The oxidative stress plays a prominent role in the cytotoxicity of PENAO-DCA combination. (A) Cellular ROS levels in U87 and BAH1 cells after 6 hr treatment with 5 μM PENAO, 20 mM DCA and their combination. (B) Mitochondrial ROS levels in U87 and BAH1 cells after 6 hr treatment with PENAO, DCA and combination. (C) Percentage of apoptotic cells (Annexin V positive) after 24 hr PENAO-DCA treatment +/− 0.5 mM NAC or +/−0.5 mM GSH-MEE or +/− 0.5 mM BSO. (D) The expression of phosphorylated histone (γ-H2AX) after 24 hr treatment with PENAO, DCA and PENAO-DCA combination (PENAO and DCA concentrations as in A). Western blots presented are representative of 3 independent experiments. Results are presented as means ± s.d. of three experiments. *p < 0.05, **p < 0.01, ***p < 0.001, #p < 0.01 vs PENAO.