CDK1 siRNA干扰在Taxol诱导细胞凋亡中的作用

目的研究转染细胞周期依赖性蛋白激酶1（cyclin．dependent kinase1,CDK1）siRNA、以及转染后进行凋亡刺激对细胞周期和凋亡的影响,探讨CDK1在细胞凋亡中的确切作用,揭示细胞周期与细胞凋亡协调的分子机制。方法以人宫颈癌细胞株HeLa细胞为研究对象,脂质体转染CDK1siRNA,转染后48h加紫杉醇（Tax01）（20μg／m1）刺激凋亡,Western印迹检测CDK1和抗凋亡蛋白BCL2表达,AnnexinV／PI法检测细胞的凋亡,流式细胞仪分析DNA含量检测细胞周期。结果转染CDK1 siRNA后,CDK1蛋白的表达下降,细胞周期G2／M期比例增加,细胞凋亡率与对照相比没有明显升高。只加Taxol刺激12h后细胞凋亡率增加并伴有S期和G2／M期比例增加。转染CDKlsiRNA后再用Taxol刺激,其细胞凋亡率没有明显改变,G2／M期阻滞效应也没有叠加。BCL2蛋白只在加Taxol刺激组表达下降,与CDK1表达减少没有相关性。结论siRNA沉默导致的CDK1表达降低只导致细胞周期G2／M期阻滞,没有引起细胞凋亡;CDK1的表达降低对紫杉醇所诱导的细胞周期阻滞和细胞凋亡效应没有明显影响。     

AS-mCLB1重组质粒体外抗肿瘤及化疗增敏作用

研究反义全长小鼠细胞周期蛋白B1重组质粒(pAS-mCLB1)体外抗肿瘤及化疗增敏作用。扩增后少量抽提并纯化pAS-mCLB1,通过脂质体将其转染入小鼠露易丝肺癌(LL/2)细胞,RT-PCR和Western印迹测定细胞内细胞周期蛋白B1的表达,观察转染后细胞形态变化,MTT法检测细胞增殖活性,流式细胞仪检测细胞周期及凋亡。细胞转染48h后,用化疗药物健择(gemcitabine;0.2μmol/L)处理24h,MTT法测定健择对细胞的杀伤作用。研究提示pAS-mCLB1转染后LL/2细胞形态明显异常,细胞内细胞周期蛋白B1表达显著下调,细胞周期阻滞于G1期,增殖受抑,凋亡增加;健择对pAS-mCLB1转染后LL/2细胞的杀伤作用显著增强。重组质粒pAS-mCLB1体外具有明显的抗肿瘤作用,并能增强肿瘤细胞对化疗药物的敏感性,估计上述作用与其下调肿瘤细胞内细胞周期蛋白B1表达,从而诱导细胞周期阻滞及凋亡等作用相关。     

抑制VEGF基因表达对乳腺癌细胞细胞周期的影响

目的：研究针对VEGF基因的siRNA（small interferenceRNA）对乳腺癌MCF-7细胞细胞周期的影响。方法：依据Promega公司在网上提供的设计软件,设计针对VEGF基因的siRNA,合成DNA模板,体外转录合成siRNA。脂质体转染法将合成的siRNA转染入MCF-7细胞,以未转染细胞以及错义序列siRNAscr转染细胞为对照。用细胞计数法检测siRNA对MCF-7细胞增殖的影响：流式细胞法检测细胞周期变化,RT—PCR法比较转染前后p21、CyclinDl表达水平的变化,Westemblot检测转染前后磷酸化ERK的表达。结果：细胞计数法结果显示,转染24h后siRNA明显抑制MCF-7细胞增殖,转染48h后,抑制效率稳定。siRNA转染后能有效地抑制MCF-7细胞的增殖,阻滞细胞周期于G0／G1期,S期细胞明显减少,G0／G1期细胞比例逐渐增多;p21mRNA表达显著上调,抑制CyclinD1mRNA及磷酸化ERK蛋白的表达。结论：体外转录合成的siRNA可能通过上调细胞周期蚤白激酶抑制剂p21的表达,下调CyclinDl及磷酸化ERK的表达,将细胞周期阻滞于G0／G1期,从而显著抑制MCF-7细胞的增殖。     

