APEX1 and neoplasm: Several key repair genes play important roles in BER pathway, such as the X-ray repair cross-complementing 1 (XRCC1), 8-oxoguanine DNA glycosylase (OGG1), and apurinic/apyrimidinic endonuclease 1 (APEX1) genes, which are associated with human tumor susceptibility and radiation toxicity [8–10].