Inhibition of JNK suppresses FGF4-mediated proliferation of mESCs.

(A) mESCs were pretreated with MAPK inhibitor or anti-FGF4 antibody 30 min before addition of 50 ng/ml recombinant FGF4, and cell proliferation rate was determined 48 h after treatment using a cell proliferation assay kit. In addition, siRNAs directed against JNK or GFP were transfected into mESCs. At 24 h post-transfection, cells were exposed to 50 ng/ml FGF4 and cell proliferation rate (B) and ³H-TdR incorporation (C) were measured 48 h after treatment. *p<0.05, **p<0.01, and ***p<0.001 vs. untreated cells. ^##p<0.01 and ^###p<0.001 vs. cells treated with FGF4 only.