Leukotriene B4 receptor antagonist LY293111 induces S-phase cell cycle arrest and apoptosis in human pancreatic cancer cells

We have previously shown that the leukotriene B4 receptor antagonist, LY293111 inhibits proliferation and induces apoptosis in human pancreatic cancer cells both in vitro and in vivo. In the current study, we investigated the molecular mechanisms of LY293111-induced apoptosis and cell cycle arrest. Two human pancreatic cancer cell lines were used in this study, MiaPaCa-2 and AsPC-1. Cell cycle analysis by flow cytometry showed a dramatic increase in the percentage of apoptotic cells as well as S-phase arrest after treatment with 250 nmol/l LY293111 for up to 48 h. Western blotting indicated that LY293111 treatment induced cytochrome c release from the mitochondria into the cytosol, accompanied by caspase-9, caspase-7 and caspase-3 activation, and cleavage of poly ADP-ribose polymerase. Caspase-8 was not activated by LY293111. A decrease was found in the expression of the antiapoptotic proteins, Bcl-2 and Mcl-1, and an increase in the proapoptotic protein, Bax. LY293111 reduced the expression of CDK2, cyclin A and cyclin E, consistent with the S-phase arrest observed in these cells. The expression of cyclin-dependent kinase inhibitors, p21 and p27 was not affected by LY293111 treatment. In conclusion, LY293111 induces apoptosis in human pancreatic cancer cells through the mitochondria-mediated pathway. LY293111 also induces S-phase arrest with downregulation of CDK2, cyclin A and cyclin E. Blockade of leukotriene B4 metabolic pathway may provide a novel treatment for human pancreatic cancer.     

黄芩素通过抑制JAK2/STAT1通路减轻Aβ25-35诱导的PC12细胞损伤

本研究旨在探讨黄芩素对Aβ25-35诱导PC12细胞损伤的保护作用及机制.采用20 μmol·L-1 Aβ25-35损伤PC12细胞,通过细胞形态观察、Hoechst 33342染色和炎症因子检测考察黄芩素对Aβ25-35损伤PC12细胞的保护作用,采用Western blotting方法检测凋亡相关蛋白半胱氨酸天冬氨...     

Apigenin induces apoptosis in human lung cancer H460 cells through caspase- and mitochondria-dependent pathways

Apigenin (4,5,7-trihydroxyflavone), a promising chemopreventive agent presented in fruits and vegetables, has been shown to induce cell cycle arrest and apoptosis in many types of human cancer cell lines. However, there is no available information to address the effects of apigenin on human lung cancer H460 cells. In the present studies, H460 cells were treated with apigenin for different time and then were analyzed for the morphological changes, induction of apoptosis, protein levels associated with apoptosis and results in dose-dependent induction of morphological changes, decrease in the percentage of viability, induced DNA damage and apoptosis; down-modulation of the protein expression of Bid, Bcl-2, procaspase-8; up-regulation of protein levels of Bax, caspase-3, AIF, cytochrome c, GRP78 and GADD153; decreased the levels of mitochondrial membrane potential and increased the productions of reactive oxygen species (ROS) and Ca(2+) in H460 cells. Taken together, this is the first systematic in vitro study showing the involvement of apoptosis regulatory proteins as potential molecular targets of apigenin in human lung cancer H460 cells.     

Disruption of cell adhesion and caspase-mediated proteolysis of beta- and gamma-catenins and APC protein in paclitaxel-induced apoptosis

