Construction and Biological Effects in vitro of Double－Directed Tissue－Specific HSV－tk／GCV Anti－Tumor System

Objective: To construct a specifically targeted gene delivery and expression system, and to investigate the special killing effect of the HSV-tk/GCV system on human liver cancer cells in vitro.Methods: The anti-transferrin receptor (TfR) ScFv-GAL4 fusion protein expression vector ScFv-GAL4-pET28a and the eukaryotic expression plasmid pEBAF/tk-GAL4rec were constructed by recombinant DNA technology. After the induction by IPTG, we obtained the anti-TfR ScFv-GAL4 fusion protein as delivery vector to transfect pEBAF/tk-GAL4rec into the human liver cancer cell lines HepG2 and SMMC7721 and the human lung cancer cell line A549 that overexpress TfR via receptor-mediated endocytosis. The positive cell clones were selected by hygromycin and named HepG2/tk, SMMC7721/tk and A549/tk,respectively. Cell killing after GCV application was determined by MTT. Results: The correct structure of the ScFv-Gal4 fusion protein and the plasmid pEBAF/tk-GAL4rec was confirmed by double enzyme digestion, SDS-PAGE and sequencing. HepG2/tk cells that express alphafetoprotein (AFP) to high levels(845 ng/ml) were very sensitive to GCV, while SMMC7721/tk cells that express AFP at low levels (2ng/ml) and AFP-negative A549/tk cells were only slightly or not sensitive to GCV. Conclusion: The double-directed and tissue-specific HSV-tk/GCV anti-tumor system shows good targeting to tumor cells.     

靶动脉灌注NaHCO3提高部分抗肿瘤药物疗效的基础及临床研究

Objective: To observe the influence of pH value on the proliferation of LAK cells and on the killing effect of rIL-2,IFN-α2b, TNF-α, LAK cells and doxorubicin on malignant tumor cells, and investigate the possibility of increasing the efficacy of rIL-2 or IFN-α2b and doxorubicin by infusing sodium bicarbonate (NaHCO3) through target arteries. Methods: Separating single nucleus cells from peripheral blood of healthy men, and observing the influence of pH on the activation of single nucleus cells by rIL-2. MTT assay was used to measure the killing effect of rIL-2, IFN-α2b and TNF-α on 7404 cells and the increased effect of doxorubicin on rIL-2 and IFN-α2b, the cytotoxity of LAK cells in different pH. Forty-two patients with advanced primary liver cancer were obtained by stratified random, NaHCO3, rIL-2/IFN-α2b and doxorubicin were infused through target arteries. The efficacy was estimated after two cycles. Results: The conditions of pH 7.3 and pH 7.6 in vitro helped the proliferation of LAK cells and the killing effect of rIL-2, IFN-α2b and LAK cells on 7404 cells. In the condition of pH 6.8 there was almost no killing effect for LAK cells. In the condition of pH 7.0, 7.2, 7.4 and 7.6, the killing rate of TNF-α to 7404 cells increased by degrees, and in pH 7.4 the killing effect was the optimum. After two cycles treatments in the 42 patients with advanced primary liver cancer,the response rate (CR PR) was 88% (37/42). The median overall response and median overall survival were increased, and no complication associated with infusing sodium bicarbonate was observed. Conclusion: The killing effect of rIL-2, IFN-α2b, TNF-αand doxorubicin on malignant tumor cells was enhanced by increasing the pH value.     

Study of Multi-directional Derivation of Cord Blood Mononuclear Cells and Observation of Killing Activity to MGC-803 Gastric Cancer Cell Strain In Vitro

