周期性张应力对牙周膜成纤维细胞凋亡的影响

目的:在体外条件下,探讨周期张应力作用对人牙周膜成纤维细胞凋亡的影响及PI3k/Akt信号通路在细胞凋亡中的作用。方法:应用多通道细胞牵张应力加载系统,以HPDLFs(人牙周膜成纤维细胞)为对象构建细胞体外培养-力学刺激模型,对照组为0h,0h+LY294002,加力组1 h,6 h,12 h,12 h+LY294002,24 h,力值定为15%,频率为1/6HZ,即10循环/分钟。采用Hoechst33258染色检测细胞形态和凋亡情况,应用RT-PCR技术检测Bcl-2、Bax的表达情况。结果:Hoechst 33258细胞染色结果显示,对照组的细胞核为弥散均匀的圆形或椭圆形荧光,实验组的细胞核或细胞质内出现可见致密浓染的颗粒、新月体或环状荧,RT-PCR结果显示Bcl-2与Bax基因表达均呈现时间依赖性。12 h HPDLFs的细胞凋亡数达最高峰值(P<0.01),24 h细胞凋亡峰值开始下降,但仍高于未加力组(P<0.05)。与对照组相比加入LY294002后,Bcl-2/Bax比值较加载相同时间的加力组小(P<0.05)。结论:一定的时间范围内,周期性张应力能促进HPDLFs凋亡;随着时间的延长(24h),细胞凋亡受到抑制;PI3K/Akt信号传导通路可能参与在周期性张应力介导的HPDLFs的凋亡。     

液泡分选蛋白4B对骨关节炎软骨细胞凋亡的调控作用

目的:探讨液泡分选蛋白4B(VPS4B)对骨关节炎软骨细胞凋亡的调控作用。方法:通过内侧半月板部分切除加前交叉韧带切断的方法建立骨关节炎SD大鼠模型,通过RT-PCR和免疫组化检测VPS4B在大鼠关节软骨中的表达。番红O/固绿染色方法检测大鼠膝关节软骨组织形态变化。通过用10 ng/mL的IL-1β诱导人软骨肉瘤细胞SW1353 24 h来模拟骨关节炎样软骨细胞损伤,Western blot检测SW1353细胞中VPS4B、凋亡相关因子(cleaved caspase-3和cleaved PARP)和磷酸化p38的表达。转染si-RNA敲低SW1353细胞中VPS4B表达,并评估其对IL-1β诱导的SW1353细胞凋亡标记和p38 MAPK信号通路的影响。膜联蛋白V (Annexin V)和碘化丙啶(PI)染色用于检测软骨细胞凋亡。结果:VPS4B在模型组大鼠的关节软骨中明显上调(P0.05)。IL-1β诱导24 h后,SW1353细胞中的VPS4B、cleaved caspase-3、cleaved PARP和p-p38蛋白表达水平均明显增加。而转染VPS4B-si RNA敲低VPS4B的表达后,cleaved caspase-3、cleaved PARP和p-p38蛋白表达水平均被抑制,并且抑制了IL-1β诱导细胞的凋亡率。结论:VPS4B在骨关节炎发病过程中明显上调,VPS4B的上调通过激活p38 MAPK信号通路来促进软骨细胞凋亡。     

水飞蓟宾诱导肺腺癌Anip973 细胞凋亡的分子机制研究

目的:探讨水飞蓟宾诱导肺腺癌Anip973细胞系细胞凋亡的分子机制。方法:采用MTT法、倒置显微镜和电子显微镜等形态学检测以及流式细胞仪(FCM)技术检测、DNALadder分析、凋亡分子PARP的表达检测细胞凋亡,同时进行凋亡相关蛋白Bax、Bcl-2、caspase-3和caspase-9表达活性分析。结果:(1)水飞蓟宾对人肺腺癌Anip973细胞系细胞的增殖有显著抑制作用;(2)水飞蓟宾作用Anip973细胞48h后,随着浓度的增加,倒置显微镜下可见细胞数目减少,胞体变小、变圆,到高浓度时出现较多的死亡细胞;(3)扫描电镜观察发现,随着水飞蓟宾作用浓度的增加,Anip973细胞中出现增多的凋亡细胞,凋亡细胞表现出典型的超微结构特征;(4)流式细胞仪检测的结果发现,随着药物作用时间的延长,Anip973细胞的G1期细胞比例增多,S期细胞明显减少,G2期细胞略有减少,并出现明显的凋亡峰。(5)水飞蓟宾作用后的Anip973细胞出现明显的DNALadder和PARP降解增加等凋亡特征;(6)水飞蓟宾作用后,Anip973细胞中的凋亡相关蛋白Bax表达增加、caspase-3和caspase-9酶活性增加,而Bcl-2表达降低。结论:水飞蓟宾在体外有抑制人肺腺癌细胞Anip973的增殖作用,并通过激活线粒体依赖的caspase凋亡通路,诱导其凋亡。     

