西妥昔单抗增强放疗对人胃癌细胞株MGC803及BGC823的作用及其机制

目的 观察西妥昔单抗（C225）联合放疗对人胃癌细胞株MGC803及BGC823增殖的影响，并探讨其机制。方法 （1）采用MTT法观察C225联合放疗对细胞生长增殖的影响，评价两者联合效应；（2）采用FCM检测C225联合放疗对细胞周期分布及细胞凋亡的影响；（3）通过Western blot法检测C225联合放疗对EGFR细胞信号蛋白及其下游信号蛋白AKT、MAPK磷酸化的影响。结果 （1）当C225联合三种不同剂量放疗时，均可显著抑制细胞的增殖，两者具有协同作用。（2）单用C225可使细胞阻滞于G0/G1期，并减少S期细胞比例。在C225作用后，G0/G1期及S期MGC803细胞比例分别为67.3％及24.8％，BGC823细胞则分别为71.9％及18.8％。单用放疗可使细胞阻滞于G2/M期。在放疗作用于MGC803细胞及BGC823细胞后，G2/M期比例分别为18.2％及19.5％。当C225与放疗联合作用时，G2/M期MGC803细胞及BGC823细胞比例进一步升高，分别为25.7％及26.4％，而S期细胞比例进一步下降，分别为18.6％及13.5％。（3）在C225处理后MGC803细胞及BGC823细胞的凋亡率分别为4.9％及9.9％，放疗处理后MGC803细胞及BGC823细胞的凋亡率分别为11.7％及19.8％，与对照组相比差异均具有统计学意义。当C225与放疗联合作用时，MGC803细胞及BGC823细胞的凋亡率分别为20.1％及47.3％，与单用放疗组相比差异均具有统计学意义。（4）C225与放疗联合应用时，可使细胞EGFR信号蛋白表达下降，并能使其下游信号蛋白AKT、MAPK磷酸化活性降低。结论 （1）西妥昔单抗可增强放疗对MGC803和BGC823细胞株的生长抑制作用；（2）其增敏作用的机制可能与抑制EGFR信号转导通路、诱导细胞周期阻滞和细胞凋亡增加等有关。

Effects and Mechanisms of Enhanced Radiation Response Combined with Cetuximab on Human Gastric Carcinoma Cell Lines MGC803 and BGC823

Objective To study the effects of C225 combined with radiotherapy on the proliferation of human gastric carcinoma cell lines MGC803 and BGC823,and to evaluate the mechanisms of the combination effects. Methods (1) The effects of combination treatment on the proliferation of MGC803 and BGC823 cells were evaluated by MTT assay and Q value was calculated to assess the combined effect.(2) Flow cytometry(FCM)analysis was applied to observe the cell cycle distribution and apoptosis of human gastric carcinoma cell lines MGC803 and BGC823 treated by C225 combined with radiotherapy.(3)Western blot was used to detect the expression of EGFR,p-Akt and p-p38MAPK, respectively. Results(1) the combination of C225 and radiation could obviously inhibit the proliferation of MGC803 and BGC823 cells, which showed synergistic effect.(2) Cetuximab alone could induce G₀/G₁ cell cycle arrest of the MGC803 and BGC823 cells,and reduce cells within S phase. When exposed to C225 alone, the percentages of MGC803 cells within G0/G1 phase and S phase were 67.3％and 24.8％，respectively；while the percentages in BGC823 cells were 71.9％and 18.8％，respectively. G^₂/M cell cycle arrest was induced in the cells exposed to radiation alone, and the percentages of G2/M cell cycle arrest in MGC803 and BGC823 cells were 18.2％and 19.5％,respectively. The combination of radiation and C225 resulted in the accumulation of G2/M arrest in MGC803 and BGC823 cells, which were up to 25.7％ and 26.4％ respectively; and also caused a concurrent reduction of cells within S phase, which were 18.6％and 13.5％, respectively. (3)The apoptosis rates of MGC803 and BGC823 cell lines in C225 arm were 4.9% and 9.9%, respectively; and the apoptosis rates were 11.7％ and 19.8％ in radiation arm; both significantly higher than those in the control arm. In the combination arm, The apoptosis rates of MGC803 and BGC823 cell lines were 20.1％ and 47.3％, respectively, significantly higher than that in radiation arm.(4)The combination of C225 and radiation could decrease the expression of EGFR and decrease the activation of its downstream signaling pathway proteins such as p-Akt and p-p38MAPK.Conclusion (1) C225 or X-ray alone could inhibit the proliferation of human gastric carcinoma cell lines MGC803 and BGC823,and exhibit synergistic effect when combined.(2) The mechanism of synergistic effect of C225 in combination with X-ray may be attributed to the inhibition of EGFR signaling pathway, which resulted in: ①the proportion of cancer cells increased in phase G₂/M, and decreased in phase S; ② more apoptosis were induced. Consequently, the proliferation inhibition effect on gastric cancer cells was enhanced.