GF 109203X inhibits the ERK1/2 constitutive phosphorylation in HS2 cells.

(A) 663 HS1 cells were either grown in the presence of 2 U/mL Epo and 10% serum or starved in Epo and serum for 4 hours before being stimulated with 10 U/mL Epo and 10% serum or not. A quantity of 10 μM GF 109203X was added for the last hour of starvation. (B) 606 HS2 cells were either grown in the absence of Epo and 10% serum or starved in Epo and serum for 4 hours before being stimulated with 10 U/mL Epo and 10% serum or not. They were treated with 10 μM GF 109203X for the last hour of starvation. Cell lysates were immunoblotted with anti–phospho-ERK1/2 (A, B upper panels) and anti-ERK1/2 (A, B lower panels) antibodies. The positions of phosphorylated ERK1 and ERK2 (P-ERK1, P-ERK2) and ERK1 and ERK2 were indicated.