Transfected K562 Cells Research Articles

Tumor suppressor miR-520a inhibits cell growth by negatively regulating PI3K/AKT signaling pathway in acute myeloid leukemia.

Short regulatory RNAs, called microRNAs (miRNAs), have been found to possess regulatory functions in cancer and, as such, have recently been evaluated for their therapeutic role against various human malignancies. The present work aimed to investigate whether miR-520a can play a therapeutic role in the treatment of human acute myeloid leukemia. Human myeloid leukemia cell lines (Kasumi-1, Kasumi-3, Kasumi-6, BDCM, and K562) and a normal myeloid cell line (NCI-H5N6) were used for the study. Cell lines were subjected to real-time quantitative polymerase chain reaction (RT-qPCR), evaluation of cell viability and proliferation by MTT assay and colony formation assays. Dual acridine orange (AO)/ethidium bromide (EB) staining was applied for transfected K562 cells with miR-negative control (NC) or miR-520a mimics, and annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) dual staining and flow cytometry were performed to analyze cancer cell apoptosis followed by western blot. Cancerous cell lines exhibited lower gene expression of miR-520a, and its overexpression significantly reduced (p < 0.05) the proliferation and viability of cancer cells. Cancer cells demonstrated the induction of Bax/Bcl-2-mediated apoptosis following miR-520a overexpression. The miR-520a was shown to target the PI3K/AKT signaling pathway in human acute myeloid leukemia to exercise its regulatory role in cancer. The study showed that miR-520a actively regulated cell proliferation in acute myeloid leukemia and illustrated the mechanism by which it exerts its regulatory role, emphasizing the possibility of targeting miR-520a as an efficient therapeutic strategy against human acute myeloid leukemia.

Construction of Lentiviral Vector for miR-217 Overexpression and Knockdown and Its Effect on CML.

We attempted to construct a myeloid leukemia cell strain for stable overexpression and knock-down of miR-217 and explored the possible mechanism underlying miR-217 in chronic myeloid leukemia (CML). MiR-217 overexpression and the knock-down lentiviral vector with puromycin resistance were constructed and packaged within recombinant lentivirus. Stably transfected K562 cells were obtained through puromycin screening, and the qPCR assay detected the relative expression of the target gene. The proliferation, apoptosis, and methylation level of PER2 within cultured cells were detected using the CCK-8 assay, flow cytometry, and TaqMan real‑time fluorescence quantitative methylation-specific PCR. qPCR and Western blot detected the expression of miR-217-related genes within the constructed K562 cell model. Colony PCR and sequencing proved that recombinant lentivirus expression vectors pSE16 and pSE17 were correctly constructed. The lentivirus titer was 2.95 × 109 and 2.61 × 109IU/mL. The miR-217 expression level was high in pSE5316-K562 cells, and that of the miR-217 sponge was high in pSE5317-K562 cells. Overexpressed miR-217 could inhibit the K562 cell proliferation and induce apoptosis. Inhibition of miR-217 enhanced the expression of DNMT3A, decreased the PER2 expression, and elevated the degree of PER2 methylation. The miR-217 overexpression and knock-down of the K562 cell line were successfully constructed, providing a tool for further exploring the miR-217 mechanism in CML. DNMT3A could be the molecular target of miR-217 by regulating PER2 gene methylation and getting involved with the occurrence and development of CML.

Effects of hsa-miR-9-3p and hsa-miR-9-5p on Topoisomerase IIβ Expression in Human Leukemia K562 Cells with Acquired Resistance to Etoposide.

DNA topoisomerase IIα (TOP2α/170; 170 kDa) and topoisomerase IIβ (TOP2β/180; 180 kDa) are targets for a number of anticancer drugs, whose clinical efficacy is attenuated by chemoresistance. Our laboratory selected for an etoposide-resistant K562 clonal subline designated K/VP.5. These cells exhibited decreased TOP2α/170 and TOP2β/180 expression. We previously demonstrated that a microRNA-9 (miR-9)-mediated posttranscriptional mechanism plays a role in drug resistance via reduced TOP2α/170 protein in K/VP.5 cells. Here, it is hypothesized that a similar miR-9 mechanism is responsible for decreased TOP2β/180 levels in K/VP.5 cells. Both miR-9-3p and miR-9-5p are overexpressed in K/VP.5 compared with K562 cells, demonstrated by microRNA (miRNA) sequencing and quantitative polymerase chain reaction. The 3'-untranslated region (3'-UTR) of TOP2β/180 contains miRNA recognition elements (MRE) for both miRNAs. Cotransfection of K562 cells with a luciferase reporter plasmid harboring TOP2β/180 3'-UTR plus miR-9-3p or miR-9-5p mimics resulted in statistically significant decreased luciferase expression. miR-9-3p and miR-9-5p MRE mutations prevented this decrease, validating direct interaction between these miRNAs and TOP2β/180 mRNA. Transfection of K562 cells with miR-9-3p/5p mimics led to decreased TOP2β protein levels without a change in TOP2β/180 mRNA and resulted in reduced TOP2β-specific XK469-induced DNA damage. Conversely, K/VP.5 cells transfected with miR-9-3p/5p inhibitors led to increased TOP2β/180 protein without a change in TOP2β/180 mRNA and resulted in enhancement of XK469-induced DNA damage. Taken together, these results strongly suggest that TOP2β/180 mRNA is translationally repressed by miR-9-3p/5p, that these miRNAs play a role in acquired resistance to etoposide, and that they are potential targets for circumvention of resistance to TOP2-targeted agents. SIGNIFICANCE STATEMENT: Results presented here indicate that miR-9-3p and miR-9-5p play a role in acquired resistance to etoposide via decreased DNA topoisomerase IIβ 180 kDa protein levels. These findings contribute further information about and potential strategies for circumvention of drug resistance by modulation of microRNA levels. In addition, miR-9-3p and miR-9-5p overexpression in cancer chemoresistance may lead to future validation as biomarkers of responsiveness to DNA topoisomerase II-targeted therapy.

