This service exclusively searches for literature that cites resources. Please be aware that the total number of searchable documents is limited to those containing RRIDs and does not include all open-access literature.
Prohibitin (PHB) is a multifunctional protein conserved in eukaryotic systems and shows various expression levels in tumor cells. However, regulation of PHB is not clearly understood. Here, we focused on the regulation of PHB expression by Wnt signaling, one of dominant regulatory signals in various leukemic cells. High mRNA levels of PHB were found in half of clinical leukemia samples. PHB expression was increased by inhibition of the MAPK pathway and decreased by activation of EGF signal. Although cell proliferating signals downregulated the transcription of PHB, treatment with lithium chloride, an analog of the Wnt signal, induced PHB level in various cell types. We identified the TCF-4/LEF-1 binding motif, CATCTG, in the promoter region of PHB by site-directed mutagenesis and ChIP assay. This β-catenin-mediated activation of PHB expression was independent of c‑MYC activation, a product of Wnt signaling. These data indicate that PHB is a direct target of β-catenin and the increased level of PHB in leukemia can be regulated by Wnt signaling.
Although the bcr-abl translocation has been shown to be the causative genetic aberration in chronic myeloid leukemia (CML), there is mounting evidence that the deregulation of other genes, such as the transcription factor interferon regulatory factor 4 (IRF-4), is also implicated in the pathogenesis of CML. Promoter methylation of CpG target sites or direct deletions/insertions of genes are mechanisms of a reversible or permanent silencing of gene expression, respectively. Therefore, we investigated whether IRF-4 promoter methylation or mutation may be involved in the regulation of IRF-4 expression in leukemia cells. Whereas promoter mutations or structural rearrangements could be excluded as a cause of altered IRF-4 expression in hematopoietic cells, the IRF-4 promoter methylation status was found to significantly influence IRF-4 transcription. First, treatment of IRF-4-negative lymphoid, myeloid and monocytic cell lines with the methylation-inhibitor 5-aza-2-deoxycytidine resulted in a time- and concentration-dependent increase of IRF-4 mRNA and protein levels. Second, using a restriction-PCR-assay and bisulfite-sequencing we identified specifically methylated CpG sites in IRF-4-negative but not in IRF-4-positive cells. Third, we clearly determined promoter methylation as a mechanism for IRF-4 down-regulation via reporter gene assays, but did not detect an association of methylational status and mRNA expression of DNA methyltransferases or methyl-CpG-binding proteins. Together, these data suggest CpG site-specific IRF-4 promoter methylation as a putative mechanism of down-regulated IRF-4 expression in leukemia.
Multidrug resistance (MDR) phenotype of malignant cells is the major problem in the chemotherapy of neoplasia. The treatment of leukemia with retinoids is aimed on the induction of leukemic cells differentiation. However the interconnections between retinoid regulated differentiation of leukemic cells and regulation of MDR remains unclear.
Rearrangements of MLL (encoding lysine-specific methyltransferase 2A and officially known as KMT2A; herein referred to as MLL to denote the gene associated with mixed-lineage leukemia) generate MLL fusion proteins that bind DNA and drive leukemogenic gene expression. This gene expression program is dependent on the disruptor of telomeric silencing 1-like histone 3 lysine 79 (H3K79) methyltransferase DOT1L, and small-molecule DOT1L inhibitors show promise as therapeutics for these leukemias. However, the mechanisms underlying this dependency are unclear. We conducted a genome-scale RNAi screen and found that the histone deacetylase SIRT1 is required for the establishment of a heterochromatin-like state around MLL fusion target genes after DOT1L inhibition. DOT1L inhibits chromatin localization of a repressive complex composed of SIRT1 and the H3K9 methyltransferase SUV39H1, thereby maintaining an open chromatin state with elevated H3K9 acetylation and minimal H3K9 methylation at MLL fusion target genes. Furthermore, the combination of SIRT1 activators and DOT1L inhibitors shows enhanced antiproliferative activity against MLL-rearranged leukemia cells. These results indicate that the dynamic interplay between chromatin regulators controlling the activation and repression of gene expression could provide novel opportunities for combination therapy.
