抗VEGF发卡状核酶抑制肝癌VEGF表达和移植瘤生长

目的:采用抗人血管内皮生长因子(vascular endothelial growth factor,VEGF)发卡状核酶基因转染肝癌细胞,观察核酶对VEGF表达及肿瘤生长的影响。方法:采用脂质体介导的方法,将人工合成的抗VEGF发卡状核酶基因转染肝癌细胞SMMC-7721,同时制备空载体和细胞对照,经G418筛选获得阳性克隆,基因组水平鉴定核酶在细胞中的表达,半定量RT-PCR法和免疫组化法观察核酶对SMMC-7721细胞VEGF表达的影响。接种各组细胞于裸鼠皮下,观察瘤体体积大小和质量,免疫组化法观测各组肿瘤微血管变化和VEGF的表达。结果:核酶基因成功导入到肿瘤细胞中,转基因细胞的增殖速率明显下降(P<0.01),转染核酶组细胞VEGF水平明显下降(P<0.01)。移植瘤成瘤率和生长速度减慢(P<0.01),肿瘤组织VEGF表达和血管形成减少(P<0.01)。结论:抗人VEGF发卡状核酶基因在体内、体外均可抑制肝癌VEGF表达,通过减少血管形成抑制肿瘤生长,为进一步开展肝癌血管靶向基因治疗提供实验依据。     

恩度诱导抑制性VEGFA选择性剪切异构体VEGF165b的表达及其意义

目的:探讨重组人血管内皮抑制素(恩度)对人肝癌细胞SMMC-7721VEGF165b表达的影响,及上调VEGF165b表达后,SMMC-7721对恩度敏感性的变化.方法:采用RT-PCR法和蛋白质印迹法检测恩度干预SMMC-7721后VEGF165b的表达变化;稳定转染VEGF165b真核表达质粒到SMMC-7721,RT-PCR和免疫细胞荧光共聚焦显微镜检测VEGF165b、HIF-1α和下游靶基因VEGFA表达的变化;MTT法检测恩度对人肝癌细胞生长抑制率的影响.结果:100和400 μg/mL恩度能够诱导VEGF165bmRNA和蛋白表达上调,而外源性VEGF165b下调HIF-1α及下游靶基因VEGFA的表述.转染空质粒后,500和1000μg/mL恩度引起SMMC-7721的生长移植率分别为1.6%和0.4%,转染VEGF165b后,500 μg/mL和1000 μg/mL恩度引起的生长移植率分别为8.5%(P=0.000 0)和20.2%(P=0.000 0).结论:恩度抗肿瘤新生血管的作用部分是通过上调VEGF165b介导的,VEGF165b增加SMMC-7721细胞对恩度的敏感性,两者治疗肿瘤有协同作用.     

VEGF特异性核酶对Hela细胞VEGF表达的调节

目的：构建VEGF特异性发夹状核酶基因真核表达载体，观察其对Lela细胞VEGF表达的调节。方法：将核酶基因克隆入pcDNA3中，构建了抗VEGF发夹状核酶真核表达载体pcDNA3-RZ,并进行了核酶的体外切割活性检测。将真核表达载体转染人宫颈癌Hela细胞，采用RNA斑点杂交、流式细胞仪免疫荧光及免疫细胞化学方法，检测Hela细胞中VEGFmRNA和VEGF蛋白的表达水平。结果：所构建的重组表达载体pcDNA3-RZ正确，体外切割检测该核酶具有较高的切割活性。转染了pcDNA-RZ的Hela细胞中VEGFmRNA和VEGF蛋白的表达水平明显下降。结论：成功地构建了抗VEGF发夹状核酶基因真核表达载体，该载体能明显抑制Hela细胞VEGF的表达。     