A Gene Transfer-Positive Cell Sorting System Utilizing Membrane-Anchoring Affinity Tag.

Gene delivery efficiency is an essential limit factor in gene study and gene therapy, especially for cells that are hard for gene transfer. Here we develop an affinity cell sorting system that allows efficient enrichment of gene transfer-positive cells. The system expresses an enhanced green fluorescent protein (EGFP) fused with an N-terminal high-affinity Twin-Strep-Tag (TST) that will be anchored to the cell membrane at the out-surface through a glycosylphosphatidylinositol (GPI) membrane-anchoring structure. The EGFP permits microscopy and flow cytometry analysis of the gene transfer-positive cells, and the TST tag at the N terminal of EGFP allows efficient affinity sorting of the positive cells using Strep-Tactin magnetic beads. The cell sorting system enables efficient isolation of gene transfer-positive cells in a simple, convenient, and fast manner. Cell sorting on transfected K-562 cells resulted in a final positive cell percentage of up to 95.0% with a positive cell enrichment fold of 5.8 times. The applications in gene overexpression experiments could dramatically increase the gene overexpression fold from 10 times to 58 times, and in shRNA gene knockdown experiments, cell sorting increased the gene knockdown efficiency from 12% to 53%. In addition, cell sorting in CRISPR/Cas9 genome editing experiments allowed more significant gene modification, with an editing percentage increasing from 20% to 79%. The gene transfer-positive cell sorting system holds great potential for all gene transfer studies, especially on those hard-to-transfect cells.

Effects of hsa‐miR‐9‐3p and hsa‐miR‐9‐5p on Topoisomerase IIβ Expression in Human Leukemia K562 Cells with Acquired Resistance to Etoposide

DNA topoisomerase IIα (TOP2α/170; 170kDa) and Topoisomerase IIβ (TOP2β/180; 180kDa) are important targets for DNA damage‐stabilizing anticancer drugs, whose clinical efficacy is often attenuated by chemoresistance. Our laboratory has characterized an etoposide‐resistant human leukemia K562 clonal subline, designated K/VP.5. These cells show a decrease in both TOP2α/170 and TOP2β/180 expression. We recently demonstrated that a microRNA (miRNA)‐mediated post transcriptional mechanism plays a role in drug resistance via reduced TOP2α/170 protein levels in K/VP.5 cells. We hypothesize that a miRNA mechanism is similarly responsible for decreased TOP2β/180 levels in K/VP.5 cells. Both miR‐9‐3p and miR‐9‐5p are overexpressed in K/VP.5 compared with K562 cells, demonstrated by miRNA sequencing, and validated by quantitative polymerase chain reaction (qPCR). The 3’‐untranslated region (UTR) of TOP2β/180 contains a well‐defined miRNA recognition element (MRE) for miR‐9‐5p and putative MREs for miR‐9‐3p. Co‐transfection of K562 cells with a luciferase reporter plasmid harboring TOP2β/180‐3’UTR plus miR‐9‐3p and/or miR‐9‐5p mimics resulted in a statistically significant decrease in luciferase expression. miR‐9‐5p MRE mutation prevented this decrease validating direct interaction between this miRNA and TOP2β/180 mRNA. Transfection of K562 cells with miR‐9‐3p or miR‐9‐5p mimics led to decreased TOP2β protein levels without a change in TOP2β/180 mRNA. Inversely, K/VP.5 cells transfected with miR‐9‐3p or miR‐9‐5p inhibitors led to increased TOP2β/180 protein and no change in TOP2β/180 mRNA. Taken together, these results strongly suggest that TOP2β/180 mRNA is translationally repressed by miR‐9‐3p and miR‐9‐5p, and that these miRNAs play a role in acquired resistance to etoposide via regulation of TOP2β/180. Further experiments are underway to characterize miR‐9‐3p and miR‐9‐5p effects on TOP2β/180‐specific cytotoxicity.