静态压力对人牙周膜干细胞凋亡相关蛋白表达的影响

目的:探讨体外模拟正畸牙移动过程中机械压力对人牙周膜干细胞(HPDLSC)凋亡相关蛋白表达的影响。方法:将体外培养的HPDLSC分别在自行研发的加压力装置中进行100、200 Kpa加压1、6和12 h后,检测和比较其凋亡相关蛋白caspase-3和caspase-8的表达;流式细胞仪检测其凋亡状态。结果:100 Kpa加压1 h的HPDLSCs中caspase-3和caspase-8的蛋白表达及其凋亡水平均显著高于对照组(P0.05),而加力12 h的HPDLSCs中caspase-3和caspase-8的蛋白表达和凋亡水平与对照组比较无统计学差异(P0.05)。200 Kpa加力1 h的HPDLSCs中caspase-3和caspase-8的蛋白表达和凋亡水平均显著低于对照组(P0.05),而加力12 h的HPDLSCs中caspase-3和caspase-8的蛋白表达和凋亡水平与对照组比较无统计学差异(P0.05)。结论:在体外模拟正畸牙移动过程中,不同强度静态压力作用不同时间对人牙周膜干细胞的凋亡作用不同,100 Kpa静态加力加压1 h可更有效地促进人牙周膜干细胞的凋亡,而200 Kpa静态加力加压1 h可抑制人牙周膜干细胞的凋亡。     

水飞蓟宾诱导肺腺癌Anip973细胞凋亡的分子机制研究

目的：探讨水飞蓟宾诱导肺腺癌Anip973细胞系细胞凋亡的分子机制。方法：采用MTT法、倒置显微镜和电子显微镜等形态学检测以及流式细胞仪（FCM）技术检测、DNALadder分析、凋亡分子PARP的表达检测细胞凋亡,同时进行凋亡相关蛋白Bax、Bcl-2、caspase-3和caspase-9表达活性分析。结果：（1）水飞蓟宾对人肺腺癌Anip973细胞系细胞的增殖有显著抑制作用;（2）水飞蓟宾作用Anip973细胞48h后,随着浓度的增加,倒置显微镜下可见细胞数目减少,胞体变小、变圆,到高浓度时出现较多的死亡细胞;（3）扫描电镜观察发现,随着水飞蓟宾作用浓度的增加,Anip973细胞中出现增多的凋亡细胞,凋亡细胞表现出典型的超微结构特征;（4）流式细胞仪检测的结果发现,随着药物作用时间的延长,Anip973细胞的G1期细胞比例增多,S期细胞明显减少,G2期细胞略有减少,并出现明显的凋亡峰。（5）水飞蓟宾作用后的Anip973细胞出现明显的DNALadder和PARP降解增加等凋亡特征;（6）水飞蓟宾作用后,Anip973细胞中的凋亡相关蛋白Bax表达增加、caspase-3和caspase-9酶活性增加,而Bcl-2表达降低。结论：水飞蓟宾在体外有抑制人肺腺癌细胞Anip973的增殖作用,并通过激活线粒体依赖的caspase凋亡通路,诱导其凋亡。     

TGF-β1在应力介导的牙周膜成纤维细胞增殖中的作用及其机制

目的:探讨周期性张应力作用下人牙周膜成纤维细胞(HPDLF)转化生长因子β1(TGF-β1)对其细胞增殖的作用,及对其I型胶原基因表达的作用和影响.方法:在成功构建人牙周膜成纤维细胞体外培养力学刺激模型的基础上,利用多通道细胞牵张应力加载系统,对细胞分别施加2、6、12与24 h的周期性张应力,以不加力组为对照组,观察各组细胞形态变化,利用细胞计数试剂8检测细胞增殖活性,并利用ELISA试剂盒检测加力后各组TGF-β1的表达,并对加力12h组加入TGF-β1抑制剂SB431542,利用RT-PCR检测技术检测对I型胶原基因表达的影响.结果:与对照组比较,加力2h细胞增殖稍降低,6h增殖活性增强,12h达到峰值,24h增殖活性明显受到抑制;TGF-β1的表达与细胞增殖成正相关;TGF-β1受到抑制后细胞增殖受到影响,I型胶原的表达也受到影响.结论:人牙周膜成纤维细胞的增殖在一定时间的周期性张应力作用下先增加然后再抑制,其中TGF-β1参与细胞增殖,并且TGF-β1对人牙周膜成纤维细胞I型胶原的表达起促进作用.     

