牡荆素对人肝细胞癌SMMC-7721细胞的增殖抑制作用及其机制的影响

目的: 研究牡荆素(vitexin)对人肝癌细胞SMMC-7721的增殖抑制作用, 并初步探讨其作用机制。方法: 体外培养人肝癌细胞SMMC-7721, 分别采用MTT法和Hoechst33258核染色法检测牡荆素对人肝癌细胞SMMC-7721活力的影响以及观察细胞形态学变化;流式细胞仪检测细胞凋亡率和线粒体膜电位(ΔΨm) 变化;蛋白免疫印迹法检测p53、Bcl-2、Bax等相关凋亡蛋白水平的表达情况。结果: 牡荆素培养人肝癌细胞SMMC-7721 48, 72, 96 h后能明显抑制细胞增殖, 呈时间-剂量依赖性(P<0.05), 其IC₅₀分别是150.37, 116.24, 90.19 μmol·L^-1。牡荆素作用于人肝癌细胞SMMC-7721 72 h后, 以浓度依赖性方式增加细胞凋亡率、降低线粒体膜电位(ΔΨm) 以及上调p53、Bax、Caspase-3等相关促凋亡蛋白的表达, 下调Bcl-2抗凋亡蛋白的表达。结论: 牡荆素能抑制人肝癌细胞SMMC-7721增殖诱导凋亡, 呈时间-剂量依赖性, 其作用机制可能通过依赖P53途径下调Bcl-2, 上调Casepase-3、Bax、P53、PARP等基因表达, 进而诱导凋亡有关。     

美洲大蠊多肽提取物对SMMC-7721细胞凋亡及Bcl-2和Bax蛋白表达的影响

目的：研究美洲大蠊多肽提取物诱导人肝癌细胞SMMC-7721凋亡及其分子机制。方法：采用不同质量浓度的美洲大蠊多肽提取物作用于SMMC-7721,以Cell Counting Kit-8（CCK-8）法检测细胞抑制率;Hoechst33342/PI与Annexin V-FITC/PI双染法相结合检测SMMC-7721细胞的凋亡;蛋白免疫印迹（Western blotting）法检测细胞凋亡相关因子Bcl-2和Bax蛋白表达。结果：不同质量浓度的美洲大蠊多肽提取物可抑制SMMC-7721细胞的增殖,诱导其凋亡,呈一定的量效关系;Western Blot法显示Bax表达增多,Bcl-2蛋白表达减少,Bcl-2/Bax比值降低。结论：美洲大蠊多肽提取物可明显诱导SMMC-7721细胞凋亡,抑制其增殖,其机制可能与下调Bcl-2蛋白表达,上调Bax蛋白表达,降低Bcl-2/Bax比值有关。     

Cytotoxic effects and pro-apoptotic mechanism of TBIDOM, a novel dehydroabietylamine derivative, on human hepatocellular carcinoma SMMC-7721 cells

We have investigated the antiproliferative effects of TBIDOM (N-(4-(2,2,2-trifluoroethyl) benzylidene) (7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenanthren-1-yl) meth-anamine) and have explored its possible mechanisms on human hepatocellular carcinoma SMMC-7721 cells. The proliferative status of cells treated with TBIDOM was measured by the colorimetric MTT assay. Cellular apoptosis was analysed using Hoechst 33342 staining and flow cytometry. Reduction of mitochondrial membrane potential (Delta psi(m)) was also detected by flow cytometry. Western blotting assay was used to evaluate the release of cytochrome c and expression of p53, Bcl-2 and Bax proteins. It was shown that TBIDOM displayed a significant inhibitory effect on growth of SMMC-7721 cells in a dose- and time-dependent manner. Hoechst 33342 staining and flow cytometry analysis showed an increase of apoptosis rate and decrease of mitochondrial membrane potential after SMMC-7721 cells were exposed to TBIDOM for 24 h. Pretreatment of SMMC-7721 cells with TBIDOM significantly induced a decrease of Bcl-2 protein expression and an increase of caspase-3 activity and Bax protein expression. The results indicated that TBIDOM could effectively inhibit proliferation by induction of apoptosis and could be a promising candidate in the development of a novel class of antitumour agent.     

