Objective To study mitochondrial transcription factor A（Tfam）, 8-oxoguanine DNA glycosylase（Ogg）-1 and DNA polymerase gamma（Polg）, which is relative to mitochondrial DNA repair system, regulated by γ-irradiation in oral squamous cell carcinoma（OSCC）. Methods OSCC-2 and 5 cells were cultured in vitro and treated with γ-irradiation. Cell survival rate was calculated with methyl thiazolyl tetrazolium assay. Using Western blot, PCR and RT-PCR detected the protein and mRNA level of Tfam, Ogg-1 and Polg. Results After OSCC-2 and 5 cells were irradiated at a dose of 30 Gy, the cell proliferation were （35.33±6.03）% and （75.67±4.16）% respectively. The level of tfam mRNA were increased, but higher tfam mRNA levels were observed in OSCC-5 cells at 6 h after irradiation. Besides, the expression of Ogg-1 and Polg was also stronger in the irradiated OSCC-5 cells. In addition, each small interfering RNA（siRNA） down-regulated the corresponding protein expression. Transfection of the siRNA increased apoptosis of the irradiated cells. Conclusion In vitro, γ-irradiation can inhibit the proliferation and up-regulate the expression of Tfam, Ogg-1 and Polg of OSCC-2 and 5 cells.
