人类白细胞抗原-GRNA干扰载体的构建及效应检测

目的构建表达人类白细胞抗原-G(HLA-G)基因shRNA载体,探讨其对NK细胞杀伤效应的影响。方法构建4个HLA-G-shRNA真核表达质粒,瞬时转染至人肝癌Bel-7402细胞,检测HLA-G mRNA和蛋白水平的表达。将NK-92MI细胞(效应细胞)与转染后的Bel-7402细胞(靶细胞)共同培养,以LDH释放法观察不同效靶比时NK-92MI细胞对靶细胞的杀伤效应。结果经酶切及测序鉴定证实,插入序列与设计的序列相符。RT-PCR和Western blot结果均表明重组载体抑制了Bel-7402细胞HLA-G基因的表达。NK-92MI细胞对转染HLA-GshRNA的Bel-7402细胞杀伤作用明显增强(P<0.01)。封闭NK-92MI细胞KIR2DL4受体后,杀伤作用减弱(P<0.01)。结论成功构建了HLA-G shRNA载体,下调HLA-G可以增强NK细胞对肝癌细胞的杀伤效应,HLA-G与NK细胞表面KIR2DL4受体结合后,向NK细胞传递抑制效应。     

端粒酶逆转录酶基因启动子调控FADD表达载体诱导人结肠细胞凋亡的研究

目的 构建人端粒酶逆转录酶(hTERT)基因启动子调控Fas相关死亡结构域蛋白(FADD)肿瘤细胞特异性表达载体,观察其对人结肠癌细胞凋亡的作用.方法 利用hTERT基因核心启动子和FADD基因片段,构建hTERT基因启动子调控FADD 的肿瘤细胞特异性表达载体.用脂质体转染法,将其分别转染人结肠癌细胞和正常细胞,观察人结肠癌细胞和正常细胞的端粒酶活性、细胞周期及凋亡.结果 hTERT基因核心启动子调控FADD 表达载体,在所检测的肿瘤细胞中具有明显的转录活性;而在正常细胞中则无明显的转录活性.Colon320细胞、LoVo细胞、SW480细胞与WI-38细胞凋亡率在不同转染时间比较,差异有统计学意义(P均<0.01).WI-38转染pLNCX-hTERT-FADD与pLNCX-hTERT-GFP在24、48、72、96、120h凋亡率比较,差异均无统计学意义(P均>0.05).结论 hTRET基因核心启动子具有肿瘤特异性,构建hTERT基因核心启动子调控FADD 表达载体可能是一种新的肿瘤治疗途径.     

体外腺病毒介导的HSV-tk/GCV对产生AFP的人肝癌细胞的影响

目的 观察腺病毒介导的单纯疱疹病毒胸苷激酶基因（HSV-tk）/丙氧鸟苷（GCV）自杀基因系统在体外对人肝癌细胞的选择性杀伤效应。方法 采用含有甲胎蛋白基因启动子、增强子和HSV-tk基因的嵌合基因,插入腺病毒中形成重组腺病毒（AdrAFPTK）,将该重组腺病毒分别感染体外培养的甲胎蛋白阳性人肝癌细胞BEL-7402和甲胎蛋白阴性人肝癌细胞SMMC-7721,逆转录聚合酶链式反应（RT-PCR）检测HSV-tk基因的转录表达,观察GCV对人肝癌细胞的选择性杀伤作用。结果GCV在体外对重组腺病毒转染的甲胎蛋白阳性的人肝癌细胞BEL-7402有明显的杀伤作用和“旁观者效应”,而对重组腺病毒转染的甲胎蛋白阴性的人肝癌细胞SMMC-7721无明显作用。结论 在体外,表达HSV-tk基因的甲胎蛋白的人肝癌细胞可被受甲胎蛋白基因表达调控序列控制的自杀基因HSV-tk特异性杀伤,表现出极高的细胞专一性。重组腺病毒AdrAFPTK可望用于肝癌的特异性基因治疗。     