抗端粒酶核酶质粒的构建筛选及其对CNE-2Z细胞增殖与凋亡的影响

背景与目的:已证实端粒酶(telomerase,TLMA)对肿瘤的进展和肿瘤细胞的无限增殖起着重要的决定作用。核酶是具有特殊核酸内切酶活性的反义RNA,可序列特异性地与靶RNA分子配对并切割靶基因RNA。有报道人低分化鼻咽癌CNE-2Z细胞端粒酶阳性,本实验目的是构建抗端粒酶RNA模板区特异性核酶的真核表达载体并用电穿孔法将其导入人低分化鼻咽癌CNE-2Z细胞,研究该核酶对CNE-2Z细胞增殖、凋亡的影响。方法:设计合成针对端粒酶RNA模板区的锤头状核酶基因teloRZ作为端粒酶抑制剂,构建3种带有绿色荧光蛋白(greenfluorescentprotein,GFP)报道基因和嘌呤霉素(puromycin)抗性基因的teloRZ真核表达质粒pGFPuro-teloRZ2.1、pGFPuro-teloRZ7.1、pGFPuro-teloRZ7.7,这3种质粒的不同点在于teloRZ基因和puromycin抗性基因按3种不同方向设计,然后将上述3种质粒及载体质粒pPAT-GFP电转染CNE-2Z细胞,用荧光显微镜检测GFP表达情况;用流式细胞仪、荧光染色法检测细胞增殖指数及凋亡等指标。结果:CNE-2ZGTR7.1细胞(转染目的基因质粒pGFPuro-teloRZ7.1的CNE-2Z细胞)增殖指数(25.100±0.141)%明显低于CNE-2Z细胞(未转染质粒的细胞)的(53.663±16.981)%、CNE-2ZG细胞(转染空载质粒pPAT-GFP的CNE-2Z细胞)的(61.575±5.166)%、CNE-2ZGTR2.1     

过表达CHD5基因对肝癌细胞SMMC-7721生物学行为的影响

目的:探讨过表达CHD5基因对人肝癌细胞SMMC-7721生物学行为的影响。方法:采用脂质体法将CHD5过表达质粒及对照质粒分别转染SMMC-7721细胞,Western blotting检测SMMC-7721细胞中CHD5蛋白的表达情况,CCK-8法检测SMMC-7721细胞生长增殖能力的变化,流式细胞仪检测细胞凋亡,Transwell实验检测细胞迁移和侵袭能力的变化。结果:转染CHD5过表达质粒后,SMMC-7721细胞CHD5蛋白表达水平显著增高（P<0.01）,抑制了细胞增殖、迁移和侵袭（P<0.05）,促进了细胞凋亡（P<0.05）。结论:过表达CHD5基因可抑制SMMC-7721细胞的增殖、迁移和侵袭并诱导其凋亡。     

反义RNA技术对抑制人肝癌细胞SMMC-7721中POLD1基因表达的研究

目的:应用反义RNA技术抑制人肝癌细胞SMMC-7721中POLD1基因的表达,探索采用该技术干预肝癌的可行性。方法:制备人POLD1基因的反义RNA表达质粒,同时建立空白对照组与阴性对照组,由此将实验分为阴性对照组(转染空载体的SMMC-7721细胞)、空白对照组(肝癌细胞SMMC-7721)和实验组(转染人POLD1基因反义RNA表达质粒的肝癌SMMC-7721细胞)3组。MTT实验分析细胞增殖变化,并在转染SMMC-7721细胞48h后,实时荧光定量PCR和蛋白质印迹法检测POLD1基因的表达。结果:MTT实验显示,与空白对照和阴性对照组相比,转染了反义RNA的实验组细胞增殖受到明显抑制。在转染后24～72h,实验组吸光度24h为0.306 7±0.015 4,48h为0.459 2±0.033 2,72h为0.567 1±0.061 1,与空白和阴性对照组相比,P值均<0.05。实时荧光定量PCR实验显示,实验组POLD1的mRNA表达明显下调为0.142 5±0.020 5,阴性对照组为1.017±0.188,空白对照组为1.00±0.00(F=26.5,P<0.05),说明POLD1基因表达受抑制。蛋白质印迹实验显示,POLD1基因蛋白水平(p125)变化趋势与mRNA相同,均为下调,其中实验组为0.222 3±0.009 7,阴性对照组为0.237 9±0.005 9,空白对照组为0.235 4±0.003 4(F=1 365.754,P值均<0.05),说明反义RNA可抑制p125蛋白表达,结论与基因水平趋势一致。结论:针对POLD1基因设计的反义RNA体外抑制了肝癌细胞SMMC-7721的增殖,这与POLD1在基因和蛋白水平的表达下调有关。     

