Monensin treatment enhances the mutant EGFR-Src association. Cells were growth factor-deprived for 48 hr and incubated with DMSO (D) or 10 μM monensin (M) for 3 hr. 1 mg aliquots of cell lysate proteins were immunoprecipitated with anti-EGFR antibody 528 and resolved together with 50 μg aliquots of whole cell lysates followed by immunoblotting with antibodies against the indicated proteins. The levels of EGFR and Src bands on blots were quantified using densitometry and immunoprecipitated Src relative to immunoprecipitated EGFR levels (Src/EGFR) were determined using the ImageJ software. Src/EGFR ratios in monensin-treated cells versus DMSO-treated cells are noted.