EGCG通过调控DNA结合蛋白Ku70促进肺癌细胞凋亡

目的 观察表没食子儿茶素没食子酸酯[（-）-epigallocatechin-3-gallate，EGCG]对人肺腺癌细胞株的凋亡诱导作用，探讨Ku70在EGCG促肺癌细胞凋亡中的作用机制。方法 构建pSliencer 4.1-CMV-shKu70质粒干扰Ku70的表达，建立细胞系；MTT法和Annexin V/PI双染色流式细胞术检测细胞的增殖及凋亡；Western blot法检测Bax、caspase-3（17 kDa）、Ku70蛋白的表达；免疫共沉淀法检测Ku70和Bax之间的相互作用。结果 EGCG可明显抑制A549的增殖（P<0.01），并诱导其凋亡（P<0.05），上调Bax、caspase-3表达，下调Ku70表达。抑制Ku70的表达后，EGCG对A549细胞的抑制增殖和促进凋亡作用更加明显，进一步显著上调caspase-3的表达（P<0.05），但是Bax的表达无明显变化；同时EGCG可以减弱Ku70-Bax之间的相互作用（P<0.05）。结论 EGCG可抑制人肺腺癌细胞增殖及诱导细胞凋亡，其机制与抑制Ku70的表达，抑制Ku70-Bax之间的相互作用，激活Bax，启动caspase级联反应有关。

EGCG Induced Apoptosis by Regulating DNA-binding Protein Ku70 in Lung Cancer Cells

OBJECTIVE To investigate the effect of (-)-epigallocatechin-3-gallate(EGCG) on lung adenocarcinoma cell growth and to explore the mechanism of Ku70 in promoting apoptosis of lung cancer cells by EGCG. METHODS Construction of pSliencer 4.1-CMV-shKu70 plasmid interfered with the expression of Ku70 and established cell lines. Induction of apoptosis was examined by MTT method and Annexin V/PI double staining flow cytometry. Western blot analysis was used to detect the protein expression of cleaved Bax, caspase-3(17 kDa) and Ku70. Immunoprecipitation was used to detect the interaction between Ku70 and Bax. RESULTS EGCG significantly inhibited the the proliferation of A549(P<0.01), and EGCG could induce apoptosis of A549 cells(P<0.05), up-regulate the expression of Bax and caspase-3 and down-regulate the expression of Ku70. After the expression of Ku70 was inhibited, the effect of EGCG on the proliferation inhibition and apoptosis promotion of A549 cells was more obvious, and the expression of caspase-3 was further up-regulated, the levels of proteins changes were significantly(P<0.05), but the Bax level was not significantly changed. At the same time, EGCG could interfere the interaction between Ku70-Bax(P<0.05). CONCLUSION EGCG may inhibit proliferation and induce apoptosis in lung adenocarcinoma cell. The mechanism is related to inhibition of Ku70 expression, inhibition of interaction between Ku70-Bax, activation of Bax, and initiation of caspase cascade.