目的 研究bcl-xS基因对体内大肠癌细胞生长的影响及作用机制。方法 将bcl-xS基因稳定转染的人大肠癌LoVo细胞接种于裸鼠体内并使其生长，然后取移植瘤标本原位末段标记并进行电镜观察，同时将neo基因转染的及未经转染的LoVo细胞分别接种于裸鼠体内，作为对照。结果 经bcl-xS转染的LoVo细胞移植瘤有明显的散在或成团的凋亡细胞，而经neo转染的LoVo细胞则无明显的细胞凋亡。结论 本研究结果提示bcl-xS基因在体内有诱导细胞凋亡的作用。 Objective To study the effect of bcl-xS gene on the growth of colorectal cancer cells in vivo and its mechanism. Methods The human colorectal cancer LoVo cells stably transfected with bcl-xS gene were inoculated into nude mice and allowed to grow. Then the transplanted tumor samples were stained with electron microscopy and the neo gene was transfected with or without Transfected LoVo cells were inoculated into nude mice respectively and served as controls. Results LoVo cells transplanted with bcl-xS had obvious scattered or agglutinated apoptotic cells, while neo-transfected LoVo cells showed no obvious apoptosis. Conclusion The results of this study suggest that bcl-xS gene can induce apoptosis in vivo.