To discover the genes responsible for the apoptosis evoked by glucocorticoids in leukemic lymphoid cells, we have begun gene array analysis on microchips. Three clones of CEM cells were compared: C7-14, C1-15 and C1-6. C7-14 and C1-15 are subclones from the original clones C7 (sensitive to apoptosis by glucocorticoids) and C1 (resistant). C1-6 is a spontaneous revertant to sensitivity from the C1 clone. Previously we presented data on the sets of genes whose expression is altered in these cell clones after 20 h exposure to dexamethasone (Dex). The two sensitive clones, which respond by undergoing apoptosis starting about 24h after Dex is added, both showed >2.5-fold induction of 39 genes and 2-fold reduction of expressed levels from 21 genes. C1-15, the resistant clone, showed alterations in a separate set of genes. In this paper, we present further analysis of the data on genes regulated in these cell clones after 20 h Dex and compare them with the genes regulated after 12h Dex. Some, but not all the genes found altered at 20 h are altered at 12h, consistent with our hypothesis that sequential gene regulation eventually provokes full apoptosis. We also compare the levels of basal gene expression in the three clones. At the basal level no single gene stands out, but small sets of genes differ >2-fold in basal expression between the two sensitive and the resistant clone. A number of the genes basally higher in the resistant clone are potentially anti-apoptotic. This is consistent with our hypothesis that the resistant cells have undergone a general shift in gene expression.
Glucocorticoids (GC's) play an integral role in treatment strategies designed to combat various forms of hematological malignancies. GCs also are powerful inhibitors of the immune system, through regulation of appropriate cytokines and by causing apoptosis of immature thymocytes. By activating the glucocorticoid receptor (GR), GCs evoke apoptosis through transcriptional regulation of a complex, interactive gene network over a period of time preceding activation of the apoptotic enzymes. In this study we used microarray technology to determine whether several disparate types of hematologic cells, all sensitive to GC-evoked apoptosis, would identify a common set of regulated genes. We compared gene expression signatures after treatment with two potent synthetic GCs, dexamethasone (Dex) and cortivazol (CVZ) using a panel of hematologic cells. Pediatric CD4+/CD8+ T-cell leukemia was represented by 3 CEM clones: two sensitive, CEM-C7-14 and CEM-C1-6, and one resistant, CEM-C1-15, to Dex. CEM-C1-15 was also tested when rendered GC-sensitive by several treatments. GC-sensitive pediatric B-cell leukemia was represented by the SUP-B15 line and adult B-cell leukemia by RS4;11 cells. Kasumi-1 cells gave an example of the rare Dex-sensitive acute myeloblastic leukemia (AML). To test the generality of the correlations in malignant cell gene sets, we compared with GC effects on mouse non-transformed thymocytes.
Glucocorticoids are commonly used in the first-line treatment of hematological malignancies, such as acute lymphoblastic leukemia, due to the ability of these steroids to activate pro-apoptotic pathways in human lymphocytes. The goal of the current study was to examine the gene expression and enzyme activity of the microsomal enzyme, 11- β hydroxysteroid dehydrogenase type 2 (HSD11B2, HSD2), which is responsible for the oxidation of bioactive glucocorticoids to their inert metabolites. Using the glucocorticoid-sensitive human leukemic cell line, CEM-C7, we were able to detect the expression of HSD2 at the level of mRNA (via RT-PCR), protein (via immunohistochemistry and immunoblotting), and enzyme activity (via conversion of tritiated cortisol to cortisone). Furthermore, we observed that HSD2 enzyme activity is down regulated in CEM-C7 cells that were pretreated with the synthetic glucocorticoid, dexamethasone (100 nM, <15 hours), and that this down regulation of enzyme activity is blocked by the administration of the glucocorticoid receptor antagonist, RU-486. Taken collectively, these data raise the possibility that the effectiveness of glucocorticoids in the treatment of human leukemias may be influenced by: (1) the ability of these neoplastic cells to metabolize glucocorticoids via HSD2 and (2) the ability of these steroids to regulate the expression of this key enzyme.
