目的：探讨胞嘧啶脱氨酶基因对胃癌细胞的杀伤作用。方法：应用胞嘧啶脱氨酶（ＣＤ）基因，通过逆转录病毒载体转入人胃癌细胞Ｍ８５中，经０．４ ｍ ｇ／ｍ ｌ的Ｇ４１８筛选阳性克隆的Ｍ８５细胞产生杀伤作用同时，还对与其共培养的亲代Ｍ８５细胞产生明显的杀伤作用，即“旁观者效应”。进一步将转基因Ｍ８５细胞和未转基因Ｍ８５细胞接种至裸鼠皮下，发现两者成瘤性无明显差异；前药５－ＦＣ对未转基因肿瘤的生长无影响，而对转基因肿瘤的生长明显抑制。结论：本研究为ＣＤ基因治疗胃癌向临床过渡提供了依据。 Objective: To investigate the killing effect of cytosine deaminase gene on gastric cancer cells. METHODS: CD gene was used to transform into human gastric cancer cell M85 by retroviral vector. The positive clone M85 cells were screened by G418 at 0.4 m g/ml for killing effect. The co-cultured parental M85 cells produced a marked killing effect, a “bystander effect.” Further, transgenic M85 cells and non-transgenic M85 cells were inoculated subcutaneously into nude mice and no significant difference in tumorigenicity was found between the two groups; 5-FC, a prodrug, had no effect on the growth of untransformed tumors but significantly inhibited the growth of transgenic tumors. Conclusion: This study provides a basis for CD gene therapy to clinical transition to gastric cancer.