Human Myeloid Leukemia K562 Cells Research Articles

CD52 is a novel target for the treatment of FLT3-ITD-mutated myeloid leukemia

Internal tandem duplication (ITD) of FMS-like tyrosine kinase 3 (FLT3) confers poor prognosis and is found in approximately 25% of cases of acute myeloid leukemia (AML). Although FLT3 inhibitors have shown clinical benefit in patients with AML harboring FLT3-ITD, the therapeutic effect is limited. Here, to explore alternative therapeutics, we established a cellular model of monoallelic FLT3ITD/WT cells using the CRISPR-Cas9 system in a human myeloid leukemia cell line, K562. cDNA microarray analysis revealed elevated CD52 expression in K562–FLT3ITD/WT cells compared to K562–FLT3WT/WT cells, an observation that was further confirmed by quantitative real-time-PCR and flow cytometric analyses. The elevated expression of CD52 in K562–FLT3ITD/WT cells was decreased in wild-type FLT3 (FLT3-WT) knock-in K562–FLT3ITD/WT cells. In K562–FLT3ITD/WT cells, a STAT5 inhibitor, pimozide, downregulated CD52 protein expression while an AKT inhibitor, afuresertib, did not affect CD52 expression. Notably, an anti-CD52 antibody, alemtuzumab, induced significant antibody-dependent cell-mediated cytotoxicity (ADCC) in K562-FLT3ITD/WT cells compared to K562–FLT3WT/WT cells. Furthermore, alemtuzumab significantly suppressed the xenograft tumor growth of K562–FLT3ITD/WT cells in severe combined immunodeficiency (SCID) mice. Taken together, our data suggested that genetically modified FLT3-ITD knock-in human myeloid leukemia K562 cells upregulated CD52 expression via activation of STAT5, and alemtuzumab showed an antitumor effect via induction of ADCC in K562–FLT3ITD/WT cells. Our findings may allow establishment of a new therapeutic option, alemtuzumab, to treat leukemia with the FLT3-ITD mutation.

Down-regulation of Survivin and Bcl-2 concomitant with the activation of caspase-3 as a mechanism of apoptotic death in KG1a and K562 cells upon exposure to a derivative from ciprofloxacin family

Ciprofloxacin derivatives belong to a family of antibiotics called fluoroquinolones. Recently, these compounds have been recommended for the treatment of cancer. In the present study, we assessed the cytotoxicity of several new synthetic ciprofloxacin derivatives and the apoptosis-inducing activity of the most efficient derivative in two human myeloid leukemia K562 and KG1-a cell lines. Among the prepared ciprofloxacin derivatives, 1-cyclopropyl-7-(4-(2-((3,7-dimethyloct-6-en-1-yl)oxy)-2-oxoethyl)piperazin-1-yl)-6-fluoro-4-oxo-1,4dihydroquinoline-3-carboxylic acid (4-DMOCP) was more active compound with IC50 of 19.56 and 22.13 μM for K562 and KG1-a, respectively. Apoptotic activity of the 4-DMOCP was examined morphologically through Hoechst 33258 staining, Annexin V/PI double staining, and caspase-3 activity assays. Changes in the expression level of some apoptosis-related genes and protein, including Bcl-2, Bax, Survivin, p53, Caspase-8 and Caspase-9 were evaluated by the real-time quantitative PCR (qRT PCR) and western blotting. The qRT PCR analysis showed that 4-DMOCP induces apoptosis in both cell lines via the down-regulation of Survivin and Bcl2, up-regulation of caspase-8 and -9, as well as a time-dependent increase in the Bax/Bcl2 transcripts. The mRNA level of p53 was also increased in both cell lines. In addition, western blot analysis revealed that treatment with the compound, down-regulated the protein expression levels of Bcl2 and Survivin and up-regulated the protein level of Bax in both cell lines. These findings suggest that these new compounds can be good candidates for the treatment of acute and chronic myeloid leukemia.

Nobiletin Promotes Megakaryocytic Differentiation through the MAPK/ERK-Dependent EGR1 Expression and Exerts Anti-Leukemic Effects in Human Chronic Myeloid Leukemia (CML) K562 Cells.