A Deep Exon Cryptic Splice Site Promotes Aberrant Intron Retention in a Von Willebrand Disease Patient.

A translationally silent single nucleotide mutation in exon 44 (E44) of the von Willebrand factor (VWF) gene is associated with inefficient removal of intron 44 in a von Willebrand disease (VWD) patient. This intron retention (IR) event was previously attributed to reordered E44 secondary structure that sequesters the normal splice donor site. We propose an alternative mechanism: the mutation introduces a cryptic splice donor site that interferes with the function of the annotated site to favor IR. We evaluated both models using minigene splicing reporters engineered to vary in secondary structure and/or cryptic splice site content. Analysis of splicing efficiency in transfected K562 cells suggested that the mutation-generated cryptic splice site in E44 was sufficient to induce substantial IR. Mutations predicted to vary secondary structure at the annotated site also had modest effects on IR and shifted the balance of residual splicing between the cryptic site and annotated site, supporting competition among the sites. Further studies demonstrated that introduction of cryptic splice donor motifs at other positions in E44 did not promote IR, indicating that interference with the annotated site is context dependent. We conclude that mutant deep exon splice sites can interfere with proper splicing by inducing IR.

ABCG2 Is Overexpressed on Red Blood Cells in Ph-Negative Myeloproliferative Neoplasms and Potentiates Ruxolitinib-Induced Apoptosis.

Myeloproliferative neoplasms (MPNs) are a group of disorders characterized by clonal expansion of abnormal hematopoietic stem cells leading to hyperproliferation of one or more myeloid lineages. The main complications in MPNs are high risk of thrombosis and progression to myelofibrosis and leukemia. MPN patients with high risk scores are treated by hydroxyurea (HU), interferon-α, or ruxolitinib, a tyrosine kinase inhibitor. Polycythemia vera (PV) is an MPN characterized by overproduction of red blood cells (RBCs). ABCG2 is a member of the ATP-binding cassette superfamily transporters known to play a crucial role in multidrug resistance development. Proteome analysis showed higher ABCG2 levels in PV RBCs compared to RBCs from healthy controls and an additional increase of these levels in PV patients treated with HU, suggesting that ABCG2 might play a role in multidrug resistance in MPNs. In this work, we explored the role of ABCG2 in the transport of ruxolitinib and HU using human cell lines, RBCs, and in vitro differentiated erythroid progenitors. Using stopped-flow analysis, we showed that HU is not a substrate for ABCG2. Using transfected K562 cells expressing three different levels of recombinant ABCG2, MPN RBCs, and cultured erythroblasts, we showed that ABCG2 potentiates ruxolitinib-induced cytotoxicity that was blocked by the ABCG2-specific inhibitor KO143 suggesting ruxolitinib intracellular import by ABCG2. In silico modeling analysis identified possible ruxolitinib-binding site locations within the cavities of ABCG2. Our study opens new perspectives in ruxolitinib efficacy research targeting cell types depending on ABCG2 expression and polymorphisms among patients.

Hsa-miR-9-3p and hsa-miR-9-5p as Post-Transcriptional Modulators of DNA Topoisomerase IIα in Human Leukemia K562 Cells with Acquired Resistance to Etoposide.

DNA topoisomerase IIα protein (TOP2α) 170 kDa (TOP2α/170) is an important target for anticancer agents whose efficacy is often attenuated by chemoresistance. Our laboratory has characterized acquired resistance to etoposide in human leukemia K562 cells. The clonal resistant subline K/VP.5 contains reduced TOP2α/170 mRNA and protein levels compared with parental K562 cells. The aim of this study was to determine whether microRNA (miRNA)-mediated mechanisms play a role in drug resistance via decreased expression of TOP2α/170. miRNA-sequencing revealed that human miR-9-3p and miR-9-5p were among the top six of those overexpressed in K/VP.5 compared with K562 cells; validation by quantitative polymerase chain reaction demonstrated overexpression of both miRNAs. miRNA recognition elements (MREs) for both miRNAs are present in the 3'-untranslated region (UTR) of TOP2α/170. Transfecting K562 cells with a reporter plasmid harboring the TOP2α/170 3'-UTR together with either miR-9-3p or miR-9-5p mimics resulted in a statistically significant decrease in luciferase expression. Mutating the miR-9-3p or miR-9-5p MREs prevented this decrease, demonstrating direct interaction between these miRNAs and TOP2α/170 mRNA. Transfection of K562 cells with miR-9-3p or miR-9-5p mimics led to decreased TOP2α/170 protein levels without a change in TOP2α/170 mRNA and resulted in attenuated etoposide-induced DNA damage (gain-of-miRNA-inhibitory function). Conversely, transfection of miR-9-3p or miR-9-5p inhibitors in K/VP.5 cells (overexpressed miR-9 and low TOP2α/170) led to increased TOP2α/170 protein expression without a change in TOP2α/170 mRNA levels and resulted in enhancement of etoposide-induced DNA damage (loss-of-miRNA-inhibitory function). Taken together, these results strongly suggest that these miRNAs play a role in and are potential targets for circumvention of acquired resistance to etoposide. SIGNIFICANCE STATEMENT: Results presented here indicate that miR-9-3p and miR-9-5p decrease DNA topoisomerase IIα protein 170 kDa expression levels in acquired resistance to etoposide. These findings contribute new information about and potential strategies for circumvention of drug resistance by modulation of microRNA levels. Furthermore, increased expression of miR-9-3p and miR-9-5p in chemoresistant cancer cells may support their validation as biomarkers of responsiveness to DNA topoisomerase II-targeted therapy.

