Fig. 4

Osthole inhibits STAT3 phosphorylation in TNBC cells. a MDA-MB-231 and BT-549 cells were treated with 200 μM osthole for the indicated times, and levels of P-STAT3 were determined by Western blot analysis. GAPDH and STAT3 were used as internal control. b MDA-MB-231 and BT-549 cells were exposed to osthole at indicated concentrations for 24 h or 12 h, respectively. P-STAT3 levels were determined by immunoblotting. GAPDH and STAT3 were used as internal control. c Cells were pretreated with 200 μM osthole for 24 h (MDA-MB-231) or 12 h (BT-549) and then stimulated with IL-6 (50 ng/mL) for 30 mins. STAT3 phosphorylation was determined by western blot. d Immunofluorescence staining of cells showing distribution of P-STAT3 (red) in MDA-MB-231 cells. DAPI was used as counter stain. e MDA-MB-231 cells were pretreated with osthole for 24 h before exposure to IL-6 (50 ng/mL) for 30 min. Nuclear extracts were subjected to P-STAT3 and STAT3 immunoblotting. Lamin B was used as loading control