Differentiation therapy is an alternative strategy used to induce the differentiation of blast cells toward mature cells and to inhibit tumor cell proliferation for cancer treatment. Nobiletin (NOB), a polymethoxyflavone phytochemical, is present abundantly in citrus peels and has been reported to possess anti-cancer activity. In this study, we investigated the anti-leukemic effects of NOB on cell differentiation and its underlying mechanisms in human chronic myeloid leukemia (CML) K562 cells. NOB (100 μM) treatment for 24 and 48 h significantly decreased viability of K562 cells to 54.4 ± 5.3% and 46.2 ± 9.9%, respectively. NOB (10–100 μM) significantly inhibited cell growth in K562 cells. Flow cytometry analysis and immunoblotting data showed that NOB (40 and 80 μM) could modulate the cell cycle regulators including p21, p27, and cyclin D2, and induce G1 phase arrest. NOB also increased the messenger RNA (mRNA) and protein expression of megakaryocytic differentiation markers, such as CD61, CD41, and CD42 as well as the formation of large cells with multi-lobulated nuclei in K562 cells. These results suggested that NOB facilitated K562 cells toward megakaryocytic differentiation. Furthermore, microarray analysis showed that expression of EGR1, a gene associated with promotion of megakaryocytic differentiation, was markedly elevated in NOB-treated K562 cells. The knockdown of EGR1 expression by small interference RNA (siRNA) could significantly attenuate NOB-mediated cell differentiation. We further elucidated that NOB induced EGR1 expression and CD61 expression through increases in MAPK/ERK phosphorylation in K562 cells. These results indicate that NOB promotes megakaryocytic differentiation through the MAPK/ERK pathway-dependent EGR1 expression in human CML cells. In addition, NOB when combined with imatinib could synergistically reduce the viability of K562 cells. Our findings suggest that NOB may serve as a beneficial anti-leukemic agent for differentiation therapy.

Effects of WNK1 on Human Chronic Myeloid Leukemia K562 Cells via MAPK7 Phosphorylation and Its Relative Mechanism

To investigate the biological effects and mechanism of WNK1 on K562 cells through regulating MAPK7. Cells were routinely cultured in vitro, the expression of WNK1 and MAPK7 in different blood tumor cell lines was analyzed by RT-qPCR and Western blot analysis.K562 cells were transfected with siRNA-WNK1 lentivirus.The effect of WNK1 on K562 cell proliferation was analyzed by using CCK-8 reagent.And K562 cell apoptosis was analyzed by using flow cytometry. The expression level of phosphorylated MAPK7 protein and total MAPK7 protein in K562 cells was analyzed by Western blot. The mRNA and protein of WNK1 were highly expressed in HL60, THP-1, U266 and K562 cells, however, the expressions were the highest in K562 cells (P<0.05), while the changes of mRNA and protein expressions of MAPK7 were not significantly in HL60, THP-1, U266 and K562 cells (P>0.05), but the phosphorylated MAPK7 expression was the highest in K562 cells (P<0.05). Proliferation of K562 cells transfected by WNK siRNA was significantly suppressed, and apoptosis was obviously increased (P<0.05). And the pMAPK7 protein expression in K562 cells transfected by WNK1 siRNA significantly decreased (P<0.05), however, the total MAPK7 protein expression in K562 cells showed no obvious change (P>0.05). WNK1 is highly expressed in K562 cells, which can promote the proliferation of K562 cells and reduce apoptosis probably by promoting phosphorylation of its downstream MAPK7.

3'-sialyllactose targets cell surface protein, SIGLEC-3, and induces megakaryocyte differentiation and apoptosis by lipid raft-dependent endocytosis.

3'-sialyllactose is one of the abundant components in human milk oligosaccharides (HMOs) that protect infants from various viral infections in early stages of immune system development. 3SL is a combination of lactose and sialic acid. Most sialic acids are widely expressed in animal cells and they bind to siglec proteins. In this study, we demonstrate that 3SL specifically binds to CD33. It induces megakaryocyte differentiation and subsequent apoptosis by targeting cell surface protein siglec-3 (CD33) in human chronic myeloid leukemia K562 cells. The 3SL-bound CD33 was internalized to the cytosol via caveolae-dependent endocytosis. At the molecular level, 3SL-bound CD33 recruits the suppressor of cytokine signaling 3 (SOCS3) and SH2 domain-containing protein tyrosine phosphatase 1 (SHP1). SOCS3 is degraded with CD33 by proteasome degradation, while SHP-1 activates extracellular signal-regulated kinase (ERK) to induce megakaryocytic differentiation and subsequent apoptosis. The present study, therefore, suggests that 3SL is a potential anti-leukemia agent affecting differentiation and apoptosis.