Cell adhesion is important in the regulation of cell proliferation, migration, survival, and apoptosis. The major components of cell adhesion are the cadherin family of proteins, alpha-, beta- and gamma-catenins, and cytoskeletons. In addition, beta-catenin, when associated with adenomatous polyposis coli (APC) protein, an oncosuppressor, is implicated in the regulation of beta-catenin/APC-related signaling pathways. To examine the correlation between impairment of cell adhesion events and apoptosis, we used human non-small-cell lung cancer H460 and H520 cell lines as models to determine whether paclitaxel-induced apoptosis is associated with disruption of the components of cell adhesion and their functions. Paclitaxel treatment resulted in cells rounding up and losing contact with their neighboring cells, suggesting that the drug does indeed affect cell adhesion and related events. Western blot analysis revealed that paclitaxel caused a time- and concentration-dependent cleavage of beta-catenin, gamma-catenin, and APC protein, but not alpha-catenin or E-cadherin. These cleavages of beta-catenin and gamma-catenin were apoptosis-dependent, not mitosis-dependent. Paclitaxel treatment led to the proteolysis and activation of caspase-3 and -7, but not caspase-1. Furthermore, paclitaxel-induced apoptosis and cleavage of beta-catenin and gamma-catenin were inhibited by the pan-caspase inhibitor Z-VAD-FMK and partially inhibited by the caspase-3 inhibitor Z-DEVD-FMK but were not affected by the caspase-1 inhibitor AC-YVAD-CMK. Although the pan-caspase inhibitor blocked the cleavage of beta-catenin as well as DNA fragmentation, it did not affect paclitaxel-induced M-phase arrest and only partially prevented cell-growth inhibition. Biochemical studies revealed that cleaved beta-catenin was detected only in the Triton X-100 insoluble fraction, suggesting that it might localize in nuclear and/or membrane structures. Interestingly, the paclitaxel-induced beta-catenin fragment lost its ability to bind to E-cadherin, alpha-catenin, or APC protein and to serve as a substrate for tyrosine kinase. All our data demonstrate that the caspase-mediated cleavage of beta-catenin, gamma-catenin, and APC protein might contribute to paclitaxel-induced apoptosis.     

蛋白激酶CK2抑制剂-醌茜素在非小细胞肺癌中的抗肿瘤作用

目的：研究蛋白激酶CK2抑制剂-醌茜素在非小细胞肺癌中的抗肿瘤作用,探讨蛋白激酶CK2成为非小细胞肺癌治疗新靶点的可能。方法：使用MTT法检测细胞增殖,研究醌茜素对非小细胞肺癌细胞A549、H460细胞增殖的影响,探究醌茜素作用于A549、H460增殖的可能途径。使用流式细胞术检测醌茜素作用于A549、H460后,细胞的凋亡以及周期的变化。使用Trans-well迁移实验检测细胞迁移能力,探究醌茜素对A549、H460迁移的影响。结果：醌茜素能够抑制A549、H460细胞的增殖,并且该抑制作用具有时间依赖性及浓度依赖性（P<0.01,P<0.01）。在25 μmol·L^-1及50 μmol·L^-1浓度下,醌茜素能够促进细胞A549、H460凋亡（P<0.01,P<0.01;P<0.01,P<0.01）。在实验条件下,醌茜素对A549的周期影响差异没有统计学意义,但醌茜素在50 μmol·L^-1浓度下对H460具有周期阻滞作用,G2/M期的比例明显增加（P<0.01）。醌茜素能够显著抑制A549、H460细胞的迁移活动。结论：蛋白激酶CK2抑制剂-醌茜素能够抑制非小细胞肺癌细胞系A549、H460增殖、迁移,促进其凋亡,发挥抗肿瘤作用,有可能成为一种具有潜力的非小细胞肺癌分子靶向治疗的新型药物。     

Nipradilol inhibits apoptosis by preventing the activation of caspase-3 via S-nitrosylation and the cGMP-dependent pathway

To study whether nipradilol, which is used as an ophthalmic solution for the treatment of glaucoma, has a cytoprotective effect, we investigated its effect on the apoptosis induced by serum withdrawal in PC12 cells. Nipradilol has alpha1- and beta-adrenoceptor-blocking and nitric oxide (NO)-donating properties. We also investigated the effects of timolol, prazosin and S-nitroso-N-acetylpenicillamine (SNAP) on PC12 cell death. Serum withdrawal from PC12 cells resulted in apoptosis, and the survival rate was decreased in a time-dependent manner. The addition of nipradilol to the medium showed a cytoprotective effect on PC12 cell death in a dose-dependent manner, but timolol and prazosin did not. We measured caspase-3 activity to clarify the mechanism of the inhibition of apoptosis in the presence or absence of dithiothreitol (DTT). The caspase-3 activity could be reactivated by DTT. In addition, to investigate the relationship of the cGMP-dependent pathway to the nipradilol-induced cytoprotective effect, we tested the effect of the protein kinase G inhibitor KT5823. KT5823 partially reversed the nipradilol-mediated cytoprotective effect. These results indicate that the cytoprotective effect of nipradilol in PC12 cell death was due to the caspase-3 inhibition mediated by NO-related S-nitrosylation and activation of protein kinase G.     

