中文摘要：

目的观察S100A2与胰腺癌继发耐放射细胞株的相关性。方法检测胰腺癌细胞株及其继发耐放射株中S100A2基因及蛋白质的表达水平，以及应用去甲基化试剂5-氮杂-2-脱氧胞苷处理耐放射细胞株后的改变，并检测相关放射敏感性的改变。结果胰腺癌细胞株SW1990耐放射株与亲本株相比S100A2的基因、蛋白质水平均明显较低（2—3倍），耐放射细胞株经5-氮杂-2-脱氧胞苷处理后S100A2的mRNA、蛋白质水平均较用药前明显升高（2—5倍），且处理后的细胞株耐放射性明显降低。结论S100A2在胰腺癌继发耐放射细胞株中的低表达可能是引起其继发耐放射特性的机制之一。

英文摘要：

Objective To investigate the association of S100A2 expression with the secondary radioresistance in pancreatic cancer cells. Methods Human pancreatic cancer cells of the line SW1990, parental line, and the secondarily radioresistant human pancreatic cancer cells of the line SW1990/R were cultured and inoculated into the wells of a 6-well plate. 5-Aza-2＇-deoxycytidine （5-aza-DC） of different concentrations was added into the culture fluid. Forty-eight hours later X-ray irradiation was conducted. Cloning efficiency assay was used to assess the cell survival. The cell cycle was analyzed by flow cytometry. The mRNA expression of S100A2 was examined by real-time RT-PCR and the protein expression of S100A2 was examined by immunofluorescence quantitative analysis. Results The S100A2 mRNA expression level of the SW1990 line was significantly higher than that of the SW1990/R line. Treated by 5-aza-dC, the S100A2 mRNA expression level of the SW1990/R line increased by 2 - 3 times. The S100A2 protein expression level of the SW1990 line was significantly higher than that of the SW1990/R line （ t = 3. 648, P = 0. 022）. Treated by 5-aza-dC, the S100A2 protein expression level of the SW1990/R line increased, by 5 times at most （t = - 11. 404, P = 0. 001 ）. The G2/M of the SW1990 line was 16.2%, significantly higher than that of the SW1990/R line （ 16.2% ） , and the G2/M levels of the SW1990/R line treated by 5- aza-dC of different concentrations were all increased dose-dependently. The colony-forming rates of the SW1990/R line of the 5-aza-dC ＋ irradiation groups were all significantly lower than that of the SW1990/R line of the pure irradiation group, even the dose of 5-aza-dC was as low as 0. 025 μm. The SF2 （ cell survival rate with the irradiation dose of 2 Gy） of the 5-aza-dC ＋ irradiation group was 0. 122, significantly lower thanthat of the pure irradiation group （0.460）. Conclusion The expression level of S100A2 is low in the radioresistant pancreatic cancer cells, which may be one of the