细胞外调节蛋白激酶通路对胃癌细胞化疗效果的影响

Activation of ERK signaling pathway reduces the chemotherapy sensitivity in gastric cancer cells

目的:观察细胞外调节蛋白激酶(extracelluar regulated protein kinase,ERK)信号通路对胃癌细胞化疗效果的影响并探讨其机制.方法:足叶乙甙作用于胃癌SGC7901和BGC823细胞,采用MTT比色法检测细胞的生存率,采用流式细胞仪和Hoechst33258荧光染色检测细胞周期分布和凋亡,Western杂交法检测ERK1/2的磷酸化以及c-Myc和P53蛋白表达水平.同时采用PD98059抑制ERK信号通路后观察足叶乙甙对细胞增殖、凋亡、c-Myc和P53表达的影响.结果:足叶乙甙呈时间-剂量依赖性抑制SGC7901和BGC823细胞的生长并明显诱导细胞的凋亡,同时上调ERK1/2的活性(磷酸化水平),并增强c-Myc和P53的表达,与对照组比较,足叶乙甙组凋亡率明显增高(19.48%±1.57%vs5.67%±0.81%,17.38%±1.49%vs4.97%±0.73%,均P<0.01),PD98059可明显增强足叶乙甙的细胞生长抑制作用并提高细胞的凋亡水平,与足叶乙甙组比较,足叶乙甙组+PD98059组凋亡率(34.35%±2.84%,32.11%±3.25%)明显增加(P<0.01);同时上调足叶乙甙诱导的P53表达,并抑制c-Myc表达的上升趋势.结论:足叶乙甙可活化胃癌细胞ERK信号通路而影响胃癌细胞的化疗效果,其机制可能是通过抑制P53并上调c-Myc的表达,从而抑制细胞的凋亡实现.

AIM： To investigate the relationship between the activation of mitogen-activated protein kinase （MAPK）/extracelluar regulated protein kinases （ERK） signaling pathway and chemoresistance in human gastric cancer cell lines SGC7901 and BGC823. METHODS： Cells were exposed to etoposide with or without PD98059 （a special inhibitor of 1VIAPK/ERK pathway）. Cell cycle distribution and cell apoptosis analysis were determined using flow cytometry and Hoechst 33258 staining. Cytotoxicity was assessed by determining cell survival with 3-（4, 5-dimethyl thiazol-2-yl）-2, 5-diphenyl tetrazolium bromide （MTT）. Western blotting was performed to evaluate the phosphorylation level of ERK1/2 and protein expres- sion of c-Myc and P53. RESULTS： Etoposide caused a time- and dose-dependent reduction of cell viability in SGC7901 and BGC823 cells. PD98059 enhanced the cell inhibitory efficiency of etoposide. Compared with control group, the apoptosis rate was elevated in etoposide group （19.48% ± 1.57% vs 5.67% ± 0.81%, 17.38% ± 1.49% vs 4.97% ± 0.73%, all P 〈 0.01）. Cells treated with and PD98059 showed significantly higher level of apoptotic phenotype than those treated with etoposide alone. The apotosis rate was 34.35% ± 2.84% and 32.11% ± 3.25% in etoposide and PD98059 groups, respectively （P 〈 0.01）. Phosphorylation level of ERK1/2 and expression of c-Myc were significantly induced by etopo- side in a time-dependent manner, but there was slight effect on protein expression of P53. PD98059 up-regulated expression of P53 and suppressed the up-regulated c-Myc expression induced by etoposide, strikingly. CONCLUSION： Chemotherapy agent etopo- side was able to activate MAPK/ERK signaling pathway of gastric cancer cells SGC7901 and BGC823, which decrease the chemotherapy sen- sitivity via suppressing the expression of P53 and enhancing the expression of c-Myc. This may be one of the mechanisms responsible for gastric cancer chemoresistance.