Inhibition of the BER pathway enhances TET-induced global DNA demethylation. (A) Western blot analysis showed siRNA-mediated TDG knockdown in D1 clone cells with or without Dox treatment (2 μg/ml, 3 days). (B) DNA dot blot assay showed that TDG knockdown increased genomic 5caC content but not 5hmC in D1 clone cells treated with Dox (2 μg/ml, 3 days). (C) Western blot analysis of γH2AX showed that TDG knockdown decreased DNA DSBs in D1 clone cells treated with Dox (2 μg/ml, 3 days). (D) TDG knockdown enhanced TET-induced DNA demethylation in D1 clone cells treated with Dox (2 μg/ml, 3 days). (E) TDG knockdown reversed cell growth inhibition in D1 clone cells treated with Dox (2 μg/ml, 3 days). The cell numbers were counted 3 days after Dox treatment and those of non-treated cells were set as 1. (F) Western blot analysis showed siRNA-mediated APEX1 knockdown in D1 clone cells with or without Dox treatment (2 μg/ml, 3 days). (G) APEX1 knockdown promoted TET-induced DNA demethylation in D1 clone cells treated with Dox (2 μg/ml, 3 days). Bisulfite-pyrosequencing was used for DNA methylation analysis. Error bars represent SD from 3 independent experiments. * P < 0.05, * *P < 0.01 by Student's t test.