Visualization and quantitation of epidermal growth factor receptor homodimerization and activation with a proximity ligation assay

OBJECTIVES Activation of the epidermal growth factor receptor (EGFR) results from receptor homodimerization and autophosphorylation and confers sensitivity to tyrosine kinase inhibitors in some tumors. However, the visual detection and quantitation of activated EGFR in the clinical setting has not been established. MATERIALS AND METHODS A proximity ligation assay (PLA) was applied to detect EGFR homodimers in non-small cell lung cancer (NSCLC) cell lines and tissue specimens. RESULTS PLA signals corresponding to EGFR homodimers were higher in NSCLC cell lines and tissue specimens positive for activating EGFR mutations than in those wild type (WT) for EGFR. Stimulation with EGF in NSCLC cells WT for EGFR or forced overexpression of EGFR in Ba/F3 cells resulted in marked EGFR homodimerization. The extent of EGFR homodimerization appeared related to that of EGFR autophosphorylation in NSCLC cells WT for EGFR. CONCLUSION PLA may provide a new tool for detection and quantitation of EGFR homodimers in NSCLC and other tumors.