H-520 cells express high levels of EGFR. The percentage of EGFR expressing cells in H-520 cells was determined by FACS. The upper panel (A) shows isotype control, which stains only with secondary antibody. The lower panel (B) shows that 82% of the H-520 cells expressed EGFR as stained positively for EGFR mAb. One representative of three experiments was shown.