8种天然药物与硼替佐米对HBsAg抑制作用及蛋白质组学分析

目的:比较硼替佐米和几种天然药物体外对HBV的抑制作用,并探索硼替佐米抑制HBV的分子机制。方法:采用MTT法观察不同浓度药物对HBV-Tg小鼠原代肝细胞的毒性,确定最大无毒浓度,用ELISA方法检测培养24h后细胞上清中HBsAg的变化,比较不同药物对HBsAg的抑制率。经1μmol/L硼替佐米处理原代肝细胞24h后,提取蛋白质,采用双向凝胶电泳分离总蛋白,得到差异表达的蛋白质点进行分析比对。以RT-PCR及West blot验证选定的差异蛋白,分析其与HBV抑制作用的关系。结果:在8种天然药物中以扁蒴藤素对HBV作用最强,IC50为0.43μmol/L,EGCG的IC50是24.9μmol/L,且安全性较好。硼替佐米作用原代肝细胞蛋白质组分析发现了21个差异斑点,其中包括HSP60异构体(gi/26353954)。RT-PCR检测发现经硼替佐米作用后HSP60、HSP90表达下调,HSP70表达上调,而West blot鉴定HSP60变化不大。但是经EGCG作用后HSP90表达的下调与对HBsAg的抑制是一致的。结论:调节宿主细胞的蛋白质降解与折叠将有利于寻找新型抗HBV药物。     

乌司他丁对大鼠脑缺血再灌注损伤后的保护作用及其机制研究

目的:探究乌司他丁在脑缺血再灌注损伤中的脑保护作用机制。方法:原代分离培养雄性SD大鼠脑皮质细胞,部分细胞经siRNA沉默HSP70基因。细胞先以无糖培养基在低氧条件下培养,12 h后复糖复氧模拟体外缺血再灌注损伤,并实施乌司他丁预处理干预,流式细胞术检测各组细胞的凋亡率,western-blotting检测Bcl-2,Bax,HSP70,JNK和p-JNK蛋白的表达。结果:与对照组比较,模型组脑组织细胞凋亡率明显增多(P0.05)、Bcl-2和Bax的表达量均有上调,Bcl-2/Bax的比值显著降低(P0.01)、HSP70的表达无显著变化;与模型组比较,乌司他丁处理组脑组织细胞凋亡率明显降低(P0.05)、Bax的表达量显著下调(P0.05),Bcl-2/Bax的比值显著上调(P0.05),HSP70的表达显著上调(P0.05),JNK的表达无显著变化、p-JNK则显著下调(P0.05)。HSP70沉默后乌司他丁的脑保护作用消失,对以上蛋白的表达无显著影响。结论:乌司他丁可能是通过上调HSP70表达进而抑制JNK信号转导通路对缺血再灌注引起的脑损伤起保护作用。     

紫草素逆转埃克替尼对肺癌EGFR-TKI 耐药及其机制的研究

目的:观察紫草素联合埃克替尼对肺腺癌耐药细胞H1975增殖的影响,探讨克服耐药可能的作用机制。方法:应用MTT法检测紫草素(1.25~20μmo/L)、埃克替尼(5~100μmol/L)及两药联合干预对H1975细胞生长的抑制作用;流式细胞术观察紫草素(1.25μmol/L)、埃克替尼(10μmol/L)及联合使用对H1975凋亡作用;Western blot检测不同干预对H1975细胞EGFR、p-EGFR、AKT、p-AKT、ERK、p-ERK和凋亡相关蛋白PARP表达水平的影响。结果:MTT检测结果显示,与单药组相比,联合用药组细胞H1975增殖能力明显减弱,差异有统计学意义(P0.05);流式细胞术结果显示,联合用药组细胞的凋亡率达到(52.45±3.04)%,较紫草素组细胞凋亡率(22±1.17)%和埃克替尼处理组细胞凋亡率(15.35±5.85)%明显提高,差异有统计学意义(P0.05)。Western blot结果显示,单药组下调了p-EGFR、p-Akt蛋白水平的表达,而联合用药组显著抑制了p-ERK、PARP蛋白水平的表达,差异有统计学意义(P0.05),EGFR、AKT、ERK蛋白表达无差异(P0.05)。结论:紫草素联合埃克替尼能明显抑制H1975细胞增殖,促进肿瘤细胞凋亡;抗肿瘤机制可能与调节EGFR信号通路相关蛋白表达有关。     