瘦素对血管平滑肌细胞周期蛋白D1、CDK2表达的影响

目的观察瘦素对人平滑肌细胞周期时相及cyclin D1、CDK2表达的影响,探讨瘦素促进平滑肌细胞增殖的作用机制。方法取对数生长期的平滑肌细胞同步于G0期,分为加入浓度为0、20、40、80、100、200ng/ml瘦素的各组。作用24h后分别用MTT法检测细胞活性,用流式仪进行细胞周期时相的检测,Western blot法测定Cyclin D1、CDK2的表达。结果随着瘦素浓度的增加G0/G1期的平滑肌细胞逐渐减少,S期和G2/M期细胞逐渐增加,PI增殖指数逐渐增加。cyclin D1、CDK2蛋白的表达呈剂量依赖性的上升趋势。以上两项检测均在100ng/ml处达最高。结论瘦素上调cyclinD1、CDK2蛋白的表达,可能是促进平滑肌细胞增殖的机制之一。     

CDK4基因沉默对非小细胞肺癌A549 增殖和代谢的影响

目的:通过特异性小干扰RNA(small interfering RNA,si RNA),使CDK4基因沉默,探讨该基因沉默对肺癌A549细胞增殖和代谢的影响及其可能的作用机制。方法:将靶向CDK4小干扰RNA(si RNA-CDK4)和阴性对照干扰片段(si RNA-control)成功转染A549细胞后,利用实时荧光定量PCR和蛋白质免疫印迹法分别检测CDK4在m RNA和蛋白水平的变化;细胞计数法、CCK-8法和软琼脂糖克隆形成实验检测A549增殖的变化和克隆形成能力;FCM法检测A549细胞的细胞周期;18F-FDG摄取实验、乳酸检测试剂盒及海马技术检测A549细胞中葡萄糖、乳酸的量及氧耗的变化;利用RT-PCR检测CDK4基因沉默后A549细胞中糖代谢相关酶m RNA水平的变化。结果:将靶向CDK4小干扰RNA(si RNA-CDK4)转染A549细胞后,可明显抑制CDK4的m RNA和蛋白表达(P0.001,P0.01)。CDK4蛋白抑制后,细胞增殖在48、72和96 h均明显降低(P值均0.05),G1期细胞比例明显增多,S期细胞比例明显减少(P值均0.05);18F-FDG摄取量下降(42.21±1.90)%(P0.05),乳酸的生成量减少(29.39±5.35)%(P0.05),而细胞的基础耗氧量增加(67.17±3.58)%(P0.01);糖酵解相关酶PFKFB3、PKM2、LDHA在m RNA水平均明显减低(P0.001,P0.01,P0.001)。结论:抑制CDK4表达可明显降低糖酵解水平,并增加耗氧量;同时可引起细胞周期阻滞,抑制肿瘤细胞增殖。其机制可能与CDK4直接或间接调节糖酵解相关酶的表达有关。     

mcl-1特异性siRNA对HepG2细胞增殖及凋亡的影响

目的：肝癌分子靶向治疗是目前研究的热点,肝癌相关基因mcl-1在肝癌增殖及凋亡中的作用尚不明确,本研究拟探讨mcl-1特异性siRNA对体外培养肝癌细胞HepG2增殖及凋亡的影响。方法：设计、合成有效的mcl-1特异性siRNA序列,体外转染HepG2细胞;通过绘制细胞生长曲线和MTT实验检测mcl-1特异性siRNA对HepG2细胞增殖的影响;通过AnnexinV／PI双标记流式细胞仪检测mcl-1特异性siRNA对HepG2细胞凋亡率的影响。结果：通过绘制细胞生长曲线发现,mcl-1特异性siRNA能够抑制HepG2细胞的增殖（P〈0．05）,MTT实验提示转染mcl-1特异性siRNA24h、48h、72h后,HepG2细胞存活率均显著下降（P〈O．05）;流式细胞仪检测分析发现,转染mcl．1特异性siRNA后AnnexinV＋／PI-细胞百分率显著增高（P〈0．01）,提示mcl-1具有促进HepG2细胞凋亡的作用。结论：Mcl-1蛋白具有促进肝癌细胞增殖,抑制肝癌细胞凋亡的作用,这种分子特性符合肿瘤靶向治疗的要求,Mcl-1可能成为肝癌靶向治疗的潜在靶点。     