Objective： To study multi-directional derivation of cord blood mononuclear cells to CD3AK, LAK and CIK cells as well as changes of killing activity to gastric cancer cell strain in vitro. Methods： CD3mAb and IL-2 were used to induce CD3AK cells, and IL-2 was used to induce LAK cells; IFN-γ was used in the beginning, then IL-1, CD3mAb and IL-2 were used to induce CIK cells after 24 h for observing amplification and analyzing their relationship. The phenotypes of the cultured CIK cells were analyzed by flow cytometry. Subsequently, by using MGC-803 gastric cancer cell strain as target cells, the killing activity of CD3AK, LAK and CIK cells was evaluated by using MTT method. Results： The amplification activity of CD3AK and CIK cells was all far higher than LAK cells （P〈0.05）. The amplification activity had no obvious difference between CIK cells and CD3AK cells at prophase, but that was far higher in CIK cells than CD3AK cells at about 20^th day （P〈0.05）. The flow cytometry revealed that the amount of CD3^＋ CD56^＋ cells, major effector cells after CIK cells being cultured was significantly increased （P〈0.05）, moreover, the amount of CD8^＋ cells was significantly increased as well （P〈0.05）. The killing activities of CD3AK and CIK cells to the MGC-803 gastric cancer cell strain were all significantly higher than LAK cells, while the killing activity of CIK cells was stronger than CD3AK cells （P〈0.05）. Conclusion： CIK cells have stronger amplification activity and killing activity, and can be taken as more effective killing cells applied to the tumor adoptive immunotherapy.     

荷CEA-rV的DC增强CD3AK对CEA阳性肿瘤特异性杀伤作用的研究

Objective： To survey the special killing activity of CD3AK on anti-CEA-positive tumor enhanced by umbilical cord blood dendritic cell （DC） loaded with CEA recombinant vaccinia virus （CEA-rV）. Methods： Freshly isolated umbilical blood mononuclear calls （UBMC） were cultivated for 3 h. Suspension cells and attached calls were used to induce CD3AK calls and DC separately. DC was loaded with CEA-rV on the 3rd day to prepare CEA-rV＋DC. CD3AK cells were co-cultured with CEA- rV＋DC on the 8th day, to prepare CEA-rV＋DC＋CD3AK. The killing activity of each effector＇s cell, which included UBMC, CD3AK, DC＋CD3AK and CEA-rV＋DC＋CD3AK, was measured respectively by MTT reduction assay. Results： （1） 4 target cells were con- firmed by CEA monoclonal antibody of rabbit anti-human. Lovo and A549 were really CEA positive cell lines, while Bel-7402 and K562 were CEA negative cell lines. （2） It was showed by flow-cytometry that the mature DC cultured at 10th day expressed MHC I, II molecules such as CD86, CDS0, CD83 and CD40 highly, but CD123 lowly. The expression rates of CD86, CDS0, CD83 and CD40 was 82.7%, 51.1%, 57.5% and 69.4%, respectively. The appearances and intra-cellular structures of DC were observed through light and electron microscope. The diameter of mature DC was 15-20 μm presented the irregular morphologic appearanca, much prominences and pseudopodium. There were abundant mitochondria and endoplasmic reticulum in DC endochylema. （3） The rates of CD3, CD4, CD8 and CD28 in CD3AK cells group were 2 folds higher than that in UBMC group by FACS. It was said that the numbers of the mature T lymphocyte in CD3AK cells group were much greater than that in UBMC group. （4） The killing activities to 4 target cells of 3 effector＇s cells, which included CEA-rV＋DC＋CD3AK, DC＋CD3AK and CD3AK, were much greater than that of UBMC （P〈0.01）. Moreover, comparing with the killing activities of 4 effector＇s： CEA-rV＋DC＋CD3AK group 〉 DC＋CD3AK group 〉 CD3AK group 〉 UBMC group. It showed that, cytokine, DC and CEA-rV could efficiently elevate the killing activity of UBMC on broad-spectrum tumor cells. （5） Comparing with the killing activities of CEA-rV＋DC＋CD3AK and CD3AK cells to CEA positive and negative cells, the killing activities of CEA-rV＋DC＋CD3AK to CEA positive tumor calls, Lovo and A549 calls （P〈0.01） were remarkably better than that to CEA negative tumor cells BEL-7402 and K562 cells （P〈0.05）. It was said that the CEA-rV＋DC could obviously enhance the killing activity of CD3AK on CEA positive tumor cells. Comparing with the killing activities of CEA-rV＋DC＋CD3AK and DC＋CD3AK cells, the killing activity of CD3AK on CEA negative tumor cells was no statistical difference （P〉0.05）. However, the killing activity to CEA positive cells of CEA-rV＋DC＋CD3AK group was notably higher than that of DC＋CD3AK group. Namely, CEA-rV could distinctly promote the special killing activity to CEA positive tumor cells of CD3AK, but could not do it to CEA negative tumor cells. Conclusion： CEA-rV＋DC could obviously enhance the special killing activity of CD3AK on CEA positive tumor cell lines, while the DC only couldn＇t. The results indicated that the CEA-rV played an important role during the special killing activity of CD3AK cells to CEA positive tumor cells.     