EB病毒潜伏膜蛋白1调控细胞凋亡的cDNA阵列分析

为探讨EB病毒潜伏膜蛋白（LMP1）介导细胞凋亡和抑制细胞凋亡双重效应的机制,采用已建立的受四环素调控的LMP1表达的鼻咽癌系统（pTet-on-LMP1 HNE2),定量诱导pTet-on-LMP1 HNE2细胞LMP1动态表达,分别与含有细胞凋亡相关基因为主的Atlas apoptosis cDNA expression array膜杂交,分析LMP1介导 的表达差异基因。结果表明：①LMP1介导细胞凋亡和抑制细胞凋亡的基因的表达,同时上调或下调某些细胞凋亡相关基因的表达;②LMP1不仅介导细胞凋亡和抑制凋亡基因的表达,同时介导细胞分裂分化和增殖基因的表达,LMP1同时介导功能不同甚至功能相反的基因表达;③LMP1介导的基因表达与其表达持续时间和表达水平相关,不同表达水平和不同表达时间介导的基因表达谱不同。因此,LMP1具有介导细胞凋亡和抑制凋亡基因表达的双重生物学效应,同时介导细胞增殖、细胞周期、细胞凋亡等多种生物学效应基因的表达,从而参与细胞的癌变。     

维生素C诱导人宫颈癌Caski细胞凋亡及其分子机制的研究

为了研究维生素C对人宫颈癌Caski细胞体外抑制、诱导凋亡的作用及其分子机制,使用不同剂量维生素C处理人宫颈癌Caski细胞,采用噻唑蓝(MTT)法检测药物对细胞增殖的抑制作用;流式细胞仪检测Cas-ki细胞周期变化;琼脂糖电泳法观察凋亡细胞DNA Ladder现象;Western blot检测凋亡相关蛋白Bcl-2、Bax和E6的表达以及Caspase 3的激活;荧光染色观察细胞线粒体膜电位的改变.分析发现,维生素C可显著抑制人宫颈癌Caski细胞增殖,呈现明显的时间和剂量依赖性;将细胞阻滞于S期;诱导细胞凋亡,下调Bcl-2和E6、上调Bax蛋白表达,促进Caspase3活化,降低线粒体膜电位.表明维生素C在体外可有效抑制人宫颈癌Caski细胞增殖,诱导细胞凋亡.     

蛇床子素促进人骨肉瘤细胞株SAOS-2凋亡

目的:观察蛇床子素(osthole)对人骨肉瘤细胞SAOS-2增殖和凋亡的影响及潜在的调控机制。方法:采用MTT法、TUNEL染色技术和流式细胞术检测不同浓度蛇床子素对骨肉瘤细胞凋亡的影响;Western blot检测蛇床子素对骨肉瘤细胞中与细胞凋亡密切相关的蛋白(Bax、Bcl-2)的变化。结果:蛇床子素作用于SAOS-2细胞后,MTT结果显示SAOS-2细胞的活力受到明显抑制,且与蛇床子素浓度和时间相关;Western blot结果显示细胞中的促凋亡蛋白Bax表达上调,抗凋亡蛋白Bcl-2表达明显减弱,且呈剂量依赖性。结论:蛇床子素可显著抑制人骨肉瘤细胞的增殖且促进其凋亡的作用,可能与上调凋亡蛋白Bax和下调抗凋亡蛋白Bcl-2的表达有关。     

