scholarly journals Proposed megakaryocytic regulon of p53: the genes engaged to control cell cycle and apoptosis during megakaryocytic differentiation

2012 ◽  
Vol 44 (12) ◽  
pp. 638-650 ◽  
Author(s):  
Pani A. Apostolidis ◽  
Stephan Lindsey ◽  
William M. Miller ◽  
Eleftherios T. Papoutsakis
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Line ◽  
Target Genes ◽  
Control Cell ◽  
P53 Expression ◽  
Megakaryocytic Differentiation ◽  
Knock Down ◽  
Cell Cycling ◽  
And Control

During endomitosis, megakaryocytes undergo several rounds of DNA synthesis without division leading to polyploidization. In primary megakaryocytes and in the megakaryocytic cell line CHRF, loss or knock-down of p53 enhances cell cycling and inhibits apoptosis, leading to increased polyploidization. To support the hypothesis that p53 suppresses megakaryocytic polyploidization, we show that stable expression of wild-type p53 in K562 cells (a p53-null cell line) attenuates the cells' ability to undergo polyploidization during megakaryocytic differentiation due to diminished DNA synthesis and greater apoptosis. This suggested that p53's effects during megakaryopoiesis are mediated through cell cycle- and apoptosis-related target genes, possibly by arresting DNA synthesis and promoting apoptosis. To identify candidate genes through which p53 mediates these effects, gene expression was compared between p53 knock-down (p53-KD) and control CHRF cells induced to undergo terminal megakaryocytic differentiation using microarray analysis. Among substantially downregulated p53 targets in p53-KD megakaryocytes were cell cycle regulators CDKN1A (p21) and PLK2, proapoptotic FAS, TNFRSF10B, CASP8, NOTCH1, TP53INP1, TP53I3, DRAM1, ZMAT3 and PHLDA3, DNA-damage-related RRM2B and SESN1, and actin component ACTA2, while antiapoptotic CKS1B, BCL2, GTSE1, and p53 family member TP63 were upregulated in p53-KD cells. Additionally, a number of cell cycle-related, proapoptotic, and cytoskeleton-related genes with known functions in megakaryocytes but not known to carry p53-responsive elements were differentially expressed between p53-KD and control CHRF cells. Our data support a model whereby p53 expression during megakaryopoiesis serves to control polyploidization and the transition from endomitosis to apoptosis by impeding cell cycling and promoting apoptosis. Furthermore, we identify a putative p53 regulon that is proposed to orchestrate these effects.

TET2 Downregulation Leads to AML Cells Sensitive to Decitabine

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3643-3643
Author(s):  
Qingxiao Chen ◽  
Jingsong He ◽  
Xing Guo ◽  
Jing Chen ◽  
Li Yang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Line ◽  
Cell Lines ◽  
Methylation Status ◽  
Control Cell ◽  
Gene Array ◽  
Expression Level ◽  
Cell Cycle Profile ◽  
Knock Down ◽  
Specific Pcr