Functional Coupling of Ion Channels in the Process of Mechano-Dependent Activation in the Membrane of K562 Cells

Mechanically gated cation channels that are activated upon deformation of the membrane are key participants in the transmission of mechanical signals from the cell surface to cytoplasmic structures. It has remained unclear how mechanically dependent reactions involving ion channels in native cells are realized. In this study, we analyzed the development of the activity of single channels in K562 human myeloid leukemia cells in response to the delivery of a mechanical stimulus, this being stretching of the membrane area. The registration of ion currents using the classic versions of the patch–clamp method allowed revealing the functional clustering and interaction of various types of channels in the plasma membrane during mechanotransduction. In K562 cells, coupled activation of mechanosensitive calcium-conducting channels and calcium-activated potassium channels was detected. Real-time recordings of currents demonstrate that the calcium influx from the extracellular medium into the cytoplasm through mechanically gated channels activates potassium channels that are colocalized with them, which do not have their own mechanosensitivity. In experiments on K562 cells and transformed 3T3-SV40 fibroblasts, the preservation of the functional conjugation of the channels during their mechanically gated activation after the action of the microfilament destructor cytochalasin D was shown. The results suggest that clusters including potassium SK channels and Piezo1/2 proteins forming stretch-activated cation channels function in the plasma membrane of K562 and 3T3-SV40 cells.

Effect of Dehydrocostus Lactone on Proliferation of K562 Cells and Its Mechanism

To explore the inhibitory effect of dehydrocostus lactone on the proliferation of human chronic myeloid leukemia K562 cells and the underlying mechanisms. Cell viability was evaluated by CCK-8 assay. Flow cytometry was used to assess the effect of dehydrocostus lactone on the cell cycle and apoptosis of K562 cells. The levels of BCR/ABL-STATs-related molecules were analyzed by using Western blot. The CCK-8 assay showed that dehydrocostus lactone at graded concentration of 4, 6, 8, 10, 12 μmol/L could significantly inhibit the proliferation of K562 cells after exposure for 24 h. The proliferation inhibition rate was (24.32±3.05%), (42.91±3.89%), (46.35±4.93%), (77.06±5.42%) and (89.04±4.25%) respectively, showing statistically significantly different from (2.08±0.27%) in the control (P＜0.05). Also, the treatment with 5 and 10 μmol/L of dehydrocostus lactone induced K562 cell apoptosis, the apoptotic rate of K562 cells was significantly higher than that the control group (P＜0.05), and up-regulated the expression level of BAX and p21. Furthermore, dehydrocostus lactone (5 and 10 μmol/L) also increased the percentage of cells in G2/M [(8.53±1.71)% to (17.42±2.72) and (31.79±4.38%)](P＜0.05). The study results also revealed that dehydrocostus lactone significantly inhibited the expression of BCR/ABL STAT3, STAT5, CyclinB1, CDK1 and BCL-2, and up-regulated the expression level of BAX and p21. Dehydrocostus lactone can suppress the proliferation of K562 cells and induce the apoptosis of K562 cells through BCR/ABL-STAT signaling pathways.

Myelodysplastic Syndrome-Associated SRSF2 Mutations Cause Splicing Changes by Altering Binding Motif Sequences.

Serine/arginine-rich splicing factor 2 (SRSF2) is a member of the SR protein family that is involved in both constitutive and alternative mRNA splicing. Mutations in SRSF2 gene are frequently reported in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). It is imperative to understand how these mutations affect SRSF2-mediated splicing and cause MDS. In this study, we characterized MDS-associated SRSF2 mutants (P95H, P95L, and P95R). We found that those mutants and wild-type SRSF2 proteins showed nuclear localization in HeLa cells. In vitro splicing reaction also revealed that mutant proteins associated with both precursor and spliced mRNAs, suggesting that the mutants directly participate in splicing. We established the human myeloid leukemia K562 cell lines that stably expressed myc-tagged wild-type or mutant SRSF2 proteins, and then performed RNA-sequence to analyze the splicing pattern of each cell line. The results revealed that both wild-type and mutants affected splicing of approximately 3,000 genes. Although splice site sequences adjacent to the affected exons showed no significant difference compared to the total exons, exonic motif analyses with both inclusion- and exclusion-enhanced exons demonstrated that wild-type and mutants have different binding sequences in exons. These results indicate that mutations of SRSF2 in MDS change binding properties of SRSF2 to exonic motifs and this causes aberrant splicing.