抗 VEGF发夹状核酶基因抑制 VEGF表达及卵巢癌细胞增殖的实验研究

背景与目的:研究表明血管内皮生长因子(vascular endothelial growth factor,VEGF)在与上皮性卵巢癌有关的血管形成过程中可能发挥着重要作用.目前,核酶策略已成为一种基因治疗的策略,用于阻断肿瘤形成或肿瘤的生长与转移.VEGF在卵巢肿瘤形成中的作用尚不十分清楚.我们试图采用抗 VEGF发夹状核酶基因阻断卵巢癌中 VEGF的自分泌和 /或旁分泌通路,以检测其对卵巢癌细胞增殖的影响.方法:采用脂质体介导的方法将自行设计和构建的抗 VEGF发夹状核酶基因真核表达载体转染人卵巢癌 SKOV3细胞,采用 G418筛选获得阳性克隆 ; RNA斑点杂交检测核酶基因在卵巢癌细胞中的表达 ; 免疫组化、间接免疫荧光染色及流式细胞仪结合免疫荧光检测转染前后卵巢癌细胞中 VEGF表达 ; 通过 MTT、细胞贴壁克隆形成实验、软琼脂克隆形成实验及细胞周期分析观察其对卵巢癌细胞增殖的影响.结果:与 SKOV3细胞相比,转染后的 SKOV3-RZ细胞 VEGF表达明显降低(P< 0.01); 细胞生长减慢,细胞贴壁克隆形成及软琼脂克隆形成率明显降低 [(12.7± 1.4)% 和(9.4± 2.0)% 比(30.1± 1.9)% 和(24.8± 1.5)%,P< 0.001];G1期细胞显著增多(77.6% 比 57.9%,P< 0.01),S期细胞显著减少(17.0% 比 29.9%,P< 0.01). 结论:抗 VEGF发夹状核酶基因可显著抑制卵巢癌细胞 SKOV3增殖 ; 本研究为进一步开展肿瘤血管靶向基因治疗提供了实验依据.     

介导MDR1的RNAi腺病毒载体的构建

目的介导MDR1的RNAi腺病毒载体,探讨RNA干扰MDR1基因对人肝癌细胞的作用。方法根据MDR1mRNA序列构建表达MDR1mRNA特异的shRNA的腺病毒穿梭质粒pshuttle-MDR1。与腺病毒载体体内重组为pAd-MDR1后转染人肝癌细胞SMMC-7721,以FCM检测细胞表面膜蛋白P-gp表达阳性率,以共聚焦显微镜检测细胞内Rh123的潴留,WesternBlot检测P-gp蛋白量的变化。结果构建成pshuttle-MDR1经限制性酶切和PCR证实与设计一致,将pAd-MDR1转染肝癌细胞SMMC-7721后,FCM检测细胞表面膜蛋白P-gp表达阳性率为22.9%和30.8%,远低于对照组(85.8%)。WesternBlot经病毒感染的SMMC-7721/R的P-gp含量明显低于对照SMMC-7721/R,而与SMMC-7721/S细胞接近。结论成功构建了pshuttle-MDR1腺病毒载体,并有效干扰了肝癌细胞细SMMC-7721MDR1的表达。     

