Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Embryonic stem cells (ESCs) derived from the inner cell mass of blastocysts maintain their pluripotency through a complex interplay of different signaling pathways and transcription factors including Leukemia Inhibitory Factor (LIF), homeo-domain protein Nanog and POU-domain-containing transcription factor Oct3/4. LIF can maintain the self-renewal of mouse ESCs by activating the Jak/Stat3 pathway; however, it is dispensable for human ESCs. Nanog, a homeo-domain transcription factor alone is sufficient for sustaining the self-renewal of ESCs. Overexpression of Nanog by heterologous promoters can maintain self-renewal of human and mouse ESCs in the absence of LIF/Stat3 pathway. The mechanisms that control the expression of Nanog, however, remain poorly understood. In this report we demonstrate that retinol, the alcohol form of Vitamin A, can suppress the differentiation of ESCs by up-regulating the expression of Nanog. Retinol is mainly associated with differentiation through its active metabolite retinoic acid during early development of the embryo. The activation of Nanog by retinol is not mediated via retinoic acid signaling and appears to be independent of previously described LIF/Stat3, bone morphogenic proteins, Wnt/beta-catenin, and Oct3/4-Sox2 pathways. These studies therefore, reveal a previously unknown function of retinol and offer a model system to define alternate regulatory pathways that control the self-renewal of ESCs as well as to identify upstream "master" regulatory factors that are responsible for maintaining the integrity of stem cells.
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PMID:Suppression of ES cell differentiation by retinol (vitamin A) via the overexpression of Nanog. 1745 18

Leukemia-specific chromosome translocations involving the nucleoporin CAN/NUP214 lead to expression of different fusion genes including DEK-CAN, CAN-ABL, and SET-CAN. DEK-CAN and CAN-ABL1 are associated with acute myeloid leukemia and T-cell acute lymphoblastic leukemia, respectively, whereas SET-CAN was identified in a patient with acute undifferentiated leukemia. In addition, SET is overexpressed in solid tumors of the breast, uterus, stomach, and rectum. Ectopic expression of SET-CAN inhibits vitamin-D(3)-induced differentiation of the human promonocytic U937cells, whereas ectopic SET expression induces differentiation. Here, we assessed the leukemogenic potential of SET-CAN in the hematopoietic system of transgenic mice. Although SET-CAN mice showed expansion of an early progenitor cell pool and partial depletion of lymphocytes, the animals were not leukemia-prone and did not show shortening of disease latency after retroviral tagging. This suggests that SET-CAN expression in acute undifferentiated leukemia might determine the primitive phenotype of the disease, whereas secondary genetic lesions are necessary for disease development. Surprisingly, SET-CAN mice developed spontaneous hyperplasia of the stomach mucosa, which coincided with overexpression of beta-catenin and vastly increased numbers of proliferating gastric mucosa cells, suggesting a role of SET-CAN in proliferation of certain epithelial cells.
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PMID:SET-CAN, the product of the t(9;9) in acute undifferentiated leukemia, causes expansion of early hematopoietic progenitors and hyperproliferation of stomach mucosa in transgenic mice. 1756 77

This study investigated the response of acute lymphoblastic leukaemia (ALL) cells to Wnt proteins. Accumulation of beta-catenin was measured by Western blotting and immunofluorescence microscopy. Reverse transcription polymerase chain reaction (RT-PCR) analysis of B-cell progenitor acute lymphoblastic leukaemia (ALL) cells revealed expression of Wnt genes, including WNT2B in 33%, WNT5A in 42%, WNT10B in 58% and WNT16B in 25% of cases. The Wnt receptors, (Frizzled) FZD7 and FZD8 were also expressed in most cases while FZD3, FZD4 and FZD9 were occasionally detected. Stimulation of ALL cells with Wnt-3a activated canonical Wnt signalling with increased expression and nuclear translocation of beta-catenin. This resulted in a 1.7- to 5.3-fold increase in cell proliferation, which was associated with enhanced cell cycle entry. A significant increase in the survival of ALL cells under conditions of serum deprivation was also observed. Microarray analysis and quantitative RT-PCR revealed that activation of the Wnt/beta-catenin pathway led to altered expression of genes involved in cell cycle regulation and apoptosis in normal and leukaemic B-cell progenitors. Our results demonstrate that Wnt-3a provides proliferative and survival cues in ALL cells. This data suggests that targeting the Wnt signalling pathway may be a useful therapeutic strategy in ALL.
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PMID:Activation of Wnt/beta-catenin pathway mediates growth and survival in B-cell progenitor acute lymphoblastic leukaemia. 1761 20