体外腺病毒介导的HSV—tk／GCV对产生AFP的人肝癌细胞的影响

目的 观察腺病毒介导的单纯疱疹病毒胸苷激酶基因（HSV-tk)/丙氧鸟苷（GCV）自杀基因系统在体外对人肝癌细胞的选择性杀伤效应。方法 采用含有甲胎蛋白基因启动子，增强子和HSV-tk基因的嵌合基因，插入腺病毒中形成重组腺病毒（AdrAFPTK),将该重组腺病毒分别感染体外培养的甲胎蛋白阳性人肝癌细胞BEL-7402和甲胎蛋白阴性人肝癌细胞SMMC-7721，逆转录聚合酶链式反应（RT-PCR）检测HSV-tk基因的转录表达，观察GCV对人肝癌细胞的选择性杀伤作用。结果 GCV在体外对重组腺病毒转染的甲胎蛋白阳性的人肝癌细胞BEL-7402有明显的杀伤作用和“旁观效应”，而对重组腺病毒转染的甲胎蛋白阴性的人肝癌细胞SMMC-7721无明显作用。结论 在体外，表达HSV-tk基因的甲胎蛋白的人肝癌细胞可被受甲胎蛋白基因表达调控序列控制的自杀基因HSV-tk特异性杀伤，表现出极高的细胞专一性，重组腺病毒AdrAFPTK可望用于肝癌的特异性基因治疗。     

Ki-67核心启动子在胃癌SCG-991细胞中的转录活性

目的 观察Ki-67核心启动子在人胃癌细胞中的转录活性.方法 使用缺失分析法分别从5'端和3'端对Ki-67基因启动子逐段缺失,得到不同长度的8个和3个截短DNA片段.分别插入pGL3-Basic载体后转染人胃癌SCG-991细胞,使用双荧光素酶检测系统鉴定转录活性,确定Ki-67基因核心启动子.比较Ki-67核心启动子与另2种肿瘤启动子hTERT和Survivin的转录活性.结果 自5'端缺失得到的-223～+771截短片段在SCG-991细胞内转录活性达到病毒SV40启动子活性的56.5%;自3'端缺失的-223～+30截短片段转录活性更强,为-223～+771片段活性的2.1倍,是hTERT启动子的1.7及Survivin启动子和15.3倍.结论 Ki-67核心启动子区域为-223～+30,在胃癌SCG-991细胞中的转录活性超过SV40启动子,以及hTERT启动子及Survivin启动子.     

siRNA抑制肝癌细胞甲硫氨酸腺苷转移酶2A基因表达

目的构建siRNA体内表达载体pSilence-2．1-U6-siRNA，筛选出抑制甲硫氨酸腺苷转移酶(MAT)2A表达的有效靶序列，为MAT2A的功能研究奠定了基础。方法以MAT2A为目的基因，以产生siRNA质粒载体pSilence-2．1-U6为表达模板，细胞内转录合成4条siRNA，并构建携带荧光素酶报告基因的重组质粒载体plucF-MAT2A。脂质体转染法将重组质粒载体plucF-MAT2A与产生siRNA的质粒pSilence-2．1-U6共转染293T细胞，定量测量荧光素酶活性，初步筛选出抑制荧光素酶表达的有效siRNA，然后将有效的siRNA转染Bel-7402肝癌细胞，半定量逆转录-聚合酶链反应(RT-PCR)检测MAT2A mRNA表达，并检测转染后肝癌细胞MAT的活性及细胞凋亡情况，进一步证实siRNA对MAT2A表达的抑制效果。结果所合成的4条小干扰RNA中有2条抑制荧光素酶表达，抑制效率分别为81％和89％，并特异性抑制肝癌细胞MAT2A mRNA表达，降低了肝癌细胞中MAT活性，诱导肝癌细胞凋亡。结论siRNA抑制肝癌细胞MAT2A基因表达。     

双启动子引导自杀基因靶向杀伤5-FU耐药肿瘤细胞的研究

目的：探讨胸苷酸合成酶（TS）基因启动子和p16基因启动子引导胸苷激酶（TK）自杀基因靶向杀伤5－FU耐药肿瘤细胞的作用。方法：构建TS、p16双启动子重组表达载体,将TK基因插入TS、p16启动子之间,转染耐药人直肠癌细胞系HR－8348、外周血单个核细胞。通过克隆形成实验、细胞存活率测定和裸鼠移植瘤治疗实验,观察双启动了引导TK基因特异杀伤肿瘤细胞的作用。结果：将TS、p16双启动子重组质粒载体转入耐药HR－8348细胞,检测TS、TK基因表达阳性,TK基因与TS表达一致。转染组和对照组肿瘤细胞集落形成分别为：9／300、92／300。转染组瘤细胞集落形成率明显降低（t=33.885,P＜0．01）,癌细胞生长抑制率显著提高。对裸鼠移植瘤的生长抑制率为74．5％。在转染的外周血单个核细胞,p16表达阳性,TS、TK表达阴性。转染双启动子重组质粒对正常外周血单个核细胞无损伤作用。结论：TS和p16双启动子可引导TK基因靶向性杀伤5－FU耐药肿瘤细胞,保护肌体正常细胞,提高自杀基因治疗的安全性。     