人剪切修复基因XPD转染对人肝癌细胞SMMC-7721的生物学影响

目的 将人剪切修复基因XPD稳定转染人SMMC-7721肝癌细胞,观察转染后细胞内野生型p53、XPD、周期素依赖性蛋白激酶(CDK)7、c-myc等基因表达的变化以及对细胞生长的影响,探讨野生型XPD基因与p53、CDK7、c-myc的相互作用及细胞凋亡机制.方法 将表达绿色荧光蛋白并含有人类全长野生型XPD的pEGFP-N2-XPD重组体质粒稳定转染人SMMC-7721肝癌细胞中,选择培养基筛选单克隆稳定转染重组质粒的人SMMC-7721肝癌细胞(SMMC-7721-pEGFP-N2-XPD)和稳定转染空载质粒的人SMMC-7721肝癌细胞(SMMC.7721-pEGFP-N2),并将人SMMC-7721肝癌细胞作为空白对照,利用荧光显微镜观测绿色荧光蛋白表达,用逆转录-聚合酶链反应(RT-PCR)、Westem blot法检测转染XPD基因后细胞内XPD、p53、CDK7、c-myc的表达量变化,并用细胞增殖力检测(MTT)法及流式细胞仪分别检测细胞增殖及凋亡和细胞周期变化.结果 ①免疫荧光显微镜下,SMMC.7721.pEGFP.N2.XPD和SMMC-7721-pEGFP-N2细胞中观察到绿色荧光蛋白表达,说明pEGFP-N2-XPD重组质粒和pEGFP-N2空载质粒成功转染.②RT-PCR检测:SMMC-7721-pEGFP-N2-XPD中p53 mRNA、XPD mR-NA表达量与SMMC-7721-pEGFP-N2和SMMC-7721相比均明显增高(P<0.01),CDK7 mRNA、c-myc mRNA在SMMC-7721-pEGFP-N2-XPD的表达量比两对照组明显降低(P<0.01),而两对照组各个基因的表达没有明显差异(P>0.05).③Western blot检测:SMMC-7721-pEGFP-N2-XPD细胞的p53、XPD蛋白表达最较两对照组升高(P<0.01),CDK7、c-myc的蛋白相对表达量比两对照组降低(P<0.01),两对照组差异没有统计学意义(P>0.05).④M1Tr检测:SMMC-7721-pEGFP-N2-XPD的细胞增殖力较对照组减弱(P<0.05),两对照组筹异没有统计学意义(P>0.05).⑤流式细胞仪检测:SMMC-7721-pEGFP-N2-XPD细胞进入s期出现障碍,停滞在G1期的细胞增多.结论 将XPD成功稳定转染到人SMMC-7721肝癌细胞中,XPD、p53在转录和蛋白水平的表达明显升高,CDK7、c-myc表达明显降低,野生型XPD基因的过表达可能抑制CDK7、c-myc表达,改变细胞周期,并促进p53抑制肝癌细胞增长,促进细胞凋亡.     

人血管内皮生长因子shRNA对小鼠肝癌移植瘤生长的影响

目的:使用VEGF shRNA真核表达载体对裸鼠的负瘤局部注射,观察对其生长影响.方法:使用VEGF shRNA 真核表达载体转染肝癌细胞系SMMC-7721,ELISA法检测转染前后肝癌细胞系SMMC-7721的VEGF蛋白表达量,观察VEGF shRNA 真核表达载体对裸鼠的负瘤局部注射后负瘤的生长变化.结果:VEGF shRNA大部分阻断肝癌细胞系SMMC-7721的VEGF蛋白表达,裸鼠的负瘤生长速度变慢.结论:VEGF shRNA可明显使裸鼠的负瘤生长速度变慢,为将VEGF shRNA 真核表达载体应用于肝癌的基因治疗提供依据.     