Anti-Tumor Effect of Curcumin on Human Cervical Carcinoma HeLa Cells In Vitro and In Vivo

Objective: To investigate the anti-tumor effect of curcumin on human cervical carcinoma HeLa cells in vitro and in vivo. Methods: (1) Human cervical carcinoma cell line HeLa was cultured in vitro. HeLa cells were treated with 5-50 μmol/L curcumin for 24. 48, 72 h and the growth inhibition rates of HeLa cells were measured by MTT method. Cell apoptosis was inspected by electron microscopy and flow cytometry (FCM). (2) A transplanted tumor model by injecting HeLa cells into subcutaneous tissue of BABL/C mice was established and its growth curve was measured. 30 BABL/C mice with tumors were divided into 2 groups at random and 0.2 ml saline or 0.2 ml 250 μmol/L curcumin was injected into abdominal cavity respectively once everyday and lasted for ten days. The changes of tumor volume were measured continuously and tumor inhibition rate was calculated. At last the expressions of caspase-3 and bax protein in transplanted tumors were detected by immunohistochemistry. Results: (1) Curcumin inhibited the proliferation of Lela cells on a dose-depending manner. Apoptosis of cells could be observed by FCM. Partial cells presented the characteristic morphological changes of apoptosis under electron microseope. (2) When 1×107 HeLa cells were inoculated for each mouse, 100% of the mice developed growing tumors after seven days. An inhibition effect was observed in treatment group, and the inhibition rate of curcumin was 74.33%. The expressions of caspase-3 and bax in the transplanted tumors were increased in curcumin group. Conclusion: Curcumin is effective as an anti-cancer drug not only in vitro but also in vivo.     

Experiment studies of antitumor proliferation and metastasis of a new chinese herb AT-1

Objective: To study the effects of a new Chinese herb AT-1 on the tumor cell proliferation and metastasis in vitro.Methods: Tumor cell proliferation activity was tested by MTT. The ability of tumor cell invasion and migration was assayed by counting the number of tumor cells going throw matrigel. The expression changes of CD44 genes in PG cells treated with AT-1 were tested by FACS. Results:Compared with the control, the proliferation activity of the cells treated with the At-1 was restrained. The invasion and migration ability of PG cells and the expression of the cell adherence related gene CD44 was decreased treatment with AT-1. Conclusion: AT-1 is a new antitumor proliferation and metastasis agent. Its antitumor metastasis effect might be achieved by decreasing the expression of the cell adherence-associate gene CD44.     

Evaluation of miR-122-regulated suicide gene therapy for hepatocellular carcinoma in an orthotopic mouse model

Objective： Intratumoral administration of adenoviral vector encoding herpes simplex virus （HSV） thymidine kinase （TK） gene （Ad-TK） followed by systemic ganciclovir （GCV） is an effective approach in treating experimental hepatocellular carcinoma （HCC）. However, hepatotoxicity due to unwanted vector spread and suicide gene expression limited the application of this therapy, miR-122 is an abundant, liver-specific microRNA whose expression is decreased in human primary HCC and HCC-derived cell lines. These different expression profiles provide an opportunity to induce tumor-specific gene expression by miR-122 regulation. Methods： By inserting miR-122 target sequences （miR-122T） in the 3＇ untranslated region （UTR） ofTK gene, we constructed adenovirus （Ad） vectors expressing miR-122-regulated TK （Ad-TK-122T） and report genes. After intratumoral administration of Ad vectors into an orthotopic miR-122-deficient HCC mouse model, we observed the miR-122-regulated transgene expression and assessed the antitumor activity and safety of Ad-TK-122T. Results： Insertion of miR-122T specifically down-regulated transgene expression in vitro and selectively protected the miR-122-positive cells from killing by TK/GCV treatment. Insertion of miR-122T led to significant reduction of tansgene expression in the liver without inhibition of its expression in tumors in vivo, resulting in an 11-fold improvement of tumor-specific transgene expression. Intratumoral injection of Ad vectors mediated TK/GCV system led to a vector dosage-dependent regression of tumor. The insertion of miR-122T does not influence the antitumor effects of suicide gene therapy. Whereas mice administrated with Ad-TK showed severe lethal hepatotoxicity at the effective therapeutic dose, no liver damage was found in Ad-TK-122T group. Conclusions： miR-122-regulated TK expression achieved effective anti-tumor effects and increased the safety of intratumoral delivery of adenovirus-mediated TK/GCV gene therapy for miR-122-deficient HCC.     