丙型肝炎病毒p7蛋白上调去唾液酸糖蛋白受体1基因的表达

目的探讨HCVp7对去唾液酸糖蛋白受体1(ASGPR1)启动子转录的调节作用。方法据生物信息学确定ASGPR1的启动子区域,聚合酶链反应(PCR)扩增ASGPR1p,克隆至真核报告载体pCAT3-Basic中,构建pCAT3-ASG-PR1p报告载体;以该质粒转染肝癌细胞系HepG2,用酶联免疫吸附试验(ELISA)检测氯霉素乙酰转移酶(CAT)的表达活性;并与pcDNA3.1(-)-HCVp7共转染HepG2细胞系,用ELISA检测CAT的表达活性。结果成功获得ASGPR1p启动子的正确克隆。pCAT3-ASGPR1p和pcDNA3.1(-)-HCVp7共转染HepG2细胞的CAT表达活性是pCAT3-Basic空载体的7.7倍,是pCAT3-ASGPR1p的2.4倍。结论 ASGPR1启动子有顺式激活下游基因的活性,HCVp7对ASGPR1基因的表达有上调作用。     

MAT2A siRNA对荷瘤鼠肝癌细胞生长的影响

目的探讨MAT2A小干扰RNA对荷瘤鼠肝癌细胞生长和细胞凋亡的影响。方法采用脂质体转染法将MAT2A小干扰RNA质粒表达载体转染人肝癌细胞系Bel-7402细胞，建立持续转录小干扰RNA的细胞系，并将该细胞系皮下接种裸鼠，观察肿瘤生长情况；为进一步观察裸鼠体内抑瘤性，将皮下接种稳定表达小干扰RNA的Bel-7402细胞系的裸鼠分为三组：A、盐水对照组，B、空质粒对照组，C、siRNA治疗组；于接种后第12天，每组动物行纯化质粒DNA瘤内注射，观察肿瘤大小；治疗后2周，处死所有动物，取肿瘤，测量大小；部分石蜡包埋切片、HE染色，部分进行凋亡检测。结果得到稳定转染siRNA载体、并能持续表达siRNA的Bel-7402细胞系，将稳定建系的细胞传代，持续表达siRNA细胞系肿瘤细胞生长明显缓慢。皮下接种建系的Bel-7402细胞建立荷瘤鼠模型，可以观察到siRNA组肿瘤生长缓慢，平均第13天才长出皮下可及、但肉眼看不到的肿瘤，而接种control siRNA组，平均第9天可长出肉眼可见的肿瘤；用裸鼠肿瘤模型观察siRNA的体内抑瘤效果，质粒DNA注射后，对照组瘤体10．93mm^3，空质粒对照组为11．13mm^3，而siRNA质粒转染组为4．26mm^3（P〈0.01）；HE染色显示，对照组和空质粒组质粒DNA注射后，病灶充满肿瘤细胞；而siRNA组质粒DNA注射后，病灶内有大量炎性细胞浸润，坏死明显，仅见少量肿瘤细胞；且siRNA明显诱导荷瘤鼠肝癌细胞凋亡，其凋亡指数为（28．79±2．13）％，较盐水对照组（9．54±1．89）％和空质粒治疗组（10．24±2．06）％明显升高（t=15．41，P〈0．01）。结论靶向MAT2A基因的siRNA诱导荷瘤鼠肝癌细胞凋亡，抑制肝癌细胞生长。     