IGFBP-3在真核细胞中的分泌表达及功能分析

将人胰岛素样生长因子结合蛋白3(IGFBP-3)的cDNA片段亚克隆入pSectagA载体, 构建真核分泌型表达载体pSectag-IGFBP3。采用脂质体转染的方法将真核表达载体转染人肾癌786-O细胞, 转染48 h后用免疫印迹法检测IGFBP-3的表达状况; 同时以Annexin V-EGFP/PI染色, 流式细胞仪检测细胞凋亡率, 观察分泌表达的IGFBP-3对宿主细胞的促凋亡作用。转染48 h后, 经Western blotting检测, 在细胞培养上清中有分泌表达的IGFBP-3蛋白。流式细胞技术检测结果表明, 表达产物可直接作用于宿主细胞, 发挥促肿瘤细胞凋亡的作用。由此表明所构建的重组表达质粒pSectag-IGFBP3能在真核细胞水平正常表达并发挥生物学功能, 为进一步探索IGFBP-3的作用机制奠定了基础。     

CDK2在肿瘤中的非细胞周期功能

细胞周期依赖性激酶(Cyclin-dependent kinases,CDKs)是真核生物细胞周期有序驱动的核心调控子,CDK2作为CDK家族成员,调控细胞周期G1-S期和S-G2期的转变。近年来研究表明,CDK2在哺乳动物细胞周期调控中的作用不是必需的,但与肿瘤发生发展密切相关。CDK2参与调节多种致癌信号通路,其含量或活性失调常常导致肿瘤细胞失控性增殖,影响肿瘤细胞分化、衰老、凋亡、染色体不稳定等多种生物学功能。该文综述了CDK2在肿瘤中的非细胞周期功能。     

TBP-like Protein（TLP）通过G2／M期阻滞抑制HeLa细胞的增殖

TBP—likeprotein（TLP）是真核细胞中一种常见的转录因子,在调节生长发育方面起着重要的作用。该实验构建重组质粒pEGFP—N1．TLP,研究TLP对人宫颈癌细胞HeLa增殖的影响。利用流式细胞仪检测质粒的转染效率,通过激光共聚焦显微镜观察外源TLP蛋白的亚细胞定位。经过MTT检测、RNAi—TLP诱导的基因沉默7LHoechst33258染色研究TLP对HeLa细胞的增殖抑制作用。流式细胞术、Westernblot和RT-PCR实验结果表明,TLP将HeLa细胞周期阻滞于G2／M期,并抑制周期相关基因CDKl和CyclinBl的转录和翻译。研究表明,外源TLP在HeLa细胞的细胞核中表达,通过降低细胞周期相关基因CDKl和CDKl的表达水平,将HeLa细胞的细胞周期阻滞于G2／M期,从而抑制细胞的增殖。     

IGFBP-3在真核细胞中的分泌表达及功能分析

将人胰岛素样生长因子结合蛋白3(IGFBP-3)的cDNA片段亚克隆入pSectagA载体, 构建真核分泌型表达载体pSectag-IGFBP3。采用脂质体转染的方法将真核表达载体转染人肾癌786-O细胞, 转染48 h后用免疫印迹法检测IGFBP-3的表达状况; 同时以Annexin V-EGFP/PI染色, 流式细胞仪检测细胞凋亡率, 观察分泌表达的IGFBP-3对宿主细胞的促凋亡作用。转染48 h后, 经Western blotting检测, 在细胞培养上清中有分泌表达的IGFBP-3蛋白。流式细胞技术检测结果表明, 表达产物可直接作用于宿主细胞, 发挥促肿瘤细胞凋亡的作用。由此表明所构建的重组表达质粒pSectag-IGFBP3能在真核细胞水平正常表达并发挥生物学功能, 为进一步探索IGFBP-3的作用机制奠定了基础。     

Identification of human and mouse p19, a novel CDK4 and CDK6 inhibitor with homology to p16ink4.