Continuous Cytostatic Effects of BCR-ABL Tyrosine Kinase Inhibitors (TKIs) after Washout in Human Leukemic K562 Cells.

Tyrosine kinase inhibitors (TKIs) are used as the first choice for chronic myeloid leukemia (CML) pharmacotherapeutics. Some patients taking these drugs showed good therapeutic reactivity despite the disappearance of drugs from blood. We investigated whether these drugs have sustained effects even after their disappearance and whether their effects depend on their amounts of intracellular accumulation. Cell proliferation after exposure of K562 cells or Multidrug resistance-1 (MDR-1)-transfected K562 cells was determined by a cell counting kit-8 assay. The intracellular accumulation amount of the drug showing a sustained cytostatic effect was measured by ultra high performance liquid chromatography mass spectrometry. Cell viability decreased in a culture time-dependent manner after washing out nilotinib and dasatinib. The sustained cytostatic effect of dasatinib, but not that of nilotinib, correlated with the intracellular accumulation level. In contrast, imatinib showed continuous a cytostatic effect after drug washout for long-term exposure but not after drug washout for short-term exposure. These results suggest that a good response in patients with a low serum concentration of imatinib, nilotinib or dasatinib may be due to the cytostatic effect of that drug continues even after its disappearance in plasma.

H22954, a novel long non-coding RNA down-regulated in AML, inhibits cancer growth in a BCL-2-dependent mechanism.

Long non-coding RNAs (lncRNAs) are important in cancer biology. In this study, we analyzed differentially expressed genes in CD34 + hematopoietic cells and identified a novel lncRNA, H22954, which was down-regulated in acute myeloid leukemia (AML) patients. In cultured AML cells and mouse xenograft models, H22954 expression inhibited cell proliferation and tumor growth, respectively. Bioinformatic analysis and RNA antisense purification assay indicated that H22954 targeted the 3' untranslated region of the BCL2 gene. In luciferase assays, H22954 expression inhibited BCL2 expression. In transfected K562 cells and mouse xenograft tumors, H22954 overexpression reduced BCL-2 protein levels and promoted cell death. In AML patients, H22954 expression inversely correlated with BCL-2 protein levels in bone marrow cells, blast cell numbers and disease prognosis. These results indicate that H22954 is a novel regulator of BCL-2 and that reduced H22954 expression may play an important role in the pathogenesis of AML.

MiR‐9 as Post‐Transcriptional Modulator of DNA Topoisomerase IIα (TOP2α) in Human Leukemia K562 Cells with Acquired Resistance to the Anticancer Drug Etoposide

