胞嘧啶脱氨酶对表达不同水平癌胚抗原的大肠癌细胞株的杀伤作用

Targeting Antitumor Effect of Cytosine Deaminase Gene on Human Colon Carcinoma Implanted in the Nude Mice.

目的:探讨特异性胞嘧啶脱氨基酶(cytosine deaminase,CD)/5-氟胞嘧啶(5-fluorocytosine,5-FC)系统对表达不同水平癌胚抗原(CEA)的大肠癌细胞株的选择性杀伤作用。方法:用脂质体法将逆转录病毒载体G1CEACDNa和pCD2分别转导入大肠癌LoVo和SW480细胞株。将转染成功pCD2、G1CEACDNa及未转基因之LoVo和SW480细胞分别接种到BALB/c裸鼠皮下。成瘤2周后,每天腹腔注射500mg/kg的5-FC,观察治疗效果。治疗21d后处死动物,肿瘤标本称重后,以RT-PCR法检测目的基因在肿瘤组织中的表达;显微镜下观察肿瘤病理学变化。结果:目的基因在肿瘤组织中获稳定表达。治疗21d后,在LoVo细胞肿瘤中,G1CEACDNa阳性组和pCD2阳性组肿瘤分别重(60.8±15.3)mg和(410.5±56.3)mg,与未转基因组[(3018.5±453.5)mg]比较均有明显差异(p<0.01,t=4.512; P<0.01,t=3.320);G1CEACDNa阳性组与pCD2阳性组比较,亦有显著差异(P<0.05,t=2.375)。在SW480肿瘤细胞中,G1CEACDNa阳性组和pCD2基因阳性组肿瘤分别重(356.5±23.5)mg和(463.5±56.9)mg,与对照组[(3263.5±450.6)mg]比较有显著差异(P<0.01,t=4.547;P<0.01,t=4.475),但G1CEACDNa阳性组与pCD2基因阳性组之间无明显差异(P>0.05)。

Objective: To investigate the targeting antitumor effect of cytosine deaminase(CD)/5-fluorocytosine(5-FC) system on human colorectal carcinoma implanted in the nude mice. Methods: Recombinant retroviral vector GlCEACDNa and retroviral vector pCD2 were introduced separately by way of the lipofectamine technique in the human colorectal carcinoma cell lines LoVo(high CEA expression) and SW480(low CEA expression) respectively. 5×106 parental cells and the cells transfected with pCD2 retroviral vector and G1CEACDNa retroviral vector were injected subcutaneously into the flank of BALB/c nude mice respectively. 500 mg/kg 5-FC were given ip. daily for 21 days when the tumors became palp able. All the mice were sacrificed by the end of the treatment. RT-PCR was then performed to detect the expression of targeted gene in carcinomatous tissue and pathological study was made. Results: The targeted genes were detected in tumor tissues. An obvious antitumor effect was observed in nude mice bearing tumors transfected with CEACD or CD genes; as compared to mice bearing tumors not transfected with targeted genes, in the LoVo cells group(P< 0.01, t= 4.512; P< 0.01, t=3.320) and in the SW480 cells group(P<0.01, t=4.547; P<0.01, t=4.475). Furthermore, a higher antitumor effect was observed in nude mice bearing CEACD tumors than that in those bearing CD tumors (P<0.05,t=2.375) in the LoVo cells group, but not in the SW480 cells group. Conclusions: The CEA tissue-specific CD/5-FC system has an obvious targeting anti-tumor effect on human colorectal LoVo cell and SW480 cell carcinomas, and the killing effect on the LoVo-CEACD cell tumor is stronger than that on the SW480-CEACD cell tumor.