RESUMO
Objective@#To explore the functions of DNA-PKcs in cellular low dose hyper-radiosensitivity.@*Methods@#Colony-formation assay was used to detect the survival fractions of M059K and M059J cell lines treated by X-ray irradiation. Micronucleus assay and γ-H2AX foci assay were used to measure the radiation-induced DNA damage. Western blot was used to detect the relative expression levels of phospho-Chk1, total Chk1, phospho-Chk2 and total Chk2 of M059K and M059J cells.@*Results@#The hyper-radiosensitivity was observed in M059K cells irradiated with X-ray of doses lower than 1 Gy. DNA damage levels did not show HRS/IRR in the cell lines we used. pChk1/Chk1 in M059K cells was significantly increased during 20 min to 60 min after 0.2 Gy X-ray irradiation (t=14.157, 13.661, 14.177, 11.317, 14.512, P<0.05); pChk2/Chk2 in M059K cells was markedly increased during 20 min to 50 min after 0.2 Gy X-ray irradiation (t=13.182, 13.868, 14.155, 14.477, P<0.05).@*Conclusions@#M059K cells show the phenomenon of low dose hyper-radiosensitivity, which may be related to activation of proteins in G2/M phase checkpoints regulated by DNA-PKcs.