Immunofluorescence analysis of Phospho-EGFR pTyr992 was performed using 90% confluent log phase A-431 cells treated with 200 ng/mL of EGF for 10 minutes. The cells were fixed with 4% paraformaldehyde for 10 minutes, permeabilized with 0.1% Triton™ X-100 for 10 minutes, and blocked with 1% BSA for 1 hour at room temperature. The cells were labeled with Phospho-EGFR (Tyr992) Polyclonal Antibody (Product # PA5-17835) at 1:250 dilution in 0.1% BSA and incubated overnight at 4 degree Celsius and then labeled with Goat anti-Rabbit IgG (Heavy Chain) Superclonal™ Secondary Antibody, Alexa Fluor® 488 conjugate (Product # A27034) a dilution of 1:2000 for 45 minutes at room temperature (Panel a: green). Nuclei (Panel b: blue) were stained with SlowFade® Gold Antifade Mountant with DAPI (Product # S36938). F-actin (Panel c: red) was stained with Rhodamine Phalloidin (Product # R415, 1:300). Panel d represents the merged image showing membranous localization. Panel e represents cells treated with antagonist, Afatinib (1µM for 6hrs) followed by EGF (200 ng/mL for 10 minutes), showing reduced Phospho-EGFR staining. Panel f shows untreated cells with no signal. Panel g represents control cells with no primary antibody to assess background. The images were captured at 60X magnification.