INVESTIGATION OF THE THERAPEUTIC EFFECT OF EXPRESSION OF TRAIL IN VIVO ON MOUSE HEPATOCELLULAR CARCINOMA

Objective: To construct an eukaryotic expressing plasmid of mouse TRAIL (mTRAIL), and investigate its ability to induce the apoptosis of hepatocellular carcinoma cells in vitro and in vivo, its inhibitory effect on the growth of hepatocellular carcinoma, and its synergism with pCH510, an eukaryotic expressing plasmid of recombinant human FN polypeptide.Methods: The eukaryotic expressing plasmid of mTRAIL was constructed by RT-PCR and DNA recombination techniques. Gene transfection was performed in vitro and in vivo. The apoptosis rate of hepatocellular carcinoma cells was measured by Flow Cytometry. The apoptosis of hepatocellular carcinoma cells was measured by Flow Cytometry.The apoptosis of hepatocellular carcinoma cells was detected by TdT-mediated dUTP nick end labeling (TUNEL) and histochemistry techniques. The inhibitory effect of gene transfection on solid tumor was observed in mice. Results: The cDNA of mTRAIL was amplified by RT-PCR from the RNA of mouse spleen cells, and cloned into the eukaryotic expressing vector pcDNA3.1. The recombinant plasmid was designated as pX1. The BHK cells transfected with plasmid pX1 could attack H22 hepatocellular carcinoma cells and induce the apoptosis of them. The transfection of plasmid pX1 through injection into mouse muscles could inhibit the growth of hepatocellular carcinoma by inducing the apoptosis of tumor cells. Plasmid pX1 and pCH510 had a synergistic inhibitory effect on the hepatocellular carcinoma growth. Conclusion: Plamid pX1 could be expressed in cells and in vivo in mouse. The expression of pX1 in vivo and in vitro could induce the apoptosis of hepatocellular carcinoma ceils and inhibit the growth of hepatocellular carcinoma. Plasmid pX1 and pCH510 had a synergistic inhibitory effect on the hepatocellular carcinoma growth.     

肿瘤坏死因子相关的凋亡诱导配体对胰腺癌细胞抗肿瘤作用的研究

Objective To investigate the antitumor effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)gene transfection mediated by adenovirus into human pancreatic carcinoma cell line Panc-1, and the mechanisms involved in this effect. Methods TRAIL gene was transfected into pancreatic cancer cell line Panc-1 by an adenovirus vector (Ad-TRAIL).Level of TRAIL mRNA expression was determined using RT-PCR, and TRAIL protein synthesis was evaluated with Western blot. Cell-growth activities were determined by MTT assay. The bystander effect was observed by co-culturing the Panc-1cells with the transfected TRAIL gene at different ratios. Apoptosis in pancreatic cancer cells was detected by flow cytometry.Procaspase-8 and procaspase-3 were determined by Western blot. Results The stable overexpression of TRAIL was detected in Panc-1 cells transfected by Ad-TRAIL. Ad-TRAIL significantly inhibited of cell viability of Panc-1 cells. Furthermore,co-culture of cancer cells transfected with TRAIL with that nontransfected resulted in the cell death of both cells by bystander effect. Moreover, the percentage of apoptotic cells was significantly higher in the Ad-TRAIL-treatment group compared to the control groups (P ＜ 0.01). And there was a diminished amount of procaspase-8 and procaspase-3 after infection with Ad-TRAIL. Conclusion The overexpression of TRAIL gene in Panc-1 cells by Ad-TRAIL exerts its antitumor effects, and themechanisms involved in this effect may be proapoptosis and bystander effect.     

