The radiosensitising effect of difluorodeoxyuridine, a metabolite of gemcitabine, in vitro
The radiosensitising effect of difluorodeoxyuridine, a metabolite of gemcitabine, in vitro
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DOI：
10.1007/s00280-005-0158-5
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发表时间：
2006-08-01
影响因子：
3
通讯作者：
Vermorken, JB
中科院分区：
文献类型：
--
作者：
Pauwels, B;Korst, AEC;Vermorken, JB
目的：吉西他滨是一种具有放射增敏特性的活性抗肿瘤药物。吉西他滨在细胞内和细胞外都能被脱氧胞苷脱氨酶迅速代谢为二氟脱氧尿苷（dFdU），这是一种几乎没有抗肿瘤活性的化合物。然而，其血浆浓度在已知会导致生长抑制的水平上能维持较长时间（>24小时）。这是第一项在体外研究dFdU放射增敏潜力的研究。
方法：人癌细胞系ECV304和H292在接受放射治疗（RT）前24小时用不同浓度的dFdU（0 - 100 μM）处理。通过改变dFdU和放射治疗之间的间隔来研究放射增敏效应的时间依赖性。此外，用流式细胞术研究dFdU对细胞周期的影响，并通过膜联蛋白V染色和半胱天冬酶3裂解来确定在放射增敏条件下细胞凋亡的诱导情况。
结果：dFdU在ECV304和H292细胞中均产生明显的浓度依赖性放射增敏效应。剂量增强因子（DEF）随着dFdU浓度的增加而增加：在ECV304细胞中，用10、25和50 μM dFdU处理后，DEF分别为1.10、1.60和2.17；在H292细胞中，用25、50和100 μM处理后，DEF分别为1.08、1.31和1.60。随着dFdU处理和放射之间0 - 24小时间隔的增加，DEF降低。在放射增敏条件下，dFdU和放射联合导致细胞凋亡诱导增加。此外，dFdU对细胞周期的影响，即在S期早期的阻滞，与吉西他滨对细胞周期的影响相当。
结论：dFdU是吉西他滨的主要代谢产物，在体外产生浓度和时间依赖性的放射增敏效应。由于在使用吉西他滨治疗后，该代谢产物在血浆中存在较长时间（>24小时），它可能在一定程度上是放疗和吉西他滨之间相互作用的原因。这一观察结果可能对吉西他滨和放疗联合的最佳治疗方案具有重要意义。
Purpose: Gemcitabine is an active antitumour agent with radiosensitising properties. Gemcitabine is rapidly metabolised, intracellularly as well as extracellularly, by deoxycytidine deaminase to difluorodeoxyuridine (dFdU), a compound with little antitumour activity. However, plasma concentrations are maintained for a prolonged period (> 24 h) at levels known to cause growth inhibition. This is the first study that investigates the radiosensitising potential of dFdU in vitro. Methods: ECV304 and H292, human cancer cells, were treated with different concentrations dFdU (0-100 mu M) during 24 h before radiation treatment (RT). The schedule dependency of the radiosensitising effect was studied by varying the interval between dFdU and radiation treatment. In addition, the cell cycle effect of dFdU was investigated with flow cytometry, and the induction of apoptosis under radiosensitising conditions was determined by Annexin V staining and caspase 3 cleavage. Results: dFdU caused a clear concentration-dependent radiosensitising effect in both ECV304 and H292 cells. Dose enhancement factor (DEF) increased with an increasing concentration of dFdU: DEFs were 1.10, 1.60 and 2.17 after treatment with 10, 25 and 50 mu M dFdU, respectively, in ECV304 cells and 1.08, 1.31 and 1.60 after treatment with 25, 50 and 100 mu M, respectively, in H292 cells. DEFs decreased with an increasing interval of 0-24 h between dFdU treatment and radiation. Under radiosensitising conditions, the combination dFdU and radiation resulted in an increased induction of apoptosis. In addition, the cell cycle effect of dFdU, an arrest at the early S phase, is comparable with the cell cycle effect of gemcitabine. Conclusions: dFdU, the main metabolite of gemcitabine, causes a concentration- and schedule- dependent radiosensitising effect in vitro. Since the metabolite is present in plasma for a long period (> 24 h) after treatment with gemcitabine, it might be partly responsible for the interaction between radiotherapy and gemcitabine. This observation might have important consequences for the optimal schedules of the combination gemcitabine and radiation therapy.