Human Leukemia Cell Line U937 Research Articles

Effects of exposure to alternating low-intensity, intermediate-frequency electric fields on the differentiation of human leukemic cell line U937.

Studying the bioeffects of electric fields have been the subject of ongoing research which led to promising therapeutic effect, particularly in cancer treatment. Here, we investigated the impact of low-intensity, intermediate-frequency alternating electric fields on the differentiation of human myeloid leukemia cell line U937. The results showed a near twofold increase in differentiation of U937 cells treated for 24 h by alternating 600 kHz, 150 V/m electric fields, in comparison to their control groups. This measure was evaluated by latex bead phagocytosis assay, nitro blue tetrazolium test, and cell cycle analysis which revealed a significant shift in the number of cells from G2 +M to G0 +G1 phases. The simulation result for the intracellular field intensity showed around 50% attenuation with respect to the applied external field for our setup which ruled out masking of the applied field by the internal electric noise of the cell. Based on previous studies we postulate a possible calcium-related effect for the observed differentiation, yet the exact underlying mechanism requires further investigation. Finally, our results may offer a potential therapeutic method for leukemia in the future.

Enzymatic Synthesis of 2-Chloropurine Arabinonucleosides with Chiral Amino Acid Amides at the C6 Position and an Evaluation of Antiproliferative Activity In Vitro

A number of purine arabinosides containing chiral amino acid amides at the C6 position of the purine were synthesized using a transglycosylation reaction with recombinant E. coli nucleoside phosphorylases. Arsenolysis of 2-chloropurine ribosides with chiral amino acid amides at C6 was used for the enzymatic synthesis, and the reaction equilibrium shifted towards the synthesis of arabinonucleosides. The synthesized nucleosides were shown to be resistant to the action of E. coli adenosine deaminase. The antiproliferative activity of the synthesized nucleosides was studied on human acute myeloid leukemia cell line U937. Among all the compounds, the serine derivative exhibited an activity level (IC50 = 16 μM) close to that of Nelarabine (IC50 = 3 μM) and was evaluated as active.

Hesperetin Induces Autophagy and Delayed Apoptosis by Modulating the AMPK/Akt/mTOR Pathway in Human Leukemia Cells In Vitro

Hesperetin has been reported to have anticancer properties. However, the molecular mechanisms underlying its action on leukemia cells remain unclear. This in vitro study evaluated the possible mechanisms of hesperetin in leukemia cells (HL-60 and U937). Cell viability was evaluated using a cell counting kit-8 (CCK-8) assay. Apoptosis and autophagy assays were conducted through annexin V/PI staining and acidic vesicular organelle (AVO) staining. Cell cycle analysis was conducted through propidium iodide (PI) and flow cytometry. The expression of proteins related to apoptosis and autophagy, including cleaved-PARP-1, Bcl-2, Bax, LC3-I/II, Beclin-1, Atg5, p62, phospho-AMPK, AMPK, phospho-mTOR, mTOR, phospho-Akt, and Akt, in human leukemia cells were evaluated using Western blotting. Hesperetin dose-dependently inhibited leukemia cell viability. However, we found a low degree of apoptosis and cell cycle arrest induced by hesperetin in U937 cells. These findings imply the presence of additional mechanisms modulating hesperetin-induced cell death. Next, we evaluated autophagy, the possible mechanism modulating cell death or survival, to clarify the underlying mechanism of hesperetin-induced cell death. Hesperetin also dose-dependently increased the ratio of LC3II/I, Atg5, and Beclin 1 and decreased p62. Moreover, 3-methyladenine (3-MA) and bafilomycin A1 (Baf-A1) inhibited hesperetin-induced autophagy. We suggest that hesperetin can protect cancer cells during the transient period and may extend survival. Furthermore, a decrease in p-mTOR and p-Akt expression and an increase in p-AMPK expression were observed. Collectively, these findings suggest that hesperetin induces autophagy by modulating the AMPK/Akt/mTOR pathway. Hesperetin promoted cell death in the human leukemic cell line U937 by inducing a low degree of slight apoptosis, cell cycle arrest, and autophagy. It is therefore a potential adjuvant to antileukemia therapy and may be combined with other chemotherapeutic drugs to reduce chemoresistance and side effects.

