Cellular localization, expression and mRNA levels of EGFR. (A) Immunofluorescence was performed with an antibody against EGFR (green). The nuclei were stained with propidium iodide (red). EGFR was identified at the cell membrane of both cell types and in clusters near the nucleus in A549 cells. (B) EGFR expression in A549 and HK2 cells by Western blotting. (C) Quantification of EGFR expression. (D) RT-PCR quantification of mRNA levels transcribed by the ErbB1 gene. All results are representative of three or more independent experiments. *p ≤ 0.05. Bars = standard deviation.