Midostaurin (PKC412) inhibits immunoglobulin E-dependent activation and mediator release in human blood basophils and mast cells.

BACKGROUND: KIT tyrosine kinase inhibitors (TKI), such as nilotinib or midostaurin (PKC412), are increasingly used in clinical trials to counteract neoplastic cell growth in patients with aggressive mast cell (MC) disorders. However, these patients suffer not only from MC infiltration and consecutive organ damage but also from MC mediator-related symptoms. METHODS: We examined the effects of three KIT TKI, imatinib, nilotinib, and midostaurin, on IgE-dependent mediator release in normal human blood basophils and cultured cord blood cell-derived MC, and on spontaneous histamine secretion in the MC leukaemia cell line HMC-1 and the basophil cell line KU812. RESULTS: The multi-kinase inhibitor midostaurin that interacts with KIT and protein kinase C was found to counteract anti-IgE-induced mediator release in blood basophils and cultured cord blood cell-derived MC in all samples examined. By contrast, no effects of imatinib or nilotinib on histamine secretion in basophils or MC were found. The effects of midostaurin on histamine release were dose-dependent and occurred at pharmacologic concentrations (IC(50) 10-100 nm). Midostaurin was also found to inhibit the IgE-dependent up-regulation of CD63 on cultured cord blood cell-derived human MC, but did not inhibit IgE-dependent up-regulation of CD63 or CD203c in human blood basophils. CONCLUSION: Midostaurin may be a beneficial drug in aggressive systemic mastocytosis not only because of its growth-inhibitory effects but also because of its additional effects on activation and mediator release in MC and basophils.

CD203c is overexpressed on neoplastic mast cells in systemic mastocytosis and is upregulated upon IgE receptor cross-linking.

The ectoenzyme E-NPP3 (CD203c) has recently been identified as a novel activation-linked cell surface antigen on basophils. In the present study, we examined expression of CD203c on normal mast cells (MC)and bone marrow (bm) MC derived from 85 patients with systemic mastocytosis (SM), including cases with indolent SM (ISM, n=72), SM with associated clonal hematologic non-MC-lineage disease (SM-AHNMD, n=6), aggressive SM (ASM, n=3), and mast cell leukemia (MCL, n=4). Surface expression of CD203c was analyzed by multicolor flow cytometry. In patients with SM, bm MC expressed significantly higher amounts of CD203c compared to normal bm MC (median MFI in controls: 260 versus median MFI in SM: 516, p<0.05). Slightly lower amounts of CD203c were detected on MC in SM-AHNMD and ASM compared to ISM. To demonstrate CD203c expression in MC at the mRNA level, neoplastic MC were highly enriched by cell sorting, and were found to express CD203c mRNA in RT-PCR analysis. Cross-linking of the IgE receptor on MC resulted in a substantial upregulation of CD203c, whereas the KIT-ligand stem cell factor (SCF) showed no significant effects. In conclusion, CD203c is a novel activation-linked surface antigen on MC that is upregulated in response to IgE receptor cross-linking and is overexpressed on neoplastic MC in patients with SM.

The differentially spliced mouse tagL gene, homolog of tag7/PGRP gene family in mammals and Drosophila, can recognize Gram-positive and Gram-negative bacterial cell wall independently of T phage lysozyme homology domain.

Tag7/PGRP, a recently characterized antimicrobial protein, is conserved from insects to mammals. Recently its involvement in Toll signalling in Drosophila was demonstrated. A number of genes representing a new family homologous to PGRP were identified in Drosophila and human. Here we describe a splicing pattern of the tagL gene, mouse member of tag7/PGRP family. Some of the identified splice variants lacked characteristics for the family T phage lysozyme homology domain (also known as PGRP domain). Accordingly to the predicted transmembrane domains, mouse TagL may be secreted as inducible proteins or retained on intracellular membranes. All detected splice variant isoforms of TagL bound Gram-positive, Gram-negative bacteria and peptidoglycan. This binding did not depend on the presence of T phage lysozyme homology domain but was associated with the C-terminal portion of the polypeptides. Thus, this variety of isoforms of a single gene may play a role in circulating bacteria recognition in mammals.

Met-enkephalin induces cytolytic processes of apoptotic type in K562 human erythroid leukemia cells.

Cytolytic activity of Met-enkephalin, an endogenous opioid peptide, was studied within the 10(-7)-10(-17) M concentration range in K562 human erythroid leukemia cells. Cytolytic activity was determined by the trypan blue inclusion method after 13, 15 and 18 h of Met-enkephalin co-incubation with target cells. Discrete maxima of cytolytic activity were detected at concentrations of 10(-9)-10(-10), 10(-13) and 10(-15) M. Cytolysis was accompanied by internucleosomal DNA fragmentation which is indicative of the mechanism of cell death being apoptosis.

