Apoptosis In Human Leukemia Cells Research Articles

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.

Molecular mechanism for apoptosis of leukemia cells induced by chromosome region maintenance 1 selective inhibitor KPT-330

Objective To investigate the induction effect and molecular mechanisms of chromosome region maintenance 1(CRM1) selective inhibitor KPT-330 on apoptosis of human leukemia cells. Methods Human acute promyelocytic leukemia cells(NB4), human chronic myelogenous leukemia cells (K562) and human promyelocytic leukemia cells(HL-60) were divided into a control group(without KPT-330 treatment) and KPT-330 treatment group(NB4, K562 and HL-60 were treated with 0.01, 0.10, 0.20, 0.50, 1.00, 5.00, 10.00 μmol/L KPT-330, respectively). Cell counting kit-8 assay was used to quantify the growth inhibition of cells after exposure to KPT-330.Fluorescence microscope was used to observe the morphological change in leukemia cells when treated with KPT-330.Annexin V/propidium iodide staining followed by flow cytometry was used to detect the apoptosis of leukemia cells.Then, Western blot was used to detect the expression level of CRM1 and the activation of apoptosis marker cysteinyl aspartate specific proteinase-9(Caspase-9), cysteinyl aspartate specific proteinase-3(Caspase-3) and poly ADP-ribose polymerase(PARP). Long non-coding RNA(lncRNA) microarray was used to analyze the differentially expressed genes differentially by the cluster analysis. Results The inhibition of cell proliferation of leukemia cells was in a dose-dependent manner with KPT-330 treatment.Expression of CRM1 was also down-regulated when leukemia cells were treated with KPT-330.Compared with the control group, abnormal cells were observed under fluorescence microscopy.Much more cells showed apoptotic feature after being treated with 0.20 μmol/L and 1.00 μmol/L KPT-330, the apoptosis rate of NB4, K562 and HL-60 were respectively(4.95±0.21)%, (14.05±0.07)%, (4.95±0.63)%(0.20 μmol/L 24 h); (6.10±0.56)%, (20.75±0.21)%, (5.85±0.07)% (0.20 μmol/L 48 h); (41.15±0.21)%, (35.45±0.35)%, (15.65±0.07)% (1.00 μmol/L 24 h); (52.45±0.35)%, (47.45±2.47)%, (16.80±1.98)% (1.00 μmol/L 48 h), respectively, and the differences were statistically significant compared to the control group[24 h NB4, K562, HL-60: (3.30±0.28)%, (9.50±0.56)%, (2.00±0.14)%; 48 h NB4, K562, HL-60: (3.70±0.14)%, (3.50±0.28)%, (2.15±0.21)%](all P<0.05). G2 phase cells obviously reduced and subG1 phase cells increased.The expression level of cleaved Caspase-3, cleaved Caspase-9 and cleaved PARP increased.Molecular function analysis showed that apoptosis induced by KPT-330 in leukemia cells was partially rela-ted to Glutathione metabolism and Toll-like receptor signaling pathway. Conclusions KPT-330 can effectively inhibit proliferation and induce apoptosis of leukemia cells.KPT-330-induced apoptosis in leukemia cells is partially related to Glutathione metabolism and Toll-like receptor signaling pathway. Key words: KPT-330; Chromosome region maintenance 1; Leukemia cell; Apoptosis; Long non-coding RNA

Molecular Mechanism Analysis the Apoptosis of Leukemia Cells Induced By CRM1 Selective Inhibitor KPT-330

