中文摘要：

目的探讨不同剂量X线辐射对人结直肠癌Cac02细胞系中microRNA一-221（miR-221）和p57^kip2表达的影响。方法常规培养Cac02细胞系并分为5组，分别给予不同剂量X线（0、2、4、6和8Gy）照射，24h后提取细胞总RNA和蛋白质，应用real-time Q-PCR检测细胞中miR-221和p57^kip2 mRNA的表达水平，Western blot检测p57^kip2蛋白的表达变化。结果Cac02细胞系在不同照射剂量下，miR-221表达水平随着照射剂量的增加而增加，而p57^kip2蛋白表达水平则随着照射剂量的增加而逐步降低，且呈剂量依赖效应，两者差异均具有统计学意义（P〈0．05）。结论放射线辐射剂量可影响结直肠癌细胞中miR-221/p57^kip2调控通路．抑制miR-221表达可能会提高结直肠癌细胞的放射敏感度。

英文摘要：

Objective To investigate the effects of X-ray dose on the expression of microRNA-221（miR-221） and p57^kip2 in human colorectal carcinoma （CRC） cells. Methods Conventionally cultured Caco2 cells were divided into 5 groups with different doses of X-ray （0, 2, 4,6 and 8 Gy） respectively. The total RNA and protein of the cells were extracted after irradiation for 24 h,The expression level of miR-221 and p57^kip2 mRNA were detected by real-time Q-PCR. The expression of p57^kip2 in cells was detected by Western blot analysis. Results The radiation dose of X-ray had significant effect on the expression of miR-221 and p57^kip2 protein in human Caco2 cells in a dose-dependent manner. The miR-221 expression level improved gradually with the increase of irradiation dose while the p57^kip2 protein expression level reduced gradually （P〈0.05）. Conclusion Radiation dose could affect the miR-221/p57^kip2 regulation pathways in CRC cells. Suppressed miR-221 expression may enhance the radiosensitivity of CRC cells.