Oncogenic transcription factors such as the leukemic fusion protein RUNX1/ETO, which drives t(8;21) acute myeloid leukemia (AML), constitute cancer-specific but highly challenging therapeutic targets. We used epigenomic profiling data for an RNAi screen to interrogate the transcriptional network maintaining t(8;21) AML. This strategy identified Cyclin D2 (CCND2) as a crucial transmitter of RUNX1/ETO-driven leukemic propagation. RUNX1/ETO cooperates with AP-1 to drive CCND2 expression. Knockdown or pharmacological inhibition of CCND2 by an approved drug significantly impairs leukemic expansion of patient-derived AML cells and engraftment in immunodeficient murine hosts. Our data demonstrate that RUNX1/ETO maintains leukemia by promoting cell cycle progression and identifies G1 CCND-CDK complexes as promising therapeutic targets for treatment of RUNX1/ETO-driven AML.
The gene encoding PTPROt (truncated isoform of protein tyrosine phosphatase receptor-type O) is methylated and suppressed in chronic lymphocytic leukemia (CLL). PTPROt exhibits in vitro tumor-suppressor characteristics through the regulation of B-cell receptor (BCR) signaling. Here we generated transgenic (Tg) mice with B-cell-specific expression of PTPROt. Although lymphocyte development is normal in these mice, crossing them with TCL1 Tg mouse model of CLL results in a survival advantage compared with the TCL1 Tg mice. Gene expression profiling of splenic B-lymphocytes before detectable signs of CLL followed by Ingenuity Pathway Analysis revealed that the most prominently regulated functions in TCL1 Tg vs non-transgenic (NTg) and TCL1 Tg vs PTPROt/TCL1 double Tg are the same and also biologically relevant to this study. Further, enhanced expression of the chemokine Ccl3, the oncogenic transcription factor Foxm1 and its targets in TCL1 Tg mice were significantly suppressed in the double Tg mice, suggesting a protective function of PTPROt against leukemogenesis. This study also showed that PTPROt-mediated regulation of Foxm1 involves activation of p53, a transcriptional repressor of Foxm1, which is facilitated through suppression of BCR signaling. These results establish the in vivo tumor-suppressive function of PTPROt and identify p53/Foxm1 axis as a key downstream effect of PTPROt-mediated suppression of BCR signaling.
The aim of this study was to investigate the inhibitory mechanism of pure curcumin on WT1 expression in leukemic K562 cells. Pure curcumin suppressed WT1 expression, independent of effects on protein degradation or WT1 mRNA stability. Chromatin immunoprecipitation and reporter gene assays indicate that pure curcumin treatment attenuates WT1 auto-regulation. Interestingly, PKCα inhibition mimicks the repressive effects of pure curcumin in K562 cells. Conversely, myristoylated PKCα over-expression increased WT1 expression and reversed the inhibitory effect of pure curcumin. Our study indicates that pure curcumin attenuates WT1 auto-regulatory function through inhibition of PKCα signaling in K562 cells.
Treatment of leukemia has become much difficult because of resistance to the existing anticancer therapies. This has thus expedited the search for alternativ therapies, and one of these is the exploitation of mesenchymal stem cells (MSCs) towards control of tumor cells. The present study investigated the effect of human umbilical cord-derived MSCs (UC-MSCs) on the proliferation of leukemic cells and gauged the transcriptomic modulation and the signaling pathways potentially affected by UC-MSCs. The inhibition of growth of leukemic tumor cell lines was assessed by proliferation assays, apoptosis and cell cycle analysis. BV173 and HL-60 cells were further analyzed using microarray gene expression profiling. The microarray results were validated by RT-qPCR and western blot assay for the corresponding expression of genes and proteins. The UC-MSCs attenuated leukemic cell viability and proliferation in a dose-dependent manner without inducing apoptosis. Cell cycle analysis revealed that the growth of tumor cells was arrested at the G0/G1 phase. The microarray results identified that HL-60 and BV173 share 35 differentially expressed genes (DEGs) (same expression direction) in the presence of UC-MSCs. In silico analysis of these selected DEGs indicated a significant influence in the cell cycle and cell cycle-related biological processes and signaling pathways. Among these, the expression of DBF4, MDM2, CCNE2, CDK6, CDKN1A, and CDKN2A was implicated in six different signaling pathways that play a pivotal role in the anti-tumorigenic activity exerted by UC-MSCs. The UC-MSCs perturbate the cell cycle process of leukemic cells via dysregulation of tumor suppressor and oncogene expression.