Taiwan cobra cardiotoxin III inhibits Src kinase leading to apoptosis and cell cycle arrest of oral squamous cell carcinoma Ca9-22 cells

Cardiotoxin III (CTX III), a basic polypeptide with 60-amino acid residues isolated from Naja naja atra venom, has been reported to have cytotoxic activity. CTX III exerted cytotoxicity with the S-phase cell cycle arrest, correlated with a marked decrease in the expression levels of cyclin A, cyclin B, and cyclin-dependent kinase 1 (CDK1), and apoptosis, accompanied with Bax and Bad up-regulation, and the down-regulation of Bcl-2, p-Bad, and X-linked inhibitor of apoptosis (XIAP) with cytochrome c release and sequential activation of caspase-9 and caspase-3 in Ca9-22 cells. Mechanistic studies showed that CTX III suppressed the phosphorylation of Src, EGFR, STAT3, STAT5, Akt, and activation of PI3 K (p110). Moreover, Src inactivation was observed earlier than that of the EGFR and the Src inhibitor PP2 suppressed the levels of phospho-EGFR, phospho-STAT3, phospho-STAT5, phospho-Akt, and PI3 K(p110). The PP2 also caused the S-phase arrest and apoptosis, and led to down-regulation of Bcl-2, p-Bad, XIAP, cyclin A, cyclin B, and CDK1, and up-regulation of Bax and Bad, similar to that observed in CTX III treatment. Taken together, these results indicate that CTX III induces apoptosis and S-phase arrest in Ca9-22 cells via concomitant inactivation of the Src, EGFR, STAT3, STAT5, PI3 K(p110), and Akt signaling pathways.     

Induction of G2/M arrest, endoreduplication, and apoptosis by actin depolymerization agent pextenotoxin-2 in human leukemia cells, involving activation of ERK and JNK

Pectenotoxin-2 (PTX-2) is a natural compound from marine sponges and has been known to inhibit cytokinesis through the depolymerization of actin filaments. To investigate the role of actin dysfunction by PTX-2 in human leukemia cells, we analyzed the effect of PTX-2 on the cell cycle and apoptosis. Cell cycle analysis showed that the depolymerization of actin with PTX-2 induces G2/M phase arrest at 12 h and endoreduplication at 24 h. Analysis of the cell cycle regulatory proteins demonstrated that PTX-2 increases phosphorylation of cdc25c and decreases the protein levels of cdc2 and cyclin B1. The M phase specific marker protein, phospho-histone 3, was also increased by PTX-2. Furthermore, p21 and CDK2, which are associated with the induction of endoreduplication, were also upregulated. PTX-2 also inhibited the growth of leukemia cells and caused a marked increase in apoptosis, as characterized by annexin-V+ cells and caspase-3 activity. Interestingly, we found that induction of G2/M phase arrest, endoreduplication, and apoptosis by PTX-2 is regulated by the extracellular signal-regulated kinase (ERK) and c-jun N-terminal kinase (JNK) pathway. Inhibitors of ERK and JNK more increased the phosphorylation of cdc25c expression at G2/M arrest stages, and decreased p21 and CDK2 expression at endoreduplication stages and Bax expression at apoptotic stages in the presence of PTX-2. These molecular mechanisms provide that PTX-2 induces G2/M phase arrest, endoreduplication, and apoptosis through the ERK and JNK signal pathway via actin depolymerization.     

The Involvement of Microtubular Disruption in Methylmercury-Induced Apoptosis in Neuronal and Nonneuronal Cell Lines

Methylmercury (MeHg) is known to interfere with cell cycle progression by disruption of microtubules. The relationship between the changes in cell cycle and the induction of apoptosis caused by MeHg was investigated in cultured mammalian cells. MeHg caused nuclear fragmentation and DNA ladder formation in rat pheochromocytoma (PC12) and mouse neuroblastoma cells exposed to MeHg. Flow cytometric analysis revealed that the occurrence of apoptosis was preceded by the accumulation of cells in G2/M after MeHg treatment. Exposure to colchicine, a well-characterized mitotic inhibitor, also caused G2/M-phase arrest followed by the appearance of apoptotic cells. These results suggest that G2/M-phase arrest through the disruption of microtubules is an important event in the development of apoptosis by MeHg. MeHg treatment led to G2/M-phase arrest followed by apoptosis in nonneuronal HeLa cells also. Bcl-2 was phosphorylated by MeHg treatment in HeLa cells but not in PC12 cells; however, p53 expression was not changed in either cell line. Thus, MeHg induces apoptosis via a p53-independent pathway in both cell lines, however, different pathways may be activated after the disruption of microtubules in PC12 and HeLa cells.     