Stimulation of intercellular communication of poor-communicating cells by gap-junction-competent cells enhances the HSV-TK/GCV bystander effect in vitro

We have previously shown that gap-junctional intercellular communication (GJIC) appears to play a role in the bystander effect that is observed in anticancer suicide gene therapy mediated by herpes simplex virus (HSV) thymidine kinase (tk) and ganciclovir (GCV). We now report that when connexin-expressing (Cx+) cells are present within a noncommunicating population of cells (Cx-), there is GJIC between the Cx+ and Cx- cells and that due to this stimulation of GJIC, the bystander effect also occurs when the 2 cell types are mixed. We transfected HeLa cells, which do not express any detectable level of connexin, with Cx43. The Cx+ and Cx- HeLa cells were further transfected with the tk gene, giving 4 phenotypes: Cx+tk-, Cx+tk+, Cx-tk+ and Cx-tk-. We observed GJIC between Cx+ and Cx- cells, but not between Cx- and Cx- cells, regardless of the tk genotype. Similarly, we observed the HSV-tk/GCV bystander effect in Cx+tk-/Cx-tk+ and Cx+tk+/Cx-tk- cocultures. The extent of the bystander effect in cocultures of Cx+tk- and Cx-tk+ cells was stronger than in cocultures of Cx+tk+ and Cx-tk- cells when each mixture had the same ratio of Cx+ and tk+ cells. These results suggest that Cx-expressing HeLa cells stimulate GJIC capacity between them and non-Cx-expressing HeLa cells, which mediates the bystander effect in mixtures of Cx+ cells and Cx- cells in vitro. Thus, Cx expression even in only a limited fraction of tumor cells may enhance the efficacy of the HSV-tk/GCV strategy by inducing a bystander effect.     

双自杀基因对Raji淋巴瘤细胞杀伤的增强作用

目的 :观察反转录病毒介导的双自杀基因对 Raji淋巴瘤细胞的杀伤增强作用 ,探讨淋巴瘤的基因治疗方法。方法 :通过脂质体将含有双自杀基因的反转录病毒载体 p WZL neo CDglytk导入病毒包装细胞 PA317,经 G4 18筛选后大量培养产病毒的阳性克隆 PA317/ CD+ tk细胞株 ,收集病毒上清 ,浓缩后转染 Raji淋巴瘤细胞 ,再次经 G4 18筛选 ,获得稳定表达双自杀基因的 Raji/ CD+ tk细胞株。用RT- PCR检测双自杀基因的表达。给予前体药物 5 -氟胞嘧啶 (5 - flourocytosine,5 - FC)和 /或无环鸟苷(Ganciciovir,GCV)后 ,MTT法测定细胞的存活率及 CDglytk双自杀基因对 Raji细胞的杀伤作用。结果 :双自杀基因在 Raji细胞中可稳定表达 ,联合使用 5 - FC和 GCV时 Raji细胞的存活率 (13.83% )明显低于单独使用 GCV (5 0 .6 5 % )或 5 - FC(5 7.6 8% )时 ,各组比差异具有显著性 (P<0 .0 1)。结论 :反转录病毒介导双自杀基因对 Raji淋巴瘤的杀伤作用明显增强     

逆转录病毒介导的双自杀基因对K562细胞杀伤作用的实验研究

目的 :观察逆转录病毒介导的双自杀基因对K5 6 2细胞的杀伤作用 ,探讨慢性粒细胞白血病的基因治疗方法。方法 :通过脂质体将含有双自杀基因的逆转录病毒载体PWZLneoCDglytk导入包装细胞PA317,经G4 18筛选后大量培养产病毒的阳性克隆PA317 CD +tk细胞株 ,收集病毒上清 ,浓缩后转染K5 6 2细胞 ,再次经G4 18筛选 ,获得稳定表达双自杀基因的K5 6 2 CD +tk细胞株。用RT PCR检测双自杀基因的表达。给予前体药物 5 氟胞嘧啶 (5 flourocytosine ,5 FC)和 或无环鸟苷 (Ganciciovir,GCV)后MTT法测定转基因组及未转基因组K5 6 2细胞的存活率。结果 :双自杀基因在K5 6 2细胞中可稳定表达 ,联合使用 5 FC和GCV对细胞增殖的杀伤作用及旁杀伤效应高于单独使用 5 FC或GCV。结论 :逆转录病毒介导自杀基因可有效杀死K5 6 2细胞 ,双自杀基因较单一自杀基因具有更强的抗肿瘤作用     