Deregulated accumulation of nuclear beta-catenin enhances transcription of beta-catenin target genes and promotes malignant transformation. Recently, acute myeloid leukemia (AML) cells with activating mutations of FMS-like tyrosine kinase-3 (FLT3) were reported to display elevated beta-catenin-dependent nuclear signaling. Tyrosine phosphorylation of beta-catenin has been shown to promote its nuclear localization. Here, we examined the causal relationship between FLT3 activity and beta-catenin nuclear localization. Compared to cells with wild-type FLT3 (FLT3-WT), cells with the FLT3 internal tandem duplication (FLT3-ITD) and tyrosine kinase domain mutation (FLT3-TKD) had elevated levels of tyrosine-phosphorylated beta-catenin. Although beta-catenin was localized mainly in the cytoplasm in FLT3-WT cells, it was primarily nuclear in FLT3-ITD cells. Treatment with FLT3 kinase inhibitors or FLT3 silencing with RNAi decreased beta-catenin tyrosine phosphorylation and nuclear localization. Conversely, treatment of FLT3-WT cells with FLT3 ligand increased tyrosine phosphorylation and nuclear accumulation of beta-catenin. Endogenous beta-catenin co-immunoprecipitated with endogenous activated FLT3, and recombinant activated FLT3 directly phosphorylated recombinant beta-catenin. Finally, FLT3 inhibitor decreased tyrosine phosphorylation of beta-catenin in leukemia cells obtained from FLT3-ITD-positive AML patients. These data demonstrate that FLT3 activation induces beta-catenin tyrosine phosphorylation and nuclear localization, and thus suggest a mechanism for the association of FLT3 activation and beta-catenin oncogeneic signaling in AML.
Leukemia 2007 Dec
PMID:FLT3 regulates beta-catenin tyrosine phosphorylation, nuclear localization, and transcriptional activity in acute myeloid leukemia cells. 1785 58

Atiprimod (Atip) is a novel oral agent with anti-inflammatory properties. Although its in vitro activity and effects on signaling in multiple myeloma (MM) have been previously reported, here we investigated its molecular and in vivo effects in MM. Gene expression analysis of MM cells identified downregulation of genes involved in adhesion, cell-signaling, cell cycle and bone morphogenetic protein (BMP) pathways and upregulation of genes implicated in apoptosis and bone development, following Atip treatment. The pathway analysis identified integrin, TGF-beta and FGF signaling as well as Wnt/beta-catenin, IGF1 and cell-cycle regulation networks as being most modulated by Atip treatment. We further evaluated its in vivo activity in three mouse models. The subcutaneous model confirmed its in vivo activity and established its dose; the SCID-hu model using INA-6 cells, confirmed its ability to overcome the protective effects of BM milieu; and the SCID-hu model using primary MM cells reconfirmed its activity in a model closest to human disease. Finally, we observed reduced number of osteoclasts and modulation of genes related to BMP pathways. Taken together, these data demonstrate the in vitro and in vivo antitumor activity of Atip, delineate potential molecular targets triggered by this agent, and provide a preclinical rational for its clinical evaluation in MM.
Leukemia 2007 Dec
PMID:Biological pathways and in vivo antitumor activity induced by Atiprimod in myeloma. 1788 85