NF-kB 拮抗剂PDTC 对HepG2 细胞的抑制及对caspase-3 表达的影响

目的:研究NF-kB拮抗剂PDTC诱导人肝癌HepG2细胞凋亡及其对凋亡相关基因caspase-3表达的影响,初步探讨其诱导凋亡的可能机制。方法:以不同浓度的PDTC处理人肝癌HepG2细胞,利用MTT法检测对人肝癌HepG2细胞凋亡的影响;利用RT-PCR和Western-blot检测caspase-3mRNA和蛋白的表达。结果:不同浓度PDTC作用人肝癌HepG2细胞不同时间后,能够显著抑制HepG2细胞的生长增殖,存在剂量和时间依赖性(P<0.05);PDTC能够上调HepG2细胞中caspase-3mRNA和蛋白的表达。结论:NF-kB拮抗剂PDTC对人肝癌HepG2细胞产生显著抑制,并能上调HepG2细胞中caspase-3mRNA和蛋白的表达。     

NF-kB拮抗剂PDTC对HepG2细胞的抑制及对caspase-3表达的影响

目的：研究NF-kB拮抗剂PDTC诱导人肝癌HepG2细胞凋亡及其对凋亡相关基因caspase-3表达的影响,初步探讨其诱导凋亡的可能机制。方法：以不同浓度的PDTC处理人肝癌HepG2细胞,利用MTT法检测对人肝癌HepG2细胞凋亡的影响;利用RT-PCR和Western-blot检测caspase-3mRNA和蛋白的表达。结果：不同浓度PDTC作用人肝癌HepG2细胞不同时间后,能够显著抑制HepG2细胞的生长增殖,存在剂量和时间依赖性（P〈0.05）;PDTC能够上调HepG2细胞中caspase-3mRNA和蛋白的表达。结论：NF-kB拮抗剂PDTC对人肝癌HepG2细胞产生显著抑制,并能上调HepG2细胞中caspase-3mRNA和蛋白的表达。     

阿司匹林诱导人恶性睾丸生殖细胞瘤NTera-2细胞凋亡

阿司匹林,又称乙酰水杨酸,已证实有抑制肿瘤细胞增殖、诱导肿瘤细胞凋亡和抑制血管生成等多种抗癌功能.除已知对环氧合酶COX-2的活性有抑制外,阿司匹林抗癌分子机制尚不十分清楚.已报道阿司匹林可以降低多种癌症发生风险,但应用于人类睾丸肿瘤治疗的研究报道很少.本文研究了阿司匹林对人恶性睾丸肿瘤NTera-2细胞凋亡的机制.通过MTT方法检测细胞活力,发现阿司匹林以时间和剂量依赖方式抑制NTera-2细胞增殖.不同浓度阿司匹林处理NTera-2细胞后,采用Hoechest 33258染色方法和Annexin V-FITC/PI流式法分别检测NTera-2细胞的形态学变化、凋亡小体形成、细胞凋亡水平;RT-PCR结果显示,NTera-2细胞中Fas和caspase-8的表达以阿司匹林剂量依赖性上升;蛋白印迹结果显示,FasL的蛋白表达水平下降并活化caspase-8、caspase-3蛋白表达,PARP出现剪切体. 进一步的实验证明,caspase广谱抑制剂Z-VAD-FMK能够减弱阿司匹林诱导NTera-2细胞凋亡. 结果显示,阿司匹林能明显抑制NTera-2细胞活力,并通过激活caspase 通路诱导NTera-2细胞的凋亡,为进一步利用阿司匹林治疗人类睾丸肿瘤的研究奠定基础.     