表达人端粒酶逆转录酶小干扰RNA的增殖腺病毒对肝癌细胞的抑制作用

目的 观察表达人端粒酶逆转录酶小干扰RNA(hTERT-siRNA)的增殖腺病毒(ZD-hTERT)对人肝癌Bel-7402细胞增殖及凋亡影响.方法 ZD-hTERT、增殖腺病毒ZD-EGFP、表达hTERT-siRNA的增殖缺陷腺病毒Ad-hTERT、增殖缺陷腺病毒Ad-EGFP分别感染人肝癌Bel-7402细胞.Western blot法检测ElA表达;逆转录-聚合酶链反应(RT-PCR)、Western blot法检测hTERT表达;噻唑蓝(MTT)比色法检测细胞存活;结晶紫染色法检测细胞毒作用;原位末端标记法(TUNEL)检测凋亡.结果 感染ZD-hTERT、ZD-EGFP的Bel-7402细胞表达ElA;抑制hTERT表达作用依次为ZD-hTERT>Ad-hTERT>ZD-EGFP>Ad-EGFP;抑制Bel-7402细胞生长及细胞毒作用依次为ZD-hTERT>ZD-EGFP=Ad-hTERT>Ad-EGFP.感染ZD-hTERT、ZD-EGFP、Ad-hTERT、Ad-EGFP的Bel-7402细胞凋亡率(%)分别为(88.1±2.2)、(39.2±2.1)、(42.1±5.1)、(7.5±2.1),ZD-hTERT诱导凋亡作用最高(P<0.01).结论 表达hTERT-siRNA的增殖腺病毒能显著抑制人肝癌Bel-7402细胞hTERT基因表达,进而抑制其增殖,促进其凋亡.     

腺病毒驱动KDR启动子介导CD/TK融合基因系统对肝癌细胞的靶向杀伤作用

目的 研究腺病毒介导的KDR启动子驱动CD/TK双自杀基因系统（AdKDR- CDglyTK）对肝癌细胞选择性杀伤作用。方法 将质粒pAdEasy-KDR-CDglyTK在293细胞内包装、扩增后，体外感染表达KDR的BEL-7402细胞株和对照组不表达KDR的LS174T细胞株，并给予不同浓度的前药5-FC和/或GCV，观察该体系对不同细胞株的杀伤效应及其旁观者效应。结果 所得病毒滴度为2.5×10^12pfu/ml。两种细胞的感染率相似，其感染率随腺病毒滴度的递增而增加。RT-PCR方法 检测发现：感染AdKDR-CDglyTK的BEL-7402有目的 基因CDglyTK的表达，感染AdKDR- CDglyTK的LS174T细胞无目的 基因表达。表达KDR的BEL-7402细胞对前药具有较高的敏感性，不表达KDR的LS174T细胞对前药不敏感（F=750.03，P〈0.001）。融合基因的疗效优于任一单自杀基因（F=275.89，P〈0.05）。将感染腺病毒的细胞与未感染细胞以不同比例混合培养，观察到该体系明显的旁观者效应。结论 KDR基因启动子可调控双自杀基因系统选择性杀伤表达KDR的肝癌细胞。     

上调miR-449a表达对肝癌细胞生长和侵袭能力的影响

目的:探讨miR-449a在肝癌(HCC)细胞中的表达及其对HCC细胞生物学行为的影响。方法:用qRT-PCR检测miR-449a在正常肝细胞L02和4种HCC细胞株(HepG2、Hep3B、SMMC-7721和Bel-7402)的表达。用脂质体法将miR-449a模拟物或阴性对照序列转染HCC细胞后,分别用CCK-8法、流式细胞术、Transwell小室实验检测细胞增殖、细胞周期、侵袭能力的变化,并观察以上两种不同转染的HCC细胞在裸鼠体内的成瘤情况。结果:miR-449a在4种HCC细胞株的表达水平均明显低于L02细胞(均P0.05),其中在Bel-7402细胞表达的水平最低。与转染阴性对照序列的Bel-7402细胞比较,转染miR-449a模拟物的Bel-7402细胞增殖活性明显降低、G_1/S期阻滞明显增加、穿室细胞数明显减少(均P0.05);与转染阴性对照序列的Bel-7402细胞比较,转染miR-449a模拟物的Bel-7402细胞在裸鼠体内成瘤后的移植瘤质量与体积均明显减小(0.748 g vs.1.234 g;33.667 mm~3 vs.1 400.500 mm~3,均P0.05)。结论:HCC细胞中miR-449a表达降低,上调miR-449a表达可以抑制HCC细胞在体内外的生长。     

Adenovirus mediated prostate specific enzyme prodrug gene therapy using prostate specific antigen promoter enhanced by the Cre-loxP system

