搜索结果: 'NeuroCult Proliferation'

The constitutive activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway commonly occurs in cancers and is a crucial event in tumorigenesis. Chronic myelogenous leukemia (CML) is characterized by a reciprocal chromosomal translocation (9;22) that generates the Bcr-Abl fusion gene. The PI3K/Akt pathway is activated by Bcr-Abl chimera protein and mediates the leukemogenesis in CML. However,the mechanism by which Bcr-Abl activates the PI3K/Akt pathway is not completely understood. In the present study,we found that pleckstrin homology domain leucine-rich repeat protein phosphatases 1 and 2 (PHLPP1 and PHLPP2) were depleted in CML cells. We investigated the interaction between PHLPPs and Bcr-Abl in CML cell lines and Bcr-Abl+ progenitor cells from CML patients. The Abl kinase inhibitors and depletion of Bcr-Abl induced the expression of PHLPP1 and PHLPP2,which dephosphorylated Ser-473 on Akt1,-2,and -3,resulting in inhibited proliferation of CML cells. The reduction of PHLPP1 and PHLPP2 expression by short interfering RNA in CML cells weakened the Abl kinase inhibitor-mediated inhibition of proliferation. In colony-forming unit-granulocyte,erythroid,macrophage,megakaryocyte; colony-forming unit-granulocyte,macrophage; and burst-forming unit-erythroid,treatment with the Abl kinase inhibitors and depletion of Bcr-Abl induced PHLPP1 and PHLPP2 expression and inhibited colony formation of Bcr-Abl+ progenitor cells,whereas depletion of PHLPP1 and PHLPP2 weakened the inhibition of colony formation activity by the Abl kinase inhibitors in Bcr-Abl+ progenitor cells. Thus,Bcr-Abl represses the expression of PHLPP1 and PHLPP2 and continuously activates Akt1,-2,and -3 via phosphorylation on Ser-473,resulting in the proliferation of CML cells. View Publication

Current data suggests an association between elevations in interleukin 1 (IL-1)α,IL-1β,and IL-6 and the proliferation of neural progenitor cells (NPCs) following brain injury. A limited amount of work implicates changes in these pro-inflammatory responses with diminished NPC proliferation observed as a function of aging. In the current study,adolescent (21day-old) and 1year-old CD-1 male mice were injected with trimethyltin (TMT,2.3mg/kg,i.p.) to produce acute apoptosis of hippocampal dentate granule cells. In this model,fewer 5-bromo-2'-deoxyuridine (BrdU)+ NPC were observed in both naive and injured adult hippocampus as compared to the corresponding number seen in adolescent mice. At 48h post-TMT,a similar level of neuronal death was observed across ages,yet activated ameboid microglia were observed in the adolescent and hypertrophic process-bearing microglia in the adult. IL-1α mRNA levels were elevated in the adolescent hippocampus; IL-6 mRNA levels were elevated in the adult. In subgranular zone (SGZ) isolated by laser-capture microdissection,IL-1β was detected but not elevated by TMT,IL-1a was elevated at both ages,while IL-6 was elevated only in the adult. Naïve NPCs isolated from the hippocampus expressed transcripts for IL-1R1,IL-6Rα,and gp130 with significantly higher levels of IL-6Rα mRNA in the adult. In vitro,IL-1α (150pg/ml) stimulated proliferation of adolescent NPCs; IL-6 (10ng/ml) inhibited proliferation of adolescent and adult NPCs. Microarray analysis of SGZ post-TMT indicated a prominence of IL-1a/IL-1R1 signaling in the adolescent and IL-6/gp130 signaling in the adult. View Publication

There has been a new interest in using aldehyde dehydrogenase (ALDH) activity as one marker for stem cells since the Aldefluor flow cytometry-based assay has become available. Diethylaminobenzaldehyde (DEAB),used in the Aldeflour assay,has been considered a specific inhibitor for ALDH1A1 isoform. In this study,we explore the effects of human ALDH isoenzymes,ALDH1A2 and ALDH2,on drug resistance and proliferation,and the specificity of DEAB as an inhibitor. We also screened for the expression of 19 ALDH isoenzymes in K562 cells using TaqMan Low Density Array (TLDA). We used lentiviral vectors containing the full cDNA length of either ALDH2 or ALDH1A2 to over express the enzymes in K562 leukemia and H1299 lung cancer cell lines. Successful expression was measured by activity assay,Western blot,RT-PCR,and Aldefluor assay. Both cell lines,with either ALDH1A2 or ALDH2,exhibited higher cell proliferation rates,higher clonal efficiency,and increased drug resistance to 4-hydroperoxycyclophosphamide and doxorubicin. In order to study the specificity of known ALDH activity inhibitors,DEAB and disulfiram,we incubated each cell line with either inhibitor and measured the remaining ALDH enzymatic activity. Both inhibitors reduced ALDH activity of both isoenzymes by 65-90%. Furthermore,our TLDA results revealed that ALDH1,ALDH7,ALDH3 and ALDH8 are expressed in K562 cells. We conclude that DEAB is not a specific inhibitor for ALDH1A1 and that Aldefluor assay is not specific for ALDH1A1 activity. In addition,other ALDH isoenzymes seem to play a major role in the biology and drug resistance of various malignant cells. View Publication