自噬在应力诱导成肌细胞凋亡中的作用初探

目的:探讨自噬在周期性张应力介导的成肌细胞凋亡中的作用,以明确应力诱导内质网应激引起自噬与凋亡之间的关系。方法:在成功构建L6大鼠体外培养--力学刺激模型的基础上,采用Western Blot法分析周期性张应力对自噬相关蛋白LC3蛋白表达的影响,并通过Annexin V-FITC/PI流式细胞术检测细胞凋亡情况。加力组分别给予1,6,12,24 h的力学刺激(拉伸变形率为15%,频率为10循环/min),3-MA组和Rapamycin组在加力2 h前分别加入自噬抑制剂3-甲基腺嘌呤和自噬激活剂雷帕霉素并且加力24 h,0 h组与实验组在同时种板但是不给予力刺激。采用SPSS17.0统计软件对以上数据进行统计分析。结果:成肌细胞中的LC3II/LC3I值随加力时间延长呈上升趋势,24 h达最高(P0.05);抑制组的细胞凋亡率(18.75±1.06%)相对于0 h组(0.726±0.13%)和加力24 h组(14.84±1.14%)的明显升高(P0.05);Rapamycin组相对于加力24 h组的细胞凋亡率明显下降(8.88±1.08%vs 14.84±1.14%),但是细胞凋亡率仍然高于0 h组的(8.88±1.08%vs 0.726±0.13%)。结论:在一定时间范围内,周期性张应力可诱导成肌细胞发生自噬,并且自噬活性与作用时间成正比;自噬可以降低应力介导的成肌细胞凋亡的活性。     

Pathological Cyclic Strain-Induced Apoptosis in Human Periodontal Ligament Cells through the RhoGDIα/Caspase-3/PARP Pathway

Aim

Human periodontal ligament (PDL) cells incur changes in morphology and express proteins in response to cyclic strain. However, it is not clear whether cyclic strain, especially excessive cyclic strain, induces PDL cell apoptosis and if so, what mechanism(s) are responsible. The aim of the present study was to elucidate the molecular mechanisms by which pathological levels of cyclic strain induce human PDL cell apoptosis.

Materials and Methods

Human PDL cells were obtained from healthy premolar tissue. After three to five passages in culture, the cells were subjected to 20% cyclic strain at a frequency of 0.1 Hz for 6 or 24 h using an FX-5000T system. Morphological changes of the cells were assessed by inverted phase-contrast microscopy, and apoptosis was detected by fluorescein isothiocyanate (FITC)-conjugated annexin V and propidium iodide staining followed by flow cytometry. Protein expression was evaluated by Western blot analysis.

Results

The number of apoptotic human PDL cells increased in a time-dependent manner in response to pathological cyclic strain. The stretched cells were oriented parallel to each another with their long axes perpendicular to the strain force vector. Cleaved caspase-3 and poly-ADP-ribose polymerase (PARP) protein levels increased in response to pathological cyclic strain over time, while Rho GDP dissociation inhibitor alpha (RhoGDIα) decreased. Furthermore, knock-down of RhoGDIα by targeted siRNA transfection increased stretch-induced apoptosis and upregulated cleaved caspase-3 and PARP protein levels. Inhibition of caspase-3 prevented stretch-induced apoptosis, but did not change RhoGDIα protein levels.

Conclusion

The overall results suggest that pathological-level cyclic strain not only influenced morphology but also induced apoptosis in human PDL cells through the RhoGDIα/caspase-3/PARP pathway. Our findings provide novel insight into the mechanism of apoptosis induced by pathological cyclic strain in human PDL cells.     

Interaction between caspase-3 and caspase-5 in the stretch-induced programmed cell death in the human periodontal ligament cells

In our previous studies, programmed cell death (PCD) was induced in human periodontal ligament (PDL) cells, through activation of caspase-3 and upregulation of CASP5 gene (encoding caspase-5 protein), in response to mechanical stretch loading. The aim of this study is to explore the relationship between the inflammatory caspase, caspase-5, and the apoptotic executioner protein, caspase-3, in human PDL cells. Here, we found that cyclic stretching upregulated the activity and the protein expression level of caspase-3 and -5 and the addition of the caspase-3 inhibitor or caspase-5 inhibitor significantly inhibited the stretch-induced PCD. Meanwhile, the inhibition of caspase-5 inhibited the activation of caspase-3 and vice versa. The result of coimmunoprecipitation also demonstrated that the expression of caspase-3 was immunoprecipitated with caspase-5. Thus, our study revealed that the in vitro application of cyclic stretching induced PCD by activation of caspase-3 and -5 in human PDL cells, and these two caspases could interact with each other after mechanical stretch loading. The study may facilitate further studies on the mechanism of stretch-induced PCD and help us understand the force-related periodontal homeostasis and remodeling better.     

