Lentivirus-mediated RNA interference of Ku70 to enhance radiosensitivity of human mammary epithelial cells

Purpose: To investigate the radiosensitising effect of Ku autoantigen 70 (Ku70) and Ku autoantigen 80 (Ku80) knockdown by lentivirus-mediated RNA interference (RNAi) in the MCF10A immortalised human mammary epithelial cell line. Materials and methods: MCF10A cells were infected with lentiviral vectors for RNAi of Ku70. The Ku70-knockdown cell line (Ku70i) and a mock-infected control cell line (LVTHM) were used to perform radiation experiments. For the invitro Micronucleus (MN) assay, both cell lines were irradiated with doses of 2 and 4 Gy 60Co γ-rays. For cell survival experiments, doses ranging between 0 and 8 Gy were used. Results: Western blot analysis showed that the Ku70 lentiviral vector was effective in silencing the expression of both Ku70 and Ku80. A significantly higher radiation-induced MN yield was obtained in the Ku70i cell line compared to the control LVTHM cell line. RNAi of Ku70 also resulted in a lower survival yield after irradiation compared to the control cell line. Analysis of cell death mechanisms showed that MCF10A cells (Ku70i and LVTHM) do not undergo apoptosis, but undergo post-irradiation cellular senescence. Conclusion: RNAi of Ku70 resulted in increased chromosomal and cellular radiosensitivity in the MCF10A human mammary cell line after irradiation with 60Co γ-rays. These results further strengthen the role of the Ku protein in correct DNA double strand break (DSB) repair. © 2010 Informa UK Ltd.