Objective: To investigate the effect and mechanisms of KPT-330 on cell apoptosis of human leukemia cells. Methods: CCK-8 assay was used to quantify the growth inhibition of cells after exposure to KPT-330 for 24 hours. Fluorescence microscope was used to observe the morphological change of leukemia cell when treated with KPT330 for 24 hours. Annexin V/propidium iodide staining followed by flow cytometric analysis was used to detect apoptosis of leukemia cells. Then Western blot was used to detect the expression level of CRM1 and the activation of apoptosis related protein Caspase-9 Caspase-3 and PARP level. LncRNA microarray was used to analyze the differentially expressed genes from the cluster analyses. Results: The inhibition of cell proliferation of leukemia cells was in a dose-dependent manner and KPT-330 treatment induced expression of CRM1 down-regulated .Abnormal cells were observed under fluorescence microscopy. Cell apoptosis, cell cycle and activation of apoptosis markers demonstrates that KPT-330 induced apoptosis in leukemia cells. LncRNA microarray analysis showed differently expressed mRNAs and lncRNAs in KPT-330 treated HL-60 cells compared with control group. Molecular function analysis showed that KPT-330 induced apoptosis in leukemia cells partially related with Glutathione metabolism and Toll-like receptor signaling pathway. Conclusion: In this study, KPT-330 treatment resulted in inhibition of cell proliferation and induction of apoptosis in leukemia cells. LncRNA microarray analysis showed differentially expressed genes and lncRNAs in KPT-330 treated HL-60 cells and we demonstrated that KPT-330 induced apoptosis in leukemia cells partially related with Glutathione metabolism and Toll-like receptor signaling pathway. These results may provide new clue about molecular mechanism of KPT-330 induced apoptosis; however, underlying details will be required to determine further. Taken together, our findings suggest that for the first time that KPT-330 may act as new candidate’s drug for leukemia. DisclosuresNo relevant conflicts of interest to declare.

Induction of DNA damage and apoptosis in human leukemia cells by efavirenz.

As part of the efforts to drug repurposing, some HIV drugs have recently been identified to exert anticancer effects. Selected nucleoside analogues of nucleosidic reverse-transcriptase inhibitors (NRTIs) have been shown to interfere with RNA transcription of HI viruses as well as with the replication of DNA in cancer cells. Non-nucleosidic reverse transcriptase inhibitors (NNRTIs) are believed to have less effects on human DNA replication and, thus, on cancer cell proliferation. Assessment of the effect of the NNRTI efavirenz in human cancer cells, however, revealed a high sensitivity of leukemia cells to this agent at pharmacologically relevant concentrations of less than 10µg/ml. Cell death induced by efavirenz was caused by apoptosis, as shown by FACScan analysis (Annexin binding) and western blot analysis (cleavage of caspases and PARP). Western blot analyses also revealed a pronounced activation and phosphorylation of the DNA damage marker proteins p53, chk2 and H2AX, indicating DNA replication and genomic integrity as primary targets of efavirenz in leukemia cells.

Subcellular localization of DJ-1 in human HL-60 leukemia cells in response to diallyl disulfide treatment

Diallyl disulfide (DADS) has been demonstrated to exert potent anticancer effects in vitro and in vivo. Previous studies indicate that DADS may induce the differentiation and/or apoptosis of human leukemia cells in vitro. However, the mechanisms underlying these anticancer effects remain elusive. The aim of the present study was to investigate alterations in the subcellular localization of protein deglycase DJ-1 (also known as Parkinsonism associated deglycase-7, PARK-7) in the cytoplasm, nucleus and mitochondria of human leukemia HL-60 cells induced by DADS, in order to provide novel experimental evidence for the molecular mechanisms underlying the anticancer mechanisms of DADS in leukemia cells. HL-60 cells induced by DADS were collected at different time points, and proteins from the cytoplasm, nucleus and mitochondria of the cells were isolated using specific cellular component isolation kits. The protein expression levels of DJ-1 in these subcellular fractions of HL60 cells following exposure to DADS for varying lengths of time, were determined using western blotting, immunocytochemistry and immunofluorescence techniques. Following exposure of HL-60 cells to 1.25 mg/l DADS for 8 h, the protein expression levels of DJ-1 were significantly decreased in the cytoplasm, while nuclear fractions exhibited a significant increase in DJ-1 expression when compared with untreated controls. The protein expression levels of DJ-1 in mitochondria of HL-60 cells were significantly decreased following treatment with 5 and 10 mg/l DADS. These results demonstrate that exposure of HL-60 cells to low concentrations of DADS may promote DJ-1 protein translocation from the cytoplasm to the nucleus, which suggests that DJ-1 may function as a transcription factor or cofactor binding protein in the process of cell differentiation. The expression of DJ-1 in mitochondria may be associated with induction of apoptosis in HL-60 cells treated with moderate doses of DADS.

