Abstract: Objective To study the effect of HTERT RNA interference on γ ray irradiation induced DNA damage response in breast cancer cell line MCF-7. Methods A retrovirus carrying HTERT- siRNA was used to repress the expression of telomerase catalyze unit HTERT in breast cancer cell line MCF-7. The HTERT expression level of the cells was confirmed by real-time RT-PCR and Western blot. 3 Gy dosage of γ ray from 137Cs was applied to irradiate the cells, cells were then collected and fixed before and 1, 2, 4, 8 and 12h after irradiation, and Phospho-53BP1 antibody was used for immunofluorescent dyeing of the cells. Cells were also collected before and 1h, 4h, 12h after irradiation and phosphorylation level of 53BP1 was detected by Western blot as well. Results The HTERT expression level of Cells treated with HTERT -siRNA was repressed by 3.20 folds (2-△△Ct) when compared with the control cells. The HTERT protein level also decreased by 2.56 folds. DNA damage response of cells treated with HTERT -siRNA was repressed obviously. Conclusion DNA damage response induced by γ ray irradiation in breast cancer cell line MCF-7 could be repressed through RNA interference of HTERT expression level.

Key words: Telomerase, γ ray, Breast Cancer Cell Line MCF-7, DNA Damage Response