S-腺苷蛋氨酸对人胃癌细胞系SGC-7901和BGC-823的影响

目的 观察S-腺苷蛋氨酸(SAM)对体外培养的人胃癌细胞系SGC-7901和BGC-823细胞增殖、细胞周期、凋亡和侵袭力的影响,及对这两种细胞中c-myc 和尿激酶型纤溶酶原激活剂(uPA)基因甲基化状态及表达的影响.方法 采用四甲基偶氮唑盐法检测SAM对SGC-7901和BGC-823细胞增殖的影响.应用不同浓度(0、2、4 mmol/L)的SAM处理SGC-7901和BGC-823细胞72 h后,用流式细胞仪检测各组细胞周期和凋亡;Transwell法检测各组细胞侵袭力;分别使用逆转录聚合酶链反应(RT-PCR)、蛋白质印迹法和甲基化特异性PCR(MSP)方法检测各组细胞中c-myc和uPA基因mRNA和蛋白的表达及甲基化状态.结果 0.5～32 mmol/L SAM处理SGC-7901和BGC-823细胞24、48、72 h后,随SAM浓度增大和作用时间延长,细胞增殖受到明显抑制(均P<0.05),生长抑制率也逐渐增大,72 h IC50分别为SGC-7901 5.40 mmol/L、BGC-823 4.01 mmol/L.经过不同浓度(0、2、4 mmol/L)SAM处理SGC-7901和BGC-823细胞72 h后,随SAM浓度增加,G0/G1期细胞比例均逐渐增加,且差异有统计学意义(分别P<0.05和P<0.01),细胞增殖指数明显低(分别P<0.05和P<0.01);与对照组凋亡率(0.33±0.09)比较,SGC-7901 2 mmol/L组(5.79±0.75)和4 mmol/L组(10.19±0.60)均高(均P<0.01);与对照组凋亡率(0.95±0.19)比较,BGC-823 2 mmol/L组(6.23±0.75)和4 mmol/L组(11.82±1.14)均高(均P<0.01).细胞侵袭力均受到明显抑制,差异均有统计学意义(均P<0.01),SGC-7901 2、4 mmol/L组侵袭抑制率分别是51.07%和80.69%,BGC-823 2、4 mmol/L组侵袭抑制率分别是48.57%和84.10%.除了BGC-823细胞的2 mmol/L组c-myc 基因,其余各组细胞c-myc 基因和uPA基因的mRNA表达均明显减弱(分别P<0.05和P<0.01);c-myc基因和uPA基因均恢复甲基化状态.结论 SAM可促进SGC-7901和BGC-823胃癌细胞凋亡,抑制增殖,使细胞在G0/G1期受阻;使细胞侵袭力受到抑制;能够逆转胃癌细胞c-myc基因和uPA基因的低甲基化状态,调控c-myc基因和uPA基因的表达.

Effects of S-adenosylmethionine on gastric cancer cell lines SGC-7901 and BGC-823

Objective To observe the effects of S-adenosylmethionine (SAM) on cell proliferation, cell cycles, apoptosis and invasive capacity of gastric cancer cell lines SGC-7901 and BGC-823 and detect the methylation status and expression of c-myc and urokinase-type plasminogen activator ( uPA). Methods The effect of SAM on proliferation of SGC-7901 and BGC-823 cells were determined by MTT assay. SGC- 7901 and BGC-823 cells were treated with different concentrations of SAM(0, 2, 4 mmol/L)for 72 h. Then flow cytometry was used to detect the change of cell cycles and apoptosis; Transwell assay to detect the invasion; RT-PCR and Western blot to detect the expression of c-myc and uPA; and MSP to detect the methylation of c-myc and uPA. Results SAM displayed a growth-inhibiting effect on SGC-7901 and BGC- 823 cells in a dose- and time-dependent manner after exposure to SAM at different concentrations (0. 5±32 mmol/L) for 24, 48 and 72 h, cell proliferation were significantly restrained (all P <0. 05); 72 h IC50 SGC- 7901 5.40 mmol/L and BGC-823 4.01 mmol/L After treating SGC-7901 and BGC-823 with different concentrations of SAM, the cell percentages of G0/G1 phase significantly increased ( P < 0. 05 and P < 0.01) while the cell proliferation indices significantly decreased (P<0. 05 and P<0. 01). Compared with control group(0. 33 ±0. 09), the cell apoptosis of 2 mmol/L(5. 79 ±0. 75)and 4 mmol/L groups( 10. 19 ± 0. 60) of SGC-7901 were obviously reduced (all P <0. 01). Compared with control group (0. 95±0. 19), the cell apoptosis of 2 mmol/L (6. 23±0. 75 ) and 4 mmol/L groups (11. 82±1.14) of BGC-823 were obviously reduced (all P <0. 01). The cell invasive capacity were significantly restrained (P <0. 01 ). The invasion inhibition ratio of 2 mmol/L and 4 mmol/L groups of SGC-7901 were 51.07 % and 80.69% respectively. The invasion inhibition ratio of 2 mmol/L and 4 mmol/L groups of BGC-823 were 48. 57% and 84. 10% respectively. The expressions of c-myc and uPA significantly decreased (P <0.05 and P <0. 01). There was no expression of c-myc in 2 mmol/L group of BGC-823. The methylation of c-myc and uPA genes in two cell lines were reversed after SAM treatment. Conclusions SAM can induce the apoptosis of SGC-7901 and BGC-823, block the cell cycles at G0/G1 phase and suppress the proliferation and invasion of these two cell lines. SAM can reverse the methylation of c-myc and uPA in these two cell lines and reduce their expression. SAM may act as a methyl donor to restrain the development and progression of tumor when hypomethylation is widely present in cancer.