Titanium dioxide nanoparticles induce apoptosis through the JNK/p38-caspase-8-Bid pathway in phytohemagglutinin-stimulated human lymphocytes

We investigated the signaling pathways underlying nano-TiO₂-induced apoptosis in cultured human lymphocytes. Nano-TiO₂ increased the proportion of sub-G1 cells, activated caspase-9 and caspase-3, and induced caspase-3-mediated PARP cleavage. Nano-TiO₂ also induced loss of mitochondrial membrane potential, which suggests that nano-TiO₂ induces apoptosis via a mitochondrial pathway. A time-sequence analysis of the induction of apoptosis by nano-TiO₂ revealed that nano-TiO₂ triggered apoptosis through caspase-8/Bid activation. We also observed that inhibition of caspase-8 by z-IETD-fmk suppressed the caspase-8/Bid activation, caspase-3-mediated PARP cleavage, and apoptosis. Nano-TiO₂ activated two MAPKs, p38 and JNK. In addition, the selective p38 inhibitor SB203580 and selective JNK inhibitor SP600125 suppressed nano-TiO₂-induced apoptosis and caspase-8 activation to moderate and significant extents, respectively. Knockdown of protein levels of JNK1 and p38 using an RNA interference technique also suppressed caspase-8 activation. Our results suggest that nano-TiO₂-induced apoptosis is mediated by the p38/JNK pathway and the caspase-8-dependent Bid pathway in human lymphocytes.     

Coxiella burnetii induces apoptosis during early stage infection via a caspase-independent pathway in human monocytic THP-1 cells

The ability of Coxiella burnetii to modulate host cell death may be a critical factor in disease development. In this study, human monocytic THP-1 cells were used to examine the ability of C. burnetii Nine Mile phase II (NMII) to modulate apoptotic signaling. Typical apoptotic cell morphological changes and DNA fragmentation were detected in NMII infected cells at an early stage of infection. FACS analysis using Annexin-V-PI double staining showed the induction of a significant number of apoptotic cells at an early stage of NMII infection. Double staining of apoptotic cell DNA and intracellular C. burnetii indicates that NMII infected cells undergoing apoptosis. Interestingly, caspase-3 was not cleaved in NMII infected cells and the caspase-inhibitor Z-VAD-fmk did not prevent NMII induced apoptosis. Surprisingly, the caspase-3 downstream substrate PARP was cleaved in NMII infected cells. These results suggest that NMII induces apoptosis during an early stage of infection through a caspase-independent pathway in THP-1 cells. In addition, NMII-infected monocytes were unable to prevent exogenous staurosporine-induced apoptotic death. Western blot analysis indicated that NMII infection induced the translocation of AIF from mitochondria into the nucleus. Cytochrome c release and cytosol-to-mitochondrial translocation of the pore-forming protein Bax in NMII infected cells occurred at 24 h post infection. These data suggest that NMII infection induced caspase-independent apoptosis through a mechanism involving cytochrome c release, cytosol-to-mitochondrial translocation of Bax and nuclear translocation of AIF in THP-1 monocytes. Furthermore, NMII infection increased TNF-α production and neutralization of TNF-α in NMII infected cells partially blocked PARP cleavage, suggesting TNF-α may play a role in the upstream signaling involved in NMII induced apoptosis. Antibiotic inhibition of C. burnetii RNA synthesis blocked NMII infection-induced PARP activation. These results suggest that both intracellular C. burnetii replication and secreted TNF-α contribute to NMII infection-triggered apoptosis during an early stage of infection.     

Induction of apoptosis in human leukemia K562 cells by cyclic lipopeptide from Bacillus subtilis natto T-2

A new cyclic lipopeptide (CLP) purified from Bacillus subtilis natto T-2 dose dependently inhibited growth in human leukemia K562 cells. The results of fluorescent staining indicated that CLP brought about apoptosis in K562 cells. Flow cytometric analysis also demonstrated that CLP caused dose-dependent apoptosis of K562 cells through cell arrest at G1 phase. Western blotting revealed that CLP-induced apoptosis in K562 cells was associated with caspase-3 and poly(ADP-ribose)polymerase (PARP) protein. It is estimated that CLP inhibited proliferation in K562 cells by inducing apoptosis.     

