Figure 3. Involvement of STAT3 in As³⁺-induced Akt activation and EZH2 S21 phosphorylation. (A) BEAS-2B cells were pretreated with a negative control, 20 μM STAT3 Inhibitor V (STAT3 In) or DMSO as a vehicle control for 4 h. The cells were then incubated in the presence or absence of 20 μM As³⁺ for an additional 2 h. (B) As³⁺ induces STAT3 reporter gene activity. BEAS-2B cells were transfected with a STAT3 reporter system containing a 40:1 mixture of a STAT3 firefly luciferase reporter vector and a renilla luciferase reporter vector. Twenty-four hours after transfection, the cells were treated with the indicated concentrations of As³⁺ for 6 h. Dual-luciferase activity was determined at the end of the cell culture period. The right panel shows a time-course study of As³⁺-induced STAT3 reporter gene activity. *: p < 0.05; **: p < 0.005. (C) As³⁺ reduces immunofluorescent signal of Y705-phosphorylated (pY705) STAT3. (D) As³⁺ induces nuclear accumulation of the S727-phosphorylated STAT3. Data are representative of three experiments.