Changes in IDH2, TET2 and KDM2B Gene Expression After Treatment With Classic Chemotherapeutic Agents and Decitabine in Myelogenous Leukemia Cell Lines

BackgroundHematological malignancies are a heterogeneous group of tumors with increased proliferative and auto-replicative capacity. Despite treatment advances, post-treatment quality of life remains highly affected. Studies addressing the molecular mechanisms of these diseases are critical for the development of effective, rapid and selective therapies, since few therapeutic strategies succeed in being effective without triggering high-grade toxicities or debilitating late effects. Our aim of this study was to verify changes in the expression of genes involved in the malignant phenotype of hematological malignancies, by treating human cell lines in vitro with classic chemotherapeutic agents and the demethylating agent, decitabine.MethodsKASUMI-1 and K-562 human myeloid leukemia cell lines were plated at a density of 3 × 104 cells/well and treated with increasing concentrations of different chemotherapeutic agents commonly used in the clinical setting. After 24 and 48 h of treatment, cell viability was tested, and RNA was extracted. Complementary DNA (cDNA) was synthesized and quantitative real-time polymerase chain reaction (qPCR) was performed to evaluate the gene expression of IDH2, TET2 and KDM2B.ResultsA modulation in gene expression was observed before and after treatment with classic chemotherapeutic agents. It was possible to demonstrate a difference in gene expression when cells were treated with chemotherapeutic agents or decitabine alone when compared to chemotherapeutic agents in association with decitabine.ConclusionsThe genes tested, and the modulation of their expression during in vitro treatments suggest that IDH2, TET2, and KDM2B should be further investigated as potential biomarkers for ongoing treatment response and follow-up for patients diagnosed with hematological malignancies of the myeloid lineage.

Induction of apoptosis and erythroid differentiation of human chronic myelogenous leukemia K562 cells by low concentrations of lidamycin.

Apoptosis induction and differentiation of promyelocytic leukemic cells into mature cells are major strategies for the drug-based treatment of leukemia. Lidamycin (LDM) which is a member of the enediyne antibiotic family exhibits extreme cytotoxicity. In the present study, the induction of apoptosis and differentiation in human chronic myeloid leukemia K562 cells by low concentrations of lidamycin were investigated. K562 cells were treated with lidamycin at various concentrations for 48h, and accumulated in the metaphase as determined in previous experiments. Cell viability was determined using a Cell Counting Kit-8 (CCK-8) assay and the IC50 value of lidamycin was 0.1±3.2nM. Induction of apoptosis was investigated morphologically by acridine orange/ethidium bromide (AO/EtBr) staining. Growth inhibition and apoptosis induction were observed in cells treated with low concentrations of lidamycin. In addition, western blot analysis revealed that treatment of the K562 cells with lidamycin at low concentrations upregulated the expression of caspase-8 and caspase-3. The induction of differentiation in human chronic myeloid leukemia K562 cells by lidamycin at low concentrations was also investigated. The nitroblue tetrazolium reduction ability of K562 cells was increased following treatment with lidamycin. Low concentrations of lidamycin triggered erythroid differentiation among K562 cells, indicated by morphological changes, increased hemoglobin content, and the expression of cell surface antigens such as CD71. Additionally the expression of GATA-binding factor1 (GATA-1) protein in low concentration lidamycin-treated K562 cells was increased. The results of the present study suggest that a low-concentration lidamycin exerts effects on apoptosis and erythroid differentiation induction by increasing the expression of caspases and GATA-1 protein. Lidamycin may serve a positive role in relevant targeted chemotherapy and may represent a potential candidate for chronic myelogenous leukemia differentiation-inducing treatment.