In vivo and in vitro activation of caspase-8 and -3 associated with Helicobacter pylori infection

In vivo and in vitro studies have shown an increase in apoptosis in gastric epithelial cells in persons infected with Helicobacter pylori. H. pylori-induced activation of caspase-8 and -3 was evaluated using a human gastric adenocarcinoma cell line (AGS) and gastric tissue from humans and monkeys colonized with H. pylori. The enzymatic activity of caspase-8 was detected only in AGS cells exposed to H. pylori up to 24 h. The active form of caspase-8 was present by Western blot after exposure to H. pylori for 3 h and persisted through 24 h. Caspase-3 activity was present in AGS cells exposed to H. pylori for 3 h, reaching a maximum after 24 h (a sevenfold increase in activity). Caspase-8-mediated cleavage of procaspase-3 generated a 20-kDa band (indicative of the presence of active caspase-3) present only in AGS cells exposed to H. pylori. Active caspase-3 staining was markedly increased in gastric mucosa from infected persons and animals, compared to uninfected controls by immunohistochemistry. Stimulation of downstream events leading to apoptosis, such as the cleavage of PARP (poly adenosine-diphosphate-ribose polymerase) and DFF45 (DNA fragmentation factor 45) as a result of activation of caspase-3, was evaluated. PARP was cleaved, resulting in the presence of both an 89- and a 24-kDa band along with DFF45, resulting in the presence of 10- and 12-kDa bands only in gastric cells exposed to H. pylori. Our data show that H. pylori stimulates the activation of caspases and downstream mediators of caspase-induced apoptosis. This suggests that H. pylori-induced apoptosis is mediated through caspase pathways, which include the activation of caspase-8 and subsequent cleavage and activation of caspase-3. This is consistent with caspase-3 activation that was found in the gastric mucosa of humans and monkeys infected with H. pylori.     

Activation of PKC but not of ERK is required for vitamin E-succinate-induced apoptosis of HL-60 cells.

Vitamin E-succinate (VES) induced HL-60 human leukemia cells to undergo apoptosis. Treatment with VES induced membrane translocation of Fas; cleavages of caspase-3, PARP, and lamin B; hypophosphorylation of retinoblastoma protein; and increase of p21(WAF1) protein level. During the induction of apoptosis, activity of PKC was gradually increased with downregulation of VES-induced ERK activity and accompanied by activation of caspase-3. Inhibition of PKC by GF109203X blocked VES-mediated membrane translocation of PKC-alpha and cleavage of caspase-3 cascade, resulting in prevention of VES-induced apoptosis. On the contrary, PKC activation by cotreatment with LPC or thapsigargin and VES synergistically increased VES-mediated apoptosis. However, inhibition of ERK activity by PD98059 showed no significant effect on VES-induced PKC activity and apoptosis. Taken together, our data suggest that VES induces activation of PKC and PKC-dependent hypophosphorylation of retinoblastoma protein, which results in induction of apoptosis, and that VES-induced early activation of ERK and ERK-dependent induction of p21(WAF1) are not required for apoptosis.     

Involvement of caspase-3 activation in squamocin-induced apoptosis in leukemia cell line HL-60

Annonaceous acetogenins have potent antitumor effect in vitro and in vivo. Squamocin is one of the annonaceous acetogenins and has been reported to have antiproliferative effect on cancer cells. Our results from this study showed that squamocin inhibited proliferation of HL-60 cells with IC50 value of 0.17 microg/ml and induced apoptosis of HL-60 cells. Investigation of the mechanism of squamocin-induced apoptosis revealed that treatment of HL-60 cells with squamocin resulted in extensive nuclear condensation. DNA fragmentation, cleavage of the death substrate poly (ADP-ribose) polymerase (PARP) and induction of caspase-3 activity. Pretreatment of HL-60 cells with caspase-3 specific inhibitor DEVD-CHO prevented squamocin-induced DNA fragmentation, PARP cleavage and cell death. The expression levels of protein bcl-2, bax have no change in response to squamocin treatment in HL-60 cells, whereas stress-activated protein kinase (SAPK/JNK) was activated after treatment with squamocin in HL-60 cells. These results suggest that apoptosis of HL-60 cells induced by squamocin requires caspase-3 activation and is related to SAPK activation.