microRNAs (miRNAs) are short, noncoding RNAs that inhibit translation by binding primarily to the 3′‐untranslated region (3′‐UTR) of mRNA. The enzyme TOP2α induces covalent complexes with DNA and produces transient double‐strand DNA breaks crucial for processes such as replication and normal chromosomal dysjunction at mitosis. TOP2α is an important target for clinically effective anticancer agents, such as etoposide (VP‐16) since these drugs stabilize the otherwise short‐lived enzyme‐DNA covalent complexes, thereby inducing cytotoxic DNA damage. However, the efficacy of these agents is limited by chemoresistance. Our lab has characterized acquired resistance to VP‐16 in human leukemia K562 cells. This cloned resistant cell line, K/VP.5, contains reduced levels of TOP2α compared to parental K562 cells. The goal of this project is to test the hypothesis that TOP2α levels are decreased in K/VP.5 cells, in part, through miRNA‐mediated mechanisms.Pooled miRNA qPCR profiling experiments were performed to investigate the expression levels of ~500 miRNAs in K562 and K/VP.5 cells. hsa‐miR‐9‐3p and ‐5p (miR‐9‐3p and ‐5p) were overexpressed in K/VP.5 cells compared to K562 cells. The TOP2α 3′‐UTR harbors putative miRNA recognition elements (MRE) for these miRNAs. Therefore, these miRNAs were chosen for further study. To assess post‐transcriptional regulation of TOP2α by miRNAs, a dual luciferase reporter plasmid harboring the entire 3′‐UTR of TOP2α mRNA (998 bp) was constructed (psiTOP2α/UTR). Transfection with psiTOP2α/UTR demonstrated decreased luciferase expression in K/VP.5 compared with K562 cells (p&lt;0.001), suggesting altered post‐transcriptional regulation in resistant cells. K562 cells that were co‐transfected with psiTOP2α/UTR and miR‐9‐5p or ‐3p mimic resulted in a decrease in luciferase expression only for miR‐9‐5p (p&lt;0.001). Mutating the putative miR‐9‐5p seed sequence prevented the decrease in luciferase activity, demonstrating a direct interaction of this miRNA with the MRE of TOP2α. Immunoblotting for TOP2α in K562 cells transfected with miR‐9‐3p or ‐5p mimic resulted in decreased TOP2α protein compared to mock transfected K562 cells (miR‐9‐3p; p&lt;0.05, miR‐9‐5p; p=0.01). In contrast, immunoblotting for TOP2α in K/VP.5 cells transfected with miR‐9‐3p or ‐5p inhibitor resulted in an increase of TOP2α protein (p&lt;0.05), strongly suggesting a role for both miRNAs in acquired resistance to VP‐16.Our findings indicate that miR‐9‐3p and ‐5p reduce TOP2α expression levels. In addition, results presented here contribute to the elucidation of chemoresistance mechanisms and have the translational potential for circumvention of drug resistance by modulation of miRNA concentrations.Support or Funding InformationPatrick and Jane O'Neill Endowed Scholarship, Honors and Scholars Enrichment Grant, Research Scholars AwardThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Disruption of SOX6 gene using CRISPR/Cas9 technology for gamma-globin reactivation: An approach towards gene therapy of β-thalassemia.

Elevation of Hemoglobin F ameliorates symptoms of β-thalassemia, a common autosomal recessive disorder. The transcription factor SOX6 plays a key role in the γ to β-globin gene switching. In the current investigation, a mutation was induced using the CRISPR/Cas9 technology in the binding domain region of SOX6 to reactivate γ-globin expression. Three CRISPR/Cas9 cassettes were provided, whose single-guide RNAs targeted different regions in the SOX6 gene-binding domain. After transfection of K562 cells with CRISPR a, b and c, and subsequent erythroid differentiation, the indel percentage of the cells was about 30%, 25%, and 24%, respectively. Relative quantification showed that the γ-globin mRNA level increased to 1.3-, 2.1-, and 1.1-fold in the cells treated with CRISPR/Cas9 a, b, and c, respectively, compared with untreated cells. Our results show that mutation induction in the binding site of the SOX6 gene leads to γ-globin reactivation. These findings support the idea that CRISPR interrupts the SOX6 binding site, and, as a result, SOX6 is incapable of binding the γ-globin promoter. In conclusion, SOX6 disruption could be considered as a therapeutic approach for β-thalassemia treatment. CRISPR/Cas9 was selected for this purpose as it is the most rapidly evolving technology.

SF3B1 Gene Expression in Erythroid Cells Is Regulated By Intron Retention Via a Posttranscriptional Mechanism Involving Cryptic Exons Proposed to Function As Splicing Decoys

Proper expression of the MDS-disease gene, SF3B1, ensures appropriate pre-mRNA splicing in erythroid progenitors and during terminal erythropoiesis. We previously showed that the SF3B1 gene is post-transcriptionally regulated in a differentiation stage-specific manner by intron retention (IR), such that ~50% of its transcripts in mature erythroblasts retain intron 4. Based on new mechanistic studies, we propose a model in which mostly unannotated and noncoding exons within intron 4 function as splicing decoys; i.e., they promote retention of intron 4 by interacting with, and blocking splice sites of, the adjacent exons 4 and 5. A total of six putative decoy exons were revealed via RT-PCR and RNA-seq analysis of RNA from erythroblasts treated with inhibitors of nonsense-mediated decay. That decoy exons have IR-promoting activity is suggested by several criteria. First, the frequency of interaction between constitutive exons 4 and 5 and putative decoy exons within intron 4, measured by the abundance of splice junctions in RNA-seq read data, is temporally correlated with levels of intron 4 retention during terminal erythropoiesis. Both IR and decoy splice junctions were low in early stage erythroblasts and much higher in mature erythroblasts. Second, selected decoy exons exhibited IR-promoting activity in the context of minigene splicing reporters expressing the exon 3-6 region of SF3B1 in transfected K562 cells. The wild type minigene reproduced the intron-specific retention phenotype, since it was fully spliced at introns 3 and 5 but exhibited substantial retention of intron 4, whereas deletion of decoy exon 4e, or mutation of its splice sites, substantially decreased IR. Third, RBP (RNA binding protein) cross-linking data from K562 cells show that 3‘ splice site factors including U2AF1 and U2AF2 can bind specifically to 3‘ splice sites of intron 4's decoy exons. Finally, several experiments showed that IR-promoting activity of decoy exons is a more general phenomenon that likely governs IR in other erythroid genes. We observed not only that SF3B1 intron 4 decoy exons could promote IR in heterologous contexts, but also that predicted decoy exons from other erythroblast transcripts could promote IR in the SF3B1 minigene. Apart from this experimental data, comparative genomics revealed that the SF3B1 decoy exons are extremely conserved among vertebrate genomes, with two of the exons being essentially identical from fish to humans. Together this data supports the hypothesis that a subset of up-regulated IR events in late erythroblasts are controlled by decoy exons that block productive splicing at the flanking exons. We propose that regulated IR is an important post-transcriptional mechanism for adjusting cellular splicing capacity during terminal erythropoiesis by regulating expression of key splicing factors such as SF3B1. DisclosuresNo relevant conflicts of interest to declare.