Phosphorylation of ELAVL1 (Ser219/Ser316) mediated by PKC is required for erythropoiesis

Elavl1 (also known as HuR), an RNA binding protein highly conserved between zebrafish and human, regulates gene expression by stabilizing target mRNA. Our previous studies have uncovered that the predominant isoform elavl1a is required for zebrafish embryonic erythropoiesis. However, the exact mechanism of how elav11 spatiotemporally stabilizes target mRNAs to regulate specific erythropoiesis is not yet understood. Here we show that phosphorylation of elavl1a at Ser219 and Ser316 by PKC is necessarily required for cytosolic shuttling from the nucleus to stabilize gata1 mRNA and thus promotes erythropoiesis. Knockdown of elavl1a resulted in the hindrance of erythropoiesis and Hemin-induced erythroid differentiation of human myeloid leukemia K562 cells. Interestingly, inhibition of PKC reproduced the phenotype seen during zebrafish embryogenesis and erythroid differentiation of myeloid leukemia. Mechanistically, Hemin induced elavl1a export from nuclear to cytoplasmic space in K562 cells in a manner dependent on phosphorylation on Ser219 and Ser316, as overexpression of elavl1a with mutations on Ser219 and Ser316 resulted in erythropoiesis failure. Additionally, co-administration of low doses of elavl1a morpholino (MO) and three PKC inhibitors showed a combined effect in zebrafish embryonic erythropoiesis dysplasia. In conclusion, our study reveals that PKC-mediated phosphorylation of elavl1a at Ser219 and Ser316 sites controls its nucleo-cytoplasmic translocation in zebrafish, thereby regulating embryonic erythropoiesis.

Role of eIF3a in 4-amino-2-trifluoromethyl-phenyl retinate-induced cell differentiation in human chronic myeloid leukemia K562 cells

4-amino-2-trifluoromethyl-phenyl retinate (ATPR), a novel all-trans retinoic acid (ATRA) derivative designed and synthesized by our team, has been demonstrated its anti-tumor effect through inducing differentiation and inhibiting proliferation. Eukaryotic initiation factor 3a (eIF3a) plays a critical role in affecting tumor cell proliferation and differentiation. However, whether eIF3a is implicated in chronic myeloid leukemia cells differentiation remains unclear. Our results demonstrated that eIF3a could be suppressed by ATPR in K562 cells. The results also confirmed that ATPR could arrest cell cycle in G0/G1 phase and induced differentiation. Moreover, over-expression of eIF3a promoted not only protein expression of c-myc and cyclin D1, but also prevented the expression of p-Raf-1, p-ERK and the myeloid differentiation markers CD11b and CD14 and had an influence on inducing the morphologic mature. However, silencing eIF3a expression by small interfering RNA could have an adverse effect on K562 cells. In addition, PD98059 (a MEK inhibitor) could block cell differentiation of CML cells and contributed to the expression of c-myc and cyclin D1. In conclusion, these results indicated that eIF3a played an important role in ATPR-induced cell differentiation in K562 cells, its mechanism might be related to its ability in regulating the activation of ERK1/2 signaling pathway in vitro.

Novel YAP1 Activator, Identified by Transcription-Based Functional Screen, Limits Multiple Myeloma Growth.

Yes-associated protein 1 (YAP1) interacts with numerous transcription factors, including TEA-domain family proteins (TEAD) and p73. YAP1 is negatively regulated by the tumor suppressor Hippo pathway. In human cancers, the deregulation of the Hippo pathway and YAP1 gene amplification lead to the activation of YAP1, which induces epithelial-mesenchymal transition (EMT) and drug resistance. YAP1 inhibitors are expected to be useful in cancer therapy. On the other hand, in certain cancers, YAP1 upregulates p73-dependent gene transcription and behaves as a tumor suppressor. Moreover, as YAP1 regulates self-renewal and differentiation of tissue stem cells and plays an important role in tissue homeostasis, YAP1 activators may contribute to the regenerative medicine. With this in our mind, we screened for YAP1 activators by using human retinal pigment epithelial ARPE-19 cells expressing the TEAD-responsive fluorescence reporter under the coexpression of YAP1. From an extensive chemical compound library (n = 18,606) 47 candidate YAP1 activators were identified. These compounds were characterized to determine whether this assay provides bona fide YAP1 activators. Importantly, one YAP1 activator was effective against the human multiple myeloma IM-9 cells and chronic myeloid leukemia K562 cells.Implications: YAP1 activation limits growth, induces apoptosis, and may be useful at suppressing hematological cancers. Mol Cancer Res; 16(2); 197-211. ©2017 AACR.

