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目的 :以RER(replicationerror)表型的结肠癌细胞作靶细胞 ,研究大蒜素 (diallyltrisulfide ,DAT)和亚硒酸钠对肿瘤细胞微卫星序列 (microsatellitesequence,MS)突变的影响。方法 :将含有外源性MS ,(ca) 14,的穿梭质粒 pCMV CAR转染RER+ 或RER-结肠癌细胞株RKO或SW 480。外源性 (ca) 14 的突变可使质粒标记基因LacZ恢复正常读码 ,表达产生β 半乳糖核苷酶 ,后者使X gal变蓝。DAT及亚硒酸钠对MS突变的影响可直接通过X gal染色结果而判断出来。结果 :外源性 (ca) 14 的突变只发生于RKO细胞而不发生于SW 480细胞。使用DAT0 0 0 15 μg/ml及 0 0 15 μg/ml以及亚硒酸钠 5 μmol/L ,对细胞活力及增殖无影响 ,经作用 5天 ,均显示出对外源性(ca) 14 的突变有明显的抑制效应。但是低浓度亚硒酸钠 1μmol/L作用 5天 ,其抑制 (ca) 14 突变的作用不明显 ,延长作用时间到 5～ 6周 ,则又表现出对 (ca) 14 突变的明显抑制效应。结论 :外源性MS与内源性MS一样在RER+ 细胞中是不稳定的。DAT和亚硒酸钠能抑制RER+ 细胞中外源性 (ca) 14重复序列突变 ,提示它们对人癌细胞MS遗传不稳定有保护作用。
Objective: To study the effects of allyltrisulfide (DAT) and sodium selenite on the mutation of microsatellite sequence (MS) in tumor cells using RER (replicationerror) phenotype colon cancer cells as target cells. METHODS: The shuttle plasmid pCMV containing the exogenous MS (ca) 14 was transfected into the RER+ or RER- colon carcinoma cell line RKO or SW 480. A mutation in exogenous (ca) 14 restored the normalization of the plasmid marker gene LacZ, resulting in the production of beta-galactosidase, which turned blue X gal. The effect of DAT and sodium selenite on MS mutation can be directly determined by X gal staining results. Results: The exogenous (ca) 14 mutation only occurred in RKO cells but not in SW 480 cells. Using DAT0 0 15 15 μg/ml and 0 0 15 μg/ml and sodium selenite 5 μmol/L had no effect on cell viability and proliferation. After 5 days of exposure, they all showed exogenous (ca) 14 mutations. There is a clear inhibitory effect. However, when sodium selenite 1μmol/L was used for 5 days at low concentration, the effect of (ca) 14 mutation was not obvious, and the prolongation time was 5 to 6 weeks, showing a significant inhibitory effect on (ca) 14 mutation. Conclusion: Exogenous MS is as unstable in RER+ cells as endogenous MS. DAT and sodium selenite can inhibit the exogenous (ca) 14 repeat mutations in RER+ cells, suggesting that they have a protective effect on human cancer cell MS genetic instability.