An exonic missense mutation c.28G>A is associated with weak B blood group by affecting RNA splicing of the ABO gene.

The amino acid substitutions caused by ABO gene mutations are usually predicted to impact glycosyltransferase's function or its biosynthesis. Here we report an ABO exonic missense mutation that affects B-antigen expression by decreasing the mRNA level of the ABO gene rather than the amino acid change. Serologic studies including plasma total GTB transfer capacity were performed. The exon sequences of the ABO gene were analyzed by Sanger sequencing. B310 cDNA with c.28G>A (p.G10R) mutation was expressed in HeLa cells and total GTB transfer capacity in cell supernatant was measured. Flow cytometry was performed on these HeLa cells after transfection, and agglutination of Hela-Bweak cells was also examined. The mRNA of the ABO gene was analyzed by direct sequencing and real-time reverse transcriptase-polymerase chain reaction. A minigene construct was prepared to evaluate the potential of splicing. While plasma total GTB transfer capacity was undetectable in this B3 -like individual, the relative percentage of antigen-expressing cells and mean fluorescence index of the Bweak red blood cells (RBCs) were 19 and 14% of normal B RBCs, respectively. There was no significant difference of total GTB transfer capacity in cell supernatant and B-antigen expression on cell surfaces between HeLa cells transfected with B310 cDNA and B cDNA. The mRNA expression level of B310 in peripheral whole blood was significantly reduced. The amount of splicing is significantly lower in c.28G>A construct compared to that in wild-type construct after transfection in K562 cells. ABO c.28G>A mutation may cause B3 -like subgroup by affecting RNA splicing of the ABO gene.

Forced expression of Wnt antagonists sFRP1 and WIF1 sensitizes chronic myeloid leukemia cells to tyrosine kinase inhibitors.

Chronic myeloid leukemia is a clonal myeloproliferative disorder that arises from the neoplastic transformation of the hematopoietic stem cell, in which the Wnt/β-catenin signaling pathway has been demonstrated to play an important role in disease progression. However, the role of Wnt signaling antagonists in therapy resistance and disease progression has not been fully investigated. We aimed to study the effects of Wnt/β-catenin pathway antagonists-secreted frizzled-related protein 1 and Wnt inhibitory factor 1-on resistance toward tyrosine kinase inhibitors in chronic myeloid leukemia. Response to tyrosine kinase inhibitors was analyzed in secreted frizzled-related protein 1 and Wnt inhibitory factor 1 stably transfected K562 cells. Experiments were repeated using a tetracycline-inducible expression system, confirming previous results. In addition, response to tyrosine kinase inhibitor treatment was also analyzed using the secreted frizzled-related protein 1 expressing, BCR-ABL positive MEG01 cell line, in the presence and absence of a secreted frizzled-related protein 1 inhibitor. Our data suggests that total cellular β-catenin levels decrease in the presence of secreted frizzled-related protein 1 and Wnt inhibitory factor 1, and a significant increase in cell death after tyrosine kinase inhibitor treatment is observed. On the contrary, when secreted frizzled-related protein 1 is suppressed, total β-catenin levels increase in the cell and the cells become resistant to tyrosine kinase inhibitors. We suggest that Wnt antagonists carry the potential to be exploited in designing new agents and strategies for the advanced and resistant forms of chronic myeloid leukemia.

The \u03b2-globin Replicator greatly enhances the potential of S/MAR based episomal vectors for gene transfer into human haematopoietic progenitor cells