The cell cycle in mammalian cells is regulated by a series of cyclins and cyclin-dependent kinases (CDKs). The G1/S checkpoint is mainly dictated by the kinase activities of the cyclin D-CDK4 and/or cyclin D-CDK6 complex and the cyclin E-CDK2 complex. These G1 kinases can in turn be regulated by cell cycle inhibitors, which may cause the cells to arrest at the G1 phase. In T-cell hybridomas, addition of anti-T-cell receptor antibody results not only in G1 arrest but also in apoptosis. In searching for a protein(s) which might interact with Nur77, an orphan steroid receptor required for activation-induced apoptosis of T-cell hybridomas, we have cloned a novel human and mouse CDK inhibitor, p19. The deduced p19 amino acid sequence consists of four ankyrin repeats with 48% identity to p16. The human p19 gene is located on chromosome 19p13, distinct from the positions of p18, p16, and p15. Its mRNA is expressed in all cell types examined. The p19 fusion protein can associate in vitro with CDK4 but not with CDK2, CDC2, or cyclin A, B, E, or D1 to D3. Addition of p19 protein can lead to inhibition of the in vitro kinase activity of cyclin D-CDK4 but not that of cyclin E-CDK2. In T-cell hybridoma DO11.10, p19 was found in association with CDK4 and CDK6 in vivo, although its association with Nur77 is not clear at this point. Thus, p19 is a novel CDK inhibitor which may play a role in the cell cycle regulation of T cells.     

The Flavonoid Apigenin Downregulates CDK1 by Directly Targeting Ribosomal Protein S9

Flavonoids have been reported to inhibit tumor growth by causing cell cycle arrest. However, little is known about the direct targets of flavonoids in tumor growth inhibition. In the present study, we developed a novel method using magnetic FG beads to purify flavonoid-binding proteins, and identified ribosomal protein S9 (RPS9) as a binding partner of the flavonoid apigenin. Similar to treatment with apigenin, knockdown of RPS9 inhibited the growth of human colon cancer cells at the G2/M phase by downregulating cyclin-dependent kinase 1 (CDK1) expression at the promoter level. Furthermore, knockdown of RPS9 suppressed G2/M arrest caused by apigenin. These results suggest that apigenin induces G2/M arrest at least partially by directly binding and inhibiting RPS9 which enhances CDK1 expression. We therefore raise the possibility that identification of the direct targets of flavonoids may contribute to the discovery of novel molecular mechanisms governing tumor growth.     

Lentiviral Vector-Mediated siRNA Knockdown of c-MYC: Cell Growth Inhibition and Cell Cycle Arrest at G2/M Phase in Jijoye Cells

Inhibition of c-MYC has been considered as a potential therapy for lymphoma treatment. We explored a lentiviral vector-mediated small interfering RNA (siRNA) expression vector to stably reduce c-MYC expression in B cell line Jijoye cells and investigated the effects of c-MYC downregulation on cell growth, cell cycle, and apoptosis in vitro. The expression of c-MYC mRNA and protein levels were inhibited significantly by c-MYC siRNA. The c-MYC downregulation resulted in the inhibition of cell proliferation and cell cycle arrest at G2/M phase, which was associated with decreased expression of cyclin B and cyclin-dependent kinase 1 (CDK1) and increased expression of CDK inhibitor p21 proteins. In addition, downregulation of c-MYC induced cell apoptosis characterized by DNA fragmentation and caspase-3 activation. Taken together, these results suggest that lentiviral vector-mediated siRNA for c-MYC may be a promising approach for targeting c-MYC in the treatment of Burkitt lymphoma.     