The cell-context dependency for RNA binding proteins (RBPs) mediated control of stem cell fate remains to be defined. Here we adapt the HyperTRIBE method using an RBP fused to a Drosophila RNA editing enzyme (ADAR) to globally map the mRNA targets of the RBP MSI2 in mammalian adult normal and malignant stem cells. We reveal a unique MUSASHI-2 (MSI2) mRNA binding network in hematopoietic stem cells that changes during transition to multipotent progenitors. Additionally, we discover a significant increase in RNA binding activity of MSI2 in leukemic stem cells compared with normal hematopoietic stem and progenitor cells, resulting in selective regulation of MSI2's oncogenic targets. This provides a basis for MSI2 increased dependency in leukemia cells compared to normal cells. Moreover, our study provides a way to measure RBP function in rare cells and suggests that RBPs can achieve differential binding activity during cell state transition independent of gene expression.
Microenvironmental bystander cells are essential for the progression of chronic lymphocytic leukemia (CLL). We have discovered previously that LYN kinase promotes the formation of a microenvironmental niche for CLL. Here we provide mechanistic evidence that LYN regulates the polarization of stromal fibroblasts to support leukemic progression. LYN is overexpressed in fibroblasts of lymph nodes of CLL patients. LYN-deficient stromal cells reduce CLL growth in vivo. LYN-deficient fibroblasts show markedly reduced leukemia feeding capacity in vitro. Multi-omics profiling reveals that LYN regulates the polarization of fibroblasts towards an inflammatory cancer-associated phenotype through modulation of cytokine secretion and extracellular matrix composition. Mechanistically, LYN deletion reduces inflammatory signaling including reduction of c-JUN expression, which in turn augments the expression of Thrombospondin-1, which binds to CD47 thereby impairing CLL viability. Together, our findings suggest that LYN is essential for rewiring fibroblasts towards a leukemia-supportive phenotype.
4-Hydroxynonenal (HNE), produced during oxidative stress, has an antiproliferative/differentiative effect in several tumor cells. Recently, it has been observed that oxidative stress accelerates telomere loss. The length of telomeres depends on the telomerase activity, and the catalytic subunit of telomerase (hTERT) is strongly up-regulated in most human cancers and inhibited by differentiating agents. In this paper the inhibitory effect of HNE on telomerase activity and hTERT expression in three human leukemic cell lines (HL-60, U937, ML-1) is reported. To investigate the molecular mechanism involved in hTERT down-regulation by HNE, the expression of several transcription factors was also studied: in all these cell lines, c-Myc was inhibited, Mad-1 was up-regulated, and Sp-1 was not affected. Moreover, in p53 wild-type ML-1 cells, HNE up-regulated p53 expression. In HL-60 cells, DNA binding activity of c-Myc and Mad-1 to the E-box sequence of the hTERT promoter was inhibited and up-regulated, respectively. In summary, HNE inhibits telomerase activity via decreased hTERT promoter activity, by modulating c-Myc/Mad-1 transcription factor expression.
