Figure 4.

A, Time course of ERK phosphorylation after treatment of thyroid cancer cell lines with the MEK inhibitor PD0325901. Cells were harvested at the indicated times after treatment with 10 nm PD0325901 and lysates Western blotted with antibody to total (left panel) or phosphorylated ERK (right panel). B, ERK phosphorylation rebound after 24 h of treatment with MEK inhibitor. Cells were harvested at the indicated times after treatment with 10 nm PD0325901 for 25 h by changing the media and the drug was readded or added for the first time 1 h before harvesting the cells. Lysates were Western blotted with antibody to total (left panel) or phosphorylated ERK (right panel).