重楼活性单体pp-10通过抑制PI3K/Akt通路诱导人胃癌细胞BGC-823凋亡和自噬

目的:探讨重楼/七叶一枝花(Paris polyphylla)的醇提物单体pp-10诱导人胃癌BGC-823细胞凋亡和自噬及其分子机制。方法:采用MTT法和克隆形成抑制实验观察不同浓度的重楼单体pp-10对人胃癌BGC-823细胞的增殖抑制作用;Hoechst33342染色法检测pp-10作用于人胃癌BGC-823细胞后细胞核形态的改变;Annexin V-FITC/PI双染法检测细胞凋亡;Western blotting检测重楼单体pp-10对细胞凋亡和自噬相关蛋白Caspase-3、Caspase-9、(ADP-核糖)聚合酶(PARP)、Bax、Bcl-2、LC3、P62以及PI3K/Akt信号通路相关蛋白(Akt、p-Akt、m TOR、p-m TOR、P70s6k、p-P70s6k)表达的影响。结果:重楼单体pp-10能显著抑制BGC-823细胞的生长,作用呈时间-效应关系及剂量-效应关系;克隆形成抑制实验表明随着pp-10浓度的增加,细胞克隆形成逐渐减少,与对照组相比有显著差异;在荧光显微镜下观察可见其细胞核固缩、边聚、裂解等细胞凋亡形态学变化;流式细胞术检测显示,随着作用药物浓度的增高,其凋亡率逐渐升高;Western blotting结果表明,随着药物浓度的增加,线粒体相关凋亡信号通路蛋白Caspase9、Caspase3及PARP均出现酶切活化条带,细胞促凋亡蛋白Bax的表达水平增加,抗凋亡蛋白Bcl-2减少,自噬相关蛋白Ⅱ型LC3增加,P62蛋白减少,p-Akt蛋白的表达水平下降,Akt下游蛋白p-m Tor、p-p70S6K表达减少。结论:重楼单体pp-10通过抑制BGC-823细胞增殖,诱导细胞凋亡和自噬,与下调P13K/Akt信号通路有关。     

澳洲茄碱诱导胆管癌QBC939细胞凋亡及作用机制

研究澳洲茄碱对人胆管癌上皮细胞系QBC939凋亡的诱导与作用机制。采用MTT法检测不同浓度澳洲茄碱对QBC939细胞的增殖抑制作用;流式细胞术检测澳洲茄碱对QBC939细胞的凋亡诱导情况;Western blot检测澳洲茄碱对QBC939细胞中凋亡相关蛋白(Bax、Bcl-2、caspase3、caspase7、PARP、cleaved PARP)的表达影响。结果发现澳洲茄碱以浓度依赖方式能够抑制QBC939细胞的增殖;澳洲茄碱能够显著诱导QBC939细胞的凋亡;澳洲茄碱可以上调Bax、caspase3、caspase7和cleaved PARP蛋白表达,下调Bcl-2和PARP蛋白表达。表明澳洲茄碱能够通过改变凋亡相关蛋白表达,诱导胆管癌QBC939细胞的凋亡,这对于研发和治疗胆管癌相关药物具有一定的潜在价值。     