新型金属铜络合物对SMMC-7721细胞增殖与凋亡的影响

目的研究新型金属铜络合物(N-Cu)在体外对人肝癌SMMC-7721细胞增殖与凋亡的影响及其作用机制。方法将不同浓度的N-Cu(0.3～24μmol.L-1)作用于体外培养的SMMC-7721细胞,应用MTT法检测细胞生长抑制率,FCM法检测细胞周期及凋亡率,RT-PCR和Western blot法检测细胞中Bcl-2、Bax、Caspase-3 mRNA和蛋白表达的变化。结果 N-Cu可明显抑制SMMC-7721细胞的增殖,呈明显的量效与时效关系。随着药物浓度的增加,G0/G1期的细胞比率上升,G2/M和S期细胞比率下降,并促进凋亡率增加。N-Cu可上调细胞中Bax、Caspase-3基因及蛋白的表达,抑制Bcl-2基因及蛋白的表达,且均呈剂量依赖性。结论一定浓度的N-Cu可抑制SMMC-7721细胞的增殖并诱导其凋亡,阻滞细胞周期于G0/G1期。上调Bax、Caspase-3基因及蛋白的表达,降低Bcl-2/Bax比值,可能是其诱导细胞凋亡的重要机制。     

Reactive oxygen species production and Bax/Bcl-2 regulation in honokiol-induced apoptosis in human hepatocellular carcinoma SMMC-7721 cells

We investigated possible mechanism(s) where honokiol induces apoptosis in human hepatocellular carcinoma SMMC-7721 cells. MTT assay showed that honokiol has strong inhibition on SMMC-7721 cells in a dose-dependent manner. SMMC-7721 cells after honokiol treatment display morphological characteristics such as cell shrinkage, detachment from the culture plate, formation of apoptotic bodies, change to a round shape, and marked nuclear condensation and fragmentation after 32258 staining. Cell apoptosis was measured by Annexin-V/PI staining and alternatively, by the subG0/G1 percentage of the cell cycle analysis followed by FACS. An obvious loss of ΔΨ(m) and a quick burst of ROS was detected when honokiol reached 4μg/ml, which was coincident with the high apoptosis percentage in our previous research. Up-regulation of Bax and down-regulation of Bcl-2 were observed, suggesting that honokiol-induced apoptosis was associated with reactive oxygen species (ROS) production and an increase of Bax/Bcl-2 ratios.     

Effect of liquiritigenin,a flavanone existed from Radix glycyrrhizae on pro-apoptotic in SMMC-7721 cells

Liquiritigenin is a flavanone existed in Radix glycyrrhizae. The objective of this study is to explore the effects of liquiritigenin on SMMC-7721 cells and its possible mechanism. The viability of liquiritigenin treat cells was decreased in a dose-dependent manner assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylterazolium bromide (MTT), and apoptotic morphological changes also be observed, such as chromatin condensation and nuclear fragmentation. Assessment of apoptotic cells by flow cytometry indicated that cells fell into apoptosis after 0.4 mM liquiritigenin treatment. In addition, a concomitant time-dependent increase in caspase-3 activity was also observed. The level of p53 protein increased and Bcl-2 protein decreased time-dependently. Further studies found the induction of apoptosis by liquiritigenin was accompanied with the production of reactive oxygen species (ROS), disruption of mitochondrial membrane potential and depletion of antioxidant enzymes. The significant ROS generation was firstly found at 3 h and being time-dependent until 9 h. A time-dependent decrease in membrane potential occurred, and significant loss appeared at 9 h and 12 h. Furthermore, pretreatment of N-acetyl-cysteine (NAC), ROS production and apoptosis induced by liquiritigenin were both suppressed. In sum, this paper indicated the cytotoxicity of liquiritigenin on SMMC-7721 cells may via effect on generation of ROS, later lead to cell apoptosis.     