Abstract Background: Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults and have very lethal rate. Chemotherapy is the main method to treat AML, but the complete remission rate is still not very optimal. With the development of genetic and molecular biology technologies, more and more molecular biomarkers are found, some of them are useful for us to evaluate the prognosis and can help us to tailor the treatment plan for different patients. TET2, a member of the ten-eleven-translocation(TET) family genes which can modify DNA by catalyzing the conversion of 5mehtyl-cytosine(5-mC) to 5-hydroxymethyl-cytosine(5-hmC), is often inactivated through loss-of-function mutation and deletion in myeloid malignancies. Recent clinical research reported that the lower the expression of TET2 in MDS and AML patients, the better the response to decitabine (DAC, a demethylation agent) will be. However, the mechanism of the phenomenon is still unknown. Our investigation is trying to uncover the mechanism how TET2 protein levels are negatively related with AML sensitivity to decitabine. Methods: We detected TET2 mRNA expression level in acute leukemia cell lines, bone marrow AML specimens and peripheral blood mononuclear cells from healthy donors by semiquantitative real time polymerase chain reaction (qRT-PCR). Western blot is also applied to detect TET2 protein expression. In order to access TET2 methylation status, we used the methylation-specific PCR. And we also checked the mutant status of TET2 in U937 and KG-1 cell line. CCK8 and flow cytometry are used to detect cell proliferation rate, cell apoptosis, and cell cycle profile. Also, we developed TET2 knock-down and overexpression lentivirus to transfect AML cell lines to explore the mechanism why TET2 expression level is related to the response of DAC. Last, gene array is used to compare gene expression level changes between TET2 knock-down cell lines (or TET2 overexpression cell lines) and the control cell lines. Results: The AML cell lines (KG-1, U937, Kasumi, HL-60, THP-1) and AML patients specimens express lower TET2 than that of PBMC from the healthy donor (P<0.05). Among AML cell lines, U937 barely expresses TET2, while KG-1 expresses TET2 relatively higher than other AML cell lines. The methylation-specific PCR showed that TET2 in U937 was partially methylated while KG-1 was not. After using decitabine to treat U937 cell line, the TET2 methylation status was attenuated. And all the exons of TET2 were not detected any mutation in KG-1 AND U937. Then, we used CCK8 to compare the response difference to DAC between U937 and KG-1 and found that U937 is much more sensitive to DAC rather than KG-1 (P<0.05). Next, we constructed a TET2 shRNA to transfect KG-1, both qRT-PCR and WB were used to verification the knock-down efficiency. Again, CCK8 told us that KG-1 TET2 knock-down cells was more sensitive to DAC than KG-1 NC cells. Flow cytometry identified that cell cycle profile were altered between KG-1 TET2 knock-down cells and KG-1 NC cells. Gene array (KG-1 TET2 KD and KG-1 NC) showed that the expression levels of cell cycle related genes (e.g. CCNB2,RBL1), DNA replication related genes (e.g. PRIM1, RCF3, FEN1) and many other function genes were changed between the knock-down and control cell line. Conclusion: Our study showed that the sensitivity to decitabine of AML cell lines is related to TET2 expression level, knock-down TET2 in KG-1 can increase its vulnerability to decitbine. And the mechanism may be related to the changing expression levels of the genes which regulating cell cycles and DNA replication. Disclosures No relevant conflicts of interest to declare.

Eukaryotic elongation factor 1 alpha 2 alone is not sufficient to cause tumorigenicity in immortalized and neoplastic ovarian cell lines

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 15051-15051
Author(s):  
A. L. Leiser ◽  
N. Rosales ◽  
D. Spriggs
Keyword(s):  
Cell Cycle ◽  
Epithelial Cells ◽  
Cell Line ◽  
Cell Lines ◽  
Control Cell ◽  
Stable Expression ◽  
Size Difference ◽  
Ovarian Carcinomas ◽  
Anchorage Independent Growth ◽  
And Control

15051 Background: EEF1a2 is amplified and overexpressed in 25% of ovarian tumors. Previous studies have shown EEF1a2 to have oncogenic and tumorigenic properties in rodent fibroblasts. However, its role in the tumorigenesis and behavior of human ovarian carcinomas is not known. Methods: Stable expression of EEF1a2 cDNA in both T80 immortalized human ovarian surface epithelial cells and SKOV-3 cell line was followed by standard proliferation assays, soft agar assays for anchorage independent growth, cell cycle analysis, mouse xenograft injections, evaluation for changes in factors such as VEGF and ras and susceptibility to CDDP. Transient transfections with 3 different siRNA’s to EEF1a2 were performed in both cell lines. Results: Stable expression of EEF1a2 was detected by Western Blot and IP. Compared to vector only control, transfection with pCMVTag2B EEF1a2 vector did not change proliferation in either cell line. Anchorage independent growth was slightly higher in the T80 transfected cells. Cell cycle and expression of VEGF and ras were not different than control. IC50 of CDDP was similar between the transfected and control cell lines. No size difference was seen in SKOV transfected and control xenografts. T80 controls grew larger and more frequent tumors than transfected controls. Transient transfection of T80 with siRNA did not result in changes in anchorage independent growth. Conclusion: EEF1a2 alone is not sufficient to act induce tumorigenicity, affect tumor growth rate or drug susceptibility in human ovarian epithelial cells. Experiments utilizing stable siRNA vectors specific to EEF1a2 are underway, as well the combination of EEF1a2 with recognized ovarian tumor oncogenes. No significant financial relationships to disclose.

