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Experimental Studies of Therapeutic Effect of Human Endostatin Gene Transferred into Human Liver Carcinoma Cells in Nude Mice

【Abstract】ObjectiveTo construct a recombinant eukaryotic expression vector for human endostatin in order to study the inhibitory effect of liposome-mediated endostatin gene on the growth of human liver carcinoma in nude mice. MethodsHuman endostatin cDNA including IL-2 secreting peptide was cloned into eukaryotic expression plasmid pcDNA3.0 to construct recombinant plasmid pCD-sEndo. pCD-sEndo plasmid was transferred into hepatocarcinoma cell line SMMC-7721 mediated by liposome Dosper, the expression and secretion of endostatin gene was detected by RTPCR and Western blot analysis. The suspension of SMMC-7721 cells was injected subcutaneously at the back of 32 nude mice to establish the model of human liver carcinoma. The mice were divided into 4 groups randomly, and injected with Dosper+pCD-sEndo, Dosper+pcDNA3.0, Dosper and physiological brine separately. Tumor volume was measured by stages. The mice were executed after the drug had been given for 1 week, then the microvessel density (MVD) of the tumor tissue was detected with immunohistochemical method and apoptotic index of tumor cells was measured by TUNEL-stain. ResultsThe eukaryotic expression vector pCD-sEndo was successfully constructed and was confirmed by enzyme digestion and sequence analysis. Expression of endostatin gene was detected in transfected SMMS-7721 cells by RTPCR in vitro, and endostatin protein was also detected in the supernatant of transfected SMMS-7721 cells by Western blot. In vivo study, the growth of human liver carcinoma was inhibited in the group injected with endostatin gene: the average volume of tumor in this group was significantly smaller than that in other groups （P＜0.05）; the average MVD in this group was 6.2±2.5, significantly less than that in the group injected with physiological brine (32.8±6.4), Dosper （27.8±6.4）, or Dosper+pcDNA3.0 (25.5±5.5), P＜0.05. The average apoptotic index of tumor cells in treatment group, brine group, Dosper group and Desper+pcDNA3.0 group was 24.5±7.3, 7.6±2.5, 9.5±3.0 and 11.2±3.6 respectively, it was evidently higher in the treatment group than in the latter three groups. ConclusionHuman endostatin mediated by cation liposome could decrease the microvessel number of implanted human hepatocarcinoma in nude mice. It could also accelerate apoptosis of tumor cells and inhibit growth of tumor.