EGCG诱导人肝癌SMMC-7721细胞早期凋亡及基因和蛋白谱的变化研究

目的探讨表没食子儿茶素没食子酸酯(EGCG)诱导人肝癌SMMC-7721细胞早期凋亡的变化规律,以及EGCG作用后SMMC-7721细胞基因及蛋白谱的变化。方法通过MTT法初步筛选EGCG诱导SMMC-7721细胞凋亡的作用浓度,流式细胞Annexin V-FITC/PI法检测EGCG对SMMC-7721细胞增殖的抑制作用和早期凋亡的诱导效应;运用Af-fymetrix U133A2.0人基因组表达谱芯片检测EGCG作用后SMMC-7721细胞基因表达谱的变化,以及SELDI检测EGCG作用后SMMC-7721细胞蛋白图谱的变化,Real-time PCR验证3个表达差异显著基因。结果EGCG诱导SMMC-7721细胞早期凋亡的最佳作用剂量是218.2μmol·L-1,早期凋亡的作用呈剂量依赖性;SMMC-7721细胞经EGCG作用后,表达差异两倍以上的基因共196个,包括上调基因132个和下调基因64个;EGCG作用后表达差异两倍以上的蛋白共43个,包括23个表达上调蛋白,20个表达下调蛋白。Real-time PCR验证DIO2、Id3基因表达与芯片结果一致。结论EGCG有明显的诱导肝癌SMMC-7721细胞早期凋亡的作用,其诱导凋亡作用涉及多基因和多蛋白变化。     

Piperonal ciprofloxacin hydrazone induces growth arrest and apoptosis of human hepatocarcinoma SMMC-7721 cells

Aim:

To investigate the cytotoxic effects of piperonal ciprofloxacin hydrazone (QNT4), a novel antibacterial fluoroquinolone derivative, against human hepatocarcinoma SMMC-7721 cells.

Methods:

Human hepatocarcinoma cells (SMMC-7721), human breast adenocarcinoma cells (MCF-7) and human colon adenocarcinoma cells (HCT-8) were tested. The effects of QNT4 on cell proliferation were examined using MTT assay. Cell apoptosis was determined using Hoechst 33258 fluorescence staining, TUNEL assay and agarose gel electrophoresis. The topoisomerase II activity was measured using agarose gel electrophoresis with the DNA plasmid pBR322 as the substrate. Mitochondrial membrane potential (Δψm) was measured using a high content screening imaging system. Protein expression of caspase-9, caspase-8, caspase-3, p53, Bcl-2, Bax, and cytochrome c was detected with Western blot analysis.

Results:

Treatment with QNT4 (0.625–10 μmol/L) potently inhibited the proliferation of the cancer cells in time- and dose-dependent manners (the IC₅₀ value at 24 h in SMMC-7721 cells, MCF-7 cells and HCT-8 cells was 2.956±0.024, 3.710±0.027, and 3.694±0.030 μmol/L, respectively). Treatment of SMMC-7721 cells with QNT4 (0.2146, 2.964, and 4.600 μmol/L) for 24 h dose-dependently increased the percentage of apoptotic cells, elicited characteristic DNA “ladder” bands, and decreased the mitochondrial membrane potential. QNT4 dose-dependently increased topoisomerase II-mediated DNA breaks while inhibiting DNA relegation, thus keeping the DNA in fragments. Treatment of SMMC-7721 cells with QNT4 significantly increased cytochrome c in the cytosol, and decreased cytochrome c in the mitochondrial compartment. QNT4 (3–7.39 μmol/L) significantly increased the protein expression of p53, Bax, caspase-9, caspase-3, and the cleaved activated forms of caspase-9 and caspase-3 in SMMC-7721 cells. In contrast, the expression of Bcl-2 was decreased, while caspase-8 had no significant change.

Conclusion:

QNT4 induced the apoptosis of SMMC-7721 cells via inhibiting topoisomerase II activity and modulating mitochondrial-dependent pathways.     

玉米须多糖诱导人肝癌SMMC-7721细胞凋亡的研究

目的:观察不同浓度的玉米须多糖(stigma maydis polysaccharide SMPS)对肝癌SMMC-7721细胞作用的影响.方法:将玉米须多糖以不同浓度和时间作用于肝癌SMMC-7721细胞,采用 MTT比色法观察细胞毒性;应用HE染色法观察凋亡细胞的形态;原位末端标记法(TUNEL法)检测细胞凋亡率.结果:玉米须多糖以剂量依赖和时间依赖的方式抑制SMMC-7721细胞的生长.HE染色观察到凋亡细胞的形态学改变.结论:玉米须多糖抑制SMMC-7721细胞的增殖,诱导细胞凋亡.为临床治疗肝癌提供理论依据.     