Effect of &lt;i&gt;Allium sativum&lt;/i&gt; (garlic) methanol extract on viability and apoptosis of human leukemic cell lines

Purpose : To investigate the effect of Allium sativum (garlic) methanol extract on viability and apoptosis of human leukemic cells. Methods : Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at concentrations of 3.125, 6.25, 12.5, 25, 50, 100, 200, 400 and 800 ug/mL of Allium sativum extract following 48-h treatment on U-937, Jurkat Clone E6-1 and K-562 cell lines. The mode of cell death was determined by Annexin V-FITC staining and analyzed by flow cytometry. Results : The results show that the half-maximal inhibitory concentration (IC50) of A. sativum on U-937, Jurkat Clone E6-1, K-562 cell lines was 105 ± 2.21, 489 ± 4.51 and 455 ± 3.13 μg/mL, respectively, compared with negative control, while apoptosis was 17.93 ± 0.95 % for U-937 cells (p ≤ 0.05), 38.37 ± 1.88 % for Jurkat Clone E6-1 cells (p ≤ 0.001) and 16.37 ± 1.10 % for K-562 cells. A majority of the cells were inhibited by the extract via apoptosis. Only U-937 cells (6.87 ± 0.65 %) showed significant necrosis compared to negative control (p ≤ 0.05). Conclusion : K-562 cells are the most resistant against garlic extract, in contrast to Jurkat Clone E6-1 cells. Garlic extract does not induce necrosis in Jurkat Clone E6-1 and K-562 cells. Keywords : Anti-leukemic, Garlic, Allium sativum, Annexin V-FITC staining, Necrosis, Apoptosis, Flow cytometry, Jurkat Clone E6-1 cells

Ginsenoside Rh2 inhibits proliferation and induces apoptosis in human leukemia cells via TNF-α signaling pathway.

Ginsenoside Rh2, a triterpene saponin extracted from Panax ginseng, exhibits pharmacological activity against multiple cancers. However, the anticancer mechanism of ginsenoside Rh2 is unclear. In this study, we found that ginsenoside Rh2 effectively inhibits growth and induces apoptosis of HL-60 cells. Using microarray technology, we found that tumor necrosis factor-α (TNF-α) is clearly up-regulated. Furthermore, anti-TNF-α antibody relieved the Rh2-induced HL-60 cell apoptosis via suppression of caspase-8, caspase-9, and caspase-3 activation. In addition, TNF-α up-regulation was also observed in other Rh2-treated cancer cell lines. These results demonstrate that TNF-α plays a key role in ginsenoside Rh2-induced cell apoptosis.

Induction of apoptosis in human leukemia cells through an intrinsic pathway by cathachunine, a unique alkaloid isolated from Catharanthus roseus

BackgroundCatharanthus roseus (L.) G. Don consists of a range of dimeric indole alkaloids with significant antitumor activities. These alkaloids have been found to possess apoptosis-inducing activity against tumor cells in vitro and in vivo mediated by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and c-Jun N-terminal kinase (JNK) pathways, in which DNA damage and mitochondrial dysfunction play important roles. In this study, a unique bisindole alkaloid named cathachunine, along with five known dimeric indole alkaloids, was obtained from C. roseus and investigated in vitro. PurposeThe aim of this study was to investigate the antitumor activity of isolated alkaloids and the mechanism through which cathachunine exerts its antitumor effect. Study design and methodsCell growth inhibition was assessed by WST-1 and lactate dehydrogenase (LDH) assays in HL60, K562 leukemia cells and EA.hy926 umbilical vein cells. Induction of apoptosis in HL60 cells was confirmed by observation of nuclear morphology, a caspase-3 activity assay and annexin V-fluorescein isothiocyanate/propidium iodide (FITC/PI) double staining. The intrinsic apoptotic pathway induced by cathachunine was evidenced by B-cell lymphoma 2/Bcl-2-associated X protein (Bcl-2/Bax) dysregulation, loss of mitochondrial membrane potential, translocation of cytochrome c, and cleavage of caspase-3 and poly-ADP ribose polymerase (PARP). Reactive oxygen species (ROS) production after cathachunine treatment was determined by 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. Cell cycle arrest of the S phase was also observed in HL60 cells after cathachunine treatment. ResultsThe WST-1 and LDH assays showed that Catharanthus alkaloids were cytotoxic toward human leukemia cells to a greater extent than toward normal human endothelial cells, and the anti-proliferation and pro-apoptosis abilities of cathachunine were much more potent than other previously reported alkaloids. The induction of apoptosis by cathachunine occurred through an ROS-dependent mitochondria-mediated intrinsic pathway rather than an extrinsic pathway, and was regulated by the Bcl-2 protein family. ConclusionAn unprecedented bisindole alkaloid cathachunine which lost C-18′ and C-19′ was isolated from C. roseus. It exerted a potent antitumor effect toward human leukemia cells through the induction of apoptosis via an intrinsic pathway. Thus, this study provides evidence for a new lead compound from a natural source for anti-cancer investigations.

