NS-398对结直肠癌细胞HT-29放射增敏机制的初探

目的:探讨COX-2抑制剂NS-398对结直肠癌细胞系HT-29的放射增敏作用及其相关机制。方法:COX-2高表达细胞系HT-29经25μmol/LNS-398处理24h后,给以不同剂量(0、2、4、6、8Gy)X-ray照射,应用克隆形成实验测NS-398对HT-29细胞的放射增敏作用,流式细胞仪(FCM)分析NS-398对HT-29细胞凋亡及细胞周期的影响,RT-PCR和FCM观察NS-398处理后Bax、Bcl-2在mRNA及蛋白水平的表达变化。结果:25μmol/LNS-398对HT-29有明显增敏作用,细胞存活分数(SF)为0.1时,放射增敏比SER为1.76;NS-398诱导HT-29凋亡、增强HT-29对放射诱导凋亡的敏感性,同时抑制细胞增殖;BaxmRNA及蛋白表达呈NS-398剂量依赖性增高,而Bcl-2的表达无明显变化。结论:NS-398对HT-29有放射增敏作用,其机制与诱导凋亡、直接抑制细胞增殖有关。

Initial Investigation on Mechanisms of Radiosensitization of NS-398 on HT-29 Cell Lines of Colorectal Carcinoma

Objective: To investigate the radiosensitizing effect and mechanisms of COX-2 inhibitor NS-398 on colorectal cancer cell lines HT-29. Methods: Colorectal cancer cell lines HT-29 had been incubated with 25μM NS-398 before X-ray irradiation at different doses (0, 2, 4, 6 and 8Gy). The cells were assayed for clonogenic survival to determine the radiosensitizing effect of NS-398. Flow cytometry was used to determine the effects of NS-398 and radiation on apoptosis and cell cycle distribution. The changes of mRNA and protein of Bax and Bcl-2 of HT-29 were measured by RT-PCR and flow cytometry after treatment with NS-398. Results: When survival fraction was 0.1, the sensitization-enhancement ratio was 1.76. NS-398 induced apoptosis in HT-29 cells alone and enhanced its sensitivity to irradiation-induced apoptosis. NS-398 also inhibited the proliferation of HT-29 cells. The expression of Bax mRNA and protein were increased after treatment with 25μM NS-398 at a dose-dependent manner, whereas there was no changes with Bcl-2. Conclusion: The findings indicate that the COX-2 inhibitor NS-398 has radiosensitizing effect on HT-29 cells by induction of the apoptosis and inhibition of the cell proliferation.