FIGURE 7.

Inhibition of c-Src or JAK activity is not involved in TPA-induced STAT3 dephosphorylation. A, WM1205Lu cells were treated with 10 μm PP2 or PP3 (control) for 180 min. The phosphorylation level of c-Src (pY-Src) and the expression of total c-Src (t-Src) were determined by immunoblot analysis after immunoprecipitation with anti-c-Src antibody using anti-phospho-c-Src and anti-c-Src antibodies, respectively (top two panels). The expression of pY-STAT3 and total STAT3 (t-STAT3) was also determined by immunoblot analysis (bottom two panels). B, WM1205Lu cells were treated with 200 nm JAK inhibitor I or DMSO (control) for 180 min. The phosphorylation level of pY-STAT3 as well as the expression of total STAT3 were determined by immunoblot analysis using anti-pY-STAT3 and anti-STAT3 antibodies, respectively. C, WM1205Lu cells were stimulated with 100 nm TPA or 0.1% DMSO (control). The phosphorylation level of pY-Src (upper panel) as well as the expression of t-Src (lower panel) were determined at the indicated time point. The positions of pY-Src, t-Src, IgG heavy chains (IgG H.C.), pY-STAT3, and t-STAT3 in A and B are indicated by arrows. The results shown are representative of three independent experiments.