scholarly journals Sirtuin 2 in Endometrial Cancer: A Potential Regulator for Cell Proliferation, Apoptosis and RAS/ERK Pathway

2020 ◽  
Vol 19 ◽  
pp. 153303382098078
Author(s):  
Yanjuan Guo ◽  
Nannan Zhao ◽  
Jianli Zhou ◽  
Jianxin Dong ◽  
Xing Wang
Keyword(s):  
Cell Proliferation ◽  
Endometrial Cancer ◽  
Western Blot ◽  
Cell Line ◽  
Cell Lines ◽  
Erk Pathway ◽  
Uterine Epithelial Cell ◽  
Knock Down ◽  
Ishikawa Cells ◽  
And Control

Objective: The present study aimed to explore the function of sirtuin 2 (SIRT2) on cell proliferation, apoptosis, rat sarcoma virus (RAS)/ extracellular signal-regulated kinase (ERK) pathway in endometrial cancer (EC). Methods: SIRT2 expression in human EC cell lines and human endometrial (uterine) epithelial cell (HEEC) line was assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot. SIRT2 knock-down and control knock-down plasmids were transfected into HEC1A cells, respectively; SIRT2 overexpression and control overexpression plasmids were transfected into Ishikawa cells, respectively. After transfection, SIRT2, HRas proto-oncogene, GTPase (HRAS) expressions were evaluated by RT-qPCR and western blot. ERK and phosphorylated ERK (pERK) expressions were evaluated by western blot. Meanwhile, cell proliferation and cell apoptosis were measured. Results: Compared to normal HEEC cell line, SIRT2 mRNA and protein expressions were increased in most human EC cell lines (including HEC1A, RL952 and AN3CA), while were similar in Ishikawa cell line. In HEC1A cells, SIRT2 knock-down decreased cell proliferation but increased apoptosis. In Ishikawa cells, SIRT2 overexpression induced cell proliferation but inhibited apoptosis. For RAS/ERK pathway, SIRT2 knock-down reduced HRAS and inactivated pERK in HEC1A cells, whereas SIRT2 overexpression increased HRAS and activated pERK in Ishikawa cells, suggesting that SIRT2 was implicated in the regulation of RAS/ERK pathway in EC cells. Conclusion: SIRT2 contributes to the EC tumorigenesis, which appears as a potential therapeutic target.

scholarly journals The RASSF6 Tumor Suppressor Protein Regulates Apoptosis and Cell Cycle Progression via Retinoblastoma Protein

2018 ◽  
Vol 38 (17) ◽  
Author(s):  
Shakhawoat Hossain ◽  
Hiroaki Iwasa ◽  
Aradhan Sarkar ◽  
Junichi Maruyama ◽  
Kyoko Arimoto-Matsuzaki ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Loss Of Function ◽  
Cycle Progression ◽  
P53 Expression ◽  
Cycle Arrest ◽  
Hct116 Cells

ABSTRACT RASSF6 is a member of the tumor suppressor Ras association domain family (RASSF) proteins. RASSF6 is frequently suppressed in human cancers, and its low expression level is associated with poor prognosis. RASSF6 regulates cell cycle arrest and apoptosis and plays a tumor suppressor role. Mechanistically, RASSF6 blocks MDM2-mediated p53 degradation and enhances p53 expression. However, RASSF6 also induces cell cycle arrest and apoptosis in a p53-negative background, which implies that the tumor suppressor function of RASSF6 does not depend solely on p53. In this study, we revealed that RASSF6 mediates cell cycle arrest and apoptosis via pRb. RASSF6 enhances the interaction between pRb and protein phosphatase. RASSF6 also enhances P16INK4A and P14ARF expression by suppressing BMI1. In this way, RASSF6 increases unphosphorylated pRb and augments the interaction between pRb and E2F1. Moreover, RASSF6 induces TP73 target genes via pRb and E2F1 in a p53-negative background. Finally, we confirmed that RASSF6 depletion induces polyploid cells in p53-negative HCT116 cells. In conclusion, RASSF6 behaves as a tumor suppressor in cancers with loss of function of p53, and pRb is implicated in this function of RASSF6.