实时动态法分析七味红花殊胜丸抑制肝癌细胞线粒体代谢

目的：观察七味红花殊胜丸对人肝癌SMMC-7721细胞线粒体代谢酶的影响。方法：运用实时动态法分析七味红花殊胜丸对细胞活性的影响及各给药组不同时间IC₅₀值的变化情况。采用MTT法检测七味红花殊胜丸对SMMC-7721细胞的抑制率;ELISA法检测七味红花殊胜丸对SMMC-7721细胞线粒体代谢和凋亡的影响,Western Blot法检测凋亡蛋白的表达状况。结果：实时动态检测结果提示,七味红花殊胜丸5 mg·mL^-1作用48 h对SMMC-7721细胞的抑制率最高（P<0.01）;ELISA检测结果提示,七味红花殊胜丸能降低SMMC-7721细胞内ATP、ATPase、线粒体呼吸链复合物Ⅰ/Ⅱ/Ⅲ/Ⅳ酶的表达量,影响细胞的能量代谢;升高促凋亡蛋白Bax、Caspase-3和Caspase-9的表达量,降低抗凋亡蛋白Bcl-2的表达量,诱导细胞凋亡。结论：七味红花殊胜丸可通过影响细胞的能量代谢,诱导SMMC-7721细胞凋亡。     

In vitro effects on proliferation, telomerase activity and apoptosis of an eremophilanoid sesquiterpene from Senecio oldhamianus maxim in cultured human tumor cell lines

8,11-Dioxol-6-en-9alpha, 10alpha-epoxy-8beta-hydroxyeremophilane (HEM), a new eremophilanoid sesquiterpene, was isolated from Senecio oldhamianus Maxim. Its effects of cytotoxicity, telomerase activity, apoptosis and related genes expression in two human tumor cell lines, human hepatoma cells SMMC-7721 and human oophoroma cells HO-8910, were studied. Hydroxycamptothecine (HCPT) was used as a positive control. The IC50 of cytotoxicity by HEM were 24.9 +/- 2.1 and 19.4 1.6 microM in SMMC-7721 and HO-8910 cells respectively, and 0.35 +/- 0.10 and 0.27 +/- 0.08 microM for HCPT. HEM inhibited telomerase activity with the IC50 35.9 +/- 3.2 microM in SMMC-7721 and 25.6 +/- 2.6 microM in HO-8910 cells, while HCPT had no effect on telomerase activity in both tumor cell lines. HEM 20-30 microM induced apoptosis in SMMC-7721 cells from 5.7% to 18.4% and in HO-8910 cells from 7.6% to 67.1%. While HCPT 0.1-0.5 microM induced apoptosis in SMMC-7721 cells from 6.5% to 13.3% and in HO-8910 cells from 9.9% to 30.9%. HEM 30 microM significantly decreased Bcl-2 protein expression to 58.7% in SMMC-7721 and to 57.6% in HO-8910 cells. While HCPT 0.5 microM significantly decreased Bcl-2 protein expression to 64.3% in SMMC-7721 and to 70.0% in HO-8910 cells. HEM 25 microM and 30 microM significantly increased P53 protein expression 2.3-3.6-fold in SMMC-7721 and 3.0-5.7- fold in HO-8910 cells. While HCPT 0.5 microM significantly increased P53 protein expression 3.3-fold in SMMC-7721 and 2.7-fold in HO-8910 cells. Overall, HCPT exhibited a more potent effect on cytotoxicity and apoptosis in the two tumor cell lines than HEM did. However HEM can inhibit telomerase activity in the two tumor cell lines but HCPT cannot.     

Reactive oxygen species accumulation contributes to gambogic acid-induced apoptosis in human hepatoma SMMC-7721 cells

