(A) The relative increase in caspase-3/7 activity in A2780/CDDP, ES2 and IGROV1 cells before after treatment with CDDP, DJ-1 siRNA-NP and combinatorial therapy. The caspase activity was set to 100%. (B) The relative intracellular level of reduced glutathione (GSH) in ovarian cancer (A2780/CDDP, ES2 and IGROV1) cells before and after treatment with DJ-1 siRNA-NP for 24 h. The intracellular level of GSH in non-treated HEK293 cells was used as a reference and set to 100%. (C) The intracellular level of NRF2 protein in A2780/CDDP, ES2 and IGROV1 cells before after treatment with DJ-1 siRNA-NP for 24 h. Expression of proteins was evaluated by band densitometry analysis of Western blots. Band intensities of NRF2 protein in the various samples are expressed as the percentage of the β-actin band intensity, which was set to 100%. Representative Western blot images of NRF2 proteins expression in the ovarian cancer cells before and after exposure to the DJ-1 siRNA treatment are provided. (D) Relative intracellular level of H2O2 in the ovarian cancer cells after treatment with CDDP, DJ-1 siRNA-NP and combinatorial therapy. Cells incubated with media were used as the control and intracellular level of H2O2 in these cells was set to 100%. Means ± SD are shown. *p < 0.05 when compared with cancer cells treated with media.