Dephosphorylation and mitochondrial translocation of cofilin sensitizes human leukemia cells to cerulenin-induced apoptosis via the ROCK1/Akt/JNK signaling pathway.

In this study, we determined that cerulenin, a natural product inhibitor of fatty acid synthase, induces mitochondrial injury and apoptosis in human leukemia cells through the mitochondrial translocation of cofilin. Only dephosphorylated cofilin could translocate to mitochondria during cerulenin-induced apoptosis. Disruption of the ROCK1/Akt/JNK signaling pathway plays a critical role in the cerulenin-mediated dephosphorylation and mitochondrial translocation of cofilin and apoptosis. In vivo studies demonstrated that cerulenin-mediated inhibition of tumor growth in a mouse xenograft model of leukemia was associated with mitochondrial translocation of cofilin and apoptosis. These data are consistent with a hierarchical model in which induction of apoptosis by cerulenin primarily results from activation of ROCK1, inactivation of Akt, and activation of JNK. This leads to the dephosphorylation and mitochondrial translocation of cofilin and culminates with cytochrome c release, caspase activation, and apoptosis. Our study has revealed a novel role of cofilin in the regulation of mitochondrial injury and apoptosis and suggests that cerulenin is a potential drug for the treatment of leukemia.

Sophoraflavanone G Induces Apoptosis in Human Leukemia Cells and Blocks MAPK Activation.

Sophoraflavanone G (SG) was isolated from Sophora flavescens. Previously, we have found that SG is able to suppress the inflammatory response in lipopolysaccharide-stimulated RAW 264.7 macrophages. This study aimed to evaluate the effects of SG on apoptosis, and explore its molecular mechanism in human leukemia HL-60 cells. HL-60 cells were treated with various concentrations of SG (3-30 [Formula: see text]M). The viability of the HL-60 cells was assessed using the MTT method, and the nuclear condensation indicative of apoptosis was observed by DAPI fluorescence staining. In addition, apoptotic signal proteins were examined using Western blotting. The results showed that apoptosis, including DNA fragmentation and nuclear condensation, increased significantly in SG-treated HL-60 cells. SG activated caspase-3 and caspase-9, and downregulated Bcl-2 and Bcl-xL. SG also upregulated Bax and released cytochromec from the mitochondria into the cytoplasm, enabling apoptosis via the mitochondrially-mediated "intrinsic" pathway. Additionally, SG was able to cleave poly (ADP-ribose) polymerase 1 and activate mitogen-activated protein kinase (MAPK) pathways. These results suggest that SG might increase the effect of apoptosis on HL-60 cells through caspase-3 activation, mitochondrial-mediated pathways, and the MAPK pathway.

2,5-Dimethyl-celecoxib inhibits cell cycle progression and induces apoptosis in human leukemia cells.

Cyclooxygenase-2 (COX-2) is an essential regulator of cancer promotion and progression. Extensive efforts to target this enzyme have been developed to reduce growth of cancer cells for chemopreventive and therapeutic reasons. In this context, cyclooxygenase-2 inhibitors present interesting antitumor effects. However, inhibition of COX-2 by anti-COX-2 compounds such as celecoxib was recently associated with detrimental cardiovascular side effects limiting their clinical use. As many anticancer effects of celecoxib are COX-2 independent, analogs such as 2,5-dimethyl-celecoxib (DMC), which lacks COX-2-inhibitory activity, represent a promising alternative strategy. In this study, we investigated the effect of this molecule on growth of hematologic cancer cell lines (U937, Jurkat, Hel, Raji, and K562). We found that this molecule is able to reduce the growth and induces apoptosis more efficiently than celecoxib in all the leukemic cell lines tested. Cell death was associated with downregulation of Mcl-1 protein expression. We also found that DMC induces endoplasmic reticulum stress, which is associated with a decreased of GRP78 protein expression and an alteration of cell cycle progression at the G1/S transition in U937 cells. Accordingly, typical downregulation of c-Myc and cyclin D1 and an upregulation of p27 were observed. Interestingly, for shorter time points, an alteration of mitotic progression, associated with the downregulation of survivin protein expression was observed. Altogether, our data provide new evidence about the mode of action of this compound on hematologic malignancies.

