Fig. 3.

Arsenic trioxide decreases catalase protein level in Resox cells by diminishing catalase gene transcription. a, b Catalase protein levels were compared and quantified in human mammary 250 MK cells, MCF-7 and Resox cells. ^##p value < 0.01 versus 250MK cells. **p value < 0.01 versus MCF-7 cells. c, d Catalase protein levels were evaluated and quantified by immunoblotting in Resox cells after ATO treatment (24 h). **p value < 0.01 versus cells not incubated with ATO (CTL). e ROS levels were quantified by flow cytometry with CM-H2DCFDA probe. ROS levels were compared to their respective control (CTL). **p value < 0.01; ***p value < 0.001 versus cells not incubated with ATO (CTL). ^##p value < 0.01 versus cells incubated with 5 μM ATO. f Catalase mRNA were measured by qRT-PCR and compared to untreated MCF-7 cells. **p value < 0.01; ***p value < 0.001 versus cells not incubated with ATO (CTL). g Normalized luciferase activity was measured in MCF-7 and Resox cells stably transfected with the plasmid pCAT − 1518/+ 16 after ATO incubation for 24 h (n = 3). ***p value < 0.001 versus cells not incubated with ATO (CTL). Data are mean ± s.e.m. Groups were compared using one-way ANOVA followed by Tukey post hoc test for (b, d–g)