Specific human chromosomal elements enhance the performance of episomal gene-transfer vectors. S/MAR-based episomal vector pEPI-eGFP transfects CD34+ haematopoietic cells, but only transiently. To address this issue we reinforced (1) transgene transcription by replacing the CMV promoter driving eGFP with the EF1/HTLV or SFFV promoters to produce vectors pEPI-EF1/HTLV and pEPI-SFFV, respectively; and (2) plasmid replication by inserting the replication-Initiation Region (IR) from the β-globin locus into vector pEPI-SFFV to produce vector pEP-IR. All vectors supported stable transfections in K562 cells. Transfections of CD34+ cells from peripheral blood of healthy donors reached 30% efficiency. Upon evaluation of CD34+/eGFP+ cells in colony-forming cell (CFC) assays, vector pEP-IR showed superior performance after 14 days, by fluorescent microscopy: 100% eGFP+-colonies against 0% for pEPI-eGFP, 56.9% for pEPI-SFFV and 49.8% for pEPI-EF1/HTLV; 50% more plasmid copies per cell and 3-fold eGFP expression compared to the latter two constructs, by quantitative (q)PCR and RT-qPCR, respectively. Importantly, the establishment rate in CFC assays was 15% for pEP-IR against 5.5% for pEPI-SFFV and 5% for pEPI-EF1/HTLV. Vector pEP-IR shows extremely low delivery rate but supports eGFP expression in thalassaemic mouse haematopoietic progenitor cells. The IR is a novel human control element for improved episomal gene transfer into progenitor cells.

Optimization of RGD-Containing Cyclic Peptides against αvβ3 Integrin.

We have previously reported the use of one-bead-one-compound (OBOC) combinatorial technology to develop a disulfide cyclic, Arg-Gly-Asp-containing octapeptide LXW7 (cGRGDdvc), that targets αvβ3 integrin with high affinity and specificity. αvβ3 integrin is known to be overexpressed in many cancers and in tumor vasculature, and it has been established as a cancer therapeutic target. To further optimize LXW7, we have performed systematic structure-activity relationship studies. On the basis of the results, two highly focused OBOC peptide libraries were designed, synthesized, and screened against αvβ3 integrin-transfected K562 cells. One of the best ligands, LXW64, was found to have 6.6-fold higher binding affinity than LXW7, and showed preferential binding to cells expressing αvβ3 integrin. In addition to binding strongly to U-87MG glioblastoma cells in vitro, LXW64 also targets U-87MG xenografts implanted in nude mice, indicating that it is an excellent vehicle for the delivery of cytotoxic payload to tumors and tumor blood vessels that overexpress αvβ3 integrin. Mol Cancer Ther; 15(2); 232-40. ©2015 AACR.

Effect of RNAi-Mediated Knockdown of MCM7 on Human Leukemia Cells and Its Mechanism

Background: MCM7 is one of the subunits of the MCM2-7 complex that are essential for DNA replication licensing and control of cell cycle progression. It also participates in mRNA transcription and DNA damage regulation. It is found that MCM7 was highly expressed in many cancer cells including Leukemia. Thus, lentivirus-mediated siRNA targeting MCM7 was used to suppress its endogenous expression in K562 cells and develop a novel therapeutic strategy for leukemia.Method: Lentivirus-mediated siRNA targeting MCM7 were designed and infected K562 cells. Down-regulation of MCM7 mRNA and protein expression in K562 cells were determined by Real-time PCR and Western blot analysis. The proliferation of the transfected K562 cells was assessed by CCK8 assay. Cell cycle progression and apoptosis were calculated by flow cytometry. The related protein levels of the transfected K562 cells were detected by Western blot. The stably transfected K562 cells were injected into nude mice. The transplanted tumors were measured and weighed, then Western blot and Immunocytochemistry were used to evaluated the expression of the proteins for mechanism.Results: The mRNA and protein expression of MCM7 in the stably transfected K562 cells decreased with the percentage of 92.3±1.88 and 91.18%±0.93 respectively. Compared with control and negative control groups, the proliferative rate of K562 cells was significantly reduced after LV-MCM7-RNAi infection. The cell cycle progression of K562 cells was blocked, with a massive increase in the percentage of cells in the G0/G1 phase and decrease in S phase. The apoptosis rate of the transfected K562 cells was significantly higher. PLK1 and pPLK1 protein were down-regulated in response to MCM7 inhibition; P53 and bax protein were up-regulated simultaneously. In vivo, the tumor size and weight dramatically decreased in the MCM7-RNAi group than in negative control group. PLK1, pPLK1 proteins in transplanted tumors were down- regulated and P53,bax were up-regulated correspondingly.Conclusions: Lentivirus-mediated MCM7 shRNA has effectively down regulated the expression of MCM7 gene on mRNA and protein levels. Moreover, the silence of MCM7 has led to the significant decrease in proliferation, blocking the cell cycle progression of K562 cells in vitro. Simultaneity, the apoptosis of the leukemia cell was enhanced. Both of the functions above cause the inhibition of the tumor growth in nude mice. Overall, these results suggest that the proliferation and cell cycle of K562 cells could be regulated by silencing MCM7 gene which is a promising gene therapeutic method to treat gastric cancer. DisclosuresNo relevant conflicts of interest to declare.