Abstract 3799: Cordyceptin induces apoptosis through repressing hTERT expression and inducing extranuclear export of hTERT

Abstract Cordycepin is an adenosine analog originally extracted from Cordyceps militaris that possesses many pharmacological effects including immune activation and antioxidant and antitumor effects. However, the underlying relationship between apoptosis and telomerase activity in response to cordycepin exposure has not been investigated. In this study, we found that cordycepin-induced apoptosis of human leukemia cells (H937 and THP-1 cells) was associated with inactivation of telomerase and downregulation of human telomerase reverse transcriptase (hTERT) as well as the transcription factors c-Myc and Sp1, which are required for basal transcription from the hTERT gene promoter. Cordycepin also attenuated the activation of phosphoinositide-3-kinase (PI3K)/Akt signaling, thereby reducing phosphorylation and nuclear translocation of hTERT. We further showed that the PI3K inhibitor LY29004 significantly decreased telomerase activity in cordycepin-treated cells and increased cordycepin-induced cell death. These findings demonstrate that cordycepin is cytotoxic to human leukemia cells and suppresses telomerase activity through transcriptional and post-translational suppression of hTERT by inactivating the PI3K/Akt signaling pathway. Citation Format: Nam Deuk Kim, Gi-Young Kim, Yung Hyun Choi. Cordyceptin induces apoptosis through repressing hTERT expression and inducing extranuclear export of hTERT. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3799. doi:10.1158/1538-7445.AM2015-3799

P0099 Compound MacKay-03 inhibits growth and induces megakaryocytic differentiation in human leukaemia cells and augments megakaryocytopoiesis

Background MacKay-03 (3,12-O-diacetyl-7-O-angeloyl-8-methoxyingol) is a small-molecule ingol diterpene compound isolated from the plant Euphorbia neriifolia. We isolated compounds according to screening of anticancer activity and found MacKay-03 preferentially inhibited growth of human leukaemic cells. The cellular and molecular mechanism of action was investigated in the present study. Methods The methods used were: cell viability by MTT assay, morphological observation by Liu’s and immunofluorescent stain, cell cycle analysis by DNA histogram, expression of surface antigens by flow cytometry, quantitation of secreted platelet factor 4 by ELISA, expression of regulatory proteins by western blotting, knockdown of stat3 mRNA by RNA interference, and megakaryocytopoiesis by colony forming unit-megakaryocytes (CFU-MK) assay. Findings MacKay-03 inhibited growth of leukaemia K562 and HEL cells in a dose-dependent and time-dependent manner. Morphological changes characteristic of megakaryocytes—e.g. enlarged cell size, multipolar spindles, and multi-nucleation—were noted in both cell lines treated with MacKay-03. A smaller population of apoptotic cells were also observed. MacKay-03 treatment caused polyploidy and hypoploidy populations. Surface expression of megakaryocytic marker CD61 was increased by MacKay-03, whereas the erythroid marker glycophorin A was decreased. The MacKay-03-treated HEL cells extensively secreted platelet factor 4, implicating a further platelet differentiation. MacKay-03, at optimum conditions for inducing megakaryocytic differentiation, upregulated the expression of JAK2 and phosphorylated STAT3 in K562 and HEL cells. Knockdown of stat3 mRNA partially blocked megakaryocytic differentiation. Interpretation These results indicate that MacKay-03 is able to inhibit growth, induce megakaryocytic differentiation, and to a lesser extent cause apoptosis in human leukaemia cells. Furthermore, MacKay-03 augmented the formation of CFU-MK in mouse bone marrow cells. We conclude that MacKay-03 could inhibit growth of human leukaemic cells, induce megakaryocytic differentiation, and promote megakaryocytopoiesis. MacKay-03 may have the potential to be developed as a candidate drug for management of leukaemia and thrombocytopenia.

Flavonoids from Orostachys japonicus A. Berger induces caspase-dependent apoptosis at least partly through activation of p38 MAPK pathway in U937 human leukemic cells.