Liposome‑delivered baicalein induction of myeloid leukemia K562 cell death via reactive oxygen species generation.

Baicalein (BL), a potential cancer chemopreventative flavone, has been reported to inhibit cancer cell growth by inducing apoptosis and causing cell cycle arrest in various human cancer cell models. Delivery of BL via nanoliposomes has been shown to improve its oral bioavailability and long-circulating property in vivo. However, the role of BL in the inhibition of human chronic myeloid leukemia (CML) K562 cell growth and its underlying mechanisms has yet to be elucidated. In the present study, BL was formulated into liposomes with different sizes to improve its solubility and stability. The cytotoxic and pro-apoptotic effects of free BL and liposomal BL were also evaluated. The results demonstrated that 100 nm liposomes were the most stable formulation when compared with 200 and 400 nm liposomes. Liposomal BL inhibited K562 cell growth as efficiently as free BL (prepared in DMSO), indicating that the liposome may be a potential vehicle to deliver BL for the treatment of CML. Flow cytometry analysis showed that there was significant (P<0.005) cell cycle arrest in the sub-G1 phase (compared with vehicle control), indicating cell apoptosis following 20 µM liposomal BL or free BL treatment of K562 cells for 48 h. The induction of cell apoptosis by all BL preparations was further confirmed through the staining of treated cells with Annexin V-fluorescein isothiocyanate/propidium iodide. A significant increase in reactive oxygen species (ROS) generation was observed in free BL and liposomal BL treated cells, with a higher level of ROS produced from those treated with free BL. This indicated that cell apoptosis induced by BL may be via ROS generation and liposome delivery may further extend the effect through its long-circulating property.

Cordyceps militaris Fraction induces apoptosis and G2/M Arrest via c-Jun N-Terminal kinase signaling pathway in oral squamous carcinoma KB Cells.

Background:Cordyceps militaris fraction (CMF) has been shown to possess in vitro antitumor activity against human chronic myeloid leukemia K562 cells in our previous research. Materials and Methods:The in vitro inhibitory activities of CMF on the growth of KB cells were evaluated by viability assay. The apoptotic and cell cycle influences of CMF were detected by 4′,6-diamidino-2-phenylindole staining and flow cytometry assay. The expression of different apoptosis-associated proteins and cell cycle regulatory proteins was examined by Western blot assay. The nuclear localization of c-Jun was observed by fluorescence staining.Objective:The objective of this study was to investigate the antiproliferative effect of CMF as well as the mechanism underlying the apoptosis and cell cycle arrest it induces in KB cells.Results:CMF suppressed KB cells’ proliferation in a dose- and time-dependent manner. Flow cytometric analysis indicated that CMF induced G2/M cell cycle arrest and apoptosis. Western blot analysis revealed that CMF induced caspase-3, caspase-9, and PARP cleavages, and increased the Bax/Bcl-2 ratio. CMF also led to increased expression of p21, decreased expression of cyclin B1, mitotic phosphatase cdc25c, and mitotic kinase cdc2, as well as unchanged expression of p53. In addition, CMF stimulated c-Jun N-terminal kinases (JNK) protein phosphorylations, resulting in upregulated expression of c-Jun and nuclear localization of c-Jun. Pretreatment with JNK inhibitor SP600125 suppressed CMF-induced apoptosis and G2/M arrest.Conclusions:CMF is capable of modulating c-Jun caspase and Bcl-2 family proteins through JNK-dependent apoptosis, which results in G2/M phase arrest in KB cells. CMF could be developed as a promising candidate for the new antitumor agents.SUMMARY CMF exhibited strong anticancer activity against oral squamous carcinoma KB cellsCMF inhibited KB cells’ proliferation via induction of apoptosis and G2/M cell cycle arrestCMF activated JNK signaling pathway and promoted the nuclear localization of c-JunCMF regulated the apoptosis- and cell cycle-related proteins in a manner dependent on JNK/c-Jun pathway. Abbreviations used: CMF: Cordyceps militaris fraction; OSCC: Oral squamous cell carcinoma; JNK: c-Jun N-terminal kinase.

Dose-rate effect of ultrashort electron beam radiation on DNA damage and repair in vitro.