Whim Syndrome Caused By a 5 Base Pair Deletion in the C-Terminus of Chemokine Receptor CXCR4

▪Introduction: WHIM syndrome is a rare autosomal dominant, primary immunodeficiency disease characterized by warts, hypogammaglobulinemia, infections and myelokathexis (impaired neutrophil egress from bone marrow resulting in neutropenia). Mutations in the C-terminus of chemokine receptor CXCR4 cause almost all known cases of WHIM syndrome (4 truncations, 3 frame-shifts and 1 single amino acid charge-change), and result in impaired ligand-induced receptor internalization and desensitization. This enhances receptor signaling, and exaggerates normal CXCR4 function to retain neutrophils and other leukocytes in bone marrow, resulting in myelokathexis and increased susceptibility to certain infections.Methods: A 2 year old boy with recurrent infections and neutropenia was referred to the NIH Clinical Center. Four anonymized healthy donors were recruited as homozygous CXCR4WT controls. Genomic DNA was isolated from peripheral blood and the CXCR4 gene was sequenced using the Sanger method. The eukaryotic expression vector pcDNA3.1(-) was used to make 3 recombinant plasmids encoding the wild type gene, (CXCR4WT) the most common disease mutation (CXCR4R334X) and the index patient's mutation (CXCR4L329fs). K562 cells were transfected with plasmids by nucleofection. Blood leukocyte subsets and CXCR4 expression on PBMCs from healthy donors and the patient and stably transfected K562 cells with or without CXCL12 stimulation were examined by FACS analysis. Calcium flux in response to CXCL12 was analyzed in receptor-transfected and parental cell lines as well as in primary leukocytes.Results: The boy had recurrent infections, hypogammaglobulinemia, panleukopenia and myelokathexis, consistent with WHIM syndrome but both parents were healthy. Genetic analysis revealed a novel heterozygous mutation in CXCR4, designated CXCR4L329fs, involving a 5 base pair deletion from nucleotides 986-990 in the open reading frame. This deletion causes a frame-shift at codon 329 that introduces 12 missense amino acids and deletes the conserved C-terminal 24 amino acids. Interestingly a different mutation that causes a frame-shift at the same codon has been recently described as a somatic mutation in one case of Waldenström's macroglobulinemia, which deletes nucleotide 984-986 and inserts a T. The CXCR4L329fs mutation in our patient is the largest truncation mutant reported to date in WHIM syndrome, and was not identified in unaffected family members or in the general population, suggesting that it is a de novo mutation. As with the most common WHIM mutation, CXCR4R334X, this new mutation also caused decreased receptor downregulation in response to CXCL12 in both PBMCs from the patient as well as in K562 cells transfected with the cloned receptor and increased CXCR4 calcium flux signaling in stably transfected K562 cells.Conclusion:CXCR4L329fs is a novel de novo gain-of-function mutation of the C-terminus of CXCR4 that causes WHIM syndrome. DisclosuresLiu:US National Institutes of Health: Employment, Patents & Royalties: pending. Murphy:US National Institutes of Health: Employment, Patents & Royalties: pending. McDermott:US National Institutes of Health: Employment, Patents & Royalties: pending.

FGF23 gene regulation by 1,25-dihydroxyvitamin D: opposing effects in adipocytes and osteocytes.

In a closed endocrine loop, 1,25-dihydroxyvitamin D3 (1,25D) induces the expression of fibroblast growth factor 23 (FGF23) in bone, with the phosphaturic peptide in turn acting at kidney to feedback repress CYP27B1 and induce CYP24A1 to limit the levels of 1,25D. In 3T3-L1 differentiated adipocytes, 1,25D represses FGF23 and leptin expression and induces C/EBPβ, but does not affect leptin receptor transcription. Conversely, in UMR-106 osteoblast-like cells, FGF23 mRNA concentrations are upregulated by 1,25D, an effect that is blunted by lysophosphatidic acid, a cell-surface acting ligand. Progressive truncation of the mouse FGF23 proximal promoter linked in luciferase reporter constructs reveals a 1,25D-responsive region between -400 and -200 bp. A 0.6 kb fragment of the mouse FGF23 promoter, linked in a reporter construct, responds to 1,25D with a fourfold enhancement of transcription in transfected K562 cells. Mutation of either an ETS1 site at -346 bp, or an adjacent candidate vitamin D receptor (VDR)/Nurr1-element, in the 0.6 kb reporter construct reduces the transcriptional activity elicited by 1,25D to a level that is not significantly different from a minimal promoter. This composite ETS1-VDR/Nurr1 cis-element may function as a switch between induction (osteocytes) and repression (adipocytes) of FGF23, depending on the cellular setting of transcription factors. Moreover, experiments demonstrate that a 1 kb mouse FGF23 promoter-reporter construct, transfected into MC3T3-E1 osteoblast-like cells, responds to a high calcium challenge with a statistically significant 1.7- to 2.0-fold enhancement of transcription. Thus, the FGF23 proximal promoter harbors cis elements that drive responsiveness to 1,25D and calcium, agents that induce FGF23 to curtail the pathologic consequences of their excess.