Caveolin-1 is a structural protein that may function as a scaffold for plasma membrane proteins, one of which is P-glycoprotein (P-gp), product of the multidrug resistance-1 (MDR-1) gene. We tested the hypothesis that if P-gp and caveolin-1 interacted physically, caveolin-1 and MDR-1 genes might be coordinately regulated; by quantifiying their gene expression with quantitative-polymerase chain reaction. MDR-1 and caveolin-1 gene expressions were normalized to an internal control and related to a fixed calibrator by a comparative cycle-threshold (CT) method. In four different groups of marrow samples (20 normal, 56 acute myeloid leukemias (AML) at diagnosis, 48 AMLs at relapse, and 51 regenerating marrows), caveolin-1 and MDR-1 gene expressions were positively correlated. In 65 samples with MDR-1 over-expression, caveolin-1 and MDR-1 expressions were also correlated. The coordinate expression of caveolin-1 and MDR-1 suggests that they may either interact physically, or are involved in the same aberrant pathway(s) activated during MDR-1 up-regulation.
Homeobox (HOX) genes deregulation has been largely implicated in the development of human leukemia. Among the HOXB cluster, HOXB1 was silent in a number of analyzed acute myeloid leukemia (AML) primary cells and cell lines, whereas it was expressed in normal terminally differentiated peripheral blood cells.
TRIM28/KAP1/TIF1β is a crucial epigenetic modifier. Genetic ablation of trim28 is embryonic lethal, although RNAi-mediated knockdown in somatic cells yields viable cells. Reduction in TRIM28 abundance at the cellular or organismal level results in polyphenism. Posttranslational modifications such as phosphorylation and sumoylation have been shown to regulate TRIM28 activity. Moreover, several lysine residues of TRIM28 are subject to acetylation, but how acetylation of TRIM28 affects its functions remains poorly understood. Here, we report that, compared with wild-type TRIM28, the acetylation-mimic mutant TRIM28-K304Q has an altered interaction with Krüppel-associated box zinc-finger proteins (KRAB-ZNFs). The TRIM28-K304Q knock-in cells were created in K562 erythroleukemia cells by CRISPR-Cas9 (Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein nuclease 9) gene editing method. Transcriptome analysis revealed that TRIM28-K304Q and TRIM28 knockout K562 cells had similar global gene expression profiles, yet the profiles differed considerably from wild-type K562 cells. The expression levels of embryonic-related globin gene and a platelet cell marker integrin-beta 3 were increased in TRIM28-K304Q mutant cells, indicating the induction of differentiation. In addition to the differentiation-related genes, many zinc-finger-proteins genes and imprinting genes were activated in TRIM28-K304Q cells; they were inhibited by wild-type TRIM28 via binding with KRAB-ZNFs. These results suggest that acetylation/deacetylation of K304 in TRIM28 constitutes a switch for regulating its interaction with KRAB-ZNFs and alters the gene regulation as demonstrated by the acetylation mimic TRIM28-K304Q.
Cancer stem cells drive disease progression and relapse in many types of cancer. Despite this, a thorough characterization of these cells remains elusive and with it the ability to eradicate cancer at its source. In acute myeloid leukemia (AML), leukemic stem cells (LSCs) underlie mortality but are difficult to isolate due to their low abundance and high similarity to healthy hematopoietic stem cells (HSCs). Here, we demonstrate that LSCs, HSCs, and pre-leukemic stem cells can be identified and molecularly profiled by combining single-cell transcriptomics with lineage tracing using both nuclear and mitochondrial somatic variants. While mutational status discriminates between healthy and cancerous cells, gene expression distinguishes stem cells and progenitor cell populations. Our approach enables the identification of LSC-specific gene expression programs and the characterization of differentiation blocks induced by leukemic mutations. Taken together, we demonstrate the power of single-cell multi-omic approaches in characterizing cancer stem cells.
