FIG. 1.
17β-Estradiol and 4-hydroxytamoxifen activate p38 MAPK in endometrial cancer cells. (a) Activation of p38 by ERα agonists but not pure antagonist. ERα-negative Ishikawa cells were transfected with 0.5 μg of Flag-p38 and 0.5 μg of pLEN-hERα and treated with 10−8 M 17β-estradiol (E2), 10−6 M 4-hydroxytamoxifen (4-HT), 10−7 M ICI 182,780 (ICI), or ethanol (EOH) as a vehicle control for 30 min. The kinase activity was determined by immunocomplex kinase assays with GST-ATF2 as a substrate (upper panel). The level of Flag-p38 expression was determined by Western blotting with the M2 antibody (lower panel). p-ATF2, phosphorylated GST-ATF2. (b) ERα dependency of p38 activation by ERα agonists. ERα-negative Ishikawa cells were transfected with Flag-p38 and pLEN-hERα or control vectors. Cells were treated and the p38 activity was assayed as explained for panel a.