Steel factor and granulocyte-macrophage colony stimulating factor act together to enhance choline-lipid turnover during synergistically stimulated proliferation of the human factor dependent cell line, M07E

Concise review: role of DEK in stem/progenitor cell biology

Understanding the factors that regulate hematopoiesis opens up the possibility of modifying these factors and their actions for clinical benefit. DEK, a non-histone nuclear phosphoprotein initially identified as a putative proto-oncogene, has recently been linked to regulate hematopoiesis. DEK has myelosuppressive activity in vitro on proliferation of human and mouse hematopoietic progenitor cells and enhancing activity on engraftment of long-term marrow repopulating mouse stem cells, has been linked in coordinate regulation with the transcription factor C/EBPα, for differentiation of myeloid cells, and apparently targets a long-term repopulating hematopoietic stem cell for leukemic transformation. This review covers the uniqueness of DEK, what is known about how it now functions as a nuclear protein and also as a secreted molecule that can act in paracrine fashion, and how it may be regulated in part by dipeptidylpeptidase 4, an enzyme known to truncate and modify a number of proteins involved in activities on hematopoietic cells. Examples are provided of possible future areas of investigation needed to better understand how DEK may be regulated and function as a regulator of hematopoiesis, information possibly translatable to other normal and diseased immature cell systems.

Differential impact of inhibitory and activating Killer Ig-Like Receptors (KIR) on high-risk patients with myeloid and lymphoid malignancies undergoing reduced intensity transplantation from haploidentical related donors

The impact of activating KIR (aKIR) and inhibitory KIR (iKIR) on OS, relapse-related mortality (RRM) and acute GVHD (aGVHD) was prospectively studied in 84 adults with high-risk hematologic malignancies receiving reduced intensity conditioning (RIC) T-cell depleted hematopoietic SCT (HSCT) from haploidentical related donors. In this clinical model, freedom from RRM is dependent on GVL effect. Patients were divided into myeloid (n=49) and lymphoid (n=35) malignancy groups. KIR-ligand and ligand-ligand models were studied in both GVH and rejection directions and statistically correlated with outcome measures. In the myeloid group, OS was higher (P=0.009) and RRM was lower (P=0.036) in patients missing HLA-C group2 ligand to donor iKIR. OS was higher if patients had >1 missing ligand (P=0.018). In lymphoid malignancy, missing ligand to donor KIR had no impact on OS or RRM. However, OS was better with donor aKIR 2DS2 (P=0.028). There was a trend towards shorter OS in recipient with KIR 2DS1, 2DS5 and 3DS1, although sample sizes were too small to provide inferential statistics. Findings in lymphoid malignancy patients should be further studied. These results suggest that the absence of appropriate HLA ligands in the recipient to donor iKIR may induce GVL without aGVHD in myeloid malignancy patients undergoing TCD-RIC transplants.

Chromosomal aberrations in human lymphocytes exposed to the anticholinesterase pesticide isofenphos with mechanisms of leukemogenesis

Human lymphocytes were exposed to the leukemogenic pesticide isofenphos (IFP) to investigate its effects on chromosomal DNA and cholinergic homeostasis using cholinesterase activity as a marker. Isolated peripheral lymphocytes were administered concentrations of IFP ranging from 0.1 ng/ml to 10 microg/ml. The absence (Group 1) and presence (Group 2) of DNA repair inhibitors 4 mM hydroxyurea (HU), 40 microM cytosine arabinoside (ARA-C) and an NADPH regenerating system (NRS) (Group 3) were analyzed at 1, 6 and 24 h by single cell gel electrophoresis using the comet assay. Significant damage to DNA directly from IFP at 1 h by remarkably low concentrations was observed in Group 1, escalating in Group 2 with DNA repair inhibition, while Group 3 disruptions were highest due to the presence of the NRS P-450 microsomal fraction conducive to producing reactive IFP-oxon and N-desalkyl metabolites. The extent of DNA aberrations increased further in parallel within the groups at 6 and 24 h. Male and female chemical sensitivities were similar on average (P < 0.01). Cholinesterase activity measured in a satellite group was inhibited with 0.1 microg/ml IFP by 69, 62, and 48% at 1, 6, and 24 h, respectively, indicating gradual induction of compensatory synthesis. Restoration of cholinergic homeostasis may be exceptionally impaired at higher IFP concentrations from acetyl-CoA depletion [Leuk. Res. 25 (2001) 883]. In summary, these studies reveal that exposure to the organophosphate pesticide isofenphos induces human DNA mutation beyond endogenous repair capacity and disrupts cholinergic nuclear signaling affectively constructing the mutator phenotype of leukemogenesis.

Biology and mechanisms of action of synergistically stimulated myeloid progenitor cell proliferation and suppression by chemokines

A number of cytokines can act together to stimulate/enhance the proliferation of hematopoietic stem and progenitor cells in a greater than additive fashion. An example of this is the combination of a colony-stimulating factor with a potent costimulating molecule such as steel factor. Certain members of the chemokine family of cytokines can suppress this synergistically enhanced proliferation. This review focuses on cytokines involved in these stimulating/enhancing/suppressing effects with regard to biological activity and what is beginning to be learned about the intracellular signal transduction events that may be mediating these effects. Examples of intracellular mediators involved include, but are not limited to, the Raf-1/ MAP kinase pathway and cyclin-dependent kinase inhibitors p21cip-1 and p27kip-1 for cell proliferation, and eukaryotic initiation factor-4E and 4E binding protein 1 for protein synthesis.