The fate of pancreatic tumor cell lines following p16 overexpression depends on the modulation of CDK2 activity

Restitution of lost tumor-suppressor activities may be a promising strategy to target specifically cancer cells. However, the action of ectopically expressed tumor-suppressor genes depends on genetic background of tumoral cells. Ectopic expression of p16(INK4a) induces either cell cycle arrest or apoptosis in different pancreatic cancer cell lines. We examined the molecular mechanisms mediating these two different cellular responses to p16 overexpression. Ectopic expression of p16 leads to G1 arrest in NP-9 cells by redistributing p21/p27 CKIs and inhibiting cyclin-dependent kinase CDK2 activity. In contrast, in NP-18 cells cyclin E (CycE)/CDK2 activity is significantly higher and is not downregulated by p16-mediated redistribution of p21/p27. Moreover, inhibition of CDK4 activity with fascaplysine, which does not affect CycE/CDK2 activity, reduces pocket protein phosphorylation in both cell lines, but fails to induce growth arrest. Like overexpression of p16, fascaplysine induces apoptosis in NP-18 cells, suggesting that inhibition of D-type cyclin/CDK activity in cells with high levels of CycE/CDK2 activity activates an apoptotic pathway. Inhibition of CycE/CDK2 activity via ectopic expression of p21 in NP-18 cells overexpressing p16 induces growth arrest and prevents p16-mediated apoptosis. Accordingly, silencing of p21 expression by using small interfering RNA switches the fate of p16-expressing NP-9 cells from cell cycle arrest to apoptosis. Our data suggest that, after CDK4/6 inactivation, the fate of pancreatic tumor cells depends on the ability to modulate CDK2 activity.     

Apigenin causes G(2)/M arrest associated with the modulation of p21(Cip1) and Cdc2 and activates p53-dependent apoptosis pathway in human breast cancer SK-BR-3 cells

We studied the effects of apigenin on the cell cycle distribution and apoptosis of human breast cancer cells and explored the mechanisms underlying these effects. We first investigated the antiproliferative effects in SK-BR-3 cells exposed to between 1 and 100 microM apigenin for 24, 48 and 72 h. Apigenin significantly inhibited cell proliferation at concentrations over 50 microM, regardless of exposure time (P<.05), and resulted in significant cell cycle arrest in the G(2)/M phase after 48 h of treatment at high concentrations (50 and 100 microM; P<.05). To investigate the regulatory proteins of cell cycle arrest affected by apigenin, we treated cells with 50 and 100 microM apigenin for 72 h. Apigenin caused a slight decrease in cyclin D and cyclin E expression, with no change in CDK2 and CDK4. In addition, the apigenin-induced accumulation of the cell population in the G(2)/M phase resulted in a decrease in CDK1 together with cyclin A and cyclin B. In an additional study, apigenin also increased the accumulation of p53 and further enhanced the level of p21(Cip1), with no change in p27(Kip1). The expression of Bax and cytochrome c of p53 downstream target was increased markedly at high concentration treatment over 50 microM apigenin. Based on our findings, the mechanism by which apigenin causes cell cycle arrest via the regulation of CDK1 and p21(Cip1) and induction of apoptosis seems to be involved in the p53-dependent pathway.     

LYG-202 inhibits the proliferation of human colorectal carcinoma HCT-116 cells through induction of G1/S cell cycle arrest and apoptosis via p53 and p21(WAF1/Cip1) expression

