Rosier Jean-François, Bruniaux Monique, Husson Bernard, Octave-Prignot Michelle, Beauduin Marc, Grégoire Vincent
Tumoral Metabolism Research Unit, C.H. Jolimont-Lobbes, La Louvière, Belgium.
Radiother Oncol. 2004 Jan;70(1):55-61. doi: 10.1016/j.radonc.2003.10.006.
To try to get a better insight on the interaction between dFdC and ionizing radiation at the cellular level, we examined in vitro the effect of dFdC on the cell cycle of two human head and neck squamous cell carcinoma cell lines (SQD9 and SCC61).
Experimental conditions yielding radio-enhancement were used. Confluent cells were incubated with dFdC (5 microM) for different incubation times, washed, pulse-labeled with BrdUrd (10 microM), fixed and then processed for flow cytometry analysis. Alternatively, cells preincubated or not with dFdC were irradiated (5Gy) in drug-free medium, incubated at 37 degrees C for various times and then processed for flow cytometry analysis.
In both cell lines, dFdC incubated between 1 and 6 h induced a DNA synthesis inhibition with accumulation of cells in the G1-S boundary followed, when DNA reinitiated, by a synchronous progression of cells throughout the cycle. A slightly different kinetics was observed in the two cell lines. A weak correlation between dFdC radio-enhancement and distribution of cells in the cell cycle was observed. It was also observed that for longer dFdC incubation times, DNA synthesis could reinitiate while cells were still incubated with dFdC. This reinitiation could be correlated with a decrease in the intracellular dFdCTP pool to non-inhibitory levels. Finally in both cell lines, dFdC modified neither the importance nor the kinetics of the radiation-induced G1 delay.
This study provides evidence that gemcitabine used at radio-enhancing concentration induces alteration of cell kinetics and cell redistribution throughout the cell cycle. This effect is cell line-dependent. However, the weak correlation between dFdC radio-enhancement and cell cycle distribution suggests that the cell cycle effect does not constitute the most important mechanism of interaction with ionizing radiation. Our study also indicated that in the two cell lines studied, a modulation of the G1-S checkpoint was not implicated in enhancement of radiation response by dFdC.
为了更深入了解脱氧氟尿苷（dFdC）与电离辐射在细胞水平上的相互作用，我们在体外研究了dFdC对两个人类头颈部鳞状细胞癌细胞系（SQD9和SCC61）细胞周期的影响。
采用产生放射增敏作用的实验条件。将汇合的细胞与dFdC（5微摩尔）孵育不同时间，洗涤后，用溴脱氧尿苷（BrdUrd，10微摩尔）进行脉冲标记，固定，然后进行流式细胞术分析。或者，将预先用或未用dFdC孵育的细胞在无药物培养基中进行照射（5戈瑞），在37℃孵育不同时间，然后进行流式细胞术分析。
在两种细胞系中，dFdC孵育1至6小时均诱导DNA合成抑制，细胞在G1 - S边界积累，当DNA重新启动合成时，细胞随后在整个细胞周期中同步进展。在两种细胞系中观察到略有不同的动力学。观察到dFdC放射增敏与细胞周期中细胞分布之间存在微弱相关性。还观察到，对于较长的dFdC孵育时间，当细胞仍与dFdC一起孵育时，DNA合成可以重新启动。这种重新启动可能与细胞内dFdCTP池降至非抑制水平有关。最后，在两种细胞系中，dFdC既不改变辐射诱导的G1期延迟的程度，也不改变其动力学。
本研究提供了证据表明，以放射增敏浓度使用的吉西他滨会诱导细胞动力学改变以及细胞在整个细胞周期中的重新分布。这种效应具有细胞系依赖性。然而，dFdC放射增敏与细胞周期分布之间的微弱相关性表明，细胞周期效应并非与电离辐射相互作用的最重要机制。我们的研究还表明，在所研究的两种细胞系中，G1 - S检查点的调节与dFdC增强辐射反应无关。