PURPOSE: Tissue or tumor specific gene delivery is crucial for achieving successful results in suicide gene therapy. Prostate specific antigen (PSA) promoter is known to be highly specific in prostate tissue but its promoter activity is much weaker than that of constitutive viral promoters. In the current study we enhanced PSA promoter activity by combining it with the Cre-loxP system. We also applied this system to adenovirus mediated suicide gene therapy with the cytosine deaminase (CD) gene. MATERIALS AND METHODS: The Cre-loxP DNA recombination system was used to enhance PSA promoter. A plasmid with the PSA promoter-enhancer combination was constructed to drive Cre recombinase. Another plasmid contained the cytomegalovirus promoter-loxP-flanked stop signal-luciferase gene. LNCaP human prostate cancer cells were co-transfected with these 2 plasmids and luciferase activity was measured to assess promoter activities. Adenoviral vectors with the CD suicide gene were constructed in similar fashion and tested in LNCaP cells in in vitro/in vivo prostate cancer models. RESULTS: Promoter activity of the combined PSA promoter/enhancer and Cre-loxP system was 3 times stronger than that of PSA promoter/enhancer alone. It was further enhanced 7-fold in the presence of testosterone. Application of this system to CD suicide gene therapy by adenoviral vectors inhibited subcutaneous LNCaP tumor growth in nude mice. CONCLUSIONS: Combining the Cre-loxP system with PSA promoter/enhancer amplified promoter activity and was found to inhibit the growth of PSA producing prostate cancer cells in vivo.     

Suicide gene therapy on LNCaP human prostate cancer cells

The efficacy of combination suicide gene therapy was evaluated using a Herpes simplex virus-thymidine kinase/ganciclovir (HSV-TK/GCV) system and an Escherichia coli cytosine deaminase/5-fluorocytosine (CD/5-FC) system on the LNCaP human prostate cancer cell model. Two types of plasmid vectors with the HSV-TK gene were constructed. A constitutive chicken beta-actin promoter drove one and a prostate-specific antigen (PSA) promoter drove the other. Similarly, a pair of plasmids with the CD gene under a cytomegalovirus (CMV) promoter and the PSA promoter was also constructed. LNCaP cells were transfected in vitro with either or both of those plasmids using a cationic lipid reagent. Transfected cells were treated with GCV and/or 5-FC. The percentage of viable LNCaP cells 7 days after treatment with HSV-TK/GCV or CD/5-FC under a constitutive promoter was 40% and 41% of controls, respectively. The cell viability when two suicide genes were combined was 23%. The cell viabilities after four days with PSA promoter-HSV-TK vectors, CD vectors and a combination of both were 79%, 88% and 88%, respectively. Suicide gene therapy using either HSV-TK/GCV, CD/5-FC, or both, was effective in the LNCaP model. An additive effect was observed when the two suicide genes were used together. The PSA promoter did not seem to be effective enough to elicit cytotoxicity under the experimental conditions used here.     

Improved effects of a double suicide gene system on prostate cancer cells by targeted regulation of prostate-specific membrane antigen promoter and enhancer

Objective:   To explore the specific killing effect on prostate cancer cells of a dual cytosine deaminase (CD) and uracil phosphoribosyltransferase (UPRT) expression plasmid system controlled by the prostate-specific membrane antigen (PSMA) promoter and enhancer.
Methods:   The CD gene was used to construct the recombinant plasmid prostate-specific membrane antigen_{promoter/enhancer}-CD (pPSMA_E/P-CD). The specific regulatory function of the pPSMA_E/P promoter was demonstrated by detection of enhanced green fluorescent protein (EGFP) expression in the LNCaP cell line. Survival of cells transfected with different plasmids and treated with 5-fluorocytosine (5-FC) was measured by microculture tetrazolium assay. Cell cycle changes were measured by flow cytometry.
Results:   Target-specific expression of PSMA_E/P was observed in the prostate cancer cell line. Cytotoxicity of 5-FC was greater against LNCaP cells transfected with pPSMA_E/P-CD and UPRT and pPSMA_E/P-CD than control groups. Percentages of cells in S phase were 37.5% (LNCaP) and 30.6% (5-FC treatment) in the un-transfected groups, whereas they were 23.9% and 12.4% in the double and single suicide gene groups, respectively.
Conclusions:   Our findings confirm the cytotoxic efficacy of the pPSMA_E/P-CD + 5-FC and pPSMA_E/P-CD and UPRT + 5-FC suicide gene systems. The CD and UPRT gene system quickly and directly converted 5-FC into 5-FU, and then into toxic metabolites. The CD and UPRT double suicide gene system was more effective in inducing tumor cell apoptosis with 5-FC than the single suicide gene system. Thus, this construct can specifically target prostate cancer cells and might have a role in gene therapy against prostate cancer.