scholarly journals Activation of C/EBPa Myeloid-Specific Transcription Factor By NAMPT/SIRT1-Triggered Deacetylation

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2199-2199
Author(s):  
Bardia Samareh ◽  
Masoud Nasri ◽  
Inna Zimmer ◽  
Olga Klimenkova ◽  
Leonie Keller ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Transcription Factor ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Target Genes ◽  
Leukemia Cell ◽  
Myeloid Differentiation ◽  
Granulocytic Differentiation ◽  
Acute Myeloid ◽  
Myeloid Leukemia Cell

Abstract Previously, we described new mechanism of G-CSF-triggered granulocytic differentiation of hematopoietic stem cells (HSCs) via activation of the enzyme Nicotinamide Phosphorybosyltransferase (NAMPT) leading to NAD+ production and activation of NAD+ -dependent protein deacetylase sirtuin 1 (SIRT1). We found, that upon stimulation of HSCs with NAMPT, SIRT1 bound to the key myeloid transcription factor C/EBPα followed by transcriptional induction of C/EBPα target genes G-CSFR and G-CSF and granulocytic differentiation. In the present work we investigated the mechanism of NAMPT/SIRT1-triggered deacetylation of C/EBPα. We found that C/EBPα is acetylated at the position Lys 161, which is evolutionarily conserved. Lys 161 is localized in the transactivation element III (TE-III) of the transactivation domain (TAD) of C/EBPα protein, which is responsible for recruitment of SWI/SNF and CDK2/CDK4. Western blot and DUOLINK analysis using rabbit polyclonal antibody specifically recognizing acetyl-Lys 161 of C/EBPα revealed predominantly nuclear localization of acetylated C/EBPα protein in acute myeloid leukemia cell lines NB4 and HL60 as well as in primary HSCs. Induction of myeloid differentiation of HSCs by treatment with G-CSF as well as ATRA-induced differentiation of NB4 cells resulted in the deacetylation of C/EBPα. NAMPT inhibition in NB4 and HL60 cell lines using specific inhibitor FK866 led to the dramatically elevated levels of acetylated C/EBPα and reduced amounts of total C/EBPα protein, which was in line with diminished mRNA expression of C/EBPα target genes (G-CSF, G-CSFR and ELANE). Interestingly, treatment of acute myeloid leukemia cell line HL60 with NAMPT or transduction of HL-60 cells with NAMPT-expressing lentiviral construct induced myeloid differentiation of these cells even without addition of ATRA. This was in line with time- and dose-dependent increase of total C/EBPα protein levels upon NAMPT treatment. Therefore, NAMPT overcomes transcriptional repression of C/EBPα in HL-60 cells by activation of positive CEBPA autoregulation. Taken together, we described a new mechanism of regulation of C/EBPα activities in hematopoiesis and leukemogenesis by its post-translational modification via NAMPT/SIRT1-triggered de-/acetylation. Disclosures No relevant conflicts of interest to declare.

scholarly journals Monocyte-macrophage differentiation of acute myeloid leukemia cell lines by small molecules identified through interrogation of the Connectivity Map database

Cell Cycle ◽  
2015 ◽  
Vol 14 (16) ◽  
pp. 2578-2589 ◽  
Author(s):  
Gloria Manzotti ◽  
Sandra Parenti ◽  
Giovanna Ferrari-Amorotti ◽  
Angela Rachele Soliera ◽  
Sara Cattelani ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Small Molecules ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Connectivity Map ◽  
Macrophage Differentiation ◽  
Leukemia Cell Lines ◽  
Acute Myeloid ◽  
Myeloid Leukemia Cell

Acute myeloid leukemia cell lines MOLM-17 and MOLM-18 derived from patient with advanced myelodysplastic syndromes

2005 ◽  
Vol 29 (6) ◽  
pp. 701-710 ◽  
Author(s):  
Yoshinobu Matsuo ◽  
Hans G. Drexler ◽  
Akira Harashima ◽  
Ayumi Okochi ◽  
Kensuke Kojima ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Cell Lines ◽  
Myelodysplastic Syndromes ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Acute Myeloid Leukemia Cell ◽  
Leukemia Cell Lines ◽  
Acute Myeloid ◽  
Myeloid Leukemia Cell

Hypomethylation of Tumor Suppressor Genes in Acute Myeloid Leukemia: Characteristic of Cell Lines with MLL Abnormalities?.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 365-365
Author(s):  
Hilmar Quentmeier ◽  
Sonja Röhrs ◽  
Wilhelm G Dirks ◽  
Claus Meyer ◽  
Rolf Marschalek ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Tumor Suppressor ◽  
Acute Leukemia ◽  
Cell Lines ◽  
Fusion Proteins ◽  
Myeloid Leukemia ◽  
Target Genes ◽  
Leukemia Cell ◽  
Hoxa Cluster ◽  
Acute Myeloid

