以减毒沙门氏菌为载体的口服胞嘧啶脱氨酶基因治疗小鼠肿瘤

通过电转化法将真核表达载体EGFPN1和pLCDSN导入减毒鼠伤寒沙门氏菌SL3261中，经由胃管饲于C57BL／6和BALB／c小鼠。6周后接种Lewis和4T1肿瘤细胞，待种瘤增至直径为10mm左右，辅以‘腹腔注射5－氟胞嘧啶治疗。通过流式细胞仪、共聚焦显微镜和PCR等方法，在小鼠的肝脏、脾脏、小肠、肾脏、肿瘤等组织器官中均可检测到胞嘧啶脱氨酶基因的整合，绿色荧光蛋白在小鼠的脾脏和肿瘤中表达最强，其他组织表达甚弱，利用胞嘧啶脱氨酶／5－氟胞嘧啶系统进行治疗的小鼠肿瘤生长较其他组织显著受抑（P＜0.01),小鼠的生存期明显延长（P＜0.01)，未观察到明显的毒副作用。

Treatment of Tumor in Mice by Oral Administration of Cytosine Deaminase Gene Carried in Live Attenuated Salmonella

To study the possibility of oral gene therapy using live attenuated Salmonella , eukaryotic expression vectors EGFPN1, pLCDSN were introduced into a live attenuated AraA - auxotrophic mutant of Salmonella typhimurium (SL3261) and were administered orally to BALB/c and C57BL/6 mice. After six weeks, these mice were challenged with 4T 1 and Lewis cancer cells. Until the tumors reached to about 10 mm in diameter, 5 fluorocytosine was given through intraperitoneal injection. Flow cytometry, confocal microscopy and PCR methods were used to detect the integration and expression of the genes. The inhibition of the tumor and the survival time of the mice were also investigated. Results showed that cytosine deaminase gene integration could be detected in almost all kinds of mice tissue. And the GFP expression was much stronger in spleen and tumor than in other tissues. Cytosine deaminase/5 fluorocytosine system had significant antitumor activities in vivo . The antitumor activities of cytosine deaminase/5 fluorocytosine at 500 mg/kg on 4T 1 and Lewis carcinoma in BALB/c and C57BL/6 mice were more potent than the efficiency of 5 fluorouracil 10 mg/kg( P <0.05). Therefor, this experiment demonstrates the potential value of live attenuated Salmonella as carrier for oral gene therapy.