Orostachys japonicus A. Berger (A. Berger) is commonly used as a folk remedy for cancer therapy. However, the mechanisms of its anti-cancer activity are poorly investigated in human cancer cells. In this study, we investigated whether flavonoids extracted from Orostachys japonicus A. Berger (FEOJ) might have anticancer effects in human leukemia cells, focusing on cell death mechanisms. U937 human leukemic cancer cells were used. FEOJ induced apoptosis in a dose-dependent manner in human U937 cancer cells. Flow cytometry revealed significant accumulation of cells with sub-G1 DNA content at the concentrations of 200 μg/mL and 400 μg/mL. FEOJ-induced apoptosis was caspase-dependent through loss of mitochondrial membrane potential (MMP, ΔΨm) in human U937 cancer cells, which might be associated with suppression of Bcl-2 and XIAP proteins. FEOJ induced the p38 MAPK signaling pathway, playing at least in part an important role in FEOJ-induced apoptosis. This study suggested that FEOJ may induce caspase-dependent apoptosis in human leukemic cells by regulating MMP (ΔΨm) through suppressing Bcl-2 and X-IAP. In addition, the results indicated that upstream p38 MAPK signaling regulates the apoptotic effect of FEOJ. This study provides evidence that FEOJ might have anti-cancer potential for human leukemic cells.

The XIAP inhibitor Embelin enhances TRAIL-induced apoptosis in human leukemia cells by DR4 and DR5 upregulation.

The present study was designed to explore the effects of low-toxicity Embelin on TRAIL-induced apoptosis and its possible mechanism in human leukemia cells. Our study showed that low-toxicity Embelin enhanced TRAIL-induced apoptosis through DR4 and DR5 upregulation and caspase activation in HL-60 cells. Pan-caspase inhibitor Z-VAD-FMK inhibited cell apoptosis induced by TRAIL alone or combined with low-toxicity Embelin, which indicated the cytotoxic effect is mediated by caspase-dependent apoptosis. Although Embelin is an X chromosome-linked inhibitor-of-apoptosis protein (XIAP) inhibitor, an XIAP independent effect on cell death was detected in HL-60 cells exposed to low-toxicity Embelin and TRAIL. Low-toxicity Embelin upregulated DR4 and DR5 expression to enhance TRAIL-induced apoptosis. The sensitizing effects of Embelin on TRAIL-induced apoptosis were markedly attenuated when DR4/DR5 was knocked down. These data suggested that low-toxicity Embelin enhanced TRAIL-induced cell apoptosis through DR4 and DR5 upregulation, indicating that combination of low-toxicity Embelin and TRAIL may become as a potential antileukemia strategy.

In vitro anticancer activity of loquat tea by inducing apoptosis in human leukemia cells.

Fresh loquat leaves have been used as folk health herb in Asian countries for long time, although the evidence supporting their functions is still minimal. This study aimed to clarify the chemopreventive effect of loquat tea extract (LTE) by investigating the inhibition on proliferation, and underlying mechanisms in human promyelocytic leukemia cells (HL-60). LTE inhibited proliferation of HL-60 in a dose-dependent manner. Molecular data showed that the isolated fraction of LTE induced apoptosis of HL-60 as characterized by DNA fragmentation; activation of caspase-3, -8, and -9; and inactivation of poly(ADP)ribose polymerase. Moreover, LTE fraction increased the ratio of pro-apoptotic Bcl-2-associated X protein (Bax)/anti-apoptotic myeloid cell leukemia 1 (Mcl-1) that caused mitochondrial membrane potential loss and cytochrome c released to cytosol. Thus, our data indicate that LTE might induce apoptosis in HL-60 cells through a mitochondrial dysfunction pathway. These findings enhance our understanding for chemopreventive function of loquat tea.

Cordyceptin induces apoptosis through repressing hTERT expression and inducing extranuclear export of hTERT

Cordycepin is an adenosine analog originally extracted from Cordyceps militaris that possesses many pharmacological effects including immune activation and antioxidant and antitumor effects. However, the underlying relationship between apoptosis and telomerase activity in response to cordycepin exposure has not been investigated. In this study, we found that cordycepin-induced apoptosis of human leukemia cells (H937 and THP-1 cells) was associated with inactivation of telomerase and downregulation of human telomerase reverse transcriptase (hTERT) as well as the transcription factors c-Myc and Sp1, which are required for basal transcription from the hTERT gene promoter. Cordycepin also attenuated the activation of phosphoinositide-3-kinase (PI3K)/Akt signaling, thereby reducing phosphorylation and nuclear translocation of hTERT. We further showed that the PI3K inhibitor LY29004 significantly decreased telomerase activity in cordycepin-treated cells and increased cordycepin-induced cell death. These findings demonstrate that cordycepin is cytotoxic to human leukemia cells and suppresses telomerase activity through transcriptional and post-translational suppression of hTERT by inactivating the PI3K/Akt signaling pathway.

