Figure 1-6917.

A: Western blot analysis of STAT3, FLAG, TIMP1, cyclin D1, Bcl-2, and Bcl-xL expression in MCF-7 cells transfected with tTA-TRE-STAT3C and treated with increasing concentrations of tetracycline for 24 hours. There was a gradual decrease in STAT3 and FLAG with increasing concentrations of tetracycline, with FLAG being completely undetectable at 60 ng/ml. Down-regulation of cyclin D1, Bcl-2, Bcl-xL, and TIMP1 expression was identified in the same experiment. MCF-7 cells transfected with tTA alone served as negative controls. B: Western blot analysis of FLAG and TIMP1 expression in MDA-MB-436 cells transfected with tTA-TRE-STAT3C and treated with increasing concentrations of tetracycline for 24 hours. A gradual decrease in FLAG and TIMP1 was observed. MDA-MB-436 cells transfected with tTA alone served as negative controls. C: Immunofluorescence staining and confocal microscopy studies revealed that STAT3 was localized to the nucleus in MCF-7 cells transfected with tTA-TRE-STAT3C, as illustrated by the white arrows (right) whereas STAT3 was confined to the cytoplasm in cells transfected with tTA only (left).