A MEIS1 Dependent Genetic Program in Leukemia Associated with Cell Cycle Entry and ‘Stemness’

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 746-746
Author(s):  
Ashish Kumar ◽  
Baolin Wu ◽  
John H. Kersey
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Stem Cells ◽  
Neural Stem Cells ◽  
Cell Line ◽  
Fusion Proteins ◽  
Leukemia Cells ◽  
Self Renewal ◽  
Knock Down ◽  
Cell Cycle Entry

Abstract The HOX co-factor MEIS1 is expressed in several leukemias, especially those involving MLL-gene rearrangements. Experimental data have demonstrated that MLL-fusion proteins induce the expression of MEIS1 in hematopoietic cells along with increased self-renewal and recent murine experiments indicate that MEIS1 is central to the growth-promoting effects of MLL fusion proteins. However, the cellular and molecular pathways that are regulated by MEIS1 are unknown. We studied the effect of MEIS1 knock-down in a cell line derived from a leukemic MLL-AF9 knock-in mouse. Transduction of this cell line (4166) with MEIS1-shRNA bearing lentivirus led to significant reduction in MEIS1 expression compared to cells transduced with control virus. The MEIS1 knock-down cells displayed decreased cell cycle entry, while terminal myeloid differentiation and apoptosis were enhanced. To characterize the molecular effects of MEIS1 knock-down, we performed gene expression profiling of leukemia cells with and without MEIS1 expression. We extracted RNA from 5 separate experiments where 4166 cells were transduced with vector control or MEIS1 shRNA for 48 hours and analyzed gene expression profiles using Affymetrix 430 2.0 whole genome arrays. We used a regularized two-sample paired t-test to select genes that were differentially expressed among the two groups. At a false discovery rate (FDR) of ≤ 5%, 1053 probe sets displayed decreased expression with MEIS1 knockdown, while 296 probe sets showed increased expression. Analysis of gene ontology (GO) terms by DAVID (Database for Annotation, Visualization and Integrated Discovery) revealed that the list of genes down-regulated with MEIS1 knock-down was significantly enriched in genes associated with the cell cycle and its regulation (Cdk2, Cdk6, Cdkn3, Ccna2, Cdc7, Cdc42, Rbl1, Wee1) and DNA replication (Brca1, Cdc6, Cdt1, Gmnn, Mcm4, Mcm5, Mcm8). Conversely, the genes displaying increased expression with MEIS1 knockdown were associated with inhibition of proliferation eg. Cdkn1a (p21), Btg2, Btg3 and pro-apoptotic effects such as Bax. A search of the Molecular Signatures Database for previously published profiles that overlap with our list of MEIS1-dependent genes revealed that the profile of MEIS1 knockdown in our murine leukemia cells significantly overlapped with that of neural stem cells. Specifically, of the 1838 genes expressed highly in neural stem cells compared to differentiated brain and bone marrow cells (Ramalho-Santos et al, Science 2002), 155 showed an overlap with the 594 genes in our MEIS1-dependent set (594 gene identifiers contained in 1053 probe sets; p = 3.27 e−28, hypergeometric distribution). This list of 155 genes included MEIS1 and several of the cell cycle and DNA replication-associated genes. These results reveal a core self-renewal genetic program shared by leukemia and neural stem cells that is regulated by MEIS1. Activation of MEIS1 in leukemia and possibly brain tumors could thus enhance self-renewal via the up-regulation of the above common genes. Overall, our results show that MEIS1 regulates cell cycle entry in murine MLL-AF9 leukemia, an effect that enhances self-renewal in other cells as well.

