Figure 5. Status of Rab25 expression is associated with EGFR endocytosis and gefitinib response.

(A) Difference in endosomal localization of EGF-induced EGFR between H358 and H1703 cells was profiled by immunofuorescence staining with the indicated antibodies. The immunofluorescence images were obtained using a fluorescence microscope at a magnification of 400×. Each white arrow indicates co-localization (yellow). (B) Effect of Rab25 expression on EGFR endocytosis was examined in siRab25 transfected H358 cells by flow cytometry. After siRab25 or scrambled (Scr) transfection, the cells were incubated with gefitinib (10 μM) and the percentage of internalized Alexa Fluor 488-conjugated EGF (500 ng/ml) was analyzed. Each bar represents mean values acquired from three experiments with standard error (SE). * p < 0.05. (C) Correlation between Rab25 expression and gefitinib response was determined by comparative analysis. Expression of Rab25 mRNA was evaluated in eight lung cancer cell lines with wtEGFR using quantitative RT-PCR. Relative Rab25 expression values were normalized to values of GAPDH. IC₅₀ of each cell was obtained from MTT assay results. The P value represents statistical comparisons between Rab25 expression and gefitinib response. Red: gefitinib-sensitive cell lines. Blue: gefitinib-insensitive cell lines.