逆转录病毒介导的双自杀基因对淋巴瘤细胞的杀伤作用研究

目的 观察逆转录病毒介导的双自杀基因对淋巴瘤细胞的杀伤作用，探讨淋巴瘤的基因治疗方法。方法 在脂质体的介导下将含有双自杀基因的逆转录病毒载体pWZLneoCDglytk导入包装细胞PA317，经G418筛选后大量培养产病毒的阳性克隆PA317／CD tk细胞株，收集病毒上清，浓缩后转染Raji淋巴瘤细胞，再次经G418筛选，获得稳定表达双自杀基因的Raji/CD tk细胞株。采用RT-PCR法检测双自杀基因的表达。MTT法测定转基因组及末转基因组Raji细胞的存活率。结果 双自杀基因在Raji细胞中可稳定表达，联合使用5-氟胞咳暖(5-FC)和无环鸟苷(QCV)对细胞增殖的杀伤作用及旁杀伤效应高于单独使用5-FC或GCV。结论 逆转录病毒介导双自杀基因较单一自杀基因具有更强的杀伤作用。     

HSVtk/GCV自杀基因系统治疗小鼠腹水瘤的研究

目的:研究HSVtk/GCV系统对腹水瘤的治疗作用.方法:采用XTT、动物实验、透射电镜和流式细胞仪等方法.结果:HSVtk( )的P388tk细胞对GCV的敏感性约为其亲本P388细胞的37倍,且对其邻近的HSVtk(-)的P388细胞或S细胞具有旁观者效应,当P388tk细胞与P388细胞或S细胞混合培养,5μg/ml GCV处理后,P388tk细胞占混合细胞的10%,就可杀伤50%的混合细胞.动物实验中P388tk细胞或P388tk与P388细胞等量混合所致的荷瘤鼠在以CCV治疗后与对照组相比,肿瘤生长受到明显抑制,小鼠生存期明显延长;细胞死亡的机制与凋亡有关.结论:在体内和体外水平,HSVtk( )的P388tk细胞能被GCV有效杀伤,且对其邻近的HSVtk(-)的细胞产生旁观者效应.     

CD基因联合 5-Fc治疗人胃癌的实验研究

目的：通过 转基因方法观察自杀基因CD对人胃癌细胞株7901的体内外 杀伤作用,并观察组织病理变化。方法：应用逆转录病毒方法转导自杀基因CD,通过体外实验观察CD 基因对人胃癌7901细胞的杀伤性和旁观者效应;体内实验中首先在BALB／cnu/nu裸鼠建立胃癌模型,然后将病毒上清注入瘤体内,并结合应用前药,观察肿上瘤体积变化,通过病理切片观察组织病理变化。结果：CD基因在外外即显出明显的杀伤作用（含旁观者效应）,20％的转基因细胞可以杀伤70％－80％的肿瘤细胞。在实验动物体内,CD基因结合前药5－Fc可显著杀伤肿瘤,而单纯转导CD基因和只用5－Fc并不能起到杀伤作用。结论：自杀基因CD联合前药5－Fc对胃癌产生显著杀伤作用,不仅转基因细胞被杀死,而且通过旁观者效应杀伤大量周围细胞。CD／5－Fe在体内试验对胃癌有显著杀伤作用。     

A STUDY ON THE TREATMENT OF GASTRIC CANCER BY CD GENE COMBINED WITH 5-FC IN VITRO AND IN VIVO

Gastric cancer is one of the most frequentlyoccurring carcinoma in China. The effect of currentmethods such as surgical, radiotherapeutic andchemotherapeutic treatment against middle stage and advanced gastric cancer is not satisfactory. The gene therapy started a new way to the treatment of malignant diseases. The enzyme/prodrug system that increases the drug sensitivity of tumor cells has emerged as an effective method of selective elimination of tumor cells. This kind of drug sensitive ge…     

The role of cellular- and prodrug-associated factors in the bystander effect induced by the Varicella zoster and Herpes simplex viral thymidine kinases in suicide gene therapy