Zoledronic acid determines S-phase arrest but fails to induce apoptosis in cholangiocarcinoma cells

Cholangiocarcinoma is the second most common primary hepatic neoplasia and the only curative therapy is surgical resection or liver transplantation. Biphosphonates (BPs) are an emerging class of drugs widely used to treat bone diseases and also appear to possess direct antitumor activity. In two human cholangiocarcinoma cell lines (TFK-1 and EGI-1) we investigated, for the first time, the activity of zoledronic acid by determining proliferation, cell cycle analysis and apoptosis.The results obtained indicate that zoledronic acid induces cell-narrowing and growth inhibition, both reversed by 25 μM GGOH, and significantly affects the colony-forming ability of these cells. The inhibition by zoledronic acid of Rap1A prenylation was reversed in cell co-treated with GGOH. At 10-50 μM zoledronic acid exerted an S-phase cell cycle arrest which was confirmed by changes in the level of cyclins and of regulators p27^KIP1 and pRb. Interestingly, the expression level of cyclin A (putative S-phase marker) shows a dose-dependent increment in contrast to the decrement of cyclin D1 (putative G1 phase marker). However, neither hypodiploid cells nor cleaved PARP or caspase-3 was detected. The lack of TP53 or loss of its function, the large constitutive expressions of anti-apoptotic proteins Bcl-xL and HSP27 together with the low level of the pro-apoptotic Bax are the likely factors which protect cells from apoptosis.In conclusion, our study indicates that zoledronic acid induces S-phase arrest and cell-narrowing, both reversed by GGOH and, by changing the delicate balance between pro- and anti-apoptotic proteins, allows survival of cholangiocarcinoma cells.     

Variation in the kinetics of caspase-3 activation, Bcl-2 phosphorylation and apoptotic morphology in unselected human ovarian cancer cell lines as a response to docetaxel

Paclitaxel is able to cause cell death through the induction of apoptosis. Cell death characteristics for docetaxel have not yet been described in detail. We investigated four unselected human ovarian cancer cell lines for the sensitivity to a 1hr exposure to docetaxel and calculated the concentrations inhibiting 50% (IC(50)) and 90% (IC(90)) of cell growth. Of the cell lines A2780, H134, IGROV-1 (all wild-type p53) and OVCAR-3 (mutant, mt p53) A2780 was most sensitive and OVCAR-3 least sensitive. Equitoxic drug concentrations representing IC(90) values (25-510nM) were applied for 1hr to measure cell cycle distribution, DNA degradation, and to count apoptotic cell bodies and cells with multifragmented nuclei at various time-points after drug exposure. H134, IGROV-1 and OVCAR-3 showed a continued mitotic block up to at least 72hr and prolonged presence of cells with multifragmented nuclei. High percentages of apoptosis were calculated at 48hr and at later time-points. In contrast, A2780 cells accumulated in the S-phase of the cell cycle and apoptosis was hardly present. The changes in the expression levels of p53, p21/WAF1, Bax and Bcl-2, were not predictive for docetaxel-induced apoptosis. Caspase-3 activation occurred only in cells with accumulation in the G2/M phase starting as early as 8hr in OVCAR-3. Prolonged Bcl-2 phosphorylation was evident in OVCAR-3, visible at 24hr in H134 and IGROV-1, while this phenomenon did not occur in A2780. The mitogen-activated protein kinase pathway (JNKs/SAPKs or c-Jun N-terminal kinases/stress-activated protein kinases, JNK1/2; extracellular response kinase, ERK1/2; p38) did not seem to be directly involved in Bcl-2 phosphorylation or apoptosis. We conclude that docetaxel is able to activate caspase-3, induce Bcl-2 phosphorylation and apoptosis in cells that show a prolonged G2/M arrest, but cells may also die by a caspase-3-independent cell death mechanism.     

