APEX1 and ductal breast carcinoma in situ: The expression of the oxidative stress proteins (SOD1, Ape1/Ref-1, Trx, TrxR, and PDI), the DNA repair proteins (Ape1/Ref-1, NM23-H1 and MPG), and the damage markers (8-OxoG, γ-H2AX and nitrotyrosine) were examined in 60 mammary tissues that were classified as BH, DCIS or IBC.