It is reported that gambogic acid (GA), the main active compound of gamboge which is a dry resin extracted from Garcinia hanburyi tree, has potent antitumor activity both in vivo and in vitro. Activation of mitochondrial apoptotic pathway in cancer cells is one effective therapy for cancer treatment. In the present study, we focus on the effect of GA on induction of reactive oxygen species (ROS) accumulation and triggering the mitochondrial signaling pathway in human hepatoma SMMC-7721 cells. The results indicated that GA induced ROS accumulation and collapse of mitochondrial membrane potential in SMMC-7721 cells in a concentration-dependent manner and subsequently induced that release of Cytochrome c and apoptosis-inducing factor from mitochondria to cytosol, which inhibited ATP generation and induced apoptosis in the cells. Moreover, GA elevated the phosphorylation of c-Jun-N-terminal protein kinase (JNK) and p38, which was the downstream effect of ROS accumulation. Furthermore, N-acetylcysteine, a ROS production inhibitor, partly reversed the activation of JNK and p38 and the induction of apoptosis in GA-treated cells. Collectively, our study demonstrated that accumulation of ROS played an important role in GA-induced mitochondrial signaling pathway, which provided further theoretical support for the application of GA as a promising anticancer agent.     

Mechanism of apoptotosis induced by ortho-topolin riboside in human hepatoma cell line SMMC-7721

The naturally occurring cytokinin, ortho-topolin riboside (oTR), has been recently reported to have a strong anticancer effect. However, the molecular mechanism has not been elucidated. From our research we found that oTR strongly inhibited the proliferation of SMMC-7721 cells inducing apoptosis. After oTR treatment, up-regulation of the protein levels of pro-apoptotic Bax and the down-regulation of the anti-apoptotic proteins, Bcl-2 and Bcl-xL was observed, leading to the loss of mitochondrial membrane potential, the release of cytochrome c from the mitochondria into the cytosol, the downstream activation of caspase-9 and caspase-3, as well as the cleavage of poly ADP-ribose-polymerase (PARP), the effect of apoptosis could be blocked by the pan-specific caspase inhibitor z-VAD-fmk and caspase-9-specific inhibitor z-LEHD-fmk. Moreover, oTR was shown to inhibit the activation of the extracellular signal-regulated kinase-1/2 (ERK_1/2) as well as the Akt pathway. These results suggest that oTR interferes with the mitogen-activated protein kinase (MAPK) and Akt pathways and induces the apoptosis of human SMMC-7721 cells through the activation of intrinsic mitochondria-mediated pathways. However, the apoptosis was completely prevented when cells were treated with A-134974, an inhibitor of adenosine kinase, it indicated that the intracellular phosphorylation of oTR is necessary for its cytotoxic effects to SMMC-7721 cells.     

The cytotoxicity induced by brucine from the seed of Strychnos nux-vomica proceeds via apoptosis and is mediated by cyclooxygenase 2 and caspase 3 in SMMC 7221 cells.

To study the cytotoxicity of four alkaloids: brucine, strychnine, brucine N-oxide and isostrychnine from nux vomica on SMMC 7721 cells and their possible mechanisms, MET assay was used to examine the growth inhibitory effects of these alkaloids. Brucine revealed the strongest growth inhibitory effect on SMMC-7721 cells. Furthermore, as directly observed under an inverted microscope, fluorescent microscope and transmission electronic microscope, brucine caused SMMC-7721 cell shrinkage, membrane blobbing, formation of apoptotic body as well as nucleus condensation, all of which are typical characteristics of apoptotic programmed cell death. In addition, brucine dose-dependently caused SMMC-7721 cells apoptosis via formation of subdipolid DNA and phosphatidylserine externalization, as evidenced by flow cytometry analysis. The brucine-induced apoptosis was partially attributed to the activation of caspase 3 as well as cyclooxygenase 2 inhibition, since neither caspase 3 specific inhibitor, z-DEVD-fmk nor was exogenous addition of prostaglandin E(2) able to completely abrogate the brucine-induced SMMC 7721 cell apoptosis. In sum, this paper indicate that the major alkaloids present in the seed of Strychnos nux-vomica are effective against SMMC-7721 cells proliferation, among which brucine proceeds SMMC-7721 cells death via apoptosis, probably through the participation of caspase 3 and cyclooxygenase 2.     

Chelerythrine chloride from Macleaya cordata induces growth inhibition and apoptosis in human gastric cancer BGC-823 cells

This study aimed to investigate the ability of chelerythrine chloride (CHE), the main active ingredient of Macleaya cordata, to induce apoptosis in human gastric cancer BGC-823 cells. The results demonstrate that CHE inhibits cell proliferation in a time- and dose-dependent manner with accompanying S phase arrest. It also induces apoptosis by a mechanism involving a reduction in the mitochondrial membrane potential, the release of cytochrome c, activation of caspase 3 and cleavage of poly-ADP-ribose polymerase. In addition, CHE-induced apoptosis is accompanied by down-regulation of Bcl-xl and Bcl-2 proteins with no change in the levels of Bax proteins. Taken together, the results support the development of CHE as a potentially useful anticancer drug for the treatment of gastric cancer.     