Glycogen synthase kinase (GSK)-3, a negative regulator of cardiac hypertrophy, is inactivated in failing hearts. To examine the histopathological and functional consequence of the persistent inhibition of GSK-3beta in the heart in vivo, we generated transgenic mice with cardiac-specific overexpression of dominant negative GSK-3beta (Tg-GSK-3beta-DN) and tetracycline-regulatable wild-type GSK-3beta. GSK-3beta-DN significantly reduced the kinase activity of endogenous GSK-3beta, inhibited phosphorylation of eukaryotic translation initiation factor 2B epsilon, and induced accumulation of beta-catenin and myeloid cell leukemia-1, confirming that GSK-3beta-DN acts as a dominant negative in vivo. Tg-GSK-3beta-DN exhibited concentric hypertrophy at baseline, accompanied by upregulation of the alpha-myosin heavy chain gene and increases in cardiac function, as evidenced by a significantly greater Emax after dobutamine infusion and percentage of contraction in isolated cardiac myocytes, indicating that inhibition of GSK-3beta induces well-compensated hypertrophy. Although transverse aortic constriction induced a similar increase in hypertrophy in both Tg-GSK-3beta-DN and nontransgenic mice, Tg-GSK-3beta-DN exhibited better left ventricular function and less fibrosis and apoptosis than nontransgenic mice. Induction of the GSK-3beta transgene in tetracycline-regulatable wild-type GSK-3beta mice induced left ventricular dysfunction and premature death, accompanied by increases in apoptosis and fibrosis. Overexpression of GSK-3beta-DN in cardiac myocytes inhibited tumor necrosis factor-alpha-induced apoptosis, and the antiapoptotic effect of GSK-3beta-DN was abrogated in the absence of myeloid cell leukemia-1. These results suggest that persistent inhibition of GSK-3beta induces compensatory hypertrophy, inhibits apoptosis and fibrosis, and increases cardiac contractility and that the antiapoptotic effect of GSK-3beta inhibition is mediated by myeloid cell leukemia-1. Thus, downregulation of GSK-3beta during heart failure could be compensatory.
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PMID:Inhibition of glycogen synthase kinase 3beta during heart failure is protective. 1804 21

This study was aimed to investigate the expression of beta-catenin in leukemic cell lines and its relationship with pathogenesis of leukemia, semi-quantitative RT-PCR and Western blot were performed to detect the expression of beta-catenin in a panel of 15 human hematopoietic cell lines (U937, KG1a, Jurkat, K562, Namalwa, HEL, HUT78, Raji, Daudi, CEM, LCL-H, HL-60, NB4, J6-1, Ramos). Immunocytochemistry was performed in some of these cell lines to detect the location of beta-catenin. The results showed that the beta-catenin gene was widely expressed in most leukemic cell lines in various degree, the high expression of beta-catenin was found is U937, KG1a, Jurkat, K562 and Namalwa cells, middle expression of beta-catenin was observed in HEL, HUT78, Raji, Daudi and CEM cells, lower expression of beta-catenin was observed in LCL-H, HL-60, NB4, J6-1 and Ramos cells. The expression level of beta-catenin protein was identical to the expression level of beta-catenin mRNA. The expression of beta-catenin could be found in nuclei of all cells mentioned above, but their levels were different between them. Abundant beta-catenin also could be observed in nuclei of some leukemic cells by immunocytochemistry. It is concluded that overexpression of beta-catenin in leukemia cells, as a key mediator of Wnt signaling transduction pathway, indicates that the Wnt signaling transduction pathway may be aberrantly activated in leukemia.
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PMID:[Expression of beta-Catenin in Leukemic Cell Lines]. 1795 61