Digitoxin and a synthetic monosaccharide analog inhibit cell viability in lung cancer cells

Mechanisms of digitoxin-inhibited cell growth and induced apoptosis in human non-small cell lung cancer (NCI-H460) cells remain unclear. Understanding how digitoxin or derivate analogs induce their cytotoxic effect below therapeutically relevant concentrations will help in designing and developing novel, safer and more effective anti-cancer drugs. In this study, NCI-H460 cells were treated with digitoxin and a synthetic analog D6-MA to determine their anti-cancer activity. Different concentrations of digitoxin and D6-MA were used and the subsequent changes in cell morphology, viability, cell cycle, and protein expressions were determined. Digitoxin and D6-MA induced dose-dependent apoptotic morphologic changes in NCI-H460 cells via caspase-9 cleavage, with D6-MA possessing 5-fold greater potency than digitoxin. In comparison, non-tumorigenic immortalized bronchial and small airway epithelial cells displayed significantly less apoptotic sensitivity compared to NCI-H460 cells suggesting that both digitoxin and D6-MA were selective for NSCLC. Furthermore, NCI-H460 cells arrested in G(2)/M phase following digitoxin and D6-MA treatment. Post-treatment evaluation of key G2/M checkpoint regulatory proteins identified down-regulation of cyclin B1/cdc2 complex and survivin. Additionally, Chk1/2 and p53 related proteins experienced down-regulation suggesting a p53-independent cell cycle arrest mechanism. In summary, digitoxin and D6-MA exert anti-cancer effects on NCI-H460 cells through apoptosis or cell cycle arrest, with D6-MA showing at least 5-fold greater potency relative to digitoxin.     

Anti-tumor potential of 15,16-dihydrotanshinone I against breast adenocarcinoma through inducing G1 arrest and apoptosis

Chemotherapeutic drugs are usually designed to induce cancer cell death via cell cycle arrest and/or apoptosis pathways. In this study, we used the chemical drug 15,16-dihydrotanshinone I (DHTS) to inhibit breast cancer cell proliferation and tumor growth, and investigate the underlying molecular mechanisms. Human breast cancer cell lines MCF-7 and MDA-MB-231 were both used in this study, and DHTS was found to significantly decrease cell proliferation by a dose-dependent manner in both cells. Flow cytometry indicated that DHTS induced G1 phase arrest in synchronous MCF-7 and MDA-MB-231 cells. When analyzing the expression of cell cycle-related proteins, we found that DHTS reduced cyclin D1, cyclin D3, cyclin E, and CDK4 expression, and increased CDK inhibitor p27 expression in a dose-dependent manner. In addition, DHTS inhibited the kinase activities of CDK2 and CDK4 by an immunocomplex kinase assay. In addition, DHTS also induced apoptosis in both cells through mainly mitochondrial apoptosis pathways. We found that DHTS decreased the anti-apoptotic protein Bcl-xL level and increased the loss of mitochondria membrane potential and the amount of cytochrome c released. Moreover, DHTS activated caspase-9, caspase-3, and caspase-7 and caused cell apoptosis. The fact that DHTS-induced apoptosis could be blocked by pretreating cells with pan-caspase inhibitor confirmed that it is mediated through activation of the caspase-3-dependent pathway. In a nude mice xenograft experiment, DHTS significantly inhibited the tumor growth of MDA-MB-231 cells. Taken together, these results suggest that DHTS can inhibit human breast cancer cell proliferation and tumor growth, and might have potential chemotherapeutic applications.     

去甲泽拉木醛通过调控细胞周期和自噬诱导的细胞凋亡抑制K562细胞生长的机制

目的研究去甲泽拉木醛(demethylzeylasteral,ZST93)在体外抑制慢性髓系白血病(chronic myeloid leukemia,CML)细胞的增殖作用,并初步探讨其可能的作用机制。方法以K562细胞为研究对象,采用CCK-8、细胞生长曲线和倒置显微镜检测ZST93对K562细胞增殖抑制作用;细胞转染和Western blot分析细胞自噬;PI染色、Annexin V-FITC/PI和流式细胞术检测细胞周期和细胞凋亡。结果ZST93对K562细胞株的生长呈剂量和时间依赖性的抑制作用,IC₅₀值为2.59μmol·L^-1,使细胞周期阻滞于G₁期。自噬检测中发现ZST93可诱导GFP-LC3积累、LC3-Ⅰ转化为LC3-Ⅱ以及p62表达水平降低。ZST93通过调控自噬激活caspase-8,诱导外部凋亡信号通路,促使caspase-9、caspase-3和PARP剪切而被激活,针对caspase-3的抑制剂Z-DEVD-FMK能够降低ZST93诱导的K562细胞凋亡。结论ZST93可有效抑制K562细胞增殖,促进细胞周期阻滞、细胞凋亡和自噬激活,可能与自噬激活/caspase-8/caspase-3凋亡信号通路有关。     