We recently established that LYG-202, a new flavonoid with a piperazine substitution, exerts an anti-tumor effect in vivo and in vitro. In the present study, we demonstrate that LYG-202 induces G1/S phase arrest and apoptosis in human colorectal carcinoma HCT-116 cells. Data showed that the blockade of the cell cycle was associated with increased p21(WAF1/Cip1) and Rb levels and reduced expression of cyclin D1, cyclin E, and CDK4. Moreover, PARP cleavage, activation of caspase-3, caspase-8, and caspase-9, and an increased ratio of Bax/Bcl-2 were detected in LYG-202-induced apoptosis. Additionally, activation of p53 resulted in the up-regulation of its downstream targets PUMA and p21(WAF1/Cip1), as well as the down-regulation of its negative regulator MDM2, suggesting that the p53 pathway may play a crucial role in LYG-202-induced cell cycle arrest and apoptosis. Furthermore, siRNA knockdown of p53 attenuated the G1 cell cycle arrest and apoptosis induced by LYG-202, as the effects of LYG-202 on up-regulation of p21(WAF1/Cip1) and down-regulation of Bcl-2 and pro-caspase-3 were partly inhibited in p53 siRNA transfected cells compared with control siRNA transfected cells. Collectively, these data indicate that LYG-202 exerts its anti-tumor potency by activating the p53-p21 pathway for G1/S cell cycle arrest and apoptosis in colorectal cancer cells.     

Pro-apoptotic effect and cytotoxicity of genistein and genistin in human ovarian cancer SK-OV-3 cells

We investigated the effects of genistein and genistin on proliferation and apoptosis of human ovarian SK-OV-3 cells and explored the mechanism for these effects. SK-OV-3 cells were treated with genistein and genistin at various concentrations (ranging from 1 to 100 muM) either alone or in combination for 24 and 48 h. Cell proliferation was estimated using an MTT assay, and cell cycle arrest was evaluated using FACS. Caspase-3 activity and annexin-based cell cycle analysis were used as measures of apoptosis. In addition, genistein- and genistin-induced cytotoxicity was determined by measuring release of LDH. Genistein treatment for 24 or 48 h substantially inhibited SK-OV-3 cell proliferation in a dose-dependent manner, and genistin treatment for 48 h also inhibited cell proliferation. Genistein caused cell cycle arrest at G2/M phase in dose- and time-dependent manner, and genistin caused cell cycle arrest not only at G2/M phase but also at G1 phase. Genistein markedly induced apoptosis and significantly increased LDH release, whereas genistin did not affect LDH release. Moreover, exposure to both genistein and genistin in combination for 48 h induced apoptosis without increasing LDH release. Genistein and genistin inhibit cell proliferation by disrupting the cell cycle, which is strongly associated with the arrest induction of either G1 or G2/M phase and may induce apoptosis. Based on our findings, we speculate that both genistein and genistin may prove useful as anticancer drugs and that the combination of genistein and genistin may have further anticancer activity.     

FGF inhibits the activity of the cyclin B1/CDK1 kinase to induce a transient G2 arrest in RCS chondrocytes

Fibroblast growth factors (FGFs) negatively regulate long bone development by inhibiting the proliferation of chondrocytes that accumulate in the G1 phase of the cycle following FGF treatment. Here we report that FGF also causes a striking but transient delay in mitotic entry in RCS chondrocytes by inactivating the cyclin B1-associated CDK1(CDC2) kinase. As a consequence of this inactivation, cells accumulate in the G2 phase of the cycle for the first 4-6 hours of the treatment. Cyclin B1/CDK1 activity is then restored and cells reach a G1 arrest. The reduced cyclin B1/CDK1 activity was accompanied by increased CDK1 inhibitory phosphorylation, likely caused by increased activity and expression of the Myt1 kinase. FGF1 also caused dephosphorylation of the CDC25C phosphatase, that however appears due the inactivation of cyclin B1/CDK1 complex in the CDK1 feedback loop, and not the activation of specific phosphatases. The inactivation of the cyclin B1/CDK1 complex is a direct effect of FGF signaling, and not a consequence of the G2 arrest as it can be observed also in cells blocked at mitosis by Nocodazole. The Chk1 and ATM/ATR kinase are known to play essential roles in the G2 checkpoint induced by DNA damage/genotoxic stress, but inhibition of Chk1 or ATM/ATR not only did not prevent, but rather potentiated the FGF-induced G2 arrest. Additionally our results indicate that the transient G2 arrest is induced by FGF in RCS cell through mechanisms that are independent of the G1 arrest, and that the G2 block is not strictly required for the sustained G1 arrest but may provide a pausing mechanism that allows the FGF response to be fully established.