摘要
单宁酸具有抗肿瘤的生物学活性,但单宁酸难以透过细胞膜进入细胞内,其跨膜信号传递的分子机制仍不清楚。本研究选用人恶性胶质瘤U87细胞作为模型,检测单宁酸对肿瘤细胞增殖、表皮生长因子受体(epidermal growth factor receptor,EGFR)磷酸化、胞外信号调节激酶(extracellular signal-regulated kinase,ERK)以及信号转导与转录激活因子(signal transducer and activator transcription,STAT)1、STAT3等信号分子的调节作用。实验发现,单宁酸处理能够显著抑制人恶性胶质瘤U87细胞的增殖,且呈现显著的剂量效应和时间效应关系。单宁酸抑制B淋巴细胞瘤-2(B-cell lymphoma-2,Bcl-2)蛋白的表达,促进Bcl-2相关X(Bcl-2 associated X,Bax)蛋白的表达,显著提高了Bax/Bcl-2的比值。通过分离线粒体发现,单宁酸提高了线粒体Bax蛋白的水平,促进细胞凋亡诱导因子细胞色素c(cytochrome c,Cyt c)向细胞胞浆的释放,暗示细胞凋亡的发生,这与单宁酸抑制肿瘤细胞增殖的结果一致。单宁酸抑制人恶性胶质瘤U87细胞EGFR总磷酸化的水平,进一步通过检测单一位点的磷酸化水平发现,单宁酸抑制了EGFR Y1045和Y1068 2个位点的磷酸化,但是对Y845和Y992位点的磷酸化影响不大,呈现一定的位点选择性。通过检测受EGFR Y1045和Y1068位点调控的ERK以及STAT1/3信号通路发现,单宁酸显著抑制了ERK以及STAT1、STAT3等信号分子的磷酸化,进一步验证了单宁酸对EGFR特定位点的选择性抑制作用。结果表明,单宁酸可能通过选择性地抑制肿瘤细胞EGFR特定位点的磷酸化,进而抑制受该位点调控的信号转导通路,改变肿瘤细胞基因表达的模式,从而抑制肿瘤细胞的增殖。
Tannic acid(TA)possesses anti-tumor activity toward a broad range of tumor cells.However,it is hard for tannic acid to enter cells across the plasma membrane based on its chemical structure.How the signal of tannic acid is transduced into cells across the plasma membrane remains unclear.In the present study,we used human malignant glioma U87cells,in which the epidermal growth factor receptor(EGFR)and its downstream signaling are over-activated,as a model to clarify the role of tannic acid in cell proliferation,EGFR phosphorylation,extracellular signal-regulated kinase(ERK)and signaltransducer and activator transcription(STAT)1/3signaling activation.The results showed that tannic acid treatment obviously inhibited the proliferation of human glioma U87cells in a time-and dose-dependent manner.Tannic acid dramatically inhibited the expression of B-cell lymphoma-2(Bcl-2)protein but promoted the expression of Bcl-2associated X(Bax)protein,thus resulting in a significant enhancement of Bax/Bcl-2ratio in human glioma U87cells.Furthermore,we found that tannic acid enhanced the level of Bax in the mitochondria and promoted the release of cytochrome c(Cyt c)to the cytoplasm,implicating the initiation of cell apoptosis.These results confirm the inhibitory role of tannic acid in cell proliferation.Further investigations revealed that tannic acid significantly inhibited the whole level of EGF-stimulated EGFR phosphorylation in human glioma U87cells.By detecting the phosporylation of individual tyrosine sites of EGFR,we uncovered that tannic acid specifically weakened the phosphorylation of EGFR at Y1045and Y1068,but had no effect at Y845and Y992,indicating a inhibitory role of tannic acid in site-specific EGFR phosphorylation.Finally,tannic acid also blocked the phosphorylation and activation of ERK and STAT1/3,both of which were regulated by the phosphorylationof EGFR at Y1045and Y1068.In summary,tannic acid inhibited site-specific phosphorylation of EGFR in human glioma U87cells.As a consequence,the phosphorylation and activation of ERK and STAT1/3were also inhibited by tannic acid,thereby accounting for the inhibition of the proliferation of human glioma U87cells by tannic acid and laying a theoretical foundation for the anti-tumor activity tannic acid.
作者
阮海华
胡双艳
张春晨
余龙
张真
RUAN Haihua;HU Shuangyan;ZHANG Chunchen;YU Long;ZHANG Zhen(College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, China)
出处
《食品科学》
EI
CAS
CSCD
北大核心
2018年第5期199-205,共7页
Food Science
基金
国家自然科学基金青年科学基金项目(81101220)
国家自然科学基金应急管理项目(31540066)
关键词
单宁酸
表皮生长因子受体
磷酸化
U87细胞
抗肿瘤活性
tannic acid
epidermal growth factor receptor
phosphorylation
U87 cells
anti-tumor activity