2(±)-7,8,3',4',5'-Pentamethoxyflavan induces G2/M phase arrest and apoptosis in human leukemia HL60 cells

Objective Flavans are a set of naturally occurring flavonoids possessing a 2-phenylchroman nucleus,which are widely distributed in the plant kingdom.A number of flavan compounds exhibit antitumor activities.In our previous report,a straightforward synthetic procedure for 2(±)-7,8,3',4',5'-pentamethoxyflavan(PMF)was developed.To be more important,PMF showed growth inhibitory effect on various human tumor cell lines,especially against HL60 cells.In the present study,we aim to investigate the molecular mechanisms of action of PMF in HL60 cells.This is the first report of the molecular mechanisms on anti-tumor effect of flavan compounds.Methods Trypan blue exclusion experiment was used for cell growth inhibition assay.Cell apoptosis,cell cycle distribution and the mitochondrial membrane potential(MMP)were assessed by flowcytometric analysis after AO/EB,PI and Rh123 flurescence staining,respectively.Cell cycle-and apoptosis-related proteins were detected using western blotting analysis.Results PMF(1-30 μM)inhibited the growth of HL60 cells in a time-and concentration-dependent manner.Antiproliferative effect of PMF on HL60 cells was associated with G2/M cell cycle arrest,which was mediated by regulating the expression of p21,Cdc25C and cyclin A proteins and inhibiting the phosphorylation of Cdc2 at Thr161.The prolonged PMF treatment also induced apoptosis of HL60 cells,which was characterized by DNA fragmentation,cleavage of poly(ADP-ribose)polymerase,caspase-3,caspase-8 and caspase-9,changes of Bcl-2 and Bax expression and a decrease in the mitochondrial membrane potential(MMP).Furthermore,caspase-3 inhibitor,not caspase-8 inhibitor and caspase-9 inhibitor,completely blocked PMF-caused apoptosis.Conclusions PMF inhibited the growth of HL60 cells via induction of G2/M arrest and apoptosis.Blockade of cell cycle was associated with the downregulation of Cdc2 complex activity.Both death receptor and mitochondrial apoptotic pathways explained PMF-caused apoptosis.     

Coumarin induces cell cycle arrest and apoptosis in human cervical cancer HeLa cells through a mitochondria- and caspase-3 dependent mechanism and NF-kappaB down-regulation

The effects of coumarin on cell viability, cell cycle arrest and induction of apoptosis were investigated in human cervical cancer HeLa cells. Coumarin was cytotoxic with an IC50 of 54.2 microM, induced morphological changes, and caused G0/G1 arrest and apoptosis. The decreasing number of viable cells appeared to be due to induction of cell cycle arrest and apoptotic cell death, since coumarin induced morphologically apoptotic changes and internucleosomal DNA laddering fragmentation and increased the sub-G1 group. Coumarin affected the production of reactive oxygen species and Ca2+ concentration, and dose-dependently induced the depolarization of mitochondrial membrane potential. Also, coumarin treatment gradually decreased the expression of G0/G1-associated proteins which may have led to the G0/G1 arrest, and the anti-apoptotic proteins Bcl-2 and Bcl-xL, and increased the expression of the pro-apoptotic protein Bax. Coumarin decreased the mitochondrial membrane potential and promoted the release of cytochrome c and the activation of caspase-3 before leading to apoptosis. These results provide information on the mechanisms by which coumarin induces cell cycle arrest and apoptosis in human cervical cancer cells (HeLa).     

P53-mediated cell cycle arrest and apoptosis through a caspase-3- independent, but caspase-9-dependent pathway in oridonin-treated MCF-7 human breast cancer cells