HSP70在放线菌素D所致肺腺癌细胞增殖抑制和凋亡中的作用

为探讨热休克蛋白70(heatshockprotein70,HSP70)在肺腺癌中的表达及其作用,首先采用免疫印迹检测经临床支纤镜确诊并行手术切除的肺腺癌组织标本中HSP70的表达,结果显示在癌旁正常组织中HSP70的表达量显著低于其在癌组织中的表达量.其次,采用HSP70反义寡核苷酸阻断A549细胞中HSP70表达后,经MTT和Hoechst33258检测发现,HSP70下调能显著促进放线菌素D(actinomycinD,ActD)所致的A549细胞增殖抑制及凋亡,反义寡核苷酸处理组与正义或随机寡核苷酸处理组比较P值均小于0.05.进一步构建HSP70真核重组质粒并瞬时转染A549细胞后,能显著增加A549细胞中HSP70表达,同时采用MTT和流式细胞术及基因组DNA琼脂糖凝胶电泳检测发现,HSP70过表达能显著抵消ActD所致细胞增殖抑制及凋亡,转染HSP70重组质粒组与转染空载体组相比P值小于0.05.上述结果提示,HSP70在肺腺癌组织中高表达,高表达的HSP70在降低肺腺癌细胞对ActD的敏感性及促进癌细胞增殖与抑制凋亡等方面发挥了重要作用.     

丹皮酚对肝癌MHCC97-H细胞PTEN、AKT表达的影响

目的:探讨丹皮酚(Paeonol,Pae)在体外对人肝癌MHCC97-H细胞PTEN、AKT表达的影响。方法:体外培养人肝癌MHCC97-H细胞,MTT法检测丹皮酚对MHCC97-H细胞的增殖抑制作用,RT-PCR法检测PTEN、Akt1、Akt2mRNA表达,West- ern Blot法检测PTEN、p-AKT蛋白的表达。结果:丹皮酚呈时间剂量依赖性抑制人肝癌MHCC97-H细胞的增殖;肝癌MHCC97-H细胞低表达PTEN,高表达AKT,丹皮酚能显著上调MHCC97-H细胞PTEN表达,下调AKT表达。结论:丹皮酚可上调抑癌基因PTEN的表达,下调致癌基因AKT的表达,抑制MHCC97-H细胞的增殖。     

氟苯达唑对人急性髓系白血病HL-60细胞的增殖抑制作用研究

目的:研究氟苯达唑对人急性髓系白血病HL-60细胞增殖的抑制作用,明确氟苯达唑对HL-60细胞周期,凋亡发生的作用机制。方法:噻唑蓝法(MTT)检测氟苯达唑对人急性髓系白血病HL-60细胞的生长抑制作用,流式细胞术检测氟苯达唑对HL-60细胞周期,DNA片段化的影响,免疫印迹法检测Caspase, Raf, Bcl-2家族蛋白表达。结果:氟苯达唑抑制人急性髓系白血病HL-60细胞生长,HL-60细胞G2/M期增加,与阴性对照组相比,在一定的剂量和时间内,差别具有显著统计学意义;DNA片段化上升,0.25,0.5,1μM组与对照组相比差别具有显著统计学意义,促使Cleaved PARP,Cleaved-caspase 3,Cleaved-caspase 9蛋白表达量趋势增加;Bag-1和Bcl-2蛋白表达量降低;b-raf,c-raf磷酸化蛋白表达水平逐渐降低。结论:氟苯达唑通过诱导HL-60细胞阻滞于G2/M期,增加DNA片段化水平,激活Caspase, Raf, Bcl-2家族介导的凋亡相关通路抑制人急性髓系白血病HL-60细胞增殖,诱导人急性髓系白血病HL-60细胞发生凋亡而发挥抗肿瘤作用。     

Induction of cell-cycle arrest and apoptosis in human cholangiocarcinoma cells by pristimerin

