中文摘要：

背景与目的：细胞周期调控是决定细胞辐射敏感性的决定性因素之一。共济失调毛细血管扩张症突变基因（ataxia—telangiectasia mutant，ATM）功能与细胞DNA损伤修复、细胞周期检查点调控密切相关。我们前期研究通过反义RNA抑制ATM基因表达可增加鼻咽癌细胞系CNEl辐射敏感性，本研究拟探讨其辐射增敏的细胞周期阻滞调控机制。方法：ATM反义组细胞CNEl／pDOR—atm及对照组细胞CNEl／pDOR经2Gv、5Gy X线照射后不同时间点（1h、4h、8h、24h、48h）收获，应用流式细胞仪（flow cytometer，FCM）检测各细胞周期百分比及凋亡率。结果：两组细胞X线照射后均未出现明显G1期阻滞和细胞凋亡，但分别在照射后lh、4h、8h出现明显S期阻滞，24h、48h出现明显G2期阻滞，其中反义组S期细胞百分率总均数水平低于对照组（P〈0．05），而G2／M期细胞百分率总均数水平高于对照组（P〈0．05）。结论：反义RNA抑制ATM表达致CNEl辐射增敏的细胞周期调控机制可能与减少S期细胞比例，增加G1／M期细胞比例有关，与G1期阻滞和细胞凋亡的调控无关。

英文摘要：

BACKGROUND ＆ OBJECTIVE： Cell cycle regulation is one of the most important determinants to ionizing radiosensitivity of cells. ATM gene is closely related with DNA damage repair and cell cycle checkpoints control. We previously reported that suppressing ATM expression with antisense ATM RNA could enhance radiosensitivity of nasopharyngeal carcinoma （NPC） cell line CNEI. This study was to explore the involved changes of cell cycle and the mechanisms of cell cycle arrest. METHODS： ATM gene was constructed into retrovirus vector pDOR to form recombinant pDOR-atm. CNE1 cells were transfected with pDOR-atm （CNE1/pDOR-atm cells） or pDOR （CNE1/pDOR cells） and irradiated with X-ray. Cell cycle and cell apoptosis were detected by flow cytometry at different time points after irradiation. RESULTS： S phase arrest was detected at 1, 4, and 8 h after irradiation in both groups, and G2 arrest at 24, and 48 h, while no comparable G1 arrest and apoptosis were revealed. The mean percentage of S phase cells was lower, and G2 phase cells was higher in CNE1/pDOR-atm group than in CNE1/pDOR group （P〈0.05）. CONCLUSION; The mechanisms of cell cycle regulation in radiosensitized CNE1 cells by inhibiting ATM expression might be related with the decreased accumulation of S phase cells and increased accumulation of G2/M phase cells, while have no relationship with G1 arrest and apoptosis.