivo and in vitro. Allergic asthma is an inflammatory disease of the airways associated with enhanced degranulation and cytokine generation. The LM-COS (<1 kDa), consisting of glucosamine (GlcN)(n), n=3-5, were capable of inhibiting both antigen-stimulated degranulation and cytokine generation in rat basophilic leukemia RBL-2H3 cells. The protective effect of LM-COS against ovalbumin (OVA)-induced lung inflammation in asthma model mice was also examined. Oral administration of LM-COS (16 mg/kg body weight/day) resulted in a significant reduction in both mRNA and protein levels of interleukin (IL)-4, IL-5, IL-13, tumor necrosis factor (TNF)-α in the lung tissue and bronchoalveolar lavage fluid (BALF); The protein levels of IL-4, IL-13 and TNF-α in BALF were decreased by 5.8-fold, 3.0-fold and 9.9-fold, respectively, compared to those in the OVA-sensitized/challenged asthma control group. These results suggest that the oral administration of LM-COS is effective in alleviating the allergic inflammation in vivo and thus can be a good source material for the development of a potent therapeutic agent against mast cell-mediated allergic inflammatory responses and airway inflammation in allergic inflammatory diseases, including asthma.

Identification of a transforming MYB-GATA1 fusion gene in acute basophilic leukemia: a new entity in male infants.

Acute basophilic leukemia (ABL) is a rare subtype of acute leukemia with clinical features and symptoms related to hyperhistaminemia because of excessive growth of basophils. No known recurrent cytogenetic abnormality is associated with this leukemia. Rare cases of t(X;6)(p11;q23) translocation have been described but these were sporadic. We report here 4 cases of ABL with a t(X;6)(p11;q23) translocation occurring in male infants. Because of its location on chromosome 6q23, MYB was a good candidate gene. Our molecular investigations, based on fluorescence in situ hybridization and rapid amplification of cDNA ends, revealed that the translocation generated a MYB-GATA1 fusion gene. Expression of MYB-GATA1 in mouse lineage-negative cells committed them to the granulocyte lineage and blocked at an early stage of differentiation. Taken together, these results establish, for the first time, a link between a recurrent chromosomal translocation and the development of this particular subtype of infant leukemia.

Klinefelter syndrome and acute basophilic leukaemia--case report.

Patients with 47, XXY karyotype (Klinefelter syndrome) appear to have increased risk of developing cancer, especially male breast cancer, germ cell tumours and non Hodgkin lymphomas, but rarely acute myeloid leukaemia. We report a patient with acute basophilic leukaemia with 47, XXY karyotype in both the tumour and constitutional cells. Acute basophilic leukaemia is very rare disease comprising less than 1% of all acute myeloid leukaemias. Morphological characteristic of leukaemic blast cells is moderately basophilic cytoplasm containing a variable number of coarse basophilic granules. The most characteristic cytochemical reaction is metachromatic positivity with toluidine blue. Blast are myeloperoxidase negative. Also leukemic blasts express myeloid and monocyte markers. There is no consistent chromosomal abnormality identified in this leukaemia. This is the first reported case of acute basophilic leukaemia in patient with Klinefelter syndrome. In this article the medical history of the patient is given and the possible connection between Klinefelter syndrome and acute myeloid leukaemia is discussed.

Cbl-b promotes chemotherapy-induced apoptosis in rat basophilic leukemia cells by suppressing PI3K/Akt activation and enhancing MEK/ERK activation.

The ubiquitin ligase Cbl-b is a negative regulator of the PI3K/Akt pathway, the survival pathway implicated in chemotherapy resistance. However, it remains unclear whether Cbl-b can regulate chemosensitivity through modulating Akt activation. In this study, VP-16-induced RBL-2H3 cells apoptosis was accompanied by the activation of Akt and ERK. The PI3K inhibitor LY294002, not the ERK inhibitor PD98059, enhanced the apoptosis. In addition, down-regulation of Cbl-b was also detected. Over expression of Cbl-b significantly enhanced VP-16-induced cell apoptosis with inhibition of Akt activity, while a dominant negative (DN) RING Finger domain mutation completely abolished this enhancement. On the other hand, ERK activity was enhanced by Cbl-b, and the ERK inhibitor PD98059 reversed Cbl-b-enhanced apoptosis. The consistent results were also showed in the process of Ara-c treatment. These observations indicate that Cbl-b promotes RBL-2H3 apoptosis induced by VP-16 or Ara-c, probably through inhibition of Akt and activation of ERK.

A case of acute basophilic leukemia arising from chronic myelogenous leukemia with development of t(7;8)(q32;q13).

Acute basophilic leukemia (ABL) is an uncommon form of acute myelogenous leukemia recently recognized as a distinct entity in the World Health Organization classification of myeloid malignancies. A case is presented of ABL arising from chronic myelogenous leukemia with development of t(7;8)(q32;q13). Discussion includes a literature review.

Acute basophilic leukaemia: a case report.

Acute basophilic leukaemia is an uncommon form of acute leukaemia, rarely occurring as de novo disease. Due to rarity of the disease, consistent diagnostic criteria for the identification of this entity still remain the topic of discussion. Immunophenotypic profile, electron microscopy and cytogenetic analysis in addition to morphological features, are said to be highly desirable for correct identification of this entity. In set-up like ours, where such facilities are either not available or not in reach of the patients due to financial constraints, morphological features and simple technique like demonstration of metachromasia in blasts with toluidine blue stain remain the most useful diagnostic tool for identification of this rare condition. We present a case of acute basophilic leukaemia with (11q23)-MLL gene rearrangement, in an 18-year-old male with review of literature and discussion of diagnostic criteria.

Monosomy 7 as the sole abnormality of an acute basophilic leukemia.

We report the case of a 72-year-old man who had the very rare disease acute basophilic leukemia with the sole chromosomal finding of a monosomy 7. Most nuclear cells in the peripheral blood and bone marrow samples were either basophils or blasts. The blasts showed negative reaction with myeloperoxidase, periodic acid Schiff, chloroacetate esterase, alpha-naphthyl butyrate esterase, acid phosphatase, and Sudan black B. Metachromatic features of the blasts, however, were observed with toluidine blue stain. Electron microscopic evaluation showed the typical ultrastructure, with basophil and immature mast cell granules. Cytogenetic study revealed monosomy 7 in all metaphase cells, and this finding was confirmed by fluorescence in situ hybridization. The Philadelphia chromosome was absent. Review of the literature revealed abnormalities in cases of ABL. To our knowledge, the case reported here is the first to have basophilic leukemia with monosomy 7 as the only chromosome abnormality.