Pristimerin, a triterpenoid isolated from Celastraceae and Hippocrateaceae, is known to induce cytotoxicity in several cancer cell lines. However, whether pristimerin can induce apoptosis in cholangiocarcinoma cells and the underlying mechanism remain unexplored. We assessed the function of human cholangiocarcinoma QBC and RBE cell lines using various experimental methods such as the cell viability assay to elucidate the viability of cells, flow cytometry to detect the death rate of cells, and Western blot analysis to evaluate the expression of cell cycle-related proteins and autophagy-related proteins. Human cholangiocarcinoma QBC cells were transplanted to nude mice to establish an animal model, and the effect of pristimerin on tumor growth in this model was observed. QBC and RBE cell lines treated with pristimerin (0, 5, 10, and 20 μmol/L) demonstrated the induction of apoptosis in a dose-dependent manner. The cell viability assay revealed a reduction in the cell viability with an increase in the pristimerin concentration. Similarly, flow cytometry revealed a gradual increase in the cell death rate with an increase in the pristimerin concentration. In addition, pristimerin significantly lowered the expression of apoptosis-related proteins (Bcl-2, Bcl-xL, and procaspase-3), but increased the Bax expression. Furthermore, pristimerin resulted in the G0/G1 cell-cycle arrest, reducing the expression of cell cycle-related proteins (cyclin E, CDK2, and CDK4), and increased the expression of autophagy-related proteins (LC3) in QBC cell line. Treatment with pristimerin could inhibit tumor growth in the nude mouse model. Overall, this study suggests the potential effect of pristimerin on the cell-cycle arrest and apoptosis in human cholangiocarcinoma cells.     

Pristimerin-induced uveal melanoma cell death via inhibiting PI3K/Akt/FoxO3a signalling pathway

Uveal melanoma (UM) is a highly invasive intraocular malignancy with high mortality. Presently, there is no FDA-approved standard for the treatment of metastatic UM. Pristimerin is a natural quinine methide triterpenoid compound with anti-angiogenic, anti-cancer and anti-inflammatory activities. However, Pristimerin potential cytotoxic effect on UM was poorly investigated. In the present study, we found the migration and invasion of UM-1 cells were inhibited by Pristimerin which also caused a rapid increase of ROS, decreased mitochondrial membrane potential, induced the accumulation of cells in G0/G1 phase, ending with apoptotic cell death. Pristimerin inhibited Akt and FoxO3a phosphorylation and induced nuclear accumulation of FoxO3a in UM-1 cells, increased the expression of pro-apoptotic proteins Bim、p27^Kip1, cleaved caspase-3, PARP and Bax, and decreased the expression of Cyclin D1 and Bcl-2. LY294002 or Akt-siRNA inhibited the PI3K/Akt/FoxO3a pathway and promoted the Pristimerin-induced apoptosis, while Pristimerin effects were partially abolished in FoxO3a knockdown UM-1 cell cultures. Taken together, present results showed that Pristimerin induced apoptotic cell death through inhibition of PI3K/Akt/FoxO3a pathway in UM-1 cells. These findings indicate that Pristimerin may be considered as a potential chemotherapeutic agent for patients with UM.     

Inactivation of Bcl-2 through IκB kinase (IKK)-dependent phosphorylation mediates apoptosis upon exposure to 4-hydroxynonenal (HNE)

Apoptosis of macrophage foam cells loaded with modified/oxidized lipids is implicated in destabilization of advanced atherosclerotic plaques in humans. Concentration of HNE, main aldehydic product of plasma LDL peroxidation, elevates in atherosclerotic lesions as well as in cultured cells under oxidative stress. Although this reactive aldehyde has been shown to promote apoptosis with the involvement of p38 MAPK and JNK in various mammalian cell lines, roles of B-cell lymphoma 2 (Bcl-2) family proteins remain to be deciphered. We demonstrated that HNE-induced apoptosis was accompanied by concurrent downregulations of antiapoptotic Bcl-x(L) and Mcl-1 as well as upregulation of proapoptotic Bak. Furthermore, phoshorylation of Bcl-2 at Thr56, Ser70, and probably more phosphorylation sites located on N-terminal loop domain associated with HNE-induced apoptosis in both U937 and HeLa cells while ectopic expression of a phospho-defective Bcl-2 mutant significantly attenuated apoptosis. In parallel to this, HNE treatment caused release of proapoptotic Bax from Bcl-2. Pharmacological inhbition of IKK inhibited HNE-induced Bcl-2 phosphorylation. Similarly, silencing IKKα and -β both ended up with abrogation of Bcl-2 phosphorylation along with attenuation of apoptosis. Moreover, both IKKα and -β coimmunoprecipitated with Bcl-2 and in vitro kinase assay proved the ability of IKK to phosphorylate Bcl-2. In view of these findings and considering HNE inhibits DNA-binding activity of nuclear factor-κB (NF-κB) through prevention of IκB phosphorylation/ubiquitination/proteolysis, IKK appears to directly interfere with Bcl-2 activity through phosphorylation in HNE-mediated apoptosis independent of NF-κB signaling.     

