Fig. 6. EGF promotes phosphorylation of the linker region of Smad2 by ERK1/2 in oral keratinocytes. (A) OKF6 cells were serum starved overnight and then treated with EGF (20 ng/ml), TGFβ1 (10 ng/ml), or with EGF (20 ng/ml) for 30 minutes prior to the addition of TGFβ1 (10 ng/ml) for the indicated time points. The cell lysates were probed for phosphorylated ERK1/2, and then stripped and re-probed for total ERK1/2. (B) OKF6 or UMSCC1 cells were serum starved overnight and then pre-treated with DMSO (as vehicle control) or MEK1/2 inhibitor U0126 (10 µM) for 30 minutes prior to the addition of EGF (20 ng/ml) for the indicated time points. The cell lysates were probed for phosphorylated ERK1/2, and then stripped and re-probed for total ERK1/2. (C) OKF6 and UMSCC1 cells were serum starved overnight and then pre-treated with DMSO (vehicle control) or U0126 (10 µM) for 30 minutes prior to the addition of EGF (20 ng/ml) for the indicated time points. Cell lysates were probed for Smad2 phosphorylation in the linker region (p-Smad2L), and then stripped and re-probed for total Smad2. The results are representative of at least two independent experiments.