Purpose:To study the effects of high-dose （）60Co gamma ray to the cell cycles and cell cyclin D1,B1 and cyclin dependent kinase（CDK）1,4 of nasopharygeal carcinoma cell line CNE-2. Observe consecutively the mechanism of the action of high-dose gamma ray on cell cycle progress, in order So as to provide basic material for hypofractionated radiotherapy schedule for tumors.Methods:Propidium Iodide（PI） simple staining and flow cytometry（FC） were used to detect the cell cycle. The expression of cyclin D1、cyclinB1、CDK4 and CDK1 mRNA were detected by combining RT-PCR with semi-quantitative analysis.Results:Apparent G2M phase arrest was observed first after CNE-2 cells were exposed to 4.0～8.0Gy fractionated radiation with gamma rays. G1 phase arrest was enhanced with increasing absorbed dose. Then all cell phase were arrested, but the dose-dependent relation was not obvious. The expression of cyclin D1、cyclin B1 mRNA was suppressed after CNE-2 cells were exposed to 4.0～8.0Gy gamma rays（P<0.05）. There was no significant difference between the expression of CDK4 mRNA and the control group（P>0.05）. But the CDK1 mRNA was not expressed in any of the irradiated groups.Conclusions:G1 phase, S phase and G2M phase arrest were observed in CNE-2 cells exposed to 4.0～8.0Gy fractionated radiation in gamma rays. But the dose-dependent relation was not obvious. The main effects were that the cyclin D1 activity suppression lead to G1 phase arrest ,and G2M arrest was correlated to the cyclin B1/CDK1 activity after 4.0～8.0 Gy gamma rays.[