Laser-generated electron beams are distinguished from conventional accelerated particles by ultrashort beam pulses in the femtoseconds to picoseconds duration range, and their application may elucidate primary radiobiological effects. The aim of the present study was to determine the dose-rate effect of laser-generated ultrashort pulses of 4 MeV electron beam radiation on DNA damage and repair in human cells. The dose rate was increased via changing the pulse repetition frequency, without increasing the electron energy. The human chronic myeloid leukemia K-562 cell line was used to estimate the DNA damage and repair after irradiation, via the comet assay. A distribution analysis of the DNA damage was performed. The same mean level of initial DNA damages was observed at low (3.6 Gy/min) and high (36 Gy/min) dose-rate irradiation. In the case of low-dose-rate irradiation, the detected DNA damages were completely repairable, whereas the high-dose-rate irradiation demonstrated a lower level of reparability. The distribution analysis of initial DNA damages after high-dose-rate irradiation revealed a shift towards higher amounts of damage and a broadening in distribution. Thus, increasing the dose rate via changing the pulse frequency of ultrafast electrons leads to an increase in the complexity of DNA damages, with a consequent decrease in their reparability. Since the application of an ultrashort pulsed electron beam permits us to describe the primary radiobiological effects, it can be assumed that the observed dose-rate effect on DNA damage/repair is mainly caused by primary lesions appearing at the moment of irradiation.

Synthesis, characterization and in vitro biological activities of new water-soluble copper(II), zinc(II), and nickel(II) complexes with sulfonato-substituted Schiff base ligand

A water-soluble thiosemicarbazone Schiff base ligand, namely sodium 3-{[(aminocarbonothioyl)hydrazono]methyl}-4-hydroxybenzenesulfonate (NaH2L) was prepared by 1:1 condensation of sodium salicylaldehyde-5-sulfonate and thiosemicarbazide. The X-ray structure analysis of NaH2L shows that the organic fragments of the ligand are bridged by two different types of seven-coordinated sodium cations. The ligand was used in the synthesis of the following CuII, NiII, and ZnII complexes: [Cu2(HL)2(H2O)3] (1), Ni(HL)(H2O)1.5 (2), and Zn(HL)(H2O)2 (3). The metal complexes were characterized by physico-chemical and spectroscopic methods. The X-ray structure analysis of the dinuclear copper complex (1) shows that two metal centers are five coordinated having distorted square pyramidal geometries. There are significant π-π interactions between the phenyl rings of the two ligands in the complex with the centroid-centroid distance 3.8571(10)Å. Solubility in water at 25°C was measured 100g/L for NaH2L, 50g/L for 1, 100g/L for 2 and 0.1g/L for 3. The stability of NaH2L, 1 and 2 in water solution exceeded 4days. The compounds 1 and 2 showed low antimicrobial activity while the inhibition efficiency of NaH2L and 3 was negligible. The ligand and complexes were evaluated for scavenging activity of picrylhydrazyl radical (DPPH) and ferric reducing antioxidant power (FRAP), using l-ascorbic acid (Vitamin C) as a reference antioxidant. The strongest radical scavenging was found for NaH2L. Cytotoxicity of the compounds was investigated against the human chronic myeloid leukemia K562 cells by the MTT assay method. The strongest cytotoxicity was found for 1 with the IC50 value of 16±1.0μg/mL for 72h and therefore 1 was chosen for further studies. The compound 1 caused a noticeable decrease in viability of the K562 cells in a dose- and time-dependent manner and induced apoptosis in the K562 cell line.

Reactions of copper(II), nickel(II), and zinc(II) acetates with a new water-soluble 4-phenylthiosemicarbazone Schiff base ligand: Synthesis, characterization, unexpected cyclization, antimicrobial, antioxidant, and anticancer activities