Attenuation of telomerase activity by hammerhead ribozyme targeting human telomerase RNA induces growth retardation and apoptosis in human breast tumor cells

Ribozyme possesses specific endoribonuclease activity and catalyzes the hydrolysis of specific phosphodiester bonds, which results in the cleavage of target RNA sequences. Here, we evaluated the ability of hammerhead ribozymes targeting human telomerase RNA (hTR) to inhibit the catalytic activity of telomerase and the proliferation of cancer cells. Hammerhead ribozymes were designed against 7 NUX sequences located in open loops of the hTR secondary structure. We verified the ribozyme specificity by in vitro cleavage assay by using a synthetic RNA substrate. Subsequently, we introduced ribozyme expression vector into human breast tumor MCF-7 cells and assessed the biologic effects of ribozyme. Hammerhead ribozyme R1 targeting the template region of hTR efficiently cleaved hTR in vitro, and stable transfectants of this ribozyme induced the degradation of target hTR RNA and attenuated telomerase activity in MCF-7 cells. Moreover, the ribozyme R1 transfectant displayed a significant telomere shortening and a lower proliferation rate than parental cells. Clones with reduced proliferation capacity showed enlarged senescence-like shapes or highly differentiated dendritic morphologies of apoptosis. In conclusion, the inhibition of telomerase activity by hammerhead ribozyme targeting the template region of the hTR presents a promising strategy for inhibiting the growth of human breast cancer cells.     

核酶对食管癌EC9706细胞端粒酶活性及凋亡的影响

目的 :观察针对人端粒酶RNA模板区的核酶对食管癌细胞端粒酶活性和细胞凋亡的影响。方法 :利用脂质体Lipofectamine介导 ,将已构建好的带有端粒酶核酶基因的重组质粒pBBS2 12Rz及空载质粒pBBS2 12转染食管癌EC970 6细胞 ,采用TRAP ELISA法检测端粒酶活性 ,用倒置相差显微镜及流式细胞仪观察细胞生长和凋亡情况。结果 :重组质粒pBBS2 12Rz转染的食管癌EC970 6细胞的端粒酶活性明显下降 ,细胞生长速度明显变慢 ,凋亡加速。结论 :端粒酶核酶对食管癌细胞端粒酶活性和细胞生长有抑制作用 ,可望成为食管癌基因治疗的新方法     

Ribozyme对癌基因Ki-ras~(G12V) mRNA的剪切及其特异性

目的 :设计切割ki-rasG12V mRNA的特异性ribozyme(Rz2 17) ,明确其对癌基因ki-rasG12VmRNA的细胞内外切割活性 ,为以ki-rasG12VmRNA为特异性靶分子的基因治疗及癌基因ki-ras的功能研究提拱一种新的途径。方法 :依Symons总结的“锤头结构”原理 ,设计一种能特异性切割ki-rasG12VmRNA的ribozyme ,利用DNA重组技术构建ki-rasG12V外显子 1和ri-bozymeRz2l7的体外转录质粒及ribozymeRz2 17的真核表达质粒 ,体外转录获得ribozymeRz2 17及ki-rasG12V外显子 1mRNA ,在含Mg2 溶液中ribozymeRz2 17对其靶RNA分子进行切割。以RT -PCR对转染ribozymeRz2 17真核表达质粒的细胞ki-rasG12VmRNA进行半定量分析。结果 :ki-rasG12V外显子 1体外转录mRNA分子 ,能被ribozymeRz2 17定点切割而野生型ki-ras外显子 1体外转录mRNA则不被切割 ;转染ribozymeRz2 17的胰癌细胞ki-rasG12VmRNA含量减少 ,而转染ri bozymeRz2 17的肝癌细胞其内源性ki-rasmRNA含量无明显变化。结论 :ribozymeRz2 17无论在细胞内外均能剪切突变型ki-rasmRNA(G12V)而且其切割作用为突变型ki-rasG12VmRNA特异性的。     