Aim： To study the caspase-3-independent mechanisms in oridonin-induced MCF-7 human breast cancer cell apoptosis in vitro. Methods： The viability of oridonin- treated MCF-7 cells was measured by MTT （thiazole blue） assay. Apoptotic cells with condensed nuclei were visualized by phase contrast microscopy. Nucleosomal DNA fragmentation was assayed by agarose gel electrophoresis. The apoptotic ratio was determined by lactate dehydrogenase assay. Cell cycle alternation and mitochondrial membrane potential were measured by flow cytometric analysis. Bax, Bcl-2, caspase-3, caspase-9, heat shock protein （Hsp）90, p53, p-p53, p21, Poly （ADP-ribose） polymerase （PARP）, and the inhibitor of caspase-activated DNase （ICAD） protein expressions were detected by Western blot analysis. Results： Oridonin inhibited cell growth in a time- and dose-dependent manner. Cell cycle was altered through the upregulation of p53 and p21 protein expressions. Pancaspase inhibitor Z-VAD-fmk and calpain inhibitor II both decreased cell death ratio. Nucleosomal DNA fragmentation and the downregulation of △ψmit were detected in oridonin-induced MCF-7 cell apoptosis, which was involved in a postmitochondrial caspase-9-dependent pathway. Decreased Bcl-2 and Hsp90 expression levels and increased Bax and p21 expression levels were positively correlated with elevated levels of phosphorylated p53 phosphorylation. Moreover, PARP was partially cleaved by calpain rather than by capase-3. Condusion： DNA damage provoked alternations in the mitochondrial and caspase-9 pathways as well as p53-mediated cell cycle arrest, but was not related to caspase-3 activity in oridonin-induced MCF-7 cells.     

Guggulsterone inhibits tumor cell proliferation, induces S-phase arrest, and promotes apoptosis through activation of c-Jun N-terminal kinase, suppression of Akt pathway, and downregulation of antiapoptotic gene products

Guggulsterone is a plant polyphenol traditionally used to treat obesity, diabetes, hyperlipidemia, atherosclerosis, and osteoarthritis, possibly through an anti-inflammatory mechanism. Whether this steroid has any role in cancer is not known. In this study, we found that guggulsterone inhibits the proliferation of wide variety of human tumor cell types including leukemia, head and neck carcinoma, multiple myeloma, lung carcinoma, melanoma, breast carcinoma, and ovarian carcinoma. Guggulsterone also inhibited the proliferation of drug-resistant cancer cells (e.g., gleevac-resistant leukemia, dexamethasone-resistant multiple myeloma, and doxorubicin-resistant breast cancer cells). Guggulsterone suppressed the proliferation of cells through inhibition of DNA synthesis, producing cell cycle arrest in S-phase, and this arrest correlated with a decrease in the levels of cyclin D1 and cdc2 and a concomitant increase in the levels of cyclin-dependent kinase inhibitor p21 and p27. Guggulsterone-induced apoptosis as indicated by increase in the number of Annexin V- and TUNEL-positive cells, through the downregulation of anti-apoptototic products. The apoptosis induced by guggulsterone was also indicated by the activation of caspase-8, bid cleavage, cytochrome c release, caspase-9 activation, caspase-3 activation, and PARP cleavage. The apoptotic effects of guggulsterone were preceded by activation of JNK and downregulation of Akt activity. JNK was needed for guggulsterone-induced apoptosis, inasmuch as inhibition of JNK by pharmacological inhibitors or by genetic deletion of MKK4 (activator of JNK) abolished the activity. Overall, our results indicate that guggulsterone can inhibit cell proliferation and induce apoptosis through the activation of JNK, suppression of Akt, and downregulation of antiapoptotic protein expression.     

Baicalein induced in vitro apoptosis undergo caspases activity in human promyelocytic leukemia HL-60 cells.

In this study, we evaluated the potential apoptosis effects of baicalein on human promyelocytic leukemia HL-60 cells in vitro. Apoptosis induction, cell viability, morphology and caspase-3 activity were then performed to determine by flow cytometric assay, DNA gel electrophoresis, anti-ADP-ribose stain and determination of caspase-3 activity. There is a significant difference in cell death of HL-60 cells that was detected between baicalein-treated and untreated groups. Furthermore, there was a further significant increase in apoptosis induction when cells were treated with baicalein compared to without baicalein treated groups. Flow cytometric assays and DNA fragmentation gel electrophoresis also confirmed baicalein induced apoptosis in HL-60 cells. Baicalein also promoted caspase-3 activity then leading to cleavage of poly-ADP-ribose polymerase finally leading to DNA fragmentation occurrence. Furthermore, the baicalein-induced apoptosis was markedly blocked by the broad-spectrum caspase inhibitor, z-VAD-fmk. Taken together, these results suggest that treatment of human leukemia HL-60 cells with baicalein induced apoptosis through activation of caspase-3 activity.