右旋甲硫氨酸联合化疗诱导胃癌细胞凋亡的机制

目的 探索右旋甲硫氨酸(D-Met)和联合应用周期特异性化疗药物诱导胃癌细胞凋亡的机制和途径。方法 将人胃癌细胞株SGC-7901分别置于六种不同培养基中：含L-Met、含D-Mel、不含Met而替以同型半胱氨酸(Met^-Hcy^ )，或在上述培养基中分别加入5-FU。培养48h后，在蛋白和mRNA水平检测凋亡相关基因bcl-2、bax和p53的表达，以及caspase-3、caspase-8和caspase-9的活性。结果 各组间bcl-2、bax和p53蛋白表达无明显差异；各组均见bax mRNA和p53 mRNA表达，但未见bcl-2 mRNA表达。三种培养基组间caspase-3活性无统计学差异，而D-Met组的caspase-8活性明显低于L-Met和Met-Hcy^ 组，L-Met组的caspase-9活性显著高于Met^-Hcy^ 和D-Met组；与未加入化疗药物时相比，联合应用5-Fu后，各组caspase-3、caspase-8和caspase-9活性均明显提高。结论 D-Met诱导胃癌细胞凋亡至少部分系通过p53非依赖途径所介导，且可能以caspase非依赖方式进行；无证据支持bcl-2和bax参与凋亡的调节；5-FU可能既通过死亡受体信号传递途径，又通过线粒体途径诱导肿瘤细胞凋亡。

Mechanism of Gastric Cancer Cell Apoptosis Induced by D-Methionine Combined with Chemotherapy

Objective To clarify the mechanism and pathway through which D-methionine and its combination with phase-specific chemotherapy induce gastric cancer cell apoptosis in vitro. Methods Human gastric cancer cell line SGC-7901 was cultured into six different media containing L-Met, D-Met, homocysteine instead of Met (Met -Hcy +), or 5-fluorouracil (5-FU) on addition into the afore mentioned three media, respectively. After 48 h incubation, both the protein and mRNA expression of apoptosis-associated genes bcl-2, bax and p53 as well as the activity of caspase-3, caspase-8 and caspase 9 were examined. Results There was no evident change among the three media groups in the protein expression of bcl-2, bax and p53. The expression of bax mRNA and p53 mRNA was detectable in each group, but the expression of bcl-2 mRNA wasn't observed. There was no significant difference in the caspase-3 activity among the three media groups. The activity of caspase-8 in D-Met group was distinctly lower than those in L-Met group and Met -Hcy +group. The activity of caspase-9 in L-Met group was obviously higher than those in Met -Hcy + group and D-Met group. The activities of caspase-3, caspase-8 and caspase-9 in each chemotherapy-combined group were significantly elevated than those groups without 5-FU. Conclusion D-Met may induce tumor cell apoptosis at least partially through the p53-independent pathway, and in a caspase-independent way. Bcl-2 and bax is not likely to be involved in the regulation of apoptosis. 5-FU induces tumor cell apoptosis possibly through both the death receptor signaling pathway and the mitochondrium-mediated pathway.