Abstract: Objective To study the regulation of telomerase activity of MiR-138 through targeting HTERT as the downstream molecular, and its effect on telomere stability in breast cancer cell line MCF-7. Methods MiR-138 mimics were transiently transfected into breast cancer cell line MCF-7. MTT method was applied for detecting the effect on cell proliferation. The HTERT expression level of the cells was detected by real-time RT-PCR and telomerase activity was checked by TRAP Assay 48h after transfection. Meanwhile, the cells were checked simultaneously by 53BP1 antibody immunofluorescent dyeing and telomere FISH dyeing. Results The HTERT expression level of MCF-7 cells treated with MiR-138 was repressed by 2.18 folds (2-△△Ct) when compared with the control cells 48h after transfection. Telomerase activity was also decreased by 2.69 folds when compare with the control cells. 53BP1congregated into many Foci and co-localized with the telomere spots at a percentage of 20.62%±1.55%. Conclusion MiR-138 can regulate telomerase activity in MCF-7 cells by targeting HTERT as the downstream molecular, and affects the telomere stability as well.

Key words: MiR-138, Telomerase, Telomere, Breast Cancer Cell Line MCF-7