EGFR ubiquitination, c-Cbl/EGFR association, and pY1045 expression upon EGF stimulation in RBE and MMNK-1 cells. (A) EGFR ubiquitination and EGFR-associated c-Cbl before and after 3, 10, and 15 min of EGF stimulation. (B) Quantification of EGFR ubiquitination from Western blotting in RBE cells (closed circles) and MMNK-1 cells (open circles). Values are standardized to the optical intensity of EGFR and presented as values relative to that of ubiquitinated EGFR/total EGFR in RBE or MMNK-1 cells before EGF stimulation. *p < 0.05. (C) Expression of pY1045 and c-Cbl in total cell lysates before and after 3, 10, and 15 min of EGF stimulation. All results are representative of three or more independent experiments.