Objective To investigate the roles of dCK Ser-74 in radiation-induced cell death in breast cancer cells.Methods Different phenotypes of dCK plasmids were transfected into MCF-7 cells by liposome transfection,including dCK-Vector,dCK-WT (wild type),dCK-S74A (non-phosphorylation) and dCK-S74E (hyper-phosphorylation).All these cells were irradiated by 0,2,4,6,8 Gy X-rays,respectively.The transcriptional and translational level of dCK were detected with real time-PCR and Western blot,respectively.Radiosensitivity was analyzed using cell counting kit (CCK-8) and colony formation assays.Monodansylcadaverine staining (MDC) and flow cytometry were used to detect autophagy and apoptosis,respectively.Results Four phenotypes of dCK cell models were established successfully.After irradiation,the cell viabilities of MCF-7 and dCK-Vector decreased significantly as compared with mock group (t =14.469 and 9.357,P ＜ 0.05),the cell viabilities of dCK-WT,dCK-S74A and dCK-S74E showed no changes (P ＞ 0.05).The total mortalities of dCK-WT and dCK-S74E decreased significantly as compared with dCK-Vector (x2 =3.857-3.971,P ＜ 0.05),but no changes in dCK-S74A cells (P ＞0.05).The apoptosis rates in dCK-S74A,dCK-Vector and control group were up-regulated after irradiation (t =-4.531,-3.688 and-7.076,P ＜ 0.05),and the irradiation-induced apoptosis was reversed in dCK-WT and dCK-S74E (66％ and 68％ of the increase level in dCK-Vector group).The autophagy in dCK-WT and dCK-S74E increased by 22％ and 26％ (t =-9.051 and-8.411,P ＜0.01),but no changes were observed in dCK-S74A,dCK-Vector and control groups (P ＞ 0.05).Conclusions The dCK-WT and dCK-S74E could reverse the irradiation-induced apoptosis,increase the autophagy occurence,and decrease the total mortality,indicating that the phosphorylation of dCK at Ser-74 sites is related to the radiosensitivity of MCF-7 cells.