APEX1 and cancer: With the help of a variety of coactivator proteins, including NCOA/SRC1a, apurinic/apyrimidinic endonuclease-1/redox factor-1 (APE/Ref-1), and CREB-binding protein (CBP)/p300, the nuclear STAT3 binds to specific DNA sequences and activates the transcription of genes that regulate various phenotypes of cancer cells [17, 18].