APEX1 and cancer: The Apurinic/apyrimidinic endonuclease/redox factor-1 (APE1/Ref-1) is a key enzyme that in addition to its DNA base excision repair function it also exerts important cellular functions in the REDOX control of multiple transcription factors involved in cancer progression, including NF-κB, STAT3, AP-1, HIF-1, and p53 [115–118].