抗肿瘤细胞多药抗性核酶的合成及其活性的研究

目的 研究抗肿瘤细胞多药抗性（ＭＤＲ）核酶的生物学活性及其稳定性。方法 构建表达抗ＭＤＲ１核酶的逆转录病毒载体（Ｎ２Ａ＋ｔＲＮＡ＾ｅｍｔｉ－１９６ＭＤＲ１－Ｒｚ、Ｎ２Ａ＋ｔＲＮＡ＾ｍｅｔｉ－１９６ＭＤＲ１－ｓＲｚ、Ｎ２Ａ＋ｔＲＮＡ＾ｍｅｔｉ－ｌｉＭＤＲ１－ｓＲｚ）和合成了裸核酶ｃＤＮＡ。利用体外转录反应合成５种ａｎｔｉ－ＭＤＲ１核酶（ｔＮＲＡ－１９６ＭＤＲ１－Ｒｚ、ｔＲＮＡ－１９６ＭＤＲ１－ｓＲｚ     

抗VEGF165核酶对人肺腺癌细胞生物学特性的影响

目的 探讨抗血管内皮生长冈子165(VEGF165)核酶对人肺腺癌细胞生物学特性的影响。方法设计合成针对VEGF165 212位点的锤头状核酶(vascular endothelial growth factor ribozyme，VRZ)及其突变体(mutant VRz，mVRz)，体外检测核酶的剪切活性。采用亚克隆技术，构建腺病毒介导的抗VEGF165核酶真核表达载体pAdVRz，用重组腺病毒感染人肺腺癌细胞A549，分别采用Northern blot印迹杂交、流式细胞仪、透射电镜和激光共聚焦等技术，观察感染前后A549细胞的生物学性状的改变。结果成功地合成了具有明显剪切活性的抗VEGF165核酶VRz及其重组腺病毒表达载体rpAdVRz，并在A549细胞中获得表达。重组腺病毒感染细胞的VEGF165表达减少了87％，而生物学性状不受外源基因表达的影响。结论抗VEGF165核酶能够显著抑制人肺腺癌细胞内VEGF165的表达，为进一步进行肺癌的抗血管治疗提供了实验基础。     

Antitumor and antimetastatic activity of ribozymes targeting the messenger RNA of vascular endothelial growth factor receptors.

Chemically stabilized hammerhead ribozymes are nuclease-resistant, RNA-based oligonucleotides that selectively bind and cleave specific target RNAs. Due to their potential for specifically inhibiting gene expression, ribozymes are being investigated for therapeutic applications as well as for the elucidation of gene function. In particular, we have investigated ribozymes that target the mRNA of the vascular endothelial growth factor (VEGF) receptors because VEGF signaling is an important mediator of tumor angiogenesis and metastasis. Here we report pharmacodynamic studies testing anti-Flt-1 (VEGFR-1) and anti-KDR (VEGFR-2) ribozymes in animal models of solid tumor growth and metastasis. Ribozymes targeting either Flt-1 or KDR significantly inhibited primary tumor growth in a highly metastatic variant of Lewis lung carcinoma. However, only treatment with the anti-Flt-1 ribozyme resulted in a statistically significant and dose-dependent inhibition of lung metastasis in this model. The anti-Flt-1 ribozyme was then tested in a xenograft model of human metastatic colorectal cancer in which significant inhibition of liver metastasis was observed. Taken together, these data represent the first demonstration that synthetic ribozymes targeting VEGF receptor mRNA reduced the growth and metastasis of solid tumors in vivo.     

Antitumor activity of systemically delivered ribozymes targeting murine telomerase RNA.

