内皮抑素对NSCLC细胞系中VEGF受体2表达的影响及其放射增敏效应机制研究

Impacts of endostatin on expression of vascular endothelial growth factor receptor-2 in non-small cell lung cancer cells and mechanisms underlying its radiosensitizing effect

目的：研究内皮抑素对NSCLC细胞（人肺腺癌A549细胞、人肺鳞癌Calu.1细胞）中VEGF受体2（ VEGFR2）表达影响，并探索其放射增敏效应的可能机制。方法 CCK8法检测内皮抑素对细胞增殖抑制作用，计算24 h的20％药物抑制浓度（ IC20）；采用RT.PCR及蛋白印迹法检测各组VEGFR2、相关信号通路及HIF.1α mRNA与蛋白表达变化；克隆形成实验检测各组细胞放射敏感性，流式细胞术检测凋亡及周期分布。多样本均数比较采用单因素方差分析，组间比较采用两样本均数t检验。结果经内皮抑素处理后，Calu.1细胞增殖活力明显下降（F＝50.36，P＜0.01），IC20＝296.5μg／ml；VEGFR2和HIF.1αmRNA与蛋白表达水平均受抑制（F＝25.43、10.44，P 值均＜0.05）；同时Akt、ERK 1／2和p38的蛋白磷酸化水平均减低（ F＝2.89、0.24、1.09，P值均＜0.05）；其放射增敏比为1.38；凋亡率、G2＋M期阻滞增加（ F＝44.15、104.24，P值均＜0.01）。此外，与Calu.1细胞相比，内皮抑素对A549细胞放射增敏比为1.09。结论内皮抑素能促进VEGFR2高表达Calu.1细胞凋亡并能增强放射敏感性，对低表达的A549细胞效果有限。

Objective To determine the effects of endostatin on the expression of vascular endothelial growth factor receptor.2 （ VEGFR.2 ） in non.small cell lung cancer cells （ human A549 lung adenocarcinoma cells and human Calu.1 lung carcinoma cells） , and to investigate the possible mechanisms underlying its radiosensitizing effect. Methods The CCK8 method was used to determine the inhibitory effect of endostatin on cell proliferation and calculate the drug concentration that caused a 20% reduction in cell proliferation within 24 h （ IC20 ） . RT.PCR and Western blot assays were used to assess the mRNA and protein expression of VEGFR.2, proteins within its related signaling pathways, and HIF.1α, respectively. The radiosensitivity of cells in each group was determined by colony formation assay;cell apoptosis and cell cycle distribution were determined by flow cytometry. Comparison of mean values between multiple samples was made by one.way analysis of variance, and comparison of mean values between two samples was made by t test. Results Endostatin significantly inhibited the proliferation of Calu.1 cells （ F=50.36,P＆lt;0.01） with an IC20 of 296.5 μg/ml;the mRNA and protein expression of VEGFR.2 and HIF.1α was also significantly inhibited in endostatin.treated Calu.1 cells （ F=25.43,10.44, all P＆lt;0.05） . Moreover, the phosphorylation of Akt, ERK 1/2, and p38 was significantly reduced in endostatin.treated Calu.1 cells （ F=2.89,0.24, 1.09, all P＆lt;0.05） . The radiosensitivity enhancement ratios for Calu.1 cells and A549 cells were 1.38 and 1.09, respectively. Endostatin significantly induced apoptosis （ F=44.15, P＆lt;0.01） and G2/M blockage （ F= 104.24, P〈 0.01 ） in Calu.1 cells. Conclusions Endostatin induces apoptosis and enhances radiosensitivity in Calu.1 cells with high expression of VEGFR.2, but it has a limited impact on A549 cells with low expression of VEGFR.2.