TET2 Downregulation Promotes AML Cell Proliferation Via Pim-1 Expression

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5085-5085
Author(s):  
Qingxiao Chen ◽  
Jingsong He ◽  
Xing Guo ◽  
Jing Chen ◽  
Xuanru Lin ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Flow Cytometry ◽  
Cell Proliferation ◽  
Western Blot ◽  
Cell Lines ◽  
Target Genes ◽  
Leukemia Cell ◽  
Leukemic Cells ◽  
Rna Seq ◽  
Knock Down

Abstract Background: Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults which is still incurable although novel drugs and new combination of chemotherapies are used . With the development of genetic and molecular biology technologies, more and more genes are found to be related to leukemogenesis and drug resistance of AML. TET2, a member of the ten-eleven-translocation gene family which can modify DNA by catalyzing the conversion of 5-mehtyl-cytosine to 5-hydroxymethyl-cytosine , is often inactivated through mutation or deletion in myeloid malignancies. Recent research reported that TET2 knock-down can promote proliferation of hematopoietic stem cells and leukemic cells. Also, several clinical studies showed that patients with TET2 mutation or low levels of TET2 expression have more aggressive disease courses than those with normal levels of TET2. However, the mechanism of the phenomenon is unknown. Our aim is to uncover how TET2 protein level is negatively correlated with AML cell proliferation and to provide a better view of target therapy in AML. Methods: We determined the expression levels of TET2 and other target genes in acute leukemia cell lines, bone marrow AML specimens, and peripheral blood mononuclear cells from healthy donors by qRT-PCR and Western blot. We also determined the mutation status of TET2 in AML cell lines. CCK8 and flow cytometry were used to determine cell proliferation, cell apoptosis, and cell cycle profile. Methylation-specific PCR were used to examine the methylation status in gene promoter regions. Also, we developed TET2 knock-down lentivirus to transfect AML cell lines to examine the effect of TET2 depletion. Last, RNA-seq was used to compare gene expression level changes between TET2 knock-down cell lines and the control cell lines. Results: AML cells from AML cell lines (KG-1,U937, Kasumi, HL-60, THP-1, and MV4-11) and AML patients' specimens expressed lower levels of TET2 than those of PBMC from the healthy donor (P<0.05). Among AML cell lines, U937 barely expressed TET2, while KG-1 expressed TET2 at a relatively higher level than those of other AML cell lines. We constructed a TET2 shRNA to transfect KG-1,THP-1,MV-4-11,Kasumi,and HL-60, and used qRT-PCR and western blot to verify the knock-down efficiency. CCK8 confirmed that knocking down TET2 could increase leukemia cell proliferation (P<0.05). Flow cytometry showed that cell cycle profile was altered in TET2 knock-down cells compared to the negative control cells. In order to identify target genes, we performed RNA-seq on wildtype and TET2 knockdown KG-1 cells and found that the expression of cell cycle related genes, DNA replication related genes, and some oncogenes were changed. We focused on Pim-1, an oncogene related to leukemogenesis, which was significantly up-regulated in the RNA-seq profile. Western blot and qPCR verified the RNA-seq results of Pim-1 expression in the transfected cells . Also, AML patients' bone marrow samples (n=35) were tested by qPCR and 28 of them were found to express low TET2 but high Pim-1 with the other 7 being opposite. For detailed exploration in expression regulation of Pim-1 via TET2, we screened genes affecting Pim-1 expression and found SHP-1, a tumor suppress gene which is often silenced by promoter methylation in AML. Western blot band of SHP-1 was attenuated in TET2 knockdown KG-1 cells. Moreover, methylation-specific PCR showed that after knocking down TET2 in KG-1 cell line, the promoter regions were methylated much more than the control cells. These results indicated that the function of TET2 in epigenetic modulation plays an important role in regulating Pim-1 expression. Finally, using flow cytometry and CCK8 we surprisingly found that knocking down TET2 expression could lead leukemic cells (KG-1, THP-1 and MV-4-11) more sensitive to Pim-1 inhibitor (SGI-1776 free base) and decitabine (a demethylation agent treating MDS and AML) (P<0.05). Conclusion: Our study showed that knocking down TET2 promoted leukemic cell proliferation. This phenomenon may correlate to Pim-1 up-regulation. Our clinical data also showed that the expression of TET2 and Pim-1 have an inverse relationship. The mechanism of TET2 regulating Pim-1 expression may be related to the epigenetic modulation function of TET2. Finally, we found TET2 downregulation could increase leukemia vulnerability to Pim-1 inhibitor and decitbine, and provide a novel view of target therapy in AML. Disclosures No relevant conflicts of interest to declare.

