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The main mechanism of tumor suicide gene therapy or virus-divected enzyme/produrg therapy(VDEPT) is the introduction of suicide gene which come from virus or bacterial genome to tumor cell,that can make atoxic produrg fatal to tumor cell,kill these tumor cells transfected with suicide gene, and also kill the cells around them by bystander effect. cytosine deaminase(CD) gene is widely used in the suicide gene therapy of colon cancer liver metastasis,which make 5-FC to 5-FU,kill colon cancer cell effectually,and CD/5-FC associate with thermotherapy is more effective than CD/5-FC solitarily.But CD gene express itself in every cell,this can make nomal cell lethal, G1CEACDNa is a retrovirus vector which have CEA promoter(TRS),CD gene can express itself only in CEA positive colon cancer cell drived by CEA promoter,and this can make the nomal cell avoid being damaged,this can be certificated by our previousstudy, colon cancer cell LoVo transfected with G1CEACDNa is more effective than transfected with CD by 19 times.In the following study,we establish nude mice model of colon cancer liver metastasis with LoVo cell transfected with G1CEACDNa successfully,and to investigate the effectiveness of CD/5-FC thermochemotherapy in the nude mice model by intraperitoneal injection,and we find targeted suicide gene therapy associated with CD/5-FC thermochemotherapy can enhance the effect of 5-FC greatly.From this study,we found a new way in the suicide gene therapy of colon cancer liver metastasis.Plasmid G1CEACDNa were amplified in competence,and G1CEACDNa were extracted from bacteria by the means of plasmid alkaline; Plasmid G1CEACDNa were transfeced into human colon carcinoma LoVo cell through liposome technique, The cells were selectively cultured with 1mg/ml G418 until positive clones were obtained; Expression of G1CEACDNa in human colon carcinoma LoVo cell were analysed by RT-PCR.Fifteen nude mice were divided into 3 groups randomly,which were the introportal infusion group,spleen infusion group and Liver infusion group; and there were 5 nude mice in each group;colon carcinoma hepatic metastasis models were made by the means of introportal infusion,spleen infusion and Liver infusion respectively with LoVo cell,1×107 cell for each mice ,introportal infusion is a ideal way to make colon carcinoma hepatic metastasis model after 21 days of observation. sixty nude mice were divided into 4 groups randomly, which were the control group, thermotherapy grope,5-FC chemotherapy grope and 5-FC thermotherapy grope , and there were 15 nude mice in each group;colon carcinoma hepatic metastasis models were made by the means of introportal infusion with LoVo-CEACD cell,1×107 cell for each mice of all the gropes,and at the same time, The mice in the control group were injected NS into the peritoneal cavity,The mice in thermotherapy grope were were injected 43℃NS into the peritoneal cavity, The mice in the5-FC chemotherapy grope were injected 5-FC into the peritoneal cavity and the mice in the5-FC thermotherapy grope were injected 43℃5-FC into the peritoneal cavity,500mg/kg and 21days for each of the mice for all of the gropes, liver metastasis rate and the number of Iiver metastasis were the slightest for 5-FC thermotherapy grope after 21 days of observation; in common pathology, tumor cells were active, tumor giant cell and karyolobic cells were universal in control group,but in thermotherapy grope and 5-FC chemotherapy grope, tumor cells were rare, nucleus crimpled and disappeared, specifically for the 5-FC thermotherapy grope,there were no tumor cells, fibroblast cells, lymphocyte and eosinophile granulocyte can be seen everywhere;while in the transmission electron microscope(TEM), tumor cells were difformed, Karyomegaly and evident in nucleolus, there was no apoptotic body in control group;but in thermotherapy grope and 5-FC chemotherapy grope, tumor cells were condensed, karyopyknosis and karyorrhexis;especially for the 5-FC thermotherapy grope, there were apoptotic body everywhere. The expression of CD gene can be found in each group of the tumor tissue detected by RT-PCR. The main conclusions of the in vitro and in vivo experimental studies areas follows:1.Plasmid G1CEACDNa was transfected into human colon carcinoma LoVo cell through liposome technique successfully,and can express themselves in LoVo cell 2.Thermochemotherapy combined with CD/5-FC system has specific effect on liver metastasis of colon carcinoma 3.Colon carcinoma hepatic metastasis models can be more successfully made bythe means of introportal infusion than other means 4.CD gene can express itself in the tissue of colon carcinoma hepatic metastasis successfully and stably.
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