GDC-0152 induces apoptosis through down-regulation of IAPs in human leukemia cells and inhibition of PI3K/Akt signaling pathway.

The inhibitor of apoptosis proteins (IAPs) is closely related to leukemia apoptosis. The present study was undertaken to determine the molecular mechanisms by which GDC-0152, an IAP inhibitor, induces apoptosis in human leukemia cells (K562 and HL60 cells). GDC-0152 inhibited the proliferation of K562 and HL60 cells in a dose- and time-dependent manner, which was largely attributed to intrinsic apoptosis. GDC-0152 down-regulated the IAPs including X-linked inhibitor of apoptosis protein (XIAP), cellular inhibitor of apoptosis protein-1 (cIAP1), and cellular inhibitor of apoptosis protein-2 (cIAP2) expression and induced the activation of caspase-9 and caspase-3. GDC-0152-induced cell proliferation inhibition in K562 cells was prevented by pan-caspase inhibitor. GDC-0152 also inhibited PI3K and Akt expression in K562 and HL60 cells. Taken together, these findings suggest that GDC-0152 results in human leukemia apoptosis through caspase-dependent mechanisms involving down-regulation of IAPs and inhibition of PI3K/Akt signaling.

20-(s)-ginsenoside Rg3 induces apoptotic cell death in human leukemic U937 and HL-60 cells through PI3K/Akt pathways.

Leukemia is currently one of the most deadly diseases. Ginseng has been used in Asian countries for the treatment and prevention of various diseases, including leukemia, but the molecular mechanism of its antileukemia activity has not been well defined. The aim of this study was to explore the effect of 20-(s)-ginsenoside Rg3 on apoptosis in human leukemic U937 and HL-60 cells and the underlying mechanism. We found that 20-(s)-ginsenoside Rg3 reduced cell viability and induced apoptosis in U937 and HL-60 cells. The induction of apoptosis was accompanied by the downregulation of PI3K/Akt family proteins. Moreover, we observed that 20-(s)-ginsenoside Rg3 treatment resulted in activation of caspase-3 and caspase-9. Taken together, our findings suggest for the first time that 20-(s)-ginsenoside Rg3 can promote apoptosis in U937 and HL-60 cells, at least partly through the downregulation of PI3K/Akt family proteins. Moreover, the triggering of caspase-3 and caspase-9 activation mediated apoptotic induction. All these findings collectively demonstrate that the natural compound 20-(s)-ginsenoside Rg3 effectively induces apoptosis in human leukemic cells, which suggests that this compound may play a role in future therapies for leukemia.

Compound A398, a novel podophyllotoxin analogue: cytotoxicity and induction of apoptosis in human leukemia cells.

Despite advances in oncology research, cancer is one of the leading causes of death worldwide. Thus, there is a demand for the development of more selective and effective antitumor agents. This study showed that A398, a novel podophyllotoxin analogue, was cytotoxic to the HT-29, MCF-7, MOLT-4 and HL-60 tumor cell lines, being less active in human peripheral blood mononuclear cells and normal cell lines FGH and IEC-6. Tests using the HepG2 lineage indicated that its metabolites do not contribute to its cytotoxicity. In the HL-60 cells, A398 induced apoptosis in a time and concentration-dependent manner, promoting mitochondrial depolarization, inhibition of Bcl-2, phosphatidylserine exposure, activation of caspases -8, -9 and -3, and DNA fragmentation. The production of reactive oxygen species does not seem to be a crucial event for the apoptotic process. Pretreatment with specific inhibitors of kinases ERK1/2, JNK and p38 resulted in an increased percentage of death induced by A398. These results indicate that the compound induced apoptosis through activation of intrinsic and extrinsic death pathways with the mechanism involving the inhibition of the MAPKs and Bcl-2. Taken together, our findings suggest that A398 has an anticancer potential, proving itself to be a candidate for preclinical studies.