scholarly journals The RASSF6 tumor suppressor protein regulates apoptosis and the cell cycle progression via Retinoblastoma protein

2018 ◽  
Author(s):  
Shakhawoat Hossain ◽  
Hiroaki Iwasa ◽  
Aradhan Sarkar ◽  
Junichi Maruyama ◽  
Kyoko Arimoto-Matsuzaki ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Loss Of Function ◽  
Cycle Progression ◽  
P53 Expression ◽  
Cycle Arrest ◽  
Hct116 Cells

ABSTRACTRASSF6 is a member of the tumor suppressor Ras-association domain family (RASSF) proteins. RASSF6 is frequently suppressed in human cancers and its low expression is associated with poor prognosis. RASSF6 regulates cell cycle arrest and apoptosis and plays a tumor suppressor role. Mechanistically, RASSF6 blocks MDM2-mediated p53 degradation and enhances p53 expression. However, RASSF6 also induces cell cycle arrest and apoptosis in the p53-negative background, which implies that the tumor suppressor function of RASSF6 does not depend solely on p53. In this study, we have revealed that RASSF6 mediates cell cycle arrest and apoptosis via pRb. RASSF6 enhances the interaction between pRb and protein phosphatase. RASSF6 also enhances P16INK4A and P14ARF expression through suppressing BMI1. In this way, RASSF6 increases unphosphorylated pRb and augments the interaction between pRb and E2F1. Moreover, RASSF6 induces TP73-target genes via pRb and E2F1 in the p53-negative background. Finally, we confirmed that RASSF6 depletion induces polypoid cells in p53-negative HCT116 cells. In conclusion, RASSF6 behaves as a tumor suppressor in cancers with the loss-of-function of p53, and pRb is implicated in this function of RASSF6.

scholarly journals NFATC2 regulates Targets of MYC Signaling in MLL-AF9 AML

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3301-3301
Author(s):  
Shaun David Patterson ◽  
Matthew E Massett ◽  
Helen Wheadon ◽  
Xu Huang ◽  
Heather G Jørgensen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Line ◽  
Cell Lines ◽  
Expression Profiles ◽  
Control Cell ◽  
Gene Set Enrichment Analysis ◽  
Transcriptional Networks ◽  
Rna Seq ◽  
Activated T Cells ◽  
Self Renewal

