To investigate whether the amount of Ku70 could affect the apoptosis of RCC cells, flow cytometry and TUNEL assay were performed to analyze the apoptosis of the stable 786-O cell lines.The flow cytometry analysis indicated that the apoptosis rate of 786-O-Ku70 cells (0.97 ± 0.12%) was significantly reduced in comparison with those of 786-O-vector cells (3.17 ± 0.06%). The gene discussed is XRCC6; the disease is renal cell carcinoma.