Ape1 siRNA is efficient to knock down target gene expression in EB cells. (A) Western blot analysis of Ape1 protein expression in both ES and EB cells at different ages (days 3, 6, and 10). (B) Silencing of endogenous Ape1 gene by Ape1 siRNA. Western blot analysis demonstrates that Ape1 siRNA efficiently knocks down Ape1 gene expression: lane 1 represents untreated cells; lane 2: cells treated with 25 nM scrambled siRNA; lane 3: cells treated with Ape1 siRNA at 5 nM; lane 4: cells treated with Ape1 siRNA at 25 nM; and lane 5: cells treated with Ape1 siRNA at 50 nM.