Abstract Abstract 365 Background: Translocations of the Mixed Lineage Leukemia (MLL) gene occur in a subset (5%) of acute myeloid leukemia (AML) and in mixed phenotype acute leukemia in infancy, a disease with extremely poor prognosis. Animal model systems show that MLL gain of function mutations may contribute to leukemogenesis. Wild-type MLL carries histone methyltransferase activity and affects specific target genes, such us HOXA cluster genes. While the more than three dozen MLL fusion proteins known today exert different specific functions, they finally induce transcription of individual target genes. Consequently, acute lymphoblastic leukemias (ALL) with MLL mutations (MLLmu) exhibit typical gene expression profiles including high-level expression of HOXA cluster genes. Aim of this study was to find a correlation between the MLL mutational status and tumor suppressor gene methylation/expression in acute leukemia cell lines. Results: Using MS-MLPA (methylation-specific multiplex ligation-dependent probe amplification assay), methylation of 24 different TSG was analyzed in 28 MLLmu and MLLwt acute leukemia cell lines. 1.8/24 TSG were methylated in MLLmu AML cells, 6.2/24 TSG were methylated in MLLwt AML cells. Hypomethylation and expression of the tumor suppressor genes (TSG) BEX2, IGSF4 and TIMP3 turned out to be characteristic of MLLmu acute myeloid leukemia (AML) cell lines. MLL wild-type (MLLwt) AML cell lines displayed hypermethylated TSG promoters resulting in transcriptional silencing. Demethylating agents and inhibitors of histone deacetylases restored expression of BEX2, IGSF4 and TIMP3 confirming epigenetic silencing of these genes in MLLwt cells. The positive correlation between MLL translocation, TSG hypomethylation and expression suggested that MLL fusion proteins were responsible for dysregulation of TSG expression in MLLmu cells. This concept was supported by our observation that Bex2 mRNA levels in MLL-ENL transgenic mouse cell lines required expression of the MLL fusion gene. Conclusion: These results suggest that the conspicuous expression of the TSG BEX2, IGSF4 and TIMP3 in MLLmu AML cell lines is the consequence of altered epigenetic properties of MLL fusion proteins. Disclosures: No relevant conflicts of interest to declare.

Nampt/SIRT2 Hyperactivation Lead to Activation of ß-Catenin: a Possible Mechanism of Leukomogenic Transformation In CN Patients.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1486-1486
Author(s):  
Lan Dan ◽  
Ana Gigina ◽  
Karl Welte ◽  
Julia Skokowa
Keyword(s):  
Acute Myeloid Leukemia ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Myeloid Cells ◽  
Nuclear Accumulation ◽  
Healthy Individuals ◽  
Leukemia Cell Lines ◽  
Acute Myeloid ◽  
Myeloid Leukemia Cell

Abstract Abstract 1486 Recently we demonstrated that nicotinamide phosphoribosyltransferase (NAMPT) is an essential enzyme mediating granulocyte colony-stimulating factor (G-CSF)-triggered granulopoiesis via activation of NAD+/sirtuins/C/EBPs signaling cascade. Nampt levels were significantly elevated in plasma and in myeloid cells of patients with severe congenital neutropenia (CN). CN is characterized by a “maturation arrest” of granulopoiesis on the promyelocytic stage of differentiation and by leukemogenic tansformation of hematopoiesis in ca. 20 % of patients. The mechanism of the leukemic transformation is still unclear. Previously, we reported elevated levels of activated oncogene ß-catenin in nuclei of myeloid progenitor cells of CN patients. The activity and nuclear translocation of ß-catenin is regulated by glycogen synthase kinase-3 ß (GSK3ß), which activates ß-catenin degradation complex. In the present study we found that in myeloid cells of CN patients GSK3ß was inhibited by phosphorylation on Ser9, as compared to healthy individuals. Therefore, we assume that GSK3ß-ß-catenin pathway could be involved in the leukemogenic transformation of hematopoiesis. Since, Nampt was also elevated in CN patients, we aimed to investigate the connection between hyperactivated Nampt and ß-catenin in leukemogenesis. The Nampt functions in hematopoiesis are dependent on the dose of Nampt and NAD+. Thus, in vitro stimulation of CD34+ cells with Nampt led to granulocytic differentiation via activation of sirtuin/C/EBP-dependent pathway. At the same time, inhibitors of NAMPT have been identified as therapeutical targets for some cancers including leukemia. This suggested that different mechanisms are operating downstream of NAMPT in the “normal” and leukemogenic myeloid cells. Screening of the different sirtuins in primary acute myeloid leukemia (AML) blasts revealed significant upregulation of SIRT2 mRNA and protein levels, as compared to CD34+ and CD33+ hematopoietic cells of healthy individuals. SIRT2 levels were also elevated in myeloid cells of CN patients treated with G-CSF. Specific inhibition of NAMPT (using 10 nMol of FK866) or SIRT2 (using 100nMol of AC93253) significantly reduced proliferation and induced apoptosis in human myeloid leukemia cell lines (NB4, HL60 and U937). We further tested if inhibition of Nampt or SIRT2 has an effect on GSK3ß/ß-catenin pathway. GSK3ß is known to be inhibited by Akt and treatment of the acute myeloid leukemia cell lines NB4 and HL60 with FK866 or AC93253 resulted in the activation of Akt via phosphorylation on Thr308 and Ser473 and inactivation of GSK-3ß via inhibition of phosphorylation on Ser9. Moreover, activated ß-catenin protein was almost completely disappeared from the nucleus of cells treated with FK866. Taken together, our results provide strong evidence that NAMPT and SIRT2 participate in leukemogenic transformation via inactivation of GSK3ß leading to nuclear accumulation of oncogenic ß-catenin. Disclosures: No relevant conflicts of interest to declare.

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