Effect of pristimerin on apoptosis through activation of ROS/ endoplasmic reticulum (ER) stress-mediated noxa in colorectal cancer

BackgroundPristimerin, a natural quinonemethid triterpenoid found in different spp. of Celastraceae and Hippocrateaceae families, has been reported to exhibit potent antitumor activities against colorectal cancer (CRC). However, the mechanisms underlying pristimerin-induced apoptosis in CRC is not clear.PurposeThis study aimed to investigate the mechanisms of pristimerin-induced apoptosis against CRC in vitro and in vivo.MethodsCell viability and cell apoptosis analyses were conducted to assess the effects of pristimerin on CRC. Western blotting was performed to detect the expression of proteins affected by pristimerin in vitro and in vivo. HCT116 colon cancer xenografts and APC^min/+ mouse models were used to evaluate the anti-CRC effect of pristimerin in vivo.ResultsOur data showed that pristimerin induced apoptosis by regulating proapoptotic proteins of which Noxa showed higher expression. Pristimerin triggered reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress signaling activation. Pristimerin significantly elevated the expression of ER stress-related proteins, resulting in activation of the IRE1α and c-Jun N-terminal kinase (JNK) signal pathway through the formation of the IRE1α-TRAF2-ASK1 complex. Pristimerin exhibited apoptosis-inducing activities in HCT116 colon cancer xenografts and APC^min/+ mice.ConclusionBoth in vitro and in vivo data demonstrated that pristimerin induced Noxa expression and apoptosis through activation of the ROS/ER stress/JNK axis in CRC. Thus, pristimerin may be a promising antitumor agent for CRC.     

Molecular Mechanisms of Apoptosis in HL-60 Cells Induced by a Nitric Oxide-Releasing Compound

Nitric oxide (NO) generated from 1-hydroxy-2-0×0-3, 3-bis(2-aminoethyl)-l-triazene (NOC 18), an NO-releasing compound, induced monocytic differentiation of human promyelocytic leukemia HL-60 cells as assessed by expression of nonspecific esterases and morphologic maturation. Simultaneously, DNA fragmentation and morphological alterations typical of apoptosis were also induced. To investigate the mechanisms of apoptosis during differentiation of HL-60 cells induced by NO, the endogenous levels of Bcl-2 and Bax were assessed by immunoblotting. Treatment of cells with NOC 18 slightly reduced the level of Bcl-2 followed by Bax. These changes might be involved in the induction of apoptosis. The involvement of the activation of the interleukin-lβ converting enzyme (ICE) family of proteases (caspases), such as ICE and CPP32, in the pathways was also investigated. CPP32, but not ICE, was strongly activated in response to NOC 18 stimulation, thereby implicating CPP32-like activity in the induction of apoptosis. Moreover, the possible involvement of tyrosine phosphorylation in apoptosis was investigated. Pretreatment of cells with herbimycin A, an inhibitor of tyrosine kinases, suppressed DNA fragmentation and CPP32-like activity, whereas pretreatment with vanadate, an inhibitor of tyrosine phosphatases, enhanced both parameters, suggesting that tyrosine phosphorylation might be involved in the pathways of apoptosis in HL-60 cells induced by NO.     