Effects of Thiomersal on Apoptosis and Autophagy of Leukemia Cell Lines

To investigate the effects of different concentrations of thiomersal on apoptosis and autophagy regulation of human leukemia cell lines U937, CEM-C1 and BALL-1. The inhibitory effect of thiomersal on the proliferation of U937, CEM-C1 and BALL-1 cells was detected by CCK-8 assay. Annexin V-FITC/PI double staining flow cytometry was used to detect the apoptosis rate. Western blot was used to detect the effects of thiomersal on autophagy signaling pathway and the expression of PI3K, Akt, mTOR, p-mTOR, caspase-3 and LC3-II proteins. Within 24 and 48 hours, thiomersal inhibited the proliferation of U937, CEM-C1 and BALL-1 cell lines in a time and dose-dependent manner (r24 h=0.295, r24 h=0.452, r24 h=0.103; r48 h=0.821, r48 h=0.665, r48 h=0.821), but no significant time and dose-dependent effect was observed at 72 hours. After 48 hours treatment of thiomersal, the apoptosis rate of U937, CEM-C1 and BALL-1 cells increased in a dose-dependent manner (r=0.819, r=0.763, r=0.835). After 48 hours treatment of thiomersal, the expression levels of PI3K, Akt, mTOR and p-mTOR protein in U937, CEM-C1 and BALL-1 cells decreased in a concentration-dependent manner, the R value of U937 cells was -0.975, -0.899, -0.925 and -0.915, respectively, that of CEM-C1 cells was -0.960, -0.920, -0.861 and -0.927, and that of BALL-1 cells was -0.939, -0.911, -0.896 and -0.926,. which suggested that thiomersal-induced apoptosis of U937, CEM-C1 and BALL-1 cells might be due to the inhibition of PI3K/Akt/mTOR pathway. Thiomersal promoted the apoptosis of U937, CEM-C1 and BALL-1 cells via caspase-3 pathway, and the expressions of caspase-3 and LC3-II were up-regulated in a dose-dependent manner (r=0.976, r=0.914; r=0.976, r=0.986; r=0.961, r=0.974). Thiomersal can inhibit the proliferation and promote the apoptosis of U937, CEM-C1 and BALL-1 cells. A certain concentration of thiomersal can down-regulate the expression of PI3K/Akt/mTOR pathway related proteins PI3K, Akt, mTOR and p-mTOR in U937, CEM-C1 and BALL-1 cells, and activate autophagy and apoptosis by down-regulation of PI3K/Akt/mTOR pathway.

SLFN11 Is a Potential Biomarker and Modulator of Treatment Response in AML

Introduction: Despite recent advances in treatment for acute myeloid leukemia (AML), AML remains a deadly disease, with approximately 70% of patients succumbing to the disease within five years of diagnosis (SEER database 2021). Intensive induction chemotherapy carries a risk of morbidity and mortality, making it a risky treatment for patients who are unlikely to achieve a remission with DNA damaging-based treatments. Hypomethylating agents (HMAs) such as azacitidine (AZA) and decitabine (DAC) are now frequently used in AML treatment as less intensive treatment options. Thus, biomarkers to predict response to DNA damaging agents in AML are needed. We recently found a significant association between AML patient survival and high expression of Schlafen11 (SLFN11), a dynamically inducible key effector of the DNA replication stress response. SLFN11 has been shown to be associated with response to certain chemotherapy agents in some solid tumors in vitro and in vivo (Conteduca et. al. JCO 2019; Shee et. al. PLoS One 2019), but its importance in leukemia has not been well defined. It is also unknown whether SLFN11 levels affect response to HMAs. We hypothesized that SLFN11 can be used as a predictive biomarker for treatment response to DNA-damaging agents in AML but that response to HMAs would be independent of HMAs. We also hypothesized that identifying pathways upregulated in SLFN11-low cells could lead to novel combination therapies to increase sensitivity to chemotherapeutics. Methods: The human leukemia cell lines HEL and U937 cells were used for these studies. U937- and HEL-SLFN11 knockout (SLFN11KO) cells were generated using CRISPR-Cas9 gene editing technology. Cell viability was assessed by WST-1 reagent assay. SLFN11 and other protein levels were measured by Western blotting. Results: SLFN11 protein expression was readily observed by immunoblotting of HEL and U937 cell lysates. U937- and HEL-SLFN11KO cells were incubated with increasing concentrations of cytarabine (AraC), which is the backbone of most chemotherapy regimens currently used in AML treatment. Both U937- and HEL-SLFN11KO cells were more resistant to AraC than their respective control cells. To examine the mechanism of resistance in U937-SLFN11KO cells, SLFN11KO and control cells were treated with AraC for up to 8 hrs, and lysates were subjected to immunoblotting for various DNA damage response proteins. There were higher baseline levels of multiple DNA damage-related proteins (including Chk1 and Chk2) in the SLFN11KO cells. There was also prolonged activation of the DNA damage pathway in U937-SLFN11KO cells, as evidenced by phosphorylation of the ATR substrate Chk1 (Ser345) through 8 hours, whereas phospho-Chk1 levels decreased in control cells by 8 hours. Interestingly, this prolonged activation occurred without a concomitant increase in γH2AX (a marker of DNA damage and double strand breaks). Because U937-SLFN11KO cells demonstrated a more pronounced activation of the ATR/Chk1 pathway in response to AraC, we subjected U937-SLFN11KO and control cells to increasing concentrations of AraC in combination with a small dose (0.3 μM) of the ATR inhibitor VE822. Notably, ATR inhibition restored sensitivity of SLFN11KO cells to AraC. These results suggest that SLFN11KO cells are resistant to DNA damaging agents via upregulation and activation of DNA repair proteins, and that adding inhibitors of these proteins can decrease resistance to chemotherapy agents in SLFN11KO cells. In contrast, SLFN11KO cells remained sensitive to AZA and DAC, suggesting that HMAs may be preferable to AraC for patients with SLFN11-low AML. Conclusions: Low SLFN11 levels predict poor response to standard chemotherapy agents (i.e. AraC) in AML cells, suggesting that SLFN11 may prove to be an important predictive biomarker for AML patients. In addition, SLFN11-low AML cells have an increased reliance on DNA repair pathways, and inhibition of DNA repair proteins such as ATR may enhance responses to AraC in these cells. This raises the possibility of patient selection based on SLFN11 levels for specific combination approaches for the treatment of AML. Figure 1. Kaplan Meier survival curves of AML patients in the TCGA (LAML) database with high (top 50th percentile) or low (bottom 50th percentile) SLFN11 expression using UCSC Xena (Goldman et. al. Nat Biotechnol 2020). Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Effects of SIDT2 on the miR-25/NOX4/HuR axis and SIRT3 mRNA stability lead to ROS-mediated TNF-α expression in hydroquinone-treated leukemia cells.

Our previous studies indicated that the benzene metabolite hydroquinone (HQ) evokes the ROS/p38 MAPK/protein phosphatase 2A/tristetraprolin axis, leading to increased TNF-α expression in human acute myeloid leukemia cell lines U937 and HL-60. In this study, we aimed to identify the upstream pathway involved in ROS-mediated TNF-α expression. HQ treatment increased SIDT2 expression, which subsequently decreased miR-25 and SIRT3 expression in U937 cells. Notably, miR-25 downregulation promoted SIDT2 expression in HQ-treated U937 cells. SIDT2 induced lysosomal degradation of SIRT3 mRNA, but inhibited miR-25 expression through a lysosome-independent pathway. MiR-25 inhibition reduced NOX4 mRNA turnover, resulting in increased NOX4 protein levels. NOX4 induces mitochondrial ROS production and HuR downregulation. Restoration of HuR expression increased SIRT3 expression, suggesting that NOX4-mediated HuR downregulation promotes SIDT2-mediated degradation of SIRT3 mRNA. Inhibition of NOX4 or SIRT3 overexpression abolished HQ-induced ROS production, thereby abolishing TNF-α upregulation. Overall, these results indicate that SIDT2 regulates the miR-25/NOX4/HuR axis and SIRT3 mRNA destabilization, leading to ROS-mediated TNF-α upregulation in HQ-treated U937 cells. HQ-induced increase in TNF-α expression in HL-60 cells was also mediated through a similar pathway.

The Antileukemia Activity of ZSTK474 on U937 Cells

To investigate the antileukemia activity of phosphatidylinositol-3 kinase (PI3K) inhibitor ZSTK474 on human leukemia cell line U937. MTT, soft agar assay, flow cytometric analysis and western blot were used to detect the effect of ZSTK474 on U937 cell proliferation, tumorigenicity, cell cycle, cell apoptosis and phosphorylation levels of the key factor of PI3K/AKT pathway. Chou-Talalay method was used to evaluate the combination of ZSTK474 with Cytarabine or Homoharringtonine. PI3K inhibitor ZSTK474 could inhibit the proliferation and tumorigenicity of U937 cell, induce G1 cell cycle arrest and promote cell apoptosis, and enhance intracellular ROS production and decrease MMP, downregulate Cyclin D1, p-Rb, BCL-2 and upregulate p27, caspase-9, caspase-3, PARP and BAX. Furthermore, the phosphorylation of PDK1, GSK-3β, AKT and mTOR could be downregulated by ZSTK474. The combination of ZSTK474 with Homoharringtonine was synergistic. ZSTK474 can inhibit the pathway of PI3K/AKT, ZSTK474 alone or in combination with Homoharringtonine shows potential antileukemia activity on U937 cells.

Honokiol-Chlorambucil Co-Prodrugs Selectively Enhance the Killing Effect through STAT3 Binding on Lymphocytic Leukemia Cells In Vitro and In Vivo

The broad-spectrum DNA alkylating therapeutic, chlorambucil (CBL), has limited safety and shows lower therapy effect because of a short half-life while used in the clinic. Therefore, it is very necessary to develop a more efficient and safer type of CBL derivate against tumors with selective targeting of cancer cells. In addition, the natural product of honokiol (HN), the novel potent chemo-preventive or therapeutic entity/carrier, can target the mitochondria of cancer cells through STAT3 to prevent cancer from spreading and metastasizing. In this study, we designed and synthesized the honokiol–chlorambucil (HN–CBL) co-prodrugs through carbonate ester linkage conjugating with the targeted delivery help of the HN skeleton in cancer cells. Biological evaluation indicated that HN–CBL can remarkably enhance the antiproliferation of human leukemic cell lines CCRF-CEM, Jurkat, U937, MV4-11, and K562. Furthermore, HN–CBL can also selectively inhibit the lymphocytic leukemia (LL) cell survival compared to those mononuclear cells derived from healthy donors (PBMCs), enhance mitochondrial activity in leukemia cells, and induce LL cell apoptosis. Molecular docking and western blot study showed that HN–CBL can also bind with the STAT3 protein at some hydrophobic residues and downregulate the phosphorylation level of STAT3-like HN. Significantly, HN–CBL could dramatically delay leukemia growth in vivo with no observable physiological toxicity. Thus, HN–CBL may provide a novel and effective targeting therapeutic against LL with fewer side effects.

Cytotoxicity of the Sesquiterpene Lactone Spiciformin and Its Acetyl Derivative against the Human Leukemia Cell Lines U-937 and HL-60.

Spiciformin (1) is a sesquiterpene lactone with a germacrane skeleton that is found in two Tanacetum species endemic to the Canary Islands. In this study, the cytotoxicities of 1 and its acetyl derivative (2) were evaluated against human tumor cells. These sesquiterpene lactones were cytotoxic against human acute myeloid leukemia (U-937 and HL-60) cells, even in cells over-expressing the pro-survival protein Bcl-2, but melanoma (SK-MEL-1) and human mononuclear cells isolated from blood of healthy donors were more resistant. Both compounds are apoptotic inducers in human leukemia U-937 cells. Cell death was mediated by the processing and activation of initiator and effector caspases and the cleavage of poly(ADP-ribose) polymerase, and it was blocked by a broad-spectrum caspase inhibitor and (in the case of sesquiterpene lactone 2) by the selective caspase-3/7, -8, and -9 inhibitors. In addition, certainly in the case of compound 2, this was found to be associated with a decrease in mitochondrial membrane potential, downregulation of the anti-apoptotic protein Bcl-2, activation of the mitogen-activated protein kinases signaling pathway, and generation of reactive oxygen species. It will, therefore, be relevant to continue characterization of this class of compounds.

Heme Oxygenase-1/Ferritin in Protection of Leukemia Cells from Oxidative Stress Induced by Catalytic System “Teraphtal + Ascorbic Acid”

Background. As is well known, cytotoxic mechanism of antitumor agent, i.e. catalytic system “teraphtal + ascorbic acid” (“TF+AA”), is associated with production of reactive oxygen species (ROS) and induction of oxidative stress in it. The “heme oxygenase-1/ferritin” (HO-1/Ft) system contributes to antioxidant defense. Aim. To analyze HO-1/Ft value in protection of leukemia cells from toxicity induced by antitumor agent “TF+AA”. Materials & Methods. The study was based on human leukemia cell lines K562 and U937. HO-1/Ft basal and drug-induced expression on mRNA and protein levels was analyzed by real-time RT-PCR and Western blot, ROS concentration in cells was determined by flow cytometry, and drug cytotoxicity was measured by MTT assay. Results. Our data showed constitutively active HO-1 in U937 myelomonoblasts whereas in K562 erythroblasts the expression of this protein was blocked on the mRNA level. Hemin, HO-1 agonist, induces HO-1 and Ft co-expression in U937 cells on the mRNA and protein levels. HO-1/Ft activation by hemin in U937 cells does not affect their “TF+AA” sensitivity and doubles, for example, the cytarabine sensitivity. “TF+AA” appeared to cause up-regulation of HO-1/ Ft genes, the expression of which quadruples or increases by half, respectively, compared with basal level. Preincubation of U937 myelomonoblasts with deferoxamine, iron chelator, results in doubling of their “TF+AA” resistance. However, the use of iron-containing TF analogs leads to its doubled cytotoxicity. Conclusion. In leukemia cell line U937 with constitutively active НО-1/Ft the heme-dependent activation of it does not considerably contribute to protection of cells from “TF+AA” toxicity. The system “TF+AA” is НО-1 and Ft expression inducer in U937 myelomonoblasts. Cytotoxic mechanism of “TF+AA” involves intracellular pool of “labile” non-heme iron, the level of which affects the drug sensibility of leukemia cells.

Synthesis and biological evaluation of aurora kinases inhibitors based on N-trisubstituted pyrimidine scaffold

The inhibition of the members of aurora kinase family using ATP-competitive small molecules is an effective method for anticancer therapeutics. Based on our previous work, we synthesized 12 new N-trisubstituted pyrimidine derivatives and evaluated their biological activities and stabilities. Among them, compound 11j showed the best inhibition against aurora A kinase (IC50 = 7.1 nM), human leukemia cell line U937 (IC50 = 12.2 nM) and the growth of U937 xenograft tumors in vivo. By the flow cytometry and immunofluorescence analysis of U937, we found that compound 11j can induced polyploidy formation including (4N, 8N and 16N) and induce defects in both chromosome alignment and spindle formation. Furthermore, compound 11j exhibited good chemical, physical, and thermal stabilities. All these results suggested that 11j is a promising lead compound for further development of anticancer drugs.

Linezolid-induced Apoptosis through Mitochondrial Damage and Role of Superoxide Dismutase-1 in Human Monocytic Cell Line U937

Cytopenia is a major adverse event associated with linezolid therapy. The objective of this study was to examine whether the cytotoxicity of linezolid to eukaryotic cells was associated with mitochondrial dysfunction and apoptosis-like cell death in human leukemic monocyte lymphoma cell line U937. Apoptosis-like cell death was clearly observed when cells were incubated with linezolid, depending on the duration and linezolid concentration. Mitochondrial membrane potential of cells treated with linezolid collapsed in a short period of time, but the number of mitochondria did not decrease. Cytotoxicity of linezolid was relieved by the knockdown of superoxide dismutase-1 in U937 cells. On the other hand, no autophagy was observed in cells treated with linezolid. These results suggest that mitochondrial damages would be linked to the induction of apoptosis in U937 cells treated with linezolid and that its mechanism does not involve autophagy.

Invitro and invivo anticancer effects of marmesin in U937 human leukemia cells are mediated via mitochondrial-mediated apoptosis, cell cycle arrest, and inhibition of cancer cell migration.

Leukemia is one of the highly lethal cancers among all pediatric cancers. With limited drug options and the severe side effects associated with the current chemotherapy, there is pressing need to look for new and novel anticancer agents. Against this backdrop, in the present study we evaluated the anticancer activity of a natural coumarin, marmesin against human leukemia cell line U937 and normal human monocytes It was observed that marmesin exhibited an IC50 value of 40µM and exerted its cytotoxic effects in a dose-dependent manner. However, the cytotoxic effects of marmesin were comparatively lower for the normal human monocytes as evident from the IC50 of 125µM. Our results indicated that marmesin inhibits colony formation and induces apoptosis dose-dependently. We also investigated the effect of marmesin on the expression of Bax and Bcl-2 proteins. It was observed that marmesin treatment triggered upregulation of Bax and downregulation of Bcl-2 causing significant increase in the Bax/Bcl-2 ratio, marmesin could also induce ROS mediated alterations in mitochondrial membrane potential. Additionally, marmesin induced G2/M cell cycle arrest and significantly inhibited cell migration potential of leukemia cells at the IC50. Remarkably, marmesin prevent tumor growth significantly invivo at the dosage of 30mg/kg invivo. These results strongly indicate that marmesin may prove to be a novel anticancer lead for the management of leukemia.

ATIVIDADE CITOTÓXICA DO EXTRATO DE CROTON URUCURANA BAILL CONTRA LINHAGENS DE CÉLULAS LEUCÊMICAS HUMANAS U937 E THP1

Leukemias are malignant neoplasms that affect blood cells and originate in bone marrow. These are cancers of high incidence and are difficult to treat and there is a constant search for more efficient therapies. The present work investigated the cytotoxic action of the hydroalcoholic extract of Croton urucurana in human leukemia cells U937 and THP-1. The U937 and THP-1 cell lines were plated in a 100 μL/well volume (1x106 cells/mL) in 96-well plates, treated with extracts at final concentrations of 50 μg/mL, 100 μg/mL, 200 μg/mL and 400 μg/mL and 800 μg/mL for cell viability tests with MTT(-3- (4.5-dimethyl-2-thiazole) 2.5-diphenyl-2H-tetrazolium bromide). After 48h, viability was assessed by MTT and the supernatant was used for determination of the Lactate Dehydrogenase (LD) enzyme. Fluorescence microscopy was used to evaluate apoptosis. The extract was able to reduce cell viability by the MTT assay, increase LD release and induce apoptosis in both cell lines tested at concentrations of 400 and 800 μg/ mL (p≤0.05). The C. urucurana extract presented cytotoxic activity against human leukemic cell lines U937 and THP-1, presenting itself as promising in the search for new antineoplastic agents.

Study of the effects and mechanism of all-trans retinoic acid on leukemic cell line U937 cells with NPM1 mutation

目的探讨全反式维甲酸（ATRA）对NPM1突变的白血病细胞系U937细胞的作用及其机制。方法转染NPM1突变型（A型）质粒至U937细胞系构建稳定克隆A1和A2，利用Western blot法和荧光共聚焦技术鉴定细胞。MTT法检测细胞增殖活性，流式细胞术检测细胞周期和细胞凋亡，显微镜下计数检测集落形成能力，Western blot法检测细胞增殖相关信号通路蛋白表达。结果①NPM1突变型U937细胞A1和A2经ATRA处理后，细胞增殖活性分别为对照组（未经ATRA处理组）水平的52.6%和35.8%，差异均有统计学意义（t=3.649，P=0.010；t=4.906，P=0.002）。②突变型细胞A1和A2的G0/G1期比例经ATRA处理后较对照组分别增加20.1%和35.8%，差异均有统计学意义（t=4.544，P=0.010；t=15.850，P<0.001）。③U937细胞经ATRA处理后集落生长受抑制，其中空载体组集落数目下降了32.7%，野生型组下降了57.9%，突变型组（A1）下降了90.9%，差异均有统计学意义（t=8.507，P=0.010；t=22.090，P<0.001；t=90.200，P<0.001）。④突变型U937细胞经ATRA处理后p-ERK水平明显降低。⑤突变型U937细胞接受化疗药物联合ATRA处理后细胞凋亡率明显高于化疗药物单药处理组，在化疗药物处理后添加ATRA能导致更多的细胞凋亡。结论ATRA能够抑制NPM1突变的U937细胞增殖和克隆形成，将细胞阻滞于G0/G1期，显著降低其ERK磷酸化水平。在NPM1突变的U937细胞中，当ATRA在化疗药物处理后添加能够与化疗药物发挥更强的协同杀伤效果。

A novel antitumor compound nobiliside D isolated from sea cucumber (Holothuria nobilis Selenka).

An anticancer compound, triterpene glycoside, was isolated from Holothuria nobilis Selenka. Its chemical structure and configuration were determined by two-dimensional nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry. The novel active compound was identified as nobiliside D, with the molecular formula C40H61O17SNa and chemical name 3-O-[-β-D-pyranosyl (1-2)-4'-O-sulfon-ate-β-D-xylopyranosyl]-alkoxy-9-ene-3β, 12α, 17α, 25β-4 alcohol. An antitumor test was performed using xCELLigence Real-Time Cell Analysis. Nobiliside D exhibited inhibitory effects on human leukemic cell line K562, human leukemia cell line U937, human lung cancer cell line A-549, human cervix carcinoma cell line HeLa, human breast cancer cell line MCF-7 and human liver carcinoma cell line HepG2. Nobiliside exhibited the greatest inhibitory effect on K562 and MCF-7 cells with an IC50 of 0.83±0.14 and 0.82±0.11 µg/ml, respectively. When human tumor cell lines K562 and MCF-7 were treated by nobiliside D (0.5 µg/ml) for 24 h, 45.8% of K562 cells and 58.7% of MCF-7 cells were apoptotic, whereas only 0.5% of un-treated control cells were apoptotic. These data indicate the compound should offer potential as a novel drug for the treatment of a range of cancers.

RKTG overexpression inhibits proliferation and induces apoptosis of human leukemia cells via suppression of the ERK and PI3K/AKT signaling pathways.

Raf kinase trapping to Golgi (RKTG) is reported to be a tumor suppressor in a number of solid tumors due to its negative modulation of the Ras/Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (ERK) pathways. However, the role of RKTG in the progression of leukemia remains unknown. In the present study, a human leukemia U937 cell line overexpressing RKTG was established, and the effect of RKTG on proliferation, cell cycle and apoptosis of human leukemia cells was analyzed. The results of the present study demonstrated that exogenous overexpression of RKTG significantly inhibited cell proliferation, which was accompanied by cell cycle arrest. Apoptosis assay and Hoechst staining demonstrated that the percentage of apoptotic cells in RKTG overexpressing cells was markedly increased. Furthermore, western blotting showed that RKTG overexpression significantly increased the level of cleaved caspase 3, B-cell lymphoma 2 (Bcl2)-associated X apoptosis regulator and reduced the level of Bcl-2. In addition, the activation of ERK and phosphoinositide 3-kinase (PI3K)/AKT serine/threonine kinase 1 signaling pathways in human leukemia cells was also suppressed by RKTG overexpression. In conclusion, the present study demonstrated the tumor-suppressive effect of RKTG on human leukemia cells, which seem to be partially dependent on the suppression of ERK and PI3K/AKT signaling. Overexpression of RKTG may be a potential therapeutic target for the treatment of leukemia.

Combination of Homoharringtonine with Arsenic Trioxide Induces Apoptosis of Human Acute Myeloid Leukemia Cell Line U937

To investigate the effects and mechanisms of the combination of homoharringtonine (HHT) with arsenic trioxide(As2O3) on human myeloid cell line U937 in vitro. MTT method was used to determine the antiproliferating effect of different concentrations of HHT, As2O3 and their combination on U937 cells; the flow cytometry with Annexin-V-FITC/PI double staining was used to determine the apoptosis-induced effect of HHT and As2O3 alone or their combination; Western blot method was used to detect the protein expression of P-AktSer473,P-AktThr308,BCL-XL, BID,MCL-1,P-MCL-1 and so on. HHT and As2O3 could significantly inhibit proliferation of U937 cells and induce their apoptosis. The combination of these 2 drugs could significantly enhance the early apoptosis of U937 cells. After combination of these 2 drugs was used, the protein expressions of P-AktSer473,P-AktThr308,MCL-1,P-MCL-1 and BCL-XL were obviously down-regulated, but the expression of BID protein did not change. The combination treatment of HHT and As2O3 can synergistically inhibit the growth of U937 cells through inhibition of PI3K/Akt signal way and MCL-1 protein.

PH-Sensitive Nanomicelles for High-Efficiency siRNA Delivery in Vitro and in Vivo: An Insight into the Design of Polycations with Robust Cytosolic Release.

The extremely low efficient cytosolic release of the internalized siRNA has emerged recently as a central issue for siRNA delivery, while there is a lack of guidelines to facilitate the cytosolic release of internalized siRNA. To address these concerns, we studied the contribution of the pH-sensitive inner core on handling the cytosolic release of siRNA delivered by a series of PG-P(DPAx-co-DMAEMAy)-PCB amphiphilic polycation nanomicelles (GDDC-Ms) with extremely low internalization (<1/4 of lipofactamine 2000 (Lipo2000)). Significantly, just by varying the mole ratio of DPA and DMAEMA to adjust the initial disassembly pH (pHdis) of the core near to 6.8, GDDC4-Ms/siRNA could get nearly 98.8% silencing efficiency at w/w = 12 with 50 nM siRNA and ∼78% silencing efficiency at w/w = 30 with a very low dose of 5 nM siRNA in HepG-2 cell lines, while Lipo2000 only got 65.7% with 50 nM siRNA. Furthermore, ∼98.4% silencing efficiency was also realized in the hard-to-transfect human acute monoblastic leukemia cell line U937 by GDDC4-Ms/siRNA (at w/w = 15, 50 nM siRNA), in the inefficient case for Lipo2000. Additionally, the high silencing efficiency (∼80%) in skin tissue in vivo was discovered. Undoubtedly, the robust potential of GDDC4-Ms in handling the cytosolic release paves a simple but efficient new way for the design of the nonviral siRNA vector.

Multiwalled carbon nanotube buckypaper induces cell cycle arrest and apoptosis in human leukemia cell lines through modulation of AKT and MAPK signaling pathways

MWCNT buckypaper (BP) shows physico-chemical and mechanical properties that make it potentially useful as a substrate in nano-bio interface research including in tissue engineering. When used as a scaffold material, BP comes into contact with host cells and surrounding tissues; therefore it is critical to determine its biocompatibility and interaction with living systems. The aim of this study was to investigate BP effects on cell growth, apoptosis and reactive oxygen species (ROS) production in three human leukemia cell lines HL-60, U-937 and K-562. BP was able to induce both the reduction of cell proliferation, associated with an arrest in G0/G1 phase of cell cycle and the increase of apoptosis in leukemic cell lines, thus exerting both cytostatic and cytotoxic effects. The growth inhibitory effect was likely mediated by the decrease of cyclins D, E, A, B1 levels and CDK4 expression; meanwhile, the apoptotic effect, not mediated by ROS production, was presumably due to the combined action of the survival and pro-apoptotic AKT and MAPK signal transduction pathways. These results raised the issue of biocompatibility of MWCNT BP for the creation of carbon nanotubes based scaffolds to utilize as prostheses in tissue engineering.