Cytolytic processes induced by TNF in L929 and K562 differ in DNA fragmentation mechanisms.

OBJECTIVE: Cytolytic activity of TNF was analysed at L929 and K562 tumor cell lines. METHODS: TNF-mediated cytotoxicity was studied within 10(-6)-10(-17) M concentration range after 18 h of incubation with target cells. RESULTS: TNF caused reliable cytotoxicity values in both cell lines, while L929 cells were more sensitive to cytolytic action of the protein than K562 cells. Three cytotoxicity maxima were detected at each cell line: at concentrations of 10(-6) M, 10(-17) M and 10(-15) M in K562 cells and at concentrations of 10(-7) M, 10(-11) M, 10(-14), 10(-16) M in L929 cells. CONCLUSIONS: DNA fragmentation analysis demonstrated that all cytolytic processes induced by TNF in L929 cells are associated with apoptotic mechanism of cell death, while cytolytic process induced in K562 cells differed in DNA fragmentation patterns: cytolytic processes induced by 10(-6) M of TNF was of apoptotic type, while the other processes were not associated with internucleosomal DNA cleavage.

Different pathways of the release of cytotoxic proteins in LAK cells.

Human LAK cells were shown to release cytotoxic proteins by both Ca(2+)-dependent and Ca(2+)-independent mechanisms. CD3+ CD8+ CD16- and CD16+ CD8+ CD3- LAK cells were co-incubated with target cells in the presence of 4 mM EGTA. Although EGTA inhibited the exocytosis of cytolytic granules, supernatants obtained were cytotoxic for target cells. Cytotoxicity of CD3+ LAK cells and CD16+ LAK cells was due to cytotoxic proteins with MW 75 (p75), 35 (p35) and 22 (p22) kDa. LAK cells were also shown to release cytotoxic proteins by way of continuous secretion. After co-incubation in the absence of target cells LAK cells can secrete cytotoxic proteins with MW 75 (p75), 55 (p55), 38 (p38), 35 (p35), 25 (p25), 22 (p22) and 17 (p17) kDa.

Tumor cell cytolysis mediated by valorphin, an opioid-like fragment of hemoglobin beta-chain.

Valorphin, an endogenous opioid-like hemoglobin fragment, is cytotoxic for L929 and K562 tumor cells in 10(-7)-10(-13) M concentration range. Because cytolytic effects induced by valorphin in K562 cells are inhibited by naloxone, opioid receptors should be involved in induction of valorphin-mediated tumor cell death. Three distinct cytolytic processes, differing in the onset time and the development time, take place with K562 cells within 10-18 h of incubation with valorphin. All three processes are not associated with apoptotic mechanism of cell death.

[Expression analysis of proteins encoded by genes of the tag7/tagL (PGRP-S,L) family in human peripheral blood cells]. / Analiz ékspressii belkov, kodiruemykh semeistvom genov tag7/tagL(PGRP-S,L), v kletkakh perifericheskoi krovi cheloveka.

Various types of human blood cells were tested for expression of the Tag7/PGRP-SA and TagL/PGRP-L proteins, which belong to the family of proteins possessing the lysozyme-like peptidoglycan recognition protein (PGRP) domain. Expression regulation by several factors was demonstrated.

[Cloning and study of novel mammalian genes with structural homology with phage lysozyme]. / Klonirovanie i izuchenie novykh genov mlekopitaiushchikh, imeiushchikh oblast' strukturnoi gomologii s fagovym lizotsimom.

The mouse tag7 gene was cloned and characterized in our previous works. This work is devoted to identifying and cloning its homologs. The human homolog of the tag7 gene was cloned. Data of analysis of the primary structure of the human tag7 and results from the study of the production of the corresponding protein in human organs and tissues indicate that this gene plays a major role in the mammalian immune system. The mouse and human tagL gene carrying an extended region of structural homology with the tag7 gene was detected by computer analysis and was subsequently cloned. Sequence analysis suggested the possible membrane localization of the gene, whereas the specific expression pointed to the role of this gene in the immune system. Both genes, tag7 and tagL, were localized in the human chromosome 19.

Cytotoxic activity of acetylcholine receptor ligands.

Acetylcholine receptor ligands were studied for cytotoxicity in K562 human erythroid leukemia tumor cells. Cytotoxicity of carbachol, an agonist of acetylcholine receptors, atropine, an antagonist of muscarinic acetylcholine receptor, neurotoxin 11 (NT II) from Naja naja oxiana cobra venom and tubocurarine, antagonists of acetylcholine receptor of nicotinic type was exhibited in the 10-7-10-5 M concentration range. Several cytolytic processes, two for carbachol and three for other ligands, corresponding to different concentrations of each ligand were detected. All acetylcholine receptor ligands induced internucleosomal DNA fragmentation.