A new Schiff base thiosemicarbazone ligand with aqueous solubility, namely, sodium 3-{[(anilinocarbonothioyl)hydrazono]methyl}-4-hydroxy benzene sulfonate (NaH2L) was synthesized by condensation of 4-phenylthiosemicarbazide and sodium salicylaldehyde-5-sulfonate (NaSalSO3) and characterized by elemental analysis, spectroscopic methods (UV–Vis, 1H NMR, FTIR) and electrospray ionization mass spectrometry. A co-crystal (Na(H2L)·Na(SalSO3)) of NaH2L and NaSalSO3 was prepared which confirmed the expected structure of the ligand. Reactions of NaH2L·0.5H2O with copper(II), nickel(II), and zinc(II) acetates were investigated under reflux conditions in methanol to produce following complexes [Cu2(Lcycl)2(H2O)2]·2H2O (CuLcycl), Ni(HL)(H2O)3 (NiL), and Zn(HL)(H2O)3 (ZnL). In the copper case, dinuclear copper complex [Cu2(Lcycl)2(H2O)2]·2H2O (where HLcycl− represents incorporating of 1,3-benzothiazole ligand, formed by in situ cyclization of H2L−) was isolated. In the dimer structure copper atoms adopt a five-coordinate near square pyramidal geometry. Two oxygens derived from two sulfonate groups occupy the apical positions on both the metal centers and bridge them. The compounds have remarkable solubility in water at 25°C: 50, 10, 50, and 50g/L for NaH2L·0.5H2O, CuLcycl, NiL, and ZnL, respectively. The stability of the compounds was checked in acidic, neutral, and basic aqueous solutions. Antimicrobial activity results indicated CuLcycl and NiL possess activity against gram-positive bacteria and fungus while the free ligand and ZnL are inactive. Antioxidant activity of the compounds was evaluated and the ligand indicated the strongest radical scavenging relative to the complexes and l-ascorbic acid as a water-soluble standard. It was observed that copper and nickel complexes decreased the viability of the human chronic myeloid leukemia K562 cells in a dose- and time-dependent manner and the ligand and zinc complex were not active. The IC50 values were 31±2.5 and 6±1.0μg/mL (72h) for copper and nickel complexes, respectively. Morphological and DNA fragmentation assay studies clearly indicated that the nickel complex as the strongest compound induce apoptosis in the K562 cell line.

Allium Roseum L. Extract Exerts Potent Suppressive Activities on Chronic Myeloid Leukemia K562 Cell Viability Through the Inhibition of BCR-ABL, PI3K/Akt, and ERK1/2 Pathways and the Abrogation of VEGF Secretion

ABSTRACTUse of plant extracts, alone or combined to the current chemotherapy as chemosensitizers, has emerged as a promising strategy to overcome tumor drug resistance. Here, we investigated the anticancer activity of Allium roseum L. extracts, a wild edible species in North Africa, on human Chronic Myeloid Leukemia (CML) K562 cells. The dehydrated aqueous extract (DAE) disturbed the cell cycle progression and induced the apoptosis of K562 cells. Chemical analysis of DAE showed a diversity of organosulfur compounds S-alk(en)yl-cysteine sulfoxides (RCSO) and high amount of allicin, suggesting that such molecule may be behind its antitumor effect. DAE was efficient in inhibiting K562 cell viability. DAE inhibitory effect was associated with the dephosphorylation of the BCR-ABL kinase and interfered with ERK1/2, Akt, and STAT5 pathways. Furthermore, we found that DAE-induced inactivation of Akt kinase led to the activation of its target FOXO3 transcription factor, enhancing the expression of FOXO3-regulated proapoptotic effectors, Bim and Bax, and cell cycle inhibitor p27. Finally, we found that DAE reduced the secretion of vascular endothelial growth factor. Overall, our data suggest that A. roseum extract has great potential as a nontoxic cheap and effective alternative to conventional chemotherapy.

Icaritin promotes the apoptosis of leukemia K562 cells

Objective To investigate the effect and mechanism of the icaritin on the human cronic myeloid leukemia K562 cells. Methods The K562 cells at logarithmic growth phase were divided into the control group and the icaritin group. The cells in the control group were normally treated and the cells in the icaritin group were incubated with 8 μmol/L icaritin. Methyl thiazolyl tetrazolium (MTT) method and flow cytometry were used to examine the proliferation and apoptotic changes in the two groups after incubation for 72 h, respectively. Gene expression of p85 and Akt were detected by RT-PCR. The protein changes of p85, Akt, p-p85, p-Akt cleavage-caspase-3 and caspase-3 were detected by Western blot. Results Compared with the control group, the proliferation rate of K562 cells in the icaritin group was significantly decreased (P 0.05). Conclusion Icaritin could induce the proliferation and promote the apoptosis of K562 cell, and its mechanism may be achieved through activating the PI3K-Akt signal transduction pathway. Key words: Leukemia; Icaritin; K562 cells; Proliferation; Apoptosis; PI3k-Akt signal pathway