Involvement of bax/bcl-2 in wogonin-induced apoptosis of human hepatoma cell line SMMC-7721

The molecular mechanisms of wogonin-induced apoptosis of human hepatoma SMMC-7721 cells are reported. Wogonin treatment resulted in significant inhibition of SMMC-7721 cells in a time-dependent and concentration-dependent manner. Typical morphological changes and apoptotic blebbing in SMMC-7721 cells were observed after treatment with 1x10(-4) mol/l wogonin for a period of 0-48 h. Flow cytometry and Annexin-V/propidium iodide double-staining experiments revealed a dramatic increase in the number of apoptotic and G0/G1 phase cells after wogonin treatment. The proapoptotic activity of wogonin is attributed to its ability to modulate the expression of bcl-2 and bax proteins. It is observed that the expression of bax protein is dramatically increased whereas the synthesis of bc1-2 protein is significantly decreased when cells are treated with wogonin. The results presented in this paper suggested an important relationship between gene regulation and wogonin-induced apoptosis, and indicated the possibility of developing naturally occurring monoflavonoids as novel anticancer agents for better management of human cancers.     

Neurobehavioral impairments, generation of oxidative stress and release of pro-apoptotic factors after chronic exposure to sulphur mustard in mouse brain

Recent global events have focused attention on the potential threat of international and domestic chemical terrorism, as well as the possibility of chemical warfare proliferation. Sulphur mustard (SM) is one of the potent chemical warfare agents (CWA), which initiates a cascade of events that converge on the redox mechanisms common to brain injury. The present study was designed to examine the effects of chronic SM exposure on neurobehavioral impairments, mitochondrial oxidative stress in male Swiss Albino mice and its role in inducing apoptotic neuronal cell death. The animals were divided into four groups (control, low, medium and high dose) of 5 animals each. Exposure to SM was given percutaneously daily for 12 weeks. The results demonstrated impairment in neurobehavioral indices viz. rota rod, passive avoidance and water maze tests in a dose dependent manner. There was a significant increase in lipid peroxidation and protein carbonyl content whereas, decrease in the activity of manganese superoxide dismutase (MnSOD), glutathione reductase and glutathione peroxidase suggesting impaired antioxidant defense system. Immunoblotting of cytochrome c, Bcl-2, Bax and activation of caspase-3 suggest induction of apoptosis in a dose dependent manner. Finally, increased p53 expression suggests that it may target the mitochondrial pathway for inducing apoptosis in response to DNA damage signals. In conclusion, chronic SM exposure may have the potential to generate oxidative stress which may trigger the release of cytochrome c as well as caspase-3 activation in neurons leading to cell death by apoptosis in a dose dependent manner which may in the end be responsible for the disruption of cognitive functions in mice.     

Induction of apoptosis by esculetin in human leukemia U937 cells: Roles of Bcl-2 and extracellular-regulated kinase signaling

In the present study, we reported that apoptosis induced by esculetin, a phenolic compound with apoptotic activity in cancer cells, was markedly blocked by Bcl-2-overexpression, but restored by HA14-1, a small-molecule Bcl-2 inhibitor, in human leukemic U937 cells. The combined use of esculetin and HA14-1 effectively induced Bid cleavage and loss of mitochondrial membrane potential (MMP, Δψ_m) leading to the activation of caspases and cleavage of poly(ADP-ribose) polymerase (PARP) in Bcl-2-overexpressing (U937/Bcl-2) cells. Combined treatment with esculetin and HA14-1 upregulated the expression of death receptor 4 (DR4), and activation of extracellular-regulated kinase (ERK) in a time-dependent manner. In addition, esculetin and HA14-1-mediated apoptosis was reduced by ERK inhibitors through inhibition of DR4 expression, suggesting that the synergistic effect was at least partially mediated through ERK-dependent induction of DR4 expression. The results indicate that HA14-1-induced reversal of the anti-apoptotic effect of Bcl-2 confers apoptosis sensitivity to esculetin by a mitochondrial amplification step and through the ERK-dependent induction of DR4 expression in U937/Bcl-2 cells. Thus, HA14-1 reversal of Bcl-2-mediated esculetin resistance suggests a novel strategy for increasing esculetin sensitivity in Bcl-2-overexpressing leukemia cells.     

