APEX1 and sarcoma: A decrease in APE1 levels led to enhanced cell sensitization to ionizing radiation in human osteogenic sarcoma cells and lung carcinoma cells as well as in colorectal cancer cells [22], [23], [26], [27].We have previously shown that APE1 was overexpression in human colorectal cancer, and chimeric adenoviral vector Ad5/F35-mediated APE1 siRNA (Ad5/F35-siAPE1) potentiates radiosensitivity of human colorectal cancer cells [23].