Anacardic acid (6-pentadecylsalicylic acid) is derived from traditional medicinal plants,such as cashew nuts,and has been linked to anticancer,anti-inflammatory,and radiosensitization activities through a mechanism that is not yet fully understood. Because of the role of nuclear factor-kappaB (NF-kappaB) activation in these cellular responses,we postulated that anacardic acid might interfere with this pathway. We found that this salicylic acid potentiated the apoptosis induced by cytokine and chemotherapeutic agents,which correlated with the down-regulation of various gene products that mediate proliferation (cyclin D1 and cyclooxygenase-2),survival (Bcl-2,Bcl-xL,cFLIP,cIAP-1,and survivin),invasion (matrix metalloproteinase-9 and intercellular adhesion molecule-1),and angiogenesis (vascular endothelial growth factor),all known to be regulated by the NF-kappaB. We found that anacardic acid inhibited both inducible and constitutive NF-kappaB activation; suppressed the activation of IkappaBalpha kinase that led to abrogation of phosphorylation and degradation of IkappaBalpha; inhibited acetylation and nuclear translocation of p65; and suppressed NF-kappaB-dependent reporter gene expression. Down-regulation of the p300 histone acetyltransferase gene by RNA interference abrogated the effect of anacardic acid on NF-kappaB suppression,suggesting the critical role of this enzyme. Overall,our results demonstrate a novel role for anacardic acid in potentially preventing or treating cancer through modulation of NF-kappaB signaling pathway. View Publication

Defining how cancer-associated mutations perturb signaling networks in stem/progenitor populations that are integral to tumor formation and maintenance is a fundamental problem with biologic and clinical implications. Point mutations in RAS genes contribute to many cancers,including myeloid malignancies. We investigated the effects of an oncogenic Kras(G12D) allele on phosphorylated signaling molecules in primary c-kit(+) lin(-/low) hematopoietic stem/progenitor cells. Comparison of wild-type and Kras(G12D) c-kit(+) lin(-/low) cells shows that K-Ras(G12D) expression causes hyperproliferation in vivo and results in abnormal levels of phosphorylated STAT5,ERK,and S6 under basal and stimulated conditions. Whereas Kras(G12D) cells demonstrate hyperactive signaling after exposure to granulocyte-macrophage colony-stimulating factor,we unexpectedly observe a paradoxical attenuation of ERK and S6 phosphorylation in response to stem cell factor. These studies provide direct biochemical evidence that cancer stem/progenitor cells remodel signaling networks in response to oncogenic stress and demonstrate that multi-parameter flow cytometry can be used to monitor the effects of targeted therapeutics in vivo. This strategy has broad implications for defining the architecture of signaling networks in primary cancer cells and for implementing stem cell-targeted interventions. View Publication

Forced expression of MN1 in primitive mouse hematopoietic cells causes acute myeloid leukemia and impairs all-trans retinoic acid-induced granulocytic differentiation. Here,we studied the effects of MN1 on myeloid differentiation and proliferation using primary human CD34(+) hematopoietic cells,lineage-depleted mouse bone marrow cells,and bipotential (granulocytic/monocytic) human acute myeloid leukemia cell lines. We show that exogenous MN1 stimulated the growth of CD34(+) cells,which was accompanied by enhanced survival and increased cell cycle traverse in cultures supporting progenitor cell growth. Forced MN1 expression impaired both granulocytic and monocytic differentiation in vitro in primary hematopoietic cells and acute myeloid leukemia cell lines. Endogenous MN1 expression was higher in human CD34(+) cells compared with both primary and in vitro-differentiated monocytes and granulocytes. Microarray and real-time reverse-transcribed polymerase chain reaction analysis of MN1-overexpressing CD34(+) cells showed down-regulation of CEBPA and its downstream target genes. Reintroduction of conditional and constitutive CEBPA overcame the effects of MN1 on myeloid differentiation and inhibited MN1-induced proliferation in vitro. These results indicate that down-regulation of CEBPA activity contributes to MN1-modulated proliferation and impaired myeloid differentiation of hematopoietic cells. View Publication