Acquisition of chemoresistance in intrahepatic cholangiocarcinoma cells by activation of AKT and extracellular signal-regulated kinase (ERK)1/2

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignant tumor and is refractory to conventional chemotherapy. The aim of this study is therefore to elucidate the mechanism of chemoresistance in ICC which is not fully understood. We generated cisplatin resistant ICC cells via long term exposure to cisplatin and found that these cells are also resistant to 5-fluorouracil (5-FU) and gemcitabine. The chemoresistant cells showed enhanced Bcl-2 expression and reduced Bax expression compared to parental ICC cells. In addition, the resistant cells showed enhanced activation of AKT and extracellular signal-regulated kinase (ERK) 1/2. Inhibition of AKT activation by phosphoinocitide 3-kinase (PI3K) inhibitor LY294002 resulted in reduced Bcl-2 expression and enhanced Bax expression and thus induced apoptosis in the resistant cells, whereas inhibition of ERK1/2 activation by mitogen-activated protein kinase (MEK) inhibitor U0126 did not induce apoptosis without affecting the expression of Bcl-2 and Bax but decreased cell growth. Moreover, the inhibition of AKT or ERK1/2 sensitized the resistant cells to cisplatin and therefore resulted in greatly enhanced cisplatin-induced apoptosis and growth inhibition in the cells. The results indicate that AKT and ERK1/2 signaling mediate chemoresistance in the cells and could be important therapeutic targets for overcoming chemoresistance in ICC.     

Pristimerin induces apoptosis by targeting the proteasome in prostate cancer cells

Pristimerin is a natural product derived from the Celastraceae and Hippocrateaceae families that were used as folk medicines for anti inflammation in ancient times. Although it has been shown that pristimerin induces apoptosis in breast cancer cells, the involved mechanism of action is unknown. The purpose of the current study is to investigate the primary target of pristimerin in human cancer cells, using prostate cancer cells as a working model. Nucleophilic susceptibility and in silico docking studies show that C6 of pristimerin is highly susceptible towards a nucleophilic attack by the hydroxyl group of N-terminal threonine of the proteasomal chymotrypsin subunit. Consistently, pristimerin potently inhibits the chymotrypsin-like activity of a purified rabbit 20S proteasome (IC50 2.2 micromol/L) and human prostate cancer 26S proteasome (IC50 3.0 micromol/L). The accumulation of ubiquitinated proteins and three proteasome target proteins, Bax, p27 and I kappa B-alpha, in androgen receptor (AR)-negative PC-3 prostate cancer cells supports the conclusion that proteasome inhibition by pristimerin is physiologically functional. This observed proteasome inhibition subsequently led to the induction of apoptotic cell death in a dose- and kinetic-dependent manner. Furthermore, in AR-positive, androgen-dependent LNCaP and AR-positive, androgen-independent C4-2B prostate cancer cells, proteasome inhibition by pristimerin results in suppression of AR protein prior to apoptosis. Our data demonstrate, for the first time, that the proteasome is a primary target of pristimerin in prostate cancer cells and inhibition of the proteasomal chymotrypsin-like activity by pristimerin is responsible for its cancer cell death-inducing property.     

Increased stability of Bcl-2 in HSP70-mediated protection against apoptosis induced by oxidative stress

We have previously shown that heat shock protein 70 (HSP70) markedly inhibits H₂O₂-induced apoptosis in mouse C2C12 myogenic cells by reducing the release of Smac. However, the molecular mechanism by which HSP70 interferes with Smac release during oxidative stress-induced apoptosis is not understood. In the current study, we showed that HSP70 increased the stability of Bcl-2 during oxidative stress. An antisense phosphorothioate oligonucleotide against Bcl-2 caused selective inhibition of Bcl-2 protein expression induced by HSP70 and significantly attenuated HSP70-mediated cell protection against H₂O₂-induced release of Smac and apoptosis. Taken together, our results indicate that there are important relationships among HSP70, Bcl-2, release of Smac, and induction of apoptosis by oxidative stress.