Pulmonary epithelial cell expression of GM-CSF corrects the alveolar proteinosis in GM-CSF-deficient mice

Mutation of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene by homologous recombination caused alveolar proteinosis in mice. To further discern the role of GM-CSF in surfactant homeostasis, the synthesis of GM-CSF was directed to the respiratory epithelium of GM-CSF-hull mutant mice (GM-/-) with a chimeric gene expressing GM-CSF under the control of the promoter from the human surfactant protein-C (SP-C) gene. Transgenic mice bearing the SP-C-GM-CSF construct (SP-C-GM+) were bred to GM-/- mice resulting in complete correction of alveolar proteinosis in bitransgenic GM-/-, SP-C-GM+ mice. No effects of the transgene were found outside the lung. GM-CSF was increased in bronchoalveolar lavage fluid of the bitransgenic mice. Surfactant proteins-A and -B and phospholipid in bronchoalveolar lavage fluid were normalized in the GM-/-, SP-C-GM+ mice. SP-A, -B, and -C mRNAs were unaltered in lungs from GM-CSF-deficient and -replete mice. Expression of GM-CSF in respiratory epithelial cells of transgenic mice restores surfactant homeostasis in GM-/- mice. From these findings, we conclude that GM-CSF regulates the clearance or catabolism rather than synthesis of surfactant proteins and lipids.

Interferon-inducible protein 10 and macrophage inflammatory protein-1 alpha inhibit growth factor stimulation of Raf-1 kinase activity and protein synthesis in a human growth factor-dependent hematopoietic cell line

Stimulatory cytokines, including granulocyte-macrophage colony-stimulating factor (GM-CSF) and steel factor (SLF), act in a synergistic manner to stimulate the growth of hematopoietic progenitor cells, an effect also demonstrated for the growth factor-dependent human hematopoietic cell line MO7e. While little is known about the mechanisms responsible for mediating synergistic interactions of cytokines, Raf-1, a component of the MAP kinase signaling pathway, is thought to play a role in the stimulatory response evoked by several cytokines, including SLF and GM-CSF. Interferon-inducible protein-10 (IP-10) and macrophage inflammatory protein-1 alpha (MIP-1 alpha) are members of the chemokine family of suppressive cytokines. Prior exposure of hematopoietic cells to chemokines, including IP-10 and MIP-1 alpha, inhibits the synergistic action of growth factors on stimulating cell proliferation. We report that treatment of MO7e cells with the combination of GM-CSF and SLF directly stimulates statistically significant synergistic increases in the phosphorylation and activation of Raf-1 kinase, and in cellular protein synthesis levels. Pretreatment of MO7e cells with IP-10 or MIP-1 alpha blocked synergistic growth factor action, resulting in statistically significant suppression of cell proliferation, protein synthesis, and Raf-1 phosphorylation and activation. IP-10 and MIP-1 alpha treatment also evoked significant increases in intracellular cAMP levels. Pretreatment of cells with agents which serve to raise intracellular cAMP levels, or with cAMP analogs inhibited the synergistic actions of GM-CSF and SLF in a manner similar to IP-10 and MIP-1 alpha. In addition, treatment of cells with a potent inhibitor of cAMP-dependent protein kinase A blocked the suppressive action of MIP-1 alpha and IP-10 on Raf-1 kinase activity and on MO7e cell proliferation. The ability of IP-10 and MIP-1 alpha to antagonize the synergistic action of GM-CSF and SLF appears to involve inactivation of Raf-1 and the down-regulation of protein synthesis. Our findings suggest that both MIP-1 alpha and IP-10 mediate their suppressive effects in MO7e cells by stimulating increases in cellular cAMP levels and activating protein kinase A, a mechanism we believe to be unique to these chemokines and not one applied to all growth suppressive members of the chemokine superfamily (for example, interleukin 8 and platelet factor 4).

Synergistic induction of phospholipid metabolism by granulocyte-macrophage colony stimulating factor and steel factor in human growth factor-dependent cell line, M07e

Steel factor (SLF), the ligand for the c-kit proto-oncogene tyrosine kinase receptor, synergizes with several hematopoietic growth factors to produce greatly enhanced proliferation of normal human hematopoietic progenitor cells as well as that of the human growth factor-dependent myeloid cell line, M07e. The mechanisms of this phenomenon remain unknown. In an attempt to understand the cellular processes relevant to this phenomenon, we examined the effects of SLF and granulocyte-macrophage colony-stimulating factor (GM-CSF) on induced lipid metabolism in M07e cells. We find that both GM-CSF and SLF induced increased phosphatidylcholine (PC) turnover rates (biosynthesis and degradation) as measured by increased [3H]-choline labelling, with SLF being more potent than GM-CSF after 6 h of stimulation, but equipotent at 24 h of stimulation. The labelling of aqueous intermediates of PC metabolism was also increased by cytokine stimulation, most notably phosphocholine. Simultaneous stimulation with GM-CSF plus SLF resulted in a true synergistic induction of PC, lysoPC, and phosphocholine labelling. GM-CSF and SLF each induced asymmetric labelling of various phospholipid classes as measured by incorporation of different [3H]-fatty acids. [3H]-myristic acid labelling of phosphatidylserine was most prominently induced (approximately 12-fold). Cytosolic choline kinase activity was also upregulated more than twofold over control by SLF, which might contribute to the increased phosphocholine labelling. These effects may have relevance to the intracellular mechanisms of the synergistic proliferative stimulation of SLF plus GM-CSF on M07e cells.