We have reported that a novel c-Myc-binding protein, MM-1, repressed the E-box-dependent transcription activity of c-Myc through TIF1beta/KAP1, a transcriptional corepressor, and that the c-fms gene was a target gene involved in this pathway. We have also reported that a mutation of A157R in MM-1, which is often observed in patients with leukemia or lymphoma, abrogated all of the repressive activities of MM-1 toward c-Myc, indicating that MM-1 is a novel tumor suppressor. In this study, to further identify target genes of MM-1, DNA microarray analysis was carried out by comparing expression levels of genes in MM-1 knockdown and parental cells, and the wnt4 gene, a member of the Wnt-beta-catenin pathway, was identified as a target gene of MM-1. Increased expression level of the wnt4 gene, accumulation and translocation of beta-catenin to the cytoplasm and nucleus, and upregulation of TCF/Lef-1, a target protein of the Wnt-beta-catenin pathway, were found in MM-1 knockdown cells. Reporter assays using various deletion constructs of the wnt4 gene promoter showed that MM-1 recognized the region spanning -286 to -229 from a transcription start site, and MM-1 complex was found to bind to this region by chromatin immunoprecipitation and gel mobility shift assays. Furthermore, it was found that Egr-1 and MM-1 were bound to this region and that both proteins mutually down-regulate promoter activity of the wnt4 gene. Since the c-myc gene is the target gene of the Wnt-beta-catenin pathway, these findings suggest that MM-1 inhibits c-Myc by a dual mechanism.
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PMID:Negative regulation of the Wnt signal by MM-1 through inhibiting expression of the wnt4 gene. 1828 Oct 35

Cancer stem cells, which share many common properties and regulatory machineries with normal stem cells, have recently been proposed to be responsible for tumorigenesis and to contribute to cancer resistance. The main challenges in cancer biology are to identify cancer stem cells and to define the molecular events required for transforming normal cells to cancer stem cells. Here we show that Pten deletion in mouse haematopoietic stem cells leads to a myeloproliferative disorder, followed by acute T-lymphoblastic leukaemia (T-ALL). Self-renewable leukaemia stem cells (LSCs) are enriched in the c-Kit(mid)CD3(+)Lin(-) compartment, where unphosphorylated beta-catenin is significantly increased. Conditional ablation of one allele of the beta-catenin gene substantially decreases the incidence and delays the occurrence of T-ALL caused by Pten loss, indicating that activation of the beta-catenin pathway may contribute to the formation or expansion of the LSC population. Moreover, a recurring chromosomal translocation, T(14;15), results in aberrant overexpression of the c-myc oncogene in c-Kit(mid)CD3(+)Lin(-) LSCs and CD3(+) leukaemic blasts, recapitulating a subset of human T-ALL. No alterations in Notch1 signalling are detected in this model, suggesting that Pten inactivation and c-myc overexpression may substitute functionally for Notch1 abnormalities, leading to T-ALL development. Our study indicates that multiple genetic or molecular alterations contribute cooperatively to LSC transformation.
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PMID:Multi-genetic events collaboratively contribute to Pten-null leukaemia stem-cell formation. 1846 37

Wnt proteins control cell fate and differentiation during development. Alterations of the Wnt/beta-catenin signaling pathway and changes in wnt gene expression are clearly associated with leukemia. The expression of human wnt13/wnt2b is complex as it involves alternative promoters and RNA splicing giving rise to Wnt13A, -B and -C mRNA isoforms, which encode proteins with different intracellular localizations and functions. We investigated the expression of the human wnt13 in relation to leukemic cell differentiation. Differentiated endothelial cells expressed the highest levels of Wnt13 mRNA isoforms among various endothelial and leukemic cell lines. The differentiation of U937 cells towards monocyte/macrophages resulted in an increase of Wnt13B and -C mRNAs while Wnt13A mRNAs were decreased. The differentiation of K562 cells towards megakaryocytes was accompanied with the up-regulation of all Wnt13 mRNA isoforms. In the two differentiation systems, Wnt13B and -C expression correlated with the expression of the MAF-B transcription factor. Our data demonstrate the differential regulation of wnt13 promoters and pinpoint a Wnt13 isoform switch during differentiation of the leukemic U937 cells towards the monocyte/macrophage lineage, thereby suggesting new players in this process.
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PMID:Differential expression of Wnt13 isoforms during leukemic cell differentiation. 1857 37


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