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| Circadian Rhythms of Cell Cycle in Human Nasopharyngeal Carcinoma Cell and Chronoradiation |
| FAN Zhi-jun, LIU Shi-yu, LI Ke, WANG Huan-kun, CHEN Liang |
| Radiation Therapy Department, No.3 Hospital of Dalian, Dalian 116033 China |
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Abstract Objective To study the circadian rhythms of cell cycle in human nasopharyngeal carcinoma (NPC) cells and effect of chronoradiation on NPC cells in order to provide necessary data for making clinical chronoradiotherapy schedule of NPC. Methods Single sell suspension was obtained from NPC cell line CNE-2 cultured in vitro at different times within a day and stained with propidium iodide. The cell cycles were measured by flowcytometry. According to the cell survival curve, NPC cells were irradiated by radiation on the acrophase and nadir of G2/M phase. The cell survival fraction (SF) was examined by microclonogenic and the clonogenic assays. Results One-way ANOVA showed that the proportion of cancer cells in each phase varied according to circadian time with statistical significance(P < 0.05); Both microclonogenic and the clonogenic assays showed that the SF of cells irradiated on the acrophase of G2/M phase was lower than that of cells irradiated on the nadir (P < 0.05). Conclusion Cell cycle of nasopharyngeal carcinoma cell line CNE-2 cells might vary according to circadian rhythms. The difference of the survival fraction (SF) of NPC cells irradiated according to circadian rhythms predicted the superiority of chronoradiotherapy.
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Received: 18 May 2013
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