FIG. 7.

MPA induces Stat3 transcriptional activation. C4HD (A) and T47D (B) cells were transiently transfected with 2 μg/well of a luciferase reporter plasmid containing four copies of the m67 high-affinity binding site and with 1 μg/well of a CMV-βgal expression vector as an internal control. In the indicated lanes, C4HD cells were cotransfected with the DN Jak1 and DN Jak2 expression vectors or pretreated with PP2. Cells were also transfected with a pTATA-Luc reporter lacking the m67 insertion. The total amount of transfected DNA was standardized by adding the empty vector. After transfection, cells were treated with MPA and MPA-RU486 at 37°C for 48 h or left untreated growing in ChFCS. C4HD cells were then harvested and lysed. Luciferase and β-galactosidase activities were measured as described in Materials and Methods. Results are presented as n-fold induction of luciferase activity with respect to cells growing in ChFCS. The data shown represent the mean of six independent experiments ± the standard error of the mean. For b versus a and c versus b, P < 0.001.