Abstract Background: Acute myeloid leukemia (AML) arises due to an accumulation of genetic lesions within myeloid progenitors and oncogenic transformation is often characterised by disordered transcription. Recently the histone lysine demethylase KDM4A was shown to be essential for AML blast survival and self-renewal. shRNA knockdown (KD) of KDM4A led to downregulated expression of the transcription factor NFATC2 an MLL-AF9 AML model, suggesting that it is a key target of KDM4A oncogenic function. The Nuclear Factor of Activated T Cells (NFAT) family of transcription factors control cell cycle genes and self-renewal pathways in hematopoietic tissues and are well-defined as oncogenic regulators in various malignancies. NFATs have recently been attributed roles in the development of FLT3 ITD AML and resistance to tyrosine kinase inhibitors (TKIs) in myeloid leukemias but there is little evidence detailing the role(s) of NFATC2 specifically in AML. We hypothesized that NFATc2 activity is essential for the survival of AML cells and the oncogenic transcriptional networks within these. Aims: To determine if AML cells are dependent on NFATC2 for survival and to elucidate the transcriptional and binding targets of NFATc2 in AML. Methods: NFATC2 was depleted using shRNA KD in numerous cell line models of AML and putative transcriptional targets were elucidated using RNA-seq following KD. Binding targets of NFATc2 were determined using ChIP-seq. Transcriptomic targets of NFATc2 were validated using the Fluidigm Biomark multiplex PCR system and real time quantitative PCR. Results: KD of NFATC2 significantly impaired the colony forming capacity and expansion in liquid cultures of AML cell lines from diverse (cyto)genetic backgrounds. MLL-AF9/TP53 mut THP-1 cells showed reduced entry to the S-phase of the cell cycle and downregulation of cyclin D1 following NFATC2 depletion, suggesting that NFATC2 is critical for cell cycle progression in these cells. Overexpression of human NFATC2 in THP-1 led to an increased rate of cell growth. RNA-seq analysis of THP-1 cells with NFATC2 KD revealed &gt;20 genes with deregulated expression (FDR&lt;0.1), which have been validated using PCR methods. Overexpression of human NFATC2 resulted in significant deregulation of 9 of these genes (FDR&lt;0.1), defining a subset of genes which may regulate the observed phenotype. Additionally, these top genes were not all differentially regulated in other MLL-AF9 AML cell lines MOLM-13 and NOMO-1 following NFATC2 KD. Finally, in THP-1, gene set enrichment analysis (GSEA) of sequencing results revealed that targets of MYC and calmodulin kinase STK33 were enriched within the genes perturbed by NFATC2 depletion. Targets of MYC signaling were validated by PCR in THP-1 but were not found to be deregulated in MOLM-13 following NFATC2 KD. ChIP-seq analysis of NFATc2 binding in THP-1 cells showed that &gt;30% of NFATc2 targets were at promoter regions within 5kb of the transcription start site. Motif analysis of precipitated DNA fragments discovered two novel motifs which were enriched at NFATc2 binding sites (p&lt;0.0001). Discussion: NFATC2 was found to be essential for expansion of AML cells in various cell line models. In the MLL-AF9 driven THP-1 model a number of putative transcriptional and genomic targets were defined, which include novel targets not previously described in AML pathogenesis and targets of MYC, an established oncogenic protein in AML. The differing expression profiles observed across AML cell lines of diverse (cyto)genetic backgrounds with NFATC2 KD suggest that the regulatory targets of NFATc2 vary depending on the cellular signaling landscape. Together with the finding that NFATC2 is indispensable for AML cell survival this study has elucidated novel roles(s) for NFATC2 in AML oncogenesis. Disclosures Massett: Kymab Ltd: Current Employment. Huang: Janssen Pharmaceutical Companies of Johnson & Johnson (China): Current Employment.

scholarly journals PIM2 Pro-Survival Functions Are Mediated By RSK2 in AML

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 912-912
Author(s):  
Marie-Anne Hospital ◽  
Arnaud Jacquel ◽  
Alexa Green ◽  
Mireille Lambert ◽  
Patrick Auberger ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Line ◽  
Signaling Pathway ◽  
Nuclear Translocation ◽  
Conflicts Of Interest ◽  
Annexin V ◽  
Mapk Signaling ◽  
P53 Expression ◽  
Pim Kinases ◽  
Transcriptional Target