PURPOSE: To test ribozymes targeting mouse telomerase RNA (mTER) for suppression of the progression of B16-F10 murine melanoma metastases in vivo. EXPERIMENTAL DESIGN: Hammerhead ribozymes were designed to target mTER. The ribozyme sequences were cloned into a plasmid expression vector containing EBV genomic elements that substantially prolong expression of genes delivered in vivo. The activity of various antitelomerase ribozymes or control constructs was examined after i.v. injection of cationic liposome:DNA complexes containing control or ribozyme constructs. Expression of ribozymes and mTER at various time points were evaluated by quantitative real-time PCR. Telomerase activity was examined using the telomeric repeat amplification protocol. RESULTS: Systemic administration of cationic liposome:DNA complexes containing a plasmid-expressed ribozyme specifically targeting a cleavage site at mTER nucleotide 180 significantly reduced the metastatic progression of B16-F10 murine melanoma. The antitumor activity of the anti-TER 180 ribozyme in mice was abolished by a single inactivating base mutation in the ribozyme catalytic core. The EBV-based expression plasmid produced sustained levels of ribozyme expression for the full duration of the antitumor studies. In addition to antitumor activity, cationic liposome:DNA complex-based ribozyme treatment also produced reductions in both TER levels and telomerase enzymatic activity in tumor-bearing mice. CONCLUSIONS: Systemic, plasmid-based ribozymes specifically targeting TER can reduce both telomerase activity and metastatic progression in tumor-bearing hosts. The work reported here demonstrates the potential utility of plasmid-based anti-TER ribozymes in the therapy of melanoma metastasis.     

Retrovirus-mediated transfer of anti-MDR1 hammerhead ribozymes into multidrug-resistant human leukemia cells: screening for effective target sites.

One of the underlying mechanisms of multidrug resistance (MDR) is cellular over-production of P-glycoprotein (P-gp), which acts as a drug efflux pump. P-gp is encoded by a small group of related genes termed MDR; only MDR1 is known to confer drug resistance. To overcome P-gp-mediated drug resistance, we have developed two anti-MDR1 hammerhead ribozymes driven by the beta-actin promoter. Upon transduction of the ribozymes into MDR cells, vincristine resistance was decreased. These two ribozymes were constructed, which showed different cleavage activities. In this study, to determine suitable target sites for the anti-MDR1 ribozyme, the exon 1b-intron 1 boundary, the translation-initiation site, the intron 1-exon 2 boundary and the exon 2-intron 2 boundary, codons 179 and 196 of the MDR1 gene were selected as candidates. To improve the ribozyme activity, a retroviral vector containing RNA polymerase III promoter was used. Stable retrovirus producer cells were generated by transfecting the retroviral vector plasmids carrying the ribozyme into the packaging cell line. Retroviral vector transduction of human leukemia cell lines expressing MDR1 was accomplished by co-culturing these with virus producer cells. Stably transduced cells were selected by G418 and pooled to determine the efficacy of each ribozyme. These ribozyme-transduced cells became vincristine-sensitive concomitant with the decreases in MDR1 expression, P-gp amount and drug efflux pump function. Among the ribozymes tested, the anti-MDR1 ribozyme against the translation-initiation site exhibited the strongest efficacy. This retrovirus-mediated transfer of anti-MDR1 ribozyme may be applicable to the treatment of MDR cells as a specific means to reverse resistance.     

Ribozyme-mediated cleavage of the human survivin mRNA and inhibition of antiapoptotic function of survivin in MCF-7 cells

Survivin is a new member of the inhibitor of apoptosis protein (IAP) family that is implicated in the control of cell proliferation and the regulation of cell life span. This protein is selectively expressed in most human carcinomas but not in normal adult tissues. To down-regulate a human survivin expression as a strategy for cancer gene therapy, we designed two hammerhead ribozymes (RZ-1, RZ-2) targeting human survivin mRNA. RZ-1 and RZ-2 efficiently cleaved the human survivin mRNA at nucleotide positions +279 and +289, which was identified by in vitro cleavage assay using in vitro transcribed ribozymes and truncated survivin mRNA substrate. To investigate the function of the ribozymes in cells, the sequences of the ribozymes were cloned into replication-deficient adenoviral vector and transferred to breast cancer cell, MCF-7. The infection with adenovirus encoding the ribozymes resulted in a significant reduction of survivin mRNA (74% and 73%, respectively) and protein. As revealed by nuclear condensation/ fragmentation and flow cytometry analysis, inhibition of survivin gene by ribozymes increased apoptosis and sensitivity induced by etoposide or serum starvation. Our results suggest that the designed hammerhead ribozymes against survivin mRNA are good candidates for feasible gene therapy in the treatment of cancer.