The Effects Of Of ～(60)Co Gamma Ray With Different Fractionated Doses To The Cell Cycle Kinetics And Proliferation Of Nasopharygeal Carcinoma Cell Line CNE-2

Objective To study the effects of (60)^Co gamma ray with different fractionated doses on the cell cycle,cyclin D1 and B1, proliferating cell nuclear antigen(PCNA) and cyclin dependent kinase1,4(CDK1,4) of nasophary-geal carcinoma cell line CNE-2.The changs of gamma ray to the effects of CNE-2 cell cycle kinetics and proliferation were observed consecutively.And to approach the molecul mechanism of gamma ray to CNE-2 cells proliferation and cell cycle kinetics.So as to provide basic material for the hypofractionated radiotherapy scheme of tumor. Methods The (60)^Co gamma radiation dose-rate is 108¹11mGy /min. The irradiated groups (including 4.0,6.0 or 8.0 Gy fractionated radiation groups).Each group was iradiated one time per day for 5 days with 24 hours interval.The control group was not irradiated.Propidium Iodide(PI) simple staining and flow cytometry(FC) were used to detect the cell cycle.The expression of cyclin D1,cyclin B1,PCNA,CDK4 and CDK1 mRNA were detected by combining RT–PCR with semi-quantitative analysis. Results â‘ With a single dose of 4.0,6.0 or 8.0 Gy Radiation of (60)^CO gamma ray caused CNE-2 cells accumulated in S and G2 phase of the cell cycle at 3 h after radiation.It was manifested that the percentage of cells of S and G₂ phase had a significant increase compared to the control group.After given in 4.0,6.0 or 8.0 Gy per fractions for 3 times in 3 days, the CNE-2 cells of G₁ phase increased while the percentage of cells of S and G₂ phase decreased. After given in 4.0 or 6.0 Gy per fractions for 5 times in 5days, the percentage of cells of G₁ phase decreased,while the cells of G₂ phase increased.At same time, the abnormal DNA content is observed. After given in 8.0 Gy per fractions for 5 times in 5days,the percentage of cells of G₁ and G₂ phase increased slightly,while the cells of S phase decreased.â‘¡The expression of cyclin B1 mRNA was suppressed after CNE-2 cells exposed to 4.0,6.0 or 8.0Gy fractionated radiation in gamma ray(P<0.05).There was not significant difference in the expression of cyclin B1 among irradiated groups(P>0.05).The CDK1 mRNA was not expressed in all irradiated groups,while the cells of control groups expressed normally.There was significant difference in the expression of cyclin D1 between the irradiated groups and the control group(P<0.05).The expression of cyclin D1 was suppressed After given in 6.0 or 8.0 Gy fractions in 5 days. However,there was not significant difference in the expression of cyclin D1 among the irradiated groups after treated with 3 fractions of 4.0, 6.0 or 8.0 Gy in 3 days (P>0.05).There was not significant difference in the expression of both CDK4 mRNA and PCNA between each irradiated groups and the control group (P>0.05).Conclusions â‘ G1,S and G2 phase delay were observed after CNE-2 cells exposed to the fractionation of the (60)^Co gamma ray dose(4.0,6.0 or 8.0Gy). G₁ arrest exhibited an dose-dependent increase.â‘¡Radiation-induced G₂/M arrest was associated with the expression level of CDK1 and cyclin B1 mRNA after CNE-2 cells exposed to 4.0,6.0 or 8.0Gy fractionated radiation in gamma ray. While G₁ arrest was associated with decreased expression level of cyclin D1 mRNA.The CDK4 function in radiation-induced G₁ arrest is indirect,maybe it caused G₁ arrest by affecting other factors function.â‘¢There was not significant difference in the expression of cyclin B1 among irradiated groups(P>0.05).This suggestied a same effect for the expression of cyclin B1 are suppressed in CNE-2 cell with 4.0,6.0 or 8.0Gy fractionated radiation in gamma ray.And increasing fractionated dose could not enhanced the suppressed effect.â‘£The expression level of PCNA increased slihgtly after CNE-2 cells exposed to 4.0,6.0 or 8.0Gy fractionated radiation in gamma ray,but significant difference was not observed (P>0.05).This indicates that PCNA participate only partly in the complicated CNE-2 cells proliferation procedure .