The Effect Of Cdc25c On Low-dose Hyper-radiosensitivity In Tumor Cells

Objective To study the effect of cdc25c and cell cycle checkpoint on HRS/IRR and the possible mechanism of HRS/IRR in tumor cells.Methods Exponentially growing HT29 cells and Siha cells were irradiated with X-rays at different doses. Cell surviving fractions after irradiating with different radiation doses were measured by the clonogenic survival assay depend on (?)uorescence-activated cell sorter. Cell cycle distribution after irradiating was examined with flow cytometry. The level of Phospho-Cdc25c(216) in cells was detected by Western blot after irradiating.Result HRS/IRR was observed in HT29 cells after low dose irradiating and not observed in Siha cells. The cell cycle distribution of HT29 cells had no change at dose below 0.3Gy. When the radiation dose was beyond 0.3Gy, G2/M phase arrest was observed in HT29 cells. Nevertheless, G2/M phase arrest was observed in Siha cells despite of radiation dose. At the dose less than 0.3Gy, the expression of Phospho- Cdc25C(ser216) was not observed in HT29 cells, but observed in Siha cells. When the dose is greater than 0.3Gy, Phospho-Cdc25c (ser216) was observed both in HT29 cells and in Siha cells.Conclusions The activity of Cdc25c may play an important role in G2/M phase arrest and HRS/IRR.