Potentiation of 1-beta-D-arabinofuranosylcytosine-mediated mitochondrial damage and apoptosis in human leukemia cells (U937) overexpressing bcl-2 by the kinase inhibitor 7-hydroxystaurosporine (UCN-01)

Antileukemic interactions between the nucleoside analog 1-beta-D-arabinofuranosylcytosine (ara-C) and the kinase inhibitor 7-hydroxystaurosporine (UCN-01) have been examined in relation to Bcl-2 expression/phosphorylation, mitochondrial damage, caspase activation, and loss of clonogenic potential. Subsequent exposure of ara-C-pretreated U937 cells (1 microM; 6 hr) to UCN-01 (300 nM; 24 hr) resulted in marked potentiation of pro-caspase-3 and -9 cleavage/activation, poly(ADP-ribose)polymerase degradation, diminished mitochondrial membrane potential (Deltapsi(m)), enhanced cytochrome c release, reduction in the S-phase fraction, and induction of classic apoptotic morphologic features. Enforced expression of full-length Bcl-2 significantly protected cells (at 24 hr) from ara-C/UCN-01-induced caspase activation and apoptosis, but was ineffective in preventing loss of Deltapsi(m) and cytochrome c release. Ectopic expression of a Bcl-2 N-terminal phosphorylation loop-deleted protein (Bcl-2Delta(32-80)) was more potent than its full-length counterpart in blocking drug-induced loss of Deltapsi(m, ) caspase activation, and apoptotic morphology, but not cytochrome c release. Examination of cells at later intervals revealed that ectopic expression of Bcl-2 or Bcl-2Delta(32-80) could only delay, but not prevent, mitochondrial damage, caspase activation, and cell death induced by ara-C/UCN-01 treatment. Despite their initial ability to inhibit apoptosis, neither full-length nor truncated Bcl-2 protein restored clonogenic potential to drug-treated cells. These findings indicate that subsequent exposure of ara-C-pretreated human leukemia cells to UCN-01 potently triggers mitochondrial damage and apoptosis, and that these events are postponed but not prevented by ectopic expression of Bcl-2 or its phosphorylation loop-deleted counterpart.     

γ-Tocotrienol induces apoptosis in human T cell lymphoma through activation of both intrinsic and extrinsic pathways

Tocotrienols are members of vitamin E family and possess broad biological activities including antioxidant, anti-inflammatory and antitumor effects. In the present study, we examine the potential of α-tocotrienol (AT) and γ-tocotrienol (GT) in inhibiting the proliferation of human T cell lymphoma Jurkat cells and elucidate the pathways involved in anti tumor effects of GT. GT but not AT inhibited proliferation and induced apoptosis in Jurkat cells in a dose dependent manner. GT treatment resulted in elevated mitochondrial ROS production, activation of JNK and suppression of ERK and p38 MAPK. GT also induced calcium release, loss of mitochondrial membrane potential and cytochrome c release from the mitochondria. These changes were accompanied by increase in Bax expression with a concomitant decrease in Bcl-xl expression suggesting activation of mitochondrial apoptotic pathway. GT induced increase in mitochondrial ROS was abrogated by catalase. Besides, GT also up-regulated surface expression of Fas and FasL on Jurkat cells. Further, caspase activation and PARP degradation were also seen in cells treated with GT. Inhibitors of caspase-8 and caspase-9 significantly abrogated GT mediated apoptosis. In contrast GT was not toxic to normal human peripheral blood mononuclear cells suggesting differential cytotoxicity towards normal lymphocytes and transformed lymphoma cells. Cellular uptake studies with tocotrienols showed higher intracellular accumulation of GT as compared to AT which may be responsible for its better antitumor activity. Our results show antitumor effects of GT in human lymphoma cells via increased mitochondrial ROS generation and activation of both intrinsic and extrinsic apoptotic pathways.