Drug resistance remains a serious problem in leukemia therapy. Among newly developed nucleoside antimetabolites, clofarabine has broad cytotoxic activity showing therapeutic promise and is currently approved for relapsed acute lymphoblastic leukemia. To investigate the mechanisms responsible for clofarabine resistance, we established two clofarabine-resistant lymphoblastic leukemia cell lines from parental lines. To elucidate the mechanisms against clofarabine resistance in two newly established clofarabine-resistant cell lines, we measured the expression of export pumps multidrug resistance protein 1, multidrug resistance-associated protein 1, and ATP-binding cassette subfamily G member 2. There were no differences in the expression between clofarabine-sensitive and -resistant cell lines. Next, we determined expression of deoxycytidine kinase (dCK), which phosphorylates clofarabine to exert cytotoxicity, in clofarabine-sensitive and -resistant cells. Clofarabine-resistant cells showed significantly decreased expression of dCK RNA when compared with sensitive cells. To elucidate the mechanisms of decreased dCK expression in clofarabine-resistant cells, we analyzed the methylation status of CpG islands of the dCK promoter and found no differences in methylation status between clofarabine-sensitive and -resistant cells. Next, we measured the acetylation status of histone and found that total histone acetylation, and histone H3 and H4 acetylation on chromatin immunoprecipitation assay were significantly decreased in resistant cells. Melatonin is an indolamine that functions in the regulation of chronobiological rhythms to exert cytotoxic effects. We examined the effects of melatonin in clofarabine-resistant cells and found that melatonin treatment led to significantly increased cytotoxicity with clofarabine in resistant cells via increased acetylation. Melatonin may be a useful candidate for overcoming clofarabine resistance in two newly established clofarabine resistant leukemia cell lines.
Hox genes play important roles in haematopoietic development in mammals. ASH1 is a member of the trithorax group (trxG) that is required for proper expression of Hox genes and is preferentially expressed in haematopoietic stem cells. We have recently reported that ASH1 methylates histone H3 at lysine 36 (K36) but its biological function has remained elusive. Here we show that ASH1 regulates Hox gene expression positively and negatively in a leukemic cell line K562 and is required for myelomonocytic differentiation of murine haematopoietic stem cells. ASH1 binds to endogenous Hox loci in K562 cells and its knockdown causes reduced expression of Hox genes. In addition, ASH1 and MLL1 induce more than 100-fold activation of Hox promoters in HeLa cells if expressed simultaneously but not individually. Notably, ASH1 harbouring a point mutation that kills methyltransferase activity is more efficient than wild type ASH1 in Hox gene activation, indicating that K36 methylation is not a prerequisite for Hox gene expression. Moreover, tethering wild type or catalytically inactive methyltransferase domain of ASH1 to a heterologous promoter causes downregulation or upregulation, respectively, of transcription, supporting a hypothesis that K36 methylation imparts repression. Knockdown of ASH1 in K562 cells in vitro causes increased expression of ε-globin gene and reduced expression of myelomonocytic markers GPIIb and GPIIIa, whereas knockdown of ASH1 in murine haematopoietic stem cells in vivo results in decreased number of macrophages and granulocytes, a phenotype similar to that induced by loss of mll1 function. Taken together, our data suggest that ASH1 and MLL1 synergize in activation of Hox genes and thereby regulate development of myelomonocytic lineages from haematopoietic stem cells.
Welcome to the FDI Lab - SciCrunch.org Resources search. From here you can search through a compilation of resources used by FDI Lab - SciCrunch.org and see how data is organized within our community.
You are currently on the Community Resources tab looking through categories and sources that FDI Lab - SciCrunch.org has compiled. You can navigate through those categories from here or change to a different tab to execute your search through. Each tab gives a different perspective on data.
If you have an account on FDI Lab - SciCrunch.org then you can log in from here to get additional features in FDI Lab - SciCrunch.org such as Collections, Saved Searches, and managing Resources.
Here is the search term that is being executed, you can type in anything you want to search for. Some tips to help searching:
You can save any searches you perform for quick access to later from here.
We recognized your search term and included synonyms and inferred terms along side your term to help get the data you are looking for.
If you are logged into FDI Lab - SciCrunch.org you can add data records to your collections to create custom spreadsheets across multiple sources of data.
Here are the facets that you can filter your papers by.
From here we'll present any options for the literature, such as exporting your current results.
If you have any further questions please check out our FAQs Page to ask questions and see our tutorials. Click this button to view this tutorial again.
Year:
Count: