Human Leukemia U937 Cells Research Articles

Portulacerebroside a Inhibits Adhesion, Migration, and Invasion of Human Leukemia HL60 Cells and U937 Cells through the Regulation of p38/JNK Signaling Pathway [Retraction

[This retracts the article DOI: 10.2147/OTT.S117523.].

Inhibition of Ferulic Acid on U937 Cell Growth and Its Related Mechanism

To investigate the effects of ferulic acid (FA) on proliferation, apoptosis and Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling pathway of human acute myeloid leukemia (AML) U937 cells. Different concentrations of FA (0、10、25、50、100、200 μmol/L) was used to treat human AML cell lines Kasumi-1, HL-60, and U937 cells respectively for 24 h. The cell survival rate was detected by cell counting kit-8 method, and the 50% inhibitory concentration (IC50) of each cell line was calculated. The U937 cells were divided into control group, FA group (50 μmol/L FA), FA+pcDNA group (50 μmol/L FA+transfected with empty plasmid), FA+pcDNA-TLR4 group (50 μmol/L FA+transfected with TLR4 overexpression plasmid). Flow cytometry was used to detect U937 cell cycle and cell apoptosis; plate clone formation test was used to detect U937 cell clone formation ability; fluorescence quantitative PCR was used to detect the TLR4, NF-κB p65 mRNA levels in U937 cells; Western blot was used to detect the expression levels of CyclinD1, CyclinE, Bcl-2 related X protein (Bax), B cell lymphoma-2 (Bcl-2), Caspase-3, TLR4, and NF-κB p65 protein in U937 cells. With the increase of FA concentration, the survival rates of Kasumi-1, HL-60 and U937 cells gradually decreased(r=-0.919, r=-0.909, r=-0.900), the IC50 of U937 cells was 50.25±2.23 μmol/L. Compared with the control group, after drug treatment of U937 cells, the ratio of G0/G1 phase cells, apoptosis rate, expression levels of Bax and Caspase-3 proteins in FA group were significantly increased (P<0.05), the number of cell clones, the ratios of S phase and G2/M phase cells, expression levels of CyclinD1, CyclinE and Bcl-2 proteins, and TLR4, NF-κB p65 mRNA and protein were significantly decreased (P<0.05); compared with FA group and FA+pcDNA group, the ratio of G0/G1 phase cells, apoptosis rate, expression levels of Bax and Caspase-3 proteins in FA+pcDNA-TLR4 group were significantly decreased (P<0.05), the number of cell clones, the ratios of S phase and G2/M phase cells, expression levels of expression levels of CyclinD1, CyclinE and Bcl-2 proteins, and TLR4, NF-κB p65 mRNA and proteins were significantly increased (P<0.05). FA inhibits U937 cell proliferation and promotes cell apoptosis by inhibiting the TLR4/NF-κB signaling pathway.

Guanidine Derivatives Containing the Chalcone Skeleton Are Potent Antiproliferative Compounds against Human Leukemia Cells.

In this study, we investigated the effects of eleven synthetic guanidines containing the 1,3-diphenylpropenone core on the viabilities of six human cancer cells. The most cytotoxic compound against human cancer cells of this series contains a N-tosyl group and a N-methylpiperazine moiety 6f. It was cytotoxic against leukemia cells (U-937, HL-60, MOLT-3, and NALM-6) with significant effects against Bcl-2-overexpressing U-937/Bcl-2 cells as well as the human melanoma SK-MEL-1 cell line. It exhibited low cytotoxicity against quiescent or proliferating human peripheral blood mononuclear cells. The IC50 value for the leukemia U-937 cells was 1.6 ± 0.6 µM, a similar value to that in the antineoplastic agent etoposide. The guanidine containing a N-phenyl substituent 6i was also as cytotoxic as the guanidine containing the N-tosyl substituent and the N-methylpiperazine group 6f against human U-937 leukemia cells and both synthetic guanidines were potent apoptotic inducers. Cell death was mediated by the activation of the initiator caspase-9 and the executioner caspase-3, and associated with the release of cytochrome c. These synthetic guanidines are potent cytotoxic compounds against several human leukemia cells and even the human melanoma cell line SK-MEL-1 and might be useful in the development of new strategies in the fight against cancer.

Antimicrobial Stewardship Initiatives and Studies by the Hospital Pharmacist: Study of Linezolid-associated Thrombocytopenia

Infectious disease chemotherapy pharmacists should evaluate the appropriate usage of antimicrobial agents within the hospital, support in-patient pharmacists in treating infections, and appropriately use antimicrobial agents throughout the infection treatment course. Hospital pharmacists are required to strive to prevent adverse events and support the appropriateness of antimicrobial use to cure infectious diseases. Our hospital's antimicrobial stewardship team provides support and information on the proper use of antimicrobial agents in collaboration with in-patient pharmacists. Among other things, thrombocytopenia in linezolid therapy can often be an obstacle to treatment. We conducted clinical and basic research on thrombocytopenia, the major adverse event associated with linezolid. We first conducted a retrospective study investigating renal dysfunction and thrombocytopenia associated with vancomycin and linezolid treatments. Renal dysfunction occurred more frequently in patients receiving vancomycin than those receiving linezolid (p=0.032). In contrast, thrombocytopenia occurred more frequently in patients treated with linezolid than those treated with vancomycin (p<0.001). A significantly higher rate of thrombocytopenia was observed in patients with linezolid treatment durations >7.5 days. Secondly, we examined whether the linezolid cytotoxicity to eukaryotic cells was associated with mitochondrial dysfunction and apoptosis-like cell death in U937 human leukemic monocyte lymphoma cells. Apoptosis-like cell death was clearly observed in cells incubated with linezolid in concentration- and duration-dependent manners. Linezolid cytotoxicity was relieved by superoxide dismutase-1 knockdown in U937 cells. These results suggest that mitochondrial damage could be linked to the induction of apoptosis in linezolid-treated U937 cells.

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

Effect of caffeine on mitochondrial biogenesis in the skeletal muscle - A narrative review.

Caffeine is one of the most widely used substances as recreational drug for performance-enhancement in sport, underpinned by a strong evidence base. Although the effects of caffeine are widely investigated within the scope of performance physiology, the molecular effects of caffeine within skeletal muscle remain unclear. Evidence from invitro and invivo models suggest that caffeine regulates the glucose metabolism in the skeletal muscle. Moreover, caffeine seems to stimulate CaMKII, PPARδ/β, AMPK and PGC1α, classical markers of exercise-adaptations, including mitochondrial biogenesis and mitochondrial content. This review summarizes evidence to suggest caffeine-effects within skeletal muscle fibers, focusing on the putative role of caffeine on mitochondrial biogenesis to explore whether caffeine supplementation might be a strategy to enhance mitochondrial biogenesis.

Carboxyl Group-Modified Myoglobin Induces TNF-α-Mediated Apoptosis in Leukemia Cells.

Previous studies have shown that chemical modification may increase the activity of proteins or confer novel activity to proteins. Some studies have indicated that myoglobin (Mb) is cytotoxic; however, the underlying mechanisms remain unclear. In this study, we investigated whether chemical modification of the carboxyl group by semicarbazide could promote the Mb cytotoxicity in human leukemia U937 cells and the underlying mechanism of semicarbazide-modified myoglobin (SEM-Mb)-induced U937 cell death. The semicarbazide-modified Mb (SEM-Mb) induced U937 cell apoptosis via the production of cleaved caspase-8 and t-Bid, while silencing of FADD abolished this effect. These findings suggest that SEM-Mb can induce U937 cell death by activating the death receptor-mediated pathway. The SEM-Mb inhibited miR-99a expression, leading to increased NOX4 mRNA and protein expression, which promoted SIRT3 degradation, and, in turn, induced ROS-mediated p38 MAPK phosphorylation. Activated p38 MAPK stimulated miR-29a-dependent tristetraprolin (TTP) mRNA decay. Downregulation of TTP slowed TNF-α mRNA turnover, thereby increasing TNF-α protein expression. The SEM-Mb-induced decrease in cell viability and TNF-α upregulation were alleviated by abrogating the NOX4/SIRT3/ROS/p38 MAPK axis or ectopic expression of TTP. Taken together, our results demonstrated that the NOX4/SIRT3/p38 MAPK/TTP axis induces TNF-α-mediated apoptosis in U937 cells following SEM-Mb treatment. A pathway regulating p38 MAPK-mediated TNF-α expression also explains the cytotoxicity of SEM-Mb in the human leukemia cell lines HL-60, THP-1, K562, Jurkat, and ABT-199-resistant U937. Furthermore, these findings suggest that the carboxyl group-modified Mb is a potential structural template for the generation of tumoricidal proteins.

Overexpressed fibroblast growth factor receptors increase 1,25-dihydroxyvitamin D-dependent differentiation of acute myeloid leukemia cells

Many malignancies are driven by mutations within the gene for fibroblast growth factor receptor 1 (FGFR1). Previously, we have shown that signal transduction from the FOP2–FGFR1 fusion protein in acute myeloid leukemia KG1 cells is responsible for a low level of expression of the vitamin D receptor gene. In this paper, we address whether other fibroblast growth factor receptors regulate the vitamin D receptor (VDR) gene. We used the human myeloid leukemia U937 and HL60 cells, the bone cancer cell line U2OS, and cell transfection methods to answer the question. For myeloid leukemia cells, overexpression of FGFRs 1–3 genes caused a shift towards monocytic differentiation; this was extracellular regulated kinase (Erk) 1,2-dependent. Overexpression of FGFRs 1–3 genes also upregulated expression of the VDR gene, further sensitizing these cells to 1,25-dihydroxyvitamin D-induced monocyte differentiation. When we increased expression in bone cells, fibroblast growth factor receptors did not upregulate VDR gene expression, nor influence the activity of VDR. Fibroblast growth factor receptors are overexpressed in many neoplasms. Therefore, it may be reasonable to use vitamin D analogs to treat these cancers, to activate VDR and drive cell differentiation.

Discovery of Hexahydrofuro[3,2-b]furans as New Kinase-Selective and Orally Bioavailable JAK3 Inhibitors for the Treatment of Leukemia Harboring a JAK3 Activating Mutant.

Janus kinase 3 (JAK3) is a potential target for the treatment of hematological malignancies. Herein, we report the discovery of a series of new orally bioavailable irreversible JAK3 kinase inhibitors. The representative compound 12n potently inhibited JAK3 kinase activity with an IC50 value of 1.2 nM and was more than 900-fold selective over JAK1, JAK2, and Tyk2. Cell-based assays revealed that 12n significantly suppressed phosphorylation of JAK3 and the downstream effectors STAT3/5 and also robustly restrained proliferation of BaF3 cells transfected with JAK3M511I activating mutation and human leukemia U937 cells harboring JAK3M511I with IC50 values of 22.9 and 20.2 nM, respectively. More importantly, 12n showed reasonable pharmacokinetic (PK) properties, and oral administration of 12n at a dose of 50 mg/kg twice daily led to tumor regression in a U937 cell inoculated xenograft mouse model. Thus, 12n represents a promising lead compound for further optimization to discover new therapeutic agents for hematological malignancies.

Cytotoxic Activity of Bark of Oroxylon indicum Benth against U937 and K562 Human Leukemic Cell Lines

Cancer, a leading cause of death, is a condition where cells have lost control over their mode of growth. We evaluated the anti- proliferative and cytotoxic and apoptogenic activity of methanolic extract of Oroxylon indicum Bark (MEOIB) on U937, K562 cells and normal lymphocytes. The cell viability was studied by MTT assay. Cell morphology was determined by Fluorescence, Confocal microscope and DNA fragmentation by agarose gel electrophoresis study. MEOIB inhibited the viability of cells in a time &amp; concentration dependent manner. The Morphologically it was found that externalization of PS from inner leaflet to outer leaflet of the cell membrane and condensed chromatin, membrane blabbing, fragmentation of nuclei in all the treated cells than control and DNA bands appeared in the form of ladder after treatment with MEOIB. The present study reveals that the MEOIB possesses potent anti-leukemic activity against U937 and K562 cell line but there no toxicity in normal lymphocytes.

Cordycepin enhances hyperthermia-induced apoptosis and cell cycle arrest by modulating the MAPK pathway in human lymphoma U937 cells.

Hyperthermia induces cancer cell death. However, the cytotoxic effect of hyperthermia is not sufficient. Cordycepin can also induce apoptosis in cancer cells and enhance the antitumoral activity of irradiation. To examine cordycepin-mediated enhancement of hyperthermia-induced apoptosis, this study investigated the combined effects and apoptotic mechanisms of hyperthermia and cordycepin on human leukemia U937 cells. Cell viability and apoptosis were measured using MTT assays, Hoechst 33342 staining and Annexin V/PI double staining. The distribution of the cell cycle and sub-G1 phase, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were examined by flow cytometry. The expression of related proteins was analyzed by western blotting. Combined treatment with hyperthermia and cordycepin markedly augmented apoptosis by upregulating Bax and suppressing Bcl-2, Bid and activated caspase 3 and 8 expression, and apoptosis was decreased by Z-VAD-fmk (a pan caspase inhibitor). We also found that the MMP was significantly decreased and excessive ROS generation occurred. The combination treatment also induced arrest in the G2/M phase by downregulating cyclin dependent kinase 1 (CDK1) and cyclin B1 protein expression. Furthermore, it was observed that mitogen-activated protein kinase (MAPK) pathway including ERK, JNK and p38 signals was involved in the induction of apoptosis. The phosphorylated p38 and JNK were increased and ERK phosphorylation was decreased by the combined treatment. In addition, N-acetyl-L-cysteine (NAC) significantly protected the cells by restoring ROS levels and the activity of caspase-3, inactivating the MAPK pathway. Cordycepin significantly enhanced hyperthermia-induced apoptosis and G2/M phase arrest in U937 cells. The combined treatment enhanced apoptosis through the MAPK pathway and mitochondrial dysfunction, and these effects could be rescued by NAC. We report for the first time that cordycepin can be used as a hyperthermia sensitizer to treat leukemia.

Exploiting spectral information in Opto-Electronic Tweezers for cell classification and drug response evaluation

Cell responses to varying electric fields can reveal insights on cell biology with important implications for pharmaceutical and basic research. In this work, we exploit spectral information content in Opto-Electronic Tweezers (OET) systems through machine learning for label-free characterization of cell dielectric properties aimed at cell classification and drug response evaluation. A customized Polymethyl-methacrylate (PMMA) chip with ITO substrates and an a-Si layer was designed for OET-based manipulation of cells and integrated with an inverted microscope. We obtained OET cell signatures as spectra responses of kinematic and dynamic descriptors, which are the result of time-lapse measurements at increasing frequencies of the OET. Machine learning algorithms enable automatic selection and characterization of the information content present in the OET signature so derived. Experiments are performed on three biological case studies, involving 1) the discrimination of cell types among U937 human leukemia cells, PC-3 human prostate cancer cells and HaCaT human immortalized keratinocytes; 2) the evaluation of the effects of the chemotherapeutic agent etoposide on U937 cells at different concentrations; and 3) the evaluation of the effects of different exposure times of etoposide on U937 cells. The obtained results demonstrate that multiple levels of dielectric information can be extracted via OET cell signatures and clearly pose OET as a promising tool for cell discrimination and drug response evaluation.

BCL2 inhibitor ABT-199 and BCL2L1 inhibitor WEHI-539 coordinately promote NOXA-mediated degradation of MCL1 in human leukemia cells

Human leukemia U937 cells that were continuously treated with hydroquinone (HQ) were transformed into U937/HQ cells with increased MCL1 and BCL2L1 expression. Compared with their parental cells, U937/HQ cells were less sensitive to ABT-263 (BCL2/BCL2L1 inhibitor)/ABT-199 (BCL2 inhibitor) cytotoxicity. The combination of WEHI-539 (BCL2L1 inhibitor) with either ABT-199 or ABT-263 showed synergistic cytotoxicity to U937 and U937/HQ cells. Therefore, we further investigated the cytotoxic mechanism induced by the combination of WEHI-539 and ABT-199. The combined treatment of WEHI-539 and ABT-199 induced NOX4/ROS/p38 MAPK axis-mediated autophagy, which in turn accelerated β-TrCP mRNA turnover. Downregulation of β-TrCP increased Sp1 expression, thereby promoting Sp1-mediated NOXA transcription, which in turn induced NOXA-dependent MCL1 degradation. Enforced expression of MCL1 alleviated the cytotoxicity of WEHI-539 plus ABT-199 to induce the loss of mitochondrial membrane potential and cell viability. WEHI-539 alone induced Sp1/NOXA axis-mediated MCL1 downregulation, while ABT-199 significantly decreased the dose of WEHI-539 by approximately 350- and 50-fold to induce MCL1 suppression in parental and HQ-selected cells, respectively. Furthermore, WEHI-539 sensitized ABT-199-resistant U937 cells to ABT-199 cytotoxicity by inducing NOXA-mediated degradation of MCL1. Collectively, the data in this study indicate that ABT-199 and WEHI-539 cooperatively induce NOXA-dependent MCL1 degradation, and the inhibition of MCL1 mainly explains their combined cytotoxicity in parental, HQ-selected, and ABT-199-resistant U937 cells.

Retraction Note to: shRNA-mediated EMMPRIN silencing inhibits human leukemic monocyte lymphoma U937 cell proliferation and increases chemosensitivity to adriamycin.

Retraction Note to: shRNA-mediated EMMPRIN silencing inhibits human leukemic monocyte lymphoma U937 cell proliferation and increases chemosensitivity to adriamycin.

N-acetylcysteine Can Induce Massive Oxidative Stress, Resulting in Cell Death with Apoptotic Features in Human Leukemia Cells.

N-acetylcysteine (NAC), often used as an antioxidant-scavenging reactive oxygen species (ROS) in vitro, was recently shown to increase the cytotoxicity of other compounds through ROS-dependent and ROS-independent mechanisms. In this study, NAC itself was found to induce extensive ROS production in human leukemia HL-60 and U937 cells. The cytotoxicity depends on ROS-modulating enzyme expression. In HL-60 cells, NAC activated NOX2 to produce superoxide (O2•−). Its subsequent conversion into H2O2 by superoxide dismutase 1 and 3 (SOD1, SOD3) and production of ClO− from H2O2 by myeloperoxidase (MPO) was necessary for cell death induction. While the addition of extracellular SOD potentiated NAC-induced cell death, extracellular catalase (CAT) prevented cell death in HL-60 cells. The MPO inhibitor partially reduced the number of dying HL-60 cells. In U937 cells, the weak cytotoxicity of NAC is probably caused by lower expression of NOX2, SOD1, SOD3, and by the absence of MOP expression. However, even here, the addition of extracellular SOD induced cell death in U937 cells, and this effect could be reversed by extracellular CAT. NAC-induced cell death exhibited predominantly apoptotic features in both cell lines. Conclusions: NAC itself can induce extensive production of O2•− in HL-60 and U937 cell lines. The fate of the cells then depends on the expression of enzymes that control the formation and conversion of ROS: NOX, SOD, and MPO. The mode of cell death in response to NAC treatment bears apoptotic and apoptotic-like features in both cell lines.

Exploiting the Anti-Inflammatory Potential of White Capsicum Extract by the Nanoformulation in Phospholipid Vesicles.

The peppers of the Capsicum species are exploited in many fields, as flavoring agents in food industry, or as decorative and therapeutic plants. Peppers show a diversified phytochemical content responsible for different biological activities. Synergic activity exerted by high levels of antioxidant compounds is responsible for their important anti-inflammatory property. A methanolic extract was obtained from a new pepper genotype and tested for anti-inflammatory activity. The extract was incorporated into phospholipid vesicles to increase the bioavailability of its bioactive components. Two types of phospholipid vesicles were produced, conventional liposomes and Penetration Enhancer containing Vesicles (PEVs). They were tested in human monoblastic leukemia U937 cell line, showing no cytotoxic effect. The intracellular reactive oxygen species (ROS) and nitric oxide (NO) levels were measured to value the in vitro efficacy of the vesicles in regulating inflammatory responses. Liposomal incorporation significantly reduced ROS levels in extract-treated LPS-activated cells. Furthermore, LC-MS/MS analyses demonstrated that liposomes facilitated the transport of the extract components across the cell membrane and their accumulation into the cytoplasm.

Carboxyl group-modified α-lactalbumin induces TNF-α-mediated apoptosis in leukemia and breast cancer cells through the NOX4/p38 MAPK/PP2A axis

To clarify the mechanism of semicarbazide-modified α-lactalbumin (SEM-LA)-mediated cytotoxicity, we investigated its effect on human U937 leukemia cells and MCF-7 breast cancer cells in the current study. SEM-LA induced apoptosis in U937 cells, which showed increased NOX4 expression, procaspase-8 degradation, and t-Bid production. FADD depletion inhibited SEM-LA-elicited caspase-8 activation, t-Bid production, and cell death, indicating that SEM-LA activated death receptor-mediated apoptosis in U937 cells. SEM-LA stimulated Ca2+-mediated Akt activation, which in turn increased Sp1- and p300-mediated NOX4 transcription. The upregulation of NOX4 expression promoted ROS-mediated p38 MAPK phosphorylation, leading to protein phosphatase 2A (PP2A)-regulated tristetraprolin (TTP) degradation. Remarkably, TTP downregulation increased the stability of TNF-α mRNA, resulting in the upregulation of TNF-α protein expression. Abolishment of Ca2+-NOX4-ROS axis-mediated p38 MAPK activation attenuated SEM-LA-induced TNF-α upregulation and protected U937 cells from SEM-LA-mediated cytotoxicity. The restoration of TTP expression alleviated the effect of TNF-α upregulation and cell death induced by SEM-LA. Altogether, the data in this study demonstrate that SEM-LA activates TNF-α-mediated apoptosis in U937 cells through the NOX4/p38 MAPK/PP2A axis. We think that a similar pathway can also explain the death of MCF-7 human breast cancer cells after SEM-LA treatment.

Retracted] In vitro and in vivo anticancer effects of marmesin in U937 human leukemia cells are mediated via mitochondrial‑mediated apoptosis, cell cycle arrest, and inhibition of cancer cell migration

Following the publication of the above paper, a concerned reader drew to the Editor's attention that a pair of tumors in Fig.10 appeared to have been duplicated, although one of the tumors appeared at a larger size in the figure relative to the first one. Furthermore, the flow cytometric plots shown in Fig.2B in the above paper appeared to be remarkably similar to data presented in a paper published in Phytomedicine [SuiC‑G, Meng F‑D and JiangY‑H: Antiproliferative activity of rosamultic acid is associated with induction of apoptosis, cell cycle arrest, inhibition of cell migration and caspase activation in human gastric cancer (SGC‑7901)cells. Phyomedicine22: 796‑806, 2015]. After having conducted an independent investigation in the Editorial Office, the Editor of Oncology Reports has determined that the above paper should be retracted from the Journal on account of a lack of confidence concerning the originality and the authenticity of the data. The authors were asked for an explanation to account for these concerns, but the Editorial Office never received any reply. The Editor regrets any inconvenience that has been caused to the readership of the Journal. [the original article was published in Oncology Reports 39: 597‑602, 2018; DOI: 10.3892/or.2017.6147].

Chemical characterization of Saudi propolis and its antiparasitic and anticancer properties

Propolis, is a gummy material produced by honey bees from different parts of plants and is enriched with varied biological active compounds like flavonoids, phenolics and phenolic acids with wide applicability in the food, pharmaceutical and cosmetics industries. The current report is focused on the characterisation of propolis collected from Asir region, South-west of Saudi Arabia and its effect on Trypanosoma brucei (the causative organism of African sleeping sickness) and cytotoxic effect against U937 human leukemia cells. The Chemical composition and spectral characteristics of Saudi propolis was studied by Liquid Chromatography Mass Spectrometry (LC–MS) and High-performance liquid chromatography–evaporative light scattering detector (HPLC–ELSD).The two main active compounds isolated from Saudi propolis via column chromatography and size exclusion chromatography were fisetinidol and ferulic acid. High resolution electrospray ionization–mass spectrophotometer (HRESI–MS) and nuclear magnetic resonance (NMR) were used to elucidate the structures of the isolated compounds. All crudes extracts, fractions as well as isolated compounds were subjected for biological testing against Trypanosoma brucei (S427 WT), and their cytotoxicity against U937 human leukemia cells. Amongst the various samples investigated, S-6 fraction demonstrated highest anti-trypanosomal activity at 2.4 µg/ml MIC followed by fisetinidol at 4.7 µg/ml reflecting that the anti-trypanosomal activity is attributable to the presence of fisetinidol in the fraction. Similarly, all the tested samples exhibited cytotoxicity with an IC50 > 60 µg/ml. S-6 fractions exhibited highest cytotoxic activity against U937 cells with an IC50 of 58.7 µg/ml followed by ferulic acid with an IC50 87.7 µg/ml indicating that the cytotoxic effect of propolis might be due to the presence of ferulic acid. In conclusion, the biological activity of propolis could be attributed to the synergistic action of the two active compounds-ferulic acid and fisetinidol. The data obtained in the study is thus indicative of the role of propolis as potential anti-trypanosomal and anticancer agent for effective cancer therapy.

The anti-cancer effect of betulinic acid in u937 human leukemia cells is mediated through ROS-dependent cell cycle arrest and apoptosis

ABSTRACT Although previous studies have shown anti-cancer activity of betulinic acid (BA), a pentacyclic triterpenoid, against various cancer lines, the underlying molecular mechanisms are not well elucidated. In this study, we evaluated the mechanisms involved in the anti-cancer efficacy of BA in U937 human myeloid leukemia cells. BA exerted a significant cytotoxic effect on U937 cells through blocking cell cycle arrest at the G2/M phase and inducing apoptosis, and that the intracellular reactive oxygen species (ROS) levels increased after treatment with BA. The down-regulation of cyclin A and cyclin B1, and up-regulation of cyclin-dependent kinase inhibitor p21WAF1/CIP1 revealed the G2/M phase arrest mechanism of BA. In addition, BA induced the cytosolic release of cytochrome c by reducing the mitochondrial membrane potential with an increasing Bax/Bcl-2 expression ratio. BA also increased the activity of caspase-9 and -3, and subsequent degradation of the poly (ADP-ribose) polymerase. However, quenching of ROS by N-acetyl-cysteine, an ROS scavenger, markedly abolished BA-induced G2/M arrest and apoptosis, indicating that the generation of ROS plays a key role in inhibiting the proliferation of U937 cells by BA treatment. Taken together, our results provide a mechanistic rationale that BA exhibits anti-cancer properties in U937 leukemia cells through ROS-dependent induction of cell cycle arrest at G2/M phase and apoptosis.