To investigate the factors influencing the bystander effect--a key element in the efficacy of suicide gene therapy against cancer--we compared the effect triggered by four extremely efficient gene/prodrug combinations, i.e., VZVtk/BVDU, the thymidine kinase of Varicella zoster virus associated with (E)-5-(2-bromovinyl)-2'-deoxyuridine; VZVtk/BVaraU, the same enzyme associated with (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil; HSVtk/BVDU, the association of the Herpes simplex virus thymidine kinase with BVDU; and the classical HSVtk/GCV (ganciclovir) paradigm. The cells used, the human MDA-MB-435 breast cancer, and the rat 9L glioblastoma lines were equally sensitive in vitro to these four associations. In both cell types, the combinations involving pyrimidine analogues (BVDU, BVaraU) displayed a smaller bystander killing than the combination involving the purine analogue (GCV). In addition, the bystander effect induced by all the tk/prodrug systems was reduced in MDA-MB-435 cells in comparison to 9L cells; albeit, the viral kinases were produced at a higher level in the breast cancer cells. All systems induced apoptotic death in the two cell types, but the MDA-MB-435 cells, deprived of connexin 43, were noncommunicating in striking contrast with the 9L cells. That functional gap junctions have to be increased in order to improve the breast cancer cell response to suicide gene therapy was demonstrated by transducing the Cx43 gene: this modification enhanced the bystander effect associated in vitro with GCV treatment and, by itself, decreased the tumorigenicity of the untreated cells. However, the noncommunicating MDA-MB-435 cells triggered a significant bystander effect both in vitro and in vivo with the HSVtk/GCV system, showing that communication through gap junctions is not the only mechanism involved.     

阳离子脂质体介导pE-CEA-cd-tk对CEA阳性肺癌的杀伤作用

目的：增强E.coli cd/HSV-1 tk自杀基因的细胞毒性，实现阳离子脂质体介导pE-CEA-cd-tk/5-FC GCV体系靶向杀伤CEA阳性肺癌，方法：PCR法分别扩增出CMV增强子，CWA启动子，cd-tk，构建真核表达载体pE-CEA-cd-tk;MTT法检测pE-CEA-cd-tk/5-FC GCV体系的体外细胞毒性，体内实验采用肺腺癌细胞SPC－A－1裸鼠皮下移植瘤模型，通过肿瘤局部或鼠尾静脉注射脂质体／pE-CEA-cd-tk复合物，腹腔注射GCV＋5－FC前体药物进行治疗。结果：阳离子脂质体介导pE-CEA-cd-tk/5-FC GCV体系体外可靶向杀伤CEA阳性肺癌细胞，这种杀伤作用存在显著的细胞差异；体内可抑制小鼠皮下肺肿瘤结节的生长，荷瘤鼠存活期延长。结论：阳离子脂质体介导pE-CEA-cd-tk/5-FC GCV体系体内外对CEA阳性肺癌均具有较强的杀伤作用，有望用于CEA阳性肺癌的治疗。     

大肠杆菌胞嘧啶脱氨基酶基因联合5—氟胞嘧啶治疗胃癌的实验研究

目的 观察自杀基因CD对小鼠胃癌的体内外杀伤作用及组织病理变化。方法 应用逆转录病毒方法转导自杀基因CD,通过体外实验观察CD基因对小鼠胃癌MFC细胞的杀伤性和旁观者效应;体内实验中首先在615小鼠建立胃癌模型,然后分组将病毒上清注入瘤体内,并应用前药（5－氟胞嘧啶,5－Fc),观察对肿瘤的杀伤作用及组织病理变化。结果 CD基因在体外即显出明显的杀伤作用,20％的转基因细胞可以杀伤70％－80％以上的肿瘤细胞。体内实验表明CD基因结合前药5－Fc可显著杀伤肿瘤,而单纯转导CD基因或应用5－Fc可显著杀伤肿瘤,而单纯转导CD基因或应用5－Fc并不能起到杀伤作用。结论 自杀基因CD联合前药5－Fc对体内外小鼠胃癌细胞产生显著杀伤作用,不仅转基因细胞被杀死,而且通过旁观者效应杀伤大量周围细胞。