Figure 5.

Src was the upstream protein kinase responsible for STAT3 activation under doxorubicin (DOX) treatment. (a) MDA-MB-231 and MDA-MB-453 cells were treated with DOX (0.2 μM) for the indicated time periods and then the induction of Src activation was detected by western-blot assay. (b) MDA-MB-231 cells were co-transfected with STAT3-dependent luciferase reporter plasmid and Src siRNA and then exposed to DOX (0.2 μM) 36 h after transfection. Then the induction of STAT3 luciferase activities was determined at the indicated time periods after DOX treatment. (c) MDA-MB-231 cells were transfected with Src siRNA or control siRNA and then treated with DOX (0.2 μM) 36 h after transfection. Then the activation of STAT3 and the expressions of heme oxygenase-1 (HO-1), Beclin-1 and LC3BI/II were determined 12 h after DOX exposure. To avoid the off-target effect, two different siRNA against Src were purchased and tested. Data shown here were obtained from the most effective one. (d,e) MDA-MB-231 cells were transfected and treated as described in figure (c) and then autophagy was detected as described in Figure3(b,c). (f) MDA-MB-231 cells were transfected and treated as described in figure (c) and then cell death incidence was detected 48 h after DOX treatment.