Abstract Acute myeloid leukemia (AML) with FLT3 internal tandem duplication (FLT3-ITD) is a poor prognosis hematologic malignancy accounting for 30% of AML cases. Constitutive FLT3-ITD activation drives STAT5 signaling resulting in enhanced PIM kinases expression. PIM serine/threonine kinases (including PIM1,-2,-3) are involved in cell cycle and apoptosis regulation and thus represent emerging therapeutic targets. We previously reported an increased PIM2 protein expression in primary AML cells compared to normal CD34+ immature hematopoietic cells. Here, we aimed to study PIM kinases as potential therapeutic target in FLT3-ITD AML. In two distinct FLT3-ITD+ human AML cell lines (MV4-11 and MOLM-14) doxycycline (Dox)-induced shRNA-mediated PIM2 knockdown enhanced apoptosis, attested by an increase in early apoptotic (annexin V positive, DAPI negative) and late apoptotic (both annexin V, DAPI positive) cells. Cell death upon PIM2 knockdown was confirmed by an inhibition of colony formation in methylcellulose. Mechanisms of apoptosis induction involved release of second mitochondria-derived activator of caspases (SMAC) as well as increased p53 and Bax expression and Bax nuclear translocation, leading to loss of mitochondrial membrane potential. To gain further mechanistic insights, we performed global gene expression profiling in the MOLM-14 cell line lentivirally transduced with Dox-inducible PIM2 shRNA. Consistent with our functional analysis, cell-cycle regulatory genes (including c-MYC, CHK1 or PLK1) and pro-survival genes (including RSK2 or BCL2) were down-regulated, while pro-apoptotic genes (most notably TP53 and BAX) were up-regulated. Here we focused on RSK2, a member of the mitogen-activated protein kinase (MAPK) signaling pathway that has not been previously reported to be a target of PIM2. In the MOLM-14 cell line, PIM2 knockdown reduced RSK2 mRNA and protein levels. RSK2 knockdown using a Dox-inducible RSK2 shRNA induced apoptosis similarly to that observed following PIM2 knockdown in this cell line. In parallel with PIM2 knockdown, RSK2 down-regulation enhanced p53 expression and activity, as measured by increased expression of its transcriptional target p21, as well as Bax expression. In summary, our results suggest that RSK2 is a PIM2 transcriptional target that contributes to PIM-2-dependent cell survival mediated by a novel RSK2-p53-Bax signaling pathway. RSK2 therefore warrants further study as a potential pharmacologic target in AML (particularly in cases resistant to PIM inhibition) as well as other PIM-addicted malignancies. Disclosures No relevant conflicts of interest to declare.

MLL-AF4 Down-Regulates CDKN1B (P27) Independent of Cell Cycle Progression.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2563-2563
Author(s):  
Zhenbiao Xia ◽  
Relja Popovic ◽  
Tara Lorenz ◽  
Donna Santillan ◽  
Frank Erfurth ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Cell Line ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Leukemia Cell ◽  
Leukemia Cell Line ◽  
Luciferase Reporter ◽  
Cycle Progression ◽  
Downstream Target

Abstract The MLL gene, involved in many chromosomal translocations associated with acute myeloid and lymphoid leukemia, has more than forty known partner genes with which it is able to form in- frame fusions. MLL fusion genes transform hematopoietic cells in vitro, and cause leukemia in mouse models. However, the mechanism is still not clear. Characterizing important downstream target genes may provide rational therapeutic strategies for the treatment of MLL-associated leukemia. We explored potential downstream target genes of the most prevalent MLL fusion protein, MLL-AF4, which is primarily associated with pro-B ALL and is involved in the majority of infant leukemia. To this end, we developed an inducible MLL-AF4 fusion cell line. Overexpression of MLL-AF4 does not lead to increased proliferation in this cell line, but rather, cell growth is slowed compared to similar cell lines inducibly expressing truncated MLL. To try to understand the reason for slower cell growth, we assayed for expression of several CDK inhibitors. We found that in the MLL-AF4 induced cell line, the amount of CDKN1B (cyclin-dependent kinase inhibitor P27) was dramatically decreased both at the RNA and protein levels, in contrast, the levels of CDKN1A (P21) and CDKN2A (P16) were unchanged. Interestingly, we did not observe an increased percentage of cells in S phase of the cell cycle. To explore whether CDKN1B might be a direct target of MLL-AF4, we employed chromatin immunoprecipitation (ChIP) assays and luciferase reporter gene assays. We observed that MLL-AF4 binds to the CDKN1B promoter in vivo and represses CDKN1B promoter activity. Further, we confirmed CDKN1B promoter binding by ChIP assays in the MLL-AF4 leukemia cell line MV4-11. Our results suggest that the CDKN1B may be a downstream target of MLL-AF4, and that MLL-AF4 inhibits CDKN1B expression independent of cell cycle progression.

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